Eindhoven University of Technology MASTER Cement in development : energy and environment van der Vleuten, Frank Award date: 1994 Link to publication Disclaimer This document contains a student thesis (bachelor's or master's), as authored by a student at Eindhoven University of Technology. Student theses are made available in the TU/e repository upon obtaining the required degree. The grade received is not published on the document as presented in the repository. The required complexity or quality of research of student theses may vary by program, and the required minimum study period may vary in duration. General rights Copyright and moral rights for the publications made accessible in the public portal are retained by the authors and/or other copyright owners and it is a condition of accessing publications that users recognise and abide by the legal requirements associated with these rights. • Users may download and print one copy of any publication from the public portal for the purpose of private study or research. • You may not further distribute the material or use it for any profit-making activity or commercial gain
Transcript
Eindhoven University of Technology
MASTER
Cement in development : energy and environment
van der Vleuten, Frank
Award date:1994
Link to publication
DisclaimerThis document contains a student thesis (bachelor's or master's), as authored by a student at Eindhoven University of Technology. Studenttheses are made available in the TU/e repository upon obtaining the required degree. The grade received is not published on the documentas presented in the repository. The required complexity or quality of research of student theses may vary by program, and the requiredminimum study period may vary in duration.
General rightsCopyright and moral rights for the publications made accessible in the public portal are retained by the authors and/or other copyright ownersand it is a condition of accessing publications that users recognise and abide by the legal requirements associated with these rights.
• Users may download and print one copy of any publication from the public portal for the purpose of private study or research. • You may not further distribute the material or use it for any profit-making activity or commercial gain
De Faculteit Elektrotechniek van deTechnische Universiteit Eindhoven aanvaardtgeen verantwoordelijkheid voor de inhoudvan stage- en afstudeerverslagen.
Afstudeerwerk verricht o.l.v.:Prof.dr. L.H.Th. RietjensDr.ir. P. MasseeDrs. J. Jansen (ECN)Eindhoven, maart 1994.
TECHNISCHE UNIVERSITEIT EINDHOVEN
Acknowledgement
This report is the result of a master's thesis research, carried out betweenseptember 1993 and april 1994 at ECN. The research was undersupervision of drs. Jaap Jansen of ECN·policy studies and dr.ir. PeterMassee and prof.dr. Lee Rietjens of the Eindhoven CJniversity ofTechnology (EUT).
The present report is included as a working paper (reference·number ECN·1-94·021)in the collaborative research project of ECN, ENDA-TM (Dakar),IEl (Rio de Janeiro) and TERI (New Delhi) entitJed 'Strategies andInstruments te Promote Energy Efficiency in Developing Countries'. Thisproject sets out to make a preliminary assessment of major implementedand ongoing poUcy initiatives te improve industrial energy efficiency incleveloping countries. In addition, it sets out to identify possibiJities fortransfer of appropriate teehnology from OECD member states to enhanceenergy efficiency and environrnental performance of manufacturingindustries in the developing world.
Abstract
This report considerS the cement industry in the world. Energy use andenvironrnenUiI impacts are assessed. From this possible energyconservation and pollution reduction measures are analysed. Finally policyoptions facilitating implementation of these measures are described both onnational and international level.
Keywords
CEMENTCEMENT lNDCJSTRYENERGY CJSEENERQYCONSERVATIONPOLUmONINTERNATIONAL COOPERATIONTECHNOLOOY TRANSFER
2
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CONTENTS
PREFACE 9SOMMARY 11SYMBOLS, UNITS AND PREFIXES 13
1. INTRODUCTION 151.1 Cement 151.2 Historical development of cement 161.3 Cement production and economy 171.4 Cement and economie performance 181.5 Research objective 20
2. WORLD CEMENT INDUSTRY 212.1 OECD countries 222.2 Africa 232.3 Asia 242.4 Latin America & the Caribbean 282.5 Transition Economies 30
3. PRODUCTION PROCESS 333.1 Material flow 333.2 Historical development of technology 37
4. ENERGY USE 574.1 Energy in cement 574.2 Theoretical energy requirements 584.3 Typical practical energy requirements 614.4 Regional overview 62
4.4.1 OECD 634.4.2 Africa 644.4.3 Asia 654.4.4 Latin America & the Caribbean 664.4.5 Transition economies 67
3
5. ENERGY CONSERVATION5.1 Management measures
5.1.1 Energy audits5.1.2 Reduction of heat Josses5.1.3 Process control
5.2 Process changes5.2.1 Raw material preparation5.2.2 Pyroprocessing5.2.3 Clinker grinding5.2.4 Motors and transmissions
5.3 Material changes5.3.1 Raw material seJection5.3.2 Secondary raw materials5.3.3 Grinding aids5.3.4 MineraJizers
5.4 Energy measures5.4.1 Secondary fueJs5.4.2 Waste heat recovery5.4.3 Combined production of heat and power
5.5 Summary energy conservation options5.6 Regional scope for energy conservation
6. ENVIRONMENTAL IMPACTS6.1 Emissions to air
6.1.1 CO2 emissions6.1.2 Dust emissions6.1.3 S02 emissions6.1.4 NO. emissions6.1.5 Other emissions to air
6.2 Other environmental impacts6.2.1 Noise6.2.2 Water pollution6.2.3 Resource exploitation6.2.4 Wastes6.2.5 Use of secondary raw materials and fueJs
6.3 Global pollution situation
7. EMJSSION REDUCTION7.1 CO2 emission reduction7.2 Dust emission reduction7.3 S02 emission reduction7.4 NO. emission reduction7.5 Regional scope for CO2 emission reduction
8. POUCY 0P110NS8.1 Barriers
8.1.1 Lack of availability of technica] options8.1.2 Lack of information8.1.3 Lack of insight8.1.4 Lack of incentives8.1.5 Lack of institutional support8.1.6 Other barriers
4
697070707374757577777878788181818284868787
91919194959697989898999999
100
101101102105105106
109109109110111112113113
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8.2 Policy responses8.2.1 Technical options8.2.2 Information about options8.2.3 Insight8.2.4 Incentives8.2.5 Institutional support
9. INTERNATIONAL COOPERATION9.1 Scope for international cooperation
9.1.1 Technology transfer9.1.2 Information dissemination9.1.3 Human resources development9.1.4 Incentives9.1.5 Institutional support
9.2 Role of private sector9.3 Role of official South-South cooperation9.4 Role of bilateral North-South cooperation9.5 Role of multilateral cooperation
10. CONCLUSIONS
REFERENCES
APPENDIX 1. LITERATUURONDERZOEK
113114115116116118
121121121124125126126127128128129
131
135
147
5
LIST OF TABLES
Table 1.1 Major cement producer companies 18
TabJe 2.1 Cement production in the world (1990) 21TabJe 2.2 Basic indicators for OECD countries (1990) 22Table 2.3 Basic indicators for Africa (1990) 24Table 2.4 Basic indicators for the group of Asia (1990) 26Table 2.5 Basic indicators for Latin America & the Caribbean (1990) 29TabJe 2.6 Basic indicators for the Transition Economies (1990) 30Table 2.7 Regional distribution of cement production in the USSR in
1988 31
Table 3.1 Portland clinker compounds 35Table 3.2 Typical costs and energy requirements in bulk
transportation 36Table 3.3 Crusher data 40Table 3.4 Efficiency of different grinding systems 42Table 3.5 Heat balances of different clinkering processes 44TabJe 3.6 Data and heat balance of different cooler types 51Table 3.7 Tandem grinding compared with conventional closed circuit
bali mills 55
Table 4.1 Total energy needed to produce and transport buildingmateria Is 57
Table 4.2 Building materials unit production energy intensity(MJ/m~ 58
Table 4.3 Calculated theoretical grinding power 59Table 4.4 Theoretical heat requirement for evaporation 59TabJe 4.5 Theoretical heat requirement from reaction enthalpies 60Table 4.6 Theoretical heat requirement from simplified formulas 60Table 4.7 Theoretical energy requirement to produce Portland cement 61Table 4.8 Energy consumption in typical Portland cement plant 61Table 4.9 Estimated regional means used in calculation 62Table 4.10 Energy use in OECD 63Table 4.11 Energy use in Africa (1990) 64Table 4.12 Energy use in Asia (1990) 65Table 4.13 Energy use in Latin America & the Caribbean (1990) 66Table 4.14 Energy use in Transition Economies (1990) 67
Table 5.1 Change in fuel consumption relative to change in energylosses 71
Table 5.2 Benefits of ABB proces control system 73Table 5.3 Portland cement fineness standards in selected countries 74Table 5.4 Comparison optimal raw grinding systems 75Table 5.5 Conversion of wet process 76Table 5.6 Closed circuit clinker grinding systems with high efficiency
classifiers 77Table 5.7 Savings in primary energy by the use of interground
additives 78Table 5.8 Typical compositions in weight-percentages 79Table 5.9 Potential secondary raw materials 80
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Table 5.10 Calorie ualues ofpossible waste fuels 83Table 5.11 Energy conseruation options in cement manufacturing 87Table 5_12 Packages of conseruation options 88Table 5.13 Estimated global and regional conseruation effects 88
Table 6.1 Auerage emissions to air in EU countn-es 91Table 6.2 Typical CO2 emissions from energy use 92Table 6.3 Estimated CO2 emission from cement manufacturing 92Table 6.4 Estimated regional CO2 emissions by the cement industry
(1990) 93Table 6.5 Estimated process dust emissions 95Table 6.6 502 formation and absorption reactions 95
Table 7.1 Dust emission after cIeaning 102Table 7.2 Estimated global and regional CO2 reduction effects 107
Table 8.1 Non-OECD suppliers Iisted in ICR Buyers Guide 1992 109Table 8.2 Cost structure of cement production in some OIC countries 112
Table 9.1 Examples of international clearinghouses 125
7
LIST OF FIGURES
Figure 1.1 Cement plant at Samchok, Korea 15Figure 1.2 Cement consumption versus GNP for countries of the world
in 1990 19Figure 1.3 Cement production versus GNP for Korea, 197().1991 20
Figure 2.1 Cement production and consumption in 1990 21Figure 2.2 Cement production in OECD (1990) 22Figure 2.3 Cement production in Africa (1990) 23Figure 2.4 Cement production in Asia (1990) 25Figure 2.5 Development of cement production in China 27Figure 2.6 Cement production in Latin America [, the Caribbean
(1990) 28Figure 2.7 Cement production in the Transition Economies (1990) 30
Figure 3.1 Cement manufacturing process 34Figure 3.2 Approximation of relation fineness and partic/e size 36Figure 3.3 Development of avarage specific heat consumption 38Figure 3.4 Development of kiln technology and speci{ic heat
consumption in Japan 39.. Figure 3.5 Dryer heat use 42"Figure 3.6 Characteristics of different suspension preheater systems 47
Figure 6.2 Energy efficiency and S02 emission of different processes 97Figure 6.3 Hippos grazing in rehabilitated quarry in Kenya 99
Figure 7.1 Estimated regional CO2 emission reduction effects 107
Figure 8.1 Jncreasing levels of sophistication of technologycomponents 114
Figure 8.2 Pay-back time for wet to dry process conversion 117
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PREFACE
This report will focus on the cement industry in the world. For this purposethe world has been divided into five specific groups of countries,corresponding to the level of their economy and their geographicallocation.
The first group contains all OECD countries, considered to be highlyindustrialized. Then the developing countries of Africa, Asia and America,are grouped according to their geographical region. The fifth group, theTransition Economies, contains the former socialist countries of Middle andEastem Europe and the former USSR, which are all in a state of transitionto a market economy. Although many borders in this region have alteredrecently, the countries will be considered as they were, before entering thestage of transition.
The writer wants to stress that, in using the terms development anddeveloping countries, he does not intend to implicate a moral significaneewhatsoever, and certainly not that all countries should move in a similardirection Iike that, which most Western European countries have moved induring the last two centuries. The term development is rather used as aneconomie term based on the extent of industrialization of a given society.
9
EeN 1994
SUMMARY
Ever since the great days of Rome, cement has been considered one of themost important building materials in the world. It is used in almost everycountry of the world in strategically important economie: sectors, likeindustry, transport, agriculture and energy. Because of the nature of theproduct and the relatively high transportation cost, cement trade is limited.Therefore, cement is also produced in almost every country.
This report analyses energy use and environmental pollution in this cementproduction, as weil as options for energy conservation and pollutionreduction. The aim is to propose national and international polic:y optionsconceming energy conservation and pollution reduction in the cementindustry in developing countries.
There is a coarse relation between the use of cement and the level ofeconomic development. Espec:ially during early industrialization of aneconomy. cement consumption, and with it the cement industry, tends toexpand rapidly. This relation is important when considering thecontemporary cement industry in the different regions of the world.Characteristic for OECD countries is a high, but stabIe per capitaconsumption of cement. The market is c:urrently relatively weak because ofstagnating economie: growth. Cement consumption in the developingcountries of Africa, Asia and Latin America & the Caribbean is verydependent on the general economie: performance. The cement industry inthe Transition Economies is characterized by the recession, brought aboutby the process of transition to a market economy. This caused aconsiderable decrease in cement consumption.
The cement manufacturing process roughly consists of the followingstages: collection of raw materials (mostly calc:areous rock), drying,grinding, and blending of raw materiais, high temperature buming of theraw mix to produce dinker, and finally dinker grinding. Most technologicalinnovation has focussed on saving costs by scaling-up and improvingefficiency of kiln technology (especially conversion from wet· to dryprocess kilns). As aresuIt specific kiln fuel consumption has decreased bymore than 50% during the last 35 years. Especially in the last decadeenergy saving grinding technology received more attention.
Although concrete, the main end·use of cement, appears to be a ratherenergy effic:ient building material, the production of cement demands aconsiderable amount of energy. In cement production, energy is one of themost important cost factors. Energy costs are divided about equallybetween electric:ity (mostly for raw material and dinker grinding) and fuel(for dinker buming). Estimates, made in this report, indicate that in mostcountries the cement industry accounts for between 5% and 30% of thetotal industrial energy consumption. Especially in rapidly expandingeconomies, and in some small economies that are just starting toindustrialize, this percentage may even be considerably higher.
Energy conservation options focus on management measures (such asenergy audits, reduction of heat losses and installation of proc:ess control
11
Cement in development
equipment), process measures (installation of state-of-the-art equipment),material changes (use of secondary raw materiais), and energy measures(secondary fuels, waste heat recovery and combined heat and powersystems). Process measures and material changes offer the highestconservation potential, although the first require high investments, and thesecond might give high operational cost.
[t has been estimated that introduction of maximum process and productmeasures might give agiobal energy conservation effect of 30% and 33%respectively. The transition economies form an exception here to the extentthat for their situation process measures give the best results. Bothmeasures together would give agiobal energy conservation potentialofabout 51 %. The conservation potentia[ appears quite large in all consideredregions, but especially in Africa and Asia.
The pollution by the cement industry should not be underestimated. Theprimary emissions to air are CO2 and particulate matter. Emissions of NO.,and in some cases 502, are also demanding more attention. Especially CO2
emissions are important. The cement industry is the largest industrialcontributor to CO2 emissions in many developing countries. A positivecontribution to the problem of environmental pollution can be made by useof secondary raw materials and fuels. Cement kilns offer possibilities foruse of waste materiais, which make them an interesting alternative torefuse incineration plants and waste disposal sites.
Many energy conservation measures, irnply a[so a potential for pollutionreduction. This is c1ear for CO2, as energy conservation is often the mosteffective tooI for CO2 emission reduction. The most effective measure forCO2 emission reduction is the addition of secondary raw materia[s duringc1inker grinding. Also certain pollutant specific measures may be effective,such as dust collectors and low NO. burners.
From the above it follows that there is considerable scope for energyconservation and pollution reduction, when the present technicaI optionsare implemented. This implementation, however, is often seriously hinderedby lack of mastery of techno[ogy t [ack of information, lack of insight, lackof incentives, and lack of institutiona[ support. National policies should aimat providing the optimal environment for decentralized investmentdecisions, by optimizing their technology strategy, by improvinginformation dissemination, by human resources development, by providingproper incentives, and by establishing effective and stabIe institutionalsupport.
As some countries have [ess experience and resources than others,international cooperation is necessary to obtain the optimal result. Throughtransfer of intermediate or high technology, proper provision of information,incentives and access to finance, and through assistance in humanresources development and institutional support, the internationalcommunity cou[d help to achieve the maximum conservation effects. Alarge role could be played by private sector investment. Furthermoreimproving South-South cooperation, bilatera[ North-50uth cooperation, andespecially strengthening multilateral organizations, deserve high priority.
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SYMBOLS, UNITS AND PREFIXES
SymboLs, acronyms and abbreviationsADBCcap.EUGNPICRNGOOECDOICPCR&DSPS&TusS
CaOCaC03
Ca(OHhCfCCO2
COH20MgONH3
NO,O2
Si02
S02AI20 3
fe 203
Anno DominiBefore ChristCapitaEuropean UnionGross national productInternational Cement ReviewNon-govemmentalorganizationOrganization for Economie Cooperation and DevelopmentOrganization of Islamic CountriesPrecalcinerResearch and developmentSuspension preheaterSchooling and trainingUnited States Dollars
Calcium oxideCalcium carbonateCalcium hydroxideChlorofluorcarbonCarbon dioxideCarbon monoxideWaterMagnesium oxideAmmoniaNitrogen oxides (nitric oxide NO and nitrogen dioxide N02)
metrenormal cubic metrekilogram(metric) ton (1t=1000kg)(metric) ton of clinker(metric) ton of cement(metric) ton per hour(metric) ton per day(metric) ton per yearkelvincentigrade (IOC on centigrade scale equivalent to1K on the Kelvin scale; O°C=273.15K)secondhour (lh...3600s)day (1 d=86400s)year (1 y=365d)Joulekilo-Watt-hour (103 .J/s.3600s)
Ever since the great days of Rome, cement has been considered one of themost important building materials in the world. lt is used in almost everycountry of the world. Because of the perishabie nature of the product andthe relatively high transportation cost, cement trade is limited. Therefore,cement is also produced in almost every country.
The cement industry can be understood best by considering the coarserelation between use of cement and level of economie development, ascement is mostly used in modem infrastructure and building.
This report analyses energy use and environmental pollution in cementproduction, as weil as options for energy conservation and pollutionreduction. The focus is especially on national and international policyoptions conceming energy conservation and pollution reduction in thecement industry in developing countries.
1.1 Cement
Cement is a bonding agent used in building materiais. It is considered oneof the most important building materials in the world, because of its mainend-use, concrete. Concrete is a mixture of inert mineral aggregates ofsand and gravel or crushed stones, bound together by some hydrauliccement). One metric ton of cement produces about 3m3 of concrete.
It is hard te imagine buildings, bridges, dams, highways, etc. being builtwithout concrete. rf consideration is given to proper designing. concretestructures can be very strong and very durable. Furthermore concrete canbe economically competitive with most other building materiais. And last
A 8Ubslllnce hes hydl'llulic propertjes If It does not need the Influence of alr te harden. Thlsherdening, In the case of cement a I'elIctlon wlth water, can also'take place under water,
15
Cement in development
but not least in the manufacturing of cement less energy is required than inproducing its competitors.
Although lime and gypsum are used as specialized binders, there are noknown or foreseeable alternatives to cements as most importantconstruction adhesive.
A variety of chemicaI and physical properties can be attained by changingthe percentages of the basic chemical ingredients, by changing the finenessin the grinding process or by adding additional ingredients.
The most used kind of hydraulic cement is Portland cement (in 1983 up to95% of total production in industrialized countries [5]). Other cements that:;are used are blended cements, produced by blending c1inker, anintennediate product in Portland cement production, with chemicaI ornatural pozzolan~. Chemical pozzolans, Iike f1y-ash from coal-fired powerplants, and slag from blast fumaces, are added to produce so-called f1y-ashcement and blast fumace slag cement. Natural pozzolans, Iike somevolcanic soils, are added to produce pozzolanic cement. These cementsmay have different properties from Portland cement, but should not beconsidered inferior.
~There is a small production of special cements that wiJl not be consideredhere because of their relatively insignificant role in the world cementindustry. These special cements include white cement, masonry cement,supersulphated cement, oilwell cement and aluminous cement.
1.2 Historical development of cement
In ancient building generally Iimes were used. which hardened under theinfluence of carbon-dioxide from the air.
The history of hydraulic cements started around the year 150 BC, when theso-called pozzolan-ground was discovered near Puzzuoli in the gulf ofNaples. This substance of VOlcanic origin is probably responsible for thedurability of the Roman buildings. Pozzolan contains a large amount ofreactive silica, which wilt combine with lime at ordinary temperatures in thepresence of water to fonn stabIe insoluble compounds with cementingproperties. For the addition of these kinds of reactive glues to Iime, theRomans used the word 'caementum', meaning crushed stone.
lhe Roman invention of concrete 'Opus caementicium' is considered as arevolution in the history of building [ll. Caementum was mixed with materia(mortar). After hardening this yielded a very strong building material thatbecame the most important of the empire. Opus caementicium was usedfor walls, bridges, water works. streets and especially halls and domes,
2 Pouolllnes are siliceous or aiUceous and alumineous melerÏllls which in themselves possess little orno cementltious propertlea. but which wlll If finely divlded rellct chemically w1th calciumhydroxide andmoisture at ordlnlll')' temperelures to ferm compounds w1th cementitioua propertlea.
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1. Introduction
whieh had dimensions that were not ventured again until the twentiethcentury3.
The period from the Roman empire until the Renaissance saw Iittle changein the characteristics of cements used in building. Still only natural cementswere used, made up of lime from crushed limestone or shells and pozzolan.There is even some evidence to suggest, that there was a return to the useof non-hydraulic limes from pre-Roman times (2).
In the second half of the 18th century in many countries in Europe,dependenee on mainly Germany for pozzolan inspired research intopossible substitutes. This resulted in the discovery by Joseph Aspdin(1779-1855), that high-temperature buming of a mixture of lime and dayyielded a very strong hydraulic glue. The strength was comparable with thefrequently used limestone from the mines near Portland, Dorsetshire.Aspdin named his cement 'Portland' and although its performance hasimproved considerably, it is still called Portland cement.
A few decennia after Aspdin had introduced his superior cement, thedevelopment of concrete technology, and especially the invention ofreinforeed concrete by the French gardener Joseph Monier (1823-1906),caused a rapid expansion of the cement consumption by creating manynew construction opportunities. Cement, used in concrete, has probablybecome one of the most widely used materials in building today and itsimportanee cannot be underestimated.
1.3 Cement production and economy
Concrete is used in economie sectors like industry, transport, agrieultureand energy, whieh are considered to be strategically very important,especially to an expanding economy. It is not surprising that cement isoften counted among the basie commodities on which developmentprograms rely.
Typieally it is produced near to where it is consumed. Because of theperishabIe nature of the product and because of relatively hightransportation cost, international cement trade plays a minor role. Trade ispractieally only used for covering production deficits or venting productionsurpluses, although cement export might be a valuable way of attainingforeign currency. It should also be mentioned that sea freight rates havedecreased in the 19805 due to technological developments in shipping andhandling, leading to a somewhat increasing role of international cementtrade.
Bath the economie importanee, and the Iimited trade, explain why almostevery country wants to be self-sufficient when it comes to cement.
3 For instancl!! thl!! Panthl!!on in Rornl!!. WilS rebuilt in 126 AD wIth Iightwl!!ight concretl!!. 1lll!! tempIl!! hod11 dornl!! wIth 11 dillml!!tl!!r of Ilbout 43m. only supportl!!d by thl!! outl!!r WIlIJS. 1"hl!! fIrst building wIth 11 lIlrgl!!rspan WIlS l!!rected in 1911 AD.
17
Cement in development
In most cases cement plants still are govemment owned. However alsosome major transnational corporations are active in cement production(tabIe 1.1).
Table 1.1 Major cement producer companies
company
Holderbllnk
ltalcementl
CBR·Heldelberger*
Lafarge·Coppee
Cemex
Country
Swltzerllllld
haly
OermllllY
Frllllce
MexIco
/l\aJn Interests In
Swltzerllllld, Belglum, OermllllY, France,Spllln, Czechoslovakill, Hungary, Cllllada,USA, BllIZil, ChiIe, Costa Rica, Ecuador,Colombill, Mexico, Venezuela, Australia,l..ebanon, New Zealand, Phillipines, SouthMica, Cyprus
OermllllY, Belgium, Netherlllllds, CzechRepublic, Pollllld, Hungllry, ClIIladll, USA
Frllllce, Spain, Switzerland, Turkey,OermIlllY, USA, ClIIlada, Brazil, Morocco
MexIco, Spllln
ProductIoncapac:ity
52.5 Mt
43.0 Mt
38.0 Mt
37.0 Mt
36.0 Mt
* Acqulsltion preaently under discussion
Privatization is an actual item in many parts of the world, and thesetransnational companies are continually trying to expand andintemationalize by acquisition or merging. Espeeially in Europe this trendcan be discemed clearly with recent acquisition of Ciments Francais byltalcementi and the upcoming acquisition of CBR by Heidelberger.
To understand the situation of the cement industry worldwide, the relationbetween overall economie performance and cement consumption has alsoto be considered.
1.4 Cement and economie performance
The volume of cement consumption in a country varies directly with theperformance of the construction industry, because cement is one of thebasic building materiaIs. As the performance of the construction industry iscIosely Iinked with the overall performance of the economy, a coarserelation between cement consumption and gross national product can befound.Figure 1.2 reflects the relation between cement consumption and grossnational product in different countries of the world. This figure can beunderstood best, if it is interpreted as time-series.
As the national economy progresses through early industrialization,construction activities often accelerate and cement consumption risessharply [3]. Often present infrastructure has become overburdened by theeconomic growth and has to be expanded. In addition often more houses,schools, hospitals and other community facilities are built or upgraded tomeet the growing soeial and welfare needs. The amount of development
18 EeN 1994
1. Introduction
300001000010001100
100
2000 r-------~~-----~-~--___,I I , I I I 1 I I J I I I I t I I I -,
Figure 1.2 Cement consumption versus ONP {or countries of the world in1990 (data {rom {17]{116]{117J)
grants and Joans may be another important factor in expanding cementconsumption. Govemments sometimes invest in construction to boost theeconomy.
The development of cement consumption in highly industrialized countriesdoes not show a dear growth anymore with further economie development.The basic infrastructure already exists. Use of other high value addedbuilding materials and reversion to some of the more traditional buildingmaterials such as bricks and timber as substitutes for concrete, may evenreduce cement consumption in certain countries, in search of a higherquality of Iife. Furthermore the economy in most industrialized countries isincreasingly dominated by light industries, which do not require substantialinfrastructural investment.
To assess the significanee of this interpretation of figure 1.2, a realtime-series regression has been made for the Republic of Korea (or theperiod 1970-1991 (figure 1.3).
For the considered period a relation is found, which similar according tofigure 1.2 could be expected in a rapidly expanding economy. It should bementioned however that fjgure 1.3 considers cement production instead ofconsumption. It is assumed that the difference between consumption andproduction is negligible.
EeN 1994 19
Cement in development
2000 r---~----~~---~-~--~........,
70001000
I11,
I I t I I I I I I I I I I- - - ., - - -1- - ot - "t - r ., - t- t" - - - - - - - t- - - -., - - -1- - 1" - "'t -- - - ., - - -,- - i - , - r .- r r - - - - - - - r - - - ., - - -1- - T -- - - ., - - -,- - ï - , - r 1- r r - - - - - - - r - - - , - - -1- - 0 T-
, I I 1 , 1 1 I I I 1 ,I I I I I I I I I I Ilel: I I I I I I I I I I I1 - - - - - - ï - I -,-,- I - - - - - - - ï - - - -1- - -,- - ï - ï -I I I I I I I I I I I1 , , I I , 'I I I II I I I I I I I I I II 1 I I I I I I 1 I I
Figure 1.3 Cement production versus GNP {or Korea, 1970-1991 (data (rom[42Jf88Jf1 16})
1.5 Research objective
Considering the prevalence and importance of the cement industry. throughout the developing world, it is important to analyse possiblenegative impacts on the natural and sodal environment. This reportfocuses on energy use and environmental pollution caused by the cementindustry.
The objective is to propose policy options for international cooperation toassist individual developing countries in achieving energy savings andimproving environmental compatibility of the cement industry.
First, the global cement industry and spedfic cement manufacturingtechnology will be reviewed. In chapter four, energy use in the cementindustry will be discussed. From this, technical options will be analysedwhich can lead to energy conservation. Then the environmental impact wiIlbe analysed including the options available to reduce pollution. The reportwill finally focus on policy options to improve the present situation. It willconclude with the definition of the role, which international cooperation canplay to assist in solving of the problems experienced by individualdeveloping countries.
