CN118168269A - Transcritical depressurization liquefaction method and device for carbon dioxide energy storage system - Google Patents
Transcritical depressurization liquefaction method and device for carbon dioxide energy storage system Download PDFInfo
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- CN118168269A CN118168269A CN202410332993.6A CN202410332993A CN118168269A CN 118168269 A CN118168269 A CN 118168269A CN 202410332993 A CN202410332993 A CN 202410332993A CN 118168269 A CN118168269 A CN 118168269A
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- carbon dioxide
- energy storage
- storage system
- pressure
- transcritical
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- CURLTUGMZLYLDI-UHFFFAOYSA-N Carbon dioxide Chemical compound O=C=O CURLTUGMZLYLDI-UHFFFAOYSA-N 0.000 title claims abstract description 186
- 229910002092 carbon dioxide Inorganic materials 0.000 title claims abstract description 93
- 239000001569 carbon dioxide Substances 0.000 title claims abstract description 93
- 238000004146 energy storage Methods 0.000 title claims abstract description 44
- 238000000034 method Methods 0.000 title claims abstract description 33
- 239000007788 liquid Substances 0.000 claims abstract description 30
- 238000001816 cooling Methods 0.000 claims abstract description 21
- 230000008569 process Effects 0.000 claims description 20
- 230000009467 reduction Effects 0.000 claims description 9
- 230000009286 beneficial effect Effects 0.000 abstract description 2
- 238000005516 engineering process Methods 0.000 description 6
- 230000008859 change Effects 0.000 description 5
- 238000010276 construction Methods 0.000 description 5
- 238000009833 condensation Methods 0.000 description 3
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 3
- 238000005338 heat storage Methods 0.000 description 2
- 238000010248 power generation Methods 0.000 description 2
- 230000005494 condensation Effects 0.000 description 1
- 230000001419 dependent effect Effects 0.000 description 1
- 230000000694 effects Effects 0.000 description 1
- 230000005611 electricity Effects 0.000 description 1
- 230000007613 environmental effect Effects 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 238000005457 optimization Methods 0.000 description 1
- 230000000704 physical effect Effects 0.000 description 1
- 238000005057 refrigeration Methods 0.000 description 1
- 239000011555 saturated liquid Substances 0.000 description 1
- 238000006467 substitution reaction Methods 0.000 description 1
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- Carbon And Carbon Compounds (AREA)
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Abstract
The invention relates to a transcritical depressurization liquefaction method and device for a carbon dioxide energy storage system, and belongs to the technical field of compressed gas energy storage. The method comprises the steps of cooling supercritical carbon dioxide with fixed temperature and fixed pressure, introducing the supercritical carbon dioxide into a throttle valve, and reducing the pressure to automatically condense the supercritical carbon dioxide into liquid carbon dioxide. According to the invention, the throttle valve is arranged at the outlet of the post-cooler to replace the condenser so as to convert carbon dioxide into liquid state to be stored in the liquid storage tank, compared with a matched cooler and a condenser for cooling by a heat pump unit adopted by a conventional gas energy storage system, the throttle valve has a simple structure, can save a large amount of electric quantity for providing cold energy required by the condenser of the conventional system and matched auxiliary equipment, reduces the total occupied area of the energy storage system, and is beneficial to reducing the cost and occupied area of the energy storage system.
Description
Technical Field
The invention belongs to the technical field of compressed gas energy storage, and particularly relates to a transcritical depressurization liquefaction method and device for a carbon dioxide energy storage system.
Background
In order to change the serious unbalance phenomenon of peak load and valley load of the traditional power grid, energy storage technology is generated. The energy storage technology stores the low-valley power of the power grid, and releases the low-valley power during the peak period of power consumption, and the power system of the power grid has a storage space like a battery, so that the pressure of balanced power generation and power consumption is greatly reduced.
Today, large-scale energy storage technologies mainly include two relatively mature methods of pumped storage and compressed gas energy storage. Wherein the construction of the pumped-hydro energy storage system is highly dependent on the level differences provided for it by the local geographical conditions. Therefore, compressed gas energy storage technologies with high cycle efficiency, environmental friendliness, high durability, and low cost are considered to be promising large-scale clean physical energy storage technologies. The compressed carbon dioxide energy storage technology is favored by a plurality of researchers at home and abroad by virtue of the characteristics of wide application range, high energy storage density and compact system structure. However, the condenser for liquefying carbon dioxide in the traditional compressed carbon dioxide energy storage system requires a large amount of low-temperature cold energy, so that a chiller unit is required to be utilized for refrigeration, and the construction cost and the construction land of a pressurized storage project are greatly increased.
