Heat transfer between FCC catalyst and an electrically heated horizontal cylinder in a circulating fluidized bed

The heat transfer coefficient between a suspension of FCC particles and a h orizontal cylindrical heat transfer probe inserted into the riser or the st andpipe of a CFB has been quantified. With the heat transfer probe located in the riser 4.75 meters above the L-valve, and solids mass flux varied bet ween 0 to 100 kg/(m(2).s), the heat transfer coefficient ranged from 70 W/( m(2).K) to 475 W/(m(2).K). On a plot of heat transfer coefficient versus so lids mass flux, three zones have been identified, which correspond to the d ifference in the flow structure of the solids around the heat transfer prob e as the solids mass flux increases. Also, measurements were taken of the r adial solids flux in two orthogonal directions using an isokinetic sampling system. The data shows the asymmetry due to the perturbations introduced b y the heat transfer probe. Finally, the heat transfer in the downcomer was investigated. It has been found that the magnitude of the heat transfer coe fficient in the downcomer is dominated by the solids flux; variation in gas bypassing in the standpipe has little effect. Results obtained by traversi ng the heat transfer probe across the diameter of the standpipe suggest tha t the heat transfer coefficient is nearly independent of radial position wi thin the standpipe.