Combined cycle heat recovery system and method

Abstract

The present invention relates to the field of power generation technology and discloses a combined cycle heat recovery system and method. The combined cycle heat recovery system includes a gas turbine, a waste heat boiler, a steam turbine, a first heat exchanger and a second heat exchanger. The gas turbine is provided with a first pipeline, the waste heat boiler is connected to the gas turbine, the waste heat boiler is provided with a second pipeline, the steam turbine is connected to the waste heat boiler, the first heat exchanger is connected to the first pipeline and the second pipeline, the hot gas in the first pipeline and the hot water in the second pipeline are heat exchanged in the first heat exchanger, the second heat exchanger is connected to the waste heat boiler, the second pipeline and the steam turbine, and is suitable for exchanging heat between the flue gas in the waste heat boiler and the hot water in the second pipeline in the second heat exchanger. By arranging the first heat exchanger and the second heat exchanger, the present invention can accelerate the heating of the working medium water in the waste heat boiler into steam suitable for driving the steam turbine, shorten the startup time of the combined cycle unit, quickly increase the output of the gas turbine to its rated load, and improve the power generation efficiency.

Description

Technical Field

[0001] The present invention relates to the technical field of power generation, and in particular to a combined cycle heat recovery system and method. Background Art

[0002] In combined cycle power generation, the exhaust gas discharged by the gas turbine is introduced into the waste heat boiler, and the waste heat boiler is used for heat exchange to generate steam to drive the steam turbine. This can recycle the heat in the combined cycle and improve power generation efficiency.

[0003] When the combined cycle is started, the power generation load changes dramatically. When the high-temperature exhaust gas discharged from the gas turbine is introduced into the waste heat boiler, the large amount of heat in the exhaust gas may cause the heat exchanger pipes in the waste heat boiler to rupture, affecting the life of the waste heat boiler heat exchanger components. In addition, the temperature of the various components of the steam turbine is often low during the startup process. If the temperature of the steam introduced into the steam turbine is too high, it will cause strain damage to the turbine components.

[0004] In the existing technology, the method of suppressing the output power of the gas turbine while controlling the waiting time for steam generation in the waste heat boiler and the gradient of the steam parameter increase of the steam turbine is usually adopted to protect the waste heat boiler and the steam turbine. However, this working mode will cause the combined cycle unit to require a longer startup time before the output of the gas turbine can be increased to its rated load, thereby affecting the power generation efficiency. Summary of the Invention

[0005] In view of this, the present invention provides a combined cycle heat recovery system and method to solve the problem that the combined cycle unit has a long startup time and affects the power generation efficiency.

[0006] In a first aspect, the present invention provides a combined cycle heat recovery system, comprising:

[0007] A gas turbine, wherein the gas turbine is provided with a first pipeline suitable for outputting hot gas in the gas turbine;

[0008] a waste heat boiler connected to the gas turbine, wherein the waste heat boiler is provided with a second pipeline adapted to output hot water;

[0009] a steam turbine connected to the waste heat boiler;

[0010] a first heat exchanger connected to the first pipeline and the second pipeline, wherein the hot gas in the first pipeline and the hot water in the second pipeline exchange heat in the first heat exchanger;

[0011] The second heat exchanger is connected to the waste heat boiler, the second pipeline and the steam turbine, and is suitable for exchanging heat between the flue gas in the waste heat boiler and the hot water in the second pipeline in the second heat exchanger.

[0012] Beneficial effect: When the gas turbine is started, the flue gas output from the gas turbine exchanges heat in the waste heat boiler to heat the working medium water in the waste heat boiler, and the hot water with a lower temperature in the waste heat boiler is input into the second pipeline. When the gas turbine is working, the hot gas in the gas turbine is input into the first heat exchanger for heat exchange with the hot water in the second pipeline, and part of the flue gas in the waste heat boiler is introduced into the second heat exchanger for heat exchange with the hot water again, so that the hot water is heated to low-temperature steam and then input into the waste heat boiler for heat exchange with the flue gas. The steam temperature after heat exchange is increased and is used to drive the steam turbine to generate electricity. The hot gas temperature after heat exchange in the first pipeline is reduced and can be input into the gas turbine again to participate in work. By setting the first heat exchanger and the second heat exchanger, the working medium water in the waste heat boiler can be heated to steam suitable for driving the steam turbine to operate faster, thereby shortening the startup time of the combined cycle unit, and can quickly increase the output of the gas turbine to its rated load, thereby improving the power generation efficiency.

