Mass Transfer–Reaction Model for Sodium Sulfide Wet Air Oxidation and Reactor Optimization

ABSTRACT This study presents a multiphase transfer–reaction model integrating reaction kinetics, hydrodynamics, and gas–liquid mass transfer to simulate sodium sulfide's non‐catalytic (WAO) and catalytic (CWAO) wet air oxidation in bubble column reactors. Developed to optimize reactor parameters under 373–423 K and 3.28 MPa, the model addresses high chemical oxygen demand (COD) in petrochemical spent caustic. For WAO, a 1.6 m‐diameter, 12.5 m‐high reactor with 0.04 m/s superficial gas velocity achieves 95% COD degradation at 423 K. FeSO 4 ‐catalyzed CWAO reduces reactor size, shortens residence time (same efficiency), and boosts oxygen utilization. Compared with computational fluid dynamic (CFD)‐reaction coupling, this empirical model cuts computational cost while retaining accuracy, fitting industrial scale‐up. This study provides a sustainable framework for the design of spent caustic oxidation reactors, balancing environmental compliance with process efficiency.