A reverse osmosis membrane device and method for recycling a finishing liquid

Abstract

The application discloses a reverse osmosis membrane device for recycling finishing liquid, which comprises a finishing liquid concentration recovery device and a draw solution regeneration device, the finishing liquid concentration recovery device comprises a water inlet circulating tank, a water inlet circulating pump, a finishing liquid concentration recovery membrane assembly, a draw solution circulating pump and a draw solution circulating tank, and the draw solution regeneration device adopts two-stage reverse osmosis treatment; the application further discloses a method for recycling finishing liquid, which uses the reverse osmosis membrane device for recycling finishing liquid, the finishing liquid concentration recovery device separates the finishing liquid from water by using the osmotic pressure of the draw solution and the water inlet pressure, realizes the concentration of the finishing liquid, and the draw solution is recycled after being regenerated by the reverse osmosis membrane, and the produced water is used as desalted water. The tubular reverse osmosis membrane assembly has high interception rate for the finishing liquid, strong anti-pollution performance, and is easy to clean and replace.

Description

Technical Field

[0001] This invention relates to the field of membrane separation technology, and in particular to a reverse osmosis membrane device for recovering finishing solutions. Background Technology

[0002] With the development of membrane materials and technologies, membrane separation technology, as a novel water treatment technology, has been widely applied in wastewater treatment fields such as biological, chemical, pharmaceutical, food, and municipal industries. Membrane separation technology has become the preferred choice for wastewater upgrading and reclaimed water reuse.

[0003] The separation principle of traditional membrane technology is to select a specific membrane as the separation medium based on the size and type of the substances to be separated. Under the action of a driving force, the substances selectively permeate to achieve the purpose of separation. According to the pore size, membranes can be divided into microfiltration membranes, ultrafiltration membranes, nanofiltration membranes, and reverse osmosis membranes; according to the structure, they can be divided into symmetrical membranes, asymmetrical membranes, and composite membranes; according to the shape, they can be divided into spiral wound membranes, flat sheet membranes, hollow fiber membranes, tubular membranes, etc.

[0004] Reverse osmosis membrane modules typically employ a spiral wound structure, which places high demands on the feed water used in water treatment. Furthermore, the membranes are prone to clogging and have a short lifespan, limiting their application. Tubular membrane modules, on the other hand, offer a wider adjustable feed flow rate range, easier concentration polarization control, and are easier to clean and replace. They also have simpler feed pretreatment requirements, but are only suitable for water treatment systems with high concentrations and high solids content.

[0005] Finishing solutions belong to the field of material surface treatment technology and are generally used as metal surface treatment agents. The effective components of finishing solutions typically include composite rust inhibitors, corrosion inhibitors, surfactants, lubricants, composite additives, bactericides, solubilizers, and pH adjusters. Composite rust inhibitors often employ polybasic acids, organic acids, and organic amines, such as phosphoric acid, boric acid, sebacic acid, alkanolamines, and carboxylic amines. Corrosion inhibitors are thiazole derivatives, such as methylbenztriazole and benzotriazole. Surfactants are generally alkenyl ethers. Lubricants are fatty alcohol phosphate esters or polyether esters. In applications, to improve membrane efficiency and extend membrane lifespan, it is necessary to design membrane modules with strong antifouling properties, easy cleaning, minimal concentration polarization within the membrane module, and ease of maintenance. Summary of the Invention

[0006] To overcome the shortcomings of the prior art, the present invention provides a reverse osmosis membrane device for recovering light finishing solution, which solves the problems mentioned in the background art.

[0007] To achieve the above objectives, the present invention provides the following technical solution:

[0008] A reverse osmosis membrane device for recovering finishing solution includes an inlet water circulation tank. The outlet of the inlet water circulation tank is connected to the finishing solution inlet of the finishing solution concentration and recovery membrane assembly via an inlet water circulation pump. The finishing solution outlet of the finishing solution concentration and recovery membrane assembly is connected to the inlet of the inlet water circulation tank. The first outlet of the extract liquid circulation tank is connected to the extract liquid inlet of the finishing solution concentration and recovery membrane assembly via an extract liquid circulation pump. The extract liquid outlet of the finishing solution concentration and recovery membrane assembly is connected to the inlet of the extract liquid circulation tank.

