Energy storage system based on LNG cold energy gradient utilization and waste heat recovery

Abstract

According to the energy storage system based on LNG cold energy gradient utilization and waste heat recovery, LNG high-grade cold energy is stored through the cold storage device in the power utilization peak period, and low-grade cold energy is directly used for power generation; cold energy of the LNG is directly subjected to heat exchange with air in the electricity utilization trough period, and meanwhile cold energy of the cold storage device is applied to the air; the cold energy is utilized to the greatest extent, and the energy storage capacity of the system is increased. High-grade heat energy is utilized by heating high-pressure air at an inlet of the expansion machine through waste heat, residual low-grade heat is recycled through Kalina circulation, the energy storage system is based on an energy storage technical route of LNG cold energy gradient utilization and waste heat recycling, the efficiency and capacity of the energy storage system are improved through an external cold source and a heat source, and the energy storage efficiency is improved. And in addition, waste cold and waste heat are utilized in a gradient mode, and the good practical value is achieved.

Description

Technical Field

[0001] The present application relates to the technical field of liquid air energy storage, and in particular to an energy storage system based on cascaded utilization of LNG cold energy and waste heat recovery. Background Art

[0002] At present, China has become one of the largest clean energy utilization countries in the world. Using sustainable energy such as wind and solar energy to replace fossil raw materials has become the mainstream trend of global energy development. Liquid air energy storage has the characteristics of high energy density, flexible layout, and no geographical restrictions. It can be a solution to the volatility and intermittency of renewable energy. However, the efficiency of independent liquid air energy storage systems is low.

[0003] LNG is gasified at the receiving station, from low temperature (-162℃) to room temperature, during which a large amount of cold energy is not utilized. These high-quality cold energy has great utilization value. At present, the utilization of LNG cold energy adopts a single technology or focuses on a specific temperature range. Therefore, under the premise of not wasting cold energy, multiple methods can be used in series for different temperature ranges to utilize LNG cold energy.

[0004] It is advanced to couple the liquid air energy storage system with the utilization of LNG cold energy. Using the cold energy of LNG for the compression and liquefaction of air can greatly improve the efficiency of the liquid air energy storage system. Due to the existing LNG and liquid air energy storage technology, the cold energy of LNG is used for air compression or liquefaction, and the volatility of energy storage capacity and energy storage has not been considered. At present, the LNG-coupled liquid air energy storage system is not flexible, and the utilization of cold energy is not compatible with the energy storage system.

[0005] Traditional liquid air energy storage systems consume a lot of energy to compress the gas during the air compression process. The efficiency of the entire system is low, which leads to limited economic benefits and a long payback period for the construction system.

[0006] At present, the utilization technology of LNG is relatively simple, and the temperature range for the utilization of LNG cold energy is relatively narrow. Although coupling the utilization of LNG cold energy with the liquid air energy storage system is an advanced way of utilizing cold energy, the efficiency improvement of the coupling system is relatively limited. The power generation capacity is relatively limited during the air expansion stage due to the low air temperature. In addition, the energy utilization rate of the current coupling system design is still relatively low, and the volatility of LNG cold energy and the energy storage capacity of the entire coupling system are not considered.

[0007] At present, industries such as glass, steel, cement and graphite have the characteristics of high heat and high electricity consumption, and have abundant waste heat resources. The current waste heat utilization technology is relatively limited and has low efficiency.

[0008] In summary, due to the large amount of energy consumed in the compression process of the traditional liquid air energy storage system, the efficiency is low; the utilization of LNG cold energy is limited; the combination of LNG cold energy utilization and liquid air energy storage system has not considered problems such as system energy storage capacity and volatility, so it is not yet mature. At present, there is an urgent need for an efficient energy storage system that couples the cascaded utilization of LNG cold energy and waste heat recovery. Summary of the Invention

[0009] In view of this, it is necessary to provide an energy storage system that couples the cascaded utilization of LNG cold energy and waste heat recovery to address the current technical problem of low utilization rate of LNG cold energy and waste heat recovery.

