Coal-fired power generation and heat energy storage coupling system and operation method thereof

Abstract

The present application belongs to the field of coal-fired power generation and thermal energy storage technology, and discloses a coal-fired power generation and thermal energy storage coupling system and an operation method thereof. The method comprises: a boiler, a first pressure cylinder of a steam turbine, a second pressure cylinder of the steam turbine, a third pressure cylinder of the steam turbine, a generator, a first target temperature water storage tank, a second target temperature water storage tank, the second pressure cylinder of the steam turbine being connected with a deaerator; one side of the third pressure cylinder of the steam turbine being connected with a first-stage target pressure regenerator, a second-stage target pressure regenerator and a third-stage target pressure regenerator in sequence; the third pressure cylinder of the steam turbine and the third-stage target pressure regenerator being connected with a steam-working medium heat exchanger, the steam-working medium heat exchanger being connected with a working medium regenerator, an expansion valve and a flue gas-working medium heat exchanger in sequence, and the working medium regenerator being connected with a compressor and a working medium-water heat exchanger in sequence. The present application can realize efficient utilization of low-temperature waste heat and electric energy of a coal-fired unit, reduce the output load of the coal-fired unit, and expand the unit peak regulation interval.

Description

Technical Field

[0001] This invention relates to the fields of coal-fired power generation and thermal energy storage technology, and in particular to a coal-fired power generation and thermal energy storage coupled system and its operation method. Background Technology

[0002] Guided by the dual-carbon target strategy, my country's power system has made remarkable progress in green transformation. New energy power such as wind power and solar power is growing strongly and its substitution effect on traditional power generation methods is becoming increasingly obvious. However, the randomness and volatility of new energy output also put enormous pressure on the power system to absorb it, and the risk to the safe operation of the power grid is also rising. There is an urgent need to introduce large-scale, high-efficiency energy storage technology to achieve cross-temporal distribution of power resources.

[0003] Heat pump energy storage systems are a highly efficient electrothermal conversion energy storage technology, characterized by outstanding energy conversion efficiency, environmental friendliness, and flexible application scenarios. They can be integrated with the power system to smooth power output fluctuations and improve energy utilization. Traditional Rankine cycle heat pumps offer stable energy efficiency and outstanding environmental performance, but they have poor adaptability to low-temperature environments and require high-quality heat sources. By increasing their operating temperature range to match the temperature range of low-temperature steam and flue gas waste heat from coal-fired power plants, it is possible to utilize the unused flue gas waste heat during coal-fired power generation, helping to reduce energy consumption and improve energy utilization efficiency. Simultaneously, it can assist coal-fired power plants in reducing output load and coping with grid peak shaving and frequency regulation tasks. However, currently, there is a lack of design and operation control methods for coupled coal-fired power generation and Rankine cycle heat pump energy storage systems.

[0004] Therefore, how to provide a coal-fired power generation and thermal energy storage coupled system and its operation method is an urgent problem to be solved. Summary of the Invention

[0005] This invention provides a coal-fired power generation and thermal energy storage coupled system and its operation method to solve the problems of the above-mentioned technologies in the prior art.

[0006] According to a first aspect of the present invention, a coal-fired power generation and thermal energy storage coupling system is provided.

[0007] In one embodiment, the coal-fired power generation and thermal energy storage coupling system includes: a coal-fired unit coupled hot water storage tank system and a Rankine cycle heat pump energy storage system; the coal-fired unit coupled hot water storage tank system includes: a boiler, on the side of which are sequentially connected a first pressure cylinder of a steam turbine, a second pressure cylinder of a steam turbine, a third pressure cylinder of a steam turbine, and a generator, and the boiler is sequentially connected to the first pressure cylinder of the steam turbine and the second pressure cylinder of the steam turbine, and the second pressure cylinder of the steam turbine is connected to a deaerator; on one side of the third pressure cylinder of the steam turbine, a first-stage target pressure regenerator, a second-stage target pressure regenerator, and a third-stage target pressure regenerator are sequentially connected, the first-stage target pressure regenerator and the second-stage target pressure regenerator are connected to a first target temperature water storage tank, and the second-stage target pressure regenerator and the third-stage target pressure regenerator are connected to a second target temperature water storage tank;

[0008] The Rankine cycle heat pump energy storage system includes: a steam-working fluid heat exchanger connected to the third pressure cylinder of the steam turbine and the three-stage target pressure regenerator; the steam-working fluid heat exchanger is sequentially connected to the working fluid regenerator, the expansion valve and the flue gas-working fluid heat exchanger; the working fluid regenerator is sequentially connected to the compressor and the working fluid-water heat exchanger; the compressor is connected to the electric motor; and the working fluid-water heat exchanger is sequentially connected to the first target temperature water storage tank and the second target temperature water storage tank.

[0009] In one embodiment, the coal-fired unit coupled hot water storage tank system further includes: a preset pressure regenerator, which is sequentially connected to the boiler, the first pressure cylinder of the steam turbine, and the deaerator, and a feedwater pump is provided between the preset pressure regenerator and the deaerator; a condenser is provided between the third pressure cylinder of the steam turbine and the third-stage target pressure regenerator, and a condensate pump is provided between the condenser and the third-stage target pressure regenerator.

[0010] In one embodiment, a third valve is provided between the outlet of the air preheater in the tail flue of the boiler and the flue gas-working fluid heat exchanger, a first valve is provided between the second target temperature water storage tank and the second-stage target pressure regenerator, a fifth valve is provided between the first target temperature water storage tank and the first-stage target pressure regenerator, and a second valve is provided between the first target temperature water storage tank and the deaerator.

[0011] In one embodiment, a fourth valve is provided between the steam-working fluid heat exchanger and the third pressure cylinder of the steam turbine, a water pump is provided between the second target temperature water storage tank and the working fluid-water heat exchanger, and a dust collector is connected to one side of the flue gas-working fluid heat exchanger.

[0012] In one embodiment, both the second target temperature water storage tank and the first target temperature water storage tank use water as the heat storage medium; the operating temperature range of the second target temperature water storage tank is 70~90℃ and the pressure range is 0.1~0.5MPa, while the operating temperature range of the first target temperature water storage tank is 110~140℃ and the pressure range is 0.5~0.6MPa.

