Preparation method of ultrahigh-cleanliness blank oil for calibration of insulating oil gas content detector

Abstract

The invention relates to the technical field of calibration of insulating oil gas content detectors, in particular to a preparation method of ultrahigh-cleanliness blank oil for calibration of an insulating oil gas content detector, which comprises the following steps: 1) injecting V liters of to-be-treated insulating oil into a closed reaction container; 2) adding a quantitative amount of an additive into the closed reaction container, uniformly mixing, and introducing a fixed flow of purging gas into the treated insulating oil at a constant temperature for purging; 3) injecting excessive sodium hydroxide ethanol solution into the blown insulating oil, and stirring and mixing; 4) heating the mixed solution to 140-160 DEG C, and continuously stirring for 20-30 minutes, and 5) stopping heating and standing the mixed solution until solid-liquid layering, and removing bottom precipitates through filtration or centrifugal separation to obtain the blank oil. Through the synergistic effect of a series of special processes such as gas replacement, chemical neutralization, thermal separation-filtration and the like, rapid preparation of the ultrahigh-cleanliness blank oil is realized.

Description

Technical Field

[0001] This invention relates to the field of calibration technology for insulating oil gas content detectors, specifically a method for preparing ultra-high purity blank oil for calibrating insulating oil gas content detectors. Background Technology

[0002] Transformer oil gas content detection is one of the core routine tests for monitoring transformer operation. By detecting the changing trend of gas content in the oil, potential internal faults in the transformer (such as local overheating, arc discharge, and aging of insulation materials) can be effectively diagnosed. As the core equipment for this analysis, the insulating oil gas content analyzer has been widely used in the power system, and its detection accuracy and precision are directly related to the reliability of fault diagnosis.

[0003] Currently, gas content measuring instruments that meet industry standards do not undergo regular calibration using standard substances (i.e., standard oil samples). In recent years, with the development of ultra-high voltage technology, the requirements for gas content testing results in insulating oil have become increasingly stringent, rising from less than 3% to less than 1%. These increasingly stringent requirements have led to frequent instances of gas content exceeding the standard in insulating oil testing. A significant portion of these instances are due to errors caused by the instruments not being calibrated over a long period.

[0004] Therefore, there is an urgent need for a standard oil sample for calibrating insulating oil gas content analyzers. The key to preparing the standard oil sample is obtaining an ultra-high purity blank oil sample. The quality of the preparation of the ultra-high purity blank oil sample directly affects the accuracy of the standard oil sample's values, and thus determines the reliability of the gas content analyzer's traceability.

[0005] The preparation of blank oil samples is common in the field of insulating oil analysis. For example, the single gas elution method can be used to prepare an approximate blank oil sample containing only a few components by introducing a high-purity single gas into the insulating oil for a long time and at a high flow rate. However, the total gas content of these few components is relatively large, making it unsuitable for preparing standard oil samples for calibrating gas content detectors.

[0006] The ultra-high cleanliness blank oil sample proposed in this invention must be guaranteed to be free of any gaseous components that are gaseous at room temperature and pressure, or to ensure that the content of each gaseous component is undetectable in the chromatograph test results.

[0007] In addition, the existing methods for preparing conventional blank oil samples have the following drawbacks: First, the oil processing time is very long, sometimes taking several days, which makes it very difficult to prepare standard oil samples for calibrating gas content detectors; second, it is impossible to completely remove all gaseous components that are in a gaseous state at room temperature and pressure to achieve an ultra-high cleanliness state, either leaving one component with a high content (exceeding 10%) or multiple components with a total content exceeding 0.5%; third, the equipment is complex and has high operating costs, mostly requiring specialized degassing or gas washing devices, such as vacuum oil filters or washing machines. Summary of the Invention

[0008] The technical problem to be solved by the present invention is to overcome the defects of the prior art and provide a method for preparing ultra-high cleanliness blank oil for calibrating an insulating oil gas content detector.

