A shaft seal auxiliary steam source hot standby device and control method thereof

Abstract

The invention discloses a shaft seal auxiliary steam source hot standby device, wherein the steam inlets of the shaft seal bodies of the high-pressure cylinder, the medium-pressure cylinder and the low-pressure cylinder are connected with the shaft seal steam main pipe; the auxiliary steam pipeline is divided into two paths after passing through the shaft seal steam supply regulating valve, one of which is connected with the shaft seal steam main pipe, and the other is connected with the low-pressure heater through a first preheating valve and a throttle hole; the shaft seal overflow pipeline is connected with the low-pressure heater through the shaft seal overflow regulating valve; the extraction steam of the medium-pressure cylinder is divided into two paths after passing through the turbine extraction steam pipeline and the extraction steam check valve, one of which is connected with the extraction steam user, and the other is connected with the auxiliary steam pipeline through a second preheating valve. The device can ensure the safety of the unit operation and avoid the waste of high-quality steam.

Description

Technical Field

[0001] The invention belongs to the technical field of energy saving and safe operation of steam turbines in power plants, and relates to a shaft seal auxiliary steam source hot standby device and a control method thereof. Background Art

[0002] The shaft seal system is an important component of the power plant steam turbine. Its main function is to supply qualified steam to the ends of each cylinder of the turbine, to prevent steam from leaking outward along the cylinder shaft end, or even entering the bearing box to cause water to enter the lubricating oil, and to prevent air from leaking into the vacuum shaft seal to cause the condenser vacuum to drop. It is an important system to maintain the condenser vacuum and ensure the safe operation of the steam turbine.

[0003] During the unit startup phase, the steam for the shaft seal is provided by the auxiliary steam system, and enters the end of the steam turbine after the pressure is adjusted by the shaft seal steam supply valve group. During the load increase process of the steam turbine, the steam flow rate of the high-pressure cylinder increases, and the leakage steam of the shaft seal at the end of the high-pressure cylinder is supplied to the low-pressure cylinder shaft seal through the shaft seal mother pipe. The steam source of the shaft seal gradually transitions from the auxiliary steam to the leakage steam of the high-pressure cylinder steam seal, achieving a self-sealing effect. At the same time, the system is equipped with a shaft seal steam overflow pipeline to discharge excess steam to the condenser or low-pressure heater.

[0004] The clearance of the steam seal at the end of the steam turbine is an important factor in determining the amount of steam leakage. A larger clearance of the steam seal will cause excessive steam leakage inside the high and medium pressure cylinders of the steam turbine, reduce steam work, and affect the economic efficiency of the unit. If the clearance of the shaft seal is small, when the temperature at the main engine shaft seal changes significantly, the shaft seals at the end of the high and medium pressure cylinders and the main shaft at the shaft seal will experience rapid cooling and contraction, which may cause the shaft seal or the dynamic and static parts inside the cylinder to collide and rub, and then cause the main shaft of the steam turbine to lock at the shaft seal, which not only affects the normal operation of the unit, but also has the risk of causing serious safety accidents.

[0005] In recent years, with the continuous development of national energy conservation and emission reduction work, various efficient, new and reliable steam seal technologies have emerged to improve the economic efficiency of unit operation. At present, the shaft seal clearance of high and medium pressure cylinders of newly built mainstream 1000MW and 660MW units in my country's power industry has been reduced to 0.3mm level. Many old power plants have also achieved the goal of reducing coal consumption and improving unit operation efficiency by transforming the steam seal structure and reducing the gap of the steam seal at the end of the turbine. With the advancement of new technologies, corresponding problems have also followed. Many power plants in China have experienced shaft seal locking due to drastic changes in the steam supply temperature of the shaft seal. Analyzing the reasons, most of the locking conditions occurred during the shutdown or accident tripping of the unit. During shutdown, the shaft seal steam is switched from self-sealing to auxiliary steam. Since there is no steam flow in the auxiliary steam to shaft seal steam supply pipeline for a long time, the steam temperature in the pipeline is low. After entering the cylinder, the shaft seal body and the main shaft are rapidly cooled, resulting in locking. In view of this situation, many power plants set the minimum steam supply opening of the shaft seal steam supply valve during operation, so that the valve cannot be fully closed, or keep the pipeline open for drainage to keep the shaft seal steam supply pipeline in a hot standby state. These two methods ensure the safety of the unit, but also cause the waste of high-quality steam, which is completely contrary to the purpose of shaft seal modification. Summary of the invention

[0006] The purpose of the present invention is to overcome the shortcomings of the prior art and provide a shaft seal auxiliary steam source hot standby device, which can ensure the safety of the unit while avoiding the waste of high-quality steam.

