A novel jet-aerated tangential swirling-flow plate photobioreactor generates microbubbles that enhance mass transfer and improve microalgal growth

Abstract

To reduce bubble diameter and enhance mass transfer, a novel jet-aerated tangential swirling-flow plate photobioreactor was developed that improves the growth rate of microalgae. In this system, the circulating microalgal solution enters a jet aerator that takes up 15% CO₂ by vacuum suction and then injects into a plate photobioreactor through four centrally symmetric nozzles. Each jetflow is tangent to a tangential circle, driving vertical vortex movement of the surrounding microalgal solution, which markedly reduced the bubble diameter and enhanced mass transfer. The mass transfer coefficient was enhanced by decreasing the nozzle number (n) and increasing the ratio of tangential circle diameter to plate photobioreactor equivalent diameter (d/D). The average bubble diameter decreased by 80.2% to 0.37 mm and the mass transfer coefficient increased 4.6 times to 48.9 h^-1 when n was 4 and d/D was 0.34. Finally, the optimized system increased the biomass dry weight of microalgae by 49.4%.

Keywords: Jet aerator; Microalgae; Microbubble; Plate photobioreactor; Tangential swirling-flow.