[0009] To solve the above-mentioned technical problems, the present invention provides the following technical solution: A method for preparing ultra-high purity blank oil for calibrating an insulating oil gas content detector includes the following steps: 1) Inject V liters of insulating oil to be treated into a sealed reaction vessel; 2) Add a measured amount of additive to a closed reaction vessel and mix it evenly. At a constant temperature, purge the treated insulating oil with a fixed flow rate of purging gas to purge the dissolved gas components in the oil so that they are quickly and completely replaced and discharged by the purging gas. 3) Inject an excess of sodium hydroxide ethanol solution into the purged insulating oil, control the reaction temperature at 40~50℃, and stir until the acidic substances in the system are completely neutralized, generating a mixture containing sodium carbonate and residual sodium hydroxide. 4) Heat the mixture to 140~160℃ and stir continuously for 20~30 minutes to allow the ethanol and water to vaporize and separate upon heating, while sodium carbonate and sodium hydroxide form solid precipitates. 5) Stop heating and let the mixture stand until solid-liquid separation occurs. Remove the bottom sediment by filtration or centrifugation to obtain blank oil.

[0010] Furthermore, the gas replacement conditions in step 2) are as follows: the additive is polyisobutylene PB450, the amount added is 3‰~5‰ of the volume V of the insulating oil to be treated, the purging gas is carbon dioxide gas, the gas flow rate is V / 10 L / min, the purging pressure is 0.1MPa, and the constant temperature is 65℃.

[0011] Furthermore, in step 3), the concentration of the sodium hydroxide ethanol solution is 2 wt%.

[0012] Furthermore, in step 4), a magnetically coupled stirrer is used for stirring at a speed of 200-500 rpm for a time of 60-120 minutes.

[0013] Furthermore, in step 5), the filtration uses a polytetrafluoroethylene filter membrane with a pore size of 0.1~1μm, or the centrifugal force for centrifugation is 2000~5000g.

[0014] Furthermore, the inner wall of the sealed reaction vessel is made of stainless steel or polyetheretherketone, and it is equipped with gas inlet and outlet, liquid inlet and outlet, temperature sensor, heating and temperature control device, magnetically coupled stirrer and pressure regulating valve.

[0015] The beneficial effects achieved by this invention are: This invention achieves rapid preparation of ultra-high purity blank oil through the synergistic effect of a series of special processes, including gas replacement, chemical neutralization, and thermal separation-filtration. It overcomes the pain points of traditional technologies, such as slow preparation speed, high gas residue, substandard cleanliness, and complex equipment. Its core value lies in providing a rapidly prepareable blank oil base with near-theoretical zero background for calibrating insulating oil gas content detectors, thereby significantly improving the reliability of insulating oil gas content detection results and playing a crucial role in ensuring the safe operation of the power grid. Attached Figure Description

[0016] The accompanying drawings are provided to further illustrate the invention and form part of the specification. They are used in conjunction with embodiments of the invention to explain the invention and do not constitute a limitation thereof. In the drawings: Figure 1 This is a schematic diagram of the structural principle of the present invention.

[0017] In the diagram: 1. Closed reaction vessel. Detailed Implementation

[0018] The preferred embodiments of the present invention will be described below with reference to the accompanying drawings. It should be understood that the preferred embodiments described herein are for illustration and explanation only and are not intended to limit the present invention.

[0019] Example: A method for preparing ultra-high purity blank oil for calibrating an insulating oil gas content detector includes the following steps: Step 1) Inject V liters of insulating oil to be treated into the sealed reaction container 1.

[0020] Step 2) Add a quantitative amount of additive to the sealed reaction container 1 and mix it evenly. At a constant temperature, purge the treated insulating oil with a fixed flow rate of purging gas to purge the dissolved gas components in the oil so that they are quickly and completely replaced and discharged by the purging gas. The additive is polyisobutylene PB450, and the amount added is 3‰~5‰ of the volume V of the insulating oil to be treated. The purging gas is carbon dioxide gas, the gas flow rate is V / 10 L / min, the purging pressure is 0.1MPa, and the constant temperature is 65℃.

[0021] Step 3) Inject an excess of sodium hydroxide ethanol solution into the purged insulating oil, control the reaction temperature at 40~50℃, and stir until the acidic substances in the system are completely neutralized, generating a mixture containing sodium carbonate and residual sodium hydroxide. The concentration of the sodium hydroxide ethanol solution is 2 wt%.

