Extra-high voltage transformer oil base oil, preparation method thereof and extra-high voltage transformer oil

Abstract

The invention provides extra-high voltage transformer oil base oil, a preparation method thereof and extra-high voltage transformer oil, and relates to the technical field of transformer oil base oil, under the condition that the reaction pressure is not higher than 10.0 MPa, raw oil is sequentially subjected to hydrotreatment, hydrodewaxing treatment and finishing treatment, and refined generated oil is obtained; the raw oil is mixed distillate oil formed by naphthenic base distillate oil and paraffin base distillate oil; and carrying out gas-liquid separation and fractionation treatment on the refined generated oil to obtain the base oil. The method solves the problem of waste white clay caused by white clay refining of the base oil, the problems of complex process and large equipment investment caused by high-pressure hydrogenation, and the problems of complex flow and high production cost caused by blending of the base oil with different aromatic hydrocarbon contents, and achieves the purposes of safe production of the transformer oil, low hydrogen consumption, low production cost and the like. And the carbon-type structure, the oxidation resistance, the dissolving property and the low-temperature property are very excellent.

Description

Technical Field

[0001] The invention relates to the technical field of transformer oil base oil, in particular to an ultra-high voltage transformer oil base oil and a preparation method thereof, and ultra-high voltage transformer oil. Background Art

[0002] At present, transformer oil is generally produced with a single mineral oil component. Pure paraffin-based and cyclopentane-based transformer oils are used in transformers. They cannot fully take into account low-temperature flow properties, gas resistance, solubility and antioxidant properties and cannot reach an ideal balance. The traditional production process allows the base oil to retain some aromatics. Although it is excellent in gas resistance and solubility, it has poor antioxidant properties and will also cause environmental pollution. Although the hydrogenation production process gives the base oil significant performance advantages, such as excellent low-temperature performance, antioxidant stability and thermal stability, and no environmental pollution, it has the disadvantages of poor gas resistance and solubility. Under the action of a high-voltage electric field, some straight-chain hydrocarbon molecules in the transformer oil base oil break the CH bond in the molecule, and some CC bonds break, releasing more hydrogen. The generated gas is released from the oil in the form of tiny bubbles. If it continues to increase, it will connect to form large bubbles. The conductivity between the gas and the oil is very different. Under the action of a high electric field, air gap discharge will occur in the oil, leading to the destruction of the insulation of electrical equipment and even serious consequences.

[0003] Prior art CN102660363A discloses a transformer oil, which is composed of a paraffin-based oil fraction, a cycloalkyl oil, an alkyl high-boiling substance, an antioxidant and an anti-photosensitive agent; in the transformer oil, the paraffin-based oil fraction accounts for 60wt%-75wt%, the cycloalkyl oil accounts for 19.4wt%-28.5wt%, the alkyl high-boiling substance accounts for 5wt%-10wt%, the antioxidant accounts for 0.5wt%-1.0wt%, and the anti-photosensitive agent accounts for 0.1wt%-0.5wt%; the preparation method of the transformer oil comprises the following steps: adding the paraffin-based oil fraction, the cycloalkyl oil and the alkyl high-boiling substance into a reactor, adding white clay for refining, stirring and refining and adsorbing at high temperature, adding the antioxidant and the anti-photosensitive agent after filtering, the negative pressure of the vacuum pump is 0.8kPa, and the vacuum treatment is performed 1-3 times; the kinematic viscosity of the obtained transformer oil is 6.5mm 2 / s-9.5mm 2 / s, and the breakdown voltage is 55-80KV / 2.5mm; however, it has obvious disadvantages of high cost and low yield.

[0004] The prior art also discloses a production process for commutation high-voltage transformer oil, which is composed of 290°C-325°C fraction cycloalkyl base oil, dodecylbenzene, benzotriazole, 2(2H-benzotriazole-2-yl)-6-dodecyl-4-methylphenol, and 2,6-di-tert-butyl-p-cresol, wherein the content of the 290°C-325°C fraction cycloalkyl base oil is 70wt%-90wt%, dodecylbenzene is 10wt%-30wt%, benzotriazole is 5-200PPm, 2(2H-benzotriazole-2-yl)-6-dodecyl-4-methylphenol is 0.05wt%-3wt%, and 2,6-di-tert-butyl-p-cresol is 0-0.5wt%; the components are evenly mixed, finely filtered, vacuum dehydrated, and the finished product is produced; although the process is simple to operate and has low cost, the disadvantage is that the highly toxic 2,6-di-tert-butyl-p-cresol is used as an antioxidant, which will pollute the human body and the environment.

