Electrostatic destabilization of water-in-crude oil emulsions: Application to a real case and evaluation of the Aibel VIEC technology

In the current study, the Aibel Vessel Internal Electrostatic Coalescer (VIEC) technology was tested for a real case scenario encountered in the production train of a UK oil field. Depressurized samples were collected both upstream and downstream of the first stage separator. The separation performance was discussed with respect to water cut and droplet size distribution of the emulsions, and the effect of chemical treatment. Issues with respect to representative sampling and testing have been discussed. The application of an external AC electrical field has been shown to significantly enhance the separation of the aqueous phase from tight emulsions, both when it was used alone and in combination with a commercial demulsifier. By using the VIEC technology, the time for separation could be reduced from 8 min to 2 min and the overall BS&W in the emulsions was improved from 45% or 60% to a residual water content of 5-20%. Destabilization of a 45% water-in-oil emulsion by electrical and chemical treatment (20/40 ppm) produced oil in the 2-7% BS&W range whereas the corresponding tests without applying an electrostatic field led to a BS&W greater than 25%. The achieved results strongly suggest that the VIEC technology can resolve the stable emulsion bands encountered in the Schiehallion train and add flexibility or increased production rate to the process. The results also suggest the importance of further studies on the destabilization performances achieved by electrostatic means.     

Influence of Disperse Phase Characteristics on Stability, Physical and Antimicrobial Properties of Emulsions Containing Cinnamaldehyde

Cinnamaldehyde was delivered in emulsion form using Acetem 90-50K as a carrier and Tween 60 as emulsifier. Cinnamaldehyde interacted with Acetem 90-50K by forming H-bonds. The effect of disperse phase characteristics on storage stability, physical and antimicrobial properties was investigated. A storage test of emulsions was carried out for 15 days at two temperatures (22 and 4 °C). Emulsions and nano-emulsions showed higher stability at 22 °C than at 4 °C. Nano-emulsions displayed excellent stability versus creaming and coalescence after 15 days storage at 22 °C (z-avg <100 nm). Physical properties were greatly affected by droplet size and concentration. Emulsions became less viscous, more transparent and darker as the droplet size or concentration decreased. The antimicrobial activity was measured against Listeria monocytogenes and Escherichia coli. Escherichia coli was highly resistant to cinnamaldehyde compared to L. monocytogenes. Incubation with cinnamaldehyde at 2.5 mM caused the complete inactivation of L. monocytogenes after 1 day and of E. coli after 9 days. There was no difference in the antimicrobial effect of cinnamaldehyde due to different droplet sizes (~80 and ~5,000 nm).     

Influence of process parameters on microcapsules loaded with n-hexadecane prepared by in situ polymerization

A series of melamine–formaldehyde microcapsules containing n-hexadecane were synthesized by in situ polymerization from partial etherified melamine–formaldehyde resins. This research was conducted to clarify the influence of different parameters on the encapsulation process, i.e. during the emulsion formation step and during the shell formation using surface tension measurement, Fourier-transform infrared spectroscopy and differential scanning calorimetry. By carefully analyzing the influencing factors including phase volume ratio, types of surfactants and content, stirring rate and time, pH, reaction time, feeding weight ratio of core/shell pre-polymer, the optimum synthetic conditions were found out. The results indicated that a binary mixture of Tween-20 and Brij-35 was found suitable emulsifier at low pH. Furthermore, formaldehyde/melamine (F/M) mole ratio influenced not only the shell formation mechanism but also the particle size distribution, microcapsule morphology and resin conversion rate.     

An “O/S” Emulsion in a System Containing Tween 80 Surfactant and Hexadecane Oil

An emulsion was prepared from hexadecane and a surfactant, Tween 80 (a commercial polyoxyethylene sorbitan mono-oleate), and the destabilization process was followed by visual observation of the separation of the emulsion aided by optical microscopy to estimate droplet size versus time. The emulsions had inferior stability, and the destabilization was completed within a few days. The results showed the emulsion to destabilize with the flocculation step immediately followed by coalescence. The separation rate was at a level calculated from the sedimentation rate of a dilute emulsion. This result was not anticipated, considering the large fraction of the dispersed phase, and an assumption was made as to what counteracting factors may have affected the results.

