Treatment device for ternary precursor material production mother liquor

Abstract

The utility model provides a ternary precursor material production mother liquor treatment device which comprises an alkali liquor reaction tank, a deamination unit, a flow control unit, a pH (Potential of Hydrogen) adjusting tank, a spiral-wound membrane concentration inlet liquor storage tank and a spiral-wound membrane concentration unit, the flow control unit comprises a first-stage flow control unit and a second-stage flow control unit, and has the beneficial effects that firstly, ammonia nitrogen substances in liquid to be treated are separated out in the form of ammonia gas under the action of second-stage vacuum flash evaporation, and only relatively pure sodium sulfate is left in mother liquor; then carrying out concentration operation through a combined spiral-wound membrane element, further increasing the concentration of sodium sulfate in the mother liquor material to 20% or above, and carrying out heat removal evaporation operation on the concentrated material; the vaporization water quantity of the evaporation system is reduced, and the energy consumption of the treatment device for the ternary precursor material production mother liquor can be reduced.

Description

Technical Field

[0001] The utility model relates to the technical field of processing mother liquor in the production of ternary precursor materials, in particular to a processing device for the mother liquor in the production of ternary precursor materials. Background Art

[0002] At present, the battery production industry needs to use a large amount of ternary precursor materials. Currently, ternary precursor materials mainly include nickel, cobalt and manganese hydroxide. In the production method of ternary precursor materials, most of them adopt the complex coprecipitation chemical production process, and its production process inevitably involves the post-treatment and reuse of the mother liquor. From the production process point of view, the production mother liquor must be mixed with a small amount of heavy metal components, certain ammonia substances and a certain concentration of sodium sulfate components. The ammonia nitrogen concentration is between 3000 and 8000 mg / L, and the sodium sulfate concentration is about 5 to 10%.

[0003] At present, the core idea of ​​treating wastewater from the chemical production of ternary precursor materials is how to remove the above three substances. The most common approach is to adjust the pH to remove heavy metal components and then separate them; then deammoniate by steam stripping, and then use MVR to evaporate the wastewater to recover the sodium sulfate component.

[0004] The prior art retrieved is as follows:

[0005] Patent 1, a utility model patent with application number 202222771798.2, discloses a precursor material recovery system in a ternary precursor mother liquor, comprising a primary washing unit composed of a first buffer tank, a first washing device, a first filter and a first filter material tank; the primary washing unit comprises a first pipeline, a second pipeline, a third pipeline and a fourth pipeline; the first buffer tank and the first washing device are connected through the first pipeline, the first washing device and the first filter are connected through the second pipeline, the first filter and the first filter material tank are connected through the third pipeline, and the first filter material tank and the fourth pipeline are connected through the fourth pipeline; it also includes a secondary washing unit composed of a slurry tank, a second buffer tank, a second washing device, a second filter and a second filter material tank.

[0006] Patent 2, a utility model patent with application number 202121526004.5, discloses a ternary precursor mother liquor wastewater deamination distillation heat pump system, including a deamination wastewater tank, a preheating storage tank, a distillation tower, a steam replenishment tank, a jet heat pump, a flash tank, a first pump, a second pump, and a third pump; the outer layer of the preheating storage tank is provided with a heat-transferable heating interlayer; the steam outlet at the top of the flash tank is connected to the medium-pressure steam inlet pipeline of the jet heat pump, and the top high-pressure steam inlet of the jet heat pump is connected to the bottom steam outlet pipeline of the steam replenishment tank, and the bottom steam outlet of the jet heat pump is connected to the distillation tower pipeline.

[0007] Patent 3, an invention patent with application number 201811269761.1, discloses a near-zero emission treatment system and process for ternary precursor production wastewater, which uses precipitation to recover heavy metals and two-stage MVR technology to recycle water, ammonia, and sodium sulfate in the wastewater. The ammonia gas volatilized and escaped during the wastewater heating and heavy metal precipitation and clarification process is recovered, and the ammonia water produced is reused for production. Water vapor and ammonia gas are produced during the MVR primary evaporation and concentration separation process. Ammonia gas is recovered while condensed water is recovered for the production of ammonia water. This integrated technology for simultaneously recovering water and ammonia replaces the existing single-process high-energy consumption steam stripping ammonia recovery technology, which not only reduces the processing steps and reduces the operating costs, but also uses the secondary MVR evaporation and crystallization technology to recycle alum and condensed water.

