Gas Desorption Rules And Numerical Simulation Of Outburst Coal Seam Under High Temperature Conditions

At present,95% of coal resources are underground mining in our country,and most of the coal seam's permeability is extremely low,leading to difficulty in gas drainage.According to the principle that temperature rise promotes gas desorption of coal seam,the new thought of using drilling holes to warm up the coal seam in order to improve gas drainage rate is put forward.The methods of Theoretical analysis,experimental test as well as numerical simulation are adopted in this thesis,taking gas desorption of outbursting coal seam in Guizhou Province for the core of the study.The samples of Songhe Mine15#coal seam,Shixing Mine 15# coal seam and Mudanba Mine 12# coal seam are selected to do the gas adsorption desorbing experiments under the circumstance of different recharging pressure(1.0MPa,1.5MPa,2.0MPa)and different constant high temperature(40?,50?,60?).it analyzes the intensity relations between gas desorption of outburst coal seam and temperature.The numerical simulation is made to explore the changing rules of gas pressure of coal seam and temperature in the two conditions:1)when the pitch-row is the same,the heating temperature is 40??50??60? respectively;2)when the heating temperature is the same,the space between drills is 0.75m?1m?1.5m respectively.The main research conclusions are as follows:(1)the adsorption mainly happens after air inflation within five hours,When the gas inflation pressure doesn't change,the gas adsorbing capability of coal samples will decrease with the rise of temperature,but when the temperature is over 50?,the gas adsorbing capability of coal samples decrease slowly;when the gas inflation pressure is 1.5Mpa or 2.0Mpa,the changing relation between gas adsorbing capability and temperature is similar.(2)the gas desorption of coal samples mainly happens within 2 hours after the adsorption is balanced.The higher the temperature is,and the greater the initial gas desorption amount is.gas desorption amount accounts for about 50%~60% in the total amount in the first 30 minutes.In the initial stage of gas desorption,the velocity and accelerated velocity of gas desorption drop quickly at the first begining,with the extension of desorption time,the velocity and accelerated velocity of gas desorption tend to slow down.Within the first 1 hour,the desorption velocity changes very obviously;The rapid desorption of gas mainly occurs at this stage;The influence of temperature and pressure on the desorption velocity of gas is a relationship of After another;(3)The empirical formula of gas desorption in outburst coal seam under high temperature,WangYouan type is most suitable for highlighting the changing relations of gas desorption amount of coal samples with time going by,and the average correlation coefficient is 99.73%.Compared with other empirical formulas,its stability is the best.the gas desorption velocity and desorption time of coal seam conform to the power exponential relationship Vt=aT-b,and their correlation coefficient is up to more than90% basically;(4)the increase of temperature promotes the decrease of gas pressure of coal seam.On the working face,when the drill holes' pitch-row of the coal seam`s heating is 1.0m and the heating temperature is 50?,the research results are satisfying;the model temperature field takes the heating holes as the center,and the temperature spreads around as a circle and rises.After the temperature field of two heating holes connect and their temperature effect overlaps,the temperature of the oval area with heating holes as the center is relatively higher,spreading heat around;the changes of pressure field are similar to those of temperature field;when the temperature is from 40 to 50?,the average gas pressure of the coal seam drops 0.008 MPa as the temperature raises 1 ?.When the temperature is from 50 to 60?,the average gas pressure of the coal seam drops 0.0113 MPa.What`s more,as the holes heating temperature raises 1 ?,the average temperature of coal seam rises.The studies of gas desorption rules of coal seam with high temperature and numeral simulation offer a favorable safeguard for drilling holes to heat the coal seam`s temperature,promoting the spot test and engineering application of gas desorption of coal seam.