A REPORT

ON

CEMENT MANUFACTURING PROCESS

BY

AKASH AGRAWAL RAJ RANJAN SINGH

2014A1PS499H 2014A1PS469H

Prepared in fulfilment of

Practice School-I Course No. BITS C221

AT

RAWAN CEMENT WORKS RAIPUR A Practice School-1 of

BIRLA INSTITUTE OF TECHNOLOGY & SCIENCE, PILANI

(MAY-JULY,2016)

CHEMICALCHEMICAL

Acknowledgement

We are thankful to the Department Head, Section Head and several Engineers of our unit who gave their support and guided us in completion of our project work. They have been very kind and patient while explaining the concepts and clearing our doubts.

In particular we are indebted to our Instructor, Dr. Sunil Kumar Dubey whose words of encouragement and helpful suggestions from time to time, kept us motivated.

We are also grateful to HR Department and all staffs of Rawan Cement Works for organizing multiple learning sessions and providing us the required basic facilities and support.

And finally we would like to thank our parents for their blessings that worked beyond science in successful completion of our project effectively.

ABSTRACT

Cement is a binding material that has a property to act as binder, sets and hardens to bind material together. Grade of cement alters as the composition of additives varies and also on the excipients used in milling. This report gives brief introduction to cement manufacturing process which involves Mining of Limestone, Raw material preparation & storage, Fuel preparation, Clinkering (Pyro section), Cement Grinding & Packing & Dispatching.

TABLE OF CONTENTS

1. INTRODUCTION TO ULTRATECH CEMENT..............................................6

2. RAWAN CEMENT WORKS.......................................................................7

2.1 MINING AREA

3. ABOUT CEMENT.....................................................................................9

3.1 ROLE OF KEY INGREDIANTS

3.2 CATEGORY OF CEMENT

4. CEMENT PRODUCTION AT RAWAN..........................................................13

5. CEMENT MANUFACTURING PROCESS.....................................................13

5.1 MANUFACTURING

5.2 QUARRING/MINING OF LIMESTONE

5.3 QUALITY CONSIDERATIONS

5.4 MACHINES USED

6. RAW MEAL PREPARATIONS......................................................................17

6.1 STORAGE OF RAW MATERIAL

6.2 VRMs AT A GLANCE

6.3 FACTORS THAT CAN EFFECT THE PROCESS OF GRINDING

6.4 BLENDING SILO

7. FUEL PREPARATION..................................................................................20

7.1 FACTORS THAT ARE IMPORTANT WHILE SELECTING A FUEL

7.2 PROBLEMS FACED IN KILN WHILE USING PETCOKE

7.3 WAYS TO COUNTER THESE PROBLEMS

8. CLINKERISATION (Pyro-processing)...........................................................25

8.1 PREHEATER

8.2 COOLING OF CLINKERS

9. CEMENT GRINDING....................................................................................29

9.1 DUST COLLECTING EQUIPMENTS

10. PACKING AND DISPACHING......................................................................32

11. REFERENCES.............................................................................................33

1.INTRODUCTION TO ULTRATECH CEMENT

UltraTech Cement Ltd is the consolidation of the Aditya Birla Group's cement business since 2004.With huge demand in market, UltraTech cement has emerged as a global leader in cement industry. Largest manufacturer of grey cement, white cement and ready-mix concrete in India .Grey Cement manufacturing capacity is 69.3 million tonnes per annum and selected as Superbrand and Powerbrand. Largest manufacturer of ready-mix concrete (RMC) in India, more than 100 RMC plants in 35 cities in the country. Birla White (Jodhpur) is the largest manufacturer of white cement in India, with a capacity to produce 0.56 MTPA of white cement and 0.8 MTPA of WallCare Putty. It is also the largest manufacturer of clinker cement based in Mumbai, India. It is also

