Quartz crystal microbalance sensor, preparation method and application thereof

Abstract

The application discloses a quartz crystal microbalance sensor and a preparation method and application thereof, and belongs to the technical field of sulfur hexafluoride gas detection. The quartz crystal microbalance sensor is prepared by modifying a composite raw material on the surface of a quartz crystal microbalance crystal oscillator electrode. The modified crystal oscillator electrode is placed in the to-be-detected SF6 gas, SO2 is used as a characteristic gas, the electrode vibration frequency change curve information of the quartz crystal microbalance crystal oscillator is combined, the mass of the adsorbed SO2 is obtained through the relationship between the frequency change value and the mass of the adsorbed gas, the concentration of the SO2 gas is obtained through the gas isothermal adsorption curve, the purity of the SF6 in GIS is judged by comparing with historical data. The quartz crystal microbalance sensor has the advantages of good stability, high sensitivity, good expansibility, strong practicability, portability and the like, and can keep high consistency and reliability in long-term monitoring and multiple measurements.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of sulfur hexafluoride gas detection, and particularly relates to a quartz crystal microbalance sensor and a preparation method and application thereof. BACKGROUND

[0002] Sulfur hexafluoride (SF6) is a colorless and odorless gas, which has excellent arc extinguishing property, thermal stability and excellent electrical insulation, and its insulation capacity is 2.5 times or more than that of air, and its arc extinguishing capacity is 100 times that of air, so it is widely used in power systems, especially in high-voltage equipment. Lightning arresters, pipeline cables, and electrical equipment such as accumulators often use sulfur hexafluoride as an insulating medium; in power systems, SF6 is increasingly widely used as an insulating medium and arc extinguishing medium in high-voltage switches, large-capacity transformers, and combined electrical apparatus.

[0003] However, SF6 is a gas that can harm the human body and the environment. SF6 has a specific gravity of about 5 times that of air, and when SF6 gas leakage accidents occur, it accumulates in the switch room and is not easy to diffuse, which can easily cause operators to lack oxygen and suffocate, and even cause personnel injury accidents; at the same time, SF6 gas will decompose under the action of an electric field to produce a variety of toxic and harmful gases, such as SF4, SOF2, SO2F2, etc., which can have a serious impact on equipment and the health of operators, and SF6 gas will decompose into nearly ten kinds of toxic gases during the arc extinguishing process in the equipment, and has corrosive properties, which can directly affect the safe operation of the equipment. Therefore, it is very important to monitor its use concentration, leakage and decomposition products.

[0004] SF6 gas is used as an insulating medium in GIS (gas insulated substation) equipment, and the insulation and arc extinguishing performance of GIS equipment depends largely on the density of SF6 gas, so the density of SF6 gas needs to be monitored to ensure the normal operation of GIS equipment. The basic principle of GIS equipment fault diagnosis is to detect the content of characteristic impurity gas components in SF6 gas to determine the purity of SF6 gas, and then analyze the type of internal insulation defects, the level of discharge and the degree of aging of insulation materials, which is used as a basis for gas purification, updating and equipment maintenance. The characteristic impurity gas components generated by SF6 gas in GIS include H2S, SO2, CF4 and moisture, etc. The analysis methods for these impurity gases are: gas chromatography, sensor method, sound velocity method, electrochemical sensor method, resistance method, etc. The sensor method needs to calibrate the sensor regularly, and the detection accuracy is not high; the laboratory gas chromatography method needs to manually take gas and send samples to the laboratory for chemical analysis, which takes a long time and cannot realize online monitoring.

