Computational study of the flow characteristics and separation efficiency in a mini-hydrocyclone

The development of a simple and feasible fluid–solid separation device is critical to further advancement in the use of micro-technology. The mini-hydrocyclone, which possesses a concise geometry and simple operational process, has been proposed as a promising solution to bridge this gap since the cut-size decreases with decreasing hydrocyclone diameter. In this work, we investigated the fluid flow and particle separation ability of a 5 mm diameter mini-hydrocyclone through computational fluid dynamics (CFD) modelling. Direct numerical simulation (DNS) results with CFD have shown that the flow transition and subsequent unsteady state behaviour occurred in the mini-hydrocyclone at a low Reynolds number (Re_in = 300) because of the onset of centrifugal instability. The centrifugal instability offered an insight into the flow transition and the development of turbulent flow in hydrocyclones which have not been studied. The centrifugal instability in the mini-hydrocyclone begins as Görtler vortices developing in the boundary layer and they subsequently affect the flow field. Particle motion tracing showed that improved separation with finer cut size, d₅₀, and steeper separation sharpness were obtained as the inlet velocity was increased. The improvement can be explained by the flow characteristics when the flow transits to turbulent flow.     

Investigations on various characteristics of novel cyclone separator with helical square fins

ABSTRACT

Cyclone separators are very energy intensive devices primarily used in power and process industries to separate the particles from hot gases. Hence in the present study, the barrel wall of the cyclone separator was modified by fixing the helical square fins of sizes 5, 7.5, and 10 mm, with 30 and 50 mm pitch variations to improve its separation efficiency. Hence in the present study, various fluid dynamic characteristics which affect the separation efficiency such as axial and tangential velocities, axial pressure drops were investigated. Computational results were validated using the published experimental data for the non-finned cyclone separator and further CFD simulations were performed for novel finned cyclone separators. It was observed that for the particles’ sizes below 3 µm, finned cyclone separator with fin size 10 mm and pitch 50 mm was giving separation efficiency more than other 5 finned cyclone separators. Also 5 to 10% improvement in the separation efficiency was observed over the separation efficiency of the non-finned cyclone separator. Since main function of separating the particles from gas was unaffected rather it was improved using finned cyclone separator(s) which is important in a view of reducing serious fine particulate matter (PM2.5) emissions causing serious health issues.     

Cationic starch for microalgae and total phosphorus removal from wastewater

The city of Logan, Utah treats wastewater in 460 acres of facultative lagoons. Naturally growing algae in these lagoons uptake nutrients and remediate the wastewater, but require coagulation and flocculation for separation from wastewater. Cationic corn starch and cationic potato starch with a degree of substitution 1.34 and 0.82, respectively, were synthesized using 3‐methacryloyl amino propyl trimethyl ammonium chloride and tested on Scenedesmus obliquus and lagoon wastewater. The zeta potential of the cationic starches tested over a pH range 5.0–10.0 showed an average of +16.0 and +15.1 mV for cationic corn starch and cationic potato starch, respectively. Total suspended solids removals of 90 and 85% were achieved with cationic corn starch and cationic potato starch, respectively, when tested with S. obliquus. Tests with wastewater showed total suspended solids removals of 80 and 60% for cationic corn starch and cationic potato starch, respectively. Total phosphorus removal values from wastewater were approximately 33, 29, and 42% for cationic corn starch, cationic potato starch, and alum, respectively, for a coagulant/algae ratio of 1.4 (wt/wt). These results indicate that cationic starch has the potential to replace alum for algae harvesting and wastewater treatment making it a suitable alternative to inorganic coagulants and flocculants. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 130: 2572–2578, 2013     

Removal of Emulsified Oil from Water by Coagulation and Foam Separation

Abstract

A new method of emulsified oil separation for oily wastewater incorporating simple operation and shortened treatment time is necessary for improved wastewater treatment in some manufacturing plants. In the present study, the removal of emulsified oil from water by coagulation and foam separation using poly aluminum chloride (PAC) and milk casein was examined. By adding casein before the foam separation process, the oil removal was dramatically improved. By using surfactant (LAS) as a frother, the dosage of casein was drastically reduced. Furthermore, for processing actual oily water, LAS was unnecessary because a sufficient amount of surfactants for foaming was included in the wastewater. For treatment of the actual oily wastewater collected from a steel manufacturing plant, the optimum condition for PAC and casein was 30 mg‐Al/L and 10 mg/L, respectively, and the oil concentration decreased from 170 mg/L to 2.2 mg/L. After examining several types of oily wastewater, 96–99% of oil removal efficiency was obtained by adjusting the dosages of PAC and casein. Coagulation and foam separation using casein has shown a high potential as an alternative method to dissolved air flotation (DAF) for processing emulsified oil water.     