[0013] In an optional embodiment, the gas turbine includes:

[0014] fuel lines;

[0015] outer box;

[0016] A compressor is disposed in the outer box, and the first pipeline connects the outer box and the compressor;

[0017] A turbine is arranged in the outer box and connected to the compressor and the waste heat boiler. The fuel pipeline is arranged between the compressor and the turbine.

[0018] Beneficial effect: When the gas turbine is working, the heat generated will be transferred to the outer box. By setting a first pipeline to connect the outer box and the compressor, the hot air in the outer box can be input into the first pipeline. The heat of the hot air is used to exchange heat with the hot water in the second pipeline, which can speed up the increase of the temperature of the working water and shorten the time to generate high-temperature steam to drive the turbine to generate electricity. The air with a lower temperature after heat exchange can be input into the compressor again to participate in combustion.

[0019] In an optional embodiment, the gas turbine further comprises:

[0020] a bypass line connecting the compressor and the turbine and adapted to cool the turbine;

[0021] The third heat exchanger is connected to the second pipeline, the turbine and the steam turbine, and is suitable for exchanging heat between the hot gas after cooling the turbine and the hot water in the second pipeline in the third heat exchanger.

[0022] Beneficial effect: By setting up a bypass pipeline, part of the low-temperature compressed air compressed in the compressor can be input into the turbine to cool the turbine impeller. The compressed air after cooling the impeller does not merge with the flue gas, but flows out from the outlet of the cooling chamber. The air temperature rises and can be input into the third heat exchanger to exchange heat with hot water again, further increasing the temperature of the hot water.

[0023] In an optional embodiment, the method further includes:

[0024] The fourth heat exchanger is connected to the second pipeline and the fuel pipeline.

[0025] Beneficial effect: By providing the fourth heat exchanger, the heat of the hot water in the second pipeline can be used to heat the fuel in the fuel pipeline.

[0026] In an optional embodiment, the waste heat boiler includes:

[0027] A flue is arranged on a side of the waste heat boiler close to the gas turbine, the flue is connected to the turbine and the second heat exchanger, and the flue gas is led out from the flue bypass by adjusting a flue gas damper.

[0028] Beneficial effect: The flue gas generated by the gas turbine is transported to the waste heat boiler through the flue. By introducing part of the flue gas into the second heat exchanger through the flue, the heat in the flue gas can be used to heat the hot water in the second pipeline to increase its temperature.

[0029] In an optional embodiment, the steam turbine comprises:

[0030] An intermediate pressure cylinder connected to the waste heat boiler;

[0031] The high-pressure cylinder is connected to the waste heat boiler, the second heat exchanger and the fourth heat exchanger.

[0032] Beneficial effect: The compressed air after heat exchange in the second heat exchanger and the flue gas after heat exchange in the fourth heat exchanger are input into the high-pressure cylinder to preheat the high-pressure cylinder.

[0033] In an optional embodiment, the waste heat boiler includes:

[0034] a fifth heat exchanger, disposed in the waste heat boiler, the fifth heat exchanger being connected to the high-pressure cylinder;

[0035] a sixth heat exchanger, disposed in the waste heat boiler, the sixth heat exchanger being connected to the intermediate pressure cylinder and the second pipeline;

[0036] a seventh heat exchanger, disposed in the waste heat boiler;

[0037] A steam drum is arranged in the waste heat boiler, and the steam drum is connected to the second pipeline and the seventh heat exchanger.

[0038] Beneficial effects: The fifth heat exchanger heats the working water into high-temperature and high-pressure steam, which is used to flush the high-pressure cylinder to generate electricity. The hot water with increased temperature after heat exchange in the second pipeline flows back to the sixth heat exchanger to exchange heat with the flue gas again, generating medium-temperature and medium-pressure steam, which is used to flush the medium-pressure cylinder to generate electricity. The seventh heat exchanger uses the waste heat in the flue gas to heat the working water and inputs the hot water into the second pipeline through the steam drum.

[0039] In an optional embodiment, the high-pressure cylinder includes:

[0040] The outer shell is arranged outside the high-pressure cylinder, and the third heat exchanger and the second heat exchanger are connected to the outer shell.

