Method and system for automatically reducing carrier gas consumption of gas chromatograph through DCS (Distributed Control System)

Abstract

The invention discloses a method and a system for automatically reducing carrier gas consumption of a gas chromatograph through a DCS (Distributed Control System), aiming at the problem of poor effect of the existing method for reducing helium consumption, the carrier gas consumption of the gas chromatograph is automatically reduced by modifying a carrier gas supply path of the gas chromatograph, adding an electromagnetic valve and a logic program for controlling the electromagnetic valve to automatically switch, and automatically switching a double-pressure gas supply mode through the DCS. In a standby state, the helium pressure is reduced from 600 kPa to 200 kPa, so that the total carrier gas consumption is reduced to 30% of that of a traditional mode, and the expensive helium cost is remarkably saved; meanwhile, the continuous supply of the carrier gas avoids the risks of dry burning of a purifier, pollution of a detector and baseline drift caused by a traditional power-off and gas-off mode, the equipment safety and the detection precision are guaranteed, and frequent purging verification is not needed; the system realizes intelligent identification of the working state and automatic switching of the electromagnetic valve, improves the automation level and the operation continuity, can respond to the high-frequency detection requirement under the abnormal working condition at any time, and has remarkable economic benefits and industrial application value.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of industrial gas analysis, and particularly relates to a method and system for automatically reducing carrier gas consumption of a gas chromatograph through a DCS. BACKGROUND

[0002] In the deep cooling production of air industry, the high concentration oxygen environment of air separation device, the accumulation of methane, acetylene and other hydrocarbons reaches a certain concentration, which can cause explosion and fire accidents. At the same time, acetylene is easy to form solid precipitates under low temperature conditions, which can block the pipeline or equipment, affect the operation efficiency of the air separation device, and even cause equipment damage. In addition, the air separation device needs to produce high-purity gas products, and if too much methane or acetylene is mixed into the products, it will affect the quality of the final products. Therefore, the content of hydrocarbons in the air separation device must be controlled, and the premise of control is to accurately detect the content of hydrocarbons.

[0003] At present, the detectors of the gas chromatograph for detecting hydrocarbons include flame ionization detector FID, thermal conductivity detector TCD, pulse discharge helium ionization detector PDHID and the like. Among them, the working principle of the pulse discharge helium ionization detector PDHID is that a stable plasma is generated in pure helium gas through high-voltage pulse discharge, forming high-energy metastable helium atoms and free electrons, and the ionized electrons and ions migrate to the collecting electrode under the action of the electric field, forming a micro-current signal. The signal size is proportional to the concentration of the measured medium, and can detect trace impurities such as methane, acetylene and the like as low as ppb level.

[0004] At present, the gas chromatograph is used to detect the content of methane, acetylene and total hydrocarbons in the main cold liquid oxygen in the air separation device. The operator clicks the "detection" button on the DCS (Distributed Control System) operation station picture every 8 hours to send a detection pulse command to the gas chromatograph. It takes about 25 minutes from the start of detection to the analysis result data. The analysis result data is transmitted to the DCS control system operation station picture through a 4-20mA analog signal for display and alarm. At the same time, if the detection result is abnormal, the operator adjusts the working condition to reduce the content of methane, acetylene and total hydrocarbons in the main cold liquid oxygen in the air separation device, and increases the analysis frequency until the detection data is normal. The helium gas used by the gas chromatograph is steel bottle helium, which is reduced by a pressure reducing valve from 15Mpa pressure to 600kpa, and is used by the gas chromatograph.

[0005] In order to save the consumption of helium, the gas chromatograph is powered off and the bottled helium is closed during the period when the gas chromatograph does not perform detection and analysis, so as to reduce the consumption of helium. However, this method has many disadvantages: ① Before shutting off the helium gas, the purifier needs to be powered off and cooled down. It takes 2 to 3 hours for the temperature to drop from the working temperature to room temperature. The helium gas can only be shut off after the purifier has cooled down to room temperature, otherwise the purifier will be damaged by overheating.

