A molten salt coupled supercritical carbon dioxide power and heat supply system and working method

Abstract

This invention relates to the field of novel power cycle technology, specifically a molten salt coupled supercritical carbon dioxide power generation and heating system and its operating method. The molten salt coupled supercritical carbon dioxide power generation and heating system includes a molten salt energy storage module, comprising a high-temperature molten salt tank, a low-temperature molten salt tank, a molten salt-carbon dioxide heat exchanger, a molten salt-water heat exchanger, and an electric heater; a heating / steam module, including a heating / steam return water pipe and a steam supply header; and a carbon dioxide power generation cycle module. This invention, through bypass pipes and series heat exchangers, enables molten salt to provide heat to the carbon dioxide power generation cycle and the heating / steam system in a cascade manner, improving the overall system energy utilization efficiency, reducing the overall molten salt consumption, saving costs, and allowing the two heat-using systems to operate independently, ensuring system operational flexibility and achieving thermo-electric decoupling. This system possesses multiple functions such as energy storage, power generation, and heating / steam supply, providing a new approach for the replacement and retrofitting of aging coal-fired power units.

Description

Technical Field

[0001] This invention relates to the field of novel power cycle technology, and in particular to a molten salt coupled supercritical carbon dioxide power generation and heating system and its operating method. Background Technology

[0002] In recent years, with the global energy structure transformation and increasingly stringent environmental protection requirements, the research and application of clean energy technologies have gradually become mainstream. Supercritical carbon dioxide (sCO2) cycle power generation technology, in particular, has become an important development direction for next-generation power generation technologies due to its high thermal efficiency and low emissions. This technology, using supercritical carbon dioxide as the working fluid, achieves higher thermal efficiency at lower operating temperatures and pressures compared to traditional steam cycle systems, and reduces the demand for cooling water, demonstrating significant energy utilization advantages. However, current supercritical carbon dioxide cycle technology still faces challenges in practical applications, including system design, high-temperature resistance of equipment, and heat source stability.

[0003] Meanwhile, molten salt energy storage technology, as a mature high-temperature energy storage technology, has been widely applied in the field of solar thermal power generation. Molten salt has a high heat capacity and a long thermal storage cycle, which can effectively solve the problems of intermittency and volatility of renewable energy. However, existing molten salt energy storage systems are mostly used for solar thermal power generation, and their application in the retrofitting of traditional coal-fired power plants and coupling with other cogeneration systems has not been fully explored. Although molten salt can provide a stable heat source, its energy utilization efficiency and system flexibility still need to be improved, especially when combined with other power generation technologies. How to effectively integrate and optimize resources remains an urgent problem to be solved.

[0004] Therefore, research combining molten salt energy storage technology with supercritical carbon dioxide cycle power generation technology has gradually attracted attention, aiming to improve energy utilization efficiency, reduce energy waste, and provide new solutions for the flexibility and sustainability of modern power systems. Summary of the Invention

[0005] In view of the problems existing in the prior art, the present invention is proposed.

[0006] Therefore, the first objective of this invention is to provide a molten salt coupled supercritical carbon dioxide power generation and heating system, so that the molten salt can provide heat to the carbon dioxide power generation cycle and heating / steam system in a cascade manner.

[0007] To solve the above-mentioned technical problems, the present invention provides the following technical solution: a molten salt coupled supercritical carbon dioxide power generation and heating system, comprising: a molten salt energy storage module, including a high-temperature molten salt tank, a low-temperature molten salt tank, a molten salt-carbon dioxide heat exchanger, a molten salt-water heat exchanger, and an electric heater, wherein the molten salt-carbon dioxide heat exchanger is used in series with the molten salt-water heat exchanger; a heating / steam module, including a heating / steam return water pipe and a steam supply header, wherein both the heating / steam return water pipe and the steam supply header are connected to the molten salt-water heat exchanger, and the other end of the steam supply header is connected to the steam supply header; and a carbon dioxide power generation circulation module connected to the molten salt-carbon dioxide heat exchanger.

[0008] As a preferred embodiment of the molten salt coupled supercritical carbon dioxide power generation and heating system of the present invention, wherein: a bypass pipe is led out before the molten salt-carbon dioxide heat exchanger, and the bypass pipe is led before the molten salt-water heat exchanger; a first regulating valve and a first shut-off valve are installed on the bypass pipe.

[0009] As a preferred embodiment of the molten salt coupled supercritical carbon dioxide power generation and heating system of the present invention, wherein: a first pipeline is led out from the low-temperature molten salt tank and connected to the molten salt-water heat exchanger; a second regulating valve and a second shut-off valve are installed on the first pipeline.

