NOVELTY - A hydrogen combustion system comprises external cylinder (1); internal cylinder (2) formed by porous metal plate; hydrogen combustion catalyst (4) supported with precious metals on spherical ceramic support surface; insert pipe (3) formed by porous metal plate; preheating heaters (5) between the insert pipe and internal cylinder to preheat the hydrogen combustion catalyst; hydrogen introducing port (8); and air introducing port (9). Hydrogen supplied to the internal cylinder is combusted with air by catalytic action to exhaust as safe water vapor.    USE - Hydrogen combustion system used to combust excess hydrogen generated during operation of fuel cells, atmospheric hydrogen at film forming in semiconductor processes, electrolytically by-produced hydrogen from water electrolysis system, useless by-product hydrogen from chemical reaction processes, and to combust hydrogen gas from production units of electrolytic ozone gas and electrolytic ozone water.    ADVANTAGE - The system is simple in construction and small in size with maximum treatment efficiency through the methods in which, premixing the introduced hydrogen gas with air to dilute to the lowest level of the combustion range at supplying hydrogen gas to the hydrogen combustion system is not employed and thus pure state hydrogen gas is supplied to the system. The air necessary for the reaction is supplied by drift resulting from the differential pressure generated by thermal convection between the loading layer of hydrogen combustion catalyst and the external, thus a blower and a fan to feed reaction air forcibly are not required. Hydrogen gas is subject to combustion treatment safely and the amount of flow of hydrogen gas from the upper side of the insert pipe to the internal cylinder is minimized so that hydrogen gas is blown out of the entire surface of the insert pipe uniformly. The catalyst loaded in the internal cylinder is kept balanced optimally with the air flowing into the gap between the external and internal cylinders to obtain the maximum hydrogen treatment capacity.    DETAILED DESCRIPTION - The hydrogen combustion system comprises external cylinder constituting the exterior of a double tube construction; internal cylinder formed by porous metal plate constituting the interior of the double tube construction; hydrogen combustion catalyst supported with precious metals on spherical ceramic support surface, formed in pellet state, and packed in the internal cylinder; insert pipe formed by porous metal plate inserted in the center of the internal cylinder; preheating heaters between the insert pipe and internal cylinder to preheat the hydrogen combustion catalyst to ambient atmosphere of over catalytic reaction temperatures; hydrogen introducing port connecting to the insert pipe; and air introducing port at a bottom of the external cylinder in an area between the external and internal cylinders. Hydrogen supplied to the internal cylinder from the hydrogen introducing port via the insert pipe is combusted with air introduced from the air introducing port to the internal cylinder through a gap between the external and internal cylinders, by catalytic action to exhaust as safe water vapor.    DESCRIPTION OF DRAWING(S) - The figure is a schematic view of the hydrogen combustion system.    External cylinder (1)    Internal cylinder (2)    Insert pipe (3)    Hydrogen combustion catalyst (4)    Preheating heaters (5)    Hydrogen introducing port (8)    Air introducing port (9)