Device and method for detecting fluorine in fluorine-nitrogen mixed gas

Abstract

The invention relates to a device and a method for detecting fluorine in fluorine-nitrogen mixed gas in the technical field of fluorine detection, the fluorine concentration is detected through an ultraviolet spectrophotometer instrument by adopting an ultraviolet spectrophotometry according to the Lambert-Beer law, an independent sample cell and an independent reference cell are customized on an ultraviolet spectrophotometer, and the sample cell and the reference cell are used for detecting the fluorine concentration in the fluorine-nitrogen mixed gas. The fluorine-nitrogen mixed gas sample gas and the nitrogen reference gas are respectively introduced, no other substances participate in the reaction in the whole detection process, compared with a fluorine gas detection method in the prior art, the problem of fluorine gas conversion rate does not exist, and the device is more corrosion-resistant and long in service life; the device is provided with a fluorine-nitrogen mixed gas sampling mechanism and a sample gas pretreatment mechanism, and the two mechanisms are replaced through vacuumizing and nitrogen purging before detection, so that the cleanliness of the sample gas can be ensured, the pressure can be accurately controlled, and the stability and the accuracy of fluorine gas detection are improved; the sampling mechanism is integrally arranged in the closed explosion-proof cabinet, so that the leakage of toxic gas is prevented, the working safety is improved, and the environmental pollution is avoided.

Description

Technical Field

[0001] The invention belongs to the technical field of fluorine gas detection in fluorine chemical industry, and specifically relates to a device and method for detecting fluorine gas in fluorine-nitrogen mixed gas. Background Art

[0002] Fluorine gas is a diatomic gas with a strong pungent odor and strong oxidizing and corrosive properties. At room temperature, fluorine gas can combine with almost all elements and generate a large amount of heat energy, so fluorine gas usually exists in the form of fluorine-nitrogen mixed gas (referred to as fluorine-nitrogen mixed gas). Fluorine-nitrogen mixed gas plays an important role in many fields. For example, in the semiconductor manufacturing industry, fluorine-nitrogen mixed gas is often used to clean and remove residues in the semiconductor production process, especially in processes such as photolithography and chemical vapor deposition, to ensure the quality and performance of semiconductor devices. Fluorine-nitrogen mixed gas acts as a catalyst or oxidant in some chemical reactions and can participate in a variety of organic and inorganic chemical reactions. Fluorine-nitrogen mixed gas is also used in laboratory research and high-energy physics experiments. Fluorine-nitrogen mixed gas is used as a filling gas for detectors in some high-energy physics experiments.

[0003] There are several main methods for determining the fluorine content in fluorine-nitrogen mixed gas.

[0004] 1. Gas chromatography with dual thermal conductivity detector: The analysis is carried out by using a fluorine-chlorine oil column + conversion column and absorption column. After the sample passes through the sampling system, it enters the chromatographic analysis through the sampling valve. The sample gas passes through the conversion column, where F2 is converted to Cl2. It is separated and quantified on the fluorine-chlorine oil column. The F2 content can be converted from Cl2. The measured Cl2 can express the F2 content, but the efficiency of fluorine conversion to chlorine is not high, the data is not accurate enough, and chlorine is a highly toxic gas that will harm human health. Due to the characteristics of fluorine gas products, this method requires the use of a combination of fluorine-chlorine oil column + conversion column + absorption column. The three materials are consumables and need to be replaced regularly. There is a certain risk of failure. If the failure causes fluorine gas and other corrosive gases to enter the detector and corrode the detector, it will increase the maintenance cost. Fluorine gas will corrode the conversion column and absorption column, and the column needs to be replaced regularly to ensure normal analysis. At the same time, the use of chromatography analysis takes a long time, the analysis efficiency is not high, the accuracy and stability are low, and the data cannot be fed back to production in a timely and accurate manner, which is not conducive to timely adjustment of the raw material ratio.

[0005] 2. Dual plasma emission detector + thermal conductivity detector gas chromatography: The analysis is carried out by pre-column. After the sample passes through the sampling system, it passes through the sampling valve into the chromatographic analysis. Before entering the detector, it passes through 2 identical pre-columns. Due to the difference in retention phase time, the N2 component is guaranteed to enter the detector. Before the fluorine gas enters the detector, the valve is switched to make the fluorine gas back-flushed out of the instrument. The disadvantage is that the service life of the pre-column is limited, and the actual normal test service life is two months. At the same time, the valve diaphragm will also be corroded, and the service life is short, which increases the maintenance cost; the fluorine gas passing through the pre-column cannot be completely discharged, and the remaining fluorine gas will corrode the thermal conductivity detector, resulting in a shortened service life of the device; the gas chromatography analysis cycle is long, the efficiency is low, and the data accuracy is not high.

[0006] The existing patent document with publication number CN 114813448 A discloses a device for detecting the fluorine content in a fluorine-nitrogen mixed gas, which includes a gas supply device, a metering device, an adsorption device, and a vacuum device. This method mainly involves reacting the fluorine gas with the absorption device, and after the reaction is completed, the remaining gas is measured, and the fluorine content in the fluorine-nitrogen mixed gas is tested according to the change in the gas volume before and after entering the adsorption device for reaction. However, this method requires frequent replacement of the packing participating in the reaction of the adsorption tower, the data stability is poor, and there are also disadvantages such as incomplete reaction, inaccurate detection data, and improper tail gas treatment after detection and analysis, which may cause environmental pollution and safety hazards.