[0013] In one embodiment, the working fluid used in the Rankine cycle heat pump energy storage system is R1233zd(E), and the operating temperature is 30~150℃.

[0014] In one embodiment, the compressor is a centrifugal compressor with an inlet-outlet combined pressure ratio of 2.5.

[0015] In one embodiment, both the first target temperature water storage tank and the second target temperature water storage tank include an inlet and an outlet.

[0016] In one embodiment, the working fluid-water heat exchanger, the working fluid regenerator, the flue gas-working fluid heat exchanger, and the steam-working fluid heat exchanger are all shell-and-tube heat exchangers.

[0017] In one embodiment, the steam in the steam-working fluid heat exchanger releases heat through phase change, and the temperature range of the outlet saturated water is 70~80℃.

[0018] According to a second aspect of the present invention, an operation method for a coal-fired power generation and thermal energy storage coupled system is provided.

[0019] In one embodiment, the operation method of the coal-fired power generation and thermal energy storage coupled system includes:

[0020] When the power grid is in a low-demand period and steam at the first target temperature is sufficient, a portion of the electrical energy output from the generator of the coal-fired unit and the heat energy from the steam extracted from the third pressure cylinder of the turbine are converted into the heat energy of water for storage. When the power grid is in a low-demand period and steam at the first target temperature is insufficient, the fourth valve on the pipeline between the steam-working fluid heat exchanger and the secondary extraction steam outlet of the third pressure cylinder of the turbine is closed, causing the steam heating working fluid circuit of the Rankine cycle heat pump energy storage system to stop working. When the power grid is in a low-demand period and the flue gas temperature at the outlet of the air preheater at the boiler tail is higher than the preset value, the flue gas heating working fluid circuit of the Rankine cycle heat pump energy storage system is activated, converting a portion of the electrical energy output from the generator of the coal-fired unit into the heat energy of water for storage. The thermal energy of the electrical energy and the heat energy of the flue gas at the outlet of the boiler's tail air preheater are converted into the thermal energy of water for storage. When the power grid is in a trough and the flue gas temperature at the outlet of the boiler's tail air preheater is lower than or equal to a preset value, the third valve on the pipeline between the flue gas-working fluid heat exchanger and the boiler is closed, causing the flue gas heating working fluid circuit of the Rankine cycle heat pump energy storage system to stop working. When the power grid is in a peak period, the coal-fired unit coupled hot water storage tank system works, opening the first valve to allow part of the condensate at the outlet of the third-stage target pressure regenerator to enter the second target temperature water storage tank, and opening the fifth valve or the second valve to allow the hot water in the first target temperature water storage tank to enter the first-stage target pressure regenerator or deaerator.

[0021] In one embodiment, when the thermal energy of a portion of the electrical energy output by the generator of a coal-fired unit and the thermal energy of a portion of the steam extracted from the third pressure cylinder of the steam turbine are converted into the thermal energy of water and stored, the storage location is a water storage tank at the first target temperature.

[0022] In one embodiment, when storing the thermal energy of water converted from part of the electrical energy output by the generator of the coal-fired unit and part of the heat energy of the flue gas at the outlet of the air preheater at the tail of the boiler, the storage location is a water storage tank at the first target temperature.

[0023] In one embodiment, allowing a portion of the condensate from the outlet of the third-stage target pressure regenerator to enter the second target temperature water storage tank includes: when the temperature of the first target temperature water storage tank is lower than the condensate outlet temperature of the first-stage target pressure regenerator but higher than that of the second-stage target pressure regenerator, opening the fifth valve and closing the second valve, allowing the hot water from the first target temperature water storage tank to enter the first-stage target pressure regenerator; when the temperature of the first target temperature water storage tank is higher than the condensate outlet temperature of the first-stage target pressure regenerator, opening the second valve and closing the fifth valve, allowing the hot water from the first target temperature water storage tank to enter the deaerator.

[0024] In one embodiment, after the hot water in the first target temperature water storage tank enters the first-stage target pressure regenerator or deaerator, the method further includes: expelling extracted steam to return to the third pressure cylinder of the turbine to do work, thereby increasing the turbine output.

[0025] This invention also provides an application of a coal-fired power generation and thermal energy storage coupling system or an operation method of a coal-fired power generation and thermal energy storage coupling system in the power field.

[0026] The technical solutions provided by the embodiments of the present invention may include the following beneficial effects:

[0027] (1) The present invention uses low-temperature steam extraction and boiler tail flue gas as the heat source of the Rankine cycle heat pump energy storage system, which can effectively utilize the waste heat of the low-temperature heat source, save primary energy, and improve economic benefits.

[0028] (2) The Rankine cycle heat pump energy storage system used in this invention has a lower operating temperature range and a higher heat pump performance coefficient compared to the air Brayton heat pump energy storage system, resulting in higher energy utilization efficiency for absorbing unit loads. For example, the Carnot battery air Brayton heat pump energy storage system, which has a lower operating temperature range, can reach a maximum operating temperature of 500-600℃ due to the use of molten salt as the heat storage medium. In contrast, the Rankine cycle heat pump energy storage system of this invention has a maximum operating temperature of 150℃.

[0029] (3) The present invention uses organic working medium R1233zd(E) as the working medium of the Rankine cycle, which has the characteristics of low GWP, little impact on the environment, and is more green and environmentally friendly.

[0030] (4) The present invention uses water as a heat storage medium, which not only reduces the economic cost of the system, but also avoids the safety problems caused by high temperature and high pressure storage.

[0031] It should be understood that the above general description and the following detailed description are exemplary and explanatory only, and are not intended to limit the invention. Attached Figure Description

[0032] The accompanying drawings, which are incorporated in and form part of this specification, illustrate embodiments consistent with the invention and, together with the description, serve to explain the principles of the invention.

[0033] Figure 1 This is a schematic diagram illustrating the connection principle of a coal-fired power generation and thermal energy storage coupling system according to an exemplary embodiment;

[0034] Figure 2 This is a flowchart illustrating an operation method of a coal-fired power generation and thermal energy storage coupled system according to an exemplary embodiment.

