A multi-component monitoring system for atmospheric volatile organic compounds

Abstract

This application discloses a multi-component monitoring system for atmospheric volatile organic compounds, comprising a sample pretreatment unit, a multi-channel switching valve group, a characteristic chromatographic column group, and a detector group connected in sequence; a control system electrically connected to the detector group and the multi-channel switching valve group; a sample quantification device arranged in parallel between the interfaces of the multi-channel switching valve group; a carrier gas supply system connected to the multi-channel switching valve group via a solenoid valve; and the system enables automatic detector switching and simultaneous detection of multiple organic components in a single injection.

Description

Technical Field

[0001] This application relates to a multi-component monitoring system for atmospheric volatile organic compounds, belonging to the field of environmental monitoring technology. Background Technology

[0002] Volatile organic compounds (VOCs) are a class of organic compounds that have high saturated vapor pressure, low boiling point, and small molecular weight under standard conditions, and are easily volatilized at room temperature. They are among the main air pollutants, contributing significantly to regional ozone pollution and PM2.5 pollution. 2.5 Pollution has a significant impact. VOCs mainly include non-methane hydrocarbons, oxygenated organic compounds, halogenated hydrocarbons, nitrogen-containing organic compounds, and sulfur-containing organic compounds.

[0003] Gas chromatography (GC) is a relatively mature online VOCs analysis method with a solid foundation for development and research. GC is typically coupled with detectors such as flame ionization detectors (FID) and photoionization detectors (PID). These detectors offer high selectivity and excellent responses to certain characteristic compounds. PID detectors are particularly sensitive to a wide range of VOCs, including alkenes, benzene compounds, aldehydes, ketones, and long-chain alkanes, with analysis cycles as fast as seconds, making them suitable for real-time and emergency monitoring of VOCs in ambient air. However, PID detectors have poor responses to low-carbon saturated hydrocarbons, and their signal stability decreases significantly under high humidity conditions, making them unsuitable for high-concentration environments and industrial emission point monitoring. The FID flame ionization detector responds to almost all carbon-containing organic compounds, offering advantages such as high sensitivity, fast response, good selectivity, and a wide linear range. It is also minimally affected by environmental conditions and suitable for long-term operation. However, FID detectors rely on gas supply, and the separation time varies greatly between different species, with a single operation time potentially ranging from tens of minutes to several hours.

[0004] CN221765333 discloses a portable total hydrocarbon analyzer that solves the problem of portability of existing total hydrocarbon analyzers by configuring a main control board, EPC, FID detector, and PID detector. However, it can only detect the concentration of methane and non-methane components and does not make full use of the advantages of the two detectors.

[0005] CN221465435 discloses a portable non-methane total hydrocarbon analyzer with integrated multiple sensors, including an FID detector, a PID sensor, a carbon monoxide sensor, a carbon dioxide sensor, an oxygen sensor, and a methane sensor. The concentration of non-methane total hydrocarbons is obtained by integrating and analyzing the values ​​of each detector through an algorithm. However, this method depends on the accuracy of the six detectors, requires frequent calibration, and has high maintenance costs.

[0006] Existing technologies often utilize FID and PID detectors to develop single-detector devices for VOCs monitoring in different scenarios. While some products combine two detectors to address the detection of total hydrocarbons, methane, and non-methane total hydrocarbons, their complex structures, limited VOCs detection components, and high costs fail to fully leverage the unique detection advantages of the two instruments. Consequently, the performance of instruments equipped with two detectors is not significantly improved compared to single-detector instruments. Therefore, researching a monitoring system for atmospheric volatile organic compounds with automatic switching between dual detectors is of great significance. Summary of the Invention

[0007] The purpose of this application is to overcome the shortcomings of the prior art and provide a multi-component monitoring system for atmospheric volatile organic compounds, which can realize the simultaneous detection of multiple organic components in a single sample injection.

