Changes In Droplet Size Distribution Research Articles

Critical distribution state of droplets dispersed in oil subjected to electric and centrifugal fields

Oil-water emulsions are extensively produced in industry, which may affect subsequent work or bring about environmental problems. Hence, it is necessary to demulsify and dewater it first. A coupling unit based on high-voltage electric and swirl centrifugal fields is adopted to satisfy emulsion demulsification and dewatering. The droplet size distribution is closely related to the separation performance of the coupling unit, while the droplet size distribution changes dynamically due to coalescence and breakage of the droplets. Droplets possess corresponding distribution under different coupling conditions, and the droplets size distribution may have a specific critical distribution state, in which the separation efficiency of the coupling unit reaches the optimal. Therefore, a numerical model is established to study the critical distribution state under double-field coupling in this study. The influence of coupling conditions on the droplet size distribution is studied to obtain the critical state of droplet size distribution, and the relationship between the critical state and the inlet droplet diameter is investigated. The results show that the critical state exists, and its distribution is as follows: there is a stable region with the maximum diameter gradient within 15 µm from the tail of the large cone section to the front of the small cone section (z = 700–760 mm) of the coupling unit; in the cross sections of the small cone section Z = 660–690 mm, the distribution of droplets volume fraction are almost identical, and the droplet diameter with the largest volume fraction is close to the median diameter. Moreover, the above critical state also exists for different inlet droplet diameters.

Dispersion and mixing dynamics of complex oil-in-water emulsions in Taylor-Couette flows.

The seminal study by G. I. Taylor (1923) has inspired generations of work in exploring and characterizing Taylor-Couette (TC) flow instabilities and laid the foundation for research of complex fluid systems requiring a controlled hydrodynamic environment. Here, TC flow with radial fluid injection is used to study the mixing dynamics of complex oil-in-water emulsions. Concentrated emulsion simulating oily bilgewater is radially injected into the annulus between rotating inner and outer cylinders, and the emulsion is allowed to disperse through the flow field. The resultant mixing dynamics are investigated, and effective intermixing coefficients are calculated through measured changes in the intensity of light reflected by the emulsion droplets in fresh and salty water. The impacts of the flow field and mixing conditions on the emulsion stability are tracked via changes in droplet size distribution (DSD), and the use of emulsified droplets as tracer particles is discussed in terms of changes in the dispersive Péclet, Capillary and Weber numbers. For oily wastewater systems, the formation of larger droplets is known to yield better separation during a water treatment process, and the final DSD observed here is found to be tunable based on salt concentration, observation time and mixing flow state in the TC cell. This article is part of the theme issue 'Taylor-Couette and related flows on the centennial of Taylor's seminal Philosophical Transactions paper (Part 2)'.

Sugar beet pectins for the formulation of dressings and soft drinks: Understanding the complexity of charged hydrocolloids in industrial food emulsions

The aim of this study was to set up formulation-process-property functions for sugar beet pectin stabilized emulsions under industrially relevant processing conditions to allow for a reformulation of foods and beverages using sugar beet pectins (SBP) as emulsifiers. Therefore, model food emulsions, soft drinks, and salad dressings were produced. Model emulsions were prepared at different pH values (3, 4, and 5) and varying SBP concentrations (0.25 wt% – 2 wt%). Subsequently, the emulsions were subjected to pasteurization or salt addition and their short- and long-term stability was assessed. It could be shown that the pectin-stabilized emulsions were more sensitive to salt addition than to heat treatment. However, any physical instabilities could be avoided by using higher amounts of SBP. Furthermore, it could be shown, that SBP are able to stabilize soft drinks (0.05 wt% orange oil) as well as low-fat salad dressings (10 wt% rapeseed oil) over the typically required storage time. SBP-stabilized soft drinks showed no significant changes in droplet size distributions, cloudiness, or color, even after pasteurization and 6 months of storage. In order to stabilize the salad dressings with a rather low SBP concentration (0.25 wt%), the viscosity of the samples had to be adjusted appropriately. Overall, SBP were shown to be highly suitable for use as emulsifiers in the food and beverage industry. • Emulsions with SBP were more sensitive to higher ionic strengths at pH 3 than pH 5. • Pasteurization had no significant effect on droplet size distribution. • SBP concentration was the most important formulation parameter for stability. • An unfavorable pH and ionic strength could be compensated by higher amounts of SBP. • SBP-stabilized salad dressings were stable over 4 weeks, soft drinks over 6 months.