CFD Study on the Effect of Hydrocyclone Structure on the Separation Efficiency of Fine Particles

Abstract

Effects of geometric structure parameters of 10 mm-diameter hydrocyclones on the particle separation efficiency are studied using computational fluid dynamics (CFD). The fluid velocity profiles and particle trajectories are simulated using RFLOW software with a standard isotropic k-ε turbulent model. The JIS standard CaCO₃-17 particles are adopted as a particulate sample in simulations and experiments. Comparing the simulated results with experimental data, a maximum deviation about 20% in partition curves occurs for 5–10 µm particles. However, fairly good agreements for the cut-size predictions and the fish-hook phenomenon are obtained. The simulated cut-size d ₅₀ is only 2 µm larger than that measured in experiments, while the value of d ₁₀₀ can be accurately predicted. An increase in overflow diameter or a decrease in underflow diameter leads to a lower separation efficiency but a clearer separation sharpness due to lower fluid underflow rate. A short-and-wide rectangular inlet is more efficient for particle separation than a tall-and-narrow one. An inclined inlet conduit plays an inessential role on the efficiency improvement but gains a 2 µm reduction in d ₁₀₀. Comparing the simulated results, the hydrocyclone used in the experiments of this study exhibits a higher separation sharpness than the Rietema type and a higher efficiency than the Bradley type based on the same operation capacity and hydrocyclone size.     

Study on Riboflavin Recovery from Wastewater by a Batch Foam Separation Process

Abstract

A batch recovery of riboflavin via foam separation from industrial simulative wastewater was studied using a cationic surfactant, cetyltrimethyl ammonium bromide (CTAB). The experimental parameters examined were the surfactant concentration, air flow rate, pH, and foam height. Under optimal operating conditions obtained through an orthogonal experiment, the maximum enrichment ratio of 48.7 was achieved for riboflavin along with 99.3% removal efficiency. The optimal operating conditions had the concentration of CTAB at 0.3 g/L, air flow rate at 400 ml/min, foam height at 90 cm, and pH at 12. Therefore foam separation proved to be an effective method to recover the riboflavin in terms of the good enrichment and removal efficiency.     

Effective separation of magnetite nanoparticles within an industrial-scale pipeline reactor

ABSTRACT

Within the field of wastewater treatment, nano-adsorbents are a significant emerging technology; however, separation of the nano-scale particles after loading has proved to be an impediment to widespread industrial implementation. Magnetic collection of nanoparticles is a potential strategy for effective separation. Nano-scale magnetite is an effective adsorbent, is sufficiently magnetically susceptible, and is superparamagnetic, allowing re-dispersion following magnetic collection.

In this work, an in-line, water-cooled magnetic collection module was developed with collection efficiencies regularly exceeding 98%. Models were developed over various flow regimes. The role of cooperative magnetophoresis was demonstrated and a physical model has been proposed for adsorption upon particle agglomerations about magnetic core wires.     

泡沫分离技术和三维电极反应器联用处理淀粉废水

以泡沫分离和三维电极法作为主体工艺,对淀粉废水进行的两个月的现场中试结果表明:气水比为10时,泡沫分离工艺对废水COD去除率高达51.2%,植物蛋白回收量为2.5kg/t(原水);三维电极反应器在反应时间、输入电压和极板间距分别为70min、10V和15cm时能获得96.9%的COD去除率,吨水能耗仅为1.78kW.h。     

Effect of Pre‐Filtration on Selective Isolation of Tat Protein by Affinity Membrane Separation: Analysis of Flux,Separation Efficiency,and Processing Time

Abstract

The isolation and purification of Tat protein from bacterial lysate using avidin‐biotin interaction in microfiltration membranes have been reported in the literature. To increase the efficacy of the technique, improvements in flux, Tat separation efficiency, and processing time are essential. In the current research work a pre‐filtration step was introduced to remove unwanted high molecular weight proteins and other impurities from feed prior to affinity membrane separation. Significant enhancement in flux and separation efficiency of Tat was observed. Processing time was also reduced significantly. For example, with UF pretreatment step the total Tat recovery was around four times higher (with processing time 25% lower) than that observed with the untreated feed. The quality of purified Tat was analyzed by SDS‐PAGE, Western Blot, and biotin analysis. Flux behavior in affinity separation was described by model equations.     

