Abstract: The reactor for the production of CO and H.sub.2 containing gases by means of a partial oxidation of powdery or liquid high ash fuels in a carburation fluid including free oxygen, at high temperatures and increased pressure, includes a pressure vessel enclosing a gas-tight housing whereby an interspace is formed between the inner wall of the vessel and the outer surface of the housing. Within the housing is arranged a cooling wall enclosing the reaction chamber proper. The cooling wall includes a coil of cooling pipes embedded in a mass of refractory material such as silicium carbide. The pipes are partially supported on web sections projecting from the inner surface of the housing into the refractory lining. The web sections prevent propagation of leaking hot gas from the reaction chamber along the inner surface of the housing.