JPH0894071A - Combustion control method for combustion method - Google Patents

Abstract

PURPOSE: To provide a combustion control method for a combustion device wherein by directly detecting the turbulent flow state (a combustion state) of a combustion flame, the coefficient of exhaust gas recirculation optimum to a detecting turbulent flow is realized, the density of a nitrogen oxide pro duced along with combustion of fuel is reduced, and when the optimum coeffi cient of exhaust gas recirculation is executed, the production of carbon monox ide owing to incomplete combustion is prevented. CONSTITUTION: The turbulent flow state of a combustion flame is directly detected by a photo sensor 31, and division processing is applied on a detecting electric signal by an analogue divider in a sensor amplifier 30. Frequency analysis processing is applied on a divided electric signal by an FFT in a combustion control device 50 processing part to determine a first vibration power. The coefficient of exhaust gas recirculation is decided so that the first vibration power coincides with a precalculating second vibration power contained in a bend line table. Combustion control by an exhaust gas recirculation method is executed at the deciding coefficient of exhaust gas recirculation.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a combustion control method applied to various combustion devices such as boilers and industrial furnaces, and more particularly to a combustion device suitable for a combustion device equipped with exhaust gas recirculation treatment equipment. The present invention relates to a combustion control method.

[0002]

2. Description of the Related Art Nitrogen oxides (NO _x ) are generated when fuel is burned in a combustion device such as a boiler. Nitrogen oxides are roughly classified into fail NO _x produced from nitrogen components in fuel or thermal NO _x produced by high-temperature oxidation of nitrogen contained in combustion air. Since these nitrogen oxides are substances that cause air pollution, acid rain, etc., strict regulations are imposed on the concentration of nitrogen oxides contained in the exhaust gas.

Therefore, various nitrogen oxide generation suppressing methods have been proposed and put to practical use in order to suppress the generation of nitrogen oxides due to combustion. In order to suppress the fail NO _x , it is effective to pre-denitrify the nitrogen component contained in the fuel, but it has reached the established technical level like direct and indirect desulfurization technology including the development of catalysts. The current situation is that it has not reached it.

On the other hand, as a method of suppressing thermal NO _x , it is known that combustion control such as change of combustion condition or change of combustion method is effective, and exhaust gas recirculation is one of the techniques for changing combustion method. There is removal.

The exhaust gas recirculation method is a combustion control method for suppressing generation of thermal NO _x by mixing exhaust gas with the combustion air supplied to the combustion chamber. It is generally known that lowering the combustion temperature and lowering the oxygen concentration are effective in suppressing the production of thermal NO _x . However, in the actual combustion, if the oxygen concentration is lowered, the combustion temperature approaches the theoretical combustion and the combustion temperature rises, which can be said to be inconsistent combustion conditions.

However, in the exhaust gas recirculation method, the temperature of the exhaust gas supplied to the combustion chamber together with the combustion air is usually 200.
℃ ~ 300 ℃, which is lower than the combustion temperature,
The heat generated in the combustion chamber at the time of combustion can be absorbed, and the temperature rise in the combustion chamber due to combustion can be suppressed. Further, since the exhaust gas is a complete combustion gas containing N ₂ , CO ₂ , H ₂ O, etc. as main components, it does not burn even if it is supplied to the combustion chamber again, and the reaction heat (heat generation) accompanying the combustion is generated. Does not occur.
Furthermore, since the combustion air contains exhaust gas that contains almost no oxygen component, the oxygen concentration of the combustion air supplied to the combustion chamber is reduced compared to combustion air that does not use the exhaust gas recirculation method. To be done.

A combustion control method according to a conventional example will be described below with reference to FIG. 16 showing a schematic structure of a combustion apparatus B4 having a structure for applying the exhaust gas recirculation method. The combustion fuel is supplied to the burner 80 from a fuel tank (not shown), and the combustion fuel is atomized into the combustion chamber 81 from the burner 80. On the other hand, the combustion air passes through the combustion air duct 83 by the combustion air fan 82 and the wind box 84.
And is supplied into the combustion chamber 81 from the rear of the burner 80. At this time, the combustion air supplied into the combustion chamber 81 contains a part of the exhaust gas discharged from the combustion chamber to the chimney through the exhaust duct 85.

That is, a branch exhaust duct 86 is formed in the exhaust duct 85, and the branch exhaust duct 86 is formed.
Is connected to the exhaust gas circulation fan 87. Therefore, a part of the exhaust gas is sucked toward the branch exhaust duct 86 side. Since the exhaust gas circulation fan 87 and the combustion air duct 83 are connected by the circulation exhaust duct 88, the exhaust gas sucked into the branch exhaust duct 86 is supplied to the upstream side of the combustion air duct 83. is there.

The circulating exhaust duct 88 is provided with an exhaust gas recirculation amount adjusting damper 89 for adjusting the exhaust gas recirculating amount (mixing amount). , Is fixed to a predetermined opening by feedforward control based on experience values.

Therefore, the ratio of the exhaust gas mixed in the combustion air is constant, and the feedback control for adjusting the opening degree of the exhaust gas recirculation amount adjusting damper 89 is performed in consideration of the combustion state in the combustion chamber 81. Absent.

Now, the relationship between the exhaust gas recirculation rate and the NO _x concentration contained in the exhaust gas will be described with reference to the graph shown in FIG. This graph shows the maximum combustion amount of 28.5M
J / h A heavy oil fired boiler, combustion amount 1.8 MJ
/ H shows the measurement result, and the vertical axis is O ₂ 4%
The converted NO _x concentration is shown, and the horizontal axis shows the exhaust gas recirculation rate.

[0012] exhaust gas recirculation rate and O ₂ 4% in terms of NO _X concentration, the higher the exhaust gas recirculation rate, O ₂ 4% in terms of NO _X
There is an inversely proportional relationship in which the concentration becomes low, and it is understood that the exhaust gas recirculation rate should be increased in order to reduce the NO _X concentration. However, increasing the exhaust gas recirculation rate means that the oxygen concentration in the supplied combustion air decreases, and when the oxygen concentration extremely decreases,
Combustion failure such as blowout of flame, lift, vibration combustion, etc. will occur.

Therefore, when the opening of the exhaust gas recirculation amount adjusting damper 89 is feedforward controlled as described above, the exhaust gas recirculation amount of about 20 to 30% is taken into consideration in consideration of the change in the combustion condition due to disturbance or the like. The combustion control method using the exhaust gas recirculation method has been implemented depending on the circulation rate.

