Electrostatic effects on inertial particle transport in bifurcated tubes

Abstract

Most aerosols found naturally in the ambient environment or those dispersed from artificial devices such as dry powder inhalers, are electrically charged. It is known that a strong electrostatic charge on aerosols can result in transport behavior dramatically different from that of uncharged aerosols, even in the absence of an external electric field. In the present work, we study pneumatic transport of corona‐charged particles in bifurcated tubes. This is accomplished by tracking the motion of discrete particles numerically under the influence of drag, gravitational, and electrostatic forces. The model aerosol is fly ash powder, whose size and charge distributions have been determined experimentally. The electrical mobility of the charged particle cloud is modeled through coulombic interactions between discrete point charges. For the case of polydispersed particles electrically charged across a distribution, the deposition efficiency was found to be greater than what is indicated by the mean charge and size. In particular, use of negatively charged fly ash powder of mean size of 2 μm and mean charge of −1.5 C/kg led to significant increase in deposition efficiency (∼29%) compared with uncharged fly ash powder of the same size distribution (∼8%). Analysis of particle residence times suggests significant interaction between electrical and drag forces. These findings could have implications for pneumatic powder conveying or pulmonary drug delivery applications. © 2009 American Institute of Chemical Engineers AIChE J, 2009

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

“…As a result, the electrostatic phenomena that occur with solid particles are significant as the specific surface area increases. For example, electrostatic forces acting on charged particles affect powder flowability [3][4][5][6][7] and segregation [8]. In addition, excessively charged particles cause an electrostatic discharge, which can pose the risk of fire and explosion hazards [9].…”

Comparative Study of the Triboelectric Charging Behavior of Powders Using a Nonintrusive Approach

“…3,4 Besides the hazards involved in triboelectrification, charged powders could cause major processing problems by forming agglomerated and cohesive structures affecting smooth flow, 5,6 mixture homogeneity, 7,8 particle dispersion, and deposition. 9,10 However, electrostatically charged powders can be advantageous in applications such as electrophotography, 11,12 dry powder coatings, 13,14 and electrostatic separation processes. 15,16 In addition, numerical simulations showed that drug deposition in the lungs can be improved through a combination of controlled breathing, particle size, and charge.…”

“…Triboelectrification occurs when dissimilar surfaces are rubbed together and then separated, resulting in charge accumulation on the surfaces. , Subsequent electrostatic discharges from the surfaces of triboelectrically charged powders during powder handling and processing operations such as blending or pneumatic transport could serve as potential ignition sources for dust explosions in flammable atmospheres. , Besides the hazards involved in triboelectrification, charged powders could cause major processing problems by forming agglomerated and cohesive structures affecting smooth flow, , mixture homogeneity, , particle dispersion, and deposition. , However, electrostatically charged powders can be advantageous in applications such as electrophotography, , dry powder coatings, , and electrostatic separation processes. , In addition, numerical simulations showed that drug deposition in the lungs can be improved through a combination of controlled breathing, particle size, and charge. − Therefore, in order to optimize the performances of various powder processes, it is important to be able to first characterize and then understand the electrostatic behavior of the powders in these systems.…”

Adhesive strength distribution of charged particles on metal substrate in external electric field

“…When handled in air, the surfaces of these particles become electrostatically charged by contact or friction with other solid materials. The charged particles cause problems [1,2] such as adhesion [3][4][5][6], segregation [7], as well as fire and explosion hazards [8]. To explain the mechanism of particle charging, several models have been proposed.…”