Method for preparing restart in gas turbine exhaust heat recovery plant

Abstract

To provide a method for preparing restart in a gas turbine exhaust heat recovery plant to enable restart of the gas turbine exhaust heat recovery plant for a relatively short time.SOLUTION: A gas turbine exhaust heat recovery plant includes: a gas turbine; an exhaust heat recovery boiler that generates steam by recovering exhaust heat of the gas turbine; and a steam use facility that has a steam turbine driven by using the steam generated by the exhaust heat recovery boiler and a steam condenser. A method for preparing restart in the gas turbine exhaust heat recovery plant according to at least one embodiment includes steps of: maintaining inside of the steam condenser at a prescribed vacuum degree after the gas turbine exhaust heat recovery plant is stopped; confirming pressure of a steam drum of the exhaust heat recovery boiler; and continuing steam supply from the steam drum to a gland part of the steam turbine when the pressure of the steam drum confirmed in the step of confirming the pressure of the steam drum is prescribed pressure or greater.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present disclosure relates to a method for preparing for restart in a gas turbine exhaust heat recovery plant.

Background Art

[0002] A gas turbine exhaust heat recovery plant including a gas turbine, an exhaust heat recovery boiler, and a steam turbine is known. In the steam turbine of the gas turbine exhaust heat recovery plant, in order to prevent steam inside the turbine from leaking to the ground part or outside air from entering the turbine from the ground part, it is known to supply and seal steam to the ground part (see, for example, Patent Document 1).

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] In a gas turbine exhaust heat recovery plant that does not have an auxiliary steam supply source from the outside such as an auxiliary boiler or an existing steam connection pipe, the ground part is sealed by supplying steam generated in the exhaust heat recovery boiler to the ground part of the steam turbine. In such a gas turbine exhaust heat recovery plant, when the operation of the gas turbine is stopped, steam cannot be generated in the exhaust heat recovery boiler, so the ground part cannot be sealed. Therefore, when the operation of the gas turbine is stopped and the ground part cannot be sealed, the degree of vacuum in the condenser cannot be maintained, so the vacuum in the condenser is broken for the protection of the steam turbine.

[0005] When the condenser is depressurized, it is necessary to increase the degree of vacuum in the condenser again when restarting the gas turbine exhaust heat recovery plant. However, since it takes time to increase the degree of vacuum in the condenser, it takes a long time to return the gas turbine exhaust heat recovery plant to its normal operating state.

[0006] In view of the above circumstances, at least one embodiment of the present disclosure aims to provide a method for preparing for restart in a gas turbine exhaust heat recovery plant so that the gas turbine exhaust heat recovery plant can be restarted in a relatively short time.

Means for Solving the Problems

[0007] A method for preparing for restart in a gas turbine exhaust heat recovery plant according to at least one embodiment of the present disclosure is A method for preparing for restart in a gas turbine exhaust heat recovery plant, The gas turbine exhaust heat recovery plant includes A gas turbine, An exhaust heat recovery boiler that recovers the exhaust heat of the gas turbine to generate steam, A steam utilization facility including a steam turbine driven by the steam generated by the exhaust heat recovery boiler and a condenser, And is provided with A step of maintaining the inside of the condenser at a specified degree of vacuum after the gas turbine exhaust heat recovery plant stops, A step of checking the pressure of the steam drum of the exhaust heat recovery boiler, When the pressure of the steam drum confirmed in the step of checking the pressure of the steam drum is equal to or higher than a specified pressure, a step of continuing to supply steam from the steam drum to the ground part of the steam turbine, And is provided with

Advantages of the Invention

[0008] According to at least one embodiment of the present disclosure, the gas turbine exhaust heat recovery plant can be restarted in a relatively short time.

Brief Description of the Drawings

[0009]

Figure 1

Figure 2

Figure 3

[0010] Hereinafter, some embodiments of the present disclosure will be described with reference to the accompanying drawings. However, the dimensions, materials, shapes, relative arrangements, etc. of the components described as embodiments or shown in the drawings are not intended to limit the scope of the present disclosure thereto, but are merely illustrative examples. For example, expressions representing relative or absolute arrangements such as "in a certain direction", "along a certain direction", "parallel", "orthogonal", "center", "concentric", or "coaxial" not only strictly represent such arrangements, but also represent states of relative displacement with tolerances or angles and distances such that the same function can be obtained. For example, expressions representing that things such as "identical", "equal", and "homogeneous" are in an equal state not only strictly represent an equal state, but also represent states in which there are tolerances or differences such that the same function can be 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 a geometrically strict sense, but also represent shapes including concave and convex portions, chamfered portions, etc. within a range where the same effect can be obtained. On the other hand, the expressions "comprising", "having", "including", or "possessing" a component are not exclusive expressions excluding the existence of other components.

[0011] <Configuration of the Combined Plant> FIG. 1 is a diagram showing a schematic overall configuration of a combined plant 2 (2A) according to one embodiment. FIG. 2 is a diagram showing a schematic overall configuration of a combined plant 2(2B) according to another embodiment. In the following description, when there is no need to particularly distinguish between the combined plant 2A according to one embodiment shown in FIG. 1 and the combined plant 2B according to another embodiment shown in FIG. 2, or when collectively referring to the combined plant 2A according to one embodiment shown in FIG. 1 and the combined plant 2B according to another embodiment shown in FIG. 2, the alphabet at the end of the reference numeral is omitted and it is referred to as the combined plant 2. The combined plant 2 includes a gas turbine 4 as a prime mover, a steam turbine system 100, a steam generator 6 that includes an exhaust heat recovery boiler 5 and generates steam, and a chimney 9 that discharges the exhaust gas discharged from the exhaust heat recovery boiler 5 to the atmosphere. The steam turbine system 100 functions as steam utilization equipment that uses the steam generated by the steam generator 6. Further, the steam generator 6 and the steam turbine system 100 constitute an exhaust heat recovery plant 200 for recovering the exhaust heat of the gas turbine 4.

