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Hideo Tanaka - One of the best experts on this subject based on the ideXlab platform.
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Design of static mixers for inclined tubular Photobioreactors
Journal of Applied Phycology, 2003Co-Authors: Charles U. Ugwu, James C. Ogbonna, Hideo TanakaAbstract:Static mixers, which improve gas-liquid mass transfer inside tubular Photobioreactors and move the cells between the upper and lower parts of the tubes were designed. Each static mixer was equipped with an opening (v-cut slit) at the top (for gas dispersion) and an orifice at the lower part (for liquid circulation). When the static mixers were installed in the riser tube of an inclined tubular photobioreactor, vertical movement of the liquid was induced so that cells were moved between the surface and bottom part of the photobioreactor. The mass transfer rates in the tubular photobioreactor without static mixers decreased sharply when they were scaled up by increasing the tube diameters. However, by installation of static mixers, the mass transfer rates in 12.5-cm diameter tubes were almost as high as those of 3.8-cm tubes without static mixers. The effectiveness of the static mixers in improving the mass transfer characteristics of the tubular Photobioreactors was higher in large than small diameter tubes. The ratio of the diameters of the static mixers to the diameter of the tube, the areas of the v-cut slits and the orifice were the important design parameters that affected the mass transfer characteristics. The gas hold up and and kLa were higher when the areas of the slits (v-cut) and the orifice were reduced.
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Light supply coefficient: A new engineering parameter for photobioreactor design
Journal of Fermentation and Bioengineering, 2002Co-Authors: James C. Ogbonna, Hirokazu Yada, Hideo TanakaAbstract:Abstract The reliability of the incident light intensities, the average light intensities and the light energy supplied per unit photobioreactor volume ( E t V ) as indices of light conditions inside Photobioreactors was investigated in cuboidal Photobioreactors of various sizes. There was no good relationship between the linear growth rates of Chlorella pyrenoidosa and the incident or average light intensities in the Photobioreactors of various sizes. Although the linear growth rate increased with increase in E t V , there was much scatter of data near the curve. At a given E t V , the linear growth rates decreased with increase in the photobioreactor depth, indicating that the light distribution inside the photobioreactor must be considered for the rational design and scale-up of Photobioreactors. A concept of light distribution coefficient (Kiv) defined as the cell concentration at which 50% of the photobioreactor volume receives enough light for photosynthetic growth was therefore proposed. The linear growth rates increased with increase in Kiv but the data were scattered. At a constant Kiv, however, a linear relationship was observed between the linear growth rate and the E t V . Similarly, when the E t V was held constant, there was a good correlation between the Kiv and the linear growth rate. A light supply coefficient, defined as E t V . Kiv was then proposed as an index of the light supply efficiency of Photobioreactors. There was a linear relationship between the light supply coefficient and the linear growth rates of both C. pyrenoidosa and Spirulina plantensis in cuboidal Photobioreactors of various sizes. However, the slopes of the curves were different for the two microorganisms. When various other types of both internally illuminated and externally illuminated cylindrical Photobioreactors were used, good correlation was found between the linear growth rates of Chlorella and the light supply coefficient. This demonstrates that irrespective of the cell type, photobioreactor type and size, the proposed light supply coefficient can be used for quantitative evaluation of light condition inside the photobioreactor. It is thus a useful engineering parameter for design and scale-up of Photobioreactors.
