chap.1 processing of iron and s

8/2/2019 Chap.1 Processing of Iron and S

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Processing ofProcessing of

Iron and SteelIron and Steel

CHAPTER 1CHAPTER 1

Iron OreIron Ore

is mined from the groundis mined from the ground

it is a rock that may contain only 30% ofit is a rock that may contain only 30% of

iron.iron.

is in chemical compound or the iron isis in chemical compound or the iron is

combined with oxygen or sulfur.combined with oxygen or sulfur.

is found intermixed in rock, gravel, clay,is found intermixed in rock, gravel, clay,sand or even mud.sand or even mud.


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The iron ore is chemical compoundThe iron ore is chemical compound

with oxygen or sulfur.with oxygen or sulfur.

Sulfur Oxygen

Iron

Silicon IronSulfur Oxygen

Iron

Silicon Iron

Sulfur

Sulfur Oxygen Iron

Silicon Iron

Oxygen Iron Sulfur

Types of iron oreTypes of iron oreIron ore Iron Compound % iron

Hematite Fe2O3 70%

Magnetite Fe3O4 65%

Siderite FeCO3 48%

Limonite 2Fe2O3 H2O 52% 66%

Taconite Various 22% - 40%

Hematite


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Iron ore is found intermixed inIron ore is found intermixed in

rock, gravel, clay, sand or mudrock, gravel, clay, sand or mud

Rock Gravel

Mud

ClayRock

Iron

Oxygen

Iron

Oxygen

Iron Ore ProcessingIron Ore ProcessingCrushing the stone by Gyratory crusher - (smaller pieces)

Milling process in the roll mill or ball mill (fine particles)

Separation process by magnetic separator

Floatation process

Impurities bubble to the top and are skimmed awayand leaving an iron rich mixture

The particle is immersed in a liquid

Iron ore (~70% iron)


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Iron Ore ProcessingIron Ore Processing(Explanation)(Explanation)

First, the large chunks of stone are brokenFirst, the large chunks of stone are brokenup by giant crushers such as Gyratoryup by giant crushers such as Gyratorycrusher.crusher.

These smaller pieces are then fed into rollThese smaller pieces are then fed into rollmill or rod mill and ball mill.mill or rod mill and ball mill.

The mill rotate and hardened steel rollersThe mill rotate and hardened steel rollersor ball rotate with the ore and steadilyor ball rotate with the ore and steadilypound it into finer particles.pound it into finer particles.


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After being crushed and milled, the rockAfter being crushed and milled, the rock

particles become so fine that they feel like sugarparticles become so fine that they feel like sugar

or dry sand.or dry sand.

In this condition the valuable iron ore particlesIn this condition the valuable iron ore particles

can be separated by magnetic separator fromcan be separated by magnetic separator from

others.others.

The strong magnetic will separate the iron oreThe strong magnetic will separate the iron ore

from others particles during separator rotates.from others particles during separator rotates.

Iron Ore ProcessingIron Ore Processing

(Explanation)(Explanation)

Next the powder goes to flotation process,Next the powder goes to flotation process,

where the particles are immersed in a liquid.where the particles are immersed in a liquid.

Impurities bubble to the top and are skimmedImpurities bubble to the top and are skimmed

away and leaving an iron rich mixture.away and leaving an iron rich mixture.

After magnetic separation and flotation the oreAfter magnetic separation and flotation the ore

may contain as much as 70 % iron.may contain as much as 70 % iron.

Iron Ore ProcessingIron Ore Processing(Explanation)(Explanation)


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Steel ProcessingSteel Processing

There are 2 basic steps in steelThere are 2 basic steps in steel

processing:processing:

Step 1Step 1 -- Iron ore is converted to pig ironIron ore is converted to pig iron

Step 2Step 2 -- Pig iron is made into steelPig iron is made into steel

Steps for Making SteelSteps for Making Steel

Blast

FurnaceSteel

Making

FurnaceIron ore

Pigiron

Steel

Step 1 Step 2


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The Blast FurnaceThe Blast Furnace

Blast FurnaceBlast Furnace


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The Blast FurnaceThe Blast Furnace

A blast furnace may be more than 250A blast furnace may be more than 250

feet high, taller than 12feet high, taller than 12--storey buildingstorey building

and 30 feet in diameter.and 30 feet in diameter.

Fire resistant brick lines the inside wall ofFire resistant brick lines the inside wall of

the blast furnace.the blast furnace.

