JPH07229602A - Control device of boiler - Google Patents

Abstract

PURPOSE:To provide a safe boiler controlling device wherein even a difference exists between a real capacity and a rating capacity, no steam quantity more than the rating is fed to a load side. CONSTITUTION:A boiler steam pressure detecting device 6, devices 1, 23, 24 for controlling a fed fuel quantity and an air quantity to a boiler 20 on the basis of a detection value of this device, and a steam pressure regulator 3 controlling a pressure regulating valve 5 when a detection value of the steam pressure decreases lower than a set value by a predetermined quantity (beta) or more, are equipped, and when the detection value of a steam flow meter 8 exceeds a rating value, a control is changed to a constant steam flow quantity control wherein a control of a pressure regulating valve 6 is changed to a steam flow quantity regulater 7 by a change-over switch 10 and a boiler steam flow quantity becomes a rating value by a pressure regulating valve 5. By this, a simple and constant steam pressure control is executed at a rating load or at a lower load than a rating one, and an over load operation can be prevented, and therefore, a boiler safety performance is raised.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a boiler control device, and more particularly to a boiler having a steam pressure control device for keeping a steam pressure within a predetermined range. The present invention relates to a boiler control device that switches to flow rate control to prevent the overload operation of a boiler from continuing.

[0002]

2. Description of the Related Art A conventional boiler control device is shown in FIG. Two
0 is a boiler, 22 is a burner, and a fuel flow rate control valve 23
The fuel adjusted by is burned to generate steam in the boiler. Reference numeral 24 is a forced air blower that supplies combustion air corresponding to the flow rate of fuel burned by the burner to the wind box 25 of the boiler. The steam generated in the boiler 20 is stored in the steam drum 26, and the steam taken out from the steam drum 26 is heated to a predetermined temperature by the superheater 21 in accordance with the request from the load side and supplied to the load side via the main steam pressure control valve 5. It

In the conventional main steam pressure control, the main steam pressure regulator 1 as a control master controls the fuel supply amount and the air supply amount to the boiler. Further, due to circumstances on the load side, when the steam consumption decreases below the fuel flow minimum stop equivalent amount, the generated steam pressure tends to rise, and the excess steam is discharged to the atmosphere so as to keep the pressure at a predetermined value. That is, the main steam pressure regulator 2 (high backup) controls the main steam blow valve 4 to release steam to the outside to prevent the pressure increase of the main steam.

On the other hand, when the steam consumption on the load side exceeds the boiler rated evaporation, the main steam pressure controller 3 (low backup) is used to control the main steam pressure control valve 5 assuming that the main steam pressure drops. It is configured to control. As control set values, the main steam pressure controller 2 is a control master set value + α, and the main steam pressure controller 3 is a control master set value −β.
Therefore, in the normal operating condition, the main steam blow valve 4
Is fully closed and the main steam pressure control valve 5 is fully open.

In this state, when the initially assumed steam consumption on the air supply side exceeds the rated evaporation amount, the main steam pressure does not immediately drop, but after the rated evaporation amount is exceeded When the steam generation rate is increased to the full capacity of the actual evaporation rate and used, the steam pressure falls below the control master set value -β only when the capacity limit is exceeded, and the control function of the main steam pressure regulator 3 works, By throttling the steam pressure control valve 5, the steam pressure drop is controlled, and further overload operation of the boiler is prevented.

[0006]

The conventional main steam pressure control device controls the main steam pressure control valve on the premise that the main steam pressure decreases when the rated evaporation amount is exceeded, and the main steam pressure control device of the boiler is controlled. The control balances the pressure and steam flow rate. However, the characteristics of the boilers are different, and some boilers do not reduce the pressure to a considerable overload state. If the pressure does not drop even if the rated evaporation amount is exceeded, the control will not function well, and as a result, the overload operation will continue, which is problematic in terms of complete boiler operation.

That is, the above-mentioned prior art is a control suitable for a boiler in which the actual capacity and the rated capacity of the boiler are matched, and when the boiler is not in such a situation,
For example, when the actual capacity of the boiler far exceeds the rated capacity, the controllability thereof is difficult. The object of the present invention is to provide a boiler with a difference in actual capacity and rated capacity,
It is an object of the present invention to provide a boiler control device capable of performing a safe operation without supplying a steam amount exceeding the rated value to the load side.

