Dynamic simulation of electrostatic discharge and energy of charged particles in falling processes

Electrostatic discharge (ESD) is a primary hazard in chemical production. To eliminate the associated safety risks, it is essential to investigate the coupling between ESD and material ignition. This paper proposes a coupled DEM-FEM method for dynamically simulating the electrostatic field, modeling falling particles individually and accumulated heaps as bulk geometries, reducing the per-frame simulation time to hours and minutes, respectively. For falling particles, the feed rate dominates the electrostatic energy, followed by the charge-to-mass ratio (CMR) and permittivity, while for adhered particles, the energy increases nonlinearly with CMR and permittivity once thresholds are exceeded. For accumulated heaps, incorporating dynamic ESD keeps the field fluctuating around 3 MV/m and limits the energy to several hundred millijoules, consistent with the minimum ignition energy of energetic materials. Internal discharges occur at the bottom and side walls, whereas surface discharges include brush, propagating brush, point, and conical forms; the released energy correlates positively with reductions in electrostatic potential and field strength. Charge dissipation consistently suppresses surface discharge energy and, for a given drop in potential or field strength, yields a smaller released ESD energy. The evaluation criterion is advanced from field strength to electrostatic energy, allowing direct comparison with ignition risk. The electrostatic energy of falling, adhered, and accumulated particles lies in the microjoule, millijoule, and hundred-millijoule ranges, respectively, and can sequentially ignite dust clouds, Ti powders, and RDX. Thus, the electrostatic risk at different process locations can be differentiated and estimated accordingly.