Nitric oxide standard gas preparation system

Abstract

The invention discloses a nitric oxide standard gas preparation system which comprises a boiler, an adsorption regeneration tower, a compressor and a gas storage tank, and the boiler comprises a hearth and a tail flue; the adsorption regeneration tower is provided with an adsorbent inlet, an adsorbent outlet, a flue gas inlet, a flue gas outlet and a nitric oxide outlet, the flue gas inlet is communicated with the tail flue to receive part of flue gas discharged by the tail flue before denitration, nitric oxide in the flue gas is adsorbed in the adsorption regeneration tower, and the adsorbent outlet is communicated with the nitric oxide outlet; the gas inlet is communicated with the gas storage tank, the gas outlet is communicated with the gas storage tank, the adsorbed flue gas is discharged through the flue gas outlet, the saturated adsorbent is heated, desorbed and regenerated in the adsorption regeneration tower, and desorbed and regenerated nitric oxide is discharged through the nitric oxide outlet, and the gas outlet of the compressor is communicated with the gas storage tank. Nitric oxide discharged from the nitric oxide outlet is compressed and then stored in the gas storage tank. According to the invention, the resource utilization of the waste gas is realized, the environmental protection is facilitated, and the pollution to the environment is also reduced.

Description

Technical Field

[0001] The invention relates to the technical field of nitric oxide preparation, and in particular to a nitric oxide standard gas preparation system. Background Art

[0002] With increasingly stringent environmental protection regulations, the monitoring and control of nitrogen oxides (NOx) in flue gas emitted by thermal power units has become an important environmental protection issue. As an important component of nitrogen oxides, the accurate measurement of the concentration of nitric oxide (NO) is of great significance for evaluating the level of pollutants emitted by thermal power units. During the operation of thermal power units, the flue gas emitted contains a certain amount of nitric oxide. However, this resource has not been effectively utilized in related technologies. The preparation of nitric oxide standard gas usually requires the use of chemical synthesis or gas mixing methods, which often consume a lot of raw materials and energy, and the preparation process is complicated and costly. Summary of the invention

[0003] The present invention aims to solve one of the technical problems in the related art at least to a certain extent.

[0004] To this end, an embodiment of the present invention provides a system for preparing nitric oxide standard gas.

[0005] The nitric oxide standard gas preparation system of the embodiment of the present invention includes a boiler, an adsorption regeneration tower, a compressor and a gas storage tank, wherein the boiler includes a furnace and a tail flue; the adsorption regeneration tower has an adsorbent inlet, an adsorbent outlet, a flue gas inlet, a flue gas outlet and a nitric oxide outlet, wherein the flue gas inlet is connected with the tail flue to receive part of the flue gas before denitrification discharged from the tail flue, the nitric oxide in the flue gas is adsorbed in the adsorption regeneration tower, the adsorbed flue gas is discharged through the flue gas outlet, the adsorption saturated adsorbent is heated and decomposed and regenerated in the adsorption regeneration tower, and the decomposed and regenerated nitric oxide is discharged through the nitric oxide outlet; the air inlet of the compressor is connected with the nitric oxide outlet, and the air outlet of the compressor is connected with the gas storage tank, so that the nitric oxide discharged from the nitric oxide outlet is compressed and stored in the gas storage tank.

[0006] In some embodiments, a heating coil and a cooling coil are provided in the adsorption regeneration tower, wherein the heating coil has a hot medium inlet and a hot medium outlet, and is used to heat the adsorbent saturated with adsorption so as to decompose and regenerate the adsorbent saturated with adsorption, and the cooling coil has a cold medium inlet and a cold medium outlet, and is used to cool the decomposed and regenerated adsorbent so that the regenerated adsorbent adsorbs nitric oxide in the flue gas.

[0007] In some embodiments, the heating coil is arranged on the inner wall of the adsorption regeneration tower and is spirally arranged along the height direction of the adsorption regeneration tower; and / or the cooling coil is arranged on the inner wall of the adsorption regeneration tower and is spirally arranged along the height direction of the adsorption regeneration tower.