[0008] Although the above patents can provide diverse technologies, due to the characteristics of high ammonia ion concentration and low sodium sulfate concentration of the incoming water, in order to achieve the treatment purpose, it is inevitable to heat the entire mother liquor and perform stripping, deammoniation and evaporation at high temperature. The energy consumption of the evaporation and stripping processes is directly related to the amount of final vaporized products. The full-flow high-temperature treatment process will inevitably consume a large amount of energy, resulting in extremely high power consumption or steam consumption of the treatment device, which ultimately leads to the low economic value of the by-product sodium sulfate system. Utility Model Content

[0009] In order to overcome the above problems existing in the prior art, the utility model provides a processing device for producing mother liquor of ternary precursor materials.

[0010] The utility model discloses a processing device for producing mother liquor of ternary precursor material, comprising an alkali liquor reaction tank, a deamination unit, a flow control unit, a pH adjustment tank, a roll membrane concentration liquid inlet storage tank and a roll membrane concentration unit, wherein the deamination unit comprises a primary flash evaporation unit and a secondary flash evaporation unit, the flow control unit comprises a primary flow control unit and a secondary flow control unit, the alkali liquor reaction tank is connected to the primary flash evaporation unit, a primary flow control unit is arranged between the primary flash evaporation unit and the secondary flash evaporation unit, the secondary flash evaporation unit is connected to the secondary flow control unit, the secondary flow control unit is connected to the pH adjustment tank, the pH adjustment tank is connected to the roll membrane concentration liquid inlet storage tank, and the roll membrane concentration liquid inlet storage tank is connected to the roll membrane concentration unit.

[0011] On this basis, the primary flash unit includes a primary flash storage tank, a primary circulation pump, a primary vacuum pump and a primary flash booster. The primary flash booster is arranged in the primary flash storage tank. A primary vacuum pump is connected above the primary flash storage tank. A primary circulation pump is arranged below the primary flash storage tank. The outlet of the primary circulation pump is connected to a primary flow control unit. The connecting section between the primary circulation pump and the primary flow control unit is connected to the primary flash booster through a pipeline.

[0012] On this basis, the secondary flash unit has the same structure as the primary flash unit, and comprises a secondary flash storage tank, a secondary circulation pump, a secondary vacuum pump and a secondary flash booster. The secondary flash booster is arranged in the secondary flash storage tank, a secondary vacuum pump is connected above the secondary flash storage tank, a secondary circulation pump is arranged below the secondary flash storage tank, an outlet of the secondary circulation pump is connected to a secondary flow control unit, and a connecting section between the secondary circulation pump and the secondary flow control unit is connected to the secondary flash booster through a pipeline.

[0013] On this basis, the pressure operating condition of the secondary flash unit is lower than that of the primary flash unit.

[0014] On this basis, the roll membrane concentration unit includes a high-pressure pump, a first-stage roll membrane concentration and a second-stage roll membrane concentration. The inlet of the high-pressure pump is connected to the roll membrane concentration inlet storage tank, and the outlet of the high-pressure pump is connected to the first-stage roll membrane concentration. After the first-stage roll membrane concentration is separated, one stage of produced water and one stage of concentrated water are obtained. The first stage of produced water is sent out, and the first stage of concentrated water is connected to the inlet of the second-stage roll membrane concentration. After the second-stage roll membrane concentration is separated, two stages of produced water and two stages of concentrated water are obtained. The two-stage roll membrane concentration is connected to the roll membrane concentration inlet storage tank through a pipeline.

[0015] On this basis, the first-stage rolled membrane concentration adopts a rolled reverse osmosis membrane, and the second-stage rolled membrane concentration adopts a rolled nanofiltration membrane.

