A two-stage steam supply system for coal-fired power units coupled with thermotropic solar thermal energy storage

Abstract

This invention provides a two-stage steam supply system for coal-fired power units coupled with thermotropic solar thermal energy storage. The solar energy storage subsystem is coupled to the coal-fired power unit via a molten salt heat storage and release subsystem and two heat exchangers. The energy stored in the solar energy storage subsystem is stored as thermal energy in the main heat exchanger. High-temperature molten salt in the main heat exchanger flows sequentially through the first and second heat exchangers, releasing heat. A portion of the low-temperature steam discharged from the cylinder assembly of the coal-fired power unit enters the first heat exchanger to absorb the heat released by the high-temperature salt, generating high-temperature steam for use by the cylinder assembly. A portion of the low-temperature steam enters the second heat exchanger to absorb the heat released by the high-temperature salt a second time, raising its temperature for use as primary industrial steam. By utilizing the energy of the solar energy storage subsystem to heat the low-temperature steam, while meeting the deep peak-shaving requirements of the power grid, the system can both guarantee industrial steam supply and reduce the boiler steam output of the coal-fired power unit, thereby reducing the coal consumption for power generation and contributing to energy conservation and emission reduction.

Description

Technical Field

[0001] The embodiments of the present invention belong to the field of energy utilization technology, specifically relating to a two-stage steam supply system for coal-fired power units coupled with thermotropic solar thermal energy storage. Background Technology

[0002] Under current requirements to reduce carbon emissions, the proportion of renewable energy sources such as wind and solar power is becoming increasingly significant. However, these renewable energy sources are characterized by intermittency and volatility, posing new challenges to the power grid. Against this backdrop, combined heat and power (CHP) units, while providing industrial steam, also need to frequently participate in peak shaving. This forces existing thermal power units to meet the parameter requirements of dual-stage industrial steam supply by employing main steam desuperheating and pressure reduction methods under low-load conditions, resulting in poor thermal economy and increased coal consumption.

[0003] There are four commonly used high-pressure industrial steam supply technologies for existing cogeneration units: cold resteam extraction heating, hot resteam extraction heating, main steam desuperheating and pressure reduction heating, and main steam back-pressure turbine heating. For the most commonly used 300MW-class thermal power units in China, cold resteam extraction heating and hot resteam extraction heating are difficult to provide the required steam supply of 100t / h at an industrial parameter of 3MPa under 50% THA conditions. Main steam desuperheating and pressure reduction heating can meet the high-pressure steam supply requirements under low-load conditions, but its economic efficiency is poor and it is difficult to meet the requirements of the "three-stage" (renovation, upgrading, and transformation) linkage. Heating via main steam back-pressure turbine requires the construction of a new back-pressure turbine plant, the purchase of back-pressure turbines and related valves, resulting in high initial investment costs, especially when steam demand fluctuates, leading to unstable economic returns.

[0004] Therefore, there is an urgent need for a steam supply system that can save energy and reduce emissions. Summary of the Invention

[0005] The embodiments of the present invention aim to at least solve one of the technical problems existing in the prior art, and provide a two-stage steam supply system for coal-fired power units coupled with thermotropic solar thermal energy storage.

[0006] This invention provides a two-stage steam supply system for coal-fired power units coupled with thermotropic solar thermal energy storage, comprising: A solar energy storage subsystem, wherein the solar energy storage subsystem is used to absorb solar energy and convert solar energy into thermal energy; A molten salt thermal energy storage and release subsystem includes a thermocline thermal energy storage tank, a molten salt heat exchanger, and a main heat exchanger. The first port and the second port on the first side of the molten salt heat exchanger are respectively connected to the high-temperature outlet and the low-temperature inlet of the solar energy storage subsystem. The high-temperature side of the main heat exchanger is connected in parallel with the first side of the molten salt heat exchanger. The high-temperature port and the low-temperature port of the thermocline thermal energy storage tank are respectively connected to the first port on the second side and the second port on the second side of the molten salt heat exchanger. The first heat exchanger is connected to the low-temperature side outlet of the main heat exchanger. The second heat exchanger has a high-temperature side inlet connected to the high-temperature side outlet of the first heat exchanger, and the high-temperature side outlet of the second heat exchanger is connected to the low-temperature side inlet of the main heat exchanger. A coal-fired power unit, comprising a boiler and a cylinder assembly, wherein the steam outlet of the boiler is connected to the steam inlet of the cylinder assembly, the steam outlet of the cylinder assembly is connected to the steam inlet of the boiler, the steam outlet of the cylinder assembly is connected to the low-temperature side inlet of a first heat exchanger, the low-temperature side outlet of the first heat exchanger is connected to the steam inlet of the cylinder assembly, and the steam outlet of the cylinder assembly is connected to the low-temperature side inlet of a second heat exchanger, the low-temperature side outlet of the second heat exchanger being used for first industrial steam supply.

[0007] In some embodiments of the present invention, the pressure of the steam output from the low-temperature side outlet of the second heat exchanger is 3 MPa.

[0008] In some embodiments of the present invention, the temperature of the steam output from the low-temperature side outlet of the second heat exchanger is 300°C.

