An ammonia tank evaporation gas self-liquefaction cooling and pressure reducing system and a control method thereof

Abstract

This invention discloses a self-liquefaction cooling and depressurization system for evaporated gas from a liquid ammonia storage tank and its control method. The system includes a liquid ammonia storage tank, an evaporated gas extraction pipeline, a vapor-liquid separator, a compressor, a condenser, two condensate branches, an expansion valve, and an in-tank spray device. The condenser's liquid phase outlet is divided into two paths. A jet pump is installed on the second condensate branch, with its ejector medium inlet connected to the upstream of the second condensate branch and its main fluid inlet connected to the bottom liquid phase outlet of the vapor-liquid separator. The vapor-liquid separator is equipped with a level sensor, and each of the two condensate branches has a linkage control valve. The level sensor and the two valves are interlocked to switch the condensate path. The method uses the evaporated gas produced by the storage tank as the sole refrigerant. After compression, condensation, and adiabatic throttling by the expansion valve, a low-temperature gas-liquid two-phase refrigerant is generated and injected into the tank for direct heat exchange, achieving self-liquefaction and recovery of the evaporated gas and cooling and depressurization of the storage tank. This invention requires no external cold source, achieves zero emission of evaporated gas, has low energy consumption, and is a simple and stable system.

Description

Technical Field

[0001] This invention relates to the field of cryogenic liquid ammonia storage technology, specifically to a liquid ammonia storage tank evaporation gas self-liquefaction cooling and depressurization system and its control method. Background Technology

[0002] Ammonia fuel, as a zero-carbon fuel, has attracted widespread attention in the fields of shipping and energy storage. Ammonia is typically stored in fuel tanks as liquid ammonia at -33°C. During storage, heat leakage from the environment continuously penetrates the tank walls into the liquid ammonia inside the tank. The liquid ammonia absorbs heat and vaporizes, continuously generating ammonia vapor gas (BOG). Ammonia gas accumulates in the gas phase space of the tank, leading to an increase in tank pressure. If BOG is not effectively treated, the tank will face the risk of overpressure, and the safety valve may frequently trip to release gas, causing safety hazards and environmental pollution.

[0003] Ammonia is toxic and, as a greenhouse gas, its greenhouse effect is approximately 200 times that of carbon dioxide, so its release into the atmosphere must be avoided. Existing BOG (Boiled Air Gaseous) processing technologies mainly include the following schemes: First, recondensation and return to the tank, which uses an external refrigeration unit to provide cooling energy to condense the BOG into a liquid state and then return it to the storage tank. This scheme requires additional refrigeration units, resulting in high energy consumption and system complexity. Second, compression and external transmission, where the BOG is compressed and transported to downstream users. This scheme depends on downstream gas demand, has poor flexibility, and suffers from lag in pressure control. Third, reliquefaction processes using nitrogen expansion refrigeration or mixed refrigerant refrigeration, which involve high investment costs and poor system stability. All of the above schemes suffer to varying degrees from problems such as high energy consumption, large equipment investment, system complexity, or limited applicability.

[0004] Therefore, it is necessary to provide a liquid ammonia storage tank evaporation gas self-liquefaction cooling and depressurization system and its control method to solve the above-mentioned technical problems. Summary of the Invention

[0005] The purpose of this invention is to address the shortcomings of existing technologies by providing a self-liquefaction cooling and depressurization system and control method for evaporated gas from a liquid ammonia storage tank. The system uses the evaporated gas produced by the liquid ammonia storage tank as the sole refrigerant and achieves self-liquefaction and recovery of the evaporated gas and active cooling and depressurization of the storage tank through a closed-loop process of compression-condensation-throttling-spraying.

[0006] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0007] A liquid ammonia storage tank evaporator self-liquefaction cooling and depressurization system includes a liquid ammonia storage tank, an evaporator extraction pipeline, a vapor-liquid separator, a compressor, a condenser, a first condensate branch, a second condensate branch, an expansion valve, and an in-tank spray device. The evaporator extraction pipeline connects the vapor phase space of the liquid ammonia storage tank to the inlet of the vapor-liquid separator. The vapor phase outlet of the vapor-liquid separator is connected to the compressor's suction port, and the compressor's discharge port is connected to the condenser's heat medium inlet. The condenser's liquid phase outlet branches into two parallel branches: one is the first condensate branch, and the other is the second condensate branch. The first and second condensate branches merge and connect to a condensate main pipe, which in turn connects to the expansion valve. The expansion valve's outlet is connected via a pipeline to an in-tank spray device inside the liquid ammonia storage tank. A jet pump is installed on the second condensate branch. The jet pump's ejector medium inlet is connected upstream of the second condensate branch, its main fluid inlet is connected to the liquid phase outlet at the bottom of the vapor-liquid separator, and its mixing outlet is connected downstream of the second condensate branch. The vapor-liquid separator is equipped with a level sensor. A first linkage control valve is installed on the first condensate branch, and a second linkage control valve is installed on the second condensate branch. The level sensor is interlocked with the first and second linkage control valves to switch the on / off states of the first and second condensate branches.

