Abstract: In order to prevent coking of boiler (mainly high temperature coking), it is necessary to keep higher primary air flow. But the surplus capacity of primary air fan selected by design institute may be too larger to cause larger house service consumption rate. Simultaneously, the application of the high pressure fan can cause larger airheater leakage factor. The house service consumption rate of large CFB unit is commonly about 10%, and this is main factor restricting largescalization of CFB unit. The air and flue gas system of boiler was optimized, some necessary reformation measures were adopted. Then the house service consumption rate had been reduced by 1.62%, and good result was obtained.

Key words: circulating fluidized bed (CFB) boiler, technical parameters of fan, air preheater, optimization, house service consumption rate