Electronic pressure flow controller and non-methane hydrocarbon detection device

Abstract

The utility model discloses an electronic pressure flow controller and a non-methane total hydrocarbon detection device, the electronic pressure flow controller is respectively connected with a hydrogen / air supply device and a flame ionization (FID) detector, the electronic pressure flow controller comprises a proportional-integral (PI) control circuit, and the PI control circuit comprises an error comparator, a signal processing circuit and a signal processing circuit, the processor is used for receiving an actual measurement value detected by the sensor and calculating a difference value between a set value and the actual measurement value; a proportional-integral (PI) controller which generates an adjustment signal based on the received difference value; and the power amplifier is used for amplifying the received output electric signal into a strong current signal and adjusting the gas flow based on the strong current signal to control the ratio of the hydrogen to the air. According to the scheme, hydrogen and air parameters are accurately adjusted through the proportion-integral controller, the air flow is automatically reduced during ignition, the preset proportion is recovered after ignition succeeds, it is ensured that high-concentration organic matter is completely ionized, flame dilution is avoided, the ionization efficiency and the detection sensitivity are improved, and stable and reliable signals are provided.

Description

Technical Field

[0001] This application generally relates to the field of automation control technology. More specifically, this application relates to an electronic pressure and flow controller; further, this application also relates to a non-methane total hydrocarbon detection device. Background Technology

[0002] In the detection of non-methane total hydrocarbons, the flame ionization (FID) detector is widely used in gas chromatography analysis due to its high sensitivity and rapid response. However, existing gas flow control systems have significant technical problems when used in conjunction with FID detectors. At the moment of FID detector ignition, the hydrogen-to-air flow ratio needs to be precisely controlled to ensure successful ignition. If existing systems cannot accurately reduce the air flow to the preset value, ignition failure or instability can easily occur, increasing detection time, damaging the detector, and reducing detection efficiency and equipment lifespan. Furthermore, existing gas flow control systems mostly rely on manual or simple mechanical adjustments, making it difficult to achieve precise, rapid, and stable dynamic adjustment of gas flow and pressure. This leads to fluctuations in the hydrogen and air flow entering the FID detector, affecting the accuracy and repeatability of the detection results and failing to meet the requirements of high-precision detection.

[0003] Therefore, there is an urgent need to provide an electronic pressure and flow controller and a non-methane total hydrocarbon detection device to accurately control the hydrogen / air ratio and ensure maximum hydrogen flame combustion efficiency. Utility Model Content

[0004] In order to at least solve one or more of the technical problems mentioned above, this application proposes an electronic pressure flow controller and a non-methane total hydrocarbon detection device that can accurately control the hydrogen / air ratio and ensure the maximum efficiency of hydrogen flame combustion.

[0005] In a first aspect, this application provides an electronic pressure flow controller, which is connected to a hydrogen / air supply device and a hydrogen flame ionization (FID) detector. The electronic pressure flow controller includes a proportional-integral (PI) control circuit, which is a closed-loop control circuit and includes an error comparator for receiving measured values ​​detected by a sensor and calculating the difference between a set value and the measured value; a PI controller for generating an adjustment signal based on the received difference; and a power amplifier for amplifying the electrical signal output by the PI controller into a strong current signal and adjusting the gas flow rate based on the strong current signal to control the ratio of hydrogen to air.

[0006] In some embodiments, the error comparator is implemented by an operational amplifier U4A: the set value signal is divided by resistors R35 and R39 and then input to the non-inverting input terminal of U4A; the measured value signal is input to the inverting input terminal of U4A via resistor R41; the feedback resistor R42 connects the output terminal and the inverting input terminal of U4A, forming an error amplifier circuit.

[0007] In some embodiments, the PI controller includes an operational amplifier U4B, a resistor R33, and a capacitor C31: the error signal is input to the inverting input terminal of U4B via resistor R36; R33 and C31 are connected in parallel between the inverting input terminal and the output terminal of U4B to form a PI adjustment circuit.

[0008] In some embodiments, the power amplifier includes: an operational amplifier U4C, whose non-inverting input is connected to the output of a PI controller via a resistor R38; a protection diode D8 connected to the output of U4C; and a transistor Q5, whose base is connected to the output of D8 via a resistor R40 to drive the opening of a proportional valve.

[0009] In some embodiments, the parameters in the proportional-integral control circuit are fixed by changing resistors and capacitors with different configurations.

[0010] In some embodiments, the set value can be indirectly modified by adjusting the resistance of a digital potentiometer via software.

[0011] In some embodiments, resistors and capacitors are low-temperature drift, high-precision devices to ensure the stability of PI parameters.

[0012] In a second aspect, this application provides a non-methane total hydrocarbon detection device, which includes the aforementioned electronic pressure and flow controller.

[0013] In some embodiments, the non-methane total hydrocarbon detection device further includes: a multi-channel injection valve having multiple ports, wherein the multi-channel injection valve achieves quantitative capture and component separation of sample gas by switching between injection and detection states; a first quantitative loop and a second quantitative loop, respectively connected to the ports of the multi-channel injection valve via pipelines; multiple independent carrier gas channels, respectively connected to the ports of the multi-channel injection valve; a pre-column, used to adsorb impurities in the sample gas to purify the sample gas; and a three-way solenoid valve, respectively connected to the methane column, the total hydrocarbon column and the FID detector.

[0014] In some embodiments, the multichannel injection valve has: an injection state in which sample gas fills a first quantitative loop and a second quantitative loop; and a detection state in which carrier gas pushes the sample gas in the first quantitative loop through a total hydrocarbon column to the FID detector, and the sample gas in the second quantitative loop through a pre-column and a methane column to the FID detector.

[0015] Using the electronic pressure and flow controller provided above, this embodiment of the application employs a control circuit composed of a hardware-designed error comparator, a proportional-integral controller, and a power amplifier. This allows the FID detector to ignite without software intervention, with the hardware automatically adjusting the air intake. The controller precisely adjusts the hydrogen and air parameters, reducing the air flow during ignition and restoring the optimal ratio after successful ignition. This ensures complete ionization of high-concentration organic matter, provides a stable signal, and avoids excessive air dilution, thereby improving ionization efficiency and sensitivity. Attached Figure Description

[0016] The above and other objects, features, and advantages of exemplary embodiments of this application will become readily understood by reading the following detailed description with reference to the accompanying drawings. In the drawings, several embodiments of this application are illustrated by way of example and not limitation, and the same or corresponding reference numerals denote the same or corresponding parts, wherein:

[0017] Figure 1 The proportional-integral control circuit in the electronic pressure flow controller of this application embodiment is shown;

[0018] Figure 2 A schematic diagram of the fourteen-way valve in the sample injection state in an embodiment of this application is shown;

[0019] Figure 3 This illustration shows a schematic diagram of the 14-way valve in the detection state according to an embodiment of this application;

[0020] Figure 4 An exemplary structural block diagram of a gas chromatography apparatus according to an embodiment of this application is shown;

[0021] Figure 5 The amplifier circuit on the signal conditioning board in an embodiment of this application is shown;

[0022] Figure 6 A comparison chart of the smoothing effect of Savitzky-Golay filtering in the embodiments of this application is shown;

[0023] Figure 7 The following diagram shows a comparison of the baseline correction effects of DB4 wavelet transform in the embodiments of this application;

[0024] Figure 8 The image shows the chromatographic detection effect of a low-concentration standard gas (0.42 mg / m³) in an embodiment of this application.

