Quick start system and method for combined cycle units of decoupled steam turbine

Abstract

Disclosed in the present invention are a quick start system and method for combined cycle units of a decoupled steam turbine. The quick start system comprises a heat storage system, a waste heat boiler, a steam turbine power generation system, and a gas turbine power generation system, wherein an outlet of the gas turbine power generation system is in communication with an inlet of the waste heat boiler, and the waste heat boiler is connected to the heat storage system and the steam turbine power generation system. The system and method can improve the efficiency and flexibility of power generation of the units and prevent the problem of the emission of excess pollutants caused by insufficient combustion.

Description

A fast start-up system and method for a combined cycle unit with decoupled steam turbine Technical Field

[0001] This invention belongs to the field of power generation technology and relates to a rapid start-up system and method for a combined cycle unit with decoupled steam turbine. Background Technology

[0002] With the increasing penetration rate of renewable energy, its inherent intermittent and volatile characteristics pose significant challenges to the flexibility of power system regulation. Compared with conventional coal-fired units, gas-fired combined cycle units have become the primary choice for flexible power regulation due to their advantages such as rapid start-up and shutdown, high cycle efficiency, low pollutant emissions, and good peak-shaving performance. Following the principle of energy cascade utilization, gas turbines are typically combined with waste heat boilers and steam turbines to form combined cycle units, thereby improving energy utilization efficiency.

[0003] During the startup of a gas-steam combined cycle unit, the gas turbine can quickly ignite, accelerate, and connect to the grid. However, the waste heat boiler and steam turbine, limited by the thermal stress of the metal equipment, cannot achieve rapid startup and require a significant amount of warm-up time. In particular, the steam turbine rotor is more sensitive to thermal stress, making the excessively long startup time due to steam turbine warm-up a major factor limiting the startup speed of gas-steam combined cycle units. While waiting for the steam turbine to warm up, the gas turbine needs to operate under low-load conditions for an extended period. This not only reduces the unit's power generation efficiency but also leads to incomplete combustion resulting in excessive pollutant emissions and reduced unit flexibility. Summary of the Invention

[0004] The purpose of this invention is to overcome the shortcomings of the prior art and provide a fast start-up system and method for a combined cycle unit with decoupled steam turbine. This system and method can improve the power generation efficiency and flexibility of the unit, while avoiding excessive pollutant emissions caused by incomplete combustion.

[0005] To achieve the above objectives, the present invention discloses a rapid start-up system for a combined cycle unit with decoupled steam turbine, comprising a thermal storage system, a waste heat boiler, a steam turbine power generation system, and a gas turbine power generation system, wherein the outlet of the gas turbine power generation system is connected to the inlet of the waste heat boiler, and the waste heat boiler is connected to the thermal storage system and the steam turbine power generation system.

[0006] The waste heat boiler includes a flue gas outlet, a high-pressure subsystem, a reheat subsystem, a medium-pressure subsystem, and a low-pressure subsystem; the steam turbine power generation system includes a high-pressure feedwater inlet, a medium-pressure feedwater inlet, a high-pressure cylinder, a medium-pressure cylinder, and a low-pressure cylinder.

[0007] The outlet of the gas turbine power generation system is connected to the flue gas outlet via the shell side of the high-pressure subsystem, the shell side of the reheat subsystem, the shell side of the medium-pressure subsystem, and the shell side of the low-pressure subsystem in sequence.

[0008] The high-pressure water inlet is connected to the inlet of the high-pressure cylinder via the pipe side of the high-pressure subsystem and the third valve, and the heat storage system is connected in parallel with the third valve;

[0009] The medium-pressure water inlet is connected to the outlet of the high-pressure cylinder via a pipe through the pipe side of the medium-pressure subsystem, and then connected to the inlet of the medium-pressure cylinder via the pipe side of the reheat subsystem. The outlet of the medium-pressure cylinder is connected to the inlet of the low-pressure cylinder. The low-pressure water inlet is connected to the inlet of the low-pressure cylinder via the pipe side of the low-pressure subsystem, and the outlet of the low-pressure cylinder is connected to the exhaust pipe of the low-pressure cylinder.

[0010] The thermal storage system includes a heat release water inlet, a heat release water outlet, a thermal storage drainage outlet, a first molten salt-water heat exchanger, a second molten salt-water heat exchanger, a third molten salt-water heat exchanger, a high-temperature molten salt pump, a high-temperature molten salt tank, a low-temperature molten salt pump, and a low-temperature molten salt tank.

