A cleaning method and cleaning system for a hot-film coupled seawater desalination filter

Abstract

The application relates to a cleaning method and a cleaning system for a hot-film coupled seawater desalination filter membrane, and belongs to the technical field of membrane cleaning. The water source of the hot-film coupled seawater desalination filter membrane is concentrated brine. The cleaning method comprises the following steps: pickling a hot-film coupled seawater desalination filter membrane to be cleaned to obtain a hot-film coupled seawater desalination filter membrane after pickling; alkali cleaning the hot-film coupled seawater desalination filter membrane after pickling to obtain a hot-film coupled seawater desalination filter membrane after alkali cleaning; oxidant cleaning the hot-film coupled seawater desalination filter membrane after alkali cleaning to obtain a hot-film coupled seawater desalination filter membrane after oxidant cleaning; reducing agent cleaning the hot-film coupled seawater desalination filter membrane after oxidant cleaning to obtain a hot-film coupled seawater desalination filter membrane after cleaning. The cleaning method can effectively solve the problem of poor cleaning effect of the existing conventional membrane cleaning method on the hot-film coupled seawater desalination filter membrane with concentrated brine as the water source.

Description

Technical Field

[0001] This application relates to the field of membrane cleaning technology, and in particular to a cleaning method and system for a thermally coupled seawater desalination filter membrane. Background Technology

[0002] Thermal membrane coupled seawater desalination uses concentrated brine from thermal desalination as the water source for membrane desalination. This eliminates the environmental impact of thermal brine discharge and solves the problem of low water temperature limiting production in winter, making it a new trend in seawater desalination development. However, the concentrated brine remaining after seawater evaporation in thermal desalination, when used as feed water for ultrafiltration, contains not only conventional pollutants such as bacteria, microorganisms, and organic matter, but also high temperatures, strong corrosiveness, and high concentrations of calcium and magnesium ions.

[0003] Currently, for thermally coupled hollow fiber ultrafiltration membranes used in seawater desalination that employ concentrated brine from thermal desalination as the water source, the water source is characterized by high chloride ion content, strong corrosiveness, and high concentrations of calcium and magnesium ions. Conventional cleaning methods cannot completely remove the fouling. Summary of the Invention

[0004] This application provides a cleaning method and system for a thermally coupled seawater desalination filter membrane, in order to solve the technical problem that existing conventional membrane cleaning methods have poor cleaning effect on thermally coupled seawater desalination filter membranes using concentrated brine as the water source.

[0005] In a first aspect, this application provides a method for cleaning a thermally coupled seawater desalination membrane, wherein the water source for the thermally coupled seawater desalination membrane is concentrated brine, and the cleaning method includes:

[0006] The hot-film coupled seawater desalination filter membrane to be cleaned is acid-washed to obtain the acid-washed hot-film coupled seawater desalination filter membrane.

[0007] The acid-washed thermal membrane coupled seawater desalination filter membrane is then subjected to alkaline washing to obtain an alkaline-washed thermal membrane coupled seawater desalination filter membrane.

[0008] The alkaline-washed thermal membrane coupled seawater desalination filter membrane is then cleaned with an oxidant to obtain an oxidant-cleaned thermal membrane coupled seawater desalination filter membrane.

[0009] The thermally coupled seawater desalination membrane, after being cleaned with an oxidant, is then cleaned with a reducing agent to obtain a cleaned thermally coupled seawater desalination membrane.

[0010] Furthermore, in the pickling process, the pickling cleaning agent includes hydrochloric acid and citric acid.

[0011] Furthermore, in the pickling process, the concentration of hydrochloric acid is 0.2% to 0.4% by weight, and the concentration of citric acid is 1% to 3% by weight.

[0012] Furthermore, in the alkaline washing, the concentration of the alkaline cleaning agent is 0.05% to 0.15% by weight.

[0013] Furthermore, in the oxidant cleaning process, the oxidant cleaning agent includes sodium hypochlorite and a bactericide.

