Investigation of the explosion severity of multiphase hybrid mixtures

This study presents an experimental investigation of the maximum explosion pressure (P-max) and rate of pressure rise (dP/dt)(max) of dusts (lycopodium and brown coal), solvents (ethanol, isopropanol), gases (methane and hydrogen) as well as two- and three-phase hybrid mixtures. Experiments were performed in a standard 20 L sphere with a 10-J electrical igniter as an ignition source and a 60 ms ignition delay time. It was consistently noticed that the explosion severity of a dust and gas/spray hybrid mixture was higher than that of dust, but lower than either gas or solvent. The addition of a flammable gas/spray to a dust-air mixture increases the maximum explosion pressure to some extent and significantly increases the maximum rate of the dust mixture pressure rise, even though the concentration of the flammable gas/vapor is below its lower explosion limit. For instance, lycopodium with maximum rate of pressure rise value of 272 bar/s increased to 322, 369, 410, and 504 bar/s when methane concentration of 1, 2, 3, and 4 vol% was respectively, added. These values of maximum rate of pressure rise further increased to 430, 460, 573, and 798 bar/s when a nonexplosible concentration of a third-phase isopropanol (50% lower than the lower explosion limit) was added. From the findings of this research, it could be inferred that one cannot rely on the explosion severity of a single substance to ensure the safety of a process or system when substances with different states of aggregate are present.