Method and system for recycling cellulose ether wastewater

Abstract

The invention discloses a method and a system for recycling cellulose ether wastewater. According to the method, technologies such as pretreatment, electrodialysis treatment of an electrodialysis unit system with specific composition, evaporative crystallization and the like are utilized, and NaCl crystalline salt and desalinated water rich in alcohols are respectively recovered from the cellulose ether wastewater. Wherein a desalination chamber and a concentration chamber in the electrodialysis unit system are respectively provided with an independent water inlet, fed materials in electrodialysis only enter the desalination chamber and do not enter the concentration chamber, water entering the concentration chamber is electrodialysis circulating concentrated water, and the synergistic operation effect of each unit system ensures that alcohols do not enter the salt-containing concentrated water; and thorough separation of sodium chloride and alcohols after electrodialysis treatment is ensured. The recovered sodium chloride can be reused for production or sold as a sodium chloride product; the alcohol-rich desalted water can be reused / sold as a sewage biochemical treatment nutrient solution or used for other purposes. And by recycling sodium chloride and alcohols, resource utilization of the cellulose ether wastewater is realized, and the method has huge economic, environment-friendly and social benefits.

Description

Technical Field

[0001] The invention relates to the technical field of electrodialysis and evaporation crystallization, and in particular to a method and a system for resource utilization of cellulose ether wastewater. Background Art

[0002] Cellulose ether is commonly known as "industrial MSG" and is mainly used in the construction, food, medicine, textile, synthesis and other industries. It has developed rapidly in recent years. China is the world's largest producer and consumer of cellulose ether, with an average annual growth rate of more than 20%.

[0003] During the industrialization of cellulose ether, a high-salt wastewater will be produced. This type of wastewater has the following characteristics: 1. The salt content is about 7-10%, or even higher; 2. The organic matter content is high, and the COD content is generally 30,000-100,000 ppm, or even higher. The organic matter is mainly alcohols and a certain amount of ethers. It is precisely because the heavy salt in this type of wastewater causes microorganisms to lose their activity, and ethers are potentially toxic to microorganisms, affecting their growth and metabolism, which makes it difficult to directly biochemically treat this type of wastewater, which is not environmentally friendly and has a significant impact on human living environment and health.

[0004] Combined with the existing cellulose ether wastewater technology and the actual status of wastewater treatment, in addition to conventional pretreatment, the wastewater is currently mainly treated by the following two methods:

[0005] (1) Biochemical treatment (anaerobic + aerobic) + advanced oxidation to remove COD, even after dilution with fresh water;

[0006] (2) Evaporation and crystallization (+ fractional distillation to recover organic matter) produces solid waste landfill + condensate biochemical treatment (anaerobic + aerobic) + advanced oxidation.

[0007] However, both methods have their own shortcomings. Method (1) Since heavy salt causes microorganisms to lose their activity, and ethers are potentially toxic to microorganisms, affecting their growth and metabolism, it is difficult to achieve treatment effects. Even if fresh water is used for dilution, the system is still sensitive to load shocks, with poor operating stability and poor long-term continuous operation of equipment. It occupies a large area, and advanced oxidation also has problems such as high chloride ion interference with oxidation and high operating costs. The fresh water dilution method also violates the basic principle that wastewater treatment should not be treated by dilution. Method (2) First, remove salt by evaporation and crystallization and recover organic matter by distillation. After the condensed water is desalinated, biochemical + advanced oxidation treatment is carried out. The condensed water treatment achieves good results, but a considerable part of the organic matter adheres to the crystallized salt and precipitates during the evaporation and crystallization process, which is equivalent to converting pollutants into solid waste. The pollution is not fundamentally eliminated. At the same time, the crystallized salt produced by the evaporation and crystallization of this wastewater contains a large amount of alcohol and ether organic matter. The generated crystallized salt solid is a hazardous solid waste. The landfill cost of hazardous solid waste disposal is usually 2,000 to 4,000 yuan / ton, and the disposal cost is very high. In addition, the evaporation and crystallization process has very high energy consumption due to phase change, and the operating cost is high. Therefore, method (2) not only has high operating costs, but also fails to fundamentally solve the pollutant problem.

