CN111362480A - Method for treating reverse osmosis strong brine - Google Patents
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- C02F1/4695—Treatment of water, waste water, or sewage by electrochemical methods by electrochemical separation, e.g. by electro-osmosis, electrodialysis, electrophoresis electrodialysis electrodeionisation
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Abstract
A method for treating reverse osmosis strong brine comprises removing hardness of reverse osmosis strong brine to obtain softened strong brine; respectively introducing softened concentrated brine and reverse osmosis produced water into a bipolar membrane electrodialyzer, starting the bipolar membrane electrodialyzer to prepare acid and alkali, preparing acid and alkali from the softened concentrated brine, obtaining acid liquor and alkali liquor, and simultaneously obtaining a desalination solution. The method of the invention has simple process for treating the reverse osmosis strong brine. After the treatment by the method, the salt in the reverse osmosis strong brine is completely recycled, and an evaporation crystallization process is not adopted, so that the process investment cost and the operation energy consumption are reduced. And because the bipolar membrane electrodialysis converts the concentrated brine into acid and alkali, the generated acid and alkali can be reused in related industrial items such as water treatment and the like, thereby achieving two purposes at one stroke and reducing the operation cost.
Description
Technical Field
The invention belongs to the field of coal mine water and coal chemical wastewater treatment technology and comprehensive resource utilization, and particularly relates to a method for treating reverse osmosis strong brine.
Background
The main coal mines in China are mostly located in temperate zone semiarid continental climate areas in northern China, and natural conditions are fragile, drought and rain are few, and water resources are seriously deficient. Meanwhile, as various mines and surrounding coal chemical engineering projects are operated and put into operation successively, a large amount of production water is needed, the amount of industrial water approved by local governments is limited and high in price, and high-quality surface water is used as an industrial water source, so that the exhaustion of local water resources and the deterioration of ecological environment are inevitably accelerated. Therefore, the water discharged from the coal mine is treated in a centralized way and is reused for coal mine production water and surrounding coal chemical engineering projects, and the aim of sustainable development of related regions is favorably fulfilled. Meanwhile, the method responds to the requirements of national environmental protection departments, and realizes the zero emission of mine water treatment.
However, the mineralization of the drainage water in many coal mines is high, and the soluble salt contained in the drainage water in the mines needs to be treated, so that the requirement of the production water of the mine and peripheral enterprises can be met. At present, the established and operated high-salinity mine water treatment engineering process in Monshan area basically comprises the following steps: the first-stage reverse osmosis desalination, the second-stage reverse osmosis desalination and the evaporative crystallization salt separation enable the recovery rate of produced water to reach more than 95%, and finally the crystallized salt is sold as industrial salt, so that the full resource utilization of the mine water with high mineralization is realized.
The existing coal chemical industry wastewater treatment process generally comprises pretreatment, membrane concentration filtration and evaporation concentration crystallization treatment, the crystallized mother liquor and crystal particles are subjected to solid-liquid separation, the mother liquor returns to a stock solution pool or continues to be evaporated and crystallized, the crystals are thickened, dried and packaged, and finally, product water and crystallized salt meeting industrial salt standards are obtained.
A common problem in mine water zero-discharge technology and coal chemical treatment technology is the treatment of reverse osmosis concentrated brine. The existing evaporative crystallization process has the problems of high energy consumption, long process chain, unstable operation, low purity of crystallized salt and large amount of miscellaneous salt.
Aiming at the problems existing in the prior reverse osmosis strong brine treatment evaporation crystallization process. Chinese patent CN 106517603A' a method for processing coal chemical industry strong brine, which is characterized in that: : (1) mixing and contacting coal chemical industry strong brine with alkali liquor to obtain a solution containing solid precipitates; (2) separating solid precipitate from the solution containing the solid precipitate to obtain salt-containing solution; (3) separating the salt-containing solution to obtain a first salt solution mainly containing monovalent salt and a second salt solution mainly containing divalent salt; (4) electrolyzing the first salt solution to obtain acid liquor and alkali liquor; (5) and carrying out evaporative crystallization on the second salt solution. Most of the concentrated brine is directly converted into acid and alkali without an evaporation crystallization process, so that the evaporation amount is greatly reduced, the energy consumption and the cost are reduced, and the miscellaneous salt solid waste is reduced. However, the method has the problems of long process chain, large consumption of alkali liquor and replacement of only a part of evaporative crystallization process, and the problems of the evaporative crystallization process cannot be completely avoided.
