Device for detecting fluorine in fluorine-nitrogen mixed gas

Abstract

The utility model relates to a device for detecting fluorine in fluorine-nitrogen mixed gas, which belongs to the technical field of fluorine detection and is characterized in that fluorine concentration is detected by an ultraviolet spectrophotometer according to Lambert-Beer's law by adopting an ultraviolet spectrophotometer, an independent sample cell and an independent reference cell are customized on the ultraviolet spectrophotometer, and the sample cell and the reference cell are used for detecting fluorine concentration. 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] This utility model belongs to the field of fluorine detection technology in fluorine chemical industry, and specifically relates to a device for detecting fluorine in a fluorine-nitrogen mixture. Background Technology

[0002] Fluorine is a diatomic gas with a strong, pungent odor and potent oxidizing and corrosive properties. At room temperature, fluorine can combine with almost all elements to generate a large amount of heat, so it is usually present in the form of a fluorine-nitrogen mixture (fluorine-nitrogen gas mixture). Fluorine-nitrogen gas mixtures play an important role in many fields. For example, in the semiconductor manufacturing industry, fluorine-nitrogen gas mixtures are often used to clean and remove residues from semiconductor manufacturing processes, especially in processes such as photolithography and chemical vapor deposition, to ensure the quality and performance of semiconductor devices. Fluorine-nitrogen gas mixtures act as catalysts or oxidants in some chemical reactions, participating in a variety of organic and inorganic chemical reactions. Fluorine-nitrogen gas mixtures also have applications in laboratory research and high-energy physics experiments, serving as a filler gas for detectors in some high-energy physics experiments.

[0003] The main detection methods for determining the fluoride content in a fluoride-nitrogen mixture are as follows.

[0004] 1. Dual Thermal Conductivity Detector Gas Chromatography: This method uses a fluorochlorinated oil column combined with a conversion column and an absorption column for analysis. After sampling, the sample enters the chromatogram through a sampling valve. The sample gas passes through the conversion column, where F2 is converted to Cl2. This conversion is then quantified on the fluorochlorinated oil column, and the F2 content can be calculated from the Cl2 content. The measured Cl2 content can express the F2 content. However, the conversion efficiency of fluorine to chlorine is low, resulting in inaccurate data. Furthermore, chlorine is a highly toxic gas that can harm human health. Due to the characteristics of fluorine products, this method requires a combination of a fluorochlorinated oil column, a conversion column, and an absorption column. These three materials are consumables and need to be replaced regularly. Failure poses a risk, as it can lead to fluorine and other corrosive gases entering the detector, corroding it, increasing maintenance costs. Fluorine can also corrode the conversion and absorption columns, necessitating regular column replacement to ensure normal analysis. Additionally, chromatographic analysis is time-consuming, inefficient, and has low accuracy and stability, making it difficult to provide timely and accurate data feedback to production and hindering timely adjustments to raw material ratios.

[0005] 2. Dual Plasma Emission Detector + Thermal Conductivity Detector Gas Chromatography: This method uses a pre-column approach. After sampling, the sample passes through a sampling valve into the chromatographic column. Before entering the detector, it passes through two identical pre-columns. Due to the difference in retention times, to ensure that N2 enters the detector, a switching valve is activated before fluorine gas enters, causing fluorine gas to be backflushed and expelled from the instrument. Disadvantages include: limited pre-column lifespan (actually two months under normal testing), corrosion of the valve diaphragm, and increased maintenance costs; incomplete fluorine gas removal after pre-column exposure, which can corrode the thermal conductivity detector and shorten the instrument's lifespan; and long analysis cycles, low efficiency, and low data accuracy.

[0006] A patent document with publication number CN 114813448 A discloses a device for detecting the fluorine content in a fluorine-nitrogen mixture. This device includes a gas supply device, a metering device, an adsorption device, and a vacuum device. This method primarily involves reacting the fluorine gas with the adsorption device. After the reaction, the remaining gas is measured, and the fluorine content in the fluorine-nitrogen mixture is determined based on the change in gas volume before and after the reaction in the adsorption device. However, this method requires frequent replacement of the packing material in the adsorption tower, resulting in poor data stability. It also suffers from drawbacks such as incomplete reaction, inaccurate detection data, and potential environmental pollution and safety hazards due to improper treatment of the exhaust gas after analysis.

