High-temperature flue gas waste heat gradient utilization power generation system and method

Abstract

The invention provides a high-temperature flue gas waste heat gradient utilization power generation system and method. The system comprises a first heat storage system, a steam turbine power generation system, a second heat storage system, an organic Rankine cycle power generation system and a flue gas purification system. High-temperature flue gas is subjected to heat cascade storage and recovery through the two heat storage systems in sequence, the steam turbine power generation system and the organic Rankine cycle power generation system are coupled, and finally stable and clean electric power is output. In accordance with the core idea of energy gradient utilization and energy potential matching, gradient and full utilization of high-temperature flue gas waste heat can be achieved through gradient and stable heat storage of the two heat storage media, and therefore loss in the high-temperature flue gas waste heat recycling process and energy grade loss are reduced.

Description

Technical Field

[0001] The present invention relates to the technical field of high-temperature industrial flue gas waste heat utilization, and in particular to a high-temperature flue gas waste heat cascade utilization power generation system and method. Background Art

[0002] The utilization of waste heat from high-temperature industrial flue gas is of great significance to modern industrial production. This utilization not only helps to improve energy utilization efficiency, reduce energy consumption, and thus reduce production costs, but also significantly reduces the impact of industrial emissions on the environment. By recycling and utilizing waste heat from flue gas, companies can contribute to their own sustainable development and environmental protection, and achieve a win-win situation in terms of economic and environmental benefits. This initiative is in line with the current global trend of energy conservation, emission reduction, and green development, and is a key step in promoting the transformation of the industrial sector towards a more environmentally friendly and efficient direction.

[0003] However, the current high-temperature industrial flue gas waste heat utilization technology still has shortcomings such as the failure to recover the waste heat from medium and low-temperature flue gas, insufficient waste heat recovery, large exergy loss in waste heat utilization, and unstable and volatile waste heat output due to the discontinuity and instability of flue gas generation. Therefore, how to improve the stability and sufficiency of high-temperature industrial flue gas waste heat utilization and reduce the exergy loss and energy grade loss in the waste heat utilization process is the key to promoting the development of high-temperature industrial flue gas waste heat utilization technology. Summary of the invention

[0004] The purpose of the present invention is to overcome the above-mentioned shortcomings and provide a high-temperature flue gas waste heat cascade utilization power generation system and method. Compared with the traditional high-temperature flue gas waste heat utilization system, the present invention couples two heat storage media with stepped operating temperatures for dual heat storage, and has a wide range of applications. It can be applied to common high-temperature industrial flue gas source enterprises such as steel smelting, cement production, and coal-fired power generation. By utilizing the advantages of heat storage stability, flexibility, and fast response time of the two heat storage systems, it can overcome the shortcomings of large heat grade loss, discontinuous and insufficient waste heat recovery in the conventional flue gas waste heat recovery process, and realize stable, stepped storage and utilization of high-temperature industrial flue gas, which is suitable for large-scale medium and high temperature flue gas waste heat utilization scenarios.

[0005] The present invention provides a high-temperature flue gas waste heat cascade utilization power generation system, comprising a first heat storage system, a steam turbine power generation system, a second heat storage system, an organic Rankine cycle power generation system and a flue gas purification system; The first heat storage system is connected to high-temperature flue gas, the steam turbine power generation system and the second heat storage system respectively, so that the high-temperature flue gas exchanges heat with the first heat storage system to obtain medium- and low-temperature flue gas, and then the first heat storage system exchanges heat with the steam turbine power generation system to output electricity; the second heat storage system is connected to the organic Rankine cycle power generation system and the flue gas purification system respectively, so that the medium- and low-temperature flue gas exchanges heat with the second heat storage system to obtain low-temperature flue gas, and then the second heat storage system exchanges heat with the organic Rankine cycle power generation system to output electricity, and then the low-temperature flue gas is discharged after being purified by the flue gas purification system; Wherein, the operating temperature of the first heat storage medium in the first heat storage system is greater than the operating temperature of the second heat storage medium in the second heat storage system.

[0006] Furthermore, the first heat storage system adopts a molten salt heat storage system.

[0007] Furthermore, the second heat storage system adopts a thermal oil heat storage system.

[0008] Furthermore, the molten salt heat storage system includes a high-temperature molten salt storage tank, a first heat exchanger and a low-temperature molten salt storage tank; the input end of the high-temperature molten salt storage tank is connected to the molten salt output end of the first heat exchanger, and the output end is connected to the steam turbine power generation system; the input end of the low-temperature molten salt storage tank is connected to the steam turbine power generation system, and the output end is connected to the molten salt input end of the first heat exchanger; the flue gas input end of the first heat exchanger is connected to the high-temperature flue gas, and the flue gas output end is connected to the thermal oil heat storage system.

