JP2002129909A - Starting control method of single-shaft compound electric power plant - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a single-shaft compound electric power plant capable of minimizing an auxiliary steam supply from the other electric power plant as well as effectively using the steam when ensuring the steam used for low pressure steam turbine cooling steam in an exhaust heat recovery boiler. SOLUTION: When a low pressure drum pressure of an own can is confirmed to have a steam with necessary degree of superheat as a low pressure steam turbine cooling steam prior to starting a gas turbine, a low pressure super heater delivery valve opens prior to an auxiliary steam supply and a low pressure of the own can is supplied as the steam turbine cooling steam. This minimizes the auxiliary steam supply from the other electric power station and permits to minimize an operating limitation due to the auxiliary steam supply of the electric power plant.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a startup control method for a single-shaft combined cycle power plant having an exhaust heat recovery boiler which is directly connected to a gas turbine and a steam turbine.

[0002]

2. Description of the Related Art Combined cycle power plants have come to dominate in recent years because of their high thermal efficiency and excellent start-up characteristics compared to conventional power plants. . This combined cycle power plant combines a gas turbine plant with a steam turbine plant and an exhaust heat recovery boiler. In consideration of a reduction in installation area, a single-shaft combined power plant with a gas turbine and a steam turbine directly connected There are many.

[0003] In this single-shaft combined cycle power plant, when the gas turbine is started, a power generator, an air compressor, and a steam turbine, which are directly connected to a single shaft, are rotationally driven using power generated from the gas turbine as a drive source. At that time, since the steam turbine runs idle, abnormal heating due to windage damage occurs in the final stage and the exhaust chamber of the steam turbine. In order to prevent abnormal heating of the steam turbine, cooling steam is supplied to the low-pressure steam turbine when the gas turbine is started.

FIG. 8 is a system diagram of a low-pressure steam turbine cooling steam supply system of a conventional single-shaft combined cycle power plant. When the gas turbine 18 is started, the air compressor 19, the low-pressure steam turbine 14, and the medium-pressure steam turbine 1, which are directly connected, are arranged.
5. The high-pressure steam turbine 16 rotates. Gas turbine 1
As the rotation speed of the turbine 8 increases, the final stage of the low-pressure steam turbine 14 and the exhaust chamber are heated by windage.

In order to prevent this, when the gas turbine 18 reaches a predetermined specified number of revolutions, the low-pressure steam turbine cooling steam supply valve 25 is opened, and the auxiliary steam from the auxiliary steam system is supplied to the low-pressure steam turbine cooling steam. The low-pressure steam turbine 14 is supplied to the low-pressure steam turbine 14 through the flow control orifice 26 to cool the low-pressure steam turbine 14.

Prior to the supply of the low-pressure steam turbine cooling steam, the low-pressure main steam stop valve control valve 11 is opened by primary-side pressure control, and the low-pressure steam turbine cooling steam supply to the low-pressure steam turbine 14 is performed. In order to prevent the introduction of a drain, a drain valve 43 in front of a low-pressure steam turbine cooling steam supply valve, a low-pressure main steam stop valve, a drain valve 44 in front of a control valve, and a low-pressure main steam lead pipe drain valve 45 are installed in the system.
Is open. Reference numeral 42 denotes a drain valve in front of a low-pressure superheater outlet valve.

[0007] The low-pressure steam turbine cooling steam is branched from the shaft auxiliary steam main pipe 20, and the auxiliary steam source is supplied from another power generation facility 58 through an auxiliary steam supply pressure control valve 59 and an auxiliary steam supply valve 60. The auxiliary steam supply pressure control valve 59 is depressurized and adjusted by the auxiliary steam pressure transmitter 61, and is adjusted to an appropriate enthalpy by the shaft auxiliary steam temperature control valve 22 and the shaft auxiliary steam desuperheater 21. The shaft auxiliary steam temperature control valve 22 is adjusted by the temperature from the shaft auxiliary steam temperature detector 24. Therefore, the other power generation equipment 58 is required to supply the auxiliary steam for the low-pressure steam turbine cooling steam every time the shaft is started.

On the other hand, after the gas turbine 18 is started, the exhaust heat recovery boiler generates steam using the exhaust gas as a heat source. In the low-pressure system, the low-pressure superheater outlet valve 6 is closed, and steam generated in the low-pressure drum 1 is condensed by the low-pressure turbine bypass valve front valve 8 and the low-pressure turbine bypass valve 9 via the low-pressure superheater 2. The superheat degree is increased by the low-pressure superheater 2 while discharging steam to the heater 17. The low pressure turbine bypass valve 9 is regulated by the pressure from the pressure transmitter 10 before the low pressure turbine bypass valve. In addition, low pressure super heater 2
From the low pressure superheater outlet pressure transmitter 3
The steam temperature is detected and monitored by a low-pressure superheater outlet temperature detector 4 and the steam flow is detected by a low-pressure superheater outlet flow transmitter 5.

Here, the control pressure set value of the low-pressure turbine bypass valve 9 at the time of starting the gas turbine is a value obtained by adding a predetermined value α to the control pressure set value of the low-pressure main steam stop valve control valve 11 (control pressure set value + α). ). This is to minimize the pressure difference when the low-pressure superheater outlet steam at the time of opening the low-pressure superheater outlet valve 6 and the low-pressure steam turbine cooling steam from the auxiliary steam system supplied in advance. is there.

[0010] The pressure control of the low-pressure turbine bypass valve 9 is started before the gas turbine 18 is started. Therefore, when the low-pressure drum pressure is higher than the control pressure set value of the low-pressure main steam stop valve control valve 11 which is the control pressure set value of the low-pressure turbine bypass valve 9 by the predetermined value α at the time of starting the gas turbine, All will be discharged to the condenser 17.