[0014] Furthermore, in the oxidant cleaning, the concentration of sodium hypochlorite is 1800 PPM to 2200 PPM, and the concentration of the bactericide is 800 PPM to 1000 PPM.

[0015] Furthermore, in the reducing agent cleaning, the reducing agent cleaning agent includes at least one of sodium bisulfite and potassium bisulfite.

[0016] Furthermore, in the reducing agent cleaning, the concentration of the reducing agent cleaning agent is 0.5% to 0.8% by weight.

[0017] Secondly, this application provides a cleaning system for a thermally coupled seawater desalination membrane, used to implement the steps of the cleaning method for the thermally coupled seawater desalination membrane described in any embodiment of the first aspect, wherein the cleaning system includes:

[0018] Reverse osmosis permeate system is used to provide a source of cleaning water;

[0019] A cleaning agent preparation device is used to prepare cleaning agents; one end of the cleaning agent preparation device is connected to the reverse osmosis permeate device; the other end of the cleaning agent preparation device is sequentially connected to a cleaning water pump, a cleaning filter, and a thermally coupled seawater desalination membrane system.

[0020] An emptying system is used to empty the liquid from the thermally coupled seawater desalination membrane system before cleaning and to empty the liquid from the thermally coupled seawater desalination membrane system and the cleaning agent preparation device after cleaning; the emptying system is connected to the thermally coupled seawater desalination membrane system and the cleaning agent preparation device respectively.

[0021] Furthermore, the cleaning system also includes:

[0022] A compressed air supply system is used to perform air scrubbing on the cleaned and discharged hot-film coupled seawater desalination filter system; the compressed air supply system is connected to the hot-film coupled seawater desalination filter system.

[0023] The technical solutions provided in this application have the following advantages compared with the prior art:

[0024] This application provides a cleaning method for a thermocoupled seawater desalination membrane. The cleaning method includes acid washing, alkaline washing, oxidant cleaning, and reductant cleaning. This highly efficient cleaning method, combining "basic acid-alkaline washing + enhanced oxidation-reduction washing," effectively solves the problem of poor cleaning performance of conventional membrane cleaning methods for thermocoupled seawater desalination membranes using concentrated brine as the water source. Specifically: basic acid washing primarily targets conventional inorganic scale, metal oxides, or hydroxides; basic alkaline washing primarily removes natural organic pollutants, inorganic / organic colloidal mixed pollutants, and microorganisms; oxidant cleaning primarily targets microbial and fungal contamination; and reductant cleaning primarily targets rust contamination, metal oxides and hydroxides, and aerobic bacteria. Attached Figure Description

[0025] The accompanying drawings, which are incorporated in and form part of this specification, illustrate embodiments consistent with this application and, together with the description, serve to explain the principles of this application.

[0026] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, for those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0027] Figure 1 A schematic flowchart illustrating a cleaning method for a thermally coupled seawater desalination filter membrane provided in an embodiment of this application;

[0028] Figure 2 This is a schematic diagram of a cleaning system for a thermally coupled seawater desalination filter membrane provided in an embodiment of this application;

[0029] Figure 2 In the diagram, ① is the reverse osmosis permeate unit; ② is the cleaning agent preparation unit; ③ is the cleaning water pump; ④ is the cleaning filter; ⑤ is the thermal membrane coupling seawater desalination membrane system; ⑥ is the compressed air supply system; and ⑦ is the exhaust system. Detailed Implementation

[0030] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0031] Unless otherwise specified, all raw materials, reagents, instruments and equipment used in this application can be purchased from the market or prepared by existing methods.

[0032] Thermal membrane coupled seawater desalination uses concentrated brine from thermal desalination as the water source for membrane desalination. This eliminates the environmental impact of thermal brine discharge and solves the problem of low water temperature limiting production in winter, making it a new trend in seawater desalination development. However, the concentrated brine remaining after seawater evaporation in thermal desalination, when used as feed water for ultrafiltration, contains not only conventional pollutants such as bacteria, microorganisms, and organic matter, but also high temperatures, strong corrosiveness, and high concentrations of calcium and magnesium ions.