[0005] The prior art CN1089517243A discloses that 300°C-350°C narrow-fraction cycloalkyl oil is used as raw material, and a hydrogenation treatment-liquid phase denitrification-clay refining process is performed to achieve dearomatization, desulfurization, denitrification, and decolorization, and then an antioxidant, a pour point depressant, an anti-ultraviolet agent, an antioxidant and an anti-corrosion agent and other additives are added, and then multi-stage vacuum filtration and vacuum pump negative pressure treatment are performed to obtain AC / DC transformer oil. The disadvantages of the method are that the operation is complicated and the energy consumption is high, and clay refining is also required, which brings about the problem of handling waste clay. At the same time, many types of additives are added, which also increases the production cost.

[0006] In summary, in the prior art, transformer oil base oil needs to be refined with bleaching clay for denitrification and decolorization, which brings about the problem of waste bleaching clay treatment; the use of high-pressure hydrogenation technology has the problems of complex process flow and large one-time investment scale; the use of two transformer oil base oils with different aromatic hydrocarbon contents to blend and produce high-quality transformer oil base oil has the problems of complex process flow and high production cost.

[0007] In view of this, the present invention is proposed. Summary of the invention

[0008] One of the purposes of the present invention is to provide a method for preparing a base oil for ultra-high voltage transformer oil, which can avoid the problem of increasing equipment investment and operation severity by selecting a high-pressure hydrogenation device. Compared with the existing high-pressure hydrogenation process, the method has the characteristics of safe operation and production and low hydrogen consumption, and is suitable for industrial production.

[0009] The second object of the present invention is to provide a UHV transformer oil base oil having a relatively high content of cycloalkanes, an appropriate content of dicyclic aromatic hydrocarbons, good antioxidant stability and anti-gassing properties, and also having better low-temperature performance.

[0010] A third object of the present invention is to provide an ultra-high voltage transformer oil, which has excellent carbon structure, oxidation resistance, solubility and low temperature performance.

[0011] In order to achieve the above-mentioned purpose of the present invention, the following technical solutions are particularly adopted:

[0012] In a first aspect, a method for preparing a UHV transformer oil base oil comprises the following steps:

[0013] (a) subjecting the crude oil to a hydrogenation treatment, a hydrodecondensation treatment and an additional refining treatment in sequence under a reaction pressure of no more than 10.0 MPa to obtain a refined product oil;

[0014] Wherein, the feedstock oil comprises a mixed distillate oil formed by naphthenic distillate oil and paraffinic distillate oil;

[0015] (b) subjecting the refined product oil to gas-liquid separation and fractionation treatment to obtain the UHV transformer oil base oil.

[0016] Furthermore, the reaction pressure is 8.0MPa-10.0MPa.

[0017] Furthermore, the mass proportion of paraffin-based distillate oil in the raw oil is 10%-40%;

[0018] The mass proportion of cycloalkane distillate oil in the raw oil is 60%-90%.

[0019] Further, the paraffin-based distillate oil includes at least one of a paraffin-based normal second-line distillate oil and a paraffin-based minus first-line distillate oil;

[0020] The cycloalkyl distillate oil includes at least one of cycloalkyl normal second-line distillate oil and cycloalkyl minus first-line distillate oil.

[0021] Further, the reaction temperature of the hydrotreatment is 300°C-370°C;

[0022] Preferably, the volume ratio of hydrogen to feedstock oil in the hydroprocessing is (600-1200):1.

[0023] Furthermore, the reaction temperature of the hydrodecondensation treatment is 280°C-340°C;

[0024] Preferably, the volume ratio of hydrogen in the hydrodecondensation treatment to the generated oil obtained by the hydrotreatment is (600-1200):1.

