A method for reducing the acid value and dielectric loss of synthetic ester insulating oil

Abstract

The present invention relates to a method for reducing the acid value and dielectric loss of synthetic ester insulating oil, belonging to the field of high-voltage insulating materials. Aiming at the problems of difficult post-treatment and high cost caused by introducing impurities into the oil by the existing chemical acid reduction method, the technical solution is as follows: A method for reducing the acid value and dielectric loss of synthetic ester insulating oil includes the following steps: preparing an adsorbent using molecular sieve; adding the adsorbent into the synthetic ester insulating oil and stirring evenly; performing acid value test; performing dielectric loss test; preparing a compound adsorbent; screening the best compound agent: adding the prepared compound adsorbent into the synthetic ester insulating oil, and then respectively performing acid value test and dielectric loss test to obtain the best compound adsorbent with excellent effects in both acid value test and dielectric loss test; after mixing the best compound adsorbent and the synthetic ester insulating oil evenly, filtering to remove the adsorbent. This application reduces acid through adsorption, and can reduce the dielectric loss factor and conductivity of synthetic ester insulating oil. The post-treatment operation is simple and easy, effectively reducing the post-treatment cost.

Description

Technical Field

[0001] The present invention belongs to the field of high voltage and insulating materials, and particularly relates to a method for reducing the acid value and dielectric loss of synthetic ester insulating oil. Background Art

[0002] Synthetic ester insulating oil refers to an ester-based insulating oil synthesized artificially. Its molecular structure does not contain unstable groups such as β-H and C═C bonds, and it can take into account the characteristics of high flash point and environmental friendliness of ester-based insulating oil, and improve the problem of poor oxidation stability of natural ester insulating oil. At the same time, the molecular structure of synthetic ester insulating oil has high controllability and also has outstanding advantages in terms of physical and chemical properties such as reducing pour point. The acid value of insulating oil indicates the total value of acidic substances, that is, organic acids and inorganic acids, in the oil product. Generally, it is expressed by the number of milligrams of potassium hydroxide required to neutralize the acidic substances in 1 g of insulating oil. For unused new transformer oil, it contains almost no acidic substances and its acid value is quite small. However, when the oil product is stored for a long time, especially after the oil-filled electrical equipment is put into operation, it will inevitably come into contact with oxygen in the air, and the oil product is easily aged. In the initial stage of oxidation, mainly low-molecular organic acids are generated, and further oxidation produces high-molecular organic acids and various products. After the above-mentioned various acidic substances exist in the insulating oil, it will increase the conductivity of the oil product, reduce the insulation performance of the oil product, and may also corrode metals. At a relatively high operating temperature (above 80 °C), this oil product containing organic acids will cause the solid fiber paper insulating material to age, thereby shortening the service life of the equipment. Therefore, it is urgent to develop a synthetic ester insulating oil that combines the high flash point and rapid degradability of ester-based insulating oil, as well as the low pour point and high oxidation stability of mineral insulating oil, to meet the green development of electric power energy, the large-capacity development of electric power equipment, and reliable operation.

[0003] Currently, the commonly used method is chemical acid reduction. Chemical acid reduction refers to adding a weak base salt in ethanol production to neutralize excessive organic acids to reduce the acidity of the oil product. The chemical acid reduction method has a fast reaction, a short acid reduction time, and obvious effects. However, when using the chemical method for acid reduction, attention should be paid to controlling the dosage of chemical reagents. Chemical deacidification is the common alkali refining deacidification. Using the principle of acid-base neutralization, an appropriate amount of alkali solution is added to the crude oil to react with free fatty acids to form soapstock, and after precipitation, centrifugal separation can achieve a good deacidification effect. In addition, a large amount of impurities will be introduced and generated, and the post-treatment steps are troublesome, increasing the experimental difficulty and raising the treatment cost. For example, in the literature "Study on the Gas Phase Esterification Acid Reduction Process and Its Kinetics of Jatropha curcas Oil", the gas phase esterification acid reduction process conditions and its kinetic laws were studied using Jatropha curcas oil as the raw material, mainly investigating the effects of parameters such as the amount of methanol vapor introduced, the amount of catalyst used, and the reaction temperature on the esterification rate. However, the substances added form impurities, and this method does not consider the great difficulty coefficient of subsequent impurity treatment, and thus the cost will also increase accordingly. Summary of the Invention

