Supercritical carbon dioxide, steam Rankine and organic Rankine combined power generation system

Abstract

The invention provides a supercritical carbon dioxide, steam Rankine and organic Rankine combined power generation system which comprises a gas turbine subsystem used for combusting natural gas to generate flue gas; the supercritical carbon dioxide circulation subsystem is connected with the gas turbine subsystem and is used for generating power by using heat exchanged between the flue gas and carbon dioxide; the steam Rankine cycle subsystem is connected with the supercritical carbon dioxide cycle subsystem and used for exchanging heat with water through the flue gas used by the supercritical carbon dioxide cycle subsystem for power generation; the organic Rankine cycle subsystem is connected with the supercritical carbon dioxide cycle subsystem and the steam Rankine cycle subsystem and used for conducting power generation through heat exchange between carbon dioxide and smoke and an organic working medium, so that gradient utilization of energy is achieved, the unit energy cost is remarkably reduced, and the power generation efficiency is improved. The problem that the efficiency is suddenly reduced under the low-load working condition is solved, stable and efficient operation of the system within the full-working-condition range is guaranteed, and waste heat is recycled to the maximum extent.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of energy-saving power generation, in particular to a supercritical carbon dioxide, steam Rankine and organic Rankine combined power generation system. BACKGROUND

[0002] Improving the comprehensive utilization efficiency of energy has become the core issue in the field of energy and power. As a clean and efficient prime mover, the exhaust temperature of the simple cycle power generation of the gas turbine is usually as high as 450-750℃, which contains huge waste heat utilization potential. Effective recovery of this part of waste heat is crucial for energy saving and emission reduction and improving the overall economy of the power plant.

[0003] At present, the mainstream technology route for waste heat utilization of the gas turbine is gas-steam combined cycle. This technology generates steam through a waste heat boiler to drive a steam turbine generator set for secondary power generation. However, this technology has obvious bottlenecks: first, the system is large and complex, occupies a large area, and has high initial investment, especially not suitable for small and medium-sized distributed gas turbines or space-limited scenarios. Secondly, limited by the properties of water, the efficiency of the steam Rankine cycle will decrease significantly when recovering low-temperature waste heat, and a large amount of low-temperature heat is directly discharged, causing energy waste and thermal pollution.

[0004] To tap lower-grade waste heat, the Organic Rankine Cycle (ORC) technology is introduced. ORC uses low-boiling organic working fluids to efficiently recover waste heat in the temperature range of 150-350℃. However, ORC technology also has limitations: organic working fluids are usually flammable or toxic, posing a safety hazard; some working fluids also have high global warming potential, which is not environmentally friendly; and for the high-temperature and high-heat-flux heat source of the gas turbine exhaust, if ORC is used alone, the energy grade of the high-temperature section cannot be optimally utilized, and the economy is not good.

[0005] In recent years, supercritical carbon dioxide Brayton cycle has received widespread attention as a new technology. Carbon dioxide has high density similar to a liquid and low viscosity similar to a gas above the critical point (31.1℃, 7.38MPa), making the system very compact and efficient. Supercritical carbon dioxide cycle performs outstandingly in recovering medium-high temperature waste heat. However, supercritical carbon dioxide cycle has large cooling losses at low temperatures, and the compressor inlet needs to be maintained near the critical point, which poses high requirements for system control and component design. If used alone to recover the waste heat of the gas turbine in the full temperature range, the performance of the low-temperature section is not optimal, and it is difficult to "squeeze dry" the waste heat.

[0006] In the prior art, there are also attempts to simply superimpose two cycles, such as the "supercritical carbon dioxide-steam Rankine combined cycle" or the two-stage series mode of "steam Rankine plus ORC". But these schemes often just use the exhaust gas of the previous stage cycle as the heat source of the next stage cycle, and fail to fundamentally solve the problem of mismatched energy cascade utilization. For example, the high-temperature supercritical carbon dioxide cycle exhaust gas or the steam Rankine cycle exhaust steam still contains considerable heat, but the temperature may not be suitable for driving another medium-temperature cycle, resulting in waste of heat quality. Each cycle is usually independently designed, with low coupling degree, insufficient system integration optimization, and unable to flexibly adjust and optimize operation according to the heat source temperature and external electric, thermal, and cold load demand, limiting the further improvement of overall energy efficiency. SUMMARY

[0007] The present application is made to solve the above problems, and aims to provide a supercritical carbon dioxide, steam Rankine and organic Rankine combined power generation system.