[0025] Figure 9 The image shows the chromatographic detection effect of a high-concentration standard gas with a sample gas concentration of 1800 g / m³ in an embodiment of this application.

[0026] In the diagram: 100, Gas Chromatography Apparatus;

[0027] 101. Auxiliary system; 102. Gas path system; 103. Sample injection system; 104. Detection system; 105. Data processing system; 106. Temperature control system;

[0028] 1031, Fourteen-way valve; 1032, First metering ring; 1033, Second metering ring; 1034, Pre-column; 1035, Total hydrocarbon column; 1036, Methane column; 1, First port; 2, Second port; 3, Third port; 4, Fourth port; 5, Fifth port; 6, Sixth port; 7, Seventh port; 8, Eighth port; 9, Ninth port; 10, Tenth port; 11, Eleventh port; 12, Twelfth port; 13, Thirteenth port; 14, Fourteenth port. Detailed Implementation

[0029] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of this application. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0030] It should be understood that the terms "comprising" and "including" used in the specification and claims of this application indicate the presence of the described features, integrals, steps, operations, elements and / or components, but do not exclude the presence or addition of one or more other features, integrals, steps, operations, elements, components and / or collections thereof.

[0031] It should also be understood that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the application. As used in this specification and claims, the singular forms “a,” “an,” and “the” are intended to include the plural forms unless the context clearly indicates otherwise. It should also be understood that the term “and / or” as used in this specification and claims refers to any combination and all possible combinations of one or more of the associated listed items, and includes such combinations.

[0032] As used in this specification and claims, the term "if" may be interpreted, depending on the context, as "when," "once," "in response to determination," or "in response to detection." Similarly, the phrase "if determined" or "if [described condition or event] is detected" may be interpreted, depending on the context, as "once determined," "in response to determination," "once [described condition or event] is detected," or "in response to detection of [described condition or event]."

[0033] The specific embodiments of this application will now be described in detail with reference to the accompanying drawings.

[0034] In some embodiments, this application provides an electronic pressure flow controller, which is connected to a hydrogen / air supply device and a hydrogen flame ionization (FID) detector. The electronic pressure flow controller includes a proportional-integral (PI) control circuit, which is a closed-loop control circuit and includes an error comparator for receiving measured values ​​detected by the sensor and calculating the difference between the set value and the measured value; a PI controller for generating an adjustment signal based on the received difference; and a power amplifier for amplifying the electrical signal output by the PI controller into a strong current signal and adjusting the gas flow rate based on the strong current signal to control the ratio of hydrogen to air.

[0035] In this scheme, the electronic pressure and flow controller is connected to both the hydrogen / air supply device and the hydrogen flame ionization (FID) detector. The hydrogen / air supply device provides hydrogen as fuel and air as combustion-supporting gas to the FID detector. The basic principle of the FID detector is based on the ionization reaction of organic compounds in a hydrogen flame. When organic matter in the sample enters the combustion chamber, it is ionized under the action of the hydrogen flame. The generated ions form a tiny current in the electric field, and the magnitude of the current is proportional to the organic matter content, thereby achieving quantitative analysis of the organic matter content in the sample. To ensure the stable operation of the FID detector, the electronic pressure and flow controller is responsible for accurately controlling the flow rate and pressure of hydrogen and air. Its core relies on a closed-loop control circuit: an error comparator receives the measured value detected by the sensor and the set target flow rate value, and calculates the difference between the two. Based on this difference, the proportional-integral (PI) controller outputs a corresponding adjustment signal according to the magnitude of the difference through the proportional control part, and the integral control part eliminates continuous deviations, thus generating a comprehensive adjustment signal. The power amplifier amplifies the signal output by the PI controller into a strong current signal, which drives the gas flow regulating device to adjust the opening degree, so that the gas flow is close to the set value, forming a closed-loop feedback.

[0036] This application's solution uses an error comparator to compare the setpoint with the sensor's measured value in real time, forming a closed-loop feedback. The PI controller dynamically adjusts the output signal based on the error, and the power amplifier drives the proportional valve to precisely adjust the opening, ensuring highly stable hydrogen and air flow / pressure. Furthermore, the hardware PI control can automatically limit air flow during the ignition phase and instantly restore the optimal ratio after successful ignition. Compared to software solutions, this significantly improves ignition success rate and flame stability, avoiding interruptions in detection due to ignition failure.

[0037] In one specific implementation, the error comparator is implemented by operational amplifier U4A: the setpoint signal is divided by resistors R35 and R39 and then input to the non-inverting input of U4A; the measured signal is input to the inverting input of U4A via resistor R41; feedback resistor R42 connects the output and inverting input of U4A, forming an error amplification circuit. The PI controller includes operational amplifier U4B, resistor R33, and capacitor C31: the error signal is input to the inverting input of U4B via resistor R36; R33 and C31 are connected in parallel between the inverting input and output of U4B, forming a PI adjustment circuit. The power amplifier includes: operational amplifier U4C, whose non-inverting input is connected to the output of the PI controller via resistor R38; protection diode D8, connected to the output of U4C; and transistor Q5, whose base is connected to the output of D8 via resistor R40, driving the proportional valve opening.

[0038] like Figure 1 As shown, the error comparator in the proportional-integral controller of this scheme is an error amplifier circuit. The signal at test point T11 in this circuit is the current set value set by the software. This signal is divided by resistors R35 and R39 and then input to pin 3 (non-inverting input) of the error comparator U4A. The signal at test point T12 is the measured value output by the pressure or flow sensor. This signal is connected to pin 2 (inverting input) of the error comparator U4A via resistor R41. Resistor R42 serves as a feedback amplification resistor. Based on the principle of virtual short and virtual open circuits, the amplified error value can be obtained at test point T10, providing a basis for subsequent adjustment of the proportional-integral controller.

[0039] The proportional-integral controller is a proportional-integral amplifier circuit. In this circuit, the error signal at the test point T10 is input to the proportional-integral (PI) adjustment circuit composed of operational amplifier U4B, resistor R33 and capacitor C31 through resistor R36. The PI adjustment control is achieved through the proportional-integral action of this circuit. The final adjustment control output signal is located at the test point T13.

[0040] The power amplifier is a power amplification circuit. In this circuit, the PI control signal at the T13 test point is first further amplified by a circuit consisting of resistors R38 and R31 and operational amplifier U4C, and then detected by protection diode D8 before being output. The detected output signal provides base drive current to transistor Q5 through resistor R40, and Q5 drives the proportional valve to adjust the opening of the pipeline pressure or flow. Thus, a complete closed-loop control is formed from measuring the signal from the pressure or flow sensor to controlling the opening of the proportional valve through PI regulation.