[0009] In some embodiments of the present invention, the cylinder group includes a high-pressure cylinder, an intermediate-pressure cylinder, and a low-pressure cylinder connected coaxially in sequence. The exhaust ports of the high-pressure cylinder, the intermediate-pressure cylinder, and the low-pressure cylinder are respectively connected to the low-temperature side inlet of the first heat exchanger, and the low-temperature side outlet of the first heat exchanger is connected to the steam inlet of the high-pressure cylinder.

[0010] In some embodiments of the present invention, the coal-fired unit further includes a deaerator, wherein the exhaust port of the high-pressure cylinder, the exhaust port of the intermediate-pressure cylinder and the exhaust port of the low-pressure cylinder are respectively connected to the deaerator, and the deaerator is connected to the low-temperature side inlet of the first heat exchanger.

[0011] In some embodiments of the present invention, the deaerator is connected to the low-temperature side inlet of the second heat exchanger.

[0012] In some embodiments of the present invention, the deaerator is connected to the steam inlet of the boiler.

[0013] In some embodiments of the present invention, the exhaust port of the high-pressure cylinder includes a high-temperature exhaust port and a low-temperature exhaust port. The high-temperature exhaust port and the low-temperature exhaust port are respectively connected to the deaerator. The high-temperature exhaust port is connected to the reheat steam inlet of the boiler. The reheat steam outlet of the boiler is connected to the steam inlet of the intermediate-pressure cylinder. The high-temperature exhaust port is used for second industrial steam supply.

[0014] In some embodiments of the present invention, the pressure of the industrial steam output from the high-temperature exhaust port is different from the pressure of the industrial steam output from the low-temperature side outlet of the second heat exchanger.

[0015] In some embodiments of the present invention, the pressure of the industrial steam output from the high-temperature exhaust port is 1.5 MPa.

[0016] This invention relates to a coupled thermocentric solar thermal energy storage system for a coal-fired power unit with a two-stage steam supply system. The system couples the solar energy storage subsystem to the coal-fired power unit via a molten salt heat storage and release subsystem and two heat exchangers. The energy stored in the solar energy storage subsystem is stored as thermal energy in the main heat exchanger. High-temperature molten salt in the main heat exchanger flows sequentially through the first and second heat exchangers, releasing heat. A portion of the low-temperature steam discharged from the cylinder assembly of the coal-fired power unit enters the first heat exchanger to absorb the heat released by the high-temperature salt, generating high-temperature steam for use by the cylinder assembly. A portion of the low-temperature steam enters the second heat exchanger to absorb the heat released by the high-temperature salt, raising its temperature for use as the first industrial steam supply. By utilizing the energy of the solar energy storage subsystem to heat the low-temperature steam, the system can meet the deep peak-shaving requirements of the power grid, ensuring industrial steam supply while reducing the boiler steam output of the coal-fired power unit. This reduces the coal consumption for power generation and contributes to energy conservation and emission reduction. Attached Figure Description

[0017] Figure 1 This is a schematic diagram of a two-stage steam supply system for a coal-fired power unit that couples thermotropic solar thermal energy storage.

[0018] The labels in the attached diagram are as follows: 10. Solar energy storage subsystem; 20. Molten salt heat storage and release subsystem; 21. Cryothermal storage tank; 22. Molten salt heat exchanger; 23. Main heat exchanger; 30. First heat exchanger; 40. Second heat exchanger; 50. Coal-fired power unit; 51. Boiler; 52. Cylinder assembly; 521. High-pressure cylinder; 522. Intermediate-pressure cylinder; 523. Low-pressure cylinder; 53. Generator; 54. Deaerator; 55. Condenser; 56. Condensate pump; 57. Feedwater pump; 581. First high-pressure heater; 582. Second high-pressure heater; 583. Third high-pressure heater; 584. First low-pressure heater; 585. Second low-pressure heater; 586. Third low-pressure heater; 587. Fourth low-pressure heater. Detailed Implementation

[0019] To enable those skilled in the art to better understand the technical solutions of the present invention, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments. It should be understood that the specific embodiments described herein are only for explaining the present invention and are not intended to limit the invention. The described embodiments are some, but not all, of the embodiments of the present invention. Based on the described embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the protection scope of the present invention.