[0004] Aiming at the problems of difficult post-treatment and high cost caused by introducing impurities into oil products by the existing chemical acid reduction method, the present invention provides a method for reducing the acid value and dielectric loss of synthetic ester insulating oil. By introducing the method of molecular sieve adsorption, the purpose of acid reduction is achieved. The post-treatment of the molecular sieve is simple, and it can avoid the problems of difficult post-treatment and high cost caused by introducing impurities by the existing method.

[0005] The technical solution adopted by the present invention is as follows: A method for reducing the acid value and dielectric loss of synthetic ester insulating oil, comprising the following steps:

[0006] S1, preparing an adsorbent: Selecting molecular sieves with pore sizes of 2 - 50 nm and placing them in an acid and base system, and preparing various adsorbents with different pore sizes through drying and multiple high-temperature calcinations;

[0007] S2, mixing: Adding the various adsorbents prepared in step S1 into the synthetic ester insulating oil and stirring evenly;

[0008] S3, acid value test: Measuring the acid value of the synthetic ester insulating oil before and after adsorption respectively by the acid-base titration method, and obtaining the influence relationship between the acidity and alkalinity, pore size of the adsorbent and the acid value of the synthetic ester insulating oil;

[0009] S4, dielectric loss test: Measuring the dielectric loss factor and conductivity of the synthetic ester insulating oil before and after adsorption treatment respectively, and obtaining the influence relationship between the acidity and alkalinity, pore size of the adsorbent and the dielectric loss, conductivity of the synthetic ester insulating oil;

[0010] S5, preparing a compound adsorbent: Selecting the adsorbents with the best acid value test results in S3 and the best dielectric loss test results in S4 respectively, and then mixing the selected adsorbents, SiO2-based adsorbents and basic adsorbents to form various compound adsorbents;

[0011] S6, screening the best compound agent: Adding the various compound adsorbents prepared in S5 into the synthetic ester insulating oil respectively, and then conducting acid value tests and dielectric loss tests respectively to obtain the best compound adsorbent with the best acid value test and dielectric loss test results;

[0012] S7, mixing the best compound adsorbent and the synthetic ester insulating oil evenly according to a mass ratio of 1:(500 - 1000), and then filtering to remove the adsorbent to reduce the acid value and dielectric loss of the synthetic ester insulating oil to the greatest extent simultaneously.

[0013] Molecular sieves, also known as zeolites or zeolites, are composed of silicon oxygen [SiO4] 4- tetrahedra and aluminum oxygen [AlO4] 5-A porous aluminosilicate crystal with a framework structure formed by tetrahedra sharing oxygen atoms. In the molecular sieve structure, there are many pores with uniform diameters, arranged neatly, and a very large internal surface area. In addition, it contains metal ions with relatively low valence and large ionic radii and combined water. Since water molecules are continuously lost upon heating while the crystal framework structure remains unchanged, many cavities of the same size are formed, and these cavities are connected by many micropores with the same diameter. The pore diameter is of the order of magnitude of molecules, allowing only molecules smaller than the pore diameter to enter and be adsorbed inside the cavities, while molecules larger than the pore diameter are blocked outside. Therefore, it can screen molecules in a mixture according to their diameter size, and thus is called a molecular sieve. The uniformly distributed microporous structure and large specific surface area of the molecular sieve, reaching 300 - 1000m 2 / g, endow it with relatively high surface activity; at the same time, the molecular sieve also has a rich and diverse topological structure and is widely used in aspects such as adsorption, heterogeneous catalysis, and carriers for various guest molecules. The molecular sieve also has a certain polarity and has the ability to preferentially adsorb saturated molecules and polar molecules. Therefore, molecules with different diameter sizes, degrees of saturation, polarities, and boiling points can be separated by the molecular sieve. In addition, the molecular sieve also has advantages that other adsorbents do not have, such as strong intra-crystalline adsorption ability, ion exchange ability, excellent thermal / hydrothermal stability, and anti-coking performance.