the largest exporter of cement and clinker to African, European and Middle East Countries. Company’s subsidiaries are Dakshin Cements Limited, Harish Cements Limited, UltraTech Cement Lanka Pvt Ltd and UltraTech Cement Middle East Investments Limited. Operation in Five countries - India, UAE, Bahrain, Bangladesh, and Sri Lanka. UltraTech has 13 integrated plants , 1 clinkerization unit , 19 grinding units , 7 bulk terminals , 1 white cement plant , 2 .Wall Care putty plants and 101RMC plants. Market share - 18% approx... Employees - 14000+ .Listed in NSE 50-share index (Nifty) in listed top 50 companies. Joined CSI (Cement Sustainability Index) for Sustainable Development in 2006.For safety purposes UltraTech collaborated with DuPont Sustainable Solutions for improving company safety practices.950 + Building stores all across India.UltraTech foundation can be traced back in 80's with first cement plant at Grasim (Vikram Cement in Jawad, (M.P).Grasim acquired a stake in L&T cement Ltd in 2001.In 2004, acquired in Aditya Birla Group and its name was changed to UltraTech Cement.

2. RAWAN CEMENT WORKS

Rawan Cement Works (UltraTech Cement Ltd) is located at Grasim Vihar, Vill: Rawan, Dist. Baloda Bazaar in Chhattisgarh State. The plant is well connected to Railway Station about 25 Km far away from the nearest Railway Station, Bhatapara and the nearest Airport is at Raipur about 82 km away from the plant. The Plant capacity was soon enhanced to 1.7 MTPA in April, 1996 by putting up a separate Slag Grinding and Mixing Unit with latest cement-grinding technology.

In 2008, line calciner was commissioned to enhance clinker capacity to 1.87 MTPA. Further, the Cement capacity was enhanced to 2.17 MTPA by increasing the conversion ratio from clinker to Cement. In the year 2013, second

clinkerization unit (Brown Field Project) commissioned with a capacity of 3.3 MTPA capacity with clinker bulk loading facility.

Further, the company has enhanced its distribution network and entered in the western Orissa, North AP, UP and NE. The cement is delivered though rail & road network and OTIF delivery is ensured through ERP, SAP R/3 system. Visit of opinion leaders such as masons, builders, architects and engineers, students from different institutions is also organized from time to time.

The existing plant operation is spread over an area of in 388.37 Ha which includes the integrated unit, the colony area and other ancillary units. The existing project components of RWCW. Cement Mill 2.2 MTPA Captive Power Plant Line 1-25 MW & Line 2-30 MW Total 55 MW. Waste Heat Recovery System (WHRS) 15 MW .DG Sets (2 x 6 MW) 12 MW. Grid Power availability .Conveyor belts. RWCW Colony (within 388.27 ha land). Rawan Jhippan Lime stone mine 772.83 Ha. The plant has its own railway siding and is connected with the nearest Bhatapara railway station that will be used for new plant as well. However a separate railway siding inside the premise of RWCW would be laid down for the new plant. The RWCW premise is also connected with the national highway (NH-6 at ~70 km).

2.1 MINING AREA

The mining area -known as captive Rawan Jhippan Limestone Mines is spread across 722.834 Ha land. Existing captive mine is located less than half kilometre away from the plant area. New mining lease area (Guma Mines) 157.122 Ha.

Another factor is to maintain is the composition of different matters in blended raw material. Mines Function has two Departments: 1. Mines operation 2. Mines Maintenance Some highlighting features are as below: Total lease area – 722.834 Hectare Date of opening – 5.2.1994 Nominated Owner – Shri Rajeev Dubey , Director Agent – Shri V.D.Mali, Vice President ( Mines) Manager – Shri D. D. Chaturvedi, Manager (Mines) Excavated area – 128.8 Hectare Clinker Capacity/Year- 5 Million Tons ROM/Year- 7.5 Million Tonnes Topography- Flat with average elevation of 276 mRL Minable Reserve (proved)- 175 Million Tonnes Probable Reserves- 10.9 Million Tonnes .

Average ground level of 276m above MSL. Geology of the deposit indicates Grey & Chocolate Limestone with shale partings (belonging to Chhattisgarh Supergroup). Physio-Mechanical Properties of rock displays: AV. UNIAXIAL COMP STRENGTH: 80 - 100 MPa AV. TENSILE STRENGTH: 8 - 10 MPa.