Effect of Ultrasonication on Droplet Size in Biodiesel Mixtures

Biodiesel fuels have become more attractive recently because of their environmental benefits and cost competitiveness compared to diesel fuel. Many processing improvements have been proposed to increase the conversion rates and the yields of vegetable oil in order to lower production costs and improve biodiesel product quality. In conventional biodiesel production chemistries, alkaline transesterifications of alcohol/oil dispersions should occur primarily near the interface. Ultrasonic mixing has already been shown to increase overall conversion rates for alcohol/vegetable oil mixtures. Our data show that ultrasonic mixing produced smaller droplet sizes than conventional agitation, leading to more interfacial area for the reaction to occur. Droplet size distributions have been measured for conventional impeller and ultrasonic mixing systems using methanol/soybean oil as a model system. The dispersions were stabilized by surfactant in order to obtain droplet size distribution for mixture samples. Ultrasonic mixing produced dispersions with average droplet sizes 42% smaller than those generated using standard impellers.     

Stability of Emulsions Containing Interesterified Fats Based on Mutton Tallow and Walnut Oil

In this work, modified fats were produced by enzymatic interesterification of mutton tallow with walnut oil. As a result of forcing the fat hydrolysis process by addition of water to the enzymatic preparation (11.5, 13.0, 14.5, 16.0 wt %), additional levels of polar fractions (MAGs, DAGs, and FFAs) were observed. The aim of this work was to evaluate the stability of emulsions of modified fats containing natural emulsifiers resulting from enzymatic interesterification of mutton tallow with walnut oil. The physical‐chemical parameters of obtained fats were determined in this study. Using several methods, the stability of the formed emulsions was also evaluated. The results showed that the fats resulting from interesterification in the presence of Lipozyme RM IM (immobilized lipase from Rhizomucor miehei, Novozymes Bagsvaerd, Denmark) with 13.0, 14.5, and 16.0 wt % of water in the enzymatic preparation could form stable emulsion systems. On the other hand, the emulsion of the interesterification system where the amount of water in the enzymatic preparation was 11.5 % showed very low stability. The number of natural emulsifiers (MAGs and DAGs) that arose after interesterification was insufficient to stabilize the emulsion system. The work has shown the possibility of using interesterified fats as the fat phase. Emulsions formed on the basis of interesterified fats without any additional emulsifiers such as sunflower lecithin had properties comparable to emulsions containing mixed non‐interesterified fat containing additional emulsifier. The natural emulsifiers formed as part of enzymatic interesterification allow formation of stable emulsion systems.     

PRODUCTION OF SUB-MICROMETER SIZE O/W EMULSIONS USING A HIGH-PRESSURE WET-TYPE JET MILL

Emulsions composed of sub-micrometer size droplets were obtained by a high-pressure wet-type jet mill. Liquid paraffin as dispersed phase, aqueous sucrose solution as continuous phase, and anionic sodium dodecyl sulfate as emulsifying agent were used as the model emulsification system. Droplet size distribution, Sauter mean diameter (d₃₂), geometric standard deviation of the droplet size distribution (σ_g), and emulsion viscosity (η_e) were investigated under the various combinations of process variables: dispersed phase volume fraction (Φ), dispersed phase viscosity (η_d), continuous phase viscosity (η_c), processing pressure, and number of passages through the wet-type jet mil. d₃₂ and σ_g were correlated with the process variables. For the entire experimental range, maximum droplet diameter was varied with d₃₂ in the range of 1.7-1.9-fold, and a correlation was proposed with K (=η_d/η_c) as a variable. Above a marginal value of d₃₂, at Φ ≥ 0.1, emulsions exhibited Newtonian behavior and could be described well by the Yaron and Gal-Or model. Below the marginal values, emulsions strongly depended on d₃₂ and exhibited a shear-thinning behavior. The relation between η_e and d₃₂ for such emulsions was modeled by use of particle Reynolds number.     

