Supercritical water oxidation (SCWO) for the removal of nitrogen containing heterocyclic waste hydrocarbons. Part II: System kinetics

Abstract

This work investigated supercritical water oxidation (SCWO) of DBU (C9H16N2)11(1,8-Diazabicyclo[5.4.0]undec-7-ene) in the absence and presence of isopropyl alcohol (IPA) as co-fuel. SCWO was studied in a plug-flow reactor under different temperatures (400–525°C), initial DBU concentrations (1–10mM at reactor conditions), oxidant ratios (0.8–2), and [IPA]0/[DBU]0 ratios (0.5–4). Pseudo First Order and the Global Power Law models expressed the kinetics, and the rate constants were evaluated. Furthermore, SCWO of aqueous ammonia (NH4+) as feedstock was studied at several temperatures (400–500°C), oxidant ratios (0.8–2.0) and [IPA]0/[NH4+]0 ratios; and the same kinetic models were applied. Results showed that IPA addition increased the reaction rate constant k, affected oxidant utilisation, and greatly enhanced NH4+ removal% towards gaseous nitrogen. The influence of IPA addition was more pronounced on N-speciation than it was on TOC% removal, for all current system conditions.