VERTICAL ROLLER MILLS OCTOBER 2007 ICR V ertical roller mills became increasingly dominant for grinding raw materials for the cement industry due to their high energy efficiency and excellent drying capacity in the 70s. For many years Loesche vertical roller mills (VRM) have been a preferred technology for raw material and coal grinding in the cement industry. Today VRMs are also commonly used for grinding of cement and slag. Due to environmental aspects more and more cements are produced with a certain amount of additives, which are often by- products of different industrial processes. For additional reduction of CO 2 emissions comminution units with a high energy efficiency are installed. South America is a relatively small market in terms of global cement consumption, but its high prices and its growth potential have focused significant attention on the region. Since the 1950s, the continent’s cement industry has passed through a growth phase unparalleled anywhere else in the world. Although this trend came to a standstill in 2000, the region still ranks as one of the world’s major cement producing areas. The following article will focus on Loesche’s history, the South American cement market and operating results of Loesche Vertical Roller Mills (VRM) in selected plants in South America. by Caroline Hackländer- Woywadt * , Loesche GmbH, Germany I South American VRMs Figure 1: Cement production, consumption, exports, imports for South America 2 Figure 2: map of Loesche mills in South America Figure 3: LM 35.3 D in Brazil for coal grinding
Transcript
VERTICAL ROLLER MILLS
OCTOBER 2007 ICR
Vertical roller mills became increasingly dominant for grinding raw materials for the
cement industry due to their high energy efficiency and excellent drying capacity in the 70s. For many years Loesche vertical roller mills (VRM) have been a preferred technology for raw material and coal grinding in the cement industry. Today VRMs are also commonly used for grinding of cement and slag. Due to environmental aspects more and more cements are produced with a certain amount of additives, which are often by-products of different industrial processes. For additional reduction of CO2 emissions comminution units with a high energy efficiency are installed.
South America is a relatively small market in terms of global cement consumption, but its high prices and its growth potential have focused significant attention on the region. Since the 1950s, the continent’s cement industry has passed through a growth phase unparalleled anywhere else in the world. Although this trend came to a standstill in 2000, the region still ranks as one of the world’s major cement producing areas. The following article will focus on Loesche’s history, the South American cement market and operating results of Loesche Vertical Roller Mills (VRM) in selected plants in South America.
by Caroline Hackländer-Woywadt*, Loesche GmbH, Germany
ISouth American VRMs
Figure 1: Cement production, consumption, exports, imports for
South America2
Figure 2: map of Loesche mills in South America Figure 3: LM 35.3 D in Brazil for coal grinding
VERTICAL ROLLER MILLS
ICR OCTOBER 2007
South America’s cement marketIn 2005, a total of 166 cement plants have been in operation in South America (including Central America), comprising of 131 integrated plants and 35 separate grinding plant units.1 An intriguing characteristic of the region’s cement industry is the concentration of large company groups and international consortia. By 2005, the combined market share of the global top 10 cement producers accounts for 34 per cent in this region (compared to 35 per cent worldwide).1
According to latest market figures from 2005-10, worldwide cement consumption will increase from approximately 2300Mta to 2840Mta2. This corresponds to an average annual growth rate of 4.3 per cent. Asian countries account for 63 per cent of the global cement consumption, comprising China in the lead position with 46 per cent of global cement consumption and Far East with 11 per cent. Western Europe is world‘s No 3, followed by North America and the Middle East. India is ranked No 5 (including Bangladesh, Sri Lanka, Bhutan and Nepal). Africa/Oceania and Eastern Europe are with each five per cent closely followed by South/Central America with four per cent.2
According to OneStone forecasts, up to 2010 worldwide cement production will increase more strongly than cement consumption. The cement production particularly in South America will increase from 92Mt in 2005 to 117Mt in 2010. The cement consumption in this region was 87Mt in 2005 and will increase to 113Mt in 2010, resulting in a small production surplus of 4Mts. Table 1 shows number of cement plants, production, capacity and utilisation in South America. The cement capacity utilisation was at the lowest level of 61.5 per cent in 2005. Largest cement capacity in absolute figures was in Brazil (61Mt), Argentina (16.9Mt), Colombia (14.2Mt) and Venezuela (10.7Mt).1
Not all countries in South America are exporting cement currently. Between 1990 and 2000 the exports from South American countries rose about 45 per cent (including Mexico)3. Figure 1 shows cement exports, imports and cement consumption in 2005, and a forecast of these data until 2010 for South America. Both cement imports and exports will
slightly decrease until 2010. The trade forecast is based on various capacity extensions to go on-stream until 2010. As a result demand will be met increasingly by domestic supply rather than by foreign imports.2
Loesche mills in South AmericaThe first Loesche roller mill for grinding
of cement clinker was an LM 11 supplied in 1935 to Joao Pessao, Brazil, for the Companhia Industrias Brasileiras Portella SA. This shows the long tradition of using VRMs in South America.