[0008] Preferably, a three-way thermostatic valve is installed on the cooling water inlet pipe of the condenser. The inlet of the three-way thermostatic valve is connected to the outlet of the central freshwater cooling pump, and the main outlet of the three-way thermostatic valve is connected to the cooling side inlet of the condenser. A cooling water circuit is provided between the cooling side outlet of the condenser and the inlet of the central cooler. The bypass outlet of the three-way thermostatic valve is connected to the cooling water circuit. The inlet of the central freshwater cooling pump is connected to the outlet of the central cooler, and the central cooler cools the circulating freshwater through seawater. A temperature sensor is installed on the condensate main pipe. The temperature sensor is linked to the three-way thermostatic valve for control, and is used to adjust the opening ratio of the main outlet and the bypass outlet of the three-way thermostatic valve according to the detected ammonia medium temperature.

[0009] Preferably, a one-way valve is provided on the second condensate branch connected to the mixing outlet of the jet pump.

[0010] A method for self-liquefying, cooling, and depressurizing the evaporated gas from a liquid ammonia storage tank using the above system includes the following steps:

[0011] The ammonia vapor generated in the liquid ammonia storage tank is extracted and sent to the gas-liquid separator for gas-liquid separation. The separated gaseous ammonia is drawn by the compressor and adiabatically compressed to 1.5MPa~1.8MPa to form high temperature and high pressure gaseous ammonia.

[0012] The compressed high-temperature and high-pressure gaseous ammonia is sent into a condenser and cooled to below 40°C by heat exchange with cooling water, so that it changes phase to high-pressure room-temperature liquid ammonia.

[0013] Switch the condensate mode based on the liquid ammonia level in the vapor-liquid separator:

[0014] When the liquid ammonia level in the vapor-liquid separator is lower than the alarm level of the liquid level sensor, the first linkage control valve is opened and the second linkage control valve is closed, and the high-pressure liquid ammonia is sent directly to the expansion valve through the first condensate branch.

[0015] When the liquid ammonia level in the vapor-liquid separator reaches or exceeds the alarm level of the liquid level sensor, the first linkage control valve is closed and the second linkage control valve is opened. The high-pressure liquid ammonia enters the ejector pump through the second condensate branch and serves as the ejector medium. At the same time, the liquid ammonia at the bottom of the vapor-liquid separator is sent into the ejector pump as the main fluid. The two streams of liquid ammonia are mixed in the ejector pump and then sent to the expansion valve through the check valve.

[0016] The high-pressure liquid ammonia fed into the expansion valve expands to 0.1MPa~0.5MPa through adiabatic throttling, generating a gas-liquid two-phase refrigerant with a temperature below -34℃.

[0017] The low-temperature gas-liquid two-phase refrigerant is atomized by the in-tank spraying device and sprayed into the liquid ammonia storage tank. It directly contacts and exchanges heat with the high-temperature liquid ammonia and ammonia vapor in the liquid ammonia storage tank, causing the ammonia vapor to condense and liquefy, while reducing the temperature and pressure inside the liquid ammonia storage tank.

[0018] Compared with the prior art, the present invention has the following advantages:

[0019] 1. Using the ammonia vapor produced by the liquid ammonia storage tank as the sole refrigerant, no external cold source is required. The ammonia vapor that traditionally requires emission treatment is transformed into a refrigerant, achieving zero emission recovery of ammonia vapor and eliminating the environmental pollution and safety risks caused by ammonia being released into the atmosphere.

[0020] 2. By using a closed-loop process of compression-condensation-throttling expansion-spraying, refrigeration is achieved by utilizing the latent heat of phase change of the ammonia vapor gas itself, thus avoiding the high equipment investment and high energy consumption problems caused by the additional configuration of external refrigeration units in traditional reliquefaction schemes.

