Training Report (CEMENT PLANT)

A

     Report on Cement Manufacturing

Internship Taken

At

Birla White Cement

Khariya-Khangar (Jodhpur)

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

 

Submitted to                                         Submit by:

Mr. Dilip Singh Soda (GM)                                             Devendra Singh

Mr. Harshad Damle (HR)                                                B.Tech Mechanical

&                                                                          (4^th Year)  ; Session (2014-18)
Dept. of Mechanical Engineering                                    VIET, Jodhpur

Vyas Institute of Engineering and Technology, Jodhpur

Index

S. No	Title	Page No.
1	Acknowledgement	3
2	Units of Birla White Cement In India	4
3	Aditya Birla Group Works	5
4	Birla’s Product	7
5	Safety Items	9
6	Introduction	10
7	About Birla White Cement works	12
8	Cement	13
9	Crushing Plant	17
10	Raw Mill	23
11	Kiln Section	30
12	Electrostatic Precipitator	36
13	Clinker cooler and coal section	39
14	Cement Mill	43
15	Packaging Plant	45
16	Quality Control	46
17	Conclusion	48

Acknowledgement

I am very grateful to Mr. Harshad Damle (HR), Mr. Dilip Singh Soda (GM) and Department of Mechanical Engineering. Vyas Institute of Engineering and Technology, Jodhpur 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 member 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.

Units of Birla White Cement in India

1.     Khariya Khangar, Jodhpur (Raj)

2.     Ghaziabad (Utter Pradesh)

Aditya Birla Group Works

Aditya Birla GRASIM is a Building Materials Industry. Founded at Mumbai(1948)

Producta: Fibre and pulp, chemicals, cement and textiles.

 IIMs, IITs, BITS and LAW students can apply for the Aditya Birla Scholarships.

Aditya Birla Money Limited is a broking and distribution player, offering Equity and Derivative trading through NSE and BSE and Currency derivative on MCX-SX.

ABPS (Aditya Birla Public School).

Aditya Birla Health is to discover health care and hospitalities.

Sun Life Financial, Inc. is a Canada-based financial services company known primarily as a lifeinsurance company. It is one of the largest life insurance companies in the world, and also one of the oldest with a history spanning back to 1865.

Aditya Birla World Academy (ABWA) is a private co-educational LKG-12 day school in Mumbai in the Indian state of Maharashtra built by The Aditya Birla Group in 2008~2009.

UltraTech is the gray cement Brand of Aditya Birla Group.

Birla White is the white Cement under UltraTech Cement Pvt. Ltd. Company.

Birla’s Products

                 

     

Use of Birla Products:

1.  Putty:

Allow the surface to dry completely. Wash again with clean water and dry. Painting System: For interior/exterior walls apply 2 coats of Home Shield Damp shield 2K as putty in the affected area first on an interval of 4-5 hrs. Mixing ratio Damp shield 2K Base: Catalyst: Cement: 1:1:2 by volume.

2.  White Cement:

White concrete usually takes the form of pre-cast cladding panels, since it is not economical to use white cement for structural purposes. White Portland cement is also used in combination with inorganic pigments to produce brightly colored concretes and mortars. ... Blue concrete can also be made, at some expense.

  3.  Dr. Fixit:

    . 

Use Dr. Fixit Dampguard a heavy duty epoxy waterproofing coating for treating internal damp walls. Reduces water absorption and permeability Tough and flexible ecofriendly epoxy coating Life expectancy 4 years.

  4. UltraTech Cement:

    Portland cement is a basic ingredient of concrete, mortar and most non-specialty grout. The most common use for Portland cement is in the production of concrete

Birla White Cement Factory’s Safety Items

      

                     

Introduction

UltraTech is India’s largest white cement manufacturer. UltraTech manufactures white cement under the brand name – Birla White.

Birla White Cement is a unit of UltraTech Cement Pvt. Ltd.

It is founded by Aditya Birla group the Asia’s largest business group. It is a US $41 billion corporation, it is anchored by an extraordinary force over 120,000 employees, belonging to 42 different nationalities.

Birla White cement at Kharia-Khangar, Jodhpur (Raj.) celebrated its 25^th anniversary on 11 April 2013.

