CN206799345U - A kind of system of high-salt wastewater purified salt - Google Patents

Abstract

The utility model belongs to the technical field of industrial sewage treatment in the textile thermal power industry, in particular to a system for refining salt from high-salt wastewater. The system provided by the utility model is separated and concentrated to a concentration of sodium sulfate greater than 16% through denitrification and nanofiltration, and then sent to frozen crystallization treatment to obtain Glauber's salt with a purity greater than 95%, and its yield reaches more than 80%. The low water recovery rate can reach more than 95%; through the purification of multi-stage nanofiltration, sodium sulfate can be further intercepted, so that the purity of sodium chloride can reach more than 95%, and impurities such as nitrate can be removed by evaporation and crystallization, which can further improve the purification The reuse value of sodium chloride, the total recovery rate of sodium chloride can be greater than 80%.

Description

A system for refining salt from high-salt wastewater

technical field

The utility model belongs to the technical field of industrial sewage treatment in the textile thermal power industry, in particular to a system for refining salt from high-salt wastewater.

Background technique

With the development of industry, the shortage of water resources, the pollution of textile, thermal power and chemical industries is becoming more and more serious. At present, after 75% of the raw water is recycled by the membrane method, the post-treatment of the concentrated water left has become a difficult problem today. Even if COD and other indicators are treated at a high cost to meet the discharge requirements, the discharge of high salt water still has a serious impact on farmland irrigation and soil ecological environment. Therefore, how to extract and reuse salt resources in high-salt wastewater has become a hot spot in wastewater treatment. one.

The high-salt wastewater in the textile industry comes from the color-fixing additives. Glauber’s salt or sodium anhydride and refined salt have relatively high requirements for reuse of salt. The two main salts in the wastewater are separated, concentrated and refined to meet the requirements of reuse, and controlled Low reuse cost can bring economic benefits to enterprises. The development of post-treatment of reverse osmosis concentrated water can effectively solve the problem of high-salt wastewater recycling. transportation cost.

At present, there are some similar patents on the technology of membrane integrated treatment of high-salt wastewater to achieve emission reduction. Due to the insufficient purity of salt, the low salt concentration of membrane integration leads to high energy consumption of the total system, which cannot be widely used.

Contents of the invention

The purpose of this utility model is to provide a system for refining salt from high-salt wastewater, aiming at the deficiencies in the prior art.

For this reason, above-mentioned purpose of the utility model is realized through the following technical solutions:

A system for refining salt from high-salt wastewater, the system comprising:

- A pretreatment system, the pretreatment system is used to pretreat high-salt wastewater, and the pretreated wastewater meets the water quality requirements for entering the first-level nanofiltration and salt separation system;

- A first-level nanofiltration and salt separation system, the first-level nanofiltration and salt separation system is used to perform nanofiltration and salt separation treatment on the pretreatment system, concentrated water enters the high-pressure nanofiltration and salt separation system for nanofiltration and salt separation treatment, and the produced water enters One-stage reverse osmosis system for concentration treatment;

- High-pressure nanofiltration and salt separation system, which is used to conduct nanofiltration and salt separation treatment on the concentrated water of the first-level nanofiltration and salt separation system, and the concentrated water of the high-pressure nanofiltration and salt separation system enters the freezing and crystallization system Freezing and crystallization is carried out, and the product water enters the first-stage reverse osmosis system for concentration treatment;

- A first-stage reverse osmosis system, the first-stage reverse osmosis system is used to carry out reverse osmosis concentration treatment on the product water obtained respectively from the first-stage nanofiltration salt separation system and the high-pressure nanofiltration salt separation system, and the concentrated water of the first-stage reverse osmosis system Enter the secondary nanofiltration and salt separation system for nanofiltration and salt separation treatment;

- Two-stage nanofiltration salt separation system, the two-stage nanofiltration salt separation system is used to perform nanofiltration salt separation treatment on the concentrated water of the first-stage reverse osmosis system, and the concentrated water of the two-stage nanofiltration salt separation system enters the anion In the desalination chamber of the separation membrane electrodialysis system, the produced water enters the secondary reverse osmosis system for reverse osmosis concentration treatment;

- Two-stage reverse osmosis system, the two-stage reverse osmosis system is used to carry out reverse osmosis concentration treatment on the product water of the two-stage nanofiltration and salt separation system, and part of the concentrated water of the two-stage reverse osmosis system enters the anion-separatable membrane electrodialysis system the concentration chamber;

