Terminal Effect of Drop Coalescence on Single Drop Mass Transfer Measurements and Its Minimization

For the mass transfer to single drops during the stage of steady buoyancy-driven motion, experimental measurement is complicated with the terminal effect of additional mass transfer during drop formation and coalescence at the drop collector. Analysis reveals that consistent operating conditions and experimental procedure are of critical significance for minimizing the terminal effect of drop coalescence on the accuracy of mass transfer measurements. The novel design of a totally-closed extraction column is proposed for this purpose, which guarantees that the volumetric rate of drop phase injection is exactly equal to that of withdrawal of drops. Tests in two extraction systems demonstrate that the experimental repeatability is improved greatly and the terminal effect of mass transfer during drop coalescence is brought well under control.

Coalescence behaviour of water droplets in water‐oil interface under pulsatile electric fields

In this research, the deformation of water droplets in sunflower oil-interface under pulsatile electric field was studied experimentally. Three types of coalescence were observed:(i) complete coalescence,(ii) incomplete coalescence and(iii) no-coalescence. The first type is desirable because of leaving no secondary droplets. The second type that produced secondary droplets which caused by necking process, due to extreme elongation of droplets(mostly small droplets), was undesirable; because the small droplets were more difficult to coalesce and remove. The no-coalescence was caused by very fast coalescence and extensive pushing of droplet into the continuous phase. In this work the process was operated with the utilization of a batch cylindrical separator with high voltage system. The lower part of the cylinder was filled with the aqueous phase and its top part was filled with sunflower oil to form an interface between the two phases. The effects of electric field strength,frequency, and waveform types were investigated. It was found that, the ramp-ac waveform was the best waveform, avoiding the production of secondary droplets and in this case the frequency also played an important role.

Review on the deformable drop/bubble interaction-AFM study

The physicochemical properties of emulsions stabilized by surfactants depend on the film drainage and coalescence behavior between dispersed drops in a system.The combination of direct measurement of the interaction forces between soft matters by AFM and the prediction of the film drainage process by the SRYL model helps to explore the dynamic behavior of droplets in the emulsion system.In this review,novel experimental designs and recent advances in experimental methodologies for solving interaction forces,interfacial deformation and drop coalescence are presented,which show the advantage of using AFM as a tool for probing colloidal interactions.The effects of hydrodynamic forces,both DLVO and non-DLVO forces,on the emulsion stabilization mechanism are discussed.In addition,an outlook is presented to discuss the further development of the relevant technology and the problems that need to be solved.

Interfacial Phenomena in Solvent Extraction and Its Influence on Process Performance

Solvent extraction is now finding applications in a broader range of fields than the past. Many of these applications require process equipment with shorter contact times, and in some cases to the point where the traditional equilibrium stage approach is not a good model for predicting performance. In addition, feed streams are becoming lower in concentration of the solute. This means greater feed to solvent flow ratios are being used and so loss of organics as entrainment in the feed is more of a concern both economically and environmentally. These trends mean that a greater emphasis is being placed on the kinetics of extraction and stripping in models to predict performance and on formation and coalescence of drops to control entrainment. This paper reviews recent advances in the tools for investigating kinetics and coalescence in solvent extraction processes and some of the insights that are being uncovered in these fundamental processes in solvent extraction technology.