Experimentally validated high-fidelity simulations of a liquid jet in supersonic crossflow

Utilizing recent advancements in computational schemes for compressible, multiphase flows , this work features a parametric study of a pure liquid jet in supersonic crossflow that involves simulating the atomization process for four values of momentum-flux ratio. These simulations are validated against experimental results measured with high-speed X-ray imaging, which confirm the accuracy of the numerical approach. Also, the effect of numerical resolution on some flow behavior is investigated, revealing convergence of the jet shape and surface instability wavelength. Analysis of the resulting sprays includes statistical descriptions of the liquid distribution, liquid structures created through breakup, interfacial instabilities, and dominant flow features. As the flowrate increases, the spray penetrates further, it becomes more disperse, and less liquid impacts the wall, but the droplet size distribution changes little. The wavelength of instabilities on the windward side of the jet diverges from measured trends in subsonic crossflows. In a visualization of the time-averaged flow, counter-rotating vortices are observed along the jet core and in the wake, affecting the process of primary atomization and early droplet trajectories. • Large Eddy Simulations of liquid jet in supersonic crossflow at high Weber number. • Quantitative validation against experimental results using equivalent path length. • Shear-driven instability wavelengths differ from subsonic crossflow analogy. • Analysis of spray statistics and mean flow features.

Coalescence characteristics of droplets dispersed in oil subjected to electric and centrifugal fields

The demulsification and dewatering process is an important link in the resource utilization of waste oil. Compared with a single method, a coupling device based on high-voltage electric and swirl centrifugal fields can better realize emulsion demulsification and dewatering. As the main factor affecting the separation performance of a coupling device, the droplet size distribution changes dynamically owing to droplet coalescence. However, the coalescence characteristics of droplets under double-field coupling are unclear. Therefore, a numerical model is established in this study by coupling the electric and flow fields governing equations, and the droplet population balance equation to imitate droplet coalescence and breakup. With the finite element method, the dynamic variation and coalescence characteristics of droplets under different double-field coupling conditions are analyzed. Results show that droplet size decreases as vorticity increases, and vorticity disturbance will cause droplet size distribution instability. Droplet size is inversely proportional to oil volume fraction under the same inlet conditions. When the inlet Reynolds numbers (Re) is less than 12940, the coalescence effect is the dominant factor, but when Re is 12940, the breakage effect is the dominant factor. The regions where the droplet coalescence effect are dominant mainly include the near-wall region of the coupling and small cone and underflow pipe sections. Furthermore, the degree of coalescence does not directly determine the grade efficiency.

Novel Water-in-Oil Emulsions for Co-Loading Sialic Acid and Chitosan: Formulation, Characterization, and Stability Evaluation.

This study was designed to co-load sialic acid (SA) and chitosan in a water-in-oil (W/O) emulsion and investigated its characterization and stability. Emulsions were prepared using two different oils (olive oil and maize oil) and polyglycerol polyricinoleate (PGPR) alone or in combination with lecithin (LE) as emulsifiers. The results revealed that the aqueous phase of 5% (w/v) SA and 2% (w/v) chitosan could form a stable complex and make the aqueous phase into a transparent colloidal state. Increasing the concentration of PGPR and LE presented different effects on emulsion formation between olive oil-base and maize oil-base. Two stable W/O emulsions that were olive oil-based with 1.5% (w/v) PGPR+ 0.5% (w/v) LE and maize oil-based with 2% (w/v) PGPR+ 0% (w/v) LE were obtained. Initial droplet size distribution curves of the two stable emulsions displayed unimodal distribution, and the rheological curves displayed the characteristics of shear thinning and low static shear viscosity. Moreover, the storage stability showed that there was no significant change in droplet size distribution and Sauter mean diameter of the emulsions at room temperature (25 °C) for 30 days. These results indicated that the W/O emulsions could effectively co-load and protect sialic acid and chitosan and thus could be a novel method for increasing the stability of these water-soluble bioactive compounds.