[0007] Another patent document, CN 107290437 A, discloses a method for indirectly measuring fluorine content using a chromatograph. This method involves pressurizing the gas to be tested using a booster pump; using nitrogen as a carrier gas to carry the gas to be tested into a refrigeration unit for cooling; taking a quantitative sample of the gas, passing it through a six-way valve, and then using a quantitative tube to take 1 ml of the gas into the chemical reaction process F2→Cl2. This quantitative gas sequentially passes through a polychlorotrifluoroethylene reactor, a KCl reactor, and a NaF reactor, where F- is replaced with Cl- and impurities are removed before entering the chromatograph for quantitative analysis of Cl2 content; the chromatograph measures the Cl2 content, and the data is processed by a data acquisition unit to correlate the Cl2 content with the F2 content; the exhaust gas from the chromatograph is then discharged into a NaOH absorption tank for absorption. This device requires multiple reactor stages and suffers from drawbacks such as incomplete reaction, poor stability, and large errors. Utility Model Content

[0008] To address the above issues, this invention provides a device for detecting fluorine in a fluorine-nitrogen mixture. The testing process involves no other substances participating in the reaction, eliminating conversion rate problems and resulting in more accurate detection data. The independent gas flow cell is corrosion-resistant, has a long lifespan, and excellent sealing, reducing maintenance frequency and costs. The pretreatment mechanism precisely controls pressure, ensuring high stability, fast analysis speed, safety, environmental friendliness, and cost savings.

[0009] It should be noted that in this utility model, fluorine-nitrogen mixture and fluorine-nitrogen mixed gas have the same meaning.

[0010] To achieve the above objectives, the present invention adopts the following technical solution:

[0011] An apparatus for detecting fluorine in a fluorine-nitrogen mixture, comprising, in the direction of gas delivery, a fluorine-nitrogen mixture sampling mechanism, a sample gas pretreatment mechanism, and an ultraviolet spectrophotometer connected in series from front to back; the fluorine-nitrogen mixture sampling mechanism includes a leak-proof housing to prevent leakage of the fluorine-nitrogen mixture to the outside of the apparatus, and inside the housing, a sampling pipeline for collecting the fluorine-nitrogen mixture sample gas, a displacement pipeline for creating a clean environment for the sampling pipeline, and an output pipeline for controlling the output of the sample gas; the sampling pipeline, the displacement pipeline, and the output pipeline are also included. The components are interconnected via a main gas supply 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 has a sample cell and a reference cell inside. The sample cell and the reference cell are respectively connected to the sample gas pipeline and the reference gas pipeline of the sample gas pretreatment mechanism.

[0012] Furthermore, the sampling pipeline includes three parallel sampling pipelines with identical structures. Each sampling pipeline is connected in series with a high-pressure manual diaphragm valve, a high-pressure regulating valve, and a sampling pneumatic valve. The front end of each of the three high-pressure manual diaphragm valves corresponds to a sampling port, and the rear ends of the three sampling pneumatic valves are all centrally connected to the gas supply main pipe. Each sampling pipeline is equipped with a corresponding inlet pressure gauge.

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

[0014] Furthermore, the output pipeline includes three parallel output pipelines with identical structures. Each output pipeline is connected in series with an output check valve, a low-pressure regulating valve, and a regulating pneumatic valve. A nitrogen purging bypass is also connected in parallel on one side of each output pipeline. A purging check valve and a purging pneumatic valve are connected in series on the nitrogen purging bypass. Each purging check valve has a purging port at its front end. Each regulating pneumatic valve has an outlet at its front end. The rear end of each output pipeline is connected to the main gas supply pipeline through a control pneumatic valve. An outlet pressure gauge is installed on each output pipeline.

[0015] Furthermore, the sample gas pipeline includes a mixing manual diaphragm valve one, a needle valve one, a needle valve two, a mixing manual diaphragm valve two, and a needle valve three connected in series. A sample gas pressure gauge is installed on the pipeline between needle valve one and needle valve two. The rear end of needle valve three is connected to the sample cell of the ultraviolet spectrophotometer, and a pressure sensor three is installed at the rear end of needle valve three. All three pressure sensors are digital display pressure sensors.

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

[0017] Furthermore, the nitrogen replacement pipeline is connected between the reference gas pipeline and the sample gas pipeline. The nitrogen replacement pipeline includes a replacement pressure regulating valve, a replacement manual diaphragm valve, and a nitrogen filling check valve connected in series. 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 filling check valve is connected between the mixed gas manual diaphragm valve and the 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 amplifiers, displays, recorders, and other supporting components.