[0035] In the picture:

[0036] 1. Boiler; 2. First pressure cylinder of steam turbine; 3. Second pressure cylinder of steam turbine; 4. Third pressure cylinder of steam turbine; 5. Condenser; 6. Condensate pump; 7. Third-stage target pressure regenerator; 8. Second-stage target pressure regenerator; 9. First-stage target pressure regenerator; 10. Deaerator; 11. Feedwater pump; 12. Preset pressure regenerator; 13. Working fluid-water heat exchanger; 14. Working fluid regenerator; 15. Expansion valve; 16. Flue gas-working fluid heat exchanger; 17. Steam-working fluid heat exchanger; 18. Compressor; 19. Second target temperature water storage tank; 20. First target temperature water storage tank; 21. Generator; 22. Electric motor; 23. First valve; 24. Second valve; 25. Third valve; 26. Fourth valve; 27. Dust collector; 28. Fifth valve; 29. ​​Water pump. Detailed Implementation

[0037] The following description and accompanying drawings fully illustrate specific embodiments described herein to enable those skilled in the art to practice them. Some portions and features of certain embodiments may be included in or replace portions and features of other embodiments. The scope of the embodiments herein includes the entire scope of the claims and all available equivalents thereof. The various embodiments described herein are presented in a progressive manner, with each embodiment focusing on its differences from other embodiments; similar or identical parts between embodiments can be referred to interchangeably.

[0038] The modules in the apparatus or system of this application can be implemented entirely or partially through software, hardware, or a combination thereof. These modules can be embedded in or independent of the processor in a computer device in hardware form, or stored in the memory of a computer device in software form, so that the processor can call and execute the operations corresponding to each module.

[0039] Where there is no conflict, the embodiments and features in the embodiments of the present invention can be combined with each other.

[0040] Figure 1 An embodiment of a coal-fired power generation and thermal energy storage coupling system according to the present invention is shown.

[0041] In this optional embodiment, the coal-fired power generation and thermal energy storage coupling system includes:

[0042] The coal-fired unit is coupled with a hot water storage tank system and a Rankine cycle heat pump energy storage system. The system uses steam extracted at the first target temperature (i.e., low temperature) and flue gas from the boiler tail as the heat source for the Rankine cycle heat pump energy storage system, so as to utilize the waste heat of the heat source at the first target temperature.

[0043] The coal-fired power unit coupled hot water storage tank system includes: a boiler 1, on which a first pressure cylinder 2 (i.e., high-pressure cylinder), a second pressure cylinder 3 (i.e., intermediate-pressure cylinder), a third pressure cylinder 4 (i.e., low-pressure cylinder), and a generator 21 are sequentially connected. The boiler 1 is sequentially connected to the first pressure cylinder 2 and the second pressure cylinder 3. The second pressure cylinder 3 is connected to a deaerator 10. On one side of the third pressure cylinder 4, a first-stage target pressure regenerator 9 (i.e., first-stage low-pressure regenerator), a second-stage target pressure regenerator 8 (i.e., second-stage low-pressure regenerator), and a third-stage target pressure regenerator 7 (i.e., third-stage low-pressure regenerator) are sequentially connected. The first-stage target pressure regenerator 9 and the second-stage target pressure regenerator 8 are connected to a first target temperature water storage tank 20 (i.e., high-temperature water storage tank). The second-stage target pressure regenerator 8 and the third-stage target pressure regenerator 7 are connected to a second target temperature water storage tank 19 (i.e., low-temperature water storage tank).

[0044] The Rankine cycle heat pump energy storage system includes: a steam-working fluid heat exchanger 17 connected to the third pressure cylinder 4 of the steam turbine and the three-stage target pressure regenerator 7; the steam-working fluid heat exchanger 17 is connected in sequence to the working fluid regenerator 14, the expansion valve 15 and the flue gas-working fluid heat exchanger 16; the working fluid regenerator 14 is connected in sequence to the compressor 18 and the working fluid-water heat exchanger 13; the compressor 18 is connected to the electric motor 22; and the working fluid-water heat exchanger 13 is connected in sequence to the first target temperature water storage tank 20 and the second target temperature water storage tank 19.

[0045] In this optional embodiment, the coal-fired unit coupled hot water storage tank system further includes: a preset pressure regenerator 12 (i.e., a high-pressure regenerator), which is sequentially connected to the boiler 1, the first pressure cylinder 2 of the steam turbine, and the deaerator 10, and a feedwater pump 11 is provided between the preset pressure regenerator 12 and the deaerator 10; a condenser 5 is provided between the third pressure cylinder 4 of the steam turbine and the third-stage target pressure regenerator 7, and a condensate pump 6 is provided between the condenser 5 and the third-stage target pressure regenerator 7.

[0046] In this optional embodiment, a third valve 25 is provided between the outlet of the air preheater in the tail flue of boiler 1 and the flue gas-working fluid heat exchanger 16, a first valve 23 is provided between the second target temperature water storage tank 19 and the secondary target pressure regenerator 8, a fifth valve 28 is provided between the first target temperature water storage tank 20 and the primary target pressure regenerator 9, and a second valve 24 is provided between the first target temperature water storage tank 20 and the deaerator 10.

[0047] In this optional embodiment, a fourth valve 26 is provided between the steam-working fluid heat exchanger 17 and the third pressure cylinder 4 of the steam turbine, a water pump 29 is provided between the second target temperature water storage tank 19 and the working fluid-water heat exchanger 13, and a dust collector 27 is connected to one side of the flue gas-working fluid heat exchanger 16.

[0048] In this optional embodiment, both the second target temperature water storage tank 19 and the first target temperature water storage tank 20 use water as the heat storage medium; the operating temperature range of the second target temperature water storage tank 19 is 70~90℃ and the pressure range is 0.1~0.5MPa, and the operating temperature range of the first target temperature water storage tank 20 is 110~140℃ and the pressure range is 0.5~0.6MPa.

[0049] In this optional embodiment, the working fluid used in the Rankine cycle heat pump energy storage system is R1233zd(E), and the operating temperature is 30~150℃.

[0050] In this optional embodiment, compressor 18 is a centrifugal compressor with an inlet-outlet combined pressure ratio of 2.5.

