Ultrasonic is a new method to enhance coalbed methane recovery. A deeper comprehension of the synergistic mechanisms of combined ultrasonicchemical modification on the CH 4 adsorption−desorption capability and physicochemical properties of coal is necessary for potential field implementation, as the modification of coal reservoirs frequently necessitates the addition of chemical reagents. This paper evaluated the CH 4 adsorption−desorption properties of anthracite modified by sodium dodecyl sulfate (SDS) solution, ultrasonic modification, and combined ultrasonic-SDS modification. Fourier transform infrared spectroscopy, low-temperature nitrogen adsorption, and micro-CT were applied to elucidate the synergistic mechanism of the combined modification. The research results show that the SDS solution reduces the saturated adsorption capacity of anthracite and increases its final desorption rate by dissolving clay minerals and the physical adsorption masking effect of SDS micelles on the coal surface. Some surface groups with low bond energy are broken or evaporated under mechanical vibration and thermal effects generated by ultrasonic. The original fractures are expanded and connected, which changes the adsorption−desorption properties of anthracite. The synergistic effect of the combined modification of ultrasonic-SDS can promote the penetration range and chemical reaction efficiency of the SDS solution, which expands the effective range of ultrasonic. After combined modification, the amount of aromatics, oxygencontaining functional groups, and aliphatic hydrocarbons on the surface of coal is reduced. The connected porosity of coal samples accounts for 91.5% of the total porosity. As a result, the saturated adsorption capacity of anthracite reduces by 26.7%, and the final desorption rate increases by 28.0%. The effect of the combined ultrasonic-chemical modification is better than that of a single modification.
To investigate the influence of graded-loading rate on the creep characteristics and hardening effect of anthracite, creep tests at different graded-loading rates (0.01–0.1 mm/s) were performed on anthracite standard samples using the LDHJ-III triaxial creep-testing machine. The effect of graded-loading rate on the instantaneous strain increment, instantaneous elastic modulus, and decay characteristics of the strain rate in the creep stage were analyzed and discussed. The results revealed the following. With the increase in the graded-loading rate, especially when the loading rate was higher than 0.04 mm/s, the axial instantaneous strain increment was obvious, the radial-strain hysteresis was significant, the actual yield stress of the specimen was decreased, the “hardening” effect of the specimen was obvious, the strain rate attenuation in the creep stage was more rapid. The research results could quantitatively describe the “hardening” effect of the graded-loading rate on anthracite creep and predict the creep failure of an anthracite specimen.
Coal gangue is an accompaniment in the coal production process, also the largest industrial emissions from solid waste. Coal gangue was not only destroying the environment, but also pollution of air, water and soil. But coal gangue can be used as the recycling resources. This article outlines the various hazards and impact of coal gangue, introduced a variety of disaster prevention and management methods, expanded the current use and management of some of the results about coal gangue and prospects for future governance of the coal gangue.
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