Coal-fired power plant carbon capture system coupled with thermochemical energy storage and method

Abstract

The application discloses a coal-fired unit carbon capture system coupled with thermochemical energy storage and a method thereof. The coal-fired unit carbon capture method of the application adopts the technical scheme that in the full load section of the coal-fired unit, in the carbonizer, CaO is used to absorb and capture CO2 in the tail flue gas of the coal-fired boiler, the absorbed and captured CO2 is mixed with pure O2, the volume fraction of O2 in the mixed gas is controlled according to the load of the coal-fired unit, and the oxygen-enriched combustion is formed in the coal-fired boiler; when the power grid is in the low valley period of electricity consumption, the flue gas of the coal-fired boiler is extracted, the heat of the flue gas is used to make CaCO3 in the calciner to have a reduction reaction, the reduced CaO is stored in the CaO storage container, and part of the power generated by the coal-fired unit is used to drive the air separation device; when the power grid is in the peak period of electricity consumption, part of the power of the energy storage device is used to drive the air separation device. The application can meet the carbon capture needs of the full load section of the coal-fired unit, can improve the low load stable combustion and deep peak shaving capacity of the coal-fired unit, and can provide support for the peak load shifting of the power grid.

Description

Technical Field

[0001] This invention belongs to the field of thermal power unit technology, specifically a carbon capture system and method for coal-fired power units coupled with thermochemical energy storage. Background Technology

[0002] Regarding carbon emission reduction in the power industry, on the one hand, carbon emissions can be reduced by developing clean and low-carbon energy sources; however, on the other hand, due to my country's coal-dominated energy structure and future energy security needs, it still faces substantial challenges in carbon emission reduction. Conducting large-scale carbon capture and utilization research and demonstrations in coal-fired power plants is of significant practical importance for achieving carbon emission reduction and carbon neutrality in coal-fired power plants in the future.

[0003] In recent years, the introduction of the "dual carbon" target has led to a significant increase in the installed capacity of renewable energy in the future. This large-scale grid connection will pose unprecedented challenges to the stability of the power system. To improve the safety and flexibility of grid operation and dispatch, coal-fired power units, currently the main source of power generation, will inevitably have to undertake more frequent deep peak-shaving tasks under ultra-low loads. By coupling thermochemical energy storage and carbon capture systems, the deep peak-shaving capability of coal-fired power units will be improved to a certain extent.

[0004] In the past, coal-fired power units were limited by their load response and ultra-low load operation capabilities, which affected their ability to quickly adjust the load on the power grid and their deep peak-shaving performance. In addition, carbon capture systems require additional energy consumption, which affects the output of coal-fired power units during peak electricity demand periods. Summary of the Invention

[0005] The technical problem to be solved by the present invention is to overcome the defects of the prior art and provide a carbon capture system and method for coal-fired power units coupled with thermochemical energy storage. This system couples the application of coal-fired power units with thermochemical energy storage and carbon capture systems to meet the carbon capture needs of coal-fired power units at full load, improve the low-load stable combustion and deep peak-shaving capabilities of coal-fired power units, and provide support for peak shaving and valley filling of the power grid.

[0006] Therefore, one technical solution adopted by the present invention is: a coal-fired unit carbon capture system coupled with thermochemical energy storage, which includes a coal-fired boiler, flue gas pipeline, heat exchange system, heat transfer oil pipeline, calciner, carbonizer, CaO storage container, CaCO3 storage container, CO2 storage container, generator, air separation unit, energy storage device, mixer, power grid, CaCO3 conveying pipeline, CaO conveying pipeline, CO2 conveying pipeline, pure O2 conveying pipeline, combustion gas conveying pipeline, first switch, first transformer, second switch, second transformer and output line;

[0007] The generator is connected to the power grid via a first switch, a first transformer, and an output line;

[0008] The output line is connected to the air separation unit and the energy storage unit via a second switch and a second transformer.

