Electrostatic Separation Process Research Articles

Modeling of the Electrostatic Separation Process in a Novel Turntable Installation for the Plastic Waste Recycling Process

Modeling of the Electrostatic Separation Process in a Novel Turntable Installation for the Plastic Waste Recycling Process

Effect of ambient humidity on the tribo-electrostatic separation of granular plastic wastes

The separation of plastic mixtures from waste electrical and electronic equipment is an increasingly active domain of research. Several electrostatic separation processes and devices have been developed to recover plastic waste. All these processes are based on the use of the triboelectric effect to charge the plastic granules to separate them in an intense electric field. The objective of this study is to investigate the effect of ambient humidity on the efficiency of the triboelectric charging and electrostatic separation process, especially in an industrial environment where granular plastic waste may contain residual moisture due to previous processing by flotation or inappropriate storage. The experiments were carried out using a rotating-multi-cylinder tribocharger and a roll-type electrostatic separator. The samples were composed in equal proportions of either: (1) acrylonitrile butadiene styrene (ABS) and polystyrene (PS) or (2) polypropylene (PP) and polyethylene (PE), the average particle diameter of which was between 2 and 6 mm. The efficiency of the tribo-electrostatic separation was evaluated by measuring the purity and recovery of the products. The results confirm that separating (ABS + PS) and (PP + PE) mixtures is feasible. The best separation results were obtained when the materials were stored and processed at an ambient relative humidity of around 50%.

Behavior of Insulating Particles in an Electrostatic Separator Associated With a New Spiral-Type Tribocharger

Electrostatic separation processes are emerging as the solution of choice for recycling waste from end-of-life equipment in various industries. The separation of the different constituents of such plastic mixtures is the key to successful recycling. The main objective of this work was the development of a new spiral-type tribocharging device with application in the field of electrostatic separation. The spiral charger offers a very high charging rate compared to other triboelectric systems. It favors collisions of the particles with the inner wall, which is very efficient to separate a mixture of ternary particles. The study was conducted with samples of various medium-sized (2–5 mm) granular plastics, for several values of air velocity, pipe length, and particle mass in the turbocharging device. The spiral charger was associated with a belt-type electrostatic separator to process a granular insulating mixture, consisting of three types of plastic products Polyvinyl Chloride, Polypropylene, and Polystyrene. This work also aims at numerically simulating the dynamic behavior of insulating particles in belt-type electrostatic separators. The good separation obtained for this ternary mixture shows the efficiency of the new tribocharger.

Design of experiments for the adjustment of fuzzy logic-based controls of an Electrostatic Separation Process

Wydawnictwo SIGMA-NOT wydaje czasopisma fachowe informujące swoich czytelników o najnowszych osiągnięciach naukowych i nowoczesnych rozwiązaniach technicznych w Polsce i na świecie, popularyzuje problemy techniczne oraz poszerza wiedzę i kulturę techniczną.

Characterization and processing of low-grade iron ore from the Khanguet mine by electrostatic separation

Purpose. Choice of a method for treating the iron ore of the Khanguet mine depending on its characterization. Methodology. This work is focused on the study on physicochemical and mineralogical characterization of the poor iron ore of Khanguet mine, using multiple analysis techniques (X-ray diffraction, X-ray fluorescence, scanning electron microscope and optical microscope), to identify the chemical composition and mineral phases of the ore. The study also focused on the possibility of enrichment, using the electrostatic separation process. For this purpose, two main parameters are studied, such as, the voltage between the electrodes and the rotation speed of the roll. Findings. The results of the characterization show the possibility of using the process of electrostatic separation for the enrichment of the Khanguet ore, which allows increasing the content of Fe2O3 up to 58.46%. Originality. The originality of this work is the possibility to use the electrostatic treatment process for the poor iron ore of the Khanguet iron mine. Practical value. This study shows that the results obtained by the process of electrostatic treatment of ore are very significant; this technique makes it possible to obtain a concentrate with an iron content of 58.46% and to bring an added value to the company and the steelmaking industry, on the one hand, and, on the other hand, to eliminate reserves of these poor iron ores stored near the mining site, which is harmful for the environment.