[0010] To solve the above problems, the present application adopts the following technical solutions:

[0011] One of the purposes of the present application is to provide an energy storage system based on the cascaded utilization of LNG cold energy and waste heat recovery, including: a precooler (1), a compressor unit (2), a post-stage cooler (3), a liquefaction heat exchanger (4), a throttling device (5), a liquid air storage tank (6), a liquid air pump (7), a first-stage evaporator (8), a first-stage cold storage device (9), a second-stage cold storage device (10), a second-stage evaporator (11), a preheater (12), a pre-stage heater (13), an expansion unit (14), an ammonia evaporator (15), an LNG pump (16), a low-temperature propane tank (17), a first-stage LNG heat exchanger (18), a high-temperature propane tank (19), an organic working fluid turbine (20), an organic working fluid evaporator (21), an organic working fluid pump (22), a second-stage LNG heat exchanger (23), a third-stage LNG heat exchanger (24), an ammonia preheater (25), a distiller (26), a Kalina turbine (27), an absorber (28), a condenser (29), and an ammonia pump (30); where:

[0012] The incoming LNG is pressurized by the LNG pump (16), and the pressurized LNG enters the cold-side inlet of the first-stage LNG heat exchanger (18) through the outlet of the LNG pump (16). The LNG passing through the first-stage LNG heat exchanger (18) condenses the mixed organic working fluid in the second-stage LNG heat exchanger (23). The condensed organic working fluid is pressurized by the organic working fluid pump (22) and then enters the organic working fluid evaporator (21) and evaporates into high-pressure steam. The high-pressure steam at the outlet of the organic working fluid evaporator (21) enters the organic working fluid turbine (20) to do work. The LNG at the outlet of the second-stage LNG heat exchanger (23) is heated by the third-stage LNG heat exchanger (24) and then enters the natural gas pipeline and is supplied to users; the first-stage LNG heat exchanger (18) is also used to cool the propane from the high-temperature propane tank (19) and store it in the low-temperature propane tank (17);

[0013] Air enters the pre-cooler (1) for pre-cooling and then enters the compressor unit (2), and exits the compressor unit (2) and enters the post-stage cooler (3). The post-stage cooler (3) uses both the LNG from the outlet of the LNG pump (16) and the cryogenic propane from the outlet of the cryogenic propane tank (17) for cooling; the high-pressure air from the post-stage cooler (3) enters the liquefaction heat exchanger (4) from the outlet of the post-stage cooler (3) and is cooled by both the first-stage cold storage device (9) and the reflux air in the liquefaction heat exchanger (4). The cooled high-pressure air enters the throttling device (5) from the outlet of the liquefaction heat exchanger (4). The throttling device (5) expands and does work on the air at the outlet of the liquefaction heat exchanger (4). The atmospheric-pressure liquid air obtained from the expansion work is stored in the liquid air storage tank (6), and the low-temperature gas in the liquid air storage tank (6) flows back through the liquefaction heat exchanger (4) and the pre-cooler (1) in sequence;

[0014] During the energy release period, the liquid air storage tank (6) pumps the liquid air through the liquid air pump (7) and flows through the first-stage evaporator (8) and the second-stage evaporator (11) in sequence. When flowing through the first-stage evaporator (8) and the second-stage evaporator (11), the cold energy is stored in the first-stage cold storage device (9) and the second-stage cold storage device (10) respectively; the gaseous air from the outlet of the second-stage evaporator (11) enters the pre-heater (12) for pre-heating. The air pre-heated by the pre-heater (12) enters the pre-stage heater (13) and enters the expansion unit (14) to do work after being heated by the pre-stage heater (13); the air from the outlet of the expansion unit (14) enters the pre-heater (12) as a heat source and then is discharged into the atmosphere;

[0015] High-grade waste heat heats the air through the pre-stage heater (13); the remaining low-grade waste heat enters the ammonia evaporator (15) to heat the liquid ammonia water to evaporate ammonia gas, and the formed working medium becomes the first gas-liquid mixture and enters the distiller (26); the first gas-liquid mixture is separated in the distiller (26). The low-concentration ammonia water solution flows back to the ammonia water pre-heater (25) to heat the liquid cryogenic ammonia water, while the high-concentration ammonia gas enters the Kalina turbine (27) to expand and generate electricity to increase the electric energy output. The low-concentration ammonia water flowing out of the ammonia water pre-heater (25) and the high-concentration ammonia gas after expansion are mixed in the absorber (28) to form the second gas-liquid mixture. The second gas-liquid mixture is condensed by the cooling water in the condenser (29), and the condensed second gas-liquid mixture is pumped to the ammonia water pre-heater (25) by the ammonia water pump (30).

