Typical recycling steps of end-of-life hoses (ELH) include several shredding operations to reduce their size and break down their constituents. Subsequently, various processes such as electrostatic separation or other sorting methods may be employed to recover the constituent materials, which can be reused in new products, thus helping to reduce waste and conserve natural resources. The objective of this study was to validate the possibility of using a newly-patented tribo-electrostatic separator to sort the Polyethylene Terephthalate (PET) fibers and Polyurethane (PU) grains that compose the product obtained after the size-reduction operation of an important class of ELH. The tribo-electrostatic separator consists of a modified rotating-cylinder type triboelectric charger and two pairs of horizontal cylindrical rotating electrodes (length: 460 mm; diameter: 260 mm) connected to two high-voltage sources of opposite polarities (+/- 30 kV), a configuration that is radically different from the standard vertical electrode systems. The initial mixture of shredded ELH, which contained approximately 40 % PET fibers and 60 % PU grains, was introduced into the triboelectric charger, which consists of a cylindrical sieve (length: 460 mm; diameter: 200 mm), rotating at speeds ranging from 5 rpm to 50 rpm. The tribocharger being located in the space between the electrodes, at mid-distance between them, the PET fibers or PU grains are attracted towards the electrodes as soon as they are sufficiently charged or polarized. The tests were carried out using several configurations of the tribocharger, obtained by adding chicanes inside the cylindrical sieve and varying its angle of inclination from 0.2 degrees to 2.5 degrees. Two mixtures of two different sizes, obtained by using two distinct types of shredders were subjected to the tribo-electrostatic separation process. The evaluation of the results was carried out by measuring the mass of the fibers collected at the electrodes and comparing it with the mass of the treated ELH. The tribo-electrostatic separator achieved a PET fiber recovery rate of approximately 25 %, with a purity of around 95 %, performances that make it an efficient solution for the recycling of the polymers contained in this class of waste.

The free-fall electrostatic separator is widely used for sorting plastic particles obtained from waste. The incorporation of flexible electrodes in this installation and the appropriate adjustment of their shapes make it possible to control the particle flow in the electrostatic separation zone, reducing particle-electrode impacts and increasing the quality of recovered products. In this study, we introduce a methodology to optimize the shape and position of flexible electrodes in a free-fall separator. The optimization criterion considered is the horizontal deviation of particles collected in the separator.Theelectrodes are modeled using B & eacute;zier curves with four control points, which provide an infinite number of electrode shapes by adjusting their positions. During the optimization process, only feasible configurations that meet certain constraints are considered. For each feasible configuration, a simulation model is used to obtain the trajectory of test particles, which is experimentally validated using a high-speed camera before being used in the optimization process. A genetic algorithm is used to determine the optimal configuration, which is defined by the position of the four control points of the B & eacute;zier curve. This paper aims to achieve two main objectives: (i) experimentally validate the numerical model of particle behavior in free-fall separators equipped with two flexible electrodes using a high-speed camera; (ii) use the model obtained from the genetic algorithm to determine the optimal shape and position of the electrodes.

Waste electrical and electronic equipment (WEEE) contain heavy metals (mercury, chromium, cadmium, lead, etc.) and halogen materials (bromine, chlorine, etc.), which are toxic for humans and harmful to the environment. WEEE are subjected to shredding and grinding operations, followed by magnetic, eddy-current, optical, and float-sink separation. Electrostatic separation could be added to existing WEEE processing systems to distinctly recover the constituents of such granular waste. The aim was to find viable technical solutions to the problem of electrostatic separation of mixtures of conductive and insulating materials in the recycling industry. The feasibility tests were carried out on representative samples of 200 g of finely-ground materials (size less than 5 mm) originating from the processing of WEEE, using a roll-type electrostatic separator to distinctly recover the conductive and insulating materials. The parameters relevant to the efficiency of the separation were the distance between the electrodes, the level of the high-voltage applied to them, the rotation speed of the drum, and the size of the particles. The quality of the separation was evaluated by measuring the recovery and the purity of the conductive fraction, which in some cases could attain almost 80% and more than 88%, respectively.

