A high-speed motor-driven unit nitric acid production system

Abstract

The utility model relates to the technical field of chemical industry device, especially for a kind of nitric acid production system of high-speed motor driving unit, the system includes ammonia combustion reactor, nitrogen oxide compressor, air compressor, tail gas expander, high steam separator, high steam pressure reducing system, water injection regulating system;The power drive part of system is made of double-source collaborative drive structure by high-speed motor and tail gas expander, is connected by coupling and compressor set respectively, realizes energy recovery and energy efficiency balance;Steam drum and the waste pot in ammonia combustion reactor form forced circulation heat exchange loop, and steam superheater is arranged inside reactor, for improving steam quality;High steam pressure reducing system adopts double-valve parallel redundancy structure, cooperates with gas-closing type water injection regulating valve and desuperheater to constitute automatic pressure stabilizing temperature control system;The system has the advantages of compact structure, safe operation, high energy utilization rate and good long-term operation stability, is applicable to the energy-saving reconstruction and new project of modern nitric acid device.

Description

Technical Field

[0001] This utility model relates to the field of chemical equipment technology, specifically to a nitric acid production system driven by a high-speed electric motor. Background Technology

[0002] In existing nitric acid production systems, the core driving equipment typically uses steam turbines to drive nitrogen oxide compressors and air compressors. Steam turbines rely on high-pressure steam as their driving force, which not only consumes a large amount of internal steam resources but also leads to uneven heat distribution, complex steam regulation, and high energy consumption. With increasing demands for automation and energy conservation in chemical plants, some companies have attempted to replace steam turbines with electric motors to reduce energy consumption. However, traditional electric motors have low speeds and high starting inertia, making them unable to directly drive high-speed compressor units. Furthermore, the exhaust gas from nitric acid production has a certain pressure and temperature; if not effectively utilized, this not only wastes energy but also causes difficulties in exhaust cooling and reduces system efficiency.

[0003] Meanwhile, existing steam pressure reduction and temperature control systems mostly employ a single-valve structure. If a valve jams or temperature control malfunctions, it can easily lead to dangerous conditions such as downstream over-temperature and over-pressure, triggering interlocking shutdowns and affecting production continuity and equipment safety. While some systems have added backup valves, they lack automatic switching and pneumatic protection designs, resulting in insufficient reliability. Furthermore, the high-temperature flue gas generated by the ammonia combustion reactor has low thermal energy utilization, and the waste heat recovery system has a complex structure and insufficient heat exchange, causing energy loss and low overall system efficiency. Therefore, to address these issues, a high-speed electric motor-driven nitric acid production system is proposed. Utility Model Content

[0004] The purpose of this invention is to provide a nitric acid production system with a high-speed electric motor driven unit to solve the problems mentioned in the background art.

[0005] To achieve the above objectives, this utility model provides the following technical solution: A nitric acid production system driven by a high-speed electric motor includes: an ammonia combustion reactor, a steam drum, a mixer, a tail gas superheater, a second waste boiler, a low-pressure gas-to-gas heat exchanger, a high-speed electric motor, a nitrogen oxide compressor, an air compressor, a tail gas expander, a high-pressure steam separator, a high-pressure steam depressurization system, a water spray regulation system, a gas-liquid separator, a safety valve, a boiler water circulation pump, a gearbox, an air filter, and a low-pressure cooling separator. The power drive section of the system includes an electric drive unit and an exhaust gas energy recovery unit; The electric drive unit includes the high-speed electric motor, which is connected to the oxide nitrogen compressor via a coupling. The exhaust gas energy recovery unit includes the exhaust gas expander, which is drivenly connected to the air compressor via another coupling; The nitrogen oxide compressor and the air compressor are poweredly coupled through the gearbox; The air compressor's inlet is connected to the air filter, and its outlet is connected to the mixer; The exhaust gas expander has an inlet connected to an exhaust gas pipeline with a pressure of 3.7 to 4.0 MPa, and an outlet connected to a soft water preheater.

[0006] Preferably, the high-speed motor is a 6.6kV high-voltage motor; the high-speed motor and the exhaust gas expansion mechanism form a dual-source cooperative drive structure, which together provide power to the nitrogen oxide compressor and the air compressor.

[0007] Preferably, the steam drum forms a forced circulation heat exchange loop with the first waste boiler and the second waste boiler in the ammonia combustion reactor through a boiler water circulation pump; the ammonia combustion reactor is also equipped with a steam superheater to superheat the steam output from the steam drum.

[0008] Preferably, the high-pressure steam reduction system includes a first high-pressure steam reduction valve and a second high-pressure steam reduction valve arranged in parallel, with the first high-pressure steam reduction valve and the second high-pressure steam reduction valve serving as backups for each other; the outlet of the high-pressure steam separator is connected sequentially via the high-pressure steam reduction system, the water spray regulation system and the gas-liquid separator to deliver steam to external users or power generation equipment.

