A gas-steam combined cycle unit

Abstract

The utility model discloses a kind of gas steam combined cycle units, comprising: first unit and second unit, respectively equipped with gas turbine system, form first gas turbine and second gas turbine;First gas turbine water supply pipeline, through first gas turbine shut first valve body and second valve body;Second gas turbine water supply pipeline, through second gas turbine shut third valve body and fourth valve body;First gas turbine water supply flow regulating valve, set on first gas turbine water supply pipeline;Second gas turbine water supply flow regulating valve, set on second gas turbine water supply pipeline, including second condenser side regulating valve and second waste heat boiler side regulating valve, the technical scheme of this gas steam combined cycle unit can improve FGH system start-up problem, optimize the FGH water supply system design of two sets of units, to ensure that under different operating conditions, FGH system can be normally put into operation, improve the efficiency of gas turbine and stabilize unit load.

Description

Technical Field

[0001] This utility model relates to a gas-steam combined cycle unit. Background Technology

[0002] Gas turbines, as highly efficient power generation devices, typically use natural gas as fuel and are widely used in modern power systems. To improve the thermal efficiency of gas turbines, Mitsubishi has incorporated a natural gas heating system (FGH system) in its improved M701F4 gas turbine. This system utilizes the outlet water from the medium-pressure economizer as a heating source, and regulates the flow rate of the heating water through a flow control valve to further increase the temperature of the natural gas, thereby optimizing the operating efficiency of the gas turbine.

[0003] The existing combined cycle (FGH) power plant is equipped with two gas-fired power generation units, each featuring a gas turbine and a waste heat boiler. The first unit utilizes a high-, medium-, and low-pressure waste heat boiler, while the second unit employs a high- and low-pressure waste heat boiler. Both units use Mitsubishi's improved M701F4 gas turbine, with boilers supplied by Orient Sunrise Co., Ltd. In this design, the FGH system heats the natural gas by using water flow from the medium- or high-pressure system of the waste heat boiler as a heat source, thereby increasing the gas temperature and the gas turbine efficiency.

[0004] However, during the startup of the second unit, a load increase lockout alarm occurred after the gas turbine was connected to the grid. This alarm was triggered when the natural gas temperature was below 70°C, thus limiting the gas turbine's load increase. The root cause of this problem was a malfunction in the FGH feedwater flow control system. During this process, the FGH feedwater flow shut-off valve A failed to open, causing the FGH feedwater flow regulating valve to open; however, the FGH system failed to start normal operation.

[0005] The root cause of the problem lies in the different feedwater sources for the FGH (Feeder Gas Filter) of the first and second units. Although both units employ the same control strategy, the difference in feedwater pressure prevents the FGH feedwater system from reaching the required operating conditions during startup. The first unit's FGH feedwater is drawn from the outlet of the intermediate-pressure economizer and rapidly increased to the required pressure through the throttling action of the intermediate-pressure feedwater regulating valve, ensuring normal startup of the FGH system. In contrast, the second unit's FGH feedwater is drawn from the intermediate stage of the high-pressure economizer, with its feedwater pressure matching that of the high-pressure system. During cold startup, the high-pressure steam drum pressure of the second unit is close to 0 MPa, and as the gas turbine speed increases, the high-pressure steam drum pressure only reaches about 1.1 MPa. This prevents the FGH water-side system from reaching the required 4.5 MPa pressure during startup, thus affecting the normal operation of the FGH system.

[0006] Therefore, the natural gas heating effect of the FGH system of the second unit is poor during cold start-up, and the natural gas temperature will drop further as the gas turbine load gradually increases, eventually triggering the low natural gas temperature lockout, which affects the gas turbine's load increase and operational stability. Utility Model Content

[0007] The purpose of this utility model is to provide a technical solution for gas turbine combined cycle (FGH) units that can improve the start-up problem of the FGH system, optimize the design of the FGH feedwater system of the two units, and ensure that the FGH system can be put into normal operation under different operating conditions, thereby improving the efficiency of the gas turbine and stabilizing the unit load.