3. About Cement

There are 8 major components of cement in % are - Lime(60-65) , Silica (17-25) , Alumina (3-8) , Magnesia (1-3) , Iron oxide (0.5-6) , Calcium Sulphate( 0.1-0.5) , Sulphur Trioxide (1-3) , Alkaline (0-1).

3.1 ROLE OF CEMENT IGREDIENTS

1. Lime - it is CaO or Ca (OH) 2 is required to form silicates and aluminates of calcium. Its deficiency reduces the strength of the cement and also causes the cement to set quickly. Excess leads to disintegration and expanding of the cement.

2. Silica- Silicon dioxide also known as silica (SiO2). It should be in sufficient amount to be present in cement to di-calcium silicate and tri-calcium silicate. Silica are responsible for mechanical properties of the cement (strength, etc). Maximum of 30% to be present in cement.3. Alumina- it is Aluminium oxide. Chemical formula is Al203.Alumina imparts quick setting property to cement. Its requisite quantity lowers the clinkers temperature (Reduction of M.P of cement) to avoid the liquid cement formation inside hot kiln. Excess of it weakens the cement.

4. Magnesia- Magnesium oxide (MgO). <2% in cement or it will reduce the strength of MgO. 5. Iron oxide - Chemical formula is Fe203. It imparts colour to cement and act as a flux. At high temperatures it combines with calcium and aluminate to form Tri-calcium aluminoferrite which gives strength and hardness to the cement. 6. Calcium sulphate- Chemical Formula is CaSO4 present in cement in form of gypsum (CaSO4.2H2O) to slower/retard the setting time of cement.

3.2 CATEGORY OF CEMENT BASED ON WATER

Upon the ability of cement to be used in presence of water it is categorized as hydraulic cement and non-hydraulic cement.1. Non-hydraulic cement- It will not set in wet conditions or underwater (hydration of any kind) but it sets as it dries and reacts with carbon dioxide in air or any other aggressive chemicals.

2. Hydraulic cement-This cement settles in wet or underwater conditions and protects material from chemical attack (e.g. Portland cement). It is a mixture of silicates and oxides with four major components-

Belite (2CaO.SiO2); C2S-25% Alite (3CaO.SiO2); C3S-50% (most important, gives strength) Aluminate(3CaO.Al2O3);C3A-10% Ferrite(4CaO.Al2O3.Fe2O3);C4AF-10% Gypsum(CaSO4.2H2O)-5%

Silicates are responsible for mechanical strength of cement whereas Aluminate and Ferrite are used as flux to prevent the formation of liquid cement inside kiln.

There are many types of cement but mainly used is Portland Pozzolona Cement (PPC) is used to prevent cracks and used in casting of large volumes of concrete. It is manufactured using flash ash after coal burning and the other is Ordinary Portland cement (OPC) which is referred as grey cement and used in ordinary constructions.Grading of cement is the stress (strength) cement can bear when hydrating. Usually it takes 28 days to measure the yield strength of the cement. E.g.:- 33, 43, 53 grade OPC (in MPa), IRST-40(53-S).

SN Name ofCompound

OxideComposition

Abbreviation Approx.Percentage

Function

1 Tri-calciumSilicate

3CaO.SiO2 C3 S 45-55% Mainly responsible forearly & later

strength2 Di-calcium

Silicate2CaO.SiO2 C2 S 20-30% Mainly

responsible for laterstrength (7 days and beyond)

3 Tri-calciumAluminate

3CaO.AI2O3 C3 A 6-10% C3A increases rate ofhydration of C3S. C3A givesflash set in absence ofgypsum

4 Tetra-calciumAluminoferrite

4CaO.AI2O3Fe2O3

C4AF 15-20% It hydrates rapidly but itscontribution to strength isuncertain and generally verylow.

4. Cement Production at Rawan

We are producing cement of four to five varieties with double kiln (Line-1 and Line-2) i.e. Ordinary Portland Cement (OPC) – 43, 53; Portland Pozzolana Cement (PPC) & Portland Slag Cement (PSC).

