Expansion machine shaft seal air leakage recovery system of carbon dioxide energy storage system

Abstract

The embodiment of the utility model provides an expansion machine shaft seal air leakage recovery system of a carbon dioxide energy storage system. The expansion machine shaft seal air leakage recovery system comprises an expansion machine, an expansion machine shaft seal, a shaft seal air leakage collection pipeline, a fan and a carbon dioxide separation device. The expansion machine shaft seal is annularly arranged on a main shaft of the expansion machine and is provided with a shaft seal air leakage recovery air port; the input end of the shaft seal gas leakage collection pipeline is connected with a shaft seal gas leakage recovery gas port of the expansion machine shaft seal, the output end of the shaft seal gas leakage collection pipeline is connected with an inlet of the fan, an outlet of the fan is connected with the carbon dioxide separation device, a first outlet of the carbon dioxide separation device is connected to the gas storage, and a second outlet of the carbon dioxide separation device is communicated with the atmosphere; the carbon dioxide separation device is used for separating the carbon dioxide working medium from shaft seal leakage gas and outputting the carbon dioxide working medium to the gas storage for recovery through the first outlet. According to the expansion machine shaft seal gas leakage recovery system of the carbon dioxide energy storage system, carbon dioxide in expansion machine shaft seal gas leakage can be recovered to a gas storage, and working medium loss is reduced.

Description

Technical Field

[0001] The utility model relates to the technical field of energy storage, in particular to a leakage recovery system for the shaft seal of an expander in a carbon dioxide energy storage system. Background Art

[0002] Carbon dioxide energy storage is a new type of physical energy storage technology using carbon dioxide as the working medium, including technologies such as supercritical carbon dioxide energy storage and gas-liquid phase change carbon dioxide energy storage. Taking the gas-liquid phase change carbon dioxide energy storage technology as an example, it realizes carbon dioxide compression energy storage and expansion energy release based on the gas-liquid phase change of carbon dioxide (carbon dioxide compression and expansion). The carbon dioxide energy storage system can refer to Chinese patents CN112985144B, CN112985145B and CN114109549B. The expander, a power rotating device in the carbon dioxide energy storage system, plays an important role in the process of carbon dioxide working medium expanding and doing work. Since the shafts at both ends of the expander rotor need to extend out of the cylinder, in order to ensure that there is no dynamic and static friction between the rotor and the shafts at both ends of the rotor, a certain gap needs to be left between them, which causes air leakage problems, resulting in the loss of the working medium of the energy storage system and an increase in the operating cost of the energy storage system. In the prior art, gas seals are provided at each shaft end of the expander to reduce the shaft seal air leakage. However, for the expander of the energy storage system with frequent start-stop operation requirements, there is still inevitably a large problem of shaft seal leakage, and there is currently no good solution to the shaft seal air leakage of the expander. Summary of the Utility Model

[0003] Therefore, in order to overcome the problem of the loss of the working medium of the energy storage system caused by air leakage at the shaft seal of the expander in the prior art, an embodiment of the utility model provides a leakage recovery system for the shaft seal of an expander in a carbon dioxide energy storage system, which can recover carbon dioxide in the shaft seal air leakage of the expander to the gas storage tank and reduce the loss of the working medium.

[0004] An embodiment of the utility model provides a leakage recovery system for the shaft seal of an expander in a carbon dioxide energy storage system. The carbon dioxide energy storage system includes a gas storage tank; the leakage recovery system for the shaft seal of the expander includes: an expander, a shaft seal of the expander, a shaft seal air leakage collection pipeline, a fan and a carbon dioxide separation device; the shaft seal of the expander is arranged around the main shaft of the expander and has a shaft seal air leakage recovery air port; the input end of the shaft seal air leakage collection pipeline is connected to the shaft seal air leakage recovery air port of the shaft seal of the expander, the output end of the shaft seal air leakage collection pipeline is connected to the inlet of the fan, the outlet of the fan is connected to the carbon dioxide separation device, the first outlet of the carbon dioxide separation device is connected to the gas storage tank, and the second outlet of the carbon dioxide separation device is communicated with the atmosphere; the carbon dioxide separation device is used to separate carbon dioxide working medium from the shaft seal air leakage and output it to the gas storage tank for recovery through the first outlet.

[0005] In some embodiments, the carbon dioxide separation device includes a pressure swing adsorption device and a vacuum pump; the outlet of the blower is connected to the input end of the pressure swing adsorption device, the inlet of the vacuum pump is connected to the pressure swing adsorption device, and the outlet of the vacuum pump is used as the first outlet and is connected to the gas storage reservoir.

[0006] In some embodiments, the carbon dioxide separation device includes an absorption tower and a regeneration tower; the outlet of the blower is connected to the gas inlet of the absorption tower, the liquid outlet of the absorption tower is connected to the regeneration tower, and the gas outlet of the regeneration tower is used as the first outlet and is connected to the gas storage reservoir; the absorption tower is configured to absorb the carbon dioxide working medium in the shaft seal leakage through an absorbent to form a rich liquid and output the rich liquid to the regeneration tower, and the regeneration tower is configured to desorb the carbon dioxide working medium from the rich liquid and output it to the gas storage reservoir for recovery.

