Experimental investigation of surface roughness effect on electrostatics generation

Granules are widely used in solid processing including chemical, mining, energy, environment, food, pharmaceutical industries. As granules are transported in pipelines, electrostatics are to be generated due to granule-wall interactions. In this work, granular surface roughness was particularly investigated for the effect on electrostatics generation for three materials including coal, woodchip and biochar for better understanding of their respective performance in well-designed granule sliding tests. In addition, other factors including granule contact area, granule shape, relative humidity as well as their integrated effects with granule surface roughness on electrostatics were considered. It was found that the electrostatics increased with larger contact area as well as decreasing humidity. In addition, triangle granules were observed to generate more electrostatic charges than rectangle granules such that granule shape was important in determining electrostatics generation. Meanwhile, it was also found that electrostatics generated first increased with granule roughness but decreased after reaching a maximum point, which was independent of granule material. In this work, the electrostatics generated by woodchip granules was obviously higher than that by biochar granules. In addition, other factors such as granule shape, surface roughness for biochar granules were showed to have less effect on electrostatics generation than that for woodchip granules. (C) 2019 Published by Elsevier B.V.