Diffusional filtration of dust in a fluidized bed

Abstract

This work provides a mathematical model for calculating filtration efficiencies in a fluidized bed filter comprised of spherical particles. A numerical solution of the diffusion equation was obtained for one spherical filter element, by using the “unit cell model of Kuwabara” for the flow field. The diffusional capture factor for a single spherical filter element was obtained for Peclet numbers in the range 10 4–10 7, bed porosities, ϵ., from 0.4 to 0.999 and interception parameters from 0 to 1/20. The present theoretical results agree quite well with previous experiments for packed bed filters. The present calculations coupled with the inertial capture factors for spheres provide a plot of the deposition efficiencies on spherical filter elements situated in a fluidized bed filter. Total bed filtration efficiencies are computed from the single sphere deposition efficiencies. The high total filtration efficiencies predicted by the present work are in accordance with existing experimental evidence.