A metal Fe-doped base insulating fluid, a preparation method and application thereof

Abstract

The application provides a metal Fe-doped base insulating fluid and a preparation method and application thereof.The preparation method is as follows: 1) mixing citric acid and ferric nitrate, and stirring to obtain a mixed solution; 2) drying and grinding a mixture obtained by calcining the mixed solution obtained in the step 1) into a powder; 3) calcining the powder obtained in the step 2) to obtain a Fe-based catalyst; and 4) mixing the Fe-based catalyst obtained in the step 3) with mineral insulating oil, and post-treating to obtain a product, i.e., the metal Fe-doped base insulating fluid.The application effectively reduces the frequent false alarm and missed alarm phenomenon of the transformer three-ratio method in the prior art, realizes real-time and dynamic monitoring and early warning of the transformer, reduces the risk of false alarm and missed alarm, and improves the safety operation of the transformer.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of transformer oil dissolved gas fault early warning, and in particular to a doped metal Fe-based insulating fluid and a preparation method and application thereof. BACKGROUND

[0002] Insulating materials are affected by temperature, electric field and catalysts during the operation of the transformer, and can crack to produce certain specific gases as characteristic gases. The dissolved gases in the transformer oil can effectively reflect the good or bad operation condition of the transformer, so monitoring the content of the dissolved gases in the oil can discover the latent failure of the transformer as early as possible to prevent the development and expansion of the failure. The molecules of the solid insulating material contain a large number of anhydrous dextrorotatory sugar rings and weak C-O bonds and glucoside bonds, and their thermal stability is weaker than the carbon-hydrogen bond in the oil, and they can recombine at a lower temperature. When affected by electricity, heat and mechanical stress as well as oxygen, moisture and the like, the polymer undergoes oxidation decomposition, cracking (depolymerization) and hydrolysis chemical reactions, so that the C-O, C-H and C-C bonds are broken to generate CO and CO2. The gases produced by the decomposition of the solid insulating material change the types and concentrations of the dissolved gases in the transformer oil, resulting in changes in the codes of the three-ratio method, so that the three-ratio method of the transformer produces frequent false positives and false negatives. Thus, a series of problems such as economic losses, safety hazards and reduced trust are caused. Therefore, corresponding improvement measures need to be taken to improve the diagnostic accuracy and reduce the occurrence of false positives and false negatives. SUMMARY

[0003] The present application aims to provide a doped metal Fe-based insulating fluid and a preparation method and application thereof to solve the problems existing in the prior art, to realize real-time and dynamic monitoring and early warning of the transformer, to reduce the risk of false positives and false negatives, and to improve the safety of the transformer in operation.

[0004] In order to achieve the above-mentioned application purpose, the present application provides the following technical solutions:

[0005] The present application provides a preparation method of a doped metal Fe-based insulating fluid, comprising the following steps:

[0006] 1) mixing citric acid and ferric nitrate, and stirring to obtain a mixed solution;

[0007] 2) drying and grinding the mixture obtained by calcining the mixed solution obtained in step 1) into a powder;

[0008] 3) calcining the powder obtained in step 2) to obtain a Fe-based catalyst;

[0009] 4) mixing the Fe-based catalyst obtained in step 3) with mineral insulating oil, and post-treating to obtain a product, a doped metal Fe-based insulating fluid.

[0010] Preferably, the molar ratio of citric acid and iron ions in step 1) is 5:6.

[0011] Preferably, the mixing temperature in step 1) is 20–80°C, the stirring speed is 100–500 r / min, and the stirring time is 0.5–4 h.

[0012] Preferably, the calcination temperature in step 2) is 200–600°C, the heating rate is 1–10°C / min, and the time is 0.5–4h.

[0013] Preferably, the drying temperature in step 2) is 80–300°C and the time is 1–6 hours.

[0014] Preferably, the calcination temperature in step 3) is 400–800°C, the heating rate is 10°C / min, and the calcination time is 2–8 h.