[0008] In fact, sodium chloride and alcohol organic matter are themselves a kind of available resources, but in the conventional cellulose ether wastewater treatment, they are treated or discharged as "pollutants", which not only pollutes the environment, but also causes waste of resources. Due to the difficulty in treating wastewater, poor treatment effect and high cost, some companies also engage in "secret discharge" in order to save costs. How to properly treat cellulose ether wastewater has become an important constraint on the development of the industry. In addition, the existing technology does not have any related applications that use electrodialysis as the core treatment process to recover sodium chloride and alcohols in wastewater. Summary of the invention

[0009] In view of the shortcomings in the effects of the cellulose ether wastewater treatment technology in the prior art, the current treatment has always been unable to achieve better results. The present invention provides a method and system for resource utilization of cellulose ether wastewater, which utilizes pretreatment, electrodialysis treatment of an electrodialysis unit system of a specific composition, evaporation crystallization and other technologies to respectively recover NaCl crystal salt and desalinated water rich in alcohols from cellulose ether wastewater. The recovered sodium chloride can be reused in production or sold as a sodium chloride product; the desalinated water rich in alcohols can be reused / sold as a nutrient solution for sewage biochemical treatment or used for other purposes. By recovering sodium chloride and alcohols, the resource utilization of cellulose ether wastewater is achieved. In addition, after the treatment of the present invention, the product can be recovered as a resource benefit of the enterprise, which has great economic, environmental and social benefits in improving the wastewater treatment awareness of related enterprises producing cellulose ethers and actively and effectively implementing wastewater treatment.

[0010] In order to solve the problems of the prior art, the technical solution adopted by the present invention is:

[0011] A method for resource utilization of cellulose ether wastewater, comprising the following steps:

[0012] Step 1, pretreatment of cellulose ether wastewater

[0013] The cellulose ether wastewater is introduced into the pretreatment unit system, and is sequentially passed through the cavitation air flotation machine, dissolved air flotation machine, walnut shell filter, high-density tank, and filter for pretreatment to remove oil and solid floating matter, ensuring that the treated water quality meets the electrodialysis water inlet requirements;

[0014] Step 2: Preliminary separation of salts and alcohols in cellulose ether wastewater

[0015] The pretreated cellulose ether wastewater is introduced into the material circulation water tank in the electrodialysis unit system, and the initial water is injected into the concentrated water circulation water tank in the electrodialysis unit system. The cellulose ether wastewater passing through the material circulation water tank passes through the material circulation pump, the material heat exchanger and the material safety filter in sequence, and then enters the desalination chamber in the electrodialysis unit structure;

[0016] The initial water passes through the concentrated water circulating water tank, the concentrated water circulating pump, the concentrated water heat exchanger and the concentrated water safety filter in turn, and then enters the concentration chamber in the electrodialysis unit structure, so that the sodium ions and chloride ions in the cellulose ether wastewater pass through the anion membrane and the cation membrane in the electrodialysis unit structure respectively, and then enter the concentration chamber in the electrodialysis unit structure to obtain salt water, while the alcohols in the cellulose ether wastewater continue to stay in the desalination chamber in the electrodialysis unit structure to obtain desalinated water rich in alcohols;

[0017] Step 3: Separation of salt and alcohol in cellulose ether wastewater

[0018] The alcohol-rich desalinated water obtained in step 2 is returned to the material circulation water tank, and the salt water flows into the concentrate circulation water tank. The alcohol-rich desalinated water and the salt water are circulated in the electrodialysis unit structure through the material circulation pump and the concentrate circulation pump respectively, so that the sodium ions and chloride ions in the alcohol-rich desalinated water continuously enter the concentration chamber until it is detected that the salt content of the alcohol-rich desalinated water in the material circulation water tank is reduced to the first target concentration, and the salt content of the salt water in the concentrate circulation water tank is increased to the second target concentration, so as to complete the separation of salt and alcohol in the cellulose ether wastewater;

[0019] Step 4: Recovering Salt

[0020] The alcohol-rich desalinated water whose salt content is reduced to the first target concentration in step 3 enters the alcohol-rich desalinated water tank through the fresh water discharge pump to obtain alcohol-rich desalinated water; at the same time, the salt water whose salt content reaches the second target concentration enters the brine tank in the evaporation crystallization unit from the brine circulating water tank through the brine discharge pump, and after evaporation and crystallization treatment, it is dried to obtain NaCl crystal salt and desalted water. The desalted water is passed into the brine circulating water tank, and flows into the concentrating chamber of the electrodialysis unit structure through the brine circulating pump, the brine heat exchanger, and the brine safety filter as water replenishment for the concentrating chamber in the electrodialysis unit structure. At the same time, the desalted water can also be reused as recycled water.

