Method for extracting metal in transformer oil by using ionic liquid and recycling ionic liquid

Abstract

The invention provides a method for extracting metals in transformer oil by using ionic liquid and recycling the ionic liquid, and some functional groups in the ionic liquid, including halogen, hydroxyl, thioether, urea and thiourea, can form complexes with metal ions in the transformer oil. Therefore, the metal ions are extracted into the ionic liquid from the transformer oil, and the metal impurities in the transformer oil are removed. Metal in the transformer oil is extracted by using the ionic liquid, so that metal substances in the oil are reduced, and the insulating property of the transformer oil is improved. And after metal impurities in the oil are removed, a guarantee is provided for long-term safe operation of the transformer. After the used ionic liquid is subjected to coarse filtration, cation exchange resin treatment, reduced pressure distillation and evaporative crystallization, the recycling of the ionic liquid can be realized. Compared with other methods, the recycling conditions of the steps are economical and efficient, no organic reagent is needed, and a thought is provided for application of the ionic liquid in an electric power system.

Description

Technical Field

[0001] The invention relates to the field of extracting metals from transformer oil, and in particular to a method for extracting metals from transformer oil using ionic liquid and recycling the same. Background Art

[0002] Transformers occupy an irreplaceable core position in the power system, and their stable operation is highly dependent on transformer oil as a key insulating and cooling medium. The quality of transformer oil is directly related to the safe and efficient operation of the transformer. However, during the continuous and long operation cycle of the transformer, affected by various factors, metal impurities such as copper and iron will dissolve in the oil. The accumulation of these impurities not only weakens the insulation performance of the transformer oil, but also accelerates the aging process of the oil-paper insulation system. In extreme cases, it may induce transformer failure and endanger the stability of the entire power system. Therefore, it is of great practical significance to explore an efficient and feasible technology to remove metal impurities in transformer oil.

[0003] At present, the widely used solutions in the industry, such as adsorption and filtration, have achieved certain results in removing metal impurities, but they generally face the challenges of low removal efficiency, cumbersome operation procedures, and high economic costs. Therefore, finding more advanced, economical and easy-to-operate methods has become a key issue to be solved in this field. Existing studies have shown that ionic liquids have unique physical and chemical properties, such as extremely low vapor pressure, good thermal stability, wide liquid range, good solubility and adjustable acidity, and are widely used. Compared with other chemical, physical and chemical and biochemical methods for extracting metals, ionic liquids have greater advantages in extracting metals. They can achieve a simple operation, no secondary pollution, and high extraction efficiency of metal extraction processes. Ionic liquids can be recycled and reused, which is a treatment method worthy of promotion and application. The removal of metal impurities in transformer oil helps to improve the operating reliability and safety of transformers, extend the service life of transformers, and also provides new ideas and methods for the application of ionic liquids in the power industry. Therefore, we propose a method for extracting metals from transformer oil using ionic liquids and recycling them. Summary of the invention

[0004] The purpose of the present invention is to solve the problems in the existing background technology. In order to achieve the above invention purpose, the present invention provides the following technical scheme: a recycling method for extracting metals from transformer oil with ionic liquid, comprising the following steps:

[0005] Step 1: Take 16-30mL of transformer oil sample from actual operation and put it into a beaker;

[0006] Step 2, adding 2-4 mL of imidazole ionic liquid, pyridine ionic liquid, pyrrole ionic liquid, or tetraalkylammonium ionic liquid to the transformer oil sample in a beaker; the volume ratio of the ionic liquid to the transformer oil sample is 1:8-1:15;

[0007] Step 3, adding the ionic liquid to the transformer oil sample, stirring the mixed solution with a stirrer, the stirring temperature is 40-60° C., the stirring time is 10-30 min, and the stirring speed is 500-2000 rpm;

[0008] Step 4: When the ionic liquid is mixed with the transformer oil sample, nitrogen (N2) is introduced to protect the metal from being reduced; the flow rate of the introduced gas is 5-30 mL / min, and the ventilation time is 5-60 min;

[0009] Step 5: Use a mechanical shaker to further promote mixing, with a frequency of 50-100 Hz and a shaking time of 15-30 min; use centrifugal stratification, with a centrifugal speed of 3000-5000 r / min and a centrifugal time of 5-20 min;

[0010] Step 6: Take the ionic liquid phase after stratification, use filter paper for coarse filtration at 25-40° C. and use a 1-100 nm microporous ceramic membrane to remove solid impurities, and then use a cation exchange resin IR-120 to remove metal impurities therein to obtain ionic liquid for extracting metals from transformer oil.

