JP2002267106A - Deaeration system for power plant - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a deaeration system for a power plant to suppress lowering of NPSH as much as possible when a feed of high pressure extraction steam used in heating of condensate in a deaerator is suspended and reliably secure an NPSH margin. SOLUTION: The deaeration system for a power plant comprises a condensate control valve (1) to supply condensate (13); a deaerator (3) to heat the condensate (13) by steam (15) for deaeration; flow rate target value setters (66, 67, 68, 69) to determine a flow rate target value (RF); and a flow rate controller (71) to control an opening (FC) of the condensate control valve (1) based on a deviation between a flow rate of the condensate (13) and a flow rate target value when a feed of the steam (15) is stopped. The flow rate target value setters (66, 67, 68, 69) set a flow rate target value to a first target value, lower than a flow rate during a stop of a feed being a flow rate of the condensate (13) at a feed stop time, at a first time after a feed stop time at which a feed of the steam (15) is stopped. At a second time after the first time, a flow rate target value is determined at a second target value higher than the first target value.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a degassing system for a power plant. In particular, the present invention relates to a degassing system for a power plant that controls the pressure inside a degasser that heats and degass condensate flowing from a condenser.

[0002]

2. Description of the Related Art In a power plant, steam is generated by a heat source such as a boiler or a reactor vessel, and the steam drives a steam turbine. The steam discharged by the steam turbine is condensed by a condenser to recover the steam. A circulation cycle is used which turns the water into water and returns the condensate to the aforementioned heat source.

FIG. 11 shows an example of such a circulation cycle. The condenser 201 condenses exhaust steam discharged by a steam turbine (not shown) with cooling water to generate condensate. The condensate flowing out of the condenser 201 is supplied to the condensate pump 20
3, and the pressure is increased by the condensate booster pump 305. The pressurized condensate flows into the deaerator 210 via the deaerator water level control valve 207 and the low-pressure feedwater heater 209.

[0004] The deaerator 210 is supplied with high-pressure bleed air 211 which is steam bleed from a steam turbine (not shown). The deaerator 210 heats the condensed water by the high-pressure bleed air 211 and removes a gas component contained in the condensed water. That is, the deaerator 210 degass the condensed water.

[0005] Further, the deaerator 210 includes a main steam control valve 2.
11 are connected. Via the main steam control valve 211,
Main steam 212 used in other parts of the power plant
Is supplied to the deaerator 210 as needed. Main steam 2
12 is a high-pressure bleed 21
When 1 is not supplied, it is supplied to the deaerator 210. When the high pressure bleed air 211 is not supplied, the main steam 212
Used as a heat source to heat condensate.

The condensed water deaerated by the deaerator 210 flows down to the deaerator tank 213. The deaerated condensed water is temporarily stored in the deaerator tank 213. Deaerator tank 2
The condensate flowing out of 13 is generally referred to as water supply. The feedwater flowing out of the deaerator tank 213 is supplied to the deaerator downcomer 2
15, water supply booster pump 217, water supply pump 21
9, is supplied to the steam generator 223 via the high-pressure feed water heater 221. The steam generator 223 heats the supplied water to generate steam, and supplies the steam to a steam turbine (not shown). The steam turbine is driven by the steam. The steam turbine discharges the steam used for driving as exhaust steam and supplies it to the condenser 201 described above.

[0007] In such a circulation system, the pressure of the feed water at the inlet of the feed water booster pump 217 needs to be higher than a certain pressure. This is because when the pressure of the feedwater at the suction port of the feedwater booster pump 217 becomes lower than a certain pressure, the feedwater flushes and the pump function of the feedwater booster pump 217 is lost. When the pump function of the feedwater booster pump 217 is lost, the steam generator 223 trips, and the function of the power plant is lost. For this reason, the water supply booster pump 21
It is extremely important that the pressure of the water supply at the inlet 7 is properly controlled.

[0008] The pressure of the water supply at the inlet of the water supply booster pump 217 is called NPSH. Further, the pressure of the water supply at the suction port of the water supply booster pump 217 required to maintain the pump function of the water supply booster pump 217 is referred to as a required NPSH. Real NPSH
And the required NPSH difference is called the NPSH margin. When the power plant is operated, the NPSH is the required NPS
H is controlled to be larger than H, and a certain NPSH margin needs to be secured.

When the power plant is in a normal operation state, the power plant is controlled so that a certain NPSH margin is secured. However, when the power plant is disconnected from the power system due to a lightning strike or the like, the load on the steam turbine sharply decreases. When the load on the steam turbine suddenly decreases, the high-pressure bleed air 211 is not supplied from the steam turbine to the deaerator 210. Therefore, the deaerator 210
At this time, the condensate is not heated, and the pressure inside the deaerator 210 decreases. When the pressure inside the deaerator 210 decreases, the NPSH decreases. As described above, N
PSH lowering than the required NPSH must be prevented.

[0010] N due to interruption of the supply of high-pressure bleed air 211
The following measures are taken against the decrease in PSH to prevent the NPSH from becoming lower than the required NPSH.

As a first measure, when the supply of the high-pressure bleed air 211 is interrupted, the flow rate of the condensate flowing into the deaerator 210 is reduced. When the flow rate of the condensed water is reduced, a decrease in the temperature of the deaerator 210 is suppressed. As a result, the pressure drop inside the deaerator 210 is suppressed, and NP
The SH is prevented from being lower than the required NPSH.

As a second measure, when the supply of the high-pressure bleed air 211 is interrupted, the main steam 212 is supplied to the deaerator 210. The supply of the main steam 212 to the deaerator 210 suppresses a decrease in the pressure inside the deaerator 210, and prevents the NPSH from becoming lower than the required NPSH.

One of the NPSH control techniques is disclosed in Japanese Patent Laid-Open Publication No. Hei 6-337298. Japanese Unexamined Patent Publication (Kokai) No. 6-337298 discloses a condensate flow rate control device for controlling the condensate flow rate. As shown in FIG. 12, a known condensate flow control device 121 includes a processing device 122, a track and hold circuit 123, a multiplier 124, a subtractor 125, and a P + I
And an arithmetic unit 126. Each time the load sudden decrease occurs, the processing device 122 outputs the plant output L and the condensate flow rate S at the time of occurrence.
The condensing throttle ratio γ is calculated based on Processing device 122
Has an NPSH allowance table and a deaerator minimum water level table. The NPSH allowance table includes a load decrease width ΔL and a condensing throttle ratio γ in a specific case that has been analyzed in advance, and NP
The correspondence with the SH margin is recorded. In the deaerator minimum water level table, the correspondence between the load decrease width ΔL and the condensing throttle ratio γ in the specific case analyzed in advance and the deaerator minimum water level is recorded. The condensing throttle ratio γ is determined with reference to the NPSH allowance table and the deaerator minimum water level table. The multiplier 124 calculates a set value of the condensate flow rate S by multiplying the condensate flow rate S by the condensate throttle ratio γ. The subtractor 125 and the P + I calculator 126 determine the opening degree of the control valve that controls the flow rate of the condensed water so that the condensed water flow rate S becomes the set value.

In such an NPSH control technique for a power plant, it is desirable that a decrease in NPSH when the supply of the high-pressure bleed air 211 is interrupted is suppressed as much as possible, and that a NPSH margin is ensured.

In particular, when the NPSH is controlled by the flow rate of the condensed water, it is desirable that the supply of the high-pressure bleed air 211 be interrupted, and that the NPSH margin be secured in as short a time as possible. Because if NPSH margin is secured in a short time,
This is because the capacity of the deaerator tank can be reduced. If the NPSH margin is secured in a short time, the time during which the flow rate of the condensate water is reduced can be shortened, and therefore, the capacity of the deaerator tank can be reduced.