[0025] Further, the reaction temperature of the supplementary refining treatment is 290°C-360°C;

[0026] Preferably, the volume ratio of hydrogen in the supplementary refining treatment to the product oil obtained by the hydrodecondensation treatment is (600-1200):1.

[0027] In a second aspect, a UHV transformer oil base oil is prepared by any of the preparation methods described above;

[0028] Preferably, the base oil has a sulfur content of <1.0 mg / kg, a nitrogen content of <1.0 mg / kg, and total aromatics of <10%;

[0029] Preferably, the pour point of the base oil is less than -57°C and the kinematic viscosity at 40°C is less than 8.0 mm 2 / s, closed cup flash point>140℃.

[0030] In a third aspect, a UHV transformer oil comprises the base oil and an antioxidant as described above.

[0031] Furthermore, the added weight percentage of the antioxidant is 0.3%±0.05%;

[0032] Preferably, the aniline point of the UHV transformer oil is 72°C-78°C, the oxidation stability at 120°C for 500h, the total acid value is <0.08mgKOH / g, and the sludge is <0.008%.

[0033] Compared with the prior art, the present invention has at least the following beneficial effects:

[0034] The method for preparing the ultra-high voltage transformer oil base oil provided by the present invention uses a mixed oil formed by cycloalkane distillate oil and paraffin distillate oil as a reaction raw material under medium pressure (reaction pressure ≤ 10.0 MPa), can use a non-precious metal catalyst, and directly generates the ultra-high voltage transformer oil base oil through hydrogenation treatment, hydrodecondensation treatment, supplementary refining treatment and fractionation treatment processes. The method can not only meet the index requirements of GB2536-2011, but also avoid the problem of increasing equipment investment and operation severity by selecting a high-pressure hydrogenation device. Compared with the existing high-pressure hydrogenation process, the method has the characteristics of safe operation and production and low hydrogen consumption, and is suitable for industrialization. Production; the base oil thus obtained contains a relatively high content of cycloalkanes and an appropriate content of dicyclic aromatics, has good antioxidant stability and anti-gassing properties, and the processing of some paraffin-based distillate oils is also beneficial to improving the low-temperature performance of the base oil; in short, the present invention processes cycloalkane and paraffin-based mixed distillate oils through a specific process, and the carbon type structure, antioxidant performance, solubility and low-temperature performance of the obtained product are all excellent, and it also solves the problem of waste kaolin when base oil is refined with kaolin, the problem of complex process and large equipment investment when high-pressure hydrogenation is used, and the problem of complex process and high production cost when base oils with different aromatic content are blended.

[0035] The UHV transformer oil base oil provided by the present invention has a relatively high content of cycloalkanes and an appropriate content of dicyclic aromatic hydrocarbons, has good antioxidant stability and gassing resistance, and also has better low-temperature performance.

[0036] The ultra-high voltage transformer oil provided by the present invention has excellent carbon structure, oxidation resistance, solubility and low-temperature performance. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] In order to more clearly illustrate the specific implementation methods of the present invention or the technical solutions in the prior art, the drawings required for use in the specific implementation methods or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are some implementation methods of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0038] Figure 1 This is a stability characterization diagram of the aromatic content and pour point of the transformer oil base oil obtained in Test Example 1 of the present invention. DETAILED DESCRIPTION

[0039] The technical solution of the present invention will be clearly and completely described below in conjunction with the embodiments. Obviously, the described embodiments are part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0040] According to a first aspect of the present invention, there is provided a method for preparing a UHV transformer oil base oil, comprising the following steps:

[0041] (a) subjecting the crude oil to a hydrogenation treatment, a hydrodecondensation treatment and an additional refining treatment in sequence under a reaction pressure of no more than 10.0 MPa to obtain a refined product oil;

[0042] Wherein, the feedstock oil comprises a mixed distillate oil formed by naphthenic distillate oil and paraffinic distillate oil;

[0043] (b) subjecting the refined product oil to gas-liquid separation and fractionation treatment to obtain a UHV transformer oil base oil.