[0011] As a preferred technical solution of the present invention, it also includes extracting the ionic liquid, subjecting the treated ionic liquid phase to vacuum distillation at a gas pressure of 0.02-0.08MPa and a temperature of 110-380°C, and further purifying the ionic liquid obtained by vacuum distillation by evaporation crystallization at 110-380°C to finally obtain the ionic liquid.

[0012] As a preferred technical solution of the present invention, the ionic liquids are 1-octyl-3-methylimidazolium chloride ([C8mim]Cl), 1-octyl-3-methylimidazolium hexafluorophosphate ([C8mim][PF6]), 1-hexylpyridinium hexafluorophosphate ([HPy][PF6]), 1-butyl-3-methylimidazolium hexafluorophosphate ([C4mim][PF6]), 4-(5-nonyl)pyridine (NPy) and 1-butyl-4-methylpyridinium tetrafluoroborate ([BMP][BF4]).

[0013] As a preferred technical solution of the present invention, the ionic liquid extraction method is vacuum distillation and membrane separation, the temperature is 25-38°C, the pore size of the microporous ceramic membrane is 3-7nm, the air pressure is 0.02-0.06MPa, the temperature is 110-360°C, and the evaporation crystallization temperature is 110-370°C.

[0014] As a preferred technical solution of the present invention, in step 2, the volume ratio of the ionic liquid to the transformer oil sample is 1:8-1:12, and the stirring time is 10-25 minutes.

[0015] As a preferred technical solution of the present invention, in step 5, the oscillation frequency is 60-80 Hz, and the oscillation time is 15-25 min.

[0016] As a preferred technical solution of the present invention, in step 5, the centrifuge speed is 3000-4500r / min, and the centrifugation time is 5-15min.

[0017] As a preferred technical solution of the present invention, the flow rate of nitrogen (N2) gas is 5-20mL / min, and the ventilation time is 5-45min.

[0018] As a preferred technical solution of the present invention, the stirring temperature is 40-50°C, the stirring time is 10-25min, and the stirring speed is 1000-2000rpm.

[0019] As a preferred technical solution of the present invention, the ionic liquid is re-extracted and recycled through reduced pressure distillation, extraction, adsorption, two-phase aqueous method and membrane separation method.

[0020] Compared with the prior art, the present invention has the following beneficial effects: In the scheme of the present invention:

[0021] 1. Certain functional groups in ionic liquids, including halogens, hydroxyls, thioethers, ureas and thioureas, can form complexes with metal ions in transformer oil, thereby extracting metal ions from transformer oil into ionic liquids and removing metal impurities from transformer oil.

[0022] 2. Use ionic liquid to extract metals from transformer oil, reduce the metal content in the oil, and improve the insulation performance of transformer oil. After removing metal impurities in the oil, it provides a guarantee for the long-term and safe operation of the transformer.

[0023] 3. The used ionic liquid can be recycled after coarse filtration, cation exchange resin treatment, vacuum distillation and evaporation crystallization. Compared with other methods, the recovery conditions of the above steps are economical and efficient, and no organic reagents are required, which provides ideas for the application of ionic liquids in power systems. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 A flow chart of the method provided by the present invention. DETAILED DESCRIPTION

[0025] To make the purpose, technical solution and advantages of the embodiments of the present invention clearer, the technical solution in the embodiments of the present invention will be described clearly and completely in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of them.

[0026] Therefore, the following detailed description of the embodiments of the present invention is not intended to limit the scope of the claimed invention, but merely represents some embodiments of the present invention. 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. It should be noted that the embodiments of the present invention and the features and technical solutions in the embodiments can be combined with each other without conflict. It should be noted that similar numbers and letters represent similar items in the following figures. Therefore, once an item is defined in one figure, it does not need to be further defined and explained in subsequent figures. The normal temperature of the present invention refers to 25±2℃.