[0008] The technical solution adopted by this utility model to solve its technical problem is:

[0009] A gas-fired steam combined cycle unit, comprising:

[0010] The first unit and the second unit are each equipped with a gas turbine system, forming the first gas turbine and the second gas turbine;

[0011] The feedwater pipeline of the first gas turbine is connected to the medium-pressure economizer and the medium-pressure feedwater regulating valve through the first valve body and the second valve body of the first gas turbine, and is located between the outlet of the medium-pressure economizer and the medium-pressure feedwater regulating valve.

[0012] The second gas turbine feedwater pipeline connects the high-pressure economizer and the furnace-side pressure regulating valve through the second gas turbine shut-off third and fourth valve bodies, and is located between the intermediate stage of the high-pressure economizer and the furnace-side pressure regulating valve.

[0013] The first gas turbine feedwater flow regulating valve is installed on the first gas turbine feedwater pipeline, including the first condenser side regulating valve and the first waste heat boiler side regulating valve;

[0014] The second gas turbine feedwater flow regulating valve is installed on the second gas turbine feedwater pipeline, including the second condenser side regulating valve and the second waste heat boiler side regulating valve;

[0015] The first valve body includes an inlet channel and an outlet channel, a valve core disposed between the inlet channel and the outlet channel, a valve cover disposed above the valve core, a valve stem disposed inside the valve cover and connected to the valve core, a housing fitted outside the valve stem, and a mold cover disposed above the housing. The first valve body, the second valve body, the third valve body and the fourth valve body have the same structure.

[0016] Preferably, the regulating valve on the first condenser side is connected to the condenser of the first unit, and the regulating valve on the first waste heat boiler side is connected to the low-pressure economizer of the first waste heat boiler.

[0017] Preferably, the regulating valve on the second condenser side is connected to the second unit condenser, and the regulating valve on the second waste heat boiler side is connected to the vacuum deaerator of the second waste heat boiler.

[0018] Preferably, the first gas turbine disconnects the first valve body and the second valve body, and connects them to the input and output ends of the first gas turbine feedwater flow regulating valve, respectively.

[0019] Preferably, the second gas turbine disconnects the first valve body and the second valve body, and connects them to the input and output ends of the second gas turbine feedwater flow regulating valve, respectively.

[0020] Preferably, the gas turbine feedwater control strategies of the first and second units are the same, and include an automatic adjustment system to control the opening and closing of the shut-off valve and the flow regulating valve.

[0021] Preferably, the gas turbine feedwater flow regulating valves of the first and second units are connected to the respective gas turbine pipelines and flow setting devices via regulating valves.

[0022] Preferably, the first gas turbine feedwater flow regulating valve is connected to the inlet of the low-pressure economizer of the first waste heat boiler, and the second gas turbine feedwater flow regulating valve is connected to the inlet of the vacuum deaerator of the second waste heat boiler.

[0023] Compared with the prior art, the beneficial effects of this utility model are:

[0024] By installing dedicated feedwater flow regulating valves (including regulating valves on the condenser side and the waste heat boiler side), the feedwater flow of each gas turbine can be precisely adjusted to ensure optimal operating conditions for each turbine and prevent system performance degradation or equipment damage due to insufficient or unstable feedwater flow. Since different units draw feedwater from different waste heat boiler systems (such as medium-pressure and high-pressure economizers), pressure differences in the feedwater system may cause insufficient pressure issues for some units during startup. This solution optimizes valve arrangement and regulation methods to ensure that the feedwater system pressure can be flexibly adjusted according to the unit's operating status, thereby ensuring stable operation of the feedwater system.