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2. WORLD CEMENT INDUSTRY
This chapter will give a genera! description of the cement industry in thedifferent regions of the world.
Figure 2.1 Cement production and consumption in 1990
Figure 2.1 and table 2.2 provide an overview of the world cementproduction and consumption. Although the groups of OECD countries andtransition economies produce and consume considerably more cement percapita than the groups of Africa, Asia and Latin America & the Caribbean,it appears that the cement industry is indeed present in many parts of theworld.
In the following paragraphs each of these regions will be treated separately.As the cement industry in a country cannot be understood withoutconsideration of the general economie performance, this is also discussed.
EeN 1994 21
Cement in development
'2.1 OECD countries
Africa5%
Transitien16%
world cement production: 1147 Mt
sourC8: l17}
OECD34%
Nerth America 22%
Europe 54%
Other 24%
Figure 2.2 Cement production in OECD (1990)
The cement industry originally developed in countries of the OECD, andwith Japan, USA, Italy, Spain, Germany and France the OECD still has sixof the top-ten cement producers in the world.
Table 2.2 Basic indicators for OECD countries (1990)
Country populatjon GNP/cap cement no. of average cement(mlllions) (US$) production kllns cap8cîty consumptIon
Because of the high degree of industrialization of OECD economies, theygenerally have a well-developed infrastructure. The OECD countries show astabilized, relatively high per capita consumption of cement.
The markets of the OECD countries are characterized by a high level ofcompetition. This forces cement companies to minimize costs to remaincompetitive and consequently energy conservation has for long been amajor issue.
After a Jonger period of strong economie growth, in many OECD countriesgrowth has stagnated in the early 1990's, leading to a reduction in buildingactivities. The cement industry is currently experiencing the negativeeffects of this recession.
2.2 Africa
LA/Car.7%
Transition16%
world cement production: 1147 Mt
North Africa 55%
Sub Saharan 32%
Aep.Soulh Africa 13"hJ
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$ourcs: [171
Figure 2.3 Cement production in Atrica (1990)
The group of African countries has been made up of the subgroups NorthAfrica, sub-Saharan Africa and the Republic of South Africa.
During the last decade, the African economies showed no or only a modestimprovement in economie performance, which could not keep up withpopulation growth. Apart from the Republic of South Africa, the strongesteconomies can be found in the North African region.
Many countries in the sub-Saharan region however remain Iisted among thecountries with the lowest income and are severely indebted. PoliticaIinstability, inappropriate planning, fast population growth, tough exportmarkets and general lack of resources have in many cases hindered soundindustrial development.
23
Cement in development
Table 2.3 Basic indicators {or A{rica (J 990)
Country population GNP/cap cement no. of average cement(millions) (<.J5$) production kilns capacity consumption
The generally low level of economic development in sub-Saharan Africa isreflected by the low per capita GNP (tabie 2.3). In many African countriescement only plays a role as a building material in the 'modem sector' or inmajor public expenditure programs. This causes the per capita cementconsumption in many countries to be among the lowest in the world.
Many countries are currently pursuing a policy of Iiberalization. Forinstance in some countries like Egypt, the govemment is planning toabolish state subsidies on energy. lf cement companies are to survive,progress will have to be made with cutting cost and therefore increasingenergy efficiency.
2.3 Asia
The group of Asian countries contains more than half of the world'spopulation. [t has been made up of the subgroups West Asia, South Asia,South-East Asia and East Asia. Japan is not included here because of itsstatus as OECD member state. The region of Asia is diverse and large.Different subgroups appear to show rather different characteristics.
West AslaThe oil exporting countries are characteristic for West Asia (or the MiddleEast). In many cases these countries have invested their returns on oilexports in infrastructure and building.
Especially during the late 1970'5 and early 1980'5 increased revenues fromvery strong demand and high prices of oil led to a construction boom inSaudi Arabia and the United Arab Emirates. In these years cementconsumption practically doubled. This strong market attracted manyinvestors to build new cement plants and increase capacities of existingones. Gaps between consumption and production had to be filled with
24 EeN 1994
2. World cement industry
Transition16°M
world cement production: 1147 Mt
sou'ce: {17}
Figure 2.4 Cement production in Asia (1990)
expensive imported cement.
West Asia 12%
India 11 0Mother South Asia 2%
China 48%
other East Asia 26%
EeN 1994
However since in the mid-eighties the oil prices declined and severalinfrastructural mega-projects reached completion, cement consumption hasstabilized at a considerably lower level, thus causing huge overcapacity.Consequently, this forces the cement-companies to look for suitable exportmarkets.
South AslaIn South Asia by far the largest producer of cement is India. In view of thelack of proper infrastructure and housing, partly reflected by the low percapita consumption of cement, India's new policy of Iiberalization of theeconomy might very weil lead to considerable increa~es in cementconsumption during the next decade.
Transportation is a characteristic problem for cement producers in India.Cement has to be transported over large distances. Production capacitieshave risen mainly in Western and Southem India (being close to Iimestonedeposits) accounting for 78% of production but only 55% of demand.Furthennore the plants have not been built near coal deposits as Iimestoneis the most important ingredient in tenns of weight. This all puts a heavytoll on the Indian railway system.
Especially this problem has led the cement industry to disperse her plantsin various locations and establish a large number of mini cement plantsI.The fjrst mini cement plants were started up in 1984. In 1992 India countedaround 1BO mini cement plants producing 3Mt of cement or about 6% of
I Smllll plllJlts using 5m1l1l rolIIry kllns or verticlIl shllft kJlns. The inltilll prol!tllbl\lty celling for minicement plllJlts WilS 200 tpd which WIlS subsequently rllJsed to 66Otpd.
25
Cement in development
Table 2.4 Basic indicators for the group of Asia (1990)
. Country populmlon QtiP/cllP cement no. ot llverllge cement(mililons) (US$) productlon kilns Cllpllclty c:onsumption
, tiot Included lln estîmllled number ot 180 mini cement pillnts in Indill• tiot included lln estîmllled number ot 6000 mini cement plllllts in Chinll
source: {l6J117J1119J128J-{44J
tatal lndian production.
The Cement industry in India is backed by a strong R&D and industrialsupport services in the National Council for Cement and Building Materials(NCB). This council has been rendering meaningful assistance to theindustry by providing technicaI services in the field of energy audits,maintenance audits, mini cement plants, computer control systems, etc.
In the region of South Asia the low cement production in Bangladesh andMyanmar should be noted. The economy of these countries is practicallyfuUy dependent on agriculture.
East AslaThe region of East Asia is characterized by strong economic growth, withrapidly expanding economies in China, Hong Kong, Taiwan, thePhilippines, Korea, Malaysia, Thailand, Singapore and Indonesia. Thiseconomic growth together with major infrastructural projects has boostedcement demand. Almost without exception the countries in the region haveall recently activated large cement capacity expansion programmes.
26 EeN 1994
2. World cement industry
China is by far the largest cement producer in the world. lts cementindustry is a unique mix of small local factories (responsibie forapproximately 85% of the total production) and massive state-run giants.When the People's Republic of China was declared in 1949, cementproduction amounted to 3 million tons per year, but since then it has gonethrough three stages of evolution.
The period from 1949 until the 1960'5 was a semi-c1osed period whenChina was only open to trade with other communist regimes in the USSRand Eastem Europe. China imported a number of wet process rotary kilnsand semi-dry Lepol kilns from Eastem Europe. This taught them thetechnology, that enabled them to manufaeture their own complete kilnplants.
This period was followed from the early 1960'5 until the end of the 1970'5by a phase when ideological disputes with Moscow led to all technologicalexchanges with the Eastem bloc countries being cut. China was completelyisolated. China continued to build wet rotary kilns and Lepol kilns byherself. This period of isolation also witnessed a rapid introduction of minicement plants in China, using the vertical shaft technology. The number ofmini cement plants increased from about 200 in 1965 to more than 2800in 1975. These mini cement plants, almost all located in rural areas, hadthe advantage to re lieve the transportation system by providing regionalself-sufficiency. Also, in this period a lot of work was done on developmentof preheater and precalciner kilns.
250
0200~c:.g 150u~
"0e.0. 100'E~~ 50
1965 1970 1975 1980
year
1985 1990
EeN 1994
source: {401l100J
figure 2.5 Development of cement production in China
At the end of the 1970'5, the Chinese national economy entered a period ofopening to the outside world. China bought complete sets of preheaterjprecalciner plants from major equipment manufacturers. This raisedproduction further and also improved the level of technological knowledge
27
Cement in development
and expertise. Soon China was again designing and manufaeturingcomplete plants herself.
These rapid developments have been possibJe largely because China hasset up a number of research institutes, design centres. and universities forthe cement industry. In contrast the other rapidly expanding countries ofEast Asia have practically all been fully dependent on OECDmanufaeturers for their cement production equipment.
2.4 Latin America &the Caribbean
Afriea'5%
world cement production: 1147 Mt
Caribbean 10%
Mexico 29%
other Centra! 3%
Brazil 31 Di\)
other South 27%
souree: {17}
Figure 2.6 Cement production in Latin America [; the Caribbean (1990)
This group contains all American countries except Canada and the UnitedStates. It consists of the subgroups Caribbean islands, Central America andSouth America. In the region approximately 60% of the total produetion isaccounted for by two countries: Mexico and Brazil.
The produetion of cement in Latin America has grown between 1947 and1987 with a speetacular average rate of 6 to 7 % per year. This growth wasnot regular. There was a period of accelerated growth in the 19605 and19705. In the following decade.however. a strong recession in almost everycountry (except Chile and Colombia) caused the level of cementproduction to stagnate or even fall back.
The term "lost decade" has become almost synonymous with the countriesin Latin America and the Caribbean in the 19805. High inflation rates anddeep recessions have in many countries resulted in an overall reduetion ofthe Gross National Product per inhabitant over the last decade. In averageGNP per inhabitant of Latin America and the Caribbean went down byapproximately 0.3% per year during the period between 1980 and 1991[113].
28 EeN 1994
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2. World cement industry
Table 2.5 Basic indicators {or Latin America & the Caribbean (1990)
Country populGtlon QNP/cap cement no. ot average cement(milllons) (USS) productlon kilns capacïty consumption
The accumulation of economic failures together with high populationgrowth have resulted in a significant reduetion in per capita consumption ofcement in these countries. The most important reasons given for thisperformance are the huge fjscal deficits, unrealistic exchange rates andmost of all the debt burden.
The situation of the debt burden and inflation control is starting to changein many countries. Today many govemments pursue policies that includelowering their deficits and liberalizing the economy. Where the 19805represented an economic setback. in many countries they also showed thestart of a process of democratization. This development has presented apolitical opening for liberalization of trade. Therefore the development of animpressive economie bloek might be possible through internationalcooperation in the region [45].
In spite of the adverse economic conditions during the last decade. thecement industry in the area has generally kept up its technology andhuman resources. The new economic environment and the gap ininfrastructure is Iikely to boost cement consumption pattems during thenext decade.
Different transnational corporations have reeognised that Latin Ameriea issetting a sound basis for economic growth and leading international cementgroups Iike Holderbank have developed investment programs in manyLatin American countries.
29
Cement in development
2.5 Transition Economies
OECD34%
Atrica5%
world cement production: 1147 Mt
tonner USSR 73"A>
other 27%
souree: [17J
Figure 2.7 Cement production in the Transition Economies (1990)
This group contains the former CentraI and Eastem European countriesinduding the fermer USSR. The group is made up of 18 countries of whichRussia is by far the largest with a population of ISO million people.[t contains important cement producers of the flrst houc2, and still has ashare in the world cement production of about 17%. The former USSR,responsibIe fer up to 73% of the cement production in this group, is thesecond largest producer in the world after China.
Table 2.6 Basic indicators for the Transition Economies (1990)
Country population GNP/cllp cement no. of IIve!'llge cement(mmions) (USS) production kilns ClIpIIcity consumption
2 For Insance, the IndustrilIl production of cement In Yug05Javili dates back to 1865, and in Hungaryto 1868.
30 EeN 1994
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2. World cement industry
The level of economie development of the countries in this group variesconsiderably. However same remarks can be made for all countries in thisgroup.
In the last four years the recession, brought about by the transformationfrom socialism to the open market, has resuited a sharp deerease inbuilding activities. This has caused a considerabie deerease in cementconsumption and consequently in cement production, leading to lowcapacity utilization. However the figures pertain to 1990 and in this yearnot all countries had experienced the full strength of the recession yet,Probably this year (1994) the capacity utilization in most countries isrecorded even considerably lower.
Optimistic Jong term projections by the World Bank and UNIDO assumethat the recession will hit its bottom in the second half of the 1990s in thecase of former Czechoslovakia, Hungary and Poland. A slow inerease ofGNP and of cement production wiJl then be possible. Other countries likeRomania, Bulgaria and particularly the fermer USSR, are expected to facefurther decline until the end of this century.
Kurdowski 148] mentions a perpetual lack of cement on the Russianmarket, brought about by poer handling and distribution networks andunreasonable utilization which cause the consumption of cement per unitGNP to be twice larger than in Western Europe. This lack halts the closureof outdated, old plants. Albania has been reported to experience relatedproblems. However major capita] investments are understood to benecessary to just keep the industry going, because the equipment is in avery poer condition.Table 2.7 Regional distribution of cement production in the USSR in 1988
Region population production share total(millions) (Mt) production
The cement industry of the former USSR is mainly located on the territoryof the Russian Federation and the Ukraine (tabIe 2.7). Of the cementproduction in former Czechoslovakia about 64% accounted for by cementplants located in the Czech republic and about 36% in the Slovakia. It isunclear what the war has done to the cement industry in Yugoslavia. Beforethe war the highest cement capadty could be found in Serbia and Croatia.
The transformation to a market economy will certainly remain one of themost important factors in development of the cement industry . A relatedtrend is privatization. There will be an increasing role for foreignparticipation and joint ventures.
32 EeN 1994
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3. PRODUCTION PROCESS
This chapter wil! consider the cement manufacturing process. First, thematerial flow will be described roughly. After this, the most importanthistorical technological developments will be discussed. Finally, thecurrently available technology will be treated for the different process steps,with particular reference to energy use.
3.1 Material flow
The cement manufacturing process roughly consists of four stages: rawmaterial collection, raw material preparation, pyroprocessing (production ofthe semimanufactured product clinker) and dinker grinding (figure 3.1).
Raw material collectionIn the production of Portland cement, at least four chemical elements areneeded: calcium (as CaC03), silicon (as Si02), aluminium (as A120 3) andiron (as Fe203)' The amount of raw materials needed to produce onemetric ton of cement ranges approximately between 1500 and 1600 kg.
The main ingredient is calcareous rock, responsible for about 75 to 85% ofthe raw material requirement. The primary sourees of calcareous rock arelimestone, cement rock, oystershell and cora\. The most important souree,limestone, is mined from sedimentary formations of marine origin.Aluminium is mostly obtained from day and shale, silicon from sand, andiron from iron ore and pyrite.
Most of the materials used in the cement industry are quarried usingsurface mining techniques, although a few limestone deposits areunderground. Electric or diesel power shovels, dragline excavators, andfront-end loaders load the broken stone into diesel trucks, which generallytransport the stone to crushers.
Raw material processingThe pieces of rock are first crushed to about 15cm diameter (primarycrushing). This is done in gyratory, jaw or roller crushers. After this, thesize is further reduced in hammer or cone crushers to grinding mill feedsize, which is about 20mm diameter (secondary crushing).
The cement raw material mix, typically consisting of crushed Iimestone andthe Si02, Fe20 3 and AI20 3 sourees, is then interground in a grinding mil\.
This is done according to the process used in pyroprocessing. The mostcommon pyroprocesses are the so-called wet and dry process. In the wetprocess the raw material mix with a typical moisture content of 38% (range24-48%) is ground and fed into the kiln in the form of a slurry. In the dryprocess, the raw materials are dried, and consequently ground and fed intothe kiln in their dry state (typically 0.5% moisture, range 0-7%).
I .,-... t ..Clinker grindingFigure 3.1 Cement manufacturing process
There are Iess common variations of these two basic concepts, the semiwet and the semi-dry process. In the semi-wet process the slurry is partiallydewatered before introduction into the kiln by filtration and extrusion. Thetypical moisture content is 17-22%. In the rarely employed semi-dryprocess, powdered feed is subsequently mixed with typically 11-14% waterto achieve better homogenization before introduction into the kiln.
The choice between the different processes is mainly dictated by the rawmaterials characteristics, especially moisture content.
The raw grinding process significantly improves the chemica] uniformity ofthe raw mix, but mostly not enough. Special silos are used for storing andfurther homogenization of the raw mix.
34 EeN 1994
3. Production process
PyroprocessingClinker production (pyroprocessing) is considered as the most importantstep in the cement manufacturing process, because strength and otherproperties of cement depend on the quality of clinker produced. It is alsothe most energy-intensive step, responsible for about 80% of the energy,consumed as fuel for kiln firing.
In clinker production the raw mix is gradually heated in the kiln until itreaches a temperature of about 1600 °c. In the first (drying andpreheating) zone of the kiln, the raw mix is heated to 100-120 °c, toevaporate all moisture. After this the temperature increases to about 450 °cto Iiberate more firmly bound water of hydration from the used day.
In the second (calcining) zone, the calcium carbonate (CaCO) is thermallydecomposed in a temperature-range of 450-1100 °c to form calcium oxide(CaO), accompanied by the liberation of carbon dioxide (C02). In this zoneany present organic material is bumed and present alkalies (Na and K)partially vaporize.
The c\inkering process takes place at temperatures of 1100-1600 oe. Aseries of reactions between the calcium oxide and the other raw materialcomponents, results in the formation of tricalcium silicate (generallyreferred to as C)S), dicalcium silicate (C~), tricalcium aluminate (C)A) andtetracalcium alumino-ferrite (C4AF)1. These products are the four mainclinker mineraIs. The characteristics of produced cement clinker depend onthe relative concentrations of these different compounds (see tabIe 3.1).
Table 3.1 Portland clinker compounds
c,Sc,Sc,j'l.C.N'
soun:e: {4/
formula
3CaO.SiO,2CaO.SiO,3CaO.AI,O,4CaO.AI,O,.fe,O.
typ. functIonaVll'eight
54% Inltial set and eerly lItrength2B% !ow heat of hydrlltion. long term lItrength
5% high heat of hyclration. earty atrength10% !ow cIlnkerlng temperature durlng manufacture
EeN 1994
Produced clinker leaves the kiln in the form of dense solid modules rangingin size from 10 to 75 mmo Coming out of the kiln it is led through a clinkercooler, which serves the dual purpose of lowering clinker temperature(from 1200-1500°C to 80-300 oe) and recuperating clinker heat for reusein combustion air inside the kiln.
CLinker grindingClinker from storage or directly from the cooler is interground with 3 to 5%gypsum and a Iittle water to produce fmished cement. The gypsum isadded to control the setting time of the cement when it is mixed with water(hydrated).
1 Qenerally In wrlting of the chemical fonnulaa ot the cUnker phesea. lOme almpllflcationa are made.C la uaed fOl' ClIO. A fOl' AI,O•• f fOl' fe,O, and S fOl' SlO,.
35
Cement in development
Grinding fineness is a very important factor in cement strength. OrdinaryPortland cement has a fmeness that is usually around 300 m2/kg. Thisfineness has been defined according to Blaine specific surface2
• Figure 3.2shows the approximate relation between Blaine specific surface and particIesize.
120
Ê1002:c::ca.:; 80...gQ)
E 60ca=0
~iij 40E<n
~" 200co
Blaine surface area (m'/kg)
souree: [54[
Agure 3.2 Approximation of relation fineness and particle size [54)
At this process stage also secondary constituents like blast furnace slag, flyash and other pozzolans can be added. These secondary materials areinterground with the dinker to produce blended cements.
ShippingAfter c1inker grinding the cement is shipped in bulk or in paper bags.Depending on the specific infrastructural location of the cement plant, thefinished cement is shipped by trucks, by train or by ship.
Table 3.2 Typical costs and energy requirements in bulk transportation
TruckTrainShip
8OUrce: [57][58][591
energyMJ/t.km
1.50.60.3
fixed costsUS$/t
0.470.531.90
variabIe costsUS$/t.km
0.06480.02120.0017
2 Speclfic aurfece can be determined by the Blalne air permeabillty test. This test uses the d'Arcy·Kozeny rellltÎonship. whlch st.!Ites that the flow ol a f1uid through a packed bed ol granular partlcles Isrelated to the surfece area ol the particles in the bed.
36 EeN 1994
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3. Production process
Table 3.2 gives typical costs for different ways of shipping. Because of thelow value/weight ratio of cement (normally between U5$70 and U5$90 perton of cement) the shipping distance is generally Iimited to about 300kmby land and about 2000km by water.
3.2 Historical development of technology
The expansion of the cement industry first took place in the mostindustrialized countries of Europe, North-America and later Japan. Thelarge cement-producers of these countries had a considerable influence onthe further technological development.
Because of the great effort in research and development of cementtechnology in these industrialized countries, the market in cementtechnology is still largely dominated by European and Japanesecompanies3
•
To remain competitive with other building materials industries, the cementsector has continuously been trying to reduce its operating cost. It has hada continuing program of upscaling and energy conservation, covering awide range of technologies.
Historieally, technologieal innovation in the cement industry has focusedmainly on fuel energy consumption by improving kiln technology.Especial!y during the last decade energy saving grinding technology hasreceived much attention.
3.2.1 Kiln technology
Until about 1925, c1inker was mainJy produced by the dry process invertieal shaft kilns or smal! rotary kilns. The use of vertical shaft kilns datedback to 1824 when PortJand cement was invented. These kilns had thedisadvantage that they were operated intermittently, lead\ng to relativelyineffjcient fuel consumption, because the kiln structure had to be reheatedfor each buming. Around 1880, a modified vertical kiln was developedwhich could be operated continuously. The old vertieal shaft kilns showed avery ineffjcient energy consumption, especially those that were operatedintermittently (12,500 MJ/tcl ).
An important innovation was the introduction of continuously operatedrotary kilns. At first these were based on the dry process. Scon the wetprocess rotary kiln was introduced. where the kiln feed was handled as aslurry instead of dry powder. This process allowed for betterhomogenization of the kiln feed, easier operation, less dust emission, moreuniform cement quality and better economy.The invention of the Lepel kiln in 1928 allowed for a considerable decreasein raw material moisture content and thus for the introduction of the semi-
3 ~jor equipment manufacturers are FL Smldth Ei Co.(Denmarit), Fuller (USA), Krupp PolysiWl,Humboldt Wedag (Oermany), f1.C (Franee), Mltsubishi Heavy Industries (Japan).
37
Cement in development
8000r--------------------,
Long dry
LEPOL
Long wet
19901980
~""_~SPNSP
1970
••••••••••••••••••• 0"·'" ••••••. .. .
1930 1940 1950 1960
-:::;~6000c:oa§5000UJc:8iii 4000Q)
.=.
.Q
~3000
0.Cf)
2000 L-. _
1920
~
~:§ 7000()
year SP: Suspension preheater
NSP: New suspension preheatersouree: [84] with precalciner
Figure 3.3 Development ofavarage speci{ic heat consumption
wet production process. anti! World War 11, the heat consumption wasdrastically cut back to 4200 MJ/te,. After 1950 this process has beenfurther refined, reducing the heat requirement to approximately 3300MJ/tel'
Setter raw meal homogenization and dust collection systems and especiallythe rise in energy prices during the oil shock at the beginning of the 705 ledto the return of dry rotary kilns, which was superior to wet kilns with regardto energy use. The introduction of the four-stage suspension preheater in1951 was a decisive development in the heat economy of the cement dryproduction process. Lower exit temperatures were possible leading tohigher efficiency.
The suspension preheater process was further improved by adding aprecalciner. [n 1971 the first precalciner process was instalied. This processhad about the same fuel consumption as the suspension preheater process.The main advantage was the possibility to use low grade fuels and largerkiln throughput, because most of the calcining was performed in aseparately fired fumace.
Currently the focus is on more efficient suspension preheaters (5- and 6stage) and on development of a f1uidized bed kiln.
Certainly one of the most interesting countries with respect to energyconservation is Japan. This country has employed a policy to concentrateproduction in large scale plants, and replace kiln technology of wet andlong dry process via semi-wet Lepol to efficient suspension preheater andprecalciner processes (figure 3.4).This has resulted in lowering average heat consumption from 8300 MJ/tel in1950 to 2970 MJ/te, in 1988 [221. With approximately 2.0 GJ/tcl needed for
38 EeN 1994
3. Production process
1()()OIo
75%
c:o:g=' 500/0
ea.
25%
precslciner
...7800 Q).:.e..~(3
6800 ~~-c:
5800 .QÖ.E='lf)
4800 c:8ca
3800 ~
EeN 1994
00/0 28001950 1955 1960 1965 1970 1975 1980 1985
year
sourc.: [22)
Figure 3.4 DelJeiopment of kiln technology and specific heat consumptionin Japan
drying and chemical reactions, the average fueJ efficiency has increasedfrom 24% in 1950 to 67% in 1988. In the same period the average specificpower demand was reduced from 140 kWh/teem to 103 kWh/teem'
3.2.2 Grinding technology
In the Jast decade, especially the Japanese and European cement industryhas increasingly concentrated on saving electrical energy. Considerablesuccess has been achieved primarily due to the introduction of newgrinding systems.
Tube bali mills have Jong dominated the market in grinding technology. In1891, a French patent was the foundation for the development of thesemills, and ever since bali mills have remained the dominant grindingtechnology.
Although invention of the roller grinding miJl by Loesche (Germany) sternsfrom about 1925, this machine has only become an important competitorof the bali miJl during the last decade. They have become popular mainlybecause of the development of suspension preheater systems and becauseof their lower energy consumption. Currently roller mills dominate themarket for new grinding equipment.
After the invention in 1977 by Schoenert (Germany), high pressuregrinding roJls, also called roller presses, are currently entering the marketfor grinding technology. Most often, however, roller presses are still onlyintroduced as pregrinding systems to upgrade existing bali mills. In the
39
Cement in development
future they will probably also become important in finish grinding'appJications.
3.3 Raw material processing
3.3.1 Crushing
The specific kind of used crushing equipment depends on the specific rockcharacteristics such as hardness and moisture content. Thesecharacteristics may vary widely. For instance Iimestone deposits may varyfrom very soft. water-dispensable chalks to the hardest of marbles. Most ofthe used limestone is hard to moderately hard.
Hard materials are reduced with low-running machines, like crushing rollsand gyratory and jaw crushers, which function mainly by compressiveaction. For medium-hard materials hammer and impact crushers are moresuitable, because they achieve their action mainly by impact.
The cost of maintenance and wear of the crushing equipment far outweighpower requirements. Power demand depends mainly on raw materialproperties. On average, primary crushing requires 2.5 kWh/ton of cement,and secondary crushing 3 kWh/ton of cement.
• deflned as llItio of largest Unelll' dlmenslon befere cNshing to IlI!'gest Ilnelll' dimension after cNshlng,
source: (54)
JawcrusherIn the cement industry, jaw crushers are in general use. This is mainly duete its simple design and the circumstance that it is produced in large units.The jaw crusher serves mainly as primary crusher. The size reduction of thecrusher feed is performed between two crusher jaws. One is stationary andthe other is moved by toggle pressure.
Gyratory crusherThis crusher, also known as cone crusher, crushes the material between acone shaped stationary crushing ring and a crushing cone. The coneperforms a gyratory motion around avertical shaft, the lower end of whichis positioned in an eccentric.
40 EeN 1994
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3. Production process
The gyratory crusher does not perforrn idle motions and workscontinuously during the gyration of the cone. The capacity of a gyratorycrusher per kWh is 1.3 (for small size crushers) to 3.6 (for large crushers,up to 5000 tph) times higher than that of a jaw crusher (541. On the otherhand the wear of Iiners is higher than that of jaw crushers. This leads to themain use of gyratory crushers for large size crusher feed in primarycrushing.
RoLLer crusherCrushing in a roller crusher is based on the passage of material betweentwo rotating rolls that crush the materials by compression. The particIe sizeof the crushed material depends on the distance between both rolls. If onepair of rolls is used the reductiort ratio is 1:5 to 1:7. To gain a higherreduction ratio in one roller crusher, two pairs of crushing rolls are used,arranged one above the other. The upper pair serves as primary crusherand the lower pair as secondary crusher. Often the cement industry alsouses roller crushers for the size reduction of coa!.
