Chemical auxiliary decoupling method and device for detecting perfluoroisobutyronitrile insulated GIS (Gas Insulated Switchgear)

Abstract

The invention relates to a chemical auxiliary decoupling method and device for detecting a perfluoroisobutyronitrile insulated GIS (Gas Insulated Switchgear), in the method, first gas in the perfluoroisobutyronitrile insulated GIS to be detected is introduced into a C4F7N absorption reactor containing a concentrated strong alkali solution, and the first gas comprises C4F7N and CF4; in the C4F7N absorption reactor, a spraying reaction mode is adopted for maintaining for a first time, then spraying is stopped to react to remove C4F7N in the first gas and generate NH3, then second gas is output, the second gas comprises CF4, NH3 and water, and the second gas is transferred into an NH3 absorption reactor containing an acid solution; in the NH3 absorption reactor, a spraying reaction mode is adopted for maintaining for a second time, then spraying is stopped to remove NH3 in the second gas, third gas is obtained, and the third gas comprises CF4 and water; and enabling the third gas to slowly flow through a drying pipe for drying treatment so as to remove water molecules and obtain CF4.

Description

Technical Field

[0001] The invention relates to the technical field of perfluoroisobutyronitrile insulation GIS operation detection, and in particular to a chemically assisted decoupling method and a device for detecting perfluoroisobutyronitrile insulation GIS. Background Art

[0002] Chemically assisted decoupling method and device for detecting perfluoroisobutyronitrile insulated GIS Perfluoroisobutyronitrile (C4F7N) is regarded as a potential gas to replace sulfur hexafluoride (SF6), the first gas of traditional gas insulated switchgear (GIS), due to its excellent electrical insulation performance and low global warming potential. When C4F7N insulated GIS fails such as overheating or partial discharge, C4F7N will decompose to generate trace characteristic gases such as CF4, C2F6 and C2F5CN. Among these generated gases, CF4 has the highest content and obvious concentration changes, making it a key indicator for early diagnosis of GIS faults. Therefore, accurate detection of trace CF4 concentration is of great significance to ensure the long-term stable operation of GIS. Spectroscopic methods include absorption spectroscopy and photoacoustic spectroscopy, which are considered to be ideal for trace gas detection due to their advantages such as fast detection speed, high sensitivity and easy maintenance. However, due to the similarity of molecular bonding between C4F7N and CF4, there is a significant overlap in their infrared spectra, which makes it extremely difficult to accurately detect trace amounts of CF4 in a background containing constant C4F7N. Existing technologies are unable to effectively solve this cross-interference problem, making it impossible to accurately distinguish and detect C4F7N and CF4 by spectroscopy. Therefore, it is urgent to develop an effective decoupling method for C4F7N and CF4.

[0003] The above information disclosed in this Background section is only for enhancement of understanding of the background of the invention and therefore it may contain information that does not form the prior art that is already known to a person of ordinary skill in the art. Summary of the invention

[0004] The present invention provides a chemically assisted decoupling method and device for detecting perfluoroisobutyronitrile insulated GIS, which can significantly reduce the concentration of C4F7N in the first gas of the GIS to be detected, realize the decoupling of C4F7N and CF4, and avoid infrared cross interference.

[0005] A chemically assisted decoupling method for detecting perfluoroisobutyronitrile insulated GIS includes: Step 1, introducing the first gas in the perfluoroisobutyronitrile insulation GIS to be tested into a C4F7N absorption reactor containing a concentrated strong alkali solution, wherein the first gas includes C4F7N and CF4; Step 2, in the C4F7N absorption reactor, a spray reaction is maintained for a first time, and then the spray is terminated to remove C4F7N in the first gas and generate NH3, and then a second gas is output, wherein the second gas includes CF4, NH3 and water. Step 3, transferring the second gas to an NH3 absorption reactor containing an acid solution; Step 4, in the NH3 absorption reactor, a spray reaction is maintained for a second time and then the spraying is terminated to remove NH3 in the second gas to obtain a third gas, wherein the third gas includes CF4 and water; Step 5, allowing the third gas to slowly flow through a drying tube for drying to remove water molecules to obtain CF4.