[0005] At present, the main method for detecting the gas in SF6 equipment is to collect the gas in the equipment on site and then send it to the laboratory for in-depth analysis. The methods used are mid-infrared spectroscopy or chromatography-mass spectrometry. Some companies in the prior art have successively developed methods for detecting SF6 using infrared spectral characteristics. A Chinese patent with publication number CN114965616A and filing date of June 1, 2022 discloses a method for detecting SF6 decomposition gas, which uses traceable equipment to perform ultraviolet spectral analysis scanning on the composition of typical samples of SF6 decomposition gas, obtains the composition and concentration data of SF6 decomposition gas, and optimally selects the ultraviolet absorption wave of various gases. The infrared spectrum of the typical component CO of SF6 decomposition gas is analyzed, a measurement model is developed, and then the mutual interference of various gases is determined. A Chinese patent with publication number CN117169154A and filing date of July 21, 2023 discloses a detection device and method for detecting SF6 gas decomposition products based on infrared spectroscopy, which includes a sampling device, an infrared optical interference system, a temperature controller, a gas absorption cell, a mechanical pump, an infrared photodetector, an operational amplifier, a filter, an analog-to-digital converter, a computer, a digital-to-analog converter, and a digital display. By detecting the infrared absorption spectrum of SF6 decomposition products in the GIS system, the GIS fault can be quickly and accurately determined. The above-mentioned devices are relatively cumbersome to use. Since an infrared generating device or a laser is required, the volume is also relatively large, and they cannot be conveniently applied on site. Therefore, the sampling interval is long, which is not conducive to timely detection of equipment defects, and the cost is also relatively high.

[0006] In recent years, the emergence of methods such as Raman spectroscopy and time-of-flight mass spectrometry has enabled rapid online monitoring. For example, a research team of State Grid Shanxi Electric Power developed an SF6 detection technology based on Raman spectroscopy. This technology can use laser to irradiate SF6 gas samples to form Raman scattering spectra, and automatically compare them with standard gas spectra to obtain SF6 gas concentration and accurately analyze GIS operation problems. Compared with traditional detection devices, this device shortens the SF6 gas detection time from hours to minutes. However, this instrument is expensive and has high cost.

[0007] Given the real-time nature, short detection period, and fast analysis speed of online monitoring systems, online monitoring of SF6 electrical equipment gas components will become a trend in the future. SO2 is a stable derivative of SF6 gas under the action of arc, spark, and corona discharge, and it should not exist in equipment under normal working conditions. Therefore, the production of SO2 can to some extent represent the decline in the internal insulation performance of the equipment. Developing an SF6 detection method with excellent stability and sensitivity using SO2 as a characteristic gas to monitor SF6 gas purity in real time is of great significance to the safe operation of the power system and can meet people's increasingly high requirements for power system reliability. SUMMARY

[0008] In order to solve the problems in the prior art, the present application provides a quartz crystal microbalance sensor and a preparation method and application thereof, which has the advantages of good stability, high sensitivity, good expandability, strong practicability, portability and the like, can realize real-time and online detection of SO2 gas in SF6 in high-voltage power transmission equipment, and can maintain high consistency and reliability in long-term monitoring and multiple measurements.

[0009] The technical scheme of the present application is as follows:

[0010] One of the purposes of the present application is to provide a quartz crystal microbalance sensor, which is a quartz crystal microbalance modified with a composite raw material combination on the electrode surface of a crystal oscillator; wherein the composite raw material combination is composed of tung oil fruit kernels, sodium molybdate and polyaniline.

[0011] Further, the quartz crystal microbalance is composed of two quartz crystal microbalance crystal oscillator electrodes clamping a quartz crystal, and the crystal oscillator electrodes are uniformly coated with the composite raw material combination to form an electrochemical test loop.

[0012] Further, the quartz crystal microbalance crystal oscillator electrode is a circular electrode with a diameter of 0.5-1.0 cm and is made of gold.

[0013] The second purpose of the present application is to provide a preparation method of a quartz crystal microbalance sensor, which comprises the following steps:

[0014] S1, preparation of modification material: tung oil fruit kernels are washed in deionized water and ethanol in sequence, and then are ground and dried;

[0015] S2, preparation of composite raw material combination: tung oil fruit kernels, sodium molybdate and polyaniline are mixed according to a mass ratio, and are moved to a tube furnace for heat treatment, during which argon gas is introduced for protection, and after heat preservation, the temperature is cooled to room temperature to obtain the composite raw material combination.

[0016] S3, electrode modification: a Nafion solution with a concentration of 30% and anhydrous ethanol are added to the prepared composite raw material combination, and are stirred to obtain a uniform solution, which is uniformly coated on the electrode surface of a quartz crystal microbalance crystal oscillator, and is dried at room temperature to obtain the quartz crystal microbalance sensor.

