Physical Simulation of Temperature and Pressure Evolvementin Coal by Different Refrigeration Modes for Freezing Coring

摘要

Reductionof gas desorption capacity by cooling coal samples seemsa feasible way to improve the accuracy of gas in place estimation.To find an efficient refrigeration mode for the freezing coring technology,the freezing tests for coal containing gas (at 0, 1.09, and 2.15 MPa)are separately conducted based on the precalculation of dry ice dose.The evolvement of coal temperature and gas pressure shows that underthe catalysis of ethanol, the average cooling rate of coal graduallyaccelerates with the increased amount of ethanol (from 0 to 600 mL)in the early stage. Additionally when charging gas into the coal canister,the cooling rate of coal at each subzero temperature accelerates withthe increased adsorption pressure of gas, and the low temperaturepreservation time (<0 °C) of coal is also prolonged. Thereis a good linear relationship between gas pressure and coal temperature,which indicates that the CH adsorption and desorptionin coal are basically reversible; but the desorption hysteresis isextensively observed, associated with the occurrence of numerous ink-bottletype micropores.