[0009] The flue gas pipeline connects the coal-fired boiler and the heat exchange system;

[0010] The heat transfer oil pipeline connects the calciner and the heat exchange system;

[0011] The CaCO3 delivery pipeline connects the calciner, the carbonizer, and the CaCO3 storage container;

[0012] The CaO delivery pipeline connects the calciner, the carbonizer, and the CaO storage container;

[0013] The CO2 delivery pipeline connects the calciner, the CO2 storage container, and the mixer;

[0014] The pure O2 delivery pipeline connects the air separation unit and the mixer;

[0015] The combustion gas delivery pipeline connects the coal-fired boiler and the mixer.

[0016] Furthermore, the energy storage device and the air separation device are connected by the energy storage device output line.

[0017] Furthermore, an O2 volume fraction detection device is arranged inside the mixer.

[0018] Furthermore, flow controllers are provided on the flue gas pipeline, CaCO3 delivery pipeline, CaO delivery pipeline, CO2 delivery pipeline, pure O2 delivery pipeline, and combustion gas delivery pipeline.

[0019] Another technical solution adopted in this invention is: a carbon capture method for coal-fired power units coupled with thermochemical energy storage, which uses the above-mentioned carbon capture system for coal-fired power units coupled with thermochemical energy storage, and its contents are as follows:

[0020] At full load in the coal-fired power unit, CaO is used in the carbonizer to absorb and capture CO2 in the flue gas from the tail end of the coal-fired boiler. The absorbed and captured CO2 is mixed with pure O2, and the volume fraction of O2 in the mixed gas is controlled according to the load of the coal-fired power unit to form oxygen-enriched combustion in the coal-fired boiler. When the power grid is in a low-demand period, the flue gas from the coal-fired boiler is extracted, and the heat of the flue gas is used to reduce CaCO3 in the calciner. The CaO generated by the reduction is stored in the CaO storage container, and part of the power generated by the coal-fired power unit drives the air separation unit. When the power grid is in a high-demand period, part of the power of the energy storage device drives the air separation unit.

[0021] Compared with the prior art, the present invention has the following beneficial effects:

[0022] 1) In the past, coal-fired power units were limited by their own capacity and it was difficult to break through the bottleneck of deep peak shaving. This invention can effectively reduce the output power of the system by using calciner and air separation unit when the power grid is in a low period of electricity consumption and the system needs to quickly reduce the on-grid power, thereby achieving the purpose of breaking through the deep peak shaving power.

[0023] 2) In the past, carbon capture devices required a lot of energy, which affected the system output during peak electricity demand periods. This invention utilizes the CaCO3 / CaO reaction to extract flue gas for CaCO3 / CaO reduction during off-peak electricity demand periods. During peak electricity demand periods, flue gas extraction is stopped, and stored CaO is used to absorb CO2, effectively improving the system output.

[0024] 3) In the past, carbon capture devices required a lot of energy, which affected the system's carbon capture capacity during peak electricity demand periods. This invention utilizes the CaCO3 / CaO reaction to store a large amount of CaO during off-peak electricity demand periods, ensuring the system's carbon capture capacity throughout the day. Attached Figure Description

[0025] Figure 1 This is a schematic diagram of the carbon capture system for coal-fired power units coupled with thermochemical energy storage according to the present invention.

[0026] Among them, 1-coal-fired boiler, 2-flue gas pipeline, 3-heat exchange system, 4-heat transfer oil pipeline, 5-calciner, 6-carbonizer, 7-CaO storage container, 8-CaCO3 storage container, 9-CO2 storage container, 10-generator, 11-air separation unit, 12-energy storage device, 13-mixer, 14-O2 volume fraction detection device, 15-power grid, 16-CaCO3 conveying pipeline, 17-CaO conveying pipeline, 18-CO2 conveying pipeline, 19-energy storage device output line, 20-pure O2 conveying pipeline, 21-combustion gas conveying pipeline, 22-first switch, 23-first transformer, 24-second switch, 25-second transformer, 26-output line, 27-flow controller. Detailed Implementation

[0027] The specific embodiments of the present invention will be further described in detail below with reference to the accompanying drawings, so as to make the technical solutions of the present invention easier to understand and master. It should be understood that the specific embodiments described herein are only used to explain a part of the embodiments of the invention, and not all of the embodiments. Other embodiments obtained by those skilled in the art without creative effort are all within the scope of protection of the present invention.

