CN115089993B - Gas pre-concentration device and control method - Google Patents
Gas pre-concentration device and control method Download PDFInfo
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- CN115089993B CN115089993B CN202210742085.5A CN202210742085A CN115089993B CN 115089993 B CN115089993 B CN 115089993B CN 202210742085 A CN202210742085 A CN 202210742085A CN 115089993 B CN115089993 B CN 115089993B
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- 238000004094 preconcentration Methods 0.000 title claims abstract description 49
- 238000000034 method Methods 0.000 title claims abstract description 30
- 239000007789 gas Substances 0.000 claims abstract description 119
- 239000000523 sample Substances 0.000 claims abstract description 77
- 238000010438 heat treatment Methods 0.000 claims abstract description 30
- 238000005057 refrigeration Methods 0.000 claims abstract description 17
- 230000001105 regulatory effect Effects 0.000 claims abstract description 17
- 238000005070 sampling Methods 0.000 claims abstract description 13
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- 238000002347 injection Methods 0.000 claims description 36
- 239000007924 injection Substances 0.000 claims description 36
- 238000004458 analytical method Methods 0.000 claims description 26
- 239000012159 carrier gas Substances 0.000 claims description 26
- 238000010926 purge Methods 0.000 claims description 21
- 238000003795 desorption Methods 0.000 claims description 9
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- 239000005431 greenhouse gas Substances 0.000 abstract description 8
- 238000012544 monitoring process Methods 0.000 abstract description 4
- 239000012535 impurity Substances 0.000 description 10
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Classifications
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D8/00—Cold traps; Cold baffles
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D5/00—Condensation of vapours; Recovering volatile solvents by condensation
- B01D5/0033—Other features
- B01D5/0045—Vacuum condensation
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D5/00—Condensation of vapours; Recovering volatile solvents by condensation
- B01D5/0033—Other features
- B01D5/0051—Regulation processes; Control systems, e.g. valves
Landscapes
- Chemical & Material Sciences (AREA)
- Chemical Kinetics & Catalysis (AREA)
- Engineering & Computer Science (AREA)
- Automation & Control Theory (AREA)
- Sampling And Sample Adjustment (AREA)
Abstract
本申请公开一种气体预浓缩设备及控制方法，其设备包括进样装置、第一流量控制装置、第二流量控制装置、加热控制装置、制冷装置、捕集装置、通路调节装置和控制器；捕集装置包括捕集阱、热电偶、冷盘，热电偶的测温探头安装于捕集阱之上，捕集阱安装于所述冷盘之上；通路调节装置及捕集阱通过气体管路相连，捕集阱与加热控制装置通过导线相连；第一流量控制装置、第二流量控制装置分别与通路调节装置通过气体管路相连；制冷装置的冷端与冷盘相连，且制冷装置的冷端、捕集装置相连。本方案中的设备结构简单、浓缩效率高、重复性好，可用于多种温室气体的在线监测。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
The invention relates to the technical field of gas analysis equipment, in particular to gas pre-concentration equipment and a control method.
Background
With the increasing global warming, artificial greenhouse gas emissions have attracted widespread attention from the international society. The content of greenhouse gases such as Hydrofluorocarbons (HFCs) and Perfluorocarbons (PFCs) in the ambient air, which are completely discharged by human beings, is on the order of one trillion parts per trillion (10 -12, ppt), and the existing instrument cannot be directly analyzed due to the problem of detection limit, and the concentration of the target substances must be increased by adopting a pre-concentration mode. While greenhouse gases having both natural and artificial sources, such as carbon dioxide (CO 2), nitrous oxide (N 2 O), etc., require analysis of their isotopic content in order to distinguish the contributions of natural and artificial sources. Taking carbon dioxide (CO 2) as an example, the traditional method for measuring C-14 in the air needs to dissolve a sufficient amount of gas and alkaline solution, then convert the gas into pure CO 2 gas through processes of precipitation, roasting and the like, and finally measure the gas by adopting a liquid scintillation spectrometer. The method has the defects that the treatment process is complicated, the used instrument is expensive, and the on-line monitoring cannot be realized. At present, the existing portable technologies such as laser spectrum and the like can be used for on-line measurement of CO 2、N2 O isotopes, but the content of the isotopes in the target gas is in the order of thousandths, so that the pre-concentration of the target gas is still a necessary step.
