CN107265734B - Reverse osmosis concentrated seawater treatment system and method - Google Patents
Reverse osmosis concentrated seawater treatment system and method Download PDFInfo
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- C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
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- C02F9/00—Multistage treatment of water, waste water or sewage
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- C02F1/00—Treatment of water, waste water, or sewage
- C02F1/001—Processes for the treatment of water whereby the filtration technique is of importance
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- C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F1/00—Treatment of water, waste water, or sewage
- C02F1/02—Treatment of water, waste water, or sewage by heating
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- C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
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- C02F1/00—Treatment of water, waste water, or sewage
- C02F1/44—Treatment of water, waste water, or sewage by dialysis, osmosis or reverse osmosis
- C02F1/442—Treatment of water, waste water, or sewage by dialysis, osmosis or reverse osmosis by nanofiltration
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- C02F1/00—Treatment of water, waste water, or sewage
- C02F1/44—Treatment of water, waste water, or sewage by dialysis, osmosis or reverse osmosis
- C02F1/447—Treatment of water, waste water, or sewage by dialysis, osmosis or reverse osmosis by membrane distillation
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- C02F1/00—Treatment of water, waste water, or sewage
- C02F1/46—Treatment of water, waste water, or sewage by electrochemical methods
- C02F1/469—Treatment of water, waste water, or sewage by electrochemical methods by electrochemical separation, e.g. by electro-osmosis, electrodialysis, electrophoresis
- C02F1/4693—Treatment of water, waste water, or sewage by electrochemical methods by electrochemical separation, e.g. by electro-osmosis, electrodialysis, electrophoresis electrodialysis
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- C02F1/66—Treatment of water, waste water, or sewage by neutralisation; pH adjustment
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- C02F2103/00—Nature of the water, waste water, sewage or sludge to be treated
- C02F2103/08—Seawater, e.g. for desalination
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- Y02W10/00—Technologies for wastewater treatment
- Y02W10/30—Wastewater or sewage treatment systems using renewable energies
- Y02W10/37—Wastewater or sewage treatment systems using renewable energies using solar energy
Abstract
The invention discloses a reverse osmosis concentrated seawater treatment system and a method, wherein the method comprises the following steps: a reverse osmosis concentrated seawater treatment system is used; the reverse osmosis concentrated seawater is sequentially filtered by a security filter, the pH value is adjusted, the pressure is increased, and then the reverse osmosis concentrated seawater passes through a nanofiltration membrane element, a resin softener and a heating box to obtain hot feed liquid, the hot feed liquid passes through a membrane distillation assembly to obtain water and concentrated feed liquid, and the concentrated feed liquid is treated by a bipolar membrane electrodialysis process to obtain acid liquid and alkali liquid; the invention has high softening efficiency, low membrane distillation operation temperature, large evaporation area, high effluent quality and internal recovery of latent heat of steam; because the membrane distillation is slightly influenced by concentration, the deep concentration is carried out to obtain concentrated solution which is beneficial to the efficient operation of the bipolar membrane electrodialysis process, the value of the obtained acid-base product is higher than that of solid salt, and compared with the prior art, the method is energy-saving, and the production process is safer and more environment-friendly. The acid-base prepared by the method can be used for nanofiltration scale inhibition and resin regeneration, so that the amount of extra chemical agents added in the whole system is reduced, and the cost is reduced.
Description
Technical Field
The invention relates to a water treatment technology, in particular to a reverse osmosis concentrated seawater treatment system and method.
Background
Seawater desalination has become an important way for opening up water sources, the recovery rate of seawater desalination is generally only 40% -50%, concentrated seawater is generally directly discharged to the sea without treatment at present, and the discharge of concentrated seawater causes huge waste of resources and pollution to the marine environment, so how to treat concentrated seawater is a problem which must be faced by sustainable development of the seawater desalination industry.
Patent nos. 201110411270.8, 201110069347.8 and 201210150064.0 disclose methods for treating concentrated seawater by reverse osmosis, such as removal of calcium and magnesium ions or extraction of calcium, calcium and magnesium products by chemical addition, ion membrane, ion exchange resin, etc. as a pre-treatment, and finally concentration for salt production by evaporative crystallization. The pretreatment of the concentrated seawater in the methods needs to add a large amount of chemical agents, and the pretreated concentrated seawater is directly evaporated and crystallized, so that a large system volume and a high operation temperature are needed, and the system investment, the occupied area and the operation cost are high.
