Optimization method of supercritical water treatment of oily sludge based on double constraints of treatment efficiency and energy consumption

The high energy consumption of supercritical water oxidation (SCWO) technology is a major constraint on its industrial application. Existing studies have predominantly focused on treatment efficiency, lacking energy consumption evaluation methods and optimization of operational parameters based on energy usage. This study experimentally investigates the reaction sensitivity and interactions of temperature, oxidation coefficient, time, and pressure in the SCWO of oily sludge. The results show that temperature has the strongest reaction sensitivity for treatment efficiency, while the effect of pressure can be neglected. Enhancing another operating parameter within any given range of one operating parameter will promote the reaction. Additionally, a dual-constraint reaction prediction model, coupling treatment efficiency with energy consumption, was developed. Results show that temperature not only determines the endothermic heating of the reaction but also influences exothermic oxidation and thermal recovery through its effect on treatment efficiency. The optimal operating parameters for maximum COD removal efficiency (CRE) and minimum energy consumption were found to be T = 766 K, OC= 2.59, and t = 318 s, resulting in a CRE of 99.41 % and a theoretical energy consumption (Q_th) of 85.99 kJ. These findings provide critical insights for the industrial application of SCWO technology in treating oily sludge.