Freezing experiments on moulded coal with methane using dry ice as cold source

To investigate whether dry ice could be used as cold source for the freezing core sample technology (FCST) and the temperature changing process of coal samples under low temperature conditions, a series of freezing tests were conducted using moulded coal samples with methane under different equilibrium pressures.The cold sources were used to provide the freezing environment, which were pure dry ice and dry ice mixed with different quantities of alcohol (dry ice-alcohol mixture).Test results show that both pure dry ice and dry ice-alcohol mixture can be used as cold resources.Dry ice-alcohol mixture works better at initial freezing stage.The higher the equilibrium pressure, the quicker the decreasing temperature and the lower the minimum freezing temperature.This may reveal that when the pressure of the coal seam is higher, the FCST works better.These results also lay a foundation for building the FCST instrument to measure the in situ gas content of coal seams.