Nitric acid production system
By installing interstage coolers and heat exchangers in the nitric acid production system, the gas temperature was optimized, solving the problem of increased power consumption caused by high gas medium temperature. This enabled the efficient operation of the air compressor and nitrogen oxide compressor, improving overall production efficiency.
Patent Information
- Application Number
- CN202520290421.6
- Authority / Receiving Office
- CN · China
- Patent Type
- Utility models(China)
- Current Assignee / Owner
- Filing Date
- 2025-02-21
- Publication Date
- 2026-02-10
- Estimated Expiration
- 2035-02-21
AI Technical Summary
In existing technologies, when the gas medium compressed by the first-stage impeller of a centrifugal compressor needs to be cooled before entering the next-stage impeller, the high temperature leads to an increase in volumetric flow rate, increased power consumption, and a decrease in overall efficiency.
An interstage cooler is installed between two consecutive compression impellers to cool the gas before it enters the next stage impeller for compression. The gas temperature is optimized by heaters and heat exchangers, and the heat from the high-temperature nitrogen oxide gas is utilized to reduce energy consumption.
It reduces the energy consumption of air compressors and nitrogen oxide compressors, improves compression efficiency, meets the requirements of subsequent processes, reduces condensate formation, and improves overall production efficiency.
Smart Images
Figure CN223894539U_ABST
Abstract
Description
Technical Field
[0001] This application relates to the field of nitric acid production equipment technology, and more particularly to a nitric acid production system. Background Technology
[0002] Currently, under normal circumstances, the gas medium compressed by the first stage impeller of a centrifugal compressor needs to be cooled before entering the next stage impeller for compression.
[0003] The higher the temperature of the compressed gas, the greater the volumetric flow rate. The more work the impeller needs to do to compress the same mass flow rate of gas, the more difficult it is to compress, which leads to a decrease in the efficiency of the entire unit. Utility Model Content
[0004] In view of this, this application provides a nitric acid production system, which aims to solve one of the technical problems in the prior art.
[0005] To achieve the above objectives, the technical solution adopted in this application is as follows:
[0006] In a first aspect, embodiments of this application provide a nitric acid production system, comprising:
[0007] Drive motor;
[0008] An air compressor includes a multi-stage compression impeller and at least one interstage cooler. The drive motor drives the compression impeller. Each interstage cooler is connected to two consecutive stages of the compression impeller so that the gas compressed by the previous stage compression impeller is cooled by the interstage cooler and then flows to the next stage compression impeller.
[0009] In one embodiment of the first aspect, the nitric acid production system further includes:
[0010] A heater, which is connected to the output of the air compressor;
[0011] An oxidizing furnace is provided, and the output end of the oxidizing furnace is connected to the heater. The heater is used to heat the gas entering the oxidizing furnace from the air compressor. The oxidizing furnace is used to synthesize ammonia and compressed air output from the air compressor into nitrogen oxide gas.
[0012] In one embodiment of the first aspect, the nitric acid production system further includes:
[0013] A heat exchanger is connected to the output end of the oxidation furnace. The high-temperature nitrogen oxide gas output from the oxidation furnace flows sequentially through the heater and the heat exchanger. The high-temperature nitrogen oxide gas serves as the heat source for the heater, and the heat exchanger is used to cool the high-temperature nitrogen oxide gas.
[0014] In one embodiment of the first aspect, the nitric acid production system further includes a nitrogen oxide compressor connected to the output end of the heat exchanger.
[0015] In one embodiment of the first aspect, the nitric acid production system further includes an absorption tower connected to the output of the nitrogen oxide compressor, the absorption tower being used to produce nitric acid.
[0016] In one embodiment of the first aspect, the nitric acid production system further includes an expander connected to the output end of the absorption tower, the expander being used to treat the tail gas discharged from the absorption tower.
[0017] In one embodiment of the first aspect, the drive unit includes a steam turbine or an electric motor, and the drive unit also includes a gearbox. The output end of the steam turbine or the electric motor is connected to the gearbox, and the output end of the gearbox is connected to the air compressor to drive the multi-stage compression impeller of the air compressor.
