Blast furnace slag

In the iron ore reduction and smelting process at the blast furnace, the cast iron contains, among other things, all the elements (iron, manganese, silicon, etc.) that are reduced during the operation; the unreduced oxides, whatever their origin (ore gangue, additions, coke ash), are found in a complex product, the slag. Slag is discharged from the blast furnace ( , in liquid form, at the same time as the cast iron); its enthalpy is around 1,800 MJ/t of slag, i.e. 3.5% of the blast furnace's energy balance.