[0020] like Figure 1 As shown, this embodiment of the invention provides a two-stage steam supply system for a coal-fired unit coupled with thermotropic solar thermal energy storage, including: a solar energy storage subsystem 10, a molten salt heat storage and release subsystem 20, a first heat exchanger 30, a second heat exchanger 40, and a coal-fired unit 50. The solar energy storage subsystem 10 is used to absorb solar energy and convert it into thermal energy. The molten salt heat storage and release subsystem 20 includes a thermotropic thermal storage tank 21, a molten salt heat exchanger 22, and a main heat exchanger 23. The first port and the second port of the first side of the molten salt heat exchanger 22 are respectively connected to the high-temperature outlet and the low-temperature inlet of the solar energy storage subsystem 10. The high-temperature side of the main heat exchanger 23 is connected in parallel with the first side of the molten salt heat exchanger 22. The hot port of the thermotropic thermal storage tank 21 is connected to the first port of the second side of the molten salt heat exchanger 22, and the cold port of the thermotropic thermal storage tank 21 is connected to... The second port on the second side of the molten salt heat exchanger 22 is connected. The high-temperature side inlet of the first heat exchanger 30 is connected to the low-temperature side outlet of the main heat exchanger 23. The high-temperature side inlet of the second heat exchanger 40 is connected to the high-temperature side outlet of the first heat exchanger 30. The high-temperature side outlet of the second heat exchanger 40 is connected to the low-temperature side inlet of the main heat exchanger 23. The coal-fired unit 50 includes a boiler 51 and a cylinder group 52. The steam outlet of the boiler 51 is connected to the steam inlet of the cylinder group 52. The steam outlet of the cylinder group 52 is connected to the steam inlet of the boiler 51. The steam outlet of the cylinder group 52 is connected to the low-temperature side inlet of the first heat exchanger 30. The low-temperature side outlet of the first heat exchanger 30 is connected to the steam inlet of the cylinder group 52. The steam outlet of the cylinder group 52 is connected to the low-temperature side inlet of the second heat exchanger 40. The low-temperature side outlet of the second heat exchanger 40 is used for the first industrial steam supply.

[0021] Specifically, the two-stage steam supply system of the coal-fired unit coupled with the thermotropic layer solar thermal energy storage includes a solar energy storage subsystem 10, a molten salt heat storage and release subsystem 20, a first heat exchanger 30, a second heat exchanger 40, and a coal-fired unit 50. The solar energy storage subsystem 10 converts solar energy into thermal energy. The high-temperature outlet of the solar energy storage subsystem 10 outputs high-temperature first molten salt to the first port of the first side of the molten salt heat exchanger 22. After releasing heat in the molten salt heat exchanger 22, the high-temperature first molten salt becomes low-temperature first molten salt. The low-temperature first molten salt is discharged from the second port of the first side of the molten salt heat exchanger 22 and returns to the low-temperature inlet of the solar energy storage subsystem 10. The low-temperature first molten salt returns to the solar energy storage subsystem 10, absorbs the heat generated by solar energy, and becomes high-temperature first molten salt, thus forming the heat storage and release process of the first molten salt. The high-temperature outlet of the solar energy storage subsystem 10 outputs high-temperature first molten salt to the high-temperature side inlet of the main heat exchanger 23. After releasing heat in the main heat exchanger 23, the high-temperature first molten salt becomes low-temperature first molten salt. The low-temperature first molten salt is discharged from the high-temperature side outlet of the main heat exchanger 23 and returns to the low-temperature inlet of the solar energy storage subsystem 10. The low-temperature first molten salt returns to the solar energy storage subsystem 10 and absorbs the heat generated by solar energy to become high-temperature first molten salt, thus forming the heat storage and release process of the first molten salt.

[0022] When the solar energy storage subsystem provides heat to the molten salt heat exchanger 22, the second side of the molten salt heat exchanger 22 is the low-temperature side. The low-temperature second molten salt in the inclined temperature layer heat storage tank 21 flows out from the cold port and enters the molten salt heat exchanger 22 through the second port on the second side of the molten salt heat exchanger 22. The low-temperature second molten salt in the inclined temperature layer heat storage tank 21 absorbs the heat from the high-temperature first molten salt of the solar energy storage subsystem 10 in the molten salt heat exchanger 22 and becomes a high-temperature second molten salt. The high-temperature second molten salt is discharged from the second port on the second side of the molten salt heat exchanger 22 to the hot port of the inclined temperature layer heat storage tank 21 to store the heat in the inclined temperature layer heat storage tank 21. When the solar energy storage subsystem cannot provide heat to the molten salt heat exchanger 22, the thermocline heat storage tank 21 releases the heat of the second molten salt. The second side of the molten salt heat exchanger 22 is the high-temperature side. The high-temperature second molten salt in the thermocline heat storage tank 21 is discharged from its hot port and enters the molten salt heat exchanger 22 through the first port on the second side. The high-temperature second molten salt releases heat in the molten salt heat exchanger 22 and becomes a low-temperature second molten salt, which is discharged from the second port on the second side of the molten salt heat exchanger 22 and then returns to the cold port of the thermocline heat storage tank 21, thus realizing the heat release process of the second molten salt. The first molten salt in the molten salt heat exchanger 22 absorbs heat from the second molten salt and is discharged from the first port on the first side. It then enters the main heat exchanger 23 through the high-temperature inlet and releases heat, becoming a low-temperature first molten salt. This first molten salt is discharged from the high-temperature outlet of the main heat exchanger 23 and then enters the molten salt heat exchanger 22 through the second port on the first side, thus completing the heat release process of the first molten salt. Specifically, when the solar energy storage subsystem has sufficient heat, it supplies heat to the molten salt heat exchanger 22 and the main heat exchanger 23, while the molten salt heat exchanger 22 stores heat in the inclined thermocentric layer heat storage tank 23. When the solar energy storage subsystem lacks sufficient heat, the inclined thermocentric layer heat storage tank 23 releases heat and transfers it to the main heat exchanger 23 through the molten salt heat exchanger 22, thus supplying heat to the main heat exchanger 23.

