热压脱水对褐煤结构及其热解特性的影响

Effect of hot pressing dewatering on the structure and pyrolysis characteristics of lignite

为探究经热压脱水后褐煤的物理、化学结构变化及其热解特性,在小型反应釜上采用热压脱水方法对内蒙古锡林郭勒褐煤进行脱水提质。通过红外光谱(FT-IR)、粒度分析仪、静态氮吸附仪等实验设备探索脱水后煤样的物理、化学结构变化。采用热重天平(TG/DTG)研究了脱水煤样热解和气化反应性的变化情况,并对脱水煤样在最大失重速率区间的动力学参数进行了计算。实验结果显示:温度对于脱水率的影响明显大于压力,而压力对于脱水率的影响主要表现在低温阶段,300℃时压力对于脱水率几乎没有影响。温度相同压力较大时,羧基浓度无明显变化,但压力对C—O键的生成起到抑制作用;随着实验温度的升高,C—O键浓度、芳香度先增大后减小。热压脱水煤样的比表面积、总孔体积、平均孔径、粒度都有所降低,但压力对粒度影响较小;微孔和中孔比例增加,大孔比例降低。在压力的挤压作用下褐煤颗粒内部孔隙缩小、坍塌,使脱水煤样在热解初始阶段反应活性降低;而在高温热解阶段反应活性增大。

In order to investigate the physical,chemical structure changes of lignite by hot pressing dewatering and its pyrolysis,dewatering and upgrading on Inner Mongolia Xilingol lignite by hot pressing dewatering( HPD) method were carried out with a miniature autoclave. By means of Fourier transform infrared spectroscopy( FTIR),particle analyzer,nitrogen adsorption surface analyzer and thermogravimetric analyzer( TGA),the changes of physical and chemical structure,the variance of pyrolysis and gasification reactivity of treated samples were investigated. The kinetic parameters of coal samples were calculated within the range of maximum weight loss rate. The results indicate that the effect of temperature on dewatering rate is significantly higher than pressure,while the pressure effect on dewatering rate is mainly at low-temperature phase. The pressure has almost no effect on dewatering rate at 300 ℃. The concentration of carboxyl has no obvious change with the pressure increases at the same temperature,but the pressure has an inhibitory effect on the formation of C—O bond. The concentration of C—O bond and aromaticity increases first and then decreases along with the increase of experimental temperature. Specific surface area,total pore volume,average pore diameterand particle size are reduced in HPD samples,but the pressure has a little effect on the particle size. The proportion of micropore and mesopore increases and macropore decreases. The pore shrinkage and collapse in lignite particles decrease the reaction activity at the initial stage of pyrolysis,while increase at the high temperature pyrolysis stage.