Gas pre-concentration device and control method

Abstract

The present application discloses a gas pre-concentration device and a control method, wherein the device includes a sampling device, a first flow control device, a second flow control device, a heating control device, a refrigeration device, a capture device, a passage regulating device and a controller; the capture device includes a capture trap, a thermocouple and a cold plate, the temperature measuring probe of the thermocouple is installed on the capture trap, and the capture trap is installed on the cold plate; the passage regulating device and the capture trap are connected through a gas pipeline, and the capture trap is connected to the heating control device through a wire; the first flow control device and the second flow control device are respectively connected to the passage regulating device through a gas pipeline; the cold end of the refrigeration device is connected to the cold plate, and the cold end of the refrigeration device is connected to the capture device. The device in this scheme has a simple structure, high concentration efficiency and good repeatability, and can be used for online monitoring of multiple greenhouse gases.

Description

Technical Field

[0001] The present invention relates to the technical field of gas analysis equipment, and in particular to a gas pre-concentration device and a control method. Background Art

[0002] As global warming continues to intensify, anthropogenic greenhouse gas emissions have attracted widespread attention from the international community. The content of greenhouse gases emitted entirely by humans, such as hydrofluorocarbons (HFCs) and perfluorocarbons (PFCs), in ambient air is one part per trillion (10 -12 ,ppt) level. Due to the detection limit problem, the existing instruments cannot be directly analyzed, and pre-concentration must be adopted to increase the concentration of the target substance. For greenhouse gases with both natural and anthropogenic sources, such as carbon dioxide (CO2) and nitrous oxide (N2O), it is necessary to analyze their isotope content in order to distinguish the contribution of natural and anthropogenic sources. Taking carbon dioxide (CO2) as an example, the traditional method of determining C-14 in the air requires dissolving a sufficient amount of gas in an alkaline solution, and then converting it into pure CO2 gas through precipitation, roasting and other processes, and finally using a liquid scintillation spectrometer for measurement. Its disadvantages are that the processing process is cumbersome, the instruments used are expensive, and online monitoring cannot be achieved. At present, portable technologies such as laser spectroscopy can be used for online measurement of CO2 and N2O isotopes, but because the isotope content in the target gas is at the level of one thousandth, pre-concentration of the target gas is still a necessary step.

[0003] Most of the existing pre-concentration devices are designed for volatile organic compounds (VOCs), and use semiconductor refrigeration to condense and concentrate the target substances. However, due to the limited capacity of semiconductor refrigeration (the lowest temperature is usually only -40°C), it is difficult to concentrate greenhouse gases such as CO2 and N2O. In addition, the existing technologies all use multi-stage cold traps, which makes the pre-concentration process complicated and difficult to ensure repeatability. Summary of the invention

[0004] The technical problem to be solved by the present application is that the existing gas pre-concentration scheme has the problems of complex structure, unreliability and only applicable to individual compounds. Therefore, the present application provides a gas pre-concentration device and a method of use.

[0005] In response to the above technical problems, this application provides the following technical solutions:

[0006] The present application provides a gas pre-concentration device, comprising:

[0007] A sampling device, used for receiving a sample gas;

[0008] A first flow control device, used for connecting the carrier gas and adjusting the flow of the carrier gas;

[0009] The trapping device comprises a trap, a thermocouple and a cold plate, wherein the temperature measuring probe of the thermocouple is arranged on the trap, and the trap is arranged on the cold plate;

[0010] A heating control device connected to the thermocouple and the trap in the trapping device;

[0011] A refrigeration device, whose refrigeration end is connected to the cold plate in the capture device;

[0012] A second flow control device, used for adjusting the flow of gas input therein;

[0013] A passage regulating device, wherein a first interface of the passage regulating device is connected to the analytical instrument, a second interface is connected to one end of the trap, a third interface is connected to the inlet of a second flow control device, a fourth interface is connected to the outlet of the injection device, a fifth interface is connected to the other end of the trap, and a sixth interface is connected to the first flow control device;

[0014] The controller controls the opening and closing of the heating control device, the refrigeration device, the first flow control device and the second flow control device, controls the set temperature value of the heating control device, controls the set flow values ​​of the first flow control device and the second flow control device, and controls the connection or disconnection of different interfaces of the passage regulating device, so as to control the gas pre-concentration equipment to work in the enrichment mode, the analysis mode or the cleaning mode respectively.

[0015] In some embodiments of the gas pre-concentration equipment provided, the passage regulating device includes a six-way multi-position valve, interface one of the six-way multi-position valve serves as the first interface, interface two of the six-way multi-position valve serves as the second interface, interface three of the six-way multi-position valve serves as the third interface, interface four of the six-way multi-position valve serves as the fourth interface, interface five of the six-way multi-position valve serves as the fifth interface, and interface six of the six-way multi-position valve serves as the sixth interface.

