The Optimization Study Of Using Chlorella Side-light Optical Fiber Bio-reactor To Fix CO₂

CO2fixation by micoalgae and the optimization of optical bio-reactor have been hot topics recently. Chlorella has been a commonly used microalgae to fix CO2for its fast breeding speed, easy to cultivate, widely accessible, cost-effective and high oil content, etc. Due to its complex structure and high manufacture cost, the optical fiber bioreactor only remains in the theory stage and cannot be put into industrial production. In this study, investigation of the growth pattern of Chlorella sp. was conducted to use it to fix CO2. Due to the structure of side-lighting optical fiber is relatively simple and cost-effective, if the research can verify that the side-lighting optical fiber is efficient and has its own advantages to transfer light energy, it can be a certain theoretical basis for the optimization of optical bioreactor. Through the experimental studies, the following conclusions were obtained:(1) The rapid reproduction, and the ability to uptake of CO2effectively through photosynthesis of Chlorella sp. was verified. Its basic growth pattern was that the first four days kept a unstable adaptation, but in5-9days show a logarithmic growth state and after10days, it came into a decline phase, the whole growth cycle was15days. The optimum temperature was25℃,the optimal intensity range was6000-9000lx, the best light/dark cycle was12h:12h, the optimum CO2concentration was approximately10%, the optimum pH ranged from6to8.(2) Experiments validated the homemade optical bioreactor could satisfy the meet of Chlorella sp. and had a certain sustainability. It was found that after domestication of Chlorella sp., aeration through the bottom inlet of the bioreactor could effectively inhibit the adherent growth of the algae and the agglomerate phenomenon Nutrient supply to the algae fluid through10,30days could extend the growth cycle of Chlorella sp.. But after certain period of time, aging and death of the aglae made the agglomerate phenomenon serious and inhibited the proliferation of algae body, so the later period of growth rate was significantly reduced.(3) The light transfer effect was analyzed by varying light intensity and the spectrum of the contralateral optical fiber e. The fiber was found to be more effective than external light source. Red light could promote Chlorella sp. most efficient and blue light took a second place. Although it contained all the wavelengths of visible light, light optical fiber for its light transmittance was very low, which would have an unfavorable influence on the growth of Chlorella. Choosing red and blue light as the light source to operate alternatively, using282mm-fibers and283mm-fibers to couple with the16W light generator, the growth rate was promoted6times per watt compared with that obtained in the presence of120W external light source.