In our plant daily requirement of limestone is 4300 Tones, but due to some rejection percentage it is taken out 1.6 times more than what it is required. To acquire the desired value of LSF we mix or blend the raw limestone in different percentage.

Clinker production unit line 1- 1.87 MTPA & Line 2 – 3.3 MTPA total 5.17 MTPA.

5. Cement Manufacturing Process

5.1 MANUFACTURING

Portland Pozzolana Cement (the type of cement in common use today) is manufactured in a six step process:

Step 1 – Quarrying/Mining of LimestoneStep 2 – Raw material preparation & storageStep 3 – Fuel preparationStep 4 – Clinkering (Pyro section)Step 5 – Cement GrindingStep 6 – Packing & Dispatch

5.2 QUARRING/MINING OF LIMESTONE

Limestone mainly composed of CaO, MgO (<2%), Al2O3, Fe2O3, SiO2, etc.The raw material for manufacturing cement is limestone (about 95% which is rich in CaCO3) and 5% Laterite (source of Al2O3 and Fe2O3).

Cement manufacturing process starts from Mining of limestone (raw material of cement) which involves:-1. Core drilling (bores) holes to explore the mines means % LSF is decided by Raw Design i.e. % of High grade or Low grade limestone.

2. Drilling holes to fit explosives in them.

3. Blasting- Many explosives are available but cheap and efficient must be chosen. Mainly they are Slurry explosives (AN based) viz. power gel (Used in mines used by Rawan).

4 .Excavation and Haulage- Limestone is excavated in benches. The blasted limestone are then loaded with Hydraulic Excavators on to dumpers and then

transferred to crushers.

Total Mines area (Rawan – Jhippan Mines) = 722.834 Hectares

Efficient mining-For well blended-long term benefits to dig all the qualities of limestone so that future limestone will not be degraded. At Rawan, we mine considering long term benefits.

5.3 QUALITY CONSIDERATIONS

High Grade- CaO > 48%Cement Grade - CaO >46-47%Marginal Grade- CaO >44, < 46%Low Grade - CaO < 44%

5.4 Machines Used in Mining/Quarring

Drill Machine, Dumper, Excavators, Wheel Loaders.

6. RAW MEAL PREPARATIONS

It involves following steps:-

Crushing of Limestone. Stacking and Reclaiming of lime stone. Grinding of lime stone (VRMs/Roller Press). Storage of the Raw Meal (CF/CB Silo).

We use front acting linear stacking machine.First the limestone as mined will be fed to the crushing plant to be located in the lease area .Each crusher has some capacity in TPH.

At Rawan, we have two Crushers, one with single impact and another with double impact with 1000 and 1200 TPH capacity each.

• Crusher crushes the limestone (<1.6m) to size of less than 100mm and discharge the material onto belt conveyer to the process of scanning at Bulk material analyser (CBA). It scans the material moving on the conveyer belt through radiation emitted by Califorium (Cf252) and it gives online results of the composition of the limestone to which depends the quality of pile to be maintained.

• After crushing limestone <100 mm stones are send for stacking and reclaiming for homogenisation as we have to create a perfect composition cement. The material is stacked in longitudinal stockpiles.

• The material is then extracted transversely from stock piles by the reclaimers.

6.1 STORAGE OF RAW MATERIAL

Reclaimed limestone is sent to Raw Mill (VRM/Roller Press) for fine grinding. VRM has a separator which has the function to allow only fine particles to pass through it and it works properly only when the hot gas which uplift the finer particles is properly maintained by classifier.

Efficiency of VRM is high when output raw material is much finer than the feed. Accepted feed size is 2% of the roller diameter

6.2 VRMs AT A GLANCE

Vertical roller mills have been widely accepted for combined grinding and drying of moist raw materials in view of their excellent drying capacity and low energy consumption. Although the principle of the vertical roller mill did not change over the years, many improvements have been made in design of mill and other equipment in the grinding circuit resulting in less energy consumption and improved reliability. Introduction of external re-circulation of material, adjustable lower ring and modification of mill body to improve the air and material trajectories are examples of such design changes.

