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Oil–water separation using hydrocyclones enhanced by air bubbles

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Abstract

In order to improve the separation efficiency of dispersed oil from water by hydrocyclones, a new process of utilizing air bubbles has been developed to enhance the separation efficiency. The air bubbles attach themselves to the oil droplets and cause a decrease in the overall density of the phase, the difficulty of agglomerating can thus be circumvented. The air–liquid ratio of 1% was found to provide the best separation. When the inlet Reynolds number ranges from 14,000 to 16,000, the oil removal efficiency increases from 72% (air–liquid ratio 0%) to 85% (air–liquid ratio 1%). The process has been found to be very efficient in the separation of suspended oil from water.

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... It was recognized that the separation efficiency plateau was caused by the balance between decreasing the residence times and increasing the centripetal forces as the feed flow rate increased [87]. Besides, the separation efficiency decreased at feed flow rates above Q max as a result of either (i) an increased oil-droplet breakup (i.e., emulsification) owing to the excessive shear forces and the turbulence [86,88], and/or (ii) a lack of sufficient pressure gradients to drive the separated oil through the vortex finder as the pressure in the central of hydrocyclone was reduced at high feed flow rates [86]. ...
... Therefore, recent years, to enhance hydrocyclone separation by flotation, researchers introduced various approaches to add air bubbles into hydrocyclones. For instance, to enhance the oil-water separation in hydrocyclones, Bai et al. [88,172] utilized an air-liquid mixing pump to produce 15-60 μm air bubbles and provide high probability for oil-bubble interaction. After air bubbles with larger diameter, which could decrease the separation efficiency, were separated using an air-liquid separation pot, the air bubbles, oil, and water were fed into the hydrocyclone together. ...
... Then the air bubbles were entrapped by a single oil droplet or oil droplets with flocculated structure (Fig. 17), which resulted in that the oil was separated more easily and rapidly than that without air bubbles. Results demonstrated that: (i) the air bubbles occurred in the water could ameliorate the separation efficiency of hydrocyclones [88,172]. (ii) The separation efficiency reached the maximum when the air-liquid ratio was close to 1% [88]. Zhao et al. [173] injected the air into hydrocyclones through the micro-pore section to combine them with dispersed oil. ...
Article
Hydrocyclones are widely employed in both heavy and light industries. However, exact mechanisms underlying enhanced-separation technologies developed by optimizing operating parameters and conditions in hydrocyclones remain unclear. Accordingly, many research groups have conducted numerous investigations to expand the application range of hydrocyclones by optimizing operating parameters and conditions. This paper presents a comprehensive state-of-the-art review of the aforementioned hydrocyclone enhanced-separation technologies, which are classified into two groups: (i) operating parameters, including feed flow rate, feed pressure, feed density difference, feed particle parameters (concentration, size, shape, and arrangement), and feed fluid parameters (viscosity and rheology); and (ii) operating conditions, including electrical hydrocyclones, magnetic hydrocyclones (electromagnetic field and permanent magnetic field), magnetic fluids hydrocyclones, electrochemical hydrocyclones, flocculant-assisted hydrocyclones, hydrocyclones enhanced by flotation, hydrocyclones enhanced by control particles; hydrocyclones enhanced by adjusting back pressure, and hydrocyclones enhanced by monitoring and automatic control. These enhanced-separation technologies were analyzed and summarized based on the critical separation-performance parameters, such as separation efficiency, cut size, split ratio, energy consumption, capacity, and separation sharpness. It is hoped that both reviewed contents and proposed challenges may be helpful to the researchers and eventually yield some perspective knowledge, which results in the improvement of economic feasibility of separation by hydrocyclones.
... Hydrocyclone operates by fluid entering the cyclone tangentially via the inlet opening into the cylindrical section creating a swirling flow (vortex); the swirling flow generates a high centrifugal force required to separate the oil; therefore, higher density fluid (water) centrifuge to the wall of the cyclone whereas the lesser density fluid (oil) migrates towards the core of the cyclone. Hydrocyclone generally separate oil droplet size of 15µm and above from produced water, particles less than 15µm are difficult to separate using hydrocyclone as the separation efficiency of hydrocyclone decrease with particle size [3] Geometry and operating parameters have been used by many researchers in the optimization of hydrocyclone separation efficiency. Noroozi [4] used helical inlet to increase separation efficiency by 10% while increased inlet diameter as well was found to have also increased the separation efficiency of hydrocyclone [5] [6]. ...
... The vortex finder (overflow) and spigot (underflow) of the cyclone were exposed to the atmosphere, therefore, the gauge pressure was set to 0 atm. The density of magnetic particle was assumed to be 5175kg/m 3 Magnetic particles of size lightly higher than oil droplet to be separated was assumed to have been treated with surfactant and mixed with the oil emulsion, oil droplets are expected to attract to the surface of the magnetic particle, therefore, doping the magnetic particle (applicable for oil droplet less than 10μm). For bigger oil droplet size, magnetic particle is attracted to the surface of the oil droplet. ...
Conference Paper
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Abstract - Hydrocyclone separate oil droplet size of 15µm and above from oil-water emulsion, particles less than 15µm are difficult to separate using hydrocyclone. The aim of this paper is to improve the separation efficiency of oil particles size of less than 10 µm in hydrocyclone. This paper evaluates the use of ferromagnetic particles for improving separation efficiency of droplet size less than 10μm in liquid-liquid hydrocyclone. Eulerian-Lagrangian model was used in conjunction with the Reynolds Stress Model (RSM) for turbulence and Magneto Hydrodynamic model (MHD) account for ferromagnetic particle conductivity. It was observed that use of magnetic particles increases separation efficiency by approximately 30% and 22% for 0.018% and 0.18% feed concentration respectively for particle size between 1-10µm and 32% increment was observed for particle size between 11-15µm. The increment is attributed greatly to the increase in density of oil as a result of doping micro-sized magnetic particles with oil-emulsion. Finally, it was seen that increasing magnetic field strength from 0.5 Telsa to 1.5 Telsa increases separation efficiency in the range of 1-4% and the use of magnetic particles increase the velocities of the fluid.
... Despite their advantages, hydrocyclones have low separation efficiency when the dispersed oil droplet diameter is smaller than 15 μm. 48 In order to increase the oil removal efficiency, special hydrocyclones have been developed, such as the bubble enhanced hydrocyclone, in which the oil droplets and the bubbles collide with each other, and thus are carried out of the cyclone. 48 ...
... 48 In order to increase the oil removal efficiency, special hydrocyclones have been developed, such as the bubble enhanced hydrocyclone, in which the oil droplets and the bubbles collide with each other, and thus are carried out of the cyclone. 48 ...
Article
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Clean water supply has become one of the biggest challenges of the 21st century; therefore, water source protection is of increasing importance. Beyond environmental protection reasons, economic concerns—derived from increasing costs of processing water and wastewater discharge—also prompt industries to use advanced wastewater treatment methods, which ensure higher purification efficiency or even the recycling of water. Therefore, highly effective treatment of oily wastewaters has become an urgent necessity because they are produced in high quantities and have harmful effects on both the environment and human population. However, high purification efficiency can be difficult to achieve, because some compounds are hard to eliminate. Conventional methods are effective for the removal of floating and dispersed oil, but for finely dispersed, emulsified and dissolved oil advanced methods must be used, such as membrane filtration which exhibits several advantages. The application of this technology is restricted by fouling—the major limiting factor—which jeopardizes the membrane performance. In order to reduce fouling, in‐depth research is being conducted to make the treatment of oil‐contaminated water technically and economically feasible. The present work aims to review the conventional oil separation methods with their limitations and to focus on membrane filtration, which ensures significantly higher purification efficiencies, including the main problem: the flux reduction caused by fouling. This paper also discusses promising solutions, such as membrane modification methods, mostly with hydrophilic and/or photocatalytic nanoparticles and nanocomposites, overviewing the efforts that are being made to develop feasible technologies to treat oil‐contaminated waters.
... The literature often reports the usage of hydrocyclones for oil-water separation for low compositions of the oil phase (Liu et al., 2019;Huang et al., 2018;Huang et al., 2017;Bai et al., 2011;Zhou et al., 2010). This is probably due to their successful first application in the oil industry as de-oiling devices (Young et al., 1994) to treat produced water. ...
... In such cases, oil concentration ranges from 40 mg/L up to 3%. High efficiencies such as 92% can be achieved (Huang et al., 2018), however separation efficiencies range on average between 40% and 80% (Bai et al., 2011;Motin et al., 2017). Hamza et al. (2019) have investigated separation efficiency in a hydrocyclone for higher oil concentrations than usual to be applied in mature oil fields. ...
Article
Production separators for gas-oil-water separation are huge, require long residence times, and present several internals to improve oil-water separation. As an alternative to production separators, specially for subsea facilities, this work presents a hydrocyclone which separates a 40% oil-in-water mixture with 93% ± 2% total efficiency and flow ratio of 7%. Such high oil concentration is typical of mature wells and hydrocyclones have not been designed for such purpose before. In order to design this hydrocyclone, fractional factorial techniques have been used to consider the influence of seven geometrical variables. CFD has been used to assess the performance of each hydrocyclone of the factorial design. The selected hydrocyclone has been tested experimentally in order to validate its performance. PIV measurements have also been carried out in order to assess tangential and axial mean velocity profiles for only water flowing in the hydrocyclone. FBRM has been used to measure droplet size distribution at inlet, overflow and underflow streams. As results, computational reduced total efficiency has been experimentally confirmed. Numerical simulations captured tangential velocity near the centerline of the hydrocyclone, but failed in predicting axial velocity profiles and tangential velocity peaks and near wall regions. It has been discussed though that these are probably not responsible for oil droplets separation in the hydrocyclone when water is the continuous phase. A methodology to analyze the effect of droplet breakup and coalescence, using measured inlet, overflow and underflow cumulative size distribution, has been presented. It has been shown that for the inlet cumulative undersize distribution used, breakup was negligible and coalescence occurred only for droplet diameters higher than those separated with 100% grade efficiency. In this case, no breakup and coalescence models are thus needed in the mathematical model and this explains why reduced total efficiency has matched in both numerical simulations and experiments.
