Multipath gas dilution online detection system

Abstract

The utility model belongs to the technical field of VOCs gas detection. The utility model provides a multipath gas dilution on-line detection system. The multipath gas dilution on-line detection system is composed of a precise multi-way valve, a gas disturbance mixing cavity, an MFC, a drainage pump, an electromagnetic valve, a three-way connector and a barometer. The precise multi-way valve is provided with a plurality of sample gas inlets, a common outflow port and a sample gas common sampling port; a heating wire is arranged outside the gas disturbance mixing cavity, a frame type stirrer is arranged inside the gas disturbance mixing cavity, the tail part is designed into a funnel shape and is provided with a detection instrument interface, and the head part is provided with a diluent gas interface and a sample gas interface; the diluent gas interface is communicated with diluent gas through an MFC and a pipeline; and the sample gas interface is communicated with the sample gas common sampling port of the precise multi-way valve through the MFC, the three-way joint and the barometer through a pipeline. According to the utility model, the service life of the detector can be prolonged, pollution in an instrument cavity is reduced, and meanwhile, the multi-way valve is heated and is prevented from being blocked.

Description

Technical Field

[0001] This utility model belongs to the field of VOCs gas detection technology. Background Technology

[0002] The focus of VOCs monitoring in industrial parks is on the different types of VOCs used and emitted at different stages of industrial production, with raw materials typically exhibiting higher concentrations of volatile VOCs. The EI-TOF electron impact ion source employs hard ionization, using a high-energy electron beam to bombard the sample, generating ion fragments and molecular ions. Ions of different mass numbers pass through the flight chamber at different velocities, reaching the detector at varying times, thus enabling qualitative analysis of VOCs. When monitoring organic matter, EI-TOF can sample via capillary injection and membrane injection; here, PDMS membrane injection is primarily used. The selective permeability of PDMS membranes isolates inorganic components from ambient air, allowing only VOC components to enter the mass spectrometer vacuum chamber, significantly improving the sensitivity of portable mass spectrometers in analyzing VOCs. Gas is introduced into the device through tubes, valves, and pumps, and finally analyzed to obtain results.

[0003] Existing multi-channel gas monitoring methods utilize solenoid valves to control each gas channel separately; however, dynamic dilution modules lack gas disturbance units, or the sample gas dilution effect is poor. ① Installing solenoid valves on each inlet gas path leads to excessively long gas path switching times. ② The lack of a gas mixing disturbance unit prevents sufficient mixing of the sample gas and dilution gas, resulting in poor dilution and inaccurate measurement results. ③ Multi-channel sampling systems have cumbersome piping designs and numerous valves, which can easily cause pressure losses and fluid blockages in the piping. Summary of the Invention

[0004] In view of this, the present invention provides a multi-channel gas dilution online detection system, comprising a precision multi-channel valve, a gas disturbance mixing chamber, an MFC, a diversion pump, a solenoid valve, a tee connector, and a pressure gauge; the precision multi-channel valve is provided with multiple sample gas inlets, a common outlet port, and a sample gas common sampling port; the gas disturbance mixing chamber is externally equipped with a heating wire, internally equipped with a frame-type stirrer, and its tail is designed in a funnel shape with a detection instrument interface, while its head is equipped with a dilution gas interface and a sample gas interface; the dilution gas interface is connected to the dilution gas via the MFC through a pipeline; the sample gas interface is connected to the sample gas common sampling port of the precision multi-channel valve via the MFC, the tee connector, and the pressure gauge through a pipeline; the detection instrument interface is connected to the detection instrument gas pipeline via the solenoid valve; and the common outlet port is connected to the diversion pump through a gas pipeline.

[0005] Furthermore, the cavity material of the gas disturbance mixing chamber is quartz glass.

[0006] Furthermore, the volume of the gas disturbance mixing chamber is 1L. Attached Figure Description

[0007] Figure 1 This is a diagram of a gas turbulence mixing chamber.

[0008] Figure 2 This is a diagram of a multi-channel gas dilution online detection system.

