JP2000097403A - Control device for turbine driven feedwater pump - Google Patents

Abstract

(57) [Problem] To stabilize control when a turbine drive water supply pump is driven by using a sixth bleed air which is high-pressure steam of a power generation turbine. SOLUTION: When a boiler load exceeds a predetermined value, a turbine-driven water supply pump 14, 15 for supplying water to a boiler 11 is driven by low-pressure fifth bleeding, and when the boiler load falls below a predetermined value, by high-pressure sixth bleeding. When controlling the steam supply pressure to the turbine drive water supply pumps 14 and 15 by the control valves 28 and 29 based on the command, the control valve 17 is provided in the piping system of the sixth bleed air, and the control valve is used when the sixth bleed air is used. 17 is controlled according to the valve opening of the control valves 28 and 29.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a control device for a turbine-driven water supply pump for supplying water to a boiler by using steam extracted from a power generation turbine or a boiler in a thermal power plant as a drive source.

[0002]

2. Description of the Related Art In a thermal power generation facility, a steam generated by a boiler rotates a power generation turbine to drive a generator.
A circulation system is configured so that steam discharged from the turbine is condensed by cooling it with seawater or the like, and is further degassed and then supplied to the boiler again to generate steam. When supplying condensate water to the boiler, as a power source for the boiler feed pump,
The steam (hereinafter, referred to as bleed air) extracted from the power generation turbine is used. As the normally used bleed air, a fifth bleed air extracted from the low pressure side of the power generation turbine and a sixth bleed air extracted from the high pressure side are used. The first to fourth bleeds are for low-pressure heater condensate heating, and the seventh and eighth bleeds are for high-pressure heater feedwater heating. The above-described fifth bleed air is also used for the operation of the deaerator, and the sixth bleed air is used for the high-pressure heater water supply heating. The steam pressure is gradually increased from the first to the eighth bleeds. However, steam obtained directly from the boiler may be used as a power source of the boiler feed pump without using such bleed air.

FIG. 3 is a diagram schematically showing a boiler water supply system, in which steam generated in a boiler 11 drives a main turbine 12 to rotate a generator 13. The feed water sent from the deaerator is supplied to the boiler 11 by the turbine drive feed pumps 14 and 15 or the motor drive feed pump 16.

[0004] Two turbine driven feed pumps 14, 15
Is switched according to the boiler load (output power generation amount of the generator 13). Normally, when the load exceeds 2/4 load, the two turbine driven water supply pumps 14 and 15 are operated.
The turbine driven water supply pump 14 or 15 is operated, and since no driving steam is generated at the time of starting the boiler, the motor driven water supply pump 16 is used, and after the extracted steam is obtained, the turbine driven water supply pump 14 and / or 15 are driven. After the turbine drive water supply pump 14 and / or 15 has started to supply water stably, the motor drive water supply pump 16 is stopped.

[0005] When the boiler load exceeds 2/4 load, the amount of steam flowing into the main turbine 12 is large, and accordingly, a large amount of fifth bleed air is obtained. Since the fifth bleed air has a low pressure and is bleed from the latter stage of the main turbine 12, the bleed air contributes more to the power generation operation than the sixth bleed air, and is used for driving the turbine drive water supply pumps 14 and 15. It is reasonable to use.

When the boiler load is equal to or less than 2/4 load, the amount of steam flowing into the main turbine 12 is reduced, and the fifth bleed air is reduced accordingly.
Since the driving ability of the 15th bleeding is reduced, switching to the sixth bleeding is performed. Since the sixth bleed air is bled from a stage preceding the main turbine 12 than the fifth bleed air, the pressure is higher than the fifth bleed air.

Therefore, it is impossible to use the sixth bleed air without adjustment in the same manner as the fifth bleed air due to the restriction of the steam conditions at the inlet of the turbine drive feed pumps 14 and 15 (high pressure restriction). A control valve (PRV) 17 is attached to the steam piping system of the sixth bleed air, and the control valve 17 adjusts the pressure of the sixth bleed air to the same level as the pressure of the fifth bleed air (for example, to the average value of the pressure of the fifth bleed air). Then, the water is supplied to the turbine drive water supply pumps 14 and 15.