[0008] In some embodiments, the nitric oxide standard gas preparation system of the embodiment of the present invention also includes a desulfurization device, a dust collector and a desulfurization device which are connected to the tail flue in sequence, a first pipeline is provided between the dust collector and the desulfurization device, and a first branch pipe and a second branch pipe are provided on the first pipeline, and the two ends of the first branch pipe are respectively connected to the first pipeline and the heat medium inlet, so that part of the flue gas discharged from the dust collector is transported to the heating coil as a heat medium, and the two ends of the second branch pipe are respectively connected to the desulfurization device and the heat medium outlet, so that the flue gas after heat exchange in the heating coil is transported to the desulfurization device.

[0009] In some embodiments, a first opening and closing valve is disposed on the first branch pipe, and a second opening and closing valve is disposed on the second branch pipe.

[0010] In some embodiments, the cooling medium transported by the cold medium inlet is room temperature air.

[0011] In some embodiments, the nitric oxide standard gas preparation system of the embodiment of the present invention also includes a chimney, which is connected to the desulfurization device through a second pipeline, and a third branch is provided between the second pipeline and the flue gas inlet to allow part of the flue gas discharged from the desulfurization device to enter the adsorption regeneration tower.

[0012] In some embodiments, the nitric oxide standard gas preparation system of the embodiment of the present invention further includes an induced draft fan, which is arranged between the second pipeline and the chimney to transport the flue gas desulfurized by the desulfurization device to the chimney for discharge.

[0013] In some embodiments, a third opening and closing valve is provided on the third branch pipe.

[0014] In some embodiments, a fourth on-off valve is provided between the nitric oxide outlet and the compressor.

[0015] The nitric oxide standard gas preparation system of the embodiment of the present invention avoids the chemical synthesis or gas mixing process required in the traditional nitric oxide standard gas preparation method, directly utilizes the resources in the flue gas discharged by the thermal power unit, and does not need to consume additional raw materials and energy, thereby significantly reducing the preparation cost. Through the adsorption process, the present invention can efficiently extract nitric oxide from the flue gas, simplify the preparation process, and improve the efficiency of standard gas preparation. Therefore, the present invention realizes the resource utilization of waste gas, which not only contributes to environmental protection, but also reduces pollution to the environment. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 Schematic diagram of a nitric oxide standard gas preparation system according to an embodiment of the present invention.

[0017] Figure 2 Schematic diagram of an adsorption regeneration tower according to an embodiment of the present invention.

[0018] Reference numerals:

[0019] 100. Nitric oxide standard gas preparation system; 1. Furnace; 2. Tail flue; 3. Adsorption regeneration tower; 301. Adsorbent inlet; 302. Adsorbent outlet; 303. Flue gas inlet; 304. Flue gas outlet; 305. Nitric oxide outlet; 4. Compressor; 5. Gas storage tank; 6. Heating coil; 601. Heat medium inlet; 602. Heat medium outlet; 7. Cooling coil; 701. Cold medium inlet; 702. Cold medium outlet; 8. Desulfurization device; 9. Dust collector; 10. Desulfurization device; 11. First pipeline; 12. First branch pipe; 13. Second branch pipe; 14. First opening and closing valve; 15. Second opening and closing valve; 16. Chimney; 17. Second pipeline; 18. Third branch pipe; 19. Draft fan; 20. Third opening and closing valve; 21. Fourth opening and closing valve. DETAILED DESCRIPTION

[0020] Embodiments of the present invention are described in detail below, and examples of the embodiments are shown in the accompanying drawings. The embodiments described below with reference to the accompanying drawings are exemplary and intended to be used to explain the present invention, but should not be understood as limiting the present invention.

[0021] like Figure 1 and Figure 2 As shown, the nitric oxide standard gas preparation system 100 of the embodiment of the present invention includes a boiler, an adsorption regeneration tower 3, a compressor 4 and a gas storage tank 5. The boiler includes a furnace 1 and a tail flue 2, and the adsorption regeneration tower 3 has an adsorbent inlet 301, an adsorbent outlet 302, a flue gas inlet 303, a flue gas outlet 304 and a nitric oxide outlet 305. The flue gas inlet 303 is connected to the tail flue 2 to receive part of the flue gas before denitration discharged from the tail flue 2. Nitric oxide in the flue gas is adsorbed in the adsorption regeneration tower 3, and the adsorbed flue gas is discharged through the flue gas outlet 304. The adsorbent saturated with adsorption is heated and decomposed and regenerated in the adsorption regeneration tower 3, and the decomposed and regenerated nitric oxide is discharged through the nitric oxide outlet 305. The air inlet of the compressor 4 is connected to the nitric oxide outlet 305, and the air outlet of the compressor 4 is connected to the gas storage tank 5, so that the nitric oxide discharged from the nitric oxide outlet 305 is compressed and stored in the gas storage tank 5.