[0006] ② Before using the gas chromatograph again, helium gas should be turned on for at least 2 hours in advance to purge the detector and purifier.

[0007] ③ After the helium gas is turned off, air can easily enter the detector and purifier, causing contamination. Improper operation can also damage the gas chromatograph equipment.

[0008] ④ Resuming gas supply after stopping it will cause baseline changes in the chromatogram, affecting the detection accuracy of the gas chromatograph. Therefore, after purging the detector and purifier with helium, the entire gas chromatograph system needs to be recalibrated using standard gas.

[0009] In conclusion, the current method consumes over 6 hours during the 7.5-hour periods when the gas chromatograph is not performing analysis, involving purifier cooling, detection, pre-purifier purging, and gas chromatograph calibration. Helium is consumed during all of these periods, while the actual time without helium use is less than 1.5 hours. Therefore, the method is not effective in reducing helium consumption and carries the risk of damaging the gas chromatograph. It also increases the consumption of standard calibration gas. Summary of the Invention

[0010] The purpose of this invention is to provide a method and system for automatically reducing the carrier gas consumption of a gas chromatograph using a DCS (Distributed Control System). By modifying the carrier gas supply pipeline of the gas chromatograph, adding solenoid valves and pressure reducing valves, and developing an automatic control program for the DCS, the carrier gas supply pressure is automatically switched between the gas chromatograph in detection and analysis mode and in standby mode. This ensures that the amount of helium entering the gas chromatograph and purifier is sufficient for normal analysis, while also providing the minimum amount of helium required to maintain positive pressure in the gas chromatograph detector and prevent dry burning of the purifier in standby mode, thereby reducing the total helium consumption.

[0011] To solve the above problems, the technical solution of the present invention is as follows: A method for automatically reducing carrier gas consumption in a gas chromatograph using a DCS (Distributed Control System) includes the following steps: A carrier gas supply pipeline is provided, which includes a first supply branch and a second supply branch connected in parallel, wherein the first supply branch provides carrier gas at a first pressure and the second supply branch provides carrier gas at a second pressure lower than the first pressure. A first solenoid valve and a second solenoid valve are respectively installed on the first gas supply branch and the second gas supply branch. The working status information of the gas chromatograph is acquired through the DCS control system, and the working status includes detection and analysis status and standby and test status. When the working state is the detection and analysis state, the DCS control system controls the first solenoid valve to open and the second solenoid valve to close, and supplies carrier gas at the first pressure to the detector and purifier of the gas chromatograph through the first gas supply branch. When the working state is standby and test state, the DCS control system controls the first solenoid valve to close and the second solenoid valve to open, and supplies carrier gas at the second pressure to the detector and purifier through the second gas supply branch to maintain the positive pressure of the detector and prevent the purifier from dry burning.

[0012] According to an embodiment of the present invention, when switching the state of the first solenoid valve and the second solenoid valve, the DCS control system performs the following timing protection operation: When switching from standby and testing state to detection and analysis state, the first solenoid valve is opened first, and the second solenoid valve is closed after a first preset time delay. When switching from the detection and analysis state to the standby test state, the second solenoid valve is opened first, and the first solenoid valve is closed after a second preset time delay.

[0013] According to one embodiment of the present invention, the method further includes: Set up a manual / automatic detection mode switching function on the operator station screen of the DCS control system; When in manual mode, the operator manually issues a detection command to start the detection and analysis process; When in automatic mode, the DCS control system automatically triggers the detection and analysis status according to preset logic.

[0014] A carrier gas supply control system for a gas chromatograph includes: Carrier gas source; The first and second gas supply branches are connected in parallel. The inlet of both branches is connected to the carrier gas source, and the outlet is connected to the detector and purifier of the gas chromatograph. The first pressure reducing valve and the first solenoid valve are installed on the first gas supply branch to provide carrier gas at the first pressure. The second pressure reducing valve and the second solenoid valve installed on the second gas supply branch are used to provide carrier gas at a second pressure lower than the first pressure. The DCS control system is electrically connected to the first solenoid valve and the second solenoid valve, and the DCS control system is configured to: Acquire the working status information of the gas chromatograph, including detection and analysis status and standby and test status; When the working state is detection and analysis state, the first solenoid valve is opened and the second solenoid valve is closed. When the working state is standby and test state, the first solenoid valve is closed and the second solenoid valve is opened.

