Wet air oxidation: a review of process technologies and aspects in reactordesign

Wet air oxidation is one of the available technologies for the treatment of aqueous wastewaters. In wet air oxidation aqueous waste is oxidized in the liquid phase at high temperatures (400-573 K) and pressures (0.5-20 MPa) i n the presence of an oxygen-containing gas (usually air). The advantages of the process include low operating costs and minimal air pollution discharg es, while the main limitations are the high capital costs and safety implic ations associated with a system operating at such severe operating conditio ns. As a consequence, significant development in wet air oxidation technolo gy has concentrated on methods of reducing the prohibitive capital costs. I n the design of the process a balance must therefore be made between the en hancement of overall reaction rates with temperature and pressure against t heir effect on capital cost and operational difficulties such as corrosion and scaling of equipment. In this paper the wet air oxidation process is in troduced and a number of commercial and emerging technologies presented. Th ese technologies employ a variety of methods to ameliorate the limitations of the technology whilst maintaining acceptable overall reaction rates. The se include methods to improve mass transfer as well as the use of both homo geneous and heterogeneous catalysts to enhance reaction rate. (C) 1999 Else vier Science S.A. All rights reserved.