Influence of CO2 Cracking on Adsorption Characteristics and Fractal Characteristics of Raw Coal
To investigate the influence of carbon dioxide cracking on the adsorption characteristics of raw coal,scanning electron microscopy(SEM),mercury intrusion porosimetry(MIP),and liquid nitrogen adsorption experiments are conducted on both untreated and fractured coal samples.The outcomes reveal a notable disparity in surface morphology:the raw coal exhibits a scarcity of fractures,whereas the fractured coal surface is pervaded by an extensive network of microfractures traversing the entire coal matrix.Analysis of the mercury intrusion-extrusion curves for both coal types indicates the presence of hysteresis loops,with the hysteresis loop of the fractured coal significantly larger than that of the raw coal.Notably,above a pressure threshold of 1.1 MPa,the mercury intrusion-extrusion curves of raw coal consistently resides beneath those of the fractured coal,and the disparity between the curves intensifies with increasing pressure.Furthermore,the adsorption-desorption volume of the fractured coal far exceeds that of the raw coal,with the desorption curve of the fractured coal demonstrating a steeper decline approaching a relative pressure of 0.95,indicative of enhanced gas release kinetics.Intriguingly,the fractal dimension calculations consistently yields lower values for the fractured coal compared to the raw coal,suggesting that fracturing promotes the development of macropores and augments pore volume within the coal seams.This enhancement in pore connectivity and permeability within the fractured coal facilitates the desorption and migration of gas,particularly methane,which holds significant implications for the enhancement of coalbed methane extraction and the mitigation of coal and gas outbursts.Hence,this study provides valuable insights and serves as a reference for optimizing coalbed methane recovery strategies and enhancing mine safety.
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