The development and production of oil and gas fields would eventually result in a considerable amount of oily generated water, posing serious risks to humans and the environment. Nowadays, the oil ...concentration in the drainage stream of the produced water is strictly regulated, and many countries have established strict emission standards. As an indispensable oily wastewater treatment technology, flotation technology has attracted much attention because of its maturity, economy, practicality, and relative efficiency. Firstly, this paper summarizes and compares flotation techniques, such as dissolved gas flotation, induced gas flotation, electroflotation, and compact flotation units widely used in produced water treatment offshore in recent years. Considering the complexity of the mechanism of oil removal by air flotation, the mechanism of the oil droplet-bubble interaction is further discussed. The effects of flocculant, PH, and salinity on the oil droplet-bubble interaction in the flotation process were summarized from the perspective of the microscopic colloidal interface, which has a specific guiding role in improving the oil removal efficiency in the gas flotation process. Finally, the research status of produced water treatment by air flotation is summarized, and the feasible research direction is put forward.
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•Produced water (PW) has endangered the environment and humans.•Flotation is an important technology for the treatment of produced water.•Types and characteristics of flotation process for produced water treatment.•Interaction mechanism of oil droplet with bubble and its influencing factors.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
A fluorine doped graphene (FDG) film was deposited on the surface of roving fabric by radio frequency plasma enhanced chemical vapor deposition (RF-PECVD). The micromorphology, functional group ...types, chemical composition, molecular structure and nanostructure image of the deposited films under different discharge power were characterized by field emission scanning electron microscope (FE-SEM), Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), Raman spectroscopy and transmission electron microscope (TEM). The static and rolling−water/−oil contact angle were measured by contact angle meter. The electrochemistry properties were tested using electrochemical workstation. The superamphiphobic mechanism was studied by electrochemical impedance spectroscopy (EIS) and density functional theory (DFT), and the corresponding software were Gemry Echem Analyst and Materials Studio 7.0, respectively. The results show that the obtained FDG film has the best hydrophobic and oil repellent performance under the discharge power of 80 W. F atom in the FDG film is arranged on both side and the capacitance structure (C-model) is presented in the equivalent element by EIS fitting and DFT calculation under the discharge power of 80 W. The phenomenon proves that the electron transfer of free electrons from the position of K point in the Brillouin region of graphene surface was forbidden by the F atom, which is the mechanism of superhydrophobic and oil drainage on the FDG film surface.
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•Superamphiphobic surfaces of fluorine doped graphene were obtained by a plasma process method.•The chaotic bonding mode of carbon and fluorine tends to the -CF2 and -CF3.bonding mode.•F atom in film is arranged on both side and the capacitance structure is studied by EIS and DFT.•The mechanism of superhydrophobic and oil drainage is electron transfer forbidden by the F atom.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
Ni625–xCr3C2 coatings were prepared on 45 steel by laser cladding to improve its tribocorrosion and electrochemical property. The microstructure, phases and hardness of obtained coatings were ...analyzed using a super–depth field microscope, X–ray diffraction, and microhardness tester, respectively, and the effects of Cr3C2 mass fraction on the tribocorrosion and electrochemical properties of Ni625–xCr3C2 coatings in 3.5 % NaCl solution were investigated. The results show that the Ni625–xCr3C2 coatings are mainly composed of γ–Ni, Fe3C, Cr3C2, Mo2C, Cr7C3 and Cr23C6 phases, and their coating hardness increases with the Cr3C2 mass fraction, which are almost three times that of substrate. The coefficients of friction and wear rates of Ni625–5%Cr3C2, −10%Cr3C2 and − 15%Cr3C2 coatings are reduced compared with the Ni625 coating, and the wear mechanism is primary abrasive wear, accompanied with adhesive wear and pitting corrosion. Moreover, the polarization resistance of Ni625–5%Cr3C2, −10%Cr3C2 and − 15%Cr3C2 coatings are higher than that of Ni625 coating, showing that the corrosion resistance of Ni625–10%Cr3C2 coating was the best among the four kinds of coatings.