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A Novel Internally Illuminated Stirred Tank Photobioreactor for Large-Scale Cultivation of Photosynthetic Cells
Journal of Fermentation and Bioengineering, 2002Co-Authors: James C. Ogbonna, Hirokazu Yada, Hiroyuki Masui, Hideo TanakaAbstract:A new concept in photobioreactor design with reactor scale-up as a primary design criterion is proposed for the development of large-scale stirred tank Photobioreactors. A photobioreactor is considered as consisting of units, with each unit being composed of a light source (or light distributing object) and its surroundings. The light supply coefficient of each unit depends on its size and the light intensity of the light source. At a given light intensity, the optimum unit size which gives the desired light supply coefficient for the target process is experimentally determined. A large photobioreactor with a desired light supply coefficient is obtained by increasing the number of units. A prototype photobioreactor, consisting of 4 units, was constructed for the cultivation of Chlorella pyrenoidosa. Each unit was equipped with a centrally fixed glass tube into which the light source was inserted. The illuminating system consisted of either 4-W fluorescent or halogen lamps with controllable light intensity. By changing the light intensity, it is possible to use the photobioreactor for the cultivation of various cells with different optima light supply coefficients. Mixing was achieved by means of an impeller, designed in such a way that while rotating it does not touch the glass tubes, which also serve as baffle plates. Although the hydrodynamic stress generated by the impeller was low, a high degree of mixing was achieved even at low rotation speeds. Since the light distributing objects were not mechanically fixed to the reactor, and were separated from the broth by the glass tubes, the reactor could be sterilized by autoclaving and the light distributing objects inserted to the glass tubes after cooling. The photobioreactor was equipped with a ring sparger for aeration. When C. pyrenoidosa was cultivated in the new photobioreactor at low and moderately high light supply coefficients, both the linear growth rates and the final cell concentrations increased linearly with the light supply coefficient of the reactor. A comparison of the results obtained in this new photobioreactor with those of the commercially available Photobioreactors with either external or internal illumination showed that the cell yield from the supplied light energy was highest in the new photobioreactor.
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improvement of mass transfer characteristics and productivities of inclined tubular Photobioreactors by installation of internal static mixers
Applied Microbiology and Biotechnology, 2002Co-Authors: Charles U. Ugwu, James C. Ogbonna, Hideo TanakaAbstract:The feasibility of improving mass transfer characteristics of inclined tubular Photobioreactors by installation of static mixers was investigated. The mass transfer characteristics of the tubular photobioreactor varied depending on the type (shape) and the number of static mixers. The volumetric oxygen transfer coefficient (kLa) and gas hold up of the photobioreactor with internal static mixers were significantly higher than those of the photobioreactor without static mixers. The kLa and gas hold up increased with the number of static mixers but the mixing time became longer due to restricted liquid flow through the static mixers. By installing the static mixers, the liquid flow changed from plug flow to turbulent mixing so that cells were moved between the surface and bottom of the photobioreactor. In outdoor culture of Chlorella sorokiniana, the photobioreactor with static mixers gave higher biomass productivities irrespective of the standing biomass concentration and solar radiation. The effectiveness of the static mixers (average percentage increase in the productivities of the photobioreactor with static mixers over the productivities obtained without static mixers) was higher at higher standing biomass concentrations and on cloudy days (solar radiation below 6 MJ m–2 day–1).
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Development of Efficient Large-Scale Photobioreactors
BioHydrogen, 1998Co-Authors: James C. Ogbonna, Toshihiko Soejima, Hideo TanakaAbstract:This work was aimed at developing an efficient stirred-tank photobioreactor for the large- scale cultivation of photosynthetic cells. A quantitative method of evaluating light conditions inside Photobioreactors was first investigated and a light-supply coefficient, which is a product of a light-distribution coefficient and light energy supplied per unit volume, was proposed as an engineering parameter for design and scale-up of Photobioreactors. Using this parameter, a method of designing and scaling-up internally illuminated Photobioreactors was proposed. A photobioreactor was considered as consisting of units, and an optimum unit size was defined as a reactor volume that is optimally illuminated by a centrally located single light source. A large-scale photobioreactor with the optimum light-supply coefficient can thus be constructed by determining the optimum unit size for the target process and then increasing the number of units in three dimensions. Based on this concept, an optimum unit was constructed and then scaled-up to 20.0 L while maintaining a constant light-supply coefficient. With a 20-W fluorescent lamp, the unit size (diameter) that gave the optimum light-supply coefficient for the cultivation of Chlorella was 0.075 m. Carbon dioxide fixation by Chlorella pyrenoidosa and α-tocopherol production by Euglena gracilis cells in the 20.0-L photobioreactor were the same as those of the single unit.