Chinese patent CN107398181A 'an electrodialysis device for concentrated brine quality-dividing in coal chemical industry', proposes a new electrodialysis device for concentrated brine quality-dividing in coal chemical industry. The device can realize the concentration of strong brine and the separation of salt simultaneously, can obtain high-purity sodium chloride and sodium sulfate through subsequent processing to realize the "zero release" of coal industry strong brine, the water resource and the recycle target of salt resource. The process can realize simultaneous concentration and separation, but has the defects of high power consumption, low nanofiltration separation efficiency and influence on the purity of salt obtained by subsequent evaporation crystallization.
Disclosure of Invention
In order to solve the problems of the existing reverse osmosis strong brine evaporation crystallization treatment, the invention aims to provide a method for treating reverse osmosis strong brine, which overcomes the problems of unstable treatment and subsequent treatment process of the strong brine, large investment, large occupied area and high operation cost in the prior art.
In order to achieve the purpose, the invention adopts the following technical scheme:
a method of treating reverse osmosis strong brine comprising the steps of:
(1) removing the hardness of the reverse osmosis strong brine to obtain softened strong brine;
(2) respectively introducing softened concentrated brine and reverse osmosis produced water into a bipolar membrane electrodialyzer, starting the bipolar membrane electrodialyzer to prepare acid and alkali, preparing acid and alkali from the softened concentrated brine, obtaining acid liquor and alkali liquor, and simultaneously obtaining a desalination solution.
The further improvement of the invention is that in the step (1), the TDS of the reverse osmosis concentrated brine is more than 50000mg/L, the water temperature is 5-40 ℃, the COD is less than 200mg/L, the suspended matters are less than 3mg/L, the oil content is less than 1mg/L, and the pH is 6-8.
The further improvement of the invention is that in the step (1), the total hardness of the softened concentrated brine is less than 10 mg/L.
In a further improvement of the present invention, in the step (1), the removal of the hardness of the reverse osmosis concentrated brine is performed in an ion exchange softener, and an ion exchange resin used in the weak acid cation bed of the ion exchange softener is a weak acid cation exchange resin or a sodium ion exchange resin.
The invention is further improved in that the TDS of the reverse osmosis produced water in the step (2) is between 0 and 500 mg/L.
The further improvement of the invention is that the voltage of the bipolar membrane electrodialyzer is: 120-150V; operating current: 75-100A, circulation flow: 1000L/h, membrane surface flow rate: 2-4 cm/s, current density: 230 to 320A/m2(ii) a The current efficiency is more than or equal to 80 percent.
The invention has the further improvement that in the step (2), the acid solution is hydrochloric acid or sulfuric acid, the mass concentration of the acid solution is 3-8%, the purity is more than 90%, the alkali solution is sodium hydroxide solution, the mass concentration of the alkali solution is 3-8%, the purity is more than 90%, the TDS of the desalted water is as follows: 500-20000 mg/L.
The invention has the further improvement that the mass concentration of the acid liquor is 3.1-7.8%, and the mass concentration of the alkali liquor is 3.3-7.5%.
Compared with the prior art, the invention has the following beneficial effects:
1. according to the invention, all reverse osmosis high-salt water is subjected to simple pretreatment, and then the acid and the alkali are prepared by the bipolar membrane electrodialysis process, and the adopted bipolar membrane electrodialysis equipment has the advantages of low energy consumption, stable process, environmental protection, economy and wide application prospect;
2. the invention prepares acid and alkali by the bipolar membrane electrodialysis process of all reverse osmosis high-salt water, does not adopt an evaporation crystallization process, greatly reduces the investment cost, simultaneously reduces the energy consumption and the treatment cost, reduces the miscellaneous salt solid waste, solves the problems of difficult treatment and high treatment cost of the high-salt water, and has important significance for providing certain reference and basis for the treatment and resource utilization of the reverse osmosis high-salt water.
