Simultaneous measurements of particle charge density and bubble properties in gas-solid fluidized beds by dual-tip electrostatic probes

The aim of this work was to develop a new dual-tip electrostatic probe for in-situ measurements of particle charge density and bubble properties in bubbling fluidized beds. Probes containing two retractable, vertically-aligned tips were tested in a lab-scale two-dimensional fluidized bed operated in both single bubble injection and freely bubbling modes, with glass beads and polyethylene particles of narrow size distributions as bed materials. Different decoupling methods were proposed and employed to analyze the electrostatic signals from the probes. The estimated particle charge density and bubble rise velocity were found to follow the same trends as those measured by a Faraday cup sampling system and obtained from video images respectively, with relative errors depending on the decoupling methods and probe configurations, especially for polyethylene particles.