JPH0455615A - Method of controlling combustion in burner - Google Patents

Abstract

PURPOSE:To enable a prevention of smoke or of an occurrence of lost fire to be attained, improve a safety and further enable an air preceding control to be attained with a less amount of over-shooting by a method wherein a combustion control device performs a control calculation with two kinds of flame signal and a degree-of-opening signal and operates a combustion air adjusting valve in response to the calculation. CONSTITUTION:A degree of opening of each of fuel control valve 7 and a combustion air volume adjusting valve 9 is controlled by a modutrol motor. An arm 12 of the fuel control valve 7 is connected to an arm 15 of the modutrol motor 14 through a linkage 13. A flame of a burner 5 is monitored and a flame signal is got in reference to a varying amount of the flame. A degree-of-opening signal of the fuel control valve 7 is got from the modutrol motor 14 for use in adjusting fuel in response to a pressure of water 4 within a drum 3 heated by the flame 6 of a burner 5. These flame signal and degree-of-opening signal are inputted into a combustion control device 23 and the combustion air adjusting valve 9 is operated in response to a result of control calculation with these two kinds of signals.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a combustion control method for a burner used in combustion equipment such as a boiler.

(Prior art) In a burner that burns liquid or gaseous fuel,
It is desirable to maintain its combustion conditions optimally during combustion. The combustion state of the flame in the burner is generally determined by the mixing ratio of air and fuel (air ratio or 02i! degree ratio in exhaust gas).
varies greatly depending on In order to maintain good combustion conditions, a combustion control device has traditionally been installed in the combustion device.
This combustion WI control device is often used to perform feedback control of the exhaust gas 02 to adjust the amount of air supplied to the combustion device and, by extension, the air ratio. In addition, the light intensity signal generated by the burner flame is converted into an electrical signal using a semiconductor such as a phototransistor, photodiode, or solar cell, and the integrated value of the power spectrum obtained as a result of frequency analysis of the vibration waveform is used. There is a method and device for performing combustible writing, which is described in Japanese Unexamined Patent Publication No. 6
Please refer to Publication No. 3-306310.

In the invention described in the above publication, when controlling the position of combustion air, it is necessary to control the followability to changes in the combustion state, especially when the fuel flow rate increases, to correct for variations in the power spectrum ratio, or to The functions for practical combustion control, such as correcting the optimum sky viewing ratio at partial negative times specific to the combustion engine, were somewhat lacking. That is, it is known that the frequency components of optical vibrations emitted from combustion flames are constantly changing. Therefore, the combustion control method disclosed in the above-mentioned Japanese Patent Application Laid-Open No. 63-306310 has a strong correlation between changes in the power spectrum ratio of optical oscillations and changes in the combustion state caused by changes in the air ratio. It was completed with a focus on

However, in order to actually use the optical power spectral ratio as a combustion control index, variations in the optical power spectral ratio caused by the combustion characteristics of the flame have become a problem. This problem can be solved by performing moving average processing to reduce the width of dispersion and eliminate short-time changes, and to obtain the optimal moving average value according to the characteristics of the combustor. This can be solved by making the number of times configurable.

On the other hand, the combustion mentioned above in 5! When applying the i-control method to combustion equipment with large load fluctuations, such as boilers, it is necessary to implement air ratio control according to changes in combustion amount. Incidentally, each combustor has its own unique combustion load characteristics. i.e. load 1
At 00%, the air ratio is 1', at 80% load, the air ratio is 12, and at 50% load, the air ratio is 1! etc., it is necessary to adjust the air ratio to an appropriate level according to changes in the amount of combustion. Therefore, the optical power spectrum ratio has an appropriate set value depending on each combustion amount. For this reason, a line table of optical power spectrum ratio set values corresponding to each combustion amount is set up, and the set values and the current state are compared through this line table.

Control is carried out in this way, but if the followability is poor, especially when increasing the air volume in accordance with the rate at which the fuel increases, the required air volume may not be obtained, resulting in black smoke generation, misfires, etc. This may cause problems. For this purpose, it is necessary to know the fuel flow rate, so the rate of change of the output signal of the flow meter or the opening signal of the fuel valve is constantly monitored using a rate of change monitor.
For a sudden increase in combustion amount above a certain value, PID (
Propartional Integral a
nd Derivative Control) output signal, the opening information is further added to the output signal, and the resultant signal is output.