[0012] <Configuration of Gas Turbine> The gas turbine 4 includes a compressor 12 that compresses air, a combustor 14 that burns fuel using the compressed air generated by the compressor 12, and a turbine 16 that is driven by the combustion air generated by the combustor 14. In the illustrated form, a generator 19 is disposed on the same axis as the compressor 12 and the turbine 16, and the rotors of the compressor 12, the turbine 16, and the generator 19 are configured to rotate integrally.

[0013] <Configuration of Steam Turbine System> The steam turbine system 100 includes a plurality of steam turbines 102, 104, 106, and a condenser 108 that cools the steam discharged from the steam turbine 106 and returns it to water. The steam turbine system 100 includes, as the plurality of steam turbines, a high-pressure steam turbine 102, an intermediate-pressure steam turbine 104, and a low-pressure steam turbine 106. The steam outlet of the intermediate-pressure steam turbine 104 and the steam inlet of the low-pressure steam turbine 106 are connected via an intermediate-pressure exhaust line 110, and the steam outlet of the low-pressure steam turbine 106 and the condenser 108 are connected via a low-pressure exhaust line 112. In the illustrated embodiment, the compressor 12, the turbine 16, the generator 19, the high-pressure steam turbine 102, the intermediate-pressure steam turbine 104, and the low-pressure steam turbine 106 are arranged on the same axis and are configured such that the respective rotors rotate integrally. That is, the combined plant 2 according to some embodiments is a power generation plant.

[0014] <Configuration of steam generator> The steam generator 6 includes an exhaust heat recovery boiler 5 to which the exhaust gas (heat medium) of the gas turbine 4 is supplied.

[0015] The exhaust heat recovery boiler 5 includes an exhaust gas flow path 18 (heat medium flow path) through which the exhaust gas of the gas turbine 4 flows, a plurality of heat exchangers 20 provided in the exhaust gas flow path 18, and a plurality of steam drums 21. The plurality of heat exchangers 20 are, in order from the downstream side in the flow direction of the exhaust gas in the exhaust gas flow path 18, a first low-pressure economizer 22 (first economizer), a second low-pressure economizer 24 (second economizer), a low-pressure evaporator 26 (first evaporator), a low-pressure superheater 28, a first high-pressure economizer 30, an intermediate-pressure evaporator 32, an intermediate-pressure superheater 34, a second high-pressure economizer 36, a high-pressure evaporator 38, a first high-pressure superheater 40, a first reheater 42, a second high-pressure superheater 44, and a second reheater 46. In the flow direction of the exhaust gas in the exhaust gas flow path 18, the second low-pressure economizer 24 is located upstream of the first low-pressure economizer 22, and the low-pressure evaporator 26 is provided upstream of the second low-pressure economizer 24. An intermediate-pressure economizer 31 is provided in parallel with the first high-pressure economizer 30 between the low-pressure superheater 28 and the intermediate-pressure evaporator 32 in the exhaust gas flow path 18. The plurality of steam drums 21 includes a low-pressure drum 25, a medium-pressure drum 33, and a high-pressure drum 39.

[0016] The condenser 108 and the first low-pressure economizer 22 are connected by a feed water line 48, and a feed water pump 50 for supplying the condensed water discharged from the condenser 108 to the first low-pressure economizer 22 is provided in the feed water line 48.

[0017] The first low-pressure economizer 22 heats the water supplied from the feed water line 48 by heat exchange with the exhaust gas. A part of the water heated by the first low-pressure economizer 22 is supplied to the second low-pressure economizer 24 through a feed water line 52 connecting the first low-pressure economizer 22 and the second low-pressure economizer 24.

[0018] The second low-pressure economizer 24 heats the water supplied from the first low-pressure economizer 22 through the feed water line 52 by heat exchange with the exhaust gas. A part of the water heated by the second low-pressure economizer 24 is supplied to the low-pressure drum 25 through a feed water line 54 connecting the second low-pressure economizer 24 and the low-pressure evaporator 26.

[0019] The low-pressure evaporator 26 heats and evaporates the water supplied to the low-pressure drum 25 from the second low-pressure economizer 24 through the feed water line 54 by heat exchange with the exhaust gas to generate low-pressure steam. A feed water valve 55 for reducing the pressure of the water supplied from the second low-pressure economizer 24 is provided in the feed water line 54. A part of the low-pressure steam generated by the low-pressure evaporator 26 is supplied to the low-pressure superheater 28 through a steam line 56 connecting the low-pressure drum 25 and the low-pressure superheater 28.

[0020] The low-pressure superheater 28 superheats the low-pressure steam supplied from the low-pressure drum 25 through the steam line 56 by heat exchange with the exhaust gas to generate low-pressure superheated steam. The low-pressure superheated steam generated by the low-pressure superheater 28 flows into the medium-pressure exhaust line 110 through a steam line 58 connecting the low-pressure superheater 28 and the medium-pressure exhaust line 110, and flows into the steam inlet of the low-pressure steam turbine 106 from the medium-pressure exhaust line 110.

[0021] A part of the water heated by the second low-pressure economizer 24 is supplied to the medium-pressure economizer 31 via the feed water line 60. The feed water line 60 is provided by branching from the feed water line 54 and is connected to the medium-pressure economizer 31. The heated water flowing through the feed water line 60 is pumped into the medium-pressure economizer 31 by a medium-pressure feed water pump 62 provided in the feed water line 60.

