Neutrally buoyant particles, solids-liquid flow

Bubble formation in liquids with the presence of particles, as in slurry bubble columns and three-phase fluidized bed systems, is different from that in pure liquids. The experimental data of Massimilla et al. (1961) in an air-water ass beads three-phase fluidized bed revealed that the bubbles formed from a single nozzle in the fluidized bed are larger than those in water, and the initial bubble size inereases with the solids concentration. Yoo et al. (1997) investigated bubble formation in pressurized liquid solid suspensions. They used aqueous glyeerol solution and 0.1 mm polystyrene beads as the liquid and solid phases, respectively. The densities of the liquid and the particles were identical, and thus the partieles were neutrally buoyant in the liquid. The results indicated that initial bubble size deereases inversely with pressure under otherwise eonstant eonditions, that is, gas flow rate, temperature, solids eoneentration, orifiee diameter, and gas chamber volume. Their results also showed that the particle effect on the initial bubble size is insignificant. The difference in the finding regarding the particle effect on the initial bubble size between Massimilla et al. (1961) and Yoo et al. (1997) is possibly due to the difference in particle density. 

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