Corona Compared with Triboelectric Charging for Electrostatic Powder Coating

Abstract

The purpose of this research was to compare electrostatic and nonelectrostatic coating and determine the improvement between corona and triboelectric charging systems. Graham crackers were coated with food powder at 0, −50, or −95 kV or by tribocharging with teflon or nylon. Five sizes of sucrose from 13 to 138 μm were coated onto the crackers to determine the effect of particle size on coating efficiency. Three proteins, three carbohydrates, and one salt between 35 and 58 μm were analyzed to determine the effect of composition. Electrostatics improved transfer efficiency (TE) up to 27%, adhesion up to 40%, and reduced dust up to 99% over nonelectrostatic coating. Particle size and composition significantly affected the improvement produced by each charging method. As particle size increased, nonelectrostatic TE and adhesion increased, while dust decreased. Electrostatic TE increased and leveled off and adhesion and dust decreased with increasing particle size. Generally, corona TE, adhesion, and dust reduction was the highest, followed by teflon triboelectric, nylon triboelectric, and nonelectrostatic coating. For proteins, teflon produced higher charge to mass, TE, and adhesion than nylon. Although the corona system was most efficient, the teflon triboelectric system produced comparable results for some powders and may be necessary to produce a thick coating while minimizing back ionization and alleviating Faraday Cage effects.

The influence of particle size on separation and dustiness in powder mixtures during nonelectrostatic and electrostatic coating

“…Coarse powders fall faster than fine powders because of gravity force and miss the target, leading to separation [20]. Greater transfer efficiency for coarse powders than fine powders due to gravity force was also found by others [8,13,19]. Not only differences in targeting loss cause separation, but also the differences in adhesion loss cause separation, particularly when the mixture is coated electrostatically [15].…”

Solvent-free production of protein-enriched fractions from navy bean flour using a triboelectrification-based approach

“…For commercial applications of electrostatic separation, conductive induction, corona bombardment and triboelectrification have been used to impart surface charge (Dwari and Hanumantha Rao, 2007;Mayr and Barringer, 2006;Mazumder et al, 2006). Induction charging is based on the polarity and conductivity of the particles.…”

“…The closest reported technology explored the triboelectrification properties of different food powders for electrostatic coating (Mayr and Barringer, 2006). The authors examined the tribo-electric chargeability of fish collagen hydrolyzate, protein soy powder, protein whey powder, and native potato starch using either Teflon or nylon tribo-chargers.…”

Modeling nonelectrostatic and electrostatic powder coating

“…Small particles tend to remain airborne and are carried away by the air rather than settle on the target locations. Large particles due to their size and high inertia do not remain airborne for long periods and hence they settle on the target locations (Mayr & Barringer, 2006;Ratanatriwong et al, 2003;Ricks et al, 2002;Sumawi & Barringer, 2005). Both experiment and the simulation showed the same effect of size on transfer efficiency.…”

“…Increase in particle size increases transfer efficiency (Mayr & Barringer, 2006;Ratanatriwong, Barringer, & Delwiche, 2003;Ricks, Barringer, & Fitzpatrick, 2002;Sumawi & Barringer, 2005).…”