Mercury is a toxic pollutant whose presence in the environment results in large part from coal combustion and incineration of mercury-containing wastes. The known harmful effects of environmental mercury on humans particularly infants and children, have prompted new regulations in the U.S. limiting mercury emissions from combustion sources. In order to reduce the level of mercury released by coal-burning electric generating units, sorbents are being tested which adsorb mercury. A central requirement of any mercury removal process involving such sorbents is the establishment of thorough, intimate contact between the sorbents, typically in powder form, and the mercury-containing combustion gases.

Injecting the powdered sorbents into the gas stream upstream of a fabric filter forms a fixed adsorption bed as the sorbent accumulates on the filter, offering thorough contact between the treatment gas and the powdered sorbents. Unfortunately, fabric filters are rarely found on U.S. power plants and can be prohibitively expensive to install if they induce too large a pressure drop in the gas stream.

The objective of my research is to conduct proof-of-concept testing of an alternative approach called a virtual sorbent bed using a bench-scale prototype. A virtual sorbent bed capitalizes on the prevalence of electrostatic precipitators installed on U.S. coal-fired power plants, using the existing particle charging and electric field aspects of ESP operation as the foundation for a complementary process in which gas-particle mass transfer is greatly enhanced as a component of the electrostatic precipitation process. As a result, virtual sorbent bed technology (VSB) , if installed within an existing ESP, would enhance the removal efficiency of mercury as a co-benefit of standard ESP operation for fly ash capture from the flue gas. Significantly, this co-benefit and performance enhancement could be realized irrespective of the type of sorbent used, including native fly ash that exhibits significant capacity for mercury adsorption.

Currently, bench-scale testing of the VSB concept is underway.