MODELING A FURNACE SORBENT SLURRY INJECTION PROCESS

One possible approach to increasing the cost-effectiveness of furnace sorbent injection processes is to enhance SO2 removal by injecting the sorbent in a slurry form. Various steps involved in SO2 removal by furnace sorbent slurry injection include evaporation of slurry droplets, sorbent particle heat-up, activation of sorbent by calcination, reduction in active sorbent surface area by sintering, and sulfation of calcined sorbent. An existing model for sulfation and sintering of calcined sorbent, CaO, based upon a simple grain structure was adapted in a user-interactive computer program for simulation of the overall SO2 removal process. The slurry droplet evaporation, particle heat-up, and sorbent calcination steps were assumed to be instantaneous in the overall model compared to the sulfation step. The effect of sorbent slurry injection on furnace time/temperature profile and particle size reduction was taken into account. Available dry and slurry sorbent injection data collected at the Ontario Hydro Research Division's Combustion Research Facility were compared with model predictions with good agreement. Injection of sorbent in a slurry form was found to enhance SO2 capture in two ways: (1) It reduced sorbent sintering due to cooling of gases. (2) It reduced sorbent particle size during the slurrying process. Both of these factors improve sulfur capture. The model correctly predicted the observed effects of injection temperature and particle size on SO2 capture for a given sorbent.