[0016] In the gas pre-concentration equipment provided in some embodiments, the passage regulating device comprises a four-way two-position valve and a six-way multi-position valve, the interface 1 of the four-way two-position valve is connected to the interface 1 of the six-way multi-position valve, and the interface 3 of the four-way two-position valve is connected to the interface 6 of the six-way multi-position valve;

[0017] Interface 4 of the four-way, two-position valve serves as the first interface; interface 2 of the six-way, multi-position valve serves as the second interface; interface 3 of the six-way, multi-position valve serves as the third interface; interface 4 of the six-way, multi-position valve serves as the fourth interface; interface 5 of the six-way, multi-position valve serves as the fifth interface; interface 2 of the four-way, two-position valve serves as the sixth interface.

[0018] In the gas pre-concentration equipment provided in some embodiments, the capture trap includes a hollow cylindrical base, two straight pipe parts and a coil part connecting the two straight pipe parts, the coil part is sleeved on the outer wall of the cylindrical base, and the temperature measuring probe of the thermocouple is arranged on the inner wall of the cylindrical base.

[0019] In some embodiments, the gas pre-concentration device further comprises:

[0020] A dewatering device is provided between the sampling device and the fourth interface of the passage regulating device.

[0021] In some embodiments of the gas pre-concentration device, the sampling device includes a plurality of parallel solenoid valves, the inlets of different solenoid valves are respectively used to connect to the sample inlet or the standard gas inlet, and the controller controls the opening and closing of different solenoid valves to control the gas passage entering the sampling device; or,

[0022] The sampling device comprises a multi-way sampling valve, different inlet ends of the multi-way sampling valve are respectively used to connect to a sample inlet or a standard gas inlet, and the controller controls the gas passage entering the sampling device by controlling the conducting branch of the multi-way sampling valve.

[0023] In some embodiments, the gas pre-concentration device further comprises:

[0024] The filter is arranged between the third interface of the passage regulating device and the second flow control device.

[0025] In some embodiments, the gas pre-concentration device further comprises:

[0026] A vacuum chamber, in which the cold end of the refrigeration device and the capture device are placed;

[0027] A vacuum pump connected to the vent hole of the vacuum chamber;

[0028] or,

[0029] The cold end of the refrigeration device and the capture device are integrally covered inside the thermal insulation material.

[0030] The present application also provides a method for controlling the gas pre-concentration device according to any one of the above items, comprising the following steps:

[0031] Enrichment mode: Control the refrigeration device and the heating control device to control the trap temperature at a first preset temperature. After the sample gas passes through the injection device, it passes through the passage adjustment device and enters the trap for enrichment. The flow rate of the sample gas is controlled by the second flow control device;

[0032] Desorption mode: firstly, the different interfaces of the passage regulating device are controlled to be connected or disconnected, so that the trap is isolated from the external gas pipeline, and the heating control device is controlled to raise the temperature of the trap to a second preset temperature, and then the different interfaces of the passage regulating device are controlled to be connected or disconnected, so that the trap is connected to the gas pipeline, and the carrier gas is introduced into the trap through the first flow control device, so that the sample gas enters the analytical instrument for detection after desorption;

[0033] Purge mode: control the first flow control device to pass carrier gas into the trap to purge the trap, and control the heating control device to raise the temperature of the trap to a third preset temperature.

[0034] The control method described in some embodiments:

[0035] In the purge mode, the carrier gas enters the trap from a direction opposite to that in the enrichment mode by controlling the connection or disconnection of different interfaces of the passage regulating device;

[0036] The desorption mode also includes a decontamination step: controlling the different interfaces of the passage regulating device to be connected or disconnected so that the capture trap is connected to the gas pipeline, introducing a carrier gas into the capture trap through the first flow control device, and controlling the refrigeration device and the heating control device to control the temperature of the capture trap to a fourth preset temperature; the fourth preset temperature is between the first preset temperature and the second preset temperature.

[0037] The technical solution of this application has the following technical effects compared with the prior art:

[0038] The gas pre-concentration device and control method provided in the present application include a sampling device, a first flow control device, a second flow control device, a heating control device, a refrigeration device, a capture device, a passage regulating device and a controller; the capture device includes a capture trap, a thermocouple, and a cold plate, the temperature probe of the thermocouple is installed on the capture trap, and the capture trap is installed on the cold plate; the passage regulating device and the capture trap are connected through a gas pipeline, and the capture trap is connected to the heating control device through a wire; the first flow control device and the second flow control device are respectively connected to the passage regulating device through a gas pipeline; the cold end of the refrigeration device is connected to the cold plate, and the cold end of the refrigeration device and the capture device are connected under a vacuum environment. This scheme adopts a single capture trap to achieve the enrichment and analysis of multiple greenhouse gases, and has the advantages of simple structure, no need to use complex refrigeration methods such as liquid nitrogen, low enrichment temperature, high enrichment efficiency, good repeatability, etc.; it can be used in combination with a variety of analytical instruments, can be used for portable or online measurement instrument structure, and can be used for online monitoring of multiple greenhouse gases. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] The preferred embodiments of the present application will be described in detail below with reference to the accompanying drawings, which will help to understand the purpose and advantages of the present application, wherein:

[0040] Figure 1 This is a schematic diagram of the structure of a gas pre-concentration device according to an embodiment of the present application;

[0041] Figure 2 This is a schematic structural diagram of a gas pre-concentration device according to another embodiment of the present application;

[0042] Figure 3 for Figure 2 Schematic diagram of the gas path of the device shown in the enrichment mode;

[0043] Figure 4 for Figure 2 Schematic diagram of the gas path direction of the device in the analytical mode;

[0044] Figure 5 This is a schematic structural diagram of a gas pre-concentration device according to another embodiment of the present application;

[0045] Figure 6 for Figure 5 Schematic diagram of the gas path of the device shown in the enrichment mode;

[0046] Figure 7 for Figure 5 Schematic diagram of the gas path direction of the device in the analytical mode;

[0047] Figure 8 for Figure 5 Schematic diagram of the gas path of the device shown in the purge mode. DETAILED DESCRIPTION

[0048] The technical solution of the present application will be described clearly and completely below in conjunction with the accompanying drawings. Obviously, the described embodiments are part of the embodiments of the present application, rather than all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present application.

[0049] In the description of the present application, it should be noted that the terms "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer", etc., indicating the orientation or positional relationship, are based on the orientation or positional relationship shown in the drawings, and are only for the convenience of describing the present application and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as limiting the present application. In addition, the terms "first", "second", and "third" are used for descriptive purposes only, and cannot be understood as indicating or implying relative importance.

[0050] In the description of this application, it should be noted that, unless otherwise clearly specified and limited, the terms "installed", "connected", and "connected" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a direct connection, or an indirect connection through an intermediate medium, or it can be the internal communication of two components. For ordinary technicians in this field, the specific meanings of the above terms in this application can be understood according to specific circumstances.

[0051] In addition, the technical features involved in the different embodiments of the present application described below can be combined with each other as long as they do not conflict with each other.

[0052] This embodiment provides a gas pre-concentration device, such as Figure 1 As shown, it includes a sample injection device 1, a first flow control device 3, a second flow control device 4, a heating control device 6, a refrigeration device 10, a capture device, and a passage adjustment device 11. In some embodiments, the first flow control device 3 and the second flow control device 4 are mass flow controllers. The refrigeration device 10 is a Stirling refrigerator, which uses helium as a refrigerant. The Stirling refrigerator is driven by electricity. Compared with a traditional compressor refrigerator, it has the advantages of compact structure, low power consumption, stability and reliability, and does not need to use a refrigerant that may interfere with the analysis results.

[0053] As shown in the figure, the sample injection device 1 is used to access the sample gas; the inlet of the sample injection device 1 is connected to the sample inlet 12 through a pipeline 104, and the outlet of the sample injection device is connected to the passage regulating device 11 through a pipeline 106. The first flow control device 3 is used to access the carrier gas and adjust the flow of the carrier gas. The carrier gas inlet 13 is connected to the inlet of the first flow control device 3 through a pipeline 101. The carrier gas can be a common carrier gas such as synthetic air, nitrogen or helium. The outlet of the first flow control device 3 is connected to the passage regulating device 11 through a pipeline 102; the capture device includes a capture trap 7, a cold plate 8 and a thermocouple 5. The temperature probe of the thermocouple 5 is arranged on the capture trap 7, and the capture trap 7 is arranged on the cold plate 8; the capture trap 7 can be a coil type. The temperature probe of the thermocouple 5 is installed on the coil of the capture trap 7, and the other end of the thermocouple 5 is connected to the heating control device 6 through a wire 111, and the heating control device 6 is connected to the capture trap 7 through a wire. The refrigeration end of the refrigeration device 10 is connected to the cold plate 8 in the capture device. As shown in the figure, in some schemes, the capture trap 7 and the cold plate 8 are wrapped with a heat-insulating material 9 as a whole. The heat-insulating material 9 can be a material resistant to low temperatures of -100°C, such as epichlorohydrin rubber, epichlorohydrin rubber, and epichlorohydrin rubber. The heat-insulating material 9 can be provided to isolate the refrigeration device 10 and the capture device from the outside world, thereby avoiding a large amount of water vapor condensing on the outer wall of the refrigeration device during the cooling process, thereby effectively ensuring accurate temperature control of the capture trap 7. The second flow control device 4 is used to adjust the gas flow input therein, and the outlet of the second flow control device 4 is connected to the gas outlet 14 through a pipeline 110.