Figure 2 shows a map of South America with the state-of-the-art Loesche mills installed for grinding cement raw material, coal, limestone as well as clinker and slag. In total 39 Loesche mills have currently
Loesche’s history In 1906, the engineer Curt von Grueber established a company for the design and sale of Kent mills in Berlin, Germany. Curt von Grueber Technisches Bureau quickly became one of Europe’s leading manufacturers of cement and phosphate mills. Its range of products included Maxecon mills, Hauenschild rotary grate kilns, and all kinds of machinery for cement production. Ernst Curt Loesche joined the company as a young engineer in 1912 and became partner in 1919. In 1937, EC Loesche bought Curt von Grueber’s share in the company and became sole owner. After World War II EC Loesche decided to leave Berlin and rebuild his company in Western Germany. This was the beginning of Loesche Hartzerkleinerungs- und Zementmaschinen KG in Duesseldorf. In November 1948, after the sudden death of his father, 24-year-old Ernst Guenther Loesche took over the company. Under his leadership and with its own manufacturing facility in Neuss, Loesche KG re-established itself as a world market leader in the 1950s and 1960s. During this period, Loesche’s engineers developed numerous new technologies, including the hydropneumatic spring assembly, the Loma hot gas producer, and the pressure mill for grinding coal. In the early 1970s, Loesche faced a new challenge: improvements in kiln technology required the construction of larger mills. Loesche’s response to this development was the invention of the four-roller mill and the introduction of a modular mill system. The four-roller mill quickly became a huge worldwide success. In order to provide its customers all around the world with better local support, Loesche established subsidiaries in Spain and South Africa. In the late 1970s, Loesche adapted the modular system also for the use in coal mills. In 1983, EC Loesche retired and his son, Dr Thomas Loesche, already the third generation of the Loesche familiy, became managing director of the company. In the 1980s and early 1990s, Loesche developed promising new business activities such as an after-sales service and the construction of mills for the iron and steel industry. Other innovations included the development of an improved hot gas producer and the use of Loesche mills for grinding coal and peat briquettes. In the 1990s, Loesche came up with another ground-breaking mill design in the form of the 2+2 cement clinker mill. This mill proved a resounding success around the world. In the years that followed, Loesche GmbH expanded its range of products and services continuously and invested in the development of new technology. The collapse of economies in SE Asia in 1997 plunged the company into a deep crisis. However, new ideas and the introduction of a series of rationalisation measures enabled the company to recover. Two of the innovations that date from this period are the slide-in procedure and the introduction of the so-called ‘redundancy concept’. Nowadays, due to its innovative strategy, Loesche GmbH is one the world’s leaders in its field of grinding technology.
been sold and installed in South America. The distribution in regard to material and country is listed in Table 2.