[0021] As an improvement, the characteristics of the water quality after treatment in step 1 include but are not limited to suspended solids <1 mg / L, free residual chlorine <0.5 mg / L, and no oil.

[0022] As an improvement, the initial water used in step 2 is fresh water, specifically tap water, desalted water or purified water.

[0023] As an improvement, in step 3, the first target concentration is ≤2%, and the second target concentration is 5% to 15%.

[0024] A system for treating the above-mentioned cellulose ether wastewater for resource utilization, comprising wastewater storage equipment, fresh water supply equipment, a pretreatment unit system, an electrodialysis unit system, an evaporation crystallization unit system, a concentrated water discharge pump, a fresh water discharge pump, and an alcohol-rich desalination water tank.

[0025] Wherein, the pretreatment unit system includes a cavitation air flotation machine, a dissolved air flotation machine, a walnut shell filter, a high-density tank, a filter, and a dehydrator;

[0026] The electrodialysis unit system includes an electrodialysis unit structure, a material circulation structure, and a concentrated water circulation structure;

[0027] The electrodialysis unit structure comprises at least one electrodialysis unit, wherein the electrodialysis unit is provided with a desalination chamber and a concentration chamber which are spaced apart from each other and have independent water inlets and outlets, and polar water chambers which are provided at both ends of the electrodialysis unit and have polar water inlets and outlets, and an anion exchange membrane and a cation exchange membrane which are spaced apart from each other between the desalination chamber and the concentration chamber;

[0028] The material circulation structure includes a material circulation water tank, a material circulation pump, a material heat exchanger, and a material safety filter;

[0029] The concentrated water circulation structure includes a concentrated water circulation water tank, a concentrated water circulation pump, a concentrated water heat exchanger, and a concentrated water safety filter;

[0030] The evaporation crystallization unit system comprises a concentrated brine tank, an evaporation crystallization system, and a dryer;

[0031] Specifically, the outlet of the wastewater storage equipment is connected to the cavitation air flotation machine, the dissolved air flotation machine, the walnut shell filter, the high-density tank, and the filter in the pretreatment unit system in sequence, the suspended matter discharge port of the cavitation air flotation machine, the suspended matter discharge port of the dissolved air flotation machine, and the mud discharge port of the high-density tank are all connected to the feed port of the dewatering machine, and the backwash wastewater of the walnut shell filter, the dewatering machine filtrate, and the backwash wastewater of the filter are all returned to the wastewater storage equipment for cyclic treatment; the solid impurities generated in the dewatering machine are discharged through the discharge port;

[0032] The water outlet of the filter is connected to the water inlet of the material circulation water tank of the material circulation structure, the water outlet of the material circulation water tank is connected to the inlet of the material circulation pump, the outlet of the material circulation pump is connected to the inlet of the material heat exchanger, the outlet of the material heat exchanger is connected to the inlet of the material security filter, the outlet of the material security filter is connected to the water inlet of the desalination chamber of the electrodialysis unit, the water outlet of the desalination chamber of the electrodialysis unit is connected to the return inlet of the material circulation water tank, the discharge port of the material circulation water tank is connected to the inlet of the fresh water discharge pump, and the outlet of the fresh water discharge pump is connected to the inlet of the alcohol-rich desalination water tank;

[0033] The fresh water supply equipment is connected to the water inlet of the concentrated water circulation tank in the concentrated water circulation structure, the water outlet of the concentrated water circulation tank is connected to the inlet of the concentrated water circulation pump, the outlet of the concentrated water circulation pump is connected to the inlet of the concentrated water heat exchanger, the outlet of the concentrated water heat exchanger is connected to the inlet of the concentrated water safety filter, the outlet of the concentrated water safety filter is connected to the water inlet of the concentration chamber of the electrodialysis unit, and the water outlet of the concentration chamber is connected to the return inlet of the concentrated water circulation tank; the discharge port of the concentrated water circulation tank is connected to the concentrated water discharge pump, the outlet of the concentrated water discharge pump is connected to the inlet of the concentrated brine tank, the outlet of the concentrated brine tank is connected to the inlet of the evaporation crystallization system, and the crystallized salt outlet of the evaporation crystallization system is connected to the inlet of the dryer.

[0034] As an improvement, the condensed water outlet of the evaporation crystallization system in the evaporation crystallization unit system is connected to the water inlet of the concentrated water circulation water tank.

[0035] As an improvement, the water outlet of the concentration chamber in the electrodialysis unit system is connected to the water inlet of the concentrated water circulation tank.