[0041] In operation, when sample gas enters the detection system 104 from the methane column 1036 or the total hydrocarbon column 1035 via a three-way solenoid valve, the electronic pressure and flow controller obtains gas from the hydrogen / air supply device and delivers the gas to the FID detector according to preset flow and pressure values. During gas delivery, the controller monitors the actual gas flow and pressure in real time and compares them with the set values. Once a deviation is detected, the error comparator immediately calculates the difference and sends it to the proportional-integral controller. The proportional-integral controller generates an adjustment signal based on the difference, which is amplified by a power amplifier and drives the gas flow regulating device to adjust. The regulating device adjusts the gas flow or pressure according to the amplified signal, gradually bringing it closer to the set value. Through this continuous feedback and adjustment process, the gas flow and pressure eventually stabilize near the set value, ensuring that the FID detector operates under optimal conditions.

[0042] In one specific implementation, the output of a medium-power transistor in the power amplifier is connected to a proportional valve, driving the proportional valve to regulate the gas flow rate. Specifically, the medium-power transistor is the core component of the power amplifier, and its output is connected to the proportional valve. Those skilled in the art will understand that the regulation signal generated by the proportional-integral controller is typically a low-power electrical signal, insufficient to directly drive the proportional valve. The medium-power transistor amplifies this low-power signal into a strong current signal, thereby providing sufficient driving power to the proportional valve. A proportional valve is a valve that adjusts its opening degree according to the input electrical signal. The medium-power transistor transmits the amplified strong current signal to the proportional valve, which changes its opening degree according to the signal strength, thus regulating the gas flow rate.

[0043] The use of a medium-power transistor in conjunction with a proportional valve in this application enables direct driving regulation of gas flow. Specifically, when the strength of the regulation signal output from the proportional-integral controller increases, the medium-power transistor drives the proportional valve to open wider, thus increasing the gas flow; conversely, a weaker signal reduces the opening and decreases the flow. This design allows the system to respond quickly to the regulation signal from the proportional-integral controller, effectively avoiding control delay and achieving real-time, precise regulation of the gas flow, ensuring that the actual gas flow remains consistent with the set value. This real-time response and stability provide stable operating conditions for the FID detector, thereby improving the accuracy and reliability of the detection results.

[0044] In one specific implementation, the parameters in the proportional-integral (PI) control circuit are fixed by replacing resistors and capacitors with different configurations. Specifically, the resistors and capacitors in the PI controller determine the generation and regulation characteristics of the control signal. The selection of these components directly affects the proportional gain and integral time constant of the PI controller, thus affecting the response speed and stability of the entire control system. In this application, resistors and capacitors with appropriate resistance and capacitance values ​​are selected and replaced according to different application requirements. After replacing the resistors and capacitors, the parameters of the PI control circuit are physically fixed. The advantage of this fixing method is parameter stability, unaffected by environmental factors such as temperature and humidity, ensuring the long-term stable operation of the control system.

[0045] In one specific implementation, the resistors and capacitors employ low-temperature drift, high-precision components to ensure the stability of the PI parameters. Specifically, the solution in this application uses low-temperature drift, high-precision resistors and capacitors to guarantee the parameters and adjustment stability of the proportional-integral control. This design ensures automatic air intake adaptation during FID detector ignition, effectively guaranteeing a stable ignition success rate and a suitable hydrogen-air ratio.

[0046] In one specific implementation, the setpoint can be indirectly modified by adjusting the resistance of a digital potentiometer via software. Specifically, the setpoint is the specific value of the target parameter (such as pressure or flow rate) of the control circuit, and the digital potentiometer is an electronic component with an adjustable resistance. In the control system, there is a functional relationship between the resistance of the digital potentiometer and the setpoint; changing the resistance adjusts the target parameter. For example, in a proportional control circuit, the resistance of the digital potentiometer affects the proportional coefficient, thereby changing the pressure or flow rate setpoint. When a change in the setpoint is needed, the host computer software or the control software in the system sends a command containing the new setpoint information. The digital potentiometer connected to the system control circuit receives this command, and its internal memory and digital interface parse the command sent by the software, converting it into a corresponding resistance adjustment signal. Based on the received command, the digital potentiometer adjusts its internal resistor network, composed of analog switches and resistor arrays, changing the on / off state of the switches to alter its resistance value connected to the circuit. This change in resistance directly affects the output of the control circuit; for example, in a proportional control circuit, it affects the proportional coefficient, thereby changing the magnitude of the output signal and thus modifying the target parameter setpoint.

[0047] The adjustment method of this application supports dynamic configuration under different operating conditions. That is, when detecting different concentrations of exhaust gas or dealing with complex sample gas composition, instructions can be sent in real time through the host computer software, and the digital potentiometer updates its resistance value synchronously, which can quickly adapt to changes in detection conditions and avoid the cumbersome process of traditional hardware adjustment.

[0048] This solution employs a control circuit comprised of an error comparator, a proportional-integral (PI) controller, and a power amplifier. The PI controller precisely adjusts gas parameters such as hydrogen and air pressure and flow rate. During ignition, it automatically reduces the air flow rate and restores the optimal ratio after successful ignition, ensuring continuous and complete ionization of high-concentration organic compounds in the flame. This provides a stable and reliable signal foundation for the detection of high-concentration organic compounds. This dynamic adjustment mechanism not only avoids flame dilution caused by excessive air but also ensures complete combustion and ionization of high-concentration samples in the FID detector through precise control of the hydrogen-air ratio, thereby improving ionization efficiency and detection sensitivity.

[0049] In some embodiments, this application provides a non-methane total hydrocarbon detection device, which includes the aforementioned electronic pressure and flow controller.

[0050] The non-methane total hydrocarbon detection device provided in this application, due to the inclusion of an electronic pressure and flow controller, can precisely control the pressure / flow rate of hydrogen and air. This not only ensures that organic matter is fully ionized in the hydrogen flame, thus enhancing the intensity of the ion current signal, but also avoids chromatographic peak broadening or signal distortion caused by fluctuations in gas flow rate / pressure, ensuring peak stability and data accuracy during the detection of high concentrations of non-methane total hydrocarbons.

[0051] In one specific implementation, the non-methane total hydrocarbon detection device further includes a multi-channel injection valve with multiple ports, which achieves quantitative capture and component separation of sample gas by switching between injection and detection states; a first and second quantitative loops, which are respectively connected to the ports of the multi-channel injection valve via pipelines; multiple independent carrier gas channels, which are respectively connected to the ports of the multi-channel injection valve; a pre-column, which is used to adsorb impurities in the sample gas to purify the sample gas; and a three-way solenoid valve, which is respectively connected to the methane column, the total hydrocarbon column and the flame ionization (FID) detector, and the FID detector is used to detect the components separated by the multi-channel injection valve.

