Final Report 7 Sem

1. INTRODUCTION OF THE COMPANY 

AMBUJA CEMENTS PRIVATE LIMITED (ACL) formerly known as The DLF Cement was acquired by M/s GACL in December, 1999 and had changed its name to Ambuja Cement Rajasthan Limited in April 2000.

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It was renamed as Ambuja Cements Limited (ACL) w.e.f. April 2007.

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ACL is currently owned by a Multi-Billion Switzerland based company LAFARGE.

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It has a total of 15 Units all over India in various states which are enlisted below: UNIT Ambuja Nagar Bhatapara-1 Bhatapara-2 Bhatinda Dadri Darldaghat Farakka Magdalla Maratha Nalagarh Rabriyawas Rauri Roorkee Ropar Sankrail

STATE Gujarat Chhattisgarh Chhattisgarh Punjab Uttar Pradesh Himachal Pradesh West Bengal Gujarat Maharashtra Himachal Pradesh Rajasthan Himachal Pradesh Utrakhand Punjab West Bengal

Table 1 – ACL Units in India 

Last year ACL sold approximately 1,451,322 Metric tonnes of Cement and 189,690 Metric Tonnes of Clinker.

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2. OVERVIEW OF THE PLANT  Ambuja Cement Plant (UNIT-RABRIYAWAS), is the only branch in Rajasthan of the ACL group.  It produces up to 1.8 MTPA of Ordinary Portland cement by dry Process and 3.6MTPA of Clinker.  The plant has an electrical load 34MVA per day.  Main machinery is supplied by FLSmidth Denmark and L & T.  The Plant is equipped with 6 MW DG set & 2 X 18 MVA TPP  The Plant has technical collaboration with Nihon Cement Japan and Electrical commissioning is done by AEG-NGEF.  Originally a 4200 TPD kiln and 1.4 million TPA OPC capacity project was conceived by M/s DLF Industries Limited, New Delhi in 1992 – commissioned in October, 1996.  The Kiln was upgraded to 6500 TPD in Aug 2007 by installation of new 6 stage SLC string.  ACL is a IMS based on ISO 9001: 2008, ISO 14001: 2004 & OHSAS 18001: 2007 certified by BVC. .  It has 100% self-generated Captive Power Plants.  There are Air Cooled Condensers installed in CPPs due to water deficit in the surrounding area.

MECHANICAL DEPARTMENT

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3. MANUFACTURING PROCESS

3.1 WHAT IS CEMENT? In the most general sense of the word, cement is a binder. A substance that sets and hardens independently, and can bind other materials together. Cement can be defined as an adhesive material consisting essentially of CaO, SiO2, Al2O3, Fe2O3, etc. & which sets & hardens when mixed with water under controlled conditions. SAFETY PRECAUTION- Bags of cement routinely have health and safety warnings printed on them because not only is cement highly alkaline, but the setting process is exothermic. As a result, wet cement is strongly caustic and can easily cause severe skin burns if not promptly washed off with water. Similarly, dry cement powder in contact with mucous membranes can cause severe eye or respiratory irritation. 3.2 HOW IS IT MADE?

Fig- 3.2 Flow Chart of Cement Manufacturing at ACL

MECHANICAL DEPARTMENT

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3.3 SOME AUXILIARY MACHINE’S USED There are certain auxiliary machines that are to be kept in mind to understand the process further easily and those are:     

ANTI FRICTION BEARINGS COUPLINGS GEAR BOXES CENTRIFUGAL FANS BAG HOUSES

3.3.1 ANTI FRICTION BEARINGS A device that allows two parts to rotate or move in contact with each other.

Fig-3.3.1 Bearing Configuration

Some useful Properties:  Self-aligned bearing.  Operating temperature less than 90 degree.  Grease for lubrication through grease gun. 3.3.2 COUPLINGS This is a mechanism in which power is transmitted from one shaft to another. Some useful Properties:  Hubs between two shafts should be parallel.  Grooves are to be completely packed with grease.  Indian oil servo gem2 is the lubricant used.

MECHANICAL DEPARTMENT

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3.3.3 GEAR BOXES A machine consisting of a power source and power transmission system which provides controlled application of power. Gear box have gear and gear train to provide speed and torque from a rotating power source to another device.

