The Numerical Simulation Of Hydrodynamics In A Pressurized Bubble Column Based On Interphase Forces Model

The commercial bubble column reactors are normally operated under the conditions of pressurized state and churn turbulent bubbly flow which the superficial gas velocity always exceeded 0.1 m·s^-1.Hitherto,most of the existing research is focus on that the empirical or semi-empirical correlations to quantitative estimate the characteristic parameters and it is lack of systematic study on the flow characteristics in the pressurized bubble columns.Therefore,it is necessary to study on the turbulent pressurized bubble columns.In this work,a steady 2-D axisymmetric hydrodynamic two-fluid model of pressurized bubble column,was developed on the basis of FLUENT 15.0academic version combined with several UDF sub-models.Meanwhile,the numerical investigation upon the flow field characteristics of pressurized churn turbulent bubble column with the operation pressure varying from 0.5MPa to 2.0 MPa,and superficial gas velocity from 0.199 m·s^-11 to 0.317 m·s^-1.Furthermore,the comparisons between simulation results（Qin,2012）and cold model experimental data were implemented.The paper mainly includes the following three parts:（1）This paper systematically analyzed the influence of single bubble drag force model,bubble swarm drag force model,bubble swarm lift force and turbulent diffusion force equilibrium model and wall lubrication force model,upon the flow field characteristics of pressurized churn turbulent bubble column in well-developed flow region.The result indicates that the model with the bubble swarm interface forces including improved bubble swarm drag force model,lateral force balance model,and wall lubrication force model,is able to accurately describe the radial distribution of time averaged flow field characteristic parameters.（2）This paper simulated pressurized bubble column using the CFD model,and studied the effect of superficial gas velocity and operating pressure on flow field,and the result indicates that the model is able to reflect the influences of operation pressure and superficial gas velocity upon flow pattern and the average gas holdup absolute error value is less than 4%.The result indicates that the elevating operation pressure leads to increase of time averaged gas holdup,and decrease of time averaged gas phase velocity and axial liquid velocity,whereas for the ascending superficial gas velocity,the time averaged gas holdup,gas phase velocity and axial liquid velocity are all raising.（3）A CFD-PBM coupled model was developed by introducing bubble population balance model（PBM）based on the above model.Then this paper simulated pressurized bubble column using the coupled model,in which a model correction factor was introduced to reflect the effect of operating pressure,in bubble coalescence efficiency item,based on Luo bubble coalescence kernel model,and radial bubble diameter distribution in simulation is in good agreement with the experimental data,meanwhile the average gas holdup absolute error value is less than 3%.