煤快速热解焦的微观结构对其气化活性的影响

Effect of microstructure of rapid pyrolysis char on its gasification reactivity

在滴管炉内对中国三种不同煤阶的典型煤种在800～1 400℃进行快速热解实验,利用XRD和氮气气体吸附法对所得煤焦进行微晶结构和孔隙特征分析,在热重分析仪上进行CO2气化反应活性的测定,研究不同热解温度煤焦结构特性与气化活性之间的关系。结果表明,随着热解温度的升高,内蒙古褐煤焦和神府烟煤焦的比表面积在1 200℃达到极大值,但气化活性却相对较低;遵义无烟煤焦在800～1 200℃气化活性逐渐提高,但比表面积在900℃达到极大值,表明煤焦比表面积与气化活性不存在严格关联。煤焦碳微晶结构变化所反映出煤焦石墨化进程与煤焦气化活性随热解温度的变化具有一致的变化趋势,表明快速热解煤焦的碳微晶结构变化对煤焦气化活性的影响更大。

To investigate the relationship between microstructure of rapid pyrolysis chars under different temperatures and their gasification reactivities, three Chinese typical coals with different ranks were pyrolyzed in a drop-tube furnace at 800 - 1 400℃. The structure of chars obtained was characterized by using XRD （ X：ray diffraction） and N2 gas adsorption method, and the CO2 gasification reactivity of chars was examined using TGA （thermogravimetric analyzer）. The results show that the specific surface area increases with the increasing of pyrolysis temperature and reaches maximum value at 1 200 ℃, while the gasification reactivity of NM lignite and SF bitumite chars lowers relatively. The gasification reactivity of ZY anthracite char increases gradually at 800 - 1 200 ℃, while the maximum value of specific surface area appears at 900 ℃. It is proved that there is not a good correlation between the specific surface area and the gasification reactivity of chars. However, the change of gasification reactivity of three chars with increasing pyrolysis temperature is in accordance with the development of carbon crystallite structure of chars which reflects the graphitization progress of chars. It is concluded that the change of carbon crystallite structure of chars has a greater influence on the gasification reactivity of chars made by rapid pyrolysis.