JPS5974405A - Controller for recirculating flow rate of feed pump - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

TECHNICAL FIELD OF THE INVENTION The present invention relates to an improved recirculation flow control system for feed water pumps in thermal and nuclear power plants.

[Technical background of the invention and its problems]

In general thermal power plants, in order to prevent the pump from overheating when the feedwater pump is operated in a low flow rate range, a constant flow rate is returned from the discharge V path of the feedwater pump to the suction side. Safe operation of the water pump 1: A recirculation flow control device is provided to ensure the required minimum amount of cooling water.

That is, in FIG. 1, a circulation line 4 that reaches a deaerator 3 is branched from a discharge pipe 2 of a water supply pump 1.

The recirculation line 41 is provided with a flow-fp control valve 5 and a pressure reducing orifice 6, and a part of the water discharged from the water supply pump 1 is transferred to the 1st flow 1st flow valve 5 and 7'. It is circulated through the vacuum orifice 6 to the deaerator 3. On the other hand, a flow rate detection device 9 is installed on the discharge side of the booster pump 7 that supplies water from the deaerator 3 to the water supply pump 1, that is, on the suction pipe 8 of the water supply pump 1. θ(·, phase flowing through path 8 is exported and the above flow ml
The flow rate signal from the flow rate oscillator sent to the detection device 9 is guided to the controller 14). There, it is constantly compared with the set flow rate, and if a deviation occurs between the two, the control valve 5 is immediately
A control signal is sent to the Note that %ilθ
The set flow rate -b° of the meter 14 can be supported at one point, or J-11 can be given as a function of the pump rotation speed.

However, the suction flow i+ of the water supply pump 1: (-x output flow story)
When the flow rate decreases and reaches the set flow rate, the control valve 5 is fully opened to allow the discharge flow to flow into the circulation line 4, and through the depressurization orifice 6 to the deaerator 3. The required recirculation flow rate of the pump 1 is ensured, and overheating of the water pump 1 is prevented.

By the way, Figure 2 shows the Q, -H characteristic curve a of a general water supply pump and the system head curve -? and an example of the minimum flow (required recirculation flow rate) curve tIc.

The same figure clearly shows the Q, -H characteristic curve avr
, moves according to changes in pump rotation speed. Therefore, the flow mlQ of the water supply pump 1 and the pump discharge pressure H at a certain rotation speed n are the Q, −H curve (
It is determined by the intersection point A between α·n) and the system head curve. On the other hand, the minimum recirculation flow rate at that time is determined by point B.

However, if we find point B for each rotation speed and plot it, we get
C2 as shown in Figure 3 f2. Optimal minimum recirculation b'F
tt U changes depending on the rotational speed g2 of the pump at that time.

However, the boiler pressure of modern power plants is on the rise due to improved efficiency. Along with this, the water pump discharge pressure also tends to increase.

As the water supply pump discharge pressure increases, the circulation flow rate also increases to prevent the pump from overheating. That is, the minimum recirculation flow rate curve C in FIG. 2 is translated to the right.

As a result, the water supply pump, total discharge current shock (setting 8-1 flow rate) C
There is a tendency for the recirculation flow M ratio for C2 to approach C2. The disadvantage of this is that the flow rate through the water pump is higher than before.
Recirculation flow must flow from r.

Therefore, the water condensation fluctuations that occur when the flow control valve 5 opens and closes fall within the load range normally operated by the power plant.

[Purpose of the invention]

The purpose of the present invention is to quickly respond to ensure a minimum recirculation flow rate when the flow rate passing through the feedwater pump suddenly decreases, thereby enabling efficient operation control of the entire plant.
There are two types of water supply pumps that provide recirculation flow control systems.

[Obscenity of invention]

The present invention provides a first control loop that slowly opens and closes the flow control valve, and a second control loop that is configured to operate when the flow rate through the feed water pump suddenly decreases and the minimum recirculation flow rate cannot be ensured by the first control loop. The second one responds rapidly to ensure minimum recirculation flow.
The present invention relates to a recirculation flow rate control device C for a water supply pump, characterized in that it is provided with a control loop.

[Embodiments of the invention]

The present invention will be explained below with reference to FIG. 4 (Embodiment C shown in FIG. 1). The same reference numerals in FIG. 4 as in FIG. The rotational speed of the turbine 15 is detected by the rotational speed detector 16, and the rotational speed signal is converted by the calculator 171m into a necessary minimum recirculation flow rate signal corresponding to the rotational speed at that time, and is sent to the controller 14 as a set flow rate signal. given to.

On the other hand, the command s of the first control loop L1 is given from the water supply master signal 20. This water supply master signal 2
0 is before the main steam flow flowing out from the boiler or core,
This signal is calculated from two or three elements, such as the inflow water supply flow rate or, if a drum is provided, the drum water level, and commands the water supply flow rate to the boiler or core. Therefore, they are changed in accordance with changes in the plant load, and specifically, rLl, rL2, . . . , h in FIG. This first
The control loop L1 is to slowly open and close the recirculation flow control valve 5.

