Electrostatic Charging of Fine Powders and Assessment of Charge Polarity Using an Inductive Charge Sensor

Abstract

Electrostatic charging of powders becomes important, when particles become smaller, especially for fine powders at micron or sub-micron size. Charging of powders causes strong particle adhesion and consequently difficulties in processes such as blending or mixing, and sieving, etc. Not only does the charge of powders influence the process and the quality of the products, but also the discharge creates risks of dust explosion. Assessing powder charge and the hazards in manufacturing can be difficult. One of the major challenges is to evaluate the charge levels and polarity in the powders but this requires a significant number of tests to detect charge tendency and distributions in bulk materials, which is time-consuming. In this paper, electrostatic charging of powders in material handling processes and the associated hazards are briefly reviewed. For an assessment, the challenges for sensing electrostatic charges of particulate solids, particularly for fine powders, are discussed. It was revealed that sensing the charge polarity for representative samples of powders can be the main challenge because of the difficulty in separation of the charged particles. The inductive charge sensor showed great potential to measure charge levels and polarity distributions in powders. Experimental trials for several fine powders showed that the inductive charge sensor can be used for rapidly assessing chargeability and charge polarity distribution of powders.