[0021] 3. The system automatically switches the condensate mode according to the liquid level in the vapor-liquid separator: when the liquid level is low, the main line is directly supplied, which is simple and efficient; when the liquid level alarm is triggered, the system switches to the jet pump mixing branch, which uses the excess liquid ammonia at the bottom of the tank to participate in the circulation, quickly consumes the liquid accumulated in the separator, and prevents the liquid ammonia from being sucked into the compressor due to excessive liquid level, which may cause liquid slugging risk. At the same time, the mixing of the two liquid ammonia streams increases the liquid phase ratio before throttling, which enhances the cooling effect and balances equipment safety and cooling efficiency.

[0022] 4. The cooling water circuit is linked to the three-way temperature control valve through a temperature sensor. The flow rate of cooling water entering the condenser is adjusted in real time according to the temperature of the ammonia medium on the condensate main pipe. The heat exchange load is dynamically matched to ensure that the temperature of the medium at the condenser outlet is stably controlled below 40℃, which prevents incomplete liquefaction of ammonia and avoids pump power waste caused by excessive cooling water. Attached Figure Description

[0023] Fig. 1 This is a schematic diagram of the structure of the liquid ammonia storage tank evaporation gas self-liquefaction cooling and depressurization system of the present invention;

[0024] Fig. 2 This is a flowchart illustrating the present invention;

[0025] Among them, 1-liquid ammonia storage tank, 2-evaporator gas extraction pipeline, 3-vapor-liquid separator, 4-compressor, 5-condenser, 6-first condensate branch, 7-second condensate branch, 8-condensate main pipe, 9-expansion valve, 10-in-tank spray device, 11-jet pump, 12-check valve, 13-liquid level sensor, 14-first linkage control valve, 15-second linkage control valve, 16-three-way temperature control valve, 17-central freshwater cooling pump, 18-central cooler, 19-temperature sensor Detailed Implementation

[0026] The present invention will be further illustrated below with reference to the accompanying drawings and specific embodiments. It should be understood that these embodiments are for illustrative purposes only and not for limiting the scope of the invention. After reading this invention, any modifications of the invention in various equivalent forms by those skilled in the art will fall within the scope defined by the appended claims.

[0027] In this invention, unless otherwise explicitly specified and limited, the terms "installation," "setting," "connection," "fixed connection," 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. Unless otherwise explicitly limited, those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0028] In this invention, terms such as "upper," "lower," "bottom," and "top" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are merely relational terms determined for the convenience of describing the structural relationship of the various components or elements of this invention, and do not specifically refer to any component or element in this invention, and should not be construed as limiting this invention.

[0029] like Figs. 1-2As shown, the present invention provides a liquid ammonia storage tank evaporation gas self-liquefaction cooling and depressurization system, which mainly includes a liquid ammonia storage tank 1, an evaporation gas extraction pipeline 2, a vapor-liquid separator 3, a compressor 4, a condenser 5, a first condensate branch 6, a second condensate branch 7, a condensate main pipe 8, an expansion valve 9, an in-tank spray device 10, a jet pump 11, and related control valves and sensors.

[0030] Liquid ammonia storage tank 1 is used to store cryogenic liquid ammonia. During storage, heat from the external environment continuously enters the tank through the tank wall, causing the liquid ammonia to absorb heat and vaporize, continuously generating ammonia vapor gas (BOG) in the tank's gas phase space, thus increasing the gas phase pressure inside the tank.

[0031] Evaporation gas extraction pipe 2 connects the gas phase space of the liquid ammonia storage tank to the inlet of the vapor-liquid separator 3. When the gas phase pressure in the storage tank is higher than the static pressure inside the vapor-liquid separator, the ammonia vapor in the liquid ammonia storage tank enters the upper inlet of the vapor-liquid separator along the evaporation gas extraction pipe under the pressure difference. After the ammonia vapor enters the vapor-liquid separator at high speed, the fluid velocity drops dramatically due to the fact that the flow cross-section of the tank is much larger than that of the inlet pipe. The gas phase density of ammonia is much lower than that of liquid ammonia. Under the action of gravity, the trace amount of misty liquid ammonia carried in the ammonia vapor settles and accumulates at the bottom of the vapor-liquid separator, while the pure gaseous ammonia floats up and remains in the upper gas phase space of the vapor-liquid separator, completing the coarse gas-liquid separation.

