Gas turbine combined cycle power generation system based on flow regulation and control and operation method

Abstract

The invention discloses a gas turbine combined cycle power generation system based on flow regulation and control and an operation method. In the system flow structure, an air compression process is divided into two sub-processes, namely a fresh air pre-compression process and a main compression process after mixing of fresh air and high-pressure exhaust of a gas turbine; a combustion chamber outlet high-temperature smoke expansion process is divided into two sub-processes, namely a main expansion process with a constant expansion ratio and an exhaust smoke residual pressure recovery expansion process, and the flow structure can enable the air inlet pressure and the exhaust pressure of the gas turbine to be high pressure under the designed working condition and to be gradually reduced under the variable working condition; during variable load operation, the pressure ratio of fresh air pre-compression and the exhaust pressure and temperature of a gas turbine are adjusted through variable rotating speed and inlet guide vane angle to realize the inlet flow of a main gas compressor, and meanwhile, the pressure ratio of the main gas compressor and the expansion ratio of a main expansion turbine can be kept unchanged; the system is characterized in that the load of the gas turbine is adjusted through flow change, and the gas initial temperature and the expansion ratio of a main turbine of the gas turbine are not changed in the process.

Description

Technical Field

[0001] The present invention relates to the technical field of gas turbine combined cycle, and particularly to a gas turbine combined cycle power generation system and an operation method based on flow regulation, which are applicable to conventional natural gas gas turbine combined cycle, IGCC combined cycle and their pure oxygen combustion conditions. Background Art

[0002] Under the guidance of the "dual carbon" goal, the way of energy utilization and the energy structure in China are undergoing profound changes. The proportion of renewable energy is increasing, posing challenges to the peak shaving ability of the power grid. Gas turbine combined cycle units are becoming increasingly important in the energy system due to their advantages of high efficiency, strong peak shaving ability and low emissions. However, their power range under off-design conditions is narrow, and the efficiency decreases rapidly at partial loads, which restricts the economy and practicability of their peak shaving operation. With the further increase in the proportion of renewable energy, gas turbine combined cycle systems will undertake more and more peak shaving tasks and operate under partial load conditions for a long time. Optimizing the partial load characteristics of the combined cycle system and improving the power generation efficiency of the unit under off-design conditions are of great significance for improving energy utilization efficiency. How to improve the efficiency and power range of combined cycle units at partial loads is crucial for improving energy utilization efficiency.

[0003] Currently, there are mainly three variable load regulation strategies for gas turbines: 1) Regulate according to the law of constant gas turbine inlet temperature (T3). As the load decreases, the turbine expansion ratio gradually decreases, causing the turbine exhaust temperature to gradually increase and the gas temperature entering the waste heat boiler to gradually rise. However, the steam turbine does not allow over-temperature operation. When the load decreases to the point where the turbine exhaust temperature reaches the upper limit, this regulation method ends. The constant T3 regulation strategy is usually adopted in the high load area. Limited by the exhaust temperature of the gas turbine, the load regulation range is relatively narrow, about between 82% and 100% of the gas turbine load; 2) Regulate according to the law of constant gas turbine exhaust temperature (T4). As the load decreases, the gas turbine expansion ratio decreases and the turbine inlet temperature decreases to ensure a constant turbine exhaust temperature. This method has a slightly lower combined cycle efficiency compared to using the constant T3 regulation, but is more beneficial to the safe operation of the gas turbine and the waste heat boiler. The applicable range of the constant T4 regulation strategy can be as low as 50% load condition; 3) Pure fuel quantity regulation strategy. This strategy does not rely on IGV to regulate the air flow, and the air flow is almost constant at different loads. The unit power is reduced by reducing the fuel quantity entering the combustion chamber. Limited by the operating characteristics of the compressor and the gas turbine, when this strategy is adopted, both T3 and T4 show a downward trend, and the efficiency is the worst among the three strategies. It is generally used for load regulation when the IGV reaches the minimum opening at low loads. From a technical perspective, the existing load regulation methods are mainly achieved based on the reduction of the turbine inlet temperature.

[0004] The efficiency of the above methods drops by 11% - 14% at 40% - 100% load, with a large decline amplitude.

[0005] The operating method of maintaining high initial parameters by reducing the working fluid flow rate, such as heating at the compressor inlet, regulating the back pressure of the turbine exhaust, etc., can improve the off-design characteristics. However, the working fluid flow rate can only be reduced to (IGV reduced to 60%, IGV + inlet heating reduced to about 50%) of the design flow rate based on the existing conditions. For the operating method based on flow regulation, further exploration is still needed. Summary of the Invention

[0006] The object of the present invention is to provide a combined cycle power generation system in which the combined cycle efficiency remains basically unchanged under the design conditions and off-design conditions when the load varies below 10%. The flow rate can be adjusted by regulating the compression ratio of the pre-compression of fresh air, the high-pressure exhaust pressure of the gas turbine (recommended range 2 - 5 bar), the inlet temperature of the main compressor, and the opening degree of the compressor IGV, while keeping the inlet temperature of the main turbine unchanged and the expansion ratio basically unchanged or slightly reduced, so as to solve the problems raised in the above-mentioned background technology. The content of the present invention is also applicable to the case of oxy-fuel combustion.