[0027] Example 1: Please refer to Figure 1 , a method for extracting metals from transformer oil with ionic liquid and recycling it, comprising the following steps: taking 16-30 mL of a transformer oil sample actually in operation and putting it into a beaker, adding 2-4 mL of imidazole ionic liquid, pyridine ionic liquid, pyrrole ionic liquid, or tetraalkylammonium ionic liquid thereto. The volume ratio of the ionic liquid to the transformer oil sample is 1:8-1:15. The ionic liquid is added to the transformer oil sample, and the mixed solution is stirred with a stirrer, the stirring temperature is 40-60°C, the stirring time is 10-30 min, and the stirring speed is 500-2000 rpm.

[0028] When the ionic liquid is mixed with the transformer oil sample, nitrogen (N2) is introduced to protect the metal from being reduced. The flow rate of the introduced gas is 5-30mL / min, and the ventilation time is 5-60min. A mechanical oscillator is used to further promote mixing, with a frequency of 50-100Hz and an oscillation time of 15-30min. Centrifugal stratification is adopted, with a centrifugal speed of 3000-5000r / min and a centrifugal time of 5-20min.

[0029] Ionic liquids can be re-extracted and recycled by vacuum distillation, extraction, adsorption, two-phase aqueous method and membrane separation. Take the ion liquid phase after stratification, use filter paper for coarse filtration at 25-40°C and 1-100nm microporous ceramic membrane to remove solid impurities, and then pass through cation exchange resin IR-120 to remove metal impurities. Then the treated ionic liquid phase is subjected to vacuum distillation at a pressure of 0.02-0.08MPa and a temperature of 110-380°C.

[0030] The ionic liquid obtained by vacuum distillation is further purified by evaporation and crystallization at 110-380° C. to obtain an ionic liquid. The above extraction and separation steps are repeated for the obtained ionic liquid.

[0031] Preferably, the volume ratio of the ionic liquid to the transformer oil sample is 1:8-1:12, and the stirring time is 10-25 min.

[0032] Preferably, the oscillation frequency is 60-80 Hz and the oscillation time is 15-25 min.

[0033] Preferably, the centrifuge speed is 3000-4500 r / min, and the centrifugation time is 5-15 min.

[0034] Preferably, the nitrogen (N2) gas flow rate is 5-20 mL / min, and the ventilation time is 5-45 min.

[0035] Preferably, the stirring temperature is 40-50° C., the stirring time is 10-25 min, and the stirring speed is 1000-2000 rpm.

[0036] Preferably, the ionic liquid is selected from 1-octyl-3-methylimidazolium chloride ([C8 mim]Cl), 1-octyl-3-methylimidazolium hexafluorophosphate ([C8mim][PF6]), 1-hexylpyridinium hexafluorophosphate ([HPy][PF6]), 1-butyl-3-methylimidazolium hexafluorophosphate ([C4mim][PF6]), 4-(5-nonyl)pyridine (NPy) and 1-butyl-4-methylpyridinium tetrafluoroborate ([BMP][BF4]).

[0037] Preferably, the ionic liquid extraction method is vacuum distillation and membrane separation, the temperature is 25-38°C, the pore size of the microporous ceramic membrane is 3-7nm, the air pressure is 0.02-0.06MPa, the temperature is 110-360°C, and the evaporation crystallization temperature is 110-370°C.

[0038] The operation process of ionic liquid extraction of metallic copper and ionic liquid recovery and recycling: Taking the extraction of metallic copper from transformer oil samples as an example, 16 mL of transformer oil sample was measured and placed in a beaker. Then, 2 mL of 1-octyl-3-methylimidazolium chloride ([C8 mim]Cl) was added to the transformer oil sample in the beaker. The volume ratio of ionic liquid to transformer oil sample was 1:8. The mixed solution was stirred with a stirrer to fully mix the ionic liquid and transformer oil sample. The stirring temperature was 45 ° C, the stirring time was 10 min, and the stirring speed was 1000 rpm. When the ionic liquid was mixed with the transformer oil sample, in order to protect the metal from being reduced, nitrogen (N2) was introduced with a gas flow rate of 10 mL / min and a ventilation time of 25 min. A mechanical oscillator was used for oscillation at a frequency of 75 Hz and an oscillation time of 20 min. Centrifugal stratification was adopted with a centrifugal speed of 3000 r / min and a centrifugal time of 5 min. The ionic liquid phase after stratification was taken, and solid impurities were removed by coarse filtration and 4nm microporous ceramic membrane at 30°C, and then the metal impurities were removed by cation exchange resin IR-120. Then the treated ionic liquid phase was subjected to vacuum distillation at a pressure of 0.04MPa and a temperature of 130°C. The ionic liquid obtained by vacuum distillation was further purified by evaporation crystallization at 130°C, and finally the ionic liquid was obtained. The above extraction and separation steps were repeated for the obtained ionic liquid. The other control group did not add ionic liquid.

