Separation Of Fine Particles Research Articles

Effect of dense medium properties on the separation performance of a dense medium cyclone

Extensive separation tests were carried out on a 6″ dense medium cyclone loop with the use of density tracers to study the effects of medium stability and rheology on the separation of fine particles. The medium properties were modified by changing the magnetic particle size and medium density. Four magnetite samples with RRB size modulus d 63.2 ranging from 4.7 to 33 μm were used, and the medium densities were varied from 1.2 to 1.7 s.g. It was found that, while the separation efficiency and cutpoint shift for coarse particles (>2.0 mm) were mainly determined by the medium stability, the separation performance of fine particles (<0.5 mm) was more sensitive to the change in medium rheology.

Separation and classification of fine hematite particles using a glass bead column bed

It was found that polydispersed hematite particles with a size distribution ranging from 0.1 to 0.6 μm dispersed in water could be efficiently removed from water or divided into two size classes depending on the pH by passing them through a column bed of glass bead. Complete solid/liquid separation of hematite particles was observed in the pH range between 3 to 7, where hematite particle are positively charged, while glass beads are negative. In the pH range from approximately 7.5 to 10, the smaller particles were adsorbed onto the glass beads, while the remaining larger ones passed through the glass bead column bed as an effluent. The size classification was most efficient at pH 8. In the pH range above 11, adhesion of hematite to glass beads was not observed. A tenfold increase in flow rate had virtually no influence on the results. The experimental results were explained in terms of the DLVO theory, with a sphere-plate model.

Cyclone Separators for Fine Particles and Difficult Operating Conditions

The separation of fine particles from gases with particle sizes of about 1μm is still a difficult problem, especially at high solids loadings of the gas stream and high gas temperatures. Practical experiences show that the separation efficiency really obtained with hot gas cleaning is generally less than calculated. Based on new experiments and a better calculation procedure, it is also possible to use cyclone separators for these separation problems. For a successful solution, it is necessary to increase the knowledge about the gas/solids flow and to pay attention to the boundary layer flow within the cyclone, but also to think about new multi-stage separation processes.

Study of the Shape Separation of Fine Particles Using Fluid Fields

Study of the Shape Separation of Fine Particles Using Fluid Fields

The Role of Colloid Interactions in Solid-Liquid Separation

Forces between particles in water become especially important when the particles are in the colloidal size range (less than a few mm). To a first approximation inter-particle forces or colloid interactions are linearly dependent on particle size and they become stronger, relative to external forces, as particle size decreases. The separation of fine particles from water by processes such as coagulation, filtration and flotation can be crucially dependent on the manipulation of colloid interactions, usually to promote attachment of particles to each other or to surfaces. The most important types of colloid interaction are briefly discussed. These include van der Waals forces, electrical interaction, hydration forces, hydrophobic interaction and effects associated with adsorbed polymers, such as steric repulsion and polymer bridging. These are all short-range interactions, which have little influence on the transport of particles but which can have a major effect on collision efficiencies and on the adhesion between particles. Some examples of solid-liquid separation processes in which colloid interactions are important are given.

Concentration of oil-in-water emulsion using the air-sparged hydrocyclone

The air-sparged hydrocyclone was originally designed for use in the mineral processing industry. Certain properties that make it very effective in that area have now been exploited in a wastewater treatment application - the removal of emulsified oil from water. Statistical design experimental procedures were used to investigate the interrelationship between several operating variables. This led to optimisation of the oil removal process with this unit and production of treated water with 95% removal of the turbidity resulting from the emulsified oil. The optimization work also led to an understanding of the mechanism of oil removal. This is compared with the mechanism of separation of fine particles using the same device. The use of the air-sparged hydrocyclone in a one- or two- stage oil removal process was explored and efficiencies compared under various operating conditions.

The process of separation of fine mineral particles by flotation with hydrophobic polymeric carrier

A new process to concentrate fine and ultrafine mineral particles from aqueous suspensions is reported. This process is based on the attachment of mineral particles to the surface of polymeric carrier particles via hydrophobic interactions. The carrier used here was polypropylene treated with oleic acid and studies were conducted with various mineral fines model systems. Polypropylene particles coated with mineral particles can be separated from the pulp either by screening, settling or by flotation resulting from their relative densities. Flotation takes place when mineral particles are “carried” up to the air/pulp interface as aggregates with densities less than unity (levitation). Detachment of carried mineral particles was performed by stirring in alkaline suspensions. This introductory article reports basic features, main operating parameters and examines some practical examples of the process at bench scale.

