Hydrodynamics And Mass Transfer Of Rotating Packed Bed Under Floating Conditions

The strategic significance and economic competitiveness of offshore exploration have become increasingly prominent,with the exploration of most onshore oil and gas fields entering the late stage.However,due to the high cost and limited production space of floating platforms,process intensification technology is needed to achieve devices miniaturization.As a typical process intensification device,rotating packed bed（RPB）has been applied in many separation processes such as natural gas desulfurization,dehydration and seawater deoxidation.The device volume can be 1-2 orders of magnitude smaller than that of the traditional packed bed.However,the effects of floating motions on the hydrodynamic and mass transfer characteristics of RPBs are still unclear.Therefore,hydrodynamic experiments,computational fluid dynamics（CFD）simulation and theoretical model were adopted in this study to investigate the transfer characteristics and process intensification mechanism of RPBs under floating conditions.The hydrodynamic and mass transfer characteristics of the floating RPBs are studied in detail.The influence law of motion characteristic parameters and multiple degrees of freedom（DOF）on transfer characteristics in RPB was investigated,and the influence mechanism of floating motions on hydrodynamic and mass transfer characteristics was revealed.The numerical simulation methods of gas-liquid flow in the RPB under multi-DOF motions were established.This study provided theoretical support and scientific guidance of RPBs in ocean engineering applications.The main research contents are as follows:1.The gas flow characteristics within the RPB under floating conditions were investigated.The pressure drop characteristics of the gas phase under floating conditions were investigated experimentally.The pressure drop in the floating condition is generally smaller than that in the stationary condition with periodic fluctuations.The evolution of the slip velocity distribution and the local velocity vector were analyzed by CFD simulations.The turbulence enhancement and weakening zone were found to appear alternately,leading to the maldistribution factor of slip velocity in the RPB with periodic fluctuations.Based on the vector distribution and the theoretical analysis,it is found that the additional motion enhances or weakens the slip velocity components of the gas phase,leading to the formation of the turbulence enhancement zone and turbulence weakening zone,as well as the change of the relative flow direction of the gas flow.2.The local flow characteristics of the liquid phase within the RPB under floating conditions were investigated.Visualization experiments and CFD simulations were used to study the dispersion behavior of the liquid jet impacting the single-layer wire mesh in the RPB.A theoretical model of liquid dispersion was developed to describe the stretching and breakup stages.The stretching stage was found to depend on the liquid initial momentum and acquired impulse,while the breakup stage was determined by the competition of ligaments recoil and pinch-off behaviors.The rebound velocity in the external force field under floating condition is corrected.The model error is within±20%,indicating the influence mechanism of floating conditions on the local liquid dispersion within the RPB was revealed.3.The flow characteristics of the gas-liquid flow within the RPB under floating conditions are investigated.The Eulerian model coupled with the porous medium model was used to study the effects of multi-DOF motions on the pressure drop,gas-liquid distribution,liquid holdup and turbulent kinetic energy.It is found that the tilting and rolling conditions lead to the secondary distribution of liquid in the packing zone,leading to the changes of liquid holdup and pressure drop.The formation mechanism of the secondary axial distribution of the liquid phase is further analyzed,which is considered to be controlled by the gravity component and gas flow directions.4.The mass transfer characteristics within the RPB under floating conditions were investigated.The effective mass transfer specific surface area（a_e）within the RPB under tilting and rolling motion was investigated by chemical absorption method.The gravitational component caused by the tilting was found to lead to the liquid convergence,resulting in the loss of a_e at low rotational speed.However,increasing the rotational speed can effectively restrain the liquid convergence and increase a_e.In addition,a_e was investigated under different motion periods and operating conditions,and the relative rates of change and fluctuations can reach 17.4%and 10.7%,respectively.Combined with the hydrodynamic characteristics,it is believed that the effects of tilting and rolling conditions on a_e are determined by the secondary axial distribution of the liquid.5.The application performance of the RPB under floating conditions was investigated using the MEA-CO₂ system.The effects of operating conditions and motion periods on the mass transfer coefficient and removal efficiency were investigated.It was found that the efficiency was promote under most conditions.When the RPB rotational speed was above 600 r/min,the axial convergence of liquid and the decrease of absorption efficiency could be effectively avoided.When the rotational speed was above 1400 r/min,the tangential velocity of liquid dominated and the influence of secondary axial distribution decreased.By comparing with the performance of conventional packed beds under floating conditions,the advantages of RPBs in marine floating platform applications are confirmed.