[0008] The present application provides a supercritical carbon dioxide, steam Rankine and organic Rankine combined power generation system, which has the following characteristics, comprising:

[0009] A gas turbine subsystem for burning natural gas to generate flue gas;

[0010] A supercritical carbon dioxide cycle subsystem connected to the gas turbine subsystem for generating power by exchanging heat between the flue gas and carbon dioxide;

[0011] A steam Rankine cycle subsystem connected to the supercritical carbon dioxide cycle subsystem for generating power by exchanging heat between the flue gas after use by the supercritical carbon dioxide cycle subsystem and water;

[0012] An organic Rankine cycle subsystem connected to the supercritical carbon dioxide cycle subsystem and the steam Rankine cycle subsystem respectively for generating power by exchanging heat between the carbon dioxide of the supercritical carbon dioxide cycle subsystem and the flue gas after use by the steam Rankine cycle subsystem and an organic working fluid.

[0013] In the supercritical carbon dioxide, steam Rankine and organic Rankine combined power generation system provided by the present application, the gas turbine subsystem can further comprise:

[0014] A compressor for compressing air;

[0015] A combustion chamber connected to the compressor for containing compressed air and natural gas for combustion to generate flue gas;

[0016] A flue gas turbine connected to the compressor and the combustion chamber respectively for generating power by using the flue gas.

[0017] In the supercritical carbon dioxide, steam Rankine and organic Rankine combined power generation system provided by the application, the supercritical carbon dioxide circulation subsystem can further comprise:

[0018] The flue gas carbon dioxide heat exchanger is connected with the flue gas turbine and is used for exchanging heat between the flue gas discharged by the flue gas turbine and the carbon dioxide.

[0019] The supercritical carbon dioxide turbine is connected with the flue gas carbon dioxide heat exchanger and is used for generating power by using the carbon dioxide discharged by the flue gas carbon dioxide heat exchanger.

[0020] The regenerator is connected with the steam Rankine circulation subsystem, the flue gas carbon dioxide heat exchanger and the supercritical carbon dioxide turbine respectively and is used for heating the compressed carbon dioxide by using the carbon dioxide discharged by the supercritical carbon dioxide turbine and conveying the heated compressed carbon dioxide to the flue gas carbon dioxide heat exchanger.

[0021] The carbon dioxide cooler is connected with the organic Rankine circulation subsystem and is used for cooling the carbon dioxide discharged by the organic Rankine circulation subsystem.

[0022] The supercritical carbon dioxide compressor is connected with the carbon dioxide cooler and the regenerator respectively and is used for compressing the carbon dioxide discharged by the carbon dioxide cooler into compressed carbon dioxide and inputting the compressed carbon dioxide into the regenerator.

[0023] In the supercritical carbon dioxide, steam Rankine and organic Rankine combined power generation system provided by the application, the steam Rankine circulation subsystem can further comprise:

[0024] The steam generator is connected with the flue gas carbon dioxide heat exchanger and is used for converting water into hot steam by using the heat of the flue gas discharged by the flue gas carbon dioxide heat exchanger.

[0025] The steam turbine is connected with the steam generator and is used for generating power by using the hot steam of the steam generator.

[0026] The condenser is connected with the steam turbine and is used for condensing the steam discharged by the steam turbine into water.

[0027] The water pump is connected with the condenser and is used for pressurizing the water discharged by the condenser.

[0028] The preheater is connected with the water pump, the regenerator and the steam generator respectively and is used for preheating the water discharged by the water pump by using the carbon dioxide discharged by the regenerator and conveying the preheated water to the steam generator.

