Molten salt coupling supercritical carbon dioxide power generation and heat supply system and working method

Abstract

The invention relates to the technical field of novel power circulation, in particular to a power generation and heat supply system with molten salt coupled with supercritical carbon dioxide and a working method of the power generation and heat supply system with the molten salt coupled with the supercritical carbon dioxide. 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, the heat / steam supply module comprises a heat / steam supply water return pipe and a steam supply main pipe; and a carbon dioxide power generation circulation module. By means of the bypass pipeline, the series heat exchanger and the like, molten salt can provide heat for carbon dioxide power generation circulation and a heat / steam supply system in a cascade mode, the energy utilization efficiency of the whole system is improved, the overall consumption of the molten salt is reduced, cost is saved, the two heat utilization systems can operate independently, and the operation flexibility of the systems is guaranteed; thermoelectricity decoupling is realized; the system has multiple functions of energy storage, power generation, heat / steam supply and the like, and a new thought can be provided for replacement and transformation of an old coal power unit.

Description

Technical Field

[0001] The present invention relates to the technical field of novel power cycles, and in particular to a molten salt coupled supercritical carbon dioxide power generation and heating system and a working method. Background Art

[0002] In recent years, with the transformation of the global energy structure and the continuous improvement of environmental protection requirements, the research and application of clean energy technology has gradually become mainstream. In particular, supercritical carbon dioxide (sCO2) cycle power generation technology has become an important development direction of the new generation of power generation technology due to its high thermal efficiency and low emissions. By using supercritical carbon dioxide as a working fluid, this technology can achieve higher thermal efficiency at lower operating temperatures and pressures than traditional steam cycle systems, and reduces the demand for cooling water, which has significant energy utilization advantages. However, the current supercritical carbon dioxide cycle technology still faces challenges in system design, equipment high temperature resistance, and heat source stability in practical applications.

[0003] At the same time, molten salt energy storage technology, as a mature high-temperature energy storage technology, has been widely used in the field of solar thermal power generation. Molten salt has a high thermal capacity and a long heat storage cycle, which can effectively solve the intermittent and volatility problems of renewable energy. However, existing molten salt energy storage systems are mostly used for solar thermal power generation, and their application in the transformation of traditional coal-fired power plants and coupling with other thermal power systems have 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 on 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 above problems existing in the prior art, the present invention is proposed.

[0006] Therefore, the first object of the present invention is to provide a molten salt coupled supercritical carbon dioxide power generation and heating system, so that the molten salt can provide heat for the carbon dioxide power generation cycle and the heating / steam system in a step-by-step manner.

[0007] To solve the above technical problems, the present invention provides the following technical solutions: 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 heat / steam module, including a heat / steam return pipe and a steam supply main pipe, wherein the heat / steam return pipe and the steam supply main pipe are both connected to the molten salt-water heat exchanger, and the other end of the steam supply main pipe is connected to the steam supply main pipe; a carbon dioxide power generation circulation module, connected to the molten salt-carbon dioxide heat exchanger.

[0008] As a preferred solution of the molten salt coupled supercritical carbon dioxide power generation and heating system described in the present invention, a bypass pipe is led out in front of the molten salt-carbon dioxide heat exchanger, and the bypass pipe is led in front of the molten salt-water heat exchanger; a first regulating valve and a first stop valve are installed on the bypass pipe.

[0009] As a preferred solution 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 front of the molten salt-water heat exchanger; a second regulating valve and a second stop valve are installed on the first pipeline.

[0010] As a preferred solution of the molten salt coupled supercritical carbon dioxide power generation and heating system of the present invention, wherein: the heating / steam return pipe is equipped with a third regulating valve and a third stop valve; the steam supply main pipe is equipped with a fourth regulating valve and a fourth stop valve.

