Reaction mechanism and kinetics of oil-bearing sewage disposal by supercritical water oxidation

The conventional treatments are unable to effectively remove the chemical oxygen demand (COD) of waste water produced during oil extraction, and thus, it has seriously threatened the environment and the normal production of oil-field. An advanced method for oil-bearing sewage treatment, supercritical water oxidation (SCWO), was proposed. The oxidative degradation was investigated and the process of SCWO was explained with mechanism of free radical reaction. The experimental results show that SCWO is a high-efficiency treatment and disposal technique for organic wastes. Temperature and residence time serve as the main influence factors in removing COD of oil-bearing sewage, with which the COD removal rate obviously increases. The reaction of SCWO is 1.62 order in sewage COD and 0.22 order in oxygen, the frequency factor and activation energy are (3.53±3.33)×10³ and (92.2±9.9) kJ·mol^-1 under 26 MPa, respectively. The deviation between the model and experimental data is ranged within ±10%. The existing problems in the process of SCWO and the possible solutions are discussed.