[0016] The present application adopts the above technical solutions, and the beneficial effects are as follows:

[0017] The energy storage system based on the cascaded utilization of LNG cold energy and waste heat recovery provided by this application stores the high-grade cold energy of LNG in a cold energy storage device during the peak electricity consumption period, and directly uses the low-grade cold energy for power generation; during the low electricity consumption period, the cold energy of LNG is directly exchanged with air, and at the same time, the cold energy of the cold energy storage device is applied to air; the cold energy is utilized to the greatest extent, increasing the energy storage capacity of the system. By using the high-grade thermal energy to heat the high-pressure air at the inlet of the expander and recovering the remaining low-grade heat by the Kalina cycle, the above-mentioned energy storage system is based on the energy storage technical route of the cascaded utilization of LNG cold energy and waste heat recovery, uses external cold sources and heat sources to improve the efficiency and capacity of the energy storage system, and conducts cascaded utilization of waste cold and waste heat, having excellent practical value. Description of the Drawings

[0018] In order to more clearly illustrate the technical solutions of the embodiments of this application, the following will briefly introduce the drawings required to be used in the description of the embodiments of this application or the prior art. Obviously, the following described drawings are only some embodiments of this application. For those of ordinary skill in the art, without creative efforts, other drawings can be obtained based on these drawings.

[0019] Figure 1 It is a schematic structural diagram of the energy storage system based on the cascaded utilization of LNG cold energy and waste heat recovery provided by an embodiment of the present invention. Detailed Embodiments

[0020] The following will describe in detail the embodiments of this application. The examples of the embodiments are shown in the drawings, where the same or similar reference numerals represent the same or similar elements or elements with the same or similar functions from beginning to end. The embodiments described below with reference to the drawings are exemplary and are intended to explain this application and should not be construed as a limitation of this application.

[0021] In the description of this application, it should be understood that the orientation or positional relationships indicated by the terms "upper", "lower", "horizontal", "inner", "outer", etc. are based on the orientation or positional relationships shown in the drawings, and are only for the convenience of describing this application and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this application.

[0022] In addition, the terms "first" and "second" are only used for descriptive purposes and cannot be construed as indicating or implying relative importance or implicitly indicating the quantity of the indicated technical features. Thus, the features defined with "first" and "second" may explicitly or implicitly include one or more of such features. In the description of this application, "a plurality" means two or more unless otherwise specifically defined.

[0023] In order to make the purpose, technical solutions and advantages of this application clearer, the following takes the multi-functional detection of atherosclerosis in blood vessels as an example, and in combination with the accompanying drawings and embodiments, this application will be further described in detail.

[0024] Please refer to Figure 1 , the structural schematic diagram of the energy storage system based on the cascaded utilization of LNG cold energy and waste heat recovery provided by the embodiment of this application includes: a precooler (1), a compressor unit (2), a post-stage cooler (3), a liquefied heat exchanger (4), a throttling device (5), a liquid air storage tank (6), a liquid air pump (7), a first-stage evaporator (8), a first-stage cold storage device (9), a second-stage cold storage device (10), a second-stage evaporator (11), a preheater (12), a pre-stage heater (13), an expansion unit (14), an ammonia evaporator (15), an LNG pump (16), a low-temperature propane tank (17), a first-stage LNG heat exchanger (18), a high-temperature propane tank (19), an organic working fluid turbine (20), an organic working fluid evaporator (21), an organic working fluid pump (22), a second-stage LNG heat exchanger (23), a third-stage LNG heat exchanger (24), an ammonia preheater (25), a distiller (26), a Kalina turbine (27), an absorber (28), a condenser (29) and an ammonia water pump (30). The connection relationship and implementation method of each component will be described in detail below.

[0025] In this embodiment, for the energy storage system based on the cascaded utilization of LNG cold energy and waste heat recovery provided by the embodiment of this application, the energy storage system provided by this application includes: a cold storage device, an organic Rankine cycle device, a compression device, an expansion device, and a Kalina cycle device.

[0026] Please combine with Figure 1 As shown in, during the peak electricity consumption period, the cold storage device includes a low-temperature propane tank (17), a high-temperature propane tank (19) and a first-stage LNG heat exchanger (18).

[0027] Furthermore, from a functional perspective, the cold storage device includes an LNG cold energy storage device and a liquid air cold storage device (the first-stage cold storage device (9), the second-stage cold storage device (10)). The LNG cold energy storage device stores the high-grade cold energy of LNG during the peak electricity consumption period; during the low electricity consumption period, it conveys the stored cold energy to the air during the air compression and liquefaction process. The LNG cold energy storage device can use the cold energy of LNG throughout the day for the liquefaction and compression of air, increasing the energy storage capacity of the system.