[0022] The medium-pressure economizer 31 heats the water supplied from the second low-pressure economizer 24 via the feed water line 60 by heat exchange with the exhaust gas. The water heated in the medium-pressure economizer 31 is supplied to the medium-pressure drum 33 via the feed water line 64 connecting the medium-pressure economizer 31 and the medium-pressure evaporator 32.

[0023] The medium-pressure evaporator 32 heats and evaporates the water supplied from the medium-pressure economizer 31 to the medium-pressure drum 33 via the feed water line 64 by heat exchange with the exhaust gas to generate medium-pressure steam. A feed water valve 65 for reducing the pressure of the water supplied from the medium-pressure economizer 31 is provided in the feed water line 64. A part of the medium-pressure steam generated in the medium-pressure evaporator 32 is supplied to the medium-pressure superheater 34 via the steam line 66 connecting the medium-pressure drum 33 and the medium-pressure superheater 34.

[0024] The medium-pressure superheater 34 superheats the medium-pressure steam supplied from the medium-pressure drum 33 via the steam line 66 by heat exchange with the exhaust gas to generate medium-pressure superheated steam. The medium-pressure superheated steam generated in the medium-pressure superheater 34 is supplied via the steam line 68 to the high-pressure exhaust line 114 connecting the steam outlet of the high-pressure steam turbine 102 and the steam inlet of the first reheater 42. The medium-pressure superheated steam generated in the medium-pressure superheater 34 flows into the first reheater 42 via the steam line 68 and the high-pressure exhaust line 114.

[0025] A part of the water heated by the second low-pressure economizer 24 is supplied to the first high-pressure economizer 30 via the feed water line 70 connecting the second low-pressure economizer 24 and the first high-pressure economizer 30. The heated water flowing through the feed water line 70 is pumped into the first high-pressure economizer 30 by a high-pressure feed water pump 72 provided in the feed water line 70.

[0026] The first high-pressure economizer 30 heats the heated water supplied from the second low-pressure economizer 24 via the water supply line 70 by heat exchange with the exhaust gas. The heated water heated by the first high-pressure economizer 30 is supplied to the second high-pressure economizer 36 via the water supply line 74 connecting the first high-pressure economizer 30 and the second high-pressure economizer 36.

[0027] The second high-pressure economizer 36 heats the high-pressure heated water supplied from the first high-pressure economizer 30 via the water supply line 74 by heat exchange with the exhaust gas. The high-pressure heated water heated by the second high-pressure economizer 36 is supplied to the high-pressure drum 39 via the water supply line 76 connecting the second high-pressure economizer 36 and the high-pressure drum 39.

[0028] The high-pressure evaporator 38 heats and evaporates the water supplied to the high-pressure drum 39 from the second high-pressure economizer 36 via the water supply line 76 by heat exchange with the exhaust gas to generate high-pressure steam. A water supply valve 77 for reducing the pressure of the water supplied from the second high-pressure economizer 36 is provided in the water supply line 76. The high-pressure steam generated by the high-pressure evaporator 38 is supplied to the first high-pressure superheater 40 via the steam line 78 connecting the high-pressure drum 39 and the first high-pressure superheater 40.

[0029] The first high-pressure superheater 40 superheats the high-pressure steam supplied from the high-pressure drum 39 via the steam line 78 by heat exchange with the exhaust gas to generate high-pressure superheated steam. The high-pressure superheated steam generated by the first high-pressure superheater 40 is supplied to the second high-pressure superheater 44 via the steam line 80 connecting the first high-pressure superheater 40 and the second high-pressure superheater 44. A desuperheater 81 for reducing the temperature of the high-pressure superheated steam flowing through the steam line 80 is provided in the steam line 80.

[0030] The second high-pressure superheater 44 further superheats the high-pressure superheated steam supplied from the first high-pressure superheater 40 via the steam line 80 by heat exchange with the exhaust gas. The high-pressure superheated steam superheated by the second high-pressure superheater 44 is supplied to the high-pressure steam turbine 102 via the steam line 97 connecting the second high-pressure superheater 44 and the steam inlet of the high-pressure steam turbine 102.

[0031] The first reheater 42 superheats the steam supplied from the steam outlet of the high-pressure steam turbine 102 to the first reheater 42 via the high-pressure exhaust line 114 and the steam supplied from the intermediate-pressure superheater 34 to the first reheater 42 via the steam line 68 and the high-pressure exhaust line 114 by heat exchange with the exhaust gas. The steam superheated in the first reheater 42 is supplied to the second reheater 46 via the steam line 82 connecting the first reheater 42 and the second reheater 46. A desuperheater 83 for desuperheating the steam flowing through the steam line 82 is provided in the steam line 82.

[0032] The second reheater 46 superheats the steam supplied via the steam line 82 by heat exchange with the exhaust gas. The steam superheated in the second reheater 46 is supplied to the intermediate-pressure steam turbine 104 via the steam line 98 connecting the second reheater 46 and the steam inlet of the intermediate-pressure steam turbine 104.

[0033] (Regarding the gland steam) Each of the steam turbines 102, 104, 106 is provided with a gland section 95 for sealing the gap between the casing and the rotor of the steam turbines 102, 104, 106. Gland steam for sealing is supplied to each gland section 95. The gland steam can be supplied to each gland section 95 by the gland steam supply line 91. A pressure regulating valve 93 for adjusting the set pressure of the steam supplied to each gland section 95 is provided in the gland steam supply line 91.