[0009] Figure 3 This is a gas sampling route diagram.

[0010] Figure 4 This is a flushing air path diagram.

[0011] Figure 5 This is a diagram of the pipeline depressurization gas path. Detailed Implementation

[0012] Example

[0013] E I-TOF: Electron Impact Time-of-Flight Mass Spectrometer

[0014] Dilution gas: A substance used to dilute the sampling gas, usually nitrogen.

[0015] To address the shortcomings of existing technologies, this invention utilizes a precision multi-way valve to switch between different sampling pipelines and a gas disturbance unit. This not only shortens the gas path switching time but also allows for precise dilution ratios to be set for high-concentration gases. Diluting the sample gas concentration improves detector lifespan and reduces contamination within the instrument chamber. Gas backflushing of the pipeline section from the precision multi-way valve to the mixing valve reduces pipeline adsorption, while heating the multi-way valve prevents blockage.

[0016] This invention designs an online detection system based on E I-TOF for multi-channel gas dilution in industrial parks, enabling accurate detection of high-concentration volatile organic compounds emitted from multiple locations within the park, and reducing the impact of high-concentration sample gas on the lifespan of the E I-TOF detector and internal contamination of the instrument.

[0017] The basic scheme of this utility model is based on the switching and selection of the sample gas in the monitoring pipeline by a precision multi-way valve, the sample gas in the pipeline is diluted with dilution gas, and the sample gas and dilution gas are diluted in a certain ratio under the precise flow control of MFC, and the diluted sample gas is introduced into E I-TOF for detection.

[0018] This utility model provides a multi-channel gas dilution online detection system, which consists of a precision multi-channel valve, a gas disturbance mixing chamber, a monitoring instrument, a diversion pump, and gas pipeline connection accessories.

[0019] like Figure 1As shown, the gas disturbance mixing chamber 1 is made of quartz glass and has a volume of 1L. It is used to make the diluted gas mix more evenly and improve the accuracy of the detection results.

[0020] An external heating wire is provided for heating the cavity;

[0021] An internal frame-type stirrer is installed to enhance gas mixing within the chamber;

[0022] The tail is designed in a funnel shape and is equipped with a testing instrument interface 101 for connecting to testing equipment;

[0023] The head is equipped with a dilution gas interface 102 and a sample gas interface 103 for connecting the sample gas and dilution gas at the front end. The intake flow rates of the dilution gas and sample gas are precisely controlled by a mass flow controller (MFC) as needed. The diameter of the sample gas and dilution gas pipelines is 6 mm, the flow velocity of the sample gas in the pipeline is 1.8 m / s, the sampling flow rate of each channel is not less than 3 L / min, and the sampling time of each channel is not less than 30 s.

[0024] The dilution gas interface is connected to the dilution gas 3 via a pipeline through the mass flow controller MFC2.

[0025] The sample gas interface is connected to the sample gas common sampling port of the precision multi-way valve 6 via a pipeline through the mass flow controller MFC2, the three-way connector 4, and the pressure gauge 5.

[0026] The interface of the testing instrument is connected to the gas pipeline of the testing instrument 8 via the solenoid valve 7.

[0027] The precision multi-way valve is equipped with multiple sample gas inlets, common outflow ports, and sample gas common sampling ports.

[0028] The common outlet port is connected to the dredging pump 9 via a gas pipeline.

[0029] The system has the following states during operation:

[0030] (1) Sample gas was sampled after dilution:

[0031] like Figure 3As shown, the sample gas sampling process is as follows: The sample gas enters the sampling pipeline, passes through a filter, flow meter, and the sample gas inlet of the precision multi-way valve, and then enters the precision multi-way valve. The precision multi-way valve selects one of the sample gas lines from all the sampling pipelines on site and sends it to the detector for gas analysis. The gas from the remaining pipelines that are not selected for analysis is drawn away by a pump through the common outlet port of the precision multi-way valve. The selected pipeline sample gas enters the gas turbulence mixing chamber through the common sampling port of the valve body, pressure gauge, tee connector, MFC, and sample gas interface. At this time, the flow rate of the MFC at the dilution gas end can be adjusted according to the sampling location of the sampling pipeline on site. If the sampling port is located in the production workshop or solvent storage room, the MFC flow rate can be increased. After mixing, the gas enters the monitor for measurement.