Coal grinding millsToday a coal grinding plant must be in a position to process coals of varying grindability and origin, while maintaining
its cost effectiveness and allowing a high degree of availability. In recent years, the Loesche coal mill has undergone constant development in order to meet the requirements given above. The combination of standard features with more unusual design characteristics within the mill (see Table 3) enables the
economic and fail-safe preparation of hard coals, lignite and petcoke.4 In South America 21 Loesche mills for coal grinding are installed (four in power plants, eight in steel plants, nine in cement plants).
Three coal mills are in operation at a steel plant in Brazil: One LM 23.2 D and two LM 35.3 D. The first, an LM
35.3 D began operation in March 1996 as the first mill of its size and was followed by the LM 23.2 D in 2004. With the company expansion a third blastfurnace was installed and another coal mill was commissioned in April 2007 (see Figure 3). Guaranteed figures of the three mills are compared in Table 4 with achieved operating data in the performance runs.
VERTICAL ROLLER MILLS
Table 1: cement production, capacity and utilisation in South America
Country Plants 2005 Production Capacity Utilisation
Integrated Units Grinding Units 2005 (Mt) 2010 (Mt) 2005 (Mt) 2010 (Mt) 2005 (%) 2010 (%)
Argentina 14 3 7.6 9.7 16.9 18.9 45.8 51.3
Bolivia 5 2 1.4 2.4 1.9 2.1 73.7 100.0
Brazil 47 12 36.7 47.0 61.0 66.0 60.2 71.2
Chile 5 2 4.0 5.3 6.0 6.9 66.7 76.8
Colombia 13 2 9.9 11.9 14.2 16.0 69.7 74.4
Ecuador 4 1 3.8 5.0 4.5 6.4 84.4 78.1
Peru 5 1 5.1 6.3 8.6 9.6 59.3 65.6
Venezuela 7 2 6.2 8.0 10.7 11.9 57.9 67.2
Other SA 31 10 17.5 22.1 26.0 32.1 55.6 65.8
(incl C.America)
Total 131 35 92.2 117.7 149.8 169.9 61.5 69.1
Table 2: Loesche mills in South America: LM per country
Raw material Clinker/Slag Coal Limestone Total
LM Size LM 24.2 LM 15.2 LM 9.2 LM 14.2
up to up to up to up to
LM 63.4 LM 56.2+2 LM 35.3 LM 17.2
Argentina 2 – 1 – 3
Brazil 4 – 11 1 16
Chile – 2 4 1 7
Colombia 1 – 5 – 6
Peru – 3 – – 3
Uruguay 1 – – – 1
Venezuela 1 2 – – 3
Total 9 7 21 2 39
Table 3: design characteristics of Loesche coal mills Standard design Special featuresResistant to shock pressure up to 3.5 bar abs. Increased shock pressure resistance up to 8 bar abs.
Stop buffers ensure no metal contact Grinding Pressure relief system
between roller and table
Individual guidance of Grinding Rollers Grinding pressure control unit
2, 3 or 4 roller design (dependent on throughput) Speed controlled mill drive
Flat grinding table with conical rollers
arranged under 15° => shear forces
Hydro-pneumatic spring system
Figure 4: LM 63.4 in Lamali, Argentina, for raw material grinding
ICR OCTOBER 2007
Raw material grinding millsDepending on the grindability of the raw materials the LM 63.4, biggest raw material mill installed in South America, can provide raw meal for kilns producing up to 11,500tpd of clinker. In Loma Negra, Argentina, the LM 63.4 is limited by poor grindability of the raw materials. Worldwide three mills of this size are in operation. To make use of already existing design elements, installed in smaller Loesche mills, the foundations of the pedestals for the rocker arms and
the hydraulic cylinders have been changed. On mills of this size a ring foundation made of concrete is used around the lower mill body on which the pedestals are located. This allows to reduce the size of the pedestals which makes fabrication more easy. In total, nine Loesche mills for raw material grinding are installed in South America with sizes from LM 24.2 up to LM 63.4. In Table 5 the performance data for the LM 63.4 (see Figure 4) at Loma Negra, Argentina, and the LM 45.4 (see Figure 5) in Laranjeiras, Brazil, are shown exemplarily.
