Meitan kexue jishu (Dec 2024)
Experimental study on adsorption characteristics of coal by acidification−gas wettability alteration
Abstract
In the deep mining stage of coal mine, the permeability of coal seam decreases with the increase of in-situ stress. Coal seam acidification technology improves the permeability by dissolving the fillers in pores and fissures, but water blocking effect limits the development of this technology, and the addition of gas wetting reversal agent can effectively reduce the water blocking effect after acidification. In order to explore the effect of adding wetting reversal agent on the adsorption characteristics of coal during acidification, raw coal (RC), distilled water impregnated coal (DWC), acid liquid immersed coal (ALC)and acid liquid-gas wetting reversal agent impregnated coal (ARC)were prepared, and methane isothermal adsorption experiment, XRD experiment and high-pressure mercury pressure experiment were carried out after drying treatment, respectively. The results of methane isothermal adsorption experiments show that the adsorption constant a of ARC is greater than that of RC and DWC, but less than that of ALC，indicating that water infiltration reduced the adsorption capacity of coal for methane, while acidification promoted the improvement of adsorption performance, and the addition of gas wetting reversal agent reduced the adsorption capacity of coal for methane. XRD results showed that the chlorite minerals disappeared and the components of kaolinite, illite and alastite were significantly reduced in ALC and ARC; The quartz content of ARC was significantly reduced. The results of high-pressure mercury pressure showed that the pore capacity of RC, ALC and ARC were greater than that of DC, and that of ARC was smaller than that of DWC and ALC. Through the theoretical analysis of the experimental results, the influence mechanism of acidification-gas wettability alteration on the adsorption characteristics of coal was clarified. the addition of gas wetting reversal agent reduced the methane adsorption performance of coal, and promoted acidification reaction and produced new substances, and changed the pore characteristics of coal under the action of water wedge and drying. In the practice of coal seam acidification, cleaning should be carried out in time to avoid re-solidification of reactants after water loss and plugging of pores.
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