The exhaust gas recirculation rate is the amount of combustion air.
[Nm³/ H] exhaust gas recirculation amount [Nm³/ H]
Is obtained by the following formula. Exhaust gas recirculation rate = Exhaust gas recirculation amount / Combustion air amount Furthermore, O₂4% conversion NO_XConcentration [ppm] is measured
Measurement NO with variations_XStandardized concentration [ppm]
Is an index used to facilitate comparative examinations.
In the formula shown below, conversion O₂= 4
Conversion NO obtained _XThe concentration. Where the fuel is liquid
In some cases, O₂4% conversion NO_XConcentration converted NO_XConcentration and
If the fuel is a gas, O₂0% conversion N
O_XConcentration or O₂6% conversion NO_XConcentration converted N
O_XUsed as a concentration. Conversion NO_X= (21-conversion O₂) / (21-Exhaust gas
O₂) × Measurement NO_X

[0015]

However, in the combustion control method using the exhaust gas recirculation method, which determines the exhaust gas recirculation rate by the conventional feedforward control, the optimum exhaust gas recirculation rate for the actual combustion state is determined. As a result, there is a problem that the generation of nitrogen oxides cannot be suppressed as much as possible.

That is, in the case of the feedforward control, since the actual combustion state is not detected, for example, the absolute volume change of the combustion air due to the change of the outside air temperature, the change of the ventilation amount from the exhaust duct 85 to the chimney. Fluctuations in the exhaust gas recirculation rate due to

Therefore, it is necessary to take a safety margin when determining the exhaust gas recirculation rate, and the exhaust gas recirculation rate tends to be set low. Under such an exhaust gas recirculation rate, sufficient reduction of nitrogen oxides cannot be expected even when other combustion control methods such as the two-stage combustion method are combined.

Thus, in the exhaust gas recirculation method, which is extremely effective as a method for suppressing nitrogen oxides, it is not possible to raise the exhaust gas recirculation rate to the limit because of the combustion chamber 81.
This is because it was not possible to directly detect the internal combustion state.

An EGR control device for an internal combustion engine, which is not a control device for a continuous combustion type combustion device, controls the opening and closing of the EGR valve by directly detecting the combustion state in the internal combustion engine. It is disclosed in the publication.

In this control device, the tip of the optical fiber is arranged in the combustion chamber, and the combustion light in the combustion chamber is guided to the photoelectric conversion element by using the optical fiber as a transmission medium and converted into an electric signal. Is equipped with. Therefore, if this idea is applied to a combustion device, it becomes possible to directly detect the combustion state, and it seems that the exhaust gas recirculation method can be effectively utilized.

However, since the combustion mechanism is different between the single-shot combustion type internal combustion engine in which the combustion is interrupted at each combustion (explosion) and the continuous combustion type combustion device in which the combustion is not interrupted, it is practically simply used. Cannot be transformed. That is, since the control device described in the publication does not include means for detecting and analyzing the turbulent flow state of the combustion flame, it is possible to simply detect the emission intensity due to the explosion, but the change in the combustion condition. It is not possible to detect the turbulent flow state of the combustion flame due to.

Further, since the control device disclosed in the publication merely executes ON / OFF control of the EGR valve with a certain emission intensity as a boundary value, it does not aim at optimizing the exhaust gas recirculation rate. Objects cannot be effectively suppressed. Further, no correction means for disturbance such as radiant heat in the combustion furnace is provided, and as a result, it can be applied only under an exhaust gas recirculation rate with a safety margin.

The present invention was made in order to solve the above-mentioned conventional problems, and by directly detecting the turbulent flow state (combustion state) of the combustion flame, the exhaust gas optimum for the detected turbulent flow state is obtained. The purpose is to realize a recirculation rate and to reduce the concentration of nitrogen oxides generated with the combustion of fuel. Also, in executing the optimum exhaust gas recirculation rate,
An object of the present invention is to provide a combustion control method for a combustion device that does not generate carbon monoxide due to incomplete combustion.

[0024]

In order to achieve the above object, a combustion control method for a combustion apparatus according to the invention of claim 1 is a combustion control method for a combustion apparatus for supplying an inert gas together with combustion air to a combustion chamber. A first process of detecting the turbulent flow state of the combustion flame in the combustion chamber by the turbulent flow state detection means, and an inert gas so as to realize a predetermined turbulent flow state in which the turbulent flow state of the combustion flame does not result in incomplete combustion. And a second step of adjusting the supply amount of

The combustion control method for a combustion apparatus according to a second aspect of the present invention is a combustion apparatus having an exhaust gas recirculation system for supplying a part of the exhaust gas discharged from the combustion chamber to the combustion chamber again together with the combustion air. In the combustion control method, the turbulent flow state detection means detects the turbulent flow state of the combustion flame in the combustion chamber, and from the turbulent flow state data detected by the turbulent flow state detection means, the vibration component of flame light and the emission intensity of the flame are detected. A third step of extracting the representative components, and a third step
For the vibration component extracted in the process, a combination of a frequency analysis process for calculating an intensity integral value in the entire frequency range and an effect removal process for removing the influence of the emission intensity representative component on the vibration component. The fourth process of obtaining the first vibration power by applying the above is compared with the first vibration power obtained in the fourth process and the second vibration power calculated in advance to realize a predetermined turbulent flow state. A fifth step of determining an exhaust gas recirculation amount in order to match the first vibration power with the second vibration power,
And a sixth step of adjusting the exhaust gas recirculation amount adjusting valve based on the exhaust gas recirculation amount determined in the process to adjust the amount of exhaust gas mixed into the combustion air.

Here, in the fourth step, the influence removing process of dividing the vibration component by the emission intensity representative component is performed, and the frequency analysis process is performed on the vibration component subjected to the influence removing process. Thus, the process of obtaining the first vibration power may be performed. In addition, the fourth step,
The first vibration power may be obtained by performing the frequency analysis process on the vibration component and performing the influence removal process of dividing the vibration component subjected to the frequency analysis process by the emission intensity representative component. .

The turbulent flow state detecting means is preferably an optical sensor for converting the turbulent flow state of flame light into an electric signal and outputting it as turbulent flow state data, or the turbulent flow state detecting means is preferable. Preferably, the ion current sensor converts the turbulent flow state of flame light into an electric signal and outputs it as turbulent flow state data.

[0028]

In the combustion control method for the combustion apparatus having the structure described in claim 1, in the first step, the turbulent flow state detecting means detects the turbulent flow state of the combustion flame in the combustion chamber. In the subsequent second step, based on the turbulent flow state of the combustion flame obtained by the turbulent flow detection means, the turbulent flow state of the combustion flame is set to a predetermined turbulent state that does not lead to incomplete combustion. Adjust the amount of active gas supplied. Then, the supply amount of the inert gas is supplied into the combustion chamber together with the combustion air.

Further, in the combustion control method for the combustion apparatus having the structure described in claim 2, in the third step, the turbulent flow state detecting means detects the turbulent flow state of the combustion flame in the combustion chamber to determine the turbulent flow state. The vibration component of the flame light and the representative component of the emission intensity of the flame are extracted from the turbulent flow state data detected by the detection means. Here, when the optical sensor is used as the turbulent flow state detecting means, the turbulent flow state of the flame light is detected by the optical sensor, and the electric current corresponding to the turbulent flow state is replaced and output. When an ion current sensor is used as the turbulent flow state detection means, the turbulent flow state of flame light is detected by the ion current sensor,
A current corresponding to the turbulent state is output.

