Numerical simulation was made of transient mass transfer to a surfactant contaminated uoyancy-driven drop controlled by appreciable resistance in both liquid phases. For this purpose, the momentum equations were formulated and solved in a boundary-fitted orthogonal coordinate system. On the basis of resolved hydrodynamics of the contaminated drop, the transient mass transfer was formulated and solved in the same coordinate system. In order to check the applicability of the numerical scheme, single drop extraction experiments were conducted in a totally closed droplet file column with the terminal effect efficiently eliminated. The MIBK-acetic acid-water system was used with small quantities of SDS (sodium dodecyl sulphate), Trito X-100, or Tween 80 introduced into the continuous phase. For these experimental cases, the flow field and the drag coefficient of a contaminated drop were simulated first. The numerical prediction of the drag coefficient is found in good agreement with the correxponding experimental data. It illustrates that the behavior of a drop approaches that of a rigid sphere and that about 100 times higher bulk concentration of SDS than that of Triton X-100 is required for the same extent contamination of a MIBK drop of the same size. Then the information of the flow field of a contaminated MIBK drop was used in simulating the transient mass transfer of solute into the drop. The resulted extraction fraction and overall mass transfer coefficient are in reasonable coincidence with the experimental data. Both numerical results and experimental data show that overall mass transfer coefficient of a heavily contaminated drop is only about one third of that in the pure system. This can be explained well by the distribution of the local Sherwood number, which drops down abruptly along the rear stagnant surface. Also the interfacial resistance of adsorbed surfactant was incorporated in the mass transfer model and then estimated by the least square fitting the simulation with data. The numerical results also show that Tween 80 presents obvious interfacial resistance on the acetic acid diffusing across the interface, whereas SDS and Triton X-100 show no interfacial resistance. It is Suggested that the numerical simulation can be resorted in some solvent extraction systems containing surfactants to conduct numerical experiments and parametric study.

A new HPLC stationary phase, 1-methylnaphthalene modified Polystyrene-divinylbenzene resin (MNPSDVB), has been prepared to separate C60 and C70. High Column loading capacity and large separation factor of C60 and C70 were obtained in MNPSDVE column with the strong solvent, o-xylene, as the mobile phase.

The Pulsed packed column (PPC) uses pultation to enhance mass transfer. Systermat expertments (Spaay et al., 1971; Bender et al., However, only comentional packion such as Rasching rings and Pall rings were used in these experirenus. Packing types have been shown to inlluence the hydrodynumics and mass transfer characteristics of PPC (Bender et al., 1979; Simans et al., 1986). Several kinds of high efficiency packing, including randosn packing and structured packing, have been developed in recent years, but there are only a few studies on the characteristies of PPC (Hoting and Vogelpohl, 1996a, b) with these new packings. SMRs (Fei et al, 1991) are newfy devetoped mini rings with an elaborate geometrical design A photo of the SMR is shown in Figure 1. It has three afches and a lower height/diameter ratio (about 0.3), which has been shown to enhance the dispersion-coalescence cycle and contral the non-ideal flow of the two phases in the packing elements. Experiments (Fei et al., 1993) showed that the SMR has lower axial mixing and higher mass transfer etficiency than many corwentional packing, This, studies on the hydrodynamics and ruass transter characteristics of PPC with stainless steel SMR is presented in thas work. Experiments with cenamic and starless steel Rasching rings were also done for comparison.

Terminal velocity and mass transfer coefficient data for drop swarms were measured in a 0.1m diameter glass column filled with SMR (Super Mini Ring) packing, using a computerized video imaging system; 30% TBP-Kerosene/acetic acid/water and 50% imaging system; 30% TBP-Kerosene/acetic acid/water were us ed as the working systems. A unmber of techniques for the prediction of the observed mass transfer data were considered, and a new model to predict the mass transfer film coefficient, which accounts for the effects of surface contaminants on the mobility of the interface, is presented and shown to fit the experimental data. The effects of drop size and the presence of packing on ovelall dispersed phase mass transfer coefficient are presented. It is shown that overall dispersed phase mass transfer coefficient increases with increasing drop diameter, and decreases in the presence of SMR packing.

This work shows the superiority of a proposed modified rotating disc contactor extraction column (MRDC) over the traditional rotating disc contactor extraction column (RDC). Four types of MRDC, all constructed with additional perforated rotor discs installed inside stator rings, were used for hydrodynamic and mass transfer experiments and the results were compared with those of an RDC operation under the same conditions. Experimental results reveal that axial mixing can be effectively suppressed and mass transfer efficiency enhanced in the MRDC. The hydrodynamic and mass transfer experiments were also coincidental with findings of the laser Doppler velocimetry (LDV) velocity field measurements and computational fluid dynamic (CFD) simulations for both the RDC and the MRDCs, in that vortices between adjacent stator rings enhance mixing and mass transfer within a compartment, while vortices between discs cause axial mixing between compartments. One type of MRDC has been successfully applied in revamping a commercial caprolactam extraction column.

It is shown from CFD simulation and particle image velocimetry (PIV) measurements that the flow field around ring packing is impacted by their height/diameter ratio and inclination. The results indicate that it is better to decrease the height/diameter ratio of ring packing to intersify the separation processes in the packing bed. Baded on a systematic study, a new Plum Flower Mini Ring (PFMR) was developed to meet the demands of separation column intensification. A comparison of the PFMR, Pall Ring and Intalox Saddle in a 600mm diameter column with an air-oxygen-water system over a wide range of liquid loads is presented. It was shown from the experiments that the PFMR had a much lower pressure drop, much larger throughput and better mass transfer efficiency than Pall Rings and Intalox Saddles.

To characterize the flow instability in mechanically agitated vessels, digital particle image velocimetry (DPIV) was used to measure the near-instantaneous flow fields in a baffled, stirred vessel, equipped with a Rushton turbine impeller of large diameter ratio of impeller to vessel. From the measured near-instantaneous flow fields, distinct large-scale flow patterns were identified and the formation mechanisms of the patterns were explored via multi-scale analysis. Further investigations show that the flow patterns are rather complex. Macro-instability (MI) appears as a swith among those flow patterns. Spectral distribution function P(ƒ), equivalent to probability distribution function from a purely mathematical point of view, was introduced to extract information on MI fron the time series of the vorticity of the fluctuation velocity field. The two-dimensional distribution of MI and its dependence on Reynolds number were studied. Results show that probability analysis via spectral distribution function can be successfully used to quantify the relative intensity of macro-instabilities. Low-frequency, large-scale fluctuations of flow patterns were much more intensive in the lower and upper corner of the vessel than in the rest parts of the vessel. The fluctuations of flow patterns also had an offset to the core of the vessel due to the influence of baffles. Compared with visual observation technique, this new analysis method via DPIVis more objective and can be used to give deep understanding to the spatio-temporal properties of macro-instability.