[0025] By installing multiple regulating valves in the gas turbine feedwater pipeline, the scheme can ensure that the feedwater flow of the first and second units maintains reasonable flow and pressure during the conversion and regulation between the gas turbine and the waste heat boiler, thereby improving the overall thermal efficiency and economy of the system. The scheme optimizes the feedwater flow regulation method between the gas turbine and the waste heat boiler. In particular, during unit start-up and load changes, it can balance the supply pressure and avoid the gas turbine's load increase limitation or system failure due to feedwater system instability, thus ensuring smooth start-up and stable operation of the system. Attached Figure Description

[0026] Figure 1 This is a schematic diagram of the first unit structure of a gas-fired steam combined cycle unit according to the present invention;

[0027] Figure 2 This is a schematic diagram of the second unit structure of a gas-fired steam combined cycle unit according to the present invention;

[0028] Figure 3 This is a front view of the first valve body of a gas-steam combined cycle unit according to the present invention;

[0029] Figure 4 This is a three-dimensional structural diagram of the first valve body of a gas-steam combined cycle unit according to the present invention;

[0030] Figure 5 This is a schematic block diagram of a gas-steam combined cycle unit according to the present invention;

[0031] Figure 6 To control the data curves before implementation of optimization;

[0032] Figure 7 To control the data curves after optimization. Detailed Implementation

[0033] The principles and features of this utility model are described below with reference to the accompanying drawings. The examples given are for illustrative purposes only and are not intended to limit the scope of this utility model. The utility model is described more specifically in the following paragraphs by way of example with reference to the accompanying drawings. The advantages and features of this utility model will become clearer from the following description and claims. It should be noted that the drawings are all in a very simplified form and use non-precise proportions, and are only used to facilitate and clarify the illustration of the embodiments of this utility model.

[0034] In the description of this utility model, it should be understood that the terms "upper," "lower," "front," "rear," "left," "right," "vertical," and "horizontal," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing this utility model and for simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this utility model. Furthermore, the terms "first," "second," etc., are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Thus, features defined with "first," "second," etc., may explicitly or implicitly include one or more of that feature. In the description of this utility model, it should be noted that, unless otherwise explicitly specified and limited, the terms "installed," "connected," and "joined" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication between two components.

[0035] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items. Example

[0036] See Figure 1-5 As shown, a gas-fired steam combined cycle unit includes:

[0037] The first unit and the second unit are respectively equipped with gas turbine systems, forming the first gas turbine 1 and the second gas turbine 2;

[0038] The first gas turbine feedwater pipeline 3 is connected to the medium-pressure economizer 4 and the medium-pressure feedwater regulating valve 5 through the first gas turbine 1 shutting off the first valve body 13 and the second valve body, and is located between the outlet of the medium-pressure economizer 4 and the medium-pressure feedwater regulating valve 5.

[0039] The second gas turbine feedwater pipeline 6 connects the high-pressure economizer 7 and the furnace-side pressure regulating valve 8 through the second gas turbine 2 shutting off the third and fourth valve bodies, and is located between the intermediate stage of the high-pressure economizer 7 and the furnace-side pressure regulating valve 8.

[0040] The first gas turbine feedwater flow regulating valve is installed on the first gas turbine feedwater pipeline 3, including the first condenser side regulating valve 9 and the first waste heat boiler side regulating valve 10.

[0041] The second gas turbine feedwater flow regulating valve is installed on the second gas turbine feedwater pipeline 6, including the second condenser side regulating valve 11 and the second waste heat boiler side regulating valve 12.

[0042] The first valve body 13 includes an inlet channel 14 and an outlet channel 15, a valve core disposed between the inlet channel 14 and the outlet channel 15, a valve cover 16 disposed above the valve core, a valve stem disposed inside the valve cover 16 and connected to the valve core, a housing 17 fitted over the valve stem, and a mold cover 18 disposed above the housing 17. The first valve body 13, the second valve body, the third valve body, and the fourth valve body have the same structure.

[0043] The first valve body 13, the second valve body, the third valve body and the fourth valve body have the same structure.

[0044] Precise feedwater flow control can be achieved by installing flow regulating valves on the feedwater pipelines of each gas turbine, especially on the condenser and waste heat boiler sides. This fine regulation ensures that the operating efficiency of each gas turbine is maximized, avoiding reduced thermal efficiency or system instability caused by feedwater flow mismatch.