[0023] The third molten salt at a low temperature of 300°C enters the main heat exchanger 23 through the low temperature side inlet and absorbs the heat released by the high temperature first molten salt, becoming a high temperature third molten salt. The high temperature third molten salt at 590°C exits from the low temperature side outlet of the main heat exchanger 23. The third molten salt at 350°C enters the first heat exchanger 30 through the high temperature side inlet and releases heat, becoming a medium temperature third molten salt at 350°C. The medium temperature third molten salt exits from the high temperature side outlet of the first heat exchanger 30. The medium temperature third molten salt enters the second heat exchanger 40 through the high temperature side inlet and releases heat again, becoming a low temperature third molten salt at 300°C. The low temperature salt exits from the high temperature side outlet of the second heat exchanger 40 and enters the main heat exchanger 23, forming a cycle of heat absorption and release for the third molten salt.

[0024] The low-temperature steam discharged from the exhaust port of cylinder group 52 is transported to the low-temperature side inlet of the first heat exchanger 30. The low-temperature steam absorbs the heat released by the high-temperature salt in the first heat exchanger 30 and becomes the first high-temperature steam, which is discharged from the low-temperature side outlet of the first heat exchanger 30 to the steam inlet of cylinder group 52.

[0025] The low-temperature steam discharged from the exhaust port of cylinder group 52 is transported to the low-temperature side inlet of the second heat exchanger 40. The low-temperature steam absorbs the heat released by the medium-temperature salt in the second heat exchanger 40 and is heated to become the second high-temperature steam, which is then discharged from the low-temperature side outlet of the second heat exchanger 40 as the first industrial steam supply.

[0026] It should be noted that, in this embodiment, the hotter molten salt (lower density) in the thermocline storage tank 21 will naturally float on top of the colder molten salt (higher density). That is, the hot port of the thermocline storage tank 21 is located at its top, and the cold port of the thermocline storage tank 21 is located at its bottom. Between the hot molten salt area and the cold molten salt area, a transition layer with a significant temperature gradient will be formed. This layer is the thermocline.

[0027] The coupled thermocentric solar thermal energy storage dual-stage steam supply system for coal-fired power units in this embodiment of the invention couples the solar energy storage subsystem 10 with the coal-fired power unit 50 through a molten salt heat storage and release subsystem 20 and two heat exchangers. The energy stored in the solar energy storage subsystem 10 is stored as thermal energy in the main heat exchanger 23. The high-temperature third molten salt in the salt storage tank flows sequentially through the first heat exchanger 30 and the second heat exchanger 40 to release heat. Part of the low-temperature steam discharged from the cylinder group 52 of the coal-fired power unit 50 enters the first heat exchanger 30 to absorb the heat released by the high-temperature salt and generate high-temperature steam for use by the cylinder group. Part of the low-temperature steam enters the second heat exchanger 40 to absorb the heat released by the high-temperature salt and is heated to be used as the first industrial steam supply. By using the energy of the solar energy storage subsystem 10 to heat the low-temperature steam, the industrial steam supply demand can be guaranteed while meeting the deep peak shaving requirements of the power grid. At the same time, the steam output of the boiler 51 of the coal-fired power unit 50 can be reduced, thereby reducing the coal consumption for power generation of the coal-fired power unit 50 and contributing to energy conservation and emission reduction.

[0028] In some embodiments of the present invention, the cylinder group 52 includes a high-pressure cylinder 521, an intermediate-pressure cylinder 522, and a low-pressure cylinder 523 connected coaxially in sequence. The exhaust ports of the high-pressure cylinder 521, the intermediate-pressure cylinder 522, and the low-pressure cylinder 523 are respectively connected to the low-temperature side inlet of the first heat exchanger 30, and the low-temperature side outlet of the first heat exchanger 30 is connected to the inlet of the high-pressure cylinder 521. Specifically, the exhaust ports of the three cylinders 521, 522, and 523 can be directly connected to the low-temperature side inlet of the first heat exchanger 30, or they can be indirectly connected to the low-temperature side inlet of the first heat exchanger 30 through other components. The first heat exchanger 30 heats the low-temperature steam to generate high-temperature steam that can be used by the high-pressure cylinder 521. The high-temperature steam is discharged from the low-temperature side outlet of the first heat exchanger 30 and enters the high-pressure cylinder 521 through the inlet of the high-pressure cylinder 521. Furthermore, the steam outlet of boiler 51 is connected to the steam inlet of high-pressure cylinder 521. The high-temperature steam output from boiler 51 enters high-pressure cylinder 521 through its inlet for use. The reheat steam outlet of boiler 51 is connected to the steam inlet of intermediate-pressure cylinder 522. The reheat steam output from boiler 51 enters intermediate-pressure cylinder 522 through its inlet for use. The steam outlet of intermediate-pressure cylinder 522 is connected to the steam inlet of low-pressure cylinder 523. A portion of the steam in intermediate-pressure cylinder 522 enters low-pressure cylinder 523 through its inlet for use.

