Sodium chloride brine concentration system and method

Abstract

The application provides a sodium chloride concentrated brine treatment system and method, which comprises a membrane concentration unit, a salt separation treatment unit and a recovery treatment unit arranged in sequence; the membrane concentration unit is used for performing membrane concentration treatment on the sodium chloride concentrated brine to obtain a concentrated solution; the salt separation treatment unit is used for performing salt separation treatment on the concentrated solution by using an organic solvent to obtain a sodium chloride product salt and a mixed solution containing the organic solvent; and the recovery treatment unit is used for performing recovery treatment on the mixed solution. By using the organic solvent to perform the salt separation treatment on the concentrated solution, the addition of the organic solvent can reduce the polarity of the concentrated solution, effectively reduce the solubility of the sodium chloride salt in the concentrated solution, and improve the precipitation amount of the sodium chloride salt; by performing the recovery treatment on the mixed solution by the recovery treatment unit, not only can the double resource utilization of the organic solvent and the salt-containing wastewater be realized, but also the treatment cost can be reduced, thereby laying a good foundation for promoting green development.

Description

Technical Field

[0001] This invention relates to the field of water treatment technology, and in particular to a sodium chloride concentrated brine treatment system and method. Background Technology

[0002] To meet increasingly stringent environmental protection requirements, more and more industrial enterprises are adopting a "dual-membrane" treatment process consisting of ultrafiltration and reverse osmosis to deeply treat and concentrate wastewater, striving to achieve zero wastewater discharge. However, the treatment of high-concentration brine (typically TDS > 10000 mg / L) generated during membrane concentration has become a key challenge restricting the entire zero-discharge process.

[0003] For the treatment of concentrated sodium chloride brine, mechanical vapor recompression (MVR) or multi-effect evaporation crystallization technology is currently the main methods used to crystallize the salt. However, these evaporation crystallization processes are not only energy-intensive, but also produce concentrated mother liquor in addition to the product salt. The concentrated mother liquor, after drying and incineration, forms solid mixed salts, but due to the high content of organic matter and heavy metals in these solid mixed salts, their resource utilization is quite difficult. Summary of the Invention

[0004] The purpose of this invention is to provide a sodium chloride brine treatment system and method to solve one or more of the problems existing in the prior art, such as high energy consumption and difficulty in resource utilization of the generated miscellaneous salts when using evaporation crystallization process to treat sodium chloride brine.

[0005] To achieve the above objectives, the present invention provides the following technical solution: a sodium chloride brine treatment system, comprising a membrane concentration unit, a salt precipitation treatment unit, and a recovery treatment unit arranged sequentially; the membrane concentration unit is configured to: perform membrane concentration treatment on the sodium chloride brine to obtain a concentrated solution; the salt precipitation treatment unit is configured to: perform salt precipitation treatment on the concentrated solution using an organic solvent to obtain sodium chloride product salt and a mixture containing the organic solvent; the recovery treatment unit is configured to: perform recovery treatment on the mixture.

[0006] Optionally, the salt precipitation treatment unit includes a desalination device, a solid-liquid separation device, and a drying device arranged sequentially. The desalination device is equipped with a stirrer. The desalination device is connected to the recovery treatment unit. The desalination device is configured to desalinate the concentrate using an organic solvent to obtain a solid salt mixture and a mixture containing the organic solvent, and to transport the mixture to the recovery treatment unit. The stirrer is configured to stir the mixed solution in the desalination device at a preset stirring intensity of 100 rpm to 200 rpm and a preset stirring time of 10 minutes to 15 minutes. The solid-liquid separation device is configured to perform solid-liquid separation on the solid salt mixture to obtain solid salt. The drying device is configured to dry the solid salt to obtain the sodium chloride product salt.

[0007] Optionally, the organic solvent comprises a first volume percentage of dioxane, a second volume percentage of ethyl propionate, a third volume percentage of polyethylene glycol, a fourth volume percentage of ethanol, and a fifth volume percentage of cyclohexanone.

[0008] Optionally, the first volume percentage ranges from 15% to 30%, the second volume percentage ranges from 10% to 15%, the third volume percentage ranges from 10% to 20%, the fourth volume percentage ranges from 15% to 25%, and the fifth volume percentage ranges from 10% to 20%.

[0009] Optionally, the preset addition ratio of the organic solvent can range from 10% to 15%.

[0010] Optionally, the recovery and treatment unit includes a membrane distillation device and a catalytic reaction device arranged sequentially; the membrane distillation device is configured to: perform membrane distillation treatment on the mixture to obtain organic solvent permeate and saline concentrate, and convey the organic solvent permeate to the salt precipitation treatment unit and the saline concentrate to the catalytic reaction device; the catalytic reaction device is configured to: perform low-temperature wet catalytic oxidation treatment on the saline concentrate to obtain effluent and a steam-water mixture, and convey the effluent to the inlet end of the membrane concentration unit and the steam-water mixture to the catalytic reaction device.

[0011] Optionally, the membrane distillation apparatus includes a first preheater, a first heater, a membrane module, and a condenser arranged sequentially; the first preheater is configured to receive the mixture and the distillate output from the condenser, such that the mixture and the distillate exchange heat to obtain the organic solvent permeate and the preheated mixture, and the temperature of the preheated mixture is set to 30°C–40°C; the first heater is configured to heat the preheated mixture to obtain the heated mixture, and the temperature of the heated mixture is set to 60°C–80°C; the membrane module is configured to perform membrane separation on the heated mixture to obtain organic solvent vapor and the salt-containing concentrated water; the condenser is configured to condense the organic solvent vapor to obtain the distillate.

[0012] Optionally, the membrane module includes a cross-linked fluorinated modified polytetrafluoroethylene nanofiber membrane with a pore size of 0.1 μm to 0.3 μm, a porosity of 60% to 75%, a thickness of 200 μm to 300 μm, and a contact angle greater than 130°.

