Gas chromatograph and chromatographic analysis method for analyzing sulfide in fuel hydrogen

Abstract

The invention relates to a gas chromatograph and a chromatographic analysis method for analyzing sulfides in fuel hydrogen, the gas chromatograph comprises an electronic flow controller, a sample injection valve, a flow path selection valve and a plasma emission detector, two branches are arranged between the sample injection valve and the flow path selection valve, the first branch comprises a chromatographic column I, a cutting valve I and a chromatographic column II which are used for separating H2, CH4S and CS2 from sample gas, the second branch comprises a chromatographic column III, a cutting valve II and a chromatographic column IV which are used for separating fuel hydrogen, H2S and COS from the sample gas, and the plasma emission detector is used for quantitatively detecting CH4S, CS2, H2S and COS which are completely separated. Therefore, operation, use and maintenance are simple, only helium is used as carrier gas, and sensitivity is high.

Description

Technical Field

[0001] This invention relates to chromatography technology, and more specifically to a gas chromatograph and chromatographic analysis method for the analysis of sulfides in fuel hydrogen. Background Technology

[0002] Sulfides in fuel hydrogen, including CS2, CH4S, H2S, and COS, can poison fuel cell catalysts, causing irreversible degradation. Therefore, detecting sulfides in fuel hydrogen is a crucial indicator of its quality. Currently, the detection of sulfide impurities in fuel hydrogen generally employs a combination of methods. Two common configurations are as follows.

[0003] Option 1: Using a combination of gas chromatography (GC) and sulfur chemiluminescence detector (SCD), the advantage is that it is inexpensive and easy to operate; the disadvantage is that it can only measure total sulfides.

[0004] Option 2: Using a mass spectrometer detector (MSD). Its advantage lies in high detection accuracy; its disadvantages are high cost and high operator skill requirements. This option combines a helium ionization chromatograph, a flame ionization chromatograph (FICE), and a gas chromatograph-mass spectrometer (GC-MS), requiring multiple instruments to detect sulfide impurities in fuel hydrogen, resulting in high costs. The FICE requires H2 as a carrier gas, which is flammable and explosive, increasing the cost of safe operation and the difficulty of daily management. Because it involves multiple instruments such as the GC-MS, the skill requirements for operation and maintenance are also high, increasing labor costs.

[0005] The above methods integrate too many detectors in a single chromatogram to achieve the analysis and detection of all components; the sensitivity is relatively low, greater than 10 ppb; the operation is difficult and labor costs are high; the characteristics of low temperature separation are required to separate the main component from the analyte; and they are not suitable for industrial online continuous detection.

[0006] Therefore, an optimized detection and analysis solution is still needed. Summary of the Invention

[0007] To address the aforementioned problems, the present invention aims to provide a gas chromatograph and chromatographic analysis method for the analysis of sulfides in fuel hydrogen, which can be used for the analysis of trace (ppb level) sulfides in fuel hydrogen.

[0008] According to one aspect of the present invention, a gas chromatograph for analyzing sulfides in fuel hydrogen is provided, comprising: an electronic flow controller, an injection valve, a flow path selection valve, and a plasma emission detector, wherein the electronic flow controller is capable of controlling the carrier gas flow rate, and two branches are provided between the injection valve and the flow path selection valve, wherein the first branch includes a chromatographic column I, a cutting valve I, and a chromatographic column II, wherein the chromatographic column I is used to separate H2 and CH4S, CS2 from the sample gas from the injection valve, the cutting valve I is used to cut and vent the main components of the fuel hydrogen, and the chromatographic column II is used for further separation. The first branch consists of a chromatographic column III, a cutting valve II, and a chromatographic column IV. Column III separates the fuel hydrogen from the sample gas from the injection valve into fuel hydrogen and H2S and COS. Cutting valve II cuts and vents the main components of the fuel hydrogen. Column IV is used to further separate the remaining fuel hydrogen and H2S and COS. The chromatographic column IV is used to further separate the remaining fuel hydrogen into fuel hydrogen and H2S and COS. The chromatographic column IV is used to quantify the separated H2S and COS.