[0022] Step 4) Heat the mixture to 140~160℃ and stir continuously for 20~30 minutes to allow the ethanol and water to vaporize and separate upon heating, while sodium carbonate and sodium hydroxide form solid precipitates. The stirring is performed using a magnetically coupled stirrer at a speed of 200-500 rpm for 60-120 minutes.

[0023] Step 5) Stop heating and let the mixture stand until solid-liquid separation occurs. Remove the bottom precipitate by filtration or centrifugation to obtain blank oil. The filtration uses a polytetrafluoroethylene filter membrane with a pore size of 0.1~1μm, or the centrifugal force for centrifugation is 2000~5000g.

[0024] Furthermore, the inner wall of the sealed reaction vessel 1 is made of stainless steel or polyetheretherketone.

[0025] Sealed reaction vessel 1, as shown Figure 1 As shown, it is equipped with gas inlet and outlet, liquid inlet and outlet, and can also be equipped with existing intelligent mechanisms such as temperature sensors, heating and temperature control devices, magnetic coupling stirrers and pressure regulating valves to cooperate in processing and achieve the preparation of ultra-high purity blank oil.

[0026] The advantages of this invention specifically include the following: First, this invention can rapidly and efficiently remove multi-element gases, achieving ultra-low background residue. Specifically: For the volume V of insulating oil to be treated, a quantitative amount of polyisobutylene PB450 additive (V*3‰~V*5‰ volume) is added, combined with carbon dioxide purging at a constant flow rate (V / 10 L / min) at 65℃. The advantages are: utilizing the effect of the additive on the viscosity of the insulating oil at 65℃, the gas-liquid contact area during gas replacement is greatly increased. Taking advantage of the high diffusivity and high miscibility of CO2 with the oil phase, gases such as N2, O2, H2, CO, CH4, C2H4, C2H6, and C2H2 can be rapidly carried out of the oil phase through the gas replacement principle. Compared with conventional methods, the process is simpler, can be completed under normal pressure, and does not require a high-vacuum sealed system or vacuum pump system; the gas removal rate is increased by more than 30%, and the final total residual gas content in the oil can reach ≤0.5 ppm (not detected by chromatograph); the entire process time is reduced by more than 80%, greatly improving efficiency.

[0027] The specific comparative experiments are as follows: Preparation of insulating oil to be treated: The insulating oil to be treated for the experiment was prepared by dissolving various gaseous components into the insulating oil. The chromatographic data of the components in the oil after preparation are shown in the table below:

[0028] Then, multiple portions of the above-mentioned insulating oil to be treated were quantitatively taken, and blank oil was prepared by conventional vacuum method, conventional gas washing method, and the preparation method of the present invention, respectively.

[0029] Experiment 1 data: Conventional vacuum method was used for treatment: 20L of insulating oil was treated with a vacuum oil filter (absolute pressure less than 1 kPa, temperature 120℃). After degassing for 12 hours, the component data of the oil were analyzed by chromatography, as shown in the table below:

[0030] Conventional gas washing method was used for treatment: 20L of insulating oil was treated using carbon dioxide as the purge gas at room temperature and pressure. After treatment for a specified time, the component data of the oil were analyzed by chromatography, as shown in the table below:

[0031] Conclusion 1: After 12 hours of treatment using the conventional vacuum method (vacuum oil filter), only hydrogen and carbon monoxide components were reduced to zero background levels, while the other components did not reach zero background levels. After 12 hours of treatment using conventional carbon dioxide scrubbing, only hydrogen, carbon monoxide, methane, ethylene, ethane, and acetylene reached zero background levels, while nitrogen, oxygen, and carbon dioxide could not reach zero background levels.

[0032] In conclusion, conventional degassing methods cannot meet the requirements for ultra-high cleanliness blank oil samples.

[0033] Experiment 2 data: Using the method in step 2) of this invention, experiments were conducted with various process conditions, and the degassing effect of each combination on the oil sample to be treated was recorded in the table below:

[0034] Conclusion 2: At 65℃, with the addition of 3‰~5‰ polyisobutylene PB450 additive and a CO2 flow rate of 2L / min, the oil sample to be tested can be treated to a state of zero background for all gas components except carbon dioxide in the purge gas after 1.5 hours. 65℃ can accelerate the replacement speed. The addition of 3‰~5‰ polyisobutylene PB450 additive can not only make the oil sample cleaner and lower the background, but also greatly shorten the replacement time, reduce the amount of purge gas used, greatly improve efficiency, and save resources.

