A VOC rapid leak detector gas circuit

Abstract

The application discloses a VOC rapid leak detector gas path, comprising an FID detector, a dehydrocarbon purification path, a filtering path and a hydrogen conveying path, the air is introduced into the gas inlet end of the dehydrocarbon purification path, the exhaust end of the dehydrocarbon purification path is in conductive connection with the gas inlet end of the FID detector, and the dehydrocarbon purification path is used for guiding oxygen combustion-supporting into the FID detector; the oxygen is introduced into the gas inlet end of the filtering path, the exhaust end of the filtering path is provided with a sampling pump, the exhaust end of the sampling pump is in conductive connection with the gas inlet end of the FID detector; the exhaust end of the hydrogen conveying path is in conductive connection with the gas inlet end of the FID detector, and the hydrogen conveying path is used for providing combustible gas during detection of the FID detector. The air source is added into the gas path, the added air source enters the FID detector after dehydrocarbon impurity removal through the dehydrocarbon purification path, the normal combustion of the hydrogen flame in the detector can be ensured, and stable combustion detection of the gas path is ensured.

Description

Technical Field

[0001] This invention relates to the field of gas detection technology, and in particular to a gas path for a VOC rapid leak detector. Background Technology

[0002] VOCs refer to a general term for organic substances that easily evaporate at room temperature. However, in an environmental context, they are defined as a class of reactive volatile organic compounds, specifically those that can cause harm. VOCs are organic (carbon-based) gases emitted from many different products, also known as hydrocarbons. The evaporation of VOCs is caused by sufficient pressure. The main components of VOCs include hydrocarbons, halogenated hydrocarbons, oxygenated hydrocarbons, and nitrogenous hydrocarbons. They include benzene compounds, organochlorides, Freon series, organic ketones, amines, alcohols, ethers, esters, acids, and petroleum hydrocarbons.

[0003] Since lower VOC content in materials generally results in less harm to human health, VOC content in coatings needs to be tested. Traditional detection methods include combustible gas alarms based on catalytic combustion and gas chromatography-based detectors. However, combustible gas alarms based on catalytic combustion lack an additional oxygen supply, resulting in insufficient oxygen in the sample gas for combustion detection. Gas chromatography-based detectors, when deployed in explosion-proof environments such as petroleum and chemical plants, typically require bulky positive pressure cabinets, and due to stringent environmental requirements, necessitate instrument housings, leading to high deployment and operating costs and making on-site installation impractical. Therefore, this solution proposes a gas path for a rapid VOC leak detector to address these issues. Summary of the Invention

[0004] The purpose of this invention is to provide a gas path for a VOC rapid leak detector to solve the problems mentioned in the background art.

[0005] To achieve the above objectives, the present invention provides the following technical solution: a gas path for a VOC rapid leak detector, comprising: FID detector; The dehydrogenation purification passage introduces air into its inlet and is connected to the inlet of the FID detector. The dehydrogenation purification passage is used to guide oxygen into the FID detector for combustion. The filter path has an inlet for introducing oxygen and an outlet for being equipped with a sampling pump. The outlet of the sampling pump is connected to the inlet of the FID detector. A hydrogen supply path is provided, wherein the exhaust end of the hydrogen supply path is connected to the inlet end of the FID detector, and the hydrogen supply path is used to provide combustible gas for the FID detector during detection.

[0006] Preferably, the dehydrocarbonization purification pathway includes: A hydrocarbon separator, wherein the inlet end of the hydrocarbon separator is used for gas to enter; An air pump, the air inlet of which is connected to the exhaust outlet of the hydrocarbon remover, and the exhaust outlet of which is used to deliver the hydrocarbon-removed air into the FID detector.

[0007] Preferably, a first air resistance is provided between the exhaust end of the air pump and the air inlet end of the FID detector. The first air resistance is used to control the flow rate of the dehydrogenated air into the FID detector at a flow rate of 200-220 ml / min.

[0008] Preferably, the filtering path includes: A primary filter is provided, wherein the sample gas is introduced into the inlet of the primary filter, and the primary filter is used for separating moisture in the sample gas. A secondary filter is provided, wherein the inlet end of the secondary filter is connected to the outlet end of the primary filter, and the outlet end of the secondary filter is connected to the sampling pump. The secondary filter is used to separate dust and impurities in the sample gas.

