Effect of hydrothermal flame generation methods on energy consumption and economic performance of supercritical water oxidation systems.

Hydrothermal flames are critical to solving preheating problems and enhancing feed degradation in supercritical water oxidation (SCWO) systems. In this work, different hydrothermal flame generation methods including hot water injection, evaporation concentration, and addition of auxiliary fuel are proposed for SCWO of cutting fluids. The proposed systems are simulated using Aspen Plus 8.2, and the simulation model is validated by comparisons with experimental temperature profiles and product properties. A low ratio between the heat source flow and the feed flow (FR) requires a high heat source temperature to keep the hydrothermal flame stable and results in a high electricity consumption, and FR = 2 is chosen as the optimum condition for the SCWO system with hot water injection (SCWOH). The increase in concentration ratio and fuel concentration can effectively reduce the energy consumption for the SCWO systems with evaporation concentration (SCWOE) and addition of auxiliary fuel (SCWOF), respectively. The exergy analysis results indicate that most of exergy inputs are destructed inside the system, and the exergy distribution coefficients of the reactor exceed 80% in the SCWOE and SCWOF. Economic analysis results show the SCWOE has the lowest treatment cost of 95.9 USD/t. • Different hydrothermal flame generation methods for SCWO are proposed and simulated. • A low FR results in a high heat source temperature and electricity consumption. • Increases of concentration ratio and fuel concentration effectively reduce energy consumption. • Exergy distribution coefficients for the reactor exceed 80% in the SCWOE and SCWOF. • The optimal case of SCWOE has the lowest treatment cost of 95.9 USD/t. [ABSTRACT FROM AUTHOR]