... • Hydrocyclone [48,49] [53,54]. ...
... The technologies and processes associated with breaking and separating emulsions into the phases of oil and water can be induced chemically, electrically, and physically [23,49,[120][121][122]. This process of breaking and separating emulsions is called demulsification. ...
Article
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Water plays an essential role in production and refining processes. Many industries that use petrochemicals also require water, especially for cleaning purposes. The wastewaters released by these processes are often rich in petroleum pollutants, which requires significant treatment prior to disposal. The presence of petroleum contaminants in rivers and oceans is a significant threat to human health, as well as to many animal species. A current challenge for most industries and conventional effluent treatment plants is compliance with accepted disposal standards for oil-polluted wastewater. Of particular importance is the processing of dispersed oil in water, as well as oil in water emulsion. Conventional oil and water separation methods for processing oil in water contamination have several technology gaps in terms of applicability and efficiency. The removal and effective processing of dispersed oil and emulsions from oily wastewater is a costly and significant problem. The objective of this paper is to provide a review of the principles associated with oil in water emulsion separation, with the aim of providing a more definitive understanding of the terminology, processes, and methodologies, which will assist the development of a more efficient, innovative and environmentally friendly process for the separation of oily wastewater.
... The oily-water flotation is a series of complex processes that depend upon thermodynamic and hydrodynamic forces with physical-chemical interactions [17,18]. For attachment to occur between an oil droplet and a bubble, they need to experience an adequately close encounter. ...
... Energies 2020, 13, 927 6 of 14 W tr is the average relative velocity between the droplet and bubble due to fluctuations in the fluid flow, which can be estimated using Equation (18) based on the phenomenological statistical theories for homogeneous turbulence. ...
Article
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A modified computational fluid dynamic (CFD) model has been developed to obtain oil removal efficiency for oily wastewater treatment in large-scale flotation tanks. According to the investigation of oil droplet/bubble interactions in a flotation tank, a modified Bloom–Heindel model is used to calculate the collision and attachment efficiencies between oil droplets and bubbles. Effects of the gas flow rate, oil diameter and oil concentration on oil removal efficiency of flotation tank were analyzed experimentally. The application scope of this modified CFD model is evaluated using experimental results. In addition, the comparison between the existing model and the modified model demonstrates that this modified CFD model can make a good prediction for the separation performance of the flotation tank.
... It was found that separation was most efficient when the inlet Reynolds Numbers varied between 14,000 and 16,000. Separation efficiency in the absence of air was 72% and was maximized at 1% air to 85% when separating mixed fluid of 100 mg/L average concentration of diesel with density 0.82 g/cm 3 and viscosity 4.2 mm -2 s [58]. Despite the limited application of these pilot studies mentioned above, the potential application of these findings deserves consideration and testing with different oil types rather than just light oils and oil water proportions for typical for skimmed material (30-90%) to determine the potential field application. ...
Article
Mechanical oil recovery (i.e., booming and skimming) is the most common tool for oil spill response. The recovered fluid generated from skimming processes may contain a considerable proportion of water (10% ~ 70%). As a result of regulatory prohibition on the discharge of contaminated waters at sea, vessels and/or storage barges must make frequent trips to shore for oil-water waste disposal. This practice can be time- consuming thus reduces the overall efficiency and capacity of oil recovery. One potential solution is on-site oil-water separation and disposal of water fraction at sea. However, currently available decanting processes may have limited oil/water separation capabilities, especially in the presence of oil-water emulsion, which commonly occurs in mechanical oil recovery. The decanted water may not meet the discharge standards and cause severe ecotoxicological impacts. This paper therefore comprehensively reviews the principles and progress in oil/water separation, demulsification, and on-site treatment technologies, investigates their applicability on decanting at sea, and discusses the ecotoxicity of decanted water in the marine environment. The outputs provide the fundamental and practical knowledge on decanting and help enhance response effectiveness and consequently reducing the environmental impacts of oil spills.
... It was shown that droplets smaller than 2 μm were produced during mechanical dispersion of gas and were hardly removed during the gas flotation. An interesting concept was also reported by Bai et al., who improved the hydrocyclonic separation by introducing dispersed gas bubbles to the process [137], bearing some similarities to the CFUs. da Silva et al. combined the gas flotation with a photo-Fenton process, which further reduced the oil content through photochemical degradation [138]. ...
Article
Due to increasing volumes of produced water and environmental concerns related to its discharge, water treatment has become a major challenge during the production of crude oil and natural gas. With continuously stricter regulations for discharging produced water to sea, the operators are obliged to look for ways to improve the treatment processes or re-use the water in a beneficial way, for example as a pressure support during oil recovery (produced water re-injection). To improve the knowledge of the underlying phenomena governing separation processes, detailed information of the composition and interfacial properties of produced water is undoubtedly useful and could provide valuable input for better understanding and improving separation models. This review article summarizes knowledge gained about produced water composition and the most common treatment technologies, which are later used to describe the fundamental phenomena occurring during separation. These colloidal interactions, such as coalescence of oil droplets, bubble-droplet attachment or partitioning of components between oil and water, are of crucial importance for the performance of various technologies and are sometimes overlooked in physical considerations of produced water treatment. The last part of the review deals with the experimental methodologies that are available to study these phenomena, provide data for models and support development of more efficient separation processes.
... Greek letters Density of continuous phase (kg m 3 ) Viscosity of continuous phase (Pa s) gies include low energy consumption, low maintenance requirements, and high operational reliability . Accordingly, hydrocyclones have been widely applied in numerous fields including mineral (Narasimha et al., 2014), coal (Chu et al., 2017;Rong and Napier-Munn, 2003), chemical (Huang et al., 2017;Xu et al., 2016), petroleum (Bai et al., 2011;Mognon et al., 2015), environmental protection (Bayo et al., 2015;Son et al., 2016), waste management (Ko et al., 2013;Li et al., 2016;Schwerzler, 2005), and food (Altieri et al., 2015;Emami et al., 2007). In the continuous-carbonation process, the introduction of hydrocyclone can realize continuous and rapid classification to avoid a change in particle size after PB mixed with the reaction liquid for a long time. ...
Article
Full-text available
Pseudo-boehmite (PB) is often used as a precursor for hydrotreating catalyst support (γ-Al2O3) in the petroleum refining process. Recently, continuous-carbonation process was proposed to prepare PB in order to meet the increasing demand for macroporous γ-Al2O3, but the highly dispersed particle size of PB in this process limited its development. To obtain the PB with monodispersed particle size, a 10 mm mini-hydrocyclone was designed by 3D printing technology and used to the classification for PB. Then a high-performance zone for classification with Re of 4000–5000 was obtained. The volume ratio of particles (>10 μm) was increased from 56.3% to 83.5% at a split ratio of 15%, and the mean particle size was increased from 12.9 μm to 45.7 μm, which indicated that the highly dispersed particle size could be efficiently concentrated into monodispersed one by hydrocyclone classification. Under optimal operating conditions (Re of 4360 and Rf of 15%), the hydrocyclone was unprecedentedly applied to the continuous-carbonation preparation process of PB, and the volume ratio of particles (>10 μm) was significantly increased from 53.1% to 75.6% in the pilot test. This finding contributed to optimize continuous-carbonation process and improve product performance.
... The reason for this phenomenon is that the particles could be trapped easier by the wall of the hydrocyclone due to the stronger centrifugal force with the increase of the Re [34,35]. However, if the Re was continuously improved, the E tended to be worse owing to the increase of turbulence flow inside the hydrocyclone [36] and the reduction of the particles stagnation time [19]. Compared with NWSH, the maximum E of WSH (92%) was higher than that of NWSH (90%), because the water-sealed type could eliminate the air core (i.e., preventing the air from entering the hydrocyclone through the bottom apex) which was detrimental to the separation process [37,38]. ...
Article
The shaft-seal water system (SSWS), as one of the critical systems for slurry pump protection, is widely used to provide shaft-seal water in cutter suction dredger. In general, the shaft-seal water obtained from gravity clarifier always accompanies with numerous sand with large size (>10 μm), resulting in the inevitable intense wear of components in the slurry pump, especially, the shaft sleeve and L-shaped rubber ring in back shaft seal. Even worse, the high temperature caused by unstable shaft rotation in the present of sand will aggravate the degree of this wear. To address the above thorny problems, in this study, water-sealed hydrocyclone (WSH) was unprecedentedly applied to optimize SSWS for high-efficiency sand centrifugal separation. The dimension and structure of WSH were designed and optimized before final industrial application. High-efficiency separation zone (the separation efficiency >90%) with Re ranged of 1.88 × 10⁴–2.23 × 10⁴ was also confirmed by introducing the optimal structure of the WSH (5° of cone angle and 10 mm of bottom apex diameter). For the improved SSWS in the actual application, the Dv(50) of the shaft-seal water decreased from 38.0 μm to 9.1 μm, and the corresponding solid concentration declined from 0.51 g/L to 0.051 g/L. Furthermore, it was verified that the optimized SSWS could significantly reduce the wear of the shaft sleeve and L-shaped rubber ring, and extend the service life of L-shaped rubber ring, up to 4 months. This finding provided a new insight for the optimization of the SSWS for slurry pump, which could improve the operational stability and reliability of cutter suction dredger in the construction of marine infrastructure.
... Oil and water mixtures can in principle be separated using gravity separation techniques. Conventional methods, such as air flotation, electrical/chemical coalescence, and centrifugation [1][2][3][4][5][6][7][8][9][10][11][12], are typically adopted to purify water to a level that meets environmental standards. The main disadvantages of traditional techniques are (i) contamination and devaluing of remaining oil, (ii) the need for both sophisticated control and skilled operators, (iii) high operating costs, and (iv) a large environmental footprint. ...