[0007] In some embodiments, the number of the pressure swing adsorption devices is at least two, and at least two pressure swing adsorption devices are arranged in parallel; the working state of each pressure swing adsorption device includes an adsorption state and a desorption state, and when at least one of the at least two pressure swing adsorption devices is in the desorption state during the working state, the other is in the adsorption state; the inlet of the vacuum pump is communicated with the pressure swing adsorption device in the desorption state, and the outlet of the blower is communicated with the pressure swing adsorption device in the adsorption state.

[0008] In some embodiments, the carbon dioxide separation device further includes an absorbent reflux assembly, the input end of the absorbent reflux assembly is connected to the liquid outlet of the regeneration tower, and the output end of the absorbent reflux assembly is connected to the liquid inlet of the absorption tower; after the rich liquid desorbs the carbon dioxide working medium, it becomes the desorbed absorbent, and the absorbent reflux assembly is configured to reflux the desorbed absorbent into the absorption tower to absorb the carbon dioxide working medium.

[0009] In some embodiments, the absorbent reflux assembly includes a reflux pump and a heat exchanger, the inlet of the reflux pump is connected to the liquid outlet of the regeneration tower, the outlet of the reflux pump is connected to the hot side inlet of the heat exchanger, and the hot side outlet of the heat exchanger is connected to the liquid inlet of the absorption tower; the heat exchanger is configured to cool the desorbed absorbent.

[0010] In some embodiments, the carbon dioxide separation device further includes a rich liquid pump, the inlet of the rich liquid pump is connected to the liquid outlet of the absorption tower, the outlet of the rich liquid pump is connected to the cold side inlet of the heat exchanger, and the cold side outlet of the heat exchanger is connected to the liquid inlet of the regeneration tower; the heat exchanger is further configured to use the rich liquid to cool the desorbed absorbent.

[0011] In some embodiments, the carbon dioxide separation device further comprises a water scrubber, the gas outlet of the absorption tower is connected to the gas inlet of the water scrubber, and the gas outlet of the water scrubber is connected to the atmosphere as the second outlet.

[0012] In some embodiments, a carbon dioxide purity detection device is also included. The carbon dioxide purity detection device is connected to the carbon dioxide separation device, and the carbon dioxide purity detection device is used to detect the purity of the carbon dioxide working fluid separated by the carbon dioxide separation device.

[0013] In some embodiments, the expander shaft seal includes a front shaft seal and a rear shaft seal, the front shaft seal is arranged at the air inlet end of the expander and is arranged around the main shaft of the expander, and the rear shaft seal is arranged at the air outlet end of the expander and is arranged around the main shaft of the expander; the front shaft seal and the rear shaft seal both have shaft seal leakage recovery ports, and the shaft seal leakage collection pipeline is respectively connected to the shaft seal leakage recovery ports of the front shaft seal and the rear shaft seal; and / or, the expander shaft seal is a labyrinth shaft seal.

[0014] It can be seen from the above that the above embodiments of the utility model can achieve one or more of the following beneficial effects: the shaft seal leakage at the expander shaft seal is recovered by a fan to the carbon dioxide separation device, and the carbon dioxide working fluid is recovered to the gas storage reservoir after separation by the carbon dioxide separation device, which can minimize the loss of carbon dioxide working fluid (that is, the working working fluid in the carbon dioxide energy storage system), realize the recovery and reuse of carbon dioxide working fluid in the shaft seal leakage, achieve near-zero leakage emission of the expander shaft seal leakage, and reduce the operating cost of the carbon dioxide energy storage system. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] The specific implementation of the present utility model will be described in detail below with reference to the accompanying drawings.

[0016] Figure 1 A schematic structural diagram of an expander shaft seal leakage recovery system provided in an embodiment of the utility model.

[0017] Figure 2 for Figure 1 The schematic diagram of the structure of the expander shaft seal leakage recovery system when applied to the carbon dioxide energy storage system.

[0018] Figure 3 for Figure 2 A schematic structural diagram of a specific embodiment.

[0019] Figure 4 for Figure 2 A schematic structural diagram of another specific embodiment.

[0020] Figure 5Schematic diagram of the reaction mechanism between the absorbent and the carbon dioxide working fluid in an embodiment.

[0021]

Description of the attached drawing reference numerals

[0022] 100. Leakage recovery system for the expander shaft seal; 10. Gas storage reservoir; 20. Expander; 30. Expander shaft seal; 31. Front shaft seal; 32. Rear shaft seal; 40. Pipeline for collecting shaft seal leakage; 50. Fan; 60. Carbon dioxide separation device; 61. First outlet; 62. Second outlet; 63. Pressure swing adsorption device; 64. Vacuum pump; 65. Absorption tower; 66. Regeneration tower; 67. Absorbent reflux assembly; 671. Reflux pump; 672. Heat exchanger; 68. Water washing tower; 69. Rich liquid pump; 70. Liquid storage tank; 80. Evaporator; 90. Superheater. Detailed implementation manners

[0023] To make the above objects, features and advantages of the present utility model more obvious and understandable, the following will describe in detail the specific implementation manners of the present utility model with reference to the attached drawings.

[0024] In order to enable those of ordinary skill in the art to better understand the technical solutions of the present utility model, the following will clearly and completely describe the technical solutions in the embodiments of the present utility model with reference to the attached drawings in the embodiments of the present utility model. Obviously, the described embodiments are only a part of the embodiments of the present utility model, rather than all of the embodiments. Based on the embodiments of the present utility model, all other embodiments obtained by those of ordinary skill in the art without making creative efforts shall fall within the protection scope of the present utility model.