[0017] Further, the drying temperature in S1 is 50-70°C.

[0018] Further, the mass ratio of tung oil fruit kernels, sodium molybdate and polyaniline mixed in S2 is 2:0.5-1:0.5-1.

[0019] Further, the heat treatment process in S2 is heating to 500-550 DEG C at a heating rate of 5-10 DEG C / min in a tube furnace, and the heat treatment time is 4-5h.

[0020] Further, the heat preservation time in S2 is 1.5-2.5h.

[0021] Further, the use ratio of the composite raw material combination, Nafion solution and anhydrous ethanol in S3 is 0.1-0.3mg:1uL:10uL.

[0022] The third object of the present application is to provide an application of the quartz crystal microbalance sensor in detecting the SO2 concentration in GIS equipment and judging the SF6 concentration.

[0023] Further, the detection step is as follows:

[0024] (1) taking the modified crystal vibration electrode as a working electrode, injecting the SF6 gas sample from the running GIS into the reaction cell of the crystal vibration electrode, calculating the adsorbed SO2 gas mass according to the frequency difference in the frequency change curve information of the quartz crystal microbalance before and after the SO2 gas adsorption, and then calculating the SO2 gas concentration according to the SO2 gas adsorption curve.

[0025] (2) comparing the SO2 gas concentration calculated in the above step with the SO2 gas concentration in the database, and evaluating the purity of SF6 according to the relationship between the SO2 concentration in the running GIS and the purity of SF6.

[0026] Compared with the prior art, the present application has the following beneficial effects:

[0027] 1. The present application innovates a new type of quartz crystal microbalance sensor for detecting the impurity gas SO2 in SF6 to calculate the purity of SF6. The quartz crystal microbalance sensor has the advantages of good stability, high sensitivity, good expandability, strong practicability, portability and the like, can realize real-time and online detection of the SF6 gas in high-voltage power transmission equipment, can maintain high consistency and reliability in long-term monitoring and multiple measurements, can comprehensively evaluate the operation state of the equipment, can realize timely early warning of equipment failure, provides the possibility for real-time and on-site detection of SF6, guides production, and guarantees the safe and stable operation of power equipment.

[0028] 2、The present application designs a new type of modified composite raw material combination for SO2, the composite raw material combination is composed of tung oil fruit kernel, sodium molybdate and polyaniline, wherein the tung oil fruit kernel is a kind of high-fat acid content is biochar, after carbonization treatment, small molecular organic molecules volatilize, thereby forming a porous biochar structure on the material surface, which is beneficial to adsorb SO2 gas;Sodium molybdate is adsorbed on the surface of tung oil fruit kernel and is oxidized to molybdenum trioxide (MoO3), the form of molybdenum also has strong adsorption capacity. The sulfur atom in SO2 molecule and molybdenum ion form coordination, form Mo-S bond, and stably adsorb SO2 molecules on the surface of molybdenum;Polyaniline as a kind of high molecular compound, the rich amino group contained in the molecular chain can react with SO2 to form stable compounds, at the same time, the large amount of conjugated system existing in the structure of polyaniline can increase the adsorption capacity of polyaniline, realize the further effective adsorption of SO2, in addition, the high conductivity of polyaniline is conducive to reducing the resistance in the process of electrochemical test. The new composite raw material combination can show good selectivity and responsiveness to SO2 when the crystal vibration electrode is modified by the new composite raw material combination, and can maximize the absorption of SO2 gas existing in the system.

