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Blast furnace is an iron smelting shaft furnace with round transect. The shells are made by steel plates and internal-lined with refractory bricks. From the top down, blast furnace can be divided into five parts: throat, stack, belly, bosh and hearth.
Due to advantages of iron-smelting technology of blast furnace, such as good technical and economic indices, simple techniques, great output, high production efficiency, low energy consumption etc., iron produced by this method has accounted an absolute majority of the world total output.
In the process of production, put in iron ores, cokes and fluxes used for dregs making (limestone) from the furnace roof and blow in preheated air through the air port in the bottom part. Under high temperature, carbon monoxide that produced by the combustion of carbon in cokes (some blast furnaces also spray coal dust, heavy oil, natural gas and other auxiliary fuel) and oxygen that blew into air removes oxygen, sulfur and phosphor in the iron ores during its raise process within the furnace and reduces to get iron.
The smelted molten iron is discharged from the tap hole. The unreduced impurities in the iron ores (main is gangue SiO2) combines with limestone and other fluxes together to produce slag (main are CaSiO3 etc.), and the slag is discharged from the cinder notch. The gas produced is discharged from the furnace roof and after de dusting can be used fuel of hot blast stoves, heating furnaces, coke ovens and boilers etc. The main product of blast furnace smelt is pig iron and the byproducts are blast furnace cinder and blast furnace gas.
Blast furnace