[0011] The heat release feedwater inlet is connected to the primary side inlet of the first molten salt-water heat exchanger, and the primary side outlet of the first molten salt-water heat exchanger is connected to the heat release feedwater outlet;

[0012] The secondary outlet of the first molten salt-water heat exchanger is connected to the secondary inlet of the first molten salt-water heat exchanger via a low-temperature molten salt tank, a low-temperature molten salt pump, the primary side of the third molten salt-water heat exchanger and the primary side of the second molten salt-water heat exchanger, a high-temperature molten salt tank and a high-temperature molten salt pump.

[0013] The high-pressure water inlet is split into two paths after passing through the pipe side of the high-pressure subsystem. One path is connected to the inlet of the high-pressure cylinder via the third valve, and the second path is connected to the secondary side inlet of the second molten salt-water heat exchanger. The secondary side outlet of the second molten salt-water heat exchanger is split into two paths. One path is connected to the inlet of the high-pressure cylinder, and the other path is connected to the heat storage drainage outlet via the secondary side of the third molten salt-water heat exchanger.

[0014] The secondary outlet of the first molten salt-water heat exchanger is connected to the secondary inlet of the first molten salt-water heat exchanger via the sixth valve, the cryogenic molten salt tank, the cryogenic molten salt pump, the primary side of the third molten salt-water heat exchanger and the primary side of the second molten salt-water heat exchanger, the first valve, the high-temperature molten salt tank and the high-temperature molten salt pump.

[0015] The high-pressure feedwater inlet is split into two paths after passing through the pipe side of the high-pressure subsystem. One path is connected to the inlet of the high-pressure cylinder via the third valve, and the second path is connected to the secondary side inlet of the second molten salt-water heat exchanger via the second valve. The secondary side outlet of the second molten salt-water heat exchanger is split into two paths. One path is connected to the inlet of the high-pressure cylinder via the fourth valve, and the other path is connected to the heat storage drainage outlet via the fifth valve and the secondary side of the third molten salt-water heat exchanger.

[0016] The high-pressure cylinder, intermediate-pressure cylinder, low-pressure cylinder, and second generator are arranged coaxially.

[0017] A gas turbine power generation system includes fuel pipelines, a compressor, a combustion chamber, and a turbine. The compressor outlet and fuel pipelines are connected to the combustion chamber inlet, and the combustion chamber outlet is connected to the turbine inlet. The turbine outlet passes sequentially through the shell side of the high-pressure subsystem.

[0018] It also includes a first generator, and the turbine, compressor and first generator are arranged coaxially.

[0019] The rapid start-up method for a combined cycle turbine unit with decoupled steam turbines as described in this invention includes:

[0020] 1) The steam generation parameters of the waste heat boiler did not meet the conditions for turbine warm-up;

[0021] 2) The steam generation parameters of the waste heat boiler meet the conditions for turbine warm-up;

[0022] 3) The steam turbine warm-up process is complete;

[0023] 4) Heat release from the thermal storage system.

[0024] Specifically, the following steps are included:

[0025] 1) The steam generation parameters of the waste heat boiler did not meet the conditions for turbine warm-up;

[0026] Start the cryogenic molten salt pump and shut down the high-temperature molten salt pump. The cryogenic molten salt is discharged from the cryogenic molten salt tank through the cryogenic molten salt pump and then passes through the third molten salt-water heat exchanger and the second molten salt-water heat exchanger in sequence before being transported to the high-temperature molten salt tank. The high-temperature and high-pressure main steam is output from the high-pressure subsystem, and then exchanges heat with the molten salt through the second molten salt-water heat exchanger and the third molten salt-water heat exchanger before being discharged from the heat storage drain outlet.

[0027] 2) The steam generation parameters of the waste heat boiler meet the conditions for turbine warm-up;

[0028] Start the cryogenic molten salt pump and shut down the high-temperature molten salt pump. The cryogenic molten salt is discharged from the cryogenic molten salt tank through the cryogenic molten salt pump and then passes through the third molten salt-water heat exchanger and the second molten salt-water heat exchanger in sequence before being transported to the high-temperature molten salt tank. The high-temperature and high-pressure main steam is output from the high-pressure subsystem, and then passes through the second molten salt-water heat exchanger and the third molten salt-water heat exchanger in sequence to exchange heat with the molten salt before being discharged from the heat storage drain outlet.