[0007] To achieve the above object, the present invention provides the following technical solutions:

[0008] A gas turbine combined cycle power generation system based on flow regulation and control. This system is based on the conventional combined cycle and is improved by increasing the pressure of the compressor inlet air and the gas turbine exhaust. It is characterized in that a pre-compressor is arranged before the main compressor to increase the inlet pressure, and an expander is arranged after the main turbine to increase the exhaust pressure of the main turbine, so that the inlet and exhaust pressures of the gas turbine are at high pressures under the design conditions and gradually decrease under off-design conditions; the compression ratio of the pre-compressor and the expansion ratio of the post-expander are adjusted by regulating the rotational speed and the inlet angle of the air, and combined with the inlet temperature of the main compressor, a large adjustment of the inlet flow rate of the main compressor is achieved, while the inlet temperature and the expansion ratio of the gas turbine turbine remain basically unchanged, thereby realizing high-efficiency operation under variable load operation of the combined cycle.

[0009] Further, in terms of the system flow structure: the air compression process is divided into two sub-processes, and the expansion process of the high-temperature flue gas at the combustion chamber outlet is divided into two sub-processes. The air compression process is divided into two sub-processes, namely, the pre-compression process of fresh air by the pre-compressor and the main compression process of the fresh air and the high-pressure exhaust of the gas turbine after mixing through the main compressor;

[0010] The expansion process of the high-temperature flue gas at the combustion chamber outlet is divided into two sub-processes, including the main expansion process with a constant expansion ratio through the main turbine and the expansion process of recovering the exhaust residual pressure through the expander.

[0011] Further, the expansion process of the high-temperature flue gas at the combustion chamber outlet is specifically:

[0012] The high-pressure exhaust gas of the main compressor enters the combustion chamber to fully burn the fuel. The high-temperature flue gas at the outlet of the combustion chamber undergoes a main expansion process with a constant expansion ratio through the main turbine. The high-pressure exhaust gas of the main turbine is divided into two parts after passing through the first waste heat boiler. One part is cooled by a cooler and then mixed with fresh air to enter the main compressor for the main compression process, and the other part undergoes an expansion process for recovering the exhaust pressure of the smoke by the expander; the steam enters the steam turbine after passing through the triple-pressure reheat first waste heat boiler. The steam discharged from the low-pressure cylinder of the first steam turbine enters the condenser and then enters the water pump, and finally enters the first waste heat boiler for the steam cycle.

[0013] Further, the high-pressure exhaust gas of the main turbine is divided into two parts, specifically:

[0014] The high-pressure exhaust gas of the main turbine is divided into two parts. One part is mixed with fresh air after passing through the first waste heat boiler and enters the main compressor for the main compression process, and the other part enters the second waste heat boiler after undergoing the expansion process for recovering the exhaust pressure of the smoke by the expander.

[0015] The present invention also provides an operation method for a gas turbine combined cycle power generation system based on flow regulation. The method includes: adding a second cooler at the outlet of the pre-compressor. When the outlet of the pre-compressor is cooled, the regulation of the inlet temperature of the main compressor will be simplified. There is no need to regulate the inlet temperature of the main compressor to be constant through the cooler, and the adjustable range of the inlet temperature of the main compressor can be made larger.

[0016] Further, the method also includes: regulating the inlet pressure of the main compressor and the outlet pressure of the main turbine + keeping the inlet temperature of the main compressor constant, specifically:

[0017] When reducing the load, the flow rate and outlet pressure of the fresh air pre-compressed by the main compressor are reduced by changing the rotational speed, the angle of the inlet guide vane or their combination, and the flow rate of the expander is increased by changing the rotational speed and the angle of the inlet guide vane, so as to reduce the high-pressure exhaust gas pressure of the main turbine and the flow rate of the high-pressure flue gas mixed with the fresh air, and reduce the inlet flow rate of the main compressor by reducing the compression ratio of the fresh air pre-compression and the high-pressure exhaust gas pressure of the gas turbine; at the same time, the flow rate of the cooling water of the first cooler, the first heat exchanger and the second heat exchanger are reduced to keep the inlet temperature of the main compressor constant and keep the compression ratio of the main compressor and the expansion ratio of the main turbine basically unchanged;

[0018] When increasing the load, the flow rate and outlet pressure of the fresh air pre-compressed by the main compressor are increased by changing the rotational speed, the angle of the inlet guide vane and their combination, and the flow rate of the expander is reduced by changing the rotational speed and the angle of the inlet guide vane, so as to increase the high-pressure exhaust gas pressure of the main turbine and the flow rate of the high-pressure flue gas mixed with the fresh air, and increase the inlet flow rate of the main compressor by increasing the compression ratio of the fresh air pre-compression and the high-pressure exhaust gas pressure of the gas turbine. At the same time, the flow rate of the cooling water of the first cooler, the first heat exchanger and the second heat exchanger are increased to keep the inlet temperature of the main compressor constant and keep the compression ratio of the main compressor and the expansion ratio of the main turbine basically unchanged.