Most of the prior art preconcentration devices are designed for Volatile Organic Compounds (VOCs), and the target substances are condensed and concentrated by adopting semiconductor refrigeration, but the concentration of CO 2、N2 O isothermal chamber gas is difficult due to the limited refrigerating capacity of the semiconductor (the lowest temperature is usually only-40 ℃), and the prior art adopts multi-stage cold traps, so that the preconcentration process is complex, and the repeatability is difficult to ensure
Disclosure of Invention
The application aims to solve the technical problems that the existing gas pre-concentration scheme has complex structure, can not ensure the repeatability and is only suitable for individual compounds, and therefore, the application provides gas pre-concentration equipment and a use method thereof.
Aiming at the technical problems, the application provides the following technical scheme:
An embodiment of the present application provides a gas preconcentration device, including:
the sample injection device is used for accessing sample gas;
the first flow control device is used for accessing the carrier gas and adjusting the flow of the carrier gas;
the trapping device comprises a trapping well, a thermocouple and a cold plate, wherein a temperature measuring probe of the thermocouple is arranged on the trapping well, and the trapping well is arranged on the cold plate;
a heating control device connected to the thermocouple and the trap in the trap device;
a refrigeration device, the refrigeration end of which is connected with the cold disc in the trapping device;
a second flow rate control means for adjusting the flow rate of the gas inputted into the interior thereof;
The first interface of the passage adjusting device is connected with the analysis instrument, the second interface is connected with one end of the trap, the third interface is connected with the inlet of the second flow control device, the fourth interface is connected with the outlet of the sample injection device, the fifth interface is connected with the other end of the trap, and the sixth interface is connected with the first flow control device;
And the controller is used for controlling the heating control device, the refrigerating device, the first flow control device and the second flow control device to be opened and closed, controlling the set temperature value of the heating control device, controlling the set flow value of the first flow control device and the second flow control device and controlling different interfaces of the passage regulating device to be connected or disconnected so as to control the gas pre-concentration equipment to work in an enrichment mode, an analysis mode or a cleaning mode respectively.
In some embodiments, the gas preconcentration device provided by the present invention, the path adjustment device includes a six-way multi-position valve, an interface one of the six-way multi-position valve is used as the first interface, an interface two of the six-way multi-position valve is used as the second interface, an interface three of the six-way multi-position valve is used as the third interface, an interface four of the six-way multi-position valve is used as the fourth interface, an interface five of the six-way multi-position valve is used as the fifth interface, and an interface six of the six-way multi-position valve is used as the sixth interface.
The gas preconcentration device provided in some embodiments, the path adjusting device includes a four-way two-position valve and a six-way multi-position valve, a first port of the four-way two-position valve is connected with a first port of the six-way multi-position valve, and a third port of the four-way two-position valve is connected with a sixth port of the six-way multi-position valve;
the four-way two-position valve is characterized in that an interface IV of the four-way two-position valve is used as the first interface, an interface II of the six-way multi-position valve is used as the second interface, an interface III of the six-way multi-position valve is used as the third interface, an interface IV of the six-way multi-position valve is used as the fourth interface, an interface V of the six-way multi-position valve is used as the fifth interface, and an interface II of the four-way two-position valve is used as the sixth interface.
In some embodiments, the gas pre-concentration device provided by the invention further comprises a trap, wherein the trap comprises a hollow cylindrical base, two straight pipe parts and a coil pipe part connected with the two straight pipe parts, the coil pipe part is sleeved on the outer wall of the cylindrical base, and a temperature probe of the thermocouple is arranged on the inner wall of the cylindrical base.
The gas preconcentration device provided in some embodiments, further comprises:
and the water removing device is arranged between the sample injection device and the fourth interface of the passage adjusting device.
The gas pre-concentration device provided in some embodiments, the sample injection device comprises a plurality of parallel electromagnetic valves, the inlets of the different electromagnetic valves are respectively used for connecting a sample inlet or a standard gas inlet, and the controller controls the opening and closing of the different electromagnetic valves to control the gas passage entering the sample injection device, or
The sample injection device comprises a multi-way sample injection valve, different inlet ends of the multi-way sample injection valve are respectively used for connecting a sample inlet or a standard gas inlet, and the controller controls a gas passage entering the sample injection device by controlling a conduction branch of the multi-way sample injection valve.
