A starting method for accelerating the warm-up valve starting of a steam turbine unit

Abstract

This invention relates to a startup method for accelerating the warm-up valve startup of a steam turbine unit, comprising the following steps: S1, after warm-up and steam impurity removal, the pressure of the main steam in the main steam pipeline is P1, where P1 is 4-8 MPa, and the main steam enters the main valve chamber of the main regulating integrated valve; S2, when the average wall temperature T of the regulating valve section of the main regulating integrated valve... m Raise to temperature T m1 At that time, T m1 ≥T sat -T x1 The main steam pressure in the main steam pipeline is reduced to P2, where P2 is 1-2 MPa, and T... x1 The temperature range is 100–150℃, T sat S2 is the saturated steam temperature corresponding to the main steam pressure P2; S3, the main steam valve opens, steam enters the regulating valve chamber, and warms the valve through convection heat exchange; S4, when the average wall temperature T of the regulating valve section... m Raise to temperature T m2 At that time, T m2 ≥T s -T x2 Warm-up valve complete, main steam valve closed, where T x2 The temperature range is 50–100℃, T s S1 is the main steam temperature at pressure P1 in step S1; S5, increase the pressure of the main steam in the main steam pipeline to P3, P3≤P1, and between 4 and 8 MPa; S6, open the main steam valve and regulating valve of the main control integrated valve, and the steam enters the steam turbine.

Description

Technical Field

[0001] This invention relates to the field of steam turbine control technology, and specifically to a startup method for accelerating the warm-up valve startup of a steam turbine. Background Technology

[0002] During the cold start of a steam turbine, the main steam valve often fails to open due to the slow warm-up valve speed, requiring a long wait for the warm-up valve and slowing down the start-up speed of the entire steam turbine unit.

[0003] The entire startup process of a steam turbine generator set includes: boiler heating → pipe warm-up → steam impurity removal → valve warm-up → cylinder warm-up → start-up → load bearing. Steam is generated in the boiler and gradually heats up. The steam enters the main steam pipeline from the boiler and reaches the turbine valves for pipe warm-up. At this time, the turbine main steam valve cannot be opened. Firstly, the steam superheat is insufficient; wet steam is not allowed to enter the turbine. Secondly, the steam purity and cleanliness are not up to standard, containing various salts. If impure steam enters the turbine and condenses, it will produce water droplets or deposits with a certain degree of corrosiveness, thus corroding the equipment and affecting turbine efficiency. Steam impurity removal takes a considerable amount of time, usually about one hour. By this time, pipe warm-up is already complete, and the temperature and pressure of the main steam are already very high (380–420℃, 5–8 MPa). Because the steam parameters are too high at this time, the main steam valve is not ready to open. Since the valve body is still cold, condensation heat transfer will occur once it comes into contact with high-temperature steam, causing the surface temperature of the valve body to rise sharply and generate high thermal stress, which in turn causes fatigue damage and shortens the service life of the valve body.

[0004] The system diagram and valve structure of the steam turbine unit are attached as follows. Figure 1 and attached Figure 2 As shown, a high-power steam turbine typically uses a main control valve 2 connected to the main steam pipeline 1. The main control valve 2 includes a main valve section 21 and a control valve section 22. The main valve section 21 contains a main valve chamber 23 and a main steam valve 25, while the control valve section 22 contains a control valve chamber 24 and a regulating valve 26. The main valve chamber 23 is connected to the main steam pipeline 1 via an inlet pipe and is always in contact with the main steam. The control valve chamber 24 is used to connect to the steam turbine 3. The main steam valve 25 is located between the main valve chamber 23 and the control valve chamber 24, controlling the flow of steam from the main valve chamber 23 to the control valve chamber 24. The regulating valve 26 controls the flow of steam from the control valve chamber 24 to the steam turbine 3. No steam enters the control valve chamber 24 before the main steam valve 25 is opened. Heat can only be conducted from the main valve section 21 to the regulating valve section 22 via thermal conduction. The main steam valve 25 is only allowed to open after the valve body metal of the regulating valve section 22 reaches a certain temperature. However, warming the valve through thermal conduction is very slow.

[0005] Therefore, how to improve the warm-up process of the steam turbine unit during startup and accelerate the cold start process of the steam turbine unit is an urgent problem to be solved. Summary of the Invention

[0006] In view of the shortcomings of the prior art described above, the technical problem to be solved by the present invention is to provide a startup method for accelerating the warm-up valve startup of a steam turbine unit, which can accelerate the opening process of the main steam valve of the main control integrated valve, improve the warm-up valve speed, and thus improve the startup speed of the unit.

