Oil Droplet Size Distribution Research Articles

Influence of Nozzle Geometry and Scale-Up on Oil Droplet Breakup in the Atomization Step during Spray Drying of Emulsions

Spray drying of oil-in-water emulsions is a widespread encapsulation technique. The oil droplet size (ODS) significantly impacts encapsulation efficiency and other powder properties. The ODS is commonly set to a specific value during homogenization, assuming that it remains unchanged throughout the process, which is often inaccurate. This study investigated the impact of atomizer geometry and nozzle dimensions on oil droplet breakup during atomization using pressure-swirl atomizers. Subject of the investigation were nozzles that differ in the way the liquid is set in motion, as well as different inlet port and outlet orifice dimensions. The results indicate that nozzle inlet port area may have a significant impact on oil droplet breakup, with x90,3 values of the oil droplet size distribution decreasing from 5.29 to 2.30 µm with a decrease of the inlet area from 2.0 to 0.6 mm. Good scalability of the findings from pilot to industrial-scale was shown using larger nozzles. A simplified theoretical model, aiming to predict the ODS as a function of calculated shear rates, showed reasonable agreement to the experimental data for different atomization pressures with coefficients of determination of up to 0.99. However, it was not able to predict the impact of different nozzle dimensions, most likely due to changes in flow characteristics. These results suggest that the stress history of the oil droplets might have a larger influence than expected. Further studies will need to consider other zones of high stress in addition to the outlet orifice.

Crankcase Explosions in Marine Diesel Engines: A Computational Study of Unvented and Vented Explosions of Lubricating Oil Mist

Accidental crankcase explosions in marine diesel engines are presumably caused by the inflammation of lubricating oil in air followed by flame propagation and pressure buildup. This manuscript deals with the numerical simulation of internal unvented and vented crankcase explosions of lubricating oil mist using the 3D CFD approach for two-phase turbulent reactive flow with finite-rate turbulent/molecular mixing and chemistry. The lubricating oil mist was treated as either monodispersed with a droplet size of 60 μm or polydispersed with a trimodal droplet size distribution (10 μm (10 wt%), 250 μm (10 wt%), and 500 μm (80 wt%)). The mist was partly pre-evaporated with pre-evaporation degrees of 60%, 70%, and 80%. As an example, a typical low-speed two-stroke six-cylinder marine diesel engine was considered. Four possible accidental ignition sites were considered in different linked segments of the crankcase, namely the leakage of hot blow-by gases through the faulty stuffing box, a hot spot on the crankpin bearing, electrostatic discharge in the open space at the A-frame, and a hot spot on the main bearing. Calculations show that the most important parameter affecting the dynamics of crankcase explosion is the pre-evaporation degree of the oil mist, whereas the oil droplet size distribution plays a minor role. The most severe unvented explosion was caused by the hot spot ignition of the oil mist on the main bearing and flame breaking through the windows connecting the crankcase segments. The predicted maximum rate of pressure rise in the crankcase attained 0.6–0.7 bar/s, whereas the apparent turbulent burning velocity attained 7–8 m/s. The rate of heat release attained a value of 13 MW. Explosion venting caused the rate of pressure rise to decrease and become negative. However, vent opening does not lead to an immediate pressure drop in the crankcase: the pressure keeps growing for a certain time and attains a maximum value that can be a factor of 2 higher than the vent opening pressure.

Chia Oil Microencapsulation Using Tannic Acid and Soy Protein Isolate as Wall Materials.