Hammer crusherHammer crushers are widely used for size reduction of hard to mediumhardlimestone. They work with a high reduction ratio (up to 1:60). Sometimesthis does away with the need for multistage crushing. The crusher feed iscrushed on a grid by impact of rotating hammers.
Impact crusherCrushing by impact is carried out by throwing the raw material againstbreaker plates. They can therefore only be used with brittle rocks. Sizereduction is carried out in three ways. First, by striking the impeller barsagainst the feed. The material is thrown against deflecting plates and isreflected back into the crushing compartment, where it is hit again by theimpeller bars, untiJ it leaves the crusher through the slot between rotor andlower edge of the breaker plates. The second size reduction is carried outby impact of the material against the breaker plates. The third sizereduction step occurs by crashing the materiaJ chunks against each-other.
3.3.2 Drying
Generally in the dry process the moisture content in the raw materialnecessitates drying before or during grinding. The moisture content oflimestone can be up to 8%, that of marl up te 15% and day might have amoisture content of up to 20%.
Drying can take place during grinding by combined drying-grinding.Especially air-swept mills, such as roller mills, are suitable this. Practicalexperience leamed that separating the drying and grinding procedures maylead to the lowest energy consumption. This may be done by using aseparate drum dryer.
In principle. the drum dryer is a rotating iron cylinder placed under a slopeof 3-60. Hot gases (typically 600 0c) supplied to the drum dryer cause theevaporation of moisture. The drum dryer can be operated with kiln exit
41
Figure 3.5 Dryer heat use
Cement in development
gases or with the hot exit air fromgrate e/inker coolers. Due toinappropriate plant layouts thismay not always be possible.Therefore, many plants stilloperate separate fuel-fired dryers.An interesting altemative for fuelfired fumaces for the production ofdrying heat might be theinstallation of combined heat andpower systems.
3.3.3 Raw grinding
Heat in material15%
Evaporation50%
Heat in exit gas17%
Radiation18%
The wet process raw grinding is carried out in ball mills, while the dryprocess grinding is carried out either in ball miJIs or roller mills. A newdevelopment is the use of roller presses in raw grinding.
Table 3.4 Efficiency of different grinding systems
Grinding efficiencyD
Ball millVertical roller millRoller press
6- 9%7-15%
10-20%
• Defllled as l'lltio of theoretical and practical electriclty consumptien .source: {56}
Currently used (ball miJl) grinding operations may be very inefficient: up to94% of the energy input to the grinding mill ends up as waste heat (tabIe3.4).
BaLL millThe most commonly used type of raw grinding mill is the ball or rod mill,which consists of rotating drums in which a large number of steel balls orrods cascade onto the raw materiaIs, thereby mixing and pulverizing them.Ball mills are sometimes divided into compartments for multistage grinding.These compartments contain differently sized balls, and are separated by ae/assifying screen, which can only be passed by partie/es smaller than aspecific size.
Vertical roller millRoller mUis, until recently almost only used in Japan, consist of a flat ordished table rotating on avertical axis. Two or more fixed rollers ride overand crush the material on the tabIe. After the material passes under therollers, an airstream carries the finer portion of the pulverized material to anair classifier. Oversized partie/es are rejected by the classifier and sent backto the mill. Because a considerable amount of air is needed to carry thepulverized material from the miJl te the e/assifier, roller miJIs are particularlysuited for combining raw material drying with the grinding process. Thesemills can use large quantities of waste heat from kiIns or e/inker coolers.
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3. Production process
Roller miJls use less energy for grinding than a ball miJl, but it hasadditional fan power requirements. It is estirnated that roller mills can saveup to 30% of the energy used in conventional raw grinding.
High pressure grinding roilThe high pressure grinding roll (also: roller press) has been introduced in1965 as a means to further reduce grinding power requirements. This pressconsists essentially of two smooth rolls rotating in opposite direction. Oneroll has a fixed adjustable bearing. The pressure required for the grindingprocess is applied by a hydraulic system via the other roll. The groundmaterial emerges from between the rolls as a compacted cake, whoseconsistency depends on the grinding pressure used. Power consumption ofroller presses should be competitive with that of roller mills.
Closed circuit grindingClassifiers can be used to increase grinding efficiency in c10sed circuitgrinding. They separate the fine product-quality particles and reject thecoarser oversized particles, which are retumed to the grinding mill. Usinghigh efficiency c1assifiers, less overgrinding occurs and therefore adecrease in energy consumption is possible. By conversion to c10sed circuitgrinding process a 10% reduction in specific energy use can be obtained.
Several companies have recently developed new air c1assification systems.Most of these are only concemed with clinker grinding appIications. TheMitsubishi Oual Separator (MOS) however was developed specifically fordry raw material grinding. The Outch State Mines developed a filter screenc1assifier for wet process grinding.
3.3.4 Blending
The raw materials must be intirnately mixed and blended before they arefed into the kiln. The raw grinding process improves the chemicaluniformity of the raw mix, but often not enough.
Pneumatic dry blending silos are used for increasing the homogenity of theraw mix. Various homogenization methods are used, which almost all havein common, that air is supplied to aereation units mounted on the silobottom, 50 that the raw mix is first loosened, and then intensely aereatedover the bottom by means of a violent turbulent flow. The differenthomogenization silos may differ in their way of raw mix discharge and inthe shape of the bottom. The specific power consumption ranges from 0.1to 2.5 kWh/t of raw meal.
3.4 Pyroprocessing
Two types of kilns are used in the cement industry: vertical or shaft kilnsand rotary kilns. Shaft kilns account for about 5% of the world production.They are used in China, India and some other countries. Shaft kilns canonly be used for production rates of up to 200 tpd. whereas rotary kilns can
43
Cement in development
produce more than 10,000 tpd. Shaft kilns can only be used for the dryprocess. Rotary kilns can be used for the wet process as weil.
Table 3.5 Heat balances of different clinkering processes
In general, the wet process requires longer kilns because additional heattransfer area must be provided to evaporate water from the slurry. Becauseof the need to evaporate water from the slurry, the wet process alsoconsumes significantly more energy than the dry process.
The dry rotary kiln process has become the world standard, primarilybecause of its higher fuel efficiency. In the conventional long-dry processall c1inkering steps occur within the rotary kiln. This system has beenimproved by adding a separate preheater and a precalciner system.
The preheater replaces the preheating zone, allowing the rotary kiln to bemuch shorter. It provides the dual benefit of improved energy efficiencyand substantially increased capacity from the kiln by calcining up to 50% ofthe feed before it enters the short kiln. The precalciner system consists of aseparate combustion chamber added to a conventional preheater system.
44 ECN 1994
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3. Production process
In this system levels of 90% decarbonization are reached before theentrance of the kiln.
3.4.1 Vertical shaft kilns
In traditional vertical shaft kilns, the dried raw materials were mixed withlayers of fuel (typically coal and coke) and mostly manually loaded into theupper part of the kiln. Preheating, calcining, c1inker formation and cooHngtake place as the noduJes travel down the shaft and ultimately areconverted into cHnker. Today, most vertical shaft ki/ns are being largelyautomated to increase energy efficiency.
Still 5% of the world cement production is performed in vertical shaft ki/ns,almost all in China and India. Especially te developing countries, verticalshaft technology may have interesting characteristics, as it is very suitablefor use in mini cement plants (see chapter 8).
There is some contradiction conceming the energy efficiency of modemmini cement plants. Spence [4] reports a general energy consumption ofabout 3140 MJ/tcl for small capacities up to 200 tonne per day. The heateconomy could be that good because intergrinding fuel with the raw mixleads to a very efficient heat exchange. Sinha (99) reports however that in[ndia mini cement plants using the vertical kiln technology appear to beenergy inefficient (4200 MJ/tcl).
3.4.2 Rotary wet kiln
In the wet process the entire pyroprocessing (preheating, calcining andclinkering) takes place in a long rotary kiln. The rotary kiln consists of acylindrical steelsheIl that rotates around an axis under a small slope. Feedmaterial enters the top of the kiln in the form of a slurry and are conveyedby the slope and the rotation to the firing or discharge end. At this endfuels are bumed and the combustion gases come in direct contact with thefeed material as the two move in opposite direction through the kiln.Powdered coal, oil or gas are commonly used as fuel.
Wet rotary kiln sizes range from 1.8m diameter and 36m long to 7.5mdiameter and 230m long and rotate at 50 to 90 rotations per hour. Thematerial stays in the kiln for 3 to 5 hours. As much as a quarter of thelength of the wet kiln may contain hanging chains to faciIitate heat transferin evaporation.
In view of the higher energy requirements, caused by the need for extraevaporation, the wet process is being gradually replaced. About 40% of theprocess heat required in the wet process is used to evaporate water fromthe slurry. A considerable amount of energy can often be saved by loweringmoisture content of the kiln feed (slurry dewatering).
Slurry dewatering
45
Cement in development
Slurry dewatering may be done chemically or mechanically. In thechemicaI process slurry thinners (alkaline electrolytes or surface-activeorganic substances) are added to the cement slurry to reduce water contentrequirement, while maintaining the same viscosity. lons and molecules ofthe slurry thinner are adsorbed on the surface of the raw mix particles inthe slurry. This adsorption process prevents agglomeration of the particles,thus reducing the intemal friction and increasing the flowability of theslurry. The use of chemicaI slurry thinners can reduce the water content by5-8%.
In the mechanical process filter presses are used, which could reduce thewater content to about 18-20%. Also, a separate drier can be used asaltemative to the filtration process. The mechanical drier-process has lowercosts of installation, operation and maintenance 167].
A pelletized feed is thus obtained which can be fed directly to the kiln orthrough a preheater. The preheater system can be a grate preheater or asuspension preheater. The process using a grate preheater with a feed ofabout 20% moisture content is called a semi-wet Lepel process. Thesystem with drier dewatering uses a suspension preheater and is thereforereferred to as the semi-wet suspension preheater system. The Lepelpreheater is predominantly used in the semi-wet process.
LepolkUnThis kiln system consists of a short rotary kUn working in conjunction witha traveling grate. The preheater grate is covered with a 15-20 cm thicklayer of raw material pellets. In either a single-pass or double-pass, the hotkUn gases (1000 0c) flow through these pellets. The temperature of thegrate exit gases is reduced to about 120 oe. The efficient heat transfer inthe Lepel kiln leads to a relatively high efficiency.
Despite the enormous expansion of especially the dry suspension preheaterkilns, the Lepol kiln remained predominant in cases where raw materialcharacteristics do not allow for dry preparation of the raw mix.
3.4.3 Rotary dry kiln
Long dry kUnIn the long -dry process, the entire pyroprocessing is carried out in a longrotary kUn, which is fed with dry raw materiais. Because the need for anevaporation section has been eliminated. dry process kilns can be shorter(or may have a larger throughput) than long wet process kUnst
The exit-gas temperature is high enough (600°C) to enable waste heatrecovery with waste heat boilers for in plant power generation. In improved
Jong dry kiln designs the exit gas temperature can be reduced to 380°C byapplying chain sections and ceramic heat exchangers to the long dry kiln.With these arrangements the waste heat may still be used to dry rawmaterial with a moisture content of up to 13%.
46 EeN 1994
3. Produetion process
Suspension preheaterA separate preheater can replace the preheating zone of a long rotary kiln,allowing the use of significantly shorter kilns. In this preheater 20 to 50% ofthe feed may be calcined before entering the kiln. The c1inker buming itselfis done in a relatively short rotary kiln. The principal idea of the process isthat the rotary kiln is an effective heat exchanger only in the area of thebuming zone, where heat transfer is mostly accomplished by radiation. Theheat transfer process in the calcining zone can be shaped more economicaJly by suspending the raw material particles in the gases.
The cyclones of suspension preheater thus provide a large surface contactof the incoming feed and the kiln exhaust gases, leading to a rapid andefficient heat transfer. This improves energy efficiency substantially.Furthermore, by calcining part of the feed in the preheater, less gases willbe formed inside the kiIn, allowing for increased kiln capacity.
The cyclones are connected with gas ducts. Each cyclone and the relatedgas duet form one preheater stage. The cyclone suspension preheatertower consists mostly of four cyclones arranged one upon the other. Insome applications conventional long dry kiIns have been upgraded byadding a I-stage or 2-stage suspension preheater. Energy efficiency can beenhanced further using 5-stage or 6-stage preheater systems4• However,this is only usefu) if also the required drying capacity of the exit gases islirnited (figure 3.6).
ë 10 ..cuëoo 8~:::lêi)·ö 6Ecu
4:0'">.-c 2
02900 3000 3100 3200 3300 3400
EeN 1994
specific heat consumption (MJ/tc ')
souree: [661
Figure 3.6 Characteristics of different suspension preheater systems
The exit gas temperature of a4-stage suspension preheater is about 320°C.The preheater exit gases can be used for drying raw materia) with a
• For example, \he Illrgest production Hne In \he wood (SJam City Cement, Thlllland, ClIpllCfty up to11.000 tpd) uses 11 5-stllQe prehellter cornbln~ with two seplll'llte Hne clIlclners. The IIvllI'lIge klln fuelconsumption is liS low liS 2954 MJIt eX cJlnker.
47
Cement in development
moisture content of up to 8.5%, depending on the efficiency of the heattransfer inside the preheater.
The suspension preheater process uses more eleetricity per ton of productthan the wet process or long -dry process, because it requires considerablymore fan power. However this is more than compensated for by lower fuelconsumption .
Alkali bypassIn suspension preheater systems more alkalies remain for the time ofbuming in the kiln system and consequently in the clinker, than in othertypes of rotary kilns.
Large amounts of alkali in cement may cause setting problems, becausecertain aggregates react slowly with the alkalies and produce severecracking in the concrete. It has been found that concrete was damaged insome cases where the alkali content of the cement was more than 0.60%.However, low alkali contents are only necessary with certain reactiveaggregates, and not all aggregates are reactive!l.
In the course of the buming process alkaJies in the amount of 0.6-2.2 %K20 and 0.1-0.7 % Na20 coming from the c1ay minerals ofthe raw mix andfrom the fuel may be transferred into the clinker. Above approximately800°C the alkalies in the kiln start to volatize. Part of the alkaJies remains inthe c1inker and appears in the c1inker minerais. The volatized alkalies arrivein colder kiln zones, where they condense on the colder kiln feed. Thecondensed alkalies arrive with the preheated raw mix along the materialpath in kiln zones with higher temperature, where they again volatize. Thiscauses the so-called intemal alkali cycle.
In general, suspension preheater systems have a kiln exit as bypass. Thislowers the intemal alkali cycle and therefore reduces the concentration ofalkalies in the clinker. The bypass permits the direct removal of somecombustion gases leaving the rotary kiln by passing them around thepreheater. Because the thermal efficiency is somewhat reduced through theuse of a bypass, generally not more than 25% of the kiln exit gas isdiverted through the bypass.
The increase in heat consumption by the bypass system amounts toapproximately 17-21 MJ/I:.cl per 1% bypass volume. The additionaleleetricity consumption is about 2kWh/tcl , independent of the bypassvolume. The kiln dust tumed aside by the bypass amounts to about 1%referred to the weight of the raw mix, per 10% bypass volume.
If a 25% bypass system is used and the alkali content in the c1inker stillremains above 0.6%, it may be possible to decrease the alkali content byadding Cl to the raw mix in the form of CaCI2 to attain a higher volatility ofthe alkali components.
!l In f8ct In the Onlted Stiltes only 10% of the llQgreglltes 8re re8ctive 8nd these Me concentlllted In 8tew 8re8S.
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3. Production process
PrecalcinerThe development and adoption of precalciners has been dominated by theJapanese ever since in 1971 Ishikawajima-Harima Heavy Industriesinstalled the first precalciner system in Japan. Several major equipmentmanufacturers have developed their own versions now.
The essential factor of the precalcining process is the addition of a separatecombustion chamber to a conventional suspension preheater, most oftenbetween the third and the fourth stage. Most of the raw feed (80 to 90%) iscalcined in this so-called f1ash-fumace. The major advantage of this is thatas much as 60% of the fuel may he fired in the precalciner, correspondinglyreducing the rotary kiln firing requirements. This shift in location is possiblebecause of the fact that the highly endothermic calcination reactionrequires up to 95% of the total fuel input.
The energy efficiency of a precalciner kiln is about 3 to 6% greater than asuspension preheater kiln. Due to the reduction of calcination within thekiln, the capacity of the rotary kiln can also he increased. In the precalcinerfuel is bumed at low temperature. Consequently a substantial amount oflow-grade fuels may be used, and the generation of nitrogen oxides fromcombustion air is reduced to levels less than half those encountered inconventional suspension preheater kilns.
The precalciner can use combustion air coming from the rotary kiln ordirectly from the cooler (tertiary air). The advantage of using cooler airduct is that the capacity of the rotary kiln may be considerably larger. If theprecalciner receives its combustion air from the clinker cooler, heat lossesfrom alkali bypasses can also be considerably reduced. Alkalis are mostlyvolatilized in the rotary kiln instead of in the precalciner. The additional fuelfor calcining is introduced after the bypass port. This permits theprecalciner system to work at bypass levels of up to 100%, causing onlymoderate heat losses.
There are three basic types of precalciners:• vortex suspension systems in which the raw mix is suspended in a
vortex of hot gas;• tubular suspension systems in which hot gases and raw materials are in
contact, while travelling countercurrently in a duct;• f1uidized bed systems, in which the raw material is heated in a separate
f1uidized bed reactor.
Most used precalciners are vortex suspension systems.
3.4.4 Stationary f1uidized bed kiln
Continuously, research programmes are being carried out to improvecement kiln efficiency further. The general trend is to reduce rotary kilnsizes, with more of the calcining occurring in stationary precalciningsystems. The future might see the introduction of some fundamentalchanges in cement production.
49
Cement in development
Stationary fluidized bed systems are Iikely to make rotary kilns obsolete.Kawasaki Heavy Industries developed a fluidized bed cement kiln consistingof a multistage cyclone preheater, a sprouted bed kiln for calcining and af1uidized bed kiln to complete the c1inkering process. This system shouldoffer a lowering of the required buming temperature and thereforeincreased possibilities for use of low grade fuels. efficient heat recovery.lower NOx emission levels and a 10-15% reduction in heat consumption(69].
3.4.5 Cooler
Hot clinker coming out of the kiln (1300-1350 oe) has to be cooledbecause it cannot be conveyed and ground when it is hot and becauseproper cooling improves the quality of the cement. The recIaimed heatcontent of about 820 MJ/tcl is an important factor in energy efficiency ofthe process. Cooling greatly influences the properties of the cooled clinker.Rapid cooling reduces the amount MgO crystals thereby Iimiting the rate ofexpansion of the cement. By reducing the crystallization of other cementcomponents, rapid cooling also increases the sulfate resistance of thecement and decreases the power requirements in the c1inker grindingprocess.
There are four types of c1inker coolers: rotary coolers. satellite (planetary)coolers, grate coolers and shaft coolers (tabIe 3.6). The most used typesare planetary- and grate-coolers.
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3. Production process
Table 3.6 Data and heat balance of different cooler types
rotcry satelUte grate shaft(planetary )
Max. capacity (tpd) 3,000 5,000 10,000 3,000
Temperature (0C)- secondcry cir 800-870 700-750 920 900-1000- center exit air 374• cooler exit air 158. c1inker in 1300-1350 1200-1250 1460- c1inker out 150-210 120-200 83 250-280
Heat (MJ/t cl)- 1055 radiation/convection 235 293 17- secondary air 1006 922 1075- center exit air 297- cooler exit air 167- leaving dinker 168 126 50
Thennal efficiency· 71 % 69% 85% 83%
Power requirement 4 2.5 6 8(kWh/t cl)
• Thermal efficiency of a cooler is defmed as !he rllt10 of heat reclaJmed rrom hot cUnker to !he tatal heatcontent of cUnker leavlng the kiln.
soure:es: {54J(55J
Rotary coolerThe rotary cooler is the oldest type of c1inker cooler. The rotary coolerconsists of a revolving cylinder following the rotary kiln. The low pressurein the rotary kiln induces suction of cold air through the open end of therotary cooler. The fresh air passes the c1inker in counter-current,thoroughly contacting the cooler air. This type of cooler is not much usedanymore, although for smaller kiln capacities (up to 2000 tpd) rotarycoolers may be superior to other types, considering the reliability, simplicityand low operational costs.
Satellite coolerOriginally the satellite cooler consisted of several metal cylinders formingan integral part of the rotary kiln. The satellite coolers revolved togetherwith the rotary kiln, without separate drive. Cooling occurred crosscurrently. The total cooling air enters the kiln as combustion air. Becauseof the excessive weight of a kiln head fumished with satelJite coolers, it wasimpossible to go beyond a certain capacity.
In 1965 the F.L.Smidth Co. introduced a new design satellite cooler, the sc·called planetary cooler. The substantial feature of this design is the forwardextension of the kilo tube and the formation of an additional roller assemblyfor support. Based on this design, It was possible to apply larger satelJitecooler tubes. Based on a maximum capacity of 4000 tpd, the size of theplanetary cooler would be 2.4 m diameter x 29 m long.
51
Cement in development
Uke the rotary cooler, the planetary cooler does not need any fan power. Ituses relatively little cooling air, which can all be used as combustion air.Another advantage is its simplicity compared to the grate cooler.
Grate coolerDue to its superior heat recuperation efficiency the preferred clinker coolerfor most new cement plants is the grate cooler. This cooler has beendesigned specificalty for rapid cooling. The clinker is cooled on a travelinggrate or a reciprocating grate (altemating rows of immobile and mobilegrates), in which air is blown through the moving bed of clinker.
Subdividing of the grate into several compartments offers most effeetivecooling. The clinker frrst faits onto a narrow slow-moving grate placedunder a small slope (5°) where maximum heat recovery occurs. The clinkerthen is transferred to a faster moving wider grate to complete the coolingprocess. Both compartments may have separate air outjets, where the firstcompartment offers secondary hot air to the kiln and the secondcompartment offers so-called tertiary (center-exit) air, which can be used indryers and precalciners.
A disadvantage of grate coolers is the use of excess air, which cannot beused as combustion air. It increases heat Josses and necessitates the use ofextra equipment for dedusting. Grate coolers are rather complicatedcoolers, which therefore demand personnel of high professionalqualifications.
Shaft coolerSince a fluidized bed creates the most useful heat transfer conditions theconcept of combining a shaft cooler with a fluidized bed is being furtherdeveloped.
In the shaft cooler the upper part of the shaft has a converging diameter, toincrease the velocity of the cooling air, creating the conditions for afluidized bed in this area. Due to the fluid bed effect, according to which thematerial in the upper part of the shaft behaves Iike a liquid, the clinkerentering the cooler from the rotary kiln is immediately evenly distributedover the totaJ cross-seetion of the shaft.
The cooling air is blown into the shaft undemeath the grate and at a pointat the shafts half height. Specially formed pipes and nozzles that penetratethe clinker column, distribute the cooling air uniformly over the crosssection of the shaft. Since the cooling in the shaft cooler is performedinstantJy, the quality of the clinker cooled in this way is very good. Finallythe clinker faBs on a roller grate, on which pieces of material larger than25mm are disintegrated by the crushing action of the rollers.
3.5 Clinker grinding
3.5.1 Clinker grinding miHs
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3. Production process
Clinker from indoor or outdoor storage or directly from the cooler is groundusing essentially the same equipment as in grinding of raw materiais. BalimiJIs have been conventionally used for c1inker grinding. Because of theirinefficiency bali mills have now been superseded by the vertical roller milland recently also by the high pressure grinding roll.
The power requirement during finish grinding of cement is affeeted stronglyby the grindability of the c1inker and the desired surface area. Typicallymodem Portland cement particles have aspecific surface area of at least300 m 2jkg. As the c1inker is ground finer, the cement wiJl achieve morerapid strength development when it is contaeted with water.
3.5.2 Closed circuit grinding
Most c1inker grinding systems are c1osed-circuit systems, in whichclassifjers separate the fine, product quality particles from the coarseroversized particles that are recycled to the mill for further grinding.
In c10sed circuit grinding the grinding process is adjusted to take place inthe range of coarser particIe sizes. In this way the grinding of unwantedfiner particIe sizes, which occurs in open-circuit grinding. is beingprevented.
The particIe size distribution is thus Iimited to a narrower interval, allowingfor coarser sized grinding in the miJl and therefore reduced powerrequirements. Even when the extra power requirements for the classifierand the miJl feed transport are taken into account, total power savings of10-25% should be possible [54].
3.5.3 Classifiers
Classifiers (also called air separators) divide a given material stream intotwo separate streams. Hereby one stream should contain only fine particlesand the other, as far as possible, only coarse particles. Air is used as thecarrying medium. Thus, classifiers control the particIe size distribution.
Conuentional air separatorsThe principle of conventional air separators is that the action of an aircurrent of a certain velocity upon a mass particIe is proportional to thesurface presented by the particIe to the air current, thus to the square ofthe dimensions of the particIe. The action of the gravity force upon a massparticIe is proportional to the volume, thus to the cube of the dimensions ofthe particIe. Therefore the effect of gravity increases faster with increasingparticIe dimensions than the effect of an air current with constant velocity.
If particles in a free fall are exposed to an ascending current, according tothis principle separation is possible. In the case of large particles the effectof gravity wiJl prevaiI, causing them to fall down. Small particles wiJl beIifted up by the air current.
53
Cement in development
The dispersion separator is the most representative conventional airseparator in the cement industry. This kind of separator uses a rotatingdistribution plate to disperse the feed materiaJ into the separating space.The specific power requirements depend upon the quality of the separatorfeed, the circulated load and the desired fineness of the finished product.Duda [541 reports figures in the magnitude of 2-6 kWh/t.
High efficiency classi{lersIn the 19805 many equipment manufacturers developed classifiers whichshowed a considerably higher separating efficiency than conventionalclassifiers, allowing for considerable power savings (20-30% acc.[13]) inc1inker grinding.
The high efficiency c1assifiers primarily include a new generation of vortexclassifiers, which use a horizontal air stream in the separation zone. Largeparticles are tossed to the outside by the centrifugal force, whereas fineparticles are swept inwards by the effect of the air stream. This systemallows for longer particIe residence time in the separation zone, therebyreducing the entrapment of fine particles by the coarse ones.
3.5.4 Tandem grinding
Instead of replacing conventional grinding miJIs with state-of-the-art miJIs,many cement producers prefer to increase capacity and energy efficiencyby upgrading existing bali miIl facilities.
In this way it has become popular to combine an efficient machine, such asa vertical roller miJl or especially a high pressure grinding rolls in tandemwith a bali mill. Although the high pressure grinding roll was originallyconceived for finish grinding, it is often used as a pregrinding unit forimproving existing mill systems. The cake produced in a roller presscontains both fine and coarse particles and is therefore sent through a balimill for further grinding.
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3. Production process
Table 3.7 Tandem grinding compared with conventional closed circuitball mills
lst machine type configuration capacity powerincrease savings
In general there are three possible configurations, pregrinding, hybridgrinding and combination grinding (tabie 3.7). In pregrinding the circuit ismade up by two machines connected simply in series, where the secondmachine is a bali mill. Although this is the simplest configuration itgenerally yields only modest production and efficiency gains.
In hybrid grinding the rejects flow from the bali miIl's separator is split sothat part is sent back into the first machine and the rest is circulated backinto the bali mill. Hybrid grinding may be difficult to control. But in the caseof high pressure grinding rolls it has been shown to be more productive andefficient.
In combination grinding both machines have their own separator. In thisway combination grinding involves pregrinding the clinker to a particularfineness (in c10sed circuit) and then finish grinding it in a downstream balimill. This configuration yields the highest efficiency and capacity increases,and allows for smooth running milIs.
55
4. ENERGY USE
This chapter will focus on energy use in the cement industry. First, theenergy intensity of cement will be discussed. After this. theoreticaI andpractical energy consumption figures will be provided. The chapter wiIIcondude with a detailed regional overview of the present situation ofenergy use by the cement industry in the world.
4. 1 Energy in cement
Cement production is an energy intensive process, especially production ofPortland cement. The production of blended cements by blending c1inkerwith other materiais, sueh as fly ash and blast fumace slag, demands lessenergy. as the main energy use is in the production of c1inker. Most cementproduced in the world is Portland cement.
Although cement production demands relatively much energy, the mainend-use of cement, concrete. is a relatively energy efficient buildingmaterial, because it is made by adding inert aggregates. The energyrequirements to obtain a certain building material are Iisted in table 4.1.This includes energy requirements in obtaining raw materiaIs, in productionand transport.
