Flue gas liquefaction energy storage and carbon dioxide capture system for coal-fired power plant and use method thereof

Abstract

The invention provides a coal-fired power plant flue gas liquefaction energy storage and carbon dioxide capture system and a use method thereof.The system comprises a low-temperature water washing module used for cooling flue gas and recovering moisture and pollutants in the flue gas; the flue gas compression module compresses the flue gas and cools the flue gas through the interstage heat exchanger; the carbon dioxide separation module is used for separating liquid carbon dioxide from high-pressure flue gas; the energy storage module is used for cooling, expanding and liquefying the high-pressure flue gas and storing the high-pressure flue gas in a liquid flue gas storage tank; the energy release module separates the liquid flue gas into gaseous oxygen and liquid nitrogen, the oxygen is supplied to the boiler for combustion, and the nitrogen generates power through the expansion machine. According to the invention, water in flue gas is recovered by cleaning the flue gas with cold water; carbon dioxide in flue gas is captured by compressing the tail gas of the coal-fired power plant and cooling, and energy is stored by high-pressure flue gas from which carbon dioxide is removed through pressurization; the high-pressure flue gas is liquefied by cooling and expanding the high-pressure flue gas and is stored in a liquid storage tank; liquefied flue gas vaporization pushes the expansion machine to generate electricity and output electric energy, and the energy utilization rate is high.

Description

Technical Field

[0001] The present invention relates to the technical field of carbon capture and energy storage, and in particular to a flue gas liquefaction energy storage and carbon dioxide capture system for a coal-fired power plant and a method of using the system. Background Art

[0002] As the main fossil fuel, coal occupies an important position in my country's energy structure, but its widespread use has brought about serious carbon dioxide emissions. Carbon dioxide is a major greenhouse gas, and its excessive emissions are a key factor leading to global warming.

[0003] In the existing technology, carbon dioxide capture and storage (CCS) technology mainly includes post-combustion capture, pressure swing adsorption and electrochemical desorption. Among them, low-temperature liquefaction and separation of carbon dioxide has become a research hotspot due to its low cost. However, traditional carbon dioxide capture systems still have problems such as high energy consumption, secondary pollution and high cost. Therefore, in order to achieve zero carbon emissions throughout the life cycle of coal-fired power plants, an efficient, energy-saving and low-cost carbon dioxide capture and energy storage system is urgently needed. Summary of the invention

[0004] The purpose of the present invention is to provide a flue gas liquefaction energy storage and carbon dioxide capture system for a coal-fired power plant and a method of using the system, which can comprehensively realize carbon dioxide capture, energy storage and recovery of pollutants in the flue gas through low-temperature water washing, flue gas compression and cooling, expansion and liquefaction, optimize the energy structure, reduce carbon emissions and alleviate environmental pressure.

[0005] According to one object of the present invention, the present invention provides a coal-fired power plant flue gas liquefaction energy storage and carbon dioxide capture system, comprising:

[0006] Low-temperature water washing module, used to cool the flue gas to 0-10℃ and recover moisture and pollutants in the flue gas;

[0007] Flue gas compression module, used to compress the flue gas to 7-10MPa and cool it through the interstage heat exchanger;

[0008] A carbon dioxide separation module is used to separate liquid carbon dioxide from high-pressure flue gas and store it in a liquid carbon dioxide storage tank;

[0009] Energy storage module, used to cool and expand the high-pressure flue gas and then store it in a liquid flue gas storage tank;

[0010] The energy release module is used to separate the liquid flue gas into gaseous oxygen and liquid nitrogen. The oxygen is used for boiler combustion, and the nitrogen is used to generate electricity through the expander.

[0011] Furthermore, the cooling water of the low-temperature water washing module is provided by cooling the decompressed and expanded gaseous carbon dioxide.

[0012] Furthermore, the flue gas compression module adopts a two-stage or multi-stage compressor, and the stages are cooled by a low-temperature water heat exchanger.

[0013] Furthermore, the separation tower realizes separation by utilizing the difference in boiling points between oxygen and nitrogen.

[0014] Furthermore, the energy release module includes a liquid flue gas booster pump for pressurizing the liquid flue gas.