[0033] Currently, for thermally coupled hollow fiber ultrafiltration membranes used in seawater desalination that employ concentrated brine from thermal desalination as the water source, the water source is characterized by high chloride ion content, strong corrosiveness, and high concentrations of calcium and magnesium ions. Conventional cleaning methods cannot completely remove the fouling.

[0034] The technical solution provided by the embodiments of the present invention is to solve the above-mentioned technical problems, and the general idea is as follows:

[0035] Firstly, this application provides a method for cleaning a thermally coupled seawater desalination membrane, wherein the water source for the thermally coupled seawater desalination membrane is concentrated brine, such as... Figure 1 As shown, the cleaning method includes:

[0036] The hot-film coupled seawater desalination filter membrane to be cleaned is acid-washed to obtain the acid-washed hot-film coupled seawater desalination filter membrane.

[0037] The acid-washed thermal membrane coupled seawater desalination filter membrane is then subjected to alkaline washing to obtain an alkaline-washed thermal membrane coupled seawater desalination filter membrane.

[0038] The alkaline-washed thermal membrane coupled seawater desalination filter membrane is then cleaned with an oxidant to obtain an oxidant-cleaned thermal membrane coupled seawater desalination filter membrane.

[0039] The thermally coupled seawater desalination membrane, after being cleaned with an oxidant, is then cleaned with a reducing agent to obtain a cleaned thermally coupled seawater desalination membrane.

[0040] This application provides a cleaning method for a thermocoupled seawater desalination membrane. The cleaning method includes acid washing, alkaline washing, oxidant cleaning, and reductant cleaning. This highly efficient cleaning method, combining "basic acid-alkaline washing + enhanced oxidation-reduction washing," effectively solves the problem of poor cleaning performance of conventional membrane cleaning methods for thermocoupled seawater desalination membranes using concentrated brine as the water source. Specifically: basic acid washing primarily targets conventional inorganic scale, metal oxides, or hydroxides; basic alkaline washing primarily removes natural organic pollutants, inorganic / organic colloidal mixed pollutants, and microorganisms; oxidant cleaning primarily targets microbial and fungal contamination; and reductant cleaning primarily targets rust contamination, metal oxides and hydroxides, and aerobic bacteria.

[0041] In one embodiment of this application, the pickling agent includes hydrochloric acid and citric acid.

[0042] In this application, hydrochloric acid and citric acid are used as pickling agents in the pickling process, which are mainly used to clean and remove conventional inorganic scale, metal oxides or hydroxides in the thermally coupled seawater desalination filter membrane.

[0043] In one embodiment of this application, during the pickling process, the concentration of hydrochloric acid is 0.2% to 0.4% by weight, and the concentration of citric acid is 1% to 3% by weight.

[0044] In some specific embodiments of this application, during the pickling process, the concentration of hydrochloric acid can be 0.2% by weight, 0.3% by weight, 0.4% by weight, etc., and the concentration of citric acid can be 1% by weight, 2% by weight, 3% by weight, etc.

[0045] In one embodiment of this application, the concentration of the alkaline cleaning agent in the alkaline washing is 0.05% to 0.15% by weight.

[0046] In this application, alkaline washing primarily removes natural organic pollutants from the thermally coupled seawater desalination filter membrane. It also has a certain removal effect on inorganic / organic colloidal mixed pollutants and microorganisms. In some specific embodiments, the alkaline washing agent can be sodium hydroxide, potassium hydroxide, etc., and the concentration of the alkaline washing agent can be 0.05 wt%, 0.06 wt%, 0.07 wt%, 0.08 wt%, 0.09 wt%, 0.10 wt%, 0.11 wt%, 0.12 wt%, 0.13 wt%, 0.14 wt%, 0.15 wt%, etc.

[0047] In one embodiment of this application, the oxidant cleaning agent includes sodium hypochlorite and a bactericide in the oxidant cleaning process.

[0048] In this application, oxidant cleaning is mainly aimed at microbial and fungal contamination in the thermally coupled seawater desalination filter membrane. In some specific embodiments, commercially available non-oxidizing bactericides can be used as the bactericide.