[0009] Furthermore, the thermal oil heat storage system includes a high-temperature thermal oil storage tank, a second heat exchanger and a low-temperature thermal oil storage tank; the input end of the high-temperature thermal oil storage tank is connected to the thermal oil output end of the second heat exchanger, and the output end is connected to the organic Rankine cycle power generation system; the input end of the low-temperature thermal oil storage tank is connected to the organic Rankine cycle power generation system, and the output end is connected to the thermal oil input end of the second heat exchanger; the flue gas input end of the second heat exchanger is connected to the flue gas input end of the first heat exchanger, and the flue gas output end is connected to the flue gas purification system.

[0010] Further, the steam turbine power generation system includes a fourth heat exchanger and a steam turbine power generation device; the molten salt input end of the fourth heat exchanger is connected to the output end of the high-temperature molten salt storage tank, the molten salt output end is connected to the input end of the low-temperature molten salt storage tank, the water working medium input end is connected to liquid water, the steam output end is connected to the input end of the steam turbine power generation device, and the output end of the steam turbine power generation device is connected to the liquid water; Wherein, the water working medium input end of the fourth heat exchanger corresponds to the steam output end.

[0011] Furthermore, the organic Rankine cycle power generation system includes a third heat exchanger and an organic Rankine cycle power generation device; the heat transfer oil input end of the third heat exchanger is connected to the high-temperature heat transfer oil storage tank, the heat transfer output end is connected to the low-temperature heat transfer oil storage tank, the organic working fluid input end is connected to the liquid organic working fluid, the organic working fluid output end is connected to the input end of the organic Rankine cycle power generation device, and the output end of the organic Rankine cycle power generation device is connected to the liquid organic working fluid.

[0012] Furthermore, a first transport device is provided in the first heat storage system, which is used for transporting the first heat storage medium between various devices in the first heat storage system and between the first heat storage system and the steam turbine power generation system; The second heat storage system is provided with a second transport device for transporting the second heat storage medium between devices in the second heat storage system and between the second heat storage system and the organic Rankine cycle power generation system.

[0013] The present invention also provides a method for cascade utilization of high-temperature flue gas waste heat for power generation, which is applied to a high-temperature flue gas waste heat cascade utilization power generation system as described in any one of the above, and the method comprises: The high-temperature flue gas is input into the first heat storage system, and exchanges heat with the first low-temperature heat storage medium in the first heat storage system to obtain the first high-temperature heat storage medium and the medium- and low-temperature flue gas; The first high-temperature heat storage medium is transported from the first heat storage system to the steam turbine power generation system, and exchanges heat with the liquid water input into the steam turbine power generation system to obtain water vapor and the first low-temperature heat storage medium, so that the water vapor is used to generate electricity to output electricity, and forms the liquid water for the next heat exchange, and the first low-temperature heat storage medium is transported from the steam turbine power generation system to the first heat storage system for the next heat exchange; and the medium- and low-temperature flue gas is transported from the first heat storage system to the second heat storage system, and exchanges heat with the second low-temperature heat storage medium in the second heat storage system to obtain a second high-temperature heat storage medium and low-temperature flue gas; The second high-temperature heat storage medium is transported from the second heat storage system to the organic Rankine cycle power generation system, and exchanges heat with the liquid-phase organic working fluid input into the organic Rankine cycle power generation system to obtain a gaseous organic working fluid and the second low-temperature heat storage medium, so that the gaseous organic working fluid is used to generate electricity to output electricity, and forms the liquid-phase organic working fluid for the next heat exchange, and so that the second low-temperature heat storage medium is transported from the organic Rankine cycle power generation system to the second heat storage system for the next heat exchange; and the low-temperature flue gas is transported from the second heat storage system to the flue gas purification system, so that the low-temperature flue gas is discharged after being purified by the flue gas purification system.

