Sorbent injection for mercury control is one of the most promising technologies to reduce mercury emissions from power generation facilities, particularly units that do not require wet scrubbers for SO_2 control. Since 1992, EPRI has been assessing the performance of mercury sorbents in pilot-scale systems installed at full-scale facilities. The initial tests were conducted on a 5000 acfm pilot baghouse. Screening potential sorbents at this scale required substantial resources for installation and operation and did not provide opportunity to characterize sorbents over a wide temperature range. Data collected in the laboratory and in field tests indicate that sorbents are affected by flue gas composition and temperature. Tests carried out in actual flue gas at a number of power plants have also shown that sorbent performance can be site specific. In addition, data collected at a field site is often different from data collected in the laboratory with simulated flue gas mixed to match the major components in the site's gas. To effectively estimate the costs of mercury sorbent systems at different plants, it is necessary to obtain a measure of sorbent performance in the respective flue gases. Injection testing at multiple facilities with a large pilot system is not practical, however. Over the past five years, fixed-bed characterization testing, modeling studies, and benchscale injection testing has been undertaken to develop a low-cost technique to characterize sorbent performance in actual flue gas and to subsequently project normalized costs for mercury removal prior to full-scale demonstration. This paper describes the techniques used and summarizes field-testing results from two plants burning Powder River Basin (PRB) coal for commercial activated carbon and several other sorbent types. Full-scale projections based upon the results and data collected on larger-scale systems are also included.
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