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Title: The dynamics and control of bubbling fluidised beds
Author: Lim, Chin Nam
ISNI:       0000 0001 3610 0685
Awarding Body: University of Bristol
Current Institution: University of Bristol
Date of Award: 2004
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The objective of the dissertation is to improve the understanding of the complicated dynamics of the bubbling process in a fluidised bed. This will enable the implementation of effective control to achieve a desirable fluidisation quality. Techniques in the field of dynamics and automatic control were employed to study the bed. A planar fluidised bed was used to enable bubbling to be directly observable and measurable using real-time image analysis instrumentation. The bubble void fraction, BVF, in the bed was measured, which is the proportion of the bed occupied by the voids associated with bubbles. A simulated bubbling bed devised based on the Clift & Grace (1970, 1971a, 1971b) bubble interaction model was validated experimentally using frequency domain analysis techniques. This led to the dynamical modelling of the fluidised bed by capturing the important features that governs the overall dynamics of the bed. The fluidised bed can be thought to be a temporary store of gas and the model related the introduction of a packet of gas and its nucleation as a bubble, to the changes in the bed BVF. The model works for cases of single bubbles and freely bubbling beds, showing that activities such as bubble interaction and coalescence cause non-linearity within the bed. The criteria for good fluidisation quality were defined and were related closely to bubble population and spatial distribution in the bed. The major causes affecting it were identified as bubble interaction and the influence of geometry allowing techniques to improve the quality of the process to be proposed. A closed-loop system permitted thorough system identification of the bubbling fluidisation process, enabling the process dynamics to be extracted for controller design purposes. Fixed gain (Proportional + Integral + Derivative) and adaptive (Minimal Control Synthesis) controller schemes were implemented to control the process producing good experimental results.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available