Thermal Effect And Thermodynamical Response Of Coal Under Microwave Irradiation

Pre-drainage of gas can not only ensure the safety of coal production,but also meet the increasing energy demand of our country.However,the general permeability of coal seams in high gas mines in China is far lower than that in other countries,which determines that it is very difficult to develop coal seam gas on the ground in China.Therefore,how to improve the permeability of coal seam is one of the key technical problems to improve the effect of gas drainage.It has been found that by increasing the coal temperature,the coal body can be damaged,its permeability can be increased,and gas desorption can be promoted.The thermal effect of microwave radiation can achieve this well.However,there are few researches on Microwave antireflection,and the law is not very clear,so further research is needed.In this paper,the thermal effect and thermodynamic response characteristics of coal under microwave radiation are studied by means of theoretical derivation,laboratory experiment,numerical simulation,data analysis and comparison.Firstly,the microwave irradiation experiment of coal samples is carried out by using the existing equipment in the laboratory,and the surface temperature of coal samples is collected by using the infrared thermal imager.Using statistical method,the average surface temperature and standard deviation data of microwave irradiation coal samples are obtained by using infrared thermal imager,and the effects of irradiation processing time,microwave power and frequency,moisture content and dielectric constant of coal samples on the temperature of coal samples are analyzed.Secondly,the multi physical field simulation software COMSOL is used to simulate the microwave irradiation of coal samples,and the temperature rise and thermal stress distribution of coal samples under different microwave irradiation time,microwave power,microwave frequency,water saturation and electrical properties are obtained.The simulation results are compared with the experimental results to verify the accuracy of the model.Using the validated parameters,the simulation of coalbed methane is carried out.The distribution law of electric field,temperature field and stress field of reservoir under microwave irradiation is obtained,and a reasonable microwave irradiation scheme is given.Finally,according to the results and analysis of the experiment and simulation,combined with the research results of the existing research team,this paper puts forward a kind of device and method of vertical well hydraulic fracturing combined with microwave irradiation to strengthen the extraction of coalbed methane,as well as the device and method of horizontal well microwave irradiation to strengthen the extraction of coalbed methane,so as to solve the low gas extraction rate caused by low permeability of coal seam and difficult desorption of coalbed methane The problem.This paper contains 47 figures,16 tables and 84 references.