[0019] Further, the method further includes: regulating the main compressor inlet pressure and the main turbine outlet pressure + regulating the main compressor inlet temperature, specifically:

[0020] During load reduction, the flow rate and outlet pressure of the fresh air pre-compressed by the main compressor are reduced by changing the rotational speed, the inlet guide vane angle or a combination thereof, and the flow rate of the expander is increased by changing the rotational speed and the inlet guide vane angle, so as to reduce the high-pressure exhaust pressure of the main turbine and the flow rate of the high-pressure flue gas mixed with the fresh air. At the same time, by reducing the flow rate of the cooling water of the first cooler, the first heat exchanger and the second heat exchanger, the inlet temperature of the main compressor is increased, which can further reduce the inlet flow rate of the main compressor, and at the same time, the pressure ratio of the main compressor and the expansion ratio of the main turbine can be kept slightly reduced while the initial temperature of the turbine remains unchanged;

[0021] During load increase, the flow rate and outlet pressure of the fresh air pre-compressed by the main compressor are increased by changing the rotational speed, the inlet guide vane angle or a combination thereof, and the flow rate of the expander is reduced by changing the rotational speed and the inlet guide vane angle, so as to increase the high-pressure exhaust pressure of the main turbine and the flow rate of the high-pressure flue gas mixed with the fresh air. At the same time, by increasing the flow rate of the cooling water of the first cooler, the first heat exchanger and the second heat exchanger, the inlet temperature of the main compressor is reduced, which can further increase the inlet flow rate of the main compressor, and at the same time, the pressure ratio of the main compressor and the expansion ratio of the main turbine can be kept slightly reduced while the initial temperature of the turbine remains unchanged.

[0022] Further, the method further includes: regulating the main compressor inlet pressure and the main turbine outlet pressure + regulating the main compressor inlet temperature + regulating the IGV of the main compressor, specifically:

[0023] During load reduction, the flow rate and outlet pressure of the fresh air pre-compressed by the main compressor are reduced by changing the rotational speed, the inlet guide vane angle or a combination thereof, and the flow rate of the expander is increased by changing the rotational speed and the inlet guide vane angle, so as to reduce the high-pressure exhaust pressure of the main turbine and the flow rate of the high-pressure flue gas mixed with the fresh air. At the same time, by reducing the flow rate of the cooling water of the first cooler, the first heat exchanger and the second heat exchanger, the inlet temperature of the main compressor is increased. At the same time, the flow rate is further reduced by the IGV angle of the main compressor, which can further reduce the inlet flow rate of the main compressor, and at the same time, the pressure ratio of the main compressor and the expansion ratio of the main turbine can be kept slightly reduced while the initial temperature of the main turbine remains unchanged;

[0024] During load increase, by varying the rotational speed, the inlet guide vane angle, and their combination, the flow rate and outlet pressure of the fresh air pre-compressed by the main compressor are increased. By varying the rotational speed and the inlet guide vane angle, the flow rate of the expander is reduced, thereby increasing the high-pressure exhaust pressure of the main turbine and the flow rate of the high-pressure flue gas mixed with the fresh air. At the same time, by increasing the flow rate of the cooling water of the first cooler, the first heat exchanger, and the second heat exchanger, the inlet temperature of the main compressor is reduced. Meanwhile, by further increasing the flow rate through the IGV angle of the main compressor, the inlet flow rate of the main compressor can be further increased, while maintaining a slight decrease in the pressure ratio of the main compressor and the expansion ratio of the main turbine, but the initial temperature of the main turbine remains unchanged.

[0025] According to the specific embodiments provided by the present invention, the following technical effects of the present invention are disclosed:

[0026] 1. The present invention can adjust the output power of the combined cycle by changing the working fluid flow rate in the load range of 100% to 10%, ensuring high temperature parameters of the gas turbine under off-design conditions.

[0027] 2. The present invention can keep the initial temperature parameters of the topping cycle and the combined cycle efficiency (potential) basically unchanged under design conditions and off-design conditions in the load range of 100% to 10%, avoiding the efficiency drop of 0 to 15 percentage points of the existing combined cycle under partial load. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for use in the description of the embodiments or the prior art. Obviously, the drawings in the following description are only the embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can be obtained according to the provided drawings.

[0029] The following further describes the gas turbine combined cycle power generation system and operation method based on flow regulation according to the present invention with reference to the drawings;

[0030] Figure 1 is a schematic diagram of the first solution in the gas turbine combined cycle power generation system based on flow regulation provided by the present invention;

[0031] Figure 2 is a schematic diagram of the second solution in the gas turbine combined cycle power generation system based on flow regulation provided by the present invention.

[0032] In the figure: 1. Front compressor; 2. Main compressor; 3. Combustion chamber; 4. Main turbine; 5. First generator; 6. First waste heat boiler; 7. High-pressure cylinder of the first steam turbine; 8. Intermediate-pressure cylinder of the first steam turbine; 9. Low-pressure cylinder of the first steam turbine; 10. Second engine; 11. Condenser; 12. Water pump; 13. First cooler; 14. Expander; 15. First heat exchanger; 16. Second heat exchanger; 17. Second cooler; 18. High-pressure cylinder of the second steam turbine; 19. Intermediate-pressure cylinder of the second steam turbine; 20. Low-pressure cylinder of the second steam turbine; 21. Second waste heat boiler. Specific implementation manner

[0033] The following combines the accompanying drawings and embodiments to further describe in detail the specific implementation manner of the present invention. The following embodiments are used to illustrate the present invention, but are not used to limit the scope of the present invention.

[0034] In order to better understand the purpose, structure and function of the present invention, the following further describes the present invention in detail with reference to the accompanying drawings.

[0035] This system is based on the conventional combined cycle to regulate and transform the pressure of the compressor intake air and the gas turbine exhaust. A front compressor 1 is arranged in front of the main compressor 2 to regulate the intake air pressure, and an expander 14 is arranged behind the main turbine 4 to regulate the exhaust pressure. The exhaust pressure of the main turbine is at a high pressure under the design conditions and gradually decreases under off-design conditions; the variable load operation method of the combined cycle power generation system is: by adjusting the pressure ratio of the front compressor 1, the inlet temperature of the main compressor 2 and the expansion ratio of the rear expander, the inlet flow rate of the main compressor 2 is adjusted, and the three cooperate to achieve high-efficiency operation under the variable load operation of the combined cycle.

