Chemical cleaning apparatus and cleaning method for reverse osmosis membranes

Abstract

This invention discloses a chemical cleaning device and method for reverse osmosis membranes, comprising a reverse osmosis unit with a cleaning liquid inlet and a cleaning liquid return port, and a first drain port at its bottom; a first security filter with a first inlet, a first outlet, a chemical dosing port, and a second drain port, the first outlet being connected to the cleaning liquid inlet via a first pipeline; a rinsing unit; the cleaning liquid return port being connected to the second inlet via a third pipeline; the rinsing unit, the second pipeline, the first security filter, the first pipeline, the reverse osmosis unit, and the third pipeline being sequentially connected to form a cleaning flow path; and a chemical dosing unit for supplying cleaning liquid to the first security filter. This invention adds in-situ cleaning of the first security filter between alkaline and acid washing of the reverse osmosis unit, which removes impurities such as metal hydroxides adhering to the first security filter, preventing them from dissolving and re-entering the acid washing solution during subsequent acid washing and causing secondary contamination.

Description

Technical Field

[0001] This invention belongs to the field of reverse osmosis membrane cleaning technology, and particularly relates to a chemical cleaning device and cleaning method for reverse osmosis membranes. Background Technology

[0002] Reverse osmosis technology, as a highly efficient method for water treatment, desalination, and purification, has been widely used in municipal wastewater reuse, industrial wastewater resources, and seawater desalination. During the long-term operation of a reverse osmosis system, pollutants in the water gradually adhere to the surface of the reverse osmosis membrane, clogging the membrane pores and causing a continuous decline in the membrane flux. Therefore, it is necessary to clean the reverse osmosis system.

[0003] The main cleaning method currently is chemical cleaning, which typically uses acids and alkalis. The cleaning process involves first alkaline washing, followed by acid washing. Alkaline washing decomposes organic matter such as grease and colloids through saponification; acid washing dissolves inorganic scale such as carbonates and metal oxides. During both alkaline and acid washing processes, the cleaning solution must first be filtered through a security filter before being introduced into the reverse osmosis unit.

[0004] However, during alkaline washing, the metal hydroxides adhering to the security filter will dissolve and re-enter the pickling solution during subsequent acid washing, causing secondary pollution. Summary of the Invention

[0005] The purpose of this invention is to provide a chemical cleaning device and method for reverse osmosis membranes, aiming to solve the technical problem in the prior art where metal hydroxides adhering to the security filter are dissolved and re-enter the cleaning solution during subsequent acid washing, causing secondary pollution.

[0006] To solve the above-mentioned technical problems, the present invention is mainly achieved through the following technical solutions: In a first aspect, the present invention provides a chemical cleaning apparatus for a reverse osmosis membrane, comprising: A reverse osmosis unit has a cleaning fluid inlet and a cleaning fluid return outlet, a reverse osmosis membrane inside, and a first drain outlet at its bottom. The first security filter has a first liquid inlet, a first liquid outlet, a chemical dosing port and a second sewage outlet, and a filter element is installed inside it. The first liquid outlet is connected to the cleaning liquid inlet through a first pipeline. The rinsing unit has a second inlet and a second outlet, and a third drain outlet at its bottom. The second outlet is connected to the first inlet via a second pipeline. The cleaning fluid return port is connected to the second inlet via a third pipeline. The rinsing unit, the second pipeline, the first security filter, the first pipeline, the reverse osmosis unit, and the third pipeline are sequentially connected to form a cleaning flow path for cleaning the reverse osmosis membrane. The dosing unit has a third outlet, which is connected to the dosing port via a fourth pipeline and is configured to deliver cleaning fluid to the first security filter.

[0007] In some embodiments of this application, the rinsing unit includes: The first liquid storage tank has a second liquid outlet on its top and a third drain outlet at its bottom; A cleaning pump is installed on the second pipeline; A first switching valve is installed on the second pipeline to control the on / off state of the second pipeline.