[0036] Beneficial effects:

[0037] Compared with the prior art, the method and system for resource utilization of cellulose ether wastewater of the present invention have the following advantages:

[0038] 1. The present invention utilizes pretreatment, electrodialysis treatment of a specific electrodialysis unit system, evaporation crystallization and other technologies to recover NaCl crystal salt and desalinated water rich in alcohols from cellulose ether wastewater. The recovered sodium chloride can be reused in production or sold as a sodium chloride product; the desalinated water rich in alcohols can be reused / sold as a nutrient solution for wastewater biochemical treatment or used for other purposes.

[0039] 2. The electrodialysis unit system used in the method of the present invention has a unique structure. The desalination chamber and the concentration chamber are respectively provided with independent water inlets, and the cellulose ether wastewater only enters the desalination chamber but not the concentration chamber. The water in the concentration chamber is electrodialysis circulating concentrated water (the initial water replenishment is water of equivalent water quality such as tap water / desalted water / purified water, and the condensed water is condensed by the evaporation crystallization system after normal operation). Through this special design and operation mode, it is ensured that alcohols will not enter the salt-containing concentrated water, and the separation efficiency of sodium chloride and alcohols in the electrodialysis is guaranteed, so as to obtain concentrated water rich in sodium chloride and desalinated water rich in alcohols.

[0040] 3. The present invention uses an evaporation and crystallization system to further evaporate and crystallize concentrated water rich in sodium chloride to produce sodium chloride, which is then dried and packaged for reuse or sale, thereby realizing resource utilization of cellulose ether wastewater. The recyclable product, as a resource benefit for the enterprise, has a positive effect on improving the wastewater treatment awareness of related enterprises producing cellulose ether. The related enterprises actively and effectively implement wastewater treatment, further improving the environmental protection effect, and generating huge economic and social benefits. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] Figure 1 A schematic diagram of a process flow of a method for resource utilization of cellulose ether wastewater according to the present invention;

[0042] Figure 2 A schematic diagram of an electrodialysis unit in a device used in a method for resource utilization of cellulose ether wastewater according to the present invention;

[0043] Figure 3 The system structure diagram of the method for resource utilization of cellulose ether wastewater of the present invention includes: 1-wastewater storage equipment, 2-concave air flotation machine, 3-dissolved air flotation machine, 4-walnut shell filter, 5-high density tank, 6-filter, 7-dehydrator, 8-material circulation water tank, 9-material circulation pump, 10-material heat exchanger, 11-material security filter, 12-electrodialysis unit structure, 13-fresh water supply equipment, 14-concentrated water circulation water tank, 15-concentrated water circulation pump, 16-concentrated water heat exchanger, 17-concentrated water security filter, 18-concentrated water discharge pump, 19-concentrated brine tank, 20-evaporation crystallization system, 21-dryer, 22-fresh water discharge pump, 23-alcohol-rich desalination water tank. DETAILED DESCRIPTION

[0044] In order to make the purpose, technical solution and advantages of the embodiments of the present application clearer, the technical solution in the embodiments of the present application will be clearly and completely described below in conjunction with the drawings in the embodiments of the present application. Obviously, the described embodiments are part of the embodiments of the present application, not all of the embodiments. Based on the embodiments of the present application, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present application.

[0045] It should be noted that the connection method of the various components in the system of the present invention and the use method of equipment such as heat exchangers are all conventional technical means in the field.

[0046] Example 1

[0047] like Figure 3 As shown, a system for resource utilization of cellulose ether wastewater includes a wastewater storage device 1, a fresh water supply device 13, a pretreatment unit system, an electrodialysis unit system, an evaporation crystallization unit system, a concentrated water discharge pump 18, a fresh water discharge pump 22, and an alcohol-rich desalinated water tank 23.

[0048] The pretreatment unit system includes a cavitation air flotation machine 2, a dissolved air flotation machine 3, a walnut shell filter 4, a high-density tank 5, a filter 6, and a dehydrator 7;

[0049] The electrodialysis unit system includes an electrodialysis unit structure 12, a material circulation structure, and a concentrated water circulation structure;

[0050] The electrodialysis unit structure 12 comprises at least one electrodialysis unit, wherein the electrodialysis unit is provided with a desalination chamber and a concentration chamber with independent water inlets and outlets which are spaced apart from each other, and polar water chambers with polar water inlets and outlets which are provided at both ends of the electrodialysis unit, and an anion exchange membrane and a cation exchange membrane which are spaced apart from each other between the desalination chamber and the concentration chamber;

