HYDRODYNAMICS OF A SOLID-SUSPENDED BUBBLE COLUMN WITH A DRAFT TUBE CONTAINING LOW-DENSITY PARTICLES

Experiments were conducted to discern the relationship between the hydrodynamics of a solid-suspended bubble column with a draught tube containing low-density particles comparable to those of bioparticles used in biological applications and the operating conditions such as the gas velocity, the solids holdup and the equipment geometry. An empirical correlation for gas holdup evaluation in the draught tube is obtained and found to be a function of the fluid velocity, which is the liquid-solid mixture flow velocity, induced by the dispersion of a gas into the draught tube. The gas holdup in the annulus is correlated to be a function of the gas holdup in the draught tube because of the close relation between them. Further, correlations for the pressure drop due to fluid flow reversal at the column top and base are obtained using the fluid flow velocity. An energy balance, which was used by Miyahara et al. (1986) for the conventional bubble column with a draught tube, is employed to predict the fluid circulation velocity using gas holdup and pressure drop correlations. A reasonable agreement is found between the predicted and the measured fluid circulation velocity.