Impregnated Clay Sorbents for Mercury Removal From Flue Gas

The U.S. Environmental Protection Agency (EPA) has announced its intention to regulate mercury emissions from coal-fired power plants because of mercury¿s impact on the health and development of young children and fetuses. The estimated cost of controlling mercury emissions from power plants runs from $2 to $5 billion annually, with a significant fraction of the total dedicated to activated carbon sorbent, the baseline technology. ADA Technologies, Inc. (ADA), has discovered and tested a new class of mercury sorbents, created by amending inexpensive silicate substrates. The impregnated clay particles will be injected into flue gas streams for mercury control, as a ¿drop-in¿ replacement for activated carbon. Laboratory tests have shown that these sorbents absorb 3¿10 times the amount of mercury as activated carbon and, unlike carbon, they are unaffected by the presence of acid flue gases. The research project will extend this earlier success by using an alternative impregnation process to further increase the capacity of these sorbents. These sorbents will cost less and be more efficient than activated carbon, resulting in savings of hundreds of millions of dollars annually. Furthermore, unlike activated carbon, these silicate-based sorbents do not affect the salability of fly ash for use as a concrete additive. ADA has identified a major power industry services firm that will support a joint venture to market the new sorbent. During this Phase I research project, ADA will generate samples of the new sorbent with different reagents and test their effectiveness in the laboratory, initially in a packed bed with a simulated flue gas. A new test fixture also will be assembled to allow the most promising sorbents to be tested in a colinear gas flow. A new model for the sorption process will be developed and used to evaluate the kinetics of the sorption mechanism. In Phase II, a scaled-up production process will be developed, and pilot-scale demonstrations of the sorbent will be performed on actual coal-fired flue gas streams. ADA¿s commercialization partner will contribute to the development and testing of the sorbent. The U.S. power generation market for mercury control sorbents is estimated by EPA to be in the billions of dollars. Other potential applications include combustion sources in Europe, where mercury regulation is more stringent, and the municipal and sludge incineration markets, where mercury controls already are in place. The ¿drop-in¿ replacement nature of the impregnated clay sorbents makes these existing markets a viable target.