JPS607170B2 - Water supply flow control device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a water supply flow rate control device that switches from a turbine-driven water supply pump to a motor-driven water supply pump during load runback.

The automatic plant control system (hereinafter abbreviated as APC) in a thermal power plant equipped with a once-through boiler coordinates the control of water supply, fuel, air volume, and turbine inlet control valve according to the set values of the load setting device, as shown in Figure 1. Although this is being done in a timely manner, when an auxiliary equipment trips during normal operation, the system is equipped with a load runback system that rapidly reduces the load to the capacity of the remaining auxiliary equipment within an allowable time. Alternatively, since runback is required to a low load, followability of the boiler becomes a problem, and the success rate of load runback is very low.

In particular, in water supply flow rate control, there are many cases where the boiler stops due to excessive flow due to the minimum flow rate required on the boiler side, which leads to plant shutdown.The current water supply flow rate control method is as shown in Figure 2. Generally, during low load, a motor-driven water supply pump (hereinafter referred to as M・
The water supply is controlled by the FWB, and at high loads two turbine-driven water pumps (hereinafter referred to as T-BFP) with 50% capacity are used and controlled by the speed control valve of the turbine.

In the figure, LPH is a low pressure heater, and HPH' is a high pressure heater. When a load runback signal occurs during operation under high load, the load setting value and load change rate setting value at AP〇 are determined, and in flow control, the water supply flow rate is runback by operating the speed control valve of T/BFP. Although the value is lowered to a value commensurate with the load setting, the steam that is the driving source for the T/BFP is taken out from the low pressure part of the turbine during normal operation, and the steam conditions deteriorate during runback, causing the steam to be taken out from the low pressure part of the turbine to the high pressure part or It is necessary to switch to the supply from the auxiliary steam line, but due to the difficulty of the switching operation and time constraints, the water supply flow rate control during runback in the T-BFP does not work as a result. In view of the above problems, the present invention automatically drives the motor-driven water supply pump during load runback, and switches the water supply control from the automatic plant control device from the turbine-driven water pump to the motor-driven water supply pump to achieve stable water supply flow rate control. The object of the present invention is to obtain a water supply flow rate control device that can control the flow rate of water.

Figure 3 is a flowchart up to M/BFP driving during load runback.
Drive the FP auxiliary oil pump, open the M/BFP inlet valve, establish the bearing oil pressure, drive the M/BFP, and then
Indicates that the FP outlet valve is controlled to be open. FIG. 4 is a block diagram of water supply flow rate control according to the present invention.
It is a setting device for FP, and its output signal is a of switch 43
, are supplied to the T-BFP controller 31 through contacts.

The M.BFP flow rate signal (negative polarity) and the water supply flow rate signal from the APC are compared by a comparator 32 via contacts b, b2, respectively, and the deviation is input to the T.BFP controller 31. The output of this controller 31 is T/BFP, respectively.
It is input to the box setting device 33 and the T/BFP {B} setting device 34, and controls the T/BFP wind control valve 35 and the T/BFP side control valve 36. On the other hand, the water supply flow rate signal from the APC is T.
The BFP flow rate signal is compared with the comparator 37, and the deviation is calculated as M・B.
Input to FP controller 38.

The various runback signals 1 to 3 are changed into signals of predetermined magnitude by the setting devices RH2 to R, respectively, and then inputted to the M/BFP controller 38 through the wide contacts. M・BF
The P start signal becomes a set point increase signal, and the set value of the setter R is increased. The outputs of the controller 38 are M and B, respectively.
The FP■ setting device 39 and the M.BFP{B} setting device 401 are inputted to control the M.BFP wind control valve 41 and the M.BFP■ control valve 42, respectively. In FIG. 4, M/BFP control is performed by various runback signals.

By initializing the controller setting device to a value below the value corresponding to each final runback value, and gradually increasing the set value of the M-BFP controller with a set point increase signal after the M-BFP drive is completed, Increase the M・BFP flow rate. On the other hand, the T-BFP is controlled by a signal from the APC side, but at the same time as the M-BFP starts driving, the M-BFP outlet flow rate is subtracted from the APC signal, and the control signal is sent to the set value of the T-BFP controller. do. By gradually increasing the flow rate of M・BFP, when it exceeds the flow rate of T・BFP, the switching relay 43× is operated, and the APC signal is switched to M・BF.
Move to the P controller side and operate the T/BFP flow rate in the drop direction at a constant ratio.

When the APC signal is transferred to the M.BFP, the T.BFP.flow rate is subtracted from the APC signal and used as the controller input signal for the M.BFP.

By the above method, M・B
Switching to FP control enables stable flow control, allowing continued low-load operation and shortening the time required to return to work.
In turn, this can help improve system stability.

[Brief explanation of the drawing]

Figure 1 is a schematic diagram of the automatic plant control device, Figure 2 is a water supply flow rate system diagram, Figure 3 is a block diagram up to M/BFP drive during load runback, and Figure 4 is a water supply flow rate control block according to the present invention. It is a diagram. 35, 36, 41, 42... control valve, RH, ~R... setting device, 43×... switching switch,
31... ...T.BFP controller, 38.・…
・M・BFP controller, 33, 34, 39, 40・
...Setting device. Figure 1 Figure 2 Figure 3 Figure 4

Claims (1)

[Claims] 1 In a thermal power plant equipped with a once-through boiler, the motor-driven feed water pump is driven by a load runback signal, and the flow rate on the motor-driven feed water pump side is gradually increased to the point where it exceeds the flow rate of the turbine-driven water feed pump. A water supply flow rate control device that switches the signal from the automatic plant control device to the motor-driven water pump side before the runback point.