SUMMER TRAINING REPORT

FROM BAUXITE TO BRICKS

Submitted in partial fulfillment of the

Requirements for the award of

Degree of Bachelor of Technology in Mechanical Engineering

Submitted By:

Name: Parth Vaishnav

University Roll No. 120503041

SUBMITTED TO:

Department of Mechanical Engineering

MANIPAL UNIVERSITY

Jaipur (Rajasthan).

DECLARATION

I hereby declare that the Industrial Training Report entitled "From Bauxite to Bricks" is an

authentic record of my own work as requirements of Industrial Training during the period

from 29.06.2015 to 31.07.2015 for the award of degree of B.Tech. (Mechanical Engineering),

MANIPAL UNIVERSITY, Jaipur, Rajasthan, under the guidance of Dalmia Refractories

Limited.

(Signature of student)

(Name of Student)

(University Roll No.)

Date: ____________________

Certified that the above statement made by the student is correct to the best of our knowledge

and belief.

Head of Department

(Signature and Seal)

ii

ACKNOWLEDGEMENTS

The internship opportunity I had with Dalmia Refractories Limited was a great chance for

learning and professional development. Therefore, I consider myself as a very lucky

individual as I was provided with an opportunity to be a part of it. I am also grateful for

having a chance to meet so many wonderful people and professionals who led me though this

internship period.

I would like to express my gratitude to Mr. Prashant (senior executive, HR) and Mr. Pradeep

Kumar Sharma (senior manager, HR) for providing me with the opportunity to intern in the

organization.

Bearing in mind previous I am using this opportunity to express my deepest gratitude and

special thanks to Mr. N. Raveendiran (Deputy general manager, engineering) and Mr. D. N.

Pal (Deputy general manager, production) who in spite of being extraordinarily busy with

their duties, took time out to hear, guide and keep me on the correct path and allowing me to

carry out my project at their esteemed organization and extending during the training.

I express my deepest thanks to Mr. Govind Gopal Nandi (Assistant manager, engineering) for

taking part in useful decision & giving necessary advices and guidance and arranged all

facilities to make life easier. I choose this moment to acknowledge his/her contribution

gratefully.

It is my radiant sentiment to place on record my best regards, deepest sense of gratitude to

Mr. K. Chandu (plant manager, engineering), Mr. Atul Mishra (plant engineer, engineering),

Mr. R. R. Joshi (executive, engineering), Mr. Jaysubh Bhavani (executive engineering), Mr.

Manoj Gusani (assistant manager, production) and Mr. Shashikant Pathak (assistant manager,

production) for their careful and precious guidance which were extremely valuable for my

study both theoretically and practically.

I perceive as this opportunity as a big milestone in my career development. I will strive to use

gained skills and knowledge in the best possible way, and I will continue to work on their

improvement, in order to attain desired career objectives. Hope to continue cooperation with

all of you in the future.

iii

THE COMPANY

Founded in 1935 by Jaidayal Dalmia; the cement division of Dalmia Cement Bharat Limited

(DCBL) was established in 1939 and enjoys a heritage of 70 years of expertise and

experience. The company is headquartered in New Delhi with cement, sugar, travel agency,

magnesite, refractory and electronic operations spread across the country.

The Dalmia Bharat Group had established four cement plants in pre-independence years, two

of which were affected by the partition and Independence. The two remaining plants operate

as Dalmia Cement and we have an associate company which is Orissa Cement Limited

(OCL).

Dalmia Refractories Limited (DRL) is one of the oldest and widely respected refractory

companies in India. It enjoys market leadership in High Alumina based products in the

cement industry with a market share of more than 50%. Besides being the market leader in

India, the refractory company also supplies its products to the MENA (Middle East & North

Africa) region.

The company is headquartered at New Delhi and operates three manufacturing plants located

at Dalmiapuram (Tamil Nadu), Khambalia (Gujarat) and Katni (Madhya Pradesh). The Sales

and Customer Service team is located at strategic locations across India for faster service to

our customers.

The company’s first plant came up in the 60’s at Dalmiapuram in Tamil Nadu. The second

plant came up in the 80’s at Khambalia in Gujarat. Both these plants have capacity to produce

shaped products (bricks) as well as monolithics (castables).

iv

The third plant came up in 2010 at Katni in Madhya Pradesh. This plant is exclusively for

monolithics production.

The total annual production capacity of all these plants is more than 1 Lac Tons.

Products

Dalmia’s refractory bricks for cement plants can be put to different uses. These refractory

products show characteristics like excellent resistance to spalling, abrasion, low porosity, and

high refractoriness. Besides refractory bricks for cement plants, Dalmia’s range of refractory

materials also includes high fire clay bricks, high alumina bricks, special quality bricks,

conventional castables, low cement castables, special castables, and ramming masses &

mortars.

Services

The company believes in providing complete solution to its customers. This has inspired the

company to not only offer a range of products that caters to every need, but also to provide

associated and ancillary services that fulfill need-gaps in the refractory industry. It not only

manufactures refractory products but also provides end to end turnkey solution for projects

and has a dedicated team of projects and services experts to deliver this.

