Combined cycle system for pre-cooling the waste heat of a gas turbine based on a supercritical carbon dioxide cycle

Abstract

The present invention discloses a combined cycle system for pre-cooling the waste heat of a gas turbine based on a supercritical carbon dioxide cycle. In the system, a low-pressure and high-temperature supercritical carbon dioxide fluid sequentially undergoes heat release in a high-temperature recuperator, a low-temperature recuperator, and a generator, and then a part of the supercritical carbon dioxide fluid enters the main compressor after being cooled by a cooler and a pre-cooler. Another part of the supercritical carbon dioxide fluid enters a recompression compressor. The refrigerant is condensed and liquefied in a condenser and enters an evaporator through an expansion valve. The refrigerant in the evaporator is absorbed by the absorbent in the absorber, gasified into a saturated concentrated solution, and provides cooling capacity to the pre-cooler. The concentrated solution in the generator is heated to boiling by the waste heat in the topping cycle gas turbine power generation system and the intermediate cycle supercritical carbon dioxide power generation system to generate refrigerant vapor, and the refrigerant vapor enters the condenser. The concentrated solution formed in the generator releases heat through a heat exchanger and is decompressed by a throttle valve and enters the absorber.

Description

Technical Field

[0001] The present invention belongs to the technical field of supercritical carbon dioxide Brayton power cycle, and particularly relates to a combined cycle system for pre-cooling the waste heat of a gas turbine based on a supercritical carbon dioxide cycle. Background Art

[0002] In recent years, with the increasingly severe energy crisis and environmental problems, efficient energy utilization technologies and new power propulsion technologies have become research hotspots in the field of advanced energy and power. The gas Brayton cycle is widely used in coal-fired power plants, nuclear power plants, ship power propulsion and other fields. As the main utilization form of the gas Brayton cycle, the gas turbine can reach a turbine inlet temperature of about 1500 °C through efficient cooling technology. However, the gas turbine uses air and other compressible fluids, which consume a large amount of work during the compression process. And as an open cycle, the waste heat of the tail gas as high as 500 °C is discharged into the atmosphere, resulting in a reduction in cycle efficiency.

[0003] The combined cycle system based on the principle of cascaded energy utilization is one of the effective ways to improve energy utilization efficiency. However, the conventional gas turbine-steam combined cycle system has a large floor area, a low utilization rate of the waste heat of the gas turbine, requires a large amount of cooling water for cooling, and is easily affected by the ambient temperature. The supercritical carbon dioxide cycle has a higher cycle efficiency and a smaller volume, and can achieve a higher energy utilization rate when combined with a gas turbine.

[0004] In the supercritical carbon dioxide Brayton cycle, the compressor operates stably near the carbon dioxide critical point (304.12K, 7337.1kPa). Carbon dioxide has the characteristics of large heat capacity, low compressibility and low viscosity near the critical point, which can effectively reduce the work consumption during the compression process, thus significantly improving the cycle thermal efficiency; and carbon dioxide as a cycle working medium has advantages such as relatively moderate, non-toxic, stable, and rich reserves; in addition, the relatively high density of the carbon dioxide working medium in the supercritical state makes the size of the entire cycle device, especially the compressor, significantly reduced.

[0005] At present, the commonly used supercritical carbon dioxide Brayton cycles are all closed cycles, and only medium and high temperature heat sources are required to generate electricity. However, the exhaust gas temperature at the last stage of the turbine in the closed cycle is relatively high. Even after regeneration, the temperature of the exhausted carbon dioxide still remains at about 200 °C, indicating that the exhaust heat of the carbon dioxide in the closed cycle is not fully utilized, and a large amount of cooling water is required for cooling, increasing the volume of the cooler and consuming more circulating water pump power.

[0006] An efficient supercritical carbon dioxide Brayton cycle requires the compressor inlet state to operate near the carbon dioxide critical point. However, the carbon dioxide critical point is slightly higher than the ambient temperature. Therefore, too high an ambient temperature will result in poor cooling effect of the pre-cooler, leading to a decline in cycle performance. In addition, reducing the air inlet temperature of the gas turbine is beneficial to reducing the compression work and improving the efficiency of the cycle system. However, the gas turbine inlet is also vulnerable to fluctuations in ambient temperature, and too high an ambient temperature will cause a decline in the system performance.

[0007] Aiming at the problems that the heat in the exhaust gas of the gas turbine-supercritical carbon dioxide combined cycle system cannot be fully utilized and the combined cycle system is vulnerable to ambient temperature, a combined cycle system based on the waste heat pre-cooling of the gas turbine in the supercritical carbon dioxide cycle is proposed, realizing the cascade utilization of energy, fully utilizing the exhaust gas temperature to improve the thermal efficiency of the cycle system, and without increasing its additional system energy consumption.

[0008] The above information disclosed in the background art is only used to enhance the understanding of the background of the present invention. Therefore, it may include information that does not constitute the prior art known to those of ordinary skill in the art in this country. Summary of the Invention

[0009] Aiming at the deficiencies of the prior art, a combined cycle system based on the waste heat pre-cooling of the gas turbine in the supercritical carbon dioxide cycle is proposed. The exhaust waste heat at the outlet of the gas turbine turbine is used to drive the turbine in the supercritical carbon dioxide cycle, and the heat of the exhaust gas after heat regeneration in the supercritical carbon dioxide cycle is used to drive the absorption refrigeration cycle. The cold generated by the refrigeration cycle is used in turn for pre-cooling the air at the gas turbine inlet and the main compressor of the supercritical carbon dioxide cycle. The proposed combined cycle system realizes the cascade utilization of low-temperature cold sources and high-temperature heat sources, improves the thermodynamic performance of the total cycle system, and at the same time avoids the decline in system performance caused by too high an ambient temperature, broadening the stable operating condition range of the system.