[0029] 3、The quartz crystal microbalance sensor of the present application has high adsorption measurement precision for SO2 gas, and the measurement precision can reach nanogram level, so that the concentration of SO2 gas can be accurately measured, and the current SF6 gas measurement difficulty is indirectly solved;And the quartz crystal microbalance sensor is simple to carry, can realize on-site, online real-time monitoring, is especially suitable for real-time on-site detection and production guidance of SF6, and can maintain high consistency and reliability in long-term monitoring and multiple measurements, in addition, the quartz crystal microbalance sensor is also suitable for SO2 detection in general environment. BRIEF DESCRIPTION OF DRAWINGS

[0030] Figure 1 The structure diagram of the quartz crystal microbalance sensor of the present application is shown in the figure;

[0031] Figure 2 The process diagram of the quartz crystal microbalance sensor of the present application for detecting the content of SF6 gas is shown in the figure;

[0032] Figure 3 The isothermal adsorption curve of the quartz crystal microbalance sensor of the present application for SO2 adsorption in examples 1-3 is shown in the figure. DETAILED DESCRIPTION

[0033] The present invention is further described below in conjunction with preferred embodiments. The endpoints of the ranges and any values ​​disclosed in the present invention are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of each range, the endpoint values ​​of each range and individual point values, and the individual point values ​​can be combined with each other to obtain one or more new numerical ranges, and these numerical ranges should be regarded as specifically disclosed herein.

[0034] Unless otherwise specified, the experimental methods in the following examples are conventional methods and are performed according to the techniques or conditions described in the literature in the field or according to the product instructions.

[0035] Unless otherwise specified, the materials and reagents used in the following examples can be obtained from commercial sources.

[0036] In the following embodiments, a QCM-D quartz crystal microbalance sensor produced by Suzhou Jiasikang Biotechnology Co., Ltd. is used. The quartz crystal has a fundamental frequency of 5 MHz, an AT cut, an ambient temperature of 25° C., a chip diameter of 1 cm, and a thickness of about 300 μm.

[0037] Example 1

[0038] This embodiment provides a quartz crystal microbalance sensor for reflecting the purity of SF6 gas, and the preparation method thereof includes the following steps:

[0039] S1. Samples were collected from an outdoor high-voltage sulfur hexafluoride circuit breaker (LW16-35KV, 5 years in operation) in actual operation.

[0040] S2. Preparation of modification materials: Wash tung kernels in deionized water and ethanol, grind them and dry them at 50°C;

[0041] S3. Preparation of composite raw material combination: 10 g of tung kernels, 5 g of sodium molybdate, and 5 g of polyaniline were mixed, moved to a tube furnace, heated to 500° C. at 5° C. / min, and heat treated for 4 h with argon protection during the process. The mixture was kept at this temperature for 1.5 h and then cooled to room temperature to obtain a composite raw material combination;

[0042] S4. Electrode modification: 1 μL of Nafion solution (30%) and 10 μL of anhydrous ethanol were added to 0.1 mg of the prepared composite raw material combination, stirred to form a homogeneous solution, and evenly applied to the electrode surface of the quartz crystal microbalance oscillator. The solution was dried at room temperature to obtain the quartz crystal microbalance sensor.

[0043] S5. Gas adsorption and electrochemical measurement: The above-mentioned electrodes were placed in SF6 mixed gas, and the quartz crystal microbalance measurement method was used to record the change in crystal oscillator frequency before and after SO2 gas adsorption. The frequency before adsorption was 5024368 Hz, and the frequency after adsorption was 5024412 Hz, with a frequency difference of 44 Hz.

[0044] S6. Calculation of gas concentration: According to the formula △m=C f *△f(C f =17ng) calculate the adsorbed SO2 mass m to be 748ng; according to Figure 3 The SO2 isotherm adsorption curve (C=p / RT) shown in the figure finally obtained the SO2 concentration c as 3.634 ppm.

[0045] S7. Compare the above SO2 concentration of 3.634 ppm with the database and consult the operation history data of this type of GIS. Through comparison, it is concluded that the purity of SF6 of the equipment is 92%.

[0046] Example 2

[0047] This embodiment provides a quartz crystal microbalance sensor for reflecting the purity of SF6 gas, and the preparation method thereof includes the following steps:

[0048] S1. Samples were collected from an outdoor high-voltage sulfur hexafluoride circuit breaker (LW16-35KV, 8 years in operation) in actual operation.

