JP7268573B2 - Power generation system and method of starting power generation system - Google Patents

Description

TECHNICAL FIELD The present invention relates to a power generation system and a method for starting the power generation system.

Conventionally, a power generation system is known in which steam discharged from a high-pressure turbine is reheated and supplied to a low-pressure turbine such as an intermediate-pressure turbine or a low-pressure turbine to increase power generation efficiency. In this type of power generation system, thermal stress due to non-uniform cross-sectional temperature distribution of the turbine rotor at the initial stage of turbine start-up and vibration due to expansion difference due to temperature difference between the turbine rotor and the casing may occur. As a method of suppressing this vibration, for example, Patent Document 1 discloses a method of starting the turbine with an initial load holding time determined based on the high pressure turbine first stage rear inner wall metal temperature and the high pressure turbine first stage post steam temperature. Are listed. Further, Patent Literature 2 describes a method for adjusting the exhaust gas temperature of a gas turbine that generates steam by spraying water at a flow rate determined based on information on changes in the temperature of reheated steam over time.

JP-A-4-203304 JP 2019-27399 A

However, in the method of Patent Document 1, even if the initial load holding time is set in advance, vibration may occur depending on the operating conditions after the turbine is started, and it is necessary to readjust the initial load holding time. In addition, in the method of Patent Document 2, water is sprayed on the exhaust gas of the gas turbine to adjust the temperature so as not to generate vibration of the turbine, but it is difficult to grasp the initial load holding time sufficient to prevent vibration. could not. The conventional technology has room for improvement in terms of accurately grasping the initial load holding time that can reliably prevent the occurrence of vibration.

SUMMARY OF THE INVENTION An object of the present invention is to provide a power generation system and a power generation system start-up method that can reliably prevent the occurrence of vibrations in a turbine during start-up.

The present invention provides a boiler for generating steam, a high-pressure side turbine in which the steam generated from the boiler flows, a low-pressure side turbine in which reheated steam discharged from the high-pressure side turbine and reheated by the boiler flows, and A generator that generates power by rotation of the high-pressure side turbine and the low-pressure side turbine, a detector that detects the temperature of the reheated steam flowing into the low-pressure side turbine, and a load of the generator that controls the flow rate of the steam. and a control unit, wherein the load of the generator is changed from a no-load state to an initial load state in which an initial load smaller than a set load at the time of power supply is applied by the detection unit. The present invention relates to a power generation system that shifts to load operation at the set load after maintaining the temperature change rate of reheated steam until it becomes smaller than a predetermined value.

Preferably, the controller maintains the initial load state until the temperature exceeds a preset temperature and the temperature change rate becomes smaller than a predetermined value.

The present invention provides a power generation system comprising a generator that generates power by rotation of a high-pressure side turbine and a low-pressure side turbine, wherein steam is discharged from the high-pressure side turbine and reheated steam reheated by a boiler is supplied to the low-pressure side turbine. In the starting method, the load of the generator is changed from a no-load state to an initial load state in which an initial load smaller than the set load at the time of power supply is applied, and the temperature change rate of the reheat steam is higher than a predetermined value. The present invention relates to a method for starting a power generation system, including the steps of maintaining the initial load state until it becomes smaller, and shifting to load operation at the set load after the step of maintaining the initial load state.

In the method for starting the power generation system, it is preferable that the initial load state is maintained until the temperature exceeds a preset set temperature and the temperature change rate becomes smaller than a predetermined value. .

Advantageous Effects of Invention According to the present invention, it is possible to provide a power generation system and a method for starting a power generation system that can reliably prevent the occurrence of vibrations in a turbine during start-up.

1 is a schematic diagram showing a power generation system according to one embodiment of the present invention; FIG. FIG. 2 is a block diagram showing an electrical configuration of a control section of the power generation system according to one embodiment of the present invention; FIG. FIG. 4 is a diagram showing behavior of various data measured in an example of the power generation system according to one embodiment of the present invention; FIG. 5 is a diagram showing behavior of various data measured in a comparative example of the power generation system according to one embodiment of the present invention;

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, embodiments of the present invention will be described with reference to the drawings. However, the present invention is not limited to the following embodiments.

A power generation system 1 according to an embodiment of the present invention will be described. FIG. 1 is a schematic diagram showing a main part of a power generation system 1 according to this embodiment. The power generation system 1 is a system that uses steam to generate power in a thermal power plant.

