Enrichment And Growth Characteristics Of Microalgae In Microbioreactor

In order to meet the challenge of global shortage of fossil fuels,biomass energy represented by microalgae was obtained efficiently and producted steadily,so as to increase the proportion of biomass energy in the energy consumption structure.In this thesis,the effect of microstructures on enrichment characteristics of microalgae was first investigated by adding various microstructures into microbioreactors,and analyzing the flow field and visual experimental phenomena;according to the investigation results,a microstructure with the best enrichment performance was selected.Then,3 kinds of microbioreactors with enhanced enrichment function were designed,and the growth characteristics of microalgae and degradation performance of nutrients in microbioreactors were analyzed by visual experiment and computational fluid dynamics.Firstly,micron-scale cubes were arranged in different shapes and added to the centerline and side edges of microbioreactors.The flow field and concentration field of microalgae near microstructures were simulated,and the enrichment of microalgae was observed by microscope in real time;based on the simulation and experimental results,the enrichment process of microalgae in the microbioreactor was analyzed;the effects of different microstructures on the enrichment characteristics of microalgae were summarized and it was found that: the intermediate concave microarray was the most favorable microstructural design for the enrichment of microalgae.Then,the microstructure was designed and added into 3 microbioreactors(MBR-M,MBR-MM and MBR-DMM).Through the simulation of the microalgae cells' trajectory,it was found that the movement of free microalgae was random;this characteristic makes it possible for microalgae to be intercepted by microstructures,resulting in a gradual decrease of free microalgae from the inlet to the outlet of microbioreactor.Through the analysis of flow fields of every microbioreactor,it was found that the flow fields near microstructures in 3 micr-bioreactors differed greatly in morphology.Through the enrichment experiment of microalgae,it was found that the MBR-M with smaller width was easier to form a pure liquid flow form,while the gas in the MBR-MM and MBR-DMM with larger width was difficult to be completely expelled.Finally,the concentration fields of nitrogen and organic carbon in MBR-M,MBR-MM and MBR-DMM were simulated,and the heterotrophic medium was continuously passed into microbioreactors where a certain amount of microalgae had been enriched,so as to observe the growth of microalgae near the microstructures.At the same time,the concentration of nitrate ion and glucose in microbioreactors was measured in each period.By calculating the ratio of the total nutrient consumption and the unit volume consumption in each microbioreactor,the total biological quantity and biological density of microalgae in each microbioreactor were compared from macro perspective.This thesis systematically analyzed the enrichment and growth characteristics of microalgae in microbioreactors,by constructing a collaborative research system of visual experiment and numerical simulation.As a contribution,the design idea from the perspective of microfluidic control was proposed,for the efficient acquisition and stable production of biomass energy.This paper contains 56 figures,5 tables and 96 references.