[0022] When the nitric oxide standard gas preparation system 100 of the embodiment of the present invention is in use, part of the flue gas discharged from the tail flue 2 of the boiler before denitrification is introduced into the adsorption regeneration tower 3, and this part of the flue gas contains a certain amount of nitric oxide. In the adsorption regeneration tower 3, the nitric oxide in the flue gas is adsorbed by the adsorbent, and other flue gas components are discharged from the flue gas outlet 304. When the adsorbent is saturated with adsorption, the flue gas inlet 303 is closed to prevent the flue gas from entering the adsorption regeneration tower 3. Then, the adsorbent is heated and analyzed and regenerated in the adsorption regeneration tower 3 by heating to release nitric oxide gas. The released nitric oxide gas is discharged through the nitric oxide outlet 305 and is sucked into the air inlet of the compressor 4, and then compressed, discharged from the air outlet of the compressor 4, and stored in the gas storage tank 5 to form the required nitric oxide standard gas.

[0023] The nitric oxide standard gas preparation system 100 of the embodiment of the present invention avoids the chemical synthesis or gas mixing process required in the traditional nitric oxide standard gas preparation method, directly utilizes the resources in the flue gas discharged by the thermal power unit, and does not need to consume additional raw materials and energy, thereby significantly reducing the preparation cost. Through the adsorption process, the present invention can efficiently extract nitric oxide from the flue gas, simplify the preparation process, and improve the efficiency of standard gas preparation. Therefore, the present invention realizes the resource utilization of waste gas, which not only contributes to environmental protection, but also reduces pollution to the environment.

[0024] In some embodiments, a heating coil 6 and a cooling coil 7 are provided in the adsorption regeneration tower 3. The heating coil 6 has a hot medium inlet 601 and a hot medium outlet 602, and the heating coil 6 is used to heat the adsorbent saturated with adsorption to decompose and regenerate the adsorbent saturated with adsorption. The cooling coil 7 has a cold medium inlet 701 and a cold medium outlet 702, and the cooling coil 7 is used to cool the decomposed regenerated adsorbent to allow the regenerated adsorbent to adsorb nitric oxide in the flue gas.

[0025] A heat medium (such as steam or hot water) is introduced into the heating coil 6 to heat the adsorbent saturated with adsorption. The purpose of heating is to increase the porosity of the adsorbent, so that the nitric oxide molecules adsorbed in the pores are separated from the adsorbent, and the adsorbent is regenerated by analysis. The design of the heat medium inlet 601 and outlet allows the heat medium to circulate in the heating coil 6, maintaining a certain temperature gradient to ensure the heating efficiency and uniformity of the adsorbent.

[0026] A cold medium (such as circulating water or cold air) is introduced into the cooling coil 7 to cool the adsorbent that has just undergone the heating regeneration process. The purpose of cooling is to reduce the temperature of the adsorbent so that it can re-adsorb nitric oxide in the flue gas. The design of the cold medium inlet 701 and outlet allows the cold medium to circulate in the cooling coil 7 to maintain the temperature of the adsorbent within the optimal adsorption range.

[0027] The nitric oxide standard gas preparation system 100 of the embodiment of the present invention can ensure that the adsorbent is maintained in the best working state at different stages through the cyclic process of heating regeneration and cooling adsorption, thereby improving the adsorption efficiency. Reasonable temperature control can reduce the wear and thermal stress of the adsorbent and extend its service life. By accurately controlling the temperature during the adsorption and regeneration process, it can be ensured that the prepared nitric oxide standard gas has a high degree of purity and stability. The design of the heating coil 6 and the cooling coil 7 increases the flexibility of the system, and the temperature of the hot medium and the cold medium can be adjusted according to actual needs to adapt to different operating conditions and flue gas components.