[0028] Further, the first-stage cold energy storage device (9) and the second-stage cold energy storage device (10) use propane as the cold energy storage material, and two low-temperature propane tanks (17) and a high-temperature propane tank (19) are used to complete the cold energy storage process. It can be understood that the above two-stage cold energy storage device stores the cold energy of liquid air and is used for the pre-cooler to pre-cool the air and the liquefaction heat exchanger to supplement the cold energy of the high-pressure air, making the most of the cold energy in the system.

[0029] In this embodiment, the first-stage cold energy storage device (9) and the second-stage cold energy storage device (10) can use solid-phase packed bed cold energy storage or liquid storage tank cold energy storage. The solid-phase packed bed can use quartz sand particles, pebbles or industrial waste residues as the packed bed material, and helium, air or organic gas as the heat transfer medium. The liquid-phase cold energy storage working medium for the liquid storage tank cold energy storage can use methanol, propane or other alkanes.

[0030] It can be understood that this embodiment stores the cold energy of liquid air through multi-stage cold energy storage. Compared with other technologies coupled with LNG, the cold energy is excessive and the cold energy of liquid air is not considered. The present invention makes the most of the cold energy. The cold energy in the first-stage cold energy storage device is used to pre-cool the air, and the cold energy in the second-stage cold energy storage device is used for air liquefaction, greatly improving the energy utilization rate and the efficiency of the system.

[0031] In this embodiment, the organic Rankine cycle device is a device for utilizing surplus cold energy. The surplus cold energy utilization device uses an organic working medium to recover the low-grade cold energy of LNG. The normal temperature water is exchanged heat and evaporated with the high-pressure organic working medium through a heat exchanger. The gaseous organic working medium expands and generates electricity in the expander. The organic working medium is condensed by using the cold energy of LNG, and the condensed organic working medium is pressurized by using a pump. The entire organic Rankine cycle realizes the utilization of the surplus low-grade cold energy of LNG.

[0032] Specifically, the organic working medium used in the surplus cold energy utilization device is a mixture of alkanes, which is a mixture of ethane, propane, n-butane and isobutane.

[0033] In this embodiment, the compression device includes a compression section and a cooling section. In the compression section, the air is compressed at low temperature by the compressors at all levels of the compressor unit (2). In the cooling section, the air is pre-cooled through the pre-cooler (1), and then cooled through the inter-stage cooler after the compressor unit (2). The cold energy used by the pre-cooler (1) is the cold energy stored in liquid air, coming from the second-stage cold energy storage device (10). The after-stage cooler (3) uses LNG and propane in the low-temperature propane tank (17) to cool the air simultaneously during the energy storage period.

[0034] In this embodiment, the compressor unit (2) is a multi-stage air compressor, and the air compressor is a piston type, a screw type or a centrifugal type.

[0035] Furthermore, the compressor unit (2) is arranged in series, and the LNG stream and the cryogenic propane stream enter the post-stage cooler (3) in parallel, so that the cold energy of the LNG is utilized to the greatest extent during the air storage stage.

[0036] Furthermore, the liquid air cold storage device uses the cold energy of the stored liquid air for supplementary cooling of the compressed air through the liquefaction heat exchanger (4). The outlet of the liquefaction heat exchanger (4) is connected to the throttling device (5). The throttling device (5) throttles the high-pressure low-temperature air. The air from the expansion device is separated into gas and liquid, and the gaseous air flows back as the cold source of the pre-cooler (1) and the liquefaction heat exchanger (4); the liquid air is stored in the liquid air storage tank 6.

[0037] Furthermore, the liquid air storage tank (6) is connected to the liquid air pump (7), the first-stage evaporator (8), the second-stage evaporator (11), and the pre-heater (12). During the peak electricity consumption period, i.e., the energy release period, the liquid air pump (7) pressurizes and transports the liquid air from the liquid air storage tank (6). The first-stage evaporator (8) and the second-stage evaporator (11) gasify the pressurized liquid air and store the cold energy in the liquid air cold storage device, reducing the loss of cold energy and improving the efficiency of the system. The pre-heater (12) heats the gasified air through the air at the outlet of the expander, improving the energy utilization efficiency of the system.

