Characteristics Of Solid Particles Research Articles

A modified kinematic model for particle flow in moving beds

Granular materials are utilized in a wide variety of industrial applications. The complex hydrodynamics of granular flow is still not fully understood. The flow characteristics of solid particles in a two-dimensional moving bed were studied experimentally and theoretically. The effects of mass velocity, properties of particles and the shape of moving bed on flow pattern were examined. The experiments show that the mass velocity of solid particles and the placement of baffles in stagnant zones have no effect on flow pattern. The shape, size and repose angle of particles affect the flow pattern greatly. The particles have more liquidity and the mixture between particles is easier with the increasing of sphericity degree of particles and the decreasing of particle size. The shape of flowing zone becomes more sharp-angled with the increasing of the repose angle, and the stagnant zone becomes larger. The kinematic model was used to simulate the particle flow. For center discharge the simulation results are in agreement with experiment data very well, while for eccentric discharge the simulation couldn't show the effects of side walls on particle flow. An analytic solution of kinematic model was obtained by Lie transformation group. It shows that the velocity of particle flow is the maximum when x equals 0. The method of translational coordinate was used to modify the traditional kinematic model in order to make sure the x value of each point on the maximum particles velocity distribution lines is zero. The modified kinematic model could simulate the eccentric discharge well, and the field of kinematic model applications was expanded.

Adhesion of an Aqueous Polymeric Suspension to Inert Particles in a Spouted Bed

Among the several unit operations that seek the modification of superficial characteristics of solid particles, the spouted bed appears as efficient technology for coating of coarse particles (d p >1 mm). This work aimed at investigating the fluid-dynamics of the conventional spouted bed during a coating process, using several inert particles such as polystyrene, polypropylene, polyethylene of low density, ABS®, placebo tablet and glass beads, and analyze the influence of the physical properties of the particles and of the polymeric coating suspension on the fluid dynamics. The suspension was characterized by the surface tension, density, rheology, and contact angle between the suspension and the solid surface. It was verified that the particles having a high contact angle with the suspension (polystyrene, polypropylene, and low-density polyethylene) were not coated, and drying of the suspension was obtained in these cases. For the other particles (ABS, tablet, and glass beads), coating efficiencies in the range of 76–90% were obtained. The shape, angle of repose, and density of particles affected the fluid-dynamic during the coating, and also the inter-particle friction and the particle circulation velocity in the bed.

Interactions of selenate with copper(I) oxide particles.

The chemical mechanisms responsible for the immobilization of selenate (SeO4(2-) from aqueous solutions on cuprite (Cu2O) particles were determined from batch experiments. This was achieved by performing both solution-phase analyses and characterization of solid particles by X-ray photoelectron spectroscopy and transmission electron microscopy techniques, after equilibration of cuprite particles with selenate-containing solutions at various pH values, solid-to-solution ratios, and ionic strengths. Two distinct mechanisms have been pointed out. In the acidic medium, where the acid-catalyzed dissolution of cuprite into CuI species occurs, the immobilization of selenate implies a redox reaction with transient CuI leading to the precipitation of copper(II) selenite, CuSeO3. In the absence of protons added in the medium, Cu2O is chemically stable and immobilization of SeO4(2-) is essentially due to adsorption in the form of an outer-sphere surface complex. The uptake level of selenate by Cu2O is markedly lower than that observed for selenite species in the same conditions.

Heat transfer of multiple impinging jets with gas–solid suspensions

The heat transfer mechanism of multiple impinging jets with gas–solid suspensions has been investigated experimentally and numerically. By heat transfer experiments, the effects of nozzle Reynolds number, solid loading ratio, distance from jet exit to impingement surface, spacing between jets and solid particle characteristics on the heat transfer coefficient were cleared. In the case of using graphite particles, the heat transfer coefficient enhancement as against single phase flow are found all over the heat transfer surface. While, in the case of using glass beads particles, the heat transfer coefficient is decreased compared with single phase flow. Numerical simulation were also performed by using Yokomine et al.'s model in which both turbulence augmentation and suppression due to particles can be taken into account. In the case of graphite particle, particles flow near the heat transfer surface with making belt-shaped dense region after impingement and its heat capacity and function of turbulence augmentation are used effectively. When the glass beads are used, particles are scattered after impingement and turbulent kinetic energy near the heat transfer surface is decreased.