[0019] Furthermore, the leak-proof housing is a sealed explosion-proof cabinet, with a sealed exhaust pipe at the top for centralized discharge of leaked gas. This exhaust pipe is connected to a tail gas adsorption device. The tail gas adsorption device can be an adsorption tower, containing packing material capable of reacting with fluorine gas. After being harmlessly treated by the adsorption tower, the leaked fluorine-nitrogen mixture can be safely discharged. Alternatively, the tail gas adsorption device can be a recovery tower, where the leaked fluorine-nitrogen mixture is returned to the fluorine-nitrogen mixture storage tank, allowing for the recovery and reuse of the tail gas and saving on the cost of fluorine-nitrogen mixture consumption.

[0020] The detection method corresponding to the device for detecting fluorine in the aforementioned fluorine-nitrogen mixture mainly uses an ultraviolet spectrophotometer as the detection instrument and ultraviolet spectrophotometry as the detection method. The analytical principle is based on Beer-Lambert's law:

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

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

[0023] Where A is absorbance; T is transmittance (transmittance), i.e., the ratio of emitted light intensity to incident light intensity; C is the concentration of the absorbing substance; b is the thickness of the absorption layer; and k is a proportionality coefficient, which is related to the properties of the absorbing substance, temperature, and wavelength λ of the incident light.

[0024] This utility model also includes other components that enable its normal use, all of which are conventional means in the field. In addition, the devices or components not limited in this utility model, such as nitrogen gas source, sample gas source, ultraviolet spectrophotometer, vacuum generator, and various manual diaphragm valves, pressure regulating valves, check valves, pneumatic valves, needle valves, pressure gauges, pressure sensors, etc. on the fluorine-nitrogen mixed gas sampling mechanism and sample gas pretreatment mechanism, all adopt the prior art in the field.

[0025] The beneficial effects of this utility model are as follows:

[0026] The present invention provides a device for detecting fluorine gas in a fluorine-nitrogen mixture, which has the following advantages compared with the prior art:

[0027] 1. Accurate Data: Most existing detection methods require reaction conversion, resulting in low conversion rates. Using this device, no other substances participate in the reaction, eliminating the problem of low conversion rates.

[0028] 2. Rapid Analysis: This invention uses ultraviolet spectrophotometry to directly detect the F2 content in a fluorine-nitrogen mixture. Based on Beer-Lambert's law, the concentration of the gas being measured can be calculated quickly, and the results can be presented rapidly, greatly shortening the analysis time and reducing the analysis cycle. It can quickly obtain analytical data and provide timely feedback to production.

[0029] 3. Scientifically designed analytical system: Equipped with sampling device, vacuum device, exhaust gas adsorption device, metering device, and leak prevention device, it can quickly and effectively replace the gas path system.

[0030] 4. High testing accuracy and good stability: No other substances participate in the reaction during the testing process, so there are no problems such as 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 two mechanisms, a total of three pressure sensors, and eight pressure gauges, which can display the sample gas pressure in real time, making it easy to adjust the injection pressure. The digital display 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 the actual situation, which has multiple options and improves the accuracy and stability of the detection results.

[0031] 5. Long service life: The flow cell used in this invention is corrosion resistant and has a long service life; the independent gas cell has good sealing performance, significantly reduces pipeline interfaces, increases safety, reduces maintenance frequency, and lowers maintenance costs, solving the problem of gas corrosion of detectors caused by the failure of conversion columns and absorption columns in chromatography.

[0032] 6. Safe, environmentally friendly, and cost-effective: The exhaust gas can be connected to the adsorption tower, treated, and then discharged into the atmosphere, ensuring safety, environmental protection, and no pollution; no driver or carrier gas is required, only nitrogen is used as the reference gas, and an exhaust gas reflux recovery tower can be selected. The independent sample gas inlet and outlet ensures that no other gases are mixed in, allowing for reuse and reducing analysis costs.

[0033] 7. Simple operation: Thanks to the pneumatic valve, the analysis system can be programmed with replacement logic to achieve one-click automatic replacement, making operation simple and convenient. Attached Figure Description

[0034] Figure 1 This is a schematic diagram of the fluorine-nitrogen mixed gas sampling mechanism in the embodiment.

[0035] Figure 2 This is a schematic diagram of the sample gas pretreatment mechanism in the embodiment.

[0036] Figure 3 This is a schematic diagram of the principle of the ultraviolet spectrophotometer in the embodiment.

