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Iron Making
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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.