3. The acid and alkali generated by preparation can be directly used in the process of water treatment requiring acid and alkali, including pH adjustment, pressure membrane (reverse osmosis, ultrafiltration and nanofiltration) cleaning process, ion exchange resin regeneration, decarburization process, catalytic oxidation, hardness removal and silicon removal process and the like.
Drawings
The accompanying drawings, which are included to provide a further understanding of the invention and are incorporated in and constitute a part of this specification, illustrate embodiments of the invention and together with the description serve to explain the principles of the invention and not to limit the invention. In the drawings:
FIG. 1 is a schematic flow diagram of a reverse osmosis concentrated brine treatment process of the present invention;
reference numerals: 1-reverse osmosis device, 2-reverse osmosis concentrated water tank, 3-ion exchange softener, 4-reverse osmosis water producing tank, 5-bipolar membrane electrodialyzer, 6-acid storage tank, 7-alkali storage tank and 8-raw water tank.
Detailed Description
The following describes in detail specific embodiments of the present invention. It should be understood that the detailed description and specific examples, while indicating the present invention, are given by way of illustration and explanation only, not limitation.
In the invention, the reverse osmosis concentrated brine is a general term in the field of water treatment, is well known to those skilled in the art, and refers to concentrated water generated after industrial wastewater of coal mines, coal chemical industry and the like is subjected to reverse osmosis concentration. In the present invention, the reverse osmosis concentrated brine refers to concentrated brine having a Total Dissolved Solids (TDS) content of 50000mg/L or more.
A method of treating reverse osmosis strong brine comprising the steps of:
(1) removing the hardness of the reverse osmosis strong brine to obtain softened strong brine;
wherein the TDS of the reverse osmosis concentrated brine is more than 50000mg/L, the water temperature is 5-40 ℃, the COD is less than 200mg/L, the suspended matters are less than 3mg/L, the oil content is less than 1mg/L, and the pH is 6-8.
The total hardness of the softened concentrated brine is less than 10 mg/L.
The ion exchange resin used in the weak acid cation bed is weak acid cation exchange resin or sodium ion exchange resin.
(2) Respectively introducing softened concentrated brine and reverse osmosis produced water into a bipolar membrane electrodialyzer, starting the bipolar membrane electrodialyzer to prepare acid and alkali, preparing acid and alkali from the softened concentrated brine, obtaining acid liquor and alkali liquor, and simultaneously obtaining a desalination solution.
Wherein the TDS of the reverse osmosis produced water is between 0 and 500 mg/L.
Voltage of bipolar membrane electrodialyzer: 120-150V; operating current: 75-100A, circulation flow: 1000L/h, membrane surface flow rate: 2-4 cm/s, current density: 230 to 320A/m2(ii) a The current efficiency is more than or equal to 80 percent.
The acid solution is hydrochloric acid or sulfuric acid, the mass concentration of the acid solution is 3-8%, the purity is more than 90%, the alkali solution is sodium hydroxide solution, the mass concentration of the alkali solution is 3-8%, the purity is more than 90%, and the desalted water TDS: 500-20000 mg/L.
According to the method, the reverse osmosis concentrated brine is introduced into the softener through the step (1), and calcium and magnesium ions in the concentrated brine are removed through the ion exchange resin, so that the total hardness of the concentrated brine is reduced, and the scaling tendency of subsequent bipolar membrane electrodialysis is reduced.
Through the step (2), reverse osmosis concentrated brine and reverse osmosis produced water are respectively introduced into bipolar membrane electrodialysis, and through an electrodialysis experiment, acid and alkali solution with certain quality can be prepared, so that concentrated brine resources are effectively utilized, and generated acid and alkali can be reused in related industrial projects, thereby saving acid and alkali resources.