[0036] The air compression process (if it is pure oxygen combustion here, it is oxygen, the same below) is divided into two parts, the pre-compression process of the fresh air by the front compressor 1 and the main compression process of the fresh air and the high-pressure exhaust of the gas turbine after mixing by the main compressor 2; the expansion process of the high-temperature flue gas at the outlet of the combustion chamber is divided into two parts, the main expansion process with a constant expansion ratio by the main turbine 4 and the expansion process for recovering the exhaust residual pressure by the expander 14; there are two schemes for the combined cycle system. Scheme one is shown in the appendix Figure 1 , and scheme two is shown in the appendix Figure 2 .

[0037] In the system flow structure of the present invention, the air compression process (if it is pure oxygen combustion here, it is the oxygen compression process) is divided into two parts: the pre-compression process of fresh air and the main compression process after the fresh air is mixed with the high-pressure exhaust gas of the gas turbine. The expansion process of the high-temperature flue gas at the outlet of the combustion chamber is divided into two parts: the main expansion process with a constant expansion ratio and the expansion process for recovering the exhaust residual pressure. During variable load operation, the flow rate at the inlet of the main compressor is adjusted by adjusting the compression ratio of the fresh air pre-compression, the pressure and temperature of the high-pressure exhaust gas of the gas turbine. At the same time, the compression ratio of the main compressor 2 and the expansion ratio of the main expansion turbine can be kept unchanged. The compression ratio of the fresh air pre-compression is adjusted by changing the rotational speed or the angle of the inlet guide vane. The pressure of the high-pressure exhaust gas of the gas turbine is adjusted by adjusting the flow rate of the expander 14, and the flow rate adjustment of the expander 14 is achieved by changing the rotational speed and the angle of the inlet guide vane. The characteristic of this system is that the load of the gas turbine is adjusted by changing the flow rate, and the initial temperature and expansion ratio of the gas in the main turbine of the gas turbine remain unchanged during this process. For example, when the high-pressure exhaust gas pressure of the main turbine 4 is set to 3 bar, only by adjusting the exhaust gas pressure, the flow rate can be reduced to 1 / 3 of the design flow rate. Further considering temperature control, the flow rate can be reduced to 1 / 6 of the design flow rate. If the IGV control of the main compressor is further considered, the flow rate can be reduced to 1 / 10 of the design flow rate, so as to keep the combined cycle efficiency basically unchanged under the design condition and variable operating conditions in the load range of 100% - 10%, avoiding the efficiency drop of 0 - 15 percentage points under partial load of the existing combined cycle.

[0038] Specifically, Figure 1 as shown, the present invention provides a gas turbine combined cycle power generation system based on flow regulation, including: a pre-compressor 1, a main compressor 2, a combustion chamber 3, a turbine 4, a first generator 5, a first waste heat boiler 6, a first cooler 13, a first heat exchanger 15 and a second cooler 17;

[0039] The outlet of the pre-compressor 1 is connected to the inlet of the second cooler 17; the outlet of the second cooler 17 is connected to the inlet of the main compressor 2; the outlet of the main compressor 2 is connected to the inlet of the combustion chamber 3; the outlet of the combustion chamber 3 is connected to the inlet of the turbine 4; the outlet of the turbine 4 is connected to the inlet of the first waste heat boiler 6; the outlet of the first waste heat boiler 6 is connected to the inlet of the first heat exchanger 15; the outlet of the first heat exchanger 15 is connected to the inlet of the first cooler 13; the outlet of the first cooler 13 is connected to the inlet of the main compressor 2; the first waste heat boiler 6 is also connected to a power cycle system; the first generator 5 is coaxially connected to the turbine 4 and the main compressor 2.

[0040] The power cycle device includes: a high-pressure cylinder 7 of the first steam turbine, an intermediate-pressure cylinder 8 of the first steam turbine, a low-pressure cylinder 9 of the first steam turbine, a second engine 10, a condenser 11, a water pump 12, an exhaust residual pressure expander 14 and a second heat exchanger 16;

[0041] The high-pressure steam outlet of the first waste heat boiler 6 is connected to the inlet of the high-pressure cylinder 7 of the first steam turbine; the medium-pressure steam outlet of the first waste heat boiler 6 is connected to the inlet of the medium-pressure cylinder 8 of the first steam turbine; the low-pressure steam outlet of the first waste heat boiler 6 is connected to the inlet of the low-pressure cylinder 9 of the first steam turbine; the outlet of the high-pressure cylinder 7 of the first steam turbine is connected to the inlet of the medium-pressure cylinder 8 of the first steam turbine; the outlet of the medium-pressure cylinder 8 of the first steam turbine is connected to the inlet of the low-pressure cylinder 9 of the first steam turbine; the outlet of the low-pressure cylinder 9 of the first steam turbine is connected to the inlet of the condenser 11, the outlet of the condenser 11 is connected to the inlet of the water pump 12, the outlet of the water pump 12 returns to the inlet of the first waste heat boiler 6, and the outlet of the first waste heat boiler 6 is respectively connected to the inlet of the first heat exchanger 15 and the inlet of the second heat exchanger 16; the outlet of the second heat exchanger 16 is connected to the inlet of the exhaust gas pressure expansion machine 14 to form a circulation loop;

[0042] The second engine 10 is coaxially connected to the high-pressure cylinder 7 of the steam turbine, the medium-pressure cylinder 8 of the steam turbine, and the low-pressure cylinder 9 of the steam turbine.

