(260b) Decoupling Pressure Fluctuation Signals for the Monitoring of Bubble Behaviour In Dense Fluidized Beds

Pressure fluctuations in gas-solids fluidized beds have been commonly used to monitor the fluidization quality in commercial fluidized bed reactors, due to their easy measurement and non-intrusive nature. Pressure fluctuations are composed of several sources, including local bubble-induced fluctuations, global bed oscillations and pressure waves originating in other locations (e.g. bed surface, distributor and windbox) and propagating in the fluidized beds. The interaction and coupling among signals from different sources in fluidized beds create the complexity of measured local pressure fluctuations and the difficulty for their direct use for monitoring local bubble flow.

            A few attempts have been made in the past to extract local pressure fluctuations associated with the local bubble motion from raw pressure signals by decoupling measured pressure fluctuation signals using two or more pressure probes based on the power spectrum or coherence function analysis of signals. The differential pressure and the incoherent component of local pressure signals were believed to reflect the local bubble motion, with the mean amplitude proportional to the local mean bubble size.

            This presentation will examine complex pressure fluctuations in gas-solids fluidized beds and their applications for the determination of local bubble properties based on a few recent studies in our research lab and recent literature data. Discussions will also be given on future improvement in techniques for decoupling fluidized bed pressure fluctuation signals in order to increase the reliability of using pressure fluctuation signals for monitoring the reactor performance based on on-line monitoring of local and global bubble flow behaviour.