Main steam pipe cleaning method

Abstract

To provide a main steam pipe cleaning method capable of starting flashing in a pipe for a relatively short time.SOLUTION: A main steam pipe cleaning method according to at least one embodiment of this disclosure includes steps of: opening at least either one of a manhole of a condenser provided above an inflow part provided in the condenser for returning cooling water that has cooled compressed air from a compressor of a gas turbine to the condenser of which vacuum breaker is opened and a cooling pipe group for cooling and condensing steam in the condenser or a manhole of a steam turbine connected to the condenser; and returning the cooling water to the condenser after the opening step is performed.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present disclosure relates to a main steam pipe cleaning method. [Background technology]

[0002] For example, in a relatively large boiler such as a heat recovery boiler in a plant equipped with a gas turbine combined cycle, flushing of the inside of the main steam pipe is carried out using steam generated in the boiler before the plant starts operation during boiler construction or boiler maintenance (see, for example, Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 7-332014 Summary of the Invention [Problem to be solved by the invention]

[0004] However, to perform the flashing described above, a gas turbine is operated to generate main steam in a boiler, and the operation of the gas turbine requires cooling air that cools the compressed air from the compressor. The cooling water, which is at a relatively high temperature and pressure after cooling the compressed air, is recovered in a condenser.

[0005] Therefore, in the past, in order to perform the above-mentioned flushing, a vacuum pump was operated to reduce the internal pressure of the condenser, and the internal pressure of the condenser was kept lower than atmospheric pressure. However, it takes a certain amount of time for the internal pressure of the condenser to reach a specified vacuum level.

[0006] In addition, in order to make the internal pressure of the condenser reach the specified vacuum level, it is necessary to supply gland steam to the gland section that seals the gap between the steam turbine casing and rotor to prevent foreign matter from entering from the outside. However, it takes some time before the auxiliary boiler or the like becomes capable of supplying ground steam.

[0007] In view of the above circumstances, at least one embodiment of the present disclosure has an object to provide a main steam pipe cleaning method that can start flushing inside the pipe in a relatively short time. [Means for solving the problem]

[0008] A main steam pipe cleaning method according to at least one embodiment of the present disclosure includes: 1. A main steam pipe cleaning method for cleaning a main steam pipe that supplies main steam to a steam turbine, comprising: opening at least one of an inlet portion provided in the condenser for returning cooling water after cooling compressed air from a compressor of a gas turbine to the condenser whose vacuum breaker valve is opened and a manhole of the condenser provided above a group of cooling pipes for cooling and condensing steam in the condenser, or a manhole of a steam turbine connected to the condenser; returning the cooling water to the condenser after performing the opening step; Equipped with. [Effects of the Invention]

[0009] According to at least one embodiment of the present disclosure, flushing inside the main steam pipe can be initiated in a relatively short time. [Brief explanation of the drawings]

[0010] [Figure 1] 1 is an overall configuration diagram of a power generation plant according to an embodiment; [Figure 2] 1 is a flowchart showing a procedure for cleaning a main steam pipe by a main steam pipe cleaning method according to an embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0011] Hereinafter, several embodiments of the present disclosure will be described with reference to the accompanying drawings. However, the dimensions, materials, shapes, relative arrangements, etc. of components described as embodiments or shown in the drawings are merely illustrative examples and are not intended to limit the scope of the present disclosure. For example, expressions expressing relative or absolute arrangement such as "in a certain direction," "along a certain direction," "parallel," "orthogonal," "center," "concentric," or "coaxial" not only express such an arrangement exactly, but also express a state in which there is a relative displacement with a tolerance or an angle or distance to the extent that the same function is obtained. For example, expressions such as "identical," "equal," and "homogeneous" that indicate that something is in an equal state not only indicate a state of strict equality, but also indicate a state in which there is a tolerance or a difference to the extent that the same function is obtained. For example, expressions representing shapes such as a square shape or a cylindrical shape not only represent shapes such as a square shape or a cylindrical shape in the strict geometric sense, but also represent shapes including uneven portions, chamfered portions, etc., to the extent that the same effect can be obtained. On the other hand, the expressions "comprise," "include," "have," "includes," or "have" of one element are not exclusive expressions that exclude the presence of other elements.