[0018] In one embodiment of the first aspect, the nitric acid production system further includes a boiler connected to the oxidizer and the steam turbine, the boiler being used to collect steam generated by the oxidizer and to input the steam into the steam turbine.
[0019] In one embodiment of the first aspect, both the air compressor and the nitrogen oxide compressor are centrifugal compressors; the expander is a centripetal or axial flow expander.
[0020] In one embodiment of the first aspect, the nitrogen oxide compressor includes at least two stages of compression impellers, and the expander includes at least two stages of expansion impellers.
[0021] Compared with the prior art, the beneficial effects of this application are as follows: This application proposes a nitric acid production system, including a drive motor and an air compressor. The air compressor includes a multi-stage compression impeller and at least one interstage cooler. The drive motor drives the compression impeller. Each interstage cooler is connected to two consecutive compression impellers, so that the gas compressed by the previous stage compression impeller is cooled by the interstage cooler and flows to the next stage compression impeller. After the compressed air in the previous stage is cooled, the temperature of the compressed air decreases, and the volumetric flow rate corresponding to the same mass flow rate of gas decreases before entering the next stage impeller for compression. This can reduce the overall energy consumption of the air compressor and improve the compression efficiency of the air compressor. Attached Figure Description
[0022] To more clearly illustrate the technical solutions of the embodiments of this application, the accompanying drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of this application and should not be regarded as a limitation of the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.
[0023] Figure 1 This application shows one of the structural schematic diagrams of a nitric acid production system in some embodiments;
[0024] Figure 2 This is shown as a second schematic diagram of the structure of a nitric acid production system in some embodiments of this application;
[0025] Figure 3 This application shows a schematic diagram of the structure of a nitric acid production system in one of its embodiments.
[0026] Figure 4 The fourth schematic diagram of the nitric acid production system in some embodiments of this application is shown;
[0027] Figure 5 The fifth of some embodiments of the nitric acid production system shown in this application is a schematic diagram of its structure.
[0028] Figure 6 A process flow diagram of a nitric acid production system in some embodiments of this application is shown.
[0029] Key component symbols: 1000 - Nitric acid production system; 110 - Drive motor; 111 - Steam turbine; 112 - Gearbox; 113 - Electric motor; 120 - Air compressor; 130 - Nitrogen oxide compressor; 140 - Expander; 200 - Interstage cooler; 300 - Oxidation furnace; 400 - Heater; 500 - Heat exchanger; 600 - Absorption tower; 700 - Boiler. Detailed Implementation
[0030] The embodiments of this application are described in detail below. Examples of the embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain this application, and should not be construed as limiting this application.
[0031] In the description of this application, it should be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "clockwise", "counterclockwise", "axial", "radial", "circumferential", etc., indicating the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, are only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this application.
[0032] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this application, "multiple" means two or more, unless otherwise explicitly specified.
[0033] In this application, unless otherwise expressly specified and limited, the terms "installation," "connection," "linking," and "fixing," etc., should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components. Those skilled in the art can understand the specific meaning of the above terms in this application according to the specific circumstances.
[0034] In this application, unless otherwise expressly specified and limited, "above" or "below" the second feature can mean that the first feature is in direct contact with the second feature, or that the first feature is in indirect contact with the second feature through an intermediate medium. Furthermore, "above," "on top of," and "over" the second feature can mean that the first feature is directly above or diagonally above the second feature, or simply that the first feature is at a higher horizontal level than the second feature. "Below," "below," and "under" the second feature can mean that the first feature is directly below or diagonally below the second feature, or simply that the first feature is at a lower horizontal level than the second feature.
[0035] like Figure 1 As shown, an embodiment of this application provides a nitric acid production system 1000, mainly used for producing nitric acid. The nitric acid production system 1000 includes a drive motor 110 and an air compressor 120.
[0036] The air compressor 120 is used to compress air to a certain pressure.