[0054] The first interface J1 of the passage regulating device 11 is connected to the interface 15 of the analytical instrument through a pipeline 103, and the analytical instrument is used to detect the output gas to be tested; the second interface J2 is connected to one end of the capture trap 7 through a pipeline 108, the third interface J3 is connected to the inlet of the second flow control device 4 through a pipeline 109, the fourth interface J4 is connected to the outlet of the sample injection device 1 by connecting to the pipeline 106, the fifth interface J5 is connected to the other end of the capture trap 7 through a pipeline 107, and the sixth interface J6 is connected to the pipeline 102 and connected to the first flow control device 3; the controller controls the opening and closing of the first flow control device 3, the second flow control device 4, the heating control device 6 and the refrigeration device 10, controls the set temperature value of the heating control device 6, controls the set flow values ​​of the first flow control device 3 and the second flow control device 4, and controls the different interfaces of the passage regulating device 1 to be connected or disconnected, thereby controlling the gas pre-concentration device to work in enrichment mode, analysis mode or cleaning mode respectively. Among them, the set temperature value and the set flow value can be adjusted and set by programming according to the actual scenario.

[0055] The equipment in the above scheme includes a sampling device 1, a first flow control device 3, a second flow control device 4, a heating control device 6, a refrigeration device 10, a capture device, a passage adjustment device 11 and a controller. The equipment has a simple structure, high concentration efficiency and good repeatability, and can be used for online monitoring of various greenhouse gases.

[0056] In addition, as shown in the figure, the second flow control device 4 can be arranged either upstream or downstream of the passage regulating device 11. In this embodiment, it is preferably arranged downstream of the passage regulating device 11, which can prevent the flow control device from generating trace amounts of impurity gases such as the sealing ring of the main body of the flow control device from interfering with the test results. In actual application, according to the type of target gas and the characteristics of the flow control device, the second flow control device 4 can also be installed upstream of the passage regulating device 11.

[0057] In some schemes, such as Figure 2-Figure 4 As shown, the passage regulating device 11 includes a six-way multi-position valve 11A. As a preferred embodiment, the six-way multi-position valve 11A is a six-way twelve-position valve. The six-way twelve-position valve includes a valve body, a valve core and a driver. The cross section of the valve body is circular and contains 6 pipeline interfaces, which are evenly distributed on the same cross section of the valve body. The valve core is installed at the center of the valve body. The cross section is circular. A plurality of concave flow channels are arranged along the circumference. There are intervals between the flow channels. When the controller controls the driver to drive the valve core to rotate, for any interface, it can be connected to another adjacent interface through the flow channel, or only connected to the flow channel, or not connected to any flow channel. Therefore, in addition to realizing the function of the six-way two-position valve, the six-way multi-position valve 11A can also realize the isolation of two opposite interfaces, so it can be used for the capture trap 7 to analyze under isolation conditions. As shown in the figure, interface 1 of the six-way multi-position valve 11A serves as the first interface, interface 2 of the six-way multi-position valve 11A serves as the second interface, interface 3 of the six-way multi-position valve 11A serves as the third interface, interface 4 of the six-way multi-position valve 11A serves as the fourth interface, interface 5 of the six-way multi-position valve 11A serves as the fifth interface, and interface 6 of the six-way multi-position valve 11A serves as the sixth interface.

[0058] In other schemes, such as Figure 5-Figure 8As shown, the passage regulating device 11 includes a four-way two-position valve 11B and a six-way multi-position valve 11A, the interface 1 of the four-way two-position valve 11B is connected to the interface 1 of the six-way multi-position valve 11A via a pipeline 113, and the interface 3 of the four-way two-position valve 11B is connected to the interface 6 of the six-way multi-position valve 11A via a pipeline 114; the interface 4 of the four-way two-position valve 11B serves as the first interface and is connected to the interface 15 of the analytical instrument via a pipeline 115; the interface 2 of the six-way multi-position valve 11A serves as the second interface; the interface 3 of the six-way multi-position valve 11A serves as the third interface; the interface 4 of the six-way multi-position valve 11A serves as the fourth interface; the interface 5 of the six-way multi-position valve 11A serves as the fifth interface; the interface 2 of the four-way two-position valve 11B serves as the sixth interface and is connected to the first flow control device 3 via a pipeline 112.

[0059] Both of the above two passage regulating devices 11 can realize the switching of the gas pre-concentration device in different working modes. Figure 5 In the scheme shown, when executing the sweep mode, the airflow direction of the carrier gas can also be controlled to switch, so that the trap 7 can be purged more effectively by reverse air intake.

