Post on 12-Jan-2016
description
Coke oven and coal chemical plant
Summer internship report on
By
R. RAGHAVENDRA RAO (12021A2502).
K. AVINASH KUMAR (12021A2543).
Introduction Visakhapatnam steel plant is the one having shore
based steel plant in the world
Location:
26 kms south west of the city of the Visakhapatnam.
installed capacity:
liquid steel - 3 million tones.
saleable steel - 2.656 Million Tons.
three international standards for
Quality (ISO-9001),
Environment Management (ISO- 14001).
Occupational Health & Safety (OHSAS-18001).
The plant was inaugurated formally on 20th January 1971 by the prime minister.
Major departments in VSP
Raw materials handling plant
Coke ovens and coal chemical Plant.
Sinter plant
Blast furnaces
Steel melt shop
Rolling mills LMMM (Light and medium merchant
mill)
WRM (Wire rod mill)
MMSM (Medium merchant and structure mill)
COAL YARDCOAL PREPERATION PLANT
BATTERY1,2,3,4
COKE DRY COOLING PLANT1,2,3,4
COKE SORTING PLANT
Breeze coke(0-10mm)To Sinter plant
Nut coke(10-25mm)To Sinter plant
BF coke(25-80mm)To Blast Furnace
10000cHot coke
1750cCooled coke
Turbine(15MW power generation)
steamHeating withCO Gas
TAR DISTILLATION PLANT
BENZOL DISTILLATION PLANT
MBC WaterTreatment Plant
AMMONIUM SULPHATE PLANT
Benzene TolueneHeavy crude benzolSolvent oil
Tar pitchLight oilPhenolNaphthalene oilWash oilAnthracine oilHP Naptha,D N Oil
POND( Gangavaram)
Raw CO Gas
Ammonium sulphate(Pushkala)
To BATTERIES ,BF SP,MILLS ,SMSCO&CCP FLOW CHART Cleaned CO Gas
NH3 liquor
Crude Tar
Crude Benzol
PGC,SEPERATOR
FGC
EXAUSTER
H2SO4
SOLAR OIL
WHY COKE OVENS?TO CONVERT COAL TO COKE IN ABSENCE OF AIR WHICH IS USED AS A REDUCING AGENT IN BLAST FURNACE
BENZOL PLANTRECOVERY PLANTTAR PLANT&MBC PLANT
CPP
B-1&CDCP-1B-2& CDCP-2B-3&CDCP-3
COKE SORTING PLANT
Coke ovens & coal chemical plant
The coke oven and coal chemical plant is mainly divided into the following department:
Coal Preparation Plant(C.P.P)
Coke Oven Batteries
Coke Dry Cooling Plant(C.D.C.P)
Coke Sorting Plant(C.S.P)
Coal Chemical Plant (C.C.P)
Coal and coke COAL:
Coal is used in the form of coke to serve the purpose of iron ore reduction in blast furnace. It also serves as a heat source.
COKE:
It is a strong porous hard mass that is obtained by heating of the coal in the absence of air at high temperature.
NEED FOR MANUFACTURE OF COKE FROM COAL:
Natural coal is too dense and fragile to be used as fuel.
The ASH CONTENT in coke is very low i.e.) around 10%. So it does not arise problems of striking on the grates.
As compared to coal coke is of high quality and is highly reactive.
As coke is a rigid hard mass it does not create the problems of dust nuscence.
Types of coal
There are 2 types of coal:
(1) Coking Coal. (2) Non-Coking Coal.
The different coking coals used in VSP are:
M.C.C - Medium coking coal - BENGAL, BIHAR
I.C.C - Imported coking coal - AUSTRALIA
I.S.S.A.C - Imported coking coal - AUSTRALIA
SOFT - Imported coking coal - AUSTRALIA
In VSP coking coal is used for producing metallurgical coke where as non-coking coal is used for producing thermal power (in boilers).
