selected as flotation collectors,and compared with conventional nonpolar collector diesel oil.The measurement of adhesion force between particles and bubbles and molecular dynamics simulation of reagent adsorption were used to reveal the mechanism of unsaturated fatty acids enhancing flotation of low-rank coal.The flotation results show that the flotation performance of unsaturated fatty acid collectors is better than that of nonpolar diesel oil,and the flotation yield of low-rank coal increases with the increase of fatty acid unsaturation.Scanning Electron Microscopy (SEM),Fourier Transform Infrared spectroscopy,(FTIR)and X-ray Photoelectron Spectroscopy (XPS)were used to analyze the surface morphology and surface functional groups of the low-rank coal.SEM results show that the surface of low-rank coal is loose and contains a large number of pores and cracks.which is not conducive to the spreading of chemicals on coal surface and the mineralization of bubbles and particles.The results of FTIR and XPS show that the surface of low-rank coal contains a large number of oxygen-containing functional groups,and surface hydrophobicity of coal samples is poor,resulting in low flotation recovery.The adhesion force between bubble and coal surface in different collector solutions was measuredThe maximum adhesion between bubble and coal surface increased with the increase of collector unsaturation in diesel oil.oleic acid,linoleic acid and linolenic acid systems,which indicated that the floatability of coal particles increased with the increase of collector unsaturation.Furthermore,the molecular dynamics simulation of unsaturated fatty acids adsorption was analyzed,and the results showed that unsaturated fatty acids spread coal surface through hydrogen bonding between their polar groups and the polar groups on coal surface With the increase number of double bonds,the polarity of unsaturated fatty acids increases,and the spread degree of unsaturated fatty acids on coal surface increases gradually,which leads to the increase of particle floatability.It is the main reason for the increase of flotation recovery of low-rank coal with the increase of un aturated fatty acids Keywords:low-rank coal flotation;fatty acid unsaturation,double bond;molecular dynamics simulation; maximum adhesion force 煤炭是我国的主要化石能源，在未来相当长的时间内，其在我国能源结构中的主导地 位不会发生改变。我国煤炭资源种类富主要包括较高变质程度的无烟煤、中等变质 程度的烟煤以及低变质程度的褐煤、低阶煤等，但其数量及储量极不均衡。其中低阶煤储 量巨大，约为8128亿吨，低阶煤已成为我国能源生产和供应的重要保障，这部分煤炭资 源的合理开发与清洁利用对我国经济发展和环境保护具有重要意义5,6。近年来我国高效选 煤工艺和大型选煤设备的发展取得了长足的进步，块煤重介质分选技术已逐渐成熟。随着 采煤机械化程度的提高颓煤质的下降，我国煤泥呈现出“贫、杂、细”等特点，煤泥分选 问题进一步凸显门。符选是利用煤和矸石的天然亲疏水性差异实现细颗粒选择性分离的界 面分选技术，疏水性颖粒粘附至气泡形成矿化气絮团并上浮至泡沫相成为精矿产品，亲水 性矸石颗粒则继续留在矿浆相中随着尾矿排出，从而实现不同界面性质颗粒之间的分离⑧ 在煤矣选过程中，非极性烃类油常被用作捕收剂，可提高颗粒的疏水性，从而提高 颗粒与气泡的粘附概率。但低阶煤孔隙发达，表面含有大量含氧官能团，例如醇羟基、酚 羰基、羧基等0，这些含氧官能团能够与极性水分子结合，在低阶煤表面形成稳定的水 化膜，阻碍捕收剂在颗粒表面的铺展，这导致了捕收剂用量的增加，经济成本的大幅提高 ,。浮选效率低、捕收剂用量大、成本高是制约细粒低阶煤高效利用的主要问题。 近年来，对低阶煤或氧化煤的浮选过程强化研究受到了广泛关注，特别是含氧的醇、 醛、酸、酯类极性捕收剂发展引起了研究人员的极大兴趣3,5。极性捕收剂的加入可对 低阶煤表面进行改性，促进颗粒与气泡间的相互作用，提高浮选回收率。其中Jia和Gui等 人3，的研究表明，极性含氧捕收剂与煤表面的含氧亲水位点间存在氢键作用，可改善煤 样表面疏水性，从而提高浮选低阶煤或氧化煤浮选回收率。Xg等人采用极性含氧捕收 剂CC浮选氧化煤，可获得较好的浮选效果。