TO REDUCE SPM LEVEL AT SCREEN HOUSE AT CHP ASH FREE BATTERY 5,6,7

( C O K E P L A N T , TATA S T E E L LT D . , J A M S H E D P U R )

AVISHEK GHOSH

JADAVPUR UNIVERSITY KOLKATA

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First and foremost I would like to express sincere gratitude to the project guide,Mr. Vikash Kumar ,Manager (Mech). I was privileged to experience a sustainedenthusiastic and involved interest from this side. He also made me aware of allthe safety issues and helped me to get equipped with all the personal protective,thus making me work in safe working conditions.

This fueled my enthusiasm even further and encouraged me to boldly step intowhat was totally dark and unexplored expense before me.

I would also like to thank Mr. Mahapatra for helping me with gaining on siteknowledge. And for being ready with a positive comment at all time, whether itwas an off hand comment to encourage me or a constructive piece of criticism.

ACKNOWLEDGEMENT

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CONTENTS

SL. No. TOPIC Pg. No.

1 ACKNOWLEDGEMENT 1

2 A BRIEF INTRODUCTION TO TATA STEEL 3

3 COKE PLANT 5

4 SYNTHESIS OF COKE FROM COAL 6

5 FUNCTIONAL ELEMENTS OF COKE PLANT 7

6 AN OVERVIEW OF THE COKE PLANT 11

7 PROCESSES IN SCREEN HOUSE 12

8 AN OVERVIEW OF THE SCREEN HOUSE 13

9 MECHANICAL MECHANISM BEHIND VIBRATION 14

10 SECONDARY SCREENING SYSTEM 15

11 WORKING OF CONVEYERS 16

12 TO REDUCE SPM LEVEL AT SCREEN HOUSE AT CHP (COKE HANDLING PLANT) ASH FREE BATTERY

5 6 7 IN COKE PLANT (CASE STUDY OF CHP#3)

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13 RECOMMENDATIONS 21

14 CASE STUDY OF SCREENING OF COKE FROM CDQ IN CHP#3 22

15 SAFETY PRECAUTIONS TO BE TAKEN IN COKE PLANT 23

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Established in 1907, Tata Steel is the world’s 6th largest steel company with an existing annual crude steel capacity of 30 million tones. Asia’s first integrated steel plant and India‘s largest integrated private sector steel company is now the world’s second most geographically diversified steel producer, with operations in 26 countries and commercial presence in over 50 countries.

Tata Steel completed 100 glorious years of existence on august 26, 2007 following the ideals and philosophy laid down by its founder, Jamshetji Nusserwanji Tata. The first private sector steel plant which started with a production capacity of 1,00,000 tones has transformed into a global giant.

A BRIEF INTRODUCTION TO TATA STEEL

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Tata Steel plan to grow and globalize through organic and inorganic routes. Its 6.8 million tons per annum (MTPA). Jamshedpur Works plan to achieve 10MT capacity by 2010. The Company also has three Greenfield steel projects in the states of Jharkhand, Orissa and Chhattisgarh proposed steel making facilities in Vietnam.

Tata Steel is a global player with a balance presence in European developed and fast growing Asian market and with a strong position in the construction, automotive and packaging markets. It’s Jamshedpur steel works produce hot and cold rolled coils and sheets, galvanized sheets, tubes, wire rods, construction rebars.

In an attempt to ‘discommodities’ steel, the Company has introduced several branded steel products, including Tata Steelium (the world’s first branded Clod Rolled Steel), Tata Shaktee (Galvanized Corrugated Sheets), Tata Tiscon (rebars),Tata Pipes, Tata Bearings, Tata Structural, Tata Agrico (hand tools and implements) and Tata Wiron(galvanized wire products).Tata Steel’s vision is to be the global steel industry benchmark for Value Creation and Corporate Citizenship.

