Reactive Scrubbing for Mercury Removal and Stabilization

The release of mercury into the environment via combustion processes has become an issue of concern for the US and the entire world. Major sources either are regulated or are under review to develop regulations to reduce emissions. ADA Technologies has successfully demonstrated the performance of a novel reactive scrubbing technology for the removal of vapor-phase mercury from incinerator exhaust gas streams. The technology has two major features; first, it is very efficient in the capture of mercury, and second, the final reaction product is granular solid mercuric sulfide, which is a compact, concentrated form of mercury that is stable under all environmental conditions. Indeed, the final reaction product can be handled as a nonhazardous waste, as it easily passes the EPA TCLP test for mercury leaching. In Phase I, lab-scale tests, over 99% of the vapor-phase mercury was captured in the scrubber, and was successfully converted to a stable mercuric sulfide compound in the secondary waste treatment process. TCLP tests run on the treated waste showed mercury leachate levels well below the 200 part per billion standard of the protocol. An economic model of the scrubber process was created, and used to evaluate the cost of reactive scrubbing applied to and existing hazardous waste incinerator. The model predicted a cost savings for the reactive scrubbing technology of over 28% when compared to current technology of activated carbon injection. The Phase II project will be directed at refining the process through the identification of most cost-effective technologies for specific functions, including separation of reaction product solids and contact of the gas stream being treated with the scrubbing liquid. The secondary treatment process to generate the concentrated mercuric sulfide final reaction product will also be optimized in a series of laboratory tests. These process improvements will be incorporated into a portable pilot-scale reactive scrubber system to be demonstrated on slipstreams of exhaust gas from operating incinerators in the Phase II Option task. ADA has partnered with Aketon Technologies, a subsidiary of CH2M HILL, to commercialize the reactive scrubbing technology. Aketon will participate in the Phase II design of the portable pilot-scale system, and has the expertise and market presence to deliver scrubber systems to customers. ADA will provide technical support to this partnership to optimize the operation of the reactive scrubbing technology for a range of applications.