Table 4.1 Totat energy needed to produce and transport buildingmateriats
High energy
Medium energy
Lewenergyb
Material
AluminiumSteelGlassPortland cementB
UrneBricksConcrete- precast- blocks- in situ
TimberSand, aggregateSoit
Energy requirement(MJ/kg)
100-25030-5012-255-8
3-52-71-8
0.8-3.50.8-1.6
0.5-60-0.30-0.1
EeN 1994
Only up to about 5% of the produced cement Is ulJed directly. The rest Is U5ed as Intermediate productIn the production of concrete. .
Energy requirement fot' low energy materiala Is chiefly in transportation
source: {4}
57
Cement in development
1t is not entirely correct to compare building materials only on a weightbasis as some materials require more weight for the same use than others.Fog [5J also gives a comparison, based on overall energy requirements tomeet a certain practical use (tabie 4.2). lt appears that concrete remainsvery attractive.
Table 4.2 Building materials unit production energy intensity (MJ/m2)
practical use concrete steel asphalt bricks
building wall 418 586bridge 3,765 7,950roadway 837 3,138
source' (SJ
In cement production, energy is one of the most important cost factors. Itaccounts for typically 30-40% of the total manufacturing cost. The cementindustry accounts for 1-6% of total commercial energy consumption inmost countries. This makes the cement industry one of the largestindustrial energy end-users.
4.2 Theoretical energy requirements
[n cement production eleetrical energy is mainly needed for surfaceproduction (grinding) and heat is needed for drying and chemical reactions(pyroprocessing) .
Surface productionThe theoreticaI energy requirement for surface production is mostlyestirnated by methods supported on empiricaI basis. The most usedmethod is the working index (WI) according to Bond [54], which is a directmeasure for the required grinding energy. The working index is defined asthe energy needed to reduce the size of one ton of material of infinitedimensions to a size where 80% has a smaller diameter than O.lmm.
The grinding power requirements can be estimated from Bond's forrnula:
1 1W"'lO.~.CI---)
1Pf!
where WW1
PfCf
= power requirement in kWh/t= Bond working index= maximum diameter of 80% of the product in j.lm= maximum diameter of 80% of the feed in j.lm= correction factor for fine grinding (P< 70j.lm)
Assuming a commonly found miJl feed size of 20 mm and a product size of75 j.lm in the case of raw material grinding and a product size of 42 j.lm inthe case of cHnker grinding (i.e. fineness of 300 m2/kg Blaine; correction
58 EeN 1994
4. Energy use
factor of 1.08) the following theoretica1 power requirements can becalculated [87].
TabJe 4.3 Calculated theoretical grinding power
Material
Cement raw materialsPortlandcHnker
Work indexkWh/t
11.6514.87
PowerkWh/t
12.623.6
This calculation gives areasonabie estimate of the required power forexisting grinding systems. It should be kept in mind that it only gives anempirica I estimate. No generally accepted grinding theory has been foundup to now.
DryingThe theoretica! heat requirement in drying is equal to the evaporationenthalpy of water contained in raw materiais, and especially in lirnestone.
Limestone moisture contentrelative to CaC03 content
1%5%
10%20%40%
• aasumed clinker ClIO content 0163.91"
H20 evaporationB
kg/t"I
1157
114228456
EnthalpyMJ/td
27139278556
1112
EeN 1994
Chemical reactionsThe theoretica I heat requirement of the cHnker burning process is equal tothe reaction enthalpy connected with the conversion of the dry raw mix intothe reaction products of the cHnker related to 20 "C and 1 kg of cHnker(tabie 4.5).
Calculating theoretica I heat requirements Iike this is often considered acomplicated and tedious method. Therefore simplified formulas have beendeveloped which allow to attain directly the theoreticaI heat requirementfrom the analytical data of raw mix and c1inker [64]. In this method all rawmaterial components of the c1inker are arithmetically converted into freeoxides, to which the required amount of heat is charged (tabIe 4.6).
TotaiThe calculated theoretical energy requirements are summarized in table4.7.
Table 4.7 Theoretical energy requirement to produce Portland cement
Heat EIectricity TotalMJ/t.:, kWh/t.:em MJ/t.:em
Raw material grinding 21.1 76Drying 278 265Chemical reactions 1711 1630Clinker grinding 23.6 85
Total 1989 44.7 2056
Share in total 92% 8% 100%
assumed: Umestone molsture content: 10'J(i, rew materieI to cIlnker ratio: 1.61. cement to cUnker ratio:1.05. Energy equlvelent of 1 kWh: 3.6 fI>J.
4.3 Typical practical energy requirements
In practice energy costs are divided about equally between fuel andelectricity, even though the production of one ton of Portland cementdemands about 3 times as much fuel-energy as eleetricity (tabIe 4.8).
Table 4.8 Energy consumption in typical Portland cement plant
Fuel Electricity TotalMJ/t.", kWh/t.:em MJ/t.:em
Raw material collection 1% 5% 2%Raw material preparation 33% 8%Pyroprocessing 99% 22% 79%C1inker grinding 38% 10%Conveying, packing,etc. 5% 1%
Total 3535 110 4517
Share of total 75% 25% 100%
Exemple of everage dry proce5S wlth 4·stage suspenslon preheater system wIth grate cooler end a capoc:ltyol 1700 tpd. Drying Is performed wlth klln weste gases. (Energy equivalent assumed is 1 kWh. 10.460 fI>J,I.e. energy conversion retio in power plent of 35%; cement to cIlnker ratio: 1.05).
source: {13/
Fuel is mainly used in the buming process and in drying, and electricity isused in crushing, grinding, conveying and in pollution reduction.
The typical process described in table 4.8 shows a total process efficiencyof 46% divided into a heat efficiency of 56% and an electrical efficiency of41 %. The remaining energy loss is attributed to inefficiency duringeleetricity production.
61
Cement in development
The process described in table 4.8 has to be considered as a typical dryprocess, not as the state-of-the-art. In chapter 3.2.1 it has been mentionedthat the average fuel consumption in the Japanese cement industry is 2970MJ/t.,I' and the average electricity use 103 kWh/teem' This is considerablymore efficient than the process indicated above.
4.4 Regional overview
The foJlowing paragraphs wiJl give a general overview of the energy use inthe cement industry in the different regions of the world, using the followingindicators:
• The amount of additives used in cement production. The specificamount of fuel needed decreases approximately Iinearly with theamount of additives used.
• The share of the wet process in total cement production. This is anindication of how modem a cement industry is. In general, an expansionof the cement industry is performed with modem equipment. As aresuitthere is a coarse relation that energy efficiency tends to be higher wherethe cement market is expanding.
• The average heat requirement per ton of c1inker.
• The average power requirement per ton of cement.
• An estimate of the total energy use by the cement sector in a certaincountry, both in GJ and as a share of industrial and total commercialenergy consumption. The total energy requirements can be calculatedfrom the total production, the average amount of additives used, theaverage fuel consumption and the average electricity consumption.
Wherever data are missing, estimated regional means will be used(tabie 4.9). It should be kept in mind that the figures of table 4.9 arecoarse estimates of the real situation. They will only be used ascalculation figures and are only to a Iimited extent indicative of thecharacteristics of the individual countries in the different regions.
Table 4.9 Estimated regional means used in calculation
Region Additives Heat wet Heat dry Electricityprocess process (kWh/teem)(MJ/tcl ) (MJ/tcl )
In the calculation energy losses in generation of eleetricity wiJl beincluded proportional to the shares of primary and secondary electricityin total electricity consumption. Primary electricity (geothermal, hydro,nuclear, solar, tide, wind, and wave) is assessed at the heat value ofeleetricity: 1 kWh = 3.6 MJ. Secondary electricity (thermal) is assessedon approximate primary fuel requirements: 1 kWh - 10.46 MJ.
4.4.1 OECD
In the OECD countries very IittJe new cement capacity has been built in thelast decade. Still, energy efficiency has improved considerably mainlyspurred by the pressure of competition.
Table 4.10 Energy use in OECD
country additives wet hellt power estimated tatal energy c:onsumption
In the competitive situation of the OECD countries energy prices are veryimportant in determining the efforts taken in energy conservation.Therefore, especially in Western Europe and Japan the cement industryhas gained much in energy efficiency. For instance Germany and Japanboth have high electricity prices and both are pioneers in the fjeld of energyefficient grinding technology.
From table 4.10 it can be seen that the OECD countries mostly employ thedry process. Furthermore a high amount of additives is used, bringing theenergy demand to produce one tonne of cement further down.
The total energy consumption of the cement sector is relatively low,although if becomes a major contribuant to industrial energy use in the
63
Cement in deveJopment
case of less developed OECD member countries, such as Greece andTurkey.
A considerable amount of secondary fuels is used in the cement industry ofOECD countries, mostly petcokes and Iignite. In some cases, rubber tyresand other wastes are bumed. Jt should be noted however that the OECDcement industry still depends very much on coal.
4.4.2 Africa
There is only Iittle information about energy use in the African cementindustry. A few countries have been reported to produce compositecements. Therefore, at least a Iimited amount of additives must be used.
Table 4.11 Energy use in Africa (1990)
country lldditlves wet heat power estlmated totlll energy consumption
As the cement industry in most Aft"ican countries is comparatively young,most countries use the dry production process. However it shouJd be notedthat many plants have been built immediateJy after decolonization andtherefore do not employ the most efficient dry process production lines.
Jt can be seen that in some countries the cement industry plays a majorrole with regard to industrial energy consumption. This indicates the greatneed for further examination of energy use and conservation options in theAft"ican cement industry.
No reports have been found of the use of secondary fuels in the Africancement industry. Jndeed most countries appear to be dependent on fuel oil,which in many cases has to be imported.
Several times energy Josses due to suboptimal operation have beenreported in Africa. Among the major causes are power failures, inadequatemaintenance, lack in spare parts and inappropriate management.
64 EeN 1994
4. Energy use
4.4.3 Asia
Table 4.12 shows the energy characteristics of the Asian cement industry.Production of blended cements appears to be quite unknown in Asia as noreports about cement blends have been found.
In many countries the wet process still accounts for a considerable share inthe total production. Almost only the most dynamic economies in theregion of East-Asia have a cement industry based on modem dry processproduction lines.
Teble 4.12 Energy use in Asia (1990)
country lIdditlves ~ heat power esl:lmated total energy coosumptlon
(MJIt.J (kWhIt-) (I OOOTJ) re1.total re1.totalIndustry comm.
West AsiIIIraqIranIsreelJordanSaudl ArabieSyriaUAE
South AallIIndie'BangllldeshMyanmarPakistanSri Lanka
• Nol Included en estlmated number c:l180 mlnl cement pilInts operatIng In India." Nol Included en estimeted number c:l6000 minI cement plents active In Chlne.
source: {16].{28]-{44].{1I5].{1I6].{1l8{
In the case of China many cement plants still employ old, energy-inefficienttechnology. However in the 1980's China introduced policies aimed atimproving quality and reducing costs of mini cement plants. Ordinaryvertical shaft kilns are being mechanized end automatic control for thefiring zone is being installed. Furthermore the wet process which can befound in most large-scale plants in China is being converted to the dryprocess.
The role of the cement sector energy consumption eppears to be ofsignificant importance, especially in the fastest growing economies of Asia.This illustrates the importance of the cement industry during theindustrialization process, as weil as the need for energy conservation to
65
Cement in development
limit the extent of the expansion of energy supply, required by thedevelopment process.
Use of secondary fuels appears to be relatively unpractised throughout theAsian cement industry. Furthermore only lsrael and Thailand have beenreported to use secondary fuels, in both cases considerable amounts ofpetcoke. Most countries use oil and coa!.
4.4.4 Latin America & the Caribbean
Table 4.13 Energy use in Latin America [; the Caribbean (1990)
country oddJtlves wet he!lt power estlrnllted totlll energy consumptlon
The Latin American cement industry appears to use a certain amount ofadditives in cement production. This means that they are not completelyunfamiliar with blended cements, but there is considerable scope for furtherexpansion of blended cement production.
Because the cement industry in many countries has grown fast during the19605 and 19705 relatively many dry processes can be found. Howeverprocesses using precalciners are relatively rare. They are only employed inlarge numbers in Mexico and some other countries where huge investrnentprogrammes have taken place lately, often financed by participatinginternational cement groups.
Especially in the Middle American countries the role of the cement industryin the total industrial energy use appears to be of major importance. In thisregion, energy conservation activities in the cement industry may be ofmajor importance to the development process.
66 EeN 1994
EeN 1994
4. Energy use
[n Latin America & the Caribbean most cement production is fueled by oil,fellowed by coal and gas. Only few other fuels are used. Costa Rica hasbeen reported to bum wood residue fuels and has the possibility to alsobum petroleum coke and palmnut shells. Brazil has been reported to useup to 12% of charcoal.
4.4.5 Transition economies
The cement industry in the former Central and Eastem European countriesis rather differentiated. Hungary, fenner Yugoslavia and fonnerCzechoslovakia employ rather modem equipment. Most other countries stillpredominantly employ the wet process and have a considerable share ofold and outdated plants.
TabJe 4.14 Energy use in Transition Economies (1990)
country additives wet heat power estimated tatal energy consumption
Most countries produce a wide range of cements including blendedcements. Hungarian, Poland, fenner USSR and fermer Czechoslovakia arereported to have a large production of Blast Fumace Slag cement andPortland f1y ash cement. Bulgaria also uses a large amount of trass.
Characteristic of this region is the large amount of wet process kilns inoperation. Consequently, specific energy use is quite high. An importantrole has been played in this respect by the fonner USSR which had greatdifficulties to master the dry process. It should however not be fergottenthat especially in Russia and the Ukraine raw material deposits are usedwith a high moisture content; on average higher than 16%.
Many cement plants in the region are operated on natural gas that isimported from Russia. [n 1992 Russia started to demand payments for thisgas in hard currency. [t is not clear what effect this has caused to the fuelsituation in cement plan~ outside Russia.
Former Czechoslovakia, Poland and Hungary have been reported to usemazut, a viscous Iiquid residue from distiJIation of Russian petroleum, forup to 15% of the fuel requirements. In fermer Czechoslovakia one cementplant is meeting 10% of its heat requirements by buming of waste tyres.More plants are planning to start doing likewise.
67
5. ENERGY CONSERVATION
Measures to improve energy efficiency in industrial processes can bedivided into specific groups according to their point of action.
energy material
managementProcesstechnology
product
energy loss
material loss
EeN 1994
Figure 5.1 Schematic process
Figure 5.1 shows a simplified model of an industrial process, consisting ofactual process technology, energy and material inputs, product output andlosses. Furthermore, every industrial process is managed (operation,maintenance. etc.). lt is the objective of energy conservation to reduce theratio of energy input and product output. Energy efficiency measures canthus be employed by changing process management, by changing actualprocess technology and by changing process inputs.
First measures aimed at process management wiJl be discussed. Thesemeasures do not require a major change of technology or inputs. Thereforethey do not set high capital requirements and are mostly readilyimplementable. Measures entailing process technology changes havemostly been put forward in chapter 3. Most of them set high capitalrequirements and consequently have to be regarded as longer termoptions. Saving energy by improving the raw material situation may have avery direct effect on the product output, as for instance in production ofblended cements, by adding secondary raw materiais. Last but not leastthere is also a possibility for fuel conversion. This might relieve expensiveand scarce commercial energy supplies. (t might also try to recuperateenergy losses by adding them back to the energy input.
At the end of this chapter an estirnate of the regional energy conservationpotential wiJl be made, based on the discussed energy conservationmeasures.
69
Cement in development
5.1 Management measures
The low energy efficiency found in many plants, especially those that arequite old, often results from improper operating and maintenanceprocedures. Management measures offer relatively simple methods toreduce energy losses. These methods comprise improving operationalprocedures and improving maintenance procedures.
Although very important, the only thing that can be said aboutmaintenance procedures is that they should be carried out properlyon aregular basis, i.e. preventive maintenance is preferabIe to repair. Especiallyin developing economies cement plants often lack proper maintenance.This causes suboptimal operation and significant reductions in energyefficiency. Timely maintenance ensures better efficiency and reliability.
To detect which operational measures for energy conservation can betaken an energy audit might be a very important tooI. [n the followingenergy audits and the options to improve operational procedures will bediscussed. The available options include reduction of heat losses,introduction of computer control systems and changing of cementstandards.
Most measures that can be taken in energy conservation refer to methods,technology or materiaIs. However, the human factor in energy managementshould not be forgotten in conservation programs. In cement productioneverybody receives energy inforrnation one way or the other and carries outmeasures that correspond to his position in the hierarchy and his function.Energy saving programs will be more effective if the people concemedknow the objectives, are properly motivated and know how they canachieve their objectives through practical actions.
5.1.1 Energy audits
The first step on the way to energy conservation is finding out where andhow energy is spent in a cement plant. A detailed investigation andmeasurement of existing plant operation parameters, helps to identify theareas with the greatest potential for improvement and the most appropriatemeasures for achieving this improvement. These so-called audits can becarried out within a few weeks, most often by experts in cooperation withthe plant staff.
An energy audit attempts to establish a balance sheet with energy inputson one side and energy outputs on the other side [721173]. An experiencedoperator wiJl then be able to diagnose the process areas where excessiveheat losses occur and thereby to prescribe procedures for improvements.
70 EeN 1994
5. Energy conservation
5.1.2 Reduction of heat Josses
Improper process operation might cause significant heat losses. Processescan often be much more energy efficient if operation methods areimproved.
Heat Jasses are especially big during suboptimal operation of a cementplant. For instance, it is very important for to obtain a stabIe, uninterruptedoperation of the kiln department. Whenever the kiln has to be shut down,heat is wasted when the system is started up again, because production wiltremain low until the temperatures throughout the system are brought up tonormal. It takes a long time to balance the system, ranging from 30minutes to several hours. All factors that might cause such a kiIninterruption, whether intemal or extemal to the plant, have te be identifiedand eHminated as much as possible.
Another example is that kiln heat losses are often bigger than necessarybecause it is difficult to manually adjust the kiln to the optimal bumingzone temperature. The kiln is often operated at a higher temperature,causing unnecessary heating and consequently higher heat losses.
Ouring normal operation, the most important heat losses occur in thepyroprocessing department. These heat Jasses consist of heat content ofexhaust gases leaving the system, radiation and convection losses, andheat content of the cHnker when leaving the system. Table 5.1 gives therelative importance of the different sources of heat 1055. It can be seen thattypically heat recovery in the cooler is the most important influencingvariabIe.
Table 5.1 Change in fuel consumption relative to change in energy losses
energy 1055
exhaust gas enthalpywall heat 1055 in preheater stage 1wall heat 1055 in preheater stage 2wall heat 1055 in preheater stage 3wall heat 1055 in preheater stage 4rotary kiln shell heat 1055
total cooler heat 1055
sourc:e: [65}
0.870.220.440.761.181.181.46
EeN 1994
Heat content of exhaust gasesIncluded in this are combustion gases from buming of fuel, carbon dioxidefrom calcination of raw materiais, dust entrained in exhaust gases, dryerexit gases and vent air from the cHnker cooler. These heat Jasses will alldiminish as the exhaust temperature is lowered. The exhaust temperaturedepends on the amount of primary combustion air and on intemal heattransfer efficiency:
• The amount of primary combustion air may be reduced by addingrelatively more secondary air (by improving cHnker cooler efficiency the
71
Cement in development
secondary air temperature is maximized resulting in a correspondingdecrease in consumption of primary air) and by reducing air infiltrationat the kiln inlet and outlet seals (proper insulation). Thus, fuel savingsof about 3% can be obtained. Lew primary air levels also mean thatf1ame temperatures are high and conditions for controlling the f1ameshape are most favourable.
• Adding rotary kiln length and increasing kiln speed will enhance intemalheat transfer. Also extra devices, such as chains, trefoils and lifters willenhance intemal heat transfer. These devices provide a larger contactsurface area between the hot combustion gases and the kiln feedmaterial. Chains can absorb heat from the gas stream for transfer to theraw material as the chains flow through the bed material. Trefoilsystems consist of refractory arches constructed in the transition zonebetween the preheating and the calcining sections of the kiln. Thesearches divide the feed into separate streams and thereby enhance heattransfer. Lifters consist of rows of discontinuities, which cause thematerial to tumble, rather than to slide along the shell Iining. Thetumbling action increases the contact surface area, and therefore heattransfer efficiency. Results of using these devices have been difficult tomeasure. Energy efficiency improvements from 5 to 20% have beenreported [81.
Heat losses by radiation and convectionThe heat loss by radiation and convection is controlled by the insulatingmaterials shielding the pyroprocessing vessels from the high intemaltemperatures. Usually this material is of refractory brick. It is important toselect bricks that are both durable and insulating. In the case of rotatingkilns, the rotating equipment imposes a weight restriction on the use ofinsulation. New refractory ceramic materials however have been developedwhich are both light and highly insulating.
Since the radiation and convection losses are proportional to the exteriorsurface, the trend towards shorter rotary kilns has led to reduced kiln shellheat losses. For a given installation kiln shell heat losses will also diminishas the throughput of the system is increased. This demonstrates how fuelcan be saved by increasing kiln capacity.
Heat content of ciinkerEfforts to optimize the heat transfer conditions in the c1inker cooler byimproving the distribution of c1inker and air wiJl increase the recuperationefficiency and thereby reduce the primary energy demand of the kiln mosteffectively.
Heat transfer in the grate cooler can be improved by a using deeper bed ofc1inker in the recuperation zone. This can, for example, be accomplishedby narrowing the grate width or reducing the thrust rate,
72 EeN 1994
5. Energy conservation
5.1.3 Process control
Heat losses due to suboptirnal operation might be reduced by installing acomputer control system. For instance a kiln control system could keep thebuming process stabie and react quickly to changing conditions. Thisincreases both kiln and c1inker grinding energy efficiency, because theoperating temperature will be lower (and consequently the heat losses) andproduced c1inker wiJl be Iess reactive. It is important that these benefjts canbe obtained at relatively low investment costs.
Most modem kiln control systems do not attempt to make a theoreticalmodel of the complicated processes occurring inside the kiln, but ratheruse so-called "fuzzy-Iogic". The concept is that the control system isdesigned to imitate the thinking and actions of the best operators andhence it uses typical "rules of thumb" that operators use.
Asea Brown Bovery reports very good results from cement plants usingtheir fuzzy-Iogic LINKman system. Considerable energy is saved, c1inkerquaJity is improved, and production is increased (tabIe 5.2). Furthermorethe system enhances knowledge conceming the process and processdynamics and offers a useful tooI for process management.
Table 5.2 Benefits of ABB proces contral system
- Production increased by- Fuel consumption reduced by- "28th day strength" improved- Grinding power reduced by- Key variables standard
deviation reduced by
source: f74}
5.1.4 Changing of standards
Typicallyachieved
2.5-5 %2.5-5 %
25-100 %7.5-10 %
25-50 %
Bestachieved
10%10%
200%10%
100%
EeN 1994
Most countries have their own cement standards. These standards defmechemical composition and specific surface, required for obtaining a certainstrength and durability, and thus form the foundation on which the processis defjned. Operational procedures include adjustment of the processtechnology to meet the required standards. Energy savings can be obtainedby relaxing standards referring to cement fjneness and alkali content.
FinenessOften cement standards cause cement to be ground much fjner thannecessary for a certain strength and durability, leading to a considerablewaste in grinding energy. Finer grinding requires about 5% more power per10m2/kg Blaine extra surface.
In some countries (like for instance Nigeria) all produced cement is subjectto the same standard (tabIe 5.3). This standard has to be appropriate for all
73
Cement in development
Table 5.3 Portland cement fineness standards in selected countries
finenessm2/kg blaine
BrazilCentraI AmericaIndiaNetherlandsNigeriaTanzaniaThailandUnited KingdomUnited States of America
soun::e: {15J
240-300280225-350200250225280225-350280
building purposes, including those placing high requirements on cementquality. For most building purposes, however, cement of a lower finenesswould suffice. It is therefore advisable to develop accurate standards for thedifferent end-use purposes. Proper testing could reveal opportunities forreducing the grinding fineness requirement.
A possibility to lower grinding fineness requirements is offered by the use ofmineralizers (see 5.3.4). Mineralizers are known to cause higher reactivityin c1inker. This causes the same cementing properties to be reached atlower specific surface levels. Considering this, it seems advisable todevelop cement standards that consider performance requirements ratherthan fineness.
ALkali speci{lcationAs mentioned before alkalis contained in raw materials may react withcertain aggregates and thus cause cracking of concrete. Therefore, manycountries have set alkali specifications. Because of this, alkalis areremoved from the kiln system, causing significant heat losses.
However, only very few aggregates react with alkalis. Examiningaggregates reactivity might therefore reveal opportunities for relaxing alkalispecifications in cement standards, leading to possible energyconservation.
5.2 Process changes
Process changes generally require large capital expenditure and may entailsubstantial downtime with resulting loss of production during theconversion period. The high costs of such conversions are often onlyjustified on the combined effects of the energy savings and increasedproduction capacity . But, although the costs are high also the benefits maybe significant.
In every step of the cement process, equipment efficiency can be increasedconsiderably, by improving conventional technology or introducing stateof-the-art technology. There is also a generaI possibility to save energy by
74 EeN 1994
5. Energy conservation
improving all motor drives. As motors are used throughout the process. thisoption will be discussed separately.
5.2.1 Raw material preparation
The most important energy conservation in raw material preparation ispossible by upgrading grinding technology. Currently. the bali millrepresents the majority of all existing raw miJl systems. The verticaJ rollermill dominates the market for new miHs. It is more reliable and 15-25%more energy efficient than a bali mill. According to table 5.4, the use ofhigh pressure grinding rolls, does not offer a cJear advantage over thevertica I roller miJl in terms of power, costs or reliability.
Table 5.4 Comparison optimal raw grinding systems
systemB
bali millvertical rollerroller press
power cons.kWh/~
31.922.027.1
power rel.tobali mill
1006985
costmillion OSS
16.0214.9516.28
EeN 1994
• ror 150 tph system wlttl 6% molsture content, using closed circuit grinding after prlrnary crushing.• essumed raw meteriel/cement ratio: 1.55.
soun:e: {62}
Beese 163] however reports replacing a conventional bali mill system by ahigh pressure grinding roll system. The average power consumption in rawmaterial grinding dropped by 40%. The total investment was about 15%lower than for a new roller grinding unit.
Energy consumption of existing raw miJl systems can be reduced at lowestcost by conversion to c10sed circuit grinding. This gives about 10% powerreduction.
5.2.2 Pyroprocessing
Process conversionThe largest energy efficiency improvements of pyroprocessing equipmentcan be obtained by conversion to the dry process with preheater andprecalciner, especially of wet processes (tabJe 5.5).
Wet processes can be converted either fully or partially depending on rawmaterials characteristics. Osually full conversions result in higher kilncapacity. This might make it necessary to increase the process capacityboth upstream and downstream of the kiln. Therefore modifications have tobe carried out, not only to the raw miJl and the kiln, but also te thehandling and storage equipment.
In partial conversions the raw miJl remains wet and only the kiln isconverted, most often to the semi-wet process. This may be preferabie if
c:onversion to effklent 4 or 5 stage suspenslon preheaterIpreclllciner system wlth fuel consumption3250 MJ/t,.lInd power consumption 130 kWh/t_.
source: (l9)
the raw material contains a high amount of moisture (over 20%), if thehandling characteristics of certain raw materials are such that they can bestbe handled in a slurry, or in the case of remote quarries with a lack ofconventional transport infrastructure, leaving transport by pipeline as theonly altemative. In such cases, a filter press may be introduced and the wetkUn may be replaced by a Lepol kUn, offering energy savings of typically2.2 GJ/t of clinker (30% savings in total energy use).
Jmprouing cyclonesIn suspension preheater towers, the cyclones offer significant resistance tothe gas flow. Many preheaters are limited by the induced draught fan.Improving fan systems and introducing low pressure drop cyclones hasproven to be able to increase capacity by 100% and obtain pyroprocessingpower savings of up to 30% in a CNCP cement plant in Brazil 168J.
Jmprouing coolerImprovement of cooler efficiency can be obtained by replacing rotary orsatellite coolers with advanced grate or shaft coolers. This might increasecooler efficiency by 10-20%, thus reducing heat losses due to heat inclinker by 125-250 MJ/t of clinker. Depending on the process used, thiscould reduce total energy requirements by about 3-6%.
Furthermore, most existing grate coolers offer the possibility to increaseenergy efficiency by making some minor technical improvements.