[0032] (2) Flushing the pipeline:

[0033] After the detector completes sampling of the sample gas in the pipeline, the system flushes the pipeline. Nitrogen dilution gas can be used for pipeline flushing. At this time, the exhaust end of the three-way connector and the two-position two-way solenoid valve are closed, and nitrogen gas is introduced. The multi-way valve is heated by the temperature control system, so that the VOCs adsorbed on the valve orifice are thermally desorbed, carried out by nitrogen gas, and pumped away by the drainage pump. The purpose is to flush the pipeline and mixing chamber, and at the same time prevent the multi-way valve from becoming blocked.

[0034] (3) Depressurize and vent the pipeline:

[0035] The system is equipped with a pressure gauge after the multi-way valve to monitor the gas pressure of the sample gas from the sampling port to the detector. When the pressure gauge shows a rise in negative pressure, the MFC terminal of the three-way connector is closed to allow the gas to be vented from the gas vent section of the three-way connector, and the cause of the pressure gauge rise is investigated.

[0036] (1) By selecting a precision multi-way valve, the present invention can switch the sampling target pipeline in a timely manner, which shortens the gas path switching time compared to installing a solenoid valve in each sampling pipeline.

[0037] (2) By designing an efficient gas disturbance mixing chamber, the dilution effect of the sample gas is improved, ensuring the accuracy of the sample dilution ratio, so as to achieve the purpose of accurate measurement.

[0038] (3) In this invention, pure nitrogen is used as a dilution gas to dilute the sample gas. It can also be used as a pipeline flushing gas to flush the section from the mixing chamber to the multi-way valve, thus avoiding VOCs adsorption and valve blockage.

[0039] (4) In the sampling system of the present invention, a multi-way valve is used instead of a solenoid valve to reduce the use of valve body, and a three-way valve is used instead of a solenoid valve. Both of these can effectively reduce pipe resistance and pressure loss. At the same time, a pressure gauge is used to effectively monitor the pipeline status and release pressure in a timely manner.

[0040] 1. Structure of the gas disturbance mixing chamber.

[0041] 2. The precision multi-way valve switches the pipeline and simultaneously draws out the sample gas from other pipelines except the measuring pipeline by the diversion pump.

[0042] This detection system can be used to measure high-concentration sample gases in industrial parks, improving the accuracy of the detection data without affecting the instrument itself.

[0043] Other alternatives include changing the mixing unit method, such as using a rotor mixer; and changing the detection instrument, such as using a PTR-TOF. Through these modifications, multi-sample gas dilution and mixing monitoring can still be achieved without departing from the overall concept of this invention.

Claims

1. A multi-channel gas dilution online detection system, characterized in that, It consists of a precision multi-way valve, a gas turbulence mixing chamber, an MFC, a dredging pump, a solenoid valve, a three-way connector, and a pressure gauge; The precision multi-way valve is equipped with multiple sample gas inlets, common outflow ports, and sample gas common sampling ports; The gas disturbance mixing chamber is equipped with a heating wire on the outside, a frame stirrer inside, a funnel-shaped tail with a detection instrument interface, and a dilution gas interface and a sample gas interface at the head. The dilution gas interface is connected to the dilution gas via MFC and a pipeline; The sample gas interface is connected to the sample gas common sampling port of the precision multi-way valve via a pipeline through an MFC, a three-way connector and a pressure gauge; The interface of the testing instrument is connected to the air circuit of the testing instrument via a solenoid valve. The common outlet port is connected to the dredging pump via a gas pipeline.

2. The online gas dilution detection system according to claim 1, characterized in that, The cavity material of the gas disturbance mixing chamber is quartz glass.

3. The online gas dilution detection system according to claim 1, characterized in that, The volume of the gas disturbance mixing chamber is 1L.

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