Disclosure of Invention
The invention aims to overcome the defects of the prior art, and provides a reverse osmosis concentrated seawater treatment system and method by combining the advantages of deep concentration of membrane distillation under a low-temperature condition and efficient preparation of acid and alkali under a high-salinity condition by bipolar membrane electrodialysis.
The technical scheme of the invention is summarized as follows:
a reverse osmosis concentrated seawater treatment system comprises a cartridge filter 1, wherein the cartridge filter 1 is sequentially connected with a high-pressure pump 2, a nanofiltration membrane element 3, a resin softener 4, a heating box 5, a membrane distillation circulating pump 6 and a hot feed liquid inlet 7-1 of a membrane distillation assembly 7 through pipelines; a hot feed liquid outlet 7-3 of the membrane distillation assembly 7 is connected with a cooler 8 through a pipeline and then is respectively connected with a cold feed liquid inlet 7-2 of the membrane distillation assembly 7 and a raw material liquid tank 10 through pipelines; the raw material liquid tank 10 is connected with the negative electrode of the bipolar membrane electrodialysis membrane stack 18 through a pipeline, and the raw material liquid tank 10 is sequentially connected with the raw material liquid circulating pump 14 and the positive electrode of the bipolar membrane electrodialysis membrane stack 18 through pipelines; a cold feed liquid outlet 7-4 of the membrane distillation assembly 7 is connected with the heating box 5 through a pipeline; a water production outlet 7-5 of the membrane distillation component 7 is connected with a water production tank 9 through a pipeline; a hollow fiber microporous hydrophobic membrane 7-6 and a hollow fiber condenser pipe 7-7 are arranged in the membrane distillation component 7, and two ends of the hollow fiber microporous hydrophobic membrane are respectively connected with a hot feed liquid inlet 7-1 and a hot feed liquid outlet 7-3; two ends of the hollow fiber condenser tube 7-7 are respectively connected with a cold feed liquid inlet 7-2 and a cold feed liquid outlet 7-4; the acid tank 11 is connected with the negative electrode of the bipolar membrane electrodialysis membrane stack 18 through a pipeline, and the acid tank 11 is connected with the acid circulating pump 15 through a pipeline; the acid circulating pump 15 is respectively connected with the anode of the bipolar membrane electrodialysis membrane stack 18 and the acid storage tank 21 through pipelines; the alkali tank 12 is connected with the negative electrode of the bipolar membrane electrodialysis membrane stack 18 through a pipeline, the alkali tank 12 is connected with the alkali circulating pump 16 through a pipeline, and the alkali circulating pump 16 is respectively connected with the positive electrode of the bipolar membrane electrodialysis membrane stack 18 and the alkali storage tank 20 through pipelines; the polar water tank 13 is connected with the negative electrode of the bipolar membrane electrodialysis membrane stack 18 through a pipeline, and the polar water tank 13 is sequentially connected with the polar water circulating pump 17 and the positive electrode of the bipolar membrane electrodialysis membrane stack 18 through pipelines; the alkali storage tank 20 is sequentially connected with an alkali adding pump 23 and the resin softener 4 through pipelines; the acid storage tank 21 is connected with the acid adding pump 22 through a pipeline; the acid adding pump 22 is respectively connected with the inlet of the high-pressure pump 2 and the resin softener 4 through pipelines; two ends of the stabilized voltage power supply 19 are respectively and electrically connected with the anode of the bipolar membrane electrodialysis membrane stack 18 and the cathode of the bipolar membrane electrodialysis membrane stack 18.
The nanofiltration membrane element is a high-selectivity nanofiltration membrane element, and the model of the high-selectivity nanofiltration membrane element is XCN, HYDRApro or DK.
The resin in the resin softener is macroporous weak acid cation resin resistant to high TDS, and the model of the macroporous weak acid cation resin resistant to high TDS is IRC83 or IRC76 CRF.
The positive and negative poles of the regulated power supply 19 are switched with each other.
