Explain the construction and working principle of cupola furnace
Answers
A cupola furnace is a device used for melting cast iron, some bronzes and Ni-resist iron in foundries.
Construction
The cupola furnace is constructed in the shape of a vertical hollow cylindrical steel shell. Inside it is lined with a refractory material. It supported by four cast iron legs which stand on a concrete base. There are two cast iron doors which are hinged to the bed plate. They are used to close the bottom of the furnace. A wind box encircles the bottom of the furnace. A blast pipe connects it to the furnace blower. The blower forces the air through the cupola and helps in supplying the oxygen needed for burning the fuel. There is a mesh screen on the top part of the furnace. On top of it there is a cone shaped spark arrester. It allows the waste gas to go out and deflects the dust and sparks.
Working
A cupola furnace works on the counter current principle. It uses the energy generated from the combustion or oxidation of coke. Scrap, alloys and coke are put in from the top of the furnace. Then air which is often heated and contains added oxygen is introduced near the bottom of the furnace. When the coke burns heat is produced which helps to melt the scrap. The liquefied iron goes out of the cupola from a taphole at the bottom.