[0039] Determination of metallic copper content and ionic liquid recycling performance:

[0040] After the extraction is completed, the transformer oil phase is taken for analysis. The content of metallic copper in the oil is determined using an oil analysis spectrometer. Compared with the control group, the content of metallic copper has decreased by 60.1%. It can be effectively recycled for 8 times, and the content of metallic copper has decreased by 58.1%, 59.7%, 60.2%, 59.4%, 59.8%, 60.3%, 58.7%, and 57.9% respectively.

[0041] Example 2: Operation process of extracting metallic copper with ionic liquid and recovering and recycling the ionic liquid:

[0042] Taking the extraction of metallic copper from transformer oil as an example, 18 mL of transformer oil sample was measured and placed in a beaker. Then, 2 mL of 1-hexylpyridinium hexafluorophosphate ([HPy][PF6]) was added to the transformer oil sample in the beaker. The volume ratio of the ionic liquid to the transformer oil sample was 1:9. The mixed solution was stirred with a stirrer to fully mix the ionic liquid and the transformer oil sample. The stirring temperature was 40°C, the stirring time was 15 min, and the stirring speed was 1200 rpm. When the ionic liquid and the transformer oil sample were mixed, nitrogen (N2) was introduced at a gas flow rate of 12 mL / min and a ventilation time of 30 min to protect the metal from being reduced. A mechanical oscillator was used for oscillation at a frequency of 80 Hz and an oscillation time of 15 min. Centrifugal stratification was used with a centrifugal speed of 3000 r / min and a centrifugal time of 5 min. The ionic liquid phase after stratification was taken, and solid impurities were removed by coarse filtration and a 3 nm microporous ceramic membrane at 25°C, and then the metal impurities were removed by cation exchange resin IR-120. Then the treated ionic liquid phase was subjected to vacuum distillation at a pressure of 0.02 MPa and a temperature of 230°C, and the ionic liquid obtained by vacuum distillation was further purified by evaporation crystallization at 230°C to obtain an ionic liquid, and the above extraction and separation steps were repeated for the obtained ionic liquid. Another control group was not subjected to the addition of ionic liquid.

[0043] Determination of metallic copper content and ionic liquid recycling performance:

[0044] After the extraction, the transformer oil phase was taken for analysis. Compared with the control group, the content of metallic copper decreased by 33.7%. It can be effectively recycled for 5 times, and the content of metallic copper decreased by 31.8%, 32.4%, 30.7%, 33.4% and 31.6% respectively.

[0045] Example 3: Operation process of ionic liquid extraction of metallic copper: Taking the extraction of metallic copper from transformer oil sample as an example, 20 mL of transformer oil sample was measured and placed in a beaker. Then, 2 mL of 1-butyl-3-methylimidazole hexafluorophosphate ([C4mim][PF6]) was added to the transformer oil sample in the beaker. The volume ratio of the ionic liquid to the transformer oil sample was 1:10. A stirrer was used to stir the mixed solution so that the ionic liquid and the transformer oil sample were fully mixed. The stirring temperature was 50°C, the stirring time was 15 min, and the stirring speed was 1400 rpm. When the ionic liquid was mixed with the transformer oil sample, nitrogen (N2) was introduced to protect the metal from being reduced, with a gas flow rate of 16 mL / min and a ventilation time of 25 min. A mechanical oscillator was used for oscillation at a frequency of 60 Hz and an oscillation time of 15 min. Centrifugal stratification was adopted, with a centrifugal speed of 4000 r / min and a centrifugal time of 15 min. The ionic liquid phase after stratification was taken, and solid impurities were removed by coarse filtration and 5nm microporous ceramic membrane at 30°C, and then the metal impurities were removed by cation exchange resin IR-120. Then the treated ionic liquid phase was subjected to vacuum distillation at a pressure of 0.04MPa and a temperature of 360°C, and the ionic liquid obtained by vacuum distillation was further purified by evaporation crystallization at 360°C, and finally the ionic liquid was obtained, and the above extraction and separation steps were repeated for the obtained ionic liquid. The other control group did not perform the operation of adding ionic liquid.