[0006] In the chemically assisted decoupling method for detecting perfluoroisobutyronitrile insulated GIS, in step 1, the concentrated strong alkali solution includes NaOH or KOH solution, and its concentration is greater than 2 mol / L.

[0007] In the chemically assisted decoupling method for detecting perfluoroisobutyronitrile insulated GIS, in step 1, the volume of the concentrated strong alkaline solution is 0.5 times that of the first gas to be detected.

[0008] In the chemically assisted decoupling method for detecting perfluoroisobutyronitrile insulated GIS, the first time is 1 to 40 minutes.

[0009] In the chemically assisted decoupling method for detecting perfluoroisobutyronitrile insulated GIS, the flow rate of the spraying liquid in step 2 and step 4 is greater than 1000 standard cubic centimeters per minute.

[0010] In the chemically assisted decoupling method for detecting perfluoroisobutyronitrile insulated GIS, in step 3, the acid solution includes H2SO4 solution with a concentration of 0.5 mol / L.

[0011] In the chemically assisted decoupling method for detecting perfluoroisobutyronitrile insulated GIS, in step 3, the volume of the acid solution is 0.5 times the volume of the gas to be tested.

[0012] In the chemically assisted decoupling method for detecting perfluoroisobutyronitrile insulated GIS, the second time is 3 to 5 minutes.

[0013] In the chemically assisted decoupling method for detecting perfluoroisobutyronitrile insulated GIS, the desiccant includes quicklime, the volume of the drying tube is greater than 3000 mL, and the gas flow rate is less than 100 standard cubic centimeters per minute.

[0014] A device for implementing the method comprises: A C4F7N absorption reactor comprising a first reaction container for introducing a first gas to be measured and a first nozzle for spraying a concentrated strong alkali solution; A gas delivery liquid pipeline connected to the C4F7N absorption reactor to derive the second gas; an NH3 absorption reactor connected to the gas liquid pipeline, the NH3 absorption reactor comprising a second reaction container for introducing a second gas and a second nozzle for spraying a concentrated strong alkali solution; A drying pipe is connected to the NH3 absorption reactor to dry the third gas from the NH3 absorption reactor.

[0015] Compared with the prior art, the present invention has the following advantages: the present invention adopts a strong alkaline solution to absorb C4F7N in the first gas of the GIS to be tested, thereby realizing efficient and selective absorption of C4F7N, while CF4 is not absorbed due to its chemical inertness; an acid solution and a desiccant are used to remove the reaction byproducts NH3 and H2O that have cross-interference effects on CF4 detection, which is beneficial to the accurate detection of trace CF4 in the C4F7N background, and provides a solid guarantee for the long-term stable operation of the GIS equipment. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] By reading the detailed description of the preferred specific embodiments below, various other advantages and benefits of the present invention will become clear to those of ordinary skill in the art. The drawings in the specification are only for the purpose of illustrating the preferred embodiments and are not considered to be limitations of the present invention. Obviously, the drawings described below are only some embodiments of the present invention. For those of ordinary skill in the art, other drawings can also be obtained based on these drawings without creative work. Moreover, the same reference numerals are used to represent the same components throughout the drawings.

[0017] In the attached picture: Figure 1 : is a comparison diagram of infrared absorption spectra of C4F7N and CF4 in the present invention, A is a strong infrared absorption spectrum peak of CF4 located near 7790 nm, B is an infrared absorption peak of C4F7N causing cross interference to CF4 detection, and C is a transmission wavelength range of the filter used for CF4 spectroscopy detection in the embodiment; Figure 2 1 is a chemical equation and a schematic diagram of the reaction process of the chemically assisted decoupling process in the present invention, ① and ② are ionic reaction equations of C4F7N absorption and NH3 absorption, respectively, and steps 1 to 4 correspond to the four-step elementary reactions of reaction ①, wherein TS2 to TS4 represent the transition states of the last three elementary reactions; Figure 3 Schematic diagram of a device for a chemically assisted decoupling method for spectroscopically detecting trace amounts of CF4 in C4F7N insulating GIS according to an embodiment of the present invention.