On the other hand, the dotted lines B', O', and D' in Fig. 2 indicate the brass instrument 23.
When the water supply flow rate in FIG. 2 decreases and moves to the left until reaching the dotted line C', the performance device 23
starts the calculation. The output signal of the arithmetic unit 23 is transmitted to the arithmetic unit 21
is input. Arithmetic unit 21id- is an arithmetic unit in which a signal changes at a rate of change preset by a rate of change limiter. The output of this arithmetic unit 21 is input to a priority unit 22. In addition,
The signal from the second control loop L2 is also input to the priority device 22, and the priority device 22 gives priority to the signal that causes the flow rate control valve 5 to open.

Figures 5, 6 and 7 g21? FIG. 5 shows the relationship between the O-H characteristic curve L of FIG. 2 and the minimum recirculation flow rate curve C. The plant load is now decreasing at a constant rate of decline, and the water supply flow rate is also decreasing accordingly. Fifth
Figure ζ: If the g2 supply water flow rate is gradually decreasing as shown in Figure 6 C2 even when the flow rate passes the C' dotted line to the left, the first control loop L1 in Figure 4 operates. According to the water supply master signal 20, the calculator 23.21
Gently open and close the tilN regulating valve 5 to ensure the recirculation volume of the water supply pump 1 by C2flill 11
do.

In Fig. 7, when the flow rate passes the point C' to the left, the water supply flow rate drops to an angle, and with only the signal of the first control loop L1,
This shows a state in which the recirculation flow rate for preventing overheating of the water supply pump cannot be maintained and the second control loop L2 is operating. This second control loop includes the suction flow rate detection device 9 of each pump 1.
．． The flow from No. 10 - It (No. 4 is compared with the set flow), the deviation signal is led to the adjustment h114, and the signal after proportional and integral operation is given to the priority device 22.

〔Effect of the invention〕

As described above, according to the present invention, since the rate of change in the water supply flow rate is gradual due to normal operational load changes in the power generation plant due to power supply commands, etc., the first control loop controls the opening and closing of the flow rate regulating valve. However, the disturbance of water supply to the boiler side or the reactor core side can be reduced. Further, the second control loop can back up the first control loop in response to a sudden drop in the water supply flow rate.

[Brief explanation of the drawing]

No. 11 A circuit diagram showing a conventional recirculation flow rate control device,
Figure 2 is a diagram showing the Q, -HBIj curve, system head curve and minimum flow curve of the water supply pump;
FIG. 4 is a circuit diagram showing a recirculation flow rate control device for a water supply pump according to the present invention, and FIGS. Figure 7 CF is a Q-H characteristic diagram for explaining the water supply pump recirculation flow control device of the present invention. 1... Water supply pump 2... Discharge pipe line 3... Deaerator 4... Recirculation line 5... Flow [,1
4 section valve 7...Booster pump 8...Water pump suction flow rate 9...For flow rate detection device...Flow rate converter
14...Controller I5...Turbine 16
...Rotation speed C2 vs. 17...Arithmetic unit 20.
...Water supply master signal 2■...Calculator 22
...Priority unit 23...Arithmetic unit (8733) Agent Patent attorney Yoshiaki Inomata (and one other person) Diagram 2 Procedure amendment honor (method) Kenkamo 3, everyone. Commissioner of the Japan Patent Office 1, Indication of the case, Japanese Patent Application No. 183646/1983, 2, Name of the invention: Recirculation flow rate control device for water supply pump 3, Relationship with the person making the amendment Patent applicant (307) Tokyo Shibaura Electric Co., Ltd. 4. Agent Address: 1-9 Toranomon, Minato-ku, Tokyo 105 IO Minato Densei Building Inomata Patent φ Office Phone: 501-6058 (8733) Patent Attorney Yoshiaki Inomata 5 Date of Amendment Order: February 22, 1988 (Delivery date) 6. Subject of amendment ■, Attached drawing 7, Contents of amendment (1) Additional submission of drawings 5, 6, and 7 attached to this application has been completed. that's all

Claims (1)

[Claims] In the circulation system that returns a constant flow rate from the discharge pipe of the water supply pump to the suction side via the recirculation flow pre-adjustment valve, the recirculation flow rate adjustment valve is taken out from the rotation speed command No. 41 of the water supply pump and passed through the auxiliary device. a first control loop that supports an opening/closing command signal; a second control loop that compares the suction flow of the water pump with a set value that changes the suction flow of the water pump in response to changes in the rotation speed of the water pump and outputs a deviation signal; In response to the output signals of the first control loop and the second control loop, when the water supply fluctuates slowly, the recirculation flow pre-regulating valve is controlled to open and close in response to the output signal of the first control loop, and when there is a sudden drop in water supply, the A recirculation flow rate control device for a water supply pump, characterized by comprising a priority device that makes an output signal of a control loop correspond to a recirculation flow rate adjustment valve as a backup signal.