JPH09250734A - Automatic controller for boiler - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suppress change in a main steam pressure or temperature by automatically determining the corrected value of a heating value from an analytical curve depending on the correlation of a heating value and moisture for each kind of coal obtained by a special chemical analysis and the measured value of the moisture of coal by a moisture meter. SOLUTION: An automatic correcting circuit using a moisture meter 16 capable of continuously and automatically measuring the surface moisture of coal is provided in a system for supplying coal. When a coal feeder 3 and a mill inlet primary air damper 4 are adjusted based on a master signal, the corrected value of a heating value is automatically determined based on the surface moisture of coal measured by the moisture meter 16 provided on a coal conveyor, relative to an analytical curve depending on the correlation of a heating value and moisture for each kind of coal obtained by a special chemical analysis and a fed coal amount feedback signal 2. Thus, the change of a main steam pressure or temperature can be suppressed and the burden of an operator can be reduced.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an automatic control system for a coal-fired boiler, and more particularly to a control system suitable for suppressing fluctuations in the control system due to fluctuations in the water content of coal.

[0002]

2. Description of the Related Art FIG. 5 is a diagram showing a portion related to fuel amount control of a boiler automatic control circuit according to a conventional example.

In the prior art shown in FIG. 5, the deviation of the main steam pressure from the feedback signal (the signal from the main steam pressure transmitter 1) is calculated based on the load request signal (MWD).
Output to the controller 10, and the controller 10 sends a signal to each operating end of the coal feeder 3 and the mill inlet primary air damper 4 according to the deviation command, and finally the main steam pressure determined by the load request signal. A loop is configured to control the fuel amount so that the deviation of the actual pressure with respect to the set value is eliminated.

In the control circuit shown in FIG. 5, a selector station 15 for remote manual correction of heat generation is provided at a portion A.
Is provided, and the fluctuation of the calorific value due to the influence of the water content of coal in the coal storage yard mainly in the summer and winter is manually corrected.

Further, in the part B, as shown in FIG.
By switching the master gain by selecting the type of coal and changing the type of coal, the difference in control response caused by changes in the calorific value, viscosity, ash content, etc. peculiar to each type of coal is compensated by the preset gain. There is.

In FIG. 5, 2 is a flow rate transmitter (coal feeder), 5 is a first-order delay calculator, 6 is a subtractor, 7 is a multiplier, 8 is a change rate limiter, and 9 is manual / automatic. A switch, 11 is a function generator, 12 is a voltage / current converter, 13 is an electro-pneumatic converter, and 14 is a manual setting device.

[0007] In particular, as a variable factor of the control system, there is a change in the calorific value of the coal due to a change in the water content in the coal. This is as shown in the schematic diagram of an example of the coal transfer system in FIG.
This is because the moisture content of coal changes due to rainfall and the like because the roof of the coal storage yard is not shielded outdoors.

In the case of the system shown in FIG. 6, the coal unloaded from the coal transport ship is temporarily loaded in the coal storage yard and then supplied to the coal bunker by the next stage equipment such as a coal conveyor. In FIG. 6, 18 is a coal conveyer, 19
Is a switching damper, 20 is a screen, 21 is a crusher,
22 is a scraper, and 23 is a magnet separator.

An example of the influence of the calorific value variation due to the amount of coal water is shown in the case of a boiler calorific value of 125 MW.
The amount of coal supplied per unit is 0 to 25 t / h, and in the case of a certain coal type, the calorific value of coal is 7340 kcal / k in the dry season.
The value of g is 6740 kcal / kg during the rainy season, and there is a difference of about 5.5 t / h in the average coal supply amount between the dry season and the rainy season.

[0010]

As described above, in the present control system, the operator manually corrects the coal calorific value of the manual analysis result obtained periodically, and as a result, the main steam pressure and temperature are corrected. Is a method that is generally performed, and it is difficult to construct a control system that automatically corrects the calorific value of coal, because continuous automatic measurement of calorific value is not possible. there were.

Those related to the present invention are disclosed in, for example, JP-A-53-76432 and JP-A-6-2215.
No. 42 publication and the like are listed.

However, Japanese Patent Laid-Open No. 53-76432 discloses a system in which gamma rays are used to detect changes in the amount of heat generated due to changes in coal quality (type of coal) and the gate is controlled to obtain a predetermined boiler output. However, since the method using gamma rays is used as a carbonaceous detector, it is necessary to have a dedicated operator and to set up a specific area as a gamma ray handling station, making it easy for all people involved in boiler operation. There was a difficulty that it could not be handled.

Further, in JP-A-6-221542, the mill outlet air temperature of the coal combustion system, the mill inlet air temperature, the mill inlet air amount, the coal feed amount, the mill power, the coal specific water content, etc. are input. It is a control device that calculates the calorific value of coal based on the calculation result of heat balance and tries to obtain the required coal supply amount that is not affected by the amount of surface moisture of coal, but the number of parameters is complicated and the calculation point is There is a problem in that the accumulative error of each measurement value becomes large and the accuracy deteriorates because a large number are required.

As described above, in the prior art, the calorific value of coal changes to a lower value when the water content is high and a higher value when the water content is low, but in the prior art, this is manually corrected intermittently. Since it is done, the main steam pressure and temperature change until the heat value changes and the correction is added.Because of the manual correction, the relationship between the coal heat value and the main steam pressure is clearly understood. In some cases, it is necessary to repeat the adjustment of over / under correction, the adjustment is difficult and complicated, and the operator's burden is increased.

