1789.  KALBACH, J. C. (Hydrocarbon Research, Inc.). Coal Carbonization and Gasification. United States Patent 2,634,198, Apr. 7, 1953. Chem. Abs., vol. 47, 1953, p. 6122.

Coal gas and water gas are produced from coal in a fluidized-bed process in a single vessel. The ground coal is partly carbonized during conveyance by recycle gas in a pipe passing through the fluidized bed to a funnel-shaped chamber within the reactor. The resulting coal gas is thus isolated from the water gas. The partly carbonized material is fed into the main bed at a temperature of 1,300º-1,800º F., where water gas is produced by fluidization with steam and O₂.