Types of coal and its propertiess.no Type of coal % moisture %Ash Mean
maximum Refluctance
1 M.C.C 25 - 28 17 – 22 0.9
2 I.C.C 24 - 26 8 – 10 1.10 – 1.3
3 I.S.S.A.C 23 - 25 8 - 10 1.16 – 1.3
4 SOFT 30 - 34 8 - 10 0.9 – 1.0
Charge coal quality
S No Parameter Values
1 Total Moisture(%) 7-92 Volatile Matter(%) 25-263 Ash Content(%) 10 max4 CSN 6.5-85 MMR 1.12-1.186 Sulphur 0.6 max
7 % -3mm fraction 74-78
CONTENTS IN 1 TON OF COAL:
Coke -746 kgs
Crude Tar -32 kgs
Crude Benzol -6.9 kgs
Ammonia -4.1 kgs
CO Gas- 150 kgs
Losses -61 kgs
Coke Ovens
PURPOSE OF COAL PREPARATION PLANT:
The main purpose of this plant is to prepare the coal by removing the foreign matter and bringing to the size suitable for carbonization or coking process.
PURPOSE OF BATTERY :
Coal is converted into coke by high temperature carbonization in the ovens of the battery.
COKE DRY COOLING PLANT:
After pushing the coke from the Battery with a temperature of 1050°c, it is transferred into C.D.C.P for cooling purpose.
COKE SORTING PLANT:
Coke from C.D.C.P enters the C.S.P section. Here coke is crushed, screened and later conveyed to different consumers.
Coke oven Battery
BATTERY-1 - 1989
BATTERY-2 - 1991
BATTERY-3 - 1992
RAW MATERIAL - Coal blend.
PRODUCT - Coke with 1-3% volatile
matter.
BY-PRODUCT - Raw coke oven gas.
Objective:- To produce good quality of metallurgical coke.
Coke oven Battery COKE OVEN BATTERY CONSISTS OF 67 OVENS.
These ovens are OTTO-HOFFOMEN’S by-product oven type.
The total length of the battery is 100 mts.
It consists of rectangular chambers of length 16 mts,
height 7 mts
width 0.14 mts with removal door ends.
Battery has 4 machines:
Pusher car
Charging car
Door extractor car
Loco car
Coke side
COKE OVEN BATTERY:
coking period of 17-18 hrs by indirect heating with coke oven gas or mixed gas (CO gas + BF gas) in absence of air at 1150°c.
coking process is continued until most of the volatile matter is removed.
CHARGING CAR:
32 T of coal is charged in each oven up to a height of 6.7 mts out of 7 mts in each oven.
levelling which is done by a leveling bar fixed to the pusher car.
PUSHER SIDE
COKE OVENS
MAIN PRODUCTS
BF COKE
NUT COKE
BREEZE COKE
COKE DUST
BY-PRODUCTS FROM CO GAS:
TAR
AMMONIA
BENZOL
CLEANED CO GAS
Composition of CO gas
Hydrogen: 58-60%
Methane : 24-25%
Carbon monoxide: 6-7%
CmHn: 2-2.5%
Nitrogen: 3-4%
Carbondioxide:1.5-2%
Oxygen: 0.2%
Ammonia: 8-10 gm/NCum
Benzol: 25-30gm/NCum
Naphthalene: 0.8-1.1 gm/NCum
Coal Chemical Plant Many by products are extracted from the coke oven gas at this
department. It consists of the following sections:
Primary gas cooler.
Exhauster house.
Ammonium sulphate plant.
Final gas cooler.
M.B.C plant.
Tar distillation plant.
Benzol plant. Benzol distillation plant.
Hydro refining.
Extractive distillation.
Primary gas cooler PURPOSE OF PGC:
The main purpose of PGC is to cool the gas from 90°c to 30°c.
The cooler consists of three zones:
This is a shell and tube heat exchanger in which the CO gas
exchanges with
service water in the top two zones and
chilled water in the bottom zone.
Naphthalene and traces of tar present in the gas condense and this is collected at the bottom of the PGC.