[0025] It should be noted that the terms "first", "second", etc. in the description and claims of the present utility model and the above attached drawings are used to distinguish similar objects, and do not necessarily need to be used to describe a specific order or sequence. It should be understood that such terms can be interchanged under appropriate circumstances so that the embodiments of the present utility model described here can be implemented in an order other than those illustrated or described here. In addition, the terms "include" and "have" and any variations thereof are intended to cover non-exclusive inclusion. For example, a process, method, system, product or device that includes a series of steps or units does not necessarily have to be limited to those clearly listed steps or units, but may include other steps or units not clearly listed or inherent to these processes, methods, products or devices.

[0026] It should also be noted that the division of multiple embodiments in the present utility model is only for the convenience of description and should not constitute a special limitation. The features in various embodiments can be combined and cross-referenced without contradiction.

[0027] Refer to Figure 1, an embodiment of the present utility model provides a leakage recovery system 100 for the expander shaft seal of a carbon dioxide energy storage system. The carbon dioxide energy storage system includes a gas storage reservoir 10. The leakage recovery system 100 for the expander shaft seal includes: an expander 20, an expander shaft seal 30, a shaft seal leakage collection pipeline 40, a fan 50, and a carbon dioxide separation device 60. The expander shaft seal 30 is annularly arranged on the main shaft of the expander 20 and has a shaft seal leakage recovery air port. The input end of the shaft seal leakage collection pipeline 40 is connected to the shaft seal leakage recovery air port of the expander shaft seal 30, the output end of the shaft seal leakage collection pipeline 40 is connected to the inlet of the fan 50, the outlet of the fan 50 is connected to the carbon dioxide separation device 60, the first outlet 61 of the carbon dioxide separation device 60 is connected to the gas storage reservoir 10, and the second outlet 62 of the carbon dioxide separation device 60 is communicated with the atmosphere. The carbon dioxide separation device 60 is used to separate the carbon dioxide working medium from the shaft seal leakage and output it to the gas storage reservoir 10 for recovery through the first outlet 61.

[0028] Among them, the carbon dioxide working medium is the working medium in the carbon dioxide energy storage system. According to the different positions and stages of the carbon dioxide working medium, the carbon dioxide working medium can have different forms, such as liquid state, gaseous state, gas-liquid mixed state, etc. However, carbon dioxide in these different states can all be called the carbon dioxide working medium.

[0029] Refer to Figure 2 , in a carbon dioxide energy storage system, it includes a liquid storage tank 70, an evaporator 80, a superheater 90, an expansion energy release part represented by the expander 20, a gas storage reservoir 10, and Figure 2 a compression energy storage part not shown in

[0030] Among them, the gas storage reservoir 10 is a double-layer membrane structure, including an inner film, an inner membrane, and an outer membrane; the outer membrane is used to resist wind and snow. There is an interlayer cavity between the inner membrane and the outer membrane. The gas in the interlayer cavity supports the outer membrane upward to maintain its shape, so that the gas storage reservoir 10 is not easily collapsed. The inner membrane and the inner film form an accommodation cavity for storing gaseous carbon dioxide, and its internal pressure and temperature can be maintained within a certain range to meet the energy storage requirements. Exemplarily, the pressure of the gaseous carbon dioxide in the gas storage reservoir 10 can be close to the ambient pressure, that is, the surrounding atmospheric pressure. In some embodiments, the temperature in the gas storage reservoir 10 is in the range of -40°C to 70°C. Exemplarily, -40°C, 0°C, 15°C, 20°C, 25°C, 30°C, 35°C, 40°C, 50°C, 60°C, 70°C, etc. can be selected. The air pressure difference between the air pressure in the gas storage reservoir 10 and the outside atmosphere is less than 1000 Pa.

[0031] The pressure of the liquid carbon dioxide in the liquid storage tank 70 is between 2 MPa and 10 MPa. Exemplarily, 2 MPa, 5 MPa, 6 MPa, 7 MPa, 7.2 MPa, 7.5 MPa, 8 MPa, 10 MPa, etc. can be selected.

[0032] Optionally, the temperature of the liquid carbon dioxide in the liquid storage tank 70 may not exceed 50°C, especially not exceed 30°C, for example, between 20°C and 30°C. Exemplarily, when the liquid carbon dioxide flows into the liquid storage tank 70, the temperature is between 20°C and 30°C, so that the temperature of the liquid carbon dioxide in the liquid storage tank 70 does not exceed 30°C.

[0033] Exemplarily, the temperature of the liquid carbon dioxide in the liquid storage tank 70 is between 20°C and 30°C, and the pressure is between 7 MPa and 7.5 MPa. In this way, potential safety hazards caused by accidental temperature increase and pressure increase of the liquid carbon dioxide in the liquid storage tank 70 can be avoided, making the carbon dioxide energy storage system more suitable for deployment in densely populated areas such as residential areas, schools, hospitals, stations, and commercial centers.

