|The impurities are removed react with calcium oxide to make a liquid slag that floats on top of the molten iron. The slag is collected after the denser iron has been run out of a tap hole near the bottom of the furnace. |
The production of iron in a Blast Furnace is a continuous process. The furnace is heated constantly and is re-charged with raw materials from the top while it is being tapped from the bottom. Iron making in the furnace usually continues for about ten years before the furnace linings have to be renewed.
The energy costs of the operation are kept to a minimum by collecting and cleaning the hot gas that leaves the furnace. This gas contains a lot of carbon monoxide. It can be re-used as a fuel for other steelmaking processes or to heat up the air blast to the furnace.