SUSPENSION-TO-WALL HEAT-TRANSFER IN A 12-MW(TH) CIRCULATING FLUIDIZED-BED COMBUSTOR

An experimental investigation was carried out to study the effects of operating parameters on the local suspension-to-wall heat transfer in the combustor of a 12-MW(th) circulating fluidized-bed (CFB) boiler. T he heat transfer coefficients were measured with a conduction-type hea t flux meter at five different vertical levels. The measurements cover ed a range of superficial gas velocities from 4 to 6 m/s, a bulk bed t emperature from 800 to 850 degrees C and a suspension density from 6 t o 70 kg/m(3) for 270-mu m silica sand particles. The heat transfer coe fficient for the membrane wall in the combustion chamber of the CFB bo iler was in the range of 100 to 180 W/m(2) K for the range of operatin g conditions employed in this work. The beat transfer coefficient decr eased with increasing height and increased with increasing bulk bed te mperature, superficial gas velocity and suspension density. Based on t he experimental data, a simple correlation is proposed for predicting the suspension-to-membrane wall heat transfer coefficient. The results were analysed and compared with the experimental data of other worker s.