In the following fourth step, a frequency analysis process for calculating an intensity integral value in the entire frequency region for the vibration component among the respective components extracted in the third step, and the emission intensity representative component is the vibration component. The first vibration power is obtained by performing a combination with an effect removal process for removing the effect on the first vibration power.

Next, in the fifth step, the first vibration power obtained in the fourth step is compared with the second vibration power calculated in advance to realize a predetermined turbulent flow state, and the first vibration power is compared. The exhaust gas recirculation amount that makes the value equal to the second vibration power is determined.

Then, in the sixth process, the exhaust gas recirculation amount adjusting valve is adjusted based on the exhaust gas recirculation amount determined in the fifth process, and the amount of exhaust gas mixed into the combustion air is determined.

Here, in the combustion control method of the combustion apparatus having the structure described in claim 4, in the fourth step, first, the influence removing process of dividing the vibration component by the emission intensity representative component is extracted in the fifth step. The first vibration power is obtained by applying the frequency analysis process to the vibration component subjected to the effect removal process.

Further, in the combustion control method for the combustion apparatus having the structure described in claim 5, in the fourth step, first, the frequency analysis processing is performed on the vibration component extracted in the fifth step, and the frequency analysis is performed. The first vibration power is obtained by performing the effect removal process of dividing the processed vibration component by the emission intensity representative component.

[0035]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Several embodiments in which the present invention is applied to a boiler for supplying steam to a heating device in a factory will be described below with reference to the drawings.

First, the construction of a boiler B1 to which the combustion control method for a combustion apparatus according to the first embodiment is applied will be described with reference to FIGS. The boiler B1 includes a main body 10 including a combustion chamber 11, an exhaust gas duct 12 that guides exhaust gas in the combustion chamber 11 to a stack (not shown), and a combustion air supply duct 13 that supplies combustion air into the combustion chamber 11. And an exhaust gas recirculation duct 14 for recirculating a part of the exhaust gas to the combustion air supply duct 13, and a fuel supply unit 20 for supplying fuel into the combustion chamber 11.

The main body 10 is formed in a horizontally long, substantially cylindrical shape, and inside the main body 10, a combustion chamber 11 in which a mixture of fuel and combustion air is combusted, and a liquid such as water that functions as a heat medium are combusted. And a liquid chamber 15 for heating by the flame F. Further, the combustion chamber 11 and the liquid chamber 15 are AA of FIG.
As shown in the line sectional view, it is partitioned by the furnace wall 16.

A burner 17 for spraying and burning the air-fuel mixture in the combustion chamber 11 is attached to the right side wall of the combustion chamber 11, and an exhaust gas duct 12 is connected to the left side wall.

The burner 17 comprises a fuel supply section 20 and a fuel supply pipe 2 for supplying fuel to the burner 17.
1 and a combustion air supply duct 13 that supplies combustion air to the burner 17. Therefore, an air-fuel mixture in which the fuel and the combustion air are mixed is generated, and the air-fuel mixture is ignited, whereby continuous combustion of the air-fuel mixture occurs and a combustion flame F is generated.

A peep window 18 is formed on the left side surface of the combustion chamber 11, and a sensor amplifier 30 for detecting the turbulent flow state of the combustion flame F is provided in the peep window 18 via an optical fiber OF. It is connected.

The liquid chamber 15 is filled with a liquid L, such as water, which functions as a heat medium while leaving a slight space S at the upper portion thereof, and the combustion generated when the air-fuel mixture is burned in the burner 17 is generated. The heat is transferred to the liquid L in the liquid chamber 15 via the furnace wall 16. Further, as shown in FIG. 2, a plurality of smoke pipes 19 are arranged in the liquid chamber 15, and the exhaust gas generated by the combustion in the combustion chamber 11 passes through the smoke pipes 19, passes through the exhaust gas duct 12, and becomes a chimney. Is released from the liquid to the atmosphere, the heat of the exhaust gas is also absorbed by the liquid L in the liquid chamber 15.
Be transmitted to.

As a result, the liquid L is heated to become vapor, and the space S in the liquid chamber 15 is filled with vapor.
Then, since a steam pipe (not shown) is connected to the space S in the liquid chamber 15, the steam filling the space S passes through the steam pipes and each heating device (not shown).
Is supplied to, for example, to raise the room temperature in the factory. Liquid L having a large specific heat such as water is placed on the furnace wall 16.
Are in contact with each other, the temperature of the furnace wall 16 rises only to about 200 to 300 ° C. A pressure sensor PS is arranged in the space S in the liquid chamber 15 to detect fluctuations in the vapor pressure in the liquid chamber 15.

The fuel supply unit 20 includes a fuel tank 22, a fuel pump 23 for pumping the fuel in the fuel tank 22 to the burner 17, a fuel tank 22 and the fuel pump 23.
A fuel supply pipe 21 connected to the burner 17 and a fuel flow rate adjusting valve 24 for adjusting the flow rate of fuel supplied to the burner 17 are provided.
The fuel flow rate adjusting valve 24 is connected to the first control motor 26 for adjusting the opening degree via the link mechanism 25a.

The first control motor 26 is a motor capable of rotating the drive shaft by an angle corresponding to the input signal, and even when the steam generated in the liquid chamber 15 is consumed by the heating device. , Is controlled according to the pressure fluctuation detected by the pressure sensor PS so as to keep the vapor pressure in the liquid chamber 15 constant. Further, the fuel flow rate adjusting valve 24
A fuel flow meter 27 for detecting the fuel flow rate is disposed between the fuel pump 23 and the fuel pump 23.

The combustion air supply duct 13 sucks the outside air and supplies the combustion air to the burner 17, the blower fan WF,
And a combustion air amount adjustment damper AD that adjusts the amount of combustion air supplied to the burner 17. The combustion air amount adjustment damper AD is connected to the first control motor 26 via the link mechanism 25b, and is controlled in conjunction with the fuel flow rate adjustment valve 24 in this manner to maintain a constant air-fuel ratio. Has been realized.

The exhaust gas recirculation duct 14 is arranged so as to connect the exhaust gas duct 12 and the combustion air supply duct 13 on the upstream side of the combustion air amount adjusting damper AD. An exhaust gas recirculation amount adjustment damper RD for adjusting the circulation amount is provided. The exhaust gas recirculation amount adjusting damper RD is connected to the second control motor 40 via a link mechanism 41, and is drive-controlled by a control method described later so as to realize an optimum exhaust gas recirculation rate.