[0052] The non-methane total hydrocarbon detection device of this application includes a multi-channel injection valve, a first quantitative loop 1032, a second quantitative loop 1033, a pre-column 1034, a total hydrocarbon column 1035, and a methane column 1036. The multi-channel injection valve is a fourteen-port valve 1031 with fourteen ports and two main operating states: injection state and detection state. Specifically, in the injection state, the sample gas is quantitatively filled into the first and second quantitative loops 1032 and 1033, ensuring accurate and consistent sample gas volume entering the subsequent detection stage, providing a foundation for accurate subsequent detection. When the system switches to the detection state, the carrier gas propels the sample gas in the first and second quantitative loops 1032 and 1033 for detection. This design allows for the effective separation and detection of different components in the sample gas.

[0053] The first and second quantitative loops 1032 and 1033 are connected to the port of the fourteen-way valve 1031 via pipelines, respectively, and are used to achieve precise quantification of the sample gas. The pre-column 1034 is also connected to the port of the fourteen-way valve 1031 via pipelines and is used to adsorb impurities in the sample gas to purify it. The total hydrocarbon column 1035 and the methane column 1036 are the core components for multi-component gas separation and detection. The core function of the total hydrocarbon column 1035 is to convert the total hydrocarbons in the sample gas into a single chromatographic peak, preparing for further determination of the total hydrocarbon concentration. The core function of the methane column 1036 is to separate methane from other non-methane hydrocarbons in the sample gas, allowing methane to remain in the methane column 1036 for a certain period before eluting as a separate peak, while other non-methane hydrocarbons are retained or backflushed out, preparing for further determination of the methane concentration in the sample gas.

[0054] In addition, the non-methane total hydrocarbon detection device in this scheme also includes multiple independent carrier gas channels and a three-way solenoid valve, with each channel connected to a fourteen-way valve. In this way, different carrier gases can carry different components in the sample gas into the corresponding chromatographic columns for separation according to set paths and flow rates, and then send them to the FID detector for detection. This design of multiple independent carrier gas channels ensures stable flow of the sample gas in different detection paths, avoids mutual interference between gas paths, and improves the accuracy and reliability of detection. The three-way solenoid valve is a key component connecting the methane column 1036, the total hydrocarbon column 1035, and the FID detector. It can switch the on / off state and flow direction of the gas path according to the system's control commands, ensuring that the sample gas accurately enters the FID detector for detection after separation by the corresponding chromatographic column.

[0055] The non-methane total hydrocarbon detection device provided in this application uses a multi-channel injection valve instead of a traditional multi-valve combination. The multi-channel injection valve switches between injection and detection states simultaneously, achieving sample gas capture, quantification, and component separation. This reduces the number of valves and eliminates the problem of asynchronous switching, improving detection repeatability and data accuracy. Simultaneously, the pre-column 1034 adsorbs impurities in the sample gas, purifying it and further enhancing the accuracy and repeatability of the detection results.

[0056] like Figure 2As shown, in a specific implementation scheme, during the injection state: sample gas fills the first and second quantitative loops; carrier gas purges the pre-column to remove residual impurities. The multi-channel injection valve is a fourteen-port valve. During the injection state: sample gas enters through the first port of the fourteen-port valve, and exits sequentially through the fourteenth port, the first quantitative loop, the eleventh port, the tenth port, the second quantitative loop, the third port, and the second port; the first carrier gas enters through the twelfth port of the fourteen-port valve, and enters the FID detector sequentially through the thirteenth port, the total hydrocarbon column, and the three-way solenoid valve; the second carrier gas enters through the ninth port of the fourteen-port valve, and exits sequentially through the eighth port, the pre-column, the fourth port, and the fifth port to complete the purging; the third carrier gas enters through the sixth port of the fourteen-port valve, and enters the FID detector sequentially through the seventh port, the methane column, and the three-way solenoid valve.

[0057] In this scheme, when the 14-way valve 1031 is in the sample inlet state, the sample gas enters from the first port 1 of the 14-way valve 1031, flows sequentially through the fourteenth port 14, the first metering loop 1032, the eleventh port 11, the tenth port 10, the second metering loop 1033, the third port 3, and the second port 2, and finally exits. This process ensures that the sample gas is quantitatively filled in the first and second metering loops 1033, providing an equal volume of sample gas for subsequent accurate detection.

[0058] The first carrier gas enters through port 12 of the 14-way valve 1031, passes through port 13, the total hydrocarbon column 1035, and the three-way solenoid valve, before entering the detection system 104, ensuring that the total hydrocarbon column 1035 is in a standby state. The third carrier gas enters through port 6 of the 14-way valve 1031, passes through port 7, the methane column 1036, and the three-way solenoid valve, before entering the detection system 104, keeping the methane column 1036 in a standby state. Additionally, the second carrier gas enters through port 9 of the 14-way valve 1031, passes through port 8, the pre-column 1034, port 4, and port 5 in sequence, and then exits to complete the purging process. This purging process removes residual impurities from the pre-column 1034, preventing interference with subsequent sample gas detection, improving separation efficiency, ensuring analytical accuracy, and extending the lifespan of the pre-column 1034 and the chromatographic column.

[0059] like Figure 3As shown, in a specific implementation scheme, under the detection state: the sample gas enters through the first port of the fourteen-way valve and exits through the second port; the first carrier gas enters through the twelfth port of the fourteen-way valve, and sequentially passes through the eleventh port, the first metering loop, the fourteenth port, the thirteenth port, the total hydrocarbon column, and the three-way solenoid valve before entering the FID detector; the second carrier gas enters through the ninth port of the fourteen-way valve, and sequentially passes through the tenth port, the second metering loop, the third port, the fourth port, the pre-column, the eighth port, the seventh port, the methane column, and the three-way solenoid valve before entering the FID detector; the third carrier gas enters through the sixth port of the fourteen-way valve and exits through the fifth port.

[0060] In this scheme, when the 14-way valve 1031 is in the detection state, the sample gas enters through the first port 1 of the 14-way valve 1031 and exits through the second port 2. The first carrier gas enters through the 12th port 12 of the 14-way valve 1031, flows sequentially through the 11th port 11, the first metering ring 1032, the 14th port 14, and the 13th port 13, and finally enters the total hydrocarbon column 1035. That is to say, the sample gas filled in the first metering ring 1032 is separated by the first carrier gas through the total hydrocarbon column 1035. The separated sample gas components enter the detection system 104 through the three-way solenoid valve to realize the detection of total hydrocarbon concentration. The second carrier gas enters through the 9th port 9 of the 14-way valve 1031, flows sequentially through the 10th port 10, the second metering ring 1033, the third port 3, the fourth port 4, the pre-column 1034, the 8th port 8, the 7th port 7, and the methane column 1036, and finally enters the detection system 104 through the three-way solenoid valve. In other words, the second carrier gas is responsible for carrying the sample gas in the second quantitative ring 1033 into the pre-column 1034 and the methane column 1036 for separation. The pre-column 1034 first performs preliminary purification of the sample gas, removing impurities and interfering substances. Subsequently, the sample gas enters the methane column 1036 for further separation, and finally enters the detection system 104 to realize the detection of the methane concentration in the sample gas.

