The Trnsport Research Through PDMS Membrane During The Continuous Ethanol Fermentation-Vapor Permeations Process

Fuel ethanol as a renewable clean energy, has been put more and more attention. It provides a simple and effective way to attribute the sustainable development of human society. Moreover it will conserve oil resources, reduce environmental pollution, benefit agriculture and other related important industries. One of the most effective methods for avoiding product inhibition is in-situ ethanol separation, which can not only improve the productivity of fermentation, but also simplify the process of separation and purification. For improving the traditional ethanol fermentation techniques, the technology of outer gas cycle vapor permeation was developed to produce fermentation ethanol.The previous research showed that for the continuous fermentation-separation process, the pressure above the fermentation broth is negative. For ensuring the stability of the system and the stripping gases, pumping in N2to the fermentation reaction during the continuous fermentation-separation process was proposed. Also the transport behavior and model were researched.Firstly, the effect of N2on the ethanol production and the cell was studied. The result indicated it has little effect on ethanol productivity. The permeation rate of nitrogen, ethanol, water and carbon dioxide was investigated. The results above showed the feasibility of the technique we put forward. For the continuous fermentation-separation process, the method improved the ethanol productivity by30percents.Then, in multi-component feed systems, the effect of ethanol vapor concentration and temperature of vapor on ethanol flux and permeability were examined. The results showed that CO2has a plastic effect on PDMS and water has little effect on the behavior of ethanol vapor. The solution-diffusion model derived from Fick’s first law was used in establishing the models to describe the vapor permeation flux as a function of the vapor activity level. The upstream sorption concentration was predicted using the multi-component UNIQUAC-HB equations. The diffusion model was predicted using improved Long’s model. The accuracy of the model is verified by the results in the multi-component system and coupling experiments.