In an apparatus for continuous heat treatment, a mechanically fluidized stream of material consisting preferably of a granular or highly viscous material is heated in a rotating chamber in co-current with heat energy originating from a burner (1), in which solid, liquid or gaseous fuel is burned. A portion of the energy liberated by the combustion heats the internal part of a thin-walled chamber (5), the external part of which at the material inlet (10) transfers energy to said stream of material in the form of radiant heat. The remaining portion of the energy liberated by the combustion, bound in the exhaust gases from the combustion process, are subjected to heat exchange in a primary convective heat exchanger (7) and one or more secondary heat exchangers (8) in counter-current with a gaseous process medium, preferably atmospheric air, said process medium transferring further energy to said stream of material in the form of convective energy.