Article
Wastewaters containing oil-in-water (O/W) emulsions are generated daily in various industrial processes such as petroleum refining, petrochemical and metal finishing. Environmental and economic concerns related to the disposal of oily wastewaters emphasize demands for materials and methods that can effectively separate oil from water. Pressure-driven membrane processes have been employed for oil/water separations. The major challenge that hinders the suitability of membrane technology for industrial oily wastewater treatment is the adsorption of oil and surfactants onto the membrane surface and/or within the pores of the membrane, which severely deteriorates the membrane performance. Materials with both hydrophobic and oleophilic properties have attracted significant attention in recent years for oil removal from water. These oil-removing type of materials can be used for membrane filtration or selective and efficient absorption of oil from water. The application of oil-removing materials can successfully introduce special wettability to the oily wastewater treatment. However, these materials are fouled quickly by oil droplets because of their intrinsic oleophilic properties. The attached oil droplets on the membrane surface severely affect separation efficiency. Besides, the adhered oil droplets are hardly removable from the surface resulting in reduced life-cycle of oleophilic materials, and this thus necessitates the need for costly post-treatment processes. Therefore, it is essential to develop high-performance materials for oil/water separation with elevated separation efficiency and significant antifouling properties. This study aims to review the state-of-the-art superhydrophilic and underwater superoleophobic (SUS) membranes that are being developed to overcome the aforementioned challenges. This allows to probe the maximal potential of developing such materials, and to explore the feasibility of using these novel membranes for de-oiling processes conventionally performed using expensive and low-performance skim tanks and adsorbents. In this review, according to the various materials that have been used for membrane fabrication, development methods for membrane synthesis with SUS properties based on polymeric SUS membranes and organic-inorganic hybrid SUS membranes including grafting, non-solvent phase separation (NIPS) polymeric membrane with hierarchical glue/tape-free surface, surface coating, in situ mineralization combined with polymeric materials and surface coating of polymeric membranes with inorganic nanoparticles, respectively, are assessed, in view of suggesting the success potential of these methods.
... The first is called tangential or reversed flow cyclone and the other is axial cyclone (Nieuwstadt and Dirkzwager, 1995). In tangential flow cyclones, the flow is put into to the separator tangentially, which was first proposed in 1891 for the gas-liquid separation (Bai et al., 2011). The hydrocyclone and gas-liquid cylindrical cyclone (GLCC) are common tangential flow cyclones. ...
Article
Full-text available
Gas-liquid separation technology is widely used in various fields of industrial production. In this research, a new kind of gas-liquid separator was proposed for the separation of gas-liquid mixture under different flow patterns. An inclined experimental system with an angle of 60 degrees from the vertical was established to test the new designed gas-liquid separator using of water and air as the working fluid. The experiment was conducted with the water flow rates covering 2.85–4.17 m3/h and the gas volume fraction covering 5–90%. Experiment results show that the separator can enable high efficient separation of gas-liquid mixtures under different patterns, especially under unstable flow patterns. The liquid level inside the separator is an important factor affecting the performance of the separator. On the basis of this, the critical liquid level of the separator was proposed for the practical application of the separator. This study fills the gap in the field of gas-liquid separation and provides a method for the separation of gas-liquid mixtures under different flow patterns.
... This kind of wastewater comes from a variety of sources, such as crude oil production, petrochemical industry and metal processing [1]. Many strategies, including gravity settling [2], air flotation [3], packed bed coalescence [4], centrifugal separation [5], hydrocyclone [6], have been introduced, but they are typically ineffective when dealing with finely emulsified oily wastewater streams because oil in these stable emulsions is stabilized by surfactants and its droplet size is normally in the range of 1-10 μm in diameter as reported by many researchers [7][8][9]. ...
... Water treatment plants are designed for water recovery and they need to separate multiphase flows. One of the main variables involved in this process is residence time (Barceló et al., 2010;Bai et al., 2011). A device used for this purpose in the oil and gas industry is a skimmer tank, which is a device designed for separating water from oil-water mixture (Trofaier et al., 2015) in order to comply with environmental requirements (Siboro et al., 2015). ...
... Water treatment plants are designed for water recovery and they need to separate multiphase flows. One of the main variables involved in this process is residence time (Barceló et al., 2010;Bai et al., 2011). A device used for this purpose in the oil and gas industry is a skimmer tank, which is a device designed for separating water from oil-water mixture (Trofaier et al., 2015) in order to comply with environmental requirements (Siboro et al., 2015). ...
Article
Water recovery from oil wells is an environmental necessity. In order to achieve this goal, an air bubble technique is used to separate water from oil. This technique is being developed for usage in oil fields, and computational fluid dynamic (CFD) simulation is helping to improve the cleaning efficiency of the process. In this paper, the separation of an oil-water mixture using an air bubble stream in an open tank, skimmer tank, is implemented. The simulation was performed using commercial computational fluid dynamics software, CFD, Star CCM®. The separation of liquid mixtures with different densities is performed in this equipment using flotation along with drag forces created by fine air bubbles. The models required to simulate the process were deeply researched to secure the quality and the accuracy of the solution while making sure the time required for solution was manageable. The results show that 100-micron air bubbles are able to efficiently separate oil from water, reducing the time required for the process as long as the bubbles do not coalesce. The oil concentration at the over flow is close to 70%, and 0.5 litres of water per kilogram of oil are required in the cleaning process.
... Young et al. (1994) studied the optimization of hydrocyclones and found several factors, such as oil droplet size, oil-water density differential, and specific physical dimensions, to affect separation efficiency. Bai et al. (2011) presented a method of improving the oil-water separation efficiency through the introduction of air bubbles into the liquid stream. The efficiency of deoiling water was found to be most optimal with inlet streams containing less than 1% concentration of oil and faced emulsification problems with oil concentration greater than 10% (Gomez et al. 2001). ...
Conference Paper
As the world's population grows, its thirst for water continues to increase. Yet, the total amount of freshwater that is available naturally does not replenish quickly enough to match this growth. Consequently, increase in water consumption and continuous drainage has resulted in a growing shortage for industrial use. In the oil and gas industry, significant volumes of water are used to carry out various treatments such as water injection, matrix acidizing, and multistage hydraulic fracturing. Fresh water is clean and contains low salt content, making it the ideal water source to mix these treatments with ease. However, as unconventional and tighter formations are developed, the use of water in such treatments exponentially increases. Trucking, piping and shipping freshwater for oil and gas purposes becomes both uneconomical and unethical, especially for offshore operations. Seawater has been gaining attention as a viable alternative to freshwater in the oil and gas industry. Ideally, the most cost-effective way is to use raw seawater. However, raw seawater contains ions and microorganisms that can introduce or exacerbate scaling, corrosion, bacterial problems, and most importantly hinder desired fluid performance. Therefore, seawater is typically treated to remove adequate quantities of these components. Since treatment of seawater is increasing in popularity, it is important to realize which components are necessary to remove, to achieve a balance between treatment cost and treatment benefit. In this review, a complete picture of seawater as an alternative to fresh water will be presented. This includes examining the reason for using seawater, the challenges faced, the technologies developed, and many applications of seawater based treatment fluids. Through this, readers should be able to gain a complete picture of the problem at hand and the solutions available to tackle it.
... Different from the direct burning of the oil, separation of oil and water has been gaining popularity as a more effective strategy because it allows for collection and even reuse of the spilled oil (Kajitvichyanukul et al. 2006). To this end, several methods have been in practice or proposed, including mechanical separation (e.g., the use of skimmers, booms, pumps, mechanical separators, etc.), wettability-based separation (e.g., the use of hydrophobic/oleophilic materials to separation oil from water), chemical dispersant-based approach, microorganism-based selective digestion of oil, etc (Nordvik et al. 1996;El-Kayar et al. 1993;Mostefa et al. 2004;Head et al. 2006;Bai et al. 2011;Xue et al. 2014). However, most of the above-mentioned separation methods often require tedious operations, are energy-intensive, or ...
Book
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Despite the fact that nanotechnology has been present for a few decades, there is a big gap between how nanotechnology is perceived and what nanotechnology can truly offer in all sectors of water. The question to be answered is 'what more can we expect from nanotechnology' in the water field? The rational nano-design starts with well-defined problem definitions, necessitates interdisciplinary approaches, involves 'think-outside-the-box', and represents the future growth point of environmental nanotechnology. However, it is still largely new to the educated public and even scientists and engineers in water fields. Therefore, it is the purpose of this book to promote the concept of rational nano-design and to demonstrate its creativity, innovation, and excitement. This book presents a series of carefully selected rationally designed nano- materials/devices/surfaces, which represent drastically different, ground-breaking, and eye-opening approaches to conventional problems to embody the concept of nano-design and to illustrate its remarkable potential to change the face of the research in water industry in the future. Each of the book contributors is world-renowned expert in the burgeoning field of rational nano-design for applications. Rational Design of Next-generation Nanomaterials and Nanodevices for Water Applications is intended for undergraduates, graduates, scientists and professionals in the fields of environmental science, material science, chemistry, and chemistry engineering. It provides coherent and good material for teaching, research, and professional reference. Contents: Introduction to rational nano-design for water applications; Design and Application of Magnetic-core Composite Nano/Micro Particles for Environmental Remediation; Rational Design of Functional Nanoporous Materials to Confine Water Pollutant in Controlled Nano-space; Hierarchical materials as a design concept for multifunctional membranes; Smart membrane materials for controllable oil-water separation; Design of the next-generation Forward Osmosis draw solution; Nanotechnology for Microbial Fuel Cells. https://www.iwapublishing.com/books/9781780406855/rational-design-next-generation-nanomaterials-and-nanodevices-water-applications
... A conventional hydrocyclone consists of feed inlet, cylindrical and conical section, a vortex finder, and an apex. It is also an efficient separator for separating fine and coarse particles, widely used in mineral processing [1,2], petrochemical engineering [3][4][5], food engineering [6,7], pulping [8], electrochemical engineering [9], waste water and effluent treatment [10,11] and other industries handling with slurries. Feed is injected tangentially which creates centrifugal force inside the hydrocyclone. ...