[0008] In some embodiments of this application, the dosing unit includes: A medicine storage tank, on which the third liquid outlet is formed; A dosing pump is installed on the fourth pipeline; The second switching valve is installed on the fourth pipeline and is used to control the on / off state of the fourth pipeline.

[0009] In some embodiments of this application, the chemical cleaning apparatus for the reverse osmosis membrane further includes: Control module; A third switching valve is installed on the first pipeline and is used to control the opening and closing of the first pipeline; A fourth switching valve is installed on the third pipeline and is used to control the on / off state of the third pipeline; The first switching valve, the second switching valve, the third switching valve, the fourth switching valve, the cleaning pump, and the dosing pump are all electrically connected to the control module.

[0010] In some embodiments of this application, the chemical cleaning apparatus for the reverse osmosis membrane further includes: A first pressure gauge is disposed at the first liquid inlet and electrically connected to the control module, and is configured to detect the liquid inlet pressure of the first liquid inlet; A second pressure gauge is disposed at the first liquid outlet and electrically connected to the control module, and is configured to detect the liquid pressure at the first liquid outlet.

[0011] In some embodiments of this application, the chemical cleaning apparatus for the reverse osmosis membrane further includes: A pH meter is installed at the second sewage outlet and electrically connected to the control module. It is configured to detect the pH of the water at the second sewage outlet. A metal ion detector is installed at the first liquid outlet and is configured to detect the concentration of metal ions in the water at the first liquid outlet.

[0012] In a second aspect, the present invention provides a cleaning method for a reverse osmosis membrane using a chemical cleaning apparatus as described in any one of the embodiments of the first aspect above, comprising the following steps: S1: Alkaline washing of the reverse osmosis unit: S2: Perform in-situ cleaning of the first security filter; S3: Acid washing of the reverse osmosis unit; S4: Rinse the reverse osmosis unit with clean water and raise it to normal operating pressure.

[0013] In some embodiments of this application, step S1, which involves alkaline washing of the reverse osmosis membrane, includes: Add alkali solution to the storage tank and deliver it to the first security filter; start the cleaning pump to circulate the alkali solution in the cleaning flow path; after the first preset time of alkali washing, discharge the alkali solution from the cleaning flow path.

[0014] In some embodiments of this application, step S2, which involves in-situ cleaning of the first security filter, includes: Add acid to the storage tank and transfer the acid to the first security filter. After the acid has soaked the first security filter for a second preset time, open the second drain outlet to discharge the acid and rinse the first security filter with clean water. Detect the metal ion concentration and pH at the second drain outlet. If the metal ion concentration is ≤ the first preset value and the pH is ≥ 6.5, proceed to the next step. Otherwise, if the metal ion concentration is > the first preset value or the pH is < 6.5, repeat steps S1 and S2.

[0015] In some embodiments of this application, step S3, acid washing of the reverse osmosis unit includes: Add acid to the storage tank and transport the acid to the first security filter; start the cleaning pump to circulate the acid in the cleaning flow path; after the third preset acid washing time, discharge the acid from the cleaning flow path.

[0016] Compared with the prior art, the present invention has the following beneficial technical effects: The chemical cleaning device for reverse osmosis membranes disclosed in this invention includes a reverse osmosis unit, a first security filter, a rinsing unit, and a dosing unit. The first security filter can filter the washing solution entering the reverse osmosis unit, intercepting impurities such as small particles, colloids, and rust, and preventing the reverse osmosis membrane from clogging. By adding in-situ cleaning of the first security filter between alkaline washing and acid washing of the reverse osmosis unit, impurities such as metal hydroxides attached to the first security filter can be removed, avoiding dissolution and re-entry into the acid washing solution during subsequent acid washing, which would cause secondary pollution. Attached Figure Description

[0017] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort. Figure 1 This is a schematic diagram of the structure of the chemical cleaning device for reverse osmosis membranes provided by the present invention.

