A liquefied compressed ammonia energy storage and refrigeration integrated system without a regenerator

Abstract

The present invention discloses an integrated liquefied compressed ammonia energy storage and refrigeration system without a cold accumulator, belonging to the field of large-scale physical energy storage. The system includes an ammonia compressor, a motor, a high-temperature heat accumulator, a medium-temperature heat accumulator, a low-temperature heat accumulator, a first throttle valve, a high-pressure liquid ammonia storage tank, a liquid ammonia pump, a low-temperature regenerator, a medium-temperature regenerator, a high-temperature regenerator, an ammonia expander, a generator, a condenser, a low-pressure liquid ammonia storage tank, a second throttle valve, an evaporator, a pressurized water storage tank, a Hitec molten salt storage tank, a HitecXL molten salt storage tank, and a radiator. The present invention uses ammonia as the working medium and realizes the liquefaction of the energy storage working medium through air cooling or water cooling, solving the problem of difficult liquefaction of the working medium in the original liquefied compressed energy storage system. The system does not require a two-phase expander and a cold accumulator, and can also output cold energy without affecting the electricity storage efficiency, having advantages such as high energy efficiency, being unrestricted by geographical environment, being environmentally friendly, and having a short payback period for funds.

Description

Technical Field

[0001] The present invention relates to the technical field of compressed gas energy storage, and particularly to an integrated liquefied compressed ammonia energy storage and refrigeration system without a regenerator. Background Art

[0002] Solar energy and wind energy also have volatility and randomness, and cannot adapt to the changing demands of the user side by adjusting their own power output. The traditional "source follows load" mode will no longer be applicable to the new power system. Measures such as energy storage must be taken, relying on the coordinated interaction of "source, grid, load, and storage" to achieve dynamic balance of power supply and demand. With the increasing proportion of renewable energy, it has become more and more difficult for thermal power plants to perform peak shaving.

[0003] Compressed gas energy storage technology uses off-peak electricity to pressurize gas for energy storage. Traditional compressed gas energy storage systems generally use air or carbon dioxide as working fluids. In order to reduce the huge volume occupied by the gas, liquefied compressed gas energy storage technology has received extensive attention. The high-pressure gas passing through the compressor enters the regenerator, where the temperature is reduced to near the liquefaction temperature, and then is liquefied by an expander. The liquefied normal-temperature low-pressure liquid air is stored in a liquid storage tank.

[0004] After retrieval, the Chinese patent with the application number CN108645116A discloses a liquefied air energy storage system with a coil regenerator, aiming to combine the heat exchange equipment of the liquefaction unit and the cold storage equipment of the cold storage unit in the liquefied air energy storage system, reuse the cold quantity of the cold energy medium, and reduce equipment costs.

[0005] However, whether it is air or carbon dioxide, it is relatively difficult to be liquefied under low-pressure conditions. For example, the liquefaction temperature of air is about -200°C. The liquefaction of air and carbon dioxide requires the regenerator to provide cold quantity, and then can be efficiently liquefied through a two-phase expander. The regenerator and the two-phase expander usually have high costs; in addition, the cold quantity in the regenerator can only be provided for the gas liquefaction process and cannot be output to users. Summary of the Invention

[0006] The purpose of the present invention is to provide an integrated liquefied compressed ammonia energy storage and refrigeration system without a regenerator to solve the problems of difficult liquefaction of the working fluid in the existing compressed gas energy storage system, high liquefaction cost, large heat preservation difficulty, and inability to output the cold quantity of the regenerator externally, and to provide an integrated energy storage and refrigeration system with high energy efficiency and good economy.

[0007] To achieve the above purpose, the present invention adopts the following technical solutions:

[0008] To solve the above technical problems, the present invention provides an integrated liquefied compressed ammonia energy storage and refrigeration system without a cold accumulator, which includes an energy storage and refrigeration unit and an energy release unit; wherein, the energy storage and refrigeration unit includes an evaporator, an ammonia compressor, an electric motor, a heat storage system, a first throttle valve, and a high-pressure liquid ammonia storage tank; the energy release unit includes a liquid ammonia pump, a regenerative heat exchange system, an ammonia expander, a generator, a condenser, a second throttle valve, and a low-pressure liquid ammonia storage tank.

