PURPOSE: To convert CO+H2O into H2+CO2 securely, by equipping a cylinder having a fire pipe to which a water gas fire in a flue of cupola is introduced and a corridor of flue at its top and bottom respectively with devices for feeding SiC.

CONSTITUTION: The cylinder 1 equipped with the fire pipe 2 and the corridor 4 of flue at its top wall is provided with the plural devices 3 for feeding SiC. The high-temperature water gas fire of a looking-down flue of cupola of the ventilation type from which dust is removed is introduced to the pipe 2 and converted with steam from the steam pipe S as shown in the formula. The preparation stand R in the corridor 4 is a stirring position required for separation of two phases of vapor and liquid. When SiC is fed from the extruders P of the devices 3 to the cylinder 1, SiC creates first the preparation stand R of gravitational flow on the corridor 4, and then the valley V of mountain and hill with a slope of 45° on the central surface of the stand from the devices 3 at both sides. The fire and steam are made to flow from the valley V with the minimum resistance→the center of the stand R→the side of the stand R→below the flue. Since the stand R is not eroded by the high-temperature steam, CO, H2, and CO2, it is not lost, to carry out secure conversion.