Article

Tubular photobioreactor design for algal culture. J Biotech

Department of Chemical Engineering, University of Almería, E-04071 Almeria, Spain.
Journal of Biotechnology (Impact Factor: 2.88). 01/2002; 92(2):113-31. DOI: 10.1016/S0168-1656(01)00353-4
Source: PubMed

ABSTRACT Principles of fluid mechanics, gas-liquid mass transfer, and irradiance controlled algal growth are integrated into a method for designing tubular photobioreactors in which the culture is circulated by an airlift pump. A 0.2 m(3) photobioreactor designed using the proposed approach was proved in continuous outdoor culture of the microalga Phaeodactylum tricornutum. The culture performance was assessed under various conditions of irradiance, dilution rates and liquid velocities through the tubular solar collector. A biomass productivity of 1.90 g l(-1) d(-1) (or 32 g m(-2) d(-1)) could be obtained at a dilution rate of 0.04 h(-1). Photoinhibition was observed during hours of peak irradiance; the photosynthetic activity of the cells recovered a few hours later. Linear liquid velocities of 0.50 and 0.35 m s(-1) in the solar collector gave similar biomass productivities, but the culture collapsed at lower velocities. The effect of dissolved oxygen concentration on productivity was quantified in indoor conditions; dissolved oxygen levels higher or lower than air saturation values reduced productivity. Under outdoor conditions, for given levels of oxygen supersaturation, the productivity decline was greater outdoors than indoors, suggesting that under intense outdoor illumination photooxidation contributed to loss of productivity in comparison with productivity loss due to oxygen inhibition alone. Dissolved oxygen values at the outlet of solar collector tube were up to 400% of air saturation.

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    • "Other types of PBRs, like horizontal tubular PBRs with a shorter light path to produce microalgae at a higher density, are used by aquaculture facilities more often lately (Zmora et al. 2013). Mixing in these systems is induced through recirculation of the microalgal culture in the tubular PBR using pumps, of which centrifugal pumps and airlift pumps are the most common ones (Alías et al. 2004; Molina et al. 2001). Centrifugal pumps are efficient in gas–liquid mass transfer (Fadavi and Chisti 2005) and energy use (Norsker et al. 2011). "
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    • "The facility consists in ten tubular fence-type photobioreactors, which detailed features can be found in (Acién et al., 2001). Figure 1 shows a scheme of the tubular photobioreactor (Molina et al., 2001). The system is composed of a vertical external-loop airlift pump that drives the culture fluid through the vertical tubular solar receiver and a bubble column. "
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    • "Suspension stirring through blowing air in at the bottom of the reactor facilitates gas exchange and temperature equalization in the highly turbulent upper zone [25] [26]. Grima et al. [27] reported that excessive levels of dissolved oxygen released from photosynthesis inhibit photosynthesis and cause the reaction of photo-oxidation, which leads to damage of algal cells. Therefore, it was necessary to inject carbon dioxide to prevent photo-oxidation and to prevent excessive increase of pH [25]. "
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