Dispersed Oil Droplets Research Articles

An improved design method for compact vertical separator combined with the theoretical method and numerical simulation

Hydrocyclone is mostly used in high efficiency and compact separators to simplify the process flow, and reduce the occupied area and weight of separation equipments. However, the separation outer cylinder size is determined by the traditional Stokes law and the size of traditional droplets, the calculation result would be bigger than expected. So, a new improved design method is put forward in this paper. Firstly, the theoretical calculation is conducted on the effective diameter of the dispersed phase oil droplets according to the droplet coalescence principle and the population balance equation (PBE), and then the numerical simulation verification of multiple load cases is conducted on the two possible maximum particle sizes of the oil droplets by means of the VOF multiphase flow model. Then the floating velocity of oil droplets can be obtained by the droplet sedimentation velocity calculation model, and finally, the size of the outer cylinder of the compact vertical separator can be determined. This method can greatly reduce the size of the outer cylinder of the separator and realize the compactness of the overall structure of the separator. The feasibility of the structure and the reliability of the separation effect have also been verified by field tests.

The Role of Wind Waves in Oil Spill Natural Dispersion in the Sea

The paper analyzes the available parametrizations for calculating oil dispersion in water. A new parametrization of oil droplet flux into water has been elaborated based on a number of recent experimental studies on wind waves and oil droplet dispersion during wave breaking. The turnover rate (TOR) of the sea surface is proposed to determine the primary flux of oil droplets into water. The parameter of lognormal distribution (median) of oil droplets is calculated versus their sizes in a wide range of oil density, viscosity, interfacial tension, and wind speed.

Experimental study of the factors affecting the flow pattern transition in horizontal oil–water flow

Flow patterns are important for pressure gradient calculation and corrosion protection. In this study, the characteristics of oil–water flow were investigated in a horizontal acrylic pipe with an inner diameter of 14.6 mm. The effects of oil viscosity, pipe diameter, pipe material and oil type were studied. Mineral oils with viscosity values of 20, 237 and 456 mPa·s were used as the working fluids. The flow patterns were identified by a high-speed camera and pressure gradients. The size of the dispersed oil droplets increased with increasing oil viscosity. The mixture velocity required to initiate ST&MI flow from SS flow increased with increasing oil viscosity. The transition boundaries extended to high velocities with increasing pipe diameter. In large-diameter pipes, the low-viscosity oil–water flow patterns were stratified flow, dispersed flow and their transition flow, and the high-viscosity oil–water flow patterns were annular flow in addition to these other flows. In small-diameter pipes, stratified flow, dispersed flow, annular flow and intermittent flow patterns were found for both low- and high-viscosity oil–water flow.

Experimental investigation of emulsified oil dispersion on bulk foam stability

Recently aqueous foams have shown promising results to overcome viscous fingering and gravity segregation problems during gas injection process. However, one of the main challenges is the stability of the foams in the presence of oil bank at the front of injected foam. Oil can penetrate into the foam structure in the form of continuous phase or emulsions which might deteriorate lamellae and plateau borders that can result in bubble coalescence and foam rupture. The combination of the surfactant solution, responsible for stabilizing foams, with oil increases the potential for the formation of oil emulsions. In this condition emulsions stability and phase behaviour have the main influence on the bulk foam stability. The objective of this research is to conduct a comprehensive study on the effect of emulsified oil, at different concentrations and salinities on the stability of bulk foams used during oil displacement processes. This was achieved using a foam column test, in which foam is generated and its decay monitored with time. The half-life for each sample was noted and a comparison was made for different cases. Furthermore, changes in the foam bubble sizes and distribution were observed and analysed using an image processing software. A gradual reduction in the half-life of foam was observed with increasing concentration of emulsified oil. The degree to which a foam structure is destabilized by the emulsified oil droplets is dependent on the type and concentration of surfactant employed in generating the foam. At 2 wt% concentration of emulsion, the half-life recorded for foam generated by AOS surfactant, was 107 min, while for the foam generated by SDBS was only 39 min. Further analysis of the results showed a reduction in the number of dispersed oil droplets with increasing the salinity. In addition, the effect of increased salinity of the emulsion on foam stability was again found to be a function of the type of the surfactant is present in the foam system.