[0015] Furthermore, the high-pressure flue gas is cooled by heat exchange with ethanol and propane in the energy storage module.

[0016] Furthermore, the liquid nitrogen is passed through an expander to generate electricity.

[0017] Furthermore, the switching of the energy storage and release processes is controlled by a switching valve.

[0018] Furthermore, the energy release module recovers the cold energy of the expanded exhaust gas through a high-temperature water storage tank and an inter-stage heat exchanger.

[0019] According to another object of the present invention, the present invention provides a method for using the above-mentioned coal-fired power plant flue gas liquefaction energy storage and carbon dioxide capture system, comprising the following steps:

[0020] S1. Carbon dioxide capture and energy storage

[0021] S101, low temperature water washing and preliminary treatment

[0022] The flue gas enters the low-temperature water washing module from the desulfurization tower and exchanges heat with 0-10℃ water;

[0023] The flue gas is cooled to 0-10℃, the moisture and some pollutants are condensed and recovered, and the condensate is recycled;

[0024] S102, Flue gas compression

[0025] The low-temperature flue gas is compressed to a high-temperature and high-pressure state by a first-stage compressor;

[0026] After being cooled in the first and second stage heat exchangers, the flue gas temperature is reduced and part of the liquid carbon dioxide is condensed;

[0027] S103, Separation and Storage

[0028] The gas-phase high-pressure gas and liquid carbon dioxide are separated in the gas-liquid separator, and the liquid carbon dioxide is stored in a storage tank, part of which is supplied for external use and part of which is used for refrigeration cycle;

[0029] S2. High-pressure gas energy storage

[0030] S201, High-pressure gas cooling and expansion

[0031] The gas phase high pressure gas is cooled by the flue gas cooler and then passes through the ethanol and propane storage tanks for deep cooling;

[0032] Then it enters the expansion refrigerator to do work, and the gas and liquid phases are separated;

[0033] S202, Liquid Storage and Recycling

[0034] The liquid part enters the liquid flue gas storage tank;

[0035] The gaseous part passes through the heat exchanger to recover cold energy and then returns to the compressor inlet;

[0036] S3, Energy Release

[0037] S301, pressurization and separation

[0038] The liquid flue gas is pressurized by a booster pump and separated into gaseous oxygen and liquid nitrogen in a separation tower by utilizing the temperature difference;

[0039] Gaseous oxygen is used for boiler combustion to reduce flue gas emissions;

[0040] S302, heat exchange and expansion power generation

[0041] Liquid nitrogen is heated to room temperature after heat exchange;

[0042] After passing through the interstage heater to form high-temperature and high-pressure gas, it then enters the expander to perform work to generate electricity;

[0043] Finally, exhaust emissions.

[0044] The technical solution of the present invention uses cold water close to zero degrees to clean the flue gas and recover the moisture in the flue gas; captures the carbon dioxide in the flue gas by compressing the tail gas of the coal-fired power plant and cooling it, and uses the high-pressure flue gas after the carbon dioxide is removed by pressurization for energy storage, thereby realizing the reuse of the high-pressure gas and reducing energy consumption; the high-pressure flue gas is cooled and expanded to liquefy the high-pressure flue gas and store it in a liquid storage tank, thereby saving storage space; the liquefied flue gas is vaporized to drive the expander to generate electricity and output electrical energy; the system makes full use of the pressure energy in the flue gas, captures carbon dioxide and reduces carbon emissions, and the system is simple and has high energy utilization rate. BRIEF DESCRIPTION OF THE DRAWINGS

[0045] In order to more clearly illustrate the specific implementation methods of the present invention or the technical solutions in the prior art, the drawings required for use in the specific implementation methods or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are some implementation methods of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0046] Figure 1It is a schematic diagram of the overall structure of an embodiment of the present invention.

