جستجوی مقالات مرتبط با کلیدواژه « emulsion » در نشریات گروه « مهندسی شیمی، نفت و پلیمر »

Low-salinity waterflooding is a practical method to maintain the pressure of reservoirs and increase oil recovery. However, an aspect that requires further investigation is the impact of water salinity on the instability and deposition of asphaltene in the reservoir that may lead to formation damage and injectivity loss. To investigate this type of damage and the associated mechanisms, dynamic tests were performed using a Hele-Shaw cell. Oil and water were co-injected to mimic the injection area condition around the well-bore, and the effect of brine salinity on emulsification and asphaltene precipitation/deposition was investigated. Moreover, two different scenarios were considered to localize the deposited asphaltene: i) in the presence of an asphaltene instability stimulator such as normal pentane, ii) in absence of normal pentane. Furthermore, two compositionally different crude oils were used: Ab-Timur and Koupal. The results for Ab-Timur oil showed that the brine salinity and the type of ions have a significant effect on in-situ emulsification and asphaltene deposition. For this oil, the most stable emulsion with a droplet size of 151 μm was obtained in twice-diluted-seawater and the amount of asphaltene precipitation was 18.3% of the cell volume in the presence of normal alkane. It can be concluded that there is a direct relationship between emulsion stability and asphaltene precipitation: the more stable the emulsion, the more asphaltene deposition. For both oils, it was observed that with ten-times-diluted seawater there are trapped oil areas which are bypassed by the flowing water. Areal microscopic observation showed that the oil-water interface remains unchanged even by increasing injection rate, due to formation of a rigid layer around the oil. Ultimately, this shows that in the actual process of low-salinity waterflooding in oil fields, there is a possibility of asphaltene instability at some salinity ranges that can cause oil trapping due to oil-brine interface hardening.

During the fiber and/or yarn spinning processes, sizing, weaving or dyeing of the textiles, various finishing treatments are performed on the fibers, yarns or fabrics to increase the added value of the final product or to avoid the technical problems during the textile production. Finishing treatments in addition to making changes in the physical and chemical structure of the yarn and fabric, new characteristics are added to the textiles and as a result, their applications are expanded in order to meet the needs of the customers. Emulsion polymerization has many applications in various fields, especially textile industries, due to its advantages such as simplicity of the production process, possibility of synthesizing polymers with high molecular weight and low energy consumption. Admicellar polymerization also provides the possibility of applying very thin polymeric coatings on various substrates. Therefore, due to the ease of the coating process, it has a great ability to improve the surface properties of textiles. Emulsion and admicellar polymerization processes are widely used in the textile industry for finishing the fibers, yarns and fabrics to improve the properties of textiles. In this article, the emulsion and admicellar polymerization processes is introduced. Then, their applications in the textile industry finishing processes including water and fire repellent, electrical conductivity, antimicrobial, ultraviolet shedding, fragrance textiles as well as the production of water-soluble adhesives for use in fabrics dyeing and printing were reviewed.

Oil-associated salts, depending on their origin, usually contain sodium, potassium, and magnesium. One of the best and most effective ways to separate salt water from crude oil is to use an electrostatic field. In this method, the droplets are polarized in the presence of an electric field and an electrostatic force is created between them, which causes the droplets to approach and coagulate. Using an electric field, the coagulation rate of a dispersed phase in an emulsion can be increased. Therefore, methods based on electric current have been proposed. From an energy efficiency point of view, electrical separation is the best way to break the emulsion and desalinate the oil. Therefore, an electric current is used when the salt water droplets are difficult to separate from the oil. The basic principles of electrostatic desalination of crude oil can be summed up as the application of small droplets of water under an electric field and the formation of larger droplets of water with higher settling velocities.

Precipitate migration during smart water injection plays a significant role in improving the oil recovery. This study showed that the process of mixing two incompatible water causes sulfate precipitate production while introducing oil to the combination results in an emulsion formation. The main objective of this study is to investigate the fine solids present in the water and their roles in emulsion formation and how they affect the oil recovery. Three types of formation water were used in this study. These 3 water types contained high concentrations of barium, calcium and strontium ions respectively. The smart water contains high concentration of sulfates. Moreover, crude oil and model oils (containing Stearic acid) were used in order to study the emulsion formation conditions. The composition of both primary oil and floating oil were studied using UV analyzing method. Finally, the effect of emulsion formation in porous media on oil recovery was studied. Experiments showed that mixing smart and formation water results in Barium, calcium and Strontium Sulfate precipitation. By introducing oil to the combination of the two water types, a reduction in the amount of precipitate was observed. Finally, the results, which were obtained by implementing UV, showed that amount of stearic acid and also the precipitates were decreased in the oil phase. Therefore, this must be due to the interaction among polar components of the oil phase and the precipitate fines, which it causes an emulsion formation. Water flooding using a smart water containing sulfate ion, and the one that does not contain sulfate, have shown that precipitates which have caused an emulsion formation increases the recovery factor from 14 to 47 percent.