[0009] Preferably, an orifice plate flow meter is installed between the exhaust end of the secondary filter and the inlet end of the sampling pump, and the orifice plate flow meter is used to measure the flow rate of the sample gas flowing through the sampling pump.

[0010] Preferably, the exhaust end of the sampling pump is configured with two paths, one of which is provided with a second air resistance between it and the air inlet of the FID detector, and the other of which is connected to an oxygen detection path.

[0011] Preferably, the second gas resistance is used to control the sample gas to enter the FID detector at a flow rate of 15-30 ml / min.

[0012] Preferably, the oxygen detection pathway includes: A PID detector, wherein the air inlet of the PID detector is connected to another path of the exhaust end of the sampling pump; An oxygen sensor, wherein the inlet end of the oxygen sensor is connected to the exhaust end of the PID detector.

[0013] Preferably, the hydrogen transport path includes: A hydrogen storage cylinder, wherein the hydrogen storage cylinder is used for low-pressure storage of hydrogen; A pressure sensor is installed at the vent end of the hydrogen storage tank; A three-stage pressure reducing valve, wherein the inlet end of the three-stage pressure reducing valve is connected to the exhaust passage of the hydrogen storage cylinder, and the exhaust end of the three-stage pressure reducing valve is used to deliver hydrogen to the FID detector.

[0014] Preferably, an adjustable gas resistance is connected between the exhaust end of the three-stage pressure reducing valve and the inlet end of the FID detector. The adjustable gas resistance is used to control the flow rate of hydrogen into the FID detector at 15-30 ml / min.

[0015] The technical effects and advantages of this invention are as follows: (1) An air source is added to the gas path of the present invention. After the added air source is dehydrogenated and purified through the dehydrogenation purification passage, it enters the FID detector to ensure the normal combustion of hydrogen flame in the detector and ensure that the gas path can achieve stable combustion detection.

[0016] (2) The present invention eliminates safety hazards during sample gas detection through the design of the filtration path, without the need for deployment in a specific location. Furthermore, the present invention can measure the total hydrocarbon and oxygen concentrations through the oxygen detection path, providing a useful reference for the treatment and monitoring of volatile organic compounds. Attached Figure Description

[0017] Figure 1 This is a schematic diagram of the gas path connection principle of the present invention.

[0018] In the diagram: 1. FID detector; 2. Hydrocarbon remover; 3. Air pump; 4. First gas resistance; 5. Primary filter; 6. Secondary filter; 7. Orifice plate flow meter; 8. Sampling pump; 9. Second gas resistance; 10. PID detector; 11. Oxygen sensor; 12. Hydrogen storage tank; 13. Pressure sensor; 14. Three-stage pressure reducing valve; 15. Adjustable gas resistance. Detailed Implementation

[0019] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0020] This invention provides, for example Figure 1 The gas path of a VOC rapid leak detector shown includes an FID detector 1, a dehydrogenation purification passage, a filtration passage, and a hydrogen supply passage. Air is introduced into the inlet of the dehydrogenation purification passage, and the exhaust end of the dehydrogenation purification passage is connected to the inlet of the FID detector 1. The dehydrogenation purification passage is used to supply oxygen to the FID detector 1 for combustion. It should be noted that FID detector 1 is a flame ionization detector, a detector used in gas chromatography. The working principle of FID detector 1 is based on the flame ionization principle, and the specific steps are as follows: Sample introduction: The sample gas separated by gas chromatography enters the detection chamber through the injection port of FID detector 1; The core of the FID detector 1 is a flame composed of hydrogen and air (or oxygen). The sample gas is injected into the flame through a nozzle, and the flame temperature is extremely high (typically above 1000°C). Ionization, in a flame, organic molecules in a sample are decomposed by high temperature, forming positively charged ions and free electrons. The number of these ions and electrons is proportional to the concentration of organic matter in the sample. Current measurement involves applying an electric field between the electrodes of FID detector 1. The generated positive ions move under the influence of the electric field and generate a current. The intensity of this current is proportional to the concentration of organic compounds in the sample. Signal output: The FID detector 1 converts the current signal into a readable output, which is usually displayed on the chromatogram in the form of a peak graph.