[0009] Preferably, the electronic flow controller uses helium as the carrier gas.

[0010] Preferably, the injection valve is a ten-way dual injection valve, and the cutting valve I, cutting valve II, and flow path selection valve are six-way gas diaphragm valves.

[0011] Preferably, chromatographic columns I, II, III, and IV are metal capillary chromatographic columns.

[0012] Preferably, the separation columns of chromatographic column II and chromatographic column IV are capable of completely separating CH4S, CS2, H2S and COS respectively at 45°C.

[0013] Preferably, the gas chromatograph for analyzing sulfides in fuel hydrogen further includes a signal processor and a display device.

[0014] According to another aspect of the present invention, a chromatographic analysis method for analyzing sulfides in fuel hydrogen is provided, implemented using the gas chromatograph described above for analyzing sulfides in fuel hydrogen, comprising the following steps:

[0015] The carrier gas flow rate is controlled by an electronic flow controller and injected through a ten-port dual injection valve. H2 and CH4S and CS2 are separated by chromatographic column I. The main component of fuel hydrogen is cut off and discharged by cutting valve I. Then, the fuel hydrogen that is not completely cut off is separated again by chromatographic column II, and CH4S and CS2 are further separated. The completely separated CH4S and CS2 are quantitatively detected by a plasma emission detector.

[0016] The carrier gas flow rate is controlled by an electronic flow controller and injected through an injection valve. Column III separates the fuel hydrogen from H2S and COS. Cutting valve II removes the main fuel hydrogen component, and column IV further separates any remaining fuel hydrogen, and then further separates H2S and COS. The completely separated H2S and COS are then quantitatively detected using an inductively coupled plasma atomic emission spectrometer (ICP-AES).

[0017] The carrier gas used in the electronic flow controller is helium with a purity of ≥99.999%.

[0018] The temperature of each chromatographic column is kept constant during operation.

[0019] Preferably, the chromatographic analysis method for analyzing sulfides in fuel hydrogen further includes the following steps:

[0020] S1, System Leak Detection: Observe the signal value of the leak detection signal channel of the plasma emission detector. If it reaches within ±20% of the reference value, it is considered that the gas path system of the gas chromatograph has been purged clean and there is no leak.

[0021] Preferably, the chromatographic analysis method for analyzing sulfides in fuel hydrogen further includes the following steps:

[0022] S3, Standard Gas Detection: Confirm the peak width and retention time of CH4S, CS2, H2S, and COS based on the standard gas, and pre-set the integration windows for these four components. The standard gas configuration concentrations are: 5ppm CH4S, 5ppm CS2, 5ppm H2S, and 5ppm COS. The high-concentration sulfide standard gas is diluted to 200ppb using a dilution device.

[0023] Preferably, the chromatographic analysis method for analyzing sulfides in fuel hydrogen further includes the following steps: Sample pretreatment: using a 316L single-stage pressure reducing valve, the sample gas pressure is reduced to 10 psig and then introduced into the gas chromatograph. The sample gas flow rate is 100 sccm, and the sampling volume is 0.906 ml. Sample analysis: using the sample gas to purge the quantitative loop at a set flow rate for a predetermined time, the sample gas is continuously introduced into the gas chromatograph without interruption during analysis. The gas chromatograph is an autosampler, and the carrier gas flow rate is 31.0 sccm.

[0024] According to the present invention, a chromatographic method for analyzing impurities in sulfides is established. Using a highly integrated gas chromatograph, all the above analytical requirements can be met, demonstrating significant technological advantages. Compared with existing technologies, it is simple to operate and has low cost; its industrial design simplifies operation, use, and maintenance; it only requires helium as the carrier gas, without introducing any additional hazardous sources. The current method is selective, further reducing background interference and thus achieving higher sensitivity, perfectly solving current application challenges. Attached Figure Description

[0025] Figure 1 The overall architecture of a gas chromatograph for determining the concentration of sulfides in fuel hydrogen is shown.

