Performance Evaluation of a Laboratory-scale Fluidized Bed Set-up

Author : Alkuino, Liwayway Sagun
Major Adviser : Arquiza, Apollo C.
Committee Members : Valencia, Sixto A.; Tapang, Edwin
Year : 1994
Month : April
Type : Thesis
Degree: BS
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A study was done to evaluate the performance of the laboratory-scale fluidized bed set-up Designed by Bautista (1991). Three, four, five millimeter glass beads and sodium alginate beads were used in the experiment. The general pattern of the behavior of the beads was observed and it was found out that pressure drop across the bed and the bed voidage increases with an increase in the superficial velocity of the fluid. Linear relationships for the logarithm of pressure drop and velocity were obtained for each material. These relationships may be used to predict the pressure drop across the bed at any particular velocity. The equations obtained were used to supplement the development of a computer program. it was also observed that density of the materials affects the fluidization of the bed. Glass beads which have densities ranging from 127.45 lb/ft³ to 148.27 lb/ft³ have higher pressure drop than beads with density of 63.177 lb/ft³ like sodium alginate. The effect of the particle size was not observed in the both glass beads and sodium alginate.

The performance of the fluidized bed set-up using glass beads was unsatisfactory in terms of its ability to fluidize the system completely. Using glass beads, the theoretical minimum fluidizing velocity which is equal to 0.07440 ft/s was high such that if the velocity of fluid was increased beyond this point to observe fluidization, the water will overflow. For sodium alginate, the behavior of the bed at the onset of fluidization was not observed because the calculated Uₘ? which was only 0.00001 ft/s was very low. The point of incipient fluidization was not also determined for both materials because the pressure drop of the system continues to increase as the fluid velocity is increased beyond the computed minimum fluidizing velocity. The increase of the pressure drop is accounted to the pressure drop contributed by the set-up. Generally, the performance of the set-up is unsatisfactory for both glass beads and sodium alginate because the complete behavior of the system can not be observed.

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