[0010] The object of the present invention is achieved through the following technical solutions. A combined cycle system based on the waste heat pre-cooling of the gas turbine in the supercritical carbon dioxide cycle includes a top cycle gas turbine power generation system I, an intermediate cycle supercritical carbon dioxide power generation system II, and a bottom cycle absorption refrigeration cycle pre-cooling system III, where,

[0011] The top cycle gas turbine power generation system I includes a pre-cooler X, a gas turbine compressor M, a gas turbine combustion chamber L, a gas turbine turbine J, a waste heat boiler heat exchanger I, an intermediate heat exchanger D, and a generator Q connected in sequence;

[0012] The intermediate cycle supercritical carbon dioxide power generation system II includes a main compressor A, a low-temperature recuperator B, an intermediate heat exchanger D, a recompression compressor C, a high-temperature recuperator E, a waste heat boiler heat exchanger I, a high-pressure turbine F, a low-pressure turbine G, a cooler Y, and a pre-cooler V connected in sequence;

[0013] The bottom-cycle absorption refrigeration cycle precooling system Ⅲ includes a solution pump N, an absorber O, a throttle valve P, a solution heat exchanger R, a generator Q, a condenser S, an expansion valve T, an evaporator U, a solution pump W, a precooler V, and a precooler X connected in sequence, where;

[0014] In the top-cycle gas turbine power generation system Ⅰ, air is cooled by the precooler X and then enters the gas turbine compressor M for pressurization, mixes with gaseous fuel, and enters the combustion chamber L for combustion. The high-temperature and high-pressure gas after combustion enters the gas turbine J of the gas turbine for expansion work. The high-temperature waste heat tail gas sequentially enters the waste heat boiler heat exchanger I, the intermediate heat exchanger D, and the generator Q to release heat, and then is discharged into the atmosphere;

[0015] In the intermediate-cycle supercritical carbon dioxide power generation system Ⅱ, the working fluid is compressed and pressurized by the main compressor A, absorbs heat in the low-temperature recuperator B, then enters the intermediate heat exchanger D to absorb heat, mixes with the fluid of the recompression compressor C, enters the high-temperature recuperator E for heat regeneration, and then absorbs heat once through the waste heat boiler heat exchanger I to become a high-temperature and high-pressure fluid. The high-temperature and high-pressure fluid expands and does work through the high-pressure turbine F, then enters the waste heat boiler heat exchanger I to absorb heat again. The reheated fluid expands and does work through the low-pressure turbine G. After doing work, compared with the high-temperature and high-pressure fluid, the low-temperature and high-pressure fluid sequentially passes through the high-temperature recuperator E, the low-temperature recuperator B, and the generator Q to release heat, and then a part of the fluid is cooled by the cooler Y and the precooler V and enters the main compressor A, and another part of the fluid enters the recompression compressor C;

[0016] In the bottom-cycle absorption refrigeration cycle precooling system Ⅲ, the refrigerant is condensed and liquefied by the condenser S, enters the evaporator U through the expansion valve T. The refrigerant in the evaporator U is absorbed by the absorbent in the absorber O, gasifies into a saturated concentrated solution, and provides cold energy to the precooler X in the top-cycle gas turbine power generation system Ⅰ and the precooler V in the intermediate-cycle supercritical carbon dioxide power generation system Ⅱ. The concentrated solution is pressurized by the solution pump N and absorbs heat in the solution heat exchanger R and is transported to the generator Q. The concentrated solution in the generator Q is heated to boiling by the waste heat in the top-cycle gas turbine power generation system Ⅰ and the intermediate-cycle supercritical carbon dioxide power generation system Ⅱ to generate refrigerant vapor. The refrigerant vapor enters the condenser S, and the concentrated solution formed in the generator Q releases heat through the heat exchanger R and is depressurized by the throttle valve P and enters the absorber O.

[0017] In the combined cycle system for precooling the waste heat of the gas turbine based on the supercritical carbon dioxide cycle, the cold-end outlet of the precooler X is connected to the inlet of the gas turbine compressor M, the outlet of the gas turbine compressor M is connected to the inlet of the combustion chamber L, the outlet of the combustion chamber L is connected to the inlet of the gas turbine J of the gas turbine, the outlet of the gas turbine J of the gas turbine is connected to the tail gas inlet of the waste heat boiler heat exchanger I, the tail gas outlet of the waste heat boiler heat exchanger I is connected to the hot-end inlet of the intermediate heat exchanger D, and the cold-end outlet of the intermediate heat exchanger D is connected to the heating-end inlet of the generator Q.