The gas preconcentration device provided in some embodiments, further comprises:
and a filter provided between the third port of the passage adjustment device and the second flow rate control device.
The gas preconcentration device provided in some embodiments, further comprises:
the cold end of the refrigerating device and the trapping device are arranged in the vacuum cabin body;
The vacuum pump is connected with the vent hole of the vacuum cabin;
Or alternatively
And the cold end of the refrigerating device and the trapping device are integrally coated in the heat insulation material.
The embodiment of the application also provides a control method of the gas pre-concentration equipment, which comprises the following steps:
the enrichment mode comprises the steps of controlling a refrigerating device and a heating control device to control the temperature of a trap at a first preset temperature, enabling sample gas to enter the trap for enrichment after passing through a sample injection device and a passage adjusting device, and controlling the flow of the sample gas through a second flow control device;
The desorption mode comprises the steps of firstly controlling the connection or disconnection of different interfaces of the passage regulating device to isolate the trap from an external gas pipeline, controlling the heating control device to raise the temperature of the trap to a second preset temperature, then controlling the connection or disconnection of different interfaces of the passage regulating device to enable the trap to be connected with the gas pipeline, and introducing carrier gas into the trap through the first flow control device to enable the sample gas to enter an analysis instrument for detection after being desorbed;
And in the purging mode, the first flow control device is controlled to introduce carrier gas into the trap to purge the trap, and the heating control device is controlled to raise the temperature of the trap to a third preset temperature.
The control method described in some embodiments:
in the purge mode, carrier gas is caused to enter the trap from a direction opposite to the enrichment mode by controlling the different interfaces of the pathway adjustment device to be connected or disconnected;
The desorption mode further comprises a step of controlling different interfaces of the passage regulating device to be connected or disconnected to enable the trap to be connected with a gas pipeline, introducing carrier gas into the trap through the first flow control device, and controlling the refrigerating device and the heating control device to control the trap temperature to be a fourth preset temperature, wherein the fourth preset temperature is between the first preset temperature and the second preset temperature.
Compared with the prior art, the technical scheme of the application has the following technical effects:
The application provides gas pre-concentration equipment and a control method, wherein the equipment comprises a sample injection device, a first flow control device, a second flow control device, a heating control device, a refrigerating device, a trapping device, a passage adjusting device and a controller, wherein the trapping device comprises a trapping trap, a thermocouple and a cold disc, a temperature measuring probe of the thermocouple is arranged on the trapping trap, the trapping trap is arranged on the cold disc, the passage adjusting device and the trapping trap are connected through a gas pipeline, the trapping trap is connected with the heating control device through a wire, the first flow control device and the second flow control device are respectively connected with the passage adjusting device through a gas pipeline, the cold end of the refrigerating device is connected with the cold disc, and the cold end of the refrigerating device and the trapping device are connected in a vacuum environment. The scheme can realize enrichment and analysis of various greenhouse gases by adopting a single trap, has the advantages of simple structure, no need of using liquid nitrogen and other complex refrigeration modes, low enrichment temperature, high enrichment efficiency, good repeatability and the like, can be matched with various analysis instruments for use, can be used for portable or online measuring instrument junctions, and can be used for online monitoring of various greenhouse gases.
Drawings
The objects and advantages of the present application will be better understood by describing in detail preferred embodiments thereof with reference to the accompanying drawings in which:
FIG. 1 is a schematic diagram of a gas preconcentration device according to one embodiment of the present application;
FIG. 2 is a schematic diagram of a gas preconcentration device according to another embodiment of the present application;
FIG. 3 is a schematic diagram of the gas path orientation of the apparatus of FIG. 2 in the enrichment mode;
FIG. 4 is a schematic diagram of the gas path of the apparatus of FIG. 2 in an analysis mode;
FIG. 5 is a schematic view showing the structure of a gas pre-concentration apparatus according to still another embodiment of the present application;
FIG. 6 is a schematic diagram of the gas path orientation of the apparatus of FIG. 5 in the enrichment mode;
FIG. 7 is a schematic diagram of the gas path of the device of FIG. 5 in an analysis mode;
FIG. 8 is a schematic view of the path of the apparatus of FIG. 5 in purge mode.
