JPS5944509B2 - How to operate a water pump - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method of operating a water supply pump, and in particular to a method for automatically operating a water supply pump that supplies water to a steam generator in a power generation facility, etc. by switching from an electric motor-driven water supply pump to a turbine-driven water pump using generated steam. This invention relates to a control method for transitioning to a state.

Generally, as a water supply device to a boiler in power plant equipment, etc., a motor-driven water supply pump and a turbine-driven water supply pump are installed in parallel, and at the beginning of startup, water is supplied by the motor-driven water supply pump in automatic operation.
When it becomes necessary to supply water at or above the rated flow rate of the motor-driven water supply pump (equivalent to 25% of the water supply flow rate at normal rated output), the turbine-driven water supply pump is started and the main water supply flow rate is controlled by this pump. It has increased.

In other words, FIG. 1 is a schematic system diagram of power plant equipment, in which steam generated in a steam generator 1 is sent to a high pressure turbine 2, an intermediate pressure turbine 3, and a low pressure turbine 4.
After each work is done, the water is condensed in the condenser 5,
The water is sent to a deaerator 10 via a condensate pump 6, a desalination device 7, a condensate booster pump 8, and a low-pressure feed water heater 9.

The feed water deaerated in the deaerator 10 is transferred to the motor-driven feed water pump 11a1 or the turbine-driven feed water pumps 11b, 1 connected to the deaerator 10 and connected in parallel with each other.
1c to the high-pressure feedwater heater 12, and further returned to the steam generator 1.

Therefore, as mentioned above, if the amount of water supplied by the motor-driven water supply pump 11a becomes insufficient, first, the turbine-driven water supply pump 11b, which has a water supply capacity of 50% of the normal rated power generation, is used. Automatic operation switching is performed.

In this case, it is necessary to suppress fluctuations in the flow rate of the main water supplied to the steam generator 11 without causing any disturbance as much as possible.

Therefore, as the turbine-driven water supply pump 11b is started and the water supply flow rate increases, the water supply flow rate of the motor-driven water supply pump 11a decreases in an attempt to keep the main water supply constant.
Automatic operation switching is performed when the ratio of water supplied by the motor-driven water supply pump 11a and the turbine-driven water supply pump 11b reaches a predetermined value.

However, in the current operation of power generation equipment, automatic operation switching is performed when the flow rate is equivalent to 25% of the unit rating based on the rated capacity of the motor-driven water supply pump, which causes the following problems.

That is, as shown in FIG. 1, a motor-driven water supply pump 11a1 and a turbine-driven water supply pump 11b.

Minimum flow valves 13a and 13b forming a recirculation system on the pump outlet side, respectively, are provided at 11c.

13c is provided so that the pump can be operated independently without supplying water to the steam generator 1.

These minimum flow valves 13a to 13c are automatically fully closed when the pump inlet water supply flow rate increases to a specified value, and conversely, the inlet water supply flow rate decreases and is set to the specified value (a value ζ smaller than the fully closed specified value). The mechanism is such that it automatically opens fully when the temperature drops below (1).

Therefore, the turbine-driven water supply pump 11b is started to gradually increase the water supply flow rate, and when the flow rate exceeds the pump's artificial water supply flow rate regulation value, the minimum flow valve 13
b is fully closed, and the flow rate of the feed water flowing into the recirculation system 14b of the turbine-driven feed water pump 11b is simultaneously added to the main water supply to the steam generator, causing a rapid increase.

Therefore, in order to quickly and completely fill up the sudden increase in the amount of main water supply, the automatic motor-driven water supply pump 11a
is controlled to rapidly reduce the water supply flow rate to keep the main water supply amount constant.

However, at this time, the water supply is reduced too much to the point where the minimum flow valve 13a of the motor-driven water supply pump 11a is fully opened, and conversely, the water supply is reduced too much.
It often happens that a portion of the water supply flow rate flows into the recirculation system 14a, resulting in a reduction in the main water supply.