[0015] According to one embodiment of the present invention, the first pressure does not exceed 600 kPa, and the second pressure does not exceed 200 kPa.

[0016] According to an embodiment of the present invention, the DCS control system includes: The status determination module is used to receive detection command pulse signals from the DCS operator station or automatically generate detection trigger signals according to a preset time interval to determine the working status. The solenoid valve control module is used to send switching control signals to the first solenoid valve and the second solenoid valve. The timing protection module is used to perform a delay control of opening first and then closing when switching the state of the solenoid valve to prevent the detector and purifier from running out of gas.

[0017] According to one embodiment of the present invention, the DCS control system further includes an operator station screen display module, which is configured as follows: Displays the real-time operating status and analysis results of the gas chromatograph; Provides manual / automatic detection mode switching function; In manual mode, it receives detection commands manually issued by the operator.

[0018] According to one embodiment of the present invention, the system further includes a pressure monitoring device, which is respectively installed at the outlet end of the first gas supply branch and the second gas supply branch, for real-time monitoring of the carrier gas pressure supplied to the gas chromatograph and feeding back the pressure signal to the DCS control system.

[0019] According to one embodiment of the present invention, the carrier gas is helium, and the gas chromatograph is an industrial online gas chromatograph equipped with a pulsed discharge helium ionization detector, used to detect the hydrocarbon content in the main cooling liquid oxygen of the air separation unit.

[0020] Because the present invention adopts the above technical solution, it has the following advantages and positive effects compared with the prior art: This invention discloses a method for automatically reducing carrier gas consumption in a gas chromatograph using a DCS system. Addressing the issue of ineffective existing methods for reducing helium consumption, this method modifies the carrier gas (i.e., helium) supply path of a pulsed discharge helium ionization (PDHID) gas chromatograph by adding a solenoid valve and a logic program for automatically switching the solenoid valve. The DCS automatically switches to a dual-pressure supply mode, reducing the helium pressure from 600 kPa to 200 kPa in standby mode. This reduces total carrier gas consumption to 30% of the traditional method (standby consumption is only 20%), significantly saving on expensive helium costs. Simultaneously, the continuous supply of carrier gas avoids the risks of purifier dry burning, detector contamination, and baseline drift caused by power outages and gas interruptions, ensuring equipment safety and detection accuracy, and eliminating the need for frequent purging calibrations. The system achieves intelligent identification of operating status and automatic switching of solenoid valves, improving automation and operational continuity. It can respond to high-frequency detection needs under abnormal operating conditions at any time, offering significant economic benefits and industrial application value. Attached Figure Description

[0021] Figure 1 This is a schematic diagram of the gas path of a conventional PDHID gas chromatograph in one embodiment of the present invention; Figure 2 This is a schematic diagram of the control of an improved gas chromatograph according to an embodiment of the present invention; Figure 3 This is a schematic diagram of the detection logic of the DCS control system in one embodiment of the present invention. Detailed Implementation

[0022] The following detailed description, in conjunction with the accompanying drawings and specific embodiments, provides a method and system for automatically reducing carrier gas consumption in a gas chromatograph using a DCS (Distributed Control System). The advantages and features of the invention will become more apparent from the following description and claims.

[0023] Please refer to Figure 1 Helium is an essential gas used in gas chromatography (GC) analysis. During detection and analysis, helium carries the sample gas into the detector for analysis and also serves as a background gas. In standby mode, helium is needed to purge the detector and column to prevent air contamination of the detector and column due to gas supply interruption.

