Device and process method for producing dilute nitric acid by double-pressurization method

Abstract

The invention belongs to the technical field of nitric acid production, and particularly relates to a device and a process method for producing dilute nitric acid by a double-pressurization method. The device comprises an absorption tower and an ammonia evaporator, the absorption tower has 30 layers, and coil pipes are distributed on each layer; 26-30 layers of the absorption tower are upper-section refrigerating machine circulation sections, the refrigerating machine set is adopted for heat exchange, 26-30 layers of coil pipes enter the absorption tower from an outlet of the refrigerating machine set for heat exchange and enter the refrigerating water tank after heat exchange, the refrigerating water tank pumps water into the refrigerating machine set through a second refrigerating water pump, and circulation is conducted in this way. The tail gas absorption of the absorption tower is promoted, and the dilute nitric acid concentration is improved.

Description

Technical Field

[0001] The invention belongs to the technical field of nitric acid production, and in particular relates to a device and a process method for producing dilute nitric acid by a double-pressure method. Background Art

[0002] Nitric acid has a wide range of uses and is often used to produce a series of nitrate nitrogen fertilizers. Since nitric acid is both oxidizing and acidic, it is also used to refine metals, etc. Nitric acid production processes are generally divided into five types according to pressure, namely, normal pressure method, full medium pressure method, comprehensive method, full high pressure method and double pressure method. Normal pressure method and comprehensive method are early nitric acid production processes with small production capacity, high consumption, heavy pollution and low acid concentration, and have been eliminated. The full medium pressure method and full high pressure method are oxidation and absorption under pressure, the production intensity has been improved, the process is simple and the investment is small, but the production intensity is still low, the loss is large, and the NOx content in the tail gas is still above 2000ppm, which needs to be treated to meet the emission standards. The double pressure method is the most commonly used nitric acid production process. Its ammonia loss and platinum catalyst consumption are low, the absorption rate is high, the nitric acid produced is high in concentration and strength, and the NOx content in the tail gas is low.

[0003] Application No. 201110323653.X discloses a process for producing high-concentration dilute nitric acid, which is to jointly produce dilute nitric acid and concentrated nitric acid, using a double-pressurized dilute nitric acid device, improving the production of super-azeotropic nitric acid with a mass concentration greater than 68.4%, and then using super-azeotropic nitric acid distillation and rectification technology to produce concentrated nitric acid with a mass concentration greater than 98%. This process has a high production cost and a low output, and does not effectively reduce the NOx content in the exhaust gas.

[0004] In the production process of dilute nitric acid, the best conditions for absorbing process gas NOx are high pressure and low temperature environment. However, in the existing process, due to the "four-in-one unit" in the double-pressurized dilute nitric acid device (the four-in-one unit consists of four units including a steam turbine, an exhaust gas expander, an axial flow compressor, and a NOX compressor. Among them, the steam turbine and the exhaust gas expander are the prime movers, which use high-temperature and high-pressure steam and exhaust gas to expand and do work respectively. Axial flow compressor: The process gas enters the impeller through the suction chamber and rotates at high speed with the impeller. At the same time, the gas with increased pressure and speed is obtained and enters the diffuser, which further converts the kinetic energy of the gas into potential energy, that is, further increases the pressure. High gas pressure. After the high-pressure gas comes out of the diffuser, it passes through the bend and the return flow device and enters the next stage for the same compression. Finally, the high-pressure gas comes out of the last stage diffuser (or impeller) and enters the volute for further expansion before being discharged out of the machine and entering the process pipeline. The air compressor in the air compressor affects the absorption pressure. There is a certain gap between the actual heat recovery efficiency of the tail gas turbine and the design value, and the gas temperature at the outlet of the waste heat boiler is high, resulting in the temperature of NOx being too high, and the optimal conditions for absorbing process gas NOx cannot be achieved, and too much energy is consumed in the process of absorbing NOx. In the high temperature season in summer, the air compressor pumping volume of the four-in-one unit decreases, and the production load is low, resulting in a decrease in the production capacity of dilute nitric acid in the high temperature season.

[0005] Therefore, it is necessary to develop a dual-pressurization production method that can promote tail gas absorption and increase the concentration of dilute nitric acid. Summary of the invention

[0006] In order to solve the above technical problem, that is, to promote tail gas absorption and increase the concentration of dilute nitric acid, the present invention provides the following technical solution:

[0007] First,

[0008] A device for producing dilute nitric acid by a double-pressure method includes an absorption tower and an ammonia evaporator. The absorption tower has 30 layers, and each layer is provided with a coil. The device also includes a freezing water tank and a freezing unit.

