A method for preparing a filter membrane with a lifespan detection function

Abstract

The present invention discloses a method for preparing a filter membrane with a life detection function, which relates to the technical field of insulating oil regeneration. In the present invention, an indicator fluorescent agent is applied to indicate the life of the filter membrane. By performing a surface coating treatment of the pH indicator fluorescent agent on the filter membrane, a colored indicator surface layer is formed on the surface of the filter membrane. The acid value of the aged oil filtered through the filter membrane is not only reduced, but also during the whole process of filtration, it is possible to detect in real time whether the filter membrane has reached its service life according to the color change of the fluorescent agent on the surface layer of the filter membrane, thereby improving the filtration accuracy and efficiency of transformer oil. The filter membrane prepared by the present invention has excellent membrane life detection accuracy and can meet the high-efficiency purification and filtration in the field of transformer insulating oil.

Description

Technical Field

[0001] The present invention relates to the technical field of insulating oil regeneration, and particularly to a method for preparing a filter membrane with a life detection function. Background Art

[0002] Insulating oil is a key component of oil-immersed power transformers. However, during the long-term operation of transformers, the insulating oil continuously oxidizes, generating by-products such as carboxylic acids, ketones, aldehydes, alcohols, and moisture. These by-products will increase the acid value, water content, dielectric loss, and conductivity of the insulating oil. The acid value parameter is an important indicator that can cause serious damage to power transformers and substations. Purifying and regenerating the aged transformer oil can promote the sustainable development of energy.

[0003] Currently, the semi-permeable membrane filtration method is a research hotspot for the purification and regeneration of transformer insulating oil. However, how to quickly detect the service limit of the filter membrane and improve the purification and regeneration efficiency of transformer insulating oil is a technical problem that needs to be solved. Summary of the Invention

[0004] The purpose of the present invention is to provide a method for preparing a filter membrane with a life detection function to solve the problems existing in the above-mentioned prior art, quickly detect the service limit of the filter membrane, and effectively improve the purification efficiency of transformer oil.

[0005] To achieve the above purpose, the present invention provides the following solutions:

[0006] One of the technical solutions of the present invention: Provide the application of an indicator fluorescent agent in indicating the life of a filter membrane, and the indicator fluorescent agent is fluorescein or ETH 5294.

[0007] Further, the filter membrane is a glass fiber membrane, a polyvinylidene fluoride membrane, or a polypropylene membrane.

[0008] ETH 5294 is a hydrophobic pH indicator and is used as a transmission or fluorescence probe molecule in many types of hydrophobic sensor membranes and is oil-soluble.

[0009] Fluorescein is easily soluble in ethanol and ether, soluble in benzene and alkaline solutions, and insoluble in water, belonging to a hydrophobic lipophilic indicator.

[0010] Another technical solution of the present invention: Provide a method for preparing a filter membrane with a life detection function, including the following steps: Load the indicator fluorescent agent onto the surface of the filter membrane through a surface coating process to obtain the filter membrane with a life detection function; the indicator fluorescent agent is fluorescein or ETH 5294.

[0011] Further, the filter membrane preparation method includes the following steps: Immerse the filter membrane in a solution containing the indicator fluorescent agent, and then carry out curing and drying to obtain the filter membrane with a life detection function.

[0012] Further, the solution containing the indicator fluorescent agent is obtained by stirring polydimethylsiloxane (PDMS), a modifying reagent with low surface energy, and the indicator fluorescent agent at 40 - 50°C for 20 - 40 min, and the mass concentration of the indicator fluorescent agent is 10% - 12%.

[0013] Further, the filter membrane is first ultrasonically cleaned with ethanol and deionized water for 20 - 40 min respectively, and then placed in a vacuum drying oven for vacuum drying; the temperature of the vacuum drying is 40 - 50°C, and the time is 40 - 50 min.

[0014] Further, the soaking time is 30 - 40 min.

[0015] Further, the curing temperature is 60 - 80°C, and the curing time is 1 - 2 h, so that the indicator can be evenly and completely coated on the filter membrane.

[0016] Further, the drying temperature is 40 - 60°C, the drying is vacuum drying, and the time is 2 - 4 h.

[0017] Further, the curing temperature is higher than the drying temperature.

[0018] Technical solution three of the present invention: Provide a filter membrane with a life detection function prepared by the above preparation method.

[0019] Technical solution four of the present invention: Provide the application of the above filter membrane with a life detection function in the purification and regeneration of insulating oil.