[0013] Optionally, the catalytic reaction apparatus includes a second preheater, a second heater, and a catalytic reaction tower arranged sequentially; the second preheater is configured to receive the saline concentrate and the steam-water mixture output from the catalytic reaction tower, so that the saline concentrate and the steam-water mixture exchange heat to obtain preheated saline concentrate, and the temperature of the preheated saline concentrate is 80℃~90℃; the second heater is configured to heat the preheated saline concentrate to obtain heated saline concentrate, and the temperature of the heated saline concentrate is 120℃~150℃; the catalytic reaction tower is configured to subject the heated saline concentrate to a low-temperature wet catalytic oxidation reaction, with a reaction pressure of 0.4 MPa~0.6 MPa and a residence time of 60 minutes~90 minutes, to obtain effluent and a steam-water mixture, and to transport the effluent to the inlet of the membrane concentration unit and the steam-water mixture to the second preheater.

[0014] To achieve the above objectives, the present invention also provides a method for treating concentrated sodium chloride brine, wherein the concentrated sodium chloride brine is treated using the concentrated sodium chloride brine treatment system described in any one of the above claims, the treatment method comprising:

[0015] The sodium chloride brine was subjected to membrane concentration treatment to obtain a concentrated solution;

[0016] The concentrate was subjected to salt precipitation treatment using an organic solvent to obtain sodium chloride product salt and a mixture containing the organic solvent.

[0017] The mixture is then recycled.

[0018] Compared with the prior art, the sodium chloride concentrated brine treatment system and method provided by the present invention have the following beneficial effects:

[0019] The sodium chloride brine treatment system provided by this invention includes a membrane concentration unit, a salt precipitation treatment unit, and a recovery treatment unit arranged sequentially. The membrane concentration unit is configured to perform membrane concentration treatment on the sodium chloride brine to obtain a concentrated solution. The salt precipitation treatment unit is configured to perform salt precipitation treatment on the concentrated solution using an organic solvent to obtain sodium chloride product salt and a mixture containing the organic solvent. The recovery treatment unit is configured to perform recovery treatment on the mixture. Therefore, the sodium chloride brine treatment system provided by this invention first increases the salt content of the sodium chloride brine by performing membrane concentration treatment on the sodium chloride brine, thereby reducing the energy consumption of subsequent treatment units. Then, the salt precipitation treatment unit uses an organic solvent to perform salt precipitation treatment on the concentrated solution after membrane concentration treatment. The addition of the organic solvent reduces the polarity of the concentrated solution, thereby effectively reducing the solubility of sodium chloride salt in the concentrated solution and increasing the precipitation amount of sodium chloride salt. Finally, the mixed liquid containing organic solvents obtained after salt precipitation treatment is recycled through the recycling unit. This not only enables the dual resource utilization of organic solvents and saline wastewater, but also reduces treatment costs, laying a good foundation for promoting green development.

[0020] Since the sodium chloride concentrated brine treatment method and the sodium chloride concentrated brine treatment system provided by this invention belong to the same inventive concept, the sodium chloride concentrated brine treatment method provided by this invention has at least all the advantages of the sodium chloride concentrated brine treatment system provided by this invention. For the advantages of the sodium chloride concentrated brine treatment method provided by this invention, please refer to the relevant description of the beneficial effects of the sodium chloride concentrated brine treatment system provided by this invention, which will not be repeated here. Attached Figure Description

[0021] Figure 1 This is a structural block diagram of a sodium chloride concentrated brine treatment system provided in Embodiment 1 of the present invention;

[0022] Figure 2 This is a process flow diagram of a sodium chloride concentrated brine treatment system provided in Embodiment 1 of the present invention;

[0023] Figure 3 This is a schematic flowchart of a method for treating concentrated sodium chloride brine according to Embodiment 2 of the present invention;

[0024] The annotations in the attached figures are explained as follows:

[0025] 1- Membrane concentration unit; 11- First-stage reverse osmosis unit; 12- Second-stage reverse osmosis unit;

[0026] 2-Salt treatment unit, 21-Desalination device, 211-Agitator, 22-Solid-liquid separation device, 23-Drying device;

[0027] 3-Recovery and processing unit, 31-Membrane distillation device, 311-First preheater, 312-First heater, 313-Membrane module, 314-Condenser, 32-Catalytic reaction device, 321-Second preheater, 322-Second heater, 323-Catalytic reaction tower. Detailed Implementation

[0028] The sodium chloride concentrated brine treatment system and method proposed in this invention will be further described in detail below with reference to the accompanying drawings and specific embodiments. The advantages and features of this invention will become clearer from the following description. It should be noted that the drawings are all in a very simplified form and use non-precise proportions, only used to facilitate and clarify the illustration of the embodiments of this invention. Please refer to the drawings to make the objectives, features, and advantages of this invention more apparent and understandable. It should be understood that the structures, proportions, sizes, etc., depicted in the accompanying drawings are only used to complement the content disclosed in the specification, for those skilled in the art to understand and read, and are not intended to limit the implementation conditions of this invention. Any modifications to the structure, changes in proportions, or adjustments to the size, if they are the same as or similar to the effects and objectives achieved by this invention, should still fall within the scope of the technical content disclosed in this invention. Specific design features of the invention disclosed herein, including, for example, specific dimensions, orientations, positions, and shapes, will be determined in part by the specific application and usage environment. Furthermore, in the embodiments described below, sometimes the same reference numerals are used together across different drawings to indicate the same parts or parts having the same function, and repeated descriptions are omitted.

[0029] In the description of this invention, unless otherwise explicitly specified and limited, the terms "installation," "connection," "linking," and "fixing" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0030] It should be understood that, unless specifically stated or obvious from the context, as used herein, the term “about” is understood to mean within the normal tolerance range in the field, such as within 2 standard deviations of the mean. “About” can be understood as within 10%, 9%, 8%, 7%, 6%, 5%, 4%, 3%, 2%, 1%, 0.5%, 0.1%, 0.05%, or 0.01% of the stated value. Unless otherwise specified from the context, all numerical values ​​provided herein are modified by the term “about”.

