Use of regression model of two-step flotation in a hydrocyclone for analysis of effects of design and regime parameters on separation efficiency

An algorithm for a calculation of indices at separation of suspensions with non-Newtonian properties, two-step flotation in hydrocyclone with application of a regression model was developed. An analysis of an influence of governing similarity criteria that describe the suspension separation by two-step flotation in the hydrocyclone and of rheological constants of a separated media on a distribution of a recovery efficiency of solid particles from a suspension over an operation height of a hydrocyclone was carries out.     

Analysis of droplet behavior in a de-oiling hydrocyclone

A mechanical separation process in a de-oiling hydrocyclone is described in which disperse oil droplets are separated from a continuous water phase. This separation process is influenced by droplet breakage and coalescence. Based on experimental data and simulation results in a stirred tank, a modified breakage model, which can be applied to droplet breakage in the de-oiling hydrocyclone, is developed. Then, a simulation model is developed coupling the numerical solution of the flow field in the hydrocyclone based on computational fluid dynamics (CFD) with population balances. The homogenous discrete method and the inhomogeneous discrete method are applied for solving the population balance model (PBM). The investigations show that the numerical results obtained by the simulation model coupled with the modified PBM using the inhomogeneous discrete method are in good accordance with experimental data under a high flow rate. According to this simulation model, the effect of three different inlet designs on the separation efficiency of the de-oiling hydrocyclone has been discussed. The results indicate that the separation efficiency of the de-oiling hydrocyclone can be improved with an appropriate inlet design.     

Modeling of the Concentration Field of Solid Phase in a Hydrocyclone in Suspension Separation by Pressure Flotation

A mathematical model of suspension separation by pressure flotation in a hydrocyclone was developed. The continuity equation was solved numerically for a flux of particles of the solid phase in a flow of a non-Newtonian suspension in a hydrocyclone. The concentration field of solid particles was determined. The effect of the defining similarity criteria on the distribution of concentrations was studied.     

A mathematical model for predicting oil-water separation efficiency in a de-oiling hydrocyclone

The de-oiling hydrocyclone is among the most effective devices to recover oil from oily wastewater. In this work, a new model is theoretically developed to predict the separation efficiency of oil droplets in hydrocyclones. According to the analysis of the flow pattern, the droplet dynamics, and oil concentration distribution in the de-oiling hydrocyclone, the differential equation for the new model is established based on the principle of the mass balance of oil droplet. The proposed model can be finally expressed as a simple explicit function including the main geometrical dimensions and operating parameters. The availability of this model is validated by comparison of the calculated grade efficiency with experimental data and other theoretical separation model.     

Flow Hydrodynamics of non-Newtonian Fluid in a Cylindrical-Conical Hydrocyclone

A system of equations of rheodynamics that describes the flow of a non-Newtonian fluid with a free surface in a cylindrical-conical hydrocyclone was solved numerically. The fields of velocities and pressure, as well as the dependence of the thickness of the fluid film on the axial coordinate, were calculated. The influence exerted by the rheological properties of the fluid, by the defining similarity criteria on the flow hydrodynamics was studied.     

Modeling of Degassing of Viscoplastic Liquids in a Cylindrical Hydrocyclone

Russian Journal of Applied Chemistry - A mathematical model of degassing of viscoplastic liquids in a cylindrical hydrocyclone, taking into account the action of inertia forces and Coriolis forces...     

Simulation of suspension separation by two-stage pressure-head flotation in a cylindrical direct-flow hydrocyclone

A mathematical model of separation of suspensions with a non-Newtonian dispersion medium by two-stage pressure-head flotation in a cylindrical direct-flow hydrocyclone was developed. A system of differential equations describing convective diffusion and motion of a particle-bubble complex was solved numerically. The concentration field was modeled and integral separation parameters were determined.     

Optimizing Geometric Parameters in Hydrocyclones for Enhanced Separations: A Review and Perspective

Hydrocyclones have been extensively applied for solid–liquid or liquid–liquid separations in various industries. However, the exact mechanisms underlying the enhanced separation technologies based on the optimization of geometric parameters of hydrocyclones remain unclear, and a number of research teams have performed numerous studies to enlarge the application scope of hydrocyclones by optimizing geometric parameters. This review provides a comprehensive state-of-the-art review of hydrocyclone enhanced-separation technologies. The enhanced-separation technologies are categorized into ten groups: cylindrical section, inlet, vortex finder, underflow pipe, conical section, hydrocyclone inclination angle, hydrocyclone insertion, conical-section/apex water injection, reflux device, and multi-hydrocyclone arrangement. These enhanced-separation technologies were analyzed and summarized according to the key separation-performance parameters of hydrocyclones, such as separation efficiency, cut size, split ratio, energy consumption, and capacity. It is expected that both the reviewed contents and the proposed challenges and future methodologies and technologies may provide research fellows working in this field with an improved understanding of enhanced separation technologies of hydrocyclones.     