油田污水处理技术研究

阐述了油田污水中分散油和乳状油的处理方法,并分析了目前污水处理中存在的问题,探讨了油田污水处理的发展趋势。     

Synthesis and characterization of hexagonal BN-based aerogels for absorbing oils

Porous oil absorbents have been extensively studied in recent years. Boron nitride (BN) is an ideal inorganic material to withstand severe absorption conditions due to its excellent inertness and high-temperature resistance. A large challenge of BN aerogels is their high preparation costs due to requiring high temperatures and dangerous atmospheres. A facial synthesis of h-BN-based aerogels by the cast-freezing method is reported here, which has the advantages of producing a light and recyclable material (~0.035 g/ml) at a low cost and with low energy consumption. In this work, carboxymethylcellulose (CMC) is used as the compounder to interact with BN and form an aerogel that has controllable porosity (38–86 μm) and hydrophobicity (~140°). The porous structure, components, and reaction mechanisms are analyzed by SEM, XRD, mercury porosimetry, etc.. The pore distributions can be controlled by the concentrations of CMC and crosslinking agents. The intercalation effect on BN is carried out by CMC, which increases the specific surface area. Finally, the oil absorption performances are measured. The oil absorption capacity is up to 31.55 g/g (~97% ml/ml) because of the high specific surface area of the prepared material; additionally, the capacity of this material shows no obvious decrease after 6 cycles. Therefore, h-BN-based aerogels are expected to be applied in the oil absorption field and have the potential to be applied in the biochemical and nuclear fields.     

MODELING OF LEAKAGE IN LIQUID SURFACTANT MEMBRANE SYSTEMS

The stability of double emulsions or liquid surfactant membranes, an important topic in liquid membrane extraction processes, was investigated. The percentage of liquid membrane leakage which reflects the stability of the liquid surfactant membranes was measured as a function of time using sodium hydroitide as a tracer. Water-in-oil emulsions were prepared with SOLTROL 220, an isoparaffinic solvent, and solvent extracted neutral oils—S100N and S500N. A stochastic model for droplet formation under the conditions of isotropic turbulence was developed. It assumes the presence of complete randomness in the process of emulsification. The mean growth rate obtained from this model is in excellent agreement with microdroplet formation data from the literature. A model for leakage of internal reagent into the bulk phase for liquid membrane systems was derived from the droplet formation model, assuming macrodroplet breakup to be the main mechanism responsible for microdroplet release. The internal reagent was assumed to have negligible diffusivity through the membrane. Experimental data on the leakage of sodium hydroxide into deionized water were found to be in good agreement with the model predictions. The model is quite robust, accounting for apparently different types of behavior observed by a number of investigators.     

Kinetics of ultrasonically induced coalescence within oil/water emulsions: Modeling and experimental studies

A model for the coalescence of the oil phase within aqueous emulsions driven by the application of a low-intensity, resonant ultrasonic field has been developed. Under the application of a resonant ultrasonic field, the density and compressibility difference between the dispersed and continuous phases results in a net force that pushes droplets toward pressure antinodes where coalescence subsequently occurs. A mathematical model that determines the relative transport of two individual droplets under the action of acoustic and other relevant forces was recently published. That approach is utilized here in the development of a population balance model which predicts global coalescence rates and the evolution of the droplet size distribution under the influence of the ultrasonic field. These results are experimentally validated and good qualitative agreement between model predictions and experimental observations of the evolution of the droplet size distribution is observed. Discrepancies between the experimental and modeling results are attributed to spatial non-uniformities in the acoustic field utilized in the experiments and the associated lateral radiation forces. The contribution of these forces to overall coalescence rates is described in terms of an effective strength of the acoustic field within the acoustic chamber.     

Novel evaluation method for the water- in- oil (W/O) emulsion stability by Turbidity Ratio Measurements

The turbidity ratio method of evaluating the stabilities of water-in-oil emulsions has been established with two wavelengths (450 and 850 nm) by taking the intensity ratio of two beams. The slopes of turbidity ratio of several water-in-oil emulsions with time were calculated to evaluate the emulsion stabilities at different HLB (Hydrophilie-Lipophile Balance), the amounts of emulsifiers, and water contents. The results of the turbidity ratio technique were consistent with the amount of phase separation of emulsions incubated for 30 days at room temperature. From the turbidity ratio measurements, we determined that the required HLB of diesel oil was about 6.0, and that the stability of emulsion increased with the amount of emulsifier. The increasing amount of the water showed a negative effect on emulsion stability. Finally, this method provides a useful tool for the quick evaluation of the required HLB and the condition of emulsification throughout this study.     