[0009] The 26th to 30th floors of the absorption tower are the upper refrigeration cycle sections, which use refrigeration units for heat exchange. The return water inlet of each coil on the 26th to 30th floors is connected to the water inlet of the refrigeration unit after passing through a freezing water tank. The water outlet of the refrigeration unit is connected to the upper water inlet of each coil on the 26th to 30th floors, and a second freezing water pump is provided between the refrigeration unit and the freezing water tank. The chilled water enters the 26th to 30th floor coil of the absorption tower from the freezing unit for heat exchange, and enters the freezing water tank after heat exchange. The chilled water in the freezing water tank is pumped into the refrigeration unit by a second freezing water pump, and the cycle continues.

[0010] Furthermore, the absorption tower is divided into three sections, wherein layers 1-12 are the lower circulating water cooling section, layers 13-25 are the middle ammonia cooling closed-loop circulation section, and layers 26-30 are the upper refrigerator circulation section.

[0011] Furthermore, each of the 1st to 12th layers of the absorption tower is provided with a circulating water inlet and a return water inlet connected to the coils of the 1st to 12th layers, for receiving circulating water inlet from an external source and returning the circulating water that has undergone heat exchange with the gas of the 1st to 12th layers to the circulating water main pipe.

[0012] Furthermore, through the circulation of circulating water in the lower circulating water cooling section, the temperature of layers 1-12 of the absorption tower is within the range of 29±5 degrees.

[0013] Furthermore, each of the 13th to 25th layers of the absorption tower is provided with an inlet and a return port of raw chilled water connected to the coils of the 13th to 25th layers, and an ammonia evaporator is connected between the inlet of raw chilled water and the return port of raw chilled water through a pipeline; a chilled water pump is provided between the ammonia evaporator and the return port of raw chilled water collected from the absorption tower.

[0014] Furthermore, by circulating the original chilled water in the middle section of the ammonia cooling closed-loop cycle and cooling the original chilled water in the middle section of the ammonia cooling closed-loop cycle, the temperature of the absorption tower 13-25 layers is within the range of 19±5 degrees.

[0015] Furthermore, through heat exchange in the upper refrigerator cycle section, the temperature of the 26th to 30th floors of the absorption tower is between 15 and 22 degrees.

[0016] Second,

[0017] The present invention provides a process for producing double-pressurized nitric acid, and a device for producing dilute nitric acid by using the double-pressurization method.

[0018] Further, including:

[0019] Evaporation of liquid ammonia: Evaporating liquid ammonia into gaseous ammonia to provide gaseous ammonia required for ammonia oxidation;

[0020] Air pressurization and purification: The air is purified and pressurized to provide the air required for ammonia oxidation;

[0021] Ammonia oxidation: After ammonia and air are fully mixed, they enter the oxidation furnace to generate NO;

[0022] Further oxidation of NO: After leaving the oxidation furnace, NO enters the various heat exchangers in the low-pressure section for cooling, and NO and oxygen in the air continue to oxidize and generate;

[0023] Absorption: After being pressurized by the nitrogen oxide compressor, it enters the high-pressure section; in the high-pressure section, it continues to be cooled and is ready to enter the absorption tower;

[0024] Generation of nitric acid: The final process gas enters the absorption tower, where it is absorbed by water to generate nitric acid and then produced.

[0025] Compared with the prior art, the present invention has the following beneficial effects:

[0026] In the prior art, the 1-14 layers of the absorption tower are the lower circulating water cooling section; the 15-30 layers of the absorption tower are the upper ammonia cooling closed-loop circulation section. The present invention transforms the existing absorption tower cooling heat exchange pipe, peels off the upper five layers (26-30 layers) of the original ammonia cooling closed-loop circulation pipe and uses chilled water cooling of a refrigeration unit instead. In order to ensure the heat balance of the original ammonia cooling closed-loop circulation and the ammonia pressure is not affected, the lower circulating water cooling section is moved up two layers (13-14 layers) into the closed-loop circulation pipe, so that the cooling condition of the entire absorption tower becomes that the original 1-14 layers of the circulating water cooling section in the lower section become 1-12 layers; the middle ammonia cooling closed-loop circulation section is changed from 15-30 layers to 13-25 layers; the five layers of the upper original closed-loop circulation pipeline are replaced by the refrigeration unit added later for circulating cooling.

