混合原理及设备课程作业

1、Progress of liquid-liquid fast mixing equipment and the latest relevant researchMeng xianqiang huayan1406 2014200142Abstract On the basis of liquid-liquid mixing mechanism, several kinds of commonly used liquid of rapid mixing equipment and mixing process mechanism were reviewed. Four types of liqui

2、d-liquid mixers (a jet mixer, impinging stream mixer, static mixer and dynamaic mixer) reported in the patents are analyzed,and discussed on their specific features. The prospect of the research and industrial liquid-liquid fast mixing equipment are also pointed out.Keywords micromixing; liquid-liqu

3、id fast mixing; jet mixer; impinging stream mixer; static mixer; dynamic mixer IntroductionOn this day in 21th Century, in the field of fine chemical, polymer engineering, pharmaceutical engineering and bio-chemical industry, the rapid liquid-liquid reaction exist widely. Such as, in the use of liqu

4、id-liquid coprecipitation process for the preparation of solid particles in the legal system, the mixing effect of liquid-liquid directly affects the size of particle distribution. In the preparation of polymers by using liquid-liquid fast reaction system, the effect of two phase mixing of liquid-li

5、quid will also directly affect the distribution of relative molecular mass of polymers. When the liquid appears in complex parallel competitive reactions or consecutive competitive reaction, the reaction products or intermediate products and raw materials will further reaction, thus affecting the fi

6、nal product distribution, product yield and quality. Scientists survey found that，the chemical industry is relatively developed and the mixed problem result to economic losses of several billion dollars each year in the United States. Therefore, the design of efficient liquid-liquid mixing equipment

7、, realize the initial liquid-liquid fast mixing could improve product quality, reduce the by-products and optimize the entire production process. Based on the analysis of liquid-liquid mixing mechanism, this paper discussed the newest achievements on liquid-liquid equipment research and rapid mixing

8、 aspects, the prospect of the research and prospect of industrial liquid liquid fast mixing device and mixing process are also pointed out.1 Liquid-liquid mixing mechanismLiquid-liquid mixing mechanism mainly laminar mixing and turbulence,the mixing of high viscosity liquid is usually laminar m

9、ixing. In most of the chemical production process, the liquid viscosity is low and has strong turbulence1. The mechanism of turbulent mixing is more complex, in general, when two kinds of liquid meet, the mixing process below will occur.1.1 MacromixingAt the beginning of mixing, because of the effec

10、t of turbulence, the existence of large whirlpool inside liquid2 .With the mixed, larger eddies in turbulent tensile, shear stress, by interchanging the position of mass transfer, at the same time, the energy transfer from large vortex to small vortex3.1.2 Mesoscopic mixingFurther effects of small e

11、ddies in turbulent tensile, shear stress, vortex further deformation, micro clusters are split into smaller, slightly smaller scale until4. At this scale, micro clusters of small vortex mainly through the vortex crushing segmentationFigure 1(a) and vortex diffusion into smaller scaleFigure 1(b). (a)

12、 the vortex crushing segmentation (b) the vortex diffusion1.3 MicromixingMicromixing is mixed at the molecular scale. When the vortex micell size is small enough, molecular diffusion will play a role in very short range, stochastic distribution so that mixture to the molecular scale. This is a mixtu

13、re of highly uniform at the molecular level5.Overall, the mixing process of these three scales is sequentially, but to some extent it is also performed at the same time. So, the whole mixing process requires mixing process considering the above three scales. Based on the characteristics of liquid-li

14、quid fast mixing, mixing process of micro mixing molecular level should be in the shortest possible time6.2 Liquid-liquid fast mixing equipment and process In industrial production, the main use of turbulent mixing mechanism to realize the liquid liquid mixing.The mixing equipment mainly has stirred

15、 tank mixer, jet mixer, impinging stream mixer, static mixer, dynamic mixer etc. The industry uses mechanical agitation form to realize the process of mixing the macro mixing time is long, and the mixing process is mainly affected by the macro mixing control. Mesoscopic mixing and micro mixing proce

