Report on Cement manufacturing process

A Report on

Internship Taken At

DCM Shriram LimitedKota (Raj.)

Submitted in partial fulfillment of the requirement for the degree of Bachelor of Technology, Mechanical Engineering

Duration- June 5, 2015- July 20,2015Academic session – 2015-16

Submitted to

Mr. Sanjeev Mittal(GM-Cement, DCM)&HOD Dept. of mechanical Engineering.Career Point University, Kota

Submitted by:

Rohan SharmaB.Tech Mechanical(4th year)Career Point University. Kota

Index

S.No Title Page no.

1 Acknowledgement 2

2 Introduction 3

3 About DCM Shriram cement works 4

4 Cement 5

5 Crushing plant 7

6 Raw mill 12

7 Kiln section 18

8 Electrostatic precipitator 22

9 Clinker cooler and coal section 24

10 Cement mill 26

11 Packaging plant 28

12 Quality control 29

13 Conclusion 30

Acknowledgement Industrial Internship Training Report 2015-16 | 1

I am very grateful to Mr. Nigam Prakash (jt. VP HR), Mr. Sanjeev Mittal (GM-Cement) and Department of Mechanical Engineering, Career Point University, Kota for giving me this opportunity to undergo practical training in this esteemed organization. They took personal interest in my training and provided me all the necessary guidance, and required help.

My thanks to all staff members who supervised my work from time to time and helped me in understanding the entire cement manufacturing process and all other machinery. They were the key in teaching the complexities of whole system.

My special thanks to Mr.Ashish Mittal, Mr.S.C Sharma and Mr.Vidhyasagar for supporting me throughout the training in terms of guidance, motivation and all other essential spheres.

Industrial Internship Training Report 2015-16 | 2

Introduction

The origin of the DCM dates back to 1889, when Delhi Cloth & General Mills was established. Founded by Lala Sri Ram, DCM started its journey with the incorporation of a public limited Company on March 26, 1889 in the name and style of Delhi Cloth & General Mills Co. Limited under the provisions of Act VI of 1882. Over the years, the DCM Group became one of India's largest conglomerates. Consisting of a large number of Companies/Divisions, reputed for their product quality, dynamism and business integrity along with their quick response to changes in the environment. It expanded and diversified its activities into a number of manufacturing activities such as Textiles, Sugar, Chemicals, Rayon, Tyre Cord, Fertilizers, Information Technology and Engineering Products etc. The name of the Company was changed on October 6, 1983 to DCM Limited.

One of the main reasons for the Group's success is its focus on technology and quality. With the backing of its people, its technology and its alliances, the DCM Group is able to tackle any challenges that come its way.

World over, the 80's was the decade of diversification. However, the 90's were a time for consolidation and focusing on core business areas. The DCM Group, too, decided to move out of those business ventures, which did not fit, into its overall strategic vision. Its thrust is now on value-added products, on high technology sunrise industries.

The business of the Company was reorganized with effect from 1.4.1990 under a Scheme of Arrangement under section 391 / 394 of the Companies Act, 1956 approved by the shareholders, creditors and the financial institutions and sanctioned by the Honorable High Court of Delhi at New Delhi in 1990. Under the said reorganization, all units of the Company existing at that time stood vested and / or continued to vest in terms of the said Scheme into four separate companies namely,

DCM Limited DCM Shriram Industries Limited DCM Shriram Consolidated Limited Shriram Industrial Enterprises Limited


About DCM Shriram cement works

Shriram Cement is a unit of DCM Shriram Ltd.

SCW is a wet process cement plant based on calcium hydroxide sludge of sister calcium carbide plant, located in the same complex. SCW was commissioned in 1987 with the technical know-how from M/s. Lafarge Coppee Lavelin, France. Products of the plant are OPC-53 grade, Shriram Nirman (PPC) and Shriram Silver (PPC). Besides these products, trading of POP is also carried out. The plant is certified for ISO 9001, 14001 and OHSAS 18001 for its effective Quality, Environment, and Occupational Health and Safety Management Systems. It has also been awarded five star certificates by British Safety Council for its effective safety systems.Installed capacity of SCW is 4.0-lakh tons cement per annum.

Shriram cement is known for high quality for last several years. Following are the major special properties:

Cement manufactured by SCW is marketed under the "Shriram" brand. Shriram cement has created for itself strong brand equity, enjoying a premium

over competitor brands, and is recognized as a market leader in its areas of distribution.

Shriram Cement is available in three different varieties, Shriram 53, Shriram Nirman and Shriram Silver. Shriram Silver is specialty cement, which is used for mosaic floor and grit wash.