Article
Several design modifications have been done to improve particle separation efficiency in a hydrocyclone. The effects of a rib which is introduced into the cylindrical part of the hydrocyclone are discussed here. CFD (Computational fluid dynamics) is a useful tool to study the velocity and pressure distribution of complex turbulent flow in a hydrocyclone. Flow simulations are carried out using a three-dimensional double precision, segregated, steady-state solver tool. Reynolds stress model is employed for turbulent model which is suitable for the anisotropic turbulent flow. A comparison study for pressure drop and flow velocity for the conventional and ribbed hydrocyclone have done. The obtained CFD simulated results in correlation with experimental data shows that the pressure drop reduces by 13.9% at a velocity of 2.5. m/s by using rib. An experimental finding shows that the cut size particle diameter for conventional and ribbed hydrocyclone are 36. μm and 28. μm respectively at the velocity of 2.5. m/s.
... Because of the vast variety of applications of hydrocyclones in mineral processing, the chemical and environmental industries, water and wastewater treatment, the biological and food industries, etc. [8,9], hydrocyclones deal with different materials, operating conditions, and particles. Hence, different parameters must be considered for an evaluation of the hydrocyclone performance. ...
Article
This paper presents the separation performance and liquid flow characteristics of a miniaturized uniflow hydrocyclone in removing micron and sub-micron heavy metal particles from water. This new laboratory hydrocyclone is designed based on the idea of improving the separation efficiency besides the simplifying of geometry and fluid flow. Furthermore, the hydrocyclone device is downscaled to enhance the separation of the fine particles. Instead of traditional hydrocylones, there is only one swirling flow of liquid and both outlet ports are in the same direction. Small values of Eu number disclose low energy requirement in this arrangement. The effects of feed flow rate and solid content were studied. The results show good separation efficiency ranging from 0.69 to 0.9 for varying flow rate of 15 to 45 ml/s. There is a point at which the highest separation performance is obtained besides satisfying energy consumption, determined as high-performance point of separation. Also, experiments with varying solid content from 0.1 to 4 g/l disclose that the solid content has a slight effect on separation performance, below 3 g/l but it may causes significant changes, above that solids concentration.
... Several traditional techniques for cleaning up oil spillages and to separate oil and water phases in water coproduced during hydrocarbon exploitation have previously been utilized including physical processes (flotation, vacuum and centrifuge, hydrocyclone) (Li et al., 2007;Al-Shamrani et al., 2002;Harvey and Stokes, 1973;Bai et al., 2011), filtration membrane (Prince et al., 2016;Zhu et al., 2016b), bioremediation (use of microorganisms or biological agents) Pasumarthi et al., 2013;Bovio et al., 2017;Kasai et al., 2002;Crisafi et al., 2016;Jean et al., 2008;Liu et al., 2010;Majumder et al., 2014) and in situ burning (Lin et al., 2002(Lin et al., , 2005Gu enette, 1997;Potter andBuist, 2008. Fritt-Rasmussen et al., 2015). ...
Article
The process of separating oil and water from oil/water mixtures is an attractive strategy to answer the menace caused by industrial oil spills and oily wastewater. In addition, water coproduced during hydrocarbon exploitation, which can be an economic burden and risk for freshwater resources, can become an important freshwater source after suitable water-oil separation. For oil-water separation purposes, considerable attention has been paid to the preparation of hydrophobic-oleophilic materials with modified surface roughness. However, due to issues of thermodynamic instability, costly and complex methods as well as lack of ecofriendly compounds, most of hydrophobic surface modified particles are of limited practical application. The study presents a facile procedure, to synthesize crystalline particles of calcite, which is the most stable polymorph of CaCO3 from industrial CaCO3 using oleic acid as an additive in a one-pot synthesis method. The XRD results show that the synthesized particles were a well-crystallized form of calcite. The FTIR results reflect the appearance of the alkyl groups from the oleic acid in synthesized particles which promotes the production of calcite with ‘rice shape’ (1.64 μm) (aggregated by spherical nanoparticle of 19.56 nm) morphology with concomitant changes in its surface wettability from hydrophilic to hydrophobic. The synthesized particles exhibited near to super hydrophobicity with ∼99% active ratio and a contact angle of 143.8°. The synthesized hydrophobic calcite particles had an oleophilic nature where waste diesel oil adsorption capacity of synthesized calcium carbonate (HCF) showed a very high (>99%) and fast (7 s) oil removal from oil-water mixture. The functional group of long alkyl chain including of Cdouble bond; length as m-dashO bounds may play critical roles for adsorption of diesel oils. Moreover, the thermodynamically stable crystalline polymorph calcite (compared to vaterite) exhibited excellent recyclability. The isothermal study reflects the comparatively high value of correlation coefficient (R2 = 0.94) for the Langmuir isotherm compared to those of the Freundlich isotherm (R2 = 0.82) showed that the adsorption of diesel oil onto the hydrophobic CaCO3 adsorbent was much better described by the Langmuir isotherm. The kinetics study of second-order rate expression (R2 = 0.99) more fitted with the experimental data compare to first-order model (R2 = 0.92). The synthesized calcite exhibited a significant dual oleophilic and hydrophobic nature that can be applicable for oil adsorption/or removal purpose in oil contaminated areas in environment and/or industrial oily wastewater for green, simple, and inexpensive environmental cleanup.
... Because of the vast applications of hydrocyclones in mineral processing, chemical and environmental industries, water and wastewater treatment, biological and food industries etc. [8,9], hydrocyclones deal with different materials, operating conditions, and particles. Hence, different parameters must be considered for evaluation of a hydrocyclone performance. ...
Article
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Separation efficiency of different shape particles from water was studied experimentally using a mini-hydrocyclone. Spherical and flaky (plate-like) aluminum particles with the same particle size distributions were used in the present study. Also, the effects of feed flow rate and temperature on separation performance were studied. The results were investigated in terms of slurry recovery, total efficiency and partition curves. The separation efficiency of spherical particles increased with increasing particle size, temperature, and feed flow rate, as expected. Fishhook effect, as a noticeable phenomenon, was observed for spherical particles. In the case of flaky particles, separation behavior showed an unusual behavior. The separation efficiency decreased with increasing particle size, in the largest fraction of particles, which has not been reported and addressed in this way. Furthermore, separation performance of flaky particles was affected by temperature and flow rate, differently. Fishhook effect was not observed in separation of flaky particles. Partition curve configuration and its variation by change in temperature and flow rates were discussed for both particles. A theoretical argument about particle motion and behavior carried out based on present observations and former investigations.
... The optimal operation parameters such as flow rate and flow split are also necessary for obtaining adequate separation (Husveg et al., 2007). In order to enhance the oil-water separation efficiency, some efforts have been made to improve certain performance indices by introducing special structural modifications or implementing optimal operations (Bai et al., 2011;Chu et al., 2000;Oropeza-Vazquez et al., 2003). Different mathematical models are theoretically developed for evaluation and improvement of the hydrocyclone performance (Amini et al., 2012). ...
Article
Electrocoagulation is a simple and efficient treatment method involving the electrodissolution of sacrificial anodes and formation of hydroxo-metal products as coagulants, while the simultaneous production of hydrogen at the cathode facilitates the pollutant removal by flotation. Oil is one of the most important hydrocarbon products in the modern world. It can cause environmental pollution during various stages of production, transportation, refining and use. Electrocoagulation treatment is particularly effective for destabilization of oil-in-water emulsions by neutralizing charges and bonding oil pollutants to generated flocs and hydrogen bubbles. The development of electrocoagulation technologies provided a promising alternative for oil removal from wastewater. This paper presents a review of emerging electrochemical technologies used for treating oil-containing wastewater. It includes a brief description of the oily wastewater origin and characteristics. The treatment processes developed so far for oily wastewater and the electrocoagulation mechanisms are also introduced. This paper summarizes the current applications of electrocoagulation for oil removal from wastewater. The factors that influence the electrocoagulation treatment efficiencies as well as the process optimization and modeling studies are discussed. The state-of-the-art and development trends of electrocoagulation process for oil removal are further introduced.
... The oily discharge has detrimental effects on terrestrial and marine life [4]. Several conventional methods have been implemented for oil and water separation, including hydro cyclones, [5] flotation systems, [6] gravity separators, coalescers, [7] and centrifuges [8]. However, these conventional technologies suffer substantially with the decrease in the size of oil droplets [9,10]. ...
Article
Oily wastewater treatment has great significance due to environmental and industrial perspectives. Oily wastewater has emerged as one of the leading causes of water contamination. Owing to the lower efficiencies of the conventional methods, membrane technology is an emerging solution for separating the stabilized oil contaminants from water. In this work, a novel procaine-based zwitterionic geminal surfactant (PZGS) i.e., 3,3'-((((4,4'-(decanedioylbis(azanediyl)) bis(benzoyl))bis(oxy)) bis(ethane-2,1-diyl)) bis(diethylammoniumdiyl)) bis(propane-1-sulfonate) synthesized by utilizing procaine hydrochloride and 1,3-propane sultone precursors. The PZGS was well-characterized by ¹H-NMR, ¹³C-NMR, and FTIR spectroscopy. The synthesized PZGS was utilized to fabricate procaine-based zwitterionic gemini surfactant incorporated PVDF membranes (PZGS-Mx-PVDF), and the membranes were thoroughly investigated by scanning electron microscopy (SEM), Fourier-transform infrared spectroscopy (FTIR), atomic force microscopy (AFM), and contact angle goniometry. It is observed that the performance of these newly fabricated membranes (PZGS-Mx-PVDF) was significantly improved after incorporating PZGS into the PVDF membranes. The surface of membranes has become water-friendly as the water contact angle substantially changed from 84.1° to 58.1°. In controlled addition of PZGS, the PZGS-M2-PVDF membrane has shown a substantially improved flux of 4.5 times to pristine PVDF. The maximum oil rejection of >99.3% was attained using the PZGS-M1-PVDF membrane. A high flux recovery ratio (FRR) of about 83% was observed with the PZGS-M2-PVDF membrane. The PZGS-Mx-PVDF membranes have shown a good flux recovery ratio after continuous use of oil-in-water emulsions. The excellent separation efficiency, high permeation flux, and good flux recovery ratio indicated that the introduced PZGS-Mx-PVDF membranes have a significant potential for oily wastewater treatment.