Hydrodynamics of nonlinear viscoplastic fluid in cylindrical hydrocyclone

A flow of non-linear viscoplastic fluid film in a cylindrical hydrocyclone was simulated. The distribution of the velocity component and also a dependence of a fluid film thickness on an axial coordinate were determined by numerical solution of a set of rheodynamic model equations for various rheological properties of the liquid and dimensionless quantities. An influence of plastic properties of the liquid on damping of the circumferential component of the velocity was examined. The results were physically substantiated.     

Effect of Rheological Properties of the Dispersion Medium on Separation of Suspensions in Hydrocyclones with Various Working Space Configurations

The model of separation of suspensions with a non-Newtonian dispersion medium in a cylindroconical hydrocyclone, which takes into account the effect of the Coriolis force on solid particles, was constructed and applied to analysis of the rheological properties of the dispersion medium on separation of suspensions in hydrocyclones with various working space configurations.     

Chemical Modification of Upgraded Bentonite as Filler of Natural Rubber/Organobentonite Composite

Bentonite is an abundant natural resource that has great prospects for used as filler in natural rubber industry after certain modification, either through physical or chemical process. Reduction of mineral impurities in the bentonite was done to form upgraded bentonite by using hydrocyclone, and chemical modification of upgraded bentonite to form organobentonite was done by addition of commercially surfactant. Natural rubber/organobentonite composites made by melting compound technique at roll mill. The results showed that the reduction process of mineral impurities in the bentonite had been able to reduce the content of impurities, such as Fe₂O₃, CaO, and K₂O. Meanwhile, by using XRD dan FTIR analysis, an increase in the dose of surfactant on upgraded bentonite might increase the organic content and basal spacing of organobentonite. Low mineral impurities organobentonite was capable of producing natural rubber/organobentonite composite with faster vulcanization time and some better mechanical properties (such as elongation at break and modulus 100%) than natural rubber/carbon black composite.     

铬酸钠碳氨转化过程的相图分析

研究了铬酸钠碳氨转化过程中Na＋, NH4+// CrO42－, HCO3－-H2O体系的溶解度和相图.根据溶解度和相图对铬酸钠的氨水溶液碳氨转化过程固相析出行为进行分析.结果表明: 相图中存在NaNH4CrO4·2H2O复盐结晶区,浓度较高的铬酸钠氨水溶液转化过程中NaC(HO)3、(NH4)2CrO4和NaNH4CrO4·2H2O结晶可能同时析出,形成混晶.为避免同时析出铬酸铵、碳酸氢钠结晶,铬酸钠氨水初始溶液浓度应稍低于相图中P2(P2′)对应的组成,即为1 g H2O中Na2CrO4 0.8633～1.1377 g,氨0.0611～0.0986 g.     

The influence of fibre wall thickness on the undissolved residuals in CMC solutions

An industrial calcium sulfite pulp was fractionated in a hydrocyclone to four fractions that differed in dimensions and composition due to differences in density. The intention was to investigate whether the fibre dimensions had any influence on the properties of carboxymethyl cellulose (CMC) produced from the fractions and especially how the properties of the unreacted material differed. It was surprisingly found that the fraction containing thin-walled fibres gave CMC and dissolved residuals in the CMC-solution that had the lowest degree of substitution (DS). It was therefore believed that the thin-walled fibres were collapsed and more closely bound in the fibre network after drying of the pulp and that this impeded the chemical diffusion in the subsequent CMC-process, i.e. the diffusion of the CMC-chemicals into the cell wall was slower. There was thus a correlation between thinner fibres and a lower degree of substitution for CMC made from such fibres. It was also found that tick-walled fibres had a higher degree of substitution than the thin-walled fibres but that the highest degree of substitution was obtained if a mixture of thin- and thick-walled fibres were used.     

A Multivariate Analysis on the Influence of Indigenous Crude Oil Components on the Quality of Produced Water. Comparison Between Bench and Rig Scale Experiments

A matrix of 30 crude oils have been analyzed to investigate if there is any correlation between the physiochemical properties of the crude oils and the quality of the produced water. As an approach to study produced water quality, oil. and brine water (3.5 wt%) have been mixed together, and transmission profiles from the separation process have been investigated by means of Turbiscan LAb. The Turbiscan LAb enables the study of stability of colloidal dispersions without any dilution or modification of the sample. The oil-in-water emulsions (30:70) were made by mixing oil and water at low speed to be sure that they separate within a short period of time. Drop size distributions were investigated for all crude oil emulsions by using a Coulter Counter (COULTER Multisizer II). The correlations between transmission profiles and crude oil characteristics were made by using principal component analysis (PCA), a method that helps visualize the most important information contained in a data set and find combinations of variables that describe major trends. A Vortoil K-liner hydrocyclone connected to a mixing rig has been used to separate oil and water in larger scale experiments. The objective with these experiments was to compare the results with separation experiments done at bench scale. Six crude oils have been investigated at the separation rig, and both droplet size distribution and dispersed oil concentration have been performed. The main conclusions from this work are that Turbiscan LAb is a suitable technique to study the separation of oil-in-water with good reproducibility. The results from the multivariate data analysis show that the crude oils group according to if they are light or heavy and according to if they get high or low transmission. From the larger scale experiments it has been shown that the droplet sizes, oil/water density differential, and viscosity have a significant impact on separation efficiency.     

