Sequestration and Separation of Mercury in Wet Flue Gas Desulfurization Systems

Mercury regulations passed by the EPA will require stringent mercury emission control from wet flue gas desulfurization scrubbers, used in the production of electricity from coal. The first problem is that a portion of the mercury captured by the wet scrubber is re-emitted. The second problem is that FGD by-products, including gypsum, will increase from 31 million tons in 2004 to 86 million tons by 2020. Therefore, the continued regulatory characterization of FGD by-products as non-hazardous will be a critical factor for their marketability for beneficial end-use, such as wallboard, as well as for disposal. This project addresses these problems by using novel additives in the scrubber, both to prevent mercury re-emission and to form physically separable and stable products with these additives, which will allow the mercury to be sequestered from remainder of the FGD solids. Phase I will perform a bench-scale study to identify technically effective additives. Phase II will determine additive usage and costs, identify methods to manufacture these additives, and design full-scale hardware for technology implementation. Commercial Applications and other Benefits as described by the awardee: The technology should minimize mercury emissions into the environment and enable mercury-free FGD byproducts to be generated, which can be used safely in end-applications such as wallboard. The impact of the technology should be significant, because it is projected that two-thirds of U.S. coal-fired power plants will have wet FGD scrubbers and more than 50 percent of U.S. electricity production is from coal firing.