TATA STEEL has been ranked as the "World's Best Steel Maker", for the third time by World Steel Dynamics in its annual listing in February, 2006. Tata Steel has been conferred the Prime Minister of India's Trophy for the Best Integrated Steel Plant five times.

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COKE PLANT

The TATA iron and steel company is responsible for the production of IRON and STEEL in very huge quantities. The production area is very large, which comprises of various plants connected in series which depends on each other for the production. In this process one of the most important part plays the COKE PLANT, which produces coke(2.3 MT p.a) after processing raw coal (pyrolysis). This produced coke is sent further for heating the blast furnace and hence the process continues. The processing of coal into coke, happens at various stages starting right from the SCP machine which charges raw coal into hot ovens where the coal gets carbonized at very high temperatures of 950-1200c for about 20 hrs. CO and BF gases are used for heating the oven. The heated coal looses its moisture content and gets converted into coke. This heated coke is then removed from the oven by a PUSHER RAM of SCP machine which is guided into a loco vehicle. This vehicle carries the hot coke for further cooling into a CDQ(coke dry quenching) chamber where cooling is done by the supply of nitrogen in the absence of air. After this process the coke is further supplied to screening and crushing, after the coke is ready to be supplied further in different plants (BLAST FURNANCE).

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SYNTHESIS OF COKE FROM COAL

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SERVICE

BUNKER

SCP

MACHINE

BATTERYS

(5,6&7)CGC CAR

DOOR

EXTRACTOR

LOCO AND

QUENCHING

UNITS (COLD

DRY & WET)

SCREENING

UNIT

COALSEARCH BUNKER

Coke to the Blast Furnace

NUT COKE

BREEZE

COKEPEARL COKE

Coke separated according to size

COAL TRANSFORMATION OF COAL TO COKE COKE

FLOW CHART SHOWING TRANSFORMATION OF COKE FROM COAL

Coal unloaded by wagon tippler and transported via conveyers

FUNCTIONAL ELEMENTS OF COKE PLANT

Coal Bunker: Coal is fed to the Service Bunker 3 & 4 through an arrangement of conveyor belts. There are two sides in each bunker North and South. Each side is having 4 pockets in order to have uniform filling of coal.

SCP Machines: SCP (Stamping-Charging-Pushing) machine is one of the most vital equipment in the coke plant, which covers up most important operations in this plant. This machine is very large weighing about 700tons and is able to move on 16 wheels with 8 drives on a track longitudinally with a precise positioning arrangement. There are 3 SCP machines provided in the coke plant (mc#0, mc#1, mc#2). There is a PLC room provided which contains all the electrical drives in it & is responsible for controlling all the electrical inputs at various locations in the machine

Charging gas cleaning car: It is a car which is used to clean the charging gas before emitting it into the atmosphere. Its operation area is at the roof of battery and it can travel from north to south along the battery.

Coal Bunker

SCP Machine

*Actual SCP Machine at Tata Steel (Manufactured by TRF Limited.)

Charging gas cleaning car8

Batteries: Coal cake from SCP machine is charged into Batteries 5,6 & 7.There are three batteries in operation with a total of 144 nos. Stamp Charged ovens (size of each oven- 13.760m X .460m X 4.570m).Using ENCODER, SCP machine locates the OVEN in which the cake is to be charged . The Door of the Oven is opened by SCP machine and held. Cake is then fed into the Oven and then Door is closed. The gases used in the oven for heating purpose are CO & BF gases. Temperatures in the oven ranges between 950-1200c. The inner surface of the oven are made of some refractory materials. CGC car is used in order to clean the extra coke oven gas before discharging the gas into the Atmosphere. There is also a door cleaning section in each battery where the door of the oven are cleaned by water jet.

Ovens in a Battery

Battery

Door Extractor: Door extractor acts as a buffer between battery Oven and

Loco. It opens the coke side door and reposition itself to place the coke guide car in front of that Oven. It helps the Quenching Loco to collect all the hot coke from the oven through Pushing. LPR is used for the positioning of the Door extractor.

