DCC Training Report Final

VOCATIONAL
TRAINING REPORT
At DANKUNI
COAL COMPLEX
A GENERAL CASE STUDY
OF THE PROCESS FLOW
Submitted By:
Abhradeep Bhattacharya, Anish Nandy,
Ritayan Ghosh, Sagnik Mukherjee,
Souparna Roy and Sucharita Paul
B.Tech, 3rd Year, Mechanical
Engineering, TECHNO INDIA
COLLEGE OF TECHNOLOGY

1
DANKUNI COAL COMPLEX
SOUTH EASTERN COALFIELDS LTD.
DANKUNI, HOOGHLY, WEST BENGAL
CERTIFICATE OF APPROVAL
This is to certify that the project report on "A CASE STUDY ON PRODUCTION
PROCESSES AT VARIOUS PLANT SECTIONS IN DANKUNI COAL COMPLEX" has been
submitted by Abhradeep Bhattacharya, Anish Nandy, Ritayan Ghosh, Sagnik Mukherjee, Souparna
Roy and Sucharita Paul, 3rd
Year students of MechanicalEngineering departmentstudyingin Techno
India College of Technology, Rajarhat, under my guidance.
They have successfully completed "VocationalTraining" program for a period of 2 weeks,
starting from 29th
December, 2014 to 10th
January,2015 in this company and have visited andstudied
the processes of this plant thoroughly.
As per our measurements and reporting structure,their conduct and performance have been
found to be ……………………………. during their training period.
Mr. S. Pal
Sr. Manager (Chemical)
In-charge of Training Dept.
Dankuni Coal Complex
PO: DCC, Dist: Hooghly, Pin: 712310

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ACKNOWLEDGEMENT
Properexecution ofany project depends mainly on the interaction with the personnel of all
branches and levels in a plant. We found almost everyone in Dankuni Coal Complex offering
helping hands to us during our training program.
At first we like to thank Mr. S. K. Mukhopadhyay, HEAD of MECHANICAL
ENGINEERING DEPARTMENT, Mr. S. K. Das, TRAINING And PLACEMENT OFFICER,
TECHNO INDIA COLLEGE OF TECHNOLOGY, KOLKATA for giving us the permission for
the training.
We are thankful to Mr. S. K. Neogi (G.M., DCC) for allowing us to undergo the vocational
training.
We express our sincere gratitude to Mr. Sudipta Pal, Sr. Manager (Chem.), I/C training, for
constructive ideas and suggestions in preparation of this project report, under whose supervision
this project has been executed successfully.
We also extended our thanks to Mr. D. Adhikari (Retort House), Mr. S. S. C. Kumar
(G.C.P.), Mr. N. Pal (Retort House), Mr. A. Chakraborty (P.G.P.), Mr. T. Pathak (C.H.P.),
Mr. M. Mukherjee (T.D.P.), Mr. Banik (HOD, Mechanical) and Mr. G. Mukherjee (Gas
Compressor), for sharing their invaluable knowledge and cooperating with us, as well as taking
out time for us amidst their busy work schedules.
Last but not the least, we acknowledge the immense encouragement and assistance of our
parents in preparation of this project and successful completion of our winter vacation training.

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DECLARATION
We, Abhradeep Bhattacharya, Anish Nandy, Ritayan Ghosh, Sagnik Mukherjee,
Souparna Roy and Sucharita Paul, 3rd year students of Mechanical Engineering branch in
TECHNO INDIA COLLEGE OF TECHNOLOGY, underwent our winter training from
DANKUNI COAL COMPLEX under S.E.C.L., for 2 weeks from 29th December, 2014 to 10th
January, 2015.
Name Signature
1. Abhradeep Bhattacharya
2. Anish Nandy
3. Ritayan Ghosh
4. Sagnik Mukherjee
5. Souparna Roy
6. Sucharita Paul

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PREFACE
Industrial training is a necessary part of all engineering courses to familiarize a student
with the industrial environment so that they can correlate the theoretical knowledge and practical
application.
The report reflects our observations and experience in Dankuni Coal Complex. Although
the training period is not so long to cover up the entire industry and its various systems due to its
vastness, we have tried our best to cover up as much as possible.
Although every care has been taken to check mistakes, yet it is difficult to claim perfection.
If any of the recommendations forwarded by the study is found by the management worthwhile
and important, we would consider our efforts to have been rewarded.

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TABLE OF CONTENT
Sl.
No.
TOPIC PAGE
1 About Coal India Limited 6
2 Brief History of DCC 7
3 Product Profile Of DCC 8
4 Proximate analysis of coal 9
5 Material Handling Plant 11
6 Producer Gas Plant 19
7 Retort Plant 24
8 Gas Cleaning Plant 29
9 Tar Distillation Plant 40
10 De-mineralized Water Plant 45
11 Effluent Treatment Plant 47
12 Utilities 53
13 Safety 56
14 Conclusion 61

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ABOUT COAL INDIA LTD.
CIL comprises eight companies; their names along with their offices are listed below:
Name Head Office
1. Bharat Cooking Coal
Ltd.(B.C.C.L)
Dhanbad
2. Eastern Coal Field Ltd.(E.C.F.L) Sanctoria
3. Central Coal Field Ltd.(C.C.F.L) Ranchi
4. Northern Coal Field Ltd.(N.C.F.L) Singrauli
5. Western Coal Field Ltd.(W.C.F.L) Nagpur
6. Maharatrathi Coal Field
Ltd.(M.C.F.L)
Sambalpur
7. South Eastern Coal Field
Ltd.(S.E.C.L)
Bilaspur
8. Central Mining Planning and
Development Institute
Ltd.(C.M.P.D.I.L)
Ranchi
Main Head Office is at N.S. Road, Kolkata govern all the eight companies.
The senior office staffs consist of the following members in each of the above-mentioned companies:
1. Chairman cum Managing Director (CMD).
2. Director Technical D (T).
3. Personal Director D (P).
4. Financial Director D (F).

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BRIEF HISTORY OF DCC
Dankuni Coal Complex was set up by Coal India Ltd. under the recommendation of the Fuel Policy
Committee, to meet the growing need of "Environment Friendly Fuel" at D.C.C, non-caking coal processed to
produce solid domestic coke and town gas to meet the requirement of the domestic and industrial sectors. The
foundation stone of this plant was laid by the late Prime Minister Smt. Indira Gandhi way back in 1981.
D.C.C. is situated beside Durgapur Expressway in the north and Janai Road Railway station of the grand
chord in the South. The complex site spread over an area of 140 acres.
 Commission on the project:
Heavy Engineering Corporation Ltd. Ranchi (Consultancy services) has been awarded the work
of turnkey execution of the plant. They have collaborated with Badcock Woodall Duckham Ltd., U.K.,
and Simon Carves India Ltd.
 Company setup:
Until 31.03.1996, D.C.C. was under the direct control of Coal India Ltd. but 01.04.1996 the plant
was leased to South Eastern Coal Field Ltd.
 Address- Dankuni coal complex,
P.O.-Dankuni Dist-Hooghly
Pin-712310
 Add. of head office: Seepat road
Bilaspur, Pin- 495001
 Feed: Non-Coking and Non-Caking Coal from SECL
 Product: Coal Gas (Town Gas)
 By-Products: Soft Coke, Tar, Ammonium Sulphate and Light Oil.
 Category of Industries: Red ( Large Scale )
 Factory license no.:11809
 Project cost: ₹ 135 crore
 Name of the G.M.: Shri S. K. Neogi
 No. of shifts: 3 shift per day in rotation and also general shift.
 Objective of the plant:
 About 800 tonnes per day of solid Smokeless Fuel, branded as CILCOKE.

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 About 18 million cubic feet of Coal gas per day for supply in and around Calcutta and Howrah
 About 70 to 75 tonnes of Tar Chemicals per day.
Both solid and gaseous fuels, being very clean in nature, would subsequently contribute to the reduction
of pollution level of Calcutta and Howrah.
 Plant location and weather:
The weather of the plant site is suitable one, though humidity is a bit high. The temperature varies
from minimum 10 C to maximum of 40 C. The rainfall in the month of May to August is noticeable.
PRODUCT PROFILE OF DCC
CIL
Coke
More than
35 mm
65-68%
fixed
carbon
3% volatile
matter
Usedas fuel
and
Reductant.
Coke
Fines
0-6,0-10,6-
35mm
65-68%
fixed
carbon
3% volatile
matter
Coal
Gas
Calorific
value:33
therm
Usedas
replaceme
nt of
furnace oil,
also
domestic
purpose.
Coal
Tar
Gross
Calorific
Value:
10230
cal/kg
Usedas
fuel,
source of
Tar
chemicals
Tar
Chem
icals
LightOil-
usedas
solvent
and paint
Pitch- used
in
elctrodes
Coal
Fines
0-25 mm:
Used by
thermal
power
plants
3-
5mm:Bricke
ting
industry
65-68%
fixed carbon
3% volatile
matter

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PROXIMATE ANALYSIS OF RAW COAL

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MATERIAL HANDLING PLANT
Material Handling Section is designed for the receiving Coal in Railway Wagons and other raw material by tracks
and for dispatch coke and coal fines. Elaborate System of Belt Conveyors is provided for the transport of Coal and Coke
within the Plant.
Main component of coal handling plant:
 Wagon Tippler:
It is used for unloading of Incoming Coal Wagons and it is one of the most vital equipment of MHP. The
Wagon Tippler has two "Slip Ring Induction Motors" of capacity 53KW each. Each Motor has 5-step rotor
resistance. Steps 1 to 4 are used for acceleration and Speed control of Tippler. Step 5 is permanently used in the
Rotor Circuit. Each Motor has D.C Electromagnetic Brake. The Magnet operates to Release and Brake-thereby
allows Tippler to rotate. The cylindrical cage of the tippler consists of two circular ring fitted with gear teeth and
connected to a platform with travel rails, support rollers, girders, counter weights, hydraulic clamping device for
wagon, from top as well as side during tippling. These are giant machines having gear boxes and motor assembly
and are used to unload the coal wagons into the coal hoppers in less time where it moves down to the vibratory
feeder to the discharge chute.

