Release Behavior of As, Hg, Pb, and Cd during Coal Gasification

The release behavior of As, Hg, Pb, and Cd in Yima during coal gasification was investigated in a fixed-bed reactor. Their modes of occurrence in coal and residues after gasification were determined by XRD and sequential chemical extraction. Pb is mostly associated with mineral matter formations in parent coal. A large proportion of Cd and As is stably associated with organic matter and sulfides. Hg is mainly that of being bound to organic matter but could be easily changed during coal gasification. It is found that bleeding ratios of As, Hg, Pb, and Cd increased with an increase of the gasification temperature, especially for Pb and As under CO2 atmosphere at high temperature. Among the toxic trace elements studied herein, Hg and Cd were found to be more volatile and enriched in the gas phase while Pb and As were mainly relegated to the solid phase during coal gasification.