JP2708271B2 - Auxiliary steam pressure control device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Object of the Invention (Industrial Application Field) The present invention relates to an auxiliary steam pressure control for preventing a pressure drop of an auxiliary steam header common to units provided in a combined cycle power plant. Related to the device.

(Prior Art) FIG. 6 shows a general system diagram of a combined cycle power plant having an auxiliary steam header common to the above units.

That is, the exhaust gas energy of the gas turbine 1 is introduced into the exhaust heat recovery boiler 3 through the exhaust gas pipe 2, and the low-, medium-, and high-pressure economizer, evaporator, and superheater installed in the exhaust heat recovery boiler 3 (see FIG. (Not shown) and a low-pressure / medium-pressure / high-pressure drum 4 and a low-pressure steam 5, a medium-pressure steam 6 and a high-pressure steam 7, respectively.
Is guided to the steam turbine 8. The steam that has finished its work in the steam turbine 8 is condensed in the condenser 9, pressurized by the water supply pump 10, and circulated again to the exhaust heat recovery boiler 3.

In the above cycle, the auxiliary steam pipe 12 is drawn out of the middle pressure steam 6 and the high pressure steam turbine exhaust reheat 11 guided from the exhaust heat recovery boiler 3 to the steam turbine 8, and the steam flow rate is controlled by the auxiliary steam pressure control valve 13. The steam is supplied to the auxiliary steam header 14 while being controlled.

The auxiliary steam pressure control valve 13 detects the secondary pressure, that is, the pressure in the middle of the auxiliary steam supply pipe 15 from the control valve 13,
The signal is converted by an auxiliary steam pressure transmitter 16 and guided to an auxiliary steam pressure controller 17, where it is compared with a set value and controlled.

The auxiliary steam header 14 is connected to another axis control device and an axis auxiliary steam supply line 18 configured in the same manner as described above in all other plant shafts, so as to mutually supply and receive auxiliary steam. ing.

In FIG. 6, the start-up state of the plant shafts from the gas turbine 1 to the exhaust heat recovery boiler 3, the steam turbine 8, the condenser 9, the water supply pump 10, and the auxiliary steam pipe 12 will be described.

When the plant shaft starts to start, the amount of auxiliary steam is
Auxiliary steam supply line connected to auxiliary steam header 14
Auxiliary steam is supplied from 19 (when the auxiliary steam temperature of the auxiliary steam header 14 is high, a temperature reducer may be provided to reach an optimum temperature, but not shown here).

Here, a large amount of the auxiliary steam is used for steam turbine gland seals, condensate (feed water) deaeration, and gas turbine start-up acceleration.

However, the plant shaft itself does not have sufficient auxiliary steam supply conditions because of the start-up process, so that replenishment from another plant shaft is required, and auxiliary steam must be introduced from the auxiliary steam header 14.

Here, a large amount of auxiliary steam is temporarily
If it is further extracted, the pressure of the auxiliary steam header 14 decreases for the following reasons, and the required flow rate cannot be secured.
That is, the auxiliary steam header 14 is not a large-capacity tank but a pipe, and as soon as a large amount of auxiliary steam flows out, the accumulated steam amount decreases immediately, resulting in a decrease in pressure.

The auxiliary steam control device 16 connected to the auxiliary steam control line and the auxiliary steam supply line 18 connected to the auxiliary steam header 14 is installed on the secondary side of the auxiliary steam pressure regulating valve 13, and through a long pipe, the auxiliary steam pressure Connected to header 14. Therefore, the pressure of each plant shaft decreases after a delay after the pressure of the auxiliary steam header 14 decreases. This cannot be prevented as a physical phenomenon because the vapor is a compressible fluid.

The actual operation of the power generation plant is as follows. Due to a decrease in power demand on the weekend, the stopped power generation plants are started up one after another on the early morning of Monday, and each plant axis of the combined power generation plant is also started up one after another. Therefore, it is important to secure the auxiliary steam pressure at this time.