[0018] In the combined cycle system for pre-cooling the waste heat of a gas turbine based on a supercritical carbon dioxide cycle, the outlet of the main compressor A is connected to the inlet of the cold end of the low-temperature recuperator B, the outlet of the hot end of the low-temperature recuperator B is connected to the inlet of the cold end of the intermediate heat exchanger D, the outlet of the recompression compressor C is connected to the outlet of the hot end of the intermediate heat exchanger D and the inlet of the cold end of the high-temperature recuperator E, the outlet of the cold end of the high-temperature recuperator E is connected to the inlet of the hot end of the low-temperature recuperator B, the outlet of the hot end of the high-temperature recuperator E is connected to the inlet of the primary hot end of the waste heat boiler heat exchanger I, the outlet of the primary cold end of the waste heat boiler heat exchanger I is connected to the inlet of the high-pressure turbine F, the outlet of the high-pressure turbine F is connected to the inlet of the secondary hot end of the waste heat boiler heat exchanger I, the outlet of the secondary hot end of the waste heat boiler heat exchanger I is connected to the inlet of the low-pressure turbine G, the outlet of the low-pressure turbine G is connected to the inlet of the hot end of the high-temperature recuperator E, the outlet of the cold end of the low-temperature recuperator B is connected to the inlet of the hot end of the generator Q, the outlet of the cold end of the generator Q is connected to the inlet of the recompression compressor C and the inlet of the hot end of the cooler Y, the outlet of the cold end of the cooler Y is connected to the inlet of the hot end of the pre-cooler V, and the outlet of the cold end of the pre-cooler V is connected to the inlet of the main compressor A.

[0019] In the combined cycle system for pre-cooling the waste heat of a gas turbine based on a supercritical carbon dioxide cycle, the vapor outlet of the generator Q is connected to the inlet of the condenser S, the outlet of the concentrated solution of the generator Q is connected to the inlet of the hot end of the solution heat exchanger R, the outlet of the hot end of the solution heat exchanger R is connected to the inlet of the dilute solution of the generator Q, the outlet of the cold end of the solution heat exchanger R is connected to the inlet of the throttle valve P, the outlet of the solution pump N is connected to the inlet of the cold end of the solution heat exchanger R, the refrigerant inlet of the hot end of the evaporator U is connected to the outlet of the expansion valve T, the refrigerant outlet of the cold end of the evaporator U is connected to the vapor inlet of the absorber O, the cooling water inlet of the hot end of the evaporator U is connected to the outlet of the solution pump W, the cooling water outlet of the cold end of the pre-cooler V is connected to the inlet of the solution pump W, the outlet of the throttle valve P is connected to the inlet of the concentrated solution of the absorber O, and the outlet of the absorber O is connected to the inlet of the solution pump N.

[0020] In the combined cycle system for pre-cooling the waste heat of a gas turbine based on a supercritical carbon dioxide cycle, the main compressor A, the recompression compressor C, the high-pressure turbine F, and the low-pressure turbine G are coaxially connected and connected to the generator H through a coupling.

[0021] In the combined cycle system for pre-cooling the waste heat of a gas turbine based on a supercritical carbon dioxide cycle, the gas turbine compressor M and the gas turbine turbine J are coaxially connected and connected to the generator K through a coupling.

[0022] In the combined cycle system for pre-cooling the waste heat of a gas turbine based on a supercritical carbon dioxide cycle, the evaporator U in the bottom cycle absorption refrigeration cycle pre-cooling system III provides cooling capacity and exchanges heat with the pre-cooler X in the top cycle gas turbine power generation system I and the pre-cooler V in the intermediate cycle supercritical carbon dioxide power generation system II in sequence. The gas turbine inlet temperature is constantly maintained at 15 °C, and the main compressor inlet temperature in the intermediate cycle supercritical carbon dioxide power generation system is maintained at 32 °C.

[0023] In the combined cycle system for pre-cooling the waste heat of a gas turbine based on a supercritical carbon dioxide cycle, the top cycle gas turbine power generation system I and the intermediate cycle supercritical carbon dioxide power generation system II provide heat to the generator Q in the bottom cycle absorption refrigeration cycle pre-cooling system III. The low-pressure high-temperature fluid serves as the waste heat source, and its temperature is between 100 °C and 200 °C.

[0024] In the combined cycle system for pre-cooling the waste heat of a gas turbine based on a supercritical carbon dioxide cycle, the top cycle gas turbine power generation system I provides heat to the waste heat boiler heat exchanger I in the intermediate cycle supercritical carbon dioxide power generation system II. The high-temperature waste heat tail gas serves as the waste heat source, and its temperature is 500 °C.

[0025] In the combined cycle system for pre-cooling the waste heat of a gas turbine based on a supercritical carbon dioxide cycle, the working medium of the top cycle gas turbine power generation system I is carbon dioxide, and the entire cycle process is in a supercritical state.

[0026] In this article, the low-pressure high-temperature fluid refers to a fluid with relatively lower pressure and relatively higher temperature compared with the high-pressure high-temperature fluid, and the dilute solution is a solution with a lower concentration than the saturated concentrated solution.

[0027] Compared with the prior art, the present invention has the following advantages:

[0028] The invention utilizes the waste heat of the gas turbine to be used for power generation in the carbon dioxide cycle in sequence, and the waste heat of a lower grade is used for refrigeration. The generated cooling capacity is used for pre-cooling the gas turbine compressor and the carbon dioxide cycle compressor, solving the problem that the conventional cycle system is easily affected by environmental temperature changes. It can achieve that the gas turbine inlet temperature is constantly maintained at about 15 °C, and the main compressor inlet temperature in the intermediate cycle supercritical carbon dioxide power generation system is maintained at about 32 °C. It not only fully utilizes the waste heat in the gas turbine system without increasing its additional system energy consumption, but also improves the thermal efficiency and stability of the combined cycle system. Brief Description of the Drawings

[0029] Upon reading the detailed description of the preferred specific embodiments below, various other advantages and benefits of the present invention will become apparent to those of ordinary skill in the art. The accompanying drawings are only for the purpose of illustrating the preferred embodiments and are not considered to be a limitation of the present invention. Obviously, the drawings described below are only some embodiments of the present invention, and those of ordinary skill in the art can obtain other drawings based on these drawings without creative efforts. Moreover, throughout the drawings, the same reference numerals are used to denote the same components.

