Influencing Factors And Experimental Study On Electrothermal High Temperature Field Of Outburst Coal In Guizhou

Coal is an indispensable energy to support China's industrial development.With the development of deep mining,the permeability of coal seam also decreases,and more and more coal and gas outbursts occur in mines.More than half of the coal mines in Guizhou are high outburst mines.However,the actual effect of borehole extraction,the most important technical measure for gas control,is not ideal.Based on the principle of temperature rising to promote gas desorption in coal seams,this paper proposes using MI heating cable to generate electric heating high temperature field in outburst coal seams to promote gas desorption and improve gas extraction rate.In this paper,theoretical analysis and experimental research methods are used to study the electrothermal high temperature field produced by MI heating cables.The electrothermal high temperature field under different heating temperatures(100,200,300),different cable layouts(single cable layouts,double cables layouts,three cables layouts)and water injection coal samples are analyzed.1)A large-scale experimental platform system has been established.Its external dimension is 1750mm×1700mm×2100mm,and the internal dimension of the cavity is 1500mm×1500mm×1500mm.The structure of the cavity is reinforced concrete.When heating coal samples,the cavity is a container restraining coal samples.By applying pressure on coal samples in the cavity,the actual compression state of coal seams is simulated.2)The main influencing factors of the high temperature field are analyzed,which are water injection coal sample,the heating temperature of MI heating cable and the layout of MI heating cable.3)When the cable arrangement is fixed,the heating temperature increases,and the rate of temperature rise per unit time increases.When the temperature in the coal sample reaches a stable state,the temperature of the coal sample in the sensor position will fluctuate or remain constant until the heating stops.With the increase of the heating temperature,the maximum heating temperature of the coal sample after reaching a stable state will increase.The heating radius will increase accordingly.4)Under certain heating temperature,different cable arrangement has a significant influence on the high temperature field of electrothermal.It is concluded that the influence of the number of MI heating cables on the electric-thermal high-temperature field needs to be judged by their spacing.The closer the MI heating cables are,the larger the heating range of the electric-thermal high-temperature field and the higher the temperature of the coal sample.The farther the distance is,the range of the electricthermal high-temperature field is limited to the surrounding of a single MI heating cable,and the temperature of the coal sample is lower.5)The heating effect and range of high temperature electric heating field of injected coal sample are obviously improved.Under the same heating temperature and cable arrangement,the unit time temperature of coal injection increases rapidly,the maximum heating temperature increases,and the effective heating radius of electrothermal high temperature field increases.6)The experiment shows that the optimum arrangement of electrothermal high temperature field is three cables at 100? for heating water injection coal sample.Its effective heating radius is 524 mm,and the maximum heating temperature is not more than 70?.