[0018] The present invention is further explained below in conjunction with the accompanying drawings and embodiments. DETAILED DESCRIPTION

[0019] The specific embodiments of the present invention will be described in more detail below with reference to the accompanying drawings. Although the specific embodiments of the present invention are shown in the accompanying drawings, it should be understood that the present invention can be implemented in various forms and should not be limited by the embodiments set forth herein. On the contrary, these embodiments are provided in order to enable a more thorough understanding of the present invention and to fully convey the scope of the present invention to those skilled in the art.

[0020] It should be noted that certain words are used in the specification and claims to refer to specific components. Those skilled in the art should understand that technicians may use different nouns to refer to the same component. This specification and claims do not use the difference in nouns as a way to distinguish components, but use the difference in the functions of the components as the criterion for distinction. As mentioned throughout the specification and claims, "including" or "comprising" is an open term, so it should be interpreted as "including but not limited to". The subsequent description of the specification is a preferred embodiment of the present invention, but the description is based on the general principles of the specification and is not intended to limit the scope of the present invention. The scope of protection of the present invention shall be determined by the attached claims.

[0021] To facilitate understanding of the embodiments of the present invention, further explanation will be given below by taking specific embodiments as examples in conjunction with the accompanying drawings, and each of the accompanying drawings does not constitute a limitation on the embodiments of the present invention.

[0022] like Figures 1 to 3 As shown, the chemically assisted decoupling method for detecting perfluoroisobutyronitrile insulated GIS includes the following steps: Step 1, introducing the first gas in the perfluoroisobutyronitrile insulation GIS to be tested into a C4F7N absorption reactor containing a concentrated strong alkali solution, wherein the first gas includes C4F7N and CF4; Step 2, in the C4F7N absorption reactor, a spray reaction is maintained for a first time, and then the spray is terminated to remove C4F7N in the first gas and generate NH3, and then a second gas is output, wherein the second gas includes CF4, NH3 and water. Step 3, transferring the second gas to an NH3 absorption reactor containing an acid solution; Step 4, in the NH3 absorption reactor, a spray reaction is maintained for a second time and then the spraying is terminated to remove NH3 in the second gas to obtain a third gas, wherein the third gas includes CF4 and water; Step 5, allowing the third gas to slowly flow through a drying tube for drying to remove water molecules to obtain CF4.

[0023] In a preferred embodiment of the chemically assisted decoupling method for detecting perfluoroisobutyronitrile insulated GIS, in step 1, the concentrated strong alkali solution includes NaOH or KOH solution, and its concentration is greater than 2 mol / L.

[0024] In a preferred implementation of the chemically assisted decoupling method for detecting perfluoroisobutyronitrile insulated GIS, in step 1, the volume of the concentrated strong alkaline solution is 0.5 times that of the first gas to be detected.

[0025] In a preferred embodiment of the chemically assisted decoupling method for detecting perfluoroisobutyronitrile insulated GIS, the first time is 1 to 40 minutes.

[0026] In a preferred embodiment of the chemically assisted decoupling method for detecting perfluoroisobutyronitrile insulated GIS, the flow rate of the spraying liquid in step 2 and step 4 is greater than 1000 standard cubic centimeters per minute.

[0027] In a preferred embodiment of the chemically assisted decoupling method for detecting perfluoroisobutyronitrile insulated GIS, in step 3, the acid solution includes H2SO4 solution with a concentration of 0.5 mol / L.

[0028] In a preferred implementation of the chemically assisted decoupling method for detecting perfluoroisobutyronitrile insulated GIS, in step 3, the volume of the acid solution is 0.5 times the volume of the gas to be detected.