[0032] The gas phase outlet of the vapor-liquid separator 3 is connected to the suction port of the compressor 4. The compressor runs continuously, creating a negative pressure at the suction port. This negative pressure, combined with the pressure difference between the liquid ammonia storage tank and the vapor-liquid separator, stably draws in pure gaseous ammonia from the upper part of the vapor-liquid separator. The compressor performs adiabatic compression work on the low-pressure gaseous ammonia, increasing the internal energy of the gas molecules. The pressure and temperature rise simultaneously, pressurizing the gaseous ammonia to 1.8 MPa. After compression, the temperature of the ammonia gas rises to approximately 100°C, forming high-temperature, high-pressure gaseous ammonia.

[0033] The exhaust port of compressor 4 is connected to the heat medium inlet of condenser 5. High-temperature, high-pressure gaseous ammonia enters the condenser under pressure differential, where it exchanges heat with low-temperature circulating fresh water flowing through the pipe side, releasing sensible heat of compression and latent heat of condensation. Under a pressure of 1.8 MPa, the saturated condensation temperature of ammonia is approximately 40°C. The fresh water continuously removes heat, causing the ammonia temperature to drop below 40°C, and the gaseous ammonia completely transforms into high-pressure, room-temperature liquid ammonia.

[0034] The liquid outlet of condenser 5 branches into two parallel branches: a first condensate branch 6 and a second condensate branch 7. These two branches merge and connect to the condensate main pipe 8, which in turn connects to the inlet of expansion valve 9. An ejector pump 11 is installed on the second condensate branch. The ejector medium inlet of the ejector pump is connected upstream of the second condensate branch, the main fluid inlet of the ejector pump 11 is connected to the liquid outlet at the bottom of the vapor-liquid separator 3, and the mixing outlet of the ejector pump is connected downstream of the second condensate branch. A one-way valve 12 is installed on the mixing outlet pipe of the ejector pump. The one-way valve is oriented from the ejector pump towards the condensate main pipe to prevent backflow of the medium from the condensate main pipe side to the ejector pump.

[0035] The vapor-liquid separator is equipped with a liquid level sensor 13, a first linkage control valve 14 is installed on the first condensate branch, and a second linkage control valve 15 is installed on the second condensate branch. The liquid level sensor is interlocked with the first and second linkage control valves to switch the on / off state of the first and second condensate branches.

[0036] The system switches the condensate mode based on the liquid ammonia level in the vapor-liquid separator, as follows:

[0037] When the liquid ammonia level in the vapor-liquid separator is lower than the alarm level of the level sensor 13, the level sensor sends a signal to open the first linkage control valve 14 and close the second linkage control valve 15. At this time, all the high-pressure, room-temperature liquid ammonia output from the condenser is directly sent to the condensate main pipe through the first condensate branch, and then transported to the expansion valve. In this mode, the branch where the jet pump is located is completely cut off, there is no medium flow, and the system operates in a single-path main circulation mode, which is simple and efficient.

[0038] When the liquid ammonia level in the vapor-liquid separator 3 reaches or exceeds the alarm level of the level sensor 13, the level sensor triggers an interlock signal, closing the first linkage control valve 14 and opening the second linkage control valve 15. At this time, the high-pressure, room-temperature liquid ammonia output from the condenser enters the ejector medium inlet of the ejector pump through the second condensate branch, serving as the ejector medium. Simultaneously, the liquid ammonia accumulated at the bottom of the vapor-liquid separator flows out from the liquid phase outlet at the bottom of the tank under the pressure difference between the high pressure inside the tank and the inlet of the ejector pump, and is sent to the main fluid inlet of the ejector pump, serving as the main fluid. The high-pressure liquid ammonia ejector medium is ejected at high speed from the nozzle, forming a local negative pressure in the ejector pump cavity, continuously drawing in the liquid ammonia flowing from the bottom of the vapor-liquid separator. After the two streams of liquid ammonia are homogenized and mixed at high speed in the pump, they are sent to the condensate main pipe through the one-way valve 12, and then transported to the expansion valve.

[0039] High-pressure liquid ammonia in the condensate main flows through the narrow throttling channel of expansion valve 9 under the influence of the huge pressure difference before and after the expansion valve, undergoing free adiabatic expansion. During this process, there is no external heat exchange; the fluid performs work on the surroundings, its internal energy decreases rapidly, and its temperature drops sharply to below -34°C. Some of the high-pressure liquid ammonia flashes into low-temperature ammonia gas, ultimately forming a low-temperature gas-liquid two-phase mixed refrigerant.