[0015] Preferably, the mass ratio of the Fe-based catalyst to the mineral insulating oil in step 4) is 1:5 to 1:40.

[0016] Preferably, the mixing in step 4) is carried out under stirring conditions, with a stirring rate of 100-400 r / min and a stirring time of 5-30 min.

[0017] Preferably, the post-processing in step 4) consists of ultrasonic treatment, vacuum preservation, and drying.

[0018] Preferably, the ultrasonic treatment time is 1 to 6 hours.

[0019] Preferably, the vacuum preservation time is 4 to 10 hours.

[0020] Preferably, the drying temperature is 40–120°C and the drying time is 12–36 hours.

[0021] Another object of the present invention is to provide a doped metal Fe-based insulating fluid prepared by the preparation method described above.

[0022] Another object of the present invention is to provide an application of a Fe-based insulating fluid doped with metal in the field of early warning of dissolved gas faults in transformer oil.

[0023] Compared with the prior art, the present invention has the following beneficial effects:

[0024] 1) The unique functional groups on the Fe-based catalyst improve CO2 adsorption efficiency. 2) CO2 has a high affinity for the active sites on the Fe-based catalyst surface, while CH4 has a lower affinity. Detailed Implementation

[0025] This invention provides a method for preparing a doped Fe-based insulating fluid, comprising the following steps:

[0026] 1) Mix citric acid and ferric nitrate, and stir to obtain a mixed solution;

[0027] 2) After igniting the mixed solution obtained in step 1), the mixture is dried and ground into powder;

[0028] 3) The powder obtained in step 2) is calcined to obtain an Fe-based catalyst;

[0029] 4) Mix the Fe-based catalyst obtained in step 3) with mineral insulating oil, and then perform post-processing to obtain the product, Fe-based insulating fluid doped with metal.

[0030] In this invention, the molar ratio of citric acid and iron ions in step 1) is preferably 5:6.

[0031] In this invention, the mixing temperature in step 1) is preferably 20-80°C, more preferably 30-70°C; the stirring speed is preferably 100-500 r / min, more preferably 150-400 r / min; and the stirring time is preferably 0.5-4 h, more preferably 1-3 h.

[0032] In this invention, the calcination temperature in step 2) is preferably 200-600°C, more preferably 300-500°C; the heating rate is preferably 1-10°C / min, more preferably 3-8°C; and the time is preferably 0.5-4h, more preferably 1-3h.

[0033] In this invention, the drying temperature in step 2) is preferably 80-300°C, more preferably 100-250°C; the drying time is preferably 1-6 hours, more preferably 2-5 hours.

[0034] In this invention, the calcination temperature in step 3) is preferably 400-800℃, more preferably 500-700℃; the heating rate is preferably 10℃ / min; and the calcination time is preferably 2-8h, more preferably 3-6h.

[0035] In this invention, the mass ratio of the Fe-based catalyst to the mineral insulating oil in step 4) is preferably 1:5 to 1:40, and more preferably 1:10 to 1:20.

[0036] In this invention, the mixing in step 4) is carried out under stirring conditions, the stirring rate is preferably 100-400 r / min, more preferably 200-300 r / min; the stirring time is preferably 5-30 min, more preferably 10-20 min.

[0037] In this invention, the post-processing in step 4) consists of ultrasonic treatment, vacuum preservation, and drying.

[0038] In this invention, the ultrasonic treatment time is preferably 1 to 6 hours, more preferably 2 to 4 hours.

[0039] In this invention, the vacuum preservation time is preferably 4 to 10 hours, more preferably 5 to 8 hours.

[0040] In this invention, the drying temperature is preferably 40-120°C, more preferably 50-100°C; the drying time is preferably 12-36 hours, more preferably 18-30 hours.

[0041] Another object of the present invention is to provide a doped metal Fe-based insulating fluid prepared by the preparation method described above.