First, the overall configuration of the power generation system 1 will be described. As shown in FIG. 1, the power generation system 1 includes a boiler 10, a high pressure turbine 20 as a high pressure side turbine, an intermediate pressure turbine 30 and low pressure turbines 41 and 42 as low pressure side turbines, a generator 50, a condensate A vessel 60 , a feed water heating facility 70 , and a temperature detection section 80 are provided. In addition, the power generation system 1 mainly includes a main steam pipe 101, a low-temperature reheat steam pipe 103, a high-temperature reheat steam pipe 107, a crossover pipe 111, and Condensate pipes 113, 114 and water supply pipes 119, 120, 121, 126 are provided. Furthermore, the power generation system 1 includes a control unit 90 that executes start-up control of the power generation system 1 .

The boiler 10 is a device that generates steam, and includes a superheater 11 and a reheater 12 . The superheater 11 is a device that superheats steam generated in the boiler 10 to generate high-temperature and high-pressure superheated steam. The reheater 12 is a device that reheats steam discharged from the high pressure turbine 20 .

The high-pressure turbine 20, the intermediate-pressure turbine 30, the low-pressure turbines 41 and 42, and the generator 50 are coaxially arranged with their shafts connected to each other. In this specification, of the bearings at both ends of the high pressure turbine 20 and the intermediate pressure turbine 30, the high pressure turbine side is referred to as the first bearing 21, and the intermediate pressure turbine side is referred to as the second bearing 31.

The high pressure turbine 20 is connected to the superheater 11 of the boiler 10 by a main steam pipe 101 and is connected to the reheater 12 of the boiler 10 by a low temperature reheat steam pipe 103 . A main heat steam stop valve 102 is arranged in the main steam pipe 101 . A check valve 104 is arranged in the cold reheat steam pipe 103 . Also, the main steam pipe 101 and the low-temperature reheat steam pipe 103 are connected to each other by a bypass line 105 . A bypass valve 106 is arranged in the bypass line 105 .

The intermediate pressure turbine 30 is connected with the reheater 12 of the boiler 10 by a hot reheat steam pipe 107 . A temperature detection unit 80 for detecting the temperature of the reheat steam and a composite reheat valve 108 are arranged in the high-temperature reheat steam pipe 107 . A bypass line 109 is connected to the high-temperature reheat steam pipe 107 at a position between the temperature detector 80 and the composite reheat valve 108 . Bypass line 109 is connected to condenser 60 . A bypass valve 110 is arranged in the bypass line 109 .

The low-pressure turbines 41 and 42 are connected with the intermediate-pressure turbine 30 by a crossover pipe 111 . A condenser 60 is arranged downstream of the low-pressure turbines 41 and 42 .

The generator 50 is driven by the rotation of the high-pressure turbine 20, the intermediate-pressure turbine 30, and the low-pressure turbines 41 and 42 to generate electricity.

The condenser 60 is a device that recovers the steam discharged from the low-pressure turbines 41 and 42 and the steam sent from the bypass line 109 and returns it to water. The condenser 60 is provided with a cooling pipe 112 through which cooling water flows and a main cooling pump 61 that pumps the cooling water to the cooling pipe 112 . On the downstream side of the condenser 60, a condensate extraction pump 62 for pumping water condensed in the condenser 60 and a gland steam condenser 63 for draining the gland steam are arranged.

The feed water heating facility 70 is a facility that heats the water discharged from the condenser 60 and supplies it to the boiler 10 as feed water. The feedwater heating equipment 70 includes low-pressure feedwater heaters 71 to 73 and high-pressure feedwater heaters 76 to 78 that heat the feedwater, a deaerator/feedwater treatment device 74 that deaerates the feedwater, and a feedwater pump unit 75 that pumps the feedwater. And prepare.

Next, the flow of fluid such as steam during operation of the power generation system 1 will be described.

Superheated steam generated by the boiler 10 and superheated by the superheater 11 is sent to the high pressure turbine 20 through the main steam pipe 101 to rotate the high pressure turbine 20 . The steam used to rotate the high pressure turbine 20 is sent to the reheater 12 of the boiler 10 via the low temperature reheat steam pipe 103 .

The reheated steam, which is the steam reheated by the reheater 12 , is sent to the intermediate pressure turbine 30 through the high temperature reheat steam pipe 107 to rotate the intermediate pressure turbine 30 . Steam used to rotate the intermediate pressure turbine 30 is sent to the low pressure turbines 41 and 42 via the crossover pipe 111 .

The steam sent to the low pressure turbines 41,42 rotates the low pressure turbines 41,42. Steam used to rotate the low pressure turbines 41 and 42 is sent to the condenser 60 .