(3) Collecting acid and alkali generated by bipolar membrane electrodialysis into an acid storage barrel and an alkali storage barrel respectively, and returning the desalted liquid to a raw water pool;
in the step (3), acid liquor and alkali liquor generated by electrodialysis reach certain concentration, and are sent into an acid storage barrel and alkali, and the desalted solution is sent out to a raw water pool;
(4) the acid and the alkali with a certain concentration are generated and reused in the water treatment process or the coal chemical industry process.
In the step (4), the hydrochloric acid, sulfuric acid and sodium hydroxide solution generated by the method can be directly used in the processes of water treatment requiring acid and alkali, such as pH adjustment, pressure membrane (reverse osmosis, ultrafiltration and nanofiltration) cleaning process, ion exchange resin regeneration, decarburization process, catalytic oxidation, hardness removal and silicon removal and the like. Coal chemical projects are similar.
The invention is suitable for the condition that the mass ratio of the sodium sulfate to the sodium chloride in the reverse osmosis concentrated salt water is more than or equal to 9/1 or the mass ratio of the sodium chloride to the sodium sulfate is more than or equal to 9/1.
And (4) sending the generated desalinated liquid into a raw water regulating reservoir through the step (3), and then continuously treating to remove impurities, so that the advantage of fully utilizing the salt resources in the water through cyclic treatment is achieved.
The acid and alkali obtained by the preparation can be reused in industrial water treatment projects such as coal mines, coal chemical industry and the like through the step (4), so that the method has the advantage of cyclic utilization, and meanwhile, the cost is saved for enterprises.
According to a preferred embodiment of the present invention, as shown in fig. 1, the present invention comprises the following means: a reverse osmosis device 1, a reverse osmosis concentrated water tank 2, an ion exchange softener 3, a reverse osmosis water producing tank 4, a bipolar membrane electrodialyzer 5, an acid storage tank 6, an alkali storage tank 7 and a raw water tank 8, wherein the concentrated brine generated by the reverse osmosis device 1 is stored in the reverse osmosis concentrated water tank 2, introducing reverse osmosis strong brine into an ion exchange softener 3 to remove the total hardness, introducing the water produced by the softener and the water produced by a reverse osmosis water producing pool 4 into a bipolar membrane electrodialyzer 5 together, performing a bipolar membrane acid-base preparation experiment, when the acid-base generated by the bipolar membrane electrodialysis device reaches a certain concentration (the concentration is determined according to actual needs), acid and alkali are sent into a corresponding acid storage tank 6 and an alkali storage tank 7, and desalted water is sent into a reverse osmosis front-stage raw water tank 8 for circular treatment to remove total hardness, silicon and COD in the water, so that the water inlet requirements of reverse osmosis water inlet and subsequent electrodialysis devices are met.
Therefore, the ion exchange softener plays a role in softening reverse osmosis strong brine, and the bipolar membrane electrodialysis plays a role in recycling the strong brine into acid and alkali. The invention adopts the coupling technology of hardness reduction pretreatment and bipolar membrane electrodialysis to respectively reduce hardness, classify quality and utilize resources of reverse osmosis strong brine, and does not adopt an evaporative crystallization process, thereby reducing process investment cost and operation energy consumption. And because the bipolar membrane electrodialysis converts the concentrated brine into acid and alkali, the generated acid and alkali can be reused in related industrial items such as water treatment and the like, thereby achieving two purposes at one stroke and reducing the operation cost.
The method of the invention has simple process for treating the reverse osmosis strong brine. After the treatment by the method, the salt in the reverse osmosis strong brine is completely recycled, and an evaporation crystallization process is not adopted, so that the process investment cost and the operation energy consumption are reduced. And because the bipolar membrane electrodialysis converts the concentrated brine into acid and alkali, the generated acid and alkali can be reused in related industrial items such as water treatment and the like, thereby achieving two purposes at one stroke and reducing the operation cost.
The whole process is described in detail below by way of examples, but the scope of the claims of the present invention is not limited by the examples. Meanwhile, the embodiments only give some conditions for achieving the purpose, but do not mean that the conditions must be satisfied for achieving the purpose.