[0029] In the supercritical carbon dioxide, steam Rankine and organic Rankine combined power generation system provided by the application, the organic Rankine circulation subsystem can further comprise:

[0030] The flue gas organic working medium heat exchanger is connected with the steam generator and is used for exchanging heat between flue gas discharged by the steam generator and organic working medium.

[0031] The organic working medium expander is connected with the flue gas organic working medium heat exchanger and is used for doing work and generating electricity by using organic working medium discharged by the flue gas organic working medium heat exchanger.

[0032] The organic working medium cooler is connected with the organic working medium expander and is used for cooling organic working medium discharged by the organic working medium expander.

[0033] The organic working medium pump is connected with the organic working medium cooler and is used for pressurizing organic working medium discharged by the organic working medium cooler.

[0034] The carbon dioxide organic working medium heat exchanger is connected with the flue gas organic working medium heat exchanger, the organic working medium pump, the preheater and the carbon dioxide cooler respectively and is used for heating organic working medium discharged by the organic working medium pump by using carbon dioxide discharged by the preheater, delivering the heated organic working medium to the flue gas organic working medium heat exchanger and delivering the carbon dioxide to the carbon dioxide cooler.

[0035] In the supercritical carbon dioxide, steam Rankine and organic Rankine combined power generation system provided by the application, the compression ratio of the compressor can be 15-30.

[0036] In the supercritical carbon dioxide, steam Rankine and organic Rankine combined power generation system provided by the application, the inlet flue gas temperature of the flue gas turbine can be 1200-1700℃.

[0037] In the supercritical carbon dioxide, steam Rankine and organic Rankine combined power generation system provided by the application, the outlet flue gas temperature of the flue gas turbine can be 450-750℃.

[0038] In the supercritical carbon dioxide, steam Rankine and organic Rankine combined power generation system provided by the application, the power generation proportion can be adjusted by adjusting the working medium flow and heat exchange condition of each branch in the supercritical carbon dioxide circulation subsystem, the steam Rankine circulation subsystem and the organic Rankine circulation subsystem.

[0039] Effects of the application

[0040] The supercritical carbon dioxide, steam Rankine, and organic Rankine combined power generation system of the present invention comprises: a gas turbine subsystem for burning natural gas to generate flue gas; a supercritical carbon dioxide cycle subsystem connected to the gas turbine subsystem for generating electricity by exchanging heat between the flue gas and carbon dioxide; a steam Rankine cycle subsystem connected to the supercritical carbon dioxide cycle subsystem for generating electricity by exchanging heat between the flue gas after use in the supercritical carbon dioxide cycle subsystem and water; and an organic Rankine cycle subsystem connected to both the supercritical carbon dioxide cycle subsystem and the steam Rankine cycle subsystem for generating electricity by exchanging heat between the carbon dioxide from the supercritical carbon dioxide cycle subsystem and the flue gas after use in the steam Rankine cycle subsystem and organic working fluid. Therefore, the supercritical carbon dioxide, steam Rankine, and organic Rankine combined power generation system of the present invention achieves cascaded energy utilization, significantly reduces unit energy costs, solves the problem of sharp efficiency drops under low load conditions, ensures stable and efficient operation of the system across the entire operating range, and maximizes waste heat recovery. Attached Figure Description

[0041] Figure 1 This is a schematic diagram of the structure of the supercritical carbon dioxide, steam Rankine and organic Rankine combined power generation system in an embodiment of the present invention. Detailed Implementation

[0042] In the description of this application, it should be noted that, unless otherwise expressly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection, an electrical connection, or a connection that allows communication between them; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication between two components or the interaction between two components. Those skilled in the art can understand the specific meaning of the above terms in this application according to the specific circumstances.

[0043] To make the technical means, creative features, objectives and effects of this invention easy to understand, the following embodiments, in conjunction with the accompanying drawings, specifically illustrate the supercritical carbon dioxide, steam Rankine and organic Rankine combined power generation system of this invention.