[0010] As a preferred embodiment of the molten salt coupled supercritical carbon dioxide power generation and heating system of the present invention, wherein: a third regulating valve and a third shut-off valve are installed on the heating / steam return water pipe; and a fourth regulating valve and a fourth shut-off valve are installed on the steam supply main pipe.

[0011] As a preferred embodiment of the molten salt coupled supercritical carbon dioxide power generation and heating system of the present invention, the heating / steam module further includes a heat network heat exchanger, which is connected to the molten salt-water heat exchanger through a pipeline to form a loop.

[0012] As a preferred embodiment of the molten salt coupled supercritical carbon dioxide power generation and heating system of the present invention, the molten salt energy storage module uses solar salt (60%wt NaNO3+40%wt KNO3) as molten salt, and the temperature range of the molten salt is 270℃~560℃.

[0013] As a preferred embodiment of the molten salt coupled supercritical carbon dioxide power generation and heating system of the present invention, wherein: the high-temperature molten salt tank is made of a metal material that can withstand temperatures of 560°C and above, the low-temperature molten salt tank is made of a metal material that can withstand temperatures of 270°C and above, and the molten salt-water heat exchanger has a higher temperature and is made of a metal material that can withstand temperatures of 350°C and above.

[0014] As a preferred embodiment of the molten salt coupled supercritical carbon dioxide power generation and heating system of the present invention, the steam heated by the molten salt-water heat exchanger can be used as a heat source for the heat network heat exchanger, and can be recycled after releasing heat in the heat network heat exchanger.

[0015] The second objective of this invention is to propose a method for operating a power generation and heating system using molten salt coupled with supercritical carbon dioxide, comprising the following steps: during periods of low electricity prices, low-temperature molten salt is electrically heated and stored in a high-temperature molten salt tank; when power generation is required, the molten salt provides heat for the supercritical carbon dioxide power generation cycle through a molten salt-carbon dioxide heat exchanger; when heating is required, if the amount of molten salt in the molten salt-carbon dioxide heat exchanger is sufficient, the molten salt from the outlet of the molten salt-carbon dioxide heat exchanger is directly used in the steam / heating module; when the amount of molten salt in the molten salt-carbon dioxide heat exchanger is insufficient, a portion of the high-temperature molten salt is directly mixed through a bypass pipe and a portion of the low-temperature molten salt is mixed through a first pipe to the required temperature before entering the molten salt-water heat exchanger for use in the heating / steaming module; when only steam is required, all the required molten salt is mixed through a bypass pipe with a portion of the low-temperature molten salt passing through the first pipe to the required temperature before being sent to the molten salt-water heat exchanger to provide heat to the heating / steaming module; when there is no industrial steam supply, the steam heated by the molten salt-water heat exchanger can be used as a heat source for the heating network heat exchanger, and the heating network can be recycled.

[0016] As a preferred embodiment of the working method of the molten salt coupled supercritical carbon dioxide power generation and heating system of the present invention, the molten salt is sent to the molten salt-water heat exchanger through a bypass pipeline, and the temperature is controlled by a regulating valve and mixed with the low-temperature molten salt from the first pipeline to meet the heating demand under different operating conditions.

[0017] The beneficial effects of this invention are as follows: This invention proposes a novel circulating system and operating method for power generation and heating using molten salt coupled with supercritical carbon dioxide. Through bypass pipes, series heat exchangers, etc., molten salt can provide heat to the carbon dioxide power generation cycle and the heating / steam system in stages, improving the energy utilization efficiency of the entire system, reducing the overall amount of molten salt used, saving costs, and allowing the two heat-using systems to operate independently, ensuring the system's operational flexibility and achieving thermoelectric decoupling. Through molten salt mixing after the low-temperature molten salt tank, the inlet temperature of the molten salt-water heat exchanger can be guaranteed when the power generation demand is low and the steam supply demand is high. This system has multiple functions such as energy storage, power generation, and heating / steam supply, and can provide a new approach for the replacement and renovation of old coal-fired power units. Attached Figure Description

[0018] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort. Wherein:

[0019] Figure 1 This is a schematic diagram of a power generation and heating system using molten salt coupled with supercritical carbon dioxide.

[0020] Figure 2 A flowchart illustrating the working method of a power generation and heating system coupled with molten salt and supercritical carbon dioxide.

[0021] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, the specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings.

[0022] Many specific details are set forth in the following description in order to provide a full understanding of the invention. However, the invention may also be practiced in other ways different from those described herein, and those skilled in the art can make similar extensions without departing from the spirit of the invention. Therefore, the invention is not limited to the specific embodiments disclosed below.

