Thixotropic Behavior of Oil‐in‐Water Emulsions Stabilized with Ethoxylated Amines at Low Shear Rates

Oil‐in‐water (O/W) emulsification is a lubricating pipeline method based on the reduction of the energy frictional loss produced during viscous flow. The flow behavior of heavy O/W emulsions formulated with nonionic surfactants is described. The effects of pH and salinity of the aqueous phase on droplet diameter, stability, and apparent viscosity of O/W emulsions were evaluated. The low‐shear Couette flow of O/W emulsions displayed intense shear‐thinning and thixotropic behavior. Thixotropy was associated to the droplet deformation energy caused by shear rate changes. The droplet deformation and alignment led to the apparent viscosity reduction compared to the fluid at rest. Thixotropic behavior is supposed to balance between the breakdown and recovery of droplet ordered structures. Emulsion formulation parameters were influenced by the aqueous phase pH, enabling to manage the emulsion properties. The droplet mean diameter of < 18 µm resulted in very stable emulsions.     

Heavy crude oil viscosity reduction and rheology for pipeline transportation

Different methods of reducing the viscosity of heavy crude oil to enhance the flow properties were investigated. Experimental measurements were conducted using RheoStress RS100 from Haake. Several factors such as shear rate, temperature and light oil concentration on the viscosity behavior have been studied. This study shows that the blending of the heavy crude oil with a limited amount of lighter crude oil provided better performance than the other alternatives. Experimental measurements in terms of shear stress τ-shear rate and yield stress τ₀ were conducted on the mixture of heavy crude oil-light crude oil (O-light). The results showed a significant viscosity reduction of 375 mPa s at a room temperature of 25 °C. This study shows that the heavy crude oil required a yield stress of 0.7 Pa, whereas no yield stress was reported for the heavy crude oil-light crude oil mixture.     

渤海稠油热采添加剂室内模拟驱油实验研究

化学辅助降粘是提高稠油采收率的重要方法之一。针对渤海稠油目前存在的蒸汽热采过程中原油乳化使粘度迅速增大的问题,研制一种热采添加剂,可以在蒸汽热采过程中注入地层,降低原油乳化率及粘度,增加采收率。该热采添加剂由实验室自制二嵌段聚醚类添加剂、酚醛树脂类添加剂和成熟使用的KLD添加剂复配而成。实验结果表明该热采添加剂具有较好的防乳效果、降粘效果和较好的降低界面张力的特性。通过室内模拟驱油实验,该热采添加剂在添加量为0.3%时,其岩心原油最终采收率达到了91.61%。     

Predicting the Viscosity of Non‐Newtonian Water‐in‐Oil Emulsions Based on the Lederer Model

The accurate prediction of the viscosity of emulsions is highly important for oil well exploitation. Commonly used models for predicting the viscosity of water‐in‐oil (W/O) emulsions composed by two or three factors cannot always fit well the viscosity of W/O emulsions, especially in the case of non‐Newtonian W/O emulsions. An innovative and comprehensive method for predicting the viscosity of such emulsions was developed based on the Lederer, Arrhenius, and Einstein models, using experimental data. Compared with the commonly applied W/O emulsion viscosity models, the proposed method considers more factors, including temperature, volume fraction of water, shear rate, and viscosity of the continuous (oil) and dispersed phase (water). Numerous published data points were collected from the literature to verify the accuracy and reliability of the method. The calculation results prove the high accuracy of the model.     

Effects of Sand Fraction on Toluene‐diluted Heavy Oil in Water Emulsions in Turbulent Flow

The impact of the presence of sand on emulsification of toluene‐diluted heavy oil in simulated process water was systematically studied as a function of agitation time, in a stirred tank. Droplet size distributions were measured by light scattering technique. Optical microscopy and high‐speed video micrography were used to visually monitor agitation and emulsion stability. Results showed that the Sauter mean diameters of the droplets decreased with increasing sand content. Droplet breakage followed a first‐order kinetic model for all mixing speeds. Plots of droplet volume percent frequency versus droplet size followed lognormal distribution. The distribution span broadened into lower sizes with increased sand content. Emulsions were stable for over 48 h after formation.     