[0014] Furthermore, when the first heat storage system adopts a molten salt heat storage system and the second heat storage system adopts a thermal oil heat storage system, the method specifically includes: The high-temperature flue gas is input into the first heat exchanger in the molten salt heat storage system, and exchanges heat with the low-temperature molten salt in the first heat exchanger to obtain high-temperature molten salt and the medium- and low-temperature flue gas; wherein the low-temperature molten salt is transported to the first heat exchanger from the low-temperature molten salt storage tank in the molten salt heat storage system; The high-temperature molten salt is transported by the first heat exchanger to the high-temperature molten salt storage tank in the molten salt heat storage system; and the medium- and low-temperature flue gas is transported by the first heat exchanger to the second heat exchanger in the thermal oil heat storage system; The high-temperature molten salt is transported from the high-temperature molten salt storage tank to the fourth heat exchanger in the steam turbine power generation system, and exchanges heat with the liquid water input into the fourth heat exchanger to obtain the water vapor and the low-temperature molten salt; and the medium-low temperature flue gas is heat-exchanged with the low-temperature heat transfer oil in the second heat exchanger to obtain high-temperature heat transfer oil and low-temperature flue gas; wherein the low-temperature heat transfer oil is transported from the low-temperature heat transfer oil storage tank in the heat transfer oil heat storage system to the second heat exchanger; The water vapor is transported by the fourth heat exchanger to the steam turbine power generation device in the steam turbine power generation system to drive the steam turbine power generation device to generate electricity to output electricity and form the liquid water for the next heat exchange. The low-temperature molten salt is transported by the fourth heat exchanger to the low-temperature molten salt storage tank for the next heat exchange. In addition, the high-temperature heat transfer oil is transported by the second heat exchanger to the high-temperature heat transfer oil storage tank in the heat transfer oil heat storage system. The low-temperature flue gas is transported by the second heat exchanger to the flue gas purification system. The high-temperature heat transfer oil is transported from the high-temperature heat transfer oil storage tank to the third heat exchanger in the organic Rankine cycle power generation system, and is heat-exchanged with the liquid-phase organic working fluid input into the third heat exchanger to obtain the gas-phase organic working fluid and the low-temperature heat transfer oil, and the low-temperature flue gas is purified by the flue gas purification system and then discharged; The gaseous organic working fluid is transported by the third heat exchanger to the organic Rankine cycle power generation device in the organic Rankine cycle power generation system to drive the organic Rankine cycle power generation device to generate electricity to output electricity and form the liquid organic working fluid for the next heat exchange. The low-temperature heat transfer oil is transported by the third heat exchanger to the low-temperature heat transfer oil storage tank for the next heat exchange.

[0015] Compared with the prior art, the present invention has the following beneficial effects: 1) The present invention successively stores and recovers the heat of high-temperature flue gas through two heat storage systems, and couples the steam turbine power generation system and the organic Rankine cycle power generation system respectively, and finally outputs stable and clean electricity. The present invention adheres to the core idea of ​​"energy cascade utilization and energy potential matching". Through the cascade and stable heat storage of two heat storage media, the cascade and full utilization of the waste heat of high-temperature flue gas can be achieved, thereby reducing the exergy loss and energy grade loss in the process of high-temperature flue gas waste heat recovery and utilization.

[0016] 2) Compared with the traditional high-temperature flue gas waste heat utilization system, the present invention couples two heat storage media with step-by-step operating temperatures for dual heat storage, which has a wide range of applications and can be applied to common high-temperature industrial flue gas source enterprises such as steel smelting, cement production, and coal-fired power generation.

[0017] 3) The present invention adds a flue gas-molten salt heat exchange system (i.e., a molten salt heat storage system) and a flue gas-thermal oil heat exchange system (i.e., a thermal oil heat storage system), and utilizes the advantages of molten salt and thermal oil heat storage, such as stability, flexibility, and fast response time, to smooth out the heat fluctuations caused by fluctuations in parameters such as flow, composition, and temperature of high-temperature flue gas, and can overcome the shortcomings of large heat grade loss, discontinuous and insufficient waste heat recovery in the conventional flue gas waste heat recovery process, thereby achieving stable, cascaded storage and utilization of high-temperature industrial flue gas, and outputting stable electrical energy, which is suitable for large-scale medium and high temperature flue gas waste heat utilization scenarios.

[0018] 4) The present invention adds an organic Rankine cycle power generation system and utilizes the advantages of the organic Rankine cycle, such as being able to utilize low-grade heat sources, being able to operate at relatively low temperatures, and being highly efficient, to fully recover the waste heat of high-temperature industrial flue gas, thereby reducing the exergy loss and energy grade loss in the process of utilizing the waste heat of flue gas. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Other features, objects and advantages of the present invention will become more apparent from the detailed description of non-limiting embodiments made with reference to the following drawings: Figure 1 A schematic structural diagram of a high-temperature flue gas waste heat cascade utilization power generation system provided in an embodiment of the present invention.

[0020] In the figure: 1. High-temperature molten salt storage tank; 2. First high-temperature molten salt pump; 3. First heat exchanger; 4. First low-temperature molten salt pump; 5. Low-temperature molten salt storage tank; 6. High-temperature thermal oil storage tank; 7. First high-temperature thermal oil pump; 8. Second heat exchanger; 9. Flue gas purification device; 10. First low-temperature thermal oil pump; 11. Low-temperature thermal oil storage tank; 12. Second low-temperature thermal oil pump; 13. Second high-temperature thermal oil pump; 14. Third heat exchanger; 15. Organic Rankine cycle power generation device; 16. Second low-temperature molten salt pump; 17. Second high-temperature molten salt pump; 18. Fourth heat exchanger; 19. Steam turbine power generation device. DETAILED DESCRIPTION

[0021] The present invention is described in detail below in conjunction with specific embodiments. The following embodiments will help those skilled in the art to further understand the present invention, but are not intended to limit the present invention in any form. It should be noted that, for those skilled in the art, several changes and improvements may be made without departing from the concept of the present invention. These all fall within the scope of protection of the present invention.