[0031] Example 1

[0032] This embodiment provides a concentrated sodium chloride brine treatment system. For details, please refer to [link to documentation]. Figure 1 , Figure 1 This is a structural block diagram of the sodium chloride concentrated brine treatment system provided in this embodiment. (From...) Figure 1 As can be seen, the processing system includes a membrane concentration unit 1, a salt precipitation treatment unit 2, and a recovery treatment unit 3 arranged sequentially. The membrane concentration unit 1 is configured to perform membrane concentration treatment on the concentrated sodium chloride brine to obtain a concentrated solution. The salt precipitation treatment unit 2 is configured to perform salt precipitation treatment on the concentrated solution using an organic solvent to obtain a mixture of sodium chloride product salt and the organic solvent. The recovery treatment unit 3 is configured to perform recovery treatment on the mixture. Therefore, the concentrated sodium chloride brine processing system provided in this embodiment first increases the salt content of the concentrated sodium chloride brine by performing membrane concentration treatment on the concentrated sodium chloride brine using the membrane concentration unit 1, which can reduce the energy consumption of subsequent processing units. Then, the salt precipitation treatment unit 2 uses an organic solvent to perform salt precipitation treatment on the concentrated solution after membrane concentration treatment. The addition of the organic solvent can reduce the polarity of the concentrated solution, thereby effectively reducing the solubility of sodium chloride salt in the concentrated solution, and thus increasing the precipitation amount of sodium chloride salt. Finally, the mixed liquid containing organic solvents obtained after salt precipitation treatment is recycled through the recycling unit 3. This not only enables the dual resource utilization of organic solvents and saline wastewater, but also reduces treatment costs, laying a good foundation for promoting green development.

[0033] It should be noted that the present invention does not impose excessive limitations on the water quality of the sodium chloride concentrated brine. Exemplarily, in some embodiments, the water quality of the sodium chloride concentrated brine is as follows: TDS (Total Dissolved Solids) of 10000 mg / L to 15000 mg / L, sodium ion concentration of 4500 mg / L to 5500 mg / L, chloride ion concentration of 5500 mg / L to 6500 mg / L, and TOC (Total Organic Carbon) of 100 mg / L to 200 mg / L.

[0034] For a better option, please see Figure 2 , Figure 2This is a process flow diagram of the sodium chloride concentrated brine treatment system provided in this embodiment. (From...) Figure 2 As can be seen, in some embodiments, the membrane concentration unit 1 includes a primary reverse osmosis unit 11 and a secondary reverse osmosis unit 12 arranged sequentially. The primary reverse osmosis unit 11 is configured to perform primary membrane concentration treatment on the sodium chloride brine to obtain a primary concentrated solution. The secondary reverse osmosis unit 12 is configured to perform secondary membrane concentration treatment on the primary concentrated solution to obtain the concentrate. Therefore, by first performing primary membrane concentration treatment on the sodium chloride brine using the primary reverse osmosis unit 11, the sodium chloride brine can be initially concentrated to obtain a primary concentrated solution. Then, by performing secondary membrane concentration treatment on the primary concentrated solution using the secondary reverse osmosis unit 12, the primary concentrated solution can be further concentrated to obtain the concentrate, thereby increasing the salt content in the sodium chloride brine and reducing the energy consumption of subsequent treatment units.

[0035] Exemplary examples, in some of these exemplary embodiments, the primary reverse osmosis unit 11 can be an RO reverse osmosis unit with one to two stages, and the secondary reverse osmosis unit 12 can be a DTRO reverse osmosis unit. The sodium chloride brine is pumped into the RO reverse osmosis unit and concentrated 2 to 3 times. The resulting primary concentrated solution has the following characteristics: TDS approximately 20,000 mg / L to 40,000 mg / L, sodium ion concentration approximately 10,000 mg / L to 20,000 mg / L, chloride ion concentration approximately 12,000 mg / L to 22,000 mg / L, and TOC approximately 300 mg / L to 600 mg / L. Next, the primary concentrated solution is pumped into the DTRO reverse osmosis unit for further concentration at an operating pressure of 10-15 MPa, resulting in a 4-5 fold concentration. The resulting concentrate contains approximately 150,000 mg / L to 200,000 mg / L of TDS, approximately 80,000 mg / L to 100,000 mg / L of sodium ions, approximately 80,000 mg / L to 120,000 mg / L of chloride ions, and approximately 1,500 mg / L to 3,000 mg / L of TOC.

[0036] For the preferred options, please continue reading. Figure 2 ,like Figure 2As shown, in some embodiments, the salt treatment unit 2 includes a desalination device 21, a solid-liquid separation device 22, and a drying device 23 arranged sequentially. The desalination device 21 is equipped with a stirrer 211. The desalination device 21 is connected to the recovery treatment unit 3. The desalination device 21 is configured to desalinate the concentrate using an organic solvent to obtain a solid salt mixture and a mixture containing the organic solvent, and to transport the mixture to the recovery treatment unit 3. The stirrer 211 is configured to stir the mixed solution in the desalination device 21 according to a preset stirring intensity and a preset stirring time. The solid-liquid separation device 22 is configured to perform solid-liquid separation on the solid salt mixture to obtain solid salt. The drying device 23 is configured to dry the solid salt to obtain the sodium chloride product salt. Therefore, by adding an organic solvent to the desalination device 21 to desalinate the concentrate, the addition of the organic solvent reduces the polarity of the concentrate, thereby effectively reducing the solubility of sodium chloride in the concentrate, causing the sodium chloride to gradually precipitate from the concentrate, resulting in a mixture of solid salts and a mixture containing the organic solvent. Simultaneously, by installing a stirrer 211 in the desalination device 21 for stirring, the precipitation rate of sodium chloride can be increased. Further, the solid salt mixture is separated by a solid-liquid separation device 22; then, the solid salt is dried by a drying device 23 to obtain sodium chloride product salt.

[0037] It should be noted that, in some embodiments, the TDS of the mixture containing the organic solvent discharged through the desalination device 21 is about 15000 mg / L to 20000 mg / L, and the TOC is about 2800 mg / L to 4200 mg / L. The mixture enters the recovery treatment unit 3 through a pipeline for recovery.

[0038] Additionally, it should be noted that the present invention does not impose excessive limitations on the types of the desalination device 21, the solid-liquid separation device 22, the drying device 23, and the agitator 211. Exemplarily, in some exemplary embodiments, the desalination device 21 may be a desalination tower, the solid-liquid separation device 22 may be a centrifuge, the drying device 23 may be a dryer, and the agitator 211 may be a paddle agitator.

