PURPOSE: To eliminate various defects when a water-cooled construction is given to the inner walls of a combustion chamber and to various kinds of devices installed in it for the purpose of raising their heat resistance by means of applying heat resistant painting to them.

CONSTITUTION: Heat-resistant paint layers A, B are applied to the internal and external faces of a combustion chamber in the body (a) of a combustion furnace and flame guiding channel (c') that is in connection with the combustion chamber and, further, rotating cylindrical body 3 that is installed in the combustion chamber 2 and provided with projections 5 and supply air ports 4, blast pipe 8, fuel supply mechanism 11, discharge mechanism 16. Blowers 7, 10 are connected to the external ends of the rotating cylindrical body 3 and blast pipe 8 through dampers 6, 9, and an isolation cover plate is installed laterally to a gate of an external hopper-with freedom to run on the gate. The external hopper has a waste fuel charging device positioned above it and a fuel supply mechanism 11 positioned below it.