An example of a state when the auxiliary steam pressure cannot be secured will be described with reference to FIG.

FIG. 1A shows a plant axis (hereinafter, referred to as a No. 1 axis) that has completed startup and is performing a load (power generation) operation.
The consumption of auxiliary steam is essentially zero. However, in this case, a part of the steam generated by the plant shaft operation is supplied to the auxiliary steam header 14 via the other shaft control device and the auxiliary steam supply line 18, so that the supply water corresponding to the amount is supplied. Must. Since the quality of this makeup water contains a large amount of gas harmful to plant equipment, it must be degassed by steam heating. Auxiliary steam is used for this steam heating.Even if the auxiliary shaft is supplied to other shafts, even if it is a plant shaft that generates rated power, it is necessary to use auxiliary steam for deaeration of makeup water. Become.

FIG. 2B shows a plant shaft (same as NO. 2 shaft) after the completion of gas turbine acceleration. This shaft circulates through steam for a steam turbine grant seal and inside the own plant shaft. Auxiliary steam, which is the sum of the condensate (supply water) and the steam for heating and degassing, is required.

FIG. 3C shows the plant axis (also the NO. 3 axis) at the start of the gas turbine acceleration.
In addition to the amount of auxiliary steam on the shaft (for steam turbine gland seal and condensate (water supply) deaeration), auxiliary steam for gas turbine start-up and acceleration is required.

In the above example, each problem when the auxiliary steam is not sufficiently supplied will be described below.

In other words, for the No. 1 shaft, make-up water supplied from the make-up water system is not sufficiently degassed, resulting in deterioration of water quality. In the worst case, damage to equipment and contamination of the tubes of the heat exchanger cause a decrease in plant efficiency. Flourish.

For the NO.2 axis, the start-up schedule is extended until the condensate (water supply) deaeration time is extended to the specified value or less during the plant axis activation process. Further, with respect to the steam turbine gland seal, if the pressure becomes insufficient, the air may be sucked in and the vacuum of the condenser may be reduced, which also significantly delays the start-up schedule.

The shaft No. 3 has the same steam turbine gland seal and make-up water deaeration as the shaft No. 2, but other than that, the gas turbine cannot be started or accelerated, or the start-up schedule is greatly delayed. I have to.

(Problems to be Solved by the Invention) As described above, at present, the following problems remain in the conventional general auxiliary steam pressure control device.

That is, when a plurality of plant shafts are connected to an auxiliary steam header common to one unit, and supply and reception of the auxiliary steam are mutually performed via the auxiliary steam header, each of the auxiliary steam pressure control devices has a single loop. In order to detect pressure at a position distant from the auxiliary steam header without being related to each other, a pressure drop is detected later than a change in the pressure of the auxiliary steam header. Accelerated.

In other words, when the auxiliary steam is rapidly consumed in any of the plurality of shafts, the pressure of the auxiliary steam header drops rapidly, but the auxiliary steam pressure control device of each plant axis detects the pressure drop later than this pressure drop. Therefore, the pressure drop of the auxiliary steam header is rapidly accelerated.

For this reason, the start-up schedule of the plant has been greatly delayed, such as abnormal reduction of the pressure of the steam turbine gland seal, deterioration of the water quality of the plant, and inability to start up the gas turbine.

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and an object of the present invention is to provide a unit capable of performing stable control by minimizing a pressure drop of an auxiliary steam header common to units.

[Configuration of the invention]

(Means for Solving the Problems) An auxiliary steam pressure control device according to the present invention includes an auxiliary steam header common to units in a combined cycle power plant, an auxiliary steam pressure transmitter, a pressure regulator, and a pressure regulator for each axis. And an auxiliary steam pressure control device provided with a valve. The auxiliary steam pressure control device predicts the auxiliary steam consumption from the auxiliary steam header, and calculates the auxiliary steam consumption and the supplyable steam amount for each axis, thereby supporting the plant axis that can be supplied. An auxiliary steam general control unit that operates the steam pressure control valve in advance, each priority unit provided for each axis from the auxiliary steam pressure controller to the same pressure control valve and the auxiliary steam general control device, Are connected.