[0024] The purifier removes impurities from rare gases by heating the getter alloy. While the helium purity in gas cylinders is typically 99.999%, the purifier can achieve a purity exceeding 99.9999%. Higher helium purity results in higher detection accuracy for the gas chromatograph. Furthermore, the purifier must not be de-energized while in operation; otherwise, it will be damaged. Therefore, as long as the purifier is powered on, helium must be supplied to the PDHID gas chromatograph even when not performing analysis to prevent damage.

[0025] In other words, gas chromatographs require the use of helium gas throughout the entire process of detection and analysis, as well as in standby and test-ready states.

[0026] To reduce helium consumption, this embodiment improves the gas path control of existing gas chromatographs. It can automatically switch the carrier gas supply pressure between the gas chromatograph in detection and analysis mode and the gas chromatograph in standby mode. This ensures that the amount of helium entering the gas chromatograph and purifier can meet the needs of normal analysis, while also providing the minimum amount of helium required to maintain the positive pressure of the gas chromatograph detector and prevent the purifier from dry burning in standby mode, thereby achieving the goal of reducing the total helium consumption.

[0027] The improved gas path control of the gas chromatograph, namely the gas chromatograph carrier gas supply control system, includes: Carrier gas source; The first and second gas supply branches are connected in parallel. The inlet of both branches is connected to the carrier gas source, and the outlet is connected to the detector and purifier of the gas chromatograph. The first pressure reducing valve and the first solenoid valve are installed on the first gas supply branch to provide carrier gas at the first pressure. The second pressure reducing valve and the second solenoid valve installed on the second gas supply branch are used to provide carrier gas at a second pressure lower than the first pressure. The DCS control system, electrically connected to the first and second solenoid valves, is configured as follows: Acquire the working status information of the gas chromatograph, including detection and analysis status and standby and test status; When the working state is detection and analysis state, the first solenoid valve is opened and the second solenoid valve is closed. When the working state is standby and test state, the first solenoid valve is closed and the second solenoid valve is opened.

[0028] The carrier gas is helium, and the gas chromatograph is an industrial online gas chromatograph equipped with a pulsed discharge helium ionization detector, used to detect the hydrocarbon content in the main refrigerated liquid oxygen of the air separation unit. The first pressure does not exceed 600 kPa, and the second pressure does not exceed 200 kPa.

[0029] Furthermore, the DCS control system includes: The status determination module is used to receive detection command pulse signals from the DCS operator station or automatically generate detection trigger signals according to a preset time interval to determine the working status. The solenoid valve control module is used to send switching control signals to the first solenoid valve and the second solenoid valve. The timing protection module is used to perform a delay control of opening first and then closing when switching the state of the solenoid valve to prevent the detector and purifier from running out of gas.

[0030] The DCS control system also includes an operator station display module, which is configured as follows: Displays the real-time operating status and analysis results of the gas chromatograph; Provides manual / automatic detection mode switching function; In manual mode, it receives detection commands manually issued by the operator.

[0031] Furthermore, the system also includes a pressure monitoring device, which is installed at the outlet of the first gas supply branch and the second gas supply branch, respectively, to monitor the carrier gas pressure supplied to the gas chromatograph in real time and feed the pressure signal back to the DCS control system.

[0032] Specifically, based on the working principle of the gas chromatograph, the helium requirement differs between the detection and analysis modes and the standby mode. In the detection and analysis mode, helium carries the sample gas into the detector for analysis and also serves as the background gas, requiring a relatively large amount of helium. In the standby mode, only the amount of helium needed to maintain the positive pressure of the detector and prevent the purifier from drying out is required. Therefore, the helium consumption can be controlled by changing the helium supply pressure to the gas chromatograph.

[0033] Please refer to Figure 2 The pipeline from the helium cylinder outlet was split into two. One line went into the original pressure reducing valve R1, maintaining the outlet pressure of R1 at the original set value of 600 kPa to provide working helium for the gas chromatograph in analytical detection mode. The other line went into the newly added pressure reducing valve R2, providing helium to maintain the positive pressure of the detector and prevent the purifier from dry burning in the standby mode. After repeated on-site adjustments and tests, it was determined that setting the outlet pressure of R2 to 200 kPa was more appropriate, which can provide the amount of helium to maintain the positive pressure of the detector and prevent the purifier from dry burning, while also maintaining a certain safety margin.