[0040] The outlet of the expansion valve is connected to the in-tank spray device 10 inside the liquid ammonia storage tank via a pipeline. Driven by the pressure difference before and after the expansion valve, the low-temperature gas-liquid two-phase refrigerant is transported along the pipeline to the in-tank spray device. After being atomized by the swirling nozzles, it forms a large number of tiny low-temperature droplets, which are evenly distributed above the liquid surface of the storage tank. The low-temperature droplets directly contact and exchange heat with the high-temperature liquid ammonia inside the tank, continuously carrying away the heat loss absorbed by the tank from the environment, reducing the overall liquid temperature of the tank, inhibiting the vaporization of liquid ammonia from the source, and reducing the continuous generation of evaporating gas. At the same time, the high-temperature vaporizing gas at the top of the tank comes into full contact with the low-temperature atomized refrigerant, rapidly condensing back into liquid ammonia, directly reducing the total amount of gaseous medium in the tank. This dual heat exchange effect simultaneously reduces the gaseous pressure of the tank, preventing overpressure and safety valve activation. The heated ammonia gas after heat exchange is collected again in the tank's gaseous space and enters the vapor-liquid separator again along the evaporating gas extraction pipeline, completing a complete closed-loop circulation of the medium.

[0041] A three-way thermostatic valve 16 is installed on the cooling water inlet pipe of condenser 5. The inlet of the three-way thermostatic valve is connected to the outlet of the central freshwater cooling pump 17, and the main outlet of the three-way thermostatic valve is connected to the cooling side inlet of the condenser. A cooling water circuit is provided between the cooling side outlet of the condenser and the inlet of the central cooler 18. The bypass outlet of the three-way thermostatic valve is connected to the cooling water circuit. The inlet of the central freshwater cooling pump 17 is connected to the outlet of the central cooler, which cools the circulating freshwater using seawater.

[0042] A temperature sensor 19 is installed on the condensate main pipe. The temperature sensor is linked to a three-way thermostatic valve for control, adjusting the opening ratio of the main outlet and bypass outlet of the three-way thermostatic valve according to the detected ammonia medium temperature. The temperature sensor collects the temperature of the ammonia medium in the condensate main pipe in real time, with a target control threshold of 40℃. When the measured medium temperature is above 40℃, it indicates that the ammonia condensation is incomplete and the heat exchange is insufficient. The sensor sends a temperature rise signal to the three-way thermostatic valve, which closes the bypass outlet opening, allowing most of the low-temperature fresh water to flow into the condenser through the main outlet. This increases the condenser cooling water flow, enhances the heat exchange and liquefaction of ammonia, and quickly reduces the medium temperature to below 40℃. When the measured medium temperature is below 40℃, it indicates that the condensation heat exchange is excessive and the cooling water is in excess. The sensor sends a low-temperature signal to the three-way thermostatic valve, which opens the bypass outlet opening, allowing a large amount of low-temperature fresh water to bypass the condenser and flow directly into the cooling water circuit through the bypass outlet. This reduces the condenser cooling water flow, lowers the useless power consumption of the seawater pump and freshwater pump, and achieves energy-saving operation. When the temperature is stably maintained at 40℃, the three-way thermostatic valve maintains a fixed bypass opening, and the cooling water system operates in a steady state.

[0043] This invention can be widely applied to the treatment of evaporation gas in storage tanks of marine liquid ammonia transport ships, the treatment of evaporation gas in ammonia fuel storage tanks of dual-fuel ammonia ships, and the control of evaporation gas in onshore liquid ammonia storage tanks, and can replace the configuration of traditional reliquefaction equipment.

[0044] The foregoing description illustrates and describes preferred embodiments of the present invention. As previously stated, it should be understood that the present invention is not limited to the forms disclosed herein and should not be construed as excluding other embodiments. It can be used in various other combinations, modifications, and environments, and can be altered within the scope of the inventive concept described herein through the foregoing teachings or techniques or knowledge in related fields. Any modifications and variations made by those skilled in the art that do not depart from the spirit and scope of the present invention should be within the protection scope of the appended claims.