76 EeN 1994
5. Energy conservation
5.2.3 Clinker grinding
Table 5.6 Closed circuit clinker grinding systems with high efficiencyclassifiers
system
bali miJl
vertica I roller
roller press
fineness power power investmentm 2/kg kWh/~ relative relative
Replacing conventional bali mills by roller mills can reduce the specificenergy consumption considerably (tabIe 5.6). In the case of c10sed circuitgrinding, energy savings of up to 25-30 percent can be expected.Depending on grinding fineness even larger energy savings can be obtainedby installing a high pressure grinding roll.
Conversion of existing open-circuit bali mill grinding systems towardsc10sed circuit grinding using a high efficiency classifier, could improvegrinding efficiency by 25-40%. Furthermore existing bali mills could bemade 10-15% more efficient by installing a high pressure grinding roll as apregrinding unit.
5.2.4 Motors and transmissions
In a typical cement plant some 500 to 700 electric motors are used fromkW to MW sizes. The amount of power that can be saved by improving theenergy efficiency of the drives can be significant. Converting conventional3-phase induction motors to new high efficiency types offers power savingsranging from 3 to 8% 176].
Cement plants can also introduce power factor capacitors and solid stateenergy savers. Power factor capacitors are used to increase the powerfactor. By reducing blind current demands they reduce individual motorlosses. However, power factor capacitors are normally sized at full motorcapacity and therefore effectiveness is lost at partial loads, where manymotors operate.
Solid state energy savers use microprocessors to lower the motor voltagewhen a motor is running partially loaded or unloaded. This voltagereduction results in lowering the phase currents. Consequently energysaving is obtained because of reduced magnetic and resistive losses. Power1055 reductions are highest at no load (20-50%) and fall to zero at between20 and 50% of full load [77].
77
Cement in development
Electric adjustable speed drives may be effective, especially in fan systems,by adapting fan power to actual draught requirements. They include DCdrives and variabIe frequency AC drives. In the Jatter case there are threetypes: variabie voltage invertor, current source invertor and pulse widthmodulated invertor. These drives work at high efficiency (88-95%), theyrequire little maintenance, have very wide speed ranges, goed controlaccuracy (0.5%) and near unity power factor.
5.3 Material changes
Energy might be saved by careful selection of natural raw materiais.However most energy can be saved by introducing secondary raw materialsto produce blended cements. Other material change options are theaddition of grinding aids and mineralizers, which act as catalysts in thegrinding and pyroprocessing respectively.
5.3.1 Raw material selection
Raw material characteristics such as moisture content and hardness have aconsiderable influence on energy use during pyroprocessing and grinding.For instance, the Netherlands is facing increased fuel requirements, causedby the fact that the marl limestone deposits are limited. The neededlimestone has to be quarried deeper and deeper. The deeper it is quarried,the higher the moisture content, and consequently the higher the energyrequirements in the evaporation process. Therefore, proper selection ofquarry sites could conserve a considerable amount of energy.
5.3.2 Secondary raw materials
The blending of Portland cement clinker with certain materials withcementitious or pozzolanic properties makes it possible to produce morecement from the same amount of clinker and as aresuIt to reduce theenergy consumption per ton of cement. The manufacture of blendedcements requires less energy per ton than the manufacture of Portlandcement, roughly in proportion to the amount of secondary materials added(tabIe 5.7).
Table 5.7 Savings in primary energy by the use of interground additives
additive
slagslagtrasslimestone
source: (12)
78
ratio of clinker tointerground additive
100/070/3050/5070/3080/20
primary energyconsumption
10077647886
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5. Energy conservation
The use of blended cements not only reduces the amount of primary rawmaterials needed and the energy consumption, but also the emissions ofdust. S02. NO.. and CO2 per ton of produced cement. Often wastes can beused which would otherwise have to be disposed in another way.
Because of these substantial advantages blended cements are produced inmany countries in the world. In 1991 a total of 59 countries had standardsfor cements with secondary constituents, divided into 876 different classesand types.
Experience in these countries leamed that a considerable amount ofchemical pozzolans (Iike f1y ash, blast fumace slag and cement kiln dust)or natural pozzolans (Hke trass) can be added without changing thecharacter of the cement as general purpose cement.
Table 5.8 Typical compositions in weight-percentages
SiOzAlZO)CaOMgOFeZO)
blast fumaceslag
32-46%7-16%
32-45%5-15%
f1yash
44-51%16-26%
2-12%1-3%
7-15%
cHnker
22%6%
63%3%3%
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The used additives mostly contain the same compounds as clinker, but indifferent concentrations. The most important blended cements are Portlandblast fumace slag cement, Portland f1y-ash cement and Portland pozzolanacements. Where more than one additive is used the product is referred toas composite cements.
Many other waste products from industrial processes could potentially alsoserve as raw material to the cement industry (tabie 5.9). However their useis limited by the requirements for cHnker quality, environmentalcompatibility and cost-effectiveness (which is heavily infJuenced by thequality-assurance measures). Especially increasing operational costs maybe a strong barrier to introduction of use of secondary raw materiais.
These secondary raw materials can be added in different stages of theproduction process. Most often they are introduced into the cHnker grindingprocess, but they mayalso be added in the raw material mix.
FlyashFly ash is obtained in the dust collection equipment of fumaces fired withpulverized coal, particularly those of power plants. It mainly consists ofSi02, AI20) and FeZa)' It is finely divided and usually requires IiWe or noprocessing before being used in blended cements.
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Cement in development
Table 5.9 Potential secondary raw materials
Main constituent Secondary raw material
CaO/CaC03/Ca(OHh industriallime, Urne sludg, industrialsludge, drinking water sludge
Fe203 roasted pyrites, synthetic haematite. tinslag, red mud
CaSO.. desulphogypsum, chemical gypsum
souree: (7a]
Generally up to 30% of pulverized f1y ash is added to produce cements withequal or better performance and market acceptancel. Best results areobtained by adding the f1y ash in the fmishing compartrnent of the grindingmill. The clinker is ground finer than for pure Portland cement tocompensate for 1055 of early strength. These extra grinding powerrequirements are negligible compared to the fuel savings.
Blast furnace slagBlast fumace slag is produced as waste material in the manufacture of pigiron. The amount can be as high as 1 ton per ton of iron. The slag isgranulated by rapidly quenching, 50 that the solid product is in a glassyform. Slower cooling would allow crystallization which reduces thereactivity of the slag.
Two cement-types are produced by blending clinker with blast fumaceslag. The first, Portland blast fumace slag cement is manufactured byintergrinding Portland cement with up to 80% of the granulated slag. Thephysical characteristics of this cement differ from conventional Portlandcement in early strength development that is somewhat slower and insulphate resistance that is superior.
The second type is known as supersulphated cement. lt is commonly madeby intergrinding a mixture of 80-85% granulated slag, 10-15% anhydrite(CaSO..) and about 5% of Portland cement or Iime. Supersulphatedcements require more water for hydration than Portland cement and thestrength decreases more rapidly as the aggregate content is increased. It isresistant to aggressive agents such as sulphates and weak acids.
Granulated slags tend to be more difficult to grind than Portland cementclinker, making final grinding more energy intensive. The energy savings,which can be obtained by replacing a considerable amount of PortJandc1inker by blast fumace slag or anhydrite, far outweigh these costs.
I <Jslng stationllry f1uidized bed ki Ins 11 f1y lIsh content ol 65% might even be possible.
80 EeN 1994
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5. Energy conservation
Natural pozzolansPortland-pozzolan cements can be produced by intergrinding or blendingc1inker with up to 40% of natural pozzolan. Natural pozzolans consist ofglassy material of volcanic origin, for instance pozzolan soil or trass. In thedeveloping world natural pozzolans occur in many countries thoughtraditionally they have only rarely been utilized.
Natural pozzolan additions reduce susceptibility to chemical attack, but therate of gaining strength is somewhat lower than for ordinary Portlandcement. At later ages, beyond one year, the strength of the concretecontaining pozzolan generally becomes higher than that of Portlandcement.
5.3.3 Grinding aids
Grinding aids are materiais, which facilitate grinding in bali mills byeliminating bali coating or by dispersing the ground material. Most grindingaids are substances that become strongly absorbed by the ground particles,50 that surface energy requirements are satisfied and no other particles arecontracted to cause agglomeration.
They increase the efficiency of air separation by dispersing the particles 50
that the smaller ones are not carried along by the larger. There is adecrease in volume of the circulating load as a result of more fine particlesbeing released as finished product. Grinding aids are used to produce finerquality cement or to increase grinding mill throughput. Duda [541 reports athroughput increase of 10-50% depending on the fineness of the grindingprocess.
Grinding aids may be added in solution or solid to the mill feed or directlyto the miJl itseJf, in quantities from 0.006 to 0.08 % of the c1inker weight.When additives are to be used in c1inker grinding, they must have beenshown not to be harmful to the finished cement.
5.3.4 Mineralizers
Mineralizers may save a significant amount of the pyroprocessing energyby intensifying the clinkering process reactions and lowering thetemperature required for c1inker buming. A large number of substancesoffer this catalysing effect. Catalysts made by fusing CaC03 with Na2C03and K2C03 appear to be the most effective. Much research remains to bedone, but it is estimated that the unit thermal energy requirement might bereduced by up to 5% for 200°C lowering of buming temperature [551.
5.4 Energy measures
Possible energy measures open to the cement industry comprise use ofsecondary fuels, waste heat recovery. and combined heat and powercycles.
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Cement in development
5.4.1 Secondary fuels
In the cement industry, the commonly used fuels are oil, coal and naturalgas. The basic requirement of a kiln fuel is that it must have a sufficientlyhigh calorie value to produce a buming zone temperature of 1500-1600 0c.The lower limit is about 18.8 GJ/t. In precalciners the required calorie valueis considerably lower, because the temperature does not have to be veryhigh.
Many secondary fuels can therefore be used in cement kilns to replace partof the high grade kiln fuel, which thereby can be preserved for applicationswhere use of high grade fuel is more appropriate. In other words, the use ofsecondary fuels does not offer energy savings in terms of reducing theenergy required for the process, but it does however prevent exergy waste2
that is caused when using heat of a high-grade fuel at a relatively lowtemperature.
Cement kilns have some inherent operating properties, which make themeven very appropriate for buming waste materiais. They offer high processtemperatures, long retention time, and goed absorption and immobilizationof polluting elements in the clinker. Buming wastes in cement kilns allowsto make productive use of materials that might otherwise be wasted.Wastes that might be harmful to the environment will be absorbed almostcompletely in the c1inker without impairing its quality. Thus, buming wastein cement kilns might save the public considerable investment andoperating costs for refuse incineration plants or waste disposal sites.
2 Exergy is the pIIrt c:J a certain lIITlount c:J energy whlch Cllll be used as lClbour.
82 EeN 1994
5. Energy conservation
Paper48%
Glass3%Metal
5%
Mise. inorganie3%
source: [82}
Figure 5.2 Typical US landfill composition
Over 70% of the waste which ends up in landfills has sufficient caloric valueto be utilized in an industrial fumace such as a cement kiln (figure 5.2).Waste fuels that have been used in various plants include municipal wastes,rice hulls, wood wastes, rubber tyres, hazardous wastes, waste oil, spentpot liners, sewage sludge, petroleum cokes, coconut shells, peanut shells.Many of these wastes have a sufficiently high caloric value to be used inthe kiln bumer, making this an interesting option for both new and oldcement plants (tabIe 5.10).
The potential to save primary energy by buming waste materials dependson the amount that is substituted. Currently in some cement plants about15-30% of the primary fuel has been substituted by car tyres and wasterubber, dried sewage sludge or refuse derived fuel [80]. In many cases
83
Cement in development
higher substitution rates are possible. especially in precalciners. In principleall primary fuel can be replaced.
The major barrier to using waste materials as fuels is the lack ofinforrnation and experience in identifying potential problems and solutions.Because of the higher ash content in wastes compared to conventionalfuels, there is concern that buildup problems could increase. Anotherproblem may be the development of efficient and economie collection anddistribution systems. the absence of which has acted as a deterrent inmany cases. Problems are being encountered in developing appropriatestorage. conveying and feeding systems, thereby leading to higher use ofmanual labour. For developing countries this does not have to be aproblem in view of the frequent availability of cheap labour.
5.4.2 Waste heat recovery
Waste heat from kiln and c1inker cooler systems can often be made usefuI.Considerable therrnal energy is present in the different waste gas f1ows.This therrnal energy can be used as heat-input in other parts of the processor be converted into electricity.
Direct use of waste heatWaste heat from kiln and cooler systems can often be used directly fordrying of raw materials or coaI. With the usual bypass system the bypassheat cannot be used directly for drying purposes because this would causethe undesirable substances removed with the bypass to be retumed to theprocess. The gas can be utilized for drying only after its dust loading hasbeen removed. In cases where separate fuel-fired dryers are used, the useof waste heat in drying may lead to significant energy savings.
Often however. kiln exit gases and the exhaust gases from c1inker coolerscannot be utilized in drying because of the plant layout. In such cases theheat content of the gases could be utilized for 'over-the-fence' purposessueh as water heating, greenhouse heating. office heating and fish farrning.There is even the example of recovery by a hood-system of the heatradiated from the kiln shelI, and use of this heat for space heating in thecement plant control room 11 Ol. However, such opportunities may belimited by economie viability.
Conversion of waste heat to electricityWhen the large amounts of waste heat rejected from cement manufacturingcannot be used directly they can still be used for generating electricity.
Although many cement plants generated steam or electricity with wasteheat from kiln gases up to the 19505, this has not been in practice verymuch during the last decades. The amount of available waste heat wasreduced considerably by improving heat exchange between kiln heat andraw materiais, and in many cases the heat has been put to use in drying.The increasing cost of the additional labour demanded for waste heat boileroperation was another important Iimiting factor.
84 EeN 1994
5. Energy conservation
Technological innovation and rising electricity prices have again madeproduction of electricity from waste gases feasible. Utilization of exhaustgases from plants with efficient suspension preheater and precalciner kiJnshas appeared again at the beginning of the 19805 in SwitzerJand andJapan. Even in these efficient cement plants it has appeared possible togenerate at least one third of the electrical power required in cementproduction by utilizing preheater and cooler exit air.
Power generation from exhaust gas heat is now required by law in Taiwanwhen new plants are built. In 1987 research predicted a payback time of 3to 5 years for favourable conditions (84].
Two types of cogeneration systems can be used: steam Rankine systemsand organic Rankine systems. Steam systems have been used for wasteheat with temperatures higher than 550 oe. They are typically instaliedbetween the kiln and the dust removal system. They use the exhaust gasesfrom long dry kilns and preheater bypasses. The exhaust gas is ductedthrough the waste heat boiler, where heat is transferred to the water toproduce superheated steam. This steam is expanded through a turbinewhich drives a generator. It is then condensed and recycled to the wasteheat boiler.
waste heat
wasteheatboiler
souree: f8J
expander
shaft power
pump
coolingwater
EeN 1994
Figure 5.3 Rankine cogeneration cycle
Organic Rankine bottoming cycles (ORC) may provide a practical way torecover the low-temperature heat associated with preheater and precalcinerkilns. The ORC is similar to the steam rankine system with the exceptionthat a low boiling-point organic fluid replaces water as heat transfermedium.
The major barrier to the adoption of these systems is the lack of adequateinformation and technology for dealing with high temperature dirty wastegases. Same constituents of waste gas dust may cause buildup problems in
85
Cement in development
waste heat boilers. Filters could be used in cleaning waste gases beforethey enter heat recovery equipment, but considerable technologicaIdevelopment still is necessary.
5.4.3 Combined production of heat and power
Combined heat and power systems (CHP) produce electricity and heatfrom the same source. In modem CHP systems about 80% of the inputenergy is utilized (for instance 30% electricity and 50% heat). In modempower plants only up to 40% of the employed heat is converted toelectricity and the rest is lost with the cooling water.
Combined heat and power systems can be attractive to the cement industrywhere extra heat is required, which cannot be obtained from waste heat.For instance, CHP systems could supply dryers with hot gases, when thepyroprocessing system is that efficient, that it does not supply enoughwaste heat. The electricity produced can be used effectively for poweringgrinding and conveying machines. There is also the possibility of deliveringelectricity into the public grid, which is especially attractive when peakpower compensation is paid.
86 EeN 1994
5. Energy conservation
5.5 Summary energy conservation options
In the following table the major conservation options are Iisted together withthe approximate effect they may have.
Table 5.11 Energy conservation options in cement manufacturing
Option
Energy managementReduction of heat lossesProcess contro!Changing standards- fineness- alkali specification
Process changesRaw mill conversionProcess conversionFan/cyclone conversionCooler conversionC1inker mill conversionMotor conversion
Primaryfuel saving
20%]0%
5%
45%30%8%
Electricitysaving
]0%
]0%
]0%
20%8%
Raw material changesRaw material seleetion8
Secondary raw materialsGrinding aidsMineralizers
Energy conversionSecondary fuelsWaste heat recovery- drying- cogenerationCombined heat Ei power»
80%5%
5%
100%
15%33%
EeN 1994
• Posslbllity for energy conservation dependll very much on the natural rellOUrces.• Using combined heat and power sylltemll electricity can be generated at doubled effICiency. This means a50% reductlon ol primary energy needll in electricity generation.
5.6 Regional scope for energy conservation
In paragraph 4.4 estimates were made of the total energy consumption bythe cement industry in the different countries of the world. Based on theseestimates, an indication of the energy conservation potential can be given.
The following energy conservation measures have been used for thispurpose:• All processes are replaced by state-of-the-art dry processes, to achieve
average heat consumption of 3000 MJ/tel and electricity consumption of100 kWh/tan (approximation of the average Japanese situation).
• All produetion is changed to the use of 50% additives.
87
Cement in development
• Only primary electricity is used. This means that energy losses inconversion and distribution are negligible.
Of four different packages, formed from combinations of these options, theconservation potential has been estimated (tabIe 5.12).
Table 5.12 Packages of conservation options
Package State-of-the- Additives Only primaryart process 50% electricity
Process X
Product X
Both X X
Maximum X X X
lt should be noted that proper energy management is a necessary conditionto maintain the mentioned low specific energy consumption. Therefore,these conservation packages are based upon management measures,process changes, and raw material changes. Energy measures are incIudedonly with regard to the efficiency of electricity generation.
Of course further (primary) energy conservation could be obtained fromother energy conversion measures, such as the introduction of the use of aconsiderable amount of secondary fuels. However, these measures are notused in the estimates of this paragraph.
Table 5.13 Estimated global and regional conservation effects
The results have been summarized for the diff.erent regions (tabIe 5.13 andfigure 5.4). There appears to be a significant scope for energy conservationthroughout the world. Especially in deveJoping countries in Africa and Asia,and in the transition economies the potential appears to be quite large.
lt is interesting to notice that almost in every region the 'product' packageoffers a higher potential conservation effect than the 'process' package,although until now, most conservation efforts have been aimed at process
measures. Product measures deserve more attention. In this regard thetransition economies form an interesting exception. There, conservationefforts should mainly focus on installation of modem process equipment.
The estimates made in this paragraphs have largely been based on theestimated energy indicators of table 4.9. This introduces an uncertainty inthe calculation, which could be large when considering individual countries,but which is suspected to be limited when regional and global means areconsidered3
•
3 The validity of this remarit has been tested by using considerably Iower estlmates ei specifJc heatconsumption for the wet process (5500 MJ/td ) and the dry process (3200 MJ/tJ. The resulting globalconservation effect la then estlmated at 26% for the 'process' pockage, 49% Cor 'bath' and 59% for'maximum' .
89
6. ENVIRONMENTAL IMPACTS
This chapter will consider the environmental impacts of the cementindustry. The focus wiII mainly be on the emissions to air.
6. 1 Emissiens te air
Primary emissions to air in the manufacture of Portland cement are CO2
and particulate matter. Other emissions include NO•• and small amounts of502,
Table 6.1 Auerage emissians ta air in EU countries
emission
CO2
Dust- process dust- fugitive dust502
NO.
source: (B5/
6.1.1 CO2 emissions
896 kg/teem
0.39 kg/t~
0.36 kg/teem0.79 kg/td2.32 kg/tcl
Carbon dioxide is produced from two sources during pyroprocessing: fromthe decarbonization reactions
CaCO) -+1 kg -+
CaO0.56kg
+ CO2
0.44kg- 1620kJ
EeN 1994
and from combustion of fuel to meet the energy requirements. Furthermoreuse of secondary electricity is responsible for a CO2 emission during thethermal generation of electricity.
The amount of CO2 emission coming from decarbonization is directlyproportionaJ to the CaCO) content in the raw materiais. Decarbonizing onekg of CaCO) produces 0.44 kg of CO2 and 0.56 kg of CaO.
A c1inker CaO content' of 64% (tabie 4.6) thus yields 503 kg CO2/tdl •
Generally the c1inker CaO content ranges from 60-67%. The emission perton of cement is inversely proportional to the amount of gypsum and
I Often co, emissions are prel!el'lted in tons of carbon. One ton of CO, is equivalent to 0.273 tons ofcarbon. Thus a CaO content dM% yields 137 t C/td •
91
Cement in development
secondary raw materials added. Adding on!y 5% gypsum to producePortland cement results in a decarbonization emission of 479 kg CO2/teen,.
The CO2 emission from energy use depends on the type of fuel and ofcourse on the energy consumption. The carbon content in different fuelsmay differ considerably.
Table 6.2 Typical CO2 emissions {rom energy use
fuel
coalgaspetroleum
fuel energykg CO2/MJ
0.0940.0560.073
electricity8
kg CO2/kWh
0.850.500.66
• lIssumed efficiency of power plant is 40%
With this information the CO2 emlSSlon can be calculated for a typicalcement plant, fuelled with oH and obtaining its electricity from oi! firedpower plants.
Table 6.3 Estimated CO2 emission {rom cement manu{acturing
Source use CO2 productionper t cement kg/t cement
Urne 1083 kg 479Fuel energy 3440 MJ 323Electricity 110 kWh 94
Total 896 (=0.245 t C)
The world cement production contributes considerably to the globalgreenhouse gas emissions. Considering the large share of the cementindustry in the total industrial energy consumption in many developingcountries (paragraph 4.4), and the typical fact that in the cement industryenergy use only accounts for up to half of the total CO2 emissions, it maybe concluded that in many developing countries the cement industry is thelargest industrial contributer to CO2 emissions.
Table 6.4 gives an indication of the global CO2 emissions by the cementindustry, using the assumptions made in paragraph 4.4 and estimatedaverage emission figures of 503 kgC02 (137 kgC) from decarbonization ofone ton of c1inker, 0.08 kgC02 (0.02 kgC) per MJ kiln fuel, and 0.65kgC02 (0.18kgC) per kWh electricity.
[t appears that in 1990 the cement industry was responsible for theemission of 245 MtC or about 2.8% of the global CO2 emissions.
92 EeN 1994
6. Environmental impacts
Table 6.4 Estimated regional CO2 emissions by the cement industry (1990)
CO2 total CO2 fuel CO2 electra CO2 decarb(MtCeq) (MtCeq) (MtCeq) (MtCeq)
OECD 70 24 5 41
Africa 12 5 1 7
Asia 107 44 6 56
Latin America 17 7 1 10
Transition Econ. 39 17 3 19
World 245 97 16 133
In figure 6.1 this is iIIustrated by the global annual increase of greenhousegases in the atmosphere. The percentage accounted for by cement in thisfigure only showed the contribution of lime decarbonization. Consideringthe about equal emission in cement production due to energy use, indeedthe cement industry appears to be responsible for about 2.8% of the globalCO2 emissions or 1.8% of global emissions of greenhouse gases.
CfC1400
C023700
l.and use change 33.0'A>
Gas flartng O.6'A>
Gaseous luels 10.6'A>
Uquid luels 27.1 'A>
Solld luels 27.1 'A>
Cemenl 1.6'A>
EeN 1994
Bource: [121}
Figure 6.1 Attributed atmospheric concentration increases of greenhousegases (Mt carbon)
It should be noted that in figure 6.1, the assumption is made that onlyabout 43% of the greenhouse gas emissions remains in the atmosphere toincrease greenhouse heating. This part is apportioned to the differentsources of greenhouse gases according to their share of the grossemissions.
93
Cement in development
6.1.2 Dust emissions
Dust emissions may be process emissions or fugitive emissions. Fugitiveemissions tend to settle mainly within the confinement of the plant, whereasprocess emissions, once dispersed from tall stacks, could conceivablycontribute to long range air pollution.
Process emissions can generally be captured and controlled. They inc\udekiln exhaust gas emissions, which after suitably filtering are emitted to theatrnosphere via a tall stack, and other process emissions, which mainly areexhausted directly after dedusting and can therefore be expected to settlenear to the plant. Fugitive emissions come from uncontained dust sources.Such emissions can only be suppressed by wetting, shielding from wind,limiting the extent of material transfer, and good housekeeping. They tendto settle within the plant or its immediate vicinity.
Dust is identified as one of the most polluting substances due to thepotential deleterious effect upon human health and the environment. Theeffect on human health is a function of
• Chemical nature; dusts with a high content of free silica are of mostconcern, because exposure may lead to pneumoconiosis. Most dustsfrom cement plants contain less than 1% of free silica. This means thatthe dusts are to a large extent inert, without specific toxic effects, butshould be controlled to the extent that inhalation of significant quantitiesof dust is undesirable.
• Size and shape of dust partic\es, which to a large extent determine theease with which dust wiJl penetrate in the respiratory system. Concern isespecially related to particles in the range of 5-15 IJm. Less than 20%by weight of the emitted particles fall within this range.
The deleterious effect of cement dusts on nature has been found only inareas of unusually high disposition. Alkaline dust deposition has beenshown to produce measurable change in soil pH and to change thecomposition of lichen communities. Cement dusts occasionally tend tocrust on leaf surfaces, rather than being washed off by the rain. Therefore,effects on leaf albedo and leaf surface microflora would be more likely thanfor other dusts.
Sources of dust at cement plants exist in all stages of cementmanufacturing: quarrying and crushing, raw material storage, grinding andblending (dry process only), c1inker production and cooling, finishedgrinding and packaging (tabie 6.5). [t is obvious that the dust emissionfigures vary considerably from plant to plant according to the used process,raw materials and fuels.
Generally dust emissions from fugitive sources are of about the sameimportance as dust emissions from the mentioned process sources.
94 EeN 1994
6. Environmental impacts
Table 6.5 Estimated process dust emissions
source
CrushingRaw mills- air swept- c10sed cycleKiln• long wet- Lepol- long dry- dry suspension preheaterGrate clinker caoiersCement grinding c10sed cycleCoal grinding air swept
oost exhaust estimatedcontent gas f10ws max. emissiongINm3 Nm3/t kg/t
- 50 10- 80 4
200-600 600·2400 144050-200 500-900 180
10-100 3400-4600 4605- 20 2200-2800 56
50-100 1900-2400 24030- 70 1700-2300 161
5- 50 600-1500 7550-150 500-1500 225
200-600 1700-5000 3000
sources: [85J[541
6.1.3 S02 emissions
SuJphur may be an elemental constituent of the raw materiais, normallypresent in the form of metal sulphates or sulphides. The amount of sulphurvaries widely according to the deposits used. The sulfates are decomposedto form sulphur dioxide (S02) in the kiln buming zone. The sulphides havealready reacted to S02 in the upper stage cycJones (tabie 6.6).
Table 6.6 S02 formation and absorption reactions
Part of process S02 formations S02 absorption
raw mill endprecipiUltor
Prehelltlng zone
Celclning zone
Bumlng zone
source: (901
sulphldes + 0 oxldes + SO. coco.+SO....... CllSO.+C02orgcnlc: S + O S02
FIlel S + O2 S02 Ca(l+S02 ...... CllSO.CeSO. + C caO + S02 + CO CaSO.+l/2 O2...... caSO.
FIlel S + O2 SOl Ne20+S02+1/2 0 Ne.so.sulphotes oxides +50.+1/2 O. K.O+SO.+1/2 0 K.so.
CaO+S02+1/2 0 ClISO.
IECN 1994
Sulphur is also present in most fueJs, particularly in coal and petroleumcoke, where the level of sulphur may be as high as 5%. On combustion ofthese fuels the sulphur compounds are oxidized to S02'
The sulphur compounds are condensed again in the low temperature end ofthe kiln and are carried along with the cJinker. In the hot zone of the kiln aportion re-evaporates, establishing an intemal cycle within the kiln.