Features of VRM• Grinding• Drying• Transportation • Classifying• Flexibility in choosing raw materials and product yield

It is much energy efficient than ball mill.

At Rawan, we have one VRM (Loesche) for ‘Unit – 1’ and 3 numbers of Roller Press (KHD) for Unit – 2.

6.3 FACTORS THAT CAN EFFECT THE PROCESS OF GRINDING

Gas properties, Material Properties, Product Requirement, Site Condition, Mill Adjustments, Classifier Adjustments, and Process Control loop. These factors whether internal or external should be balanced to keep the desired composition.

6.4 BLENDING SILO

Gravity blending of raw materials coupled with on-line raw mix control has become the answer to reduced blending power consumptions. Using gravity blending innovations in technology for plant modifications can result in a power savings of up to 10 times the original system design.

Thus , Conversion of existing fluidized blend silos to a gravity method provides excellent opportunities for existing cement plant to reduce operating costs will maintaining it increasing the efficiency of the blending system.

7. FUEL PREPARATION

Types of Fuel used

• Indigenous coal

• Lignite coal

• Imported coal

• Pet Coke

• Combustible waste (Rice husk, chocolate, Maggi, Bamboo dust, etc.) and rubber tyres too.

Volatile Matter is the percentage loss in weight (minus the moisture) when sample is heated for seven minutes, out of contract with air, at 925c, under standard conditions. Higher the VM %, easier to grind that material as much matter will be lost in heating so naturally the strength would be less.

Pet coke is difficult to grind because of its low VM % value.

Ash % consideration is also very important because on burning ash form silica. So if we choose a low CaO % material then it will further decrease its conc. and our cement formed will be waste.

7.1 FACTORS THAT ARE IMPORTANT WHILE SELECTING A FUEL

• Availability of fuel in the bulk.

• Calorific value of the fuel.

• Cost of the fuel

• Easy handling of the fuel

• Quantity of the fuel

7.2 PROBLEMS FACED IN KILN WHILE USING PETKOKE• A coating is formed at inlet, smoke chambers and inner cyclones.• Rings of sulphates are formed.• If the combustion is improper, CO is emitted.• Hard clinker, if over-burning takes place.• Quality issues arises due to alteration in efficiency of Kiln.

7.3 WAYS TO COUNTER THESE PROBLEMS

• Usage of Air blasters at coating prone area for time to time removal of coatings.

• Routine cleaning of Kiln to maintain efficiency and quality.• Usage of advanced burners i.e. modified firing system.

8. CLINKERISATION (Pyro-processing)

The chemical reactions which take place during the process are called as clinkerization and product obtained is called clinker.

The process starts with the homogenization of raw material to get stable raw meal for best clinker quality. The raw material are delivered in bulk crushed and homogenised into a mixture which is fed into rotatory kiln. It revolves on larger roller bearings. This huge kiln is heated by a 1400c flame inside it.

The kiln is slightly inclined(around 4degree) to allow for the materials to slowly reach the other end, where quick cooling(100-200c) is required otherwise Alite(C3S) will convert directly to Belite(C2S). As the kiln revolves, the materials roll and slide downward for approx. 4hrs.

Basically, the raw material is fed in top of preheater tower and passes through a series of cyclones in the tower. Hot gas from the kiln and, often hot air from clinker cooler are blown through the cyclones. Heat is transferred efficiently from hot gases to the raw meal.

Before entering the kiln because of high surface area of meal particles, large temperature difference between hot gas and cooler meal, typically 30-40% of the meal is de-carbonated before entering the kiln.

Four basic oxides in the correct proportions make cement clinker; calcium oxide (65%), Silicon oxide (20%), alumina oxide (10%) and iron oxide (5%). These elements are mixed homogeneously (called 'raw meal' or slurry) will combine when heated by a flame at a temperature of approximately 1450c. New compounds are formed; silicates, aluminates and ferrites of calcium. Hydraulic hardening of cement is due to hydration of these compounds.