A reverse osmosis concentrated seawater treatment method comprises the following steps:
(1) use of a reverse osmosis concentrated seawater treatment system according to any one of claims 1 to 4;
(2) introducing reverse osmosis concentrated seawater into a cartridge filter 1 for filtering to remove granular impurities to obtain pretreated produced water;
(3) adjusting the pH of the pretreated produced water to 2-4 by using acid fed by an acid feeding pump 22, pressurizing to 1.5-2.5 MPa by a high-pressure pump 2, introducing into a nanofiltration membrane element 3 for primary softening treatment, and removing 70-90% of hardness ions and organic matters with molecular weight of more than 200 to obtain nanofiltration soft water; the nanofiltration soft water is introduced into a resin softener 4 for deep softening treatment to remove more than 99% of hardness ions to obtain resin soft water, and the resin soft water enters a heating box and is heated to 60-90 ℃ to obtain hot feed liquid; when the resin of the resin softener is saturated, starting an acid adding pump 22 and an alkali adding pump 23 in sequence to regenerate the resin;
(4) the hot feed liquid is conveyed to a hollow fiber microporous hydrophobic membrane 7-6 of a membrane distillation assembly through a membrane distillation circulating pump 6 to generate steam, the hot feed liquid after generating the steam is cooled to 20-30 ℃ through a cooler 8, the cooled feed liquid is divided into two strands, one strand is used as cold feed liquid and returns to a hollow fiber condenser pipe 7-7 of the membrane distillation assembly to recover steam latent heat, fresh water is generated at the same time, and the fresh water is introduced into a water production tank 9 to be collected; the cold feed liquid after recovering the latent heat of the steam is conveyed to a heating box 5 for secondary heating, and the circulation is carried out; when the feed liquid in the heating box is concentrated to the mass concentration of 15-25%, the other feed liquid is conveyed to a raw material liquid tank 10 to obtain concentrated feed liquid;
(5) starting a raw material liquid circulating pump 14, an acid circulating pump 15, an alkali circulating pump 16 and a polar water circulating pump 17 in sequence, respectively conveying the concentrated liquid, the acid liquid, the alkali liquid and the polar water to the anode of the bipolar membrane electrodialysis membrane stack, starting a voltage stabilizing power supply 19 after the flow is stable, and adjusting the current density to be 20mA/cm of the operation current density of the bipolar membrane electrodialysis membrane stack2～50mA/cm2Generating acid and alkali by the bipolar membrane electrodialysis membrane stack;
when the acid liquor mass concentration of the acid tank reaches 5-12%, the acid liquor is conveyed to an acid storage tank 21 through an acid circulating pump 15; when the mass concentration of the alkali liquor in the alkali tank reaches 5% -12%, the alkali liquor is conveyed to an acid storage tank 20 through an alkali circulating pump 16.
The cooling liquid of the cooler 8 is concentrated water of a nanofiltration membrane element, original reverse osmosis concentrated seawater or seawater.
The initial acid liquid in the acid tank 11 is a pre-prepared hydrochloric acid aqueous solution with the mass concentration of 0.2% -0.5%, the initial alkali liquid in the alkali tank 12 is a pre-prepared sodium hydroxide aqueous solution with the mass concentration of 0.2% -0.5%, and the polar water in the polar water tank is a pre-prepared sodium sulfate aqueous solution or potassium sulfate aqueous solution with the mass concentration of 1% -3%.
The invention is essentially different from the traditional reverse osmosis concentrated seawater treatment method, improves the reverse osmosis concentrated seawater treatment efficiency, and also has the following advantages:
1. the coupled softening process of nanofiltration softening and resin softening is adopted, so that the advantages of two softening technologies are fully exerted, and the softening efficiency is higher.
2. The membrane distillation process has low operation temperature, large evaporation area and high effluent quality, and the latent heat of steam can be internally recycled; in addition, because the membrane distillation process is less influenced by concentration, deep concentration can be carried out to obtain concentrated solution which is beneficial to the efficient operation of the bipolar membrane electrodialysis process.
3. The bipolar membrane electrodialysis process avoids high energy consumption in the traditional evaporation and crystallization processes, the value of the obtained acid-base product is higher than that of a solid salt product, and compared with the traditional salt electrolysis method and diaphragm electrolysis method for preparing acid-base, the bipolar membrane electrodialysis process is more energy-saving, and the production process is safer and more environment-friendly.
4. The acid and alkali prepared by the bipolar membrane electrodialysis process can be used for nanofiltration scale inhibition and resin regeneration, so that the amount of extra chemical agents added in the whole system is reduced, and the operation cost is obviously reduced.