Development of a Self-Emulsifying Adjuvant for Use in Swine Vaccines

Emulsion-based adjuvants are commonly used in animal vaccine formulations for several reasons including affordability, stability, and efficacy in inducing disease-protecting immune responses. Here we report a novel, cost-effective, stable, self-emulsifying adjuvant (SEA1) that is prepared by a simple low shear process or low-energy mixing without the use of expensive and complex proprietary equipment. Characterization of the SEA1 adjuvant showed good stability at different temperatures (4°C, 20°C, and 37°C) after one month of storage. Minimal changes in droplet size distribution, polydispersity index, Zeta potential and pH in 1-month-old SEA1 preparations were observed when compared with a fresh SEA1 preparation. SEA1 emulsion-based experimental vaccine preparations effectively stimulated humoral immunoglobulin (IgG) responses in mice and swine and were comparable to commercially available adjuvants Montanide ISA 201 and 206.

Stabilization mechanism of water-in-oil emulsions by medium- and long-chain diacylglycerol: Post-crystallization vs. pre-crystallization

The restriction of using trans-fatty acid is driving the food industries to develop natural, healthy and efficient emulsifiers for the fabrication of water-in-oil (W/O) emulsions. In this work, medium- and long-chain diacylglycerol (MLCD) with high nutritional features and surface activities was used for the preparation of emulsion. The influence of crystallization procedures (pre- or post-crystallization) on the emulsions’ stability was examined in terms of the change in droplet size distribution (DSD), sedimentation, microstructure and thermal properties. The sedimentation and coalescence of emulsions were reduced when higher amount (8%, w/w) of MLCD was used. The post-crystallized emulsions showed narrower DSD and less sedimentation compared to the pre-crystallized emulsions. Pre-crystallized emulsion prepared using shear speed of 10,000 rpm showed improved stability due to the reduction of crystal size. MLCD was able to form typical interfacial crystal shells in post-crystallized emulsions whereas only large crystals were formed in the continuous phase in the pre-crystallizations. Therefore, the post-crystallized emulsions had higher thickness and sedimentation was effectively reduced. The findings in this work could be the basis for the future application of MLCD and provide insights on how the physical stabilities of emulsions can be affected when different crystallization processes are employed.

Numerical Simulation of the Oil Droplet Size Distribution Considering Coalescence and Breakup in Aero-Engine Bearing Chamber

In order to improve the inadequacy of the current research on oil droplet size distribution in aero-engine bearing chamber, the influence of oil droplet size distribution with the oil droplets coalescence and breakup is analyzed by using the computational fluid dynamics-population balance model (CFD-PBM). The Euler–Euler equation and population balance equation are solved in Fluent software. The distribution of the gas phase velocity field and the volume fraction of different oil droplet diameter at different time are obtained in the bearing chamber. Then, the influence of different initial oil droplet diameter, air, and oil mass flow on oil droplet size distribution is discussed. The result of numerical analysis is compared with the experiment in the literature to verify the feasibility and validity. The main results provide the following conclusions. At the initial stage, the coalescence of oil droplets plays a dominant role. Then, the breakup of larger diameter oil droplet appears. Finally, the oil droplet size distribution tends to be stable. The coalescence and breakup of oil droplet increases with the initial diameter of oil droplet and the air mass flow increasing, and the oil droplet size distribution changes significantly. With the oil mass flow increasing, the coalescence and breakup of oil droplet has little change and the variation of oil droplet size distribution is not obvious.