In addition, regarding the current power spectrum ratio of Hana, if the change exceeds the lower limit value according to the set value of the polygon table, the lower limit monitor displays the result of ratio calculation corresponding to the change rate in the same way as the flow rate change rate. It was added to the output signal to increase the amount of air from 5. Incidentally, among the lower limit monitor outputs of the rate of change of the fuel flow rate and the power spectrum ratio, the one having a larger absolute value is selected and added to the PID output signal.

In view of the current situation, the inventor of the present invention has conducted various researches and found that
By adding the control function described above, it was possible to obtain a combustion*+tS device that can stably perform combustion control even for combustion equipment such as a boiler that has rapid load fluctuations.

This device, which is prior art to the present invention, provides a burner toward the inside of the double-structured inner container, adjusts the amount of fuel and air added to the burner, and controls the amount of fuel and air added to the
This was achieved in a smoke tube boiler in which the amount of combustion was controlled by controlling the temperature of the liquid contained in the chamber to a constant value, and a pressure gauge was installed to detect the pressure between the inner and outer vessels. an optical sensor for controlling the amount of fuel supplied to the burner by comparing the output value of the pressure gauge with a set value by means of a pressure regulator and monitoring the flame of the burner; The structure includes a combustion subwriting device that receives the output signal of this optical sensor and controls the air rod.A patent application has already been filed for this technology (Japanese Patent Application No. 1-303531).
issue).

(Problem to be Solved by the Invention) When controlling combustion air using the combustion control device of the prior art described above, the operation output of the control device is calculated based on the PID calculation for the deviation between the measured value and the set value, and when the fuel flow rate increases. It is output by either the ratio calculation by the fuel change rate monitor or the ratio calculation by the measurement ffiff. In particular, when the fuel flow increases rapidly, the ratio calculation is performed by the operation of the fuel change rate monitor or measurement 1 direct adjustment monitor mentioned above, and the amount of combustion air is increased by forcibly opening the damper. This makes it possible to perform excellent air advance control without any delay.

However, in this prior art, since the damper was controlled only by PID calculation, the damper may not be able to follow the decreasing speed of the fuel flow rate, and in this case, the damper There were cases where the flame was blown out because it was opened more than necessary. Therefore, if each operating point of the PID is set so that the damper follows the decreasing speed of the fuel flow rate, hunting may occur during normal control, making control difficult. That is, when the fuel flow rate suddenly changes from the maximum amount to the minimum amount, there is a problem in that the damper may not be able to follow the change in the fuel placement.

According to the present invention, even if the fuel flow rate suddenly changes from the maximum amount to the minimum amount as described above, the combustion tIll? This was done for the purpose of obtaining 11 methods.

(Means for Solving the Problems) The present invention provides a first method for solving the problems described above.
As shown in the figure, the flame 6 of the burner 5 is monitored to obtain a flame signal from the amount of change thereof, and the flame 6 is adjusted according to the pressure of the water 4 in the drum 3 heated by the flame 6 of the burner 5. Modutrol motor I4 to fuel control valve 7
The flame signal and the opening signal are taken into the combustion control device 23, and the combustion air control valve 9 is controlled based on the result of control calculation in the combustion control device 23 using these two types of signals. A combustion control method for the burner 5 is obtained, which is characterized by operating the burner 5.

(Function) According to the combustion control method configured as above, the two-combustion control device 23 performs control calculations using two types of signals, the flame signal and the opening signal, and controls the combustion air control valve 9 based on the results. By operating the damper, even when the fuel flow rate suddenly changes from the maximum amount to the minimum amount, the damper can follow the change in the fuel flow rate.

(Example) Hereinafter, a burner combustion method according to the present invention will be described. First, an apparatus for realizing the method of the present invention will be described with reference to FIG. 1 is a smoke tube boiler, 2 is its outer wall, 3
is a drum provided in the upper part of the outer wall 2. drum 3
The inside of the container is filled with water 4. A burner 5 is attached to a part of the outer wall 2, and the flame 6 emitted by the burner 5 is designed to spray the lower part of the tram 3 laterally. A fuel supply pipe 8 having a fuel control valve 7 connected therebetween is connected to the burner 5 to supply fuel to the burner 5. The burner 5 is further connected to an air supply duct 1O equipped with a combustion air amount control valve 9 in the middle, so that combustion air from a blower fan 11 is supplied.

The fuel control valve 7 and the combustion air amount control valve 9 are both controlled in opening by a modutrol motor, and the arm 12 of the fuel control valve 7 is coupled to the arm I5 of the modutrol motor 14 via a link 13. The arm I5 of the combustion air control valve 9 is connected to the arm of the modutrol motor 18 via the Jacque 1f. It is connected to 9.