... Hydrocyclones are devices used to separate heterogeneous mixture in mineral processing [1], petrochemical [2], environmental [3] and other industries. The separation mechanism of hydrocyclone is elucidated by determining the three velocity components of the flow field. ...
Article
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The separation mechanism of hydrocyclone is elucidated by determining the three velocity components of the flow field. In this study, volumetric 3–component velocimetry measurement system was developed to investigate the three–dimensional three–component flow field inside a 35mm mini–hydrocyclone. Measurement results show the magnitude of maximum tangential, axial, radial velocity component in r-z plane of the cylindrical and cone part is about 4:2:1. The parameter n of tangential velocity in the free vortex area is fitted to be 0.5–0.7, which is a variable along axial direction. Radial velocity is non–axisymmetric, while the other two are quasi–axisymmetric. The asymmetry of the radial velocity is found to be the consequence of the existing downward progression of secondary vortices. In addition, the locus of vertical velocity was constructed in three dimensional and the shortcut flow rate was calculated using three dimensional axial velocity. These knowledge helps the further understanding of the separation mechanism of the hydrocyclone.
... It was found that separation was most efficient when the inlet Reynolds Numbers varied between 14,000 and 16,000. Separation efficiency in the absence of air was 72 % and was maximized 1 % to 85 % at 1% air when separating mixed fluid of average 100 mg/L of diesel with density 0.82 g/cm 3 and viscosity 4.2 mm − 2 s (Bai et al., 2011). Despite the limited application of these pilot studies mentioned above, the potential application of these findings deserves consideration and testing with different oil types rather than just light oils and oil water proportions for typical for skimmed material (30-90 %) to determine the potential field application. ...
... The main component of a separator is called the segment section, which provides enough residence time for the less-dense phase to coalesce and separate from the denser phase. The inner components structure of a gravity separator directly affects its performance by changing the residence time of the mixture [5,6]. Keller [7] studied the effect of the inner component, the filter media system, on the separation process with an oil density between 11 to 70 API. ...
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In this paper, the geometric design of a gravity-based separator is studied with a computational fluid dynamics method. ANSYS Fluent (18.2) is used to model the ratio of horizontal and vertical lengths with three dimensionless groups. A dimensional analysis method is used to develop a new correlation of separator geometric design. Corresponding plots were created and analyzed using nonlinear regression on the x–y Cartesian coordinate system. Also, manual iterations were performed to determine the coefficients in the general correlation relationship. The dimensional analysis results show that the Reynolds and Euler numbers have a direct correlation with separator design, which means increasing the Reynolds and Euler numbers require a separator with a larger length to height ratio to achieve the same separation efficiency. However, the Weber number has an inverse correlation with separator design, which means an increase in the Weber number requires a separator with a smaller length to height ratio. The new correlation developed in this paper can be used as a reference for separator geometry design to separate immiscible fluids with a wide range of fluid properties.
... The concentration of dispersed oil and grease is an important parameter for water quality and safety (Osibanjo et al., 2011;Westerhoff et al., 2018). Oil and grease includes fats, oils, waxes, and other related constituents found in water and wastewater (Achanta et al., 2011;Lugt and Pallister, 2012;Radulescu et al., 2018), and their low solubility reduces their rate of microbial degradation (Bai et al., 2011). The petroleum industry has grown at a fast rate since its inception and became an indispensable element of most communities and has led togeneration of waste products. ...
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This study determined the concentration of oil and grease and inferred its impacts on algae, invertebrates and fish. Water samples were collected in April and September from 2012 to 2018 at the upstream and downstream transects and in the reservoir, and analysed for oil and grease following standard procedures. Environmental compliance was compared to NEMA’s discharge standard of 10 mg/l, and its PAH effluent discharge standard of ≤ 0.1 mg/l. At all sites, average concentrations of oil and grease were below 10 mg/l throughout the sampling period. Out of the 14 data sets for each transect, only 3 along the upstream transect, and 2 at each of the downstream transect and the reservoir were compliant with the effluent discharge standard. Although impacts of oil and grease on aquatic biota were not assessed, their relatively high concentration compared to total Polycyclic Aromatic Hydrocarbon (> 0.1 µg/l) is considered hazardous to most aquatic organisms. The diverse activities around the project area implied that sources of oil and grease were proportionately diverse. Hence, the observed trends may not solely be attributed to the hydropower project. Accordingly, assessment of the various sources of oil and grease and their impact on aquatic biota in the area is recommended.
... Currently, the most popular industrial technologies available for the treatment of oil pollutants involve the conventional physical methods, such as: (i) coagulation and dissolved-air flotation [7][8][9][10], (ii) gravitybased separators [11], (iii) centrifugation [12] and (iv) hydrocyclone [13,14]. However, when the oil concentration in wastewater is low (i.e. ...
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This article addresses the applicability of the ultrafiltration ceramic membrane for separation of oily wastewaters generated during maritime transportation. The UF experiments were performed in a cross-flow system using a pilot-scale installation. The membrane used had a separation cut-off equal to 8 kDa and an active area of 0.0038 m². The experiments were conducted in a wide range of temperature (303 and 323 K), tangential flow rate (2.9-8.2 m/s) and transmembrane pressure (0.28-0.40 MPa). The excellent separation properties of the ceramic UF membrane have been confirmed. It allowed to obtain a high-quality, oil-free permeate with the turbidity at the level of about 0.2 NTU. However, wastewaters caused the intensive membrane fouling, which significantly decreased the process performance. Most often, the permeate flux was stabilized after about 100 min of the process running and the steady-state flux at 30% of its maximum value was obtained. The effects of wastewater pre-filtration and feed pH on the UF process performance have been studied. It was found that the pre-filtration of oily wastewaters adversely affects the permeate flux. For analyzing the fouling mechanisms, Hermia’s model was used. Importantly, different ways of membrane rinsing were applied. Regardless of the degree of membrane contamination, the effective membrane cleaning was achieved using 1-3 wt% NaOH and H3PO4 solutions.
... Liu et al. studied the cyclonic separation function mechanism of the cyclonic-static micro bubble flotation column and investigated the impact of the parameters including the feeding rate, aeration rate, circulating pressure, and underflow split ratio on the cyclonic separation efficiency [17]. Bai et al. developed a new process of utilizing air bubbles to enhance the separation efficiency of dispersed oil from water by hydrocyclones [18]. Fakhru'l-Razi et al. analyzed the technology development for oil and gas produced water treatment [19]. ...
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To improve the separation efficiency of oil field-produced water, a novel oil-water separation apparatus is developed. The high-efficiency cyclone separation apparatus could meet the continued increase of oil field-produced water and comply with the improvements in emission standards. Effectivity of the self-designed apparatus in oil removal was determined in laboratory and field tests. The effects of inlet flow, oil concentration and aeration amount were determined through laboratory tests. The particle size distribution of the influent and effluent oil-produced water was presented also. Results show that under optimal process conditions, i.e., the inlet flow rate is 2.0 m3/h, imported oil concentration is 1189 mg/L, and aeration rate is 0.6 L/min, effective separation can reach 93.1%. The oil removal rate is generally above 90% and the range of influent concentration is 900–1200 mg/L in the field test. Compared to the traditional oilfield produced water treatment device, the self-designed apparatus can combine both air flotation separation and cyclonic separation. The joint effect of the two kinds of separation, can promote the collision adsorption probability of micro bubbles and oil droplets, and effectively improve the separation efficien
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The purification of industrial sulfur‐containing tail gas mainly adopts the wet flue gas desulfurization of gas–liquid mass transfer, and a new separator utilizes the gas–liquid coupling field to rapidly update the effective phase boundary area in the reaction process to enhance the mass transfer effect. This study used NaOH solution as the reaction liquid phase to determine the effects of the selection of overflow port of gas cyclone–liquid jet absorption separator on gas desulfurization efficiency under the changing rates of gas and absorption liquid flow. Results showed that desulfurization efficiency decreased as the diameter of the overflow port increased but increased as the depth of the overflow port increased. The optimal design ratio Dx/D1 of overflow tube diameter Dx and separator tube diameter D1 is 0.35, and the optimal design ratio S/H1 of overflow tube insertion depth S and separator tube length H1 is 0.62. At constant operating conditions, overflow port selection can increase desulfurization efficiency by up to 20%, which provides optimization guidance for the structural design of a gas cyclone–liquid jet absorption separator.
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The appearance and development of nanotechnology gave new and efficient modalities for pollutants removal from wastewaters by using new compounds called nanomaterials which possess unique structural and morphological properties. In this paper we investigated the application of CoFe2O4 nanomaterial for increasing the efficiency of oily wastewater treatment by flotation. CoFe2O4 nanomaterial was prepared by precipitation method. Prior testing their application in wastewater treatment by flotation, the oxide nanomaterial was structural and morphological characterized by XRD and TEM analyses. The influence of CoFe2O4nanomaterial on oily wastewater depollution by flotation process was investigated by measuring the following parameters: treatment efficiency [%] and the stability of froth.