Here, the properties of the fifth bleed air and the sixth bleed air are summarized as follows. First, in the fifth bleed air, two turbine-driven water supply pumps 1 with a boiler load of 2/4 load or more were used.
4 and 15, and the bleed pressure changes proportionally to the change in boiler load. Therefore, the rotation speed of the turbine drive water supply pumps 14 and 15 also changes proportionally to the boiler load. There is a so-called self-control characteristic.

On the other hand, the sixth bleed air has the ability to drive one turbine-driven water supply pump when the boiler load is 2/4 load or less, and the bleed pressure changes proportionally with a change in the boiler load. For the above-mentioned reason, the control valve 17 is attached so as to control the inlet pressure of the turbine drive water pump to be constant. That is, the inlet pressure of the turbine drive water supply pump is detected by the pressure transmitter 18, and the difference between the detected value and the set value set by the setter 19 (the average value of the pressure of the fifth bleed air) is detected by the subtractor 20. Then, the control valve 17 is controlled by the proportional-integral controller 21 so that the inlet pressure becomes equal to the pressure set by the setter 19.
Therefore, the rotation speed of the turbine-driven water supply pump does not change in proportion to the change in the boiler load, but maintains a constant rotation speed, and there is no so-called self-control characteristic.

FIG. 4 is a diagram showing a conventional detailed control system of a turbine-driven water supply pump. The same components as those shown in FIG. 3 are denoted by the same reference numerals. 22 and 23 are check valves, 24
Is a pressure transmitter, 25 is an automatic boiler control (AB
C) The device. The automatic boiler control device 25 compares a water supply command (boiler load) required by the boiler with an actual water supply flow rate by a subtractor 26, and inputs a deviation thereof to a proportional-integral controller 27, which controls the control valve ( GOV) 28,
29 is controlled.

As described above, the turbine driven water supply pumps 14 and 15 are driven by the fifth bleed or the sixth bleed.
First, when the boiler load exceeds 2/4 load, the fifth bleed air extracted from the main turbine 12 is supplied to the control valves 28 and 29 via the check valve 22. At this time, the pressure P5 of the fifth bleed air detected by the pressure transmitter 24
In the case of P5> X (Kg / cm ² ) (X is a pressure indicating that the boiler load is 2/4 or more), the control valve 17 of the sixth bleed is interlocked by a system (not shown) and Since it is closed, the sixth bleed air is not supplied.

Therefore, the pressure control system of the sixth bleed air stops,
The pressure of the fifth bleed becomes a value proportional to the boiler load. That is, if the boiler load increases, the fuel supply amount and the air supply amount to the boiler increase by a system not shown, and the pressure P5
Rise, the rotation speeds of the turbine drive water supply pumps 14 and 15 increase, and the water supply flow rate increases. Further, if the boiler load decreases, the pressure P5 decreases and the turbine drive water supply pump 1
The number of rotations of 4, 15 decreases, and the flow rate of water supply decreases. That is, the turbine driven feed pump 1 is moved in the direction required by the boiler.
4 and 15 follow. From the above, the excess or deficiency due to this control need only be corrected by the control of the automatic boiler control device 25.
Air), and stable control characteristics can be obtained.

The control by the automatic boiler control device 25 is performed by controlling the control valves 28 and 29 based on the deviation between the feed water flow command and the actual feed water flow (see FIG. 5). That is, "water supply flow command value> actual water supply flow rate"
In this case, if the control valves 28 and 29 increase their opening degrees and the rotation speeds of the turbine drive water supply pumps 14 and 15 increase to increase the water supply flow rate, and if "water supply flow rate command value = actual water supply flow rate" is satisfied, control is performed. The system balances. Conversely, when "water supply flow rate command value <actual water supply flow rate", the control valves 28 and 29 decrease their opening degrees, the rotation speeds of the turbine drive water supply pumps 14 and 15 decrease, and the water supply flow rate decreases. The control system is balanced when “water supply flow command value = actual water supply flow rate” is satisfied.