[0049] In one embodiment of this application, during the oxidant cleaning, the concentration of sodium hypochlorite is 1800 PPM to 2200 PPM, and the concentration of the bactericide is 800 PPM to 1000 PPM.

[0050] In some specific embodiments of this application, during the oxidant cleaning, the concentration of sodium hypochlorite can be 1800 PPM, 1900 PPM, 2000 PPM, 2100 PPM, 2200 PPM, etc., and the concentration of the bactericide can be 800 PPM, 900 PPM, 1000 PPM, etc.

[0051] As one embodiment of this application, in the reducing agent cleaning, the reducing agent cleaning agent includes at least one of sodium bisulfite and potassium bisulfite.

[0052] In this application, the reducing agent cleaning is mainly aimed at rust contamination, metal oxides and hydroxides, as well as aerobic bacteria in the thermally coupled seawater desalination filter membrane.

[0053] In one embodiment of this application, the concentration of the reducing agent cleaning agent in the reducing agent cleaning is 0.5% to 0.8% by weight.

[0054] In this application, the concentration of the reducing agent cleaning agent in the reducing agent cleaning process can be 0.5% by weight, 0.6% by weight, 0.7% by weight, 0.8% by weight, etc.

[0055] Secondly, this application provides a cleaning system for a thermally coupled seawater desalination membrane, used to implement the steps of the cleaning method for the thermally coupled seawater desalination membrane described in any embodiment of the first aspect, such as... Figure 2 As shown, the cleaning system includes:

[0056] Reverse osmosis permeate system is used to provide a source of cleaning water;

[0057] A cleaning agent preparation device is used to prepare cleaning agents; one end of the cleaning agent preparation device is connected to the reverse osmosis permeate device; the other end of the cleaning agent preparation device is sequentially connected to a cleaning water pump, a cleaning filter, and a thermally coupled seawater desalination membrane system.

[0058] An emptying system is used to empty the liquid from the thermally coupled seawater desalination membrane system before cleaning and to empty the liquid from the thermally coupled seawater desalination membrane system and the cleaning agent preparation device after cleaning; the emptying system is connected to the thermally coupled seawater desalination membrane system and the cleaning agent preparation device respectively.

[0059] In some specific embodiments of this application, the reverse osmosis water production device is specifically the fresh water produced by thermal membrane coupled seawater desalination reverse osmosis, which is sent to the cleaning water tank to provide a water source for cleaning.

[0060] In some specific embodiments of this application, the venting system specifically discharges the cleaning waste liquid through a discharge valve to a neutralization tank, where it is neutralized and then sent to a wastewater treatment plant for further treatment and recycling.

[0061] In this application, the cleaning system for the thermally coupled seawater desalination filter membrane is based on the above-described cleaning method for the thermally coupled seawater desalination filter membrane. The specific steps of the cleaning method for the thermally coupled seawater desalination filter membrane can be referred to the above embodiments. Since the cleaning system for the thermally coupled seawater desalination filter membrane adopts some or all of the technical solutions of the above embodiments, it has at least all the beneficial effects brought about by the technical solutions of the above embodiments, which will not be elaborated here.

[0062] As one embodiment of this application, the cleaning system further includes:

[0063] A compressed air supply system is used to perform air scrubbing on the cleaned and discharged hot-film coupled seawater desalination filter system; the compressed air supply system is connected to the hot-film coupled seawater desalination filter system.

[0064] In this application, the air scrubbing technology using compressed air after cleaning and soaking and before cleaning cycle cleverly combines physical cleaning methods with chemical cleaning methods.

[0065] In summary, this application provides a method and system for cleaning hollow fiber ultrafiltration membranes used in thermally coupled seawater desalination, overcoming the technical problem of incomplete cleaning using conventional methods after the hollow fiber ultrafiltration membrane becomes clogged. Using this invention not only solves the problem of incomplete cleaning but also extends the cleaning cycle of the hollow fiber ultrafiltration membrane by three times.