Shriram market Plaster of Paris under the brand name Shriram Nirman POP, which is a cosmetic product, used for finishing of walls and making cornices and molding and different designs of fall ceiling.

Cement Industrial Internship Training Report 2015-16 | 4

Cement is a binder, a substance that sets and hardens and can bind other materials together. Cement is essentially a binding material used for making concrete, which in turn the basic material for building dams, bridges and other construction works. Cement has an exceptional strength under compressive loads and also it can take any shape.

Types of cement Ordinary Portland cement (OPC) Portland pozzolona cement (PPC) Sulphate resisting cement Rapid hardening cement Oil well cement Masonry cement Portland blast furnace slag cement Super Sulphate cement High alumina cement White grade cement Quick setting cement Hydrophobic cement Silver grade cement

In DCM Shriram cement works three types of Cement is manufactured: Ordinary Portland cement Portland pozzolona cement Silver grade cement

There are three processes of manufacturing cement which are known as the wet, dry, and semidry processes and are so termed when the raw materials are ground wet and fed to the kiln as a slurry, ground dry and fed as a dry powder, or ground dry and then moistened to form manufacturing of cement.

In DCM Shriram cement works cement is manufactured via wet process.

The manufacture of cement is a very carefully regulated process comprising the following stages:

1. Quarrying - a mixture of limestone and clay.2. Grinding - the limestone and clay with water to form slurry.3. Burning - the slurry to a very high temperature in a kiln, to produce clinker.4. Grinding - the clinker with about 5% gypsum to make cement.

Raw Materials Extraction

The limestone and clay occur together in quarries. It is necessary to drill and blast these materials before they are loaded in trucks. The quarry trucks deliver the raw materials to the crusher where the rock is crushed to smaller than 12mm. The raw materials are then stored ready for use.

Raw Materials Preparation


About 80% moisture contained slurry comes from carbide plant and acetylene plant, which is the by-product of those plants. Adjusting the relative amount of limestone and clay being used very carefully controls the chemical composition of the slurry. The slurry is stored in large basins ready for use known as decanter and DP tanks and then further fined by raw mill.

Clinker Burning

The slurry is fed into the upper end of a rotary kiln, while at the lower end of the kiln; a very intense flame is maintained by blowing in finely ground coal. The slurry slowly moves down the kiln and is dried and heated until it reaches a temperature of almost 1500 degrees Celsius producing "clinker". This temperature completely changes the limestone and clay to produce new minerals, which have the property of reacting with water to form a cementitious binder. The hot clinker is used to preheat the air for burning the coal, and the cooled clinker is stored ready for use.

Cement Milling

The clinker is finely ground with about 5% gypsum in another mill, producing cement. (The gypsum regulates the early setting characteristic of cement). The finished cement is stored in silos then carted to our wharf or packing plant facilities.

Figure 1: Process layout of cement manufacturing

Crushing Plant


The crushing plant receives limestone from mines and in two stages operation crushes it into size of 12mm. there are two crushers, primary crusher of L&T (double toggle jaw crusher) and secondary crusher of Economer (Hammer crusher). Crushers have capacity of 100 ton per hour and are driven by 132 KW motors. The crushed limestone is stored in yard of 2 miles.

Equipments and their Flow Diagram:

Figure 2: Process layout of crushing plant

Unloading hopper:

Industrial Internship Training Report 2015-16 |

Stacker system

C-4 Conveyer

Vibrating screen

C-3 Conveyer

Hammer Mill

vibro feeder

Intermideate hopper

C-2 Conveyer

C-1 Conveyer

Jaw Crusher

Apron feeder

Unloading Hopper

7

The limestone from Bundi and Ramganjmandi comes into plant in loaded trucks and is unloaded here in the chambers having rectangular sections .The capacity of Unloading Hopper is 60 Metric ton.

Apron feeder:

Apron feeders were designed for uniform and regulated feed of loose and lump materials from feed bin to crushing aggregates and transporters of different types. The transporting cloth of apron feeders is a closed circuit, consisting of plates, which are connected hingedly. The productivity of feeders is regulated at the expense of cloth speed changing and size of bin outlet. The transporting cloth is activated with drive sprocket; direction and chain supporting are implemented with the shaped rolls. To regulate the cloth tension the screw mechanism of back sprocket movement is used. The capacity of Apron feeder is 150 tons per hour.

Figure 3: Apron feeder

Jaw Crusher:


Jaw crusher is also named jaw breakers, rock crusher, or rock breaker. Jaw crusher is mainly used to primarily and secondarily crush many kinds of mining rocks, and the highest anti-pressure strength of crushed material is 320Mpa.

