Preliminary Study On The Gas-liquid Interfacial Area In Intensified Reactor

The gas-liquid interfacial area a,a key parameter in the study of gas-liquid mass transfer intensification,is determined by the bubble Sauter mean diameter d32 and the gas holdup φG,which depend on the gas-liquid reactor design parameters.Therefore,it is important to explore the relationship between the interfacial area a and gas-liquid reactor design parameters for the optimization of intensified gas-liquid reactor.In the paper,theoretical and experimental studies on two types of gas-liquid intensified reactors(one is a new jet stirred reactor and the other is a microinterface intensified reactor)were carried out,and the interface characterization methods of gasliquid systems were discussed.The main research contents and conclusions are as follows:1.Through the transformation of the traditional downcomer,the factors affecting the diameter of the bubble in the new jet stirred reactor were discussed.After detailed process analysis,the mathematical model reflecting the influence of the downcomer structure was established.Theoretical analysis shows that:(1)To avoid unfavorable limit conditions,the longer downcomer,the higher initial liquid level of the reactor,the larger the cross-sectional area ratio(k)of the downcomer and the nozzle and the longer the liquid column in the downcomer is are necessary;(2)The larger the number of side holes,that the smaller the pore size of the side hole,the smaller the bubble in the reactor,which confirmed by experiments.2.For bubble image processing,the study has compiled a bubble recognition program on the MATLAB software platform,which can quickly and accurately obtain the bubble size information in a large number of images of the MIR system.The topics are the selection of the light source,the calibration of the camera,the image processing process and the model verification.Among them,the LED light source is the best;and the camera calibration is performed in five basic steps:1)image,camera and calibration mode preset;2)image calibration;3)result evaluation;4)necessary modification of calibration method,and recalibration;5)output calibration parameter.The bubbles are measured by a self-developed recognition program and compared to the predicted model.3.The influence of operating conditions in MIR on mass transfer characteristic parameters were discussed by cold model experiment.Within the scope of the conditions studied,the main conclusions are as follows:(1)MIR can not only generate microbubbles,but also the size distribution of microbubbles is narrow.The size of the microbubbles passing through the fixed bed is significantly increased;(2)The gas holdup before and after the fixed bed increases nonlinearly with the increase of superficial gas velocity and gas-liquid ratio;(3)The increase of bed particles size causes d32 to decrease first and then increase,then the change is slower,while the gas holdup and gas-liquid interfacial area show a trend of first increasing and then decreasing.