微波辐照对褐煤表面含氧官能团及孔隙结构的影响

Variation of oxygen-containing functional groups and pore structure in lignite under microwave irradiation

在微波场下对蒙东褐煤进行了6种不同功率及不同干燥时间的提质试验,采用化学滴定的方法测定不同的微波处理条件下褐煤表面含氧官能团的含量;采用低温氮吸附仪分析了褐煤的孔隙结构特征。通过研究发现：微波辐照初期褐煤表面水分和部分内在水分脱除,造成褐煤孔隙结构破坏,大孔收缩或坍塌,使得褐煤比表面积迅速降低,孔容积和平均孔径减小;微波辐照中期,主要是褐煤表面含氧官能团大量分解成CO2和H2O等气体,从褐煤内部孔道中穿过,使得比表面积和孔体积有所升高;微波辐照后期,脱水停止,含氧官能团分解产生的气体逸出以后,褐煤内部产生的胶凝物质冷却回流封堵褐煤孔隙,褐煤比表面积和总孔体积又呈现下降的趋势。认为：微波处理功率600～800W、处理时间4～8min可提高提质后褐煤稳定性。

The lignite from eastern Inner Mongolia is treated under six different powers and different drying times in microwave field. Chemical titration and low temperature liquid nitrogen adsorption are used to examine the amounts of oxygen- containing functional groups and pore structure. It is concluded that,in the initial period of microwave heating,damage of lignite pore structure occurs,with shrink or collapse of macroporous,due to surface and internal moisture loss,which contributes to the quick decline in lignite surface area and decrease in pore volume and average pore size. In the mid of microwave heating,the oxygen functional groups decomposes into gases such as CO2 and H2O,which passes through the internal channels of lignite,leading to increases in specific surface area and pore volume. After the stop of dehydration and the release of decomposed gases of oxygen functional groups,the gum materials generated under high temperature cool down,reflux and block the lignite pore,thus lead to the decreases in the specific surface area and pore volume. It is found that,post- upgrading stability can be enhanced treated 4 ～ 8min under 600 ～ 800 W microwave power.