Next, the pressure P5 obtained by the pressure transmitter 24 is P5 <Y (Kg / cm ² ) (where Y <X. X,
Y is determined by the hysteresis characteristic provided to the control system. )
, The fully closed interlock of the control valve 17 is released by a system (not shown), and the controller 21 controls the check valve 22,
Automatic control is started so that the outlet pressure at 23 becomes equal to the value set by the setting device 19. When the outlet pressure of the check valves 22 and 23 becomes equal to or higher than the pressure of the fifth bleed air, the check valve 22 is automatically closed, and the inflow of steam from the sixth bleed air to the fifth bleed air is prevented. Further, in the automatic boiler control device 25, the feed water flow command and the actual feed water flow are compared in the same manner as described above, and the control valves 28 and 29 are controlled based on the comparison result.

In the case of "water supply flow rate command> actual water supply flow rate", the valve openings of the control valves 28 and 29 are increased, whereby the check valve 2
The pressure at the outlet of the control valve 3 decreases with a slight delay, and this pressure drop is detected by the pressure transmitter 18 and the control valve 17
Is controlled to increase the valve opening. And this control valve 1
7, the turbine drive feed pump 1
The amount of steam flowing into the boilers 4 and 15 increases, and the feedwater flow rate further increases. The operation of the subtractor 26 of the automatic boiler control device 25 becomes “feedwater flow command <actual feedwater flow rate”, and the controller 27 controls the control valve 28. , 29 to reduce the valve opening. Due to the decrease in the valve opening of the control valves 28 and 29, the outlet pressure of the check valve 23 rises with a slight time delay.
Of the valve decreases. When the valve opening of the control valve 17 decreases, the amount of steam flowing into the turbine-driven water supply pumps 14 and 15 decreases, and the flow rate of the feedwater decreases further. Command> actual supply water flow rate ", and the controller 27 operates to increase the valve opening of the control valves 28 and 29.

As described above, at the time of the water supply control by the sixth bleed, the cycling operation (see FIG. 6) in which the control of the water supply flow rate is performed endlessly in an oscillating manner is performed.
The balance condition of "actual water supply flow rate" cannot be established. This is because the control valve 17 and the control valves 28 and 29 are independently controlled in series, and the control valve 17 and the control valves 28 and 29 are controlled independently.
Is small, the steam pipe in that portion does not work as a buffer, that is, the control operation is mutually interfered. In order to prevent this, the diameter and length of the steam pipe may be increased, but in this measure, the driving steam is cooled on the way and contains water droplets, and in the long term, these water droplets are used for the turbine drive water supply pump 14, It cannot be employed because it causes erosion (substantial damage) to the blades of the fifteen turbines.

Therefore, conventionally, in the boiler load zone in which the sixth bleed air is used, the gain of the controllers 21 and 27 is extremely reduced.

[0018]

However, in this measure, the rate of change in load operation of the thermal power plant must be reduced, which adversely affects emergency response, and of course, in the event of a stop accident. However, there is a problem that the load side (consumer) is disadvantageous and unnecessary energy is required for restart.

The present invention has been made in view of the above points, and an object thereof is to provide a turbine in which the supply water flow rate is controlled stably even when the sixth bleed air is used. An object of the present invention is to provide a control device for a driving water supply pump.

[0020]

According to a first aspect of the present invention, a turbine-driven water supply pump for supplying water to a boiler is driven by steam from the boiler when a boiler load exceeds a predetermined value. Performed by low-pressure steam extracted from the driven main turbine, performed by high-pressure steam extracted from the main turbine when the boiler load falls below a predetermined value, and according to the boiler load when using the low-pressure steam and the high-pressure steam. In a control device of a turbine drive water supply pump for controlling a steam supply pressure to the turbine drive water supply pump by a first control valve based on the supplied water supply command, a second control valve is provided in a piping system of the high pressure steam,
The second control valve is configured to be controlled according to the water supply command.

