In steelmaking, blast furnaces convert iron ore into crude iron by the reducing action of carbon at high temperatures. This crude iron or ‘pig iron’ still contains a lot of carbon and other impurities that need to be removed, partially or totally, by a reaction with oxygen.
In the basic process pure oxygen is blown from above into the pig iron bath at a certain location using a water-cooled lance. It is important to keep the pig iron melt agitated, for a homogeneous reaction between the blown-in oxygen and carbon from the melt.