Design And Construction Of A Pilot Scale Pervaporation Membrane System For Seawater Desalination

Due to the over exploitation of freshwater resources and water pollution, the problem of water shortage is getting worse and worse. However, the problem can be greatly alleviated by producing fresh water from seawater via desalination.In the last 30 years, the technology of seawater desalination has been extended world widely. And the most applied technology for seawater desalination is reverse osmosis (RO). Although RO exhibits high energy efficiency and great salt rejection for desalination, there are still some challenges exist such as low water recovery, fouling problem and so on. Thus far, new desalination technologies are required. Pervaporation is one of the well developed membrane process. It is typically applied in organic solvent dehydration or the removal of small amount of organics from contaminated water. Recently, a novel sulfonated pervaporation membrane has been developed that exhibits a very high water flux. This membrane has a potential to be used in the process of seawater desalination because of its high waterflux, resistance to organic fouling and the ability of separating highly concentrated salt water. In this study, we designed and constructed a novel pervaporation system using the sulfonated pervaporation membrane for seawater desalination. To design the membrane module, we used white corundum grinding wheel as the membrane substrate, stainless steel as the frame and connection components. Our work mainly includes the following aspects. (1) Determine the best membrane operation conditions by exploring the influences of temperature and salt concentration of the feed, vacuum of the downstream to the water flux. (2) Using a mathematical model to simulate the temperature profiles of both the up and down streams of the membrane. (3) Using FLUENT software to estimate the influence of frame spacing to the flow resistance of the water vapor in the permeate side of the membrane. (4) According to the results of the simulations and estimations, the optimum sizes of membrane and grinding wheel as well as the supporting device were selected. The pervaporation equipment included (ⅰ) feed liquid circulation heating system, (ⅱ) vacuum condensation system, and (ⅲ) measurement and control system. After the equipment been constructed, the FLUENT software was utilized to simulate the flow distribution of the feed solution. The simulated results perfectly matched with the experimental results obtained by staining test method. Finally, the system productivity was assessed. A water production of 70 L/d was achieved when a water solution containing 3.5 wt% salt was selected as a feed.