PURPOSE: To enable the production of steam utilized for cooling the incinerator and for other purpose by a method wherein the wall of a combustion chamber is constituted by a water-wall tube itself and the tube in communicated with the water supply system of a boiler for utilizing effectively enough the remaining heat of the combustion chamber.

CONSTITUTION: The cooling water in the water-wall tube 13 surrounding the combustion chamber 5 goes from a lower drum 20, passes a circulation pipe 4, rises through a lower header 18 and then the water-wall tube 13, pasaes an upper header 19, and further circulates to an upper drum 21. In the meantime, the part of water evaporated through heat exchange is constantly supplied by a pump 10. The gas sent into the combustion chamber 5 through the primary airing pipe 16 and discharged after combustion as exhaust gas is introduced into the burner 14 of a boiler 9 through a flue 8, which fresh air is supplied to the burner 14 through the secondary airing pipe 17, and there the complete combustion is performed. By the heat of this combustion the heat exchange in the boiler 9 is conducted, while the burnt gas is discharged as exhaust gas and smoke.