[0029] 3) The steam turbine warm-up process is complete;

[0030] Once the steam turbine warm-up process is complete, the high-temperature molten salt pump and the low-temperature molten salt pump will be shut down, and the thermal storage system will stop operating.

[0031] 4) Heat release from the thermal storage system;

[0032] When the combined cycle unit needs heat, the high-temperature molten salt pump is started and the low-temperature molten salt pump is turned off. The high-temperature molten salt is discharged from the high-temperature molten salt tank through the low-temperature molten salt pump and then passes through the first molten salt-water heat exchanger before being transported to the high-temperature molten salt tank. The feedwater enters the first molten salt-water heat exchanger from the heat release feedwater inlet and is heated into high-temperature and high-pressure steam, and then discharged from the heat release feedwater outlet.

[0033] The present invention has the following beneficial effects:

[0034] In practical operation, the decoupled steam turbine combined cycle unit rapid start-up system and method described in this invention utilizes thermal storage technology to decouple the steam turbine start-up process. The gas turbine and waste heat boiler start up normally to full load. In the initial stage of start-up, when the steam produced by the waste heat boiler has not yet reached the steam turbine warm-up steam parameters, the produced steam is stored by the thermal storage system. As the start-up process progresses, when the steam produced by the waste heat boiler exceeds the steam turbine warm-up steam parameters, the produced steam is first diverted, cooled, and depressurized through the thermal storage system before entering the steam turbine for warm-up. After warm-up is completed, the thermal storage system stops operating, and the combined cycle unit operates normally. The heat stored in the thermal storage system can be released reasonably according to the subsequent application scenarios to improve energy utilization efficiency, enhance the unit's efficiency and flexibility, and avoid excessive pollutant emissions caused by incomplete combustion. Attached Figure Description

[0035] The accompanying drawings, which form part of this specification, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an undue limitation of the invention. In the drawings:

[0036] Figure 1 is a structural diagram of the present invention.

[0037] Wherein, 1 is the first generator, 2 is the compressor, 3 is the combustion chamber, 4 is the turbine, 5 is the high-pressure subsystem, 6 is the reheat subsystem, 7 is the medium-pressure subsystem, 8 is the low-pressure subsystem, 9 is the flue gas outlet, 10 is the high-pressure feedwater inlet, 11 is the medium-pressure feedwater inlet, 12 is the low-pressure feedwater inlet, 13 is the high-pressure cylinder, 14 is the medium-pressure cylinder, 15 is the low-pressure cylinder, 16 is the low-pressure cylinder exhaust pipe, 17 is the second generator, and 18 is the heat release feedwater. Inlet, 19 is the first molten salt-water heat exchanger, 20 is the heat release feedwater outlet, 21 is the high-temperature molten salt pump, 22 is the high-temperature molten salt tank, 23 is the first valve, 24 is the second valve, 25 is the third valve, 26 is the second molten salt-water heat exchanger, 27 is the fourth valve, 28 is the fifth valve, 29 is the third molten salt-water heat exchanger, 30 is the heat storage drainage outlet, 31 is the low-temperature molten salt pump, 32 is the low-temperature molten salt tank, and 33 is the sixth valve. Detailed Implementation

[0038] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0039] In the description of this invention, it should be understood that the terms "comprising" and "including" indicate the presence of the described features, integrals, steps, operations, elements and / or components, but do not exclude the presence or addition of one or more other features, integrals, steps, operations, elements, components and / or collections thereof.

[0040] It should also be understood that the terminology used in this specification is for the purpose of describing particular embodiments only and is not intended to limit the invention. As used in this specification and the appended claims, the singular forms “a,” “an,” and “the” are intended to include the plural forms unless the context clearly indicates otherwise.

[0041] It should also be further understood that the term "and / or" as used in this specification and the appended claims refers to any combination and all possible combinations of one or more of the associated listed items, and includes such combinations. For example, A and / or B can represent three cases: A alone, A and B simultaneously, and B alone. Additionally, the character " / " in this invention generally indicates that the preceding and following objects have an "or" relationship.

[0042] It should be understood that although terms such as first, second, third, etc., may be used in the embodiments of the present invention to describe the preset range, these preset ranges should not be limited to these terms. These terms are only used to distinguish the preset ranges from one another. For example, without departing from the scope of the embodiments of the present invention, the first preset range may also be referred to as the second preset range, and similarly, the second preset range may also be referred to as the first preset range.

