低阶煤泥表面疏水性差,难以通过常规浮选实现高效分选提质。此外,低阶煤与氧气反应活性高,易发生自燃,但由于煤层或煤堆内部氧气含量低,其主要还是以受高温烘烤作用(类似于低温热解环境氛围)为主,而低温热解转化已逐渐成为低阶煤高效利用的途径之一。因此,探究低温热解对低阶煤表面疏水性的影响,并揭示热解固体产物半焦的可浮性变化规律,对低阶煤的高效合理利用具有指导意义。以不黏煤为研究对象,采用热重分析仪(TGA)描绘煤样热解过程中的失重特性;气相/液相色谱(GC/LC)检测热解过程中挥发性产物的组成;X射线光电子能谱仪(XPS)、扫描电镜(SEM)表征热解前后煤样表面官能团和微观形貌的变化规律;诱导时间测定仪和单元浮选试验分析煤样热解前后疏水性和可浮性的变化情况。结果表明:煤样经低温热解后失重明显,大量挥发性组分(氢气、甲烷等气态产物,苯酚为主的液态产物)逸出,直接导致煤表面亲水性含氧官能团含量相对减少,疏水性官能团含量相对增加;热解半焦表面孔隙、裂痕显著增加,粗糙度增大;与原煤相比,热解半焦诱导时间显著缩短,浮选产率明显增高。低温热解增强了不黏煤表面的疏水性,提升了浮选回收率,从而促进了低阶煤“低温热解转化-半焦浮选提质”联合工艺的发展。

Low-grade coal is difficult to obtain high efficiency by conventional flotation due to its poor surface hydro- phobicity. In addition,the reactivity between low-grade coal and oxygen is high,so it is prone to spontaneous combus- tion. However,there is less oxygen in coal bed or internal dump,so the coal mainly suffers high temperature baking ( similar to low temperature pyrolysis environment). Low temperature pyrolysis has gradually become one of the ways of efficient transformation and utilization of low-grade coal. Therefore,it is of great significance to explore the effect of low temperature pyrolysis on the hydrophobicity of low-grade coal and to reveal the change of the floatability of pyrolysis solid products. In this paper,non-caking coal was used as the object of study,and the weight loss characteristics of coal sample pyrolysis were depicted by thermo-gravimetric analyzer(TGA). Gas / liquid chromatography(GC / LC) was used to detect the composition of volatile products during pyrolysis. X-ray photoelectron spectroscopy( XPS) and scanning electron microscopy(SEM) were used to characterize the functional groups and microstructure of coal samples before and after pyrolysis. The induction time and unit flotation tests were used to analyze the changes of hydrophobicity and floatability of coal samples before and after pyrolysis. The results show that the coal sample is deprived by low tempera- ture pyrolysis,and a large number of volatile components(hydrogen,methane and other gaseous products,phenol-based liquid products) escapes,which leads directly to the content of hydrophilic oxygen-containing functional groups on the coal surface. The content of hydrophobic functional groups increased,the surface porosity and cracks increased signifi- cantly and the roughness increased. Compared with the raw coal,the pyrolysis half-coke induction time was shortened and the flotation yield was significantly increased. The low temperature pyrolysis enhances the hydrophobicity of the non-stick coal surface,and improves the flotation recovery rate,which promotes the technology development of “ low temperature pyrolysis-semi-coke flotation and upgrading”.