Identification of rare-earth minerals associated to K-feldspar: Capacsaya project in Peru

A recently discovered the rare-earth-rich site in Capacsaya, located at 123 km northwest of Cusco, at the south of Peru, contains significant quantities of light and heavy rare-earth elements such as neodymium, lanthanum, cerium, europium, and yttrium. This work reports the identification of rare-earth elements and their associated minerals using scanning electron microscopy, energy-dispersive X-ray spectroscopy and X-ray diffraction analyses. Five (5) samples extracted from different locations at the Capacsaya site were characterized and identified K-feldspar as the mineral associated with the rare-earth elements in a representative sample with a high concentration of lanthanum and cerium. The results showed rare-earth elements contained within the mineral phase monazite, being cerium the dominant element in the phase (La, Ce, Nd)PO_4. Finally, through the electrostatic separation process we demonstrate that it was possible to achieve an efficient separation of the K-feldspar phase in the particle size range 75–150 upmum.

Numerical Simulation and Experimental Observation of Charged Particles Trajectories in Roll-Type Electrostatic Separators

Accurate prediction of the effects of the various factors that might influence the outcome of novel electrostatic separation process requires reliable physical and mathematical models for the numerical simulation of particle trajectories. The major objective of this article was to demonstrate that the use of a high-speed camera for recording particle trajectories could be instrumental in refining the understanding of the complex physical phenomena that occur in these electrostatic devices and in improving their operating conditions, based on valid numerical simulation results. The experiments were carried out with spherical conductive particles, using a roll-type corona-electrostatic separator. The particles trajectories were recorded using a high-speed camera at acquisition frame rate of 200 fps. The electrical field computation and the resolution of the differential equation of motion of the particles under the action of electrical and mechanical forces exerted on them enabled the prediction of the outcome of the separation process. The study was carried out for particles of different sizes, for different high voltages applied to the electrodes and for different electrode positions. The simulation results were in good agreement with the experimental data.

Cement matrix containing lightweight aggregate based on Non-Metallic Fraction Printed Circuit Boards (NMFPCB'S)

Materials such as river sand, used in construction, have a high demand, and thus generate great environmental impacts while being extracted, such as erosion of the rivers banks and your siltation. With the increasing restriction of river sand extraction which can generate a reduction in the product's offer in the civil construction sector, it is necessary to develop waste recycling technologies for the production of sands with less environmental impact. One of the alternatives for the production of mortar for construction is the replacement of sands extracted from rivers by waste from other industries, such as the electronics industry that presents large and growing production worldwide, due to technological advances. Thus, this work aims to evaluate the influence of partial replacement of quartz sand by lightweight aggregate based non-metallic fraction of printed circuit boards (NMFPCB's) on the properties of cementitious matrix in the fresh and hardened states. For this, the electronic components of the printed circuit boards (PCBs) were removed, they were grinded and then through magnetic and electrostatic separation processes to separate the most valuable and abundant part of metals. The water to cement ratio was 0.48 in all the experiments, the Portland cement to sand ratio was 1:3 (in mass) for the control, and the mortars with NMFPCB's replacement of sand by volume of 25% and 50% were also made. These were characterized mechanically by axial compressive strength test at different ages. The partial results showed that with the increase of sand substitution by NMFPCB's there was a reduction of the mortar consistency index in the fresh state. Results showed that matrix that suffered the substitution of sand by light aggregate, decreased the compressive strength in relation to the reference, but have potential to use in construction industry as blocks or non-structural elements.

Electrostatic separation of particles used as complement to mechanical recycling plant of industrial waste

ABSTRACT This paper concerns the implementation of the electrostatic separation process as complement of the mechanical sorting separators in the recycling industry. Preliminary experiments carried out on the laboratory separator have established the limit values for the speed of the rotating electrode and the high supply voltage for the industrial prototype. Industrial tests have validated the use of electrostatic separation as a complement to the other techniques used for the treatment of waste electrical cables.

