Hydrodynamics And Mass Transfer Performance Of Banded Structured Catalytic Packing

With the development of computer technology,computational fluid dynamics(CFD)technology is widely used in the development and application of regular packing and random packing,but it is rarely involved in the field of structured catalytic packing.Because of the complexity of the structure of the structured catalytic packing itself,the existing simulation studies mainly through the simplification of the catalyst filling area and then transfer the research focus to the flow field within the mesh member,and do not effectively describe the interraction between the external flow field and the internal reaction mass transfer.And the traditional experimental methods can not clearly observe the internal flow field information of the structured catalytic packing,and can not give a reasonable explanation for the characteristics of fluid mechanics and mass transfer in the local area.In view of the above problems,this article innovatively applies the concept of REU to banded structured catalytic packing,and systematically proposes a CFD simulation strategy.By partitioning the local feature area of structured packing,a REU model set describing the complete packing is established.And combining with experimental results,the microscopic fluid flow,macroscopic hydrodynamic parameters,and local component concentration distribution characteristics in the filler were studied.REUs are established for describing banded structured catalytic packing and applied to single-phase flow studies by ANSYS software.According to the CFD simulation results and experimental measurement results,a new model for the pressure drop calculation of banded structured catalytic packing dry tower is created.The model divides the area of pressure drop loss into the inlet and outlet area,the central standard crossing area,the filling element joint,and the wall area and the influence of the geometric characteristics on the total pressure drop is taken into account.The contribution values of the total pressure drop in each area are determined and they are 44.5%,30.4%,19.0%,and 6.1%,respectively.A three-dimensional gas-liquid countercurrent flow CFD model was established using the VOF method based on a simplified REUs,and an important momentum source terms,surface tension,were considered.Based on the simulation and experimental results,the effects of geometric structure,gas-phase kinetic energy factor and liquid spray density on the liquid film flow characteristics,liquid holding capacity and effective mass transfer area were discussed.The results show that the characteristics of the packing structure and the gas phase kinetic energy factor can effectively enhance the turbulence intensity of the liquid film surface,but the mechanism of the gas phase kinetic energy factor and the liquid spray density acting on the liquid holding capacity and the effective mass transfer area are different.Based on the study of gas-liquid countercurrent flow and the characteristics of the catalytic packing structure,a two-dimensional multiphase flow mass transfer model with chemical reaction is established.The fluid domain was established using the grid splicing technique and the reaction zone was described using the porous media model.The influence of interphase mass transfer and gas phase countercurrent on the internal reaction process and component concentration distribution of the filler was investigated.This article presents a systematic CFD simulation strategy for banded structured catalytic packing.According to the content of the study,the model group formed by the gradual simplification from REUs has the characteristics of less calculation and clear division of feature areas,which can better simulate the influence of macroscopic parameters on the microscopic flow and mass transfer behavior of the filler.That have a certain guiding significance for the design and optimization of banded structured catalytic packing.