The final product of this phase is called 'clinker'. These solid grains are then stored in huge silos.

Net theoretical heat required for 1kg clinker is 420kcals. Here in Rawan Plant around 750kcals is consumed because of all above wastages. So, optimizations in heat flow is required especially hot air recirculation and efficiency of cyclones, preheater and crushers is to be improved.

In Rawan, to produce 1 ton of clinker approx. 1.6 ton of raw material is used.

All these wastage goes into CO2, ignited material (over burned), inefficiency of cyclone, etc.

8.1 PRE-HEATERPre- Heater at Line-1 is a setup of 3 strings, 6 stage each, used for preheating of raw mix coming from Blending Silo. Each stage is a cyclone connected with each other through riser duct. A cyclone is a conical vessel through which hot gas passes. The hot gas rises in such a way that it produces a vortex within the cyclone. The gas leaves the vessel from the top whereas the feed reaches to the bottom.

Raw mix is fed from top riser duct by bucket elevator. Meanwhile exchange of heat takes place between heated air and raw mix. The travel time of raw mix particle in preheater is 50-60sec. During this period of time raw mix is preheated from 75°C to 950-1000 °C, whereas the rising hot air is cooled from 1100 °C to 320 °C.

Line 1

System design capacity-clinker - 5600TPD

Total number of string - 3 no.No of pre calciners - 2 no.Height - 105m No of floor - 8PH exit gas temp. - 250-300CPH inlet gas temp. - 950-1000C

8.2 COOLING OF CLINKERS

There are many types of coolers but we consider only one i.e. Grate cooler.

The purpose of clinker cooler is to cool the clinker.

• From an engineering viewpoint, cooling is necessary to prevent damage to clinker handling equipment such as conveyors.

• From process and chemical point of view, it is beneficial to minimise clinker temperature as it enter the cement mill. As milling process generates heat so excessive mill temperatures are undesirable. So it’s better to have clinker cool before it enters the miller.

• From an experimental point of view and cost also, cooler reduces energy consumption by extracting heat from the clinker, enabling it (secondary heat) to be used again in pre-heater and kiln.

• From cement performance point of view, faster cooling of clinker enhances the silicate reactivity.

Heat Exchangers are used to facilitate easy transfer of heat.At Rawan, we use cross flow type heat exchangers.

9. CEMENT GRINDINGCement is finally produced by finely milling the clinker, which is the main component, as well as gypsum additives (fly ash, kiln slag, lime filter, etc).

The materials are added in precisely defined proportions, in keeping with the quality plan and relevant standards and specifications. In addition, heat dissipation can be improved by water injection. The properties of cement, such as its setting time and strength, are adjusted by the addition of gypsum and by grinding to specific degree of fineness.

The cement produced is usually transported by pneumatic or mechanical means and then stored in silos or horizontal stores.

9.1 DUST COLLECTING EQUIPMENTS

1. ESP (electrostatic precipitators) are used for gas cleaning in almost every section of cement manufacturer. ESP can be controlled or altered depending on particle size, temperature and applied voltage.

2. Bag House (filters):- Bag house or bag filter is the generic name of Air pollution control Equipment. It is designed to around the use of engineered fabric filter tubes, envelopes or cartridges in the dust capturing, separation or filtering process.

Cement industry use Bag filters and Bag houses for control of emissions in kilns and raw mill circuit, Coal mills and cement mill.

In Rawan, around 4% of the total raw material is collected in bag house as total gas used in plant comes here in the end.

10. PACKING AND DISPACHING

The final product which is cement is packed according to grade (like in Ultratech we have like UltraTech Premium/Super, etc.) is shipped either in bulk (ships, barges, tanker trucks, railroad cars, etc.) or in strong paper bags which are filled by machine.

11. REFERENCES

1. www.ultratechcement.com

2. www.cementkilns.com 3. www.civiltoday.com 4. www.adlbadiacement.com 5. www.wikipedia.com 6. Orientation slides7. Z Perry8. McCabe Smith