[0029] In a preferred implementation of the chemically assisted decoupling method for detecting perfluoroisobutyronitrile insulated GIS, the second time is 3 to 5 minutes.

[0030] In a preferred embodiment of the chemically assisted decoupling method for detecting perfluoroisobutyronitrile insulated GIS, the desiccant includes quicklime, the volume of the drying tube is greater than 3000 mL, and the gas flow rate is less than 100 standard cubic centimeters per minute.

[0031] A device for implementing the method comprises: The C4F7N absorption reactor 1 comprises a first reaction container for introducing a first gas to be measured and a first nozzle 5 for spraying a concentrated strong alkali solution; A gas delivery liquid pipeline 2, which is connected to the C4F7N absorption reactor 1 to derive the second gas; An NH3 absorption reactor 8, which is connected to the gas liquid pipeline 2, and the NH3 absorption reactor 8 includes a second reaction container for introducing a second gas and a second nozzle for spraying a concentrated strong alkali solution; A drying pipe 3 is connected to the NH3 absorption reactor to dry the third gas from the NH3 absorption reactor.

[0032] In one embodiment, both the NH3 absorption reactor and the C4F7N absorption reactor are provided with a piston 6, and the first nozzle or the second nozzle is provided on the piston 6 to be close to or away from the solution.

[0033] The NH3 absorption reactor and the C4F7N absorption reactor each include a liquid pump 4 for pumping the solution. The liquid pump 4 is an acid and alkali resistant liquid pump.

[0034] The gas transmission liquid pipeline 2 is provided with a three-way valve to control the flow direction of the gas.

[0035] A desiccant is arranged in the drying tube and CF4 is led out from the bottom. The spectroscopy detection device 7 is connected to the bottom of the drying tube 3 to monitor the photoacoustic signal of CF4. Further, the spectroscopy detection device includes a non-resonant photoacoustic cell.

[0036] In one embodiment, the method includes, Step 1: introduce the GIS first gas to be tested into a C4F7N absorption reactor containing a concentrated strong alkali solution.

[0037] Step 2, in the C4F7N absorption reactor, a spray reaction is maintained for a first period of time and then the spraying is terminated.

[0038] Step 3, transferring the gas after step 2 to an NH3 absorption reactor containing an acid solution.

[0039] Step 4, in the NH3 absorption reactor, a spray reaction is maintained for a second time and then the spraying is terminated.

[0040] Step 5, allowing the gas after step 4 to slowly flow through the drying tube for drying. The concentrated strong alkali solution can be selected from NaOH or KOH solution, and its concentration is generally greater than 2 mol / L. The solution volume is determined based on the volume of the gas to be measured, and generally can be taken as 0.5 times the volume of the gas to be measured. The first time ranges from 1 to 40 minutes, which can be adjusted according to the actual detection time requirements. The flow rate of the spraying liquid in steps 2 and 4 should be greater than 1000 standard cubic centimeters per minute (sccm). The acid solution can be selected from H2SO4 solution, and the concentration can be taken as 0.5 mol / L. The solution volume is also determined based on the volume of the gas to be measured, and generally can be taken as 0.5 times the volume of the gas to be measured. The second time ranges from 3 to 5 minutes, which can be adjusted according to the actual detection time requirements. Quicklime can be used as the desiccant, the volume of the drying tube should be greater than 3000 mL, and the gas flow rate should be controlled to be less than 100 sccm.