Francisco G. Acíen - One of the best experts on this subject based on the ideXlab platform.
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Outdoor production of Tisochrysis lutea in pilot-scale tubular Photobioreactors
Journal of Applied Phycology, 2016Co-Authors: Davide Ippoliti, Ismael Martín, José M. Fernández Sevilla, Rossella Pistocchi, Alicia Gonzalez, Francisco G. AcíenAbstract:In this paper we study the outdoor production of Tisochrysis lutea in pilot-scale tubular Photobioreactors (3.0 m3). Experiments were performed modifying the dilution rate and evaluating biomass productivity and quality, in addition to the overall performance of the system. Results confirm that T. lutea can be produced outdoors on a commercial scale in continuous mode, obtaining productivities of up to 20 g m−2 day−1 of biomass, which are rich in proteins (45 % d.wt.) and lipids (25 % d.wt.). The utilization of this type of photobioreactor allows one to control the levels of contamination and pH within the cultures, but daily variations in solar radiation impose elevated dissolved oxygen concentrations and insufficient temperature conditions on the cells inside the reactor. Excessive dissolved oxygen reduces biomass productivity to 68 % of that which is maximal, whereas inadequate temperature reduces it to 63 % of maximum. Thus, by optimally controlling these parameters, biomass productivity can be almost doubled. These results confirm the potential for producing this valuable strain on a commercial scale in optimally designed/operated tubular Photobioreactors as a viable biotechnological industry.
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Optimization of biomass production in outdoor tubular Photobioreactors
Journal of Process Control, 2015Co-Authors: G.a. De Andrade, Jose Luis Guzman, Manuel Berenguel, Daniel J Pagano, Francisco G. AcíenAbstract:Abstract This paper is concerned with microalgal biomass production optimization in outdoor tubular Photobioreactors. The main purpose of such optimization system is to calculate the culture medium flow rate in order to maximize the biomass production over a determined period of time. Two different methods are shown in this work: (i) an optimal and (ii) a near-optimal strategy. The optimal strategy belongs to the optimal control theory. In this context, a direct method is used to discretize the control problem and a nonlinear programming technique is applied into the resulting optimization problem. The near-optimal strategy calculates only the culture medium injection time, while the culture medium flow rate is maintained constant during this time. For this aim, a photobioreactor model, under real environmental and culture conditions, is used to compute the injection time. This strategy is mostly important for those Photobioreactors that are not equipped with a continuous culture medium valve. Simulation and experimental results allow the user to evaluate the effectiveness of the biomass production optimization strategies proposed in this work, compared with a classical harvesting strategy.
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a lumped parameter chemical physical model for tubular Photobioreactors
Chemical Engineering Science, 2014Co-Authors: Ignacio Fernandez, Francisco G. Acíen, Manuel Berenguel, Jose Luis Guzman, Gustavo A De Andrade, Daniel J PaganoAbstract:Abstract This work presents a dynamic lumped parameter model for microalgal production in tubular Photobioreactors. The model is made up of fluid-dynamic processes, mass transfers and biological phenomena, all of them being based on chemical, physical, and biological principles. The aim of this work is to develop a simplified model including the main non-linear dynamics of the process, so that a trade-off between complexity and performance can be found. The model can be used for advanced control purposes, as a tool for the design and operation optimization of Photobioreactors, or even as a supervision system of unmeasured variables. The characteristic parameters of the model were calibrated and validated under different conditions of solar radiation, using experimental data from a pilot facility consisting in an outdoor tubular photobioreactor. Furthermore, the proposed model is compared to other existing models (linear, distributed parameters and NARMAX) through a set of detailed simulations.