[0043] Depending on the context, the word "if" as used here can be interpreted as "when," "when," "in response to determination," or "in response to detection." Similarly, depending on the context, the phrase "if determination" or "if detection (of the stated condition or event)" can be interpreted as "when determination," "in response to determination," "when detection (of the stated condition or event)," or "in response to detection (of the stated condition or event)."

[0044] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. The components of the embodiments of the present invention described and shown in the accompanying drawings can generally be arranged and designed in various different configurations. Therefore, the following detailed description of the embodiments of the present invention provided in the accompanying drawings is not intended to limit the scope of the claimed invention, but merely to illustrate selected embodiments of the invention. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without inventive effort are within the scope of protection of the present invention.

[0045] The accompanying drawings illustrate various structural schematic diagrams according to embodiments disclosed in this invention. These drawings are not to scale, and some details have been enlarged for clarity, and some details may have been omitted. The shapes of the various regions and layers shown in the drawings, as well as their relative sizes and positional relationships, are merely exemplary and may deviate from reality due to manufacturing tolerances or technical limitations. Furthermore, those skilled in the art can design regions / layers with different shapes, sizes, and relative positions as needed.

[0046] Example 1

[0047] Referring to Figure 1, the rapid start-up system for a decoupled steam turbine combined cycle unit according to the present invention includes a first generator 1, a compressor 2, a combustion chamber 3, a turbine 4, a high-pressure subsystem 5, a reheat subsystem 6, a medium-pressure subsystem 7, a low-pressure subsystem 8, a flue gas outlet 9, a high-pressure feedwater inlet 10, a medium-pressure feedwater inlet 11, a low-pressure feedwater inlet 12, a high-pressure cylinder 13, a medium-pressure cylinder 14, a low-pressure cylinder 15, a low-pressure cylinder exhaust pipe 16, a second generator 17, a heat release feedwater inlet 18, a first molten salt-water heat exchanger 19, a heat release feedwater outlet 20, a high-temperature molten salt pump 21, a high-temperature molten salt tank 22, a first valve 23, a second valve 24, a third valve 25, a second molten salt-water heat exchanger 26, a fourth valve 27, a fifth valve 28, a third molten salt-water heat exchanger 29, a thermal storage drain outlet 30, a low-temperature molten salt pump 31, a low-temperature molten salt tank 32, and a sixth valve 33.

[0048] The heat release feedwater inlet 18 is connected to the primary side inlet of the first molten salt-water heat exchanger 19, and the primary side outlet of the first molten salt-water heat exchanger 19 is connected to the heat release feedwater outlet 20.

[0049] The secondary outlet of the first molten salt-water heat exchanger 19 is connected to the secondary inlet of the first molten salt-water heat exchanger 19 via the sixth valve 33, the low-temperature molten salt tank 32, the low-temperature molten salt pump 31, the primary side of the third molten salt-water heat exchanger 29 and the primary side of the second molten salt-water heat exchanger 26, the first valve 23, the high-temperature molten salt tank 22 and the high-temperature molten salt pump 21.

[0050] The outlet of compressor 2 and the fuel pipeline are connected to the inlet of combustion chamber 3. The outlet of combustion chamber 3 is connected to the inlet of turbine 4. Turbine 4, compressor 2 and first generator 1 are arranged coaxially. The outlet of turbine 4 is connected to exhaust outlet 9 in sequence through the shell side of high pressure subsystem 5, the shell side of reheat subsystem 6, the shell side of medium pressure subsystem 7 and the shell side of low pressure subsystem 8.

[0051] The high-pressure water inlet 10 is divided into two paths after passing through the pipe side of the high-pressure subsystem 5. One path is connected to the inlet of the high-pressure cylinder 13 via the third valve 25, and the second path is connected to the secondary side inlet of the second molten salt-water heat exchanger 26 via the second valve 24. The secondary side outlet of the second molten salt-water heat exchanger 26 is divided into two paths. One path is connected to the inlet of the high-pressure cylinder 13 via the fourth valve 27, and the other path is connected to the heat storage drainage outlet 30 via the fifth valve 28 and the secondary side of the third molten salt-water heat exchanger 29.