[0042] Another object of the present invention is to provide an application of a Fe-based insulating fluid doped with metal in the field of early warning of dissolved gas faults in transformer oil.

[0043] Various exemplary embodiments of the present invention will now 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, features, and embodiments of the present invention.

[0044] It should be understood that the terminology used in this invention is merely for describing particular embodiments and is not intended to limit the invention. Furthermore, with respect to numerical ranges in this invention, it should be understood that each intermediate value between the upper and lower limits of the range is also specifically disclosed. Every smaller range between any stated value or intermediate value within a stated range, and any other stated value or intermediate value within said range, is also included in this invention. The upper and lower limits of these smaller ranges may be independently included or excluded from the range.

[0045] Unless otherwise stated, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art. While only preferred methods and materials have been described herein, any methods and materials similar or equivalent to those described herein may be used in the implementation or testing of this invention. All references to this specification are incorporated by way of citation to disclose and describe methods and / or materials associated with those references. In the event of any conflict with any incorporated reference, the content of this specification shall prevail.

[0046] Various modifications and variations can be made to the specific embodiments described in this specification without departing from the scope or spirit of the invention, as will be apparent to those skilled in the art. Other embodiments derived from this specification will also be obvious to those skilled in the art. This application specification and embodiments are merely exemplary.

[0047] The terms “include,” “including,” “have,” “contain,” etc., used in this article are all open-ended terms, meaning that they include but are not limited to.

[0048] Unless otherwise specified, "room temperature" and "normal temperature" in this invention refer to 25±2℃.

[0049] All raw materials used in the following embodiments of the present invention are commercially available.

[0050] Example 1

[0051] (1) Preparation of Fe-based insulating fluid

[0052] A mixed solution was prepared by mixing 2 mol / L ferric nitrate solution (99.0% purity) and 0.5 mol / L citric acid (99.5% purity) at 35°C with magnetic stirring at 350 r / min for 2 h. The solution was then slowly heated to 400°C (heating rate 5°C / min) in a muffle furnace and held at this temperature for 2 h until the mixture was completely burned down to the remaining residue. The residue was then dried in an oven at 120°C for 2 h. After drying, the residue was ground into powder. The powder was then heated to 550°C (heating rate 10°C / min) in a tube furnace with flowing air and calcined for 3 h. The Fe-based catalyst prepared above was mixed with mineral insulating oil at a mass ratio of 1:20 under magnetic stirring (250 r / min, 15 min) at 35 °C. The sample was then ultrasonically treated for 3 h, and then placed in a vacuum environment for 6 h to eliminate the bubbles generated by ultrasonic treatment. Finally, it was dried in an oven at 70 °C for 20 h to prepare the Fe-based insulating fluid doped with metal.

[0053] (2) CO2 and CH4 gas content test

[0054] High-purity CO2 (30 mL / min, 5 h) was introduced into the insulating fluid using a standard gas meter, and the fluid was heated at 200 °C for 3 h. Oil gas chromatography was used to analyze the gas content in the insulating fluid; the CO2 concentration decreased by 12.3%, while the CH4 content increased by 11.9%.

[0055] Example 2

[0056] (1) Preparation of Fe-based insulating fluid

[0057] A mixed solution was prepared by mixing 1.5 mol / L ferric nitrate solution (99.0% purity) and 1 mol / L citric acid (99.5% purity) at 40°C with magnetic stirring at 200 rpm for 1 h. The solution was then slowly heated to 300°C (heating rate 5°C / min) in a muffle furnace and maintained at this temperature for 1.5 h until the mixture was completely burned down to the remaining residue. The residue was then dried in an oven at 150°C for 2 h. After drying, the residue was ground into powder. The powder was then heated to 700°C (heating rate 10°C / min) in a tube furnace with flowing air and calcined for 5 h. The Fe-based catalyst prepared above was mixed with mineral insulating oil at a mass ratio of 1:30 under magnetic stirring (300 r / min, 20 min) at 35 °C. The sample was then ultrasonically treated for 4 h, and then placed in a vacuum environment for 6 h to eliminate the bubbles generated by ultrasonic treatment. Finally, it was dried in an oven at 80 °C for 12 h to prepare the Fe-based insulating fluid doped with metal.