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

[0012] As a preferred solution 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 solution of the molten salt coupled supercritical carbon dioxide power generation and heating system described in the present invention, the high-temperature molten salt tank adopts a metal material that can withstand temperatures of 560°C and above, the low-temperature molten salt tank adopts a metal material that can withstand temperatures of 270°C and above, and the molten salt-water heat exchanger has a higher temperature and adopts a metal material that can withstand temperatures of 350°C and above.

[0014] As a preferred solution 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 recycled after releasing heat in the heat network heat exchanger.

[0015] The second object of the present invention is to propose a working method of a molten salt coupled supercritical carbon dioxide power generation and heating system, comprising the following steps: in a period 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 heat supply is required, when the amount of molten salt in the molten salt-carbon dioxide heat exchanger is sufficient, the molten salt at the outlet of the molten salt-carbon dioxide heat exchanger is directly used to enter the steam supply / heat module for use; when the amount of molten salt in the molten salt-carbon dioxide heat exchanger is insufficient, part of the high-temperature molten salt is directly passed through a bypass pipe, and part of the low-temperature molten salt is mixed through a first pipe to the required temperature and then enters the molten salt-water heat exchanger for the heat supply / steam module; when there is only a demand for steam supply, all the required molten salt is mixed with part of the low-temperature molten salt passing through the first pipe through a bypass pipe to the required temperature and then sent to the molten salt-water heat exchanger to provide heat to the heat supply / 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 heat network heat exchanger, and the heat network is recycled.

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

[0017] The beneficial effects of the present invention are as follows: the present invention proposes a new circulation system and working method for power generation and heat supply of molten salt coupled with supercritical carbon dioxide. By means of bypass pipes, series heat exchangers and the like, molten salt can provide heat for the carbon dioxide power generation cycle and the heat / steam system in a step-by-step manner, thereby improving the energy utilization efficiency of the entire system, reducing the overall usage of molten salt, and saving costs. The two heat systems can also be operated independently to ensure the operational flexibility of the system and achieve thermal and electrical decoupling. By mixing the molten salt 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 large. The system of this scheme has multiple functions such as energy storage, power generation, and heat / steam supply, and can provide new ideas for the replacement and transformation of old coal-fired power units. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following briefly introduces the drawings required for describing the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work. Among them:

[0019] Figure 1 Schematic diagram of the molten salt coupled supercritical carbon dioxide power generation and heating system.

[0020] Figure 2 This is a flow chart of the working method of the molten salt coupled supercritical carbon dioxide power generation and heating system.

[0021] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, the specific embodiments of the present invention are described in detail below in conjunction with the accompanying drawings.

[0022] In the following description, many specific details are set forth to facilitate a full understanding of the present invention, but the present invention may also be implemented in other ways different from those described herein, and those skilled in the art may make similar generalizations without violating the connotation of the present invention. Therefore, the present invention is not limited to the specific embodiments disclosed below.

[0023] Secondly, the term "one 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 term "in one embodiment" that appears in different places in this specification does not necessarily refer to the same embodiment, nor is it an embodiment that is mutually exclusive with other embodiments, either individually or selectively.

[0024] Example 1

[0025] Reference Figure 1 and Figure 2 , which is the first embodiment of the present invention, and the 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 comprises a molten salt energy storage module 100, comprising 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 heat / steam module 200, comprising a heat / steam return pipe 201 and a steam supply main pipe 202, the heat / steam return pipe 201 and the steam supply main pipe 202 are both connected to the molten salt-water heat exchanger 104, and the other end of the steam supply main pipe 202 is connected to the steam supply main pipe; a carbon dioxide power generation circulation module 300, connected to the molten salt-carbon dioxide heat exchanger 103;

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

[0027] When in use, 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 through the molten salt-carbon dioxide heat exchanger 103, thereby generating electricity. At the same time, the molten salt-water heat exchanger 104 provides heat to the heat / steam module 200 through heat transfer to meet the heating demand.