[0052] The medium-pressure water inlet 11 is connected to the outlet of the high-pressure cylinder 13 via a pipe through the pipe side of the medium-pressure subsystem 7, and then connected to the inlet of the medium-pressure cylinder 14 via the pipe side of the reheat subsystem 6. The outlet of the medium-pressure cylinder 14 is connected to the inlet of the low-pressure cylinder 15. The low-pressure water inlet 12 is connected to the inlet of the low-pressure cylinder 15 via the pipe side of the low-pressure subsystem 8. The outlet of the low-pressure cylinder 15 is connected to the low-pressure cylinder exhaust pipe 16.

[0053] The high-pressure cylinder 13, the medium-pressure cylinder 14, the low-pressure cylinder 15, and the second generator 17 are arranged coaxially.

[0054] The first molten salt-water heat exchanger 19, the second molten salt-water heat exchanger 26, the third molten salt-water heat exchanger 29, the high-temperature molten salt pump 21, the high-temperature molten salt tank 22, the low-temperature molten salt pump 31, and the low-temperature molten salt tank 32 constitute a thermal storage system. The high-pressure subsystem 5, the reheat subsystem 6, the intermediate-pressure subsystem 7, and the low-pressure subsystem 8 constitute a waste heat boiler. The high-pressure cylinder 13, the intermediate-pressure cylinder 14, the low-pressure cylinder 15, and the second generator 17 constitute a steam turbine power generation system. The first generator 1, the compressor 2, the combustion chamber 3, and the turbine 4 constitute a gas turbine power generation system.

[0055] Example 2

[0056] Referring to Figure 1, the rapid start-up system for a combined cycle unit with decoupled steam turbines according to the present invention includes the following steps:

[0057] After passing through the filter, the air enters the compressor 2 and is compressed into high-pressure air. It then enters the combustion chamber 3 and mixes with fuel for combustion, forming high-temperature, high-pressure gas. This gas then enters the turbine 4 to drive the turbine and perform work. A small portion of the rotational mechanical energy generated by the turbine 4 is used to drive the compressor 2 to compress air, while the remainder drives the first generator 1 to generate electricity. The gas, still at a high temperature after performing work in the turbine 4, enters the waste heat boiler, which consists of the high-pressure subsystem 5, reheat subsystem 6, intermediate-pressure subsystem 7, and low-pressure subsystem 8, for heat exchange. After heat exchange, it is discharged into the atmosphere through the exhaust outlet 9. High-pressure feedwater enters the high-pressure subsystem 5 through the high-pressure feedwater inlet 10 to generate high-pressure superheated steam. Intermediate-pressure feedwater enters the intermediate-pressure subsystem 7 through the intermediate-pressure feedwater inlet 11 to generate intermediate-pressure superheated steam, which mixes with the cold reheat steam discharged from the high-pressure cylinder 13 and enters the reheat subsystem 6 to generate intermediate-pressure hot reheated steam. Low-pressure feedwater enters the low-pressure subsystem 8 through the low-pressure feedwater inlet 12 to generate low-pressure superheated steam. The high-pressure subsystem 5, medium-pressure subsystem 7, and low-pressure subsystem 8 consist of multi-stage economizers, evaporators, and superheaters arranged in an alternating pattern, while the reheat subsystem 6 consists of multiple superheaters. Since the high-pressure feedwater flow rate is much greater than that of the medium-pressure and low-pressure feedwater flow rates, the steam production performance of the waste heat boiler mainly depends on the high-pressure steam parameters.

[0058] 1) The steam generation parameters of the waste heat boiler did not meet the conditions for turbine warm-up;

[0059] In the early stages of combined cycle unit startup, the gas turbine's exhaust temperature and flow rate are low, and the steam production parameters of the waste heat boiler are also low. Before the turbine warm-up conditions are met, traditional combined cycle units will directly discharge into the atmosphere or condenser, resulting in a large waste of heat energy. In this invention, this heat energy will be recovered through a heat storage system. The specific process is as follows: open the first valve 23, the second valve 24, and the fifth valve 28; close the third valve 25, the fourth valve 27, and the sixth valve 33; start the low-temperature molten salt pump 31; and close the high-temperature molten salt pump 21. The low-temperature molten salt is discharged from the low-temperature molten salt tank 32 through the low-temperature molten salt pump 31 and then passes through the third molten salt-water heat exchanger 29, the second molten salt-water heat exchanger 26, and the first valve 23 before being transported to the high-temperature molten salt tank 22. High-temperature and high-pressure main steam is output from high-pressure subsystem 5, and then passes through second valve 24, second molten salt-water heat exchanger 26, fifth valve 28 and third molten salt-water heat exchanger 29 to exchange heat with molten salt, and then is discharged from heat storage drainage outlet 30.

