In the prior art (supra) gas was produced from coal by first passing a bed of coal through a furnace on a moving grate and then letting it move downwardly through a shaft furnace and thence into a fixed bed gasifier. The coal on the moving grate was air starved, most of the volatiles were driven off and a minimum of fixed carbon was burned. The off gases were downdrafted through the coal in the shaft furnace, air and steam were fed to the coal in the fixed bed gasifier and the off gases from the shaft furnace in the fixed bed gasifier were drawn off for utilization in a boiler. While the prior art processes offered many advantages, the capital costs were high. The object now is to produce comparable reactions, the same efficient utilization of the coal and equal amounts and quality of the gaseous end products, but with far less capital costs. By this invention, the shaft furnace and the fixed bed gasifier are eliminated and the process is carried out in a single furnace chamber. The coal is continuously transported on two moving grates, a first one higher than the second such that the coal from the first grate discharges onto the second. The grate speeds are so regulated that the bed transported on the first or higher grate is relatively thin while the bed on the lower grate is relatively thick. The reactions are detailed in the following summary of the invention and in the apparatus shown in the drawing, in which the sole FIGURE is a diagramatic cross section through the furnace in which the process is carried out.