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Gewählte Master / Diploma Thesis:

Roland Schropp (2019): Development of an inductive measurement system based on a beat frequency oscillator to investigate particle mixing in circulating fluidized beds.
Master / Diploma Thesis - Institut für Verfahrens- und Energietechnik (IVET), BOKU-Universität für Bodenkultur, pp 75. UB BOKU obvsg FullText

Data Source: ZID Abstracts
Abstract:
A simple and low-cost beat frequency oscillator (BFO) device has been developed in this thesis that was capable of performing inductive measurements of residence time distributions (RTD) using ferromagnetic tracer particles in a cold flow model featuring a circulating fluidized bed (CFB). The main bed material were glass beads sized 145 μm, spiked with ferritic stainless steel 1.4742 tracer particles of 45-100 μm in size. The fluidized bed chamber had a footprint of 200 x 400 mm and a moving bed height of 300-400 mm and the bed was fluidized with velocities of up to 0.278 m/s. Solids circulation in the particle loop was controlled by a screw conveyor, with mass flows of up to 210 kg/h. The measurement coils were mounted at the particle inlet and outlet pipes and were used as frequency determining parts of LC-oscillators. The ferquency deflection was measured differentially from a beat wave with a reference oscillator according to the BFO principle. Pulse injection RTD measurements were started with the removal of a magnet applied to the downcomer upstream of the inlet measurement coil. The frequency deflection was correlated to mass fractions of tracer material inside a measurement coil, which proved to be a linear relation for mass fractions of up to 0.11 kg/kg and the small residual error was non- systemic. The minimum fluidization velocity umf was determined to be equal to the minimum bubbling velocity umb at 0.028 m/s and bubbling activity was shown to be more homogeneous in lower regions of the bed and more vigorously fluctuating close to the surface. Excellent effective temporal resolution of the measurement method was shown with capturing the tracer injection peak, while problems related to signal drift were encountered during the longer termed RTD measurement. Idealized reactor models were fitted to the RTD curve and the char- acteristics and deviations of the data were discussed.

Beurteilende(r): Pröll Tobias
1.Mitwirkender: Hofer Gerhard

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