[0027] By adding a refrigeration unit to further reduce the temperature of the exhaust gas at the top of the absorption tower, the exhaust gas absorption is promoted, the water content is reduced and the concentration is increased, which can increase the concentration of dilute nitric acid and save costs. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 This is one of the structural schematic diagrams of the device for producing dilute nitric acid by the double-pressure method of the present invention;

[0029] Figure 2 This is the second structural schematic diagram of the device for producing dilute nitric acid by the double-pressure method of the present invention.

[0030] Figure numerals: 10 is an absorption tower; 20 is a chilled water tank; 30 is an ammonia evaporator; 40 is a chilled water pump 1; 50 is a refrigeration unit; 60 is a chilled water pump 2; 70 is a coil; 80 is a circulating water pump; 90 is a circulating water main. DETAILED DESCRIPTION

[0031] The technical solution of the present invention will be clearly described below in conjunction with the accompanying drawings. Obviously, the described embodiments are not all embodiments of the present invention, and all other embodiments obtained by ordinary technicians in the field without making creative work are within the protection scope of the present invention.

[0032] It should be noted that the directions or positional relationships indicated by terms such as “center”, “up”, “down”, “horizontal”, “left”, “right”, “front”, “back”, “lateral” and “longitudinal” are based on the directions or positional relationships shown in the accompanying drawings and are only for the convenience of describing the present invention and simplifying the description. They do not indicate or imply that the device or element referred to must have a specific direction, be constructed and operated in a specific direction, and therefore should not be understood as a limitation on the present invention.

[0033] Modification description: In the prior art, the 1-14 layers of the absorption tower are the lower circulating water cooling section; the 15-30 layers of the absorption tower are the upper ammonia cooling closed-loop circulation section. The present invention modifies the existing absorption tower cooling heat exchange pipes, and the upper five layers (26-30 layers) of the original ammonia cooling closed-loop circulation pipes are stripped out and replaced with chilled water cooling by a refrigeration unit. In order to ensure the heat balance of the original ammonia cooling closed-loop circulation and the ammonia pressure is not affected, the lower circulating water cooling section is moved up two layers (13-14 layers) into the closed-loop circulation pipe. In this way, the cooling condition of the entire absorption tower becomes that the original 1-14 layers of the circulating water cooling section in the lower section become 1-12 layers; the middle ammonia cooling closed-loop circulation section is changed from 15-30 layers to 13-25 layers; the five layers of the upper original closed-loop circulation pipeline are replaced by the later added refrigeration unit for circulating cooling.

[0034] Example 1

[0035] Combination Figure 1 , Figure 2 As shown, the present invention provides a device for producing dilute nitric acid by a double-pressure method, comprising an absorption tower 10, a freezing water tank 20, a refrigeration unit 50, and an ammonia evaporator 30.

[0036] The absorption tower 10 has 30 layers, and each layer is provided with a coil 70, and water is contained in the coil 70. The coils of each layer are provided with independent water inlets and water return ports.

[0037] The absorption tower 10 is used to absorb the NO2 from the nitrogen oxide compressor in the four-in-one unit after pressurization, and the NO2 is absorbed by water to generate nitric acid. The temperature of the absorption tower 10 needs to be lowered during the whole process to ensure that the best conditions for absorbing process gas NOx in the dilute nitric acid production process are high pressure and low temperature environment.

[0038] The absorption tower 10 is divided into three sections, wherein the 1-12th floor is the lower circulating water cooling section, the 13-25th floor is the middle ammonia cooling closed loop circulation section, and the 26-30th floor is the upper refrigerator circulation section.

[0039] The lower circulating water cooling section adopts circulating water heat exchange. The 1st to 12th layers of coils 70 of the absorption tower 10 are connected in parallel to each other and then connected to the circulating water main pipe 90, wherein the upper water inlet of each layer of coils 70 of the 1st to 12th layers is connected to the outlet of the circulating water pump 80, and the return water inlet of each layer of coils 70 of the 1st to 12th layers is connected to the circulating water main pipe 90.

[0040] The circulating water pump 80 extracts the circulating water from the circulating water main pipe 90 and delivers the circulating water to the 1st to 12th layers of the coil pipe 70 of the absorption tower 10 through the upper water port of each layer of the coil pipe 70. In the coil pipe 70, the circulating water exchanges heat with the gas entering the absorption tower 10, thereby reducing the temperature of the gas. After the heat exchange, the temperature of the circulating water increases, and then it flows back to the circulating water main pipe 90 through the return water port of each layer of the coil pipe 70, and is then re-extracted from the circulating water main pipe 90 for circulation.