[0022] It should be noted that similar reference numerals and letters denote similar items in the following drawings, and therefore, once an item is defined in one drawing, further definition and explanation thereof is not required in subsequent drawings.

[0023] In conjunction with the accompanying drawings, some embodiments of the present invention are described in detail below. In the absence of conflict, the following embodiments and features in the embodiments may be combined with each other.

[0024] Embodiment 1: See also Figure 1 , an embodiment of the present invention provides a high-temperature flue gas waste heat cascade utilization power generation system, including a first heat storage system, a steam turbine power generation system, a second heat storage system, an organic Rankine cycle power generation system and a flue gas purification system; The first heat storage system is connected to the high-temperature flue gas, the steam turbine power generation system and the second heat storage system respectively, so that the high-temperature flue gas exchanges heat with the first heat storage system to obtain medium- and low-temperature flue gas, and then the first heat storage system exchanges heat with the steam turbine power generation system to output electricity; the second heat storage system is connected to the organic Rankine cycle power generation system and the flue gas purification system respectively, so that the medium- and low-temperature flue gas exchanges heat with the second heat storage system to obtain low-temperature flue gas, and then the second heat storage system exchanges heat with the organic Rankine cycle power generation system to output electricity, and then the low-temperature flue gas is discharged after being purified by the flue gas purification system; Among them, high-temperature flue gas is generated by processes such as steel smelting, cement production, and coal-fired power generation. The operating temperature of the first heat storage medium in the first heat storage system is greater than the operating temperature of the second heat storage medium in the second heat storage system. It should be noted that the operating temperature difference between the first heat storage medium and the second heat storage medium must meet a preset threshold.

[0025] Specifically, a first transport device is provided in the first heat storage system, which is used for transporting the first heat storage medium between the devices in the first heat storage system and between the first heat storage system and the steam turbine power generation system; A second transport device is provided in the second heat storage system, which is used for transporting the second heat storage medium between the devices in the second heat storage system and between the second heat storage system and the organic Rankine cycle power generation system.

[0026] In a specific embodiment, the first heat storage system adopts a molten salt heat storage system, and the second heat storage system adopts a thermal oil heat storage system; The molten salt heat storage system includes a high-temperature molten salt storage tank 1, a first high-temperature molten salt pump 2, a first heat exchanger 3, a first low-temperature molten salt pump 4, a low-temperature molten salt storage tank 5, a second low-temperature molten salt pump 16 and a second high-temperature molten salt pump 17; The thermal oil heat storage system includes a high-temperature thermal oil storage tank 6, a first high-temperature thermal oil pump 7, a second heat exchanger 8, a first low-temperature thermal oil pump 10, a low-temperature thermal oil storage tank 11, a second low-temperature thermal oil pump 12 and a second high-temperature thermal oil pump 13; The steam turbine power generation system includes a fourth heat exchanger 18 and a steam turbine power generation device 19; The organic Rankine cycle power generation system includes a third heat exchanger 14 and an organic Rankine cycle power generation device 15; The flue gas purification system comprises a flue gas purification device 9 .

[0027] Specifically, the flue gas input end of the first heat exchanger 3 is connected to the high-temperature flue gas, and the flue gas output end is connected to the flue gas input end of the second heat exchanger 8; the input end of the low-temperature molten salt storage tank 5 is connected to the molten salt output end of the fourth heat exchanger 18 through the second low-temperature molten salt pump 16, and the output end is connected to the molten salt input end of the first heat exchanger 3 through the first low-temperature molten salt pump 4; the input end of the high-temperature molten salt storage tank 1 is connected to the molten salt output end of the first heat exchanger 3 through the first high-temperature molten salt pump 2, and the output end is connected to the molten salt input end of the fourth heat exchanger 18 through the second high-temperature molten salt pump 17; The water working medium input end of the fourth heat exchanger 18 is connected to liquid water, the steam output end is connected to the input end of the steam turbine power generation device 19, and the output end of the steam turbine power generation device 19 is connected to liquid water; wherein the water working medium input end of the fourth heat exchanger 18 corresponds to the steam output end, and the liquid water is low-temperature liquid water; The flue gas output end of the second heat exchanger 8 is connected to the input end of the flue gas purification device 9, and the output end of the flue gas purification device 9 is connected to the atmosphere; the input end of the low-temperature thermal oil storage tank 11 is connected to the thermal oil output end of the third heat exchanger 14 through the second low-temperature thermal oil pump 12, and the output end is connected to the thermal oil input end of the second heat exchanger 8 through the first low-temperature thermal oil pump 10; the input end of the high-temperature thermal oil storage tank 6 is connected to the thermal oil output end of the second heat exchanger 8 through the first high-temperature thermal oil pump 7, and the output end is connected to the thermal oil input end of the third heat exchanger 14 through the second high-temperature thermal oil pump 13; Among them, the output end of the flue gas purification device 9 discharges low-temperature flue gas that meets the standards. Whether it meets the standards can be set and judged according to national standards, industry standards, enterprise standards, etc. The organic working medium input end of the third heat exchanger 14 is connected to the liquid organic working medium, the organic working medium output end is connected to the input end of the organic Rankine cycle power generation device 15, and the output end of the organic Rankine cycle power generation device 15 is connected to the liquid organic working medium; wherein the liquid organic working medium is a low-temperature liquid organic working medium.

