Design And Experiment Of A New Concentric-tube Photobioreactor For Microalgae Culture

In order to enhance heat and mass transfer performance in the photobioreactor, aconcentric-tube photobioreactor and a tubular photobioreactor with spiral inner tubewere presented, with aeration through pores on inner tube, exhaustion through exhaustpipe on out-tube. To some extent, aeration and exhaustion of dissolved oxygen alongthe long direction of tube can overcome the length limitation of tube resulted by thegradients of dissolved oxygen when large-scale microalgae cultivation. In the newdesign, microalgae cell can get the nutrient substance easily. By detecting the biomassconcentration, dissolved oxygen and pH, the new concentric-tube photobioreactor waspreliminary tested by Chlorella vulgaris in BG-11medium. The main research andconclusions are summarized as follow:（1） A new design of concentric-tube photobioreactor was presented to overcome thelength limitation of tube, which resulted by concentration gradient. In order to test theperformance of the new design, a multi-functional microalgae system for simulationlarge-scale cultivation was founded. It can control and optimize the culture conditionof microalgae, test the microalgae ability of waste gas and sewage treatment.（2） The experiment compared the influence of conical flask with concentric-tube tobiomass concentration. The results show that after72times larger scale than theconical flask, the specific growth rate was decreased by33.24%and the biomassproductivity was decreased by69.84%in the concentric-tube photobioreactor.Therefore, the concentric-tube photobioreactor have some superiority on microalgaelarge-scale cultivation and environment optimization.（3） In the concentric-tube photobioreactor the specific growth rate was increased by42.94%and the biomass productivity was increased by137.50%than the tubularphotobioreactor at the same condition. Compare to provide gas at the two ends of thetube, the concentric-tube photobioreactor aeration through pores on inner tube, thespecific growth rate was increased by17.39%and the biomass productivity wasdecreased by46.15%. Therefore, the concentric-tube photobioreactor aeration throughpores on inner tube not only enhances the illumination surface area, but also promotesthe microalgae growth.（4） In the process of cultivation, when compressed air into the photobioreactor, the concentration of dissolved oxygen in the medium was ranging in6.0-7.0mg/L and itwas steady that microalgae can stand with. pH was rising from7.5to9.0during the10days which was suitable （4.5-10.6） for microalgae, but it can be controlled by CO₂which can be mixed into the air before compressed into the photobioreactor.This study presented a new design of concentric-tube photobioreactor andpreliminary test the photobioreactor performance in microalgae cultivation.Meanwhile, it provide experimental basis for optimize the photobioreactor byanalyzing the influence of structure in the concentric-tube photobioreactor. Thus, thisstudy may be helpful for parameter optimization of the concentric-tubephotobioreactor which may be used in high efficiency large-scale microalgaecultivation...