Abstract: A recirculating fluidized bed furnace (FIG. 3) having a combustion chamber 4 operating at a fluidization velocity of 10 meters per second delivering combustion products to a separating section 10 with the combustion gases flowing over boiler banks 30-36 in a pass 30 and the solids particles falling to a weir chamber 14. Heat is extracted from the particles in a compartmented heat transfer bed space 20 operating at a fluidization velocity of 0.5 meters per second receiving the particles from the weir chamber 14 and discharging them to the base of the combustion chamber 4.The furnace is combined with a coal devolatilizer 60 discharging combustible gases through a burner 68 to a gas turbine 70 and char to the furnace combustion chamber 4. A compressor 72 coupled to the gas turbine 70 delivers air to an air heater 74 in the heat transfer bed space 20, which heated air is supplied to the devolatilizer 60 and the burner 68.