Energy optimization and economic evaluation of continuous supercritical water oxidation process

Abstract Supercritical water oxidation (SCWO) is an efficient and environmentally friendly technology for treating high‐salinity organic wastewater, yet its industrialization remains constrained by high treatment cost. In this study, a continuous SCWO process was developed and three process models employing air, liquid oxygen, and oxygen‐enriched air as oxidants, respectively, were constructed using Aspen Plus V11. With exergy efficiency as response value, response surface methodology was adopted to optimize key operating parameters such as reaction temperature, pressure, residence time, and excess oxygen coefficient (EOC). An exergy analysis of individual equipment and a comprehensive economic evaluation were subsequently performed under the optimal conditions. The results indicate that the liquid oxygen‐based process achieved the highest exergy efficiency of 60.64% under optimal conditions of 542°C, 23.8 MPa, 47 s, and an EOC of 1.2, outperforming the air‐based and oxygen‐enriched air‐based processes by 17.33% and 11.03%, respectively. The equipment with the greatest exergy loss is HEAT4. It also exhibited the lowest cost of $2,868,216, corresponding to savings of $793,970 and $1,451,164 relative to the air and oxygen‐enriched air process, respectively. Overall, within the defined steady‐state modeling boundary, comprehensive energy optimization and economic evaluation reveals that the liquid oxygen‐based process is the optimal choice.