A Hydro-Kinematic approach for the design of compact corrugated plate interceptors for the de-oiling of produced water

A Hydro-Kinematic approach is proposed for the design of compact corrugated plate interceptors (CPIs) for the de-oiling of produced water. For a given set of design targets of a specific flow rate, maximum retention time and minimum captured oil droplet diameter, the Hydro-Kinematic approach proposes a systematic way to determine the CPI unit dimensions and operating conditions with the minimum volume and area per unit input flow rate. The approach takes into account the hydrodynamic constraints in the design of the CPI imposed by the behavior of the dispersed oil droplets in response to the hydrodynamic field. Design charts and equations are given to ease the design process for a wide range of design target parameters. The same approach can be used to determine the best operating conditions for existing CPI units.

Adhesion of mechanically and chemically dispersed crude oil droplets to eggs of Atlantic cod (Gadus morhua) and haddock (Melanogrammus aeglefinus)

Crude oil accidentally spilled into the marine environment undergoes natural weathering processes that result in oil components being dissolved into the water column or present in particulate form as dispersed oil droplets. Oil components dissolved in seawater are typically considered as more bioavailable to pelagic marine organisms and the main driver of crude oil toxicity, however, recent studies indicate that oil droplets may also contribute. The adhesion of crude oil droplets onto the eggs of pelagic fish species may cause enhanced transfer of oil components via the egg surface causing toxicity during the sensitive embryonic developmental stage. In the current study, we utilized an oil droplet dispersion generator to generate defined oil droplets sizes/concentrations and exposed Atlantic cod (Gadus morhua) and haddock (Melanogrammus aeglefinus) to investigate if the potential for dispersed oil droplets to adhere onto the surface of eggs was species-dependent. The influence of a commercial chemical dispersant on the adhesion process was also studied. A key finding was that the adhesion of oil droplets was significantly higher for haddock than cod, highlighting key differences and exposure risks between the two species. Scanning electron microscopy indicates that the differences in oil droplet adhesion may be driven by the surface morphology of the eggs. Another important finding was that the adhesion capacity of oil droplets to fish eggs is significantly reduced (cod 37.3%, haddock 41.7%) in the presence of the chemical dispersant.

Responsive Emulsions Stabilized by Amphiphilic Supramolecular Graft Copolymers Formed in Situ at the Oil-Water Interface.

Amphiphilic supramolecular graft copolymers which can stabilize oil-in-water (o/w) emulsions and enable responsive demulsification were demonstrated in this study. Linear poly[( N, N-dimethylacrylmide)- stat-(3-acrylamidophenylboronic acid)] (PDMA- stat-PAPBA) copolymers with phenylboronic acid (PBA) groups and linear polystyrene homopolymers with cis-diol terminals (PS(OH)2) were synthesized by reversible addition-fragmentation chain transfer polymerization. By the homogenization of the biphasic mixtures of an alkaline water solution of PDMA- stat-PAPBA copolymer and a toluene solution of PS(OH)2 homopolymer, stable o/w emulsions could be generated, although neither PDMA- stat-PAPBA nor PS(OH)2 alone was able to stabilize the emulsion. It was verified that the dispersed oil droplets in the emulsions were stabilized by the amphiphilic PDMA- stat-PAPBA- g-PS supramolecular graft copolymers, which were formed in situ at the oil-water interface by the complexation between the lateral PBA groups of PDMA- stat-PAPBA and the diol terminals of PS(OH)2 during homogenization. These emulsions showed pH- and glucose-responsive demulsification because of the reversible B-O bonds between the PDMA- stat-PAPBA backbones and the PS side chains. The effects of polymer concentrations on emulsion formation were also investigated. The current study provides an alternative method for the facile preparation of responsive polymeric emulsifiers, which potentially may be extended to other polymer pairs containing PBA and cis-diol groups.