Features of Jaw Crusher:

Simple structure, reliable working condition, easy maintenance, low operating costs;

High crushing ratio, even final particle size products; Deep broken cavity, no dead zone, increased capacity; Safe and reliable lubrication system, convenient replacement parts; Stand-alone energy-saving 15% ~ 30%; The discharging size of jaw crusher can be adjusted to meet the users' different

requirements.

Structure of Jaw Crusher:

The structure of jaw crusher: main frame, eccentric shaft, a large belt pulley, fly wheel, swing jaw, side guard plate, toggle plate, Rear bracket, adjust gap screw, reset spring, and fixed jaw and swing jaw board etc., and the toggle plate also plays a role of protection. The length of toggle is 898 mm (movable jaw) and 790 mm (fixed jaw).

Figure 4:Jaw crusher

Working Principle of Jaw Crusher:


The motor drives the movable jaw plate to do periodic motion towards the fixed jaw plate by the eccentric shaft.

The angle between toggle plate and movable jaw plate increases when movable jaw plate moves. So the movable jaw plate moves towards the fixed jaw plate.

The material between the movable jaw plate and fixed jaw plate will be crushed in this process. The angle between toggle plate and movable jaw plate decreases when

Movable jaw plate moves down, the movable jaw plate move leaves fixed jaw plate by pulling rod and spring, the final crushed material will be discharged from the outlet.

The capacity of Jaw Crusher is 130 tons per hour

Hammer crusher:

Hammer crusher is a kind of machine widely used in crushing medium hardness materials such as Limestone, slag, coke and coal in Cement, chemical industry, electric power, metallurgy, etc. Hammer crusher broken materials mainly rely on impact. The crushing process is roughly like this, materials into the hammer crusher, and broken by the impact of high-speed rotary hammerhead. Then the broken materials obtained kinetic energy from the hammerhead and rushed to frame and screen with high speed.

Figure 5

The materials collisions with each other at the same time, after repeatedly broken, the materials less than sieve article eduction from the gap. Individual larger materials


impact by the hammerhead again, grinding, extrusion and broken. At last, deduction from the gap. Thus obtaining products with required size. It is made by manganese steel.

Working principle

The main working part of the Crusher is the rotor with hammer rings. The rotor is consisted of hammer ring shaft and the ring hammer, etc. The rotor driven by motor rotates at a high speed in the crushing chamber. The materials are conveyed into the chamber from the top inlet, then impact by the high-speed rotating hammer ring, thus crashed, squeezed ground among the materials and finally achieved the goal of crushing. At the bottom of the rotor, there are grate plate equipped, the crushed materials which smaller than the grate hole size can be discharged through the grate plate, while the larger ones will be crushed by the hammer ring till the required size and be discharged.

The capacity of Hammer mill is 130 tons per hour.

Vibrating screen or DSM screen

The function of DSM (Dynamic screen manager) screen is to only pass the particles with size of not more than 12mm. It consists of vibration damper of 6-12 mm. The rejected particles are again feed into crusher and the remaining is sent to the yard via belts. Before coming to screen the particles are moved below the magnetic separator so that all particles with magnetic properties shall be kept aside from the process. After the screen there is placed a dust collector.

Raw material handling section

The stored limestone is reclaimed is from yard by the help of reclaimer. This equipment is supplied by space age limited. Its capacity is 100 ton per hour. The reclaimer shaves one side of the pile in such manner that further blending of Limestone occurs. The reclaimed limestone is conveyed to the raw mill through belts.

Figure 6: Reclaimer & Stacker

Raw Mill


A Raw mill section used to grind raw materials into " rawmix" during the manufacture of cement. Rawmix is then fed to a cement kiln, which transforms it intoClinker, which is then ground to make cement in the cement mill. The raw milling stage of the process effectively defines the chemistry (and therefore physical properties) of the finished cement, and has a large effect upon the efficiency of the whole manufacturing process.

Figure 7: Raw Mill


Figure 8: process layout of Raw Mill

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slurry from carbide plant

decanter

DP Tank 1 DP Tank 2

Drum Filters

Raw mill

DSM Screen

Slurry mixer tank

feeder

crushed limestone from crushing plant

13

Decanter and DP Tank

Calcium hydroxide sludge available from acetylene plant is pumped into the decanter. The decanter is a large tank with a diameter of 25 m .it is operated on recirculation till sludge of 68% - 69% moisture is reached in the outlet. The decanter sludge is than pumped into DP Tank (Daily precipitation tank). There are two such tanks having capacity of 600 m3/hour. Here, sludge is continuously agitated to that sludge doesn’t solidify. From decanter, sludge is also sent to lagoons where it is naturally decanted over the years before cement plant inception. Mechanical shovel and dumpers do this. The pumping capacity of DP Tank is 65m3/hour.it pumps the sludge to the feeder on the top of the Raw mill building.