[0023] Secondly, the term "an embodiment" or "embodiment" as used herein refers to a specific feature, structure, or characteristic that may be included in at least one implementation of the present invention. The phrase "in one embodiment" appearing in different places throughout this specification does not necessarily refer to the same embodiment, nor is it an embodiment that is mutually exclusive, either alone or selectively, with other embodiments.

[0024] Example 1

[0025] Reference Figure 1 and Figure 2 This is the first embodiment of the present invention. This embodiment provides a molten salt coupled supercritical carbon dioxide power generation and heating system. The molten salt coupled supercritical carbon dioxide power generation and heating system includes a molten salt energy storage module 100, including a high-temperature molten salt tank 101, a low-temperature molten salt tank 102, a molten salt-carbon dioxide heat exchanger 103, a molten salt-water heat exchanger 104, and an electric heater 105. The molten salt-carbon dioxide heat exchanger 103 and the molten salt-water heat exchanger 104 are used in series. A heating / steam module 200 includes a heating / steam return water pipe 201 and a steam supply header 202. Both the heating / steam return water pipe 201 and the steam supply header 202 are connected to the molten salt-water heat exchanger 104, and the other end of the steam supply header 202 is connected to the steam supply header. A carbon dioxide power generation circulation module 300 is connected to the molten salt-carbon dioxide heat exchanger 103.

[0026] The molten salt energy storage module 100 is configured in series with the molten salt-carbon dioxide heat exchanger 103 and the molten salt-water heat exchanger 104 to form a cascade utilization of heat. The carbon dioxide power generation cycle module 300 is connected to the molten salt-carbon dioxide heat exchanger 103 to receive heat provided by the molten salt and drive the supercritical carbon dioxide power generation cycle. The return water flows from the heating / steam return water pipe 201 through the molten salt-water heat exchanger 104 to absorb heat and increase its temperature, and then enters the steam supply header from the steam supply header 202.

[0027] In operation, the molten salt energy storage module 100 stores molten salt heated by an electric heater. When power generation is required, the molten salt transfers heat to the supercritical carbon dioxide power generation cycle module 300 via the molten salt-carbon dioxide heat exchanger 103, thereby generating electricity. Simultaneously, the molten salt-water heat exchanger 104 provides heat to the heating / steam module 200 through heat transfer to meet heating needs.

[0028] Example 2

[0029] Reference Figure 1 and Figure 2 This is the second embodiment of the present invention, which is based on the previous embodiment.

[0030] Specifically, a bypass pipe 103a is led out before the molten salt-carbon dioxide heat exchanger 103, and the bypass pipe 103a is led to the molten salt-water heat exchanger 104; the bypass pipe 103a is equipped with a first regulating valve 103b and a first shut-off valve 103c.

[0031] A bypass pipe 103a is provided before the molten salt-carbon dioxide heat exchanger 103, so that the molten salt can enter the molten salt-water heat exchanger 104 directly without passing through the molten salt-carbon dioxide heat exchanger 103. A first regulating valve 103b and a first shut-off valve 103c are installed on the bypass pipe 103a to regulate the molten salt flow rate and control the molten salt temperature.

[0032] Specifically, a first pipe 102a is led out from the low-temperature molten salt tank 102 and connected to the molten salt-water heat exchanger 104; a second regulating valve 102b and a second shut-off valve 102c are installed on the first pipe 102a.

[0033] The molten salt in the low-temperature molten salt tank 102 can be mixed with the molten salt after the molten salt-carbon dioxide heat exchanger through the first pipe 102a, thereby regulating the temperature of the molten salt entering the molten salt-water heat exchanger. The second regulating valve 102b and the second shut-off valve 102c are used to further control the flow rate of the molten salt and regulate its temperature to ensure that it meets the system requirements.

[0034] Specifically, the heating / steam return water pipe 201 is equipped with a third regulating valve 201a and a third shut-off valve 201b; and the steam supply main pipe 202 is equipped with a fourth regulating valve 202a and a fourth shut-off valve 202b.

[0035] Specifically, the heating / steam module 200 also includes a heat network heat exchanger 203, which is connected to the molten salt-water heat exchanger 104 through a pipeline to form a loop;

[0036] The heat exchanger 203 is connected to the molten salt-water heat exchanger 104 to form a loop, using the steam heated by the molten salt-water heat exchanger to provide a heat source for the heating network. Through this loop, the heating network can circulate the heat provided by the molten salt, improving energy utilization efficiency.

