Experimental study on the relationship between the charge amount of polypropylene granules and electrostatic discharges while silo loading

摘要

This paper is a report of the relationship between the charge amount (charge to mass ratio) of polypropylene granules (PP; typical particle size of 2 to 3 mm, 300 kg) and the electrostatic discharges that happened while loading of metal silo (diameter, 1.5 m; straight body length, 3 m; capacity, 4.8 m~3). The feedback control system was used in order to control the charge amount of PP granules. The electrostatic discharges inside the silo were also observed by using a conventional image-intensifier system. The results obtained from the experiments show that (1) two kinds of electrostatic discharges inside a metal silo while loading PP granules, i.e., brush discharges and incendiary bulk surface discharges were clearly observed. (2) the number of brush discharges and incendiary bulk surface discharges increased with the increase in the charge to mass ration of PP granules, and then almost reaching saturation. And (3) brush discharges and incendiary bulk surface discharges began to happen at the -1.16 μC/kg and -2.33 μC/kg point, respectively in this study.