[0044] Example

[0045] Figure 1 This is a schematic diagram of the structure of the supercritical carbon dioxide, steam Rankine and organic Rankine combined power generation system in an embodiment of the present invention.

[0046] like Figure 1As shown, the embodiment provides a supercritical carbon dioxide, steam Rankine and organic Rankine combined power generation system 100, comprising: a gas turbine subsystem 1, a supercritical carbon dioxide cycle subsystem 2, a steam Rankine cycle subsystem 3, and an organic Rankine cycle subsystem 4.

[0047] The gas turbine subsystem 1 is used for burning natural gas to generate flue gas.

[0048] The gas turbine subsystem 1 comprises: a compressor 10, a combustion chamber 11, and a flue gas turbine 12.

[0049] The compressor 10 is used for compressing air. The compression ratio of the compressor is 15-30.

[0050] The combustion chamber 11 is connected with the compressor 10, and is used for accommodating compressed air and natural gas for combustion to generate flue gas.

[0051] The flue gas turbine 12 is connected with the compressor 10 and the combustion chamber 11 respectively, and is used for generating power by using flue gas. The inlet flue gas temperature of the flue gas turbine is 1200-1700℃, and the outlet flue gas temperature of the flue gas turbine is 450-750℃.

[0052] The supercritical carbon dioxide cycle subsystem 2 is connected with the gas turbine subsystem 1, and is used for generating power by using heat exchange between flue gas and carbon dioxide.

[0053] The supercritical carbon dioxide cycle subsystem 2 comprises: a flue gas carbon dioxide heat exchanger 20, a supercritical carbon dioxide turbine 21, a regenerator 22, a carbon dioxide cooler 23, and a supercritical carbon dioxide compressor 24.

[0054] The flue gas carbon dioxide heat exchanger 20 is connected with the flue gas turbine 12, and is used for exchanging heat between flue gas discharged by the flue gas turbine 12 and carbon dioxide.

[0055] The supercritical carbon dioxide turbine 21 is connected with the flue gas carbon dioxide heat exchanger 20, and is used for generating power by using carbon dioxide discharged by the flue gas carbon dioxide heat exchanger 20.

[0056] The regenerator 22 is connected with the steam Rankine cycle subsystem 3, the flue gas carbon dioxide heat exchanger 20 and the supercritical carbon dioxide turbine 21 respectively, and is used for heating compressed carbon dioxide by using carbon dioxide discharged by the supercritical carbon dioxide turbine 21, and conveying the heated compressed carbon dioxide to the flue gas carbon dioxide heat exchanger 20.

[0057] The carbon dioxide cooler 23 is connected with the organic Rankine cycle subsystem 4, and is used for cooling carbon dioxide discharged by the organic Rankine cycle subsystem 4.

[0058] The supercritical carbon dioxide compressor 24 is connected with the carbon dioxide cooler 23 and the regenerator 22 respectively, and is used for compressing the carbon dioxide discharged by the carbon dioxide cooler 23 into compressed carbon dioxide and inputting the compressed carbon dioxide into the regenerator 22.

[0059] The steam Rankine cycle subsystem 3 is connected with the supercritical carbon dioxide cycle subsystem 2, and is used for generating power by exchanging heat between the flue gas used by the supercritical carbon dioxide cycle subsystem 2 and water.

[0060] The steam Rankine cycle subsystem 3 comprises a steam generator 30, a steam turbine 31, a condenser 32, a water pump 33 and a preheater 34.

[0061] The steam generator 30 is connected with the flue gas carbon dioxide heat exchanger 20, and is used for converting water into hot steam by using the heat of the flue gas discharged by the flue gas carbon dioxide heat exchanger 20.

[0062] The steam turbine 31 is connected with the steam generator 30, and is used for generating power by using the hot steam of the steam generator 30.

[0063] The condenser 32 is connected with the steam turbine 31, and is used for condensing the steam discharged by the steam turbine 31 into water.

[0064] The water pump 33 is connected with the condenser 32, and is used for pressurizing the water discharged by the condenser 32.