[0046] Determination of metallic copper content and ionic liquid recycling performance:

[0047] After the extraction is completed, the transformer oil phase is taken for analysis. The content of metallic copper in the oil is determined using an oil analysis spectrometer. Compared with the control group, the content of metallic copper decreased by 36.8%. It can be effectively recycled for 6 times, and the content of metallic copper decreased by 34.3%, 36.5%, 36.7%, 35.8%, 34.7%, and 35.3% respectively.

[0048] Example 4: Operation process of ionic liquid extraction of metallic copper: Taking the extraction of metallic copper from transformer oil sample as an example, 28 mL of transformer oil sample was measured and placed in a beaker. Then, 2 mL of 4-(5-nonyl)pyridine (NPy) was added to the transformer oil sample in the beaker. The volume ratio of the ionic liquid to the transformer oil sample was 1:14. The mixed solution was stirred with an agitator to fully mix the ionic liquid and the transformer oil sample. The stirring temperature was 55°C, the stirring time was 15 min, and the stirring speed was 1600 rpm. When the ionic liquid was mixed with the transformer oil sample, nitrogen (N2) was introduced to protect the metal from being reduced, with a gas flow rate of 18 mL / min and a ventilation time of 30 min. A mechanical oscillator was used for oscillation at a frequency of 80 Hz and an oscillation time of 15 min. Centrifugal stratification was adopted, with a centrifugal speed of 4000 r / min and a centrifugal time of 15 min. The ionic liquid phase after stratification was taken, and solid impurities were removed by coarse filtration and 6nm microporous ceramic membrane at 35°C, and then the metal impurities were removed by cation exchange resin IR-120. Then the treated ionic liquid phase was subjected to vacuum distillation at a pressure of 0.06MPa and a temperature of 280°C, and the ionic liquid obtained by vacuum distillation was further purified by evaporation crystallization at 280°C, and finally the ionic liquid was obtained, and the above extraction and separation steps were repeated for the obtained ionic liquid. The other control group did not perform the operation of adding ionic liquid.

[0049] Determination of metallic copper content and ionic liquid recycling performance: After the extraction is completed, the transformer oil phase is taken for analysis. The content of metallic copper in the oil is determined using an oil analysis spectrometer. Compared with the control group, the content of metallic copper decreased by 44.5%. It can be effectively recycled for 7 times, and the content of metallic copper decreased by 42.8%, 43.7%, 43.1%, 44.2%, 41.2%, 40.6%, and 43.3%, respectively.

[0050] Example 5: Operation process of ionic liquid extraction of metallic copper. Taking the extraction of metallic copper from transformer oil sample as an example, 30 mL of transformer oil sample was measured and placed in a beaker. Then, 2 mL of 1-butyl-4-methylpyridinium tetrafluoroborate ([BMP][BF4]) was added to the transformer oil sample in the beaker. The volume ratio of the ionic liquid to the transformer oil sample was 1:15. The mixed solution was stirred with an agitator to fully mix the ionic liquid and the transformer oil sample. The stirring temperature was 60°C, the stirring time was 25 min, and the stirring speed was 2000 rpm. When the ionic liquid was mixed with the transformer oil sample, nitrogen (N2) was introduced to protect the metal from being reduced. The gas flow rate was 30 mL / min and the ventilation time was 45 min. A mechanical oscillator was used for oscillation at a frequency of 90 Hz and an oscillation time of 15 min. Centrifugal stratification was adopted, the centrifugal speed was 4500 r / min, and the centrifugal time was 20 min. The ionic liquid phase after stratification was taken, and solid impurities were removed by coarse filtration and 7nm microporous ceramic membrane at 35°C, and then the metal impurities were removed by cation exchange resin IR-120. Then the treated ionic liquid phase was subjected to vacuum distillation at a pressure of 0.08MPa and a temperature of 150°C. The ionic liquid obtained by vacuum distillation was further purified by evaporation crystallization at 150°C, and finally the ionic liquid was obtained. The above extraction and separation steps were repeated for the obtained ionic liquid. The other control group did not add ionic liquid.