A two-step air classification and electrostatic separation process for protein enrichment of starch-containing legumes

A two-step dry fractionation process was investigated that further enriches protein from starch-containing legumes. Legumes (pea, lentil, and chickpea) were subjected to milling, air classification, and subsequent triboelectrostatic separation. The air classification first removes starch, whereas the subsequent electrostatic separation removes fiber from the resulting protein concentrate. Successful enrichment was achieved with pea and lentil, but this was not the case for chickpea due to the smaller starch granules and higher fat content. The best conditions for pea were air classification at an air-classifier wheel speed of 8000 rpm. Subsequently, electrostatic separation was optimized with two passes. With this, a protein purity was obtained of 63.4 g/100 g dry basis and a yield of 15.8 g/100 g dry solids. For the overall two-step dry fractionation process, a protein-enriched fraction with a yield of 4.0 g/100 g pea could be obtained, leading to 7.8% of total protein recovered from yellow pea. Industrial relevanceTo enrich protein from starch-containing legumes a novel dry method combining air classification and electrostatic separation was developed. Compared to conventional wet extraction, this dry route is much less energy-consuming and preserves the native functionality of the proteins. By adding electrostatic separation to air classification, a higher pea protein purity (up to 63.4–67.6 g/100 g) could be obtained, which is higher than that obtained by air classification only (57.1 g/100 g). It is estimated that for an improved dry fractionation process with increased recovery of material, the yield and protein recovery may be further increased with factor ~ 2.8 compared to the current results.

Improving the recovery of copper from electric cable waste derived from automotive industry by corona-electrostatic separation

The aim of this work is to demonstrate the possibility of using electric field forces for the recovery of copper from a fine PVC/Cu granular mixture of low metal content (less than 15%), obtained as “PVC fraction” in the recycling process of electric cable waste from automotive industry, using vibrating table technology. Electrostatic separation of copper granules which are “impurities” in the PVC fraction, increased the overall recovery of copper close to 100%. Granular size classification proved to be a very useful operation in the electrostatic separation process of a particular mixture. The −0.63 mm size class contains the majority of the copper granules and the electrostatic separation allows the recovery of up to 95% copper contained in the granular waste, at purity higher than 99.8%. Copper represents less than 1% in the +0.63 mm size class and can also be recovered with high purity by improving the chopping technology of the cable waste, as well as the separation between the copper and the high conductivity rubber granules.

Shredding as simultaneous size-reduction and tribo-charging operation for improved performances of an electrostatic separation process for granular plastic wastes

Triboelectrostatic separation is a technology which allows the selective sorting of polymer materials based on their surface charging characteristics. Before they are subjected to electrostatic separation, the materials to be sorted are reduced to a proper size (typically less than 5 mm). The present paper aims to evaluate the possibility of using shredding as simultaneous size-reduction and tribo-charging operation and examine the effect of shredding and size reduction on triboelectric charging and electrostatic separation efficiency. The study was performed on typical pieces of PC-ABS and HIPS originating from waste electric and electronic equipment (WEEE). Experiments start by feeding equal quantities of plastic pieces into the shredder. The rotary cutters of the shredder stir the plastic pieces, a charge transfer occurs between the plastic particles by repeated collisions and rubbing against each other. After a certain time, a granular mixture was recovered from the shredder and immediately introduced in a roll type triboelectrostatic separator. The charge of the selectively sorted products was measured using a Faraday cage connected to an electrometer. Four screen mesh diameters were compared (2 mm, 3 mm, 5 mm, and 7 mm). The experimental results confirm that granules can get enough charge during shredding for being successfully sorted by the roll-type electrostatic separator. Particle size is definitively an important factor influencing the outcome of the triboelectrostatic separation. Fine shredding is not favorable, as it requires shredding for extended periods and favors the formation of particle agglomeration. High separation efficiency was obtained for relatively coarse particles.