[0016] Compared with the prior art, the beneficial effects of the utility model are:

[0017] (1) The utility model first uses the effect of secondary vacuum flash evaporation to precipitate ammonia nitrogen in the liquid to be treated in the form of ammonia gas, leaving only relatively pure sodium sulfate in the mother liquor, and then uses a combined spiral membrane element to perform a concentration operation to further increase the sodium sulfate concentration in the mother liquor material, so that the sodium sulfate concentration is concentrated to more than 20%, and the concentrated material is then sent to a thermal evaporation operation; the amount of vaporized water in the evaporation system is reduced, and the energy consumption of the treatment device for the production of the mother liquor of the ternary precursor material can also be reduced. The treatment device reduces the cost consumption of the final by-product sodium sulfate, and improves the value of the sodium sulfate by-product system;

[0018] (2) The utility model uses vacuum analysis to separate ammonia nitrogen from the production mother liquor, and does not need to heat up the entire production mother liquor, thus reducing the consumption level of the deammoniation process; it uses membrane concentration to concentrate the sodium sulfate in the production mother liquor, and this process does not need to heat up the entire production mother liquor, while reducing the total amount of water evaporated, thus reducing the consumption level of sodium sulfate concentration production;

[0019] (3) The utility model adopts a membrane concentration method of two-stage water production circulation and graded desalination, so that the membrane concentration device does not need to overcome 20% of the sodium sulfate osmotic pressure to complete the concentration process, breaking through the limitation that the traditional membrane concentration device must be completely greater than the final concentrated liquid osmotic pressure, thereby achieving a higher sodium sulfate concentration of the spiral membrane concentration;

[0020] (4) In the present invention, the operating pressure of the membrane concentration unit is lower than 20% of the osmotic pressure of sodium sulfate, thereby avoiding the boosting equipment and pressure-resistant equipment of ultra-high pressure spiral membrane concentration, further achieving the consumption level during sodium sulfate concentration, while broadening the selectivity of the equipment and reducing the equipment cost level. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 This is a schematic diagram of the structure of a processing device for producing mother liquor of a ternary precursor material of the utility model;

[0022] In the figure: 101, alkali solution reaction tank, 102, primary flash unit, 201, primary flash storage tank, 202, primary circulation pump, 203, primary vacuum pump, 204, primary flash booster, 103, primary flow control unit, 104, secondary flash unit, 401, secondary flash storage tank, 402, secondary circulation pump, 403, secondary vacuum pump, 404, secondary flash booster, 105, secondary flow control unit, 106, pH adjustment tank, 107, spiral membrane concentration inlet storage tank, 108, spiral membrane concentration unit, 801, high pressure pump, 802, first stage spiral membrane concentration, 803, second stage spiral membrane concentration. DETAILED DESCRIPTION

[0023] The present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0024] The utility model discloses a processing device for producing mother liquor of ternary precursor material, referring to Figure 1, including an alkali liquid reaction tank 101, a deamination unit, a flow control unit, a pH adjustment tank 106, a roll membrane concentration liquid storage tank 107 and a roll membrane concentration unit 108. In this embodiment, the deamination unit includes a primary flash evaporation unit 102 and a secondary flash evaporation unit 104, and the flow control unit includes a primary flow control unit 103 and a secondary flow control unit 105.

[0025] First, the mother liquor after heavy metal removal, with an ammonia nitrogen concentration of 4762 mg / L and a sodium sulfate concentration of 90 g / L, enters the alkali liquid reaction tank 101. The pH value of the alkali liquid reaction tank 101 is detected to be 11.2. A 10% sodium hydroxide solution is added to further increase the pH value of the mother liquor to 11-13. The alkali liquid reaction tank 101 is connected to the primary flash unit 102. The primary flash unit 102 includes a primary flash storage tank 201, a primary circulation pump 202, a primary vacuum pump 203 and a primary flash booster 204. The primary flash booster 204 is arranged in the primary flash storage tank 201. The primary vacuum pump 203 is connected above the primary flash storage tank 201. The primary circulation pump 202 is arranged below the primary flash storage tank 201. The outlet of the primary circulation pump 202 is connected to the primary flow control unit 103. The connecting section of the primary circulation pump 202 and the primary flow control unit 103 is connected to the primary flash booster 204 through a pipeline.

