Studies On Application Of A Novel Composite Silicone Rubber Membrane To Comtinuous Ethanol Fermentation And Evaluation For Its Pervaporation Performance

The membrane separation technology has been achieving the rapid progress for the near decades. As one of the newest developments on membrane separation, pervaporation is a promising technique for the separation of liquid mixtures, such as azeotropic and isomeric mixtures, which are difficult or impossible to separate by conventional methods. The paper has mainly studied the pervaporation performance of a novel silicone rubber compound membrane in the concoctive aqueous ethanol solution and the actual fermentation broth with a membrane bioreactor system (MBR), and how to control the operation parameters of continuous fermentation, and their influence on the membrane separation performance. This paper consists of the following three parts:Firstly, a summarized review was done for the present situation, the prospect and the application about the membrane separation and particularly pervaporation technology. The elementary theory and features about the pervaporation technology was introduced. On the basis of this review, a research proposal was presented.Secondly, in accordance with the setup of the MBR and the features of the composite silicone rubber membrane, a principal theoretical analysis was carried out for the pervaporation process. Some details on the membrane materials, structuresand forming techniques, as well as the membrane bioreactor were analyzed. Then, effects of some process parameters on the membrane separation performance was discussed.Finally, for feasibility of application of the new silicone rubber membrane reactor system to the continuous fermentation for ethanol production, the fermentation kinetics and the mass transfer behaviors of the membrane in the MBR were investigated experimentally. The control test for the concoctive aqueous ethanol solution and the actual fermentation broth was carried out in the MBR system. The experimental result showed that, for the actual fermentation broth, the yeast cell did not cause fouling or other performance declines with the membrane.Through the serial batch fermentation experiments, the microbial features suitable for the ethanol continuous fermentation with the MBR has been realized initially, and then the continuous fermentation experiment was carried out. Under the fermentation temperature of 25 ℃, with the initial glucose concentration of l00g/L, the initial inoculation concentration of the microbe Ig/L, the initial volume of 2L, and the properly low circulating flow rate of the broth, a long-term continuous fermentation process was achieved for 461.5h. During the continuous fermentation process, the composite silicone rubber membrane exhibited an excellent performance with permeating flux of 500 ~ 800 and separation factor of 5 ~ 8.5. In the process the cellular concentration and the ethanol concentration fluctuated lightly without obvious inferior effects on the continuous fermentation.