Experimental Investigation on the Influence of Bed Height and Bed Particle Size on Bed Expansion for a Bubbling Fluidized Bed

Knowledge of the basic mechanisms of the bed expansion ratio in gas fluidized beds is essential for an optimum design. The influence of bed height and bed particle sizes on the bed expansion ratio in a cylindrical fluidized bed was investigated. Four sizes of alumina Geldart Type-B particles of mean diameters 125, 177, 250 and 320 μm respectively were investigated at varying bed heights and superficial gas velocity under ambient conditions. Results showed that the expansion ratio of bed increased by increasing superficial gas velocity of all bed particle sizes employed. Smaller bed particles gave rise to a higher bed expansion when compared to larger-sized bed particles. The use of bed particles of relatively large size resulted in reduced bed expansion owing to decreased bubble formation. The expansion ratio was also determined to be inversely proportional to the bed height; this being a result of the larger resistance offered to the flow of fluidizing gas by the high static bed.