[0016]

SUMMARY OF THE INVENTION An object of the present invention is to reduce the NPSH as much as possible when the supply of high-pressure bleed air used for heating condensate to a deaerator is interrupted.
An object of the present invention is to provide a degassing system for a power plant in which a PSH margin is reliably ensured.

Another object of the present invention is to provide a degassing system for a power plant in which the supply of high-pressure bleed air used for heating condensate to a deaerator is interrupted in as short a time as possible. Is to provide.

[0018]

Means for solving the problem are expressed as follows. The technical items appearing in the expression are appended with numbers, symbols, and the like in parentheses (). The numbers, symbols, and the like refer to technical matters constituting at least one of the embodiments of the present invention, particularly, technical matters expressed in the drawings corresponding to the embodiments. The reference numbers, reference symbols, and the like attached to are the same. Such reference numbers,
Reference symbols clarify the correspondence and bridging between the technical matters described in the claims and the technical matters in the embodiments. Such correspondence / bridge does not mean that the technical matters described in the claims are interpreted as being limited to the technical matters of the embodiments.

A deaeration system for a power plant according to the present invention comprises a condensate control valve (1) for supplying a condensate (13) and a deaeration for heating and condensing the condensate (13) with steam (15). (3), a target flow rate setting device (66, 67, 68, 69) for determining a target flow rate (RF), and a flow rate of the condensate (13) when the supply of steam (15) is stopped. A flow controller (71) for controlling an opening (FC) of the condensate control valve (1) based on a deviation (EF) between (F) and a flow target value (RF).
And Flow rate target value setting device (66, 67, 68,
69), when the supply of steam (15) is stopped, the flow rate target value (RF) is changed to the first time (t ₁ ) after the supply stop time (t = 0) when the supply of steam (15) is stopped. ), A first target value (γ ₁ × FH) smaller than the flow rate at supply stop (FH), which is the flow rate (F) at the supply stop time, and the first target value (γ ₁ × FH) after the first time (t ₁ ) At the second time (t ₃ ), the flow target value (RF) is set to a second target value (γ ₂ × FH) larger than the first target value (γ ₁ × FH).
Set forth in

At this time, the flow rate target value setting device (66, 6)
7, 68, 69) at a third time (t ₅ ) after the second time (t ₃ ), the flow target value (RF) is larger than the first target value (γ ₁ × FH), and The second target value (γ ₂
× FH) is preferably set to a third target value (γ ₃ × FH) smaller than the third target value (γ ₃ × FH).

At this time, the flow rate target value setting device (66,
67, 68, and 69) monotonically decrease the flow rate target value so as to become the first target value at the first time after the supply stop time, and a flow rate target value setting unit (6).
6, 67, 68, 69) is the supply stop time (t =
0) and the first time (t ₁ ), and the time when the flow rate target value (RF) becomes the third target value (γ ₃ × FH) or less for the first time is defined as a fourth time (t ₆ ). Then, the target value difference (R) between the third target value (γ ₃ × FH) and the flow target value (RF)
F-γ ₃ · FH) at the fourth time (t ₆ ) and the third time (t
₅ ) when the integrated value integrated in the time interval with
It is preferable to control the target flow value (RF) such that

Further, the flow controller (71) determines the deviation (E
It is desirable to control the opening (FC) such that the greater the absolute value of F), the higher the response of the opening (FC) to the deviation (EF).

The flow controller (71) performs a proportional operation to determine the opening degree (FC), and a proportional band (P _B2 ) that defines the proportional operation is based on the absolute value of the deviation (EF). It is desirable to decrease monotonically in a broad sense.

The flow controller (71) performs an integration operation to determine an opening (FC), and an integration time (T _I2 ) for defining the integration operation is determined with respect to the absolute value of the deviation (EF). ,
It is desirable to decrease monotonically in a broad sense.

The power plant degassing system further includes a water level controller (6a).
Includes a deaerator tank (3b) for storing the condensate (13), and the water level controller (6a) controls the deaerator tank (3b) stored in the deaerator tank (3b) before the supply stop time (t = 0). It is desirable to control the opening (FC) based on the water level (H) of the water (13).

The degassing system for a power plant according to the present invention comprises a steam control valve (15), a deaerator (3), a pressure measuring device (8), and a target value setting device (92, 93, 94). , A steam control valve controller (96). Steam control valve (1
5) supplies the first steam (14). The deaerator (3) has a first steam (14), a second steam (15) supplied from a different source than the first steam (14), and a condensate (1).
3) are supplied. The deaerator (3) degass the condensate (13) by heating it with at least one of the first steam (14) and the second steam (15). The pressure measuring device (8) measures a deaerator pressure (P) which is a pressure inside the deaerator (3). The target value setters (92, 93, 94) determine a pressure target value (RP). The steam control valve controller (93) controls the opening (PC) of the steam control valve (15) based on the difference (EP) between the deaerator pressure (P) and the target pressure value (RP). When the supply of the second steam (15) is cut off, the target value setters (92, 93, 94) set the pressure target value (RP) to the first pressure (PH), and set the second steam (15). After the time at which the supply of 15) is interrupted, the pressure target value (RF) is reduced to the second pressure (RP1) with the passage of time. At this time, the steam control valve controller (93) increases the response of the opening degree (PC) to the difference (EP) as the target pressure value (RF) increases.

At this time, the steam control valve controller (93)
The opening degree (PC) may be determined by performing a proportional operation.
At this time, a proportional band (P _B3 ) defining the proportional operation
Preferably decreases monotonically in a broad sense with respect to the pressure target value (RP).

Further, the steam control valve control device (93)
An I controller (93), and a proportional band (P _B3 ) defining the operation of the PI controller (93) is a pressure target value (RP).
It is preferable to decrease monotonically in a broad sense.

A target value setting device (92, 93, 94)
After the deaerator pressure (PF) immediately before the supply of the second steam (15) is cut off is set to the first pressure (PH) and the pressure target value (RP) is set to the first pressure (PH). It is desirable to reduce the target pressure value (RP) from the first pressure (PH) to the second pressure (RP1) at a constant reduction rate.

[0030]

BRIEF DESCRIPTION OF THE DRAWINGS FIG.
A power plant degassing system according to an embodiment of the present invention will be described.

First Embodiment FIG. 1 shows a degassing system for a power plant according to a first embodiment of the present invention.
The power plant degassing system includes a condensate control valve 1, a low-pressure feedwater heater 2, a deaerator 3, a condensate flow meter 4, a deaerator tank water level gauge 5, a condensate control valve controller 6, a main steam A control valve 7, a deaerator pressure gauge 8, a main steam controller 9, and a drain 10 are provided. The deaerator 3 includes a deaerator main body 3a and a deaerator tank 3b.
And

The condensate control valve 1 is supplied with condensate 11 from a condenser (not shown). The flow rate of the condensed water 11 is controlled by the opening degree of the condensed water control valve 1. The condensed water 11 that has passed through the condensate control valve 1 is supplied to the low-pressure feed water heater 2. The low-pressure feed water heater 2 uses a low-pressure bleed air 12 that is steam extracted from a low-pressure turbine (not shown) to condense the condensate water 1.
Heat 1 The heated condensate 11 is hereinafter referred to as condensate 13
It is described. The condensate 13 flows into the deaerator main body 3 a of the deaerator 3.

A high-pressure bleed air 15, which is steam extracted from a high-pressure turbine (not shown), is introduced into the deaerator main body 3a. Further, the main steam 14 is introduced into the deaerator main body 3a via the main steam control valve 7. The flow rate of the main steam 14 flowing into the deaerator main body 3a is controlled by the opening of the main steam control valve 7.

The condensed water 13 flowing into the deaerator main body 3a is further heated by the main steam 14 and / or the high-pressure bleed air 15 to be deaerated. The deaerated condensate 13 is stored in the deaerator tank 3b. The deaerated condensed water 13 is supplied as water and supplied to a water supply booster pump (not shown). Water is supplied from a water supply booster pump to a steam generator (not shown).

