The tuyere bottom consists of a horizontal and one or more inclined sections(3,4). In the inclined tuyere bottom are contained one or more horizontal bottoms or bottoms with variable angles of inclination. Individual areas of the tuyere bottom are permanently or adjustably not charged with air. The fluidised bed is cooled by immersion heating surfaces(5) which are directed perpendicularly or inclined in the lower region and are inclined in the upper region.