[0028] Example 2

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

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

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

[0032] Specifically, a 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; a second regulating valve 102b and a second stop 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 pipeline 102a, so as to adjust the temperature of the molten salt entering the molten salt-water heat exchanger. The second regulating valve 102b and the second stop valve 102c are used to further control the flow rate of the molten salt and adjust its temperature to ensure that it adapts to the system requirements.

[0034] Specifically, the heat supply / steam return pipe 201 is equipped with a third regulating valve 201a and a third stop valve 201b; the steam supply main pipe 202 is equipped with a fourth regulating valve 202a and a fourth stop valve 202b.

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

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

[0037] Specifically, 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°C to 560°C;

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

[0039] Specifically, the high-temperature molten salt tank 101 is made of metal materials 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 materials 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 network heat exchanger 203 and recycled after releasing heat in the heat network heat exchanger 203, thereby further improving the energy utilization rate of the system.

[0041] When heat or steam supply is needed, molten salt provides heat through the molten salt-water heat exchanger, and the flow and temperature are precisely controlled by a regulating valve; when the system's power generation demand is low, the molten salt directly enters the molten salt-water heat exchanger through a bypass pipe, and the temperature is adjusted by mixing with the low-temperature molten salt in the first pipe to avoid wasting heat, while providing heat to the heat network system.

[0042] Example 3

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

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

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

[0046] When heat supply is needed, when the amount of molten salt in the molten salt-carbon dioxide heat exchanger is sufficient, the molten salt at the outlet of the molten salt-carbon dioxide heat exchanger is directly used to enter the steam / heat supply module for use; when the amount of molten salt in the molten salt-carbon dioxide heat exchanger is insufficient, part of the high-temperature molten salt is directly passed through the bypass pipe, and part of the low-temperature molten salt is passed through the first pipe and mixed to the required temperature before entering the molten salt-water heat exchanger for use in the heat / steam module;

[0047] When there is only a demand for steam supply, all the required molten salt is mixed with part of the low-temperature molten salt passing through the first pipeline through the bypass pipeline to the required temperature and then sent to the molten salt-water heat exchanger to provide heat to the heat / 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 heat network heat exchanger and recycled by the heating network.

[0049] The normal operation of the system is: when storing energy, low-temperature molten salt is heated by electricity at a low electricity price and then stored in a high-temperature molten salt tank. When releasing heat, carbon dioxide is used to generate electricity through a molten salt-carbon dioxide heat exchanger and to provide heat through a molten salt-water heat exchanger;

[0050] When the system power generation demand is low and the steam supply demand is large, 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 directly sent to the front of the molten salt-water heat exchanger through the molten salt-carbon dioxide heat exchange bypass pipeline, and mixed with the molten salt after the low-temperature molten salt tank to the required temperature of the molten salt-water heat exchanger. It is used for the heat / steam module through the molten salt-water heat exchanger, and finally the low-temperature molten salt returns to the low-temperature molten salt tank for circulation.

[0051] When the system only has a steam supply demand, all the required molten salt is directly sent to the front of the molten salt-water heat exchanger through the molten salt-carbon dioxide heat exchange bypass pipeline, and mixed with the molten salt after the low-temperature molten salt tank to the required temperature of the molten salt-water heat exchanger. It is used for the heat / steam module through the molten salt-water heat exchanger, and finally the low-temperature molten salt returns to the low-temperature molten salt tank for circulation. The heat / steam module can heat the return water to the corresponding steam supply parameters through the molten salt-water heat exchanger and then supply it to the steam supply main pipe.

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

[0053] The core of this working method is to flexibly adjust the flow and temperature of molten salt according to demand, ensuring that the system can efficiently provide the required power generation or heating capacity under different working conditions. By storing the thermal energy of molten salt through electric heating and then adjusting the flow through the bypass pipeline according to demand, it not only ensures the efficient use of heat, but also makes the system more flexible.