Porous materials from oppositely charged nanoparticle gel emulsions

Sol–gel processing is an important colloidal processing route for the synthesis of macroporous materials of tunable microstructure. More recently, methods that use particle stabilized foams or emulsions have been developed. However, such methods generally involve the use of an external surface active additives that bind the particles together during processing. In this work, we present a simple and scalable additive-free method for the fabrication of porous materials that are both macroporous and microporous in nature. In particular, we show that silica-alumina porous materials can be fabricated by processing oppositely charged nanoparticle gel emulsions which are a dispersion of oil droplets in a space spanning network of colloidal particles. The nanoparticle gel emulsions obtained are initially characterized by optical microscopy and oscillatory rheology. The water and oil in these emulsion gels are removed by drying and it is finally sintered at 1000 °C to obtain porous material. The pore size and their distribution in the three-dimensional porous material is characterized using scanning electron microscopy (SEM) and X-ray tomography. Microscopy observations revealed a homogeneous distribution of macro-pores of 20–40 μm in diameter along the width, breadth and thickness of the porous material with an average porosity of 40% measured from 2D X-ray computed tomography images. One of the important features of the porous materials thus fabricated is the presence of nanosized pores due to the inherent porosity of the nanoparticle gel as well as micron sized pores due to the oil droplets.

Enhanced demulsification from aqueous media by using magnetic chitosan-based flocculant

A series of quaternized chitosan (QC)-grafted magnetic nanoparticles (MNPs) were successfully synthesized for demulsification from aqueous environments. Fe3O4 MNPs were synthesized by using a coprecipitation method, followed by surface coating with silica and aminopropyl to form a surface for further grafting of QC molecular chains. The synthetic magnetic flocculants were characterized by various technologies and their demulsification performances were evaluated in detail as a function of dosage, QC grafting ratio (Gq), pH and magnetic field. Results showed that pH did not significantly affect oil–water separation performance and MNPs with high Gq exhibited enhanced separation efficiency. The separation capacity was estimated to be >105 mg of diesel oil/mg of magnetic flocculant. Recycling experiment indicated the magnetic flocculant could be recycled up to at least 7 cycles at various pH levels. The grafted QC layer endowed the hybrid MNPs with permanent positive surface charges, thus allowing them to flocculate negatively charged oil droplets via electrostatic patching. The magnetic field could not only accelerate the separation of resulting flocs, but also remove the MNPs-coated dispersed oil droplets. In conclusion, QC-grafted MNPs provide a potentially new technique for developing environmentally friendly and highly efficient magnetic flocculant for practical demulsification applications.

Investigation of synergistic effect of nanoparticle and surfactant in macro emulsion based EOR application in oil reservoirs

The present paper deals with the characterization of oil in water (O/W) emulsion stabilized by the synergistic effect of surfactant and nanoparticle for their application in enhanced oil recovery (EOR). The emulsions have been formulated using n-decane and paraffin oil, silica nanoparticle and two different surfactants, viz., anionic sodium dodecyl sulfate (SDS) and cationic cetyl trimethyl ammonium bromide (CTAB). The nanoparticle shows a synergetic effect in presence of surfactants which prevents the coalescence of dispersed oil droplets and lowers the interfacial tension (IFT) at the oil-water interface. The stability of emulsions was evaluated by particle size distribution, creaming behaviour, zeta potential and phase behaviour. The viscosity of emulsions remains stable at wide range temperature indicating thermal stability. The viscoelastic study indicates that the emulsions behave as a gel-like structure with a higher value of storage modulus (G′) than loss modulus (G″). The addition of polymer leads to improvement in viscosity and stability of the emulsion, proving its usefulness in the reservoir for recovery of heavy oil.

The Physical State of Emulsified Edible Oil Modulates Its in Vitro Digestion.