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Technical Specification of Wagon Tippler:
Type Rotary, Gravity Clamping
Gross Load Capacity 110T
Tippling Time per cycle 1.5min
Maximum Angle of Rotation 165ᵒ to 175ᵒ
Overall Dimension of Tippler
Length 19.8m
Breadth 9.6m
Height 8.5m
Length of platform 16.7m
Drive Motors 55KW, 40%duty, 145V
Rail gauge 1676mm
Shunting carriage back 1360mm
 In Hauler and Out Hauler:
There is arrangement of shunting IN & OUT of individual wagon from the Tippler. These are called:
1. INHAULER: Used to transport Wagon into the Tippler prior to unloading.
2. OUTHAULER: Used to transport Wagon out of the Tippler after unloading.
 Vibrating Feeders:
These are electromagnetic vibrating feeders or sometimes in the
Form of dragging chains which are provided below the coal hoppers. The equipment is
Used for control and continuous removal of coal and coal hopper. Thus we can say that a
Vibrating feeder is used to transfer the large size materials and granular materials from the
Hopper to receiving device uniformly, periodically and continuously in the production
Flow and to feed materials into the crusher continuously and uniformly. Characteristics of vibratory feeder-Smooth
vibration, reliable operation, long service life, low noise, low power consumption, easy to adjust, simple
structure, easy to install, light weight, small volume, simple maintenance.
 Belt Conveyors:
These are synthetic rubber belts that moves on metallic rollers called "idlers" and are used for shifting of coal
from one place to other places, conveyers are seen on virtually all in the Coal Handling Plant (CHP). The gradient
of conveyors is 32ᵒ to 35ᵒ. Rollers under conveyor belts are at 30ᵒ. The Main Conveyer Belt paths can be classified
as:
o COAL STORAGE ROUTE
o COAL CHARGING ROUTE
o COKE DISCHARGING ROUTE
The efficiency of the MHP depends on the availability and reliability of the conveyer system.There are different
types of drums/pulleys drive the belts. In conveying side carrier roller, head drum, snap drum, tension drum (to
prevent sagging) are there. In returning side, return roller is there. Due to the vibration along the belts, they may be
misplaced. To adjust their position carrier adjustable roller and return adjustable roller are there. In this case of
emergency sufficient measures have been taken to ensure safety. For example — a "pull cord switch" is available
at regular intervals throughout the belt which helps in stopping the belt at any position in order to prevent accident.
A brief description of conveyors in MHP is given below.
Screen analysis of coal at C-7 and C-8 belt:

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Belt +100mm(%) +40mm(%) +25mm(%) +10mm(%) -
10mm(%)
Stones(%)
C-7 23.3 47.4 25.9 1.7 1.7 10.1
C-8 - nil 61.0 36.4 2.6 -
 Mobile Tipper:
It is the discharge outlet that helps in dropping the coal at a specified point. When this tripper fills up a
particular space it is shown by an indication of the tippler shifts to next position.
The main Drive Mechanism of Mobile Tippler consists of:
o Main Drive Motor: This drives the moving carriage chain by Sprocket Mechanism.
o Hydraulic Thrusters Motor: Used for Braking the Carriage.
o Cable Drum Drive Mechanism: It is used for Reeling of Power Cable.
Brief Description of Coal and Coke Handling:
 The sized coal (0-200mm) unloaded from wagon tippler (WT-1) will be received in the hoppers placed below the
wagon tippler. The hoppers have two openings each. The hopper which is provided with rack a(id pinion gate (G-
1) feeds the coals to inclined belt conveyor (C2) through heavy duty vibratory feeder (HDVF-1,2) and discharge
chute(DC-l).
 A-dust suppression system (DSS-1) is installed in wagon tippler complex for suppression of coal dust arising from
the materials unloaded from wagons by tippler. A vertical sump pump (SP-1) is installed at the sump in wagon
tippler pit to pump out any accumulated water with coal dust. Coal (-200mm) from the conveyor C2 will be fed
either to the conveyor C4 above coal storage bunker or to the conveyor C5 above coal storage bunker or to the
conveyor C3 above open coal stock area through discharge chute with flap gate(FG-2) manually operated. The
junction house is provided with a Dust Extraction System (DE-2) for removal of coal dust from junction house.
 The conveyor (C3) above open coal stock area is provided with Mobile Tippler (MT-1) for a stock piling the coal
on the ground. The tippler is operated for uniform stocking of coal on the open ground. This coal can be fed to the

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manual unloading hopper with the help of Pay-loader as and when required. About three thousand tonnes of coal
can be stocked in open coal stockpile.
 The conveyor C4 above coal storage and out loading bunker has a Mobile tripper (MT-2) to fill up the coal storage
bunker, which has twenty openings with Rack and Pinion Gates (G-3-22). The storage bunker feeds the coal to
reclaim conveyor (C5) through discharge chutes(DCJ-3-22)and vibratory feeders(VF-1-20).The reclaim conveyor
(C5) will feed the coal to conveyor (C6) from coal storage and out loading bunker to crusher /screen house through
discharge chute (DC-24). The unloaded coal from wagon tippler can also be diverged to crusher (Screen House by
passing coal bunker). This diversion can be achieved by shifting the tippler (MT-2) on to the end bunker. The end
bunker is provided with a rack and pinion gate (G-2) and discharge chute (DC-23) and vibratory feeder. This end
bunker is normally used for direct transfer of coal.
 Conveyor (C6) from coal storage bunker to crusher/screen house is meant for feeding 450 TPH coal to
crusher/screen house for crushing and screening. A belt weigher (BW-1) is provided on this belt conveyor for
recording the quantities of coal supplied to, crusher /screen house. Magnetic separator (MS-1) is suitably provided
on this inclined conveyor to remove iron scrap-in coal to protect the crusher from damage. Besides these, a. metal
detector (NMD-1) is also mounted over the conveyor for detecting any metallic pieces above 40mm3 size and
stopping the conveyor in case of their detection. Detection shall be indicated through a suitable audible hooter
system.
 Coal from the above conveyor (C6) is fed to the single deck vibratory screen (VS-1/VS-2) via a discharge chute
with flap gate (FG-2). Oversized coal +100 to -200, after being separated in the screen is fed to the double roll
crusher (CR-1/CR-2) for crushing to below 100 mm and is discharged through discharge chute (DC-25/DC-26).
The output of crusher and sized coalto 100mm from single deck screen is again fed to double deck vibratory screen
(VDSH/VDS-2) through discharge chute (DC-27/DC-28).
 The coal fractions 0 to -10, +10 to -25 and -t-25 to -100 are separated in double deck vibratory screen .0 to -10mm
coal is rejected which are fed to reject conveyor (C9) through discharge chute (DC-31/DC-32). These rejected coal
fines are accumulated in coal fine bunker from the reject conveyor by discharge chutes. The coal fine bunker has
170 Tones capacity and it has two openings with rack and pinion gates (G-23-24) to load the coal fines into trucks.
Discharge, plough with chute is also provided to unload the coal fin§s from conveyor C9 directly on the
ground/truck.
 The size +10 to -25mm coal will be fedto the conveyor C8 with belt weigher (BW-3) for feeding producer gas plant
conveyor (C12) via discharge chute (DC-33) with flap gate. This coal can be diverted to coal fines bunker through
flap gate when larger size coal meant for retort house will be fed to producer gas plant through conveyor and chute
with flap gate as and when required.
 The sized coal +25 to -100mm is fed to conveyor C7 with belt weigher (BW-2) for feeding to Retort via fixed
tripper (FT-1) and discharge chute with flap gate (FG-S) at the end. Belt weigher is provided for recording the
quantities of coalsupplied to retort house and PGP. The crusher house is provided with dust extraction system (DE-
3) for removal of coal dust generated in screens,crushers etc. Conveyor (C10 and C11) for distribution of coal in
retort house nave Mobile Tipplers (MT-3 and MT-4) for feeding the coal to individual retort bunker. Conveyors
(CO-1, CO-2, CO-3 and CO-4) below the four rows of retorts receive coke from retorts through coke chute and
transfer to conveyors (CO-5 and CO-6) in front of retort house through discharge chute with flap gates (FG-6-9).
Of the two parallel conveyors, only one will be loaded at a time. Through discharge chute (DC-35, 36) the coke
will be transferred to the connecting conveyors (CO-7, CO-8) to coke screening house. These two conveyors are
provided with belt weighers (BW-4, BW-5)! For weighing and recording the coke transported to coke Screening
House.
 Coke from these conveyors is fed to one of the single deck Vibratory Screen (VS-3/VS-4) through discharge chute
(DC 37/DC 38).Required size is +10mm and above. After being separated in the screen,-it is fed to storage line
conveyors (CO-9 and CO-10). Coke fine bunkers have two openings with rack and pinion gate (G26/27) for
unloading the coke fines to the trucks.The coke fines bunker is placed below the vibratory screens.The coke storage

15
line conveyors (CO-9, CO-10) are provided with mobile tipplers (MT-5 -MT-6) to feed the coke in one of the two
coke bunkers with fine openings each. These openings have rack and pinion gates (G 28-32 and G 33-37) to load
the coke into trucks. The coke handling system outside retort house up to the storage bunkers have two lines, one
of which will be working and the other kept as stand-by.
 The provision has also been made to feed the coke from the coke storage line conveyor CO-9 to conveyor CO-11
with mobile tippler (MT-7) through discharge chute (DC-39) for stock piling the coke on the ground. An operator
will operate the tippler for uniform stocking of coke on the ground from' where a dis-loader (DL-1) will reclaim the
coke for loading to waiting trucks.
Coal Conveyor Belts:
Belt Length (m) Width (mm) Capacity
(MT)
Places between it conveys
C1 80 1200 250 Manual bunker to C2 belt
C2 200 1200 1000 From wagon tippler
C3 210 1200 1000 To open stock yard
C4 500 1200 1000 To coal bunker
C5 200 1000 450 Coal bunker to C6 belt
C6 200 1000 450 To crushers
C7 220 800 300 To C11 belt
C8 200 600 60 To C12 belt
C9 190 650 110 Coal fines to coal fines bunker
C10 120 800 300 From C7 to B1, B3, B5 benches of RH
C11 120 600 300 From C7 to B2, B4 benches of Retort House
C12 120 600 60 Coal to PGP
202A 80 600 From C12 to G1,G2,G3 gasifiers of PGP
202B 80 600 From C12 TO G4, G5 gasifiers of PGP
Coke Conveyor Belts:
Belt Length
(m)
Width
(mm)
Capacity
(MT)
Places between it conveys
CO1 140 800 55 Coke from Retort benches B1, B3 and B5
CO2 140 800 55 Coke from Retort benches B1, B3 and B5
CO3 90 800 125 Coke from Retort benches B2, B4

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CO4 90 800 125 Coke from Retort benches B2, B4
CO5 90 800 125 Coke to coke bunkers
CO7 200 800 125 Coke to coke screening house
CO8 200 800 125 Coke to coke screening house
CO11 125
CO12 125
Crushing and Screening Section:
A magnetic separating system is arranged on the belts (C-6 and C-2) to remove magnetic materials (mainly iron)
from Coal to protect the Crusher. There are some "shear pins" attached to the crusher to protect the crusher from damage
during uneven crushing stress or anything like that. A Metal Detector is also placed over the Conveyer to detect metallic
pieces. Coal from Storage Bunker is fed to the Single Deck Vibrating Screen (VS-1/2) via Discharge Chute. After being
separated from this Screen Coal is fed to fixed jaw roller crusher for crushing below 100mm. The output of the Crusher
goes out via Single Deck Vibrating Screen through Discharge Chute.
Coal fractions are carried out in different places via different Conveyers.
The size -25 to -40mm coal will be fed to the conveyer C-8 with belt weigh for feeding Producer Gas Plant. The sized coal
+40 to -100 mm is fed to conveyer C-7 with the belt weigh for feeding the Retort via fixed tripper and discharge chute at
the end. Coal of size -25mm are called "coal fines" which are conveyed by conveyer C-9. The coalfine bunker has 170 tons
capacity. The fines are sold to Thermal Power Plants (NTPC is one of the big consumers of coal fines).
Double Roll Crusher:
Type Toothed Double Roll Crusher
Quantity 2
Capacity 50T/hr
Feed size 100mm to 200mm

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Product size -100mm
Motor 50HP, 1440rpm
Weight of crusher 6Tonnes
Manufacturer Shahjee
Process flow for Coal Handling Plant
Raw Coal(-
200mm) from
rail wagons
Material Handling
Plant
Through Wagon Tippler
& hopper feed to
inclined belt conveyor
Coal Storage
bunkers(20
nos.,each
500MT)
CrusherHouse
(450 MT/ House)
Conveyor Belt
VibratoryScreen
through
discharge chute
Crushed Coal
(0-100mm)
25-40 mm
To Producer
Gas Plant(PGP)
To RetortHouse Bunkers
(5 nos./each 500 MT)
40- 100mm
Coal Fines(0-25
mm)
Coal FinesBunker(1
unit/170 MT capacities)
Collected at
regularintervals and
sold mainly to
power sectors