[0041] By adjusting the flow rate and temperature of the circulating water through the process of circulating water supply and return, the temperature of the 1-12 layers of the absorption tower 10 is lowered so that the temperature of the 1-12 layers of the absorption tower 10 is controlled within the range of 29±5 degrees, that is, about 32 degrees.

[0042] The working process of the lower circulating water cooling section:

[0043] Circulating water enters: Circulating water enters the 1st to 12th layers of the absorption tower 10 from the upper water inlet of each layer of the coil 70 of the 1st to 12th layers;

[0044] Flowing through the coils 70 in the 1st to 12th layers: When the circulating water flows through the coils 70 in the 1st to 12th layers of the absorption tower 10, it exchanges heat with the gas rising from the bottom of the absorption tower 10. The circulating water in the coils 70 absorbs the heat of the gas, thereby reducing the temperature of the gas;

[0045] Circulating water outflow: After heat exchange, the temperature of the circulating water increases, and the circulating water flows out from the return water port of each coil 70 of the 1st to 12th layers;

[0046] Circulating water return: The circulating water flowing out of the absorption tower 10 returns to the circulating water main pipe 90. The circulating water main pipe 90 again extracts the circulating water from the circulating water main pipe 90 and returns it to the upper water inlet of each layer of the coil 70 of the 1st to 12th layers, forming a continuous circulation process.

[0047] The 13-25 layers in the middle of the absorption tower 10 and the middle ammonia cooling closed-loop circulation section use the original chilled water for heat exchange. The original chilled water is circulated in the ammonia cooling closed-loop in the ammonia evaporator 30 and the 13-25 layers of the absorption tower 10 plates. The original chilled water refers to the same heat exchange medium as that used in the 15-30 layers of the absorption tower 10 before the modification.

[0048] The water inlet of each layer of coil 70 of the 13th to 25th layers of the absorption tower 10 is connected to the outlet of the ammonia evaporator 30, and the water outlet of each layer of coil 70 of the 13th to 25th layers is connected to the chilled water pump 40, and the chilled water pump 40 is connected to the inlet of the ammonia evaporator 30. The original chilled water is pressurized by the chilled water pump 40 and finally flows back to the absorption tower 10. The temperature of the original chilled water rises in the absorption tower 10, and after entering the ammonia evaporator 30 for cooling, it enters the water inlet of each layer of coil 70 of the 13th to 25th layers, thus forming a closed-loop cycle.

[0049] Specifically, the original chilled water in the coil 70 of the 13-25th layer of the absorption tower 10 is transported into the ammonia evaporator 30 with heat, and the liquid ammonia in the ammonia evaporator 30 is evaporated into gaseous ammonia of about 0.52MPa by the temperature of the original chilled water (the temperature of the original chilled water is about 22 degrees at this time), and the temperature of the original chilled water is reduced at the same time, and it is transported into the ammonia evaporator 30 again. Thus, a mid-stage ammonia cooling closed-loop cycle is formed. The temperature of the 13-25th layer of the absorption tower 10 is within the range of 19±5 degrees, that is, about 22 degrees. The gaseous ammonia is used for other sections.

[0050] Middle section ammonia cooling closed loop circulation process:

[0051] Raw chilled water enters: Raw chilled water enters from the upper water inlet of the coil 70 of the 13th to 25th layers in the middle section of the absorption tower 10.

[0052] Flowing through the coil: In the 13th to 25th floors, the raw chilled water exchanges heat with the rising gas through the coil 70. The raw chilled water in the coil 70 absorbs the heat of the gas, thereby reducing the temperature of the gas.

[0053] Original chilled water return: After heat exchange, the temperature of the original chilled water increases, and the original chilled water with increased temperature flows out from the return water outlet of each coil 70 of the 13th to 25th layers, and is pressurized by the chilled water pump 40 and returned to the ammonia evaporator 30. The cold energy absorbed by the evaporation of liquid ammonia reduces the temperature of the original chilled water, and the temperature of the original chilled water decreases.

[0054] Closed-loop circulation: The original chilled water after final cooling is sent to the water inlet of each coil 70 of the 13th to 25th layers again to form a closed-loop circulation.