[0018] Explanation of reference numerals in the attached figures: 1. Reverse osmosis unit; 11. Cleaning solution inlet; 12. Cleaning solution return port; 13. Reverse osmosis membrane; 14. First drain outlet; 15. Inlet; 16. Product water outlet; 2. First security filter; 21. First liquid inlet; 22. First liquid outlet; 23. Chemical dosing port; 24. Second drain outlet; 25. First pipeline; 3. Flushing unit; 31. Second liquid inlet; 32. Second liquid outlet; 33. Third drain outlet; 34. Second pipeline; 35. Third pipeline; 36. First storage tank; 37. Cleaning pump; 38. First switch valve; 4. Dosing unit; 41. Third outlet; 42. Fourth pipeline; 43. Storage tank; 44. Dosing pump; 45. Second switch valve; 5. Third switching valve; 6. Fourth switching valve; 7. First pressure gauge; 8. Second pressure gauge; 9. Water storage tank; 10. Flushing pump. Detailed Implementation

[0019] The technical solution of the present invention will be clearly and completely described below with reference to specific embodiments. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0020] In a first aspect, embodiments of this disclosure provide a chemical cleaning apparatus for a reverse osmosis membrane 13, the chemical cleaning apparatus for the reverse osmosis membrane 13 including a reverse osmosis unit 1, a first security filter 2, a flushing unit 3 and a chemical dosing unit 4.

[0021] The reverse osmosis unit 1 has a cleaning fluid inlet 11 and a cleaning fluid return port 12. The reverse osmosis unit 1 is equipped with a reverse osmosis membrane 13, and a first drain port 14 is formed at the bottom of the reverse osmosis unit 1.

[0022] The first security filter 2 has a first liquid inlet 21, a first liquid outlet 22, a chemical dosing port 23, and a second drain port 24. The chemical dosing port 23 is located on the top cover of the first security filter 2. The first security filter 2 has a filter element inside. The first liquid outlet 22 is connected to the cleaning liquid inlet 11 through a first pipe 25.

[0023] The rinsing unit 3 has a second inlet 31 and a second outlet 32. The bottom of the rinsing unit 3 has a third drain outlet 33. The second outlet 32 ​​is connected to the first inlet 21 through a second pipe 34. The cleaning fluid return port 12 is connected to the second inlet 31 through a third pipe 35. The rinsing unit 3, the second pipe 34, the first security filter 2, the first pipe 25, the reverse osmosis unit 1, and the third pipe 35 are sequentially connected to form a cleaning flow path to clean the reverse osmosis membrane 13.

[0024] The dosing unit 4 has a third liquid outlet 41, which is connected to the dosing port 23 via a fourth pipeline 42. The dosing unit 4 is configured to deliver cleaning fluid to the first security filter 2.

[0025] Specifically, the chemical cleaning device for the reverse osmosis membrane 13 includes a reverse osmosis unit 1, a first security filter 2, a rinsing unit 3, and a dosing unit 4. The first security filter 2 can filter the washing solution entering the reverse osmosis unit 1, intercepting impurities such as small particles, colloids, and rust, and preventing the reverse osmosis membrane 13 from clogging. The first security filter 2 is cleaned in situ between the alkaline washing and acid washing of the reverse osmosis unit 1. This removes impurities such as metal hydroxides attached to the first security filter 2, preventing them from being dissolved and re-entering the acid washing solution during the subsequent acid washing process, thus avoiding secondary pollution.

[0026] Specifically, the pore size of the filter element is 5~10μm.

[0027] In some embodiments of this application, the rinsing unit 3 includes a first liquid storage tank 36, a cleaning pump 37, and a first switching valve 38.

[0028] The first liquid storage tank 36 is used to store clean water or cleaning fluid. The second liquid outlet 32 ​​is formed on the first liquid storage tank 36, and the third drain outlet 33 is formed at the bottom of the first liquid storage tank 36.

[0029] A cleaning pump 37 is installed on the second pipeline 34. The cleaning pump 37 is used to provide power for the liquid in the second pipeline 34 to flow from the first storage tank 36 toward the first security filter 2.

[0030] The first switching valve 38 is disposed on the second pipeline 34, and the first switching valve 38 is used to control the opening and closing of the second pipeline 34.

