Study On Minimum Ignition Temperature And Inhibition Technologies Of Coal Dust Cloud

Coal will produce large amount of coal dust during the manufacturing, processing, transporting and storing. Coal dust disperses and suspends in the air forming flammable explosive coal dust cloud, which may cause combustion and explosion accidents in the existence of ignition source. Inert dust inhibition technologies are the key to prevent the occurrence of coal dust combustion and explosion accidents, and ensure the safety production of coal dust. Therefore, it’s significant to study the combustion and explosion characteristics of coal dust and explore the inhibition mechanism and rules of inert dust on coal dust combustion and explosion.The research and development status of dust inhibition technologies both at home and abroad and the suppression mechanism of inert dust were discussed in the paper. The effect of diffusing pressure, concentration, particle size and environmental factors on the minimum ignition temperature(MIT) of coal dust cloud was studied qualitatively and quantitatively by use of a standard Godbert-Greenwald furnace apparatus. The inhibition mechanism and rules of inert dust ammonium dihydrogen phosphate(NH3H2PO4), calcium dihydrogen phosphate(Ca(H2PO4)2), potassium dihydrogen phosphate(KH2PO4), sodium bicarbonate(Na HCO3), potassium bicarbonate(KHCO3), calcium carbonate(CaCO3), aluminum hydroxide(Al(OH)3), silica(SiO2), sodium chloride(NaCl) and potassium chloride(KCl) on the MIT of coal dust cloud were explored. The results show that:(1) The MIT of coal dust cloud decreases at first and then increases with the increasing of diffusing pressure, and there is the best diffusing pressure, at this diffusing pressure, the MIT of coal dust cloud is minimum. The best diffusing pressure of high coal dust concentration cloud is higher than that of the low coal dust concentration cloud, and the best diffusing pressure is 0.02, 0.03, 0.03, 0.035 MPa respectively, when the coal dust concentration is 0.454, 1.364, 2.273, 4.540 kg/m3; The MIT of coal dust cloud decreases with the increasing of environmental temperature, and increases with the increasing of environmental humidity.(2) The MIT of coal dust cloud decreases at first and then increases slowly with the increasing of the coal dust concentration, and there is the most sensitive concentration, at this concentration, the MIT of coal dust cloud is minimum; The most sensitive concentration of coal dust cloud increases with the increasing of diffusing pressure, and the most sensitive concentration of coal dust cloud is 1.364, 2.273, 2.273 kg/m3 respectively, when the diffusing pressure is 0.02, 0.03, 0.03, 0.035 MPa; The MIT of coal dust cloud increases with the increasing of the coal dust particle size.(3) The MIT of coal dust cloud increases with the increasing of inert dust content,and there is mutation concentration, at this concentration, the inhibitory effect of inert dust on the MIT of coal dust cloud is significantly improved; The MIT of coal dust cloud decreases with the increasing of inert dust particle size, and the influence of inhibitory effect for CaCO3 by the change of particle size is stronger than NH4H2PO4.(4) The inhibitory effect of inert dust of physical inhibition mechanism on the MIT of coal dust cloud successively is CaCO3 > Al(OH)3 > SiO2, and the mutation concentration of CaCO3, Al(OH)3 and SiO2 is 40%;the inhibitory effect of CaCO3 is maximum, and the complete inhibition concentration of CaCO3 is 66.7%. The inhibitory effect of inert dust NaCl of chemical inhibition mechanism is stronger than KCl, and the mutation concentration of NaCl is 40%. The inhibitory effect of inert dust of physical and chemical inhibition mechanism on the MIT of coal dust cloud successively is NH4H2PO4 > Ca(H2PO4)2 > KH2PO4 > NaHCO3 > KHCO3. The inhibitory effect of dihydric phosphate is stronger than bicarbonate, and the inhibitory effect of NaHCO3 is stronger than KHCO3.(5) The inhibitory effect of NH4H2PO4 is maximum, and that of CaCO3, Ca(H2PO4)2 and KH2PO4 is excellent, but that of SiO2, KCl and KHCO3 is weak. The inhibitory effect of mixed dust of NH4H2PO4 and CaCO3 is between that of NH4H2PO4 and CaCO3, furthermore, The inhibitory effect of mixed inert dust increases with the increasing of the content of NH4H2PO4.