[0037] Figure 4 This is a standard gas operating curve diagram of the ultraviolet spectrophotometer in the embodiment.

[0038] Figure 5 This is the chromatogram of a fluorine-nitrogen mixture obtained by gas chromatography using a thermal conductivity detector in the comparative example.

[0039] Figure 6 This is a flowchart of the method for detecting fluorine in a fluorine-nitrogen mixture according to this invention.

[0040] The components in the diagram are labeled as follows: light source 100, monochromator 200, chopper 300, sample cell 500, reference cell 400, detector 600, amplifier 700, display 800, and recorder 900. Detailed Implementation

[0041] The technical solution of this utility model will be clearly and completely described below with reference to specific embodiments. Obviously, the described embodiments are only some embodiments of this utility model, and not all embodiments.

[0042] Example

[0043] This embodiment provides a device for detecting fluorine in a fluorine-nitrogen mixture, which includes a fluorine-nitrogen mixture sampling mechanism, a sample gas pretreatment mechanism, and an ultraviolet spectrophotometer connected in series from front to back, according to the fluorine-nitrogen mixture conveying direction.

[0044] like Figure 1 As shown, the fluorine-nitrogen mixed gas sampling mechanism includes a leak-proof housing to prevent the fluorine-nitrogen mixed gas from leaking to the outside of the device, and a sampling pipeline for collecting fluorine-nitrogen mixed gas sample gas, a displacement pipeline for creating a clean environment for the sampling pipeline, and an output pipeline for controlling the output of the sample gas. The sampling pipeline, displacement pipeline and output pipeline are interconnected through a gas supply main pipe, and a pressure sensor PT1 is installed on the gas supply main pipe.

[0045] 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 has a sample cell and a reference cell inside, and the sample cell and the reference cell are respectively connected to the sample gas pipeline and the reference gas pipeline of the sample gas pretreatment mechanism.

[0046] Specifically, the sampling pipeline includes three parallel sampling lines with identical structures. Each sampling line is connected in series with a high-pressure manual diaphragm valve, a high-pressure regulating valve, and a sampling pneumatic valve. The front end of each of the three high-pressure manual diaphragm valves corresponds to a sampling port. The three sampling ports can be used for fluorine gas detection in fluorine-nitrogen mixtures in storage tanks / cylinders / container grids / torpedo trucks, providing multiple selectivity. The rear ends of the three sampling pneumatic valves are all centrally connected to the gas transmission main. Each sampling line is equipped with an inlet pressure gauge. The three sampling ports are designated as SAM1, SAM21, and SAM3, the three high-pressure manual diaphragm valves are designated as HPI(1), HPI(2), and HPI(3), the three high-pressure regulating valves are designated as REG(1), REG(2), and REG(3), the three inlet pressure gauges are designated as LPG(1), LPG(2), and LPG(3), and the three sampling pneumatic valves are designated as LPI(1), LPI(2), and LPI(3).

[0047] Specifically, 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 VENT is provided at the front end of the vacuum pipeline. The rear end of the vacuum pipeline is connected to the gas supply main through a vacuum pneumatic valve LPI (5).

[0048] A displacement check valve CVP and a displacement pneumatic valve PGI are connected in series on the displacement pipeline. The displacement check valve has a displacement port PN2 at its front end, and the displacement pneumatic valve is connected to the main gas supply pipeline at its rear end. A vacuum pressure gauge and a pressure sensor PT2 are installed on the vacuum pipeline.

[0049] The vacuum generator is a vacuum pump (not shown in the figure) or a Venturi vacuum generator VGM. Nitrogen gas is introduced through GN2 to generate a vacuum negative pressure, which is used to replace the vacuum circuit of the entire sampling mechanism to ensure the cleanliness of the gas circuit system of the sampling mechanism. The vacuum pipeline also includes a reserved pipeline that can be connected to an external vacuum pump. The rear end of the reserved pipeline is also connected to the main gas supply pipe through a reserved pneumatic valve LPI (4).