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dynamic model of microalgal production in tubular Photobioreactors
Bioresource Technology, 2012Co-Authors: Ignacio Fernandez, Francisco G. Acíen, J.m. Fernández, Jose Luis Guzman, J J Magan, Manuel BerenguelAbstract:Abstract A dynamic model for microalgal culture is presented. The model takes into account the fluid-dynamic and mass transfer, in addition to biological phenomena, it being based on fundamental principles. The model has been calibrated and validated using data from a pilot-scale tubular photobioreactor but it can be extended to other designs. It can be used to determine, from experimental measurements, the values of characteristic parameters. The model also allows a simulation of the system’s dynamic behaviour in response to solar radiation, making it a useful tool for design and operation optimization of Photobioreactors. Moreover, the model permits the identification of local pH gradients, dissolved oxygen and dissolved carbon dioxide; that can damage microalgae growth. In addition, the developed model can map the different characteristic time scales of phenomena inside microalgae cultures within tubular Photobioreactors, meaning it is a valuable tool in the development of advanced control strategies for microalgae cultures.
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Characterization of a flat plate photobioreactor for the production of microalgae
Chemical Engineering Journal, 2008Co-Authors: E. Sierra, Francisco G. Acíen, J.m. Fernández, José Luis Zambrana García, C. González, Emilio MolinaAbstract:Abstract This paper presents the characterization of a flat panel photobioreactor (0.07 m wide, 1.5 m height and 2.5 m length) for the production of microalgae. Several factors are considered. The orientation was studied first resulting east/west the most favourable because the total solar radiation intercepted was maximum, increasing 5% with regard to horizontal placement, and the exposure resulted to be the most homogeneous over the year. Then, gas holdup, mass transfer, mixing and heat transfer were studied as a function of the aeration rate. This is a key operating variable because it determines the power supply, which governs the fluid-dynamics of the system and subsequently influences other transport phenomena. The gas holdup and mass transfer coefficient found were consistent with referenced values for bubble columns observed in tubular photobioreactor. A power supply of 53 W/m 3 promoted a mass transfer rate high enough to avoid the excessive accumulation of dissolved oxygen in this flat panel photobioreactor. This is similar to the 40 W/m 3 necessary in bubble columns and much lower than the 2000–3000 W/m 3 required in tubular Photobioreactors. However, this power supply is in the order of magnitude of 100 W/m 3 , which has been reported to damage some microalgal cells, whereas no damage has been referenced in tubular Photobioreactors. Even at low power supplies the mixing time was shorter than 200 s, longer than the 60 s measured for bubble columns, but quite faster than the typical values found for tubular Photobioreactors (1–10 h). With regard to heat transfer, global coefficients were determined for the internal heat exchanger and for the external surface of the photobioreactor. The observed behaviour was similar to that referenced for bubble columns, although the values of heat transfer coefficients measured were lower than in bubble columns. The heat transfer coefficient of the internal heat exchanger (over 500 W/m 2 K) was much higher than the coefficient of the external surface of the reactor (30 W/m 2 K). Internal heat exchangers are therefore useful to control the temperature of the culture in this type of photobioreactor. The major disadvantage of this reactor is the potential high stress damage associated with aeration. The main advantages are the low power consumption (53 W/m 3 ) and the high mass transfer capacity (0.007 1/s). The characterization carried out allows improving the design and establishing the proper operating conditions for the production of microalgae using this type of photobioreactor.
Charles U. Ugwu - One of the best experts on this subject based on the ideXlab platform.