[0021] Specifically, the dehydrocarbonization purification pathways include: Hydrocarbon remover 2 has an inlet for air intake. A sampling probe is installed at the inlet of the hydrocarbon remover 2 to facilitate the capture of the introduced air. The hydrocarbon remover 2, also known as a hydrocarbon dehydrogenator or hydrocarbon stripper, is a device used to remove hydrocarbon compounds from gases or liquids, primarily to reduce the concentration of hydrocarbon compounds. Hydrocarbon removers 2 include several types, including: Hydrocarbon removal by adsorption: Activated carbon, molecular sieves, or other adsorbent materials are used to adsorb hydrocarbon compounds from gases. Gas passes through a tower filled with adsorbent, where hydrocarbon compounds are adsorbed, and the purified gas is discharged from the top of the tower.

[0022] Hydrocarbon removal by washing: This method uses liquid detergents (water or chemical solutions) to wash gases. The gas passes through a liquid layer, where components in the liquid react with or dissolve the hydrocarbons in the gas, thus removing the hydrocarbon compounds. Common washing methods include soaking and spray washing.

[0023] Catalytic oxidation for hydrocarbon removal: With the aid of a catalyst, hydrocarbon compounds in a gaseous mixture are oxidized into carbon dioxide and water. This method is commonly used for treating high concentrations of hydrocarbons and can effectively reduce the emission of harmful substances.

[0024] Hydrocarbon removal by thermal decomposition: This method involves heating hydrocarbon compounds to break them down into smaller molecules, which are then removed from the hydrocarbons. Thermal decomposition is typically used to process high molecular weight hydrocarbons.

[0025] Air pump 3, the air inlet of air pump 3 is connected to the exhaust end of hydrocarbon remover 2. The exhaust end of air pump 3 is used to deliver the hydrocarbon-removed air into FID detector 1. After air pump 3 is started, it performs a suction action, drawing the air through hydrocarbon remover 2 into the pump body, and then discharging it from the exhaust end. A first air resistance 4 is set between the exhaust end of air pump 3 and the air inlet of FID detector 1. The first air resistance 4 is used to control the hydrocarbon-removed air to enter FID detector 1 at a flow rate of 200-220 ml / min. It should be noted that in this scheme, the intake end of the hydrocarbon remover 2 is equipped with a sampling probe for air collection. After the collected air undergoes hydrocarbon removal, the flow rate is controlled by the first air resistance 4, and then it is delivered to the FID detector 1. With the continuous injection of hydrocarbon-removed air, the FID detector 1 can continuously obtain oxygen when performing combustion detection, thereby ensuring complete combustion and further ensuring the stability and accuracy of the detection.

[0026] This solution incorporates an air source. If only the sample gas source and hydrogen gas source are burning inside the detector, the FID detector 1 will extinguish when it encounters sample gas with low oxygen content. Adding an air source, after dehydrocarbonization and impurity removal, ensures the normal combustion of the hydrogen flame inside the FID detector 1 and prevents extinguishing, thereby ensuring the continuous and stable combustion detection of the FID detector 1.

[0027] Oxygen is introduced into the inlet of the filter passage, and a sampling pump 8 is installed at the outlet of the filter passage. The outlet of the sampling pump 8 is connected to the inlet of the FID detector 1. After the sampling pump 8 is started, its inlet generates negative pressure to perform a suction action. At this time, the filter passage installed at the inlet of the sampling pump 8 generates negative pressure to suck up the sample gas. The outlet of the sampling pump 8 is set to two paths, which are controlled by a three-way valve. A second air resistance 9 is set between one of the outlets of the sampling pump 8 and the inlet of the FID detector 1. The other outlet of the sampling pump 8 is connected to the oxygen detection passage. It should be noted that in this scheme, the sample gas is divided into two streams at the exhaust end of the sampling pump 8. 96% of the gas flow is delivered to the oxygen detection path to measure the oxygen content, while the remaining 4% is delivered to the FID detector 1 for combustion detection. This ratio setting can maximize the accuracy of oxygen content measurement of the sample gas. Furthermore, the small portion of the sample gas used as combustion test gas is also sampled for detection, which is both representative and minimizes the amount of gas used for combustion detection. This makes the combustion measurement of this device faster, reduces the amount of gas used for combustion measurement, avoids fuel waste, and further improves the safety of combustion measurement.

