Ammonia gas recycling and circulating system of low-temperature liquid ammonia storage tank and ammonia gas recycling method of low-temperature tank

Abstract

The invention relates to a low-temperature liquid ammonia storage tank gas ammonia recovery circulating system and a low-temperature tank gas ammonia recovery method, and belongs to the technical field of ammonia synthesis refrigeration and storage in a synthesis ammonia process. The system comprises a low-temperature tank, a gas ammonia pipeline, an ammonia compressor refrigeration system for synthesis ammonia production, an ammonia receiving tank and a liquid ammonia pipeline, gas ammonia volatilized by the low-temperature tank is conveyed to a refrigerating system of a synthetic ammonia production line through a gas ammonia pipeline, the gas ammonia is converted into liquid ammonia through an integrated compressor and a condenser, and the liquid ammonia is buffered by an ammonia receiving tank and then circularly returned to the low-temperature tank through a liquid ammonia pipeline. According to the scheme, operation of independent cold insulation equipment is avoided, energy consumption is effectively reduced, the equipment utilization rate is increased, the problem of system ammonia imbalance is solved, and remarkable energy-saving benefits and popularization value are achieved.

Description

Technical Field

[0001] This invention relates to the field of synthetic ammonia technology, specifically to a gaseous ammonia recovery and circulation system for storing cryogenic liquid ammonia and a method for recovering gaseous ammonia from cryogenic tanks. Background Technology

[0002] In the synthetic ammonia industry, cryogenic liquid ammonia storage is a crucial step in ensuring production continuity and safety. Liquid ammonia continuously volatilizes within storage tanks due to ambient temperature fluctuations, generating gaseous ammonia. A recovery system is needed to maintain stable tank pressure and material balance. Current technologies generally employ independent refrigeration systems to handle gaseous ammonia in storage tanks. These systems compress and pressurize the gaseous ammonia using an ice machine, then cool and liquefy it via a condenser, ultimately returning the liquid ammonia to the storage tank for recycling. The core of this system lies in relying on specialized refrigeration equipment to complete the recovery and conversion process of gaseous ammonia.

[0003] However, existing ammonia recovery technologies suffer from high energy consumption, insufficient equipment operating efficiency, and difficulty in maintaining system material balance. Summary of the Invention In view of the above situation and to overcome the defects of the prior art, the present invention provides a gaseous ammonia recovery and circulation system for storing cryogenic liquid ammonia and a method for recovering gaseous ammonia from cryogenic tanks, which at least partially solves the problems mentioned in the background art.

[0004] The technical solution adopted in this invention is as follows: In a first aspect, this application provides a gaseous ammonia recovery and circulation system for storing cryogenic liquid ammonia, comprising: A cryogenic tank, including a gaseous ammonia output end and a liquid ammonia input end, is used to store liquid ammonia and output gaseous ammonia generated by the volatilization of liquid ammonia. The ammonia pipeline has one end connected to the ammonia output end of the cryogenic tank and the other end connected to the inlet end of the ammonia compressor refrigeration system for synthetic ammonia production. A first control valve is installed on the ammonia pipeline. The ammonia compressor refrigeration system for synthetic ammonia production integrates an ammonia compressor and a condenser. Its inlet end receives gaseous ammonia transported by the gaseous ammonia pipeline, and outputs liquid ammonia after compression and cooling. The ammonia receiving tank has a liquid ammonia inlet and a liquid ammonia outlet. Its liquid ammonia inlet is connected to the liquid ammonia outlet of the ammonia compressor refrigeration system used for synthetic ammonia production. It is used to store liquid ammonia and realize liquid level buffer regulation. The liquid ammonia pipeline has one end connected to the liquid ammonia output end of the ammonia receiving tank and the other end connected to the liquid ammonia input end of the cryogenic tank. A second control valve is installed on the liquid ammonia pipeline.

[0005] In a further implementation, the ammonia compressor of the ammonia compressor refrigeration system for synthetic ammonia production compresses gaseous ammonia to 1.0-1.6 MPa, and the condenser cools the compressed gaseous ammonia to 20°C to 40°C to convert it into liquid ammonia.

[0006] In a further implementation, the liquid level in the ammonia receiving tank is maintained in the range of 40%-60%.

[0007] In a further implementation plan, the diameter of the gaseous ammonia pipeline is DN150, and the diameter of the liquid ammonia pipeline is DN250.

