| Gas explosion,a typical explosion of complex component combustible gases and air mixture,has been the focus of industrial production management.Moreover,it is theoretically significant and practically valuable to explore the explosion characteristics of CO/CH4 mixture system.As CH4 is the main component of combustible gas in mine fire area,CO is one of the most important indicators of coal oxidation and rock formation pyrolysis.,CO is mainly comes from the escape and oxidation of coal and all kinds of underground exhaust gas.Meanwhile,it can provide an important basis for the research and development of early prediction and secondary explosion prevention and comprehensive management technology of gas explosion disaster to.In this paper,the explosion limit and critical oxygen concentration of CO/CH4 system with the addition of inert gas(N2)were measured by using HY12474C combustible gas explosion limit measuring device.The visualized spherical closed explosive test device was employed to determine the maximum explosion pressure of CO/CH4 mixture system and its rising rate and duration time.The impact of CO on the macroscopic characteristics of CH4 explosion was analyzed.The ICCD was adopted to examine the emission spectra of·H,·OH and CH2O in the CO/CH4 explosive intermediates.Finally,the change of reaction energy and Gibbs free energy regarding the relevant elementary reaction were calculated by exploiting the Gaussian 09 software.Then,the reaction path was determined by the reaction intrinsic coordinate method.From the point of view of chemical reaction thermodynamics and the reaction kinetics,the microcosmic mechanism of CO on CH4 chain explosion was further studied.The following conclusions are obtained by theoretical analysis,experimental measurement and simulation calculation.(1)With the addition of CO from 0 to 2%,the upper explosion limit of CH4 explosion increased slightly,then decreased to a small extent,while the lower explosion limit of that kept falling down.The critical oxygen concentration of CH4 decreased by a small amount of CO from 11.70%to 10.67%.The converging point of the upper and lower explosion limits of CH4 also decreased,and the explosion triangle moved and shifted to the left.(2)The presence of a small amount of CO brought about linear increase of the maximum explosion pressure of 7%methane while it led to linear decrease of the maximum explosion pressure of 11%methane.In addition,the increase is greater than the decrease.Nevertheless,the maximum explosion pressure of 9.5%methane rose first,and then reduced by CO.(3)With the increase of CO volume fraction,the peak intensity of free radical H,OH and CH2O increased gradually in 7%CH4 explosion while it decreased by degrees in 11%CH4 explosion.Regarding 9.5%CH4 explosion,the peak intensity of free radical·H,· OH and CH2O increased first and then decreased by CO.In addition,the time of peak appearance was shortened in 7%CH4 explosion,but it was prolonged in 11%CH4 explosion.Concerning 9.5%CH4 explosion,the time of peak appearance was shortened at beginning and then prolonged by CO.(4)The reaction of CO+O2?CO2+·O first triggered the explosion chain reaction of CO/CH4 mixture system.Moreover,it played a leading role in that explosion process.In CO/CH4/air mixture,the presence of CO resulted in the decreases of intermediate products(H2O2,·CH3,·OH)during the process of CH4 explosion in which CO gave priority to the generation of inert gas CO2. |
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