Influence of Particle Contact Number on Triboelectric Separation Selectivity

Johann Landauer,Petra Foerst

doi:10.3390/pr7100716

Abstract

Triboelectric separation is a promising technology to separate fine powders. To enable triboelectric separation for its application in industry, the impact of the process and product parameters must be examined. In this study, with regards to different wall materials in the charging step (PTFE, POM, PE, PVC, and PMMA), the influence of the powder composition of a binary starch-protein mixture with a protein content of 15 wt.%, 30 wt.% and 45 wt.% was studied. By increasing the protein content in the feed, the separation selectivity increased. No dependency of the empirical triboelectric series was determined for all powder compositions. The variation in the protein content of the initial powder and turbulent flow profiles results in a variation in the contact number of particles calculated. An increase in the contact number of particles leads to an increase in the protein content separated on the cathode, whereas the protein content on the anode is only slightly affected. These findings underpin the assumption that particle-particle interaction plays a decisive role in triboelectric charging of fine powders.

Highlights

Triboelectric charging occurs when two surfaces come in contact and are separated [1].This phenomenon is called contact, surface or triboelectric charging [2,3]
The particle size distributions of powders collected on the cathode after separation feature higher peaks at 1 μm for initial protein contents of 30 wt. % and 45 wt. % compared to 15 wt. % (Figure 2)
Starch particles collide more frequently with protein particles, whereas protein particles collide more frequently among themselves. These findings indicate the influence of the pristine particle sizes as well as the initial protein content on triboelectric charging

Summary

Introduction

Triboelectric charging occurs when two surfaces come in contact and are separated [1].This phenomenon is called contact, surface or triboelectric charging [2,3]. When the simplest triboelectric experiment with a balloon rubbed on hair is performed, both surfaces get charged. In this example, rubbing increases the number of contacts between balloon and hair and, ensures sufficient contact between surfaces. This insight can be transferred to the triboelectric charging of dry powders. By dispersing powder in a gas stream high numbers of particle-particle and particle-wall collisions happen This high interaction rate of dispersed and moved particles can be the manipulated variable for triboelectric separation of powders, since the mechanism of triboelectric charging is still unknown [5]

Methods

Results

Discussion

Conclusion