Based on the above statements and prior art analysis, it is known how to reduce the construction costs of compressed energy storage projects by freeing the chiller units and the construction land is the direction of optimization of compressed carbon dioxide energy storage.
Disclosure of Invention
In view of the above problems, the present invention provides a transcritical depressurization liquefaction method and device for a carbon dioxide energy storage system.
A first object of the present invention is to provide a transcritical pressure reduction liquefaction process for a carbon dioxide energy storage system comprising:
The supercritical carbon dioxide with fixed temperature and fixed pressure is cooled and then is introduced into a throttle valve to be decompressed and self-condensed into liquid carbon dioxide.
In the embodiment of the invention, the fixed temperature is 30.98 ℃ or higher.
In the embodiment of the invention, the fixed pressure is 7.38MPa or more.
In the embodiment of the invention, the supercritical carbon dioxide introduced into the throttle valve is reduced in pressure and self-condensed into liquid carbon dioxide, and the gaseous carbon dioxide generated by incomplete liquefaction is also included.
In the embodiment of the invention, the gaseous carbon dioxide generated by incomplete liquefaction is recycled and used as a source of supercritical carbon dioxide with fixed temperature and fixed pressure.
In an embodiment of the invention, the liquid carbon dioxide is stored.
A second object of the present invention is to provide a transcritical depressurization liquefaction device for a carbon dioxide energy storage system, comprising a gas circulation pipeline, a throttle valve disposed on the gas circulation pipeline, and a cooling device;
the cooling device is arranged at the periphery of the gas circulation pipeline;
in the gas flowing direction, the cooling device and the throttle valve are orderly sequenced;
The gas circulation pipeline is used for circulating supercritical carbon dioxide with fixed temperature and fixed pressure,
The cooling device is used for cooling supercritical carbon dioxide which circulates in a gas circulation pipeline at a fixed temperature and a fixed pressure;
The throttle valve is used for reducing pressure of cooled supercritical carbon dioxide with fixed temperature and fixed pressure to automatically condense the supercritical carbon dioxide into liquid carbon dioxide.
In the embodiment of the invention, the transcritical depressurization liquefying device further comprises a liquid storage device;
the liquid storage device is communicated with the gas circulation pipeline and is used for storing liquid carbon dioxide;
in the gas flowing direction, the throttle valve and the liquid storage device are sequentially ordered.
The invention has the beneficial effects that:
According to the transcritical depressurization liquefaction method and device for the carbon dioxide energy storage system, the throttling valve is arranged at the outlet of the post-stage cooler to replace the condenser so as to convert carbon dioxide into liquid state to be stored in the liquid storage tank, compared with a matched cold machine adopted by a conventional gas energy storage system and a condenser for cooling a heat pump unit, the throttling valve is simple in structure, a large amount of electricity and matched auxiliary equipment for providing cold energy required by the conventional system condenser can be saved, the total occupied area of the energy storage system is reduced, and the cost and occupied area of the energy storage system are reduced.
Meanwhile, the phenomenon of abrupt change of the enthalpy value of supercritical carbon dioxide at the critical point, namely, the enthalpy value of carbon dioxide can be greatly reduced in a section of pressure crossing the critical point. In the process of transcritical depressurization and throttling, more saturated liquid with low enthalpy tends to be obtained in the throttling process with approximate isenthalpic content, namely, the liquefaction rate of the transcritical depressurization and throttling is higher than that of the common phase change process.
The cooling process prior to throttling is above the critical pressure due to the carbon dioxide pressure throughout the energy storage system. Therefore, in the cooling process, the power of the heat exchanger is increased due to the phenomenon of sudden change of the transcritical enthalpy value. At this time, the residual quantity of the stored hot water can be increased, so that the efficiency of the whole system is directly affected, and the circulation efficiency of the system is increased.
Additional features and advantages of the invention will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. The objectives and other advantages of the invention may be realized and attained by the structure particularly pointed out in the written description and claims hereof as well as the appended drawings.
Drawings
In order to more clearly illustrate the embodiments of the present invention or the technical solutions of the prior art, the following description will briefly explain the drawings used in the embodiments or the description of the prior art, and it is obvious that the drawings in the following description are some embodiments of the present invention, and other drawings can be obtained according to these drawings without inventive effort for a person skilled in the art.