[0008] In a further embodiment, the volume of the ammonia receiving tank is 41.1 m³.

[0009] Secondly, this application provides a method for recovering ammonia from cryogenic tank gas, comprising the following steps: S1. The gaseous ammonia generated by the volatilization of liquid ammonia in the cryogenic tank is transported to the ammonia compressor refrigeration system for synthetic ammonia production via the gaseous ammonia pipeline at a pressure of 0.6KPa-3KPa. S2. The ammonia compressor refrigeration system for synthetic ammonia production compresses and cools gaseous ammonia into liquid ammonia, and then transports it to the ammonia receiving tank for storage. S3. Liquid ammonia in the ammonia receiving tank is sent back to the cryogenic tank via the liquid ammonia pipeline, completing the gaseous ammonia recovery cycle.

[0010] The beneficial effects achieved by the present invention using the above method are as follows: By connecting the gaseous ammonia output of the cryogenic tank to the inlet of the ammonia compressor refrigeration system for ammonia production via a gaseous ammonia pipeline, directional transport and efficient recovery of gaseous ammonia are achieved, avoiding the need for independent cold insulation equipment and significantly reducing system energy consumption. Based on the integrated ammonia compressor and condenser design of the ammonia compressor refrigeration system for ammonia production, the transported gaseous ammonia can be compressed and cooled, stably converting it into liquid ammonia and improving the reliability of the recovery process. Connecting the liquid ammonia output of the ammonia compressor refrigeration system to the ammonia receiving tank enables temporary storage and level buffering of liquid ammonia, ensuring system stability under dynamic operating conditions. Connecting the liquid ammonia output of the ammonia receiving tank to the liquid ammonia input of the cryogenic tank via a liquid ammonia pipeline and installing a second control valve forms a closed-loop circulation path for liquid ammonia, effectively solving the problem of material imbalance after gaseous ammonia recovery from the storage tank. The cryogenic tank simultaneously performs the dual functions of liquid ammonia storage and gaseous ammonia output, simplifying the system architecture and improving the overall utilization rate of the equipment. Attached Figure Description

[0011] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0012] Figure 1 This is a schematic diagram of the ammonia recovery and circulation system of the cryogenic liquid ammonia storage tank in an embodiment of the present invention.

[0013] Figure 2 This is a flowchart illustrating the method for recovering ammonia from cryogenic tanks in an embodiment of the present invention.

[0014] Among them, 1. Low temperature tank, 2. Gaseous ammonia pipeline, 3. Ammonia compressor refrigeration system for synthetic ammonia production, 4. Ammonia receiving tank, and 5. Liquid ammonia pipeline. Detailed Implementation

[0015] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0016] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those familiar to those skilled in the art. Furthermore, any methods and materials similar to or equivalent to those described herein may be applied to this invention. The preferred embodiments and materials described herein are for illustrative purposes only and do not limit the scope of this application.

[0017] The endpoints and any values ​​of the ranges disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.

[0018] In current industrial practice, large cryogenic liquid ammonia storage tanks, during long-term static or intermittent feeding processes, experience continuous evaporation of liquid ammonia due to the infiltration of ambient heat, generating a large amount of low-pressure gaseous ammonia. Directly venting this gaseous ammonia not only wastes ammonia resources and poses potential environmental risks, but also exacerbates pressure fluctuations within the tank due to the ineffective removal of heat load, threatening storage and transportation safety. Using a separately installed safety refrigeration unit for ammonia condensation and recovery presents problems such as high equipment investment, high power consumption, and complex operation and maintenance. More critically, when this gaseous ammonia is directly integrated into the main ammonia compressor refrigeration circuit of the synthetic ammonia production system, the original system design only caters to the circulating gaseous ammonia produced by the synthesis section. Introducing low-pressure, low-density gaseous ammonia containing trace impurities from the cryogenic tank can easily trigger a chain reaction of problems, including compressor suction mismatch, sudden changes in condensation load, insufficient liquid ammonia subcooling, and uncontrolled downstream ammonia receiving tank levels. Ultimately, this leads to pressure imbalance in the entire ammonia circulation system, increased cavitation risk of the cold ammonia pump, and even triggering interlocking shutdowns.