An object of the present invention is to provide an automatic controller for a boiler which can suppress fluctuations in main steam pressure and temperature and reduce the burden on operators.

[0016]

[Means for Solving the Problems] The above objects are a moisture meter installed in a coal supply system and capable of continuously and automatically measuring the surface moisture of coal, and a calorific value for each coal type separately obtained by chemical analysis. It is achieved by including a calibration curve based on the correlation between the water content and the water content, and a correction unit that automatically determines the correction value of the calorific value from the coal water content measured by the water content meter.

[0017]

BEST MODE FOR CARRYING OUT THE INVENTION According to the present invention, a moisture meter capable of continuously and automatically measuring the surface moisture of coal is installed in a coal supply system, and the surface moisture of coal is continuously and automatically measured and separately determined by chemical analysis. The calorific value correction value is automatically determined from the calibration curve and the coal moisture measurement value based on the correlation between the calorific value and water content for each coal type, and it is incorporated into the fuel amount control circuit as an automatic calorific value correction circuit. It is a thing.

A detailed description will be given below with reference to the accompanying drawings.
The same parts as those in the conventional example are designated by the same reference numerals, and duplicate description will be omitted.

FIG. 1 is a system diagram of an automatic boiler control apparatus according to a first embodiment of the present invention.

FIG. 1 shows an example of an instrumentation system diagram in which automatic correction of coal calorific value by a moisture meter under mill control is incorporated, and corresponds to FIG. That is, in the part A, an automatic correction circuit by the coal moisture meter 16 is provided in place of the conventional selector station 15 shown in FIG. The master signal adjusts the coal feeder 3 and the mill inlet primary air damper 4. Among these, for the feedback signal 2 of the coal feeding amount,
The calorific value is corrected by the surface moisture of the coal measured by the coal moisture meter 16 provided on the coal conveyor.

The coal moisture and the FG (function generator 11) for calorific value correction are as shown in FIG. That is, a calibration curve is created based on the correlation between the measured coal moisture and the calorific value based on the result of the manual analysis [example of (1) in FIG. 2], and the correction value of the calorific value of the coal can be determined by the moisture measured value.

Symbols (b) and (c) in FIG. 2 show examples of calibration curves for different types of coal (or combination of coal types). To do.

The selection of coal type is carried out by the operator's manual selection method or a control computer to determine the type of coal according to the coal properties.
There are methods such as automatic selection of coal type.

In order to stabilize the control system, a height limiter 17 is provided so that the control width can be set.

The calibration curve of water content and calorific value shown in FIG. 2 is created in the initial adjustment stage, and the value of the surface water content of coal measured with a moisture meter and the calorific value at this time are obtained by manual analysis. A calibration curve is created by repeating this work and plotting the results.

This calibration curve is converted into the function generator 1 in the control system.
It replaces the function of No. 1, and once you create the function,
The calorific value of coal can be obtained by continuous automatic measurement of water content.

According to the same inventive idea, in the above-mentioned control system, the actual data of the coal moisture and the calorific value based on the analysis result are accumulated and calculated in a computer, and the function generator (FG) shown in the control system is shown. Control accuracy is also improved by combining 11 as an alternative.

FIG. 4 shows a coal moisture meter 16 (16
The example which installed a, 16b) is shown.

Thus, the coal moisture meter 16 is installed on the coal conveyor 18d, and the calorific value is automatically corrected in the same manner as described above.

According to the present invention, the relationship between the surface moisture of the coal and the calorific value is determined by the parameter, and the calorific value is automatically corrected by continuously and automatically measuring the moisture. The problem of over / under, and the complexity of adjustment are eliminated.

Further, with respect to the problems such as the handling chief and the specific area in the above-mentioned Japanese Patent Laid-Open No. 53-76432, the moisture meter of the present invention does not require any countermeasure. Similarly, JP-A-6-2
Instead of the control method based on the heat balance calculation in Japanese Patent No. 21542, the present invention solves problems such as control responsiveness and accuracy by continuously measuring the surface water content of the directly supplied coal and automatically correcting the calorific value.

[0032]

According to the present invention, fluctuations in main steam pressure and flow due to fluctuations in the calorific value of coal, which are caused by the influence of moisture mainly due to seasonal fluctuations such as rainfall, are automatically corrected. As compared with the conventional control system, labor saving can be achieved, and there is an effect that reliability can be improved and controllability can be stabilized.

[Brief description of drawings]

FIG. 1 is an instrumentation system diagram of a mill control according to an embodiment of the present invention.

FIG. 2 is an explanatory diagram showing a calibration curve for a heat generation amount correction function.

FIG. 3 is an explanatory diagram showing a master gain switching line for each coal type.

FIG. 4 is a coal transfer system diagram according to an embodiment of the present invention.

FIG. 5 is an instrumentation system diagram of a mill control according to a conventional example.

FIG. 6 is a coal transfer system diagram according to a conventional example.

[Explanation of symbols]

 3 Coal feeder 11 Function generator 16 Coal moisture meter 17 High and low limiter 18 Coal conveyor

Claims (1)

[Claims] 1. A moisture meter installed in a coal supply system capable of continuously and automatically measuring the surface moisture of coal, and a calibration based on the correlation between the calorific value and moisture of each coal type separately obtained by chemical analysis. An automatic control device for a boiler, comprising: a line and a correction unit that automatically determines a correction value for a calorific value from a coal moisture measurement value obtained by a moisture meter.