The conventional route, aka the indirect reduction method, for making steel consists of sintering or pelletization plants, coke ovens, blast furnaces, and basic oxygen furnaces.

Thermal energy I suppose, but in most cases it is used for electricity. The steel industry uses coal (or coke rather) in blast furnaces.

Mendelevium 101 LOL

Coal is burned mostly in fireboxes in coal fired power plants. Coal is also sometimes burned in furnaces in industrial facilities that refine and process various metals. Coal is also roasted (heated without oxygen so that it does not burn) to produce coke, which is widely used in steel mills (mostly as a carbon source and fuel in blast furnaces).

what are blast and crucible furnaces