[0041] Beneficial effect: The compressed air after heat exchange in the second heat exchanger and the flue gas after heat exchange in the fourth heat exchanger are input into the outer shell to preheat the inside of the outer shell, reduce the temperature difference between the rotor inside the high-pressure cylinder and the outer shell, and avoid damage to the rotor due to the large temperature difference between the inside and outside of the rotor when the high-pressure cylinder is running.

[0042] In an optional embodiment, the method further includes:

[0043] The separator is arranged on the second pipeline and located between the third heat exchanger and the second heat exchanger.

[0044] Beneficial effect: By setting up a separator, the hot water and steam in the working water after heat exchange in the third heat exchanger can be separated, the separated steam enters the second heat exchanger to continue heat exchange, and the separated hot water flows back to the second pipeline for further heat exchange.

[0045] In a second aspect, the present invention further provides a combined cycle heat recovery method, using the above-mentioned combined cycle heat recovery system, the heat recovery method comprises:

[0046] Supply working water to the waste heat boiler to ensure that the waste heat boiler can output sufficient working water to the second pipeline and then start the gas turbine;

[0047] During the load increase phase of the gas turbine, after reaching the initial load, the heat in the gas turbine is input into the first heat exchanger for heat exchange with the second pipeline to heat the working medium water in the second pipeline;

[0048] When the gas turbine continues to increase its load from the initial load, the flue gas in the waste heat boiler is input into the second heat exchanger, so that the second heat exchanger exchanges heat with the second pipeline, and the working medium water after heat exchange is input into the waste heat boiler and heated again to steam;

[0049] When the gas turbine reaches rated load, the steam turbine operates at sliding pressure, and the second pipeline inputs steam to the steam turbine to generate electricity.

[0050] Because the combined cycle heat recovery method adopts the combined cycle heat recovery system and has the same effect as the combined cycle heat recovery system, it will not be described in detail here. BRIEF DESCRIPTION OF THE DRAWINGS

[0051] In order to more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the specific embodiments or the description of the prior art. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0052] Figure 1 is a schematic diagram of a combined cycle heat recovery system according to an embodiment of the present invention;

[0053] Figure 2 The figure is a flow chart of a combined cycle heat recovery system according to an embodiment of the present invention.

[0054] Description of reference numerals:

[0055] 1. Gas turbine; 101. First pipeline; 102. Fuel pipeline; 103. External tank; 104. Compressor; 105. Turbine; 106. Bypass pipeline; 107. First pump; 108. Second pump; 109. Bleeding device;

[0056] 2. Waste heat boiler; 201. Second pipeline; 202. Flue; 203. Fifth heat exchanger; 204. Sixth heat exchanger; 205. Seventh heat exchanger; 206. Steam drum; 207. Third pump; 208. Fourth pump; 209. Fifth pump;

[0057] 3. Steam turbine; 301. Intermediate pressure cylinder; 302. High pressure cylinder; 3021. Casing;

[0058] 4. First heat exchanger;

[0059] 5. Second heat exchanger;

[0060] 6. The third heat exchanger;

[0061] 7. Fourth heat exchanger;

[0062] 8. Separator. DETAILED DESCRIPTION

[0063] To make the purpose, technical solutions, and advantages of the embodiments of the present invention more clear, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without making creative efforts shall fall within the scope of protection of the present invention.

[0064] The following combination Figure 1 and Figure 2 , describing embodiments of the present invention.

[0065] According to an embodiment of the present invention, on the one hand, a combined cycle heat recovery system is provided, such as Figure 1 As shown, it includes a gas turbine 1, a waste heat boiler 2, a steam turbine 3, a first heat exchanger 4 and a second heat exchanger 5. The gas turbine 1 is provided with a first pipeline 101, which is suitable for outputting hot gas in the gas turbine 1. The waste heat boiler 2 is connected to the gas turbine 1. The waste heat boiler 2 is provided with a second pipeline 201, which is suitable for outputting hot water. The steam turbine 3 is connected to the waste heat boiler 2. The first heat exchanger 4 is connected to the first pipeline 101 and the second pipeline 201. The hot gas in the first pipeline 101 and the hot water in the second pipeline 201 are heat exchanged in the first heat exchanger 4. The second heat exchanger 5 is connected to the waste heat boiler 2, the second pipeline 201 and the steam turbine 3, and is suitable for exchanging heat between the flue gas in the waste heat boiler 2 and the hot water in the second pipeline 201 in the second heat exchanger 5.