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Design of static mixers for inclined tubular Photobioreactors
Journal of Applied Phycology, 2003Co-Authors: Charles U. Ugwu, James C. Ogbonna, Hideo TanakaAbstract:Static mixers, which improve gas-liquid mass transfer inside tubular Photobioreactors and move the cells between the upper and lower parts of the tubes were designed. Each static mixer was equipped with an opening (v-cut slit) at the top (for gas dispersion) and an orifice at the lower part (for liquid circulation). When the static mixers were installed in the riser tube of an inclined tubular photobioreactor, vertical movement of the liquid was induced so that cells were moved between the surface and bottom part of the photobioreactor. The mass transfer rates in the tubular photobioreactor without static mixers decreased sharply when they were scaled up by increasing the tube diameters. However, by installation of static mixers, the mass transfer rates in 12.5-cm diameter tubes were almost as high as those of 3.8-cm tubes without static mixers. The effectiveness of the static mixers in improving the mass transfer characteristics of the tubular Photobioreactors was higher in large than small diameter tubes. The ratio of the diameters of the static mixers to the diameter of the tube, the areas of the v-cut slits and the orifice were the important design parameters that affected the mass transfer characteristics. The gas hold up and and kLa were higher when the areas of the slits (v-cut) and the orifice were reduced.
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improvement of mass transfer characteristics and productivities of inclined tubular Photobioreactors by installation of internal static mixers
Applied Microbiology and Biotechnology, 2002Co-Authors: Charles U. Ugwu, James C. Ogbonna, Hideo TanakaAbstract:The feasibility of improving mass transfer characteristics of inclined tubular Photobioreactors by installation of static mixers was investigated. The mass transfer characteristics of the tubular photobioreactor varied depending on the type (shape) and the number of static mixers. The volumetric oxygen transfer coefficient (kLa) and gas hold up of the photobioreactor with internal static mixers were significantly higher than those of the photobioreactor without static mixers. The kLa and gas hold up increased with the number of static mixers but the mixing time became longer due to restricted liquid flow through the static mixers. By installing the static mixers, the liquid flow changed from plug flow to turbulent mixing so that cells were moved between the surface and bottom of the photobioreactor. In outdoor culture of Chlorella sorokiniana, the photobioreactor with static mixers gave higher biomass productivities irrespective of the standing biomass concentration and solar radiation. The effectiveness of the static mixers (average percentage increase in the productivities of the photobioreactor with static mixers over the productivities obtained without static mixers) was higher at higher standing biomass concentrations and on cloudy days (solar radiation below 6 MJ m–2 day–1).
James C. Ogbonna - One of the best experts on this subject based on the ideXlab platform.
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Photobioreactor design for photobiological production of hydrogen
Biohydrogen II, 2007Co-Authors: James C. Ogbonna, H TanakaAbstract:Publisher Summary Although numerous efforts are underway to develop cell strains which can overcome problems of biohydrogen production by a biophotolysis process, some of the problems can be reduced by development of efficient Photobioreactors. The problems of photoinhibition and dark hydrogen uptake can be reduced by using a photobioreactor that is uniformly illuminated at the optimum light intensity. Also, the problem of sensitivity of the enzymes to oxygen can be minimized by using a photobioreactor with high mass transfer capacity so that the generated oxygen can be simultaneously and efficiently removed from the reactor. Thus, the development of innovative technologies for efficient hydrogen production should be encouraged no matter the present costs of such systems. The first step should be to develop very efficient systems and the second step should then be aimed at reducing the construction/operation costs of those systems that are proven to be efficient. It seems that biohydrogen production requires a long term process development. Furthermore, environmental problems and future circumstances may favor the use of such systems instead of the present seemingly cheap systems.
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Design of static mixers for inclined tubular Photobioreactors
Journal of Applied Phycology, 2003Co-Authors: Charles U. Ugwu, James C. Ogbonna, Hideo TanakaAbstract:Static mixers, which improve gas-liquid mass transfer inside tubular Photobioreactors and move the cells between the upper and lower parts of the tubes were designed. Each static mixer was equipped with an opening (v-cut slit) at the top (for gas dispersion) and an orifice at the lower part (for liquid circulation). When the static mixers were installed in the riser tube of an inclined tubular photobioreactor, vertical movement of the liquid was induced so that cells were moved between the surface and bottom part of the photobioreactor. The mass transfer rates in the tubular photobioreactor without static mixers decreased sharply when they were scaled up by increasing the tube diameters. However, by installation of static mixers, the mass transfer rates in 12.5-cm diameter tubes were almost as high as those of 3.8-cm tubes without static mixers. The effectiveness of the static mixers in improving the mass transfer characteristics of the tubular Photobioreactors was higher in large than small diameter tubes. The ratio of the diameters of the static mixers to the diameter of the tube, the areas of the v-cut slits and the orifice were the important design parameters that affected the mass transfer characteristics. The gas hold up and and kLa were higher when the areas of the slits (v-cut) and the orifice were reduced.
