Process for freezing and denitrating sodium chlorate mother liquor by aid of membrane methods

Abstract

The invention discloses a process for freezing and denitrating sodium chlorate mother liquor by the aid of membrane methods. The process includes steps of (1), diluting the sodium chlorate mother liquor, to be more specific, adding the sodium chlorate mother liquor into water and diluting the sodium chlorate mother liquor to allow the concentration of sodium chlorate in the sodium chlorate motherliquor to be lower than 200 g / L so as to obtain sodium chlorate diluent; (2), carrying out pretreatment including rough filtration, pH (potential of hydrogen) value regulation, dechlorination and finefiltration on the sodium chlorate diluent to obtain sodium chlorate pretreated liquor; (3), carrying out concentration, to be more specific, feeding the sodium chlorate pretreated liquor into a nano-filtration membrane concentration system by the aid of booster pumps and acquiring permeated liquor and concentrated liquor; (4), carrying out freezing and denitrating, to be more specific, feeding the concentrated liquor into a freezing system, crystallizing the concentrated liquid, and carrying out solid and liquid separation by the aid of a centrifugal machine to obtain mirabilite and crystallization mother liquor; (5), carrying out recycling by means of mixing the crystallization mother liquor and the sodium chlorate mother liquor with each other. The process for freezing and denitrating the sodium chlorate mother liquor by the aid of the membrane methods has the advantages that the process is simple, is low in cost and has a high additional value, new chemical impurities can be prevented from being introduced into the sodium chlorate mother liquor, and impurities in the sodium chlorate mother liquor can be effectively removed by the aid of the process.

Description

technical field [0001] The invention relates to the technical field of the electrolysis process of halogens or their compounds, in particular to a sodium chlorate mother liquor membrane freezing and denitrification process. Background technique [0002] Sodium chlorate is usually obtained through the electrolysis of industrial salt. The main impurities in raw salt, such as calcium, magnesium, and sulfate ions, are enriched during the production process, which will seriously affect the electrolysis operation. Calcium and magnesium ions will generate hydroxide on the cathode side and cause deposition on the electrode, which will increase the resistance and increase the cell voltage. The mother liquor of sodium chlorate contains unelectrolyzed sodium chloride, and the presence of sodium sulfate will reduce the concentration of sodium chloride in the electrolyte in the sodium chlorate electrolytic cell, which is unfavorable for the balance of the electrolytic reaction. In the m...

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Problems solved by technology

However, this process is currently only applicable to light brine or refined brine in the ionic membrane caustic soda industry, and cannot be directly applied in the electrolysis industry to manufacture sodium chlorate

[0006] Because a large amount of strong oxidizing sodium chlorate contained in the sodium chlorate mother liquor will damage the nanofiltration membrane, cause the nanofiltration membrane to rupture, resulting in high production cost and use cost, resulting in that it cannot be directly used in the electrolysis industry to manufacture sodium chlorate. application

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