[0049] S2. Preparation of modification materials: Tung oil nut kernels were washed in deionized water and ethanol, then ground and dried at 60°C;

[0050] S3. Preparation of composite raw material combination: 10 g of tung kernels, 2.5 g of sodium molybdate, and 4 g of polyaniline were mixed, transferred to a tube furnace, and heated to 525° C. at 7° C. / min for 4.5 h, with argon protection during the treatment. The mixture was kept at this temperature for 2 h, and then cooled to room temperature to obtain a composite raw material group;

[0051] S4. Electrode modification: 1 μL of Nafion solution (30%) and 10 μL of anhydrous ethanol were added to 0.2 mg of the prepared composite raw material combination, stirred to form a homogeneous solution, and evenly applied to the electrode surface of the quartz crystal microbalance oscillator. The solution was dried at room temperature to obtain the quartz crystal microbalance sensor.

[0052] S5. Gas adsorption and electrochemical measurement: The above-mentioned electrodes were placed in SF6 mixed gas, and the quartz crystal microbalance measurement method was used to record the change in crystal oscillator frequency before and after SO2 gas adsorption. The frequency before adsorption was 5024368 Hz, and the frequency after adsorption was 5024455 Hz, with a frequency difference of 87 Hz.

[0053] S6. Calculation of gas concentration: According to the formula △m=C f *△f(C f =17ng) calculate the adsorbed SO2 mass m to be 1479ng; according to Figure 3 The SO2 isotherm adsorption curve (C=p / RT) shown in the figure finally obtained the SO2 concentration c as 4.967 ppm.

[0054] S7. Compare the above SO2 concentration of 4.967 ppm with the database and consult the operation history data of this type of GIS. Through comparison, it is found that the purity of SF6 of the equipment is 86%.

[0055] Example 3

[0056] This embodiment provides a quartz crystal microbalance sensor for reflecting the purity of SF6 gas, and the preparation method thereof includes the following steps:

[0057] S1. Samples were collected from an outdoor high-voltage sulfur hexafluoride circuit breaker (LW16-110KV, 5 years in operation) in actual operation.

[0058] S2. Preparation of modification materials: Tung oil nut kernels were washed in deionized water and ethanol, then ground and dried at 70°C;

[0059] S3. Preparation of composite raw material combination: 10 g of tung kernels, 4 g of sodium molybdate, and 2.5 g of polyaniline were mixed, moved to a tube furnace, heated to 550° C. at 10° C. / min, and heat treated for 5 h with argon protection during the process. The mixture was kept at this temperature for 2.5 h and then cooled to room temperature to obtain a composite raw material combination;

[0060] S4. Electrode modification: 1 μL of Nafion solution and 10 μL of anhydrous ethanol were added to 0.3 mg of the prepared composite raw material combination, stirred to form a uniform solution, and evenly applied to the electrode surface of the quartz crystal microbalance oscillator. The solution was dried at room temperature to obtain the quartz crystal microbalance sensor.

[0061] S5. Gas adsorption and electrochemical measurement: The above-mentioned electrodes were placed in SF6 mixed gas, and the quartz crystal microbalance measurement method was used to record the change in crystal oscillator frequency before and after SO2 gas adsorption. The frequency before adsorption was 5024368 Hz, and the frequency after adsorption was 5024454 Hz, with a frequency difference of 86 Hz.

[0062] S6. Calculation of gas concentration: According to the formula △m=C f *△f(C f =17ng) calculate the adsorbed SO2 mass m to be 1462ng; according to Figure 3 The SO2 isotherm adsorption curve (C=p / RT) shown in the figure finally obtained the SO2 concentration c as 4.886 ppm.

[0063] S7, compare the SO2 concentration 4.886ppm with the database, consult the operation history data of the type of GIS, and calculate the purity of SF6 of the device as 90%.

[0064] Comparative Example 1

[0065] Based on the test sample setting of Example 1, the concentration is determined by gas chromatography.

[0066] Comparative Example 2

[0067] Based on the test sample setting of Example 2, the concentration is determined by gas chromatography.

[0068] Comparative Example 3

[0069] Based on the test sample setting of Example 3, the concentration is determined by gas chromatography.

[0070] Comparative Example 4

[0071] Based on the test sample setting of Example 3, wherein S1 is: in the environment of indoor temperature 25℃, configure fixed concentration of N2 gas, the concentration is 5ppm.

