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.     

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.     

CFD simulation of floating particles suspension in a stirred tank

Computational fluid dynamics (CFD) simulations were performed to predict the floating particles suspension in a baffled tank stirred by a standard Rushton turbine. An Eulerian multiphase model and a standard k-ε turbulence model with mixture properties were used in the CFD simulation. The impeller rotation was solved using a moving reference frame method. Flow pattern, power number and solid holdup distribution were obtained and compared with the results in literature. The effects of operating condition on floating particles suspension characteristics were studied. It indicated that the influences of impeller speed and solid loading on particle suspension varied with particle sizes. For small particles, the impeller speed and solid loading have no obvious effects on solid holdup distribution and suspension quality. For large particles, particle suspension quality becomes better first, and then keeps almost unchanged with enhancing of the impeller speed. Suspension quality is better for higher solid loading of large particles. Within the scope of the present study, solid loading has no great effect on suspension quality. Suspension quality becomes worse with increasing of the particle size. Large particles are easy to accumulate in the centres of the liquid free surface and the upper circular loop, and the vicinity of the shaft.     

Preparation of agglomeration-free hematite particles coated with silica and their reduction behavior in hydrogen

To prepare silica-coated hematite particles without agglomeration, the effects of solid fraction, ion content in solution, and designed layer thickness on agglomeration and dispersion behavior after silica coating were examined. Since the ion concentration remained high in suspension after the hematite particles were prepared, these particles formed aggregates by the compression of an electric double layer on the hematite and silica layer produced a solid bridge between primary hematite particles. Silica bridge formation and agglomeration were almost completely prevented by decreasing the ion concentration and solid fraction of the hematite particles. Furthermore, the effects of the silica-layer thickness and structure on the reduction of hematite to iron under hydrogen gas flow and the iron core stability under air were discussed. When the solid fraction was low in suspension to prevent agglomeration during coating, a densely packed structure of nanoparticles formed by heterogeneous nucleation was observed on the silica-layer surface. Since this structure could not completely prevent oxide diffusion, the layer thickness was increased to 40 nm to obtain a stable iron core under air. Although a dense uniform layer was produced at a high solid fraction during coating, its thickness was reduced to 20 nm to completely reduce hematite to iron.     

Quantitative analysis of the fractionation of finely dispersed particles in a centrifugal separator

The kinetic characteristics of solid microparticles moving in the interdisk flow of a liquid separator with conical inserts were analyzed. On this basis, a technique was substantiated and calculation was performed for the process of isolation of particles with desired size from a finely dispersed powder in a liquid suspension.     

Effect of Design Parameters of the Centrifuge Rotor on Separation of Supensions

Centrifugal separation of low-concentration suspension in a biconical rotor of a centrifuge was modeled numerically. A system of equations describing the motion of solid particles in a fluid flow was constructed and solved. The effect of geometric parameters of the centrifuge rotor on the separation efficiency was demonstrated.     

On the viscosity of composite suspensions of aluminum and ammonium perchlorate particles dispersed in hydroxyl terminated polybutadiene--New empirical model

The rheological properties of fuel suspensions with various solid loadings up to close their maximum packing fraction and suspending media having different viscosities are investigated using the rotational viscometer at relatively low shear rates in which suspensions behave as Newtonian fluids. Aluminum (Al) and ammonium perchlorate (AP) particles are major solid components of any solid fuel system which should be distributed uniformly inside a polymeric binder based on hydroxyl terminated polybutadiene (HTPB). The experimental data generated in this investigation indicates that the relative viscosity of the suspensions is independent of viscosity of polymer binder, but in addition to solid content, geometrical aspects of the solid particles affect strongly the relative viscosity of suspensions. Maximum packing fraction of filler is found to be suitable quantitative measure of filler characteristics such as size, size distribution, shape and structure. Consequently, it is revealed that the relative viscosity of fuel suspension is a unique function of reduced volume fraction (Phi). Based on analogy of viscosity enhancement of reactive resin with cure conversion and suspension with filler content, an empirical model with two adjustable parameters originated from resin gelation model is suggested. According to this model and experimental results obtained in this investigation, a generalized model is proposed to describe the relative viscosity as a function of solid content in which the adjustable parameters are found to be general constants. The generalized model which is expressed as mu(r) = (1-Phi)(0.3 Phi-2) is found to be quite accurate to predict the experimental data. Furthermore, the applicability and accuracy of the generalized model are evaluated using the viscosity data of some suspension systems reported in the literature.     