[0007] Another patent document with publication number CN 107290437 A discloses a method for indirectly measuring fluorine gas content using a chromatograph, which uses a booster sampling pump to boost the gas to be detected; nitrogen is used as a carrier gas to bring the gas to be detected into a refrigerator for cooling; a quantitative amount of the gas to be detected is taken through a six-way valve and 1 ml is taken through a quantitative tube to enter the chemical reaction process F2→Cl2, and the quantitative gas passes through a polytrifluorochloroethylene reactor, a KCl reactor, and a NaF reactor in sequence, and F- is replaced with Cl- and impurities are removed before entering a chromatograph for quantitative analysis of the Cl2 content; the Cl2 content is measured by a chromatograph, and the Cl2 content is processed by a data acquisition machine to correspond to the F2 content, and the waste gas after the chromatograph is detected is discharged into a NaOH absorption tank for absorption. This device needs to pass through multiple reactors, and has the disadvantages of incomplete reaction, poor stability, and large errors. Summary of the invention

[0008] In view of the above situation, the present invention provides a device and method for detecting fluorine gas in fluorine-nitrogen mixed gas. During the test process, no other substances participate in the reaction, there is no conversion rate problem, and the detection data is more accurate; an independent gas flow pool is corrosion-resistant, has a long service life, good airtightness, reduces the number of maintenance times, and reduces maintenance costs; a pretreatment mechanism accurately controls the pressure, has high stability, fast analysis speed, safety, environmental protection, and cost savings.

[0009] It should be noted that, in the present invention, fluorine-nitrogen mixed gas and fluorine-nitrogen mixed gas have the same meaning.

[0010] In order to achieve the above purpose, the present invention adopts the following technical solutions:

[0011] A device for detecting fluorine gas in a fluorine-nitrogen mixed gas comprises a fluorine-nitrogen mixed gas sampling mechanism, a sample gas pretreatment mechanism and an ultraviolet spectrophotometer connected in series from front to back in accordance with the conveying direction of the fluorine-nitrogen mixed gas; the fluorine-nitrogen mixed gas sampling mechanism comprises a leak-proof shell for preventing the fluorine-nitrogen mixed gas from leaking to the outside of the device, and a sampling pipeline arranged inside the shell for collecting fluorine-nitrogen mixed gas sample gas, a replacement pipeline for creating a clean protection environment for the sampling pipeline, and an output pipeline for controlling the output of the sample gas, the sampling pipeline, the replacement pipeline and the output pipeline They are interconnected through a gas main pipe, on which a pressure sensor is installed; the sample gas pretreatment mechanism includes a sample gas pipeline for connecting to the output pipeline of the fluorine-nitrogen mixed gas sampling mechanism, a nitrogen replacement pipeline for pre-purging the sample gas pipeline, and a reference gas pipeline for introducing nitrogen reference gas into the sample gas pretreatment mechanism; the ultraviolet spectrophotometer includes an ultraviolet spectrophotometer, which is provided with a sample cell and a reference cell, and the sample cell and the reference cell correspond to the sample gas pipeline and the reference gas pipeline connected to the sample gas pretreatment mechanism respectively.

[0012] Furthermore, the sampling pipeline includes three sampling pipelines that are connected in parallel and have the same structure. Each sampling pipeline is connected in series with a high-pressure manual diaphragm valve, a high-pressure pressure regulating valve and a sampling pneumatic valve. The front ends of the three high-pressure manual diaphragm valves each correspond to a sampling port, and the rear ends of the three sampling pneumatic valves are all centrally connected to the gas main; an air inlet pressure gauge is installed on each sampling pipeline.

[0013] Furthermore, the replacement pipeline includes a vacuum pipeline for evacuating the sampling pipeline and a replacement pipeline for filling the sampling pipeline with nitrogen for replacement. The vacuum pipeline and the replacement pipeline are connected in parallel. A vacuum generator is connected to the vacuum pipeline. A vacuum port is provided at the front end of the vacuum pipeline. The rear end of the vacuum pipeline is connected to the gas main through a vacuum pneumatic valve. A replacement check valve and a replacement pneumatic valve are provided in series on the replacement pipeline. A replacement port is provided at the front end of the replacement check valve. The rear end of the replacement pneumatic valve is connected to the gas main. A vacuum pressure gauge and a pressure sensor are installed on the vacuum pipeline. The vacuum generator can be a vacuum pump or a Venturi vacuum generator. The vacuum pipeline also includes a reserved pipeline. The rear end of the reserved pipeline is also connected to the gas main through a reserved pneumatic valve.

[0014] Furthermore, the output pipeline includes three output pipelines which are connected in parallel and have the same structure, and each output pipeline is connected in series with an output check valve, a low-pressure pressure regulating valve and a regulating pneumatic valve in sequence. A nitrogen purge bypass is also arranged in parallel on one side of each output pipeline, and a purge check valve and a purge pneumatic valve are arranged in series on the nitrogen purge bypass, and a purge port is correspondingly arranged at the front end of each purge check valve; an air outlet is correspondingly arranged at the front end of each regulating pneumatic valve, and the rear end of each output pipeline is connected to the gas main through a control pneumatic valve; and an air outlet pressure gauge is correspondingly installed on each output pipeline.

[0015] Furthermore, the sample gas pipeline includes a gas mixing manual diaphragm valve 1, a needle valve 1, a needle valve 2, a gas mixing manual diaphragm valve 2 and a needle valve 3 which are connected in series in sequence, and a sample gas pressure gauge is provided on the pipeline between the needle valve 1 and the needle valve 2, the rear end of the needle valve 3 is connected to the sample pool of the ultraviolet spectrophotometer, and the rear end of the needle valve 3 is provided with a pressure sensor 3. The pressure sensor 1, the pressure sensor 2 and the pressure sensor 3 are all digital pressure sensors.

[0016] Furthermore, the reference gas pipeline includes a nitrogen manual diaphragm valve, a reference pressure regulating valve and a needle valve four connected in series in sequence, the nitrogen comes from an external nitrogen gas source, and the rear end of the needle valve four is connected to a reference cell of an ultraviolet spectrophotometer; the reference gas pipeline and the sample gas pipeline are two independent parallel pipelines.

[0017] Furthermore, the nitrogen replacement pipeline is connected across the reference gas pipeline and the sample gas pipeline, and the nitrogen replacement pipeline includes a replacement pressure regulating valve, a replacement manual diaphragm valve and a nitrogen charging check valve which are connected in series in sequence. The front end of the replacement pressure regulating valve is connected between the nitrogen manual diaphragm valve and the reference pressure regulating valve, and the rear end of the nitrogen charging check valve is connected between the second manual diaphragm valve for mixing gas and the third needle valve.