[0028] In a specific implementation scenario, the high-temperature flue gas waste heat cascade utilization power generation system includes the following process flow: 1) When high-temperature industrial flue gas flows into the first heat exchanger 3, the first high-temperature molten salt pump 2, the first low-temperature molten salt pump 4, the first high-temperature thermal oil pump 7 and the first low-temperature thermal oil pump 10 are started; 2) The high-temperature industrial flue gas flows into the first heat exchanger 3, and exchanges heat with the low-temperature molten salt from the low-temperature molten salt storage tank 5 and transported by the first low-temperature molten salt pump 4 in the first heat exchanger 3, thereby completing the first heat exchange of the high-temperature flue gas; 3) The low-temperature molten salt after heating becomes high-temperature molten salt, and is transported to the high-temperature molten salt storage tank 1 through the first high-temperature molten salt pump 2; at the same time, the high-temperature industrial flue gas after the first heat exchange enters the second heat exchanger 8, and exchanges heat with the low-temperature heat transfer oil from the low-temperature heat transfer oil storage tank 11 and transported by the first low-temperature heat transfer oil pump 10 in the second heat exchanger 8, thereby completing the second heat exchange of the high-temperature flue gas; 4) The low-temperature heat transfer oil after heating becomes high-temperature heat transfer oil, and is transported to the high-temperature heat transfer oil storage tank 6 through the first high-temperature heat transfer oil pump 7; at the same time, the temperature of the high-temperature flue gas that has completed the second heat exchange is further reduced, and enters the flue gas purification device 9 for further purification, and finally meets the standards and is discharged into the atmosphere; 5) After the molten salt heat storage system and the thermal oil heat storage system are running stably, start the second low-temperature thermal oil pump 12, the second high-temperature thermal oil pump 13, the second low-temperature molten salt pump 16 and the second high-temperature molten salt pump 17; 6) The high-temperature molten salt stored in the high-temperature molten salt storage tank 1 is transported to the fourth heat exchanger 18 through the second high-temperature molten salt pump 17, and exchanges heat with liquid water to generate high-temperature water vapor, which enters the steam turbine power generation device 19 to expand and generate power. Finally, the water vapor after the work is completed condenses into liquid water, which can be used as the liquid water source of the fourth heat exchanger; 7) At the same time, the high-temperature heat transfer oil stored in the high-temperature heat transfer oil storage tank 6 is transported to the third heat exchanger 14 through the second high-temperature heat transfer oil pump 13, and exchanges heat with the liquid organic working fluid, thereby generating high-temperature gaseous organic working fluid vapor, and enters the organic Rankine cycle power generation device 15 to expand and generate power. Finally, the gaseous organic working fluid vapor after doing work is condensed into liquid organic working fluid, which can be used as a liquid organic working fluid source for the third heat exchanger.

[0029] In this implementation scenario, the temperature of the high-temperature industrial flue gas is greater than 600 o C, the melting temperature of the molten salt material used is 200 ~ 500 o C, the decomposition temperature of molten salt material is 400 ~ 800 o C, and the higher the industrial flue gas flow temperature, the higher the melting temperature of the molten salt material used; the solidification temperature of the heat transfer oil used is lower than 60 o C, decomposition temperature is 300 ~ 500 o C; the solidification temperature of the organic working fluid used in the organic Rankine cycle is less than -20 o C.

[0030] In this embodiment, this high-temperature flue gas waste heat cascade utilization power generation system uses common high-temperature industrial flue gas waste heat such as steelmaking furnace flue gas, cement production flue gas, coal-fired power plant flue gas as the energy source, and utilizes the advantages of heat storage stability, flexibility, and fast response time of molten salt and thermal oil heat storage systems. It can overcome the shortcomings of large waste heat quality loss and discontinuous waste heat recovery in conventional flue gas waste heat recovery processes, realize the cascade storage and utilization of high-temperature industrial flue gas, and is suitable for large-scale medium and high temperature flue gas waste heat utilization.