[0047] In the figure: 1. Low-temperature water washing module; 2. Collecting water tank; 3. Primary compressor; 4. Secondary compressor; 5. Gas-liquid separator; 6. Liquid carbon dioxide storage tank; 7. Flue gas cooler; 8. Expansion refrigerator; 9. Separator; 10. Liquid flue gas storage tank; 11. Ethanol storage tank; 12. Propane storage tank; 13. Flue gas recooler; 14. Liquid flue gas booster pump; 15. Separation tower; 16. Air heater; 17. High-temperature water storage tank; 18. Primary expander; 19. Secondary expander; 20. Low-temperature water storage tank. DETAILED DESCRIPTION

[0048] The technical solution of the present invention will be clearly and completely described below in conjunction with the embodiments. Obviously, the described embodiments are part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0049] In the description of the present invention, it should be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", "clockwise", "counterclockwise" and the like indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the referred device or element must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as limiting the present invention.

[0050] In addition, the terms "first" and "second" are only used for descriptive purposes and cannot be understood as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Therefore, the features defined as "first" and "second" may explicitly or implicitly include one or more of the features. In the description of the present invention, "multiple" means two or more, unless otherwise clearly and specifically defined. In addition, the terms "installed", "connected" and "connected" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be indirectly connected through an intermediate medium, or it can be the internal connection of two components. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0051] Example 1

[0052] like Figure 1 As shown,

[0053] A coal-fired power plant flue gas liquefaction energy storage and carbon dioxide capture system, comprising the following modules:

[0054] Low-temperature water washing module: exchanges heat between flue gas and cold water close to zero degrees, cools the flue gas to 0-10°C, condenses and recovers moisture and pollutants in the flue gas;

[0055] Flue gas compression module: compresses flue gas through multi-stage compressors to form high-temperature and high-pressure flue gas, and cools the flue gas through inter-stage heat exchangers;

[0056] Carbon dioxide separation module: uses a gas-liquid separator to separate liquid carbon dioxide and store it in a liquid carbon dioxide storage tank;

[0057] Energy storage module: cools and expands the high-pressure flue gas to liquefy it and store it in a liquid flue gas storage tank;

[0058] Energy release module: Gaseous oxygen and liquid nitrogen are separated through liquid flue gas pressurization and separation towers. The oxygen is burned in the boiler burner; the nitrogen is converted into electrical energy for output through an expander.

[0059] Specifically, when the system captures CO2 and stores energy:

[0060] The flue gas from the desulfurization tower first enters the low-temperature water washing module 1, exchanges heat with low-temperature water at a temperature of 0-10°C, cools the flue gas to 0 to 10°C, condenses and recovers moisture and some pollutants in the flue gas, and the condensate is sent to the boiler chemical water workshop through the collection water tank 2 for recycling after purification;

[0061] Subsequently, the treated low-temperature flue gas enters the first-stage compressor 3 for compression to form high-temperature and high-pressure flue gas, and is cooled to 40-50°C by the interstage heat exchanger to further condense the moisture in the flue gas;

[0062] The flue gas then enters the secondary compressor 4, where it is further compressed to 7-10 MPa and the temperature rises to 200-300°C. The flue gas temperature is cooled again by the second interstage heat exchanger to drop to 30-50°C, and part of the liquid carbon dioxide is condensed and enters the gas-liquid separator 5 together with the high-pressure flue gas. In the gas-liquid separator, the gas phase high-pressure gas is discharged from the top of the separator, and the liquid phase carbon dioxide is discharged into the liquid carbon dioxide storage tank 6;

[0063] In this embodiment, the carbon dioxide separation module includes a gas-liquid separator 5 and a liquid carbon dioxide storage tank 6. The gas-liquid separator is connected to the flue gas compression module. Liquid carbon dioxide is separated by the gas-liquid separator and stored in the liquid carbon dioxide storage tank.

[0064] Part of the liquid carbon dioxide in the liquid carbon dioxide storage tank will be supplied to the outside through pipelines or tank trucks, and the other part will be reduced in pressure and expanded to become gaseous carbon dioxide of about 0.5-0.7MPa, -10-0℃ for cooling the circulating water of the low-temperature water washing module;

[0065] In this embodiment, the interstage heat exchanger arranged between the compressors provides high-pressure low-temperature water of about 2-3 MPa and 20-30°C through the low-temperature water storage tank 20, and the high-temperature water after heat exchange and temperature increase enters the high-temperature water storage tank.