[0026] Figure 2 The standard gas spectrum is shown (CH4S, CS2, H2S, COS equilibrium gas helium). Detailed Implementation

[0027] Exemplary embodiments of the present invention will now be described in detail with reference to the accompanying drawings. The exemplary embodiments described below and illustrated in the drawings are intended to teach the principles of the invention, enabling those skilled in the art to implement and use the invention in various environments and for various applications. Therefore, the scope of protection of the present invention is defined by the appended claims, and the exemplary embodiments are not intended, and should not be considered, a limiting description of the scope of protection of the present invention. Furthermore, for ease of description, the dimensions of the various parts shown in the drawings are not necessarily drawn to actual scale. Orientations or positional relationships described in the drawings are based on the orientations or positional relationships shown in the drawings and are only for the purpose of facilitating the description of the present invention and simplifying the description, and are not intended to indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of the present invention. Unless otherwise specifically stated, the order and numerical values ​​of the components and assembly steps set forth in the embodiments do not limit the scope of the present invention. Moreover, any numerical range stated herein is intended to include all sub-ranges contained therein, and a numerical range expressed as "value A to value B" refers to a range including endpoint values ​​A and B. Those skilled in the art will understand that the terms "Sn," "the nth," and "step" in this invention are used only to distinguish different steps, devices, or modules, and do not represent any specific technical meaning, nor do they indicate a necessary logical order between them. For example, two steps can be interchanged or performed in parallel.

[0028] <Overall Composition>

[0029] According to embodiments of the present invention, a gas chromatograph is provided for the analysis of sulfides in fuel hydrogen (also known as fuel hydrogen), such as... Figure 1 As shown, it includes:

[0030] The electronic flow controller 1 (EPC) for automatically controlling the flow rate of the carrier gas has the working principle of sensing changes in the flow rate or flow rate of the fluid and triggering internal mechanical or electronic mechanisms to change the state of the switch. The mechanical type relies on the fluid-driven components to achieve the switching state, while the electronic type uses sensors and electrical signals for control.

[0031] The high-precision gas diaphragm valves include a 10-way dual-inlet valve 2, a 6-way cutting valve I 4, a 6-way cutting valve II 7, and a 6-way flow path selection valve 9. The valves open and close through the elastic deformation of the diaphragm. The packingless sealing design avoids media contamination and vacuum leakage, achieving a zero-leakage sealing effect. They are suitable for scenarios with high requirements for media purity and sealing accuracy.

[0032] Chromatographic columns in the form of metal capillary columns are classified as I-3, II-5, III-6, and IV-8. Chromatography is a separation and analysis method, and separation is the core; therefore, the chromatographic column, which performs the separation function, is the heart of the chromatographic system. The requirements for chromatographic columns include high column efficiency, good selectivity, and fast analysis speed.

[0033] The plasma emission detector 10 (PED) is used for the detection of sulfides in fuel hydrogen. Its core component is a quartz flow cell with parallel electrodes arranged on both sides. A high-frequency, high-voltage alternating electric field is applied to the flow cell through these electrodes, causing the gas within the cell to form plasma. Different components separated by the chromatographic column are carried by the carrier gas and sequentially enter the flow cell, where they form plasma. Plasma formed from different gases emits light of different spectra, and the light intensity is related to the gas concentration. Therefore, by acquiring the intensity of the light signal at a characteristic wavelength, the concentration of the corresponding analyte gas can be determined.

[0034] The signal processor 11 is an electronic device used to receive, process, analyze and convert signals. Its core function is to perform filtering, amplification, demodulation and encoding of input analog or digital signals through algorithms and circuit design, and finally output a signal form that meets specific requirements.

[0035] Display device 12 is a display tool that displays certain electronic documents onto a screen through a specific transmission device. It can be divided into cathode ray tube displays (CRT), plasma displays (PDP), liquid crystal displays (LCD), as well as LED displays, 3D displays, etc.

