水热处理对褐煤的分形维数及复吸附水的影响

The effect of hydrothermal treatment on fractal dimension and re-absorbed water of lignite

目前低阶煤水热干燥处理后复吸水含量降低的原因主要归结为含氧官能团的减少和孔隙结构的变化,但是在水热条件下,煤炭颗粒形貌的变化,对其复吸水含量的影响却没有得到关注。以蒙东褐煤为样品,利用扫描电镜分析了煤炭颗粒在不同温度下水热改性后的形貌变化,通过Frenkel-Halsey-Hill(FHH)模型分析等温吸附曲线计算水热处理前后煤炭的分形维数,并研究分形维数与煤炭平衡复吸水量的关系。试验结果表明,随着水热处理温度的升高,煤炭颗粒逐渐由多棱角形向圆形和椭圆形变化,其表面的分形雏数逐渐降低,由此可以得出低阶煤炭的平衡复吸水量与分形维数具有正相关性。

At present it is generally believed that the decrease of the re-absorbed water content of the low-rank coal after hydrothermal drying treatment is mainly due to the decrease of oxygen-containing functional groups and the change of pore structure,however,under the influence of hydrothermal conditions,the effect of coal particle morphology＇s change on the content of reabsorbed water is not concerned.Taking lignite from the eastern Inner Mongolia as sample,the change of coal particle morphology after hydrothermal treatment under different temperatures was analyzed by SEM.The fractal dimensions of coal before and after hydrothermal treatment were calculated by isothermal adsorption curve and analyzed by Frenkel-Halsey-Hill model（FHH）,and the relationship between the fractal dimension and the equilibrium re-absorbed water content was studied.The test results showed that with the increase of hydrothermal treatment temperature,the coal particle＇s shape gradually changed from polygon to roundness and oval,and the fractal dimension of the surface was gradually reduced.So it concluded that the equilibrium re-absorbed water content of the low-rank coal had positive correlation with the fractal dimension.