Drawings
FIG. 1 is a schematic view of a reverse osmosis concentrated seawater treatment system according to the present invention;
1. a cartridge filter; 2. a high pressure pump; 3. a nanofiltration membrane element; 4. a resin softener; 5. a heating box; 6. a membrane distillation circulating pump; 7. a membrane distillation assembly; 7-1 hot feed liquid inlet; 7-2, a cold feed liquid inlet; 7-3 hot feed liquid outlet; a cold feed liquid outlet 7-4; 7-5 of a water production outlet; 7-6 parts of hollow fiber microporous hydrophobic membrane; 7-7 parts of hollow fiber condenser pipe; 8. a cooler; 9. a water producing tank; 10. a raw material liquid tank; 11, an acid tank; 12, an alkali tank; 13. a polar water tank; 14. a raw material liquid circulating pump; 15. an acid circulation pump; 16. an alkali circulation tank; 17. an extremely water circulating pump; 18 bipolar membrane electrodialysis membrane stack; 19. a regulated power supply; 20. an alkali storage tank; 21. an acid storage tank; 22. an acid adding pump; 23. alkali adding pump
Detailed Description
The system of the present invention is further described below with reference to the accompanying drawings.
A reverse osmosis concentrated seawater treatment system (see figure 1) comprises a cartridge filter 1, wherein the cartridge filter 1 is sequentially connected with a high-pressure pump 2, a nanofiltration membrane element 3, a resin softener 4, a heating box 5, a membrane distillation circulating pump 6 and a hot feed liquid inlet 7-1 of a membrane distillation assembly 7 through pipelines; a hot feed liquid outlet 7-3 of the membrane distillation assembly 7 is connected with a cooler 8 through a pipeline and then is respectively connected with a cold feed liquid inlet 7-2 of the membrane distillation assembly 7 and a raw material liquid tank 10 through pipelines; the raw material liquid tank 10 is connected with the negative electrode of the bipolar membrane electrodialysis membrane stack 18 through a pipeline, and the raw material liquid tank 10 is sequentially connected with the raw material liquid circulating pump 14 and the positive electrode of the bipolar membrane electrodialysis membrane stack 18 through pipelines; a cold feed liquid outlet 7-4 of the membrane distillation assembly 7 is connected with the heating box 5 through a pipeline; a water production outlet 7-5 of the membrane distillation component 7 is connected with a water production tank 9 through a pipeline; a hollow fiber microporous hydrophobic membrane 7-6 and a hollow fiber condenser pipe 7-7 are arranged in the membrane distillation component 7, the hollow fiber microporous hydrophobic membrane and the hollow fiber condenser pipe are made of polytetrafluoroethylene with the quantity ratio of 1:4, and two ends of the hollow fiber microporous hydrophobic membrane are respectively connected with a hot feed liquid inlet 7-1 and a hot feed liquid outlet 7-3; two ends of the hollow fiber condenser tube 7-7 are respectively connected with a cold feed liquid inlet 7-2 and a cold feed liquid outlet 7-4; the acid tank 11 is connected with the negative electrode of the bipolar membrane electrodialysis membrane stack 18 through a pipeline, and the acid tank 11 is connected with the acid circulating pump 15 through a pipeline; the acid circulating pump 15 is respectively connected with the anode of the bipolar membrane electrodialysis membrane stack 18 and the acid storage tank 21 through pipelines; the alkali tank 12 is connected with the negative electrode of the bipolar membrane electrodialysis membrane stack 18 through a pipeline, the alkali tank 12 is connected with the alkali circulating pump 16 through a pipeline, and the alkali circulating pump 16 is respectively connected with the positive electrode of the bipolar membrane electrodialysis membrane stack 18 and the alkali storage tank 20 through pipelines; the polar water tank 13 is connected with the negative electrode of the bipolar membrane electrodialysis membrane stack 18 through a pipeline, and the polar water tank 13 is sequentially connected with the polar water circulating pump 17 and the positive electrode of the bipolar membrane electrodialysis membrane stack 18 through pipelines; the alkali storage tank 20 is sequentially connected with an alkali adding pump 23 and the resin softener 4 through pipelines; the acid storage tank 21 is connected with the acid adding pump 22 through a pipeline; the acid adding pump 22 is respectively connected with the inlet of the high-pressure pump 2 and the resin softener 4 through pipelines; two ends of the stabilized voltage power supply 19 are respectively and electrically connected with the anode of the bipolar membrane electrodialysis membrane stack 18 and the cathode of the bipolar membrane electrodialysis membrane stack 18.
The nanofiltration membrane element is preferably a high-selectivity nanofiltration membrane element, such as: XCN, optionally: HYDRApro or DK.
XCN (Dow chemical), HYDRApro (Heidenery), DK (general electric) may also be selected from other nanofiltration membrane elements having functions similar to those of the above-mentioned high-selectivity nanofiltration membrane element.
