A type of furnace used for roasting various sulphide ores prior to metal extraction. The kiln consists of a slowly rotating cylinder inclined slightly to the horizontal with a refractory lining. Material is fed into the rotating kiln allowing it to cascade down. Hot air from a burner which provides the heat is also fed into the kiln either cocurrently but more usually countercurrently. At the end, the product is collected and any entrained product with the hot gases separated by a cyclone. They are used in the manufacture of cement and pelletizing of iron ore, titanium dioxide, and alumina.