Production method for increasing nitrate removal capacity by membrane method

Abstract

The invention relates to a production method for increasing nitrate removal capacity by a membrane method. Light brine from a brine electrolytic dechlorination working section is subjected to pretreatment, and then, enters a membrane device for filtering sodium sulfate; outlet water of the membrane device for filtering the sodium sulfate is divided into two parts; one part which is nitrate-poor brine with a concentration being lower than 3 g/l enters a primary brine device of a sodium hydroxide device for salt dissolving; the other part which is nitrate-rich brine with a concentration being higher than 45 g/l enters a refrigeration denitration unit, temperature is once decreased to -7 to -8 DEG C, and the temperature is readjusted to 1 to -3 DEG C so as to separate out Glauber's salt crystals; the Glauber's salt crystals enter a centrifuge so as to produce Glauber's salt products; and mother liquor is returned for repeated use. With the adoption of the production method provided by the invention, the content of rich nitrate is increased through refiltering the nitrate-rich brine under the conditions of existing nitrate removal device by the membrane method, and more Glauber's saltcrystals are correspondingly separated out under the condition of using the same flow of nitrate-rich brine, so that the production capacity of the nitrate removal device by the membrane method is increased, and brine with a qualified sulfate indicator is ensured to be obtained.

Description

technical field [0001] The invention relates to a denitrification process of ion membrane caustic soda primary brine by membrane method, in particular to a production method for improving the denitrification capacity of membrane method when high-concentration nitrate-containing brine is used. Background technique [0002] In chlor-alkali production, the most advanced, clean and widely used is the ion-exchange membrane caustic soda process. The light brine from the ion-exchange membrane electrolyzer must be returned to the salt system for salt formation, but the sulfate radicals contained in the light brine must be removed. , so that the content of sulfate in brine reaches a certain requirement. CN101293661A relates to the dechlorination of light brine and the removal of organic matter therein, as well as the removal of sulfate radicals. The method provided by this patent is to dechlorinate the light brine from the ion membrane electrolyzer to the allowable range of the proc...

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Problems solved by technology

[0005] Aiming at the deficiencies of the prior art and further improving the denitrification ability of the existing membrane method, the present invention provides a production method for improving the denitrification ability of the membrane method when high-concentration nitrate-containing brine is used. In the case of high root content, the quality of brine can still be maintained, meeting the quality requirements of ion-exchange membrane caustic soda plant for brine

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