Thereafter, when the low-pressure superheater outlet steam satisfies the specified superheat degree and flow rate, the low-pressure superheater outlet valve 6 is opened, and the low-pressure superheater outlet check valve 7 and the low-pressure main steam stop valve control valve 11 are operated. Through the low pressure steam turbine 14
To the low pressure turbine cooling steam by auxiliary steam. The steam supplied to the low-pressure steam turbine 14 has a steam temperature of a low-pressure main steam stop valve pre-adjustment valve temperature detector 1.
At 2, the steam pressure is detected and monitored by the pressure transmitter 13 before the low pressure main steam stop valve. Low pressure main steam stop valve control valve 1
1 is adjusted by the pressure detected by the pressure transmitter 13 before the low-pressure main steam stop valve control valve.

In the medium pressure system, the medium pressure superheater outlet valve 36 is closed, and the steam generated in the medium pressure drum 29 is passed through the medium pressure superheater 30 to the intermediate pressure turbine bypass valve front valve. 33 and the intermediate pressure turbine bypass valve 34 are controlled to a specified pressure determined by the mismatch temperature difference of the intermediate pressure turbine 15, while discharging steam to the condenser 17,
The superheat degree is increased by the medium pressure superheater 30. The intermediate pressure turbine bypass valve 34 is adjusted by the pressure from the intermediate pressure turbine bypass valve pre-pressure transmitter 35. In addition, low pressure super heater 2
From the low pressure superheater outlet pressure transmitter 3
At 1, the steam temperature is detected and monitored by a low pressure superheater outlet temperature detector 32.

Thereafter, when the intermediate-pressure superheater outlet steam satisfies the specified degree of superheat and flow rate, and the exhaust steam of the high-pressure turbine 16 reaches the pressure of the intermediate-pressure superheater outlet steam, the intermediate-pressure superheater outlet valve 36 is opened and merged with the high-pressure turbine exhaust steam via the intermediate-pressure superheater outlet check valve 37. Then, it is further heated by the reheater 38 and is ventilated to the intermediate-pressure steam turbine 15 through the reheat steam stop valve control valve 39. The steam pressure from the reheater 38 is detected and monitored by a pressure transmitter 40 before the reheat steam stop valve, and the steam temperature is detected by a temperature detector 41 before the reheat steam stop valve.

Further, a backup system is provided from the medium-pressure steam system to the shaft auxiliary steam mother pipe 20 when the supply of the auxiliary steam from the other power generation equipment 58 is cut off for some reason. The auxiliary steam backup pressure control valve front valve 28 and the shaft auxiliary steam backup pressure control valve 27 control the shaft auxiliary steam mother pipe 20 at a pressure lower than the control pressure of the auxiliary steam supply pressure control valve 59. Therefore, the shaft auxiliary steam backup pressure control valve 27 is normally closed.

The pressure and temperature at the outlet of the intermediate-pressure superheater are taken into consideration as the opening conditions of the shaft auxiliary steam backup pressure control valve front valve 28, so that the auxiliary steam is prevented from flowing back to the medium-pressure system and the degree of superheat is insufficient. It prevents the flow of extra steam into the auxiliary steam system. Also, the shaft auxiliary steam backup pressure control valve 27
Is adjusted by the pressure detected by the shaft auxiliary steam backup pressure transmitter 23. After the steam turbine is vented, the low-pressure turbine cooling steam supply valve 25 is closed when the steam flow rate at the inlet of the medium-pressure steam turbine exceeds the required flow rate of the low-pressure turbine cooling steam.

Next, a description will be given of the stoppage of the exhaust heat recovery boiler banking in which steam is left as much as possible in the exhaust heat recovery boiler when the exhaust heat recovery boiler is stopped in order to shorten the next start-up time. FIG. 9 shows a low-pressure drum 1, a medium-pressure drum 29, and a high-pressure drum 49.
FIG. 3 is a steam system diagram of a three-pressure type exhaust heat recovery boiler having the following.

In a combined cycle power generation facility having excellent start-up characteristics, during a short-term stop such as a weekend stop, the exhaust heat recovery boiler banking is stopped in order to leave as much steam as possible in the exhaust heat recovery boiler in order to shorten the next start-up time. Perform

In this case, when the gas turbine 18 is stopped, the high-pressure main steam stop valve control valve 51, the intermediate-pressure superheater outlet valve 3
6 and the low-pressure superheater outlet valve 6, immediately after closing the high-pressure turbine bypass valve front valve 52, the intermediate-pressure turbine bypass valve front valve 33, and the low-pressure turbine bypass valve front valve 8, instead of closing the high-pressure turbine bypass valve, By the valve 53, the intermediate-pressure turbine bypass valve 34, and the low-pressure turbine bypass valve 9,
An operation of reducing the pressure of the high-pressure drum 49, the intermediate-pressure drum 29, and the low-pressure drum 1 is performed.

This is to prevent each drum pressure from abnormally increasing due to the residual heat balance in the exhaust heat recovery boiler during stoppage and reaching the safety valve operating pressure. In particular, it is necessary to prevent abnormal low pressure in the low pressure system due to the low pressure system collecting heat remaining in the high pressure system.

From this, a rough guide when each drum is depressurized by the turbine bypass valve is that each drum pressure does not reach the safety valve operating pressure during stoppage. As a result,
In order to protect the low-pressure drum 1 having the lowest safety valve operating pressure, the high-pressure drum 49 uses one-half of the normal operating pressure.
It is necessary to reduce the pressure to a certain level.

After each drum pressure is reduced to a specified pressure, the high-pressure turbine bypass valve front valve 52, the intermediate-pressure turbine bypass valve front valve 33, and the low-pressure turbine bypass valve front valve 8
And the exhaust heat recovery boiler banking stop is completed.

As described above, the exhaust heat recovery boiler banking is stopped in order to leave the steam in the exhaust heat recovery boiler as much as possible in order to shorten the next start-up time, but as a result, the most important high-pressure steam is largely discharged. As a result, a pressure higher than the normal operation pressure is secured for the low-pressure steam.

