Mitigation of Electrostatic Charge and Its Adverse Effects in Gas-Solid Fluidized Beds

In gas-solid fluidized beds there is potential for electrostatic charge generation due to the collisions among particles and with the column wall. Operational challenges arising from electrostatics include particle agglomeration, accumulation of charged particles on internal surfaces (column wall, instrumentation, etc.,) requiring shutdowns for clean-ups, and electrostatic discharge resulting in a hazardous environment. Previously we have shown that the extent of charging largely depends on various conditions including the nature of surfaces in contact (i.e., surface chemistries of particles and the column wall), gas velocity and flow regime, presence of moisture, fluidization pressure and temperature, and particles size distribution [1,2]. Our latest works indicate that there is a direct relationship between the net specific charge of the particles in the bed bulk and the degree of particles’ accumulation on the fluidization column wall [2,3]. This presentation presents three techniques assisting in minimizing the generation of electrostatics in gas-solid fluidized beds. They include: (1) Reducing volume resistivity of the particles (e.g., via increase in fluidization temperature); (2) Reducing the particles surface charge/charge build-up using fluidization gasses that have low breakdown voltage strength; and (3) Adding additives (e.g., antistatic agents) that induce an opposite polarity to that of the net specific charge of the bed bulk, and in turn, bringing the bed net specific charge as close as possible to zero.

[1] Mehrani P., Murtomaa M., Lacks D.J., An overview of advances in understanding electrostatic charge buildup in gas-solid fluidized beds, Journal of Electrostatics, 87, 2017.

[2] Nimvari, M.I., Sowinski, A., Mehrani, P., Effect of Temperature on triboelectrification of polyethylene particles in a pilot-scale pressurized gas-solid fluidized bed. Powder Technology, 405, 2022.

[3] Taghavivand, M., Mehrani, P., Sowinski, A. Triboelectric effects of continuity additives and a silica catalyst support on polyethylene fluidized bed wall fouling, Chemical Engineering Science, 245, 2021.