Thermal aspects of a circulating fluidized bed with air staging

In this study, effects of air staging on wall‐to‐bed heat transfer were investigated in a laboratory scale circulating fluidized bed (0.23 m ID, 7.6 m high). The bed was operated under ambient conditions with silica sand particles (d_p=89 µm, ρ_p=2650 kg m^?3). Two different designs of secondary air (SA) injectors were used for air staging: radial and tangential. Bed‐to‐wall heat transfer measurements were carried out at three elevations above the SA injection port. The results indicate that similar to non‐SA operation, the heat transfer with air staging depends strongly on the cross‐sectional average suspension density. Tangential secondary injection was found to increase the bed‐to‐wall heat transfer above the SA injection port significantly due to increased suspension density compared with non‐SA operation. Copyright © 2005 John Wiley & Sons, Ltd.