[0051] The material circulation structure includes a material circulation water tank 8, a material circulation pump 9, a material heat exchanger 10, and a material security filter 11;

[0052] The concentrated water circulation structure includes a concentrated water circulation water tank 14, a concentrated water circulation pump 15, a concentrated water heat exchanger 16, and a concentrated water safety filter 17;

[0053] The evaporation crystallization unit system includes a concentrated brine tank 19, an evaporation crystallization system 20, and a dryer 21;

[0054] Specifically, the outlet of the wastewater storage device 1 is connected to the cavitation air flotation machine 2, the dissolved air flotation machine 3, the walnut shell filter 4, the high-density tank 5, and the filter 6 in the pretreatment unit system in sequence, and the suspended matter discharge port of the cavitation air flotation machine, the suspended matter discharge port of the dissolved air flotation machine, and the mud discharge port of the high-density tank are all connected to the feed port of the dewatering machine 7, and the backwash wastewater of the walnut shell filter, the dewatering machine filtrate, and the backwash wastewater of the filter are all returned to the wastewater storage device for cyclic treatment; the solid impurities generated in the dewatering machine are discharged through the discharge port;

[0055] The water outlet of the filter 6 is connected to the water inlet of the material circulation water tank 8 of the material circulation structure, the water outlet of the material circulation water tank 8 is connected to the inlet of the material circulation pump 9, the outlet of the material circulation pump 9 is connected to the inlet of the material heat exchanger 10, the outlet of the material heat exchanger 10 is connected to the inlet of the material security filter 11, the outlet of the material security filter 11 is connected to the water inlet of the desalination chamber of the electrodialysis unit 12, the water outlet of the desalination chamber of the electrodialysis unit is connected to the return inlet of the material circulation water tank, the discharge port of the material circulation water tank 8 is connected to the inlet of the fresh water discharge pump 22, and the outlet of the fresh water discharge pump 22 is connected to the inlet of the alcohol-rich desalination water tank 23;

[0056] The fresh water supply equipment 13 is connected to the water inlet of the concentrated water circulation water tank 14 in the concentrated water circulation structure, the water outlet of the concentrated water circulation water tank 14 is connected to the inlet of the concentrated water circulation pump 15, the outlet of the concentrated water circulation pump 15 is connected to the inlet of the concentrated water heat exchanger 16, the outlet of the concentrated water heat exchanger 16 is connected to the inlet of the concentrated water safety filter 17, the outlet of the concentrated water safety filter 17 is connected to the water inlet of the concentration chamber of the electrodialysis unit 12, and the water outlet of the concentration chamber is connected to the return inlet of the concentrated water circulation water tank; the discharge port of the concentrated water circulation water tank is connected to the concentrated water discharge pump 18, the outlet of the concentrated water discharge pump 18 is connected to the inlet of the concentrated brine tank 19, the outlet of the concentrated brine tank 19 is connected to the inlet of the connected evaporation crystallization system 20, and the crystallized salt outlet of the evaporation crystallization system 20 is connected to the inlet of the dryer 21.

[0057] Wherein, the condensed water outlet of the evaporation crystallization system 20 in the evaporation crystallization unit system is connected to the water inlet of the concentrated water circulation water tank 14;

[0058] The water outlet of the concentration chamber in the electrodialysis unit system is connected to the water inlet of the concentrated water circulation tank 14.

[0059] Example 2

[0060] The system constructed in Example 1 is used to utilize cellulose ether wastewater as a resource, comprising the following steps:

[0061] Step 1, pretreatment of cellulose ether wastewater

[0062] The cellulose ether wastewater is introduced into the pretreatment unit system, and is pretreated to remove oil and solid floating matter through a vortex flotation machine, a dissolved air flotation machine, a walnut shell filter, a high-density tank, and a filter in sequence, to ensure that the treated water quality meets the electrodialysis water inlet requirements; specifically, the characteristics of the water quality include but are not limited to suspended matter <1mg / L, free residual chlorine <0.5mg / L, and no oil;

[0063] Step 2: Preliminary separation of salts and alcohols in cellulose ether wastewater

[0064] The pretreated cellulose ether wastewater is introduced into the material circulation water tank in the electrodialysis unit system, and the initial water is injected into the concentrated water circulation water tank in the electrodialysis unit system at the same time. The cellulose ether wastewater passing through the material circulation water tank passes through the material circulation pump, the material heat exchanger and the material security filter in turn, and then enters the desalination chamber in the electrodialysis unit structure, wherein the initial water / make-up water is tap water / desalted water / purified water and other water of equivalent water quality, and the make-up water amount is about 50% of the inlet water amount;

