A Low-Cost, High-Temperature Mercury Sorbent for Coal-Fired Power Plants

The results of the Phase I project increase the likelihood that the project's new technology will make a major contribution to a healthier world environment. First, the U.S. EPA is introducing mercury-control standards on power plants requiring significant emission reductions from over 1,000 utility coal-fired boilers. A regulatory timetable has now been set, which will lead to the installation of mercury control technologies on these units. Second, an analysis of the measurements supplied in response to EPA's mercury Information Collection Request reveals that the biggest part of the U.S. utility problem is the emission of the elemental form of mercury, which current controls do not capture. During the Phase I project, two discoveries were made that help demonstrate the feasibility of Sorbent Technologies' new duct-injection sorbent approach. First, the new elemental-mercury sorbents were found to work through a chemisorption process. Project experiments showed this to be responsible for high sorbent stability and surprisingly good high-temperature performance. Powdered activated carbons (PACs), the best sorbents currently available, capture mercury primarily through a weak physical adsorption. In fixed-bed experiments at representative utility flue-gas temperatures, the new sorbents demonstrated elemental-mercury capacities ten (10) times higher than typical PACs. With the new technology, it may be possible to achieve net mercury-removal costs that are one-tenth that of current technologies. The second discovery was that the sorbents can be made from commercially available substrate many times smaller than PACs. This would relieve the bulk-gas mass-transfer limitations that many believe inherently constrain PACs from achieving high performance under economical conditions.