[0014] Modify the molecular sieve to form an adsorbent, select an appropriate amount of the adsorbent to conduct acid value tests and dielectric loss tests on the synthetic ester insulating oil, and select the adsorbents with good acid value test and dielectric loss test results respectively. Since the adsorbent with good acid reduction effect may not necessarily have good dielectric loss test results, for this reason, a compounding method is used to obtain a compound adsorbent, and finally the best compound adsorbent with good acid value test and dielectric loss test results is selected. Subsequently, batch treatment is carried out, and after treatment, only suction filtration is required to remove the best compound adsorbent in the synthetic ester insulating oil. This method of the present application reduces acid through adsorption, and at the same time reduces the dielectric loss factor and conductivity of the synthetic ester insulating oil. Moreover, only suction filtration is required to remove the adsorbent, and the post-treatment operation is simple and easy, effectively reducing the post-treatment cost.

[0015] Further, the specific process of S1 is as follows:

[0016] S1.1, Mix a molecular sieve with a pore diameter of 2 - 50 nm and aluminosilicate with a particle size of 50 - 80 μm in a weight ratio of 100:(2 - 8), place it in a dynamic kiln for heating activation to form an activated mixed powder, and then cool the activated mixed powder to below 40°C; the function of this step is to modify the adsorbent in an acidic system;

[0017] S1.2. Mix the cooled activated mixed powder evenly with clinoptilolite powder with a particle size of 100 - 200 nm and chabazite powder with a particle size of 50 - 80 nm, and calcine at 450 - 480 °C for 5 - 8 hours to obtain the primary raw material powder; the function of this step is to modify the adsorbent in an alkaline system;

[0018] S1.3. Mix montmorillonite and chitosan evenly at a weight ratio of 10:(1 - 3), calcine at 500 - 520 °C for 1 - 5 hours under a nitrogen protection atmosphere, and then grind into secondary raw material powder with a particle size of 200 - 270 microns; the function of this step is to modify the adsorbent in an alkaline system;

[0019] S1.4. Mix the secondary raw material powder and the primary raw material powder evenly at a mixing ratio of 1:(20 - 25) by weight, and calcine at 400 - 450 °C for 2 - 3 hours under a nitrogen protection atmosphere to obtain the adsorbent. The function of this step is to modify the adsorbent in a neutral system;

[0020] Further, in S1.1, the dynamic kiln includes a rotary disk feeding mechanism, a chain - type rapid discharging mechanism, and a kiln cavity structure. The rotary disk feeding mechanism is equipped with a reflector, and a material layer with a graded distribution according to the ball diameter is obtained by dynamic slope grading; the chain - type rapid discharging mechanism uses broaching - type layered discharging, and the kiln cavity structure is a spiral cylindrical surface with dynamic characteristics.

[0021] Further, in S2, the adsorbent and synthetic ester insulating oil are mixed at a mass ratio of 1:(500 - 1000).

[0022] Further, in S5, the adsorbent, SiO2 - type adsorbent, and alkaline adsorbent are mixed at a mass ratio of (25 - 50%):(25 - 50%):(25 - 50%).

[0023] Further, in S5, the SiO2 - type adsorbent is coarse - pore silica gel; the alkaline adsorbent is alkaline alumina.

[0024] Further, in S6, the compound adsorbent and synthetic ester insulating oil are mixed at a mass ratio of 1:(500 - 1000).

[0025] Further, the suction filtration method is suction filtration with a PTFE microporous filter membrane. The advantages of suction filtration with a PTFE microporous filter membrane are as follows: (1) The PTFE microporous filter material is small in volume, which can save space and reduce costs; (2) The PTFE microporous filter material has good air permeability, which can effectively improve the filtration speed and filtration efficiency; (3) The PTFE microporous filter material has strong corrosion resistance. The PTFE microporous filter material itself has high-strength corrosion resistance and can effectively resist various corrosive media, thereby increasing the service life of the filter; (4) The PTFE microporous filter material has extremely high filtration accuracy and can effectively remove suspended solids, thus improving the filtration effect of the filter.