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PRODUCER GAS PLANT
Objective:
The main aim of this plant is burning of coal in presence of air and steam to produce clean and low Calorific value
fuel gas to heat 5 benches of Continuous Vertical Retort (CVR) located in the Retort House.
Pyrolysis is the process of cracking of macromolecule into smaller more volatile components. This process of
Pyrolysis is conducted in a Gasifier where coal is burnt with limited supply of air and steam to produce Top gas,
Bottom gas and Solid residue (Cinder).
During gasification the fuel( biomass) is heated to high temperature, which results in the production of volatile
compounds and solid residues. The quantity and composition of the volatile compounds depends on the reactor
temperature and type, the characteristics of the fuel and a degree to which various chemical reaction occur within
the process. The primary reactions that occurs in presence of oxygen results in conversion of the fuel to CO and
CO2. These reaction are very fast and exothermic which provide energy to sustain other gasification reaction.
Gasification of other solid material occurs at high temperature and produces Gases, Tar and Ash. Generally these
reactions are carried out in presence of reactive agents such as O2 and Steam. H2 produced is added to the reactor
to aid in chemical conversion of char to volatile compound.
TYPES OF ELECTRICAL DRIVES /EQUIPMENTS in P.G.P
a. Hydraulic Pump for Gasifiers: This Motor driven pumps are used to supply high pressure Hydraulic
fluid to a set of reciprocating cylinders which moves the
Gasifiers Grate in a Circular motion thereby providing
automatic removal of ash & Char from the Gasifier.
The reciprocating motion of the Hydraulic cylinder is
achieved through a no. of Electrically operated Solenoid
Valves & Limit Switches.
b. Vibrating Screens: These Motors driven screens are used
to feed properly sized coal from individual Coal Bunkers
into the Lock Hopper of the Gasifiers.
c. Coal Fines Conveyers: Down sized Coal from the vibrating Screens are carried by this Chain Conveyer
for Storage in Storage Bunker.
d. Air Blower: The process of manufacture of producer Gas, air & Steam is required to be blown over bed
of Red Hot Coal. Air Blower serves purpose of maintaining this Air flow. This in turn helps to maintain
positive Draft at the Inlet Header of the Gas Pipe of the Retort.
e. Electrostatic Precipitators (ESP): Two nos. of ESP are used to separate Tar particles from Top Gas.
This is achieved by passing the gas in between a Discharge Electrode and a Collecting Pipe maintained at

20
very high Potential Difference (60 KV DC). At such a high Potential difference ionized air particles is
achieved by the effect of negative Corona. The negatively charged particles are attracted to positive
Collecting pipes (positive is earthen) and hence separated from the Top Gas.
f. Production capacity:
Producer gas 128000 Nm3
Gross calorific value 1600kcal/Nm3
Tar 5MT
Ash 62MT
Coal charging 57MT
General Principle:
It has five gas producers or gasifiers numbered A, B, C, D and E. Each gasifier has distillation
zone at the top and gasificationzone at the bottom is water jacketed and supplies LP steam for
gasification. The overhead coal bunker feeds coal through lockhoppers. Air blower supplies air
into the gasifier. Top gas coming from the top of the gasifiers contains volatile matters and is
passed through tar knock out pots, electrostatic precipitators (ESP) at about 110°C to 150°C. Hot
gas from the bottom gasificationzone passes through dust cycles to make it free from coke dust,
ash etc. The bottom gas and top gas are then mixed together and sent to the Retort House as fuel
for generating coal gas.
Flow Diagramfor Producer Gas Plant
Main plant component:
 Coal Charging System:
MHP
Charging of Raw
Coal(25-40 mm)
5 nos.of Double Stage
Gasifier-3.6mDiameter
Coal Gasificationduringthe
flow of Coal from Topto
Bottom
Top Distillation zone
Bottom Gasification
zone
Hot Gas (650°C-700°C);
Gasification Zone
Distillation Zone(Top)
Tar andVolatile Matter
Bottom
Ash;Collectedand
dumpedoutside
Passed through
Dust cyclone
Gas free from
coke dust, ash etc.
Electrostatic
Detarrer
Tar Sentto TDP
for dehydration
MixedGas to Retort
House (at around200°C)

21
Blended coal is fed from stockyards, storage top, magnetic separator, and crushing screening plant to the
conveyor transfer station situated between the RH and gasifier house.
Two 60ton/hr capacity cross conveyor transfer the coal to the five 70T capacity individual gasifier across
bins, coal is also charged from the base of the hopper into a vibratory screen which receives the 10 mm fraction as
employed in a storage hopper.
Screened coal of +10 to -25 mm size is fed through 600 kg coal capacity "lock hopper" located
immediately above each gasifier at a maximum rate of 300kg/hr into the distribution zone. A charge release from
each hopper is controlled by the overall bed height of gasifier through a mechanical location sensing arm. Each
gasifier lock hopper has an inlet valve at the top and an outlet valve at the base. When the lock hopper is ready to
receive coal, its inlet valve opens and the vibrating screens associated with the hopper start to operate while the
outlet valve remaining close.
A timer allows a charge of about 250 kg of screened coalto enter the hopper. The screen then stops and
the inlet valve closes. When a signal from the gasifier indicates that
Coal has fallen to a predetermined level the valve at the base of the lock hopper open and the contents at the
hopper are discharged into the gasifier.
 The Gasifier:
The 3.6 m diameter grate gasifier is of the fixed bed type in which air and steam are passed Upwards through
a bed of the hot carbonaceous material, the product gas contains predominantly at CO2,CO, H2, N2. The capacity
of each gasifier is 4500kg/hr. Each gasifier has the following constructional parts from to bottom:
 Pre-heating Zone.
 Drying Zone
 Distillation Zone.
 Secondary Reduction Zone
 Primary Reduction Zone
 Oxidation Zone
 Ash Extraction Zone
 Pre-heating Zone and Drying Zone:
This is the uppermost part of the gasifier, also known as coal feed zone and here a distributor feeds coal
into the fire segments of the distillation zone.
 Distillation Zone:
It consists of two main parts. They are-
 The external clear gas passage operating at 550°C to 650°C temperature.
 The internal fire section distillation chamber, providing a distillation product gas at 1200ᵒC temperature.
The external clear gas passage is insulated from the external shell but not from the distillation zone.
 Gasification Zone:
It is a chamber supporting the upper distillation zone. It is cooled by an external water jacket,which is
connected to a steam drum located adjacent to the gasifier. This jacket-drum combination provides gasifier steam
and make up steam is supplied from Waste Heat Boilers of Retort House.
 Ash Extraction Zone:
It is the bottom part of the gasifier and is a mechanical assembly of a stationary and hydraulically driven
metal. The grate assembly is hydraulically driven together with plough to remove ash and clinker, the steam and

22
air mixture is passed through the concentric rings of the grate using water sealfrom the atmosphere. The grate
movement depends upon the bottom gas temperature. If the gasifier temperature crosses 1000ᵒC, grate movement
is faster.
 Steam Drum:
It stores the steam produce from the water cooling jacket of gasifier. Circuit pressure is 2.3 mm water
gauge and circulating the steam and the cooling jacket is connected. There are two steam drivers with the first
connected to the there gasifier while the second is connected to the remaining two gasifier. Sometimes the
temperature of top gas can be controlled by spraying steam to it. As the steam contains water droplets it absorbs
heat to vaporize and the temperature falls.
 Top Gas Cyclone:
Char particles present in the top gas are separated by this cyclone. This cyclone is fitted with an external
steam heating coil to assist removal of tar product and is connected to a sealpot for condensate removal via a
drain. About 50% of the tar in the gas is extracted here.
 Bottom Gas Cyclone:
It separates solid particles of semi coke and ash entrained in the bottom. This cyclone function at 550°C
to 650°C separates dusts fall to the tower case and is periodically extracted via a vertical pipe sealed at the lower
part.
 Tar Circuit:
Tar removed from cyclone and ESP is pumped to a reserve vesselwhere phenol water is separated and the
fluid tar product is pumped to storage tank. Tar line also stream traced to maintain the tar as a liquid.
 Air Blower:
Generally reaction air is supplied into a distribution main by 3 electric powered blowers. There is also a
trip valve (made of solenoid) which automatically being into operation the steam ejector to provide emergency air
in the event of failure of the power supply to the blower. The capacity of each blower is 9000kg/hr.
Reactions in Gasifier:
Air-carbon reaction:
𝐶 + 𝑂2 → 𝐶𝑂2,Δ𝐻 = −97000 𝑘𝑐𝑎𝑙/𝑘𝑚𝑜𝑙𝑒(𝑒𝑥𝑜𝑡ℎ𝑒𝑟𝑚𝑖𝑐)
𝐶 + 𝐶𝑂2 ↔ 2𝐶𝑂,Δ𝐻 = +38270𝑘𝑐𝑎𝑙/𝑘𝑚𝑜𝑙𝑒(𝐵𝑜𝑢𝑑𝑜𝑢𝑎𝑟𝑑 𝑟𝑒𝑎𝑐𝑡𝑖𝑜𝑛 𝑒𝑛𝑑𝑜𝑡ℎ𝑒𝑟𝑚𝑖𝑐)
The net overall reaction is:
2𝐶 + 𝑂2 ↔ 2𝐶𝑂,, Δ𝐻 = −58370𝑘𝑐𝑎𝑙/𝑘𝑚𝑜𝑙𝑒(𝑒𝑥𝑜𝑡ℎ𝑒𝑟𝑚𝑖𝑐)
Steam-carbon reactions:
𝐶 + 𝐻2 𝑂 ↔ 𝐶𝑂 + 𝐻2 𝑂, Δ𝐻 = +28440𝑘𝑐𝑎𝑙/𝑘𝑚𝑜𝑙𝑒(𝑒𝑛𝑑𝑜𝑡ℎ𝑒𝑟𝑚𝑖𝑐)
𝐶 + 2𝐻2 𝑂 ↔ 𝐶𝑂2 + 2𝐻2,Δ𝐻 = +18600𝑘𝑐𝑎𝑙/𝑘𝑚𝑜𝑙𝑒(𝑒𝑛𝑑𝑜𝑡ℎ𝑒𝑟𝑚𝑖𝑐)
𝐶𝑂 + 𝐻2 𝑂 ↔ 𝐶𝑂2 + 𝐻2,Δ𝐻 = −9840𝑘𝑐𝑎𝑙/𝑘𝑚𝑜𝑙𝑒(𝑠ℎ𝑖𝑓𝑡 𝑐𝑜𝑛𝑣𝑒𝑟𝑠𝑖𝑜𝑛 𝑟𝑒𝑎𝑐𝑡𝑖𝑜𝑛 𝑒𝑥𝑜𝑡ℎ𝑒𝑟𝑚𝑖𝑐)
Methanation reaction:
𝐶 + 2𝐻2 ↔ 𝐶𝐻4, Δ𝐻 = −20840𝑘𝑐𝑎𝑙/𝑘𝑚𝑜𝑙𝑒(𝑒𝑥𝑜𝑡ℎ𝑒𝑟𝑚𝑖𝑐)