[0060] 2) The steam generation parameters of the waste heat boiler meet the conditions for turbine warm-up;

[0061] As the startup process progresses, the steam production parameters of the waste heat boiler continuously increase. When the conditions for turbine warm-up are met, traditional combined cycle units would operate the gas turbine at a low load, ensuring that the steam parameters generated by the waste heat boiler just meet the turbine warm-up requirements. However, prolonged operation of the gas turbine at low load can lead to decreased efficiency and excessive pollutant emissions. Therefore, in this invention, the gas turbine will continue to increase its load until it reaches full load. The high-parameter steam generated by the waste heat boiler will then be diverted, cooled, and depressurized through a heat storage system before entering the steam turbine for warm-up. The specific process is as follows: Open the first valve 23, the second valve 24, the third valve 25, the fourth valve 27, and the fifth valve 28, close the sixth valve 33, start the low-temperature molten salt pump 31, and close the high-temperature molten salt pump 21. The low-temperature molten salt is discharged from the low-temperature molten salt tank 32 through the low-temperature molten salt pump 31 and then passes through the third molten salt-water heat exchanger 29, the second molten salt-water heat exchanger 26, and the first valve 23 before being transported to the high-temperature molten salt tank 22. The high-temperature and high-pressure main steam is output from the high-pressure subsystem 5, and then passes through the second valve 24, the second molten salt-water heat exchanger 26, the fifth valve 28, and the third molten salt-water heat exchanger 29 to exchange heat with the molten salt before being discharged from the heat storage drain outlet 30. As the warm-up process proceeds, the warm-up steam parameters of the steam turbine are constantly changing. Therefore, the warm-up steam parameters of the steam turbine can be made to meet the requirements by adjusting the valve openings of the first valve 23, the second valve 24, the third valve 25, the fourth valve 27, and the fifth valve 28.

[0062] 3) The steam turbine warm-up process is complete;

[0063] After the steam turbine warm-up process is completed, open the third valve 25, close the first valve 23, the second valve 24, the fourth valve 27, the fifth valve 28 and the sixth valve 33, shut down the high-temperature molten salt pump 21 and the low-temperature molten salt pump 31, and the thermal storage system stops operating. The combined cycle unit in this invention has the same operating mode as the conventional unit.

[0064] 4) Heat release from the thermal storage system;

[0065] When the combined cycle unit needs heat, such as for external heating, intake air cooling, and fuel heating, the sixth valve 33 is opened, and the first valve 23, the second valve 24, the third valve 25, the fourth valve 27, and the fifth valve 28 are closed. The high-temperature molten salt pump 21 is started, and the low-temperature molten salt pump 31 is closed. The high-temperature molten salt is discharged from the high-temperature molten salt tank 22 through the low-temperature molten salt pump 31 and then passes through the first molten salt-water heat exchanger 19 and the sixth valve 33 before being transported back to the high-temperature molten salt tank 22. The feedwater enters the first molten salt-water heat exchanger 19 from the heat release feedwater inlet 18 and is heated into high-temperature and high-pressure steam, which is then discharged from the heat release feedwater outlet 20 for different heating needs.

[0066] This invention has the following characteristics:

[0067] 1) When starting up a combined cycle unit, there is no need to consider the warm-up process of the steam turbine. The gas turbine and waste heat boiler can quickly reach full load operation, which improves the flexibility of the unit.

[0068] 2) It shortens the time range of gas turbine operation under low load conditions, reduces pollutant emissions, improves the power generation efficiency of the unit, and enhances its economic efficiency;

[0069] 3) The thermal energy stored in the thermal storage system during the start-up process can be used for different subsequent heat use scenarios, such as intake air cooling and fuel heating, which improves the system's comprehensive and complementary utilization of thermal energy and eliminates dependence on other heat sources.

[0070] 4) This invention only requires steam extraction modification to the main steam pipeline of the existing combined cycle unit, and will not change the normal operation mode of the unit. The modification risk is low and it has good scalability.

