Effects of mercury emission control technologies using halogens on coal combustion product chemical properties

Fly ash and spray dryer absorber (SDA) material samples collected during mercury emission control technology tests that incorporated the use of halogens were evaluated for select chemical composition and leachability. Corresponding samples were also collected under standard operating conditions and examined using the same protocols. Included in these evaluations were pH and total and leachable concentrations of the mercury control technology (MCT) halogen of interest (Br, Cl, or I) and Hg, As, Cr, and Se. The use of a MCT using halogens decreased the pH values of coal combustion products (CCPs) collected in fabric filters compared with that of the corresponding standard CCPs. In many cases, the total As, Cr, and Se concentrations were similar between the standard and MCT test CCPs. However, at least a slight increase in total Se was noted in each sample set from the standard to the MCT test CCPs. Short-term leaching was performed on all samples, and long-term leaching was performed on most highly alkaline samples. On the basis of percentage of maximum leachability, the MCT additive halogens were more mobile than the other elements evaluated. The Hg in fly ash and SDA material samples was stable. Generally, more As and Se leached from the MCT test CCPs than the standard CCPs. Cr leachate results were more variable. The data indicate a need to further examine the effects of MCT using halogens applications on CCPs.