Overpressure characteristics of aluminium dust explosion vented through a relief pipe

A parametric experimental study of an aluminium dust explosion, initiated in a vessel and vented through a relief pipe, was performed. The aim is to clarify the overpressure characteristics in a vessel and relief pipe, during aluminium dust explosion venting, especially when a burn-up phenomenon occurs. For a vessel of fixed size, the influence of pipe diameter and pipe length on burn-up was discussed. Results demonstrate that burn-up occurs shortly after flame only enters the initial part of the relief pipe when the original dust concentration in the vessel is at relatively high level, which is usually higher than the optimum concentration obtained from the confined vessel. When burn-up occurs, the maximal overpressure continues to increase rather than to decay along the initial part of the relief pipe. If burn-up is vigorous, a second peak on overpressure-time curve in the vessel could appear. By adding 0.1 g aluminium powders on the membrane, the second overpressure peak may even surpass the first peak. Extending pipe lengths can strengthen the overpressures around the position where burn-up occurs in the relief pipe. Reducing the pipe diameter can increase the burn-up severity in the relief pipe owing to the increased dust concentration and the pressure accumulation.

► Burn-up occurs only at relatively high dust concentrations in the vessel, usually higher than the optimum concentration.
► The occurrence of the burn-up is not deterministic, but probabilistic.
► By adding aluminium dust on the membrane, the severity of dust explosion is greatly enhanced due to burn-up.
► The pipe length and pipe diameter have a significant effect on the burn-up phenomenon.