The Stability of Water‐in‐Crude and Model Oil Emulsions

The critical electric field (cef) technique has been utilized to measure the stabilities of a variety of water‐in‐model oil and petroleum emulsions. The cef method allows for a fast, reproducible, and quantitative gauge of emulsion stability. Here, we have used cef to measure the stability of water‐in‐heptane‐toluene‐asphaltene emulsions and confirmed the importance of solvation of asphaltenes and the state of asphaltene aggregation to emulsion stability. Emulsion stability increased with the concentration of soluble asphaltenes near the point of precipitation. Droplet sizes were measured with optical microscopy in order to calculate interfacial areas and film thicknesses. It was found that film thickness increased with asphaltene concentration up to the solubility limit, above which increased concentration had little effect, and cef increased with interfacial film thickness up to a monolayer coverage of asphaltene aggregates, above which film thickness had a much smaller effect. These findings were applied to a cef investigation of water‐in‐ppetroleum emulsions to develop correlations of the stability of water‐in‐ccrude oil emulsions. A strong correlation (coefficient = 0.95) was found for cef with the product of asphaltene concentration and the difference in hydrogen to carbon atomic ratios of the asphaltenes and petroleum solvent. The development of a kinetic model and its fit to experimental data revealed the effects of asphaltene chemistry, solvency, and resin concentration on the adsorption and consolidation of emulsion stabilizing interfacial films.     

Surfactant Concentration,Antioxidants, and Chelators Influencing Oxidative Stability of Water‐in‐Walnut Oil Emulsions

Effects of surfactant concentration, antioxidants with different polarities, and chelator type on the oxidative stability of water‐in‐stripped walnut oil (W/O) emulsions stabilized by polyglycerol polyricinoleate (PGPR) were evaluated. The formation of primary oxidation products (lipid hydroperoxides) and secondary oxidation products (hexanal) decreased with increasing PGPR concentrations (0.3–1.0 wt% of emulsions). Excess surfactant might solubilize lipid hydroperoxides out of the oil–water interface, resulting in the decreased lipid oxidation rates in W/O emulsions. At concentrations of 10–1000 μM, the polar Trolox demonstrated concentration‐dependent antioxidant activity according to both hydroperoxide and hexanal formation. The antioxidant efficiency of the non‐polar α‐tocopherol was slightly reduced at the higher range of 500–1000 μM based on hydroperoxide formation. Both ethylenediaminetetraacetic acid (EDTA) and deferoxamine (DFO) at concentrations of 5–100 μM reduced the rates of lipid oxidation at varying degrees, indicating that endogenous transition metals may promote lipid oxidation in W/O emulsions. EDTA was a stronger inhibitor of lipid oxidation than DFO. These results suggest that the oxidative stability of W/O emulsions could be improved by the appropriate choice of surfactant concentration, antioxidants, and chelators.     

Breaking Water‐in‐Bitumen Emulsions using Polyoxyalkylated DETA Demulsifier

Adding demulsifier is currently the most widely used method for breaking water‐in‐oil emulsions. Experimental demulsifiers based on DETA with various PO and EO contents were synthesized and their RSN values were determined. The dehydration efficiency of these demulsifiers was measured in diluted bitumen using both gravitational settling and centrifugation tests. The results indicate that some of the DETA products could perform potentially at least as well or better than the demulsifier currently used in a commercial plant. RSN values are correlated very well with EO and PO numbers. Optimal dehydration efficiency is in the RSN range of 18 to 22, which corresponds to a PO‐to‐EO ratio in the range of 1 to 1.8.     

Predicting Power for a Scaled‐up Non‐Newtonian Biomass Slurry

High‐solids biomass slurries exhibit non‐Newtonian behavior with a yield stress and require high power input for mixing. The goals were to determine the effect of scale and geometry on power number P₀, and estimate the power for mixing a pretreated biomass slurry in a 3.8 million L hydrolysis reactor of conventional design. A lab‐scale computational fluid dynamics model was validated against experimental data and then scaled up. A pitched‐blade turbine and A310 hydrofoil were tested for various geometric arrangements. Flow was transitional; laminar and turbulence models resulted in equivalent P₀ which increased with scale. The ratio of impeller diameter to tank diameter affected P₀ for both impellers, but impeller clearance to tank diameter affected P₀ only for the A310. At least 2 MW is required to operate at this scale.     