[0031] Embodiment 2: See also Figure 1 The embodiment of the present invention provides a method for cascade utilization of high-temperature flue gas waste heat for power generation, which is applied to a high-temperature flue gas waste heat cascade utilization power generation system described in Example 1. The method includes: The high-temperature flue gas is input into the first heat storage system, and heat-exchanged with the first low-temperature heat storage medium in the first heat storage system to obtain the first high-temperature heat storage medium and medium-low temperature flue gas; The first high-temperature heat storage medium is transported from the first heat storage system to the steam turbine power generation system, and heat-exchanges with the liquid water input into the steam turbine power generation system to obtain water vapor and the first low-temperature heat storage medium, so that the water vapor is used to generate electricity to output electricity, and forms liquid water for the next heat exchange, and the first low-temperature heat storage medium is transported from the steam turbine power generation system to the first heat storage system for the next heat exchange; and the medium- and low-temperature flue gas is transported from the first heat storage system to the second heat storage system, and heat-exchanges with the second low-temperature heat storage medium in the second heat storage system to obtain the second high-temperature heat storage medium and low-temperature flue gas; The second high-temperature heat storage medium is transported from the second heat storage system to the organic Rankine cycle power generation system, and exchanges heat with the liquid-phase organic working fluid input into the organic Rankine cycle power generation system to obtain a gaseous organic working fluid and a second low-temperature heat storage medium, so that the gaseous organic working fluid is used to generate electricity to output electricity, and forms a liquid-phase organic working fluid for the next heat exchange, and so that the second low-temperature heat storage medium is transported from the organic Rankine cycle power generation system to the second heat storage system for the next heat exchange; and the low-temperature flue gas is transported from the second heat storage system to the flue gas purification system, so that the low-temperature flue gas is discharged after being purified by the flue gas purification system.

[0032] In a specific embodiment, when the first heat storage system adopts a molten salt heat storage system and the second heat storage system adopts a thermal oil heat storage system, the above method specifically includes: The high-temperature flue gas is input into the first heat exchanger 3 in the molten salt heat storage system, and exchanges heat with the low-temperature molten salt in the first heat exchanger 3 to obtain high-temperature molten salt and medium-low temperature flue gas; wherein the low-temperature molten salt is transported to the first heat exchanger 3 by the low-temperature molten salt storage tank 5 in the molten salt heat storage system; The high-temperature molten salt is transported by the first heat exchanger 3 to the high-temperature molten salt storage tank 1 in the molten salt heat storage system; and the medium- and low-temperature flue gas is transported by the first heat exchanger 3 to the second heat exchanger 8 in the heat transfer oil heat storage system; The high-temperature molten salt is transported from the high-temperature molten salt storage tank 1 to the fourth heat exchanger 18 in the steam turbine power generation system, and heat-exchanges with the liquid water input into the fourth heat exchanger 18 to obtain water vapor and low-temperature molten salt; and the medium-low temperature flue gas is heat-exchanged with the low-temperature heat transfer oil in the second heat exchanger 8 to obtain high-temperature heat transfer oil and low-temperature flue gas; wherein the low-temperature heat transfer oil is transported from the low-temperature heat transfer oil storage tank 11 in the heat transfer oil heat storage system to the second heat exchanger 8; The water vapor is transported by the fourth heat exchanger 18 to the steam turbine power generation device 19 in the steam turbine power generation system, and is used to drive the steam turbine power generation device 19 to generate electricity to output electricity, and form liquid water for the next heat exchange, and the low-temperature molten salt is transported by the fourth heat exchanger 18 to the low-temperature molten salt storage tank 5 for the next heat exchange; and the high-temperature heat transfer oil is transported by the second heat exchanger 8 to the high-temperature heat transfer oil storage tank 6 in the heat transfer oil heat storage system, and the low-temperature flue gas is transported by the second heat exchanger 8 to the flue gas purification system; The high-temperature heat transfer oil is transported from the high-temperature heat transfer oil storage tank 6 to the third heat exchanger 14 in the organic Rankine cycle power generation system, and is heat-exchanged with the liquid phase organic working fluid input into the third heat exchanger 14 to obtain the gas phase organic working fluid and the low-temperature heat transfer oil. The low-temperature flue gas is purified by the flue gas purification system and then discharged; The gaseous organic working fluid is transported by the third heat exchanger 14 to the organic Rankine cycle power generation device 15 in the organic Rankine cycle power generation system, and is used to drive the organic Rankine cycle power generation device 15 to generate electricity to output electricity, and form a liquid organic working fluid for the next heat exchange. The low-temperature heat transfer oil is transported by the third heat exchanger 14 to the low-temperature heat transfer oil storage tank 11 for the next heat exchange.