Detailed Description
The following description of the embodiments of the present application will be made apparent and fully in view of the accompanying drawings, in which some, but not all embodiments of the application are shown. All other embodiments, which can be made by those skilled in the art based on the embodiments of the application without making any inventive effort, are intended to be within the scope of the application.
In the description of the present application, it should be noted that the directions or positional relationships indicated by the terms "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer", etc. are based on the directions or positional relationships shown in the drawings, are merely for convenience of describing the present application and simplifying the description, and do not indicate or imply that the devices or elements referred to must have a specific orientation, be configured and operated in a specific orientation, and thus should not be construed as limiting the present application. Furthermore, the terms "first," "second," and "third" are used for descriptive purposes only and are not to be construed as indicating or implying relative importance.
In the description of the present application, unless explicitly stated and limited otherwise, the terms "mounted," "connected," and "connected" are to be construed broadly, and may be, for example, fixedly connected, detachably connected, or integrally connected, directly connected, or indirectly connected through an intermediary, or may be in communication with the interior of two elements. The specific meaning of the above terms in the present application will be understood in specific cases by those of ordinary skill in the art.
In addition, the technical features of the different embodiments of the present application described below may be combined with each other as long as they do not collide with each other.
The present embodiment provides a gas pre-concentration apparatus, as shown in fig. 1, which 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 trapping device, and a passage adjustment device 11. In some aspects, the first flow control device 3 and the second flow control device 4 are mass flow controllers. The refrigerating device 10 is a stirling refrigerator, helium is used as a refrigerating medium, and the stirling refrigerator is driven by electricity, so that compared with a traditional compressor refrigerator, the refrigerating device has the advantages of compact structure, low power consumption, stability and reliability, and no need of using a refrigerant which possibly causes interference to analysis results.
As shown in the figure, the sample injection device 1 is used for accessing sample gas, an inlet of the sample injection device 1 is connected with a sample inlet 12 through a pipeline 104, and an outlet of the sample injection device is connected with a passage adjusting device 11 through a pipeline 106. The first flow control device 3 is used for accessing carrier gas and adjusting the flow of the carrier gas, the carrier gas inlet 13 is connected with the inlet of the first flow control device 3 through a pipeline 101, the carrier gas can be common carrier gas such as synthetic air, nitrogen or helium, the outlet of the first flow control device 3 is connected with the passage adjusting device 11 through a pipeline 102, the trapping device comprises a trapping well 7, a cold disc 8 and a thermocouple 5, a temperature measuring probe of the thermocouple 5 is arranged on the trapping well 7, the trapping well 7 is arranged on the cold disc 8, and the trapping well 7 can be coiled. The temperature measuring probe of the thermocouple 5 is arranged on the coil pipe of the trap 7, the other end of the thermocouple 5 is connected with the heating control device 6 through a wire 111, and the heating control device 6 is connected with the trap 7 through a wire. The refrigerating end of the refrigerating device 10 is connected with the cold tray 8 in the trapping device, as shown in the figure, in some schemes, the trapping well 7 and the cold tray 8 are integrally wrapped by a heat insulation material 9, and the heat insulation material 9 can be a material resistant to low temperature of-100 ℃, such as epichlorohydrin rubber, chlorohydrin rubber. The heat preservation material 9 can isolate the refrigerating device 10 and the trapping device from the outside, so that a large amount of water vapor is prevented from being condensed on the outer wall of the refrigerating device in the cooling process, and the accurate temperature control of the trapping trap 7 is effectively ensured. The second flow control device 4 is used for adjusting the flow rate of the gas input into the second flow control device 4, and the outlet of the second flow control device 4 is connected with the gas outlet 14 through a pipeline 110.