[0037] Specifically, the molten salt energy storage module 100 uses solar salt with 60%wt NaNO3 + 40%wt KNO3 as molten salt, and the temperature range of the molten salt is 270℃~560℃;

[0038] The molten salt energy storage module uses solar salt as the molten salt, which has a high heat capacity. The temperature of the high-temperature molten salt tank is about 560℃, and the temperature of the low-temperature molten salt tank is about 270℃. The temperature of the molten salt entering the molten salt-water heat exchanger can be adjusted between 350℃ and 430℃, depending on the power of the molten salt-water heat exchanger.

[0039] Specifically, the high-temperature molten salt tank 101 is made of metal material that can withstand temperatures of 560°C and above, while the low-temperature molten salt tank 102 and the molten salt-water heat exchanger 104 are made of metal material that can withstand temperatures of 350°C and above.

[0040] Specifically, the steam heated by the molten salt-water heat exchanger 104 can be used as a heat source for the heat exchanger 203. After releasing heat in the heat exchanger 203, it can be recycled to further improve the energy utilization rate of the system.

[0041] When heating or steam is needed, molten salt provides heat through the molten salt-water heat exchanger, and the flow rate and temperature are precisely controlled by the regulating valve. When the system's power generation demand is low, molten salt enters the molten salt-water heat exchanger directly through the bypass pipe, and the temperature is regulated by the low-temperature molten salt in the first pipe to avoid wasting heat, while the heat is provided to the heating network system.

[0042] Example 3

[0043] Reference Figure 1 and Figure 2 This is the third embodiment of the present invention, which provides a method for operating a molten salt coupled supercritical carbon dioxide power generation and heating system, including the following steps:

[0044] During periods of low electricity prices, low-temperature molten salt is heated electrically and stored in a high-temperature molten salt tank;

[0045] When power generation is needed, molten salt provides heat to the supercritical carbon dioxide power generation cycle module through a molten salt-carbon dioxide heat exchanger.

[0046] When heating is required, if there is enough molten salt in the molten salt-carbon dioxide heat exchanger, the molten salt from the outlet of the molten salt-carbon dioxide heat exchanger is directly used in the steam / heating module. If there is insufficient molten salt in the molten salt-carbon dioxide heat exchanger, some high-temperature molten salt is directly mixed with some low-temperature molten salt through the bypass pipe and then mixed with the first pipe to the required temperature before entering the molten salt-water heat exchanger for use in the heating / steaming module.

[0047] When only steam supply is required, all the required molten salt is mixed with a portion of the low-temperature molten salt passing through the first pipe through the bypass pipe to the required temperature and then sent to the molten salt-water heat exchanger to provide heat to the heating / steam module.

[0048] When there is no industrial steam supply, the steam heated by the molten salt-water heat exchanger can be used as a heat source for the heating network heat exchanger, and the heating network can recycle it.

[0049] The system operates as follows: during energy storage, low-temperature molten salt is heated by low-priced electricity and then stored in a high-temperature molten salt tank. During heat release, the system utilizes carbon dioxide to generate electricity through a molten salt-carbon dioxide heat exchanger and heat from a molten salt-water heat exchanger.

[0050] When the system's power generation demand is low and steam supply demand is high, the molten salt that meets the power generation capacity is used for carbon dioxide power generation cycle through the molten salt-carbon dioxide heat exchanger. Part of the molten salt is sent directly to the molten salt-water heat exchanger through the molten salt-carbon dioxide heat exchanger bypass pipeline and mixed with the molten salt after the low temperature molten salt tank. The molten salt is then used by the molten salt-water heat exchanger to the required temperature for the heating / steam module. Finally, the low temperature molten salt is returned to the low temperature molten salt tank for cycle operation.

[0051] When the system only requires steam, all the required molten salt is sent directly to the molten salt-water heat exchanger via the molten salt-carbon dioxide heat exchanger bypass pipeline. It is then mixed with the molten salt after the cryogenic molten salt tank and heated to the required temperature by the molten salt-water heat exchanger. The molten salt is then used by the heating / steam module via the molten salt-water heat exchanger. Finally, the cryogenic molten salt is returned to the cryogenic molten salt tank for recycling. The heating / steam module can heat the return water to the corresponding steam parameters via the molten salt-water heat exchanger before supplying it to the steam supply header.

[0052] Specifically, when molten salt is sent to the molten salt-water heat exchanger through the bypass pipeline, the temperature is controlled by the first regulating valve, and the low-temperature molten salt in the first pipeline is controlled in conjunction with the second regulating valve to meet the heating demand under different operating conditions.

[0053] The core of this working method is to flexibly adjust the flow and temperature of the molten salt according to demand, ensuring that the system can efficiently provide the required power generation or heating capacity under different operating conditions. By storing the thermal energy of the molten salt through electric heating and then adjusting the flow rate through a bypass pipeline as needed, both efficient heat utilization and strong system flexibility are ensured.