[0034] In the combined plant 2 (2A) shown in FIG. 1, the gland steam supply line 91 (91A) is configured to supply the steam from the high-pressure drum 39 to each gland section 95 via, for example, the steam line 97. In the combined plant 2 (2B) shown in FIG. 2, the gland steam supply line 91 (91B) is configured to supply the steam from the intermediate-pressure drum 33 to each gland section 95 via, for example, the steam line 98.

[0035] Thus, in the combined plant 2 according to some embodiments, the ground steam is supplied by steam from the steam generator 6 of the combined plant 2, rather than from an external auxiliary steam supply source such as an auxiliary boiler or an existing steam connection pipe.

[0036] In the combined plant 2 according to some embodiments, for example, at the timing when the power generated by renewable energy such as solar energy is supplied to the power supply target, the power generation by the combined plant 2 is temporarily stopped, and the operation (rotation) of the steam turbines 102, 104, 106 is also temporarily stopped. At this time, instead of breaking the vacuum of the condenser 108 so that outside air does not flow into the casings of the steam turbines 102, 104, 106, it is desirable that the supply of the ground steam continues even after the stop of the steam turbines 102, 104, 106. This is because the time required for restarting the combined plant 2, that is, for resuming the power generation by the combined plant 2, can be shortened.

[0037] Therefore, in the combined plant 2 according to some embodiments, when the power generation by the combined plant 2 is temporarily stopped for a relatively short period, for example, about several hours, the supply of steam to the ground part 95 is continued by the steam in the steam drum 21.

[0038] Here, a method for preparing for restart in the combined plant 2 will be described. FIG. 3 is a flowchart showing the processing procedure in the method for preparing for restart according to the present embodiment. The method for preparing for restart according to this embodiment includes a step S1 of instructing the stop of the combined plant 2, a step S3 of maintaining a specified degree of vacuum in the condenser 108, a step S5 of continuing the steam supply to the ground section 95, a step S7 of changing the set pressure of the steam supplied to each ground section 95 from the first pressure to the second pressure, a step S9 of determining whether the pressure in the steam drum 21 is equal to or higher than the specified pressure, and a step S11 of continuing the steam supply to the ground section 95. The method for preparing for restart according to this embodiment includes a step S13 of determining whether to restart the combined plant 2, a step S15 of starting the gas turbine 4 and increasing the load, a step S17 of generating steam in the waste heat recovery boiler 5, a step S19 of changing the set pressure of the steam supplied to each ground section 95 from the second pressure to the first pressure, a step S21 of starting the steam turbines 102, 104, 106 and increasing the load, and a step S23 of stopping the steam supply to the ground section 95 and breaking the vacuum in the condenser 108.

[0039] (Step S1 of instructing the stop of the combined plant 2) Step S1 of instructing the stop of the combined plant 2 is a step in which the operator of the combined plant 2 instructs the stop of the combined plant 2. That is, as described above, for example, when it becomes necessary to stop the power generation in the combined plant 2 because the power generated by renewable energy such as solar energy is supplied to the power supply target, the operator gives an instruction for stopping the combined plant 2 to a control device (not shown) of the combined plant 2. Thereby, the control device stops the gas turbine 4 and the steam turbines 102, 104, 106. By implementing step S1 of instructing the stop of the combined plant 2, the gas turbine 4 and the steam turbines 102, 104, 106 stop.

[0040] (Step S3 of maintaining a specified degree of vacuum in the condenser 108) Step S3 of maintaining the condenser 108 at a specified degree of vacuum is a step for maintaining the condenser 108 at the specified degree of vacuum so that the degree of vacuum inside the condenser 108 does not decrease after the combined plant 2 stops. In step S3 of maintaining the condenser 108 at the specified degree of vacuum, a control device (not shown) of the combined plant 2 controls each part of the steam turbine system 100 and the steam generator 6 so as to maintain the inside of the condenser 108 at the specified degree of vacuum. By implementing step S3 of maintaining the condenser 108 at the specified degree of vacuum, the degree of vacuum inside the condenser 108 is maintained at the specified degree of vacuum.

[0041] (Step S5 of continuing the steam supply to the gland section 95) Step S5 of continuing the steam supply to the gland section 95 is a step for continuing the supply of gland steam to each of the gland sections 95 of the steam turbines 102, 104, and 106 that stopped due to the implementation of step S1 of instructing the stop of the combined plant 2. In step S5 of continuing the steam supply to the gland section 95, a control device (not shown) of the combined plant 2 controls each part of the steam turbine system 100 and the steam generator 6 so as to continue the supply of steam in the steam drum 21 to each of the gland sections 95. In the combined plant 2 (2A) shown in FIG. 1, by implementing step S5 of continuing the steam supply to the gland section 95, the supply of steam from the high-pressure drum 39 to each of the gland sections 95 is continued. In the combined plant 2 (2B) shown in FIG. 2, by implementing step S5 of continuing the steam supply to the gland section 95, the supply of steam from the intermediate-pressure drum 33 to each of the gland sections 95 is continued. According to the method for preparing for restart according to the present embodiment, since the supply of steam from the high-pressure drum 39 or the intermediate-pressure drum 33 having a relatively high internal pressure of the drum to each of the gland sections 95 is continued, it becomes easy to secure the duration of the supply of steam to the gland section 95.

[0042] (Step S7 of changing the set pressure from the first pressure to the second pressure) The step S7 of changing the set pressure from the first pressure to the second pressure is a step of changing the set pressure of the steam supplied to each base portion 95 from the first pressure to the second pressure. During the rated operation of the combined plant 2, the set pressure of the steam supplied to each base portion 95 is set to the first pressure. That is, during the rated operation of the combined plant 2, a control device (not shown) of the combined plant 2 sets the set pressure of the pressure regulating valve 93 in the main steam supply line 91 to the first pressure. The first pressure is, for example, 4.06 pounds per square inch in gauge pressure.

