PREDICTING COMBUSTION EFFICIENCY OF FLUIDIZED-BED COMBUSTION WITH FINES RECYCLING

Fluidized bed combustion shows potential for burning high sulfur coal and other low-grade fuels efficiently and cleanly. In order to predict the effect of recycling fines on combustion efficiency in the current fluidized bed combustor at the Ohio Agricultural Research and Development Center (OARDC), mathematical equations were developed to transform results of batch recycling data into continuous recycling. The equations developed allow design of a recycle system to achieve a specific combustion efficiency which may be required. Experimental tests in which fines were reintroduced into the burner with new fuel under a batch recycling operation were used to determine system parameters. Experimental combustion efficiency was about 89% with no recycling at 20% of excess air. Combustion efficiency for the OARDC burner with a recycle facility was predicted to be 98% for a recycle ratio of 0.85, using the theoretical model and experimental results.