Abstract: A system for feeding a coal-water paste material coaxially upwardly through a feed nozzle assembly into a pressurized fluidized bed reactor having a lower portion and a larger diameter upper portion. The feed nozzle assembly includes a nozzle unit for atomizing the coal paste feed material, and a concentric outer shroud tube enclosing the nozzle unit. The feed nozzle assembly is inserted upwardly through an opening in the bottom portion of the pressurized fluidized bed reactor into a coaxial orientation with the bed, so as to provide substantially complete combustion and/or carbonization of the coal paste material fed into the reactor to produce a combustible gas product. If desired, a sorbent material nay be fed into the fluidized bed together with the coal paste feed, so as to absorb sulfur from the coal and produce a clean fuel gas. During reactor operations at 130-200 psig pressure and 1,600.degree.-1,800.degree. F.