The projects team work involves,

Thoroughly going through the drawing of the machinery which has to be refractory lined.

Expertise solution providing on selection of proper refractory material needed to be installed

(which gives optimal thermal efficiency and long lasting life of lining)

Proper Scheduling and timely completion of projects.

v

TABLE OF CONTENTS

SR.

NO

TOPIC PAGE

NO. 1 Introduction to project 1

2 Calcination unit 2

3 Mill house 9

4 Mixing 14

5 Press section 15

6 GP, RC/K & TK 22

7 Powerhouse 29

8 Workshop 32

9 Snapshots 35

10 Indian calcined bauxite: present status & future prospects 57

vi

ABBREVIATIONS

DRL: Dalmia Refractories Limited

CBM: Continuous Ball Mill

ID: Integrated Draft

GP: Gas Plant

RC/K: Ring Chamber Kiln

TK: Tunnel Kiln

QA: Quality Assessment

IMC: Impact Mill Circuit

MPV: Micro-Pulverizer

CCM: Counter Current Mixer

FSP: Friction Screw Press

GEB: Gujarat Electricity Board

AVC: Automatic voltage controller

ACB: Air Circuit Breaker

VCB: Vacuum Circuit Breaker

MV: Maximum voltage

CTPT: Current Transformer Potential Transformer

HT: High Tension

APFC: Automatic Power Factor Control

DOL: Direct OnLine

VFD: Variable Frequency Drive

Introduction

My training at DRL revolved around the processes used for the conversion of raw bauxite

into alumina bricks and the tools and technology used. There were 9 separate units:

1. Calcination unit

2. Mill house

3. GP, RCK & T/K

4. Press section

5. Workshop

6. Production

7. QA

8. Stores and raw material

9. Powerhouse

Raw bauxite is converted to calcined bauxite in the calcination unit. Then mill house breaks

this calcined bauxite into particles of required size. Then it is mixed with clay and/or other

materials as per the demand of the client. Then it pressed into brick form in the press section.

These green bricks are then dried in the drier section. They are then baked in the RC kiln or

tunnel kiln. Then QA section handles the quality checks. The entire required inventory is

stored in stores and raw material section. Workshop section handles the fabrication of in-

house machinery. Powerhouse section transforms and regulates the electric supply to all the

machines in all the sections. Production department decides the plan of action according to

the time period required in each process and the order date decided by the client.

2

CALCINATION UNIT

Calcination is the process of subjecting a substance to the action of heat, but without fusion,

for the purpose of causing some change in its physical or chemical constitution. The objects

of calcination are usually: (1) to drive off water, present as absorbed moisture, as "water of

crystallization," or as "water of constitution"; (2) to drive off carbon dioxide, Sulphur

dioxide, or other volatile constituent; (3) to oxidize a part or the whole of the substance. In

this process, the raw bauxite which is mined is converted to calcined bauxite. The following

reaction takes place:

Al2O3.2H2O → Al2O3 + 2H2O (at 1300 degrees)

Other materials that can be calcined in this unit are clay, fireclay etc. This whole unit is self-

fabricated by the industry.

Calcination unit can be divided into 5 parts:

1. Raw material crushing and storage

2. Kiln and cooler conveying system

3. Calcined bauxite storage system

4. Coal crushing and storage (petcoke circuit)

5. Pollution control

Raw material crushing and storage

Raw material yard Dump hopper Belt conveyer (small)

Belt conveyer (large) Jaw crusher Primary bucket

elevator

Storage tank 1

Storage tank 2

3

First of all, raw bauxite from the yard is fed into the hopper through tractors or bulldozers.

The dump hopper has a sieve of 200mm. Material larger than this is broken up into pieces by

smashing it through a hammer. It is then carried by the small belt conveyer. Then the material

is carried to the jaw crusher through the big belt conveyer whose length is 8m. Width of both

the belt conveyers is 600 mm. The belt is supported through a series of guide rollers. The

whole system is driven by a motor. A jaw crusher uses compressive force for breaking of

particle. This mechanical pressure is achieved by the two jaws of the crusher of which one is

fixed while the other reciprocates. This is also operated through a motor and a belt pulley

mechanism. Its function is to grind the raw bauxite for further process to be performed. The

size of the material is now less than 40 mm. Bucket elevators is a device which transports

material from lower level to a higher level. It consists of a belt pulley mechanism connected

to a motor. But the belt has buckets attached to it. These buckets carry the material to the top

where the material is thrown into a connecting pipe which carries the material to the storage

hopper. The width of the belt is 300 mm and length is 25m. There are 180 buckets attached to

it each carrying 1.5 kg. Output capacity is 20 ton. The two storage hoppers are 120 tons each.

Dampers are used to select the storage tank/hopper.

Kiln and cooler conveying system

Bucket elevator 2

Rotary

kiln

Rotary

cooler

Burner

pipe

Bucket elevator 1

Belt conveyer 1

Belt conveyer 2

4

Two belt conveyers carry materials from two storage hoppers to the bucket elevators. The

bucket elevators feed the material into the rotary kiln. It is cylindrical heating device 38m in

length and 2.25m in diameter made of mild steel. It has refractory brick lining on the inside.