[0028] In some embodiments, the heating coil 6 is disposed on the inner wall of the adsorption regeneration tower 3 and is spirally arranged along the height direction of the adsorption regeneration tower 3 .

[0029] The nitric oxide standard gas preparation system 100 of the embodiment of the present invention can achieve uniform heating along the height direction of the adsorption regeneration tower 3 through the spirally arranged heating coil 6, ensuring that the adsorbent is evenly heated in the entire tower, thereby improving the heating efficiency and the regeneration effect of the adsorbent. The spirally structured heating coil 6 can provide a larger contact area, making the heat exchange between the heat medium and the adsorbent more sufficient.

[0030] In some embodiments, the cooling coil 7 is disposed on the inner wall of the adsorption regeneration tower 3 and is spirally arranged along the height direction of the adsorption regeneration tower 3 .

[0031] The nitric oxide standard gas preparation system 100 of the embodiment of the present invention is similar to the heating coil 6. The spiral arrangement of the cooling coil 7 can ensure uniform cooling along the height direction of the adsorption regeneration tower 3, so that the regenerated adsorbent is uniformly cooled in the entire tower to restore its adsorption capacity. The spirally arranged cooling coil 7 provides a larger contact area, which facilitates heat exchange between the adsorbent and the cold medium and improves the cooling efficiency.

[0032] In some embodiments, the nitric oxide standard gas preparation system 100 of the embodiment of the present invention further includes a desulfurization device 8, a dust collector 9 and a desulfurization device 10 which are sequentially connected to the tail flue 2. A first pipeline 11 is provided between the dust collector 9 and the desulfurization device 10, and a first branch pipe 12 and a second branch pipe 13 are provided on the first pipeline 11. The two ends of the first branch pipe 12 are respectively connected to the first pipeline 11 and the heat medium inlet 601, so that part of the flue gas discharged from the dust collector 9 is transported to the heating coil 6 as a heat medium. The two ends of the second branch pipe 13 are respectively connected to the desulfurization device 10 and the heat medium outlet 602, so that the flue gas after heat exchange in the heating coil 6 is transported to the desulfurization device 10.

[0033] The nitric oxide standard gas preparation system 100 of the embodiment of the present invention can effectively recover the heat energy in the flue gas by using the flue gas discharged from the dust collector 9 as a heat medium, and use it for the regeneration of the adsorbent, thereby improving the energy utilization rate of the system, reducing the demand for external energy, and thus reducing the energy consumption of the system. By reducing energy consumption and improving efficiency, the operating cost is reduced and the economy of the system is improved.

[0034] In some embodiments, a first opening and closing valve 14 is disposed on the first branch pipe 12 , and a second opening and closing valve 15 is disposed on the second branch pipe 13 .

[0035] The first on-off valve 14 can control the flow rate of part of the flue gas discharged from the dust collector 9 as a heat medium to adjust the heat input in the heating coil 6. In an emergency, the first on-off valve 14 can be quickly closed to prevent flue gas backflow or other unexpected situations from occurring, thereby protecting the safe operation of the system. The second on-off valve 15 can control the flow rate of flue gas after heat exchange in the heating coil 6 to adjust the amount of hot flue gas delivered to the desulfurization device 10. When the heating coil 6 or related equipment needs to be maintained or overhauled, the second on-off valve 15 can be closed to isolate the system and ensure safe operation.

[0036] In some embodiments, the cooling medium delivered by the cold medium inlet 701 is room temperature air.

[0037] Using room temperature air as the cooling medium can simplify system design and operation because no additional coolant or complex cooling systems are required. Room temperature air is a free resource and using it as the cooling medium can significantly reduce system operating costs.

[0038] In some embodiments, the nitric oxide standard gas preparation system 100 of the embodiment of the present invention also includes a chimney 16, which is connected to the desulfurization device 10 through a second pipeline 17, and a third branch 18 is provided between the second pipeline 17 and the flue gas inlet 303 to allow part of the flue gas discharged from the desulfurization device 10 to enter the adsorption regeneration tower 3.