[0065] The initial water passes through the concentrated water circulation tank, the concentrated water circulation pump, the concentrated water heat exchanger and the concentrated water security filter in sequence, and then enters the concentration chamber in the electrodialysis unit structure, so that the sodium ions and chloride ions in the cellulose ether wastewater pass through the anion membrane and the cation membrane in the electrodialysis unit structure respectively, and then enter the concentration chamber in the electrodialysis unit structure to obtain salt water (9% NaCl, no organic matter), while the alcohols in the cellulose ether wastewater continue to stay in the desalination chamber in the electrodialysis unit structure to obtain desalinated water rich in alcohols (4.3% alcohols, 1% NaCl);

[0066] Step 3: Separation of salt and alcohol in cellulose ether wastewater

[0067] The alcohol-rich desalinated water obtained in step 2 is returned to the material circulation water tank, and the salt water flows into the concentrate circulation water tank. The alcohol-rich desalinated water and the salt water are circulated in the electrodialysis unit structure through the material circulation pump and the concentrate circulation pump respectively, so that the sodium ions and chloride ions in the alcohol-rich desalinated water continuously enter the concentration chamber until it is detected that the salt content of the alcohol-rich desalinated water in the material circulation water tank is reduced to the first target concentration, and the salt content of the salt water in the concentrate circulation water tank is increased to the second target concentration, so as to complete the separation of salt and alcohol in the cellulose ether wastewater;

[0068] Step 4: Recovering Salt

[0069] The alcohol-rich desalinated water whose salt content is reduced to the first target concentration in step 3 enters the alcohol-rich desalinated water tank through the fresh water discharge pump to obtain alcohol-rich desalinated water; at the same time, the salt-containing water whose salt content reaches the second target concentration enters the concentrated brine tank in the evaporation crystallization unit through the concentrated water circulation tank and the concentrated water discharge pump, and after evaporation and crystallization treatment, it is dried to obtain NaCl crystal salt and desalted water. The desalted water can be passed into the concentrated water circulation tank, and through the concentrated water circulation pump, the concentrated water heat exchanger, and the concentrated water security filter, it flows into the concentration chamber of the electrodialysis unit structure as the water replenishment of the concentration chamber in the electrodialysis unit structure. The desalted water can also be reused as recycled water, and the sodium chloride is reused / sold after drying and packaging. Among them, the first target concentration is ≤2%, and the second target concentration is 5% to 15%.

[0070] The properties of the cellulose ether wastewater selected in this embodiment are as follows: pH 6-10, sodium chloride content of about 8% (mass fraction), alcohol organic matter content of about 3% (mass fraction), and influent containing ethers and suspended solids. After treatment according to the above steps, the results are shown in Table 1:

[0071] Table 1 Sampling test of fresh water discharge pump and concentrated water discharge pump after treatment by the method of the present invention

[0072]

[0073] After evaporation, crystallization and drying in the evaporation crystallization unit system, the NaCl crystal salt reaches the industrial salt level II and above standard (ie, the sodium chloride content ≥ 97.5%).

[0074] For the treatment of cellulose ether wastewater rich in high-concentration sodium chloride and alcohols, conventional electrodialysis equipment does not have an independent water inlet for the concentration chamber. After the wastewater is connected to the electrodialysis equipment, it enters the desalination chamber and the concentration chamber at the same time. The desalination chamber and the concentration chamber cannot be fed independently, so the raw water will also enter the concentrated water chamber. The obtained concentrated brine will contain a higher concentration of alcohols, and it is impossible to achieve a complete separation of sodium chloride and alcohols.

[0075] In summary, the electrodialysis process of the present invention adopts a specific composition (independent water inlets are respectively provided for the desalination chamber and the concentration chamber, the feed in the electrodialysis only enters the desalination chamber, not the concentration chamber, and the water in the concentration chamber is the electrodialysis circulating concentrated water (the initial water replenishment is water of equivalent water quality such as tap water / desalted water / purified water, and the evaporation crystallization system is used to condense water after normal operation)), as well as the coordinated operation effect of each unit system, to ensure that alcohols will not enter the salt-containing concentrated water, to ensure that sodium chloride and alcohols are completely separated after electrodialysis treatment, and to realize the resource utilization of cellulose ether wastewater.