[0050] Specifically, the output pipeline includes three parallel and identical output pipelines. Each output pipeline is connected in series with an output check valve, a low-pressure regulating valve, and a regulating pneumatic valve. A nitrogen purging bypass is also connected in parallel on one side of each output pipeline. A purging check valve and a purging pneumatic valve are connected in series on the nitrogen purging bypass. Each purging check valve has a purging port at its front end. Each regulating pneumatic valve has an outlet at its front end. The rear end of each output pipeline is connected to the main gas supply pipeline through a control pneumatic valve. An outlet pressure gauge is installed on each output pipeline. The three control pneumatic valves are labeled SAV1, SAV2, and SAV3; the three output check valves are labeled SCV1, SCV2, and SCV3; the three low-pressure regulating valves are labeled SREG1, SREG2, and SREG3; the three outlet pressure gauges are labeled SPG1, SPG2, and SPG3; the three regulating pneumatic valves are labeled SPIV1, SPIV2, and SPIV3; the three outlet ports are labeled UV, GC01, and GC02; the three purge ports are labeled Stander1, Stander2, and Stander3; the three purge check valves are labeled CVV1, CVV2, and CVV3; and the three purge pneumatic valves are labeled AVV1, AVV2, and AVV3.

[0051] The entire gas path system of the fluorine-nitrogen mixed gas sampling mechanism is equipped with pneumatic valves. The sampling control logic can be edited on the gas path system of the sampling mechanism. It can provide two selection modes: manual replacement and automatic replacement. When switching to automatic replacement mode, the gas path replacement can be completed with one click, which is simple and convenient to operate.

[0052] Specifically, the sample gas pipeline includes a mixed gas manual diaphragm valve V1, a needle valve V2, a needle valve V3, a mixed gas manual diaphragm valve V4, and a needle valve V5 connected in series. A sample gas pressure gauge V12 is installed on the pipeline between needle valves V1 and V2. The rear end of needle valve V3 is connected to the sample cell of the ultraviolet spectrophotometer, and a pressure sensor V13 is installed at the rear end of needle valve V3.

[0053] Pressure sensor 1, pressure sensor 2, and pressure sensor 3 are all digital display pressure sensors.

[0054] Specifically, the reference gas pipeline includes a nitrogen manual diaphragm valve V6, a reference pressure regulating valve V9, and a needle valve V10 connected in series. The nitrogen comes from an external nitrogen source, and the rear end of the needle valve V10 is connected to the reference cell of the ultraviolet spectrophotometer. The reference gas pipeline and the sample gas pipeline are two independent parallel pipelines.

[0055] Specifically, the nitrogen replacement pipeline is connected between 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 filling check valve V11 connected in series. 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 filling check valve is connected between the mixed gas manual diaphragm valve and the needle valve.

[0056] 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 0.1 nm, an analytical range of 0.1%-99.9%, and a measurement wavelength of 274 nm-294 nm. The sample cell and the reference cell are two independent gas flow cells. This ultraviolet spectrophotometer is existing technology, and its internal structural components will not be described in detail here.

[0057] Specifically, the leak-proof housing is a sealed explosion-proof cabinet. The fluorine-nitrogen mixed gas sampling mechanism is placed inside the explosion-proof cabinet. The top of the explosion-proof cabinet is sealed with an exhaust pipe EXHAUST for centralized discharge of leaked gas. The exhaust pipe is always in a slightly negative pressure state. If a leak occurs during the fluorine-nitrogen mixed gas sampling process, the exhaust system will be opened to the maximum extent to prevent toxic gases from leaking into the environment, protect the safety of experimental personnel and avoid environmental pollution.

[0058] The exhaust pipe is connected to the tail gas adsorption device via a three-way pipe. The gas flow cells for the fluorine-nitrogen mixed sample gas and the reference gas in this detection device are set up independently. No other gases are introduced during the sample gas detection process, avoiding sample gas contamination. The sample gas after analysis can be selectively treated, either by adsorption treatment through an adsorption tower or by recycling back to the fluorine-nitrogen mixed gas storage tank for reuse.

[0059] The exhaust gas adsorption device can be an adsorption tower, which is filled with packing material that can react with fluorine gas. The leaked exhaust gas from the fluorine-nitrogen mixture can be safely discharged after being treated harmlessly by the adsorption tower.

[0060] The exhaust gas adsorption device can also be a recovery tower. The leaked exhaust gas from the fluorine-nitrogen mixture flows back to the fluorine-nitrogen mixture storage tank through the recovery tower. Alternatively, the exhaust gas can be recycled and reused to save on the cost of fluorine-nitrogen mixture consumption.

[0061] like Figure 6 As shown, when using the device for detecting fluoride in a fluoride-nitrogen mixture described in the above embodiments to detect fluoride, the detection instrument used is an ultraviolet spectrophotometer, the detection method used is ultraviolet spectrophotometry, and the analytical principle is based on Beer-Lambert's law:

[0062] When the wavelength of the incident light is constant, the absorbance of the medium being measured is directly proportional to its concentration and the thickness of the absorption layer.