[0039] It is understandable that the flue gas temperature after desulfurization is usually around 50°C, which is relatively low. Reintroducing part of the flue gas discharged from the desulfurization device 10 into the adsorption regeneration tower 3 can improve the adsorption efficiency of the adsorbent, because the lower the temperature, the higher the adsorption efficiency of the adsorbent.

[0040] In some embodiments, the nitric oxide standard gas preparation system 100 of the embodiment of the present invention further includes an induced draft fan 19, which is disposed between the second pipeline 17 and the chimney 16 to transport the flue gas desulfurized by the desulfurization device 10 to the chimney 16 for discharge.

[0041] The provision of the induced draft fan 19 can increase the flow power of the flue gas and ensure that the flue gas flows smoothly from the desulfurization device 10 to the chimney 16. The induced draft fan 19 can help maintain a negative pressure state in the desulfurization device 10, thereby improving the desulfurization efficiency and preventing pollutants from escaping.

[0042] In some embodiments, a third on-off valve 20 is provided on the third branch pipe.

[0043] The third on-off valve 20 can control the flow of part of the flue gas discharged from the desulfurization device 10 into the adsorption regeneration tower 3, so as to adjust the flow direction and distribution of the flue gas as needed. When the system fails or maintenance is required, the third on-off valve 20 can be quickly closed to prevent the flue gas from flowing back or other unexpected situations, thereby protecting the system safety.

[0044] In some embodiments, a fourth on-off valve 21 is provided between the nitric oxide outlet 305 and the compressor 4 .

[0045] The fourth on-off valve 21 is arranged between the nitric oxide outlet 305 and the compressor 4, and can control the flow of nitric oxide, and open or close the channel of nitric oxide according to system requirements. In an emergency or system maintenance, the fourth on-off valve 21 can be quickly closed to prevent leakage of nitric oxide or other unexpected situations, thereby ensuring system safety. The fourth on-off valve 21 allows the operator to adjust the flow of nitric oxide according to actual needs, such as when performing calibration or calibration.

[0046] In the description of the present invention, it is to be understood that the terms “center”, “longitudinal”, “lateral”, “length”, “width”, “thickness”, “up”, “down”, “front”, “back”, “left”, “right”, “vertical”, “horizontal”, “top”, “bottom”, “inside”, “outside”, “clockwise”, “counterclockwise”, “axial”, “radial”, “circumferential”, etc., indicating orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the referred device or element must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as limiting the present invention.

[0047] In addition, the terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first" and "second" may explicitly or implicitly include at least one of the features. In the description of the present invention, the meaning of "plurality" is at least two, such as two, three, etc., unless otherwise clearly and specifically defined.

[0048] In the present invention, unless otherwise clearly specified and limited, the terms "installed", "connected", "connected", "fixed" and the like should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral one; it can be a mechanical connection, an electrical connection, or communication with each other; it can be a direct connection, or an indirect connection through an intermediate medium, it can be the internal connection of two elements or the interaction relationship between two elements, unless otherwise clearly defined. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0049] In the present invention, unless otherwise clearly specified and limited, a first feature being "above" or "below" a second feature may mean that the first and second features are in direct contact, or the first and second features are in indirect contact through an intermediate medium. Moreover, a first feature being "above", "above" or "above" a second feature may mean that the first feature is directly above or obliquely above the second feature, or simply means that the first feature is higher in level than the second feature. A first feature being "below", "below" or "below" a second feature may mean that the first feature is directly below or obliquely below the second feature, or simply means that the first feature is lower in level than the second feature.

[0050] In the present invention, the terms "one embodiment", "some embodiments", "examples", "specific examples", or "some examples" etc. mean that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the described specific features, structures, materials or characteristics may be combined in any one or more embodiments or examples in a suitable manner. In addition, those skilled in the art may combine and combine the different embodiments or examples described in this specification and the features of the different embodiments or examples, without contradiction.

[0051] Although the embodiments of the present invention have been shown and described above, it is to be understood that the above embodiments are exemplary and are not to be construed as limitations of the present invention. A person skilled in the art may change, modify, replace and vary the above embodiments within the scope of the present invention.

