THE CONTRIBUTIONS OF ATTRITION AND FRAGMENTATION TO CHAR ELUTRIATION FROM FLUIDIZED-BEDS

The elutriation rates of unburned carbon from a 20-cm-i.d. bubbling fluidized bed were evaluated for a variety of coals. Elutriation rates were determined from cyclone catches while carbon loadings in the fluidized bed were evaluated from transient gas and particle emissions. The elutriation rates were well correlated with carbon loading in the bed, but there was no evidence that they depend on superficial velocity through the bed. These results suggest that fragmentation, rather than attrition, is primarily responsible for carbon loss during fluidized bed combustion. The experiments found evidence that the fragmentation rates were dependent on coal rank.