研究发现，CC中含有大量极性基团，如-selected as flotation collectors, and compared with conventional nonpolar collector diesel oil. The measurement of adhesion force between particles and bubbles and molecular dynamics simulation of reagent adsorption were used to reveal the mechanism of unsaturated fatty acids enhancing flotation of low-rank coal. The flotation results show that the flotation performance of unsaturated fatty acid collectors is better than that of nonpolar diesel oil, and the flotation yield of low-rank coal increases with the increase of fatty acid unsaturation. Scanning Electron Microscopy (SEM), Fourier Transform Infrared spectroscopy, (FTIR) and X-ray Photoelectron Spectroscopy (XPS) were used to analyze the surface morphology and surface functional groups of the low-rank coal. SEM results show that the surface of low-rank coal is loose and contains a large number of pores and cracks, which is not conducive to the spreading of chemicals on coal surface and the mineralization of bubbles and particles. The results of FTIR and XPS show that the surface of low-rank coal contains a large number of oxygen-containing functional groups, and surface hydrophobicity of coal samples is poor, resulting in low flotation recovery. The adhesion force between bubble and coal surface in different collector solutions was measured. The maximum adhesion between bubble and coal surface increased with the increase of collector unsaturation in diesel oil, oleic acid, linoleic acid and linolenic acid systems, which indicated that the floatability of coal particles increased with the increase of collector unsaturation. Furthermore, the molecular dynamics simulation of unsaturated fatty acids adsorption was analyzed, and the results showed that unsaturated fatty acids spread on coal surface through hydrogen bonding between their polar groups and the polar groups on coal surface. With the increase number of double bonds, the polarity of unsaturated fatty acids increases, and the spread degree of unsaturated fatty acids on coal surface increases gradually, which leads to the increase of particle floatability. It is the main reason for the increase of flotation recovery of low-rank coal with the increase of unsaturated fatty acids. Keywords: low-rank coal flotation; fatty acid unsaturation; double bond; molecular dynamics simulation; maximum adhesion force 煤炭是我国的主要化石能源，在未来相当长的时间内，其在我国能源结构中的主导地 位不会发生改变[1-3]。我国煤炭资源种类丰富，主要包括较高变质程度的无烟煤、中等变质 程度的烟煤以及低变质程度的褐煤、低阶煤等，但其数量及储量极不均衡。其中低阶煤储 量巨大，约为 8128 亿吨[4]，低阶煤已成为我国能源生产和供应的重要保障，这部分煤炭资 源的合理开发与清洁利用对我国经济发展和环境保护具有重要意义[5, 6]。近年来我国高效选 煤工艺和大型选煤设备的发展取得了长足的进步，块煤重介质分选技术已逐渐成熟。随着 采煤机械化程度的提高和煤质的下降，我国煤泥呈现出“贫、杂、细”等特点，煤泥分选 问题进一步凸显[7]。浮选是利用煤和矸石的天然亲疏水性差异实现细颗粒选择性分离的界 面分选技术，疏水性颗粒粘附至气泡形成矿化气絮团并上浮至泡沫相成为精矿产品，亲水 性矸石颗粒则继续留在矿浆相中随着尾矿排出，从而实现不同界面性质颗粒之间的分离[8, 9]。 在煤炭浮选过程中，非极性烃类油常被用作捕收剂，可提高颗粒的疏水性，从而提高 颗粒与气泡的粘附概率。但低阶煤孔隙发达，表面含有大量含氧官能团，例如醇羟基、酚 羰基、羧基等[10-12]，这些含氧官能团能够与极性水分子结合，在低阶煤表面形成稳定的水 化膜，阻碍捕收剂在颗粒表面的铺展，这导致了捕收剂用量的增加，经济成本的大幅提高 [13, 14]。浮选效率低、捕收剂用量大、成本高是制约细粒低阶煤高效利用的主要问题。 近年来，对低阶煤或氧化煤的浮选过程强化研究受到了广泛关注，特别是含氧的醇、 醛、酸、酯类极性捕收剂发展引起了研究人员的极大兴趣[13, 15, 16]。极性捕收剂的加入可对 低阶煤表面进行改性，促进颗粒与气泡间的相互作用，提高浮选回收率。其中 Jia 和 Gui 等 人[13, 17]的研究表明，极性含氧捕收剂与煤表面的含氧亲水位点间存在氢键作用，可改善煤 样表面疏水性，从而提高浮选低阶煤或氧化煤浮选回收率。Xing 等人[9]采用极性含氧捕收 剂 CC 浮选氧化煤，可获得较好的浮选效果。研究发现，CC 中含有大量极性基团，如- 录用稿件，非最终出版稿