A Brief Introduction To Bhilai A Brief Introduction To Bhilai Steel PlantSteel Plant

• Bhilai Steel Plant - a symbol of Indo-Soviet techno-economic collaboration, is one of the first three integrated steel plants set up by Government of India to build up a sound base for the industrial growth of the country

• The agreement for setting up the plant with a capacity of 1 MT of Ingot steel was signed between the Government of erstwhile U.S.S.R. and India on 2nd February,1955

India entered the main stream of the steel producers with the commissioning of its first Blast Furnace on 4th February, 1959 by the then President of India, Dr Rajendra Prasad

Commissioning of all the units of 1 MT stage was completed in 1961.

A dream came true-the massive rocks from the virgin terrains of Rajhara were converted into valuable iron & steel.

BSP is the sole manufacturer of rails and producer of the widest and heaviest plates in India. Bhilai specializes in the high strength UTS 90 rails, high tensile and boiler quality plates, TMT bars, and electrode quality wire rods.

It is a major exporter of steel products with over 70% of total exports from the Steel Authority of India Limited being from Bhilai.

The distinction of being the first integrated steel plant with all major production units and marketable products covered under ISO 9002 Quality Certification belongs to BSP.

• Not content with the Quality Assurance system for production processes, Bhilai has one in for ISO 14001 certification for its Environment Management System and its Dalli Mines

• Besides environment-friendly technology like Coal Dust Injection System in the Blast Furnaces, de-dusting units and electrostatic precipitators in other units, BSP has continued a vigorous forestation drive, planting trees each year averaging an impressive 1000 trees per day in the steel township and mines.

IRON ORE

IRON ORE GROUP OF MINESIRON ORE GROUP OF MINES

• Dalli Rajhara is situated approximately 90 Kms south-west of Bhilai.

• There are five working mines:(i) Rajhara Mechanised Mine (ii) Dalli Mechanised Mine(iii) Jharandalli Mechanised Mine(iv) Dalli Manual Mine (v) Mahamaya Manual Mine.

• Aridongri deposit has been surrendered & handed over to state government.

Initial ReserveInitial Reserve

6 Rajhara-West 3

20 Kokan 2

102 Rajhara Mech. 1

Reserve (M.T.)Name of Mine Sl. No

21 Mahamaya 7

29 Dalli Manual 6

31 Jharandalli 5

108 Dalli Mech. 4

327 Total

10 Dulki 8

Reserve as on 01.04.2007Reserve as on 01.04.2007

Sl.No Name of Mine Reserve(M.T.) Fe% SiO2% Al2O3%

1 Rajhara Mech. 32.97 4 67.31 1.76 0.8

2 Dalli Mech. 36.53 64.09 4.38  

3 Jharandalli 11.08 63.44 4.36 1.9

4 Dalli Manual 4.5 62.33 4.7 2.61

5 Mahamaya 4.8 62 5 2.9

6 Dulki 8.52 63.67 3.6 2.76

  Total 98.4 64.88 3.48 1.83

MINES MANAGEMENTMINES MANAGEMENT

IRON ORE-FROM DALLI RAJARAHA

RAJARAHA-10000TONNES/DAY

TOTAL 24000TONNES/DAY

DALLI-20000TONNES/DAY(12%LOSS)

TRANSPORTED BY BOBS WAGON

TRANSPORTED BY BOBS WAGONTRANSPORTED BY BOBS WAGON

QUALITY OF ORE:

IRON - 62 to 65% SILICA - 4.5 to 5% AI2O3 - 2.5 to 2.75%

FLUX GROUP OF MINESFLUX GROUP OF MINES• The Flux group comprises two mines,

namely Nandini Lime Stone Mine, and Hirri Dolomite Mine.

The ore reserve as on 01.04.2007 is as under:

Sl.No Name of Mine Reserve(M.T.) Cao % Mgo% SiO2

%

1 Nandini (Lime Stone) 105.87 41.84 6.22 6.72

2 Hirri (Dolomite) 21.74 30.93 20.67 3.93

RAW MATERIALS HANDLED, RAW MATERIALS HANDLED, SOURCES & CONSUMERSSOURCES & CONSUMERS

Raw Material Sources Consumers

Iron ore fines Dalli Rajhara SP-2 & SP-3

Low Si Lime Stone JAiselmer, Katni,

Kuteshwar RMP-2, SMS-2

High Si Lime Stone Nandini SP-2 & SP-3

High Si Dolomite Hirri SMS-2 ,SP-2, SP-3,

Iron Ore Dalli, Rajhara B.Furnace-7/ Highline

Bunkers

High Si Mn Ore Ramteke Tirodi Moil Blast Furnace No.1 & 7

Function of coke ovens and Function of coke ovens and coal chemical Departmentcoal chemical Department

Convert coal into coke

To recover volatile matter and CO gas and extract coal chemicals

Coke-Making ProcessCoke-Making Process

• Coking is the process of heating coal in the absence of air in coke ovens to drive volatile matter from it.

