Rotary kiln Wikipedia
A rotary kiln is a pyroprocessing device used to raise materials to a high temperature (calcination) in a continuous process. Materials produced using rotary kilns include: Cement; Lime; Refractories; Metakaolin; Titanium dioxide; Alumina; Vermiculite; Iron ore pellets; They are also used for roasting a wide variety of sulfide ores prior to metal extraction.