Supercritical water oxidation as a technology for the treatment of model and industrial wastewaters: reaction kinetics and reactor configurations

[摘要] This work investigates the advantages of a multi-stage supercritical water oxidation (SCWO) reactor over a single-stage configuration in treating dimethylformamide (DMF), a model compound representing nitro-organic wastewaters. Single-stage SCWO of complex wastewaters was also investigated. A PFR rig was designed and constructed to investigate reactor temperature, initial DMF concentration, stoichiometric ratio, residence time and oxidant distribution effects on component yields. Reaction temperature was the critical variable for treatability; T>500\(^0\)C caused near-complete DMF/TOC removal at relatively short residence times (approx. 6 s). DMF SCWO displayed Arrhenius-type kinetics, and the DMF (1) and O\(_2\) (0.36) reaction orders, activation energy (140 kJ mol\(^-\)\(^1\)) and pre-exponential factor (1x10\(^1\)\(^2\) M\(^0\)\(^.\)\(^3\)\(^6\) s\(^-\)\(^1\)) were evaluated. Certain injection configurations resulted in higher TOC removals than single-stage, particularly when the second injection occurred at 0.5L and delivered 50 – 67% of the oxidant, although ammonia yield exceeded those in single-stage SCWO at these points. Single-stage SCWO outperformed a small number of configurations. T>500\(^0\)C was shown to be suitable to treat complex wastes. Complete conversion of TOC to products likely occurs within 10\(^2\) s. It was seen that TOC value alone may not be a suitable input when attempting to determine treatability in SCWO and that composition must also be considered.

[发布机构] University:University of Birmingham;Department:School of Chemical Engineering

[关键词] T Technology;TP Chemical technology