23
Composition of producer gas:
CO 26% to 28%
H2 18% to 21%
CO2 4% to 6%
N2 49.2% to 40.8%
O2 0.2% to 0.4%
CH4 2.6% to 3.8%
C.V. 1500kcal/Nm3 to 1650kcal/Nm3
Inputs and outputs to the gasifier:
Input Output
Coal Ash and Dust
Water Bottom Product Gas
Steam Top Product Gas
Air Tar
Mass balance on producergas plant:
Basis: One gasifier/hr
Inputs:
Coal 0.833MT
Steam 1.0MT
Air 2MT
Outputs:
Producer Gas 3MT
Ash 0.585MT
Tar 0.25MT
Producer Gas composition mass basis:
CO2 11.78kg
CO 0.286kg
O2 32.5kg
CH4 2.86kg
H2 1.61kg
N2 57.25kg

24
Steam balance on gasifier:
o Moisture in tar (5% moisture) ------------------------------- 0.0125MT
o Steam consumption for reaction---------------------------- 0.9795MT
Total steam (output)-------------------------------------------- 0.992MT
Total steam (input)---------------------------------------------- 1.00MT
Reason of using wet blast instead of air blast:
Dry air blown producer gas is a mixture of one third carbon monoxide and two third nitrogen. Its calorific value
and coal gas efficiency is low. All these demerits are removed by using a wet blast i.e. by adding steam to the blast of air.
The advantages of using wet blast are:
The total content of combustibles ( CO + H2 + CH4) is raised and the inerts (N2 + CO2) content is lowered thereby
increasing C.V.
o A part of the sensible heat liberated by the combustion of carbon is converted into the potential heat of hydrogen
and carbon monoxide. The cold gas efficiency of wet blast producer is higher than that of only air blown
producer.
o Endothermic reaction between carbon and steam prevents the clinker formation.
Factors affecting the composition of producergas:
o Nature of fuel: High volatile bituminous coal gives a richer gas, containing small proportion methane. Tar vapour
also enriches the gas when it is used hot. Coke gives a gas free of tar vapour.
o Operating temperature: Low temperature favours high production of CO2. High temperature favours high
production of CO.
o Effect of steam: Water in the coal feed or steam in the air blast increases the proportion of H2 and CO in the gas,
thus raising its calorific value. If excess steam is added, the temperature of gasification is reduced; more CO2 is
formed and the calorific value of the gas is decreased. If steam is not added, there are chances of clinker
formation.
RETORT HOUSE
Here Coal is carbonized in Continuous Vertical Retorts while continuously moving downward through the
Carbonizing Zone. Destructive distillation of coal is the process of pyrolysis conducted in a distillation apparatus
retort in absence of air to form the volatile products, which are collected from the top and solid residue from the
bottom. This application relates to a method and apparatus in which coal is converted to gas, liquid and solid
products by a integral combination of pyrolysis, gasification and possibly Fischer- Tropsch synthesis. Destruction
distillation is not a unit operation like distillation, but a set of chemical reactions. The process entails the
“cracking” (breaking up of macromolecules into smaller, more volatile, components and this remains a viable
route to many compounds).

25
Objective:
Here in this part of D.C.C the non- coking coal of sizes +35 mm to -100 mm, having moisture content of 3-5%,
is fed into a continuous vertical retort from the top and is carbonized while moving down wards through the retort.
Due to the carbonization of coal, the products formed are:
(a) Solid: carbonized coke.
(b) Liquid: tar
(c) Gaseous distillation product.
Thus the objective of this process is the production of coke, tar and gases.
Production:-
About 800 tons per day of solid smokeless coal branded as CILCOKE is manufactured from low ash, low
Phosphorous, low Sulphur Coal source.
Fixed Carbon content: 62-67%
Gas: 23%
Volatile Matter: 3-5%
Phosphorous: 0.03-0.04%
Calorific Value: 5000-5500 Kcal/kg
Brief Information about the Main Components used in RetortHouse:-
a. Hydraulic Pump Motors: This Motor
provides pressurized Oil needed to work
Hydraulic circuits in the Coke Discharge of the
Retort.
b. Flushing Liquor Pump Motor: It circulates
Ammoniacal Liquor for spraying at the gas off-
take of individual Retort in order to cool the
gas, temperature to 80̊Cfor condensation of Tar
& Ammonia which are collected in suitable time, otherwise this Tar would clog the Steam gas pipe &
equipment.

26
c. ID Fan Motors: These fans are used to circulate the flue gasses coming out of the Combustion Zone of CVR,
through Fire Tubes of the Waste Heat Boilers.
d. Askania: It is a Pressure Controlling Device .
The Butterfly valve of Askania is kept within the
Coal gas line in between the Gas Tank Pipe &
Main pipe to GCP . It maintains a positive
pressure of 3.5 mm H2O Gauge inside the Retort
so that infiltration is avoided.
It consists of metallic diaphragm& Hydraulic
system , similar to that of Retort . When the Pressure inside the Retort increases the Butterfly Valve opens to
reduce the Pressure in Collecting Main & vice versa. A Bypass line is also present in the Coal Gas Line,
before Askania Butterfly Valve System, which is operated manually to maintain positive pressure in case
when the Askania fails. When Exhauster Gas Pressure is increased the Gas is vented fron the Retort House
through Vent Valve to the Atmosphere.
e. Goose neck: From the top each retort a goose neck comes out which is connected to the collecting main. As
coal gas+ tar comes out in vaporized form through the neck of the retort, arrangement is made within the
goose neck to cool it down from 200 deg C to 75 deg C by spraying NH3 Liquor.
f. Coke Trolley: These are basically discharge Chutes mounted on Motor driven Trolley cars & facilitates the
discharge of Coke on the Coke belts.
g. Coke Quenching Water Pumps: These Motor driven pumps are used to supply water for Quenching of Red
hot Coke discharged from the Retort onto the belt.
h. Sump Pump Motors: Discharge system in the Retort as well as in other parts of the plants are designed so
that Rain Water may be collected at some pits from where this water is collected & discharged into the
drainage system of the plant with the help of Sump Pumps.

27
Flow Diagramfor RetortHouse
Process descriptionof retort:
A brief process description is given below:
o In the Continuous Vertical Retort, coal is carbonized in a comparatively thin layer, while continuously moving
downwards through the carbonizing zone. At the starting of a retort bench some coke is fed to ovens even before
feeding coal. This is to control the temperature along the bed so that the gasification of raw coal can be controlled.
o By this method the coal is gradually carbonized and converted to coke by the time it reaches the base of the retort.
o The various gases and by-products, which are evolved during carbonization, are extracted from the top of the
retort and are supplemented by Water Gas, which is produced by injecting process steam into the base of the
retort. This steam utilizes the sensible heat of the coke and therefore assists towards cooling and quenching the
coke.
o Final cooling of coke is achieved by means of water sprays, so that it is ultimately discharged from the retort in a
relatively cool and dry condition without flame or smoke.
o In order to support the carbonization process, it is necessary to maintain the retort at a high temperature and to
achieve this; the producer gas is burnt in combustion flues arranged on both sides of each retort. The combustion
MHP
Sized Coal Coal descended
and gradual
Carbonisation at
Vertical Retorts
Combustion of
Producer Gas
Gaseousmaterial
containingTar and
ammoniacal liquor
Retort top
Retort Bottom Gradual carbonisation
of Coal to Coke
Steamintroduced;Coke cooling
and productionof WaterGas;
EnhancesGas yieldandprovides
for HeatTransferto incomingcoal
Sucked by
Exhauster
through Primary
cooler
To
GCP
Heat Extraction &
Water quenching
Coke Hopper: Cooled
Coke isdischarged
every2 hours.
Screened
and sent
to stock
yard.
Coke fines:0-10mm
Coke:10-35mm
CIL COKE: +35mm

28
flue comprises six horizontal "passes" arranged one above the other and the products of combustion travel the full
length of each horizontal pass before entering the pass above. Good temperature control is required to ensure
efficient plant operation with smooth coal travel and is one of the most important aspects of retort house
management.
Temperature profile along the six passes:
1st pass 1150ᵒC to 1200ᵒC
2nd pass 1200ᵒC to1250ᵒC
3rd pass 1250ᵒC to 1275ᵒC
4th pass 1275ᵒC to 1225ᵒC
** To measure the temperature "Disappearing Filament Type Pyrometer" is used
o PGfor combustion is introduced via a header main, known as "CO main". After leaving this main producer gas
for each pair of retorts enters the setting via "CO neck". A dumper in this neck (CO neck dumper) is used to
regulate the PGpressure in the distribution flues leading to combustion chamber. Flue passes in zigzag manner
through flue chamber. Such design of flue chamber is to increase the heat transfer area and to increase the heat
transfer time.
o The combined waste gases from all the combustion chambers in the retort bench pass into the waste gas main via
waste gas necks,each waste gas handling the products of combustion from the combustion chambers of five retort
benches. The waste gas from the whole bench is conveyed to the WHBs, where the major portion of the sensible
heat is utilized for raising steam. The draft required in the combustion flues is produced by an ID fan with
exhausted waste gases through the tubes of the waste heat boiler and discharge them to atmosphere via a chimney.
o Coal for carbonization is fed from the main overhead coal storage bunker via hand operated valves into the
individual retort auxiliary coal hopper, which holds approximately one hour's supply of coal. The coal feeds
continuously by gravity from the auxiliary hoppers into the retorts.
o The gas evolved from the coal passes from the top of the retort through a gas off take pipe situated at the outer
end of the major axis.
o A constant supply of hot ammoniacal liquor is sprayed into the gas off take pipes in order to keep them free from
Tar and pitch deposits and to cool the gas. This liquor passes forward with the gas into the collecting mains from
where it flows via seal pot to a Tar and liquor separating tank for recirculation.
o The cooled gas passes vertically from the centre of the collecting mains into the foul main and onto the RH
governor. The RH governor is a hydraulically actuated butterfly valve.. The purpose of which is to maintain the
pressure of the gas leaving the retorts at more or less level gauge condition. From the retort house governor, the
gas passes to a suction main, which leads to the GCP and a turbine driven exhauster.
o In the mean time, the coke is being continuously extracted from the retort by means of the coke extractor gear and
deposited in the retort coke receiving hopper, which is situated underneath the coke extraction box of each retort.
From the retort coke receiving hoppers, the coke is periodically discharged via special water sealed discharge
doors onto belt conveyors, which remove the coke from the retort house to the coke grading plant or storage area.

29
GAS CLEANING PLANT
Objective:
The Gas Cleaning Plant helps in the removal of impurities (tar, NH3, H2S) from the coal gas from retort.
Processdescription:
The coal gas together with (tar, NH3, H2S) enters the GCP section from retort house. A negative pressure in GCP
is maintained by 2 exhausters: one is driven by motors and the other is driven by steam. The gas first enters the
primary cooler where the gas is cooled from 75-35°C. There are 3 vertical primary coolers in GCP. Here 75-80%
tar together with ammoniacal liquor is separated from the coal gas and is collected from the bottom of each
collector.

