Study On The Mechanism And Process Of Deoxygenation In A Rotor-Stator Reactor

As one of the novel high-gravity equipment,a Rotor-Stator Reactor(RSR)was developed on the basis of a Rotating Packed Bed(RPB).The RSR consists mainly of a series of rotor-rings located on a rotor seat connected to a motor by a shaft and a series of stator-rings comprising of pins mounted concentrically on the cover cap.The rotor-rings and stator-rings are alternately configured in a radial direction.The rotor-rings serve as shearing and dispersing component,whichcan break liquid into micro-or nano-droplets and films and thus enhance the gas-liquid mass transfer.On the other hand,the stator-rings serve as disturbing component,and can change the route of liquid flow.As a result,liquid is more uniformly distributed in an RSR as compared to an RPB.All of these factors can greatly enhance micromixing and mass transfer performance in an RSR.This study therefore employed an RSR for theremoval of dissolved oxygen(DO)from water in attempt to overcome theproblems of poor mass transfer efficiency,huge equipment size and high energy consumption that are typically associated with the conventional DO removal techniques.Hydrodynamic charateristics and mass transfer mechanism in an RSR were studied.Mass transfer and deoxygenation performance of different deoxygenation processes in the RSRwere also compared.The main research contents are as follows:1.Electrical conductance and response time technique was employed to experimentally investigate the hydrodynamic characteristics of an RSR.The effects of various operating conditions such as rotational speed,liquid volumetric flow rate and number of rotor-ring layers on the liquid flow were examined,and correlations to predict the hydrodynamic characteristics of RSR were established.Results show that the predicted results are in agreement with experimental values with deviations within±10%,thus indicating the feasibility of employing the correlations to predict liquid average velocity,residence time,holdup and number of liquid droplets in an RSR.2.Various deoxygenation processes including nitrogen stripping coupled with vacuum degassing(vacuum-N2-H2O-O2),nitrogen stripping(N2-H2O-O2)and vacuum degassing(vacuum-H2O-O2)were employed to study mass transfer characteristics of an RSR.The effects of various operating conditions such as the rotational speed,liquid volumetric flow rate,gas volumetric flow rate and vacuum level on the mass transfer coefficient(Kxa)were examined.Results show that Kxa increased with an increase in rotational speed,liquid volumetric flow rate,gas volumetric flow rate and vacuum level.Results also indicate that the bestmass transfer performance was observedinthe vacuum-N2-H2O-O2 process,followed by the N2-H2O-O2 and vacuum-H2O-O2processes.3.The N2-H2O-O2 processwas also employed to investigate mass transfer characteristics in an RSR in terms of the overall volumetric mass-transfer coefficient(Kxa).A gas-liquid mass transfer model was established to predict Kxa.Results showthat the predicted values of Kxa are in agreement with the experimental values with deviation within±15%.The results herein can provide better understanding of mass transfer characteristics in RSR.4.Principal component regression model(PCR)was used to establish a mass transfer model.The prediction performance of PCR was compared to that of multiple linear regression model(MLR).The results indicate that the mass transfer model established by PCR can be used for the vacuum-N2-H2O-O2 process where the variables have a strong correlation,and the predicted results were better than those by the MLR.The values of Kxa predicted by thePCR models in the N-2-H2O-O2process.are in agreement with the experimental values with deviations within ±15%.Moreover,the application range of PCR model is wider than that of mechanism model.5.The performance of deoxygenation efficiency(?)in an RSR was examined by four different deoxygenation processes(N2-H2O-O2,CO2-H2O-O2,vacuum-H2O-O2 and vacuum-N-2-H2O-O2).The effects of various operating conditions such as the rotational speed,liquid volumetric flow rate,gas volumetric flow rate and vacuum level on deoxygenation efficiency were examined.Results show that ? increased with an increase in rotational speed,gas volumetric flow rate and vacuum level,but decreased with an increase in liquid volumetric flow rate.The deoxygenation efficiency achieved was 97.32,97.01,89.56 and 89.95%in the vacuum-N2-H20-O2,N2-H20-O2,CO2-H2O-O2 and vacuum-H-2O-O2 processes,respectively.