[0045] Introducing multiple regulating valves and pressure regulating devices into the water supply pipeline can effectively control the water flow at different pressure levels (such as medium and high pressure) and ensure that the pressure remains within a reasonable range when the system load changes. This stable pressure control can improve the stability and safety of the unit and avoid system failures caused by pressure fluctuations.

[0046] This solution can balance the demands of various subsystems by adjusting feedwater flow and pressure during gas turbine startup and load fluctuations, ensuring stable system operation under different conditions. Especially during the startup phase of combined cycle units, it can ensure optimal operating conditions for each unit, thereby reducing startup time and improving the unit's rapid response capability.

[0047] The first condenser-side regulating valve 9 is connected to the first unit condenser, and the first waste heat boiler-side regulating valve 10 is connected to the first waste heat boiler low-pressure economizer; the second condenser-side regulating valve 11 is connected to the second unit condenser, and the second waste heat boiler-side regulating valve 12 is connected to the second waste heat boiler vacuum deaerator.

[0048] By connecting the first condenser-side regulating valve 9 to the condenser of the first unit and the first waste heat boiler-side regulating valve 10 to the low-pressure economizer, the waste heat released by the condenser can be efficiently recovered and utilized. This allows the system to better preheat the feedwater through the low-pressure economizer, improving thermal efficiency and reducing fuel consumption.

[0049] Connecting the second waste heat boiler-side regulating valve 12 to the vacuum deaerator effectively removes dissolved gases (such as oxygen) from the water, preventing scale or corrosion formation in the boiler system. This design improves water treatment efficiency, extends equipment lifespan, and ensures stable operation of the steam system.

[0050] The design of the regulating valve allows for flexible adjustment of water flow and pressure between the condenser and waste heat boiler according to the actual operating conditions of the system, ensuring that different units operate under optimal conditions. This flexibility enhances the system's responsiveness, enabling it to adapt quickly to changes in load or operating conditions, thereby improving the stability and efficiency of the entire unit.

[0051] The first gas turbine 1 shuts off the first valve body and the second valve body, and connects them to the input and output ends of the first gas turbine feedwater flow regulating valve, respectively; the second gas turbine 2 shuts off the first valve body and the second valve body, and connects them to the input and output ends of the second gas turbine feedwater flow regulating valve, respectively.

[0052] By connecting the valve bodies of the first gas turbine 1 and the second gas turbine 2 to the input and output terminals of their respective feedwater flow regulating valves, precise regulation of the feedwater flow for each gas turbine can be achieved. This allows for dynamic adjustment of the feedwater flow based on the operating status of each gas turbine (such as load changes, temperature changes, etc.), ensuring maximum thermal efficiency, avoiding excessive or insufficient feedwater supply, and thus optimizing system operation.

[0053] Each gas turbine is equipped with an independent feedwater flow control valve, enabling the system to quickly adjust the feedwater flow according to load changes. This flexibility helps the system respond quickly to load fluctuations or start-up demands, thereby maintaining system stability during load changes and reducing unnecessary energy waste.

[0054] By precisely controlling the feedwater flow rate of the gas turbine, excessive thermal shock and unbalanced water flow can be reduced, preventing system failures or component damage caused by unstable water flow or overheating. This helps extend the service life of critical equipment, while reducing maintenance costs and downtime, and improving the overall reliability of the system.

[0055] The gas turbine feedwater control strategies for the first and second units are the same, and include an automatic adjustment system to control the opening and closing of shut-off valves and flow control valves; the gas turbine feedwater flow control valves of the first and second units are connected to their respective gas turbine pipelines via control valves and flow setting devices; the first gas turbine feedwater flow control valve is connected to the inlet of the low-pressure economizer of the first waste heat boiler, and the second gas turbine feedwater flow control valve is connected to the inlet of the vacuum deaerator of the second waste heat boiler.

