Brought to you by | Bibliotheek TU Delft Authenticated | 172.16.1.226 Download Date | 8/14/12 8:51 AM Bubble Size Reduction in a Fluidized Bed by Electric

The reduction of the size of bubbles can improve both selectivity and conver-sion in gas-solid fluidized beds. Results are reported of the reduction of bubble size by the application of electric fields to uncharged, polarizable particles in flu-idized beds. It is shown how average bubble diameters can be drastically reduced, with little change of the bed expansion. A literature review shows that to main-tain smooth fluidization, electric fields in the direction of the gas flow, with a relatively low alternating frequency, are optimal. To measure average bubble di-ameters, a spectral decomposition technique of pressure fluctuation time series is used. Using this method, based on non-intrusive measurements, a characteristic length scale for bubble diameters can be found. It is shown experimentally, using video analysis, that this length scale is of constant proportionality for a given bed material and bed dimensions. The proportionality of the length scale to bubble diameter is independent of measuring height or gas velocity. With this, we have a tool for measuring bubble diameters in both 2-D and 3-D fluidized beds. Electri