Performance Analysis Of LT-MED Plants

As we all know, that the shortage of fresh water resource has been one of the three biggest environmental problems in the 21 century. So the seawater desalination technology has been attached more and more importance in a lot of countries.In the dissertation, the experiences and achievements about seawater desalination technology were summarized, and more research has been done on low temperature multiple effect desalination. For reducing the consumption of the heating steam and increasing its economy, the plants of LT-MED with condensed water flash and extra vapor elicitation was designed, and based on these, the physical model and mathematic model of LT-MED with condensed water flash and extra vapor elicitation was established. Distribution of the films, layout of the tube bundles, design of the liquid distributor and the heat transfer was presented and discussed in detail on the physical design of horizontal tube falling-film evaporator. Equal-area design method and equal temperature difference design method of MED were offered, and performance parameter was compared by solving the mathematic model.The performances of five effects desalination plants are calculated in different way by change of the feeding fashion, heating steam temperature, discharging brine concentration of each effect, intake seawater temperature. As a result, gained output ration, heat exchange area, the mss flow of distillate product and cooling seawater etc were discussed. In addition, the influence of effects on the performances of 5 effect desalination plants was also discussed. Results indicate that the distillate product and gained output ratio increases greatly with the increase in effects, and the results is valuable.Finally, an optimum mathematical model of LT-MED system with condensed water flash and extra vapor elicitation was developed. The influence of effects and scale on freshwater product cost is analyzed, and the production intensity of optimum design method and normal equal-area design method were compared. The conclusions provide a significant engineering guidance in the specific extent of engineering design.