The steam sent to the condenser 60 is cooled by heat exchange with cooling water flowing through the cooling pipe 112 and returned to water. The condensate returned to water by the condenser 60 is pumped by the condensate extraction pump 62 , flows through the condensate pipe 113 , and is sent to the feedwater heating facility 70 via the gland steam condenser 64 .

Feedwater sent to the feedwater heating facility 70 flows through the condenser pipe 114 , is heated by the low-pressure feedwater heaters 71 to 73 , and is sent to the deaerator/feedwater treatment device 74 via the feedwater pipe 119 . Further, by opening the bypass valve 116 arranged in the bypass line 115 and the bypass valve 118 arranged in the bypass line 117, the feed water is supplied to the deaerator/feed water treatment device 74 without passing through the low-pressure feed water heaters 71 to 73. can also be sent to

The deaerator/feed water treatment device 74 performs degassing to remove dissolved oxygen contained in the feed water. The degassed water supply is sent to the water supply pump unit 75 via the water supply pipe 120 . The water supply pump unit 75 pumps degassed water supply to the water supply pipe 121 .

The feed water pressure-fed to the feed water pipe 121 is heated by the high-pressure feed water heaters 76 to 78 and sent to the boiler 10 via the feed pipe 126 . By opening the bypass valve 123 arranged in the bypass line 122 and the bypass valve 125 arranged in the bypass line 124, the feed water can be sent to the boiler 10 without passing through the high pressure feed water heaters 76-78.

The feed water sent to the boiler 10 becomes superheated steam in the boiler 10 and the superheater 11 and is supplied to the high pressure turbine 20 via the main steam pipe 101 .

Next, the controller 90 will be described. FIG. 2 is a block diagram showing an electrical configuration of the controller 90 of the power generation system 1. As shown in FIG.

As shown in FIG. 2, the controller 90 is a computer including a temperature change rate calculator 91 and an output determiner 92 . The control unit 90 is electrically connected to the boiler 10, the temperature detection unit 80, and the like. The controller 90 controls the load of the generator 50 based on information from the temperature detector 80 .

Control of the load of the generator 50 by the controller 90 will be described. When the power generation system 1 starts up, the control unit 90 supplies superheated steam to the high pressure turbine 20 and increases the rotation speed of the generator 50 to a predetermined rotation speed. The predetermined rotational speed in this embodiment is, for example, 3600 rpm. At this time, the generator 50 is in a no-load state in which it does not output electricity.

After a predetermined time has elapsed, the control unit 90 switches to initial load holding in which an initial load smaller than the set load (rated load) at the time of power supply is applied. At this time, the control unit 90 performs control to increase the amount of steam generated from the boiler 10 in order to maintain the rotation speed of the generator 50 .

When the amount of steam increases, the reheated steam discharged from the high pressure turbine 20 and reheated by the reheater 12 passes through the high temperature reheat steam pipe 107 to the intermediate pressure turbine 30 and the low pressure steam while maintaining a high pressure and high temperature state. It flows into turbines 41 , 42 . The temperature of the reheat steam is detected by a temperature detector 80 arranged between the reheater 12 and the composite reheat valve 108 in the high temperature reheat steam pipe 107 .

The detection result of the reheat steam temperature is monitored by the temperature change rate calculator 91 of the controller 90 . The temperature change rate calculation unit 91 calculates the temperature change rate of the reheat steam from the continuously received temperature detection results of the reheat steam. The temperature change rate of the reheat steam may be obtained by differentiating the temperature of the reheat steam, or may be an increase in the temperature of the reheat steam per unit time.

The control unit 90 determines that the temperature of the reheat steam detected by the temperature detection unit 80 exceeds a preset set temperature, and the temperature change of the reheat steam calculated by the temperature change rate calculation unit 91 is detected. When the output determining unit 92 determines that the rate has become smaller than a predetermined value, the output of the generator 50 starts increasing and switches to load operation at the set load. The predetermined value can be empirically determined according to each facility and conditions.

According to the power generation system 1 according to the present embodiment, the amount of steam for increasing the output of the generator 50 is increased at the timing when the temperature rise of the reheat steam stabilizes. This allows additional heat to be applied to each turbine while the high pressure turbine 20 as well as the intermediate pressure turbine 30 and low pressure turbines 41 and 42 are homogeneously warmed. Therefore, when the output increases, the uneven cross-sectional temperature distribution of the turbine rotor and the transient temperature difference between the turbine rotor and the casing are less likely to occur, and the thermal stress caused by the vibration of the turbine and the vibration caused by the difference in elongation between the turbine rotor and the casing. can suppress the occurrence of

Next, examples of the present invention will be described. However, the present invention is not limited to the following examples.