In most circumstances however only a small fraction of the S02 generatedinside the kiln is released into the atmosphere, since it reacts with CaO oreven with CaC03 at temperatures as low as 120°C, which prevail in the raw
95
Cement in development
miJl, and it is mainly incorporated in the cement c1inker during the sinteringstage. In this stage the S02 reacts with the vaporized alkalis.
The net result is that the S02 is largely trapped within the kiln or the rawmill and consequently removed with the clinker. The extent to which theintemal removal occurs within the kiln largely depends upon the alkalinecontent and the amount of excess oxygen present, and can vary widelyfrom one manufacturing plant to another.
Where gases are sufficiently cooled to facilitate the use of fabric filters, 50%of the remaining S02 may be captured by sorption on the filter fabric.For most cases, between 88 and 100 % of all S02 generated is removedfrom the exhaust gas. At low temperatures S02 can be further oxidized toform SOJ' However due to the short retention time of the exhaust gases inlow temperature zones of the system, more than 99% of any sulphuremitted via the stack will be in the form of S02'
S02 emissions from cement industries in general would appear to be ofminor significance in influencing air quality. In the European Communitycement plants generate about 2.0% of the S02 released by industry andless than 1.0% of the total S02 emission.
Emission standards advised by the Commission of the EuropeanCommunity are in the range of 400-750 mg/NmJ. Most modem kilnsystems wiJl have much smaller S02 emissions. Only in cases where theraw material contains more than 0.1-0.2 % sulphur in the form of sulphidesor organic sulphur or where the kiln system is provided with a large kilngas bypass, the Iimits may be exceeded. This is caused by the fact that inthese cases the present S02 will not encounter enough free Iime andalkaline contents to assure complete reabsorption.
Due to the less intensive contact between gas and material in conventionalwet and long dry kilns, on average specific S02 emissions from these kilnsmay be 4-8 times higher than that from efficient suspension preheater andprecaIciner kilns. This may add a strong argument to the argument ofenergy inefficiency, in the case for dosing down such kilns or convertingthem into more modem types (figure 6.2).
6.1.4 NOx emissions
Nitrogen oxides are formed during fuel combustion. The NO. emissions aremade up of fuel NO. and thermal NO.. Fuel NO. is formed from nitrogencontent in the fuel. Coal may contain up to 2% nitrogen, which is easilyoxidized by oxygen to form mainly NO. In an oxygen deficient atmospherehowever, these nitrogen compounds may decompose to form molecularnitrogen (N2). Thermal NO. is formed as the molecular nitrogen componentof combustion air reacts with the oxygen component at high temperatures(above 1200°C). The formation of NO. largely depends on the nitrogencontent of the fuel, the temperature of the flame and the gases in thecombustion chamber, the amount of excess air in the bumer, the residencetime in the buming zone and the bumer configuration.
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6. Environmental impacts
20,..--------------------,
wel
15
5 ecatclner
Standerd
3000 3500 4000 4500 5000 5500 6000 6500 7000
Heat requirement (MJ/t cl)
-0"..: f84JfllOJ
Figure 6.2 Energy efficiency and S02 emission of different processes
For the situation in cement rotary kilns, where f1ame temperatures mayexceed 2000°C, thermal NO dominates the NOs formation mechanisms. Incontrast the fuel combustion temperature in a precalciner is weil below1200°C and mainly fuel NO is formed here. In the lower temperature zonesof the system further oxidation of NO to N02 may take place. However,N02 normally accounts for Iess than 10% of the NO. emission from acement kiln stack.
In the European Community NOs emissions from cement plants account forapproximately 10% or more of those attributable to all industrial sourcesand possibly about 3 % of those derived from human activity.
The emission standard advised by the Commission of the EuropeanCommunity lies within the range of 1300-1800 mg NOiNm3
•2 However
some European countries use much lower standards of 800 mg N02/Nm 3
or even 500 mg N02/Nm3• While virtually all kilns can meet the proposedCEC standards. only about half the kilns can immediately comply with alimit of 800 mg/Nm3 and only very few with a 500 mg/Nm3 limit.
6.1.5 Other emissions to air
• Trace metals. In common with most mineral deposits, the used rawmaterial and coal incorporate various trace metals. During the cementproduction process these metal constituents tend to vaporite in the kiln.They flow out of the kiln with the f1ue gas. In lower temperature areasthese vapours mostly condense and are incorporated in the clinker.
2 It is costumary to wrlte NO. conlents In mg NO./Nm). Arty present NO wlll be multlpUed by 11
However, a small portion is carried out with the bulk f1ue gas stream. Inthe dust removal system the level of trace metals in the exhaust gas isreduced according Iy.
The level of metal emissions is c10sely related to the volatility of themetal concerned and the extent of dust removal. Of elements with lowvoJatility (such as As, Cr, Ni, V, Pb, Zn) only up to 0.05% of the rawmaterial and fuel content is present in the filtered exhaust gas, ofelements with average volatiJity (such as Cd) up to 0.20%.
• Carbon monoxide (CO) emissions are generally negligible due to therequirement to operate the kiln in an excess oxygen condition. Suchemissions are restricted to start-up or upset conditions of the kilnsystem.
• Hydrocarbons can result from incomplete fuel combustion. Again theseemissions are virtually restricted to plant malfunctions and start-upconditions. These emissions are more prevalent in coal-fjred kilnsystems than those kilns using oil or gas.
6.2 Other environmental impacts
6.2.1 Noise
In cement plants and on quarry sites considerable amounts of noise maybe produced. Especially quarrying, crushing, and grinding operations maybe very noisy. For instance in clinker grinding operations the producednoise often far exceeds the human pain threshold.
Noise of grinding installations can be reduced effectively by shielding. Ofcourse process changes may reduce noise levels significant, but these arevery seldom carried out for the purpose of noise reduction alone.
6.2.2 Water pollution
Water is used in cooling of the kiln. In this process it does not contact theinternal raw materia! stream. Therefore it can be assumed that the polJutionof the water is negligible.
There is same waste water that has been in contact with the processmateriaIs, Iike the runoff of accumulated dust piles (especially in the wetprocess) and storage runoff water.
The biggest waste water pollution in cementmanufacturing is present whena sa-ca lied leaching process is used. This process is sometimes used todissalve kiln dust alkalies in water thereby removing them and allowing thekiln dust to be recyc1ed. When this water is discarded, it containsconsiderable amounts of solids.
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6. Environmental impacts
In cases where the water pollution is objectionable, waste water treatmentmust be applied.
6.2.3 Resource expJoitation
Considerable damage may be caused to the environment where cementraw materials are quarried. Surface mining has a detrimental effect uponthe present landscape.
In somecases even ecologically very vulnerabJe deposits are exploited. Forexample in Sri Lanka and India entire sections of coral reef have beenremoved to produce cement. Small coral islands in the Philippines andIndonesia have likewise been mined out of existence [92].
The cement industry has in many cases taken responsibility to reducequarry environmental impact, by revegetating old quarries. For example inKenya hippos are grazing again where few years ago only machinesoccupied the landscape (figure 6.3).
"~yf',(. ....
6.2.4 Wastes
The cement process produces no major byproducts or wastes. Whereverbyproducts or wastes may occur, the cement manufacturing process offersthe possibility of retuming them to the process.
In some rare cases however, kUn dust containing a high amount of alkaliscannot be reintroduced into the kUn. In these cases the dust is cleaned in aJeaching process or discarded in a landfill.
6.2.5 Use of secondary raw materiaJs and fuels
As mentioned before, significant amounts of wastes can be used inproduction of blended cements, and the cement process has some inherent
99
Cement in development
operating properties, which make it very appropriate for using wastematerials as fuel (high process temperatures, long retention time, goodabsorption and immobilization of polluting elements in the clinker).
In this way the cement industry allows to make productive use of materialsthat might otherwise be wasted. With regard to investments and operatingcosts necessary to process wastes, the cement industry might be aninteresting alternative to refuse incineration plants or waste disposal sites.
6.3 Global pollution situation
As insufficient reports have been found dealing with the environmentalcompatibility of the cement industry, a clear overview of the pollutioncharacteristics of the different regions of the world cannot be given.
Various reports have been found, indicating that dust control equipment isnot working properly in many developing countries. As other emissionsreceive no attention at all outside the OECD, it can therefore be concludedthat in many countries, the environmental pollution by the cement industryis not high on the agenda.
This pollution should therefore not be underestimated. Considering also thegrowing consciousness of the importance to reduce emissions with possibletransboundary and global impact, the situation is bound to change withinthe next few years. The cement industry will have to take major efforts intrying to increase its environmental sustainability.
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7. EMI55ION REDUCTION
Due to the nature of the process, clean air preservation has since long beenimportant to the cement industry. Generally in European countries, the totalinvestrnent for air pollution control equipment represents approximately 1213% of the investrnent for the total cement plant 185]. Annual operatingcosts amount to 5-7% of the total plant operating costs. This representsdust emission control equipment only.
Formerly all attention was centred on reduction of dust emlsslons.Reduction of CO2 , NOz and in sonie cases 502 is rapidly demanding moreattention.
Many of the measures, discussed in chapter 5, mayalso lead to emissionreduction. This is clear for CO2, as energy conservation is often the mosteffective tooi for reduction of CO2 emissions. It has also been mentionedalready that modem kiln systems produce less 502' Furthermore productchanges by replacing part of the c\inker with secondary raw materiais, maybe very effective to reduce all emissions, as the production of c1inker is themajor source of most emissions. Apart from the measures mentionedbefore, certain pollutant specific measures exist. These specific measureswill be discussed below.
Because the primary environmental impact of the cement industry is CO2
emissions, regional CO2 emission reduction potentials will be ca\culated forthe different regions at the end of this chapter.
7.1 CO2 emission reduction
lt has already been mentioned that energy conservation is the mosteffective way of reducing CO2 emissions. Especially the use of secondaryraw materials has a major impact on CO2 emissions, by reducing both theamount of bumed fuel as weil as decarbonization. This is illustrated by theestimates made in paragraph 7.5.
Apart from these measures, the only possibility for reduction of CO2emissions is removal and storage. Removal could be possible by using anabsorption medium, which might be removed by heating. Removed CO2could, for instance, be stored in empty natural gas fields.
Currently the cost of such operation are very high (about USS 30 per tonCO2, USS 24 per ton Portland cement, excl. additional energyrequirements). As cement has a low value to weight ratio (app. uSS 80 perton Portland cement), this would cause the cement price to rise sharply.Consequently cement would probably in many applications be substitutedby other building materiais.
However much research is being done on this subject and the future mightstill show wide application in case of an important technological
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Cement in development
breakthrough or in case all other options for CO2 emission reduction giveinsufficient results.
7.2 Dust emission reduction
Significant reductions in present dust emlSSlons can be obtained byimproving the emission control situation especially at older and improperlyoperated and maintained cement plants.
For the control of process emissions, the cement industry uses cyclonecollectors, fabric filters, electrostatic precipitators (ESP) and gravel bedfilters (tabIe 7.1). To meet the emission standards, sometimescombinations of these collectors are employed.
Table 7.1 Dust emission a{ter c/eaning
emissionmg/Nm3
Fabric filtersESPGravel bed filters
Emission Iimits in Europe
sources: [54J[94J
203545
50-100
For the control of fugitive emissions good housekeeping is the bestsolution.
The most desirabIe method for disposal of the dust collected by anemission control system is injection into the kiln buming zone for inclusionin the c1inker, thus increasing energy efficiency. [f the alkali content of theraw materials is too high (more than 0.6%), however, some dust has to bediscarded or treated before introduction into the kiln.
CyclonesCyclones are relatively inexpensive and easy to use, but are restricted intheir use since particles with small dimensions are not captured effectively.Because of this Iimitation, multi-cyclones are used as primary controlequipment in c1inker coolers only where particIe sizes are large and highefficiencies can be reached.
The principle use of cyclones in modem plants (apart from beingcomponents of suspension preheaters) is in precleaning gas, therebyrelieving high performance filtering devices (such as ESP or fabric filters)from high dust loadings.
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7. Emission reduction
Typical removal efficiencies1 obtained by cyclones under stabIe conditions:• Clinker cooler: 95%• Finishing mills: 50-70%
These efficiencies cannot be expected to be reached under upset conditionsor if the cydones are poorly maintained.
Fabric filtersFabric filters are favoured in many gas c1eaning operations within thecement manufacturing process because of their simplicity, reliabiJity,efficiency (more than 99.5%) and economie competitiveness. Modem fabricfilters also allowon line maintenance without seriously reducing filterefficiency.
The configuration of most modem fabric filters comprises a number ofcylindrical sleeves of filter doth. Depending on the working temperature,polyester, polyamide. or acrylic filters are used.
Dust-Iaden exhaust gases cross the cylindrical layers of clOth from theoutside to the inside, where they are exhausted into the atmosphere. Dustparticles are captured by impact of individual particles against filter fabric.or by applied electrostatic forces between dust particles and filter fibres.Periodic dedusting of the filters is achieved by a reverse flow of air directedfrom the inside to the outside of the cylinder, thereby applying a pneumaticshock to the dusted filter cloth' The filter is usually constructed in severalcompartments, to allow for maintenance without shutting the unit down.
Fabric filters cannot be applied to moistureous gases nor at temperaturesabove 190°C. The increased use of heat exchangers to recover waste heatfrom exhaust gases may reduce exhaust gas temperatures considerably.Another disadvantage of fabric filters is the high operating cost.The residual dust content of gases treated with fabric filters is often in theorder of 20mg/Nm3
• This can only be reached in weil maintained filters.Often imperfect sealing causes air leaks that considerably affect c1eaningefficiency.
ELectrostatic precipitators (ESP)Electrostatic precipitators are characterized by their ability to work underconditions of high humidity and high temperature (up to 370 oe). They canbe designed to work with lower pressure drops than fabric filters. therebyreducing fan power requirements. Their principle disadvantages are thatthey are not commonly available in modular form for facilitating on-Iinemaintenailce, and that they must be bypassed during unstable operatingconditions, because of potential explosion hazards occurring fromincomplete combustion in the kiln.
ESPs are now the classica I devices for removing dust from kiln gases. Theyare also used in dry grinding installations and some c1inker mills. ESPs can
1 removlIl effICiency is defined liS !he mlo cl !he qUlIr1t!ty cl removed dust to !he qUlIr1t!ty cllntrocluced dust.
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Cement in development
be designed to yield a residual dust content in the exit gas of the order of35mg/Nm3
• When maintained and operated properly most modem cementplant kUn precipitators can attain a collection efficiency of more than99.9%.
To limit the impact of not being modularized for on-Iine maintenance, ESPsare ususally arranged so that the dust-Iaden gas stream is split to passthrough separate parallel chambers, which are each separated electricallyin several sections along its length. In case of a localized fault one of thesechambers may be electrically shut down for maintenance.
Dust-Iaden exhaust gases are first led through intemal or extemalprecleaners to reduce the dust load on the electrical section.
The principle of dust collection in the electrical part is based on theprinciple of gas ionization in a strong inhomogeneous electrical field, whichis forrned between negative corona discharge electrodes and positivecollecting electrodes. With a sufficiently high electrical field between thetwo electrodes the discharge electrode starts emitting electrons. Theseelectrons are attracted to the positive electrode. The electrons ionize thesedust particles. Consequently. the negative particles are attracted to thecollecting electrode. A small amount of dust particles wiJl be chargedpositively and will move to the discharging electrode. At the electrodes thedust particles are neutralized. By rapping or vibration the dust particles canbe removed from the electrode and collected in a dust bin.
Practically all electrostatic precipitators in the cement industry employ DCvoltage to the electrodes. A recent development in the field of ESPs is theuse of high voltage pulses of short duration, allowing for the attainment ofhigher voltages and improved particIe charging without arching. Thisdevelopment might offer better c1eaning efficiency at lower powerconsumption.
GraveL bed filtersThe use of gravel bed filters is Iimited to low humidities, but they arecapable of cleaning gases with temperatures in excess of 500°C. They areparticularly suited to applications involving hot dry gases, such as thoseemitted from c1inker coolers.
At the entrance of the filter, the dust-laden gas is initially centrifugallydedusted (as in acyclone). After this it passes through a series of beds ofgravel or silica. Individual filter units are c1eaned by isolating the bed fromthe gas flow and flushing by a counter-current flow of air.The residual dust content of gases treated with gravel bed filters is45mg/Nm3 under norrnal conditions. Gravel bed filters involve high capitaIrequirements and high operating costs (due to a high pressure drop). Theirapplication is generally Iimited to grate coolers.
Fugitive emission controlFugitive emissions can be controlled effectively by wet suppression. Theapplication of water sprays causes agglomeration of dust particles, whichthen become too heavy to be airbome. Wet suppression however does not
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7. Emission reduction
stop emlsslons of fine dusts, and it may not be compatible withdownstream processing operations.
Another effective measure may be locating hocding devices aboveemission points and ducting the captured air via induced draught fans tocontrol devices (such as filters) where the captured dust is collected.Further reductions in fugitive emissions may be attained by properlysealing of potential emission sources such as silos of raw materiais, c1inkerand product.
7.3 502 emission reduction
If necessary the concentration of S02 in kiln exit gases can be reduced byadding bumt Iime (CaO) or calcium hydroxide (Ca(OHh), or in the mostextreme cases by adding a separate desulphurization unit.
Introducing CaO or Ca(OHh into the top preheater cyclones causes extracaption of S02' This is economical where a relatively small reduction inS02 emission is required. In case of greater reductions a special absorptionunit may be more economical. Such a unit may be based on the circulatingf1uidized bed principle, which provides an intimate contact between theexhaust gas and the present CaO or Ca(OHh.
Desulphurization of kiln bypass gases may be done in a so-called GasSuspension Absorber (GSA). Part of the bypass dust separated in thededusting cyclone is recirculated to the bypass gas outIet. This ensures ahigh absorption rate in the calcined bypass dust. If the reduction still is toclow, small amounts of hydrated Urne may be added to the GSA.
7.4 NOx emission reduction
NOl emission can be reduced most effectively by reducing NOl formation,which depends on the temperature of the f1ame and the gases in thecombustion chamber, the amount of excess air in the bumer, the residencetime in the buming zone and the bumer configuration. If this does not givethe desired effect selective non-catalytic removal may offer an end-of-pipesolution.
Optimizing burning conditionsOptimizing bumer conditions might imply introduction of low-NOI bumers,but in many cases also conventional bumers offer the possibility foroptimization.
NOl formation can be reduced by up to 30% by increasing the momentumofaxial air to primary kiln bumers and sirnultaneously taking measures toreduce f1uctuations in fuel feed rates. Even larger reductions have beenreported by Nielsen (91] in a bumer system where the f1ame temperaturewas reduced by reduction of the amount of primary combustion air to 6-8%of the theoretically required combustion air.
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Cement in development
Another effective measure may be the installation of an expert kiln controlsystem, which optimizes the dynamic interrelationship between excessoxygen, free lime, buming zone temperature and kiln back endtemperature. It has thus been possible to significantly reduce NO.. emissionlevels by up to 20% and at the same time to optimize fuel efficiency, kilncapacity and c1inker quality.
In precalciner systems NO.. formation can be reduced by stagedcombustion [951. In this system the calciner volume is divided into twosections. All the calciner fuel, but only part of the tertiary air is supplied tothe lower calciner section. Consequently, the fuel is bumed under reducingconditions in this section. This causes the nitrogen content of the fuel andthe NO in the kiln gas to be mainly reduced to free nitrogen.The remaining part of the tertiary air is supplied to the upper calcinersection, where complete combustion of the unbumt fuel and recombinationof the radicals from the lower section takes place. In this way a reduction ofNO.. emission by up to 50% could be possible.
Selective non-catalytic NOx removalIn some cases, it may be necessary to employ selective non-catalyticreduction with ammonia, which has been tested successfully in severalkilns. The ammonia must be injected into the kiln system where the gastemperature is 900-1000°C (mostly at the kiln outlet or into the calciner).At this temperature NO is effectively reduced to free nitrogen withoutescape of unreacted NH3 into the atrnosphere. The overall reaction is:
By injection of NH3 into the calciner a reduction of NO emission by 60-70%has been obtained using a NH3/NO ratio of approximately 1.0.
7.5 Regional scope for CO2 emission reduction
In paragraph 5.6 estimates were made of the regional scope for energyconservation, using 4 different packages of measures. Now, the samemeasures are considered with respect to their impact on CO2 emissions.
Apart from the assumptions described in paragraphs 4.4 and 5.6, thefollowing estimates were used in calculating the reduction effects:• Production of one ton of c1inker gives 503 kg of CO2 emission from
decarbonization.• Use of 1 MJ of kiln fuel gives 0.08 kg of CO2 emission.• Use of 1 kWh of secondary electricity gives 0.65 kg of CO2 emission.
The results of the calculations are shown in table 7.2 and figure 7.1. Theyindicate a c1ear difference between the impact of process technologyimprovement and the impact of the use of secondary raw materiais. Thelatter measure appears to be far more attractive for CO2 emission reductionin all considered regions. It can be concluded that, from a c1imate changepoint of view, introduction of the use of secondary raw materials on a largescale deserves the highest priority.
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7. Emission reduction
Table 7.2 Estimated global and regional CO2 reduction effects
Furtherrnore a noticeable result is that the effect of the 'both' and'maximum' package on CO2 emissions is smaller than on energy use. Thiscan be understood from the relatively large contribution of decarbonizationto the total CO2 emission.
OECD Africa Asia LA&Car. Transition
EeN 1994
Figure 7.1 Estimated regional CO2 emission reduction effects
107
8. POLICY OPTIONS
There is considerable scope for energy efficiency improvement and environmental pollution reduction, as can be seen from chapters 5 and 7.Several technical options are available, which in many cases may beeconomically attractive. However, until now these options have only beenappJied to a Jimited extent. Energy and environmental policies should,therefore, aim at overcoming existing barriers which retard dissemination ofthese measures. This chapter wiJl first try te identify existing barriers. Nextnational policy options will be proposed.
8.1 Barriers
8.1.1 Lack of availability of technical options
Energy conservation and pollution reduction measures, as mentioned inchapters 5 and 7, refer to technologicaJ measures. [n many cases technology may not be available.
In principle, technology is available from foreign and domestic sources. Inpractice, technology can only be procured from a Jimited number ofequipment manufacturers. Most equipment manufacturers active on theworld market are based in OECD countries, and only very few in developing countries and Transition Economies.
This can be iIIustrated by [CR's Buyers Guide (123). In this guide over 800suppliers to the cement industry are Jisted, of which only about 40 situatedoutside the OECD region (tabie 8.1).
Table 8.1 Non-OECD suppliers listed in ICR Buyers Guide 1992
country
South AfriceIrllllIsrllel[ndiePaklstllllChlneIndonesleS·KoreePhilippines5ingeporeMexicoBrllZllCzechoslovakieYugoslllvie
Evidently, more non-OECD equipment manufacturers supply the cementindustry. For instance, China and the fermer USSR have been reported tobe capabJe of building their own plants, up to a certain extent of sophistica-
109
Cement in development
tion of technology. Equipment manufacturers outside major producingcountries, such as USSR and China, will almost certainly be forced tooperate on international markets, because the size of their domestic marketfor capital goeds for the cement industry is Iimited, and would thereforeprobably be mentioned by ICR.
A possible explanation of the limited number of non-OECD equipmentmanufacturers mentioned by ICR, could be that possible non-OECDmanufacturers be subsidiaries of one of the major OECD manufacturers.From the 1992 annual reports of FLS (DenmarkjUSA) and Krupp Polysius(Germany), this has not been found to be the case.
[t is concluded that, with respect to the cement industry, most developingcountries have a very Iimited technological capability.
Technology from domestic sources is therefore often not available. Thelimited technological capability not only leads to lacking design, engineering and installation capacity, but also to suboptimal operation of technology, and inadequate repair and maintenance. It is obvious that inefficiencyand avoidabie pollution result, when a technology has been purchased, forwhich the capability for adequate application is lacking.
Where technology is not domestically available, foreign sources could beappropriate. In developing countries, a lack of foreign exchange coupledwith politicaI barriers all toe often precludes the acquisition of energyconservation and pollution abatement technology from OECD equipmentmanufacturers.
For instance, large down-times of electrostatic precipitators have beenreported in many developing countries, arising from a lack of spare parts.Often these can only be bought in OECD countries. Rapid repair may beimpaired by long delivery times and demands on foreign exchange.
8.1.2 Lack of information
Information about possible measures often reaches decision makers onlypartially or not at all. Moreover, the information is often biased, focusing onmodem high technology only. The major equipment manufacturers areactively providing information via seminars, training, etc. to countries whichthey consider potential markets (currently South-East Asia). Generally theirintentions are strictly commercial and therefore not all options, that wouldbe interesting from a societal point of view may be revealed this way.
A goed example could be found in mini cement plants (box 1). UntiJ the1980s, application of mini cement technology had mostly been limited toChina. Although this technology could have been very suitable for otherdeveloping countries, it was not applied elsewhere, simply because of lackof relevant information on its application in China.
Energy conservation options may be perceived as risky, when propertechnical and financial information is absent. For instance, adoption of newtechnologies is known to possibly entail many problems. Without informati-
110 EeN 1994
8. Policy options
Box 1..Mini cement plimts
TocJay approximately 5% of the cement in the world is produced inmini cement plants, mainly in China and India. Most of the mini~ernentplants empJoy the vertical shaft technology, although in IndiaSame ···have been reported to use rotary kUns. Mostly, productioncapacity is weU beJow 200 tpd.
. . Sinha (1990) repOrts that mini cement plants might represent a viabie•..... alternative to large scale plants. The resource cost of cement produ. ited is not higher than that produced in a reJativeJy effk:ient large
rotarykiln. . .'--:-.-0:-:...<. .. .... .":: "-:
..•.. Resource utlllzat{on mini cement plants compared to large plants
Resource
Capital
Raw materlal
Fuel
. Labo\lr
. TransportJIo\anagement
Cltillzatfon in m\n1 cementplants
Cost 27%-50% lower pertonne ofannual capaclty.Mac:hinery co\lld be manufbctured and fuumced locally.More f1exibility,sultable forsmen rew meterial depoSlts.effective labour intensivequarrying.Acc. to Spenee (1983) lower conslJITl;ption (3.14 GJ/t"JlIce.to Sinha (1990) higher (4.2-4.6 GJ/t".).Lew cost, low skin, high intensity(200 tpy per employeeversus 600 tpy perempl()yee).l..ower cost for c:~~t ...Proprietorlal, better CllOtrot, mefficientthrough Inexperlence.
ECN 1994
.aOur<;e:14]!991
Apartfrom effic:ient· resource utilizati<>o,the establishment of minicement plants might help to disperseproduction fac:iI1ties and may
··contribute to rural development end rural industrializatien.
Important disadvantages of mini cement pIants are instabie quality of· produced cement end the fact that the· used technology is nQt '1ery .·innovative as only few countries utilize it.. . ....
. . . -..· . ;.:-.:. <--.... :-:::.. -.. . -:;:
· It foJlows that mini cement is essentiaUy an)ntermediate technology,suitabIe tor industrializatien withinthêconstraintsof lowcapitalavailabUity, ineffectiveinfrastructure an(iUmited access toadvan<:ed .technology, as experienc;ed by many developingcoûntries. . .
on concerning succesfui cases of technology transfer, this could be animportant barrier.
Detailed information about the financial costs and benefits of a certainmeasure is also often lacking. Without this information, certainly no option'Nill be implemented.
8.1.3 Lack of insight
Decision-makers may often lack insight into the reasons and possibilitiesfor action. As compared to energy system expansions, policy makers on anational level often have Iittle interest in energy conservation and pollution
111
Cement in development
reduction. This may be one of the reasons for a low priority on theiragenda l
•
Furthermore, officials at cement plants might lack proper insight into thefunctioning of the cement plant and are therefore not able to identify areasfor improvement. This problem all toe often results from technologytransfer from industrialized to developing countries without paying properattention to compatibility with the local social and cultural environment,such as the level of schooling and training, and the experience in efficientorganization .
.8.1.4 Lack of incentives
Options will only be implemented if decision makers have a reason to doSQ. Most often incentives for energy conservation are sufficiently present,because it is characteristic for the cement industry that, in generaI, energycosts make up 30-40% of the total manufacturing cost (tabie 8.2). Therefore, a slight increase in energy prices might already be followed by considerabIe energy conservation investrnents.
Table 8.2 Cost structure of cement production in some OIC countries
Country Depreciation Labour Rew meterial Energy Others
In many developing countries energy prices may have been set belowproduction and distribution costs. In this way improper signals are sent tothe consumer about the relative value of using energy efficiently. Furthermore, pollution standards are often failing and where they are present,inability to enforce them in many cases makes them useless.