[0065] The preheater 34 is connected with the water pump 33, the regenerator 22 and the steam generator 30 respectively, and is used for preheating the water discharged by the water pump 33 by using the carbon dioxide discharged by the regenerator 22 and then inputting the preheated water into the steam generator 30.

[0066] The organic Rankine cycle subsystem 4 is connected with the supercritical carbon dioxide cycle subsystem 2 and the steam Rankine cycle subsystem 3 respectively, and is used for generating power by exchanging heat between the carbon dioxide of the supercritical carbon dioxide cycle subsystem 2 and the flue gas used by the steam Rankine cycle subsystem 3 and the organic working medium.

[0067] The organic Rankine cycle subsystem 4 comprises a flue gas organic working medium heat exchanger 40, an organic working medium expander 41, an organic working medium cooler 42, an organic working medium pump 43 and a carbon dioxide organic working medium heat exchanger 44.

[0068] The flue gas organic working medium heat exchanger 40 is connected with the steam generator 30, and is used for exchanging heat between the flue gas discharged by the steam generator 30 and the organic working medium.

[0069] The organic working medium expander 41 is connected with the flue gas organic working medium heat exchanger 40, and is used for generating power by using the organic working medium discharged by the flue gas organic working medium heat exchanger 40.

[0070] The organic working medium cooler 42 is connected to the organic working medium expander 41, and is used to cool the organic working medium discharged by the organic working medium expander 41.

[0071] The organic working medium pump 43 is connected to the organic working medium cooler 42, and is used to pressurize the organic working medium discharged by the organic working medium cooler 42.

[0072] The carbon dioxide organic working medium heat exchanger 44 is connected to the flue gas organic working medium heat exchanger 40, the organic working medium pump 43, the preheater 34 and the carbon dioxide cooler 23, and is used to heat the organic working medium discharged by the organic working medium pump 43 by using the carbon dioxide discharged by the preheater 34, and deliver the heated organic working medium to the flue gas organic working medium heat exchanger 40, and deliver the carbon dioxide to the carbon dioxide cooler 23.

[0073] The power generation ratio is adjusted by adjusting the working medium flow and heat exchange conditions of each branch in the supercritical carbon dioxide cycle subsystem 2, the steam Rankine cycle subsystem 3 and the organic Rankine cycle subsystem 4.

[0074] The working principle of the supercritical carbon dioxide, steam Rankine and organic Rankine combined power generation system in the embodiment is as follows:

[0075] First, the air is compressed by the air compressor 10, and then the compressed air is combusted with the natural gas in the combustion chamber 11. The flue gas generated by the combustion enters the flue gas turbine 12, and the flue gas expands to do work and generate power in the flue gas turbine 12. Then, the flue gas enters the flue gas carbon dioxide heat exchanger 20 to exchange heat with the carbon dioxide. Then, the flue gas enters the steam generator 30 to heat the water into hot steam. Then, the flue gas continues to enter the flue gas organic working medium heat exchanger 40 to exchange heat with the organic working medium, and then is discharged.

[0076] The carbon dioxide in the flue gas carbon dioxide heat exchanger 20 obtains heat, and then enters the supercritical carbon dioxide turbine 21 to expand to do work and generate power. The carbon dioxide after doing work enters the preheater 34 to preheat the water, and then continues to enter the organic working medium heat exchanger 44 to exchange heat with the organic working medium. After the heat exchange, the carbon dioxide enters the carbon dioxide cooler 23 to be cooled to the critical point. Then, the carbon dioxide is compressed by the supercritical carbon dioxide compressor 24, and then enters the flue gas carbon dioxide heat exchanger 20 to continue to exchange heat with the flue gas, and completes a cycle.

[0077] The water in the steam generator 30 is heated into hot steam by the flue gas. The hot steam enters the steam turbine 31 to expand to do work and generate power, and then enters the condenser 32 to be condensed into water. The water is pressurized by the water pump 33, and then enters the preheater 34 to be preheated by the carbon dioxide, and then flows into the steam generator 30 to complete a cycle.

