PURPOSE: To miniaturize the titled heat exchanger and to reduce cost by a method wherein the case of the heat exchanger used in a cement baking equipment, a gaseous fuel and air are supplied separately or in a mixed state into upper and lower chambers partitioned by a porous heat resistant member so as to transfer the powdered material collected by a separator to the next duct.

CONSTITUTION: The powdered material thrown out into exhaust gases from a throwout port 4 is collected by the separator C4 and then into an air sliding conveyer S4 where the powdered material is fluidized by air supplied into an upper chamber 11 from an air supply pipe 17 through a lower chamber 12 and a porous heat resistant member 13 and is transferred to the next duct D2. Thus, by repeating the above process, the powdered material is burned temporarily through an air sliding conveyer S2, a temporary combusion furnace 1, an exhaust gas duct DO, a separator C1 and an air sliding conveyer S1 and during the process, the powdered material is not only preheated but also burned temporarily so that the degree of the temporary burning is reduced at the terminating end of the process to thereby miniaturize, and reduce the capacity of, the temporary combustion furnace.