Abstract
Coal and oil shale are often mined and utilized together, and mixed dust is easily formed in these processes. In order to ensure safe production in these processes, the explosion characteristics of mixed dust were studied. Using a Godbert-Greenwold (G-G) Furnace experimental device, Hartmann tube experimental device, and 20 L explosion vessel, the oil shale and coal mixed dust ignition sensitivity experiment, flame propagation experiment, and explosion characteristics experiment were carried out. The minimum ignition temperature (MIT), minimum ignition energy (MIE), maximum explosion pressure (Pmax), maximum rate of pressure rise ((dp/dt)max), and explosibility index (KSt) parameters and the flame propagation behavior of the mixed dust were analyzed in detail. A scanning electron microscope (SEM) analysis of the coal and oil shale dust before and after the explosion was carried out to study the changes in the microscopic morphology of the dust particles. The results show that due to the oil shale having a high volatile content and low moisture content, in the mixture, the greater the percentage of oil shale, the more likely the dust cloud is to be ignited and the faster the explosion flame is propagated; the greater the percentage of oil shale, the greater the (dP/dt)max and KSt will be and, under a high dust concentration, a greater Pmax will be produced. During explosion, coal dust will experience particle pyrolysis and the gas phase combustion of the volatile matter, followed by solid phase combustion of coal char, whereas oil shale dust will only experience particle pyrolysis and the gas phase combustion of the volatile matter.
Highlights
The minimum ignition temperature (MIT) of the oil shale–coal dust mixtures was tested in a G-G furnace, using the MIT test procedure for combustible dust cloud recommended by GB/T 16429-1996 and ASTM E1491-2006
Coal and oil shale dust are ignited because when they are exposed to an external high temperature or energy, their volatile matter will be thermally pyrolyzed
Thermogravimetric analysis revealed that the raw oil shale dust and coal dust samples did not vary significantly in volatile pyrolysis temperature
Summary
Coal and oil shale are often fired together to generate power and, to improve oil recovery, they are co-pyrolyzed to produce oil [2,3] Both coal and oil shale dust have a large risk of explosion. Minimum ignition temperature (MIT), minimum ignition energy (MIE), flame propagation velocity (V F ), maximum explosion pressure (Pmax ), maximum rate of pressure rise ((dP/dt)max ), and explosibility index (KSt ), as essential measuring indicators providing a powerful basis for preventing and controlling dust explosion [6,7], have contributed greatly to research on coal dust explosion risk. We tested the ignition sensitivity parameters—MIT and MIE—and flame propagation and explosibility parameters—Pmax , (dP/dt)max , and KSt —of paragenetic coal and oil shale samples. Our research results can provide useful support for preventing the explosion of coal–oil shale mixed dust
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