[0043] It should be noted that: the feature of Scheme 1 is that the fresh air is pre-compressed by the pre-compressor 1 and then mixed with the fresh air and the high-pressure exhaust gas of the gas turbine and then undergoes the main compression process by the main compressor 2. The high-pressure exhaust gas of the main compressor enters the combustion chamber 3 to make the fuel burn fully. The high-temperature flue gas at the outlet of the combustion chamber undergoes the main expansion process with a constant expansion ratio by the turbine 4. The high-pressure exhaust gas of the main turbine 4 is divided into two parts after passing through the waste heat boiler 6. One part is cooled by the cooler and then mixed with the fresh air and enters the main compressor 2 for the main compression process. The other part undergoes the exhaust gas pressure recovery and expansion process of the exhaust gas pressure expansion machine 14. The water vapor enters the steam turbine after passing through the triple-pressure reheat waste heat boiler 6. The water vapor discharged from the low-pressure cylinder of the steam turbine enters the condenser and then enters the water pump, and finally enters the waste heat boiler for the water vapor cycle.

[0044] As Figure 2 shown, the power cycle device further includes: the high-pressure cylinder 7 of the first steam turbine, the medium-pressure cylinder 8 of the first steam turbine, the low-pressure cylinder 9 of the first steam turbine, the second engine 10, the condenser 11, the water pump 12, the exhaust gas pressure expansion machine 14, the second waste heat boiler 21, the high-pressure cylinder 18 of the second steam turbine, the medium-pressure cylinder 19 of the second steam turbine, and the low-pressure cylinder 20 of the second steam turbine;

[0045] The inlet of the exhaust gas pressure expansion machine 14 is connected to the inlet of the first waste heat boiler 6, and the outlet of the exhaust gas pressure expansion machine 14 is connected to the inlet of the second waste heat boiler 21;

[0046] The high-pressure steam outlet of the first waste heat boiler 6 is connected to the inlet of the high-pressure cylinder 7 of the first steam turbine; the medium-pressure steam outlet of the first waste heat boiler 6 is connected to the inlet of the medium-pressure cylinder 8 of the first steam turbine; the low-pressure steam outlet of the first waste heat boiler 6 is connected to the inlet of the low-pressure cylinder 9 of the first steam turbine; the outlet of the high-pressure cylinder 7 of the first steam turbine is connected to the inlet of the medium-pressure cylinder 8 of the first steam turbine; the outlet of the medium-pressure cylinder 8 of the first steam turbine is connected to the inlet of the low-pressure cylinder 9 of the first steam turbine, and the outlet of the low-pressure cylinder 9 of the first steam turbine is connected to the inlet of the condenser 11; the outlet of the condenser 11 is connected to the inlet of the water pump 12; the outlet of the water pump 12 is respectively connected to the inlet of the first waste heat boiler 6 and the inlet of the second waste heat boiler 21; the second engine 10 is coaxially connected to the high-pressure cylinder 7, the medium-pressure cylinder 8 and the low-pressure cylinder 9 of the first steam turbine;

[0047] The high-pressure steam outlet of the second waste heat boiler 21 is connected to the inlet of the high-pressure cylinder 18 of the second steam turbine; the medium-pressure steam outlet of the second waste heat boiler 21 is connected to the inlet of the medium-pressure cylinder 19 of the second steam turbine; the low-pressure steam outlet of the second waste heat boiler 21 is connected to the inlet of the low-pressure cylinder 20 of the second steam turbine; the outlet of the high-pressure cylinder 18 of the second steam turbine is connected to the inlet of the medium-pressure cylinder 19 of the second steam turbine; the outlet of the medium-pressure cylinder 19 of the first steam turbine is connected to the inlet of the low-pressure cylinder 20 of the second steam turbine;

[0048] The third motor is coaxially connected to the high-pressure cylinder 18, the medium-pressure cylinder 19 and the low-pressure cylinder 20 of the second steam turbine.

[0049] As Figure 2 In the second solution compared with the first solution as Figure 1 The difference is that the high-pressure exhaust gas of the main turbine 4 is divided into two parts. One part enters the main compressor 2 for the main compression process after being mixed with fresh air through the first waste heat boiler 6, and the other part enters the second waste heat boiler 16 after the exhaust pressure recovery expansion process of the exhaust pressure expansion machine 14.

[0050] A cooler 17 is added at the outlet of the pre-compressor 1. If the outlet of the pre-compressor 1 is cooled, the regulation of the inlet temperature of the main compressor will be simplified, that is, there is no need to regulate the inlet temperature of the main compressor to be constant through the cooler 13, and the adjustable range of the inlet temperature of the main compressor is larger (expanded from the original about 90 - 120 to about 30 - 120 °C).