[0031] Specifically, the first liquid storage tank 36 and the first security filter 2 are connected by the second pipeline 34, which facilitates the first security filter 2 to filter the liquid flowing to the reverse osmosis unit 1.

[0032] In some embodiments of this application, the dosing unit 4 includes a drug storage tank 43, a dosing pump 44, and a second switching valve 45.

[0033] The storage tank 43 is used to store cleaning solutions such as acid or alkali, and the third outlet 41 is formed on the storage tank 43.

[0034] A dosing pump 44 is installed on the fourth pipeline 42, and the dosing pump 44 is used to provide power for the cleaning fluid in the fourth pipeline 42 to flow to the first security filter 2.

[0035] The second switching valve 45 is disposed on the fourth pipeline 42, and the second switching valve 45 is used to control the opening and closing of the fourth pipeline 42.

[0036] Specifically, by setting up a medicine storage tank 43, which is connected to the first security filter 2 via a fourth pipeline 42, it is convenient to provide cleaning fluid to the first security filter 2 through the medicine storage tank 43.

[0037] In some embodiments of this application, the chemical cleaning device for the reverse osmosis membrane 13 further includes a control module, a third switching valve 5, and a fourth switching valve 6.

[0038] The third switching valve 5 is installed on the first pipeline 25, and the third switching valve 5 is used to control the opening and closing of the first pipeline 25.

[0039] The fourth switching valve 6 is disposed on the third pipeline 35, and the fourth switching valve 6 is used to control the opening and closing of the third pipeline 35.

[0040] The first switching valve 38, the second switching valve 45, the third switching valve 5, the fourth switching valve 6, the cleaning pump 37, and the dosing pump 44 are all electrically connected to the control module.

[0041] Specifically, by setting up a control module, a third switching valve 5, and a fourth switching valve 6, it is beneficial to achieve automated and intelligent control.

[0042] For example, the first switching valve 38, the second switching valve 45, the third switching valve 5, and the fourth switching valve 6 include electrically controlled valves.

[0043] In some embodiments of this application, the chemical cleaning device for the reverse osmosis membrane 13 further includes a first pressure gauge 7 and a second pressure gauge 8.

[0044] The first pressure gauge 7 is disposed at the first liquid inlet 21 and is electrically connected to the control module. The first pressure gauge 7 is configured to detect the liquid inlet pressure of the first liquid inlet 21.

[0045] The second pressure gauge 8 is disposed at the first liquid outlet 22. The second pressure gauge 8 is electrically connected to the control module and is configured to detect the liquid outlet pressure of the first liquid outlet 22.

[0046] Specifically, by setting a first pressure gauge 7 and a second pressure gauge 8, it is convenient to detect the pressure of the first liquid inlet 21 and the first liquid outlet 22 in real time.

[0047] In some embodiments of this application, the chemical cleaning apparatus for the reverse osmosis membrane 13 further includes a pH meter and a metal ion meter.

[0048] A pH meter is installed at the second drain outlet 24 and is electrically connected to the control module. The pH meter is configured to detect the pH of the water at the second drain outlet 24.

[0049] A metal ion detector is installed at the first liquid outlet 22 and is configured to detect the concentration of metal ions in the water at the first liquid outlet 22.

[0050] Specifically, a pH meter is installed to facilitate the detection of the pH value of the water discharged from the second sewage outlet 24; a metal ion detector is installed to facilitate the detection of the concentration of metal ions in the water at the first liquid outlet 22.

[0051] In some embodiments of this application, the reverse osmosis unit 1 is further provided with an inlet 15 and a product water outlet 16. The reverse osmosis unit 1 is the core component of the reverse osmosis system. The reverse osmosis system also includes a second security filter, an equipment inlet pump, a high-pressure water supply pump, and a water storage tank 9. The equipment inlet pump is connected to the inlet end of the second security filter through a first water supply pipe. The equipment inlet pump is used to provide power for the water in the first water supply pipe to flow toward the second security filter. The outlet end of the second security filter is connected to the inlet 15 of the reverse osmosis unit 1 through a second water supply pipe. The high-pressure water supply pump is installed on the second water supply pipe to provide power for the water in the second water supply pipe to flow toward the reverse osmosis unit 1. The product water outlet 16 is connected to the inlet end of the water storage tank 9 through a third water supply pipe. In this way, the clean water flowing out of the product water outlet 16 can flow into the water storage tank 9 for storage.

