Development And Application Of Key Technologies And Equi Pments For Large-scale Reverse Osmosis Desalination

Seawater desalination is an effective measure to increase the total amount of water resources,improve the structure of water resources and improve the security of water resources.It is the strategic choice to solve the crisis of fresh water resources.Nowadays,reverse osmosis seawater desalination technology is developing towards large scale,high efficiency and energy saving.Large-scale seawater desalination projects have the advantages of low unit cost and Low energy consumption.With the development of society,China's demand for seawater desalination is increasing,and the scale of construction is increasing.Although China has the capacity of large-scale seawater desalination project and domestic key equipment is making progress,there is still a big gap between China and foreign advanced technology.It is very important to develop domestic large-scale reverse osmosis seawater desalination technology and key equipment.This paper relies on the National Science and Technology Support Program"Demonstration of large-scale membrane desalination system integration and municipal water supply project"?2012BAB17B01?project and the National Key R&D Program of China " Development and demonstration of key technologies and equipment of membrane desalination for large-scale application "?2017YFC0403700?project research.The whole process of domestic large-scale reverse osmosis seawater desalination project is studied,including water intake technology,pretreatment process,large pretreatment horizontal filter,large single reverse osmosis system,post-water mineralization treatment,etc.,and the application of domestic key equipment in large-scale seawater desalination system is analyzed.The results are as fo lows:1?The water intake design scheme of the Liuheng seawater desalination project is fixed shore water intake.HDPE pipe and spiral welded steel pipe for seawater intake;Adding a cage filter to the water intake?2?The pilot test of coagulation-air flotation pretreatment process for treating low turbidity seawater,determining ferric chloride as the best coagulant,and bone cement as the best coagulant;The coagulation-precipitation pretreatment process was carried out in the Liuheng 20?000 m³/d desalination project.The sedimentation tank is combined with the inclined tube sedimentation tank by a flap flocculation sedimentation tank.It is determined that FeCl₃ is used as a coagulant,and the engineering application effect is good.3?The large horizontal filter designed has obvious effects on the removal of turbidity,Fe and SDI,and the application effect is good in engineering,are more economical and more economical than the vertical filters.4?The water distribution mode of the 10,000 m³/d single reverse osmosis desalination system is to feed water from the middle to both ends;Membrane stack design adopts 18×6 vertical and horizontal arrangement,which is more economical and practical.5?Domestic reverse osmosis membranes,energy recovery devices,and high pressure pumps are used in the 10,000 m³/d single reverse osmosis desalination systems.The system desalination rate is>99.5%,the high pressure pump effciency is 75%,the energy recovery device efficiency is greater than 90%,the whole system is running stably,and the system water consumption per ton is less than 2.6kWh/m³.6?The project uses CO₂ with dissolved shell filler technology to produce mineralized water.The pH of the reverse osmosis product water is increased from 5-6 to 7-7.5.the hardness is increased from 20 mg/L to 80 mg/L,and the water conductivity is raised from 200 ?s to 350-420 ?s.