[0030] In the drawings:

[0031] Figure 1 is a schematic diagram of the modules of a combined cycle system for pre-cooling the waste heat of a gas turbine based on a supercritical carbon dioxide cycle according to an embodiment of the present invention;

[0032] Figure 2 is a schematic diagram of a combined cycle system for pre-cooling the waste heat of a gas turbine based on a supercritical carbon dioxide cycle according to an embodiment of the present invention;

[0033] Figure 3 is a temperature-entropy diagram of a combined cycle system for pre-cooling the waste heat of a gas turbine based on a supercritical carbon dioxide cycle according to an embodiment of the present invention;

[0034] Among them, the label names are: Ⅰ Top cycle gas turbine power generation system; Ⅱ Intermediate cycle supercritical carbon dioxide power generation system; Ⅲ Bottom cycle absorption refrigeration cycle precooling system; A Main compressor; B Low-temperature recuperator; C Recompression compressor; D Intermediate heat exchanger; E High-temperature recuperator; F High-pressure turbine; G Low-pressure turbine; H Generator; I Waste heat boiler heat exchanger; J Gas turbine; K Generator; L Gas turbine combustion chamber; M Gas turbine compressor; N Solution pump; O Absorber; P Throttle valve; Q Generator; R Solution heat exchanger; S Condenser; T Expansion valve; U Evaporator; V Precooler; W Solution pump; X Precooler; Y Cooler; 1' Precooler inlet; 2' Gas turbine compressor inlet; 3' Burner air inlet; 4' Gas turbine inlet; 5' Waste heat boiler heat exchanger inlet; 6' Hot end inlet of the intermediate heat exchanger; 7' Hot end inlet of the generator; 8' Ambient air inlet; 1 Main compressor inlet; 2 Cold end inlet of the low-temperature recuperator; 3 Confluence point; 3a Cold end inlet of the intermediate heat exchanger; 3b Recompression compressor outlet; 4 Primary hot end inlet of the waste heat boiler heat exchanger; 5 High-pressure turbine inlet; 6 Secondary hot end inlet of the waste heat boiler heat exchanger; 7 Low-pressure turbine inlet; 9 Hot end inlet of the low-temperature recuperator; 8 Hot end inlet of the high-temperature recuperator; 10 Generator inlet; 11 Diverging point; 11a Hot end inlet of the cooler; 11b Recompression compressor inlet; 12 Hot end inlet of the precooler; 01 Hot end inlet of the condenser; 02 Expansion valve inlet; 03 Hot end refrigerant inlet of the evaporator; 04 Cold end refrigerant inlet of the absorber; 05 Solution pump inlet; 06 Cold end inlet of the solution heat exchanger; 07 Dilute solution inlet of the generator; 08 Hot end inlet of the solution heat exchanger; 09 Throttle valve inlet; 010 Concentrated solution inlet of the absorber; 011 Normal temperature cooling water inlet; 012 Normal temperature cooling water outlet; 013 Low temperature cooling water inlet; 014 Low temperature cooling water outlet; 015 Low temperature cooling water inlet of the precooler; 016 Solution pump inlet; 017 Normal temperature cooling water inlet; 018 Normal temperature cooling water outlet.

[0035] The present invention will be further explained below in conjunction with the accompanying drawings and embodiments. Specific embodiments

[0036] The following will refer to the attached Figures 1 to 3 The specific embodiments of the present invention will be described in more detail. Although specific embodiments of the present invention are shown in the drawings, it should be understood that the present invention can be implemented in various forms and should not be limited by the embodiments set forth herein. On the contrary, these embodiments are provided so that the present invention can be more thoroughly understood and the scope of the present invention can be fully conveyed to those skilled in the art.

[0037] It should be noted that in the description of the specification and claims, certain terms are used to refer to specific components. Those skilled in the art should understand that technicians may use different terms to refer to the same component. The specification and claims do not use the difference in terms as a way to distinguish components, but use the difference in the functions of components as the criterion for distinction. For example, the terms "comprising" or "including" mentioned throughout the specification and claims are open-ended terms, so they should be interpreted as "including but not limited to". The subsequent description in the specification is the preferred embodiment for implementing the present invention, but the description is for the purpose of the general principles of the specification and does not limit the scope of the present invention. The protection scope of the present invention shall be subject to what is defined by the appended claims.

[0038] For the convenience of understanding the embodiments of the present invention, the following will further explain with specific embodiments in conjunction with the drawings, and each drawing does not constitute a limitation to the embodiments of the present invention.

[0039] For better understanding, as Figures 1 to 2 shown, the combined cycle system for pre-cooling the waste heat of a gas turbine based on a supercritical carbon dioxide cycle includes a top cycle gas turbine power generation system I, an intermediate cycle supercritical carbon dioxide power generation system II, and a bottom cycle absorption refrigeration cycle pre-cooling system III; the top cycle gas turbine power generation system includes a pre-cooler X, a gas turbine compressor M, a gas turbine combustion chamber L, a gas turbine turbine J, a waste heat boiler heat exchanger I, an intermediate heat exchanger D, and a generator Q connected in sequence; the intermediate cycle supercritical carbon dioxide power generation system includes a main compressor A, a low-temperature recuperator B, an intermediate heat exchanger D, a recompression compressor C, a high-temperature recuperator E, a waste heat boiler heat exchanger I, a high-pressure turbine F, a low-pressure turbine G, a cooler Y, and a pre-cooler V connected in sequence; the bottom cycle absorption refrigeration cycle pre-cooling system includes a solution pump N, an absorber O, a throttle valve P, a solution heat exchanger R, a generator Q, a condenser S, an expansion valve T, an evaporator U, a solution pump W, a pre-cooler V, and a pre-cooler X connected in sequence.

