Name: Ellingham Diagram: Introduction
Uploaded: 2019-07-19
Duration: 7 min 42 s
Description: The Ellingham diagram proved to be a cornerstone for the process of reducing metal oxides to their native form. Watch this video to learn about the Ellingham...

Question

Write down the reactions taking place at different zones of blast furnace during the extraction of iron.

Accepted Answer

The metal iron is usually extracted from haematite ore. For the extraction of iron, smelting is carried out in a blast furnace. That is, the oxide ores of iron, after concentration through calcination or roasting are mixed with limestone and coke and fed into a blast furnace from its top. Here, the oxide is reduced to the metal. The following reactions take place inside it. That is,

The falling coke reacts with hot air inside to give,

$C + O_{2} \to {CO}_{2} + Heat$ .

The reaction is exothermic. The upward carbon dioxide comes in contact with the layers of coke and gets reduced to carbon monoxide. That is,

${CO}_{2} + C \to 2 CO - Heat$

The carbon monoxide thus formed acts as a reducing agent and reduced iron oxides to iron. In blast furnace, iron oxides are reduced at different temperature ranges. That is,

${Fe}_{2} O_{3} + 3 CO \to 2 Fe + 3 {CO}_{2} ↑$ $(675 - 975 K)$

$3 {Fe}_{2} O_{3} + CO \to 2 {Fe}_{3} O_{4} + {CO}_{2} ↑$

${Fe}_{3} O_{4} + CO \to 3 FeO + {CO}_{2} ↑$

$FeO + CO \to \underset{Molten}{Fe} + {CO}_{2} ↑$

$2 FeO + C \to \underset{Molten}{2 Fe} + {CO}_{2} ↑$ $(900 - 1500 K)$

The molten iron thus formed is collected at the bottom of the furnace.

The limestone added acts as a flux and removes the silicious impurities in the form of slag. That is,

${CaCO}_{3} \overset{∆}{\to} CaO + {CO}_{2}$

$CaO + {SiO}_{2} \to \underset{Slag}{{CaSiO}_{3}}$

$CaO + {Al}_{2} O_{3} \to \underset{Slag}{Ca {({AlO}_{2})}_{2}}$

The molten slag is lighter than the molten iron and floats on the top which can be removed through the outlet-holes provided. Carbon monoxide, coming out of the furnace is used to heat the air-blast initially given to the furnace.

Write down the reactions taking place at different zones of blast furnace during the extraction of iron.

Important Questions on General Principles and Processes of Isolation of Elements

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