EPTT 2020

12th Spring School on Transition and Turbulence

Evaluation of Geometric Alternatives to Promote Mixing in a Tubular Photobiorreactor

Submission Author: Leonardo Machado da Rosa , SC
Co-Authors: Daniela Koerich, Lisiane Fernandes de Carvalho, Leonardo Machado da Rosa
Presenter: Leonardo Machado da Rosa

doi://10.26678/ABCM.EPTT2020.EPT20-0106

 

Abstract

Microalgae are microorganisms capable of produce value-added materials such as biofuels, bioplastics andcompounds used in pharmaceutics, cosmetics, and human and animal nutrition. Moreover, microalgae have the ability tofix atmospheric CO2 and treat wastewater. Within the photobioreactor, areas further from the illuminated walls have lesslight radiation. Therefore, agitation is necessary so that all cells have contact with a sufficient amount of light radiation, and thereby promote photosynthesis. In addition, an efficient mixture between microorganisms and the substrate is alsonecessary in order for microalgae to consume it, producing materials of interest. In this work, 4 geometric configurationsare evaluated in terms of their ability to prevent the segregation of microalgae in a tubular photobioreactor, in addition to the smooth tube: a turbulent vortex promoter in cylindrical shape, a ring baffle, and a helical-shaped static mixer. These systems were evaluated using the Computational Fluid Dynamics (CFD) technique, with which three-dimensional simulations were performed, in a turbulent, transient multiphase regime. The pressure drop promoted by each device inserted in the pipeline was also evaluated, as alternatives that require the imposition of very high pressure to maintain the flow rate can make the process unfeasible. Other evaluation criteria were the swirl number of the flow, the uniformity index of the microalgae concentration, the turbulent kinetic energy, and the shear stress promoted by each photobioreactor configuration. Results showed that, depending on the obstacle used, the mixing between the phases can be enhanced, in terms of the swirl number and the turbulent kinetic energy, without the need for high pressure. However, the shear stressmay reach values that can be dangerous to the microalgae growth.

Keywords

Mixing, microalgae, CFD, vortices

 

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