Implementation of Faraday cup electrostatic charge measurement technique in high-pressure gas–solid fluidized beds at pilot-scale

• A high-pressure fluidized bed designed to study electrostatic charging.
• Faraday cup charge measurement technique was implemented in the fluidized bed.
• The mechanism of wall coating formation due to electrostatics was studied.
• Elevating the system pressure increased the extent of fluidized bed wall coating.
• Reactor wall coating contained both positively and negatively charged particles.

Elevation of operating pressure in gas–solid fluidized beds affects the bed hydrodynamics, which in turn could affect the extent of bed electrification and reactor wall coating due to electrostatic charge generation. In this work, a pilot plant high-pressure gas–solid fluidization system housing the Faraday cup electrostatic charge measurement technique is introduced in order to study the underlying mechanism of electrostatic charge generation causing fluidized bed wall fouling at pressures up to 25 barg. A previously developed on-line electrostatic charge measurement technique containing two Faraday cups was successfully implemented in the high-pressure system. The effect of operating pressure on gas–solid fluidized bed electrification was examined under operating pressures of 0 and 25 bar (gauge) by fluidizing polyethylene resin directly received from a commercial reactor. Experimental results showed that the magnitude of reactor wall coating increased with the increase of operating pressure. The wall coating contained positively as well as negatively charged particles indicating the occurrence of bipolar charging within the fluidized bed. Finally, based on the experimental results obtained in this work the mechanism of fluidized bed column wall coating formation was discussed.

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