The first interface J1 of the passage adjusting device 11 is connected with the interface 15 of the analysis instrument through a pipeline 103, the analysis instrument is used for detecting output gas to be detected, the second interface J2 is connected with one end of the trap 7 through a pipeline 108, the third interface J3 is connected with an inlet of the second flow control device 4 through a pipeline 109, the fourth interface J4 is connected with the outlet of the sample injection device 1 through a pipeline 106, the fifth interface J5 is connected with the other end of the trap 7 through a pipeline 107, the sixth interface J6 is connected with the pipeline 102 so as to be connected with the first flow control device 3, and the controller controls the first flow control device 3, the second flow control device 4, the heating control device 6 and the refrigerating device 10 to open and close, controls a set temperature value of the heating control device 6, controls a set value of the first flow control device 3 and the second flow control device 4 and controls different interfaces of the passage adjusting device 1 to be communicated or disconnected so as to control gas pre-concentration equipment to be respectively in an enrichment mode, an analysis mode or a cleaning mode. The set temperature value and the set flow value can be adjusted and set in a programming mode according to an actual scene.
The equipment in the scheme comprises a sample injection device 1, a first flow control device 3, a second flow control device 4, a heating control device 6, a refrigerating device 10, a trapping device, a passage adjusting device 11 and a controller, and has the advantages of simple equipment structure, high concentration efficiency and good repeatability, and can be used for on-line monitoring of various greenhouse gases.
In addition, as shown, the second flow rate control device 4 may be provided upstream of the passage adjustment device 11 or downstream of the passage adjustment device 11. In this embodiment, the flow control device is preferably disposed downstream of the passage adjusting device 11, so that it is possible to avoid interference of the test result caused by trace impurity gas generated by the seal ring of the flow control device. In practice, the second flow rate control device 4 may be installed upstream of the passage adjustment device 11, depending on the type of target gas and the characteristics of the flow rate control device.
In some embodiments, as shown in fig. 2-4, the passage adjusting 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, the valve body includes 6 pipe interfaces, the pipe interfaces are uniformly distributed on the same cross section of the valve body, the valve core is installed in the center of the valve body, the cross section is circular, a plurality of concave runners are circumferentially arranged, spaces are provided between the runners, and when the controller controls the driver to drive the valve core to rotate, for any one interface, the communication between the runner and another adjacent interface, or the communication between the runner and the other interface can be realized, or the communication between the other interface and the other interface is not communicated with any runner. Therefore, the six-way multi-position valve 11A can realize isolation of two interfaces besides the function of the six-way two-position valve, so that the six-way multi-position valve can be used for analyzing the trap 7 under the isolation condition. As shown in the figure, the first port of the six-way multi-position valve 11A is used as the first port, the second port of the six-way multi-position valve 11A is used as the second port, the third port of the six-way multi-position valve 11A is used as the third port, the fourth port of the six-way multi-position valve 11A is used as the fourth port, the fifth port of the six-way multi-position valve 11A is used as the fifth port, and the sixth port of the six-way multi-position valve 11A is used as the sixth port.
In other embodiments, as shown in fig. 5-8, the path adjusting device 11 includes a four-way two-position valve 11B and a six-way multi-position valve 11A, where the interface of the four-way two-position valve 11B is connected to the interface one of the six-way multi-position valve 11A via a pipe 113, the interface three of the four-way two-position valve 11B is connected to the interface six of the six-way multi-position valve 11A via a pipe 114, the interface four of the four-way two-position valve 11B is used as the first interface and is connected to the interface 15 of the analyzer via a pipe 115, the interface two of the six-way multi-position valve 11A is used as the second interface, the interface three of the six-way multi-position valve 11A is used as the third interface, the interface four of the six-way multi-position valve 11A is used as the fourth interface, the interface five of the six-way multi-position valve 11A is used as the fifth interface, and the interface two of the four-way two-position valve 11B is used as the sixth interface and is connected to the first flow control device 3 via a pipe 112.
Both the above two passage adjusting devices 11 enable the switching of the gas pre-concentration apparatus in different modes of operation, whereas in the solution shown in fig. 5, the switching of the gas flow direction of the carrier gas can also be controlled when the purge mode is performed, and a more efficient purging of the trap 7 is performed by reverse air intake.
