As the World's population continues to grow, technology must be developed to treat wastes of all kinds, and at the same time the energy demand of this increasing population must be met. In both cases waste treatment and energy conversion must be performed with increasing attention to air and water quality on the Earth. Supercritical water (SCW) Systems have the potential to address these problems in an environmentally sound way. Supercritical water oxidation (SCWO) is a promising technology for destroying highly toxic organic compounds present in aqueous waste streams. Capitalizing on the properties of water in the supercritical regime (above 647 K and 22.1 MPa for pure water), spontaneous and rapid oxidation of hydrocarbons is obtained with a very high efficiency, forming water, carbon dioxide, and-depending on the species of heteroatom present in the organic waste--one or more acids. The extreme operating conditions (i.e., the presence of acids under highly oxidizing conditions in SCWO feeds, high temperatures and high pressures), however, require identification and/or development of constructional materials that are capable of withstanding such an environment. This presentation reviews the advantages of the SCWO technology as well as some major concerns related to the selection of constructional materials and to the control of corrosion in this environment. The degradation characteristics of several candidate constructional materials, including iron-, nickel- and titanium-base alloys, ceramics and noble metals are described. In addition, a number of potential methodologies for reducing corrosion damage in SCWO systems are discussed.
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