[0052] In a second aspect, embodiments of this disclosure provide a cleaning method for a reverse osmosis membrane 13 using a chemical cleaning apparatus as described in any one of the embodiments of the first aspect above, comprising the following steps: S1: Alkaline washing of reverse osmosis unit 1: S2: Perform in-situ cleaning of the first security filter 2; S3: Perform acid washing on reverse osmosis unit 1; S4: Rinse reverse osmosis unit 1 with clean water and raise it to normal operating pressure.

[0053] In some embodiments of this application, step S1 involves alkaline washing of the reverse osmosis membrane 13, including: Add alkali solution to the storage tank 43, start the dosing pump 44 to deliver the alkali solution to the first security filter 2; turn off the dosing pump 44 and start the cleaning pump 37 to circulate the alkali solution in the cleaning flow path; after the first preset time of alkali washing, turn off the cleaning pump 37, open the first drain port 14, the second drain port 24, and the third drain port 33, and keep the first inlet port 21 and the first outlet port 22 open for 10 minutes. Utilize the pressure difference formed by the residual pressure of the system and the first pipeline 25 and the second pipeline 34 to ensure that the alkali solution in the first security filter 2 is completely emptied, so as to avoid the residual alkali solution reacting with the subsequent hydrochloric acid solution and affecting the cleaning effect.

[0054] Specifically, the first preset time includes 5 to 60 minutes.

[0055] For example, the first preset time is 5 min, 10 min, 15 min, 20 min, 25 min, 30 min, 40 min, 50 min or 60 min.

[0056] Specifically, through alkaline cleaning, metal ions in the water react with the alkaline solution to form insoluble metal hydroxide complexes. At the same time, microbial flocs attached to the surface of the reverse osmosis membrane 13 are stripped off by the alkaline solution, forming a mixed pollutant of metal hydroxide and microbial flocs.

[0057] In some embodiments of this application, the outlet of the water storage tank 9 is connected to the third inlet of the first liquid storage tank 36 via a fourth water supply pipe. A flushing pump 10 is provided on the fourth water supply pipe, and the flushing pump 10 is configured to provide power for the reverse osmosis water in the fourth water supply pipe to flow from the water storage tank 9 toward the first liquid storage tank 36.

[0058] Specifically, the conductivity of reverse osmosis water is ≤50μS / cm.

[0059] In some embodiments of this application, step S2, which involves in-situ cleaning of the first security filter 2, includes: Close the first inlet 21 and the first outlet 22 on the first security filter 2, open the dosing port 23, add acid to the storage tank 43, and deliver the acid to the first security filter 2. The amount of acid injected should be enough to submerge the top of the filter element by 5-10 cm to ensure that the outer surface of the filter element is in full contact with the acid. After the acid has soaked the first security filter 2 for a second preset time, open the second drain port 24 to discharge the waste liquid that has dissolved the pollutants. Turn on the flushing pump 10 and the first switch valve 38 to input reverse osmosis water into the first security filter 2 to flush the filter element. The flushing flow rate is 50% of the normal operating flow rate of the first security filter 2, and the flushing time is 5-8 minutes. Detect the metal ion concentration and pH at the second drain port 24. If the metal ion concentration is ≤ the first preset value and the pH is ≥ 6.5, proceed to the next step; otherwise, if the metal ion concentration is > the first preset value or the pH is < 6.5, repeat steps S1 and S2.

[0060] For example, the acid solution includes hydrochloric acid.

[0061] Specifically, the hydrochloric acid concentration is 0.25%~0.35%, which can ensure efficient dissolution of pollutants while avoiding corrosion of the filter element.

[0062] In some embodiments of this application, the second preset time is 1 to 5 hours.