It is rotated about its center through a motor arrangement. Motor is connected to the gear box

which is connected to a pinion which in turn meshes with the girth gear attached on the kiln.

They provide the appropriate speed reduction from 450 -500 rpm of the motor to 1-2 rpm.

The gearbox is of O or U type and provides speed reduction of 1:30 to 1:50. It also has tyres

at 3 places rolling on the supporting rollers. Lubrication used is graphite plate. There heating

zones can be distinguished inside the kiln:

1. Pre-heating zone (50-600 deg); outside temp: 300 deg

2. Calcination zone ( 1300 deg); outside temp: 320 deg

3. Sintering zone (1500 deg); outside temp: 330 deg

Burner pipe provides the heat to the outlet end of the kiln. Heating process takes 2 hours.

Kiln is titled by 10 degrees to facilitate material travel. From the kiln the material travels to

the rotary cooler which is 19m in length and 1.25m in diameter. The mechanism of rotating is

same as that of kiln. It has additional guide rollers on the side. It cools down the material with

the help of lifter buckets which rotate the material inside the cooler. The cooling process

takes 45 mins. It also has three zones:

1. 600 degrees

2. 300 degrees

3. Atmospheric temperature

Calcined bauxite storage system

A vibratory feeder is an instrument that uses vibration to "feed" material to a process

or machine. Vibratory feeders use both vibration and gravity to move material. Gravity is

used to determine the direction, either down, or down and to a side, and then vibration is used

to move the material. It is then transferred by belt conveyer to vibrating screen. It has a sieve

which vibrates to reject large particles and allow only smaller particles. In this case particles

Rotary

cooler

Vibro-feeder Belt

conveyer

Vibrating screen Belt

conveyer

Storage yard

5

larger than 30 mm are not allowed. It is then carried to the storage yard by belt conveyer of

width 400mm.

Coal crushing and storage

(Either/or)

Coal is fed into the hopper. Now coal can ground by two methods. Both the methods,

pulverizing and ball milling, are explained later in the mill house section. But by using CBM

method, whole hopper- screw conveyer arrangement can be avoided. Furthermore as CBM is

a closed system, there is no dust, so no need for dust bags. Now the ground coal is fed into

the hopper through a bucket elevator. This hopper ends into a screw conveyer. Screw

conveyer is a mechanism that uses a rotating helical screw blade to move material. Now the

material falls into rotary air lock. Its function is to regulate the flow from one chamber to

another while maintaining a good air lock condition. It has a fan like structure with buckets as

rotors. Now root blower attached to this circuit provides the necessary draft to carry coal to

the burner pipe. Primary fan system provides air for the combustion of coal inside the burner

pipe. The flow pipes of primary fan and coal intersect just before entering the burner pipe.

Initial ignition of coal is done through mostly diesel. After the coal ignites at 900 degrees,

temperatures of up to 1500 degrees are achieved.

Hopper CBM Bucket elevator Hopper Screw conveyer

(small)

Rotary air lock Root blower Burner pipe

Primary fan

Pulverizer

Dust filter

Hopper Screw conveyer (big)

6

Pollution and control

An ID fan is connected to the inlet side of the kiln. ID fan is essentially is used to create

suction or induce a draft. In this case, it has two functions. Firstly, heat is distributed

throughout the kiln from the burner pipe due to suction from the ID fan. Also the residual

gases generated inside the kiln and dust is forced out of the kiln through the ID fan. They are

operated through motor-belt-pulley arrangement. Now a multicyclone dust separator is

connected prior to ID fan. This is done to protect the blades of the ID fan. Multicyclone uses

rotational and gravitational effects to separate dust particles. A high speed rotating (air) flow

is established within a cylindrical or conical container called a cyclone. Air flows in a helical

pattern, beginning at the top (wide end) of the cyclone and ending at the bottom (narrow) end

before exiting the cyclone in a straight stream through the centre of the cyclone and out the

top. Larger (denser) particles in the rotating stream have too much inertia to follow the tight

curve of the stream, and strike the outside wall, then fall to the bottom of the cyclone where

they can be removed. Now the smoke with fine dust particles passes through the ID fan to

Venturi scrubber. A Venturi scrubber consists of three sections: a converging section, a throat

section, and a diverging section. The inlet gas stream enters the converging section and, as

the area decreases, gas velocity increases (in accordance with the Bernoulli equation). Liquid

is introduced either at the throat or at the entrance to the converging section. The inlet gas,

forced to move at extremely high velocities in the small throat section, shears the liquid from

its walls, producing an enormous number of very tiny droplets. Particle and gas removal

occur in the throat section as the inlet gas stream mixes with the fog of tiny liquid droplets.

The inlet stream then exits through the diverging section, where it is forced to slow down. Its

particle removing efficiency is almost 99%. Now the gaseous smoke is forced out of the

chimney through another ID fan. The particulate waste is dumped into the ground where it is

dilutes with aqueous CaCO3. This results in further precipitation of particulate waste and the

water can be reused.