[0055] The upper section of the absorption tower 10 has 26-30 layers, and the upper section of the refrigeration cycle section adopts a refrigeration unit for heat exchange. The upper water inlet of each layer of the coil 70 of the 26-30 layers of the absorption tower 10 is connected to the refrigeration unit 50. The refrigeration unit 50 is connected to a freezing water tank 20 via a freezing water pump 260. The freezing water tank 20 is connected to the return water inlet of each layer of the coil 70 of the 26-30 layers of the absorption tower 10.

[0056] Because the absorption tower 10 is an absorption zone, absorption is an exothermic reaction. After absorption, dilute nitric acid is produced, the temperature rises and needs to be cooled. The hot water (about 15 degrees) is cooled by the refrigeration unit 50 and then pressurized by the chilled water pump 2 60 to enter the 26-30 layers of the upper section of the absorption tower 10. The return water (about 22 degrees) enters the chilled water tank 20, and the chilled water in the chilled water tank 20 is sent to the refrigeration unit 50 for cooling through the chilled water pump 2 60, forming a closed loop.

[0057] The water in the coils 70 of the 26th to 30th layers of the upper section of the absorption tower 10 is transported to the chilled water tank 20 , and then the water in the chilled water tank 20 is transported to the refrigeration unit 50 through the chilled water pump 2 60 .

[0058] The working process of the upper freezer cycle section:

[0059] Chilled water enters: Chilled water enters from the upper water inlet of the coil 70 on the 26th to 30th floors of the upper section of the absorption tower 10.

[0060] Flowing through the coil: In the 26-30 floors, the chilled water exchanges heat with the rising air through the coil 70. The chilled water in the coil 70 absorbs heat from the air, thereby reducing the temperature of the air.

[0061] Chilled water return: After heat exchange, the temperature of the chilled water increases, and the chilled water with increased temperature flows out from the return water port of each coil 70 of the 26th to 30th layers to the chilled water tank 20 for storage.

[0062] Heat exchange of the refrigeration unit 50: The water is pressurized by the chilled water pump 2 60 and returned to the refrigeration unit 50. The refrigeration unit 50 takes away the heat of the chilled water, and the temperature of the chilled water is reduced.

[0063] Closed loop: The chilled water after cooling is finally pressurized by the chilled water pump 60 and returned to the upper water inlet of each layer of coils 70 of the 13th to 25th layers of the absorption tower 10, forming a closed loop. The temperature of the upper section of the absorption tower 10 is effectively controlled.

[0064] In the prior art, the 1-14th layers of the absorption tower are heat exchanged with circulating water, and the 15-30th layers are heat exchanged with original refrigerated water, and the concentration of the prepared dilute nitric acid ranges from 52% to 55%.

[0065] The absorption tower of this embodiment uses circulating water for heat exchange in layers 1-12, original chilled water for heat exchange in layers 13-25, and a refrigeration unit for heat exchange in layers 25-30, and the concentration of the prepared dilute nitric acid is 62%-68%.

[0066] It can be seen that the present invention further reduces the temperature of the tail gas at the upper part of the absorption tower by adding a refrigeration unit, thereby promoting tail gas absorption, achieving water reduction and concentration, and can increase the concentration of dilute nitric acid and save costs.

[0067] Example 2

[0068] A process for producing double-pressurized nitric acid, using the device for producing dilute nitric acid by the double-pressurization method of Example 1, the process comprising:

[0069] Evaporation of liquid ammonia: Evaporating liquid ammonia into gaseous ammonia to provide gaseous ammonia required for ammonia oxidation;

[0070] Air pressurization and purification: The axial compressor in the four-in-one unit pressurizes the atmosphere to provide the air required for ammonia oxidation; the air needs to undergo three levels of purification before pressurization to ensure the quality of the air entering the oxidation furnace;

[0071] Ammonia oxidation: After being fully mixed, ammonia and air enter the oxidation furnace and undergo oxidation reaction under the catalytic action of the Pt mesh to generate NO;

[0072] Further oxidation of NO: After leaving the oxidation furnace, NO enters the various heat exchangers in the low-pressure section for cooling. When the temperature is lower than 200°C, NO and oxygen in the air continue to oxidize to generate NO2;

[0073] Absorption of NO2: After being pressurized by the nitrogen oxide compressor in the four-in-one unit, NO2 enters the high-pressure section; in the high-pressure section, NO2 continues to be cooled and is ready to enter the absorption tower 10;

[0074] Generation of nitric acid: The final process gas enters the absorption tower 10, where it is absorbed by water to generate nitric acid and then produced.