In addition, in order to correct the increase in water supply due to the closing of the minimum flow valve 13b of the turbine-driven water supply pump 11b, an operation is performed to reduce the water supply flow rate of the turbine-driven water supply pump 11b by computer control, and this corrective operation causes the motor-driven water supply pump 11b to reduce the water supply flow rate. 11a is returned to a value close to the original water supply flow rate, and in some cases, the minimum flow valve is fully closed again, causing fluctuations in the main water supply even at this rate.

In this way, when switching from motor-driven water supply pump operation to turbine-driven water supply pump operation, the main water supply flow rate is affected by the opening and closing operations of the minimum flow valves of each pump and fluctuates. Due to fluctuations in the water supply flow rate, the entire power generation unit is likely to fall into an unstable state, which may lead to a dangerous situation.

Figure 4 shows the amount of water supplied to the electric motor-driven water pump (M-BFP), the amount of water supplied to the turbine-driven water pump (T-BFP), and the total main water flow rate (FWW) to the steam generator.
F) is a diagram illustrating changes in F), in which the turbine-driven water supply pump becomes capable of supplying water at tl - after that, when the water supply increases and its minimum flow valve is fully closed, the amount of water supplied by the turbine-driven water supply pump increases rapidly, and this As a result, the main water supply flow rate significantly exceeds 25% of the target rated flow rate, as shown at point A.

On the other hand, in response to the increase in water supply by the turbine-driven water pump, the flow rate of the electric motor-driven water pump is reduced in order to keep the main water supply flow constant; The minimum flow valve suddenly dropped to the point where it was fully open, and this overlapped with the correction operation of the turbine-driven water supply pump, causing the main water supply flow rate to drop significantly from the target value as shown at point 8, making the main water supply flow unstable. In extreme cases, the water supply flow rate image alarm of the steam generator may cause a trip accident.

Furthermore, as mentioned above, since the main water supply flow rate itself fluctuates, a deviation occurs between the water supply command for the motor-driven water pump and the turbine-driven water pump and the actual pump inlet water supply flow rate, which easily causes the turbine drive Problems also arise, such as not being able to shift the water supply pump to automatic operation, resulting in a time delay.

In view of these points, it is an object of the present invention to provide a water pump operating method that allows automatic operation switching from an electric motor-driven water pump to a turbine-driven water pump to be performed in a stable state.

FIG. 2 is a control system diagram in which the turbine-driven water supply pump is started by a control device such as an electronic computer, and the inlet steam control valves 1 and 7 of the turbine 16 that drive the turbine-driven water supply pump 15 are driven by a morph drive. By controlling the inlet steam regulating valve 17, the rotation speed of the turbine 16 is controlled, and the rotation speed of the pump 15 connected to the turbine is increased or decreased to control the water supply flow rate.

In other words, by sending a control signal from the electronic computer 18 to the inlet steam control valve 17 and opening the control valve 17, it is possible to increase the rotation speed of the turbine-driven water supply pump and increase the water supply flow rate at the pump outlet. be.

On the other hand, the motor-driven water supply pump 19 follows the water supply command up to 25% of the rated power output, and the outlet control valve 21 responds to the signal from the plant automatic operation control system 20.
By controlling the amount of water supplied, the amount of water supplied is controlled.

Therefore, after setting the output so that the main water supply amount reaches 25% of the rated value and the output after the generator works together increases to 25% of the rated value, the signal from the electronic computer 18 is first sent to the inlet steam via the switching device 22. The inlet steam is sent to the control valve 17, and the inlet steam control valve 1
7 in the opening direction to increase the rotation speed of the turbine 16 and increase the water supply flow rate of the turbine-driven water supply pump.

When the outlet water supply flow rate of the turbine-driven water supply pump 15 begins to flow, the electronic computer 18 sends a power generation unit output command to the plant automatic operation control system 20 to send water supply amount α by the electric motor-driven water supply pump 19 and water supply by the turbine-driven water supply pump to be described later. Target main water supply flow rate X that corresponds to the sum of the amount
An output setting signal corresponding to is given, and the main water supply is set to rise to the main water supply flow rate X at a rate of change determined by the schedule at startup.

In response to this output setting signal, the automatic motor-driven water supply pump tries to further increase the water supply, but at the same time, the water supply amount from the turbine-driven water supply pump 15 increases, so the water supply amount due to the motor-driven water supply pump ζ is Decrease.