Rotary

kiln

Multicyclone I.D

fan

Venturi scrubber

ID fan Chimney

7

8

9

MILL HOUSE

The purpose of the mill house is to grind and reduce the material into required size. There are

4 IMCs, 2 CBMs, and 2 MPVs in the mill house. Calcined bauxite produced at the end of

calcination unit is processed here. Other materials used are clay, other types of bauxite, white

fuse alumina, brown fuse alumina etc. Each circuit undergoes weekly maintenance. All the

parts are self-fabricated in IMC.

IMC

10

First of all the material is fed into the hopper by bulldozers. The overly large particles are

manually broken by hammers. Then it is carried down to impact mill through conveying

feeder. Impact mills work on the principle that most materials will crush, shatter, or pulverize

upon impact using a simple four step operation:

1. Material is fed into the mill’s chamber typically by gravity.

2. The material is struck by ganged hammers (generally rectangular pieces of hardened

steel) which are attached to a shaft which rotates at a high speed inside the

chamber. The material is crushed or shattered by the repeated hammer impacts,

collisions with the walls of the grinding chamber as well as particle on particle impacts.

3. Perforated metal screens, or bar grates covering the discharge opening of the mill retain

coarse materials for further grinding while allowing properly sized materials to pass as

finished product.

4. Hard, heavy materials such as glass, stone or metals exit the mill via gravity.

Pneumatic suction is used to assist in the discharge of lighter materials such as wood,

paper or other low bulk density products.

Now, the material is carried up by primary bucket elevator. Then the material is fed into

the primary magnetic separator. The magnetic separator separates any ferrous content in

the material. A powerful magnet is placed inside a rotating drum such that when the

material comes in contact with one side it sticks to the drum but when it reaches the other

side it can be released into a separate pipe. The drum is rotated through a motor. Now this

material is fed into a vibrating screen. This screen acts like a sieve which allows only small

particles to pass through. It is tilted at an angle which facilitates the screening. There are

three screens available, so material is available in 3 grades: 0-2mm, 2-3mm, 3-5mm. The

material rejected during screening is carried back to the impact mill. Now the screened

material passes through a secondary magnetic separator. Then it is finally carried to storage

hopper by a secondary bucket elevator. The material in the range of 2-5mm, if needed to

grind further, is fed into a separate hopper and into the roll crusher. Roll crusher consists of

two rollers placed parallel to each other. The material passed between them is continuously

crushed. Then this material is added to material going into the primary bucket elevator.

The reason for using roll crusher instead of impact mill is that impact mill uses impact

force to crush the material. So it can’t possibly crush the material to a particular required

size. There are total of 38 storage hoppers in the mill house. Dust collecting apparatus is

connected to each part. Dust is suctioned through ID fan. This dust is not all waste. It can

be used further in making bricks.

CBM

Material is fed into the hopper through bulldozers. The hopper is connected to the inlet of the

ball mill. A ball mill consists of a hollow cylindrical shell rotating about its axis. This is done

Hopper CBM Secondary

bucket elevator

Storage hopper

11

through a motor and a belt pulley assembly to reduce speed. It is connected between two

roller bearings on both sides. It is also slightly tilted at an angle to facilitate material travel. It

is partially filled with balls. The grinding media is the balls, which may be made of steel

(chrome steel), stainless steel or rubber. A ball mill works on the principle of impact: size

reduction is done by impact as the balls drop from near the top of the shell. There a

cylindrical sieve plate midway, after which the grinding media is switched to cylinders. This

is done as cylinders have greater contact area compared to balls. Sieve plate allows only fine

particles to pass through the other side. Now the ground material is carried storage hopper

through the secondary elevator. The CBM unlike IMC can continuously grind material as it is

not a circuit.

MPV

Material is fed into the hopper through bulldozers. Then this material is passed through jaw

crusher for reduction of its size. This is done because Pulverizer can’t grind material bigger

than a certain size. Now this material is fed into another hopper through a primary bucket

elevator. This hopper feeds material into the Pulverizer. The Micro Pulverizer is a high-speed

hammer and screen mill, which accomplishes size reduction by mechanically impacting

process material. This method of size reduction is characterized by relative high energy and

short residence time, minimizing heat buildup during the milling process. The Micro

Pulverizer consists of a rotor assembly fitted with hammers and operates generally at high

speeds. A cover fitted with a liner, a retaining screen at the point of mill discharge and a feed

screw mechanism whereby the unground material is uniformly fed to the grinding chamber.

The grinding action in the Micro Pulverizer is the impact between rapid moving hammers and

particles themselves. The energy of the moving hammers dissipates itself into the particles by

virtue of their inertia thus causing size reduction. This material is sucked in by the fan

attached with the pulverizer and transports it to the cyclone. Material is precipitated inside the

cyclone which is connected to a screw conveyer. The air inside the cyclone is transferred

back to the pulverizer assembly through a pipe. The remaining air-material mixture is passed

through bag filter. They are high ratio fabric filters using non-woven media/pleated fabric

cartridge. The principle of operation is given on the next page. Bag filters are connected to

the screw conveyer which transports the material to the storage hopper via the secondary

bucket elevator. The bag filters have almost 99% efficiency.