Figure 9: DP Tanks

Figure 10: Decanter


Feeder

The feeder is a ferries wheel driven by a variable DC drive. There are three hoppers in a raw mill building .one for the limestone received from the yard after proper blending, second for high grade limestone used sometimes to improve the limestone content to the burn ability or melting characteristics of raw mix the clinkerization section.

Raw mill

Layout

A Raw/Ball mill is a horizontal cylinder partly filled with steel balls (or occasionally other shapes) that rotates on its axis, imparting a tumbling and cascading action to the balls. Material fed through the mill is crushed by impact and ground by attrition between the balls. The grinding media are usually made of high-chromium steel. The smaller grades are occasionally cylindrical ("pebs") rather than spherical. There exists a speed of rotation (the "critical speed") at which the contents of the mill would simply ride over the roof of the mill due to centrifugal action. The critical speed (rpm) is given by: nC = 42.29/√ d, where d is the internal diameter in meters. Ball mills are normally operated at around 75% of critical speed, so a mill with diameter 5 meters will turn at around 14 rpm.

The mill is usually divided into at least two chambers,(Depends upon feed input size presently mill installed with Roller Press are mostly single chambered), allowing the use of different sizes of grinding media. Large balls are used at the inlet, to crush clinker nodules or limestone (which can be over 25 mm in diameter). Ball diameter here is in the range 60–80 mm. In a two-chamber mill, the media in the second chamber are typically in the range 15–40 mm, although media down to 5 mm are sometimes encountered. As a general rule, the size of media has to match the size of material being ground: large media can't produce the ultra-fine particles required in the finished cement, but small media can't break large clinker particles.

A current of air is passed through the mill. This helps keep the mill cool, and sweeps out evaporated moisture, which would otherwise cause hydration and disrupt material flow. The dusty exhaust air is cleaned, usually with bag filters.

Figure 11: Layout of Mill


Specification

A Raw mill is driven by 750 KW motor that rotates the mill at 17 rpm. The length of mill is 13 m and diameter is 2.25 m. Both the compartments of mill are filled with grinding media apart from sludge and limestone.in first compartment high steel balls are put which are responsible for coarse grinding.

First chamber is filled in accordance with following data:

Size of ball (in mm) % In tank

90 380 870 860 9

The second compartment contains balls of high chromium steel, which are responsible for grinding limestone and iron. About 36 % of compartment is filled with these balls.

Second chamber is filled in accordance with following data:

Size of balls (in mm) % In tank

50 20

40 10

30 6

A circular section called diphagram, which is having 12 small screens at different periphery, separates both the compartments. Molasses is also added in raw mill .it is required to increase the slow ability of the raw mix at low moisture.

DSM Screen

The raw mill outlet slurry goes to war man pump, which pumps the slurry to DSM Screen. Here the fine particles passé through the drum filters and goes to slurry mixer. The coarse particle goes back to the mill to further grinding.

Slurry mixer tank

The slurry mixer is 12.5 m diameter tanks having arms on which air nozzles are fixed. Compressed air through these nozzles about 1.5 kg/cm3 agitates the slurry and prevents it from becoming solid. From here the slurry is feed into kiln by slurry pumps. Industrial Internship Training Report 2015-16 | 16

Figure 12: DSM Screen Figure 13: Slurry mixer tank


Kiln SectionA Rotary kiln is a pyro processing device used to raise materials to a high temperature (calcination) in a continuous process. The basic components of a rotary kiln are the shell, the refractory lining, support Tyres and rollers, drive gear and internal heat exchangers.

Figure 14: Kiln

Kiln Shell

This is made from rolled mild steel plate, usually between 15 and 30 mm thick, welded to form a cylinder, which may be up to 230 m in length and up to 6 m in diameter. This will be usually situated on an east/west axis to prevent eddy currents. Upper limits on diameter are set by the tendency of the shell to deform under its own weight to an oval cross section, with consequent flexure during rotation. Length is not necessarily limited, but it becomes difficult to cope with changes in length on heating and cooling (typically around 0.1 to 0.5% of the length) if the kiln is very long.

