Respiratory gas recovery system and method for low-temperature storage tank

Abstract

The invention relates to a low-temperature storage tank respiratory gas recovery system and method. In the low-temperature storage tank respiratory gas recovery system, a low-temperature cold accumulation working medium storage tank and a medium-temperature cold accumulation working medium storage tank are connected to form a storage tank top gas phase space, the storage tank top gas phase space is connected with a solid phase regenerator, the solid phase regenerator is connected with a buffer tank through an inspiration pipeline and an expiration pipeline, and the inspiration pipeline and the expiration pipeline are arranged in parallel. According to the low-temperature storage tank respiratory gas recovery system and method, excessive respiratory gas in the gas-phase space at the top of the storage tank is buffered through the buffer tank, so that the pressure of the gas-phase space at the top of the storage tank is relieved, and safety and stability of the gas-phase space at the top of the storage tank are guaranteed; moreover, the characteristics of the solid phase regenerator can be utilized to realize safer and more stable temperature control on the respiratory gas, and the heat exchange process is not limited by the gas flow and the gas flow direction of the respiratory gas, that is, the influence of nitrogen dissolution on respiratory gas buffer treatment does not need to be considered by adopting the low-temperature storage tank respiratory gas recovery system disclosed by the invention.

Description

Technical Field

[0001] The present invention relates to the field of energy storage technology, and in particular to a low-temperature storage tank breathing gas recovery system and method based on solid-phase cold storage. Background Art

[0002] Liquid air energy storage technology has outstanding advantages such as clean, low carbon, safe, and long life. It is one of the most promising and competitive long-term energy storage technologies. Cold storage technology is the core of the liquid air energy storage system. According to the different cold storage media, cold storage technology is specifically divided into liquid phase cold storage, phase change cold storage, and solid phase cold storage. The liquid air energy storage system based on liquid phase cold storage is more efficient. However, during the storage and release process, as the liquid phase cold storage medium enters and exits the cold storage medium storage tank, the pressure of the gas phase space at the top of the tank will also change. When the pressure of the top gas phase space reaches the upper or lower limit of the tank design pressure, in order to ensure the safety of the system and meet environmental protection requirements, the breathing gas needs to be recovered and processed.

[0003] However, the existing liquid air energy storage breathing gas recovery systems generally have the following defects. For example: the breathing gas recovery system connected to the top of the atmospheric pressure cold storage medium tank, since the allowable pressure fluctuation range of the atmospheric pressure tank is generally narrow, the tank is prone to overpressure and negative pressure during the breathing gas recovery process; the breathing gas recovery system connected to the top of the high-pressure cold storage medium tank has the problem of excessively high investment costs, and is only suitable for small liquid air energy storage systems; and for large liquid air energy storage systems, the temperature and pressure changes involved in the breathing gas processing process are very likely to lead to problems such as increased related equipment costs and partial waste of cooling capacity.

[0004] More importantly, existing liquid air energy storage systems usually use nitrogen as the protective gas for the cold storage medium during actual operation, so the dissolution of nitrogen in the cold storage medium is inevitable. However, existing liquid air energy storage systems are usually designed directly according to the insoluble nitrogen, and in actual operation, the dissolution of nitrogen in the cold storage medium has a great influence on the change in the volume of breathing gas and the direction of airflow. It can be seen that the prior art still has the problem that for large-scale liquid air energy storage systems, the dissolution of nitrogen in the cold storage medium makes it difficult to accurately design the heat exchanger equipment of the breathing gas system. Summary of the invention

[0005] The present invention provides a low-temperature storage tank breathing gas recovery system and method, which are used to solve the problem in the prior art that, for large-scale liquid air energy storage systems, it is difficult to accurately design the breathing gas system heat exchanger equipment due to the dissolution of nitrogen in the cold storage working medium.

[0006] The present invention provides a low-temperature storage tank breathing gas recovery system, comprising a low-temperature cold storage working fluid storage tank, a medium-temperature cold storage working fluid storage tank, a buffer tank and a solid-phase cold storage device; the low-temperature cold storage working fluid storage tank is connected to the medium-temperature cold storage working fluid storage tank and forms a gas phase space at the top of the storage tank, the gas phase space at the top of the storage tank is connected to the solid-phase cold storage device, the solid-phase cold storage device is connected to the buffer tank through an intake pipeline and an exhalation pipeline respectively, and the intake pipeline and the exhalation pipeline are arranged in parallel.

[0007] The low-temperature storage tank breathing gas recovery system provided by the present invention also includes a pressure reducing valve and a pressure gauge. The pressure reducing valve is installed in series on the air intake pipeline, and the pressure gauge is connected to the gas phase space at the top of the storage tank. The pressure gauge is controlled in linkage with the pressure reducing valve.

[0008] The low-temperature storage tank breathing gas recovery system provided by the present invention also includes an exhaust gas treatment pipeline, which is connected between the gas phase space at the top of the storage tank and the solid phase cold storage device; the exhaust gas treatment pipeline is equipped with an emission control valve, and the pressure gauge is linked to the emission control valve for control.

[0009] According to the low-temperature storage tank breathing gas recovery system provided by the present invention, the gas outlet end of the tail gas treatment pipeline is connected to a flare system.