In the above embodiments, the trap 7 may be in the shape of a straight tube, a bent tube or a coil, and made of stainless steel, glass or quartz. The trap 7 is filled with an adsorbent and an adsorbent positioning device, and the positioning device is made of stainless steel or quartz. In some preferred embodiments, as shown in fig. 5, the trap 7 includes a hollow cylindrical base 23, two straight pipe portions, and a coil portion connecting the two straight pipe portions, the coil portion is sleeved on an outer wall of the cylindrical base 23, and a temperature probe of the thermocouple 5 is disposed on an inner wall of the cylindrical base 23. In this scheme, the one end of cylindrical base 23 contacts with cold dish 8, and the other end contacts with the coil pipe, and cylindrical base 23 plays the effect of buffering at the temperature rise and fall in-process, can improve temperature control's accuracy.
Wherein, preferably, the gas pre-concentration device further comprises a vacuum cabin 24 for replacing the heat insulation material 9, the cold end of the refrigerating device 10 and the trapping device are arranged in the cabin body of the vacuum cabin 24, the vacuum cabin 24 is further provided with a vacuum pump 17, and the vacuum pump 17 is connected with the vent hole 18 of the vacuum cabin 24 through a pipeline 116 and a pipeline 117. The trapping device is placed in the body of the vacuum chamber 24 to achieve the effect of isolating the heat source. The vacuum chamber 24 is generally made of metal, such as aluminum or stainless steel, and includes a base and a housing. The base and the shell are sealed by a sealing ring or a sealing gasket. The vacuum pump 17 provides vacuum to the vacuum chamber 24, and because the vacuum has excellent heat insulating properties, condensation of gaseous impurities on the surface of the trap 7 can be avoided, so that lower temperature and more accurate temperature control can be achieved.
Further, as shown in the above figures, the gas pre-concentration device further comprises a water removal device 2, and the water removal device 2 is arranged between the sample injection device 1 and the fourth interface of the passage adjustment device 11. The water removing device 2 is formed by drying a Nafion semi-permeable membrane, and the Nafion semi-permeable membrane drying pipe is of a double-layer structure and is separated by a semi-permeable membrane which can allow water molecules to pass through. When the inner layer is filled with the sample gas, the outer layer is reversely filled with dry nitrogen or air, so that the sample gas can be effectively dried. The Nafion semi-permeable membrane drying tube has the advantages of simple structure and small occupied space, so that the Nafion semi-permeable membrane drying tube is particularly suitable for portable or movable equipment.
Preferably, as shown in fig. 5, the sample injection device 1 may include a plurality of parallel electromagnetic valves, the inlets of the different electromagnetic valves are respectively used for connecting the sample inlet 12 or the standard gas inlet 19, the controller controls the gas passage entering the sample injection device 1 by controlling the opening and closing of the different electromagnetic valves, or the sample injection device 1 includes a multi-way sample injection valve (such as a ten-way sample injection valve), the different inlet ends of the multi-way sample injection valve are respectively used for connecting the sample inlet 12 or the standard gas inlet 19, and the controller controls the gas passage entering the sample injection device by controlling the conduction branch of the multi-way sample injection valve. In the drawing, the sample injection device 1 includes a first electromagnetic valve 20 and a second electromagnetic valve 21 connected in parallel, where the first electromagnetic valve 20 is connected with the standard gas inlet 19 through a pipeline 118, the second electromagnetic valve 21 is connected with the sample inlet 12 through a pipeline 119, the number of the electromagnetic valves can be selected according to practical situations, generally, 2-16 electromagnetic valves connected in parallel are used, and the pipeline 118 and the pipeline 119 can be implemented by copper pipes.
In some aspects, the gas pre-concentration device may further comprise a filter 22 arranged between the third interface of the path adjustment means 11 and the second flow control means 4. The filter 22 can prevent particulate matters in the gas from entering the second flow control device 4, improve the accuracy of flow control and prolong the service life of equipment.
