Experiment And Research On Matrix Pulsating Combustion Of Low Concentration Mine Gas

Mine gas is mainly hydrocarbon gas adsorbed on the surface of coal-based particles,partially free in coal pore or dissolved in coal seam water.It belongs to unconventional natural gas,and its main component is methane.Low concentration gas is a clean and efficient energy source.The calorific value of 100%methane concentration is about 35900kJ/Nm~3,which is 2-5 times that of coal.The calorific value is equal to that of natural gas.In addition,the warming potential of methane of equal mass is 21 times that of carbon dioxide,and its greenhouse effect is much larger than that of carbon dioxide.The destruction of the ozone layer is seven times that of carbon dioxide,posing a serious challenge to atmospheric safety.The methane concentration in the gas is low and within the explosion limit.It is difficult to use the conventional combustion method.Pulsating combustion is a new combustion technology which is different from steady combustion.It has the characteristics of high combustion intensity,high combustion efficiency,high heat transfer efficiency and low pollutant emission.It has attracted more and more attention.Based on the low concentration gas utilization in the second mining area of Jinjia Coal Mine of Guizhou Panjiang Group,this paper applies the low concentration gas combustion to the pulsating combustion technology for the characteristics of the thin gas of coal mine gas flammable gas and the difficulty of using conventional combustion methods.A single-tube low concentration gas pulsation combustion experimental platform with an output of 50kW was built.The experimental results show that the diameter of the combustion chamber is 194mm,the length is 350mm,the internal diameter of the tail pipe is 67mm,and the length of the tail pipe is 600mm,a pulsating combustion with a minimum methane concentration of 3.9%was achieved,with an average combustion efficiency of 94.1%and no NOx formation.In this paper,the flow field of a multi-tube matrix pulsating combustor is numerically simulated,and the optimal opening size of the matrix pulsating combustor is obtained.The diameter of the opening is 108mm,125mm,95mm,132mm and 105mm.According to the experimental data of single-tube combustor and the numerical simulation results,a low-concentration gas matrix pulsating combustor experimental system with a rated power of 1250kW was designed and built in the second mining area of Jinjia Coal Mine,and the combustion characteristics experiment was carried out.The experimental results show that matrix pulsating combustion can achieve low concentration gas combustion with a lean limit of 4.0%.When the methane concentration is lower than 4.0%,combustion cannot continue.When the methane concentration is 4%,tempering speed is 0.65m/s,fire removal speed is 1.85m/s;in the concentration range of 4.0%~6.0%,with the decrease of methane concentration,tempering speed gradually decreases;in the concentration range of 4.0%~6.0%,with the concentration of methane increases,the fire removal speed increases.