[0012] The configuration of a power plant 1 to which a main steam pipe cleaning method according to one embodiment is applied will be described with reference to FIG. FIG. 1 is a diagram showing the overall configuration of a power generation plant according to one embodiment. As shown in FIG. 1, a power plant 1 according to one embodiment mainly includes a gas turbine 2, a steam turbine 3, and a heat recovery steam generator 5.

[0013] The configuration of the power plant 1 according to one embodiment may be a single-shaft type in which the gas turbine 2 and the steam turbine 3 share a common rotating shaft, or may be a multi-shaft type in which the gas turbine 2 and the steam turbine 3 each have an independent rotating shaft. Note that Fig. 1 shows a multi-shaft power plant 1.

[0014] In one embodiment, a generator (not shown) is connected to each of the rotating shafts of the gas turbine 2 and the steam turbine 3. As a result, when the rotating shafts of the gas turbine 2 and the steam turbine 3 rotate, each of the generators (not shown) is driven to generate electric power.

[0015] The gas turbine 2 according to one embodiment includes an air compressor (not shown), a turbine (not shown), and a combustor (not shown). The air compressor takes in and compresses atmospheric air and supplies it to the combustor. The combustor uses the compressed air supplied from the air compressor as combustion air to combust fuel gas. The combustion gas generated by combustion in the combustor is supplied to the turbine to drive it. The combustion gas (exhaust gas) that has passed through the turbine is guided to a heat recovery steam generator 5, where it is used as a heat source for generating steam, and then discharged.

[0016] In the power plant 1 according to one embodiment, part of the compressed air generated by the air compressor is cooled by the compressed air cooler 21 to become turbine cooling air, which is used to cool high-temperature parts of the turbine (for example, the moving and stationary blades and the rotor). A part of the feedwater of the heat recovery boiler 5 is used as a cooling source for the compressed air in the compressed air cooler 21. The compressed air cooler 21 is provided midway through a cooling water flow path 22 through which part of the feed water for the heat recovery boiler 5 flows.

[0017] In the power plant 1 according to one embodiment, the fuel supplied to the combustor is heated by the fuel heater 26. As a heating source for the fuel in the fuel heater 26, a part of the feedwater of the heat recovery steam generator 5, which is different from the feedwater used in the compressed air cooler 21, is used. The fuel heater 26 is provided midway through a heated water flow path 27 through which part of the feed water for the heat recovery steam generator 5 flows.

[0018] The heat recovery steam generator 5 according to one embodiment includes an exhaust gas flow path (not shown) through which exhaust gas from the gas turbine 2 flows, a plurality of heat exchangers (not shown) provided in the exhaust gas flow path, and a plurality of steam drums (not shown). The heat recovery steam generator 5 is configured to heat condensate 79 from a condenser 7 (described later) to generate main steam for driving the steam turbine 3.

[0019] The steam turbine 3 according to one embodiment includes a high-pressure turbine 11 , an intermediate-pressure turbine 12 , and a low-pressure turbine 13 . A manhole 15 is provided in the casing of the low-pressure turbine 13 . High-pressure steam obtained by superheating saturated steam from a high-pressure drum (not shown) of the heat recovery boiler 5 in a high-pressure superheater (not shown) within the heat recovery boiler is supplied to the high-pressure turbine 11 via a main steam pipe 8 connecting the heat recovery boiler 5 and the high-pressure turbine 11. The intermediate-pressure turbine 12 is supplied with intermediate-pressure steam from a reheater (not shown) of the heat recovery steam generator 5 via a main steam pipe (not shown) that connects the heat recovery steam generator 5 and the intermediate-pressure turbine 12 . In addition to the reheated steam that has done work in the intermediate-pressure turbine 12, the low-pressure turbine 13 is supplied with steam superheated in a low-pressure superheater (not shown) in the heat recovery boiler 5 via a main steam pipe (not shown) that connects the heat recovery boiler 5 and the low-pressure turbine 13.

