| Freshwater resources has been a kind of scarce resource in the globe,and more and more countries and regions are facing the freshwater crisis.Looking for new water resources to solve freshwater crisis is the present important problem faced by various countries and various areas all over the world.Seawater desalination as the most direct way to open up new water resources is the most effective,and it has attracted widespread attention.The seawater desalination technology mainly includes the reverse osmosis method,electrodialysis method and distillation method which includes multi-effect evaporation and multi-stage flash.At present,used in mass production of seawater desalination technology is mainly the reverse osmosis(RO)technology,low temperature multi-effective distillation(MED)and the method of multi-stage flash(MSF).Among them,the reverse osmosis desalination technology because of low investment cost,simple equipment,large water rate and so on,is the most widely applied in the field of domestic and international desalination,accounted for more than 60%,but the output water by membrane method has higher salt concentration,and membrane flux are greatly influenced by the water temperature.The output water by the method of thermal desalination technology has lower salt concentration,higher quality.But efficiency of water using is low,and cost of water is high.These shortcomings become the bottleneck of the further promotion.Therefore,the research and development of new desalination technology to improve seawater utilization and system economy is of great significance.Thermal membrane coupling method of seawater desalination technology is a integration technology which integrates the method of thermal desalination technology with membrane method desalination technology.It obtains higher efficiency through the optimization of process systems and the rational allocation of resources to reduce the desalination water cost.Thermal membrane coupling method seawater desalination technology is the most advanced technology in the desalination field and it will be the main direction of future research desalination.At first,the process system of reverse osmosis desalination has been designed in this paper,and the author established mathematical model of water production and efficiency of the reverse osmosis desalination system,produced the water characteristics and economic evaluation software of reverse osmosis desalination system by using MATLAB software,compared of the various volumes of the reverse osmosis membrane with water production performance and economy by using the software,drew a conclusion that the reverse osmosis membrane SW30XLE-400 has the best performance,analyzed water production and economy of the reverse osm osis membrane desalination system which scale is 10000 t/d,and the results showed that when the freshwater production unchanged,the water flow and the desalination rate increased with the increase of feed concentration,but the recovery rate of decline,cost of water and energy consumption increased significantly.In this paper,a detailed introduction has been made of part of the low-temperature multi-effect distillation desalination system and working principle,and the process system of the low-temperature multi-effect distillation desalination has been designed,and mathematical model of water production and efficiency of the low-temperature multi-effect distillation desalination system has been established,water production performance analysis and economic evaluation of the low-temperature multi-effect distillation desalination system has been made according to the mathematical model,and the result is that the system water ratio 5.532.MED-RO thermal desalination membrane coupling system was establis hed by combing the low-temperature multi-effect distillation desalination system with the reverse osmosis desalination system in this paper.Water production performance analysis and economic evaluation of the MED-RO thermal desalination membrane coupling system has been made through optimizing producing water ratio of membrane method and thermal method.The final analysis conclusion is that water production concentration of thermal desalination membrane coupling system increased with the increase of producing water ratio,and cost of water decreases with the increase of producing water ratio.When the producing water ratio is 1.2,the water production concentration is 297.47 mg/L,and cost of water is 0.7174 $/ t,at the same time,thermal membrane coupling method in seawater desalination system obtain optimal water production characteristics and optimal efficiency. |
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