Prediction of 10-mm Hydrocyclone Separation Efficiency Using Computational Fluid Dynamics

It has been estimated that particles within the flow field of a 10-mm or mini-hydrocyclone experience local accelerations as high as 10 000 gravitation units. Although their operation is simple, the turbulent, swirling flow field within these devices offers a unique challenge to computational fluid dynamics (CFD). In addition to the computational challenge, very few experimental measurements have been reported in the literature on the flow field of the mini-hydrocyclone to which the CFD results may be compared. This research addresses the issue of predicting the separation efficiency of a volute entry 10-mm hydrocyclone. The feed flow rate is 4.5 litres/m (l/m) yielding a Reynolds number (based on the hydrocyclone diameter) of 9500 and a swirl number of 8.4. Using previously published flow simulation data, a multiphase system (consisting of a discrete oil phase and a continuous water phase) was analyzed for the purpose of obtaining separation information. These separation data were compared with laboratory separation experiments. Results indicate differences less than 20% for each droplet diameter. This information increased the level of confidence in the simulated flow field since there are no published velocity field data for the 10-mm hydrocyclone.     

螺旋分选机处理煤泥的工艺效果检测与分析

介绍了螺旋分选机的工作原理,对其分选工艺效果进行了全面的计算和定量分析。按照煤用重选设备工艺性能评定方法,对可能偏差、不完善度、数量效率、灰分误差、总错配物含量等指标进行分析,获得真实确切的工艺指标和技术经济指标,判别螺旋分选机技术状态,得出其分选下限为0.125 mm。     

A New Hybrid Flotation—Microfiltration Cell

Abstract

The investigated hybrid cell combines the advantages of both flotation and membrane separation, while overcoming their limitations and having as an outcome clean water from a industrial wastewater. Hence, metals recovery from dilute aqueous solutions was a promising application of this innovative process, further to solid/liquid separation. The specific objective was to apply the process for the efficient separation of effluents containing metals (here, zinc). The main examined parameters were the following: the metal initial concentration, flotation surfactant applied, and air flowrate. The successful contribution of precipitate flotation was highlighted, while the observed metal removals were of the order of ～100%.     

Synthesis of a starch–acrylic acid–chitosan copolymer as flocculant for dye removal

Flocculants prepared with modified natural polymers have recently attracted extensive attention in the field of water treatment. In this work, acrylic acid was successfully grafted onto the backbones of starch and chitosan by free radical polymerization. The synthesis parameters of initiator concentration, reaction temperature, and neutralization degree of acrylic acid were optimized as 0.4 wt %, 50 °C, and 70%, respectively, according to the flocculation performance. The ternary copolymer starch–acrylic acid–chitosan (SAAC) could completely remove Acid Blue 113 from 100 mg/L of simulated wastewater (color removal efficiency 99.7%) at the flocculant dosage of 100 mg/L. The SAAC also had effective flocculation capability in a wide range of flocculant dosages and pH values of wastewater. The ternary copolymer based on two natural polymers has enormous potential as flocculant with its advantages of low price, ecofriendliness, and high performance. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47437.     

Effect of separation mechanism on the kinetics of Zn(II) flotation

ABSTRACT

In this study, the kinetics study and separation mechanism of zinc ion removal from synthetic wastewater were investigated using the foam separation process. With increasing the pH, Zn(II) recovery increased, in which foam fractionation occurred at pH 1.5, 3 and 5.5 and ion flotation at pH 8. The kinetics study was also used to determine separation mechanism. The order of Zn(II) foam fractionation was n = 1, while the order of Zn(II) ion flotation was n = 2 at the first stage and n = 0 at the second stage. Water recovery kinetics also increased with increasing ionic strength.     