[0020] In one embodiment, the main steam pipe 8 is provided with a main steam valve 81 that is provided midway along the main steam pipe 8 and that allows and prohibits the flow of saturated steam (main steam) from a high-pressure drum (not shown) of the heat recovery boiler 5. A branch pipe 83 that branches off from the main steam pipe 8 and can guide the main steam to the atmosphere or the condenser 7 is connected to the main steam pipe 8 upstream of the main steam valve 81 . The branch pipe 83 is provided with a steam valve 85 that allows or prohibits the flow of main steam through the branch pipe 83. The steam valve 85 is configured to be able to perform any of the following operations: prohibiting the flow of main steam through the branch pipe 83, releasing the main steam into the atmosphere, or directing the main steam to the condenser 7.

[0021] In the power plant 1 according to one embodiment, the main steam pipe (not shown) connecting the heat recovery steam generator 5 and the medium-pressure turbine 12, and the main steam pipe (not shown) connecting the heat recovery steam generator 5 and the low-pressure turbine 13 have the same configuration as the main steam pipe 8, including the main steam valve 81, branch pipe 83, and steam valve 85.

[0022] In the power plant 1 according to one embodiment, the exhaust gas from the low-pressure turbine 13 is guided to the condenser 7 connected to the low-pressure turbine 13 and condensed. The condensate 79 generated in the condenser 7 is introduced into the heat recovery steam generator 5 by a condensate pump 41 provided in a feedwater flow path 42 connecting the condenser 7 and the heat recovery steam generator 5.

[0023] In the power plant 1 according to one embodiment, the feedwater flow path 42 downstream of the condensate pump 41 and the cooling water flow path 22 upstream of the compressed air cooler 21 are connected by a connection flow path 43. Condensate 79 from the condenser 7 can flow into the cooling water flow path 22 upstream of the compressed air cooler 21 via the connection flow path 43. The connection flow path 43 is provided with a flow rate control valve 44 that can adjust the flow rate of the condensate 79 in the connection flow path 43 and that allows or prohibits the flow of the condensate 79 in the connection flow path 43.

[0024] The steam turbine 3 according to one embodiment has a gland portion 16 for sealing a gap between a casing and a rotor of the steam turbine 3. Auxiliary steam from an auxiliary boiler 17 separate from the heat recovery steam generator 5 is supplied to the gland portion 16 as gland steam.

[0025] The condenser 7 according to one embodiment includes a group of cooling pipes 71 for cooling and condensing steam in the condenser 7, a vacuum pump 73 for reducing the pressure inside the condenser 7, a manhole 75 provided in the housing of the condenser 7, and a vacuum breaker valve 74 for opening the condenser 7 to the atmosphere.

[0026] As described above, a portion of the feed water of the heat recovery boiler 5 is used to cool the compressed air in the compressed air cooler 21. After cooling the compressed air in the compressed air cooler 21, the feed water is returned to the condenser 7. The condenser 7 according to one embodiment is provided with a first inlet 76 which is an inlet into which the feedwater flows after cooling the compressed air in the compressed air cooler 21.

[0027] Similarly, as described above, a portion of the feedwater of the heat recovery steam generator 5 is used to heat the fuel in the fuel heater 26. After heating the fuel in the fuel heater 26, the feedwater is returned to the condenser 7. The condenser according to one embodiment is provided with a second inlet 77, which is an inlet into which the feedwater flows after the fuel has been heated in the fuel heater .

[0028] The first inlet portion 76 and the second inlet portion 77 are provided above the water surface of the condensate 79 in the condenser 7 and below the cooling pipe group 71. Note that the first inlet portion 76 may be provided above the cooling pipe group 71.