[0009] Preferably, the water spray regulation system includes an air-to-close water spray regulation valve and a desuperheater; the water spray regulation valve is in the open state in case of failure to prevent the subsequent pipeline from overheating.

[0010] Preferably, the low-pressure cooling separator is used to condense and separate condensable acid from the process gas, and the separated gas enters the nitrogen oxide compressor; the safety valve is installed on the steam pipeline for system overpressure protection.

[0011] Preferably, the process gas combustion temperature of the ammonia combustion reactor is controlled at 870-875°C; the exhaust gas after it has done work in the exhaust gas expander enters the soft water preheater for cooling before being discharged.

[0012] Compared with the prior art, the beneficial effects of this utility model are: In this invention, by replacing the traditional steam turbine drive structure with a "high-speed electric motor + exhaust gas expander dual-source coordinated drive system," the device achieves high-efficiency energy conversion and comprehensive energy saving. The high-speed electric motor is a 6.6kV high-voltage motor that directly drives the nitrogen oxide compressor through a coupling and is linked to the air compressor through a gearbox, making power transmission more precise and stable. At the same time, the exhaust gas expander utilizes the pressure energy of nitric acid exhaust gas (3.7-4.0MPa) to expand and perform work, converting the originally wasted exhaust gas energy into mechanical work, achieving energy recovery and system energy efficiency balance, and significantly reducing power consumption.

[0013] This system features a forced circulation heat exchange loop between the steam drum and the first and second waste boilers within the ammonia combustion reactor. A steam superheater is integrated inside the reactor, effectively improving heat exchange efficiency and steam quality. The combustion temperature is controlled within the range of 870–875℃ to ensure stable generation of nitrogen oxides. The system employs a dual-valve parallel high-pressure steam reduction system. When the main valve malfunctions, the backup valve automatically activates. Combined with an air-to-close water spray regulating valve and a desuperheater, this forms an automatic temperature control protection structure. In case of an anomaly, the water spray channel automatically opens to prevent overheating of subsequent pipelines, enhancing the system's operational safety and redundancy reliability.

[0014] Furthermore, the low-pressure cooling separator located on the exhaust gas side efficiently separates condensed acid, improving the operational stability of subsequent compressors; the safety valve, positioned on the steam pipeline, allows for timely discharge under overpressure conditions, preventing equipment damage; the exhaust gas, after expansion and work by the exhaust gas expander, is cooled by a soft water preheater before being discharged, further improving thermal energy utilization and reducing emission temperature. The overall system is compact, has high energy efficiency, and strong automatic protection capabilities, significantly enhancing the safety, economy, and long-term operational stability of nitric acid production units. Attached Figure Description

[0015] Figure 1 This is a flowchart of the present invention.

[0016] In the diagram: 1. Ammonia combustion reactor; 2. Steam drum; 3. Mixer; 4. Tail gas superheater; 5. Second waste boiler; 6. Low-pressure gas-to-gas heat exchanger; 7. High-speed electric motor; 8. Oxide nitrogen compressor; 9. Air compressor; 10. Tail gas expander; 11. High-pressure steam separator; 12. First high-pressure steam pressure reducing valve; 13. Second high-pressure steam pressure reducing valve; 14. Water spray regulating valve; 15. Desuperheater; 16. Gas-liquid separator; 17. Safety valve; 18. Boiler water circulation pump; 19. Gearbox; 20. Air filter; 21. Low-pressure cooling separator. Detailed Implementation

[0017] The technical solutions of the present utility model will be clearly and completely described below with reference to the accompanying drawings of the embodiments. Obviously, the described embodiments are only some embodiments of the present utility model, and not all embodiments. Based on the embodiments of the present utility model, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the protection scope of the present utility model.

[0018] In the description of this invention, it should be understood that the orientation or positional relationship indicated by directional terms such as "front, back, up, down, left, right", "horizontal, vertical, horizontal" and "top, bottom" is generally based on the orientation or positional relationship shown in the accompanying drawings, and is only for the convenience of describing this invention and simplifying the description. Unless otherwise stated, these directional terms 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 on the scope of protection of this invention; the directional terms "inner" and "outer" refer to the inner and outer contours relative to the outline of each component itself.

[0019] Please see Figure 1 This utility model provides a technical solution: A nitric acid production system driven by a high-speed electric motor includes components such as an ammonia combustion reactor 1, a steam drum 2, a mixer 3, a tail gas superheater 4, a second waste boiler 5, a low-pressure gas-to-gas heat exchanger 6, a high-speed electric motor 7, a nitrogen oxide compressor 8, an air compressor 9, a tail gas expander 10, a high-pressure steam separator 11, a high-pressure steam depressurization system, a water spray regulation system, a gas-liquid separator 16, a safety valve 17, a boiler water circulation pump 18, a gearbox 19, an air filter 20, and a low-pressure cooling separator 21.