[0039] It should be noted that the preset stirring intensity and the preset stirring duration can be set according to the actual application scenario. For example, in some embodiments, the preset stirring intensity can be 100 rpm to 200 rpm, and the preset stirring duration can be 10 minutes to 15 minutes.

[0040] Furthermore, the organic solvent comprises a first volume percentage of dioxane, a second volume percentage of ethyl propionate, a third volume percentage of polyethylene glycol, a fourth volume percentage of ethanol, and a fifth volume percentage of cyclohexanone. Thus, by using an organic solvent with suitable components, the amount of sodium chloride salt precipitated can be increased.

[0041] Preferably, the first volume percentage ranges from 15% to 30%, the second volume percentage ranges from 10% to 15%, the third volume percentage ranges from 10% to 20%, the fourth volume percentage ranges from 15% to 25%, and the fifth volume percentage ranges from 10% to 20%. Thus, by setting the volume percentages of each component in the organic solvent within appropriate ranges, the amount of sodium chloride precipitated can be further increased.

[0042] Furthermore, the preset addition ratio of the organic solvent ranges from 10% to 15%.

[0043] It should be noted that the preset addition ratio of the organic solvent refers to the volume ratio of the organic solvent to the concentrate. For example, when the inlet of the desalination device 21 receives 100 ml of the concentrate, it is expected that 10 ml to 15 ml of the organic solvent will be added to the desalination device 21.

[0044] To better understand the present invention, the salt precipitation process of the concentrated solution is described below by way of example.

[0045] First, when the concentrate is transported to the desalination tower, an organic solvent is added to the tower at a dosage ratio of 10% to 15%. The main components of the organic solvent are 15% to 30% dioxane, 10% to 15% ethyl propionate, 10% to 20% polyethylene glycol, 15% to 25% ethanol, and 10% to 20% cyclohexanone (by volume). The concentrate and the organic solvent are mixed and stirred using a paddle stirrer at a preset stirring intensity of 100 to 200 rpm for a preset stirring time of 10 to 15 minutes to form a mixed solution. Then, the mixed solution is allowed to stand for 0.5 to 1 hour, and then added at a dosage of 6 g / (m³). 2 ·h)~8g / (m 2The solid salt mixture gradually concentrates and precipitates at a rate of h), forming fine crystal nuclei with a size of 5 to 10 micrometers. With prolonged settling time, these nuclei gradually enlarge, forming visible crystal particles. After 2 to 3 hours of settling, approximately 70% to 85% of the solid salt mixture crystallizes out in the desalination tower, with crystal nuclei of 100 to 200 micrometers in size, and settles to the bottom of the tower, with a sediment thickness of approximately 8 to 10 centimeters. The crystallized solid salt mixture is then discharged from the bottom outlet of the desalination tower to a centrifuge for solid-liquid separation. The separated solid salt is then dried in a dryer to obtain sodium chloride product salt with a purity greater than 90%. Simultaneously, the organic solvent mass fraction in the upper layer of the desulfurization tower is approximately 20% to 30%, and this mixture is piped into the recovery unit 3 for recycling.

[0046] Please continue reading Figure 2 ,like Figure 2 As shown, in some embodiments, the recovery and treatment unit 3 includes a membrane distillation device 31 and a catalytic reaction device 32 arranged sequentially. The membrane distillation device 31 is configured to perform membrane distillation on the mixture to obtain organic solvent permeate and saline concentrate, and to transport the organic solvent permeate to the salt precipitation treatment unit 2 and the saline concentrate to the catalytic reaction device 32. The catalytic reaction device 32 is configured to perform low-temperature wet catalytic oxidation on the saline concentrate to obtain effluent and a steam-water mixture, and to transport the effluent to the inlet of the membrane concentration unit 1 and the steam-water mixture to the catalytic reaction device 32. Thus, by performing membrane distillation on the mixture containing organic solvents using the membrane distillation device 31, organic solvent permeate and saline concentrate can be separated, allowing the organic solvent permeate to be returned to the salt precipitation treatment unit 2 for recycling. Furthermore, the concentrated saline solution is fed to the catalytic reactor 32, where it undergoes low-temperature wet catalytic oxidation treatment to efficiently remove organic matter, yielding purified effluent and a mixture of steam and water. Next, the effluent is fed to the inlet of the membrane concentration unit 1 and mixed with concentrated sodium chloride brine for further membrane concentration, recovering the salt content in the effluent. The steam-water mixture is then fed to the catalytic reactor 32, where the heat from the mixture is fully utilized to preheat the concentrated saline solution entering the reactor.

[0047] Preferably, the membrane distillation apparatus 31 includes a first preheater 311, a first heater 312, a membrane module 313, and a condenser 314 arranged sequentially. The first preheater 311 is configured to receive the mixture and the distillate output from the condenser 314, so that the mixture and the distillate exchange heat to obtain the organic solvent permeate and the preheated mixture. The first heater 312 is configured to heat the preheated mixture to obtain the heated mixture. The membrane module 313 is configured to perform membrane separation on the heated mixture to obtain organic solvent vapor and the salt-containing concentrate. The condenser 314 is configured to condense the organic solvent vapor to obtain the distillate. Thus, by receiving the mixture output from the salt precipitation unit 2 and the distillate output from the condenser 314 through the first preheater 311, the heat of the distillate can be recovered to preheat the mixture. The preheated mixture is then heated by the first heater 312 to evaporate it. The evaporated organic solvent vapor is then separated from the salt concentrate by the membrane module 313. The organic solvent vapor passes through the membrane module 313 and enters the condenser 314, while the salt concentrate is transported to the catalytic reaction unit 32. Furthermore, the organic solvent vapor is cooled by the condenser 314 to form distillate, which is output from the condenser 314 to the first preheater 311, thereby obtaining organic solvent permeate.