[0009] The second outlet of the extractant circulation tank is connected in sequence to the inlet of the first-stage extractant regeneration membrane module via the first-stage inlet pump, the booster pump, and the first-stage extractant regeneration membrane module. The concentrate outlet of the first-stage extractant regeneration membrane module is connected to the inlet of the extractant circulation tank and the inlet of the first-stage circulation pump. The outlet of the first-stage circulation pump is connected to the inlet of the first-stage extractant regeneration membrane module. The product water outlet of the first-stage extractant regeneration membrane module is connected to the inlet of the first-stage product water tank.

[0010] The outlet of the primary product water tank is connected to the inlet of the secondary extract regeneration membrane module via the secondary inlet pump. The concentrate outlet of the secondary extract regeneration membrane module is connected to the inlet of the extract circulation tank and the inlet of the secondary circulation pump. The outlet of the secondary circulation pump is connected to the inlet of the secondary extract regeneration membrane module. The product water outlet of the secondary extract regeneration membrane module is connected to the secondary product water tank.

[0011] As described above, the photo-finishing solution concentration and recovery membrane module includes a cylindrical membrane shell, inside which a membrane tube bundle is disposed. The membrane shell has openings at both ends, namely an outlet water opening and an inlet water opening, respectively. The outlet water opening is connected to an outlet water cap, and the inlet water opening is connected to an inlet water cap. A photo-finishing solution outlet and a photo-finishing solution inlet are respectively disposed at the center of the outlet water cap and the inlet water cap. An outlet water sealing end and an inlet water sealing end are respectively disposed at both ends of the membrane tube bundle, wherein the outlet water sealing end is close to the outlet water opening end, and the inlet water sealing end is close to the inlet water opening end. A draw liquid outlet is disposed on the side wall of the membrane shell near the outlet water opening end, and a draw liquid inlet is disposed on the side wall of the membrane shell near the inlet water opening end.

[0012] As described above, the outer wall of the inlet cap and the outer wall of the membrane shell are detachably connected by multiple inlet clamps, and the outer wall of the outlet cap and the outer wall of the membrane shell are detachably connected by multiple outlet clamps.

[0013] As mentioned above, the membrane bundle is a tubular reverse osmosis membrane.

[0014] As mentioned above, online conductivity meters are installed in the inlet water circulation tank, the extract liquid circulation tank, the primary product water tank, and the secondary product water tank.

[0015] As described above, pressure sensors and flow meters are installed on the pipes of the finishing liquid inlet, finishing liquid outlet, draw liquid inlet, and draw liquid outlet.

[0016] As described above, the diameter of a single membrane tube in the membrane tube bundle is 6-8 mm, the filter material of the membrane tube is a polyamide composite membrane, the length of the membrane tube is 1-3 m, the flow velocity inside the membrane tube is 1-2 m / s, and the operating pressure inside the membrane tube is 0.2-0.5 MPa.

[0017] As mentioned above, the draw solution used in the draw solution circulation tank is a sodium chloride solution with a concentration of 20-30 g / L.

[0018] As mentioned above, the primary draw solution regeneration membrane module and the secondary draw solution regeneration membrane module adopt spiral wound reverse osmosis membranes. The operating pressure of the primary draw solution regeneration membrane module is 3-4 MPa, and the permeate conductivity is less than 300 μs / cm. The operating pressure of the secondary draw solution regeneration membrane module is 0.6-1.0 MPa, and the permeate conductivity is less than 10 μs / cm.

[0019] A method for recovering finishing solutions, utilizing a reverse osmosis membrane device for recovering finishing solutions as described above, is characterized by including a treatment step for finishing solutions with low concentrations and a treatment step for finishing solutions with high concentrations.

[0020] For processing steps involving low concentrations of the finishing solution to be recovered:

[0021] Step 1.1: The initial state of the draw liquid circulation tank is empty. The draw liquid circulation pump, primary water inlet pump, booster pump, primary circulation pump, secondary water inlet pump and secondary circulation pump are closed, and the water inlet circulation pump is turned on.

[0022] Step 1.2: When the conductivity of the finishing solution in the inlet water circulation tank reaches the preset concentration, drain the finishing solution from the inlet water circulation tank to the finishing solution storage tank, and re-enter the inlet water circulation tank with a low concentration of finishing solution; monitor the conductivity in the extract liquid circulation tank. When the conductivity of the product water in the extract liquid circulation tank is greater than 10 μS / cm, turn on the primary inlet water pump, booster pump, and primary circulation pump. Keep the inlet water circulation pump on, and keep the extract liquid circulation pump, secondary inlet water pump, and secondary circulation pump off.