[0054] It should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention, and all such modifications or substitutions should be covered within the scope of the claims of the present invention.

Claims

1. A molten salt coupled supercritical carbon dioxide power generation and heating system, characterized in that: include, The molten salt energy storage module (100) includes a high-temperature molten salt tank (101), a low-temperature molten salt tank (102), a molten salt-carbon dioxide heat exchanger (103), a molten salt-water heat exchanger (104), and an electric heater (105). The molten salt-carbon dioxide heat exchanger (103) and the molten salt-water heat exchanger (104) are used in series. The heating / steam module (200) includes a heating / steam return water pipe (201) and a steam supply main pipe (202). Both the heating / steam return water pipe (201) and the steam supply main pipe (202) are connected to the molten salt-water heat exchanger (104). The other end of the steam supply main pipe (202) is connected to the steam supply main pipe. A carbon dioxide power generation cycle module (300) is connected to the molten salt-carbon dioxide heat exchanger (103); A bypass pipe (103a) is led out before the molten salt-carbon dioxide heat exchanger (103), and the bypass pipe (103a) is led out before the molten salt-water heat exchanger (104); The bypass pipe (103a) is equipped with a first regulating valve (103b) and a first shut-off valve (103c); The first pipe (102a) is led out from the low-temperature molten salt tank (102) and connected to the front of the molten salt-water heat exchanger (104); The first pipeline (102a) is equipped with a second regulating valve (102b) and a second shut-off valve (102c).

2. The molten salt coupled supercritical carbon dioxide power generation and heating system as described in claim 1, characterized in that: The heating / steam return water pipe (201) is equipped with a third regulating valve (201a) and a third shut-off valve (201b). The steam supply header (202) is equipped with a fourth regulating valve (202a) and a fourth shut-off valve (202b).

3. The molten salt coupled supercritical carbon dioxide power generation and heating system as described in claim 1, characterized in that: The heating / steam module (200) also includes a heat network heat exchanger (203), which is connected to the molten salt-water heat exchanger (104) through a pipeline to form a loop.

4. The molten salt coupled supercritical carbon dioxide power generation and heating system as described in claim 1, characterized in that: The molten salt energy storage module (100) uses solar salt (60%wt NaNO3 + 40%wt KNO3) as molten salt, and the temperature range of the molten salt is 270℃~560℃.

5. The molten salt coupled supercritical carbon dioxide power generation and heating system as described in claim 1, characterized in that: The high-temperature molten salt tank (101) is made of metal material that can withstand temperatures of 560°C and above, and the low-temperature molten salt tank (102) and the molten salt-water heat exchanger (104) are made of metal material that can withstand temperatures of 350°C and above.

6. The molten salt coupled supercritical carbon dioxide power generation and heating system as described in claim 1, characterized in that: The steam heated by the molten salt-water heat exchanger (104) can be used as a heat source for the heat exchanger (203), and can be recycled after releasing heat in the heat exchanger (203).

7. A method for operating a power generation and heating system coupled with molten salt and supercritical carbon dioxide, characterized in that: Includes the following steps: During periods of low electricity prices, low-temperature molten salt is heated electrically and stored in a high-temperature molten salt tank; When power generation is needed, molten salt provides heat to the supercritical carbon dioxide power generation cycle module through a molten salt-carbon dioxide heat exchanger. When heating is required, if there is enough molten salt in the molten salt-carbon dioxide heat exchanger, the molten salt from the outlet of the molten salt-carbon dioxide heat exchanger is directly used in the steam / heating module. If there is insufficient molten salt in the molten salt-carbon dioxide heat exchanger, some high-temperature molten salt is directly mixed with some low-temperature molten salt through the bypass pipe and then mixed with the first pipe to the required temperature before entering the molten salt-water heat exchanger for use in the heating / steaming module. When only steam supply is required, all the required molten salt is mixed with a portion of the low-temperature molten salt passing through the first pipe through the bypass pipe to the required temperature and then sent to the molten salt-water heat exchanger to provide heat to the heating / steam module. When there is no industrial steam supply, the steam heated by the molten salt-water heat exchanger can be used as a heat source for the heating network heat exchanger, and the heating network can recycle it.

8. The operating method of the molten salt coupled supercritical carbon dioxide power generation and heating system as described in claim 7, characterized in that: When the molten salt is sent to the molten salt-water heat exchanger through a bypass pipeline, the temperature is controlled by the first regulating valve to meet the heating demand under different operating conditions.

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