The CFD Simulation Of Internal Flow Field In Spinning Band Column

Application of spinning band column(SBC)can be traced back to earlier last century to efficiently separate unusual mixture under high vacuum and liquid state. SBC is a specific type of distillation apparatus, which spins a band throughout a major portion of the length of the column, in order to achieve better mixing and contact of the falling liquid and the rising gas. With the development of high vacuum technique, application and research on spinning band column are carried out more and more deeply and widely. However, theoretical research on SBC is very little. Computational fluid dynamics (CFD) simulation belongs to an innovative method of studying spinning band distillation process.CFD simulations with software Fluent6.2 were mainly accomplished to study flow field of SBC, and an experiment of residence time distribution in SBC was also completed to observe distribution of liquid phase and obtain qualitative conclusions. According to these conclusions and phenomenon, simulating results were evaluated and verified. What's more in this paper, study on gas/liquid flow was concentrated on the liquid distribution in the cross-section, flow state of the film and gas/liquid velocity field.Taking advantage of CFD simulating software, based on three hypotheses to simplify modeling and computation process, mathematic theoretic models were built in three dimensions and pure fluid dynamics simulations were executed of gas/liquid flow in the spinning band column under atmospheric temperature and pressure. Realizablek ?εturbulent model is used to simulate gas-liquid flow generated by the spinning band. At the same time, volume of fluid (VOF) was also built to track the liquid film flow on the wall of column as well as enhanced-wall function method to further deal with near-wall flow.With respectively changing the rotate speed, gas/liquid velocity, liquid film flow state on the wall was simulated as well as velocity field. Simulating results show that surface area of the liquid film on the wall is enlarged with increase of rotate speed and rate of feed, and then its mass and heat transfer process are enhanced. And the gas velocity influenced the liquid film flow state little, when the band was rotated.The simulated field of concentration of liquid phase was presented. Simulations for average residence time were consistent with experimental data at different rotate speeds and rates of feed. This proved that the results of simulation were effective.Furthermore, Eulerian multiphase model was also applied to study gas/liquid velocity field. As the spinning band rotation speed increases (rotate speed >1000rpm), the gas/liquid flow field shows that there is a separated interface between gas and liquid phases. This phenomenon is not good for gas-liquid intimate contact. The band structure was ameliorated, results show that the separate interface between gas and liquid phase diminish even at a high rotate speed.