In some embodiments of the present application, there is further provided a method for controlling a gas pre-concentration apparatus, in which 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, and the method may include the steps of:
The enrichment mode is implemented by controlling a refrigerating device and a heating control device to control the trap temperature at a first preset temperature, enabling sample gas to enter the trap for enrichment after passing through a sample injection device and a passage adjusting device, and controlling the flow of the sample gas through a second flow control device;
The method comprises the steps of firstly controlling the connection or disconnection of different interfaces of a passage adjusting device to isolate a trap from an external gas pipeline, controlling a heating control device to raise the temperature of the trap to a second preset temperature, then controlling the connection or disconnection of different interfaces of the passage adjusting device to enable the trap to be connected into the gas pipeline, and introducing carrier gas into the trap through a first flow control device to enable sample gas to enter an analysis instrument for detection after desorption;
And the step of executing the purging mode is to control the first flow control device to introduce 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.
For the device structure shown in fig. 2, the execution process of the above different modes includes:
enrichment mode as shown in fig. 3, the cold head of the refrigeration unit 10 transfers low temperature to the cold plate 8, reducing the temperature of the trap 7 to a first preset temperature. After passing through the sample injection device 1, the sample gas enters the six-way multi-position valve 11A through the water removal device 2. The controller controls the six-way multi-position valve 11A to enable the fourth interface to be communicated with the fifth interface, the second interface to be communicated with the third interface, and the first interface to be communicated with the sixth interface. Sample gas enters from the fourth port of the six-way multi-position valve 11A, and flows out from the fifth port of the six-way multi-position valve 11A into the trap 7. The target gas component is enriched in the trap 7, the residual gas returns to the second port of the six-way multi-position valve 11A, flows out from the third port 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 analysis instrument through the first flow control device 3 to purge the pipeline and the analysis instrument.
In general, the first preset temperature, the flow rate of the second flow control device 4, and the like are required to be determined according to the boiling point and polarity of the target gas component, the concentration thereof in the sample gas, and the detection requirements of the analysis instrument. In this embodiment, the first preset temperature is set to-100 ℃, so that effective enrichment of target gas components such as CO 2、N2 O, CFCs can be achieved. Setting the first preset temperature to-160 ℃, effective enrichment of target components such as CF 4, PFCs, HFCs and the like can be achieved. The flow rate of the second flow rate control device 4 can be set at 100-500 ml/min, and the larger the flow rate is, the longer the enrichment time is, the higher the pre-concentration ratio is.
(1.2) Desorption mode first, the trap 7 is isolated from the external gas line by controlling the six-way multi-position valve 11A, as shown in fig. 2. The temperature of the trap 7 is raised to a second preset temperature by the heating control device 6, so that the target gas components enriched in the trap 7 are desorbed and released into the internal pipeline of the trap 7. And then, the six-way multi-position valve 11A is controlled to enable the first interface to be communicated with the second interface, the third interface to be communicated with the fourth interface and the fifth interface to be communicated with the sixth interface, carrier gas is introduced into the trap 7 through the first flow control device 3, and the desorbed target gas component is sent into an analysis instrument for detection through the first interface of the six-way multi-position valve 11A as shown in fig. 4.
In general, the second preset temperature, carrier gas flow rate and sample injection time need to be determined according to the boiling point and polarity of the target component and the impurity gas, and the requirements of downstream analysis instruments. In this embodiment, the second preset temperature, carrier flow and sample introduction time were set to-30 ℃, 50 ml/min and 2 min, respectively, when pre-concentration was performed for N 2 O. If the flow of the second flow control device 4 in the enrichment stage is set to be 500 ml/min and the enrichment time is set to be 20 min, the sample injection amount is 10L, the pre-concentration ratio is 100:1, and the concentration of the target gas component can be increased to 100 times of that of the sample gas.
(1.3) Purge mode the purge process is used to thoroughly remove the impurities remaining in the trap 7, returning the trap 7 to the enrichment readiness state. The state of the pipeline of the preconcentration equipment in the purging process is shown in fig. 4, and the same sample injection stage is adopted in the desorption step, wherein the difference is that the temperature of the trap 7 needs to be further increased to a third preset temperature. In this embodiment, the carrier gas purge flow is maintained at 50ml per minute and the third preset temperature is 100 ℃. The higher third preset temperature helps to thoroughly remove residual impurities in the trap 7 and improves the repeatability of the system.
Further, the time of the purging process may be determined according to the characteristics of the trap 7, which in this embodiment is 5 min. After the purging process is finished, the temperature of the trap 7 is reduced to a first preset temperature, and the six-way multi-position valve 11 is switched back to the enrichment step key state to prepare for pre-concentration of the next sample.
