A system for online monitoring of VOCs and NOx

Abstract

The utility model relates to a kind of system of on-line monitoring VOCs and NOx, belong to gas monitoring equipment technical field, including air pump, gas path system, VOCs detection unit, NOx detection unit and workstation, air pump is connected with gas path system, gas path system is connected with the gas path in VOCs detection unit and NOx detection unit respectively, VOCs detection unit and NOx detection unit are electrically connected with workstation;Air pump accesses the gas in environment into gas path system, workstation controls VOCs detection unit and NOx detection unit to monitor the air sample in gas, the system simple structure, small portable, high integration can simultaneously accurately detect VOCs and NOx, reduce detection time and cost, improve efficiency.

Description

Technical Field

[0001] This utility model relates to an online monitoring system, specifically a system for online measurement of total hydrocarbons, methane, non-methane total hydrocarbons, and nitrogen oxides (NOx) in ambient air based on a combination of FID (flame ionization detector) and electrochemical sensors, belonging to the technical field of gas monitoring equipment. Background Technology

[0002] Volatile organic compounds (VOCs) are a class of organic compounds that have high saturated vapor pressure (typically greater than 13.33 Pa), low boiling points, small molecular weights, and are easily volatilized at room temperature under standard conditions. 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. Nitrogen oxides (NOx) are compounds composed of nitrogen and oxygen, mainly including nitric oxide (NO), nitrogen dioxide (NO2), and dinitrogen trioxide (N2O3). NOx mainly originates from anthropogenic sources such as vehicle exhaust and industrial emissions, as well as natural processes such as lightning. Studies indicate that ozone photochemical pollution, generated from the secondary reactions of VOCs and NOx under sunlight, has seriously affected human health and ecosystem stability. However, the concentrations of ozone and its precursors (NOx and VOCs) exhibit highly nonlinear behavior at different times and in different regions, making ozone pollution control extremely complex. Therefore, promoting simultaneous online monitoring of VOCs and NOx in ambient air is a crucial foundation for achieving ozone pollution control.

[0003] With the formal implementation of the "Portable Gas Chromatography-Flame Ionization Detector Method for the Determination of Total Hydrocarbons, Methane, and Non-Methane Total Hydrocarbons in Exhaust Gas from Stationary Sources" (HJ 1332-2023) in July 2024, portable GC-FID has become the standard method for determining total hydrocarbons, methane, and non-methane total hydrocarbons in exhaust gas from stationary sources. Meanwhile, the FID flame ionization detector has advantages such as high sensitivity, fast response speed, and good selectivity. Electrochemical sensor methods are currently a commonly used technique for monitoring NOx. It utilizes the reaction between nitrogen oxides and the electrolyte within the sensor to generate a current, the magnitude of which is directly proportional to the concentration of nitrogen oxides. This technique offers high sensitivity and fast response.

[0004] While individual monitoring technologies for VOCs and NOx are relatively mature, no miniaturized monitoring system can integrate an FID detector and an electrochemical sensor to achieve accurate and rapid monitoring of both precursors. Furthermore, in practical fieldwork, detecting ozone precursors requires separate VOCs and NOx monitoring instruments, necessitating multiple operators to manage each instrument, significantly increasing detection time and cost, and reducing efficiency.

[0005] The current patent CN221960094U describes a system for online monitoring of odorous gases using GC-FID / FPD. This system integrates FID and FPD to monitor VOCs and odorous gases in ambient air online. FID is used to detect VOCs, and FPD is also used to detect VOCs, serving as a supplement to the FID detector to detect more VOCs. However, it does not simultaneously detect NOx.

[0006] Patent CN216792012U describes a dual-channel, multi-component flue gas emission online monitoring system that can simultaneously monitor the concentrations of different types of waste gas components, including NOx and VOCs. It can be widely applied to online monitoring of waste gas at the end-point emission points of current mainstream waste gas treatment technologies, such as oxidation incineration processes. However, this monitoring system, designed for online monitoring of enterprise emission outlets, is structurally complex, large in area, unsuitable for portable use, and costly. Furthermore, it can only be used for online monitoring of emission outlets and is not applicable to other monitoring scenarios, such as environmental concentration monitoring. Its operation is complex and its applicability is poor.

[0007] Therefore, developing an online monitoring system for VOCs and NOx that can overcome the above-mentioned shortcomings has become a technical problem that urgently needs to be solved by those skilled in the art. Utility Model Content

[0008] The technical problem to be solved by this utility model is to overcome the shortcomings of the prior art and provide a system for online monitoring of VOCs and NOx. This system has a simple structure, is small and portable, and has a high degree of integration. It can accurately detect VOCs and NOx at the same time, reduce detection time and cost, and improve efficiency.