Cellulose nanofibrils as rheology modifier in mayonnaise – A pilot scale demonstration

The applicability of cellulose nanofibrils (CNFs) as viscosifying agent in a starch-reduced low-fat mayonnaise and in an oil-reduced full-fat mayonnaise has been considered. For low-fat mayonnaise a 50 wt% reduction in the ordinary starch content was performed, while for full-fat mayonnaise, the oil content was reduced from 79 to 70 wt%. To study if the stability was affected when CNFs were added, analyses as visual and accelerated stability tests, droplet size measurements and rheology studies, determining the shear viscosity, and the loss and storage moduli, were conducted after 1 day, 1 week and 1 month of storage in room temperature. Even though changes in droplet size distributions and rheological properties indicated some coalescence, the visual stability was not changed after 1 month of storage for any of the samples. The decrease in viscosity and moduli inflicted by reduction of starch or fat, could be regained by the addition of CNFs at 0.75 wt % and 0.42 wt %, respectively. Based on the results in this work, mayonnaise with reduced starch or fat content can be produced when CNFs are used as a viscosifying agent.

Statistical modeling of electrowetting-induced droplet coalescence for condensation applications

Coalescence of water droplets strongly influences dropwise condensation on hydrophobic surfaces. This work reports a study on experimental data-based statistical modeling to predict the coalescence dynamics of an ensemble of water droplets under the influence of an electrowetting (EW) field. Previous related studies have primarily used high speed visualization to characterize coalescence. However, this study uses statistical modeling to analyze the parameter space associated with EW-induced coalescence, noting that physics-based modeling of EW-induced coalescence is challenging. The objective of this study is to quantify the influence of the applied voltage, frequency of the AC waveform and the geometry of the EW device on two parameters related to droplet coalescence (droplet radius enhancement and reduction in wetted area). Multiple supervised learning techniques are used to identify dominant variables and statistically model the influence of these variables on coalescence. Data for the statistical models is obtained via image analysis from coalescence experiments.The statistical models lead to a reference tool to predict droplet coalescence-related parameters versus the applied voltage and electrode geometry. Importantly, data analysis shows that droplet coalescence is independent of the AC frequency; this conclusion would be challenging to infer from conventional analysis. It is also seen that an EW field significantly narrows the droplet size distribution. Overall, this study leads to a detailed understanding of the factors that impact EW-induced coalescence and provides a tool (which matches experimental data) to predict the change in droplet size distribution. These findings are key to quantifying the influence of EW on condensation rates and heat transfer. This work leverages the large amount of data from experiments to develop statistical analysis-based predictive models. This approach can be utilized for predictive modeling of other data-rich but complex physical phenomena.

The effect of adjuvants on spray droplet size from hydraulic nozzles.

BackgroundWhen spraying simple liquids through a hydraulic nozzle, the mechanisms that affect breakup into droplets have recently been described. However, it is unknown how the droplet size distribution changes when surfactant‐based adjuvants are added to the spray.ResultsWhen spraying different surfactant‐based solutions containing commercial adjuvants, the breakup of the different liquids behaves in the same way as for water‐only sprays, but the droplet sizes are smaller. By replacing the equilibrium surface tension with the dynamic surface tension at a surface age of ~20 ms, the volume mean droplet size variation with the Weber number, flow rate and nozzle geometry follows the predictions established for pure water sprays. When we rescale the droplet size distribution with the mean droplet size, all distributions collapse onto a single curve and can be described by a compound Gamma function.ConclusionAddition of a number of surfactant‐based adjuvants to an agricultural spray is observed to lead to a slight decrease in the volume mean droplet size. We show that the effects of these adjuvants on the drop size can be understood by taking into account the nozzle geometry, the flow rate, the liquid and air densities and the dynamic surface tension of the surfactant solutions at a surface age of approximately 20 ms. © 2020 The Authors. Pest Management Science published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.

