印尼褐煤吸湿特性及其热力学参数解析

Study on Moisture Re-adsorption Characteristics and Thermodynamic Parameter Analysis of Indonesian Lignite

利用水分再吸收实验装置测定了印尼褐煤在30℃和40℃下的等温脱附(吸附)曲线,研究粒径和干燥温度对褐煤吸湿特性的影响;利用多孔介质等温吸附热力学原理,计算得到了印尼褐煤的等温吸附热。结果表明:印尼褐煤等温吸湿曲线的形状是典型的可冷凝蒸汽在孔隙物质中物理吸附的S型;干燥后的印尼褐煤平衡水分(equilibrium moisture content,EMC)与粒径无关,而与干燥温度有关,随着干燥温度的提高,平衡水分降低。印尼褐煤的等温吸附热随着平衡水分的增大而降低,当EMC<7%时,干燥煤的吸附热略高于水的蒸发潜热,可以推断水分子在干燥褐煤孔隙表面再吸附机理是水分子物理吸附在褐煤孔隙表面形成体相水和毛细水,没有与煤的表面官能团形成氢键。

Using the moisture re-adsorption experimental rig, the desorption and adsorption isotherms of an Indonesian lignite were studied at the temperature of 30 ℃and 40℃. The effect on moisture re-adsorption characteristics of coal particle size and drying temperature were studied. According to the principle of thermodynamics of porous media isothermal adsorption, the Indonesian lignite isothermal adsorption heat was calculated. The results show the irreversibility of the moisture desorption and adsorption isotherms of the coal in the desorption-adsorption cycles, indicating that the irreversible coal structure changes during drying conditions, which is dependent on drying temperature and independent of the coal particle size. The equilibrium moisture content decreased with the increasing drying temperature. The adsorption heat is a little higher than the latent heat of evaporation while the equilibrium moisture content is more than 7%. The water vapor is physically adsorbed on the particle surface and capillary pore surfaces. The formation of hydrogen bond between the water molecules and the surface functional groups during the moisture re-adsorption process is not evident.