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Light supply coefficient: A new engineering parameter for photobioreactor design
Journal of Fermentation and Bioengineering, 2002Co-Authors: James C. Ogbonna, Hirokazu Yada, Hideo TanakaAbstract:Abstract The reliability of the incident light intensities, the average light intensities and the light energy supplied per unit photobioreactor volume ( E t V ) as indices of light conditions inside Photobioreactors was investigated in cuboidal Photobioreactors of various sizes. There was no good relationship between the linear growth rates of Chlorella pyrenoidosa and the incident or average light intensities in the Photobioreactors of various sizes. Although the linear growth rate increased with increase in E t V , there was much scatter of data near the curve. At a given E t V , the linear growth rates decreased with increase in the photobioreactor depth, indicating that the light distribution inside the photobioreactor must be considered for the rational design and scale-up of Photobioreactors. A concept of light distribution coefficient (Kiv) defined as the cell concentration at which 50% of the photobioreactor volume receives enough light for photosynthetic growth was therefore proposed. The linear growth rates increased with increase in Kiv but the data were scattered. At a constant Kiv, however, a linear relationship was observed between the linear growth rate and the E t V . Similarly, when the E t V was held constant, there was a good correlation between the Kiv and the linear growth rate. A light supply coefficient, defined as E t V . Kiv was then proposed as an index of the light supply efficiency of Photobioreactors. There was a linear relationship between the light supply coefficient and the linear growth rates of both C. pyrenoidosa and Spirulina plantensis in cuboidal Photobioreactors of various sizes. However, the slopes of the curves were different for the two microorganisms. When various other types of both internally illuminated and externally illuminated cylindrical Photobioreactors were used, good correlation was found between the linear growth rates of Chlorella and the light supply coefficient. This demonstrates that irrespective of the cell type, photobioreactor type and size, the proposed light supply coefficient can be used for quantitative evaluation of light condition inside the photobioreactor. It is thus a useful engineering parameter for design and scale-up of Photobioreactors.
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A Novel Internally Illuminated Stirred Tank Photobioreactor for Large-Scale Cultivation of Photosynthetic Cells
Journal of Fermentation and Bioengineering, 2002Co-Authors: James C. Ogbonna, Hirokazu Yada, Hiroyuki Masui, Hideo TanakaAbstract:A new concept in photobioreactor design with reactor scale-up as a primary design criterion is proposed for the development of large-scale stirred tank Photobioreactors. A photobioreactor is considered as consisting of units, with each unit being composed of a light source (or light distributing object) and its surroundings. The light supply coefficient of each unit depends on its size and the light intensity of the light source. At a given light intensity, the optimum unit size which gives the desired light supply coefficient for the target process is experimentally determined. A large photobioreactor with a desired light supply coefficient is obtained by increasing the number of units. A prototype photobioreactor, consisting of 4 units, was constructed for the cultivation of Chlorella pyrenoidosa. Each unit was equipped with a centrally fixed glass tube into which the light source was inserted. The illuminating system consisted of either 4-W fluorescent or halogen lamps with controllable light intensity. By changing the light intensity, it is possible to use the photobioreactor for the cultivation of various cells with different optima light supply coefficients. Mixing was achieved by means of an impeller, designed in such a way that while rotating it does not touch the glass tubes, which also serve as baffle plates. Although the hydrodynamic stress generated by the impeller was low, a high degree of mixing was achieved even at low rotation speeds. Since the light distributing objects were not mechanically fixed to the reactor, and were separated from the broth by the glass tubes, the reactor could be sterilized by autoclaving and the light distributing objects inserted to the glass tubes after cooling. The photobioreactor was equipped with a ring sparger for aeration. When C. pyrenoidosa was cultivated in the new photobioreactor at low and moderately high light supply coefficients, both the linear growth rates and the final cell concentrations increased linearly with the light supply coefficient of the reactor. A comparison of the results obtained in this new photobioreactor with those of the commercially available Photobioreactors with either external or internal illumination showed that the cell yield from the supplied light energy was highest in the new photobioreactor.