An emulsion mixture system (usually water, oil and emulsifer) consists of two immiscible phases, the dispersed phase and the dispersion medium (dispersant-continuous). Due to their specifc rheological and physical-chemical properties, emulsions are commonly used in different industries such as cosmetics-pharmaceuticals, food and destruction (road construction, building destruction, etc.). One of the important requirements is appropriate stability of the emulsions over a certain period of time. Emulsions are thermodynamically unstable and several factors affect their instability including the variables of production process and storage conditions. Therefore, emulsifers are suitable to exhibit long-term stability and their performance can be determined by identifying the hydrophilic-lipophilic balance (HLB) characteristic in these compounds. HLB value is a number which is given by the emulsifer to indicate the hydrophilic and lipophilic tendencies of the material. The present work introduces the concept of HLB and methods for determination this character in various ionic and nonionic emulsifers. Considering the relation of the emulsifer HLB to its stability, different methods for evaluation the emulsions stabilities are discussed.

Water injection especially low-salinity water injection has provided a low-cost EOR method for more oil recovery. In recent years, most of the studies on low-salinity waterflooding have been focused on the investigation of the effect of water injection on rock/oil/water interaction. The purpose of this study is to investigate the fluid/fluid interaction which has received less attention in comparison with the rock/fluids interaction. In this experimental work, a series of bottle tests have been performed with 20 percent of crude oil and 80 percent of saline water (for five different common salts in the seawater) with different salinities from 6,000 to 40,000 ppm. By sampling the emulsified portion at the oil/water interface, the size distribution of the water droplets in oil has been obtained. Moreover, the size of water droplets have varied from 0.02 to 1.65 mm, and relative frequency of categories was 0.73 at its maximum. The size of water droplets decreases with a decease in the salinity. Among the salts, calcium chloride is more effective in comparison with others as the water droplet size is the lowest among three other salts, and consequently it could attract more natural surface active materials from oil to water-oil interface. The sorting of salts from highest to lowest stable emulsion is calcium chloride, magnesium chloride, sodium sulfate and sodium chloride. Ultimately, this is due to the interactions of ions in saline water with oil, charge density of ions and their surface activity.

Hydrogels are water-saturated polymeric networks with many different structures which areused in different applications such as: biomedical, pharmacy and biosensors and separation of biomolecules and cells. In recent years, hydrogels, because of their stable and flexible structure, have received attention in mass transfer technology. Temperature-, pressure-, pH- and electric field-responsive hydrogels are novel control systems in microfluidic applications. The transport phenomena have been greatly improved by this emerging new hydrogel-based composite technology. In this respect, this composite is used to enhance mass transport in hydrogels by forming a colloidal environment, which is useful in an application such as tissue engineering. As a new type of hydrogel-based composite, emulsion-filled gels are water-saturated polymers doped with oil droplets. These materials have major advantages in drug delivery systems and food science applications.The characteristics of these new gels are being studied in order to discover their new applications extended to other physic-chemical fields.

Many food products are comprised of an emulsion gel structure in which emulsion droplets are dispersed within a gel network. Formation of a stable emulsion which is later turned into a gel using processing techniques including heating, acidification or enzyme assisted-clotting is a crucial stage in the production of an emulsion-gel system. In the present study the influence of various concentrations of whey protein concentrate (3-8% w/w) and water soluble fraction of Persian gum (0.3-0.6% w/w) on the quality attributes of oil-in-water emulsion prior and after heat treatment (at 90 oC for 30 min) was evaluated. To this end, changes in the zeta potential, size of droplets, rheological behaviour of emulsions and also their microstructure were investigated. The results showed that increasing the concentration of whey protein concentrate in the system reduced the size of the emulsion droplets. On the other hand, the addition of 0.6% soluble fraction of Persian gum led to larger droplets. More over, heating emulsion samples resulted in a rise in the size of droplets and broadened their size distribution curves. However, Persian gum at lower level (0.3%) was found to considerably increase the stability of emulsion against heat. The viscosity of emulsion was shown to be greatly dependent on the soluble fraction of Persian gum concentration and dramatically increased upon heating which was attributed to depletion flocculation and protein aggregation. In addition, all samples exhibited Newotonian behaviour before and after heat treatment except at higher proportions of whey protein concentrate and Persian gum, which changed to shear thinning following heating. These findings confirm the capability of Persian gum for production of heat stable emulsions which may find various applications in food formulation such as Emulsion-gels.