[0020] Use a vacuum filtration device and a filter membrane with a life detection function to filter the aged transformer insulating oil. The vacuum filtration device consists of a circulating vacuum pump, a sintered glass funnel, and a conical flask.

[0021] Further, the application process includes the following steps: Use the filter membrane with a life detection function to purify and regenerate the insulating oil. When the fluorescence of the filter membrane with a life detection function changes, replace the filter membrane with a life detection function and continue the purification and regeneration or end the purification and regeneration.

[0022] In the present invention, the fluorescent indicator is evenly coated on the filter membrane and integrated with the filter membrane. When the filter membrane changes color, it indicates that the filter membrane changes from neutral or weakly acidic to acidic at this time. Therefore, continuing to filter the aged oil cannot reduce the acidic aging substances in the oil.

[0023] Among them, the end point of the life of the fluorescein indicator loaded on the surface of the filter membrane is from yellow - green to purple - green; the end point of the life of the ETH5294 indicator loaded on the surface of the filter membrane is from dark gray to brown.

[0024] The present invention discloses the following technical effects:

[0025] The present invention applies an indicator fluorescent agent to indicating the service life of a filter membrane. By performing a surface coating treatment of a pH indicator fluorescent agent on the filter membrane, a colored indicator surface layer is formed on the surface of the filter membrane. The acid value of the aged oil filtered through this filter membrane not only decreases, but also during the entire filtration process, it is possible to detect in real time whether the filter membrane has reached its service life based on the color change of the fluorescent agent on the surface layer of the filter membrane, thereby improving the filtration accuracy and efficiency of transformer oil.

[0026] The hydrophobic and lipophilic filter membrane prepared by the present invention has excellent detection accuracy of membrane service life and can meet the high-efficiency purification and filtration in the field of transformer insulating oil. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required to be used in the embodiments. Obviously, the drawings in the following description are only some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can be obtained based on these drawings.

[0028] Figure 1 It is the acid value of the initial aged insulating oil (aged oil) of the present invention and the insulating oil after being treated by the filter membranes of Examples 1-3 and Comparative Examples 1-2.

[0029] Figure 2 It is the comparison of the acid values of the filter membrane in Comparative Example 1 of the present invention for treating different volumes of aged oil.

[0030] Figure 3 It is the time for the aged oil treated by the filter membranes prepared in Examples 1-3 of the present invention and the volume of the aged oil treated. The left vertical coordinate is the volume of the aged oil when the filter membrane life reaches the maximum limit, and the time on the right vertical coordinate is the time consumed when the filter membrane life reaches the maximum limit. DETAILED DESCRIPTION OF THE INVENTION

[0031] Now, various exemplary embodiments of the present invention will be described in detail. This detailed description should not be considered as a limitation of the present invention, but rather as a more detailed description of certain aspects, characteristics, and implementation schemes of the present invention.

[0032] It should be understood that the terms described in the present invention are only for describing specific implementation manners and are not used to limit the present invention. Additionally, for the numerical ranges in the present invention, it should be understood that each intermediate value between the upper and lower limits of the range is also specifically disclosed. Any intermediate value within any stated value or stated range, as well as each smaller range between any other stated value or intermediate value within the stated range, is also included in the present invention. The upper and lower limits of these smaller ranges can be independently included or excluded from the range.

[0033] Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. Although this invention only describes preferred methods and materials, any methods and materials similar or equivalent to those described herein may also be used in the practice or testing of this invention. All documents mentioned in this specification are incorporated by reference to disclose and describe the methods and / or materials related to those documents. In case of conflict with any incorporated document, the content of this specification shall prevail.

[0034] Without departing from the scope or spirit of this invention, various improvements and changes can be made to the specific embodiments of the specification of this invention, which are obvious to those skilled in the art. Other embodiments obtained from the specification of this invention are obvious to those skilled in the art. The specification and examples of this invention are merely exemplary.

[0035] Regarding the use of "comprising", "including", "having", "containing", etc. herein, they are all open-ended terms, meaning including but not limited to.

[0036] In the examples and comparative examples of this invention, the test standard for the acid value of insulating oil is: GB / T 28552 - 2012. Instrument for measuring the acid value of insulating oil: DKSZ - 3H type fully automatic acid value tester, Wuhan Dingsheng Electric Power Automation Co., Ltd. The acid value of the aging transformer oil to be treated is 0.186 mgKOH / g, the water content is 34.2 mg / L, the dielectric loss factor is 1.079%, and the breakdown voltage is 30.44 kV.