The use of proteins to produce oil-containing microcapsules has been previously analyzed; however, their chemical modification, in order to improve their performance as wall materials, is a strategy that has not been widely developed yet. This study aimed to analyze the chemical modification of the proteins through cross-linking reactions with tannic acid and to evaluate their performance as wall materials to the microencapsulation of oils rich in polyunsaturated fatty acids. The cross-linking reaction of isolated soy protein and tannic acid was carried out at pH 10-11 and 60 °C. Subsequently, emulsions were made with a high-speed homogenizer and microcapsules were obtained by spray drying. Microcapsules were characterized by particle size, morphology (SEM), total pore area and % porosity (mercury intrusion methodology), superficial properties (contact angle), and size distribution of oil droplets (by laser diffraction). Additionally, encapsulation efficiency was determined as a function of total and surface oil. Oil chemical stability and quality were studied by Rancimat, hydroperoxide values, and fatty acid profiles. In addition, a storage test was performed for 180 days, and released oil and polyphenols were determined by in vitro gastric digestion. Moreover, the fatty acid composition of the oil and the total polyphenol content and antioxidant capacity of polyphenols were analyzed. The results showed that spray-dried microcapsules had an encapsulation efficiency between 54 and 78%. The oxidative stability exhibited a positive correlation between the amount of polyphenols used and the induction time, with a maximum of 27 h. The storage assay showed that the peroxide value was lower for those cross-linked microcapsules concerning control after 180 days. After the storage time, the omega-3 content was reduced by 49% for soy protein samples, while cross-linked microcapsules maintained the initial concentration. The in-vitro digestion assay showed a decrease in the amount of oil released from the cross-linked microcapsules and an increase in the amount of polyphenols and a higher antioxidant capacity for all samples (for example, 238.10 mgGAE/g and 554.22 mg TE/g for undigested microcapsules with TA 40% versus 322.09 mgGAE/g and 663.61 mg TE/g for digested samples). The microcapsules showed a high degree of protection of the encapsulated oil, providing a high content of polyunsaturated fatty acids (PUFAS) and polyphenols even in prolonged storage times.

Cinnamon essential oil Pickering emulsions: Stabilization by bacterial cellulose nanofibrils and applications for active packaging films

Pickering emulsions are emulsions stabilized by solid particles with a wide range of potential applications as they typically provide more stable systems than surface-stabilized emulsions. Among the various solid stabilizers, bacterial cellulose (BC) may open up new opportunities for future Pickering emulsions due to its unique nano-size, amphiphilicity and other excellent properties. In this study, BC, TEMPO-oxidized BC (TOBC) and dialdehyde cellulose (DAC) were used as emulsifiers to stabilize cinnamon essential oil (CEO) Pickering emulsions. The microstructure, oil droplet size distribution, storage and loss moduli of the Pickering emulsions were affected by the type of emulsifier used. Compared to BC and DAC nanofibers, TOBC nanofibers exhibited better emulsifying capacity. TOBC (1%)-stabilized Pickering emulsion showed smaller droplet size, narrower size distributions, better stability and sustained release ability. Moreover, the Pickering emulsions showed high antibacterial activities against Gram-positive bacteria S. aureus and Gram-negative bacteria E. coli. Active gelatin composite films containing TOBC (1%)-stabilized CEO Pickering emulsions were successfully fabricated and showed good antibacterial and antioxidant properties, which make them suitable for food packaging application.

Important Role and Properties of Granular Nanocellulose Particles in an In Vitro Simulated Gastrointestinal System and in Lipid Digestibility and Permeability.

This research evaluated the role and feasibility of the granular nanocellulose particles (GNC) from sugarcane bagasse obtained from enzymatic hydrolysis in reducing lipid digestibility and permeability in an in vitro simulated gastrointestinal (GI) system. GNC concentration (0.02%, w/v) had significantly affected the released free fatty acids (FFA), with a reduction of approximately 20%. Pickering emulsion of a GNC and olive oil simulation mixture revealed higher oil droplet size distribution and stability in the initial stage than the vortexed mixture formation. The difference in particle size distribution and zeta potential of the ingested GNC suspension and GNC-olive oil emulsion were displayed during the in vitro gastrointestinal simulation. GNC particles interacted and distributed surrounding the oil droplet, leading to interfacial emulsion. The GNC concentration (0.01-0.10%, w/v) showed low toxicity on HIEC-6 cells, ranging from 80.0 to 99% of cell viability. The release of FFA containing the ingested GNC suspension and GNC-olive oil emulsion had about a 30% reduction compared to that without the GNC digestion solution. The FFA and triglyceride permeability through the HIEC-6 intestinal epithelium monolayer were deceased in the digesta containing the ingested GNC and emulsion. This work indicated that GNC represented a significantly critical role and properties in the GI tract and reduced lipid digestion and absorption. This GNC could be utilized as an alternative food additive or supplement in fatty food for weight control due to their inhibition of lipid digestibility and assimilation.

Effect of Heat Treatment on Yellow Field Pea (Pisum sativum) Protein Concentrate Coupled with Membrane Ultrafiltration on Emulsification Properties of the Isolated >50 kDa Proteins.

