Abstract: Coal is continuously converted into a saturated hydrocarbon gas containing substantially no unsaturated hydrocarbon and having a high calorific value and a uniform composition by the operations of: providing a first treating gas having a predetermined temperature, pressure and composition, by mixing, in a first conditioning chamber, a first substantially inert burnt gas which has been prepared by burning a mixture of a fuel and air, containing therein 2% by volume or less of free oxygen, with steam and, if necessary, hydrogen gas; thermally cracking, in a first treating chamber, the coal particles with the first treating gas while fluidizing said coal particles; separately providing a second treating gas having a predetermined temperature, pressure and composition by mixing, in a second conditioning chamber, a second substantially inert burnt gas which has been prepared by burning a fuel, and contains therein 2% by volume or less of free hydrogen gas, with hydrogen gas and, if necessary, an additional gas; hy

Abstract: A nitrogenous ingredient is eliminated from solid fuel, for example, coal, by treating in a treating chamber, the coal with a treating gas having a predetermined temperature and composition at a temperature of 650.degree. to 1200.degree.C, the treating gas being prepared by uniformly mixing, in a conditioning chamber located upstream from the treating chamber, a predetermined amount of steam or water and hydrogen gas or a mixture gas containing at least 30% by volume of hydrogen gas together with an inert burnt gas containing at most 2% by volume of oxygen gas.