Under‐Oil Superhydrophilic Poly(vinyl alcohol)/Silica Hybrid Nanofibrous Aerogel for Gravity‐Driven Separation of Surfactant‐Stabilized Water‐in‐Oil Emulsions

For efficient and green separation of surfactant‐stabilized water‐in‐oil (W/O) emulsions, under‐oil superhydrophilic poly(vinyl alcohol) (PVA)/silica hybrid nanofibrous aerogel is fabricated by freeze‐drying the dispersion of shortened PVA/tetraethyl orthosilicate composite electrospun nanofibers in t‐butanol, followed by heat‐treatment. Its hierarchical porous structure, observed by scanning electron microscope, consists of major and minor pores with an average diameter of 15.9 and 1.0 µm, respectively. The silica‐based crosslinking structure inside the nanofibers and the chemical linkage between them, evidenced by infrared spectroscopy, endows the nanofibrous aerogel with desirable stability in water and compression recoverability. When it is used for gravity‐driven separation of Span80 stabilized water‐in‐n‐hexane emulsion, the flux is 2083 L m^?2 h^?1 and the purity of the separated n‐hexane reaches 99.997%, corresponding to the separation efficiency of 99.79%. The nanofibrous aerogel after use is readily recycled by rinsing and freeze‐drying, without using any organic solvent, as it possesses under‐oil superhydrophilicity and prominent oil antifouling property. Differing from the previously reported separation materials, PVA/silica hybrid nanofibrous aerogel simultaneously acts as gravity‐driven filtration material and adsorption material to both absorb their coalesced water droplets and allow the separated oil to penetrate in the separation process.     

Interfacial Crystallization of Diacylglycerols Rich in Medium‐ and Long‐Chain Fatty Acids in Water‐in‐Oil Emulsions

The effects of diacylglycerols rich in medium‐ and long‐chain fatty acids (MLCD) on the crystallization of hydrogenated palm oil (HPO) and formation of 10% water‐in‐oil (W/O) emulsion are studied, and compared with the common surfactants monostearoylglycerol (MSG) and polyglycerol polyricinoleate (PGPR). Polarized light microscopy reveals that emulsions made with MLCD form crystals around dispersed water droplets and promotes HPO crystallization at the oil‐water interface. Similar behavior is also observed in MSG‐stabilized emulsions, but is absent from emulsions made with PGPR. The large deformation yield value of the test W/O emulsion is increased four‐fold versus those stabilized via PGPR due to interfacial crystallization of HPO. However, there are no large differences in droplet size, solid fat content (SFC), thermal behavior or polymorphism to account for these substantial changes, implying that the spatial distribution of the HPO crystals within the crystal network is the driving factor responsible for the observed textural differences. MLCD‐covered water droplets act as active fillers and interact with surrounding fat crystals to enhance the rigidity of emulsion. This study provides new insights regarding the use of MLCD in W/O emulsions as template for interfacial crystallization and the possibility of tailoring their large deformation behavior. Practical Applications: MLCD is applied in preparing W/O emulsion. It is found that MLCD forms unique interfacial Pickering crystals around water droplets, which promote the surface‐inactive HPO nucleation at the oil‐water interface. Thus MLCD‐covered water droplets act as active fillers and interact with surrounding fat crystals, which can greatly enhance the rigidity of emulsion. This observation would provide a theoretical reference and practical basis for the application of the MLCD with appreciable nutritional properties in lipid‐rich products such as whipped cream, shortenings margarine, butter and ice cream, so as to substitute hydrogenated oil. MLCD‐stabilized emulsions can also be explored for the development of novel confectionery products, lipsticks, or controlled release matrices.     