[0058] (2) CO2 and CH4 gas content test

[0059] High-purity CO2 (30 mL / min, 5 h) was introduced into the insulating fluid using a standard gas meter, and the fluid was heated at 200 °C for 3 h. Oil gas chromatography was used to analyze the gas content in the insulating fluid; the CO2 concentration decreased by 43.9%, while the CH4 concentration increased by 39.7%.

[0060] Example 3

[0061] (1) Preparation of Fe-based insulating fluid

[0062] A mixed solution was prepared by mixing 3 mol / L ferric nitrate solution (99.0% purity) and 2 mol / L citric acid (99.5% purity) at 50°C with magnetic stirring at 200 r / min for 2 h. The solution was then slowly heated to 250°C (heating rate 4°C / min) in a muffle furnace and held at this temperature for 1.5 h until the mixture was completely burned down to the remaining residue. The residue was then dried in an oven at 120°C for 4 h. After drying, the residue was ground into powder. The powder was then calcined in a tube furnace with flowing air to 550°C (heating rate 10°C / min) for 3.5 h. The molar ratio of citric acid to precursor metal ions was CA:Fe = 5:6. The Fe-based catalyst prepared above was mixed with mineral insulating oil at a mass ratio of 1:35 using magnetic stirring (220 r / min, 15 min) at 35 °C. The sample was then ultrasonically treated for 2.5 h, and then placed in a vacuum environment for 6 h to eliminate bubbles generated during ultrasonic treatment. Finally, it was dried in an oven at 90 °C for 20 h to prepare the Fe-based insulating fluid doped with metal.

[0063] (2) CO2 and CH4 gas content test

[0064] High-purity CO2 (30 mL / min, 5 h) was introduced into the insulating fluid using a standard gas meter, and the fluid was heated at 200 °C for 3 h. Oil gas chromatography was used to analyze the gas content in the insulating fluid; the CO2 concentration decreased by 24.8%, while the CH4 concentration increased by 22.9%.

[0065] Example 4

[0066] (1) Preparation of Fe-based insulating fluid

[0067] A mixed solution was prepared by mixing 2.5 mol / L ferric nitrate solution (99.0% purity) and 1.5 mol / L citric acid (99.5% purity) at 30°C with magnetic stirring at 300 r / min for 0.5 h. The solution was then slowly heated to 200°C (heating rate 3°C / min) in a muffle furnace and maintained at this temperature for 1 h until the mixture was completely burned down to the remaining residue. The residue was then dried in an oven at 180°C for 3 h. After drying, the residue was ground into powder. The powder was then heated to 650°C (heating rate 10°C / min) in a tube furnace with flowing air and calcined for 3 h. The molar ratio of citric acid to precursor metal ions was CA:Fe = 5:6. The Fe-based catalyst prepared above was mixed with mineral insulating oil at a mass ratio of 1:25 at 40℃ using magnetic stirring (200 r / min, 10 min). The sample was then ultrasonically treated for 2 h, and then placed in a vacuum environment for 5 h to eliminate the bubbles generated by ultrasonic treatment. Finally, it was dried in an oven at 70℃ for 15 h to prepare the Fe-based insulating fluid doped with metal.

[0068] (2) CO2 and CH4 gas content test

[0069] High-purity CO2 (30 mL / min, 5 h) was introduced into the insulating fluid using a standard gas meter, and the fluid was heated at 200 °C for 3 h. Oil gas chromatography was used to analyze the gas content in the insulating fluid; the CO2 concentration decreased by 21.6%, while the CH4 concentration increased by 19.6%.

