A novel dual-material probe for in situ measurement of particle charge densities in gas–solid fluidized beds

• Particle charge density and bubble velocity were measured by a dual-material probe.
• Probe measurements were compared with Faraday cup and video data retrieved from 2D fluidized bed.
• Probe signals and video images were synchronized for calibration of the probe.
• Current peaks are related to particle charge density and bubble rise velocity.
• Differences in signals between the two tips arise mainly from charge transfer.

Particle charge density is vitally important for monitoring electrostatic charges and understanding particle charging behavior in fluidized beds. In this paper, a dual-material probe was tested in a gas–solid fluidized bed for measuring the charge density of fluidized particles. The experiments were conducted in a two-dimensional fluidized bed with both single bubble injection and freely bubbling, at various particle charge densities and superficial gas velocities. Uniformly sized glass beads were used to eliminate complicating factors at this early stage of probe development. Peak currents, extracted from dynamic signals, were decoupled to determine charge densities of bed particles, which were found to be qualitatively and quantitatively consistent with charge densities directly measured by Faraday cup from the freely bubbling fluidized bed. The current signals were also decoupled to estimate bubble rise velocities, which were found to be in reasonable agreement with those obtained directly by analyzing video images.

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