A hybrid rheological model for particulate suspension in zeolite crystal growth

A hybrid constitutive model is developed to represent the thixotropic behavior of particulate suspension during zeolite crystallization from solution. This model is valid over the complete solid fraction range typical for such a process. It employs two internal variables, agglomeration and contiguity, to describe the degree to which the gel particles form short- and long-range networks. The contiguity is used to weigh the effects of hydrodynamic to chain-like network deformation on the suspension viscosity. Heterogeneous nucleation and surface reaction-controlled crystal growth are assumed to describe the evolution of microstructure and solid fraction of gel and crystals. Such a model successfully captures the thixotropic behavior of zeolite particulate suspension by comparison of the predictions with a set of experimental data.     

Diffusional-kinetic model of the joint dissolution of interacting poorly soluble substances

A model of the dissolution and interaction of two poorly soluble substances with the formation of a readily soluble product was developed. The kinetic characteristics of the process were described for the dissolution of two solid substances in a planar slit between them filled with a solvent and for the dissolution of intensely stirred suspension of particles of two substances.     

电流变液中悬浮粒子形状与其固态结构之间的关系

采用近邻相互作用近似方法,计算了电流变液中悬浮粒子的形状对电流变液呈固态时基本结构的影响.结果表明:基本结构将随着悬浮粒子形状的变化而变化,特别是在扁椭球情况下,固态结构的相互作用能出现几个数量级的变化.     

Suspension polymerization of thermotropic monomer: Formation of droplets or beads

Ordered beads were obtained by the suspension copolymerization of amesogenic methacrylate-based monomer and methacrylic acid. The stability of these particles and the liquid crystal organization inside the particles depend mainly on the time of polymerization and on the crosslinking. Suspended droplets of monomers or polymers can be obtained as well as solid spheres. The solid particles exhibit ordered microstructures with a liquid crystal configuration that has a variable form depending on polymerization time and observation temperature. Bead characteristics such as morphology, size and polydispersity, and porosity are discussed and compared with those of non-mesomorphic beads. The mesomorphic beads are smaller and their porosity lower. The presence of a crosslinker during the polymerization process leads to more mechanically stable particles with retention of polymorphism.     

Suspension polymerization of thermotropic monomer: Formation of droplets or beads

Ordered beads were obtained by the suspension copolymerization of amesogenic methacrylate-based monomer and methacrylic acid. The stability of these particles and the liquid crystal organization inside the particles depend mainly on the time of polymerization and on the crosslinking. Suspended droplets of monomers or polymers can be obtained as well as solid spheres. The solid particles exhibit ordered microstructures with a liquid crystal configuration that has a variable form depending on polymerization time and observation temperature. Bead characteristics such as morphology, size and polydispersity, and porosity are discussed and compared with those of non-mesomorphic beads. The mesomorphic beads are smaller and their porosity lower. The presence of a crosslinker during the polymerization process leads to more mechanically stable particles with retention of polymorphism.     

Study of energy dissipation in a suspension of particles with magnetic hysteresis in alternating supercritical-frequency field

Results of the experimental study of energy dissipation in a dielectric suspension of magnetohard γ-Fe₂O₃ particles exposed to alternating magnetic field with a frequency exceeding the limiting frequency of mechanical rotations of ferroparticles in a carrier liquid are reported. The rate of energy absorption is investigated as depending on the field amplitude and particle concentration. A drastic increase in the absorption is observed with a rise in the amplitude in the 450–800 Oe range. It is revealed that the energy dissipated in the suspension, as calculated per volume of ferroparticles, is maximal at low particle concentrations. When the concentration increases, the energy dissipation decreases by one-third becoming equal to that in a solid unordered ferrodispersion. The results obtained qualitatively agree with the theory of dissipation in suspensions of single-domain particles characterized by a magnetic hysteresis.     

Effects of Microcrystalline Cellulose on Suspension Stability of Cocoa Beverage

The rheological properties and particle size distributions of cocoa beverage as well as aggregate structures of solid particles were studied to elucidate the effects of microcrystalline cellulose (MCC) on suspension stability of solid particles in cocoa beverage. Fluidity curve, dynamic viscoelasticity, particle size distribution, and SEM observation were made for beverage samples containing 0.1–0.5 wt% MCC and 11 model samples with various combinations of six ingredients. This revealed that cocoa and MCC particles are highly cohered into an aggregate and the aggregated particles further interact weakly with the milk component, leading to stabilization of the whole system of cocoa beverage.     

