Methods for removing calcium and magnesium and co-producing water and salt by low-cost process during sea water desalination

A technology for removing calcium and magnesium, applied in chemical instruments and methods, seawater treatment, water/sewage multi-stage treatment, etc., can solve the problems of unbearable cost pressure, large refining cost and large water volume

Inactive Publication Date: 2012-11-28
王凯勋
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  • Abstract
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  • Application Information

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Problems solved by technology

However, the lime soda ash method and caustic soda ash method used to refine brine are used to refine calcium and magnesium, the refini

Method used

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  • Methods for removing calcium and magnesium and co-producing water and salt by low-cost process during sea water desalination
  • Methods for removing calcium and magnesium and co-producing water and salt by low-cost process during sea water desalination

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Embodiment Construction

[0034] Brief description of the process:

[0035] 1. Concentrated water process: Concentrated seawater or seawater from the previous process is pressurized into the system through a pump. First, the mother liquor containing sodium sulfate and Glauber’s salt are added to the Glauber’s salt preparation tank at an appropriate temperature and under stirring conditions. Or Yuanming powder, so that the concentration of sulfate ions in the concentrated water meets the requirements for removing calcium and magnesium ions.

[0036] Then, in the causticizing reaction tank for magnesium removal, milk of lime is added to the concentrated seawater that has been added with sodium sulfate, calcium hydroxide reacts with magnesium ions to form magnesium hydroxide precipitate, calcium hydroxide reacts with sodium sulfate to generate calcium sulfate and NaOH was provided to separate the precipitate by adding flocculant and static sedimentation.

[0037] The alkaline concentrated water from whic...

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Abstract

The invention discloses methods for removing calcium and magnesium and co-producing water and salt by a low-cost process during sea water desalination. By the methods, on the basis of removing the calcium and magnesium in the sea water desalination industry, water and salt producing processes can be integrated, so that fresh water can be produced when the crude salt is produced; sea water is treated by a low-cost method for removing calcium and magnesium ions, so that the sea water cannot be scaled, and the sea water desalination and vacuum salt production are linked; the sea water is refined by a lime-mirabilite-carbon dioxide method, and the used raw materials are lime, mirabilite and carbon dioxide which are cheap and readily available; the process comprises the following steps of removing magnesium, namely adding a proper amount of mirabilite into the sea water, adding lime milk, and reacting the magnesium ions to form magnesium hydroxide precipitations so as to remove the magnesium; causticizing, namely causticizing superfluous calcium hydroxide and sodium sulfate to form calcium hydroxide and sodium sulfate precipitations, and separating the produced sodium sulfate precipitation; removing calcium, namely introducing flue gas into concentrated sea water subjected to magnesium removal and causticizing, reacting the calcium hydroxide and the carbon dioxide to form sodium carbonate, reacting the sodium carbonate and the calcium ions to form calcium carbonate so as to remove calcium.

Description

Technical field [0001] The invention relates to the problem of removing calcium and magnesium in the seawater desalination industry. On the basis of this, the integration of industrial water production and salt production processes can be realized, and refined raw salt can be obtained while fresh water is produced. [0002] The invention uses the lime-glauber's salt-carbon dioxide method to refine the concentrated seawater containing calcium and magnesium ions in the seawater desalination process, so as to solve the problem of scaling in the subsequent processing process. In the early stage of the process, due to the low concentration of seawater, the reverse osmosis method with low energy consumption is adopted; in the middle stage of the process, low-temperature multiple-effect or high-temperature multiple-effect or similar thermal methods that can adapt to medium concentrations are used; in the latter stage of the process, vacuum salt production is used The process obtains ...

Claims

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Application Information

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IPC IPC(8): C02F9/04C02F103/08
CPCY02A20/131
Inventor 王凯勋
Owner 王凯勋
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