[0076] The system influent pretreatment selected in this embodiment includes but is not limited to flotation, coagulation, clarification, filtration, etc., wherein filtration is not limited to walnut shell filtration, medium filtration, microfiltration, ultrafiltration, etc. Other pretreatment measures can be added according to the cellulose ether wastewater in different plant areas to make the wastewater meet the electrodialysis influent requirements. The electrodialysis unit system can choose to adopt a primary electrodialysis process method, and consider whether to add a secondary electrodialysis depending on the system's separation requirements for sodium chloride and alcohols and the separation of sodium chloride and alcohols by electrodialysis; similarly, three or more levels of electrodialysis can also be selected. The evaporation crystallization unit system can choose falling film evaporation + forced circulation crystallization combined with evaporation crystallization or directly adopt a forced circulation crystallization process, depending on the scale of the system. The evaporation crystallization system can select multi-effect evaporation or vapor compression cycle (MVR) technology according to conditions, and can choose to discharge a small amount of mother liquor or set up a mother liquor drying system to dry the mother liquor as needed, depending on site conditions and specific water quality conditions.

[0077] The present invention and its embodiments are described schematically above, and the description is not restrictive. The drawings show only one embodiment of the present invention, and the actual structure is not limited thereto. Therefore, if a person skilled in the art is inspired by it and designs a structural method and an embodiment similar to the technical solution without creativity without departing from the purpose of the invention, they shall all fall within the protection scope of the present invention.

Claims

1. A method for resource utilization of cellulose ether wastewater, characterized in that: The following steps are involved: Step 1, pretreatment of cellulose ether wastewater The cellulose ether wastewater is introduced into the pretreatment unit system, and is sequentially passed through the cavitation air flotation machine, dissolved air flotation machine, walnut shell filter, high-density tank, and filter for pretreatment to remove oil and solid floating matter, ensuring that the treated water quality meets the electrodialysis water inlet requirements; Step 2: Preliminary separation of salts and alcohols in cellulose ether wastewater The pretreated cellulose ether wastewater is introduced into the material circulation water tank in the electrodialysis unit system, and the initial water is injected into the concentrated water circulation water tank in the electrodialysis unit system. The cellulose ether wastewater passing through the material circulation water tank passes through the material circulation pump, the material heat exchanger and the material safety filter in sequence, and then enters the desalination chamber in the electrodialysis unit structure; The initial water passes through the concentrated water circulating water tank, the concentrated water circulating pump, the concentrated water heat exchanger and the concentrated water safety filter in turn, and then enters the concentration chamber in the electrodialysis unit structure, so that the sodium ions and chloride ions in the cellulose ether wastewater pass through the anion membrane and the cation membrane in the electrodialysis unit structure respectively, and then enter the concentration chamber in the electrodialysis unit structure to obtain salt water, while the alcohols in the cellulose ether wastewater continue to stay in the desalination chamber in the electrodialysis unit structure to obtain desalinated water rich in alcohols; Step 3: Separation of salt and alcohol in cellulose ether wastewater The alcohol-rich desalinated water obtained in step 2 is returned to the material circulation water tank, and the salt water flows into the concentrate circulation water tank. The alcohol-rich desalinated water and the salt water are circulated in the electrodialysis unit structure through the material circulation pump and the concentrate circulation pump respectively, so that the sodium ions and chloride ions in the alcohol-rich desalinated water continuously enter the concentration chamber until it is detected that the salt content of the alcohol-rich desalinated water in the material circulation water tank is reduced to the first target concentration, and the salt content of the salt water in the concentrate circulation water tank is increased to the second target concentration, so as to complete the separation of salt and alcohol in the cellulose ether wastewater; Step 4: Recovering Salt The alcohol-rich desalinated water whose salt content is reduced to the first target concentration in step 3 enters the alcohol-rich desalinated water tank through the fresh water discharge pump to obtain alcohol-rich desalinated water; at the same time, the salt water whose salt content reaches the second target concentration enters the brine tank in the evaporation crystallization unit from the brine circulating water tank through the brine discharge pump, and after evaporation and crystallization treatment, it is dried to obtain NaCl crystal salt and desalted water. The desalted water is passed into the brine circulating water tank, and flows into the concentrating chamber of the electrodialysis unit structure through the brine circulating pump, the brine heat exchanger, and the brine safety filter as water replenishment for the concentrating chamber in the electrodialysis unit structure. At the same time, the desalted water can also be reused as recycled water.