A major advance in the recycling of conductive and non-conductive materials contained in granular mixtures originating from industrial waste has been achieved thanks to the development of an innovative corona-electrostatic separator. The aim of this paper is to prove that the new device, equipped with two coaxial vertical cylindrical electrodes, offers a reliable and efficient solution for the selective sorting of copper and plastics from shredded small electrical cables waste. Careful control of operating parameters, such as voltage and air flow, is crucial to achieving optimum separation. Experiments conducted according to the response surface modeling methodology have shown that using a voltage of 30 kV and a flow rate of 1690 m3/min gives the highest recovery rates (beyond 90% for both products) and at purity levels of roughly 80% for plastics and 98% for copper. Further testing under various environmental conditions is recommended to assess the robustness of the electrostatic separation process.

Since the middle of the last century, the electrostatic separation imposed itself as a standard technology in mineral beneficiation. During the last 40 years, it has been more and more widely applied for the recycling of valuable materials (metals, plastics) from industrial wastes. The present paper was aimed to review several recent solutions developed by the authors to surpass several major technical challenges: (i) push the limits of the existing electrostatic separation applications in the recycling industry, in terms of hourly throughput, recovery and purity of the products; (ii) process more complex granular or powdery mixtures, including brominated plastics, and flake-like materials; (iii) recover textile fibers from shredded waste. Described in this short review are: (i) a newly patented modular multi-functional electrostatic separator; (ii) an original procedure for the tribo-electrostatic separation of ternary mixtures of plastics containing brominated flame retardants; (iii) a modified industrial installation for the tribo-electrostatic separation of polyethylene and polystyrene flakes from packaging waste; (iv) a patent-pending equipment for the recovery of PET fibers from end-of-life tires. Research should continue to expand the application of the electrostatic separation in at least the following areas: (i) recycling of composite materials; (ii) recovery of fine powders in food and pharmaceutical industry; (iii) extracting high-value metals from micronized waste electric and electronic equipment.

The recycling of end-of-life tires involves their shredding followed by grinding, which leads to a mixture containing ferrous materials, textile fibers and rubber. Ferrous materials are extracted by electromagnetic separation. The remaining mixture is composed of agglomerates of textile (mainly Polyethylene Terephthalate - PET) fibers and rubber granules. The objective of this study was to validate the possibility of using a new patent-pending tribo-electrostatic separator to sort the constituents of this mixture. The triboelectrostatic separator is made up of a triboelectric charger and two pairs of cylindrical rotating electrodes connected to two HV sources of opposite polarity. The mixture to be treated is introduced inside the triboelectric charger consisting of a sieve cylinder rotating at speeds ranging from 5 rpm to 50 rpm. The electrodes on the left and on the right are connected to two HV sources (± 30 kV) of positive and negative polarities respectively. The electrodes can move horizontally and vertically allowing the test of several geometric configurations of the electrodes and tribocharger system. Thus, the charging zone is also a separation zone so that when the fibers or the gums are sufficiently charged, they are attracted by the electrodes of opposite polarities. The tests were carried out by varying the voltage from ± 5 kV up to ± 20 kV in steps of ± 5 kV. Each test lasted 3 min with a maximum rotation speed of the tribocharger. The comparison between the electrode configurations was made by measuring the mass of the fibers collected at the electrodes.

Abstract The novel device used in this study is a free fall electrostatic separator equipped with flexible electrodes. This special feature enabled the experimentation of different electric field configurations, avoiding as much as possible the impacts of particles on electrode walls, which is the major drawback of standard free-fall electrostatic separators. The present work was focused on the numerical modelling and simulating the trajectories of charged insulating particles. The study was aimed at contributing to a more in-depth understanding of the various physical phenomena that occur during electrostatic separation. An accurate numerical model of particle movement was developed. The results of the numerical simulations were validated using the experimental data obtained with an appropriate image acquisition tool.