Hopper Jaw crusher Primary elevator Hopper

Pulverizer +fan Cyclone Screw conveyer Secondary

elevator

Storage hopper

Bag filter

12

JAW CRUSHER DESIGN

13

PULVERIZER DESIGN

14

BAG FILTERS: PRINCIPLE OF OPERATION

Material at the end of the IMC is coarse. While material at the end of MPV and CBM is fine.

CBM is used of harder materials like bauxite while MPV is used for softer materials like

clay. Speed of the pulverizer is the greatest. So it consumes the most amount of energy. The

material at the end of MPV is almost 90% pure. CBM takes up the least space. Mill house has

total of 41 storage hoppers.

Mixing

Weighing car moves on rails and collects the necessary materials in necessary proportions

from the respective storage hoppers. There is an electronic panel which displays the weight

and other necessary parameters. It has the capacity of 1 ton. The materials and their

proportions are decided according to the order of the type of bricks placed by the client. Then

this mixture is poured into the CCM along with binder of some kind. Common binders used

are water, acid, molasses. There is a horizontal shaft which is connected to a motor on one

end and has a bevel gear attached to it on the other end. The horizontal shaft rotates and this

in turn rotates the vertical shaft connected through the bevel gear. This shaft has a spur gear

Storage hopper Weighing car CCM

15

at its end which meshes with the container of the CCM. Also there are 2 vertical shafts with a

star mixer at its end inside the container. These shafts are also given rotation through the

bevel gears attached at their other ends. So the material is given a homogenous mix.

Press section

The material mixed into the CCM falls into the bucket. The construction of bucket is such

that it is hollow through the axis and a self-weight passes through it. So when it is rested on a

trolley or is hooked into the electric hoist, it can hold the material. The electric hoist

transports it on the top of the press hopper. When the bucket is unhooked, the self-weight

displaces the material falls into the press hopper.

ELECTRIC HOIST

CCM Bucket Electric

hoist

Press hopper FSP

Drier section

16

ELECTRIC HOIST: DIAGRAM

17

FSP: PARTS

18

FSP

19

FRICTION WHEEL

20

FLYWHEEL

21

There are a total of 18 FSPs in the press section. Of which 16 are of 150 ton capacity, 1 is of

400 ton and 1 is of 100 ton. The friction wheel material is mild steel. The material from the

press hopper is fed into the mould manually. The mould is prepared in the mould setting

section according to the dimensions provided by the client. But only the length and the

breadth can be set in the mould. The thickness of the brick is adjusted manually by the

operator by weighing the material before feeding into the press. In the mould setting section,

first of all, the mould plate is machined according to the dimensions provided in the

workshop. The mould plate material is HCHCr (high carbon high chromium) steel/ die steel.

It has high wear and abrasion resistant properties. It is heat treatable and will offer a hardness

in the range 55-62 HRC, and is machinable in the annealed condition. The mould plate is then

fixed inside the mould manually with the help of screws and measurements are taken with the

inside caliber. Then this mould is taken to the mould casting section. The mould is filled with

castables and water. Vibrator is used for reducing the casting time. The mould can be fixed

into the FSP after 24 hours. The used mould is dismantled in the mould dismantling section

with the help of sledgehammers. After FSP, the bricks shaped (green bricks) are taken to the

drier section on trolleys for elimination of any trace of water. The bricks are kept there for

about 24 hours at 110 degrees. The heat is provided by a suction fan connected to the RC

kiln. After drier section, the bricks are taken to RC kiln or tunnel kiln through trolleys for

further processing.

22

GAS PLANT

Gasification of coal is the main purpose of the gas plant. Coal is fed into the hopper through a

hoist. Then through hopper the coal is transferred into great tower. It is a container where is

coal is heated. Coal is rested on a hollow conical shaped lid through which steam and air can

enter. The great tower has water jacket on half of its outer surface while half of it has lining

of refractory bricks on the inside. When coal is heated in the great tower, it passes heat to the

GP Cyclone chamber

Junction

box

RC/k T/k

Hopper

23

water jacket which converts it to steam. There is a fan which supplies air. These air and steam

pipelines intersect and enter the great tower from the bottom. There is an ash bowl on the

bottom of the great tower which traps ash and other residue. It is in the form of a spur gear

which meshes with another gear which is attached to a motor. So it auto-cleans itself when it

is rotated. Other functions of the ash bowl include: to protect the blast cone and to help the

distribution of the blast. When coal is heated in presence of air:

C+O2→ CO2

Then carbon dioxide is decomposed into carbon monoxide when it passes through carbon. It

is a reversible reaction which is readily influenced by temperature.

CO2+C↔ 2CO

When carbon combines with oxygen the heat evolved is:

C+O2→ CO2+ 14,520 B.TH.U.

2C+O2→ 2CO+ 4,410 B.TH.U.

The final reaction can be given as:

C+O2+H2O→ (CO+H2+O2) producer gas

There are 3 gas plants. The two gas plants are for RC/k (diameter 2.3m) and 1 gas plant is for

T/k (diameter 1.6m).the temperature of about 1000-1500 degrees is achieved in the gas plant.

