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: 2.87). 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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    • "It is the volume ratio of the gas phase in the distribution between gas and liquid phases or the residence time of the gas in the liquid. Given that aeration can occur in the riser, gas hold-up in the riser should be higher than the downcomer (without aeration) to create a liquid circulation pattern (Blanco et al., 2013; Molina et al., 2001; Wang et al., 2012). The design volume of the reactor and the gas–liquid contact area for mass transfer also depend on the gas hold-up, which is related to the bubble size and gas–liquid interfacial area for mass transfer. "
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    ABSTRACT: Microalgae have been used as energy resources in recent decades to mitigate the global energy crisis. As the demand for pure microalgae strains for commercial use increases, designing an effective photobioreactor (PBR) for mass cultivation is important. Chlorella vulgaris, a local freshwater microalga, was used to study the algal biomass cultivation and lipid production using various PBR configurations (bubbling, air-lift, porous air-lift). The results show that a bubbling column design is a better choice for the cultivation of Chlorella vulgaris than an air-lift one. The highest biomass concentration in the bubbling PBR was 0.78 g/L while the air-lift PBR had a value of 0.09 g/L. Key operating parameters, including draft-tube length and bubbling flowrate, were then optimized based on biomass production and lipid yield. The highest lipid content was in the porous air-lift PBR and the air-lift PBR with shorter draft tube (35 cm) was also better than a longer one (50 cm) for algal cultivation, but the microalgae attached on the inner tube of PBR always occurred. The highest biomass concentration could be produced under the highest gas flowrate of 2.7 L/min whereas the lowest dry cell mass was under the lowest gas flowrate of 0.2 L/min.
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    • "In indoor cultures, key parameters for microalgal growth (illumination, temperature, pH, nutrient levels, and contamination with predators) can be closely controlled. On the other hand, outdoor cultures presented high variability in these variables, since it is difficult to achieve higher production rates during extended periods (Lopez-Elias et al., 2005; Masojidek et al., 2003; Molina et al., 2001). Contamination with predators could be avoided if closed systems are chosen instead of open systems. "
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    ABSTRACT: Microalgae are photosynthetic microorganisms that can be found in diverse natural environments, such as water, rocks, and soil. They present higher photosynthetic efficiency than terrestrial plants, and are responsible for a significant fraction of the world oxygen production. The high growth rate attributed to microalgae gives them irrefutable economic potential. Besides the production of high-value products (for human and animal nutrition, cosmetics, and pharmaceuticals), they have recently been studied for some environmental and energy applications: (1) CO2 capture; (2) bioenergy production; and (3) nutrient removal from wastewater. However, none of these applications are economically viable, mainly due to the requirements of water, nutrients, and energy. Thus, this chapter gives an overview of all steps of the microalgal production chain, presenting a variety of research advances.
    No preview · Article · Dec 2015
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    • "It is the volume ratio of the gas phase in the distribution between gas and liquid phases or the residence time of the gas in the liquid. Given that aeration can occur in the riser, gas hold-up in the riser should be higher than the downcomer (without aeration) to create a liquid circulation pattern (Blanco et al., 2013; Molina et al., 2001; Wang et al., 2012). The design volume of the reactor and the gas–liquid contact area for mass transfer also depend on the gas hold-up, which is related to the bubble size and gas–liquid interfacial area for mass transfer. "

    Full-text · Dataset · Dec 2015
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