[0040] The cold end outlet of the pre-cooler X is connected to the inlet of the gas turbine compressor M, the outlet of the gas turbine compressor M is connected to the inlet of the combustion chamber L, the outlet of the combustion chamber L is connected to the inlet of the gas turbine turbine J, the outlet of the gas turbine turbine J is connected to the tail gas inlet of the waste heat boiler heat exchanger I, the tail gas outlet of the waste heat boiler heat exchanger I is connected to the hot end inlet of the intermediate heat exchanger D, and the cold end outlet of the intermediate heat exchanger D is connected to the heating end inlet of the generator Q.

[0041] The outlet of the main compressor A is connected to the inlet of the cold end of the low-temperature recuperator B. The outlet of the hot end of the low-temperature recuperator B is connected to the inlet of the cold end of the intermediate heat exchanger D. The outlet of the recompression compressor C is connected to the outlet of the hot end of the intermediate heat exchanger D and the inlet of the cold end of the high-temperature recuperator E. The outlet of the cold end of the high-temperature recuperator E is connected to the inlet of the hot end of the low-temperature recuperator B. The outlet of the hot end of the high-temperature recuperator E is connected to the inlet of the primary hot end of the waste heat boiler heat exchanger I. The outlet of the primary cold end of the waste heat boiler heat exchanger I is connected to the inlet of the high-pressure turbine F. The outlet of the high-pressure turbine F is connected to the inlet of the secondary hot end of the waste heat boiler heat exchanger I. The outlet of the secondary hot end of the waste heat boiler heat exchanger I is connected to the inlet of the low-pressure turbine G. The outlet of the low-pressure turbine G is connected to the inlet of the hot end of the high-temperature recuperator E. The outlet of the cold end of the low-temperature recuperator B is connected to the inlet of the hot end of the generator Q. The outlet of the cold end of the generator Q is connected to the inlet of the recompression compressor C and the inlet of the hot end of the cooler Y. The outlet of the cold end of the cooler Y is connected to the inlet of the hot end of the precooler V. The outlet of the cold end of the precooler V is connected to the inlet of the main compressor A.

[0042] The vapor outlet of the generator Q is connected to the inlet of the condenser S. The outlet of the concentrated solution of the generator Q is connected to the inlet of the hot end of the solution heat exchanger R. The outlet of the hot end of the solution heat exchanger R is connected to the inlet of the dilute solution of the generator Q. The outlet of the cold end of the solution heat exchanger R is connected to the inlet of the throttle valve P. The outlet of the solution pump N is connected to the inlet of the cold end of the solution heat exchanger R. The refrigerant inlet of the hot end of the evaporator U is connected to the outlet of the expansion valve T. The refrigerant outlet of the cold end of the evaporator U is connected to the vapor inlet of the absorber O. The cooling water inlet of the hot end of the evaporator U is connected to the outlet of the solution pump W. The cooling water outlet of the cold end of the precooler V is connected to the inlet of the solution pump W. The outlet of the throttle valve P is connected to the inlet of the concentrated solution of the absorber O. The outlet of the absorber O is connected to the inlet of the solution pump N;

[0043] The main compressor A, the recompression compressor C, the high-pressure turbine F, and the low-pressure turbine G are coaxially connected and connected to the generator H through a coupling; the gas turbine compressor M and the gas turbine J are coaxially connected and connected to the generator K through a coupling.

[0044] The evaporator U in the bottom-cycle absorption refrigeration cycle precooling system provides cooling capacity and exchanges heat with the precooler X in the top-cycle gas turbine power generation system and the precooler V in the intermediate-cycle supercritical carbon dioxide power generation system in sequence; the gas turbine inlet temperature is kept constant at about 15 °C, and the main compressor inlet temperature in the intermediate-cycle supercritical carbon dioxide power generation system is kept at about 32 °C.

[0045] The top-cycle gas turbine power generation system and the intermediate-cycle supercritical carbon dioxide power generation system provide heat for the generator Q in the bottom-cycle absorption refrigeration cycle precooling system, and the waste heat source temperature is between 100 °C and 200 °C;

[0046] The top - cycle gas turbine power generation system provides heat for the heat - recovery boiler heat exchanger I in the intermediate - cycle supercritical carbon dioxide power generation system, and the temperature of the heat source is about 500 °C.

[0047] In one embodiment, the circulating working fluid of the main - cycle power generation system is carbon dioxide, and the whole cycle process is in a supercritical state.

[0048] In one embodiment, the low - pressure high - temperature supercritical carbon dioxide fluid sequentially passes through the high - temperature recuperator, the low - temperature recuperator, and the generator to release heat. Then, a part of the supercritical carbon dioxide fluid enters the main compressor after being cooled by the cooler and the precooler, and another part of the supercritical carbon dioxide fluid enters the recompression compressor. The refrigerant is condensed and liquefied through the condenser and enters the evaporator through the expansion valve.

[0049] In one embodiment, water is used as the absorbent and ammonia water is used as the refrigerant, or water is used as the refrigerant and lithium bromide is used as the absorbent in the bottom - cycle indirect - cooling system, and the temperature of the generated cooling water is about 0 °C.