[0066] Specifically: When the system performs high-pressure gas energy storage:

[0067] The gas phase high pressure gas is discharged from the gas-liquid separator 5 and enters the flue gas cooler 7 for cooling. After its temperature is reduced by the flue gas cooler 7, it enters the expansion refrigerator 8 to perform work. After the work is performed, the gas-liquid two-phase fluid is separated by the separator 9, and the liquid gas is stored in the liquid flue gas storage tank 10.

[0068] In this embodiment, the gas phase high pressure gas is cooled by the flue gas cooler, and then passes through the ethanol storage tank 11 and the propane storage tank 12 in sequence and then enters the expansion refrigerator to perform work. In this process, Figure 1 As shown, it is necessary to close switching valve 1, switching valve 3, switching valve 5 and switching valve 7, and open switching valve 2, switching valve 4 and switching valve 6. The cooled high-pressure flue gas first exchanges heat with ethanol through the gas distributor in the ethanol storage tank and then enters the propane storage tank, exchanges heat with liquid propane through the gas distributor and further cools down.

[0069] After the high-pressure flue gas is cooled, it will enter the flue gas recooler 13 for heat exchange before entering the expansion refrigerator 8, and then enter the expansion machine 8 for expansion to do work and liquefaction. The gas-liquid two-phase fluid after passing through the expander 8 passes through the separator 9, and the liquid enters the liquid flue gas storage tank 10. After the gas is heated by the flue gas recooler 13, it is heated again by the flue gas cooler 7, and returns to the inlet of the primary compressor 3 after recovering its cold energy.

[0070] Specifically: When the system releases energy:

[0071] The liquid from the liquid flue gas storage tank 10 first passes through the liquid flue gas booster pump 14 to be pressurized to 7-10 MPa, and then passes through the separation tower 15, where it absorbs external heat and is separated into gaseous oxygen and liquid nitrogen in the separation tower due to the difference in boiling points between oxygen and nitrogen. The gaseous oxygen is discharged from the top of the separation tower 15 and burned in the boiler burner to reduce the amount of boiler flue gas.

[0072] Liquid nitrogen is discharged from the bottom of the separation tower, vaporized in the propane storage tank, and cools the liquid propane, and then enters the ethanol storage tank for heat exchange to lower the temperature of ethanol; during this process, it is necessary to close switching valve 2, switching valve 4 and switching valve 6, and open switching valve 1, switching valve 3, switching valve 5 and switching valve 7.

[0073] Then it exchanges heat with the air through the air heater 16, absorbs the heat of the air, and heats itself to room temperature; the high-pressure flue gas heated to room temperature passes through the interstage heater, exchanges heat with the high-temperature water from the high-temperature water storage tank 17, forms a high-temperature and high-pressure gas of about 200°C and 7 to 10MPa, and enters the first-stage expander 18 to generate work and electricity; similarly, the gas after doing work enters the interstage heat exchanger again, exchanges heat with the high-temperature water from the high-temperature water storage tank, and forms a high-temperature and high-pressure gas of 200°C and 7 to 10MPa again, and enters the second-stage expander 19 to generate work and electricity, and the exhaust gas is discharged through the chimney.

[0074] The present invention uses cold water close to zero degrees to clean the flue gas and recover the moisture in the flue gas; captures the carbon dioxide in the flue gas by compressing the tail gas of the coal-fired power plant and cooling it, and uses the high-pressure flue gas after the carbon dioxide is removed by pressurization for energy storage, thereby realizing the reuse of the high-pressure gas and reducing energy consumption; the high-pressure flue gas is cooled and expanded to liquefy the high-pressure flue gas and store it in a liquid storage tank, thereby saving storage space; the liquefied flue gas is vaporized to drive the expander to generate electricity and output electrical energy; the system makes full use of the pressure energy in the flue gas, captures carbon dioxide and reduces carbon emissions, and the system is simple and has a high energy utilization rate.

[0075] The present invention is based on an integrated system of flue gas liquefaction energy storage and carbon dioxide capture, which solves the problems of high carbon emissions and low energy utilization in existing coal-fired power plants, and provides a new technical path for achieving the goal of low-carbon and sustainable development.

