Study on wetting characteristics of high-rank coal treated with nanofluids

To thoroughly investigate the effect of nanofluids on the wetting characteristics of high-rank coal and to enhance the dust suppression performance of coal seam water injection technology,this study selected high-rank coal samples from the Tiandi Wangpo Coal Mine in Jincheng,Shanxi Province,and the Zhaogu No. 2 Coal Mine in Xinxiang,Henan Province. Contact angle experiments were conducted to examine the influence of SiO₂ nanofluids on coal wettability. Low-field nuclear magnetic resonance (NMR) equipment was employed to perform Carr-Purcell-Meiboom-Gill (CPMG) sequence measurements on coal samples treated with SiO₂ nanofluids at various mass fractions. The results indicate that the optimal improvement in coal wettability is achieved at a nanofluid mass fraction of 1. 50%. Nanofluids significantly enhance water migration and adsorption within the coal matrix,and the enhancement effect increases with increasing concentration. The wetting process exhibits a three-stage characteristic:initial water storage in mesopores and macropores,followed by migration and adsorption into micropores,and finally reaching equilibrium. This study elucidates the wetting modification mechanism of nanofluids on high-rank coal at the microscopic level,providing a theoretical basis and technical support for improving coal seam water injection effectiveness and mine dust control.