超滤(UF)技术处理乳化油废水的研究

采用超滤工艺一间歇式错流操作模型一处理乳化油废水,选用了聚乙烯乙二醇超滤膜(PEG)和卷式膜组件,采用不同的超滤模型对超滤过程中超滤膜透水率、乳化油废水中的COD去除率的变化进行了实验研究,实验结果表明该模型对乳化油废水具有良好的处理效果。     

Antioxidant Activity of Hybrid Grape Pomace Extracts Derived from Midwestern Grapes in Bulk Oil and Oil‐in‐Water Emulsions

Natural antioxidants to inhibit oxidation in edible oils are in high demand. Grape pomace is an abundant, inexpensive source of polyphenolic antioxidants, which are responsible for numerous health benefits. We examined pomace from eight varieties of Midwestern hybrid grapes for phenolic content and antioxidant activity. Ethanolic extracts produced from the pomace of each grape variety were added to two model systems, bulk soybean oil and oil‐in‐water emulsions, to determine antioxidant activity. Oxidation was monitored in each model system at a temperature appropriate to that particular system. While the extracts had relatively little effect in bulk oil, we observed dose‐dependent antioxidant effects of some extracts in oil‐in‐water emulsions. Oxidation in bulk oils was assessed via total polar compounds and polymerized triacylglycerols. Oxidation in emulsions was assessed by peroxide value, headspace oxygen measurements, gas chromatography of headspace volatiles, and fatty acid analysis. Pomace extracts derived from red grapes generally outperformed those from white grapes, with the Marechal Foch variety showing high antioxidant activity at intermediate concentrations. At higher concentrations, Marechal Foch, Corot Noir, Frontenac, and Norton extracts showed promising antioxidant activity. This is the first report on antioxidant activity in an oil and emulsion setting for many of these grape varieties.     

Comparison of Oil‐in‐Water Emulsion between Ultrasonic Irradiation and Mechanical Stirring

To compare oil‐in‐water emulsification behaviors between ultrasonic irradiation and impeller stirring, experiments and calculation by mathematical models were performed. For ultrasonic irradiation, the peak diameter of dispersed oil droplets decreased with an increase in input power and reductions in ultrasonic frequency, ratio of dispersed volume, and interfacial tension. For mechanical stirring, it declined with higher mechanical rotation speed. The results calculated by the mathematical models approximately agreed with the experiments. Ultrasonic irradiation was better than mechanical stirring by an impeller for producing a fine emulsion at higher supplied energy rate into liquid, whereas the tendency was inverse for a rough emulsion at lower input energy rate.     

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.     

Viscosity Reduction of Indian Heavy Crude Oil by Emulsification to O/W Emulsion Using Polysorbate-81

Pipeline transportation is the most convenient means of transportation of crude oil continuously and economically from production site to refinery. However, transportation of heavy crude oil (HCO) through pipelines is difficult due to its high viscosity. The high viscosity of heavy crude oil is mainly due to the presence of poly-aromatic compounds like resins and asphaltenes. Emulsification of HCO using surfactant is believed to be the most favorable technique to reduce the viscosity of HCO for efficient pipeline transport. In the present study, oil-in-water (O/W) emulsion has been formulated using a non-ionic surfactant Polyoxyethylene (5) sorbitan monooleate (PS-81) at different pH, surfactant concentration, and oil content. Box–Behnken response surface method has been used to optimize two responses, apparent viscosity and emulsion stability index (ESI). The optimal values of the parameters found are 75%v/v oil content, 2.5%w/v surfactant concentration, and pH value of 7 at which experimental value of emulsion viscosity is 0.2162 Pa·s, at 150 RPM, with a reduction of viscosity by 95.8% and having ESI of 98.16 after 24 h at 30°C.     