[0056] By adopting the same gas turbine feedwater control strategy for both Unit 1 and Unit 2, and introducing an automatic control system, coordinated control of the two units can be achieved, ensuring operational consistency. The automatic control system can monitor system status in real time and automatically adjust the opening and closing of shut-off valves and flow control valves to ensure the gas turbine feedwater flow is within the optimal range. This helps improve operational efficiency, reduce human error, and enhance the system's adaptability.

[0057] The feedwater flow regulating valve of the first gas turbine 1 is connected to the inlet of the low-pressure economizer, and the feedwater flow regulating valve of the second gas turbine 2 is connected to the inlet of the vacuum deaerator, thus optimizing the waste heat recovery effect. The low-pressure economizer helps recover waste heat, increases water temperature, and reduces boiler fuel consumption; the vacuum deaerator reduces the corrosion risk of the boiler system by removing dissolved gases from the water. By precisely controlling the feedwater flow, heat energy recovery and utilization can be maximized, improving the thermal efficiency of the entire system and saving energy.

[0058] This design, through the combination of regulating valves and flow setting devices, allows each unit to independently and flexibly adjust the feedwater flow to meet varying operating load demands. Furthermore, due to the consistency of the control strategy, both units can operate smoothly under different load and environmental conditions, reducing system fluctuations and ensuring stability. The introduction of automatic adjustment improves the system's response speed to load changes, enhancing the overall flexibility and operational reliability of the units.

[0059] The purpose of the FGH water supply shut-off valve A interlock opening logic is to determine whether the FGH has been pressurized.

[0060] Based on historical curves and the actual situation of the unit, the interlocking opening logic of the feedwater shut-off valve A of the second gas turbine FGH is optimized as follows:

[0061] The original logic "Delay for 5 seconds if the outlet feedwater pressure of the second gas turbine FGH (20LAB96CP103) is greater than 4.5MPa" is replaced with: "Delay for 5 seconds if the outlet feedwater pressure of the second gas turbine FGH (20LAB96CP103) is greater than the outlet pressure of the second gas turbine TCA flow control valve (waste heat boiler side) (20LAB86CP104)" and "Delay for 5 seconds if the outlet pressure of the second gas turbine TCA flow control valve (waste heat boiler side) (20LAB86CP104) is greater than 0.8MPa".

[0062] The reasons are as follows:

[0063] 1. Add a comparison and judgment between the feedwater pressure at the outlet of the second gas turbine FGH (20LAB96CP103) and the outlet pressure at the outlet of the second gas turbine TCA flow control valve (waste heat boiler side) (20LAB86CP104).

[0064] The outlet of the TCA flow control valve (waste heat boiler side) of the second gas turbine is connected to the high-pressure steam drum, and it directly reflects the pressure of the high-pressure steam drum of the second waste heat boiler. After the water side of the second gas turbine FGH is pressurized, the feedwater pressure at the FGH outlet is the stagnation pressure, which is the pressure of the high-pressure system of the second waste heat boiler. It will be consistent with the pressure of the high-pressure steam drum. Due to the height difference of the pressure measuring point, in actual process, after the water side of the second gas turbine FGH is pressurized, the feedwater pressure at the outlet of the second gas turbine FGH is greater than the outlet pressure of the TCA flow control valve (waste heat boiler side). This can be used as a judgment that the water side pressurization of the second gas turbine FGH is complete when the pressure is high or when the pressure of the high-pressure system is high.

[0065] 2. Add a comparison criterion that the outlet pressure (20LAB86CP104) of the second gas turbine TCA flow control valve (waste heat boiler side) is greater than 0.8MPa. During cold start-up, the pressure of the second waste heat boiler high-pressure system is close to 0, and the feedwater pressure at the outlet of the second gas turbine FGH is also close to 0. A simple pressure comparison is insufficient to determine whether the second gas turbine FGH has completed pressurization. The pressure comparison should be performed after the boiler-side high-pressure system has started pressurizing.