[0029] The coal-fired unit 50 also includes a generator 53, which is coaxially connected to the high-pressure cylinder 521, the intermediate-pressure cylinder 522 and the low-pressure cylinder 523. The generator 53 converts mechanical energy into electrical energy through the operation of the high-pressure cylinder 521, the intermediate-pressure cylinder 522 and the low-pressure cylinder 523.

[0030] In some embodiments of the present invention, the coal-fired unit 50 further includes a deaerator 54. The exhaust ports of the high-pressure cylinder 521, the intermediate-pressure cylinder 522, and the low-pressure cylinder 523 are respectively connected to the deaerator 54. The deaerator 54 is connected to the low-temperature side inlet of the first heat exchanger 30. The exhaust ports of the three cylinders, high-pressure cylinder 521, intermediate-pressure cylinder 522, and low-pressure cylinder 523, are connected to the deaerator 54 to remove oxygen and other non-condensable gases (such as carbon dioxide) from the solution in the low-temperature steam discharged from the three cylinders, preventing equipment corrosion; at the same time, it heats the feedwater and improves the system thermal efficiency.

[0031] In some embodiments of the present invention, the deaerator 54 is connected to the low-temperature side inlet of the second heat exchanger 40. Specifically, the steam outlet of the deaerator 54 is connected to the low-temperature side inlet of the second heat exchanger 40, and the deaerated low-temperature steam enters the second heat exchanger 40 to absorb the heat released by the molten salt in the second heat exchanger 40 and generate high-temperature steam for use as the first industrial steam supply.

[0032] In some embodiments of the present invention, the deaerator 54 is connected to the steam inlet of the boiler 51. Specifically, the steam outlet of the deaerator 54 is also connected to the steam inlet of the boiler 51 to supply water to the boiler 51.

[0033] The steam outlet of deaerator 54 is connected to the low-temperature inlet of the first heat exchanger 30, the low-temperature inlet of the second heat exchanger 40, and the steam inlet of boiler 51, respectively. This means the low-temperature steam from the deaerator 54 outlet is divided into three streams that enter boiler 51, the first heat exchanger 30, and the second heat exchanger 40. Because the molten salt flowing through the first heat exchanger 30 has a higher temperature and releases more heat, the low-temperature steam entering the first heat exchanger 30 absorbs a significant amount of heat released by the high-temperature salt, thus heating up to become high-temperature steam usable by high-pressure cylinder 521. Since the high-temperature salt releases some heat in the first heat exchanger 30, becoming medium-temperature salt, and its temperature is higher than that of the low-temperature steam, the low-temperature steam enters the second heat exchanger 40 and absorbs the heat from the medium-temperature salt, heating up to become higher-temperature steam for use as the first industrial steam supply. The low-temperature steam output from the deaerator 54 outlet to boiler 51 is heated by boiler 51 to generate high-temperature steam usable by high-pressure cylinder 521.

[0034] In some embodiments of the present invention, the coal-fired unit 50 further includes a high-pressure heater, wherein the exhaust port of the high-pressure cylinder 521 and the exhaust port of the intermediate-pressure cylinder 522 are respectively connected to the high-temperature side inlet of different high-pressure heaters, the high-temperature side outlet of the high-pressure heater is connected to the inlet of the deaerator 54, the outlet of the deaerator 54 is connected to the low-temperature side inlet of the high-pressure heater, and the low-temperature side outlet of the high-pressure heater is connected to the steam inlet of the boiler 51. Specifically, in this embodiment, there are three high-pressure heaters. The first exhaust port of the high-pressure cylinder 521 is connected to the high-temperature side inlet of the first high-pressure heater 581, the second exhaust port of the high-pressure cylinder 521 is connected to the high-temperature side inlet of the second high-pressure heater 582, the first exhaust port of the intermediate-pressure cylinder 522 is connected to the high-temperature side inlet of the third high-pressure heater 583, the high-temperature side outlet of the first high-pressure heater 581 is connected to the high-temperature side inlet of the second high-pressure heater 582, and the high-temperature side outlet of the second high-pressure heater 582 is connected to the high-temperature side inlet of the third high-pressure heater 583. The second exhaust port of the intermediate-pressure cylinder 522 is connected to the inlet of the deaerator 54. The outlet of deaerator 54 is connected to the low-temperature side inlet of the third high-pressure heater 583. The low-temperature side outlet of the third high-pressure heater 583 is connected to the low-temperature side inlet of the second high-pressure heater 582. The low-temperature side outlet of the second high-pressure heater 582 is connected to the low-temperature side inlet of the first high-pressure heater 581. The low-temperature side outlet of the first high-pressure heater 581 is connected to the steam inlet of boiler 51. The low-temperature side outlet of the first high-pressure heater 581 is also connected to the low-temperature side inlet of the first heat exchanger 30. A feedwater pump 57 can also be installed between deaerator 54 and the third high-pressure heater 583 to pump the low-temperature steam output from deaerator 54 into the third high-pressure heater 583, providing a certain flow force.