The opening FC of the condensate control valve 1 is controlled by a condensate flow meter 4, a deaerator tank water level gauge 5, and a condensate control valve controller 6. The condensate flow meter 4 measures the flow rate F of the condensate 13. The deaerator tank water level gauge 5 measures the water level H of the deaerator tank 3b. The condensate control valve controller 6 sets the opening FC of the condensate control valve 1 based on either the flow rate F of the condensate 13 or the water level H of the deaerator tank 3b. Whether the opening FC of the condensate control valve 1 is controlled based on the flow rate F or the water level H is determined according to the operation mode set in the condensate control valve controller 6.

The condensate control valve controller 6 is set to one of the normal mode, the condensed throttle mode, and the return mode by the condensed throttle instruction signal SC2 and the return instruction signal SC3. When the power plant including the power plant deaeration system is in normal operation, both the condensing throttle instruction signal SC2 and the return instruction signal SC3 are set to the “L” state,
The condensate control valve controller 6 is set to the normal mode. In this case, the opening FC of the condensate control valve 1 is controlled so that the water level H of the deaerator tank 3b becomes the rated water level RH1.

The load on the power plant suddenly decreases, and the high pressure bleed air 1
5 is shut off, the condensing throttle instruction signal SC2 becomes "
The "H" state, the return instruction signal SC3 becomes "L" state, and the condensate control valve controller 6 is set to the condensate throttle mode, in which case the flow rate of the condensate 13 is reduced as described later. The opening FC of the condensate control valve 1 is controlled so that the pressure inside the deaerator main body 3a is prevented from decreasing.
NPSH margin is secured.

Thereafter, when any of the following conditions (1) to (4) is satisfied, the condensing throttle instruction signal SC2 becomes "L", the return instruction signal SC3 becomes "H", and the condensate control valve Controller 6 is set to the return mode. Conditions: (1) Reset is performed manually. (2) The flow rate of the supply water supplied to the steam generator is larger than the flow rate of the condensate 13 flowing into the deaerator. (3) The water level H of the deaerator tank 3b becomes lower than a predetermined water level. (4) A predetermined time has elapsed since the condensate control valve controller 6 was set to the condensate throttle mode. While the condensate control valve controller 6 is set to the condensed throttle mode, the flow rate of the condensate 13 is reduced, and when the condensate control valve controller 6 is set to the return mode, the deaeration tank 3b
Is in a state lower than the rated water level RH1. When the condensate control valve controller 6 is set to the return mode,
The condensate control valve controller 6 controls condensate control such that the rate of change of the water level H of the gas tank 3b is kept within a predetermined range, and the water level H of the deaerator tank 3b finally reaches the rated water level RH1. The opening FC of the valve 1 is de-controlled. It should be noted that the condensing throttle instruction signal SC2 and the return instruction signal SC3 do not go into the “H” state at the same time.

On the other hand, the opening PC of the main steam control valve 7 is controlled by a deaerator pressure gauge 8 and a main steam controller 9. The deaerator pressure gauge 8 measures a deaerator pressure P, which is a pressure inside the deaerator main body 3a. The main steam controller 9 determines the opening PC of the main steam control valve 7 based on the deaerator pressure P. The main steam controller 9 supplies a load sudden decrease signal SC1 indicating that the load of the power plant has suddenly decreased and the supply of the high-pressure bleed air 15 has been interrupted.
Is entered. The main steam controller 9 outputs the load sudden decrease signal SC1.
The pressure target value RP of the deaerator pressure P is changed according to.

When the high-pressure bleed air 15 is supplied,
The pressure target value RP is set to be equal to or lower than the pressure of the high-pressure bleed air 15 directly introduced into the deaerator main body 3a. Therefore, when the high-pressure bleed air 15 is supplied to the deaerator main body 3a, the deaerator pressure P cannot be controlled by the opening PC of the main steam control valve 7 that supplies the main steam 14. That is, when the high-pressure bleed air 15 is supplied to the deaerator main body 3a, the main steam controller 9 does not contribute to the control of the deaerator pressure P. The main steam controller 9 controls the high pressure bleed air 15 when starting and stopping the power plant or when the load on the power plant is suddenly reduced.
The deaerator pressure P is controlled when the high-pressure bleed air 15 is not supplied to the deaerator main body 3a, such as when the supply of air is cut off.

Next, the configuration of the condensate control valve controller 6 will be described in detail. FIG. 2 shows the configuration of the condensate control valve controller 6. The condensate control valve controller 6 includes a water level control system 6a, a flow control system 6b, and a changeover switch 6c. The water level control system 6a
The first condensate control valve opening FC1 is determined based on the water level H of the deaerator tank 3b. The flow control system 6b determines the second condensate control valve opening FC2 based on the flow rate F of the condensate 13.
The changeover switch 6c switches the first condensate control valve opening FC1 and the second condensate control valve opening F based on the condensing throttle instruction signal SC2.
C2 is output as the opening FC of the condensate control valve 1. When the condensing throttle instruction signal SC2 is in the “L” state, the changeover switch 6c switches the first condensing control valve opening F
C1 is determined as the opening FC of the condensate control valve 1. When the condensing throttle instruction signal SC2 is in the “H” state, the changeover switch 6c changes the second condensing control valve opening FC2 to the opening F of the condensing control valve 1.
Determined in C. That is, the condensate control valve controller 6 is in the normal mode,
When in any state of the return mode, the opening FC of the condensate control valve 1 is controlled by the water level control system 6a. When the condensate control valve controller 6 is in the condensed throttle mode,
The opening FC of the condensate control valve 1 is controlled by the flow control system 6b.

The water level control system 6a includes a rated water level setter 61,
A return mode water level setter 62, a changeover switch 63, a differentiator 64, and a PI controller 65 are included. Rated water level setting device 61
Outputs the rated water level RH1. The rated water level RH1 is a target value of the water level H of the deaerator tank 3b when the condensate control valve controller 6 is in the normal mode.

The return mode water level setting unit 62 generates a return mode target value RH2 which is a target value of the water level H of the deaerator tank 3b when the condensate control valve controller 6 is in the return mode. It is assumed that the condensing throttle instruction signal SC2 is in the “L” state, the return instruction signal SC3 is in the “H” state, and the condensate control valve controller 6 is set to the return mode. When the condensate control valve controller 6 is set to the return mode, the return mode water level setter 62 tracks the water level H of the deaerator tank 3b measured by the deaerator tank water level gauge 5, and returns to the return mode. A target value RH2 is generated. The return mode target value RH2 is
The water level H of the deaerator tank 3b is followed with a delay of a predetermined delay time. By controlling the water level H of the deaerator tank 3b to match the return mode target value RH2, the rate of change of the water level H of the deaerator tank 3b is limited to a certain range.

The changeover switch 63 sets the return instruction signal SC3
RH1 and the condensing throttle mode target value R
Either H2 is output as the water level target value RH. The changeover switch 63 sets the return instruction signal SC3 to “L”.
When in the state, that is, when the condensate control valve controller 6 is in the normal mode, the rated water level RH1 is output as the water level target value RH. The changeover switch 63 sets the return instruction signal SC3
Is in the "L" state, that is, when the condensate control valve controller 6 is in the return mode, the condensate throttle mode target value RH2 is output as the water level target value RH. The differentiator 64 calculates a deviation EH between the water level target value RH and the water level H of the deaerator tank 3b. The PI controller 65 performs PI control based on the deviation EH. The PI controller 65 performs PI control defined by the proportional band P _B1 and the integration time T _I1 . In the present embodiment, P _B1 = 200 (%) and T _I1 = 60 (sec). The PI controller 65 performs PI control based on the deviation EH, and outputs a first condensate control valve opening FC1. As described above, the first condensate control valve opening FC1 becomes the opening FC of the condensate control valve 1 when the condensate control valve controller 6 is in one of the normal mode and the return mode.