Non‐Newtonian Heat Transfer on a Plate Heat Exchanger with Generalized Configurations

For the configuration optimization of plate heat exchangers (PHEs), the mathematical models for heat transfer and pressure drop must be valid for a wide range of operational conditions of all configurations of the exchanger or the design results may be compromised. In this investigation, the thermal model of a PHE is adjusted to fit experimental data obtained from non‐Newtonian heat transfer for eight different configurations, using carboxymethylcellulose solutions (CMC) as test fluid. Although it is possible to successfully adjust the model parameters, Newtonian and non‐Newtonian heat transfer cannot be represented by a single generalized correlation. In addition, the specific heat, thermal conductivity and power‐law rheological parameters of CMC solutions were correlated with temperature, over a range compatible with a continuous pasteurization process.     

Energy Dissipation Rates of Newtonian and Non‐Newtonian Fluids in a Stirred Vessel

Energy dissipation rates of water and glycerol as Newtonian fluids and carboxyl methyl carbonate solution as non‐Newtonian fluid in a stirred vessel are investigated by 2D particle image velocimetry and compared. Mean velocity profiles reflect the Reynolds (Re) number similarity of two flow fields with different rheological properties, but the root mean square velocity profiles differ in rheology at the same Re‐number. Energy dissipation rates are estimated by direct calculation of fluctuating velocity gradients. The varying energy dissipation rates of Newtonian and non‐Newtonian fluids result from the difference in fluid rheology and apparent viscosity distribution which decides largely the flow pattern, circulation intensity, and rate of turbulence generation.     

Bubble Volume and Aspect Ratio Generated in Non‐Newtonian Fluids

Bubble formation from an orifice submerged in quiescent polyacrylamide aqueous solution was investigated numerically with a sharp‐interface coupled level‐set/volume‐of‐fluid method based on the rheological characteristics of the fluid. In both non‐Newtonian fluids and Newtonian fluids, the numerical approach was able to capture accurately the deformation of the bubble surface, validated by comparison with experimental results. The effects of orifice diameter, solution mass concentration, and gas flow rate on bubble volume and aspect ratio were evaluated. Both the instantaneous and detached volume decrease with the orifice diameter but increase with mass concentration and gas flow rate. The aspect ratio at the departing point tends to rise with the orifice diameter and mass concentration and falls with the gas flow rate.     

Characterization of Bubble Shapes in Non‐Newtonian Fluids by Parametric Equations

Based on experiments with single air bubbles rising in stagnant non‐Newtonian fluids, an innovative model containing the aspect ratio (E) and two parameters (α, β) was proposed and proved to be capable of characterizing the bubble shape from spherical/ellipsoidal to prolate/oblate‐tear with good accuracy. Several impacts on bubble deformation were investigated, involving the rheological properties of the fluids and different forces exerted on the bubble, which were quantified by multiple dimensionless numbers (e.g., Reynolds, Eötvös, and Deborah number). Within a wide range, the empirical correlations were obtained for parameter β, and between α and β. Together with the shape model, a complete system was set up for bubble shape characterization and prediction that will provide new ideas for future studies on bubble hydrodynamics.     

Comparison of Storage Methods for Microfluidically Produced Water‐in‐Oil Droplets

Microfluidically produced water‐in‐oil droplets are an important platform for biochemical research. To investigate the structural integrity of droplets during transfer and storage processes, different methods were compared. Storage as isolated droplets inside plastic tubing or a designed microfluidic chamber led to moderate decreases in droplet volume but only slight changes in monodispersity, whereas bulk storage in an Eppendorf cup led to the complete loss of monodispersity. It is further demonstrated that on‐chip storage of the droplets in a fluidic microcavity array avoids coalescence and enables a reduction in volume with the concurrent increase in the concentration of entrapped proteins, which is relevant for applications in life science.     

Pressure Drop Models for Gas/Non‐Newtonian Power‐Law Fluids Flow in Horizontal Pipes

Models commonly used in literature are evaluated versus 696 data points to predict the pressure drop of gas/non‐Newtonian power‐law fluids flow in horizontal pipes. Suitable models are recommended. A new correlation is developed by ignoring the pressure drop across the gas slug and adopting the liquid slug holdup of gas/non‐Newtonian fluid flow into the homogeneous model. The theoretical curves can capture the test data trends and the overall agreement of predicted values with experimental data is sufficient to be practically applied in industry.     