Next, the circuit configuration of the input circuits such as the pressure sensor PS and the output circuits such as the first and second control motors 26 and 40 arranged in the boiler B1 will be described. The pressure sensor PS is connected to the input side of the pressure regulator 45, and the first control motor 26 is connected to the output side of the pressure regulator 45. The pressure regulator 45 takes in the pressure data in the liquid chamber 15 detected by the pressure sensor PS and outputs a drive signal to the first control motor 26 so that the pressure in the liquid chamber 15 is kept constant. The opening degree of the fuel flow rate adjusting valve 24 is adjusted. As a result, the pressure in the liquid chamber 15 is always maintained at a predetermined value, and stable supply of steam to the heating device is realized.

The sensor amplifier 30 and the fuel flow meter 27 are connected to the input side of the combustion control device 50, and the second control motor 40 is connected to the output side of the combustion control device 50.
Are connected. The combustion control device 50 takes in an analog signal from the sensor amplifier 30 and a fuel flow rate signal from the fuel flow meter 27, and executes a frequency analysis process, an exhaust gas recirculation amount determination process, etc., which will be described later, to perform the second control motor 40. Control the opening of. As a result, the optimum exhaust gas recirculation rate for the current turbulent flow of the combustion flame F is realized, and NO
The generation of _X is suppressed.

The combustion control device 50 includes a control panel 46.
Are connected so that signals can be exchanged between them. For example, when some trouble occurs in the boiler B1, the combustion control device 50 outputs a command signal for forcibly stopping the operation of the boiler B1 to the control panel 46.

Next, the configuration of the sensor amplifier 30 will be described in detail with reference to the block circuit diagram shown in FIG. The sensor amplifier 30 includes an optical sensor 31, a current / voltage converter 3
2, a DC / AC converter 33, an integrator 34, an analog divider 35, and an amplifier 36. The optical fiber OF is connected to the input side of the optical sensor 31, the current / voltage converter 32 is connected to the output side, and the DC / AC converter 33 is connected to the output side of the current / voltage converter 32. And an integrator 34 are connected. In addition, the DC / AC converter 3
3 and an output side of the integrator 34, the analog divider 35
Is connected, and the amplifier 3 is connected to the output side of the analog divider 35.
6 is connected to the combustion control device 5 on the output side of the amplifier 36.
0 is connected.

The optical sensor 31 is an infrared detecting element that detects the turbulence of the combustion flame F light, converts it into a current signal, and outputs it. For example, a germanium photodiode or a phototransistor is suitable.

Next, the contents of processing executed in the sensor amplifier 30 will be described with reference to FIG. First, combustion chamber 1
The turbulent flow state (flicker of light) of the combustion flame F in 1 is transmitted through the observation window 18 and the optical fiber OF to the optical sensor 31.
The turbulent flow state is converted into a current signal.
The amplitude of the vibration component (turbulence of the combustion flame F) included in the current signal obtained at this time changes in proportion to the change of the emission intensity component of the combustion flame F.

That is, when the emission intensity component of the combustion flame F is large, the amplitude of the vibration component is apparently large,
When the emission intensity component is small, the amplitude of the vibration component is apparently small. As a result, the actual vibration component cannot be obtained accurately. Therefore, the vibration component is smoothed by the extraction process and the division process described below.

The current / voltage converter 32 converts the current signal output from the optical sensor 31 into a voltage signal as shown in FIG. 5 (a). The waveform of this voltage signal oscillates with the passage of time around a predetermined DC voltage. Then, in this voltage signal waveform, the average value of the DC voltage represents the emission intensity component, and the vibration component flickers (disturbs) in the combustion flame F.
Is represented.

The DC / AC converter 33 removes the emission intensity component from the voltage signal waveform of FIG. 5A and converts only the vibration component into an AC voltage signal. As a result, only the vibration component is extracted from the current signal output from the optical sensor 31 as shown in FIG. On the other hand, the integrator 34 is shown in FIG.
The voltage signal waveform is subjected to integration processing to smooth the vibration component in the voltage signal waveform and calculate the average light emission intensity component. Here, the time constant of the integrator 34 can be arbitrarily set, and is adjusted as necessary. In this embodiment, the emission intensity component itself is used as the emission intensity representative component and used in the subsequent arithmetic processing.

The output signal from the current / voltage converter 32 is integrated and smoothed by the integrator 34 in the analog divider 35 in the subsequent stage, for example, the output signal from the DC / AC converter 33. This is because when the (oscillation component) is divided not by the output signal from the integrator 34 but by the output signal from the current / voltage converter 32, the following problems occur.

That is, the signal (vibration component) output from the DC / AC converter 33 changes with time, and the signal output from the current / voltage converter 32 also changes with time. Therefore, when the output signal from the DC / AC converter 33 is divided by the output signal from the current / voltage converter 32, there is no problem in the division in the low frequency range, but the output waveform is distorted by the division in the high frequency range,
This is because a large error will occur.

The analog divider 35 divides the output signal (vibration component) from the DC / AC converter 33 by the output signal (emission intensity component) from the integrator 34 to eliminate the influence of the emission intensity component. Output a signal. This electric signal is constituted only by the component caused by the disturbance of the combustion flame F. As a result, the actual vibration component can be accurately obtained.

Therefore, as shown in FIG. 6, after the current / voltage conversion, two different waveforms a and b are obtained, and even if the emission intensity components are different, the influence of the disturbance of the combustion flame F is affected. Are the same, an electric signal having substantially the same waveform can be obtained by performing the extraction process and the division process.

That is, in the case of the waveform a having a large amplitude, the voltage of the average value (emission intensity component) becomes high, so that the amplitude of the first electric signal obtained as a result of the division processing becomes small. On the other hand, in the case of the waveform b having a small amplitude, the voltage of the average value (light emission intensity component) becomes low, so that the amplitude of the second electric signal obtained as a result of the division processing is as small as the first electric signal. Become. As described above, in this embodiment, the vibration component is divided by the emission intensity component to remove the amplitude variation of the vibration component due to the influence of the emission intensity component.

The electric signal thus obtained is composed of a low frequency component signal having a predetermined amplitude and a high frequency component signal included in the signal and having a smaller amplitude than the low frequency component signal. Has been done.

Then, the amplifier 36 amplifies the amplitude of the electric signal after the division processing to a predetermined level, and outputs the electric signal to the combustion control device 50. Next, the content of processing executed in the combustion control device 50 will be described with reference to FIG.

In this combustion control device 50, the first vibration power of the combustion flame F is calculated based on the analog signal output from the sensor amplifier 30, and the first vibration power optimum for the fuel flow rate detected by the fuel flow meter 27 is calculated. (2) The opening degree of the exhaust gas recirculation amount adjustment damper RD is adjusted to adapt to the vibration power.

First, the A / D converter 51 converts the analog input signal from the sensor amplifier 30 into a digital signal. After A / D conversion, the DSP 52 (digital signal processor) is
FFT (Fast Fourier Transform) processing is performed on the digital signal.