[0041] Example 1: The concentration of trace CF4 in a mixed gas of C4F7N and N2 with a volume fraction of 7% is detected by photoacoustic spectroscopy in the spectroscopy method. In the example, the concentrated strong alkali solution is 100mL of 3 mol / L KOH solution, the strong acid solution is 100mL of 0.5 mol / L H2SO4 solution, and the desiccant is quicklime. The piston reactors in the example are all made of Hastelloy C-276 alloy. The spectroscopy detection device in the example adopts a non-resonant photoacoustic spectroscopy structure, according to Figure 1 The infrared absorption spectra of C4F7N and CF4 described above select a silicon-based infrared filter with a transmission range of 7550nm~7950nm. The detection target of the embodiment is achieved according to the following steps: a C4F7N-N2 mixed gas with a volume fraction of 7% without CF4 is configured for chemical pretreatment, and the photoacoustic response of the background gas is measured to obtain a detection baseline value; according to the concentration gradient, 10μL / L~400μL / L of CF4 is added to the C4F7N-N2 mixed gas with a volume fraction of 7%, and the photoacoustic response is measured after chemical pretreatment to obtain the relationship between the photoacoustic signal and the CF4 concentration, and the detection system is calibrated; a certain concentration of trace CF4 is added to the C4F7N-N2 mixed gas with a volume fraction of 7%, and the photoacoustic response is measured after chemical pretreatment, and the concentration is inverted using the calibration relationship in the previous step.

[0042] First, the baseline value was determined: 200 mL of C4F7N-N2 mixed gas with a volume fraction of 7% was prepared using a gas mixing system composed of a gas mass flow controller, and introduced into a C4F7N absorption reactor containing a concentrated strong alkali solution, which was a piston reactor, with a liquid spray rate of 2000 sccm maintained for 20 minutes, and a Figure 2 The C4F7N in the solution undergoes a hydrolysis reaction① to absorb C4F7N. In this process, four elementary reactions occur. First, C4F7N reacts with OH ionized by high concentration KOH. - The ion undergoes barrier-free nucleophilic addition reaction, followed by tautomerism to generate imidic acid, followed by proton transfer reaction to generate tetrahedral alkoxide intermediate, and finally the intermediate undergoes amino elimination reaction to generate carboxylate and ammonia.

[0043] After the C4F7N absorption reaction is completed, the gas is introduced into the NH3 absorption reactor containing a strong acid solution, which is a piston reactor, and a liquid spray rate of 2000sccm is maintained for 5 minutes to produce Figure 2 The NH3 absorption reaction in the reactor is to absorb the by-product NH3. In this process, ammonia gas dissolves in water to form ammonia water, which then undergoes an acid-base neutralization reaction with sulfuric acid to form ammonium salt.

[0044] After the NH3 absorption reaction is completed, the gas is slowly passed through a drying tube containing quicklime at a flow rate of 50 sccm to absorb water vapor mixed in due to the solution reaction.

[0045] The gas after chemical pretreatment was introduced into a non-resonant photoacoustic cell to measure the photoacoustic signal value. The above experiment was repeated 10 times, and the average detection baseline value was 122.3 mV, with a standard deviation of 3.2 mV.

[0046] The photoacoustic response relationship of C4F7N obtained in the laboratory is shown in formula (1): (1) The inversion of C4F7N concentration showed that the remaining C4F7N concentration after chemical treatment was 1789.43 μL / L, and the absorption efficiency was 97.1%.

[0047] Then, the detection system was calibrated: 200 mL of C4F7N-N2 mixed gas with a volume fraction of 7% and CF4 concentrations of 10, 20, 50, 100, 200 and 400 μL / L was prepared using a gas mixing system (composed of a gas mass flow controller), and the same chemical pretreatment steps as in the baseline value determination step were performed. In this process, C4F7N in the background gas undergoes a hydrolysis reaction and is absorbed, while CF4 does not react due to its high chemical stability. The photoacoustic response value after chemical treatment was then measured. The above experiment was repeated 10 times, and the average response value was taken as the photoacoustic response value of CF4 at this concentration. The CF4 photoacoustic response relationship was obtained as shown in formula (2), and the linear fit goodness of fit was 0.997.

[0048] (2) The detection noise value was taken as the standard deviation of the baseline value, and the signal-to-noise ratio was taken as 1 as the standard to calculate that the detection limit of CF4 of the system was 6.02 μL / L.