Emulsified lipid digestion was tailored by manipulating the physical state of dispersed oil droplets in whey protein stabilized oil-in-water (O/W) emulsions, where the oil phase consisted of one of five ratios of soybean oil (SO) and fully hydrogenated soybean oil (FHSO). The evolution in particle size distribution, structural changes during oral, gastric, and intestinal digestion, and free fatty acid release during intestinal digestion were all investigated. Irrespective of the physical state and structure of the dispersed oil/fat, all emulsions were stable against droplet size increases during oral digestion. During gastric digestion, the 50:50 SO:FHSO emulsion was more stable against physical breakdown than any other emulsion. All emulsions underwent flocculation and coalescence or partial coalescence upon intestinal digestion, with the SO emulsion being hydrolyzed the most rapidly. The melting point of all emulsions containing FHSO was above 37 °C, with the presence of solid fat within the dispersed oil droplets greatly limiting lipolysis. Fat crystal polymorph and nanoplatelet size did not play an important role in the rate and extent of lipid digestion. Free fatty acid release modeled by the Weibull distribution function showed that the rate of lipid digestion (κ) decreased with increasing solid fat content, and followed an exponential relationship (R2 = 0.95). Overall, lipid digestion was heavily altered by the physical state of the dispersed oil phase within O/W emulsions.

Formulation, characterization and antimicrobial properties of black cumin essential oil nanoemulsions stabilized by OSA starch.

Preparation of oil-in-water nanoemulsions has emerged as a subject of interest for the encapsulation of lipophilic functional ingredients to increase their stability and activity. In this study, black cumin essential oil nanoemulsions (BCO-NE) using different ratios of essential oil with canola and flax seed oils (ripening inhibitors) were formulated and stabilized with octenyl succinic anhydride (OSA) modified waxy maize starch. The nanoemulsions exhibited monomodal size distributions with mean droplet diameter below 200nm and zeta potential above -30, indicating a strong electrostatic repulsion between the dispersed oil droplets. Further, during storage (4weeks at 25°C±2) emulsions showed shear thinning phenomena and stability towards coalescence. Antimicrobial properties of nanoemulsions were determined by minimum inhibitory concentration and time-kill method against two Gram-positive bacterial (GPB) strains (Bacillus cereus and Listeria monocytogenes). Negatively charged BCO-NE showed prolonged bactericidal activities as compared to pure BCO due to better stability, controlled release and self-assembly with GPB cell membrane followed by destruction of cellular constituents. Our results suggest the application of BCO-NE may be exploited in aqueous food systems for extending the shelf life and other functional properties.

Composite gels structured by a gelatin protein matrix filled with oil bodies

Abstract Oil body extracts from sesame seeds and hazelnuts were subjected to centrifugation to recover oil body concentrated creams, which were then suitably diluted with gelatin solutions to prepare mixtures of 25.0 wt% of oil and 2.0–6.0 wt% of gelatin. The gelling behaviour of the mixtures was followed by applying dynamic rheometry while gradually lowering the temperature down to 4 °C to allow network formation. The composite gels based on the oil body cream was composed of adequately dispersed oil droplets within a continuous gelatin matrix. The oil droplet incorporation brought about a significant shortening in the gelation time (20–30%) of gelatin and an increase in the gelling temperature of more than 30%. In addition, the incorporation of the naturally emulsified oil droplets at lower gelatin contents led to a limited but significant strengthening of the gelatin gel structure, indicated by an increase in the storage modulus. These results suggest that the extracted oil bodies are incorporated within the matrix, and function as active fillers of the composite gel.

DISPERSANT PERFORMANCE: FINDING NEW RESULTS IN EXISTING DATA

Abstract No. 092 Abstract: Chemical dispersants are used to mitigate oil spills in aquatic environments. Dispersants promote the breakdown of oil into smaller droplets that more readily diffuse into the water column. Federal agencies, industry, and academia have a long history of investigating dispersant performance at diverse scales and environmental conditions, including several recent publications. Several studies estimate dispersant performance as dispersion effectiveness (DE, measured as the percent of oil retained in the water column for a period of time after treatment), the concentration of oil in the dispersed in the water column, or the size of dispersed oil droplets. While many organizations have drawn qualitative conclusions from this body of work, a quantitative meta-analysis drawing together historic and recent research on the topic of dispersant effectiveness has not been conducted. This paper analyzed controlled studies measuring performance of dispersants across lab, tank, and large-scale studies. Although this paper examined only a subset of commonly tested oils, the findings strongly support that treatment with dispersants is correlated with increased effectiveness across several metrics, studies, and test methodologies. The conclusions provided by this analysis could be a critical tool for weighing the risks and benefits of using dispersants to respond to oil spills in aquatic environments.