In this embodiment, the A / D converter 51 having a 12-bit resolution is used.
Further, it is possible to set up to 500 Hz as the upper limit value of the measurement frequency range during the FFT processing.

Here, the FFT processing will be described with reference to FIG. FIG. 7 is a graph showing the relationship between the power spectrum intensity obtained by the FFT processing and the measurement frequency, where the vertical axis represents the power spectrum intensity (dB) and the horizontal axis represents the frequency (Hz). Further, represents the power spectrum at the exhaust gas recirculation rate 1.00, represents the power spectrum at the exhaust gas recirculation rate 1.10, and represents the power spectrum at the exhaust gas recirculation rate 1.15.

The FFT processing is an arithmetic processing for obtaining the strength of each frequency component in the digital signal.
Intensity waveform (power spectrum) of each frequency component by frequency analysis of digital signal by T processing
Is obtained. The waveform area of this power spectrum represents the turbulent flow state and brightness of the combustion flame F. In this way, since a strong correlation is established between the waveform area of the power spectrum and the turbulent flow state of the combustion flame F,
The turbulent flow state can be quantified by obtaining the waveform area of the power spectrum.

For the above reason, in the present embodiment, the FFT processing unit 53 integrates the intensity waveform of each frequency component in the entire frequency region, and the waveform area of the power spectrum, that is,
The first vibration power is calculated.

By the division process in the sensor amplifier 30, the influence of the emission intensity component on the amplitude of the vibration component is excluded from the electric signal used for calculating the first vibration power. Therefore, the first vibration power exhibits a primary characteristic with respect to the exhaust gas recirculation rate without being affected by the emission intensity component.

This state will be described with reference to FIGS. 8 and 9. FIG. 8 is a graph showing the relationship between the change rate of the first vibration power and the exhaust gas recirculation rate, wherein the vertical axis shows the change rate of the first vibration power and the horizontal axis shows the exhaust gas recirculation rate. . The rate of change of the first vibration power is an index indicating the degree of change of the first vibration power at other exhaust gas recirculation rates based on the first vibration power when the exhaust gas recirculation rate is 1.00. is there.

FIG. 9 is a graph for explaining the general relationship between the first vibration power and the exhaust gas recirculation rate, where the vertical axis represents the first vibration power and the horizontal axis represents the exhaust gas recirculation rate. ing.

As can be seen from FIGS. 8 and 9, there is a negative correlation (first-order characteristic) between the first vibration power and the rate of change of the first vibration power, and the exhaust gas recirculation rate. This is supported by the fact that as the exhaust gas recirculation rate increases, the proportion of oxygen concentration in the combustion air supplied to the burner 17 decreases, the flame lengthens, and the turbulence of the combustion flame F decreases. You can

Here, the thermal N generated during combustion
As described above, the O _X can be suppressed by increasing the exhaust gas recirculation rate. However, if the exhaust gas recirculation rate is increased, the oxygen concentration in the combustion air is reduced, resulting in incomplete combustion and generation of CO.

That is, the region on the right side of the CO generation boundary point shown in FIG. 9 represents an incomplete combustion region in which CO is generated, and the first vibration power obtained is set under the set exhaust gas recirculation rate. When it applies to such an incomplete combustion region, it is necessary to lower the exhaust gas recirculation rate.

Specifically, the turbulent flow state of the combustion flame F is directly detected by using the first vibration power, and is compared with the second vibration power measured in advance at the CO generation boundary point. As a result, it is possible to increase the exhaust gas recirculation rate to the limit, it is possible to effectively suppress the generation of NO _X.

Next, the first moving average processing section 54 uses the FFT.
The first vibration power obtained by the processing unit 53 is averaged by the average number set in the first moving average number table 55. This process is a process for reducing the variation between the data obtained by the FFT process. That is, each piece of data obtained by the FFT process has variations, and accurate control of the exhaust gas recirculation rate cannot be executed by using such variations of data.

On the other hand, the second moving average processing unit 56 averages the fuel flow rate signals detected by the fuel flow meter 27 by the average number set in the second moving average number table 57. Then, referring to the broken line table 58, the second vibration power corresponding to the averaged fuel flow rate is read into the first adder 59.

In this broken line table 58, as shown in FIG. 10, the second vibration power as a target value for the fuel flow rate is stored in advance. Here, FIG. 10 is a graph showing the relationship between the fuel flow rate stored in the broken line table 58 and the second vibration power, where the vertical axis represents the second vibration power,
The horizontal axis represents the fuel flow rate. Note that the horizontal axis represents the minimum fuel flow rate of 0% and the maximum fuel flow rate of 100%, and the fuel flow rate% is used as a scale.

Further, the broken line graph shown in FIG. 10 is the graph of FIG. 9 showing the relationship between the second vibration power and the exhaust gas recirculation rate at a certain fuel flow rate, for example, for each fuel flow rate in 10% increments. It is a graph obtained by arranging a graph perpendicular to a paper surface.

Each point plotted in this graph is a boundary value of the second vibration power generated by CO at the fuel flow rate, and CO is generated in the region located below the polygonal line connecting the points. Incomplete combustion region. Therefore, the first obtained through the FFT processing unit 53
When the vibration power falls in the region below the broken line, the exhaust gas recirculation rate should be reduced.

Therefore, the first adder 59 subtracts the first vibration power of the combustion flame F detected by the optical sensor 31 from the second vibration power corresponding to the fuel flow rate to obtain the difference between the two. For example, in FIG. 10, the first obtained
If the vibration power is located below the broken line, the deviation takes a negative value, and if located above the broken line, the deviation takes a positive value.

Subsequently, the dead zone processing section 60 performs dead zone processing on the deviation signal obtained by the first adder 59. That is, the dead zone is set in advance in the dead zone processing section 60, and if the deviation fluctuates within the dead zone, it is considered that the deviation signal has not fluctuated.
As a result, unnecessary control processing due to measurement errors caused by the optical sensor 31 and the like is suppressed, and proper operation of the boiler B1 is guaranteed.

The PID calculation unit 61 performs the PID calculation on the deviation signal which has been subjected to the dead zone processing in the dead zone processing unit 60, and eliminates the deviation between the first vibration power and the second vibration power by using the second control motor 40. A drive signal for drive control is calculated and output to the second adder 62.

That is, as described above, by searching the graph shown in FIG. 10 in the direction perpendicular to the paper surface,
The optimum exhaust gas recirculation rate is obtained for the obtained first vibration power, and the drive signal is calculated by performing arithmetic processing on this. Then, the output limiter 63 limits the signal that has passed through the second adder 62.

That is, the output limiter 63 is set with the upper limit value and the lower limit value of the signal strength output to the second control motor 40. Therefore, the second
When the signal passed through the adder 62 exceeds the upper limit value or falls below the lower limit value, a process for forcibly matching the upper limit value or the lower limit value is executed.