[0060] In the above schemes, the shape of the trap 7 can be a straight tube type, a curved tube type or a coil type, and the material is stainless steel, glass or quartz. The trap 7 is filled with an adsorbent and an adsorbent positioning device, and the material of the positioning device is stainless steel or quartz. In some preferred schemes, such as Figure 5 As shown, the trap 7 includes a hollow cylindrical base 23, two straight pipe parts and a coil part connecting the two straight pipe parts, the coil part is sleeved on the outer wall of the cylindrical base 23, and the temperature measuring probe of the thermocouple 5 is arranged on the inner wall of the cylindrical base 23. In this solution, one end of the cylindrical base 23 contacts the cold plate 8, and the other end contacts the coil. The cylindrical base 23 plays a buffering role in the process of heating and cooling, which can improve the accuracy of temperature control.

[0061] Among them, preferably, the above-mentioned gas pre-concentration equipment also includes a vacuum cabin 24 to replace the insulation material 9, the cold end of the refrigeration device 10 and the capture device are placed in the cabin body of the vacuum cabin 24, and the vacuum cabin 24 is also equipped with a vacuum pump 17, and the vacuum pump 17 is connected to the vent 18 of the vacuum cabin 24 through pipelines 116 and pipelines 117. The capture device is placed in the cabin body of the vacuum cabin 24 to achieve the effect of isolating the heat source. The cabin body of the vacuum cabin 24 is usually made of metal, such as aluminum or stainless steel, and includes a base and an outer shell. The base and the outer shell are sealed by a sealing ring or a sealing gasket. The vacuum pump 17 provides vacuum for the vacuum cabin 24. Since the vacuum has excellent thermal insulation properties, it can also prevent gas impurities from condensing on the surface of the capture trap 7, so that lower temperature and more accurate temperature control can be achieved.

[0062] Furthermore, as shown in the above figures, the gas pre-concentration device also includes a dehydration device 2, and the dehydration device 2 is arranged between the sample injection device 1 and the fourth interface of the passage regulating device 11. The dehydration device 2 is a Nafion semipermeable membrane drying tube, and the Nafion semipermeable membrane drying tube has a double-layer structure separated by a semipermeable membrane that allows water molecules to pass through. When the sample gas is introduced into the inner layer, dry nitrogen or air is introduced into the outer layer in reverse to achieve effective drying of the sample gas. The Nafion semipermeable membrane drying tube has the advantages of simple structure and small space occupation, and is therefore particularly suitable for portable or movable equipment.

[0063] Preferably, if Figure 5 As shown, the sampling device 1 may include a plurality of parallel electromagnetic valves, the inlets of different electromagnetic valves are respectively used to connect to the sample inlet 12 or the standard gas inlet 19, and the controller controls the opening and closing of different electromagnetic valves to control the gas passage into the sampling device 1; or, the sampling device 1 includes a multi-way sampling valve (such as a ten-way sampling valve), and the different inlet ends of the multi-way sampling valve are respectively used to connect to the sample inlet 12 or the standard gas inlet 19, and the controller controls the gas passage into the sampling device by controlling the conducting branch of the multi-way sampling valve. As shown in the figure, the sampling device 1 includes a first electromagnetic valve 20 and a second electromagnetic valve 21 in parallel as an example, wherein the first electromagnetic valve 20 is connected to the standard gas inlet 19 via a pipeline 118, and the second electromagnetic valve 21 is connected to the sample inlet 12 via a pipeline 119. The number of electromagnetic valves can be selected according to actual conditions, generally 2 to 16 parallel electromagnetic valves, and the pipelines 118 and 119 can be implemented with copper pipes.

[0064] In some embodiments, the gas pre-concentration device may further include a filter 22, which is disposed between the third interface of the passage regulating device 11 and the second flow control device 4. The filter 22 can prevent particles in the gas from entering the second flow control device 4, thereby improving the accuracy of flow control and extending the life of the device.

[0065] In some embodiments of the present application, a control method for a gas pre-concentration device is further provided. In the method, the set temperature value of the heating control device includes a first preset temperature, a second preset temperature, a third preset temperature and a fourth preset temperature. The method may include the following steps:

[0066] The steps of executing the enrichment mode are as follows: controlling the refrigeration device and the heating control device to control the temperature of the trap at a first preset temperature, the sample gas passes through the injection device, and then passes through the passage adjustment device to enter the trap for enrichment, and the flow of the sample gas is controlled by the second flow control device;

[0067] The steps of executing the desorption mode are as follows: first, controlling the different interfaces of the passage regulating device to be connected or disconnected, so that the trap is isolated from the external gas pipeline, controlling the heating control device to raise the temperature of the trap to a second preset temperature, then controlling the different interfaces of the passage regulating device to be connected or disconnected, so that the trap is connected to the gas pipeline, and passing the carrier gas into the trap through the first flow control device, so that the sample gas desorbs and enters the analytical instrument for detection;

[0068] The steps of executing the purge mode are as follows: controlling the first flow control device to pass carrier gas into the trap to purge the trap, and controlling the heating control device to raise the temperature of the trap to a third preset temperature.