[0048] Exemplary embodiments include, in some of these exemplary implementations, the first preheater 311 may be a plate heat exchanger; the first heater 312 may be a steam heater; the membrane module 313 may be a cross-linked fluorinated modified polytetrafluoroethylene nanofiber membrane with a pore size of 0.1 μm to 0.3 μm, a porosity of 60% to 75%, a thickness of 200 μm to 300 μm, and a contact angle greater than 130°. This membrane module 313 has good amphoteric properties and chemical stability, and can efficiently separate organic solvents from mixed solutions; the condenser 314 may be a shell-and-tube condenser.

[0049] To facilitate understanding of the present invention, the following exemplary embodiments are described in conjunction with... Figure 2 The membrane distillation process of the mixture is illustrated by way of example.

[0050] First, the mixture is discharged from the desalination tower to the first preheater 311. The first preheater 311 preheats the mixture by receiving the distillate discharged from the condenser 314, raising the temperature of the mixture to 30°C to 40°C. Then, the preheated mixture enters the first heater 312, where it is heated by steam to 60°C to 80°C. The organic solvent in the mixture forms organic solvent vapor and passes through the membrane module 313 to the other side of the membrane module 313. The salt concentrate in the mixture is discharged from the concentrate side of the membrane module 313 to the catalytic reaction unit 32. The salt concentrate has a TDS of approximately 15000 mg / L to 20000 mg / L, a TOC of approximately 1500 mg / L to 2000 mg / L, and a temperature of approximately 60°C to 80°C. Next, the organic solvent vapor enters the condenser 314 to cool and form a distillate. The temperature of the distillate is about 40°C to 50°C. The distillate is then sent to the first preheater 311 to preheat the mixture entering the first preheater 311. After four stages of membrane distillation at a membrane flux of 10 L / (m2·h) to 20 L / (m2·h), organic solvent permeate with a mass fraction of about 80% to 90% is obtained. This organic solvent permeate is returned to the desalination unit 21 for recycling.

[0051] It should be noted that the organic solvent in the mixture is recovered by the membrane distillation device 31 at an operating temperature of approximately 60°C to 80°C, which is lower than the temperature required by traditional distillation technology, thus reducing energy consumption. Furthermore, the membrane distillation process utilizes a cross-linked fluorinated modified polytetrafluoroethylene nanofiber membrane, making it difficult for impurities in the mixture to pass through, enabling the recovery of high-purity organic solvents. In addition, the membrane distillation process involves heat exchange between the distillate and the mixture, further reducing the energy consumption for heating the mixture.

[0052] For further details, please continue to see [link / reference]. Figure 2 ,like Figure 2 As shown, in some embodiments, the catalytic reaction device 32 includes a second preheater 321, a second heater 322, and a catalytic reaction tower 323 arranged sequentially; the second preheater 321 is configured to receive the salt-containing concentrated water and the steam-water mixture output from the catalytic reaction tower 323, so that the salt-containing concentrated water and the steam-water mixture exchange heat to obtain preheated salt-containing concentrated water; the second heater 322 is configured to heat the preheated salt-containing concentrated water to obtain heated salt-containing concentrated water; the catalytic reaction tower 323 is configured to cause the heated salt-containing concentrated water to undergo a low-temperature wet catalytic oxidation reaction to obtain effluent and a steam-water mixture, and to transport the effluent to the inlet end of the membrane concentration unit 1 and the steam-water mixture to the second preheater 321.

[0053] For example, in some exemplary embodiments, the second preheater 321 may be a plate heat exchanger; the second heater 322 may be a steam heater; and a nitrogen-doped biochar catalyst may be provided in the catalytic reaction tower 323, the nitrogen-doped biochar catalyst accounting for 60% to 75% of the total volume of the catalytic reaction tower 323.

[0054] To facilitate understanding of the present invention, the following exemplary embodiments are described in conjunction with... Figure 2 The low-temperature wet catalytic oxidation process for the saline concentrate is illustrated by way of example.

[0055] First, the saline concentrate is discharged from the membrane distillation unit 31 to the second preheater 321. The second preheater 321 preheats the saline concentrate by receiving the steam-water mixture output from the catalytic reaction tower 323, raising the temperature of the saline concentrate to 80°C–90°C. Then, the preheated saline concentrate enters the second heater 322, where it is heated to 120°C–150°C by steam before entering the catalytic reaction tower 323 for a low-temperature wet catalytic oxidation reaction. The reaction pressure is 0.4 MPa–0.6 MPa, and the residence time is 60–90 minutes. The catalyst in the catalytic reaction tower 323 promotes the activation of oxygen molecules, generating hydroxyl radicals, which can rapidly oxidize and decompose the organic matter in the saline concentrate, yielding purified effluent and a steam-water mixture. The TDS of the effluent is approximately 15000 mg / L–20000 mg / L, and the TOC is approximately 200 mg / L–400 mg / L. Next, the soda-water mixture is sent back to the second preheater 321 to preheat the saline concentrate entering the second preheater 321, and the effluent is sent to the inlet of the membrane concentration unit 1.

[0056] It should be noted that the concentrate obtained after concentration by the DTRO reverse osmosis unit is then processed by the traditional MVR evaporation and crystallization process. The electricity consumption is about 50 to 55 kWh per ton of concentrate, and the steam consumption is 0.1 to 0.15 tons. If the electricity price is calculated at 0.7 yuan / kWh and the steam price is calculated at 120 yuan / ton, the electricity consumption is about 35 to 38 yuan, the steam cost is about 12 to 18 yuan, and the total operating cost is about 47 to 56 yuan. The sodium chloride brine treatment system provided in this embodiment treats the concentrated solution obtained after DTRO reverse osmosis. The main operating cost is the energy consumption of the membrane distillation unit 31 in the process of recovering organic solvent. It takes about 0.1 to 0.15 tons of organic solvent to treat 1 ton of the concentrated solution. The power of the membrane distillation unit 31 is about 100 kW to 120 kW. It takes about 3 to 4 hours to recover 1 ton of organic solvent by membrane distillation. If the electricity price is calculated at 0.7 yuan / kWh, the operating cost of treating 1 ton of the concentrated solution is about 30 to 50 yuan. The operating cost of the sodium chloride brine treatment system provided in this embodiment is lower than that of the traditional MVR evaporation crystallization process.