[0061] In addition, this design includes a third carrier gas path, which enters through the sixth port 6 of the fourteen-way valve 1031, passes through several ports, and finally exits through the fifth port 5. This third carrier gas path primarily serves to balance the gas pressure and maintain unobstructed flow. Entering through the sixth port 6 and exiting through a specific pathway from the fifth port 5, it ensures stable pressure throughout the entire gas system 102, prevents airflow turbulence caused by pressure fluctuations, and guarantees that other carrier gases can properly propel the sample gas for detection. This design also helps prevent blockages or excessive pressure in the gas path, contributing to the stable operation of the entire detection system 104.

[0062] It is worth noting that the carrier gas supply device in this application has three physical outlets, supplying three separate carrier gas streams. During sample injection, the three carrier gas streams perform purging, pre-separation, and carrier transport functions respectively. During detection, the same three carrier gas streams switch to carry the sample gas into the chromatographic column and detector. This design, by reusing carrier gas paths and dynamically allocating them, enables flexible adjustment of the carrier gas supply method, thereby meeting the needs of different detection procedures.

[0063] Those skilled in the art will understand that, in other embodiments, the number of physical outlets of the carrier gas supply device can be further increased. For example, when the device has six independent physical outlets, six independent carrier gas paths can be configured to correspond to all the gas path functions required for the sample introduction and detection states, respectively. Under this design, the carrier gas paths required for each state in the sample introduction and detection states are continuously supplied by dedicated physical outlets, without the need for valve switching, thereby simplifying the gas path switching operation process and improving detection efficiency.

[0064] This scheme, by setting up a pre-column 1034 and purging it with carrier gas, removes impurities and interfering substances from the sample gas when detecting low-concentration gases, thereby improving the accuracy and sensitivity of the detection. Simultaneously, the carrier gas, through purging, removes residual impurities and interfering substances from the pre-column 1034, further ensuring the purity of the sample gas entering the detection system 104. Furthermore, the pre-column 1034 and purging setup also help protect subsequent chromatographic columns and detectors; by preventing the accumulation of impurities and interfering substances on their surfaces, the risk of equipment failure due to contamination is reduced, thereby extending the lifespan of the device and reducing maintenance costs.

[0065] In one specific implementation, the multi-channel injection valve is driven by compressed air and the injection and detection states are switched synchronously by a controller.

[0066] In this design, the 14-way valve 1031 is connected to a compressed air supply device, and its opening and closing action can be precisely controlled by adjusting the pressure and flow rate of compressed air. The controller, as a key component of the entire gas chromatography apparatus 100, is responsible for coordinating the operation of all components. It synchronously switches the injection and detection states of the 14-way valve 1031 according to a preset program and time sequence. In the injection state, the controller controls the 14-way valve 1031 to open the corresponding channel, allowing the sample gas to smoothly enter and fill the first and second quantitative loops. Simultaneously, it controls the carrier gas flow direction to purge the pre-column 1034 to remove residual impurities. After the quantitative loops are filled with sample gas, the controller quickly switches the 14-way valve 1031 to the detection state. At this time, the carrier gas flow direction is switched to different channels, pushing the sample gas in the two quantitative loops into the total hydrocarbon column 1035 and the methane column 1036 for separation. Simultaneously, it coordinates the opening and closing of the three-way solenoid valve to ensure that the separated sample gas accurately enters the detection system 104.

[0067] In some specific implementation schemes, the first quantitative loop 1032 and the second quantitative loop 1033 can be made of metal tubes or polyetherketone (PEEK) resin tubes. Metal tubes, due to their high temperature resistance, corrosion resistance, and high mechanical strength, can adapt to different temperature and pressure conditions during analysis, ensuring stable performance over long-term use. Polyetherketone resin tubes, on the other hand, possess excellent chemical stability and biocompatibility, good tolerance to various organic solvents and gases, and low surface adsorption, reducing sample gas adsorption loss and improving detection accuracy and sensitivity. Furthermore, to ensure consistent injection volume each time and to guarantee consistent sample gas volume entering the total hydrocarbon column 1035 and the methane column 1036, the volumes of the first quantitative loop 1032 and the second quantitative loop 1033 are set to be the same. This setting is crucial for improving the reliability and accuracy of analytical results.

[0068] In one specific implementation, a three-way solenoid valve is located at the intersection of the output ends of the methane column 1036 and the total hydrocarbon column 1035 to guide the separated components to the FID detector.

[0069] In this design, a three-way solenoid valve is located at the intersection of the output ends of the methane column 1036 and the total hydrocarbon column 1035, serving as the pivot connecting the chromatographic column and the detection system 104. Its main function is to precisely control the opening and closing of the gas path and its flow direction according to the system's control commands, ensuring that different components in the sample gas accurately enter the detection system 104 after separation. This avoids cross-interference between different components and improves the accuracy and reliability of the detection results.

[0070] In one specific implementation, each carrier gas channel is equipped with an independent electronic pressure-flow controller. The flow rate and pressure of each carrier gas channel can be precisely controlled by the proportional-integral control circuit on the electronic pressure-flow controller. This precise control ensures that the sample gas enters the chromatographic column at a uniform flow rate and maintains an appropriate residence time within the column, laying the foundation for accurate separation and detection of subsequent components. Simultaneously, the closed-loop feedback control mode composed of hardware circuitry has a faster response speed than traditional software control, quickly adapting to changes in sample gas concentration and adjusting carrier gas parameters in real time. This ensures stable separation of total hydrocarbons and methane over a wide concentration range, meeting the needs of high-concentration and low-concentration exhaust gas detection.

[0071] The non-methane total hydrocarbon detection device provided in this solution achieves full-process control of quantitative sample injection, purging, and detection by precisely switching channel states. It works in conjunction with multiple carrier gas paths to accurately detect total hydrocarbons, methane, and non-methane total hydrocarbons in the sample gas, ensuring data accuracy and experimental repeatability.

[0072] In some embodiments, this application also provides a gas chromatography apparatus 100, which includes the above-described non-methane total hydrocarbon detection device.

[0073] In this application, the multi-channel injection valve in the non-methane total hydrocarbon detection device switches between injection and detection states with a single valve, replacing the traditional multi-valve combination. This reduces the number of valves and the complexity of pipeline connections, lowers the system size and assembly difficulty, and avoids detection errors caused by asynchronous switching of multiple valves, thereby improving overall operational stability.

[0074] like Figure 4 As shown, in a specific implementation scheme, the gas chromatography apparatus 100 in this scheme includes an auxiliary system 101, a gas path system 102, a sample injection system 103, a detection system 104, and a data processing system 105. Specifically, the auxiliary system 101 includes at least a carrier gas supply device, a compressed air supply device, and a hydrogen / air supply device. The carrier gas supply device is a carrier gas cylinder, which provides carrier gas to the gas chromatography apparatus 100. This carrier gas can carry the collected sample gas into the sample injection device and load the separated component sample gas into the detection system for detection. The compressed air supply device is a compressed air tank, which provides compressed air to the apparatus. This compressed air provides a gas source to the gas chromatograph chamber, maintaining the chamber at a positive pressure state and ensuring the positive pressure explosion-proof nature of the gas chromatograph body. The hydrogen / air supply device is a hydrogen-air integrated unit, which provides hydrogen and air to the detection system 104 to create a stable hydrogen flame environment, allowing organic substances to be excited and generate ions in the hydrogen flame, thereby realizing the detection of organic components in the sample gas.

