Numerical simulation of gas-liquid two-phase flow in the N2-acetic acid system under elevated pressures and temperatures based on CFD-PBM model

The oxidation reaction process of p-xylene is studied under elevated pressure and temperature conditions using acetic acid as a solvent. In this study, a numerical simulation is employed, coupling Computational Fluid Dynamics (CFD) with Population Balance Modeling (PBM), to investigate the hydrodynamic behavior of gas holdup in the column of the N2-acetic acid system. The effects of superficial gas velocity, temperature, and solid holdup on the hydrodynamic behavior of the gas holdup in the column are discussed at the system pressure of 1.0 MPa, the superficial gas velocity ranging from 0.11 m/s to 0.27 m/s and the temperature between 25 degrees C and 105 degrees C. In addition, a comparison is presented with the gas holdup of the air-water system. The results indicate that the simulated gas holdup aligns with the experimental value within the +/- 10% error range. Furthermore, the gas holdup increases with the increase of temperature and superficial gas velocity, while decreases with an increase in solid holdup. Additionally, the gas holdup in the N2-acetic acid system was found to be higher than in the airwater system. The research results of gas holdup and other hydrodynamic parameters in the N2-acetic acid system can offer valuable insights for the design and scale-up of the bubble column oxidation reactor.