[0009] To solve the above technical problems, this utility model provides a system for online monitoring of VOCs and NOx, including an air pump, an air path system, a VOCs detection unit, a NOx detection unit, and a workstation. The air pump is connected to the air path system, which is connected to the air paths in the VOCs detection unit and the NOx detection unit respectively. The VOCs detection unit and the NOx detection unit are electrically connected to the workstation.

[0010] An air pump connects to the gas in the environment and introduces it into the gas path system. The workstation controls the VOCs detection unit and NOx detection unit to monitor the air sample in the gas.

[0011] The further defined technical solution of this utility model is:

[0012] Furthermore, in the aforementioned online monitoring system for VOCs and NOx, multiple air pumps are installed on the gas path system to supply different gases.

[0013] Technically, multiple independent air pumps are installed to supply different gases as needed, such as zero gas, hydrogen, tail gas, sample gas, and hydrocarbon-removed air, ensuring the normal operation of the monitoring system.

[0014] In the aforementioned online monitoring system for VOCs and NOx, the VOCs detection unit includes pipelines, an SPE filter, an electronic pressure controller, a 10-way valve, a quantitative loop, a chromatographic column, a hydrocarbon remover, an air pump, and an FID detector. The pipelines include a sample gas pipeline and a carrier gas pipeline, which are respectively connected to the 10-way valve. Two quantitative loops connected to the 10-way valve are symmetrically arranged on the 10-way valve. The 10-way valve is connected to the chromatographic column through a pipeline. The chromatographic column is connected to the FID detector through a pipeline. The FID detector is equipped with multiple air pumps, one of which is also connected to the hydrocarbon remover. An electronic pressure controller is installed on the pipeline between the FID detector and the chromatographic column.

[0015] An SPE filter is installed at the inlet of the sample gas pipeline, and an electronic pressure controller is installed on the carrier gas pipeline.

[0016] In the aforementioned online monitoring system for VOCs and NOx, an insulation layer is wound around the upper part of the sample gas pipeline between the SPE filter and the ten-way valve, and a heat tracing pipe is wound around the outside of the insulation layer.

[0017] Technically, the sample gas pipeline of this invention is wrapped with an insulation layer (preferably rigid polyurethane foam) and a heat tracing pipe, which provides heating and insulation throughout the process. This ensures the sample temperature during system operation, prevents condensation, and ensures normal operation and accurate monitoring.

[0018] In the aforementioned online monitoring system for VOCs and NOx, the chromatographic columns include a PLOT Q column and a packed column. The packed column is a total hydrocarbon column, and the PLOT Q column and the packed column are connected in parallel.

[0019] In terms of technical effects, the chromatographic column of the VOCs detection unit of this utility model is a PLOT Q chromatographic column and a packed column, which are used to separate methane and total hydrocarbons respectively. The parallel arrangement of the two chromatographic columns can detect more substances in VOCs.

[0020] In the aforementioned online monitoring system for VOCs and NOx, a heater is installed below the PLOT Q chromatographic column via a support.

[0021] The technical improvement is achieved by adding a heater, which keeps the chromatographic column at a set high temperature during operation, ensuring the column's operation and maintaining monitoring accuracy.

[0022] In the aforementioned online monitoring system for VOCs and NOx, the NOx detection unit includes an SPE filter, an air pump, an electrochemical sensor, and a circuit control panel. One end of the electrochemical sensor is connected to a pipe for sample inlet. An SPE filter is installed at the inlet of the pipe, and an air pump is also installed on the pipe. The air pump is located between the SPE filter and the electrochemical sensor and is connected to the circuit control panel.

[0023] The beneficial effects of this utility model are:

[0024] This invention incorporates an SPE filter, through which air samples enter the gas path system. The SPE filter can capture and remove particulate matter and microorganisms from the fluid.

[0025] This invention combines an FID detector and an electrochemical sensor to simultaneously monitor total hydrocarbons, methane, non-methane total hydrocarbons, and NOx gases in ambient air online and accurately quantify their concentrations.

[0026] This invention reduces the number of instruments required for ozone precursor monitoring from two to one, saving monitoring costs and reducing the time spent operating different instruments, thus improving work efficiency.

[0027] This invention, by simultaneously monitoring VOCs and NOx concentrations, can clearly identify ozone generation control zones and determine specific pathways for ozone management. Attached Figure Description

[0028] Figure 1 This is a schematic diagram of the structure of a system for online monitoring of VOCs and NOx according to an embodiment of the present invention;

[0029] Figure 2 for Figure 1 A schematic diagram of the structure of the VOCs detection unit in the middle;

[0030] Figure 3 for Figure 1 A schematic diagram of the NOx detection unit in the middle;

