Developing a three-dimensional tangential swirl plate photobioreactor to enhance mass transfer and flashlight effect for microalgal CO2 fixation

A novel three-dimensional tangential swirl plate (TTSP) photobioreactor was proposed to strengthen flow perpendicular to central cross-section between two side walls, resulting in more widespread turbulence for improving microalgal CO2 fixation. The axes of four center-symmetrically arranged nozzles were tangential to a horizontal cylinder to form two staggered vortexes. When angle h between nozzle axis and central cross-section increased from 0 degrees to 22.1 degrees and then to 40.0 degrees, mixing time and average bubble diameter first decreased to the minimum (16.55 s and 0.57 mm) and then increased. When relative diameter of tangential cylinder d/D increased from 0.11 to 0.34 and then to 0.56, flashlight frequency and light time ratio first increased to the maximum (0.21 Hz and 42.8%) and then decreased. Accordingly, flashlight frequency was 90.9% higher in TTSP photobioreactor than that in two-dimensional jet-aerated tangential swirl plate (JTSP) photobioreactor, leading to an increase in microalgal CO2 fixation rate by 30%. (C) 2021 Elsevier Ltd. All rights reserved.