SUPERCRITICAL WATER OXIDATION - AN EMERGING TECHNOLOGY

Environmental constraints continue to force the chemical-petrochemical industry to seek new technologies to process waste streams. The treatment of dilute aqueous streams containing hazardous organic substances has always presented both technical and economic challenges. The MODAR Supercritical Water Oxidation (SCWO) process meets these challenges. The MODAR process for hazardous waste destruction operates at nominal conditions of 600-degrees-C and 23 MPa. Under these conditions, organic compounds are completely miscible with supercritical water and with oxygen and nitrogen, and can be rapidly oxidized to CO2 and H2O. Inorganic salts, on the other hand, exhibit sharply reduced solubilities, and to a large extent precipitate at reaction conditions. These physical and chemical phenomena lead to an implementation of the MODAR process wherein hazardous wastes are oxidized and inorganic salts are separated in a single reaction vessel. The process is capable of achieving high destruction efficiencies of hazardous organic constituents in excess of 99.99% in a single step. The process precludes the formation of the primary pollutants, NO(x) and SO2, and accommodates in situ acid gas neutralization. The basic chemistry and operating parameters of the process were developed by MODAR, Inc. in bench- and pilot-scale operations. More recently, scale-up issues have been identified and addressed in a cooperative engineering development program between ABB Lummus Crest Inc. and MODAR, Inc. The results of this development program have produced a basis for design of commercial plants. This development program and kev features and concepts of the design are highlighted in this paper.