Research On The Law Of The Gas Desorption At Negative Pressure

In this paper, base on the method of negative pressure sampling from underground mines and the problem to determine the reasonable negative values of gas drainage work, a preliminary study regarding the desorption law of the coal gas with negative pressure is achieved by developing experimental platform of gas negative pressure desorption, simulating gas desorption test, analyzing the error between empirical equations and experimental data comparatively and verifying the new empirical equation.In different adsorption equilibrium pressure and desorption negative pressure, simulation tests of the gas desorption process for the coal sample from the No. 15 coal seam in Yangquan Sijiazhuang mine are proceeded. Also, at identical adsorption equilibrium pressure, the effect of different negative pressure on gas desorption quantity and desorption speed is discussed in this paper; the effect of different adsorption equilibrium pressure on gas desorption quantity and desorption speed is studied at the same negative pressure; the relation between negative pressure and residual gas is explained with the uniform adsorption equilibrium pressure as well.The gas desorption simulation test data is processed by using Origin and 1stOpt software at different adsorption equilibrium pressure and negative pressure. Through using common seven categories of empirical equations, the simulated and measured data by means of regression analysis is processed, and then the results show that the Bolt equation, Wang Youan equation and exponential equation, can better describe the gas desorption process of the coal samples with the negative pressure from the aspect of cumulative gas desorption quantity. By means of the error analysis between accumulative gas adsorption quantity acquired by laboratory experiments and calculated by empirical equation, the result shows that Wang Youan equation is the best equation model to describe the gas desorption law of chosen coal samples with the negative pressure.According to Wang Youan equation model, considering the two influence factors- adsorption equilibrium pressure and negative pressure, a new gas desorption empirical equation of coal with negative pressure condition is obtained. Using the new empirical equation, all test data and gas simulation desorption data are proceeded with the method of regression analysis and error calculation in conditions of other adsorption equilibrium pressure and desorption negative pressure, in that way the accuracy and applicability of the new empirical equation are verified.