[0026] The beneficial effects of the present invention are as follows: This application is a method for reducing the acid value and dielectric loss of synthetic ester insulating oil. Molecular sieves are modified to form adsorbents. An appropriate amount of adsorbents is selected to conduct acid value tests and dielectric loss tests on synthetic ester insulating oil. Adsorbents with good acid value test and dielectric loss test results are selected, and then mixed to obtain a compound adsorbent. Finally, the optimal compound adsorbent with good acid value test and dielectric loss test results is selected. Subsequently, batch processing is carried out, and only suction filtration is required after processing to remove the optimal compound adsorbent in the synthetic ester insulating oil. This method of the present application reduces acid by adsorption, and at the same time reduces the dielectric loss factor and conductivity of synthetic ester insulating oil. Moreover, only suction filtration is required to remove the adsorbent, and the post-treatment operation is simple and easy, effectively reducing the post-treatment cost. Description of the Drawings

[0027] Figure 1 It is a comparison chart of the dielectric loss factor of oil products;

[0028] Figure 2 It is a comparison chart of the DC resistivity of oil products;

[0029] Figure 3 It is a comparison chart of the relative dielectric constant of oil products. Detailed Embodiments

[0030] The technical solutions of the embodiments of the present invention will be explained and described below with reference to the drawings of the present invention. However, the following embodiments are only the preferred embodiments of the present invention and not all of them. Based on the embodiments in the embodiments, other embodiments obtained by those skilled in the art without creative efforts all fall within the protection scope of the present invention.

[0031] The method for reducing the acid value and dielectric loss of synthetic ester insulating oil in this embodiment includes the following steps:

[0032] S1, preparing the adsorbent: Select molecular sieves with pore diameters of 2 - 50 nm and place them in an acid and alkali system. Through drying and multiple high-temperature calcinations, various adsorbents with different pore diameters are formed. The specific process is as follows:

[0033] S1.1, Mix molecular sieve with pore size of 2 - 50 nm and aluminum silicate with particle size of 50 - 80 μm at a weight ratio of 100:(2 - 8), place it in a dynamic kiln for heating activation to form an activated mixed powder, and then cool the activated mixed powder to below 40°C; at this time, the particle size of the activated mixed powder is 79 nm;

[0034] S1.2, Mix the cooled activated mixed powder evenly with clinoptilolite powder with particle size of 100 - 200 nm and chabazite powder with particle size of 50 - 80 nm, and calcine at 450 - 480°C for 5 - 8 hours to obtain the primary raw material powder;

[0035] S1.3, Mix montmorillonite and chitosan evenly at a weight ratio of 10:(1 - 3), calcine under a nitrogen protection atmosphere at 500 - 520°C for 1 - 5 hours, and then grind it into a secondary raw material powder with a particle size of 200 - 270 microns;

[0036] S1.4, Mix the secondary raw material powder and the primary raw material powder evenly at a mixing ratio of 1:(20 - 25) by weight, and calcine at 400 - 450°C for 2 - 3 hours under a nitrogen protection atmosphere to obtain the adsorbent.

[0037] S2, Mixing: Add the adsorbent prepared in step S1 into synthetic ester insulating oil and stir evenly; the adsorbent and synthetic ester insulating oil are mixed at a mass ratio of 1:1000;

[0038] S3, Acid value test: Measure the acid value of synthetic ester insulating oil before and after adsorption respectively by acid - base titration method to obtain the influence relationship of the acidity and alkalinity, pore size of the adsorbent on the acid value of synthetic ester insulating oil;

[0039] S4, Dielectric loss test: Measure the dielectric loss factor and conductivity of synthetic ester insulating oil before and after adsorption treatment respectively to obtain the influence relationship of the acidity and alkalinity, pore size of the adsorbent on the dielectric loss and conductivity of synthetic ester insulating oil;

[0040] S5, Prepare compound adsorbents: Select the adsorbents with the best results in the acid value test in S3 and the dielectric loss test in S4 respectively. In this embodiment, the adsorbents with the best results in the acid value test in S3 and the dielectric loss test in S4 are the same kind. Mix the selected adsorbents, SiO2 - type adsorbents and basic adsorbents in different mass percentages to form a variety of compound adsorbents; the adsorbents, SiO2 - type adsorbents and basic adsorbents are mixed at a mass percentage of (25 - 50%):(25 - 50%):(25 - 50%); in S5, the SiO2 - type adsorbent is coarse - pore silica gel; the basic adsorbent is basic alumina.

