Experimental study on influencing factors of gas concentration in drilling holes

In order to study the influence of negative pressure, gas pressure and permeability coefficient on gas extraction concentration. Through the independent development of physical simulation of underground gas extraction influence experiment platform, through the control variable method, the variation law of gas extraction concentration with different negative pressure of gas extraction, different gas pressure and different permeability coefficient is studied. The results show that when the air leakage is less than the CO2 intake flow and the CO2 purity, the CO2 extraction concentration is relatively high, so the best negative pressure of extraction should be between 30kPa-40kpa. As the initial pressure of coal seam increases, the CO2 intake flow increases and the CO2 purity also increases. When the permeability coefficient increases, the pumping concentration can be increased by increasing the negative pressure of pumping.