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Microfiltration SiO2/carbon membranes were fabricated by compositing SiO2 microspheres into carbon membrane matrix through facile blending, shaping and pyrolysis. The chemical groups, thermal stability, pore structure, microstructure, morphology, mechanical strength and surface hydrophilicity of the membranes were characterized by the technologies of Fourier-transform infrared spectroscopy, thermogravimetry, bubble pressure method, X-ray diffraction, Scanning/Transmission electron microscope, compressive stress and water/oil contact angle, respectively. The effect of SiO2 amount on the structure and separation performance of the membranes for the purification of oil-water emulsion was investigated. The results showed that the incorporation of SiO2 microsphere improved the surface hydrophilicity/oleophobicity, matrix density, oil removal and anti-fouling ability of carbon membranes. The highest oil removal is up to 99.99%, along with the water permeation flux of 5550 kg·m⁻² h⁻¹ MPa⁻¹ for resultant carbon membranes made by the precursor containing 8 wt% SiO2 microspheres. The present work offers an easy approach for preparing microfiltration carbon membranes with highly efficient removal of oil from wastewater.
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A novel hydrocyclone with guide vanes, named as axial hydrocyclone (AHC), is designed to tackle the problem of oil–water separation faced by most mature oilfields. Optimal design of the AHC is carried out by using numerical methods. The effects of guide vanes, cone angle, tapered angle and overflow pipe on the oil–water separation are discussed in this paper. The results show that a double swirling flow is generated in the tapered section where oil–water separation occurs. Both the cylindrical and the tapered section have important influences on AHC performance. On the basis of single factor results, response surface methodology is employed to optimize the AHC design. The experimental results indicate that the novel AHC has an excellent performance for the oil–water separation.
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The problem of wastewater pollution with oil and oil products is currently highly acute. The paper presents a numerical simulation of the separation process of a water-oil emulsion in an element of a separation device with inserts of a porous medium. The inserts of the porous medium served as flow laminarizers and provided the intensification of the separation process. The analysis of the influence of the parameters of the porous insert and the parameters of the emulsion flow on the separation efficiency is carried out.
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Preparation of effective membrane with special surface treatment for oil/water separation having promising future and low manufacturing cost. The suggested membrane was fabricated by a simple treatment via increasing the hydrophilicity of the cotton fabric surface. The cotton fabric was impregnated in poly(acrylic acid‐co‐N‐methylol acrylamide), poly(AA‐co‐NMA), where NMA acts as bonding agent. Sodium hypophosphite (SHP) was added to the modification solution to enhance the bonding between the cotton fabric and the PAA. The modified fabric was thermally dried and cured at different temperatures. It was found that, the presence of 3.5% NMA and addition of 5% SHP to the modification solution then curing at 190°C gave the highest amount of bonded PAA to the cotton fabric. The success of the modification process was confirmed by scanning electron microscope, Fourier transformer infrared and the increase in the contact angle of the cotton fabric after modification. Furthermore, the prepared membrane was evaluated for oil (n‐hexane, toluene, and petroleum ether)/water separation and also for heavy metal ions removal (Cd2+ and Co2+). Neutralization of the produced membrane with ammonium hydroxide resulting in a higher contact angle and consequently higher separation efficiency for oil/water mixtures and higher performance for heavy metal ions removal compared to the unneutralized one. The hydrogel‐coated membrane using facile technique which includes impregnation of cotton fabric in poly(acrylic acid‐co‐N‐methylol acrylamide) solution followed by drying and curing. The designated membrane exhibited good oil /water separation and heavy metal ions removal (Cd2+ and Co2+).
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The increasing amount of oil wastewater is causing serious damage to the environment. Oily water is a worrisome by-product of the oil industry due to its growing volume in mature basins and complex chemical composition. Low-cost polymers are being used as alternative materials to treat oily waters after treatment by conventional methods, oil and grease (O&G) concentration being the primary parameter for final disposal. In this respect, guar gum can be used to treat petroleum-contaminated waters, with the advantage of being a low-cost, highly-hydrophilic natural polymer. In this study, guar gum, under specific conditions, shapes itself into three-dimensional structures with interesting physicochemical properties. The salting out effect occurs with reticulation of the polymeric chains by borate ions and in the presence of electrolytes, reducing the solubility of the polymeric network in the solution and leading to an electrolyte- and polymer-rich phase. When the guar gum gel was prepared in situ in the produced water, after the salting out effect, the oil was imprisoned in the interstices of the collapsed gel. The gelling guar gum was highly efficient in synthetic oily waters. In the case of initial O&G above 100ppm, the oil removal percentage was above 90%.
Chapter
In the world of increasing industrialization and global population, environmental pollution has continued to rise over last few decade. Photocatalysis came forward as capable method in removal of various recalcitrant pollutants from atmosphere. The nano-photocatalytic semiconductors are majorly used in the form of slurry, and removal of these nano-photocatalytic materials turns out to be quite challenging and costly. Therefore, to resolve the problem of recollection of material, voluminous strategies have been executed for immobilising nano-photocatalyst on various substrates including carbon-based compounds, glass, zeolites, polymers, clay and ceramics and various natural fibres. The strategies including sol-gel, dip coating, polymer-assisted hydrothermal discharge, photo-etching, electrophoretic deposition, cold plasma discharge (CPD), RF magnetron sputtering and spray pyrolysis are discussed in this chapter. At last, characterization techniques used for studying various properties of immobilized catalyst are discussed in brief.
Chapter
Supply of clean, freshwater for safe consumption has become a greatest challenge. Water resources are contaminated by anthropogenic as well as man-made activities day by day. Thus, it is required to utilize advanced wastewater treatment to ensure higher environmental protection and reuse the discharged water effectively. Oily wastewater is extremely toxic for aquatic organism as well as human being. Treating oil-contaminated water can be difficult because some of the microscopic compounds are hard to eliminate. The currently used methods are suitable for removing floating and suspended oily droplets from water. However, these conventional methods are not efficient for eliminating small, finely dispersed, colloidal oily particles. Application of membrane filtration is also restricted up to a certain extent due to fouling. In-depth research has been carried out to reduce membrane fouling. This chapter overviews the conventional techniques for elimination of oils from aqueous effluents. The chapter focuses the limitations of the conventional processes. The subsequent section of the chapter also illustrates the importance of using photocatalytic membrane. The concluding part of the chapter illustrates the future aspects of membrane technology and promising solutions associated with membrane modification methods using photocatalytic and/or hydrophilic nanomaterials and nanocomposite to enhance the permeate quality and water flux.
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The need to have an efficient oil-water separator leads to improve and optimize the hydrocyclones. One way to improve the efficiency of a deoiling hydrocyclone is using air injection. In the present study, the effects of air injection on the three-phase flow field, oil droplet distribution, separation efficiency, and the working principles of deoiling hydrocyclones are investigated using the Eulerian-Eulerian multifluid model. The numerical results of two and three-phase flow are in good agreement against the experimental data. The oil core which is formed at the center of the deoiling hydrocyclones disappeared due to the air injection. The injected air creates an air-core inside the deoiling hydrocyclone and flows out through the overflow. The results show that the air injection increases the migration velocity of oil droplets and the length of the reverse flow region, leading to the enhancement of the separation efficiency. The air injection also increases the turbulence level and consequently increases the breakup rate of the oil droplets inside the deoiling hydrocyclone with air injection. Therefore, the air-liquid ratio and the injected bubble diameter should be regulated to increase the efficiency of the air-injected deoiling hydrocyclone. The results of different air injection diameters show that the small injection diameter is preferable due to the more penetration inside the deoiling hydrocyclone and increase the reverse flow region. The simulation results show that the air injection with bubble diameter of 42 μm increases the hydrocyclone efficiency up to 95.6 %.
Chapter
Catalytic complexes of photosensitizer Radachlorin® (sodium salts of chlorin e6, chlorin p6, purpurin 5) with polyvinylpyrrolidone (PVP) and detonation nanodiamonds (DND) have been synthesized and studied by optical absorption spectroscopy, luminescence excitation, dynamic light scattering and viscometry methods. Binary complexes PVP-Radachlorin® demonstrated electrostatic and donor–acceptor binding of Radachlorin® with PVP detected by spectrophotometric titration when Q-band (~650 nm) displayed bathochromic shift and enhancement with isosbestic point indicating a single type of binding sites. Similar changes in luminescence emission spectra in binary complexes were observed earlier at higher polymer contents. The yield of singlet oxygen under UV-irradiation (405 nm) of Radachlorin® increased in PVP-Radachlorin® complex. Dynamic light scattering and viscometry confirmed the stability of complexes and no agglomeration. Ternary complexes DND-PVP-Radachlorin® provided a generation of singlet oxygen by UV-irradiation exciting diamonds which do not emit but transfer the energy to surrounding molecules. The results allow develop effective catalysts for chemical and medical applications as well as for disinfection, active filtration and cleaning air, water, surfaces. Novel catalytic complexes based on chemically inert diamonds are resistant to the singlet oxygen and profitable for long-term usage.
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This study develops a treatment strategy for produced water. This kind of water can include formation water, injection water, and any chemicals added downhole or within the separation process. Regardless of the parameters, produced water contains several kinds of components such as heavy metals, salts, radionuclides, oil and grease, suspended solids, dissolved solids, and other dissolved and volatile organic compounds. To manage this highly polluted water, several strategies can be considered; one of these strategies is produced water reuse that makes this kind of water as an acceptable resource for industries, irrigations, and livestock instead of a waste stream. The main goal of this study is to prepare produced water for reuse methods by removing the major contaminant which is salt (ionic compounds). During these experiments, the specific species causing membrane fouling and the approaches to reduce the fouling process will be determined.