[0066] The present application is further illustrated below with reference to specific embodiments. It should be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of the application. Experimental methods in the following embodiments that do not specify specific conditions are generally determined according to national standards. If there is no corresponding national standard, then general international standards, conventional conditions, or conditions recommended by the manufacturer are followed.

[0067] Example 1

[0068] This example provides a cleaning method for a thermally coupled seawater desalination membrane, wherein the water source for the thermally coupled seawater desalination membrane is concentrated brine, and the cleaning method includes:

[0069] The hot-film coupled seawater desalination filter membrane to be cleaned is acid-washed to obtain an acid-washed hot-film coupled seawater desalination filter membrane; in the acid washing, the concentration of hydrochloric acid is 0.3% by weight and the concentration of citric acid is 2% by weight.

[0070] The acid-washed hot-film coupled seawater desalination filter membrane is subjected to alkaline washing to obtain an alkaline-washed hot-film coupled seawater desalination filter membrane; in the alkaline washing, the concentration of sodium hydroxide as the alkaline washing agent is 0.10% by weight.

[0071] The alkaline-washed thermal membrane coupled seawater desalination filter membrane is then subjected to oxidant cleaning to obtain an oxidant-cleaned thermal membrane coupled seawater desalination filter membrane; in the oxidant cleaning, the concentration of sodium hypochlorite is 2000 PPM and the concentration of the non-oxidizing bactericide is 900 PPM.

[0072] The thermally coupled seawater desalination membrane, after being cleaned with an oxidant, is then cleaned with a reducing agent to obtain a cleaned thermally coupled seawater desalination membrane; in the reducing agent cleaning, the concentration of sodium bisulfite is 0.6% by weight.

[0073] The cleaning method for the above-mentioned thermally coupled seawater desalination filter membrane adopts the following... Figure 2 The cleaning system for the heat-film coupled seawater desalination filter membrane shown is implemented. Figure 2 The components are: ① Reverse osmosis permeate system (abbreviated as reverse osmosis permeate); ② Cleaning agent preparation system (also known as cleaning water tank); ③ Cleaning water pump; ④ Cleaning filter (abbreviated as filter); ⑤ Thermally coupled seawater desalination membrane system (abbreviated as hollow fiber ultrafiltration system); ⑥ Compressed air supply system (abbreviated as compressed air); ⑦ Exhaust system (abbreviated as exhaust). The basic principle is as follows:

[0074] The cleaning process uses ① reverse osmosis permeate to provide water for preparing the cleaning solution in the ② cleaning tank. After the solution is prepared, it is pumped through ③ cleaning pump and ④ cleaning filter, then sent to the ⑤ hollow fiber ultrafiltration system. The cleaning solution then returns to the ② cleaning tank, and the cycle repeats. Before the next cycle, the ⑥ compressed air system is used for air scrubbing. Additionally, before cleaning, the water in the ⑤ hollow fiber ultrafiltration system is replaced with the cleaning solution through the ⑦ evacuation system; after cleaning, the cleaning solution in the ⑤ hollow fiber ultrafiltration system and the ② cleaning tank are emptied through the ⑦ evacuation system.

[0075] Adopting such Figure 2The cleaning system for the heat-coupled seawater desalination membrane shown includes the following specific processes for cleaning the membrane:

[0076] 1) Before shutdown at step ①, perform an online backwash once to remove loose material from the membrane surface. The online backwash includes hydraulic cleaning provided by step ③, air cleaning provided by step ⑥, and mixed air-water cleaning provided by both step ③ and step ⑥.

[0077] 2) After the online backwash is completed, open ⑦ and drain the concentrated brine in ①. Make sure there is no water flowing out from the bottom to prevent the reagent from reacting with the concentrated brine ions.

[0078] 3) Add water to step ②, and repeatedly flush the ultrafiltration membrane and pipes using step ③ until the quality of the added water and the drain water is the same. Replace the concentrated brine in the ultrafiltration membrane and pipes, and flush away any residual liquid that may have remained in the pipes after the last cleaning.

