Design of a Small-Scale Supercritical Water Oxidation Reactor. Part II: Numerical Modeling and Validation

The experimental data from the laboratory-scale supercritical water oxidation reactor was leveraged to validate the CFD approach allowing for efficient and accurate modeling of the process. The reactor operating on ethanol as a pilot fuel was modeled using CFD with global oxidation mechanism. Fluid properties were determined using polynomial fit approximations, which yielded excellent agreement with NIST data over a range of temperatures at an isobaric pressure of 25 MPa. The model predicts the fluid temperature within 30°C of measured values for different inlet fuel concentrations. The ethanol decomposition of ~99% occurs within 20% of the reactor length at T~600 °C. The analysis of Damkohler ( Da ) and Reynolds ( Re ) numbers shows that the reactor operates in a distributed reaction region, owing to the excellent combustion stability of the inverted gravity reactor configuration. The modeling approach can aid the design of future more complex SCWO reactors and process optimization.