[0008] To achieve the above objectives, the technical solution adopted in this application is as follows: This application provides a multi-component monitoring system for atmospheric volatile organic compounds, including: The sample pretreatment unit, multi-channel switching valve group, characteristic chromatographic column group and detector group are connected in sequence by tubing; A control system electrically connected to the detector group and the multi-channel switching valve group; A sample quantification device connected in parallel between the interfaces of a multi-channel switching valve group; A carrier gas supply system connected to a multi-channel switching valve group via a solenoid valve; The detector group includes an FID detector and a PID sensor arranged in parallel; the multi-channel switching valve group includes a 10-way switching valve and a 14-way switching valve connected in series; the sample quantification device includes a total hydrocarbon quantification loop, a methane quantification loop and a benzene series quantification loop connected in parallel; the characteristic chromatographic column group includes a total hydrocarbon chromatographic column, a methane chromatographic column and a benzene series chromatographic column; the carrier gas supply system is provided with at least four independent carrier gas channels, and the carrier gas backflushing fluid channel is realized through the multi-channel switching valve group.

[0009] Furthermore, the ninth port of the ten-way switching valve is connected to the fourteenth port of the fourteen-way switching valve; the fifth port of the ten-way switching valve and the tenth port of the fourteen-way switching valve are both connected to the detection port of the FID detector.

[0010] Furthermore, the first port of the ten-way switching valve is connected to the sample pretreatment unit and the PID sensor respectively via a three-way valve, the second port of the ten-way switching valve is connected to the benzene series quantitative loop, the fourth port of the ten-way switching valve is connected to the benzene series chromatographic column, and the tenth port of the ten-way switching valve is connected to the sample outlet.

[0011] Furthermore, the second port of the fourteen-port switching valve is connected to the total hydrocarbon metering loop, the fourth port of the fourteen-port switching valve is connected to the total hydrocarbon chromatographic column, the sixth port of the fourteen-port switching valve is connected to the methane metering loop, and the seventh port of the fourteen-port switching valve is connected to the methane chromatographic column.

[0012] Furthermore, the carrier gas backflushing fluid passage includes: The third carrier gas backwashes the methane column via the twelfth port of the fourteen-port switching valve, and the residual components in the methane column are discharged through the eighth port of the fourteen-port switching valve. The fourth carrier gas backwashes the benzene series column via the third port of the ten-port switching valve, and the residual components in the benzene series column are discharged through the seventh port of the ten-port switching valve.

[0013] Furthermore, the air inlet of the PID sensor is independently connected to an air pump, and its signal output is connected to the control system.

[0014] Furthermore, the sample pretreatment unit includes a particulate filter and a heat tracing pipeline. The heat tracing pipeline is wrapped with heating wire and insulation material, and the surface of all carrier gas passages is treated with silanization.

[0015] Furthermore, the methane chromatographic column is a PLOT Q chromatographic column with a heating device at its bottom; the benzene series chromatographic column is a PEG chromatographic column; and the total hydrocarbon chromatographic column is a packed column.

[0016] Furthermore, the combustion air supply line of the FID detector is connected to a hydrocarbon remover, and the flame outlet direction of the FID detector is perpendicular to the base plate on which it is mounted.

[0017] Furthermore, the components separated by the benzene series chromatographic column include any one or more of benzene, toluene, ethylbenzene, p-xylene, m-xylene, o-xylene, cumene, and styrene.

[0018] Compared with the prior art, the beneficial effects achieved by this application are as follows: This application uses an FID detector and a PID sensor in combination, and automatically switches the operation of the two detectors according to the VOCs concentration of the sample. It makes full use of the advantages of the PID sensor's fast detection speed and the FID sensor's accurate quantification and response to key VOCs components, so as to complete the long-term monitoring of low-concentration VOCs and the accurate analysis of high-concentration VOCs components, combining the advantages of fast response and high precision. By optimizing the gas path topology design of the 10-way switching valve and the 14-way switching valve, the gas path connection of the whole machine is optimized, enabling simultaneous parallel analysis of multi-component detection in a single injection, thereby improving detection efficiency. The column is backwashed with carrier gas to eliminate interference from residual components and ensure the accuracy of continuous detection; the entire gas path is silanized and heated, which significantly reduces the risk of adsorption and condensation of active substances. Attached Figure Description