[0010] The low-temperature storage tank breathing gas recovery system provided by the present invention also includes a compressor and an air cooler, which are installed in series on the exhalation pipeline, and the compressor and the air cooler are connected in sequence between the solid phase cold storage device and the cache tank.

[0011] According to the low-temperature storage tank breathing gas recovery system provided by the present invention, the low-temperature cold storage working fluid storage tank is connected to the medium-temperature cold storage working fluid storage tank through a first pipeline, and a first valve body is installed on the first pipeline; the gas phase space at the top of the storage tank is connected to the solid phase cold storage device through a second pipeline, and a second valve body is installed on the second pipeline; a third valve body is installed on the exhalation pipeline, and a fourth valve body is installed on the inhalation pipeline.

[0012] The present invention also provides a method for recovering breathing gas from a cryogenic storage tank, which is performed using the cryogenic storage tank breathing gas recovery system as described above; the method for recovering breathing gas from a cryogenic storage tank includes an exhalation step and an inhalation step.

[0013] The exhalation step includes: if the pressure of the gas phase space at the top of the storage tank reaches a predetermined upper limit value, the gas phase space at the top of the storage tank releases airflow to the solid phase cold storage device, and the airflow flowing through the solid phase cold storage device enters the cache tank through the exhalation pipeline for storage.

[0014] The air intake step includes: if the pressure of the gas phase space at the top of the storage tank reaches a predetermined lower limit value, the gas phase space at the top of the storage tank inhales airflow from the cache tank, and the airflow stored in the cache tank is sucked out through the air intake pipeline and flows through the solid phase cold storage device, and finally enters the gas phase space at the top of the storage tank.

[0015] According to the breathing gas recovery method of a low-temperature storage tank provided by the present invention, in the exhalation step, the airflow released from the gas phase space at the top of the storage tank first flows through the solid-phase cold storage device to increase the temperature, and then enters the buffer tank for storage after being pressurized and cooled in the exhalation pipeline; in the inhalation step, the airflow in the buffer tank first undergoes a pressure reduction process in the inhalation pipeline, and then is inhaled into the gas phase space at the top of the storage tank after being cooled in the solid-phase cold storage device.

[0016] According to the low-temperature storage tank breathing gas recovery method provided by the present invention, in the inhalation step, if the pressure of the gas phase space at the top of the storage tank reaches a predetermined upper limit value, the pressure reducing valve of the inhalation pipeline is triggered to open.

[0017] According to the low-temperature storage tank breathing gas recovery method provided by the present invention, the low-temperature storage tank breathing gas recovery method also includes an exhaust gas treatment step; in the exhaust gas treatment step, if the pressure of the gas phase space at the top of the storage tank exceeds a predetermined upper limit value and reaches a danger warning value, the exhaust gas emission pipeline is triggered to open, so that the airflow released from the gas phase space at the top of the storage tank enters the exhaust gas emission pipeline.

[0018] The low-temperature storage tank breathing gas recovery system provided by the present invention comprises a low-temperature cold storage working fluid storage tank, a medium-temperature cold storage working fluid storage tank, a buffer tank and a solid-phase cold storage device; the low-temperature cold storage working fluid storage tank is connected to the medium-temperature cold storage working fluid storage tank and forms a gas phase space at the top of the storage tank, the gas phase space at the top of the storage tank is connected to the solid-phase cold storage device, the solid-phase cold storage device is connected to the buffer tank through an intake pipe and an exhalation pipe respectively, and the intake pipe and the exhalation pipe are arranged in parallel. In the low-temperature storage tank breathing gas recovery system and method, the excess breathing gas in the gas phase space at the top of the storage tank is buffered by the buffer tank, thereby alleviating the pressure of the gas phase space at the top of the storage tank and ensuring the safety and stability of the gas phase space at the top of the storage tank.

[0019] On this basis, a solid phase cold storage device is used to recover the cold energy of the airflow during the caching process of the breathing gas in the storage tank, so that the characteristics of the solid phase cold storage device can be used to achieve safer and more stable temperature control of the breathing gas, and the breathing gas is not restricted by the gas flow and airflow direction during the heat exchange process, so as to effectively avoid the situation where the airflow direction of the breathing gas is opposite to the energy storage stage and the energy release stage of the energy storage system. That is, compared with the traditional liquid medium heat exchange device, the low-temperature storage tank breathing gas recovery system of the present invention does not need to consider the impact of nitrogen dissolution on the breathing gas caching process, thereby solving the problem of difficulty in accurately designing the heat exchanger equipment of the breathing gas system caused by the dissolution of nitrogen in the cold storage medium in the large-scale liquid air energy storage system.

[0020] Furthermore, a solid phase cold storage device is used to recover the cold energy of the exhaled airflow from the gas phase space at the top of the storage tank, so that the breath air can be quickly reheated. This can effectively avoid the defect of expensive equipment costs caused by directly low-temperature compression of the breath air, avoid the waste of airflow cold energy, and improve the overall safety and stability of the system.

[0021] Furthermore, the solid phase cold storage device uses solid phase cold storage materials for heat exchange and cold storage. Its principle is to use the low temperature characteristics of the cold storage material to absorb and maintain cold during the cooling stage. Compared with traditional heat exchangers using liquid phase cold storage materials and phase change cold storage materials, it is safer and more environmentally friendly.