[0023] For processing steps involving high concentrations of finishing solutions to be recovered:

[0024] Step 2.1: The draw liquid circulation tank is filled with draw liquid. The draw liquid circulation pump, secondary water inlet pump, secondary circulation pump, water inlet circulation pump, primary water inlet pump, booster pump and primary circulation pump are all turned on. When the conductivity of the finishing liquid in the water inlet circulation tank reaches the preset concentration, the finishing liquid in the water inlet circulation tank is discharged to the finishing liquid storage tank, and low concentration finishing liquid is re-entered into the water inlet circulation tank.

[0025] The present invention has the following significant technical advantages: (1) The present invention can effectively recover light-finishing liquids of different concentrations; (2) The tubular reverse osmosis membrane module used in the first step of the treatment has a larger flow channel and surface flow rate than the spiral wound membrane module, has better anti-fouling performance, and reduces the impact of subsequent purification equipment being blocked by pollutants; (3) The membrane module has a simple structure and is easy to install and disassemble, making the membrane module easy to clean and maintain; (4) The reverse osmosis membrane device has a low operating pressure and a high degree of automation. The membrane device can be flexibly designed according to the requirements of the light-finishing liquid concentration. When the light-finishing liquid concentration requirement is low, the draw liquid system can be omitted. Attached Figure Description

[0026] Figure 1 This is a schematic diagram of a reverse osmosis membrane device used for recovering finishing solutions;

[0027] Figure 2 This is a schematic diagram of a tubular reverse osmosis membrane module.

[0028] In the diagram: 1-Inlet water circulation tank; 2-Inlet water circulation pump; 3-Finishing solution concentration and recovery membrane module; 4-Draw liquid circulation pump; 5-Draw liquid circulation tank; 6-First-stage inlet water pump; 7-Booster pump; 8-First-stage circulation pump; 9-First-stage draw liquid regeneration membrane module; 10-First-stage product water tank; 11-Second-stage inlet water pump; 12-Second-stage circulation pump; 13-Second-stage draw liquid regeneration membrane module; 14-Second-stage product water tank; 21-Finishing solution inlet; 22-Inlet water sealing end; 23-Draw liquid inlet; 24-Membrane shell; 25-Membrane tube bundle; 26-Draw liquid outlet; 27-Outlet water sealing end; 28-Finishing solution outlet; 29-Outlet water clamp; 30-Inlet water clamp; 31-Inlet water cap; 32-Outlet water cap. Detailed Implementation

[0029] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be described in detail below with reference to the accompanying drawings. It should be understood that the specific embodiments described herein are for illustrative purposes only and are not intended to limit the invention. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without inventive effort are within the scope of protection of this invention.

[0030] Example 1

[0031] A reverse osmosis membrane device for recovering finishing solution includes a finishing solution concentration and recovery device and a draw solution regeneration device. The finishing solution concentration and recovery device includes a feed water circulation tank 1, a feed water circulation pump 2, a finishing solution concentration and recovery membrane module 3, a draw solution circulation pump 4, and a draw solution circulation tank 5. The draw solution regeneration device adopts a two-stage reverse osmosis process and includes a first-stage feed water pump 6, a booster pump 7, a first-stage circulation pump 8, a first-stage draw solution regeneration membrane module 9, a first-stage product water tank 10, a second-stage feed water pump 11, a second-stage circulation pump 12, a second-stage draw solution regeneration membrane module 13, and a second-stage product water tank 14.

[0032] The polishing solution concentration and recovery membrane module 3 includes a polishing solution inlet 21, an inlet sealing end 22, an extractant inlet 23, a membrane shell 24, a membrane tube bundle 25, an extractant outlet 26, an outlet sealing end 27, a polishing solution outlet 28, an inlet end cap 31, and an outlet end cap 32. The membrane shell 24 is cylindrical, and the membrane tube bundle 25 is disposed inside the membrane shell 24. The membrane shell 24 has openings at both ends, which are the outlet opening end and the inlet opening end, respectively. The outlet opening end is connected to the outlet end cap 32, and the inlet opening end is connected to the inlet end cap 31. The polishing solution outlet 28 and the polishing solution inlet 21 are respectively disposed at the center of the outlet end cap 32 and the inlet end cap 31. The outlet sealing end 27 and the inlet sealing end 22 are respectively disposed at both ends of the membrane tube bundle 25, wherein the outlet sealing end 27 is close to the outlet opening end, and the inlet sealing end 22 is close to the inlet opening end. For easy disassembly and cleaning, the outer wall of the inlet end cap 31 and the outer wall of the membrane housing 24 are detachably connected by multiple inlet end clamps 30, and the outer wall of the outlet end cap 32 and the outer wall of the membrane housing 24 are detachably connected by multiple outlet end clamps 29. A draw liquid outlet 26 is provided on the side wall of the membrane housing 24 near the outlet opening, and a draw liquid inlet 23 is provided on the side wall of the membrane housing 24 near the inlet opening. For the brightening solution concentration and recovery membrane module 3, the brightening solution to be treated flows in from the brightening solution inlet 21, the concentrated water obtained through the membrane tube bundle 25 flows out from the brightening solution outlet 28, and the draw liquid flows in from the draw liquid inlet 23 and flows out from the draw liquid outlet 26. The function of the draw liquid is to increase the osmotic pressure on the product water side of the brightening solution concentration and recovery membrane module 3 to obtain a high concentration of recovered brightening solution. When a lower concentration of finishing solution is required, no finishing solution flows into the inlet 23, and the outlet 26 serves as the outlet for the produced water.