[0019] Figure 1 This is a schematic diagram of the working state of the PID sensor provided in the embodiments of this application; Figure 2 This is a schematic diagram of the working state of the FID detector and PID sensor provided in the embodiments of this application; In the diagram: 1-Ten-way switching valve, 2-Fourteen-way switching valve, 3-PID sensor, 4-FID detector, 5-Control system, 6-Three-way valve, 7-Air pump, 8-Benzene series quantitative ring, 9-Total hydrocarbon quantitative ring, 10-Methane quantitative ring, 11-Solenoid valve, 12-Total hydrocarbon column, 13-Methane column, 14-Heating device, 15-Four-way valve, 16-Hydrocarbon remover, 17-Heating wire, 18-Benzene series column, 19-Particulate filter. Detailed Implementation

[0020] The present application will be further described below with reference to the accompanying drawings. The following embodiments are only used to more clearly illustrate the technical solution of the present application, and should not be used to limit the scope of protection of the present application.

[0021] Example 1:

[0022] This embodiment provides a multi-component monitoring system for atmospheric volatile organic compounds, including a ten-way switching valve 1, a fourteen-way switching valve 2, a PID sensor 3, an FID detector 4, a control system 5, a three-way valve 6, an air pump 7, a benzene series quantitative ring 8, a total hydrocarbon quantitative ring 9, a methane quantitative ring 10, a solenoid valve 11, a total hydrocarbon chromatographic column 12, a methane chromatographic column 13, a heating device 14, a four-way valve 15, a hydrocarbon remover 16, a heating wire 17, a benzene series chromatographic column 18, and a particulate filter 19.

[0023] The 10-way switching valve 1, the 14-way switching valve 2, the PID sensor 3, and the FID detector 4 are connected to the air circuit via pipelines; the PID sensor 3 and the FID detector 4 are electrically connected to the control system 5. Both the PID sensor 3 and the FID detector 4 have independent air pumps 7, controlled by the control system 5. The two detectors can operate simultaneously or independently, and the instrument operation mode is set and controlled by the control system 5.

[0024] The ten-way switching valve 1 has ports q1 to q10 in clockwise order; the fourteen-way switching valve 2 has ports a1 to a14 in clockwise order, and the connection of each port is as follows: The first port q1 of the ten-way switching valve is connected to the sample inlet via the three-way valve 6; The second port q2 of the ten-way switching valve is connected to the benzene series metering ring 8; The third port q3 of the ten-way switching valve is connected to the solenoid valve 11 and the fourth carrier gas line; The fourth port q4 of the ten-way switching valve is connected to the benzene series chromatography column 18; The fifth port q5 of the ten-way switching valve is connected to the four-way valve 15 and the detection port of the FID detector; The sixth port q6 of the ten-way switching valve is connected to the first and second carrier gas outlets; The seventh port q7 of the ten-way switching valve is connected to the fourth carrier gas outlet; The eighth port q8 of the ten-way switching valve is connected to the benzene series chromatography column 18; The ninth port q9 of the ten-way switching valve is connected to the fourteenth port a14 of the fourteen-way valve. The tenth port q10 of the ten-way switching valve is connected to the sample outlet; The first port a1 of the 14-way switching valve is connected to the benzene series metering ring 8; The second port a2 of the 14-way switching valve is connected to the total hydrocarbon metering ring 9; The third port a3 of the 14-way switching valve is connected to the solenoid valve 11 and the first carrier gas path; The fourth port a4 of the fourteen-way switching valve is connected to the total hydrocarbon chromatographic column 12; The fifth port a5 of the 14-way switching valve is connected to the total hydrocarbon metering ring 9; The sixth port a6 of the 14-way switching valve is connected to the methane metering ring 10; The seventh port a7 of the fourteen-way switching valve is connected to the methane chromatography column 13; The eighth port a8 of the fourteen-way switching valve is connected to the third carrier gas outlet; The ninth port a9 of the fourteen-way switching valve is connected to the solenoid valve 11 and the second carrier gas. The 10th port a10 of the 14-way switching valve is connected to the 4-way valve 15 and the detection port of the FID detector; The eleventh port a11 of the fourteen-way switching valve is connected to the methane chromatography column 13; The 12th port a12 of the 14-way switching valve is connected to the solenoid valve 11 and the third carrier gas line; The thirteenth port a13 of the fourteen-way switching valve is connected to the methane metering ring 10; The fourteenth port a14 of the fourteen-way switching valve is connected to the ninth port q9 of the ten-way switching valve.