[0019] After recognizing the above problems, this application proposes and discloses a gaseous ammonia recovery and circulation system for storing cryogenic liquid ammonia and a method for recovering gaseous ammonia from cryogenic tanks. This system can reuse existing synthetic ammonia refrigeration capacity and is compatible with the characteristics of gaseous ammonia from cryogenic tanks, ensuring the dynamic material and energy balance of the entire system.

[0020] Example 1: like Figure 1 As shown, this embodiment illustrates a cryogenic liquid ammonia storage tank ammonia gas recovery and circulation system, comprising: Cryogenic tank 1 has a gaseous ammonia output end and a liquid ammonia input end, used to store liquid ammonia and output gaseous ammonia generated by the volatilization of liquid ammonia; Ammonia gas pipeline 2 is connected at one end to the ammonia gas output end of the cryogenic tank 1 and at the other end to the gas inlet end of the ammonia compressor refrigeration system 3 for ammonia synthesis production. A first control valve is installed on ammonia gas pipeline 2. The ammonia compressor refrigeration system 3 for synthetic ammonia production integrates an ammonia compressor and a condenser. Its inlet end receives gaseous ammonia transported by gaseous ammonia pipeline 2, and outputs liquid ammonia after compression and cooling. The ammonia receiving tank 4 has a liquid ammonia input end and a liquid ammonia output end. Its liquid ammonia input end is connected to the liquid ammonia output end of the ammonia compressor refrigeration system 3 for synthetic ammonia production, and is used to store liquid ammonia and realize liquid level buffer regulation. The liquid ammonia pipeline 5 is connected at one end to the liquid ammonia output end of the ammonia receiving tank 4 and at the other end to the liquid ammonia input end of the cryogenic tank 1. A second control valve is installed on the liquid ammonia pipeline 5.

[0021] In this embodiment, the cryogenic tank 1 serves as the source of gaseous ammonia. Its gaseous ammonia output end is typically located in the gas phase space at the top of the tank and is led out through a flange or welded interface. The tank material can be selected from 9% Ni steel or austenitic stainless steel with excellent low-temperature toughness. The inner wall is polished to reduce ammonia adsorption. The design pressure is not less than 1.6 MPa and the volume is not less than 500 m³, and it has the ability to store liquid ammonia at −33℃ for a long time. Its liquid ammonia input end is located at the bottom of the tank and is used to receive the cold liquid ammonia that has been circulated back, so as to realize the temperature gradient compensation and pressure suppression inside the tank.

[0022] In this embodiment, the ammonia gas pipeline 2 is the first channel connecting the storage tank and the main refrigeration system. Its function is not only to transport the medium, but also to perform pressure matching and initial flow adjustment. The pipeline is made of seamless carbon steel pipe or low-temperature alloy steel pipe, and the inner surface is pickled and passivated to prevent ammonia stress corrosion.

[0023] In this embodiment, the first control valve is located near the outlet of the cryogenic tank. It can be a pneumatic diaphragm regulating valve or an explosion-proof electric ball valve, and has 0-100% linear regulation capability and fast shut-off function. It is used to respond to the liquid level signal of the ammonia receiving tank 4 or the system differential pressure signal to realize active closed-loop control of the ammonia flow rate.

[0024] In this embodiment, the ammonia compressor refrigeration system 3 for ammonia production is not a new piece of equipment, but rather a functional reuse of an existing unit in the ammonia synthesis plant that serves the deep condensation of circulating ammonia in the synthesis loop. This system typically consists of a multi-stage centrifugal or reciprocating ammonia compressor and a horizontal / vertical shell-and-tube condenser integrated in the same skid, with a rated processing capacity covering 10–50 t / h of gaseous ammonia. Its inlet end is equipped with a dedicated interface and pressure buffer chamber, which can receive low-pressure gaseous ammonia from the cryogenic tank 1, and dynamically match the total intake load under different operating conditions through frequency conversion speed regulation or inlet guide vane adjustment on the compressor suction side. The compression and condensation processes are completed continuously, ensuring that the gaseous ammonia has been pressurized to a suitable condensation pressure range before entering the condenser, thereby efficiently transforming into saturated or slightly subcooled liquid ammonia in the condenser.

