Study On Experiments And CFD Simulation Of Raceway Pond Photobioreactors For Microalgae

The raceway pond is the most widely used photobioreactor (PBR) for large-scale cultivation of microalgae. Raceway pond photobioreactor for energy microalgae was systematic studied using the Computational Fluid Dynamics (CFD) technology in this paper. The hydrodynamic characteristics analysis (average velocity magnitude along the light direction, average fluid velocity and the volume percentage of dead zone) in different raceway ponds were carried out.First of all, the paddlewheels of raceway pond and raceway pond with internals were investigated employing CFD.(1) Optimization the different paddle number was carried out in 10 meters long middle-scale raceway pond. It can be found that the raceway pond mixing effect is best when the number of the paddle is six.(2) The paddle inclination angle was studied on mixing effect in 4.5 meters long raceway pond. The structure of the paddlewheels could be apparently increasing the average velocity magnitude along the light direction and decreasing the power. Mixing effect is best when the angle is 15 degrees.(3) In order to improve the average velocity magnitude along the light direction, pin fins were developed in 2.25 meters long raceway pond. CFD simulation results show that this structure can increase the average velocity magnitude along the light direction. Mixing effect is best when the diamond pin fin number is 5 and diagonal long is 30 millimeters.Then research on the amplification of raceway pond was carried out. With the increase of the raceway pond size, average velocity magnitude along the light direction values of 4.5 meters and 25 meters long raceway pond decreased by 41.0% and 62.2% with 2.25 meters long raceway pond. Microalgae cultivation experiments found that with the increase of the raceway pond size, microalgae productivities reduces, too.Finally, a new type of raceway pond is designing using CFD technology, namely airlift raceway pond photobioreactor. CFD simulation and microalgae cultivation experiments results show that average velocity magnitude along the light direction of this new type raceway pond is higher than that of 2.25 miters raceway pond.