Often even strong disincentives may be present, such as artificially lowcement prices and lack of market. As cement is a basic commodity,cement prices are often dictated by the national govemment [5]. Regulatedlow cement prices are often a barrier to the realisation of adequate returnson investrnent. Where cement plants are facing overcapacity, investmentswill also be Iess profitable. As aresuIt intemally generated financial resources for reinvestrnent in, among other things, energy conservation andpollution reduction may be severely limited.
Levine [103] reports that often energy conservation is not high on the l!IQenda of key decisionmllkers in developing countries. or even not 1It all. Energy policles mllinly focus on supply side measures.Furthermore it should be noted thllt flnanCÎal Ilnd IeDdership resources l!II'e often scal'Ce and cllnnot be usedfor every purpose. Focussing on efficiency in the energy sector Clln melln trDde-offs in other sectors In thenellr term. The benefits to the econorny Ilnd environment mostly occur in the Jonger term.
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B. Policy options
8.1.5 Lack of institutional support
Several institutions might play the role of providing a balanced environmentand define and reach targets effectively. Institutional support for energyconservation and pollution reduction measures however is often inappropriate, such as the aforementioned state intervention dictating low energy andcement prices. Especially in public enterprises, state intervention may leadto the absence of performance criteria and hence the absence of the needto operate a cement plant efficiently.
Major problems are also encountered in raising funds, especially when itcomes to scarce hard currency. In addition existing infrastructure is ofteninadequate. For example several reports state considerable process downtime due to frequent power breaks in the public electricity grid (28][36a].
8.1.6 Other barriers
• Influence of industrial lobby. For instance, it has been noted that Minicement plants may be an efficient alternative to large scale rotary kilnplants. Spence [10 1] mentions that in India the lobby of large scalecement industries has been severely hindering the introduction of minicement plants in fear of competition and loss of power.
• Extemal constraints. Measures may be impossible because of extemalphysical and geographical barriers, like the nature of raw materials andthe location of the market.
8.2 PoBcy responses
In line with the recent global trend towards market-oriented policies favouring private sector activity, policies for energy conservation and pollutionreduction are thought to be most effective, when creating a self-sustainingprocess that stimulates improvement. This implies providing a decisionmaking framework, that encourages decentralized choices.
National policies should aim at overcoming present barriers. Consideringthe aforementioned barriers, decentralized decision making in the cementindustry requires five main inputs:• available technica I options,• information about these options.• insight into the possibilities of the plant. and the importance of energy
conservation and pollution reduction,• incentives to make investrnent attractive,• institutional support.
ff these inputs are sufficiently present, decision makers in a cement plantwill be well-placed to make choices as to which measures are most appropriate for their specific situation.
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8.2.1 Technical options
Technical options are determined by availability of technology. It is important to understand that the term technology does not only refer to machines and industrial plants. Technology is made up of both tangible andintangible elements [1101:• technoware (objects-embodied), such as production tools and facilities,• humanware (people-embodied), such as skiHs and experience,• infoware (document-embodied), such as facts and information,• orgaware (institution-embodied), such as organization, arrangements
and Iinkages.
humanware
orgaware
.au"",: [710[
technoware
infoware
Figure 8.1 Increasing levels of sophistication of technology components
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8. Policy options
All energy conservation and pollution reduction measures, considered inthis report, refer to technology measures2
• To be effective. technologymeasures require a certain level of sophistication of the different elementsof technology (figure 8.1).
As the required technology is not presently avaiJable in most developingcountries. their technology policies should pursue an adequate mix of'import-adapt' (discussed in chapter 9) or 'research-based' strategies.
A research and development based strategy, creating a national or regionaltechnology capability, could be most appropriate. The creation of a national technology capability would have the advantages of ensuring masteryof operation, maintenance and repair of technologies, manufacture of spareparts, and adaptation of technology to the level of training of workforce andmanagement.
In view of the frequent lack of adequate research and development facilitiesand the insufficiency of financial resources, the target of mastering highlycomplex modem technology seems utopian in most instances. On theother hand. deveJoping countries could establish the necessary conditionsfor the manufacture of capital goods of lower technological complexity (forexampJe mini cement plants, box 1). This in turn, would make it possible tograduaJly progress towards mastery of increasingly complex technologies,weJl adapted to the technological environment and the level of industrialization attained by these countries.
8.2.2 Information about options
Establishment of impartial industrial information services on a national orregional level should be seriously considered, which shouJd be able to be inclose contact with individuaJ industrial plants. The disseminated informationshould include statistical, financial and technica I details, and should beaimed to outreach as far as possible. Domestic industriaI informationservices furthermore offer the possibility to store technical and organizationar experience. They may help to retain individual and collective know-howand serve as a base to national research and development programs.
National or regional cement industry associations, that exist in manycountries, could be appropriate for this task. Also development banks couldplay an important role in this respect. A good example is provided by theIslamic Development Bank, which disseminated very diverse and interesting information on the cement industry through publication of (28).
2 There Is en Important dlacusalon, whetner technology mey oIfer lln llpproprillte 1I01utlon to problems,whlch hllve lergely been crellted by technology In tne finlt plllce. As the llltemlltive might Imply 11 dnlstlc re·eVlllulltlon of the present economie system, Includlng the role of cement, 1IOIutions deacribed here wlll be
llmited to technology 1IOlutIons.
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8.2.3 Insight
It has been mentioned that people inside a cement plant often lack insightinto energy and environmental problems and into operation of their plant.Consciousness-raising would therefore be necessary.
To obtain a better understanding of the cement plant, mastery of know-how(application of practical and technicaI knowledge to a given productionprocess 11021) and mastery of production-organization should be improved.
Mastery of know-how can be obtained by training the workers (manualworkers, technicians and engineers). Apart from training workers individually, mastery of organization requires the training of the workforce as awhole (collective know-how). Smooth running of production depends on aworkforce that has same awareness of the plant as a whoIe, of its Iimits andits vulnerable points. This type of training could, for instance, be attainedby moving workers from one assignment to another Uob rotation), to seehow and by what stages the finished product is produced.
Full mastery of know-how and organization requires a certain extent ofadaptation of technology to the training level of the workforce or a certainextent of human resource development (schooling and training) to the levelof the technology.
In some cases specialist know-how can be brought in from the outside(preferably from national or regional sources). A good example is providedby the !ndian National Council for Cement and Building Materials (NCB)which provides in-site energy audit services through its mobile energydiagnostic unit. Another important example is conducting feasibility studiesby extemal experts. The extemal consultancy skills shou!d in the processbe transferred as much as possible to the responsible employees in thecement plant.
8.2.4 Incentives
Action can be motivated by supplying proper incentives. Energy conservation and pollution contro! require different specific measures and wiIltherefore be treated separately.
Incentives {or energy efficiency improvementCertainly properly high energy prices have proven to belong to the mostimportant incentives for energy conservation in industrialized countries, asthey directly influence feasibility of energy conservation investments.
For instance, figure 8.2 shows the dependence of pay-back time on fuelprices, for the conversion of a long wet process kiln to the modern dryprocess (calculated from table 5.5).
However, in many developing countries energy prices are kept artificiallylow. Increasing energy prices has proven to be a very strong incentive toefficiency improvement. On the other hand, energy price increases may be
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8. Policy options
12
10
-I!?C'll 8Cl>>--Cl>E 6~
,:,e.(.)C'll.0
I 4>-C'llQ.
1 2 3 456
tuel costs (US$/GJ)
7 8 9 10
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Figure 8.2 Pay-back time {or wet to dry process conversion
very painful to society as energy services are deeply woven into people'sJives3
• But energy prices. that reflect the cost of production. distribution,pollution abatement, and damage, wiJl lead to a more balanced and,therefore, potentially more sustainable economie development, as resources will be allocated more efficiently.
Setting targets may be very useful in motivating management and workersto save energy. These targets could be set effectively at bath sectoral andcompany level in cooperation with govemment institutions4
• In order tomonitor progress mandatory periodic reporting schemes have been successful in several industrialized countries.
Targets could be effectively supported by financiar and economie incentives. Various methods include subsidies, tax incentives and credit onpreferential terms.
FinalIy, legislation and regulation may be strong incentives for action. Forinstanee supply of permits can be made dependant on whether certainefficiency standards are met.
The suggested incentives will only be effective if cement prices are relativeIy free, and if markets are more or less competitive. The World Bankreports that 'it is dear that in the absence of competitive markets or other
3 For Instance energy price Increaaes in Nigerill In 1993 led to mllja riots end eventulIlIy to the rllll orthe govemment.
4 Covenllnls between the govemment end brenches or Industry. In whlch tergels ere set IIccordlng tonlltlonlll objectlves, constltute 11 comerstone intrument or !he Dutch energy conservlltion progrem. These
covenents ere blIsed on mutulIl IIgreement.
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peIiormance-based incentive structures, the availability of state-of-the-arttechnology alone will not have a great impact on energy efficiency' 1112].
This may be very relevant where cement plants are publicIy owned. Oftenthis results in absence of peIiormance criterea, and as a consequenceabsence of efficient operation.
Incentives {or poLLution reductionRegulation (standards, permits and licenses) is the mostly used policyinstrument to reduce environmental pollution throughout the industrializedworld. Regulation will not be effective if it lacks the required monitoring andenforcement mechanisms. Although regulation has been criticized for beingeconomically inefficient and difficult to enforce, it has yielded significantprogress in reducing environmental pollution 1104].
It should be mentioned that creating a cooperative environment is considered a more effective approach than regulation and enforcement. Govemments and cement industry could work together at increasing environmental sustainability, by making agreements on targets and monitoring.
As can be seen from the influence of energy prices, intemalization ofenvironmental costs in the pricing system, could be a very effectiveincentive to promote pollution reduction measures. The only actors thatcan price unmarketed goods are govemments. Govemments can chargeproducers for the effects of pollution on the environment by applyingeconomie instruments.
These financial and fiscal incentives can introduce more f1exibility, costeffectiveness and efficiency into pollution control measures, as theypromote private sector activity. However, up until now these incentiveshave only proven themselves effective in supplement of regulation 1104].
8.2.5 Institutional support
Improving institutional support in a number of fjelds may be very importantfor measures to be taken effectively. Depending on the specific supportfunction, these institutions may be needed on a nationallevel (govemment,development banks), on a sectoral level (cement or energy organizations)and on micro-economic level (conservation department inside cementcompany).
Govemments could play the important role of leading institutional development. Their action should incIude strategie planning (setting of targets),promoting integration among actors and different conservation programmes, monitoring of progress, and leading policy formulation.
At the sectoral level, institutions could be very useful, which have the theobjective to promote energy conservation and pollution reduction concepts,technologies and methods, and assist in design and implementation ofmeasures.
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At the plant level an energy conservation department could be a veryimportant institution, to have a c1ear responsibility for conservation, and tomobilize top management support for measures. This way, energy conservation (and pollution reduction) programmes can be incorporated into thefirm's strategie planning.
Institutional support is not only important in the above mentioned fields oftechnology policies, information dissemination, schooling and training, andsupply of incentives, but also in fmancial, infrastructural and technicalassistance.
FinanciaL assistanceAccess to investment capital is of major importanee. The potentially shortpayback periods and foreign-exchange saving characteristics of manyenergy efficiency investments make them potentially very attractive tofinancial institutions. Institutional support can be useful in providing financi·al intermediation (receive, appraise and bundIe investment projects forpotential commercial bank, World Bank and other funding) and in loweringinvestment risks (e.g. by setting appropriate standards, promoting andassisting with demonstration projects and disseminating information).
Development banks may be very weil suited for allocation of resources toproject and programme financing in the form of medium and long terminvestments. They should be able to assess the financial and macro·economie consequences of a certain investment, and thus act as a catalystin optimizing the technology mix. Furthermore development banks havethe possibility of establishing systematic contacts with national or international technology data banks, engineering firms and research and development institutes. Therefore they may offer non·financial services as weil,such as consultancy, technological information and training programmes.By establishing contacts with other development banks, they could besuited weil to cooperate and draw on experience available in other countries.
PhysicaL infrastructurePublic works institutions should be strengthened to improve the reliability ofinfrastructure. In this regard especially public energy infrastructure shouldbe strengthened, for instanee to reduce the number and duration of powerfailures to assure continuous processing.
TechnicaL assistanceThis includes providing extema\ know-how to the cement industry, helpinggovemments to establishenergy efficiency, emission and cement standards, identify and lobby against macroeconomie and sectoral barriers, serveas a focal point for drawing on technica I assistance from bilateral aidagencies, NGOs, etc.
As mentioned before, especially technicaI assistance in conducting auditsand feasibility studies may be very effective. Often management at cementplants is not capable of doing these things. Providing these services by anextemal consultancy organization might reveal interesting options and
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provide valuable information to the management conceming most appropriate action for their spedfic situation.
Development banks and cement assodations could be most suitable forthis task.
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9. INTERNATIONAL COOPERATION
Based on the policy options put forward in the preceding chapter, thecurrent chapter wil! propose options for international cooperation, aimed atstrengthening national energy conservation and pol!ution reduction initiativeSt
9.1 Scope for international cooperation
In energy conservation and pollution reduction, some countries have lessexperience and resources than others. International cooperation might be avery important factor in obtaining the best overall results from energyconservation and pollution reduction options. This cooperation could againfocus on technical options (through technology transfer), information(through effective information dissemination), insight and capacity building(through human resource development), incentives, and institutionalsupport.
9.1.1 Technology transfer
To improve the avaiJability of conservation technologies, it appears to bedesirabIe, that developing countries have their own approach to technologicaI development in the cement industry, based upon strengthening theirtechnological capability, both by absorption and adaptation of new technologies from abroad, and by active utilization of domestically generatedtechnological assets.
In the past many cement technologies have been transferred betweencountries. This had the advantage of doing away with the need to gothrough a step-by-step development of each new technology. However,problems and failures have been numerous, often caused by transferringtechnology without paying attention to compatibility with tlJe Iocal environment.
Compatibility of technology with the receiver environment appears to beessential for success of technology transfer. In generaI two approachescould be discemed: adaptation of technology to the present environmentand adaptation of the present environment to the desired technology. Themost important step in adaptation of technology is the selection of appropriate technology. Adaptation of environment becomes necessary when itcomes to transfer of high technology.
Appropriate technoLogyAppropriate technology is considered to be technology that is compatiblewith, or easily adaptable to the natural, economic and social environment,and that offers a possibility for further development.
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Generally spoken, a number of typical problems occur in cases wheredeveloping countries have adopted advanced cement-technologies thathave primarily been developed for use in industrialized countries [4]:
• As was discussed in chapter 8, lack of mastery of engineering, knowhow and organization of imported advanced technology causes efficienttechnology to be used inefficiently, because of inadequate operation,maintenance and repair.
• lmports of cement technology from industrialized countries have sethuge capital requirements. This has placed a considerable burden onscarce foreign reserves.
• Modem cement technology tends to be laboursaving. This is lessappropriate for many developing countries, with abundant low-skilledlabour but scarce capital resources. lts adaptation might cause anincrease in unemployment, particularly unwelcome in view of the rapidrise in population and potential workforce in many developing countries.
• Modem large scale cement technology is often incompatible with thepresent market and physical infrastructure. Large centralized productionrequires effective transportation and distribution. However thetransportation and distribution facilities are often not very adequate andtherefore tend to increase the cost of cement substantially. This appliesin particular to rural areas.
• Adoption of a modem large scale cement industry, might lead to furthercentralization of the modem sector and thus to increased urbanization.
In view of these difficulties, developing countries should be very careful inselecting appropriate technology for their cement industry. The followingcriteria might be used for determining the appropriateness of technology:compatibility with the domestic technological capability, cheapness, smaller-scale, employment generating, irnport-saving, suitable for rural areas,energy-efficient. A good example of such appropriate technology may befound in mini cement plants (box 1).
Appropriate cement technologies can most likely be found in countries withsimilar level of development, where technologies have been designed tofunction in a sirnilar environment. Therefore there is ample scope for 50ca lied South-South cooperation (cooperation between developingcountries). Another possible 50urce of appropriate technology may beadaptation of technology from industrialized countries. This adaptation,however, places high demands on understanding of the characteristics andlirnits of the receiver environment in developing countries.
Hitherto, transfer of appropriate technologies has received very Iittleattention in the cement industry. In most cases only state-of-the-arttechnology has been transferred. As transfer of appropriate technology ismore likely to be successful, serious attention should be paid to this issue.
International cooperation in transfer of appropriate technology should focuson giving opportunities to select technologies properly. This includes
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careful examination of the demands and Iimits of a country's domestictechnological capability, and provision of an institutional framework thatfocuses on technology imports not only from industrialized countries, butfrom developing countries as weil.
High technologyOsually, import of high technology (defined as advanced, state-of-the-arttechnology) has been considered most suitable to obtain the largestpossible results and to achieve increasing rates of industrialization andmodemization. Transfer of high technology involves importing technologyfrom industrialized countries (North-South cooperation).
Success of imported high technology can only be sustainable where theneeded change in local environment is Iimited to an attainable level. Toassess this change, attention should be paid to the four basic componentsof technology, discussed in chapter 8: technoware, humanware, infoware,and orgaware. Where these components are not sufficiently present in thereceiver environment, they should be included in technology transfer. Inthis way countries with a limited technological capability could leapfrogsuccessfully into advanced cement technologies.
The most advised strategy is te gradually 'unpackage' imported technologies [108). This means separating the components of an imported 'technology package') and exploring the possibility of supplying some of theelements domestically.
Gradual 'unpackaging' can be a way to reduce the cost of technologyacquisition. More significantly, it can stimulate the development of certaintechnical skilIs and capabilities within the country or enterprise and therebystrengthen the domestic technological capability. This might give the abilityto change and further develop the available technology and ultimately toinvent new technologies. In the process, dependenee on extemal soureesmay be reduced2•
Channels for technology transferGenerally spoken, technology transfer may take place through public orprivate channels. Public channels can have the form of developmentsupport and technical aid on a bilateral or multilateral base.
Private channels can have the form of• international trade (often in form of tum-key projects),• international cooperation between companies (in form of franchise and
Iicense agreements, joint ventures or co-production),• investrnents of transnational corporations,• sale of patents,• activities of non governmental organizations (NGO's).
) The most pockaged form of technology tnInsrer, forelgn dIrect Investment, consists of a varlety eielements such as awnel'llhip, finence, capItal goods, dieembodled technology/know-how, management endmarketing.
2 Assumlng that the development of the dómestlc technologIcai capacity outpaces the developmentof technology requlrements, largely dJctated by the International technology race.
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These channels differ as to the amount of packaging and the involvementand influence of the receiver country. International cooperation, forinstance in the form of joint venture agreements, offers most possibiIity forunpackaging and therefore could be the most appropriate vehicJe fortechnology transfer to the cement industry of developing countries.
Presently international trade, in the form of turnkey projects, and activitiesof transnational corporations are the most used transfer channels in thecement sector. To obtain a process of unpackaging in these channels, subcontracting should be encouraged as much as possible.
Access ta technalagyInternational cooperation could also be important in increasing accessibiIityof technology. Especially for developing countries. the price of technologytransfer may limit accessibility to technology significantly. This price notonly reflects the cost of producing technology itself, but also use value. Inaddition technology has a scarcity value arising from product and processpatents, intellectual property protection or secrecy.
In Agenda 21 [1221 the United Nations mention that this problem should betackled by govemments and international organizations. The latter wouldhave to purchase patents and Iicences on commercial terms and transferthem to developing countries on noncommercial terms, as part of assistance in sustainable development.
9.1.2 Information dissemination
Apart from playing an important role in technology transfer, informationdissemination is also essential to policy making. Effective industrial information channels are required which succeed in reaching decision-makersat individual cement plants.
These people should have access to reliable, impartial, industrial information conceming all options that are available for their specific situation.International cooperation could play an important role by establishinginformation channels to the proposed national or regional informationdissemination institutions.
In some regions an extensive cement industry information network alreadyexists. For example most Western European countries have their ownnational cement association, which are united in CEMBUREAU - TheEuropean Cement Association. CEMBUREAU disseminates mostly statistical information about cement production. Dissemination of technicalinformation is mostly left to the equipment manufacturers. The majorcement groups often also have their research departrnent and informationchannels. Furthermore specialized cement industry magazines exist whichfeature both technical and economic information (such as "Zement-KalkGips", "World Cement" and "International Cement Review").
Information dissemination towards developing countries could take theform of international industrial databases and clearinghouses. In thisconnection it is essential to establish relations with international organizati-
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ons specializing in industrial information. Several international clearinghouses have been created for this purpose (tabie 9.1).
Table 9.1 Examples of international clearinghouses
clearinghouse organization
International Referral system for sourees on envi-ronmental information (INFOTERRA) UNEP
Industrial and technological information bank(INT1B) UNIDO
International environment bureau (lEB) ICC
Industry and environment office (IEO) UNEP
Energy sector management assistance program-me (ESMAP) World Bank/UNDP
Asia -Pacific mechanism for exchange of technolo-gy information (MErI) ESCAP
International technology transfer board (IEITAB) EPA (US)
However, for effective information about the cement industry only, it maybe better to forge stronger links between the regional cement associations(which now exist throughout the world). In turn, these regional associationscould exchange information with national information centres or cementproducers.
To be effective the information exchange should not only include statisticalinformation, but also technicaI and financial details. To give an example offinanciaI information, pre-feasibility studies could prove to be very useful.
Moreover, exchange of experiences is very important. In this way a betterunderstanding of the specific aspects of the cement industry in specificcountries or regions may be provided, allowing for a strong base for nuthertechnological and economie development of the cement industry.
9.1.3 Human resources development
Rather than focussing on increased transfer of technology only, international cooperation in energy conservation in the cement industry wouldprobably be more effective when focussing on human resources development. This includes capacity building with respect to mastery of technology, capability to undertake audits, feasibility studies, and technoJogy transfer, and furthermore planning. implementation and evaluation of conservation programmes.
Thus, for instanee, operating efficiency of already present cement plants,that are currently facing lack of mastery of technology, could be improved
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ànd the domestic capability for maintenance and repair in a certain countrycould be enhanced. Mastery of engineering, know-how and organizationdeserve much attention.
UNCTAD [1081 mentions that especially management and policy researchshould be upgraded in many developing countries. In line with this, assistance with feasibility studies deserves a high priority.
Human resources development in the cement industry requires strengthening research and development, training and engineering institutions.Regional cooperation in these fields can offer a solution to the problem oflack of resources. International cooperation should support these initiatives,either directly, by giving technica I and fmancial support, or indirectly, bycooperation and subcontracting agreements.
9.1.4 Incentives
The international community can give strong incentives to a country topursue a policy of energy conservation and pollution reduction by makinginternational agreements. This involves setting targets and standards, whichshould be monitored properly. An international system of standards shouldof course take into account the specific characteristics of the differentcountries and regions and allow for a certain level of flexibility. For instance, the demands on industrialized countries could be higher than ondeveloping countries.
To be effective such agreements must be taken seriously by all parties.Industrialized countries should play an important role here through 'Ieadingby example'.
9.1.5 Institutional support
Support from international institutions may be of great help to achieve thebest policy results in developing countries. Apart from the above mentionedinstitutional support in information dissemination and human resourcedevelopment, this support should include providing resources and assistance in the following fields:
Access to {lnanceInternational development funding should pay more attention to investing inenergy conservation and pollution reduction projects in the cement industry. Providing investment capital only on certain conditions of clean production could give a strong incentive to effective action. For instance theWorld Bank has set certain environmental standards that every new projectmust meet.
Most financial support may come from private investment. Sources may beeither local or foreign. Therefore, it is important that support be given todevelopment of intemal capita I markets, and promotion of foreign investments. Development of risk-sharing investment to provide capitaI without
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loss of domestic control over the enterprise that is fmanced, may beanother strategie option for developing countries. In this regard alsomultilateral organizations, like the International Finance Corporation (IFC),could play an important role3
•
Altemative sources of international financing are currently under discussionsuch as tradeable emission rights, international environmental offsets, anddebt-for-nature swap programmes. Although many alternative proposals tofinance sustainable development exist, in the United Nations Conference onEnvironment and Development in Rio de Janeiro in 1992 the internationalcommunity was more inclined to reinforce existing funding mechanismssuch as the Global Environment Facility (GEF), presently managed by theWorld Bank.
Technical assistanceTechnical assistance can be useful in specific fjelds. This may includeassistance in engineering, management and policy making. As mentionedbefore especially in auditing and feasibility studies some help may bewelcome.
It is important that technicaI assistance is always done in cooperation withthe receivers. This alJows for a transfer of knowledge and skilJs to obtaindomestic human resource development. Thus, technicaI assistance couldbe most effective by making itself redundant.
Support to institutional developmentAs especially industrialized countries have relatively much experience insetting up effective institutions, they could be useful in assisting institutionaldevelopment in deveJoping countries. It should however be noted that eachspecific situation poses its own demands. Simply transferring institutionalstructures will therefore be inappropriate. Cooperation in institutionaldevelopment will be most effective.
9.2 Role of private sector
In technology transfer, the role of private sector activity through foreigndirect investment is becoming increasingly important. Almeida [1111mentions that 'It is widely accepted that transnational corporations dominate foreign direct investment and technology sales'.
Because of the sheer size of their operations, transnational corporationsplay a significant role in generation of greenhouse gases and other pollutants in the cement sector, considering for instance the major role Holderbank plays in cement production in Latin America (tabIe 1.1). On the otherhand, transnational corporations often realize the potential commercialadvantages of environmentally sound production and have the organiza-
3The IFC, member of the World BlInk QTOUP, provides up to 35% of the rlsk-bearing clIpiUll requJred
(or 11 project. By pllrticiPlltion in firlllncing, the IFC cllIlms 10 liet liS 11 clltlllyst to privlIte sector Jnvestments.
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Cement in development
~ion and resources to exploit them. For instance the Holderbank cementplants in Latin America are reported to be more efficient and less pollutingthan the average Latin American plant.
Almeida also mentions that 'changes in home country legislation areindicated by transnational corporations as the most notabIe consideration inmotivating the companies' environmental policies and programmes on acompany-wide basis'. As the most important transnational cement corporations have their base in Europe or Japan, this means that they could actas a catalyst in improving energy efficiency and pollution reduction. Ofcourse the impact of regulation in host countries is not negligible. Therefore, incentives should also be present in the host countries.
National and international policies should provide guidelines for foreigndirect investment, such that technology transfer is both succesfuI andbeneficial to the reciever country. Inclusion of the proper technologycomponents and a maximum degree of unpackaging should be attempted.
Foreign direct investment does not flow to every country in equal amounts.It is obvious that this investment takes place primarily in countries wheremarket perfonnance is interesting enough. Therefore, only few developingcountries benefit from such investments. In countries that do not attractmuch private foreign investment, public international cooperation offers theonly solution.
9.3 Role of official South-South cooperation
Official cooperation between developing countries is often at a very lowlevel. As the problems experienced by developing countries often show acertain amount of similarity, South-South cooperation could be moreeffective than North-South cooperation.
South-South cooperation can cover many fjelds such as appropriatetechnology transfer and deveJopment of human, financial, institutional andinfrastructural resources. Many countries have acquired experience in thearea of industrialization (e.g. India, China, BraziI, South Africa, .. ) and havea contribution to make.
Furthennore regional South-South cooperation could be very important,where individual countries' resources are insufficient. The establishment ofregional institutions could give effective intennediation possibiJities both forcontacts between the participating countries, and for contacts with industrialized countries.
9.4 Role of bilateral North-South cooperation
Through bilateral development cooperation, industrialized countries couldand shouJd assist developing countries in energy conservation and pollutionreduction policies, as they generally have most experience and resources.
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9. International cooperation
Rather than shaping conditions of dependence, North-South cooperationshould be aimed at strengthening a country's (or region's) indigenouspossibilities. This requires open and impartial information dissemination,support of institution formation and makes joint ventures and joint researchpreferabIe vehicles for technology transfer.
Bilateral cooperation can have a more direct influence as weil. Technologytransfer, technicaI assistance and support in human resources development, institutional development and financing deserve attention here. Evenin incentive·formation bilateraJ cooperation could be useful. For instancethe Netherlands has made sustainable development agreements with Benin,Bhutan and Costa Rica, which allow for mutual control.
9.5 Role of multilateral cooperation
International development banks and multilateral organizations could be themost effective interfaces between different countries. Strengthening thecapacity and capability of multilateral organizations therefore deservesmore attention.