[0034] The liquid storage tank 70 is used, for example, to store a liquid working medium or a gas-liquid mixed working medium in a high-pressure state, such as liquid carbon dioxide or gas-liquid mixed carbon dioxide. The gas storage reservoir 10 is used, for example, to store a gaseous working medium in an atmospheric pressure state, such as gaseous carbon dioxide. It can adopt a gas film gas storage reservoir with a variable volume. When carbon dioxide is filled in, the volume of the gas film gas storage reservoir increases, and when carbon dioxide flows out, the volume of the gas film gas storage reservoir decreases, so as to keep the pressure in the gas film gas storage reservoir constant. The gaseous working medium flowing out of the gas storage reservoir 10 is converted into a pressurized liquid working medium through the compression energy storage unit and finally flows into the liquid storage tank 70, and the energy storage is completed during this process. This process is called the energy storage stage. The liquid working medium flowing out of the liquid storage tank 70 is converted into a gas through the evaporator 80, and after further heating through the superheater 90, it enters the expander 20 to expand and do work or generate electricity. The gaseous carbon dioxide after the work is completed flows into the gas storage reservoir 10. This process is the energy release stage, releasing the energy stored during the energy storage process.

[0035] The expander shaft seal 30 is used to seal both ends of the main shaft of the expander 20 to reduce the amount of gas leakage. During the energy release stage of the carbon dioxide energy storage system, the expander 20 is working, and part of the carbon dioxide working fluid in the expander 20 inevitably leaks out from the expander shaft seal 30. In this embodiment, the shaft seal leakage gas collection pipeline 40 can be used to collect and transmit the shaft seal leakage gas recovery port of the expander shaft seal 30. The fan 50 is, for example, a centrifugal fan or an axial flow fan, etc., which is used to provide conveying power for the conveying of the shaft seal leakage. The fan 50 is, for example, started synchronously with the expander 20 to pump the shaft seal leakage gas to the carbon dioxide separation device 60 during the operation of the expander 20. Part of the air will be mixed into the shaft seal leakage transmitted from the blower 50 to the carbon dioxide separation device 60. The carbon dioxide separation device 60 is used to separate the carbon dioxide working medium in the shaft seal leakage. The separated carbon dioxide working medium is transmitted from the first outlet 61 to the gas storage reservoir 10 for recovery. It can be mixed with the original carbon dioxide working medium in the gas storage reservoir 10 or the carbon dioxide working medium output from the expander 20 to the gas storage reservoir 10. When the carbon dioxide energy storage system enters the energy storage stage again, it can be compressed by the compression energy storage unit to achieve energy storage. The remaining gas (mainly air) after the carbon dioxide in the shaft seal leakage in the carbon dioxide separation device 60 is separated is discharged to the atmosphere through the second outlet 62.

[0036] Therefore, the expander shaft seal leakage recovery system 100 provided in the embodiment of the utility model utilizes the fan 50 to recover the shaft seal leakage at the expander shaft seal 30 to the carbon dioxide separation device 60, and the carbon dioxide working fluid is recovered to the gas storage reservoir 10 after separation by the carbon dioxide separation device 60, which can reduce the loss of carbon dioxide working fluid (that is, the working working fluid in the carbon dioxide energy storage system) as much as possible, realize the recovery and reuse of carbon dioxide working fluid in the shaft seal leakage, realize the near-zero leakage emission of the expander shaft seal leakage, and reduce the operating cost of the carbon dioxide energy storage system. And the residual gas after separation is discharged into the atmosphere, which can avoid the direct leakage of carbon dioxide into the external environment of the system to cause pollution or even accidents.

[0037] In some embodiments, reference Figure 3 The carbon dioxide separation device 60 specifically includes a pressure swing adsorption device 63 and a vacuum pump 64. The outlet of the fan 50 is connected to the input end of the pressure swing adsorption device 63, the inlet of the vacuum pump 64 is connected to the pressure swing adsorption device 63, and the outlet of the vacuum pump 64 is connected to the gas storage reservoir 10 as a first outlet 61. The pressure swing adsorption device 63 is provided with a second outlet 62, and the second outlet 62 is, for example, provided at the top of the pressure swing adsorption device 63.

[0038] In the pressure swing adsorption device 63, an adsorption bed is provided, for example. The adsorption bed includes, for example, adsorption packing and a support structure for supporting the packing, etc. The adsorption packing can be, for example, activated carbon packing, zeolite molecular sieve packing, metal-organic framework compound packing, etc. When the fan 50 conveys the shaft seal leakage to the pressure swing adsorption device 63, when the shaft seal leakage passes through the adsorption bed, the carbon dioxide working medium in the shaft seal leakage is adsorbed by the adsorption packing, and the remaining gas (mainly air) passes through the packing bed and is discharged from the second outlet. When the adsorption amount of the carbon dioxide working medium adsorbed by the adsorption bed reaches saturation or the adsorption duration reaches a preset duration, the pressure in the pressure swing adsorption device 63 is reduced, and the vacuum pump 64 is started, so that the carbon dioxide working medium is desorbed from the adsorption packing and the desorbed carbon dioxide working medium is conveyed by the vacuum pump 64 to the gas storage tank 10 for recovery.

[0039] In the related art, the shaft seal leakage is condensed and then recovered. The condensation process requires providing corresponding cooling capacity. In this embodiment, the separation and recovery of the carbon dioxide working medium in the shaft seal leakage are realized through the combination of the pressure swing adsorption device 63 and the vacuum pump 64. Compared with the condensation recovery method, there is no need to provide an additional cold source, which can reduce the system construction cost and difficulty.