The producer gas is then passed through cyclone chamber where the dust settles. Then the gas

enters the junction box through a gas flow line. There are 2 outlet gas flow lines from the

junction box, each for the 2 sides of the RC/k. For any given time, only one gas flow line is

active. This is regulated by the junction box. There are 2 seal pots for 2 lines. If a seal pot is

completely filled with water, the gas is sealed from that side i.e. it cannot pass.

24

RC/k

The green bricks from the drier section are brought to the kiln through trolleys. Then the

loading of these bricks into the designated chambers takes place. A RC kiln consisting of a

series of adjacent chambers in a ring or oval or rectangle through which the fire moves,

taking several days to make a circuit; waste gas from the fire preheats ware in chambers

toward which the fire is moving, while combustion air is preheated by ware in chambers

already fired. There are 82 chambers in the kiln. It is made of refractory bricks. Leg seal

connects each chamber to the gas flow line. For heating the bricks, gas connector is

connected to the leg seal, which is provided with a valve. Gas enters the chamber through

underground pipelines. The draft connector is connected on the opposite side which provides

25

draft to the chamber. In "Cement, concrete and bricks", a book published in 1914, Alfred B.

Searle gives a clear and detailed description of the exact working of a rectangular RC kiln on

the basis of a drawing.

"Assuming that the kiln is in full work, what takes places is as follows: the fuel is fed

into the feed holes covering three chambers (1, 2 and 3). A light charge of fuel is being

placed in each hole every quarter of an hour. Number 1 will be almost finished. The hot

gases from the burning fuel will be carried by the draught through the five succeeding

chambers (4, 5, 6, 7 and 8) and will gradually pre-heat the bricks without requiring any

attention. After this the gases will be of so low a temperature that they are no longer

useful and are taken through the flue in chamber 8 into the main flue and so to the

chimney. All the dampers to the main flue in chambers 1 to 7 are meanwhile kept

closed, so that all the available heat is used in warming the bricks to be fired."

"Chambers 9, 10 and 11 contain freshly-set bricks and these must be separated from the

remainder of the kiln. Their temperature must be raised to at least 120 degrees Celsius

(248°F) by a separate supply of heat; to heat them by waste gases would usually cause

them to be badly succumbed, though for some purposes this would not matter and they

may then be taken at once into what is termed "the round of the kiln" without any

preliminary heating. Ordinarily, however, the bricks must be heated by as pure air as

possible, until their temperature is such that no condensation products can form upon

26

them. The purest warm air obtainable is that which is drawn through the chambers

containing cooling bricks (14, 15 and 16), and many kilns have specially arranged flues

for the supply of warm air for this purpose [not shown]."

"As soon as the bricks have reached a temperature of about 120 degrees Celsius

(248°F) the partition between chamber 8 and chamber 9 is removed. The damper to the

chimney in chamber 8 is closed and the supply of warm air to number 9 is shut off. The

hot gases from the fuel then pass into chamber 9 and the latter is said to be "taken into

the round of the kiln". Meanwhile, chamber 12 has been filled and chamber 13 is

empty or being emptied."

"Chambers 14, 15 and 16 contain bricks which are cooling, this being accomplished

automatically by the draught of the kiln which draws cool air through the open

doorway of chamber 13. The air thus admitted first comes into contact with almost cool

bricks, and becomes gradually hotter taking heat from the cooling bricks in its journey

until, when it reaches the burning fuel in chambers 1, 2 and 3, it is of the same

temperature as the hottest bricks in the kiln and ensures, with careful management, a

very complete combustion of the fuel with scarcely any avoidable waste of heat."

"Any description of the working of a continuous kiln must, necessarily, appear

complicated, but in reality these kilns are quite simple. As soon as a chamber is filled,

its contents are first warmed by hot air, and then it is taken into the round of the kiln as

described. It then needs no further attention until it has become so hot that a little fuel

must be fed into it in order to complete the burning. As soon as the contents of this

chamber have been heated sufficiently, the addition of coal to it is stopped, another

chamber is taken into the round of the kiln, and so on; one chamber being emptied and

another being filled continuously, and the fire travelling round and round the kiln in a

perfectly regular and continuous manner."

While loading, 1 brick space is left for determining temperature and state of the bricks

when kiln is in operation. Space is also left on the same level while sealing of the

chamber. The temperature of the kiln is then checked through an optical pyrometer

through that space. While unloading the baked bricks, a fan is employed for workers as

well as cooling of the chamber. The bricks are unloaded only after they have reached

close to the atmospheric temperature. The temperature achieved in the kiln is 1300-

1330 degrees. The time period required for completion of 1 cycle is 10-15 days. Output

27

is around 2000 tons. Residual gases produced after firing of producer gas are thrown

out of the chimney through ID fan connected to it. Their pipelines run underground.

