Dynamic simulation and predictive control for supercritical water oxidation reactor using reactor network model

Abstract

Supercritical water oxidation (SCWO) reactor is crucial for hydrogen production through autothermal gasification, where hydrogen oxidation provides heat for supercritical water gasification. However, the dynamic behavior and control strategies of industrial-scale SCWO reactors remain insufficiently explored. A computationally efficient reactor network model was developed to address this. Cold start and open-loop dynamic simulations were conducted to investigate the effects of variations in inlet gasification product mass flow rates, gasification product temperature, and oxygen mass flow rate. Results indicate that the fluid temperature stabilizes within 2 min, while the wall temperature takes approximately 1.1 h. Under slow disturbances, the outlet temperature exhibits quasi-static characteristics. The oxygen mass flow rate significantly influences reactor performance, and a dynamic matrix control (DMC) scheme using it as the control variable is designed to regulate the outlet temperature. The oxygen mass flow rate changes from 450.54 kg/h to 392.25 kg/h and 509.59 kg/h with outlet temperatures set at 850 °C and 950 °C, respectively, within 180 s. A comparison of disturbance rejection performance between DMC and PID controllers reveals that DMC responds faster and reduces overshoot, demonstrating superior performance. This study provides insights into the dynamic behavior and operational flexibility of SCWO reactors in engineering applications.