[0028] Specifically, the filtering pathways include: The primary filter 5 introduces the sample gas through its inlet. It is used for moisture separation from the sample gas. A probe for sample gas collection is installed at the inlet of the primary filter 5 to facilitate sample gas entry into the filtration path and ensure accurate sample gas collection. In the gas detection process designed in this scheme, especially when analyzing volatile organic compounds (VOCs), moisture in the sample gas can interfere with the detection results. Therefore, the primary filter 5 in this scheme is designed to separate and remove moisture from the sample gas. The primary filter 5 includes the following types: Condensers, by lowering the gas temperature, cause water vapor in the gas to condense into liquid water, thus separating moisture. They are commonly used in the pretreatment stage of gas analysis, especially when the gas has a high moisture content. Drying tubes, filled with desiccants (silica gel, molecular sieves, calcium chloride), adsorb moisture from the gas and are suitable for gas samples requiring moisture removal. The desiccant can be replaced or regenerated periodically as needed. Membrane separators utilize the selective permeability of membranes to separate moisture from other gases. Moisture is removed through the selective permeation of the membrane, making them suitable for gas samples requiring efficient moisture removal, especially in some specialized analyses. Filters use physical filtration to remove liquid water droplets from the gas. These filters are typically equipped with microporous membranes to block water droplets from passing through, suitable for the preliminary treatment of gas samples, especially when liquid water may be present in the gas. Freeze dryers freeze moisture in the sample gas and then remove ice crystals through vacuum sublimation, thus separating moisture. They are used for high-precision gas analysis and are particularly suitable for sample processing under low-temperature conditions.

[0029] This solution uses a drying tube filled with desiccant and a membrane separator, which keeps the product small and makes the device more convenient to use.

[0030] The secondary filter 6 has its inlet end connected to the exhaust end of the primary filter 5. The exhaust end of the secondary filter 6 is also connected to the sampling pump 8. The secondary filter 6 is used to separate dust and impurities in the sample gas. An orifice plate flow meter 7 is installed between the exhaust end of the secondary filter 6 and the inlet end of the sampling pump 8. The orifice plate flow meter 7 is used to measure the flow rate of the sample gas flowing through the sampling pump 8.

[0031] It should be noted that if the sample gas contains dust and impurities during the gas detection process, these solid particles will interfere with the detection results and may cause an explosion hazard during subsequent combustion detection. Therefore, a secondary filter 6 is set in this solution. The secondary filter 6 includes the following types of filters. Particulate filters capture solid particles from gases through physical barrier methods. These filters are typically made of multiple layers of filter media with different pore sizes, effectively capturing particles of varying sizes. They are suitable for removing dust, smoke, and sand-like solid impurities from gases. High-efficiency particulate air (HEPA) filters have extremely high filtration efficiency, capable of removing particles smaller than 0.3 micrometers in diameter, with a capture efficiency of 99.97% or higher. In environments requiring high cleanliness, including pharmaceuticals, electronics, and laboratories, HEPA filters are used for sample gas pretreatment. Fiber filters, made of polymers or glass fibers, capture particulate matter from gases. The filter design allows particles to be trapped by the fibers as airflow passes through, making them suitable for processing various gas samples and commonly used in industrial gases and environmental monitoring. Electrostatic filters utilize electrostatic force to capture particulate matter from gases. An electric field is applied within the filter to charge the particles, which then adsorb onto the filter media with the opposite charge. Electrostatic filters remove tiny particles and are suitable for industrial and laboratory environments.

[0032] In this scheme, the primary filter 5 and the secondary filter 6 are used to filter and remove moisture and particulate impurities from the sample gas, ensuring that the sample gas being tested is only in a gaseous state. This prevents moisture and dust impurities mixed in the air from entering the subsequent gas path, thus protecting the subsequent testing equipment while ensuring the accuracy of the subsequent tests.

