Dust Generation from Handling Powders in Industry

This article explores the hypothesis that the amount of dust generated by an industrial process that handles granular material depends on (a) the size distribution of the granules and (b) the ratio of impaction to cohesion. Here, impaction characterizes particle separation forces caused by energy input from the process, and cohesion characterizes interparticle binding forces within the material itself. A mathematical model based on this hypothesis is presented and evaluated using 441 data sets from an industrial-scale apparatus designed to measure dust generation. Dust generation was characterized in experiments using titanium dioxide, limestone, glass beads, and lactose with moisture contents ranging from 0% to 6% and size distributions of d<5 µm, 5 25 µm in aerodynamic diameter, dropped from heights of 0.25, 0.7, and 1.25 m at material flows of 0.1, 0.3, and 0.6 kg/sec. Results are presented in equations for impaction, cohesion, and dust generation as a function of particle size. The equation for dust generation was validated by comparing its predictions with 147 additional data sets. Cohesion due to material properties affected dust generation more than impaction due to the material handling process: the size distribution of the granular material was not as important as either cohesion or impaction. Results suggest that the equations presented can be used with reasonable confidence to predict dust generation, especially for the materials and process investigated in this study.