Simulation And Research Of Airlift Internal Loop Bioreactor With Fluent

The continuous three-phase airlift internal loop bioreactor was simulated with computational fluid dynamics in this paper,which included the simulation of flow hydrodynamics,the degradation of phenol and the performance of the reactor under different parameters.First,based on the Euler three-phase model,the RNG k-? turbulence model was used to close the constitutive equations.Then considering the drag force,one of the interphase forces,three drag models was applied to simulate and the most suitable momentum exchange coefficient in the momentum equation was determined.Based on the two-film theory model and Higbic penetration theory model,the mass transfer model of oxygen between air phase and liquid phase was established.The specific degradation rate of phenol in the reactor was determined considering the Monod equation and Haldane inhibition mechanism model.According to Rittmann smooth surface biofilm desorption model,the total loss coefficient of biofilm was calculated.Then the source term of phenol conservation equation was determined and the mathematical model of flow hydrodynamics and the degradation of phenol in the continuous three-phase airlift internal loop bioreactor was established.In this paper,the start stage of the reactor was simulated in 180 seconds.Some solid particles still stayed in the bottom of the reactor when aeration rate was 5.59L/min.All solid particles stayed in the riser of the reactor when aeration rate was 10.2L/min.The solid particles become more homogeneous in the reactor and need less time to become suspended when aeration rate was 15.43L/min and 20L/min.According to the simulation of liquid velocity in the downcomer,gas holdups in the reactor and the phenol diffusion process,the mathematical model of flow hydrodynamics in the reactor was verified.Then the local transient hydrodynamic properties were simulated,which involved radial distribution of gas holdups,liquid velocity and turbulent kinetic energy in the reactor.According to the simulation of oxygen iquid volume transfer coefficient and the phenol uptake rate,the mathematical model of the degradation of phenol in the reactor was verified.It was found that the gas holdups and liquid velocity increased with increasing aeration rate when the performance of the reactor was simulated with different aeration rates,and increasing rate reduced when aeration rate exceeded 15.43L/min.It was conformed that the performance of the reactor was better when the aeration rate was 15.43L/min.Gas holdups and liquid velocity increased with decreasing solid density when the performance of the reactor was simulated with different solid densities.It was found that the performance of the reactor was better when the solid particle was 0.6mm.When the performance of the reactor was simulated with different solid volumes,it was conformed that the values of gas holdups and liquid velocity were bigger,and the performance of the reactor was better when the solid volume was 1L.