[0049] Finally, perform CF4 concentration inversion: A gas mixing system composed of a gas mass flow controller was used to prepare 200 mL of C4F7N-N2 mixed gas with a volume fraction of 7% and a CF4 concentration of 30, 75, 150, 300 and 500 μL / L, and the photoacoustic signal value was measured after the same chemical pretreatment as in the above steps. The CF4 concentration was inverted using the calibration relationship, and the comparison relationship between the predicted value and the true value of the CF4 concentration was obtained as shown in Table 1. As can be seen from Table 1, the percentage error of the predicted value of the CF4 concentration is less than 15%.

[0050]

[0051] In summary, the chemically assisted decoupling method for spectroscopic detection of trace CF4 in C4F7N insulating GIS provided by the present invention significantly reduces the concentration of C4F7N in the background gas, effectively solves the cross-interference problem in the process of using spectroscopic detection of trace CF4 in C4F7N insulating GIS, and provides a feasible technical solution for the accurate detection of trace CF4 in the background of constant C4F7N.

[0052] Although the embodiments of the present invention are described above in conjunction with the accompanying drawings, the present invention is not limited to the above specific embodiments and application fields, and the above specific embodiments are only illustrative and instructive, rather than restrictive. A person of ordinary skill in the art can also make many forms under the guidance of this specification and without departing from the scope of protection of the claims of the present invention, all of which belong to the protection of the present invention.

Claims

1. A chemically assisted decoupling method for detecting perfluoroisobutyronitrile insulated GIS, characterized in that: The steps include: Step 1, introducing the first gas in the perfluoroisobutyronitrile insulation GIS to be tested into a C4F7N absorption reactor containing a concentrated strong alkali solution, wherein the first gas includes C4F7N and CF4; Step 2, in the C4F7N absorption reactor, a spray reaction is maintained for a first time, and then the spray is terminated to remove C4F7N in the first gas and generate NH3, and then a second gas is output, wherein the second gas includes CF4, NH3 and water. Step 3, transferring the second gas to an NH3 absorption reactor containing an acid solution; Step 4, in the NH3 absorption reactor, a spray reaction is maintained for a second time and then the spraying is terminated to remove NH3 in the second gas to obtain a third gas, wherein the third gas includes CF4 and water; Step 5, allowing the third gas to slowly flow through a drying tube for drying to remove water molecules to obtain CF4.

2. A chemically assisted decoupling method for detecting perfluoroisobutyronitrile insulated GIS according to claim 1, characterized in that: Preferably, in step 1, the concentrated strong alkaline solution includes NaOH or KOH solution, and its concentration is greater than 2 mol / L.

3. A chemically assisted decoupling method for detecting perfluoroisobutyronitrile insulated GIS according to claim 2, characterized in that: In step 1, the volume of the concentrated strong alkaline solution is 0.5 times that of the first gas to be tested.

4. A chemically assisted decoupling method for detecting perfluoroisobutyronitrile insulated GIS according to claim 1, characterized in that: The first time is from 1 to 40 minutes.

5. The chemically assisted decoupling method for detecting perfluoroisobutyronitrile insulated GIS according to claim 1, characterized in that: The flow rates of the spraying liquid in step 2 and step 4 are both greater than 1000 standard cubic centimeters per minute.

6. The chemically assisted decoupling method for detecting perfluoroisobutyronitrile insulated GIS according to claim 1, characterized in that: In step 3, the acid solution includes H2SO4 solution with a concentration of 0.5 mol / L.

7. A chemically assisted decoupling method for detecting perfluoroisobutyronitrile insulated GIS according to claim 6, characterized in that: In step 3, the volume of the acid solution is 0.5 times the volume of the gas to be measured.

8. The chemically assisted decoupling method for detecting perfluoroisobutyronitrile insulated GIS according to claim 1, characterized in that: The second time is 3 to 5 minutes.

9. The chemically assisted decoupling method for detecting perfluoroisobutyronitrile insulated GIS according to claim 1, characterized in that: The desiccant includes quicklime, the drying tube volume is greater than 3000 mL, and the gas flow rate is less than 100 standard cubic centimeters per minute.

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