Barley β-glucan effects on emulsification and in vitro lipolysis of canola oil are modulated by molecular size, mixing method, and emulsifier type

The purpose of this study was to examine the impact of mixing methods, emulsifier types and molecular weights of barley β-glucan (BG) on emulsification and in vitro lipolysis of canola oil-in-water emulsions. Three different emulsifiers, Triton x100 (TTN), lecithin (LCN) and whey protein isolate (WPI), and three orders of mixing high molecular weight barley BG with oil and emulsifier were studied by measuring viscosity, microstructure and particle size distribution of the systems; while extent of lipolysis was quantified by an in vitro digestion method. In addition, lipids initially emulsified with TTN were mixed with barley BG of low, medium and high molecular weight to determine the effect of BG molecular weight on canola oil emulsion structure and lipolysis. In the absence of barley BG, lipid emulsification depended on the emulsifier type with larger lipid droplets found in WPI stabilized emulsions. Incubating emulsions with fibres increased the viscosity and size of the emulsified droplets, but to different extents depending on the emulsifier type and mixing order. Addition of BG reduced lipid digestion to the greatest extent for initially small droplet sizes, but independent of viscosity. Microstructure and particle size analysis suggest that the mechanism involves droplet flocculation restricting the surface area available for lipase action. Changes in droplet size distribution were observed after digestion only for high molecular weight BG, with more large droplets. All BG samples slowed lipolysis of emulsions but to different extents depending on the molecular weight with the largest BG significantly reducing lipolysis (p < 0.05). A rationalization is proposed for the impact of different molecular weights of barley BG on the depletion flocculation of emulsions using two models. These results enhance our understanding of the impact of soluble dietary fibres on the physicochemical and structural changes that may occur to emulsified lipids within the gastrointestinal tract.

Lignin-Rich PHWE Hemicellulose Extracts Responsible for Extended Emulsion Stabilization.

Wood hemicelluloses have an excellent capacity to form and stabilize oil-in-water emulsions. Galactoglucomannans (GGM) from spruce and glucuronoxylans (GX) from birch provide multifunctional protection against physical breakdown and lipid oxidation in emulsions. Phenolic residues, coextracted with hemicelluloses using the pressurized hot water (PHWE) process, seem to further enhance emulsion stability. According to hypothesis, phenolic residues associated with hemicelluloses deliver and anchor hemicelluloses at the emulsion interface. This study is the first to characterize the structure of the phenolic residues in both GGM- and GX-rich wood extracts and their role in the stabilization of emulsions. PHWE GGM and GX were fractionated by centrifugation to obtain concentrated phenolic residues as one fraction (GGM-phe and GX-phe) and partially purified hemicelluloses as the other fraction (GGM-pur and GX-pur). To evaluate the role of each fraction in terms of physical and oxidative stabilization, rapeseed oil-in-water emulsions were prepared using GGM, GX, GGM-pur, and GX-pur as stabilizers. Changes in droplet-size distribution and peroxide values were measured during a 3-month accelerated storage test. The results for fresh emulsions indicated that the phenolic-rich fractions in hemicelluloses take part in the formation of emulsions. Furthermore, results from the accelerated storage test indicated that phenolic structures improve the long-term physical stability of emulsions. According to measured peroxide values, all hemicelluloses examined inhibited lipid oxidation in emulsions, GX being the most effective. This indicates that phenolic residues associated with hemicelluloses act as antioxidants in emulsions. According to chemical characterization using complementary methods, the phenolic fractions, GGM-phe and GX-phe, were composed mainly of lignin. Furthermore, the total carbohydrate content of the phenolic fractions was clearly lower compared to the starting hemicelluloses GGM and GX, and the purified fractions GGM-pur and GX-pur. Apparently, the phenolic structures were enriched in the GGM-phe and GX-phe fractions, which was confirmed by NMR spectroscopy as well as by other characterization methods. The frequency of the main bonding pattern in lignins, the β-O-4 structure, was clearly very high, suggesting that extracted lignin remains in native form. Furthermore, the lignin carbohydrate complex of γ-ester type was found, which could explain the excellent stabilizing properties of PHWE hemicelluloses in emulsions.