[0007] To achieve the above objectives, the present invention provides a startup method for accelerating the warm-up valve startup of a steam turbine unit, wherein the steam turbine unit includes a main steam pipeline, a main control valve, and a steam turbine, and the startup method includes the following steps:

[0008] S1. After warming up the pipes and removing impurities from the steam, the pressure of the main steam in the main steam pipeline is P1, which is between 4 and 8 MPa. The main steam enters the main valve chamber of the main control integrated valve.

[0009] S2, when the average wall temperature T of the regulating section of the main regulating valve... m Raise to temperature T m1 At that time, T m1 ≥T sat -T x1 The pressure of the main steam in the main steam pipeline is reduced to P2, where P2 is between 1 and 2 MPa, and T x1 The primary reference temperature is between 100 and 150°C. sat The saturated steam temperature corresponding to the main steam pressure P2;

[0010] S3. The main steam valve in the main control integrated valve opens, and steam enters the control valve chamber.

[0011] S4, when the average wall temperature T of the valve section m Further increase to temperature T m2 At that time, T m2 ≥T s -T x2 Warm-up valve complete, main steam valve closed, where T x2 The second reference temperature is between 50 and 100°C. s The main steam temperature at pressure P1 in step S1;

[0012] S5. Increase the pressure of the main steam in the main steam pipeline to P3, where P3 ≤ P1, and is between 4 and 8 MPa.

[0013] S6. Open the main steam valve and regulating steam valve of the main control integrated valve, and steam enters the steam turbine.

[0014] Furthermore, in step S1, P1 = 6 MPa.

[0015] Furthermore, in step S2, P2 = 2 MPa.

[0016] Furthermore, the turbine unit also includes a high-pressure bypass connected to the main steam pipeline, and a bypass valve is provided on the high-pressure bypass. In step S2, the pressure of the main steam in the main steam pipeline is reduced by increasing the opening of the bypass valve on the high-pressure bypass.

[0017] Furthermore, in step S5, the pressure of the main steam in the main steam pipeline is increased by reducing the opening degree of the bypass valve on the high-pressure bypass.

[0018] Furthermore, in step S2, T x1 =130°C.

[0019] Furthermore, the regulating valve of the main regulating integrated valve has a steam leakage hole that connects the regulating valve chamber and the steam turbine. In step S3, some steam enters the steam turbine through the steam leakage hole, causing the steam turbine speed to rise. If the speed reaches 90% of the critical resonance speed, the main steam valve is closed first and then opened again after the speed drops.

[0020] Furthermore, in step S4, T x2 =80℃.

[0021] Furthermore, in step S5, P3 = 6 MPa.

[0022] As described above, the starting method of the present invention has the following beneficial effects:

[0023] The main steam preheats the regulating valve through heat conduction through the valve shell. After preheating the regulating valve to a specific temperature, the main steam pressure is reduced, and the main steam valve is opened, allowing the main steam to enter the regulating valve chamber and be directly heated to the designated temperature, completing the valve warm-up. Then, the main steam pressure is increased, and the main regulating valve is opened normally, allowing steam to enter the turbine for startup. Compared to existing methods, this approach effectively accelerates the valve warm-up process without causing a rapid rise in valve body surface temperature, thus avoiding high thermal stress and preventing damage to the valve body, which could shorten its service life. Because the valve warm-up process is accelerated, the main steam valve opening process is also faster, shortening the turbine's cold start-up time, which is beneficial for energy conservation, emission reduction, and improved unit operational flexibility. This invention is particularly suitable for combined cycle peak-shaving power plants with high requirements for start-up speed. Attached Figure Description

[0024] Figure 1 This is a system schematic diagram of a steam turbine unit.

[0025] Figure 2 This is a schematic diagram of the main control integrated valve.

[0026] Figure 3 The graph showing the relationship between the saturated temperature and pressure of the main steam.

[0027] Figure 4 This is a flowchart illustrating the startup method of the present invention.

[0028] Explanation of icon numbers

[0029] 1. Main steam pipeline

[0030] 2. Main control integrated valve

[0031] 21 Main Valve Section

[0032] 22. Valve Control Section

[0033] 23 Main valve chamber

[0034] 24 Valve regulating chamber

[0035] 25 Main steam valve

[0036] 26 Adjusting valve

[0037] 3 Steam Turbine

[0038] 4. High-voltage bypass Detailed Implementation

[0039] The following specific embodiments illustrate the implementation of the present invention. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification.

[0040] It should be understood that the structures, proportions, sizes, etc., depicted in the accompanying drawings of this specification are merely for illustrative purposes to aid those skilled in the art in understanding and reading the content disclosed herein, and are not intended to limit the conditions under which the invention can be implemented. Therefore, they have no substantial technical significance. Any modifications to the structure, changes in proportions, or adjustments to the size, without affecting the effects and objectives achieved by the invention, should still fall within the scope of the technical content disclosed herein. Furthermore, the terms such as "upper," "lower," "left," "right," and "middle" used in this specification are merely for clarity and are not intended to limit the scope of the invention. Changes or adjustments to their relative relationships, without substantially altering the technical content, should also be considered within the scope of the invention's implementation.