[0071] Other embodiments of the invention will readily occur to those skilled in the art upon consideration of the specification and disclosure of the invention. This application is intended to cover any variations, uses, or adaptations of the invention that follow the general principles of the invention and include common knowledge or customary techniques in the art not disclosed herein. The specification and examples are to be considered exemplary only, and the true scope and spirit of the invention are indicated by the following claims.

[0072] It should be understood that the present invention is not limited to the precise structure described above and shown in the accompanying drawings, and various modifications and changes can be made without departing from its scope. The scope of the invention is limited only by the appended claims.

[0073] The above description is merely a preferred embodiment of the present invention and does not constitute any limitation on the present invention. Any simple modifications, alterations, or equivalent structural changes made to the above embodiments based on the technical essence of the present invention shall still fall within the protection scope of the present invention.

Claims

1. A combined cycle unit fast start system for decoupling a steam turbine, characterized by, The application relates to a combined cycle power generation system, which comprises a heat storage system, a waste heat boiler, a steam turbine power generation system and a gas turbine power generation system.

2. The combined cycle unit fast start system for a decoupled steam turbine of claim 1, wherein, The waste heat boiler comprises a flue gas outlet (9), a high-pressure subsystem (5), a reheating subsystem (6), a medium-pressure subsystem (7) and a low-pressure subsystem (8); the steam turbine power generation system comprises a high-pressure feedwater inlet (10), a medium-pressure feedwater inlet (11), a high-pressure cylinder (13), a medium-pressure cylinder (14) and a low-pressure cylinder (15); The outlet of the gas turbine power generation system is connected with the flue gas outlet (9) through the shell side of the high-pressure subsystem (5), the shell side of the reheating subsystem (6), the shell side of the medium-pressure subsystem (7) and the shell side of the low-pressure subsystem (8) in sequence. The high-pressure feedwater inlet (10) is connected with the inlet of the high-pressure cylinder (13) through the tube side of the high-pressure subsystem (5) and a third valve (25), and the heat storage system is connected with the third valve (25) in parallel. The medium-pressure feedwater inlet (11) is connected with the inlet of the medium-pressure cylinder (14) through the tube side of the medium-pressure subsystem (7) and a pipe after the outlet of the high-pressure cylinder (13), the outlet of the medium-pressure cylinder (14) is connected with the inlet of the low-pressure cylinder (15), the low-pressure feedwater inlet (12) is connected with the inlet of the low-pressure cylinder (15) through the tube side of the low-pressure subsystem (8), and the outlet of the low-pressure cylinder (15) is connected with a low-pressure cylinder exhaust pipe (16).

3. The combined cycle unit fast start system of claim 2, wherein, The heat storage system comprises a heat-releasing feedwater inlet (18), a heat-releasing feedwater outlet (20), a heat storage drainage outlet (30), a first molten salt-water heat exchanger (19), a second molten salt-water heat exchanger (26), a third molten salt-water heat exchanger (29), a high-temperature molten salt pump (21), a high-temperature molten salt tank (22), a low-temperature molten salt pump (31) and a low-temperature molten salt tank (32). The heat-releasing feedwater inlet (18) is connected with the primary side inlet of the first molten salt-water heat exchanger (19), and the primary side outlet of the first molten salt-water heat exchanger (19) is connected with the heat-releasing feedwater outlet (20). The secondary side outlet of the first molten salt-water heat exchanger (19) is connected with the secondary side inlet of the first molten salt-water heat exchanger (19) through the low-temperature molten salt tank (32), the low-temperature molten salt pump (31), the primary side of the third molten salt-water heat exchanger (29), the primary side of the second molten salt-water heat exchanger (26), the high-temperature molten salt tank (22) and the high-temperature molten salt pump (21) in sequence. The high-pressure feedwater inlet (10) is divided into two routes after passing through the tube side of the high-pressure subsystem (5), one of the two routes is connected with the inlet of the high-pressure cylinder (13) through the third valve (25), the other route is connected with the secondary side inlet of the second molten salt-water heat exchanger (26), the secondary side outlet of the second molten salt-water heat exchanger (26) is divided into two routes, one of the two routes is connected with the inlet of the high-pressure cylinder (13), and the other route is connected with the heat storage drainage outlet (30) through the secondary side of the third molten salt-water heat exchanger (29).