[0007] To achieve the above-mentioned purpose, the shaft seal auxiliary steam source hot standby device of the present invention comprises a high-pressure cylinder, a medium-pressure cylinder, a low-pressure cylinder, a shaft seal steam main pipe, a shaft seal steam supply main pipe, a shaft seal steam supply regulating valve, a first preheating valve, a throttle hole, a low-pressure heater, a shaft seal overflow pipe, a shaft seal overflow regulating valve, a steam turbine extraction pipe, an extraction check valve and a second preheating valve;

[0008] The steam inlets of the shaft seal bodies of the high-pressure cylinder, the medium-pressure cylinder and the low-pressure cylinder are connected to the shaft seal steam main pipe;

[0009] The outlet of the auxiliary steam header is connected to the auxiliary steam pipeline, which is divided into two paths after passing through the shaft seal steam supply regulating valve, one of which is connected to the shaft seal steam main pipe, and the other is connected to the low-pressure heater through the first preheating valve and the throttle hole;

[0010] The shaft seal overflow pipeline is connected to the low-pressure heater through the shaft seal overflow regulating valve;

[0011] The steam extraction port of the intermediate pressure cylinder is divided into two paths after passing through the steam extraction pipeline of the steam turbine and the steam extraction electric gate. One path is connected to the steam extraction user, and the other is connected to the auxiliary steam pipeline through the second preheating valve.

[0012] The auxiliary steam pipeline is connected to the shaft seal steam main pipe through the shaft seal steam supply regulating valve and the shaft seal steam supply main pipe.

[0013] The steam extraction port of the intermediate pressure cylinder is divided into two paths after passing through the steam extraction pipeline of the turbine, the steam extraction check valve and the steam extraction electric door.

[0014] The connection position of the second preheating valve and the auxiliary steam pipeline is located before the inlet of the shaft seal steam supply regulating valve.

[0015] The connection position of the shaft seal overflow pipe and the shaft seal steam main pipe is located between the high-pressure cylinder and the medium-pressure cylinder.

[0016] The connection position between the shaft seal steam supply pipeline and the shaft seal steam main pipe is located between the medium pressure cylinder and the low pressure cylinder.

[0017] A control method for a shaft seal auxiliary steam source hot standby device comprises the following steps:

[0018] When the unit is started and the shaft seal is put into use, the shaft seal overflow regulating valve is fully closed, the shaft seal steam supply regulating valve is opened, and the first preheating valve and the second preheating valve are closed at the same time;

[0019] As the load of the random unit increases, the shaft seal steam supply regulating valve is gradually closed, and then the shaft seal overflow regulating valve is opened. When the opening of the shaft seal steam supply regulating valve is ≤3%, and the opening of the shaft seal overflow regulating valve is ≥3%, the first preheating valve and the second preheating valve are opened;

[0020] When the unit is shut down, when the opening of the shaft seal steam supply regulating valve is ≥3%, and the opening of the shaft seal overflow regulating valve is ≤3%, the first preheating valve and the second preheating valve are closed;

[0021] When the unit trips or sheds load due to an accident condition, the first preheating valve and the second preheating valve are closed.

[0022] The present invention has the following beneficial effects:

[0023] When the shaft seal auxiliary steam source hot standby device described in the present invention is working, the operating status of the shaft seal system is judged by the opening of the shaft seal steam supply regulating valve and the shaft seal overflow regulating valve. After self-sealing, the auxiliary steam pipeline is connected with the turbine extraction pipeline, and the pipe warming steam extracted from the medium-pressure cylinder flows to the auxiliary steam pipeline, and then flows in reverse to the auxiliary steam manifold; at the same time, the shaft seal steam supply mother pipe is connected with the low-pressure heater, and the steam flows in reverse from the shaft seal steam mother pipe to the shaft seal steam supply mother pipe, and then flows into the low-pressure heater, so as to ensure that the auxiliary steam pipeline and the shaft seal steam supply mother pipe are kept in a hot standby state at all times, and at the same time, the pipe warming steam is effectively utilized to maintain the economy and safety of the unit. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 It is a structural schematic diagram of the present invention.