[0040] In some embodiments, the number of the pressure swing adsorption devices 63 is at least two, and at least two pressure swing adsorption devices 63 are arranged in parallel. The working state of each pressure swing adsorption device 63 includes an adsorption state and a desorption state. When at least one of the at least two pressure swing adsorption devices 63 is in the desorption state during the working state, the other is in the adsorption state. The inlet of the vacuum pump 64 is communicated with the pressure swing adsorption device 63 in the desorption state, and the outlet of the fan 50 is communicated with the pressure swing adsorption device 63 in the adsorption state. The pressure swing adsorption device 63 in the desorption state is not communicated with the atmosphere, and the pressure swing adsorption device 63 in the adsorption state is communicated with the atmosphere. In short, at least two mutually parallel pressure swing adsorption devices 63 operate alternately in a chained manner.

[0041] For example Figure 3The left and right pressure swing adsorption devices 63 shown in the figure are connected in parallel. When the right pressure swing adsorption device 63 is in the desorption state, the left pressure swing adsorption device 63 is in the adsorption state. At this time, the vacuum pump 64 is connected to the right pressure swing adsorption device 63, and the outlet of the fan 50 is connected to the input end of the left pressure swing adsorption device 63. The vacuum pump 64 desorbs the carbon dioxide working medium adsorbed in the adsorption bed in the right pressure swing adsorption device 63 and recovers it to the gas storage tank 10. The fan 50 conveys the shaft seal leakage gas to the left pressure swing adsorption device 63, and the adsorption bed in the left pressure swing adsorption device 63 adsorbs the carbon dioxide working medium in the shaft seal leakage gas. When the carbon dioxide adsorption amount of the adsorption bed in the left pressure swing adsorption device 63 reaches saturation or the adsorption duration reaches the preset duration, it is switched to the desorption state, and the right pressure swing adsorption device 63 is switched to the adsorption state. At this time, the vacuum pump 64 is connected to the left pressure swing adsorption device 63 to desorb the carbon dioxide working medium adsorbed in the adsorption bed in the left pressure swing adsorption device 63 and recover it to the gas storage tank 10. The fan 50 is connected to the right pressure swing adsorption device 63 to convey the shaft seal leakage gas to the right pressure swing adsorption device 63 so that the adsorption bed adsorbs the carbon dioxide working medium in the shaft seal leakage gas. In this embodiment, solenoid valves can be arranged on the connecting pipelines of the fan 50 and at least two pressure swing adsorption devices 63 to switch the pressure swing adsorption device 63 connected to the fan 50, and solenoid valves can be arranged on the connecting pipelines of the vacuum pump 64 and at least two pressure swing adsorption devices 63 to switch the pressure swing adsorption device 63 connected to the vacuum pump 64. Solenoid valves can be arranged at the air outlets of at least two pressure swing adsorption devices 63 to switch the pressure swing adsorption device 63 connected to the atmosphere. It should be noted that when the expander 20 works for the first time, at least two pressure swing adsorption devices 63 have not adsorbed the carbon dioxide working medium yet. At this time, one of the at least two pressure swing adsorption devices 63 is connected to the fan 50 and the other is connected to the vacuum pump 64. Although the desorption process does not occur in the pressure swing adsorption device 63 connected to the vacuum pump 64, it is also considered that the pressure swing adsorption device 63 connected to the vacuum pump 64 is in the desorption state.

[0042] In this embodiment, by setting at least two pressure swing adsorption devices 63 and alternately operating at least two pressure swing adsorption devices 63, the carbon dioxide separation device 60 can continuously separate and process the shaft seal leakage gas during the operation of the expander 20, ensuring the recovery effect of the shaft seal leakage gas.

[0043] In other embodiments, referring to Figure 4, the carbon dioxide separation device 60 includes an absorption tower 65 and a regeneration tower 66. The outlet of the fan 50 is connected to the gas inlet of the absorption tower 65, the liquid outlet of the absorption tower 65 is connected to the regeneration tower 66, and the gas outlet of the regeneration tower 66 is used as the first outlet 61 and connected to the gas storage reservoir 10. The absorption tower 65 is used to absorb the carbon dioxide working medium in the shaft seal leakage by an absorbent to form a rich liquid and output the rich liquid to the regeneration tower 66. The regeneration tower 66 is used to desorb the carbon dioxide working medium from the rich liquid and output it to the gas storage reservoir 10 for recovery.

[0044] Among them, for example, an absorbent is stored in the absorption tower 65 or the absorbent can be input into the absorption tower 65 through an external device. The absorbent can be, for example, ammonia water, MEA (HO-CH2-CH2-NH2) solution and other solutions that can absorb carbon dioxide. MEA is a primary amine and also a primary alcohol, showing weak alkalinity. The MEA solution easily reacts with carbon dioxide to produce carbamate. In this reaction, first, the alkanolamine reacts with carbon dioxide to form an amphoteric ion, and then the amphoteric ion will undergo a deprotonation process with the amine to generate a carbamate ion. Let RNH2 represent MEA, where R is CH2CH2OH. The reaction process of MEA absorbing carbon dioxide is as Figure 5 shown. For example, a spray head that can spray out the absorbent is provided in the absorption tower 65, which can make the absorbent evenly dispersed and fully contact with the shaft seal leakage.