[0079] 4) Taking advantage of the temperature of the concentrated brine in the thermal method, using ①, prepare an acid solution to replace the pipe and the aqueous solution inside the hollow fiber ultrafiltration membrane at a low flow rate. After the replacement is completed, close ⑦ and clean and circulate the hollow fiber ultrafiltration membrane for 1 hour, then soak it for half an hour. Before each circulation after soaking, wipe it with air once, and so on, repeating the process.

[0080] 5) After acid washing is completed, flush the pipes and membranes by opening step ⑦ until the quality of the replenishing water and the drain water are the same.

[0081] 6) Taking advantage of the temperature of the concentrated brine in the thermal method, using ①, prepare an alkaline solution (containing sodium hydroxide) to replace the pipe and the aqueous solution inside the hollow fiber ultrafiltration membrane at a low flow rate. After the replacement is completed, close ⑦ and clean the hollow fiber ultrafiltration membrane by circulating it for 1 hour, then soak it for 1 hour. Before each circulation after soaking, wipe it with air once, and so on, repeating the process.

[0082] 7) After the alkaline washing is completed, flush the pipes and membrane by opening step ⑦ until the quality of the replenishing water and the drain water are the same.

[0083] 8) Taking advantage of the temperature of the concentrated brine in the thermal method, using ①, prepare a sodium bisulfite solution and use it to replace the pipe and the aqueous solution inside the hollow fiber ultrafiltration membrane at a low flow rate. After the replacement is completed, close ⑦ and clean and circulate the hollow fiber ultrafiltration membrane for 1 hour, then soak it for 1 hour. Before each circulation after soaking, wipe it with air once, and so on, repeating the process.

[0084] 9) After the sodium bisulfite washing is completed, flush the pipes and membrane by opening step ⑦ until the quality of the replenishing water and the drain water are the same.

[0085] 10) Considering the comprehensive nature of ultrafiltration membrane blockage, when performing oxidant cleaning, taking advantage of the temperature of the concentrated brine in the thermal method, using ①, first prepare a sodium hypochlorite solution, then add an alkaline solution to the sodium hypochlorite solution to make its pH between 11 and 12, and replace the pipeline and the aqueous solution inside the hollow fiber ultrafiltration membrane at a low flow rate. After the replacement is completed, turn off ⑦, clean the hollow fiber ultrafiltration membrane by circulating for 1 hour, then soak for 1 hour. Before circulating after each soaking, wipe it with air once, and so on, repeating the process.

[0086] 11) After the oxidant washing is completed, flush the pipes and membranes by opening step ⑦ until the quality of the replenished water and the drain water are the same.

[0087] 12) In step 4), the water replenishment for the acid solution is provided by step ①. The temperature should be 30℃, the pH of the acid solution should be 2-4, and the cleaning time should be 4-12 hours. If the pH rises by 0.5 units or the color of the solution changes during cleaning, circulation must be stopped immediately and the solution prepared again. The cleaning flow rate is 2m³ / min per ultrafiltration membrane. 3 / h-4m 3 / h, air wiping pressure 0.1MPa, air wiping time 45-60S.

[0088] 13) In step 6), the water replenishment for the prepared alkaline solution is provided by step ①. The temperature should be 30℃, the pH of the alkaline solution should be 11-12, and the cleaning time should be 4-8 hours. If the pH drops by 0.5 units or the color of the solution changes during cleaning, circulation must be stopped immediately and the solution prepared again. The cleaning flow rate is 2m³ / h per ultrafiltration membrane. 3 / h-4m 3 / h, air wiping pressure 0.1MPa, air wiping time 45-60S.

[0089] 14) In step 8), the makeup water for preparing the sulfurous acid solution is provided by step ①, with a temperature of 30°C, a concentration of 0.5%, and a cleaning time of 4-8 hours. The cleaning flow rate is 2m³ / min per ultrafiltration membrane. 3 / h-4m 3 / h, air wiping pressure 0.1MPa, air wiping time 45-60S.

[0090] When using non-oxidizing bactericides for cleaning, it should be done after acid washing and before alkaline washing.

