UPPER EXPLOSIVE LIMIT OF DUSTS - EXPERIMENTAL-EVIDENCE FOR ITS EXISTENCE UNDER CERTAIN CIRCUMSTANCES

An experimental study of the explosibility of cornstarch using the 20-L vessel shows that, for a narrow size fraction near its limiting particle size for explosibility, an upper explosive limit exists. Upper explosive limits were also observed with both cornstarch and Pittsburgh Standard coal dust at low oxygen concentrations. These upper limits occur at accessible dust concentrations. A simple mechanism, ''the oxygen depletion'' phenomenological concept, is described. The optimum dust concentration, calculated using this mechanism, gives reasonable agreement with the experimental values, as well as explaining the variation of optimum concentration with particle size and oxygen concentration.