Micro-distribution and mechanical characteristics analysis of remaining oil

As the water drive reservoir enters extra high water cut stage (greater than 80%), remaining oil distribution becomes increasingly dispersed. Research on micro residual oil in pore appears particularly important for reservoir development at extra high water cut stage. Oil occurrence characteristics recognition helps to understand the distribution of remaining oil and the mechanical characteristics of oil is the guide for tapping the remaining oil. On the basis of pore scale oil–water two phase flow experiments, micro distribution of remaining oil is divided into four occurrence states in accordance with oil features at different stage of water flooding, the flake of remaining oil, oil column, oil droplet and oil film. A quantitative characterization method of remaining oil occurrence states is established. By using micro numerical simulation method, change rules of four occurrence states of remaining oil during the process of water displacement and the mechanical characteristics of different occurrence state of remaining oil are analyzed. Results show that the continuous oil phase gradually transforms to discontinuous phase and even to dispersed phases during the water flooding process. At extra high water cut stage, most of remaining oil are dispersed oil columns, oil droplets and oil films, which are the main target of remaining oil to be tapped. By changing water flow direction or increasing the displacement pressure gradient, the surface adsorption force acting on oil columns are overcome, and then the oil columns begin to move and finally to be produced out. Oil droplets in pore-throat center are scoured and carried out by water as the increase of the injection volume, while the oil droplets in blind ends and the oil films are extracted out by adding chemicals to reduce the interfacial tension, so as to enhance oil recovery. For water flooding reservoir, the corresponding tapping measures for four types of oil occurrence states brought forward have great meanings of improving reservoir recovery at high water cut stage.

An algorithm for modeling entrainment and naturally and chemically dispersed oil droplet size distribution under surface breaking wave conditions

A surface oil entrainment model and droplet size model have been developed to estimate the flux of oil under surface breaking waves. Both equations are expressed in dimensionless Weber number (We) and Ohnesorge number (Oh, which explicitly accounts for the oil viscosity, density, and oil-water interfacial tension). Data from controlled lab studies, large-scale wave tank tests, and field observations have been used to calibrate the constants of the two independent equations. Predictions using the new algorithm compared well with the observed amount of oil removed from the surface and the sizes of the oil droplets entrained in the water column. Simulations with the new algorithm, implemented in a comprehensive spill model, show that entrainment rates increase more rapidly with wind speed than previously predicted based on the existing Delvigne and Sweeney's (1988) model, and a quasi-stable droplet size distribution (d<~50μm) is developed in the near surface water.

The enhanced stability and biodegradation of dispersed crude oil droplets by Xanthan Gum as an additive of chemical dispersant

It is necessary for chemical dispersant to disperse oil effectively and maintain the stability of oil droplets. In this work, Xanthan Gum (XG) was used as an environmentally friendly additive in oil dispersant formulation to enhance the stability and biodegradation of dispersed crude oil droplets. When XG was used together with chemical dispersant 9500A, the dispersion effectiveness of crude oil in artificial sea water (ASW) and the oil droplet stability were both greatly enhanced. In the presence of XG, lower concentration of 9500A was needed to achieve the effective dispersion and stabilization. In addition to the enhancement of dispersion and stabilization, it was found that the biodegradation rate of crude oil by bacteria was dramatically enhanced when a mixture of 9500A and XG was used as a dispersant. Because of the low environmental impact of XG, this would be a potential way to formulate the dispersant with lower toxicity.