[0008]

In order to achieve the above object, the invention claimed in the present application is as follows. When the steam pressure detection device of the boiler, a device that controls the fuel supply amount and the air supply amount to the boiler based on the detection value of the steam pressure detection device, when the steam pressure detection value of the boiler is below a predetermined value In a boiler control device equipped with a steam pressure adjusting means for controlling a steam pressure adjusting valve, a steam flow rate detection device for extracting steam from the boiler, and a steam for adjusting the boiler steam flow rate to a predetermined value based on the detection value of this device. A flow controller,
Switching to stop the control of the steam pressure control valve by the steam pressure control means when the detected value of the steam flow rate detection device exceeds a predetermined value, and switch to boiler steam flow rate control by the steam flow control meter and the pressure control valve And a means for controlling the boiler.

[0009]

[Operation] At the time of overload operation when the evaporation amount exceeds the rated value, it is assumed that the boiler steam pressure will drop, and the steam pressure will exceed the set value + α and will fall below the set value -β. In a boiler control device provided with a control means for returning to the direction of the set value, even for a boiler whose boiler characteristics do not meet the above-mentioned premise, in the present invention, when the steam flow rate exceeds the rated load, the steam pressure constant pressure control is performed. Switching to flow rate control prevents continuation of overload operation and improves boiler safety.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT An embodiment of the present invention is shown in FIGS. The same reference numerals as those in FIG. 2 indicate the same parts, and the description of the overlapping parts will be omitted. In the present invention, the main steam flow rate controller 7 is provided and the output signal from this and the output signal from the main steam pressure controller 3 are switched according to the state of the main steam flow rate, and the main steam pressure control valve 5
Control signal.

In a normal state, the main steam pressure adjusting valve 5 is controlled by the main steam pressure adjusting gauge 3. When the main steam flow rate detected by the monitor switch 9 becomes higher than the rated flow rate, the changeover switch 10 controls the main steam pressure control valve 5 by the output of the main steam flow rate controller 7 so that the main steam pressure control valve 5 does not flow over the rated evaporation amount. . When the main steam flow rate decreases and becomes less than or equal to the rated capacity, the changeover switch 10 returns the main steam pressure control valve 5 to the normal state in which it is controlled by the output of the main steam pressure regulator 3.

In this case, the set value of the monitor switch 9 is provided with a dead band at the operating point when the evaporation amount rises and falls to prevent hunting when the evaporation amount (load) increases or decreases near the set value. To When both main steam pressure control and main steam flow rate control are not selected, the current value stands by, and when switching, bumpless is used.

Another embodiment of the present invention is shown in FIG. By providing the rate-of-change limiter 11 under the change-over switch 10, when the control mode is switched from pressure control to flow rate control, or vice versa, the control signal to the main steam pressure control valve 5 changes rapidly. Can prevent hunting. In normal operation, since the signal from the controller is directly transmitted to the main steam pressure control valve 5 without passing through the change rate limiter 11, the change rate limiter 11 works only when the mode is switched by the changeover switch 12. And a circuit for resetting this function after a fixed time period is provided.

[0014]

According to the present invention, even if the boiler has a capacity equal to or higher than the rated load, the optimum operation of the boiler is maintained and safe operation is performed without supplying the vapor amount of the rated amount or more as the evaporation amount to the load side. be able to.

[Brief description of drawings]

FIG. 1 is an overall view of a device configuration according to an embodiment of the present invention.

FIG. 2 is a configuration diagram of a conventional device.

FIG. 3 is a configuration diagram of a control unit in the present invention.

FIG. 4 is a diagram showing another embodiment of the present invention.

[Explanation of symbols]

1 ... Main steam pressure controller A, 2 ... Main steam pressure controller B, 3
Main steam pressure controller C, 4 Main steam blow valve, 5 Main steam pressure adjusting valve, 6 Main steam pressure transmitter, 7 Main steam flow controller, 8 Main steam flow transmitter, 9 Monitor switch,
10 ... Changeover switch, 11 ... Change rate limiter, 12 ... Changeover switch, 20 ... Boiler, 21 ... Superheater, 22 ... Burner, 23 ... Fuel flow control valve, 24 ... Forced air blower, 25 ...
Wind box.

Claims (1)

[Claims] 1. A steam pressure detection device for a boiler, a device for controlling a fuel supply amount and an air supply amount to the boiler based on a detection value of the steam pressure detection device, and a steam pressure detection value for the boiler is a predetermined value. In a boiler control device provided with a steam pressure adjusting means for controlling the steam pressure adjusting valve when the following becomes, a steam flow rate detecting device for taking out the steam from the boiler, and a boiler steam flow rate is predetermined based on the detection value of this device. A steam flow controller for adjusting the value to a value, and when the detected value of the steam flow detecting device exceeds a predetermined value, the control of the steam pressure adjusting valve by the steam pressure adjusting means is stopped, and the steam flow controller and the pressure adjusting device. A control device for a boiler, characterized in that a switching means for switching to a boiler steam flow rate control by means of a valve is provided.