Abstract: A method and apparatus for burning carbonaceous materials in a fluidized bed reactor comprising a bottom region and a top region, and containing a fluidized bed, with the heat of combustion being dissipated at least via wall cooling surfaces, and comprising a recirculation system, including a labyrinth separator for recirculating the separated solids to the bottom region of the fluidized bed reactor. The solids are separated from the rising flow of flue gas by the labyrinth separator, which is disposed directly in the top region of the fluidized bed reactor, and are conveyed in the reactor itself along the wall cooling surfaces and are supplied to the bottom region of the reactor, either freely or in closed or partly or completely open recirculation passages. The main area of application is with a steam generator.