[0043] In the step S7 of changing the set pressure from the first pressure to the second pressure, for example, an operator gives an instruction to a control device (not shown) of the combined plant 2 to change the set pressure of the steam supplied to each base portion 95 from the first pressure to the second pressure, and thereby the control device changes the set pressure of the pressure regulating valve 93 in the main steam supply line 91 from the first pressure to the second pressure. Thereby, the set pressure of the pressure regulating valve 93 is changed from the first pressure to the second pressure. The second pressure is lower than the first pressure, and is, for example, 1.0 pounds per square inch or more and 1.4 pounds per square inch or less in gauge pressure. By changing the set pressure from the first pressure to the second pressure which is lower than the first pressure, the consumption amount of the steam in the steam drum 21 can be reduced, so that the time for maintaining the degree of vacuum in the condenser 108 can be lengthened.

[0044] (Step S9 of determining whether or not the pressure in the steam drum 21 is equal to or higher than a specified pressure) The step S9 of determining whether or not the pressure in the steam drum 21 is equal to or higher than a specified pressure is a step in which, for example, a control device (not shown) of the combined plant 2 determines whether or not the pressure in the steam drum 21 is equal to or higher than a specified pressure. In the combined plant 2 (2A) shown in FIG. 1, the control device determines whether or not the pressure in the high-pressure drum 39 is equal to or higher than a specified pressure. In the combined plant 2 (2B) shown in FIG. 2, the control device determines whether the pressure in the medium-pressure drum 33 is equal to or higher than a specified pressure.

[0045] Here, the specified pressure is preset as a certain value that is 200 pounds per square inch or more and 450 pounds per square inch or less in gauge pressure. Thereby, while ensuring the duration of the supply of steam to each ground section 95, it is possible to perform the breaking of the vacuum of the condenser 108 at an appropriate timing in step S23 of stopping the supply of steam to the ground section 95 and breaking the vacuum of the condenser 108, which will be described later.

[0046] When the control device determines that the pressure in the steam drum 21 is equal to or higher than the specified pressure, it proceeds to step S11 of continuing the supply of steam to the ground section 95 described below. When the control device determines that the pressure in the steam drum 21 is not equal to or higher than the specified pressure, it proceeds to step S23 of stopping the supply of steam to the ground section 95 and breaking the vacuum of the condenser 108, which will be described later.

[0047] (Step S11 of Continuing the Supply of Steam to the Ground Section 95) Step S11 of continuing the supply of steam to the ground section 95 is a step for continuing the supply of ground steam to each ground section 95 when an affirmative determination is made in step S9 of determining whether the pressure in the steam drum 21 described above is equal to or higher than the specified pressure. In step S11 of continuing the supply of steam to the ground section 95, the implementation content in step S5 of continuing the supply of steam to the ground section 95 described above is continuously implemented as it is. By implementing step S11 of continuing the supply of steam to the ground section 95, the supply of ground steam to each ground section 95 is continued.

[0048] (Step S13 of Determining Whether to Restart the Combined Plant 2) Step S13 of determining whether to restart the combined plant 2 is a step in which, for example, an operator determines whether to restart the combined plant 2. That is, in step S13 of determining whether to restart the combined plant 2, for example, the operator determines whether to restart the combined plant 2 in consideration of the transition situation of the power generated by renewable energy such as solar energy and the time required to resume power generation by the combined plant 2. When the operator determines to restart the combined plant 2, the process proceeds to step S15 of starting the gas turbine 4 described below and increasing the load. When the operator determines not to restart the combined plant 2, the process returns to step S9 of determining whether the pressure in the steam drum 21 described above is equal to or higher than the specified pressure.

[0049] (Step S15 of starting the gas turbine 4 and increasing the load) Step S15 of starting the gas turbine 4 and increasing the load is a step of starting the stopped gas turbine 4 and then gradually increasing the load of the gas turbine 4. In step S15 of starting the gas turbine 4 and increasing the load, for example, the operator gives an instruction to start the gas turbine 4 to a control device (not shown) of the combined plant 2, and the control device starts the gas turbine 4 and then controls each part of the gas turbine 4 so as to gradually increase the load of the gas turbine 4. By implementing step S15 of starting the gas turbine 4 and increasing the load, the gas turbine 4 is started, and then the load of the gas turbine 4 gradually increases.

[0050] (Step S17 of generating steam in the waste heat recovery boiler 5) The step S17 of generating steam in the waste heat recovery boiler 5 is a step of generating steam in the waste heat recovery boiler 5 after the step S15 of starting the gas turbine 4 and increasing the load is carried out and the gas turbine 4 is started. In the step S17 of generating steam in the waste heat recovery boiler 5, after the gas turbine 4 is started, for example, a control device (not shown) of the combined plant 2 controls each part of the waste heat recovery boiler 5 to generate steam in the waste heat recovery boiler 5 at the timing when steam generation in the waste heat recovery boiler 5 becomes possible. By carrying out the step S17 of generating steam in the waste heat recovery boiler 5, steam is generated in the waste heat recovery boiler 5.

[0051] (Step S19 of changing the set pressure from the second pressure to the first pressure) The step S19 of changing the set pressure from the second pressure to the first pressure is a step of changing the set pressure of the steam supplied to each ground part 95 from the second pressure to the first pressure. In the step S19 of changing the set pressure from the second pressure to the first pressure, for example, an operator gives an instruction to a control device (not shown) of the combined plant 2 to change the set pressure of the steam supplied to each ground part 95 from the second pressure to the first pressure, and the control device changes the set pressure of the pressure regulating valve 93 of the ground steam supply line 91 from the second pressure to the first pressure. Note that in the step S19 of changing the set pressure from the second pressure to the first pressure, after the step S17 of generating steam in the waste heat recovery boiler 5 is carried out, the control device (not shown) of the combined plant 2 may change the set pressure of the pressure regulating valve 93 of the ground steam supply line 91 from the second pressure to the first pressure at a predetermined timing. By carrying out the step S19 of changing the set pressure from the second pressure to the first pressure, the set pressure of the pressure regulating valve 93 is changed from the second pressure to the first pressure.