T/k

Tunnel kiln is a continuous moving ware kiln in which the clay products to be fired are

passed on cars through a long horizontal tunnel. The firing of products occurs at the

central part of the tunnel. The tunnel kiln is considered to be the most advanced brick

making technology. The main advantages of tunnel kiln technology are its ability to

fire a wide variety of clay products, better control over the firing process and high

quality of the products. It is made of refractory bricks. Gas flow lines from gas plant-3

transport gas to the kiln. Trolley pusher is employed for pushing the green bricks into

the tunnel kiln at the required pace. The detailed working of tunnel kiln is given on the

next page. The residual gases are sucked into the chimney via ID fan. The temperature

range is same as the RC kiln. The time required for cycle is 3-4 days. The output

capacity is 400-700 tons.

The main difference between RC kiln and tunnel kiln is that in RC kiln the bricks are

stationary while the firing is movable, while in tunnel kiln bricks are movable and the

firing is stationary. Also mainly RC kiln is used unless the order is too large because of

the higher output of the RC kiln.

28

29

Power house

GEB power

11kV

CTPT

11kV switch board

(200A)

11kV switch board

2 (50A)

11kV switch board

1 (50A)

11kV switch board

3 (50A)

Transformer 1

(step down)

Transformer 2

(step down)

Transformer 3

(step down)

Transformer 1

panel

Transformer 1

panel

Transformer 1

panel

AVC

ACB panel

MV panel Feeders (11)

30

GEB supplies 11kV voltage to the industry in accordance with its demand. A current

transformer (CT) is used for measurement of alternating electric currents. Current

transformers, together with voltage (or potential) transformers (VT or PT), are known

as instrument transformers. When current in a circuit is too high to apply directly to

measuring instruments, a current transformer produces a reduced current accurately

proportional to the current in the circuit, which can be conveniently connected to measuring

and recording instruments. These measurements are recorded by a 11kV, 200 A HT panel,

which is further bifurcated into 3 11kV, 50 A HT panels, 1 for each transformer. VCBs are

connected to all the HT panels. A circuit breaker is a device, which can

1. Make or Break a circuit manually or by remote control under normal conditions

2. Break a Circuit automatically under fault conditions (like over current, Short circuit, etc.)

3. Make a circuit manually or by remote control under fault conditions

A vacuum circuit breaker is such kind of circuit breaker where the arc quenching takes place

in vacuum. The technology is suitable for mainly medium voltage application. The 3 stepdown

transformers are of 500 kVA capacity. At any point in time, only 2 are operational. As a step-

down unit, the transformer converts high-voltage, low-current power into low-voltage, high-

current power. The larger-gauge wire used in the secondary winding is necessary due to the

increase in current. The primary winding, which doesn’t have to conduct as much current, may

be made of smaller-gauge wire. So the voltage is stepped down to 440 V. Transformers are

connected in parallel. This is done to reduce the load. There are 3 transformer panels. They are

connected to an AVC. They do the process of maintaining voltage at the junction points of an

electrical system within given limits to ensure technically feasible conditions of operation for

users of electrical energy and of separate systems and to increase the economic efficiency of

their operation. Also ACBs are connected to the transformer panels. The type of circuit

breaker, which operates in air (where air-blast as an arc quenching medium) at atmospheric

pressure, is known to be an Air Circuit Breaker. It trips if there is an earthing fault, over

current, over voltage or under voltage. Now the power is transmitted from MV panels to

feeders which transmits power to various sections such as mill house, RC/k, lighting, FSP etc.

Feeders are 11 in number.

There is an APFC unit which has the main function of maintaining power factor (between

0.85-9) using capacitors. Power factor is ratio of real power to the apparent power (KW/KVA).

Other functions of powerhouse unit include maintaining and determining:

1. Types of motors

2. Types of starters

3. Types of VFDs

4. Types of cables

Most of the units use two types of motors:

31

1. Slip ring type

2. Squirrel cage type

90% of the time, squirrel cage motors are used. Their range is 1-100 hp.

Types of starters are:

1. DOL

2. VFD

3. Stardelta

DOL starters are used for motors ranging from1-10 hp, while stardelta starters are used for

10-100 hp. VFDs are of 2 types: dc and ac. It manages power/rpm of the motor by changing

the frequency of the ac current. For eg, it motor has 1440 rpm at 50 Hz, then it will have 1000

rpm at 40 Hz. Advantages of VFD include: power saving, reduced maintenance and good

power factor.

Cable selection depends on the hp of the motor. VFD is also selected based on hp. There are

2 things mentioned on any of the motors in the storeroom: hp and (A/B/C). The letter denotes

the rpm of the motor: A-2800, B-1440, and C-960.

There are 2 generators in the powerhouse: 1 of 250 kVA capacity, and 1 of 500 kVA

capacity.

Types of cables

Flexible Armored

Domestic Industrial

Industrial

1c (1 core) 2c/twisted 2c/3c/4c/8c/10c 2c/3c/4c/8c/10c

32

WORKSHOP

Workshop section handles the manufacturing and fabrication of in-house machinery and

machine parts. Following machines are at disposal for the same:

1. 3 lathe machines

2. 4 horizontal surface grinders

3. 1 vertical surface grinder

4. 1 rotary surface grinder

5. 1 radial drilling machine

6. 1 saw machine

7. 2 shaping machines

8. 1 bench grinder

9. 1 hardness tester

One example of use of this section can be cited that of top/bottom plates used in the FSPs.

