Abstract: Described is an apparatus for separating contaminated material from impurities contained therein, by heating by means of hot gases. The apparatus has receiving chambers for accommodating the contaimated materials, and heating chambers which surround the respective receiving chambers. Each heating chamber is divided into first and second chamber means of which one is designed to carry a flow of burner gas while the second is designed to carry a flow of coolant. The first and second chamber means extend in mutually separate relationship and in a helical configuration around the associated receiving chamber. Each receiving chamber has gas distributor members to produce a turbulent flow in the chamber.