Refractory Lining

The purpose of the refractory lining is to insulate the steel shell from the high temperatures inside the kiln, and to protect it from the corrosive properties of the process material. It may consist of refractory bricks or cast refractory concrete, or may be absent in zones of the kiln that are below around 250°C. The refractory selected depends upon the temperature inside the kiln and the chemical nature of the material being processed. In cement, maintaining a coating of the processed material on the refractory surface prolongs the refractory life. The thickness of the lining is generally in the range 80 to 300 mm. A typical refractory will be capable of


maintaining a temperature drop of 1000°C or more between its hot and cold faces. The shell temperature needs to be maintained below around 350°C in order to protect the steel from damage, and continuous infrared scanners are used to give early warning of "hot-spots" indicative of refractory failure.

Tyres and Rollers

Tyres, sometimes called riding rings, usually consist of a single annular steel casting, machined to a smooth cylindrical surface, which attach loosely to the kiln shell through a variety of "chair" arrangements. These require some ingenuity of design, since the Tyre must fit the shell snugly, but also allow thermal movement. The Tyre rides on pairs of steel rollers, also machined to a smooth cylindrical surface, and set about half a kiln-diameter apart. The rollers must support the kiln, and allow rotation that is as nearly frictionless as possible. A well-engineered kiln, when the power is cut off, will swing pendulum-like many times before coming to rest. The mass of a typical 6 x 60 m kiln, including refractories and feed, is around 1100 tones, and would be carried on three Tyres and sets of rollers, spaced along the length of the kiln. The longest kilns may have 8 sets of rollers, while very short kilns may have only two. Kilns usually rotate at 0.5 to 2 rpm, but sometimes as fast as 5 rpm. The Kilns of most modern cement plants are running at 4 to 5 rpm. The bearings of the rollers must be capable of withstanding the large static and live loads involved, and must be carefully protected from the heat of the kiln and the ingress of dust. In addition to support rollers, there are usually upper and lower "retaining (or thrust) rollers" bearing against the side of Tyres, that prevent the kiln from slipping off the support rollers.

Figure 15: Tyres & Rollers Figure 16: Refractory Lining

Drive Gear

The kiln is usually turned by means of a single Girth Gear surrounding a cooler part of the kiln tube, but sometimes driven rollers turn it. The gear is connected through a gear train to a variable-speed electric motor. This must have high starting torque in order to start the kiln with a large eccentric load. A 6 x 60 m kiln requires around 800 kW to turn at 3 rpm. The speed of material flow through the kiln is proportional to rotation speed, and so a variable speed drive is needed in order to control this. When driving through rollers, hydraulic drives may be used. These have the advantage of developing extremely high torque. In many processes, it is dangerous to allow a hot kiln to stand still if the drive power fails. Temperature differences between the top


and bottom of the kiln may cause the kiln to warp, and refractory is damaged. It is therefore normal to provide an auxiliary drive for use during power cuts. This may be a small electric motor with an independent power supply, or a diesel engine. This turns the kiln very slowly, but enough to prevent damage.

Internal heat exchangers

Heat exchange in a rotary kiln may be by conduction, convection and radiation, in descending order of efficiency. In low-temperature processes, and in the cooler parts of long kilns lacking preheaters, the kiln is often furnished with internal heat exchangers to encourage heat exchange between the gas and the feed. These may consist of scoops or "lifters" that cascade the feed through the gas stream, or may be metallic inserts that heat up in the upper part of the kiln, and impart the heat to the feed as they dip below the feed surface as the kiln rotates. The latter are favored where lifters would cause excessive dust pick-up. The most common heat exchanger consists of chains hanging in curtains across the gas stream.

Other equipment

The kiln connects with a material exit hood at the lower end and to ducts for waste gases. This requires gas-tight seals at either end of the kiln. The exhaust gas may go to waste, or may enter a preheater which further exchanges heat with the entering feed. The gases must be drawn through the kiln, and the preheater if fitted, by a fan situated at the exhaust end. In preheater installations, which may have a high pressure-drop, a lot of fan power may be needed, and the fan is often then largest drive in the kiln system. Exhaust gases contain dust and there may be undesirable constituents such as sulfur dioxide or hydrogen chloride. Equipment is installed to scrub these out before the exhaust gases pass to atmosphere, called ESP.

Thermal efficiency

The thermal efficiency of the rotary kiln is about 50-65%.

Principle of Operation

The kiln is a cylindrical vessel, inclined slightly to the horizontal, which is rotated slowly about its axis. The material to be processed is fed into the upper end of the cylinder. As the kiln rotates, material gradually moves down towards the lower end, and may undergo a certain amount of stirring and mixing. Hot gases pass along the kiln, sometimes in the same direction as the process material (co-current), but usually in the opposite direction (counter-current). The hot gases may be generated in an external furnace, or may be generated by a flame inside the kiln. Such a flame is projected from a burner-pipe (or "firing pipe"), which acts like a large Bunsen burner. The fuel for this may be gas, oil, pulverized petroleum coke or pulverized coal.

