Combustion system

A combustion chamber includes an inner cylindrical member concentrically mounted within an outer cylindrical member with a cylindrical space therebetween. The outer cylindrical member is enclosed at one end and both cylindrical members are open at an opposite end for access to the combustion area. The by-products of combustion are withdrawn from the inner cylindrical member at the closed end of the outer cylindrical member such that they reverse direction and circulate through the hot zone of the furnace in the cylindrical space. In a preferred embodiment of the invention, a porous ceramic plug which supports and spaces the tubes in concentric relationship at the one end and captures particulate by-products of the combustion holding them in the hot zone for complete combustion.