An Exprimental Study On PVA Membrane Pervaporation Separation Ethanol/H₂O Solution

With the problem of energy crisis and environmental pollution becoming more and more serious, ethanol as a new type of renewable energy drew people's attention. But there are many problems in the traditional methods of ethanol production, for example, continuous fermentation to improve productivity, reducing the energy consumption of ethano/water separation process.The development of pervaporation separation is relatively late in the membrane separation technology. For it is particularly applied to separating organic compounds with close boiling points or azeotropes that are difficult to separate by distillation or other conventional separation technologies, besides, it has the advantages of less energy consumption and more purity of product, so it has become a hot research issue in recent decades.The application of pervaporation separation in ethanol production can solve many problems in the production of ethanol.The purpose of this topic is to search for a pervaporation membrane for the separation of ethanol/water system. This paper is roughly divided into three parts:Firstly, The process of fermentation produced alcoholic is summarized, and many problems in the production process of ethanol are discussed.Secondly, the process of pervaporation separation is discussed in detail, which including the development, the characteristics, the influencing factors, the separation mechanism and the present the application status of pervaporation. Based on the comprehensive analysis of ethanol production process and pervaporation technology trends both home and abroad, present the main theoretic basis and research programsAt last, the pervaporation performance of the PVA membrane were studied using the flat-plate membrane module made in our laboratory with a diameter of 100mm(effective area:72.35cm2). The effect of operating conditions of feed temperature, feed concentration, feed flow rate and membrane downstream vacuum degree on the pervaporation performance was tested. The experimental results show that with the increase of feed concentration, the selectivity of membranes about ethanol solution show reversal phenomenon. That is, when the concentration of ethanol in the feed solution is less than 70%, PVA membrane showed preference for ethanol permeability and when the concentration of ethanol exceeds 70%, it showed preference for water permeability. With the increase of the ethanol concentration, the permeation flux of membrane first increased and then decreased. With the change of the feed solution temperature, the relationships between the permeation flux of PVA membrane and temperature consists with Arrhenius equation:J=Joexp (——Ep/RT) When the temperature of feed solution increases, the separation factor of PVA membrane increases firstly, and then decreases, it reaches its maximum when temperature is about 50℃. With the downstream vacuum increasing, the permeation flux of membrane increases, while the separation factor of membrane decreases. With the flow rate increasing, the separation factor of membrane changes very little, however, the permeation flux of membrane firstly increases, and finally maintained at a value no longer increases.