2. The method for resource utilization of cellulose ether wastewater according to claim 1, characterized in that: The characteristics of the treated water quality in step 1 include but are not limited to suspended solids <1 mg / L, free residual chlorine <0.5 mg / L, and no oil.

3. The method for resource utilization of cellulose ether wastewater according to claim 1, characterized in that: The water initially used in step 2 is fresh water.

4. The method for resource utilization of cellulose ether wastewater according to claim 1, characterized in that: In step 3, the first target concentration is ≤2%, and the second target concentration is 5% to 15%.

5. A system for treating the method for resource utilization of cellulose ether wastewater according to any one of claims 1 to 4, characterized in that: Including wastewater storage equipment, fresh water supply equipment, pretreatment unit system, electrodialysis unit system, evaporation crystallization unit system, concentrated water discharge pump, fresh water discharge pump, alcohol-rich desalination water tank, Wherein, the pretreatment unit system includes a cavitation air flotation machine, a dissolved air flotation machine, a walnut shell filter, a high-density tank, a filter, and a dehydrator; The electrodialysis unit system includes an electrodialysis unit structure, a material circulation structure, and a concentrated water circulation structure; The electrodialysis unit structure comprises at least one electrodialysis unit, wherein the electrodialysis unit is provided with a desalination chamber and a concentration chamber which are spaced apart from each other and have independent water inlets and outlets, and polar water chambers which are provided at both ends of the electrodialysis unit and have polar water inlets and outlets, and an anion exchange membrane and a cation exchange membrane which are spaced apart from each other between the desalination chamber and the concentration chamber; The material circulation structure includes a material circulation water tank, a material circulation pump, a material heat exchanger, and a material safety filter; The concentrated water circulation structure includes a concentrated water circulation water tank, a concentrated water circulation pump, a concentrated water heat exchanger, and a concentrated water safety filter; The evaporation crystallization unit system comprises a concentrated brine tank, an evaporation crystallization system, and a dryer; Specifically, the outlet of the wastewater storage equipment is connected to the cavitation air flotation machine, the dissolved air flotation machine, the walnut shell filter, the high-density tank, and the filter in the pretreatment unit system in sequence, the suspended matter discharge port of the cavitation air flotation machine, the suspended matter discharge port of the dissolved air flotation machine, and the mud discharge port of the high-density tank are all connected to the feed port of the dewatering machine, and the backwash wastewater of the walnut shell filter, the dewatering machine filtrate, and the backwash wastewater of the filter are all returned to the wastewater storage equipment for cyclic treatment; the solid impurities generated in the dewatering machine are discharged through the discharge port; The water outlet of the filter is connected to the water inlet of the material circulation water tank of the material circulation structure, the water outlet of the material circulation water tank is connected to the inlet of the material circulation pump, the outlet of the material circulation pump is connected to the inlet of the material heat exchanger, the outlet of the material heat exchanger is connected to the inlet of the material security filter, the outlet of the material security filter is connected to the water inlet of the desalination chamber of the electrodialysis unit, the water outlet of the desalination chamber of the electrodialysis unit is connected to the return inlet of the material circulation water tank, the discharge port of the material circulation water tank is connected to the inlet of the fresh water discharge pump, and the outlet of the fresh water discharge pump is connected to the inlet of the alcohol-rich desalination water tank; The fresh water supply equipment is connected to the water inlet of the concentrated water circulation tank in the concentrated water circulation structure, the water outlet of the concentrated water circulation tank is connected to the inlet of the concentrated water circulation pump, the outlet of the concentrated water circulation pump is connected to the inlet of the concentrated water heat exchanger, the outlet of the concentrated water heat exchanger is connected to the inlet of the concentrated water safety filter, the outlet of the concentrated water safety filter is connected to the water inlet of the concentration chamber of the electrodialysis unit, and the water outlet of the concentration chamber is connected to the return inlet of the concentrated water circulation tank; the discharge port of the concentrated water circulation tank is connected to the concentrated water discharge pump, the outlet of the concentrated water discharge pump is connected to the inlet of the concentrated brine tank, the outlet of the concentrated brine tank is connected to the inlet of the evaporation crystallization system, and the crystallized salt outlet of the evaporation crystallization system is connected to the inlet of the dryer.

6. The system according to claim 5, characterized in that The condensed water outlet of the evaporation crystallization system in the evaporation crystallization unit system is connected to the water inlet of the concentrated water circulation water tank.

7. The system according to claim 5, characterized in that The water outlet of the concentration chamber in the electrodialysis unit system is connected to the water inlet of the concentrated water circulation tank.

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