The aim of this paper was to determine the emulsification properties of protein aggregates obtained from heat pretreated yellow field pea protein concentrate (PPC). PPC dispersions were prepared in distilled water (adjusted to pH 3.0, 5.0, 7.0, or 9.0), heated in a water bath (100 °C) for 30 min, centrifuged and the supernatant passed first through a 30 kDa membrane and, then, the first retentate (>30 kDa) through a 50 kDa membrane. The 50 kDa membrane separation yielded a second retentate (>50 kDa proteins), which was isolated for emulsification studies. The near UV circular dichroic spectra of the protein samples showed more unfolded structures at pH 3.0 and 5.0 than at pH 7.0 and 9.0. The presence of small and spherical oil droplets of emulsions stabilized by the >50 kDa proteins at pH 3.0, 7.0, and 9.0 was confirmed by confocal laser scanning microscopy images. Emulsions stabilized at pH 7.0 and 9.0 had a narrower size distribution range than at pH 3.0 and 5.0. A narrow oil droplet size distribution range and lower interfacial protein concentrations of the emulsions stabilized by the >50 kDa proteins were observed at the corresponding pH of the heat treatment when compared to other pH values. Emulsions stabilized by the >50 kDa proteins exhibited a relatively low flocculation and coalescence index, which infers relative stability. The results from this work suggest that heat pretreatment of the PPC led to the formation of new protein aggregates, especially FT9 with enhanced emulsification properties, at some of the test conditions when compared to the unheated PPC.

The loss of crude oil droplets by filter feeders and the role of surfactants

Various methods of oil spill remediation exist, e.g., floating booms, controlled burning and the release of chemical surfactants. These surfactants facilitate the breakup of the slick into micron-sized droplets. Here, we studied the impact such a surfactant has on the size distribution of oil droplets in the water column and in the gut of the filter feeder Daphnia magna. We also studied the effect of surfactants on detachment conditions of chemically and mechanically dispersed oil (respectively MDO and CDO) droplets from capture fibers. Our results show that including solubilized dioctyl sulfosuccinate sodium salt in the mixing of the emulsion produces smaller droplets and a narrower size distribution in the water. In the gut, the size of ingested droplets does not change whether the oil is mixed mechanically or chemically. Also, surfactant coated droplets detach at a lower velocity than mechanically dispersed droplet because of their lower oil/water interfacial tension.

Tailoring Pickering Double Emulsions by in Situ Particle Surface Modification

Fundamental studies on the formation and stability of Pickering double emulsions are crucial for their industrial applications. Available methods of double emulsion preparation involve multiple tedious steps and can formulate a particular type of double emulsion, that is, water-in-oil-in-water (w/o/w) or oil-in-water-in-oil (o/w/o). In this work, we proposed a simple single-step in situ surface modification method to stabilize different types of double emulsions using hematite and silica particle systems which involves the addition of oleic acid. In the emulsification studies, we use (i) a combination of hematite and oleic acid, which is termed the binary system, and (ii) a mixture of hematite and silica particles together with oleic acid, which is designated as the ternary system. The wettability of hematite particles is tuned by direct or sequential addition of oleic acid to the water-decane medium. The direct surface modification (which involves the addition of a known quantity of oleic acid to the oil-water mixtures at once) of hematite particles in both binary and ternary systems shows transitional phase inversion from oil-in-water (o/w) to water-in-oil (w/o) emulsions. However, sequential surface modification results in the transition of a single emulsion to double emulsions. In the case of the binary system, the sequential surface modification of the hematite-particle-stabilized o/w emulsion can be converted into double emulsions of o/w/o type. However, in the case of the ternary system, i.e., in the presence of silica particles, sequential surface modification of hematite particles stabilizes both single (o/w) and double (w/o/w and o/w/o) emulsions. The critical concentration of oleic acid required to form a double emulsion is observed to be dependent on the ratio of the surface area of the silica particle to the total surface area of particles (S) and mixing protocols. A study of the size distribution of oil and water droplets of double emulsions shows that droplet size can be controlled by oleic acid concentration and magnitude of S. The arrangements of the particles at interfaces are visualized by SEM imaging. In this way, we developed an easy and novel single-step method of double emulsion preparation and provide a strategy to tailor the formation of different types of emulsions with a single/binary particle system by sequential in situ surface modification of the particles.