According to a second aspect of the present invention, in the first aspect, the second control valve is provided based on a deviation between a valve opening of the first control valve and a predetermined valve opening set value. It was configured to be controlled.

In a third aspect based on the first aspect, the second control valve is configured to determine a valve opening of the first control valve and a valve opening set value corresponding to a first stage steam pressure of the main turbine. It was configured to be controlled based on the deviation.

In a fourth aspect based on the second or third aspect, the signal of the valve opening degree of the first control valve is transmitted to the first control valve.
Of the control valve in and out of the control valve.

According to a fifth aspect, in the second to fourth aspects, the characteristic of the deviation is converted into a predetermined characteristic to control the second control valve.

[0025]

DESCRIPTION OF THE PREFERRED EMBODIMENTS [First Embodiment] FIG. 1 is a diagram showing a configuration of a control device for a turbine-driven water supply pump according to an embodiment of the present invention. The same components as those shown in FIG. 4 are denoted by the same reference numerals. 31 is a pressure transmitter for detecting the inlet pressure AP2 of the control valve 28 (first control valve);
Reference numeral 32 denotes a pressure transmitter for detecting a first-stage pressure AP1 of the turbine 14A of the turbine drive water supply pump 14, and reference numeral 33 denotes a ratio AP of pressures detected by the two pressure transmitters 31, 32.
This is a divider that calculates 1 / AP2 to obtain a valve opening signal of the control valve 28. 34 is a pressure transmitter for detecting the pressure BP2 on the inlet side of the control valve 29 (first control valve), and 35 is the first stage pressure BP1 of the turbine 15A of the turbine drive water supply pump 15.
Is a divider for calculating the ratio BP1 / BP2 of the pressure detected by the two pressure transmitters 34 and 35 to obtain a valve opening signal of the control valve 29.

Reference numeral 37 denotes an average calculator for calculating the average of the operation results of the dividers 33 and 36, and reference numeral 38 denotes a divider for the dividers 33 and 36.
And a switch for selecting one from each calculation result of the average calculator 37. 39 is the first stage pressure P of the main turbine 12
A function calculator for calculating a required valve opening with 1 (representing a boiler load) as a parameter. A valve opening setting signal obtained from the function calculator 39 and a valve opening output from the switch 38 This is a subtractor that detects a deviation of an actual signal. 41
Is a dead band setting device for converting the characteristic of the deviation outputted from the subtractor 40.
Is input to the controller 21 that controls the control valve 17 (second control valve). Reference numeral 42 denotes a water supply pump number switching device, which sends a gain setting signal from the gain setting device 43 for one water supply pump or the gain setting device 44 for two water supply pumps to the controller 21.

Next, the operation will be described. The operation when the boiler load exceeds 2/4 load is the same as the case described in the conventional example, and thus the description is omitted here.

When the boiler load is 2/4 load or less, the pressure P5 of the fifth bleed air detected by the pressure transmitter 24 becomes P5.
When 5 <Y (Kg / cm ² ), the fully closed interlock of the control valve 17 is released, and the controller 21 determines that the opening degree of the control valves 28 and 29 is equal to the first stage steam pressure P1 of the main turbine 12. Is started so as to match the valve opening set value generated by the function calculator 39 based on When the outlet pressure of the check valves 22 and 23 becomes equal to or higher than the fifth bleed pressure P5, the check valve 22 on the fifth bleed side automatically closes, and the inflow of steam from the sixth bleed to the fifth bleed is prevented. You.

The most important point of the present invention is the content of the control of the control valve 17, which will be described in detail. As described above, the signal AP1 / AP2 obtained by the divider 33 is the valve opening signal of the control valve 28, and the signal BP obtained by the divider 36
Since 1 / BP2 is the valve opening signal of the control valve 29, when the two turbine drive water supply pumps 14 and 15 are operating, the output signal of the average calculator 37 is selected by the switch 38 and subtracted. The deviation is compared with the valve opening set value in the device 40 and the deviation is sent to the dead band setting device 41.