[0023]

However, in such a conventional example, the low-pressure steam turbine cooling steam at the time of starting the shaft is:
Since the auxiliary steam is supplied from the other power generation equipment 58, the output and efficiency of the other power generation equipment 58 are reduced at the time of starting the shaft. When the other power generation facilities 58 are not operating, the other power generation facilities 58 must be started. This imposes great restrictions on the operation as a power plant.

Further, a combined cycle power plant having excellent start-up characteristics is used for load adjustment of power supply, so that frequent start-stop operations are performed. As a result, operational constraints on the power plant associated with starting the shaft become frequent. In addition, in a single-shaft combined cycle power plant considering a reduction in installation area, the length of steam turbines is increasing in order to shorten the power train span in order to cope with a further reduction in installation area. Therefore, the steam turbine cooling steam required for starting the shaft is:
It has been increasing further.

Further, since the combined cycle power plant takes DSS operation into consideration, the exhaust heat recovery boiler banking is stopped in order to shorten the start-up time at the next start-up. 1 can maintain a high pressure with respect to the normal operating pressure, and although it is often steam that can be used as low-pressure steam turbine cooling steam, these steams are not used during the start-up process. When the pressure control of the low-pressure turbine bypass valve 9 is started, the low-pressure turbine bypass valve 9 is discharged to the condenser 17.

Further, the intermediate-pressure drum 29 is a steam which can be used as low-pressure steam turbine cooling steam at the time of start-up even though the pressure is lower than the normal operation pressure of the medium-pressure drum due to the stoppage of the exhaust heat recovery boiler banking. In many cases, while having a shaft auxiliary steam backup system capable of supplying it, it is not operated so as to be actively used at startup.

From the above, the starting shaft is located in the exhaust heat recovery boiler,
In the case where steam that can be used as low-pressure steam turbine cooling steam is secured, discharge them with starting the shaft,
It is in the form of using unnecessary auxiliary steam.

[0028] An object of the present invention is to provide a system in which, when steam that can be used as low-pressure steam turbine cooling steam is secured in an exhaust heat recovery boiler, the steam is used effectively and auxiliary steam is supplied from another power generation facility. It is to provide a single-shaft combined cycle power plant that can be minimized.

[0029]

According to a first aspect of the present invention, there is provided a start control method for a single-shaft combined cycle power plant, wherein a gas turbine and a steam turbine are directly connected, and the steam turbine is driven by steam from an exhaust heat recovery boiler. A starting control method for a single-shaft combined cycle power plant that requires cooling steam for a low-pressure steam turbine among the steam turbines at the time of starting the gas turbine, based on a low-pressure drum pressure of the exhaust heat recovery boiler before starting the gas turbine. To determine whether cooling steam for the low-pressure steam turbine can be supplied from the low-pressure drum, and when it is determined that cooling steam can be supplied to the low-pressure steam turbine, supply cooling steam to the low-pressure steam turbine from the low-pressure drum. If it is determined that cooling steam cannot be supplied to the low-pressure steam turbine, Supplying cooling steam to down, characterized by starting the gas turbine.

In the start control method for a single-shaft combined cycle power plant according to the first aspect of the present invention, the low-pressure drum pressure of the can is confirmed before starting the gas turbine, and the superheat required as the low-pressure steam turbine cooling steam is satisfied. If steam is present, the low-pressure superheater outlet valve is opened prior to the supply of the auxiliary steam, and the low-pressure steam of its own can is supplied as steam turbine cooling steam. Thereby, the supply of auxiliary steam from other power generation equipment can be minimized, and the operational constraints associated with the auxiliary steam supply of the power generation plant can be minimized.

In the start control method for a single-shaft combined cycle power plant according to a second aspect of the present invention, in the first aspect of the invention, when the low-pressure steam is supplied to the low-pressure steam turbine as cooling steam, the low-pressure steam is supplied to the low-pressure steam turbine. The primary-side control pressure set value of the low-pressure turbine bypass valve that bypasses the turbine is set to a value larger than the actual pressure by a predetermined value.

In the start control method for a single-shaft combined cycle power plant according to the second aspect of the present invention, before starting the gas turbine, the pressure of the low-pressure drum of the self-can is confirmed to satisfy the degree of superheat required for the low-pressure steam turbine cooling steam. In the case where the low pressure turbine bypass valve has steam, the primary side control pressure set value of the low pressure turbine bypass valve is set to the actual pressure + α. Thus, it is possible to prevent the low-pressure system steam of the low-pressure drum from being discharged to the condenser at the time of starting the shaft, and it is possible to effectively use the low-pressure system steam.

According to a third aspect of the present invention, in the start control method for a single-shaft combined cycle power plant according to the first or second aspect, the low-pressure drum is supplied with cooling steam from the low-pressure drum to the low-pressure steam turbine. When the steam from the drum no longer satisfies the condition as the cooling steam, the supply of the steam from the low-pressure drum is stopped, and the cooling steam is supplied from the auxiliary steam system to the low-pressure steam turbine. I do.

[0034] In the start control method for the single-shaft combined cycle power plant according to the third aspect of the present invention, the superheat degree, pressure or flow rate of the steam of the self-can is controlled while the low-pressure steam is supplied to the self-can.
When the required value as the low-pressure steam turbine cooling steam falls below a required value, the low-pressure superheater outlet valve is closed, the low-pressure steam turbine cooling steam supply valve from the auxiliary steam system is opened, and backup steam is supplied. As a result, after effectively utilizing the steam that the can has, it is possible to prevent the steam with deteriorated conditions from flowing into the steam turbine and to continue supplying the low-pressure steam turbine cooling steam, thereby protecting and stabilizing the steam turbine. This enables continued startup.