[0025] In this embodiment, the ammonia receiving tank 4 is an intermediate container with three functions: temporary storage, pressure stabilization, and liquid level control. The tank is a vertical cylindrical pressure vessel with a design pressure of 1.77 MPa and a design temperature of −40℃~50℃. Its volume is determined based on the maximum instantaneous liquid ammonia reflux flow rate and the allowable liquid level fluctuation range of the system. Its liquid ammonia inlet is located at the upper end of the tank and is connected through a tangential inlet with a defoaming baffle to reduce liquid ammonia impact and entrainment. The liquid ammonia outlet is located at the lower end of the tank and is connected to the liquid ammonia pipeline 5. The tank is equipped with a dual-redundant radar level gauge and a magnetic float level gauge to monitor the liquid level in real time and output a 4–20 mA signal to the DCS system to provide adjustment basis for the second control valve. Its function of "realizing liquid level buffer regulation" refers to maintaining a certain liquid column height in the tank to form a stable static pressure head, so that the liquid ammonia pipeline 5 can obtain a controllable driving pressure difference, avoiding the instability of reflux caused by the outlet pressure fluctuation of the upstream synthetic ammonia production ammonia compressor refrigeration system 3 directly transmitted to the cryogenic tank 1.

[0026] In operation, the gaseous ammonia produced in cryogenic tank 1 enters the ammonia compressor refrigeration system 3 for synthetic ammonia production via gaseous ammonia pipeline 2 and the first control valve. Its flow rate is controlled by the liquid level in ammonia receiving tank 4. When the liquid level is low, the first control valve opens wider to increase the gaseous ammonia supply; when the liquid level is high, it closes to reduce the supply. Liquid ammonia output from system 3 enters ammonia receiving tank 4, and its liquid level changes directly drive the second control valve. When the liquid level rises, the second control valve opens wider to accelerate the reflux; when the liquid level falls, it closes to slow the reflux. Thus, the two control valves form a coupled regulating loop, jointly maintaining the liquid level in ammonia receiving tank 4 within the target range, thereby ensuring stable reflux pressure differential in liquid ammonia pipeline 5, uniform liquid intake in cryogenic tank 1, and dynamic pressure balance of the overall system. This collaborative mechanism does not rely on additional energy input; it achieves adaptive regulation entirely through the inherent pressure gradient and liquid level feedback within the system.

[0027] Without adding any new dedicated cold-keeping equipment, this application achieves the following: all the gaseous ammonia volatilized from the cryogenic liquid ammonia tank is introduced into the existing ammonia compressor refrigeration system 3 for synthetic ammonia production for efficient condensation. The resulting liquid ammonia is buffered by the ammonia receiving tank 4 and then stably returned to the cryogenic tank 1 through the liquid ammonia pipeline 5. Because the gaseous ammonia continuously volatilized from the cryogenic tank 1 is promptly drawn in and converted into liquid ammonia, energy is prevented from dissipating in gaseous form, significantly reducing the system's net energy consumption. Because the gaseous ammonia is incorporated into the main refrigeration circuit for unified processing, replacing the independent operation of the original safety ice machine, the refrigeration efficiency ratio of the entire synthetic ammonia unit is increased by 12-18%. Because the liquid level buffer and dual-valve linkage regulation mechanism of the ammonia receiving tank 4 eliminate the transient disturbances caused by the incorporation of gaseous ammonia into the main system, the overall stability of the synthetic ammonia circulating gaseous ammonia flow, condensation load, and liquid ammonia inventory is ensured. Because the liquid ammonia return directly replenishes the cooling capacity inside the tank and suppresses evaporation, the pressure fluctuation amplitude inside the cryogenic tank 1 is reduced by more than 70%, the net positive suction head (NPSH) of the cold ammonia pump is increased by 25%, and the inherent safety of the system is enhanced. The solution is simple in structure, low in retrofit cost, and highly compatible with existing ammonia synthesis plants, making it suitable for energy-saving upgrades of both new and existing plants.

[0028] Example 2: Based on Example 1, this example further provides: The ammonia compressor in the ammonia compressor refrigeration system 3 for synthetic ammonia production compresses gaseous ammonia to 1.0–1.6 MPa, and the condenser cools the compressed gaseous ammonia to 20°C–40°C, causing it to completely condense into liquid ammonia.

[0029] In this embodiment, by precisely controlling the two key thermodynamic parameters of compression pressure and condensation temperature, it can be ensured that the low-pressure gaseous ammonia from the cryogenic tank 1 can stably, efficiently, and repeatedly complete the entire gas-liquid phase change process after entering the ammonia compressor refrigeration system 3 for synthetic ammonia production.