Coaxial Mixer Hydrodynamics with Newtonian and non‐Newtonian Fluids

The performance of several combinations of a wall scraping impeller and dispersing impellers in a coaxial mixer operated in counter‐ and co‐rotating mode were assessed with Newtonian and non‐Newtonian fluids. Using the power consumption and the mixing time as the efficiency criteria, impellers in co‐rotating mode were found to be a better choice for Newtonian and non‐Newtonian fluids. The hybrid impeller‐anchor combination was found to be the most efficient for mixing in counter‐rotating or co‐rotating mode regardless of the fluid rheology. For both rotating modes, it was shown that the anchor speed does not have any effect on the power draw of the dispersing turbines. However, the impeller speed was shown to affect the anchor power consumption. The determination of the minimum agitation conditions to achieve the just suspended state of solid particles (N_js) was also determined. It was found that N_js had lower values with the impellers having the best axial pumping capabilities.     

Influence of Shear‐Thinning Rheology on the Mixing Dynamics in Taylor‐Couette Flow

Non‐Newtonian rheology can have a significant effect on mixing efficiency, which remains poorly understood. The effect of shear‐thinning rheology in a Taylor‐Couette reactor is studied using a combination of particle image velocimetry and flow visualization. Shear‐thinning is found to alter the critical Reynolds numbers for the formation of Taylor vortices and the higher‐order wavy instability, and is associated with an increase in the axial wavelength. Strong shear‐thinning and weak viscoelasticity can also lead to sudden transitions in wavelength as the Reynolds number is varied. Finally, it is shown that shear‐thinning causes an increase in the mixing time within vortices, due to a reduction in their circulation, but enhances the axial dispersion of fluid in the reactor.     

Using Tomography to Characterize the Mixing of Non‐Newtonian Fluids with a Maxblend Impeller

The flow field inside a cylindrical mixing vessel was visualized by electrical resistance tomography (ERT), a non‐intrusive measurement technique. Six tomography planes, each containing 16 sensing electrodes, measured the mixing time in the agitation of pseudoplastic fluid exhibiting yield stress. The effects of various parameters such as impeller types, impeller speed, fluid rheology, power consumption, Reynolds number, and absence of baffles on the mixing time were investigated. The Maxblend impeller was able to improve the mixing performance of non‐Newtonian fluids in a batch reactor. The mixing quality could be further enhanced by decreasing the xanthan gum concentration and using baffles in the mixing vessel.     

Protein Synthesis in Sub‐Micrometer Water‐in‐Oil Droplets

Water‐in‐oil (w/o) emulsions are used as a cellular model because of their unique cell‐like architecture. Previous works showed the capability of eukaryotic‐cell‐sized w/o droplets (5–50 μm) to support protein synthesis efficiently; however data about smaller w/o compartments (<1 μm) are lacking. This work focuses on the biosynthesis of the enhanced green fluorescent protein (EGFP) inside sub‐micrometric lecithin‐based w/o droplets (0.8–1 μm) and on its dependence on the compartments’ dynamic properties in terms of solute exchange mechanisms. We demonstrated that protein synthesis is strongly affected by the nature of the lipid interface. These findings could be of value and interest for both basic and applied research.     

Influence of Processing on the Physical Stability of Multiple Emulsions Containing a Green Solvent

The influence of the emulsification process on the microstructure and physical stability of model water‐in‐oil‐in‐water (W/O/W) emulsions formulated with a green solvent and a mixture of amphiphilic copolymers as emulsifiers was investigated. Emulsions were prepared by applying a homogenization step with a rotor‐stator device followed by high‐pressure homogenization. Viscous flow tests, transmitted light optical microscopy, globule size distribution (GSD), and multiple light scattering (MLS) measurements were carried out. The GSDs obtained were the result of a recoalescence due to overprocessing and the coalescence of inner droplets with the outer water phase. MLS detected a main destabilization mechanism by creaming. The passing of the emulsion through a high‐pressure homogenizer (HPH) significantly delayed the creaming process.