[0033] The above description of the embodiments is to facilitate the understanding and use of the invention by those skilled in the art. It is obvious that those skilled in the art can easily make various modifications to these embodiments and apply the general principles described herein to other embodiments without creative work. Therefore, the present invention is not limited to the above embodiments, and improvements and modifications made by those skilled in the art based on the disclosure of the present invention without departing from the scope of the present invention should be within the scope of protection of the present invention.

Claims

1. A high-temperature flue gas waste heat cascade utilization power generation system, characterized in that: It includes a first heat storage system, a steam turbine power generation system, a second heat storage system, an organic Rankine cycle power generation system and a flue gas purification system; The first heat storage system is connected to high-temperature flue gas, the steam turbine power generation system and the second heat storage system respectively, so that the high-temperature flue gas exchanges heat with the first heat storage system to obtain medium- and low-temperature flue gas, and then the first heat storage system exchanges heat with the steam turbine power generation system to output electricity; the second heat storage system is connected to the organic Rankine cycle power generation system and the flue gas purification system respectively, so that the medium- and low-temperature flue gas exchanges heat with the second heat storage system to obtain low-temperature flue gas, and then the second heat storage system exchanges heat with the organic Rankine cycle power generation system to output electricity, and then the low-temperature flue gas is discharged after being purified by the flue gas purification system; Wherein, the operating temperature of the first heat storage medium in the first heat storage system is greater than the operating temperature of the second heat storage medium in the second heat storage system.

2. The high-temperature flue gas waste heat cascade utilization power generation system according to claim 1 is characterized in that: The first heat storage system adopts a molten salt heat storage system.

3. The high-temperature flue gas waste heat cascade utilization power generation system according to claim 2 is characterized in that: The second heat storage system adopts a thermal oil heat storage system.

4. The high-temperature flue gas waste heat cascade utilization power generation system according to claim 3 is characterized in that: The molten salt heat storage system comprises a high-temperature molten salt storage tank (1), a first heat exchanger (3) and a low-temperature molten salt storage tank (5); the input end of the high-temperature molten salt storage tank (1) is connected to the molten salt output end of the first heat exchanger (3), and the output end is connected to the steam turbine power generation system; the input end of the low-temperature molten salt storage tank (5) is connected to the steam turbine power generation system, and the output end is connected to the molten salt input end of the first heat exchanger (3); the flue gas input end of the first heat exchanger (3) is connected to the high-temperature flue gas, and the flue gas output end is connected to the thermal oil heat storage system.

5. The high-temperature flue gas waste heat cascade utilization power generation system according to claim 4 is characterized in that: The heat transfer oil heat storage system comprises a high-temperature heat transfer oil storage tank (6), a second heat exchanger (8) and a low-temperature heat transfer oil storage tank (11); the input end of the high-temperature heat transfer oil storage tank (6) is connected to the heat transfer oil output end of the second heat exchanger (8), and the output end is connected to the organic Rankine cycle power generation system; the input end of the low-temperature heat transfer oil storage tank (11) is connected to the organic Rankine cycle power generation system, and the output end is connected to the heat transfer oil input end of the second heat exchanger (8); the flue gas input end of the second heat exchanger (8) is connected to the flue gas output end of the first heat exchanger (3), and the flue gas output end is connected to the flue gas purification system.

6. A high-temperature flue gas waste heat cascade utilization power generation system according to claim 4 or 5, characterized in that: The steam turbine power generation system comprises a fourth heat exchanger (18) and a steam turbine power generation device (19); the molten salt input end of the fourth heat exchanger (18) is connected to the output end of the high-temperature molten salt storage tank (1), the molten salt output end is connected to the input end of the low-temperature molten salt storage tank (5), the water working medium input end is connected to liquid water, the steam output end is connected to the input end of the steam turbine power generation device (19), and the output end of the steam turbine power generation device (19) is connected to the liquid water; Wherein, the water working medium input end and the steam output end of the fourth heat exchanger (18) correspond to each other.

7. A high-temperature flue gas waste heat cascade utilization power generation system according to claim 4 or 5, characterized in that: The organic Rankine cycle power generation system comprises a third heat exchanger (14) and an organic Rankine cycle power generation device (15); the heat transfer oil input end of the third heat exchanger (14) is connected to the high-temperature heat transfer oil storage tank (6), the heat transfer output end is connected to the low-temperature heat transfer oil storage tank (11), the organic working fluid input end is connected to the liquid organic working fluid, the organic working fluid output end is connected to the input end of the organic Rankine cycle power generation device (15), and the output end of the organic Rankine cycle power generation device (15) is connected to the liquid organic working fluid.

8. The high-temperature flue gas waste heat cascade utilization power generation system according to claim 1 is characterized in that: A first transport device is provided in the first heat storage system, which is used for transporting the first heat storage medium between various devices in the first heat storage system and between the first heat storage system and the steam turbine power generation system; The second heat storage system is provided with a second transport device for transporting the second heat storage medium between devices in the second heat storage system and between the second heat storage system and the organic Rankine cycle power generation system.