[0041] See Figures 1 to 4 This invention provides a method for accelerating the warm-up start-up of a steam turbine unit. The steam turbine unit includes a main steam pipeline 1, a main control valve 2, and a steam turbine 3. The main steam pipeline 1 is connected to the main valve chamber 23 of the main control valve 2, and the regulating valve chamber 24 of the main control valve 2 is connected to the steam turbine 3 through a regulating valve 26. The main control valve 2 controls the flow of steam from the main steam pipeline 1 into the steam turbine 3.

[0042] The startup method of the present invention includes the following steps:

[0043] S1. After warming up the pipes and removing impurities from the steam, the pressure of the main steam in the main steam pipe 1 is P1, which is between 4 and 8 MPa. The specific value can be selected according to the actual situation. The corresponding main steam temperature is 360-420°C, and P1 is preferably 6 MPa. The main steam enters the main valve chamber 23 of the main regulating integrated valve 2 and warms up the valve through heat conduction.

[0044] S2, when the average wall temperature T of the regulating section 22 of the main regulating integrated valve 2 is... m Raise to temperature T m1 At that time, T m1 ≥T sat -T x1 The pressure of the main steam in the main steam pipeline 1 is reduced to P2, where P2 is between 1 and 2 MPa. A suitable value can be set according to actual conditions. When the pressure is between 1 and 2 MPa, the corresponding main steam temperature is 360–400°C. P2 is preferably 2 MPa for better valve warming. Where T... x1 The primary reference temperature is between 100 and 150°C. sat This refers to the saturated steam temperature corresponding to the main steam pressure of P2. The average wall temperature T of the regulating valve section 22 is also mentioned. m It can be monitored using a temperature sensor. The first reference temperature T x1 Choose an appropriate value based on the actual situation; preferably, T x1 =130℃. Since the opening conditions of the main steam valve 25 are related to the saturation temperature of the main steam, the lower the saturation temperature, the smaller the thermal shock to the valve body. The saturation temperature of the main steam is related to the main steam pressure; see [link to relevant documentation]. Figure 3 As shown, the lower the main steam pressure, the lower the main steam saturation temperature. Therefore, reducing the main steam pressure is beneficial for the rapid opening of the main steam valve 25.

[0045] In this embodiment, see Figure 1 The turbine unit also includes a high-pressure bypass 4 connected to the main steam pipeline 1. The high-pressure bypass 4 is equipped with a bypass valve. Preferably, the pressure of the main steam in the main steam pipeline 1 is reduced by increasing the opening of the bypass valve on the high-pressure bypass 4.

[0046] S3. When the main steam valve 25 of the main control valve 2 is opened, steam enters the control valve chamber 24 and further warms the control valve through convection heat exchange. The main steam enters the control valve chamber 24 and quickly increases the temperature of the control valve section 22.

[0047] In this embodiment, the regulating valve 26 of the main regulating integrated valve 2 has a steam leakage hole connecting the regulating valve chamber 24 and the steam turbine 3. A small amount of steam will enter the steam turbine 3 through the steam leakage hole, causing the speed of the steam turbine 3 to increase. If the speed reaches 90% of the critical resonance speed, the main steam valve 25 is closed first, and after the speed drops, the main steam valve 25 is reopened. This operation may be repeated multiple times, so that the average wall temperature of the regulating valve section 22 reaches T without the steam turbine 3 speed reaching the critical resonance speed. m1 .

[0048] S4, when the average wall temperature T of the regulating valve section 22 m Further increase to temperature T m2 At that time, T m2 ≥T s -T x2 Warm-up valve complete, main steam valve 25 closed, where T x2 The second reference temperature is between 50 and 100°C. A suitable value can be selected based on actual conditions. Preferably, T... x2 =80℃, T s1 The temperature of the main steam at pressure P1 in step S1.

[0049] S5. Increase the pressure of the main steam in the main steam pipeline 1 from P2 to P3, where P3 ≤ P1 and is between 4 and 8 MPa. Specifically, an appropriate value can be set according to the actual situation, corresponding to a main steam temperature of 360–420°C. P3 is preferably 6 MPa, equal to P1. In this embodiment, preferably, the pressure of the main steam in the main steam pipeline 1 is reduced by decreasing the opening of the bypass valve on the high-pressure bypass 4.

[0050] S6. Open the main steam valve 25 and regulating steam valve 26 of the main control integrated valve 2. Steam enters the steam turbine 3, and the turbine starts to start, warm up, and carry out load, and continues the subsequent start-up operations.

