Emissions characterization and off-gas system development for processing simulated mixed waste in a plasma centrifugal furnace

Plasma arc technology is a high temperature process that completely oxidizes organic waste fractions: inorganic hazardous and radionuculide waste fractions are oxidized and encapsulated in a highly durable slag. The robust nature of the technology lends itself to application of diverse mixed and hazardous wastestreams. Over 500 hours of testing have been completed at the Department of Energy's Western Environmental Technology Office with a pilot-scale system. This testing was designed to demonstrate operability over a wide range of wastes and provide the data required to evaluate potential applications of the technology on both a technical and economic basis. In addition to characterization of the off gas for typical combustion products, the fate of radionuculide surrogates and hazardous elements within the Plasma Arc Centrifugal Treatment (PACT) system has been investigated extensively. Test results to date demonstrate that cerium, a plutonium surrogate, remains almost exclusively in the slag matrix. Hazardous elements such as chromium and lead volatilize to a greater extent and are captured by the off-gas system. Preliminary design work is underway to develop a minimum emissions off-gas system for demonstration on a engineering-scale plasma unit. The proposed system will filter particulate matter from the hot gas stream and treat them in an electric ceramic oxidizer, which replaces the conventional afterburner, prior to quenching and acid gas removal. Potential future work would use a liquid monoethanolamine system and membrane filter to separate carbon dioxide and nitrogen from the off-gas stream. The remainder of the gas streams primarily oxygen, would be recycled back to the combustion chamber. This paper will provide: 1) a summary of the design, development, and performance of the PACT off-gas system and 2) results of radionuculide surrogate and hazardous element portioning.