Efficient seawater desalination and comprehensive utilization method

Abstract

The invention discloses an efficient seawater desalination and comprehensive utilization method. The efficient seawater desalination and comprehensive utilization method comprise following steps: carrying out pretreatment on raw seawater, filtering using a microfiltration and / or ultrafiltration device to obtain pretreated seawater; adding a scale inhibitor into the pretreated seawater; pressurizing and conveying the pretreated seawater into a primary nanofiltration device; adjusting the pH value of obtained primary nanofiltration produced water to 3-7, pressurizing and feeding into a secondarynanofiltration device; mixing obtained primary nanofiltration concentrated water with obtained secondary nanofiltration concentrated water; adding a precipitant to react with SO4<2-> in an obtained concentrated water mixed solution to generate calcium sulfate precipitate; continuously adding lime emulsion into an obtained reacted mother liquor to react with Mg<2+> in the mother liquor to generatemagnesium hydroxide precipitate, adjusting the pH value of the residual mother liquor to 7-8, producing sodium chloride and calcium chloride through multi-effect evaporation, adjusting the pH value of obtained secondary nanofiltration produced water to 6.5-7.8, and pressurizing and introducing the secondary nanofiltration produced water into a reverse osmosis seawater desalination device. According to the efficient seawater desalination and comprehensive utilization method, seawater grading pretreatment process is adopted, the component difference of various concentrated water is fully utilized, seawater desalination and the chemical technology are combined, and the fresh water yield and the seawater utilization rate are increased.

Description

technical field [0001] The invention relates to a method for high-efficiency desalination and comprehensive utilization of seawater, in particular to a method for improving the water production rate of fresh water and the comprehensive utilization rate of concentrated seawater in the seawater desalination process. Background technique [0002] 96.5% of the world's water reserves are seawater, which is rich in reserves, but there is a shortage of fresh water resources, and more than 80 countries and regions have insufficient fresh water. China's per capita fresh water resources are only 1 / 4 of the world's per capita water resources, and fresh water resources are very scarce. Seawater is rich in water resources and contains almost all elements on the earth. More than 80 kinds have been determined so far, which constitute various organic and inorganic substances in seawater. Among them, there are 12 elements with a content of more than 1 mg / kg, namely sodium, potassium, magnes...

AI Technical Summary

Problems solved by technology

[0004] Chinese patent CN1994904A discloses a nanofiltration seawater desalination method and device. Nanofiltration is added before reverse osmosis, which improves the water production rate of reverse osmosis seawater desalination to a certain extent and reduces the operating pressure. However, due to the influence of scaling factors The concentration of divalent ions in the nanofiltration product water is still high, which limits the improvement of the fresh water production rate in the reverse osmosis process, and the comprehensive utilization of concentrated seawater is not involved.

[0005] Chinese patent CN104817134A discloses a full-membrane seawater desalination process using ultrafiltration-nanofiltration-reverse osmosis. The recovery rate of seawater is improved through the advanced treatment of concentrated water in the seawater nanofiltration process, but the concentration of divalent ions in the influent remains Very high, the risk of fouling in the system is very high, operation and maintenance are difficult, and the comprehensive utilization of seawater has not been realized

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