Waste minimization is a major way to achieve sustainable development. Electrostatic separation is already used in the recycling industry for processing certain mixtures of shredded plastics originating from waste electric and electronic equipment. Standard tribo-electrostatic separators use electric forces to deflect the trajectories of triboelectrically charged particles in the electric field generated between two vertical plate electrodes connected to high voltage supplies of opposite polarities. However, the efficiency of this device is often limited by the impacts between the particles and the electrodes, which diminish the recovery and the purity of the end product. An innovative electrostatic separator was specifically designed to mitigate this risk. The innovation lies in using two rotating co-axial vertical cylindrical electrodes and assisting the movement of the particles with downward-oriented air flow to reduce their impact on the electrodes and improve the quality of the recovered products. The aim of this study was to optimize the operation of the patented electrostatic separator by using experimental design methodology to obtain quadratic polynomial models of the recovery and the purity of the products as functions of the high voltage applied to the electrode system and of the air flow through the device. The experiments were conducted with a granular mixture composed of 88% polypropylene (PP) and 12% high-impact polystyrene (HIPS) particles, extracted from the recycling process of waste electrical and electronic equipment, and triboelectrically charged in a fluidized bed device. A voltage of 50 kV combined with an air flow rate of 1700 m3/min maximized the recovery and the purity of PP and HIPS products collected at the outlet of the separator. These results open promising prospects for expanding the use of tribo-electrostatic separation for efficient recycling of granular waste plastics.

Triboelectrostatic separation has already been proven its effectiveness as a solution for processing mixtures of plastics originating from waste electric and electronic equipment (WEEE). However, its adaptation to industrial conditions is not straightforward because of the diversity of particle shapes and sizes. This justifies the orientation of this work towards the functional validation of a new vibrating-table-type electrostatic separator (VTE) for granular plastics. In this separator, the granular mixtures are tribocharged in a rotating-cylinder-type device, then fed onto the Plexiglas plate of a vibrating table and subjected to an electric field created between two plate electrodes connected to DC high-voltage supplies of opposite polarities, ± 16 kV, distanced at 8 cm to 40 cm. Under the action of the electric field forces, the particles are deflected towards these electrodes and then recovered in a collector composed of 13 compartments. The experiments presented in the present work demonstrate the effectiveness of this device to separate two distinct mixtures of granules (sizes 2 mm to 6 mm) composed in equal proportions of: (1) polypropylene (PP) and high impact polystyrene (HIPS); (2) acrylonitrile butadiene styrene (ABS) and polyvinyl chloride (PVC). The efficiency of the separation quality was evaluated by measuring the purities and the recoveries of the separated products. The performances of the tribo-electrostatic separation process (60% to 85% of each plastic was recovered at purities higher than 85%) could be further improved by increasing the residence time of the granules in the rotating cylinder of the triboelectric charging device and by appropriate adjustment of the control variables of the VTE: vibration amplitude of the table, level of applied high-voltage, relative position of the electrodes.

This article describes the operation and compares the performances of two devices that can be employed for the separation of conductive and non-conductive particles: a DS-LIM (double sided linear induction motor) separator and an inclined plate electrostatic separator. The aim of the research is to find the link between these two types of separators and whether they can be connected to each other in order to increase the particle separation efficiency and reduce the consumption of electrical energy. The study enabled the evaluation of the factors that influence the performance of each separator. Thus, it was possible to accurately determine the range of particle size extracted for each separation process.

The aim of the present work is to investigate the impact of storage conditions, and more specificazlly of the relative humidity ( RH ) of ambient air, on the triboelectric charging and electrostatic separation of granular insulating mixtures containing brominated flame retardants (BFR). The study was carried out on two model granular mixtures consisting in equal quantities of Polypropylene (PP) / Polyethylene (PE) particles either BFR-free or containing 4.7% of BFR, in mass (i.e., 40000 ppm of bromine). After being stored for 24 hours either in a climatic chamber ( RH = 30%, 50%, 70%, 20 °C) or in ambient air ( RH = 56.5% ± 1.5%; 20 °C ± 2 °C), the plastic particles were tribocharged in a fluidized bed device the walls of which were made of polystyrene (PS). Then they were introduced in roll type electrostatic separator to be selectively sorted. The results showed a slight difference between the different cases studied, best separation results were obtained for mixtures stored at controlled humidity of 50% or under ambient conditions RH 55% to 58%, at temperatures ranging between 18 °C and 22 °C.

