Fluid Flow And Mass Transfer Performance Of A Rotating Packed Bed Reactor With Structured Packing

A rotating packed bed(RPB)reactor,known as Higee(high gravity)device,was one of novel chemical devices.The mass transfer and micromixing of an RPB reactor can be up to 1?3 orders of magnitude larger than that of a conventional packed column,exhibiting prominent process intensification characteristics.The fluid flow and mass transfer performance as important parameters of the reactor,which need to be studied in depth.With the development of computers,computational fluid dynamics(CFD)formed by the intersection of mathematics,fluid dynamics and computer science.CFD is a useful tool for simulation and analysis of fluid flow,mass transfer,heat transfer,and chemical reaction.The rotating packed bed(RPB)reactor has the complex packing structure as the packed column and the rotational motion as the rotational equipment,there are some progresses of the RPB reactor CFD simulation.Previous studies all based on the method to simplify the geometrical structure of packing.While,it is hard to simulate the fluid flow inside the RPB reactor accurately with the detail structure of packing.In this work,CFD simulation and experimental verification are carried out for the fluid flow and mass transfer performance of RPB reactor with structured packing.Firstly,Element array and computed tomography(CT)reconstructed method were applied to modeling the RPB reactors with wire mesh structured packing and nickel foam structured packing.The gas and liquid flow inside the RPB reactor with structured packing were predicted via CFD simulation and verified via high speed photograph visual study.The gas side end effect was predicted and verified.A novel mass transfer model base on numerical simulation were proposed and verified by mass transfer experiment.Main conclusions are as following:(1)Two typical method for modeling the packing structure,element array and computed tomography(CT)reconstructed method,were proposed.Based on these two method,wire mesh packing and foam packing were built,which provided geometrical information for CFD simulation.(2)3D geometrical model of RPB reactor with structured wire mesh packing was built.The realizable k-? model is applied to investigate the gas pressure drop,pressure distribution,and gas flow at different rotational speeds and gas flow rates.Based on the breakdown of the overall gas pressure drop,the gas pressure drop in the inner cavity zone is the major contributor to the overall gas pressure drop under most operation conditions.The 3D physical model describing the actual RPB reactor can give deep understanding of the gas flow in the entire RPB reactor as well as the gas flow behavior around every fiber of the packing.Furthermore,one special phenomenon of strong turbulence,named as gas-side end effect,was revealed in the outer annular packing zone in the rotor.(3)The liquid phase distribution and flow pattern in the packing zone of RPB reactor were systematically observed by means of visual study.Three typical flow patterns,droplet flow,ligament flow,and film flow,were discovered.Fluid domain and simulation strategy for CFD simulation were reasonably selected based on the result of visual study.The flow pattern and the size of liquid micro-element predicted by simulation and overserved by visual study were compared and verified with the overserved by visual study.The liquid holdup of packing zone of this RPB reactor was 0.002?0.02,which was predicted by simulation.(4)The liquid holdup and fluid flow in a RPB reactor with nickel foam packing were studied by CFD simualtion.The Reynolds stress model with Eulerian approach and the large eddy simulation with volume-of-fluid approach were implemented.Two liquid flow patterns of droplet and film flow were predicted to develop inside the packing zone as these were experimentally observed and confirmed by a high-speed camera.Besides,liquid flow in the outer cavity zone of the RPB reactor with nickel foam packing was also studied by simulation and verified by visual study.A visual study method,called"Sudoku" with eight shooting windows,was employed to capture the liquid flow of different zones in imaging experiments.Simulation results of liquid droplet velocity agreed well with the experimental results within a deviation of±10%.(5)Based on result of CFD simulation,the ratio of droplets for liquid were calculated.A mass transfer model based on numerical simulation was proposed with the surface renewal theory.The liquid volume mass transfer coefficient kLa was predicted and measured.The relative errors between predicted and experimental kLae was±25%.