[0044] It should be noted that cycloalkane transformer oil is rich in cycloalkanes and suitable aromatics. When the aromatic content is low, cycloalkane transformer oil has good sensitivity to antioxidants, so it has good antioxidant and solubility properties, and can also ensure good electrical properties; paraffin-based transformer oil has a high viscosity index, so under the conditions of viscosity and pour point similar to cycloalkane transformer oil, its low-temperature kinematic viscosity is small, which is more conducive to the cold start of transformer oil. Therefore, the transformer oil product obtained by processing cycloalkane and paraffin-based mixed oils will have excellent carbon structure, antioxidant properties, solubility and low-temperature properties.

[0045] The invention uses a mixed oil formed by cycloalkane distillate oil and paraffin-based distillate oil as a reaction raw material under medium pressure (reaction pressure ≤ 10.0 MPa), can adopt a non-precious metal catalyst, and directly generates a base oil for ultra-high voltage transformer oil through hydrogenation treatment, hydrodecondensation treatment, supplementary refining treatment and fractionation treatment. The invention can not only meet the index requirements of GB2536-2011, but also avoid the problems of increasing equipment investment and operation severity by selecting a high-pressure hydrogenation device. Compared with the existing high-pressure hydrogenation process, the invention has the characteristics of safe operation and production and low hydrogen consumption, and is suitable for industrial production. The base oil obtained thereby contains a relatively high content of cycloalkanes and an appropriate content of bicyclic aromatic hydrocarbons, has good antioxidant stability and gassing resistance, and the processing of part of the paraffin-based distillate oil is also beneficial to improving the low-temperature performance of the base oil.

[0046] In summary, the present invention processes cycloalkyl and paraffin mixed distillate oils through a specific process, and the obtained product has excellent carbon structure, antioxidant performance, solubility and low-temperature performance. It also solves the problem of waste clay in base oil refining using clay, the problem of complex process and large equipment investment in high-pressure hydrogenation, and the problem of complex process and high production cost in blending base oils with different aromatic contents.

[0047] In the present invention, paraffin-based distillate oil includes but is not limited to any one of paraffin-based normal second-line distillate oil, paraffin-based minus first-line distillate oil, and paraffin-based normal second-line / minus first-line mixed distillate oil, for example, paraffin-based normal second-line distillate oil, paraffin-based minus first-line distillate oil, or paraffin-based normal second-line / minus first-line mixed distillate oil, but is not limited thereto.

[0048] In a preferred embodiment, the mass proportion of the paraffin-based distillate oil in the feedstock oil may be 10%-40%, for example, 15%, 20%, 25%, 30%, 35%, but not limited thereto.

[0049] In the present invention, cycloalkyl distillate oil includes but is not limited to any one of cycloalkyl normal second-line distillate oil, cycloalkyl minus first-line distillate oil, and cycloalkyl normal second-line / minus first-line mixed distillate oil, for example, cycloalkyl normal second-line distillate oil, cycloalkyl minus first-line distillate oil, or cycloalkyl normal second-line / minus first-line mixed distillate oil, but is not limited thereto.

[0050] In a preferred embodiment, the mass proportion of cycloalkane distillate oil in the feedstock oil may be 60%-90%, for example, 65%, 70%, 75%, 80%, 85%, but not limited thereto.

[0051] In the present invention, the catalyst used for the hydroprocessing may be the non-precious metal catalyst disclosed in Patent ZL201611160651.2, but is not limited thereto.

[0052] In a preferred embodiment, the hydroprocessing catalyst includes but is not limited to an active metal oxide and a metal oxide promoter; wherein the active metal oxide may be a Group VIII metal oxide and / or a Group VIB metal oxide, for example, nickel oxide and / or tungsten trioxide.

[0053] In a preferred embodiment, the reaction pressure of the hydrotreatment may be 8.0 MPa-10.0 MPa, for example, 8.5 MPa, 9.0 MPa, 9.5 MPa, but not limited thereto.

[0054] In a preferred embodiment, the reaction temperature of the hydrotreatment may be 300°C-370°C, for example, 310°C, 320°C, 330°C, 340°C, 350°C, 360°C, but not limited thereto.

[0055] In a preferred embodiment, the volume ratio of hydrogen gas to feedstock oil in the hydrotreatment process may be (600-1200):1, for example, 700:1, 800:1, 900:1, 1000:1, 1100:1, but not limited thereto.