[0050] In one embodiment, in a combined cycle system for pre-cooling the waste heat of a gas turbine based on a supercritical carbon dioxide cycle, the air at ambient temperature in the topping cycle gas turbine power generation system is cooled by the pre-cooler X, then enters the gas turbine compressor M for pressurization and is mixed with gaseous fuel at the burner air inlet 3' and enters the combustion chamber L for combustion. The high-temperature and high-pressure gas after combustion enters the gas turbine J for expansion work. The high-temperature waste heat tail gas enters the waste heat boiler heat exchanger I, the intermediate heat exchanger D, and the generator Q in sequence to release heat, and then is discharged into the atmosphere. In the intermediate cycle supercritical carbon dioxide power generation system, the working fluid is compressed and pressurized by the main compressor A, absorbs heat through the low-temperature recuperator B, then enters the intermediate heat exchanger D to absorb heat and is mixed with the fluid of the recompression compressor C and then enters the high-temperature recuperator E for heat regeneration. Then, it absorbs heat once through the waste heat boiler heat exchanger I, and the high-temperature and high-pressure fluid formed expands and does work through the high-pressure turbine F. Then, it absorbs heat again through the waste heat boiler heat exchanger I. The reheated fluid expands and does work through the low-pressure turbine G. The fluid with lower pressure and higher temperature after doing work releases heat in sequence through the high-temperature recuperator E, the low-temperature recuperator B, and the generator Q, and then a part of the fluid enters the main compressor A after being cooled by the cooler Y and the pre-cooler V, and another part of the fluid enters the recompression compressor C. In the bottom cycle absorption refrigeration cycle pre-cooling system, the refrigerant is condensed and liquefied by the condenser S and enters the evaporator U through the expansion valve T. The refrigerant in the evaporator U is absorbed by the absorbent in the absorber O and gasifies into a saturated state to provide cooling capacity for the pre-cooler X in the topping cycle gas turbine power generation system and the pre-cooler V in the intermediate cycle supercritical carbon dioxide power generation system. The concentrated solution formed in the absorber O is pressurized by the solution pump N and absorbs heat through the solution heat exchanger R and is transported to the generator Q. The concentrated solution in the generator Q is heated to boiling by the waste heat in the topping cycle gas turbine power generation system and the intermediate cycle supercritical carbon dioxide power generation system. The pure refrigerant vapor generated enters the condenser S, and the concentrated solution formed in the generator Q releases heat through the heat exchanger R and is depressurized by the throttle valve P and enters the absorber O.

[0051] In one embodiment, the air at ambient temperature in the topping cycle gas turbine power generation system Ⅰ is cooled by the pre-cooler X, from the pre-cooler inlet 1' to the gas turbine compressor inlet 2', enters the gas turbine compressor for pressurization through the gas turbine compressor inlet 2' and is mixed with gaseous fuel at the burner air inlet 3' and enters the combustion chamber for combustion. The high-temperature and high-pressure gas after combustion enters the gas turbine J for expansion work through the gas turbine inlet 4'. The high-temperature waste heat tail gas enters the waste heat boiler heat exchanger, the intermediate heat exchanger, and the generator in sequence through the waste heat boiler heat exchanger inlet 5', the hot end inlet 6' of the intermediate heat exchanger, and the hot end inlet 7' of the generator to release heat, and then is discharged into the atmosphere through the ambient air inlet 8'.

[0052] In one embodiment, in the intermediate cycle supercritical carbon dioxide power generation system, the low-temperature and low-pressure carbon dioxide passes through the main compressor inlet 1, is compressed and pressurized by the main compressor, absorbs heat through the cold end inlet 2 of the low-temperature recuperator, then enters the intermediate heat exchanger through the cold end inlet 3a of the intermediate heat exchanger to absorb heat, mixes with the fluid of the recompression compressor at the confluence point 3, and then enters the high-temperature recuperator for heat regeneration. Then, it enters the primary heat end inlet of the waste heat boiler heat exchanger to absorb heat in the waste heat boiler heat exchanger once, and the high-temperature and high-pressure carbon dioxide fluid thus formed passes through the high-pressure turbine inlet 5, expands and does work through the high-pressure turbine, then enters the secondary heat end inlet of the waste heat boiler heat exchanger to absorb heat in the waste heat boiler heat exchanger twice. The reheated carbon dioxide fluid passes through the low-pressure turbine inlet 7, expands and does work through the low-pressure turbine. The carbon dioxide fluid with lower pressure and higher temperature after doing work passes through the high-temperature recuperator heat end inlet 8, the low-temperature recuperator heat end inlet 9, and the generator inlet 10 in sequence, releases heat through the high-temperature recuperator, the low-temperature recuperator, and the generator, and then a part of the carbon dioxide fluid passes through the cooler heat end inlet 11a to the cooler and the pre-cooler heat end inlet 12 to the pre-cooler at the shunt point 11, is cooled, and enters the main compressor through the main compressor inlet 1. Another part of the carbon dioxide fluid enters the recompression compressor through the recompression compressor inlet 11b at the shunt point 11.