[0072] Comparative Example 5

[0073] Based on the test sample setting of Example 3, wherein S1 is: in the environment of indoor temperature 25℃, configure fixed concentration of SF6 gas, the concentration is 5ppm.

[0074] Performance test

[0075] The treatment effect of Examples 1-3 and Comparative Examples 1-5 is shown in Table 1:

[0076] Table 1: Measurement data results of Examples and Comparative Examples

[0077]

[0078] As shown in Table 1, the measurement error of Examples 1, 2 and 3 is less than 5%, which is equivalent to the measurement result of gas chromatography. The test time of the method is shorter, and the time from sampling to reading can be controlled within 5 minutes, which greatly shortens the test time. The test instrument uses a quartz crystal balance tester, which has great advantages in weight and size compared with a gas chromatograph, and has the characteristics of miniaturization, which can facilitate real-time online monitoring on site.

[0079] As shown in Comparative Example 4 and Comparative Example 5, the composite material of the present application has poor adsorption for N2 gas and O2 gas, indicating that the material has good specificity for SO2.

[0080] The above merely illustrates the embodiments of the present application, and is not intended to limit the patent scope of the present application. Any equivalent structure or equivalent process conversion, or direct or indirect application in other related technical fields, made by using the content of the present application, are also included in the patent protection scope of the present application.

Claims

1. A quartz crystal microbalance sensor, characterized by, The quartz crystal microbalance sensor is a quartz crystal microbalance modified with a composite raw material combination on the electrode surface of a crystal oscillator; wherein the composite raw material combination is composed of tung oil fruit kernel, sodium molybdate and polyaniline. The quartz crystal microbalance is composed of two pieces of quartz crystal microbalance crystal oscillator electrodes clamping quartz crystals, and the crystal oscillator electrodes are uniformly coated with a composite raw material combination to form an electrochemical test loop. The quartz crystal microbalance crystal oscillator electrode is a circular electrode with a diameter of 0.5-1.0 cm, and the material is gold. Composite raw material combination preparation: mix tung oil fruit kernel, sodium molybdate and polyaniline according to the mass ratio, move to the tube furnace for heat treatment, and introduce argon gas protection during the process, cool to room temperature after heat preservation, and prepare the composite raw material combination.

2. A method of manufacturing a quartz crystal microbalance sensor according to claim 1, characterized by, It comprises the following steps: S1, modification material preparation: wash the tung oil fruit kernel in deionized water and ethanol, then grind and dry; S2, composite raw material combination preparation: mix tung oil fruit kernel, sodium molybdate and polyaniline according to the mass ratio, move to the tube furnace for heat treatment, and introduce argon gas protection during the process, cool to room temperature after heat preservation, and prepare the composite raw material combination; S3, electrode modification: add a 30% Nafion solution and anhydrous ethanol to the prepared composite raw material combination, stir to a uniform solution, uniformly coat on the electrode surface of the quartz crystal microbalance crystal oscillator, and dry at room temperature to prepare the quartz crystal microbalance sensor.

3. The method of claim 2, wherein the quartz crystal microbalance sensor is prepared by the steps of: The drying temperature in S1 is 50-70°C.

4. The method of claim 2, wherein the quartz crystal microbalance sensor is prepared by the steps of: The mass ratio of tung oil fruit kernel, sodium molybdate and polyaniline in S2 is 2:0.5-1:0.5-1.

5. The method for preparing a quartz crystal microbalance sensor according to claim 2, wherein: The heat treatment process in S2 is to heat to 500-550°C at a heating rate of 5-10°C / min in a tube furnace, and the heat treatment time is 4-5h.

6. The method of claim 2, wherein the quartz crystal microbalance sensor is prepared by the steps of: The heat preservation time in S2 is 1.5-2.5h.

7. The method for preparing a quartz crystal microbalance sensor according to claim 2, wherein: The use ratio of composite raw material combination, Nafion solution and anhydrous ethanol in S3 is 0.1-0.3mg:1μL:10μL.

8. The application of a quartz crystal microbalance sensor prepared by the preparation method of any one of claims 2-7 in detecting the SO2 concentration in GIS equipment and judging the SF6 purity.

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