Review of electrical separation methods

Manouchehri, Hamid-Reza; Rao, K. Hanumantha; Forssberg, K.S.E.

doi:10.1007/bf03402825

Cited by 16 publications

(13 citation statements)

References 12 publications

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“…This work, which describes the separation of ordered 2D Coulombic crystals of charged, millimetre-sized T and N spheres from less-charged Au N spheres, is important for at least three reasons: (i) the system of charged and uncharged spheres provides a simple, physical model for nucleation of crystals, and thus for phase separation by formation of a crystalline, ionic phase—the pattern of T and N spheres we observe upon self-assembly resembles the (100) plane of a face-centered cubic lattice; (ii) as with a previous system involving electrets,5 it demonstrates our ability to predict complex behaviors in multi-component systems based on an understanding of electrostatics; and (iii) the electrostatic separation of mesoscopic particles, charged by contact electrification, from a heterogeneous mixture is important in a number of technologies:7 examples include the purification of coal8,9 and the sorting of mixtures of plastics for recycling 10. Other methods for the separation of mesoscopic particles are based on separation by size,11 magnetic forces,12 and thermal adhesion 13…”

mentioning

confidence: 52%

Phase separation of 2D meso-scale Coulombic crystals from meso-scale polarizable “solvent”

et al. 2009

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This paper describes the phase separation of millimetre-scale spheres based on electrostatic charge. Initially, polymeric (Teflon, T;6, N) and metallic (gold-coated 6, Au N ) spheres are uniformly mixed in a two-dimensional (2D) monolayer on a gold-coated plate. Oscillating the plate vertically caused the spheres to charge by contact electrification (tribocharging). Positively charged N and negatively charged T spheres attracted each other more strongly than they attracted the capacitively charged, Au N spheres. The T and N spheres formed 2D Coulombic crystals, and these crystals separated from the Au N spheres. The extent and rate of separation increased with increasing amplitude of agitation during tribocharging, and with decreasing density of spheres on the surface. At high surface density, the T and N spheres did not separate from the Au N spheres. This system models the 2D nucleation of an ionic crystal from a polarizable liquid.This communication describes the separation of a mixture of ~3mm spheres 6, N; Teflon, T; and gold-coated Nylon, Au N )-on agitation in two-dimensions-into an ionic crystalline, two-dimensional (2D) phase having the composition T -N + , and a disordered phase comprising Au N spheres. 1 Teflon and Nylon spheres, when agitated together, charged oppositely by contact electrification. 2,3 These polymeric spheres aggregated and separated from the gold-coated spheres, which were, on average, electrically neutral (Fig. 1). The objectives of this research were: (i) to test our prediction that mixtures of oppositely charged objects would crystallize and separate from non-charged objects when agitated, and (ii) to explore the effects of experimental parameters (e.g., amplitude and frequency of agitation, and density of spheres) on the separation.Contact electrification is the process by which electrostatic charge transfers between objects when their surfaces contact and separate. 2,3 When charged, one object has a positive charge and the other a negative charge. From our work with ionic electrets-materials that have a covalently bound ion and a mobile counterion-we have shown that the transfer of ions can lead to contact electrification. 3,4 We have demonstrated that contact electrification can direct the self-assembly of micron-sized ionic electrets into ordered three-dimensional microstructures, 4 and millimetre-sized spheres into ordered 2D rings and lattices. 5,6 † This paper is part of a Soft Matter theme issue on Self-Assembly. Guest editor: Bartosz Grzybowski. ‡ Electronic supplementary information (ESI) available: Experimental procedures; derivation of eqn (1), the limits of separation (Φ), and the scaled separation (Φ*); Fig. S1 This work, which describes the separation of ordered 2D Coulombic crystals of charged, millimetre-sized T and N spheres from less-charged Au N spheres, is important for at least three reasons: (i) the system of charged and uncharged spheres provides a simple, physical model for nucleation of crystals, and thus for phase separation by formation of a cr...

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confidence: 52%

Phase separation of 2D meso-scale Coulombic crystals from meso-scale polarizable “solvent”

et al. 2009

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“…[2] While most applications utilize differences in natural or induced conductivity of materials with the corona-drum type separators, triboelectric charging behavior with free-fall separators is also used at industrial scales. [3] A sample of applications of electrostatic processing reported in the literature is listed in Table 2.…”

Section: Mineral Applicationsmentioning

confidence: 99%

Triboelectric Belt Separator for Beneficiation of Fine Minerals

Bittner

Hrach

Gasiorowski

et al. 2014

Procedia Engineering

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Separation Technologies, LLC (ST) has developed a processing system based on triboelectric charging and electrostatic separation that provides the mineral processing industry a means to beneficiate fine materials with an entirely dry technology. The environmentally friendly technology can eliminate wet processing and required drying of the final material. The process requires little if any pre-treatment of the material other than grinding and operates at high capacity -up to 40 tonnes per hour by a compact machine. Energy consumption is low, approximately 1 kWh/tonnes of material processed. Since the only potential emission of the process is dust, permitting is typically relatively easy. In contrast to the other available electrostatic separation processes that are typically limited to particles greater than 75 μm in size, the ST belt separator is ideally suited for separation of very fine (<1 μm) to moderately coarse (300 μm) materials with very high throughputs. The triboelectric particle charging is effective for a wide range of materials and only requires particle -particle contact. The small gap, high electric field, counter current flow, vigorous particle-particle agitation and self-cleaning action of the belt on the electrodes are the critical features of the ST separator. The high efficiency multi-stage separation through charging / recharging and internal recycle results in far superior separations and is effective on fine materials that cannot be separated at all by conventional electrostatic techniques. Since 1995, this triboelectric technology has been extensively used for the beneficiation of coal fly ash with eighteen separators in place and over 130 machine-years of operation at locations in North America and Europe. The technology has been also successfully applied to the beneficiation of a variety of minerals including calcium carbonates, talc, and potash. Recently, dry electrostatic separation has been successfully demonstrated for beneficiation of phosphate ores.

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“…5, the magnitude of charge density increases with increasing air velocity. The reason is, an increase of air velocity in fluidized bed causes an increase in the impact force and frequency between the particles and their contacting surfaces [13,14,23]. More importantly, Fig.…”

Section: Charging Propertymentioning

confidence: 99%

“…The electrostatic separation methods that can separate the mixed materials are corona discharge, induction electrostatic and triboelectrostatic. Corona discharge and induction electrostatic can separate a mixture of conductor/non conductor; whereas, triboelectrostatic method has the advantage of separating different types of materials [13][14][15][16]. Tribo charging phenomenon is utilized in numerous technical applications, such as electro-photography, electrostatic copy and printing techniques, electrostatic filtration, precipitation and coloring.…”

Section: Introductionmentioning

confidence: 99%

“…Hence, many efforts to find the proper physical method have been attempting for a long time. In general, physical separation techniques that can recycle the mixed plastics are classified by electrostatic separation, dry and wet gravity separation, froth flotation, NIR and color sorting [2,[10][11][12][13]. Gravity separation is difficult for materials of similar specific gravity, such as PVC and PET [11].…”

Section: Introductionmentioning

confidence: 99%

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