3.3.4 CENTRIFUGAL FANS A centrifugal fan (not to be confused with blowers) is a mechanical device for moving air or other gases with a big increase in pressure. These fans increase the speed of air stream with the rotating impellers or rotating blades.

Fig- 3.3.4 Outlook of a centrifugal fan at ACL They use the kinetic energy of the rotating blade to increase the pressure of the air/gas stream which in turn moves them against the resistance caused by ducts, dampers and other components. Centrifugal fans accelerate air radially. They are sturdy, quiet, reliable, and capable of operating over a wide range of conditions. The centrifugal fan is one of the most widely used fans as they are usually cheaper than axial fans and simpler in construction. The fan derives its energy from the power generated by the engine. It is used in transporting gas or materials and in ventilation system for buildings. The centrifugal fan uses the centrifugal power generated from the rotation of impellers to increase the pressure of air/gases. In cement industries these fans are used as    

ID (Induced draft) fans FD (Force draft) fans PA (Primary air) fans Cooling fans Pre-heater fans

MECHANICAL DEPARTMENT

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3.3.5 BAG HOUSES

Fig-3.3.5 Schematic representation of a bag house at ACL

A bag filter is a system used to enhance the quality of air released from industrial and commercial processes by collecting dust and other impurities from air or gas. A bag filter system consists of blower, dust filter, a filter-cleaning system and a dust receptacle or dust removal system. It is distinguished from air cleaners, which use disposable filters to remove dust. For the bag cleaning, reverse air method also called purging is used. Dirty air flows through the bag from inside, allowing the dust to collect on the interior surface. During cleaning, gas flow is restricted from a specific compartment. Without the flowing air, the bag relaxes. The cylindrical bag contains rings that prevent it from completely collapsing under the pressure of air. A fan blows air in the reverse direction. The relaxation and reverse air flow cause the dust cake to crumble and release into the hopper.

MECHANICAL DEPARTMENT

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3.4 MINING Limestone is the basic element of producing cement and is always found naturally under the earth and so it is extracted by mining. The Geography of Mining at ACL is:  Latitude – N26*15’ 30” To N26*18’45”  Longitude – E74* 06’ 44” To E74* 10’ 10”  Mines Attitude – 465 -370 MSL (mean sea level).  Total mining lease area – 803.425 Hecht.  Total reserves – 95.86 million tones (approx.)  Production – 12000MT/day At ACL opencast lime stone mining takes place. It refers to a method of extracting rock or minerals from the earth by their removal from an open pit or borrow. These mines are used when deposits of commercially useful minerals or rock are found near the surface. The amount or quality of limestone is predicted by a data mine software in which a spectral graph is developed. The curves obtained in this graph shows the required nature of limestone. Open-pit mines that produce building materials and dimension stone are commonly referred to as quarries. To start extracting lime stone from ground we should require an area where the limestone quantities are more with high carbonate and low SiO2. Mining can be carried out by Drilling and Blasting. In this, a deep hole is produced with a diameter of 4.5 inches. After the drilling is done 2/3 holes are filled with slurry explosives and Anfo (ammonium nitrate fuel oil). 1/3 part is stemmed with sand. After stemming detonators are fixed above the hole with detonating fuse and the blasting is done with the battery charge. During the blasting, bulk rocks are crushed in to small pieces which are easier to transport. It is a long process and safety measures should be kept in mind at all times. Some Safety measures to be kept in mind during Mining are:  Wet drilling should be done for preventing environmental pollution.  Working people should wear helmet and safety shoes during the work.  Stemming (filling of holes with hard material before the detonator is fitted) should be done properly.  Sirens should be sound before and after blasting.  During the blasting, working people should be atleast 500mts away from blasting area. After Blasting the blasted material is loaded in to dumpers with the help of excavators to transport lime stone to the crusher house.