[0051] In this optional embodiment, both the first target temperature water storage tank 20 and the second target temperature water storage tank 19 include an inlet and an outlet.

[0052] In this optional embodiment, the working fluid-water heat exchanger 13, the working fluid regenerator 14, the flue gas-working fluid heat exchanger 16, and the steam-working fluid heat exchanger 17 are all shell-and-tube heat exchangers.

[0053] In this optional embodiment, the steam heat release method in the steam-working fluid heat exchanger 17 is phase change heat release, and the temperature range of the outlet saturated water is 70~80℃.

[0054] Figure 2 An embodiment of the operation method of a coal-fired power generation and thermal energy storage coupled system of the present invention is shown.

[0055] In this optional embodiment, the operation method of the coal-fired power generation and thermal energy storage coupled system includes:

[0056] S101. When the power grid is in a low point of electricity demand and there is sufficient steam at the first target temperature, part of the electrical energy output by the coal-fired unit through the generator 21 and the heat energy extracted from the steam turbine third pressure cylinder 4 are converted into the heat energy of water for storage.

[0057] S102. When the power grid is in a low-power consumption period and the steam at the first target temperature is insufficient, close the fourth valve 26 on the pipeline between the steam-working fluid heat exchanger 17 and the secondary extraction steam outlet of the third pressure cylinder 4 of the steam turbine, so that the steam heating working fluid circuit of the Rankine cycle heat pump energy storage system stops working.

[0058] S103. When the power grid is in a low point of electricity demand and the flue gas temperature at the outlet of the air preheater at the tail of the boiler is higher than the preset value, the flue gas heating working fluid circuit of the Rankine cycle heat pump energy storage system will work to convert part of the electrical energy output by the coal-fired unit through the generator 21 and the heat energy of part of the flue gas at the outlet of the air preheater at the tail of the boiler into the heat energy of water for storage.

[0059] S104. When the power grid is in a low-power consumption period and the flue gas temperature at the outlet of the air preheater at the tail of the boiler is lower than or equal to the preset value, close the third valve 25 on the pipeline between the flue gas-working fluid heat exchanger 16 and the boiler 1 to stop the flue gas heating working fluid circuit of the Rankine cycle heat pump energy storage system.

[0060] S105. When the power grid is at its peak electricity demand, the coal-fired unit coupled with the hot water storage tank system operates, opening the first valve 23 to allow part of the condensate from the outlet of the third-stage target pressure regenerator 7 to enter the second target temperature water storage tank 19, and opening the fifth valve 28 or the second valve 24 to allow the hot water in the first target temperature water storage tank 20 to enter the first-stage target pressure regenerator 9 or the deaerator 10.

[0061] In this optional embodiment, when the thermal energy of part of the electrical energy output by the generator 21 of the coal-fired unit and the thermal energy of part of the steam extracted from the third pressure cylinder 4 of the steam turbine are converted into the thermal energy of water and stored, the storage location is the water storage tank 20 at the first target temperature.

[0062] In this optional embodiment, when storing the thermal energy of water converted from part of the electrical energy output by the generator 21 of the coal-fired unit and part of the flue gas at the outlet of the air preheater at the tail of the boiler 1, the storage location is the water storage tank 20 at the first target temperature.

[0063] In this optional embodiment, allowing a portion of the condensate from the outlet of the tertiary target pressure regenerator 7 to enter the second target temperature water storage tank 19 includes: when the temperature of the first target temperature water storage tank 20 is lower than the condensate outlet temperature of the first-stage target pressure regenerator 9 but higher than that of the second-stage target pressure regenerator 8, opening the fifth valve 28 and closing the second valve 24, allowing the hot water from the first target temperature water storage tank 20 to enter the first-stage target pressure regenerator 9; when the temperature of the first target temperature water storage tank 20 is higher than the condensate outlet temperature of the first-stage target pressure regenerator 9, opening the second valve 24 and closing the fifth valve 28, allowing the hot water from the first target temperature water storage tank 20 to enter the deaerator 10.

[0064] In this optional embodiment, after the hot water in the first target temperature water storage tank 20 enters the first-stage target pressure regenerator 9 or deaerator 10, it further includes: expelling the extracted steam and returning it to the third pressure cylinder 4 of the steam turbine to do work, thereby increasing the output of the steam turbine.

[0065] This invention also provides an application of a coal-fired power generation and thermal energy storage coupling system or an operation method of a coal-fired power generation and thermal energy storage coupling system in the power field.

[0066] To facilitate understanding of the above technical solutions of the present invention, the following further explains the above technical solutions of the present invention from the perspective of architecture and principle, as follows:

[0067] The system comprises a coal-fired power unit coupled with a hot water storage tank system and a Rankine cycle heat pump energy storage system. During grid downturns, a portion of the extracted steam from the low-pressure cylinder of the coal-fired turbine and the tail flue gas heat the working fluid at the outlet of the heat pump expansion valve. Simultaneously, driven by the electrical output of the coal-fired power unit, the heat pump compressor further pressurizes and heats the working fluid, which then heats the low-temperature water. Ultimately, the electrical energy, steam, and flue gas heat energy of the coal-fired power unit are converted into the heat energy of the water for storage. During grid upturns, a portion of the condensate from the coal-fired power unit enters the low-temperature water tank, while the hot water from the high-temperature water tank enters the condenser. By displacing the extracted steam from the low-pressure regenerator, the output of the coal-fired power unit is increased, meeting the grid's peak-shaving demands. This system enables the safe and efficient utilization of heat from coal-fired power units, expands the unit's output load range, and is an effective method for utilizing low-temperature waste heat and mitigating grid fluctuations.

[0068] The coal-fired power generation unit of this invention is a pure condensing unit. While utilizing the waste heat from the flue gas and low-temperature steam of the coal-fired unit, it also consumes the electrical energy output by the unit. This allows for an increase in the peak-shaving depth of the coal-fired unit while ensuring safe operation of the equipment. In other words, this invention improves the peak-shaving depth of the unit while simultaneously utilizing waste heat. This invention employs an organic Rankine heat pump system to store the electrical energy, flue gas, and thermal energy of the low-temperature steam from the coal-fired unit in a hot water tank, adjusting the condensate return position according to the temperature of the hot water tank.