[0018] Furthermore, the ultraviolet spectrophotometer includes a light source, a monochromator, a chopper, a sample cell, a reference cell, and a detector; the light source is a deuterium light source with a resolution of 0.1 nm, and the sample cell and the reference cell are two independent gas flow cells. The ultraviolet spectrophotometer also includes an amplifier, a display, a recorder and other supporting components.

[0019] Furthermore, the anti-leakage housing is a sealed explosion-proof cabinet, and the top of the explosion-proof cabinet is sealed and connected with an exhaust pipe for centrally discharging the leaked gas, and the exhaust pipe is connected to the tail gas adsorption device. The tail gas adsorption device can be an adsorption tower, and the adsorption tower is equipped with fillers that can react with fluorine gas. The tail gas leaked from the fluorine-nitrogen mixed gas can be safely discharged after harmless treatment by the adsorption tower; the tail gas adsorption device can also be a recovery tower, and the tail gas leaked from the fluorine-nitrogen mixed gas flows back to the fluorine-nitrogen mixed gas storage tank through the recovery tower, and the tail gas can be recycled and reused, saving the cost of the fluorine-nitrogen mixed gas.

[0020] The present invention also provides a method for detecting fluorine gas in a fluorine-nitrogen mixed gas. The method requires the use of the above-mentioned device for detecting fluorine gas in a fluorine-nitrogen mixed gas to detect fluorine gas. The detection instrument used is an ultraviolet spectrophotometer, and the detection method used is ultraviolet spectroscopy. The analysis principle is based on Lambert-Beer's law:

[0021] When the wavelength of the incident light is constant, the absorbance of the medium to be measured is proportional to its concentration and the thickness of the absorption layer.

[0022] A=lg(1 / T)=kbC

[0023] Among them, A is absorbance; T is the transmittance (transmittance), that is, the intensity of the outgoing light / the intensity of the incident light; C is the concentration of the absorbing substance; b is the thickness of the absorption layer; k is the proportionality coefficient, which is related to the property temperature of the absorbing substance and the wavelength λ of the incident light.

[0024] The specific steps of the fluorine gas detection method are as follows:

[0025] S1. Perform air tightness test on the device; close all valves on the fluorine-nitrogen mixed gas sampling mechanism, then open the replacement pneumatic valve, and introduce nitrogen into the gas main through the replacement port and the replacement check valve, then close the replacement pneumatic valve and maintain the pressure for a certain period of time; if the pressure sensor shows no pressure change, it means that the device is airtight;

[0026] S2. Evacuate the device and replace the gas with nitrogen; start the vacuum generator, evacuate the vacuum pipeline, and then open the vacuum pneumatic valve and the sampling pneumatic valve and the high-pressure manual diaphragm valve on one of the sampling pipelines in turn. At this time, the root valve of the sample gas source at the front end of the inlet corresponding to the sampling pipeline is closed, and no fluorine-nitrogen mixed gas sample gas is introduced into the sampling pipeline. Then close the vacuum pneumatic valve, open the replacement pneumatic valve again, and then close the replacement pneumatic valve, open the vacuum pneumatic valve, and then close the vacuum pneumatic valve. Repeat this process several times to ensure that the gas path environment in the gas main and the sampling pipeline is completely replaced, and then close the high-pressure manual diaphragm valve and the sampling pneumatic valve;

[0027] S3. Pass the sample gas to detect and analyze the fluorine gas content; after ensuring that the gas main and sampling pipeline are completely replaced, open the root valve of the sample gas source, and then open the high-pressure manual diaphragm valve and the sampling pneumatic valve in turn, and adjust the corresponding high-pressure pressure regulating valve, and start to pass the fluorine-nitrogen mixed gas sample gas to be tested into the gas main, and then open the control pneumatic valve, low-pressure pressure regulating valve and regulating pneumatic valve on the corresponding output pipeline in the output pipeline in turn, and send the sample gas to the sample gas pretreatment mechanism;

[0028] S4. Purge the sample cell of the UV spectrophotometer and calibrate the baseline; when the UV spectrophotometer is ready, open the manual nitrogen diaphragm valve of the sample gas pretreatment mechanism, adjust the pressure of the reference pressure regulating valve and the replacement pressure regulating valve, and then open the needle valve four and the replacement manual diaphragm valve in sequence. At this time, nitrogen enters the reference cell of the UV spectrophotometer, and then adjusts to the test pressure through the needle valve three, and fully purges the sample cell with nitrogen, and then collects the baseline on the UV spectrophotometer, and returns the baseline to zero and calibrates it;

[0029] S5. Collect sample gas and start fluorine gas detection; after the UV spectrophotometer indicates that the baseline calibration is completed, close the replacement manual diaphragm valve and the replacement pressure regulating valve, and then open the mixing manual diaphragm valve 1, needle valve 1, needle valve 2, and mixing manual diaphragm valve 2 in sequence, and adjust the pressure to the test pressure through needle valve 3, and the fluorine-nitrogen mixed gas sample gas enters the UV spectrophotometer sample cell;

[0030] S6. Detection data analysis and sample gas fluorine concentration calculation: edit the sample information on the UV spectrophotometer, and after the pressure sensor 3 displays the stable pressure, you can start the fluorine content detection and analysis. The UV spectrophotometer calculates the detection data and displays the fluorine concentration. The calculation formula is a linear equation

[0031] y=mA

[0032] Wherein, y represents the fluorine gas concentration; A represents the fluorine gas absorbance; m represents the calculation coefficient, which is a constant. When the fluorine gas absorbance is known, the fluorine gas concentration can be found on the working curve;

[0033] Establishment of working curve: by using standard sample gas and reference gas (nitrogen) to pass into the sample cell and reference cell of the UV spectrophotometer, fully replacing and filling the sample cell and reference cell, testing the standard sample gas, and recording the absorbance of fluorine gas in the standard sample gas, a standard sample gas working curve with absorbance as the horizontal axis and fluorine gas concentration as the vertical axis can be drawn. When determining the standard sample gas working curve, at least 4 standard sample gases with different component contents need to be tested, and their fluorine gas contents are: 5.03%, 10.02%, 15.05%, and 20.06%, respectively. The balance gas is nitrogen, and the standard sample gas is purchased directly from outside.