Example 1
The coal chemical industry strong brine is treated according to the flow shown in figure 1:
(1) feeding the reverse osmosis strong brine in the reverse osmosis strong brine tank 2 into an ion exchange softener 3 to remove hardness through ion exchange to obtain softened strong brine;
(2) the effluent of the ion exchange softener 3 and the produced water in the reverse osmosis water producing pool 4 are respectively introduced into a bipolar membrane electrodialyzer 5;
(3) starting an electrodialyzer to perform an acid and alkali preparation experiment, wherein anions and cations in the concentrated brine migrate in the bipolar membrane electrodialysis and are respectively combined with hydrogen ions and hydroxyl ions decomposed by the bipolar membrane to generate corresponding acid and alkali, so as to obtain acid liquor and alkali liquor and obtain desalinated solution;
(4) collecting acid and alkali generated by bipolar membrane electrodialysis into an acid storage tank and an alkali storage tank respectively, and returning the desalted liquid to a raw water pool; the method comprises the following specific steps:
the method comprises the steps of conveying a certain coal mine water reverse osmosis concentrated brine (the water quality condition is shown in table 1) into an ion exchange softener through a conveying pump, removing the total hardness of the concentrated brine through ion exchange, wherein the total hardness of effluent is less than 10mg/L, conveying produced water into a bipolar membrane electrodialysis desalination chamber through a pump, conveying reverse osmosis produced water into a bipolar membrane electrodialysis acid-base chamber, finally obtaining acid with the mass concentration of 6% and alkali liquor with the mass concentration of 6.3%, conveying the acid-base storage tank, and conveying the desalinated water back to a raw water tank through the pump.
Wherein, the operation conditions of the bipolar membrane electrodialysis unit are as follows:
the bipolar film array specification is:
the operation parameters are as follows: the voltage is 120V, the current is 90A, the operating pressure is 0.1Mpa, and the flow rate is 1000L/h;
the ion exchange softener operating conditions were as follows: the operation pressure is 0.1Mpa, and the flow rate is 1000L/h;
therefore, the method has the advantages of simple process flow, maximum resource utilization of the reverse osmosis strong brine, no adoption of an evaporation crystallization process, great energy consumption saving and cost reduction.
TABLE 1 quality table of reverse osmosis (anti-pollution membrane for desalination of sea water) strong brine
Example 2
(1) Feeding the reverse osmosis strong brine in the reverse osmosis strong brine tank 2 into an ion exchange softener 3 to remove hardness through ion exchange to obtain softened strong brine;
wherein the TDS of the reverse osmosis concentrated brine is 72000mg/L, the water temperature is 5 ℃, the COD is 100mg/L, the suspended matters are 1mg/L, the oil content is 0.5mg/L, and the pH value is 6.
The total hardness of the softened concentrated brine is 3 mg/L.
The ion exchange resin used in the weak acid cation bed in the ion exchange softener 3 is a weak acid cation exchange resin.
(2) The effluent of the ion exchange softener 3 and the produced water in the reverse osmosis water producing tank 4 are respectively introduced into a bipolar membrane electrodialyzer 5, the bipolar membrane electrodialyzer 5 is started to carry out an acid and alkali making experiment, anions and cations in the strong brine migrate in the bipolar membrane electrodialysis and are respectively combined with hydrogen ions and hydroxyl ions decomposed by the bipolar membrane to generate corresponding acid and alkali, so that acid liquor and alkali liquor are obtained, and simultaneously desalted liquid is obtained;
wherein the TDS of the reverse osmosis produced water is 500 mg/L.
Operating voltage of bipolar membrane electrodialyzer: 150V; operating current: 100A, circulation flow: 1000L/h, membrane surfaceFlow rate: 4cm/s, current density: 320A/m2(ii) a Current efficiency: 80 percent.
The acid solution is hydrochloric acid or sulfuric acid, the mass concentration of the acid solution is 6.8%, the purity is more than 90%, the alkali solution is sodium hydroxide solution, the mass concentration of the alkali solution is 7.2%, the purity is more than 90%, and the desalted water TDS: 500 mg/L.