[0063] A = lg(1 / T) = kbC

[0064] Where A is absorbance; T is transmittance (transmittance), i.e., the ratio of emitted light intensity to incident light intensity; C is the concentration of the absorbing substance; b is the thickness of the absorption layer; and k is a proportionality coefficient, which is related to the properties of the absorbing substance, temperature, and wavelength λ of the incident light.

[0065] The detection method steps corresponding to this detection device are as follows:

[0066] S1. Perform an airtightness test on the device; close all valves on the fluorine-nitrogen mixed gas sampling mechanism, then open the pneumatic replacement valve PGI, and introduce 99.999% nitrogen gas into the main gas supply pipe through the replacement port PN2 and the replacement check valve CVP until the pressure sensor PT1 shows a pressure of 100±0.5psi. Then close the pneumatic replacement valve and maintain the pressure for 30 minutes. If the pressure sensor PT1 shows no significant change in pressure, it indicates that the device has good airtightness.

[0067] S2. Evacuate and purge the apparatus with nitrogen; first, start the vacuum generator or vacuum pump to evacuate the vacuum line until the pressure sensor PT2 shows a pressure of -14.5 psi. Then, sequentially open the vacuum pneumatic valve LPI (5), the sampling pneumatic valve LPI (3), and the high-pressure manual diaphragm valve HPI (3). At this time, the sample gas source root valve (not shown in the figure) at the front end of the corresponding inlet SAM3 of the sampling line is closed. At this time, the fluorine-free nitrogen mixed sample gas is introduced into the sampling line until the pressure sensor PT1 on the main gas supply line shows a pressure of -14.5 psi and remains unchanged for 2 minutes. Close the vacuum pneumatic valve LPI (5), open the replacement pneumatic valve PGI again until the pressure sensor 1 displays a pressure of 100±0.5psi and remains unchanged for 15s. Then close the replacement pneumatic valve PGI, open the vacuum pneumatic valve LPI (5), until the pressure sensor 1 PT1 displays a pressure of -14.5psi and remains unchanged for 2min. Then close the vacuum pneumatic valve LPI (5). Repeat this six times to ensure that the gas environment in the main gas supply line and sampling line 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).

[0068] S3. Introduce sample gas for fluorine content detection and analysis; after ensuring that the main gas supply pipe and 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 sequence, and adjust the corresponding high-pressure regulating valve REG (3) to start introducing the fluorine-nitrogen mixed sample gas to be tested into the main gas supply pipe until the pressure sensor shows a pressure of 45±1psi. Then, open the control pneumatic valve SAV1, the low-pressure regulating valve SREG1 and the regulating pneumatic valve SPIV1 on the corresponding output pipeline in the output pipeline in sequence to send the sample gas to the sample gas pretreatment mechanism.

[0069] S4. Sample cell purging and baseline correction for UV spectrophotometer; 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 displacement pressure regulating valve V7 to 0.10MPa, and then open the needle valve four V10 and the displacement manual diaphragm valve V8 in sequence. At this time, nitrogen enters the reference cell of the UV spectrophotometer, and then adjusts it to the test pressure through the needle valve three V5. The pressure sensor three displays a pressure of 0.100MPa. The sample cell is thoroughly purged with nitrogen. Then, the background baseline is collected on the UV spectrophotometer, and the baseline is zeroed and corrected.

[0070] S5. Collect sample gas and start fluorine gas detection; after the UV spectrophotometer indicates that the baseline correction is complete, 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. Adjust to the test pressure through needle valve V5. The pressure sensor V13 shows a pressure of 0.100 MPa. The fluorine-nitrogen mixed sample gas enters the UV spectrophotometer sample cell.

[0071] S6. Detection Data Analysis and Sample Gas Fluorine Concentration Calculation: After editing the sample information on the UV spectrophotometer, and once the pressure sensor (V13) shows stable pressure, the fluorine content detection and analysis can begin. The UV spectrophotometer calculates and displays the fluorine concentration based on the detection data. The calculation formula is as follows:

[0072] y = mA

[0073] Where y represents the fluorine concentration; A represents the fluorine absorbance; and m represents the calculation coefficient, which is a constant. If the fluorine absorbance is known, the fluorine concentration can be found on the working curve.

