Study On Gas Desorption Characteristics Of Coal Core During Low Temperature Coring

In order to further simulate the temperature variation of coal sample and gas desorption process at variable temperature during low temperature coring process,the coal core temperature experiment and gas desorption experiment at variable temperature are carried out which are under different adsorption equilibrium pressure and different heating power,based on simulation device of low temperature coring.In the test,the coal sample of Xing Wu mine is selected in this paper and dry ice is used as cryogen.Conclusions are as follow :(1)According to the heat transfer characteristics of coal sample collection process,the low temperature coring simulation device was developed,the simulation of temperature change and coal core gas desorption characteristics of core process can be carried.(2)Numerical simulation of temperature variation in coal reactor is carried out based on COMSOL,get the temperature distributing images coal sample and temperature change curve,find out that the main way of heat transfer is heat conduction.(3)Under the same adsorption equilibrium pressure,cooling time and heating up time show a decreasing trend with increasing heating power.under the same heating power,there is an increasing trend of average cooling speed with the increase of equilibrium pressure,which shows that the adsorption of methane on coal enhances its thermal conductivity.(4)Variation of the desorption amount is divided into three stages in temperature-changing process:early increasing stage,mid stable stage and late increasing stage.Under the same heating power,the desorption amount of the first and third stage is larger and the time of second stage is shorter with the increasing adsorption equilibrium pressure.Under the same adsorption equilibrium pressure,the time of the second stage is shorter and the desorption amount of the third stage is larger with increasing heating power.(5)Variation of the desorption speed is divided into four stages during temperature-changing process:attenuation stage,stable stable,increasing stage,decreasing stage.Under the same heating power,the time of second stage is shorter and desorption speed of the third,fourth stage is increasing with the increasing adsorption equilibrium pressure.Under the same adsorption equilibrium pressure,the time of second stage is shorter and desorption speed of the third stage is increasing with increasing heating power.(6)Inhibition effect of low temperature on desorption is more marked with decreasing adsorption equilibrium pressure.