Modeling the pneumatic transport of solids with a bimodal particle size distribution

Abstract

Particle size distribution (PSD) plays a key role in fluidization behavior. The effect of PSD in fluidized, gas-solid mixtures is elucidated by considering two types of bimodal particle mixtures. In the first case, a mixture of "large" particles, which engage in particle-particle collisions, and "small" particles or fines, which follow the fluid streamlines, are considered. In this case, one net effect of the fines is to decrease the pressure drop required to convey a given solids flux in a riser. In the second case, a mixture of two sizes of larger particles in which collisions between like and unlike particles occur are considered. In this case, a reduction in particle phase stress in the bimodal mixture as compared to a monosized particle mixture with the same mean particle diameter is predicted. For dilute flow, this stress reduction is minimal but increases in significance as the suspension becomes more concentrated.