Comparison of Two Different Vertical Column Photobioreactors for the Cultivation of Nannochloropsis sp.

Abstract

A photobioreactor (PBR) for microalgae culture is a highly efficient system for biomass production. In the present study, the performance of an airlift (ALR) (with a centric-tube column) and a bubble column (BC) photobioreactors were compared considering Nannochloropsis sp. growth. The experiments were carried out keeping average light intensity, temperature, volume culture, and CO2 supply constant, while cell concentration and pH level were measured and examined. Furthermore, a computational fluid dynamics (CFD) simulation in cfx, ansys 11.0, was developed using a multiphase flow model with an Eulerian approach to evaluate the hydrodynamic behavior of both systems. The results showed that a higher cell concentration (375 × 105 cell/ml) was obtained in the airlift PBR yielding a better growth rate than the bubble column PBR. In terms of hydrodynamic performance, the existence of the centric-tube in the airlift system shows a well-defined flow pattern, better light distribution cycle, and more effective mixing. These hydrodynamic characteristic of the airlift PBR may allow a better yield for the microalgae biomass production.