[0091] The membrane flux recovery rate of the thermally coupled seawater desalination filter membrane after cleaning in this case was 99.9%, and the cleaning cycle was 3 months.

[0092] Example 2

[0093] Based on Example 1, this example provides a cleaning method and system for a thermally coupled seawater desalination filter membrane. The only difference from Example 1 is that the concentration of the alkaline cleaning agent is 0.05% by weight; the concentration of sodium hypochlorite is 1800 PPM; and the concentration of the reducing agent cleaning agent is 0.5% by weight. All other steps and parameters are the same.

[0094] The membrane flux recovery rate of the thermally coupled seawater desalination filter membrane after cleaning in this case was 99.3%, and the cleaning cycle was 2.5 months.

[0095] Example 3

[0096] Based on Example 1, this example provides a cleaning method and system for a thermally coupled seawater desalination filter membrane. The only difference from Example 1 is that the concentration of the alkaline cleaning agent is 0.05% by weight; the concentration of sodium hypochlorite is 2200 PPM; and the concentration of the reducing agent cleaning agent is 0.6% by weight. All other steps and parameters are the same.

[0097] The membrane flux recovery rate of the thermally coupled seawater desalination filter membrane after cleaning in this case was 99.5%, and the cleaning cycle was 3 months.

[0098] Comparative Example 1

[0099] Based on Example 1, this example provides a cleaning method and system for a thermally coupled seawater desalination filter membrane. The only difference from Example 1 is that the thermally coupled seawater desalination filter membrane is not acid-washed before alkaline washing, and the other steps and parameters are the same.

[0100] The membrane flux recovery rate of the thermally coupled seawater desalination filter membrane after cleaning in this case was 99.8%, and the cleaning cycle was 3 months.

[0101] Comparative Example 2

[0102] Based on Example 1, this example provides a cleaning method and system for a thermally coupled seawater desalination filter membrane. The only difference from Example 1 is that the thermally coupled seawater desalination filter membrane is subjected to subsequent oxidant and reducing agent cleaning without alkaline washing after acid washing. All other steps and parameters are the same.

[0103] The membrane flux recovery rate of the thermally coupled seawater desalination filter membrane after cleaning in this case was 99.5%, and the cleaning cycle was 2.5 months.

[0104] Comparative Example 3

[0105] Based on Example 1, this example provides a cleaning method and system for a thermally coupled seawater desalination filter membrane. The only difference from Example 1 is that the thermally coupled seawater desalination filter membrane is cleaned with a reducing agent without oxidizing agent cleaning after alkaline washing. All other steps and parameters are the same.

[0106] The membrane flux recovery rate of the thermally coupled seawater desalination filter membrane after cleaning in this case was 99.4%, and the cleaning cycle was 2 months.

[0107] Comparative Example 4

[0108] Based on Example 1, this example provides a cleaning method and system for a thermally coupled seawater desalination filter membrane. The only difference from Example 1 is that the thermally coupled seawater desalination filter membrane is not cleaned with a reducing agent after being cleaned with an oxidant. All other steps and parameters are the same.

[0109] The membrane flux recovery rate of the thermally coupled seawater desalination filter membrane after cleaning in this case was 85%, and the cleaning cycle was 1 month.

[0110] Various embodiments of this application may exist in the form of a range; it should be understood that the description in the form of a range is merely for convenience and brevity and should not be construed as a hard limitation on the scope of this application; therefore, it should be considered that the range description has specifically disclosed all possible sub-ranges and single numerical values ​​within that range. For example, it should be considered that the range description from 1 to 6 has specifically disclosed sub-ranges such as from 1 to 3, from 1 to 4, from 1 to 5, from 2 to 4, from 2 to 6, from 3 to 6, etc., and single numbers within the range, such as 1, 2, 3, 4, 5, and 6, regardless of the range. Furthermore, whenever a numerical range is referred to herein, it means including any referenced number (fraction or integer) within the referred range.