[0029] (Main steam pipe cleaning) In the power plant 1 according to one embodiment configured as described above, the inside of the main steam pipe 8 is flushed and cleaned with the main steam generated in the heat recovery boiler 5 before the power plant 1 is put into operation, such as during construction of the heat recovery boiler 5 or maintenance of the heat recovery boiler 5. Conventionally, in order to perform the above-mentioned flashing, the gas turbine 2 is operated to generate main steam in the heat recovery boiler 5, and the operation of the gas turbine 2 requires cooled air obtained by cooling compressed air from a compressor (not shown) in a compressed air cooler 21. The cooling water, which is at a relatively high temperature and pressure after the compressed air is cooled in the compressed air cooler 21, is recovered in the condenser 7.

[0030] Therefore, conventionally, in order to perform the above-mentioned flushing, the vacuum pump 73 for reducing the internal pressure of the condenser 7 is operated to maintain the internal pressure of the condenser 7 at a level lower than atmospheric pressure. However, it takes a certain amount of time for the internal pressure of the condenser 7 to reach a specified degree of vacuum.

[0031] Furthermore, in order to make the internal pressure of the condenser 7 reach a specified vacuum level, it is necessary to supply gland steam to the gland portion 16 of the steam turbine 3 in order to prevent foreign matter from entering from the outside. However, it takes some time before the auxiliary boiler 17 or the like becomes capable of supplying ground steam.

[0032] Therefore, in the power plant 1 according to one embodiment, as will be described below, the feedwater after cooling the compressed air in the compressed air cooler 21 can be recovered in the condenser 7 under atmospheric pressure, i.e., in the condenser 7 with the vacuum breaker valve 74 open, thereby enabling operation of the gas turbine 2. Then, main steam is generated in the heat recovery boiler 5 using the exhaust gas from the gas turbine 2 operated in this manner, and the inside of the main steam pipe 8 is flushed by this main steam.

[0033] 2 is a flowchart showing a procedure for cleaning the main steam pipe 8 by a main steam pipe cleaning method according to one embodiment. In the main steam pipe cleaning method according to one embodiment, an operator operates each part of the power plant 1 according to the procedure shown in FIG. A main steam pipe cleaning method according to one embodiment includes step S1 of stopping the supply of feedwater for heating fuel, step S3 of opening a manhole, step S5 of supplying water to a group of cooling pipes, step S7 of operating a vacuum pump, step S9 of lowering the temperature of the cooling water, step S11 of returning the cooling water to a condenser, step S13 of starting operation of the gas turbine, step S15 of starting operation of the heat recovery steam generator, and step S17 of starting cleaning of the main steam pipe.

[0034] (Step S1: Stopping the supply of water for heating fuel) Step S1 of stopping the supply of feedwater for heating fuel is a step of stopping the supply of feedwater for heating the fuel to be supplied to a combustor (not shown) of the gas turbine 2. In step S1 of stopping the supply of feedwater for heating fuel, an operator stops the supply of water from the heat recovery steam generator 5 to the fuel heater 26 by, for example, manually and remotely closing the on-off valve 28 provided in the heating water flow path 27. Since there is a risk that the feedwater after heating the fuel will return to the condenser 7 and be re-steamed, step S1 is carried out to stop the supply of feedwater for heating the fuel prior to carrying out step S3 of opening the manhole, which will be described later. This prevents the feedwater after heating the fuel from returning to the condenser 7 and being re-steamed, allowing step S3 of opening the manhole to be carried out safely. Furthermore, it is possible to reduce the possibility of an undesired increase in the pressure inside the condenser 7 after step S1 of stopping the supply of feedwater for heating the fuel is carried out, and also to reduce the possibility of steam inside the condenser 7 leaking to the outside.