International development banks should pay attention to bath financial andnon-financial services. These non-financial services include consultancy,information and training services. Financial support should be allocated toenergy conservation projeets in developing countries directly or through theintermediation of national development banks. Considering the importanceof enhancing capabilitie of the national development banks, on-Iending bydonor finance institutes would be preferabie. Moreover, the latter wouldimprove access to development finance of smalI· and medium-scaleenterprises.
Multilateral organizations, especially international cement associations,could play an important role in shaping information dissemination networks. They could also assist in research and training, and institutionaldevelopment.
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10. CONCLUSIONS
Cement and development• The cement industry is very important to many deve)oping countries, as
cement is produced and consumed almost everywhere. The cementindustry is especially important during rapid expansion of the economy.
Cement and energy• The cement industry is generally responsible for between 2% and 10% of
the commercial energy consumption, and between 5% and 30% of theindustrial energy use, in most developing countries. In rapidly expanding economies, this figure may even be significantly higher. In cementproduction, energy generally accounts for approximately 30% of thetotal production costs. It is concluded that energy conservation efforts inthe cement industry should have a high priority.
• A considerable technica) potential for energy conservation is present inthe cement industry. Possible measures focus on energy management,process equipment, raw material use, and energy changes.
• Conversion to state-of-the-art cement production throughout the world,might lead to 51 % energy savings, mostJy from conversion toproduction of blended cements with well-operated state-of-the-artequipment. In most regions the largest conservation effect can beobtained from introduction of the use of secondary raw materiaIs. Onlyin the Transition Economies equipment measures appear to bepotentially most effective.
• The cement industry offers the potential to use a high amount ofsecondary fuels. [n principle all primary fuels could be replaced.
Cement and environment• The environmental impact of the cement industry should not be
underestimated. Although mostly only dust emissions are recognized asserious problem, also high amounts of CO2, NO. and in some casesS02' are released in cement production. LittJe is known about theprecise environmental situation of the global cement industry. Only dustcontrol equipment appears to be present, but in many cases notworking, because of inadequate repair and maintenance.
• Considering the large share of the cement industry in industrial energyuse, and the large decarbonization emissions inherent to the process, itmay be concluded that the cement industry is the largest contributor toindustrial CO2 emissions in many developing countries.
• Installation of state-of-the-art equipment might give a considerable CO2
emission reduction, but by far the largest reduction can be obtained byintroduction of the use of secondary raw materiais. This is true for allconsidered regions.
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Conservation policies• Several barriers to energy conservation and pollution reduction mea
sures have been identified. These include foreign exchange- andpoliticaI barriers to international technoJogy transfer, Jack of domesticmastery of technology, lack of technology information, lack of incentives, and even presence of strong disincentives, lack of institutionalsupport, industrial lobbies, and external geographical and physical constraints. National policies should aim at overcoming these barriers bycreating a framework encouraging decentralized conservation decisions.
• Only very few developing countries have sufficient technologicalcapability for the cement industry. Therefore, technology policies shouldpursue an adequate mix of 'import-adapt' and 'research-based'strategies.The creation of a national engineering capability would havethe advantages of ensuring mastery of operation, maintenance andrepair of technologies, manufacture of spare parts and adaptation oftechnology to the level of training of workforce and management.
• The establishment of impartial industrial information services should beseriously considered. Dornestic cement industry associations, anddomestic development banks, could be appropriate for this task.
• Conservation action could be motivated by suppJy of proper incentives.Appropriate energy pricing would be most effective to prompt energyconservation measures. Pollution reduction efforts can be rnotivatedbest by, properly enforced, regulation.
• Furthermore national policies should focus on mastery of individual andcollective know-how, and on institutional support in the fields of finance,physical infrastructure, and technical assistance.
• On a national level, development banks could be very suitable institutions for implementing these policies, by providing both financialservices and non-financial services, such as consultancy, technologicalinformation and training programmes, and intermediation ininternational cooperation. On the sector level especially cementassociations could be important. On the plant level a separate conservation department could be a useful institution to have energy conservation integrated in strategie planning of the plant.
International cooperation• Presently in the cement industry mostly high technology is transferred
via trade, in the form of turnkey projects, and via activities of transnational corporations. In transfer of high technology from industrialized todeveloping countries, attention should be paid to include the neededamount of technoware, infoware, humanware, and orgaware.Furthermore a maximum level of unpackaging should be pursued.More attention should be paid to development and transfer of appropriate cement technologies. For most developing countries, these offerthe most sustainable conservation effects.
132 EeN 1994
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10. Conclusions
• Statistical, technical and financial information should be disseminatedthrough impartial organizations. Links between national and regionalcement associations should be strengthened for this purpose.
• Assistance in capacity building in developing countries is very important. This indudes capability to undertake audits and feasibility studies,and to plan, implement and evaluate conservation programmes.
• Furthermore, international cooperation should pay more attention tofinancing and technically assisting energy conservation and pollutionreduction initiatives.
• As cooperation between developing countries, facing similar problems(South-South cooperation) could be most effective, strengthening of thiscooperation deserves a high priority.
• Multilateral organizations could be the most effective interfaces betweendifferent countries. Multilateral organizations, especially internationalcement associations, could play a decisive role in dissemination andeffectiveness of energy conservation and pollution reduction measures,and thus increase the environmental compatibility of the global cementindustry.
Recommendations• Apart from establishing the technica I conservation potentiaJ, as has
mainly been done in this report, it is very important to analyze theeconomie potential. This may reveal which options are most costeffective. lt mayalso be a useful tooi to promote joint implementationefforts.
• It would be very interesting to make a detailed study of technologytransfer as it is currently practiced by the major equipment manufacturers. From this, possibilities for transfer of appropriate technologiescould be investigated.
• Furthermore, activities of transnational cement corporations should beinvestigated, because these corporations have in many cases improvedperformance of their cement plants in developing countries successfully.Therefore information conceming their instrurnents and strategies couldbe very useful.
• Use of less energy- and pollution-intensive building materials thancement. should be promoted (wood. soil, etc.). In applications wherecement is the only option, development of substitute materials shouldbe encouraged.
(21 Heerding, A. (1971)CEMENT IN NEDERLANDIjmuiden: CEMIJ
[31 Peng, L.S., Bee T.O. (1993)ROLE OF CEMENT IN ECONOMIC DEVELOPMENTInternational Cement Review, feb.1993, p.44-50
(4] Spenee, R.J.S., Cook, D.J. (1983)BUILDING MATERIALS IN DEVELOPING COUNTRIESChichester: John Wiley Er sons
(5] Fog, M.H., Nadkarni, K.L. (1983)ENERGY EFFICIENCY AND FUEL SUBSTITUTION IN THE CEMENTINDUSTRY WITH EMPHASIS ON DEVELOPING COUNTRIESWashington: The World Bank
[6] Arakelov, V., Schaeffer, H. (1985)USE AND CONSERVATION OF ENERGY IN THE CEMENTINDUSTRYVienna: United Nations Industrial Development OrganizationReport: UNIDO-[S/540
(7] Tresouthick, S.W., Mishulovich, A. (1991)ENERGY AND ENVIRONMENTAL CONSIDERATIONS FOR THECEMENTINDUSTRYIn: Tester,J.W., et al.: Energy and the environment in the 21st century.Cambridge: MIT Press
(8] Venkateswaran, S.R., Lowitt, H.E. (1988)THE US CEMENT INDUSTRY: AN ENERGY PERSPECTIVEColumbia: Energetics Inc.report: DOE/RL/01830-T58
(91 Garrett-Price, B.A. (1985)POTENTlAL FOR ENERGY CONSERVATION IN THE CEMENTINDUSTRYRichland (WA): Pacific Northwest Laboratoryreport: DE85-007393
(10] Gordian associates (1976)INDUSTRIAL INTERNATIONAL DATA BASE: THE CEMENTINDUSTRYNew York: Gordian Associates Inc.report: NATO/CCMS-46
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Cement in development
[11] Sapp, J.E. (1981)ENERGY AND MATERlAL FLOWS IN THE CEMENT INDUSTRYArgonne, Illinois: Argonne National LaboratoryReport: ANL/CNSV-17
[12] Scheuer, A. (1993)CUITING CONSUMPTION CUITING COSTSInternational Cement Review, february 1993, p. 40-43
[13] Scheuer, A., Ellerbrock, H.G. (1992)POSSIBLE WAYS OF SAVING ENERGY IN CEMENT PRODUCTIONZement-Kalk-Gips 7/1992, p. 175-181
[14] Sirchis, J. (1990)ENERGY EFFICIENCY IN THE CEMENT INDUSTRYCommision of the European CommunitiesLondon: Elsevier Applied Science
[15] Cembureau (1991)CEMENT STANDARDS OF THE WORLDBrussels: Cimeurope
157] Betty, D., Seott, K. (1993)A COST ANALYSIS Of BULK CEMENT DISTRIBUTIONInternational Cement Review, july 1993, p. 36-46
(58] Manning, J.M. (1992)OVER LAND AND SEAInternational Cement Review, april 1992, p.51-59
159] Kroon, P., Comelisse, H. (1989)ENERGIEBESPARING BIJ HET VERKEER & VERVOER 1973-1987,EEN EVALUATIE VAN OVERHEIDSMAATREGELENPetten: ECN-Energie Studie Centrumreport: ESC-51
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[60] Patzelt, N. (1989)MODERN MILL SYSTEMS fOR RAW MATERlAL AND CLINKERGRINDINGInternational Cement Review, august 1989, p.41-45
[61] Scheibe, W. (1993)100 YEARS Of TUBE BALL MILLS - A HISTORICAL REVIEWZement-Kalk-Gips 5/1993, p. e133-e137
[62] Brugan, J.M. (1992)STATE Of THE ART RAW GRINDINGZement-Kalk-Gips 3/1992, p. 59-62
[63] Beese, W., Hoese, H. (1992)RAW MEAL PRODUCTION WITH HrGH-PRESSURE GRINDING ROLL,A REPORT Of TWO YEARS' EXPERIENCEZement-Kalk-Gips 11/1992, p. E291-E293
[64] zurStrassen, H. (1957)THE THEORETICAL HEAT REQUIREMENT Of CEMENT BURNINGZement-Kalk-Gips 10/1957, p.1-22
[65] Rosemann, H., Locher, f.W., Jeschar, R. (1987)BRENNSTOffENERGIEVERBRAUCH UND BETRIEBSVERHALTENVON ZEMENTDREHOFENANLAGEN MIT VORCALCINIERUNGZement-Kalk-Gips 10/1987, p. 489-498
[66] Mehrotra, V.N., Sreenivasan, P., Hartmann, R. (1991)BETRIEBSERfAHRUNGEN MIT 5- UND 6-STUfIGENZYKLONVORWAERMERANLAGEN IM ZEMENTWERKDAMOH/INDIENZement-Kalk-Gips, 12/1991
[67] Grydgaard, P.E. (1993)CONVERTING TO THE SEMI-DRY PROCESSWorld Cement, january 1993
/68] Leme, f.J.P., Neto, T.M. (1990)IMPROVEMENT ON THE DRY PROCESS UNIT MATOZINHOSPLANT-CNCP-MG-BRAZIL32nd IEEE Cement Industry Technical Conference, p.341-358
[69] Kawasaki Heavy Industries, Sumitomo Cement (1992)FLUlDISED BED TECHNOLOGY fOR CEMENT PRODUCTIONInternational Cement Review, Wor! Coal Supplement, july 1992.
[70] Patzelt, N. (1992)HIGH PRESSURE GRINDING ROLLS. A SURVEY Of EXPERIENCE34th IEEE Cement Technology Technical Conference 1992
[711 Patzelt, N., Lohnherr, L. (1992)OPTIMIERUNGSMOEGLlCHKEITEN AN ROLLENMUEHLENZement-Kalk-Gips 1/1992, p. 14-20
140 EeN 1994
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References
[721 Tripathy, S.C., Roy, M.C., Balasubramanian, R. (1992)ENERGY AUDITING KIT FOR CEMENT INDUSTRIESEnergy Conversion Mgmt, vol. 33, no. 12, p.1073-1078
[731 Barreiro, c., Ferreira, B., Abreu, C., Blanck, M. (1990)ENERGY MANAGEMENT FOR RATIONAL ELECTRICITY USE32nd IEEE Cement Industry Technical Conference, p.208-236
[741 Haspel, D., Henderson, W. (1993)A NEW GENERATlON OF PROCESS OPTMISATION SYSTEMSIntemational Cement Review, june 1993, p.71-73
[75] Dekkiche. E.A. (1991)ADVANCED KILN CONTROL SYSTEMSZement-Kalk-Gips 6/1991, p. 286-290
[76] Fujimoto, s. (1993)REDUCING SPECIFIC POWER USAGE IN CEMENT PLANTSWorld Cement, july 1993
[77] Lukitsch, W.J. (1990)SOLJD STATE ENERGY SAVERS FOR MOTORS IN THE CEMENTINDUSTRY32nd IEEE Cement Industry Technical Conference, p.13-17
[78] Sprung, S. (1992)REDUCING ENVIRONMENTAL POLLUTION BY USING SECONDARYRAW MATERlALSZement-Kalk-Gips 7/1992, p.167-173
[79) Schmidt, M. (1992)CEMENT WITH INTERGROUND ADDmVES - CAPABIUTJES ANDENVIRONMENTAL RELJEF, PART 1Zement-Kalk-Gips 4/1992, p. 87-92
[80) Neumann, E. (1992)ENERGY ALTERNATIVES - THE SUBSmUTION OF FOSSIL FUELSIN CEMENT KILNSIntemational Cement Review, may 1992, p.61-67
[81] Rose, D., Cooper, D. (1992)ECOLOGICAL AND ECONOMIC ASPECTS OF CEMENTPRODUCTION WHEN USING WASTE-DERIVED FUELSZement-Kalk-Gips 1/1992. p. E2-E6
[82) Dawson, B. (1992)EMERGING TECHNOLOGIES FOR UTIUZING WASTE IN CEMENTPRODUCTIONWorld Cement, december 1992, p. 22-24
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[83] Rosenhoj, J.A. (1993)THE CEMENT KILN - THE OPTIMAL SOLUTION FOR WASTE TYREBURNINGIntemational Cement Review, may 1993, p. 30-36
[84] Onissi, T.R., Munakata, N. (1993)GENERATING ELECTRICAL POWER FROM THE EXHAUST GASESFROM ROTARY KILN PLANTSZement-Kalk-Gips 1/1993, p. E7-EI0
[85] The Commision of the European Communities (1989)CONTROL OF ATMOSPHERIC EMISSION FROM CEMENTMANUFACTURING PLANTSLondon: Environmental Resources Ltd.report: B6642-28-87
[86] Kinsey, J.S. (1987)UME AND CEMENT INDUSTRY PARTICULATE EMISSlONS:SOURCE CATEGORY REPORT VOLUME [[Kansas City: Midwest Research Institutereport: EPA/600/7 -87/007
[87] van Dijck, F.W.H.M. (1991)CO2 EMISSIE EN ENERGIEVERBR([[K BIJ DE PRODUKTIE VANCEMENTMaastricht: PBIreport: NOVEM R 90.098
[88] Marland,G., Boden,T.A., Griffin,R.C., Huang,S.F., Kanciruk,P.,Nelson,T. (1989)ESTlMATES OF CO2 EMISSIONS FROM FOSSIL FUEL BURNINGAND CEMENT MANUFACTURING BASED ON THE UNITEDNATIONS ENERGY STATISTICS AND THE US BUREAU OF MINESDATATennessee: Oak Ridge National LaboratoryReport: ORNL/CDIAC-25 NDP-030
[89] Akker, J.H.A. van den, Nieuwenhout, F.D.J. (1991)CLIMATE CHANGE AND DEVELOPING COUNTRIES: PRIORITIESFOR POLICY RESEARCH IN THE NErHERLANDSPetten: Netherlands Energy Reseach Foundationreport: ECN-C--91-011
[90] Nielsen, P.B., Jepsen, O.L. (1990)THE FORMATION OF SOx AND NOx IN VARIOUSPVROPROCESSING SYSTEMSWorld Cement, december 1990, p.528-537
[91] Nielsen, P.B. (1991)S02 AND NOx EMISSIONS FROM MODERN CEMENT KILNS WITH AVIEW TO FUTURE REGULATIONSZement-Kalk-Gips 9/91, p.235-239
142 EeN 1994
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References
[92[ Brown, L. et al. (1993)STATE OF THE WORLD 1993Worldwatch InstituteNew Vork: WW Norton & Company
[931 Haller, R.D. (1993)ECOLOGICALLY SUSTAINABLE REHABIUTATION OF QUARRYWASTELAND ALONG THE KENYAN COASTInternational Cement Review, july 1993, p. 54·57
[94[ Kroboth, K., Kuhlmann, K. (1990)CURRENT STATE OF EMISSION-REDUCTION TECHNOLOGY INEUROPEZement-Kalk·Gips 5/1990, p. 103-109
[95[ Kupper,D. (1991), Rother, W., Unland, G. (1991)TRENDS IN DESULPHURISATION AND DENITRATION TECHNIQUESIN THE CEMENT INDUSTRYWorld Cement, march 1991, p. 94-103
[961 Kreft, W. (1990)ECOLOGICAL ASPECTS OF CEMENT PRODUCTIONENVIRONMENTALLY ORIENTED APPUCATION OF TECHNOLOGYAS A CONTRIBUTION TO CUMATIC PROTECTIONZernent-Kalk-Gips 5/1990, p.123·127
[1011 Spence, R.J.S. (1978)APPROPRIATE TECHNOLOGIES FOR SMALL-SCALE PRODUCTIONOF CEMENT AND CEMENTITIOUS MATERlALSUNIDO International forum on appropriate technology NewDelhi/Anand, India 20-30 november 1978, working group no. 5background paperVienna: UNIDOreport: PB297180
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[102] Boubekeur, S. (1985)OUTLINE Of A POLICY fOR MASTERY AND SELECTION OfTECHNOLOGY IN RELATION TO CAPITAL GOODS fOR CEMENT,BRICK AND PLASTER MANUfACTURING - INTERNATIONALCOOPERATION IN THESE INDUSTRIESVienna: UNIDOreport: UNIDO-ID/WG. 434/7
[103] Levine, M.D., Meyers, S.P., Wilbanks, T. (1991)ENERGY EFFICIENCY AND DEVELOPING COUNTRIESEnviron. Sci. Techno!., Vol. 25, No. 4, 1991
[104] Bemstein, J.D. (1993)ALTERNATIVE APPROACHES TO POLLUTION CONTROL ANDWASTE MANAGEMENT REGULATORY AND ECONOMICINSTRUMENTSUNDP/UNCHS/World Bank Urban Management ProgrammeWashington: The World Bank
(105] Ministerie van Economisch Zaken (1992)UITVOERINGSNOTITIE NOTA ENERGIEBESPARINGin: Rijksbegroting 1993Tweede Kamer, 1992-1993,22800 chapter 13, nr. 3, p.46-54Den Haag: SDU Uitgeverij
[106] OECD, IEA, OLADE (1983)INTERNATIONAL COOPERATION fOR RATIONAL USE Of ENERGYIN INDUSTRY, THE L1ME SEMINAR, JULY 1983Paris: OECDReport: CONf-8307119
[107] UNCTAD (1989)TECHNOLOGY POLICY IN THE ENERGY SECTOR: ISSUES, SCOPEAND OPTIONS fOR DEVELOPING COUNTRIESGeneva: United Nationsreport: UNCTAD/TT/90
[108] UNCTAD (1990)TRANSfER AND DEVELOPMENT Of TECHNOLOGY INDEVELOPING COUNTRlES: A COMPENDIUM Of POLlCY ISSUESNew Vork: United Nationsreport: UNCTAD/ITPjTEC/4
[109] UNCTAD (1990)TECHNOLOGY TRANSfER AND DEVELOPMENT IN A CHANGINGINTERNATIONAL ENVIRONMENT: POLICY CHALLENGES ANDOPTIONS fOR COOPERATIONNew Vork: United Nationsreport: UNCTAD/ITPfTEC/21
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[110] ESCAP (1989)A FRAMEWORK FOR TECHNOLOGY BASED DEVELOPMENTTechnology Atlas ProjectTokyo: ESCAP
[111] Almeida, C. (1993)DEVELOPMENT AND TRANSFER OF ENVIRONMENTALLY SOUNDTECHNOLOGIES IN MANUFACTURING: A SURVEYGeneva: UNCTADreport: UNCTAD/OSG/DP/58
[112] World Bank (1993)ENERGY EFFICIENCY AND CONSERVATION IN THE DEVELOPINGWORLD - THE WORLD BANK'S ROLEWashington: The World Bank
[113] World Bank (1992)WORLD DEVELOPMENT REPORT 1992 - DEVELOPMENT AND THEENVIRONMENTNew Vork: Oxford University Press, Inc.
[114] Bates, R.W., Moore, E.A. (1992)COMMERCIAL ENERGY EFFICIENCY AND THE ENVIRONMENTWashington: World Bankreport: WPS 972
(115] United Nations (1992)1990 ENERGY STATISTICS YEARBOOKNew Vork: United Nations
[116] OECD/IEA (1992)ENERGY STATISTrCS AND BALANCES OF NON-OECD COUNTRIES1989-1990Paris: OECD
[117] OECD/lEA(1991) .ENERGY BALANCES OF OECD COUNTRIES 1980-1989Paris: OECD
[118] Asian Development Bank (1989)ENERGY INDICATORS OF DEVELOPING MEMBER COUNTRIES OFADBManilla: Asian Development Bank
(119] World Bank (1992)WORLD TABLES 1992Baltimore: John Hopkins University Press
[120] Instituto del Tereer Mundo (1993)THIRD WORLD GUlDE 93/94Montevideo: lnstituto del Tereer Mundo
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[1211 World Resources Institute, UNEP, UNDP (1990)WORLD RESOURCES 1990-91New Vork: Oxford University Press, Inc.
[1221 UNCED (1992)AGENDA 21: THE UNITED NATIONS PROGRAMME FOR ACTIONFROM RIONew Vork: United Nations
In het kader van het bibliotheekpracticum. zoals dat aan de Faculteit derElektrotechniek wordt afgenomen, is verslaglegging van hetliteratuuronderzoek bij dit afstudeerverslag vereist. Dat gebeurt hieronder.
1. ONDERWERP
Uteratuuronderzoek was een belangrijk gereedschap gedurende mijnvolledige onderzoek, dat plaats vond in drie delen:1) Nauwgezette analyse van de verschillende productieprocessen en
technologieen die in de cementindustrie gebruikt worden. Hierbij werdmet name gelet op mogelijkheden voor energiebesparing enemissiereductie.
2) Analyse van de toestand van de cementindustrie in verschillende regio'sin de wereld: OECD-landen, Afrika, Latijns Amerika en de Caraibben,Azie en de zogeheten economieen in transitie.
3) Analyse van beleidsopties om te komen tot verdere energiebesparing enemissiereductie in ontwikkelingslanden. Dit werd bekeken op nationaalniveau en internationaal niveau.
2. GEBRUIKTE ZOEKTERMEN
In mijn onderzoek heb ik de volgende zoektermen gebruikt (ook deNederlandse en Duitse equivalenten):
BUILDING MATERIALSCEMENTSCEMENT INDUSTRIESENERGYENERGY EFFICIENCYINDUSTRIAL POLLUTIONPOLLUTION CONTROLUNIDO
CEMENTCEMENT INDUSTRYDEVELOPING COUNTRIESENERGY CONSERVATIONINDUSTRYPOLLUTIONTECHNOLOGY TRANSFERWORLD BANK
AFRICASOOTH AMERICAAUSTRALIAUSSR
EeN 1994
Hierbij dient vermeld te worden dat bij het zoeken in de 'Energy' databaseregio's als trefwoorden gebruikt zijn:ASlACENTRAL AMERICAOCEANIANEW ZEALANDEASTERN EUROPE
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Cement in development
3. GERAADPLEEGDE BRONNEN
In onderstaande tabel staan de bronnen die ik gebruikt heb bij mijnonderzoek.
N i -Kohiriklijk ihstftUQt vóór de i ropen, BiJEEi1/ihZE i =uetdé wereld documentatïè cenfi'Um,BZ=Ministerie van Buitenlandse Zaken, VNC=Vereniging Vlln de Nederlandse Cementindustrie,CEMBUREAU=Europelln Cement Assoc:illtion.
Verder heb ik:- een aantal interessante werken op de afdeling ECN-Beleidsstudies
gevonden.- een aantal (15) jaarverslagen opgevraagd van belangrijke producenten
van cement en kapitaalgoederen.- een aantal tijdschriften gescand:
tijdschrift
Zement-Kalk-GipsInternational Cement ReviewWorld CementCiments et Chaux
4. SELECTIECRITERIA
jaargang
1985-19941990-19941990-19931990-1993
bruikbare art.
3953155
Om opgenomen te worden in mijn literatuurlijst heb ik devolgende criteriagebruikt:• Taal: Nederlands, Engels, Duits of Frans,• Beperkte levertijd,• Informatie gebruikt in rapport,• Niet vertrouwelijk,• Band met vakliteratuur,• Veelomvattend overzichtswerk.
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Appendix 1. Literatuuronderzoek
Ik heb bewust niet geprobeerd de omvang van mijn literatuurlijst zoveelmogelijk te beperken, omdat ik het rapport als overzichtswerk eenreferentie-functie wiJ geven.
5. ZOEKPROCES
Het zoekproces was met name autonoom zoeken in de genoemde bronnen.Daarbij werd natuurlijk het meeste aandacht besteed aan die bronnen diehet meeste opleverden.
1991
1990
1989
1988
1987
1986
1985
1984 periodiek1983 GEMB. {1S]
1982GEMB. {16]
1981
GEMB.{17]1980
1979
1978
1977
1976
1957
Figuur Al Sneeuwbal-methode voor literatuur over cement
Zoals uit de lijst van bronnen gezien kan worden leverde de citatie-methodeniets op. Ook de sneeuwbalmethode heeft slechts in enkele gevallen tot hetvinden van interessante nieuwe informatie geleid (in een aantal gevallen
EeN 1994 149
Cement in development
waar wel interessante verwijzingen werden gevonden, waren deze artikelsniet te verkrijgen). Dat wordt geillustreerd door figuur Al en A2, waar deonderlinge verwijzingen van de gebruikte literatuur zijn weergegeven. Defiguren geven wel een mooi overzicht van de onderlinge relaties van debelangrijkste werken.
Bij figuur Al, dient vermeld te worden dat het boek van Duda [54]. dat ikgebruikt heb de derde druk was. De eerste druk stamt uit 1976. Dit boekblijkt duidelijk een standaardwerk van groot belang. Verder valtvoornamelijk het belang op van Fog [5], Gordian [10], Spence [78], en deperiodieke uitgaven van CEMBUREAU [15][16][17] op.
Figuur A2 Sneeuwbal voor algemene literatuur over energiebesparing enindustriele milieu vervuiling
In figuur 2 valt het grote belang van de World Bank [113] op. Dit komt tendele omdat ik hier bewust gezocht heb naar de meest recente visie vangrote multilaterale organizaties zoals de UI'iCTAD en de World Bank.
150 EeN 1994
Appendix 1. Literatuuronderzoek
6. UTERATUUR VERSUS INHOUDSOPGAVE
paragraaflt.:t t3 t. :U 11 u la a ••5 '1.1 '1.1 ... 4,. \, Sol ~U ,. lS So' ., .. , .... 1,1 1.1 r,l r4 "I 1., ., 1,1 ...... •.~ '0
• Voor het vinden van overzichtswerken is de Govemments Annual Indexde belangrijkste bron geweest.
• Relatief veel goede publicaties zijn gevonden via het scannen vanvakbladen en persoonlijk contact (met VNC. CEMBUREAU en UNIDO).
• Strenge selectie voor opname van literatuur in de literatuurlijst was nietgewenst, om de referentie-functie niet te verliezen.
• Zoeken via de sneeuwbal- en citatiemethode leverden weInig op.Bovendien waren de meeste belangwekkende referenties doorgaansmoeilijk te verkrijgen.
• In een tweetal figuren is weergegeven hoe de onderlinge relatie van degebruikte literatuur is. Hier komt duidelijk een aantal belangrijke werkennaar voren.
• In een matrix is weergegeven welke literatuur waar in het rapportgebruikt is. Deze matrix geeft goed inzicht in de onderbouwing van deverschillende paragrafen vanuit de literatuur.
7.2 AANBEVEUNG
• Wellicht kan in dissertaties nog interessante infonnatie gevondenworden. Daartoe zouden "Dissertation Abstracts" en "Index to Thesis"geraadpleegd kunnen worden.