[0111] In this application, unless otherwise stated, directional terms such as "upper" and "lower" specifically refer to the drawing directions in the accompanying drawings. Furthermore, in the description of this application, terms such as "comprising" and "including" mean "including but not limited to." In this document, relational terms such as "first" and "second" are used merely to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. In this document, "and / or" describes the relationship between related objects, indicating that three relationships can exist; for example, A and / or B can represent: A alone, A and B simultaneously, or B alone. A and B can be singular or plural. In this document, "at least one" means one or more, and "more than one" means two or more. "At least one," "at least one of the following," or similar expressions refer to any combination of these items, including any combination of single or plural items. For example, "at least one of a, b, or c" or "at least one of a, b, and c" can both mean: a, b, c, ab (i.e., a and b), ac, bc, or abc, where a, b, and c can be a single or multiple.

[0112] The above description is merely a specific embodiment of this application, enabling those skilled in the art to understand or implement this application. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of this application. Therefore, this application is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features claimed herein.

Claims

1. A method for cleaning a thermally coupled seawater desalination filter membrane, characterized in that, The water source for the thermally coupled seawater desalination filter membrane is concentrated brine produced by the thermal seawater desalination process. The cleaning method includes the following steps performed in sequence: The hot-film coupled seawater desalination filter membrane to be cleaned is acid-washed to obtain the acid-washed hot-film coupled seawater desalination filter membrane. The acid-washed thermal membrane coupled seawater desalination filter membrane is then subjected to alkaline washing to obtain an alkaline-washed thermal membrane coupled seawater desalination filter membrane. The alkaline-washed hot-film coupled seawater desalination filter membrane is then cleaned with an oxidant to obtain an oxidant-cleaned hot-film coupled seawater desalination filter membrane. The oxidant cleaning agent includes sodium hypochlorite and a bactericide. The concentration of sodium hypochlorite is 1800 PPM to 2200 PPM, and the concentration of the bactericide is 800 PPM to 1000 PPM. The thermally coupled seawater desalination membrane, after being cleaned with an oxidant, is then cleaned with a reducing agent to obtain a cleaned thermally coupled seawater desalination membrane. The reducing agent includes at least one of sodium bisulfite and potassium bisulfite, and the concentration of the reducing agent is 0.5% to 0.8% by weight.

2. The cleaning method for the thermally coupled seawater desalination filter membrane according to claim 1, characterized in that, In the pickling process, the pickling cleaning agent includes hydrochloric acid and citric acid.

3. The cleaning method for the thermally coupled seawater desalination filter membrane according to claim 2, characterized in that, In the pickling process, the concentration of hydrochloric acid is 0.2% to 0.4% by weight, and the concentration of citric acid is 1% to 3% by weight.

4. The cleaning method for the thermally coupled seawater desalination filter membrane according to claim 1, characterized in that, In the alkaline washing process, the concentration of the alkaline cleaning agent is 0.05% to 0.15% by weight.

5. A cleaning system for a thermally coupled seawater desalination membrane, used to implement the cleaning method for the thermally coupled seawater desalination membrane according to any one of claims 1 to 4, characterized in that, The cleaning system includes: Reverse osmosis permeate system is used to provide a source of cleaning water; A cleaning agent preparation device is used to prepare cleaning agents; one end of the cleaning agent preparation device is connected to the reverse osmosis permeate device; the other end of the cleaning agent preparation device is sequentially connected to a cleaning water pump, a cleaning filter, and a thermally coupled seawater desalination membrane system. An emptying system is used to empty the liquid from the thermally coupled seawater desalination membrane system before cleaning and to empty the liquid from the thermally coupled seawater desalination membrane system and the cleaning agent preparation device after cleaning; the emptying system is connected to the thermally coupled seawater desalination membrane system and the cleaning agent preparation device respectively.

6. The cleaning system for the thermally coupled seawater desalination filter membrane according to claim 5, characterized in that, The cleaning system also includes: A compressed air supply system is used to perform air scrubbing on the cleaned and discharged hot-film coupled seawater desalination filter system; the compressed air supply system is connected to the hot-film coupled seawater desalination filter system.

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