MECHANICAL DEPARTMENT

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3.4.1 PRESENT STATUS OF MINING EQUIPMENTS AT ACL

Name of machinery

No. in use

Type

Capacity

Unit HP

Total H.P

PC-300

2

Back hoe

1.8 Cu.M

242

484

PC-300Rock Breaker

1

Back hoe

200T/Hour

242

242

PC-200

3

Back hoe

1.2 Cu.M.

128

384

Volvo LC290E

1

Back hoe

1.6 Cu.M.

205

205

Volvo LC240E

3

Back hoe

1.4 Cu.M.

195

585

Tipper

45

Articulate Dump

20 MT.

160

7200

Dozer

1

BD-50

---------

100

100

Dozer

1

D6H

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85

85

Atlas Roc 203 with XAH 186

2

DTH

115mm.dia

129

258

IR CM- 341

5

DTH

115mm.dia

178

890

Motor Grader

1

Volvo G930

----------

195

195

Soil Compactor

1

L&T 1107D

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Table- 3.4.1 Mining Equipment’s at ACL

MECHANICAL DEPARTMENT

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3.5 CRUSHING The limestone being extracted from the mines is dumped into a hopper surrounded by a thick metallic sheet through dumpers. The limestone is fed into the Wobbler through apron conveyer which is motor operated. The particles with a size of upto1 metre or more are sent to Lime Stone (L.S) Crusher where adequate size of material is obtained through impact type of crusher. This crushed material is now sent to Surge hopper for storage through belt conveyer. Bag filters are essentially setup wherever dust is produced to prevent its wastage. Now limestone from surge hopper is transferred to staking conveyer where large stockpile of 55,000 (approx.) tons is prepared by stacker and it is then reclaimed through reclaimer having metal blades with bucket type shapes. Considering the fact that crusher house is a vast section itself but few of its major components are as follows:  APRON CONVEYER  WOBBLER  IMPACT CRUSHER (PRIMARY)  STACKER  RECLAIMER 3.5.1 APRON CONVEYER: Apron feeders are designed for uniform and regulated feed of loose and lump materials from feed bin to crushing aggregates. It consists of specially fabricated frame on which two heavy duty endless link assemblies are wounded. Apron flights of steel are bolted on the chains and are used for conveying the material further. These link assemblies and the flights are supported and guided on top of the frame by deck rollers and are supported on return side by return rollers. The drive shaft has two sprocket assemblies that drive the apron. On the rare end of the apron conveyor is the tail wheel assembly for guiding the link assemblies. 3.5.2 WOBBLER:

Wobbler feeder being constant power machine has the highest efficiency in handling feed material with high moisture and clay content. Electrical wobbler shaft are placed on rugged designed steel fabricated frame in alternate vertical and horizontal positions to form wobbler’s bed. The wobbler has 12 shafts that rotate in the same direction with constant speed and gap of 80 mm between them. Feed material on the wobbler bed experiences tumbling motion because of its vertical and horizontal positions of shafts. Therefore oversize wobbles are fed to downstream crusher whereas the undersize slit through the gap in wobbler’s bed directly to the downstream belt conveyor.

MECHANICAL DEPARTMENT

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3.5.3 IMPACT CRUSHER: This is the most important part of any crusher house. The crusher impactor consists of impact arms which crushes the limestone. A rotor of an ‘S’ type is fitted at the centre of the impactor which are attached with blow bars at its circumference.

Fig- 3.5.3 Different components of impactor crusher

Bearings are provided to avoid vibrational stresses. These blow bars rotates with the rotor and when limestone comes between arms and rotor, due to that rotation of rotor L.S strikes the impactor arms and gets crushed. Size of the material should always be less than 75mm. Also couple of wear plates are used to prevent any wear and tear at rotor due to high impact when material enters in crusher. There also is a Vibrating screen or DSM (Dynamic screen manager) present whose function is to only pass the particles with size of not more than 12mm. The Impact crusher at ACL has the following specifications:     

Make: Type : Capacity: Motor: Size reduction:

MECHANICAL DEPARTMENT

L&T SINGLE ROTOR IMPACT CRUSHER 1200 TPH 1100KW @1000RPM 1.0m x 1.4m x 1.1m boulder to 25mm / 70-80 mm

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3.5.4 STACKER: At ACL a BS-Longitudinal Bridge Scraper Store stacker is used. A stacker is used to homogeneously stack piles of raw material. A Longitudinal Bridge Scraper is suitable for dry to moderately sticky materials with direct feed of free flowing materials whose storage capacity can easily be expanded. It uses the Chevron method to make piles. In this method material is deposited by the stacker moving to and fro over the center line of the pile. The Chevron stacking method causes segregation of the material with fine particles in the central part of the pile and coarse particles on the surface and the bottom of the pile.