Online droplet diameter measurements to improve the crude oil dehydration process

Emulsion droplet size is information of paramount importance in the design and evaluation of oil–water separators. This paper describes the application of a technique for in situ determination of water droplet diameter distribution (DDD) in actual production scenarios. We discuss the DDD and water content measurements in emulsions obtained during normal operation and plant upsets including variations of the demulsifier chemical dosage or tripping of the electrostatic coalescer grids inside a large dehydrator vessel operated on a crude oil production field in Saudi Arabia. It is demonstrated that DDD data can provide a detailed understanding of the oil–water separation phenomena occurring inside the dehydrator vessel, which helped in planning process recovery strategies in the event of a plant upset.     

单分散硅油乳液的制备

介绍了一种单分散硅油乳液制备新方法。利用二甲基二乙氧基硅烷在碱性条件下乳液聚合, 制得分散度为0.005,有效乳粒尺寸700～2000nm的单分散硅油乳液。该方法具有很好的可重复性。     

Acoustically aided separation of oil droplets from aqueous emulsions

A novel method for recovering the oil phase from aqueous emulsions has been developed. The method applies a low-intensity, resonant ultrasonic field within a rectangular chamber, which is optionally filled with a highly porous medium. Oil droplets dispersed in water have negative acoustic contrast factor and thus are driven to the pressure antinodes of the standing wave field under the influence of acoustic radiation forces. Subsequent coalescence and/or wetting onto the internal surfaces of the chamber occur. Three types of porous media (an unconsolidated bed of 3-mm glass beads, aluminum mesh or reticulated polyester mesh) having pore sizes two to three orders of magnitude larger than droplets being collected were used. The oil collection was found to be sensitive to the natural affinity between the oil and the porous medium as well as its porosity. Of the three media studied, the polyester mesh was found to be the best in terms of the percentage oil collection while the bed of glass beads performed the poorest. The oil collection was found to be highly sensitive to the residence time of the emulsion in both the porous medium and acoustic field. Oil collection also showed expected trends with applied electrical power, but it was not found to be strongly dependent on the internal surface area of the mesh for the range of feed concentration tested. These experiments enable a preliminary understanding about the mechanisms underlying the separation process.     

Analysis by droplet size classes of the liquid flow structure in a pressure swirl hollow cone spray

In this work the structure of a spray resulting from the break-up of a conical liquid sheet was investigated through experimental techniques. The disperse and continuous phase velocities and the size of droplets were measured using a phase Doppler particle analyzer. A data post-processing, applying the generalized integral method, was used to evaluate liquid volume fluxes for different droplet size classes.     

Spray and mixing characteristics of liquid jet in a tubular gas–liquid atomization mixer

For the design and optimization of a tubular gas–liquid atomization mixer,the atomization and mixing characteristics of liquid jet breakup in the limited tube space is a key problem.In this study,the primary breakup process of liquid jet column was analyzed by high-speed camera,then the droplet size and velocity distribution of atomized droplets were measured by Phase-Doppler anemometry (PDA).The hydrodynamic characteristics of gas flow in tubular gas–liquid atomization mixer were analyzed by computational fluid dynamics (CFD) numerical simulation.The results indicate that the liquid flow rate has little effect on the atomization droplet size and atomization pressure drop,and the gas flow rate is the main influence parameter.Under all experimental gas flow conditions,the liquid jet column undergoes a primary breakup process,forming larger liquid blocks and droplets.When the gas flow rate (Q_g) is less than 127 m~3·h~(-1),the secondary breakup of large liquid blocks and droplets does not occur in venturi throat region.The Sauter mean diameter (SMD) of droplets measured at the outlet is more than 140μm,and the distribution is uneven.When Q_g127 m~3·h~(-1),the large liquid blocks and droplets have secondary breakup process at the throat region.The SMD of droplets measured at the outlet is less than 140μm,and the distribution is uniform.When 127Q_g162 m~3·h~(-1),the secondary breakup mode of droplets is bag breakup or pouch breakup.When 181Q_g216 m~3·h~(-1),the secondary breakup mode of droplets is shear breakup or catastrophic breakup.In order to ensure efficient atomization and mixing,the throat gas velocity of the tubular atomization mixer should be designed to be about 51 m·s~(-1)under the lowest operating flow rate.The pressure drop of the tubular atomization mixer increases linearly with the square of gas velocity,and the resistance coefficient is about 2.55 in single-phase flow condition and 2.73 in gas–liquid atomization condition.