JPS59153002A - Controller for pressure of main steam from boiler - Google Patents

Abstract

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

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention presets the main steam pressure as a function of load;
Regarding the main steam pressure control device for a boiler that changes the main steam pressure according to changes in load, the main steam pressure is set in advance as a function of load, and the main steam pressure is varied according to changes in load. In the so-called variable pressure operation boiler, a control means as shown in FIG. 1 has conventionally been adopted. That is, the pressure is set using the function setting device 4 in response to the signal from the load element 5, and the pressure is set using the rate of change limiter or the primary lag element 3 according to the load change of the boiler.
Setting values have been given so that the rate of pressure change is appropriate for the boiler, and the fuel flow rate and air flow rate have been controlled, for example, in a drum-type boiler, according to the deviation. In addition,
In the figure, 1 is a main steam pressure detector, 2 and 8 are subtractors, 6 and 10 are controllers, 7 is a manual/automatic switch, 9 is a fuel flow rate detector, and 11 is a fuel flow rate control valve.

However, in the conventional method described above, when the load is near the start and end of the change in the set value, as shown in Figure 2, when the operation is performed, the set value of the main steam pressure changes due to a slight change in the load. In conjunction with this, it changes at the unique rate of change of the rate of change limiter or first-order lag element 3, which causes a disturbance to the boiler, and further increases the load to load C in Figure 2 or decreases the load to load A. When doing so, load changes and pressure changes occur simultaneously, causing a total disturbance to the boiler.

The present invention has been made in view of the above-mentioned circumstances, and provides a main steam pressure control device that can perform good pressure control according to the boiler load over the entire variable pressure operation range in a boiler for variable pressure operation. The purpose is to

The present invention was made by focusing on the fact that the load indicated by A in the above-mentioned Fig. 2 is usually the minimum load of the boiler, and the boiler is usually operated for a long time near this load. . In the present invention, a comparator 12 shown in FIG. 3 is added to the conventional control circuit, and a comparator 12 shown in FIG.
The rate of change limiter or the rate of change or time constant of the first-order delay element 3 is switched in response to the pressure. That is, if the input/output signal deviation of the rate of change limiter or first-order lag element 3 detected by the comparator 12 is larger than a predetermined value, the rate of change S1 of 3 (when 3 is a rate of change limiter)
Or, if the time constant of 3 is T1 (when 3 is a first-order delay element), and the input/output signal deviation of 3 is smaller than a predetermined value,
Let the rate of change or time constant k S of 3 be or T2. However, Sl > S* m Tl < Tz. In this way, the rate of change limiter or first-order lag element 3 is equipped with two types of constant setter elements 14 and 15f that can be switched, and by adopting the entire system that switches depending on the input/output signal deviation of 3, the load can be reduced. It is possible to improve the controllability of Ting's main steam pressure control system not only at the inflection point of the boiler operating pressure setting program but also over the entire boiler variable pressure operating range without sacrificing the followability during normal operation.

An embodiment of the present invention will now be described with reference to FIG.

In FIG. 3, the same parts as in FIG. 1 are given the same reference numerals, and their explanation will be omitted. The configuration shown in FIG. 3 is different from the conventional example shown in FIG.
5, the deviation from the signal obtained from the function setter 4 which gives a predetermined main steam pressure set value signal to the load and the rate of change limiter or the second lag element 3 is obtained from the subtracter 2, and the control is performed. In a main steam pressure control system that generates a signal, a comparator 12 selects the set values of a plurality of constant setters 14 and 15, and a changeover switch 13 switches the settings according to the detection signal of the comparator 12. This is the point.

In the configuration shown in Fig. 3, when the boiler load changes with respect to the main steam pressure setting as shown in Fig. 2, the system changes the boiler operating pressure according to the load, so that the boiler remains stable. When in a constant state, there is no deviation of the input/output signals of the rate of change limiter or -th delay element 30 detected by the comparator 12, so the constant setters 14 and 15 have a small rate of change (or a large time constant). element is selected.

In this system, when the boiler load changes and it becomes necessary to adjust the boiler pressure to a pressure commensurate with the load, the deviation detected by the comparator 12 becomes large, and the constant setter 14.1
5, an element with significant change (or 5 temporary constant small) is selected, and full followability can be ensured. In addition, if a disturbance occurs to the boiler load element during boiler stabilization, the deviation detected by the comparator 12 is small, so a constant setter element with a small rate of change (or a large time constant) is selected, and the boiler pressure As a control system, it can control the influence of disturbances. On the other hand, when the boiler load increases or decreases toward an inflection point on the pressure setting, such as point A or 0 shown in FIG. As the output signal changes, the input/output signal deviation of the rate of change limiter or second lag element 3 becomes smaller as the load approaches the inflection point from the transformer voltage operation region, and as the load moves away from the inflection point toward the transformer voltage operation region. growing. In other words, the constant setter element 14 or 15 is selected so that the rate of change of the pressure set value with respect to the rate of change of the load is always small near the inflection point, thereby causing unnecessary disturbance to the force. Thereby, it is possible to perform good pressure control according to the boiler load over the entire boiler variable pressure operation region.

6- As detailed above, according to the present invention, in a boiler for variable pressure operation, there is provided a main steam pressure control device for a boiler that can perform good pressure control according to the boiler load over the entire variable pressure operation region. Can be provided.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing a conventional control circuit for a variable voltage boiler, FIG. 2 is a boiler load characteristic diagram, and FIG. 3 is a block diagram showing an embodiment of the present invention. 1... Main steam pressure detector, 2, 8... Subtractor, 3.
... Rate of change limiter or first-order retarding element, 4... Function setter, 5... Load element, 6.10... Controller,
7...Manual/automatic switch, 9...Fuel flow rate detector,
11...Fuel sight control valve, 12...Comparator, 13.
...Selector switch, 14.15...Constant setting device. Applicant Sub-Agent Patent Attorney Takehiko Suzue 7- Figure 1 Figure 2 7- Figure 3

Claims (1)

[Claims] The output of the function generator that outputs the set value of main steam pressure according to the load is sent to the subtracter via the rate of change limiter or delay element, and the output obtained in the subtracter is combined with the main steam pressure detection. Is there a format in which the deviation from the device output is input to the controller?
The main steam pressure control device is characterized in that a circuit is provided for changing the rate of change or time constant of the rate of change limiter or delay element in accordance with the deviation of the input/output signal of the rate of change limiter or delay element. Boiler main steam pressure control device.