[0038] In this embodiment, the expansion device includes a pre-stage heater (13) and an expansion unit (14). The air is heated supplementary through a series of the pre-stage heat exchangers (13), and the air expands at high temperature in the expansion units (14) connected in series at each stage. By heating supplementary through the pre-stage heater (13), the output electric energy during the energy release period is significantly increased.

[0039] Furthermore, the expansion unit (14) is a multi-stage air expander, and the air expander is radial flow, axial flow, or radial-axial flow.

[0040] It can be understood that in this embodiment, the air at the outlet of the expander is used as the heat source of the pre-heater, which not only recovers the energy but also reduces the temperature difference in the pre-heater and reduces the loss of available energy.

[0041] In this embodiment, the Kalina cycle device consists of an ammonia-water pre-heater (25), an ammonia-water evaporator (15), a distiller (26), a Kalina turbine (27), an absorber (28), a condenser (29), and an ammonia-water pump (30). The Kalina cycle device further utilizes the low-grade waste heat remaining after heating the air and generates electricity through the ammonia-water solution. It further improves the electric energy output of the system, realizes the cascade utilization of waste heat, and improves the economy of the system.

[0042] It can be understood that in this embodiment, the Kalina cycle is adopted for low-grade waste heat utilization, and the water and ammonia used are environmentally friendly working fluids.

[0043] Furthermore, the high-grade waste heat of the waste heat maximally heats the air to enhance the electric energy output of the system; the Kalina cycle utilization of the remaining heat realizes the cascade utilization of heat energy.

[0044] Specifically, the waste heat may be waste heat flue gas such as coke oven waste heat flue gas, rolling mill reheating furnace waste heat flue gas, cement cooler flue gas, and graphite production waste heat flue gas.

[0045] Specifically, the LNG pump (16) pressurizes the received LNG to 7 MPa, the inlet pressure of the liquid air storage tank (6) is 0.1 MPa, and the outlet pressure of the liquid air pump (7) is 6 MPa - 20 MPa.

[0046] In this embodiment, the expansion unit (14) is a multi-stage air expander, and the air expander is radial flow type, axial flow type or radial-axial flow type.

[0047] In this embodiment, the liquefaction heat exchanger (4), the first-stage LNG heat exchanger (18), the second-stage LNG heat exchanger (23), and the third-stage LNG heat exchanger (24) are shell-and-tube heat exchangers, plate-fin heat exchangers or spiral-wound heat exchangers.

[0048] In this embodiment, the throttling device (5) includes a hydraulic turbine or an expansion valve.

[0049] The energy storage system based on LNG cold energy cascade utilization and waste heat recovery provided by the above embodiment of the present application includes the following stages.

[0050] The incoming LNG is pressurized by the LNG pump (16). The pressurized LNG enters the cold-side inlet of the first-stage LNG heat exchanger (18) through the outlet of the LNG pump (16). The LNG passing through the first-stage LNG heat exchanger (18) condenses the mixed organic working fluid in the second-stage LNG heat exchanger (23). The condensed organic working fluid is pressurized by the organic working fluid pump (22) and then enters the organic working fluid evaporator (21) and evaporates into high-pressure steam. The high-pressure steam at the outlet of the organic working fluid evaporator (21) enters the organic working fluid turbine (20) to do work. The LNG at the outlet of the second-stage LNG heat exchanger (23) enters the natural gas pipeline after being heated by the third-stage LNG heat exchanger (24) and is delivered to users; the first-stage LNG heat exchanger (18) is also used to cool the propane from the high-temperature propane tank (19) and store it in the low-temperature propane tank (17).

[0051] Specifically, the LNG pump (16) pressurizes the received LNG to 7 MPa, the inlet pressure of the liquid air storage tank (6) is 0.1 MPa, and the outlet liquid air pressure of the liquid air pump (7) is 6 MPa to 20 MPa.

[0052] It can be understood that in the above scheme of the energy storage system provided in this embodiment, LNG is heat exchanged with propane during peak electricity consumption. The LNG after heat exchange (-40℃~-60℃) is about -15℃ after the organic Rankine cycle is used to utilize cold energy for power generation. The transmission pipeline is heated by normal temperature water, which can adjust the peak-to-valley difference of the surrounding power system, reduce the electricity price for nearby industries, and can also be used as a backup power source, or for the integration of new energy power generation such as offshore wind power or solar energy, and has wide application value.