[0025] Among them, 1 is the high-pressure cylinder, 2 is the medium-pressure cylinder, 3 is the low-pressure cylinder, 4 is the shaft seal steam supply regulating valve, 5 is the shaft seal overflow regulating valve, 6 is the first preheating valve, 7 is the throttle hole, 8 is the second preheating valve, 9 is the extraction steam check valve, 10 is the extraction steam electric door, 11 is the auxiliary steam header, 12 is the low-pressure heater, 13 is the shaft seal steam main pipe, 14 is the shaft seal steam supply main pipe, 15 is the shaft seal overflow pipe, and 16 is the auxiliary steam pipe. DETAILED DESCRIPTION

[0026] The present invention is further described in detail below in conjunction with the accompanying drawings:

[0027] refer to Figure 1 The shaft seal auxiliary steam source hot standby device of the present invention comprises a high-pressure cylinder 1, an intermediate-pressure cylinder 2, a low-pressure cylinder 3, a shaft seal steam main pipe 13, a shaft seal steam supply main pipe 14, a shaft seal steam supply regulating valve 4, a first preheating valve 6, a throttle hole 7, a low-pressure heater 12, a shaft seal overflow pipe 15, a shaft seal overflow regulating valve 5, a steam turbine extraction pipe, an extraction check valve 9 and a second preheating valve 8; the steam inlets of the shaft seal bodies of the high-pressure cylinder 1, the intermediate-pressure cylinder 2 and the low-pressure cylinder 3 are connected to the shaft seal steam main pipe 13; the outlet of the auxiliary steam header 11 It is connected to the auxiliary steam pipeline 16, which is divided into two paths after passing through the shaft seal steam supply regulating valve 4, one of which is connected to the shaft seal steam main pipe 13, and the other is connected to the low-pressure heater 12 through the first preheating valve 6 and the throttle hole 7; the shaft seal overflow pipeline 15 is connected to the low-pressure heater 12 through the shaft seal overflow regulating valve 5; the steam extraction port of the intermediate pressure cylinder 2 is divided into two paths after passing through the turbine steam extraction pipeline and the steam extraction electric door 10, one of which is connected to the steam extraction user, and the other is connected to the auxiliary steam pipeline 16 through the second preheating valve 8.

[0028] The auxiliary steam pipeline 16 is connected to the shaft seal steam main pipe 13 through the shaft seal steam supply regulating valve 4 and the shaft seal steam supply main pipe 14; the connection position of the second preheating valve 8 and the auxiliary steam pipeline 16 is located before the inlet of the shaft seal steam supply regulating valve 4;

[0029] The connection position of the shaft seal overflow pipe 15 and the shaft seal steam main pipe 13 is located between the high-pressure cylinder 1 and the medium-pressure cylinder 2; the connection position of the shaft seal steam supply main pipe 14 and the shaft seal steam main pipe 13 is located between the medium-pressure cylinder 2 and the low-pressure cylinder 3.

[0030] The control method of the shaft seal auxiliary steam source hot standby device of the present invention comprises the following steps:

[0031] When the unit is started and the shaft seal is put into use, the shaft seal overflow regulating valve 5 is fully closed, the shaft seal steam supply regulating valve 4 is opened, and the first preheating valve 6 and the second preheating valve 8 are closed at the same time;

[0032] As the load of the random group increases, the shaft seal steam supply regulating valve 4 is gradually closed, and then the shaft seal overflow regulating valve 5 is opened. When the opening of the shaft seal steam supply regulating valve 4 is ≤3%, and the opening of the shaft seal overflow regulating valve 5 is ≥3%, the first preheating valve 6 and the second preheating valve 8 are opened;

[0033] When the unit is shut down, when the opening of the shaft seal steam supply regulating valve 4 is ≥3%, and the opening of the shaft seal overflow regulating valve 5 is ≤3%, the first preheating valve 6 and the second preheating valve 8 are closed;

[0034] When the unit trips or sheds load due to an accident condition, the first preheating valve 6 and the second preheating valve 8 are closed.