According to a fourth aspect of the present invention, in the start control method for a single-shaft combined cycle power plant according to the first or second aspect of the invention, the low-pressure drum is supplied with cooling steam from the low-pressure drum to the low-pressure steam turbine. When steam from the drum no longer satisfies the condition as cooling steam, cooling steam is supplied from the auxiliary steam system to the low-pressure steam turbine in addition to the steam from the low-pressure drum.

In the start control method for a single-shaft combined cycle power plant according to the fourth aspect of the present invention, the flow rate of the steam in the self-canister falls below a required value as cooling steam for the low-pressure steam turbine during the supply of the low-pressure steam to the self-can. In this case, the low-pressure steam turbine cooling steam flow control valve installed in the auxiliary steam system is opened, and control is performed such that the sum of the self-managed steam flow and the auxiliary steam flow becomes the required amount of the low-pressure steam turbine cooling steam. As a result, even when the flow rate of the self-canister steam is reduced, the supply of the low-pressure steam turbine cooling steam can be continued by supplying the minimum necessary amount of auxiliary steam from outside the system while maintaining the effective use of the self-canister steam. . As a result, it is possible to protect the steam turbine and continue the stable start-up, and it is possible to minimize the operational constraints associated with the auxiliary steam supply of the power plant.

According to a fifth aspect of the present invention, in the start control method for a single-shaft combined cycle power plant according to any one of the first to fourth aspects, cooling steam is supplied from the low-pressure drum to the low-pressure steam turbine. In this case, the cooling steam is supplied through a check valve.

In the start control method for a single-shaft combined cycle power plant according to the fifth aspect of the present invention, the check valve is installed in the low-pressure steam turbine cooling steam supply system, so that the low-pressure steam pressure is higher than the auxiliary steam system pressure. In this case, the backflow from the low-pressure steam pressure to the auxiliary steam system can be prevented, and the low-pressure steam turbine cooling steam supply valve can be on standby with the valve open.

According to a sixth aspect of the present invention, in the start control method for a single-shaft combined cycle power plant according to any one of the first to fifth aspects, cooling steam is supplied from the low-pressure drum to the low-pressure steam turbine. In the meantime, when the inlet steam flow rate of the medium pressure turbine of the steam turbine exceeds the required flow rate of the cooling steam of the low pressure steam turbine, the primary side control pressure setting of the low pressure turbine bypass valve for bypassing the low pressure steam turbine. The value is set to a value larger by a predetermined value than the primary side control pressure set value of the low pressure main steam stop valve control valve.

In the start control method for a single-shaft combined cycle power plant according to the present invention, when the flow rate at the inlet of the medium-pressure steam turbine exceeds the required flow rate of the cooling steam for the low-pressure steam turbine after the supply of the low-pressure steam to the self-canister, Then, the primary control pressure set value of the low-pressure steam turbine bypass valve is set to the low-pressure main steam stop valve control valve primary control pressure set value + α. As a result, as soon as the low-pressure steam turbine cooling steam becomes unnecessary, the turbine bypass valve can be returned to the control set value as the original protection device.

According to a seventh aspect of the present invention, there is provided a start control method for a single-shaft combined cycle power plant, wherein a gas turbine and a steam turbine are directly connected, and the steam turbine is driven by steam from an exhaust heat recovery boiler. In a start-up control method for a single-shaft combined cycle power plant that requires cooling steam for a low-pressure steam turbine of the steam turbines, the auxiliary steam supply system from another power generation facility and a medium-pressure superheater connected to a self-shaft are used. A low-pressure steam turbine cooling steam is supplied from the low-pressure steam turbine, and an auxiliary steam supply system from another power generation facility is provided in the own shaft. If it is controlled at a higher pressure than the high pressure steam supply system and the pressure and temperature of the medium pressure superheater of its own Switching the control pressure setpoint of steam supply system in the auxiliary steam supply system and own axis from Bei, and supplying the steam within the own axis as an auxiliary steam source.

In the start control method for a single-shaft combined cycle power plant according to the present invention, before starting the gas turbine, the pressure and temperature of the intermediate pressure superheater of the own shaft or the same pressure system connected thereto are confirmed. If the pressure and temperature are higher than that of the auxiliary steam system, the control pressure set values of the auxiliary steam supply system from other power generation equipment and the medium-pressure steam supply system of the own shaft are replaced, and the auxiliary steam source To supply medium-pressure steam in its own can. This makes it possible to minimize the supply of auxiliary steam from other power generation equipment, in combination with the effective use of low-pressure self-steaming steam, and to minimize operational constraints and steam loss associated with the auxiliary steam supply of the power plant.

[0043]

Embodiments of the present invention will be described below. FIG. 1 is a flowchart showing a start control method for a single-shaft combined cycle power plant according to an embodiment of the present invention. FIG. 2 is a low-pressure steam turbine cooling steam supply system of the single-shaft combined cycle plant according to the embodiment of the present invention. FIG.

In FIG. 2, the orifice 2 for adjusting the steam flow rate for cooling the low-pressure steam turbine is different from the conventional example shown in FIG.
6, a low-pressure steam turbine cooling steam supply check valve 48 is provided.
And the low-pressure steam turbine cooling steam flow control valve 47 is provided.
Is configured to be adjusted based on the flow rate detected by the low-pressure superheater outlet flow rate transmitter 5 and the flow rate detected by the low-pressure steam turbine cooling steam flow rate transmitter 46.