[0051] Content of metallic copper and recycling performance of ionic liquids:

[0052] After the extraction is completed, the transformer oil phase is taken for analysis. The content of metallic copper in the oil is determined using an oil analysis spectrometer. Compared with the control group, the content of metallic copper decreased by 29.6%. It can be effectively recycled for 4 times, and the content of metallic copper decreased by 27.1%, 28.2%, 28.4%, and 26.3% respectively.

[0053] Example 6: Same as Example 2, except that the centrifugal speed is set to 4500r / min.

[0054] After the extraction is completed, the transformer oil phase is taken for analysis. The content of metallic copper in the oil is determined using an oil analysis spectrometer. Compared with the control group, the content of metallic copper decreased by 18.7%. It can be effectively recycled for 3 times, and the content of metallic copper decreased by 16.2%, 17.3%, and 16.4% respectively.

[0055] Example 7: Same as Example 5, except that the shaking time is 30 min.

[0056] After the extraction is completed, the transformer oil phase is taken for analysis. The content of metallic copper in the oil is determined using an oil analysis spectrometer. Compared with the control group, the content of metallic copper decreased by 16.3%. It can be effectively recycled twice, and the content of metallic copper decreased by 15.7% and 16.1% respectively.

[0057] Comparative Example 1:

[0058] The extraction of metallic copper from transformer oil is the same as in Example 1, except that nitrogen (N2) is not introduced.

[0059] (2) The content of metallic copper and the recycling performance of ionic liquids:

[0060] After the extraction is completed, the transformer oil phase is taken for analysis. The content of metallic copper in the oil is determined using an oil analysis spectrometer. Compared with the control group, the content of metallic copper decreased by 12.8%. This is attributed to the fact that the oxidation of metallic copper in the transformer oil was accelerated due to the lack of N2, which led to the aging of the transformer oil too quickly, and thus reduced the efficiency of extracting metallic copper from the transformer oil. It can be effectively recycled for 3 times, and the content of metallic copper decreased by 10.3%, 12.5%, and 10.7%, respectively.

[0061] Comparative Example 2:

[0062] The extraction of metallic copper from transformer oil is the same as in Example 4, except that the step of shaking and mixing is omitted.

[0063] (2) The content of metallic copper and the recycling performance of ionic liquids:

[0064] After the extraction is completed, the transformer oil phase is taken for analysis. The content of metallic copper in the oil is determined using an oil analysis spectrometer. Compared with the control group, the content of metallic copper decreased by 31.9%. It can be effectively recycled for 5 times, and the content of metallic copper decreased by 27.3%, 30.8%, 29.6%, 28.1%, and 30.5% respectively.

[0065] Comparative Example 3:

[0066] The extraction of metallic copper from transformer oil is the same as in Example 3, except that 1-octyl-3-methylimidazole hexafluorophosphate ([C8mim][PF6]) is used.

[0067] (2) The content of metallic copper and the recycling performance of ionic liquids:

[0068] After the extraction is completed, the transformer oil phase is taken for analysis. The content of metallic copper in the oil is determined using an oil analysis spectrometer. Compared with the control group, the content of metallic copper decreased by 22.7%. It can be effectively recycled for 4 times, and the content of metallic copper decreased by 22.4%, 20.6%, 20.3%, and 21.5% respectively.

[0069] It can be seen from the above embodiments and comparative examples that the extraction efficiency of metals in transformer oil of the present invention is high under experimental conditions, the insulation performance of transformer oil is improved to a certain extent, and the safe and stable operation of the transformer is guaranteed. In addition, the recycling of ionic liquids provides a new idea for the application of ionic liquids in the field of transformers.

[0070] The embodiments described above are only descriptions of the preferred modes of the present invention, and are not intended to limit the scope of the present invention. Without departing from the design spirit of the present invention, various modifications and improvements made to the technical solutions of the present invention by ordinary technicians in this field should all fall within the protection scope determined by the claims of the present invention.