[0069] This invention includes a coal-fired power unit coupled with a hot water storage tank system and a Rankine cycle heat pump energy storage system; wherein,

[0070] The coal-fired power unit coupled hot water storage tank system includes a boiler 1, a turbine first pressure cylinder 2 (hereinafter referred to as the turbine high-pressure cylinder), a turbine second pressure cylinder 3 (hereinafter referred to as the turbine intermediate-pressure cylinder), a turbine third pressure cylinder 4 (hereinafter referred to as the turbine low-pressure cylinder), a condenser 5, a condensate pump 6, a first-stage target pressure regenerator 9 (hereinafter referred to as the first-stage low-pressure regenerator), a second-stage target pressure regenerator 8 (hereinafter referred to as the second-stage low-pressure regenerator), a third-stage target pressure regenerator 7 (hereinafter referred to as the third-stage low-pressure regenerator), a deaerator 10, a feedwater pump 11, a preset pressure regenerator 12 (hereinafter referred to as the high-pressure regenerator), a second target temperature water storage tank 19 (hereinafter referred to as the low-temperature water storage tank), and a first target temperature water storage tank. Tank 20 (hereinafter referred to as high-temperature water storage tank) and generator 21; the main steam outlet of boiler 1 is connected to the inlet of the high-pressure cylinder of the steam turbine, and the reheat steam outlet of boiler 1 is connected to the steam inlet of the intermediate-pressure cylinder of the steam turbine; the extraction steam outlet of the high-pressure cylinder of the steam turbine is connected to the steam inlet of the high-pressure regenerator, and the exhaust steam outlet of the high-pressure cylinder of the steam turbine is connected to the reheat steam inlet of boiler 1; the extraction steam outlet of the intermediate-pressure cylinder of the steam turbine is connected to the steam inlet of the deaerator 10, and the exhaust steam outlet of the intermediate-pressure cylinder of the steam turbine is connected to the steam inlet of the low-pressure cylinder of the steam turbine; the first-stage extraction steam outlet of the low-pressure cylinder of the steam turbine is connected to the steam inlet of the first-stage low-pressure regenerator, the second-stage extraction steam outlet of the low-pressure cylinder of the steam turbine is connected to the steam inlet of the second-stage low-pressure regenerator, and the third-stage extraction steam outlet of the low-pressure cylinder of the steam turbine is connected to the third-stage low-pressure regenerator. The steam inlet of the regenerator is connected, and the exhaust outlet of the low-pressure cylinder of the steam turbine is connected to the steam inlet of condenser 5; the condensate outlet of condenser 5 is connected to the condensate inlet of the third-stage low-pressure regenerator via condensate pump 6; the drain outlet of the third-stage low-pressure regenerator is connected to the drain inlet of condenser 5, and the condensate outlet of the third-stage low-pressure regenerator is connected to the condensate inlet of the second-stage low-pressure regenerator; the drain outlet of the second-stage low-pressure regenerator is connected to the drain inlet of the third-stage low-pressure regenerator, and the condensate outlet of the second-stage low-pressure regenerator is connected to the condensate inlet of the first-stage low-pressure regenerator; the drain outlet of the first-stage low-pressure regenerator is connected to the drain inlet of the second-stage low-pressure regenerator, and the condensate outlet of the first-stage low-pressure regenerator is connected to the condensate inlet of deaerator 10; the feedwater outlet of deaerator 10... The feedwater inlet of the high-pressure regenerator is connected to the feedwater inlet of the deaerator 10 via the feedwater pump 11; the condensate outlet of the deaerator 10 is connected to the condensate outlet of the high-pressure regenerator; the feedwater outlet of the high-pressure regenerator is connected to the feedwater inlet of the boiler 1; the water inlet of the low-temperature water storage tank is connected to the condensate outlet of the third-stage low-pressure regenerator; the first valve 23 is connected to the pipeline between the low-temperature water storage tank and the second-stage low-pressure regenerator; the water outlet of the high-temperature water storage tank is connected to the condensate inlets of the deaerator 10 and the first-stage low-pressure regenerator respectively; the second valve 24 is connected to the pipeline between the high-temperature water storage tank and the deaerator 10; the fifth valve 28 is connected to the pipeline between the high-temperature water storage tank and the first-stage low-pressure regenerator; the high-pressure cylinder, intermediate-pressure cylinder, and low-pressure cylinder of the turbine are connected to the generator 21 via a drive shaft.

[0071] The Rankine cycle heat pump energy storage system includes a working fluid-water heat exchanger 13, a working fluid regenerator 14, an expansion valve 15, a flue gas-working fluid heat exchanger 16, a steam-working fluid heat exchanger 17, a compressor 18, an electric motor 22, a dust collector 27, and a water pump 29. The working fluid outlet of the compressor 18 is connected to the working fluid inlet of the working fluid-water heat exchanger 13; the working fluid outlet of the working fluid-water heat exchanger 13 is connected to the high-temperature working fluid inlet of the working fluid regenerator 14; the high-temperature working fluid outlet of the working fluid regenerator 14 is connected to the expansion valve 15, and the low-temperature working fluid outlet of the working fluid regenerator 14 is connected to the working fluid inlet of the compressor 18; the working fluid outlet of the expansion valve 15 is connected to both the flue gas-working fluid heat exchanger 16 and the steam-working fluid heat exchanger 17; the working fluid outlet of the flue gas-working fluid heat exchanger 16 is connected to the low-temperature working fluid inlet of the working fluid regenerator 14; the flue gas-working fluid heat exchanger 16... The flue gas inlet is connected to the flue gas outlet of boiler 1. The third valve 25 is connected to the pipeline between the flue gas-working fluid heat exchanger 16 and boiler 1. The flue gas outlet of the flue gas-working fluid heat exchanger 16 is connected to the flue gas inlet of the dust collector 27. The working fluid outlet of the steam-working fluid heat exchanger 17 is connected to the low-temperature working fluid inlet of the working fluid regenerator 14. The steam inlet of the steam-working fluid heat exchanger 17 is connected to the third-stage extraction steam outlet of the low-pressure cylinder of the steam turbine. The fourth valve 26 is connected to the pipeline between the steam-working fluid heat exchanger 17 and the third-stage extraction steam outlet of the low-pressure cylinder of the steam turbine. The saturated water outlet of the steam-working fluid heat exchanger 17 is connected to the condensate inlet of the third-stage low-pressure regenerator. The low-temperature water in the low-temperature water storage tank enters the working fluid-water heat exchanger 13 through the water pump 29 to absorb heat, and then enters the high-temperature water storage tank for storage. The compressor 18 is connected to the motor 22 through the drive shaft.