[0036] In this gas chromatograph configuration, the electronic flow controller 1 controls the carrier gas flow rate. The ten-port dual injection valve 2 enables two sequential injections. The first injection sample gas is separated, cut, and then separated again via the first branch's column I3, six-port cutting valve I4, and column II5. It is then sent to the plasma emission detector 10 for detection via the six-port flow path selection valve 9. The signal is then processed and the results are displayed via the signal processor 11 and the display device 12. The second injection sample gas is separated, cut, and then separated again via the second branch's column III6, six-port cutting valve II7, and column IV8. It is then sent to the plasma emission detector 10 for detection via the six-port flow path selection valve 9. The signal is then processed and the results are displayed via the signal processor 11 and the display device 12.

[0037] Here, the first branch and the second branch share the same ten-way dual injection valve 2 and six-way flow path selection valve 9, which simplifies the gas path structure.

[0038] The carrier gas used by the electronic flow controller 1 is high-purity helium with a purity of ≥99.999% (5N) and a carrier gas flow rate of 31.0 sccm.

[0039] The 10-port dual injection valve 2 constitutes the injection system. For example, a pneumatic 10-port diaphragm valve can be used, brand AnalyticalFlow Products, model ELDV1-10-16LT-0005, injection method is automatic injection; quantitative loop volume: 0.906ml;

[0040] The first branch is used to separate and detect the components: CH4S and CS2. The chromatographic columns in the first branch can be either RTX-1701 30M or RTX-1 60M metal capillary columns.

[0041] The second branch is used for the separation and detection of components: H2S and COS. The chromatographic columns in the second branch can be either RTX-1 30M or RT-U-Bond 30M metal capillary columns.

[0042] Detector: Plasma emission detector 10 can be a plasma emission detector (PED), brand: LDetek, model PlasmaDetek2.

[0043] <Operation Steps and Process Parameters>

[0044] According to an embodiment of the present invention, a chromatographic analysis method for analyzing sulfides in fuel hydrogen is provided, which can be implemented using the gas chromatograph described above for analyzing sulfides in fuel hydrogen, and includes the following steps:

[0045] S1, System Leak Detection: The plasma emission detector 10 has a leak detection signal channel. Observe the signal value of this channel. If it reaches within ±20% of the reference value, it is considered that the gas chromatograph gas path system has been purged clean and there is no leak.

[0046] S2, Chromatographic Separation: After the sample gas is separated from hydrogen and other impurity gases on the pre-column, it enters the subsequent separation column for further separation. In this invention, the packed separation column can completely separate CH4S, CS2, H2S, and COS at 45°C. All chromatographic columns maintain a constant temperature during operation.

[0047] S3, Standard Gas Detection: Based on the retention times of the CH4S, CS2, H2S, and COS peaks obtained from standard gas detection, this retention time is set as the integration window time for the workstation for the four components. After determining the integration window event, the workstation will automatically integrate the peaks within that integration window time during subsequent analyses. A corresponding calibration curve is established based on the peak area and standard gas concentration measured from the analysis of the standard gas. Thus, the concentration of each sulfide impurity is obtained from the calibration curve by calculating the peak areas of the CH4S, CS2, H2S, and COS chromatographic peaks obtained when testing fuel hydrogen.

[0048] The standard gas, for example, comes from the manufacturer: Dalian Date. The prepared concentration is: 5ppm CH4S, 5ppm CS2, 5ppm H2S, 5ppm COS, and a helium balance. A dilution device is required to dilute the high-concentration sulfide standard gas to 200ppb.

[0049] S4, Sample Pretreatment: Using a 316L single-stage pressure reducing valve, reduce the sample gas pressure to 10 psig before introducing it into the gas chromatograph. Sample gas flow rate: 100 sccm, sampling volume: 0.906 ml. The sample tubing is made of 316L material, and the connectors use VCR or compression fittings to avoid leakage or dead volume in the sample tubing.