Further, an accumulator connected to the high-pressure steam system of each shaft in common with the unit is provided, the accumulator is connected to the auxiliary steam header, and a pressure control valve is interposed between the accumulator and the pressure control valve to control the pressure control valve. A priority device connected to the auxiliary steam control section may be attached to the meter.

(Operation) According to the present invention configured as described above, the auxiliary steam consumption from the auxiliary steam header is predicted, and the steam consumption and the supplyable steam amount for each axis are calculated, so that the supply of the plant shaft that can be supplied is performed. The auxiliary steam pressure regulating valve can be operated in advance, thereby minimizing the pressure drop of the auxiliary steam header.

Further, it is possible to provide a backup when the pressure of the auxiliary steam header rapidly decreases through the high-pressure steam accumulator.

(Embodiment) An embodiment of the present invention will be described below with reference to FIGS. 1 to 3. The same parts as those in the conventional example shown in FIG. 6 are denoted by the same reference numerals and description thereof is omitted. I do.

In FIG. 1, each plant shaft power generation amount load signal 20, each shaft auxiliary steam pressure signal 21, each shaft auxiliary steam flow transmitter signal 2
2.Auxiliary steam header pressure signal 23, auxiliary steam flow rate for each shaft 24, degassing steam control signal 25, gas turbine startup speed-up steam control valve signal 26, steam turbine / gland seal control valve signal 27, and auxiliary boiler steam flow signal 28 Is input to the auxiliary steam general control device 29.

An output signal 30, which is a calculation signal from the auxiliary miscellaneous tree control device 29, is sent to a priority unit 31 provided on an output line of an auxiliary steam pressure controller 17 of each plant axis and to an output line of an auxiliary boiler generated steam flow controller. The data is input to the provided priority units (not shown).

 FIG. 2 shows the configuration of the auxiliary steam general control device 29.

 First, the amount of generated steam for each plant axis is calculated.

That is, high-pressure steam has a main steam flow rate 32 and a main steam turbine bypass flow rate 33, medium-pressure steam has a medium-pressure steam flow rate 34 and a medium-pressure steam turbine bypass flow rate 35, and low-pressure steam has a low-pressure steam flow rate 36. The low-pressure steam turbine bypass flow rate 37 is calculated and obtained by the regulators 38, 39, and 40, respectively, and the power generation load for each plant axis is predicted by taking into account the power generation load coefficient 41.

Here, an actual power generation amount load signal 20 is derived, and a surplus amount of generated steam is quantitatively calculated by comparing with a predicted steam value.

Since the auxiliary steam in the embodiment is medium-pressure steam, as shown in FIG. 3 (a), the medium-pressure steam flow rate is added to the medium-pressure turbine bypass flow rate, and the expected power generation load B is obtained by the coefficient α. And the actual power generation load A.

Thereby, when the value of the difference C (= A−B) is positive, there is no spare steam supply, and when the value of C is negative,
It is determined that there is enough power to supply the auxiliary steam, and the C value is input from the power generation load function 42 to the axis-specific auxiliary steam consumption calculator 43 and the auxiliary steam flow rate calculator 44 as ± judgment.

Next, as shown in FIG. 3 (b), the auxiliary steam flow rate calculator 44 calculates the total amount of auxiliary steam consumption and its contents, the remaining power (Z value) of this axis, and the amount of medium-pressure steam generation. In the embodiment, X = self-axis auxiliary steam supply capacity (remainder), and the contents thereof are the above-mentioned ± AB determination of AB = C and the above-mentioned auxiliary supply amount 45 from another axis.