Here, at DCM SCW the kiln is 120 m long, it has a diameter of 3.75 m. it is longer than usual because it’s a wet process and additional chain zone required to bring the moisture down. The chain zone is about 23.75 m in length. The speed of kiln is varied


by a D.C drive. Kiln is coal fired and the flue gases travel up the kiln. These flue gases then passes through the ESP (electrostatic precipitator) where dust is collected and cleaned flue gases are pulled out of the system by an I.D fan which is again driven by a variable speed motor. The dust is again put into the decanter from where it goes again to the normal procedures of raw preparation

As the raw mix travel down the kiln it follows the helical path from chain zone. After chain zone comes the preheating zone where the raw mix components are heated up to the calcination temperature. A calcination zone where the raw mix gets calcinated follows this. CO2 released .the calcination zone terminates into burning zone where heat released through coal burning melt the oxide an bring them to react to clinker .the fine coal, which is used to create the flame is provided by coal mill. The length and temperature of various zone in kiln vary with the firing rate, feed rate and the I.D fan speed .the burning zone temperature is 1250°C-1400°C

Different reactions at different temperatures are given below in table:

Temperatures Reactions

180c Evaporation of water

500c and above Evolution of combined gases

900c and above Clinkerization and dehydration

1200c Production of clay and production of CO2

1200c and above Reaction between clay and lime and thus forms the cement compound

Electrostatic precipitator (ESP)


An electrostatic precipitator (ESP) is a filtration device that removes fine particles, like dust and smoke, from a flowing gas using the force of an induced electrostatic charge minimally impeding the flow of gases through the unit. In contrast to wet scrubbers, which apply energy directly to the flowing fluid medium, an ESP applies energy only to the particulate matter being collected and therefore is very efficient in its consumption of energy (in the form of electricity).

The most basic precipitator contains a row of thin vertical wires, and followed by a stack of large flat metal plates oriented vertically, with the plates typically spaced about 1 cm to 18 cm apart, depending on the application. The air or gas stream flows horizontally through the spaces between the wires, and then passes through the stack of plates. A negative voltage of several thousand volts is applied between wire and plate. If the applied voltage is high enough, an electric corona discharge ionizes the gas around the electrodes. Negative ions flow to the plates and charge the gas-flow particles. The ionized particles, following the negative electric field created by the power supply, move to the grounded plates. Particles build up on the collection plates and form a layer. The layer does not collapse, thanks to electrostatic pressure (due to layer resistivity, electric field, and current flowing in the collected layer).

Figure 17: Working of ESP

Collection efficiency

Precipitator performance is very sensitive to two particulate properties:


1) Electrical resistivity; and 2) Particle size distribution.

These properties can be measured economically and accurately in the laboratory, using standard tests. Resistivity can be determined as a function of temperature in accordance with IEEE Standard 548. This test is conducted in an air environment containing a specified moisture concentration. The test is run as a function of ascending or descending temperature, or both. Data is acquired using an average ash layer [further explanation needed] electric field of 4 kV/cm. Since relatively low applied voltage is used and no sulfuric acid vapor is present in the test environment, the values obtained indicate the maximum ash resistivity.

In an ESP, where particle charging and discharging are key functions, resistivity is an important factor that significantly affects collection efficiency. While resistivity is an important phenomenon in the inter-electrode region where most particle charging takes place, it has a particularly important effect on the dust layer at the collection electrode where discharging occurs. Particles that exhibit high resistivity are difficult to charge. But once charged, they do not readily give up their acquired charge on arrival at the collection electrode. On the other hand, particles with low resistivity easily become charged and readily release their charge to the grounded collection plate. Both extremes in resistivity impede the efficient functioning of ESPs. ESPs work best under normal resistivity conditions.

Advantages of ESP

High collection efficiency. Low resistance path for gas flow Treatment of large amount of gases and at high temperature Ability of coping with corrosive atmosphere


Clinker cooler and coal section

The clinker due to rotary of the kiln gets discharged into the grate cooler where clinker is cooled. There are four sections of grate cooler. in first section ,moving clinker bed is cooled with the fresh air is forced through the grate cooler fan no.1 . In second and third section, the clinker is cooled with the help of circulation air through fan no. 2&3. Finally the cooled clinker is about 100c. This is then feed into VSI crusher where it is broken into small pieces. From here small pieces are fed into the drag chain, which fall onto the deep where it is stored into the cement silos.