Electrostatic Separation of Copper and Glass Particles in Pretreated Automobile Shredder Residue

There is increasing demand for an efficient technique for separating automobile shredder residue (ASR) obtained from end-of-life vehicles (ELVs). A particular challenge is the physical separation of conductive materials from glass. In this study, the performance of pretreatment and induction electrostatic separation process was evaluated. The results show that a sieving/washing (combination of sieving and washing) pretreatment was the most effective for removing conductive material compared to electrostatic separation alone. The optimum separation efficiency of copper products was achieved with an applied voltage of 20 kV, a relative humidity of less than 35%, and a splitter position of 8 cm. Although the separation efficiency was slightly reduced when some small glass particles remained attached to the conductive materials, the separation efficiency of copper from the pretreated ASR dramatically increased to 83.1% grade and 90.4% recovery, compared to that of raw ASR (34.3% grade and 58.6% recovery). Based on these results, it was demonstrated that the proposed sieving/washing pretreatment was proficient at removing conductive materials from glass; thus, it has the potential to significantly improve the efficiency of electrostatic separation for ASR.

Recovery of residual metals from fine nonmetallic fractions of waste printed circuit boards using a vibrated gas-solid fluidized bed

Abstract Nonmetallic fractions are essential byproducts of the physical-mechanical recycling process of waste printed circuit boards. Large amounts of metals remain in fine nonmetallic fractions because it is very hard for recycling metals from fine size fraction by traditional technologies. In this study, a vibrated gas-solid fluidized bed was utilized to recover residual metals from fine particles (−0.25 mm size) of nonmetallic fractions obtained from the corona electrostatic separation process. The basic mineralogical characteristics and properties of nonmetallic fractions with a size of −0.25 mm indicated that a considerable amount of clavate glass fibers existed in these nonmetallic fractions. The content of residual metals in the −0.25 mm nonmetallic fractions was up to 19.84 wt%. The major metallic elements found in the nonmetallic fractions were Fe, Cu, Pb, and Sn. The results indicated that removing glass fibers from nonmetallic fractions by triboelectric separation can strengthen the gravity-segregation process between heavy and light particles in fine nonmetallic fractions, resulting in improved metal recovery from 76.39% to 81.41%. Based on this research, an industrial flowsheet for the recovery of metals from fine WPCBs is proposed.

Fly ash classification efficiency of electrostatic precipitators in fluidized bed combustion of peat, wood, and forest residues

The increasing use of biomasses in the production of electricity and heat results in an increased amount of burning residue, fly ash which disposal is becoming more and more restricted and expensive. Therefore, there is a great interest in utilizing fly ashes instead of just disposing of it. This study aimed to establish whether the utilization of fly ash from the fluidized bed combustion of peat, wood, and forest residues can be improved by electrostatic precipitator separation of sulfate, chloride, and some detrimental metals. Classification selectivity calculations of electrostatic precipitators for three different fuel mixtures from two different power plants were performed by using Nelson's and Karnis's selectivity indices. Results showed that all fly ashes behaved similarly in the electrostatic separation process SiO2 resulted in coarse fractions with Nelson's selectivity of 0.2 or more, while sulfate, chloride, and the studied detrimental metals (arsenic, cadmium, and lead) enriched into fine fractions with varying selectivity from 0.2 to 0.65. Overall, the results of this study suggest that it is possible to improve the utilization potential of fly ashes from fluidized bed combustion in concrete, fertilizer, and earth construction applications by using electrostatic precipitators for the fractionating of fly ashes in addition to their initial function of collecting fly ash particles from flue gases. The separation of the finer fractions (ESP 2 and 3) from ESP 1 field fly ash is recommended.

Experimental and numerical investigations of the Laplacian and Poissonian field in asymmetric multiple-electrode systems for electrostatic separation processes

Abstract The paper presents an experimental measurements and numerical computations of the electric field in Laplacian field model as well as Poissonian field model for various asymmetric multiple-electrode configurations prepared to electrostatic separation processes. The asymmetric multiple-electrode systems utilize additional cylindrical rods and/or L-plates connected at constant or floating potential, as in practical applications. The geometries include a cluster of spherical/cylindrical conducting particles uniformly distributed and simultaneously in contact with the ground plate. The charge simulation method integrated with genetic algorithm and method of characteristics is employed for numerical computation and analysis of the electric field in the presented models. Neglecting Deutch’s assumption, the numerical technique is applied to solve Laplace's equation or Poisson's equation with the current-continuity relation. Influence of the cluster of spherical/cylindrical particles on the electric field distribution on the ground plate surface, and its acquired charged, is established. I-V characteristics and the spatial distributions of current density and electric field are evaluated and assessed. The experimental results were found to be in a good agreement with analytical values.