[0037] In some embodiments, the air compressor 120 includes a multi-stage compression impeller and at least one interstage cooler 200, with a drive motor 110 driving the compression impeller. The compression impeller consists of multiple blades, which can accelerate and compress air when rotating at high speed, increasing the pressure and temperature of the compressed air by the air compressor 120.
[0038] Typically, the temperature and pressure of the gas medium after compression by the first-stage compressor impeller are very high. According to the principle of centrifugal compressors, the higher the temperature of the gas medium, the greater the volumetric flow rate (unit: m³ / s) for the same mass flow rate. 3 / s). The more work is required for the compressor impeller to compress the same mass flow rate of gas, the more difficult it is to compress, thus leading to a decrease in the efficiency of the entire unit.
[0039] Meanwhile, an air compressor requires at least two stages of compression to ensure that the compressed air has a high pressure and temperature to meet the requirements of subsequent nitrogen oxide gas processes. In other words, atmospheric pressure air needs to undergo at least two compressions within the air compressor. The more work is required to compress the same mass flow rate of gas medium after each stage of compression by the aforementioned impellers, the more difficult it is to compress. If the compressed air is not cooled between the two stages of compression impellers, the overall efficiency of the air compressor will decrease.
[0040] In response to the above problems, such as Figure 1 As shown, each interstage cooler 200 is connected to two consecutive compression impellers, so that the gas compressed by the previous stage compression impeller is cooled by the interstage cooler 200 before flowing to the next stage compression impeller. Cooling the compressed air from the previous stage lowers its temperature, resulting in a lower volumetric flow rate for the same mass flow rate before it enters the next stage impeller for compression. This reduces the overall energy consumption of the air compressor 120 and improves its compression efficiency.
[0041] It should be noted that after the air is cooled by the interstage cooler 200, its pressure remains unchanged but its temperature decreases. The cooled compressed air then enters the next stage of the compressor impeller for compression. This process is repeated multiple times, causing the compressed air pressure to continuously increase until it meets the requirements of the subsequent nitrogen oxide gas production process.
[0042] In addition, by setting up an interstage cooler 200, it is helpful to reduce the moisture content in the air and prevent condensation from forming, thereby improving the dryness of the compressed air.
[0043] It is understandable that the number of interstage coolers 200 can be set according to requirements. One interstage cooler 200 is installed between the first-stage and second-stage compression impellers; no interstage cooler 200 is installed between the second-stage and third-stage compression impellers; and one interstage cooler 200 is installed between the third-stage and fourth-stage compression impellers. In this way, although the compression efficiency of the third-stage compression impeller decreases, the compression efficiencies of the first, second, and fourth-stage compression impellers are all relatively high, and the final output pressure of the air compressor 120 can still meet the requirements of subsequent production processes.
[0044] Because the compressed air flowing through two consecutive stages of compression impellers is cooled, the temperature of the compressed air output from the air compressor is lower than the requirements of subsequent processes, affecting the production efficiency of subsequent processes.
[0045] In response to the above problems, such as Figure 1 As shown, in some embodiments, the nitric acid production system 1000 further includes a heater 400 and an oxidation furnace 300.
[0046] The heater 400 is connected to the output of the air compressor 120, allowing the low-temperature, high-pressure air, after multi-stage compression by the air compressor 120, to flow to the heater 400. The heater 400 is used to heat the gas entering the oxidation furnace 300 from the air compressor 120 through heat exchange.
[0047] The output terminals of the oxidizer 300 and the heater 400 are connected. The oxidizer 300 is used to synthesize nitrogen oxide gas from ammonia and compressed air output from the air compressor 120. Air and ammonia are mixed in the oxidizer 300 (ammonia can be provided by an ammonia production unit). Ammonia (NH) and oxygen (O) in the air are mixed in the oxidizer 300 and react to produce nitrogen oxide. The reaction starts at a relatively high temperature.
[0048] By setting up a heater 400 to heat the compressed air output by the air compressor 120, the temperature and pressure of the compressed air entering the oxidation furnace 300 are made to meet the process requirements for nitric acid production, thereby improving production efficiency.