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Microporous membranes are now favorably used as a separation tool for the purification of water and wastewater containing fine particles and macromolecular contaminants. However, organic fouling has often become one of the major problems hindering the wider applications of these membranes. In this study, a highly hydrophilic polyacrylonitrile (PAN) membrane with excellent anti-fouling performance was prepared from a method combining alkaline hydrolysis and non-solvent induced phase separation (NIPS) processes together simultaneously. The interplay of the PAN alkaline hydrolysis and NIPS was examined for its effects on both the structural and chemical properties of the prepared membranes. Morphological and porometric analyses confirmed that the new method produced PAN membranes with less macrovoids but highly ordered and narrow flow channels in the cross-section structure, as well as a much denser selective surface layer with small and greatly uniform pore sizes. Characterizations in membrane surface wettability and chemical compositions revealed that the new preparation approach can endow the obtained membranes with significantly enhanced surface hydrophilicity as well as oleophobicity within a much shorter preparation time, in comparison with other conventional preparation methods, including the post alkaline hydrolysis of PAN membranes. Filtration experiments for oil (hexadecane)-in-water emulsion, NOM (humic acid) or protein (BSA) solutions have all revealed that the developed membranes showed remarkably slow flux declining during filtration operation and high flux recovery by simple water flushing for membrane cleaning. Hence, it is anticipated that there is a great potential for the new approach to fabricate anti-fouling PAN membranes, especially for more challenging separation applications in water and wastewater treatment.
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In this study, the effects of emulsion properties on demulsification of the phosphoric acid–tributyl phosphate (W/O) emulsion by hydrocyclone were investigated. The droplet size distributions were measured pre and post demulsification. The demulsification performance was evaluated by calculating the average droplet size difference. The results showed that increasing kerosene addition in the oil phase improved demulsification efficiency. As the maximum amount of kerosene added in the oil phase, average droplet size difference could reach about 43 µm. In each composition, as the stirring rate increased from 3000 to 7000 r/min, the effect of initial droplet size distribution on demulsification by hydrocyclone was not obvious. A model for predicting average droplet size difference was established by dimensional analysis method. By comparing the experimental data with calculated ones, this model is available.
Chapter
Hydrocyclone has a history of about 129 years. It has been used in various industries including mineral, chemical, coal, petroleum, papermaking, environmental protection, soil remediation, waste management, agriculture, aquaculture, food, biotechnology, nanotechnology, material science technology, and thermal energy due to its high separation efficiency, small cut size, small split ratio, no moving components, and low total static pressure drop. To further expand its application range in the field of resource recovery and reuse, this chapter first simply introduces the working principle of hydrocyclones, characteristic of fluid flow in hydrocyclones, parameters evaluating performance of hydrocyclones, and the applications of hydrocyclones in resource recovery and reuse. Then this chapter comprehensively reviews the hydrocyclone‐separation technologies developed by geometric parameters, operating parameters, and operating conditions, the challenges and perspectives. It is hoped that this chapter will significantly improve the recovery‐and‐reuse effectiveness of various solids, liquids, gases, and energy by using hydrocyclone‐separation technologies.
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The preservation of marine ecosystems is one of the most severe challenges at present. In particular, oil‐water separation from oil spills and oily wastewater is important. For this reason, a low‐cost, effective, and sustainable polymeric solution is in high demand. In this work, a controlled‐wettability membrane for selective separation of oil‐water mixtures and emulsions is developed. The nanofibrous membrane is prepared via a facile and cost‐effective electrospinning technique using environmentally sustainable materials, such as recycled polyethylene terephthalate and chitosan. The effect of different concentrations of chitosan on the morphology, chemical composition, mechanical properties, wettability, and separation performance of the membrane is evaluated. The membranes exhibited underoil superhydrophobic and underwater superoleophobic behavior, which is essential to perform the selective separation. In fact, the designed filter has competitive antifouling properties (oil intrusion pressure > 45 kPa) and showed high heavy‐ and light‐oil/water separation efficiencies (>95%) both for emulsions and immiscible mixtures. Controlled‐wettability membranes for selective separation of oil‐water mixtures and emulsions are fabricated using environmentally sustainable recycled polyethylene terephthalate (r‐PET) and chitosan based electrospun nanofibers.
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The extraction of natural gas hydrates (NGH) for using as an alternative energy source necessitates the separation of sands from the mixed slurry of gas hydrates and backfill of the sand slurry onto the seafloor. Conventional hydrocyclones used for mining cannot be applied to such conditions due to the limited space of the mining pipeline. Therefore, here we propose a hydrocyclone suitable for subsea gas hydrate extraction. This study is intended to study the effects of operating parameters and geometric parameters on the performance of the hydrocyclone by experiment and computational fluid dynamics (CFD) method, and to improve the performance of the hydrocyclone. The results show that the optimal flow rate of the hydrocyclone separator is 7 m³/h; as the solid content of the inlet increases, the separation efficiency will decrease, and the pressure drop will increase. The energy consumption caused by the vortex in the blind zone can be reduced and the separation efficiency increases as the X/D decreases. The separation efficiency first increases and then decreases with the increase of L/D. The separation efficiency reaches its maximum when L/D is 1.2, but further increases in the L/D will increase the resistance loss along the journey, and the pressure drop will continue to increase. This study is applicable to solid-liquid separation in underground mining pipelines. The purpose of this study is to achieve real-time sand removal and the backfilling of sand slurry in addition to guiding industrial design.
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In order to ease the pressure on oil price, the downhole oil−water separation system has been adopted to preseparate the output production. However, both the gravity separator and the conventional hydrocyclone in this system have some restrictions, which hinder their widespread application. Therefore, it is necessary to innovate and improve the performance of the oil−water separation device. This paper presents a novel axial separator for oil−water separation based on analysis of droplet trajectory, and an experimental system was fabricated to test the separator. A high-speed camera was used to observe the droplet trajectories at the swirler, and the formation of the oil core was presented. Additionally, experimental investigation was carried out to evaluate the novel separation device in the water flow rate range of 3 to 7 m 3 /h with different inlet oil fractions. In addition, the effect of heavy phase outlet (HPO) pressure on separation efficiency was also studied. The results show that the separator exhibits good performance under the abovementioned experimental conditions. It was also found that the separation efficiency depends on the flow rate and the inlet oil fraction. Furthermore, increasing the HPO pressure is conducive to improve the separation performance.
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This research presents the design procedure for liquid-liquid hydrocyclone to separate kerosene-water emulsion. It studies the effects of varying feed flow rate (6, 8, 10, and 12 l/min), inlet kerosene concentration (250, 500, 750, 1000, and 1250 ppm) , and split ratio (0.1, 0.3, 0.5, 0.7, and 0.9) on the outcomes; separation efficiency and pressure drop ratio. This study used factorial experimental design assisted with Minitab program to obtain the optimum operating conditions. It was shown that inlet concentration of 250 ppm, 12 l/min inlet flow rate, and 0.9 split ratio gave 94.78 % as maximum separation efficiency and 0.895 as minimum pressure drop ratio.
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The study targeted an assessment of microbial diversity during oil spill in the marine ecosystem (Kaohsiung port, Taiwan) and screened dominant indigenous bacteria for oil degradation, as well as UCM weathering. DO was detected lower and TDS/conductivity was observed higher in oil-spilled area, compared to the control, where a significant correlation (R2 = 1; P < 0.0001) was noticed between DO and TDS. The relative abundance (RA) of microbial taxa and diversities (> 90% similarity by NGS) were found higher in the boundary region of spilled-oily-water (site B) compared to the control (site C) and center of the oil spill area (site A) (BRA/diversity > CRA/diversity > ARA/diversity). The isolated indigenous bacteria, such as Staphylococcus saprophyticus (CYCTW1), Staphylococcus saprophyticus (CYCTW2), and Bacillus megaterium (CYCTW3) degraded the C10–C30 including UCM of oil, where Bacillus sp. are exhibited more efficient, which are applicable for environmental cleanup of the oil spill area. Thus, the marine microbial diversity changes due to oil spill and the marine microbial community play an important role to biodegrade the oil, besides restoring the catastrophic disorders through changing their diversity by ecological selection and adaptation process.
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Methanol to olefin (MTO) process is a chemical technology for producing low-carbon olefins from coal-based or natural gas-based methanol. It has changed the pattern of low-carbon olefins relying on petroleum cracking, and opened a new process for producing low-carbon olefins. However, the wastewater generated in the MTO process is difficult to handle. Numbering-up of mini-hydrocyclone is often used to enhance the processing capacity of wastewater treatment when mini-hydrocyclone is used for oil-water separation in methanol-to-olefin process. In this paper, the efficiency and pressure drop distribution of a single mini-hydrocyclone were studied in the laboratory. In addition, according to the UU parallel configuration model, 150 mini-hydrocyclones arranged in parallel were established and used for the oil-water separation process of methanol-to-olefin reaction wastewater. The industrial operation results show that the average flow rate of long-period operation is 282 m³/h, the average pressure drop was 0.31 MPa, and the average separation efficiency of the mini-hydrocyclone group was 90 %. Especially for heavy components such as alkanes and aromatics, it had a good separation effect. Thus, it is shown that the mini-hydrocyclone group has good applicability in oil-water separation.
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The application of computational fluid dynamics (CFD) for cyclone modelling on three-dimensional unstructured meshes is reviewed. Results of numerical simulations show agreement with laser Doppler anemometry measurements. The quality of turbulence modelling determines the fidelity of CFD predictions. An unstructured mesh was used to model the flow field in a conventional high efficiency Stairmand cyclone. Steady state simulations using a Reynolds stress turbulence model on a coarse unstructured mesh provides a computationally inexpensive method.
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In many cases, finest particles in hydrocyclones present higher separation efficiencies than can be expected when considering the theory of single particle sedimentation. The analysis of sedimentation of polydisperse particle systems shows that particle movement is influenced remarkably by solids concentration and particle size distribution. Sedimentation experiments with a special centrifuge confirm the action of combined effects, of particle entrainment, of countercurrent flow of displaced water and of elevated values of pulp density and viscosity due to the disperse solid phase. These influences can be summarized in a sedimentation model which allows better calculation of the separation result of the hydrocyclone. As a consequence, the typical course of the separation curve of the hydrocyclone indicates a more or less marked so-called fish-hook in the fine particle range.