[0053] The air enters the precooler (1) for precooling and then enters the compressor unit (2), and enters the aftercooler (3) through the outlet of the compressor unit (2). The aftercooler (3) uses the LNG at the outlet of the LNG pump (16) and the low-temperature propane at the outlet of the low-temperature propane tank (17) for cooling. The high-pressure air passing through the aftercooler (3) enters the liquefaction heat exchanger (4) from the outlet of the aftercooler (3) and is liquefied by the first stage heat exchanger (4). The cold storage device (9) and the reflux air are cooled simultaneously. The cooled high-pressure air enters the throttling device (5) through the outlet of the liquefied heat exchanger (4). The throttling device (5) expands the air at the outlet of the liquefied heat exchanger (4) to perform work. The normal-pressure liquid air obtained by the expansion work is stored in the liquid air storage tank (6). The low-temperature gas reflux in the liquid air storage tank (6) flows through the liquefied heat exchanger (4) and the precooler (1) in sequence. At this point, the energy storage stage is completed.

[0054] It can be understood that in the above scheme of the energy storage system provided in this embodiment, during the off-peak period of electricity consumption, the system operates in energy storage mode, and compresses the air by driving compressors of each stage through off-peak electricity or renewable electricity. The air is pressurized to 6MPa-9MPa through a four-stage compression process with interstage cooling. At the same time, LNG passes through the LNG pump (16) and the propane of about -150°C in the low-temperature propane tank (17) in parallel to enter the interstage heat exchanger for air compression and liquefaction cooling; the high-pressure air at the outlet enters the liquefaction heat exchanger (4) and is further cooled to about -175°C. The cold energy comes from the return air and the first-stage cold storage device (9). The cooled air enters the throttling device (50) and expands (0.1MPa, about -194°C). After separation, the liquid air is stored, and the gas is used as the return air to recover the cold.

[0055] Specifically, the stored air is pressurized to 6 MPa to 20 MPa by a liquid air pump (7), and then gasified and reheated through a two-stage cold energy storage device. It is preheated by a preheater and then preheated before the stage by waste heat flue gas (300 - 400 °C), and then expands and does work through an expansion unit. However, a part of this heat has not been fully utilized, and there is still low-grade waste heat at 200 - 250 °C, which is recovered using a Kalina cycle.

[0056] In the above embodiments of the present application, the cold energy of liquid air is stored through multi-stage cold energy storage. Compared with other technologies coupled with LNG, the cold energy is in excess and the cold energy of liquid air is not considered. The cold energy is utilized to the greatest extent. The cold energy in the first-stage cold energy storage device is used to pre-cool the air, and the cold energy in the second-stage cold energy storage device is used to liquefy the air, greatly improving the energy utilization rate and the efficiency of the system.

[0057] During the energy release period of the liquid air storage tank (6), liquid air is pumped through the liquid air pump (7) and flows through the first-stage evaporator (8) and the second-stage evaporator (11) in sequence. When flowing through the first-stage evaporator (8) and the second-stage evaporator (11), the cold energy is stored in the first-stage cold energy storage device (9) and the second-stage cold energy storage device (10) respectively; the gaseous air at the outlet of the second-stage evaporator (11) enters the preheater (12) for preheating, and the air preheated by the preheater (12) enters the preheater before the stage (13), and after being heated by the preheater before the stage (13), it enters the expansion unit (14) to do work; the air at the outlet of the expansion unit (14) enters the preheater (12) as a heat source and then is discharged into the atmosphere; thus, the energy release process of the liquid air energy storage ends.

[0058] High-grade waste heat heats the air through the preheater before the stage (13); the remaining low-grade waste heat enters the ammonia evaporator (15) to heat liquid ammonia water to evaporate ammonia, and the formed working medium becomes the first gas-liquid mixture and enters the distiller (26); the first gas-liquid mixture is separated in the distiller (26), and the low-concentration ammonia water solution flows back to the ammonia water preheater (25) to heat the liquid low-temperature ammonia water, while the high-concentration ammonia gas enters the Kalina turbine (27) to expand and generate electricity to increase the power output. The low-concentration ammonia water flowing out of the ammonia water preheater (25) and the high-concentration ammonia gas after expansion are mixed in the absorber (28) to form the second gas-liquid mixture, and the second gas-liquid mixture is condensed by cooling water in the condenser (29), and the condensed second gas-liquid mixture is pumped to the ammonia water preheater (25) by the ammonia water pump (30).

