Sara Messal

Electrostatic Separation of Peeling and Gluten from Finely Ground Wheat Grains

Sieving and air classification are not efficient enough for the extraction of the high-nutritional-value constituents of wheat. The aim of this article is to validate a simple electrostatic separation method of peeling and gluten, which are two such nutriments contained in finely ground wheat grains. The electrostatic separator is composed of metallic grounded belt conveyer and a rotating roll electrode connected to a high voltage supply. The electrostatic behavior of peeling and gluten powders was characterized using surface potential decay and direct charge measurements. These first set of experiments pointed out the conductive behavior of these powders: in contact with a grounded electrode, they lose their charge in less than 10 s. In a second set of experiments, mixtures of 50% peeling and 50% gluten powders were processed by electrostatic separation. Experimental design methodology was used to model the outcome of the separation process as function of two control variables: the high-voltage applied to the roll electrode and the speed of the belt conveyor electrode. In this way, it was possible to determine the optimal operational conditions for the recovery of high-purity peeling and gluten fractions.

Optimal Sizing of a DBD Ozone Generator Using Response Surface Modeling

Dielectric barrier discharge (DBD) reactors used as ozone generators are well known today and widely used for water treatment and air disinfection. The purpose of this article is to propose an experimental procedure based on the response surface modeling in order to optimize the geometrical dimensions of the cylindrical shape ozone generator, i.e., the discharge gap and the electrodes length. Because an effective ozone generator is expected to give high ozone concentration with a minimum of power requirements, the applied high voltage was associated with the geometrical parameters to carry out a composite centered faces design. Obtained results indicate that for an efficient ozone generator, length of the electrodes needs to be optimized while the discharge gap should be minimized.

Sorting of finely-grinded granular mixtures using a belt-type corona-electrostatic separator

The commercial roll-type corona-electrostatic separators, which are currently employed for the recovery of metals and plastics from mm-size granular mixtures, are inappropriate for the processing of finely-grinded wastes. The aim of the present work is to demonstrate that a belt-type corona-electrostatic separator could be an appropriate solution for the selective sorting of conductive and non-conductive products contained in micronized wastes. The experiments are carried out on a laboratory-scale multi-functional electrostatic separator designed by the authors. The corona discharge is generated between a wire-type dual electrode and the surface of the metal belt conveyor. The distance between the wire and the belt and the applied voltage are adjusted to values that permit particles charging without having an electric wind that puts them into motion on the surface of the belt. The separation is performed in the electric field generated between a high-voltage roll-type electrode (diameter 30 mm) and the grounded belt electrode. The study is conducted according to experimental design methodology, to enable the evaluation of the effects of the various factors that affect the efficiency of the separation: position of the roll-type electrode and applied high-voltage. The conclusions of this study will serve at the optimum design of an industrial belt-type corona-electrostatic separator for the recycling of metals and plastics from waste electric and electronic equipment.

Factors That Influence the Efficiency of a Propeller-Type Tribocharging Device for Granular Plastics

This work is focused on the experimental study of a new propeller-type tribocharging device specifically designed to operate in conjunction with an electrostatic separator for mixtures of granular insulating materials. The device consists of two coaxial aluminum propellers rotating in a polyvinyl chloride (PVC) pipe; it has two control variables: the material feed-rate and the rotation speed of the propellers. Virtual instrumentation using LABVIEW software is used for measuring the mass and the electric charge of the tribocharged samples of four types of polymers: polypropylene (PP); high impact polystyrene (HIPS); high-density polyethylene (HDPE); and PVC. In accordance with the sign and the magnitude of the charge/mass ratio, the four polymers are arranged in a triboelectric series, starting from the negative polarity: PVC—HDPE—PP—HIPS. The effectiveness of the tribocharging process is validated by using a free fall electrostatic separator. The best results (purities and recoveries higher than 90%) are obtained in the case of PVC/HIPS granular mixtures.

Electrostatic separator for micronized mixtures of metals and plastics originating from waste electric and electronic equipment

In spite of their extensive use for processing mixtures of granules exceeding 1 mm in size, very few industrial electrostatic separators are capable of handling micronized metals and plastics originating from waste electric and electronic equipment. The aim of the present work is to validate the possibility of using a novel belt-type electrostatic separator for the selective sorting of such particulate mixtures, the dimensions of which are in the order of 0.1 mm. In this type of separator, the metal particles get charged by electrostatic induction in contact with the grounded metal belt electrode, while the plastics remain uncharged in the electric field and are collected separately. The experiments are performed with 2-g samples of a mixture composed in equal proportions (50% - 50%) of Aluminium and Acrylonitrile Butadiene Styrene (ABS) particles of average diameter ranging between 125 μm and 250 μm. They enabled the evaluation of the effects and the interaction of two control variables of the process: the angle of inclination of the roll-type electrode and the high voltage applied to it.

Study of a tribo-aero-electrostatic separator for mixtures of micronized insulating materials

This paper is aimed at the optimization of a new tribo-aero-electrostatic separator for micronized isolating materials mixtures, with application at the recycling of waste electrical and electronic equipment. The two high-voltage rotating-cylinder electrodes of the electrostatic separator are partly immersed in a fluidized bed containing the material to be separated. The control variables of the process are the high-voltage applied to the electrodes, the speed of the fluidization air, and the feeding rate of the separator. Experimental design methodology is employed for modeling the separation process. This enables the determination of the values of these variables that ensure the optimal operating condition of the installation.

Belt-Type Corona-Electrostatic Separator for the Recovery of Conductive and Nonconductive Products From Micronized Wastes

The commercial roll-type corona-electrostatic separators, which are currently employed for the recovery of metals and plastics from millimeter-size granular mixtures, are inappropriate for the processing of finely grinded wastes. The aim of this paper is to demonstrate that a belt-type corona-electrostatic separator could be an appropriate solution for the selective sorting of conductive and nonconductive products contained in micronized wastes. The experiments are carried out on a laboratory-scale multifunctional electrostatic separator designed by the authors. The corona discharge is generated between a wire-type dual electrode and the surface of the metal belt conveyor. The distances between the wire and the belt and the applied voltage are adjusted to values that permit particles charging without having an electric wind that puts them into motion on the surface of the belt. The separation is performed in the electric field generated between a high-voltage roll-type electrode (diameter 30 mm) and the grounded belt electrode. The study is conducted according to the experimental design methodology, to enable the evaluation of the effects of the various factors that affect the efficiency of the separation: position of the roll-type electrode and applied high voltage. The conclusions of this study will serve at the optimum design of an industrial belt-type corona-electrostatic separator for the recycling of metals and plastics from the waste electric and electronic equipment.

Multivariate Control for Three Variables of an Industrial Roll-Type Electrostatic Separator

Hotellings

Study of a Tribo-Aero-Electrostatic Separator for Mixtures of Micronized Insulating Materials

T^{2}

Experimental study of a tribo-aero-electrostatic separator for finely-grinded matter

charts have already proven their effectiveness in the multivariate control of electrostatic separation process. The aim of this work is to extend the use of these charts from two to three variables, in order to improve the statistical control of an industrial roll-type electrostatic separator designed for the recycling industry. In the case of electrostatic separation processes, the use of Hotellings