9. A method for cascaded utilization of high-temperature flue gas waste heat for power generation, applied to a cascaded utilization of high-temperature flue gas waste heat for power generation system as claimed in any one of claims 1 to 8, characterized in that: The method comprises: The high-temperature flue gas is input into the first heat storage system, and exchanges heat with the first low-temperature heat storage medium in the first heat storage system to obtain the first high-temperature heat storage medium and the medium- and low-temperature flue gas; The first high-temperature heat storage medium is transported from the first heat storage system to the steam turbine power generation system, and exchanges heat with the liquid water input into the steam turbine power generation system to obtain water vapor and the first low-temperature heat storage medium, so that the water vapor is used to generate electricity to output electricity, and forms the liquid water for the next heat exchange, and the first low-temperature heat storage medium is transported from the steam turbine power generation system to the first heat storage system for the next heat exchange; and the medium- and low-temperature flue gas is transported from the first heat storage system to the second heat storage system, and exchanges heat with the second low-temperature heat storage medium in the second heat storage system to obtain a second high-temperature heat storage medium and low-temperature flue gas; The second high-temperature heat storage medium is transported from the second heat storage system to the organic Rankine cycle power generation system, and exchanges heat with the liquid-phase organic working fluid input into the organic Rankine cycle power generation system to obtain a gaseous organic working fluid and the second low-temperature heat storage medium, so that the gaseous organic working fluid is used to generate electricity to output electricity, and forms the liquid-phase organic working fluid for the next heat exchange, and so that the second low-temperature heat storage medium is transported from the organic Rankine cycle power generation system to the second heat storage system for the next heat exchange; and the low-temperature flue gas is transported from the second heat storage system to the flue gas purification system, so that the low-temperature flue gas is discharged after being purified by the flue gas purification system.

10. A method for power generation by cascade utilization of waste heat from high-temperature flue gas according to claim 9, characterized in that: When the first heat storage system adopts a molten salt heat storage system and the second heat storage system adopts a thermal oil heat storage system, the method specifically includes: The high-temperature flue gas is input into the first heat exchanger (3) in the molten salt heat storage system, and exchanges heat with the low-temperature molten salt in the first heat exchanger (3) to obtain high-temperature molten salt and the medium- and low-temperature flue gas; wherein the low-temperature molten salt is transported to the first heat exchanger (3) from the low-temperature molten salt storage tank (5) in the molten salt heat storage system; The high-temperature molten salt is transported by the first heat exchanger (3) to the high-temperature molten salt storage tank (1) in the molten salt heat storage system; and the medium- and low-temperature flue gas is transported by the first heat exchanger (3) to the second heat exchanger (8) in the heat transfer oil heat storage system; The high-temperature molten salt is transported from the high-temperature molten salt storage tank (1) to the fourth heat exchanger (18) in the steam turbine power generation system, and exchanges heat with the liquid water input into the fourth heat exchanger (18) to obtain the water vapor and the low-temperature molten salt; and the medium-low temperature flue gas is heat exchanged with the low-temperature heat transfer oil in the second heat exchanger (8) to obtain high-temperature heat transfer oil and low-temperature flue gas; wherein the low-temperature heat transfer oil is transported from the low-temperature heat transfer oil storage tank (11) in the heat transfer oil heat storage system to the second heat exchanger (8); The water vapor is transported by the fourth heat exchanger (18) to the steam turbine power generation device (19) in the steam turbine power generation system to drive the steam turbine power generation device (19) to generate electricity to output electricity and form the liquid water for the next heat exchange; the low-temperature molten salt is transported by the fourth heat exchanger (18) to the low-temperature molten salt storage tank (5) for the next heat exchange; and the high-temperature heat transfer oil is transported by the second heat exchanger (8) to the high-temperature heat transfer oil storage tank (6) in the heat transfer oil heat storage system; and the low-temperature flue gas is transported by the second heat exchanger (8) to the flue gas purification system; The high-temperature heat transfer oil is transported from the high-temperature heat transfer oil storage tank (6) to the third heat exchanger (14) in the organic Rankine cycle power generation system, and is heat-exchanged with the liquid-phase organic working fluid input into the third heat exchanger (14) to obtain the gas-phase organic working fluid and the low-temperature heat transfer oil, and the low-temperature flue gas is purified by the flue gas purification system and then discharged; The gaseous organic working fluid is transported by the third heat exchanger (14) to the organic Rankine cycle power generation device (15) in the organic Rankine cycle power generation system, and is used to drive the organic Rankine cycle power generation device (15) to generate electricity to output electricity, and to form the liquid organic working fluid for the next heat exchange, and the low-temperature heat transfer oil is transported by the third heat exchanger (14) to the low-temperature heat transfer oil storage tank (11) for the next heat exchange.

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