[0034] After modifying the gas supply lines of the gas chromatograph in analytical and standby modes and determining the corresponding pressures, an actuator capable of remotely switching the gas supply lines is needed to avoid equipment damage caused by human error in switching gas lines. In this case, a solenoid valve is a more economical and stable actuator.

[0035] A solenoid valve XV1 is added to the pipeline before the inlet of pressure reducing valve R1 for remote control of the helium supply during normal analysis and testing. A solenoid valve XV2 is added to the pipeline before the inlet of R2 for remote control of the helium supply during standby. The opening and closing of the solenoid valve cores are controlled by energizing and de-energizing the coils of solenoid valves XV1 and XV2, thereby switching the helium supply path.

[0036] Please refer to Figure 3 This embodiment adds a logic program to the DCS to automatically perform analysis and detection every 8 hours, while retaining the original function of the operator manually issuing detection commands on the DCS workstation. The logic program automatically controls the opening and closing of the solenoid valve, enabling the supply of helium at normal pressure to the gas chromatograph before analysis and detection in automatic cyclic detection mode. In standby mode after analysis and detection, low-pressure helium is supplied to the gas chromatograph to purge and protect the purifier and detector, thereby reducing the consumption of carrier gas, i.e., helium.

[0037] from Figure 3 As can be seen from the diagram, in each 8-hour cycle, when the program countdown reaches 7 hours, that is, 30 minutes before the gas chromatograph begins its actual detection, solenoid valve XV1 is opened to open gas path 1 for normal detection helium (pressure 600 kPa). After a 1-second delay, solenoid valve XV2 is closed, and then gas path 2 for low-pressure helium (pressure 200 kPa) used in standby mode is cut off. The gas chromatograph detector is then purged for 30 minutes to stabilize the baseline. After that, the gas chromatograph officially enters the detection state, and the analysis and detection state lasts for 25 minutes, while helium at 600 kPa pressure is continuously supplied for 1 hour. Five minutes after the analysis and detection state ends, solenoid valve XV2 is opened to open gas path 2 for helium used in standby mode. After a 1-second delay, solenoid valve XV1 is closed, cutting off gas path 1 for normal detection helium. The aforementioned two 1-second delays are to ensure that when switching solenoid valves, the previously closed solenoid valve is opened first, and then the previously open solenoid valve is closed, in a specific order. This avoids the situation where two solenoid valves close simultaneously at the same time, which could cause damage to the gas chromatograph purifier and detector due to gas interruption.

[0038] In addition, operators can switch between manual and automatic detection modes on the DCS operator station screen. When the detection mode is in manual mode, the operator can manually issue detection commands to deal with detection needs in abnormal situations.

[0039] This embodiment modifies the carrier gas (i.e., helium) supply path of a pulsed discharge helium ionization (PDHID) gas chromatograph by adding a solenoid valve and a logic program to automatically switch the solenoid valve. This allows for the supply of carrier gas at different pressures to the gas chromatograph under different conditions, thereby reducing carrier gas consumption. Statistics show that after implementation, total helium consumption is only 30% of the original, with helium consumption in standby mode reduced to only 20%, significantly reducing carrier gas consumption and resulting in substantial economic benefits.

[0040] Accordingly, this embodiment also provides a method for automatically reducing the carrier gas consumption of a gas chromatograph using a DCS, including: A carrier gas supply pipeline is provided, which includes a first supply branch and a second supply branch connected in parallel, wherein the first supply branch provides carrier gas at a first pressure and the second supply branch provides carrier gas at a second pressure lower than the first pressure. A first solenoid valve and a second solenoid valve are respectively installed on the first gas supply branch and the second gas supply branch. The working status information of the gas chromatograph is obtained through the DCS control system. The working status includes detection and analysis status and standby and ready-to-test status. When the working state is detection and analysis state, the DCS control system controls the first solenoid valve to open and the second solenoid valve to close, and the first gas supply branch supplies carrier gas at the first pressure to the detector and purifier of the gas chromatograph. When the working state is standby and test state, the DCS control system controls the first solenoid valve to close and the second solenoid valve to open, and supplies carrier gas at the second pressure to the detector and purifier through the second gas supply branch to maintain the positive pressure of the detector and prevent the purifier from dry burning.