[0054] It should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solutions of the present invention may be modified or replaced by equivalents without departing from the spirit and scope of the technical solutions of the present invention, which should all be included in 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, A molten salt energy storage module (100) comprises 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), wherein the molten salt-carbon dioxide heat exchanger (103) and the molten salt-water heat exchanger (104) are used in series; A heat / steam module (200) comprises a heat / steam return pipe (201) and a steam supply main pipe (202), wherein the heat / steam return pipe (201) and the steam supply main pipe (202) are both connected to the molten salt-water heat exchanger (104), and the other end of the steam supply main pipe (202) is connected to the steam supply main pipe; The carbon dioxide power generation circulation module (300) is connected to the molten salt-carbon dioxide heat exchanger (103).

2. The molten salt coupled supercritical carbon dioxide power generation and heating system according to claim 1, characterized in that: A bypass pipe (103a) is led out from the front of the molten salt-carbon dioxide heat exchanger (103), and the bypass pipe (103a) is led to the front of the molten salt-water heat exchanger (104); The bypass pipeline (103a) is equipped with a first regulating valve (103b) and a first stop valve (103c).

3. The molten salt coupled supercritical carbon dioxide power generation and heating system according to claim 2, characterized in that: A 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 stop valve (102c).

4. The molten salt coupled supercritical carbon dioxide power generation and heating system according to claim 3, characterized in that: The heat supply / steam return pipe (201) is provided with a third regulating valve (201a) and a third stop valve (201b); The steam supply main pipe (202) is provided with a fourth regulating valve (202a) and a fourth stop valve (202b).

5. The molten salt coupled supercritical carbon dioxide power generation and heating system according to claim 4, characterized in that: The heat supply / steam module (200) further comprises a heat network heat exchanger (203), and the heat network heat exchanger (203) is connected to the molten salt-water heat exchanger (104) via a pipeline to form a loop.

6. The molten salt coupled supercritical carbon dioxide power generation and heating system according to claim 5, 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°C to 560°C.

7. The molten salt coupled supercritical carbon dioxide power generation and heating system according to claim 6, characterized in that: The high-temperature molten salt tank (101) is made of a 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 a metal material that can withstand temperatures of 350°C and above.

8. The molten salt coupled supercritical carbon dioxide power generation and heating system according to claim 7, characterized in that: The steam heated by the molten salt-water heat exchanger (104) can be used as a heat source for the heat network heat exchanger (203) and can be recycled after releasing heat in the heat network heat exchanger (203).

9. A method for operating a molten salt coupled supercritical carbon dioxide power generation and heating system, characterized in that: The following steps are involved: During periods of low electricity prices, low-temperature molten salt is heated electrically and stored in high-temperature molten salt tanks; When power generation is needed, the molten salt provides heat to the supercritical carbon dioxide power generation cycle module through the molten salt-carbon dioxide heat exchanger; When heat supply is needed, when the amount of molten salt in the molten salt-carbon dioxide heat exchanger is sufficient, the molten salt at the outlet of the molten salt-carbon dioxide heat exchanger is directly used to enter the steam / heat supply module for use; when the amount of molten salt in the molten salt-carbon dioxide heat exchanger is insufficient, part of the high-temperature molten salt is directly passed through the bypass pipe, and part of the low-temperature molten salt is passed through the first pipe and mixed to the required temperature before entering the molten salt-water heat exchanger for use in the heat / steam module; When there is only a demand for steam supply, all the required molten salt is mixed with part of the low-temperature molten salt passing through the first pipeline through the bypass pipeline to the required temperature and then sent to the molten salt-water heat exchanger to provide heat to the heat / 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 heat network heat exchanger and recycled by the heating network.

10. The working method of the molten salt coupled supercritical carbon dioxide power generation and heating system according to claim 9, characterized in that: When the molten salt is sent to the molten salt-water heat exchanger through the bypass pipeline, the temperature is controlled by the first regulating valve to meet the heating demand under different working conditions.

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