[0056] The volume space velocity of the hydroprocessing can be 0.2h -1 -1.0h -1 , for example, it can be 0.3h -1 、0.4h -1 , 0.5h -1 , 0.6h -1 、0.7h -1 、0.8h -1 、0.9h -1 , but not limited to this.

[0057] In the present invention, the catalyst used in the hydrodecondensation treatment may be a non-precious metal catalyst disclosed in Patent ZL201910897903.7, but is not limited thereto.

[0058] It should be noted that the hydrodegradation catalyst can selectively remove large molecular normal alkanes with high freezing points, thereby reducing the pour point of the hydrogenated oil.

[0059] In a preferred embodiment, the active metal oxide of the hydrodegradation catalyst may be a Group VIII metal oxide and / or a Group VIB metal oxide, for example, nickel oxide and / or tungsten trioxide.

[0060] In a preferred embodiment, the reaction pressure of the hydrodecondensation treatment may be 8.0 MPa-10.0 MPa, for example, 8.5 MPa, 9.0 MPa, 9.5 MPa, but not limited thereto.

[0061] In a preferred embodiment, the reaction temperature of the hydrodecondensation treatment may be 280°C-340°C, for example, 290°C, 300°C, 310°C, 320°C, 330°C, but not limited thereto.

[0062] In a preferred embodiment, the volume ratio of hydrogen from the hydrodecondensation treatment to the oil generated by the hydrotreatment can be (600-1200):1, for example, it can be 700:1, 800:1, 900:1, 1000:1, 1100:1, but is not limited thereto.

[0063] The volumetric space velocity of the hydrodecondensation treatment can be 0.8h -1 -3.0h -1 , for example, it can be 1.0h -1 , 1.2h -1 , 1.4h -1 , 1.6h -1 , 1.8h -1 , 2.0h -1 , 2.2h -1 , 2.4h -1 , 2.6h -1 , 2.8h -1 , but not limited to this.

[0064] In the present invention, the catalyst used for the supplementary refining treatment may be a non-precious metal catalyst disclosed in Patent ZL201910952953.0, but is not limited thereto.

[0065] In a preferred embodiment, the active metal oxide of the supplementary refining treatment catalyst may be a Group VIII metal oxide and / or a Group VIB metal oxide, for example, nickel oxide and / or tungsten trioxide.

[0066] In a preferred embodiment, the reaction pressure of the supplementary refining treatment may be 8.0 MPa-10.0 MPa, for example, 8.5 MPa, 9.0 MPa, 9.5 MPa, but not limited thereto.

[0067] In a preferred embodiment, the reaction temperature of the supplementary refining treatment may be 290°C-360°C, for example, 300°C, 310°C, 320°C, 330°C, 340°C, 350°C, but is not limited thereto.

[0068] In a preferred embodiment, the volume ratio of hydrogen from the supplementary refining treatment to the oil produced by the hydrodecondensation treatment can be (600-1200):1, for example, it can be 700:1, 800:1, 900:1, 1000:1, 1100:1, but is not limited thereto.

[0069] Among them, the volume space velocity of the refining treatment can be 0.3h -1 -2.0h -1 , for example, it can be 0.4h -1 , 0.6h -1 、0.8h -1 , 1.0h -1 , 1.2h -1 , 1.4h -1 , 1.6h -1 , 1.8h -1 , but not limited to this.

[0070] A typical preparation method of a UHV transformer oil base oil comprises the following steps:

[0071] (1) mixing the feedstock oil with hydrogen and performing a hydrogenation treatment under the action of a hydrogenation catalyst to obtain a hydrogenation product oil;

[0072] The raw oil is a mixed distillate oil formed by naphthenic distillate oil and paraffinic distillate oil;

[0073] (2) mixing the hydrotreated product oil obtained in step (1) with hydrogen, and performing a hydrodegradation treatment under the action of a hydrodegradation catalyst to obtain a hydrodegradation product oil;

[0074] (3) mixing the hydrodecompression product oil obtained in step (2) with hydrogen, and performing supplementary refining treatment under the action of a supplementary refining treatment catalyst to obtain a refined product oil;

[0075] (4) The refined product oil obtained in step (3) is subjected to gas-liquid separation by passing through a stripping tower, and the obtained liquid product is subjected to fractional distillation by passing through a vacuum tower, and a product is extracted from a side line at 300° C.-325° C. to obtain a UHV transformer oil base oil.

