A generator including a double-chamber lock comprising two tapered or vertical chambers lined with ceramics or plastics, as a charging device, at least one tubular shaft furnace comprising a water-cooled double jacket of steel, a double-walled, water-cooled inlet nozzle of copper for a gasification mixture, arranged centrally in the tubular shaft furnace above the base, a dry dust-removing device, and optionally a desulfurising device. The double-chamber lock has a mechanism which causes one of the chambers to open when the lower chamber of the double-chamber lock is flushed with inert gas after charging/opening operations, and the inlet nozzle constitutes the mixing member for the constituents of the gasification mixture, the inlet nozzle has a radius of curvature of the surface of the cylindrical portion of the nozzle which continuously becomes smaller to the outlet opening, and the direction of flow of the gases leaving the inlet nozzle is directed upwards.