[0026] In this embodiment, the pressure condition of the primary flash unit 102 is -30kPa~-80kPaG, the primary flash storage tank 201 is a steel container, equipped with a differential pressure level gauge, providing an independent spatial structure that can form a negative pressure, and the steel container is equipped with a pressure display gauge with an operating pressure of -60kPa (G). The ammonia in the mother liquor evaporates in the primary flash storage tank 201 and becomes gaseous ammonia molecules; the primary vacuum pump 203 uses a water ring vacuum pump, and through the suction action, a higher negative pressure appears in the primary flash storage tank 201 to create a negative pressure environment; the primary circulation pump 202 is connected to the primary flash booster 204, and the primary circulation pump 202 uses a PP magnetic pump with a head of 20m, so that the mother liquor in the primary flash storage tank 201 can be fully circulated and the feed liquid can be pressurized at the same time. The primary flash booster 204 uses a DN15 silicon carbide spiral nozzle, and atomized droplets are formed after passing through the primary flash booster 204. After atomization, the liquid feed has a large surface area, and the ammonia gas-liquid separation and mass transfer effect is improved, thereby meeting the mass transfer requirements for ammonia escape.

[0027] A primary flow control unit 103 is disposed between the primary flash unit 102 and the secondary flash unit 104. The primary flow control unit 103 uses an automatic ball valve interlocked with the liquid level, which can automatically adjust the flow entering the secondary flash unit 104. The pressure operating condition of the secondary flash unit 104 is lower than that of the primary flash unit 102. In this embodiment, the pressure condition of the secondary flash unit 104 is -60kPa to -95kPaG. The secondary flash unit 104 has the same structure as the primary flash unit 102. The secondary flash unit 104 includes a secondary flash storage tank 401, a secondary circulation pump 402, a secondary vacuum pump 403 and a secondary flash booster 404. The secondary flash booster 404 is arranged in the secondary flash storage tank 401. The secondary vacuum pump 403 is connected above the secondary flash storage tank 401. The secondary circulation pump 402 is arranged below the secondary flash storage tank 401. The outlet of the secondary circulation pump 402 is connected to the secondary flow control unit 105. The connecting section of the secondary circulation pump 402 and the secondary flow control unit 105 is connected to the secondary flash booster 404 through a pipeline. The secondary flash storage tank 401 adopts a steel container, and the steel container is equipped with a digital pressure gauge with an operating pressure of -88kPa (G). The secondary circulation pump 402 adopts a steel centrifugal pump with a head of 30m. The secondary vacuum pump 403 adopts a water ring vacuum pump. The secondary flash booster 404 uses a DN15 silicon carbide spiral nozzle, and its working principle is the same as that of the primary flash unit 102. Through the secondary vacuum flash evaporation, the ammonia nitrogen substance in the liquid to be treated is precipitated in the form of ammonia gas, and only relatively pure sodium sulfate remains in the mother liquor. Then, the combined spiral membrane element is used for concentration operation to further increase the sodium sulfate concentration in the mother liquor material, so that the sodium sulfate concentration is concentrated to more than 20%. After concentration, the material is sent to thermal evaporation operation; the amount of vaporized water in the evaporation system is reduced, and the energy consumption of the treatment device for the production mother liquor of the ternary precursor material can also be reduced. The cost consumption of the final by-product sodium sulfate is reduced through the treatment device, and the value of the sodium sulfate by-product system is increased; the separation of ammonia nitrogen substances in the production mother liquor is achieved by means of vacuum analysis, and the entire production mother liquor water volume does not need to be heated, thereby reducing the consumption level of the deammoniation process; the concentration of sodium sulfate substances in the production mother liquor is achieved by means of membrane concentration, and the process does not need to heat the entire production mother liquor water volume, while reducing the total amount of evaporated water, thereby reducing the consumption level of sodium sulfate concentration production.

[0028] The secondary flash unit 104 is connected to the secondary flow control unit 105. The secondary flow control unit 105 uses an automatic ball valve interlocked with the liquid level. The secondary flow control unit 105 is connected to the pH adjustment tank 106 to control the flow entering the pH adjustment tank 106. The pH is adjusted by adding acid solution into the pH adjustment tank 106. A diaphragm metering pump is used for acid addition. In this embodiment, 1-30% sulfuric acid is added to the pH adjustment tank 106. The pH adjustment tank 106 uses a pipeline mixer, and the outlet is equipped with a pH meter to control the pH in the pH adjustment tank 106 at 6-9. In this embodiment, the acid solution is 5% sulfuric acid, and the pH is controlled at 8.1-8.5. After testing, the ammonia nitrogen value of the material after the pH is adjusted is 37 mg / L. The pH adjustment tank 106 is connected to the roll membrane concentration liquid inlet storage tank 107. The roll membrane concentration liquid inlet storage tank 107 uses a PP storage tank with a stirrer.