[0009] The integrated liquefied compressed ammonia energy storage and refrigeration system without a cold accumulator provided by the present invention also has the following characteristics: ammonia is used as the energy storage working medium, and the exhaust gas at the turbine outlet can be cooled to the liquid state by the atmospheric environment.

[0010] The integrated liquefied compressed ammonia energy storage and refrigeration system without a cold accumulator provided by the present invention also has the following characteristics: the heat storage system consists of a high-temperature heat accumulator, a medium-temperature heat accumulator, and a low-temperature heat accumulator, and the heat storage medium flow rates of each heat accumulator are independent of each other; the regenerative heat exchange system consists of a high-temperature regenerative heat exchanger, a medium-temperature regenerative heat exchanger, and a low-temperature regenerative heat exchanger, and the heat storage medium flow rates of each regenerative heat exchanger are independent of each other.

[0011] The integrated liquefied compressed ammonia energy storage and refrigeration system without a cold accumulator provided by the present invention also has the following characteristics: the outlet pressure of the compressor is greater than the critical pressure of ammonia, and the exhaust gas temperature is lower than 420 °C.

[0012] The integrated liquefied compressed ammonia energy storage and refrigeration system without a cold accumulator provided by the present invention also has the following characteristics: the ammonia gas temperature at the high-temperature side outlet of the high-temperature heat accumulator is greater than 142 °C, and the ammonia gas temperature at the high-temperature side outlet of the medium-temperature heat accumulator is greater than 120 °C.

[0013] The integrated liquefied compressed ammonia energy storage and refrigeration system without a cold accumulator provided by the present invention also has the following characteristics: the heat storage medium of the high-temperature heat accumulator is Hitec molten salt with a melting point of 142 °C; the heat storage medium of the medium-temperature heat accumulator is HitecXL molten salt with a melting point of 120 °C; the heat storage medium of the low-temperature heat accumulator is pressurized water.

[0014] The integrated liquefied compressed ammonia energy storage and refrigeration system without a cold accumulator provided by the present invention also has the following characteristics: the gasification temperature of ammonia in the evaporator is less than 10 °C, and the outlet temperature of the chilled water is less than 15 °C.

[0015] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0016] It is not necessary to use ice cold storage or a packed bed cold accumulator, nor a two-phase expander. The liquefaction of the working medium can be achieved under low pressure and normal temperature conditions, which simplifies the system process, reduces the investment cost, and can also output cold energy externally to increase the investment income.

[0017] The compression heat of ammonia is recovered in a gradient manner using a high-temperature heat accumulator, a medium-temperature heat accumulator, and a low-temperature heat accumulator. The flow rates of the three heat accumulators are independent of each other. On the one hand, it is beneficial to overcome the pinch problem caused by the large specific heat capacity near the critical point. On the other hand, it avoids the use of expensive heat transfer oil.

[0018] The integrated liquefied compressed ammonia energy storage and refrigeration system without a cold storage provided by the present invention selects ammonia as the working medium. Ammonia, as a widely used natural refrigerant, has a global warming potential value and an ozone depletion potential value of zero. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] The drawings are used to provide a further understanding of the present invention and constitute a part of the specification. Together with the embodiments of the present invention, they are used to explain the present invention and do not constitute a limitation to the present invention.

[0020] Figure 1 It is a schematic structural diagram of the integrated liquefied compressed ammonia energy storage and refrigeration system without a cold storage provided by the embodiment of the present invention.

[0021] The figure includes: ammonia compressor 1, motor 2, high-temperature heat accumulator 3, medium-temperature heat accumulator 4, low-temperature heat accumulator 5, first throttle valve 6, high-pressure liquid ammonia storage tank 7, liquid ammonia pump 8, low-temperature regenerator 9, medium-temperature regenerator 10, high-temperature regenerator 11, ammonia expander 12, generator 13, condenser 14, second throttle valve 15, low-pressure liquid ammonia storage tank 16, evaporator 17, cold user 18, pressurized water storage tank 19, HitecXL molten salt storage tank 20, Hitec molten salt storage tank 21, high-temperature radiator 22, medium-temperature radiator 23, and low-temperature radiator 24. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0022] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments.

[0023] In the description of the present invention, it should be understood that the orientation or positional relationship indicated by the terms "upper", "lower", "front", "rear", "left", "right", "top", "bottom", "inner", "outer", etc. is based on the orientation or positional relationship shown in the drawings, and is only for the convenience of describing the present invention 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 thus should not be construed as a limitation to the present invention.