[0051] The present invention also provides a gas turbine combined cycle power generation method based on flow regulation. The air (or oxygen in the case of pure oxygen combustion) compression process is divided into two parts: the pre-compression process of fresh air and the main compression process after the fresh air is mixed with the high-pressure exhaust gas of the gas turbine. The expansion process of the high-temperature flue gas at the outlet of the combustion chamber is divided into two parts: the main expansion process with a constant expansion ratio and the expansion process for recovering the exhaust gas residual pressure. During variable load operation, the flow rate at the inlet of the main compressor is adjusted by adjusting the compression ratio of the fresh air pre-compression, the pressure and temperature of the high-pressure exhaust gas of the gas turbine. At the same time, the compression ratio of the main compressor and the expansion ratio of the main expansion turbine can be kept unchanged. The fresh air pre-compression realizes the compression ratio adjustment by changing the rotational speed or the angle of the inlet guide vane. The high-pressure exhaust gas pressure of the gas turbine is realized by adjusting the flow rate of the exhaust gas residual pressure expander. The flow rate adjustment of the exhaust gas residual pressure expander is realized by changing the rotational speed and the angle of the inlet guide vane, specifically including: regulating the inlet pressure of the main compressor 2 and the outlet pressure of the main expansion turbine 4 + keeping the inlet temperature of the main compressor 2 unchanged, specifically as follows:

[0052] When reducing the load, the flow rate and outlet pressure of the fresh air pre-compressed by the main compressor 2 are reduced by changing the rotational speed, the angle of the inlet guide vane or their combination. The flow rate of the exhaust gas residual pressure expander 14 is increased by changing the rotational speed and the angle of the inlet guide vane, so as to reduce the high-pressure exhaust gas pressure of the turbine 4 and the flow rate of the high-pressure flue gas mixed with the fresh air. In this way, the inlet flow rate of the main compressor can be reduced by reducing the compression ratio of the fresh air pre-compression and the high-pressure exhaust gas pressure of the gas turbine. At the same time, by reducing the flow rate of the cooling water of the first cooler 13, the first heat exchanger 15 and the second heat exchanger 16, the inlet temperature of the main compressor 2 can be kept unchanged, and the compression ratio of the main compressor 2 and the expansion ratio of the main expansion turbine can be kept basically unchanged.

[0053] When increasing the load, the flow rate and outlet pressure of the fresh air pre-compressed by the main compressor 2 are increased by changing the rotational speed, the angle of the inlet guide vane or their combination. The flow rate of the exhaust gas residual pressure expander 14 is reduced by changing the rotational speed and the angle of the inlet guide vane, so as to increase the high-pressure exhaust gas pressure of the main turbine and the flow rate of the high-pressure flue gas mixed with the fresh air. In this way, the inlet flow rate of the main compressor can be increased by increasing the compression ratio of the fresh air pre-compression and the high-pressure exhaust gas pressure of the gas turbine. At the same time, by increasing the flow rate of the cooling water of the first cooler 13, the first heat exchanger 15 and the second heat exchanger 16, the inlet temperature of the main compressor can be kept unchanged, and the compression ratio of the main compressor and the expansion ratio of the main expansion turbine can be kept basically unchanged.

[0054] The method further includes: regulating the inlet pressure of the main compressor 2 and the outlet pressure of the main expansion turbine + regulating the inlet temperature of the main compressor 2, specifically as follows:

[0055] When reducing the load, the flow rate and outlet pressure of the fresh air pre-compressed by the main compressor 2 are reduced by varying the rotational speed, the inlet guide vane angle, or a combination thereof. The flow rate of the expander (flue gas pressure-expander) 14 is increased by varying the rotational speed and the inlet guide vane angle, thereby reducing the high-pressure exhaust pressure of the main turbine 4 and the flow rate of the high-pressure flue gas mixed with the fresh air. At the same time, the inlet temperature of the main compressor is increased by reducing the flow rate of the cooling water of the first cooler 13, the first heat exchanger 15, and the second heat exchanger 16. In this way, on the basis of control method 1, the inlet flow rate of the main compressor can be further reduced, and at the same time, the pressure ratio of the main compressor and the expansion ratio of the main expansion turbine can be maintained with a small decrease while the turbine inlet temperature remains unchanged.

[0056] When increasing the load, the flow rate and outlet pressure of the fresh air pre-compressed by the main compressor 2 are increased by varying the rotational speed, the inlet guide vane angle, or a combination thereof. The flow rate of the flue gas pressure-expander 14 is reduced by varying the rotational speed and the inlet guide vane angle, thereby increasing the high-pressure exhaust pressure of the turbine 4 and the flow rate of the high-pressure flue gas mixed with the fresh air. At the same time, the inlet temperature of the main compressor 2 is reduced by increasing the flow rate of the cooling water of the first cooler 13, the first heat exchanger 15, and the second heat exchanger 16 (the reduction should not be lower than the design condition). In this way, on the basis of control method 1, the inlet flow rate of the main compressor can be further increased, and at the same time, the pressure ratio of the main compressor and the expansion ratio of the main expansion turbine can be maintained with a small decrease while the turbine inlet temperature remains unchanged.

[0057] The method further includes: controlling the inlet pressure of the main compressor 2 and the outlet pressure of the main expansion turbine + controlling the inlet temperature of the main compressor 2 + controlling the IGV of the main compressor, specifically:

[0058] When reducing the load, the flow rate and outlet pressure of the fresh air pre-compressed by the main compressor 2 are reduced by varying the rotational speed, the inlet guide vane angle, or a combination thereof. The flow rate of the flue gas pressure-expander 14 is increased by varying the rotational speed and the inlet guide vane angle, thereby reducing the high-pressure exhaust pressure of the turbine 4 and the flow rate of the high-pressure flue gas mixed with the fresh air. At the same time, the inlet temperature of the main compressor is increased by reducing the flow rate of the cooling water of the cooler 13, the first heat exchanger 15, and the second heat exchanger 16. At the same time, the flow rate can be reduced by the IGV angle of the main compressor 2. In this way, on the basis of control method 2, the inlet flow rate of the main compressor can be further reduced, and at the same time, the pressure ratio of the main compressor and the expansion ratio of the main expansion turbine can be maintained with a small decrease while the turbine inlet temperature remains unchanged.