The gas turbine to which the shaft start command of the own shaft of the single shaft combined cycle power plant is input is started (S1). In this state, it is determined whether the drum pressure of the low-pressure drum 1 of the exhaust heat recovery boiler is equal to or higher than a predetermined value (S2). When the low-pressure drum pressure is equal to or higher than a predetermined value, it is determined that the steam has satisfied the necessary degree of superheat as the low-pressure steam turbine cooling steam, and the low-pressure superheater outlet valve 6 is opened prior to the supply of the auxiliary steam, and the steam turbine cooling is performed. The low-pressure steam of the can is supplied to the low-pressure steam turbine 14 as steam (S3). In this case, the primary-side control pressure set value of the low-pressure turbine bypass valve 9 that bypasses the low-pressure steam turbine 14 is set to a value larger than the actual pressure by a predetermined value α (S4). This is to prevent the low-pressure system steam of the low-pressure drum 1 from being discharged to the condenser 17 when the shaft is started, and to effectively utilize the low-pressure system steam.

Then, it is determined whether or not the steam from the low-pressure drum 1 satisfies the condition as the cooling steam (S5). If the steam from the low-pressure drum 1 does not satisfy the condition as the cooling steam, the auxiliary steam is used. System to low pressure steam turbine 14
(S6).

This is because steam is not immediately generated in the low-pressure drum 1 even when the gas turbine 18 is started, so that the steam from the low-pressure drum 1 may not satisfy the condition as cooling steam.

In this case, the supply of steam from the low-pressure drum 1 is stopped, and cooling steam is supplied to the low-pressure steam turbine 14 from the auxiliary steam system. Alternatively, cooling steam is supplied to the low-pressure steam turbine 14 from the auxiliary steam system in addition to the steam from the low-pressure drum 1. As a result, even when the flow rate of the self-canister steam is reduced, the supply of the low-pressure steam turbine cooling steam can be continued by supplying the minimum necessary amount of auxiliary steam from outside the system while maintaining the effective use of the self-canister steam. . As a result, it is possible to protect the steam turbine and maintain a stable start,
In addition, operational constraints associated with the auxiliary steam supply of the power plant can be minimized.

On the other hand, if it is determined in step S2 that the low-pressure drum pressure is not equal to or higher than the predetermined value, it is determined that the steam does not satisfy the degree of superheat required for the low-pressure steam turbine cooling steam, and the auxiliary steam system sends the low-pressure steam turbine to the low-pressure steam turbine. Cooling steam is supplied (S6). When the cooling steam cannot be supplied from the can, the necessary cooling steam is supplied from an auxiliary steam system outside the system.

Then, it is determined whether or not the inlet steam flow rate of the medium-pressure turbine 15 of the steam turbine exceeds the required flow rate of the cooling steam of the low-pressure steam turbine 14 (S7). The primary-side control pressure set value of the low-pressure turbine bypass valve 9 that bypasses the turbine 14 is set to a value larger by a predetermined value α than the primary-side control pressure set value of the low-pressure main steam stop valve control valve 11 (S8). As a result, as soon as the low-pressure steam turbine cooling steam becomes unnecessary, the turbine bypass valve 9 can be returned to the control set value as the original protection device. Then, the supply of steam from the auxiliary steam system is stopped (S9).

Next, with reference to FIG. 2, the operation at the time of starting the shaft in the embodiment of the present invention will be described. First, before starting the gas turbine 18, the low pressure superheater outlet pressure transmitter 3
To check the pressure of the low pressure system. If this pressure has the required degree of superheat as low-pressure steam turbine cooling steam, the gas turbine 1
When the number of rotations 8 reaches a preset specified number of revolutions, the low-pressure superheater outlet valve 6 is opened prior to the supply of the low-pressure steam turbine cooling steam by the auxiliary steam, and the low-pressure steam of the own can is supplied as the steam turbine cooling steam.

Here, the determination of the presence or absence of the degree of superheat by confirming the pressure of the low-pressure system is performed by, for example, the low-pressure main steam stop valve control valve 11.
When the primary side control pressure is 5 ata and the required degree of superheat before the low-pressure main steam stop valve control valve is + 5 ° C., the following is obtained.

The pressure before the low-pressure main steam stop valve is adjusted: the saturation temperature at 5 ata + 5 ° C. = 151.11 ° C. + 5 ° C. = 156.11 ° C. (1) The enthalpy at 5ata and 156.11 ° C. = 658.792 kcal / kg ... (2)-If the steam remaining in the system is considered to be saturated steam, it is sufficient if the saturated pressure satisfies (2).・ Saturation enthalpy of 6.6ata = 658.901 kcal / kg (3) ・ From (3)> (2), it is sufficient that the low-pressure system pressure is 6.6ata or more. This makes it possible to effectively use the low-pressure steam of the can.

FIG. 3 shows a control block related to the above.
FIG. 3 is a logic circuit for determining the steam condition of the low-pressure drum 1 of the can.

The level decision unit 71 of the decision logic circuit is
Before starting the gas turbine 18, it is determined whether or not the low-pressure superheater outlet pressure from the low-pressure superheater outlet pressure transmitter 3 is equal to or higher than a predetermined value P1, and if the low-pressure superheater outlet pressure is equal to or higher than the predetermined value P1. The logic value “1” is output to the AND circuit 72.
On the other hand, when the rotation speed of the gas turbine is equal to or higher than the specified rotation speed, a logical value “1” is output to the AND circuit 72.

When the outlet pressure of the low-pressure superheater is equal to or higher than the predetermined value P1 and the number of rotations of the gas turbine is equal to or higher than the specified number, the low-pressure drum 1 causes the low-pressure drum 1 to have a sufficient degree of superheat as cooling steam Is determined, and the low-pressure steam turbine 14 determines that the cooling steam is required, and outputs an open command to the low-pressure superheater output valve 6. As a result, the low-pressure steam of the can is supplied to the low-pressure steam turbine 14 as the steam turbine cooling steam.

In this case, the switching circuit 73 is operated by the open command of the low-pressure superheater output valve 6 to open the low-pressure turbine bypass valve 9.
Is selected as the primary side control pressure set value. As a result, the low-pressure turbine bypass valve 9 does not open at the time of starting the shaft, the discharge of the low-pressure system steam of the low-pressure drum 1 to the condenser 17 can be prevented, and the low-pressure system steam can be used without waste. Becomes possible.