[0066] Specifically, in this embodiment, a combined cycle unit is formed between the gas turbine 1, the waste heat boiler 2 and the steam turbine 3. The gas turbine 1 drives the generator to generate electricity, and the waste heat boiler 2 uses the flue gas of the gas turbine 1 to heat the working medium water into steam, and then uses the steam to drive the steam turbine 3 to generate electricity.

[0067] When the gas turbine 1 is started, the flue gas output from the gas turbine 1 exchanges heat in the waste heat boiler 2, heating the working medium water in the waste heat boiler 2. The hot water with a lower temperature in the waste heat boiler 2 is input into the second pipeline 201. When the gas turbine 1 is operating, the hot gas in the gas turbine 1 is input into the first heat exchanger 4 for heat exchange with the hot water in the second pipeline 201. Part of the flue gas in the waste heat boiler 2 is introduced into the second heat exchanger 5 for further heat exchange with the hot water. The hot water is heated to low-temperature steam and then input into the waste heat boiler 2 for heat exchange with the flue gas. The temperature of the steam after heat exchange is increased and used to drive the steam turbine 3 to generate electricity. The temperature of the hot gas after heat exchange in the first pipeline 101 is reduced and can be input into the gas turbine 1 again to participate in the operation. By providing the first heat exchanger 4 and the second heat exchanger 5, the working medium water in the waste heat boiler 2 can be heated to steam suitable for driving the steam turbine 3 more quickly, thereby shortening the startup time of the combined cycle unit, quickly increasing the output of the gas turbine 1 to its rated load, and improving power generation efficiency.

[0068] In one embodiment, the gas turbine 1 includes a fuel pipeline 102, an outer box 103, a compressor 104 and a turbine 105. The compressor 104 is arranged in the outer box 103. The first pipeline 101 connects the outer box 103 and the compressor 104. The turbine 105 is arranged in the outer box 103 and is connected to the compressor 104 and the waste heat boiler 2. The fuel pipeline 102 is arranged between the compressor 104 and the turbine 105.

[0069] Specifically, in this embodiment, the compressor 104 is provided with an air inlet device 109 for pressurizing the air entering the compressor 104. The first pipeline 101 is provided with a first pump 107 for pumping the hot air in the outer box 103 to the first heat exchanger 4.

[0070] When the gas turbine 1 is working, the heat generated will be transferred to the outer box 103. By setting a first pipeline 101 to connect the outer box 103 and the compressor 104, the hot air in the outer box 103 can be input into the first pipeline 101. The heat of the hot air is used to exchange heat with the hot water in the second pipeline 201, which can accelerate the increase of the temperature of the working water and shorten the time to generate high-temperature steam to drive the steam turbine 3 to operate and generate electricity. The air with a lower temperature after heat exchange can be input into the compressor 104 again to participate in combustion.

[0071] In one embodiment, the gas turbine 1 further includes a bypass line 106 and a third heat exchanger 6. The bypass line 106 connects the compressor 104 and the turbine 105, and is suitable for cooling the turbine 105. The third heat exchanger 6 is connected to the second line 201, the turbine 105 and the steam turbine 3, and is suitable for exchanging heat between the hot gas after cooling the turbine 105 and the hot water in the second line 201 in the third heat exchanger 6.

[0072] Specifically, in this embodiment, a second pump 108 is provided between the turbine 105 and the third heat exchanger 6 for transporting the hot air after cooling the blades of the turbine 105 to the second heat exchanger 5 .

[0073] By setting up a bypass line 106, part of the low-temperature compressed air compressed in the compressor 104 can be input into the turbine 105 to cool the impeller of the turbine 105. The compressed air after cooling the blades does not merge with the flue gas, but flows out from the outlet of the cooling chamber. The air temperature increases and can be input into the third heat exchanger 6 to exchange heat with hot water again, thereby further increasing the temperature of the hot water.

[0074] In one embodiment, a fourth heat exchanger 7 connected to the second pipeline 201 and the fuel pipeline 102 is further included.

[0075] Specifically, in this embodiment, the first heat exchanger 4 , the second heat exchanger 5 , and the third heat exchanger 6 are gas-water heat exchangers, and the fourth heat exchanger 7 is a steam-gas heat exchanger.

