Describe the extraction of Iron from its Hematite ore in the Blast Furnace. | web4study

Describe the extraction of Iron from its Hematite ore in the Blast Furnace.



EXTRACTION OF IRON:

The most important raw materials or ores from which iron metal extracted are oxide ores i.e. hematite (Fe2O3) or limonite (Fe2O3. 3H2O).

The first stage involved in the manufacture of iron is the reduction of oxide ores in a blast furnace as given in fig. This involves the crushing of the oxide ore to produce lumps. These lumps are then pre-heated using hot gases from the blast furnace. This removes water and other volatile impurities present in the ore.

In the second stage, the roasted iron ores are charged with coke am limestone (CaC03) which are fed from the top of the furnace, while a blast of hot air is introduced into it from the bottom through small pipes known as tuyeres.

The temperature inside the furnace varies from about 2000°C near the bottom to about 200°C at the top. The blast of hot air oxidizes the coke to carbon dioxide with the liberation of a lot of heat

The reaction is highly exothermic. This raises the temperature. As C02 gas rises up the furnace, it reacts with more coke, forming CO gas.

EXTRACTION OF IRON

Carbon monoxide (CO) gas, thus produced then reduces the iron” oxide ores to free iron metal in the upper parts of the furnace. Here temperature is between 477°C to 727°C.

The limestone .which has been introduced together with coke, decomposes at high temperature to yield calcium oxide (CaO) which then combines with silica {Si02) and aluminium oxide (Al20 3), present as impurities to form calcium silicate (CaSi03) and calcium aluminate (Ca Al2 04).

The mixture of CaSi03 and Ca Al204 which remains molten at the furnace temperature is known as slag. The molten free iron runs downward to the bottom of the furnace and is withdrawn through a tap hole at short intervals. The slag being lighter floats on top of the molten iron and is a runoff. The slag is not wasted and is a useful by-product.

 


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