Over the years, Birla White has consistently expanded its product portfolio and strengthened quality. Today, it makes and markets several surface finishing options such as Wall Care Putty, Texture, Glass Reinforced Concrete and Level last. Looking ahead, its aim is to become a globally benchmarked organization in white cement through value-added products, continued focus on quality and customer delight. The brand also plans to reach projected revenues of Rs.3, 000 corer by 2015-16.

Birla White has one of the largest white cement plants in South East Asia, with an installed capacity of 560,000 TPA, and among the most technologically-advanced in the world. Commissioned in 1988 with a capacity of 80,000 TPA, the plant has expanded over a period of time by the debottlenecking of existing equipment, technology up gradation, modernization and the commissioning of Line-II in 1997. 

UltraTech Cement has a strong global presence in the developed European and fast-growing Asian markets with exports to 26 countries. To cater to the growing market, Birla White recently commissioned a manufacturing facility for Wall Care Putty at Katni, Madhya Pradesh, with a production capacity of 4 lakh MTPA. With this unit, Birla White will be able to efficiently service the markets in central, west and south India, improve product availability, and create a dominant position in the market.

Talking about future plans, Mr. Rahul Mohnot, Birla White Unit Head, says, “The Company’s journey from inception to becoming India's largest, and the world's 7th largest white cement manufacturer has been remarkable. Birla White cement has been growing at a CAGR (compound annual growth rate) of eight per cent during the past five years. Now, we are on the path to aggressive expansion, with plans already in place to add a third line adjacent to the existing facility to augment existing capacity by two-and-a-half times.”

About Birla White Cement Works

UltraTech is India's largest white cement manufacturer. UltraTech manufactures white cement under the brand name — Birla White.

Birla White is a critical component in wall finishes such as Grit Wash, Stone Crete and Tyrolean. It is also the main ingredient in the application of mosaic tiles and terrazzo floorings.
The range of unique stand-alone products that Birla White has introduced includes Wallcare putty, Levelplast, Textura, GRC

Products:

·         :: Wallcare putty
Birla White Wallcare Putty offers total protection against flaking. Its superior quality makes it the only putty in India to meet global standards (HDB, Singapore).

·         :: Textura
Birla White Textura offers protection for walls from weathering. Birla White Textura is available in two varieties — Spray Roller Finish, which is ideal for interiors and Trowel Finish (TF), which is best-suited for external walls.

·         :: GRC
Birla White GRC is a versatile and lightweight mouldable finishing material that is perfect for decorative elevations. Birla White GRC is made from Birla White Cement, high-silica sand, alkali-resistant glass fibres and other mixtures.

·         :: Levelplast
Birla White Levelplast is a water-resistant, white cement-based product — perfect for levelling concrete / mortar walls and ceilings, especially when there are major undulations.

Cement

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, houses, and other construction works. Cement has an exceptional strength under compressive loads and also it can take any shape. It is an engineering material that used to shape the designs of the engineer in real with desirable quality and strength.

Types of Cement-

1.           Ordinary Portland Cement (OPC)

2.           Portland pozzolona Cement (PPC)

3.           Sulphate resisting Cement

4.           Rapid hardening Cement

5.           Oil Well Cement

6.           Masonry Cement

7.           Portland blast Furnace slag Cement

8.           Super sulphate Cement

9.           High alumina Cement

10.      White grade Cement

11.      Quick setting Cement

12.      Hydrophobic Cement

13.      Silver grade Cement

In the Birla White Cement works only White grade cement is manufactured.

What makes White Cement White?

The color of white cement is determined by its raw materials and the manufacturing process. Metal oxides, primarily iron and manganese, influence the whiteness and undertone of the material. After adding pigments, white cements produce clean, bright colors, especially for light pastels

There are three processes of manufacturing cement which are as follows:

a)     Wet Process

b)    Dry Process

c)     Semi-dry Process

In Birla White Cement works cement is manufactured via Wet Process.

The manufacture of cement is a very carefully regulated process comprising the follows 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.

Ø  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.

Ø Raw Material 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 lime stone and clay being used very carefully controls the chemical composition of the slurry. The slurry is stores in large basins ready for use known as decanter and DP tanks and then further fined by raw mill.

Ø 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 lime stone and clay to produce new minerals, which have the property of reacting with water to from a cementations binder. The hot clinker is used to preheat the air for burning the coal, and the cooled clinker is stored ready for use.

Ø 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 of packing plant facilities.