[0033] In the brightening solution concentration and recovery device: the outlet of the inlet water circulation tank 1 is connected to the brightening solution inlet 21 via the inlet water circulation pump 2, and the brightening solution outlet 28 is connected to the inlet of the inlet water circulation tank 1; the first outlet of the extract liquid circulation tank 5 is connected to the extract liquid inlet 23 via the extract liquid circulation pump 4, and the extract liquid outlet 26 is connected to the inlet of the extract liquid circulation tank 5. When the concentration of the brightening solution to be recovered is low, the extract liquid circulation tank 5 is not filled with extract liquid, and the extract liquid circulation tank 5 serves as a product water tank, collecting the product water treated by the brightening solution concentration and recovery membrane module 3; when the concentration of the brightening solution to be recovered is high, the extract liquid circulation tank 5 is filled with extract liquid to increase the osmotic pressure on the product water side of the brightening solution concentration and recovery membrane module 3.

[0034] In the extractant regeneration device: the second outlet of the extractant circulation tank 5 is connected sequentially to the inlet of the primary extractant regeneration membrane module 9 via the primary inlet pump 6 and the booster pump 7. The concentrate outlet of the primary extractant regeneration membrane module 9 is connected to the inlet of the extractant circulation tank 5 and the inlet of the primary circulation pump 8, respectively. The outlet of the primary circulation pump 8 is connected to the inlet of the primary extractant regeneration membrane module 9. The product water outlet of the primary extractant regeneration membrane module 9 is connected to the inlet of the primary product water tank 10. The outlet of the primary product water tank 10 is connected to the inlet of the secondary extractant regeneration membrane module 13 via the secondary inlet pump 11. The concentrate outlet of the secondary extractant regeneration membrane module 13 is connected to the inlet of the extractant circulation tank 5 and the inlet of the secondary circulation pump 12, respectively. The outlet of the secondary circulation pump 12 is connected to the inlet of the secondary extractant regeneration membrane module 13. The product water outlet of the secondary extractant regeneration membrane module 13 is connected to the secondary product water tank 14.

[0035] Currently, conventional membrane modules are disc-type membrane modules, which operate at relatively high pressures. During operation, pressure relief can lead to foaming issues caused by the finishing solution. In this application, the finishing solution concentration and recovery membrane module 3 uses a tubular reverse osmosis membrane module, meaning the membrane bundle 25 is a tubular reverse osmosis membrane. This membrane treatment device operates at a lower pressure. Due to the high circulation flow rate and large membrane channels of the tubular membrane module, its anti-fouling performance is stronger, and it has a high tolerance to membrane fouling from the finishing solution. The higher the concentration of the finishing solution to be recovered, the higher the required osmotic pressure. To increase the concentration of the recovered finishing solution, a draw solution is introduced to provide higher osmotic pressure, achieving a higher concentration of finishing solution at a lower pressure. The draw solution regeneration device is an auxiliary device that concentrates and regenerates the draw solution, restoring its concentration. Demineralized water is obtained during the membrane treatment of the draw solution. To ensure the quality of the separated demineralized water, the draw solution regeneration device is designed in two stages. Ultimately, a high concentration of finishing solution and qualified demineralized water are recovered, with the conductivity of the demineralized water being less than 10 μS / cm.