The drive signal processed by the output limiter 63 is output to the second control motor 40, and the second control motor 40 is driven to adjust the opening degree of the exhaust gas recirculation amount adjustment damper RD. To be done.

The actual measurement data obtained by the above combustion control method according to the present embodiment is shown in FIGS. 11 and 12 and will be described. Here, the test experimental device has an evaporation rate of 10 t / h.
The flue smoke tube boiler was used, and LSA heavy oil was used as the fuel. A rotary cup type burner is used as the burner, and the maximum heat output is 28.5 MJ / h. The combustion amount was fixed at 1.8 MK / h and the measurement was performed.

FIG. 11 shows NO _X generated in the combustion chamber.
Is a graph showing the relationship between the O ₂ 4% conversion NO _X concentration and the fuel flow rate, and the vertical axis is the O ₂ 4% conversion NO _X concentration (ppm)
The horizontal axis represents the fuel flow rate (L / h). FIG. 12 is a graph showing the relationship between the CO concentration generated in the combustion chamber and the fuel flow rate, where the vertical axis represents the CO concentration (p
pm), and the horizontal axis represents the fuel flow rate (L / h).

In the graph, ◯ indicates a measured value obtained by the combustion control method by the feedforward control according to the conventional example in which the exhaust gas recirculation amount adjustment damper opening is fixed at about 34 degrees. Further, ● in the graph indicates a measured value obtained by the combustion control method by the feedback control according to the present embodiment.

First, as can be seen from FIG. 11, according to the combustion control method of the present embodiment, the NO _X concentration is suppressed in the entire fuel flow rate region, and in particular, the fuel flow rate is 1
In the range of 50 to 500 L / h, about 30% N
Reduction of O _X concentration is realized. Further, as can be seen from FIG. 12, the CO concentration, which is feared to be generated by increasing the exhaust gas recirculation rate, is only about 1 to 2% at the maximum, and it is possible to suppress nitrogen oxides and It can be said that the opposite purpose of preventing complete combustion has been achieved. That is, the combustion flame to detect turbulence state of F to determine the optimum exhaust gas recirculation rate, by combustion control on the basis of the exhaust gas recirculation rate, while avoiding incomplete combustion, effectively NO _X It can be seen that the occurrence of

In the combustion control device 50, in addition to the control described above, the correction combustion for the purpose of improving followability to changes in the turbulent flow state of the combustion flame F and optimizing the exhaust gas recirculation rate at partial load Control is taking place.

This corrected combustion control will be described with reference to FIG. The PV lower limit monitor 64 detects whether or not the average value of the first vibration powers obtained by the first moving average processing unit 54 is below a preset lower limit value. For example, when a value corresponding to −10% of the second vibration power with respect to the fuel flow rate at that time is set in the PV lower limit monitor 64, and the average value of the first vibration power falls below the set value for some reason. Is detected by the PV lower limit monitor 64.

When the PV lower limit monitor 64 detects that the average value of the first vibration power is below the set value, P
The V lower limit monitor ratio calculation unit 65 performs a predetermined ratio calculation. A predetermined ratio (for example, 10%) is preset in the PV lower limit monitor ratio calculation unit 65, and the set ratio is output to the second adder 62 via the comparison / selection unit 66.

Then, in the second adder 62, the set ratio is added to the output signal from the PID calculator 61, and the exhaust gas recirculation amount adjustment damper RD is forcibly closed. Such processing is performed when the average value of the first vibration power obtained in the first moving average processing unit 54 is lower than the set value set in the PV lower limit monitor 64. This is because it can be determined that the amount of oxygen contained in is absolutely insufficient.

Therefore, in order to avoid incomplete combustion, the exhaust gas recirculation amount adjusting damper RD is fully closed to prevent the exhaust gas from mixing with the combustion air and to increase the amount of oxygen in the combustion air. It is necessary to plan.

On the other hand, the change rate monitor 67 constantly detects the degree of change in the fuel flow rate. Specifically, a predetermined change rate (for example, 5%) is preset in the change rate monitor 67, and it is determined whether or not the fuel flow rate is rapidly increased and the change rate is equal to or higher than the predetermined change rate. Is being detected.

When the change rate monitor 67 detects that the change rate of the fuel flow rate is equal to or higher than the predetermined change rate, the fuel change rate monitor ratio calculating section 68 performs the ratio calculation. The fuel change rate monitor ratio calculation unit 68 has a predetermined ratio (%).
Is preset and outputs the set ratio to the second adder 62 via the comparison / selection unit 66. Then, the second adder 6
In 2, the set ratio is added to the output signal from the PID calculator 61, and the exhaust gas recirculation amount adjustment damper RD is forcibly closed.

When such a process is carried out, when the fuel flow rate suddenly increases, it is necessary to send the combustion air containing the oxygen amount corresponding to the increased amount to the burner 17, so that the incomplete combustion is avoided. Therefore, it is necessary to fully close the exhaust gas recirculation amount adjustment damper RD to increase the amount of oxygen in the combustion air.

That is, when the oxygen amount in the combustion air is increased in accordance with the increase in the fuel flow rate, the required oxygen amount cannot be obtained if the followability is poor, causing incomplete combustion. Therefore, the rate of change of the average value of the output signal from the fuel flow meter 27 is
The rate of change monitor 67 is constantly monitored to grasp the fuel flow rate, and for a sudden increase in the fuel flow rate above a certain value,
The opening information is further added to the PID output signal and output.

The comparison / selection unit 66 includes a PV lower limit monitor ratio calculation unit 65 and a fuel change rate monitor ratio calculation unit 68.
It is a circuit for comparing and determining which signal should be prioritized when and are activated at the same time. In the present embodiment, the comparison / selection unit 66 is set to select a signal having a large absolute value.

By the correction as described above, the situation where the amount of oxygen in the combustion air is insufficient is prevented in advance, and when the fuel flow rate suddenly increases, the combustion flow rate increases as the fuel flow rate increases. By increasing the amount of air, the combustion chamber 11
Incomplete combustion is prevented in advance.

Next, a combustion control method for the combustion apparatus according to the second embodiment will be described with reference to the drawings. First, the configuration of the boiler B2 to which the combustion control method for the combustion apparatus according to the second embodiment is applied will be described with reference to FIG.

In the boiler B2 used in the second embodiment,
The boiler B1 used in the first embodiment is the optical sensor 3
The difference is that the turbulent flow state of the combustion flame F is detected by 1 and the turbulent flow state of the combustion flame F is detected by the ion current probe 37. Since the other structures are the same, the same reference numerals as those used in the first embodiment are used and the description thereof is omitted.

The ion current probe 37 is arranged on the wall surface of the main body 10 in the longitudinal direction, and the tip of the probe 36 is arranged in the combustion flame F. The ion current probe 37 is a sensor which is grounded and detects a change in the current (frame ion current) flowing through the combustion flame F, which is a conductor, and outputs it to the sensor amplifier 30.

