JPH01230909A - Nox control method by over-air port - Google Patents

Abstract

PURPOSE:To control the fluctuation of regular or transient NOX which can not sufficiently be controlled by only a basic opening signal and easily design a denitration device by regulating the basic opening signal on the basis of the difference between an approximate NOX signal and an approximate boiler outlet NOX signal according to a boiler input signal. CONSTITUTION:At the normal time a drive device 5 is actuated and the opening of an OAP damper 4 is limited by a basic opening signal from a function generator 2 on the basis of a boiler input signal 1. At this time an approximate outlet NOX signal 7 corresponding to the load from a function generator 6, other signals from a NOX meter 9 and an O2 meter 10 are introduced in a multiplier 11 to obtain an approximate boiler outlet NOX signal 12, signals 7, 12 are compared with each other by a subtracter 8, if there is a difference between the signals 7, 12, an opening regulating signal 14 is output by a function generator 13 according to the difference and added to the basic opening signal 3 by an adder 16 through a rate-of-change limiter 15. Therefore, the basic opening signal 3 is automatically regulated by the opening regulating signal 14 even if regular and transient NOX changes are produced.

Description

[Detailed Description of the Invention] [Industrial Field of Application] The present invention provides an NO
This relates to an x control method.

[Prior Art] Normally, a denitrification device for denitrifying exhaust gas is installed downstream of a boiler, etc., and the boiler is equipped with a denitrification device that denitrates exhaust gas. Two-stage combustion air is introduced from an over air port damper (OAP damper) to control boiler outlet NOx.

[Problem to be solved by the invention] However, regardless of the fuel, such as coal, gas, oil, etc., changes in N content in the fuel, changes in load, and starting and stopping of a pulverized coal mill in a coal-fired boiler can occur. When conditions such as the above change, the boiler outlet NOx fluctuates.

Therefore, even in the denitrification device, transient NOx control is strict, and therefore the denitration device needs to be designed with a margin.

An object of the present invention is to satisfactorily suppress a steady increase in NOx and a transient increase in NOx.

[Means for solving the problem] The present invention is an attempt to solve the above technical problem.
The opening degree of the over-airport damper is controlled by a basic opening signal based on the boiler input signal, and at the same time, the boiler outlet converted NOx is calculated from the converted NOx signal based on the boiler input signal, the NOx value detected at the boiler outlet, and the 02 value.
This invention relates to a NOx control method using an over-air port, characterized in that the basic opening degree signal is adjusted by an opening degree adjustment signal based on a difference between the basic opening degree signal and the basic opening degree signal.

[Function] Therefore, in the present invention, the converted NO. based on the boiler input signal
Based on the difference between the x signal and the boiler outlet converted NOx signal,
The basic opening signal is adjusted to suppress steady NOx fluctuations and transient NOx fluctuations that cannot be controlled by the basic opening signal.

[Implementation example] Embodiments of the present invention will be described below with reference to the drawings.

Fig. 1 shows an example of a device for carrying out the method of the present invention, in which an output command (boiler human power signal) 1 is guided to a function generator 2, and a basic opening signal 3 obtained by a basic opening program is used to generate a load. The drive device 5 is operated so that the opening degree of the OAP damper 4 is changed in accordance with the change in the opening degree of the OAP damper 4.

Furthermore, the boiler human power signal 1 is input to a function generator 6 to obtain a converted NOx signal 7 according to the load using a standard NOx program and output to a subtracter 8. Raw NOx and 02 from total 10
Subtraction is performed by outputting the boiler outlet converted NOx signal 12 obtained by guiding the signal to the multiplier 11 to the subtracter 8, and the difference signal is input to the function generator 13 to generate the OAP damper opening bias. A program outputs an opening adjustment signal 14, which is added to the basic opening signal 3 by an adder 16 via a change rate limiter 15.

Further, the boiler input signal 1 is input to the function generator 17 to obtain a correction signal 18 by a load correction program, and the signal 18 is multiplied by the opening adjustment signal 14 from the function generator 13 by a multiplier 19. The function generator 17 corrects the opening adjustment signal 14 according to the load band, since the NOx reduction situation changes slightly depending on the load band, and also makes adjustment in the low load area (for example, 1/4 or less of the steady state). In order to prevent this from happening, a zero signal is output to the multiplier 19. Further, the rate of change limiter 15 inputs a signal quickly and outputs the signal slowly (gently).

Normally, the drive device 5 is operated by the basic opening signal 3 from the function generator 2 based on the boiler human power signal 1, and the OAP is activated.
The opening degree of the damper 4 is limited.

At this time, the converted NOx according to the load from the function generator 6
The subtracter 8 compares the signal 7 with the boiler outlet converted NOx signal 12 obtained by guiding the signals from the NOx meter 9 and the 02 total 10 to the multiplier 11, and if there is a difference between the signals 7 and 12, Accordingly, the opening adjustment signal 14 is generated by the function generator 13.
is outputted and added to the basic opening signal 3 by an adder 16 via a change rate limiter 15. Therefore, steady NO
Even if an x change or a transient NOx change occurs 9, the basic opening signal 3 is automatically adjusted by the opening adjustment signal 14.

Also, since the NOx reduction situation changes depending on the load band, the adjustment signal 1 is adjusted by the correction signal 18 from the function generator 17.
4 is corrected according to the load range. Also, when the load is low (for example, 1/4 or less of the steady state), the correction signal 18 is set to zero to prevent adjustment, and OAP is performed using only the basic opening signal 3.
Controls the opening degree of the damper 4.

It should be noted that the present invention is not limited only to the above embodiments (
Various changes may be made without departing from the spirit of the invention.

[Effect of the invention] As described above, the over-air port of the present invention
According to the Ox control method, the conversion N based on the boiler input signal
Since the basic opening signal is adjusted based on the difference between the Ox signal and the boiler outlet conversion NOx signal, steady or transient N that cannot be controlled by the basic opening signal alone can be adjusted.
Excellent effects such as suppressing the fluctuation of Ox and facilitating the design of the denitrification device can be achieved.

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram showing an example of an apparatus for carrying out the method of the present invention. ■ is the boiler human power signal, 2 is the function generator, 3 is the basic opening signal, 4 is the OAP damper, 6 is the function generator, 7 is the conversion NO.
x signal, 9 is NOx meter, 10 is 02 total, 12 is boiler outlet converted NOx signal, 13 is function generator, 14 is opening adjustment signal, 15 is rate of change limiter, 16 is adder, 17 is function generator 18 indicates a correction signal.

Claims (1)

[Claims] 1) The opening degree of the over-airport damper is controlled by the basic opening signal based on the boiler input signal, and at the same time, the boiler outlet converted NOx is calculated from the converted NOx signal based on the boiler input signal and the NOx value and O_2 value detected at the boiler outlet. A NOx control method using an over-air port, characterized in that the basic opening degree signal is adjusted by an opening degree adjustment signal based on a difference from the basic opening degree signal.