VSI (Vertical shaft impact) crusher:

VSI crushers use a different approach involving a high-speed rotor with wear resistant tips and a crushing chamber designed to 'throw' the rock against. The VSI crushers utilize velocity rather than surface force as the predominant force to break clinker. Applying surface force (pressure) results in unpredictable and typically non-cubical resulting particles. Utilizing velocity rather than surface force allows the breaking force to be applied evenly both across the surface of the clinker.

VSI crushers generally utilize a high speed-spinning rotor at the center of the crushing chamber and an outer impact surface of either abrasive resistant metal anvils or crushed rock. Utilizing cast metal surfaces 'anvils' is traditionally referred to as a "Shoe and Anvil VSI".

Figure 18:VSI

Cement Silos

Cement silos are on-site storage containers used for the storage and distribution of various types of cement mixtures. A cement silo can be a permanent structure, or a portable model that can be relocated when necessary. The cement silo usually is


equipped with some type of blower to help expel the stored contents into a truck or other receptacle.

A cement storage silo can be structured to hold no more than a few tons of dry cement products, or be designed to efficiently hold several hundred tons. Generally, larger silos are permanent structures that cannot be moved. It is used, where the finished product is stored until it is time for shipment. Many building sites that utilize concrete in the construction process opt for portable cement silos that can be moved around the site as the need arises.

It is not unusual for construction companies to keep several portable cement silos available for different building projects. These simple storage devices can usually be set up in a matter of hours, and then dismantled once the project is complete. Storage of the portable cement silo is relatively easy, since the components can be stored in aWarehouse until the device is needed at another building site.

Both the permanent and the portable cement silo are usually equipped with some type of blower. The blower makes it easier to expel the product from the silo. Blowers are often driven by electricity, although there are models that rely on propane or even gasoline. Blower equipment with the portable silos takes very little time to set up, and can also be stored easily when not in use.

It is important to note that the materials and the design of a cement silo will vary, depending on the type of cement product that is to be stored in the facility. Not all types of building materials are conducive to keeping all of the various components that go into cement blends from caking or absorbing moisture. For example, a silo that is structured to protect the integrity of soda ash may not work as well with lime. Along with the ingredients of the concrete, the configuration of the cement silo will be slightly different for products that are identified as high performance concrete or self-compacting concrete.

There are two cement silos, one for POC and other one for PPC and one steel silo for steel grade cement. The cement silos have a capacity of 3500 metric ton each and steel silo is having 700 metric ton capacity.

Figure 19: Silo


Cement millA cement mill is the equipment used to grind the hard, nodular clinker from the cement kiln into the fine grey powder that is cement. Most cement is currently ground in ball mills and also vertical roller mills, which are more effective than ball mills.

Clinker from the silos is extracted from the bottom through three vibro feeders installed in each silos. The clinker belt with a constant speed feed the clinker into cement mill.

For OPC, gypsum is added and for PPC, pozzolona is added. The feeding of cement mill is done through weight feeder. Gypsum from yard is fed into a hopper through a conveyer belt into pozzolona bins by diverting the material with the help of hydraulically operated diverter. Here, the ball mill is filled with grinding media varying from 100mm-150mm sizes in first chamber and in second compartment cylindrical pebbles clypeus of 20mm-25mm.

Materials ground

Portland clinker is the main constituent of most cement. In Portland cement, a little calcium sulfate (typically 3-10%) is added in order to retard the hydration of tricalcium aluminate. The calcium sulfate may consist of natural gypsum, anhydrite, or synthetic wastes such as flue-gas desulfurization gypsum. In addition, up to 5% calcium carbonate and up to 1% of other minerals may be added.

It is normal to add a certain amount of water, and small quantities of organic grinding aids and performance enhancers. "Blended cements" and Masonry cements may include large additions (up to 40%) of natural pozzolans, fly ash, limestone, silica fume or metakaolin. Blast furnace slag cement may include up to 70% ground granulated blast furnace slag.

Gypsum and calcium carbonate are relatively soft minerals, and rapidly grind to ultra-fine particles. Grinding aids are typically chemicals added at a rate of 0.01-0.03% that coat the newly formed surfaces of broken mineral particles and prevent re-agglomeration. They include 1,2-propanediol, acetic acid, triethanolamine and lignosulfonates.

Temperature control

Heat generated in the grinding process causes gypsum (CaSO4 .2H 2O) to lose water, forming bassanite (CaSO4 .0.2-0.7H 2 O) or γ-anhydrite (CaSO4. ~0.05H2O). The latter minerals are rapidly soluble, and about 2% of these in cement is needed to control tricalcium aluminate hydration. If more than this amount forms, crystallization of gypsum on their re-hydration causes "false set" - a sudden thickening of the cement mix a few minutes after mixing, which thins out on re-mixing.