On the other hand, based on the flow rate F of the condensate 13, the flow control system 6b determines the second condensate control valve opening FC2. The flow control system 6b includes a hold unit 66, a multiplier 67, a timer 68, a condensing throttle ratio generator 69, a difference unit 70, and a PI controller 71. When the condensing throttle instruction signal SC2 changes from the “L” state to the “H” state, that is, when the condensing control valve controller 6 is set to the condensing restricting mode, the hold device 66 sets the condensate 13 Latch the flow rate F. Hold device 66
Outputs the latched flow rate F of the condensate 13 as the hold flow rate FH. The timer 68 has a condensing throttle instruction signal SC2
Is started from the "L" state to the "H" state, that is, when the condensate control valve controller 6 is set to the condensed throttle mode. The timer 68 outputs an elapsed time t from the time set in the condensing throttle mode.

The condensing throttle ratio generator 69 responds to the elapsed time t.
The condensing throttle ratio γ is output. FIG. 3 shows the condensing throttle mode.
Condensing with respect to the elapsed time t from the time set in
7 shows a change in the ratio γ. At t = 0, condensing throttle ratio generator
69 sets γ = 1. Then, 0 <t <t₁While
The water throttle ratio generator 69 decreases the condensing throttle ratio γ, and t = t ₁
Where γ = γ₁(= 0). t₁<T <t₂of
, The condensing throttle ratio generator 69 calculates γ = γ₁(= 0) maintained
I do. t₂<T <t₃During, the condensing throttle ratio generator 69
The condensing throttle ratio γ is increased and t = t₄Where γ = γ₂(>
γ₁). t ₄<T <t₅During the condensing throttle ratio generator
69 is γ = γ₂To maintain. t₅<T <t₆While
The water throttle ratio generator 69 decreases the condensing throttle ratio γ, and t = t₆
Where γ = γ₃(<Γ₂). t> t₆Then
The condensing throttle ratio generator 69 calculates γ = γ₃To maintain.

The multiplier 67 calculates the product of the condensing throttle ratio γ and the hold flow rate FH to calculate the above-mentioned flow rate target value RF.
The flow rate target value RF temporally changes in the same manner as the condensing throttle ratio γ, corresponding to the temporal change of the condensing throttle ratio γ.

As shown in FIG.
Calculates the deviation EF between the flow rate target value RF and the flow rate F of the condensate 13. The PI controller 71 performs PI control based on the deviation EF. The PI controller 71 performs PI control defined by the proportional band P _B2 and the integration time T _I2 . In the present embodiment, P _B2 = 75 (%) and T _I2 = 30 (sec). The PI controller 71 performs PI control based on the deviation EF, and outputs a second condensate control valve opening FC2. As described above, the second condensate control valve opening FC2 is the opening FC of the condensate control valve 1 when the condensate control valve controller 6 is in the condensed throttle mode. Thus, when the condensate control valve controller 6 is in the condensed water throttle mode, the flow rate F of the condensed water 13 is controlled so as to match the target flow rate value RF.

Next, the configuration of the main steam controller 9 will be described in detail. As shown in FIG. 4, the main steam controller 9
Includes a steady-state pressure target value setter 92, a load sudden decrease pressure target value setter 93, a changeover switch 94, a differentiator 95, a PI controller 96, and a control parameter generator 97.

The steady state pressure target value setting device 92 outputs a predetermined first pressure target value RP1 to the changeover switch 94.
In the present embodiment, the first pressure target value RP1 is 2 (at
a).

The target pressure setter 93 for suddenly decreasing load tracks the deaerator pressure P measured by the deaerator pressure gauge 8 to generate a second target pressure value RP2. The generated second pressure target value RP2 follows the deaerator pressure P with a delay of a predetermined delay time. Pressure target value setting device 9 when load suddenly decreases
3 is a switch 9 for changing the generated second pressure target value RP2.
4 is output.

The changeover switch 94 is provided with a load sudden decrease signal SC1.
The first pressure target value RP1 and the second pressure target value RP
2 is output as the pressure target value RP. The changeover switch 94 sets the load sudden decrease signal SC1 to “L”.
In the state, the first pressure target value RP1 is output as the pressure target value RP, and when the load rapid decrease signal SC1 is in the “H” state,
The second pressure target value RP2 is output as the pressure target value RP.

FIG. 5 shows the time change of the pressure target value RP after the load of the power plant is rapidly reduced and the load rapid reduction signal SC1 is changed from the "L" state to the "H" state. Where t
= 0 is the time when the load sudden decrease signal SC1 changes from the “L” state to the “H” state. When t <0, RP = RP1 (= 2
ata).

When the load sudden decrease signal SC1 changes from "L" state to "H" state at t = 0, the target pressure value RP is set to the second target pressure value RP2. As described above, the second pressure target value RP2 is generated by tracking the deaerator pressure P. The second pressure target value RP2 follows the deaerator pressure P with a delay of a predetermined delay time. Similarly, the pressure target value RP follows the deaerator pressure P with a delay of a predetermined delay time. By controlling the deaerator pressure P to coincide with the pressure target value RP generated in this way, the rate of change of the deaerator pressure P is limited to a certain range.

Pressure target value RP that follows deaerator pressure P
Is set to the deaerator pressure PH when the load suddenly decreases at t = 0. Here, the deaerator pressure PH at the time of a rapid decrease in load is the deaerator pressure P when the supply of the high-pressure bleed air 15 is stopped due to a sudden decrease in the load on the power plant. Deaerator pressure P when load suddenly decreases
H is substantially equal to the pressure of the high pressure bleed air 15 supplied until the load sudden decrease signal SC1 changes from the “L” state to the “H” state. The deaerator pressure PH at the time of a sudden decrease in load is determined by the operating state immediately before the load of the power plant suddenly decreases. When the power plant is in rated operation, the pressure of the high-pressure bleed air 15 is approximately 12 ata, and in this case, the deaerator pressure PH when the load suddenly decreases is approximately 12 ata.

At t> 0, the supply of the high-pressure bleed air 15 is cut off, and the deaerator pressure P monotonously decreases from the deaerator pressure PH when the load suddenly decreases. Accordingly, the pressure target value RP also decreases monotonously. When the target pressure value RP falls to the first target pressure value RP1, the target pressure value RP is thereafter maintained at the first target pressure value RP1.

As shown in FIG.
Calculates the difference EP between the deaerator pressure P and the target pressure value RP. The PI controller 96 performs PI control based on the difference EP to determine the opening PC of the main steam control valve 7. As the parameters that define the operation of the PI control performed by the PI controller 96, a proportional band P _B3 and an integration time T _I3 are used.

In this embodiment, the integration time _TI3 is 6
0 (sec).

On the other hand, the proportional band P _B3 is determined by the control parameter generator 97. Control parameter generator 9
7 determines the proportional band _PB3 based on the target pressure value RP. FIG. 6 shows the correspondence between the target pressure value RP and the proportional band _PB3 . The proportional band P _B3 set in the PI controller 96 monotonically decreases in a broad sense with respect to the target pressure value RP. More specifically, when RP ≦ 3 (ata), P _B3 = 1000
(%). When 3 <RP ≦ 8 (ata), P _B3 = −1
60 · RP + 1480 (%). When RP> 8 (ata), P _B3 = 200 (%). Therefore, before the load of the power plant suddenly decreases and the load rapid decrease signal SC1 changes from the “L” state to the “H” state, the control parameter generator 97
Is P _B3 = 1000 (%). Load drop signal SC
Immediately after 1 changes from the “L” state to the “H” state, RP
= Because consisting PH (~12ata), the control parameter generator _97, and _{P B 3 = 200 (%)} . Thereafter, the pressure target value RP, since reduced to RP1 (~2ata), the proportional band _{P B3} also decreases monotonically in a broad sense.