• Ovens are heated by coke-oven gas/ blast furnace gas / mixed gas (i.e. CO & BF)

• which burns in heating flues in an oven's side walls (heating walls)

• Waste gases from this combustion pass out through a stack or chimney.

• Once charged, coal is allowed to "coke" in the absence of air, for 18 to 22 hours depending on the battery at about 1180-1225 0c

625-675625-675Sp Heat Consumption Kcal/kg

41.621.6Useful Vol /oven (CU.M)

32 T16.8 TCoal holding Capacity/Oven

6765No of Ovens

9-101-8Battery

One tone of Dry coal yields 300-310 CU/M of gas 330 Kg Tar 0.28% Ammonia or 1.0-1.04% ammonium sulphate

COKE QUALITYCOKE QUALITY

MOISTURE ASH V.M FC M40 M10 SULPHUR CSR CRI -40MM

3.6 16.8 .9 81.9 22.9

25MM MEAN SIZE

1.2 54.9

LIME STONELIME STONE

FROM NANDANI MINES

6000T/DAY BY BOBS WAGON

Sinter PlantSinter Plant

Sintering Process

Agglomeration of Iron ore fines Fluxes & metallurgical waste

Heating 1040-12000c

1. Iron ore fines 0 - 8 mm

2. Lime stone 10 - 50 mm

3. Raw Dolomite 0 - 40 mm

4. Coke Breeze 0 - 10 mm

5. Lime Dust 0 - 5 mm

6. Mill Scale 0 - 3 mm

7. Lime sludge 0 - 3 mm

8. Sinter Return 0 - 5 mm

9. Settling Tank Dust 0 - 3 mm

10. Flue Dust 0 - 3 mm

11. LD slag 0 - 10 mm

RAW MATERIALS RAW MATERIALS USED IN SINTERING PLANTUSED IN SINTERING PLANT

SINTER QUALITYSINTER QUALITY

Fe FeO SiO2 Al2O3 CaO MgO CaO-SiO2

54.26 8.12 5.58 2.79 11.16 3.06 5.58

INTRODUCTION – Iron INTRODUCTION – Iron Production BasicsProduction Basics

• The first step in the production of steel is to produce iron, and iron production involves separating iron from iron ore.

• There are mainly three basic methods of

producing iron:

1.Direct Reduction

2.Iron Smelting

3.The Blast Furnace method

• Direct Reduction method includes both gas and coal based processes. The product coming out of these processes (Sponge Iron or Direct Reduced Iron) is in the solid state. Electric Arc Furnace follows DRI process for the production of crude steel.

• In Iron smelting process coal and iron ore fines are used as charge materials and liquid product will come out of the furnace, example Corex process. EAF or BOF route is followed for steel making.

• For achieving high production rates with great degree of heat utilization Blast Furnace (BF) route is the most economical way till date.

• So Bhilai Steel Plant, which is an ore based Integrated Steel Plant had chosen Coke ovens – Blast Furnace – BOF/THF route for the production of crude steel.

What is a Blast Furnace?What is a Blast Furnace?

• BF is a counter current heat and mass exchanger, in which solid raw materials are charged from the top of the furnace and hot blast is sent through the bottom via tuyeres.

• Gas ascends up the furnace while burden and coke descend down through the furnace.

• The counter current nature of the reactions makes the overall process an extremely efficient one

• In the blast furnace process iron ore and reducing agents (coke, coal) are transformed to hot metal, and slag is formed from the gangue of the ore burden and the ash of coke and coal.

• Hot metal and liquid slag do not mix and remain separate from each other with the slag floating on top of the denser iron.

• The iron can then be separated from the slag in the cast house. The other product from the Blast Furnace is dust laden blast furnace gas, which is further cleaned in the gas cleaning plant and

is used as a fuel all over the plant.

Blast Furnace constructional Blast Furnace constructional features:features:

A blast furnace has a typical conical shape.

The sections from top down are:

• Throat, where the burden surface is.• The shaft or stack, where the ores are heated

and reduction starts.• The bosh parallel or belly and• The bosh, where the reduction is completed and

the ores are melted down.• The hearth, where the molten material is

collected and is cast via the tap hole.

