About Bokaro Steel Plant

Bokaro Steel Plant – the fourth integrated steel plant in the Public Sector-

started taking shape in 1965 in collaboration with Soviet Union. It was originally

incorporated as a limited company on 29th January 1964, and was later merged

with SAIL , first as a subsidiary and then as a unit, through the Public Sector Iron

& Steel Companies (Restructuring & Miscellaneous Provisions) Act 1978. The

construction work started on 6th April 1968.

The plant is held as the country’s first swadeshi steel plant, built with maximum

indigenous contents in terms of equipment, material and know-how. Its first

blast furnace started on 2nd October 1972 and the first phase of 1.7 MT ingot

steel was completed on 26th February 1978 with commissioning of the third

blast furnace. All units of 4MT stage have been already been commissioned and

the modernisation has further upgraded this to 4.5MT of liquid steel.

Bokaro Steel Plant is designed to produce flat products like HOT ROLLED COILS,

HOT ROLLED SHEETS, COLD ROLLED COILS, COLD RLLED SHEETS,TIN MILL

BLACK PLATE(TMBP) and GALVANISED PLAIN and CORRUGATED (GP/GC)

SHEETS. Bokaro Steel Plant has provided a strong raw material base for a variety

of modern engineering industries including automobiles, pipe and tube, LPG cyl-

inder, barrel and drum producing industries.

Bokaro Steel is working towards becoming a one-stop- shop for world-class flat

steel in India. The modernisation plans are aimed at increasing the liquid steel

production capacity, coupled with fresh rolling and coating facilities. The new

facilities will be capable of producing the most premium grades required by the

most discerning customer segments.

List of Plants Visited

1. RAW MATERIALS HANDLING

PLANT [ RMHP]

2. SINTER PLANT

3. COKE OVEN & BY-PRODUCT

PLANT [ CO &BPP]

4. BLAST FURNACE

5. STEEL MAKING SHOP &

CONTINUOUS CASTING SHOP

[ SMS & CCS]

6. RESEARCH AND CONRTOL

LABORATORY [ RCL ]

Raw Material Handling Plant [RMHP] This plant receives, blends and stores different raw materials including iron

ores fines, iron ore lumps , dolomite, limestone, and coke etc. And vends

these raw materials to the Blast Furnace, Sinter Plant and Refractory mate-

rials plant as per their requirements. It also maintains a buffer stock to take

care of any supply interruptions.

This plant consists of various machinery and are list as follows:

Rail

Car Pushers

Wagon Tipplers (4 in number)

Stackers (7 in number)

Re-claimers (6 in number)

The raw materials arriving from various mine being carried on rails

are unloaded at Tipplers. In this section the wagon carrying the raw materi-

als is rotated at angle of 170 degrees to unload the raw materials.

Subsequently, these raw materials are carried through conveyers and stored in

the form of heap, separate for each raw material. Now, Re-claimers blend and

mix the different quality of raw materials for e.g., Iron ore fines from different

mines and hence a homogenous composition is made and distributed to its

customers mainly Blast Furnace and Sinter Plant.

Some 9MT of different raw materials viz.

iron ore fines & lumps, Limestone (BF &SMS

grade), Dolomite lumps and chips, hard coal

and manganese are handled over a year.

Fig. Wagon Tippler Machine

Fig. Raw material Stacker

DIFFERENT TYPES OF RAW MATERIALS AND THEIR SOURCES

RAW MATERIAL TYPE SOURCES

IRON ORE FINES & LUMPS KIRIBURU,MEGHATA-BURU,GUA,BOLANI -

MANOHARPUR,KATLA

HIGH SILICA/SP GRADE LIMESTONE BHABANTHPUR, KHANBHANJARI

HIGH SILICA/SP GRADE DOLOMITE BHABANTHPUR,BIRMITRAPUR

LOW SILICA/SMS GRADE LIMESTONE JAISALMER,DUBAI,OMAN LOW SILICA/SMS GRADE DOLOMITE BHUTAN,BELHA

EXTERNAL AND INTERNAL HARD COKE IISCO,DPL,NINL,MBEB,VISA

EXTERNAL AND INTERNAL SINTER IISCO,NINL,RSP

CUSTOMERS OF RMHP BLAST FURNACE- Lump iron ore, external and internal sinter, hard coke,

quartzite

SINTER PLANT- Iron ore fines and flux

RMP- Low silica limestone and dolomite.

FIG. IRON ORE FINES

SINTER PLANT Sintering is a process of agglomeration of fine mineral particles into a po-

rous and lumpy mass by incipient fusion caused by heat produced by

combustion of solid fuel within the mass itself.

