脱水褐煤的孔隙结构对复吸性能影响

Effect of pore structureon moisture re-adsorption of dewatered lignite

采用低温氮吸附法对不同温度热空气(<180℃)脱水后褐煤的孔结构进行表征,得到吸附/脱附等温线,依据NLDFT理论得出孔结构参数,并应用FHH模型计算分形维数.通过实验考察脱水褐煤的复吸率(MRV),分析了孔结构变化对复吸的影响.结果表明:脱水褐煤中存在大量一端封闭的盲孔,中孔和大孔主要以开放性孔形式存在;脱水温度140℃时中孔数量明显增加,孔容、比表面积及平均孔径均随脱水温度升高而增大;脱水褐煤的分形维数为2.52±0.03,并随脱水温度升高而增大;MRV与脱水温度成正比,脱水褐煤的复吸性能由比表面积、孔容、平均孔径等因素共同影响,其中比表面积影响最显著.

Abstract： Low-temperature nitrogen adsorption method was used to detect the pore structure of dehydrated lignite derived from different temperatures （〈180℃） air-drying process, and the adsorption-desorption isotherms were obtained. The pore structure parameters were obtained by non local density functional theory （NLDFT） and fractal dimension was calculated by the model of Frenkel-Halsey-Hill （FHH）. An adsorption experiment under constant temperature and humidity was completed to investigate relationship between pore structure and moisture re- adsorption value （MRV） of dehydrated lignite. The results show that there are a lot of semi- opened microspores in dehydrated lignite and a large quantity of mesopores and macropores shaped like a slit. Fractal dimension is 2.52＋0.03 and increases with increasing temperature. The number of mesopoures significantly increases at 140 ℃ and cumulative pore volume, spe- cific surface area, average pore size increases with increasing dehydration temperature. MRV is proportional to temperature and depends on combined effects of multiple factors, including cu- mulative pore volume, specific surface area, average pore size, fractal dimension, in which the specific surface area has the most significant effect on it.