On the other hand, the contents of the auxiliary steam consumption amount Y consumed by the own shaft are obtained by inputting the auxiliary steam supply amount WAS to the other shaft and the output signal 46 of the steam turbine / gland seal pressure controller to the steam flow function 47. Shaft steam turbine / Grand seal steam volume Fx
1.Axial make-up water flow 48 and degassing steam pressure controller output signal 4
9 is input to a steam flow function 51 having a deaeration temperature target 50, and the deaerated steam amount Fx2 obtained by inputting the gas turbine speed 52 to the steam flow function 53 obtained by inputting the gas turbine speed 52 to the steam flow function 53. This is the sum of the make-up steam flow rate Fx3 and the make-up water flow rate gas turbine startup.

From this, (X-Y) of the own axis is always used as the auxiliary steam flow rate calculation unit.
The calculation is performed at 44, and the supply capacity (remainder) Z (= XY) is quantitatively output.

The supply, reception and consumption of auxiliary steam for each plant axis
The value constantly calculated and output as described above is obtained by guiding the value to the auxiliary steam distribution calculation 55 provided in the next unit auxiliary steam distribution unit 54, and the optimum auxiliary steam distribution at the unit level is obtained. Be instructed.

In other words, in a unit composed of a plurality of axes,
The supply capacity Z output in FIG. 2B is the first axis Z1 and the second axis Z1.
Z2 and the third axis Z3 are input to the auxiliary steam distribution calculation 55, and the supply and reception of the auxiliary steam as the whole unit are grasped. In addition to this, the steam flow rate 56 of the auxiliary boiler provided for each unit is added.

On the other hand, the auxiliary steam consumption target value for each plant axis is
The value output in the auxiliary steam consumption calculation 43 for each axis is introduced.

As described above, the auxiliary steam consuming side is also quantitatively calculated by introducing the operation mode of each plant axis.

Specifically, it is configured as shown in FIG. 3 (c), and the unit-unit auxiliary steam distributor 5 shown here is shown.
4. The auxiliary steam distribution calculation 55 and the auxiliary steam consumption calculation 43 for each axis will be described.

The signals Z (Z1 to Z4) calculated and output by the auxiliary steam flow calculation unit 44 described with reference to FIG. 3B are input to the auxiliary steam distribution calculation 55 on all axes, and the auxiliary boiler steam flow 56 is input. As a result, total auxiliary steam supply as a unit unit,
The amount received becomes clear.

On the other hand, by introducing the operation mode 57 of each plant axis, the supply and reception of the auxiliary steam at the present time are clarified more, and by introducing the operation schedule in the future, the auxiliary steam in the future is introduced. The accuracy of supply and receiving forecasts has been improved to stabilize auxiliary steam as a whole unit.

Typical patterns of the operation mode 57 are shown in FIGS.
As shown in (c), the consumption amount of the auxiliary steam changes with the elapse of the operation schedule.

According to the present embodiment, the operation mode for each axis of the steam plant is introduced as the operation mode 57 in the auxiliary steam consumption calculation for each axis 43 shown in FIG. (However, a plant axis that is not generating power has a zero signal.)
Is input, and the result of reconfirmation of the operation mode is output to the auxiliary steam distribution calculation 55.

In this way, a bar graph for each plant axis shown in the unit auxiliary steam distribution section 54 of FIG. 3 (c) is drawn, so that the current supply and reception of the auxiliary steam can be visually checked, and the supply capacity to other axes can be improved. A certain plant axis receives a signal output from the unit-unit auxiliary steam distribution unit 54 (for each plant axis, not shown) from a steam auxiliary header pressure transmitter 58 via an auxiliary steam pressure change rate calculation 59 to output the auxiliary steam pressure When the header pressure drop speed is high, the auxiliary steam pressure control valve of the plant shaft having sufficient supply capacity can be rapidly opened in order to moderate the pressure drop.

In addition, an auxiliary steam pressure signal 21 (auxiliary steam pressure transmitter) of its own axis is also introduced, and when the supply pressure is equal to or lower than a set value, an operation of opening an auxiliary steam pressure control valve to increase the pressure is also added. .