[0075] The sample introduction system 103 includes a sampling probe, which has no active power unit and is connected to the negative pressure chamber of the jet pump via a pipeline. When the jet pump generates a Venturi effect through compressed air, a negative pressure driving force is formed at the rear end of the sampling probe, causing the sample gas to be detected to passively flow into the sampling probe under atmospheric pressure and be transported to the non-methane total hydrocarbon detection device via a pipeline, providing a sample gas source for subsequent sample introduction and separation stages.

[0076] Those skilled in the art will understand that, in order to ensure complete vaporization of the sample gas, the gas chromatography apparatus 100 of this application also includes a temperature control system 106 connected to the sample injection system 103. The temperature control system 106 includes an electric heating module. After being powered on, the electric heating module heats up to provide an environment higher than room temperature for the chromatographic column in the gas chromatography apparatus 100, ensuring that the sample can be completely vaporized during the analysis process and that each component can be separated at a suitable temperature, thus ensuring that the separation effect of the chromatographic column reaches the best, thereby ensuring the accuracy of the system analysis data.

[0077] The gas path system 102 includes an electronic pressure and flow controller and a jet pump. The electronic pressure and flow controller is connected to both the hydrogen / air supply device and the detection system 104. The electronic pressure and flow controller is equipped with a proportional-integral (PI) control circuit, which not only avoids fluctuations in the flow rates of hydrogen and air supplied by the hydrogen / air supply device but also maintains a stable ratio of hydrogen to air. The jet pump is connected to both the compressed air supply device and the non-methane total hydrocarbon detection device via pipelines. In operation, compressed air enters the working chamber of the jet pump through the inlet. Due to the high-speed jet, the static pressure in the working chamber is lower than the external atmospheric pressure, forming a local low-pressure zone, i.e., a negative pressure field. This negative pressure field is connected to the sampling end of the sample introduction system 103 via pipelines. Under the driving force of the pressure difference between the external atmospheric pressure and the negative pressure field of the jet pump, the sample gas to be tested overcomes the pipeline resistance and enters the sample introduction system 103, achieving efficient and stable sample introduction and overcoming the dependence on a power source required by traditional positive pressure sampling.

[0078] It is worth noting that in this solution, a filter and a pressure regulating valve are connected sequentially between the compressed air supply unit and the jet pump. The filter can filter out particulate matter, oil mist, and other impurities in the compressed air, preventing them from entering the jet pump or subsequent air circuit system 102 and causing pipeline blockage, affecting the normal operation of valves, or causing other damage. The pressure regulating valve is used to adjust the compressed air pressure to keep it within the pressure range suitable for the jet pump's operation. Simultaneously, the jet pump is also connected to a pressure gauge and a flow meter. The pressure gauge can monitor the working pressure of the jet pump in real time, providing operators with intuitive readings to facilitate timely monitoring of its operating status and ensure operation within the normal pressure range, thus avoiding damage to the equipment caused by abnormal pressure. The flow meter can read the compressed air flow rate to monitor the jet pump's operating status. Operators can use flow rate changes to determine whether there are leaks, blockages, or other faults in the air circuit system 102, thereby enabling timely maintenance and adjustments.

[0079] The detection system 104 includes a flame ionization (FID) detector, which is connected to a non-methane total hydrocarbon (NMCH) detection device to detect components separated by the NMCH detection device. The detector converts the physical or chemical properties of each component in the sample gas into electrical signals, thereby enabling qualitative and quantitative analysis of the sample gas composition. The data processing system 105 is connected to the detection system 104. It processes and analyzes the electrical signals received from the detection system 104, and uses specific algorithms and software programs to ultimately calculate the concentration of each component in the sample gas.

[0080] The gas chromatograph apparatus 100 provided in this application, on the one hand, utilizes the Venturi effect of compressed air through a jet pump to create a negative pressure field, achieving efficient and stable sample gas injection in a pressure differential driven mode. This method not only breaks through the dependence on a power source for traditional positive pressure injection, providing technical support for the accurate detection of gas components, but also avoids the dilution of high-concentration sample gases, thereby eliminating the problem of chromatographic peak broadening caused by uneven dilution, and saving the cost of additional dilution equipment. On the other hand, the apparatus uses a hardware proportional-integral control circuit to achieve high-precision and high-stability control of hydrogen and air flow / pressure, ensuring that high-concentration organic compounds are completely ionized in the hydrogen flame and that low-concentration signals are clearly distinguishable, while minimizing flow fluctuations, providing a key guarantee for the reliable detection of extremely low concentrations. Therefore, the apparatus provided in this application achieves the ability to detect high-concentration and low-concentration gases without dilution or concentration.

[0081] Those skilled in the art will understand that the carrier gas does not participate in the separation process, and nitrogen or other types of inert gases are usually used as the carrier gas.

[0082] In one specific implementation, the auxiliary system 101 of the gas chromatography apparatus 100 further includes a standard gas supply device, specifically a standard gas cylinder. The gas pipeline output from the standard gas cylinder is sequentially connected to a flow meter and the injection system 103, allowing the standard gas to enter the injection system 103 after the flow rate is monitored by the flow meter. Those skilled in the art will understand that the standard gas in the standard gas cylinder refers to a standard gas with a known accurate concentration and composition. This standard gas is mainly used in the apparatus for calibration, accuracy testing, and quality control.

[0083] In one specific implementation, the data processing system 105 includes: a signal conditioning board with an amplification circuit for amplifying and outputting the current detected by the detection system 104; and a control board that acquires the amplified analog signal at a preset sampling frequency and converts the analog signal into a digital signal for transmission. The data processing system 105 also includes a host computer and a display, wherein the host computer contains analysis software that filters and corrects the digital signal before transmitting the results to the display for display.

[0084] In this solution, the data processing system 105 includes a signal conditioning board, a control board, a host computer, and a display. The signal conditioning board is the front-end part of the data processing system 105, and its main function is to perform preliminary processing on the weak signal output by the detection system 104, making it suitable for subsequent acquisition and analysis. Since the current signal output by the detection system 104 is usually very weak, directly acquiring such a signal would result in inaccurate measurement due to its weakness, or it would be easily affected by noise interference. Therefore, the signal conditioning board of this application is equipped with an amplification circuit. The function of this amplification circuit is to amplify the weak current signal output by the detection system 104 to a level that can be effectively acquired by subsequent circuits. Specifically, as follows... Figure 5 As shown, the amplification circuit in this scheme includes a series-connected logarithmic amplifier circuit, a delogarithmic circuit, a current-to-voltage conversion circuit, and a data acquisition circuit. The logarithmic amplifier circuit consists of a logarithmic amplifier A1 and a diode D1. Logarithmic amplifier A1 is a high-gain logarithmic amplifier used to amplify the weak input current signal. Diode D1, together with logarithmic amplifier A1, constitutes the nonlinear part of the logarithmic amplifier, responsible for converting the amplified signal into logarithmic form. The delogarithmic circuit, corresponding to the logarithmic amplifier, converts the logarithmic signal back to linear form. Specifically, the delogarithmic circuit is composed of diode D2. When the input signal micro-current lin is input to the logarithmic amplifier, it is processed by the logarithmic amplifier and the delogarithmic circuit, ultimately forming the relationship between the output current and the input current:

[0085] Io = sqrt(Iref × Iin), Formula 1;

[0086] Where Iref is the reference current and Iin is the input current.

