A comprehensive pressure balance model of circulating fluidized beds

Based on the concepts of clustering suspension and core-annulus flow in the riser, a pressure balance model for the entire loop of a circulating fluidized bed system was developed, where the gas now between the riser and the downcomer was first taken into account. For the present model, the following correlation for the decay factor of the voidage profile was developed within +/-30% accuracy: aD(R) = 0.019(G(s)/U-0 rho(g))(-0.22) (U-0/root gD(R))(-0.32) (rho(p) - rho(g)/rho(g))(0.41) The model was successfully validated by a comparison of the predicted pressure loop distribution, the maximum solid flux and the dense region height with the previous experimental results. By taking into account gas flow through the loop seal between the riser and the downcomer, it became possible to predict quantitatively and rigorously the effect of solid inventory on the axial voidage profiles in the riser reported by Weinstein et al. (1984) and Mori et al. (1989). It was also found that there is an operable extension of solid inventory for a given set of superficial gas velocity and solid circulating flux.