[0050] S5, Sample Analysis: Purge the quantitative loop with sample gas at the set flow rate for normal analysis for at least 30 minutes. The sample gas source is a gas cylinder or a sampling point on the production line. During analysis, the sample gas should be continuously supplied to the gas chromatograph without interruption to avoid air contamination of the quantitative loop. The gas chromatograph is an autosampler; once the gas chromatograph is in normal working order, press the Start button on the software to begin analysis.

[0051] S6, Quantitative Calculation: Based on the peak areas of CH4S, CS2, H2S, and COS obtained from standard gas analysis, these four components are calibrated. When analyzing the sample, the concentration (ppmv) of sulfides in the sample is calculated using the peak area.

[0052] <Performance Verification Data>

[0053] S7, Repeatability: Perform 7 consecutive analyses of the standard gas using the range point concentration, calculate its standard deviation (RSD), and require RSD ≤ 3%.

[0054] Limit of detection: The limit of detection for each component is calculated based on three times the signal-to-noise ratio and the peak height of the standard gas at the range point concentration. LDL (CH4S, CS2, H2S, COS) = 2 ppb.

[0055] More specifically, in step S2, during chromatographic separation, the carrier gas flow rate is controlled by the electronic flow controller 1, and the first sample is injected through the ten-port dual injection valve 2. H2 and CH4S and CS2 are separated by the first RXT-1 column I3. The main component of fuel hydrogen is cut off and discharged by the six-port cutting valve I4. Then, the fuel hydrogen that is not completely cut off is separated again by the second RXT-1 column II5, and CH4S and CS2 are further separated. The completely separated CH4S and CS2 are quantitatively detected by the plasma emission detector 10.

[0056] The carrier gas flow rate is controlled by an electronic flow controller 1. It is injected a second time by a ten-port dual injection valve 2. The fuel hydrogen and H2S and COS are separated by a third RXT-1 column III 6. The main component of the fuel hydrogen is cut off and discharged by a six-port cutting valve II 7. Then, the fuel hydrogen that is not completely cut off is separated again by a fourth RT-U-BOND column IV 8, and H2S and COS are further separated. The completely separated H2S and COS are quantitatively detected by an inductively coupled plasma emission detector 10.

[0057] <Technical Effects>

[0058] According to the present invention, a gas chromatography scheme for the analysis and detection of 1 ppb-level sulfides can be realized without the need for additional components for enrichment.

[0059] Compared with existing technologies, the technical solution of this invention is simple to operate and low in cost; it has a high degree of integration, with one set of equipment solving the overall problem; it features an industrial design, making operation, use, and maintenance simple; and it only requires helium as the carrier gas, without introducing any other hazardous sources. The plasma emission detector itself is selective, which can reduce background interference to a greater extent, thereby achieving higher sensitivity and perfectly solving current application challenges.

[0060] Although the invention has been described with reference to various specific embodiments, it should be understood that modifications can be made within the spirit and scope of the described inventive concept. Therefore, it is intended that the invention be limited to the described embodiments but will have the full scope defined by the language of the appended claims.

Claims

1. A gas chromatograph for analyzing sulfides in fuel hydrogen, characterized in that, include: The system includes an electronic flow controller (1), an injection valve (2), a flow path selection valve (9), and a plasma emission detector (10). The electronic flow controller (1) controls the carrier gas flow rate. Two branches are provided between the injection valve (2) and the flow path selection valve (9). The first branch includes a chromatographic column I (3), a cutting valve I (4), and a chromatographic column II (5). The chromatographic column I (3) is used to separate H2 and CH4S and CS2 from the sample gas from the injection valve (2). The cutting valve I (4) is used to cut and discharge the main components of the fuel hydrogen. The chromatographic column II (5) is used to further separate the fuel hydrogen that has not been completely cut. CH4S and CS2 are further separated. The plasma emission detector (10) is used to quantitatively detect the completely separated CH4S and CS2. The second branch includes column III (6), cutting valve II (7), and column IV (8). Column III (6) is used to separate fuel hydrogen and H2S and COS from the sample gas from the injection valve (2). Cutting valve II (7) is used to cut and discharge the main component of fuel hydrogen. Column IV (8) is used to separate the fuel hydrogen that has not been cut cleanly again and to further separate H2S and COS. The plasma emission detector (10) is used to quantitatively detect the completely separated H2S and COS.