[0029] The roll membrane concentration liquid inlet storage tank 107 is connected to the roll membrane concentration unit 108. The roll membrane concentration unit 108 includes a high-pressure pump 801, a first-stage roll membrane concentration 802 and a second-stage roll membrane concentration 803. The operating pressure of the roll membrane concentration unit 108 is 74 bar. The high-pressure pump 801 uses a plunger pump with a head of 900 m. The inlet of the high-pressure pump 801 is connected to the roll membrane concentration liquid inlet storage tank 107, and the outlet of the high-pressure pump 801 is connected to the first-stage roll membrane concentration 802. After the first-stage roll membrane concentration 802 is separated, a first-stage produced water and a first-stage concentrated water are obtained. The first-stage produced water is sent out to meet the production reuse requirements; the first-stage concentrated water is connected to the inlet of the second-stage roll membrane concentration 803, and the second-stage concentrated water is connected to the inlet of the second-stage roll membrane concentration 803. After separation by the roll membrane concentrator 802, second-stage produced water and second-stage concentrated water are obtained. The second-stage roll membrane concentrator 803 is connected to the roll membrane concentrate liquid inlet storage tank 107 through a pipeline, that is, it is connected to the second-stage roll membrane separation produced water pipeline, so that the second-stage produced water is refluxed, and the two materials are mixed in the roll membrane concentrate liquid inlet storage tank 107; the second-stage concentrated water can meet the final requirement of the aforementioned production mother liquor concentration; the membrane concentration method of the second-stage produced water circulation and graded desalination is adopted, so that the membrane concentration device does not need to overcome 20% of the sodium sulfate osmotic pressure to complete the concentration process, breaking through the limitation that the traditional membrane concentration device must be completely greater than the final concentrated liquid osmotic pressure, thereby realizing the roll membrane concentration with a higher sodium sulfate concentration.

[0030] In this embodiment, the first-stage spiral membrane concentration 802 adopts a spiral reverse osmosis membrane, whose operating pressure is between 6MPa-9Mpa, the pressure resistance level is 80bar, the salt removal rate is above 99%, the sodium sulfate concentration of the produced water is 4.7g / L, and the sodium sulfate of the concentrated solution is 16.4%. The second-stage spiral membrane concentration 803 adopts a spiral nanofiltration membrane, whose operating pressure is between 6MPa-9Mpa, the pressure resistance level is 80bar, the salt removal rate is between 45-70%, the sodium sulfate concentration of the produced water is 138g / L, and the sodium sulfate of the concentrated solution is 20.8%; the operating pressure of the spiral membrane concentration unit 108 is lower than 20% of the sodium sulfate osmotic pressure, thereby avoiding the boosting equipment and pressure-resistant equipment of the ultra-high pressure spiral membrane concentration, further realizing the consumption level during sodium sulfate concentration, while the selectivity of the equipment is broadened and the equipment cost level can also be reduced.

[0031] The above-mentioned connected equipment can achieve the sodium sulfate concentration of the ternary precursor material production mother liquor to be increased to 20%, and the ammonia concentration therein can be less than 300 mg / L.

[0032] In the description of the present invention, it should be understood that the terms "coaxial", "bottom", "one end", "top", "middle", "the other end", "upper", "one side", "top", "inside", "front", "center", "both ends" and the like indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as a limitation on the present invention.

[0033] In the present utility model, unless otherwise clearly stipulated and limited, the terms such as "installation", "setting", "connection", "fixation", "screwing", "pad installation" and the like should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or an integral one; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium; it can be the internal connection of two elements or the interaction relationship between two elements. Unless otherwise clearly defined, ordinary technicians in this field can understand the specific meanings of the above terms in the utility model according to the specific circumstances.