[0052] (Step S21 of starting the steam turbines 102, 104, 106 and increasing the load) The step S21 of starting up the steam turbines 102, 104, 106 and increasing the load is a step of starting up each of the stopped steam turbines 102, 104, 106 and then gradually increasing the load of each of the steam turbines 102, 104, 106. In the step S21 of starting up the steam turbines 102, 104, 106 and increasing the load, for example, when an operator gives an instruction to start up each of the steam turbines 102, 104, 106 to a control device (not shown) of the combined plant 2, the control device starts up each of the steam turbines 102, 104, 106, and then controls each part of the steam turbine system 100 so as to gradually increase the load of each of the steam turbines 102, 104, 106. Note that in the step S21 of starting up the steam turbines 102, 104, 106 and increasing the load, after the implementation of the step S17 of generating steam in the waste heat recovery boiler 5, a control device (not shown) of the combined plant 2 starts up each of the steam turbines 102, 104, 106 at a predetermined timing, and then controls each part of the steam turbine system 100 so as to gradually increase the load of each of the steam turbines 102, 104, 106. By implementing the step S21 of starting up the steam turbines 102, 104, 106 and increasing the load, each of the steam turbines 102, 104, 106 is started up, and then the load of each of the steam turbines 102, 104, 106 gradually increases.

[0053] Note that each of the above steps S15, S17, S19, S21 is the step S30 of restarting the combined plant 2 while continuously supplying steam from the steam drum 21 to the gland part 95 of each of the steam turbines 102, 104, 106. That is, each of the above steps S15, S17, S19, S21 is included in the step S30 of restarting the combined plant 2. Thereby, the combined plant 2 can be restarted while maintaining the vacuum degree of the condenser 108, so that the time required for restarting the combined plant 2 can be shortened.

[0054] In addition, step S30 of restarting the combined plant 2 includes step S19 of changing the set pressure from the second pressure to the first pressure. Thereby, since the set pressure is returned from the second pressure to the first pressure during the process of restarting the combined plant 2, the reliability of the seal in the ground part 95 during the operation of the combined plant 2 can be ensured.

[0055] (Step S23 of stopping the steam supply to the ground part 95 and breaking the vacuum of the condenser 108) Step S23 of stopping the steam supply to the ground part 95 and breaking the vacuum of the condenser 108 is a step of stopping the steam supply to the ground part 95 and breaking the vacuum of the condenser 108 when it is determined in step S9 of determining whether the pressure in the steam drum 21 is equal to or higher than a specified pressure that the pressure in the steam drum 21 is not equal to or higher than the specified pressure. In step S23 of stopping the steam supply to the ground part 95 and breaking the vacuum of the condenser 108, a control device (not shown) of the combined plant 2 controls each part of the steam generation device 6 so as to stop the steam supply to the ground part 95 and break the vacuum of the condenser 108. By implementing step S23 of stopping the steam supply to the ground part 95 and breaking the vacuum of the condenser 108, the steam supply to the ground part 95 is stopped and the vacuum of the condenser 108 is broken. Thereby, before the pressure of the steam supplied from the steam drum 21 decreases and foreign matter leaks into the ground part 95 from the outside, the pressure in the condenser 108 can be brought close to the atmospheric pressure, so that the possibility of foreign matter leaking into the ground part 95 from the outside can be reduced.

[0056] Note that when the combined plant 2 is started after step S23 of stopping the steam supply to the ground part 95 and breaking the vacuum of the condenser 108 is implemented, the processing is performed in the same procedure as when the combined plant 2 is started after a normal operation stop.

[0057] Note that the execution order of each of the above steps is not limited to the above order and can be appropriately changed within a range where no contradiction occurs.

[0058] As described above, the method for preparing for restart according to this embodiment includes step S3 of maintaining the inside of the condenser 108 at a specified degree of vacuum, step S9 of determining whether the pressure in the steam drum 21 is equal to or higher than the specified pressure, and step S11 of continuing the steam supply to the gland section 95. Thereby, even after the combined plant 2 stops, the supply of steam to the gland section 95 of the steam turbines 102, 104, 106 is continued by the steam in the steam drum 21. Thus, the possibility of foreign matter leaking in from the outside into the gland section 95 can be reduced, and the degree of vacuum of the condenser 108 can be maintained. Further, according to the method for preparing for restart according to this embodiment, since the degree of vacuum of the condenser 108 can be maintained even after the combined plant 2 stops, the time required for restarting the combined plant 2 can be shortened.

[0059] The present disclosure is not limited to the above-described embodiments, and also includes forms obtained by modifying the above-described embodiments and forms obtained by appropriately combining these forms.

