JPS607165B2 - Calorie correction method and device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention is an automatic plant control system (AP) for a supercritical pressure boiler.
The present invention relates to a calorie correction method and device when changing fuel in C).

Since supercritical pressure boilers do not have drums, the process response is far greater than that of drum-shaped boilers.

Therefore, when controlling a thermal power plant using a supercritical pressure boiler, a turbine control device and a boiler control device (ABC) are used.
) is used in conjunction with an automatic plant controller (APC). The conceptual structure of APC is as shown in FIG. 1, and the generator output command becomes the master signal for all control loops while being subjected to various corrections. ABC of drum type boiler
Since the feed water control loop has almost no interference with steam pressure and steam temperature, it can be treated as an independent loop. The water supply control loop and fuel control loop cannot be separated.The connection between the water supply control loop and the fuel control loop is performed through a water-fuel ratio controller that corrects the water-fuel ratio. It is always constant.The plant is designed so that the water-fuel ratio at this time is 1.When coal is used as the fuel, the fuel flow signal is the value obtained by multiplying the amount of coal fed by the calorie value of the coal. .

If the quality of the coal changes during plant operation, its calorie value will differ from the initial set value, so the operating point of the water-fuel ratio controller will become biased in an effort to absorb this error, resulting in poor APC controllability. Problems arise in maintaining the In order not to leak the operating point of the water-fuel ratio controller,
It is possible to correct the calorie value according to changes in the quality of the coal, but if the calorie value is suddenly changed, the output of the fuel control loop will suddenly change and cause a disturbance to the process. It takes a long time to change. An object of the present invention is to provide a method and apparatus for quickly correcting calorie values without causing any disturbance to the process. The present invention switches the output of the water-fuel ratio controller to a value corresponding to a water-fuel ratio of 1 when correcting the calorie value,
The calorie value and the output of the oxygen amount controller are changed accordingly.

The present invention will be explained below with reference to the drawings.

FIG. 2 is a conceptual block diagram of an apparatus to which the method of the present invention is applied. In Fig. 2, M is the water-fuel ratio controller.
2 is an oxygen amount controller, M3 is a fuel flow controller, and M4 is an air flow controller. These controllers have proportional/integral functions, manual cutoff functions, and output tracking functions. The bottom is a calorie setting device, for example analog. It consists of a memory (integrator) whose contents can be changed according to the increase/decrease command signal, and has an output tracking function. M6 to M8 are multipliers. The water-fuel ratio controller M outputs a water-fuel ratio correction signal k based on the difference between the steam temperature detection signal and the set value.

The water-fuel ratio correction signal k is multiplied by the master signal Z applied from the previous stage in a multiplier M6. The master signal Z is the same as the master signal, that is, the water supply command, given to the water supply flow rate control loop at the previous stage. The output signals k and Z of the calculator are given to the fuel flow controller M3 as a fuel command signal FFD. The fuel flow controller M3 receives the coal feeding amount x and the head k2 of the calorie set value k2 from the multiplier M7.
x is given as the fuel flow signal FF. The fuel flow controller M3 outputs a fuel flow control signal based on the difference between these two signals. The fuel command signal FFD and fuel flow rate signal FF are given to the calorie setter M5 as correction signals. When the tracking function is activated, the calorie setting unit operates to match the fuel flow signal FF with the fuel command signal FFD. The oxygen amount controller M2 outputs an oxygen amount correction signal k3 based on the difference between a signal detecting the amount of oxygen in the fuel gas and a set value. The calculator M8 receives the fuel command signal F.
The air command signal AFD is obtained by multiplying the FD by the oxygen amount correction signal k3.
(=k, k3Z) is determined and given as a master signal to the air flow controller M4. The air flow rate detection signal y is given to the air flow controller M4 as the air flow rate signal AF. The air flow controller M4 outputs an air flow control signal based on the difference between these two signals. The air command signal AFD and the air signal AF are also provided as correction signals to the oxygen amount controller M2. The oxygen amount control pond operates to match the air command signal AFD with the air signal AF when the tracking function is activated. The operation of the device configured in this way is as follows.

Normally, each controller performs proportional-integral operation in an automatic state, and performs fuel flow rate control and air flow rate control in accordance with a master signal. If coal with the calorie set on the calorie setting device is supplied to the boiler and the process is stabilized in that state, the water-fuel ratio will be 1 and the output signal of the water-fuel ratio controller M will be This will be 50% of the rated output. When the quality of the coal changes and its calorific value differs from the set value k2, the energy added to the water changes and the steam temperature changes, so the output signal of the water-fuel ratio controller M changes, which causes the output of the fuel flow controller M3 to change. The signal changes to change the amount of coal fed,
It counteracts the energy change due to calorie change.