[0045] After the absorbent absorbs the carbon dioxide working medium, it becomes a rich liquid. The rich liquid enters the regeneration tower 66. For example, a reboiler is provided in the regeneration tower 66, and the reboiler is, for example, located at the bottom of the regeneration tower 66. When the rich liquid enters the regeneration tower 66, the reboiler heats the rich liquid (for example, heats it to 98 °C), and at this time, carbon dioxide gas is desorbed from the rich liquid. For example, a condenser is also provided in the regeneration tower 66, and the condenser is, for example, provided at the top of the regeneration tower 66. The first outlet 61 is, for example, provided at the top of the regeneration tower 66. The condenser is used to condense the absorbent water vapor to separate it from the carbon dioxide gas, so that the carbon dioxide gas is dehydrated and discharged through the first outlet 61, and the condensed water (i.e., the absorbent) flows back into the regeneration tower 66.

[0046] In this embodiment, the chemical absorption method is used to separate the carbon dioxide working medium in the shaft seal leakage, which requires less cold source compared to the method of condensing the carbon dioxide working medium, and can reduce the equipment investment cost and difficulty.

[0047] In some embodiments, continue to refer to Figure 4, the carbon dioxide separation device 60 further includes an absorbent reflux assembly 67. The input end of the absorbent reflux assembly 67 is connected to the liquid outlet of the regeneration tower 66, and the output end of the absorbent reflux assembly 67 is connected to the liquid inlet of the absorption tower 65. After the rich liquid analyzes the carbon dioxide working medium, it becomes the analyzed absorbent. The absorbent reflux assembly 67 is used to reflux the analyzed absorbent into the absorption tower 65 to absorb the carbon dioxide working medium. In this embodiment, by setting the absorbent reflux assembly 67, the reuse of the absorbent can be realized, and the operation cost can be reduced.

[0048] In some specific embodiments, the absorbent reflux assembly 67 includes a reflux pump 671 and a heat exchanger 672. The inlet of the reflux pump 671 is connected to the liquid outlet of the regeneration tower 66, and the outlet of the reflux pump 671 is connected to the hot side inlet of the heat exchanger 672. The hot side outlet of the heat exchanger 672 is connected to the liquid inlet of the absorption tower 65. The heat exchanger 672 is used to cool the analyzed absorbent. The reflux pump 671 is, for example, a corrosion-resistant and high-temperature-resistant pump. The heat exchanger 672 can be, for example, a shell-and-tube heat exchanger, a finned heat exchanger, etc. By setting the heat exchanger 672 to cool the analyzed absorbent, the absorption efficiency of the absorbent refluxed into the absorption tower 65 can be improved, and the influence of high temperature on equipment such as nozzles in the absorption tower 65 can be reduced.

[0049] In some specific embodiments, the carbon dioxide separation device 60 further includes a rich liquid pump 69. The inlet of the rich liquid pump 69 is connected to the liquid outlet of the absorption tower 65, and the outlet of the rich liquid pump 69 is connected to the cold side inlet of the heat exchanger 672. The cold side outlet of the heat exchanger 672 is connected to the liquid inlet of the regeneration tower 66. The heat exchanger 672 is also used to cool the analyzed absorbent with the rich liquid. The rich liquid pump 69 is, for example, a corrosion-resistant pump. In the regeneration tower 66, the carbon dioxide working medium in the rich liquid needs to be analyzed by high temperature. In this embodiment, the heat exchanger 672 can preheat the rich liquid entering the regeneration tower 66, reduce the heating difficulty of the reboiler in the regeneration tower 66, and save energy. And the heat source for preheating the rich liquid comes from the heat of the analyzed absorbent, and no additional heat source needs to be provided while cooling the analyzed absorbent. Or rather, no additional cold source needs to be set for cooling the analyzed absorbent, and the heat and cold can be fully utilized to reduce the system operation cost.

[0050] In some embodiments, the carbon dioxide separation device 60 further includes a water scrubber 68. The gas outlet of the absorption tower 65 is connected to the gas inlet of the water scrubber 68, and the gas outlet of the water scrubber 68 serves as the second outlet 62 and is in communication with the atmosphere. For example, a packing layer is provided in the water scrubber 68, and in the packing layer, for example, Pall rings, Raschig rings, limited packing, etc. are provided. The water scrubber 68 is also, for example, provided with a spraying system, specifically including a spraying pump and spraying pipes. The spraying pump can spray water or other washing liquids into the packing layer. When the shaft seal leakage passes through the absorption tower 65, the carbon dioxide working medium in the shaft seal leakage is absorbed by the absorbent. Part of the absorbent is entrained in the remaining gas (mainly air). After the remaining gas entraining the absorbent enters the water scrubber 68, it contacts the washing liquid through the packing layer to remove the entrained absorbent from the remaining gas. The remaining gas after removing the absorbent can be discharged to the atmosphere through the second outlet 62. In this embodiment, by providing the water scrubber 68, the cleanliness of the remaining gas discharged to the atmosphere can be ensured, and the absorbent is prevented from being discharged into the atmosphere and causing pollution.