[0076] According to a second aspect of the present invention, there is provided a UHV transformer oil base oil, which is prepared by any of the preparation methods described above.

[0077] The UHV transformer oil base oil provided by the present invention has a relatively high content of cycloalkanes and an appropriate content of dicyclic aromatic hydrocarbons, has good antioxidant stability and gassing resistance, and also has better low-temperature performance.

[0078] In a preferred embodiment, the sulfur content of the UHV transformer oil base oil is less than 1.0 mg / kg (for example, it can be 0.8 mg / kg, 0.6 mg / kg, 0.4 mg / kg, 0.2 mg / kg, but not limited to this), the nitrogen content is less than 1.0 mg / kg (for example, it can be 0.8 mg / kg, 0.6 mg / kg, 0.4 mg / kg, 0.2 mg / kg, but not limited to this), and the total aromatics are less than 10% (for example, it can be 8%, 6%, 4%, but not limited to this).

[0079] In a preferred embodiment, the pour point of the UHV transformer oil base oil is less than -57°C (for example, -59°C, -60°C, -61°C, but not limited thereto), and the kinematic viscosity at 40°C is less than 8.0 mm 2 / s (for example, it can be 7.5mm 2 / s、7.0mm 2 / s, 6.5mm 2 / s, but not limited thereto), closed cup flash point>140°C (for example, 141°C, 142°C, 143°C, but not limited thereto).

[0080] According to a third aspect of the present invention, there is provided an ultra-high voltage transformer oil, comprising the above-mentioned base oil and an antioxidant.

[0081] The ultra-high voltage transformer oil provided by the present invention has excellent carbon structure, oxidation resistance, solubility and low-temperature performance.

[0082] In the present invention, UHV transformer oil is obtained by adding a proper amount of antioxidant to transformer oil base oil; wherein the added amount of antioxidant may be 0.3%±0.05% (eg, 0.32%, 0.34%, but not limited thereto).

[0083] In a preferred embodiment, the aniline point of the ultra-high voltage transformer oil is 72°C-78°C (for example, it can be 74°C, 76°C, but not limited to this), the oxidation stability at 120°C for 500h, the total acid value is less than 0.08mgKOH / g (for example, it can be 0.06mgKOH / g, 0.04mgKOH / g, but not limited to this), and the sludge is less than 0.008% (for example, it can be 0.006%, 0.004%, but not limited to this), which meets the index requirements of the State Grid for ultra-high voltage transformer oil.

[0084] The present invention is further described below by way of examples. Unless otherwise specified, the materials in the examples are prepared according to existing methods or purchased directly from the market. The physical properties of the catalysts used in the examples are shown in Table 1.

[0085] Table 1 Catalyst

[0086] catalyst Hydroprocessing catalyst Hydrodecondensation catalyst Supplementary refining catalyst Appearance Shamrock Shamrock Shamrock <![CDATA[Pore volume / (cm 3 ·g -1 )]]> ＞0.30 ＞0.18 ＞0.35 <![CDATA[Specific surface area / (m 2 ·g -1 )]]> ＞200 ＞180 ＞150 <![CDATA[Bulk density / (g·cm -3 )]]> 0.75-0.90 0.70-0.80 0.82-0.88 Diameter / mm 1.3-1.6 1.3-1.6 1.0-1.4 <![CDATA[Crushing strength / (N·mm -1 )]]> ＞10 ＞10 ＞15.0 <![CDATA[Mass fraction of WO3 / %]]> 25.7 - 22.3 NiO mass fraction / % 3.6 2.0 4.6 <![CDATA[Mass fraction of MoO3 / %]]> - - 7.5

[0087] Example 1

[0088] A method for preparing ultra-high voltage transformer oil comprises the following steps:

[0089] The mixed oil 1# produced by a certain refinery is used as the raw material oil (in terms of mass percentage, the paraffin-based second-line distillate oil accounts for 10%, and the naphthenic second-line distillate oil accounts for 90%). The properties of the raw material oil are shown in Table 2.