The free-fall electrostatic separator is widely used for sorting plastic particles obtained from waste. The incorporation of flexible electrodes in this installation and the appropriate adjustment of their shapes make it possible to control the particle flow in the electrostatic separation zone, reducing particle-electrode impacts and increasing the quality of recovered products. In this study, we introduce a methodology to optimize the shape and position of flexible electrodes in a free-fall separator. The optimization criterion considered is the horizontal deviation of particles collected in the separator. The electrodes are modeled using Bézier curves with four control points, which provide an infinite number of electrode shapes by adjusting their positions. During the optimization process, only feasible configurations that meet certain constraints are considered. For each feasible configuration, a simulation model is used to obtain the trajectory of test particles, which is experimentally validated using a high-speed camera before being used in the optimization process. A genetic algorithm is used to determine the optimal configuration, which is defined by the position of the four control points of the Bézier curve. This paper aims to achieve two main objectives: (i) To experimentally validate the numerical model of particle behavior in free-fall separators equipped with two flexible electrodes using a high-speed camera. (ii) To use the model obtained from the genetic algorithm to determine the optimal shape and position of the electrodes.

The main objective of this paper is to design an intelligent control to improve the separator process of electrostatic rotating electrode separator by fuzzy logic. Where the methodology of designing experiments was used to form a knowledge base, and from it extract the important variables and the way they affect the outputs, as well as the interaction between them and established the mathematical model by using Minitab 18 software, while the MTLAB programs were used to simulate the fuzzy control system. The results showed the ability of the controller to improve the separation process in a good time, which will lead to saving time and energy.

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.

Diverse configurations of needle-type electrodes are commonly used to generate DC or AC corona discharges in various industrial applications. Previous studies confirm that the amount of charges generated by corona discharge is controlled by several factors such as the level of applied voltage, the ambient conditions, as well as the geometry of the electrode system. This paper aimed to evaluate the distribution uniformity of the charges generated by multiple-row needle-type electrodes and deposited on the Polyvinyl Chloride (PVC) plate surface, either at rest ("static" regime) or in motion ("dynamic" regime) under the corona electrode. The potential at the PVC plate surface was measured by a non-contact electrostatic voltmeter. The electric potential maps resulting from the experiments carried out in "static" regime, point out that the uniformity of the corona charging effect generated by the electrodes is related to their geometry and the level of the applied voltage. In the "dynamic" regime experiments, the surface potential profiles show that the distribution of electric potential on corona-charged polymer plates depends on the number of needles and the direction of movement under corona electrode system. Comparing the results obtained in this paper with the results obtained in previous studies, lead us to a general conclusion that the uniformity can be improved, to attain values higher than 95%, and this depends on the geometry of the electrode system and on the direction of the movement of the polymer plates in the electric field.

Previous studies had shown that the distribution of charges generated by corona discharge is controlled by several factors such as the geometry of the electrode system and the level of the applied voltage. The aim of this paper was to evaluate the uniformity of charge distribution at the surface of dielectric materials (PVC plates and PP films) exposed to a corona discharge generated by a tri-needle-type electrode at rest or in motion. The surface electric potential mapping performed with a non-contact electrostatic voltmeter shown that the non-uniformity of the corona charge is related to the geometry of the electrode employed in the experiments and can be reduced to less than 5%, when choosing the appropriate values for the distance between needles and for their height above the samples. It was also found that exceeding a certain value of applied voltage accelerated the surface potential decay, a phenomenon that explains the deterioration of charge uniformity.

