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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    ABSTRACT: The tolerance to shear stress of Tetraselmis suecica, Isochrysis galbana, Skeletonema costatum, and Chaetoceros muelleri was determined in shear cylinders. The shear tolerance of the microalgae species strongly depends on the strain. I. galbana, S. costatum, and C. muelleri exposed to shear stress between 1.2 and 5.4 Pa resulted in severe cell damage. T. suecica is not sensitive to stresses up to 80 Pa. The possibility to grow these algae in a tubular photobioreactor (PBR) using a centrifugal pump for recirculation of the algae suspension was studied. The shear stresses imposed on the algae in the circulation tubes and at the pressure side of the pump were 0.57 and 1.82 Pa, respectively. The shear stress tolerant T. suecica was successfully cultivated in the PBR. Growth of I. galbana, S. costatum, and C. muelleri in the tubular PBR was not observed, not even at the lowest pumping speed. For the latter shear sensitive strains, the encountered shear stress levels were in the order of magnitude of the determined maximum shear tolerance of the algae. An equation was used to simulate the effect of possible damage of microalgae caused by passages through local high shear zones in centrifugal pumps on the total algae culture in the PBR. This simulation shows that a culture of shear stress sensitive species is bound to collapse after only limited number of passages, confirming the importance of considering shear stress as a process parameter in future design of closed PBRs for microalgal cultivation.
    Journal of Applied Phycology 03/2015; DOI:10.1007/s10811-015-0559-8 · 2.49 Impact Factor
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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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    ABSTRACT: This work presents the application of an event-based model predictive control algorithm to regulate the pH in a microalgae production process. The control aim is to maintain the pH within specific limits and to minimize CO2 losses. The control scheme is based on a Generalized Predictive Control (GPC) algorithm with sensor deadband approach. In this algorithm, the controller execution frequency is adapted to the process dynamics. The event-based scheme works with low sampling frequency if controlled variable, pH in this case, is inside an established band. Otherwise, when the pH value is outside the band, the controller actuation frequency is increased to try to drive it quickly near the setpoint based on the selected tolerance. In such a way, the event-based control algorithm allows to establish a tradeoff between control performance and number of process update actions. This fact can be directly related with reduction of CO2 injection times, what is also reflected in CO2 losses. The control structure is first evaluated through simulations using a nonlinear model for microalgal production in tubular photobioreactors. Afterwards, real experiments are presented on an industrial photobioreactor in order to verify the results obtained through simulations. Additionally, the real tests on the industrial plant are used to verify the event-based control scheme in the case of plant-model mismatch, presence of measurement noise and disturbances. Moreover, the control results are compared with classical time-based solutions using well-known control performance indexes.
    Computers & Chemical Engineering 06/2014; 65. DOI:10.1016/j.compchemeng.2014.03.001 · 2.45 Impact Factor
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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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    ABSTRACT: Scenedesmus obliquus was discussed by phycologists as a promising microalga for biofuel production based on its biomass and fatty acid productivity. In the present study, S. obliquus was pilot cultivated for large scale production in a semicontinuous culture for 3 months using polyethylene transparent bags. Cultivation of S. obliquus resulted in a maximum biomass productivity of 0.14 g L−1 d−1 and maximum esterified fatty acid productivity of 17.37 mg L−1 d−1 at light intensity of 130 μmol m−2 s−1. Using of different flocculants for biomass harvest showed maximum flocculation efficiency of 82% using 250 mg L−1 of NaOH for 2 h. Drying of the harvested biomass showed significant increase of esterified fatty acid content by 5 and 7% with respect to control at 75 and 100 °C, respectively. In addition, fatty acid profile and iodine number of S. obliquus oil meet biodiesel standard specifications which make the fatty acid of S. obliquus eligible for further research to be used as a feedstock for biofuel production. Furthermore, the present investigation showed that after oil extraction, the residual algal biomass increased survival and fresh weight of Artemia (brine shrimp) which confirms that the residual algal biomass can be significantly used as food additives for animal feeding.
    Biomass and Bioenergy 05/2014; 64. DOI:10.1016/j.biombioe.2014.03.049 · 3.41 Impact Factor
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