Molecular exchange processes in mixed oil-in-water nanoemulsions: Impact on droplet size and composition

The impact of oil water-solubility on mass transfer processes - Ostwald ripening (OR) and compositional ripening (CR) - in mixed oil-in-water nanoemulsions was investigated. Changes in droplet size distribution and composition were measured using dynamic light scattering and differential scanning calorimetry (DSC), respectively. Three nanoemulsions with similar droplet diameters (≈170 nm) were formed from oils with relatively low (octadecane), intermediate (hexadecane), or high (tetradecane) water-solubility. Mixed nanoemulsions were formed by blending these systems together (1:1). Complete oil exchange occurred within a few days for octadecane-hexadecane nanoemulsions and a few hours for tetradecane-hexadecane ones. For the latter system, rapid droplet growth (171–194 nm) occurred during the first 12 h due to CR, followed by slow droplet growth (194–204 nm) over the next 6.5 days due to OR. These results may be useful for optimizing the formulation of nanoemulsions containing multiple kinds of hydrophobic ingredient.

Copepod manipulation of oil droplet size distribution

Oil spills are one of the most dangerous sources of pollution in aquatic ecosystems. Owing to their pivotal position in the food web, pelagic copepods can provide crucial intermediary transferring oil between trophic levels. In this study we show that the calanoid Paracartia grani can actively modify the size-spectrum of oil droplets. Direct manipulation through the movement of the feeding appendages and egestion work in concert, splitting larger droplets (Ø = 16 µm) into smaller ones (Ø = 4–8 µm). The copepod-driven change in droplet size distribution can increase the availability of oil droplets to organisms feeding on smaller particles, sustaining the transfer of petrochemical compounds among different compartments. These results raise the curtain on complex small-scale interactions which can promote the understanding of oil spills fate in aquatic ecosystems.

Dispersion characteristics of pregelatinized waxy rice starch and its performance as an emulsifier for oil-in-water emulsions: Effect of gelatinization temperature and starch concentration

The dispersion characteristics and the emulsifier performance of pregelatinized waxy rice starch gelatinized at different temperatures (65, 75, and 85 °C abbreviated as PWRS 65, 75, and 85, respectively) and various concentrations (3, 5, 7, and 9 wt%) were studied. The varying degree of gelatinization resulted in different characteristics for both PWRS dispersions and emulsions. The rheological parameters of the PWRS 65 dispersion and emulsions were strongly affected by concentration; the yield stress, consistency coefficient, pseudoplasticity, and apparent viscosity increased with an increase in PWRS 65 concentration. The remaining granules resulting from an incomplete gelatinization process were able to prevent creaming at PWRS 65 concentrations of more than 5 wt% but were unable to protect against oil droplet coalescence. Consequently, a change in droplet size distribution occurred in the emulsions with PWRS 65, even at high concentrations. The higher gelatinization temperature generates a higher density polymer network, created by expanded starch during gelatinization, in the dispersion. Gelatinization at 75 and 85 °C produced a dispersion structure that was sensitive to shear stress and generated shear-thinning behavior in the emulsions with unnoticed yield stress. The better ability of PWRS in maintaining droplet size resulting from a higher temperature indicates the melted starch polymer during gelatinization provides better protection against droplet coalescence than the starch polymer in a crystalline state. PWRS 85 can be considered for further development as a food grade emulsifier because it can produce a stable emulsion.