[0041] When switching the state of the first solenoid valve and the second solenoid valve, the DCS control system performs the following timing protection operation: When switching from standby and testing state to detection and analysis state, the first solenoid valve is opened first, and the second solenoid valve is closed after a first preset time delay. When switching from the detection and analysis state to the standby test state, the second solenoid valve is opened first, and the first solenoid valve is closed after a second preset time delay.

[0042] Furthermore, the method also includes: Set up a manual / automatic detection mode switching function on the operator station screen of the DCS control system; When in manual mode, the operator manually issues a detection command to start the detection and analysis process; In automatic mode, the DCS control system automatically triggers detection and analysis based on preset logic. This preset logic is... Figure 3 The detection and control logic is shown.

[0043] The gas path control of the gas chromatograph obtained by the above method has the following advantages: 1. Carrier gas consumption is significantly reduced. By automatically switching between dual-pressure gas supply modes via DCS, the carrier gas pressure is reduced from the first pressure (e.g., 600 kPa) in the standby and test state to the second pressure (e.g., 200 kPa), reducing the total carrier gas consumption to 30% of the traditional constant pressure gas supply method. The consumption in the standby state is only 20% of the original, significantly saving expensive helium resources.

[0044] 2. Significant economic benefits Helium is a rare gas and is expensive. By adopting this method, the gas procurement cost can be reduced by about 70% while ensuring normal detection. At the same time, it avoids the consumption of standard gas for calibration caused by frequent start-stop operations, further reducing operating costs. It is especially suitable for industrial applications that require long-term continuous monitoring.

[0045] 3. Improved equipment safety By continuously supplying low-pressure carrier gas, the three major risks inherent in traditional power and gas outage methods are fundamentally resolved: This eliminates the risk of the purifier being damaged by dry burning due to gas interruption; This avoids air reflux contaminating the detector and chromatographic column; This eliminates the potential for equipment damage caused by incomplete re-purging after a gas outage.

[0046] 4. Guarantee of detection accuracy and stability The continuous supply of carrier gas maintains a positive pressure environment for the detector and a clean state for the chromatographic column, avoiding baseline drift and system instability caused by gas interruption and re-injection in traditional methods. It eliminates the need for lengthy purging and repeated calibration after each restart, ensuring accurate and reliable analytical results.

[0047] 5. High degree of automation The DCS system automatically identifies the working status and executes solenoid valve switching, realizing unattended intelligent control, avoiding operational errors and response delays caused by manual gas path switching, and improving the system's reliability and operating efficiency.

[0048] 6. Good operational continuity This solves the problem of downtime exceeding 6 hours caused by cooling, purging, and calibration in traditional methods, allowing the analyzer to be put into operation at any time, meeting the high-frequency analysis needs under abnormal conditions, and improving the safety monitoring capabilities of the production process.

[0049] 7. Wide applicability This method is not only applicable to PDHID detectors, but can also be extended to other types of industrial online gas chromatographs that use expensive carrier gases, and has general value in metallurgy, petrochemicals, industrial gas production and other fields.

[0050] The embodiments of the present invention have been described in detail above with reference to the accompanying drawings, but the present invention is not limited to the above embodiments. Even if various changes are made to the present invention, if these changes fall within the scope of the claims of the present invention and their equivalents, they shall still fall within the protection scope of the present invention.

