Effect of spatial arrangement on breakdown characteristics of synthetic particle in high voltage pulse breakage

Abstract

The performance of high voltage pulse breakage (HVPB) is largely determined by the properties of ore particles coupled with the characteristics of electrical breakdown. In this study, the effects of spatial arrangement (electrode gap and particle dimension/location) on the breakdown characteristics (channel path and electrical parameters) of synthetic particle in HVPB were investigated. The test results indicated that the channel of breakdown developed preferentially inside tested particle when the electrode gap was completely filled by the particle. Moving particle away from the centre of electrode gap or leaving water gap between electrode and particle would increase the occurrence probability of “flashover” along particle surface and deteriorate the size reduction effect of HVPB. The negative effect of moving particle away from the centre was more severe when electrode gap was small. Electrical parameters of the breakdown voltage (Vbkd) and the breakdown delay time (Td) in pre-breakdown phase, as well as the total energy transferred into breakdown channel (Echt), the averaged channel resistance (Rchavg) and the proportion of energy transferred efficiently (Ete) in channel phase were determined according to the pulse wave forms of voltage and current. Generally, all of these electrical parameters increased with the increase of electrode gap when the electrode gap was completely filled by the tested particle. At the same electrode gap, higher values of Vbkd and Td were observed in the tests having water gap between rod electrode and tested particle. By contrast, the effect of water gap on the value of Echt was less significant. The existence of water gap could also reduce the value of Rchavg if breakdown channel had to pass through water before reaching particle. Linear models were developed to describe the relations of Vbkd to Td and Echt to Rchavg in this study. In addition, exponential relation between Ete and Rchavg was developed. Based on the observations in this study, the size reduction effect of HVPB can be optimized by: (1) using larger electrode gap, provided the electrical field strength is high enough to cause breakdown; (2) filling the electrode gap completely with feed particles.