PURPOSE: To decrease power consumption in a supercharger, by cooling the device incorporated with a high temperature body by the air fed from outside, and by introducing heated air into a combustion chamber through a gas turbine to which a compressor for cooling air is directly connected.

CONSTITUTION: A refractory material 5 is lined on the inside of a cylindrical combustion chamber 1 into which a combustion air is fed from a tangential opening 3, along with pulverized coal sucked from a burner which is not shown through an opening 2, when this method is practiced in a cyclone furnace. On the other hand, cooling passages 6 and 6' are provided returnedly to the outer periphery of a combustion chamber 1, and cooling air is fed into the passage 6 from a compressor 8 through an air pipe 9. The cooling air cools the combustion chamber 1, and the heated air is led into a gas turbine 11 from the passage 6' through an air pipe 10, to let it perform a work of driving the compressor 8, and the air going out of the gas turbine 11 is led into a combustion chamber 1.