Immobilization of glucose oxidase onto a Langmuir-Blodgett ultrathin film of a cellulose derivative deposited on a self-assembled monolayer

Glucose oxidase was immobilized on a Langmuir-Blodgett film of cellulose acetate propionate deposited on a self-assembled monolayer coated substrate. These layers were characterized in terms of their ellipsometric thickness, wettability and infra-red spectra. Glucose oxidase was immobilized on this composite layer by physisorption. The presence of the enzyme on the surface was confirmed by ellipsometry, infra-red spectroscopy and by detecting its activity electrochemically. An enzyme population remained active after adsorption onto this assembly.     

Force of a gas bubble on a foreign particle in front of a freezing interface

We monitored the formation and development of a single gas bubble on the surface of a spherical particle of size 1.676 mm under unidirectional freezing and thawing (4.6-5.0 microm/s) and for the first time quantitatively estimated the force exerted on this particle by measuring the deformation of an attached elastic stick. The bubble would nucleate and grow on the particle surface closest to the ice front, while the force curve for a freezing-thawing cycle presented a hysteresis characteristic. This force was much greater than in the case without a bubble, and hence it dominated the engulfment process in the present freezing tests. The bubble force increased with increasing bubble size and was shown to be mainly attributable to the elastic force by the deformed bubble shape. Comments were made on the need to incorporate the role of bubbles in predicting the critical velocity to freeze a suspension with high dissolved gas content.     

Spreading of a fluid phase on a spherical surface

The adsorption between a liquid drop and a micro-particle in an air or an air bubble and a micro-particle in water is dominated by liquid-solid or air-solid interfacial tension and wetting area of the liquid or air on the particle surface. The wetting area is determined by the spreading of the liquid drop or the bubble on the micro-particle. To explore this spreading, a wetting model of a fluid phase on a spherical particle was built. According to the theoretical results, the contact angle is constant when a fluid phase spreads on a spherical solid surface; the micro-particle can not submerge under a fluid when only interfacial tensions are involved and the wetting is not a complete wetting. The corresponding experiments were performed to confirm the theoretical results.     

Direct synthesis of a metalloporphyrin complex on a surface

We demonstrate that well-defined monolayers of a metal complex on a surface can be prepared by direct vapor deposition of the metal atoms on monolayers of the ligand. In particular, ordered monolayers of adsorbed tetraphenylporphyrin (2H-TPP) on a silver surface were exposed to cobalt vapors, resulting in the complexation of the metal by the porphyrin. The formation of the metal complexes was monitored by means of X-ray photoelectron spectroscopy (XPS), which reveals that this metalation reaction leads to a chemical equivalence of all four nitrogen atoms. The described in situ metalation provides a convenient way to produce adsorbed monolayers of more reactive (e.g., air- or solvent-sensitive) or thermally unstable metalloporphyrins that are difficult to evaporate or even to obtain as pure compounds at room temperature.     

Fabrication and placement of a ring structure of nanoparticles by a laser-induced micronanobubble on a gold surface

We have developed a new fabrication method for a ring structure of assembled nanoparticles on a gold surface by the use of continuous Nd:YAG laser light. A micronanobubble on a gold surface, created by laser local heating, acts as a template for the formation of the ring structure. Both Marangoni convection flow and capillary flow around the micronanobubble are responsible for the driving force to assemble nanoparticles such as CdSe Q-dots into the ring structure from the solution. Because a single micronanobubble was generated by the Nd:YAG laser focusing point, the precise positioning of the ring structure was feasible directly on the gold surface, which makes it possible to fabricate various patterns of rings such as arrays and letters and even a double-ring structure without any photomasks or any templates.     

Heteroepitaxial growth of a zeolite film with a patterned surface-texture

We focus on the eteroepitaxial growth of trigonal chabazite with voids of three-dimensional intersection structures. The differences in the structures originate from the stacking sequences of the six-membered rings. Sodalite along 111 is constructed by an "abcabc" stacking sequence, while chabazite along [111] is constructed by "abab". Therefore, chabazite can grow heteroepitaxially on a sodalite substrate while keeping the relation of chabazite (111)//sodalite {111}. In this Communication, we report on the first success of the heteroepitaxial growth of a continuous zeolite (chabazite) film with a unique patterned surface-texture on a millimeter-sized sodalite single crystal. We have found that the unique texture of chabazite films is rationalized by the heteroepitaxial growth of chabazite on sodalite and the subsequent twin formation of chabazite.