The responsiveness of the opening degree PC to the difference EP increases as the proportional band PB3 _decreases . Therefore, when the load sudden decrease signal SC1 changes from the “L” state to the “H” state, the difference E
The responsiveness of the opening PC to P is determined by the load sudden decrease signal SC1.
Becomes higher than before the “L” state to the “H” state. Furthermore, the response of the opening degree PC to the subsequent difference EP decreases monotonically in a broad sense.

Next, the operation of the power plant deaeration system of this embodiment will be described.

First, control of the opening FC of the condensate control valve 1 will be described.

When the power plant is operating normally, the condensing throttle instruction signal SC2 and the return instruction signal SC3 are both in the "L" state, and the condensate control valve controller 6 is set to the normal operation mode. . At this time, the opening FC of the condensate control valve 1
Is controlled by the water level control system 6a based on the water level H of the deaerator tank 3b. At this time, the target flow rate RH is
The opening FC of the condensate control valve 1 is set to the rated water level RH1.
Is controlled such that the water level H of the deaerator tank 3b becomes the rated water level RH1.

When the load on the power plant suddenly decreases, the condensing throttle instruction signal SC2 transits to the "H" state, and the condensate control valve controller 6 is set to the condensing throttle mode. When the condensing throttle instruction signal SC2 transitions to the “H” state, the flow rate F of the condensate 13
Is latched by the hold unit 66, and the hold flow rate F
H is determined. Further, as described above, the condensing throttle ratio γ changes as shown in FIG.

As a result, the target flow rate RF changes over time as described below. When the condensate control valve controller 6 is set to the condensed throttle mode, the target flow rate RF is set to the hold flow rate FH. continue,
The flow rate target value RF is a flow rate target value γ ₃ that is finally set.
It is reduced to γ ₁ × FH (= 0) lower than × FH.
Since the flow rate F of the condensate 13 is controlled to be γ ₁ × FH (= 0), the flow rate F of the condensate 13 is set after the condensate control valve controller 6 is set to the condensed throttle mode. Decreases rapidly. As a result, a decrease in the temperature inside the deaerator main body 3a is suppressed, and an NPSH margin is secured.

However, since the flow rate F of the condensed water 13 is greatly reduced, the water level H of the deaerator tank 3b is also rapidly reduced. Therefore, the time _t 2 -t ₁ only flow target value RF is gamma ₁
After being maintained at × FH, the target flow value RF is increased, and the target flow value RF is set to γ ₂ × FH higher than γ ₃ × FH. As a result, the water level H of the deaerator tank 3b is recovered, and the water level H of the deaerator tank 3b is lower than the minimum required water level of the deaerator tank 3b (hereinafter, referred to as "minimum required water level of the deaerator"). Is prevented.

[0067] time _t 2 -t ₁ only flow rate target value RF is γ ₁
After being maintained at × FH, the flow target value RF is decreased to reach the finally set flow target value γ ₃ × FH. Thereafter, the target flow rate RF is maintained at γ ₃ × FH as long as the condensate control valve controller 6 is maintained in the condensed throttle mode.

By changing the target flow rate RF as described above, the NPSH margin is ensured, and the water level H of the deaerator tank 3b may be lower than the minimum required level of the deaerator. Can be prevented.

At this time, it is desirable that the condensing throttle ratio γ be controlled so that the area of the area A and the area of the area B shown in FIG. Here, the area S _A of the region _A and
The area _{S B} of region B,

(Equation 1) … (1)

[0070] It the area _{S A} and area _{S B} are equal, the following equation:

(Equation 2) (2) is equivalent to the following. Furthermore, the expression (2) is satisfied.

(Equation 3) It is synonymous with (3). Here, gamma ₃ · FH is a flow target value RF at after time _{t 5.}

As described above, since the condensing throttle ratio γ (and the target flow rate RF) is determined, the deaerator tank 3
Of the amount of decrease in b of the water level H, the time t ₆ after, the amount was reduced until reaching the time t _7, the time t ₇ after the time t ₅
Will be recovered by then. This is deaerator tank 3
This is effective in preventing the water level H of b from becoming lower than the minimum required water level of the deaerator.

The flow rate F of the condensate 13 and the target flow rate RF
Responsiveness of the opening FC of the condensate control valve 1 to the deviation EF is higher than responsiveness of the opening FC of the condensate control valve 1 to the deviation EH between the water level H of the deaerator tank 3b and the rated water level RH1. Is preferred. When the power plant is operating normally and the condensate control valve controller 6 is in the normal operation mode, the water level H of the deaerator tank 3b is stable, and the water level H of the deaerator tank 3b and the rated water level The deviation EH from RH1 tends to be kept small. In such a case, it is not required that the responsiveness of the opening FC of the condensate control valve 1 be high, but rather, it is desirable that hunting does not occur in the condensate control valve 1. Here, hunting means that the valve repeatedly repeats the state of slightly opening and fully closing. Therefore, when the condensate control valve controller 6 is in the normal operation mode, the responsiveness of the opening FC of the condensate control valve 1 to the deviation EH is set relatively low.

On the other hand, when the load on the power plant is suddenly reduced and the condensate control valve controller 6 is in the condensate restriction mode, the target flow rate RF changes with time, and the flow rate F of the condensate 13 and the flow rate F The deviation EF from the target value RF tends to be large. Therefore, the responsiveness of the opening FC of the condensate control valve 1 to the deviation EF is set relatively high. As a result, the flow rate F of the condensed water 13 approaches the flow rate target value RF more quickly.

Accordingly, when the condensate control valve controller 6 is in the condensed throttle mode, the control valve P controls the opening FC of the condensate control valve 1.
The proportional band P _B2 set in the I controller 71 is set smaller than the proportional band P _B1 set in the PI controller 65. More specifically, proportional band _PB2 is set to 75 (%), and proportional band _PB1 is set to 200 (%). Further, the integration time T _I2 set in the PI controller 71
Is set to be shorter than the integration time T _I1 set in the PI controller 65. More specifically, the integration time T
_I2 is set to 30 (sec), and the integration time T _I1 is
60 (sec). Since the proportional band P _B2 and the integration time T _I2 are determined in this way, the responsiveness of the opening FC of the condensate control valve 1 to the deviation EF between the flow F of the condensate 13 and the target flow value RF. Is higher than the response of the opening FC of the condensate control valve 1 to the deviation EH between the water level H of the deaerator tank 3b and the rated water level RH1.

After a predetermined time has elapsed after the condensing control valve controller 6 has been set to the condensing restricting mode, the condensing restricting instruction signal SC2 changes from the "H" state to the "L" state and returns. The instruction signal SC3 changes from the “L” state to the “H” state. The condensate control valve controller 6 is set to the return mode. As shown in FIG. 2, the water level H in the deaerator tank 3b is tracked by the return mode water level setter 62, and a water level target value RH is determined. The water level target value RH is
It is determined that the water level H of the time deaerator tank 3b is followed with a delay of a predetermined delay time. As a result, the rate of change of the water level H is limited to a certain range. Water level target value RH
Reaches the rated water level RH1, the target water level RH is fixed at the rated water level RH1. Thereafter, the return instruction signal SC3 changes to "
A transition is made from the "H" state to the "L" state, and the condensate control valve controller 6 is returned to the normal operation mode.

Next, control of the opening PC of the main steam control valve 7 will be described.

