Iron Making

RAW MATERIAL PLANT FOR IRON MAKING

IRON ORES ORE APPEARANCE COMPOSITION % OF IRON

MAGNETITE STEEL GREY OR BLACK Fe3O4 72-62

HEMATITE(a) RED HEMATITE EARTHY OR ROCK ,RED Fe2O3 70-

60

(b) BROWN HEMATITE BROWN EARTHY 2 Fe2O33H2O 60-42

SIDERITE OR SPATHIC CRYSTALLINE GREY FeCO3 48-35

IRON STONE GREY TO LIGHT BROWN FeCO3 42-30

EARTHLY OR STONEY

MAGNETITE:

HEMATITE:(RED)

HEMATITE:(BROWN)

DIFFERENT IRON ORES

LOCATION OF IRON ORE MINES IN INDIA

The most important variety of iron ore are:

Nomenclature Composition Fe %age Location

Magnetite

(Black oxide)

Fe3O4 72.4 Makarwal, Swabi, Chitral (PAK),

Land of midnight sun (Sweden), Pennsylvania(USA), Siberia(Russia)

Hematite (red, brown & black)

Fe2O3 40-65 Kala bagh, Chnari, Chaghi, Chalghazi (PAK),

Lake superior, Utah (USA), Lorraine (France), Amazon basin (Brazil)

Limonite & other hydroxide types of ores

2Fe2O3 . H2O to

Fe2O3 . 3H2O

20-55 Not found in PAK,

Britain’s East coast

Siderite FeCO3 Low in Fe

Hazara, Mardan (PAK),

South Wales, Staffordshire &west York (UK)

Iron Pyrite (yellow)

FeS 42 Mardan, Chitral (PAK)

Iron Ores

Page 12 February 2011 Siemens VAI Metals Technologies LtdEdward Long

Background -Raw Materials used

Coke Pellets, Sinter

Plus – Dolomite, limestone etc

Iron Ore

BLAST FURNACE

Raw materials•Iron ore –magnetite , Hematite ,Siderite•Coke used as fuel•Lime stone /Dolomite/ Silicon used as flux

Where from iron produced?

Raw iron is found in earth’s crust, as an ore.Iron ore mostly found as Fe2O3 (the form of iron oxide found as the mineral hematite).

Where from iron produced?

At present, blast furnace is most commonly used furnace to produce iron.The Blast furnace iron making process basically consists of the conversion of iron oxide to iron in liquid form . This requires reductant for reduction of iron oxide and heat for the above reduction reaction to take place. The primary source to fulfill both these requirements is carbon (in the form of coke).

Where from iron produced?

The blast furnace is a vertical counter-current heat exchanger as well as a chemical reactor in which burden material charged from the top descend downward and the gasses generated at the tuyere level ascend upward.

Raw Material Section in iron making

Broadly a raw material section in iron making plant has the following sections:a. Iron Ore Handling Systemb. Coke & Coal Handling Systemc. Lime & Other Material Handling Systemd. Sinter Plant

Flow Diagram

Blast Furnace

Iron

Ore

Iron Ore Section

Ore crushed & Transported from mine to plant

Ste

el P

lan

t

Blast Furnace

Iron

Ore

Mine

Stack

Yard

Material Handling System

Iron Ore Section

Iron ore chunks dugs from the earth and taken to process plant.Chunks are crushed to small fractions, and impurities are removed by magnetic separator or other means. The small iron fractions are formed into marble sized pellets in forming drums and discs. Then the pellets are transported to stack yard of steel plant.

Iron Ore Section

Iron ore is collected from mines and crushed

Iron Ore Section

Stack Yard

Processed iron ore are dumped at stack yard

Iron Ore Section

Iron ore are transported through belt conveyor

Belt Conveyor

Iron Ore Section

Material Handling System

Raw Materials are Stored and transported

inside steel plant and fed into

Blast Furnace through material handling system

Flow Diagram

Blast Furnace

Iron Ore

Coal Coke Oven Plant

Coke

Metallurgical Coke• Coke is a solid carbonaceous material derived from

destructive distillation of low-ash, low-sulfur bituminous coal.

