CHARACTERIZATION OF SOLID-WASTES FROM CIRCULATING FLUIDIZED-BED COMBUSTION

The characterization of solid wastes from full-scale circulating fluid ized bed combustors (CFBC) is necessary to ensure that disposal proced ures or utilization strategies for the waste solids are successful. Pi lot plants are extremely useful in providing hydrodynamic heat and mas s transfer data that can be used to design and predict the performance of larger units. Combustion studies indicate that data from pilot-sca le units can be used to approximate the behavior of a full-scale plant for different fuels and operating conditions, even when the pilot pla nt is not designed to properly scale the commercial unit However, the same does not seem to be true for the determination of reduced sulphur , the other is species and geotechnical or physical properties of the solid wastes generated from pilot plants. The results of analyses of s amples generated from two units are discussed. One is a 150 by 150 mm square, 7.3 m high pilot-scale CFBC located at the University of Briti sh Columbia and 22 MWe CFBC located at Chatham, New Brunswick wick. Th is unit is operated by the New Brunswick Electric Power Commission (NB EPC). Both used the same New Brunswick coal containing 7 percent sulph ur. The data presented indicate that the pilot-scale unit can signific antly overpredict the formation of sulphides, and compared with the fu ll-scale unit, produces residues with much less promise for either dis posal or utilization in low-strength concretes. The results strongly s uggest that further work is necessary to understand better the phenome na that produce sulphides and affect the geotechnical properties of wa stes.