[0076] By providing the fourth heat exchanger 7 , the heat of the hot water in the second pipeline 201 can be used to heat the fuel in the fuel pipeline 102 .

[0077] In one embodiment, the waste heat boiler 2 includes a flue 202 arranged on a side of the waste heat boiler 2 close to the gas turbine 1. The flue 202 is connected to the turbine 105 and the second heat exchanger 5. The flue gas is led out from the flue bypass by adjusting the flue gas damper.

[0078] Specifically, in this embodiment, a third pump 207 is provided between the flue 202 and the second heat exchanger 5 for transporting the flue gas in the flue 202 to the second heat exchanger 5 .

[0079] The flue gas generated by the gas turbine 1 is transported to the waste heat boiler 2 through the flue 202. By introducing part of the flue gas into the second heat exchanger 5 through the flue 202, the flue gas entering the waste heat boiler 2 is reduced, avoiding the waste heat boiler 2 from rapidly inputting a large amount of heat energy, thereby preventing problems such as thermal overload and pipeline damage. The heat in the flue gas is used to heat the hot water in the second pipeline 201, raising its temperature to generate steam as quickly as possible, thereby shortening the unit startup time.

[0080] In one embodiment, the steam turbine 3 includes an intermediate pressure cylinder 301 and a high pressure cylinder 302 . The intermediate pressure cylinder 301 is connected to the waste heat boiler 2 , and the high pressure cylinder 302 is connected to the waste heat boiler 2 , the second heat exchanger 5 , and the fourth heat exchanger 7 .

[0081] The compressed air after heat exchange in the second heat exchanger 5 and the flue gas after heat exchange in the fourth heat exchanger 7 are input into the high-pressure cylinder 302 to preheat the high-pressure cylinder 302.

[0082] In one embodiment, the waste heat boiler 2 includes a fifth heat exchanger 203, a sixth heat exchanger 204, a seventh heat exchanger 205 and a steam drum 206. The fifth heat exchanger 203 is arranged in the waste heat boiler 2, and the fifth heat exchanger 203 is connected to the high-pressure cylinder 302. The sixth heat exchanger 204 is arranged in the waste heat boiler 2, and the sixth heat exchanger 204 is connected to the medium-pressure cylinder 301 and the second pipeline 201. The seventh heat exchanger 205 is arranged in the waste heat boiler 2, and the steam drum 206 is arranged in the waste heat boiler 2, and the steam drum 206 is connected to the second pipeline 201 and the seventh heat exchanger 205.

[0083] Specifically, in this embodiment, the fifth heat exchanger 203 is a superheater, the sixth heat exchanger 204 is a reheater, and the seventh heat exchanger 205 is a medium- and low-pressure heat exchanger. The superheater, reheater, and medium- and low-pressure heat exchangers are arranged in sequence along the direction in which the flue gas enters the waste heat boiler 2. The reheater can absorb part of the heat in the flue gas to prevent the flue gas from being too hot when the load of the gas turbine 1 increases, and the temperature difference between the inside and outside of the superheater is large, thereby preventing the superheater from being damaged.

[0084] In this embodiment, a fourth pump 208 is further provided on the second pipeline 201 and is located between the first heat exchanger 4 and the seventh heat exchanger 205 , wherein the fourth pump 208 can be a booster water pump.

[0085] In this embodiment, a fifth pump 209 connected to the seventh heat exchanger 205 is further provided for supplying water to the seventh heat exchanger 205 .

[0086] The fifth heat exchanger 203 heats the working water into high-temperature and high-pressure steam, which is used to drive the high-pressure cylinder 302 to operate and generate electricity. The hot water with a higher temperature after heat exchange in the second pipeline 201 flows back to the sixth heat exchanger 204 to exchange heat with the flue gas again, generating medium-temperature and medium-pressure steam, which is used to drive the medium-pressure cylinder 301 to operate and generate electricity. The seventh heat exchanger 205 uses the waste heat in the flue gas to heat the working water and inputs the hot water into the second pipeline 201 through the steam drum 206.

[0087] In one embodiment, the high-pressure cylinder 302 includes a shell 3021 disposed outside the high-pressure cylinder 302 , and the third heat exchanger 6 and the second heat exchanger 5 are connected to the shell 3021 .

[0088] Specifically, in this embodiment, the outer shell 3021 can play a role in heat preservation of the cylinder installed inside.