[0072] Both cryogenic and high-temperature water storage tanks use atmospheric pressure water as the heat storage medium, with a pressure range of 0.5~1MPa. The operating temperature range for cryogenic water storage tanks is 70~90℃, and for high-temperature water storage tanks it is 110~140℃. This reduces the safety requirements for tank materials and ensures the system's economic efficiency.

[0073] The Rankine cycle heat pump energy storage system uses R1233zd(E) as the working fluid and adopts the Rankine cycle. The maximum operating temperature is 150℃ and the minimum operating temperature is 30℃. This can fully match the temperature range of heat exchange between the working fluid and other media, reduce irreversible system losses, and ensure system safety and high efficiency.

[0074] Compressor 18 is a centrifugal compressor with an inlet-outlet combined pressure ratio of up to 2.5. This reduces the investment in turbine equipment, lowers investment costs, and ensures system economy. The cryogenic water storage tank and the high-temperature water storage tank each have one inlet and one outlet. The working fluid-water heat exchanger 13, working fluid regenerator 14, flue gas-working fluid heat exchanger 16, and steam-working fluid heat exchanger 17 all use shell-and-tube heat exchangers. This ensures high efficiency in the heat exchange process and facilitates equipment maintenance. In the steam-working fluid heat exchanger 17, the steam releases heat through phase change, and the outlet saturated water temperature range is 70~80℃. This fully utilizes the heat of the steam, reduces system heat exchange losses, and ensures system efficiency.

[0075] An operation method for a coal-fired power generation and thermal energy storage coupled system includes:

[0076] The unit load command factor is defined as the ratio of the power currently ordered by the power grid to the unit load to the annual average power. Specifically:

[0077] ;

[0078] In the formula, P i P represents the power (MW) currently required by the power grid to load the generating units. e Let t be the load command power of the power grid to the generating unit at time t, in MW; T is the operating time of the generating unit.

[0079] The extraction coefficient is defined as the ratio of the low-temperature steam flow rate used in the Rankine cycle heat pump energy storage system to the original extraction steam flow rate at that location. Specifically:

[0080] ;

[0081] In the formula, M i M0 represents the current low-temperature steam flow rate that can be extracted for the Rankine cycle heat pump energy storage system, in t / h; M0 represents the original extraction steam flow rate at this location, in t / h.

[0082] 1) When the power grid is in a trough and low-temperature steam is sufficient, such as when the unit load command coefficient α < 0.3 and the low-temperature extraction steam coefficient ≥ 0.2, the steam heating working fluid circuit of the Rankine cycle heat pump energy storage system operates normally, converting part of the electrical energy output by the coal-fired unit through generator 21 and the heat energy of part of the steam extracted from the low-pressure cylinder of the turbine into the heat energy of water for storage; specifically, the first valve 23 on the pipeline between the low-temperature water storage tank and the secondary low-pressure regenerator is closed, the second valve 24 on the pipeline between the high-temperature water storage tank and the deaerator 10 is closed, the water pump 29 is started, and the fourth valve 26 on the pipeline between the steam-working fluid heat exchanger 17 and the secondary extraction steam outlet of the low-pressure cylinder of the turbine is opened; the coal feed rate into boiler 1 is kept constant, and the turbine operating conditions fluctuate slightly to ensure equipment safety and power generation efficiency; Rankine cycle In the heat pump energy storage system, the electric motor 22 drives the compressor 18 under the power output of the coal-fired unit, compressing the ambient temperature low-pressure working fluid at the inlet of the compressor 18 into a high temperature high-pressure working fluid. The high temperature high-pressure working fluid at the outlet of the compressor 18 releases heat in the working fluid-water heat exchanger 13 and the working fluid regenerator 14 in sequence, and then enters the expansion valve 15. The low temperature low-pressure working fluid at the outlet of the expansion valve 15 absorbs heat in the flue gas-working fluid heat exchanger 16 and the steam-working fluid heat exchanger 17 respectively, and then enters the working fluid regenerator 14 to absorb heat. The ambient temperature low-pressure working fluid at the outlet returns to the inlet of the compressor 18. The low temperature water in the low temperature water storage tank enters the working fluid-water heat exchanger 13 under the drive of the water pump 29 to absorb heat, converting part of the electrical energy of the coal-fired unit, part of the heat energy of the extracted steam and part of the heat energy of the flue gas into the heat energy of the water, and finally storing it in the high temperature water storage tank.

[0083] 2) When the power grid is in a low-temperature period and there is insufficient low-temperature steam, such as when the unit load command coefficient α < 0.3 and the low-temperature extraction coefficient < 0.2, close the fourth valve 26 on the pipeline between the steam-working fluid heat exchanger 17 and the secondary extraction steam outlet of the turbine low-pressure cylinder, and the steam heating working fluid circuit of the Rankine cycle heat pump energy storage system will stop working.

