Abstract: A dry distillation gas generator generates a dry distillation gas for burning in a separate combustion gas burner unit. Air is supplied in a gentle decelerated flow to the bottom of the dry distillation generator in a quantity sufficient to support combustion of a solid fuel in the vicinity of the air supply, but at a low enough volume to prevent the combustion proceeding to other parts of the generator, thus thermally decomposing the remainder of the solid fuel to generate the dry distillate gas. An air chamber surrounds the generator to reduce the temperature to which the solid fuel is exposed. Similarly, an air chamber is disposed below the bottom of the generator to supply air to the generator, and to moderate the temperature therein. An impurity separation tank in a conduit between the generator and the gas burner unit helps prevent particulates from entering the generator. A preheat burner in the combustion gas burner unit includes a pilot to ignite and preheat the gas.