[0041] In this embodiment, three compound adsorbents are selected:

[0042] First, the mass percentages of the adsorbent, SiO2-based adsorbent, and basic adsorbent are 50%:25%:25%;

[0043] Second, the mass percentages of the adsorbent, SiO2-based adsorbent, and basic adsorbent are 25%:50%:25%;

[0044] Third, the mass percentages of the adsorbent, SiO2-based adsorbent, and basic adsorbent are 25%:25%:50%;

[0045] S6, screening the best compounding agent: The optimal pore size of the molecular sieve of the adsorbent is 267 nm. The compounding adsorbent prepared in S5 is added to the synthetic ester insulating oil respectively, and then the acid value test and dielectric loss test are carried out respectively to obtain the best compounding adsorbent with the best results in both the acid value test and the dielectric loss test; among them, the mixing ratio of the compounding adsorbent to the synthetic ester insulating oil is 1:1000; after mixing the three compounding adsorbents with the synthetic ester insulating oil respectively, the dielectric loss factor, direct current resistivity, and relative dielectric constant of the mixed synthetic ester insulating oil at 45 °C, 65 °C, and 85 °C are tested, and the test results are as Figures 1 to 3 shown; from Figures 1 to 3 the comparison results, it can be seen that the second adsorbent has the best dielectric loss factor and direct current resistivity of the oil product at 65 °C. Since the relative dielectric constant of the oil product has little effect on the insulation performance of the synthetic ester, the second adsorbent is selected as the best adsorbent;

[0046] S7, after mixing the best compounding adsorbent with the synthetic ester insulating oil evenly according to the mass ratio of 1:1000, use a PTFE microporous filter membrane to filter out the adsorbent by suction filtration to reduce the acid value and dielectric loss of the synthetic ester insulating oil to the greatest extent simultaneously.

[0047] The molecular sieve is modified to form an adsorbent. An appropriate amount of the adsorbent is selected to carry out the acid value test and dielectric loss test on the synthetic ester insulating oil, and the adsorbents with good effects in the acid value test and dielectric loss test are selected respectively. Since the adsorbent with good acid reduction effect may not necessarily have good dielectric loss test effect, for this reason, a compounding method is used to obtain a compounding adsorbent, and finally the best compounding adsorbent with good effects in both the acid value test and the dielectric loss test is selected. Subsequently, batch treatment is carried out, and only suction filtration is required to remove the best compounding adsorbent in the synthetic ester insulating oil after treatment. This method of the present application reduces acid by adsorption, and at the same time reduces the dielectric loss factor and conductivity of the synthetic ester insulating oil, and only suction filtration is required to remove the adsorbent. The post-treatment operation is simple and easy, and effectively reduces the post-treatment cost.

[0048] In S1.1, the dynamic kiln includes a rotary disk feeding mechanism, a chain-type rapid discharging mechanism, and a kiln cavity structure. The rotary disk feeding mechanism is equipped with a reflector, and a material layer graded by pellet diameter is obtained by dynamic slope grading. The chain-type rapid discharging mechanism adopts broaching-type layered discharging, and the kiln cavity structure is a spiral cylindrical surface with dynamic characteristics.

[0049] As described above, the above is only the specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Those skilled in the art should understand that the present invention includes but is not limited to the content described in the drawings and the above specific implementation manner. Any modification that does not deviate from the functional and structural principles of the present invention will be included in the scope of the claims.

Claims

1. A method for reducing the acid value and dielectric loss of synthetic ester insulating oil, characterized in that, It includes the following steps: S1. Prepare adsorbents: Select molecular sieves with pore sizes of 2 - 50 nm and place them in an acid - base system. Through drying and multiple high - temperature calcinations, adsorbents with different pore sizes are prepared. The specific process of S1 is as follows: S1.