[0049] It should be noted that the heat source of heater 400 comes from the heat generated during the compression process, such as the interstage cooler 200 mentioned above, which helps reduce the energy consumption of the nitric acid production system 1000; or the heat source of heater 400 comes from the heat generated in other production processes in the nitric acid production system 1000, such as the heat generated in the oxidizer 300 during the synthesis of nitrogen oxide gas from ammonia and compressed air, which also helps reduce the energy consumption of the nitric acid production system 1000. For example... Figure 2The heater 400 is located at the outlet of the absorption tower 600. The heat source of the heater 400 comes from the high-temperature exhaust gas discharged from the absorption tower 600, thereby heating the compressed air discharged from the air compressor 120 and reducing energy consumption; or the heat source of the heater 400 comes from the exhaust gas heat generated in the external production system.
[0050] In some embodiments, such as Figure 3 As shown, when the temperature of the compressed air from the output air compressor 120 is high and can meet the process requirements for the reaction with ammonia in the oxidation furnace 300, the heater 400 can be eliminated, saving energy and reducing costs.
[0051] The combustion reaction in the oxidizer produces nitrogen oxides, and the nitrogen oxide gas discharged from the oxidizer has very high heat. As mentioned above, the higher the temperature of the gas medium, the greater the volumetric flow rate corresponding to the same mass flow rate of the gas. This means that the compressor impeller needs to do more work to compress the same mass flow rate of the gas medium, making it more difficult to compress, thus leading to a decrease in the overall compression efficiency of the nitrogen oxide compressor.
[0052] In addition, if the high-temperature nitrogen oxide gas output from the oxidizer is directly transported to the heat exchanger, the heat carried by the high-temperature nitrogen oxide gas will not be fully utilized. At the same time, if all the heat carried by the nitrogen oxide is cooled by the heat exchanger, the load on the heat exchanger will increase.
[0053] In response to the above problems, such as Figure 1 As shown, in some embodiments, the nitric acid production system 1000 also includes a heat exchanger 500.
[0054] The output ends of the heat exchanger 500 and the oxidizing furnace 300 are connected. The high-temperature nitrogen oxide gas output from the oxidizing furnace 300 flows sequentially through the heater 400 and the heat exchanger 500. The high-temperature nitrogen oxide gas serves as the heat source for the heater 400, allowing some of the heat from the high-temperature nitrogen oxide gas to be transferred to the compressed air of the output air compressor 120 through heat exchange, thereby raising the temperature of the compressed air to meet the requirements of the nitrogen oxide production process and cooling the high-temperature nitrogen oxide gas once.
[0055] Heat exchanger 500 is used to cool high-temperature nitrogen oxide gas, providing secondary cooling. By adding a heat exchanger, the nitrogen oxide gas is cooled to approximately 40°C before being fed into nitrogen oxide compressor 130 for compression. This process serves two purposes: firstly, heater 400 transfers some of the heat from the high-temperature nitrogen oxide gas, making full use of this heat and reducing the energy consumption of the nitric acid production system 1000; secondly, the nitrogen oxide gas, after its initial cooling, enters the heat exchanger, reducing its load, and the temperature of the cooled nitrogen oxide gas is also lower. Consequently, when the nitrogen oxide gas enters nitrogen oxide compressor 130 for compression, the energy consumption of compressor 130 is also reduced.
[0056] In some embodiments, the nitric acid production system 1000 further includes a nitrogen oxide compressor 130 and an absorption tower 600.
[0057] like Figure 1 As shown, the output ends of the nitrogen oxide compressor 130 and the heat exchanger 500 are connected, and the absorption tower 600 is connected to the output end of the nitrogen oxide compressor 130.
[0058] In one embodiment, when the nitric oxide compressor 130 is a centrifugal compressor, the nitric oxide compressor 130 also has multi-stage compression impellers. An interstage cooler 200 can be provided between two consecutive compression impellers to improve the compression efficiency of the nitric oxide compressor 130.
[0059] The nitrogen oxide compressor 130 is used to compress the nitrogen oxide gas generated by the oxidation furnace 300 and then input it into the absorption tower 600.