30
The gas from the cooler then passes through the exhauster and enters the detarrer. Here the rest of tar is completely
separated from the gas. There are 3 detarrers in GCP. The tar from the detarrer and from the primary cooler is
cooled in the decanter. The mixture of ammoniacal liquor and tar is collected in the liquor pit and pumped to the
decanter by gravity settling tank resp.
From the detarrer the gas enters the NH3 absorber section where NH3 is absorbed by 6% H2SO4 pre heated at
60°C .the slurry is collected at the bottom of the absorber, then passed at the centrifuge from where solid (NH4)2
SO4 is obtained as a fertilizer.
After NH3 absorber the gas enters the naphthalene washer, where naphthalene is removed by wash oil. The H2S
is removed from the coal gas by absorption. STRED FORD LIQUOR consists of soda ash , anthraquinone
disulphonic acid and Sodium Ammonium Vanadate (SAV) gas enters from the lower section of H2S washer .
Gas is contacted with STRED FORD LIQUOR in the special wooden packing.
The base of the washer allows sufficient delay time for the Oxidant of the H2S ions to freed Sulphur by
Pentavalent Vanadium in the STRED FORD LIQUOR. In this way H2S is removed.
GCP unit removes impurities (mainly Tar and Ammonia) from the CVR gas to produce a marketable
product. The CVR gas is cooled by primary coolers and then drawn by exhausters (at a negative suction
pressure enough for the gas flow through GCP until it reaches the gas holder).
The gas is detarred in the Electro-detarrers by passing the gas through high voltage electrodes and
then ammonia is stripped by passing through Ammonia Absorber. In absorber 5-6% sulphuric acid liquor is
sprayed on the gas producing ammonium sulphate in the form of slurry as a result of reaction with ammonia in
gas. This slurry is centrifuged to extract the crystals and the liquor overflowing is passed through a Tar Skimmer,
which skims off any tar present.
The gas is then sent to the Naphthalene Washer, where the gas is sprayed with water; through an acid
catch pot to remove any traces of H2SO4. The H2O spraying results in stripping off any ammonia left in gas
after the absorption and this gas is sent to Gas Holder for storage and maintaining pressure of the gas.
Designed for gas input of: 22500 NM3/Hr
Present input of gas is : 6300 NM3/Hr
Reasons:
 The coal input to the retort has decreased.
Composition of Gas input to the unit (% V/v):
Components Present Design
Gas 48.2
Water 50.55

31
Tar 0.37
Total Ammonia 0.74
Naphthalene 0.01
H2S 0.13
HCN Trace
Gas Pressure at inlet
of primary coolers
(-)175 MMWG (-) 165 MMWG
Gas Temp 75’C 82’C

Exhauster Parameters:
Present Parameter Design Parameter
Gas Flow Rate(NM3/Hr) 4,900 – 5,300 22,234
Suction Pressure (in
MMWG)
(-) 20 – 150 (-)330
Discharge Pressure (in
MMWG)
200 – 400 115.5
 Variation of gas pressure in the Exhauster at present compared to that of designed pressure is seen. This may b
because of water or mother liquor filling up the gas main after acid catch pot.
 Initial designing was done for a large gas intake, but now this intake has decreased owing to less gas charging an
age old equipments .
Tar analysis:
Detarrer in (g/NM3) Detarrer out
(g/NM3)
Efficiency (%)
0.15 0.052 65.33
0.138 0.049 65.5
0.064 0.029 54.7
 The gas input to GCP has decreased to 1/4th of the total capacity of the unit, due to which problems
regarding the efficiency have arisen.
 The gas pressure in some sectors has become difficult to maintain as these sectors are void and no gas
enters them as the volume is large (i.e. designed for 4 times the capacity the unit is running now at) and
this causes low efficiency.
 Improper sparking of the electrodes cause improper voltage supply, due to the deposition of a mixture of
tar and coal dust on them; and since just cleaning of the electrodes is unable to remove this deposition.
 Dust deposition (as coal dust is carried over by the gas even after the cyclone separator, due to low quality
of coal) occurs in the detarrer which leads to choking in the system.
 The equipment is old leading to its inefficiency.

32
Ammonia analysis:
 High pressure drop
across the absorber occurs
when the salt concentration
exceeds 20% (by deposition of salts).
 The ideal concentration of sulphuric acid in the liquor is 4-5 % but now the absorber is running at 6%.
 The detarrers are not working properly which is resulting in high flow of tar to the absorber and then
large collection of tar in the tar skimmer.
Present Design
Sulphuric acid input (98%) 118 MT/yr 9000 MT/yr
Ammonium Sulphate 40 MT/yr 7795 MT/yr
 As the gas input has been cut 1/4th of equipment capacity, the H2SO4 usage and (NH4)2SO4
production have also decreased.
Gas Holder:
A three staged wet type telescopic holder with variable volume stores the purified gas coming from GCP to
provide a constant pressure and flow rate of the gas to the compressor. The volume is varied with the simple
concept of weight of the holder being balanced by the weight exerted by the gas. The pressure of gas in the first
stage is 150 MMWG and as the gas gets accumulated in the holder, there is a pressure build up and when the
pressure reaches 250 MMWG ,the second stage of the holder starts moving ,changing the volume as a result of
weight balancing .
Top Stage: 9000NM3 capacity; 150 MMWG Pressure
Middle Stage: 10,000 NM3 capacity; 250 MMWG Pressure
Bottom Stage: 11,000 NM3 capacity; 350 MMWG Pressure
Holder gas analysis (% V/v):
Ammonia in
(g/NM3)
Ammonia out
(g/NM3)
Efficiency (%)
4.44 0.56 87
4.85 0.45 91
4.51 0.36 92

33
Component(%) Present Parameter Design Parameter
C02 4.6 2.0 – 5.4
CnHm 0.8 1.0 – 3.0
O2 1.2 Less than 1.0
CO 24.2 9.0 – 18.00
CH4 16.2 23.0 – 26.0
H2 39.4 47.0 – 54.0
N2 13.6 3.8 - 9.0 (normal 4-5)
Light Oil 1.1
NH3 0.1g/NM3 0.075 g/NM3
H2S <0.005 g/NM3
Tar Fog 0.03 g/ NM³ 0.005 g/ NM³
Naphthalene Nil
Net C.V(Kcal/Nm3) 3280 4200 – 4700
Mechanism:

34
Gas Holder Seal:
 The degraded quality of coal charged to the operating units at present has led to a decrease in the calorific value of th
coal gas produced.
 CH4 gas which holds the heat has reduced in amount leading ultimately to a decrease in the CV of the gas.
 A substantial decrease in the amount of high calorific gas H2 has contributed significantly to the decrease in the CV o
the gas.
 The CO content increase has helped in positive contribution to the C.V of gas.

35
 The non-calorific gas N2 increase indicates that air entering the operating system is more, which may be due to defect
in the age old equipments.
 The volatile component CnHm amount has reduced which indicates that carbonization is not optimum.
 CO2 which is a non-calorific gas is being maintained at the design parameter level.
 Ammonia removal efficiency has also reduced substantially, ultimately hampering the purity level of the coal gas sen
to the consumers.
 Non operation of the H2S removal unit also contributes to the degrading quality of the gas sold.
 Tar fog quantity has increased as the detarrers aren’t working efficiently.
 Negligible amount of Naphthalene is present in the gas at present compared to that of the previous years, because o
which Naphthalene Washing is not done now.
 The Discharge Pressure has decreased as compared to the Design parameter.
 Low efficiency of compressor due to dust accumulation.
GAS COMPRESSORS:
The purified gas from the gas holder is compressed by three I-Shaped reciprocating positive-
displacement compressors operating in parallel using pistons driven by a crankshaft, delivering the gas at high
pressure by processing the gas through the stages of 1.85, 7 and 12.5 Kgf/Cm2. The gas after each compression
stage is cooled using shell and tube heat exchangers to decrease the temperature gained by the friction created
in the compression process. The cooled gas then undergoes separation, condensing light oil and water.

36
After all three stages the gas is passed on to a Chiller (which chills the gas more than required to 5’C) and
Economiser (to make up for the extra chilling by exchanging heat between chilled and just compressed gas).
The chiller uses Freon gas to cool gas and economiser is a shell and tube heat exchanger. The chilling
results in the condensation of the water present in the gas. The moisture condensed from the gas is knocked-off
in a separator vessel. The gas at a pressure of 6-5 Kgf/Cm2 is then sold by supplying through a grid line
controlled by the West-Bengal Government.
Compressor
Analysis:
Parameters Design Parameter Present Parameter Deviation
Capacity of each
compressor
9000 NM3/Hr
Suction Pressure of stage
1
1.02 Kgf/Cm2 absolute 280 MMWG
Discharge Pressure of
stage 1
3.07Kgf/Cm2 absolute 1.85Kgf/Cm2 absolute
2
3.07 Kgf/Cm2 absolute 1.75 Kgf/Cm2 absolute
stage 2
8.59 Kgf/Cm2 absolute 7 Kgf/Cm2 absolute
3
stage 3
Stages Suction Discharge
1st 280 MMWG 1.85 Kgf/Cm2
2nd 1.75 Kgf/Cm2 7 Kgf/Cm2
3rd 5.9 Kgf/Cm2 12.5 Kgf/Cm2

37
Flow Diagram:
Main Equipments of G.C.P :-

38
A. Primary Coolers :- 3 nos of Primary Cooling tower Pumps are used to circulate water to the Primary
cooling towers For cooling of incoming coal gas from the Retort House. They also Supply cooling water
to Interstate coolers of the Gas compressor. The action is facilitated by the use of 4 nos of cooling fans.
B. Exhauster: The Electrical Motor driven unit consists of a variable speed Squirrel Cage Induction Motor
which drives a Gas Compressor used to transport the gas from the retort house to various sections of the
G.C.P and finally into the Gas Holder.
C. Detarrer :- 3 nos of Detarrer are available in D.C.C to separate the Tar fog from the Gas being produced
at the Retort. This is achieved by passing the gas in Potential Difference (30KV DC).At such a high
Potential Difference, ionization of tar particles is achieved by effect of Negative Corona.
D. Ammonia Absorber :- Here ammonia(NH3) is reacted with dill H2SO4. To form Ammonium
Sulphate. Motor Coupled to the Pump. Slurry Pump and other Liquor Pump is main drive in this section.
E. Gas Holder :- The Capacity of the Gas Holder is 30000m3. It contains clean Gas from G.C.P before being
drawn by gas compressors. The Gas Holder being a Water Seal type has a built arrangement for pressure
Release. It has 3 Zones to avoid excessive pressure inside the Holder or when the gas has higher content
of impurities.
F. Gas compressor :- There are three gas compressors .These are mainly reciprocating type, 3 stage &
used for compressing the gas to 19.5 kg/cc. These are driven by 1500KW Synchronous Motor and are
used to extract gas from the gasholder.
G. Gas chilling and Dehydration Unit :-
In dehydration unit Gas is first Dehydrated to prevent the
Condensation I.O and Moisture. Then it goes to the chilling where it is chilled with the refrigerator
Freon. This condenses the Moisture and I.O present in the gas which is knocked off in a separator and the
gas is chilled from 40 to 10 degree c and passed into the gas line.
AUXILLARY DRIVES IN THE GAS COMPRESSOR SECTION.
A. Blower : It develops positive pressure to stop Combustible gases from entering the Compressor.
B. Oil Pump Motor/Lubrication Pump : This is used to provide Lubricating Oil to different parts of the
Gas compressor.
C. Solvent Injection Pump :- This Motor driven Pump is used to spray the Tar dissolving chemicals in the
common section header of the first stage of the compressor
D. Baring Gear Motor :- After the auxiliaries are started the Synchronous motor is started by the help of the
Baring gear at a very low speed prior to actual start-up.

39
Process Flow Diagram for GCP
Retort
House
Raw Coal gas Primary
Cooler
Cooled Gas
(40°-45°C)
Exhauster 3 Nos.of Electro
Detarrers
Tar free Gas
AmmoniaAbsorber
Top: Gas Outlet via
Acid Catch Pot
2 Washer
Columns
Removes
Napthalene
STRETFORD
LIQUOR sprayed
H2S free
gas
GAS
HOLDER
Centrifugal
dehydrator
Slurry of
Ammonium
Sulphate
Dried
Ammonium
Sulphate
Ammonium
Sulphate
bagging
Compressed
and
dehydrated
LightOil;Collectedandsoldoff
CompressedGas;
Transportedviapipelines

40
TAR DISTILLATION PLANT
Coal tar is a black, viscous and sometimes semisolid fluid possessing an odor. The coal tar is found condensed
together in the aqueous gas liquor when the volatile products of the destructive distillation of coal are cooled
down.
Objective:
The primary objective of this plant is:
(a) Dehydration of crude tar in the dehydrator column.
(b) Removal of pitch from the dehydrated tar in the pitch column.
(c) Separation of tar oils into light, medium and heavy fraction.
The Various Sections ofthis Plant are:
(a) Tar Distillation Section
(b) Caustic Washing section.