[0035] (Step S3 of opening the manhole) In a main steam pipe cleaning method according to one embodiment, step S3 of opening a manhole is a step of opening at least one of the manhole 75 of the condenser 7, which is provided above the first inlet section 76 and the cooling pipe group 71, and the manhole 15 of the low-pressure turbine 13, which is connected to the condenser 7. In step S3 of opening a manhole, the worker opens either the manhole 75 of the condenser 7, which is provided above the first inlet section 76 and the cooling pipe group 71, or the manhole 15 of the low-pressure turbine 13. Note that, as a prerequisite for carrying out step S3 of opening the manhole, it is assumed that the steam turbine 3 is stopped from operating, and the vacuum breaker valve 74 of the condenser 7 is open to the atmosphere. By performing step S3 of opening the manhole, even if the feedwater after cooling the compressed air in the compressed air cooler 21 returns to the condenser 7 and is re-steamed in step S11 of returning the cooling water to the condenser, which will be described later, the possibility of an undesirable increase in the pressure inside the condenser 7 can be reduced.

[0036] In step S11, which will be described later, for returning cooling water to the condenser, if the feedwater returns to the condenser 7 after cooling the compressed air in the compressed air cooler 21, the feedwater will be re-steamed because it is at a relatively high temperature and pressure, and the atmosphere inside the condenser 7 may be filled with this re-steamed steam. In this case, in order to reduce the possibility of steam leaking to the outside through the opened manhole, it is desirable to open only the manholes located as far above as possible from the first inlet portion 76 and the water surface 79a of the condensate 79 inside the condenser 7 in step S3, which opens the manholes.

[0037] Therefore, in step S3 of opening the manholes, it is preferable to open the manhole 15 of the low-pressure turbine 13 without opening the manhole 75 of the condenser 7. Even if the atmosphere inside the condenser 7 becomes an atmosphere of re-steamed steam as described above, the possibility of this steam leaking to the outside through the manhole 15 of the low-pressure turbine 13 connected to the condenser 7 is low compared to the possibility of steam leaking to the outside through the manhole 75 of the condenser 7 when the manhole 75 of the condenser 7 is opened. This reduces the possibility of steam inside the condenser 7 leaking to the outside. When opening the manholes 75 of the condenser 7, it is desirable to open the manhole 75 that is located furthest above from the first inlet section 76 and the cooling pipe group 71.

[0038] (Step S5: Supplying water to the cooling pipe group) Step S5 of supplying water to the cooling pipe group is a step of supplying cooling water (circulating water) for cooling and condensing steam to the cooling pipe group 71. In step S5 of supplying water to the cooling pipe group, an operator supplies circulating water to the cooling pipe group 71 by, for example, manually and remotely operating a supply pump (not shown) for circulating water. As a result, even if the atmosphere inside the condenser 7 becomes an atmosphere of re-vaporized steam as described above, the steam can be condensed by the cooling pipe group 71. Therefore, it is possible to reduce the possibility that the pressure inside the condenser 7 will undesirably increase, and also to reduce the possibility that the steam inside the condenser 7 will leak to the outside.

[0039] (Step S7: Activating the vacuum pump) Step S7 of operating the vacuum pump is a step of operating the vacuum pump 73 after performing step S3 of opening the manhole. In step S7 of operating the vacuum pump, the worker operates the vacuum pump 73 by performing an operation such as manually operating the vacuum pump 73 by remote control, for example. As a result, even if the atmosphere inside the condenser 7 becomes an atmosphere of re-vaporized steam as described above, the possibility of an undesirable increase in the pressure inside the condenser 7 can be reduced, and the possibility of steam inside the condenser 7 leaking to the outside can be reduced.