FIG. 4 shows a decision logic circuit in the case where the steam condition of the low pressure drum 1 of the self can deteriorates and the system is switched to the auxiliary steam system. When the steam condition from the low-pressure drum 1 is deteriorated after the supply of the self-canister steam, the low-pressure superheater outlet valve 6 is closed, the low-pressure steam turbine cooling steam supply valve 25 is opened, and backup from the auxiliary steam system is performed.

The level determiner 71a determines whether or not the steam pressure confirmed by the low-pressure superheater outlet pressure transmitter 3 is equal to or lower than a predetermined value P1, and if it is equal to or lower than the predetermined value P1, the logical value "1" is ORed. Output to the circuit 74.

The level determiner 71b determines whether or not the steam flow rate confirmed by the low-pressure superheater outlet flow rate transmitter 5 is equal to or less than a predetermined steam flow rate Q1. "1" is output to the OR circuit 74.

Further, the arithmetic circuit 75 calculates the degree of superheat ascertained from the low pressure main steam stop valve pre-adjustment valve temperature detector 12 and the low pressure main steam stop valve pre-adjustment valve pressure transmitter 13. It is determined whether or not the degree of superheat is equal to or less than a predetermined value H1.
Output to the circuit 74.

The OR circuit 74 includes a steam pressure confirmed by the low-pressure superheater outlet pressure transmitter 3, a steam flow confirmed by the low-pressure superheater outlet flow transmitter 5, and a low-pressure main steam stop valve before and after temperature detector 12. If any of the degrees of superheat confirmed from the pressure transmitter 13 and the low-pressure main steam stop valve pre-adjustment valve lowers below a required value as the low-pressure steam turbine cooling steam, the low-pressure superheater outlet valve 6 is closed. The supply of steam from the low-pressure drum 1 is stopped, and the low-pressure steam turbine cooling steam supply valve 25 is opened to back up the cooling steam from the auxiliary steam system.

Accordingly, when the steam condition of the self-can deteriorates after the steam of the self-can is effectively used, it is possible to prevent the steam under the deteriorated condition from flowing into the steam turbine, and to reduce the cooling steam of the low-pressure steam turbine. Supply can be continued, and steam turbine protection and stable startup can be achieved.

FIG. 5 is a decision logic circuit in the case where the steam condition of the low pressure drum 1 of the can is deteriorated and a part of the cooling steam is received from the auxiliary steam system.

When the low-pressure steam turbine cooling steam supply system has the low-pressure steam turbine cooling steam flow control valve 47, the low-pressure superheater outlet flow transmitter 5
If the flow rate confirmed by the above becomes lower than the required value as the low-pressure steam turbine cooling steam, the insufficient cooling steam is supplied from the auxiliary steam system.

If the flow rate confirmed by the low-pressure superheater outlet flow transmitter 5 after the self-canister steam supply falls below a required value for the low-pressure steam turbine cooling steam, the low-pressure superheater outlet flow transmitter 5 confirms the flow rate. The sum of the flow rate and the flow rate confirmed by the low-pressure steam turbine cooling steam flow rate transmitter 46 is calculated by an adder 76a, and the deviation between the sum of the flow rates and the low-pressure steam turbine cooling steam required flow rate is calculated by an adder 76b. The low-pressure steam turbine cooling steam flow control valve 47 is adjusted so that the deviation becomes zero. In this way, backup from the auxiliary steam system is performed so that the low-pressure steam turbine cooling steam has the required value.

Thus, the supply of low-pressure steam turbine cooling steam can be continued by the minimum necessary auxiliary steam supply while the effective use of the steam in the can is continued, and the protection of the steam turbine and the stable start-up can be achieved. Become.

Here, as shown in FIG. 2, in the embodiment of the present invention, the check valve 48 is installed in the low-pressure steam turbine cooling steam supply system, and when the low-pressure steam pressure is higher than the auxiliary steam system pressure. In this case, the backflow from the low-pressure steam pressure to the auxiliary steam system is prevented. Therefore, the low-pressure steam turbine cooling steam flow control valve 47 can automatically stand by while the low-pressure steam turbine cooling steam supply valve 25 is kept open.

Next, FIG. 6 shows a judgment logic circuit when the supply of the cooling steam from the low pressure drum 1 of the can is stopped. When the inlet flow rate of the medium-pressure steam turbine exceeds the required flow rate of the low-pressure steam turbine cooling steam, the turbine bypass valve is returned to the control set value as the original protection device.

In FIG. 6, after the supply of steam from the self-canister, the arithmetic circuit 75 sets the pressure from the pressure transmitter 40 before the reheat steam stop valve and the temperature from the temperature detector 41 before the reheat steam stop valve. Then, the flow rate at the inlet of the intermediate-pressure steam turbine is determined. The adder 76 calculates the difference between the medium-pressure steam turbine inlet flow rate and the required low-pressure steam turbine cooling steam flow rate, and the level determiner 71 determines that the difference is positive, that is, the medium-pressure steam turbine inlet flow rate is low-pressure steam turbine. When the required flow rate of the cooling steam is exceeded, a command is output to the switch 73 to set the primary control pressure set value of the low-pressure turbine bypass valve 9 to the low-pressure control valve primary-side control pressure set value + α. The low-pressure steam turbine cooling steam supply valve 25 is closed.

Thus, as soon as the low-pressure steam turbine cooling steam becomes unnecessary, the supply of the auxiliary steam from the auxiliary steam system can be stopped and the turbine bypass valve 9 can be returned to the control set value as the original protection device. Becomes

Next, FIG. 7 is a decision logic circuit in the case of using medium-pressure steam in the self-can as an auxiliary steam source of the axial auxiliary steam mother pipe 20.

