Advanced characterization of particles triboelectrically charged by a two-stage system with vibrations and external electric fields

Abstract

a b s t r a c tIn this study, we propose a new method to effectively characterize particle tribocharging caused by repeated contact with a wall in an external electric field. We perform experiments using a two-stage system consisting of two inclined vibrating plates and electrodes. The mass flow rate and charge of particles were controlled at the first vibrating plate, and the charge that was transferred from the plate to the particles was obtained from the difference between the charges on particles at the lower and upper ends of the second vibrating plate. In addition, electric currents generated by the charge transfer were simultaneously measured at the second vibrating plate. From these measurements, we verified that the charge balance in this system holds. Furthermore, we found that the charge transfer depends on various factors, such as the initial charge, chemical and electrical properties, travel length of particles, and the external electric field. We also found that the equilibrium charge of particles depends on the chemical property and external electric field. The equilibrium charge and the rate of tribocharging were evaluated analytically from the relationship between the initial and transferred charges without changing the travel distance of particles. This method enables the rapid and reliable analysis of the particle tribocharging process.

Experimental and numerical study of wall layer development in a tribocharged fluidized bed

“…Laurentie et al (2010Laurentie et al ( , 2013) developed a numerical model compatible with the discrete element method (DEM) to describe the charge transfer between insulating particles. The model is based on the effective work function difference between materials and takes into account the electric field at the contact point, which has been shown to impact insulator triboelectrification (Zhou et al 2014;Mizutani et al 2015). The model has also showed good agreement with experimental results in vibrated bed experiments (Laurentie et al 2010(Laurentie et al , 2013Kolehmainen et al 2017b); in a granular hopper chute flow (Naik et al 2015); and in granular binary mixtures (Naik et al 2016).…”

“…Most attempts to model triboelectric charging are based on the concept of effective work function difference or contact potential difference between surfaces (Harper 1967;Matsuyama & Yamamoto 1995;Tanoue et al 2001;Laurentie, Traoré & Dascalescu 2013;Korevaar et al 2014;Mizutani, Yasuda & Matsusaka 2015;Grosshans & Papalexandris 2016a,b), which can be regarded as the high-density limit of the surface state theory (Lowell & Rose-Innes 1980). In short, it is assumed that charge is transferred until the resulting electric potential difference between the surfaces balances out the driving potential or the work function difference.…”

Eulerian modelling of gas–solid flows with triboelectric charging

“…The most commonly used computational models for triboelectrification are based on aforementioned concept of effective work function difference or contact potential difference between surfaces (Harper 1967;Matsuyama & Yamamoto 1995;Matsusaka et al 2010;Tanoue et al 2001;Laurentie et al 2013;Korevaar et al 2014;Mizutani et al 2015;Grosshans & Papalexandris 2016, 2017. Other modeling approaches described in the literature include particle polarization based charging (Pähtz et al 2010;Siu et al 2014;Yoshimatsu et al 2016Yoshimatsu et al , 2017b, using particle electron surface density (Duff & Lacks 2008), high and low energy electrons (Kok & Lacks 2009), particle temperature variation based charging (Gu et al 2013), and saturation charge density of the surface limited by dielectric breakdown (Korevaar et al 2014).…”

Electrostatic Separation

“…While the charge quickly decays on the metal, insulators get charged and can keep the charge on contact with metals [30,40,[129][130][131][132][133][134][135][136]. The triboelectric charging between insulators and metals can be exploited to influence the triboelectric charging step of particle mixtures, for example, by modification of the wall material of the tribocharging device [115,137].…”

“…To evaluate the result of the charging step, either the result of a subsequent electrostatic separation step can be considered, or the particle charges can be measured. A lot of different techniques for measuring charges of single particles or particle mixtures are described in the literature [51,64,81,85,136,192,198,199].…”