[0028] Example 1

[0029] Please see the appendix Figure 1This is a schematic diagram of the carbon capture system for a coal-fired power unit coupled with thermochemical energy storage according to the present invention. The system includes: a coal-fired boiler 1, a flue gas pipeline 2, a heat exchange system 3, a heat transfer oil pipeline 4, a calciner 5, a carbonizer 6, a CaO storage container 7, a CaCO3 storage container 8, a CO2 storage container 9, a generator 10, an air separation unit 11, an energy storage device 12, a mixer 13, an O2 volume fraction detection device 14, a power grid 15, a CaCO3 conveying pipeline 16, a CaO conveying pipeline 17, a CO2 conveying pipeline 18, an energy storage device output line 19, a pure O2 conveying pipeline 20, a combustion gas conveying pipeline 21, a first switch 22, a first transformer 23, a second switch 24, a second transformer 25, an output line 26, and a flow controller 27.

[0030] The generator 10 is connected to the power grid 15 through the first switch 22, the first transformer 23 and the output line 26.

[0031] The output line 26 is connected to the air separation unit 11 and the energy storage unit 12 via the second switch 24 and the second transformer 25.

[0032] Flue gas pipeline 2 connects to coal-fired boiler 1 and heat exchange system 3.

[0033] The heat transfer oil pipeline 4 connects to the calciner 5 and the heat exchange system 3.

[0034] CaCO3 delivery pipeline 16 connects to calciner 5, carbonizer 6, and CaCO3 storage container 8.

[0035] CaO delivery pipeline 17 connects to calciner 5, carbonizer 6, and CaO storage container 7.

[0036] CO2 delivery pipeline 18 connects to calciner 5, CO2 storage container 9, and mixer 13.

[0037] The energy storage device output line 19 connects to the energy storage device 12 and the air separation device 11.

[0038] The pure O2 delivery pipeline 20 connects to the air separation unit 11 and the mixer 13.

[0039] Combustion gas delivery pipeline 21 connects to coal-fired boiler 1 and mixer 13.

[0040] The O2 volume fraction detection device 14 is arranged inside the mixer 13.

[0041] A flow controller 27 is installed on flue gas pipeline 2.

[0042] A flow controller 27 is installed on the CaCO3 delivery pipeline 16.

[0043] A flow controller 27 is installed on the CaO delivery pipeline 17.

[0044] A flow controller 27 is installed on the CO2 delivery pipeline 18.

[0045] A flow controller 27 is installed on the pure O2 delivery pipeline 20.

[0046] A flow controller 27 is installed on the combustion gas delivery pipeline 21.

[0047] The operation method of the coal-fired power unit carbon capture system coupled with thermochemical energy storage according to the present invention is as follows:

[0048] At full load in the coal-fired power unit, CaO is used in the carbonizer to absorb and capture CO2 in the flue gas from the tail end of the coal-fired boiler. The absorbed and captured CO2 is mixed with pure O2, and the volume fraction of O2 in the mixed gas is controlled according to the load of the coal-fired power unit to form oxygen-enriched combustion in the coal-fired boiler. When the power grid is in a low-demand period, the flue gas from the coal-fired boiler is extracted, and the heat of the flue gas is used to reduce CaCO3 in the calciner. The CaO generated by the reduction is stored in the CaO storage container, and part of the power generated by the coal-fired power unit drives the air separation unit. When the power grid is in a high-demand period, part of the power of the energy storage device drives the air separation unit.