Fig. 1 illustrates a transcritical pressure reducing liquefaction plant for a carbon dioxide energy storage system according to an embodiment of the present invention.
Detailed Description
For the purpose of making the objects, technical solutions and advantages of the embodiments of the present invention more apparent, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention, and it is apparent that the described embodiments are some embodiments of the present invention, but not all embodiments of the present invention. All other embodiments, which can be made by those skilled in the art based on the embodiments of the invention without making any inventive effort, are intended to be within the scope of the invention.
According to an embodiment of the invention, a transcritical depressurization liquefaction method for a carbon dioxide energy storage system comprises the following steps:
The supercritical carbon dioxide with fixed temperature and fixed pressure is cooled and then is introduced into a throttle valve to be decompressed and self-condensed into liquid carbon dioxide.
The pressure reduction and condensation process is that supercritical carbon dioxide passes through a throttle valve, and the pressure of the carbon dioxide is reduced under the pressure reduction effect of the throttle valve, so that the saturation temperature of the carbon dioxide is reduced; when the saturation temperature of the carbon dioxide reaches the actual temperature, the carbon dioxide can start to liquefy, and a small part of carbon dioxide gas exists, and the part of carbon dioxide can be recycled to serve as a source of supercritical carbon dioxide with fixed temperature and fixed pressure, enter a compressor and be recompressed to form the supercritical carbon dioxide with fixed temperature and fixed pressure, and participate in the cooling and throttling process again (namely, the supercritical carbon dioxide with fixed temperature and fixed pressure is introduced into a throttling valve to be subjected to the pressure reduction and self-condensation process), so that the utilization efficiency of the carbon dioxide energy storage system on the carbon dioxide is improved.
In the embodiment of the invention, the fixed temperature is 30.98 ℃ or higher; the fixed pressure is more than or equal to 7.38MPa;
In order to improve the throttling efficiency of the transcritical depressurization and liquefaction method for the carbon dioxide energy storage system, the fixed temperature is any specific temperature value within 30.98-35 ℃, and the fixed pressure is any specific pressure value within 7.38-9.5 MPa.
In an embodiment of the invention, the liquid carbon dioxide is stored.
In the embodiment of the invention, the carbon dioxide is supercritical carbon dioxide, wherein the process of introducing the supercritical carbon dioxide into a throttle valve and performing pressure reduction and self-condensation can also be called as a transcritical process.
As shown in fig. 1, a transcritical depressurization liquefying device for a carbon dioxide energy storage system according to an embodiment of the present invention includes a gas circulation pipeline, a throttle valve disposed on the gas circulation pipeline, and a cooling device;
Specifically, the cooling device is a cooling device well known in the art, as shown in fig. 1, a heat circulation path formed by a cooler, a first heat-conducting medium storage tank and a second heat-conducting medium storage tank forms a heat storage system, so as to cool carbon dioxide to reduce the temperature to be close to a critical point, and store heat on a medium for turbine use in power generation.
In the embodiment of the invention, the transcritical depressurization liquefying device for the carbon dioxide energy storage system further comprises a liquid storage device;
The liquid storage device is communicated with the gas circulation pipeline;
in the gas flowing direction, the throttle valve and the liquid storage device are sequentially ordered.
In some embodiments of the present invention, taking a depressurization and throttling process using high-temperature and high-pressure (the temperature is 33 ℃ and the fixed pressure is 8 MPa) carbon dioxide as a working medium as an example, the specific process of the transcritical depressurization and liquefaction method for the carbon dioxide energy storage system provided by the present invention is as follows:
The pressure of the incoming carbon dioxide after passing through the cooling device is kept above the critical pressure, and the temperature is reduced to be close to the critical temperature;
The carbon dioxide flows through a throttle valve, the purpose of reducing the pressure is achieved by approximately isenthalpic throttling in the throttle valve, the saturation temperature of the carbon dioxide is reduced when the pressure is reduced, and when the saturation temperature is lower than the carbon dioxide temperature, the carbon dioxide is liquefied into liquid and a small part of gas;
at this time, the liquid carbon dioxide enters the liquid tank for storage. And the heat stored by the heat conducting medium enters the subsequent process when the heat needs to be released;
The depressurization and liquefaction rate of this process is related to the incoming flow conditions. The method is calculated by approximate isenthalpic throttling, the temperature is at a critical temperature, the temperature is reduced by 2MPa, and the liquefaction rate is more than 3 times of the liquefaction rate when the incoming flow is in a gaseous state when the incoming flow is in a supercritical state. This is because the physical properties of carbon dioxide generally change substantially linearly, but the enthalpy value of carbon dioxide changes significantly when transcritical. Leading to lower enthalpy of incoming flow at transcritical, more prone to liquid carbon dioxide with lower enthalpy, and therefore higher depressurization and liquefaction rates.