[0036] Online conductivity meters are installed in the inlet water circulation tank 1, the extractant circulation tank 5, the primary product water tank 10, and the secondary product water tank 14. The concentration of the recovered finishing liquid is adjusted according to the conductivity in the inlet water circulation tank 1. The recovery rates of the primary extractant regeneration membrane module 9 and the secondary extractant regeneration membrane module 13 are controlled according to the conductivity in the extractant circulation tank 5, the primary product water tank 10, and the secondary product water tank 14. That is, the ratio of the product water volume to the inlet water volume of the primary extractant regeneration membrane module 9 and the ratio of the product water volume to the inlet water volume of the secondary extractant regeneration membrane module 13.

[0037] Pressure sensors and flow meters are installed on the pipes of the finishing liquid inlet 21, finishing liquid outlet 28, extractant inlet 23, and extractant outlet 26.

[0038] The membrane tube bundle 25 has a single membrane tube diameter of 6-8 mm, the filter material of the membrane tube is a polyamide composite membrane, the membrane tube length is 1-3 m, the flow velocity inside the membrane tube is 1-2 m / s, and the operating pressure inside the membrane tube is 0.2-0.5 MPa.

[0039] The extraction liquid used in the extraction liquid circulation tank 5 is a sodium chloride solution with a concentration of 20-30 g / L.

[0040] The draw liquid circulation tank 5 is connected to the primary water inlet pump 6, the primary product water tank 10 is connected to the secondary water inlet pump 11, and the concentrate from the primary draw liquid regeneration membrane module 9 and the secondary draw liquid regeneration membrane module 13 flows back to the draw liquid circulation tank 5.

[0041] The primary draw solution regeneration membrane module 9 and the secondary draw solution regeneration membrane module 13 are spiral wound reverse osmosis membranes. The operating pressure of the primary draw solution regeneration membrane module 9 is 3-4 MPa, and the permeate conductivity is less than 300 μS / cm. The operating pressure of the secondary draw solution regeneration membrane module 13 is 0.6-1.0 MPa, and the permeate conductivity is less than 10 μS / cm. The significant difference in operating pressure between the primary and secondary draw solution regeneration membrane modules allows the secondary membrane module 13 to utilize a low-pressure membrane.

[0042] Examples 2 and 3 further illustrate the usage of the above-mentioned reverse osmosis membrane device for recovering finishing solution in different application scenarios.

[0043] Example 2

[0044] A method for recovering photoprocessing solution utilizes a reverse osmosis membrane device for recovering photoprocessing solution as described in Example 1. For scenarios where the concentration of the photoprocessing solution to be recovered is low (conductivity of the photoprocessing solution is less than or equal to 300 μS / cm; since the concentration and conductivity of the photoprocessing solution are positively linearly correlated, this invention uses the conductivity level to represent the concentration of the photoprocessing solution), in this embodiment, the conductivity of the photoprocessing solution in the feed water circulation tank 1 is controlled to be 250–300 μS / cm. The photoprocessing solution concentration and recovery membrane module 3 uses a membrane tube with a diameter of 6 mm, a length of 3 m, and a membrane area of ​​30 m². 2 Tubular reverse osmosis membrane modules.

[0045] Since the required concentration of the finishing solution to be recovered is low, it is not necessary to start the extractant regeneration device, which is the preferred embodiment in this case.

[0046] Step 1: The draw liquid circulation tank 5 is used as the product water tank and is initially empty. The draw liquid circulation pump 4, primary water inlet pump 6, booster pump 7, primary circulation pump 8, secondary water inlet pump 11, and secondary circulation pump 12 are shut down, while the inlet water circulation pump 2 is turned on. The operating pressure of the finishing liquid concentration and recovery membrane module 3 is 0.4-0.5 MPa. At this time, the finishing liquid flows from the inlet water circulation tank 1 through the inlet water circulation pump 2 into the finishing liquid concentration and recovery membrane module 3. The concentrated water flows back to the inlet water circulation tank 1 from the finishing liquid outlet 28 for the next round of circulation treatment, and the product water flows into the draw liquid circulation tank 5 from the draw liquid outlet 26.

[0047] Step 2: When the conductivity of the finishing solution in the feed water circulation tank 1 reaches 250-300 μS / cm, the finishing solution in the feed water circulation tank 1 is discharged to the finishing solution storage tank, and low-concentration finishing solution is re-entered into the feed water circulation tank 1; the conductivity of the extract liquid circulation tank 5 is controlled below 10 μS / cm. When the conductivity of the product water in the extract liquid circulation tank 5 is greater than 10 μS / cm, the primary feed water pump 6, the booster pump 7, and the primary circulation pump 8 are turned on, and the other pumps remain in the state of Step 1, that is, the extract liquid circulation pump 4, the secondary feed water pump 11, and the secondary circulation pump 12 are turned off, and the feed water circulation pump 2 is turned on. The product water of the finishing solution concentration and recovery membrane module 3 in the extract liquid circulation tank 5 is further processed by the primary extract liquid regeneration membrane module 9. The product water of the primary extract liquid regeneration membrane module 9 is reused as demineralized water, and the concentrate of the finishing solution concentration and recovery membrane module 3 is returned to the feed water circulation tank 1.