[0035] Secondly, this invention simultaneously removes acidic impurities and oxidation products, specifically: Acid-base neutralization mechanism: Sodium hydroxide ethanol solution not only neutralizes free acids in oil (such as carboxylic acids and phenols), but also reacts with peroxides generated by oxidation to reduce the acid value of oil, which is significantly better than conventional physical degassing methods; Synergistic effect of ethanol: Ethanol, as a solvent, enhances the dispersibility of NaOH in oil, ensuring that the neutralization reaction proceeds fully, while avoiding saponification reaction caused by a strongly alkaline environment.

[0036] Third, this invention adopts green technology and low-energy design, specifically: Ethanol / water recovery and reuse: Ethanol and water evaporated during the heating stage can be recovered by condensation, reducing raw material consumption (recovery rate > 90%), which is in line with the principles of green chemistry.

[0037] Fourth, the solid impurities in this invention can be deeply purified, specifically: Precipitation-filtration dual-stage purification: Sodium carbonate and sodium hydroxide precipitation can adsorb colloidal particles and metal ions in the oil. Combined with membrane filtration, the solid particulate matter content is ≤0.1 mg / L, meeting the ultra-clean oil standard.

[0038] Finally, the chromatographic detection results of the blank oil sample processed by steps 1) to 5) of the preparation method of this invention are as follows:

[0039] The preparation of ultra-high purity blank oil samples was achieved.

Claims

1. A method for preparing ultra-clean blank oil for calibrating an insulating oil gas content detector, characterized in that, The method comprises the following steps: 1) injecting V liters of insulating oil to be treated into a closed reaction container (1); 2) adding a quantitative amount of additives into the closed reaction container (1) and mixing uniformly, and under constant temperature, a fixed flow of purging gas is introduced into the treated insulating oil to perform purging, so that the gas components dissolved in the oil are quickly and completely replaced by the purging gas and discharged; 3) injecting an excess amount of sodium hydroxide ethanol solution into the insulating oil after purging, controlling the reaction temperature at 40-50°C, and stirring and mixing until the acidic substances in the system are completely neutralized to generate a mixed solution containing sodium carbonate and residual sodium hydroxide; 4) heating the mixed solution to 140-160°C and continuously stirring for 20-30 minutes, so that ethanol and water are separated by heating and gasification, and sodium carbonate and sodium hydroxide form solid precipitates; 5) stopping heating and standing the mixed solution until the solid-liquid layering is achieved, removing the bottom precipitates by filtration or centrifugal separation to obtain a blank oil.

2. The method for preparing ultra-clean blank oil for calibrating the insulating oil gas content detector according to claim 1, characterized in that, In step 2), the conditions for gas replacement are as follows: the additive is polyisobutylene PB450, the addition amount is 3‰-5‰ of the volume V of the insulating oil to be treated, the purging gas is carbon dioxide gas, the gas flow is V / 10 L / min, the purging pressure is 0.1 MPa, and the constant temperature is 65°C.

3. The method for preparing ultra-clean blank oil for calibrating the insulating oil gas content detector according to claim 1, characterized in that, In step 3), the concentration of the sodium hydroxide ethanol solution is 2wt%.

4. The method for preparing ultra-clean blank oil for calibrating the insulating oil gas content detector according to claim 1, characterized in that, In step 4), the stirring is performed by a magnetic coupling stirrer, the stirring speed is 200-500 rpm, and the stirring time is 60-120 minutes.

5. The method for preparing ultra-clean blank oil for calibrating the insulating oil gas content detector according to claim 1, characterized in that, In step 5), the filtration is performed by using a polytetrafluoroethylene filter membrane with a pore size of 0.1-1 μm, or the centrifugal force for centrifugal separation is 2000-5000 g.

6. The method for preparing ultra-clean blank oil for calibrating the insulating oil gas content detector according to claim 1, characterized in that, The inner wall of the closed reaction container (1) is made of stainless steel or polyether ether ketone material, and is provided with a gas inlet and outlet, a liquid inlet and outlet, a temperature sensor, a heating temperature control device, a magnetic coupling stirrer and a pressure regulating valve.

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