[0022] It can be seen that the low-temperature storage tank breathing gas recovery system described in the present invention is not restricted by the airflow rate and airflow direction during the breathing gas buffering process, so that the nitrogen dissolution situation will not affect the airflow direction and heat exchange direction of the breathing gas, thereby making the system applicable to various types of cold storage tanks where nitrogen dissolution is prone to occur and energy storage systems with such tanks, with a wide range of applications, large room for promotion, and safety and stability.

[0023] The present invention also provides a method for recovering breathing gas from a cryogenic storage tank, which is performed using the above-mentioned cryogenic storage tank breathing gas recovery system, and thus can have all the advantages of the above-mentioned cryogenic storage tank breathing gas recovery system, and the details will not be repeated here.

[0024] Moreover, the method for recovering breathing gas from a cryogenic storage tank specifically includes an exhalation step and an inhalation step. In the exhalation step, if the pressure of the gas phase space at the top of the storage tank reaches a predetermined upper limit, the gas phase space at the top of the storage tank releases airflow to the solid phase cold storage device, and the airflow flowing through the solid phase cold storage device enters the cache tank through the exhalation pipeline for storage. In the inhalation step, if the pressure of the gas phase space at the top of the storage tank reaches a predetermined lower limit, the gas phase space at the top of the storage tank inhales airflow from the cache tank, and the airflow stored in the cache tank is sucked out through the inhalation pipeline and flows through the solid phase cold storage device, and finally enters the gas phase space at the top of the storage tank. It can be seen that this method can cache and control the breathing gas based on the pressure of the gas phase space at the top of the storage tank, and can realize autonomous judgment and execution of exhalation and inhalation, thereby ensuring the stability of the pressure of the gas phase space at the top of the storage tank, improving the safety of the gas phase space at the top of the storage tank, and also improving the safety and stable operation of the connected energy storage system. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] In order to more clearly illustrate the technical solutions in the present invention or the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0026] Figure 1 It is a structural schematic diagram of the low-temperature storage tank breathing gas recovery system provided by the present invention.

[0027] Reference numerals: 1. Medium-temperature cold storage tank; 2. Low-temperature cold storage tank; 3. First valve body; 4. Second valve body; 5. Solid phase cold storage device; 6. Third valve body; 7. Compressor; 8. Air cooler; 9. Buffer tank; 10. Pressure reducing valve; 11. Fourth valve body; 12. Emission control valve; P, pressure gauge. DETAILED DESCRIPTION

[0028] In order to make the purpose, technical solution and advantages of the present invention clearer, the technical solution of the present invention will be clearly and completely described below in conjunction with the drawings of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0029] Combine the following Figure 1The cryogenic storage tank breathing gas recovery system and method of the present invention are described. In the embodiments of the present invention, the cryogenic storage tank breathing gas recovery system may be referred to as "recovery system" or "system", and the cryogenic storage tank breathing gas recovery method may be referred to as "recovery method" or "method". The recovery system and recovery method described in the present invention may refer to each other.

[0030] Figure 1 Schematic diagram of the structure of the low-temperature storage tank breathing gas recovery system provided by the embodiment of the present invention. Figure 1 As shown, the recovery system described in the embodiment of the present invention includes a low-temperature cold storage working fluid storage tank 2, a medium-temperature cold storage working fluid storage tank 1, a buffer tank 9 and a solid phase cold storage device 5. The low-temperature cold storage working fluid storage tank 2 and the medium-temperature cold storage working fluid storage tank 1 are used to connect to an external energy storage system, such as a liquid air energy storage system. Preferably, the cold storage working fluid stored in the low-temperature cold storage working fluid storage tank 2 and the medium-temperature cold storage working fluid storage tank 1 is a deep low-temperature cold storage working fluid propane. During the energy storage stage and the energy release stage of the energy storage system, as the cold storage working fluid enters and exits the storage tank, the pressure of the gas phase space at the top of each storage tank will also change accordingly. In order to avoid excessive pressure exceeding the upper limit of the tank pressure design, the low-temperature cold storage working fluid storage tank 2 is connected to the medium-temperature cold storage working fluid storage tank 1 and forms a gas phase space at the top of the tank, so that the pressure between the tanks can be stabilized within a certain range, thereby improving the safety of the system.

[0031] In order to more stably and reliably control the operation of the recovery system, it is preferred that the low-temperature cold storage working medium storage tank 2 is connected to the medium-temperature cold storage working medium storage tank 1 through a first pipeline, and the top of the low-temperature cold storage working medium storage tank 2, the first pipeline and the top of the medium-temperature cold storage working medium storage tank 1 are connected to form a commonly linked tank top gas phase space. A first valve body 3 is installed on the first pipeline, and the first valve body 3 is used to control the on and off of the first pipeline.

[0032] In some embodiments, if the low-temperature cold storage working medium storage tank 2 and the medium-temperature cold storage working medium storage tank 1 are atmospheric pressure storage tanks, then since the allowable pressure fluctuation range of atmospheric pressure storage tanks is relatively narrow, it is easy to cause overpressure and negative pressure in the storage tanks if only the gas phase space at the top of the storage tank is set. Therefore, in the embodiments of the present invention, pressure vessels can be selected as the low-temperature cold storage working medium storage tank 2 and the medium-temperature cold storage working medium storage tank 1.

