Submicrometer emulsions were generated by a high-pressure wet-type jet mill and a motionless mixer called the Ramond Supermixer. Kerosene and liquid paraffin were used as the dispersed phase, aqueous sucrose and poly(ethylene glycol) solutions of PEG 400 to PEG 20000 were used as the continuous phase, and sodium dodecyl sulfate was used as a surfactant. The droplet size distribution, the Sauter mean diameter (d 32 ), and the geometric standard deviation of the droplet size distribution (σ g ) were investigated under various combinations of the operating variables. The analysis of time-scale parameters contributed to an understanding of droplet deformation and possible re-coalescence. The relationship between the maximum droplet diameter and d 32 was determined to be a function of the ratio of the viscosity of the dispersed phase to the viscosity of the continuous phase (K). Empirical correlations were constructed for d 32 and σ g , and a larger similarity was determined to exist within the correlations, irrespective of the emulsifier that was used. Mechanistic models were developed to describe the droplet formation in view of droplet breakage phenomena with negligible re-coalescence. Separate models were proposed for both the turbulent inertia sub-range and the viscous subrange. For the viscous sub-range, a plot of the critical Weber number versus K revealed a rapid increase of droplet diameter at K < 0.05, regardless of the emulsifier.

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The absorption of dilute CO 2 into aqueous solutions of sterically hindered 2-methyl aminoethanol (MAE) and the desorption of CO 2 from CO 2 -loaded MAE solutions into N 2 stream were investigated separately for the various combinations of operational variables, using a hydrophobic microporous hollow fiber (polytetrafluoroethylene, PTFE) contained gas-liquid contactor with aqueous solutions of MAE as liquid media in the shell side at 30 C. The absorption of CO 2 in this contactor is governed by resistance in the liquid and hollow fiber phases. The resistance to diffusion in the hollow fiber phase amounts to 76-80% of the total resistance. Nevertheless, the absorption rates of CO 2 into aqueous MAE solutions in this contactor are higher than those into aqueous solutions of sterically hindered 2-amino-2-methyl-1-propanol (AMP) in the stirred tank with a plane unbroken gas-liquid interface. The process of desorption of CO 2 from CO 2 -loaded MAE solutions can be regarded as being controlled by diffusion and chemical reaction in both the stagnant film of the liquid phase and the liquid-filled pore of the hollow fiber phase under the slow or intermediate reaction regime. Both absorption and desorption rates under the simultaneous absorption-desorption operation in a single unit tend to approach the respective constant values as process time elapses. The total absorption rate here seems to be almost balanced with the total desorpion rate at the constant mass transfer rate periods.

A novel motionless mixer named Ramond supermixer (RSM) was used to disperse nanoparticle suspensions under the various process conditions. Commercially available nanoparticles, fumed silica (SiO2) of primary particle diameter (d 0) ranging from 7 to 30 nm, zirconia (ZrO2) of d 0 = 12 nm, and titanium oxide (TiO2) of d 0 = 21 nm, were dispersed either in an ion-exchanged water or in aqueous ethylene glycol solutions. The smaller the d 0, the harder it is to disperse the aggregates. Zeta potential was largely dependent on d 0 and became independent of process variables and, hence, of aggregate diameter. By evaluation of energy barrier values, the aggregation during disruption was found to be negligible. Aggregate disruption was predominant at the viscous subrange. By balancing mechanical energy with turbulent disruptive energy, a mechanistic model was developed for aggregate disruption. The analysis of fractal dimension showed that nanoaggregates are made up by orthokinetic cluster−cluster collision. Fractal dimensions are invariant throughout the disruption process. The rheological measurements further confirmed the evaluated fractal dimensionality.

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