[0034] S7. After the fluorine gas detection is completed, the finishing work is carried out; after the sample gas is collected, close the root valve of the sample gas source, and then close the various valves on the sample gas pretreatment mechanism in turn, and then open the vacuum pneumatic valve on the fluorine-nitrogen mixed gas sampling mechanism, turn on the vacuum generator for vacuum treatment, and then close the vacuum pneumatic valve, open the replacement pneumatic valve to allow nitrogen to be repeatedly purged to ensure that the internal gas path environment of the fluorine-nitrogen mixed gas sampling mechanism is completely replaced, and finally close the high-pressure manual diaphragm valve and the sampling pneumatic valve, and the fluorine gas detection is completed.

[0035] The present invention also includes other components that enable it to be used normally, all of which are conventional means in the art. In addition, devices or components not limited in the present invention, such as: nitrogen gas source, sample gas source, ultraviolet spectrophotometer, vacuum generator, and manual diaphragm valves, pressure regulating valves, one-way valves, pneumatic valves, needle valves, pressure gauges, pressure sensors, etc. on the fluorine-nitrogen mixed gas sampling mechanism and the sample gas pretreatment mechanism, all adopt the existing technology in the art.

[0036] The beneficial effects of the present invention are as follows:

[0037] The device and method for detecting fluorine gas in a fluorine-nitrogen mixed gas provided by the present invention have the following advantages over the prior art:

[0038] 1. Accurate data: Most existing detection methods require reaction conversion, which has the problem of low conversion rate. When using this method, no other substances are involved in the reaction during the test process, so there is no problem of low conversion rate.

[0039] 2. Rapid analysis: The present invention uses ultraviolet spectrometry to directly detect the F2 content in the fluorine-nitrogen mixed gas. Its principle is based on the Lambert-Beer law, which can quickly calculate the concentration of the measured gas and quickly present the results, greatly shortening the analysis time and the analysis cycle: the analysis data can be quickly obtained and timely feedback to production.

[0040] 3. The analysis system is scientifically laid out: it is equipped with a sampling device, a vacuum device, an exhaust gas adsorption device, a metering device, and an anti-leakage device, which can quickly and effectively replace the gas system.

[0041] 4. High test accuracy and good stability: No other substances participate in the reaction during the test process, and there is no problem of low conversion rate. The sample gas pretreatment mechanism can accurately control the pressure; the sample gas pretreatment mechanism is installed at the front end of the instrument. The device is equipped with 2 mechanisms, a total of 3 pressure sensors, and 8 pressure gauges, which can display the sample gas pressure in real time, and are convenient for adjusting the injection pressure. The digital pressure sensor with an accuracy of 0.001MPa can display the current analysis pressure in real time. Different pressures can be selected for analysis according to actual conditions. It has multiple options and improves the accuracy and stability of the test results.

[0042] 5. Long service life: The circulation pool used in the present invention is corrosion-resistant and has a long service life; the independent gas pool has good sealing performance, greatly reduces the number of pipeline interfaces, increases safety, reduces the number of maintenance times, reduces maintenance costs, and solves the problem of gas corrosion detectors caused by failure of conversion columns and absorption columns in chromatography.

[0043] 6. Safe, environmentally friendly and cost-saving: The analytical tail gas can be connected to the adsorption tower and emptied after treatment, which is safe, environmentally friendly and pollution-free. No driver and carrier gas are required, only nitrogen is used as the reference gas, and the tail gas reflux recovery tower can be selected. The independent sample gas inlet and outlet will not be mixed with other gases and can be reused, reducing the analysis cost.

[0044] 7. Simple operation: The analysis system is equipped with a pneumatic valve, and the replacement logic can be edited on the system to achieve one-button automatic replacement. The operation is simple and convenient. BRIEF DESCRIPTION OF THE DRAWINGS

[0045] Figure 1 Schematic diagram of the structure of the fluorine-nitrogen mixed gas sampling mechanism in Example 1.

[0046] Figure 2 Schematic diagram of the structure of the sample gas pretreatment mechanism in Example 1.

[0047] Figure 3 Schematic diagram of the principle of the ultraviolet spectrophotometer in Example 1.

[0048] Figure 4 This is the standard gas working curve diagram of the ultraviolet spectrophotometer in Example 2.

[0049] Figure 5 This is the fluorine-nitrogen mixed gas chromatogram of the thermal conductivity detector gas chromatography in the comparative example.

[0050] Figure 6 The figure is a flow chart of the method for detecting fluorine gas in a fluorine-nitrogen mixed gas in the present invention.

[0051] Marked in the figure are: light source 100, monochromator 200, light cutter 300, sample cell 500, reference cell 400, detector 600, amplifier 700, display 800, recorder 900. DETAILED DESCRIPTION

[0052] The technical solution of the present invention will be clearly and completely described below in conjunction with specific embodiments. Obviously, the described embodiments are only some embodiments of the present invention, rather than all embodiments.

[0053] Example 1

[0054] This embodiment provides a device for detecting fluorine gas in a fluorine-nitrogen mixed gas, which includes a fluorine-nitrogen mixed gas sampling mechanism, a sample gas pretreatment mechanism, and an ultraviolet spectrophotometer connected in series from front to back according to the conveying direction of the fluorine-nitrogen mixed gas.

[0055] like Figure 1As shown, the fluorine-nitrogen mixed gas sampling mechanism includes a leak-proof shell for preventing the fluorine-nitrogen mixed gas from leaking to the outside of the device, a sampling pipeline arranged inside the shell for collecting fluorine-nitrogen mixed gas sample gas, a replacement pipeline for creating a clean protective environment for the sampling pipeline, and an output pipeline for controlling the output of the sample gas. The sampling pipeline, the replacement pipeline and the output pipeline are interconnected through a gas transmission main pipe, and a pressure sensor PT1 is installed on the gas transmission main pipe.