Referring to FIG. 1, at the start of the start of the power plant, high-pressure bleed air 15 is not supplied from a high-pressure turbine (not shown). When the power plant is started, the main steam 14 is supplied to the deaerator main body 3a and the condensate 13
Is heated by the main steam 14. On the other hand, the load sudden decrease signal SC1 is set to the “L” state. As shown in FIG. 4, the pressure target value RP of the deaerator main body 3a is RP
1 (= 2 data) is set. The opening PC of the main steam control valve 7 is controlled based on the deaerator pressure P. The deaerator pressure P of the deaerator main body 3a is controlled to be RP1.

At this time, as shown in FIG. 6, the proportional band P _B3 of the PI controller 96 that determines the opening PC is 10
Set to 00 (%). The responsiveness of the opening degree PC to the deviation EP is relatively low so that hunting of the main steam control valve 7 does not occur.

When the power plant is started, the supply of the high pressure bleed air 15 from the high pressure turbine (not shown) is started, and the pressure of the high pressure bleed air 15 increases. When the activated power plant is stabilized, the pressure of the high-pressure bleed air 15 is approximately 1
2 (ata), and the deaerator pressure P is approximately 12 (a).
ta). When the power plant operates at the rated output, the deaerator pressure P is generally maintained at 12 (ata).

At this time, the target pressure value RP is the first target pressure value RP1 (= 2 data). Therefore, the deaerator pressure P becomes larger than the target pressure value RP, and the opening PC of the main steam control valve 7 is fully closed. The main steam 14 is not supplied to the deaerator main body 3a.

Thereafter, it is assumed that the load on the power generation plant suddenly decreases and the supply of the high-pressure bleed air 15 is cut off. When the supply of the high-pressure bleed air 15 is cut off, the load sudden decrease signal SC1 becomes “H”. At this time, the pressure target value RP is switched to the second pressure target value RP2. As described above, the pressure target value RP follows the deaerator pressure P with a delay of a predetermined delay time. The pressure target value RP becomes the deaerator pressure PH when the load suddenly decreases immediately after the load sudden decrease signal SC1 becomes “H”.
The deaerator pressure PH at the time of a sudden load decrease is determined by the operating state of the power plant immediately before the sudden decrease of the load. If the power plant is operating at rated output just before the load drops,
The deaerator pressure PH at the time of sudden load decrease is approximately 12 (ata). Thereafter, the deaerator pressure P monotonously decreases. At this time, the pressure target value RP is generated by tracking the deaerator pressure P, so that the rate of change of the deaerator pressure P is limited to a certain range. When the deaerator pressure P decreases to the first pressure target value RP1 (= 2 ata), the pressure target value RP also changes to the first pressure target value RP1 (= 2at).
ata). Thereafter, the target pressure value RP is kept at the first target pressure value RP1.

At this time, according to the pressure target value RP, PI
The proportional band _PB3 of the controller 96 is also changed. Immediately after the load sudden decrease signal SC1 becomes “H”, the pressure target value RP
Represents a load rapidly decreases during deaerator pressure PH, thus as shown in Figure 6, the proportional band P _{B 3} becomes 200%. Thereafter, the pressure target value RP that follows the deaerator pressure P monotonously decreases. In response to the decreasing pressure target value RP, the proportional band P _B3 is increased. As a result, the proportional band P _B3 becomes
The smaller the deaerator pressure P, the smaller it is set.

Here, in a state where the supply of the high-pressure bleed air 15 is shut off, the degasser pressure P increases as the degasser pressure P increases. Accordingly, the proportional band P _B3 is set to be smaller as the deaerator pressure P is larger, so that the supply of the high-pressure bleed air 15 is cut off and the proportional band P _B3 is set smaller as the rate of decrease of the deaerator pressure P is larger. Will be done. That is, the larger the rate of decrease of the deaerator pressure P, the higher the responsiveness of the opening PC to the deviation EP. Therefore, the deaerator pressure P
Is rapidly reduced, the main steam 15 is supplied rapidly. Thereby, the NPSH margin is more reliably secured.

On the other hand, when the deaerator pressure P and the target pressure value RP become closer to the first target pressure value RP1 after a predetermined time, the rate of change of the deaerator pressure P decreases. At this time,
The proportional band _PB3 is set to a larger value, 1000 (%), according to the target pressure value RP. The responsiveness of the main steam control valve 7 to the opening PC with respect to the deviation EP becomes lower.
When the rate of change of the deaerator pressure P is small, the responsiveness of the opening degree PC to the deviation EP decreases, thereby preventing hunting of the main steam control valve 7 when the rate of change of the deaerator pressure P is small. You.

As described above, the proportional band P _{B3 corresponds} to the pressure target value R.
The monotonic decrease in P in a broad sense means that high pressure bleeding 1
When the supply of 5 is cut off and the deaerator pressure P sharply decreases, the main steam 14 is promptly supplied.
On the other hand, when the deviation EP becomes small, such as when the power plant is started or when a certain period of time has elapsed after the supply of the high-pressure bleed air 15 has been cut off, the responsiveness of the main steam control valve 7 to the opening PC with respect to the deviation EP. Is reduced, and hunting of the main steam control valve 7 is prevented.

As described above, in the degassing system for the power plant according to the present embodiment, the condensing throttle ratio γ
(And the flow rate target value RF) are controlled as described above, and the proportional band P _B3 of the PI controller 96 is variable as described above, so that the supply of the high-pressure bleed air 15 is interrupted. The decrease is suppressed as much as possible, and the NPSH margin is reliably secured.

Further, the condensing throttle ratio γ (and the target flow rate R
By controlling F) as described above, the high pressure bleed air 1
After the supply of No. 5 is interrupted, the NPSH margin is secured in a short time. Thereby, the capacity of the deaerator tank can be reduced.

Further, by controlling the proportional band P _B3 of the PI controller 96 of the main steam controller 9 as described above,
When the supply of the high-pressure bleed air 15 is interrupted and the deaerator pressure P sharply decreases, the main steam 14 is promptly supplied to the deaerator 3 to ensure the NPSH margin. Further, hunting of the main steam control valve 7 when the change in the deaerator pressure P is small is prevented.

Second Embodiment: The power plant degassing system of the second embodiment has substantially the same configuration as the power plant degassing system of the first embodiment. In the power plant degassing system according to the second embodiment, the condensate control valve controller 6 provided in the power plant degassing system according to the first embodiment uses the condensate control shown in FIG. It has been replaced by a valve controller 6 '. The configuration and operation of the other parts of the degassing system for the power plant according to the second embodiment are the same as those of the first embodiment, and will not be described.

The condensate control valve controller 6 'shown in FIG.
Is substantially the same as the condensate control valve controller 6 shown in FIG.
It has a configuration of The condensate control valve controller 6 'is a condensate control valve.
A control parameter is added to a flow control system 6b included in the controller 6.
The generator 72 has the added configuration. Control parameters
Generator 72 has proportional band P set in PI controller 71.
_B2And integration time T_I2Is determined. Control parameter generator
The flow control system 6b to which the 72 has been added is hereinafter referred to as a flow control system.
6b '. Structure of the other part of the flow control system 6b '
The configuration and operation are the same as those of the flow control system 6b.

The control parameter generator 72 determines the proportional band P _B2 and the integration time _TI2 based on the deviation EF between the flow rate F of the condensate 13 and the target flow rate value RF. The PI controller 71
The PI operation defined by the determined proportional band _PB2 and the integration time _TI2 is performed, and the second condensate control valve opening FC2 is determined based on the deviation EF.

The proportional band P _B2 and the integration time T _I2 are determined such that the greater the absolute value | EF | of the deviation EF, the greater the response of the opening FC of the condensate control valve 1 to the deviation EF.