[0033] In some embodiments, based on the above-mentioned structural setting and taking into account the high investment cost of pressure vessels, they are not suitable for widespread use in large-scale liquid air energy storage systems. Therefore, a buffer tank 9 is additionally provided to connect the gas phase space at the top of the storage tank, and the excess breathing gas in the gas phase space at the top of the storage tank is buffered by the buffer tank 9, thereby alleviating the pressure of the gas phase space at the top of the storage tank and ensuring the safety and stability of the gas phase space at the top of the storage tank. In addition, the provision of the buffer tank 9 can make it possible for the low-temperature cold storage working fluid storage tank 2 and the medium-temperature cold storage working fluid storage tank 1 to avoid the use of pressure vessels and avoid overpressure and negative pressure in the tanks.

[0034] In some embodiments, an intake line and an exhalation line are connected between the buffer tank 9 and the gas phase workpiece at the top of the storage tank, and the intake line and the exhalation line are arranged in parallel. During the operation of the system, when the gas phase space at the top of the storage tank reaches the maximum design pressure, the breathing gas in the gas phase space at the top of the storage tank can enter the buffer tank 9 through the exhalation line for storage; when the gas phase space at the top of the storage tank reaches the minimum design pressure, the gas stored in the buffer tank 9 is sucked back to the gas phase space at the top of the storage tank through the intake line. It can be seen that the buffer tank 9, the exhalation line and the intake line together constitute an external buffer device for the gas phase space at the top of the storage tank, which can stabilize the pressure of the gas phase space at the top of the storage tank and improve the safety of the system.

[0035] In some embodiments, the recovery system further includes a compressor 7 and an air cooler 8, which are installed in series on the exhalation pipeline. During the operation of the system, when the gas phase space at the top of the storage tank reaches the maximum design pressure, the slightly positive pressure gas enters the compressor 7 from the gas phase space at the top of the storage tank for compression and pressurization, and is then cooled by the air cooler 8 and stored in the buffer tank 9 at room temperature and high pressure.

[0036] In some embodiments, the recovery system further includes a pressure reducing valve 10. The pressure reducing valve 10 is connected to the air intake pipeline. When the gas phase space at the top of the storage tank reaches the minimum design pressure, the working fluid in the buffer tank 9 enters the gas phase space at the top of the storage tank after being reduced in pressure to a slightly positive pressure state by the pressure reducing valve 10, and is automatically replenished into the corresponding storage tank under the action of pressure.

[0037] In some embodiments, in order to avoid the respiratory gas being directly compressed by low temperature in the exhalation pipeline, thereby causing the cost increase and cold waste of the compressor 7 equipment, it is preferred that the system also includes a heat exchanger. The gas phase space at the top of the storage tank is connected to the exhalation pipeline and the inhalation pipeline respectively through the heat exchanger. When the gas phase space at the top of the storage tank reaches the maximum design pressure, the slightly positive pressure gas first enters the heat exchanger to release the cold, and the respiratory gas restored to normal temperature is pressurized by the compressor 7 and cooled by the air cooler 8 during the process of flowing through the exhalation pipeline, and is stored in the buffer tank 9 at normal temperature and high pressure state; when the gas phase space at the top of the storage tank reaches the minimum design pressure, the working fluid in the buffer tank 9 is cooled to a low temperature through the heat exchanger, and then reduced to a slightly positive pressure state through the pressure reducing valve 10, and then re-absorbed into the gas phase space at the top of the storage tank. In this process, the heat exchanger not only plays a role in temperature regulation, but also assists in achieving a pressure stabilization effect, increases system stability, and effectively solves the problem of cold waste.

[0038] It should be noted that the cold storage working fluid in the medium-temperature cold storage working fluid storage tank 1 and the low-temperature cold storage working fluid storage tank 2 described in the embodiment of the present invention is a hydrocarbon medium such as propane, methane, propylene, etc., or it can be a single cold storage working fluid of halogenated hydrocarbons such as trifluoromethane and difluoromethane, or it can be a mixed cold storage working fluid composed of the above-mentioned multiple single working fluids.

[0039] It should be noted that the embodiment of the present invention uses a heat exchanger as a cold recovery device for breathing gas, and in fact does not fully consider the impact of the dissolution of nitrogen in the cold storage medium on the system.

[0040] When nitrogen dissolution is not considered, during the energy storage stage of the system, the gas flowing in the gas phase space at the top of the tank cools down, causing the volume to decrease, and the corresponding tank pressure drops; when the lower limit of the tank design pressure is reached, gas needs to be inhaled into the tank; and in the energy release stage of the system, the gas in the gas phase space at the top of the tank heats up, causing the volume to increase, and the tank pressure rises. When the upper limit of the tank design pressure is reached, gas needs to be exhaled out of the tank.

[0041] When nitrogen dissolution is considered, during the energy storage stage of the system, the gas flowing in the gas phase space at the top of the tank cools down, resulting in a decrease in volume and a drop in tank pressure. At the same time, nitrogen solubility decreases with increasing temperature, and nitrogen will escape from the working gas propane. The volume of the escaping nitrogen will to a certain extent compensate for the volume reduction caused by the cooling of the gas. Therefore, whether gas needs to be inhaled or exhaled during this stage depends on the amount of nitrogen dissolved, as described below.