[0035] The flow path of the low-temperature steam at the first exhaust port of the high-pressure cylinder 521 is as follows: high-temperature side inlet of the first high-pressure heater 581 → high-temperature side outlet of the first high-pressure heater 581 → high-temperature side inlet of the second high-pressure heater 582 → high-temperature side outlet of the second high-pressure heater 582 → high-temperature side inlet of the third high-pressure heater 583 → high-temperature side outlet of the third high-pressure heater 583 → inlet of the deaerator 54 → outlet of the deaerator 54 → low-temperature side inlet of the third high-pressure heater 583 → low-temperature side outlet of the third high-pressure heater 583 → low-temperature side inlet of the second high-pressure heater 582 → low-temperature side outlet of the second high-pressure heater 582 → low-temperature side inlet of the first high-pressure heater 581 → low-temperature side outlet of the first high-pressure heater 581 → steam inlet of the boiler 51 or low-temperature side inlet of the first heat exchanger 30.

[0036] The low-temperature steam from the second exhaust port of high-pressure cylinder 521 is divided into three branches. The first branch connects to the high-temperature side inlet of the second high-pressure heater 582, the second branch connects to the reheat steam inlet of boiler 51, and the third branch serves as the second industrial steam supply. The low-temperature steam in the first branch originates from the high-temperature side inlet of the second high-pressure heater 582, and the remaining portion follows the same low-temperature steam path as the first exhaust port of high-pressure cylinder 521. The first exhaust port of intermediate-pressure cylinder 522 originates from the high-temperature side inlet of the third high-pressure heater 583, and the remaining portion follows the same low-temperature steam path as the first exhaust port of high-pressure cylinder 521.

[0037] In some embodiments of the present invention, the coal-fired unit 50 further includes a low-pressure heater and a condenser. Multiple exhaust ports of the low-pressure cylinder 523 are connected to the high-temperature side inlet of the low-pressure heater, the high-temperature side outlet of the low-pressure heater is connected to the inlet of the condenser 55, one exhaust port of the low-pressure cylinder 523 is connected to the inlet of the condenser 55, the outlet of the condenser 55 is connected to the low-temperature side inlet of the low-pressure heater, and the low-temperature side outlet of the low-pressure heater is connected to the deaerator 54. In this embodiment, the low-pressure cylinder 523 has five exhaust ports, one of which is connected to the inlet of the condenser 55, and the other four are connected to the corresponding four low-pressure heaters. The first exhaust port of low-pressure cylinder 523 is connected to the high-temperature side inlet of the first low-pressure heater 584; the second exhaust port of low-pressure cylinder 523 is connected to the high-temperature side inlet of the second low-pressure heater 585; the third exhaust port of low-pressure cylinder 523 is connected to the high-temperature side inlet of the third low-pressure heater 586; the fourth exhaust port of low-pressure cylinder 523 is connected to the high-temperature side inlet of the fourth low-pressure heater 587; the high-temperature side outlet of the first low-pressure heater 584 is connected to the high-temperature side inlet of the second low-pressure heater 585; the high-temperature side outlet of the second low-pressure heater 585 is connected to the high-temperature side inlet of the third low-pressure heater 586; and the high-temperature side outlet of the third low-pressure heater 586... The high-temperature side outlet of the fourth low-pressure heater 587 is connected to the high-temperature side inlet of the fourth low-pressure heater 587. The high-temperature side outlet of the fourth low-pressure heater 587 is connected to the inlet of the condenser 55. The outlet of the condenser 55 is connected to the low-temperature side inlet of the fourth low-pressure heater 587 via the condensate pump 56. The low-temperature side outlet of the fourth low-pressure heater 587 is connected to the low-temperature side inlet of the third low-pressure heater 586. The low-temperature side outlet of the third low-pressure heater 586 is connected to the low-temperature side inlet of the second low-pressure heater 585. The low-temperature side outlet of the second low-pressure heater 585 is connected to the low-temperature side inlet of the first low-pressure heater 584. The low-temperature side outlet of the first low-pressure heater 584 is connected to the inlet of the deaerator 54.

[0038] The flow path of the low-temperature steam at the first exhaust port of the low-pressure cylinder 523 is as follows: high-temperature side inlet of the first low-pressure heater 584 → high-temperature side outlet of the first low-pressure heater 584 → high-temperature side inlet of the second low-pressure heater 585 → high-temperature side outlet of the second low-pressure heater 585 → high-temperature side inlet of the third low-pressure heater 586 → high-temperature side outlet of the third low-pressure heater 586 → high-temperature side inlet of the fourth low-pressure heater 587 → high-temperature side outlet of the fourth low-pressure heater 587 → inlet of the condenser 55 → outlet of the condenser 55 → inlet of the condensate pump 56 → outlet of the condensate pump 56 → low-temperature side inlet of the fourth low-pressure heater 587 → low-temperature side outlet of the fourth low-pressure heater 587 → third low-pressure heater 584 → high-temperature side outlet of the third low-pressure heater 585 → high-temperature side outlet of the fourth low-pressure heater 587 → high-temperature side outlet of the third low-pressure heater 585 → high-temperature side outlet of the third low-pressure heater 585 → high-temperature side outlet of the fourth ... fourth low-pressure heater 585 → high-temperature side outlet of the third low-pressure heater 585 Low-temperature side inlet of heater 586 → Low-temperature side outlet of third low-pressure heater 586 → Low-temperature side inlet of second low-pressure heater 585 → Low-temperature side outlet of second low-pressure heater 585 → Low-temperature side inlet of first low-pressure heater 584 → Low-temperature side outlet of first low-pressure heater 584 → Inlet of deaerator 54 → Outlet of deaerator 54 → Low-temperature side inlet of third high-pressure heater 583 → Low-temperature side outlet of third high-pressure heater 583 → Low-temperature side inlet of second high-pressure heater 582 → Low-temperature side outlet of second high-pressure heater 582 → Low-temperature side inlet of first high-pressure heater 581 → Low-temperature side outlet of first high-pressure heater 581 → Steam inlet of boiler 51 or low-temperature side inlet of first heat exchanger 30.