RAW MATERIALS USED FOR SINTERING

Iron ore fines

Flux (lime stone & dolomite)

Coke breeze

Waste Materials:

Flue dust (From Blast Furnace but added in RMHP)

Mill scale (From Slabbing Mill, H.S.M.&CCS)

L.D. Slag (From S.M.S.)

Lime dust (From R.M.P.)

Sinter return (Own generation)

DIFFERENT EQUIPMENTS OF SINTERING PLANT

RAW MATERIAL BINS AND WEIGH FEEDERS

MIXING AND NODULIZING DRUM WITH WATER INJECTION SYSTEM

SURGE BIN-SECTOR GATES WITH SERVO DRIVES AND FEED DRUM

IGNITION HOOD FURNACE WITH BURNERS

SINTER MACHINE-PALLETS with GRATE BARS

WINDBOXES WITH WASTE GAS MAIN

SPIKE CRUSHER-WITH CRASH DECK

DOUBLE ROLL CRUSHER

VIBRATORY COLD SCREEN FOR HEARTH LAYER

VIBRATORY SCREEN FOR RETURN FINES

CONVEYORS, RECEIVING CHUTES AND TRANSFER CHUTES FOR RAW

MATERIAL AND SINTER

WASTE GAS FAN WITH LCI DRIVE

DEDUSTING FAN FOR PLANT DEDUSTING

ESPs

LT and HT DRIVES

PNUEMATIC ACTUATORS & VALVES

THE NEED OF SINTER: • To utilize the fines generated during the mining operation.

• To utilize different additives like mill scale, flue dust, hearth slag etc. in

an integrated steel plant.

• The need for charging prepared burden in Blast Furnaces to increase

productivity and lower fuel rate.

SINTER MACHINE PARAMETER:

1. Hearth temperature- 1050-1150∘C

2. Machine speed- 1.7-2.0 m/minute

3. Moisture- 8.0±1%

4. Gas pressure- 200mmWc-350mmWc

5. BTP- >180∘C.

COKE OVEN & BY-PRODUCT PLANT[CO &BPP]

In this plant, coal coming from various RMHP is converted into coke by the

process of carbonisation. The coal coming from mines is brittle and generally

has low combustion rate. In the carburization, the coal is heated in coke oven

furnace and the product which we get is called coke or BF coke

The BF coke is harder and has a high combustion rate and is suitable for fur-

ther blast furnace operation.

THERE ARE FOUR SECTIONS IN COKE OVEN PLANT:

1. COAL HANDLING PLANT

2. BATTERY

3. COKE SORTING PLANT

4. BY-PRODUCT PLANT

Coals are of two types-

1. Imported coal

2. Indian coal

Indian coal has low calorific content. So we blend the Indian coal with imported

coal in the ratio of 60:40 percent. Generally, coal of better quality is imported

from Australia, New Zealand.

There are 81 silos in which different qualities from different countries coal is

stored. Each silo has capacity of 2500 Tons. After that coal is sent to coal tower

of capacity 3200 Tons.

Now coal is charged into coke oven batteries. There are total 8 batteries and 69

ovens in each. The length and height of the coke oven batteries are 15m and 5m

respectively. The capacity of one battery is 22 Tons. The coal is heated in battery

at 1200-1300∘C for 18-20 hours.

FIG. COKE OVEN BATTERIES AT BSL, BOKARO

FIG. SILOS (These are used to store coal and act as buffer stock in sine die situations)

THE FOLLOWING BY-PRODUCTS ARE PRODUCED DURING CARBURISA-

TION:

1. TAR

2. NEPTHALENE

3. AMMONIUM SULPHATE

4. BENZOL

FIG. BY-PRODUCT PLANT

BLAST FURNACE

A blast furnace is a type of metallurgical furnace used for smelting to produce

industrial metals, generally iron, but also others such as lead or copper.

In a blast furnace, fuel, ores, and flux (limestone) are continuously supplied

through the top of the furnace, while a hot blast of air (sometimes with oxygen

enrichment) is blown into the lower section of the furnace through a series of

pipes called tuyeres, so that the chemical reactions take place throughout the

furnace as the material moves downward. The end products are usually molten

metal and slag phases tapped from the bottom, and flue gases exiting from the

top of the furnace. The downward flow of the ore and flux in contact with an up

flow of hot, carbon monoxide-rich combustion gases is a counter-current

exchange process.

In contrast, air furnaces (such as Reverberatory furnaces) are naturally aspi-

rated, usually by the convection of hot gases in a chimney flue. According to this

broad definition, bloomeries for iron, blowing houses for tin, and smelt mills for

lead would be classified as blast furnaces. However, the term has usually been

limited to those used for smelting iron ore to produce pig iron, an intermediate

material used in the production of commercial iron and steel, and the shaft fur-

naces used in combination with sinter plants in base metals smelting.

