Electrostatic field strength distribution inside metal silo during polypropylene powder loading by computer simulation

Abstract

This paper investigates the electrostatic field distribution inside a grounded metal silo during the loading of large amounts of powder (up to 1000 kg) using a simulation and accurate experimental parameters. The commercial COMSOL Multiphysics 5.4 AC/DC module, which uses the finite element method, was used in this study. Using the simulation, 1000 kg of 3 mm polypropylene powder was loaded into an industrial scale silo that was created based on the actual silo dimensions used in the experimental tests. The space charge density value used in the simulation model was based on the values obtained from experimental tests. As for the result, it was found that the electrostatic field strength, Es, of the accumulated powder area (area B) was much stronger than that of the falling powder area (area A). The Es in area B was strongest in the following order: the silo side wall inside the deposited powder surface, the side wall of the silo at the surface of the powder heap, and the center portions of the accumulated powder. It was also observed that the Es increased as the amount of loaded powder increased. When 5 kg was first loaded, it was seen that the Es was strong enough to cause electrostatic discharges. Also, when a metal protrusion (4 cm in diameter) was attached to the silo, it was observed that the Es around the surface of the protrusion was the strongest, signifying that strong electrostatic discharge is likely to occur with the existence of metal protrusions. These results were supported by the results of the experimental test.