[0040] (Step S9: Decreasing the temperature of the cooling water) Step S9 of lowering the temperature of the cooling water is a step of lowering the temperature of the feedwater by supplying the condensate 79 of the condenser 7 to the feedwater for cooling the compressed air in the compressed air cooler 21. In step S9 of lowering the temperature of the cooling water, the temperature of the feedwater is lowered by supplying the condensate 79 of the condenser 7 to at least the feedwater before returning to the condenser 7. Therefore, in step S9 of lowering the temperature of the cooling water, the condensate 79 of the condenser 7 may be supplied to the feedwater before cooling the compressed air in the compressed air cooler 21, or the condensate 79 of the condenser 7 may be supplied to the feedwater after cooling the compressed air in the compressed air cooler 21. For example, in the example shown in Figure 1, in step S9 of lowering the temperature of the cooling water, an operator may manually and remotely set the opening of the flow control valve 44 provided in the above-mentioned connecting flow path 43 as appropriate, so that the condensate 79 of the condenser 7 is supplied to the above-mentioned feed water via the flow control valve 44. As a result, even if the feedwater is re-steamed in the condenser 7, the amount of steam generated can be reduced.

[0041] Step S9 of lowering the temperature of the cooling water is performed after step S13 of starting operation of the gas turbine, which will be described later, is performed, and continues even after the rotation speed of the rotor (not shown) of the gas turbine 2 reaches the rated rotation speed. That is, step S9 of lowering the temperature of the cooling water is a step of lowering the temperature of the feed water by supplying condensate 79 of the condenser 7 to the feed water at least after the rotation speed of the rotor of the gas turbine 2 reaches the rated rotation speed.

[0042] Note that the above-mentioned step S3 of opening the manhole, step S5 of supplying water to the cooling pipe group, step S7 of operating the vacuum pump, and step S9 of lowering the temperature of the cooling water may be performed in any order.

[0043] (Step S11: Returning cooling water to the condenser) Step S11 of returning the cooling water to the condenser is a step of returning the feed water, after which the compressed air has been cooled in the compressed air cooler 21, to the condenser 7, after at least step S1 of opening the manhole has been performed. In step S11 of returning the cooling water to the condenser, an operator, for example, manually and remotely opens the on-off valve 23 provided in the cooling water flow path 22, thereby recovering the feed water, after which the compressed air has been cooled in the compressed air cooler 21, into the condenser 7. This enables the gas turbine 2 to operate.

[0044] (Step S13: Start operation of the gas turbine) Step S13 of starting the operation of the gas turbine is a step of starting the operation of the gas turbine 2 after step S11 of returning the cooling water to the condenser is performed. In step S13 of starting the operation of the gas turbine, an operator issues a command to start the operation of the gas turbine 2, for example, by manual remote control. This causes the operation of the gas turbine 2 to start.

[0045] (Step S15: Start operation of the waste heat recovery boiler) Step S15 of starting the operation of the heat recovery boiler is a step of starting the operation of the heat recovery boiler 5 using the exhaust gas from the gas turbine 2. In step S15 of starting the operation of the heat recovery boiler, an operator issues an instruction to start the operation of the heat recovery boiler 5, for example, by manual remote control. This causes the operation of the heat recovery boiler 5 to start.

[0046] (Step S17: Start cleaning the main steam pipe) Step S17 of starting cleaning of the main steam pipe is a step of starting cleaning of the main steam pipe 8 with main steam generated in the heat recovery boiler 5 from exhaust gas from the gas turbine 2. In step S17 of starting cleaning of the main steam pipe, an operator manually operates the steam valve 85 of the branch pipe 83 by remote control, for example, to release the main steam into the atmosphere. It is assumed that the main steam valve 81 is closed in advance. As a result, the inside of the main steam pipe 8 is flushed with the main steam generated in the heat recovery boiler 5, and the main steam pipe 8 can be cleaned. In step S17, which starts cleaning of the main steam pipes, cleaning of the main steam pipes is also performed on the main steam pipe (not shown) connecting the heat recovery steam generator 5 and the intermediate-pressure turbine 12, and the main steam pipe (not shown) connecting the heat recovery steam generator 5 and the low-pressure turbine 13.