[0042] (1) When the volume of nitrogen released due to the cooling of the cold storage medium is less than the volume reduced by the gas cooling, it is necessary to inhale air into the tank.

[0043] (2) When the volume of nitrogen released due to the cooling of the cold storage medium is approximately equal to the volume reduced due to the cooling of the gas, equilibrium can be reached and breathing gas is no longer needed.

[0044] (3) When the volume of nitrogen released due to the cooling of the cold storage medium is greater than the volume reduced by the cooling of the gas, it is necessary to exhale outside the tank.

[0045] From the above content, it can be seen that when the amount of nitrogen dissolved in the cold storage medium changes greatly with temperature, if the breathing gas recovery system is directly used without considering the nitrogen dissolution situation, large deviations will occur at different stages, causing unstable and unsafe system operation.

[0046] In actual operation, the energy storage system usually uses nitrogen as the protective gas for the cold storage medium. The dissolution of nitrogen in the cold storage medium is inevitable. In addition, the solubility reduction caused by heating and the solubility increase caused by cooling in the cold storage medium are also related to the dissolution equilibrium time, and cannot be simply designed according to the maximum value of the dissolution amount. When the amount of nitrogen dissolved is large, it may happen that: the amount of nitrogen dissolved is small at the beginning of operation, and the energy storage process is an inhalation process. After several energy release cycles, the dissolution equilibrium is reached and it turns to the exhalation process, that is, the transition from inhalation → equilibrium → exhalation occurs. The change in the breathing gas volume of the system and the change in the direction of the breathing gas will make it difficult to set the heat exchanger described in the embodiment of the present invention more accurately, and may even cause interference with the entire breathing gas system, thereby affecting the normal operation of the system.

[0047] In some embodiments, in order to avoid serious impact of nitrogen dissolution on the breathing gas recovery system, it is preferred that the gas phase space at the top of the storage tank described in the embodiment of the present invention is connected to the solid phase cold storage device 5, and the solid phase cold storage device 5 is connected to the buffer tank 9 through the inhalation pipeline and the exhalation pipeline respectively, and the inhalation pipeline and the exhalation pipeline are arranged in parallel. In the process of caching the breathing gas in the storage tank, the solid phase cold storage device 5 is used to recover the cold of the air flow, so that the characteristics of the solid phase cold storage device 5 can be used to achieve safer and more stable temperature control of the breathing gas, and it is not restricted by the air flow and airflow direction of the breathing gas during the heat exchange process, so that the airflow direction of the breathing gas can be effectively avoided. The situation that the energy storage stage and the energy release stage of the energy storage system are opposite to each other can be effectively avoided. That is, compared with the traditional liquid medium heat exchange device, the low-temperature storage tank breathing gas recovery system of the present invention does not need to consider the impact of nitrogen dissolution on the breathing gas cache treatment, thereby solving the problem of difficulty in accurately designing the heat exchanger equipment of the breathing gas system caused by the dissolution of nitrogen in the cold storage medium in the large-scale liquid air energy storage system.

[0048] The solid phase cold storage device 5 is used to recover the cold energy of the exhaled airflow from the gas phase space at the top of the storage tank, so as to quickly reheat the breath. This can effectively avoid the defect of expensive equipment costs caused by directly compressing the breath at low temperatures, avoid the waste of cold energy of the airflow, and improve the overall safety and stability of the system. The solid phase cold storage device 5 uses solid phase cold storage materials for heat exchange and cold storage. The principle is to use the low temperature characteristics of the cold storage material to absorb and maintain cold energy during the cooling stage. Compared with traditional heat exchangers using liquid phase cold storage materials and phase change cold storage materials, it is safer and more environmentally friendly.

[0049] In some specific embodiments, the gas phase space at the top of the storage tank can store exhaled air into the buffer tank 9 in the exhalation step, and the buffer tank 9 can replenish the inhaled air into the gas phase space at the top of the storage tank in the inhalation step. The solid phase cold storage device 5 is used to absorb and store the cold released by the exhaled air in the exhalation step, and release the cold to the inhaled air in the inhalation step, so as to realize heat exchange and energy storage with the exhaled air and the inhaled air. Among them, the heat exchange direction of the solid phase cold storage device 5 is not related to the energy storage stage and the energy release stage of the energy storage system, but only to the above-mentioned exhalation step and inhalation step. That is, the execution process of the exhalation step and the inhalation step can be executed in the energy storage stage of the energy storage system, and can also be executed in the energy release stage of the energy storage system. Due to the phenomenon of nitrogen dissolution in the cold storage working medium, the above-mentioned setting ensures that the nitrogen dissolution conditions such as the nitrogen dissolution amount and the nitrogen dissolution rate will not affect the execution of the exhalation step and the inhalation step.

[0050] It can be seen that the low-temperature storage tank breathing gas recovery system described in the embodiment of the present invention is not restricted by airflow flow and airflow direction during the breathing gas buffering process, and can be applied to various types of cold storage tanks where nitrogen dissolution is prone to occur, as well as energy storage systems with such tanks. It has a wide range of applications, a large space for promotion, and is safe and stable.

