Residence time distribution of sorbent particles in a circulating fluidised bed boiler

Abstract

The residence time distribution of limestone sorbent particles has been studied in order to increase the understanding of the conditions for sulphur capture in fluidised bed boilers. Two methods were used. The ‘steady state method’ involves the study of residence time for various particle size fractions. The ‘transient method’ is based on the transient increase in the amount of sorbent carryover with the fly ash, following initial limestone addition to a fresh bed ( i.e. a bed with little or no sorbent). For the boiler investigated both methods gave similar results, showing that the major fraction of the sorbent, 80–85%, had a residence time of one hour or more.