2. The gas chromatograph for analyzing sulfides in fuel hydrogen according to claim 1, characterized in that, The electronic flow controller (1) uses helium as the carrier gas.

3. The gas chromatograph for analyzing sulfides in fuel hydrogen according to claim 1, characterized in that, The injection valve (2) is a ten-way double injection valve, and the cutting valve I (4), cutting valve II (7), and flow path selection valve (9) are six-way gas diaphragm valves.

4. The gas chromatograph for analyzing sulfides in fuel hydrogen according to claim 1, characterized in that, Columns I (3), II (5), III (6), and IV (8) are metal capillary columns.

5. The gas chromatograph for analyzing sulfides in fuel hydrogen according to claim 4, characterized in that, The separation columns of each chromatographic column II (5) and chromatographic column IV (8) can completely separate CH4S, CS2, H2S and COS respectively at 45℃.

6. The gas chromatograph for analyzing sulfides in fuel hydrogen according to claim 1, characterized in that, It also includes a signal processor (11) and a display device (12).

7. A chromatographic method for analyzing sulfides in fuel hydrogen, characterized in that, This is achieved using the gas chromatograph for sulfide analysis in fuel hydrogen as described in any one of claims 1 to 6, comprising the following steps: The carrier gas flow rate is controlled by an electronic flow controller (1), and the sample is injected through a ten-way dual injection valve (2). H2 and CH4S and CS2 are separated by chromatographic column I (3). The main components of fuel hydrogen are cut off and discharged by cutting valve I (4). Then, the fuel hydrogen that is not completely cut off is separated again by chromatographic column II (5), and CH4S and CS2 are further separated. The completely separated CH4S and CS2 are quantitatively detected by plasma emission detector (10). The carrier gas flow rate is controlled by an electronic flow controller (1), and the sample is injected through the injection valve (2). The fuel hydrogen and H2S and COS are separated by chromatographic column III (6). The main component of the fuel hydrogen is cut off and discharged by the cutting valve II (7). Then, the fuel hydrogen that is not completely cut off is separated again by chromatographic column IV (8), and H2S and COS are further separated. The completely separated H2S and COS are quantitatively detected by an inductively coupled plasma emission detector (10). The carrier gas used in the electronic flow controller (1) is helium with a purity ≥99.999%. The temperature of each chromatographic column is kept constant during operation.

8. The chromatographic analysis method for analyzing sulfides in fuel hydrogen according to claim 7, characterized in that, It also includes the following steps: S1, System Leak Detection: Observe the signal value of the leak detection signal channel of the plasma emission detector (10). If it reaches within ±20% of the reference value, it is considered that the gas path system of the gas chromatograph has been purged clean and there is no leak.

9. The chromatographic analysis method for analyzing sulfides in fuel hydrogen according to claim 7, characterized in that, It also includes the following steps: S3, Standard Gas Detection: Confirm the peak width and retention time of CH4S, CS2, H2S, and COS based on the standard gas, and pre-set the integration windows for these four components. The standard gas configuration concentrations are: 5ppm CH4S, 5ppm CS2, 5ppm H2S, and 5ppm COS. The high-concentration sulfide standard gas is diluted to 200ppb using a dilution device.

10. The chromatographic analysis method for analyzing sulfides in fuel hydrogen according to claim 7, characterized in that, It also includes the following steps: Sample pretreatment: After reducing the sample gas pressure to 10 psig using a single-stage pressure reducing valve, the sample gas was introduced into the gas chromatograph. The sample gas flow rate was 100 sccm, and the sampling volume was 0.906 ml. Sample analysis: Sample gas is used to purge the quantitative loop at a set flow rate for a predetermined time. During analysis, the sample gas is continuously introduced into the gas chromatograph without interruption. The gas chromatograph is an autosampler. Carrier gas flow rate: 31.0 sccm.

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