[0030] Example 3: Based on Example 1, this example further provides: The liquid level in ammonia receiving tank 4 is maintained in the range of 40%–60%.

[0031] In this embodiment, by setting and stabilizing the liquid ammonia storage level in the ammonia receiving tank 4 within a volume ratio range of 40% to 60%, the reliability of the liquid seal and the dynamic adjustment margin are balanced. This ensures that the cold ammonia pump continuously, stably, and without cavitation delivers liquid ammonia, and supports the safe and efficient operation of the entire gaseous ammonia recovery cycle system. This liquid level range is not an empirical threshold, but a safe operating window determined by the coupled constraints of the gaseous ammonia volatilization rate fluctuation characteristics of the cryogenic tank 1, the liquid ammonia production cycle of the ammonia compressor refrigeration system 3 for synthetic ammonia production, and the reflux capacity of the liquid ammonia pipeline 5. This avoids cavitation or flow interruption caused by insufficient liquid level, while also preventing high liquid level from weakening the buffer capacity, which could lead to overflow risks from instantaneous overfeeding or sudden liquid level rises impacting the response accuracy of downstream regulating valves.

[0032] Example 4: Based on Example 1, this example further provides: The diameter of gaseous ammonia pipeline 2 is DN150, and the diameter of liquid ammonia pipeline 5 is DN250.

[0033] In this embodiment, the DN150 ammonia pipeline is used to carry the low-pressure ammonia escaping from the cryogenic tank 1. The design is based on the fact that ammonia has a low density and a large volumetric flow rate under atmospheric pressure to 3 kPa slightly positive pressure conditions, but the requirements for pipe wall strength and sealing are relatively low. Using a DN150 pipe diameter can effectively suppress pressure drop along the flow path while ensuring that the flow velocity is within the safe range of 5–12 m / s, and ensure that the ammonia escaping enters the inlet of the ammonia compressor refrigeration system 3 for synthetic ammonia production in a stable slightly positive pressure state.

[0034] Example 5: Based on Example 1, this example further provides: The volume of ammonia receiving tank 4 is 41.1 m³.

[0035] The 41.1 m³ ammonia receiving tank is an engineering solution that balances stable liquid level control and flow suppression under typical operating conditions. It avoids the frequent occurrence of liquid level reaching the upper and lower limits due to insufficient volume, which would trigger frequent operation of control valves and exacerbate system disturbances. It also prevents excessive volume from causing prolonged liquid ammonia residence time, temperature rise, increased risk of regasification, and redundant land use and investment.

[0036] Example 6: like Figure 2 As shown, this embodiment further provides: A method for recovering ammonia from cryogenic tank gas based on the system according to any one of claims 1–5, comprising the following steps: S1. The gaseous ammonia generated by the volatilization of liquid ammonia in the cryogenic tank 1 is transported to the ammonia compressor refrigeration system 3 for synthetic ammonia production via the gaseous ammonia pipeline 2 at a pressure of 0.6kPa–3kPa. S2, the ammonia compressor refrigeration system 3 for synthetic ammonia production compresses and cools gaseous ammonia into liquid ammonia, and then transports it to the ammonia receiving tank 4 for storage; S3. Liquid ammonia in ammonia receiving tank 4 is sent back to cryogenic tank 1 via liquid ammonia pipeline 5, completing the gaseous ammonia recovery cycle.

[0037] In this embodiment, the slightly positive pressure volatilization characteristics of the cryogenic tank 1 and the wide pressure adaptability of the ammonia pipeline 2 constitute the starting point for gas phase transportation, avoiding additional energy consumption; the efficient compression and condensation of the ammonia by the ammonia compressor refrigeration system 3 for synthetic ammonia production not only completes the phase change, but also precisely controls its thermodynamic state to a suitable saturated liquid state for reflux; the buffer volume and liquid level range setting of the ammonia receiving tank 4 provide dynamic response flexibility for the system and resolve the contradiction of mismatch between gas-liquid conversion rates; the pipe diameter design and differential pressure reflux mechanism of the liquid ammonia pipeline 5 ensure the flow capacity and controllability of the liquid phase closed-loop path.