Impact of process conditions and type of protein on conjugate formation with pectin by vacuum drying

Plant proteins exhibit low solubility and functionality, limiting their use as emulsifiers. Maillard reaction-based conjugation with polysaccharides, e.g. pectin, is a strategy to improve their functionality. The commonly applied batch process involves economically unviable freeze-drying as a pre-treatment. Vacuum drying was therefore investigated as a novel approach combining the drying process and conjugate formation.First, the process parameters (time and temperature) were altered to determine the optimum conditions for conjugation between potato protein and high methoxylated pectin. Then, the conjugation between the pectin and various plant proteins (soy, pea, rapeseed) was tested to assess the impact of protein type. Conjugate samples were analysed by dry matter, decrease in free amino groups, browning index and molecular weight. Emulsifying properties were evaluated by oil droplet size and emulsion stability. Process parameters of 100 °C and 3 h were identified to favour conjugation. Corresponding potato protein conjugates had high molecular weight and improved emulsion stability at the pI of the protein. Soy protein conjugates showed the highest decrease in free amino groups and enhanced emulsion stability with prevented coalescence. Rapeseed protein conjugates exhibited the most stable emulsions with narrow oil droplet size distribution but were hampered by their inherent colouration.The results confirm that all plant proteins can be used for conjugation with pectin and the obtained conjugates are suitable as emulsifiers for food systems. However, differences in the amino acids content, chemical structure, and overall composition of plant proteins affect conjugation and must be considered in process design.

Fabrication and characterization of Pickering emulsion gels stabilized by gliadin/starch complex for the delivery of astaxanthin

Pickering emulsion gels (PEGs) are structured emulsions that have demonstrated their advantages in the delivery of bioactive compounds since the gel network inhibits droplet coalescence, Ostwald ripening, and phase separation. Herein, the gliadin/starch nanocomposites (G/SNPs) with distinct gliadin/starch ratios were prepared and used to stabilize the PEGs. The interaction between gliadin and gelatinized starch was confirmed by fluorescence and Fourier transform infrared (FTIR) spectra. The presence of gelatinized starch improved the wettability of G/SNPs. The maximum three-phase contact angle was 84° when the ratio of gliadin/starch was 1:5 (G/SNPs 1:5). The appearance, micromorphology, oil droplet size distribution, and rheological properties suggested that stable PEGs stabilized by G/SNPs were formed. The PEGs stabilized by G/SNPs 1:5 were stable for at least one year when stored at room temperature. The super stability of PEGs was related to the compact three-dimensional network structure. Moreover, PEGs were stable at pH values ranging from 3 to 11 and tolerated high ionic strength up to 1000 mmol L−1 NaCl. Furthermore, the retention rate of astaxanthin in the G/SNPs 1:5 stabilized PEGs was improved since the half-life of encapsulated astaxanthin was 2.3 times longer than that in oil. In addition, in vitro digestion suggested the bioaccessibility of astaxanthin in PEGs was 1.5 times higher than that of oil. Taken together, these results indicated that G/SNPs stabilized PEGs were promising carriers for the better delivery of hydrophobic bioactive compounds.

Oil Transport Following the Deepwater Horizon Blowout.

The Deepwater Horizon oil spill in the Gulf of Mexico in 2010 was the largest in US history, covering more than 1,000 km of shorelines and causing losses that exceeded $50 billion. While oil transformation processes are understood at the laboratory scale, the extent of the Deepwater Horizon spill made it challenging to integrate these processes in the field. This review tracks the Deepwater Horizon oil during its journey from the Mississippi Canyon block 252 (MC252) wellhead, first discussing the formation of the oil and gas plume and the ensuing oil droplet size distribution, then focusing on the behavior of the oil on the water surface with and without waves. It then reports on massive drifter experiments in the Gulf of Mexico and the impact of the Mississippi River on the oil transport. Finally, it concludes by addressing the formation of oil-particle aggregates. Although physical processes lend themselves to numerical modeling, we attempted to elucidate them without using advanced modeling, as our goal is to enhance communication among scientists, engineers, and other entities interested in oil spills.

