Study Of Gas-Liquid Transfer Enhancement And Bubble Behavior In Multi-Downcomer Sieve Tray

Bubbles on the mesoscopic scale have an extremely important effect on the mass transfer between the gas and liquid phases.The presence of large air bubbles will lead to a reduction in the residence time of the gas phase and slow renewal of the gas-liquid contact interface,which will greatly reduce the efficiency of the tower plate.Therefore,if we can break the large bubbles and reduce their size,we can increase the gas-liquid contact area,force the interface to be renewed and strengthen the mass transfer process.Based on this,this paper proposes a new method for gas-liquid mass transfer enhancement of the tower plate:droplet bubble breaking;and based on this,the conventional tower plate is optimized and a new multi-downcomer sieve tray is proposed.In this paper,we designed our own set of visualization experimental procedures to study the bubble-breaking behavior by particle image velocimetry（PIV）combined with computational fluid dynamics analysis software（CFD）.The bubble motion without the influence of droplets was chosen as the control,and the information on the bubble’s rising velocity,the center of mass position,equivalent diameter,aspect ratio,pressure-velocity variation inside the bubble,and external flow field after the influence of droplets was analyzed.The results show that the droplets enter the liquid layer and act directly or indirectly on the bubbles,and the large bubbles impacted by the droplets are torn into small bubbles.and the rise time of individual bubbles was extended to 172.663 ms;The bubbles are compressed longitudinally and stretched horizontally before they are broken,and their surface area increases to twice the original size.The flow field around the bubble is changed,the pressure inside the bubble and its velocity increase,and the surface renewal are accelerated.The results of CO₂ absorption experiments showed that the gas-liquid mass transfer effect was enhanced by using droplet-breaking bubbles.Hydrodynamic experiments on new multi-downcomer sieve tray in the air-water system to investigate the hydrodynamic parameters such as pressure drop,equivalent liquid layer height and gas content rate of new plates under different operating conditions by varying the magnitude of gas and liquid flow rates;The gas-liquid flow state on the column plate was analyzed by simulation software.Research results show that the wet plate pressure drop of the new multi-downcomer sieve tray is about 80%of that of the traditional tower plate,effectively reducing energy consumption;Under the same operating conditions,the gas content of the new tower plate is on average 66.3%higher than that of the conventional tower plate,and the gas content is more uniformly distributed.The modification of the new multi-downcomer sieve tray increases the area of mass transfer area on the column plate;it eliminates the liquid surface drop very well and makes the liquid layer distribution more uniform.The research in this thesis provides new ideas for transfer process intensification,which can serve as a theoretical guide in developing new tower trays and enhancing mass transfer.