Door Extractor

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Loco: Loco is an electrical machine which is connected to the quenching container. It contains a drive which is electrically driven to which electrical power is delivered through power rails on which it runs.

Quenching Car: It collects hot coke pushed out of the oven and takes it to the quenching stations (either wet or dry). It also brings back the quenched coke and drops it in the appropriate location of the Wharf from where the coke is taken on conveyor with the help of plough-cutter.

Quenching Unit: Quenching is the process of cooling the hot coke collected from the oven either by spraying water or blowing the air(nitrogen) through coke. There are two types of Quenching. Wet Quenching: Water is used for quenching of coke. Dry Quenching (CDQ): Nitrogen is blown through the hot coke. Cold gas is blown into the chamber containing the hot coke and hot gas is collected and chilled using heat sinker. Again this gas is used for cooling operation. The process is repeated in a cyclic manner and is controlled using PLC. Wet Quenching Dry Quenching

Loco with Quenching Car Quenching Car

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Screening Unit: In screening unit, coke graded according to sizes. Then the different sizes of coke are separated and transported to different areas as per the requirement. Coke sizes BF COKE - + 30 MM TO - 80 MM NUT COKE - + 15 MM TO - 30 MM PEARL COKE - + 8 MM TO - 15 MM COKE BREEZE - - 8 MM

Components of Screen House:

• Primary screening system (Directs the Coke from Conveyers to the screens)

•Secondary screening system (Separates Blast furnace Coke from smaller Coke)

•Grading system (Separates Nut , Pearl & Breeze Coke)

•Storage system (Stores different category of Coke)

Primary screening unit in a

Screen House

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Bunker SCPBattery(5,6,7)

with Ovens

Wet

Quenching

Cold Dry

Quenching

Wharf 6Plough

Cutter

Wharf 7

K01

K03

K1A K0

2

LOCO

Screen

House

KC1G Blast

FurnaceSearch

Bunker K5 High

Bunkers

For Boom

Loading

Nut

Coke

Breeze

Coke

Pearl

Coke

Q. Car

B.F. Coke

Coke

Coke

Coke

Coke

Hot Coke

Coal Coal Cake

BF Coke

BF Coke

BF Coke

AN OVERVIEW OF THE COKE PLANT

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PROCESSES IN SCREEN HOUSE

•Coke enters the Screen house via K03 & K1A Conveyer Belts and are send to the top of the Screen House.

•The top of the Screen House is the Primary System and K2 & K2A belt receives the coke from K03 & K1A.

•The Coke in K2 & K2A are fed into Secondary Screening System A & B , which has a vibrating system mounted on springs which runs on motor and has screens of 30 MM dia. The coke of Size +30 MM (BF Coke ) are screened off from the rest of the coke and collected into a bunker (Search Bunker) with the help of a Chute.

•The rest of the coke (-30 MM) are then supplied into Grading System (A1,A2) & (B1,B2) which has screens of 10MM dia and separates the coke into Nut , Pearl & Breeze Coke which are collected in separate bunkers .The Grading system uses eccentric shafts for vibration of the screens.

•From the Search bunker the BF coke is transported to G-Blast Furnace with the help of KC belt , sent to high bunker by K5 belt from where it is transported to other Blast Furnace or the BF coke is boom loaded.

•The separated Nut Pearl and Breeze coke are transported to other places using Dumpers and either sold off or used to make Stinger and Pallets.

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K03

K1A

K2

K2A

A

B

A1 A2

B1 B2

Coke from Wet

Quenching

Coke from Dry

Quenching B.F. Coke is separated Nut ,Pearl & Breeze Coke

are separated

Conveyer System Primary Screening System

Secondary Screening System

Grading System

Conveyers that bring Coke from the Quenching stations to the top of the screening house (Primary Screening System).

Receives the coke from K03 &K1A and gives the coke to the Secondary Screening System . It has two conveyers K2 & K2A.