[0048] The concentration and conductivity of the finishing solution are linearly related; the higher the concentration, the greater the conductivity. The conductivity and salt concentration show the same trend, and conductivity can be used to represent different salt concentrations. The higher the salt concentration, the greater the osmotic pressure that the membrane module needs to overcome to treat the finishing solution. The role of the draw solution is to increase the osmotic pressure on the product water side of the finishing solution concentration and recovery membrane module 3. To achieve water production, the reverse osmosis membrane must overcome the osmotic pressure on both sides of the membrane. Therefore, increasing the osmotic pressure on the product water side is equivalent to reducing the pressure required on the raw water side. The operating pressure of the finishing solution concentration and recovery membrane module 3 is not high, making it suitable for low-concentration finishing solutions. Therefore, low-concentration finishing solutions do not require an additional draw solution system.

[0049] Example 3

[0050] A method for recovering photoprocessing solution utilizes a reverse osmosis membrane device for recovering photoprocessing solution as described in Example 1. For scenarios requiring high concentrations of photoprocessing solution to be recovered (i.e., photoprocessing solution conductivity greater than 300 μS / cm), in this embodiment, the conductivity of the photoprocessing solution in the feed water circulation tank 1 is controlled between 1000 and 2000 μS / cm. Due to the high required concentration of the recovered photoprocessing solution, the operating pressure provided by the tubular reverse osmosis membrane is insufficient, necessitating the addition of a draw solution system to enhance the concentration permeate capacity, thereby obtaining a higher concentration of photoprocessing solution. The photoprocessing solution concentration and recovery membrane module 3 uses a membrane tube with a diameter of 6 mm, a length of 3 m, and a membrane area of ​​30 m². 2The tubular reverse osmosis membrane module uses a sodium chloride solution with a concentration of 20–30 g / L as the draw solution. The operating pressure of the finishing solution concentration and recovery membrane module 3 is 0.3–0.4 MPa, the operating pressure of the primary draw solution regeneration membrane module 9 is 2.5–3.5 MPa, and the operating pressure of the secondary draw solution regeneration membrane module 13 is 0.6–1.0 MPa. All of the following pumps are activated: draw solution circulation pump 4, secondary feed pump 11, secondary circulation pump 12, feed circulation pump 2, primary feed pump 6, booster pump 7, and primary circulation pump 8. At this time, the finishing solution flows from the inlet circulation tank 1 through the inlet circulation pump 2 into the finishing solution concentration and recovery membrane module 3. The concentrated water flows back to the inlet circulation tank 1 from the finishing solution outlet 28 and undergoes the next round of circulation treatment. The draw liquid flows from the draw liquid circulation tank 5 through the draw liquid circulation pump 4 into the draw liquid inlet 23. The mixture of draw liquid and product water is discharged from the draw liquid outlet 26 back to the draw liquid circulation tank 5. On the other hand, the draw liquid in the draw liquid circulation tank 5 passes through the primary inlet pump 6 and the booster pump 7 to the primary draw liquid regeneration membrane module 9. The product water obtained from the primary draw liquid regeneration membrane module 9 flows into the primary product water tank 10, and then flows into the secondary draw liquid regeneration membrane module 13 for further purification after passing through the secondary inlet pump 11. Finally, the product water obtained flows into the secondary inlet pump 11 and is reused as recycled demineralized water. The primary circulation pump 8 is used to increase the circulation rate of the primary draw solution regeneration membrane module 9 and to ensure the concentration of the concentrate in the primary draw solution regeneration membrane module 9. The secondary circulation pump 12 is used to increase the circulation rate of the secondary draw solution regeneration membrane module 13 and to ensure the concentration of the concentrate in the secondary draw solution regeneration membrane module 13.

[0051] Specifically, when the conductivity of the finishing solution in the inlet water circulation tank 1 reaches 1000-2000 μS / cm, the finishing solution is discharged to the finishing solution storage tank, and a low-concentration finishing solution is reintroduced into the inlet water circulation tank 1. The conductivity in the secondary product water tank 14 is controlled below 10 μS / cm to obtain the recovered demineralized water.