[0038] Through the above-described steps, this application achieves continuous, stable, and automated recovery of gaseous ammonia from cryogenic tanks. By replacing mechanical pressurization with the evaporation pressure of the storage tank itself, it solves the problems of high energy consumption and large start-up and shutdown impact caused by the frequent start-up and shutdown of the safety ice machine in traditional methods. By reusing the refrigeration capacity of the main synthetic ammonia system, it avoids redundant investment and land occupation of independent refrigeration units, thereby improving the overall utilization rate of the equipment. By linking and regulating the liquid level range (40%–60%) of the ammonia receiving tank with dual control valves, it overcomes the process compatibility problems such as the imbalance of total ammonia circulation and disordered cold energy distribution caused by the introduction of gaseous ammonia into the main refrigeration system. Ultimately, it achieves the triple technical effects of energy saving and consumption reduction (60% reduction in the start-up and shutdown frequency of the safety ice machine), stable system operation (liquid level fluctuation ±5%), and seamless process integration. It is suitable for large-scale engineering applications in the storage and transportation of cryogenic liquid ammonia in large synthetic ammonia plants.

[0039] It should be noted that, in the description of this specification, the references to terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the present invention. 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.

[0040] Although embodiments have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and variations can be made to these embodiments without departing from the principles and spirit, the scope of which is defined by the appended claims and their equivalents.

[0041] The embodiments have been described above, and such description is not restrictive. The figures shown are only one embodiment, and the actual structure is not limited to this. In short, if a person skilled in the art is inspired by this description and designs a similar structure and embodiment without departing from the inventive spirit, such design should fall within the scope of protection.

Claims

1. A gaseous ammonia recovery and circulation system for storing cryogenic liquid ammonia, characterized in that, include: The cryogenic tank (1) includes a gaseous ammonia output end and a liquid ammonia input end; A gaseous ammonia pipeline (2) is connected at one end to the gaseous ammonia output end of the low-temperature tank (1) and at the other end to the gas inlet end of the ammonia compressor refrigeration system (3) for ammonia production. A first control valve is provided on the gaseous ammonia pipeline (2). The ammonia compressor refrigeration system (3) for synthetic ammonia production integrates an ammonia compressor and a condenser. Its inlet end receives the gaseous ammonia transported by the gaseous ammonia pipeline (2), and outputs liquid ammonia after compression and cooling. The ammonia receiving tank (4) has a liquid ammonia input end and a liquid ammonia output end. Its liquid ammonia input end is connected to the liquid ammonia output end of the ammonia compressor refrigeration system (3) for synthetic ammonia production, and is used to store liquid ammonia and realize liquid level buffer regulation. The liquid ammonia pipeline (5) is connected at one end to the liquid ammonia output end of the ammonia receiving tank (4) and at the other end to the liquid ammonia input end of the cryogenic tank (1). A second control valve is provided on the liquid ammonia pipeline (5).

2. The cryogenic liquid ammonia storage tank ammonia gas recovery and circulation system according to claim 1, characterized in that, The ammonia compressor of the ammonia compressor refrigeration system (3) for ammonia production compresses gaseous ammonia to 1.0-1.6 MPa, and the condenser cools the compressed gaseous ammonia to 20°C to 40°C to convert it into liquid ammonia.

3. The cryogenic liquid ammonia storage tank ammonia gas recovery and circulation system according to claim 1, characterized in that, The liquid level in the ammonia receiving tank (4) is maintained in the range of 40%-60%.

4. The cryogenic liquid ammonia storage tank ammonia gas recovery and circulation system according to claim 1, characterized in that, The diameter of the gaseous ammonia pipeline (2) is DN150, and the diameter of the liquid ammonia pipeline (5) is DN250.

5. The cryogenic liquid ammonia storage tank ammonia gas recovery and circulation system according to claim 1, characterized in that, The volume of the ammonia receiving tank (4) is 41.1 m³.

6. A method for recovering ammonia from cryogenic tank gas based on the system described in any one of claims 1-5, characterized in that, Includes the following steps: S1. The gaseous ammonia generated by the volatilization of liquid ammonia in the low-temperature tank (1) is transported to the ammonia compressor refrigeration system (3) for synthetic ammonia production at a pressure of 0.6KPa-3KPa via the gaseous ammonia pipeline (2). S2, The ammonia compressor refrigeration system (3) for synthetic ammonia production compresses and cools gaseous ammonia into liquid ammonia and transports it to the ammonia receiving tank (4) for storage; S3. Liquid ammonia in the ammonia receiving tank (4) is sent back to the cryogenic tank (1) via the liquid ammonia pipeline (5) to complete the gaseous ammonia recovery cycle.

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