41
(c) De-Oiling & Springing Section.
(d) De-Hydration & De-Pitching Section.
(e) Primary Distillation Section.
(f) Batch Distillation Section.
(g) Solvent Recovery and BOD plant.
(h) Tank Farm.
Overall process description:
 The primary objective of the process is to produce a number of tar acid products from the crude tar and
ammonical liquor effluent from the coal carbonization plant. This is achieved in a number of process steps which
are outlined below.
 The tar is first treated dehydrated. The pitch is stripped off volatiles which are then separated into light, middle
and heavy oil fractions. The middle oil being of most important, as it is rich in tar acids. Light and heavy oil pass
to storage tanks.
 Crude tar acids in the middle oil are extracted in the form of sodium phenol ate by caustic soda. Middle oil
entrained in the sodium phenol ate solution would impair the quality of the tar acid products so is stripped off in
de-oiling section of sodium phenolates. Tar acid are recovered from the sodium phenolates by decomposition or
springing with a carbon dioxide rich gas. This is carried out in springing section. During springing sodium
phenolates are converted to sodium carbonate which in turn must be converted back to sodium hydroxide to
complete the cycle.
 Crude wet tar acids "sprung" from the sodium phenol ate are dried and phenolic pitch is removed in dehydration
and de-pitching section.
 The tar acids are separated into three fractions, crude phenols, crude cresols and crude xylenols in primary
distillation section. Each of these fractions is upgraded in a batch distillation process. Pure phenol, pure o-cresol
and mixed m-cresol and p-cresol are produced in different sections. A mixed xylenol fraction and a high boiling
tar acid fraction are also produced.
Short Description of various parts of TDP:
 Tar Acids separation from Ammonical Liquor:
 Crude tar acids are removed from the liquor by solvent extraction with isobutyl acetate.
 The tar acids are separated from the solvent and entrained solvent is recovered from the ammonical liquor in two
separate distillation section (ammonical liquor extract and raffinate stills).

42
 Di-hydric tar acid, which oxidize readily to produce coloured compounds and would therefore have an adverse
effect on the quality of the final tar acid products, are separated from the monohydric tar acids by distillation
(monohydric phenol recovery).This monohydric tar acids are combined with the crude tars from the tar stream
prior to the continuous crude tar acid fraction. They are distilled with other tar acids.
 The free ammonia in the ammonical liquor is recovered as a vapour by steam tar distillation.
 Detailed process description of tar distillation:
Crude tar is stored at elevated temperatures in storage tanks located in the tank farm. Storage at elevated temperatures
permits the decantation of much of the water associated with the tar, thus reducing the heat load on the dehydrator
column.
o Crude tar from the storage tank is drawn through crude tar filter, mixed with caustic soda pumped from the
caustic tank by dosing pump and pumped through tar and vapor exchanger and steam heated pre-heater into the
lower half of the dehydrator column. In the column the crude tar acid is contacted with a relatively large
circulating stream of hot dehydrated tar. The water and an azeotropic quantity of light oil are vaporised and
passed out of the top of the dehydrator, through the tar and vapour exchanger into light oil condenser. The
condensed oil and water flow by gravity into decanter.
o Water is drained from the bottom of the decanter and flows by gravity to effluent treatment plant. Light oil over
flows into reflux drum from where a portion is pumped as reflux to the dehydration column to aid the azeotropic
dehydration of the tar. The reminder of the light oil is returned to the top of fractionating column with a small
quantity remove to the tank from where it is either returned to crude tar storage tanks or delivered to light oil
product storage tank.
o The bottom product from the dehydration column is pumped at a high rate through pipe still economizer via
steam heated dehydrator bottom heater. The bottom product is heated by flue gas and then returned to
dehydration column. A small portion of the returning bottom stream is delivered to the lower part of pitch
column.
o Crude pitch is drawn from the bottom of the pitch column by pitch circulating pump and pumped back to the top
of the pitch column through pipe still.
o The reminder of the oil in the tar is vaporized and the pitch descends into a steam super-heater.
o Pitch overflows from the steam chamber and is pumped by product pitch pump to pitch product storage tank via
steam generator. Boiler feed water heated in pre-heater is converted to low pressure steam in the steam generator.
o
o Overheads from the pitch column are fed directly to the bottom of the fractionating column.
o Volatiles including injected steam from pitch column are separated into a light oil and water fraction (column
overheads), a middle oil fraction (liquid side steam) and a heavy oil fraction (column bottoms).The light oil and

43
water vapour flow to the tar/vapour exchanger from where,combined with the overheads from the dehydrator
column they flow into light oil condenser and into decanter. The condenser is vented through foul gas scrubber to
remove hydrogen sulphide (if any). The gases are scrubbed with water which discharges into the decanter.
Vapour is not absorbed in the scrubber are vented into the pipe still.
o The products from column bottom are pumped by heavy oil pump through pre-heater where they exchange heat
with boiler feed water and into heavy oil tank. From there the heavy oil is transferred intermittently by transfer
pump to heavy oil product storage tank, pitch blending tank and to the crude tar storage tanks (if excess).
o Middle oil flows due to gravity through middle oil cooler either to middle oil buffer tank (at start up or when the
plant downstream is offline) or directly to mixing vessel in the caustic washing section (during normal operation).
Middle oil from the buffer tank can be transferred by pump to the caustic washing section or back to crude tar
storage tanks.
o A coil drainage tank is provided for the drainage of pitch from the coil of the pipe still, from steam generator and
from the pitch column during plant shutdown. Bursting discs on dehydrator column and pitch column discharge
into this vessel. The contents of the tank may be transferred to crude tar storage tanks by pump.
 Purpose of the tar distillation section:
 Dehydrated the tar in the dehydrator column, the heat for which is supplied by circulation of the dehydrator
column through the bottom heater and the pipe still flue gas economizer.
 Remove the pitch from the dehydrated tar in the pitch column, heat being supplied by pitch circulated through the
pipe still and superheated stripping steam from the pipe still.
 Separate the tar oils into light, medium and heavy fraction.
 Caustic Washing of tar acids:
The purpose of this section is to extract tar acids from the middle oil with a caustic solution to produce water
soluble sodium phenolates. The sodium phenol ate solution flows by gravity form the bottom of the separator to
phenol ate tank in de-oiling plant.
 De-oiling of sodium phenolates:
The sodium phenol ate solution contains small quantities of neutral oil which must be removed in order to
produce good quality tar acids. This is achieved by steam distillation. Clean sodium phenol ate solution is pumped via
sodium phenol ate cooler to springing column in the springing section.
 Springing:
The tar acids are released from the sodium phenol ate solution by decomposition (springing) with carbon dioxide
rich gas in series of two packed columns.
 Recausticizing:
The sodium carbonate solution from the springing section is contacted with hard burnt lime to regenerate caustic
solution .The solid by-products of the reaction are removed by filtration. These processes are carried out in the
recausticising plant.

44
 Dehydration and de-pitching of tar acids:
The purpose of this
plant is to remove water and
phenolic pitch from the tar
acids prior to their separation
into tar acid products. Crude
tar acids are pumped to the
primary distillation columns
through pre-heater.
 Primary
distillation of tar
acids:
During primary
distillation, the crude tar acids
are separated into three
fractions. They are crude
phenol, crude cresoland crude xylenols and high boiling tar acids. This distillation is carried out on a continuous basis.
 Batch distillation of phenol:
The purpose of the section is to produce relatively pure phenol products by batch distillation of a phenol-rich
material. All major tanks in this section are fitted with steam coils to facilitate pumping by preventing solidification.
 Batch distillation of cresol:
Here a crude cresolmaterial is distilled to produce fairly pure o-cresol products and mixture of m-cresol and p-
cresol.
 Batch distillation of Xylenols and HBTAs:
In this section distillation is carried out to recover mixed xylenols and to produce a distilled high boiling tar acid
fraction. All major tanks in this section are fitted with steam coils to facilitate pumping by preventing solidification.
 Aqueous Liquor Extraction:
This section extracts the tar acids from the ammoniacal liquor using an appropriate solvent in double column
counter current system Isobutyl acetate is used as solvent.
 Ammonical Liquor extract and raffienate stills:
The objects to be achieved in this section are twofold:
 To separate the solvent from the tar acids.
 To recover entrained solvent from the raffinate. Both are achieved by distillation, the first in extract still, the
second in raffinate still.

45
 Monohydric phenols recovery:
The dihydric tar acids contained in the ammoniacal liquor oxidizes readily to produce coloured compounds
which, even in very small quantities, would have an adverse effect on the quality of the tar acid products. They must be
separated from the monohydric phenols. This is achieved by distillation.
DEMINERALIZED WATER TREATMENT PLANT
Service water that comes from underground source contains various mineral matters (generally salts of
various alkaline earth metals like calcium, iron, manganese etc.) which is deposited in the processes where the
water is vaporized or evaporated. This deposition may damage the process and the process equipments
simultaneously. To overcome this problem almost every industry has its own DM water plant.
Results of PoorWater Treatment
In the ideal situation, water would be feed to a boiler free of any impurities. Unfortunately, this is not the case.
Water clean up is always required. The following items are the most problematic to boilers and steam turbines:
 Calcium (Ca) scale:
Calcium is present in water in the forms of compounds like calcium sulfate, calcium bicarbonate, calcium
carbonate, calcium chloride, and calcium nitrate. During evaporation, these chemicals adhere to boiler tube walls
forming scale. Its formation increases with the rate of evaporation so these deposits will be heaviest where the gas
temperaturesare highest. Scale is a nonconductor of heatwhich leads to a decreasedheattransferof the boiler tubes,
and can result in tube failure due to higher tube metal temperatures. Buildup of scale also clogs piping systems and
can cause control valves and safety valves to stick.
 Magnesium scale :
Same issues as with calcium.
 Silica :
Silica can form scale at pressures below 600 psig. Above 600 psig, silica starts to volatize, passing over
with steam to potentially form deposits on the steam turbine diaphragms and blades. These deposits change the
steam path components’ profiles resulting in energy losses. The degree of loss depends upon the amount of the
deposits, their thickness and their degree of roughness.
 Sodium (Na):
Sodium can combine with hydroxide ions creating sodium hydroxide (caustic). Highly stressed areas of
boiler piping and steam turbines can be attacked by sodium hydroxide and cause stress-corrosion cracks to occur.
This was a problem in older boiler with riveted drums because of stresses and crevices in the areas of rivets and
seams.While less prevalent today, rolled tube ends are still vulnerable areasofattackaswell aswelded connections.