1. Mix molecular sieves with pore sizes of 2 - 50 nm and aluminosilicate with a particle size of 50 - 80 μm in a weight ratio of 100:(2 - 8). Place them in a dynamic kiln for heating activation to form an activated mixed powder, and then cool the activated mixed powder to below 40°C; S1.

2. Mix the cooled activated mixed powder evenly with clinoptilolite powder with a particle size of 100 - 200 nm and chabazite powder with a particle size of 50 - 80 nm, and calcine at 450 - 480°C for 5 - 8 hours to obtain a primary raw material powder; S1.

3. Mix montmorillonite and chitosan evenly in a weight ratio of 10:(1 - 3), calcine in a nitrogen - protected atmosphere at 500 - 520°C for 1 - 5 hours, and then grind it into a secondary raw material powder with a particle size of 200 - 270 microns; Place it in an alkaline system for adsorbent modification; S1.

4. Mix the secondary raw material powder and the primary raw material powder evenly in a mixing ratio of 1:(20 - 25) by weight, and calcine at 400 - 450°C for 2 - 3 hours in a nitrogen - protected atmosphere to obtain the adsorbent; S2. Mixing: Add the various adsorbents prepared in step S1 to synthetic ester insulating oil respectively and stir evenly; S3. Acid value test: Measure the acid value of synthetic ester insulating oil before and after adsorption respectively by acid - base titration; S4. Dielectric loss test: Measure the dielectric loss factor and conductivity of synthetic ester insulating oil before and after adsorption treatment respectively; S5. Prepare compound adsorbents: Select the adsorbents with the best results in the acid value test in S3 and the dielectric loss test in S4 respectively, and then mix the selected adsorbents, SiO₂ - type adsorbents and alkaline adsorbents to form various compound adsorbents; S6. Screen the best compound agent: Add the various compound adsorbents prepared in S5 to synthetic ester insulating oil respectively, and then conduct acid value tests and dielectric loss tests respectively. Select the best compound adsorbent with the best results in both acid value tests and dielectric loss tests; S7. Mix the best compound adsorbent and synthetic ester insulating oil evenly in a mass ratio of 1:(500 - 1000), and then filter to remove the adsorbent to reduce the acid value and dielectric loss of synthetic ester insulating oil to the greatest extent simultaneously.

2. The method for reducing the acid value and dielectric loss of synthetic ester insulating oil according to claim 1, characterized in that In S1.1, the dynamic kiln includes a rotary disk feeding mechanism, a chain - type rapid discharging mechanism and a kiln cavity structure. The rotary disk feeding mechanism is equipped with a reflector, and a material layer with a graded distribution according to the diameter of the material balls is obtained by dynamic slope grading; The chain - type rapid discharging mechanism adopts broaching - type layered discharging, and the kiln cavity structure is a spiral cylindrical surface with dynamic characteristics.

3. The method for reducing the acid value and dielectric loss of synthetic ester insulating oil according to claim 1, characterized in that, In S2, the adsorbent and synthetic ester insulating oil are mixed in a mass ratio of 1:(500 - 1000).

4. The method for reducing the acid value and dielectric loss of synthetic ester insulating oil according to claim 1, characterized in that, In S5, the adsorbent, SiO₂ - type adsorbent and alkaline adsorbent are mixed in a mass ratio of (25 - 50%):(25 - 50%):(25 - 50%).

5. The method for reducing the acid value and dielectric loss of synthetic ester insulating oil according to claim 1 or 4, characterized in that, In S5, the SiO₂ - type adsorbent is coarse - pore silica gel; the alkaline adsorbent is alkaline alumina.

6. The method for reducing the acid value and dielectric loss of synthetic ester insulating oil according to claim 1, wherein In S6, the compound adsorbent and the synthetic ester insulating oil are mixed at a mass ratio of 1:(500 - 1000).

7. The method for reducing the acid value and dielectric loss of synthetic ester insulating oil according to claim 1, characterized in that The suction filtration method is suction filtration with a PTFE microporous membrane.

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