When the incoming carbon dioxide is cooled to near-critical temperature, medium such as normal pressure water (heat conducting medium is cooled and stored in a first heat conducting medium storage tank) or heat conducting oil is needed for heat storage. The nature of supercritical carbon dioxide determines that the cooling enthalpy drop before transcritical depressurization and liquefaction is larger, and the power of a cooler is larger, so that the flow of normal-pressure hot water (heat conducting medium heat stored in a second heat conducting medium storage tank) is more and the temperature is higher. Thereby improving the efficiency of the whole carbon dioxide energy storage system.
Although the invention has been described in detail with reference to the foregoing embodiments, it will be understood by those of ordinary skill in the art that: the technical scheme described in the foregoing embodiments can be modified or some technical features thereof can be replaced by equivalents; such modifications and substitutions do not depart from the spirit and scope of the technical solutions of the embodiments of the present invention.
Claims (8)
1. A transcritical pressure reduction liquefaction process for a carbon dioxide energy storage system, comprising:
The supercritical carbon dioxide with fixed temperature and fixed pressure is cooled and then is introduced into a throttle valve to be decompressed and self-condensed into liquid carbon dioxide.
2. The transcritical pressure reduction liquefaction process for a carbon dioxide energy storage system of claim 1, wherein the fixed temperature is 30.98 ℃ or greater.
3. The transcritical pressure reduction liquefaction process for a carbon dioxide energy storage system of claim 1, wherein the fixed pressure is 7.38MPa or greater.
4. A transcritical pressure reducing liquefaction process for a carbon dioxide energy storage system according to claim 1, wherein the supercritical carbon dioxide fed to the throttling valve is not fully liquefied but reduced in pressure to liquid carbon dioxide.
5. The method of claim 4, wherein the gaseous carbon dioxide produced by the incomplete liquefaction is recycled as a source of supercritical carbon dioxide at a fixed temperature and a fixed pressure.
6. A transcritical pressure reducing liquefaction process for a carbon dioxide energy storage system according to any of claims 1-5 wherein said liquid carbon dioxide is stored.
7. The transcritical depressurization liquefying device for the carbon dioxide energy storage system is characterized by comprising a gas circulation pipeline, a throttle valve arranged on the gas circulation pipeline and a cooling device;
the cooling device is arranged at the periphery of the gas circulation pipeline;
in the gas flowing direction, the cooling device and the throttle valve are orderly sequenced;
The gas circulation pipeline is used for circulating supercritical carbon dioxide with fixed temperature and fixed pressure,
The cooling device is used for cooling supercritical carbon dioxide which circulates in a gas circulation pipeline at a fixed temperature and a fixed pressure;
The throttle valve is used for reducing pressure of cooled supercritical carbon dioxide with fixed temperature and fixed pressure to automatically condense the supercritical carbon dioxide into liquid carbon dioxide.
8. The transcritical pressure reduction liquefaction device for a carbon dioxide energy storage system of claim 7, further comprising a liquid storage device;
the liquid storage device is communicated with the gas circulation pipeline and is used for storing liquid carbon dioxide;
in the gas flowing direction, the throttle valve and the liquid storage device are sequentially ordered.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202410332993.6A CN118168269A (en) | 2024-03-22 | 2024-03-22 | Transcritical depressurization liquefaction method and device for carbon dioxide energy storage system |
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| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202410332993.6A CN118168269A (en) | 2024-03-22 | 2024-03-22 | Transcritical depressurization liquefaction method and device for carbon dioxide energy storage system |
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| Publication Number | Publication Date |
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| CN118168269A true CN118168269A (en) | 2024-06-11 |
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| CN202410332993.6A Pending CN118168269A (en) | 2024-03-22 | 2024-03-22 | Transcritical depressurization liquefaction method and device for carbon dioxide energy storage system |
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| Country | Link |
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- 2024-03-22 CN CN202410332993.6A patent/CN118168269A/en active Pending
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