High milling temperature causes this. On the other hand, if milling temperature is too low, insufficient rapidly soluble sulfate is available and this causes "flash set" - an


irreversible stiffening of the mix. Obtaining the optimum amount of rapidly soluble sulfate requires milling with a mill exit temperature within a few degrees of 115 °C. Where the milling system is too hot, some manufacturers use 2.5% gypsum and the remaining calcium sulfate as natural α-anhydrite (CaSO4).

Complete dehydration of this mixture yields the optimum 2% γ-anhydrite. In the case of some efficient modern mills, insufficient heat is generated. This is corrected by recirculating part of the hot exhaust air to the mill inlet.


Packaging plant

Packing of cement is done by L&T rotatory packing machine .the cement is extracted from the selected silos and through slides; cement is taken into bucket elevator and subsequently to the hopper just above the packer. There are two packing machines for the emergency case.

Rotatory packing machine is packing machine developed against influence of cement impurities in open circuit mill on packing. it has overcome the problems such as poor measurement and serious ash leakage of shutter in mechanized kiln for controlling ash discharge .it completes the procedures of ash discharge and stopping through using electromagnetic valves and air cylinder to control the loosening and closing of rubber hose ,and thereby reduces the maintenance cost and thoroughly solve the problem of large packing dust.

It is a impeller filling machine, with stable performance, easy operation, reasonable structure and convenient maintenance .it can realize the packing of cement without need of pneumatic components .it thoroughly solves the problem of ash leakage and extruding gate plate. Its outstanding advantage are energy saving and environment protection. Replacement rate of spare is remarkably reduced. Maintenance cost is also reduced. Therefore, it is widely accepted by vast users.

Figure 20: Packaging Machine


Quality control

There is a laboratory setup to continuously monitor the quality of cement, parameters of, which are defined as under:

In addition to control of temperature (mentioned above), the main requirement is to obtain a consistent fineness of the product. From the earliest times, fineness was measured by sieving the cement. As cements have become finer, the use of sieves is less applicable, but the amount retained on a 45-μm sieve is still measured, usually by air-jet sieving or wet sieving. The amount passing this sieve (typically 95% in modern general-purpose cements) is related to the overall strength-development potential of the cement, because the larger particles are essentially unreactive.

The main measure of fineness today is specific surface. Because cement particles react with water at their surface, the specific surface area is directly related to the cement's initial reactivity. By adjusting the fineness of grind, the manufacture can produce a range of products from a single clinker. Tight control of fineness is necessary in order to obtain cement with the desired consistent day-to-day performance, so round-the-clock measurements are made on the cement as it is produced, and mill feed-rates and separator settings are adjusted to maintain constant specific surface.

A more comprehensive picture of fineness is given by particle size analysis, yielding a measure of the amount of each size range present, from sub-micrometer upwards. This used to be mainly a research tool, but with the advent of cheap, industrialized laser-diffraction analyzers, its use for routine control is becoming more frequent. This may take the form of a desk-top analyzer fed with automatically gathered samples in a robotized laboratory, or, increasingly commonly, instruments attached directly to the output ducts of the mill. In either case, the results can be fed directly into the mill control system, allowing complete automation of fineness control.

In addition to fineness, added materials in the cement must be controlled. In the case of gypsum addition, the material used is frequently of variable quality, and it is normal practice to measure the sulfate content of the cement regularly, typically by x-ray fluorescence, using the results to adjust the gypsum feed rate. Again, this process is often completely automated. Similar measurement and control protocols are applied to other materials added, such as limestone, slag and fly ash.


ConclusionThe practical training has proved to be quite fruitful .It provided me to encounter with such huge machines and mechanisms. It has allowed me an opportunity to get an exposure of practical aspects and their implementation to theoretical fundamentals.

I became Familiarize with the practical engineering work in various disciplines and methods of engineering practice. This will help me improving my performance in theory classes by introducing to the practical work. It helped me to know my strengths and weaknesses so that I can improve my skills and overcome my limitations by taking appropriate measures I was exposed to real work situations and I learned how to equip them with the necessary skills so that I would be ready for the job when I’ll be graduated.

The architecture of the plant, the way various units are linked, the way of working in plant and how everything is controlled make me realize that engineering is not just learning the structured description and working of various machines but the greater part of planning management


Date post:	13-Apr-2017
Category:	Engineering
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