The CO gas from the bottom of the PGC is fed to the electrostatic precipitator.
Primary gas cooler
Gas temperature before PGC 80-95°c
Gas temperature after PGC 27-30°c
Service water inlet temperature 32-33°c
Service water outlet temperature 43°c
Gas condensate flow to each PGC 10-15 Nm3/hr
Chilled water inlet temperature 11-12°c
Chilled water outlet temperature 20°c
Total number of tubes 409
Electrostatic Precipitator
Electrostatic precipitators are cylindrical vessels with a conical bottom. Each ESP is provided with a seal pot.
The CO gas enters the ESP from the bottom.
Electrodes are nothing but SS metal rods.
High voltage of about 50,000 volts is supplied to each electrode.
Capacity30,000 Nm3/hr
Voltage 70KV
Number of electrodes 148
ESP insulator boxes temperature 80°C
Exhauster house
PURPOSE:
These are centrifugal fans Used to drive the coke oven gas from the batteries itself to various plant like ASP.
The flow of gas is controlled by Askania valve, which is a butterfly valve.
When the quantity of gas is low - valve is closed
when the gas quantity is high - valve is opened.
Capacity 67,000-76,000Nm3/hr
Power 1250KW
Maximum suction at inlet 500mm WC g
Maximum pressure at delivery 2700mm WC g
Ammonia Sulphate Plant Coke oven gas from exhauster is fed to the ASP.
PURPOSE:.
To recover AMMONIA SULFATE from co gas
CAPACITY:
41,700 Ton / year
PROCESS:
The CO gas from the exhauster is fed to the pre-heater to preheat the gas to 60-70°c. So the gas is directly fed to the saturator. Separation of ammonia sulfate from co gas takes place by using H2SO4 and further processing takes place.
SATURATOR:
NH3 + H2SO4 NH 4 (HSO 4)
NH4 (HSO4) + NH3 (NH4)2SO4
ACID TRAP
CRYSTAL RECEIVE TANK
CENTRIFUGE
DRIER
CYCLONE
MOTHER LIQUOR TANK
AMMONIA COLUMN:
(NH4)2S 2NH3 + H2S
NH4CN NH3 + HCN
(NH4)2CO3 2NH3 + CO2 + H2O
NH4HCO3 NH3 + H2O + CO2
NH4HS NH3 + H2S
Final gas cooler
Coke oven gas after ammonia recovery consists of 0.8-1.12 mg/lit of naphthalene. These naphthalene particles are removed by using solar oil.
Temperature at the bottom of FGC50-60°c
Naphthalene in CO gas after FGC 0.4 g/Nm3
FGC tar temperature 80-90°c
Specific gravity of FGC tar moisture 5%
MBC Plant Effluent water from coke oven and by product plant was sent to
the MBC from the two pump houses.
PROCESS DESCRIPTION: All Inputs are collected, mixed with air in Pre-Aerators and
distributed in Tar Settling Tanks (TST). TST works in parallel. Heavy matter and tar settle in TST and the
settled effluent overflow to collecting tank. From collecting tanks effluent is pumped to Oil Flotators via Pr.
tanks for oil removal. Two Oil Flotators can work in series or parallel. Oil is removed by froth flotation mechanism.
From Oil Flotators effluent overflow to Equalizing tanks by gravity. Here P2O5 is added and pumped to 1st stage Aerotanks for Phenol degradation.
MBC Plant In 1st Stage degradation of Phenol take place due
to bio-oxidation by activated sludge.
Effluent Overflow from 1st stage to intermediate collecting tank from where it is again pumped to 2nd stage Aerotanks.
Cyanide and Rhodanides are decomposed here by similar action like 1st stage.
Effluent from 2nd stage overflow to intermediate collecting tank and from there it is pumped to STP.
Two numbers Air blowers pumps ambient air into the system as a source of Oxygen.
1 23 4
5 6
7
8 9
1011
Process Flow Diagram for MBC.
