PROBLEM TO BE SOLVED: To provide a relatively small-scaled apparatus, in which a thermal decomposition gas produced by the thermal decomposition reaction of solid fuel in a thermal decomposition furnace is reformed into a crude fuel gas.
SOLUTION: Thermal decomposition furnace 1 is provided with an air introducing port 18 arranged at the furnace bottom part and for blowing air for combustion to the furnace, a furnace bed 30 arranged at the upper side thereof and a thermal decomposition gas discharge port 15 at the upper part of the furnace body. The furnace bed 30 is composed of a layered body of many spherical heat resistant materials 32 forming many narrow gaps, through which air for combustion is passed, in the whole zone of the furnace bed. A steam reforming furnace 5 is provided with a reforming zone 51, where the crude fuel gas is produced by the steam reforming reaction of the thermal decomposition gas, a thermal decomposition introducing port 55, a gaseous mixture introducing port 54 for introducing a gaseous mixture of steam with air to the reforming zone, a reformed gas discharge passage 70 and a gas permeable heat barrier wall 60 arranged between the reforming zone and the reformed gas discharge passage. The heat barrier wall 60 is composed of a layered body of many spherical heat resistant materials 62 forming many narrow gaps, through which the thermal decomposition gas and the gaseous mixture are passed.