Multi-scale Simulation Of Novel Porous-foam Tray And Structured Packing

Since porous foam has so many excellent performances, such as high porosity, large specific surface area, controllable pore size, et al., it was applied to the distillation tower in our team. New types of fixed tray and corrugated structured packing were developed with porous SiC foam. In view of the flow in these novel tower internals belonging to porous/fluid coupled flow field, physical model used in this paper was constructed in both macro- and micro-scale. Moreover, appropriate models for multiphase flow and porous media were established for the multi-scale simulation.As for the macro-scale simulation of the fixed tray and structured packing made of porous SiC foam, physical models were formed by ignoring the real skeleton structure of the foam. Instead, the porous pieces of the tray and the porous corrugated sheets of the structured packing were solved with porous media model. Two different types of porous media model in form of Forchheimer’s function were used in this paper, and their accuracy was determined by comparison of the simulation results and the experimental data. The simulation results for single gas phase flow were used for the analysis of the composition of dry tower pressure drop and its influencing factors. For the two phase flow modeling, Eulerian-Eulerian multiphase flow model was applied for the tray, while the VOF model was used for the packing by considering the effect of surface tension. In addition, the Eulerian-Eulerian model was closed by introducing Grace’s drag force model. The verification of these models and modeling methods were completed by comparing the results from both simulations and experiments. Then, the modeling results could be used to study the porous-SiC-foam fixed tray and structured packing about their macroscopic flow field, hydrodynamic performance and the influence from their structural parameters.The flow field distribution and the calculation of certain properties acquired from macro-simulation were not accurate enough because of ignoring the real skeletal structure of porous foam. Accordingly, the skeleton structure of the porous SiC foam was idealized as an array of tetrakaidecahedron elements for the micro-simulation. As for the micro-scale simulation of porous SiC fixed tray and structured packing, physical model was formed by cutting the array and multiphase flow model was the same as these used in macro-simulation. The verification of the micro-simulation was completed by comparing its results with the derivation of experimental data. The microscopic flow distribution characteristics and the effect of the micro-structural parameters and operating conditions were investigated from analysis of micro-simulation results. Moreover, the wettability of porous foam was also considered for the microscopic flow field.On one hand, the simulation results in this paper can be used for in-depth research and analysis of the flow and mass transfer mechanism in the porous SiC tower internals, and can also provide theoretical support for structural optimization of the internals. On the other hand, the establishment of physical models, the determination of appropriate multiphase flow models and the usage of multi-scale simulation strategies are very helpful for the study of other tower internals including porous materials.