[0037] Example 1

[0038] Prepare a filter membrane with a life detection function:

[0039] S1. Mix the low - surface - energy modification reagent polydimethylsiloxane (PDMS) with a pH - indicating fluorescent agent and place it on a magnetic stirrer to stir for 20 min at a temperature set to 40°C to obtain an indicator solution. In this example, the pH - indicating fluorescent agent is fluorescein indicator, and the indicating fluorescent agent accounts for 10% of the total mass of the mixed solution.

[0040] S2. First, ultrasonically clean the filter membrane (polyvinylidene fluoride filter membrane) with ethanol and deionized water for 20 min respectively, and then place it in a vacuum drying oven for vacuum drying. In this example, the set drying temperature of the vacuum drying oven is 40°C, and the drying time is 40 min.

[0041] S3. Immerse the dried filter membrane in the indicator solution for 30 min and then take it out, and put it into a muffle furnace for curing the filter membrane. In this example, the set temperature of the muffle furnace is 60°C, and the curing time is 1 h.

[0042] S4. Place the filter membrane obtained through the above steps in a vacuum drying oven for vacuum drying. Set the temperature to 40 °C and the time to 2 h to obtain a filter membrane with a life detection function.

[0043] Use a vacuum filtration device and the prepared filter membrane with a life detection function to filter the aged transformer oil. Before filtration, cut the membrane sample into a diameter of 5 cm and install it on a sintered glass funnel. Open the vacuum pump (0.05 MPa) to allow the oil sample to flow through the filter membrane. The end point is when the filter membrane changes from yellow-green to purple-green. Test the acid value of the oil sample before and after filtration.

[0044] Example 2

[0045] Prepare a filter membrane with a life detection function:

[0046] S1. Mix the low surface energy modifying reagent polydimethylsiloxane (PDMS) with a pH indicator fluorescent agent and place it on a magnetic stirrer for stirring for 30 min. Set the temperature to 45 °C to obtain an indicator solution. In this example, the pH indicator fluorescent agent uses fluorescein indicator, and the indicator fluorescent agent accounts for 11% of the total mass of the mixed solution.

[0047] S2. First, ultrasonically clean the filter membrane (glass fiber membrane) with ethanol and deionized water for 30 min respectively, and then place it in a vacuum drying oven for vacuum drying. In this example, the set drying temperature of the vacuum drying oven is 40 °C and the drying time is 50 min.

[0048] S3. Immerse the dried filter membrane in the indicator solution for 35 min and then take it out, and put it into a muffle furnace for curing the filter membrane. In this example, the set temperature of the muffle furnace is 70 °C and the curing time is 2 h.

[0049] S4. Place the filter membrane obtained through the above steps in a vacuum drying oven for vacuum drying. Set the temperature to 50 °C and the time to 3 h to obtain a filter membrane with a life detection function.

[0050] Use a vacuum filtration device and the prepared filter membrane with a life detection function to filter the aged transformer oil. Before filtration, cut the membrane sample into a diameter of 5 cm and install it on a sintered glass funnel. Open the vacuum pump (0.05 MPa) to allow the oil sample to flow through the filter membrane. The end point is when the filter membrane changes from yellow-green to purple-green. Test the acid value of the oil sample before and after filtration.

[0051] Example 3

[0052] Prepare a filter membrane with a life detection function:

[0053] S1. Mix the low surface energy modifying reagent polydimethylsiloxane (PDMS) with the pH indicator fluorescent agent, place the mixture on a magnetic stirrer and stir for 40 min at a temperature of 50 °C to obtain an indicator solution. In this example, the pH indicator fluorescent agent used is ETH 5294 indicator, and the indicator fluorescent agent accounts for 12% of the total mass of the mixed solution.

[0054] S2. First, ultrasonically clean the filter membrane (polypropylene filter membrane) with ethanol and deionized water for 40 min respectively, and then place it in a vacuum drying oven for vacuum drying. In this example, the set drying temperature of the vacuum drying oven is 50 °C and the drying time is 40 min.

[0055] S3. Immerse the dried filter membrane in the indicator solution for 40 min, then take it out and put it into a muffle furnace for curing of the filter membrane. In this example, the set temperature of the muffle furnace is 80 °C and the curing time is 2 h.

[0056] S4. Place the filter membrane obtained through the above steps in a vacuum drying oven for vacuum drying at a temperature of 60 °C for 4 h to obtain a filter membrane with a life detection function.

