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Energy and environmental analyses of a bioreactor for microalgae culture for energy production

Abstract : Microalgae are photosynthetic organisms considered today for energy production. Photobioreactors are closed systems that present higher productivities than open ponds. In this study, a hydrodynamic model is developed for an internal airlift reactor and validated experimentally. Microparticles are added to the reactor at concentrations found in current microalgae cultures. Results show that gas hold-up and liquid velocities are not affected by the presence of particles. Light distribution and availability in the internal airlift reactor is calculated, taking into account biomass concentrations and algae optical properties. Light is attenuated from the wall to the reactor center while this attenuation increases with biomass concentrations. Based on two biological models, biomass productivities achieved in photobioreactors are higher than in open ponds. From biomass productivities, the reactor capacity to absorb CO2 and to release O2 is estimated. Results show that at moderate irradiances, dissolved O2 levels do not reach intoxication at low air flow rates. If natural air is injected into the reactor, CO2 and TIC become limiting therefore, it is necessary to inject CO2-enriched air. The hydrodynamics of a helical airlift reactor is also presented. Two pipe diameters are tested in the helical section. A mathematical correlation is proposed to estimate the friction factor as a function of the Reynolds number and curvature ratios. To perform microalgae culture at large scale, it is necessary to obtain a positive energy and GHGs balance. Therefore, microalgae culture has to be integrated in a system where conversion processes such as biodiesel production and anaerobic digestion are performed.
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Submitted on : Tuesday, October 11, 2011 - 2:01:21 PM
Last modification on : Thursday, September 24, 2020 - 5:22:03 PM
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  • HAL Id : pastel-00631067, version 1

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Ana Rengel. Energy and environmental analyses of a bioreactor for microalgae culture for energy production. Chemical and Process Engineering. École Nationale Supérieure des Mines de Paris, 2010. English. ⟨NNT : 2010ENMP0046⟩. ⟨pastel-00631067⟩

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