CN-117776441-B - Recycling treatment method for high-salt-content wastewater

CN117776441BCN 117776441 BCN117776441 BCN 117776441BCN-117776441-B

Abstract

The invention discloses a high-salt wastewater recycling treatment method, which belongs to the field of high-salt wastewater recycling treatment in the metallurgical industry, and comprises the steps of introducing high-salt wastewater in a primary nanofiltration water inlet tank into a primary nanofiltration device for primary nanofiltration, and separating primary nanofiltration concentrated water and produced water; the method comprises the steps of introducing the obtained first-stage nanofiltration concentrated water into a freezing crystallization device for crystallization, introducing the first-stage nanofiltration concentrated water into a double decomposition reactor for double decomposition reaction, introducing a reaction product into a vacuum belt filter for heavy alkali filtration, introducing the separated sodium bicarbonate solid into a calciner, and adopting a treatment system which takes 'first-stage nanofiltration + freezing crystallization device + ammonia production device' + 'first-stage nanofiltration + second-stage nanofiltration + high-pressure reverse osmosis + evaporation device' as a core to prepare ammonia sulfate, sodium carbonate, sodium chloride salt and qualified reuse water with high added value, thereby improving the value of product salt.

Inventors

ZHANG CHUN
XIE TINGTING
HAO YUN
CAI SHUAI
LI JINGMEI

Assignees

中电环保股份有限公司

Dates

Publication Date: 20260505
Application Date: 20231229

Claims (3)

1. The method for recycling the high-salt-content wastewater is characterized by comprising the following steps of: step S1, introducing high-salt wastewater in a first-stage nanofiltration water inlet tank (1) into a first-stage nanofiltration device (2) for first-stage nanofiltration, separating out first-stage nanofiltration concentrated water and produced water, introducing the produced water into a second-stage nanofiltration device (6), and introducing the first-stage nanofiltration concentrated water into a subsequent treatment device; step S2, introducing the first-stage nanofiltration concentrated water obtained in the step S1 into freezing crystallization equipment I (4) for low-temperature treatment crystallization; step S3, introducing the reaction product in the step S2 into a double-decomposition reactor (5) for double-decomposition reaction; step S4, introducing the reaction product obtained in the step S3 into a vacuum belt filter (10) for heavy alkali filtration, introducing the separated sodium bicarbonate solid into a calciner (16), and delivering the residual mother liquor to a subsequent treatment device; S5, introducing the residual mother liquor I in the step S4 into an ammonia distillation tower for thermal separation, returning the precipitated sodium sulfate solid to a decomposition reactor (5), and conveying the residual mother liquor II to a subsequent treatment device; Step S6, introducing the residual mother liquor in the step S5 into a second (12) low-temperature treatment of the freezing and crystallizing equipment for solid-liquid separation, returning the obtained double salt to the sodium sulfate/ammonium sulfate mixed liquor, and sending the residual mother liquor III to a subsequent treatment device; S7, carrying out solid-liquid separation on the residual mother liquor obtained in the step S6 by three-way multi-effect evaporation equipment (13) to obtain ammonium sulfate and a mother liquor IV; in the step S3, ammonium bicarbonate is introduced into an absorption device (14) from ammonia and CO 2 according to a certain proportion to prepare ammonium bicarbonate aqueous solution, and then the ammonium bicarbonate aqueous solution is introduced into a carbonization tower and a cleaning tower (15) through a pump to be carbonized further to generate an ammonium bicarbonate solid-liquid mixture, wherein the introduced CO 2 content is 90% -100%, and the mass fraction of the generated ammonium bicarbonate solid-liquid mixture is 12% -24%; in the step S5, mother liquor I treated in the step S4 is introduced into an ammonia distillation tower (11) to be heated and escaped, part of the escaped ammonia is compressed and returned into an absorption device (14) to be mixed with CO 2 to participate in an ammonia bicarbonate working section, the ammonia distillation tower (11) is heated for more than 2 hours at a temperature controlled to be 75 ℃, the other part of the escaped ammonia in the step S5 is mixed with the residual liquid and the mixed solution of sodium sulfate/ammonium sulfate, the solubility of sodium sulfate is reduced, the separated sodium sulfate solid is returned to a decomposition reactor (5) to participate in double decomposition reaction as a circulating raw material, the residual liquid after separation is mother liquor II, in the steps S6 and S7, the mother liquor II is mixed with the returned mother liquor IV and then introduced into a freezing crystallization device II (12) to participate in an ammonia bicarbonate working section, the mixed solution is separated out of the mother liquor III, the mother liquor III is subjected to multiple-effect evaporation device 13, four cycles of mother liquor are obtained and a second freezing and crystallizing device (12).
2. The method for recycling the high-salinity wastewater according to claim 1, wherein the produced water in the step S1 is introduced into a secondary nanofiltration device (6) to produce secondary nanofiltration water, and the secondary nanofiltration water is subjected to high-pressure reverse osmosis (7) treatment and concentration and then enters sodium chloride evaporation crystallization equipment (8) to prepare sodium chloride and reuse water.
3. The method for recycling high-salinity wastewater according to claim 2, wherein the first-stage nanofiltration concentrated water in the step S2 enters a mother solution produced by the first low-temperature freezing crystallization device (4) and the high-pressure reverse osmosis concentrated water, and then the mother solution is introduced into a sodium chloride evaporation crystallization device (8) to prepare sodium chloride and reuse water.