[0049] Example 2

[0050] This invention provides a carbon capture method for coal-fired power units coupled with thermochemical energy storage, which is implemented using the carbon capture system for coal-fired power units coupled with thermochemical energy storage described in Example 1. The specific steps of this method are as follows:

[0051] In the full-load section of the coal-fired unit, CaO is used in carbonizer 6 to absorb and capture CO2 in the tail flue gas of coal-fired boiler 1. CaCO3 conveying pipeline 16 conveys CaCO3 from carbonizer 6 to CaCO3 storage container 8, and CaCO3 from CaCO3 storage container 8 to calciner 5. Flow controller 27 controls the flow rate of CaCO3 in CaCO3 conveying pipeline 16. CaO conveying pipeline 17 conveys CaO from calciner 5 to CaO storage container 7, and CaO from CaO storage container 7 to carbonizer 6. Flow controller 27 controls the flow rate of CaO in CaO conveying pipeline 17. CO2 conveying pipeline 18 conveys CO2 from calciner 5 to CO2 storage container 9, and CO2 from CO2 storage container 9 to mixer 13. Flow controller 27 controls the flow rate of CO2 in CO2 conveying pipeline 18. The O2 separated by the air separation unit 11 is mixed with the CO2 in the CO2 storage container 9 in the mixer 13. According to the load of the coal-fired unit, the O2 volume fraction detection device 14 controls the target O2 volume fraction of the mixed gas in the mixer 13, and the flow controller 27 controls the flow rate of the combustion gas in the combustion gas delivery pipeline 21, so as to form oxygen-rich combustion in the coal-fired boiler 1.

[0052] When the power grid 15 is in a low-demand period, flue gas from the coal-fired boiler 1 is extracted. The flue gas transfers heat to the heat transfer oil in the heat exchange system 3. The heat transfer oil releases heat in the calciner 5, causing a reduction reaction of CaCO3. The CaO delivery pipeline 17 delivers the CaO from the calciner 5 to the CaO storage container 7, and then delivers the CaO from the CaO storage container 7 to the carbonizer 6. The flow controller 27 controls the CaO flow rate in the CaO delivery pipeline 17. The CO2 delivery pipeline 18 delivers the CO2 from the calciner 5 to the CO2 storage container 9, and then delivers the CO2 from the CO2 storage container 9 to the mixer 13. The flow controller 27 controls the CO2 flow rate in the CO2 delivery pipeline 18. A portion of the power generated by the coal-fired unit drives the air separation unit 11, and this portion of the power generated by the coal-fired unit is stored in the energy storage device 12. According to the load of the coal-fired unit, the O2 volume fraction detection device 14 controls the target O2 volume fraction in the mixed gas, and the flow controller 27 controls the flow rate of the combustion gas in the combustion gas delivery pipeline 21 to form oxygen-rich combustion in the coal-fired boiler 1.

[0053] When the power grid 15 is in peak electricity consumption period, the flue gas from the coal-fired boiler is not extracted. Part of the power from the energy storage device 12 drives the air separation unit 11. According to the load of the coal-fired unit, the O2 volume fraction detection device controls the target O2 volume fraction in the mixed gas 14, and the flow controller 27 controls the flow rate of the combustion gas in the combustion gas delivery pipeline 21, so as to form oxygen-enriched combustion in the coal-fired boiler 1.

[0054] CaO mass flow rate delivered to the carbonizer M The expression is: M 2 = 56 × M 1 / 44, of which, M 1 represents the target CO2 mass flow rate in the tail gas of a coal-fired boiler, expressed in kg / s.

[0055] Flue gas extraction rate of coal-fired boilers M The expression for 4 is: M 4 =M 3 ×ΔH 1 / or / ( H 1 -H 2), where, M 3 represents the mass flow rate of CaCO3 delivered to the calciner, in kg / s; ΔH 1 represents the heat of reduction of CaCO3, expressed in J / kg; H 1 represents the enthalpy of the flue gas before it is delivered to the calciner, in J / kg; H 2 represents the enthalpy of the flue gas after it is delivered to the calciner, in J / kg; or For calciner efficiency, %.