• The volatile constituents of the coal—including water, coal-gas, and coal-tar—are driven off by baking in an airless oven at temperatures as high 1000° C.

• Metallurgical coke is produced by carbonization of coal at high temperatures to produce a macroporous carbon material of high strength and relatively large lump size.

Notes:

• Metallurgical cokes must have a high strength to support heavy loads in the blast furnace without disintegration.

Coke Manufacturing Process Bituminous coal is pulverized by ball mill into fine

powder.

Fine coal is heated in coke oven battery at 700–900 ° C in absence of air. This process is called Carbonization.

After soaking at this temperature for about 7–8 hrs., it is allowed to cool in the furnace.

Due to coking property of bituminous coal powdered coal converts into lump size and becomes very hard and highly porous.

After cooling, the coke produced is crushed into desired size.

Coke Manufacturing Process

• Strength of the coke,

• fixed Carbon (88-92%),

• sulphur content and

• ash content

is determined in the testing laboratory for

justifying the quality of the coke.

• By-products like tar may also be collected during

carbonization process.

Quality Control and Standards

Coking coal used should have

low ash content,

low sulphur and

should be highly coking in nature for better quality of coke.

Other properties like

porosity,

abrasive strength and

hardness

must be checked in the laboratory for maintaining the

quality of Metallurgical coke.

Coal & Coke SectionProcessed & Transported from mine to plant

Ste

el P

lan

tBlast

Furnace

Coal Mine

Stack Yard

Coke Oven Plant

Transportation by Material Handling System

Coke

StackMaterial Handling System

Coal & Coke Section

Coal are collected from mines. Then they are washed & crushed to pieces. After that coal is transported to stack yard of steel plant. From stack through material handling section, they are transported to coke oven section, where coal is baked and converted into coke.

Coal & Coke Section

Coal is collected from mines

Coal & Coke Section

Coal is processed, washed and crushed and then transported into stack yard of steel plant

Coal & Coke Section

Processed coal is dumped at stack yard and transported to coke oven plant by material handling system

Coal & Coke Section: Coke Oven Plant

Coke is source of thermal energy inside the Blast Furnace, which burns and the converted heat melts the iron ore.

Coal & Coke Section: Coke Oven Plant

Coke StackStorage Bunker

(Coal Tower)Stamp

Charging Car

Coke Oven Battery

Quenching Car

Water

Sprayed

Material Handling System

Coke Bridge

Waste

Coke lump collected under ground,

Crushed & Stacked

Coal Pushed in

Coke Pushed out

Liquid ChemicalOff gas

used as fuel

Waste Volatile Substance

Coal & Coke Section: Coke Oven Plant

Schematic View of Coke Oven battery. Here instead of collecting coal at stamp charging car, loose coal is directly fed into the oven from top.

Coal & Coke Section: Coke Oven Plant

Stamp Charging Machine: Erection Stage

Coal & Coke Section: Coke Oven Plant

Stamped Coal cake ready for charging into the oven

Coal & Coke Section: Coke Oven Plant

Stamped Coal cake pushed into the oven

Flow Diagram

Blast Furnace

Iron Ore

Coal

Coke Oven Plant

Coke

Flux

Flux Section

Flux crushed & Transported from source to plant

Ste

el P

lan

t

Blast Furnace

Material Handling System

Flux Stack Yard

Flux Section

Flux is added in the blast furnace to remove impurities, by producing slag. Lime is the most commonly used flux material. Lime may be used as a flux in the form of CaO, limestone (CaCO3), dolomite (magnesium calcium carbonate) or dolomitic lime (product obtained from burning or roasting of dolomite).

Flux Section

Lime is used as a flux in solid, particulate form and reacts with impurities in the charge to form a slag.It is important that the slag be kept fluid, not only to increase its ability to scavenge impurities from molten metal, but also to permit the slag to be readily removed from the furnace.