FIG. 8 shows the dependence of the proportional band P _{B2 on} the deviation EF. The control parameter generator 72 calculates the deviation EF
Of the absolute value | EF | against, as the proportional band _{P B2} decreases monotonically in a broad sense, define the proportional band _{P B2.} More specifically, 0 ≦ | EF | When _{≦ EF 1, P B2 = η} 1, E
When F ₁ ≦ | EF | ≦ EF ₂ , P _B2 = α ₁ || EF
When | + β ₁ , | EF |> EF ₂ , P _B2 = η ₂ (<
η ₁ ). Here, α ₁ = (η ₂ −η ₁ ) / (EF ₂ −EF ₁ ), β ₁ = η ₁ −α ₁ · EF ₁ .

[0094] Figure 9 shows the dependence on the deviation EF integration time TI _2. The control parameter generator 72 calculates the deviation E
The absolute value of F | EF | respect, integration time _{T I2} is to decrease monotonically broadly defines the integration time _{T I2.} More specifically, 0 ≦ | EF | When ≦ EF _{3, T I2} = η
₃ , EF ₃ ≦ | EF | ≦ EF ₄ , P _I2 = α _2.
When | EF | + β ₂ , | EF |> EF ₂ , T _I2 = η
₄ (<η ₃ ). Here, α ₂ = (η ₄ −η ₃ ) / (EF ₄ −EF ₃ ), β ₂ = η ₃ −α ₁ · EF ₃ .

Accordingly, when the condensate control valve controller 6 'is set to the condensed throttle mode, the absolute value | E of the deviation EF is set.
The responsiveness of the opening FC of the condensate control valve 1 to the deviation EF increases as F | increases. As a result, when the absolute value | EF | of the deviation EF is large, the flow rate F of the condensate 13 is more quickly brought close to the target flow rate value RF, and when the absolute value | EF | 1 hunting is prevented.

Third Embodiment: The power plant degassing system according to the third embodiment has substantially the same configuration as the power plant degassing system according to the first embodiment. In the power plant degassing system according to the second embodiment, the condensate control valve controller 6 provided in the power plant degassing system according to the first embodiment uses the condensate control valve shown in FIG. The configuration and operation of the other parts of the degassing system for a power plant according to the third embodiment are described below.
This is the same as the first embodiment, and will not be described.

As shown in FIG. 2, the condensate control valve controller 6 includes a PI controller 65 for controlling the opening FC of the condensate control valve 1 based on the water level H of the deaerator tank 3b. And a PI controller 71 for controlling the opening FC of the condensate control valve 1 based on the flow rate F of the condensate 13. The condensate control valve controller 6 ″ is shown in FIG. As described above, the PI controller 65 and the PI controller 71 are integrated into one PI controller 74. This is preferable in that the number of PI controllers is reduced.

Next, the configuration of the condensate control valve controller 6 ″ will be described in detail. The condensate control valve controller 6 ″ includes a rated water level setter 61, a return mode water level setter 62, and a changeover switch 6.
3. Includes a differentiator 64.

The operations of the rated water level setting device 61, the return mode water level setting device 62, the changeover switch 63, and the difference device 64 are the same as those described in the first embodiment. The rated water level setter 61 outputs the rated water level RH1. Rated water level RH
1 is a target value of the water level H of the deaerator tank 3b when the condensate control valve controller 6 is in the normal mode.

The return mode water level setter 62 generates a return mode target value RH2 which is a target value of the water level H of the deaerator tank 3b when the condensate control valve controller 6 is in the return mode. It is assumed that the condensing throttle instruction signal SC2 is in the “L” state, the return instruction signal SC3 is in the “H” state, and the condensate control valve controller 6 is set to the return mode. When the condensate control valve controller 6 is set to the return mode, the return mode water level setter 62 tracks the water level H of the deaerator tank 3b measured by the deaerator tank water level gauge 5, and returns to the return mode. A target value RH2 is generated. The return mode target value RH2 is
The water level H of the deaerator tank 3b is followed with a delay of a predetermined delay time. By controlling the water level H of the deaerator tank 3b to match the return mode target value RH2, the rate of change of the water level H of the deaerator tank 3b is limited to a certain range.

The changeover switch 63 sets the return instruction signal SC3
RH1 and the condensing throttle mode target value R
Either H2 is output as the water level target value RH. The changeover switch 63 sets the return instruction signal SC3 to “L”.
When in the state, that is, when the condensate control valve controller 6 is in the normal mode, the rated water level RH1 is output as the water level target value RH. The changeover switch 63 sets the return instruction signal SC3
Is in the "L" state, that is, when the condensate control valve controller 6 is in the return mode, the condensate throttle mode target value RH2 is output as the water level target value RH. The differentiator 64 calculates a deviation EH between the water level target value RH and the water level H of the deaerator tank 3b.

The condensate control valve controller 6 ″ further comprises a hold unit 66, a multiplier 67, a timer 68, and a condensate throttle ratio generator 6.
9 and a differentiator 70. When the condensing throttle instruction signal SC2 changes from the “L” state to the “H” state, that is, when the condensing control valve controller 6 is set to the condensing restricting mode, the hold device 66 sets the condensate 13 Latch the flow rate F. The hold device 66 outputs the flow rate F of the condensed water 13 latched as the hold flow rate FH. The timer 68 is started when the condensing throttle instruction signal SC2 changes from the "L" state to the "H" state, that is, when the condensing control valve controller 6 is set to the condensing restricting mode. The timer 68 outputs an elapsed time t from the time set in the condensing throttle mode.

The condensing throttle ratio generator 69 outputs a condensing throttle ratio γ according to the elapsed time t. The condensing throttle ratio γ is shown in FIG.
As shown in FIG. The change is as described in the first embodiment. Multiplier 67
Calculates the target flow rate RF by multiplying the hold flow rate H by the condensing throttle ratio γ. The differentiator 70 calculates a deviation EF between the flow rate target value RF and the flow rate F of the condensate 13.

The condensate control valve controller 6 ″ further includes a changeover switch 73, a PI controller 74, and a control parameter generator 75.
And The changeover switch 73 is a condensed throttle instruction signal SC
According to 2, any one of the above-described deviation EH and deviation EF is output as the deviation E. The changeover switch 73 is turned on when the condensing throttle instruction signal SC2 is in the “L” state,
When the condensate control valve controller 6 ″ is set to the normal operation mode or the return mode, the deviation EH is output as the deviation E.

The PI controller 74 determines the opening FC of the condensate control valve 1 based on the deviation E. The PI controller 74 performs PI control based on the deviation E. And proportional band P _B that defines the operation of the PI control, the integral time T _I, defined by the control parameter generator 75.

[0106] The control parameter generator 75, in response to an instruction signal SC2 aperture condensate defines a proportional band _{P B,} the integral time _{T I.} The control parameter generator 75 sets P _B = 200 when the condensing throttle instruction signal SC2 is at “L” level, that is, when the condensing control valve controller 6 ”is set to the normal operation mode or the return mode. (%), T _I = 60 (sec) On the other hand, when the condensing throttle instruction signal SC2 is at the “H” level, that is, when the condensing control valve controller 6 ” When the condensing throttle mode is set, it is determined that P _B = 75 (%) and T _I = 30 (sec).

In the condensate control valve controller 6 "having such a configuration, when the condensate control valve controller 6" is in either the normal operation mode or the return mode, the opening FC of the condensate control valve 1 is controlled. Is controlled based on a deviation EH between the water level H of the deaerator tank 3b and the water level target value RH. In this case, the proportional band _{P B} of the PI controller 74, the integration time _{T I, P B = 200 (} %), T I = 60 (sec). It is determined.

When the condensate control valve controller 6 ″ is in the return mode, the opening FC of the condensate control valve 1 is controlled based on the deviation EF between the flow rate F of the condensate 13 and the target flow rate RF. You.
In this case, the proportional band _{P B} of the PI controller 74, the integration time T
The _{I, P B = 75 (%} ), T I = 30 (sec). It is determined.

