Study On The Dynamic Behavior Of Gas-Liquid Two-phase Flow And Phenol Biodegradation In Bioreactors

In recent years, the coupled computational fluid dynamic (CFD) model, combining hydrodynamics with biochemical reactions has received increasing interests. However, in current literatures, few models have taken into account the effects of the local hydrodynamics on the dynamic behavior of the bioreaction and investigated the kinetics coupling with hydrodynamics in bioreactors.In order to experimentally investigate the local hydrodynamic performances in the bioreactor, the nanoparticles are used to resemble the biomass, and the Laser Doppler Anemometer (LDA) and conductivity probes are used for measuring the local gas holdup and liquid velocity in a lab-scale gas-liquild-TiO2 nanoparticles three-phase bubble column. A three-dimensional computational fluid dynamic (CFD) model was developed to simulate the structure of gas-liquild-TiO2 nanoparticles three-phase flow in the bubble column. And the time-averaged and time-dependent predictions were compared with experimental data for model validation.For further investigation, the experimental validation of the local hydrodynamic characteristics of the gas-mineral salt solution two-phase system, with the phenol concentration of 1200 mg/L and with the absence of cells, is performed in a bubble column bioreactor and an internal loop airlift bioreactor, respectively. And the model is improved by using the Shear Stress Transport model instead of k-εmodel for turbulence closure. The results indicate that the model simulations have a satisfying agreement with the experimental data. And the local instantaneous flow features are successfully predicted in above two types of bioreactors by the proposed model.And then, the effect of different initial cell concentrations and initial phenol concentrations on the liquid physical properties of the fermentation broth in the processes of phenol biodegradation are experimentally investigated. The cell concentration plays an important role in influencing the liquid physical properties, and with the increasing cell concentration, the apparent viscosity and surface tension of the fermentation broth increase.Finally, the experimental performances about the phenol biodegradation by yeast Candida tropicalis at different initial concentrations of phenol and cell are carried out in above two types of bioreactors. With the increase of initial cell concentration and the decrease of initial phenol concentration, the cell concentration increase and phenol concentration decrease, and the capability of cell to overcome the substrate inhibition...