[0052] Specifically, level gauges are installed in the inlet water circulation tank 1, the extract liquid circulation tank 5, the primary product water tank 10, and the secondary product water tank 14.

[0053] Specifically, the draw solution needs to be cleaned or replaced periodically during use. When the permeate flux of the finishing solution concentration and recovery membrane module 3 decreases significantly, chemical cleaning is required. During cleaning, the membrane housing 24 is emptied and rinsed clean, and then a cleaning pump is used for circulating chemical cleaning.

[0054] As a preferred embodiment, after the finishing solution is continuously circulated in the water inlet circulation tank 1, the concentration will continue to increase, and the concentrated water needs to be discharged periodically. The water inlet circulation tank 1 is set into two sets, and the two sets of water inlet circulation tank 1 switch operation during operation to ensure the continuity of operation.

[0055] This invention combines tubular reverse osmosis and forward osmosis technologies. Tubular membrane modules are resistant to fouling, but their conductivity on the concentrate side is low due to low operating pressure. Introducing a draw solution can solve this problem. Forward osmosis technology uses the draw solution (which provides osmotic pressure, driving water molecules to spontaneously migrate from the high chemical potential side to the low chemical potential side) as the driving force for water production. Reverse osmosis uses external pressure as the driving force for water production (i.e., using external pressure to overcome the osmotic pressure on both sides of the membrane to migrate water molecules from the low-pressure side to the high-pressure side). This allows the invention to be applied to different finishing solutions to be recycled.

[0056] The present invention can effectively recover the finishing solution, and the membrane module has strong resistance to fouling and is easy to clean and restore.

[0057] Finally, it should be noted that the above specific embodiments are only used to illustrate the technical solutions of the present invention and not to limit it. Although the present invention has been described in detail, 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, and all such modifications or substitutions should be covered within the scope of the claims of the present invention.

Claims

1. A method for recovering finishing solutions, employing a reverse osmosis membrane device for recovering finishing solutions, characterized in that, This includes processing steps for low-concentration finishing solutions to be recycled and processing steps for high-concentration finishing solutions to be recycled. The reverse osmosis membrane device for recovering finishing solution includes an inlet water circulation tank (1), the outlet of the inlet water circulation tank (1) is connected to the finishing solution inlet (21) of the finishing solution concentration and recovery membrane assembly (3) through an inlet water circulation pump (2), the finishing solution outlet (28) of the finishing solution concentration and recovery membrane assembly (3) is connected to the inlet of the inlet water circulation tank (1), the first outlet of the extract liquid circulation tank (5) is connected to the extract liquid inlet (23) of the finishing solution concentration and recovery membrane assembly (3) through an extract liquid circulation pump (4), and the extract liquid outlet (26) of the finishing solution concentration and recovery membrane assembly (3) is connected to the inlet of the extract liquid circulation tank (5). The second outlet of the draw liquid circulation tank (5) is connected in sequence to the inlet of the first-stage draw liquid regeneration membrane module (9) via the first-stage inlet pump (6) and the booster pump (7). The concentrate outlet of the first-stage draw liquid regeneration membrane module (9) is connected to the inlet of the draw liquid circulation tank (5) and the inlet of the first-stage circulation pump (8). The outlet of the first-stage circulation pump (8) is connected to the inlet of the first-stage draw liquid regeneration membrane module (9). The product water outlet of the first-stage draw liquid regeneration membrane module (9) is connected to the inlet of the first-stage product water tank (10). The outlet of the primary product water tank (10) is connected to the inlet of the secondary extract regeneration membrane module (13) via the secondary inlet pump (11). The concentrate outlet of the secondary extract regeneration membrane module (13) is connected to the inlet of the extract circulation tank (5) and the inlet of the secondary circulation pump (12). The outlet of the secondary circulation pump (12) is connected to the inlet of the secondary extract regeneration membrane module (13). The product water outlet of the secondary extract regeneration membrane module (13) is connected to the secondary product water tank (14). The optical finishing solution concentration and recovery membrane module (3) adopts a tubular reverse osmosis membrane module; the diameter of a single membrane tube in the membrane tube bundle (25) of the optical finishing solution concentration and recovery membrane module (3) is 6~8mm, the filter material of the membrane tube is a polyamide composite membrane, the length of the membrane tube is 1~3m, the flow velocity inside the membrane tube is 1~2m / s, and the operating pressure inside the membrane tube is 0.2~0.5Mpa; For processing steps involving low concentrations of the finishing solution to be recovered: Step 1.1: The initial state of the draw liquid circulation tank (5) is empty. The draw liquid circulation pump (4), the first-stage water inlet pump (6), the booster pump (7), the first-stage circulation pump (8), the second-stage water inlet pump (11), and the second-stage circulation pump (12) are closed, and the water inlet circulation pump (2) is turned on. Step 1.2: When the conductivity of the finishing solution in the inlet water circulation tank (1) reaches the preset concentration, the finishing solution in the inlet water circulation tank (1) is discharged to the finishing solution storage tank, and the low concentration finishing solution is re-entered into the inlet water circulation tank (1); monitor the conductivity in the extract liquid circulation tank (5), and when the conductivity of the product water in the extract liquid circulation tank (5) is greater than 10 μS / cm, turn on the first-stage inlet water pump (6), the booster pump (7) and the first-stage circulation pump (8), keep the inlet water circulation pump (2) on, and keep the extract liquid circulation pump (4), the second-stage inlet water pump (11) and the second-stage circulation pump (12) off; For processing steps involving high concentrations of finishing solutions to be recovered: Step 2.1: The draw liquid circulation tank (5) is filled with draw liquid. The above-mentioned draw liquid circulation pump (4), secondary water inlet pump (11), secondary circulation pump (12), water inlet circulation pump (2), primary water inlet pump (6), booster pump (7) and primary circulation pump (8) are all turned on. When the conductivity of the finishing liquid in the water inlet circulation tank (1) reaches the preset concentration, the finishing liquid in the water inlet circulation tank (1) is discharged to the finishing liquid storage tank, and the low concentration finishing liquid is re-entered into the water inlet circulation tank (1).

