Effect of fluidizing gases, humidity, and grounding on particle charging dynamics in gas-solids fluidized beds

• Argon lowers particle charge saturation by reducing dielectric breakdown strength. • Below dielectric breakdown, charge saturation is determined by generation-dissipation. • Humidity enhances charging of hydrophobic particle but does not alter final charge. • Humidity enhances charge dissipation in hydrophilic particle due to lower resistivity. • Grounding does not significantly influence charging dynamics nor saturation charge. This study examines charging dynamics of HDPE and glass particles in gas–solid fluidized beds, focusing on effects of fluidizing gases, humidity, and reactor grounding. Experiments revealed that charge accumulation in HDPE particles is significantly influenced by breakdown strength of fluidization gas, with argon leading to earlier and lower charge saturation. For glass particles, low saturation charge density results from the balance between weak charge generation and strong charge dissipation, rather than dielectric breakdown. Humidity had a material-dependent effect; it enhanced the charging of HDPE particles but did not impact their final saturation levels, while for glass particles, it promoted charge dissipation. Grounding the column, contrary to common expectations, did not significantly reduce electrostatic charges or alter charging dynamics for either particle type because the particle–particle contact controls charge transfer for dielectric particles. These findings highlight the complex interactions between gas type, humidity, and particle and wall materials, emphasizing the need for tailored strategies to manage electrostatic charges in industrial fluidized bed systems.