By the way, in general, in order to smoothly switch a turbine-driven water supply pump to control by an automatic operation control system that controls an electric motor-driven water supply pump, it is necessary that the water supply flow rate before and after the switching be equal.

On the other hand, when an electric motor-driven water supply pump and a turbine-driven water supply pump are controlled by a command signal from the same automatic operation control system, the water supply amount varies depending on the rated water supply amount of each pump, and the rated water supply amount is 25% of the rated power output. In the case of a turbine-driven water supply pump having a rated water supply capacity of 50% as well as an electric motor-driven water supply pump having a capacity of 50%, the ratio of the water supply amount is 1:2 in correspondence to the ratio of the rated water supply capacity.

Therefore, the ratio between the water supply amount α of the motor-driven water supply pump and the water supply amount β of the turbine-driven water supply pump that achieves the target main water supply amount X is made to correspond to the ratio of the rated water supply capacity of each pump.

That is, in the case of a water supply pump having a rated water supply capacity of 25% and a rated water supply capacity of 50%, α:β is set to 1=2.

Furthermore, the above α is set to approximately 1/2 of the rated water supply flow rate of the electric motor-driven water supply pump, and the above β is at least the steam generation system using the turbine-driven water pump at the time when the minimum flow valve of the turbine-driven water supply pump is about to fully close. Set it so that it is larger than the water supply flow rate to the side.

Therefore, the water supply flow rate by the turbine-driven water supply pump 15 gradually increases, and the supply water of the above β is supplied (in this case, the above β is the supply water to the steam generator at the time when the minimum flow valve 23 becomes full). Since the flow rate is set higher than the water supply flow rate, the minimum flow valve 23 is closed during the flow, and the supply water γ that was flowing into the recirculation system at that time is added to the main water supply (see Fig. 3).

Therefore, the main water supply flow rate also increases rapidly, as shown by a in FIG.

However, in this case, the main water supply flow rate is still being increased toward the target main water supply flow rate, and a drastic correction is suddenly made to return the main water supply flow rate to the flow rate at the point of sudden increase. It is not necessary, and a correction operation that takes some time to correct the flow rate to a flow rate close to the target main water supply amount may be performed.

Therefore, when the minimum flow valve 23 of the turbine-driven feedwater pump 15 is fully closed, the electric computer 18 sends a signal to throttle the inlet steam valve 17t and the water supply in response to the increased flow rate from the recirculation system. The turbine-driven water supply pump 15 is operated to slightly reduce the amount of water supplied, and the electric motor-driven water supply pump is also operated to slightly reduce the main water supply in order to maintain the rate of increase in main water supply. The rate of decrease in water supply is relatively small, and furthermore, the water supply target value α due to the electric motor-driven water supply pump Q is about 1/2 of its rated water supply amount, which has a considerable margin compared to the fully open flow rate of the minimum flow valve 24. Since the minimum flow valve 24 is set to a certain value, the minimum flow valve 24 will not close.

Once the temporary increase in water supply is corrected in this way,
A signal to open the artificial steam control valve 17 is sent from the electronic computer 18, and the turbine-driven water supply pump is controlled to reach the target water supply amount β, and the water supply amount of the motor-driven water supply pump 19 is also adjusted to α. The main water supply amount has settled down to the predetermined target main water supply amount, and the timing for switching the turbine-driven water supply pump to automatic operation has been established.

After that, the switching operation can be performed for any period of time.

Therefore, the switching device 22 is switched from manual to automatic.

The turbine-driven water supply pump is operated by a water supply command from the plant automatic operation control system 20.

On the other hand, the water supply pump driven by one electric motor will be excluded from automatic operation, and the amount of water supplied will be reduced.

When a predetermined main water supply flow rate is supplied by one turbine-driven water supply pump, the motor-driven water supply pump is stopped, and the switch from water supply by the motor-driven water supply pump to water supply by the turbine-driven water supply pump is completed.

Thereafter, the amount of water supplied is increased by the turbine-driven water supply pump in accordance with the output command of the power generation unit.

An example will be shown in which the method according to the present invention is applied to a power generation facility with an output of 500 MW.