One-step High Internal Phase Pickering Emulsions stabilized by uncracked micronized orange pomace

High Internal Phase Emulsions (HIPE) were formulated using 1% w/w orange pomace (i.e. uncracked micro-scaled byproduct powder) as sole stabilizer, from a quick and simple process, with 80% of sunflower oil and 20% of water in the liquid phase. Various indicators were monitored over a 2-month storage at Tamb, such as droplet size distribution, flow and viscoelastic properties, multi-scale microstructure (light and confocal microscopy). HIPPEs were stable towards coalescence and drainage, showing the complementarity between the anchoring insoluble fraction acting as Pickering particles at the oil-water interface and the viscosifying/film-forming soluble compounds. The oil droplet size distribution remained the same, and no significant change could be quantified regarding the elastic modulus, the yield stress or the viscosity of the emulsions in 60 days. However, changing the oil source from sunflower to another vegetal or synthetic oil could lead to unstable systems.

Oil Load Reduction of Oilfield-Produced Water by Applying Swirl–Cyclonic Flotation: A Pilot-Scale Investigation

A swirl–cyclonic flotation (SCF) apparatus was fabricated by combining hydrocyclone and air flotation separation to reduce the oil droplet load of oilfield-produced water. The apparatus was designed as three concentric cylinders with functions of swirling, air flotation separation, and oil collection. Influencing factors such as influent flow, oil concentration, and aeration rate were investigated in the pilot-scale test. The oil concentration of the effluent was below 100 mg/L during the continuous operation under an influent flow rate of 1.5 m3/h and an aeration rate of 0.4 L/min without addition of any chemicals. Results could be explained by the improvement in the floating velocity of oil droplets, resulting in oil load reduction. The oil and water separation mechanism of the SCF apparatus was determined by analysis of oil droplet size distribution. Compared with other flotation apparatus, the SCF apparatus had the advantages of high oil removal efficiency, low retention time, and stable water treatment quality. The apparatus also had no chemical agents added and had less floor area, leading to reduced chemical cost. The designed SCF apparatus has potential industrial application as pretreatment for oil–water load reduction.

Production of stable emulsions using β‐glucans extracted from Pleurotus ostreatus to encapsulate oxidizable compounds

AbstractThe basidiomycete Pleurotus ostreatus is a sustainable food source known to be rich in β‐glucans, functional compounds in mushrooms recognized for their numerous health, nutraceutical, and physicochemical properties. The aim of the present study was to extract β‐glucans from P. ostreatus powder and to study the feasibility of using the extract to prepare oil‐in‐water emulsions formulated for the encapsulation of lipophilic antioxidants by spray drying, for example, with an oil droplet size about 2 μm, a dry matter content of 40% w/w, and with a physical stability of at least 2 hrs. Hot‐water soluble β‐glucans fraction was extracted from P. ostreatus powder following a method adapted from literature. Emulsions were prepared by rotor‐stator homogenization using maltodextrin as wall material, β‐glucans extract as emulsifier, and commercial sunflower oil as a model for lipophilic active compounds. The emulsion stability was estimated from the evolution over time of the oil droplet size distribution measured by laser light diffraction and experimental data were investigated using one‐way ANOVA. Extracts containing up to 27% w/w water‐soluble β‐glucans were produced. Physically stable mono‐modal emulsions were obtained when maltodextrin/β‐glucans weight ratio was lower than about 500 to avoid depletion and β‐glucans/oil weight ratio was more than 0.014 to stabilize oil droplets. The usage of emulsifiers made‐up by polymeric constituents with inherent bioactivity, such as mushroom β‐glucans, could be a sustainable and healthy alternative to common emulsifiers.Practical applicationsA great deal of interest has been expressed in a unique dietary fiber, named β‐glucans, from the basidiomycete Pleurotus ostreatus, a mushroom which can grow efficiently on various clean by‐products of food processing, thus representing a sustainable food source. β‐Glucans' functionality is associated with their many healthy and physicochemical properties, for instance emulsifying properties. The usage of emulsifiers made‐up by polymeric constituents with inherent bioactivity, such as mushroom β‐glucans, could be a sustainable and healthy alternative to common emulsifiers.