The current value flowing through the combustion flame F is
Changes with the disturbance of the ion current probe 37.
The turbulent flow state of the combustion flame F can be detected in the same manner as when the flicker of the combustion flame F is detected by using the optical sensor 31 by detecting the flame current using.

Therefore, as obtained in the first embodiment, the sensor amplifier 3 with respect to the flame ion current.
0, the exhaust gas recirculation rate can be controlled corresponding to the turbulent flow state by the first vibration power obtained by performing the arithmetic processing in the combustion control device 50. Therefore, it is possible to suppress the thermal NO _x generated by combustion and avoid the situation where CO is generated due to incomplete combustion.

Next, a combustion control method for the combustion apparatus according to the third embodiment will be described with reference to FIG. The third
The configuration of the boiler (not shown) to which the combustion control method of the combustion apparatus according to the embodiment is applied is the same as the configuration of the boiler B1 to which the combustion control method of the combustion apparatus according to the first embodiment is applied, and therefore the description thereof is omitted. Is omitted.

In the combustion control method for the combustion apparatus according to the first and second embodiments, the analog divider 35 in the sensor amplifier 30 is used.
After the division correction by, the corrected signal is digitally converted by the A / D converter 51 in the combustion control device 50. Then, the first vibration power is obtained through frequency analysis of the digital signal by the FFT processing unit 53.

On the other hand, in the third embodiment, as shown in FIG. 14, signal correction by division is performed by A / A conversion of analog signals.
The signal output from the optical sensor 31 is processed by executing it after the D conversion and the FFT processing.

The sensor amplifier 30 has a DC / AC converter 33 instead of the analog divider 35 in the first embodiment.
And a fourth amplifier 36b connected to the integrator 34.

On the other hand, the combustion control device 50 includes the third amplifier 3
The third A / D converter 51a corresponding to 6a and the fourth A / D converter 51b corresponding to the fourth amplifier 36b are provided. Further, the combustion control device 50 is the F in the first embodiment.
Instead of the FT processing unit 53 (see FIG. 1), an FFT / light quantity correction unit 70 surrounded by a broken line is provided. This FFT /
The light quantity correction unit 70 includes an FFT processing unit 71 and a division division unit 7.
2, an end determination unit 73 that determines the end of division and division, and a corrected first vibration power calculation unit 74.

The third amplifier 36a is a DC / AC converter 3
The vibration component output from the third amplifier is amplified, and the fourth amplifier 36b
Amplifies the emission intensity component output from the integrator 34. At this time, the amplification factor (gain) of the third amplifier 36a and the amplification factor of the fourth amplifier 36b are adjusted so as to be completely matched.

The vibration component amplified by the third amplifier 36a is digitized by the third A / D converter 51a, and the FFT processing section 71 determines each frequency in the frequency analysis by the intervention of the DSP 52 based on the digital signal. Compute the power spectrum of the corresponding signal. Then, the division calculator 72 uses the power spectrum value calculated by the FFT processor 71 as the fourth A / D converter 51b.
It is divided by the emission signal intensity signal digitized by.

The end determination section 73 determines whether or not the division processing has been executed in the division division section 72 for the number of times (N) corresponding to the resolution of the FFT processing. That is, FFT
The division processing in the division division unit 72 is repeated until all the power spectrum values calculated by the processing are subjected to the respective division corrections. Then, finally, the corrected power spectrum corresponding to each frequency is calculated over the entire measurement frequency region subjected to the frequency analysis processing.

For example, when the measurement frequency range in the frequency analysis is 0 to 200 Hz and the FFT resolution is 200 lines, the divided division unit 72 and the end determination unit 73 perform loop processing to correspond to each frequency at 1 Hz intervals. 200 corrected power spectrum values are calculated.

The corrected first vibration power calculator 74 calculates the corrected first vibration power by summing all the calculated correction power spectrum values. According to the previous example, the total sum of 200 corrected power spectrum values is
It is obtained as the first vibration power excluding the influence of the emission intensity.

The first vibration power obtained in the third embodiment is equivalent to the first vibration power obtained in the first embodiment and can be used as an index of the exhaust gas recirculation rate in the boiler.

As described above in detail with reference to some embodiments, according to the combustion method of the combustion apparatus according to the above embodiments, the turbulent flow state of the combustion flame F is directly measured by the optical sensor 31 and the ion current probe 37. The detected turbulent flow state data (electrical signal) is subjected to division processing and frequency analysis processing to obtain the first vibration power. Then, the exhaust gas recirculation rate is determined so as to match the first vibration power with the second vibration power corresponding to the pre-calculated turbulent flow state, and by the exhaust gas recirculation method under the determined exhaust gas recirculation rate. Combustion control is being executed.

Therefore, the amount of exhaust gas contained in the combustion air can be increased to the limit, the combustion temperature can be lowered, and the oxygen concentration can be suppressed. As a result, the thermal NO _X concentration generated during the combustion of fuel can be greatly suppressed. In addition, the second line in the broken line table 58 used when determining the exhaust gas recirculation rate.
The vibration is calculated from the CO generation boundary value which is an index of incomplete combustion. Therefore, even if the exhaust gas recirculation rate is increased to the limit, carbon monoxide will not be generated due to incomplete combustion due to insufficient oxygen concentration.

The electric signal detected by the optical sensor 31 and the like is extracted into a vibration component and a light emission intensity component, and the analog divider 35 divides the vibration component by the light emission intensity component. Therefore, unlike the conventional combustion control method in which the emission intensity of the combustion flame F is simply detected,
The exhaust gas recirculation rate can be determined without considering the influence of the emission intensity component.

That is, the influence (disturbance) of the emission intensity component can be excluded from the vibration component, and only the vibration component due to the turbulent flow state of the combustion flame F can be extracted. As a result, the power spectrum shape of the combustion flame F becomes substantially the same regardless of the combustion state, so that the first vibration power with high accuracy can be obtained without setting a high set frequency during frequency analysis.

Furthermore, in the combustion control method according to the third embodiment, the ion current probe 37 is used as the turbulent flow state detecting means. Therefore, unlike the infrared detection element such as the optical sensor 31, the first vibration power and the exhaust gas recirculation rate can be primarily associated with each other without being affected by the radiant heat in the combustion furnace 11. As a result, the turbulent flow state of the combustion flame F can be directly detected, and a more precise exhaust gas recirculation rate can be determined.

The present invention has been described above based on the embodiments, but the present invention is not limited to the above embodiments, and various modifications and improvements can be made without departing from the spirit of the present invention. It is easily guessed.

For example, although the combustion control method is applied to the steam generating boiler in this embodiment, it may be applied to an industrial furnace for heat treatment or the like. Even in such a case, it is desired to reduce nitrogen oxides, and by applying the combustion control method for the combustion apparatus according to the present embodiment, nitrogen oxides can be significantly reduced.