Description

Recycling treatment method for high-salt-content wastewater Technical Field The invention belongs to the technical field of high-salt wastewater reclamation treatment in the metallurgical industry, and particularly relates to a high-salt wastewater reclamation treatment method. Background High-salt wastewater generally refers to wastewater containing not less than 1% by mass of the total salt content in the form of dissolved salt, and the ions contained in such wastewater are mainlySince the high-salt wastewater contains a large amount of components such as Na +、Ca2+、K+, and contains soluble inorganic salts, the high-salt wastewater produced in some industries contains organic matters, and thus the treatment is relatively difficult. The prior high-salt-content wastewater treatment and recycling system mainly adopts the technical processes of a high-efficiency clarification tank, ozone catalytic oxidation, a biological aerated filter, a multi-medium filter, an ultrafiltration system, a weak acid cation bed, a primary reverse osmosis system, a high-pressure reverse osmosis system, nanofiltration and salt separation, and evaporation crystallization, and the separation and recovery of main components in the high-salt wastewater are realized through the above methods. However, the target salt separated and recovered by the high-salt wastewater treatment and recycling system is mainly sodium chloride salt and sodium sulfate salt, the utilization rate of the high-salt wastewater is low, the production of product salt is excessive, the value of the product salt is low, and the sales is difficult, so that the high-salt wastewater treatment and recycling method is provided. Disclosure of Invention The invention aims to provide a recycling treatment method for high-salt wastewater, which aims to solve the problems in the background technology. In order to achieve the purpose, the invention provides the following technical scheme that the method for recycling the high-salt-content wastewater comprises the following steps: Step S1, introducing high-salt wastewater in a first-stage nanofiltration water inlet tank into a first-stage nanofiltration device for first-stage nanofiltration, separating out first-stage nanofiltration concentrated water (TDS: about 160000 mg/L) and produced water (TDS: about 160000mg/L, mainly sodium sulfate); s2, introducing the first-stage nanofiltration concentrated water obtained in the step S1 into freezing crystallization equipment I for low-temperature treatment crystallization; Step S3, introducing the reaction product in the step S2 into a double-decomposition reactor for double-decomposition reaction; Step S4, introducing the reaction product obtained in the step S3 into a vacuum belt filter for heavy alkali filtration, introducing the separated sodium bicarbonate solid into a calciner, and delivering the residual mother liquor to a subsequent treatment device; s5, introducing the residual mother liquor I in the step S4 into an ammonia distillation tower for thermal separation, returning the precipitated sodium sulfate solid to a decomposition reactor, and delivering the residual mother liquor II to a subsequent treatment device; Step S6, introducing the residual mother liquor obtained in the step S5 into a second low-temperature treatment of a freezing crystallization device for solid-liquid separation, returning the obtained double salt to the sodium sulfate/ammonium sulfate mixed solution, and sending the residual mother liquor III to a subsequent treatment device; And S7, carrying out solid-liquid separation on the residual mother liquor obtained in the step S6 by three-way multi-effect evaporation equipment to obtain ammonium sulfate and a mother liquor IV. Further, the second-stage nanofiltration produced water in the step S1 is subjected to high-pressure reverse osmosis treatment and concentration (TDS: 100000mg/L, mainly sodium chloride) and then enters sodium chloride evaporation crystallization equipment to prepare sodium chloride and reuse water. Furthermore, the first-stage nanofiltration concentrated water in the step S2 enters a mother solution produced by a low-temperature freezing crystallization device I and high-pressure reverse osmosis concentrated water to be mixed, and then the mother solution is introduced into a sodium chloride evaporation crystallization device to prepare sodium chloride and reuse water. Further, in the step S3, ammonium bicarbonate is introduced into an absorption device from ammonia gas and CO 2 according to a certain proportion to prepare an ammonium bicarbonate aqueous solution, and then the ammonium bicarbonate aqueous solution is pumped into a carbonization tower and a cleaning tower for further carbonization to generate an ammonium bicarbonate solid-liquid mixture, wherein the content of introduced CO 2 is 90% -100%, and the mass fraction of the generated ammonium bicarbonate solid-liquid mixture is 12% -24%. In step S4, the sodium bicarbo