Study on the effect of NMR-based surfactants on pore wetting of high-order coal

High-order coal has the characteristics of weak water absorption due to the development of micropores. From the perspective of micropores, it is of great significance to study the improvement effect of different types of surfactants on the wettability of high-end coal, which is of great significance for dust prevention and dust reduction of high-end coal. Taking the high-order coal of Zhaozhuang Mine in Shanxi Province and Nuodong Mine in Guizhou as the research object, the low-field nuclear magnetic resonance (LNMR) measurement system was used to carry out the coal sample sedimentation experiment and the coal sample-solution permeation pore water distribution determination experiment, and analyze the improvement law of micropore wettability of surfactant solution on high-order coal samples under different compound ratios. The results show that: In the sedimentation of eight surfactant monomer solutions, the sedimentation rate of coal samples in surfactant solution gradually increased with the increase of mass fraction, and the sedimentation rate of coal samples in each solution tended to balance at 0.5% mass fraction, among which the sedimentation effect of Trolatong X-100 (X-100), fatty alcohol polyoxyethylene ether (JFC-U) and sodium dodecyl benzene sulfonate (SDBS) was faster than that of other surfactant solutions. Based on the low-field NMR experiment T₂ spectroscopy, a dual quantitative evaluation method was established, and it was found that when the three preferred surfactant solutions were compounded with volume ratios of 1∶1, 1∶2 and 2∶1 under the condition that the mass fraction was 0.5%, the compound solution played a synergistic role in the wettability of the micropores of high-order coal, and the wetting improvement effect of the compound surfactant solution was higher than that of the surfactant monomer solution. When the volume ratio of the nonionic surfactant JFC-U solution and the anionic surfactant SDBS solution were compounded 2∶1, the effect on improving the wetting of high-order coal was obvious. In the compound solution of nonionic and nonionic surfactants, the wetting improvement effect of compound surfactant solution on coal samples was positively correlated with the content of JFC-U. The research results can provide a reference for the selection of surfactant types and the research methods of coal sample wettability during wet dust control in coal mines.