[0087] The current-to-voltage conversion circuit consists of operational amplifier A2 and resistor R. It converts the output current into a voltage signal for subsequent analog-to-digital conversion. In this invention, when the output current Io flows through resistor R, a voltage drop is generated across R. Operational amplifier A2 amplifies this voltage drop to obtain a voltage signal proportional to the output current. The acquisition circuit in this solution is an AD acquisition circuit (analog-to-digital converter), which converts the analog voltage signal into a digital signal for subsequent digital processing. That is, the output of the AD acquisition circuit is a digital signal, which can be transmitted to a host computer or other digital processing devices through a digital interface.

[0088] The above solution details the signal conditioning board in the data processing system 105. The control board will be described in detail below. The control board in this solution is responsible for acquiring and digitizing the amplified analog signal, and then transmitting the processed data to the host computer. Specifically, the control board converts the acquired analog signal into a digital signal using an analog-to-digital converter (ADC), and then transmits it to the host computer via a network interface.

[0089] Those skilled in the art will understand that the sampling frequency determines the accuracy of signal acquisition and the integrity of the data. A higher sampling frequency can more accurately reproduce the details of the signal and reduce signal distortion. Traditional detection devices typically have a sampling frequency of 10 to 20 sps (samples per second), while the preset sampling frequency in this solution is 80 sps. This means the control board acquires the amplified analog signal at a sampling frequency of 80 sps, which translates to 80 signal points per second. This frequency is significantly higher than traditional solutions, not only greatly improving the accuracy and effectiveness of the data but also helping to reduce noise interference, playing a crucial role in improving the accuracy of low-concentration detection.

[0090] The host computer is the core of data processing. It receives digital signals from the control board, starts the analysis software, and calls its built-in algorithms to perform noise reduction and smoothing processing on the data, as well as baseline correction.

[0091] This application employs Savitzky-Golay (SG) filtering to smooth the detection data. Its principle is based on the least squares method, using polynomial fitting to achieve data smoothing. This method can eliminate random noise while preserving useful information in the analyzed signal. The most direct manifestation in the signal spectrum is the removal of "glitch" in the spectrum, making the entire spectrum smoother. For example... Figure 6 As shown, the smoothed data exhibits significantly improved smoothness compared to the original data, effectively suppressing signal noise while maintaining the overall data trend without distortion, demonstrating excellent smoothing performance. This noise reduction and smoothing process is an essential data processing technique in the detection of high and low concentrations of exhaust gas, and a good smoothing effect plays a crucial role in ensuring the accuracy and stability of the detection results.

[0092] Those skilled in the art will understand that there are many baseline correction methods, such as the default baseline method, peak cluster baseline method, tangent sliding method, curve fitting method, etc. However, the methods mentioned above have obvious drawbacks. The default baseline method has problems such as the inability to predict data drift and baseline differences between individual devices. The peak cluster baseline method has high baseline uncertainty when the peak spacing is small and there are many clutter signals. The tangent sliding method will result in large deviations in baseline drawing in practical application scenarios such as large baseline drift and tailing peaks. Although the baseline obtained by the curve fitting method has small error, the computational cost is relatively large.

[0093] Given the many shortcomings of the baseline correction methods mentioned above, the proposed solution employs multi-order discrete wavelet transform for baseline correction to ensure the accuracy of chromatographic peak identification and peak area calculation. This correction accuracy is particularly crucial for the identification and qualitative and quantitative analysis of low-concentration peaks.

[0094] Multi-order discrete wavelet transform is essentially a multi-scale signal processing and analysis technique. Its core principle is to decompose and reconstruct the signal, breaking it down into sub-signals of different frequencies to accurately capture the signal's time and frequency characteristics. During decomposition, the signal is progressively decomposed into sub-signals corresponding to wavelet functions at different scales. During reconstruction, some low-frequency signals can be zeroed out as needed, thereby achieving denoising and compression of the signal.

[0095] For example, in the data processing of this device, DB4 wavelet is specifically selected to perform layer-by-layer decomposition of the signal data. At each decomposition level, the signal is first downsampled by a low-pass filter to obtain approximation coefficients cA, and then downsampled by a high-pass filter to obtain detail coefficients cD. This decomposition process is repeated according to a preset order, ultimately obtaining the required number of frequency bands. By selectively processing the approximation and detail coefficients, the baseline and target signals are effectively separated, improving the correction effect.

[0096] It is worth noting that the signal decomposition process can be calculated using the following formula:

[0097] cA = s(t)×φ(t), Formula 2;

[0098] cD = s(t)×ψ(t), Formula 3;

[0099] Where s(t) is a given signal, and φ(t) and ψ(t) represent the impulse response functions of the low-pass filter and the high-pass filter, respectively, which are determined by the filter coefficients of the DB4 wavelet.

[0100] In this scheme, when using the multi-order discrete wavelet transform method for baseline correction, the number of decomposition levels and the selection of the wavelet function are key parameters affecting the correction effect. Specifically, the number of decomposition levels depends on the complexity of the signal; more levels result in finer frequency band division and higher signal resolution, but also increase computational complexity and data processing volume. The characteristics of the wavelet function directly affect the quality of signal decomposition. In actual chromatographic data processing, it is necessary to dynamically select an appropriate wavelet function (such as the DB4 wavelet used in this device) and decomposition order based on signal characteristics (such as noise level and peak width distribution) to balance correction accuracy and computational efficiency.

[0101] The baseline correction process is as follows: First, the original signal is decomposed into multiple levels using DB4 wavelets to generate approximation coefficients cA (representing baseline trend) and detail coefficients cD (representing chromatographic peak characteristics). Then, the approximation coefficients are set to zero to remove the baseline, retaining only the detail coefficients containing the target signal. Finally, the new approximation coefficients and detail coefficients are inversely transformed and recombined to form a new original signal with the baseline removed, thus achieving baseline correction of the signal data. The baseline correction effect is compared to... Figure 7 As shown in the figure, the curves before and after baseline correction show that the entire chromatographic data is completely close to zero after baseline correction, and baseline drift and noise interference are effectively suppressed, which fully verifies the effectiveness of the method under complex working conditions.

[0102] This solution uses analysis software to filter and correct digital signals, thereby removing noise and interference from the signals and adjusting the signal baseline to make it closer to the true value.

[0103] The monitor receives processed data from the host computer and displays it in graphical or tabular form. Users can visually view the detection results, such as the shape, position, and area of ​​chromatographic peaks, through the monitor. Additionally, the monitor can provide a user interface, allowing users to adjust analytical parameters, view data from different time periods, or perform other operations.