[0060] The absorption tower 600 is used to bring nitrogen oxide gas into full contact with water inside the tower, so that the nitrogen oxide gas is absorbed by the water or undergoes a chemical reaction to produce nitric acid.
[0061] Typically, the gas inlet of the absorption tower 600 is located at the bottom of the tower. By compressing the nitrogen oxide gas before it enters the absorption tower 600, the nitrogen oxide gas is rapidly and evenly distributed into the tower, thereby improving the efficiency of nitric acid generation.
[0062] In some embodiments, the nitric acid production system 1000 further includes an expander 140. For example... Figure 1 As shown, the expander 140 is connected to the output end of the absorber tower 600. The expander 140 is used to treat the exhaust gas discharged from the top of the absorber tower 600. The exhaust gas contains a small amount of nitrogen oxide gas. The expander 140 treats the exhaust gas before discharging it into the air.
[0063] In some embodiments, the drive unit 110 includes a steam turbine 111 or a motor 113, and the drive unit 110 also includes a gearbox 112. The output end of the steam turbine 111 or the motor 113 is connected to the gearbox 112. The nitric acid production system 1000 also includes a boiler 700.
[0064] like Figure 1 , Figure 2 and Figure 3 As shown, the output end of the steam turbine 111 is connected to the gearbox 112, and the output end of the gearbox 112 is connected to the air compressor 120 to drive the multi-stage compression impeller of the air compressor 120.
[0065] like Figure 4 As shown, the output of motor 113 is connected to gearbox 112, and the output of gearbox 112 is connected to air compressor 120 to drive the multi-stage compression impeller of air compressor 120. Because it is driven by motor 113, the steam generated by boiler 700 can be used in other applications where needed.
[0066] It should be noted that gearbox 112 may not be used in some cases. For example... Figure 5 As shown, the output end of the motor 113 is connected to the air compressor 120 to drive the multi-stage compression impeller of the air compressor 120 to rotate.
[0067] like Figure 1 As shown, boiler 700 is connected to oxidizer 300 and steam turbine 111. Boiler 700 is used to collect steam generated by oxidizer 300 and input steam into steam turbine 111. This supplements the power required by air compressor 120 and nitrogen oxide compressor 130 in the nitric acid generation system to compress gas.
[0068] In addition, the expander 140 directly supplies mechanical work to the air compressor 120 and the nitrogen oxide compressor 130, thereby reducing the energy consumption of the entire nitric acid production system 1000.
[0069] In some embodiments, the air compressor 120 and the nitrogen oxide compressor 130 are both centrifugal compressors; the expander 140 is a centripetal or axial flow expander 140. The air compressor 120, the nitrogen oxide compressor 130 and the expander 140 are all rotary turbine machines, which generate centrifugal or centripetal force through the rotation of the impeller to perform work.
[0070] In some embodiments, the nitrogen oxide compressor 130 includes at least two stages of compression impellers to output high-pressure nitrogen oxide gas, thereby improving nitric acid production efficiency. The expander 140 includes at least two stages of expansion impellers to increase the mechanical work output by the expander 140 and supply it to the air compressor 120 and the nitrogen oxide compressor 130.
[0071] like Figure 6 As shown, this application also provides a method for producing nitric acid, which is carried out using the nitric acid production system 1000 in any of the above embodiments, including:
[0072] Step S1: Atmospheric pressure air is input into the air compressor 120. An interstage cooler 200 is installed between two consecutive compression impellers to cool the compressed air generated by the previous stage compression impeller and input the cooled air into the next stage compression impeller for compression.
[0073] Step S2: The compressed air output from the air compressor 120 is heated by the regenerator and then fed into the oxidation furnace 300;
[0074] Step S3: The compressed air is mixed with ammonia and fed into the oxidizer 300 to react and obtain nitrogen oxide gas. The steam generated by the oxidizer 300 is fed into the boiler 700. The boiler 700 feeds the steam into the steam turbine 111, which drives the air compressor 120 and the nitrogen oxide compressor 130 to perform compression work.