The dead band setting device 41 has a function of converting the magnitude of the deviation signal. If the dead band setting value is increased, the deviation smaller than a predetermined value is cut and is not sent to the controller 21. Conversely, the dead band setting value is set to 0
Then, the deviation is sent to the controller 21 without being cut. The dead band setting device 41 is effective for preventing the useless operation of the control valve 17 and performing a reasonable valve opening operation when adjusting the present control system in an actual plant.

In the above, the signal of “command value of feedwater flow rate> actual feedwater flow rate” is output from the subtractor 2 by the automatic boiler controller 25.
6, the controller 27 operates to increase the valve opening of the control valves 28 and 29 in response to the deviation obtained therefrom. As a result, AP1 / AP2, BP1 / B
The value of P2 increases, and the average value also increases. In the subtractor 40, “valve actual opening> valve opening setting value” is calculated, and the deviation is sent to the dead band setting device 41. Therefore,
When the deviation is larger than the dead band set value, the controller 21 controls the control valve 17 to increase the valve opening. The gain of the controller 17 at this time is
The switch 42 has selected the gain setting unit 44 for two pumps.

The operation from the control of the control valves 28 and 29 by the control command from the automatic boiler control device 25 to the control of the control valve 17 according to the control result is as follows.
It is performed almost simultaneously with little time delay. Therefore, the conventional cycling phenomenon is avoided. That is, in the case of “water supply flow rate command> actual water supply flow rate” or vice versa, the control valves 28 and 29 and the control valve 17 are controlled almost simultaneously in the same direction. Can be realized in a short time, and the load change rate is not limited, and almost ideal stable operation can be performed. This is because the control valves 28 and 29 do not move and the control valve 17 does not move unless the boiler load changes. From the above, a so-called self-control characteristic can be realized.

When only one turbine drive feed pump is operating, the output signal of the divider 33 or 36 on the side of the operating turbine drive feed pump 14 or 15 is selected by the switch 38. The signal is sent to the subtractor 40, and the gain setting device 43 for one pump is selected by the switching device 42, and the gain for one device is set in the controller 21.

[Other Embodiments] In the above embodiment, the valve opening set value to be set in the subtractor 40 is obtained by performing a function operation on the first-stage pressure P1 of the main turbine. May be fixed to a constant value. At this time, if the characteristic conversion by the dead band setting device 41 is ignored, the valve opening of the control valve 17 is controlled almost completely in proportion to the valve opening of the control valves 28 and 29. That is, the control valve 2
If 8, 29 does not move, the control valve 17 does not move even if the boiler load changes.

In the present embodiment, the control valves 28, 2
Since the valve opening signal of No. 9 is obtained by calculation by comparing the input and output pressures, an effective valve opening can be obtained, and there is an advantage that it is not affected by the characteristics of the control valves 28 and 29. There are pressure transmitters 31, 32, 3
Since the pressures are measured and processed at 4, 35, there is a problem that there is a slight time delay and the cost is high.

To solve this problem, the control valve 28,
It is sufficient to use a valve lift signal indicating the actual valve opening degree of 29 (a movement amount signal of a lever of a cam mechanism for controlling the opening / closing degree of the valve) or an output signal of the controller 27. The advantages and disadvantages in this case are the above-mentioned inside out.

Further, in the above embodiment, two turbine-driven water supply pumps are provided as indicated by reference numerals 14 and 15, and control valves 28 and 29 are respectively associated therewith to perform pressure control according to the water supply flow rate command. Since the sixth bleed air supplied thereto is controlled by one control valve 17, both control valves 28, 29
Are operated at the same time, the average value of the valve opening signals is obtained and the valve opening of the control valve 17 is controlled in accordance with the average value. The control may be performed by providing a control valve (corresponding to the control valve 17) and a control valve (control valves 28 and 29) for controlling the sixth bleed air.

