2050 – 03 – Using the Blast Furnace
Usually, iron makes up only about half to seventy percent of the iron ore that eventually becomes pig iron. To create pig iron, that ore is combined in a blast furnace with limestone, coke, and sometimes scrap steel and iron.
Blast furnace’s heat removes impurities from the iron. To create that heat, hot air gets pumped through the lower portion of the blast furnace. Within the furnace, temperatures can be blistering — as high as 3000 degrees Fahrenheit (1650 C). The coke reacts chemically with oxygen. The product of that reaction is carbon monoxide and a large amount of heat. Carbon monoxide takes away the oxygen from the iron as it exits the furnace.
When the iron ore melts, the coke and the limestone bond to the impurities, producing a substance called slag. The slag sits on top of the iron and is cleared away, leaving only pig iron.