[0084] 3) When the power grid is in a trough and the flue gas temperature at the boiler tail is high, such as when the unit load command coefficient α < 0.3 and the flue gas temperature at the boiler tail is higher than 130℃, the Rankine cycle heat pump energy storage system flue gas heating working fluid circuit operates normally, converting part of the electrical energy output by the coal-fired unit through generator 21 and the heat energy of part of the flue gas at the tail of boiler 1 into the heat energy of water for storage; specifically, the first valve 23 on the pipeline between the low-temperature water storage tank and the three-stage low-pressure regenerator is closed, the second valve 24 and the fifth valve 28 are closed, the water pump 29 is started, and the third valve 25 on the pipeline between the flue gas-working fluid heat exchanger 16 and boiler 1 is opened; the coal feed rate into boiler 1 is kept constant, and the turbine operating conditions fluctuate slightly to ensure equipment safety and power generation efficiency. In the Rankine cycle heat pump energy storage system, the electric motor 22 drives the compressor 18 under the power output of the coal-fired unit, compressing the ambient temperature low-pressure working fluid at the inlet of the compressor 18 into a high temperature high-pressure working fluid. The high temperature high-pressure working fluid at the outlet of the compressor 18 releases heat in the working fluid-water heat exchanger 13 and the working fluid regenerator 14 in sequence, and then enters the expansion valve 15. The low temperature low-pressure working fluid at the outlet of the expansion valve 15 absorbs heat in the flue gas-working fluid heat exchanger 16 and then enters the working fluid regenerator 14 to absorb heat. The ambient temperature low-pressure working fluid at the outlet returns to the inlet of the compressor 18. The low temperature water in the low temperature water storage tank enters the working fluid-water heat exchanger 13 under the drive of the water pump 29 to absorb heat, converting part of the electrical energy of the coal-fired unit and part of the heat energy of the flue gas into the heat energy of the water, and finally storing it in the high temperature water storage tank.

[0085] 4) When the power grid is in a low-power period and the flue gas temperature at the boiler tail is low, such as when the unit load command coefficient α < 0.3 and the flue gas temperature at the boiler tail is less than 130℃, close the third valve 25 on the pipeline between the flue gas-working medium heat exchanger 16 and the boiler 1, and the flue gas heating working medium circuit of the Rankine cycle heat pump energy storage system will stop working.

[0086] 5) When the power grid is at its peak demand, if the unit load command coefficient α ≥ 0.3, and the coal-fired unit coupled hot water storage tank system is operating normally, close the third valve 25 on the pipeline between the flue gas-working fluid heat exchanger 16 and the boiler 1, close the fourth valve 26 on the pipeline between the steam-working fluid heat exchanger 17 and the secondary extraction steam outlet of the turbine low-pressure cylinder, turn off the water pump 29, and open the first valve 23; when the temperature of the high-temperature water storage tank is lower than the condensate outlet temperature of the primary low-pressure regenerator, open the fifth valve 28 on the pipeline between the high-temperature water storage tank and the secondary low-pressure regenerator, close the second valve 24 on the pipeline between the high-temperature water storage tank and the deaerator 10, and some condensate enters the low-temperature water storage tank through the first valve 23, while the hot water in the high-temperature water storage tank enters the primary low-pressure regenerator through the fifth valve 28. In the regenerator, the amount of condensate entering the secondary low-pressure regenerator decreases, while the amount of condensate entering the deaerator 10 remains unchanged. Exhausted steam returns to the low-pressure cylinder of the turbine to perform work, increasing turbine output, improving the power generation of the coal-fired unit, and expanding the unit's load operating range. When the temperature of the high-temperature water storage tank is higher than the condensate outlet temperature of the primary low-pressure regenerator, the second valve 24 is opened and the fifth valve 28 is closed. Some condensate enters the low-temperature water storage tank through the first valve 23, and the hot water in the high-temperature water storage tank enters the condenser through the second valve 24. At this time, the amount of condensate entering the primary and secondary low-pressure regenerators decreases, while the amount of condensate entering the deaerator 10 remains unchanged. Exhausted steam returns to the low-pressure cylinder of the turbine to perform work, increasing turbine output, improving the power generation of the coal-fired unit, and expanding the unit's load operating range.

[0087] This invention is not limited to the structures described above and shown in the accompanying drawings, and various modifications and changes can be made without departing from its scope. The scope of this invention is limited only by the appended claims.

Claims

1. A coal-fired power generation and thermal energy storage coupled system, characterized in that, include: Coal-fired power unit coupled with hot water storage tank system and Rankine cycle heat pump energy storage system; The coal-fired power unit coupled hot water storage tank system includes: a boiler (1), on which a first pressure cylinder (2), a second pressure cylinder (3), a third pressure cylinder (4) and a generator (21) are sequentially connected. The boiler (1) is connected to the first pressure cylinder (2) and the second pressure cylinder (3) in sequence. The second pressure cylinder (3) is connected to the deaerator (10). The third pressure cylinder (4) of the steam turbine is connected in sequence to a first-stage target pressure regenerator (9), a second-stage target pressure regenerator (8) and a third-stage target pressure regenerator (7). The first-stage target pressure regenerator (9) and the second-stage target pressure regenerator (8) are connected to a first target temperature water storage tank (20). The second-stage target pressure regenerator (8) and the third-stage target pressure regenerator (7) are connected to a second target temperature water storage tank (19). The Rankine cycle heat pump energy storage system includes: a steam-working fluid heat exchanger (17) connected to the third pressure cylinder (4) of the steam turbine and the three-stage target pressure regenerator (7), the steam-working fluid heat exchanger (17) being connected in sequence to a working fluid regenerator (14), an expansion valve (15) and a flue gas-working fluid heat exchanger (16), the working fluid regenerator (14) being connected in sequence to a compressor (18) and a working fluid-water heat exchanger (13), the compressor (18) being connected to a motor (22), and the working fluid-water heat exchanger (13) being connected in sequence to a first target temperature water storage tank (20) and a second target temperature water storage tank (19).

2. The coal-fired power generation and thermal energy storage coupled system according to claim 1, characterized in that, The coal-fired unit coupled hot water storage tank system further includes: a preset pressure regenerator (12), which is connected in sequence to the boiler (1), the first pressure cylinder (2) of the steam turbine and the deaerator (10), and a feed water pump (11) is provided between the preset pressure regenerator (12) and the deaerator (10). A condenser (5) is provided between the third pressure cylinder (4) of the steam turbine and the third-stage target pressure regenerator (7), and a condensate pump (6) is provided between the condenser (5) and the third-stage target pressure regenerator (7).