When the process settles again by this operation, the output signal of the water-fuel ratio controller M has changed from the previous settling state (50%) by the amount that the calorie of the coal has changed. The output signal of the water/fuel ratio controller M becomes smaller than 50% when the calorie increases, and becomes larger than 50% when the calorie decreases. Also, the output signals of the oxygen amount controller M2 and the air flow rate controller M4 have new values. At this time, the following relationship holds true on the input side of the fuel flow controller M3 and on the input side of the air flow controller M4. k, Z=k2×
[1'k, k〆=y'
{2' In this state, set value k of calorie setting device M5
Make the following changes.

The calorie set value k2 is changed based on the following principle. That is, if the calorie set value k2 matches the actual calorie value of coal, the output signal of the water-fuel ratio controller M should be 50%, which corresponds to a water-fuel ratio of 1. Therefore, conversely, water-fuel ratio controller M
, forcibly set the output signal to 50% and change the calorie set value k2 accordingly, the calorie set value k2 will eventually match the actual calorie value. Therefore, the water-fuel ratio controller M. k to make the output signal of 50%
．． When the calorie setting value Aki2 is changed from k2 to k,′ (50%), the output signal of oxygen amount controller M2 is changed from k3 to k3·k,/k,′. change.

Then, FFD=k,′Z
'3-FF = No. k2 X [4) side = k・' No. k3 fence.

The fuel flow controller M3 operates based on the difference between FFD and FF, and the air flow controller M4 operates based on the difference between AFD and AF, which are determined by k. 'z−k2
Bitterness x = sheep (k・z−k2X)=o'6}k. 'k3 mother Z
−y=k·k3Z−y=0{71.

That is, the deviation input signals of both controllers are both zero. Therefore, the output signals of both controllers do not change and no disturbance is applied to the process. That is, even if the calorie correction is performed quickly, no disturbance is caused to the process. Then, the operating point of the water-fuel ratio controller M is returned to its original state, maintaining good controllability. Correction of the calorie set value k2 and the output signal of the oxygen amount control point can be easily performed by using the tracking function.

That is, when the calorie setter M5 is set to the tracking mode, the output signal k2 is changed so that the fuel flow signal FF matches the fuel command signal FFD.If the output signal when they match is k2', then k,'Z =k2'x
■However, from the m formula, Z
= device
'Z=y (11), but by substituting the relationship in equation (2), we get k3'=k3 (12).

Such correction can be automated by the following means.

FIG. 3 shows an example of a sequence control circuit for automatically performing calorie correction. In FIG. 3, Ro is an OR circuit, R is an AND circuit, and T is an off-delay timer. The calorie correction command is given to the AND circuit R when the output signal of the water-fuel ratio, that is, the water-fuel ratio control M, exceeds a predetermined upper or lower limit, or when the operator presses a push button. The AND circuit R is opened when the calorie correction permission condition is satisfied, that is, when the process is in a stable state, and outputs the calorie correction command through the off-delay timer T to the tracking commands A, B, C and the manual switching command ○, Output as E. Tracking commands A, B
and C are a water-fuel ratio controller M, a calorie setting device M5, and an oxygen amount control, respectively.

M2 to put them in tracking mode. As a result, the water-fuel ratio controller M follows the output setting value and sets the output to 50%, the calorie setting device M5 changes the output signal k2 so that the fuel flow signal FF matches the fuel command signal FFD, and the oxygen amount controller M2 changes the output signal k3 so that the air command signal AFD matches the air flow rate signal AF. Manual switching commands D and E
are provided to the fuel flow controller M3 and air flow controller M4, respectively, also putting them into manual control mode.

In the manual control mode at this time, no output adjustment operation is performed outside the operation, so the output signals of both controllers are kept unchanged. This ensures that both controllers do not react to input signal deviations that occur during tracking. Due to the action of the off-delay timer T, tracking commands A, B, and C and manual switching commands D and E disappear after a certain period of time, and each controller returns to the automatic control state.