Flux Section

Formation of slag has a adverse effect also.Lime in reaction with silica or silicates present in the ore forms dicalcium silicate, which has 38000C melting point. It form a coating on lime particles and prevent it from further reaction.Auxiliary flux is used for the purpose of facilitating the reaction between lime and silica or silicates. Fluorspar is a example of auxiliary flux.

Flow Diagram

Blast Furnace

Iron Ore

Coal

Coke Oven Plant

Coke

Flux

SinterFines from

different sources

Sinter Plant Section

In order to enhance the productivity of blast furnaces, a high percentage of sinter charge is a prerequisite. Sinter is an agglomeration of iron ore fines, coke and limestone in the form of cakes. To ensure sinter burden in the blast furnaces at 75 per cent, a total of 3 million tonnes of sinter was envisaged for a production of about 2 million tonnes of hot metal.

Sinter Plant Section

Sinter Plant

Sinter Plant Section

Sinter Plant

Sinter Plant Section

Simple Flow Diagram of Sinter Plant

Sinter Plant Section

The raw materials used are as follows - Iron ore fines (-10 mm), coke breeze (-3 mm), Lime stone & dolomite fines (-3mm) and other metallurgical wastes. The proportioned raw materials are mixed and moistened in a mixing drum. The mix is loaded on sinter machine through a feeder onto a moving grate (pallet) and then the mix is rolled through segregation plate so that the coarse materials settle at the bottom and fines onto the top.

Sinter Plant Section

The top surface of the mix is ignited through stationary burners at 1200oC. As the pallet moves forward, the air is sucked through wind box situated under the grate. A high temperature combustion zone is created in the charge -bed due to combustion of solid fuel of the mix and regeneration of heat of incandescent sinter and outgoing gases. Due to forward movement of pallet , the sintering process travels vertically down. The different zones created on a sinter-bed are shown in the simple flow diagram of sinter plant.

Sinter Plant Section

Sinter is produced as a combined result of locally limited melting , grain boundary diffusion and recrystallization of iron oxides. On the completion of sintering process, finished sinter cake is crushed and cooled. The cooled sinter is screened and + 6 mm fraction is dispatched to blast furnace through material handling system and -6 mm is re-circulated as return sinter.

Blast Furnace

All the raw material is charged into the blast furnace, from top, through variable throat armour or any other means. The purpose of a blast furnace is to chemically reduce and physically convert iron oxides into liquid iron called "hot metal".

Blast Furnace

The blast furnace is a huge, steel stack lined with refractory brick, where iron ore, coke and limestone are dumped into the top, and preheated air is blown into the bottom. The raw materials require 6 to 8 hours to descend to the bottom of the furnace where they become the final product of liquid slag and liquid iron. These liquid products are drained from the furnace at regular intervals.

Blast Furnace

The hot air that was blown into the bottom of the furnace ascends to the top in 6 to 8 seconds after going through numerous chemical reactions. Once a blast furnace is started it will continuously run for four to ten years with only short stops to perform planned maintenance.

Blast Furnace

Blast Furnace

Pig Iron - Properties & uses

Definition:- “It is a high-carbon iron made by reduction of iron ore in the blast furnace”.

• Metallic iron, which is a product of reduction of of iron ore, appears in the lower part of ‘stack’ & in the ‘bosh’.

• It contains ~ 1 % C and found to in spongy form. As this material sinks down in the B.F. and is heated further, iron dissolves C in increasing quantities. This reduces the melting temp & it melts and draws off to the ‘hearth’ in the form of drops.

Pig Iron… (Continue)

– Pig iron is really a complex alloy. In addition to Fe, it contains up to 10 % of other elements, mainly, C, Mn, Si, S & P.

– Total amount of C in the pig iron is usually between 3 – 4% & is present either as compound, iron carbide (Fe3C) or as un-

combined carbon in the form of graphite.

– Pig iron low in S & high in P may be used in the manufacture of acid steel & high-duty iron castings.