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Explain the refining of Aluminium and Iron in industries.
Aluminium
Bauxite is extracted by open-pit mining. The richer ores are used as mined. The lower grade ores may be beneficiated by crushing and washing to remove clay and silica waste. The production of the metal comprises two basic steps:

Processing
Refining. Production of alumina from bauxite by the Bayer process in which bauxite is digested at high temperature and pressure in a strong solution of caustic soda. The resulting hydrate is crystallized and calcined to the oxide in a kiln or fluid bed calciner.

Reduction. Reduction of alumina to virgin aluminium metal employing the Hall-Heroult electrolytic process using carbon electrodes and cryolite flux.

Iron
Large scale iron ore smelting has been carried out in numerous types of blast furnaces since the industrial revolution, with the basic ingredients of coke, iron ore and limestone remaining unchanged, being loaded into the blast furnace from where the molten iron is tapped into molds.

Processing
Iron ore is obtained in the conventional method of open cast or underground mining and conveying the ore to the surface preparation are where it is crushed, washed, and transported to the smelter.

Here the ore is put into a blast furnace along with limestone and coke and subjected to hot air blasting and heat which converts the ore to molten iron. This is tapped from the bottom of the furnace into molds known as pigs and allowed to solidify into pig iron.

This pig iron is converted to wrought iron or processed into steel by several methods.

This is the first article in a series on metallurgy, where we will examine the processing of iron ore into different grades of steel. We start with the mining and preparation of the iron ore and shipping it to the smelter.


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