Although the above description has been made of the case where the present invention is applied to the water supply system of a thermal power generation facility, the present invention can be similarly applied to other facilities in which a main turbine is driven by steam generated by a boiler to perform desired work. Of course.

[0039]

As described above, according to the first aspect, even when the turbine-driven water supply pump is driven by using the high-pressure steam extracted from the main turbine as in the sixth bleed,
The rotation speed of the turbine-driven water supply pump is controlled stably in accordance with the water supply request, and so-called self-control characteristics are obtained.

According to the second aspect of the present invention, the control of the second control valve is performed in accordance with only the flow rate of the supplied water, similarly to the first control valve.

According to the third aspect of the invention, the control of the second control valve according to the valve opening of the first control valve is further added to the control of the first stage steam pressure of the main turbine. Finer control is performed.

According to the fourth aspect, the signal of the valve opening of the first control valve can be obtained as an effective signal without being affected by the input / output characteristics of the first control valve. Control.

According to the fifth aspect, the second control valve is controlled after the signal for controlling the second control valve is converted into a signal having a predetermined characteristic. There is an advantage that it is easy to make a local or on-site adjustment.

[Brief description of the drawings]

FIG. 1 is a diagram showing a control system of a turbine-driven water supply pump according to a first embodiment of the present invention.

FIG. 2 is a control characteristic diagram at the time of using a sixth bleed air of the embodiment.

FIG. 3 is a diagram showing a schematic configuration of a conventional turbine power generation system.

FIG. 4 is a diagram showing a control system of a conventional turbine-driven water supply pump.

FIG. 5 is a control characteristic diagram when a conventional fifth bleed air is used.

FIG. 6 is a control characteristic diagram when a conventional sixth bleed air is used.

[Description of Signs] 11: Boiler, 12: Main turbine, 13: Generator,
14, 15: turbine driven feed pump, 16: electric motor driven feed pump, 17: control valve, 18: pressure transmitter, 19: setter, 20: subtractor, 21: proportional differential controller, 22, 23: check valve , 24: pressure transmitter,
25: automatic boiler control device, 26: subtractor, 27: proportional differential controller, 28, 29: control valve, 31, 32: pressure transmitter, 33: divider, 34, 35: pressure transmitter, 36: division Device, 37: average calculator, 38: switcher, 39: function calculator, 40: subtractor, 41: dead band setting device, 42: switcher, 43: gain setting device for one pump, 44: pump 2 Table gain setting device.

Claims (5)

[Claims] A turbine-driven water supply pump for supplying water to a boiler is driven by low-pressure steam extracted from a main turbine driven by steam from the boiler when the boiler load exceeds a predetermined value. When the pressure is lower than the predetermined value, the steam supply pressure to the turbine-driven water supply pump is adjusted based on a water supply command corresponding to the boiler load when the low-pressure steam and the high-pressure steam are used. A control device for a turbine-driven water supply pump controlled by a control valve according to claim 2, wherein a second control valve is provided in a piping system of the high-pressure steam,
A control device for a turbine-driven water supply pump, wherein the control valve is controlled according to the water supply command. 2. The apparatus according to claim 1, wherein said second control valve is controlled based on a deviation between a valve opening of said first control valve and a preset valve opening set value. Claim 1
3. The control device for a turbine-driven water supply pump according to claim 1. 3. The control apparatus according to claim 2, wherein the second control valve is controlled based on a deviation between a valve opening of the first control valve and a valve opening set value corresponding to a first stage pressure of a main turbine. The control device for a turbine-driven water supply pump according to claim 1, wherein: 4. A signal of the opening degree of the first control valve,
The control device for a turbine-driven water supply pump according to claim 2, wherein the control value is obtained by a ratio of an inlet pressure and an outlet pressure of the first control valve. 5. The control device for a turbine-driven water supply pump according to claim 2, wherein the characteristic of the deviation is converted into a predetermined characteristic to control the second control valve. .