Experimental Investigation of Bubble Growth in in a Half-Cylindrical Gas-Solid Fluidized Bed

Fluidized beds are widely used in various processes such as mixing, catalytic and non-catalytic reactions, etc. In this article, the hydrodynamic characteristics of a gas-solid semi-cylindrical fluidized bed, which are affected by bubble properties including shape, size and rising velocity, are investigated for glass beads of 420 μm. For this purpose, a digital image analysis technique was employed to study the bubble behavior. The experiments were carried out in a semi-cylindrical fluidized bed with a diameter of 14 cm at ambient pressure and temperature. The static bed height was 21 cm (L/D=1.5) in all cases and the superficial gas velocity was varied in the range of 0.2 to 0.8 m/s. All properties of bubbles were investigated by increasing the superficial gas velocity and against the height of the bed. The results showed that aspect ratio, size and rising velocity of bubbles increase with increasing the superficial gas velocity. The size and rising velocity of bubbles, which were obtained experimentally, were found to be in good agreement with the values calculated by existing correlations with relative errors of 3.5% and 7 %, respectively. Moreover, all above mentioned properties of bubbles increase by increasing the height of the bed. The advantage of a semi-cylindrical bed over a cylindrical one is that through its flat surface, the phenomena inside the bed can be observed by a non-intrusive method. The results of these experiments can help to understand the complicated hydrodynamic behavior of fluidized beds.