Mercury vapor control by means of corona discharge

The work reported here describes the construction and performance of a novel corona discharge flue gas reactor designed to oxidize mercury vapor, allowing the mercuric oxide to be subsequently captured in a downstream particulate control device. A corona discharge in flue gas produces oxidizing radicals, such as OH and atomic oxygen, which can then react with elemental mercury. Optimum performance demands that the corona discharge, and hence the oxidizing radicals, be uniformly distributed within the flow volume of the reactor. When a uniform volume distribution of electrons is achieved, then uniform exposure and treatment of the gas is assured, and maximum energy efficiency can be obtained. By means of a laboratory based, pilot scale system, it is shown that the spatially distributed corona discharge produced by the corona reactor operating at low power level and short residence time yields a high level of mercury vapor oxidation. The mercuric oxide, in the form of solid particles, can then be removed by a conventional electrostatic precipitator or fabric filter. It is also shown that low temperature, high humidity conditions enhance mercury oxidation. For an application to solid waste incineration, this suggests the placement of the reactor downstream of the spray dryer andmore » upstream of the fabric filter. Economic analysis indicates that this method of mercury vapor control is very competitive with adsorption by activated carbon. For example, if mercury control regulations are promulgated for coal burning power plants, the corona discharge technology could potentially save the US utility industry and electricity consumers up to 250 million dollars per year. 10 refs., 6 figs., 2 tabs.« less