Leach Characteristics of Coal-Gasification Char

A methodology is presented for assessing the potential for release of elements from solid waste resulting from gasification of coal and is applied to the case of a coal char formed from the Hygas steam-oxygen process. The char was subjected to both batch and continuous-flow leach tests under a variety of simulated model water types and environmental conditions. Leachates were analyzed for 25 elements. It is apparent that boron was extracted in potentially environmentally significant quantities in every test and that this element should be monitored closely in future environmental assessment studies on coal conversion-process solid wastes. Batch-extraction studies were good indicators of which elements may be leached but poor indicators of total quantities. This study was performed with subbituminous coal char produced at 63% carbon conversion; additional studies are in progress to assess leaching characteristics of bituminous coal char produced at higher carbon conversion.