[0089] The compressed air after heat exchange in the second heat exchanger 5 and the flue gas after heat exchange in the fourth heat exchanger 7 are input into the outer shell 3021 to preheat the cylinder body in the outer shell 3021, thereby reducing the temperature difference between the rotor and the cylinder body inside the high-pressure cylinder 302, and avoiding damage to the rotor due to the large temperature difference between the rotor and the cylinder body when the high-pressure cylinder 302 is running.

[0090] In one embodiment, the separator 8 is further included and is arranged on the second pipeline 201 and is located between the third heat exchanger 6 and the second heat exchanger 5 .

[0091] Specifically, in this embodiment, the separator 8 is a steam-water separator.

[0092] By setting up the separator 8, the hot water and steam in the working water after heat exchange in the third heat exchanger 6 can be separated, the separated steam enters the second heat exchanger 5 to continue heat exchange, and the separated hot water flows back to the second pipeline 201 for further heat exchange.

[0093] According to an embodiment of the present invention, on the other hand, a combined cycle heat recovery method is provided. The combined cycle heat recovery system of this embodiment is used. Figure 2 As shown, the heat recovery method includes:

[0094] Supply working medium water to the waste heat boiler 2 to ensure that the waste heat boiler 2 can output sufficient working medium water to the second pipeline 201 and then start the gas turbine 1;

[0095] Specifically, during the startup phase of the gas turbine 1 , a rated feedwater flow rate is set for the fifth pump 209 to ensure that the hot water flow rate drawn from the steam drum 206 is sufficient to supply the working medium of the waste heat boiler 2 .

[0096] During the load increase phase of the gas turbine 1, after reaching the initial load, the heat in the gas turbine 1 is input into the first heat exchanger 4 for heat exchange with the second pipeline 201, thereby heating the working medium water in the second pipeline 201;

[0097] Specifically, during the load increase stage of the gas turbine 1, after reaching the initial load (generally 20-40% of the rated load), the first pump 107 is turned on to extract the hot air from the outer box 103 of the gas turbine 1 to the first heat exchanger 4, heat the hot water in the second pipeline 201, and input the hot water into the separator 8 to wait for the hot water to reach saturation and vaporize into steam. At the same time, the low-temperature air compressed in the compressor 104 is input into the turbine 105 to cool the blades of the turbine 105. The cooled gas is high-temperature air with a certain pressure. The high-temperature air is input into the third heat exchanger 6 through the second pump 108 to exchange heat with the hot water in the second pipeline 201.

[0098] When the gas turbine 1 continues to increase its load from the initial load, the flue gas in the waste heat boiler 2 is input to the second heat exchanger 5, so that the second heat exchanger 5 exchanges heat with the second pipeline 201, and the working medium water after heat exchange is input to the waste heat boiler 2 for further heat exchange into steam;

[0099] Specifically, when the gas turbine 1 continues to increase its load from the initial load, part of the flue gas in the flue 202 is pumped into the second heat exchanger 5 by the third pump 207 for further heat exchange.

[0100] When the gas turbine 1 reaches rated load, the steam turbine 3 operates at sliding pressure, and the second pipeline 201 inputs steam to the steam turbine 3 to drive the steam turbine 3 to generate electricity.

[0101] Specifically, when the gas turbine 1 reaches the rated load, the steam turbine 3 operates at sliding pressure. When the steam at the outlet of the high-pressure cylinder 302 of the steam turbine 3 does not reach the rated parameters due to the thermal lag effect, the second pipeline 201 can provide reheated steam with qualified parameters to the fifth heat exchanger 203 of the waste heat boiler 2, and heat it to supersaturated steam to start the medium-pressure cylinder 301 of the steam turbine 3, thereby optimizing the startup of the unit.

[0102] Although the embodiments of the present invention have been described with reference to the accompanying drawings, those skilled in the art may make various modifications and variations without departing from the spirit and scope of the present invention. Such modifications and variations are all within the scope defined by the appended claims.