[0070] Example 5

[0071] (1) Preparation of Fe-based insulating fluid

[0072] A mixed solution was prepared by mixing 2.5 mol / L ferric nitrate solution (99.0% purity) and 1.5 mol / L citric acid (99.5% purity) at 40°C with magnetic stirring at 400 r / min for 1.5 h. The solution was then slowly heated to 300°C (heating rate 6°C / min) in a muffle furnace and maintained at this temperature for 1.5 h until the mixture was completely burned down to the remaining residue. The residue was then dried in an oven at 100°C for 3 h. After drying, the residue was ground into powder. The powder was then heated to 600°C (heating rate 10°C / min) in a tube furnace with flowing air and calcined for 4 h. The molar ratio of citric acid to precursor metal ions was CA:Fe = 5:6. The Fe-based catalyst prepared above was mixed with mineral insulating oil at a mass ratio of 1:20 at 40℃ using magnetic stirring (150 r / min, 10 min). The sample was then ultrasonically treated for 2 h, and then placed in a vacuum environment for 5 h to eliminate the bubbles generated by ultrasonic treatment. Finally, it was dried in an oven at 80℃ for 15 h to prepare the Fe-based insulating fluid doped with metal.

[0073] (2) CO2 and CH4 gas content test

[0074] High-purity CO2 (30 mL / min, 5 h) was introduced into the insulating fluid using a standard gas meter, and the fluid was heated at 200 °C for 3 h. Oil gas chromatography was used to analyze the gas content in the insulating fluid; the CO2 concentration decreased by 15.7%, while the CH4 content increased by 13.8%.

[0075] Example 6

[0076] (1) Preparation of Fe-based insulating fluid

[0077] A mixed solution was prepared by mixing 1.5 mol / L ferric nitrate solution (99.0% purity) and 1 mol / L citric acid (99.5% purity) at 40°C with magnetic stirring at 200 rpm for 1 h. The solution was then slowly heated to 300°C (heating rate 5°C / min) in a muffle furnace and maintained at this temperature for 1.5 h until the mixture was completely burned down to the remaining residue. The residue was then dried in an oven at 150°C for 2 h. After drying, the residue was ground into powder. The powder was then heated to 700°C (heating rate 10°C / min) in a tube furnace with flowing air and calcined for 5 h. The Fe-based catalyst prepared above was mixed with mineral insulating oil at a mass ratio of 1:30 under magnetic stirring (300 r / min, 20 min) at 35 °C. The sample was then ultrasonically treated for 4 h, and then placed in a vacuum environment for 6 h to eliminate the bubbles generated by ultrasonic treatment. Finally, it was dried in an oven at 80 °C for 12 h to prepare the Fe-based insulating fluid doped with metal.

[0078] (2) CO2 and CH4 gas content test

[0079] High-purity CO2 (30 mL / min, 5 h) was introduced into the insulating fluid using a standard gas meter, and the fluid was heated at 200 °C for 3 h. Oil gas chromatography was used to analyze the gas content in the insulating fluid; the CO2 concentration decreased by 43.9%, while the CH4 concentration increased by 39.7%.

[0080] Example 7

[0081] The other conditions are the same as in Example 1, except that the concentration of the ferric nitrate solution is adjusted to 0.4 mol / L.

[0082] High-purity CO2 (30 mL / min, 5 h) was introduced into the insulating fluid using a standard gas meter, and the fluid was heated at 200 °C for 3 h. Oil gas chromatography was used to analyze the gas content in the insulating fluid; the CO2 concentration decreased by 4.3%, while the CH4 concentration increased by 2.2%.

[0083] Example 8

[0084] The other conditions are the same as in Example 1, except that the mass ratio of metallic Fe to mineral insulating oil is 1:60.

[0085] High-purity CO2 (30 mL / min, 5 h) was introduced into the insulating fluid using a standard gas meter, and the fluid was heated at 200 °C for 3 h. Oil gas chromatography was used to analyze the gas content in the insulating fluid; the CO2 concentration decreased by 3.5%, while the CH4 concentration increased by 2.7%.