46
 Chloride (Cl) :
Chlorides of calcium, magnesium, and sodium, and other metals are normally found in natural water
supplies. All of these chlorides are very soluble in water and therefore, can carry over with steam to the steam
turbine. Chlorides are frequently found in turbine deposits and will cause corrosion of austenitic (300 series)
stainless steel and pitting of 12 Cr steel. Corrosion resistant materials protect themselves by forming a protective
oxide layer on their surface. These oxides are better known by their generic name “ceramic.” All ceramics will pit
if exposed to chlorides. If the metal piece is under tensile stress either because of operation or residual stress left
during manufacturing, the pits formed by chlorides attacking the passivated layer will deepen even more. Since the
piece is under tensile stress,cracking will occur in the stressed portions. Usually there will be more than one crack
presentcausingthe pattern to resemble a spider’s web. The most common source of chloride contamination is from
condenser leakage.
 Iron (Fe) :
High iron is not found in raw water but high concentrations can come from rusted piping and exfoliation
of boiler tubes. Iron is found in condensatereturnin a particle formasitdoesnotdissolve in water.The detrimental
aspectof iron iscalledsteamturbinesolid particle erosion,whichcausessignificanterosion ofsteamturbine steam
path components.
 Oil :
Oil is an excellent heat insulator, and adherence of oil on tube surfaces exposed to high temperatures can
cause overheating and tube damage.
 Oxygen (O2) :
Oxygen is found in feed water and its partial pressure is relatively high so it will requires a near saturation
temperature to disassociate itself from water. Oxygen in combination with water will attack iron and cause
corrosion. The reaction occurs in two steps:
The ferric hydroxide is highly insoluble and precipitates on heated surfaces. The precipitate is called magnetite or
rust. The closer the water is to the saturation temperature, the more corrosion will occur.
 Carbon Dioxide (CO2) :
Carbon dioxide can react with water to form carbonic acid (H2CO3). Carbonic acid will cause corrosion in
steam and return lines. Carbon dioxide can originate from condenser air leakage or bicarbonate (HCO3) alkalinity
in the feed water.
Process description:
Various steps regarding the demineralisation are given below:
 The Service Water (SW) is passed through the oxidizer where all the Ferrous compound are converted to Ferric
compound in presence of Magnesium Oxide (MgO) bed. Here MgO acts as a catalyst to this conversion.
 Alum (K2SO4,Al2(SO4)3, 24H2O) is dosed by means of proportional doser to achieve coagulation of suspended
solids present in the raw water.

47
 Suspended impurities are removed by passing the water through an "Up Flow Dual Media Filter".
 The water free of suspended solid particles is fed to Strong Acid Cation (SAC) exchanging resin column where
Calcium, Magnesium, Sodium etc. alkali earth metal ions are replaced with Hydrogen ions
 This acidic water from SAC is then passed through the Degassing Tower counter current to the up flow of low-
pressure air, which results in decomposition of carbonic acid and removal of Carbon dioxide.
 Degassed water is stored in Degassed water tank. Water is then pumped from that tank to Weak Base Anion
(WBA) exchanging resin column for removal of negative ions such as Sulphates and Chlorides. These are
replaced by Hydroxyl ions from the resin.
 Part of the water coming out from WBA containing silica is stored in Chlorine Free Water (CFW) tank after
dosing 5% caustic solution to raise the pH of water to 8 to 8.5.
 Rest of the water from WBA is sent to Strong Basic Anions (SBA) exchanging resin column where the Silica ions
and traces of Chloride ions (if any) are replaced with Hydroxyl ions from the resins.
 The DM water from the SBA outlet is stored in DMW storage tank and sent to Retort House (RH) as per
requirement.
EFFLUENT TREATMENT PLANT
Every plant needs Effluent Treatment Plant (ETP) treatment plant to decrease the hazardous materials
concentration before draining it out to
environment. If the water from various
processes is disposed of without proper
treatment, it affects the eco systems of
environment very much. The treatment
scheme is decided as per the contents of the
effluent water, which is different for different
industry. Here, in DCC the main content of
effluent is Tar Acid. To lower its
concentration in water Tar acid consuming
bacteria are used.
The ETP of DCC consists of following
units:
 Muster Pit:
It is rectangular shaped concrete tank. The effluent mainly from solvent recovery plant and most section of
the plant is stored here including sewage. Concentration of tar acids, BOD,COD are very high in this pit. The size
is 10 m (L) X 5 m (B) X 4 m (D).
 Equalization Tank:
It is a rectangular tank of dimensions – 10.9 m (L) X 6.95 m (B) X 1.15 m (D). The water and effluent (1:1
ratio) from Muster Pit is mixed here and acts as a primary treatment unit.

48
 Feed Box:
It is rectangular box of iron of
dimensions – 0.8 m (L) X 0.75 m (B)
X 0.5 m (D) and situated between two
aerator basins. The dilute effluent
from equalization tank is run through
the feed box.
 Aerator Tank:
There are two aeratortanks or
basins (diameter- 15 m X height- 4
m), which are vertical, cylindrical in
shape. The height and width ratio is
4.5:1. The total volume if aeratedtank
is 1450 m3
. The detention time is
effective for 16 hours. The
concentrated effluent is diluted by
water, naturally occurring
microorganisms act upon the tar acids, and BOD, COD loads also reduced.
 Clarifier:
It is also vertical, cone shaped cylindrical basin (O.D.
– 8.7m, I.D. – 7.6m, Launder depth = 0.7m, Cylinder height-
2.35m and C.D. - 4.5m). The radius and SWD (Submerged
Water of the tank are 4000mm and 2500mm respectively.
However, the overall volume of the tank available for the
process action is 250 m3
. The effluent from aerator tank
contains huge quantity of suspended or rotation (10-12m/hour)
of flocculator, the suspended particles get settled in the bottom
and clarified water is passed through the upper portion. The
sludge is the discharged on the sludge drying beds.
 Effluent Pit:
The water free from suspended solids is accumulated
in a rectangular tank (75m X 20m X 1m), which is known as
effluent pit. This tank has been divided into three sections, the treated effluent after crossing each section finally is
discharged partially outside of the plant, and a major portion is re-circulated for quenching in the Retort House.
 Sludge Drying Beds:
It is rectangle in shape and sludge from bottom of clarifier is accumulated in this tank. Some portion of the
semi-solid sludge from the clarifier is recycled towards feed box as a source of bacterial seed.
 Tar/Oil Separation Unit:
DCC has also constructed Tar/oil separation unit in between Muster Pit and Equalization Tank to remove
or minimize the tar or oil content in the effluent, which is mainly in emulsified form. The unit has been constructed
so that effluent discharge content of tar or oil into the equalization be substantially minimum.
Process description:

49
 Effluent from solvent recovery section, domestic sewage,GCP, TDP, Retort House, floor washing etc. comes to
Muster Pit.
 Tar or Oil separation plant separates Tar and Oil taking a feed from Muster Pit.
 Then the Oil or Tar free effluent comes to Equalization Box.
 From Equalization Box an effluent stream goes to Feed Box and mixes with a sludge recirculation stream.
 That mixed stream is sent to Aerator- A and Aerator- B.
 After a certain period of aeration, the aerated effluent stream is sent to Clarifier.
 In Clarifier, the water and sludge are separated and the clarified water is collected from the top of the Clarifier and
sludge is collected from the bottom of the Clarifier.
 The clarified water is stored in Effluent Pit. From that pit, water is drawn for further use in Retort House (about
60% of the stored water but this may vary according to the requirement) and a part of it is drained out.
 The collected sludge is sent to Sludge Drying Bed where the sludge is dried.

53
UTILITIES
Utility is very important part of an Industry. So every Industry whatever it may be must have a Utility Section.
In D.C.C the Utility Section can be divided into:
De-Mineralized Water Plant:
In D.C.C main water source is underground water. This water is obtained by deep tube well. As the water
contains minerals it is highly corrosive in nature which may be harmful to the equipments used in D.C.C so the
water needs to de-mineralized.
Pump House:
Process/Service water, Fire Water & Drinking water required for the operation of the plant is supplied from the
Pump House. To meet the requirement of Service Water there are two nos. of Motor driven Vertical Shaft
Pumps. Similarly for the Fire Water there are two nos. of Motor driven Vertical Shaft Pumps and 1 Pump is
Diesel Engine driven used for Emergency Section.
Effluent Treatment Plant:
Here the wastes from different sections of the Plants such as Solvent Recovery, Domestic Sewage, Effluent
from GCP, TDP and Retort House is treated and discharged.
Central Laboratory:
The laboratory holds the key for the formation of product by testing the raw cola or the source coal and then
limiting the operating temperature and pressure etc.
Generally two types of analysis are done:
1. Proximate analysis.
2. Ultimate analysis.
Coal gas testing is done by Orsat apparatus.
Cooling Tower:
A tower- or building-like device in which
atmospheric air (the heat receiver) circulates in
direct or indirect contact with warmer water (the
heat source) and the water is thereby cooled (see
illustration). A cooling tower may serve as the heat
sink in a conventional thermodynamic process,
such as refrigeration or steam power generation, or
it may be used in any process in which water is
used as the vehicle for heat removal, and when it is
convenient or desirable to make final heat rejection
to atmospheric air. Water, acting as the heat-
transfer fluid, gives up heat to atmospheric air, and
thus cooled, is re-circulated through the system, affording economical operation of the process.

54
Two basic types of cooling towers are commonly used. One transfers the heat from warmer water to cooler air
mainly by an evaporation heat-transfer process and is known as the evaporative or wet cooling tower. Evaporative
cooling towers are classified according to the means employed for producing air circulation through them:
atmospheric, natural draft, and mechanical draft. The other transfers the heat from warmer water to cooler air by
a sensible heat-transfer process and is known as the non-evaporative or dry cooling tower. Non-evaporative
cooling towers are classified as air-cooled condensers and as air-cooled heat exchangers, and are further classified
by the means used for producing air circulation through them. These two basic types are sometimes combined,
with the two cooling processes generally used in parallel or separately, and are then known as wet-dry cooling
towers.
Evaluation of cooling tower performance is based on cooling of a specified quantity of water through a given
range and to a specified temperature approach to the wet-bulb or dry-bulb temperature for which the tower is
designed. Because exact design conditions are rarely experienced in operation, estimated performance curves are
frequently prepared for a specific installation, and provide a means for comparing the measured performance with
design conditions.
One induced draft cooling tower (of treated timber fill) would be provided to cater for the need DCC. This cooling
tower would be handling about 1500m3/hr of re-circulating water from the tar distillation plant, Gas cleaning
plant, Gas compressors and various other sections. The makeup water for this cooling tower will be taken from
the discharge of makeup water transfer pump.
Dosing Pump:
Dosing pumps are low-volume pumps with controllable discharge rates that are used to inject additives or
difficult-to-mix fluids into mixing, pumping, or batch/tank systems. Dosing pumps are usually made from plastic,
thermoplastic, or stainless steel and feature mounting holes or accessories. Dosing pumps often have a controller
which enables the fluid flow to be monitored and adjusted easily.
Dosing pumps can operate based on the principles of dynamic pumps or positive displacement pumps depending
on the design. Dynamic pumps produce a variable flow suited for
generating high flow rates with low viscosity fluids, while positive
displacement pumps produce a constant flow suited for producing high
pressures (and low flow rates) with high viscosity fluids. Most dosing
pumps are positive displacement pumps, which provide steady, low
flow for a variety of types of media. In D.C.C. it is used as-
1) Ammonia dosing pump mark
2) Coagulant acid dosing pump
3) Alum dosing pump
Centrifugal Pumps:
Centrifugal pumps are a sub-class of dynamic axisymmetric work-absorbing turbomachinery.[1] Centrifugal
pumps are used to transport fluids by the conversion of rotational kinetic energy to the hydrodynamic energy of
the fluid flow. The rotational energy typically comes from an engine or electric motor. The fluid enters the pump

55
impeller along or near to the rotating axis and is accelerated by the impeller, flowing radially outward into a
diffuser or volute chamber (casing), from where it
exits.Common uses include water, sewage,
petroleum and petrochemical pumping. The reverse
function of the centrifugal pump is a water turbine
converting potential energy of water pressure into
mechanical rotational energy.
In D.C.C. it is used as-
1) Filtered water pump
2) Neutral effluent pump
3) Raw water pump
4) De mineralized water pump
5) Acid unloading pump
6) Horizontal pump
STEAM TURBINE
A steam turbine is a device that extracts thermal energy from pressurized
steam and uses it to do mechanical work on a rotating output shaft. Its
modern manifestation was invented by Sir Charles Parsons in 1884.
Because the turbine generates rotary motion, it is particularly suited to be
used to drive an electrical generator for electricity generation in the coal
complex by use of steam turbines. The steam turbine is a form of heat engine
that derives much of its improvement in thermodynamic efficiency from the
use of multiple stages in the expansion of the steam, which results in a closer
approach to the ideal reversible expansion process.Steam turbines are one of the most versatile and oldest prime
mover technologies that are still in general production. Steam turbines are widely used for combined heat and
power (CHP) applications.The capacity of steam turbines can range from 50 kW to several hundred MWs for
large utility power plants.
The thermodynamic cycle for the steam turbine is the Rankine cycle. This cycle is the basis for conventional
power generating stations and consists of a heat source that converts water to high-pressure steam. The developed
condensate from the process returns to the feedwater pump for continuation of the cycle.
The two types of steam turbines most widely used are the back pressure and the extraction-condensing types. The
choice between backpressure turbine and extraction-condensing turbine depends mainly on the quantities of
power and heat, quality of heat, and economic factors.