PIG IRON PROCESSINGPIG IRON PROCESSING


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The blast furnace is charged with iron ore,The blast furnace is charged with iron ore,

limestone, and coke.limestone, and coke.

A blast of preheated air burns the coke,A blast of preheated air burns the coke,

producing heat to melt the iron, whichproducing heat to melt the iron, which

falls to the bottom of furnace.falls to the bottom of furnace.

C + OC + O22 = CO= CO22 + Heat+ Heat

COCO22+ C = 2CO+ C = 2CO

Reaction at high temperature, so Carbon dioxide will reduce to carbonmonoxide as below:

The molten limestone combines with mostThe molten limestone combines with mostof the impurities in the ore to form a slag,of the impurities in the ore to form a slag,which separates from the liquid ironwhich separates from the liquid ironbecause it is lighter and floats.because it is lighter and floats.

The liquid iron and the liquid slag areThe liquid iron and the liquid slag are

removed periodically from the bottom ofremoved periodically from the bottom ofthe furnace.the furnace.

FeS + CaO + C= CaS + FeO + COFeS + CaO + C= CaS + FeO + CO


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The liquid iron is poured into mold to formThe liquid iron is poured into mold to form

what is known as pig of iron.what is known as pig of iron.

Pig iron is hard and brittle.Pig iron is hard and brittle.

It contains considerable amounts ofIt contains considerable amounts of

dissolved carbon, manganese, silicon,dissolved carbon, manganese, silicon,

phosphorus and sulfur.phosphorus and sulfur.

Step 1: Iron OreStep 1: Iron Ore Pig IronPig IronIron ore + Limestone + Coke

(Charcoal) are put into the furnaceA blast of preheated air burns the

coke and produce the heat

Melting process of ironMelting iron falls to the bottom

Molten limestone mixed withimpurities in ore SLAG (lighter

and float)

Molten iron and molten slag areremoved from the bottom

Iron is poured into mouldPIG IRON


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Air

Ore+

Limestone+

Coke

Slag

Iron

Air

Cast into pig iron

In the Blast FurnaceIn the Blast Furnace


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Pig IronPig Iron

Contains considerable amounts ofContains considerable amounts of

dissolved 4dissolved 4--5% carbon, manganese,5% carbon, manganese,

silicon, phosphorus and sulfur.silicon, phosphorus and sulfur.

Hard and brittleHard and brittle


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PIG IRONPIG IRON

There are several types ofThere are several types of

converter/furnace that used in makingconverter/furnace that used in making

steel:steel:

Open Hearth FurnaceOpen Hearth Furnace

Basic Oxygen FurnaceBasic Oxygen Furnace

Electric Arc FurnaceElectric Arc Furnace

Step 2: Pig IronStep 2: Pig Iron SteelSteel


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Open Hearth FurnaceOpen Hearth Furnace

The oldest converter.The oldest converter.

Basically a large bowl made of firebrick.Basically a large bowl made of firebrick.

Molten iron

Hot Air Hot Air

Steel is cast into ingot

OHF ProcessingOHF Processing

Pig iron and scrap metal are putinto the furnace

Hot air is blown across the surfaceand produce the heat

Excess carbon and impurities areburned off

Refining process

At the end of the refining process,

desired amount of carbon oralloying elements are added

Molten steel is drawn and cast intoingots

STEEL


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Basic Oxygen FurnaceBasic Oxygen Furnace

It is a rapid process (10 times faster thanIt is a rapid process (10 times faster than

OHF).OHF).

Lower cost.Lower cost.

Molten iron

Oxygen

Lance

Pig iron + scrap metal

BOF ProcessingBOF Processing

Pig iron + scrap are dumped intothe furnace vessel

A lance is lowered from above intothe charge

Pure oxygen is blown through thelance

The oxygen burns off the carbonvery rapidly

Once the carbon is removed, the

lance is withdrawn

Desired amount of carbon and

alloying elements are added

Steel is cast into ingotSTEEL


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Electric Arc FurnaceElectric Arc Furnace

It requires about 440 kW/ton of steel.It requires about 440 kW/ton of steel.

Capacity range: 1Capacity range: 1 100 tons100 tons

No air is required for melting processNo air is required for melting process

Materials Outlet

Molten iron

EAF ProcessingEAF Processing

Pig iron + scrap are loaded intothe furnace

Electrode are lowered from the topof the furnace close to the iron

An arc is struck to the iron to meltthe iron and burn off the carbon

Steel is cast into ingot

STEEL

chap.1 processing of iron and s

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