Blast furnaces are a common feature of the steel industry. Used to produce high-grade iron, commonly known as “pig iron”, blast furnaces are also used to produce cast iron and low-grade iron, known as “foundry iron”. In the process of iron production, carbon and other substances such as silicon and manganese are added to the iron ore to produce metallic iron.
The process of preparing the iron ore for use in the furnace is called sintering. A large scale sintering machine is required to break down the larger lumps of ore into a form that can be fed into the blast furnace.
Once the iron ore is ready, it is then loaded into the blast furnace and heated in the presence of oxygen and carbon monoxide at temperatures approaching 1000°C. This process reduces the iron ore to iron and it also removes some of the impurities in the ore such as silica, phosphorus, and sulfur.
In some cases, a flux, such as limestone or dolomite, is added to the mixture to react with the impurities to form slag. The slag can either be removed immediately or allowed to flow off as a waste material, depending upon the intended use of the iron.
The molten iron formed in the blast furnace is further treated in a converter or Bessemer process to produce high-grade iron, or “pig iron”. At this stage, the iron is still relatively pure and contains relatively little carbon. The pig iron is then further treated in the open-hearth process to remove excess carbon, sulfur and other impurities.
These impurities are then removed and sold as by-products such as slag and industrial chemicals. The remaining iron is then used in the production of steel.
Blast furnaces can be found in many steel mills throughout the world and are a common site in the steel production industry. They are an essential part of the process of producing high-grade iron and steel. The unique combination of heat and oxygen used in the process of smelting iron is the reason why blast furnaces continue to be an important part of the steel industry.