Production of Saponin Biosurfactant from <Emphasis Type="Italic">Glycyrrhiza glabra</Emphasis> as an Agent for Upgrading Heavy Crude Oil

Saponins are the main group of phytogenic biosurfactants extracted from plants. One of the significant applications of these compounds is upgrading and viscosity reduction of heavy crude oil water in oil (W/O) emulsions. In this research, use of saponin extracted from Glycyrrhiza glabra was investigated for viscosity reduction of heavy crude oil and upgrading its API properties. The extracted saponin was characterized using Fourier transform infrared (FTIR) and nuclear magnetic resonance (NMR) spectroscopy. Phase behavior analysis demonstrated a reduction in initial viscosity and improved API gravity of the heavy oil from 2350 mPa·s and 19 to 900 mPa·s and 27, respectively. In addition, the emulsification index (E ₂₄) was found to be 98 % at a saponin concentration of 8 % w/v. It was observed that the emulsions were stable in the pH range of 5.5–13, temperature from 30 to 80 °C and salinity up to 6 % w/v of NaCl solution. Average diameter of W/O droplets evaluated by dynamic light scattering (DLS) were in the range of 10–15 µm. The results obtained from the present research revealed that the extracted saponin improved the physical characteristics of heavy crude oil. We propose the use of saponin as a potential alternative to conventional emulsifiers for upgrading heavy crude oil in petroleum industry.     

Antioxidant Activity of Seaweed Extracts: In Vitro Assays,Evaluation in 5 % Fish Oil‐in‐Water Emulsions and Characterization

In this study the antioxidant activity of absolute ethanol, 50 % ethanol and water extracts of two species of seaweeds, namely Fucus serratus and Polysiphonia fucoides, were evaluated both in in vitro assays and in 5 % fish oil‐in‐water (o/w) emulsions. The 50 % ethanolic extracts of P. fucoides showed higher antioxidant activity both in in vitro assays and in 5 % oil‐in‐water emulsion in the presence or absence of iron. In spite of the higher phenolic content and very good antioxidant activity in some of the in vitro assays, the absolute ethanol extracts of both the species showed a pro‐oxidative tendency in 5 % fish oil‐in‐water emulsion in the presence or absence of iron. In order to investigate the reason for the higher antioxidant activity of 50 % ethanolic extracts of P. fucoides, these extracts were further fractionated into polyphenol‐rich, protein‐rich, polysaccharide‐rich and low‐molecular‐weight fractions. These fractions were tested both in in vitro and in 5 % oil‐in‐water emulsions. The results of the present study showed that the main effect was due to the phenolic compounds. In conclusion, the 50 % ethanolic extracts of P. fucoides can be a potential source of natural antioxidants as these extracts have antioxidant activities similar to those of synthetic antioxidants such as BHT.     

Numerical Simulation of Oil‐Water Core Annular Flow in a U‐Bend Based on the Eulerian Model

The oil‐water core annular flow through a U‐bend is simulated by computational fluid dynamics based on the Eulerian model. More flow parameters and the effect of annulus thickness on core annular flow are discussed. Conformity between the simulated and experimental data is observed. The development of oil‐water core annular flow in the U‐bend is analyzed, and the distributions of pressure and velocity are discussed. Results of the Eulerian model and volume‐of‐fluid (VOF) model are compared and the influence of oil properties on total pressure gradient is investigated. The suitable range of annulus thickness is identified. The results provide suitable operation conditions for designing the U‐bend pipefitting.     

