JPH046301A - Water separator pressure control device - Google Patents

Abstract

PURPOSE:To prevent the occurrence of overshoot and to control a pressure to a constantly optimum value by providing a control means having a function generator to generate a set value lower than a final target value before the starting of the feed of steam and generate a set value gradually increasing toward the final target value. CONSTITUTION:A set value signal generated by a signal generator 6 is lower than a set value being a final target value generated by a signal shifter 8 and produces a value at which overshoot is prevented from occurring in a water separator. A pressure in the water separator is rapidly increased simultaneously with the starting of the feed of steam. At a point of time when, compared with a set value signal gradually changes in a specified rate of change from a rate of change limiter 5, a pressure in the water separator is increased, a comparator 2 compares and detects the pressure and a detecting signal is transmitted to a pressure regulator 3. The pressure regulator 3 opens an SP valve 4 and is operated in a manner to decrease pressure in the water separator.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a water separator pressure control device used in a once-through boiler for thermal power generation.

[Prior Art] A water separator used in a once-through boiler for thermal power generation receives steam from a BE valve installed at its inlet.
Steam is supplied from the outlet to the boiler heater. The water separator pressure control valve (hereinafter referred to as "SP valve") branched from the water separator outlet controls the pressure inside the water separator by releasing excess steam, but conventional pressure control methods It was always controlled to operate at a constant set value regardless of the presence or absence of steam supply.

[Problem to be solved by the invention] However, when the water separator starts to be used, BE
When the valve opens and steam supply starts, the pressure inside the water separator also rises, but as mentioned above, the pressure of the SP valve is always controlled to the final target value as the set value.
Pressure control was not performed until the pressure inside the water separator exceeded the final target value, causing a large overshoot.

The present invention has been made in view of the above-mentioned circumstances, and its purpose is to avoid overshooting,
An object of the present invention is to provide a water separator pressure control device that can always control the pressure inside a water separator to an optimal pressure.

[Means for Solving the Problems] That is, the present invention generates a set value lower than the final target value before the start of steam supply, and generates a set value that gradually increases toward the final target value after the start of steam supply. It is equipped with a PID (proportional, integral, differential) control system having a function generator.

[Function] By having the control system as described above, after the start of steam supply to the water separator, pressure control starts from the time when the pressure inside the water separator exceeds a set value lower than the final target value, and from then on, the set value The pressure inside the water separator is gradually increased as the pressure rises until it reaches the final target value, so there is no overshoot caused by a delay in starting pressure control, and the pressure inside the water separator is always maintained at the optimal pressure. can be controlled.

[Example] An embodiment of the present invention will be described below with reference to the drawings.

Figure 1 shows its configuration. 1 is a water separator pressure transmitter, 2 is a comparator that compares the output of this water separator pressure transmitter with a set value, and 3 is a response to the comparison output of comparator 2. 4 is a water separator pressure control valve (SP valve) that is activated by adjusting the pressure regulator 3; 5 is a water separator pressure control valve (SP valve) that gradually adjusts the input sudden change signal at a constant rate of change; 6 is a signal generator that generates a set value signal before starting steam supply, and 7
is the signal generator value that generates the final target setpoint signal,
8 receives the signal from the signal generator 6 before starting the steam supply,
After the steam supply starts, a signal switching device switches and selects the signal from the signal generator value 7 and supplies it to the rate of change limiter 5,
The rate of change limiter 5, signal generator 6, signal generator value 7, and signal switch 8 constitute a function generator 9.

The operation of the above configuration will be explained below using FIG. 2.

Before steam is supplied to the water separator, a set value signal from the signal generator 6 is selected by the signal switch 8 and is applied to the comparator 2 via the rate of change limiter 5. Here, the set value signal generated by the signal generator 6 is lower than the final target set value generated by the signal switch 8, and is set to a value that does not cause overshoot in the water separator. be.

When the BE valve is opened and steam supply to the water separator is started, the signal switch 8 switches and selects the final target set value signal from the signal generator value 7 instead of the signal from the signal generator 6. , is sent to the rate of change limiter 5. Change rate limiter 5
By switching the signal, a set value signal that changes rapidly is converted into a signal that gradually changes at a constant rate of change as shown in FIG. 2, and the converted signal is applied to the comparator 2. The pressure inside the water separator increases rapidly with the start of steam supply, and when the pressure inside the water separator becomes higher than the set value signal that gradually changes at a constant rate of change from the change rate limiter 5. The comparator 2 compares and detects this and sends a detection signal to the pressure regulator 3. The pressure regulator 3 opens the SP valve 4 in accordance with this signal and operates to release excess steam to lower the pressure inside the water separator.Then, the pressure in the water separator is gradually increased from the rate of change limiter 5 until the final The SP valve 4 is similarly controlled to open and close in accordance with the set value signal that reaches the target value.

[Effects of the Invention] As described above, according to the present invention, a set value that is lower than the final target value is generated before the start of steam supply, and a set value that gradually increases toward the final target value after the start of steam supply. After starting steam supply to the water separator, pressure control is started from the point when the pressure inside the water separator exceeds a set value lower than a preset final target value. From then on, as the set value increases, the pressure inside the water separator is gradually increased until it reaches the final target value, so there is no overshoot caused by a delay in starting pressure control, and the pressure inside the water separator is always maintained. A water separator pressure control device capable of controlling pressure to an optimum pressure can be provided.

[Brief explanation of drawings]

FIG. 1 is a functional block diagram showing the configuration of an embodiment of the present invention, and FIG. 2 is a diagram showing the pressure control state according to FIG. 1. ]... Water separator pressure transmitter, 2... Comparator, 3... Pressure regulator, 4... Water separator pressure control valve (SP valve), 5... Rate of change limiter, 6...・
- Signal generator, 7... Signal generator value, 8... Signal switch, 9... Function generator.

Claims (1)

[Claims] A control having a function generator that generates a set value lower than the final target value before the start of steam supply to the water separator, and generates a set value that gradually increases toward the final target value after the start of steam supply to the water separator. A water separator pressure control device characterized by comprising means.