[0104] The gas chromatography apparatus 100 provided in this application achieves significant technological improvements and application value through synergistic optimization of hardware and software. At the hardware level, a proportional-integral control circuit is employed, coupled with a low-temperature drift, high-precision resistive container, to precisely adjust the hydrogen-to-air ratio to ensure complete ionization of high-concentration organic matter. Simultaneously, a stable injection environment is constructed through the synergistic effect of a jet pump negative pressure injection and a fixed-volume quantitative loop. At the software level, the combination of a high sampling frequency of 80 sps and high-precision baseline correction using multi-order discrete wavelet transform significantly enhances the signal detection capability for low-concentration substances. This hardware-software synergy enables the apparatus to achieve both large-range detection and precise detection of extremely low-concentration substances. Furthermore, the hardware-driven response speed is faster than traditional software control, allowing for real-time dynamic adjustment of gas flow to avoid control delays and ensure stable hydrogen-to-air ratios under complex operating conditions. Simultaneously, the signal processing flow combining SG filtering and wavelet transform effectively suppresses noise interference, bringing the data close to zero after baseline correction, significantly reducing signal fluctuations, and further improving the stability and reliability of detection. This provides high-precision and widely adaptable technical support for scenarios such as waste gas analysis.

[0105] The gas chromatography apparatus 100 provided by this utility model, through negative pressure sampling, precise gas path pressure / flow control, and a reasonable injection detection backflush design, combined with highly reliable ignition control, logarithmic amplifier circuit signal processing, and high-precision data processing algorithms, achieves gas chromatography analysis of both high-concentration and low-concentration volatile organic compounds (VOCs) using a single device. Experimental verification results when a low-concentration standard gas (C-based concentration of 0.42 mg / m³) is introduced are as follows: Figure 8 As shown, the chromatographic data signal of the device is clear and stable, the chromatographic peaks are clearly identifiable, and the data stability is high after repeated gas purging. Experimental verification results are as follows when a high concentration of standard gas (C-based concentration of 1800 g / m³) is introduced. Figure 9 As shown, the chromatographic data signal is still recognizable, and the data signal has not yet reached the maximum amplification value of the amplifier circuit. In other words, the device provided in this application successfully achieves the purpose of gas chromatographic analysis of high and low concentration exhaust gases.

[0106] The detection method provided in this application can detect both low-concentration and high-concentration volatile organic compounds (VOCs), effectively overcoming the limitations of existing technologies. Existing technologies require dilution to detect high-concentration gases, which can lead to peak broadening, prolonged detection time, and increased costs. Detection of low-concentration gases relies on an enrichment module, which needs to be cleaned and replaced regularly to avoid interference, adding extra maintenance costs. In contrast, this method does not require additional dilution gases or frequent maintenance of the enrichment module, significantly reducing detection costs and operational complexity.

[0107] While numerous embodiments of this application have been shown and described herein, it will be apparent to those skilled in the art that such embodiments are provided by way of example only. Many modifications, alterations, and alternatives will arise for those skilled in the art without departing from the spirit and intent of this application. It should be understood that various alternatives to the embodiments of this application described herein may be employed in the practice of this application. The appended claims are intended to define the scope of protection of this application and therefore cover equivalents or alternatives within the scope of these claims.

[0108] While numerous embodiments of this application have been shown and described herein, it will be apparent to those skilled in the art that such embodiments are provided by way of example only. Many modifications, alterations, and alternatives will arise for those skilled in the art without departing from the spirit and intent of this application. It should be understood that various alternatives to the embodiments of this application described herein may be employed in the practice of this application. The appended claims are intended to define the scope of protection of this application and therefore cover equivalents or alternatives within the scope of these claims.

Claims

1. An electronic pressure and flow controller, which is connected to a hydrogen / air supply device and a hydrogen flame ionization (FID) detector, characterized in that, The electronic pressure and flow controller includes a proportional-integral (PI) control circuit, which is a closed-loop control circuit and includes: An error comparator is used to receive the measured value detected by the sensor and calculate the difference between the set value and the measured value. A proportional-integral (PI) controller that generates an adjustment signal based on the received difference; and A power amplifier amplifies the electrical signal received from the proportional-integral controller into a strong current signal, and adjusts the gas flow rate based on the strong current signal to control the ratio of hydrogen to air.

2. The electronic pressure and flow controller according to claim 1, characterized in that, The error comparator is implemented by operational amplifier U4A: The setpoint signal is divided by resistors R35 and R39 and then input to the non-inverting input terminal of U4A. The measured signal is input to the inverting input terminal of U4A via resistor R41; The feedback resistor R42 is connected to the output terminal and the inverting input terminal of U4A to form an error amplifier circuit.

3. The electronic pressure and flow controller according to claim 2, characterized in that, The PI controller includes an operational amplifier U4B, a resistor R33, and a capacitor C31. The error signal is input to the inverting input terminal of U4B via resistor R36; R33 and C31 are connected in parallel between the inverting input and output of U4B to form a PI control circuit.

4. The electronic pressure and flow controller according to claim 3, characterized in that, The power amplifier includes: The non-inverting input of the operational amplifier U4C is connected to the output of the PI controller via resistor R38. Protection diode D8 is connected to the output terminal of U4C; The base of transistor Q5 is connected to the output terminal of D8 via resistor R40, which drives the opening of the proportional valve.

5. The electronic pressure and flow controller according to any one of claims 1-4, characterized in that, The parameters in the proportional-integral control circuit can be fixed by changing the resistors and capacitors with different configurations.

6. The electronic pressure and flow controller according to any one of claims 1-4, characterized in that, The set value can be indirectly modified by adjusting the resistance of the digital potentiometer through software.

7. The electronic pressure and flow controller according to any one of claims 1-4, characterized in that, The resistors and capacitors use low-temperature drift, high-precision components to ensure the stability of PI parameters.

8. A non-methane total hydrocarbon detection device, characterized in that, It includes the electronic pressure and flow controller as described in any one of claims 1-7.

9. The non-methane total hydrocarbon detection device according to claim 8, characterized in that, The non-methane total hydrocarbon detection device also includes: A multi-channel injection valve is provided with multiple ports, and the multi-channel injection valve realizes quantitative capture and component separation of sample gas by switching between injection and detection states; The first and second quantitative loops are respectively connected to the inlet of the multi-channel injection valve through pipelines; Multiple independent carrier gas channels are connected to the inlet of the multi-channel injection valve, respectively; A pre-column, used to adsorb impurities in the sample gas to purify it; and The three-way solenoid valve is connected to the methane column, the total hydrocarbon column, and the FID detector, respectively.

10. The non-methane total hydrocarbon detection device according to claim 9, characterized in that, The multi-channel injection valve described herein has: Sample introduction status: Sample gas fills the first and second quantitative loops; Detection status: The carrier gas pushes the sample gas in the first quantitative loop through the total hydrocarbon column to the FID detector, and the sample gas in the second quantitative loop through the pre-column and the methane column to the FID detector.

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