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The shape and size of a hydrocyclone affects its internal flow structure and separation performance. The types of internal flows that can develop in hydrocyclone separators at low and high Reynolds numbers based on the Navier-Stokes equation and the RANS-equation, respectively, were examined. Three types of hydrocyclone were investigated: A 5-mm hydrocyclone, a 76-mm Rietema hydrocyclone and a 250-mm hydrocyclone with different cone angles. Computational fluid dynamic simulations of the mean velocity and pressure fields are reported.
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Hydrocyclones are used for dewatering of solid-liquid suspensions in many industries. Generally, however, large diameter cyclones are used and their application is restricted to large (>25 μm) particles. Small diameter (10 mm) hydrocyclones have the potential to be applied to fine particle (<10 μm) suspensions and, in particular, to collect the sub-micron fraction. This is due to the very small cutsizes that are achieved in these cyclones. In order to apply these small hydrocyclones industrially, knowledge of the range of their classification performance is required. It is found that these cyclones exhibit a fish-hook partition curve, and a high bypass fraction. The very small cutsize (<5 μm) and the relatively large bypass makes the effective collection of sub-micron particles possible. While in most hydrocyclone applications it is found that the bypass fraction equals the water recovery to the underflow, in 10 mm hydrocyclones the bypass fraction is considerably larger than the water recovery. This results in a high particle recovery to the underflow, as well as low water recovery, resulting in a high concentration ratio. Results will be presented to show the separation performance of different hydrocyclone outlet configurations and pressure drops. A general model will be presented that describes the fish-hook and that gives an explanation for its origin. It will be shown that 10 mm hydrocyclones yield a new operating regime for their application to sub-micron solid-liquid separation, as a result of high solids recoveries and low water recoveries.
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A special electrical hydro-cyclone is developed and tested. In the underflow collection box of the hydro-cyclone, it has a central metal rod electrode and a cylindrical metal wall between which the desired DC electrical potential or no potential is applied. Effect of central rod diameter and length on separation cut size was examined. The aqueous suspensions of silica particles with a median diameter of 754nm were tested using a 20mm-diameter hydro-cyclone without underflow.It was found that the zeta potential of particles increased proportionally with the value of pH. The electrical potential exhibits a stronger effect when the suspension indicates high pH value. The cut size decreases with the increase of initial pH values. This result is due to the increased negative zeta potential under high pH condition and negatively charged particles are easily collected by electrostatic force.The cut size decreases with the increase of electrode diameter. The cut size becomes smallest under high pH, large electrode diameter and long electrode length conditions. For the negatively charged particles, the center electrode should be negative polarity and outer cylindrical wall should be positive. By use of the electrostatic force, the cut size decreases about 9.2% smaller compared to the standard case without electrostatic force.
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Magnetic hydro cyclones combine centrifugal and magnetic forces to effect separation of magnetic particles. This paper discusses the design of the magnetic circuitry. A numerical analysis method was used and five indices were developed for evaluating and comparing designs. A new multipole design was shown to have advantages over the 2-pole design reported in the literature.
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The purpose of this work was to evaluate the applicability of hydrocyclone technology to separate glaze components for reuse in an industrial process. A laboratory size hydrocyclone system was constructed using industrial components. Preliminary work showed that clean separation of the waste into three particle size ranges; < 5, 5 – 20, and > 20 Am, would allow for each component to be recycled. Hydrocyclones were used to separate particles which have different sedimentation velocities, calculated based on Stokes Law, but could not separate systems with particles that had different sizes and densities but similar sedimentation velocities. Thus, particle behavior in the system correlated to what is predicted by Stokes Law, which is based on laminar flow. The particle size distributions of the separated glaze waste shifted towards the target values of < 5, 5 – 20, and > 20 Am, but were broad and overlapped slightly. A more efficient system would be required for the waste to be completely reusable. Selective agglomeration of glaze constituents was proposed to increase efficiency of separation by creating narrower, more distinct particle size distributions. Sedimentation and titration tests were used to estimate the isoelectric point of glaze constituents. Hypothetical calculations demonstrated that selective agglomeration could be used to significantly increase the sedimentation velocity of particles. D 2005 Published by Elsevier B.V.
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 The internal three-dimensional flow field in a hydrocyclone was studied using laser velocimetry. Seven axial planes were investigated for three different inlet flow rates and three independent and different rejects rates. Results at each measurement plane showed that the measured tangential velocity profile behaves like a forced vortex at the region near the air core, and like a free vortex in the outer portion of the flow. The peak nondimensional tangential velocity decreases as the distance from the inlet region increases, however, the peak dimensional tangential velocity increases as the distance from the inlet region increases. The nondimensional peak tangential velocities are approximately equal for all of the flow rates. The magnitude of the tangential velocity increased in the inner forced vortex region as the rejects rate was increased. Backflows exist in the axial velocity profile near the inlet region, but these reversed flows disappear in the exit region. The dimensional vorticity is proportional to inlet flow rate and decreases with increasing rejects flow rates.
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Previous models of magnetic hydrocyclones were successful in improving the separation of magnetically-susceptible particles from a carrying liquid. Problems occurred, however, with magnetic particles flocculating and accumulating within the hydrocyclone. The liquid flow patterns in the hydrocyclone became distorted, leading to a dilute solid product. A new design of magnetic hydrocyclone has been developed using Nd-Fe-B magnets, which overcomes the problems of magnetic accumulation. The magnets are used to pre-direct the hydrocyclone feed. Compared with a conventional hydrocyclone, this magnetic hydrocyclone is approximately 13% more efficient in the recovery of magnetite, with no change to the liquid content of the product. In an appropriate industrial application, the use of this type of magnetic hydrocyclone could produce significant reductions in the size of installation and processing time
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The flow behavior in hydrocyclone is quite complex. This complexity of flow processes has led designers to rely on empirical equations for predicting the equipment performance. The publications on empirical models of the hydrocyclone far out-number few fluid-flow-modeling attempts. Empirical models correlate a classification parameter, such as the cut-size, with device dimensions and slurry properties. However, these can only be used within the extremes of the experimental data from which the model parameters were determined. On the other hand, models based on Computational Fluid Dynamics (CFD) techniques have proven to be useful in simulating fluid flow in hydrocyclones, and in predicting the separation efficiency of solid particles in the separator for a wide range of operating and design conditions. The shape and size of a hydrocyclone separator has a direct influence on the internal flow structure of the continuous phase and, thereby, the separation of the particulate phase. Hydrocylcones usually have a single inlet that distributes the feed stream near the end wall between the vortex finder and the sidewall. Effect of spigot diameter, i.e., 10 and 20 mm and inlet water velocities (5.91–12.35 m/s) on the water splits and particle classification in the hydrocyclone have been studied. The cut size of the hydrocyclone, operated at very low pulp density, has been predicted using discrete phase modeling technique. The studies revealed that with an increase in feed flow rate and decrease in spigot diameter the cyclone sharpness of separation improves. These predictions were found similar in line with the experimental observations.
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In the computational fluid dynamics study of hydrocyclones, the air-core dimension is key to predicting the mass split between the underflow and overflow. In turn, the mass split influences the prediction of the size classification curve. Three models, the renormalization group κ–ε model, the Reynolds stress model, and the large-eddy simulation model, are compared for the predictions of air-core dimension, mass split, and axial and tangential velocities. The large-eddy simulation model, since it produces some detailed features of the turbulence, is clearly closer in predicting the experimental data than the other two. It is shown that particle tracking done with the velocity field obtained from the large-eddy simulation model accurately predicts the experimental size–classification curve.
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Gas flotation is widely used for oily wastewater cleanup. The crux for flotation is the adhesion of the gas bubble to the oil drop. A spreading stage of oil onto the gas is vital for efficient bubble–oil rise. Thus spreading and non-spreading oils will present different fluid configurations and stabilities for bubble rise and a positive oil on a water–gas interface spreading coefficient is needed for spreading to occur. This paper provides photographic evidence of the spreading of the oil around the gas bubble. The importance of a positive spreading coefficient of the oil around the gas bubble for gas flotation is clear.
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Oily wastewater cleanup can be carried out by gas flotation. When properly operated gas flotation units can reduce oil concentrations of wastewater effluents to well below 40 mg/l. Gas flotation is particularly valuable for heavy oils (oils having a density close to that of water). The flotation process relies on the attachment of gas bubbles to the dispersed oil droplets. This attachment is heavily dependent on the complex processes involving the surface characteristics of the oil droplets and their interaction with gas, and can only be optimally achieved if the surface science conditions are properly understood. The attachment mechanisms include the oil/bubble contact, the interactions of chemical additives (usually surfactants) in aiding this contact and the spreading of the oil around the gas bubble. Additionally, initial agglomeration of the oil emulsion droplets is needed to increase the droplet size to within the range needed for effective flotation, ∼60 μm. This paper examines the essential surface science of the gas flotation process, particularly the gas attachment to oil droplets and the use of surfactants. We discuss the stages of attachment of the gas bubble to the oil droplet, and provide further photographic evidence concerning the importance of the spreading of the oil around the gas bubble for gas flotation.
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A CCD high-speed video microscopy system operating at 1000 frames per second was used to obtain direct quantitative measurements of the trajectories of fine glass spheres on the surface of air bubbles. The glass spheres were rendered hydrophobic by a methylation process. Rupture of the intervening water film between a hydrophobic particle and an air bubble with the consequent formation of a three-phase contact was observed. The bubble-particle sliding attachment interaction is not satisfactorily described by the available theories. Surface forces had little effect on the particle sliding with a water film, which ruptured probably due to the submicrometer-sized gas bubbles existing at the hydrophobic particle-water interface.