The modutrol motor 14 is operated by a signal from the pressure regulator 21 given via the signal @2 (), but the operating signal (opening of the fuel control valve 7) generated by a potentiometer or the like (not shown) is The combustion control device @23 is supplied with a signal line 22.

The modutrol motor 18 is supplied with an output signal from the combustion control device 23 via a signal line 24 .

The pressure regulator 21 compares the water pressure (steam pressure) in the tank 3 with a preset set pressure, and sends a signal to close the fuel control valve 7 when the water pressure in the drum 3 exceeds the set pressure. A modutrol motor! It is designed to output to 4. For this reason, the output side of a drum pressure transmitter 25 for detecting the pressure inside the drum 3 is connected to the input side of the pressure regulator 21. A viewing window 26 is provided on the outer wall of the smoke tube boiler 1 opposite to the part where the burner 5 is attached. .Light guide 2
At the base end of 7 is a sensor amplifier 28 that detects the state of the flame 6.
The output side of this sensor amplifier 28 is connected to the input side of the combustion control device 23 by a signal line 29. As the sensor amplifier, a well-known phototransistor or photodiode, and a transistor amplifier that amplifies its output signal can be used.

Next, a method of the present invention using the combustion control device having such a configuration will be explained. First, the drum 3 is filled with water 4, and then the burner 5 is ignited by igniting a pilot burner (not shown). As the fuel, gas or heavy oil can be considered. The burner 5 is supplied with an air flow generated by a blower fan 11 in addition to fuel.

The state of the flame 6 of the burner 5 can be seen from the viewing window 26 through the light guide 27.
The signal is monitored from start to finish by the sensor amplifier 28 that is transmitted through the sensor amplifier 28, and after being amplified to an appropriate level, it is input to the combustion control device @23. On the other hand, a pressure transmitter 25 provided at the upper center of the drum 3 detects the pressure inside the drum 3 and sends its output signal to the pressure regulator 21.

The pressure regulator 21 compares the signal from the pressure transmitter 25 with a preset pressure value, and then performs an adjustment function so that the pressure value within the drum 3 is always constant. This adjustment is performed by controlling the rotational direction of the modutrol motor 14 and opening and closing the fuel control valve 7. Note that the opening degree signal of this fuel control valve 7 is transmitted from the modutrol motor 14 that drives this fuel control valve 7, and is sent from the combustion control device @23.
is applied to When the burner 5 operates and a flame 6 is generated, the strength of the flame 6 is constantly monitored by the sensor amplifier 28 transmitted through the light guide 27, converted into a current signal, amplified to an appropriate level, and then combusted. Control device 2
3 is input. The combustion control device 23 calculates and processes both this signal and the opening signal of the fuel control valve 7, and uses the resulting output signal to control the modutrol motor 18.
control

Next, referring to FIG. 2, the details of the control performed inside the combustion control device 23 in FIG. 1 will be explained. First, the following preparations are made for the combustion control device 23. In other words, the operation signal upper and lower limit limiter is applied to the operation output output by the PID calculation, the fuel amount change rate monitor ratio calculation, and the -1 fixed value lower limit monitor ratio calculation so that the value set for a certain fuel amount is obtained. establish. The upper and lower limit values are set in advance in accordance with the fuel flow rate and compiled into a table. As a result, if the manipulated output value input to the limiter is within the upper and lower limits, it will be output as is, but if it exceeds the upper limit (or lower limit), it will be forced to the respective limit value. Limited output.

By operating in this manner, for example, in the case where the fuel flow rate suddenly decreases, even if the damper closing operation based on the PID calculation is delayed in response to the rate of decrease in fuel, the operation output upper limit corresponding to the fuel flow rate will be applied. Since the damper is forcibly closed, there is no delay in following the fuel amount.Also, since the damper opening degree is forcibly controlled by the lower limit, smoke or misfire may occur if the damper closes more than necessary. In addition, when the rate of change monitor operates when the fuel flow rate increases and calculates the ratio, the damper is opened more than necessary, causing overshoot, but the upper limit prevents the damper from being opened more than necessary. This prevents the valve from opening and enables advance air control with minimal overshoot using the minimum amount of air required.

Explain the operation. The electrical signal input from the sensor amplifier 28 (see Figure 1) is FFT (FastFo
The vibration frequency is analyzed by the processing unit 30 and output as a power spectrum ratio, then averaged by the moving average processing unit 31 by the number of times set in the moving average number table 32, and the branching unit 33 calculates the frequency by an adder. 34 and the Pv lower limit monitor 35. The polygon table 36 contains the moving average frequency table 3 of the opening signal of the fuel flow meter 37 or the fuel control valve 7 (see FIG. 1).
The current fuel N flow rate or fuel control valve opening signal is inputted via a moving average processing section 39 that performs a moving average at a number of times set to 8.

