Effects of adding CaO on the release and transformation of arsenic and sulfur during coal pyrolysis

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.