[0051] In this invention, before step S1, the turbine unit starts up, steam, water and oil are introduced, vacuum is drawn, the turbine 3 runs at turning speed, the main steam pipeline 1 and the steam turbine 3's drain valves are opened, the boiler starts up, the high-pressure electric isolation valve is opened, the main steam pipeline 1 is warmed up, and the steam is cleaned of impurities, so that the pressure of the main steam entering the main steam pipeline 1 is P1.

[0052] The starting method of the present invention has the following beneficial effects:

[0053] The main steam first preheats the regulating valve through heat conduction through the valve shell. After preheating the regulating valve to a specific temperature, the main steam pressure is reduced to make the main steam valve 25 ready to open, allowing the main steam to enter the regulating valve chamber 24 and directly heat the valve shell to the specified temperature, thus completing the valve warm-up. Compared with existing methods, this method can effectively accelerate the valve warm-up process and avoid the rapid rise in valve body surface temperature, which would generate high thermal stress and damage the valve body, thus preventing a shortened service life. Because the valve warm-up process is accelerated, the opening process of the main steam valve 25 is also accelerated, which can shorten the cold start-up time of the turbine unit, thus saving energy, reducing emissions, and improving the operational flexibility of the unit. This invention is particularly suitable for combined cycle peak-shaving power plants with high requirements for start-up speed.

[0054] In summary, this invention effectively overcomes the various shortcomings of the prior art and has high industrial application value.

[0055] The above embodiments are merely illustrative of the principles and effects of the present invention and are not intended to limit the invention. Any person skilled in the art can modify or alter the above embodiments without departing from the spirit and scope of the present invention. Therefore, all equivalent modifications or alterations made by those skilled in the art without departing from the spirit and technical concept disclosed in the present invention should still be covered by the claims of the present invention.

Claims

1. A startup method for accelerating the warm-up valve startup of a steam turbine unit, the steam turbine unit comprising a main steam pipeline (1), a main control integrated valve (2), and a steam turbine (3), characterized in that: The startup method includes the following steps: S1. After warming up the pipe and removing impurities from the steam, the pressure of the main steam in the main steam pipe (1) is P1, which is between 4 and 8 MPa. The main steam enters the main valve chamber (23) of the main regulating integrated valve (2). S2, when the average wall temperature T of the regulating section (22) of the main regulating integrated valve (2) is... m Raise to temperature T m1 At that time, T m1 ≥T sat -T x1 The pressure of the main steam in the main steam pipe (1) is reduced to P2, where P2 is between 1 and 2 MPa, and T x1 The primary reference temperature is between 100 and 150°C. sat The saturated steam temperature corresponding to the main steam pressure P2; S3. The main steam valve (25) in the main control integrated valve (2) is opened, and steam enters the control valve chamber (24); S4, when the average wall temperature T of the regulating valve section (22) m Further increase to temperature T m2 At that time, T m2 ≥T s -T x2 After the warm-up valve is completed, the main steam valve (25) is closed, where T x2 The second reference temperature is between 50 and 100°C. s The main steam temperature at pressure P1 in step S1; S5. Increase the pressure of the main steam in the main steam pipeline (1) to P3, where P3 ≤ P1 and is between 4 and 8 MPa; S6. Open the main steam valve (25) and regulating steam valve (26) of the main control integrated valve (2) and steam enters the steam turbine (3).

2. The startup method according to claim 1, characterized in that: In step S1, P1 = 6 MPa.

3. The startup method according to claim 1, characterized in that: In step S2, P2 = 2MPa.

4. The startup method according to claim 1, characterized in that: The turbine unit also includes a high-pressure bypass (4) connected to the main steam pipeline (1), and a bypass valve is provided on the high-pressure bypass (4). In step S2, the pressure of the main steam in the main steam pipeline (1) is reduced by increasing the opening of the bypass valve on the high-pressure bypass (4).

5. The startup method according to claim 4, characterized in that: In step S5, the pressure of the main steam in the main steam pipeline (1) is increased by reducing the opening of the bypass valve on the high-pressure bypass (4).

6. The startup method according to claim 1, characterized in that: In step S2, T x1 =130℃.

7. The startup method according to claim 1, characterized in that: The regulating valve (26) of the main regulating integrated valve (2) has a steam leakage hole that connects the regulating valve chamber (24) and the steam turbine (3). In step S3, some steam enters the steam turbine (3) through the steam leakage hole, causing the speed of the steam turbine (3) to rise. If the speed reaches 90% of the critical resonance speed, the main steam valve (25) is closed first. After the speed drops, the main steam valve (25) is opened again.

8. The startup method according to claim 1, characterized in that: In step S4, T x2 =80℃.

9. The startup method according to claim 1, characterized in that: In step S5, P3 = 6 MPa.

Images