[0060] The content described in each of the above embodiments is understood as follows, for example. (1) A method for preparing for restart in a gas turbine exhaust heat recovery plant (combined plant 2) according to at least one embodiment of the present disclosure, the gas turbine exhaust heat recovery plant (combined plant 2) includes a gas turbine 4, an exhaust heat recovery boiler 5 that recovers the exhaust heat of the gas turbine 4 to generate steam, steam turbines 102, 104, 106 driven by the steam generated by the exhaust heat recovery boiler 5, and a condenser 108. A steam utilization facility (steam turbine system 100). A method for preparing for restart in a gas turbine exhaust heat recovery plant (combined plant 2) according to at least one embodiment of the present disclosure includes a step of maintaining a specified degree of vacuum in the condenser 108 after the gas turbine exhaust heat recovery plant (combined plant 2) stops (step S3 of maintaining a specified degree of vacuum in the condenser 108), and a step of checking the pressure of the steam drum 21 of the exhaust heat recovery boiler 5 (step S9 of determining whether the pressure in the steam drum 21 is equal to or higher than a specified pressure) When the pressure of the steam drum 21 confirmed in the step of checking the pressure of the steam drum 21 (step S9 of determining whether the pressure in the steam drum 21 is equal to or higher than a specified pressure) is equal to or higher than the specified pressure, a step of continuing to supply steam from the steam drum 21 to the gland section 95 of the steam turbines 102, 104, 106 (step S11 of continuing to supply steam to the gland section 95)

[0061] According to the method in (1) above, since the supply of steam from the steam in the steam drum 21 to the gland section 95 of the steam turbines 102, 104, 106 is continued even after the gas turbine exhaust heat recovery plant (combined plant 2) stops, the possibility of foreign matter leaking in from the outside to the gland section 95 can be reduced, and the degree of vacuum in the condenser 108 can be maintained. Further, according to the method in (1) above, since the degree of vacuum in the condenser 108 can be maintained even after the gas turbine exhaust heat recovery plant (combined plant 2) stops, the time required for restarting the gas turbine exhaust heat recovery plant (combined plant 2) can be shortened.

[0062] (2) In some embodiments, in the method of (1) above, in the step of maintaining a specified degree of vacuum inside the condenser 108 (step S3 of maintaining a specified degree of vacuum inside the condenser 108), it is preferable to change the set pressure of the steam supplied to the ground section 95 from a first pressure, which is the set pressure before the stop of the gas turbine exhaust heat recovery plant (combined plant 2), to a second pressure lower than the first pressure.

[0063] According to the method of (2) above, since the consumption amount of the steam in the steam drum 21 can be reduced, the time for maintaining the degree of vacuum in the condenser 108 can be lengthened.

[0064] (3) In some embodiments, in the method of (2) above, the first pressure may be 4.06 pounds per square inch gauge. The second pressure may be 1.0 pounds per square inch gauge or more and 1.4 pounds per square inch gauge or less.

[0065] According to the method of (3) above, the first pressure and the second pressure may be the above pressures.

[0066] (4) In some embodiments, in the method of (1) above, while the supply of steam from the steam drum 21 to the ground sections 95 of the steam turbines 102, 104, 106 is continuing, a step of restarting the gas turbine exhaust heat recovery plant (combined plant 2) (step S30 of restarting the combined plant 2) may be provided.

[0067] According to the method of (4) above, since the gas turbine exhaust heat recovery plant (combined plant 2) can be restarted while maintaining the degree of vacuum in the condenser 108, the time required for restarting the gas turbine exhaust heat recovery plant (combined plant 2) can be shortened.

[0068] (5) In some embodiments, in the method of (4) above, in the step of restarting the gas turbine exhaust heat recovery plant (combined plant 2) (step S30 of restarting the combined plant 2), the gas turbine 4 is started to increase the load of the gas turbine 4, the exhaust heat of the gas turbine 4 is recovered to generate steam in the exhaust heat recovery boiler 5, and the steam turbines 102, 104, 106 are started by the steam generated in the exhaust heat recovery boiler 5 to increase the load of the steam turbines 102, 104, 106.

[0069] According to the method of (5) above, the gas turbine exhaust heat recovery plant (combined plant 2) can be restarted while maintaining the degree of vacuum in the condenser 108, so that the time required for restarting the gas turbine exhaust heat recovery plant (combined plant 2) can be shortened.

[0070] (6) In some embodiments, in the method of (2) or (3) above, while the supply of steam from the steam drum 21 to the gland section 95 of the steam turbines 102, 104, 106 is continued, it is preferable to include a step of restarting the gas turbine exhaust heat recovery plant (combined plant 2) (step S30 of restarting the combined plant 2).

[0071] According to the method of (6) above, the gas turbine exhaust heat recovery plant (combined plant 2) can be restarted while maintaining the degree of vacuum in the condenser 108, so that the time required for restarting the gas turbine exhaust heat recovery plant (combined plant 2) can be shortened.

[0072] (7) In some embodiments, in the method of (6) above, in the step of restarting the gas turbine exhaust heat recovery plant (combined plant 2) (step S30 of restarting the combined plant 2), start the gas turbine 4 to increase the load of the gas turbine 4, recover the exhaust heat of the gas turbine 4 to generate steam in the exhaust heat recovery boiler 5, change the set pressure from the second pressure to the first pressure, and start the steam turbines 102, 104, 106 with the steam generated in the exhaust heat recovery boiler 5 to increase the load of the steam turbines 102, 104, 106.

[0073] According to the method of (7) above, since the gas turbine exhaust heat recovery plant (combined plant 2) can be restarted while maintaining the degree of vacuum in the condenser 108, the time required for restarting the gas turbine exhaust heat recovery plant (combined plant 2) can be shortened. Further, according to the method of (7) above, since the set pressure is returned from the second pressure to the first pressure during the process of restarting the gas turbine exhaust heat recovery plant (combined plant 2), the reliability of the seal in the ground portion 95 during the operation of the gas turbine exhaust heat recovery plant (combined plant 2) can be ensured.