Claims

1. A method for automatically reducing carrier gas consumption in a gas chromatograph using a DCS system, characterized in that, include: A carrier gas supply pipeline is provided, which includes a first supply branch and a second supply branch connected in parallel, wherein the first supply branch provides carrier gas at a first pressure and the second supply branch provides carrier gas at a second pressure lower than the first pressure. A first solenoid valve and a second solenoid valve are respectively installed on the first gas supply branch and the second gas supply branch. The working status information of the gas chromatograph is acquired through the DCS control system, and the working status includes detection and analysis status and standby and test status. When the working state is the detection and analysis state, the DCS control system controls the first solenoid valve to open and the second solenoid valve to close, and supplies carrier gas at the first pressure to the detector and purifier of the gas chromatograph through the first gas supply branch. When the working state is standby and test state, the DCS control system controls the first solenoid valve to close and the second solenoid valve to open, and supplies carrier gas at the second pressure to the detector and purifier through the second gas supply branch to maintain the positive pressure of the detector and prevent the purifier from dry burning.

2. The method for automatically reducing carrier gas consumption of a gas chromatograph using a DCS as described in claim 1, characterized in that, When switching the state of the first solenoid valve and the second solenoid valve, the DCS control system performs the following timing protection operation: When switching from standby and testing state to detection and analysis state, the first solenoid valve is opened first, and the second solenoid valve is closed after a first preset time delay. When switching from the detection and analysis state to the standby test state, the second solenoid valve is opened first, and the first solenoid valve is closed after a second preset time delay.

3. The method for automatically reducing carrier gas consumption of a gas chromatograph using a DCS as described in claim 1, characterized in that, Also includes: Set up a manual / automatic detection mode switching function on the operator station screen of the DCS control system; When in manual mode, the operator manually issues a detection command to start the detection and analysis process; When in automatic mode, the DCS control system automatically triggers the detection and analysis status according to preset logic.

4. A carrier gas supply control system for a gas chromatograph, characterized in that, include: Carrier gas source; The first and second gas supply branches are connected in parallel. The inlet of both branches is connected to the carrier gas source, and the outlet is connected to the detector and purifier of the gas chromatograph. The first pressure reducing valve and the first solenoid valve are installed on the first gas supply branch to provide carrier gas at the first pressure. The second pressure reducing valve and the second solenoid valve installed on the second gas supply branch are used to provide carrier gas at a second pressure lower than the first pressure. The DCS control system is electrically connected to the first solenoid valve and the second solenoid valve, and the DCS control system is configured to: Acquire the working status information of the gas chromatograph, including detection and analysis status and standby and test status; When the working state is detection and analysis state, the first solenoid valve is opened and the second solenoid valve is closed. When the working state is standby and test state, the first solenoid valve is closed and the second solenoid valve is opened.

5. The gas chromatograph carrier gas supply control system as described in claim 4, characterized in that, The first pressure does not exceed 600 kPa, and the second pressure does not exceed 200 kPa.

6. The gas chromatograph carrier gas supply control system as described in claim 4, characterized in that, The DCS control system includes: The status determination module is used to receive detection command pulse signals from the DCS operator station or automatically generate detection trigger signals according to a preset time interval to determine the working status. The solenoid valve control module is used to send switching control signals to the first solenoid valve and the second solenoid valve. The timing protection module is used to perform a delay control of opening first and then closing when switching the state of the solenoid valve to prevent the detector and purifier from running out of gas.

7. The gas chromatograph carrier gas supply control system as described in claim 4, characterized in that, The DCS control system further includes an operator station display module, which is configured as follows: Displays the real-time operating status and analysis results of the gas chromatograph; Provides manual / automatic detection mode switching function; In manual mode, it receives detection commands manually issued by the operator.

8. The gas chromatograph carrier gas supply control system as described in claim 4, characterized in that, It also includes a pressure monitoring device, which is installed at the outlet of the first gas supply branch and the second gas supply branch, respectively, to monitor the carrier gas pressure supplied to the gas chromatograph in real time and feed the pressure signal back to the DCS control system.

9. The gas chromatograph carrier gas supply control system as described in claim 4, characterized in that, The carrier gas is helium, and the gas chromatograph is an industrial online gas chromatograph equipped with a pulsed discharge helium ionization detector, used to detect the hydrocarbon content in the main cooling liquid oxygen of the air separation unit.

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