3. The coal-fired power generation and thermal energy storage coupled system according to claim 1, characterized in that, A third valve (25) is provided between the outlet of the air preheater in the tail flue of the boiler (1) and the flue gas-working fluid heat exchanger (16). A first valve (23) is provided between the second target temperature water storage tank (19) and the secondary target pressure regenerator (8). A fifth valve (28) is provided between the first target temperature water storage tank (20) and the primary target pressure regenerator (9). A second valve (24) is provided between the first target temperature water storage tank (20) and the deaerator (10).

4. The coal-fired power generation and thermal energy storage coupled system according to claim 1, characterized in that, A fourth valve (26) is provided between the steam-working fluid heat exchanger (17) and the third pressure cylinder (4) of the steam turbine. A water pump (29) is provided between the second target temperature water storage tank (19) and the working fluid-water heat exchanger (13). A dust collector (27) is connected to one side of the flue gas-working fluid heat exchanger (16).

5. The coal-fired power generation and thermal energy storage coupled system according to claim 1, characterized in that, Both the second target temperature water storage tank (19) and the first target temperature water storage tank (20) use water as the heat storage medium; The operating temperature range of the second target temperature water storage tank (19) is 70~90℃ and the pressure range is 0.1~0.5MPa. The operating temperature range of the first target temperature water storage tank (20) is 110~140℃ and the pressure range is 0.5~0.6MPa.

6. The coal-fired power generation and thermal energy storage coupled system according to claim 1, characterized in that, The Rankine cycle heat pump energy storage system uses R1233zd(E) as the working fluid and operates at a temperature of 30~150℃.

7. The coal-fired power generation and thermal energy storage coupled system according to claim 1, characterized in that, The compressor (18) is a centrifugal compressor with an inlet-outlet combined pressure ratio of 2.

5.

8. The coal-fired power generation and thermal energy storage coupled system according to claim 1, characterized in that, Both the first target temperature water storage tank (20) and the second target temperature water storage tank (19) include an inlet and an outlet.

9. A coal-fired power generation and thermal energy storage coupling system according to claim 1, characterized in that, The working fluid-water heat exchanger (13), the working fluid regenerator (14), the flue gas-working fluid heat exchanger (16), and the steam-working fluid heat exchanger (17) are all shell-and-tube heat exchangers.

10. A coal-fired power generation and thermal energy storage coupling system according to claim 1, characterized in that, The steam-working fluid heat exchanger (17) uses phase change heat release as its heat release method, and the temperature range of the outlet saturated water is 70~80℃.

11. An operation method for a coal-fired power generation and thermal energy storage coupled system, characterized in that, include: When the power grid is in a low point of electricity demand and there is sufficient steam at the first target temperature, part of the electrical energy output by the generator (21) of the coal-fired unit and part of the heat energy extracted from the third pressure cylinder (4) of the steam turbine are converted into the heat energy of water for storage. When the power grid is in a low point of electricity demand and the steam at the first target temperature is insufficient, close the fourth valve (26) on the pipeline between the steam-working fluid heat exchanger (17) and the secondary extraction steam outlet of the third pressure cylinder (4) of the steam turbine, so that the steam heating working fluid circuit of the Rankine cycle heat pump energy storage system stops working. When the power grid is in a low point of electricity demand and the flue gas temperature at the outlet of the boiler tail air preheater is higher than the preset value, the flue gas heating working fluid circuit of the Rankine cycle heat pump energy storage system works to convert part of the electrical energy output by the generator (21) of the coal-fired unit and part of the heat energy of the flue gas at the outlet of the boiler (1) tail air preheater into the heat energy of water for storage. When the power grid is in a low point of electricity consumption and the flue gas temperature at the outlet of the air preheater at the tail of the boiler is lower than or equal to the preset value, close the third valve (25) on the pipeline between the flue gas-working fluid heat exchanger (16) and the boiler (1) to stop the working of the flue gas heating working fluid circuit of the Rankine cycle heat pump energy storage system. When the power grid is at its peak electricity demand, the coal-fired unit coupled with the hot water storage tank system operates, opening the first valve (23) to allow part of the condensate from the outlet of the third-stage target pressure regenerator (7) to enter the second target temperature water storage tank (19), and opening the fifth valve (28) or the second valve (24) to allow the hot water in the first target temperature water storage tank (20) to enter the first-stage target pressure regenerator (9) or the deaerator (10).

12. The operation method of a coal-fired power generation and thermal energy storage coupled system according to claim 11, characterized in that, When the part of the electrical energy output by the generator (21) of the coal-fired unit and the part of the heat energy extracted from the third pressure cylinder (4) of the steam turbine are converted into the heat energy of water for storage, the storage location is the water storage tank (20) at the first target temperature.

13. The operation method of a coal-fired power generation and thermal energy storage coupled system according to claim 11, characterized in that, When the part of the electrical energy output by the generator (21) of the coal-fired unit and the heat energy of the flue gas at the outlet of the air preheater at the tail of the boiler (1) are converted into the heat energy of water for storage, the storage location is the water storage tank (20) at the first target temperature.

14. The operation method of a coal-fired power generation and thermal energy storage coupled system according to claim 11, characterized in that, The process of directing a portion of the condensate from the outlet of the third-stage target pressure regenerator (7) into the second target temperature water storage tank (19) includes: When the temperature of the first target temperature water storage tank (20) is lower than the condensate outlet temperature of the first target pressure regenerator (9) but higher than that of the second target pressure regenerator (8), the fifth valve (28) is opened and the second valve (24) is closed, so that the hot water of the first target temperature water storage tank (20) enters the first target pressure regenerator (9). When the temperature of the first target temperature water storage tank (20) is higher than the condensate outlet temperature of the first target pressure regenerator (9), the second valve (24) is opened and the fifth valve (28) is closed, and the hot water from the first target temperature water storage tank (20) enters the deaerator (10).

15. The operation method of a coal-fired power generation and thermal energy storage coupled system according to claim 11, characterized in that, After the hot water in the first target temperature water storage tank (20) enters the first-stage target pressure regenerator (9) or deaerator (10), the process further includes: The extracted steam is returned to the third pressure cylinder (4) of the turbine to do work, increasing the turbine output.

16. The application of the coal-fired power generation and thermal energy storage coupling system according to any one of claims 1-10 or the operation method of the coal-fired power generation and thermal energy storage coupling system according to any one of claims 11-15 in the power field.

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