Microalgae cell disruption using three-phase fluidized bed with agitator

Abstract

Microalgal cells disruption was investigated by using three-phase fluidized bed in which air, microalgal suspension and glass beads (diameter 1 mm) are treated as gas, liquid, and solid phases, respectively. An agitator was also employed to enhance the cell disruption performance. Chlorella ellipsoidea TISTR 8260, Chroococcus sp. TISTR 8625 and Chlorococcum sp. TISTR 8509 are used in this investigation within concentration range varied between (9-15) X10⁶ cells/cm³. Superficial gas and liquid velocities are varied from 0-40 cm/min, while agitation speed is varied between 0 and 3000 rpm. Percentage of cell ruptured, disruption rate, microalgal cell volume and amount of chlorophyll were measured to confirm the disruption performance of the equipment. The results show that each single variable provides almost equal influence on the disruption of all microalgae. Superficial gas and liquid velocities at10 cm/min show the highest value of cell disruption at 41.8 and 38.5%, respectively. An increase in superficial gas or liquid velocities resulted in a decrease in the percentage of cell disruption for all species investigated. Meanwhile, agitation speed of 3000 rpm provided the highest percentage of cell disruption at 38.5%. In the systems employing all disruption factors, namely, superficial gas and liquid velocities and agitation this cell disruption could be enhanced up to 93.6%. Based on the experimental results , dominating disruption mechanisms could be implied as; the grinding effect beads due to particle-particle interaction and particle-cell interaction, and shear stress due to the fluid flow.