The Institute of Gas Technology's (IGT) two-stage fluidized-bed/cyclonic combustor promises increased combustion efficiency, greatly reduced formation of NO{sub x}, significantly lower CO, THC, SO{sub x}, and HCl emissions, lower particulate emission, and production of environmentally benign residue (ash, spent sorbent). The first stage of the combustor is a turbulent fluidized bed, which operates under substoichiometric conditions so that the fuel-bound nitrogen is prevented from producing NO{sub x}. Sorbent is injected to promote the capture of sulfur and/or chlorine in solid form. The cyclonic combustor constitutes the second stage of the two-stage combustor. High-intensity, high-efficiency combustion of the reducing gases from the first stage takes place in this cyclonic combustor under conditions that minimize the formation of NO{sub x} while providing low CO and THC emissions. 10 refs., 7 figs., 3 tabs.