[0053] In one embodiment, taking lithium bromide solution as the absorbent and water as the refrigerant as an example for the working mode of the bottom cycle absorption refrigeration cycle pre-cooling system, the dilute lithium bromide solution formed in the absorber passes through the solution pump inlet 05, is pressurized by the solution pump, absorbs heat through the cold end inlet 06 of the solution heat exchanger, and is transported to the generator through the dilute solution inlet 07 of the generator. The dilute solution in the generator is heated to boiling by the waste heat of the top cycle and intermediate cycle power generation systems to generate pure water vapor, which enters the condenser through the condenser heat end inlet 01 and releases heat to the environment. The refrigerant water after releasing heat passes through the expansion valve inlet 02, is depressurized by the expansion valve, and enters the evaporator through the evaporator heat end refrigerant inlet 03. The water in the evaporator is absorbed by the lithium bromide solution in the absorber through the absorber cold end refrigerant inlet 04, is vaporized into a saturated state, and provides cooling capacity to generate low-temperature cooling water. The generated low-temperature cooling water is used in sequence to pre-cool the top cycle gas turbine inlet and the intermediate cycle main compressor inlet (014 - 015 - 016). After the cooling water is heated, it passes through the solution pump inlet 05, is pressurized by the solution pump, and then enters the evaporator through the low-temperature cooling water inlet 013 to complete the pre-cooling process. The remaining concentrated lithium bromide solution in the generator releases heat through the solution heat exchanger hot end inlet 08 to the solution heat exchanger, is depressurized through the throttle valve inlet 09 by the throttle valve, and returns to the absorber through the absorber concentrated solution inlet 10.

[0054] From Figure 3It can be seen that the numbers represent the circulating flow paths of the fluid. As the fluid circulates in the top-cycle gas turbine power generation system I, the intermediate-cycle supercritical carbon dioxide power generation system II, and the bottom-cycle absorption refrigeration cycle pre-cooling system III, the waste heat in the supercritical carbon dioxide cycle system is fully utilized. Not only is the waste heat in the gas turbine system fully utilized without increasing its additional system energy consumption, but also the thermal efficiency and stability of the combined cycle system are improved.

[0055] Although the embodiments of the present invention have been described above in conjunction with the accompanying drawings, the present invention is not limited to the above specific embodiments and application fields. The above specific embodiments are merely illustrative and guiding, rather than restrictive. Those of ordinary skill in the art can also make many forms under the inspiration of this specification and without departing from the scope protected by the claims of the present invention, and these all fall within the scope of protection of the present invention.

Claims

1. A combined cycle system for pre-cooling the waste heat of a gas turbine based on a supercritical carbon dioxide cycle, characterized in that, it includes a top cycle gas turbine power generation system, an intermediate cycle supercritical carbon dioxide power generation system, and a bottom cycle absorption refrigeration cycle pre-cooling system, wherein, the top cycle gas turbine power generation system includes a pre-cooler X, a gas turbine compressor M, a gas turbine combustion chamber L, a gas turbine turbine J, a waste heat boiler heat exchanger I, an intermediate heat exchanger D, and a generator Q connected in sequence; the intermediate cycle supercritical carbon dioxide power generation system includes a main compressor A, a low-temperature recuperator B, an intermediate heat exchanger D, a recompression compressor C, a high-temperature recuperator E, a waste heat boiler heat exchanger I, a high-pressure turbine F, a low-pressure turbine G, a cooler Y, and a pre-cooler V connected in sequence; the bottom cycle absorption refrigeration cycle pre-cooling system includes a solution pump N, an absorber O, a throttle valve P, a solution heat exchanger R, a generator Q, a condenser S, an expansion valve T, an evaporator U, a solution pump W, a pre-cooler V, and a pre-cooler X connected in sequence, where; in the top cycle gas turbine power generation system, air is cooled by the pre-cooler X, then enters the gas turbine compressor M for pressurization and is mixed with gaseous fuel and enters the combustion chamber L for combustion. The high-temperature and high-pressure gas after combustion enters the gas turbine turbine J for expansion work. The high-temperature waste heat tail gas enters the waste heat boiler heat exchanger I, the intermediate heat exchanger D, and the generator Q in sequence to release heat, and then is discharged into the atmosphere; in the intermediate cycle supercritical carbon dioxide power generation system, the working fluid is compressed and pressurized by the main compressor A, absorbs heat through the low-temperature recuperator B, then enters the intermediate heat exchanger D to absorb heat and is mixed with the fluid of the recompression compressor C and then enters the high-temperature recuperator E for heat recovery, and then passes through the waste heat boiler heat exchanger I to absorb heat once to become a high-temperature and high-pressure fluid. The high-temperature and high-pressure fluid expands and does work through the high-pressure turbine F, and then enters the waste heat boiler heat exchanger I to absorb heat twice, the reheated fluid expands and does work through the low-pressure turbine G. After doing work, compared with the high-temperature and high-pressure fluid, the low-pressure and high-temperature fluid passes through the high-temperature recuperator E, the low-temperature recuperator B, and the generator Q in sequence to release heat, and then a part of the fluid is cooled by the cooler Y and the pre-cooler V and enters the main compressor A, and another part of the fluid enters the recompression compressor C; in the bottom cycle absorption refrigeration cycle pre-cooling system, the refrigerant is condensed and liquefied by the condenser S and enters the evaporator U through the expansion valve T. The refrigerant in the evaporator U is absorbed by the absorbent in the absorber O and gasifies into a saturated concentrated solution and provides cooling capacity to the pre-cooler X in the top cycle gas turbine power generation system and the pre-cooler V in the intermediate cycle supercritical carbon dioxide power generation system. The concentrated solution is pressurized by the solution pump N and absorbs heat through the solution heat exchanger R and is transported to the generator Q. The concentrated solution in the generator Q is heated to boiling by the waste heat in the top cycle gas turbine power generation system and the intermediate cycle supercritical carbon dioxide power generation system to generate refrigerant vapor. The refrigerant vapor enters the condenser S, and the concentrated solution formed in the generator Q releases heat through the heat exchanger R and is depressurized by the throttle valve P and enters the absorber O.