CO2‐Switchable Oil/Water Emulsion for Pipeline Transport of Heavy Oil

By mixing an aqueous solution of tertiary amine, N,N‐dimethylethanolamine (DMEA), with naphthenic acid (RCOOH) derived from heavy oil, a CO₂ switchable zwitterionic surfactant (RCOO^?DMEAH⁺) aqueous system was constructed. The CO₂ switchability of this zwitterionic surfactant was confirmed by visual inspection, pH measurements, and conductivity tests, i.e., the RCOO^?DMEAH⁺ decomposed into RCOOH, DMEAH⁺ and HCO₃^? after bubbling CO₂ through but switched back to its original state by subsequent bubbling N₂ through at 80 °C to remove the CO₂. The interfacial tension tests of heavy oil in DMEA aqueous solutions indicated that the solution containing 0.5 wt% of DMEA and 0.2 wt% of NaCl resulted in the lowest interfacial tension. The O/W emulsion formed when aqueous solutions of DMEA were used to emulsify heavy oil exhibited the best performance when the oil/water volume ratio, DMEA concentration, and NaCl concentration were 65:35, 0.5 and 0.2 wt%, respectively. The feasibility of pipeline transport of the O/W heavy oil emulsion was evaluated. The results illustrated that the demulsification of the O/W emulsion after transport could be easily realized by bubbling CO₂ through. Although demulsification efficiency still needs to be improved, the recycling of the aqueous phase after demulsification by removal of CO₂ looks promising.     

Antioxidant activity of pine bark procyanidins in bulk corn oil and corn oil‐in‐water emulsions

In this work, the ability of pine bark procyanidins to hinder oxidation in bulk corn oil and corn oil‐in‐water‐emulsion has been investigated. A preliminary characterisation of the obtained aqueous (AF) and organic (OW) fractions and subfractions suggested a very polar character and showed that both fractions possess remarkable antioxidant activity when minimum concentrations of 2 mg/mL are used. OW fractions and subfractions derived from both pine varieties were able to inhibit oxidation in oils. More specifically, two organic subfractions were the most efficient for retarding the degradation process, with levels of 62% and 50% after 8 days of treatment, respectively. Organic subfractions obtained from both varieties of pine also rendered possible inhibition levels in oil‐in‐water‐emulsions up to 80% after 4 days of oxidation, more than 3 times higher than the levels provided by tocopherol, a well‐known model commercial antioxidant, which confirms the excellent antioxidant potential of procyanidins from pine bark. Practical application: Lipid deterioration leads to losses in quality and nutritional value and to the development of off‐flavours in many foodstuffs. One way to overcome this drawback is by using antioxidants of natural origin, which is a subject of a great scientific and industrial interest, reflected by the growing number of papers and patents published during the last years. Since aqueous and organic fractions obtained from Pinus pinaster and Pinus radiata bark turned out to be an adequate source of procyanidins in previous investigations of our group, their possible antioxidant role in model lipid systems was investigated. This approach entails also another benefit in terms of waste valorisation, since pine bark is a typical residue of agroforestal industries.     

Isolation of Fucoxanthin from Brown Algae and Its Antioxidant Activity: In Vitro and 5% Fish Oil‐In‐Water Emulsion

Fucoxanthin, a nonprovitamin A carotenoid, is a yellowish‐brown pigment found abundantly in brown algae. Along with chlorophyll a, it is bound to proteins and acts as a light‐harvesting and a light‐transferring pigment. The occurrence of carotenoids and chlorophylls in photosynthetic tissues complicates the isolation of pure fucoxanthin. The present study deals with a method for the isolation of fucoxanthin by low‐temperature crystallization and testing its antioxidant activity both in in vitro assays and in 5% oil‐in‐water emulsion. The yield of fucoxanthin obtained with this method ranged from 0.1% to 0.5% of dried algae depending on the species. Fucoxanthin showed good α,α‐diphenyl‐β‐picrylhydrazyl radical‐scavenging and iron‐chelating properties. However, it showed low reducing power and was poor in the inhibition of lipid oxidation in a liposome model system. When tested in 5% fish oil‐in‐water emulsion with iron as an oxidation inducer, fucoxanthin showed antioxidant activity by resulting in low levels of volatile oxidation products and low tocopherol loss compared to control and butylated hydroxytoluene.