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

Claims

1. A coal-fired power plant flue gas liquefaction energy storage and carbon dioxide capture system, characterized in that: include: Low-temperature water washing module, used to cool the flue gas and recover moisture and pollutants in the flue gas; A flue gas compression module, used for compressing the flue gas and cooling it through an inter-stage heat exchanger; A carbon dioxide separation module is used to separate liquid carbon dioxide from high-pressure flue gas and store it in a liquid carbon dioxide storage tank; Energy storage module, used to cool and expand the high-pressure flue gas and then store it in a liquid flue gas storage tank; The energy release module is used to separate the liquid flue gas into gaseous oxygen and liquid nitrogen. The oxygen is used for boiler combustion, and the nitrogen is used to generate electricity through the expander.

2. The coal-fired power plant flue gas liquefaction energy storage and carbon dioxide capture system according to claim 1, characterized in that: The cooling water of the low-temperature water washing module is provided by cooling the gaseous carbon dioxide which is expanded under reduced pressure.

3. The coal-fired power plant flue gas liquefaction energy storage and carbon dioxide capture system according to claim 1, characterized in that: The flue gas compression module adopts a two-stage or multi-stage compressor, and the interstage is cooled by a low-temperature water heat exchanger.

4. The coal-fired power plant flue gas liquefaction energy storage and carbon dioxide capture system according to claim 1, characterized in that: The energy release module includes a separation tower, which realizes separation by utilizing the difference in boiling points between oxygen and nitrogen.

5. The coal-fired power plant flue gas liquefaction energy storage and carbon dioxide capture system according to claim 1, characterized in that: The energy release module comprises a liquid flue gas booster pump for boosting the pressure of the liquid flue gas.

6. The coal-fired power plant flue gas liquefaction energy storage and carbon dioxide capture system according to claim 1, characterized in that: The high-pressure flue gas is cooled by heat exchange with ethanol and propane in the energy storage module.

7. The coal-fired power plant flue gas liquefaction energy storage and carbon dioxide capture system according to claim 1, characterized in that: Liquid nitrogen passes through an expander to generate electricity.

8. The coal-fired power plant flue gas liquefaction energy storage and carbon dioxide capture system according to claim 1, characterized in that: The switching of energy storage and energy release processes is controlled by a switching valve.

9. The coal-fired power plant flue gas liquefaction energy storage and carbon dioxide capture system according to claim 1, characterized in that: The energy release module recovers the cold energy of the expanded exhaust gas through a high-temperature water storage tank and an interstage heat exchanger.

10. The method for using the coal-fired power plant flue gas liquefaction energy storage and carbon dioxide capture system according to claim 1, characterized in that: The steps include: S1. Carbon dioxide capture and energy storage S101, low temperature water washing and preliminary treatment The flue gas enters the low-temperature water washing module from the desulfurization tower and exchanges heat with 0-10℃ water; The flue gas is cooled to 0-10℃, the moisture and some pollutants are condensed and recovered, and the condensate is recycled; S102, Flue gas compression The low-temperature flue gas is compressed to a high-temperature and high-pressure state by a first-stage compressor; After being cooled in the first and second stage heat exchangers, the flue gas temperature is reduced and part of the liquid carbon dioxide is condensed; S103, Separation and Storage The gas-phase high-pressure gas and liquid carbon dioxide are separated in the gas-liquid separator, and the liquid carbon dioxide is stored in a storage tank, part of which is supplied for external use and part of which is used for refrigeration cycle; S2. High-pressure gas energy storage S201, High-pressure gas cooling and expansion The gas phase high pressure gas is cooled by the flue gas cooler and then passes through the ethanol and propane storage tanks for deep cooling; Then it enters the expansion refrigerator to do work, and the gas and liquid phases are separated; S202, Liquid Storage and Recycling The liquid part enters the liquid flue gas storage tank; The gaseous part passes through the heat exchanger to recover cold energy and then returns to the compressor inlet; S3, Energy Release S301, pressurization and separation The liquid flue gas is pressurized by a booster pump and separated into gaseous oxygen and liquid nitrogen in a separation tower by utilizing the temperature difference; Gaseous oxygen is used for boiler combustion to reduce flue gas emissions; S302, heat exchange and expansion power generation Liquid nitrogen is heated to room temperature after heat exchange; After passing through the interstage heater to form high-temperature and high-pressure gas, it then enters the expander to perform work to generate electricity; Finally, exhaust emissions.

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