Combustion furnace particularly for burning refuse

A combustion furnace particularly for burning refuse, comprising a furnace housing having an inlet adjacent one end for the infeed of material to be burned and a discharge spaced from said inlet, and a grate extending between said inlet and said discharge and having an overall sloping angle sloping downwardly to said discharge, said grate including a plurality of separate individual grate step portions arranged one after the other between said inlet and said discharge and each sloping downwardly in a direction opposite to said overall slope of said grate, said housing including spaced inner and outer walls and an intermediate partition arranged in substantially parallel relationship and defining an inflow passage for air between the intermediate wall and the inner wall from the top of said furnace along each side, said inflow passage having openings into said furnace in the vicinity of said grate and the space between said partition wall and the outer wall defining a return conduit communicating with the end of said inflow conduit for the outflow of the air which is in excess of that required for combustion.