It has 32MM dia. screens mounted on springs which uses an eccentric shaft rotated by a motor to produce the vibration . This separates the Blast Furnace Coke.

It has 10MM dia. screens in series which are made to vibrate by an eccentric shafts rotated by a motors. This separates the Coke into Nut Pearl and Breeze according to the size and collects them in different location.

AN OVERVIEW OF THE SCREEN HOUSE

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Axis of Rotation

ECCENTRIC SHAFT

• The shaft is made to rotate about the axis of rotation by a Heavy Duty Motor by the help of belts connected to the motor and the shaft.

• Links are connected to the Eccentric portion of the shafts allow free rotation of the shaft within it.

• As the shaft rotates the links are set into regular vibratory motion (To and Fro).

• These links are connected to the screens which are mounted on Heavy Duty Springs.

• The To and Fro motion is transmitted to the screens by the connecting links which makes the screens to vibrate and helps in separating different components of Coke.

MECHANICAL MECHANISM BEHIND VIBRATION

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Eccentric Shaft(32MM dia)

Screen

Dry Fog

to reduce

Dust

Motor Drive to rotate the

Eccentric Shaft

Springs on which the

Screen is mounted

Coke

B.F.

Coke

Chute to the

Search Bunker

SECONDARY SCREENING SYSTEM

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Conveyer system

WORKING OF CONVEYERS

Conveyers are belts of rubber whose motion is governed by the rotational motion of the head end and tail end idler. The idlers are large rotating cylinders which has grooves cut on them which helps it to grip tightly on the idler. External torque for the belt motion is provided by either the head end or the tail end idler or both.

• Weight pulley are used to provide tension and to start the motion of the conveyers.

• Traffic Idler helps to maintain the U or V shape of the conveyers and helps it to carry the Coke.

• Traffic Training Idler are used chance direction of motion of the conveyers.

• Compact Idler has annular rubber bands attached to it and acts as shock absorber.

• Return Idler prevents the conveyers from slacking.

• Return Training Idler prevents the conveyers from slacking as well as changes the direction of motion.

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TO REDUCE SPM LEVEL AT SCREEN HOUSE AT CHP (COKE HANDLING PLANT) ASH FREE BATTERY 5 6 7 IN COKE PLANT

(CASE STUDY OF CHP#3)

The Screen House in the Coke Plant has a very high Dust and SPM level (with a min value of 8 to 9 mg per cubic meter of air.

This makes the environment very hazardous for the workers to work inside it.

The safe value of SPM in air is 3 mg per cubic meter of air.

PROBLEMS:

• Large quantity of dust and SPM (Suspended Particulate Matter) is generated in the screen house during screening particularly during screening operation.

• More dust is generated during Screening of coke from CDQ (Cold Dry Quenching).

• Dust is particularly high in the Primary and Secondary Screening Unit.

• Dust is generated when ever the Coke transferred from one conveyer to other or from a conveyer to the screen.

• Dust is also high where the coke made to fall freely without channeling.

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SOLUTIONS:

1. The most obvious solution is to use Dry Fog device.

This device uses nozzle which sprays a mixture of compressed air and water vapor. The quantity of air is more so that the mixture spreads well. It is always used in the tail end from where the coke falls. This is a good means of preventing dust and can successfully control dust for Wet Quenching. In screening Wet Quenched Coke the SPM level can be maintained around 5. Installation of more Dry Fog devices and their proper maintenance can reduce the SPM level to safe value.

2. Use of Scrappers in the Head End of the Conveyers.

These are metal latches which are attached to the Head End of the conveyers. These are particularly very effective for Wet Quenching where the Coke remains moist and the much of the Coke Dust remains attached to the conveyers. The Scrappers Scrapes off these moist Coke Dust and prevents it from mixing with air and cause the SPM level to increase. These are generally fitted in the back of the Head End to prevent intermixing of Coke and Dust Particles. Proper maintenance and regular cleaning of the Scrappers can reduce the SPM level effectively in case of Wet Quenched Coke.