[0051] In some embodiments, the expander shaft seal leakage recovery system 100 further includes a carbon dioxide purity detection device. The carbon dioxide purity detection device is connected to the carbon dioxide separation device 60 and is used to detect the purity of the carbon dioxide working medium separated by the carbon dioxide separation device 60. When the carbon dioxide separation device 60 includes a pressure swing adsorption device 63 and a vacuum pump 64, the carbon dioxide purity detection device is, for example, provided in front of the inlet of the vacuum pump 64. When it is detected that the purity of the carbon dioxide working medium is greater than or equal to a preset purity, the vacuum pump 64 is started to recover the carbon dioxide working medium to the gas storage reservoir 10. The preset purity is, for example, 99%. When the carbon dioxide separation device 60 includes an absorption tower 65 and a regeneration tower 66, the carbon dioxide purity detection device is, for example, provided at the gas outlet of the regeneration tower 66. For example, a solenoid valve can be provided at the gas outlet of the regeneration tower 66. When it is detected that the purity of the carbon dioxide working medium is greater than or equal to the preset purity, the solenoid valve is opened so that the carbon dioxide separated by the regeneration tower 66 can be output into the gas storage reservoir 10. By providing the carbon dioxide purity detection device, the carbon dioxide working medium separated by the carbon dioxide separation device 60 can be recovered into the gas storage reservoir 10 after its purity reaches the preset purity, ensuring that the carbon dioxide working medium recovered from the shaft seal leakage meets the purity requirements of the carbon dioxide energy storage system.

[0052] In some embodiments, the expander shaft seal 30 includes a front shaft seal 31 and a rear shaft seal 32. The front shaft seal 31 is provided at the intake end of the expander 20 and surrounds the main shaft of the expander 20, that is, the front shaft seal 31 is arranged near the end of the expander 20 connected to the superheater 90. The rear shaft seal 32 is provided at the outlet end of the expander 20 and surrounds the main shaft of the expander 20, that is, the rear shaft seal 32 is arranged near the end of the expander 20 connected to the gas storage tank 10. Both the front shaft seal 31 and the rear shaft seal 32 have shaft seal leakage recovery gas ports, and the shaft seal leakage collection pipeline 40 is respectively connected to the shaft seal leakage recovery gas ports of the front shaft seal 31 and the rear shaft seal 32. The shaft seal leakage collection pipeline 40 can collect the shaft seal leakage at the front shaft seal 31 and the rear shaft seal 32 to the fan 50, and the fan 50 can stabilize the pressure of the shaft seal leakage at a preset pressure value, for example, the preset pressure value is 50 kPa. The shaft seal leakage recovery gas port of the front shaft seal 31 is, for example, located at the end of the front shaft seal 31 away from the expander 20, and the shaft seal leakage recovery gas port of the rear shaft seal 32 is, for example, located at the end of the rear shaft seal 32 away from the expander 20, so that the shaft seal leakage collection pipeline 40 can collect the shaft seal leakage at the outermost end of the expander shaft seal 30 as much as possible, which can minimize the amount of shaft seal leakage sucked out by the fan 50 and ensure the working efficiency of the expander 20.

[0053] Among them, the expander shaft seal 30 is, for example, a labyrinth shaft seal. Specifically, both the front shaft seal 31 and the rear shaft seal 32 are labyrinth shaft seals. By arranging a series of annular sealing teeth in sequence to form a series of throttling gaps and expansion cavities, the carbon dioxide working medium leaked from the expander 20 can generate a throttling effect in these tortuous labyrinth gaps, which can achieve a flow resistance effect and reduce air leakage. The labyrinth shaft seal structure is simpler. The air pressure at the shaft seal leakage recovery gas port of the front shaft seal 31 and the shaft seal leakage recovery gas port of the rear shaft seal 32 is slightly positive pressure (slightly higher than the external ambient pressure). In this embodiment, the fan 50 is used to increase the gas pressure in the shaft seal leakage collection pipeline 40 to realize the suction of the shaft seal leakage, which can ensure the collection of the shaft seal leakage. The shaft seal leakage can be separated by the carbon dioxide separation device 60 and recycled to the gas storage tank 10, with lower requirements for sealing performance. Compared with the gas seal, the layout of the gas supply pipeline can be saved and the system construction cost can be reduced.

[0054] According to the above embodiments, the expander shaft seal leakage recovery system of the carbon dioxide energy storage system provided by the embodiments of the present invention can recover the carbon dioxide working medium in the expander shaft seal leakage to the gas storage tank 10, minimize the loss of the carbon dioxide working medium (that is, the working medium in the carbon dioxide energy storage system) as much as possible, realize the recycling of the carbon dioxide working medium in the shaft seal leakage, achieve nearly zero leakage emission of the expander shaft seal leakage, and reduce the operation cost of the carbon dioxide energy storage system.

[0055] The above are only the preferred embodiments of the present utility model, and do not impose any form of limitation on the present utility model. Although the present utility model has been disclosed above with the preferred embodiments, it is not intended to limit the present utility model. Any person skilled in the art, without departing from the scope of the technical solution of the present utility model, can make some changes or modifications to the above-disclosed technical content to form equivalent embodiments of equivalent changes. However, as long as it does not depart from the content of the technical solution of the present utility model, any simple modification, equivalent change and modification made to the above embodiments based on the technical essence of the present utility model still fall within the scope of the technical solution of the present utility model.