- Anion separable membrane electrodialysis system, the desalination chamber of the anion separable membrane electrodialysis system is passed into the concentrated water of the secondary nanofiltration salt separation system, and part of the concentrated water of the secondary reverse osmosis system is passed into the concentration chamber;

- Electrodialysis concentration system, the fresh water side of the electrodialysis concentration system is passed into the remaining concentrated water of the secondary reverse osmosis system, the concentrated water side is passed into the concentrated water of the anion-separatable membrane electrodialysis system, and the concentrated water obtained by the electrodialysis concentration system Water enters the evaporative crystallization system;

- Freezing crystallization system, which is used for freezing and crystallizing the concentrated water from the high-pressure nanofiltration and salt separation system to obtain Glauber's salt; and

- An evaporative crystallization system, which is used for evaporative crystallization to treat the concentrated water obtained from the electrodialysis concentration system, and obtain more pure sodium chloride through evaporation separation.

While adopting the above-mentioned technical solution, the utility model can also adopt or adopt the following further technical solutions in combination:

The system also includes a bipolar membrane electrodialysis system, and part of the concentrated water of the first-stage reverse osmosis system is passed into the salt chamber of the bipolar membrane electrodialysis system.

The pretreatment system includes: dosing precipitation system, filtration oxidation system and softening dealkalization system to remove impurities such as chroma, hardness, alkalinity and silicon to meet the requirements of salt production.

The fresh water of the anion-separatable membrane electrodialysis system is reused to the inlet of the first-stage nanofiltration and salt separation system for nanofiltration and salt separation.

The fresh water of the electrodialysis concentration system is recycled to the inlet of the secondary reverse osmosis system for reverse osmosis concentration treatment.

Most of the mother liquor in the freeze crystallization system is recycled to the inlet of the high-pressure nanofiltration salt separation system for nanofiltration salt separation.

The system provided by the utility model is not only suitable for the relatively water-deficient northern regions, but also suitable for the southern regions that require strict control of salinity discharge for environmental emissions, especially in textile parks such as Zhejiang, Guangdong, and Shandong where the textile industry is relatively developed. The water can meet the process water requirements of the textile thermal power industry. It not only recovers the water but also recovers the heat energy contained in the waste water, reducing the cost of power generation and steam. Glauber's salt and sodium chloride salt produced by salt division can be used as textile auxiliaries, which saves raw material costs, solves the bottleneck problem of high-salt wastewater treatment, and brings better social and social benefits to industrial parks or enterprises. economic benefits.

The system provided by the utility model is separated and concentrated to a concentration of sodium sulfate greater than 16% through denitrification and nanofiltration, and then sent to frozen crystallization treatment to obtain Glauber's salt with a purity greater than 95%, and its yield reaches more than 80%. The low water recovery rate can reach more than 95%; through the purification of multi-stage nanofiltration, sodium sulfate can be further intercepted, so that the purity of sodium chloride can reach more than 95%, and impurities such as nitrate can be removed by evaporation and crystallization, which can further improve the purification The reuse value of sodium chloride, the total recovery rate of sodium chloride can be greater than 80%.

The system provided by the utility model utilizes the advantages of each section in stages and makes the most reasonable combination. The lack of a certain section in the whole process will lead to a reduction in the recycling effect and an increase in energy consumption, but due to the different sizes of the system , the water quality is different, for small systems, in order to save investment, the method of direct reuse of concentrated brine can be used to reduce energy consumption, and also reduce the investment cost of evaporation and frozen crystallization. The manufacturer can simplify the process combination according to the actual reuse needs, The full reuse of wastewater resources is realized through the high-efficiency integrated membrane process route.

Description of drawings

Fig. 1 is the schematic diagram of the system of a kind of high-salt wastewater refining salt provided by the utility model;

In the figure: 101-dosing precipitation system; 102-filtration oxidation system; 103-softening dealkalization system; 201-low pressure nanofiltration concentration system; 202-high pressure nanofiltration concentration system; 203-secondary nanofiltration system; 301-one 302-two-stage reverse osmosis system; 303-three-stage reverse osmosis system; 401-anion separable membrane electrodialysis system; 402-electrodialysis concentration system; 403-bipolar membrane electrodialysis system; 501-refrigeration Crystallization system; 502-evaporative crystallization system.

detailed description

The utility model is described in further detail with reference to the accompanying drawings and specific embodiments.