[0051] In order to achieve stable and reliable pipeline control between the gas phase space at the top of the storage tank and the solid phase cold storage device 5, the gas phase space at the top of the storage tank is preferably connected to the solid phase cold storage device 5 through a second pipeline, and the second pipeline is equipped with a second valve body 4. The second valve body 4 can control the on and off of the second pipeline.

[0052] Similarly, in order to achieve stable and reliable pipeline control of the exhalation pipeline, it is preferred that a third valve body 6 is installed on the exhalation pipeline, and the third valve body 6 is used to control the on-off of the exhalation pipeline.

[0053] Similarly, in order to achieve stable and reliable pipeline control of the inhalation pipeline, it is preferred that a fourth valve body 11 is installed on the inhalation pipeline, and the fourth valve body 11 is used to control the on-off of the exhalation pipeline.

[0054] In some specific embodiments, the system further comprises the above-mentioned pressure reducing valve 10. The pressure reducing valve 10 is installed in series in the air intake pipeline to reduce the pressure of the gas flowing through, so that the breathing gas is reduced to a slightly positive pressure state before entering the solid phase cold storage device 5, thereby improving the safety of system operation.

[0055] In some embodiments, the compressor 7 and the air cooler 8 are installed in series on the exhalation pipeline, and the compressor 7 and the air cooler 8 are sequentially connected between the solid phase cold storage device 5 and the buffer tank 9. This arrangement ensures that the breathing gas after fully releasing the cold can be pressurized by the compressor 7 before entering the buffer tank 9, and then cooled by the air cooler 8 and reliably stored in the buffer tank 9, thereby improving the safety of system operation.

[0056] In some embodiments, the system also includes a tail gas treatment pipeline. The tail gas treatment pipeline is connected between the gas phase space at the top of the storage tank and the solid phase cold storage device 5. The tail gas treatment management can discharge the excess gas working fluid removed from the gas phase space at the top of the storage tank to the outside, so as to quickly release the pressure in time when the system is in overpressure operation, thereby improving the stability of system operation. In order to achieve reliable and stable pipeline control of the tail gas treatment pipeline, the tail gas treatment pipeline is preferably equipped with an emission control valve 12. The emission control valve 12 is used to control the on and off of the tail gas treatment pipeline. Since the cold storage working fluid used in the energy storage system is a combustible gas such as propane, in order to ensure that the gas emissions meet environmental protection standards, the outlet end of the tail gas treatment pipeline is preferably connected to a flare system, and the flare system is used to ignite the emitted tail gas to ensure that the tail gas emissions do not cause environmental pollution.

[0057] In some embodiments, the system further includes a pressure gauge P. The pressure gauge P is connected to the gas phase space at the top of the storage tank, and is used to monitor the gas pressure of the gas phase space at the top of the storage tank in real time. Preferably, the pressure gauge P is controlled in linkage with the pressure reducing valve 10, so that the pressure reducing valve 10 can be dynamically opened and closed according to the gas phase space at the top of the storage tank, and the air flow pressure value in the air intake pipeline can be adjusted in real time, further improving the safety of system operation. Preferably, the pressure gauge P is controlled in linkage with the discharge control valve 12, so that in the case of overpressure operation of the system, excess gas can be quickly discharged to quickly release pressure for the system.

[0058] Based on Figure 1 The cryogenic storage tank breathing gas recovery system shown in the embodiment of the present invention further describes the cryogenic storage tank breathing gas recovery method in detail. The method is executed by using the above-mentioned cryogenic storage tank breathing gas recovery system, so it can have all the advantages of the above-mentioned cryogenic storage tank breathing gas recovery system, and the details are not repeated here.

[0059] In some embodiments, a cryogenic tank breathing gas recovery method includes an exhalation step and an inhalation step.

[0060] The exhalation step includes: if the pressure of the gas phase space at the top of the storage tank reaches a predetermined upper limit value, the gas phase space at the top of the storage tank releases airflow to the solid phase cold storage device 5, and the airflow flowing through the solid phase cold storage device 5 enters the cache tank 9 through the exhalation pipeline for storage.

[0061] The air intake step includes: if the pressure of the gas phase space at the top of the storage tank reaches a predetermined lower limit value, the gas phase space at the top of the storage tank inhales airflow from the buffer tank 9, and the airflow stored in the buffer tank 9 is sucked out through the air intake pipeline and flows through the solid phase cold storage device 5, and finally enters the gas phase space at the top of the storage tank.

[0062] It can be seen that this method can cache and control the breathing gas based on the pressure of the gas phase space at the top of the storage tank, and can realize autonomous judgment and execution of exhalation and inhalation, thereby ensuring the pressure stability of the gas phase space at the top of the storage tank, improving the safety of the gas phase space at the top of the storage tank, and also improving the safety and stable operation of the connected energy storage system.

[0063] In the above-mentioned exhalation step, the airflow released from the gas phase space at the top of the storage tank first flows through the solid phase cold storage device 5 to release cold energy and thus heat up, and then enters the buffer tank 9 for storage after being pressurized and cooled in the exhalation pipeline. Correspondingly, in the above-mentioned inhalation step, the airflow medium in the buffer tank 9 first undergoes a pressure reduction process in the inhalation pipeline, and then is inhaled into the gas phase space at the top of the storage tank after being cooled in the solid phase cold storage device 5. This process ensures that the breathing gas can flow smoothly between the gas phase space at the top of the storage tank and the buffer tank 9, achieving reliable caching at normal temperature and pressure, and can also achieve stable and reliable recovery to a slightly positive pressure state and return to the gas phase space at the top of the storage tank.