Claims

1. A combined cycle heat recovery system, characterized in that: include: A gas turbine (1), wherein the gas turbine (1) is provided with a first pipeline (101), the first pipeline (101) being suitable for outputting hot gas in the gas turbine (1); A waste heat boiler (2) is connected to the gas turbine (1), and a second pipeline (201) is provided on the waste heat boiler (2), and the second pipeline (201) is suitable for outputting hot water; A steam turbine (3) connected to the waste heat boiler (2); a first heat exchanger (4) connected to the first pipeline (101) and the second pipeline (201), wherein the hot gas in the first pipeline (101) and the hot water in the second pipeline (201) exchange heat in the first heat exchanger (4); a second heat exchanger (5) connected to the waste heat boiler (2), the second pipeline (201) and the steam turbine (3), and adapted to exchange heat between the flue gas in the waste heat boiler (2) and the hot water in the second pipeline (201) in the second heat exchanger (5); The gas turbine (1) comprises a fuel pipeline (102), an outer box (103), a compressor (104), a turbine (105) and a bypass pipeline (106); a fourth heat exchanger (7) is connected to the second pipeline (201) and the fuel pipeline (102); the compressor (104) is arranged in the outer box (103); the first pipeline (101) connects the outer box (103) and the compressor (104); the turbine (105) is arranged in the outer box (103) and is connected to the compressor (104) and the waste heat boiler (2); the fuel pipeline (102) is arranged between the compressor (104) and the turbine (105); the bypass pipeline (106) connects the compressor (104) and the turbine (105) and is suitable for cooling the turbine (105); The waste heat boiler (2) comprises a flue (202), a fifth heat exchanger (203), a sixth heat exchanger (204), a seventh heat exchanger (205), and a steam drum (206); the flue (202) is arranged on a side of the waste heat boiler (2) close to the gas turbine (1); the flue (202) is connected to the turbine (105) and the second heat exchanger (5); the fifth heat exchanger (203) is arranged in the waste heat boiler (2); the sixth heat exchanger (204) is arranged in the waste heat boiler (2); the seventh heat exchanger (205) is arranged in the waste heat boiler (2); the steam drum (206) is arranged in the waste heat boiler (2); and the steam drum (206) is connected to the second pipeline (201) and the seventh heat exchanger (205); The steam turbine (3) comprises an intermediate-pressure cylinder (301) and a high-pressure cylinder (302), wherein the intermediate-pressure cylinder (301) is connected to the waste heat boiler (2), the sixth heat exchanger (204) is connected to the intermediate-pressure cylinder (301) and the second pipeline (201), the high-pressure cylinder (302) is connected to the waste heat boiler (2), the second heat exchanger (5) and the fourth heat exchanger (7), and the fifth heat exchanger (203) is connected to the high-pressure cylinder (302).

2. The combined cycle heat recovery system according to claim 1, characterized in that: The gas turbine (1) further comprises: The third heat exchanger (6) is connected to the second pipeline (201), the turbine (105) and the steam turbine (3), and is suitable for exchanging heat between the hot gas after cooling the turbine (105) and the hot water in the second pipeline (201) in the third heat exchanger (6).

3. The combined cycle heat recovery system according to claim 2, characterized in that: The high-pressure cylinder (302) comprises: The outer shell (3021) is arranged outside the high-pressure cylinder (302), and the third heat exchanger (6) and the second heat exchanger (5) are connected to the outer shell (3021).

4. The combined cycle heat recovery system according to claim 3, characterized in that: Also includes: The separator (8) is arranged on the second pipeline (201) and is located between the third heat exchanger (6) and the second heat exchanger (5).

5. A combined cycle heat recovery method, characterized in that: Using the combined cycle heat recovery system according to any one of claims 1 to 4, the heat recovery method includes: Supplying working fluid water into the waste heat boiler (2) to ensure that the waste heat boiler (2) can output a sufficient amount of working fluid water to the second pipeline (201) and then start the gas turbine (1); During the load increase phase of the gas turbine (1), after reaching the initial load, heat in the gas turbine (1) is input into the first heat exchanger (4) and exchanged with the second pipeline (201) to heat the working medium water in the second pipeline (201); When the gas turbine (1) continues to increase its load from the initial load, the flue gas in the waste heat boiler (2) is input into the second heat exchanger (5), so that the second heat exchanger (5) exchanges heat with the second pipeline (201), and the working medium water after heat exchange is input into the waste heat boiler (2) to be heated again into steam; When the gas turbine (1) reaches rated load operation, the steam turbine (3) operates at sliding pressure, and the second pipeline (201) inputs steam to the steam turbine (3) to drive the steam turbine (3) to generate electricity.

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