A Review of Metal Dusts Deflagration Hazards

Dust explosions have been a hazard for as long as man has been processing, storing and transporting bulk materials and powders.

Most of the reported incidents have involved organic products in the past, mainly because most of the combustible materials in commerce are organic. Nevertheless, this trend is changing due to the increase use of metals, especially in the automotive, electronics and emerging 3D-printing industries.

Metal dusts are a particular class of combustible dusts. The term “metal dusts” encompasses a large family of materials with diverse ignitability and explosibility properties. In particular fine particles of aluminum, can be extremely sensitive to ignition sources, exploding as very severe deflagrations, and making difficult the prevention and mitigation of such deflagrations.

The present paper reviews the unique deflagration characteristics of metal dusts. This involves both the modes of combustion of metal particles and the large scale deflagration characteristics. The limitations of the common scaling procedure using the Kst factor are clearly demonstrated by reviewing results from small and large scale tests. The role of important physical characteristics and external factors determining the severity of dust explosions is highlighted. In particular the high flame temperature of light metals makes the mechanism of radiative heat transfer a key parameter, which must sufficiently be taken into account in the formulation of scaling laws.