Explosibility hazard of iron sulphide dusts as a function of particle size

The explosion characteristics of pyrite and pyrrhotite have been determined as a function of particle size. Explosion tests were conducted in a 201 Siwek chamber using various size fractions of mine samples. It was determined that the critical mass mean diameter for explosibility (i.e. maximum explosible diameter) lies in the range 49-63 mu m for the pyrrhotite sample and 85-145 mu m for pyrite. A decrease in particle size for each material was found to cause an increase in explosion pressure and rate of pressure rise, and a decrease in the minimum explosible concentration. That pyrite is more of an explosion hazard than pyrrhotite was confirmed and quantified. Testing with FeS and FeS2 chemicals demonstrated the limited applicability of commercial samples to prediction of explosibility behaviour of mine samples. Previous work on coal and metal dusts was analysed to suggest the importance of both homogeneous and heterogeneous reactions in explosion propagation for sulphide dusts.