A study of the potential for improved separation of fine particles by use of rotating spirals

In previous work an analysis of the primary flow and secondary circulation on a spiral was developed and an approximate model was derived for the free motion of particles within the slurry. The main features of the fluid and particle motion were subsequently investigated experimentally and found to be in reasonable agreement with predictions based on free motion on a spiral trough. The theoretical basis is briefly reviewed and the current limitations of the model are discussed. The extensions to the theory needed to include an external rotation are then introduced and the results of a range of simulations for both coal and heavy mineral spirals are presented.

A nucleation process for the separation of fine particles from flue gas

A more efficient (> 99.9%) nucleation method that removes a wider range of gas stream fine particles (several μm down to 7 nm) than previous methods is proposed. As the gas stream passes through supersaturated vapor in a flow cloud chamber (FCC), water vapor condenses onto the particles which settle out with appreciable velocities. Particles with a travelling distance less than the chamber length are removed. Three types of test aerosol are used to demonstrate the efficiency of this cleaning method, which is found to increase with increasing supersaturation, wettability of particles, particle size, and length of the FCC, and to decrease as flow rate, particle concentration, and height of the chamber increase. Suggestions on how to achieve desired efficiencies at less cost are also given.

Investigations on fine particle separation using an electrostatic nozzle scrubber

Numerical simulations of particle/drop interactions shows an increased separation especially in the fine particle range. Using this principle charged particles are deposited on oppositely electrostatic charged drops. An electrostatic nozzle scrubber for particle separation was developed. In this paper the charging system for both components and first results of grade efficiency measurements are presented.

流体場を利用した粒子の形状分離に関する基礎的検討 湿式サイクロン中における不規則形状粒子の運動特性

In order to apply hydrodynamic fields to the shape separation of fine particles, the dependencies of dynamic properties of particles in a cyclone on the particle shape were discussed. Glass beads, glass powders, silica sands and mica particles in a 10-100μm size range were classified into five fractions by wet cylclones. The equivalent diameters of classified particles were measured by a free settling method, and the geometric parameters were obtained from SEM microphotos. The Stokes diameters in free settling were in agreement with the mean values which were estimated for an ellipsoid and a thin disc to settle in random orientation. On the other hands, Stokes diameters in the cyclones were smaller than those in free settling. The discrepancy between these diameters was large especially for flaky mica particles, suggesting that a cyclone can be used to separate flaky particles from blocky ones.

Influence of temperature on particle separation in granular bed filters

The present study deals with the influence of temperature on the separation of fine dust particles in granular bed filters. Collection within the diffusion regime for particles smaller than 0.5 μm becomes more effective with increasing temperature. However, for larger particles subject to the influence of inertial forces, a drop in separation efficiency is to be expected due to increasing drag forces. With the aid of experimentally determined grade efficiencies at temperatures up to 800 °C, the influence of temperature and other important filtration parameters such as the filter medium's grain size or the filter face velocity, are quantitatively derived and discussed. Investigations concerning the long-term filter behavior have shown that the formation of a filter cake significantly improves separation efficiency. This not only depends upon the characteristics of the dust in question, but also is a function of the grain size of the filter medium and the filtration velocity. Under cake filtration conditions, high collection efficiencies may also be attained at temperatures up to 800 °C.

Hydrophobic interaction in flocculation and flotation 1. Hydrophobic flocculation of fine mineral particles in aqueous solution

In this paper the flocculation behavior of fine mineral particles rendered hydrophobic by the surfactant and the mechanism of hydrophobic flocculation are discussed. Experimental studies with quartz, rhodochrosite, hematite and rutile show that changes in wettability of mineral surface significantly affects the stability of fine particle suspensions. The hydrophobization of particle surface is often accompanied by a distinct flocculation which may by no means be interpreted by Derjaguin—Landau—Verwey—Overbeek (DLVO) theory. The theoretical approach to hydrophobic flocculation and calculation related to the quartz—amine system as well as to the rhodochrosite—oleate system shows that the potential energy of hydrophobic interaction between mineral particles rendered hydrophobic by surfactant far exceeds that resulting from double layer or van der Waals interactions. Flocculation induced by hydrophobic interaction between fine mineral particles plays a predominant role in many techniques of fine particle separation, such as shear flocculation, emulsion flotation, carrier flotation, spherical agglomeration, etc.