Analysis of flame gas velocity and temperature distribution from double-pipe nozzle jet in a production unit for spherical particles by flame spray method

The flame spray method for preparing spherical powders is a technique in which solid particles are forced to fuse into spheres by exposing them directly to the combustion flame, and has already been applied to producing ceramic (metal) spherical powders. With this technique, it is critical to analyze quantitatively the fusing and sphering characteristics of solid particles, and thus the distributions of gas velocity and temperature of the flame gas have to be calculated first. However, little research has been conducted regarding this subject. In this study, a combustion model is formulated to calculate the profiles of gas velocity and temperature for the fuel gas flame jetted from the commonly used coaxial double-pipe nozzle. The calculation agrees roughly with the flame shape observed in experiments, implying the possibility of using this model to calculate the heat transfer from flame gas to solid powders. © 1997 Scripta Technica, Inc. Heat Trans Jpn Res 25(4): 201–213, 1996

A model for prediction of the effective thermal conductivity of granular materials with liquid binder

A model is developed to predict the effective thermal conductivity of a three-component system containing sand particles bonded with liquid binders. The effective thermal conductivities of the bonded and unbonded sands are measured by the line-heat-source method at room temperature. The parameters of a two-component model are determined from the measurements for unbonded sands. Finally the model for the three-component systems such as bonded sand is developed using the assumption of the coalescence of the liquid binder at the particle contact points. Comparison between the experimental results and the model predictions shows that the model developed in this study predicts well the effective thermal conductivities of fluid-saturated sand or sand bonded with liquid binders. Also, this model can be used to determine the effects of the parameters such as the thermal conductivities and the volume fractions of components and the geometrical characteristics of solid particles on the effective thermal conductivity of granular materials with or without the liquid binder.

Optical studies on the turbulent motion of solid particles in a pipe flow

An extension of an axial viewing optical technique (first used by Lee, Adrian & Hanratty) is described which allows the determination of the turbulence characteristics of solid particles being transported by water in a pipe. Measurements are presented of the mean radial velocity, the mean rate of change radial velocity, the mean-square of the radial and circumferential fluctuations, the Eulerian turbulent diffusion coefficient, and the Lagrangian turbulent diffusion coefficient. A particular focus is to explore the influence of slip velocity for particles which have small time constants. It is found that with increasing slip velocity the magnitude of the turbulent velocity fluctuations remains unchanged but that the turbulent diffusivity decreases. The measurements of the average rate of change of particle velocity are consistent with the notion that particles move from regions of high fluid turbulence to regions of low fluid turbulence. Measurements of the root-mean-square of the fluctuations of the rate of change of particle velocity allow an estimation of the average magnitude of the particle slip in a highly turbulent flow, which needs to be known to analyse the motion of particles not experiencing a Stokes drag.

Recent work in Japan on the mixing of solids

During the last ten years, about sixty papers dealing with solids mixing, segregation, sampling and simulation have been published in the academic journals in Japan. This review surveys the literature related to the motion and flow characteristics of solid particles, the power consumption of mixers, continuous mixing, and simulation of the mixing processes.

高分子凝集剤を使用した場合の水中沈積物の特性について

高分子凝集剤を使用した場合の水中沈積物の特性について

Determination of Turbulence Characteristics of Solid Particles in a Two-Phase Stream by Optical Autocorrelation

Application of optical autocorrelation techniques enables determination of Lagrangian correlation, scale, and intensity of turbulent motion of solid particles in a two-phase stream. This method allows measurement of both longitudinal and transverse correlations.

Sedimentation in Emulsions of Water Petroleum

Introduction An appreciable number of the oil fields in Western Canada are accumulations of heavy black oils in more or less unconsolidated sandstones. When the crude oils are produced by conventional means, they are frequently contaminated with both sand and oilfield water. The water is usually present as emulsified water, and the sand and other solid material are suspended in the emulsions. The presence of the solid material in the crude oils is troublesome and, in general, little is known about the behavior of suspended solid particles in emulsions. The Stokes equation describes the behavior of suspended particles in homogeneous fluids in terms of particle size, density differential, and fluid viscosity. In the case of an emulsion, particle size and density differential introduce no difficulties, but considerable doubt centers around the viscosity term. For crude oil emulsion the Simha equation and the data presented by Fukushima and Ichimura show a non-linear dependence of the viscosity ratio on the water concentration. While it is undoubtedly reasonable to use these data for predicting the viscosity of a specific emulsion, and while it is equally reasonable to expect the calculated viscosity to predict the settling rate of a solid spherical particle in the emulsion by means of Stokes equation, there seems to be no direct evidence that this calculation is indeed sound for describing the settling rates of solid particles in emulsions of water in crude oils. Procedure A direct approach to the problem was thus indicated. Laboratory equipment was designed and built for the direct determination of the rate-of-fall characteristics of solid particles in emulsions of water in oil. Although the apparatus incorporated the basic design of conventional falling-ball viscometers, the study was concerned directly with the rate-of-fall characteristics of particles in emulsions, rather than with the viscosity of the emulsions as such.