[0024] Such as Figure 1As shown in the figure, it is a liquefied compressed ammonia energy storage and refrigeration integrated system without a regenerator provided by this embodiment. Among them, the energy storage and refrigeration unit includes an evaporator 17, an ammonia compressor 1, a heat storage system, a first throttle valve 6, and a high-pressure liquid ammonia storage tank 7; the energy release unit includes a liquid ammonia pump 8, a heat recovery system, an ammonia expander 12, a generator 13, a condenser 14, a second throttle valve 15, and a low-pressure liquid ammonia storage tank 16;

[0025] The low-temperature side of the evaporator 17, the compressor 1, the heat storage system, the first throttle valve 6, and the high-pressure liquid ammonia storage tank 7 are connected in sequence through pipelines; the input end of the ammonia compressor 1 is mechanically connected to the output end of the motor 2;

[0026] The liquid ammonia pump 8, the heat recovery system, the ammonia expander 12, the high-temperature side of the condenser 14, the second throttle valve 15, and the low-pressure liquid ammonia storage tank 16 are connected in sequence through pipelines; the output end of the ammonia expander 12 is mechanically connected to the input end and output end of the generator 13;

[0027] The heat storage system includes a high-temperature heat storage tank 3, a medium-temperature heat storage tank 4, and a low-temperature heat storage tank 5. The high-temperature side heat exchange tubes of the high-temperature heat storage tank 3, the medium-temperature heat storage tank 4, and the low-temperature heat storage tank 5 are connected in sequence.

[0028] The heat recovery system includes a high-temperature heat recuperator 11, a medium-temperature heat recuperator 10, and a low-temperature heat recuperator 9. The low-temperature side heat exchange tubes of the high-temperature heat recuperator 11, the medium-temperature heat recuperator 10, and the low-temperature heat recuperator 9 are connected in sequence.

[0029] The high-temperature radiator 22, the low-temperature side of the high-temperature heat storage tank 3, the Hitec molten salt storage tank 20, and the high-temperature side of the high-temperature heat recuperator 11 are connected in a loop through pipelines. The Hitec molten salt flows in the loop through a circulation pump.

[0030] The medium-temperature radiator 23, the low-temperature side of the medium-temperature heat storage tank 4, the HitecXL molten salt storage tank 21, and the high-temperature side of the medium-temperature heat recuperator 10 are connected in a loop through pipelines. The HitecXL molten salt flows in the loop through a circulation pump.

[0031] The low-temperature radiator 24, the low-temperature side of the low-temperature heat storage tank 5, the pressurized water storage tank 21, and the high-temperature side of the low-temperature heat recuperator 9 are connected in a loop through pipelines. The pressurized water flows in the loop through a circulation pump.

[0032] The following will be further described in detail through a specific process.

[0033] During the energy storage stage, the evaporator 17 absorbs the heat of the chilled water, the liquid ammonia at the outlet of the low-pressure liquid ammonia storage tank 16 is vaporized, and at the same time, low-temperature chilled water is produced. The chilled water is connected to the cold user 18 through a pipeline. The outlet temperature of the chilled water should be less than 15°C. In this embodiment, the outlet temperature of the chilled water is preferably 15°C.

[0034] Further, the ammonia compressor 1 sucks in low-temperature and low-pressure ammonia gas from the exhaust of the evaporator 17 and discharges high-temperature compressed ammonia gas. The exhaust pressure should be greater than the critical pressure of ammonia. In this embodiment, the exhaust pressure is preferably 15 MPa, and the corresponding exhaust temperature is 340.4 °C.

[0035] Further, the high-temperature heat accumulator 3 exchanges heat between the 340.4 °C high-temperature ammonia gas and the Hitec molten salt working fluid; the 340.4 °C high-temperature ammonia gas releases a part of the compression heat and becomes ammonia gas at 167.4 °C; the 160.9 °C Hitec molten salt absorbs the compression heat and becomes molten salt working fluid at 272.5 °C and enters the HitecXL molten salt storage tank 19 for storage.

