Effect of fluid viscosity on liquid-solid fluidization

Four kinds of solid particles were fluidized and tested in aqueous solutions of glycerol ranging in viscosity from 7 to 1400 cP. Two trends in which the fluidization behavior of particles is significantly affected by fluid viscosity were observed, and a physical model was proposed based on these phenomena. On the one hand, increasing the fluid viscosity could decrease the bubble size, which results in smoother fluidization. On the other hand, because of the effect of the laminar layer, particle agglomeration could occur when the fluid viscosity is high enough, which results in heterogeneous behavior in the fluidized bed. At the critical point, these two trends balance each other, and the best fluid quality is observed. For all particles in this work, although the values of optimal viscosity are different, the values of the particle terminal Reynolds number are about 0.004 at the critical point.