[0047] According to the main steam pipe cleaning method according to the embodiment described above, even if the feedwater after cooling the compressed air in the compressed air cooler 21 is returned to the condenser 7, it is possible to reduce the possibility of an undesired increase in the pressure inside the condenser 7. Therefore, since there is no need to reduce the pressure inside the condenser 7 to below atmospheric pressure, cleaning of the main steam pipe 8 can be started in a relatively short time. Furthermore, according to the main steam pipe cleaning method according to the above-described embodiment, there is no need to reduce the pressure inside the condenser 7 to below atmospheric pressure, and therefore, when cleaning the main steam pipe 8, there is no need to supply gland steam to the gland portion 16 that seals the gap between the casing and the rotor of the steam turbine 3. As a result, there is no need to supply gland steam from the auxiliary boiler 17 or the like, and therefore no waiting time is required until the auxiliary boiler 17 or the like is able to generate gland steam, and cleaning of the main steam pipe 8 can be started in a relatively short time. Furthermore, according to the main steam pipe cleaning method according to the embodiment described above, the feedwater after cooling the compressed air in the compressed air cooler 21 can be returned to the condenser 7 with the inside of the condenser 7 open to the atmosphere via either of the manholes 15, 75 and the vacuum breaker valve 74, so the gas turbine 2 can be operated even with the inside of the condenser 7 open to the atmosphere via either of the manholes 15, 75 and the vacuum breaker valve 74. This allows the heat recovery boiler 5 to generate the main steam required for cleaning the main steam pipe 8.

[0048] The present disclosure is not limited to the above-described embodiments, but also includes modifications to the above-described embodiments and appropriate combinations of these modifications.

[0049] The contents described in each of the above embodiments can be understood, for example, as follows. (1) A main steam pipe cleaning method according to at least one embodiment of the present disclosure is a main steam pipe cleaning method for cleaning a main steam pipe 8 that supplies main steam to a steam turbine 3. The main steam pipe cleaning method according to at least one embodiment of the present disclosure includes: a step of opening at least one of an inlet portion (first inlet portion 76) provided in the condenser 7 for returning cooling water (feed water after cooling the compressed air in the compressed air cooler 21) after cooling the compressed air from the compressor of the gas turbine 2 to the condenser 7 with the vacuum breaker valve 74 open, and a manhole 75 of the condenser provided above a group of cooling pipes 71 for cooling and condensing the steam in the condenser 7 (step S3 of opening the manhole); and a step S11 of returning the cooling water (feed water after cooling the compressed air in the compressed air cooler 21) to the condenser 7 after performing the opening step (step S3 of opening the manhole).

[0050] According to the method (1) above, even if the cooling water (the feed water after cooling the compressed air in the compressed air cooler 21) used to cool the compressed air from the compressor of the gas turbine 2 is returned to the condenser 7, the possibility of an undesired increase in the pressure inside the condenser 7 can be reduced. Therefore, since there is no need to reduce the pressure inside the condenser 7 to below atmospheric pressure, cleaning of the main steam pipe 8 can be started in a relatively short time. Furthermore, according to the method (1) above, there is no need to reduce the pressure inside the condenser 7 to below atmospheric pressure, so when cleaning the main steam pipe 8, there is no need to supply gland steam to the gland portion 16 that seals the gap between the casing and rotor of the steam turbine 3. As a result, there is no need to supply gland steam from the auxiliary boiler 17 or the like, so there is no waiting time until the auxiliary boiler 17 or the like is able to generate gland steam, and cleaning of the main steam pipe 8 can be started in a relatively short time. Furthermore, according to the method (1) above, the cooling water (feed water after cooling the compressed air in the compressed air cooler 21) used to cool the compressed air from the compressor of the gas turbine 2 can be returned to the condenser 7 while the inside of the condenser 7 is open to the atmosphere through either of the manholes 15, 75 and the vacuum breaker valve 74. This allows the gas turbine 2 to be operated even while the inside of the condenser 7 is open to the atmosphere through either of the manholes 15, 75 and the vacuum breaker valve 74. This makes it possible to generate main steam required to clean the main steam pipe 8, for example, in the heat recovery boiler 5.

[0051] (2) In some embodiments, in the method (1) above, in the opening step (step S3 of opening the manhole), it is preferable to open the manhole 15 of the steam turbine (low-pressure turbine 13) connected to the condenser 7 without opening the manhole 75 of the condenser 7.