[0056] The O2 mass flow rate and O2 volume fraction in the mixed gas are determined based on the load of the coal-fired unit.

[0057] CO2 mass flow rate in mixed gas M The expression for 6 is: M 6 =M 5 ×α / (1- α ),in, M 5 represents the mass flow rate of O2 in the gas mixture, in kg / s; α , where is the target O2 volume fraction in the gas mixture.

[0058] The above description of the embodiments is provided to enable those skilled in the art to understand and apply the present invention. It will be apparent to those skilled in the art that various modifications can be made to the above embodiments, and the general principles described herein can be applied to other embodiments without inventive effort. Therefore, the present invention is not limited to the above embodiments, and any improvements and modifications made to the present invention by those skilled in the art based on the disclosure thereof should be within the scope of protection of the present invention.

Claims

1. A carbon capture method for coal-fired power units coupled with thermochemical energy storage, characterized in that, The coal-fired unit carbon capture system includes a coal-fired boiler (1), flue gas pipeline (2), heat exchange system (3), heat transfer oil pipeline (4), calciner (5), carbonizer (6), CaO storage container (7), CaCO3 storage container (8), CO2 storage container (9), generator (10), air separation unit (11), energy storage device (12), mixer (13), power grid (15), CaCO3 conveying pipeline (16), CaO conveying pipeline (17), CO2 conveying pipeline (18), pure O2 conveying pipeline (20), combustion gas conveying pipeline (21), first switch (22), first transformer (23), second switch (24), second transformer (25), and output line (26); The generator (10) is connected to the power grid (15) via a first switch (22), a first transformer (23), and an output line (26); the output line (26) is connected to the air separation unit (11) and the energy storage unit (12) via a second switch (24) and a second transformer (25); the flue gas pipeline (2) is connected to the coal-fired boiler (1) and the heat exchange system (3); the heat transfer oil pipeline (4) is connected to the calciner (5) and the heat exchange system (3); the CaCO3 conveying pipeline (16) is connected to the calciner... The calciner (5), carbonizer (6), and CaCO3 storage container (8) are connected; the CaO conveying pipeline (17) is connected to the calciner (5), carbonizer (6), and CaO storage container (7); the CO2 conveying pipeline (18) is connected to the calciner (5), CO2 storage container (9), and mixer (13); the pure O2 conveying pipeline (20) is connected to the air separation unit (11) and mixer (13); the combustion gas conveying pipeline (21) is connected to the coal-fired boiler (1) and mixer (13); The aforementioned carbon capture method for coal-fired power units includes: during the full-load section of the coal-fired power unit, in a carbonizer, using CaO to absorb and capture CO2 in the flue gas at the tail end of the coal-fired boiler; mixing the absorbed and captured CO2 with pure O2; controlling the volume fraction of O2 in the mixed gas according to the load of the coal-fired power unit to form oxygen-enriched combustion in the coal-fired boiler; during the off-peak period of the power grid, extracting the flue gas from the coal-fired boiler, obtaining the heat from the flue gas to cause a reduction reaction of CaCO3 in a calciner, storing the reduced CaO in a CaO storage container, and using part of the power generated by the coal-fired power unit to drive the air separation unit; during the peak period of the power grid, using part of the power from an energy storage device to drive the air separation unit.

2. The carbon capture method for coal-fired power units coupled with thermochemical energy storage according to claim 1, characterized in that, The energy storage device (12) and the air separation device (11) are connected by the energy storage device output line (19).

3. The carbon capture method for coal-fired power units coupled with thermochemical energy storage according to claim 1, characterized in that, An O2 volume fraction detection device (14) is arranged inside the mixer (13).