Numerical values for power generation equipment (1) Main water supply flow rate rating 1720T/H (
2) Motor-driven water pump (M-BFP) rated water supply flow rate
470T/H (3) Turbine-driven water pump (T-RFP) rated water supply flow rate
940 T/H (4) M-BFP minimum flow valve operation inlet water supply flow rate (
9 closed 230 T/H fully open 105 T/H (5) T-Bpp minimum flow valve operation inlet water supply flow rate
(Fully closed 520T/H fully open 24
0 T/H (6) T-RFP recirculation system water supply flow rate required control setting value
270T/Hα:MB
Water supply amount 230T/H, approximately 1/2 of FP rated flow rate β: Water supply amount after T-BFP minimum flow valve is fully closed 460T/H
T/H X: Target main water supply amount during automatic switching 690T/Hy:
Output command setting value 40%i:
270'l/H Then, these set values are stored in the computer and control is performed with respect to the target.

In addition, FIG. 3 shows the relationship between the control operation and the water supply flow rate in the above embodiment.

In this case, A is the point at which the turbine-driven water supply pump starts supplying water to the pump outlet side, B is the point at which the minimum flow valve of the turbine-driven water supply pump becomes fully closed and the turbine-driven water supply rapidly increases, and C is the point at which the turbine-driven water supply pump starts supplying water to the pump outlet side. D is the point at which the water supply suddenly changes and is under corrective control, and the automatic switching timing is established when the motor-driven water supply pump and the turbine-driven water supply pump start supplying the specified water supply flow rate.

As explained above, in the present invention, the main water supply flow rate at the time of automatic switching from the motor-driven water supply pump to the turbine-driven water supply pump is increased from the conventional 25% equivalent to the rated water supply flow rate of the motor-driven water supply pump, and The amount of water supplied by the turbine-driven water supply pump during the main water supply amount is greater than the water supply flow rate at the time when the minimum flow valve of the turbine-driven water supply pump is about to fully close, and the amount of water supplied by the motor-driven water supply pump is Since the main water supply flow rate is set to approximately 1/2 of the rated water flow rate of Compared to the conventional method, fluctuations in the main water supply during automatic switching are small, and the automatic operation control of the turbine-driven water pump can be performed extremely easily.

Note that the target upper limit of the main water supply flow rate setting value may be within the range up to the rated water supply capacity of the turbine-driven water supply pump, but if this is too high, the time during which switching is possible will be lengthened accordingly, and the above conditions It is better to set the value as low as possible within the range that satisfies the following.

[Brief explanation of drawings]

Figure 1 is a schematic system diagram of the power plant equipment, Figure 2 is a control system diagram of the water pump, Figure 3 is a diagram showing the relationship between control operations and water supply flow rate, and Figure 4 is water supply flow rate under conventional control. FIG. 15...Turbine-driven water supply pump, 16...
...Turbine, 17...Inlet steam control valve, 1
8...Electronic computer, 19...Electric motor-driven water supply pump, 20...Plant automatic operation control system, 23, 24...Minimum flow valve.

Claims (1)

[Claims] 1. In a system in which water is supplied to a steam generator by a water supply system consisting of a motor-driven water supply pump and a turbine-driven water supply pump that are arranged in parallel with each other, the pump that supplies water is switched from the motor-driven water supply pump to the turbine-driven water supply pump. In this case, after the turbine-driven water supply pump becomes capable of supplying water, the target setting value of the main water supply flow rate supplied to the steam generator is set to a value that is equal to or higher than the rated water supply flow rate of the electric motor-driven water supply pump and within the target main water supply flow rate. The amount of water supplied by the turbine-driven water supply pump is greater than the actual water supply flow rate at the time when the minimum flow valve of the turbine-driven water supply pump is about to fully close, and the amount of water supplied by the motor-driven water supply pump is less than the rated water supply of the motor-driven water supply pump. Set the main water supply flow rate to approximately 1/2 of the flow rate, increase the water supply flow rate of the turbine-driven water supply pump, and after the main water supply flow rate of both water supply pumps reaches the above set value and becomes stable, the turbine A method of operating a water supply pump characterized by switching the driven water supply pump to an automatic operation state.