[0090] The crude oil is mixed with hydrogen and then passed through the hydrotreating catalyst of the first hydrogenation reactor, the hydrodecondensation catalyst of the second hydrogenation reactor, and the supplementary refining catalyst in sequence. The feed volume space velocity is 1.0h -1 , hydrogen-oil volume ratio is 600:1, and the system hydrogen partial pressure is 9.5MPa;

[0091] The loading volume ratio of the three catalysts for hydrotreatment, hydrodecondensation and supplementary refining is 3:1:2, and the average reaction temperatures of the three catalysts are 355°C, 345°C and 350°C respectively;

[0092] The reaction product is separated into gas and liquid by a stripping tower, and the obtained liquid is fractionated by a vacuum tower, and the product is extracted from the side line of the vacuum tower at 300°C-325°C to obtain the UHV transformer oil base oil;

[0093] The obtained transformer oil base oil was added with 2,6-di-tert-butyl-p-cresol as an antioxidant to obtain an ultra-high voltage transformer oil, and its analysis data is shown in Table 3.

[0094] Example 2

[0095] This embodiment provides a method for preparing ultra-high voltage transformer oil. The difference from Embodiment 1 is that this embodiment uses mixed oil 2# as raw material oil (in terms of mass percentage, paraffin-based second-line distillate oil accounts for 20% and cycloalkane-based second-line distillate oil accounts for 80%), and the properties of the raw material oil are shown in Table 2;

[0096] The rest is the same as in Example 1 to obtain UHV transformer oil, and its analysis data is shown in Table 3.

[0097] Example 3

[0098] This embodiment provides a method for preparing ultra-high voltage transformer oil. The difference from embodiment 1 is that this embodiment uses mixed oil 3# as raw material oil (in terms of mass percentage, paraffin-based second-line distillate oil accounts for 30% and cycloalkane-based second-line distillate oil accounts for 70%), and the properties of the raw material oil are shown in Table 2; the average reaction temperature of the hydrodecondensation catalyst is 350°C;

[0099] The rest is the same as in Example 1 to obtain UHV transformer oil, and its analysis data is shown in Table 3.

[0100] Example 4

[0101] This embodiment provides a method for preparing ultra-high voltage transformer oil. The difference from embodiment 1 is that this embodiment uses mixed oil 4# as raw material oil (in terms of mass percentage, paraffin-based second-line distillate oil accounts for 35% and cycloalkane-based second-line distillate oil accounts for 65%), and the properties of the raw material oil are shown in Table 2; the average reaction temperature of the hydrodecondensation catalyst is 350°C;

[0102] The rest is the same as in Example 1 to obtain UHV transformer oil, and its analysis data is shown in Table 3.

[0103] Table 2 Crude oil

[0104] Crude oil Mixed oil 1# Mixed oil 2# Mixed oil 3# Mixed oil 4# <![CDATA[Density (20 °C), g / cm 3 > 0.9026 0.8969 0.8911 0.8882 Sulfur content / ppm 2243 2196 2149 2126 Nitrogen content / ppm 531 553 574 585 Pour point / ℃ -24 -21 -15 -15 Mass spectrum composition / % 0 0 0 0 Alkanes 14.7 17.1 19.5 20.7 Cycloalkanes 49.9 48.3 46.7 45.9 Aromatics 35.4 34.6 33.8 33.4

[0105] Table 3 Transformer oil

[0106]

[0107] Test Example 1

[0108] The experiment was carried out with the same raw materials, process flow and operating conditions as in Example 3. The device was operated continuously for 120 days, and the transformer oil was sampled and analyzed for aromatic content and pour point every 48 hours. The periodic data were obtained as follows: Figure 1 shown.

[0109] Depend on Figure 1It can be seen that the pour point of the ultra-high voltage transformer oil base oil obtained by the present invention is -57°C, and the aromatic content is between 9% and 10%. It has the advantages of low pour point and low aromatic content, and its properties are stable, and it is a high-quality transformer oil base oil product.

