Some hydrodynamic characteristics of inverse three phase fluidized-bed reactors

Some hydrodynamic characteristics of inverse three-phase fluidized beds were investigated. Using two types of particles having different characteristics (d(s) = 4 mm, rho(s) = 920 kg m(-3), and d(s) = 0.175 mm and rho(s) = 690 kg m(-3), respectively) allowed us to observe two different expansion mechanisms: a pseudo-fluidized state promoted by the density difference between the solid and the surrounding gas-liquid mixture, and a fluidized state due to the liquid circulation induced by the rise of the bubbles. Both contributed to the solid mixing and axial solid distribution in the system. Systematic holdup measurements were done on two reactor diameter and two types of gas sparger. A correlation for the liquid holdup and bed porosity could be proposed by means of a modified gas drift flux definition. The latest was a function of gas velocity only and gave a good accuracy among the range of solid amount, gas and liquid velocity used. (C) 1999 Elsevier Science Ltd. All rights reserved.