Electrostatic separation is able to process mixtures of plastics from waste electrical and electronic equipment. The efficiency of the electrostatic separation depends on the electric charge acquired by the particles in the appropriate tribocharging devices. The aim of this work is to validate the possibility of using a roll-type electrostatic separator to sort mixtures of particles that are difficult to process by other means. In this type of separator, the plastic particles are charged by triboelectric effect. Two types of charging devices have been used: fluidized bed and rotating multicylinder. Two series of experiments were performed with samples composed in equal proportions of: first, acrylonitrile butadiene styrene (ABS) and polystyrene (PS); second, polypropylene (PP) and polyethylene (PE). A third series of experiments were carried out with a mixture of three plastics: PP, PE, and ABS, and the last series of experiments were carried out with a mixture of four plastics of (PE/PP/ABS/PS), with an average particle diameter ranging between 3 and 6 mm. The efficiency of the electrostatic separation was evaluated by measuring the charge, purity, and recovery of the granules collected at the outlet of the electrostatic separation. The results confirm that the separation of ABS/PS and PP/PE mixtures is feasible and the best separation results were obtained using the fluidized bed tribocharger.

Square plates of polypropylene (PP), dimensions 100 mm × 100 mm × 4.5 mm, were treated by atmospheric dielectric barrier discharge (DBD) generated between two disk-type electrodes (Ø 75 mm), energized from an ac amplifier 30 kV, 20 mA. The study aimed at evaluating the factors that affect the roughness and the triboelectric behavior of the plasma-treated samples. The alteration of surface aspect after each treatment was clearly visible with the naked eye and the changes were confirmed by measurements carried out with a portable roughness meter (Surftest SJ-210) and a digital microscope (Keyence VHX-7000). The roughness of the PP samples increased from an initial arithmetic mean Ra = 0.06 μm (±0.01 μm) and standard deviation Rq = 0.08 μm (±0.01 μm) to Ra = 0.22 μm (±0.03 μm) and Rq = 0.25 μm (±0.03 μm), respectively. These increases were highly dependent on the air gap distance (10.5–13.5 mm), the treatment time (5–20 min), and the configuration of the DBD cell, i.e., the number (one or two) and the thickness (4–5 mm) of the glass dielectric barriers. Untreated and DBD-treated samples were tribocharged in a linear tribometer, to evaluate the effect of the cold plasma treatment on the electric potential generated on the polymer surface by the triboelectric effect. The electric potential measured by a noncontact electrostatic voltmeter (Trek, 341B) was higher and better distributed over the surface of the plasma-treated samples.

The aim of the present paper is to study the efficiency of a new configuration of a roll type electrostatic separator for sorting brominated flame retardants (BFR) polymers from BFR-free polymers. The main characteristic of this separator is that the standard grounded rotating roll electrode is coated with a thin film of Polyurethane (PU). A wire-type corona electrode connected to a DC high voltage supply and placed at distance of 35 mm of the surface of the roll was used to charge the PU film at a polarity opposite to that of the static high-voltage electrode. The study was conducted on a granular polymer mixture composed of equal quantities of Polyethylene (PE) containing 40000 ppm of brominated flame retardants (4.7%) and BFR-free PE. The granular mixture to be sorted was first tribocharged in a fluidized bed tribocharger, the walls of which are made of PE, and was then introduced in the corona charged insulating roll type electrostatic separator to be selectively sorted under the action of electrical and mechanical forces. The results show that the best separation results are obtained in the case where the high-voltage static electrode is connected to a positive DC power supply and the insulating roll charged with a negative corona discharge, with this configuration 70 % of BFR-free PE can be recovered with a purity of around 80 %.

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 is the development of a new spiral-type tribo-charging device with an 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. We studied tribocharging characteristics of several types of medium-sized (2-5 mm) granular plastics. The study is conducted with samples of various e insulating materials, 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 (PVC), Polypropylene (PP) and Polystyrene (PS). The good separation obtained for this ternary mixture shows the efficiency of the new tribocharger.