Estimation of bed expansions in a freely-bubbling three-dimensional gas-fluidized bed

Abstract

Knowledge of bed expansions is important in the design and operation of gas-solid fluidized beds. This paper presents a study on the estimation of expanded bed height in a large three-dimensional gas-fluidized bed with a square section of 0.61 x 0.61 m 2 . All experiments were performed at the freely bubbling mode and the bed expansions were recorded by a video camera. Bed materials were used 593 μm raw perlite and 1233 μm sand falling within the categories of Geldart's Groups B and D, respectively. The bed height at minimum fluidization ranged from 0.0398 to 0.3176 m, while the excess air velocity from 0.034 ms -1 to 0.7453 m s -1 . Equations related to the bed expansion were given using a modified form of two-phase theory of fluidization. A correlation for the average bed expansion (void fraction) was also presented that has been derived from the principal form found successful in gas-liquid systems as follows: R = 0.5482 d p -0.129 (U o - mf ) 0.111 with an average deviation of less than 1%. The experimental findings were compared with previously reported results and were discussed in the light of available correlations. © 1998 John Wilev & Sons, Ltd.