[0039] In some embodiments of the present invention, the exhaust port of the high-pressure cylinder 521 includes a high-temperature exhaust port and a low-temperature exhaust port, that is, the first exhaust port is a low-temperature exhaust port and the second exhaust port is a high-temperature exhaust port. The high-temperature exhaust port and the low-temperature exhaust port are respectively connected to the deaerator 54, the high-temperature exhaust port is connected to the reheat steam inlet of the boiler 51, the reheat steam outlet of the boiler 51 is connected to the steam inlet of the intermediate-pressure cylinder 522, and the high-temperature exhaust port is used for the second industrial steam supply. The high-temperature steam discharged from the high-pressure cylinder 521 is discharged through the high-temperature exhaust port. The first part of the high-temperature steam is used as the second industrial steam supply, the second part of the high-temperature steam enters the reheat steam inlet of the boiler 51, is heated by the reheater of the boiler 51, and is discharged through the reheat exhaust port, and the third part of the high-temperature steam enters the second high-pressure heater 582.

[0040] In some embodiments of the present invention, the pressure of the industrial steam output from the high-temperature exhaust port is different from the pressure of the industrial steam output from the low-temperature side outlet of the second heat exchanger 40. The steam output from the high-temperature exhaust port is used as the second industrial steam supply, and the steam output from the low-temperature side outlet of the second heat exchanger 40 is used as the first industrial steam supply. The steam pressures of the first industrial steam supply and the second industrial steam supply are different to achieve different industrial applications.

[0041] In some embodiments of the present invention, the pressure of the industrial steam output from the high-temperature exhaust port is 1.5 MPa, that is, the pressure of the second industrial steam supply is 1.5 MPa.

[0042] In some embodiments of the present invention, the pressure of the steam output from the low-temperature side outlet of the second heat exchanger 40 is 3 MPa, that is, the pressure of the first industrial steam supply is 3 MPa.

[0043] In some embodiments of the present invention, the temperature of the steam output from the low-temperature side outlet of the second heat exchanger 40 is 300°C, that is, the temperature of the first industrial steam supply is 300°C.

[0044] The molten salt heat storage and release subsystem 20 provides a portion of the main steam Q1, and the boiler 51 provides Q2. Considering the overheating limit of the boiler 51 reheater, the amount of cold reheat steam that can be extracted is Q1 + r × Q2 (where r is the allowable extraction coefficient, generally 5%~8%). Corresponding to the conventional cogeneration boiler 51 supplying steam, when the main steam provided by boiler 51 is Q1 + Q2, considering the overheating limit of boiler 51 reheater, the amount of cold reheat steam that can be extracted is r × (Q1 + Q2) (where r is the allowable extraction coefficient). In summary, with the same amount of main steam entering the high-pressure cylinder 521, this invention proposes a system with a larger cold reheat extraction capacity, increasing the extraction capacity by (1-r) × Q1. After the molten salt heat storage and release subsystem 20 is coupled with the coal-fired unit 50, the molten salt heat storage and release subsystem 20 removes the limitation of the boiler 51 reheater on the amount of steam extracted by sharing the heating load. Thus, under the same main steam consumption, the actual steam extraction heating capacity of the unit is greatly improved, thereby achieving "thermal-electric decoupling" more efficiently.

[0045] The dual-stage steam supply system for coal-fired power units with coupled thermotropic solar thermal energy storage, as described in this invention, fully utilizes solar thermal energy and combines it with multi-stage heating of condensate into superheated steam for industrial steam supply, achieving multi-stage energy utilization of the thermal system. Furthermore, by utilizing the molten salt system portion of the unit's main steam, the cold reheat steam heating flow rate can be significantly increased, reducing heating energy consumption. In summary, this invention not only achieves multi-stage solar energy utilization but also ensures industrial steam supply needs under deep peak-shaving conditions, resulting in energy conservation and emission reduction. Compared with a conventional 350MW supercritical unit (main steam pressure 24.2MPa, main steam temperature 566℃, reheat steam temperature 566℃, back pressure set at 4.9kPa), when the industrial steam supply parameters are pressure 3MPa, temperature 280℃, extraction steam rate 100t / h, and main steam flow rate set at 1008.51t / h, the coal consumption for power generation of the present invention is only 235.41 g / kWh, while the coal consumption for power generation of the conventional cogeneration scheme is only 276.57 g / kWh. The coal consumption for power generation of the present invention is reduced by 41.16 g / kWh, demonstrating a significant coal-saving effect.