Distribution of charge in the process of coating Fe powder by electrolysis in a fluidized bed

Theoretical calculations of the amount of Ni that is applied electrolytically in the form of a coating on Fe powder particles in a fluidized bed are based upon the assumption of distribution of charge between the surface of the solid cathode and the powder particles present in the working volume of the electrolyte. The experimentally measured data show good agreement with theory. The efficiency of the coating process is rather low because of inhibition of the process by hydroxocomplexes formed in the course of electrolysis. The inhibition effect becomes more significant in the case of high suspension density, small powder particles, high current density, and prolonged time of electrolysis. Received: 5 May 1997 / Accepted: 30 June 1997     

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.     

Effects of cosolvents on helical substituted polyacetylene particles prepared through suspension polymerization

Acetylenic monomers undergo aqueous suspension polymerization providing particles constructed by helical substituted polyacetylene. Different from suspension polymerization of vinyl monomers, a cosolvent is indispensable to dissolve Rh catalyst and solid acetylenic monomers. The cosolvent is found to play essential roles in monomers' polymerization and the particles' formation. To systemically explore the effects of cosolvents, three monomers, M1 (achiral, liquid), M2 (achiral, solid), and M3 (chiral, solid), and six cosolvents (divided into two groups by their miscibility with water) are used for performing suspension polymerization in aqueous media at 30 °C, with Rh⁺B^– (C₆H₅)₄ as catalyst and polyvinylpyrrolidone as stabilizer. FTIR spectra and gel permeation chromatography confirm the occurrence of polymerization. Raman spectra demonstrate the high cis contents of the polymer chains. Scanning electron microscope images show that the polymer particles obtained under optimal conditions are in spherical morphology. Circular dichroism and UV‐vis spectroscopy demonstrate the helical structures of the polymer chains forming the chiral particles. Dynamic light scattering characterization is carried out to characterize the nanoparticles. The type and amount of the cosolvent affect the polymerization remarkably. Cosolvents with higher polarity lead to smaller polymer particles, while lower polar cosolvents provide larger ones. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2017 , 55, 2670–2678     

Emergence of convective instability in the process of electroreduction of a polytetrafluoroethylene suspension in a tetraalkylammonium salt solution in dimethyl sulfoxide on the surface of a mercury-pool cathode

The electroreduction of mechanically activated solid particles of a polytetrafluoroethylene suspension on a mercury-pool cathode in DMSO solutions containing (C₂H₅)₄NClO₄ is investigated visually and by taking polarization measurements. It is established that the process is accompanied by the emergence of a convective instability, which manifests itself in a spontaneous ordered motion of solid particles in two mutually opposite vertical directions and in the fluctuations of electric current. The assumption is put forth about the formation, in these conditions, of spatial (cellular) and space-time dissipative structures. The basis for the above phenomena is a nonuniform distribution of local values of the current density and potential at the surface of the mercury-pool cathode, which gives rise to vertical and horizontal gradients of the temperature of the liquid phases and the interfacial tension of mercury.     

Ultrasonic attenuation by nanoporous particles. Part II: experimental

In Part I of this paper O'Brien presented a new theory that describes the dissipation of ultrasonic energy by porous colloidal particles in suspension. In this paper we present experimental measurements on several such suspensions and compare the resulting ultrasonic attenuation spectra with O'Brien's theory. We find that microporous colloids (e.g. zeolites) and mesoporous colloids (e.g. porous silicas) both show greater attenuation of ultrasound than would solid particles of the same size and effective density, as predicted by O'Brien. Fitting theoretical spectra to the experimental data provides information about the porosity and pore diameters in the particles. This makes the technique potentially suitable as a convenient method of characterizing nanoporous materials, especially those already in suspension.     

Solid phase radioimmunoassay for testosterone in human serum using antibodies coupled to magnetizable cellulose

Summary A simple user-friendly, solid phase radioimmunoassay for testosterone in human serum based on magnetic particles is described. IgG fractions precipitated from polyclonal testosterone antiserum were coupled to magnetizable cellulose particles using carbonyl diimidazole. The prepared antibody solid phase was stable for one year when stored at 4 °C. The optimized assay involves the incubation of 50 ml of testosterone standards (0.3-10 ng/ml), 100 ml of magnetizable cellulose particle coupled antibody suspension and 100 ml of ¹²⁵I-testosterone derivative for 4 hours at 37 °C. At the end of the incubation, the tubes were placed on a magnetic rack for 10 minutes after the addition of wash buffer and decanted. The sensitivity of the assay is 0.2 ng/ml. The intra-assay variation was <15% throughout the assay range. The recovery varied from 88 to 115%. On dilution of samples having high levels of testosterone, linearity ranged between 87 and 125%. Correlation coefficient of 0.978 was obtained when the developed solid phase assay was compared to the earlier established liquid phase assay.