A system for refining salt from high-salt wastewater. The nanofiltration concentration system is aimed at concentration of sodium sulfate, and is divided into a low-pressure nanofiltration concentration system 201 and a high-pressure nanofiltration concentration system 202 according to the pressure of the membrane. The low-pressure nanofiltration concentration system 201 has from Anion-separatable membrane electrodialysis system 401 circulates the dilute liquid circulating volume, and the feed water of high-pressure nanofiltration concentration system 202 includes the return flow of mother liquor of frozen crystallization system 501 and the concentrated water of low-pressure nanofiltration concentration system 201. When the system is large, The nanofiltration concentration system that can re-concentrate the mother liquor can be set separately, which is more conducive to the product quality control of the freezing crystallization system. The selected nanofiltration membranes are all denitrification membranes with a high rejection rate of sodium sulfate.

The pretreatment system of the high-salt wastewater refined salt system is a dosing precipitation system 101, a filtration oxidation system 102, and a softening dealkalization system 103. and sodium chloride salt requirements, and ensure the safe and stable operation of the membrane combination system. The regenerated brine required for pretreatment can use part of concentrated water from the primary reverse osmosis system 301 or the secondary reverse osmosis system 302 , while the required acid and alkali are produced from the bipolar membrane electrodialysis system 403 .

The separation of polyvalent salts is completed through the nanofiltration system, separated by high-pressure nanofiltration and concentrated to a concentration of about 16% of sodium sulfate, and sent to the freezing and crystallization system 501, which contains a certain amount of sodium chloride salt, which is more conducive to improving the crystallization of Glauber's salt. Yield. For the southern region, it is recommended to obtain Yuanmingfen with evaporative drying equipment, which is conducive to storage.

303 is a three-stage reverse osmosis system. Usually, it is determined based on the conductivity of the recycled water whether the system needs to be equipped with a three-stage reverse osmosis system. For example, the product water and evaporated condensed water of the two-stage reverse osmosis system 302 need to pass through the three-stage reverse osmosis system. 303 is desalinated again to control the conductivity value of the reused water to be less than 200μs/cm, which fully meets the water requirements of various process points in the textile industry, and the total water reuse rate can reach more than 95%.

For the electrodialysis system, this process is divided into two kinds of concentration processes: the anion separable membrane electrodialysis system 401 and the electrodialysis concentration system 402. The fresh water that the separable membrane electrodialysis system 401 enters is the repurification of sodium sulfate containing salt through repurification. Denitrification nanofiltration concentrated water, and the concentrated water of the separable membrane electrodialysis system 401 is a part of the concentrated water of the two-stage reverse osmosis system 302. When the salinity in the fresh water of the separable membrane electrodialysis system 401 is reduced to a low concentration, let Its fresh water returns to the feedwater of the low-pressure nanofiltration concentration system 201; while its concentrated water enters the concentrated water side of the electrodialysis concentration system 402 for further concentration, and the fresh water of the electrodialysis concentration system 402 is the remaining concentrated Water, when the fresh water in the electrodialysis concentration system 402 is depleted to 2~3%, it will return to the feed water of the secondary reverse osmosis system 302, and the concentrated water in the electrodialysis concentration system 402 will be concentrated until the concentration of sodium chloride reaches 18 through continuous circulation. ~20% is transported to the evaporation crystallization system 502 or directly reused. The bipolar membrane electrodialysis system 403 is used to prepare the alkali required for pretreatment and dosing and the acid required for regeneration. The incoming brine of the bipolar membrane electrodialysis system 403 only needs to separate an appropriate amount of brine from the concentrated reverse osmosis concentrated water of the first-stage reverse osmosis system 301, and the light brine of the bipolar membrane electrodialysis system 403 is returned to the first-stage reverse osmosis system 301 Reconcentration was performed.

The system for refining salt from high-salt wastewater provided by the utility model realizes a low-energy recycling system by combining energy recovery processes with nanofiltration and reverse osmosis systems. Using the principle of self-priming backwashing with high brine to reduce membrane fouling and cleaning frequency.

When the mother liquor of the frozen crystallization system 501 circulates to the point where it is difficult to control the impurity amount of COD and monovalent salt, it needs to be discharged in an appropriate amount to ensure the product quality of thenardite and sodium chloride salt. For the southern region, the thenardite can be evaporated to obtain 98% accuracy in Yuanming powder, the product is more conducive to storage. The evaporation and crystallization system 502 adopts the combined process of MVR evaporation and multi-effect evaporation. In addition to producing refined salt that can be reused, a small amount of miscellaneous salt is still discharged.

