A process for producing lean gases in which solid fuels are gasified under superatmospheric pressure by a treatment with free oxygen-containing gases, water vapor, and other gasifying agents. In the process, fuel and gasifying agent are caused to flow in opposite directions, about 1.5 to 3.5 kg of water vapor are added per standard m.sup.3 of free oxygen in the gasifying agent, about 70% of the lump coal to be gasified has a particle size from above 2 mm to about 30 mm and the remaining coal has a particle size below about 2 mm. The ballast content, consisting of water and ash, amounts to at least about 15% by weight, most of the mineral constituents have a particle size of about 2 to 30 mm and the ash which becomes available in the gasification process is withdrawn from the reactor shaft at temperatures above about 250.degree. C. Raw gas is withdrawn at temperatures above about 350.degree. C, coal is reacted in a water-cooled, double-walled reactor chamber and the resulting jacket steam is used to cool the grate and as a reactant. The rate at which steam consisting of extraneous steam and jacket steam is added to the gasifying agent is so adjusted in the above-mentioned range of about 1.5 to 3.5 kg per standard m.sup.3 of oxygen, that the nitrogen content of the dry raw product gas does not exceed about 50% by volume.