[0057] Example 2

[0058] This embodiment provides a method for treating concentrated sodium chloride brine, using the concentrated sodium chloride brine treatment system described in any of the above embodiments. For details, please refer to... Figure 3 , Figure 3 This is a schematic flowchart of the sodium chloride concentrated brine treatment method provided in this embodiment. From... Figure 3 As can be seen, the processing method includes:

[0059] S100: The sodium chloride brine is concentrated using a membrane to obtain a concentrated solution;

[0060] S200: The concentrate is subjected to salt precipitation treatment using an organic solvent to obtain sodium chloride product salt and a mixture containing the organic solvent;

[0061] S300: The mixture is recycled.

[0062] Since the sodium chloride brine treatment method provided in this embodiment belongs to the same inventive concept as the sodium chloride brine treatment system provided in any of the above embodiments, the sodium chloride brine treatment method provided in this embodiment has at least all the advantages of the sodium chloride brine treatment system provided in the above embodiments. For the advantages of the sodium chloride brine treatment method provided in this embodiment, please refer to the relevant description of the beneficial effects of the sodium chloride brine treatment system provided in the above embodiments, which will not be repeated here.

[0063] To better understand the present invention, the following two specific examples of treating concentrated sodium chloride brine using the method provided by the present invention will be used to illustrate the present invention.

[0064] Example 1: In this example, the water quality of the concentrated sodium chloride brine is as follows: TDS approximately 12000 mg / L, sodium ion concentration approximately 5000 mg / L, chloride ion concentration approximately 6200 mg / L, and TOC approximately 110 mg / L. The process of treating this concentrated sodium chloride brine using the method provided by this invention is described below.

[0065] First, the concentrated sodium chloride brine is sent to an RO reverse osmosis unit for concentration by 2.5 times, and then sent to a DTRO reverse osmosis unit for concentration by 5 times to obtain a concentrate. In this concentrate, the TDS is approximately 160,000 mg / L, the sodium ion concentration is approximately 82,000 mg / L, the chloride ion concentration is approximately 85,000 mg / L, and the TOC is approximately 1,750 mg / L.

[0066] Then, the concentrate enters the desalination tower, where an organic solvent is added at a dosage ratio of 12%. The main components of the organic solvent are 20% dioxane, 15% ethyl propionate, 20% polyethylene glycol, 25% ethanol, and 20% cyclohexanone (by volume). The concentrate and the organic solvent are mixed using a paddle stirrer at a preset stirring intensity of 150 rpm for a preset stirring time of 12 minutes to form a mixed solution. After the mixed solution is allowed to stand for 0.7 hours, it is then diluted with 7 g / (m³) of water. 2 The solid salt mixture gradually concentrates and precipitates at a rate of h), forming fine crystal nuclei with a size of 6-7 micrometers. With prolonged settling time, these nuclei gradually enlarge, forming visible crystal particles. After 2.5 hours of settling, approximately 75% of the solid salt mixture in the desalination tower crystallizes out, with crystal nuclei approximately 150 micrometers in size, and settles to the bottom of the tower, with a sediment thickness of approximately 9 centimeters. The crystallized solid salt mixture is discharged from the bottom outlet of the desalination tower to a centrifuge for solid-liquid separation. The separated solid salt is then dried in a dryer to obtain sodium chloride product salt with a purity of approximately 92%. Simultaneously, the organic solvent mass fraction in the upper layer of the desulfurization tower mixture is approximately 25%, with a TDS of approximately 17000 mg / L and a TOC of approximately 3220 mg / L.

[0067] Next, the mixture is discharged from the desalination tower to the membrane distillation unit 31 for recovery. The membrane module 313 in the membrane distillation unit 31 uses a cross-linked fluorinated modified polytetrafluoroethylene nanofiber membrane with a pore size of 0.2 micrometers, a porosity of 60%, a thickness of 238 micrometers, and a contact angle of 135°. This membrane module 313 exhibits good amphoteric properties and chemical stability, enabling efficient separation of organic solvents from the mixed solution. The mixture first enters the first preheater 311 to be preheated to 35°C, then enters the first heater 312, where it is heated to 60°C by steam. The organic solvents in the mixture form organic solvent vapors and pass through the membrane module 313 to the other side. The salt-containing concentrate in the mixture is discharged from the concentrate side of the membrane module 313 to the catalytic reaction unit 32. The TDS of this salt-containing concentrate is approximately 16500 mg / L, the TOC is approximately 1850 mg / L, and the temperature is approximately 60°C. Next, the organic solvent vapor enters condenser 314 to cool and form distillate, with a temperature of approximately 45°C. The distillate is then sent to the first preheater 311 to preheat the mixture entering the first preheater 311. After four stages of membrane distillation at a membrane flux of 15 L / (m²·h), organic solvent permeate with a mass fraction of approximately 82% is obtained. This organic solvent permeate is returned to the desalination tower for recycling. The saline concentrate is first discharged from the concentrate side of membrane module 313 to the second preheater 321 in the catalytic reaction unit 32 for preheating to 82°C, then enters the second heater 322. After being heated to 135°C by steam, it enters the catalytic reaction tower 323 for a low-temperature wet catalytic oxidation reaction at a reaction pressure of 0.5 MPa and a residence time of 75 minutes. The catalytic reaction tower 323 contains a nitrogen-doped biochar catalyst, which occupies 65% of the total volume of the catalytic reaction tower 323. The catalyst in catalytic reaction tower 323 promotes the activation of oxygen molecules, generating hydroxyl radicals that rapidly oxidize and decompose organic matter in the saline concentrate, yielding purified effluent and a mixture of steam and water. The effluent has a TDS of approximately 16530 mg / L and a TOC of approximately 255 mg / L. This steam and water mixture is then sent back to the second preheater 321 to preheat the saline concentrate entering the preheater. The effluent is then sent to the inlet of the membrane concentration unit 1 and mixed with sodium chloride brine for further membrane concentration treatment.

[0068] In summary, compared with the traditional MVR evaporation crystallization process, which has an operating cost of 49 yuan / ton of water, the sodium chloride brine treatment method provided by this invention reduces the membrane distillation operating cost to approximately 35.6 yuan / ton of water, resulting in lower energy consumption. Furthermore, the salt-containing concentrated water produced by membrane distillation is treated by the catalytic reaction device 32 and then transported to the inlet of the membrane concentration unit 1 for further treatment, thus avoiding the problem of handling mixed salts.

