Developing laser diffraction as an approach to categorize the dispersion propensity of combustible dust

Abstract

The dispersion of combustible dust into airborne clouds constitutes one of the five prerequisites for dust explosions. The process is predominantly governed by initial conditions, with specific material characteristics exerting measurable influences. For example, dust with good dispersibility has a higher tendency to form clouds and stay airborne. Dust prone to breakage is more likely to be distributed in smaller sizes. This study develops an experimental approach employing sequential particle size analysis through a dry dispersion laser diffractometer. Nine industrially relevant dust samples (i.e., ascorbic acid, corn starch, lycopodium, niacin, potato starch, skimmed milk, sulfur, wheat flour, and wood) were characterized under controlled dispersion pressures from 0.1 to 3.4 bar. The results show the degree of dispersion or comminution can be distinguished by monitoring the change in size distribution. In general, the fine fraction in the distribution increases at first upon increasing the dispersing energy due to improved dispersion. At higher energies, the amount of fines rises again if the particles start to break up. Sample-specific response patterns emerge in the pressure titration curves: smooth plateaus indicate optimal dispersion for easily dispersible and robust dusts, versus continuous size reduction trajectories revealing poor dispersion and fragile dusts. This qualitative categorizing method enables simultaneous evaluation of both dispersion efficiency and particle integrity, supplementing the pathway for assessing dust explosion hazards across laboratory and industrial scenarios.