4. The carbon capture method for coal-fired power units coupled with thermochemical energy storage according to claim 1, characterized in that, Flow controllers (27) are provided on the flue gas pipeline, CaCO3 conveying pipeline (16), CaO conveying pipeline (17), CO2 conveying pipeline (18), pure O2 conveying pipeline (20) and combustion gas conveying pipeline (21).

5. The carbon capture method for coal-fired power units coupled with thermochemical energy storage according to claim 1, characterized in that, In the full-load section of the coal-fired unit, CaO is used in the carbonizer to absorb and capture CO2 in the flue gas at the tail end of the coal-fired boiler. The CaCO3 conveying pipeline transports CaCO3 from the carbonizer to the CaCO3 storage container, and then the CaCO3 in the CaCO3 storage container is transported to the calciner. The CaO conveying pipeline transports CaO from the calciner to the CaO storage container, and then the CaO in the CaO storage container is transported to the carbonizer. The CO2 conveying pipeline transports CO2 from the calciner to the CO2 storage container, and then the CO2 in the CO2 storage container is transported to the mixer. The absorbed and captured CO2 is mixed with pure O2. According to the load of the coal-fired unit, the O2 volume fraction detection device controls the target O2 volume fraction in the mixed gas to form oxygen-enriched combustion in the coal-fired boiler.

6. The carbon capture method for coal-fired power units coupled with thermochemical energy storage according to claim 5, characterized in that, During periods of low electricity demand in the power grid, flue gas from the coal-fired boiler is extracted. The flue gas transfers heat to the heat transfer oil in the heat exchange system. The heat transfer oil releases heat in the calciner, causing a reduction reaction of CaCO3. The CaO delivery pipeline transports the CaO from the calciner to the CaO storage container, and then the CaO from the CaO storage container to the carbonizer. The CO2 delivery pipeline transports the CO2 from the calciner to the CO2 storage container, and then the CO2 from the CO2 storage container to the mixer. A portion of the power generated by the coal-fired unit drives the air separation unit, and this portion of the power generated by the coal-fired unit is stored in the energy storage device. Based on the load of the coal-fired unit, the O2 volume fraction detection device controls the target O2 volume fraction in the mixed gas, forming oxygen-enriched combustion in the coal-fired boiler.

7. The carbon capture method for coal-fired power units coupled with thermochemical energy storage according to claim 6, characterized in that, During peak electricity demand periods, the flue gas from coal-fired boilers is not extracted. Instead, a portion of the power from the energy storage device drives the air separation unit. Based on the load of the coal-fired unit, the O2 volume fraction detection device controls the target O2 volume fraction in the mixed gas, thus creating oxygen-rich combustion within the coal-fired boiler.

8. The carbon capture method for coal-fired power units coupled with thermochemical energy storage according to claim 5, characterized in that, CaO mass flow rate delivered to the carbonizer M The expression is: M 2=56 ×M 1 / 44, of which, M 1 represents the target CO2 mass flow rate in the tail gas of a coal-fired boiler, expressed in kg / s. Flue gas extraction rate of coal-fired boilers M The expression for 4 is: M 4 =M 3 ×ΔH 1 / η / ( H 1 -H 2), where, M 3 represents the mass flow rate of CaCO3 delivered to the calciner, in kg / s; ΔH 1 represents the heat of reduction of CaCO3, expressed in J / kg; H 1 represents the enthalpy of the flue gas before it is delivered to the calciner, in J / kg; H 2 represents the enthalpy of the flue gas after it is delivered to the calciner, in J / kg; η For calciner efficiency, %.

9. The carbon capture method for coal-fired power units coupled with thermochemical energy storage according to claim 4, characterized in that, The O2 mass flow rate and O2 volume fraction in the mixed gas are determined based on the load of the coal-fired unit. CO2 mass flow rate in mixed gas M The expression for 6 is: M 6 =M 5 ×α / (1- α ), in, M 5 represents the mass flow rate of O2 in the gas mixture, in kg / s; α , where is the target O2 volume fraction in the gas mixture.

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