[0078] The organic working medium in the flue gas organic working medium heat exchanger 40 exchanges heat with the flue gas and then enters the organic working medium expander 41 to expand and generate power, and then the organic working medium enters the organic working medium cooler 42 to be cooled, and then is pressurized by the organic working medium pump 43 and enters the carbon dioxide organic working medium heat exchanger 44 to be heated by the carbon dioxide, and then the heated organic working medium enters the flue gas organic working medium heat exchanger 40 to complete a cycle.

[0079] Effects of the embodiment

[0080] According to the supercritical carbon dioxide, steam Rankine and organic Rankine combined power generation system of the embodiment, because the system comprises: a gas turbine subsystem for burning natural gas to generate flue gas; a supercritical carbon dioxide cycle subsystem connected with the gas turbine subsystem and used for generating power by exchanging heat between the flue gas and carbon dioxide; a steam Rankine cycle subsystem connected with the supercritical carbon dioxide cycle subsystem and used for generating power by exchanging heat between the flue gas used by the supercritical carbon dioxide cycle subsystem and water; and an organic Rankine cycle subsystem connected with the supercritical carbon dioxide cycle subsystem and the steam Rankine cycle subsystem and used for generating power by exchanging heat between the carbon dioxide of the supercritical carbon dioxide cycle subsystem and the flue gas used by the steam Rankine cycle subsystem and the organic working medium, the supercritical carbon dioxide, steam Rankine and organic Rankine combined power generation system of the embodiment realizes gradient utilization of energy, significantly reduces the unit energy cost, solves the problem of efficiency drop under low load conditions, ensures stable and efficient operation of the system in the whole operating range, and maximizes the recovery of waste heat.

[0081] The embodiment also uses the supercritical carbon dioxide cycle subsystem to generate power, which is suitable for efficient recovery of heat in the medium-high temperature section, and the system structure is compact and the efficiency is significantly higher than that of the steam Rankine cycle under the same conditions.

[0082] The embodiment also uses the steam Rankine cycle subsystem to absorb waste heat in the medium temperature section to generate steam to drive a steam turbine to generate power.

[0083] The embodiment also uses the organic Rankine cycle subsystem to generate power from lower grade waste heat, which uses a low-boiling organic working medium to effectively avoid thermal decomposition problems at high temperatures, and is particularly suitable for maintaining system performance when the heat source temperature fluctuates or is low.

[0084] Those skilled in the art should understand that the present application is not limited to the above embodiments, and the above embodiments and descriptions in the specification are only to illustrate the principles of the present application, and various changes and improvements can be made without departing from the spirit and scope of the present application, and these changes and improvements all fall within the scope of the claimed present application. The scope of protection of the present application is defined by the appended claims and their equivalents.

Claims

1. A supercritical carbon dioxide, steam Rankine, and organic Rankine combined power generation system, characterized by, The application relates to a combined cycle power generation system. The combined cycle power generation system comprises: a gas turbine subsystem for combusting natural gas to generate flue gas; a supercritical carbon dioxide cycle subsystem connected to the gas turbine subsystem for generating power by exchanging heat between the flue gas and carbon dioxide; a steam Rankine cycle subsystem connected to the supercritical carbon dioxide cycle subsystem for generating power by exchanging heat between the flue gas after being used by the supercritical carbon dioxide cycle subsystem and water; 2. The supercritical carbon dioxide, steam Rankine, and organic Rankine combined power generation system of claim 1, an organic Rankine cycle subsystem connected to the supercritical carbon dioxide cycle subsystem and the steam Rankine cycle subsystem respectively for generating power by exchanging heat between carbon dioxide of the supercritical carbon dioxide cycle subsystem and the flue gas after being used by the steam Rankine cycle subsystem and an organic working medium. The gas turbine subsystem comprises: a compressor for compressing air; a combustor connected to the compressor for containing the compressed air and the natural gas to combust and generate flue gas; a flue gas turbine connected to the compressor and the combustor respectively for generating power by using the flue gas.