Example 3
(1) Feeding the reverse osmosis strong brine in the reverse osmosis strong brine tank 2 into an ion exchange softener 3 to remove hardness through ion exchange to obtain softened strong brine;
wherein the TDS of the reverse osmosis concentrated brine is 53000mg/L, the water temperature is 40 ℃, the COD is 50mg/L, the suspended matters are 2mg/L, the oil content is 0.7mg/L, and the pH is 7.
The total hardness of the softened concentrated brine is 5 mg/L.
The ion exchange resin used in the weak acid cation bed in the ion exchange softener 3 is sodium ion exchange resin.
(2) The effluent of the ion exchange softener 3 and the produced water in the reverse osmosis water producing tank 4 are respectively introduced into a bipolar membrane electrodialyzer 5, the bipolar membrane electrodialyzer 5 is started to carry out an acid and alkali making experiment, anions and cations in the strong brine migrate in the bipolar membrane electrodialysis and are respectively combined with hydrogen ions and hydroxyl ions decomposed by the bipolar membrane to generate corresponding acid and alkali, so that acid liquor and alkali liquor are obtained, and simultaneously desalted liquid is obtained;
wherein the TDS of the reverse osmosis produced water is 200 mg/L.
Operating voltage of bipolar membrane electrodialyzer: 120V; operating current: 75A, circulation flow: 1000L/h, membrane surface flow rate: 4cm/s, current density: 230A/m2(ii) a Current efficiency: 90 percent.
The acid solution is hydrochloric acid or sulfuric acid, the mass concentration of the acid solution is 3.1%, the purity is more than 90%, the alkali solution is sodium hydroxide solution, the mass concentration of the alkali solution is 3.3%, the purity is more than 90%, and the desalted water TDS: 20000 mg/L.
Example 4
(1) Feeding the reverse osmosis strong brine in the reverse osmosis strong brine tank 2 into an ion exchange softener 3 to remove hardness through ion exchange to obtain softened strong brine;
wherein the TDS of the reverse osmosis concentrated brine is 51000mg/L, the water temperature is 20 ℃, the COD is 50mg/L, the suspended matters are 1mg/L, the oil content is 0.3mg/L, and the pH value is 8.
The total hardness of the softened concentrated brine is 2 mg/L.
The ion exchange resin used in the weak acid cation bed in the ion exchange softener 3 is a weak acid cation exchange resin.
(2) The effluent of the ion exchange softener 3 and the produced water in the reverse osmosis water producing tank 4 are respectively introduced into a bipolar membrane electrodialyzer 5, the bipolar membrane electrodialyzer 5 is started to carry out an acid and alkali making experiment, anions and cations in the strong brine migrate in the bipolar membrane electrodialysis and are respectively combined with hydrogen ions and hydroxyl ions decomposed by the bipolar membrane to generate corresponding acid and alkali, so that acid liquor and alkali liquor are obtained, and simultaneously desalted liquid is obtained;
wherein the TDS of the reverse osmosis produced water is 300 mg/L.
Operating voltage of bipolar membrane electrodialyzer: 130V; operating current: 80A, circulation flow rate: 1000L/h, membrane surface flow rate: 3cm/s, current density: 280A/m2(ii) a Current efficiency: 85 percent.
The acid solution is hydrochloric acid or sulfuric acid, the mass concentration of the acid solution is 5.1%, the purity is more than 90%, the alkali solution is sodium hydroxide solution, the mass concentration of the alkali solution is 5.5%, the purity is more than 90%, and the desalted water TDS: 10000 mg/L.
Example 5
(1) Feeding the reverse osmosis strong brine in the reverse osmosis strong brine tank 2 into an ion exchange softener 3 to remove hardness through ion exchange to obtain softened strong brine;
wherein the TDS of the reverse osmosis concentrated brine is 75000mg/L, the water temperature is 30 ℃, the COD is 80mg/L, the suspended matters are 2mg/L, the oil content is 0.8mg/L, and the pH value is 6.
The total hardness of the softened concentrated brine is 2 mg/L.
The ion exchange resin used in the weak acid cation bed in the ion exchange softener 3 is sodium ion exchange resin.
