Measurement of Fluidizaton Dynamics in a Fluidized Bed using Capacitance Tomography

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Author Last Name: 
M S Beck, T Dyakowski and S J Wang
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Research Area: 
Powder Flow
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United Kingdom

A sensor with 12 sensing electrodes and 24 driven guard clcctrodes has been constructed. This provides an increase of 80% in the measured capacitances and enables narrower cross sectional slices to be imaged.

A series of experiments on both bubbling and fast fluidization flow regimes were conducted at University of Bradford. The tomographic data were compared with measurements taken with an existing mass flux probe as well as pressure transducer measurements. The results showed that for a bubbling fluidization the data obtained from ECT measurements agreed very well with the data obtained from the pressure drop measurements. A satisfactory correlation of the tomographic data was obtained for a fast fluidization flow regime.

A new method for setting the system measurement range has been incorporated into our Windows software to measure a mean solid concentration in the range 2 to 10%. This method allows more accurate measurement of low solid concentrations (up to 5% by volume).

To order to study the dynamic behaviour of a fluidized bed by using Deterministic Chaos Theory it is necessary to calculate statistical invariants from hundreds of thousands of data points. Our existing software has been modified to carry out such an analysis. The application of a singular value decomposition technique combined with the data from an ECT system is presented (Dyakowski et al, 1996).

AVS software has been used to visualize the movement of a bubble chain through a fluidized bed. In the future we intend to use this software to visualise slugging and turbulent flow regimes.