56
SAFETY
Safety Policy of Dankuni Coal Complex
1. OBJECTIVE:
Coal gas and coal derivative chemical production being complex activities, Dankuni Coal Complex, a unit of
SECL recognises that the Company has a moral, economic, social, and legal obligation to prevent hazards, provide safe
work environment and guard/eliminate all accident-prone hazards and risks. The Company, therefore,adopts and
promulgates the Policy, in confirmatory to Governmental guide line, set out below for the purpose of creating and
maintaining safety , health and environment as stipulated under section &A of Factories Act Amended 1987.
2. THE POLICY:
2.1. Occupational Health Safety and Welfare of the employees and people living around, people exposed directly to the
activities of the plant, will be the major concern of the Company besides production.
2.2. Dankuni Coal Complex will be managed with the conviction that all injuries are preventable and all risks of health can
be contained. The designs and operations of facilities and training of employees will be directed towards this end.
2.3.The Occupational Health and Health Safety Policy of the Company shall serve as an instrument for creating strong
awareness about safe work practices and working conditions at all levels of the organisation, gradually translating it to
employees' "Way of Life".
2.4.The Company shall provide and maintain a safe environment; surrounding the work places in terms of Ecology,
Pollution and other aspects, thereby playing a dominant role for excellence in environment.
2.5.A11 the manufacturing units, raw materials' sections and other supportive units of the Company will adopt techniques
for manufacturing, handling and disposing of all the substances safely and without creating unacceptable risk to the
equipment, human being or the environment in which they are located.
2.6. The Company will follow all acts,laws, rules, and regulations of the State and CentralGovernment. Wherever laws or
regulations may not be available or protective enough to prevent hazards, the Company will adopt its own safety and Health
Standards, taking clues from provisions of Mining Act. The Company shall not carry out any operation if the environmental
standards are not acceptable.
2.7.Training in Safety and Occupational Health shall be imparted to all levels of employees in the Plant, and in specialised
institutions to ensure that all employees gather the required knowledge and information to carry out their jobs without
endangering themselves, other employees, Plant, equipment, environment etc.
2.8. The Company shall have a well-documented and approved On-site Emergency Plan and identified key persons to
execute the plan in case of untoward incidents of all emergencies.
2.9.The Company shall declare a written document containing details in respect to the work practices,plant and machinery,
raw materials, work in progress and finished product, movement systems and procedures, building and immovable assets.

57
2.10. Every employee of the Company will adhere to the spirit as well as letter of this policy. The Managers, Senior
Executives, and Trade Unions shall have a special obligation to keep the employees informed and educated about
Occupational Risks and remedial measures.
3.0. SAFETY ORGANISATION:
3.1. The Company shall have a Safety Department headed by a Safety Officer appointed as per provisions of Safety Rules
framed by the West Bengal Govt.
3.2. The Company shall have a Safety Committee headed by the Chairman and participated by other members of the
Management and Trade Unions. The Committee will be so framed that it contained representatives from shop floor to other
departments and also fulfils and provisions of Factories Act.
3.3. Functions of the Organisation:
a) The Safety Department shall have the following functions:
I. Accident prevention, control, reporting, and analysis.
II. Safety promotional activities to create a climate conducive for safety consciousness, cultivation of safety culture
and safe habits amongst employees.
III. To organise programme for publicity, training, education, seminars, workshops, campaigns and special drive.
IV. To ensure use of appropriate personal protective equipment by all employees.
V. Co-ordination and liaison with fire brigade.
VI. Maintenance, upkeep, and availability of appropriate safety appliances.
VII. Collect, compile, report, and information, statistics pertaining to safety and accidents and despatch to appropriate
authorities.
VIII. The Safety Department shall have the jurisdiction over the works.
b) The Safety Committee will offer support services to the Safety Department in implementing the Safety and Health
Policy of the Company.
 SAFETY RELAVANT COMPONENTS IN DANKUNI COAL COMPLEX
 Systems preventing deviation from permissible operating conditions:
 Pressure relief system:
Rupture disk, safety valves are attached with the high pressure lines, vessels and equipment. Water seals provided
in the gas lines.
 Temperature,pressure and flow sensors:
Temperature,pressure and flow sensors are provided with all the process equipment to control operation
parameters as well as to avoid unwanted situation.
 System regulating pressure,temperature and flow:
Controllers are attached to the equipment to regulate the process parameters like temperature,pressure and flow.
 System preventing overflow:

58
Level controllers are attached to the boilers and hazardous liquid storage tanks to prevent occurrence of dangerous
situations. All storage tanks of hazardous chemicals are provided with guard wall to retain the leakage materials
within it.
 System preventing formation of explosive mixture, fire and explosion:
Positive pressure is maintained in the gas generation units and gas flow line to prevent access of air,which can
lead to form an explosive mixture. Fire and explosion protection arrangement like flame arrestor to the vent pipe
of flammable liquid storage tanks, lightning arrestor to the flammable liquid storage tanks, flame proof lighting
and electrical appliances in the flammable zones and earthing of all the storage tanks and equipment were
provided.
 Diesel generators as an alternative power source:
These generators are automatically started whenever power supply is interrupted.
 Steam as an alternate power:
There is a provision of running of exhauster,certain emergency pumps and ejectors with steam.
 Water supply:
Plant has its own water supply arrangement. Five deep tube wells and an open reservoir of 5 million
gallon capacity are adequate for continuous supply of process water,drinking water and fire fighting water.
 Alarm systems:
All the emergency equipment like gas compressor, exhauster,liquor pumps are provided with audio -
visual alarm system.
 Technical Protective measures:
o All parts of the plant are covered with the fire hydrant system. Whenever it is required pumps are started by the
pump operators to pressurize the fire hydrant system. Adequate storage capacity to supply water continuously
more than 4 hours for the purpose of fire fighting.
o Flammable liquid storage tanks are protected by guard wall fencing as per provisions of Indian Petroleum Rules.
o In case of failure of gas compressor, there is a system of flaring of coal gas and in case of power failure; there is a
system of venting of the coal gas to prevent pressurisation of the system.
All the flammable liquid storage tanks are provided with bund wall to prevent spreading ofthe liquid in case of
tank failure. Arrangement for discharge ofstatic charge has been provided with the equipment which may
generate static charge at the time ofoperation. Hazard Management
1. Identification of Hazards
Process
Related
Materials
Related
Hazards while handlinghightemperatures,highpressure,steam
generationetc.
Hazards while handlingtoxicgases,corrosive materials,heavyitemsetc

59
2. Quantification of Hazards
The impact/ damages that can be caused due to the occurrence of a hazard has to be quantified with respect to
extent of impact on humans, effect on property, long term and short term effects etc.
3. Mitigation of Hazards
Resources that should be in place, so as to minimize the impact of the hazards, must be always ready for
emergency action. Things like fire fighting engines, fire extinguishers, breathing equipment, gas masks etc.
should be maintained in proper ready-to-use condition.
4. Preventive Measures
There always is an on-site emergency plan, whenever any job which can be hazardous is being carried out. For
example, in the plant, whenever any Welding job is being carried out, then the Safety officer is informed at first,
who deploys his team to be present at the site with proper precautionary gears (e.g. fire extinguishers, gas masks
etc.). If the required manpower for safety team is not present, then two welding jobs are not permitted
simultaneously within the plant.
5. Associated costs
Apart from the costs of manpower employment, there are the costs of the upkeep and maintenance of fire-
extinguishers, fire handlers, oxygen cylinders etc. Apart from it mock drills, safety weeks, workshops on hazard
and how to prevent them are carried out, for which budget is allocated every year.
A list of possible hazards at different levels of production and their corresponding prevention plans are given
below:
:
Type of Hazard Department / Location Preventive Measure
Dust – Inhalation and eye
irritation
Material Handling Plant Sprinkler system, Nose guard
Noise Crusher house, feeder sections
at PGP, Retort bunkers.
Use of ear plug by workers in
proximity.
Smoke & Gas Retort House, PGP coal
bunker
Proper ventilation, using Nose
Guards.
Human
Behavioural
Hazards due to erroneousbehaviour,unsafemethods, mishandlingof
itemsandnot followinglaidoutnorms.

60
Wagon unloading- contact
with moving parts, snapping
of hauler ropes, fall from
narrow steep way while
breaking of coal.
Wagon Tippler at MHP. Use of safety helmets and
shoes, not allowing
unauthorised entry, engaging
skilled workers, adequate
illumination, maintenance of
brakes & ropes.
Fire and explosion Charging floor, bottom gas
line, ash pan floor, bottom
floor.
Proper vigil while operations,
maintaining proper water
supply, safety permit before
welding, ready to use
extinguishers.
Heat Stress Charging floor, heating floor. Use of main cooler fan, skilled
workers, use of asbestos
gloves, suits, face shields etc.
Acid and steam burn – leakage
of sulphuric acid, mother
liquor tank etc.
Ammonia absorber area. Use of PVC gloves, suits;
paint of acid tanks &other
absorber parts to prevent
corrosion, maintenance of
pumps etc.
 Safety motivational activities:
o Workers participation in the safety committee.
o Safety Day Celebration.
o Safety contests.
o Preparation and circulation of MSDS.
o Training to the all level of workers.
o Display of safety posters, slogans etc.

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CONCLUSION
During the last 14 days, we have been on Vocational Winter Vacation Training in Dankuni Coal Complex.
We have gained some basic knowledge about Practical Applications of Engineering Theory into Practice. We are
very much hopeful that in the coming years of our Career, this Experience will help us to integrate Theory and
Practical and develop ourselves into a through bred professional. As a student of Technical Education it is very
fortunate to us that all types of Live Problems and their Remedies are seen by us. We have seen how the Critical
Problems may be solved in a Simple way. Another experience that we have gathered in these days is about
Precautions and Safety measures. We would once again like to thank sincerely all those who have extended their
hand of co-operation to make our Training days in Dankuni Coal Complex a success. We are thankful to all the
Employees and Management staffs for giving us their Valuable time in their Occupational Busy Schedules.

DCC Training Report Final

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