[0025] A particulate filter 19 is installed at the sample inlet. Below the filtered sample gas pipeline is a heat tracing pipeline wrapped with heating wire 17 and heat insulation material for full heating and heat preservation. The carrier gas, hydrogen and combustion air pipelines are equipped with solenoid valves 11, and the four carrier gas pipelines are all independent gas pipelines.

[0026] The air required for combustion of the FID detector 4 is supplied by the air pump 7 and enters the FID detector 4 through the hydrocarbon remover 16; the FID detector 4 is fixed in such a way that the flame outlet direction is perpendicular to the base plate.

[0027] Column 13 is a PLOT Q column used to separate methane. A heating device 14 for temperature regulation is installed below column 13. Column 12 is a packed column used to separate total hydrocarbons. Column 18 is a PEG column used to separate benzene, toluene, ethylbenzene, p-xylene, m-xylene, o-xylene, cumene, and styrene.

[0028] The multi-component atmospheric volatile organic compound monitoring system provided in this application features a fully silanized gas path system to reduce the adsorption of active substances in the pipeline. A heat tracing line is added to the sample gas inlet pipeline to ensure the sample temperature during system operation and prevent condensation. All heat tracing lines are insulated to ensure the sample gas temperature remains within the set range during system operation.

[0029] Example 2:

[0030] like Figure 1 The diagram shown is a schematic of the working state of the PID sensor provided in this embodiment of the application. The air sample enters the three-way valve 6 after passing through the particulate filter 19. The two ports of the three-way valve 6 are connected to the PID sensor 3 and the first port q1 of the ten-way switching valve, respectively. Part of the air sample after being filtered by the particulate filter 19 is discharged through the first port q1 and the tenth port q10 of the ten-way switching valve. The other part of the air sample enters the PID sensor 3 through the air pump. The PID sensor 3 uses the plasma generated by the ultraviolet lamp to ionize the gas molecules to be measured, generating positive ions and free electrons. These ionized particles form an ion flow under the action of the electric field and output a current signal. The PID sensor 3 transmits the detection status to the control system 5 through an electrical signal, and determines the VOCs concentration in the air sample by the current intensity.

[0031] In this feasible application, a VOCs concentration warning value is set in the control system 5. When a single PID sensor detects that the VOCs concentration exceeds the warning value, the control system 5 switches to a state where both the FID detector and the PID sensor work together. Figure 2 As shown.

[0032] When the FID detector 4 and the PID sensor 3 work together, the process includes the following three stages: (1) Sample introduction stage Air samples pass through particulate filter 19 and enter three-way valve 6. The two ports of three-way valve 6 are connected to PID sensor 3 and the first port q1 of ten-way switching valve 1, respectively. A portion of the air sample enters PID sensor 3 via an air pump. PID sensor 3 uses plasma generated by an ultraviolet lamp to ionize the gas molecules to be measured, producing positive ions and free electrons. These ionized particles form an ion flow under the influence of an electric field and output a current signal. PID sensor 3 transmits the detection information to the control system via an electrical signal, and the VOCs concentration in the air sample is determined by the current intensity. The other portion of the air sample passes through benzene series quantitative loop 8, total hydrocarbon quantitative loop 9, and methane quantitative loop 10, and is discharged through the tenth port q10 of ten-way switching valve 1. The injection stops when the air sample has filled all three quantitative loops.