[0033] In this design, an orifice plate flow meter 7 is included. The orifice plate flow meter 7 is a differential pressure flow meter used to measure the flow rate of gases, liquids, and steam. Its basic principle is to calculate the flow rate by utilizing the pressure difference generated when fluid passes through a throttling element with a specific geometry (orifice plate). The working principle is as follows: Fluid flows through an orifice plate, passing over a flat plate with a central orifice. The diameter of this orifice is smaller than the inner diameter of the pipe, forming a throttling section. Bernoulli's principle, according to Bernoulli's equation, states that when a fluid flows through a throttling section, the flow velocity increases and the pressure decreases. The pressure difference (i.e., differential pressure) of the fluid before and after the orifice plate is in a certain relationship with the flow rate. Pressure difference measurement involves sensing pressure upstream and downstream of the orifice plate to measure the pressure difference. The relationship between this pressure difference and the flow rate can be determined by the flow coefficient and the physical properties of the fluid. Flow rate calculation: Flow rate (Q) can be calculated using the following formula, expressed as: (1); Among them, C d The flow coefficient is represented by A, which depends on the geometry of the orifice plate and the flow characteristics of the fluid; ΔP represents the cross-sectional area of ​​the orifice; ρ represents the pressure difference across the orifice plate; and ρ represents the density of the fluid.

[0034] Furthermore, the second gas resistance 9 is used to control the sample gas flow rate into the FID detector 1 at 15-30 ml / min. Through the control of the second gas resistance 9, a stable flow of sample gas into the FID detector 1 is ensured. The oxygen detection pathway includes: The PID detector 10 has its inlet connected to the exhaust outlet of the sampling pump 8. The PID detector 10, also known as a photoionization detector, is an instrument used to detect volatile organic compounds (VOCs) and other pollutants in gases. The working principle of the PID detector 10 is based on the concept of photoionization, and the specific steps are as follows: The light source, PID detector 10, uses an ultraviolet (UV) lamp, usually a xenon lamp, which can emit ultraviolet light of a specific wavelength (generally between 9.0 eV and 10.6 eV).

[0035] Photoionization occurs when a gas sample passes through the PID detector 10. Ultraviolet light irradiates the sample gas, causing the organic molecules (VOCs) in the gas to be ionized, forming positively charged ions and free electrons. Under the influence of an electric field, the ions and electrons produced by ionization move and form an electric current. The signal output is provided by the PID detector 10, which measures the current generated by ionization. The intensity of the current is proportional to the concentration of organic compounds in the sample gas. Finally, the PID detector 10 converts this current signal into a readable output, which is displayed in concentration units (ppm).

[0036] Oxygen sensor 11, with its inlet end connected to the exhaust end of PID detector 10, is used in this gas detection scheme to measure the oxygen concentration in the sample gas. It employs one or more of the following types, but not including: Electrochemical oxygen sensors measure oxygen concentration through electrochemical reactions. Inside the sensor, oxygen molecules diffuse through a membrane into the electrolyte, react with electrodes, and generate a current. The intensity of this current is proportional to the oxygen concentration in the gas. Optical oxygen sensors typically use fluorescence or absorption principles to measure oxygen concentration. Light emitted from a light source passes through the sample gas, and oxygen molecules affect the characteristics of the light (fluorescence lifetime or absorption intensity), allowing the calculation of the oxygen concentration. Resistive oxygen sensors utilize changes in resistance caused by changes in oxygen concentration. They typically use zirconium oxide or other conductive materials as sensing elements, and changes in oxygen concentration affect the sensor's conductivity. Solid oxide electrolyte sensors (SOFCs) use solid oxides (zirconia) as the electrolyte. At high temperatures (typically 600°C or higher), oxygen ions can pass through the electrolyte, generating a current. The magnitude of this current is proportional to the oxygen concentration.

