Activated carbon for mercury control: Implications for fly ash management

Abstract

As more utilities begin to use activated carbon injection (ACI) for mercury control, the potential for the presence of elevated concentrations of mercury, other air toxic elements, and activated carbon to impact fly ash management needs to be evaluated. Several Energy & Environmental Research Center (EERC) projects have allowed the collection of comparative baseline fly ash samples and associated fly ash–activated carbon (AC) samples from full-scale demonstrations of ACI for mercury emission control. These samples were evaluated for mercury and air toxic element content and mobility and for performance criteria to facilitate a better understanding of the impact of these components to specific utilization applications, including use as a mineral admixture in concrete. These data are compared with published data from samples collected at similar large-scale mercury emission control tests. The data presented are in agreement with previous results from the EERC, the U.S. Environmental Protection Agency, and elsewhere that mercury associated with fly ash is stable and unlikely to be released under most management conditions. Additionally, this paper will discuss the potential for fly ash–AC samples to be used as a mineral admixture in concrete and other large-volume use applications.