[0069] Example 2: In this example, the water quality of the concentrated sodium chloride brine is as follows: TDS approximately 14500 mg / L, sodium ion concentration approximately 5300 mg / L, chloride ion concentration approximately 6420 mg / L, and TOC approximately 178 mg / L. The process of treating this concentrated sodium chloride brine using the method provided by this invention is described below.

[0070] First, the concentrated sodium chloride brine is sent to an RO reverse osmosis unit for concentration by 3 times, and then sent to a DTRO reverse osmosis unit for concentration by 5 times to obtain a concentrate. In this concentrate, the TDS is approximately 197,500 mg / L, the sodium ion concentration is approximately 85,000 mg / L, the chloride ion concentration is approximately 96,300 mg / L, and the TOC is approximately 2,500 mg / L.

[0071] Then, the concentrate enters the desalination tower, where an organic solvent is added at a dosage ratio of 15%. The main components of the organic solvent are 30% dioxane, 10% ethyl propionate, 15% polyethylene glycol, 25% ethanol, and 20% cyclohexanone (by volume). The concentrate and the organic solvent are mixed and stirred using a paddle stirrer at a preset stirring intensity of 150 rpm for a preset stirring time of 14 minutes to form a mixed solution. After the mixed solution is allowed to stand for 1 hour, it is then diluted with 7.8 g / (m³). 2 The solid salt mixture gradually concentrates and precipitates at a rate of ·h), forming fine crystal nuclei with a size of 7-8 micrometers. With prolonged settling time, these nuclei gradually enlarge, forming visible crystal particles. After 3 hours of settling, approximately 80% of the solid salt mixture in the desalination tower crystallizes out, with crystal nuclei approximately 180 micrometers in size, and settles to the bottom of the tower, with a sediment thickness of approximately 9 centimeters. The crystallized solid salt mixture is discharged from the bottom outlet of the desalination tower to a centrifuge for solid-liquid separation. The separated solid salt is then dried in a dryer to obtain sodium chloride product salt with a purity of approximately 91%. Simultaneously, the organic solvent mass fraction in the upper layer of the desulfurization tower mixture is approximately 23%, with a TDS of approximately 18500 mg / L and a TOC of approximately 3650 mg / L.

[0072] Next, the mixture is discharged from the desalination tower to the membrane distillation unit 31 for recovery. The membrane module 313 in the membrane distillation unit 31 uses a cross-linked fluorinated modified polytetrafluoroethylene nanofiber membrane with a pore size of 0.3 micrometers, a porosity of 70%, a thickness of 280 micrometers, and a contact angle of 140°. This membrane module 313 exhibits good amphoteric properties and chemical stability, enabling efficient separation of organic solvents from the mixed solution. The mixture first enters the first preheater 311 and is preheated to 40°C, then enters the first heater 312, where it is heated to 65°C by steam. The organic solvents in the mixture form organic solvent vapors and pass through the membrane module 313 to the other side. The salt-containing concentrate in the mixture is discharged from the concentrate side of the membrane module 313 to the catalytic reaction unit 32. The TDS of this salt-containing concentrate is approximately 17900 mg / L, the TOC is approximately 1920 mg / L, and the temperature is approximately 65°C. Next, the organic solvent vapor enters condenser 314 to cool and form distillate, with a temperature of approximately 50°C. The distillate is then sent to the first preheater 311 to preheat the mixture entering the first preheater 311. After four stages of membrane distillation at a membrane flux of 16 L / (m²·h), organic solvent permeate with a mass fraction of approximately 85% is obtained. This organic solvent permeate is returned to the desalination tower for recycling. The saline concentrate is first discharged from the concentrate side of membrane module 313 to the second preheater 321 in the catalytic reaction unit 32 for preheating to 90°C, then enters the second heater 322. After being heated to 140°C by steam, it enters the catalytic reaction tower 323 for a low-temperature wet catalytic oxidation reaction at a reaction pressure of 0.5 MPa and a residence time of 85 minutes. The catalytic reaction tower 323 contains a nitrogen-doped biochar catalyst, which occupies 70% of the total volume of the catalytic reaction tower 323. The catalyst in catalytic reaction tower 323 promotes the activation of oxygen molecules, generating hydroxyl radicals that rapidly oxidize and decompose organic matter in the saline concentrate, yielding purified effluent and a mixture of steam and water. The effluent has a TDS of approximately 17580 mg / L and a TOC of approximately 311 mg / L. This steam and water mixture is then sent back to the second preheater 321 to preheat the saline concentrate entering the second preheater 321. The effluent is then sent to the inlet of the membrane concentration unit 1 and mixed with sodium chloride brine for further membrane concentration treatment.

[0073] In summary, compared with the traditional MVR evaporation crystallization process, which has an operating cost of 50.2 yuan / ton of water, the sodium chloride brine treatment method provided by this invention has a membrane distillation operating cost of approximately 37.1 yuan / ton of water, resulting in lower energy consumption. Furthermore, the salt-containing concentrated water produced by membrane distillation is treated by the catalytic reaction device 32 and then transported to the inlet of the membrane concentration unit 1 for further treatment, thus avoiding the problem of handling mixed salts.

[0074] In summary, the sodium chloride concentrated brine treatment system and method provided by the present invention have the following advantages: The sodium chloride concentrated brine treatment system provided by the present invention includes a membrane concentration unit, a salt precipitation treatment unit, and a recovery treatment unit arranged sequentially; the membrane concentration unit is configured to: perform membrane concentration treatment on the sodium chloride concentrated brine to obtain a concentrated solution; the salt precipitation treatment unit is configured to: perform salt precipitation treatment on the concentrated solution using an organic solvent to obtain a mixture of sodium chloride product salt and the organic solvent; the recovery treatment unit is configured to: perform recovery treatment on the mixture. Therefore, the sodium chloride concentrated brine treatment system provided by the present invention first increases the salt content of the sodium chloride concentrated brine by performing membrane concentration treatment on the sodium chloride concentrated brine through the membrane concentration unit, which can reduce the energy consumption of subsequent treatment units. Then, the salt precipitation treatment unit uses an organic solvent to perform salt precipitation treatment on the concentrated solution after membrane concentration treatment. The addition of the organic solvent can reduce the polarity of the concentrated solution, thereby effectively reducing the solubility of sodium chloride salt in the concentrated solution, and thus increasing the precipitation amount of sodium chloride salt. Finally, the mixed liquid containing organic solvents obtained after salt precipitation treatment is recycled through the recycling unit. This not only enables the dual resource utilization of organic solvents and saline wastewater, but also reduces treatment costs, laying a good foundation for promoting green development.