[0069] against Figure 2 The device structure shown in the figure, the execution process of the above different modes includes:

[0070] (1.1): Enrichment mode, such as Figure 3 As shown, the cold head of the refrigeration device 10 transfers the low temperature to the cold plate 8, so that the temperature of the trap 7 is reduced to the first preset temperature. After the sample gas passes through the sample injection device 1, it passes through the water removal device 2 and enters the six-way multi-position valve 11A. The controller controls the six-way multi-position valve 11A so that its interface 4 is connected to the interface 5, the interface 2 is connected to the interface 3, and the interface 1 is connected to the interface 6. The sample gas enters from the interface 4 of the six-way multi-position valve 11A, and flows out from the interface 5 of the six-way multi-position valve 11A into the trap 7. The target gas component is enriched in the trap 7, and the remaining gas returns to the interface 2 of the six-way multi-position valve 11A, and then flows out from the interface 3 of the six-way multi-position valve 11A, and is discharged from the gas outlet 14 after the flow is controlled by the second flow control device 4. In the above scheme, during the enrichment process, the carrier gas can be introduced into the interface 15 of the analytical instrument through the first flow control device 3 to purge the pipeline and the analytical instrument.

[0071] In general, the first preset temperature and the flow rate of the second flow control device 4 need to be determined according to the boiling point and polarity of the target gas component, its concentration in the sample gas and the detection requirements of the analytical instrument. In this embodiment, the first preset temperature is set to -100°C, which can achieve effective enrichment of target gas components such as CO2, N2O, CFCs, etc. Setting the first preset temperature to -160°C can achieve effective enrichment of target components such as CF4, PFCs, HFCs, etc. The flow rate of the second flow control device 4 can be set at 100~500 ml / min. The larger the flow rate and the longer the enrichment time, the higher the pre-concentration ratio.

[0072] (1.2) Desorption mode: First, the trap 7 is isolated from the external gas pipeline by controlling the six-way multi-position valve 11A, such as Figure 2 As shown. The temperature of the trap 7 is raised to a second preset temperature by the heating control device 6, so that the target gas component enriched in the trap 7 is desorbed and released into the internal pipeline of the trap 7. Afterwards, the six-way multi-position valve 11A is controlled to connect the interface 1 with the interface 2, the interface 3 with the interface 4, and the interface 5 with the interface 6, and the carrier gas is introduced into the trap 7 through the first flow control device 3, as shown. Figure 4 As shown, the desorbed target gas component is sent to the analytical instrument for detection through the interface 1 of the six-way multi-position valve 11A.

[0073] In general, the second preset temperature, carrier gas flow rate and injection time need to be determined according to the boiling point and polarity of the target component and impurity gas, as well as the requirements of the downstream analytical instrument. In this embodiment, when pre-concentrating N2O, the second preset temperature, carrier gas flow rate and injection time are set to -30°C, 50 ml / min and 2 min, respectively. If the flow rate of the second flow control device 4 in the enrichment stage is set to 500 ml / min, and the enrichment time is set to 20 min, the injection volume is 10 L, and the pre-concentration ratio is 100:1, the concentration of the target gas component can be increased to 100 times that of the sample gas.

[0074] (1.3) Purge mode: The purge process is used to completely remove the impurities remaining in the trap 7 and restore the trap 7 to the enrichment preparation state. The pipeline status of the pre-concentration equipment during the purge process is as follows: Figure 4 As shown, the sample injection stage is the same as the desorption step, except that the temperature of the trap 7 needs to be further increased to the third preset temperature. In this embodiment, the carrier gas purge flow rate is maintained at 50 ml / min, and the third preset temperature is 100° C. The higher third preset temperature helps to completely remove the residual impurities in the trap 7 and improve the repeatability of the system.

[0075] Furthermore, the duration of the purge process can be determined according to the characteristics of the trap 7, and in this embodiment is 5 minutes. After the purge process is completed, the temperature of the trap 7 drops to the first preset temperature, and the six-way multi-position valve 11 switches back to the enrichment step focus state to prepare for the next sample pre-concentration.

[0076] According to the equipment and control method provided in the above scheme, it takes about 30 minutes to complete the pre-concentration process of a sample. If the pre-concentration ratio is reduced to 50:1, it only takes 20 minutes. Therefore, the pre-concentration equipment of this scheme can be used for high-frequency online analysis or on-site rapid detection of environmental gases.