16、ss is the main factor to the whole of the mixing process .It is also relatively difficult to study of the process 7. Research progress of equipment and mixing process of rapid mixing below were reviewed above several liquid.2.1Jet mixerJet mixer is the realization of liquid-liquid fast mixed commonl

17、y used equipment. It is designed to be fast moving liquid flow with high velocity jet to slow or stationary liquid. At present, jet mixer is widely used in industry. Chemical processes such as the use of phosgenation producing isocyanate. Later, the German Bayer was improved on this kind of jet mixe

18、r, the jet of fluid by uniformly distributed holes injection into the mainstream body, thus realizing rapid mixing of two fluids, the mixing effect is greatly improved8. Today, the information flow and get the test technology of modern field experimental basis to set up the physical model of the mix

19、ing process. At the same time, using the method of computational fluid dynamics to predict the jet mixing process in theory. Provide a theoretical basis for the design and optimization of jet mixer. The application of these theories make jet mixer more and more system.2.2 Impinging stream mixerIt is

20、 the two group of liquid in a certain way of high speed impact to achieve a method of liquid liquid fast mixing. Through the fierce impact of two shares of high-speed flow of the fluid, energy is quickly dispersed, therefore, effectively reduce the segregation degree of two fluid streams, achieve ra

21、pid mixing results9. A form of impinging stream mixer is the jet liquid two strands of high speed turbulent flow in the opposite direction of collision between the implementation of mixed, the other is a thin layer of liquid film will be two shares or mutual impact after the rapid mixing. The latest

22、 research in mainly concentrated on the lower liquid flow channel mixer in size, reducing the space fluid mixing before the scale, however, for the reaction system with solid product, mixed space now smaller easy blockage caused by equipment. In order to solve this problem, two shares or more strand

23、s of fluid was atomized, to impact the realization of mixed, the mixer can effectively prevent the blocking reaction process of solid material production equipment. The impinging stream mixer of diverse forms, and the structure is relatively complex, therefore, the present study of most of two strea

24、ms of liquid flow in the mixing process in the mixing chamber of the impact.2.3 Static mixerStatic mixer with different structure for fluid pipeline can make the mixed liquid in a wide range. The fluid is often affected by the mixing element constraints in the flow through the static mixer. Its main

25、 advantage is the range of Reynolds number fluid in a wide mix within and without the need for the design of moving parts can achieve the purpose of mixing. At present, many institutions in the world to develop new structure of static mixer. At the same time, the development of computational fluid d

26、ynamics provides the possibility of static mixer rapid complex internal structure as the research, so that the study of the static mixer is becoming more and more popular.2.4 Dynamic mixer Dynamic mixer shell or in the pipeline with high-speed rotating parts. In these components under the action of

27、will produce large shearing force, realize the mixing effect in different fluid under the shear stress. The form of dynamic mixer is not fixed. The new study says, the reactor is designed into a horizontal, installation guide cylinder symmetrical on both sides, so that the liquid impact at the cente

28、r opposite the reactor, the formation of a highly turbulent impinging zone, mixed very strong10. The liquid reflux after the impact to the draft tube inlet circulation. Using the structure of the circular flow can not only use traditional mixer but the advantages of rapid mixing and can make the ave

29、rage residence time of materials can be arbitrarily set. Therefore, the rapid mixing process part of the reaction can not be instantaneous.3 The research prospect of liquid-liquid fast mixing equipment With the continuous research of experimental method and theoretical method, people for the liquid-

30、liquid fast mixing device and mixing process has more indepth study.First, the design of fast mixing equipment has been from the past experience design gradually transition to the theoretical guidance of design. At the same time, the measurement results of flow field for computational fluid dynamics

31、 simulation provides the basis of experiment, the experimental and theoretical mutual authentication, which promotes the development and research on rapid mixing process and mixing equipment.Secondly, rapid mixing equipment design form is no longer single, scientists will be some form of rapid mixing process of organic combination developed fast mixing equipment according to the characteristics of composite process.Finally, due to the rapid mixing pr