Decoupling electrostatic signals from gas–solid bubbling fluidized beds

• Decoupling methods are devised for electrostatic probe signals.
• Criteria are provided for selecting suitable passing bubbles.
• Measured local charge densities agree with Faraday cup values.
• Effects of selection criteria on decoupled results are evaluated.

Electrostatic signals registered by collision probes in gas–solid fluidized beds contain useful information. However, the signal has been poorly understood, with questions, such as what the signal means and how to extract useful information, being unanswered. In this study, different decoupling methods based on a simple charge transfer and induction model are proposed and applied to obtain both the particle charge density and the bubble rise velocity by decoupling electrostatic charge/current signals from a previously developed dual-material probe in both two- and three-dimensional freely bubbling fluidized beds. A signal processing procedure including a bubble selection algorithm is proposed and applied to screen electrostatic signals from the probe in bubbling fluidized beds. Decoupled results from two selected methods showed consistent trends and had the same order of magnitudes as those obtained from the analysis of video images and Faraday cup measurements. The effects of the bubble selection algorithm criteria on interpreted results are also investigated.

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