Study On Experimental Of Coal Bed Methane Desorption Under Sonic Vibrating And Temperature

With the depth of coal mining increased, the intrinsic properties of coal seams (micro-porosity, low permeability and high adsorption) becoming more and more significantly. Because of the features of high adsorption, the accidents in coal production process occurred frequently and gas resources can not be effectively used. According to the technical achievements of high-pressure pulsed water jet cutting and drilling in the coal seam drilling to improve the gas extraction and cavitation sonic and temperature effects during cavitation process, this article proposed a new idea: using cavitation sonic and temperature effects to promote gas desorption.Supported by Innovation Groups Fund Project"Theory of rock cracking by high pressure water jet and its basic application research in underground engineering (ID: 50621403)"of National Natural Science Foundation, this paper studied on the mechanism to promote gas desorption by cavitation sonic and temperature effects, get the way on the promotion of coal seam gas desorption by cavitation sonic and temperature effects; Through the determination of the relevant experimental parameters, designed and fabricated the test bench of cavitation sonic effects; Through the study on experimental,we can get some laws on the gas desorption with time and different cavitation conditions.Main contents and results of this paper is as follows:①Through the study on the mechanism to promote gas desorption by cavitation sonic and temperature effects, we can obtain: The pulse vibration applied mechanical vibration to coal, its equivalent to impose different stress field to coal, under an external stress field to promote gas desorption; The elevated temperature makes the gas molecules gain energy required to desorption, the higher the temperature the more energy available, the desorption of gas desorption from coal out of the body more easily.②Through the study on the propagation of cavitation sonic in coal, it obtain the energy equation of wave propagation in coal; Consider the absorption of acoustic energy of coal and coal for thermal conductivity, it get coal temperature changed equation of wave propagation in coal; Cavitation bubble collapse would produce a certain intensity of sound pressure spectrum and radiation pressure.③Designed the test bench of gas desorption under cavitation sonic and temperature effects; Through the relationship between the pump pressure and the length of the cavitation cloud, design the height of cavitation cavity h = 160mm; Using the maximum principal stress theory strength conditions, design the wall thickness of cavitation chamberδ=15mm; Based on the conditions necessary for the experiment, this article designed the overall structure of cavitation sonic test bench.④The results show that: Cavitation sonic and temperature effects can promote gas desorption; the amount of gas desorption and desorption times are different in different cavitation numbers condition, a best cavitation number had existed, which can make the amount of gas desorption maximum and the time minimum; When the cavitation number of 0.0200,the amount of gas desorption increased by 39.6%and the time reduced by 16.7%; Pump pressure and the amount of gas desorption to meet the quadratic relationship curves, there existed a best pump pressure which can make the amount of gas desorption maximum and the time minimum; With the increase of confining pressure, the pump pressure on the gas desorption weakened; Confining pressure and the amount of gas desorption to meet the linear relationship, with the confining pressure increases, reducing the amount of gas desorption reduced; As the temperature increases, also increases the amount of gas desorption; Under the same cavitation condition elevated temperature, gas desorption will increase; Cavitation sonic and temperature effects has more amount of gas desorption than the action of a single factor.