The output signal 30 after these calculations is applied to the priority unit 31 shown in FIG.

The priority unit 31 is incorporated in an auxiliary steam pressure control system provided for each plant axis. That is, the auxiliary steam pressure (supply line to the unit common auxiliary steam) of each plant shaft is
As shown in FIG. 1, the auxiliary steam pressure is detected by an auxiliary steam pressure transmitter 16 installed between the auxiliary steam pressure control valve 13 and the auxiliary steam header 14, and is compared with a set value by an auxiliary steam pressure controller 17 (shown in FIG. 1). Normally, this signal is directly sent to the auxiliary steam pressure control valve 13, but in this embodiment, the priority
31 is provided to enable the distribution of auxiliary steam as a whole unit.

 Next, a specific operation of the above embodiment will be described.

a) Based on the power generation load signal 20 of each plant shaft, the amount of auxiliary steam consumed between the start-up process and the rated load is predicted and calculated for each shaft and each unit.

b) Based on the power generation amount load signal 20 of each plant shaft, the amount of auxiliary steam that can be supplied between the start-up process and the rated load is predicted and calculated for each shaft.

c) Auxiliary steam pressure and flow rate (supply and receive) and prediction calculation for each plant axis Judgment of the steam condition on the own axis from the ministry (whether the auxiliary steam can be supplied from the own axis or not, It is necessary to supply auxiliary steam from other shafts or from other shafts, but the quantity value is some).

d) The amount of steam for deaeration of each plant shaft is estimated and calculated from the output signal of the flow meter, the deaeration flow controller or the opening of the deaeration flow control valve.

e) The steam amount for the steam turbine / gland seal of each plant shaft is estimated and calculated from the output signal of the flow meter and the seal pressure controller or the opening of the seal pressure control valve.

f) The amount of steam for deaeration of each plant shaft can be predicted and calculated from the flow rate and temperature of make-up water supplied to the condenser of the own shaft.

g) Based on the steam generation amount and the power generation load amount of each plant shaft and the auxiliary steam amount supplied from the own shaft, a reduction value of the power generation load of the own shaft is predicted and calculated.

h) From the results of a) to g) above, if auxiliary steam can be supplied from another plant axis, the shortage of the own axis is predicted and calculated, and the supplementable other axis and the supply flow distribution amount for each axis are determined. The prediction calculation is performed, and the auxiliary steam pressure control valve 13 of the other axis is opened in advance to supply the auxiliary steam to the auxiliary steam header 14.

i) In addition, the pressure and the pressure drop rate of the auxiliary steam header 14 are constantly monitored and calculated, and when the pressure drops below the set pressure, and when the drop rate below the set pressure becomes a specified value or more, from among a plurality of axes, Auxiliary steam pressure control valve 13 in axial order of supply surplus
Is operated to supply steam to the auxiliary steam header 14.

j) In the shaft for supplying the auxiliary steam, make-up water corresponding to the amount is supplied, and the amount of auxiliary steam for deaeration is predicted and calculated according to the amount of the make-up water, and is taken in from the auxiliary steam header. In this case also, the axial order of the supply surplus power is used.

k) In the above h) to j), when there is no surplus supply of auxiliary steam, the auxiliary boiler is instructed to replenish and distribute. If the auxiliary boiler cannot be supplied, a reduction in the amount of power generation corresponding to the auxiliary withdrawal amount is predicted and calculated for each plant axis to prevent confusion at the power supply command center.

 Another embodiment will be described with reference to FIG.

The auxiliary steam header 14 common to the shafts is provided with a pressure control valve 60 and an accumulator 61, and the accumulator 61 is connected to high-pressure steam 7, 7 'of each shaft.