According to the apparatus and control method provided in the above scheme, it takes about 30 minutes to complete the pre-concentration process of one sample, and if the pre-concentration ratio is reduced to 50:1, only 20 minutes are required. Therefore, the pre-concentration device of the scheme can be used for high-frequency online analysis or on-site rapid detection of the environmental gas.
In the above control method, an additional impurity removal step may be included between the execution steps of the enrichment mode and the desorption mode in addition to the above steps. The equipment pipeline state in this step is the same as that in fig. 4, but the trap 7 is heated to a fourth preset temperature. The temperature value is between the first preset temperature and the second preset temperature, and can be used for removing interference of certain impurities, so that interference of the impurities on qualitative and quantitative analysis results when the impurities are directly thermally desorbed into an analysis instrument after enrichment is avoided.
For the device structure shown in fig. 5, the execution process of the above different modes includes:
(2.1) enrichment mode As shown in FIG. 6, the cold head of the refrigeration unit 10 transfers a low temperature to the cold plate 8, reducing the temperature of the trap 7 to a first preset temperature. The second electromagnetic valve 21 in the sample injection device 1 is opened, and the sample gas enters the six-way multi-position valve 11A through the water removal device 2. The controller controls the six-way multi-position valve 11A to be communicated with the interface IV and the interface V, the interface II to be communicated with the interface III, and the interface I to be communicated with the interface V. Sample gas enters from the fourth interface, and the fifth interface flows out into the trap 7. The target gas component is enriched in the trap 7, the residual gas returns to the second port of the six-way multi-position valve 11A, flows out from the third port, and is discharged from the gas outlet 14 after the flow is controlled by the second flow control device 4.
(2.2) Desorption mode first, the trap 7 is isolated from the external gas line by controlling the six-way multi-position valve 11A, as shown in fig. 5. The temperature of the trap 7 is raised to a second preset temperature by the heating control device 6, so that the target gas components enriched in the trap 7 are desorbed and released into the internal pipeline of the trap 7. Then, the six-way multi-position valve 11 is controlled to enable the first interface to be communicated with the second interface, the third interface to be communicated with the fourth interface, the fifth interface to be communicated with the sixth interface, the four-way two-position valve 11B is controlled to enable the first interface to be communicated with the fourth interface, the second interface to be communicated with the third interface, carrier gas is introduced into the trap 7 through the first flow control device 3, and as shown in fig. 7, the target gas component which is desorbed is sent to the first interface of the four-way two-position valve 11B through the first interface and then sent to the analysis instrument through the pipeline 115 through the fourth interface to be detected.
(2.3) Purge mode, control four-way two-position valve 11B to connect interface one with interface two and interface three with interface four, as shown in FIG. 8. At the moment, the carrier gas enters the trap from the direction opposite to the enrichment step to purge, which is helpful for thoroughly removing the residual impurities, so that the enrichment efficiency and repeatability of the device for pre-concentration can be further improved, and the analysis precision is improved.
In the above scheme, the first preset temperature is below-100 ℃, the second preset temperature is above-60 ℃, and the third preset temperature is above 80 ℃. The first preset temperature is used for sample enrichment, and the lower first preset temperature can trap the low-boiling-point greenhouse gases as completely as possible, so that the trapping efficiency is improved. The second preset temperature is used for sample resolution and is typically above the boiling point of the target gas. The third preset temperature is used for purging the trap, and the higher temperature is beneficial to thoroughly removing the residual components in the trap. Meanwhile, the gas pre-concentration device in the scheme can be used for analysis of off-line sampling samples and also can be used for on-line analysis. When a plurality of offline sampling samples need to be analyzed, the samples can be automatically switched through 2-16 electromagnetic valves connected in parallel or 1 multi-position sampling valves. When on-line analysis is performed, the sample and the standard gas can be switched through 2 parallel electromagnetic valves.
It is apparent that the above examples are given by way of illustration only and are not limiting of the embodiments. Other variations or modifications of the above teachings will be apparent to those of ordinary skill in the art. It is not necessary here nor is it exhaustive of all embodiments. While obvious variations or modifications are contemplated as falling within the scope of the present application.
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