[0031] In the diagram: 1-Gas path system, 2-VOCs detection unit, 3-NOx detection unit, 4-Workstation, 5-Ten-way valve, 6-Quantitative loop, 7-Electronic pressure controller, 8-SPE filter, 9-Methane column, 10-Total hydrocarbon column, 11-Heater, 12-Hydrocarbon remover, 13-Air pump, 14-FID detector, 15-Heating pipe, 16-Electrochemical sensor. Detailed Implementation

[0032] The technical solutions of the present utility model will be clearly and completely described below with reference to the accompanying drawings of the embodiments. Obviously, the described embodiments are only a part of the embodiments of the present utility model, and not all of them; the technical features involved in the various embodiments of the present utility model described below can be combined with each other as long as they do not conflict with each other. Based on the embodiments of the present utility model, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the protection scope of the present utility model. Example 1

[0033] This embodiment provides a system for online monitoring of VOCs and NOx, see reference. Figure 1 The system includes an air pump 13, a gas path system 1, a VOCs detection unit 2, a NOx detection unit 3, and a workstation 4. The gas path system 1 is equipped with multiple air pumps 13 for receiving different gases. The air pumps 13 are connected to the gas path system 1. The gas path system 1 has undergone full silanization treatment, forming a silane conversion film on the inner wall of the gas path tube to reduce the adsorption of active substances in the tube. The gas path system 1 is configured to connect to the required gas paths of the VOCs detection unit 2 and the NOx detection unit 3 as needed to ensure normal operation. The VOCs detection unit 2 and the NOx detection unit 3 are electrically connected to the workstation 4. The VOCs detection unit 2 and the NOx detection unit 3 are each equipped with an independent air pump 13. Through the control of the workstation, the two detection units can work simultaneously or operate independently. The air pump 13 receives the gas from the environment and enters the gas path system 1. The workstation 4 controls the VOCs detection unit 2 and the NOx detection unit 3 to monitor the air samples in the gas.

[0034] See Figure 2The VOCs detection unit 2 is fixed with the flame outlet direction perpendicular to the base plate. The VOCs detection unit 3 includes pipelines, an electronic pressure controller 7, an SPE filter 8, a 10-way valve 5, a quantitative loop 6, a chromatographic column, a hydrocarbon remover 12, an air pump 13, and an FID detector 14. The pipelines include a sample gas pipeline and a carrier gas pipeline, which are connected to the 10-way valve 5. An SPE filter 8 is installed at the inlet of the sample gas pipeline. An insulation layer is wrapped around the sample gas pipeline between the SPE filter 8 and the 10-way valve 5, and a heat tracing pipe 15 is wrapped around the insulation layer to ensure the sample temperature is within the set range during system operation and to prevent condensation. An electronic pressure controller 7 is installed on the carrier gas pipeline. Two quantitative loops 6 are symmetrically arranged on the 10-way valve 5 and connected to it. The 10-way valve 5 is connected to the chromatographic column through a pipeline. The chromatographic column includes a PLOT Q chromatographic column 9 for separating methane substances, a packed column 10 (empty column) for separating total hydrocarbons, and a PLOT... The Q column 9 and the packed column 10 are connected in parallel and can be controlled by a workstation to work simultaneously or operate separately to ensure work efficiency. A heater 11 is installed below the PLOT Q column 9 via a support to regulate the temperature. The column is connected to the FID detector 14 via a pipe. The FID detector 14 is equipped with two air pumps 13. One of the air pumps 13 is also connected to a hydrocarbon remover 12 to introduce the air required for combustion in the FID detector 14. The other air pump is connected to hydrogen. An electronic pressure controller 7 is installed on the pipe between the FID detector 14 and the column.

[0035] See Figure 3 The NOx detection unit 3 includes an SPE filter 8, an air pump 13, an electrochemical sensor 15, and a circuit control panel. One end of the electrochemical sensor 15 is connected to a pipe for sample inlet. The SPE filter 8 is installed at the inlet of the pipe. The air pump 13 is also installed on the pipe. The air pump 13 is located between the SPE filter 8 and the electrochemical sensor 15. The air pump 13 is connected to the circuit control panel.

[0036] In this embodiment, the VOCs detection unit 2 and the NOx detection unit 3 share some of the sample inlet pipeline and workstation; the zero gas, hydrogen and tail gas pipelines are equipped with electronic pressure controllers 7, and are all independent gas pipelines, which is conducive to the operation of the work.

[0037] In this embodiment, an existing data transmission module and display module are also provided to facilitate use, according to usage requirements.

[0038] In practice, the specific steps include:

[0039] (1) An air sample from the environment is collected by the air pump 13 and enters the gas path system 1. Zero gas (usually helium) is used as the carrier gas and enters the gas path system 1. The gas samples enter the VOCs detection unit and the NOx detection unit respectively.