[0059] In the above embodiment of the present application, waste heat is first used in the liquid air energy storage system and then the waste heat is recovered by the Kalina cycle, thus realizing the cascade utilization of heat energy. Compared with the traditional waste heat recovery technology, the present invention takes into account the cascade utilization of energy and combines heat energy utilization with energy storage. It can reduce equipment investment and improve power generation effect, and has high economic efficiency.

[0060] The energy storage system based on the cascaded utilization of LNG cold energy and waste heat recovery provided in the above-mentioned embodiments of the present application combines the cascaded utilization of LNG cold energy and waste heat recovery with the liquid air energy storage system, thereby reducing the electric energy consumed by air compression during the energy storage process through the cold energy of LNG; and heating the air during the energy release period through waste heat, thereby increasing the electric energy output.

[0061] The energy storage system based on the cascade utilization of LNG cold energy and waste heat recovery provided in the above-mentioned embodiments of the present application realizes the cascade utilization of LNG cold energy, stores high-grade cold energy during the energy release period in the cold storage medium, and uses low-grade cold energy for organic working fluid power generation, thereby realizing the cascade utilization of LNG cold energy to the greatest extent and improving the utilization rate of LNG cold energy.

[0062] Compared with conventional liquid air energy storage systems, the energy storage system based on LNG cold energy cascade utilization and waste heat recovery proposed by the present invention has better performance, more output power, better economic benefits, and is conducive to practical industrial applications.

[0063] It can be understood that the technical features of the above-described embodiments can be arbitrarily combined. In order to make the description concise, not all possible combinations of the technical features in the above-described embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0064] The above are only preferred embodiments of the present application, and only specifically describe the technical principles of the present application. These descriptions are only for explaining the principles of the present application and cannot be interpreted as limiting the scope of protection of the present application in any way. Based on the explanation here, any modifications, equivalent substitutions and improvements made within the spirit and principles of the present application, and other specific implementation methods of the present application that can be associated with the technicians in this field without creative work, should be included in the scope of protection of the present application.

Claims

1. An energy storage system based on the cascaded utilization of LNG cold energy and waste heat recovery, characterized in that, Including: Precooler (1), compressor unit (2), after-cooler (3), liquefaction heat exchanger (4), throttling device (5), liquid air storage tank (6), liquid air pump (7), first-stage evaporator (8), first-stage cold storage device (9), second-stage cold storage device (10), second-stage evaporator (11), preheater (12), preheater before stage (13), expansion unit (14), ammonia evaporator (15), LNG pump (16), low-temperature propane tank (17), first-stage LNG heat exchanger (18), high-temperature propane tank (19), organic working fluid turbine (20), organic working fluid evaporator (21), organic working fluid pump (22), second-stage LNG heat exchanger (23), third-stage LNG heat exchanger (24), ammonia preheater (25), distiller (26), Kalina turbine (27), absorber (28), condenser (29) and ammonia pump (30); wherein: The incoming LNG is pressurized by the LNG pump (16), and the pressurized LNG enters the cold-side inlet of the first-stage LNG heat exchanger (18) through the outlet of the LNG pump (16). The LNG passing through the first-stage LNG heat exchanger (18) condenses the mixed organic working fluid in the second-stage LNG heat exchanger (23). The condensed organic working fluid is pressurized by the organic working fluid pump (22) and then enters the organic working fluid evaporator (21) and evaporates into high-pressure steam. The high-pressure steam at the outlet of the organic working fluid evaporator (21) enters the organic working fluid turbine (20) to do work. The LNG at the outlet of the second-stage LNG heat exchanger (23) is heated by the third-stage LNG heat exchanger (24) and then enters the natural gas pipeline and is delivered to users. The first-stage LNG heat exchanger (18) is also used to cool the propane from the high-temperature propane tank (19) and store it in the low-temperature propane tank (17); Air enters the precooler (1) for precooling and then enters the compressor unit (2), and exits the compressor unit (2) and enters the after-cooler (3). The after-cooler (3) is cooled by both the LNG at the outlet of the LNG pump (16) and the low-temperature propane at the outlet of the low-temperature propane tank (17). The high-pressure air passing through the after-cooler (3) enters the liquefaction heat exchanger (4) from the outlet of the after-cooler (3) and is cooled by both the first-stage cold storage device (9) and the return air in the liquefaction heat exchanger (4). The cooled high-pressure air enters the throttling device (5) from the outlet of the liquefaction heat exchanger (4). The throttling device (5) expands and does work on the air at the outlet of the liquefaction heat exchanger (4). The atmospheric-pressure liquid air obtained by the expansion work is stored in the liquid air storage tank (6), and the low-temperature gas in the liquid air storage tank (6) flows back through the liquefaction heat exchanger (4) and the precooler (1) in sequence; During the energy release period, the liquid air storage tank (6) pumps liquid air through the liquid air pump (7) and flows through the first-stage evaporator (8) and the second-stage evaporator (11) in sequence. When flowing through the first-stage evaporator (8) and the second-stage evaporator (11), the cold energy is stored in the first-stage cold energy storage device (9) and the second-stage cold energy storage device (10) respectively; the gaseous air at the outlet of the second-stage evaporator (11) enters the preheater (12) for preheating, the air preheated by the preheater (12) enters the pre-stage heater (13), and after being heated by the pre-stage heater (13), it enters the expansion unit (14) to do work; the air at the outlet of the expansion unit (14) enters the preheater (12) as a heat source and then is discharged into the atmosphere; High-grade waste heat heats the air through the pre-stage heater (13); the remaining low-grade waste heat enters the ammonia evaporator (15) to heat liquid ammonia water to evaporate ammonia gas, and the formed working medium becomes the first gas-liquid mixture and enters the distiller (26); the first gas-liquid mixture is separated in the distiller (26), the low-concentration ammonia water solution flows back into the ammonia water preheater (25) to heat the liquid low-temperature ammonia water, while the high-concentration ammonia gas enters the Kalina turbine (27) to expand and generate electricity to increase the electric energy output. The low-concentration ammonia water flowing out of the ammonia water preheater (25) and the high-concentration ammonia gas after expansion are mixed in the absorber (28) to form the second gas-liquid mixture, and the second gas-liquid mixture is condensed by cooling water in the condenser (29), and the condensed second gas-liquid mixture is pumped to the ammonia water preheater (25) by the ammonia water pump (30).

