The Study On Mass Transfer Characteristics Of The IJSR

In recent years,in the face of severe environmental and energy situation,the whole society is more and more demanding on energy saving and consumption reduction.It is an important means to improve the competitive power of chemical enterprises by using high efficient mass transfer equipment.The gas-liquid reaction system is widely used in the process industry,such as the production of phthalic acid and adipic acid.The mass transfer enhancement of gas-liquid interface is an important target in the process of gas-liquid reaction,and it is also an important subject in the research of high efficiency and energy saving mass transfer equipment.Through decades of experimental research and experience accumulation,it is found that in the process of gas-liquid mixing and mass transfer,the injection mass transfer equipment can produce better mixing effect and higher mass transfer coefficient.So as to improve the utilization rate of raw materials,the selectivity and yield of products.In the study of multiphase jet reaction,the main research object is gas-liquid two-phase reaction,such as the gas-liquid mechanical properties,mixing characteristics,mass transfer characteristics and so on.Bubble size is one of the important hydrodynamic parameters that influence the interfacial mass transfer and the final reaction rate.In terms of the established system,the structural parameters and operating parameters of the mass transfer equipment will have different effects on the bubble size,thus affecting the mass transfer effect.The energy efficiency and the mass effect of the reaction process are directly related to the mass transfer coefficient kG,kL and ks in the system,as well as the interfacial area a.These parameters are affected by the bubble size,distribution,superficial gas velocity and gas holdup.For the established reaction system and reaction conditions,these factors are mainly affected by the structure of the reactor,especially the stirring and mixing mode.As for the mass transfer process,kLa is a macroscopic parameter,which does not fully reflect detailed information on gas-liquid mass transfer interface and it's both sides.Therefore,in order to obtain more microcosmic information and better understand the gas-liquid mass transfer mechanism,kL and a should be studied separately,which can help us to determine which factor(kL or a)control the mass transfer process.This paper employs the dissolved oxygen method to determine the volumetric mass transfer coefficient kL?.And a digital image analysis method is established through cooperation to determine the gas-liquid interfacial area a,and then the liquid mass transfer coefficient kL was obtained.Thus the mass transfer characteristics of one kind of gas-liquid hybrid mass transfer equipment(IJSR)designed by the laboratory have been investigated.The effects of the structure parameters and operating parameters of the mass transfer equipment on the mass transfer characteristics of the equipment are discussed,so as to better understand the mass transfer mechanism of the equipment.Through our study,it is found that the number of the holes in the down-tube has no significant effect on the mass transfer efficiency of the equipment However,the aperture ratio of the down-tube does have an effect on the mass transfer.The down-tube with small aperture ratio limits the increasing of the gas-liquid interfacial area a by limiting the increasing of superficial velocity vg,thus has a negative effect on mass transfer effect(kL?).The aperture ratio doesn't have the similar effect on kL.From the point of view of operating parameters,there is a quadratic function relationship between the mass transfer coefficient kLa and the superficial velocity vg.This is due to the fact that there exists a quadratic function relationship between the gas-liquid interfacial area a and vg.Furthermore,the static liquid height does have an effect on the mass transfer.There exists an optimal height within the range of our study.But the effect of the static liquid height on a and kL is different.The higher the static liquid height,the smaller the gas-liquid interfacial area a.This phenomenon is more obvious under the condition of large superficial gas velocity vg.The existence of the optimal height is mainly because of the existence of an optimal liquid height for the kL at higher superficial gas velocity.