The tuyeres are used to implement a hot blast, which is used to increase the ef-

ficiency of the blast furnace. The hot blast is directed into the furnace through

water-cooled copper nozzles called tuyeres near the base. The hot blast temper-

ature can be from 900 °C to 1300 °C (1600 °F to 2300 °F) depending on the stove

design and condition. The temperatures they deal with may be 2000 °C to 2300

°C (3600 °F to 4200 °F). Oil, tar, natural gas, powdered coal and oxygen can also

be injected into the furnace at tuyere level to combine with the coke to release

additional energy and increase the percentage of reducing gases present which

is necessary to increase productivity.

Fig. TUYERES OF BLAST

FURNACE

THERE ARE FIVE BLAST FURNACES IN BOKARO STEEL PLANT OF 2000 CUBIC

METERS FOR PRODUCING HOT METAL .

Bell-less Top charging, modernised double Cast houses, Coal Dust Injection and

cast house slag granulation technologies have been deployed in the furnaces.

The process of iron making is automated, using PLC Charging System and Com-

puter controlled Supervision System. The waste products like blast furnace slag

and gas are either used directly within plant or processed for recycling or re-use.

Design and Features of All Furnaces

Particulars BF1 BF2 BF3 BF4 BF5 USEFUL VOLUME (IN CUBIC METER)

2000 25000 2000 2000 2000

WORKING VOLUME(IN CUBIC METER) 1758 2250 1758 1758 1758

HEARTH DIAMETER(in meter) 9.5 10.2 9.5 9.5 9.5

NO. OF TUYERES 20 28 20 20 20

HOT BLAST TEMP. (⁰C) 1000 1150 1000 1000 1000

Top Pressure(kg/cm.sq.) 1.5 2.5 1.5 1.5 1.5

RATED CAPACITY (tonne/day) 2640 4500 2640 2640 2640

FIG. FURNACE CONTROL ROOM OF BLAST FURNACE 2, BSL, SAIL, BOKARO

(OVERVIEW OF BF2)

STEEL MAKING SHOP

After production of hot metal in blast furnace, it is sent to steel making shop for

production of steel.

Ladle of pig iron is sent to mixer. Ladles are brought to SMS from BF through lo-

comotive engine. The capacity of each ladle is 100 tonnes.

There are two mixers in SMS each having capacity of 2500 tonnes.

The functions of mixers are as follows:

1. To maintain temperature

2. To homogenize the composition

3. To storage

Then it is sent to LD Converter. There are two LD Converters each of capacity 300

tonnes.

Pig iron is charged into converter and then through lance pipe the melt is oxi-

dized. Thus oxidizing all the impurities in melt and forming lighter oxides which is

separated out due to lesser specific gravity.

The oxygen supply by the lance is 99.9% pure. The blowing time is about 15-18

minutes. There is exothermic reaction takes place. The temperature range is

1700-1800∘C.Now it is sent to secondary refining unit (SRU). In SRU we use Ar

gas.

The main functions of SRU are:

1. Homogenization

2. De oxidation

3. Temperature & composition adjustment

4. Desulphurization

5. Dispatching to casting

Bokaro has two Steel Melting Shops ­ SMS­I and SMS­I I. SMS­I has 5 LD convert-

ers of 130T capacity each. It is capable of producing rimming - steel through the

ingot route. SMS­II has 2 LD converters, each of 300 T capacity, with suppressed

combustion system and Continuous Casting facility. It produces various Killed

and Semi ­Killed steel.

FIG. LD CONVERTER

After completion of steel making, it is sent to Continuous Casting Shop (CCS).

This technique entails cooling of steel continuously as it descends down through

the cooling line.

The ladle of steel is poured into Tundish with capacity 25-50 tons and is heated

with propane torched to be fluid. It is then send in mould further encountering

liquid pool and spray cooler.

As it descends down we finally get a slab around a period of 80-90 minutes.

Then solidify at 600∘C.Finally with the help of a torch cutting machine (TCM), re-

quired length of slab is cut. There is another shop where ingot casting is done.

RESEARCH AND CONTROL LAB

In this laboratory they check the composition of steel and other materials like

refractories. Also check the steel and pig iron lollypop samples to add or control

the composition of that product. They also test the materials mechanical prop-

erties like tensile strength, compressive strength, fracture defects, toughness,

etc. They have a chart of steels that are used in different area. On basis of these

compositions chart they prepare the required steel for different –different areas

or organization.