褐煤微波脱水过程中水分的迁移规律和界面改性研究

针对褐煤脱水能耗高、易复吸的难题，运用自制微波脱水系统，对蒙东褐煤进行5种不同功率和4种不同粒度的脱水实验。建立了褐煤微波脱水的数学模型并采用有限差分法求解，实验结果与模型计算结果吻合良好。采用扫描电镜(SEM)和低温氮吸附仪测定脱水前后煤样的表面形态和孔隙结构。采用化学滴定法测定羧基和酚羟基官能团的变化。通过恒温恒湿复吸实验和热重分析确定煤样的复吸和自燃特性。发现微波脱水后褐煤复吸水分远低于热风干燥褐煤的19.87%，着火点也由原煤的275 ℃提高到295 ℃以上。说明微波脱水后褐煤的界面稳定性得到改善，不易复吸和自燃。

Moisture migrationand interfacial modification of lignite in microwave dehydration process

In order to solve the problems of high energy consumption and high reabsorption，microwave dehydration technology of lignite was applied in this paper.The lignite with four different particle sizes from eastern Inner Mongolia was treated by a self-developed microwave system under five different powers.The mathematical model for the moisture changes of lignite was developed and the relevant results were determined by finite difference method.And the computational results were in good agreement with the experimental results.The scanning electron microscope(SEM)and low temperature nitrogen absorption method were applied to study the surface features and porous structure of coal samples.Distribution of oxygen-functional groups of carboxyl and phenol-hydroxyl was evaluated based on the chemical analysis results.Readsorption experiment in constant temperature and humidity with thermogravimetric analysis were performed to study the characteristics of readsorption and spontaneous combustion.It was found that the moisture after the readsorption of the lignite dried by microwave was far lower than 19.87%，the moisture after the readsorption of the lignite dried by hot air，and the ignition temperature were increased to more than 295 ℃ from 275 ℃.The results indicated that the interfacial stability of lignite is improved by microwave，and the dehydrated lignite is difficult to reabsorb water and combust spontaneously after microwave drying.