[0020] This system is divided into three functional units: (1) Electric drive and energy recovery unit; (2) Steam pressure stabilization and temperature control unit; (3) Process gas circulation and heat exchange unit.

[0021] Each unit is connected by power and pipelines, forming a complete thermal and energy cycle link in the nitric acid production system.

[0022] I. Electric Drive and Energy Recovery Unit The power sources for this system include an electric drive unit and an exhaust gas energy recovery unit.

[0023] The electric drive unit uses a 6.6kV high-speed electric motor 7, which is directly connected to the oxide nitrogen compressor 8 via a coupling to achieve high-speed mechanical energy output. The oxide nitrogen compressor 8 and the air compressor 9 are coupled together via a gearbox 19 to match the speed requirements of different equipment, allowing the two compressors to operate collaboratively in the same drive chain. The air compressor 9 has an air filter 20 connected to its inlet to remove dust and impurities from the air, and a mixer 3 connected to its outlet to provide clean air for the ammonia combustion reaction.

[0024] The exhaust gas energy recovery unit employs an exhaust gas expander 10, whose inlet is connected to the high-pressure exhaust gas pipeline of the nitric acid system, with an exhaust gas pressure of 3.7–4.0 MPa. After entering the expander, the exhaust gas expands and performs work, driving the air compressor 9 to rotate, thus recovering residual energy. The expanded exhaust gas temperature is significantly reduced, and after heat exchange and cooling via a soft water preheater, it is discharged, achieving both heat energy recovery and improving the exhaust gas emission temperature conditions. Through this dual-source synergistic drive structure, the system operates stably under the dual power of the electric motor and the expander, significantly reducing total power consumption.

[0025] II. Steam Pressure Stabilization and Temperature Control Unit The steam side of the system consists of components such as steam drum 2, high-pressure steam separator 11, high-pressure steam depressurization system, water spray regulation system, and gas-liquid separator 16. The steam generated in steam drum 2 enters the high-pressure steam depressurization system after moisture is removed by the high-pressure steam separator 11.

[0026] The high-pressure steam reduction system consists of a first high-pressure steam reduction valve 12 and a second high-pressure steam reduction valve 13 connected in parallel. The two valves serve as backups for each other. When the main valve malfunctions or closes abnormally, the backup valve can automatically switch to operation to ensure stable steam pressure output of the system and prevent the unit from shutting down due to overpressure.

[0027] The outlet of the high-pressure steam depressurization system is sequentially connected to the water spray regulating system and the gas-liquid separator 16. The water spray regulating system includes an air-to-close water spray regulating valve 14 and a desuperheater 15. When the system temperature rises abnormally or the control signal is interrupted, the water spray regulating valve 14 automatically opens, and atomized water enters the desuperheater 15 to mix with the high-temperature steam for desuperheating. Unatomized condensate is discharged through a steam trap to ensure the purity of subsequent steam. The steam separated by the gas-liquid separator 16 is sent to external users or power generation equipment for use, realizing the external utilization of steam energy. A safety valve 17 is installed on the steam pipeline and can open in time to release pressure when the system experiences overpressure conditions, preventing equipment damage.

[0028] III. Process Gas Circulation and Heat Exchange Unit In this system, the ammonia combustion reactor 1 is used to mix and burn gaseous ammonia with air, with the reaction temperature controlled at 870–875°C. After evaporation and superheating, the ammonia gas is mixed with air supplied by the air compressor 9, and then enters reactor 1 via mixer 3 for combustion to generate nitrogen oxides. A steam superheater is installed inside reactor 1 to superheat the steam output from steam drum 2, thereby improving steam quality and recovering some of the reaction heat energy.

[0029] The high-temperature nitrogen oxide gas generated by the reaction is sequentially cooled and heat-exchanged through the tail gas superheater 4, the second waste boiler 5, the low-pressure gas-to-gas heat exchanger 6, and the low-pressure cooling separator 21. The steam drum 2 forms a forced circulation loop with the first and second waste boilers via the boiler water circulation pump 18, allowing the steam-water mixture to circulate in a closed system for efficient heat exchange. After cooling, the process gas passes through the low-pressure cooling separator 21 to remove condensed acid before entering the nitrogen oxide compressor 8 for pressurization. The pressurized gas then enters the nitric acid absorption tower, reacts with demineralized water to produce nitric acid, and is subsequently sent to the finished acid tank for storage.

