ENVIRONMENTALLY CRITICAL ELEMENTS IN CHANNEL AND CLEANED SAMPLES OF ILLINOIS COALS

Sixteen trace and minor elements that occur in coal are listed among 1 89 substances identified as 'hazardous air pollutants' (HAPs) in the U S Clean Air Act Amendments of 1990. We investigated the occurrence and cleanability of the 16 HAPs in Illinois coals, as a contribution to t he discussion about the potential effect of pending environmental regu lations on the future use of these coals in power generation. The aver age ash content of the samples of conventionally cleaned as-shipped co als is about 20% lower than that of standard channel samples. Conventi onal cleaning reduces the average concentrations of As, Cd, Co, Hg, Mn , Ni, Ph, Sb and Th in the as-shipped coals by more than 20% relative to channel samples. Thus, basing assessments of health risks from emis sions of HAPs during coal combustion on channel samples without approp riate adjustment would overestimate the risk. Additional cleaning by f roth-flotation reduces the ash content of finely-ground as-shipped coa ls by as much as 76% at an 80% combustibles recovery. Although the ave rage froth-flotation cleanability for the majority of HAPs is less tha n that for ash, the cleanabilities in some individual cases approaches , or even exceeds, the cleanability for ash, depending on the modes of occurrences of the elements. (C) 1997 Elsevier Science Ltd.