[0059] During load increase, the flow rate and outlet pressure of the fresh air pre-compressed by the main compressor 2 are increased by varying the rotational speed, the inlet guide vane angle, and their combination, and the flow rate of the exhaust pressure expander 14 is reduced by varying the rotational speed and the inlet guide vane angle, so as to increase the high-pressure exhaust pressure of the turbine 4 and the flow rate of the high-pressure flue gas mixed with the fresh air; at the same time, the inlet temperature of the main compressor 2 is reduced by increasing the flow rate of the cooling water of the first cooler 13, the first heat exchanger 15, and the second heat exchanger 16 (the reduction shall not be lower than the design condition). Meanwhile, the flow rate can be further increased by the IGV angle of the main compressor, so that the inlet flow rate of the main compressor can be further increased on the basis of the control method 2, and at the same time, the pressure ratio of the main compressor and the expansion ratio of the main expansion turbine can be maintained with a small decrease while the initial temperature of the turbine remains unchanged.

[0060] The above description of the disclosed embodiments enables those skilled in the art to implement or use the present invention. Various modifications to these embodiments will be apparent to those skilled in the art, and the general principles defined herein can be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention will not be limited to the embodiments shown herein, but rather to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A gas turbine combined cycle power generation system based on flow control, which is based on a conventional combined cycle to improve the pressure of the compressor intake and the gas turbine exhaust, and is characterized in that: A pre-compressor (1) is arranged before the main compressor (2) to increase the intake pressure, and an expander (14) is arranged after the main turbine (4) to increase the exhaust pressure of the main turbine (4), so that the intake and exhaust pressures of the gas turbine are at high pressures under design conditions, and the pressures are gradually reduced under variable conditions; the pressure ratio of the pre-compressor (1) and the expansion ratio of the post-expander are adjusted by adjusting the speed and intake angle, and the inlet flow rate of the main compressor (2) is greatly adjusted in combination with the inlet temperature of the main compressor (2), while the inlet temperature and expansion ratio of the gas turbine turbine remain basically unchanged, thereby achieving high-efficiency operation under variable load operation of the combined cycle.

2. The gas turbine combined cycle power generation system based on flow control according to claim 1 is characterized in that: In terms of the system flow structure: the air compression process is divided into two sub-processes, and the high-temperature flue gas expansion process at the combustion chamber outlet is divided into two sub-processes. The air compression process is divided into two sub-processes, the new air is pre-compressed by the pre-compressor (1) and mixed with the new air and the high-pressure exhaust gas of the combustion engine before being compressed by the main compressor (2); The high-temperature flue gas expansion process at the combustion chamber outlet is divided into two sub-processes, including a main expansion process with a constant expansion ratio through a main turbine (4) and an exhaust gas residual pressure recovery expansion process through an expander (14).

3. The gas turbine combined cycle power generation system based on flow control according to claim 2 is characterized in that: The high-temperature flue gas expansion process at the combustion chamber outlet is specifically as follows: The high-pressure exhaust gas of the main compressor (2) enters the combustion chamber (3) to fully burn the fuel. The high-temperature flue gas at the outlet of the combustion chamber (3) passes through the main turbine (4) to undergo a main expansion process with a constant expansion ratio. The high-pressure exhaust gas of the main turbine (4) passes through the first waste heat boiler (6) and is divided into two parts. One part is cooled by the cooler and mixed with new air to enter the main compressor (2) to undergo a main compression process. The other part passes through the exhaust gas residual pressure recovery expansion process of the expander (14). The water vapor enters the steam turbine after the first waste heat boiler (6) is reheated by three pressures. The water vapor discharged from the low-pressure cylinder (9) of the first steam turbine enters the water pump (12) after passing through the condenser (11), and finally enters the first waste heat boiler (6) to undergo a water vapor circulation.

4. The gas turbine combined cycle power generation system based on flow control according to claim 3 is characterized in that: The high-pressure exhaust gas of the main turbine (4) is divided into two parts, specifically: The high-pressure exhaust gas of the main turbine (4) is divided into two parts. One part passes through the first waste heat boiler (6) and is mixed with fresh air to enter the main compressor (2) for the main compression process. The other part passes through the exhaust gas residual pressure recovery expansion process of the expander (14) and enters the second waste heat boiler (21).

5. An operation method of a gas turbine combined cycle power generation system based on flow control, applied to the gas turbine combined cycle power generation system based on flow control according to any one of claims 1 to 4, characterized in that: include: A second cooler (17) is added at the outlet of the pre-compressor (1). When the outlet of the pre-compressor (1) is cooled, the control of the inlet temperature of the main compressor (2) is simplified, and the inlet temperature of the main compressor (2) does not need to be controlled by the cooler (13). In addition, the adjustable range of the inlet temperature of the main compressor (2) can be expanded.