[0063] In some other embodiments of this application, the second preset time is 1.5 to 2.5 hours.

[0064] For example, the second preset time is 1.5h, 2h or 2.5h.

[0065] Specifically, after alkaline washing, a mixture of contaminants containing metal hydroxides and microbial flocs passes through the first security filter 2. The metal hydroxide complexes are generated by the reaction of Fe3+, Ca2+, and other compounds in the water with the alkaline solution (NaOH) during the alkaline washing stage. The filter cartridge traps most of the contaminants, but the alkaline solution discharge relies heavily on residual pressure, meaning the trapped contaminants cannot be completely removed and remain in large quantities inside and on the surface of the filter cartridge.

[0066] If acid washing is performed directly, the acid solution flowing through the first security filter 2 will cause the residual metal hydroxide complexes on the filter element to redissolve. At the same time, the bacterial flocs will disperse in the acidic environment. These dissolved and dispersed contaminants will enter the reverse osmosis membrane 13 system with the acid solution, re-adhere to the surface of the reverse osmosis membrane 13 and penetrate deep into the membrane pores, forming irreversible blockage and causing secondary pollution to the reverse osmosis membrane 13. This results in an extremely low membrane flux recovery rate of the reverse osmosis membrane 13, which cannot meet the operating requirements of the reverse osmosis system. In addition, the repeated adhesion of contaminants will accelerate membrane aging and reduce its service life. Furthermore, the first security filter 2 will require frequent replacement due to excessive contaminants, leading to a significant increase in operation and maintenance costs.

[0067] By cleaning the first security filter 2 in situ, the mixed contaminants of metal hydroxide complexes and bacterial flocs trapped in the first security filter 2 filter element can be completely removed, blocking the path of contaminants to re-enter the reverse osmosis membrane 13 system from the source.

[0068] Specifically, by using reverse osmosis water for flushing, new contaminants can be avoided. The flushing flow rate is controlled at 50% of the normal operating flow rate to prevent excessive flow from causing filter element damage or secondary contaminant adhesion.

[0069] For example, subsequent acid washing is only initiated when Fe3+ ≤ 0.1 mg / L to ensure that the pollutant removal meets the standards.

[0070] In some embodiments of this application, the mass concentration of the alkaline solution is 0.1% to 0.5%, and the temperature is 25 to 35°C.

[0071] In some embodiments of this application, step S3, acid washing of the reverse osmosis unit 1, includes: Add acid to the storage tank 43, start the dosing pump 44 to deliver the acid to the first security filter 2; turn off the dosing pump 44 and start the cleaning pump 37 to circulate the acid in the cleaning flow path; after the third preset acid washing time, turn off the cleaning pump 37, open the first drain port 14, the second drain port 24, and the third drain port 33, and keep the first inlet port 21 and the first outlet port 22 open for 10 minutes. Use the pressure difference formed by the residual pressure of the system and the first pipeline 25 and the second pipeline 34 to ensure that the acid in the first security filter 2 is completely emptied, so as to remove the acid in the cleaning flow path.

[0072] The reverse osmosis system is flushed at low pressure. Specifically, the flushing pump 10 is turned on, and the reverse osmosis water is transported from the storage tank 9 to the first storage tank 36 through the fourth water supply pipeline. The cleaning pump 37 and the first drain outlet 14 are turned on, and the reverse osmosis system is flushed at low pressure of 0.3MPa for 10 minutes. Then the system pressure is gradually increased to the normal operating pressure.

[0073] Example 1: Reverse osmosis system in the water treatment workshop of a large steel enterprise (water production capacity 500 m³ / h, continuous operation for 5 years, the flux of the first-stage RO membrane decreased to 61% of the design value, the flux of the second-stage RO membrane decreased to 65% of the design value, and the flux of the concentrate RO membrane decreased to 58% of the design value). First security filter 2: filter element pore size 5μm, volume 0.5m³, normal operating flow rate 500m³ / h; Alkaline washing process: using 0.3% NaOH solution, temperature 30℃, washing time 45min.

