A new photobioreactor for continuous microalgal production in hatcheries based on external‐loop airlift and swirling flow

Abstract

This study deals with the scale of a new photobioreactor for continuous microalgal production in hatcheries. The combination of the state-of-art with the constraints inherent to hatcheries has turned the design into a closed, artificially illuminated and external-loop airlift configuration based on a succession of elementary modules, each one being composed of two transparent vertical interconnected columns. The liquid circulation is ensured pneumatically (air injections) with respect to a swirling motion (tangential inlets). A single module of the whole photobioreactor was built-up to scale its geometry (diameter and length) and to optimize its design (air sparger, tangential inlets). The volumetric productivities were predicted by modeling radiative transfer and growth of Isochrysis affinis galbana (clone Tahiti). The hydrodynamics of the liquid phase was modeled in terms of global flow behavior (circulation and mixing times, Péclet number) and of swirling motion decay along the column (Particle Image Velocimetry). The aeration performances were determined by overall volumetric mass transfer measurements. Continuous cultures of Isochrysis affinis galbana (clone Tahiti) were run in two geometrical configurations, generating either an axial or a swirling flow. Lastly, the definitive options of design are presented as well as a 120-L prototype, currently implemented in a French mollusk hatchery and commercialized.

Continuous cultivation of photosynthetic microorganisms: Approaches, applications and future trends

“…Despite the mentioned advantages of continuous systems, batch cultivation is the most common method used in the cultivation of microalgae and cyanobacteria (Bougaran et al, 2003;Guedes et al, 2014;Loubière et al, 2009;Marchetti et al, 2012;Qiu 2010). The reasons for this preference are similar to those in other industries, like the brewing industry, where, despite the evident advantages of continuous systems, batch systems are still preferred (Brányik et al, 2006(Brányik et al, , 2012Pires et al, 2014).…”

“…Regarding the contamination risk, it is important to emphasize that the potential for culture collapse due to inadvertent contaminants is not an exclusive phenomenon of continuous cultivations, and does also occur in batch cultures (Rusch and Christensen, 2003). Other limitations such as the inability to provide constant natural illumination, which can restrict continuous systems to indoors; microbial attachment to walls during long cultivation periods (thus hampering light penetration); and the possibility of spontaneous genetic mutations in the microbial strains in a long-term operation, are also referred as limitations of continuous systems (Eriksen et al, 1998;Loubière et al, 2009;Marchetti et al, 2012;Paulová et al, 2013;Sharma and Stal, 2014;Tsygankov et al, 1998).…”

Microalgae as Future Fuel: Real Opportunities and Challenges

“…The other region, called the down comer, is where the medium flows down toward the bottom and circulates within the riser and the down comer. An airlift reactor based on the circulation mode is further categorized into internal loop or external loop [44]. Residence time of gas in different zones affects gas-liquid Flat Plate Photobioreactors (FPP): FPP consist of two rectangular panels made of glass or Perspex spaced about 25 mm or apart, illuminated on both sides and stirred by aeration (Figure 4).…”

Industrial Cultivation Systems for Intensive Production of Microalgae

“…12.12A) or another type of swirling flow inducer (Fig. 12.12B) can enhance the turbulence mixing degree in the photobioreactor [60,66,67,83,84,85,86,87]. In photobioreactors operated with gas-liquid two-phase flow, the turbulent mixing is bubble induced [88].…”