The resin in the resin softener is macroporous weak acid cation resin resistant to high TDS, and the model of the macroporous weak acid cation resin resistant to high TDS is IRC83 or IRC76 CRF.
IRC83 (dow chemical company) or IRC76CRF (dow chemical company).
Macroporous weak acid cation resin with the property similar to the model can be selected.
The positive and negative poles of the regulated power supply 19 are switched.
The process of the present invention is further illustrated by the following examples.
Example 1
A reverse osmosis concentrated seawater treatment method comprises the following steps:
(1) using the reverse osmosis concentrated seawater treatment system;
(2) subjecting reverse osmosis concentrated seawater (salt content of 45887 mg/L, pH of 8.0, wherein Ca is contained in the seawater2+521 Mg/L, Mg2+1620 mg/L) is introduced into a cartridge filter 1 (a filter element with the filtering precision of 5 mu m is adopted) for filtering, and the particulate impurities are removed to obtain the pre-treatment produced water;
(3) adjusting the pH of the pretreated produced water to 4 with acid fed by an acid feeding pump 22, pressurizing to 1.5MPa by a high-pressure pump 2, introducing a nanofiltration membrane element 3 (adopting XCN type) for primary softening treatment, removing 70-90% of hardness ions and organic matters with molecular weight of more than 200, and obtaining nanofiltration soft water (the salt content of the nanofiltration soft water is 38100 mg/L, wherein Ca2+196 Mg/L, Mg2+210 mg/L), introducing the nanofiltration soft water into a resin softener 4 (adopting IRC83 type macroporous weak acid cation resin) for deep softening treatment, removing over 99% of hardness ions, and obtaining resin soft water (the salt content of the resin soft water is 38450 mg/L, wherein Ca is in the resin soft water2+2.2 Mg/L, Mg2+1.6 mg/L), feeding resin soft water into a heating box, heating to 90 ℃ to obtain hot feed liquid, and starting an acid adding pump 22 and an alkali adding pump 23 in sequence to regenerate the resin after the resin of the resin softener 4 is saturated;
(4) the hot feed liquid is conveyed to a hollow fiber microporous hydrophobic membrane 7-6 of a membrane distillation assembly through a membrane distillation circulating pump 6 to generate steam, the hot feed liquid after generating the steam is cooled to 30 ℃ through a cooler 8 (the cooling liquid adopts original reverse osmosis concentrated seawater), the cooled feed liquid is divided into two strands, one strand of the cooled feed liquid is returned to a hollow fiber condenser pipe 7-7 of the membrane distillation assembly as cold feed liquid to recover steam latent heat, fresh water is generated (the salt content of the fresh water is 9.3 mg/L and meets the national drinking water standard), the fresh water is introduced into a water production tank 9 to be collected, the cold feed liquid after recovering the steam latent heat is conveyed to a heating box 5 to be heated for the second time, the circulation is carried out, when the feed liquid of the heating box is concentrated to the mass concentration of 15%, the other strand of the feed liquid is conveyed to a;
(5) starting a raw material liquid circulating pump 14, an acid circulating pump 15, an alkali circulating pump 16 and a polar water circulating pump 17 in sequence, and respectively conveying the concentrated liquid, the acid liquid, the alkali liquid and the polar water to the anode of a bipolar membrane electrodialysis membrane stack (the bipolar membrane is a BPM-I type bipolar membrane, the cathode membrane is a JAM-II type homogeneous anion exchange membrane, and the anode membrane is a JCM-II type homogeneous cation exchange membrane); after the flow is stable, starting a voltage-stabilized power supply 19, and adjusting the current density to 20mA/cm2Generating acid and alkali by the bipolar membrane electrodialysis membrane stack;
when the acid liquor mass concentration in the acid tank reaches 5%, the acid liquor is conveyed to an acid storage tank 21 through an acid circulating pump 15; when the mass concentration of the alkali liquor in the alkali tank reaches 5%, the alkali liquor is conveyed to an acid storage tank 20 through an alkali circulating pump 16;
the cooling liquid of the cooler 8 is concentrated water of a nanofiltration membrane element, original reverse osmosis concentrated seawater or seawater;
the initial acid solution in the acid tank 11 is a pre-prepared hydrochloric acid aqueous solution with the mass concentration of 0.2%, the initial alkali solution in the alkali tank 12 is a pre-prepared sodium hydroxide aqueous solution with the mass concentration of 0.2%, the polar water in the polar water tank is a pre-prepared sodium sulfate aqueous solution with the mass concentration of 1%, and the finally prepared acid solution and alkali solution have the mass concentrations of 5% and 5% respectively.