2. The method for recovering finishing solution according to claim 1, characterized in that, The light-refining solution concentration and recovery membrane module (3) includes a cylindrical membrane shell (24), and a membrane tube bundle (25) is provided inside the membrane shell (24). The membrane shell (24) has two openings, namely an outlet water opening and an inlet water opening. The outlet water opening is connected to the outlet water cap (32), and the inlet water opening is connected to the inlet water cap (31). A light-refining solution outlet (28) and a light-refining solution inlet (21) are respectively provided at the center of the outlet water cap (32) and the inlet water cap (31). An outlet water sealing end (27) and an inlet water sealing end (22) are respectively provided at both ends of the membrane tube bundle (25), wherein the outlet water sealing end (27) is close to the outlet water opening end, and the inlet water sealing end (22) is close to the inlet water opening end. A draw liquid outlet (26) is provided on the side wall of the membrane shell (24) near the outlet water opening end, and a draw liquid inlet (23) is provided on the side wall of the membrane shell (24) near the inlet water opening end.

3. The method for recovering finishing solution according to claim 2, characterized in that, The outer wall of the water inlet cap (31) and the outer wall of the membrane shell (24) are detachably connected by multiple water inlet clamps (30), and the outer wall of the water outlet cap (32) and the outer wall of the membrane shell (24) are detachably connected by multiple water outlet clamps (29).

4. The method for recovering finishing solution according to claim 2, characterized in that, The membrane bundle (25) is a tubular reverse osmosis membrane.

5. A method for recovering finishing solution according to claim 4, characterized in that, Online conductivity meters are installed in the inlet water circulation tank (1), the extract liquid circulation tank (5), the primary product water tank (10), and the secondary product water tank (14).

6. A method for recovering finishing solution according to claim 5, characterized in that, Pressure sensors and flow meters are installed on the pipes of the finishing liquid inlet (21), finishing liquid outlet (28), extracting liquid inlet (23), and extracting liquid outlet (26).

7. A method for recovering finishing solution according to claim 6, characterized in that, The extraction liquid used in the extraction liquid circulation tank (5) is a sodium chloride solution with a concentration of 20~30g / L.

8. A method for recovering finishing solution according to claim 7, characterized in that, The primary draw liquid regeneration membrane module (9) and the secondary draw liquid regeneration membrane module (13) are spiral wound reverse osmosis membranes. The operating pressure of the primary draw liquid regeneration membrane module (9) is 3~4 MPa, and the permeate conductivity is less than 300 μs / cm. The operating pressure of the secondary draw liquid regeneration membrane module (13) is 0.6~1.0 MPa, and the permeate conductivity is less than 10 μs / cm.

Images