ENERGY RECOVERY FROM FLUIDIZED-BED COMBUSTION

Fluidized-bed processing was developed and commercialized during the late 1930s and early 40s on coal gasification and metallurgical applications in Germany, and for the catalytic cracking of heavy oils to produce high-octane gasoline in the U. S. A significant development is the increasing application of fluidized-bed combustion for the utilization of waste materials and low-grade fuels as alternative energy sources. Because of its unique ability to handle a wide variety of liquids and solids as fuels in an energy-efficient and environmentally acceptable manner, fluidized-bed combustion is ideally suited to many applications. A simple approach may be used to analyze the energy balance when considering alternatives. This paper shows how a thorough evaluation will require optimization of design parameters, taking into account feed moisture, volatiles content, method of feeding, ash fusion temperature, and special atmospheric emission considerations. Data on the Fluo-Solid combustion system are presented which demonstrate that the emissions of SO//x and NO//x are controlled at their source, by addition of a sorbent for sulfur capture, and by low combustion temperatures and in some cases staged combustion, to limit formation of nitrogen oxides.