添加CaO对煤热解过程中砷和硫迁移转化的影响

摘要

利用高频炉反应器在800-1200℃对添加质量分数10%CaO的云南镇雄煤( YNZX)进行了快速热解实验,采用连续化学提取、X射线衍射( XRD)、扫描电子显微镜-能谱( SEM-EDX)和X射线光电子能谱( XPS)等分析手段,考察了CaO添加对煤快速热解过程中砷和硫迁移转化的影响。结果表明,CaO能显著抑制砷与硫的释放。 CaO对砷释放的抑制率在800℃时最高达41.19%,对硫释放的抑制率在1000℃时最高,为39.89%；两者的抑制率呈负相关。 As-Ca复合物和CaS的形成是砷与硫释放率降低的主要原因；添加CaO后,As-Ca复合物的生成使残渣态砷含量增加,CaS的形成使硫化物结合态砷含量减少。热解后硫元素在CaO表面富集,占据更多的吸附活性位,对砷的固定产生抑制作用；添加CaO后焦中硫仍主要以硫化物的形式存在,亚硫酸盐的含量有所增加。%The pyrolysis experiments of YNZX coal with 10% CaO at 800-1 200℃ were conducted in a high frequency furnace. The effects of adding CaO on the release and transformation of arsenic and sulfur during pyrolysis have been investigated with the aid of sequential chemical extraction, XRD, SEM-EDX, and XPS. The results show that CaO can inhibit the release of arsenic and sulfur significantly. The retention rate to arsenic amounts to 41 . 19% at 800 ℃, and that to sulfur reaches 39 . 89% at 1 000 ℃, there is a negative correlation between the two retention rates. The formation of As-Ca compounds and CaS accounts for the decrease of release rates of arsenic and sulfur. The sulfur is enriched on the surface of CaO, which occupies more active adsorption sites after pyrolysis and inhibits the retention of arsenic, most sulfur is presented as sulfides in char and the amount of sulfites increases after adding CaO.