[0035] The present invention can be used for both newly built units and the reconstruction of existing units. When the unit is running, the auxiliary steam for the shaft seal is maintained in a hot standby state. When the unit is shut down or tripped due to an accident, it is ensured that the temperature of the auxiliary steam supplied to the shaft seal system does not fluctuate greatly, thereby avoiding friction between the shaft seal body and the main shaft, and even safety accidents such as locking.

Claims

1. A shaft seal auxiliary steam source hot standby device, It is characterized in that It comprises a high-pressure cylinder (1), an intermediate-pressure cylinder (2), a low-pressure cylinder (3), a shaft seal steam main pipe (13), a shaft seal steam supply main pipe (14), a shaft seal steam supply regulating valve (4), a first preheating valve (6), a throttle hole (7), a low-pressure heater (12), a shaft seal overflow pipe (15), a shaft seal overflow regulating valve (5), a steam turbine extraction pipe, an extraction check valve (9) and a second preheating valve (8); The steam inlets of the shaft seal bodies of the high-pressure cylinder (1), the medium-pressure cylinder (2) and the low-pressure cylinder (3) are connected to the shaft seal steam main pipe (13); The outlet of the auxiliary steam header (11) is connected to the auxiliary steam pipeline (16), and the auxiliary steam pipeline (16) is divided into two paths after passing through the shaft seal steam supply regulating valve (4), one of which is connected to the shaft seal steam main pipe (13), and the other is connected to the low-pressure heater (12) through the first preheating valve (6) and the throttle hole (7); The shaft seal overflow pipe (15) is connected to the low-pressure heater (12) via the shaft seal overflow regulating valve (5); The steam extraction port of the intermediate pressure cylinder (2) is divided into two paths after passing through the steam turbine steam extraction pipeline and the steam extraction electric door (10), one of which is connected to the steam extraction user, and the other is connected to the auxiliary steam pipeline (16) through the second preheating valve (8); The auxiliary steam pipeline (16) is connected to the shaft seal steam main pipe (13) via the shaft seal steam supply regulating valve (4) and the shaft seal steam supply main pipe (14); The steam extraction port of the medium pressure cylinder (2) is divided into two paths after passing through the steam extraction pipeline of the steam turbine, the steam extraction check valve (9) and the steam extraction electric door (10).

2. The shaft seal auxiliary steam source hot standby device according to claim 1, It is characterized in that The connection position between the second preheating valve (8) and the auxiliary steam pipeline (16) is located before the inlet of the shaft seal steam supply regulating valve (4).

3. The shaft seal auxiliary steam source hot standby device according to claim 1, It is characterized in that The connection position between the shaft seal overflow pipe (15) and the shaft seal steam main pipe (13) is located between the high-pressure cylinder (1) and the medium-pressure cylinder (2).

4. The shaft seal auxiliary steam source hot standby device according to claim 1, It is characterized in that The connection position between the shaft seal steam supply main pipe (14) and the shaft seal steam main pipe (13) is located between the medium pressure cylinder (2) and the low pressure cylinder (3).

5. A control method for a shaft seal auxiliary steam source hot standby device, It is characterized in that The shaft seal auxiliary steam source hot standby device according to any one of claims 1 to 4 comprises the following steps: When the unit is started and the shaft seal is put into use, the shaft seal overflow regulating valve (5) is fully closed, the shaft seal steam supply regulating valve (4) is opened, and the first preheating valve (6) and the second preheating valve (8) are closed at the same time; As the load of the random group increases, the shaft seal steam supply regulating valve (4) is gradually closed, and then the shaft seal overflow regulating valve (5) is opened. When the opening of the shaft seal steam supply regulating valve (4) is ≤3%, and the opening of the shaft seal overflow regulating valve (5) is ≥3%, the first preheating valve (6) and the second preheating valve (8) are opened; When the unit is shut down, when the opening of the shaft seal steam supply regulating valve (4) is ≥3% and the opening of the shaft seal overflow regulating valve (5) is ≤3%, the first preheating valve (6) and the second preheating valve (8) are closed; When the unit trips or dumps load due to an accident, the first preheating valve (6) and the second preheating valve (8) are closed.

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