Oil Flotators
Air Blower
Tar Settling Tank
Equalizing Tanks
1st Aerotank 2nd Aerotank
Heat Exchanger
STP.
P1
P2
A11
A15
A21
A25 E1
E2
PT1PT2
EFFLUENT QUALITY AT DIFFERENT STAGES OF MBC PLANT.
Sl Parameter Unit Inlet After 1st Stage After 2nd Stage
01 Phenol PPM 400 3-5 1
02 Cyanide PPM 20 12 1.5-3.5
03 Thiocyanate PPM 400 350 10
04 Free NH3 PPM 250 90-100 80-100
05 Total NH3 PPM 600 500 500
06 Tar & Oil PPM 500 30-35 25
07 TSS PPM 100 200-300 150-200
08 BOD PPM - 1000 150
09 COD PPM 2500 1200 300
10 PH 7-9 7-9 7-9
Equipment capacities
EQUIPMENT NUMBER AVAILABLE CAPACITY
TAR SETTLING TANK 5 230M3
FLOTATORS 2 270M3
EQUALIZATION TANKS 2 1600M3
FIRST STAGE AERO TANKS 5 600M3
SECOND STAGE AERO TANKS 5 800M3
CENTRIFUGAL AIR BLOWER 3 18500M3/HR
BACTERIA CULTIVATION TANKS 2 100M3
PURIFIED WATER COLLECTING TANK 2 100M3
TAR Distillation
Tar Distillation Section.
Pitch Cooling & Loading Area.
Naphthalene & Anthracene Fraction Crystallization section (NAFC).
Tar & Oil Storage.
Tar & oil storage Decanter 1 no Reciprocating pump 2 no Furnace Fist stage
1st Evaporator
WaterReciprocating pump 2 no
Furnace 2nd stage2 nd Evaporator
Soft pitch
Reactor
MH Pitch
Collecting TankPitch Bays
For cooling
Cutting & Bagging
Light Oil
Phenol
Naphthalene
Wash Oil
Anthracene – I OIl
Anthracene – II OIl
Distillation column
To NAFC
TAR DISTILLATION PLANT
TAR Distillation Tar received from FGC unit to TOS unit. From TOS tar is pumped to Decanter in TDS unit. After removal of water from decanter moisture content in tar
reduces to 5-6%. Tar is heated in the first stage of furnace to a temp.of120-150 deg C
and sent to first stage evaporator. In first stage evaporator complete de-moisturisation is done.
Tar after first stage evaporator is again heated in II stage of furnace to a temp. of 330-350deg C.
In the second stage evaporator oil fraction is separated from top of second stage evaporator(35-40%) and soft pitch from bottom.
The oil fraction is sent to the distillation column, where individual oil products are tapped , cooled collected in storage tanks.
Benzol Plant(OBJECTIVES)
To recover Crude Benzol from Benzolised Oil.
To remove Impurities from Crude Benzol.
To produce Pure Products from C.B.
Benzol Distillation Section. Hydro Refining Unit. Extractive Distillation Unit.
Benzol Plant(SUB-SECTIONS)
BENZOL DISTILLATION UNIT
CRUDE BENZOL
DBO TO SCRUBBERS
LIVE STEAM
S
T
R
I
P
P
I
N
G
C
O
L
U
M
N
C
B
ONE
C
O
L
U
M
N
CB-I
COOLERS TO CFPS
C
B
TWO
C
O
L
U
M
N
CB-I
STEAM
STEAM
CB-II
B.O
Benzol Distillation Section
Extractive Distillation Unit
To separate non aromatics from benzene & tolune.
To produce pure benzene, pure tolune, Light solvent oil &still bottom oil from BTXS Raffinate.
Hydrorefining Unit
To remove Sulphour Compounds from Crude Benzol.
To produce BTXS Raffinate for processing in Extrative Distillation Unit.
To separate Crude Benzol from Benzolised Oil.
To separate HCB from Crude Benzol.
ANY QUERIES…?
THANK YOU…