Example 2
A reverse osmosis concentrated seawater treatment method comprises the following steps:
(1) using the reverse osmosis concentrated seawater treatment system;
(2) subjecting reverse osmosis concentrated seawater (salt content of 47620 mg/L, pH 8.0, wherein Ca is2+Is 572 Mg/L, Mg2+1690 mg/L) is introduced into a cartridge filter 1 (a filter element with the filtering precision of 5 mu m is adopted) for filtering, and the granular impurities are removed to obtain the pre-treatment produced water;
(3) adjusting pH of the pretreated produced water to 2 with acid fed from acid feeding pump 22, pressurizing to 2.5MPa with high pressure pump 2, and introducing nanofiltration membrane element 3 (adopting HYDRApro model or DK model) for initial treatmentSoftening, removing 70-90% of hardness ions and organic matters with molecular weight above 200 to obtain nanofiltration soft water (containing salt content of 39120 mg/L, wherein Ca)2+285 Mg/L, Mg2+249 mg/L), introducing the nanofiltration soft water into a resin softener 4 (adopting IRC76CRF macroporous weak acid cation resin), deeply softening, removing over 99% of hardness ions, and obtaining resin soft water (the resin soft water has a salt content of 40320 mg/L, wherein Ca is contained in the resin soft water2+3.0 Mg/L, Mg2+1.4 mg/L), feeding resin soft water into a heating box, heating to 60 ℃ to obtain hot liquid, and starting an acid adding pump 22 and an alkali adding pump 23 in sequence to regenerate the resin after the resin of the resin softener 4 is saturated;
(4) the hot feed liquid is conveyed to a hollow fiber microporous hydrophobic membrane 7-6 of a membrane distillation assembly through a membrane distillation circulating pump 6 to generate steam, the hot feed liquid after generating the steam is cooled to 20 ℃ through a cooler 8 (the cooling liquid adopts seawater or concentrated water of a nanofiltration membrane element), the cooled feed liquid is divided into two strands, one strand of the cooled feed liquid is returned to a hollow fiber condenser pipe 7-7 of the membrane distillation assembly as cold feed liquid to recover steam latent heat, fresh water is generated (the salt content of the fresh water is 11.6 mg/L and meets the national drinking water standard), the fresh water is introduced into a water production tank 9 to be collected, the cold feed liquid after recovering the steam latent heat is conveyed to a heating box 5 to be heated for the second time, and the circulation is carried out, when the feed liquid of the heating box is concentrated to 25% in mass concentration, the other strand of the feed liquid is conveyed to a feed;
(5) starting a raw material liquid circulating pump 14, an acid circulating pump 15, an alkali circulating pump 16 and a polar water circulating pump 17 in sequence, and respectively conveying the concentrated liquid, the acid liquid, the alkali liquid and the polar water to the anode of a bipolar membrane electrodialysis membrane stack (the bipolar membrane is a BPM-I type bipolar membrane, the cathode membrane is a JAM-II type homogeneous anion exchange membrane, and the anode membrane is a JCM-II type homogeneous cation exchange membrane); after the flow is stable, starting a voltage-stabilized power supply 19, and adjusting the current density to 50mA/cm2Generating acid and alkali by the bipolar membrane electrodialysis membrane stack;
when the acid liquor mass concentration in the acid tank reaches 12%, the acid liquor is conveyed to an acid storage tank 21 through an acid circulating pump 15; when the mass concentration of the alkali liquor in the alkali tank reaches 12%, the alkali liquor is conveyed to an acid storage tank 20 through an alkali circulating pump 16;
the cooling liquid of the cooler 8 is concentrated water of a nanofiltration membrane element, original reverse osmosis concentrated seawater or seawater;
the initial acid solution in the acid tank 11 is a pre-prepared hydrochloric acid aqueous solution with the mass concentration of 0.5%, the initial alkali solution in the alkali tank 12 is a pre-prepared sodium hydroxide aqueous solution with the mass concentration of 0.5%, the polar water in the polar water tank is a pre-prepared potassium sulfate aqueous solution with the mass concentration of 3%, and the finally prepared acid solution and alkali solution have the mass concentrations of 12% and 12% respectively.