(2) The effluent of the ion exchange softener 3 and the produced water in the reverse osmosis water producing tank 4 are respectively introduced into a bipolar membrane electrodialyzer 5, the bipolar membrane electrodialyzer 5 is started to carry out an acid and alkali making experiment, anions and cations in the strong brine migrate in the bipolar membrane electrodialysis and are respectively combined with hydrogen ions and hydroxyl ions decomposed by the bipolar membrane to generate corresponding acid and alkali, so that acid liquor and alkali liquor are obtained, and simultaneously desalted liquid is obtained;
wherein the TDS of the reverse osmosis produced water is 100 mg/L.
Operating voltage of bipolar membrane electrodialyzer: 140V; operating current: 90A, circulation flow rate: 1000L/h, membrane surface flow rate: 2cm/s, current density: 270A/m2(ii) a Current efficiency: 85 percent.
The acid solution is hydrochloric acid or sulfuric acid, the mass concentration of the acid solution is 7.3%, the purity is more than 90%, the alkali solution is sodium hydroxide solution, the mass concentration of the alkali solution is 7.5%, the purity is more than 90%, and the desalted water TDS: 3000 mg/L.
The method of the invention has simple process for treating the reverse osmosis strong brine. After the treatment by the method, the salt in the reverse osmosis strong brine is completely recycled, and an evaporation crystallization process is not adopted, so that the process investment cost and the operation energy consumption are reduced. And because the bipolar membrane electrodialysis converts the concentrated brine into acid and alkali, the generated acid and alkali can be reused in related industrial items such as water treatment and the like, thereby achieving two purposes at one stroke and reducing the operation cost.
The preferred embodiments of the present invention have been described in detail, however, the present invention is not limited to the specific details of the above embodiments, and various simple modifications may be made to the technical solution of the present invention within the technical idea of the present invention, and these simple modifications are within the protective scope of the present invention.
It should be noted that the various features described in the above embodiments may be combined in any suitable manner without departing from the scope of the invention.
In addition, any combination of the various embodiments of the present invention is also possible, and the same should be considered as the disclosure of the present invention as long as it does not depart from the spirit of the present invention.
Claims (7)
1. A method for treating reverse osmosis strong brine is characterized by comprising the following steps:
(1) removing the hardness of the reverse osmosis strong brine to obtain softened strong brine;
(2) respectively introducing softened concentrated brine and reverse osmosis produced water into a bipolar membrane electrodialyzer, starting the bipolar membrane electrodialyzer to prepare acid and alkali, preparing acid and alkali from the softened concentrated brine, obtaining acid liquor and alkali liquor, and simultaneously obtaining a desalination solution.
2. The method for treating the reverse osmosis concentrated brine according to claim 1, wherein the TDS of the reverse osmosis concentrated brine in the step (1) is more than 50000mg/L, the water temperature is 5-40 ℃, the COD is less than 200mg/L, the suspended matters are less than 3mg/L, the oil content is less than 1mg/L, and the pH is 6-8.
3. The method of claim 1 wherein step (1) softens the brine to a total hardness of less than 10 mg/L.
4. The method as claimed in claim 1, wherein the removing of the hardness of the reverse osmosis concentrated brine in the step (1) is performed in an ion exchange softener, and the ion exchange resin used in the weak acid cation bed of the ion exchange softener is weak acid cation exchange resin or sodium ion exchange resin.
5. The method for treating reverse osmosis concentrated brine according to claim 1, wherein the TDS of the reverse osmosis produced water in the step (2) is 0-500 mg/L.
6. The method of claim 1 wherein the voltage of the bipolar membrane electrodialyzer is: 120-150V; operating current: 75-100A, circulation flow: 1000L/h, membrane surface flow rate: 2-4 cm/s, current density: 230 to 320A/m2(ii) a The current efficiency is more than or equal to 80 percent.
7. The method for treating reverse osmosis concentrated brine according to claim 1, wherein in the step (2), the acid solution is hydrochloric acid or sulfuric acid, the acid solution has a mass concentration of 3-8% and a purity of more than 90%, the alkali solution is sodium hydroxide solution, the alkali solution has a mass concentration of 3-8% and a purity of more than 90%, and the desalted water TDS: 500-20000 mg/L.
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