4. The combined cycle unit fast start system of claim 3, wherein, The secondary side outlet of the first molten salt-water heat exchanger (19) is connected with the secondary side inlet of the first molten salt-water heat exchanger (19) in sequence through the sixth valve (33), the low-temperature molten salt tank (32), the low-temperature molten salt pump (31), the primary side of the third molten salt-water heat exchanger (29) and the primary side of the second molten salt-water heat exchanger (26), the first valve (23), the high-temperature molten salt tank (22) and the high-temperature molten salt pump (21).

5. The combined cycle unit fast start system of claim 3, wherein, The high-pressure feed water inlet (10) is divided into two paths after passing through the tube side of the high-pressure subsystem (5), one of the two paths is connected with the inlet of the high-pressure cylinder (13) through the third valve (25), and the second path is connected with the secondary side inlet of the second molten salt-water heat exchanger (26) through the second valve (24), the secondary side outlet of the second molten salt-water heat exchanger (26) is divided into two paths, one of the two paths is connected with the inlet of the high-pressure cylinder (13) through the fourth valve (27), and the other path is connected with the heat storage and drainage outlet (30) in sequence through the fifth valve (28) and the secondary side of the third molten salt-water heat exchanger (29).

6. The combined cycle unit fast start system of claim 2, wherein, The high-pressure cylinder (13), the medium-pressure cylinder (14), the low-pressure cylinder (15) and the second generator (17) are coaxially arranged.

7. The combined cycle unit fast start system of claim 2, wherein, The gas turbine power generation system comprises a fuel pipeline, a compressor (2), a combustion chamber (3) and a turbine (4), the outlet of the compressor (2) and the fuel pipeline are connected with the inlet of the combustion chamber (3), the outlet of the combustion chamber (3) is connected with the inlet of the turbine (4), and the outlet of the turbine (4) is connected with the shell side of the high-pressure subsystem (5) in sequence.

8. The combined cycle unit fast start system of claim 2, wherein, The system further comprises a first generator (1), and the turbine (4), the compressor (2) and the first generator (1) are coaxially arranged.

9. A method for quick start-up of a combined cycle unit of a cogeneration engine, characterized in that, The quick start system of the combined cycle unit of the decoupling steam turbine based on claim 3 comprises: 1) the steam turbine warm-up condition is not reached by the steam parameters of the waste heat boiler; 2) the steam turbine warm-up condition is reached by the steam parameters of the waste heat boiler; 3) the steam turbine warm-up process is completed; 4) the heat storage system releases heat.

10. The method of claim 9, wherein, Specifically comprising the following steps: 1) the steam turbine warm-up condition is not reached by the steam parameters of the waste heat boiler; The low-temperature molten salt is discharged from the low-temperature molten salt tank (32) through the low-temperature molten salt pump (31), and then passes through the third molten salt-water heat exchanger (29) and the second molten salt-water heat exchanger (26) in sequence, and is transported into the high-temperature molten salt tank (22), the high-temperature and high-pressure main steam is output from the high-pressure subsystem (5), and then is discharged from the heat storage and drainage outlet (30) after being exchanged with the molten salt through the second molten salt-water heat exchanger (26) and the third molten salt-water heat exchanger (29); 2) the steam turbine warm-up condition is reached by the steam parameters of the waste heat boiler; The low-temperature molten salt is discharged from the low-temperature molten salt tank (32) through the low-temperature molten salt pump (31), and then passes through the third molten salt-water heat exchanger (29) and the second molten salt-water heat exchanger (26) in sequence, and is transported into the high-temperature molten salt tank (22); the high-temperature and high-pressure main steam is output from the high-pressure subsystem (5), and then is discharged from the heat storage and drainage outlet (30) after being exchanged with the molten salt through the second molten salt-water heat exchanger (26) and the third molten salt-water heat exchanger (29); 3) The steam turbine warm-up process is completed; When the steam turbine warm-up process is completed, the high-temperature molten salt pump (21) and the low-temperature molten salt pump (31) are closed, and the heat storage system stops running; 4) The heat storage system releases heat; When the combined cycle unit needs heat, the high-temperature molten salt pump (21) is started, the low-temperature molten salt pump (31) is closed, the high-temperature molten salt is discharged from the high-temperature molten salt tank (22) through the low-temperature molten salt pump (31), then passes through the first molten salt-water heat exchanger (19) in turn, and is transported into the high-temperature molten salt tank (22); the feed water enters the first molten salt-water heat exchanger (19) from the heat-releasing feed water inlet (18), is heated into high-temperature high-pressure steam, and is discharged from the heat-releasing feed water outlet (20).

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