Hydrodynamic and mass transfer characterization of a flat-panel airlift photobioreactor with high light path

This work evaluates the volumetric mass transfer coefficient (k_La), the gas hold-up (ε) and the mixing time (t_m) as a function of superficial gas velocity (U_G) in a flat-panel photobioreactor (PBR) with high light path. CO₂ utilization efficiency and volumetric power consumption (P/V) were also evaluated. A 50 L working volume photobioreactor was developed, 0.67 m in length, 0.57 m in height and 0.15 m in width (light path). The height-width ratio was 3.8, which is lower than reported in most PBRs. Initially, experiments were performed with air and tap water (biphasic system) and, subsequently, using a Spirulina sp. culture (triphasic system: air, culture medium, cells). Minimum and maximum superficial gas velocity values were 5 × 10^-5 and 8.4 × 10^-3 m s^-1, respectively. Maximum values for k_La and ε were 20.34 h^-1 (0.0057 s^-1) and 0.033 in the biphasic system, and 31.27 h^-1 (0.0087 s^-1) and 0.065 in the triphasic system. CO₂ utilization efficiency was 30.57%. Results indicate that the hydrodynamic and mass transfer characteristics of this photobioreactor are more efficient than those reported elsewhere for tubular and other flat-plate PBRs, which opens the possibility of using PBRs with higher light paths than yet proposed.