粒径对不同煤阶煤焦气化反应活性的影响研究

选取气流床气化炉所使用不同煤阶的八种煤焦,通过多级筛分制得单分散煤粉样本,利用热重分析仪考察了气化温度、煤焦粒径对不同煤阶煤焦CO_2气化反应的影响。对比了不同碳转化率阶段下的反应差异,并讨论了高碳转化率阶段的情况。研究表明,随着煤阶的升高,煤焦碳微晶结构更为有序,其气化活性也随之降低。煤焦粒径对气化反应的影响与煤阶有关。对于无烟煤,平均粒径300μm的无烟煤煤焦转化率达到95%所需时间可达40μm煤焦的7倍;对于褐煤与烟煤,由于其孔隙结构较为发达,粒径变化对煤焦气化活性的影响并不明显。综合煤阶、气化温度、煤焦粒径对气化反应活性的影响发现,相较低阶煤,提高气化温度、减小煤焦粒径能够更有效地提升高阶煤气化反应活性。

Effect of particle size on gasification of char with different coal ranks

Eight coal chars of different coal ranks were prepared to investigate the effects of coal rank, reaction temperature and particle size on char-CO₂ gasification using a thermogravimetric analyzer (TGA). The variation of char-CO₂ gasification rate with carbon conversion was studied, especially at high conversion stage. As a result, the crystalline structures of higher rank chars are more orderly, resulting in a lower gasification rate. For high rank coals like anthracite, the CO₂ gasification rate of char with 40 μm size is about 7 times higher than that with 300 μm size to reach 95% conversion at 1 300℃. For low rank coals, particle size has little effect on the gasification rate. The results indicate that the effect of particle size on char-CO₂ gasification is dependent on coal rank. The specific surface area of high rank coals is much smaller than that of low rank coals, which contributes to the significant effect of particle size on high rank coal gasification. The effect of gasification temperature and particle size on gasification rate for high rank coals is more significant than that for low rank coals.