•The grains of Ni625–xCr3C2 coatings are refined by the addition of Cr3C2.•The hardness of Ni625–xCr3C2 coatings is increased with the Cr3C2 mass fraction.•The wear mechanism of Ni625–xCr3C2 coatings is abrasive wear, adhesive wear and pitting corrosion.•The polarization resistance and charge transfer resistance are increased with the Cr3C2 mass fraction.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
Flotation technology is widely utilized to remove emulsified oil droplets from Produced water. Organic acid adsorption on the oil droplet surface affects bubble attachment, reducing oil removal ...efficiency. This investigation exploited the principle of similar dissolution to synthesize condensate bubbles (CB). The surface properties of oil droplets and CB and air bubbles (AB) were appraised using FTIR, zeta potential, interfacial tension, and contact angle measurements. The research also investigated the effects of acetic acids (AA) on the adhesion of oil droplets to AB and CB along with the underlying mechanism via the Extended Derjaguin-Landau-Verwey-Overbeek (EDLVO) interaction theory and the Stefan-Reynolds model of liquid film thinning, integrated with adhesion times. Flotation efficiency and kinetic dissimilarities between AB and CB were also examined. The results indicated that CB exhibits superior lipophilic hydrophobicity compared to AB, reduced induction and spreading times upon oil droplet attachment, and maximized oil removal efficiency. Furthermore, CB could mitigate the impact of AA on adhesion. The interaction barriers between CB and oil droplets were minimal, and the thinning rate of the hydration film was quicker than in AB. The conventional first-order model proved effective in fitting the AB flotation, whereas a delay constant was applied to the model of the CB flotation rate.
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•Acetic acid changed the hydrophobicity of the oil droplet surface.•Oil droplet-bubble adhesion interaction mechanisms were explored.•The spreading coefficient was negatively correlated with induction time.•Hydrophobic force was the main driver of condensate bubble-oil droplet adhesion.•Determined delay constants for a kinetic model of condensate bubble flotation.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
Stable foam will be generated in the separation equipment after pressure reduction of crude oil, which reduce the separation efficiency and damage the power equipment. It is found that the foam ...formed by asphaltene-rich crude oil is particularly stable in oilfield production, and the action mechanism of asphaltene for foam remains unclear. Hence, a self-made foaming device was performed to investigate the foamability and foam stability of oil-based foam, and the impact of asphaltene concentration and oil phase composition on foam properties was elucidated from the interfacial properties, viscosity, foam structure and the microstructure of asphaltene. Results show that low asphaltene concentrations promote foaming and mitigate the foam destruction. In contrast, high asphaltene concentrations are detrimental to foaming and reduce foam stability. The changes in interfacial properties and viscosity caused by asphaltene are not the main factors affecting foam performance. Besides, we proposed that asphaltene present in the oil phase as non-adsorbed particle, and the foam stability is influenced by the shape, volume fraction and size distribution of the particles. Furthermore, the boundary conditions for the effect of asphaltene on foam performance are innovatively put forward. This work contributes to understand the mechanism by which the asphaltene enhances foam stability and provides theoretical support for defoaming techniques in crude oil foam.
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•The dynamic interface properties of asphaltene at oil-gas interface are studied.•Effects of asphaltene concentration and solubility on foam property are discussed.•Viscosity and interfacial property are not the main factors affecting foam property.•The dominant effect on foam are the shape and size of asphaltene aggregates.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
The dynamic behaviors of two droplets and droplet cluster under an alternating current (AC) electric field are investigated. Two droplets generally undergo transformation from complete coalescence to ...partial coalescence and finally to non‐coalescence as the electric capillary number Cap increases. The critical electric capillary number Capc for complete coalescence in the AC electric field remains unchanged and is twice as large as that in the direct current (DC) electric field when the frequency f ≥ 250 Hz. Charge transfer and reversal of electric field result in the reversal of the direction of electric force, which is the fundamental mechanism of non‐coalescence of two droplets and chain formation in droplet cluster. The number of rebounds dramatically increases as f increases, promoting the stability of droplet chain. The droplet chains in the high‐frequency AC electric field are longer and more stable than those in the low‐frequency AC electric field.
