褐煤润湿性及水分复吸的量热法研究

摘要

The wettability of lignite and demineralized lignite and conventional mineral matter were evaluated by calorimetric measurement.The effects of moisture re-adsorption on the wetting heat of lignite were investigated and the moisture re-adsorption behavior of dried lignite was analyzed by dynamics models.The results show that wetting heat of organic components in lignite is much higher than that of mineral matter in lignite,indicating its dominated role for heat released of wetting process.The lignite with more content of oxygen-containing groups has a higher value of wetting heat.After the treatment by acid solution,the wetting heat of lignite decreases.For the Manglai lignite,the wetting heat decreases from 101.61 J/g to 66.79 J/g after demineralition.Among the mineral matter in lignite,wetting heat of kaolinite is higher than that of calcite and quartz.The moisture re-adsorption behavior was fitted properly by second-order dynamical model,and the correlation coefficient is greater than 0.99.With the increasing content of moisture readsorbed,wetting heat of lignite decreases.When the moisture re-adsorption reaches to 28.76％,wetting heat of the Manglai lignite decreases from 101.61 J/g to 5.04 J/g.The monolayer or cluster of water molecules adsorbed on surface of lignite is devoted to wetting heat decreasing,while the influence of water adsorbed in pores or capillary condensation is not obviously.%利用量热法分别对褐煤、脱灰褐煤和常见矿物质的润湿热进行测定,考察水分复吸对褐煤润湿性的影响,并对干燥褐煤水分复吸动力学进行分析.结果表明:褐煤中有机质的润湿热远大于其矿物质的润湿热,是褐煤润湿放热的主体.褐煤中含氧官能团越多,润湿热值越大.酸洗脱灰降低了褐煤的亲水性.芒来褐煤脱灰后,润湿热由101.61 J/g降至66.79 J/g,褐煤矿物质中高岭石的润湿热高于方解石和石英的润湿热;干燥褐煤的水分复吸符合二级动力学模型,相关系数大于0.99;褐煤复吸水分越多,其润湿热越小,芒来褐煤复吸水分增加到28.76％(质量分数)时,其润湿热由101.61 J/g降至5.04 J/g.水分复吸过程中,在表面形成的单层吸附或团簇吸附是褐煤润湿热降低的主要影响因素,而孔隙吸附或毛细凝聚吸附对其润湿热影响较小.