[0034] The above description shows and describes the preferred embodiments of the utility model. As mentioned above, it should be understood that the utility model is not limited to the form disclosed herein, and should not be regarded as excluding other embodiments, but can be used in various other combinations, modifications and environments, and can be modified within the scope of the utility model concept described herein through the above teachings or the technology or knowledge of the relevant field. The changes and modifications made by those skilled in the art do not depart from the spirit and scope of the utility model, and should be within the scope of protection of the claims attached to the utility model.

Claims

1. A processing device for producing mother liquor of ternary precursor material, characterized in that: The invention comprises an alkali liquid reaction tank (101), a deammoniation unit, a flow control unit, a pH adjustment tank (106), a roll membrane concentration inlet storage tank (107) and a roll membrane concentration unit (108); the deammoniation unit comprises a primary flash evaporation unit (102) and a secondary flash evaporation unit (104); the flow control unit comprises a primary flow control unit (103) and a secondary flow control unit (105); the alkali liquid reaction tank (101) is connected to the primary flash evaporation unit (102); a primary flow control unit (103) is arranged between the primary flash evaporation unit (102) and the secondary flash evaporation unit (104); the secondary flash evaporation unit (104) is connected to the secondary flow control unit (105); the secondary flow control unit (105) is connected to the pH adjustment tank (106); the pH adjustment tank (106) is connected to the roll membrane concentration inlet storage tank (107); and the roll membrane concentration inlet storage tank (107) is connected to the roll membrane concentration unit (108).

2. The device for processing mother liquor of ternary precursor material production according to claim 1, characterized in that: The primary flash unit (102) comprises a primary flash storage tank (201), a primary circulation pump (202), a primary vacuum pump (203) and a primary flash booster (204); the primary flash booster (204) is arranged in the primary flash storage tank (201); the primary vacuum pump (203) is connected to the top of the primary flash storage tank (201); the primary circulation pump (202) is arranged below the primary flash storage tank (201); the outlet of the primary circulation pump (202) is connected to the primary flow control unit (103); and the connecting section between the primary circulation pump (202) and the primary flow control unit (103) is connected to the primary flash booster (204) via a pipeline.

3. The processing device for producing mother liquor of ternary precursor material according to claim 1, characterized in that: The secondary flash unit (104) has the same structure as the primary flash unit (102). The secondary flash unit (104) comprises a secondary flash storage tank (401), a secondary circulation pump (402), a secondary vacuum pump (403) and a secondary flash booster (404). The secondary flash booster (404) is arranged in the secondary flash storage tank (401). The secondary vacuum pump (403) is connected to the upper part of the secondary flash storage tank (401). The secondary circulation pump (402) is arranged below the secondary flash storage tank (401). The outlet of the secondary circulation pump (402) is connected to the secondary flow control unit (105). The connecting section between the secondary circulation pump (402) and the secondary flow control unit (105) is connected to the secondary flash booster (404) through a pipeline.

4. The processing device for producing mother liquor of ternary precursor material according to claim 1, characterized in that: The pressure operating condition of the secondary flash unit (104) is lower than that of the primary flash unit (102).

5. The processing device for producing mother liquor of ternary precursor material according to claim 1, characterized in that: The roll membrane concentration unit (108) includes a high-pressure pump (801), a first-stage roll membrane concentration (802) and a second-stage roll membrane concentration (803). The inlet of the high-pressure pump (801) is connected to the roll membrane concentration inlet storage tank (107), and the outlet of the high-pressure pump (801) is connected to the first-stage roll membrane concentration (802). After separation, the first-stage roll membrane concentration (802) obtains a first stage of produced water and a first stage of concentrated water. The first stage of produced water is sent out, and the first stage of concentrated water is connected to the inlet of the second-stage roll membrane concentration (803). After separation, the second-stage roll membrane concentration (803) obtains a second stage of produced water and a second stage of concentrated water. The second-stage roll membrane concentration (803) is connected to the roll membrane concentration inlet storage tank (107) through a pipeline.

6. The device for processing mother liquor of ternary precursor material production according to claim 5, characterized in that: The first-stage rolled membrane concentration (802) uses a rolled reverse osmosis membrane, and the second-stage rolled membrane concentration (803) uses a rolled nanofiltration membrane.

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