Study On The Explosion Characteristics And Suppression Of Coal Dust In The Limited Space

Coal dust explosion is one of the main disasters during coal mine safety production activities in China, coal dust explosion or explosion including coal dust will cause immeasurable loss. At present, studies on coal dust explosion characteristics and its influencing factors under different initial and environmental conditions has been quite comprehensive. However, studies on the relationship between microstructure of coal dust and severity of explosion still exist omissions. Therefore, further study on coal dust explosion process and reaction mechanism is of great importance for prevention, control and reduction of coal dust explosion.Based on the standard 20 L spherical vessels for explosion test, large amounts of coal dust explosion and suppression experiments have been carried out. Combined with various modern test and analysis methods, characteristics of coal dust explosion, analysis of explosion products and suppression of coal dust explosion are studied in this thesis. The innovations of this paper are as follows.Conducting studies on characteristics of coal dust explosion with different particle size disparity and revealing the effect of particle size disparity on coal dust explosion. It turns out that the maximum explosion pressure decreases by 0.08 MPa, the maximum rate of explosion pressure decreases by 10.64MPa/s when particle size disparity increases from 1.84 to 3.60. In other words, for the selected coal dust, severity of explosion decreases as particle size disparity increases.Defining a new measure of coal dust explosion- detonation time and revealing the difference between characteristics of coal dust explosion with various particle size and particle size disparity. Research results show that τ1 and τ2 decrease significantly as coal dust particle size decreases under the same concentration. For the coal dust with nearly particle size and different particle size disparity, τ1 and τ2 decrease significantly as coal dust particle size disparity decreases under low coal dust concentration(Cdust≤250g/m3). The decreasing trend gradually slow with the increasing of coal dust concentration.Combined with gas chromatography, infrared spectrum and scanning electron microscope and other modern test and analysis methods, the gas and solid products after explosion of coal dust at different rank are analyzed systematically. Based on the quantitative analysis of holes on the surface of solid products, it turns out that number of holes on the surface of the coal dust explosion products decreases constantly and pore area increases remarkably(holes of coal samples from Neimeng, Ningxia and Huaibei are 12690, 3904, 2718 while pore area are 80500, 106351, 132099 pixels respectively) as coal metamorphism reduces. It proofs that holes on the surface of high volatile coal dust products are less while pore area is large, which reflects its higher reactivity.Suppression experiments of coal dust had been carried out and the effects of three different kinds of suppressant on coal dust explosions had been analyzed systemically. It can be noticed that the residual oxygen content increases rapidly with increasing of mass percent of NH4H2PO4 when the content of surface functional groups changes significantly before and after addition of suppressant powder. Especially, when the mass percentage is more than 50%, NH4H2PO4 is more suitable for suppression of coal dust explosion.