Claims

1. A recycling method for extracting metals from transformer oil using ionic liquids, characterized in that: The following steps are involved: Step 1: Take 16-30mL of transformer oil sample from actual operation and put it into a beaker; Step 2, adding 2-4 mL of imidazole ionic liquid, pyridine ionic liquid, pyrrole ionic liquid, or tetraalkylammonium ionic liquid to the transformer oil sample in a beaker; the volume ratio of the ionic liquid to the transformer oil sample is 1:8-1:15; Step 3, adding the ionic liquid to the transformer oil sample, stirring the mixed solution with a stirrer, the stirring temperature is 40-60° C., the stirring time is 10-30 min, and the stirring speed is 500-2000 rpm; Step 4: When the ionic liquid is mixed with the transformer oil sample, nitrogen (N2) is introduced to protect the metal from being reduced; the flow rate of the introduced gas is 5-30 mL / min, and the ventilation time is 5-60 min; Step 5: Use a mechanical shaker to further promote mixing, with a frequency of 50-100 Hz and a shaking time of 15-30 min; use centrifugal stratification, with a centrifugal speed of 3000-5000 r / min and a centrifugal time of 5-20 min; Step 6: Take the ionic liquid phase after stratification, use filter paper for coarse filtration at 25-40° C. and use a 1-100 nm microporous ceramic membrane to remove solid impurities, and then use a cation exchange resin IR-120 to remove metal impurities therein to obtain ionic liquid for extracting metals from transformer oil.

2. The recycling method for extracting metals from transformer oil using ionic liquid according to claim 1, characterized in that: The method also includes extracting the ionic liquid, subjecting the treated ionic liquid phase to vacuum distillation at a gas pressure of 0.02-0.08 MPa and a temperature of 110-380° C., further purifying the ionic liquid obtained by vacuum distillation by evaporation crystallization at 110-380° C., and finally obtaining the ionic liquid.

3. The recycling method for extracting metals from transformer oil using ionic liquid according to claim 2, characterized in that: The ionic liquids selected are 1-octyl-3-methylimidazolium chloride ([C8 mim]Cl), 1-octyl-3-methylimidazolium hexafluorophosphate ([C8mim][PF6]), 1-hexylpyridinium hexafluorophosphate ([HPy][PF6]), 1-butyl-3-methylimidazolium hexafluorophosphate ([C4mim][PF6]), 4-(5-nonyl)pyridine (NPy) and 1-butyl-4-methylpyridinium tetrafluoroborate ([BMP][BF4]).

4. The recycling method for extracting metals from transformer oil using ionic liquid according to claim 3, characterized in that: The ionic liquid extraction method is a vacuum distillation method and a membrane separation method, the temperature is 25-38°C, the pore size of the microporous ceramic membrane is 3-7nm, the air pressure is 0.02-0.06MPa, the temperature is 110-360°C, and the temperature of evaporation crystallization is 110-370°C.

5. The recycling method for extracting metals from transformer oil using ionic liquid according to claim 4, characterized in that: Step 2: The volume ratio of the ionic liquid to the transformer oil sample is 1:8-1:12, and the stirring time is 10-25 minutes.

6. The recycling method for extracting metals from transformer oil using ionic liquid according to claim 5, characterized in that: Step 5: The oscillation frequency is 60-80 Hz and the oscillation time is 15-25 min.

7. The recycling method for extracting metals from transformer oil using ionic liquid according to claim 6, characterized in that: Step 5: The centrifuge speed is 3000-4500 r / min, and the centrifugation time is 5-15 min.

8. The recycling method for extracting metals from transformer oil using ionic liquid according to claim 7, characterized in that: The nitrogen (N2) gas flow rate is 5-20mL / min, and the ventilation time is 5-45min.

9. The recycling method for extracting metals from transformer oil using ionic liquids according to claim 8, characterized in that: The stirring temperature is 40-50°C, the stirring time is 10-25min, and the stirring speed is 1000-2000rpm.

10. The recycling method for extracting metals from transformer oil using ionic liquid according to claim 9, characterized in that: The ionic liquid is re-extracted and recycled through vacuum distillation, extraction, adsorption, two-phase aqueous method and membrane separation method.

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