Fluidized beds have been applied in many industrial processes (e.g. coal combustion,
gasification and granulation) as an effective means for providing excellent gas and
solids contact and mixing, as well as good heat transfer. Although research on the
fluidized bed has been carried out for more than 70 years, uncertainties and difficulties
still remain. These challenges exist primarily due to the complex and dynamic flow
structure within fluidized beds and the lack of reliable measurement techniques. The
positron emission particle tracking (PEPT) technique, developed at the University of
Birmingham, enables individual particles to be tracked non-invasively in opaque
three-dimensional (3-D) fluidized beds and offers favourable temporal and spatial
resolutions. PEPT is considered to be a powerful tool for fluidized bed studies and was
utilized in the current study to investigate the dynamic behaviour of solid and gas in
fluidized beds. The experiments in this study were conducted in a 150-mm inner
diameter (I.D.) column and operated in the bubbling fluidization regime at ambient
conditions. The effects of various factors on the solid flow structure were examined:
solid properties, superficial gas velocity, bed height-to-diameter aspect ratio (H/D) and
pore size of the air distributor. The solid flow structure was classified into four patterns,
namely patterns A, B, C and D, in which pattern C was newly observed in this thesis.
The solid motion, bubble behaviour (i.e., bubble spatial distribution, bubble size and
bubble rise velocity) and solid mixing were assessed for each flow pattern to
understand their unique fluidization behaviours. This assessment was achieved by the
development of three methods: a method to reconstruct bubble behaviours based on
solid motion, and two methods for estimating the solid mixing profile in this thesis.
The results were discussed and compared with the published literature. The bubble rise
velocity and bubble size calculated in this research from the PEPT-measured data was
in agreement with other research, particularly that of Kunii and Levenspiel, Yasui and
Johanson, and Mori and Wen. Finally, a parameter was developed to predict and
control flow patterns based on particle kinetic energy and various factors. The
outcomes of this study advance the understanding of the complicated dynamics of
bubbling fluidized beds and may benefit several industries in the enhancement of
fluidized bed design and control to achieve desirable qualities and efficiencies