A considerable amount of exergy is contained in the liquid slag tapped from blast furnaces. Relatively new processes for heat recovery from these slags are described in this paper. The slags yield a useful, dry granulated product with a glass content that depends on the process employed. Exergy in liquid and solid slags can be exploited to produce both steam and heated air. The steam may be used to generate electricity, while hot air is employed to preheat the combustion air for the blast furnace. Using a second law analysis, it is proved that the second alternative is preferred for blast-furnace slag when heated air is used for combustion in the hot blast stoves of the blast furnace.