Abstract: The invention relates to a method for heat-treating fine-grained materials which tend to agglomerate at high temperatures and which have an average grain size of preferably 0 to 1000 &mgr;m within temperature ranges around and above the agglomeration temperature, in a fluidized bed of another, coarse-grained material. The temperature range in which the coarse-grained material tends to agglomerate and sinter to the reactor walls is higher than that of the fine-grained material. The coarse-grained material used is a material of the same type, a similar type or a different type with an average grain size of 1 to 10 mm. The fine-grained material is fed in directly over the tuyere bottom of a closed furnace chamber containing the fluidized bed, performs a circulating movement in said fluidized bed and once the heat treatment has been carried out, is pneumatically withdrawn from the fluidized bed into the top section of the furnace, and cooled immediately.