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…