Exergy analysis of circulating fluidized bed boiler

Abstract

According to the exergy efficiency analysis of circulating fluidized bed (CFB) boiler, various exergy loss rates are discussed in this paper. Combustion exergy loss and heat transfer exergy loss are the major losses of CFB boiler, accounting for more than 45% of the fuel chemical exergy by CFB boiler exergy analysis method. For 300MW and its below assembling unit, the exergy efficiency of CFB boiler is generally less than 50%. The boiler exhaust exergy loss rate is about 1%, which is much less than heat loss rate calculated by heat balance method, but there is still a great potentiality to be reduced. As far as CFB boiler is concerned, chemical incomplete combustion exergy loss rate and radiating exergy loss rate are both too small to be negligible. Unburned carbon exergy loss should be focused on due to its high energy quality. CFB boiler slag has a higher proportion of coal ash. Therefore, it is important to reduce the slag physical exergy loss for improving CFB boiler efficiency.