As shown in FIG. 2, in the embodiment of the present invention, in the medium pressure steam system, backup supply of auxiliary steam to the axial auxiliary steam mother pipe 20 is performed. The pressure of the shaft auxiliary steam mother pipe 20 is controlled by an auxiliary steam supply pressure control valve 59 from another power generation facility 58. In this case, the shaft auxiliary steam mother pipe 20 is controlled at a lower pressure by the shaft auxiliary steam backup pressure control valve 27, and backup supply of the auxiliary steam is performed.

Prior to starting the gas turbine 18, the adder 76 a determines the pressure of the medium pressure system from the medium pressure superheater outlet pressure transmitter 31 and the pressure of the pressure auxiliary steam pressure transmitter 61 of the shaft auxiliary steam mother pipe 20. Is calculated, and the level determiner 71a outputs a logical value “1” to the AND circuit 72 when the pressure of the intermediate-pressure system is higher than the pressure of the axial auxiliary steam mother pipe 20.

Similarly, the adder 76b calculates the deviation between the temperature of the medium pressure system from the medium pressure superheater outlet temperature detector 32 and the temperature of the shaft auxiliary steam temperature detector 24 of the shaft auxiliary steam mother pipe 20. When the temperature of the medium-pressure system is higher than the temperature of the auxiliary steam main pipe 20, the level determiner 71b sets the logical value "1" to A.
Output to ND circuit 72.

The AND circuit 72 outputs a command to the switching circuits 73a and 73b to supply auxiliary steam when the pressure and temperature of the steam in the medium pressure system are higher than the pressure and temperature of the auxiliary steam main pipe 20. The pressure control set values of the pressure control valve 59 and the shaft auxiliary steam backup pressure control valve 27 are switched, and the shaft auxiliary steam backup pressure control valve front valve 28 is opened.

As a result, it is possible to use the medium-pressure steam of the self-can as an auxiliary steam source for the shaft auxiliary steam mother pipe 20.
Combined with the above-described effective use of the low-pressure self-canister steam, it is possible to minimize the supply of auxiliary steam from other power generation equipment 58.

[0078]

As described above, according to the present invention, it is possible to prevent the self-shaft from wastefully discharging the steam held in the exhaust heat recovery boiler at the time of starting the shaft, and to use the steam as steam for starting the self-shaft. It can be used. In other words, the self-can low-pressure steam is used, and the self-can medium-pressure steam is used as a backup for the backup. .

Accordingly, it is possible to minimize the supply of auxiliary steam from other power generation equipment due to the start of the shaft, thereby minimizing the influence on operation constraints and the steam loss on the power generation plant. Become.

[Brief description of the drawings]

FIG. 1 is a flowchart showing a startup control method for a single-shaft combined cycle power plant according to an embodiment of the present invention.

FIG. 2 is a system diagram of a low-pressure steam turbine cooling steam supply system of the single-shaft combined cycle power plant according to the embodiment of the present invention.

FIG. 3 is a circuit diagram of a logic circuit for determining a steam condition of the low-pressure drum of the can according to the embodiment of the present invention.

FIG. 4 is a circuit diagram of a determination logic circuit in a case where the steam condition of the low-pressure drum of the can is deteriorated and the system is switched to the auxiliary steam system in the embodiment of the present invention.

FIG. 5 is a circuit diagram of a determination logic circuit according to the embodiment of the present invention when the steam condition of the low pressure drum of the can is deteriorated and a part of the cooling steam is received from the auxiliary steam system.

FIG. 6 is a circuit diagram of a determination logic circuit when the supply of cooling steam from the low-pressure drum of the can is stopped according to the embodiment of the present invention.

FIG. 7 is a circuit diagram of a determination logic circuit in a case where medium-pressure steam of the can is used as an auxiliary steam source of the axial auxiliary steam mother pipe in the embodiment of the present invention.

FIG. 8 is a system diagram of a low-pressure steam turbine cooling steam supply system of a conventional single-shaft combined cycle power plant.

FIG. 9 is a steam system diagram of a three-pressure exhaust heat recovery boiler having a low-pressure drum, a medium-pressure drum, and a high-pressure drum.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Low pressure drum, 2 ... Low pressure superheater, 3 ... Low pressure superheater outlet pressure transmitter, 4 ... Low pressure superheater outlet temperature detector, 5 ... Low pressure superheater outlet flow transmitter, 6 ... Low pressure superheater outlet valve, 7 ... Low pressure superheater outlet check valve, 8 ... Low pressure turbine bypass valve front valve, 9 ... Low pressure turbine bypass valve, 10 ... Low pressure turbine bypass valve front pressure transmitter, 11 ... Low pressure main steam stop valve control valve, 12 ... Low pressure main Temperature detector before steam stop valve control valve, 13
... Low-pressure main steam stop valve before and after the pressure transmitter, 14 ... Low-pressure steam turbine, 15 ... Medium-pressure steam turbine, 16 ... High-pressure steam turbine, 17 ... Condenser, 18 ... Gas turbine, 19 ...
Air compressor, 20: shaft auxiliary steam mother pipe, 21: shaft auxiliary steam cooler, 22: shaft auxiliary steam temperature control valve, 23: shaft auxiliary steam backup pressure transmitter, 24: shaft auxiliary steam temperature detector, 25 ... Low-pressure steam turbine cooling steam supply valve, 26 ... Low-pressure steam turbine cooling steam flow adjustment orifice, 27 ...
Auxiliary steam backup pressure control valve, 28 ... Auxiliary steam backup pressure control valve front valve, 29 ... Medium pressure drum, 30
... Medium pressure superheater, 31 ... Medium pressure superheater outlet pressure transmitter, 32
... Medium pressure superheater outlet temperature detector, 33 ... Medium pressure turbine bypass valve front valve, 34 ... Medium pressure turbine bypass valve, 35 ... Medium pressure turbine bypass valve front pressure transmitter, 36 ... Medium pressure superheater outlet valve, 37 ... medium pressure superheater outlet check valve, 38 ... reheater,
39: Reheat steam stop valve control valve, 40: Reheat steam stop valve control valve before pressure transmitter, 41: Reheat steam stop valve control valve front temperature detector, 42: Low pressure superheater outlet valve front drain valve, 43 ... Drain valve before low pressure steam turbine cooling steam supply valve, 44 ... Drain valve before low pressure main steam stop valve adjusting valve, 45 ... Low pressure main steam reed pipe drain valve, 46 ... Low pressure steam turbine cooling steam flow transmitter, 47 ... Low pressure steam Turbine cooling steam flow control valve, 4
8 ... Low pressure steam turbine cooling steam supply check valve, 49 ... High pressure drum, 50 ... High pressure superheater, 51 ... High pressure superheater stop valve control valve, 52 ... High pressure turbine bypass valve front valve, 53 ... High pressure turbine bypass valve, 58 ... other power generation equipment, 59 ... auxiliary steam supply pressure control valve, 60 ... auxiliary steam supply valve, 61 ... auxiliary steam pressure transmitter, 71 ... level judgment device, 72 ... AND
Circuit 73: switching circuit, 74: OR circuit, 75: arithmetic circuit, 76: adder