As can be seen from the above test results, the method of the present invention can be used for treating the reverse osmosis concentrated seawater to obtain potable fresh water and industrially usable acid and alkali.
The heating box can use waste heat, geothermal energy or low-grade heat sources such as solar energy in industrial production for heating.
The nanofiltration concentrated water can be further treated in various ways, calcium and magnesium products can be extracted by a double-alkali method or directly subjected to alkali precipitation and then returned to security filtration pretreatment, so that zero emission of the whole process is realized.
Adopting sodium sulfate, potassium sulfate and other solutions as polar water, and electrolyzing to generate H+And OH-And the phase neutralization avoids the generation of harmful gas.
The invention uses the coupling process of nanofiltration softening and resin softening, fully exerts the advantages of nanofiltration softening in the high-hardness field and the advantages of resin softening in the low-hardness field, has lower hardness of the produced water after the resin softening, and is beneficial to deep concentration by a membrane distillation process.
Because the membrane distillation theoretically realizes 100 percent interception of ions, the produced water has better quality and can be directly recycled. In addition, because the membrane distillation is less influenced by concentration, the deep concentration of the reverse osmosis concentrated seawater can be carried out, and the obtained concentrated feed liquid is beneficial to further reducing the system volume of the bipolar membrane electrodialysis and improving the current efficiency of the bipolar membrane electrodialysis, so that the treatment efficiency of the reverse osmosis concentrated water treatment method is high.
Claims (7)
1. A reverse osmosis concentrated seawater treatment system comprises a cartridge filter (1), and is characterized in that the cartridge filter (1) is sequentially connected with a high-pressure pump (2), a nanofiltration membrane element (3), a resin softener (4), a heating box (5), a membrane distillation circulating pump (6) and a hot feed liquid inlet (7-1) of a membrane distillation assembly (7) through pipelines; a hot feed liquid outlet (7-3) of the membrane distillation assembly (7) is connected with a cooler (8) through a pipeline and then is respectively connected with a cold feed liquid inlet (7-2) of the membrane distillation assembly (7) and a raw material liquid tank (10) through a pipeline; the raw material liquid tank (10) is connected with the negative electrode of the bipolar membrane electrodialysis membrane stack (18) through a pipeline, and the raw material liquid tank (10) is sequentially connected with the raw material liquid circulating pump (14) and the positive electrode of the bipolar membrane electrodialysis membrane stack (18) through pipelines; a cold feed liquid outlet (7-4) of the membrane distillation component (7) is connected with the heating box (5) through a pipeline; a water production outlet (7-5) of the membrane distillation component (7) is connected with a water production tank (9) through a pipeline; a hollow fiber microporous hydrophobic membrane (7-6) and a hollow fiber condenser pipe (7-7) are arranged in the membrane distillation component (7), and two ends of the hollow fiber microporous hydrophobic membrane are respectively connected with a hot feed liquid inlet (7-1) and a hot feed liquid outlet (7-3); two ends of the hollow fiber condenser pipe (7-7) are respectively connected with a cold feed liquid inlet (7-2) and a cold feed liquid outlet (7-4); the acid tank (11) is connected with the negative electrode of the bipolar membrane electrodialysis membrane stack (18) through a pipeline, and the acid tank (11) is connected with the acid circulating pump (15) through a pipeline; the acid circulating pump (15) is respectively connected with the anode of the bipolar membrane electrodialysis membrane stack (18) and the acid storage tank (21) through pipelines; the alkali tank (12) is connected with the negative electrode of the bipolar membrane electrodialysis membrane stack (18) through a pipeline, the alkali tank (12) is connected with the alkali circulating pump (16) through a pipeline, and the alkali circulating pump (16) is respectively connected with the positive electrode of the bipolar membrane electrodialysis membrane stack (18) and the alkali storage tank (20) through pipelines; the polar water tank (13) is connected with the negative electrode of the bipolar membrane electrodialysis membrane stack (18) through a pipeline, and the polar water tank (13) is sequentially connected with the polar water circulating pump (17) and the positive electrode of the bipolar membrane electrodialysis membrane stack (18) through pipelines; the alkali storage tank (20) is sequentially connected with an alkali feeding pump (23) and the resin softener (4) through pipelines; the acid storage tank (21) is connected with the acid adding pump (22) through a pipeline; the acid adding pump (22) is respectively connected with the inlet of the high-pressure pump (2) and the resin softener (4) through pipelines; two ends of the stabilized voltage power supply (19) are respectively and electrically connected with the anode of the bipolar membrane electrodialysis membrane stack (18) and the cathode of the bipolar membrane electrodialysis membrane stack (18).
