Abstract: An incinerator for burning waste material includes an outer steel housing having a refractory liner that defines a combustion chamber. A series of channels are secured to the inner surface of the housing and provide vertical air flow passages. The lower ends of the passages are open to the atmosphere, while the upper ends are connected to a plenum and air is drawn through the passages by a blower to thereby preheat the air and cool the outer housing. A portion of the preheated air is directed to the stack for secondary combustion purposes, while a second portion of the preheated air is returned through vertical passages in the end of the housing to a pair of lower plenums and then introduced into the lower end of the combustion chamber for primary combustion purposes. The incinerator also has an improved feed assembly for feeding waste material to the combustion chamber, which includes a hopper, a triple hydraulic cylinder and a ram movable within the hopper.