Dry Fog device

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3. Use of Electrically operated Dust Catcher.

This device employ concepts of static electricity to separate dust. In this process the dust is first ionized by using Corona discharge in the location where it is generated. A oppositely charged plate is fit in the way of the dust particles where they are adsorbed by the plate. The motion of the ionized dust particles can be controlled forcefully by using forced air by draught fans. This is a very efficient way but its very costly so may not be a proper way for a old plant. But this can be used where ever there is a new set up of a screen house.

4. Covering the regions of Dust Generation by Cloth or Rubber Sheet or Metal Sheet.

In this process the regions of major dust generation are identified and then the region is covered by either Cloth or Rubber Sheet or Metal sheet. This prevents the generated dust from coming out of the system and so dose not pollute the environment by increasing the SPM level. The covering must be flexible enough to let the Coke laden Conveyer to pass through easily.

Sheet to prevent dust from

coming out of the system

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5. Use of large Draught Fans to direct the air flow

In this process large Heavy Duty Draught Fans are employed in specific directions. The SPM are carried by air and gets mixed with it to make the environment polluted and hazardous. Now by directing the air flow by using the draught fans we can govern the nature of mixing of dust and SPM with air and thus can control the SPM level in air.

6. Use of Binder or Oil

Binders and oils has a nature of bindings materials together so can be used in binding or clustering particles together. If binders are used in Coke they can bind them together and can reduce dust but in the CHP the Coke remains hot (300 degree centigrade) and binder and oils has low ignition temperature and can catch fire causing accident. This can only be used when the Coke is Quenched to much lower temperature. Which may not be economical.

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RECOMMENDATIONS

• More dry fog to be installed and the existing to be well maintained.

• More scrappers to be used and should be kept under proper supervision.

• Dust Catchers to be used if possible.

• Covering should be used where ever possible.

• More Draught fans to be installed and used when the dust production is more.

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CASE STUDY OF SCREENING OF COKE FROM CDQ IN CHP#3

Background: The dry coke quenched from CDQ is supplied to G Blast Furnace after screening for right sizing. Since moisture content of dry coke is less than 0.5% which generates more dust during screening.

Current Situation: The CDQ coke is only handled in belt conveyor # K1A and its has several discharge points till it reaches the KC1 belt of G Furnace. During this entire process lot of dust is emitted at all transfer points which makes the environment hazardous.

Goal: To reduce the SPM level of screen house building below 5 mg/ m 3 .

Analysis: The main cause for fugitive emission in coke handling is due to the moisture content , the lesser the moisture content the higher is the dust formation.The CDQ coke contains very fine coke particles in the form of very fine dust, which causes dust emission at every discharge point while handling.

Recommendations: To cover all the discharge points of the conveyor system handling dry (CDQ) coke. To increase the number of dry fog dust suppression system (DFDS) .Covering of primary and secondary screen’s with installation of new dry fog dust suppression system (DFDS).Covering of grading screen’s with installation of new dry fog dust suppression system (DFDS).

Result: After installation of new dust suppression system at recommended points and covering of the discharge points dust has got reduced to below 7 mg/ m 3.

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SAFETY PRECAUTIONS TO BE TAKEN IN COKE PLANT

• Always wear PPE like helmet, safety shoes, goggles, fire retardant cloths, gas detectors and dust masks.

• Do not go close to the moving vehicles including loco, conveyer, SCP mc and other rotating machines.• Do not touch any part of the oven and stay away from open ovens.• Never cross the SCP track area.• Do not try to walk close to the railway wagon and bench rope near the tippler.• Do not touch any Conveyers or any pulley in the conveyer system.• Don’t go very close to the screening unit or touch any part of the screening unit even if it is not working.• Always wear mask inside the screen house.• Be careful about hanging objects.• Don’t go very close to the loading dumpers or the dozers.• After work wash your hands and face thoroughly with soap.

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