Blast furnace feeding practice

Iron is produced by the reduction of iron ore (oxides of iron), by coke in blast furnaces. Limestone is used as a fluxing agent. It dissociates into quicklime in the blast furnace, and helps to remove impurities in the iron ore (mainly silica and alumina) by reacting with them to form a molten slag. The slag also assists in the removal of other impurities. Traditionally, all of the limestone was charged with the other raw materials into the blast furnace. In current practice, limestone is also used as a component of the feed to sinter strands, which are used to agglomerate finely divided iron ore before it is fed into the blast furnace. 

Limiting demand for them is clearly one way of approaching this problem but it may not be practicable if competition, which stimulates demand, is intense. Since many materials can be recycled, this is an alternative, or indeed complementary, approach. Some materials have been recycled for many years, ferrous metals being perhaps the most notable examples. Thus at the end of their useful life automobiles are crushed and the (rusted) metal returned as part of the feed to the blast furnace where it is reconverted into iron and steel. Paper and cardboard are other well-known examples. 

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