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Title: Residence time distributions in circulating fluidised beds
Author: Harris, A. T.
Awarding Body: University of Cambridge
Current Institution: University of Cambridge
Date of Award: 2001
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The major focus of the work is on the measurement and simulation of the particle residence time distribution in the square cross section riser of a laboratory scale, cold model, circulating fluidised bed. To this end, a novel measurement technique was developed using phosphorescent tracer particles and a light based tracer injection and detection system. Experimental results confirm that the RTD is sensitive to changes in superficial gas velocity, external solids flux and the geometry of the riser exit. Simulations made using a novel stochastic particle RTD model are in good agreement with the experimental results. The measurements of the particle RTD, separately confirm the findings of a study of the riser exit using local pressure measurements, that demonstrate the influence of the riser exit on the solids flow pattern can be significant. A series of dimensionless correlations were developed to predict this influence. The effect of the exit has been shown to be dependent upon only one dimensionless group, the riser exit Froude number, FrR. A dimensionless correlation was also developed for predicting the thickness of the annular film present at the wall of CFB risers operating in the fast fluidisation regime. This correlation is superior to those published in the literature. A further series of correlations were developed to predict the size, shape, decent velocity, solids concentration and wall coverage of the particle clusters that are a characteristic feature of the gas-solid suspension in a CFB riser.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available