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BFBNIB, FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SBCE, SBMB, UL, UM, UPUK
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•Alkali used in ASP flooding has impact on droplet–interface electrocoalescence.•Elevated water conductivities by adding Na2CO3 would inhibit partial coalescence.•Increased Na2CO3 ...solution concentrations retard the penetration of vortex ring.•Application of electric fields with different waveforms affects coalescence.•The optimal waveform inhibiting partial coalescence changes with frequency.
During the process of electro-dehydration, the electric field strength should be set below a critical value (Ecrit) to inhibit droplet–interface partial coalescence. The alkali present in alkaline–surfactant–polymer flooding may affect Ecrit because they change the electrical properties of produced liquids. In view of this, this study investigated the effects of Na2CO3 solution concentration, electric field waveform, and frequency on the root mean square (RMS) values of Ecrit. The results show that elevated Na2CO3 concentrations increase Ecrit, owing to the enhanced solution conductivity which may affect the charge transfer during coalescence. The convection of ions is associated with penetration of fluid into the bulk phase and an increase in Na2CO3 concentration decreases the penetration velocity. Moreover, increasing the AC or pulsed electric field frequency can increase Ecrit, and the optimal waveform (i.e., with the largest Ecrit) varies with frequency. These findings will be useful for optimizing electro-coalescence systems.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
•A mathematical model describing the kinetic behavior of oil droplets in water under horizontal wall constraints is developed and the model is validated based on a microscopic experimental ...system.•The dynamics behavior of oil droplets in water near the wall is analyzed from the perspective of damped vibration.•A motion pattern diagram of oil droplets near the wall with (G, Oh) as the regulation parameter is established to identify the motion law of oil droplets at different Mo numbers.
The interaction problem of a freely-rising oil droplet in water due to the horizontal wall constraint is solved numerically. The motion equation, water film drainage equation, and Young-Laplace equation are coupled to establish a dimensionless mathematical model for describing the bounce behavior of oil droplets in water. In addition to buoyancy and flow resistance, the motion equation also introduces added mass force and film induced force caused by interaction with the wall. Further analysis shows that the coupling model conforms to the dynamics characteristics of a damped vibration system from the perspective of vibration. Based on the analysis of vibration parameters, We found that the bounce behavior of oil droplets is directly related to the oil-water system's Eo number and Oh number, in addition to the size dependence. Moreover, the bounce pattern diagram with (G, Oh) as the control parameter provides a suitable identification for the transition law of the bounce number of oil droplets under the horizontal wall constraint. The findings of this study facilitate quantifying the processes of oil droplet adhesion, coalescence, and spreading and provide a sub-model reference for the description of complex oil-water systems.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
Amorphous carbon–containing CrAlCN coating was deposited on Cr12MoV steel by cathodic arc ion plating. The effect of amorphous carbon on the tribological performance of obtained coating under the ...different normal loads was investigated using a ball–on–disc tester, and the lubrication and wear mechanisms of amorphous carbon were discussed in detail. The results show that the CrAlCN coating is composed of AlN, CrN and CrC phases with the amorphous carbon. The average coefficient of friction of CrAlCN coatings under the normal loads of 2, 4 and 6 N are 0.458, 0.586, and 0.666, respectively, where the amorphous carbon plays a self–lubrication role in the friction process. The wear degree is deteriorated with the increase of normal load, and the wear mechanism is changed from abrasive wear to adhesive wear.
•The amorphous carbon–containing CrAlCN coating presents the high nanohardness and elastic modulus•The CrAlCN coating improves the friction reduction and wear resistance performances.•The amorphous C in the CrAlCN coating plays the roles of friction reduction and wear resistance.•The wear mechanism of CrAlCN coating is changed with the increase of normal load.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