Fig shows the process layout of cement manufacturing

Crushing Plant

The crushing plant receives lime stone 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 Economy (Hammer crusher). Crushers have capacity of 100 ton per hour and driven by 132 KW motors. The crushed limestone is stored in yard.

·        Equipment and their flow diagram:

§  Unloading Hopper:

The limestone from mines comes into plant in loaded trucks and is unloaded here in the chamber 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 plants, which are connected with hinge. The productivity of feeder 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.

Fig shows Apron Feeder

§  Jaw Crusher:

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

          Features of Jaw Crusher:

-         Simple structure, reliable working condition, easy maintenance, low operating costs.

-         High crushing ratio, even 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 user’s different requirements.

Structure of Jaw Crusher:

The 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 toggle plate also plays a role of protection. The length of toggle is 898mm (movable jaw) and 790mm (Fixed jaw).

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 material will be discharged from the outlet.

The Capacity of Jaw Crusher is 130 ton per hour.

§  Hammer Crusher:

Hammer crusher is a kind of machine 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.

The materials collision with each other at the same time, after repeatedly broken, the materials less than sieve article deduction 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.

Fig shows Hammer Crusher

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 conveyer 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 the larger ones will be crushed by the hammer ring till the required size and be discharged.

The capacity of Hammer crusher is 130 ton 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 vibrating 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 reclaimed. This equipment is supplied by space age limited. Its capacity is 100 ton per hour. The reclaimed shaves one side of the pile is such manner that further blending of limestone occurs. The reclaimed limestone is conveyed to the raw mill through belts.

Fig shows raw material handling

Raw Mill

 A raw mill section used to grind raw materials into “raw mix” during the manufacture of cement. Raw mix is then fed to a cement kiln, which transforms it into clinker, which is then ground to make 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.

Fig shows Raw mill

Ø 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 25m. It is operated on recirculation till sludge of 68%-69% moisture is reached in the outlet. The decanter sludge is then 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 of DP Tank is 65m3/hour. It pumps the sludge to the feeder on the top of the Raw mill building.

Fig. shows DP tanks

Ø Feeder:

The feeder is a ferries wheel driven by a variable DC drive. There are three hopper 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 clinker section.

Ø 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) ^ (1/2), where d is the internal diameter in meters. Ball mills are normally operated at around 75% of critical speed, so a mill with diameter 5m will turn at around 14rpm.

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 25mm in diameter). Ball diameter here is in the range 60mm-80mm. In a two-chamber mill, the media in the second chamber are typically in the range 15-40mm, although media down to 5mm 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 brake large clinker particles.

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

Fig. shows raw milling layout

Specification:

A raw mill is driven by 750KW motor that rotates the mill at 17rpm. The length of mill is 13m and diameter is 2.25m. Both the compartments of mill are filled with grinding media apart from slidge 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	3
80	8
70	8
60	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 ball (in mm)	% in Tank
50	20
40	10
30	6

A circular section called diaphragm, 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.

Ø DSM Screen:

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

Ø Slurry mixer tank:

The slurry mixer is 12.5m diameter tanks having arms on which air nozzles fixe. Compressed air through these nozzles about 1.5Kg/cm3 agitates the slurry and prevents it from becoming solid. From here the slurry is feed into kiln by slurry pumps.

Fig shows slurry mixture

Kiln Section

A rotary kiln is a pyre processing device used to raise materials to a high temperature (calcinations) in a continuous process. The basic components of a rotary kiln are the shell, the refractory lining, support Tyre and rollers, drive gear and internal heat exchangers.

Fig shows rotary kiln

Ø Kiln Shell:

This is made from rolled mild steel plate, usually between 15 and 30mm thick welded to from a cylinder, which may be up to 230m in length and up to 6m 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.

Ø Refractory Lining:

The purpose of the refractory lining is to insulate the steel shell form the high temperature 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, of may be absent in zones of the kiln that are below around 250 degrees calculus. The refractory selection 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 80mm to 300mm. A typical refractory will be capable of maintaining a temperature of 1000 degrees or more between its hot and cold faces. The shell temperature needs to be maintained below around 350 degrees in order to protect the steel from damage, ad continuous infrared scanners are used to give early warning of “hot-spots” indicative of refractory failure.

