Browsing by Author "Nadjem Abdelkader"

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    Etude et exploitation des charges électriques dans les procédés électrostatiques
    (2018-12-18) Nadjem Abdelkader
    The development of electrostatic applications involving electrical charges, such as the electrostatic separation process, is often accompanied by the need to develop triboelectric charging methods to control and promote the level of charges accumulated on the surfaces of insulating materials for the proper functioning of this process. The objective of this work is to contribute in improving the triboelectric charging of plastic granular materials using the surface treatment technique by dielectric barrier discharge (DBD) under atmospheric conditions. The first part of this work was devoted to the study of the effect of several electrical and geometrical factors of DBD on the discharge characteristics and, therefore, the surface modification of plastic granular materials and their triboelectric behavior. During our experiments, the DBD-treated particles acquired a high electrical charge and we obtained satisfactory results. The study of these DBD factors has also determined the optimal values to improve the acquired charge and the coordination of all these factors can produce better results. The experimental study also demonstrated the importance of using surface treatment of particles prior their charging to improve the separation results of a composite mixture of two types of materials by evaluating recovery rates and purity of the separated products. We also presented the experimental study of an electrostatic separator in order to contribute to the improvement of the free-fall separator and thus to prove the effectiveness of the proposed prototype. The results show the effectiveness and the importance of introducing an inclined plane and its role in improving the recovery rate of separated products. Very high recovery rates were obtained.
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    Influence of the geometrical parameters of a dielectric barrier discharge reactor on the subsequent tribocharging of granular polymers
    (2018-04-09) Nadjem Abdelkader
    Tribocharging of insulating materials is a pivotal step in several electrostatic applications in which the charge value has an important consequence on the outcome of the process. The Dielectric Barrier Discharge (DBD) at atmospheric pressure is an excellent energetic plasma source having the aptitude to change surface properties and, thereby, to enhance triboelectric charging of granular insulating materials. This paper aimed to investigate the influence of dielectric barrier geometrical parameters on the triboelectric charge of the DBD-treated Polypropylene (PP) and Polyvinyl Chloride (PVC) mm-size granules. The studied parameters include the air gap between the upper barrier and the surface of the granular layer, the number of granular layers, as well as the material forming the dielectric barrier and its position. After being treated for 3 s, the granules were triboelectrically charged in a vibratory device for 2 min. The charge the DBD-treated and untreated particles acquire by tribocharging was measured using a Faraday pail connected to an electrometer. Experimental results show that the air gap and the properties of the dielectric barrier can influence the mean value of the discharge current and enhance significantly the triboelectric charge of DBD-treated granules. Best results were obtained when the air gap did not exceed 4 mm and material with high permittivity was used as a barrier.
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    Semolina extraction from wheat bran using an electro-­ separation­process
    (2021-02-04) Nadjem Abdelkader
    The present paper is aimed at studying the improvement of the semolina extraction from durum wheat grains through a recycling of wheat bran, as a by-product, issued from traditional milling and sieving. Abrasion of the wheat bran and then electrostatically separating obtained components allowed a recovery of a significant amount of semolina, reaching 50% of the treated mass. Three components were obtained after separation, namely, semolina, fine bran, and relatively big bran. The electrostatic characterization, including surface potential decay and charge measurement, showed a clear conductive character with a slight difference between components in terms of charge conservation. This electric conductive behavior of the wheat bran leads to choose an induction-type electrostatic separator to extract residual semolina from the grinding process. The design of experiments methodology was used to study the influence of the main parameters: the applied high voltage, the conveyor speed, and the speed of the rotating part. The process was optimized taking into consideration both the quantity and quality of the recovered semolina, targeting a high recovery rate with the best possible quality. The physical and chemical analysis showed a good quality of the recovered semolina with 1.1% ash content.
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    Triboelectrification of granular insulating materials as affected by dielectric barrier discharge (DBD) treatment
    (2017-04-01) Nadjem Abdelkader
    The aim of this paper is to point out the influence of dielectric barrier discharge treatment on tribocharging of granular insulating materials. Particles of Polyvinyl Chloride (PVC) and Polypropylene (PP) were subjected to an AC dielectric barrier discharge (DBD) plasma treatment in ambient airprior to tribocharging in a vibratory device. The charge to mass ratio was measured for treated and untreated materials. Electrostatic separation of a mixture of granular materials (PVC and PP) to measure the effectiveness of DBD treatment was evaluated by processing treated and untreated PVC/PP granular mixtures in a free-fall electrostatic separator. The obtained results clearly indicate that DBD has the capability to influence surface charging proprieties of polymer granular materials. In case of short treatment time, typically less than 3 s, a marked increase in the charge to mass ratios was observed for both PVC (about 35%) and PP (roughly 45%). In the same way, the quantity of DBD-treated materials, recovered after electrostatic separation, was increased by about 104% and 30% for PVC and PP, respectively, as compared to untreated case. The DBD treatment time is a key factor to increase the tribo electric effect.