Assessing sorbent injection mercury control effectiveness in flue gas streams

One promising approach for removing mercury from coal-fired, utility flue g as involves the direct injection of mercury sorbents. Although this method has been effective at removing mercury in municipal waste incinerators, tes ts conducted to date on utility coal-fired boilers show that mercury remova l is much more difficult in utility flue gas. EPRI is conducting research t o investigate mercury removal using sorbents in this application. Bench-sca le, pilot-scale, and field tests have been conducted to determine the abili ty of different sorbents to remove mercury in simulated and actual flue gas streams. This paper focuses on recent bench-scale and field test results evaluating the adsorption characteristics of activated carbon and fly ash and the use of these results to develop a predictive mercury removal model. Field tests with activated carbon show that adsorption characteristics measured in the lab agree reasonably well with characteristics measured in the field. Howe ver, more laboratory and field data will be needed to identify other gas ph ase components which may impact performance. This will allow laboratory tes ts to better simulate field conditions and provide improved estimates of so rbent performance for specific sites. In addition to activated carbon resul ts, bench-scale and modeling results using fly ash are presented which sugg est that certain fly ashes are capable of adsorbing mercury.