[0033] (2) Analysis phase After sample injection, the 10-port switching valve 1 and the 14-port switching valve 2 are switched to... Figure 1 Status, in Figure 1 In the process, the first carrier gas is introduced into the third port a3 of the fourteen-way switching valve, which pushes the total hydrocarbon quantitative loop 5 sample into the total hydrocarbon chromatographic column 12. Subsequently, the sample enters the FID detector 4 through the four-way valve 15 with the carrier gas for detection.

[0034] The third carrier gas is introduced into the twelfth port a12 of the fourteen-way switching valve, which pushes the sample in the methane quantitative loop 10 into the methane chromatographic column 13. The sample is separated in the methane chromatographic column 13. Methane gas is separated first, and then later than total hydrocarbons. It enters the FID detector 4 through the four-way valve 15 with the carrier gas for detection.

[0035] The fourth carrier gas is introduced into the third port q3 of the ten-way switching valve, propelling the sample in the benzene series quantitative loop 8 into the benzene series chromatographic column 18. VOC components in the sample begin to separate in the benzene series chromatographic column 18. Benzene, toluene, ethylbenzene, p-xylene, m-xylene, o-xylene, cumene, and styrene are successively separated from the benzene series chromatographic column 18 and, along with the carrier gas, enter the FID detector 4 via the four-way valve 15 for detection. Total hydrocarbons, methane, benzene, toluene, ethylbenzene, p-xylene, m-xylene, o-xylene, cumene, and styrene sequentially enter the FID detector 4 for combustion. After processing by the electrometer plate, the combustion signals are converted into electrical signals and sent to the control system 5. The control system 5 analyzes the electrical signals to determine the concentration of each VOC component in the sample.

[0036] (3) Backflush stage After the sample components are detected, the 10-way switching valve 1 and the 14-way switching valve 14 are switched to... Figure 2In this state, the third carrier gas is introduced into the 12th port a12 of the 14-way valve. The carrier gas enters the methane column 13 in the opposite direction of injection via the 11th port a11 of the 14-way valve, and backflushs out other residual components in the methane column 13 through the 8th port a8 of the 14-way valve, thereby achieving the effect of cleaning the methane column.

[0037] The fourth carrier gas is introduced into the third port a3 of the ten-way switching valve. The carrier gas enters the benzene series chromatography column 18 in the opposite direction of injection via the fourth port q4 of the ten-way switching valve. Other residual components in the benzene series chromatography column 18 are backflushed out via the seventh port q7 of the ten-way switching valve, thus achieving the effect of cleaning the benzene series chromatography column.

[0038] This application utilizes the combined use of an FID detector and a PID sensor, automatically switching between the two detectors based on the sample's VOC concentration. It fully leverages the advantages of the PID sensor's high detection speed and the FID sensor's accurate quantification and responsiveness to key VOC components, enabling long-term monitoring of low-concentration VOCs and precise analysis of high-concentration VOC components. Furthermore, by employing a 10-port switching valve and a 14-port switching valve, the overall gas path connection is optimized, allowing for the detection of multiple benzene compounds in ambient air in a single injection.

[0039] This application requires only one instrument for VOCs monitoring and can perform backflushing and cleaning of two chromatographic columns and an FID detector. It can simultaneously meet the needs of real-time emergency monitoring of ambient air and online monitoring of high-temperature and high-humidity exhaust gas from stationary pollution sources, saving monitoring costs and reducing the time spent operating different instruments, thus improving work efficiency.

[0040] The above description is only a preferred embodiment of this application. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the technical principles of this application, and these improvements and modifications should also be considered within the scope of protection of this application.

