Occurrence and extraction of iron

Iron is the most abundant metal which occurs in the earth's crust. There are two forms of iron - cast iron and wrought iron - cast iron is the least pure form of iron whereas wrought iron is the purest form of iron. There are many ores of iron. Among all the ores hematite and magnetite are the important ones. Hematite is mostly found in the northern region in India whereas magnet is found in the southern states.

Extraction

Extraction of Iron is done in many steps like oxidation, combustion, fusion, reduction, etc. During extraction cast iron is formed first which is then converted to wrought iron. Hematite is the ore that is used for extraction of cast iron. The ore is crushed into small pieces and is washed with water to remove the sand particles. Then the washed ore is heated in the presence of air. This process removes the moisture and is called as calcination. In this process, sulphur and phosphorus forms oxides. Carbonate forms oxide and ferrous oxide converts into ferric oxide.

Blast furnace is used in the extraction of iron, which is made of steel lined with bricks. The ore, coke and limestone are sent into this furnace from top. The furnace has an inlet for hot air and two outlets for slag and molten iron. The coke that is sent in burns and produces carbon dioxide. This CO₂ reduces to CO in presence of coke.

The limestone subjected into the furnace decomposes and produce CaO. This CaO later combines with silica and forms slag.

Molten stag formed is lighter and is removed out by the outlet produced for it. All the above reactions takes place from the bottom to the middle region of the furnace. Only the reduction of oxides of iron to iron is done at the top of the furnace.

Thus, the iron that is formed melts and moves down to the base of the furnace. This is called as cast iron. This cast iron is again heated with hematite to remove the impurities.

Thus, wrought iron which is the purest form of iron is formed.