Mechanism of SC-CO2 extraction-induced changes to adsorption heat of tectonic coal

Abstract

To investigate the change and control mechanism of coal adsorption behavior under supercritical CO2 (SC–CO2), the changes in coal composition, structure and adsorption of coals before and after SC-CO2 action were addressed by means of Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), low temperature liquid nitrogen adsorption instrument and calorimeter. The influence of changes in coal composition and structure on its adsorption was quantitatively analyzed by grey correlation analysis. The results show that the effect of SC-CO2 fluid treatment is proportional to the degree of coal damage. After SC-CO2 treatment, the integral adsorption heat of CO2 changes from −11.10 J/g to 13.744J/g, and the microcrystalline structure parameters and inorganic components in coal have the greatest influence on it. At the same time, it is also affected by temperature and pressure. With the increase of microcrystalline structure parameters d002, La and Lc, the integral adsorption heat of the samples showed a 'V' trend, and the increasing trend was the same as the decreasing trend of ash yield. On the whole, SC-CO2 fluid treatment enhances the adsorption of gas by coal samples to a certain extent.