Claims

1. An expansion machine shaft seal air leakage recovery system for a carbon dioxide energy storage system, characterized in that, The carbon dioxide energy storage system includes a gas storage reservoir; the expander shaft seal leakage recovery system includes: an expander, an expander shaft seal, a shaft seal leakage collection pipeline, a fan, and a carbon dioxide separation device; the expander shaft seal is arranged around the main shaft of the expander and has a shaft seal leakage recovery air port; the input end of the shaft seal leakage collection pipeline is connected to the shaft seal leakage recovery air port of the expander shaft seal, the output end of the shaft seal leakage collection pipeline is connected to the inlet of the fan, the outlet of the fan is connected to the carbon dioxide separation device, the first outlet of the carbon dioxide separation device is connected to the gas storage reservoir, and the second outlet of the carbon dioxide separation device is communicated with the atmosphere; the carbon dioxide separation device is used for separating carbon dioxide working medium from the shaft seal leakage and outputting it to the gas storage reservoir for recovery through the first outlet.

2. The leakage recovery system for the expander shaft seal of the carbon dioxide energy storage system according to claim 1, characterized in that The carbon dioxide separation device includes a pressure swing adsorption device and a vacuum pump; the outlet of the fan is connected to the input end of the pressure swing adsorption device, the inlet of the vacuum pump is connected to the pressure swing adsorption device, and the outlet of the vacuum pump is used as the first outlet and is connected to the gas storage reservoir.

3. The leakage recovery system for the expander shaft seal of the carbon dioxide energy storage system according to claim 1, characterized in that, The carbon dioxide separation device includes an absorption tower and a regeneration tower; the outlet of the fan is connected to the gas inlet of the absorption tower, the liquid outlet of the absorption tower is connected to the regeneration tower, and the gas outlet of the regeneration tower is used as the first outlet and is connected to the gas storage reservoir; the absorption tower is used for absorbing the carbon dioxide working medium in the shaft seal leakage with an absorbent to become a rich liquid and outputting the rich liquid to the regeneration tower, and the regeneration tower is used for desorbing the carbon dioxide working medium from the rich liquid and outputting it to the gas storage reservoir for recovery.

4. The expander shaft seal air leakage recovery system of the carbon dioxide energy storage system according to claim 2, wherein, The number of the pressure swing adsorption devices is at least two, and at least two pressure swing adsorption devices are arranged in parallel; the working state of each pressure swing adsorption device includes an adsorption state and a desorption state, and when at least one of the at least two pressure swing adsorption devices is in the desorption state during the working state, the other is in the adsorption state; the inlet of the vacuum pump is communicated with the pressure swing adsorption device in the desorption state, and the outlet of the fan is communicated with the pressure swing adsorption device in the adsorption state.

5. The leakage recovery system for the expander shaft seal of the carbon dioxide energy storage system according to claim 3, characterized in that, The carbon dioxide separation device further includes an absorbent reflux assembly, the input end of the absorbent reflux assembly is connected to the liquid outlet of the regeneration tower, and the output end of the absorbent reflux assembly is connected to the liquid inlet of the absorption tower; after the rich liquid desorbs the carbon dioxide working medium, it becomes the desorbed absorbent, and the absorbent reflux assembly is used for refluxing the desorbed absorbent into the absorption tower to absorb the carbon dioxide working medium.

6. The leakage recovery system for the expander shaft seal of the carbon dioxide energy storage system according to claim 5, wherein, The absorbent reflux assembly includes a reflux pump and a heat exchanger, the inlet of the reflux pump is connected to the liquid outlet of the regeneration tower, the outlet of the reflux pump is connected to the hot side inlet of the heat exchanger, and the hot side outlet of the heat exchanger is connected to the liquid inlet of the absorption tower; the heat exchanger is used for cooling the desorbed absorbent.

7. The leakage recovery system for the expander shaft seal of the carbon dioxide energy storage system according to claim 6, wherein, The carbon dioxide separation device further includes a rich liquid pump. The inlet of the rich liquid pump is connected to the liquid outlet of the absorption tower, the outlet of the rich liquid pump is connected to the cold side inlet of the heat exchanger, and the cold side outlet of the heat exchanger is connected to the liquid inlet of the regeneration tower; the heat exchanger is further configured to cool the desorbed absorbent by using the rich liquid.

8. The leakage recovery system for the expander shaft seal of the carbon dioxide energy storage system according to claim 3, wherein, The carbon dioxide separation device further includes a water washing tower. The gas outlet of the absorption tower is connected to the gas inlet of the water washing tower, and the gas outlet of the water washing tower serves as the second outlet and is communicated with the atmosphere.

9. The leakage recovery system for the expander shaft seal of the carbon dioxide energy storage system according to claim 1, characterized in that, It further includes a carbon dioxide purity detection device. The carbon dioxide purity detection device is connected to the carbon dioxide separation device, and the carbon dioxide purity detection device is used to detect the purity of the carbon dioxide working medium separated by the carbon dioxide separation device.

10. The expander shaft seal air leakage recovery system of the carbon dioxide energy storage system according to any one of claims 1 to 9, characterized in that, The expander shaft seal includes a front shaft seal and a rear shaft seal. The front shaft seal is provided at the air inlet end of the expander and surrounds the main shaft of the expander, and the rear shaft seal is provided at the air outlet end of the expander and surrounds the main shaft of the expander; both the front shaft seal and the rear shaft seal have shaft seal leakage recovery air ports, and the shaft seal leakage collection pipeline is respectively connected to the shaft seal leakage recovery air ports of the front shaft seal and the rear shaft seal; and / or, the expander shaft seal is a labyrinth shaft seal.

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