[0077] In the above control method, in addition to the above steps, an additional impurity removal step may be included between the execution steps of the enrichment mode and the desorption mode. Figure 4 The same, but the trap 7 is heated to a fourth preset temperature. This temperature value is between the first preset temperature and the second preset temperature, and can be used to remove interference from certain impurities, so as to prevent these impurities from interfering with the qualitative and quantitative analysis results when they are directly thermally desorbed into the analytical instrument after enrichment.

[0078] against Figure 5 The device structure shown in the figure, the execution process of the above different modes includes:

[0079] (2.1) Enrichment pattern: Figure 6 As shown, the cold head of the refrigeration device 10 transfers the low temperature to the cold plate 8, so that the temperature of the capture trap 7 is reduced to the first preset temperature. The second solenoid valve 21 in the sample injection device 1 is opened, and the sample gas enters the six-way multi-position valve 11A after passing through the water removal device 2. The controller controls the six-way multi-position valve 11A so that interface four is connected to interface five, interface two is connected to interface three, and interface one is connected to interface six. The sample gas enters from interface four and flows out from interface five into the capture trap 7. The target gas component is enriched in the capture trap 7, and the remaining gas returns to interface two of the six-way multi-position valve 11A, and then flows out from interface three, and is discharged from the gas outlet 14 after the flow is controlled by the second flow control device 4.

[0080] (2.2) Desorption mode: First, the trap 7 is isolated from the external gas pipeline by controlling the six-way multi-position valve 11A, such as Figure 5 As shown. The temperature of the trap 7 is raised to the second preset temperature by the heating control device 6, so that the target gas component enriched in the trap 7 is desorbed and released into the internal pipeline of the trap 7. Afterwards, the six-way multi-position valve 11 is controlled to connect the interface 1 with the interface 2, the interface 3 with the interface 4, and the interface 5 with the interface 6, and the four-way two-position valve 11B is controlled to connect the interface 1 with the interface 4, and the interface 2 with the interface 3, and the carrier gas is introduced into the trap 7 through the first flow control device 3, as shown. Figure 7As shown, the desorbed target gas component is sent to the interface 1 of the four-way two-position valve 11B through the interface 1, and then sent to the analysis instrument through the interface 4 through the pipeline 115 for detection.

[0081] (2.3) Purge mode: Control the four-way two-position valve 11B to connect port 1 with port 2, and port 3 with port 4. Figure 8 At this time, the carrier gas will enter the trap from the opposite direction of the enrichment step for purging, which helps to completely remove the remaining impurities, and thus can further improve the enrichment efficiency and repeatability of the pre-concentration equipment, thereby improving the accuracy of the analysis.

[0082] In the above scheme, the first preset temperature is below -100°C, the second preset temperature is above -60°C, and the third preset temperature is above 80°C. The first preset temperature is used for sample enrichment. The lower first preset temperature can capture low-boiling greenhouse gases as completely as possible, thereby improving the capture efficiency. The second preset temperature is used for sample analysis, which is usually higher than the boiling point of the target gas. The third preset temperature is used for purging the trap, and a higher temperature is conducive to the complete removal of residual components in the trap. At the same time, the gas pre-concentration equipment in the above scheme can be used for the analysis of offline sampled samples, as well as for online analysis. When multiple offline sampled samples need to be analyzed, the samples can be automatically switched through 2 to 16 parallel solenoid valves or 1 multi-position injection valve. When performing online analysis, the sample and the standard gas can be switched through 2 parallel solenoid valves.

[0083] Obviously, the above embodiments are merely examples for the purpose of clear explanation, and are not intended to limit the implementation methods. For those skilled in the art, other different forms of changes or modifications can be made based on the above description. It is not necessary and impossible to list all the implementation methods here. The obvious changes or modifications derived therefrom are still within the scope of protection of this application.