Exposure to crude oil micro-droplets causes reduced food uptake in copepods associated with alteration in their metabolic profiles

Acute oil spills and produced water discharges may cause exposure of filter-feeding pelagic organisms to micron-sized dispersed oil droplets. The dissolved oil components are expected to be the main driver for oil dispersion toxicity; however, very few studies have investigated the specific contribution of oil droplets to toxicity. In the present work, the contribution of oil micro-droplet toxicity in dispersions was isolated by comparing exposures to oil dispersions (water soluble fraction with droplets) to concurrent exposure to filtered dispersions (water-soluble fractions without droplets). Physical (coloration) and behavioral (feeding activity) as well as molecular (metabolite profiling) responses to oil exposures in the copepod Calanus finmarchicus were studied. At high dispersion concentrations (4.1–5.6mg oil/L), copepods displayed carapace discoloration and reduced swimming activity. Reduced feeding activity, measured as algae uptake, gut filling and fecal pellet production, was evident also for lower concentrations (0.08mg oil/L). Alterations in metabolic profiles were also observed following exposure to oil dispersions. The pattern of responses were similar between two comparable experiments with different oil types, suggesting responses to be non-oil type specific. Furthermore, oil micro-droplets appear to contribute to some of the observed effects triggering a starvation-type response, manifested as a reduction in metabolite (homarine, acetylcholine, creatine and lactate) concentrations in copepods. Our work clearly displays a relationship between crude oil micro-droplet exposure and reduced uptake of algae in copepods.

Simulation of phase separation with large component ratio for oil-in-water emulsion in ultrasound field

This paper presents an exploration for separation of oil-in-water and coalescence of oil droplets in ultrasound field via lattice Boltzmann method. Simulations were conducted by the ultrasound traveling and standing waves to enhance oil separation and trap oil droplets. The focus was to the effect of ultrasound irradiation on oil-in-water emulsion properties in the standing wave field, such as oil drop radius, morphology and growth kinetics of phase separation. Ultrasound fields were applied to irradiate the oil-in-water emulsion for getting flocculation of the oil droplets in 420kHz case, and larger dispersed oil droplets and continuous phases in 2MHz and 10MHz cases, respectively. The separated phases started to rise along the direction of sound propagation after several periods. The rising rate of the flocks was significantly greater in ultrasound case than that of oil droplets in the original emulsion, indicating that ultrasound irradiation caused a rapid increase of oil droplet quantity in the progress of the separation. The separation degree was also significantly improved with increasing frequency or irradiation time. The dataset was rearranged for growth kinetics of ultrasonic phase separation in a plot by spherically averaged structure factor and the ratio of oil and emulsion phases. The analyses recovered the two different temporal regimes: the spinodal decomposition and domain growth stages, which further quantified the morphology results. These numerical results provide guidance for setting the optimum condition for the separation of oil-in-water emulsion in the ultrasound field.

Can gelatinous zooplankton influence the fate of crude oil in marine environments?

Gelatinous zooplankton are known for their capacity to excrete copious amounts of mucus that can be utilized by other organisms. The release of mucus is exacerbated by stressful conditions. Despite the recognized importance of cnidarian mucus to production and material flux in marine ecosystems, the role of gelatinous zooplankton in influencing the fate of oil spills is unknown. In this study we used laboratory experiments to observe the influence of mucus from the moon jellyfish (Aurelia aurita) on the aggregation and degradation of crude oil. The results show that jellyfish swimming in a dispersed solution of oil droplets produced copious amounts of mucus and the mucus aggregates that were shed by the animals contained 26 times more oil than the surrounding water. Incubation experiments showed that hydrocarbon degrading bacteria cell densities more than doubled in the presence of mucus and after 14days, resulted in a significant increase in oil degradation. These results suggest that jellyfish can aggregate dispersed oil droplets and embed them within a matrix that favors hydrocarbon degrading bacteria. While this study lends support to the hypothesis that the presence of gelatinous zooplankton can impact oil spills large scale mesocosm studies will be needed to fully quantify the influence on a natural system.