[0064] In some embodiments, in the above-mentioned air intake step, if the pressure of the gas phase space at the top of the storage tank reaches a predetermined upper limit, the pressure reducing valve of the air intake pipeline is triggered to open. This step can ensure that the pressure state of the gas phase space at the top of the storage tank is linked with the medium flow in the air intake pipeline in a timely manner, that is, when the pressure of the gas phase space at the top of the storage tank is too low, air can be sucked from the buffer tank 9 in time to replenish the pressure, thereby avoiding system damage caused by long-term low pressure and improving the reliability of system operation.

[0065] In some embodiments, the cryogenic tank breathing gas recovery method further includes an exhaust gas treatment step. In the exhaust gas treatment step, if the pressure of the gas phase space at the top of the tank exceeds a predetermined upper limit and reaches a dangerous warning value, the exhaust gas emission pipeline is triggered to open, so that the airflow released from the gas phase space at the top of the tank enters the exhaust gas emission pipeline. This step can discharge gas in a timely and rapid manner when the pressure of the gas phase space at the top of the tank is too high, so as to reduce the pressure and maintain stability of the system in a timely manner.

[0066] Based on the above-mentioned recycling system and method, the specific operation process of the system is given in the embodiment of the present invention as follows.

[0067] The system is in the Exhalation phase: Execute the Exhalation step.

[0068] Specifically, the first valve body 3 on the first pipeline between the medium-temperature cold storage working fluid storage tank 1 and the low-temperature cold storage working fluid storage tank 2 is in an open state. When the gas phase space at the top of the storage tank reaches the upper limit of the design pressure, that is, when the indication of the pressure gauge P reaches the upper limit of the tank pressure design, the two cold storage working fluid storage tanks need to exhale outwards. At this time, the second valve body 4 and the third valve body 6 are opened to allow the low-temperature breathing gas to flow out from the gas phase space at the top of the storage tank and release the cold energy through the solid phase cold storage device 5, that is, the solid phase cold storage device 5 absorbs and stores the cold energy from the exhaled gas, and the exhaled gas reheated to room temperature enters the compressor 7 for pressurization, and is cooled to 30°C by the air cooler 8 and then enters the buffer tank 9 for storage; when the pressure of the gas phase space at the top of the storage tank stops increasing, the second valve body 4 and the third valve body 6 can be closed.

[0069] It should be noted that the exhalation phase does not need to limit the system to be in the energy storage phase or the energy release phase. It is sufficient to trigger the relevant control loop to execute the exhalation phase only when the pressure of the gas phase space at the top of the storage tank reaches the maximum value.

[0070] The system is in the Inspiratory phase: Execute the Inspiratory step.

[0071] Specifically, the first valve body 3 between the medium-temperature cold storage working fluid storage tank 1 and the low-temperature cold storage working fluid storage tank 2 is in an open state. When the gas phase space at the top of the storage tank reaches the lower limit of the design pressure, that is, when the indication of the pressure gauge P reaches the lower limit of the tank pressure design, the two cold storage working fluid storage tanks need to inhale air into the tanks. At this time, the second valve body 4 and the fourth valve body 11 are opened, and the interlock is automatically triggered to open the pressure reducing valve 10. The normal temperature and high-pressure breathing gas stored in the buffer tank 9 is reduced in pressure to a slightly positive pressure state through the pressure reducing valve 10, and then enters the solid phase cold storage device 5 to absorb cold energy, and after cooling to a low temperature, it enters the cold storage working fluid storage tank as the suction gas to replenish the pressure.

[0072] It should be noted that the air intake stage does not need to limit the system to be in the energy storage stage or the energy release stage. It is only necessary to trigger the relevant control loop to execute the air intake stage when the pressure of the gas phase space at the top of the storage tank reaches the minimum value.

[0073] Furthermore, to ensure the safe operation of the system, when the breathing gas volume exceeds the upper limit of the system design, in order to avoid overpressure operation of the system, the excess breathing gas needs to be transported to the flare system through the tail gas discharge pipeline. That is, when the pressure gauge P reaches the upper limit and a high alarm occurs, the interlock is automatically triggered to open the discharge control valve 12, thereby discharging the excess breathing gas in the gas phase space at the top of the storage tank to the flare system.

[0074] It should be noted that when the system and method described in the embodiment of the present invention are designed according to the situation where nitrogen is completely undissolved, the two cold storage tanks in the above system inhale air into the tank during the energy storage stage and exhale air out of the system during the energy release stage.

[0075] It should be noted that, when the system and method described in the embodiment of the present invention take nitrogen dissolution into consideration, since the breathing gas direction of the system may be opposite, the breathing gas volume varies with the different time required for the nitrogen to reach dissolution equilibrium in the working fluid and the different storage and release operation times. However, since the system described in the embodiment of the present invention adopts the solid-phase cold storage device 5 as the cold recovery mechanism of the breathing gas, unlike the heat exchanger using the liquid phase heat exchange medium, the solid-phase cold storage device 5 has no strict requirements on the air intake direction and air intake volume, and therefore the above-mentioned nitrogen dissolution situation will not affect the normal operation of the system.