[0036] Further, the medium-temperature heat accumulator 4 exchanges heat between the 167.4 °C medium-temperature ammonia gas and the HitecXL molten salt; the 167.4 °C medium-temperature ammonia gas releases a part of the compression heat and becomes ammonia gas at 132.9 °C; the 126.4 °C HitecXL molten salt absorbs the compression heat and becomes molten salt at 158.7 °C and enters the Hitec molten salt storage tank 20 for storage.

[0037] Further, the low-temperature heat accumulator 5 exchanges heat between the 132.9 °C low-temperature ammonia gas and the pressurized water; the 132.9 °C low-temperature ammonia gas releases a part of the compression heat and becomes liquid ammonia at 40 °C; the 32.5 °C pressurized water absorbs the compression heat and becomes pressurized water at 127.9 °C and enters the pressurized water storage tank 21 for storage.

[0038] Further, the high-pressure liquid ammonia discharged from the low-temperature heat accumulator 5 is throttled by the first throttle valve 6, the pressure is reduced to 10 MPa, and enters the high-pressure liquid ammonia storage tank 7 for storage.

[0039] Further, in the energy release stage, the liquid ammonia pump 8 pressurizes the liquid ammonia at the outlet of the high-pressure liquid ammonia storage tank 7, and the pressure is restored to the compressor exhaust pressure of 15 MPa.

[0040] Further, the low-temperature recuperator 9 exchanges heat between the 40 °C liquid ammonia and the 127.9 °C pressurized water working fluid; the 40 °C liquid ammonia absorbs the heat of the pressurized water and becomes low-temperature ammonia gas at 121.9. The 127.9 °C pressurized water releases the compression heat and becomes pressurized water at 51.2 °C, is cooled to 32.5 °C by the low-temperature radiator 24, and enters the pressurized water storage tank 21 for storage.

[0041] Further, the medium-temperature recuperator 10 exchanges heat between the 121.9 °C low-temperature ammonia gas and the 158.7 °C molten salt; the 121.9 °C low-temperature ammonia gas absorbs the heat of the molten salt and becomes medium-temperature ammonia gas at 150.1 °C. The 158.7 °C molten salt releases the compression heat and becomes molten salt at 135.1 °C, is cooled to 126.4 °C by the low-temperature radiator 23, and enters the Hitec molten salt storage tank 20 for storage.

[0042] Further, the high-temperature recuperator 9 exchanges heat between the medium-temperature ammonia gas at 150.1 °C and the molten salt at 272.5 °C; the medium-temperature ammonia gas at 150.1 °C absorbs the heat of the molten salt and becomes high-temperature ammonia gas at 267.5 °C. The molten salt at 272.5 °C releases the compression heat and becomes molten salt at 162.6 °C, which is cooled to 160.9 °C by the low-temperature radiator 22 and enters the HitecXL molten salt storage tank 19 for storage.

[0043] Further, the high-temperature ammonia gas enters the ammonia expander 12 to do work, outputs energy to drive the generator 13 to generate electricity, and discharges low-pressure ammonia gas. The exhaust pressure of the ammonia expander should be greater than the saturation pressure of ammonia at normal temperature.

[0044] Further, the ammonia gas at the turbine outlet enters the condenser 14 and is cooled to a liquid state by the ambient air.

[0045] Further, the low-pressure liquid ammonia is throttled by the second throttle valve 15, the pressure is further reduced, and it enters the low-pressure liquid ammonia storage tank 16 for storage. The outlet pressure of the second throttle valve 15 should be less than the saturation pressure at normal temperature.

[0046] This embodiment provides a liquefied compressed ammonia energy storage and refrigeration integrated system without a cold storage regenerator. The energy storage and refrigeration unit includes an evaporator, an ammonia compressor, a heat storage system, a throttle valve, and a high-pressure liquid ammonia storage tank; the energy release unit includes a liquid ammonia pump, a regenerative system, an ammonia expander, a generator, a condenser, a throttle valve, and a low-pressure liquid ammonia storage tank; the heat storage system consists of a high-temperature heat storage device, a medium-temperature heat storage device, and a low-temperature heat storage device, and the heat storage medium flow rates of each heat storage device are independent of each other; the regenerative system consists of a high-temperature recuperator, a medium-temperature recuperator, and a low-temperature recuperator, and the heat storage medium flow rates of each recuperator are independent of each other. Compared with the prior art, the high-temperature heat storage device, the medium-temperature heat storage device, and the low-temperature heat storage device are used to recover the compression heat of ammonia in a gradient manner. The flow rates of the three heat storage devices are independent of each other. On the one hand, it is beneficial to overcome the pinch point problem caused by the large specific heat capacity near the critical point and increase the inlet temperature of the expander. On the other hand, it avoids the use of expensive heat transfer oil. The present invention does not require an ice cold storage or a packed bed cold storage regenerator, nor does it require a two-phase expander, and can liquefy the working medium under low pressure and normal temperature conditions, simplify the system process, reduce the investment cost, and can also output cold to increase the investment income.