The above-mentioned specific embodiments are used to explain the utility model, and are only preferred embodiments of the utility model, rather than limiting the utility model. Within the spirit of the utility model and the scope of protection of the claims, the utility model is made Any modification, equivalent replacement, improvement, etc., all fall into the protection scope of the present utility model.

Claims (6)

1. A system for refining salt from high-salt wastewater, characterized in that the system comprises: - a pretreatment system, the pretreatment system is used to pretreat high-salt wastewater, and the pretreated wastewater meets the water quality requirements for entering the first-level nanofiltration and salt separation system; - A first-level nanofiltration and salt separation system, the first-level nanofiltration and salt separation system is used to perform nanofiltration and salt separation treatment on the pretreatment system, concentrated water enters the high-pressure nanofiltration and salt separation system for nanofiltration and salt separation treatment, and the produced water enters One-stage reverse osmosis system for concentration treatment; - High-pressure nanofiltration salt separation system, the high-pressure nanofiltration salt separation system is used to perform nanofiltration salt separation treatment on the concentrated water of the first-level nanofiltration salt separation system, and the concentrated water of the high-pressure nanofiltration salt separation system enters the freezing and crystallization system Freezing and crystallization is carried out, and the product water enters the first-stage reverse osmosis system for concentration treatment; -A first-stage reverse osmosis system, the first-stage reverse osmosis system is used to carry out reverse osmosis concentration treatment on the product water obtained respectively from the first-stage nanofiltration salt separation system and the high-pressure nanofiltration salt separation system, and the concentrated water of the first-stage reverse osmosis system Enter the secondary nanofiltration and salt separation system for nanofiltration and salt separation treatment; -Secondary nanofiltration and salt separation system, the secondary nanofiltration and salt separation system is used to perform nanofiltration and salt separation treatment on the concentrated water of the primary reverse osmosis system, and the concentrated water of the secondary nanofiltration and salt separation system can enter the anion In the desalination chamber of the separation membrane electrodialysis system, the produced water enters the secondary reverse osmosis system for reverse osmosis concentration treatment; - a two-stage reverse osmosis system, the two-stage reverse osmosis system is used to perform reverse osmosis concentration treatment on the produced water of the two-stage nanofiltration and salt separation system, and part of the concentrated water of the two-stage reverse osmosis system enters the anion-separatable membrane electrodialysis system the concentration chamber; -anion separable membrane electrodialysis system, the desalination chamber of the anion separable membrane electrodialysis system is passed into the concentrated water of the secondary nanofiltration salt separation system, and part of the concentrated water of the secondary reverse osmosis system is passed into the concentration chamber; - an electrodialysis concentration system, the fresh water side of the electrodialysis concentration system is passed into the remaining concentrated water of the secondary reverse osmosis system, the concentrated water side is passed into the concentrated water of the anion separable membrane electrodialysis system, the concentrated water obtained by the electrodialysis concentration system Water enters the evaporative crystallization system; - freezing and crystallization system, said freezing and crystallization system is used for freezing and crystallizing the concentrated water from the high-pressure nanofiltration and salt separation system to obtain Glauber's salt; and - An evaporative crystallization system, which is used for evaporative crystallization to treat the concentrated water obtained from the electrodialysis concentration system, and to obtain more pure sodium chloride through evaporative separation. 2. The system for refining salt from high-salt wastewater according to claim 1, characterized in that, the system also includes a bipolar membrane electrodialysis system, and the first-stage reaction is passed into the salt chamber of the bipolar membrane electrodialysis system Permeate part of the concentrated water of the system. 3. The system for refining salt from high-salt wastewater according to claim 1, wherein the pretreatment system includes: dosing precipitation system, filtration oxidation system and softening dealkalization system to remove chroma, hardness, alkali degree and silicon impurities, to meet the requirements of salt production. 4. The system for refining salt from high-salt wastewater according to claim 1, characterized in that the fresh water from the anion-separatable membrane electrodialysis system is reused to the inlet of the primary nanofiltration salt separation system for nanofiltration salt separation. 5 . The system for refining salt from high-salt wastewater according to claim 1 , wherein the fresh water in the electrodialysis concentration system is recycled to the inlet of the secondary reverse osmosis system for reverse osmosis concentration treatment. 6. The system for refining salt from high-salt wastewater according to claim 1, characterized in that most of the mother liquor in the freezing and crystallization system is recycled to the inlet of the high-pressure nanofiltration and salt separation system for nanofiltration and salt separation.