[0056] like Figure 2 As shown, the sample gas pretreatment mechanism includes a sample gas pipeline for connecting to the output pipeline of the fluorine-nitrogen mixed gas sampling mechanism, a nitrogen replacement pipeline for pre-purging the sample gas pipeline, and a reference gas pipeline for introducing nitrogen reference gas into the sample gas pretreatment mechanism; the ultraviolet spectrophotometer includes an ultraviolet spectrophotometer, which is provided with a sample cell and a reference cell, and the sample cell and the reference cell correspond to the sample gas pipeline and the reference gas pipeline connected to the sample gas pretreatment mechanism respectively.

[0057] Specifically, the sampling pipeline includes three sampling pipelines connected in parallel and having the same structure, each sampling pipeline is connected in series with a high-pressure manual diaphragm valve, a high-pressure pressure regulating valve and a sampling pneumatic valve, the front ends of the three high-pressure manual diaphragm valves correspond to a sampling port respectively, and the three sampling ports can be used for fluorine gas detection of fluorine-nitrogen mixed gas in storage tanks / cylinders / containers / torpedo vehicles respectively, with multiple selectivities, and the rear ends of the three sampling pneumatic valves are centrally connected to the gas main; and an intake pressure gauge is installed on each sampling pipeline. The three intake ports are respectively denoted as SAM1, SAM21, and SAM3, the three high-pressure manual diaphragm valves are respectively denoted as HPI (1), HPI (2), and HPI (3), the three high-pressure pressure regulating valves are respectively denoted as REG (1), REG (2), and REG (3), the three intake pressure gauges are respectively denoted as LPG (1), LPG (2), and LPG (3), and the three sampling pneumatic valves are respectively denoted as LPI (1), LPI (2), and LPI (3).

[0058] Specifically, the displacement pipeline includes a vacuum pipeline for evacuating the sampling pipeline and a displacement pipeline for filling the sampling pipeline with nitrogen for displacement. The vacuum pipeline and the displacement pipeline are connected in parallel. A vacuum generator is connected to the vacuum pipeline. A vacuum port VENT is provided at the front end of the vacuum pipeline. The rear end of the vacuum pipeline is connected to the gas main through a vacuum pneumatic valve LPI (5).

[0059] A replacement one-way valve CVP and a replacement pneumatic valve PGI are arranged in series on the replacement pipeline. A replacement port PN2 is arranged at the front end of the replacement one-way valve, and the rear end of the replacement pneumatic valve is connected to the gas main pipe; a vacuum pressure gauge and a pressure sensor PT2 are installed on the vacuum pipeline.

[0060] The vacuum generator is a vacuum pump (not shown in the figure) or a Venturi vacuum generator VGM, which generates vacuum negative pressure by introducing nitrogen through GN2, and is used for vacuum air path replacement of the entire sampling mechanism to ensure the cleanliness of the sampling mechanism air path system. The vacuum pipeline also includes a reserved pipeline that can be externally connected to a vacuum pump. The rear end of the reserved pipeline is also connected to the gas main through a reserved pneumatic valve LPI (4).

[0061] Specifically, the output pipeline includes three output pipelines which are connected in parallel and have the same structure. An output check valve, a low-pressure pressure regulating valve and a regulating pneumatic valve are connected in series on each output pipeline in sequence. A nitrogen purge bypass is also arranged in parallel on one side of each output pipeline. A purge check valve and a purge pneumatic valve are arranged in series on the nitrogen purge bypass. A purge port is correspondingly arranged at the front end of each purge check valve; an air outlet is correspondingly arranged at the front end of each regulating pneumatic valve, and the rear end of each output pipeline is connected to the gas main through a control pneumatic valve; and an air outlet pressure gauge is correspondingly installed on each output pipeline. The three control pneumatic valves are recorded as SAV1, SAV2, and SAV3 respectively, the three output check valves are recorded as SCV1, SCV2, and SCV3 respectively, the three low-pressure pressure regulating valves are recorded as SREG1, SREG2, and SREG3 respectively, the three outlet pressure gauges are recorded as SPG1, SPG2, and SPG3 respectively, the three regulating pneumatic valves are recorded as SPIV1, SPIV2, and SPIV3 respectively, the three outlets are recorded as UV, GC01, and GC02 respectively; the three purge ports are recorded as Stander1, Stander2, and Stander3 respectively, the three purge check valves are recorded as CVV1, CVV2, and CVV3 respectively, and the three purge pneumatic valves are recorded as AVV1, AVV2, and AVV3 respectively.

[0062] The entire gas circuit system of the fluorine-nitrogen mixed gas sampling mechanism is equipped with a pneumatic valve, and the sampling control logic can be edited on the gas circuit system of the sampling mechanism. Two selection modes, manual replacement and automatic replacement, can be provided. When switching to the automatic replacement mode, the gas circuit replacement can be completed by one-key operation, and the operation is simple and convenient.

[0063] Specifically, the sample gas pipeline includes a mixing manual diaphragm valve 1 V1, a needle valve 1 V2, a needle valve 2 V3, a mixing manual diaphragm valve 2 V4 and a needle valve 3 V5 which are connected in series in sequence, and a sample gas pressure gauge V12 is arranged on the pipeline between needle valve 1 and needle valve 2, the rear end of needle valve 3 is connected to the sample pool of the ultraviolet spectrophotometer, and a pressure sensor 3 V13 is arranged on the rear end of needle valve 3.

[0064] The pressure sensor 1, pressure sensor 2 and pressure sensor 3 are all digital pressure sensors.

[0065] Specifically, the reference gas pipeline includes a nitrogen manual diaphragm valve V6, a reference pressure regulating valve V9 and a needle valve four V10 connected in series in sequence, the nitrogen comes from an external nitrogen source, and the rear end of the needle valve four is connected to the reference cell of the ultraviolet spectrophotometer; the reference gas pipeline and the sample gas pipeline are two independent parallel pipelines.