[0052] According to the method (2) above, even if, for example, the cooling water (feed water after cooling the compressed air in the compressed air cooler 21) after cooling the compressed air from the compressor of the gas turbine 2 is re-steamed in the condenser 7 and the atmosphere inside the condenser 7 becomes an atmosphere of this steam, the possibility of this steam leaking to the outside from the manhole 15 of the steam turbine (low-pressure turbine 13) connected to the condenser 7 is low compared to the possibility of steam leaking to the outside from the manhole 75 of the condenser 7 when the manhole 75 of the condenser 7 is opened. This reduces the possibility of steam inside the condenser 7 leaking to the outside.

[0053] (3) In some embodiments, the method of (1) or (2) above may include a step S9 in which, after the rotation speed of the rotor of the gas turbine 2 reaches the rated rotation speed, the temperature of the cooling water (the supply water before or after cooling the compressed air in the compressed air cooler 21) is lowered by supplying the condensate 79 of the condenser 7 to the cooling water (the supply water before or after cooling the compressed air in the compressed air cooler 21).

[0054] According to the method (3) above, even if the cooling water (the feed water after cooling the compressed air in the compressed air cooler 21) is re-steamed in the condenser 7, the amount of steam generated can be reduced.

[0055] (4) In some embodiments, in any of the methods (1) to (3) above, it is preferable to include step S5 of supplying water to the cooling pipe group 71 (cooling water for cooling and condensing steam in the cooling pipe group 71) and step S7 of operating the vacuum pump 73 to reduce the pressure in the condenser 7 after performing the opening step (step S3 of opening the manhole).

[0056] According to the above method (4), the possibility that the steam in the condenser 7 will leak to the outside can be reduced.

[0057] (5) In some embodiments, any of the methods (1) to (4) above may further include a step S1 of stopping the supply of feedwater for heating the fuel to be supplied to the gas turbine 2.

[0058] According to the method (5) above, the feedwater after heating the fuel does not return to the condenser 7 and is re-steamed, thereby reducing the possibility of an undesired increase in the pressure inside the condenser 7 and reducing the possibility of steam inside the condenser 7 leaking to the outside. [Explanation of symbols]

[0059] 1. Power Plant 2. Gas turbine 3. Steam turbine 5. Waste heat recovery boiler 7 Condenser 8 Main steam pipe 13 Low-pressure turbine 15 Manhole 21 Compressed air cooler 26 Fuel heater 44 Flow control valve 73 Vacuum Pump 74 Vacuum breaker valve 75 Manhole 76 1st inflow section 77 Second inflow section 79 Condensate

Claims

1. 1. A main steam pipe cleaning method for cleaning a main steam pipe that supplies main steam to a steam turbine, comprising: opening at least one of an inlet portion provided in the condenser for returning cooling water after cooling compressed air from a compressor of a gas turbine to the condenser whose vacuum breaker valve is opened and a manhole of the condenser provided above a group of cooling pipes for cooling and condensing steam in the condenser, or a manhole of a steam turbine connected to the condenser; returning the cooling water to the condenser after performing the opening step; Equipped with Main steam pipe cleaning method.

2. In the opening step, the manhole of the steam turbine connected to the condenser is opened without opening the manhole of the condenser. The main steam pipe cleaning method according to claim 1.

3. a step of lowering a temperature of the cooling water by supplying condensate from the condenser to the cooling water after at least a rotation speed of the rotor of the gas turbine has reached a rated rotation speed; Equipped with The main steam pipe cleaning method according to claim 1 or 2.

4. supplying water to the cooling pipe group; After performing the opening step, activating a vacuum pump to depressurize the condenser; Equipped with The main steam pipe cleaning method according to claim 1 or 2.

5. stopping the supply of feedwater for heating fuel supplied to the gas turbine; Equipped with The main steam pipe cleaning method according to claim 1 or 2.

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