Claims

1. A self-liquefaction, cooling, and depressurization system for evaporated gas from a liquid ammonia storage tank, characterized in that: The system includes a liquid ammonia storage tank, an evaporator gas extraction pipeline, a vapor-liquid separator, a compressor, a condenser, a first condensate branch, a second condensate branch, an expansion valve, and an in-tank spray device. The evaporator gas extraction pipeline connects the vapor phase space of the liquid ammonia storage tank to the inlet of the vapor-liquid separator. The vapor phase outlet of the vapor-liquid separator is connected to the compressor suction port, and the compressor discharge port is connected to the heat medium inlet of the condenser. The liquid phase outlet of the condenser branches into two parallel branches: one is the first condensate branch, and the other is the second condensate branch. The first and second condensate branches merge and connect to the condensate main pipe, which is connected to the inlet of the expansion valve. The expansion valve... The outlet is connected to the in-tank spraying device inside the liquid ammonia storage tank via a pipeline; a jet pump is installed on the second condensate branch, the ejector medium inlet of the jet pump is connected to the upstream of the second condensate branch, the main fluid inlet of the jet pump is connected to the liquid phase outlet at the bottom of the vapor-liquid separator, and the mixing outlet of the jet pump is connected to the downstream of the second condensate branch; the vapor-liquid separator is equipped with a liquid level sensor, a first linkage control valve is installed on the first condensate branch, and a second linkage control valve is installed on the second condensate branch. The liquid level sensor is interlocked with the first linkage control valve and the second linkage control valve to switch the on / off state of the first condensate branch and the second condensate branch.

2. The liquid ammonia storage tank evaporation gas self-liquefaction cooling and depressurization system according to claim 1, characterized in that: A three-way thermostatic valve is installed on the cooling water inlet pipe of the condenser. The inlet of the three-way thermostatic valve is connected to the outlet of the central freshwater cooling pump, and the main outlet of the three-way thermostatic valve is connected to the cooling side inlet of the condenser. A cooling water circuit is provided between the cooling side outlet of the condenser and the inlet of the central cooler. The bypass outlet of the three-way thermostatic valve is connected to the cooling water circuit. The inlet of the central freshwater cooling pump is connected to the outlet of the central cooler. The central cooler cools the circulating freshwater through seawater. A temperature sensor is installed on the condensate main pipe. The temperature sensor is linked to the three-way thermostatic valve for control. It is used to adjust the opening ratio of the main outlet and the bypass outlet of the three-way thermostatic valve according to the detected ammonia medium temperature.

3. The liquid ammonia storage tank evaporation gas self-liquefaction cooling and depressurization system according to claim 1, characterized in that: A one-way valve is installed on the second condensate branch connected to the mixing outlet of the jet pump.

4. A method for self-liquefying, cooling, and depressurizing the vaporized gas from a liquid ammonia storage tank using the system described in any one of claims 1 to 3, characterized in that, Includes the following steps: The ammonia vapor generated in the liquid ammonia storage tank is extracted and sent to the gas-liquid separator for gas-liquid separation. The separated gaseous ammonia is drawn by the compressor and adiabatically compressed to 1.5MPa~1.8MPa to form high temperature and high pressure gaseous ammonia. The compressed high-temperature and high-pressure gaseous ammonia is sent into a condenser and cooled to below 40°C by heat exchange with cooling water, so that it changes phase to high-pressure room-temperature liquid ammonia. Switch the condensate mode based on the liquid ammonia level in the vapor-liquid separator: When the liquid ammonia level in the vapor-liquid separator is lower than the alarm level of the liquid level sensor, the first linkage control valve is opened and the second linkage control valve is closed, and the high-pressure liquid ammonia is sent directly to the expansion valve through the first condensate branch. When the liquid ammonia level in the vapor-liquid separator reaches or exceeds the alarm level of the liquid level sensor, the first linkage control valve is closed and the second linkage control valve is opened. The high-pressure liquid ammonia enters the ejector pump through the second condensate branch and serves as the ejector medium. At the same time, the liquid ammonia at the bottom of the vapor-liquid separator is sent into the ejector pump as the main fluid. The two streams of liquid ammonia are mixed in the ejector pump and then sent to the expansion valve through the check valve. The high-pressure liquid ammonia fed into the expansion valve expands to 0.1MPa~0.5MPa through adiabatic throttling, generating a gas-liquid two-phase refrigerant with a temperature below -34℃. The low-temperature gas-liquid two-phase refrigerant is atomized by the in-tank spraying device and sprayed into the liquid ammonia storage tank. It directly contacts and exchanges heat with the high-temperature liquid ammonia and ammonia vapor in the liquid ammonia storage tank, causing the ammonia vapor to condense and liquefy, while reducing the temperature and pressure inside the liquid ammonia storage tank.

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