[0037] It should be noted that both the first air resistance 4 and the second air resistance 9 adopt existing air resistance structures. Air resistance (also known as gas resistance or gas flow resistance) refers to the resistance or friction force experienced by gas during flow. This resistance is usually related to factors such as the gas flow velocity, the geometry of the flow path, and the gas density and viscosity. The causes of air resistance mainly include the following aspects: Frictional resistance occurs when gas flows, and the friction between the gas and the pipe wall or other surfaces causes energy loss, generating resistance. Inertial resistance arises because the inertia of the flowing gas means it needs to overcome resistance when accelerating or decelerating. Turbulence and eddies can also increase flow complexity and resistance. Finally, geometry affects air resistance; the shape, size, and curvature of the fluid flow path all influence air resistance. For example, the diameter of a pipe, bends, and valves can all cause variations in flow resistance.

[0038] Air resistance is calculated using the Darcy-Weisbach equation, expressed as: (2); Where ΔP represents the pressure loss (Pa); The friction factor is dimensionless; L represents the pipe length (m); D represents the pipe diameter (m); ρ represents the gas density (kg / m³). 3 ); v represents the gas flow velocity (m / s); The gas flow rate can be calculated using the above formula, thereby enabling control of the gas flow rate.

[0039] The exhaust end of the hydrogen supply line is connected to the inlet end of the FID detector 1. The hydrogen supply line is used to provide combustible gas for detection by the FID detector 1. Specifically, the hydrogen transport route includes: Hydrogen storage cylinder 12 is used for low-pressure hydrogen storage. It is a container specifically designed for the safe storage of hydrogen. In this setup, to effectively achieve low-pressure hydrogen storage, hydrogen storage cylinder 12 needs to maintain the following key points: The hydrogen storage cylinder 12 is constructed using high-strength alloy materials (aluminum alloy, carbon fiber composite, or stainless steel) to withstand the pressure of the internal hydrogen and ensure a tight seal. These materials possess good corrosion resistance and mechanical strength, preventing hydrogen leakage. The design of the hydrogen storage cylinder 12 needs to take into account the physical properties of hydrogen, including its low density and high diffusivity. Therefore, the cylinder structure is typically cylindrical or spherical to minimize stress concentration and optimize space utilization. The interior of the hydrogen storage cylinder 12 is coated or lined to reduce the reaction between hydrogen and the cylinder wall, improving storage efficiency and safety. Low-pressure storage refers to storing hydrogen at relatively low pressures (1-10 bar). Compared to high-pressure storage (200-700 bar), low-pressure storage offers higher safety and is generally less expensive to design and manufacture. At low pressure, hydrogen is stored in a gaseous state. The volume of the hydrogen storage cylinder 12 and the temperature of the hydrogen affect the hydrogen density and storage capacity. According to the ideal gas law, the volume of a gas is directly proportional to its pressure and temperature. The hydrogen storage cylinder 12 has excellent sealing performance to prevent hydrogen leakage. Commonly used sealing materials include fluororubber and other hydrogen-resistant materials. The hydrogen storage cylinder 12 is equipped with safety valves to prevent explosion or rupture due to excessive internal pressure. These valves can automatically release gas when a specific pressure is reached.

[0040] Pressure sensor 13 is located at the exhaust end of hydrogen storage cylinder 12. The detection end of pressure sensor 13 is located at the cylinder body of hydrogen storage cylinder 12 and close to the exhaust end of hydrogen storage cylinder 12. Pressure sensor 13 monitors and displays the pressure inside hydrogen storage cylinder 12 and monitors whether hydrogen storage cylinder 12 is leaking, thereby ensuring stable monitoring of the use status of hydrogen storage cylinder 12. The three-stage pressure reducing valve 14 has its inlet end connected to the exhaust passage of the hydrogen storage cylinder 12. The exhaust end of the three-stage pressure reducing valve 14 is used to deliver hydrogen to the FID detector 1. An adjustable gas resistance 15 is connected between the exhaust end of the three-stage pressure reducing valve 14 and the inlet end of the FID detector 1. The adjustable gas resistance 15 is used to control the flow rate of hydrogen into the FID detector 1 at a rate of 15-30 ml / min.