[0110] Test Example 2

[0111] The main factor restricting the long-term operation of industrial equipment is the rapid increase in the pressure drop of the equipment. In addition to the raw material factor, the growth rate of the pressure drop is also directly related to the porosity of the catalyst itself, the permeability of the bed, and the quality of logistics distribution. The hydrogenation catalyst has a high porosity and good permeability, which is conducive to the diffusion of reactants and products, reduces the pressure drop of the decondensation catalyst bed, and is beneficial to the long-term operation of the equipment.

[0112] In order to verify the stability of the catalyst in the preparation method of the present invention and facilitate the long-term operation of the device, the catalyst stability was tested on a medium-sized hydrogenation test device with a process flow similar to that of an industrial device.

[0113] The experiment was carried out with Example 2 and Example 3. The device was operated continuously for 2600 hours. The static pressure drop between the inlet a of the first hydrogenation reactor R1 and the outlet b of the second hydrogenation reactor R2 was measured at the 300th hour and the 2600th hour. The periodic data were shown in Table 4.

[0114] Table 4 Reactor pressure drop

[0115]

[0116] From the above data, it can be seen that after the device has been running continuously for 2600 hours, the total pressure drop has increased by 0.03 MPa compared with 300 hours, which fully meets the index requirements of industrial devices. It can be seen that the three hydrogenation catalysts used in the present invention are beneficial to the diffusion of reactants and products, can reduce the pressure drop of the catalyst bed, and are beneficial to the long-term operation of the device.

[0117] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for preparing a UHV transformer oil base oil, characterized in that: The following steps are involved: (a) subjecting the crude oil to a hydrogenation treatment, a hydrodecondensation treatment and an additional refining treatment in sequence under a reaction pressure of no more than 10.0 MPa to obtain a refined product oil; Wherein, the feedstock oil comprises a mixed distillate oil formed by naphthenic distillate oil and paraffinic distillate oil; (b) subjecting the refined product oil to gas-liquid separation and fractionation treatment to obtain the UHV transformer oil base oil.

2. The preparation method according to claim 1, characterized in that: The reaction pressure is 8.0MPa-10.0MPa.

3. The preparation method according to claim 1 or 2, characterized in that: The mass proportion of paraffin-based distillate oil in the raw oil is 10%-40%; The mass proportion of cycloalkane distillate oil in the raw oil is 60%-90%.

4. The preparation method according to claim 3, characterized in that: The paraffin-based distillate oil includes at least one of a paraffin-based normal second-line distillate oil and a paraffin-based minus first-line distillate oil; The cycloalkyl distillate oil includes at least one of cycloalkyl normal second-line distillate oil and cycloalkyl minus first-line distillate oil.

5. The preparation method according to claim 1, characterized in that: The reaction temperature of the hydrotreatment is 300°C-370°C; Preferably, the volume ratio of hydrogen to feedstock oil in the hydroprocessing is (600-1200):

1.

6. The preparation method according to claim 1, characterized in that: The reaction temperature of the hydrodecondensation treatment is 280°C-340°C; Preferably, the volume ratio of hydrogen in the hydrodecondensation treatment to the generated oil obtained by the hydrotreatment is (600-1200):

1.

7. The preparation method according to claim 1, characterized in that: The reaction temperature of the supplementary refining treatment is 290°C-360°C; Preferably, the volume ratio of hydrogen in the supplementary refining treatment to the product oil obtained by the hydrodecondensation treatment is (600-1200):

1.

8. A UHV transformer oil base oil, characterized in that: It is prepared by the preparation method according to any one of claims 1 to 7; Preferably, the base oil has a sulfur content of <1.0 mg / kg, a nitrogen content of <1.0 mg / kg, and total aromatics of <10%; Preferably, the pour point of the base oil is less than -57°C and the kinematic viscosity at 40°C is less than 8.0 mm 2 / s, closed cup flash point>140℃.

9. A UHV transformer oil, characterized in that: The invention comprises the base oil as claimed in claim 8 and an antioxidant.

10. The UHV transformer oil according to claim 9, characterized in that: The added weight percentage of the antioxidant is 0.3%±0.05%; Preferably, the aniline point of the UHV transformer oil is 72°C-78°C, the oxidation stability at 120°C for 500h, the total acid value is <0.08mgKOH / g, and the sludge is <0.008%.

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