Improved Sorbent for Removing Mercury from Hazardous Waste Incinerators

Under this Phase II research project, TDA Research, Inc. (TDA) is developing a novel non-carbon sorbent to control mercury emissions from flue gases, hazardous waste incinerators, and coal-fired power plants. The sorbent easily could be injected into the flue gas and recovered in a particulate control device (PCD) along with the fly ash, minimizing capital investment. Unlike the carbon materials used to date, TDA’s sorbent does not alter the properties of the by-product fly ash and render it unsuitable as a cement additive. TDA materials combine an oxidation catalyst/oxidizing agent in the same particle. The catalyst oxidizes the difficult-to-remove elemental mercury to the much easier to stabilize Hg+2. The oxidized mercury then tightly binds to the sorbent. As a result of this dual function, the sorbents have high capacity, good activity, and can work at much higher temperatures because the mercury is tightly bound to the surface. Under Phase I of this research project, TDA demonstrated the technical feasibility of using the non-carbon sorbent for mercury removal. The sorbent achieved a higher mercury capacity than the Norit-FGD carbon, the benchmark sorbent in mercury emission control from flue gases at 150°C (over 2,000 µg/g) in a fixed-bed experimental setup under representative simulated flue gas. Unlike the carbon sorbents, which do not work at higher temperatures, TDA’s formulation also performed well at high temperatures, absorbing 250 µg/g at 245°C. The high-temperature operation capability of the sorbent allows its use on the hot side of an electrostatic precipitator. Under Phase II, TDA will continue to optimize the sorbent formulation and scale up its production. In collaboration with Apogee Scientific, Inc., TDA will demonstrate the performance of the formulation in a pilot-scale flow apparatus using actual flue gas generated by burning Powder River Basin coal. TDA’s commercial partners will assist in the scale-up, evaluation, and commercialization efforts to improve the chances of successful sorbent development. This technology may find immediate use for mercury abatement in hazardous waste incinerators. In addition, the same technology would be applicable to the much smaller application of mercury abatement in municipal waste incinerators and waste-to-energy facilities. These facilities are becoming more prevalent in the United States and are particularly common in Europe, where trouble-prone packed beds of carbon currently are used. Regulated coal-fired power plants account for 60 percent of the electric power generated in the United States.