[0041] It should be noted that the three-stage pressure reducing valve 14 is a pressure regulating device used in gas or liquid systems. It reduces the input high-pressure fluid to the required low pressure and maintains a stable output pressure. The design of the three-stage pressure reducing valve 14 typically includes three main parts or stages, enabling progressive pressure reduction for higher control accuracy and safety.

[0042] The working principle of the three-stage pressure reducing valve 14 includes the following steps: Pre-pressure reduction: In the first stage, the fluid passes through a primary pressure reduction mechanism, initially reducing the pressure to a moderate level. This stage typically uses a spring-loaded valve, with the output pressure set by adjusting the spring's preload. Secondary pressure reduction: The fluid then flows to the second stage of pressure reduction, which further reduces the pressure. The valves in this stage are usually designed to be more sophisticated and provide greater pressure stability. Finally, the fluid undergoes a third stage of pressure reduction to adjust to the required final low-pressure output. This stage is typically designed very precisely to ensure that the output pressure meets the specific application requirements.

[0043] The three-stage pressure reducing valve 14 includes: a valve body made of corrosion-resistant and pressure-resistant materials to adapt to different working environments; a regulating mechanism, including a spring, valve disc, and valve seat, responsible for adjusting flow and pressure; a pressure gauge for real-time monitoring of output pressure; and safety devices, including a safety valve or pressure relief valve, to prevent overpressure.

[0044] The adjustable gas resistance 15 is used for gas delivery, flow control, and gas mixing. It regulates flow by changing the resistance in the gas flow path, typically offering advantages such as convenient adjustment and simple operation. In conjunction with the three-stage pressure reducing valve 14, the adjustable gas resistance 15 mechanically and stably controls the flow rate of hydrogen into the FID detector 1, eliminating the need for software control and allowing for easy debugging and operation. The working principle of the adjustable gas resistance 15 includes the following steps: Gas flow: When gas flows in a pipe, it is affected by resistance. By adjusting the structure of the gas resistance, the flow characteristics of the gas can be changed. The adjustable air resistance 15 is designed to change the flow path of the fluid, controlling the gas velocity and flow rate by adjusting the opening of valves, nozzles or orifices. Flow rate calculation, through fluid dynamics equations, can determine the relationship between flow rate and gas resistance. Typically, flow rate is related to pressure difference and gas density.

[0045] The types of adjustable air resistance 15 include, but are not limited to, the following: Control valves are devices that regulate airflow by rotating or moving a valve stem to change the valve opening; adjustable nozzles are designed to adjust flow rate by changing the nozzle diameter or shape, suitable for gas injection and mixing applications; orifice plates or throttling devices regulate gas flow rate by changing the orifice size when installed in a pipeline; orifice plate design typically needs to consider fluid velocity and pressure loss; adjustable flow meters, some of which have regulating functions, can monitor flow rate in real time and adjust it as needed.

[0046] In actual use, the following operating procedures apply; In the first process, when the air pump 3 is started, one of the sampling heads draws air into the gas path. At this time, the air entering the gas path is dehydrogenated by the hydrocarbon remover 2. The dehydrogenated air is pumped by the air pump 3 and throttled by the first gas resistance 4, and delivered to the FID detector 1 at a flow rate of 200-220 ml / min to provide oxygen for combustion detection of the FID detector 1. In the second process, the hydrogen in the hydrogen storage cylinder 12 is discharged under the pressure monitoring of the pressure sensor 13 and controlled by the three-stage pressure reducing valve 14. The discharged hydrogen enters the FID detector 1 at a flow rate of 15-30 ml / min under the throttling control of the adjustable gas resistance 15, providing fuel for the combustion detection of the FID detector 1. Step 3: Sampling pump 8 is started, and the probe used to collect sample gas draws in the sample gas. The sample gas first passes through primary filter 5 to remove moisture, then passes through secondary filter 6 to remove dust and impurities, and then passes through orifice plate flow meter 7 for metering control, and is then pumped out by sampling pump 8. The sample gas pumped by the sampling pump 8 is divided into two streams for detection. One stream, accounting for 96% of the sample gas, is sent to the PID detector 10 for detection of volatile organic compound content, and then sent to the oxygen sensor 11 for detection of oxygen content. The other stream, accounting for 4% of the sample gas, is throttled by the second gas resistance 9 and enters the FID detector 1 at a flow rate of 15-30 ml / min for combustion detection under the conditions of hydrogen combustion and air-assisted combustion of the sample gas.