The time limit value of the off-delay timer T is determined to be sufficient to complete tracking, but it may be omitted if the tracking speed is fast. In this way, by combining the apparatus shown in FIG. 2 with the apparatus shown in FIG. 3, calorie correction can be performed automatically and quickly without causing any disturbance to the process.

Note that the multiplier rudder ~M8 may be replaced with an adder. Furthermore, there are various means for implementing sequence control, such as by using a program. Also, during tracking, the fuel flow controller M3
Although the manual control mode was used to hold the output signal of the air flow controller M4 unchanged, if there is an output holding function, it may be used. As described above, the present invention provides a method and apparatus that can quickly perform calorie correction without causing any disturbance to the process.

Using the method and apparatus of the present invention, a thermal power plant using a desk-burning coal-fired supercritical pressure boiler can be effectively controlled.
It should be noted that the present invention is applicable not only to coal-fired combustion but also to gas, heavy oil, and other fuels whose calorie content fluctuates due to muddy phosphorus.

[Brief explanation of the drawing]

Fig. 1 is a conceptual block diagram of a thermal power generation control device using a supercritical pressure boiler, and Fig. 2 is a conceptual block diagram of an embodiment of the present invention.
FIG. 3 is a block diagram of a sequence control circuit combined with the device of FIG. 2. M. ...Water-fuel ratio controller, M2...Oxygen amount controller, M3...Fuel flow rate controller, M4...Air flow rate controller, M5...
...Calorie setting device, rudder ~ M8... Chicken calculator. Younger brother' diagram Younger brother Z Fungi younger brother J diagram

Claims (1)

[Scope of Claims] 1. A fuel command signal obtained by correcting the water-fuel ratio of the master signal of the water supply flow rate control loop by the output of the water-fuel ratio controller and a fuel flow signal including a calorie setting value term are given, and based on the difference between the two signals. A fuel flow controller that controls the fuel flow rate; and an air flow controller that is given an air command signal and an air flow signal obtained by correcting the oxygen amount of the fuel command signal using the output of the oxygen amount controller, and controls the air flow rate based on the difference between the two signals. In an automatic plant control device for a supercritical pressure boiler having and a calorie correction method for correcting the output signal of the oxygen content controller. 2. A fuel system that is given a fuel command signal obtained by correcting the water-fuel ratio of the master signal of the water supply flow rate control loop using the output of the water-fuel ratio controller and a fuel flow signal that includes a calorie setting value term, and performs fuel flow rate control based on the difference between the two signals. A supercritical pressure system comprising: a flow rate controller; and an air flow controller that is provided with an air command signal obtained by correcting the oxygen amount of the fuel command signal by the output of the oxygen amount controller and an air flow rate signal, and controls the air flow rate based on the difference between the two signals. In an automatic boiler plant control system, a calorie setting device and an oxygen amount controller each having a tracking function are used, and when correcting the output signal of the water-fuel ratio controller, the calorie setting device is set so that the fuel flow signal matches the fuel command signal. The controller performs a tracking operation on the calorie set value, and the oxygen amount controller performs an output signal tracking operation so that the air command signal matches the air flow rate signal, and has an output holding function as a fuel flow controller and an air flow controller. A calorie correction device that uses two controllers and keeps both controllers in an output holding state when correcting the output signal of the water-fuel ratio controller. 3. A fuel system that is given a fuel command signal obtained by correcting the water-fuel ratio of the master signal of the water supply flow rate control loop using the output of the water-fuel ratio controller and a fuel flow signal that includes a calorie setting value term, and performs fuel flow rate control based on the difference between the two signals. A supercritical pressure boiler having a flow rate controller, and an air flow controller that is given an air command signal obtained by correcting the oxygen amount of the fuel command signal by the output of the oxygen amount controller and an air flow rate signal, and controls the air flow rate based on the difference between the two signals. In an automatic plant control device, a water-fuel ratio controller, a calorie setting device, and an oxygen amount controller each having a tracking function are used, a fuel flow rate controller and an air flow rate controller each having an output holding function, and a sequence control device is used. With this sequence control device, during calorie correction,
A tracking command is given to the water-fuel ratio controller, calorie setting device, and oxygen amount controller to cause the water-fuel ratio controller to perform a tracking operation so that the output signal matches the output setting value, and the calorie setting device receives the fuel flow signal as the fuel command. The oxygen amount controller performs a tracking operation on the output signal so that the air command signal matches the air flow rate signal, and output holding commands are given to the fuel flow controller and the air flow controller. , a calorie correction device that maintains this state until tracking is completed.