These plates are to be manufactured and resized according to each order of bricks given by

the client. So these plates are sized, tempered and then are surface grinded in the workshop

section. Parts and diagrams of different machines are attached below:

Saw machine

33

Lathe machine

34

Vertical surface grinder

35

SNAPSHOTS

Calcination unit:

Vibrating sieve: calcined bauxite storage

Burner pipe

36

Rotatory kiln

Rotary cooler

37

Chimney

38

Jaw crusher

Pollution and control circuit

39

Venturi scrubber

CBM: coal crushing and storage

40

Rotary air lock: coal crushing and storage

Mill house:

IMC

41

Magnetic separator: IMC

Dust collection apparatus

Magnetic drum: magnetic separator

42

Vibrating sieve

CBM:

43

MPV:

Pulverizer

Cyclone, bag filters

44

Screw conveyer

Bucket elevator

45

MIXING:

CCM

Weighing car

46

PRESS SECTION:

100 ton FSP

GAS PLANT:

ash bowl at the bottom

47

Inside of the gas plant

RC kiln:

Loading of bricks

48

Draft connector

Gas flow line

49

Gas connector+ leg seal

Tunnel kiln:

ID fans from RC and tunnel kiln connected to the chimney

50

Trolley pusher

Inside of tunnel kiln

51

Trolleys

Firing section

52

Workshop:

Reciprocating table surface grinder

Lathe machine

53

shaping machine

Power house:

ACB panel

54

Generator

MV panels

55

APFC

Step down transformer

56

HT panel

57

Indian calcined bauxite- present status and future

prospects

The vast resource of bauxite occurs in various parts of the Country and India occupies 5th

position in the World bauxite map. Despite availability of large bauxite resources there are

limited occurrences of high grade bauxite deposits. Gujarat occupies the top position in

resources and production of high alumina bauxite suitable for valued added refractory,

abrasive industry. However, this bauxite has significant calcium content, which deteriorates

its value for refractory industry. Some high alumina and high Titania deposits are found in

Maharashtra and Central India (Chhattisgarh, Jharkhand & Madhya Pradesh) region and

small scattered deposits are also exploited in various parts of the country. In many cases the

non-metallurgical grades are specially selected high quality bauxite from metal grade

deposits for which normally higher prices can be obtained. With the fast depletion of good

quality bauxite resources, it has become necessary to use suitable beneficiation process,

mainly to bring down iron and titania content in Indian bauxite. In the current scenario, China

is the leading country to supply refractory bauxite in the World after Russia, India and

Guyana. Guyana is the main competitor to China in the International market and further new

production from UC Rusal due on stream in 2012. After the China, Russia, India and Guyana,

other producers of refractory grade bauxite in the world are Brazil, Greece, Malaysia, and

Australia. Brazil has small refractory grade production for the domestic market and also for

proppant production. In the present paper, the high grade bauxite deposits of India are

highlighted and the Indian calcined bauxite is compared with world producers.

As indicated, high grade bauxite of Gujarat is getting exhausted and some of the good

deposits of Kachchh are reserved for proposed alumina refinery. This is quite paradoxical

situation as large bauxite resources of Eastern Ghats region, most suitable for alumina

production, are lying unutilized due to environmental and tribal issues. This may further

aggravate the scarcity of high grade bauxite in the Country and survival of non-metallurgical

industries may become difficult and alternate options have to be evolved. It is often possible

to mine and selectively sort-out bauxite of various grades including metallurgical quality

from the same deposit. These special grades of bauxite can also be produced by adopting

simple physical beneficiation processes such as wet scrubbing and sieving. In the World

bauxite scenario, there are two types of producers of special grade bauxite:

58

In case of extensive deposits where special bauxite can be mined directly, or side by side

with metal grade ore, on a large scale and on a routine basis, such as Guyana,

Australia(Weipa), China (diaspore type) and Suriname.

Selective mining by the small producers (e.g. Kachchh, Gujarat) or from small, individual

deposits (Bintan, Indonesia and Malaysia)

Conclusions

Bauxite for refractory and abrasive industries meet very stringent physicochemical

requirement and specifications particularly for components like alumina, iron oxide, titania,

etc. compared to ore used for metallurgical industry.

Indian high grade bauxite, particularly those of Gujarat, are considered of inferior quality in

the World due to high titania, iron and CaO, although Indian calcined bauxite is easy to grind

compared to imported material.

Presently China is the biggest producer and supplier of calcined bauxite in the World

followed by Guyana and compared to their products, Indian calcined bauxite possess more of

iron, titania and calcia.

Simultaneous production of various grades of bauxite from the particular deposit, as

demonstrated in case of Weipa bauxite mine of Australia, can change the economics of

mining and even small deposit of 1 to 2 million tons may be viable for exploitation.

The laboratory beneficiation test results show that it is possible to produce high grade, high

alumina bauxite by de-ironing Eastern Ghat ore. However further detail studies are required

to work out techno-economics of the process.

Transforming iron and titania into high temperature phases is new direction of R&D work

for developing calcined bauxite suitable for refractory industry.