Cement/slag grinding millsSeven Loesche mills with sizes from LM 15.2 up to LM 56.2+2 for grinding of cement and slag are installed in South America. In general all Loesche mills for cement and slag grinding are provided with the technology of Master – and Support-rollers. This technology is characterised by pair-arranged rollers which form a unit. Each pair of rollers consists of a small S(support)-roller, which de-aerates, compacts and prepares the feed material, which ensures optimum
feed for the larger M(master)-roller. The M-rollers with their hydropneumatic spring system comminute the material in a stable bed. The downward travel of the rollers is limited by mechanical buffers to prevent metal-to-metal contact between roller and grinding table. The system with M- and S-roller is introduced since more than 10 years, whereas 3+3 system has been developed for bigger throughputs. Most of the customers in South America are producing blended cements with various contents of components like pozzolan, slag and limestone. The smallest one, an LM 15.2, is not equipped with the 2+2/3+3-technology for technical reasons and is installed for tin slag grinding in a tin smelting and refinery plant. Table 6 lists guarantee figures in comparison to achieved data for the LM 15.2 (tin slag grinding) and for two LM 56.2+2 (blended cement grinding, see Figure 6). Final commentsWith nearly 40 mills for different fields of application Loesche mills are well distributed in South America. High availability, reliable operation and superior energy efficiency are characteristic features of the described mills. The design provides the operators with a wide range of flexibility, which makes it easy to meet changing market demands while maintaining low production costs. Loesche supplies customised systems for all the grinding operations required in a cement plant as well as for coal grinding in steel plants. _________________________ I
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Figure 5: LM 45.4 in Laranjeiras, Brazil, for raw material grinding
Figure 6: LM 56.2+2 in Arequipa, Peru, for cement grinding
Table 4: performance data of coal mills
Plant Steel works Steel works Steel works
Country Brazil Brazil Brazil
Location A B C
Feed material Coal Coal Coal
Mill size LM 35.3 D LM 23.2 D LM 35.3 D
First operation March 1996 February 2004 April 2007
spec. power consumption 8.82 kWh/t 8.05 kWh/t 8.05 kWh/t
(mill motor)
ICR OCTOBER 2007
References* 1 Dr-Ing, Manager Clinker/Slag grinding, Loesche GmbH, Duesseldorf/Germany 1. Cement Projects Focus 2010, Part 3: Cement Production & Capacity. Market Report by OneStone Intelligence GmbH.
2. Cement Projects Focus 2010, Part 2: Cement Consumption & Trade. Market Report by OneStone Intelligence GmbH.
3. The cement industry in Latin America; part 1: General Survey. Juan de las Cuevas Toraya, José Salom Compañy; Cement International, 5/2004, Vol 2, 42-49.
4. Salewski, G, Schaefer, H-U, Loesche mills for the Cement Industry: Recent Advances and Developments. 18th AFCM Technical Symposium Optimization in the Cement Industry, April 2002, Kuala Lumpur, Malaysia.
VERTICAL ROLLER MILLS
Table 5: performance data of raw material mills Plant Cement plant Cement plantCountry Brazil Argentina
Location Laranjeiras Lamali
Feed material Cement raw material Cement raw material
Mill size LM 45.4 LM 63.4
First operation August 2006 March 2001
Guarantees
Production rate 380tph 450tph
R 0.09mm <17% <15%
R 0.2mm <1.5%
spec. power consumption <4 kWh/t +2% <20.6 kWh/t
(mill motor) (mill motor,
classifier, aux., fan)
Results
Production rate 391tph 466.8tph
R 0.09mm 16.14% 13.51%
R 0.2mm 1.3%
spec. power consumption 4.08 kWh/t 18.56 kWh/t
(mill motor) (mill motor, classifier,
aux, fan)
Table 6: performance data of raw material mills Plant Tin plant Cement plant Cement plantCountry Peru Peru PeruLocation Pisco Arequipa Pacasmayo