[0047] Finally, it should be noted that the above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A gas path for a VOC rapid leak detector, characterized in that, include: FID detector (1); The dehydrogenation purification passage introduces air into its inlet end and is connected to the inlet end of the FID detector (1). The dehydrogenation purification passage is used to guide oxygen into the FID detector (1) for combustion. The filter path has an inlet end for introducing oxygen and an outlet end for a sampling pump (8). The outlet end of the sampling pump (8) is connected to the inlet end of the FID detector (1). The hydrogen supply path is connected to the inlet of the FID detector (1) via an exhaust end. The hydrogen supply path is used to provide combustible gas for detection by the FID detector (1).

2. The gas path of a VOC rapid leak detector according to claim 1, characterized in that, The hydrocarbon removal and purification pathway includes: Hydrocarbon remover (2), the inlet end of which is used for air intake; An air pump (3) is provided, the air inlet of which is connected to the exhaust outlet of the hydrocarbon remover (2), and the exhaust outlet of the air pump (3) is used to deliver the hydrocarbon-removed air into the FID detector (1).

3. The gas path of a VOC rapid leak detector according to claim 2, characterized in that, A first air resistance (4) is provided between the exhaust end of the air pump (3) and the air inlet end of the FID detector (1). The first air resistance (4) is used to control the air after hydrocarbon removal to enter the FID detector (1) at a flow rate of 200-220 ml / min.

4. The gas path of a VOC rapid leak detector according to claim 1, characterized in that, The filtering path includes: A primary filter (5) is used to introduce sample gas into the inlet end of the primary filter (5), and the primary filter (5) is used for moisture separation in the sample gas. The secondary filter (6) is connected to the exhaust end of the primary filter (5) through an air inlet. The exhaust end of the secondary filter (6) is connected to the sampling pump (8). The secondary filter (6) is used to separate dust impurities in the sample gas.

5. The gas path of a VOC rapid leak detector according to claim 4, characterized in that, An orifice plate flow meter (7) is provided between the exhaust end of the secondary filter (6) and the inlet end of the sampling pump (8). The orifice plate flow meter (7) is used to measure the flow rate of the sample gas flowing through the sampling pump (8).

6. The gas path of a VOC rapid leak detector according to claim 1, characterized in that, The exhaust end of the sampling pump (8) is configured to have two paths. A second air resistance (9) is provided between one of the exhaust paths of the sampling pump (8) and the air inlet of the FID detector (1). The other path of the exhaust path of the sampling pump (8) is connected to an oxygen detection path.

7. The gas path of a VOC rapid leak detector according to claim 6, characterized in that, The second gas resistance (9) is used to control the sample gas to enter the FID detector (1) at a flow rate of 15-30 ml / min.

8. The gas path of a VOC rapid leak detector according to claim 6, characterized in that, The oxygen detection pathway includes: PID detector (10), the air inlet of the PID detector (10) is connected to the other end of the exhaust of the sampling pump (8); Oxygen sensor (11), the inlet end of which is connected to the exhaust end of PID detector (10).

9. The gas path of a VOC rapid leak detector according to claim 1, characterized in that, The hydrogen transport route includes: Hydrogen storage cylinder (12), the hydrogen storage cylinder (12) is used for low-pressure storage of hydrogen; Pressure sensor (13), wherein the pressure sensor (13) is disposed at the exhaust end of the hydrogen storage cylinder (12); Three-stage pressure reducing valve (14), the inlet of which is connected to the exhaust passage of hydrogen storage cylinder (12), and the exhaust end of which is used to deliver hydrogen to FID detector (1).

10. The gas path of a VOC rapid leak detector according to claim 9, characterized in that, An adjustable gas resistor (15) is connected between the exhaust end of the three-stage pressure reducing valve (14) and the inlet end of the FID detector (1). The adjustable gas resistor (15) is used to control the flow rate of hydrogen into the FID detector (1) at a flow rate of 15-30 ml / min.

Images