A STUDY ON THE INFLUENCE OF FINER LIMESTONE ON THE CHARACTERISTICS OF DESULFATION AND ASH AT LARGE SCALE CIRCULATING FLUIDIZED BED COMBUSTOR

摘要

CFBC (Circulating fluidized bed combustor) assures relatively high combustion efficiency due to the high mixing rate and long retention time of the solids. Furthermore it can remove Sox by means of direct supply of limestone to the combustor without additional desulfation facility and reduce Nox emission since combustion temperature is relatively very low (900°C). The additional advantage of CFBC is that it can be applied to the wide range of particle size of coal and it has the smaller area for heat transfer. In this study, characteristics of desulfation and combustion to reuse finer limestone usually abandoned. According to the results, Ca/S molar ratio with coarse limestone (0.1mm under 25%) was 2.97 and Ca/S molar ratio with finer limestone (0.1mm under 50%) was 3.07. It showed a slight decrease of desulfation efficiency with 3.4% comparing to the large increase of finer limestone about 2 times. With variation of operation parameters, Ca/S molar ratio increased from 3.17 to 3.25, when the combustor temperature rose from 875°C to 880°C. Ca/S molar ratio was 2.7 at 150MW, 2.9 at 180MW and 3.3 at 200MW. It showed that if the output increased, Ca/S molar ratio also increased. When we examined the combustion characteristics with finer limestone, the effect was very slight.