Impact of a jet orifice on the hydrodynamics and the oil droplet size distribution

Experiments were performed to understand the impact of the orifice on droplet size in the shear breakup region. Oil jet was released vertically from two orifice types: a pipe and a converging nozzle. The roll-up vortices were observed clearly near the edge of the jet with nozzle orifice while elongated oil ligaments in the jet direction were mostly observed near the edge of the jet with pipe orifice. The size of the droplets shed from the near field shear layer increased along the jet direction for both orifice types. At different distances from the orifice, the characteristic shed droplet size (d50) was up to 40% larger with pipe orifice. Multiphase, large-eddy simulations (LES) with two orifice types were conducted to interpret the droplet size distribution (DSD) observed in the experiments. A thicker boundary layer that was initially formed inside the pipe dominated the near field of the jet with the pipe. The turbulent kinetic energy dissipation rate (ε) was higher with pipe orifice and the peak values of ε were found closer to the jet centerline with the pipe where oil holdup is larger. The viscous shear stress with the nozzle was higher than that of the pipe orifice within the initial two diameters from the orifice and slightly lower or higher at the following distances studied. The Reynolds shear stress was significantly larger with the nozzle at different distances from the orifice. The tangential vorticity within one diameter from the orifice was also dramatically higher with the nozzle. The key parameter in the shed droplet size of a liquid jet in liquid was found to be the shear layer thickness at the orifice, similar to prior works of a liquid jet in gas. A thicker shear layer at the pipe orifice induced a larger droplet size. The increase in the instabilities and shear layer thickness in the jet direction increased the droplet size in the jet direction.

Surface active ionic liquid and Tween-80 blend as an effective dispersant for crude oil spill remediation

Chemical oil spill dispersants are toxic to the marine environment, spurring a search for environmentally friendly dispersant formulations. We have formulated an oil spill dispersant composed of two biocompatible surfactants, Tween 80 (T) and surface-active ionic liquid (SAIL), [BMIM] [Lausar] (1-butyl-3-methylimidazolium lauroyl sarcosinate). Various micellar, interfacial, and thermodynamic properties of Tween 80 and ionic liquid (T/IL) blends were studied. The T/IL blends were solubilized in simulated seawater, and their oil (light Arab crude oil) dispersion effectiveness was determined by the baffled flask test. A synergistic interaction was observed between T and IL, such that a blend is effective as an oil dispersant, but neither is effective on its own. The stability of crude oil droplets was maximized at a 40/60 (w/w) of T/IL. The dispersion effectiveness at this specific ratio was found to be 81.19%, with a dispersant to oil ratio (DOR) of 1:25 (volume). The size and size distribution of dispersed oil droplets at function of DOR were investigated using optical microscopy and particle size analyzer. The results showed that the sizes of oil droplets decreased with DOR. We conclude that T/IL blends have unique properties which make them viable alternatives for oil spill remediation.

Formation and characterisation of high-internal-phase emulsions stabilised by high-pressure homogenised quinoa protein isolate

High pressure homogenised (HPH) quinoa protein isolates (QPI) suspensions (1, 3, and 5 wt%) were used to prepare high-internal-phase emulsions (HIPEs) (ɸ=0.8). The viscoelastic behaviours of HIPEs were characterised by oscillatory rheology, while the oil droplet size distribution and microstructural characteristics were examined by static light scattering and confocal laser scanning microscopy (CLSM). At all QPI concentrations, HIPEs behaved as viscoelastic gels due to network formation as a result of interactions between jammed oil droplets and protein aggregates. As the QPI concentration increased, the oil droplet size decreased from ~80 to~40 µm and the elastic modulus G´(1 Hz) increased from ~100 to~580 Pa. Effects of prolonged storage (30 days) and heat treatment (80 °C, 30 min) on the rheological behaviour and microstructures of HIPEs were also investigated. All emulsions showed excellent stabilities against phase separation, oil coalescence, and creaming during storage or under heat treatment. Prolonged storage induced a substantial increase in G´, while no significant change in oil droplet size was observed. CLSM revealed that the interfacial layer became thicker and large protein aggregates were formed during storage, which led to a more dense and compact packing of droplets and greater gel strength. Heat treatment induced a 3–5 folds enhancement in the gel strength due to protein denaturation and proteins and oil droplets aggregation. These findings provide useful information for the design and preparation of HIPEs stabilised by quinoa proteins.