Mechanism of micro-particle motion across falling liquid cylinder for PM2.5 separation (Ⅱ)Efficiency of PM2.5 separation from heavy-duty diesel exhausts

根据（Ⅰ）报提出的液柱交叉流PM_2.5颗粒附面运动与吸收机理及模型计算方法,设计了以钻井废水吸收钻井柴油机尾气PM_2.5的液柱交叉流吸收现场试验装置。吸收器具有高温绝热蒸发与低温绝热冷凝两个操作空间,柴油机尾气通过绝热蒸发空间降温增湿,携带水蒸气到绝热冷凝空间通过扩散在液柱表面冷凝,形成热泳和扩散双重强化PM_2.5吸收分离机制。模型计算显示该机制下0.01～1.0 μm范围内颗粒粒径与分离效率关系不显著,设计工况下单液柱分离效率1.17%～1.36%。由200排三角形布置的液柱构成的吸收器总体分离效率90%～93%。该过程可同时蒸发废水461.2 kg·h^-1。但颗粒分离效率随蒸发负荷及液柱温度的上升而降低,温升10℃、单液柱分离效率降低60%。现场模型试验装置监测数据与本文模型计算总分离效率基本接近。     

Facile ZIF‐8 functionalized hierarchical micronanofiber membrane for high‐efficiency separation of water‐in‐oil emulsions

The efficient separation and recovery of oil from water‐in‐oil emulsion poses a great challenge because of the rapid development of the petrochemical industry throughout the world. In this study, a facile method to develop a ZIF‐8 functionalized hierarchical micronanofiber membrane for high‐efficiency oil/water separation was investigated. The electrospun PVDF/ZnO membrane was made, on which ZIF‐8 crystal seeds were then created with the revitalizing step and expanded in the growth step, and finally functionalized hierarchical micronanofiber PVDF‐g‐ZIF‐8 membrane was obtained. Results showed that oleophilic ZIF‐8 crystals on the surface of PVDF membrane dramatically increased the wettability of oil and tuned PVDF membrane from olephobicity to oleophilicity. The hydrophobic/lipophilic PVDF‐g‐ZIF‐8 membrane with a water contact angle up to 158° and a toluene contact angle down to 0° provides its separation efficiency for water‐in‐oil emulsion of 92.93% in an environmentally friendly and energy‐saving manner. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 46462.     

Diffusion Transport Vector for Multicomponent Gas Separation in Ultracentrifuge

Abstract

Simplified diffusion transport vector expressions for multicomponent gas mixture mass transfer analysis have been derived. Approximate relations for the general diffusion coefficients for multicomponent gas separation in an ultracentrifuge for both isotope and nonisotope mixtures are developed. Taking into account that diffusion coefficients matrices are diagonally dominant, a simple relationship for diffusion transport vectors for the case of isotope separation is derived. It is shown that the relative inaccuracies in separative power and separation factors calculation are less than 1-2%. Analogous relationships for diffusion coefficients for the separation of a nonisotope mixture containing small admixtures in the main gas are suggested. These relationships can be used when the total mole fraction of the admixtures is less than 5%.     

改性淀粉在低浓度含镉废水处理中的应用实验

对淀粉（St）接枝共聚丙烯酰胺（AM）并与巯基乙酸（MCAA）反应进行了研究,将得到的产物用于低浓度含镉废水处理取得了较好的效果。研究了淀粉与丙烯酰胺配比不同对St-AM接枝率和接枝效率的影响并对巯基化后得到的产物St-AM-MCAA的巯基含量进行了测定。对低浓度（0.4mg/L）含镉废水的处理研究发现：含镉废水在pH=8,添加量为50mg时镉去除率可达89.7%;St-AM-MCAA较St-AM产物能提高Cd2+去除率10%以上。     

Protein Recovery from Sweet Potato Starch Wastewater by Foam Separation

In this study, an inclined foam separation column was designed to effectively recover protein from sweet potato starch wastewater. The effects of the influent protein concentration, pH, air flow rate, influent volume, foaming time, and inclined column angle on foam separation performance were assessed. The optimum foam separation conditions consisted of influent protein concentration 4.51 mg/mL, pH 4, air flow rate 0.15 mL/min, influent volume 500 mL, foaming time 100 min, and inclined column angle 30°. In these conditions, protein recovery percentage and enrichment ratios were 84.1% and 1.3, respectively. The biochemical oxygen demand (BOD₅) and chemical oxygen demand (COD_Cr) of the residual solution (620 and 950 mg/mL, respectively) were lower than those of the original (influent) solution.