[0074] (8) In some embodiments, in any of the methods of (1) to (7) above, when the pressure of the steam drum 21 confirmed in the step of checking the pressure of the steam drum 21 (step S9 of determining whether the pressure in the steam drum 21 is equal to or higher than the specified pressure) is lower than the specified pressure, stop the supply of steam from the steam drum 21 to the ground portion 95 and perform a step of breaking the vacuum of the condenser 108 (step S23 of stopping the supply of steam to the ground portion 95 and breaking the vacuum of the condenser 108).

[0075] According to the method of (8) above, before the pressure of the steam supplied from the steam drum 21 drops and foreign matter leaks in from the outside to the ground portion 95, the pressure in the condenser 108 can be brought close to atmospheric pressure, so the possibility of foreign matter leaking in from the outside to the ground portion 95 can be reduced.

[0076] (9) In some embodiments, in the method of (8) above, the specified pressure may be 200 pounds per square inch or more and 450 pounds per square inch or less in gauge pressure.

[0077] According to the method of (9) above, it is possible to perform vacuum breaking of the condenser 108 at an appropriate timing while ensuring the duration of steam supply to the ground portion 95.

[0078] (10) In some embodiments, in any of the methods of (1) to (9) above, the waste heat recovery boiler 5 may have a high-pressure drum 39, a medium-pressure drum 33, and a low-pressure drum 25. The steam drum 21 may be the high-pressure drum 39 or the medium-pressure drum 33.

[0079] According to the method of (10) above, since the internal pressure of the drum is relatively high, it becomes easier to ensure the duration of steam supply to the ground portion 95.

Explanation of Reference Numerals

[0080] 2(2A) Combined Plant 2(2B) Combined Plant 4 Gas Turbine 5 Waste Heat Recovery Boiler 6 Steam Generator 19 Generator 21 Steam Drum 25 Low-Pressure Drum 33 Medium-Pressure Drum 39 High-Pressure Drum 91(91A) Ground Steam Supply Line 91(91B) Ground Steam Supply Line 93 Pressure Regulating Valve 95 Ground Portion 100 Steam Turbine System 102 High-Pressure Steam Turbine (Steam Turbine) 104 Medium-Pressure Steam Turbine (Steam Turbine) 106 Low-Pressure Steam Turbine (Steam Turbine) 108 Condenser 200-row heat recovery plant

Claims

1. A method for preparing for restart in a gas turbine exhaust heat recovery plant, comprising: The gas turbine exhaust heat recovery plant includes: A gas turbine; An exhaust heat recovery boiler that recovers the exhaust heat of the gas turbine to generate steam; A steam utilization facility including a steam turbine driven by the steam generated by the exhaust heat recovery boiler, and a condenser; And After the gas turbine exhaust heat recovery plant stops, maintaining the inside of the condenser at a specified vacuum degree; Checking the pressure of the steam drum of the exhaust heat recovery boiler; When the pressure of the steam drum confirmed in the step of checking the pressure of the steam drum is equal to or higher than a specified pressure, continuing to supply steam from the steam drum to the gland part of the steam turbine; And A method for preparing for restart in a gas turbine exhaust heat recovery plant.

2. In the step of maintaining the inside of the condenser at a specified vacuum degree, changing the set pressure of the steam supplied to the gland part from a first pressure, which is the set pressure before the gas turbine exhaust heat recovery plant stops, to a second pressure lower than the first pressure. The method for preparing for restart in a gas turbine exhaust heat recovery plant according to Claim 1.

3. The first pressure is 4.06 pounds per square inch in gauge pressure. The second pressure is 1.0 pound per square inch or more and 1.4 pounds per square inch or less in gauge pressure. The method for preparing for restart in a gas turbine exhaust heat recovery plant according to Claim 2.

4. While continuing to supply steam from the steam drum to the gland part of the steam turbine, restarting the gas turbine exhaust heat recovery plant. And The method for preparing for restart in a gas turbine exhaust heat recovery plant according to Claim 1.

5. In the step of restarting the gas turbine exhaust heat recovery plant: Starting the gas turbine and increasing the load of the gas turbine; Recovering the exhaust heat of the gas turbine and generating steam in the exhaust heat recovery boiler; Starting the steam turbine with the steam generated in the exhaust heat recovery boiler and increasing the load of the steam turbine. The method for preparing for restart in a gas turbine exhaust heat recovery plant according to Claim 4.

6. While continuing to supply steam from the steam drum to the gland section of the steam turbine, a step of restarting the gas turbine exhaust heat recovery plant. Comprising. A method for preparing for restart in the gas turbine exhaust heat recovery plant according to claim 2 or 3.

7. In the step of restarting the gas turbine exhaust heat recovery plant, Starting the gas turbine and increasing the load of the gas turbine, Recovering the exhaust heat of the gas turbine and generating steam in the exhaust heat recovery boiler, Changing the set pressure from the second pressure to the first pressure, Starting the steam turbine with the steam generated in the exhaust heat recovery boiler and increasing the load of the steam turbine. A method for preparing for restart in the gas turbine exhaust heat recovery plant according to claim 6.

8. When the pressure of the steam drum confirmed in the step of checking the pressure of the steam drum is less than the specified pressure, stopping the supply of steam from the steam drum to the gland section and performing a vacuum break of the condenser. Comprising. A method for preparing for restart in the gas turbine exhaust heat recovery plant according to any one of claims 1 to 5.

9. The specified pressure is 200 pounds per square inch or more and 450 pounds per square inch or less in gauge pressure. A method for preparing for restart in the gas turbine exhaust heat recovery plant according to claim 8.

10. The exhaust heat recovery boiler has a high-pressure drum, a medium-pressure drum, and a low-pressure drum. The steam drum is the high-pressure drum or the medium-pressure drum. A method for preparing for restart in the gas turbine exhaust heat recovery plant according to any one of claims 1 to 5.

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