Experimental Investigation of Oil Droplet Size Distribution in Underwater Oil and Oil-Air Jet

Abstract Understanding the droplet size distribution of subsea oil releasing is important to predict the subsequent transport and degradation of the spilled oil. Single- and multi-phase oil jet experiments were conducted in the Ohmsett facility, including pure oil jet and oil-air jet through a 10.7-mm pipe and a 4.7-mm pipe. Measurements of the vertical jet hydrodynamics and the oil size distribution were obtained. The reported results help to extend subsea oil spills experiment scale into a meso-scale, and the measurement range of the oil size is widened up to 2 cm. Moreover, the application of dispersant and involvement of air phase provided valuable scientific evidence for the usage of dispersants to treat oil spills. The data confirmed the effectiveness of the dispersant that reduces oil droplet size and also suggested that the participation of the gas phase facilitated the decreasing of oil droplet size. The results were compared to the numerical simulation tool VDROP-J. While the hydrodynamics showed good consistency, the system-dependent coefficient needed a slight revision to coincide with presented data. This also confirmed the significance of experimental materials for further validation and development of oil spill models, where we also provided guidance and discussion on conducting and post-processing the oil spill experiment.

Subsea Mechanical Dispersion (SSMD) a Possible New Option for the Oil Spill Response Toolbox?

Abstract The size distribution of oil droplets formed in subsea oil and gas blowouts is known to have a strong impact on their subsequent fate in the environment. Small droplets have low rising velocities, are more influenced by oceanographic turbulence and have larger potential for natural biodegradation. Subsea Dispersant Injection (SSDI) is an established method for achieving this goal, lowering the interfacial tension between the oil and water and significantly reducing oil droplet size. However, despite its many advantages, the use of SSDI could be limited both by logistical constraints and legislative restrictions. Adding to the toolkit a method to achieve subsea dispersion, without the use of chemicals, would therefore enhance oil spill response capability. This option is called Subsea Mechanical Dispersion (SSMD). An extensive feasibility study on SSMD has been performed and the main findings are reported in this paper. The work was initiated by BP in 2015 and later followed up by a consortium of Equinor, Total Norge, Aker BP and Lundin. The first phase explored multiple principles of generating subsea dispersions (ultrasonic, mechanical shear forces and water jetting) through both laboratory experiments and modelling. These studies clearly indicate that SSMD has an operational potential to significantly reduce oil droplet sizes from a subsea release and influence the fate and behaviour of the released oil volume. The recent work reported in this paper on operationalisation, upscaling and large-scale testing of subsea water jetting. This work is performed by SINTEF in close cooperation with Exponent (computational fluid dynamics and shear stress modelling) and Oceaneering (operationalisation and full-scale prototyping).

Characterizing Dispersion Effectiveness at Varying Salinities

ABSTRACT Chemical dispersant formulations typically provide maximum oil dispersion in waters between 30–40 ppt (parts per thousand) salt content, which encompasses typical ocean salinity (~34 ppt). As a result, most laboratory studies of oil dispersion effectiveness (DE) are conducted at low to average ocean salinity. Ocean salinity can vary locally from below 20 ppt during ice and snow melt, to extremely high (over 100 ppt) during freeze up periods or within natural brine pools in deeper waters. In this study, the influence of salinity on DE was evaluated using the baffled flask test (BFT) at a dispersant-to-oil ratio (DOR) of 1:25. Benchtop experiments were conducted with Alaskan North Slope (ANS) crude oil in the presence or absence of chemical dispersant at 5 and 25°C and varying salinities (0.2 to 125 ppt). In addition to DE as determined by BFT, oil droplet size distribution (DSD) and fluorescence intensity was measured via a LISST-100X particle size analyzer (Sequoia Scientific, Inc., Bellevue, WA) and ECO fluorometer (Sea Bird - WET Labs, Inc.; Philomath, OR), respectively. Results indicate that in the presence of dispersant, maximum DE occurred at 25ppt, and decreases above and below this salinity. Concentration of small droplets (<10 μm) was twice as high at 35ppt than at the other salinities in the presence of dispersant at 25°C. Treatments without dispersant did not vary significantly as a function of salinity. Flume tank experiments over a range of salinities support the lab scale results of DSD. These results provide a more comprehensive picture pertaining to the influence of salinity on dispersant usage at high salinities.