[0086] Comparative Example 1

[0087] (1) The preparation method of Fe-doped insulating fluid is the same as in Example 1, except that the tubular furnace calcination process is omitted.

[0088] (2) CO2 and CH4 gas content test

[0089] High-purity CO2 (30 mL / min, 5 h) was introduced into the insulating fluid using a standard gas meter, and the fluid was heated at 200 °C for 3 h. Oil gas chromatography was used to analyze the gas content in the insulating fluid; the CO2 concentration decreased by 1.5%, while the CH4 concentration increased by 0.9%.

[0090] By comparing Comparative Example 1 and Example 1, it can be seen that high-temperature calcination is beneficial to improving the catalytic activity of Fe-based catalysts, indicating that the metal Fe catalyst after high-temperature calcination has a certain activity for CO2 methanation.

[0091] Comparative Example 2

[0092] (1) The preparation method of Fe-based insulating fluid is the same as in Example 2, except that the ultrasonic treatment step is omitted.

[0093] (2) CO2 and CH4 gas content test

[0094] High-purity CO2 (30 mL / min, 5 h) was introduced into the insulating fluid using a standard gas meter, and the fluid was heated at 200 °C for 3 h. Oil gas chromatography was used to analyze the gas content in the insulating fluid; the CO2 concentration decreased by 7.4%, while the CH4 concentration increased by 6.8%.

[0095] Comparative Example 3

[0096] (1) Same as Example 2, except that it is doped with metallic iron.

[0097] (2) CO2 and CH4 gas content test

[0098] High-purity CO2 (30 mL / min, 5 h) was introduced into the insulating fluid using a standard gas meter, and the fluid was heated at 200 °C for 3 h. Oil gas chromatography was used to analyze the gas content in the insulating fluid; the CO2 concentration decreased by 0.5%, while the CH4 concentration increased by 0.4%.

[0099] As can be seen from the above embodiments and comparative examples, the Fe-based insulating fluid doped with metal of the present invention has a certain catalytic conversion activity for the methanation of dissolved CO2, which is of great significance for alleviating transformer faults and ensuring the safe and stable operation of transformers.

[0100] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. Application of a doped metal Fe-based insulating fluid in the field of dissolved gas fault pre-warning in transformer oil; The preparation method of the doped metal Fe-based insulating fluid comprises the following steps: 1) mixing citric acid and ferric nitrate and stirring to obtain a mixed solution; 2) drying and grinding the mixture obtained by burning the mixed solution obtained in step 1) into a powder; 3) calcining the powder obtained in step 2) to obtain a Fe-based catalyst; 4) mixing the Fe-based catalyst obtained in step 3) with mineral insulating oil, and post-treating to obtain a product doped metal Fe-based insulating fluid; The molar ratio of citric acid to iron ions in step 1) is 5:6; The temperature of the mixing in step 1) is 20-80℃, the stirring speed is 100-500 r / min, and the stirring time is 0.5-4 h; The temperature of the burning in step 2) is 200-600℃, the temperature rising rate is 1-10℃ / min, and the time is 0.5-4 h; The temperature of the drying in step 2) is 80-300℃, and the time is 1-6 h; The temperature of the calcination in step 3) is 400-800℃, the temperature rising rate is 10℃ / min, and the calcination time is 2-8 h; The mass ratio of the Fe-based catalyst to mineral insulating oil in step 4) is 1:5-1:40; the mixing in step 4) is carried out under stirring at a stirring speed of 100-400 r / min for 5-30 min; The post-treatment in step 4) comprises ultrasonic treatment, vacuum preservation and drying in sequence; the ultrasonic treatment time is 1-6 h; the vacuum preservation time is 4-10 h; the drying temperature is 40-120℃, and the time is 12-36 h.