Ø 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*60m 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, spaced along the length of the rollers, while very short kiln may have only two. Kilns usually rotate at 0.5 to 2 rpm but sometimes as fast as 5rpm. The kiln of most modern cement plants are running at 4 to 5rpm. 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 tyres, that prevent the kiln from slipping off the support rollers.

Fig shows tyres and rollers of rotary kiln

Ø 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 mist have high starting torque in order to start the kiln with a large eccentric load. A 6*60m kiln required around 800KW to turn at 3rpm. 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 a=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.

Ø 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 kiln 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 of “lifters” that cascade the feed through the gas stream, or may be metallic insert that heat up in the upper part of 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 steam.

Ø 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 wh9ich 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 to atmosphere, called ESP.

Ø Thermal Efficiency:

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

Ø 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 Birla white cement the kiln is 120m long. It has a diameter of 3.75m. It is longer than usual because its wet process and additional chain zone required to bring the moisture down. The chain zone is about 23.75m 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 leaned flue gases ate pulled out of the system by an LD 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 sown the kiln is 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 calcination follows this. CO2 released, the calcination zone terminates into burning zone where hear released through coal burning melt the oxide a 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 very with the firing rate feed rate and to I.D. fan speed. The burning zone temperature is 1250-1400 degrees.

Different reactions at different temperature are given below in table:

Temperature	Reactions
1800C	Evaporation of water
5000C and above	Evolution of combined gases
9000C and above	Clinkerization of dehydration
12000C	Production of clay &production of CO2
12000C 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 its consumption of energy (in the form of electricity).

The most basic precipitator contains a raw of thin vertical wires, and followed by a stack of large flat metal plates oriented vertically, with the plants typically spaced about 1 cm to 18cm 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 several thousand volts is applied between wire and plates. 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).

Fig shows ESP and Working

Ø Collection Efficiency:

Precipitator performance is very sensitive to two particulate properties:

1)    Electric resistivity;

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 electric field of 4KV/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 and 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 charges, 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:

a)     High collection efficiency.

b)    Low resistance path for gas flow.

c)     Treatment of large amount of gases and at high temperature.

d)    Ability of copying 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 gate 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 of air through fan no 2 and 3. Finally the cooled clinker is about 100 degrees. This is then feed into VSI crusher where it is broken into small pieces. From here small piece are fed into the drag chain, which fall on the deep where it is stored into the cement silos.

Ø VSI (Vertical Shaft Impact) crusher:

VSI crusher use a different approach involving a high speed with wear resistant tips and a crushing chamber designed to “throw” the rock against. The VSI crushers utilize velocity rather than surface forces 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 metal anvils or crushed rock. Utilizing cast metal surfaces ‘anvils’ is traditionally referred to as a ‘Shoe and Anvil VSI’.

Fig shows VSI Crusher

Ø 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 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 moves 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 device can usually be set up in a matter of hours, and then dismantled once the project is complete. Storage of the portable cement silos are relatively easy, since the components can be stored in a Warehouse 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 tie 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 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 for white grade cement. The cement silos have a capacity of 3500 metric ton each.

         

Fig shows silos for Cement

Cement Mill

A cement mill is the equipment use to grind the hard, nodular clinker from the cement kiln into the fine grey powder that is cement. Most cement I 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 vibratory feeders installed in each silos. The clinker belt with a constant speed feed the clinker into cement mill.

The gypsum 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.

Ø Material Ground:

Portland clinker is the main constituent of most cement. In 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.

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

Ø Temperature Control:

Heat generated in the grinding process cause gypsum to lose water, forming bassanite or gamma-anhydrite. The latter minerals are rapidly soluble, and about 2% of these in cement is needed to control tricalcium aluminates 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 an ill exit temperature within a few degrees of 115 where the milling system is too hot. Some manufacturers use 2.5% gypsum and the remaining calcium sulfate as natural alpha-anhydrite.

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

Packaging Plant

Packing of cement is done by L&T rotator 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 about the packer. There are two packing machines for the emergency case.

Rotator 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 an 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.

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 cement have become finer, the use of sieves is less applicable, but the amount retained on a 45 micrometer 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 un-reactive.

          The main measure of fineness today is specific surface. Because cement particles react with water at their surface, the specific 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 setting is 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 desktop 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.

Conclusion

          The 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 become 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 over my limitations by taking appropriate measure 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 in not just learning the structured description and working of various machines but the greater part of planning management.