The accumulator 61 is connected to the common shaft auxiliary header 14 via the pressure control valve 60. The pressure control valve 60 is provided with a pressure controller 62. When the pressure of the shaft common auxiliary steam header 14 falls below a certain value and the supply of auxiliary steam to other plant shafts is insufficient, the pressure does not recover. It has been made to work as a backup.

Therefore, if the pressure set value of the normal auxiliary steam header 14 is 20 kg / cm ² g, for example, the set pressure value is (20−α) k
g / cm ² g.

When this line operates, the signal from the auxiliary steam general control device 29 is given priority
And the auxiliary steam supply amount is insufficient for each unit. In this case, the pressure regulating valve 50 of this line is opened to supplement auxiliary steam.

The normal auxiliary steam supply for each plant shaft is medium-pressure steam 6, but the steam supplied to the accumulator 61 is high-pressure steam 7. Therefore, when the plant shaft is stopped or when the high-pressure steam is not rising sufficiently, the check valve 64
By closing the motor-operated valve 65, the backflow of steam is prevented.

In the case of this embodiment, before the power generation amount decreases in the above K), the accumulator steam supply pressure control valve 60 is opened,
The pressure drop of the auxiliary steam header 14 can be prevented.

〔The invention's effect〕

As described above, according to the present invention, it is possible to minimize the pressure drop of the auxiliary steam header generated by temporarily consuming a large amount of auxiliary steam in the common auxiliary steam unit (unit unit), and to achieve a stable auxiliary steam. There is an effect that header pressure can be obtained.

[Brief description of the drawings]

FIG. 1 is a system diagram showing one embodiment of the present invention, FIG. 2 is a configuration diagram of an auxiliary steam general control device, FIG. 3 (a) is a configuration diagram of an auxiliary steam supply surplus presence / absence calculation unit, FIG. b) is a configuration diagram of an auxiliary steam distribution amount calculation unit, FIG. 4C is a configuration diagram of an auxiliary steam supply / reception calculation unit and a monitoring unit, FIG. 4 is a system diagram showing another embodiment, and FIG. a), (b), and (c) are graphs showing auxiliary steam consumption curves for each operation mode in each plant axis, and FIG. 6 is a system diagram showing a conventional example. 1 ... gas turbine, 3 ... waste heat recovery boiler, 8 ... steam turbine, 12 ... auxiliary steam pipe, 13 ... auxiliary steam pressure control valve, 14 ... auxiliary steam header, 16 ... auxiliary steam pressure transmission , 17 …… Auxiliary steam pressure controller, 18 …… Other axis control device and auxiliary steam supply line, 19 …… Auxiliary steam receiving line, 29
…… Auxiliary steam controller, 31,63 …… Priority unit, 41 ……
Power generation load coefficient, 42: Generator load function, 43: Auxiliary steam consumption calculation by axis, 44: Auxiliary steam flow calculation unit, 54: Unit auxiliary steam distribution unit, 55: Auxiliary steam distribution calculation,
60: Pressure control valve, 61: Accumulator, 62: Pressure controller.

Claims (2)

(57) [Claims] 1. An auxiliary steam pressure control device comprising an auxiliary steam header common to units in a combined cycle power plant, and an auxiliary steam pressure transmitter, a pressure regulator, and a pressure control valve for each shaft, Auxiliary steam general control unit that predicts the amount of auxiliary steam consumed from the header, calculates the amount of auxiliary steam consumed and the amount of steam that can be supplied for each axis, and preliminarily operates the auxiliary steam pressure control valve of the plant axis that can be supplied. And an auxiliary steam pressure control device, wherein each priority unit provided between the auxiliary steam pressure controller and the pressure control valve for each axis is connected to the auxiliary steam general control device. 2. An accumulator connected to the high-pressure steam system of each shaft in common with the unit, the accumulator and the auxiliary steam header being connected, and a pressure control valve interposed therebetween to control the pressure control valve. 2. The auxiliary steam pressure control device according to claim 1, wherein a priority device connected to the auxiliary steam general control unit is attached to the pressure controller to be controlled.