[0030] The heat exchange process described above achieves the coupled utilization of combustion heat energy and process steam energy, reducing system energy consumption. The exhaust gas after expansion and work by the exhaust gas expander 10 is discharged after heat exchange in a soft water preheater, effectively utilizing waste heat and reducing environmental heat emissions.

[0031] Through the above structural combination, this invention achieves a highly efficient and energy-saving design that integrates a high-speed electric motor directly driving the compressor unit with exhaust gas energy recovery. Simultaneously, it incorporates dual-valve redundancy and a gas-shutdown protection mechanism in the steam pressure stabilization and temperature control stages, ensuring high safety and reliability. This system can significantly reduce energy consumption and extend equipment operating cycles while ensuring the stability of the nitric acid production process, demonstrating promising prospects for industrial applications.

[0032] Contents not described in detail in this specification are existing technologies known to those skilled in the art. Standard parts used in this invention can all be purchased commercially, and irregularly shaped parts can be custom-made according to the description and drawings. The specific connection methods for each part all employ conventional methods such as bolts, rivets, and welding, which are already mature technologies. The machinery, parts, and equipment all use conventional models from the prior art, and the circuit connections also employ conventional connection methods from the prior art, which will not be detailed here.

[0033] Although embodiments of the present invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the present invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A nitric acid production system using a high-speed electric motor-driven unit, characterized in that: include: Ammonia combustion reactor (1), steam drum (2), mixer (3), tail gas superheater (4), second waste boiler (5), low-pressure gas-to-gas heat exchanger (6), high-speed motor (7), nitrogen oxide compressor (8), air compressor (9), tail gas expander (10), high-pressure steam separator (11), high-pressure steam decompression system, water spray regulation system, gas-liquid separator (16), safety valve (17), boiler water circulation pump (18), gearbox (19), air filter (20) and low-pressure cooling separator (21); The power drive section of the system includes an electric drive unit and an exhaust gas energy recovery unit; The electric drive unit includes the high-speed electric motor (7), which is connected to the oxide nitrogen compressor (8) via a coupling. The exhaust gas energy recovery unit includes the exhaust gas expander (10), which is drivenly connected to the air compressor (9) via another coupling; The nitrogen oxide compressor (8) and the air compressor (9) are poweredly coupled through the gearbox (19); The air compressor (9) is connected to the air filter (20) at its inlet and to the mixer (3) at its outlet. The exhaust gas expander (10) has an inlet connected to an exhaust gas pipeline with a pressure of 3.7 to 4.0 MPa, and an outlet connected to a soft water preheater.

2. The nitric acid production system of a high-speed electric motor driven unit according to claim 1, characterized in that: The high-speed motor (7) is a 6.6kV high-voltage motor; the high-speed motor (7) and the exhaust gas expander (10) form a dual-source cooperative drive structure, which together provide power for the nitrogen oxide compressor (8) and the air compressor (9).

3. The nitric acid production system of a high-speed electric motor driven unit according to claim 1, characterized in that: The steam drum (2) forms a forced circulation heat exchange loop with the first waste pot and the second waste pot (5) in the ammonia combustion reactor (1) through the boiler water circulation pump (18); the ammonia combustion reactor (1) is also equipped with a steam superheater to superheat the steam output from the steam drum (2).

4. The nitric acid production system of a high-speed electric motor driven unit according to claim 1, characterized in that: The high-pressure steam depressurization system includes a first high-pressure steam depressurization valve (12) and a second high-pressure steam depressurization valve (13) arranged in parallel, with the first high-pressure steam depressurization valve (12) and the second high-pressure steam depressurization valve (13) serving as backups for each other; the outlet of the high-pressure steam separator (11) is connected in sequence via the high-pressure steam depressurization system, the water spray regulation system and the gas-liquid separator (16) to deliver steam to users outside the boundary or power generation equipment.

5. The nitric acid production system of a high-speed electric motor driven unit according to claim 1, characterized in that: The water spray regulation system includes an air-to-close water spray regulating valve (14) and a desuperheater (15); the water spray regulating valve (14) is in the open state when there is a fault, so as to prevent the subsequent pipeline from overheating.

6. The nitric acid production system of a high-speed electric motor driven unit according to claim 1, characterized in that: The low-pressure cooling separator (21) is used to condense and separate condensed acid in the process gas, and the separated gas enters the nitrogen oxide compressor (8); the safety valve (17) is installed on the steam pipeline for system overpressure protection.

7. The nitric acid production system of a high-speed electric motor driven unit according to claim 1, characterized in that: The process gas combustion temperature of the ammonia combustion reactor (1) is controlled at 870-875℃; the exhaust gas after it has done work through the exhaust gas expander (10) enters the soft water preheater for cooling before being discharged.

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