In most of the oil fields, the produced oil contains some amounts of brine in form of water in oil emulsion. The general method to break the emulsion is chemical demulsifying process. Recently, biological methods have got more attention in emulsion separation applications. In this project, the Acinetobacter Calcoaceticus strain has been used to produce a demulsifying agent for emulsion breakage. The supernatant from centrifuging the fermentation media showed an appropriate ability in separation of the water-in-oil emulsion in two phases. To improve the produced demulisifier performance, the important conditions such as the culturing media pH, temperature and C/N ratio were optimized by using Box Behnken surface response methodology. The maximum emulsion breakage in the optimized conditions (i.e. pH=5, T=35 and C/N=10) was obtained equal to 95%. The results revealed that this strain has a high potential in production of effective surface active agents for breaking the oil emulsions.

Several emulsions were synthesized using a crude oil sample named Nowruz as the oil phase، the deionized water as the water phase and Span 40-type surfactant as the emulsifier and parameters affecting the rheological properties of emulsions were studied. In order to investigate the quality of emulsions، their stability was monitored in a three month period. A power-law model was used for the dependence of emulsion viscosity on shear rate and Liu، Richardson، Mooney، and Krieger-Dougherty models were used for the dispersed phase volume fraction dependency. It was observed that the data obtained from modeling were consistent with the experimental data. The results obtained by microscopic analysis revealed that the phase inversion phenomenon took place in the range of 40 to 50% of the dispersed phase (water) content. Temperature was found to be a significantly effective factor in all the samples including the crude oil and its emulsions. It was observed that an increase in temperature could cause a considerable decrease in viscosity، shear stress، and dynamic moduli. An increase in water volume fraction caused an increase in viscosity and dynamic moduli up to the phase inversion point and resulted in a reverse trend beyond this point. The investigation of shear rate effect demonstrated a Newtonian behavior for the crude oil and shear-thinning effect for the emulsions over a wide range of shear rates. The shear-thinning effect increased with an increase in water content and surfactant concentration. The results showed a decrease in loss tangent and a notable increase in viscosity، shear stress، dynamic moduli، and elasticity of emulsions with an increase in surfactant concentration.

Two steps synthetic method for the preparation of a novel emulsion stabilizer called poly(ricineoleic acid-b-ethyleneglycol-b-ricineoleic acid) with average mass molecular weight of 7000 Daltons is investigated. In the first step, oligoricineoleic acid with average mass molecular weight of 1800 Daltons is synthesized (yield 70%). In the second step, the desired copolymer is synthesized from the reaction of two moles of oligomer with one mole of polyethylene glycol and its stabilizing effect on an water/oil emulsion is investigated. For the formulation of the emulsion, the synthesized copolymer is first dissolved at 45oC in diesel oil while stirring, and then this solution is added dropwise to the solution of saline water (1M). Then the mixture is stressed under ultrasonic waves for 5 s to afford smaller drops, after which the emulsion shows good stability. A thin layer film of emulsion- produced from injection of emulsion (0.1 μL) is studied by light microscope equipment. In this study the number of oil droplets and the average diameter of droplets are determined. Also the mole fractions (φ = 0.32) are calculated. This copolymer can be used as a stabilizer in invert emulsion muds, which are used in perforating industry and as a thickener in food and cosmetic industries.

The invert-emulsion drilling fluids are commonly used to drill reactive formations because they inhibit water interaction with sensitive shales and dispersive formations. In an invert-emulsion drilling fluid solid additives should not be wet. In the absence of oil wetting agents, solid particles including weighting agents and shale are usually preferentially water-wet in mineral oils/brine emulsions saturated with calcium chloride or sodium chloride. Phospholipid and alkylimidazoline were used to make the solids oil-wet. Then the wettability of Barite and Calcite in invert-emulsion was studied along with evaluation of yield point and gel strength of drilling fluids. These oil- wetting agents caused Barite and Calcite to be moderately to strongly oil-wet resulting in lower yield point and gel strength for fluid. Alkylimidazoline is the comparatively more effective oil-wetting agent in different invert-emulsion drilling fluids.