[0066] According to the query curve, when the second gas turbine reaches a speed of about 2650 r / min during cold start-up, the high-pressure system pressurizes to 0.8 MPa. If the logic judgment meets the interlocking opening condition of the FGH feedwater shut-off valve A at this time, the FGH should be in normal operation by the time the gas turbine is connected to the grid.

[0067] Optimization effect

[0068] See Figure 6-7 As shown, after implementing the above control optimization, the load limitation time after the gas turbine is connected to the grid is shortened from the original 37 minutes to 12 minutes, avoiding prolonged operation of the gas turbine at low load and resulting in fuel waste. The 25-minute time reduction saves approximately 10,600 cubic meters of natural gas. 3 .

[0069] The above embodiments of this utility model are not intended to limit the scope of protection of this utility model. The implementation of this utility model is not limited thereto. All other modifications, substitutions or alterations made to the above structure of this utility model based on the above content of this utility model and in accordance with the common technical knowledge and conventional means in the field, without departing from the basic technical idea of ​​this utility model, shall fall within the scope of protection of this utility model.

Claims

1. A combined cycle gas turbine and steam turbine unit, characterized in that, include: The first unit and the second unit are each equipped with a gas turbine system, forming the first gas turbine and the second gas turbine; The feedwater pipeline of the first gas turbine is connected to the medium-pressure economizer and the medium-pressure feedwater regulating valve through the first valve body and the second valve body of the first gas turbine, and is located between the outlet of the medium-pressure economizer and the medium-pressure feedwater regulating valve. The second gas turbine feedwater pipeline connects the high-pressure economizer and the furnace-side pressure regulating valve through the second gas turbine shut-off third and fourth valve bodies, and is located between the intermediate stage of the high-pressure economizer and the furnace-side pressure regulating valve. The first gas turbine feedwater flow regulating valve is installed on the first gas turbine feedwater pipeline, including the first condenser side regulating valve and the first waste heat boiler side regulating valve; The second gas turbine feedwater flow regulating valve is installed on the second gas turbine feedwater pipeline, including the second condenser side regulating valve and the second waste heat boiler side regulating valve. The first valve body includes an inlet channel and an outlet channel, a valve core disposed between the inlet channel and the outlet channel, a valve cover disposed above the valve core, a valve stem disposed inside the valve cover and connected to the valve core, a housing fitted outside the valve stem, and a mold cover disposed above the housing. The first valve body, the second valve body, the third valve body and the fourth valve body have the same structure.

2. The combined cycle gas turbine unit according to claim 1, characterized in that, The regulating valve on the first condenser side is connected to the first unit condenser, and the regulating valve on the first waste heat boiler side is connected to the first waste heat boiler low-pressure economizer.

3. The combined cycle gas turbine unit according to claim 2, characterized in that, The regulating valve on the second condenser side is connected to the second unit condenser, and the regulating valve on the second waste heat boiler side is connected to the second waste heat boiler vacuum deaerator.

4. The combined cycle gas turbine unit according to claim 3, characterized in that, The first gas turbine disconnects the first valve body and the second valve body, and connects them to the input and output ends of the first gas turbine feedwater flow regulating valve, respectively.

5. The combined cycle gas turbine unit according to claim 4, characterized in that, The second gas turbine disconnects the first and second valve bodies and connects them to the input and output ends of the second gas turbine feedwater flow regulating valve, respectively.

6. The combined cycle gas turbine unit according to claim 3, characterized in that, The gas turbine feedwater control strategies for Unit 1 and Unit 2 are the same, and include an automatic regulation system to control the opening and closing of shut-off valves and flow regulating valves.

7. The combined cycle gas turbine unit according to claim 6, characterized in that, The gas turbine feedwater flow regulating valves of the first and second units are connected to the respective gas turbine pipelines and flow setting devices via regulating valves.

8. The combined cycle gas turbine unit according to claim 7, characterized in that, The first gas turbine feedwater flow regulating valve is connected to the inlet of the low-pressure economizer of the first waste heat boiler, and the second gas turbine feedwater flow regulating valve is connected to the inlet of the vacuum deaerator of the second waste heat boiler.

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