Experimental examination of factors that affect dust generation.

A method is presented to examine factors that affect the amount and size distribution of dust generated by falling granular material in still air. This work was conducted by using an apparatus with separate dust generating and dust measuring sections. The dust generated by a falling material was carried into an elutriation column equipped with a slotted Sierra high-volume impactor at the top. This apparatus can measure dust generation rates for particles between 0.4 and 25 microns in aerodynamic diameter as well as the amount of air entrained by the falling material. Four granular materials were tested, and a simple model was developed to describe the dust generation rate of these materials as a function of particle size, drop height, material flow, and moisture content. Moisture content strongly influenced the interparticle binding forces and the amount of dust generated. Drop height and material flow influenced the material separation forces and also significantly influenced the amount of dust generated.