Electrostatic charging behaviour of polypropylene particles during pulse pneumatic conveying with spiral gas flow pattern

Abstract

The electrostatic charging behaviour of 5-µm and 1500-µm polypropylene particles were studied during pulse pneumatic conveying with a spiral air flow. The conveying line was made of stainless steel with a total length of 1.3 m and inner diameter of 0.035 m. Effects of conveying gas velocity as well as particles mass loading were studied on particles charge-to-mass (Q/m) ratio. A high-speed camera set at 5000 frames per second (fps) capturing speed was used to record the particles movement pattern within the conveying line. Results clearly indicated a relationship between the particles motion pattern and their electrostatic charging behaviour. A direct relationship was observed between the conveying gas velocity and particles Q/m, whereas in general, particles Q/m magnitude was found to be inversely related with the mass loading. The Q/m of larger particles was found to be greater than that for the smaller particles. Additionally, charge measurements were performed and compared between a cyclone-type Faraday cage and a through-type Faraday cage with a filter bag inside. It was observed that the charge measured by these Faraday cages could differ drastically depending on particles size. The back pressure created inside the filter bag was suspected to be a significant contributor for such as observation.