[0074] Establishment of the working curve: By introducing standard sample gas and reference gas (nitrogen) into the sample cell and reference cell of the ultraviolet spectrophotometer to fully replace and fill the sample cell and reference cell, the standard sample gas is detected, and the absorbance of fluorine gas in the standard sample gas is recorded. The working curve of the standard sample gas can then be plotted with absorbance as the abscissa and fluorine concentration as the ordinate.

[0075] When determining the standard gas working curve of the ultraviolet spectrophotometer, at least four standard sample gases with different component contents need to be tested, with fluorine contents of 5.03%, 10.02%, 15.05%, and 20.06%, respectively. The equilibrium gas for all four standard sample gases is nitrogen. All standard sample gases are purchased directly from the external manufacturer, Dalian Date Gas Co., Ltd.

[0076] Table 1 Standard Gas Composition Table

[0077]

[0078] The standard gas operating curve of the ultraviolet spectrophotometer, such as Figure 4 As shown in the figure, the linearity of the working curve indicates that the curve fitting R² > 0.9999, demonstrating that the ultraviolet spectrophotometric detection method is accurate and reliable.

[0079] S7. After the fluorine gas detection is completed, perform the final work; after the sample gas collection is completed, close the root valve of the sample gas source, then close each valve on the sample gas pretreatment mechanism in sequence, then open the vacuum pneumatic valve LPI(5) on the fluorine-nitrogen mixed gas sampling mechanism, turn on the vacuum generator to perform vacuum treatment until the pressure sensor PT1 shows a pressure of -14.5psi and remains unchanged for 2 minutes, then close the vacuum pneumatic valve LPI(5), open the replacement pneumatic valve PGI to introduce nitrogen gas for repeated purging until the pressure sensor PT1 shows a pressure of 100±0.5psi and remains unchanged for 15 seconds. Then close the replacement pneumatic valve PGI and 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. Then close the vacuum pneumatic valve LPI (5) and repeat this process six times. The last time, the pressure sensor 1 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). This fluorine gas detection and analysis of the sample gas is now complete.

[0080] It should be noted that the sample gas used in this test was a fluorine-nitrogen mixture purchased externally, with a fluorine concentration of 19.93% and a nitrogen concentration of 80.07%.

[0081] Comparative Example

[0082] To verify the accuracy of the ultraviolet spectrophotometry method for fluorine detection in the above embodiments, a standard sample gas with a fluorine concentration of 19.93% and a nitrogen concentration of 80.07% was used. Simultaneously, gas chromatography with a thermal conductivity detector was performed for three consecutive days as a comparative example. The detection results are shown in the table below:

[0083] Table 2. Chromatographic nitrogen detection data

[0084]

[0085] Table 3. Chromatographic data for fluorine gas detection.

[0086]

[0087] In addition, the comparative example also used standard sample gas with a fluorine concentration of 19.93% and a nitrogen concentration of 80.07%, and conducted tests at four pressures: 0.100 MPa, 0.050 MPa, 0.018 MPa, and 0.004 MPa. Each pressure was tested three times, with 10 sets of data per test. To avoid randomness in the data, the gas source was turned off after each test, and the gas was replaced and retested. The results are shown in Table 4 below.

[0088] Table 4. Ultraviolet Spectrophotometry Test Data

[0089]

[0090] As shown in Table 4 above, using this detection device, the relative standard deviation is 0.016% to 0.111%, which is much less than 1%, and the deviation from the standard sample is 0.0011% to 0.0256%, indicating that the fluorine-nitrogen mixed gas fluorine detection device provided by this utility model has very good accuracy.

[0091] Example of chromatogram and results for gas chromatography analysis of fluorine-nitrogen mixtures using a thermal conductivity detector, such as... Figure 5 As shown in Tables 2 and 3. Figure 5 As can be seen, compared with chromatography, ultraviolet spectrophotometry has more obvious advantages in both stability and accuracy for the detection of fluoride concentration in fluoride-nitrogen mixtures.

[0092] The technical solution of this utility model is not limited to the specific embodiments described above. Without departing from the scope and spirit of the described embodiments, many modifications and changes will be obvious to those skilled in the art. Any technical modifications made within the spirit and principles of this utility model shall fall within the protection scope of this utility model.

