Miloud Kachi

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.

Experimental Study of Charge Neutralization at the Surface of Granular Layers of Insulating Materials

Neutralization of the residual electric charge is often a prerequisite for the optimal processing of insulating granules, thin films, or textile media. The aim of this paper is to evaluate the factors that might affect the ability of ac corona discharge to eliminate the charge at the surface of polyethylene granular materials. The effectiveness of the neutralization is evaluated from the measurement of surface potential distribution before and after exposing the samples to a flux of bipolar ions. The corona discharge was generated by energizing at various high-voltage (HV) levels (16, 20, and 25 kV) and frequencies (1, 20, 50, 100, 200, and 400 Hz) a wire-type corona electrode suspended at 30 mm above the granular layer disposed at the surface of a grounded plate. The results show that the neutralization efficiency can be improved by increasing the frequency of the HV. An optimal value voltage can be experimentally determined for the case of practical interest when the frequency of the power supply is 50 Hz. In the same case, successive exposures to the ac corona discharge may enhance the efficiency of the neutralization.

Experimental study of charge neutralization at the surface of granular layers of insulating materials

Neutralization of the residual electric charge is often a prerequisite for the optimal processing of insulating granules, thin films, or textile media. The aim of this paper is to evaluate the factors that might affect the ability of ac corona discharge to eliminate the charge at the surface of polyethylene granular materials. The effectiveness of the neutralization is evaluated from the measurement of surface potential distribution before and after exposing the samples to a flux of bipolar ions. The corona discharge was generated by energizing at various high-voltage (HV) levels (16, 20, and 25 kV) and frequencies (1, 20, 50, 100, 200, and 400 Hz) a wire-type corona electrode suspended at 30 mm above the granular layer disposed at the surface of a grounded plate. The results show that the neutralization efficiency can be improved by increasing the frequency of the HV. An optimal value voltage can be experimentally determined for the case of practical interest when the frequency of the power supply is 50 Hz. In the same case, successive exposures to the ac corona discharge may enhance the efficiency of the neutralization.

Installations for the neutralization of granular insulating materials obtained by electrostatic separation

Preventing accumulation of static charges and finding means for its elimination have been topics of active research in the field of electrostatic separation technologies for granular mixtures of insulating mixtures. Four installations are examined as potential solutions for the neutralization of the residual charges in separation processes. The experiments are performed with mm-size granules of Acrylonitrile Butadiene Styrene (ABS) and High-Impact Polystyrene (HIPS) recovered from industrial wastes. The granules are corona charged at a potential similar to that acquired by triboelectric effect. They are spread across an electrode connected either to the ground or to a high voltage (HV) of opposite polarity, then exposed to either DC or AC corona, in view of neutralizing the residual charge. The use of AC corona gives the best results, attaining neutralization rates as high as 95.3 % for ABS and 87.3 % for HIPS granules.