Claims

1. A multi-component monitoring system for atmospheric volatile organic compounds, characterized in that, include: The sample pretreatment unit, multi-channel switching valve group, characteristic chromatographic column group and detector group are connected in sequence by tubing; The control system (5) is electrically connected to the detector group and the multi-channel switching valve group; A sample quantification device connected in parallel between the interfaces of a multi-channel switching valve group; A carrier gas supply system connected to a multi-channel switching valve group via a solenoid valve (11); The detector group includes an FID detector (4) and a PID sensor (3) arranged in parallel; the multi-channel switching valve group includes a ten-way switching valve (1) and a fourteen-way switching valve (2) connected in series; the sample quantification device includes a total hydrocarbon quantification loop (9), a methane quantification loop (10), and a benzene series quantification loop (8) connected in parallel; the characteristic chromatographic column group includes a total hydrocarbon chromatographic column (12), a methane chromatographic column (13), and a benzene series chromatographic column (18); the carrier gas supply system is provided with at least four independent carrier gas channels, and the carrier gas backflushing fluid channel is realized through the multi-channel switching valve group.

2. The atmospheric volatile organic compound multi-component monitoring system according to claim 1, characterized in that, The ninth port of the ten-way switching valve (1) is connected to the fourteenth port of the fourteen-way switching valve (2); the fifth port of the ten-way switching valve (1) and the tenth port of the fourteen-way switching valve (2) are connected to the detection port of the FID detector (4).

3. The atmospheric volatile organic compound multi-component monitoring system according to claim 1, characterized in that, The first port of the ten-way switching valve (1) is connected to the sample pretreatment unit and the PID sensor (3) respectively through the three-way valve (6), the second port of the ten-way switching valve (1) is connected to the benzene series quantitative loop (8), the fourth port of the ten-way switching valve (1) is connected to the benzene series chromatographic column (18), and the tenth port of the ten-way switching valve (1) is connected to the sample outlet.

4. The atmospheric volatile organic compound multi-component monitoring system according to claim 1, characterized in that, The second port of the fourteen-way switching valve (2) is connected to the total hydrocarbon quantitative loop (9), the fourth port of the fourteen-way switching valve (2) is connected to the total hydrocarbon chromatographic column (12), the sixth port of the fourteen-way switching valve (2) is connected to the methane quantitative loop (10), and the seventh port of the fourteen-way switching valve (2) is connected to the methane chromatographic column (13).

5. The atmospheric volatile organic compound multi-component monitoring system according to claim 1, characterized in that, The carrier gas backflushing fluid passage includes: The third carrier gas backwashes the methane column (13) through the twelfth port of the fourteen-port switching valve (2), and the residual components in the methane column (13) are discharged through the eighth port of the fourteen-port switching valve (2). The fourth carrier gas backwashes the benzene series chromatographic column (18) through the third port of the ten-way switching valve (1), and the residual components in the benzene series chromatographic column (18) are discharged through the seventh port of the ten-way switching valve (1).

6. The atmospheric volatile organic compound multi-component monitoring system according to claim 1, characterized in that, The air inlet of the PID sensor (3) is independently connected to the air pump (7), and its signal output is connected to the control system (5).

7. The atmospheric volatile organic compound multi-component monitoring system according to claim 1, characterized in that, The sample pretreatment unit includes a particulate filter (19) and a heat tracing pipeline. The heat tracing pipeline is wrapped with a heating wire (17) and insulation material, and the surface of all carrier gas passages is treated with silanization.

8. A multi-component monitoring system for atmospheric volatile organic compounds according to claim 1, characterized in that, The methane column (13) is a PLOT Q column with a heating device (14) below it; the benzene series column (18) is a PEG column; and the total hydrocarbon column (12) is a packed column.

9. The atmospheric volatile organic compound multi-component monitoring system according to claim 1, characterized in that, The combustion air supply line of the FID detector (4) is connected to a hydrocarbon remover (16), and the flame outlet direction of the FID detector (4) is perpendicular to the base plate on which it is installed.

10. A multi-component monitoring system for atmospheric volatile organic compounds according to claim 1, characterized in that, The benzene series chromatographic column (18) separates one or more of benzene, toluene, ethylbenzene, p-xylene, m-xylene, o-toluene, cumene, and styrene.

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