2. The energy storage system based on the cascaded utilization of LNG cold energy and waste heat recovery as claimed in claim 1, wherein The compressor unit (2) is a multi-stage air compressor, and the air compressor is a piston type, a screw type or a centrifugal type.

3. The energy storage system based on the cascaded utilization of LNG cold energy and waste heat recovery according to claim 2, wherein, The compressor unit (2) is arranged in series, and the LNG stream and the low-temperature propane stream enter the after-stage cooler (3) in parallel.

4. The energy storage system based on the cascaded utilization of LNG cold energy and waste heat recovery according to claim 1, characterized in that, The expansion unit (14) is a multi-stage air expander, and the air expander is a radial flow type, an axial flow type or a radial-axial flow type.

5. The energy storage system based on the cascaded utilization of LNG cold energy and waste heat recovery according to claim 1, characterized in that, The liquefaction heat exchanger (4), the first-stage LNG heat exchanger (18), the second-stage LNG heat exchanger (23) and the third-stage LNG heat exchanger (24) are shell-and-tube heat exchangers, plate-fin heat exchangers or wound-tube heat exchangers.

6. The energy storage system based on cascaded utilization of LNG cold energy and waste heat recovery according to claim 1, characterized in that, The first-stage cold energy storage device (9) and the second-stage cold energy storage device (10) can use solid-phase packed bed cold energy storage or liquid storage tank cold energy storage. The solid-phase packed bed can use quartz sand particles, pebbles or industrial waste residues as the packed bed material, and use helium gas, air or organic gas as the heat transfer medium. The liquid-phase cold energy storage working medium for the liquid storage tank cold energy storage can use methanol, propane or other alkanes.

7. The energy storage system based on cascaded utilization of LNG cold energy and waste heat recovery according to claim 1, characterized in that, The waste heat includes coke oven waste heat flue gas, rolling mill heating furnace waste heat flue gas, cement grate cooler flue gas, and graphite production waste heat flue gas.

8. The energy storage system based on the cascaded utilization of LNG cold energy and waste heat recovery according to claim 1, characterized in that, The throttling device (5) includes a hydraulic turbine or an expansion valve.

9. The energy storage system based on cascaded utilization of LNG cold energy and waste heat recovery according to claim 1, characterized in that, The organic working medium evaporator (21) uses normal temperature water as a heat source.

10. The energy storage system based on the cascaded utilization of LNG cold energy and waste heat recovery according to claim 1, characterized in that, The organic working fluid of the organic Rankine cycle is an alkane mixture, and the alkane mixture is a mixture of ethane, propane, n-butane, and isobutane.

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