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improvement of mass transfer characteristics and productivities of inclined tubular Photobioreactors by installation of internal static mixers
Applied Microbiology and Biotechnology, 2002Co-Authors: Charles U. Ugwu, James C. Ogbonna, Hideo TanakaAbstract:The feasibility of improving mass transfer characteristics of inclined tubular Photobioreactors by installation of static mixers was investigated. The mass transfer characteristics of the tubular photobioreactor varied depending on the type (shape) and the number of static mixers. The volumetric oxygen transfer coefficient (kLa) and gas hold up of the photobioreactor with internal static mixers were significantly higher than those of the photobioreactor without static mixers. The kLa and gas hold up increased with the number of static mixers but the mixing time became longer due to restricted liquid flow through the static mixers. By installing the static mixers, the liquid flow changed from plug flow to turbulent mixing so that cells were moved between the surface and bottom of the photobioreactor. In outdoor culture of Chlorella sorokiniana, the photobioreactor with static mixers gave higher biomass productivities irrespective of the standing biomass concentration and solar radiation. The effectiveness of the static mixers (average percentage increase in the productivities of the photobioreactor with static mixers over the productivities obtained without static mixers) was higher at higher standing biomass concentrations and on cloudy days (solar radiation below 6 MJ m–2 day–1).
Wei Cong - One of the best experts on this subject based on the ideXlab platform.
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a novel photobioreactor structure using optical fibers as inner light source to fulfill flashing light effects of microalgae
Bioresource Technology, 2013Co-Authors: Shengzhang Xue, Qinghua Zhang, Xia Wu, Chenghu Yan, Wei CongAbstract:Abstract In this work, a novel photobioreactor structure using optical fibers being fixed vertically to culture flow direction as inner light source was proposed to fulfill flashing light effects (FLE) of microalgae, so as to obtain high light efficiency. Three types of optical-fiber photobioreactor fulfilling FLE of microalgae, i.e. air-driven panel, pump-driven panel and stirred tank type, were proposed and a 130 L airlift panel one was practically constructed on which both cold (light profile, liquid velocity) and hot model tests were carried out. Results demonstrated that it could produce uniformed light/dark frequencies being over 10 Hz and microalgae productivity increased by 43% and 38% for Spirulina platensis and Scenedesmus dimorphus respectively, compared with the control. This suggested the structure to be a viable and promising option for future Photobioreactors.
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Study of hydrodynamic characteristics in tubular Photobioreactors.
Bioprocess and Biosystems Engineering, 2012Co-Authors: Qinghua Zhang, Shengzhang Xue, Kehong Liang, Wei CongAbstract:In this work, the hydrodynamic characteristics in tubular Photobioreactors with a series of helical static mixers built-in were numerically investigated using computational fluid dynamics (CFD). The influences of height and screw pitch of the helical static mixer and fluid inlet velocity on the cell trajectories, swirl numbers and energy consumption were examined. In order to verify the actual results for cultivation of microalgae, cultivation experiments of freshwater Chlorella sp. were carried out in photobioreactor with and without helical static mixer built-in at the same time. It was shown that with built-in helical static mixer, the mixing of fluid could be intensified, and the light/dark cycle could also be achieved which is of benefit for the growth of microalgae. The biomass productivity of Chlorella sp. in tubular photobioreactor with helical static mixer built-in was 37.26 % higher than that in the photobioreactor without helical static mixer.