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) F01D 17/00 F01D 17/00 G 19/00 19/00 L 25/12 25/12 A F01K 23/10 F01K 23/10 X // H02P 9/04 H02P 9/04 F (72) Inventor Makoto Yamaki 66-2 Horikawa-cho, Saiwai-ku, Kawasaki-shi, Kanagawa Prefecture Inside Toshiba Engineering Corporation (72) Inventor Satoshi Akimaru Tokyo 1-1-1 Shibaura, Minato-ku, Tokyo F-term in the head office of Toshiba Corporation (reference) 3G071 AA07 AB01 BA07 CA01 FA03 FA06 HA03 HA05 3G081 BA04 BA11 BB00 BC07 BD00 DA03 DA06 5H590 AA02 CA01 CA08 CA29 CE01 EA01 FA01 HA13 HA16 HA18 HA18

Claims (7)

[Claims] A gas turbine and a steam turbine are directly connected to each other, and the steam turbine is driven by steam from an exhaust heat recovery boiler. When the gas turbine is started, a low-pressure steam turbine among the steam turbines needs cooling steam. In the start control method of the single-shaft combined cycle power plant, before starting the gas turbine, it is determined whether cooling steam of the low-pressure steam turbine can be supplied from the low-pressure drum based on the low-pressure drum pressure of the exhaust heat recovery boiler, When it is determined that the cooling steam can be supplied to the low-pressure steam turbine, the cooling steam is supplied from the low-pressure drum to the low-pressure steam turbine, and when it is determined that the cooling steam cannot be supplied to the low-pressure steam turbine, the cooling steam is supplied from the auxiliary steam system. A single-shaft combined power generation system, comprising supplying cooling steam to a low-pressure steam turbine and starting the gas turbine. Power plant startup control method. 2. When the steam of the low-pressure drum is supplied to the low-pressure steam turbine as cooling steam, a primary-side control pressure set value of a low-pressure turbine bypass valve that bypasses the low-pressure steam turbine is increased by a predetermined value from an actual pressure. The start control method for a single-shaft combined cycle power plant according to claim 1, wherein the start value is set to a large value. 3. When supplying the cooling steam from the low-pressure drum to the low-pressure steam turbine, when the steam from the low-pressure drum no longer satisfies the condition as the cooling steam, the supply of the steam from the low-pressure drum is stopped. The start control method for a single-shaft combined cycle power plant according to claim 1 or 2, wherein cooling steam is supplied from the auxiliary steam system to the low-pressure steam turbine. 4. While supplying cooling steam from the low-pressure drum to the low-pressure steam turbine, when the steam from the low-pressure drum no longer satisfies the condition as cooling steam, the auxiliary steam is added to the steam from the low-pressure drum. 3. The method according to claim 1, wherein cooling steam is supplied from a steam system to the low-pressure steam turbine. 5. The cooling steam is supplied via a check valve when the cooling steam is supplied from the low-pressure drum to the low-pressure steam turbine. The method for controlling startup of a single-shaft combined cycle power plant according to claim 1. 6. When cooling steam is being supplied from the low-pressure drum to the low-pressure steam turbine, when an inlet steam flow rate of an intermediate-pressure turbine among the steam turbines exceeds a required flow rate of cooling steam of the low-pressure steam turbine. A first control pressure set value of a low pressure turbine bypass valve that bypasses the low pressure steam turbine is set to a value larger by a predetermined value than a primary control pressure set value of a low pressure main steam stop valve control valve. The start control method for a single-shaft combined cycle power plant according to any one of claims 1 to 5. 7. A gas turbine and a steam turbine are directly connected, the steam turbine is driven by steam from an exhaust heat recovery boiler, and a low-pressure steam turbine among the steam turbines needs cooling steam at the time of starting the gas turbine. In a start control method for a single-shaft combined cycle power plant, an auxiliary steam supply system from another power generation facility and a shaft auxiliary steam system supplied with steam from a medium-pressure steam supply system connected to a medium-pressure superheater of the own shaft are provided. When the cooling steam of the low-pressure steam turbine is supplied from the shaft auxiliary steam system, and the auxiliary steam supply system from other power generation equipment is controlled at a higher pressure than the medium-pressure steam supply system of the own shaft, If the pressure and temperature of the medium-pressure superheater have steam higher than the shaft auxiliary steam system, the control pressure setting of the auxiliary steam supply system from other power generation facilities and the own shaft medium-pressure steam supply system A start control method for a single-shaft combined cycle power plant, which comprises replacing fixed values and supplying medium-pressure steam of the own shaft as an auxiliary steam source.