[0075] The above technical features constitute the best embodiment of the present invention, which has strong adaptability and best implementation effect. Non-essential technical features can be added or reduced according to actual needs to meet the needs of different situations.

[0076] Finally, it should be noted that the above content is only used to illustrate the technical solution of the present invention, rather than to limit the scope of protection of the present invention. Simple modifications or equivalent substitutions of the technical solution of the present invention by ordinary technicians in this field do not deviate from the essence and scope of the technical solution of the present invention.

Claims

1. A device for producing dilute nitric acid by a double pressure method, comprising an absorption tower and an ammonia evaporator, wherein the absorption tower has 30 layers, and each layer is provided with a coil, characterized in that: It also includes a freezing water tank and a refrigeration unit. The 26th to 30th floors of the absorption tower are the upper refrigeration cycle sections, which use refrigeration units for heat exchange. The return water inlet of each coil on the 26th to 30th floors is connected to the water inlet of the refrigeration unit after passing through a freezing water tank. The water outlet of the refrigeration unit is connected to the upper water inlet of each coil on the 26th to 30th floors, and a second freezing water pump is provided between the refrigeration unit and the freezing water tank. The chilled water enters the 26th to 30th floor coil of the absorption tower from the freezing unit for heat exchange, and enters the freezing water tank after heat exchange. The chilled water in the freezing water tank is pumped into the refrigeration unit by a second freezing water pump, and the cycle continues.

2. The device for producing dilute nitric acid by double pressure method according to claim 1, characterized in that: The absorption tower is divided into three sections, with layers 1-12 being the lower circulating water cooling section, layers 13-25 being the middle ammonia cooling closed-loop circulation section, and layers 26-30 being the upper refrigerator circulation section.

3. The device for producing dilute nitric acid by double pressure method according to claim 2, characterized in that: Each of the 1st to 12th layers of the absorption tower is provided with a circulating water inlet and a return water inlet connected to the coils of the 1st to 12th layers, for receiving circulating water inlet from an external source and returning the circulating water that has undergone heat exchange with the gas of the 1st to 12th layers to the circulating water main pipe.

4. The device for producing dilute nitric acid by double pressure method according to claim 3, characterized in that: Through the circulating water cooling of the lower circulating water cooling section, the temperature of the 1-12 layers of the absorption tower is within the range of 29±5 degrees.

5. The device for producing dilute nitric acid by double pressure method according to claim 2, characterized in that: Each of the 13th to 25th layers of the absorption tower is provided with an inlet and a return port of raw chilled water connected to the coils of the 13th to 25th layers, and an ammonia evaporator is connected between the inlet of raw chilled water and the return port of raw chilled water through a pipeline; A chilled water pump is provided between the ammonia evaporator and the return water inlet of the collected raw chilled water of the absorption tower.

6. The device for producing dilute nitric acid by double pressure method according to claim 5, characterized in that: Through the circulating cooling of the original chilled water in the middle ammonia cooling closed-loop circulation section, the temperature of the 13th to 25th floors of the absorption tower is within the range of 19±5 degrees.

7. The device for producing dilute nitric acid by double pressure method according to claim 1, characterized in that: Through heat exchange in the upper refrigerator cycle section, the temperature of the 26th to 30th floors of the absorption tower is between 15 and 22 degrees.

8. A process for double-pressurized nitric acid, characterized in that: A device for producing dilute nitric acid using the double pressure method described in any one of claims 1 to 7.

9. The process for producing double-pressurized nitric acid according to claim 8, characterized in that: include: Evaporation of liquid ammonia: Evaporating liquid ammonia into gaseous ammonia to provide gaseous ammonia required for ammonia oxidation; Air pressurization and purification: The air is purified and pressurized to provide the air required for ammonia oxidation; Ammonia oxidation: After ammonia and air are fully mixed, they enter the oxidation furnace to generate NO; Further oxidation of NO: After leaving the oxidation furnace, NO enters the various heat exchangers in the low-pressure section for cooling, and NO and oxygen in the air continue to oxidize to generate NO2; NO2 absorption: NO2 is pressurized by the nitrogen oxide compressor and enters the high-pressure section; in the high-pressure section, NO2 continues to be cooled and is ready to enter the absorption tower; Generation of nitric acid: The final process gas enters the absorption tower, where it is absorbed by water to generate nitric acid and then produced.

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