[0075] Since the sodium chloride concentrated brine treatment method and the sodium chloride concentrated brine treatment system provided by this invention belong to the same inventive concept, the sodium chloride concentrated brine treatment method provided by this invention has at least all the advantages of the sodium chloride concentrated brine treatment system provided by this invention. For the advantages of the sodium chloride concentrated brine treatment method provided by this invention, please refer to the relevant description of the beneficial effects of the sodium chloride concentrated brine treatment system provided by this invention, which will not be repeated here.

[0076] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention.

Claims

1. A sodium chloride concentrated brine treatment system, characterized in that, It includes a membrane concentration unit, a salt precipitation treatment unit, and a recovery treatment unit arranged in sequence; The membrane concentration unit is configured to: perform membrane concentration treatment on the sodium chloride brine to obtain a concentrated solution; The salt precipitation treatment unit is configured to: use an organic solvent to perform salt precipitation treatment on the concentrate to obtain sodium chloride product salt and a mixture containing the organic solvent; The recycling unit is configured to: recycle the mixture; The organic solvent includes 15% to 30% by volume of dioxane, 10% to 15% of ethyl propionate, 10% to 20% of polyethylene glycol, 15% to 25% of ethanol and 10% to 20% of cyclohexanone. The recovery and treatment unit includes a membrane distillation device and a catalytic reaction device arranged sequentially. The membrane distillation device is configured to: perform membrane distillation treatment on the mixture to obtain organic solvent permeate and salt concentrate, and transport the organic solvent permeate to the salt precipitation treatment unit and the salt concentrate to the catalytic reaction device. The catalytic reaction device is configured to: perform low-temperature wet catalytic oxidation treatment on the salt concentrate to obtain effluent and a steam-water mixture, and transport the effluent to the inlet end of the membrane concentration unit and the steam-water mixture to the catalytic reaction device.

2. The sodium chloride concentrated brine treatment system as described in claim 1, characterized in that, The salt precipitation treatment unit includes a desalination device, a solid-liquid separation device, and a drying device arranged in sequence. The desalination device is equipped with a stirrer. The desalination device is connected to the recovery treatment unit. The desalination device is configured to desalinate the concentrate using an organic solvent to obtain a solid salt mixture and a mixture containing the organic solvent, and to transport the mixture to the recovery processing unit. The stirrer is configured to stir the mixed solution in the desalination device at a preset stirring intensity of 100 rpm to 200 rpm and a preset stirring duration of 10 minutes to 15 minutes. The solid-liquid separation device is configured to perform solid-liquid separation treatment on the solid salt mixture to obtain solid salt; The drying apparatus is configured to dry the solid salt to obtain the sodium chloride product salt.

3. The sodium chloride concentrated brine treatment system as described in claim 1, characterized in that, The preset addition ratio of the organic solvent is in the range of 10% to 15%, wherein the preset addition ratio of the organic solvent refers to the volume ratio of the organic solvent to the concentrate.

4. The sodium chloride concentrated brine treatment system as described in claim 1, characterized in that, The membrane distillation apparatus includes a first preheater, a first heater, a membrane module, and a condenser arranged sequentially. The first preheater is configured to receive the mixture and the distillate output from the condenser, so that the mixture and the distillate exchange heat to obtain the organic solvent product water and the preheated mixture, and to make the temperature of the preheated mixture 30°C~40°C. The first heater is configured to heat the preheated mixture to obtain the heated mixture, and to make the temperature of the heated mixture 60°C to 80°C. The membrane module is configured to perform membrane separation treatment on the heated mixture to obtain organic solvent vapor and the salt-containing concentrated water; The condenser is configured to condense the organic solvent vapor to obtain a distillate.

5. The sodium chloride concentrated brine treatment system as described in claim 4, characterized in that, The membrane module includes a cross-linked fluorinated modified polytetrafluoroethylene nanofiber membrane with a pore size of 0.1 μm to 0.3 μm, a porosity of 60% to 75%, a thickness of 200 μm to 300 μm, and a contact angle greater than 130°.

6. The sodium chloride concentrated brine treatment system as described in claim 1, characterized in that, The catalytic reaction device includes a second preheater, a second heater, and a catalytic reaction tower arranged in sequence. The second preheater is configured to receive the salt-containing concentrated water and the steam-water mixture output from the catalytic reaction tower, so that the salt-containing concentrated water and the steam-water mixture exchange heat to obtain the preheated salt-containing concentrated water, and to make the temperature of the preheated salt-containing concentrated water 80°C~90°C. The second heater is configured to heat the preheated saline concentrate to obtain heated saline concentrate, and to make the temperature of the heated saline concentrate 120°C to 150°C. The catalytic reaction tower is configured to subject the heated salt concentrate to a low-temperature wet catalytic oxidation reaction at a reaction pressure of 0.4 MPa to 0.6 MPa and a residence time of 60 to 90 minutes, to obtain effluent and a steam-water mixture, and to deliver the effluent to the inlet of the membrane concentration unit and the steam-water mixture to the second preheater.

7. A method for treating concentrated sodium chloride brine, characterized in that, The sodium chloride brine treatment system as described in any one of claims 1 to 6 is used to treat sodium chloride brine, the treatment method comprising: The sodium chloride brine was subjected to membrane concentration treatment to obtain a concentrated solution; The concentrate was subjected to salt precipitation treatment using an organic solvent to obtain sodium chloride product salt and a mixture containing the organic solvent. The mixture is then recycled.

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