3. The supercritical carbon dioxide, steam Rankine, and organic Rankine combined power generation system of claim 2, The supercritical carbon dioxide cycle subsystem comprises: a flue gas-carbon dioxide heat exchanger connected to the flue gas turbine for exchanging heat between the flue gas discharged by the flue gas turbine and carbon dioxide; a supercritical carbon dioxide turbine connected to the flue gas-carbon dioxide heat exchanger for generating power by using the carbon dioxide discharged by the flue gas-carbon dioxide heat exchanger; a regenerator connected to the steam Rankine cycle subsystem, the flue gas-carbon dioxide heat exchanger and the supercritical carbon dioxide turbine respectively for heating compressed carbon dioxide by using the carbon dioxide discharged by the supercritical carbon dioxide turbine and delivering the heated compressed carbon dioxide to the flue gas-carbon dioxide heat exchanger; a carbon dioxide cooler connected to the organic Rankine cycle subsystem for cooling carbon dioxide discharged by the organic Rankine cycle subsystem; a supercritical carbon dioxide compressor connected to the carbon dioxide cooler and the regenerator respectively for compressing the carbon dioxide discharged by the carbon dioxide cooler into the compressed carbon dioxide and inputting the compressed carbon dioxide into the regenerator. The steam Rankine cycle subsystem comprises:

4. The supercritical carbon dioxide, steam Rankine, and organic Rankine combined power generation system of claim 3, a steam generator connected to the flue gas-carbon dioxide heat exchanger for converting water into hot steam by using heat of the flue gas discharged by the flue gas-carbon dioxide heat exchanger; a steam turbine connected to the steam generator for generating power by using the hot steam of the steam generator; a condenser connected to the steam turbine for condensing steam discharged by the steam turbine into water; a water pump connected to the condenser for pressurizing water discharged by the condenser; a preheater connected to the water pump, the regenerator and the steam generator respectively for preheating water discharged by the water pump by using carbon dioxide discharged by the regenerator and delivering the preheated water to the steam generator. The organic Rankine cycle subsystem comprises: a flue gas-organic working medium heat exchanger connected to the steam generator for exchanging heat between flue gas discharged by the steam generator and the organic working medium.

5. The supercritical carbon dioxide, steam Rankine, and organic Rankine combined power generation system of claim 4, ​ ​ ​ An organic working fluid expander connected to the flue gas organic working fluid heat exchanger, for using the organic working fluid discharged from the flue gas organic working fluid heat exchanger to generate power; An organic working fluid cooler connected to the organic working fluid expander, for cooling the organic working fluid discharged from the organic working fluid expander; An organic working fluid pump connected to the organic working fluid cooler, for pressurizing the organic working fluid discharged from the organic working fluid cooler; A carbon dioxide organic working fluid heat exchanger connected to the flue gas organic working fluid heat exchanger, the organic working fluid pump, the preheater and the carbon dioxide cooler respectively, for using the carbon dioxide discharged from the preheater to heat the organic working fluid discharged from the organic working fluid pump, and delivering the heated organic working fluid to the flue gas organic working fluid heat exchanger, and delivering the carbon dioxide to the carbon dioxide cooler.

6. The supercritical carbon dioxide, steam Rankine and organic Rankine combined power generation system according to claim 2, wherein: wherein, The pressure ratio of the compressor is 15-30.

7. The supercritical carbon dioxide, steam Rankine and organic Rankine combined power generation system according to claim 2, wherein: wherein The inlet flue gas temperature of the flue gas turbine is 1200-1700℃.

8. The supercritical carbon dioxide, steam Rankine and organic Rankine combined power generation system according to claim 2, wherein: wherein, The outlet flue gas temperature of the flue gas turbine is 450-750℃.

9. The supercritical carbon dioxide, steam Rankine and organic Rankine combined power generation system according to claim 1, wherein: wherein The power generation proportion is adjusted by adjusting the working fluid flow rate and heat exchange condition of each branch in the supercritical carbon dioxide cycle subsystem, the steam Rankine cycle subsystem and the organic Rankine cycle subsystem.

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