Claims

1. A device for detecting fluorine gas in a fluorine-nitrogen mixture, characterized in that: The device includes a fluorine-nitrogen mixed gas sampling mechanism, a sample gas pretreatment mechanism, and an ultraviolet spectrophotometer connected in series. The fluorine-nitrogen mixed gas sampling mechanism includes a leak-proof housing, and a sampling pipeline, a displacement pipeline and an output pipeline disposed inside the leak-proof housing. The sampling pipeline, the displacement pipeline and the output pipeline are connected by a gas supply main pipe. A pressure sensor is installed on the gas supply main pipe. A vacuum pressure gauge and a pressure sensor are installed on the displacement pipeline. An outlet pressure gauge is installed on the output pipeline. 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. A pressure sensor is installed on the sample gas pipeline; The ultraviolet spectrophotometer includes an ultraviolet spectrophotometer, which has an independent sample cell and a reference cell. The sample cell and the reference cell are respectively connected to the sample gas pipeline and the reference gas pipeline of the sample gas pretreatment mechanism.

2. The device for detecting fluorine in a fluorine-nitrogen mixture according to claim 1, characterized in that: The sampling pipeline includes three parallel sampling lines with identical structures. Each sampling line is connected in series with a high-pressure manual diaphragm valve, a high-pressure regulating valve, and a sampling pneumatic valve. Each high-pressure manual diaphragm valve has a corresponding inlet at its front end, and the rear ends of the three sampling pneumatic valves are all centrally connected to the gas supply main pipe. Each sampling line is equipped with an inlet pressure gauge.

3. The device for detecting fluorine in a fluorine-nitrogen mixture according to claim 2, characterized in that: The replacement pipeline includes a vacuum pipeline and a replacement pipeline for nitrogen replacement of the sampling pipeline. The vacuum pipeline and the replacement pipeline are connected in parallel. A vacuum generator is connected to the vacuum pipeline, and 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 supply main pipeline through a vacuum pneumatic valve. A replacement check valve and a replacement pneumatic valve are connected in series on the replacement pipeline. A replacement port is provided at the front end of the replacement check valve, and the rear end of the replacement pneumatic valve is connected to the gas supply main pipeline. A vacuum pressure gauge and a pressure sensor are installed on the vacuum pipeline.

4. The device for detecting fluorine in a fluorine-nitrogen mixture according to claim 3, characterized in that: The output pipeline includes three parallel and identical output lines. Each output line is connected in series with an output check valve, a low-pressure regulating valve, and a regulating pneumatic valve. A nitrogen purging bypass is connected in parallel on one side of each output line. A purging check valve and a purging pneumatic valve are connected in series on the nitrogen purging bypass. Each purging check valve has a purging port at its front end. Each regulating pneumatic valve has a corresponding air outlet at its front end. The rear end of each output line is connected to the main gas supply line through a control pneumatic valve. Each output line is equipped with an outlet pressure gauge.

5. The device for detecting fluorine in a fluorine-nitrogen mixture according to claim 4, characterized in that: The sample gas pipeline includes a mixed gas manual diaphragm valve 1, a needle valve 1, a needle valve 2, a mixed gas manual diaphragm valve 2, and a needle valve 3 connected in series. A sample gas pressure gauge is installed on the pipeline between needle valve 1 and needle valve 2. The rear end of needle valve 3 is connected to the sample cell of an ultraviolet spectrophotometer, and a pressure sensor 3 is installed at the rear end of needle valve 3.

6. The apparatus for detecting fluorine in a fluorine-nitrogen mixture according to claim 5, characterized in that: The reference gas pipeline includes a nitrogen manual diaphragm valve, a reference pressure regulating valve, and a needle valve four connected in series. The rear end of the needle valve four is connected to the reference cell of the ultraviolet spectrophotometer.

7. The apparatus for detecting fluorine in a fluorine-nitrogen mixture according to claim 6, characterized in that: The nitrogen replacement pipeline is connected between the reference gas pipeline and the sample gas pipeline. The nitrogen replacement pipeline includes a replacement pressure regulating valve, a replacement manual diaphragm valve and a nitrogen filling check valve connected in series. 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 filling check valve is connected between the mixed gas manual diaphragm valve and the needle valve.

8. The apparatus for detecting fluorine in a fluorine-nitrogen mixture according to claim 1, characterized in that: 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, and the sample cell and the reference cell are two independent gas flow cells.

9. The apparatus for detecting fluorine in a fluorine-nitrogen mixture according to claim 1, characterized in that: The leak-proof housing is a sealed explosion-proof cabinet. The top of the explosion-proof cabinet is sealed with an exhaust pipe for centralized discharge of leaked gas, and the exhaust pipe is connected to the exhaust gas adsorption device.

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