The Optimization And Scale-up Of Flat-plate Photobioreactors Based On The Hydrodynamics And Light Regime Characteristics

Microalgae are widely used in the fields of energy, food, feed and environmental protection. Photobioreactors (PBRs) are the key devices for microalgae cultivation. The optimization and scale-up of PBRs have attracted more and more attentions with the upsurge of microalgae energy research. Flat-plate PBR has become the research emphasis of enclosed PBRs because of large illumination surface area, short light path and small floor area.The flat-plate PBR was chosen as research object in this paper. To verify the key factors influencing the performance of PBRs determined by our laboratory, the microalgae cultivation results, mixing and light regime parameters were analyzed comprehensively by combining the Computational Fluid Dynamics (CFD) technology with microalgae cultivation, and then the scale-up of flat-plate PBRs was carried out based on the key factors. The work mentioned above provided a theoretical basis for the optimization and scale-up of PBRs.Firstly, the performance of type-A and type-C flat-plate PBRs were evaluated by the average radial velocity of fluid and light/dark cycle time (LDCT) obtained by CFD. For the type-A flat-plate PBRs, the performance of A5was the best, followed by A3and AO; for the type-C flat-plate PBRs, the order of performance was as follows:C4, C3, and CO.Then, the photoinduction cultivation of Chlorella pyrenoidosa was carried out to verify the performance of type-A and type-C flat-plate PBRs. The cultivation results were agreed with the predictions by CFD simulation very well. These results demonstrated that for the flat-plate PBRs with same light path and scale, the performance of flat-plate PBRs was improved with the increase of the average radial velocity of fluid and the decrease of LDCT.By combing the microalgae cultivation results before and after the scale-up of flat-plate PBRs with the mixing and light regime parameters, it could be concluded that it was necessary to keep the LDCT, specific irradiation rate and volume-averaged light intensity unchanged aiming to maintain the same performance.Finally, the effects of fluid shear stress on microalgae photoautotrophic were investigated The results indicated that Chlorella pyrenoidosa could be able to withstand the maximum fluid shear stress within10×10-2Pa, and the influence of fluid shear stress was related to the physiological state of microalgae cells.