Explosion Characteristics and Flame Propagation Behavior of Mixed Dust Cloud of Coal Dust and Oil Shale Dust

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.

Ignition of Slurry Fuel Droplets with Different Heating Conditions

“…However, in terms of fire safety, this approach has a great advantage. Unregulated fuel combustion (most common for pulverized coal or other dry fine fuel [33]) at thermal power plants or boiler houses may occur due to the contact with heated surfaces (for example, parts of mechanisms). Based on the results of the assessments (Figure 10), it can be concluded that the ignition is most difficult with the conductive heat supply to a fuel.…”

“…The results of the experiments are a fundamental experimental basis for assessing the adequacy of ignition and combustion models for promising slurry fuels (for example, [33]), developed to study the characteristics and conditions for initiating these processes with prepotency of different mechanisms of energy supplying to the fuel, in particular, convective, conductive, radiation or mixed. Therefore, the established numerical values of the ignition delay times, extreme ignition initiation temperatures and maximum combustion temperatures can be used to analyze the completeness of the processes, effects and factors in modern models of ignition and combustion of promising slurry fuels.…”

Research on deflagration characteristics and thermodynamic mechanism of micron aluminum powders

“…The experiment uses an ignition powder head with a total mass of 0.48 g (the ignition powder is mixed with zirconium powder, barium peroxide, and barium nitrate in a ratio of 4:3:3), the total energy is 2 KJ, which can prevent the use of too high ignition energy from causing overdrive. [29][30][31] Then, use a high-pressure gas cylinder to pressurize the gas storage tank with a volume of 0.6 L to 2 MPa, and use a vacuum pump to vacuum the explosion tank to À0.06 MPa to ensure that the explosion tank is at normal pressure when the powder is ignited. Finally, the solenoid valve is opened by the automatic control system, and the powder is dispersed into the 20 L spherical explosive device through the hemispherical diffuser through the high-pressure gas, forming a uniform dust cloud.…”

Experiment on influence of inert powder on deflagration of oil shale dust research

“…It is found that compared with coal dust, oil shale dust is more easily ignited, with faster explosion flame propagation velocity (V f ) and higher maximum explosion pressure rise rate ((dP/dt) max ), and its explosion mechanism is also different. 10,13,14 This article studies the effects of KH 2 PO 4 , NaHCO The mine is located in the oil shale mining area of the Huangxian Basin in the northern part of the Shandong Peninsula. The main depositional environment of the oil shale is lacustrine swamp facies.…”

“…In recent years, the relevant researches mainly focus on the explosive characteristics of oil shale dust itself, but there are few researches on the inhibition effect and mechanism of the inert powder on the deflagration of oil shale dust. It is found that compared with coal dust, oil shale dust is more easily ignited, with faster explosion flame propagation velocity ( V f ) and higher maximum explosion pressure rise rate ((d P /d t ) max ), and its explosion mechanism is also different 10,13,14 . This article studies the effects of KH 2 PO 4 , NaHCO 3 , CaCO 3 , Al(OH) 3 on oil shale dust deflagration, compares the suppression effects of different inert powders on the flame propagation characteristics of oil shale dust, and the in‐depth analysis of the suppression mechanism of Al(OH) 3 powder provides a reference for the application of oil shale dust suppression.…”