[0057] Use a vacuum filtration device and the prepared filter membrane with a life detection function to filter the aged transformer oil. Before filtration, cut the membrane sample into a diameter of 5 cm and install it on a sintered glass funnel. Open the vacuum pump (0.05 MPa) to make the oil sample flow through the filter membrane. The end point is when the filter membrane changes from dark gray to brown. Test the acid value of the oil sample before and after filtration.

[0058] Comparative Example 1

[0059] Purify and regenerate the aged transformer oil for the filter membrane (polyvinylidene fluoride filter membrane) after ultrasonic cleaning and drying. The ultrasonic cleaning and drying steps are the same as in Example 1.

[0060] Use a vacuum filtration device and the prepared filter membrane to filter the aged transformer oil. Before filtration, cut the membrane sample into a diameter of 5 cm and install it on a sintered glass funnel. Open the vacuum pump (0.05 MPa) to make the oil sample flow through the filter membrane. The end point is when the oil sample in the filter flask is completely filtered. Test the acid value and life detection of the oil sample before and after filtration.

[0061] In this comparative example, when performing life detection, the life of the filter membrane is detected by comparing the acid value in the oil under different filtration capacities. This process takes much longer than in Examples 1 - 3 and is inefficient.

[0062] In the present invention, real-time detection is carried out. In Comparative Example 1, the use limit is reached by filtering a fixed volume of aged oil in batches and measuring the acid value separately until the acid value of the aged oil no longer decreases, indicating that the filter membrane has no effect, that is, the use limit is reached. The method is cumbersome and time-consuming.

[0063] Comparative Example 2

[0064] In this comparative example, methyl red indicator was used as the indicator, and the remaining experimental steps were the same as those in Example 1.

[0065] Figure 1 This is the acid value of the initial aged insulating oil (aged oil) of the present invention and the insulating oil after being treated by the filter membranes of Examples 1-3 and Comparative Examples 1-2.

[0066] Figure 2 This is the comparison of the acid values of the aged oil with different volumes treated by the filter membrane of Comparative Example 1 of the present invention. It can be seen that when filtering 200 mL, 400 mL, 600 mL, and 800 mL of aged oil, the acid value decreases in turn. When it is 1000 mL, the acid value of the aged oil increases, indicating that the filter membrane has reached its service life when filtering 800 mL of oil, and the acid value in the oil cannot be further reduced subsequently.

[0067] Figure 3 This is the time for the aged oil treated by the filter membranes prepared in Examples 1-3 of the present invention and the volume of the aged oil treated. The left vertical coordinate is the volume of the aged oil treated when the filter membrane life reaches the maximum limit, and the time on the right vertical coordinate is the time consumed when the filter membrane life reaches the maximum limit.

[0068] The above-described embodiments are only descriptions of the preferred embodiments of the present invention, and do not limit the scope of the present invention. Without departing from the design spirit of the present invention, various deformations and improvements made by those of ordinary skill in the art to the technical solutions of the present invention shall fall within the protection scope determined by the claims of the present invention.

Claims

1. A method for preparing a filter membrane for purification and regeneration of insulating oil with a life detection function, characterized in that: The following steps are involved: The filter membrane is immersed in a solution containing an indicating fluorescent agent, and then solidified and dried to obtain the insulating oil purification and regeneration filter membrane with a life detection function; The filter membrane is a glass fiber membrane, a polyvinylidene fluoride filter membrane or a polypropylene filter membrane; The solution containing the indicating fluorescent agent is obtained by mixing dimethylsiloxane and the indicating fluorescent agent, the mass concentration of the indicating fluorescent agent is 10%-12%; the indicating fluorescent agent is fluorescent yellow or ETH 5294; The curing temperature is 60-80° C., and the curing time is 1-2 hours; the drying temperature is 40-60° C., and the drying time is 2-4 hours; the curing temperature is higher than the drying temperature.

2. The filter membrane for purification and regeneration of insulating oil with life detection function prepared by the preparation method as claimed in claim 1.

3. Application of the filter membrane for purification and regeneration of insulating oil with life detection function as claimed in claim 2 in purification and regeneration of insulating oil, characterized in that: The following steps are involved: The insulating oil is purified and regenerated by using the insulating oil purification and regeneration filter membrane with a life detection function. When the insulating oil purification and regeneration filter membrane with a life detection function undergoes a fluorescence change, the insulating oil purification and regeneration filter membrane with a life detection function is replaced to continue purification and regeneration or terminate purification and regeneration.

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