[Example]
FIG. 3 is a diagram showing the behavior of various data at the initial stage of activation of the power generation system 1 in the embodiment of the present invention. (A) of FIG. 3 shows the output of the generator 50 and the elongation of the turbine, (B) of FIG. 3 shows the temperature and pressure of the reheat steam, and (C) of FIG. 4 is a diagram showing vibration of a first bearing 21 and vibration of a second bearing 31; FIG. The vertical axis on the left side of FIG. 3A is the generator output, and the vertical axis on the right side of the page is the turbine elongation. The vertical axis on the left side of the paper surface of FIG. 3B is the temperature of the reheat steam, and the vertical axis on the left side of the paper surface is the pressure of the reheat steam. The vertical axis in (C) of FIG. 3 is the magnitude of vibration of the first bearing 21 and the second bearing 31 . The horizontal axis of (A) to (C) in FIG. 3 indicates the elapsed time. In this example, the power generation system 1 of the above embodiment was used. Further, in this embodiment, the output (generator output) of the generator 50 in initial load holding for maintaining the initial load state is set to 25 MW, and the generator output in load operation is set to 125 MW.

As shown in FIG. 3A, the turbine elongation increased at a constant rate from the start of holding the initial load. As shown in FIG. 3B, the temperature of the reheated steam increased rapidly from the start of holding the initial load, but the temperature stabilized around 120 minutes and the rate of change in temperature decreased. As shown in FIG. 3C, the vibration of the second bearing 31 was 94 μm 50 minutes after the start of holding the initial load (when the holding of the initial load was completed in a comparative example to be described later), but gradually decreased. 120 minutes after the start of holding the initial load, it was 87 μm. It is believed that this is because the thermal imbalance of the high pressure turbine 20 has decreased.

In this embodiment, 120 minutes after the start of holding the initial load, the output determination unit 92 determines that the temperature change rate of the reheat steam has become smaller than a predetermined value, and the load operation starts to start increasing the output of the generator 50. switched. Although the temperature of the reheat steam rose again to increase the power output, the vibration of the second bearing 31 remained at a stable low value of 60 μm when reaching 125 MW. This is presumably because the entire turbine is in a homogeneously warmed state at the start of load operation, so thermal imbalance in the high-pressure turbine 20 is less likely to occur even if additional heat is applied.

[Comparative example]
A comparative example of the present invention was carried out using a power generation system having the same configuration as that of the above example except for the control unit 90 . In the comparative example, the output of the generator 50 was set to 25 MW while the initial load was maintained, and the output during load operation was set to 125 MW, as in the example. On the other hand, the initial load retention time is 50 minutes, which is set in advance.

FIG. 4 is a diagram showing the behavior of various data at the initial stage of activation of the power generation system in the comparative example of the present invention. 4A is a diagram showing the output and rotational speed of the generator 50, and FIG. 4B is a diagram showing the vibration and phase of the second bearing 31. FIG. The vertical axis on the left side of FIG. 4A is the output of the generator, and the vertical axis on the right side of the paper is the rotation speed of the generator. The vertical axis on the left side of FIG. 4B is the vibration of the second bearing 31 , and the vertical axis on the right side of the page is the phase of the second bearing 31 . The horizontal axis of (A) to (B) in FIG. 4 indicates the elapsed time.

As shown in FIG. 4, the vibration of the second bearing 31 sharply increased with the start of holding the initial load (parallel), and maintained a high value until the completion of holding the initial load. After switching to load operation, it can be confirmed that the vibration of the second bearing 31 exceeded about 100 μm. This is because the high-pressure turbine 20 was not uniformly warmed 50 minutes after the start of holding the initial load, and the temperature of the reheated steam was further increased in this state, so the thermal imbalance of the high-pressure turbine 20 increased. This is thought to be because As shown in FIG. 3 of the embodiment, 50 minutes after the start of holding the initial load, the temperature of the reheated steam has not risen completely, and it can be confirmed that the temperature is not stable.

According to the power generation system 1 and the method for starting the power generation system according to the present embodiment described above, the following effects are obtained.

The power generation system 1 according to the present embodiment includes a boiler 10 that generates steam, a high pressure turbine 20 through which the steam generated from the boiler 10 flows, and reheated steam discharged from the high pressure turbine 20 and reheated by the boiler 10 flows. Intermediate pressure turbine 30, low pressure turbines 41, 42; generator 50 that generates power by rotation of high pressure turbine 20, intermediate pressure turbine 30, low pressure turbines 41, 42; A temperature detection unit 80 that detects the temperature of the hot steam and a control unit 90 that controls the load of the generator 50 based on the flow rate of the steam. After maintaining the initial load state in which an initial load smaller than the set load at the time of power supply is applied until the temperature change rate of the reheat steam detected by the temperature detection unit 80 becomes smaller than a predetermined value, the load at the set load Move on to driving.