Fig-3.5.4 BS Longitudinal Bridge Scrapper

The Longitudinal Bridge Scraper store, type BS, operates with two piles. One pile is stacked while the other is being reclaimed. A capacity of each pile covering 3½ to 7 days requirements is normally recommended for cement production. It can be operated by machine operation from operator cabin located on electrical platform. The Stacker at ACL has the following specifications:      

Design: FLS Make: L&T Purpose: Homogenization of crushed material in the form of pile. Type of pile: Longitudinal having length 200m and height 11m. Capacity of stacking pile: 60,000 tones per pile. Stacking capacity: Approx. 1000 TPH

MECHANICAL DEPARTMENT

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3.5.5 RECLAIMER: Reclaimer is another important equipment after Stacker as the stock pile generated by it is then reclaimed and sent further through reclaimer belt to the raw material hoppers.

Fig-3.5.5 Bridge Type Scrapper Reclaimer Reclaiming takes place from the face of a pile at the natural angle of material slide. The bridge runs on rails on either side of the stockpile. On the bridge a raking harrow system is mounted whose sweeping movements cause the material to slide to the pile base. To loosen sticky and non-free flowing materials active live-harrows are available. A scraper chain system conveys the material to the outgoing belt conveyor. Skew running is automatically compensated for. The system merely requires an operator when shunting from one pile to another. The reclaimer at ACL has the following Characteristics:       

Design: FLS Make: L&T Reclaiming capacity: 500 TPH Chain Speed: 0.5m/sec Rake inclination: 36° Rake speed approx: 0.1 to 0.3 m/sec Traveling speed: - During reclaiming: 0.05 to .005 m/min - During pile changing: 10 m/min

MECHANICAL DEPARTMENT

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3.6 RAW MILL Vertical roller mills are widely used for preparing kiln feed for the production of clinker. The purpose of the mill is to produce a homogenous material with an adequate chemical composition, proper fineness and with the correct particle size in order to fulfill the process needs. The VRM principle is shown in the figure below:

Fig-3.6 The VRM principle

There are two Raw Mills at ACL, The ATOX 40 and The ATOX 37.5, their respective specifications are given in the below table.

SPECIFICATION

ATOX 40

ATOX 37.5

Table Diameter

4m

3.75 m

Roller Diameter

2.4 m

3.55 m

Capacity

340 TPH

250 TPH

Drive

2200 kw

2000 kw

D.C

D.C

Separator Drive

Table- 3.6 Specification of the ATOX 40 and ATOX 37.5

MECHANICAL DEPARTMENT

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3.6.1 WORKING OF A RAW MILL In the vertical roller mill which is used for drying and grinding cement raw material. Conveyor belts take the raw material to the mill, the magnetic separator and a metal detector are located at the conveyor belt that transfers the material to the mill. Passing through a 2-way chute, the material is delivered to a mill via a rotary loch providing an air seal. If the metal detector responses, the 2-way chute is switched over directing the contaminating material to a waste receptacle. The material supplied to the mill is controlled by mill differential pressure.

Fig- 3.6.1 Flow Process of a VRM The material is ground to the required fineness in the mill and is dried simultaneously. Various drying gases (kiln gases and hot gases from hot gas generator) serve to dry the material. If possible the hot gases of kiln are always used for drying process, while the heat output of hot gas generator is adapted to suit the changing demands. The finished product is carried out of the classifier with the gas flow from which it is largely separated in battery of cyclones. The gas volume flow required for the grinding process is produced by a fan and is set by a regulating device. For taking any spillage material, the mill is equipped with an external material recirculation. Any material falling through the nozzle ring is covered by scrappers arranged below the grinding bowl through the reject chute, from there the material is returned to the mill feed by means of a conveyor belt and a bucket elevator. MECHANICAL DEPARTMENT

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3.6.2 PROCESS DATA OF RAW MILL

3.6.2.1 FEED MATERIAL  Surface moisture – 1% for design (max 5%)  Grain size – 0-125mm  Bulk density – 1.28 T/m3 3.6.2.2 FINISHED PRODUCT  Grinding capacity >= 550T/hr  Grinding fineness