[0046] It is understood that the above embodiments are merely exemplary implementations used to illustrate the principles of the present invention, and the present invention is not limited thereto. For those skilled in the art, various modifications and improvements can be made without departing from the spirit and essence of the present invention, and these modifications and improvements are also considered to be within the scope of protection of the present invention.

Claims

1. A double-stage steam supply system of a coal-fired unit coupled with a thermocline solar energy photothermal energy storage, characterized in that, include: A solar energy storage subsystem, wherein the solar energy storage subsystem is used to absorb solar energy and convert solar energy into thermal energy; A molten salt thermal energy storage and release subsystem includes a thermocline thermal energy storage tank, a molten salt heat exchanger, and a main heat exchanger. The first port and the second port on the first side of the molten salt heat exchanger are respectively connected to the high-temperature outlet and the low-temperature inlet of the solar energy storage subsystem. The high-temperature side of the main heat exchanger is connected in parallel with the first side of the molten salt heat exchanger. The high-temperature port and the low-temperature port of the thermocline thermal energy storage tank are respectively connected to the first port on the second side and the second port on the second side of the molten salt heat exchanger. The first heat exchanger is connected to the low-temperature side outlet of the main heat exchanger. The second heat exchanger has a high-temperature side inlet connected to the high-temperature side outlet of the first heat exchanger, and the high-temperature side outlet of the second heat exchanger is connected to the low-temperature side inlet of the main heat exchanger. A coal-fired power unit, comprising a boiler and a cylinder assembly, wherein the steam outlet of the boiler is connected to the steam inlet of the cylinder assembly, the steam outlet of the cylinder assembly is connected to the steam inlet of the boiler, the steam outlet of the cylinder assembly is connected to the low-temperature side inlet of a first heat exchanger, the low-temperature side outlet of the first heat exchanger is connected to the steam inlet of the cylinder assembly, and the steam outlet of the cylinder assembly is connected to the low-temperature side inlet of a second heat exchanger, the low-temperature side outlet of the second heat exchanger being used for first industrial steam supply.

2. The coal-fired unit double-stage steam supply system coupled with the thermocline solar energy light and heat energy storage according to claim 1, characterized in that, The pressure of the steam output from the low-temperature side outlet of the second heat exchanger is 3 MPa.

3. The coal-fired unit double-stage steam supply system coupled with thermocline solar energy according to claim 1, characterized in that, The temperature of the steam output from the low-temperature side outlet of the second heat exchanger is 300°C.

4. The coal-fired unit two-stage steam supply system coupled with thermocline solar energy and heat energy storage according to claim 1, characterized in that, The cylinder assembly includes a high-pressure cylinder, an intermediate-pressure cylinder, and a low-pressure cylinder connected coaxially in sequence. The exhaust ports of the high-pressure cylinder, the intermediate-pressure cylinder, and the low-pressure cylinder are respectively connected to the low-temperature side inlet of the first heat exchanger, and the low-temperature side outlet of the first heat exchanger is connected to the inlet of the high-pressure cylinder.

5. The coal-fired unit two-stage steam supply system coupled with thermocline solar energy and heat energy storage according to claim 4, characterized in that, The coal-fired unit also includes a deaerator. The exhaust ports of the high-pressure cylinder, the intermediate-pressure cylinder, and the low-pressure cylinder are respectively connected to the deaerator. The deaerator is connected to the low-temperature side inlet of the first heat exchanger.

6. The two-stage steam supply system for coal-fired power units with coupled thermotropic solar thermal energy storage as described in claim 5, characterized in that, The deaerator is connected to the low-temperature side inlet of the second heat exchanger.

7. The two-stage steam supply system for coal-fired power units with coupled thermotropic solar thermal energy storage as described in claim 5, characterized in that, The deaerator is connected to the steam inlet of the boiler.

8. The two-stage steam supply system for coal-fired power units with coupled thermotropic solar thermal energy storage as described in claim 5, characterized in that, The exhaust port of the high-pressure cylinder includes a high-temperature exhaust port and a low-temperature exhaust port. The high-temperature exhaust port and the low-temperature exhaust port are respectively connected to the deaerator. The high-temperature exhaust port is connected to the reheat steam inlet of the boiler. The reheat steam outlet of the boiler is connected to the steam inlet of the intermediate-pressure cylinder. The high-temperature exhaust port is used for secondary industrial steam supply.

9. The two-stage steam supply system for coal-fired power units with coupled thermotropic solar thermal energy storage as described in claim 8, characterized in that, The pressure of the industrial steam output from the high-temperature exhaust port is different from the pressure of the industrial steam output from the low-temperature side outlet of the second heat exchanger.

10. The two-stage steam supply system for a coal-fired unit with coupled thermotropic solar thermal energy storage according to claim 9, characterized in that, The pressure of the industrial steam output from the high-temperature exhaust port is 1.5 MPa.

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