Apparatus and system for producing coal gas from coal, air and water. Pulverized coal is introduced into a rising stream of air and steam in a retort to constitute a fluidized or entrained bed. The coal reacts with the steam and air to form a gas consisting of hydrogen, carbon monoxide, carbon dioxide, nitrogen, methane and higher hydrocarbons. In some cases the air may be eliminated to produce nitrogen-free gas. In other instances, the production of methane and higher hydrocarbons may be suppressed to produce a gas consisting primarily of hydrogen and carbon monoxide. The retort is constructed so that product gas and air may be burned in an annular space surrounding the central reaction column to produce hot flue gas. Steam tubes may be disposed in the annular space so that the steam and air introduced to the central reaction chamber may be super-heated by the hot flue gas. A further annular space or "wet wall" may be provided surrounding the first annular space through which the intake water is passed, so that the intake water may be brought to a boiling point and converted to steam prior to its being introduced into the steam superheating tubes. This construction causes the walls to the retort to be maintained at a higher temperature than the reaction inside the column, so that all the heat radiated from the walls of the reaction column is directed inwardly, and no heat is lost through the walls. The product gas from the retort is then cooled and passed through a water spray which cools the gas to nearly room temperature, and removes all the fly ash and other particulate matter from the gas.