Numerical analysis of mixing performance in Y-junction mixers and its impact on yields from supercritical water hydrolysis

• Published in: The Journal of supercritical fluids 2025-01, Vol.215, p.106425, Article 106425
• Main Authors: Kim, Gyudong, Kim, Sooin, Jeong, Hanseob, Chung, Jaewon
• Format: Article
• Language: English
• Subjects: Discrete phase model; Richardson number; Supercritical water hydrolysis; Y-junction mixer; Yield: Large Eddy Simulation
• ISSN: 0896-8446
• DOI: 10.1016/j.supflu.2024.106425

This study investigates the mixing behavior in a Y-junction mixer for supercritical water hydrolysis using large eddy simulation with a discrete phase model. Yield changes were simulated using a two-step reaction model with first-order kinetics, based on particles’ temporal temperature data. Effective mixing produced closely matched mass and particle flow temperature distributions, both exhibiting bell-shaped profiles near the mixed temperature. Although variations in flow rate within ±25 % and changes in the inlet temperatures of supercritical water from 350 °C to 430 °C and subcritical water from 100 °C to 170 °C did not significantly affect the overall mixing performance, they did alter the mixed temperature and, subsequently, yield changes. Additionally, backflow occurred when Richardson number for the subcritical inlet reached approximately 7. In effective mixing, simulated yields were approximately 15 % lower than the ideal theoretical yields, calculated using the reaction rate constant at the mixed temperature. [Display omitted] •Numerically analyzed Y-junction mixing using LES with DPM.•Close match in mass and particle temperature distributions under effective mixing.•Employed two-step reaction with first-order kinetics to simulate yield changes.•Simulated yields approach ideal theoretical values under effective mixing.•Validated Richardson number as an important indicator for backflow occurrence.