The development of statistical ToF‐SIMS applied to minerals recovery by froth flotation

The role of surface chemistry in recovery of minerals is central to several processes such as froth flotation, leaching, and electrostatic separation. In separation of base metals (eg, Cu, Pb, Zn, and Ni) by froth flotation of their minerals, usually sulphides, the attachment of these mineral particles, after hydrophobic collector addition, to air bubbles is used in operation. The stability of this bubble/particle attachment in both pulp and froth phases is dependent on the hydrophobic/hydrophilic ratio of surface species on individual mineral particle surfaces. The surfaces of individual mineral particles are a complex, distinctly non‐uniform array of hydrophobic collector molecules and hydrophilic species (eg, oxidation products, adsorbed ions, fine particles, and precipitates). Hence, this ratio varies widely between different particles of the same mineral. It has been shown to determine whether particles report, correctly or incorrectly, to concentrate or tail (residue). To improve poor flotation recovery or grade, the analysis needed is the variation of this ratio by particle and as a statistical distribution between different mineral phases across a flotation circuit (eg, feed, successive concentrates, and tails). This requires surface analysis of a large number of particles with high spatial resolution and chemical speciation. In this Surface Science Western special issue article, methods to achieve this, using time‐of‐flight secondary ion mass spectrometry and principal component analysis, developed between the Ian Wark Research Institute and Surface Science Western over 25 years are reviewed with applications to flotation. They are equally applicable to interferences in leaching, extraction, and electrostatic separation processes. Copyright © 2017 John Wiley & Sons, Ltd.

Modelowanie procesu separacji elektrostatycznej wybranych mieszanin polimerowych

Modelowanie procesu separacji elektrostatycznej wybranych mieszanin polimerowych

ANALIZA ROZKŁADU POLA ELEKTRYCZNEGO W SEPARATORZE BĘBNOWYM O RÓŻNEJ KONFIGURACJI ELEKTROD

The static electric field is used in many industrial processes, such as electrostatic separation process. One of the devices that uses a difference in electrical properties of the particles is drum separator. In this device, particles of varying conductivity are electrified in the corona zone and fall on the drum. The particles of high conductivity lose their charges and brake off the drum while the particles of small conductivity keep their charges and are held on the drum surface. To determine the effectiveness of separation is necessary to determine the particle trajectories. Trajectories of separated particles are affected by many factors, among which the most important are: the electrodes configuration, value of high voltage (both factors determine the distribution of the electric field between the electrodes). The article presents the results of analysis of a distribution of the electric field in the drum separator for different configurations of electrodes and the applied voltage.

Physicochemical characterization of a navy bean (Phaseolus vulgaris) protein fraction produced using a solvent-free method

A solvent-free electrostatic separation method was employed to separate navy bean flour (NBF) into protein-rich (PR) and starch-rich (SR) fractions. The physicochemical properties of NBF and separated fractions were compared to proteins (navy bean isolate (NBI) and 7S globulin) prepared using a wet process. Gel electrophoresis confirmed that the protein distribution in the isolated fractions was similar to that of NBF. The protein profile of NBI and 7S globulin was found to be devoid of certain proteins that were found in the NBF and PR fraction. Amino acid analysis revealed that the NBI and 7S globulin had a lower content of sulfur-containing amino acids compared to NBF and the electrostatically isolated fractions. CD and fluorescence spectroscopy confirmed that denaturation of the proteins during the acid precipitation is likely. This novel solvent-free electrostatic separation process preserves the native protein structure found in NBF and improves the recovery of some of the smaller MW proteins.