6. The method for operating a gas turbine combined cycle power generation system based on flow control according to claim 5, characterized in that: Also includes: The main compressor inlet pressure and main turbine outlet pressure are regulated + the main compressor inlet temperature remains unchanged, specifically: When the load is reduced, the flow rate and outlet pressure of the new air pre-compressed by the main compressor (2) are reduced by changing the speed, the inlet guide vane angle or a combination thereof, and the flow rate of the expander (14) is increased by changing the speed and the inlet guide vane angle, thereby reducing the high-pressure exhaust pressure of the main turbine (4) and the high-pressure flue gas flow mixed with the new air, and reducing the inlet flow rate of the main compressor (2) by reducing the pressure ratio of the new air pre-compression and the high-pressure exhaust pressure of the combustion engine; at the same time, the inlet temperature of the main compressor (2) is kept unchanged, and the pressure ratio of the main compressor (2) and the expansion ratio of the main turbine (4) are kept basically unchanged by reducing the flow rate of cooling water of the first cooler (13), the first heat exchanger (15) and the second heat exchanger (16); When the load is increased, the flow rate and outlet pressure of the new air pre-compressed by the main compressor (2) are increased by changing the speed, the inlet guide vane angle and their combination, and the flow rate of the expander (14) is reduced by changing the speed and the inlet guide vane angle, thereby increasing the high-pressure exhaust pressure of the main turbine (4) and the high-pressure flue gas flow mixed with the new air, and increasing the pressure ratio of the new air pre-compression and the high-pressure exhaust pressure of the combustion engine to increase the inlet flow rate of the main compressor (2). At the same time, by increasing the flow rate of cooling water of the first cooler (13), the first heat exchanger (15) and the second heat exchanger (16), the inlet temperature of the main compressor (2) is kept unchanged and the pressure ratio of the main compressor (2) and the expansion ratio of the main turbine (4) are kept basically unchanged.

7. The method for operating a gas turbine combined cycle power generation system based on flow control according to claim 5, characterized in that: Also includes: Main compressor inlet pressure and main turbine outlet pressure control + main compressor inlet temperature control, specifically: When the load is reduced, the flow rate and outlet pressure of the new air pre-compressed by the main compressor (2) are reduced by changing the speed, the inlet guide vane angle or a combination thereof, and the flow rate of the expander (14) is increased by changing the speed and the inlet guide vane angle, thereby reducing the high-pressure exhaust pressure of the main turbine (4) and the flow rate of high-pressure flue gas mixed with the new air. At the same time, the inlet temperature of the main compressor (2) is increased by reducing the flow rate of cooling water of the first cooler (13), the first heat exchanger (15) and the second heat exchanger (16), so that the inlet flow rate of the main compressor (2) can be further reduced, and at the same time, the pressure ratio of the main compressor (2) and the expansion ratio of the main turbine (4) can be kept slightly reduced but the initial temperature of the turbine remains unchanged; When the load is increased, the flow rate and outlet pressure of the new air pre-compressed by the main compressor (2) are increased by changing the speed, the inlet guide vane angle and their combination, and the flow rate of the expander (14) is reduced by changing the speed and the inlet guide vane angle, thereby increasing the high-pressure exhaust pressure of the main turbine (4) and the flow rate of the high-pressure flue gas mixed with the new air. At the same time, the inlet temperature of the main compressor (2) is reduced by increasing the flow rate of the cooling water of the first cooler (13), the first heat exchanger (15) and the second heat exchanger (16), so that the inlet flow rate of the main compressor (2) can be further increased, while the pressure ratio of the main compressor (2) and the expansion ratio of the main turbine (4) are kept slightly reduced but the initial temperature of the turbine remains unchanged.

8. The method for operating a gas turbine combined cycle power generation system based on flow control according to claim 5, characterized in that: Also includes: Main compressor inlet pressure and main turbine outlet pressure control + main compressor inlet temperature control + main compressor IGV control, specifically: When the load is reduced, the flow rate and outlet pressure of the new air pre-compressed by the main compressor (2) are reduced by changing the speed, the inlet guide vane angle and their combination, and the flow rate of the expander (14) is increased by changing the speed and the inlet guide vane angle, thereby reducing the high-pressure exhaust pressure of the main turbine (4) and the flow rate of high-pressure flue gas mixed with the new air. At the same time, the inlet temperature of the main compressor is increased by reducing the flow rate of cooling water of the first cooler (13), the first heat exchanger (15) and the second heat exchanger (16). At the same time, the flow rate is further reduced by the IGV angle of the main compressor (2), which can further reduce the inlet flow rate of the main compressor (2), while maintaining a small reduction in the pressure ratio of the main compressor (2) and the expansion ratio of the main turbine (4), but the initial temperature of the main turbine (4) remains unchanged; When the load is increased, the flow rate and outlet pressure of the new air pre-compressed by the main compressor (2) are increased by changing the speed, the inlet guide vane angle and their combination, and the flow rate of the expander (14) is reduced by changing the speed and the inlet guide vane angle, thereby increasing the high-pressure exhaust pressure of the main turbine (4) and the high-pressure flue gas flow mixed with the new air. At the same time, the inlet temperature of the main compressor (2) is reduced by increasing the flow rate of cooling water of the first cooler (13), the first heat exchanger (15) and the second heat exchanger (16). At the same time, the flow rate is further increased by the IGV angle of the main compressor (2), which can further increase the inlet flow rate of the main compressor (2), while maintaining a small reduction in the pressure ratio of the main compressor (2) and the expansion ratio of the main turbine (4) but keeping the initial temperature of the main turbine (4) unchanged.

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