Systematic Cross section of BFSystematic Cross section of BF

Cross Sectional Viewof BF

The basic raw materials and their The basic raw materials and their functionsfunctions

• Iron Ore: Iron bearing materials; provides iron to the Hot Metal

• Sinter: Iron bearing material. Fines that are generated in the plant are effectively utilized by converting them to sinter. Provides the extra lime required for the iron ore that is charged in the blast furnace.

• Coke: Acts as a reductant and fuel, supports the burden and helps in maintaining permeable bed.

• Limestone: Acts as Flux. Helps in reducing the melting point of gangue present in the iron bearing material

• Manganese Ore: Acts as additive for the supply of Mn in the Hot Metal

• Quartzite: Acts as an additive• Coal Dust: Acts as an auxiliary fuel, reduces

coke consumption in the BF• Coal Tar: Acts as an auxiliary fuel, reduces coke

consumption in the BF• Pellets: Iron bearing materials. Although not in

use right now, there is a proposal to utilize the fines below the sinter grade for pellet manufacturing and the pellets formed are going to be charged in the BF.

• The raw materials from various places are transported to the bunkers placed near the furnaces and properly screened and weighed.

• These batched proportions of the raw materials are conveyed to the top of the blast furnace via skip car or conveyors and are charged in the blast furnace.

• The distribution is maintained in such a fashion that alternate layers of coke and iron-containing burden (sinter and iron ore) are formed inside the BF. The blast, which is heated in the stoves, is called Hot Blast and this is blown into the BF via tuyeres.

• The hot blast gasifies the reductant components in the furnace, those being coke as well as auxiliary materials injected via the tuyeres.

• In this process, the oxygen in the blast is transformed into gaseous carbon monoxide.

• The resulting gas has a high flame temperature of between 2,100 and 2,300°C.

Hot blast Temp 950 –9700c

Hot Metal 1400-14250cTop Gas Temp 6000c

Up take temp 3500c

Periphery Temp 650 -8000c

Slag Temp 1450 14800c

Stove Dom temp 12000c

Flue gas 2700c

Different Temperature in BF

Vital functions of The hot gasVital functions of The hot gas

• Heats up the coke in the bosh/belly area.• Melting the iron ore in the burden, creating

voidage.• Heats up the material in the shaft zone of the

furnace.• Removes oxygen of the ore burden by chemical

reactions.• Upon melting, the iron ore produces hot metal

and slag, which drips down through the coke.

• zone to the hearth, from which it is removed by casting through the tap hole. In the dripping zone the hot metal and slag consume coke, creating voidage.

• Additional coke is consumed for final reduction of iron oxide and carbon dissolves in the hot metal, which is called carburization.

• Thus the liquid products Hot Metal and Slag settle in the Hearth.

TappingTapping

• Hot Metal and Slag are removed periodically from the blast furnace. The process is called “Tapping” the blast furnace.

• The other gaseous product, which is going to the top of the furnace, contains dust in it. It is cleaned in the Primary (dust catcher); Secondary (ventury and scrubber) and Tertiary (electro static precipitator) gas cleaning system and the cleaned gas is used as a fuel all over the plant.

• It will take minimum 6-8 hours for the solid raw materials that are charged from the top to reach the bottom, whereas gaseous products that are sent through the tuyeres will go out in 2-8 seconds.

• The efficiency of the process is judged by two parameters

• Productivity (Unit: tonnes/m3/day)

• Fuel Rate (Unit: kg/thm)

Reactions in the Blast Furnace:Reactions in the Blast Furnace:

• UPPER STACK ZONEReduction of Oxides

3 Fe 2O3 + CO = 2 Fe3O4 + CO2Fe3O4 + CO = 3FeO + CO2FeO + CO = Fe + CO2

• Decomposition of Hydrates• Water - Gas Shift Reaction• CO + H2O = CO2 + H2• Carbon Deposition• Decomposition of Carbonates

• MIDDLE STACK ZONE

• Direct / Indirect Reduction

FeO + CO = Fe + CO2CO2 + C = 2COFeO + C = Fe + CO

• Gas utilization

• LOWER STACK ZONE

• Calcinations of Limestone

• Reduction of Various elements

• Reduction of unreduced Iron

• Reduction of Silicon

• Reduction of Mn, P, Zn etc.

• Formation / melting of slag, final reduction of FeO and melting of Fe.

Steel Making AnimationSteel Making Animation