[0040] (2) After the air sample is purified by the SPE filter 8 and heated by the heat tracing tube 15, it enters the ten-way valve 5. The metering loop 6 is connected to the ten-way valve 5. The air sample is discharged through the ten-way valve 5 and the metering loop 6. Zero gas is introduced into the ten-way valve 5 through the carrier gas pipeline and controlled by the electronic pressure air device 7. The gas sample and the carrier gas are connected by changing the gas path of the ten-way valve at a time. The gas sample enters the metering loop through the ten-way valve. The valve is closed at a time. The gas sample in the metering loop 6 is sent into the PLOT Q column 9 and the packed column 10 through the carrier gas. The temperature program device separates the sample by gradient temperature program, separating total hydrocarbons and methane. The two types of substances, total hydrocarbons and methane, enter the FID detector respectively. After the methane is separated by the PLOT Q column 9, the tail gas is controlled by the electronic pressure controller 7 to enter the PLOT. The Q column vents the remaining gas, and the total hydrocarbons and methane enter the FID detector for combustion in sequence. The air required for combustion in the FID detector is supplied by the air pump 13 and enters the FID detector via the hydrocarbon remover 12. After being processed by the electrometer plate, it is converted into an electrical signal and enters the workstation 4. The workstation 4 analyzes the electrical signal to obtain the concentration of total hydrocarbons and methane in the gas sample.

[0041] (3) The air sample is pumped by the air pump 13 and enters the electrochemical sensor 16 through the SPE filter 8. When the NO2 molecules in the sample react chemically with the electrodes on the surface of the electrochemical sensor 16, a current signal is generated. The current signal is connected to the workstation 4, and the concentration of nitrogen oxides in the sample is determined by the intensity of the current signal.

[0042] This invention presents a small, portable system with higher integration that can simultaneously and accurately detect total hydrocarbons, methane, non-methane total hydrocarbons, and NOx gases. It reduces the number of instruments required and utilizes a combination of an FID detector and an electrochemical sensor to complete the quantitative detection of the concentrations of two ozone precursors in a single sample injection, greatly improving detection efficiency.

[0043] In addition to the embodiments described above, this utility model may have other implementations. All technical solutions formed by equivalent substitution or equivalent transformation fall within the protection scope claimed by this utility model.

Claims

1. A system for online monitoring of VOCs and NOx, characterized in that: It includes an air pump (13), an air path system (1), a VOCs detection unit (2), a NOx detection unit (3), and a workstation (4). The air pump (13) is connected to the air path system (1). The air path system (1) is connected to the air paths in the VOCs detection unit (2) and the NOx detection unit (3), respectively. The VOCs detection unit (2) and the NOx detection unit (3) are electrically connected to the workstation (4). The air pump (13) connects to the gas in the environment and enters the gas path system (1). The workstation (4) controls the VOCs detection unit (2) and the NOx detection unit (3) to monitor the air sample in the gas. The VOCs detection unit (2) includes pipelines, an electronic pressure controller (7), an SPE filter (8), a ten-way valve (5), a quantitative loop (6), a chromatographic column, a hydrocarbon remover (12), an air pump (13), and an FID detector (14). The pipelines include a sample gas pipeline and a carrier gas pipeline, which are respectively connected to the ten-way valve (5). Two quantitative loops (6) connected to the ten-way valve (5) are symmetrically arranged on the ten-way valve (5). The ten-way valve (5) is connected to the chromatographic column through a pipeline. The chromatographic column is connected to the FID detector (14) through a pipeline. The FID detector (14) is equipped with multiple air pumps (13), one of which is also connected to the hydrocarbon remover (12). An electronic pressure controller (7) is installed on the pipeline between the FID detector (14) and the chromatographic column. The SPE filter (8) is installed at the inlet of the sample gas pipeline, and an electronic pressure controller (7) is installed on the carrier gas pipeline. An insulation layer is wrapped around the upper part of the sample gas pipeline between the SPE filter (8) and the ten-way valve (5), and a heat tracing pipe (15) is wrapped around the outside of the insulation layer. The chromatographic column includes a PLOT Q chromatographic column (9) and a packed column (10), wherein the packed column (10) is a total hydrocarbon chromatographic column, and the PLOT Q chromatographic column (9) and the packed column (10) are connected in parallel; The NOx detection unit (3) includes an SPE filter (8), an air pump (13), an electrochemical sensor (16), and a circuit control panel. One end of the electrochemical sensor (16) is connected to a pipe for sample inlet. The SPE filter (8) is located at the inlet of the pipe. The air pump (13) is also located on the pipe. The air pump (13) is located between the SPE filter (8) and the electrochemical sensor (16). The air pump (13) is connected to the circuit control panel.

2. The system for online monitoring of VOCs and NOx according to claim 1, characterized in that: The gas system (1) is equipped with multiple air pumps (13) for connecting different gases.

3. The system for online monitoring of VOCs and NOx according to claim 1, characterized in that: A heater (11) is provided below the PLOT Q column (9) via a support.

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