[0075] Step S4: Input the nitrogen oxide gas output from the oxidizing furnace 300 into the regenerator for heat exchange and cooling;
[0076] Step S5: Input the nitrogen oxide gas that has passed through the regenerator into the heat exchanger 500 for cooling treatment;
[0077] Step S6: The cooled nitrogen oxide gas is compressed in nitrogen oxide compressor 130;
[0078] Step S7: The compressed nitrogen oxide gas is introduced into the absorption tower 600 to produce nitric acid.
[0079] This application reduces the intake temperature of the air compressor and nitrogen oxide compressor 130 by adding an interstage cooler 200 to the nitric acid production process, thereby reducing the energy consumption of the compressor. By adding a regenerator, the compressed air entering the oxidizer 300 has a certain temperature and pressure, which meets the production process requirements of nitrogen oxide gas. Furthermore, the heat exchanger 500 is used to transfer some of the heat from the high-temperature nitrogen oxide gas generated by the reaction in the oxidizer 300, reducing the load on the heat exchanger and improving the operating efficiency of the entire nitric acid production system 1000.
[0080] In the description of this specification, the references to terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., refer to specific features, structures, materials, or characteristics described in connection with that embodiment or example, which are included in at least one embodiment or example of this application. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. Moreover, without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described in this specification, as well as the features of different embodiments or examples.
[0081] Although embodiments of this application have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting this application. Those skilled in the art can make changes, modifications, substitutions and variations to the above embodiments within the scope of this application.
Claims
1. A nitric acid production system, characterized in that, include: Drive motor; An air compressor includes a multi-stage compression impeller and at least one interstage cooler. The drive motor drives the compression impeller. Each interstage cooler is connected to two consecutive stages of the compression impeller so that the gas compressed by the previous stage compression impeller is cooled by the interstage cooler and then flows to the next stage compression impeller.
2. The nitric acid production system according to claim 1, characterized in that, The nitric acid production system also includes: A heater, which is connected to the output of the air compressor; An oxidizing furnace is provided, and the output end of the oxidizing furnace is connected to the heater. The heater is used to heat the gas entering the oxidizing furnace from the air compressor. The oxidizing furnace is used to synthesize ammonia and compressed air output from the air compressor into nitrogen oxide gas.
3. The nitric acid production system according to claim 2, characterized in that, The nitric acid production system also includes: A heat exchanger is connected to the output end of the oxidation furnace. The high-temperature nitrogen oxide gas output from the oxidation furnace flows sequentially through the heater and the heat exchanger. The high-temperature nitrogen oxide gas serves as the heat source for the heater, and the heat exchanger is used to cool the high-temperature nitrogen oxide gas.
4. The nitric acid production system according to claim 3, characterized in that, The nitric acid production system also includes a nitrogen oxide compressor, which is connected to the output end of the heat exchanger.
5. The nitric acid production system according to claim 4, characterized in that, The nitric acid production system also includes an absorption tower connected to the output end of the nitrogen oxide compressor, and the absorption tower is used to produce nitric acid.
6. The nitric acid production system according to claim 5, characterized in that, The nitric acid production system further includes an expander connected to the output end of the absorption tower, the expander being used to treat the tail gas discharged from the absorption tower.
7. The nitric acid production system according to any one of claims 2 to 6, characterized in that, The drive unit includes a steam turbine or an electric motor, and the drive unit also includes a gearbox. The output end of the steam turbine or the electric motor is connected to the gearbox, and the output end of the gearbox is connected to the air compressor to drive the multi-stage compression impeller of the air compressor.
8. The nitric acid production system according to claim 7, characterized in that, The nitric acid production system also includes a boiler connected to the oxidizer and the steam turbine. The boiler is used to collect the steam generated by the oxidizer and input the steam into the steam turbine.
9. The nitric acid production system according to claim 6, characterized in that, Both the air compressor and the nitrogen oxide compressor are centrifugal compressors; the expander is a centripetal or axial flow expander.
10. The nitric acid production system according to claim 6, characterized in that, The nitrogen oxide compressor includes at least two stages of compression impellers, and the expander includes at least two stages of expansion impellers.