2. The system of claim 1, wherein the nanofiltration membrane element is a high selectivity nanofiltration membrane element having a model of HYDRApro or DK.
3. The system of claim 1, wherein the resin in the resin softener is a high TDS tolerant large pore weak acid cation resin of type IRC83 or IRC76 CRF.
4. The system of claim 1, wherein the positive and negative poles of the regulated power supply (19) are switched with each other.
5. A reverse osmosis concentrated seawater treatment method is characterized by comprising the following steps:
(1) use of a reverse osmosis concentrated seawater treatment system according to any one of claims 1 to 4;
(2) introducing reverse osmosis concentrated seawater into a cartridge filter (1) for filtering to remove granular impurities to obtain pretreated produced water;
(3) adjusting the pH of the pretreated produced water to 2-4 by using acid added by an acid adding pump (22), then pressurizing to 1.5-2.5 MPa by using a high-pressure pump (2), introducing into a nanofiltration membrane element (3) for primary softening treatment, and removing 70-90% of hardness ions and organic matters with molecular weight of more than 200 to obtain nanofiltration soft water; the nanofiltration soft water is introduced into a resin softener (4) for deep softening treatment to remove more than 99% of hardness ions to obtain resin soft water, and the resin soft water enters a heating box and is heated to 60-90 ℃ to obtain hot feed liquid; when the resin of the resin softener is saturated, an acid adding pump (22) and an alkali adding pump (23) are started in sequence to regenerate the resin;
(4) the hot feed liquid is conveyed to a hollow fiber microporous hydrophobic membrane (7-6) of a membrane distillation assembly through a membrane distillation circulating pump (6) to generate steam, the hot feed liquid after generating the steam is cooled to 20-30 ℃ through a cooler (8), the cooled feed liquid is divided into two strands, one strand is used as cold feed liquid and returns to a hollow fiber condenser pipe (7-7) of the membrane distillation assembly to recover steam latent heat, fresh water is generated at the same time, and the fresh water is introduced into a water production tank (9) to be collected; the cold feed liquid after recovering the latent heat of the steam is conveyed to a heating box (5) for secondary heating, and the circulation is carried out; when the feed liquid in the heating box is concentrated to the mass concentration of 15-25%, the other feed liquid is conveyed to a raw material liquid tank (10) to obtain concentrated feed liquid;
(5) starting a raw material liquid circulating pump (14), an acid circulating pump (15), an alkali circulating pump (16) and a polar water circulating pump (17) in sequence, respectively conveying the concentrated liquid, the acid liquid, the alkali liquid and the polar water to the anode of the bipolar membrane electrodialysis membrane stack, starting a voltage stabilizing power supply (19) after the flow is stable, and adjusting the operation current density of the bipolar membrane electrodialysis membrane stack to be 20mA/cm2～50mA/cm2Generating acid and alkali by the bipolar membrane electrodialysis membrane stack;
when the acid liquor mass concentration of the acid tank reaches 5-12%, the acid liquor is conveyed to an acid storage tank (21) through an acid circulating pump (15); when the mass concentration of the alkali liquor in the alkali tank reaches 5-12%, the alkali liquor is conveyed to an acid storage tank (20) through an alkali circulating pump (16).
6. The method according to claim 5, characterized in that the cooling liquid of the cooler (8) is concentrate of a nanofiltration membrane element, raw reverse osmosis concentrate or sea water.
7. The method according to claim 5, characterized in that the initial acid solution in the acid tank (11) is a pre-prepared hydrochloric acid aqueous solution with a mass concentration of 0.2-0.5%, the initial alkali solution in the alkali tank (12) is a pre-prepared sodium hydroxide aqueous solution with a mass concentration of 0.2-0.5%, and the polar water in the polar water tank is a pre-prepared sodium sulfate aqueous solution or potassium sulfate aqueous solution with a mass concentration of 1-3%.
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| CN111362480A (en) * | 2020-04-03 | 2020-07-03 | 中煤能源研究院有限责任公司 | Method for treating reverse osmosis strong brine |
| CN112777866A (en) * | 2021-01-06 | 2021-05-11 | 杭州上拓环境科技股份有限公司 | Seawater zero-emission treatment system and treatment method |
| US11502322B1 (en) | 2022-05-09 | 2022-11-15 | Rahul S Nana | Reverse electrodialysis cell with heat pump |
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