Claims

1. A nitric oxide standard gas preparation system, characterized in that: include: A boiler, comprising a furnace (1) and a tail flue (2); An adsorption regeneration tower (3), the adsorption regeneration tower (3) having an adsorbent inlet (301), an adsorbent outlet (302), a flue gas inlet (303), a flue gas outlet (304) and a nitric oxide outlet (305), the flue gas inlet (303) being in communication with the tail flue (2) to receive a portion of the flue gas discharged from the tail flue (2) before denitration, the nitric oxide in the flue gas being adsorbed by the adsorbent in the adsorption regeneration tower (3), the adsorbed flue gas being discharged through the flue gas outlet (304), the adsorbed saturated adsorbent being heated and decomposed and regenerated in the adsorption regeneration tower (3), and the decomposed and regenerated nitric oxide being discharged through the nitric oxide outlet (305); A compressor (4) and an air storage tank (5), wherein an air inlet of the compressor (4) is connected to the nitric oxide outlet (305), and an air outlet of the compressor (4) is connected to the air storage tank (5), so that the nitric oxide discharged from the nitric oxide outlet (305) is compressed and stored in the air storage tank (5).

2. The nitric oxide standard gas preparation system according to claim 1, characterized in that: The adsorption regeneration tower (3) is provided with a heating coil (6) and a cooling coil (7), wherein the heating coil (6) has a hot medium inlet (601) and a hot medium outlet (602), and the heating coil (6) is used to heat the adsorbent saturated with adsorption so as to decompose and regenerate the adsorbent saturated with adsorption, and the cooling coil (7) has a cold medium inlet (701) and a cold medium outlet (702), and the cooling coil (7) is used to cool the decomposed and regenerated adsorbent so as to allow the regenerated adsorbent to adsorb nitrogen monoxide in the flue gas.

3. The nitric oxide standard gas preparation system according to claim 2, characterized in that: The heating coil (6) is arranged on the inner wall of the adsorption regeneration tower (3) and is spirally arranged along the height direction of the adsorption regeneration tower (3); And / or the cooling coil (7) is arranged on the inner wall of the adsorption regeneration tower (3) and is spirally arranged along the height direction of the adsorption regeneration tower (3).

4. The nitric oxide standard gas preparation system according to claim 3, characterized in that: The invention also comprises a desulfurization device (8), a dust collector (9) and a desulfurization device (10) which are sequentially connected to the tail flue (2); a first pipeline (11) is provided between the dust collector (9) and the desulfurization device (10); a first branch pipe (12) and a second branch pipe (13) are provided on the first pipeline (11); two ends of the first branch pipe (12) are respectively connected to the first pipeline (11) and the heat medium inlet (601), so that part of the flue gas discharged from the dust collector (9) is transported to the heating coil (6) as the heat medium; two ends of the second branch pipe (13) are respectively connected to the desulfurization device (10) and the heat medium outlet (602), so that the flue gas after heat exchange in the heating coil (6) is transported to the desulfurization device (10).

5. The nitric oxide standard gas preparation system according to claim 4, characterized in that: The first branch pipe (12) is provided with a first opening and closing valve (14), and the second branch pipe (13) is provided with a second opening and closing valve (15).

6. The nitric oxide standard gas preparation system according to claim 2, characterized in that: The cooling medium transported by the cooling medium inlet (701) is room temperature air.

7. The nitric oxide standard gas preparation system according to claim 4, characterized in that: It also includes a chimney (16), which is connected to the desulfurization device (10) via a second pipeline (17), and a third branch (18) is provided between the second pipeline (17) and the flue gas inlet (303) so that part of the flue gas discharged from the desulfurization device (10) enters the adsorption regeneration tower (3).

8. The nitric oxide standard gas preparation system according to claim 7, characterized in that: It also includes an induced draft fan (19), which is arranged between the second pipeline (17) and the chimney (16) to transport the flue gas desulfurized by the desulfurization device (10) to the chimney (16) for discharge.

9. The nitric oxide standard gas preparation system according to claim 8, characterized in that: The third branch pipe is provided with a third opening and closing valve (20).

10. The nitric oxide standard gas preparation system according to claim 1, characterized in that: A fourth on-off valve (21) is provided between the nitric oxide outlet (305) and the compressor (4).

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