In this fold line table 36, Mo! A power spectrum ratio setting value corresponding to the A flow rate or fuel control valve opening signal is selected from the table and outputted to the adder 34, and at the same time,
The power spectrum ratio lower limit setting value at this time is output to the PV lower limit monitor 35.

The adder 34 compares the set value output from the line table 3 with the current value input from the moving average processing section 31.5 The result is led from the dead zone processing section 40 to the PID calculation section 41, and is calculated as a deviation. The corresponding output value is output to the adder 42.

In the adder 42, the P■ lower limit monitor 43 compares the power spectrum ratio lower limit value set in the broken line table 36 with the power spectrum ratio current value manually input from the branching section 33, and the current value is determined as the power spectrum lower limit setting. If it is less than the value, the PV adjustment monitor ratio calculation section 43 calculates a corrected output according to the amount of change, and outputs it to the comparison selection section 44. The current fuel flow rate or fuel valve opening signal is calculated as a rate of change by a change rate monitor 46 from a 5-branch unit 45 and input to the comparison and selection unit 44 via a rate-of-change monitor ratio calculation unit 47.

The comparison and selection section 44 selects the one with the largest absolute value among the spectrum ratio lower limit change rate and the fuel flow rate or fuel valve opening signal and outputs it to the adder 42 . The adder 42 adds this signal to the signal outputted from the arithmetic unit 41 from P and outputs it to the output upper/lower limiter 48 . The operation output for which the upper limit output is set by the output upper/lower limit limiter 48 is output to the air amount n mode valve 9 (see FIG. 1). The input signal from the adder 42 and the signal from the output limiter table 49 are input to the output upper/lower limiter 48 . The output power table 49 is the fuel input from the branch point 50: a! Upper and lower limits of the operating output are set corresponding to the signal or the fuel control valve opening signal. FIG. 3 shows these set values, where 2■ represents the upper limit and ■ represents the lower limit.

The output upper/lower limit limiter 48 compares the human input signal from the output limiter table 49 with the input signal from the adder 42, and determines whether the signal from the adder 42 is within the upper or lower limit value range of the output limiter table 49. If there is, the signal is output as is, and if it exceeds the upper limit or falls below the lower limit, operation signals of the upper limit value and lower limit value are forcibly output to the air amount control valve 9, respectively.

(Effects of the Invention) As described above, the present invention monitors the flame of the burner to obtain a flame signal from the amount of change in the flame, and also adjusts the fuel according to the pressure of the water in the tram heated by the flame of the burner. The opening signal of the fuel control valve is obtained from the modutrol motor, and these flame signals and opening signals are taken into the combustion control device, and the combustion control device controls the combustion based on the result of subscript calculation using these two types of signals. Since this is a burner combustion control method characterized by operating an air control valve, this is a problem with the prior art described above. This solves the problem of the damper not being able to follow the change in fuel flow rate when the fuel flow rate changes suddenly from the maximum amount to the minimum amount, and also provides the following effects. .

■ Since the minimum opening degree of the damper can be set for each fuel flow rate, the damper is not throttled more than necessary through control, smoke generation and misfires can be prevented, and highly safe control can be achieved.

■ The upper limit of the damper opening can be set when the ratio calculation is performed using the fuel change rate monitor and PV lower limit monitor.
Air advance control with less overshoot is possible without increasing the amount of air more than necessary.

[Brief explanation of the drawing]

Figure 1 is a system diagram of a combustion device that implements the method of the present invention;
The figure shows the process performed inside the combustion control device in Figure 1.
FIG. 3 is a flowchart for explaining the contents of S, and is a graph showing the upper and lower limits of the operating output corresponding to the fuel control valve opening signal set inside the combustion control device in FIG. 1... Smoke tube boiler 2 - Outer wall 3 - Tram 5... Burner 6 - Flame 7 - Combustion control valve 9 - Combustion air control valves 14, 18 - Modutroll motor 21 - Pressure regulator 23 -・Combustion control device 28-・Sensor amplifier patent

Claims (1)

[Claims] (1) The modutrol motor monitors the burner flame and obtains a flame signal from the amount of change in the flame, and also controls the fuel control valve opening according to the pressure of water in the drum heated by the burner flame. A signal is obtained, these flame signals and opening degree signals are taken into a combustion control device, and the combustion air control valve is operated in the combustion control device based on the result of control calculation using these two types of signals. Burner combustion control method.