Cloud albedo changes in response to anthropogenic sulfate and non-sulfate aerosol forcings in CMIP5 models

Abstract. The effects of different aerosol types on cloud albedo are analysed using the linear relation between total albedo and cloud fraction found on a monthly mean scale in regions of subtropical marine stratocumulus clouds and the influence of simulated aerosol variations on this relation. Model experiments from the Coupled Model Intercomparison Project phase 5 (CMIP5) are used to separately study the responses to increases in sulfate, non-sulfate and all anthropogenic aerosols. A cloud brightening on the month-to-month scale due to variability in the background aerosol is found to dominate even in the cases where anthropogenic aerosols are added. The aerosol composition is of importance for this cloud brightening, that is thereby region dependent. There is indication that absorbing aerosols to some extent counteract the cloud brightening but scene darkening with increasing aerosol burden is generally not supported, even in regions where absorbing aerosols dominate. Month-to-month cloud albedo variability also confirms the importance of liquid water content for cloud albedo. Regional, monthly mean cloud albedo is found to increase with the addition of anthropogenic aerosols and more so with sulfate than non-sulfate. Changes in cloud albedo between experiments are related to changes in cloud water content as well as droplet size distribution changes, so that models with large increases in liquid water path and/or cloud droplet number show large cloud albedo increases with increasing aerosol. However, no clear relation between model sensitivities to aerosol variations on the month-to-month scale and changes in cloud albedo due to changed aerosol burden is found.

Parametric studies of formation and morphology of sub-micron sized GO stabilized PS/GO containers encapsulating 8-HQ

The work identifies parameters and proposes mechanisms that are crucial in making smart containers with encapsulating agents by Pickering emulsion route for anti-corrosion coating and advanced materials applications. We demonstrate the unmodified graphene oxide (GO) particles as potential stabilizers for oil-in-water emulsions not requiring any modification to the properties of the emulsion phases. The model system, GO stabilized styrene in water, was used to explore the mechanistic details of the stable emulsion formation and subsequent formation of polystyrene/graphene oxide (PS/GO) containers after emulsion polymerization. The results indicate a clear size effect during packing of GO at oil-water interface and smaller GO sheets produced homogenous emulsion without any residual water volume. The emulsion droplet size distribution changes from bimodal to monomodal with the increase in GO concentration and it reverses with oil–water phase ratio. For the first time, a correlation was developed between these variables and the size, polydispersity index (PDI), morphology, conversion, and yield of the containers produced by emulsion polymerization. The parametric controls required for preparing PS/GO containers with narrow size distribution (PDI = 0.23), smaller size and various morphologies are discussed, with a probable mechanism. All these studies were carried out in presence of a corrosion inhibitor, 8-Hydroxyquinoline (8-HQ), to be encapsulated in the container. The containers were produced with 75% encapsulation efficiency.

Population balance of droplets in a pulsed disc and doughnut column with wettable internals

Population balance of droplets was studied in a square-sectioned pulsed disc and doughnut column with wettable internals. It was found that a liquid film of the dispersed phase was formed on the internals. To describe the interaction between the droplets and the liquid film, three more terms need to be added into the source term of the classic population balance equation (PBE). To determine the source term of the PBE, functions including the droplet-layer coalescence frequency, residual droplet size distribution, droplet dispersion frequency from the liquid layer, droplet breakup frequency, and daughter droplet size distribution were measured experimentally. The droplet-layer coalescence frequency increases as the pulsation intensity decreases because of the longer contacting time. The residual droplet size is around half of the original coalescing droplet and affected little by the pulsation. The droplet dispersion frequency gets higher with the increasing of the pulsation intensity or the thickness of the liquid layer. The droplet breakup frequency is positively related to the energy input and droplet size. The daughter droplet size distribution changes from inverted U-shaped to M-shaped as the pulsation intensity rises. Based on the experimental results, empirical correlations were proposed to calculate these functions. Furthermore, the correlation equations were applied in a simplified population balance model to calculate the droplet number density in the column. The predicted results agree well with the experimental data, which proved the feasibility of the correlations.