As a result, the temperature of the reheated steam sent to the intermediate pressure turbine 30 and the low pressure turbines 41 and 42 is stabilized, and the entire turbine is warmed more homogeneously before shifting to load operation and increasing the output of the generator 50. can be done. Therefore, it is possible to suppress the vibration caused by the difference in elongation between the turbine rotor and the casing, and it is possible to extend the life of the turbine. Moreover, since the output of the generator 50 can be adjusted while checking the temperature change rate of the reheat steam, the vibrations applied to the high pressure turbine 20, the intermediate pressure turbine 30, and the low pressure turbines 41 and 42 can be reliably suppressed.

Further, the control unit 90 shifts from the initial load state to the load operation at the set load when the preset temperature is exceeded and the temperature change rate is smaller than a predetermined value.

As a result, it is possible to more reliably prevent the transition from the initial load state to the load operation before the temperature of the entire turbine has fully risen.

The power generation system startup method according to the present embodiment includes a power generator 50 that generates power by rotation of the high pressure turbine 20, the intermediate pressure turbine 30, and the low pressure turbines 41 and 42. Steam is discharged from the high pressure turbine 20, and A power generation system start-up method for flowing heated reheated steam to an intermediate pressure turbine 30 and low pressure turbines 41 and 42, wherein the load of the generator 50 is reduced from a no-load state to an initial load lower than the set load during power supply. a step of maintaining the initial load state in which the load is applied until the temperature change rate of the reheat steam becomes smaller than a predetermined value; and a step of shifting to load operation at the set load after the step of maintaining the initial load state. ,including.

As a result, the initial load state is maintained until the temperature change rate of the reheat steam becomes small, so that the load operation can be started while the entire turbine is uniformly warmed. Therefore, it is possible to reliably prevent the vibration of the high-pressure turbine 20 from occurring during start-up due to the thermal imbalance of the turbine.

Further, in the method for starting the power generation system according to the present embodiment, the initial load state is maintained until the preset temperature is exceeded and the temperature change rate becomes smaller than a predetermined value.

As a result, it is possible to more reliably prevent the transition from the initial load state to the load operation before the temperature of the entire turbine has fully risen.

Although the preferred embodiments of the present invention have been described above, the present invention is not limited to the above-described embodiments and can be modified as appropriate. In the above embodiment, the condition for transitioning to normal operation is that the temperature exceeds the preset set temperature and the rate of change in temperature is less than a predetermined value. can be done. For example, the only transition condition may be that the temperature change rate is smaller than a predetermined value, or other conditions may be added.

10 boiler 20 high pressure turbine (high pressure side turbine)
30 intermediate pressure turbine (low pressure side turbine)
41, 42 low pressure turbine (low pressure side turbine)
50 generator 80 detector (temperature detector)
90 control unit

Claims (4)

a boiler for generating steam;
a high-pressure side turbine through which steam generated from the boiler flows;
a low-pressure side turbine through which reheated steam discharged from the high-pressure side turbine and reheated by the boiler flows;
a generator that generates power by rotation of the high pressure side turbine and the low pressure side turbine;
a detection unit that detects the temperature of the reheat steam flowing into the low-pressure turbine;
a control unit that controls the load of the generator according to the flow rate of the steam;
with
The control unit
The load of the generator is changed from a no-load state to an initial load state in which an initial load smaller than a set load at the time of power supply is applied by the detection unit, and the temperature change rate of the reheat steam is detected by the detection unit is higher than a predetermined value. A power generation system that maintains the load until it becomes small, and then shifts to load operation at the set load. The control unit
2. The power generation system according to claim 1, wherein the initial load state is maintained until a preset temperature is exceeded and the temperature change rate becomes smaller than a predetermined value. A method for starting a power generation system comprising a generator that generates power by rotation of a high-pressure side turbine and a low-pressure side turbine, discharging steam from the high-pressure side turbine, and supplying reheated steam reheated by a boiler to the low-pressure side turbine. hand,
A step of maintaining the load of the generator from a no-load state to an initial load state in which an initial load smaller than the set load at the time of power supply is applied until the temperature change rate of the reheat steam becomes smaller than a predetermined value. and,
and a step of shifting to load operation at the set load after the step of maintaining the initial load state. 4. The power generation system start-up method according to claim 3, wherein the initial load state is maintained until the temperature exceeds a preset temperature and the temperature change rate becomes smaller than a predetermined value.

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