[0074] The first step is to perform alkaline washing on reverse osmosis unit 1; The second step is to perform in-situ cleaning of the first security filter 2; the details are as follows: (1) Draining residual liquid: After the alkaline washing is completed, turn off the cleaning pump 37, open the first drain port 14, the second drain port 24 and the third drain port 33, keep the first inlet port 21 and the first outlet port 22 open for 10 minutes, and drain the alkaline liquid in the first security filter 2. (2) Hydrochloric acid injection and soaking: Close the first inlet 21 and the first outlet 22, open the dosing port 23, add 0.3% hydrochloric acid solution to the storage tank 43, turn on the dosing pump 44, and the hydrochloric acid is delivered to the first security filter 2. The acid solution is submerged to 8cm above the top of the filter element (the injection volume is about 0.6m³), and soak for 2 hours. (3) Flushing: Open the second drain outlet 24 to discharge the waste liquid, and close the second drain outlet 24; start the flushing pump 10, use reverse osmosis permeate with a conductivity of about 50 μS / cm for flushing, the flushing flow rate is 100 m³ / h (50% of the normal flow rate), flush for 7 minutes, during which the pH of the effluent is measured by a pH meter and rises from 1.5 to 6.8, then stop flushing; (4) Testing: The Fe³⁺ concentration in the outlet flushing water was found to be 0.08 mg / L, which meets the standard of ≤0.1 mg / L; The third step is to acid wash the reverse osmosis unit 1; use a hydrochloric acid solution with a mass concentration of 0.15%, at a temperature of 25°C, and for a washing time of 50 minutes. The fourth step is to rinse at low pressure for 10 minutes at 0.3 MPa after pickling, and then gradually increase the pressure to 1.2 MPa to restore system operation.

[0075] The results are as follows: Membrane flux: the flow rate of the first-stage RO permeate increased from 149 m³ / h to 183 m³ / h (an increase of 22.8%), the flow rate of the second-stage RO increased from 166 m³ / h to 198 m³ / h (an increase of 19.3%), and the flow rate of the concentrate RO increased from 20 m³ / h to 35 m³ / h (an increase of 40%). Cleaning intervals: The cleaning interval for primary RO is extended from 45 days to 90 days (100% increase), for secondary RO from 120 days to 180 days (50% increase), and for concentrate RO from 20 days to 45 days (125% increase). Filter replacement: The frequency of filter replacement per month has been reduced from 4 times to 1 time; Operational stability: After 6 months of continuous operation, the membrane flux decay rate was only 5%, far lower than the 15% before implementation, and the conductivity of the product water remained stable at 15~20μS / cm, meeting the requirements for industrial water use.

[0076] This application utilizes in-situ acid washing of the newly added first security filter 2. Through a combination of precise acid injection, directional soaking and stripping, and standard rinsing and testing, the mixed contaminants of metal hydroxide complexes and bacterial flocs trapped in the filter element of the first security filter 2 can be thoroughly removed, thus blocking the path of contaminants re-entering the membrane system in the traditional alkaline washing to acid washing process from the source.

[0077] In the description of the above embodiments, specific features, structures, materials, or characteristics may be combined in any suitable manner in one or more embodiments or examples.

[0078] The above are merely specific embodiments of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A chemical cleaning device for reverse osmosis membranes, characterized in that, include: A reverse osmosis unit has a cleaning fluid inlet and a cleaning fluid return outlet, a reverse osmosis membrane inside, and a first drain outlet at its bottom. The first security filter has a first liquid inlet, a first liquid outlet, a chemical dosing port and a second sewage outlet, and a filter element is installed inside it. The first liquid outlet is connected to the cleaning liquid inlet through a first pipeline. The rinsing unit has a second inlet and a second outlet, and a third drain outlet at its bottom. The second outlet is connected to the first inlet via a second pipeline. The cleaning fluid return port is connected to the second inlet via a third pipeline. The rinsing unit, the second pipeline, the first security filter, the first pipeline, the reverse osmosis unit, and the third pipeline are sequentially connected to form a cleaning flow path for cleaning the reverse osmosis membrane. The dosing unit has a third outlet, which is connected to the dosing port via a fourth pipeline and is configured to deliver cleaning fluid to the first security filter.

