Rotary kiln is rotary calcining kiln and one of building material equipments. According to dealing with different materials, there are cement kiln, matallurgy chemical kiln and lime kiln.
Rotary kiln is the key equipment of cement clinker in dry-process and wet-process production line. Metallurgy chemical kiln is mainly used in iron ore magnetic calcination, silicon thermal refining magnesium, chromium nickel ore calcination, refractory calcination and active lime and calcined dolomite for steel mill and ferroalloy works.

Rotary kiln is a slightly horizontal tilt, rotating slowly around the axis of the cylindrical container. The material to be processed is fed into the upper end of the cylinder. As the kiln rotates, the material gradually moves downward and may be stirred and mixed to some extent. High-temperature gases sometimes pass through the kiln in the same direction (parallel flow) as the processed material, but usually in the opposite direction (countercurrent). Hot gases may be produced in an external furnace or by a kiln flame. Such flames are projected from the burner tube (or "ignition tube"), which acts like a large burner. The fuel can be natural gas, oil or pulverized coal.