Abstract: A double wall reaction chamber assembly comprising a cylindrical inner wall and a cylindrical outer wall axially parallel thereto, the inner wall having an annular junction with a thickened annular junction flange on the outer surface thereof. The lower end of the outer wall being fused to the outer surface of the thickened annular junction. The outer surface of the inner wall and the inner surface of the annular junction flange define a sloping annular drainage channel to a downwardly sloping drainage port, enabling liquid to drain from the junction. The double wall reaction chamber assembly has a cylindrical inner wall and a cylindrical outer wall axially parallel thereto. It has a lower end fused to the inner wall. A gas distribution tube has a gas inlet end and a gas distributor end, the gas distributor end comprising a split tee having a junction.