2. The combined cycle system for pre-cooling the waste heat of a gas turbine based on a supercritical carbon dioxide cycle according to claim 1, wherein, The cold end outlet of the precooler X is connected to the inlet of the gas turbine compressor M. The outlet of the gas turbine compressor M is connected to the inlet of the combustion chamber L. The outlet of the combustion chamber L is connected to the inlet of the gas turbine J. The outlet of the gas turbine J is connected to the tail gas inlet of the waste heat boiler heat exchanger I. The tail gas outlet of the waste heat boiler heat exchanger I is connected to the hot end inlet of the intermediate heat exchanger D. The cold end outlet of the intermediate heat exchanger D is connected to the heating end inlet of the generator Q.

3. The combined cycle system for pre-cooling the waste heat of a gas turbine based on a supercritical carbon dioxide cycle according to claim 1, wherein, The outlet of the main compressor A is connected to the cold end inlet of the low-temperature recuperator B. The hot end outlet of the low-temperature recuperator B is connected to the cold end inlet of the intermediate heat exchanger D. The outlet of the recompression compressor C is connected to the hot end outlet of the intermediate heat exchanger D and the cold end inlet of the high-temperature recuperator E. The cold end outlet of the high-temperature recuperator E is connected to the hot end inlet of the low-temperature recuperator B. The hot end outlet of the high-temperature recuperator E is connected to the primary hot end inlet of the waste heat boiler heat exchanger I. The primary cold end outlet of the waste heat boiler heat exchanger I is connected to the inlet of the high-pressure turbine F. The outlet of the high-pressure turbine F is connected to the secondary hot end inlet of the waste heat boiler heat exchanger I. The secondary hot end outlet of the waste heat boiler heat exchanger I is connected to the inlet of the low-pressure turbine G. The outlet of the low-pressure turbine G is connected to the hot end inlet of the high-temperature recuperator E. The cold end outlet of the low-temperature recuperator B is connected to the hot end inlet of the generator Q. The cold end outlet of the generator Q is connected to the inlet of the recompression compressor C and the hot end inlet of the cooler Y. The cold end outlet of the cooler Y is connected to the hot end inlet of the precooler V. The cold end outlet of the precooler V is connected to the inlet of the main compressor A.

4. The combined cycle system for pre-cooling the waste heat of a gas turbine based on a supercritical carbon dioxide cycle according to claim 1, wherein, The vapor outlet of the generator Q is connected to the inlet of the condenser S. The outlet of the concentrated solution of the generator Q is connected to the hot end inlet of the solution heat exchanger R. The hot end outlet of the solution heat exchanger R is connected to the dilute solution inlet of the generator Q. The cold end outlet of the solution heat exchanger R is connected to the inlet of the throttle valve P. The outlet of the solution pump N is connected to the cold end inlet of the solution heat exchanger R. The hot end refrigerant inlet of the evaporator U is connected to the outlet of the expansion valve T. The cold end refrigerant outlet of the evaporator U is connected to the vapor inlet of the absorber O. The hot end cooling water inlet of the evaporator U is connected to the outlet of the solution pump W. The cold end cooling water outlet of the precooler V is connected to the inlet of the solution pump W. The outlet of the throttle valve P is connected to the concentrated solution inlet of the absorber O. The outlet of the absorber O is connected to the inlet of the solution pump N.

5. The combined cycle system for pre-cooling the waste heat of a gas turbine based on a supercritical carbon dioxide cycle according to claim 1, wherein, The main compressor A, the recompression compressor C, the high-pressure turbine F, and the low-pressure turbine G are coaxially connected and connected to the generator H through a coupling.

6. The combined cycle system for pre-cooling the waste heat of a gas turbine based on a supercritical carbon dioxide cycle according to claim 1, wherein, The gas turbine compressor M and the gas turbine J are coaxially connected and connected to the generator K through a coupling.

7. The combined cycle system for pre-cooling the waste heat of a gas turbine based on a supercritical carbon dioxide cycle according to claim 1, Among them, the evaporator U in the bottom cycle absorption refrigeration cycle pre-cooling system Ⅲ provides cooling capacity and exchanges heat with the pre-cooler X in the top cycle gas turbine power generation system and the pre-cooler V in the intermediate cycle supercritical carbon dioxide power generation system in sequence. The gas turbine inlet temperature is constantly maintained at 15 °C, and the main compressor inlet temperature in the intermediate cycle supercritical carbon dioxide power generation system is maintained at 32 °C.

8. The combined cycle system for pre-cooling the waste heat of a gas turbine based on a supercritical carbon dioxide cycle according to claim 1, Among them, the top cycle gas turbine power generation system and the intermediate cycle supercritical carbon dioxide power generation system provide heat to the generator Q in the bottom cycle absorption refrigeration cycle pre-cooling system. The low-pressure high-temperature fluid serves as the waste heat source, and its temperature is between 100 °C and 200 °C.

9. The combined cycle system for pre-cooling the waste heat of a gas turbine based on a supercritical carbon dioxide cycle according to claim 1, Among them, the top cycle gas turbine power generation system provides heat to the waste heat boiler heat exchanger I in the intermediate cycle supercritical carbon dioxide power generation system. The high-temperature waste heat tail gas serves as the waste heat source, and its temperature is 500 °C.

10. The combined cycle system for pre-cooling the waste heat of a gas turbine based on a supercritical carbon dioxide cycle according to claim 1, Among them, the working medium of the top cycle gas turbine power generation system is carbon dioxide, and the entire cycle process is in a supercritical state.

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