[0076] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A cryogenic tank breathing gas recovery system, characterized in that: It includes a low-temperature cold storage working medium storage tank, a medium-temperature cold storage working medium storage tank, a buffer tank and a solid-phase cold storage device. The low-temperature cold storage working medium storage tank and the medium-temperature cold storage working medium storage tank are both used to connect the energy storage system; the low-temperature cold storage working medium storage tank is connected to the medium-temperature cold storage working medium storage tank and forms a gas phase space at the top of the storage tank, the gas phase space at the top of the storage tank is connected to the solid-phase cold storage device, and the solid-phase cold storage device is connected to the buffer tank through an intake pipe and an exhalation pipe respectively, and the intake pipe and the exhalation pipe are arranged in parallel; The gas phase space at the top of the storage tank can store exhaled air in the buffer tank during the exhalation step, and the buffer tank can replenish inhaled air to the gas phase space at the top of the storage tank during the inhalation step; The solid phase cold storage device is used to absorb and store the cold energy released by the exhaled air in the exhalation step, and release the cold energy to the inhaled air in the inhalation step, so as to realize heat exchange and energy storage with the exhaled air and the inhaled air; Among them, the heat exchange direction of the solid phase cold storage device is not related to the energy storage stage and the energy release stage of the energy storage system.

2. The cryogenic tank breathing gas recovery system according to claim 1, characterized in that: It also includes a pressure reducing valve and a pressure gauge, wherein the pressure reducing valve is installed in series on the air suction pipeline, and the pressure gauge is connected to the gas phase space at the top of the storage tank, and the pressure gauge is linked to the pressure reducing valve for control.

3. The cryogenic tank breathing gas recovery system according to claim 2, characterized in that: It also includes an exhaust gas treatment pipeline, which is connected between the gas phase space at the top of the storage tank and the solid phase cold storage device; the exhaust gas treatment pipeline is equipped with an emission control valve, and the pressure gauge is linked to the emission control valve for control.

4. The cryogenic tank breathing gas recovery system according to claim 3, characterized in that: The gas outlet end of the tail gas treatment pipeline is connected with a flare system.

5. The cryogenic tank breathing gas recovery system according to any one of claims 1 to 4, characterized in that: It also includes a compressor and an air cooler, which are installed in series on the exhalation pipeline, and the compressor and the air cooler are connected in sequence between the solid phase cold storage device and the cache tank.

6. The cryogenic tank breathing gas recovery system according to any one of claims 1 to 4, characterized in that: The low-temperature cold storage working medium storage tank is connected to the medium-temperature cold storage working medium storage tank through a first pipeline, and a first valve body is installed on the first pipeline; the gas phase space at the top of the storage tank is connected to the solid phase cold storage device through a second pipeline, and a second valve body is installed on the second pipeline; a third valve body is installed on the exhalation pipeline, and a fourth valve body is installed on the inhalation pipeline.

7. A method for recovering breathing gas from a cryogenic storage tank, characterized in that: The method is performed using the cryogenic storage tank breathing gas recovery system according to any one of claims 1 to 6; the cryogenic storage tank breathing gas recovery method comprises an exhalation step and an inhalation step; The exhalation step comprises: If the pressure of the gas phase space at the top of the storage tank reaches a predetermined upper limit, the gas phase space at the top of the storage tank releases airflow to the solid phase cold storage device, and the airflow flowing through the solid phase cold storage device enters the cache tank through the exhalation pipeline for storage; The inhalation step comprises: If the pressure of the gas phase space at the top of the storage tank reaches a predetermined lower limit, the gas phase space at the top of the storage tank draws in air from the cache tank, and the airflow stored in the cache tank is sucked out through the air intake pipeline and flows through the solid phase cold storage device, and finally enters the gas phase space at the top of the storage tank.

8. The method for recovering breathing gas from a cryogenic storage tank according to claim 7, characterized in that: In the exhalation step, the airflow released from the gas phase space at the top of the storage tank first flows through the solid phase cold storage device to increase the temperature, and then enters the cache tank for storage after being pressurized and cooled in the exhalation pipeline; In the air intake step, the airflow in the buffer tank is first subjected to a pressure reduction process in the air intake pipeline, and then is cooled by the solid phase cold storage device before being sucked into the gas phase space at the top of the storage tank.

9. The method for recovering breathing gas from a cryogenic storage tank according to claim 8, characterized in that: In the air intake step, if the pressure of the gas phase space at the top of the storage tank reaches a predetermined upper limit value, the pressure reducing valve of the air intake pipeline is triggered to open.

10. The method for recovering breathing gas from a cryogenic storage tank according to claim 7, characterized in that: The cryogenic storage tank breathing gas recovery method further comprises an exhaust gas treatment step; In the exhaust gas treatment step, if the pressure of the gas phase space at the top of the storage tank exceeds a predetermined upper limit and reaches a danger warning value, the exhaust gas emission pipeline is triggered to open, so that the airflow released from the gas phase space at the top of the storage tank enters the exhaust gas emission pipeline.

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