2. The chemical cleaning apparatus for reverse osmosis membranes according to claim 1, characterized in that, The rinsing unit includes: The first liquid storage tank has a second liquid outlet on its top and a third drain outlet at its bottom; A cleaning pump is installed on the second pipeline; A first switching valve is installed on the second pipeline to control the on / off state of the second pipeline.

3. The chemical cleaning apparatus for reverse osmosis membranes according to claim 2, characterized in that, The dosing unit includes: A medicine storage tank, on which the third liquid outlet is formed; A dosing pump is installed on the fourth pipeline; The second switching valve is installed on the fourth pipeline and is used to control the on / off state of the fourth pipeline.

4. The chemical cleaning apparatus for reverse osmosis membranes according to claim 3, characterized in that, The chemical cleaning apparatus for reverse osmosis membranes further includes: Control module; A third switching valve is installed on the first pipeline and is used to control the opening and closing of the first pipeline; A fourth switching valve is installed on the third pipeline and is used to control the on / off state of the third pipeline; The first switching valve, the second switching valve, the third switching valve, the fourth switching valve, the cleaning pump, and the dosing pump are all electrically connected to the control module.

5. The chemical cleaning apparatus for reverse osmosis membranes according to claim 4, characterized in that, The chemical cleaning apparatus for reverse osmosis membranes further includes: A first pressure gauge is disposed at the first liquid inlet and electrically connected to the control module, and is configured to detect the liquid inlet pressure of the first liquid inlet; A second pressure gauge is disposed at the first liquid outlet and electrically connected to the control module, and is configured to detect the liquid pressure at the first liquid outlet.

6. The chemical cleaning apparatus for reverse osmosis membranes according to claim 4, characterized in that, The chemical cleaning apparatus for reverse osmosis membranes further includes: A pH meter is installed at the second sewage outlet and electrically connected to the control module. It is configured to detect the pH of the water at the second sewage outlet. A metal ion detector is installed at the first liquid outlet and is configured to detect the concentration of metal ions in the water at the first liquid outlet.

7. A cleaning method using a chemical cleaning apparatus for reverse osmosis membranes as described in any one of claims 1 to 6, characterized in that, Includes the following steps: S1: Alkaline washing of the reverse osmosis unit: S2: Perform in-situ cleaning of the first security filter; S3: Acid washing of the reverse osmosis unit; S4: Rinse the reverse osmosis unit with clean water and raise it to normal operating pressure.

8. The cleaning method for a chemical cleaning apparatus for reverse osmosis membranes according to claim 7, characterized in that, In step S1, the reverse osmosis membrane is subjected to alkaline washing, including: Add alkali solution to the storage tank and deliver it to the first security filter; start the cleaning pump to circulate the alkali solution in the cleaning flow path; after the first preset time of alkali washing, discharge the alkali solution from the cleaning flow path.

9. The cleaning method for a chemical cleaning apparatus for a reverse osmosis membrane according to claim 7, characterized in that, In step S2, the in-situ cleaning of the first security filter includes: Add acid to the storage tank and transfer the acid to the first security filter. After the acid has soaked the first security filter for a second preset time, open the second drain outlet to discharge the acid and rinse the first security filter with clean water. Detect the metal ion concentration and pH at the second drain outlet. If the metal ion concentration is ≤ the first preset value and the pH is ≥ 6.5, proceed to the next step. Otherwise, if the metal ion concentration is > the first preset value or the pH is < 6.5, repeat steps S1 and S2.

10. The cleaning method for a chemical cleaning apparatus for a reverse osmosis membrane according to claim 7, characterized in that, Step S3, acid washing of the reverse osmosis unit includes: Add acid to the storage tank and transport the acid to the first security filter; start the cleaning pump to circulate the acid in the cleaning flow path; after the third preset acid washing time, discharge the acid from the cleaning flow path.

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