[0066] Specifically, the nitrogen replacement pipeline is connected across the reference gas pipeline and the sample gas pipeline. The nitrogen replacement pipeline includes a replacement pressure regulating valve V7, a replacement manual diaphragm valve V8 and a nitrogen charging check valve V11 which are connected in series in sequence. The front end of the replacement pressure regulating valve is connected between the nitrogen manual diaphragm valve and the reference pressure regulating valve, and the rear end of the nitrogen charging check valve is connected between the mixing manual diaphragm valve 2 and the needle valve 3.

[0067] like Figure 3 As shown, the ultraviolet spectrophotometer includes a light source 100, a monochromator 200, a chopper 300, a sample cell 500, a reference cell 400, a detector 600, an amplifier 700, a display 800, and a recorder 900; the light source is a deuterium light source with a resolution of 0.1nm, an analysis range of 0.1%-99.9%; and a measurement wavelength of 274nm-294nm. The sample cell and the reference cell are two independent gas flow cells. The ultraviolet spectrophotometer is a prior art, and its internal structural components are not described in detail here.

[0068] Specifically, the leakage-proof housing is a closed explosion-proof cabinet, and the fluorine-nitrogen mixed gas sampling mechanism is placed inside the explosion-proof cabinet. The top of the explosion-proof cabinet is sealed and connected with an exhaust pipe EXHAUST for centrally discharging the leaked gas, and the exhaust pipe is always in a slightly negative pressure state. If leakage occurs during the fluorine-nitrogen mixed gas sampling process, the exhaust system is opened to the maximum extent to prevent toxic gases from leaking into the environment, thereby protecting the safety of experimenters and avoiding environmental pollution.

[0069] The exhaust pipe is connected to the tail gas adsorption device through a three-way pipe. The gas circulation pools of the fluorine-nitrogen mixed gas sample gas and the reference gas of the detection method are independently set, and no other gas is involved in the sample gas detection process, thereby avoiding sample gas contamination. The sample gas after analysis and use can be selectively processed, or adsorbed by an adsorption tower, or refluxed to the fluorine-nitrogen mixed gas storage tank for recycling and reuse.

[0070] The tail gas adsorption device may be an adsorption tower, in which fillers capable of reacting with fluorine gas are installed, and the leaked tail gas of the fluorine-nitrogen mixed gas may be safely discharged after harmless treatment in the adsorption tower.

[0071] The tail gas adsorption device can also be a recovery tower. The leaked tail gas of the fluorine-nitrogen mixed gas flows back to the fluorine-nitrogen mixed gas storage tank through the recovery tower. The tail gas can also be recycled and reused to save the cost of the fluorine-nitrogen mixed gas.

[0072] Example 2

[0073] like Figure 6 As shown, this embodiment provides a method for detecting fluorine gas in a fluorine-nitrogen mixed gas, and the fluorine gas detection is performed using the device for detecting fluorine gas in a fluorine-nitrogen mixed gas described in Example 1.

[0074] The detection instrument used is an ultraviolet spectrophotometer, the detection method used is ultraviolet spectroscopy, and the analysis principle is based on Lambert-Beer's law:

[0075] When the wavelength of the incident light is constant, the absorbance of the medium to be measured is proportional to its concentration and the thickness of the absorption layer.

[0076] A=lg(1 / T)=kbC

[0077] Among them, A is absorbance; T is the transmittance (transmittance), that is, the intensity of the outgoing light / the intensity of the incident light; C is the concentration of the absorbing substance; b is the thickness of the absorption layer; k is the proportionality coefficient, which is related to the property temperature of the absorbing substance and the wavelength λ of the incident light.

[0078] In this embodiment 2, sampling is performed by the injection port SAM3 alone as an example. The same operation is performed when sampling is performed by the other two injection ports SAM1 and SAM2 alone.

[0079] The specific steps of the fluorine gas detection method are as follows:

[0080] S1. Perform air tightness test on the device; close all valves on the fluorine-nitrogen mixed gas sampling mechanism, then open the replacement pneumatic valve PGI, and introduce 99.999% nitrogen into the gas main through the replacement port PN2 and the replacement check valve CVP until the pressure sensor PT1 displays a pressure of 100±0.5psi, then close the replacement pneumatic valve and maintain the pressure for 30 minutes; if the pressure sensor PT1 displays no obvious change in pressure, it means that the device is airtight;

[0081] S2. Evacuate the device and replace the gas with nitrogen; first start the vacuum generator or vacuum pump to evacuate the vacuum pipeline until the pressure sensor PT2 shows a pressure of -14.5 psi, then open the vacuum pneumatic valve LPI (5), the sampling pneumatic valve LPI (3) and the high-pressure manual diaphragm valve HPI (3) in sequence. At this time, the sample gas source root valve (not shown in the figure) at the front end of the sampling port SAM3 corresponding to the sampling pipeline is closed. At this time, no fluorine-nitrogen mixed gas sample gas is introduced into the sampling pipeline until the pressure sensor PT1 on the gas main shows a pressure of -14.5 psi and remains unchanged for 2 minutes, then Close the vacuum pneumatic valve LPI (5), and open the replacement pneumatic valve PGI again until the pressure sensor 1 displays a pressure of 100 ± 0.5 psi and remains unchanged for 15 seconds, then close the replacement pneumatic valve PGI, and open the vacuum pneumatic valve LPI (5) until the pressure sensor PT1 displays a pressure of -14.5 psi and remains unchanged for 2 minutes, then close the vacuum pneumatic valve LPI (5), and repeat this six times to ensure that the gas path environment in the gas main and the sampling pipeline is completely replaced, then close the high-pressure manual diaphragm valve HPI (3), the sampling pneumatic valve LPI (3) and the vacuum pneumatic valve LPI (5);

