Filtration of Airborne Particulates By Gravel Filters: II. Collection Efficiency And Pressure Drop In Filtering Fume

Abstract

The collection efficiency of gravel layers to remove ammonium chloride fume from dry air streams is initially low, but increases sharply with increasing particulate load W on the gravel. The pressure drop ΔP across the gravel layer is low and changes little with particulate load until it reaches a threshold load W/_P , whereupon AP increases abruptly with erratic fluctuations. The effects of gravel size, layer thickness, and air flow velocity upon Δ vs. W, AP vs. W, W_P, and the cumulative collection efficiency from zero load to W_P are presented. The application of these data for air filtration is also discussed.