Separation of fine particles by laminar flow in a tilted slender tube slowly rotating around the longitudinal axis

Fractionation of fine (∼10-μm) particles by their size, density, or both was studied. A laminar flow of suspended particles through a tilted slender tube that slowly rotates around the tube axis separated fine particles into two fractions according to the sedimentation velocity of the particles. The threshold of separation was mainly governed by the rotation period, which depends on the particle size. Nearly spherical particles of silica gel were separated experimentally. A two-step operation yielded a fraction of particles of uniform size (half-width, ∼0.7 μm) with a mean diameter of ∼5 μm. The particle-size threshold was close to the theoretical value

Magnetic separation of fine particle dusts using a superconducting magnet and wire meshes

We have observed a phenomenon that flow patterns of gases are influenced by a magnetic field. To explain this phenomenon, a model called a ‘‘magnetic curtain’’ has been introduced. In this paper we apply this phenomenon to magnetic separation of fine particle dust in air. We use a superconducting magnet and fine ferromagnetic wires to obtain high magnetic field and high field gradient. Magnetic separation of fine particles is well realized. The efficiency of fine particle filtration increases with increasing magnetic field and also increases with particle size. The percentage of captured particles is 80% for particles larger than 1 μm, 60% for 0.5–1.0 μm, and 35% for 0.3–0.5 μm, respectively, when the field intensity is 4.5 T and the gradient is 1500 T/m.

Packed-Bed Column Flotation of Fine Coal. Part I. Laboratory Tests and Flotation Circuit Design

An advanced packed column (or static tube) flotation system developed at Michigan Technological University offers the potential for sharp separation of fine coal particles from mineral matter and can be readily incorporated into practice for efficient coal processing at reduced costs. The essential element of the system is the packed-bed cell design in combination with a controlled dispersion reagent scheme. A clean coal concentrate of less than 3% ash (in some cases below 1%) was produced in a single stage of the packed column flotation at more than 90% heating value recovery from several of the major U.S. bituminous coals, including Lower Kittanning and Pittsburgh seams. A two-stage flotation circuit with intermediate regrind of the first stage concentrate for re-treatment in the second stage improved the coal quality, and/or recovery.

Prediction of separation process results in OGMS

The wet magnetic separation of ore fine particles containing 32–40% of iron in the form of hematite is experimentally investigated. The extraction parameter distribution W( X) of particles is obtained at the open-gradient magnetic separator, X = κD 2, κ - being the relative magnetic susceptibility of a paramagnetic or diamagnetic particle, D, its size.

Continuous separation of fine particles in nonaqueous media in a lamella electrosettler

In this paper, we describe the continuous operation of a lamella electrosettler and measurement of concentration profiles inside a lamella electrosettler to establish the existence of three sedimentation layers. This device was tested with a kerosene slurry containing fine alumina particles stabilized with a commercial surfactant, Aerosol OT. The measurement of concentration distribution of alumina particles inside the lamella electrosettler was made using our x-ray densitometer system. As a limiting case for low feed flow rates and low applied electric field strengths, a kinematic clear-fluid interface height formula was derived that describes the steady horizontal interface height as a function of angle of inclination, strength of applied electric field, and net clarified fluid overflow rate. A predictive hydrodynamic model of a continuous lamella electrosettler based on two-phase flow theory was developed and the experimentally obtained alumina concentration distributions were compared with the computed predictions of the hydrodynamic model. The computed variation in suspension layer concentration qualitatively agreed with the experimental measurements.

傾斜回転液管を用いた微粒子の連続分離法

傾斜回転液管を用いた微粒子の連続分離法

Electro-Acoustic Dewatering (EAD) a Novel Approach for Food Processing, and Recovery

Abstract Separation of liquids from fine particle suspensions plays an important role in many industrial processes. In the past few years a number of technologies have been developed for the separation of slurries with coarse particle suspensions and intermediate particle sizes. However, separation of fine particles from their suspensions can be difficult and prohibitively costly. Battelle has developed a solid/liquid separation technology that utilizes differences in electro-kinetic and acoustic properties to enhance the efficiency of conventional solid/liquid separation techniques such as vacuum filters or presses. This method can dewater colloidal stable suspensions better than conventional techniques. Typical applications of this technology to food processing will be presented. Mechanisms involved during separation will also be discussed.