[0082] S3. Pass the sample gas to detect and analyze the fluorine gas content; after ensuring that the gas main and the sampling pipeline are completely replaced, open the root valve of the sample gas source, and then open the high-pressure manual diaphragm valve HPI (3) and the sampling pneumatic valve LPI (3) in turn, and adjust the corresponding high-pressure pressure regulating valve REG (3), and start to pass the fluorine-nitrogen mixed gas sample to be tested into the gas main until the pressure sensor shows that the pressure is 45±1psi, and then open the control pneumatic valve SAV1, low-pressure pressure regulating valve SREG1 and regulating pneumatic valve SPIV1 on the corresponding output pipeline in the output pipeline in turn, and send the sample gas to the sample gas pretreatment mechanism;

[0083] S4. Purge and baseline correction of the UV spectrophotometer sample cell; after confirming that the UV spectrophotometer is ready, open the nitrogen manual diaphragm valve V6 of the sample gas pretreatment mechanism, adjust the pressure of the reference pressure regulating valve V9 and the replacement pressure regulating valve V7 to 0.10MPa, and then open the needle valve four V10 and the replacement manual diaphragm valve V8 in sequence. At this time, nitrogen enters the reference cell of the UV spectrophotometer, and then adjusts to the test pressure through the needle valve three V5. The pressure sensor three displays a pressure of 0.100MPa. The sample cell is fully purged with nitrogen, and then the background baseline is collected on the UV spectrophotometer, and the baseline is zeroed and calibrated;

[0084] S5. Collect sample gas and start fluorine gas detection; after the UV spectrophotometer prompts that the baseline correction is completed, close the replacement manual diaphragm valve V8 and the replacement pressure regulating valve V7, and then open the mixing manual diaphragm valve V1, needle valve V2, needle valve V3, and mixing manual diaphragm valve V4 in sequence, and adjust the test pressure through the needle valve V5. The pressure sensor V13 shows that the pressure is 0.100MPa, and the fluorine-nitrogen mixed gas sample gas enters the sample cell of the UV spectrophotometer;

[0085] S6. Detection data analysis and sample gas fluorine concentration calculation: edit the sample information on the UV spectrophotometer, and after the pressure sensor V13 shows that the pressure is stable, you can start the fluorine content detection and analysis. The UV spectrophotometer calculates the detection data and displays the fluorine concentration. The calculation formula is:

[0086] y=mA

[0087] Wherein, y represents the fluorine gas concentration; A represents the fluorine gas absorbance; m represents the calculation coefficient, which is a constant. When the fluorine gas absorbance is known, the fluorine gas concentration can be found on the working curve;

[0088] Establishment of working curve: By using standard sample gas and reference gas (nitrogen) to pass into the sample cell and reference cell of the ultraviolet spectrophotometer instrument, fully replacing and filling the sample cell and reference cell, conducting standard sample gas detection, and recording the absorbance of fluorine gas in the standard sample gas, a standard sample gas working curve can be drawn with absorbance as the horizontal axis and fluorine gas concentration as the vertical axis.

[0089] When measuring the standard gas working curve of the ultraviolet spectrophotometer, at least four standard sample gases with different component contents need to be tested. The fluorine gas contents are 5.03%, 10.02%, 15.05%, and 20.06%, respectively. The balance gas of the four standard sample gases is nitrogen. The standard sample gases are all purchased directly from an external manufacturer, Dalian Date Gas Co., Ltd.

[0090] Table 1 Standard gas composition table

[0091]

[0092]

[0093] UV spectrophotometer standard gas working curve, such as Figure 4 As shown in the figure, the linearity of the working curve shows that the curve fitting R2>0.9999, indicating that the UV spectrometry detection method is accurate and reliable.

[0094] S7. After the fluorine gas detection is completed, the finishing work is carried out; after the sample gas collection is completed, the root valve of the sample gas source is closed, and then the various valves on the sample gas pretreatment mechanism are closed in turn, and then the vacuum pneumatic valve LPI (5) on the fluorine-nitrogen mixed gas sampling mechanism is opened, and the vacuum generator is turned on for vacuum treatment until the pressure sensor PT1 displays a pressure of -14.5psi and remains unchanged for 2 minutes, and then the vacuum pneumatic valve LPI (5) is closed, and the displacement pneumatic valve PGI is opened to pass nitrogen for repeated purging until the pressure sensor PT1 displays a pressure of 100±0.5psi and remains unchanged for 15 seconds. Then close the replacement pneumatic valve PGI, and then open the vacuum pneumatic valve LPI (5) for another purge until the pressure sensor 1 displays a pressure of -14.5 psi and remains unchanged for 2 minutes, and then close the vacuum pneumatic valve LPI (5). Repeat this six times, and the last time until the pressure sensor PT1 displays -14.5 psi and remains unchanged for 2 minutes, to ensure that the internal gas path environment of the fluorine-nitrogen mixed gas sampling mechanism is completely replaced. Finally, close the high-pressure manual diaphragm valve HPI (3), the sampling pneumatic valve LPI (3) and the vacuum pneumatic valve LPI (5), and the fluorine gas detection and analysis of the sample gas is completed.

[0095] It should be noted that the sample gas tested this time was a fluorine-nitrogen mixed gas purchased externally, with a fluorine concentration of 19.93% and a nitrogen concentration of 80.07%.

[0096] Comparative Example

[0097] In order to verify the accuracy of the method of fluorine gas detection by ultraviolet spectrometry in Example 2, a standard sample gas with a fluorine gas concentration of 19.93% and a nitrogen concentration of 80.07% was also used, and a thermal conductivity detector gas chromatography method was used for three consecutive days as a comparative example. The test results are shown in the following table:

[0098] Table 2 Chromatographic nitrogen detection data

[0099]

[0100] Table 3 Chromatographic fluorine gas detection data

[0101]

[0102] In addition, the comparative example also uses standard sample gas with a fluorine concentration of 19.93% and a nitrogen concentration of 80.07%, and tests are performed at four pressures of 0.100MPa, 0.050MPa, 0.018MPa, and 0.004MPa, respectively. Each pressure is tested three times, with 10 sets of data each time. To avoid accidental data, the gas source is turned off each time, and the gas is re-supplied and re-tested after replacement. The results are shown in Table 4 below:

[0103] Table 4 UV spectrometry test data

[0104]

[0105] As shown in Table 4 above, using this detection method, its relative standard deviation is 0.016%-0.111%, which is much less than 1%, and the deviation from the standard sample is 0.0011%-0.0256%, indicating that the fluorine gas detection method for fluorine-nitrogen mixed gas provided by the present invention has good accuracy and is accurate and reliable.

