Statistical characterization of images — Anisotropy

The purposes of the paper are to contribute to the understanding of the notion of anisotropy of images and to expose details on a method for deriving global and local statistical features on materials, based on anisotropy. We introduce a definition of anisotropy related to the edges and improve measures of anisotropy. The images dealt with correspond mainly to non-woven fabrics based on polymeric fibers. A discussion of the applicative potential is included

Effects of the grid geometry on the performances of a triode-type corona electrode system

International audienceThe triode-type electrode system is frequently employed for accurately controlling the corona charging of insulating materials. The primarily aim of this paper is to characterize the effects of grid geometry of the triode-type corona electrode system by current-voltage and current density distribution measurements. The ionizing element of the electrode system is a thin Tungsten wire (diameter: 200 μm) attached to a cylinder (diameter: 26 mm) and distanced at 34 mm from its axis. The wire-cylinder assembly is a “dual” electrode, facing a grid electrode, connected to a well-defined potential, and a grounded plate electrode. The geometry of the grid has a very significant influence on the current-voltage characteristics of the triode system, on the corona onset voltage value and on the repartition of the current density. The experimental results obtained for different geometries of the grid electrode system are interpreted in order to make some recommendations regarding its design

Corona discharge as affected by the presence of various dielectric materials on the surface of a grounded electrode

International audienceThis paper is aimed at the characterization of the corona discharge generated from a high-voltage wire electrode facing a grounded plate that carries dielectric layers composed of granules, sheets, and non-woven media. Current-voltage and current-frequency characteristics were measured, respectively in DC and AC modes, for several values of the thickness of the PE granular layer, PET sheets and PP non-woven media considered in the present study. The measurements show that the corona onset voltage and the behavior of the current-voltage characteristics are dependent on both nature and thickness of the dielectric layer. Both the estimated capacitive component and the ionic component in AC mode vary with the amplitude and the frequency of the voltage. The ionic component is particularly affected by material non-uniformity

Electrostatic separation of mineral and vegetal powders with a custom built corona separator: application to biorefinery of rice husk

In a dry biorefinery scheme, the separation of plant materials into powders rich in the constituents of interest is a crucial step. In recent years, electrostatic separation of agri-resources has sparked a growing interest for its potentialities, but optimization efforts remain to be done especially in case of fine powders. In this study a custom-designed corona-electrostatic separator has been built and its usage for the separation of mineral (ash from rice husk) and vegetal powders (cellulose fibers) with different particle size distributions has been studied. First, the powders have been characterized by their electric charge decay curves and their behaviour on the separator was studied. At a second time, separation tests have been carried out with blends of these two powders, and with native, finely ground, rice husk powder (constituted of both mineral and vegetal particles). In each case, the efficiency of the process was evaluated

Electrostatic separation of mineral and vegetal powders with a custom built corona separator: application to biorefinery of rice husk

In a dry biorefinery scheme, the separation of plant materials into powders rich in the constituents of interest is a crucial step. In recent years, electrostatic separation of agri-resources has sparked a growing interest for its potentialities, but optimization efforts remain to be done especially in case of fine powders. In this study a custom-designed corona-electrostatic separator has been built and its usage for the separation of mineral (ash from rice husk) and vegetal powders (cellulose fibers) with different particle size distributions has been studied. First, the powders have been characterized by their electric charge decay curves and their behaviour on the separator was studied. At a second time, separation tests have been carried out with blends of these two powders, and with native, finely ground, rice husk powder (constituted of both mineral and vegetal particles). In each case, the efficiency of the process was evaluated

Tribo-electrostatic separation of a quaternary granular mixture of plastics

International audienceMany tribo-electrostatic separation studies of binary mixtures of millimeter-sized plastic particles have been performed. The objective of this work is an experimental investigation for separating a quaternary mixture comprising four different plastic types issued from waste electrical and electronic equipment. The feasibility of the separation of such quaternary mixtures by the sliding mode tribocharging with a metal wall was demonstrated. The separation of a mixture comprising PA, PC, high impact polystyrene, and polyvinyl chloride granules is better in terms of both purity and recovery when charging the particles by sliding contact with the metal wall, then in the case of a fluidized bed device

Triboelectrostatic separation of brominated flame retardants polymers from mixed granular wastes

International audienceThe general purpose of the present paper is to study the feasibility of removing brominated flame retardants (BFR) polymers from mixed granular wastes using tribo-electrostatic separation. The study was carried out on mixtures consisting in equal quantities of high impact polystyrene (HIPS) particles either BFR-free or containing 40000 ppm of brome (4.7%). Three triboelectric charging devices were used: a vibrating tribocharger (a container made of stainless steel, polystyrene or polypropylene and fixed on a vibrating table); a rotating cylinder tribocharger made of polyvinyl chloride; a fluidized bed tribocharger, the walls of which were made of poly methyl methacrylate. The selective sorting of the granular mixture was performed using a roll type electrostatic separator. The results confirm that separating BFR HIPS from BFR-free HIPS is feasible. Best separation results were obtained for the mixture tribocharged in the fluidized bed tribocharger