As described above, the condensate control valve controller 6 ″ included in the power plant deaeration system according to the third embodiment has the following features.
The operation is substantially the same as that of the condensate control valve controller 6 included in the power plant deaeration system of the first embodiment.
However, the power plant degassing system of the third embodiment is preferable in that the number of PI controllers can be reduced as compared with the power plant degassing system of the first embodiment.

[0110]

According to the present invention, the NP when the supply of the high-pressure bleed air used for heating the condensate in the deaerator is interrupted
Provided is a degassing system for a power plant in which a decrease in SH is suppressed as much as possible and a NPSH margin is reliably ensured.

Further, according to the present invention, after the supply of the high-pressure bleed air used for heating the condensate in the deaerator is interrupted,
A degassing system for a power plant in which an NPSH margin is secured in a short time as possible.

[Brief description of the drawings]

FIG. 1 shows a degassing system for a power plant according to a first embodiment of the present invention.

FIG. 2 shows a configuration of a condensate control valve controller 6;

FIG. 3 shows a time change of the condensing throttle ratio γ.

FIG. 4 shows a configuration of a main steam controller 9.

FIG. 5 shows a temporal change of a target pressure value RP.

FIG. 6 shows the dependence of a proportional band _PB3 defining a proportional operation of the PI controller 65 on a pressure target value RP.

FIG. 7 shows a configuration of a condensate control valve controller 6 ′ included in a power plant deaeration system according to a second embodiment.

FIG. 8 is a graph showing the relationship between the absolute value | EF |
4 shows the dependence of the proportional band P _B2 .

FIG. 9 is a graph showing the relationship between the absolute value | EF |
The dependence of the integration time T _I2 is shown.

FIG. 10 shows a configuration of a condensate control valve controller 6 ″ included in a power plant deaeration system according to a third embodiment.

FIG. 11 shows a circulation cycle of circulating water in a conventional power plant.

FIG. 12 shows a conventional condensate flow control device.

[Explanation of symbols]

 1: Condensate control valve 2: Low pressure feed water heater 3: Deaerator 3a: Deaerator main body 3b: Deaerator tank 4: Condensate flow meter 5: Deaerator tank water level meter 6: Condensate control valve control 6a: Water level control system 6b: Flow control system 6c: Changeover switch 7: Main steam control valve 8: Deaerator pressure gauge 9: Main steam controller 10: Drain 11: Condensed water 12: Low pressure extraction 13: Condensed water 14 : Main steam 15: High pressure extraction 61: Rated water level setting device 62: Return mode water level setting device 63: Changeover switch 64: Differential device 65: PI controller 66: Hold device 67: Multiplier 68: Timer 69: Condensing throttle ratio Generator 70; Differentiator 71: PI controller 72: Control parameter generator 73: Changeover switch 74: PI controller 75: Control parameter generator 92: Steady state pressure target value setting unit 93: Load sudden decrease pressure target value setting Container 94: Switch Switch 95: Difference device 96: PI controller 97: Control parameter generator

Claims (12)

[Claims] A condensate control valve for supplying condensate; a deaerator for heating and degassing the condensate with steam; a flow rate target value setting device for determining a flow rate target value; Is stopped, comprising a flow controller that controls an opening degree of the condensate control valve based on a deviation between the flow rate of the condensate water and the flow rate target value, the flow rate target value setting device includes: When the supply of the steam is stopped, the flow rate target value is calculated at a first time after the supply stop time at which the supply of the steam is stopped, by a supply stop time flow rate that is the flow rate at the supply stop time. Is also set to the small first target value, and the second target value after the first time is set.
A degassing system for a power plant, wherein at time, the flow target value is set to a second target value larger than the first target value. 2. The degassing system for a power plant according to claim 1, wherein the target flow rate setting device sets the target flow rate value to be larger than the first target value at a third time after the second time. And a power plant degassing system set to a third target value smaller than the second target value. 3. The degassing system for a power plant according to claim 2, wherein the target flow rate setting device sets the target flow rate value to the first target value at the first time after the supply stop time. The flow rate target value setting device determines the supply stop time and the first
When the time between the time and the time when the flow rate target value becomes the third target value or less for the first time is the fourth time, the target value difference between the third target value and the flow rate target value is calculated as A degassing system for a power plant that controls the flow rate target value such that an integrated value integrated in a time section between the fourth time and the third time is substantially zero. 4. The degassing system for a power plant according to claim 1, wherein the flow rate controller increases a response of the opening degree to the difference deviation as the absolute value of the deviation increases.
A degassing system for a power plant that controls the opening. 5. The degassing system for a power plant according to claim 1, wherein the flow rate controller performs a proportional operation to determine the opening, and a proportional band defining the proportional operation is defined by an absolute value of the deviation. On the other hand, a degassing system for power plants that monotonically decreases in a broad sense. 6. The degassing system for a power plant according to claim 1, wherein the flow rate controller performs an integration operation to determine the opening, and an integration time for defining the integration operation is an absolute value of the deviation. A degassing system for power plants that monotonically decreases in a broad sense relative to the value. 7. The degassing system for a power plant according to claim 1, further comprising a water level controller, wherein said deaerator includes a deaerator tank for storing said condensate water, and wherein said water level controller is A degassing system for a power plant that controls the opening degree based on a water level of the condensed water stored in the deaerator tank before a supply stop time. 8. A steam control valve for supplying a first steam, wherein the first steam, a second steam supplied from a supply source different from the first steam, and condensate are supplied, and A deaerator for degassing the condensate by heating the condensate with at least one of the first steam and the second steam; and a pressure measuring device for measuring a deaerator pressure that is a pressure inside the deaerator. A target value setting device that determines a pressure target value, and a steam control valve controller that controls an opening degree of the steam control valve based on a difference between the deaerator pressure and the pressure target value, The target value setter sets the pressure target value to the first pressure when the supply of the second steam is cut off, and after a time when the supply of the second steam is cut off, Accordingly, the pressure target value is reduced to a second pressure. A degassing system for a power plant in which the responsiveness of an opening degree is increased as the pressure target value increases. 9. The degassing system for a power plant according to claim 8, wherein the steam control valve controller determines the opening by performing a proportional operation, and the proportional band defining the proportional operation is the pressure target value. Degassing system for power plants that monotonically decreases in a broad sense. 10. The degassing system for a power plant according to claim 8, wherein the steam control valve control device is a PI controller, and a proportional band that regulates the operation of the PI controller is a pressure band relative to the pressure target value. Degassing system for power plants that monotonously decreases in a broad sense. 11. The deaerator for a power plant according to claim 8, wherein the target value setting device sets the deaerator pressure when the supply of the second steam is cut off as the first pressure, In addition, the deaeration system for a power plant, wherein the pressure target value is reduced from the first pressure to the second pressure at a constant decreasing rate after the pressure target value is set to the first pressure. 12. A steam control valve for supplying a first steam, wherein the first steam, a second steam supplied from a supply source different from the first steam, a second steam, and a condensate are supplied. And
A deaerator body for heating and degassing the condensed water by at least one of the first steam and the second steam, a steam control valve for supplying the deaerator body, and an inside of the deaerator body A pressure measuring device that measures a deaerator pressure that is a pressure of a target value setting device that determines a target value; and, based on a difference between the deaerator pressure and the pressure target value, the deaerator pressure is set to A steam control valve controller that controls an opening of the steam control valve so as to match a pressure target value, wherein the target value setter is configured to cut off the target value when the supply of the second steam is cut off. Is set to the first pressure, and after the time when the supply of the second steam is cut off, the pressure target value is reduced to the second pressure with the passage of time, and the steam control valve controller The opening degree is determined by integral control, and the proportional band defining the proportional integral control is the target band. A degassing system for power plants that monotonically decreases in a broad sense with respect to the value.