[0106] An example of the chromatogram and results of the fluorine-nitrogen mixed gas analyzed by thermal conductivity detector gas chromatography, such as Figure 5 As shown in Table 2, Table 3 and Figure 5 It can be seen that compared with chromatography, the ultraviolet spectrometry has more obvious advantages in detecting fluorine gas concentration in fluorine-nitrogen mixed gas by ultraviolet spectrometry, both in terms of stability and accuracy.

[0107] The technical solution of the present invention is not limited to the above-mentioned specific embodiments. Without departing from the scope and spirit of the described embodiments, many modifications and changes are obvious to ordinary technicians in this technical field. Any technical deformation made within the spirit and principles of the present invention falls within the protection scope of the present invention.

Claims

1. A device for detecting fluorine gas in a fluorine-nitrogen mixed gas, characterized in that: The device comprises a fluorine-nitrogen mixed gas sampling mechanism, a sample gas pretreatment mechanism and an ultraviolet spectrophotometer which are sequentially connected in series; The fluorine-nitrogen mixed gas sampling mechanism comprises a leak-proof housing, and a sampling pipeline, a replacement pipeline and an output pipeline arranged inside the leak-proof housing, wherein the sampling pipeline, the replacement pipeline and the output pipeline are connected through a gas transmission main pipe; The sample gas pretreatment mechanism comprises a sample gas pipeline for connecting to the output pipeline of the fluorine-nitrogen mixed gas sampling mechanism, a nitrogen replacement pipeline for pre-purging the sample gas pipeline, and a reference gas pipeline for introducing nitrogen reference gas into the sample gas pretreatment mechanism, wherein a pressure sensor 3 is installed on the sample gas pipeline; The ultraviolet spectrophotometer comprises an ultraviolet spectrophotometer, wherein a sample pool and a reference pool are arranged independently of each other, and the sample pool and the reference pool correspond to a sample gas pipeline and a reference gas pipeline connected to a sample gas pretreatment mechanism respectively.

2. A device for detecting fluorine gas in a fluorine-nitrogen mixed gas according to claim 1, characterized in that: The sampling pipeline includes three sampling lines, each of which is provided with a valve and a pressure gauge.

3. The device for detecting fluorine gas in a fluorine-nitrogen mixed gas according to claim 1, characterized in that: The displacement pipeline comprises a vacuum pipeline and a displacement pipeline, wherein a vacuum generator is connected to the vacuum pipeline; a displacement check valve and a displacement pneumatic valve are connected in series to the displacement pipeline, and both the vacuum pipeline and the displacement pipeline are connected to the gas main.

4. The device for detecting fluorine gas in a fluorine-nitrogen mixed gas according to claim 1, characterized in that: The output pipeline includes three output pipelines, one side of each output pipeline is connected in parallel with a nitrogen purge bypass, and the rear end of each output pipeline is connected to the gas main pipeline.

5. The device for detecting fluorine gas in a fluorine-nitrogen mixed gas according to claim 1, characterized in that: The sample gas pipeline includes a mixing manual diaphragm valve 1, a needle valve 1, a needle valve 2, a mixing manual diaphragm valve 2 and a needle valve 3 connected in series in sequence. A sample gas pressure gauge is provided on the pipeline between needle valve 1 and needle valve 2. The rear end of needle valve 3 is connected to the sample pool of the ultraviolet spectrophotometer. The rear end of needle valve 3 is provided with a pressure sensor 3.

6. The device for detecting fluorine gas in a fluorine-nitrogen mixed gas according to claim 1, characterized in that: The reference gas pipeline comprises a nitrogen manual diaphragm valve, a reference pressure regulating valve and a needle valve four which are connected in series in sequence, and the rear end of the needle valve four is connected to a reference cell of an ultraviolet spectrophotometer.

7. The device for detecting fluorine gas in a fluorine-nitrogen mixed gas according to claim 1, characterized in that: The nitrogen replacement pipeline is connected between the reference gas pipeline and the sample gas pipeline, and the nitrogen replacement pipeline comprises a replacement pressure regulating valve, a replacement manual diaphragm valve and a nitrogen filling one-way valve which are connected in series in sequence.

8. The device for detecting fluorine gas in a fluorine-nitrogen mixed gas according to claim 1, characterized in that: The ultraviolet spectrophotometer comprises a light source, a monochromator, a light cutter, a sample cell, a reference cell and a detector; the light source is a deuterium light source.

9. The device for detecting fluorine gas in a fluorine-nitrogen mixed gas according to claim 1, characterized in that: The anti-leakage housing is a closed explosion-proof cabinet, and the top of the explosion-proof cabinet is sealed and connected with an exhaust pipe for centrally exhausting leaked gas, and the exhaust pipe is connected to the tail gas adsorption device.

10. A method for detecting fluorine gas in a fluorine-nitrogen mixed gas, characterized in that: The method uses the device described in any one of claims 1 to 7 to detect fluorine gas, adopts ultraviolet spectrometry, and includes the following steps: S1. Replace the device with nitrogen; S2. Pass fluorine and nitrogen mixed gas into the sample gas pretreatment mechanism; S3. After the UV spectrophotometer baseline is calibrated, nitrogen is introduced into the reference cell; S4. Adjust the sample gas pipeline pressure to the test pressure, and then allow the fluorine-nitrogen mixed gas sample gas to enter the UV spectrophotometer sample cell; S5. After the pressure displayed by pressure sensor 3 is stable, the fluorine gas content detection and analysis can be started.

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