Claims

1. A gas pre-concentration device, It is characterized in that include: A sampling device, used for receiving a sample gas; A first flow control device, used for connecting the carrier gas and adjusting the flow of the carrier gas; The trapping device comprises a trap, a thermocouple and a cold plate, wherein the temperature measuring probe of the thermocouple is arranged on the trap, and the trap is arranged on the cold plate; A heating control device connected to the thermocouple and the trap in the trapping device; A refrigeration device, whose refrigeration end is connected to the cold plate in the capture device; A second flow control device, used for adjusting the flow of gas input therein; A passage regulating device, wherein the first interface of the passage regulating device is connected to the analytical instrument, the second interface is connected to one end of the trap, the third interface is connected to the inlet of the second flow control device, the fourth interface is connected to the outlet of the injection device, the fifth interface is connected to the other end of the trap, and the sixth interface is connected to the first flow control device; a controller for controlling the opening and closing of the heating control device, the refrigeration device, the first flow control device and the second flow control device, controlling the set temperature value of the heating control device, controlling the set flow values ​​of the first flow control device and the second flow control device, and controlling the connection or disconnection of different interfaces of the passage regulating device so as to control the gas pre-concentration device to work in the enrichment mode, the analysis mode or the cleaning mode respectively; The passage regulating device comprises a four-way two-position valve and a six-way multi-position valve, wherein the interface 1 of the four-way two-position valve is connected to the interface 1 of the six-way multi-position valve, and the interface 3 of the four-way two-position valve is connected to the interface 6 of the six-way multi-position valve; Interface 4 of the four-way two-position valve is used as the first interface; interface 2 of the six-way multi-position valve is used as the second interface; interface 3 of the six-way multi-position valve is used as the third interface; interface 4 of the six-way multi-position valve is used as the fourth interface; interface 5 of the six-way multi-position valve is used as the fifth interface; interface 2 of the four-way two-position valve is used as the sixth interface; The six-way multi-position valve is a six-way twelve-position valve, which includes a valve body, a valve core and a driver. The cross-section of the valve body is circular, and the valve body includes 6 pipeline interfaces, which are evenly distributed on the same cross-section of the valve body. The valve core is installed at the center of the valve body. The cross-section of the valve core is circular, and multiple concave flow channels are arranged along the circumference, with intervals between the flow channels. When the controller controls the driver to drive the valve core to rotate, for any interface, it is achieved: it is connected to another adjacent interface through the flow channel, or it is only connected to the flow channel, or it is not connected to any flow channel.

2. The gas pre-concentration device according to claim 1, Features: The capture trap comprises a hollow cylindrical base, two straight pipe parts and a coil part connecting the two straight pipe parts, the coil part is sleeved on the outer wall of the cylindrical base, and the temperature measuring probe of the thermocouple is arranged on the inner wall of the cylindrical base.

3. The gas pre-concentration device according to claim 2, It is characterized in that Also includes: A dewatering device is provided between the sampling device and the fourth interface of the passage regulating device.

4. The gas pre-concentration device according to claim 3, Features: The sampling device comprises a plurality of electromagnetic valves connected in parallel, the inlets of different electromagnetic valves are respectively used to connect to the sample inlet or the standard gas inlet, and the controller controls the gas passage entering the sampling device by controlling the opening and closing of different electromagnetic valves; or, The sampling device comprises a multi-way sampling valve, different inlet ends of the multi-way sampling valve are respectively used to connect to a sample inlet or a standard gas inlet, and the controller controls the gas passage entering the sampling device by controlling the conducting branch of the multi-way sampling valve.

5. The gas pre-concentration device according to claim 3, It is characterized in that Also includes: The filter is arranged between the third interface of the passage regulating device and the second flow control device.

6. The gas pre-concentration device according to claim 3, It is characterized in that Also includes: A vacuum chamber, in which the cold end of the refrigeration device and the capture device are placed; A vacuum pump connected to the vent hole of the vacuum chamber; or, The cold end of the refrigeration device and the capture device are integrally covered inside the thermal insulation material.

7. A method for controlling a gas pre-concentration device according to any one of claims 1 to 6, It is characterized in that The following steps are involved: The steps of executing the enrichment mode are as follows: controlling the refrigeration device and the heating control device to control the temperature of the trap at a first preset temperature, the sample gas passes through the injection device, and then passes through the passage adjustment device to enter the trap for enrichment, and the flow of the sample gas is controlled by the second flow control device; The steps of executing the desorption mode are as follows: first, controlling the different interfaces of the passage regulating device to be connected or disconnected, so that the trap is isolated from the external gas pipeline, controlling the heating control device to raise the temperature of the trap to a second preset temperature, then controlling the different interfaces of the passage regulating device to be connected or disconnected, so that the trap is connected to the gas pipeline, and passing the carrier gas into the trap through the first flow control device, so that the sample gas desorbs and enters the analytical instrument for detection; The steps of executing the purge mode are as follows: controlling the first flow control device to pass carrier gas into the trap to purge the trap, and controlling the heating control device to raise the temperature of the trap to a third preset temperature.

8. The control method according to claim 7, Features: In the purge mode, the carrier gas enters the trap from a direction opposite to that in the enrichment mode by controlling the connection or disconnection of different interfaces of the passage regulating device; The desorption mode also includes a decontamination step: controlling the different interfaces of the passage regulating device to be connected or disconnected so that the capture trap is connected to the gas pipeline, introducing a carrier gas into the capture trap through the first flow control device, and controlling the refrigeration device and the heating control device to control the temperature of the capture trap to a fourth preset temperature; the fourth preset temperature is between the first preset temperature and the second preset temperature.

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