[0047] The above is only a preferred specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Any person skilled in the art within the technical scope disclosed by the present invention, according to the technical solution of the present invention and its inventive concept, makes equivalent substitutions or changes, and all should be covered within the protection scope of the present invention.

Claims

1. An integrated liquefied compressed ammonia energy storage and refrigeration system without a regenerator, characterized in that, The system includes an ammonia compressor, an electric motor, a high-temperature heat accumulator, a medium-temperature heat accumulator, a low-temperature heat accumulator, a first throttle valve, a high-pressure liquid ammonia storage tank, a liquid ammonia pump, a low-temperature recuperator, a medium-temperature recuperator, a high-temperature recuperator, an ammonia expander, a generator, a condenser, a low-pressure liquid ammonia storage tank, a second throttle valve, an evaporator, a pressurized water storage tank, a Hitec molten salt storage tank, a HitecXL molten salt storage tank, and a radiator; The output end of the evaporator successively passes through an ammonia compressor, a high-temperature heat accumulator, a medium-temperature heat accumulator, a low-temperature heat accumulator, a first throttle valve, and a high-pressure liquid ammonia storage tank to form an energy storage and refrigeration unit of the energy storage system; The output end of the liquid ammonia pump successively passes through a low-temperature recuperator, a medium-temperature recuperator, a high-temperature recuperator, an ammonia expander, a condenser, a second throttle valve, and a low-pressure liquid ammonia storage tank to form an energy release unit of the energy storage system; The high-temperature radiator, the low-temperature side of the high-temperature heat accumulator, the Hitec molten salt storage tank, and the high-temperature side of the high-temperature recuperator are connected in a pipeline loop; The medium-temperature radiator, the low-temperature side of the medium-temperature heat accumulator, the HitecXL molten salt storage tank, and the high-temperature side of the medium-temperature recuperator are connected in a pipeline loop; The low-temperature radiator, the low-temperature side of the low-temperature heat accumulator, the pressurized water storage tank, and the high-temperature side of the low-temperature recuperator are connected in a pipeline loop.

2. The integrated liquefied compressed ammonia energy storage refrigeration system without an accumulator according to claim 1, wherein Ammonia is used as the energy storage working medium, and the exhaust gas at the turbine outlet can be cooled to the liquid state by the atmospheric environment.

3. The integrated liquefied compressed ammonia energy storage refrigeration system without a cold accumulator according to claim 1, characterized in that, The heat storage system consists of three parts: a high-temperature heat accumulator, a medium-temperature heat accumulator, and a low-temperature heat accumulator, and the heat storage medium flow rates of each heat accumulator are independent of each other.

4. The integrated liquefied compressed ammonia energy storage refrigeration system without a cold accumulator according to claim 1, characterized in that The outlet pressure of the compressor is greater than the critical pressure of ammonia, and the exhaust gas temperature is lower than 500 °C.

5. The integrated liquefied compressed ammonia energy storage and refrigeration system without an accumulator according to claim 3, characterized in that The ammonia gas temperature at the outlet of the high-temperature side of the high-temperature heat accumulator is greater than 142 °C, and the ammonia gas temperature at the outlet of the high-temperature side of the medium-temperature heat accumulator is greater than 120 °C.

6. The integrated liquefied compressed ammonia energy storage and refrigeration system without a regenerator according to claim 4, wherein The heat storage medium of the high-temperature heat accumulator is Hitec molten salt, the heat storage medium of the medium-temperature heat accumulator is HitecXL molten salt, and the heat storage medium of the low-temperature heat accumulator is pressurized water.

7. The integrated liquefied compressed ammonia energy storage refrigeration system without a cold accumulator according to claim 4, characterized in that, The gasification temperature of ammonia in the evaporator is less than 10 °C, and the chilled water outlet temperature is less than 15 °C.

Images