By the way, since an industrial furnace is generally a combustion device for heat-treating a work, the combustion temperature in the combustion chamber is higher than the combustion temperature of the boiler, and a refractory material is attached to the furnace wall of the combustion chamber. The temperature of the refractory material reaches about 1000 ° C. Therefore, when the turbulent flow state of the combustion flame F is detected by using the optical sensor 31 including an infrared element, the radiant heat from the refractory material or the like deteriorates the detection accuracy.

That is, when the influence of radiation from other than the combustion flame F is large, only the emission intensity component is greatly increased and the amplitude of the vibration component is hardly changed, as compared with the case where there is no influence.

As a result, on the assumption that the change of the vibration component changes in proportion to the change of the emission intensity component, the combustion of each of the above-mentioned embodiments in which the signal processing is performed by dividing the vibration component by the emission intensity component. The control method is no longer valid.

Therefore, it is necessary to correct the amplitude of the vibration component by a method that does not use the emission intensity component and is not affected by the radiant heat. This combustion control method is such that when the temperature of the combustion flame F itself rises, the vibration component also increases with the increase of the emission intensity component. This is a method considering that the amplitude of the vibration component hardly changes although the component increases.

Specifically, a value representative of the amplitude of the vibration component that is not affected by radiant heat is taken, and that value is used as a substitute value (emission intensity component) for the emission intensity component. As a result, even in a combustion apparatus that is affected by radiant heat, the vibration component that changes with changes in the combustion state is reliably made constant, and the first vibration power that corresponds to the exhaust gas recirculation rate on a one-to-one basis is always maintained. Obtainable.

A high pass filter may be interposed between the analog divider 35 and the amplifier 36 in the sensor amplifier 30. That is, the amplifier 36 of the sensor amplifier 30
In the amplification of the electric signal in (1), the amplification factor is adjusted so that the maximum amplitude of the electric signal falls within the allowable input voltage with reference to the signal in the low frequency range having a large amplitude. Therefore, the electric signal in the high frequency region of the amplified electric signal has a relatively small amplitude as compared with the amplitude of the electric signal in the low frequency region, and may not be recognized by the A / D converter 51 having a low resolution. is there.

Therefore, the low-frequency component signal in the electric signal is removed by a high-pass filter, and the primary characteristic is set between the vibration power and the exhaust gas recirculation rate without using a high-priced high-resolution A / D converter. You can have it. As a result, the exhaust gas recirculation rate can be controlled by the first vibration power.

Further, the optical sensor is not limited to a germanium photodiode or a phototransistor, and any element capable of converting the light (flicker) of the combustion flame F into an electric signal may be used. This is because if the light can be converted into an electric signal, the combustion control method in each embodiment can be implemented.

Furthermore, in the above embodiment, the combustion control method is applied to the boiler and the combustion furnace as the combustion device, but it goes without saying that it is effective for other combustion devices.

Furthermore, in addition to the amplitude representative value used in the third embodiment, the voltage value of the electric signal detected at every constant time is taken out, and the square root of the squared value is taken as the amplitude representative value. You may use as. That is, any data obtained from the vibration component can be used as the amplitude representative value.

Further, in each of the above embodiments, the second vibration power is stored in advance in the broken line table 58, but the combustion state (whether incomplete combustion or not) is detected by providing a carbon monoxide detection sensor or the like. However, a more optimal exhaust gas recirculation rate may be determined from this detection data and the first vibration power.

In the case where such a configuration is provided, as compared with the case where the exhaust gas recirculation rate is calculated from the broken line table 58,
The exhaust gas recirculation rate closer to the limit can be realized, and the generation of nitrogen oxides can be significantly suppressed.

Although not stated in the claims, the technical idea grasped from each of the above embodiments is as follows.
The effect will be described below. (1) In the combustion control method for a combustion device according to any one of claims 1 to 3, the emission intensity representative component is an electric power output from the optical sensor 31 or the ion current sensor. A combustion control method for a combustion device, wherein the emission intensity component is extracted from a signal separately from the vibration component.

With such a structure, in a combustion apparatus such as a boiler having a relatively low furnace wall temperature, it is possible to provide a primary characteristic between the turbulent flow state of the combustion flame F and the vibration power. Can be used to control the exhaust gas recirculation rate. (2) In the combustion control method for a combustion apparatus according to any one of claims 1 to 3, the emission intensity representative component is an electric power output from the optical sensor 31 or the ion current sensor. A combustion control method for a combustion device, which is a representative amplitude value extracted from the amplitude of the vibration component in the signal.

In the case of having such a structure, since the amplitude of the vibration component which is not affected by the radiant heat is used as the representative component of the emission intensity, even in the combustion device where the high temperature radiant heat is generated, the turbulent state of combustion flame It becomes possible to have a primary characteristic with the vibration power, and the exhaust gas recirculation rate can be controlled by the vibration power.

[0140]

According to the combustion control method of the combustion apparatus of the present invention, the turbulent flow state detecting means directly detects the turbulent flow state of the combustion flame, and the turbulent flow state is detected based on the detected turbulent flow state. The supply amount of the inert gas is adjusted so as to realize a predetermined turbulent flow state.

Therefore, the optimum supply amount of the inert gas for the detected turbulent flow state can be determined. As a result, the turbulent state of the combustion flame does not lead to incomplete combustion,
It is possible to reduce the concentration of nitrogen oxides generated with the combustion of fuel.

Further, in the combustion control method for the combustion apparatus according to the second aspect of the present invention, the turbulent flow state detecting means directly detects the turbulent flow state of the combustion flame, and the vibration is detected from the detected turbulent flow state data. The component and the emission intensity representative component are respectively extracted. Further, the first vibration power is obtained by combining the extracted vibration component with the frequency analysis process and the influence exclusion process, and the exhaust gas recirculation amount is made to match the first vibration power with the second vibration power prepared in advance. Adjusting the adjusting valve.

Therefore, the exhaust gas recirculation rate optimum for the detected turbulent flow state can be realized. As a result, the combustion temperature decreases and the amount of oxygen in the combustion air decreases, so that it is possible to reduce the concentration of nitrogen oxides generated with the combustion of the fuel. Further, when executing the optimum exhaust gas recirculation rate, it is possible to avoid generation of carbon monoxide due to incomplete combustion.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram of a combustion device to which a combustion control method for a combustion device according to a first embodiment is applied.

2 is an enlarged cross-sectional view of the combustion apparatus shown in FIG. 1 taken along the line AA in FIG.

FIG. 3 is a functional block diagram illustrating signal processing in the sensor amplifier in the combustion control method for the combustion device according to the first embodiment.

FIG. 4 is a functional block diagram illustrating signal processing in the combustion control device in the combustion control method for the combustion device according to the first embodiment.

5A to 5C are waveform charts for explaining the behavior of various electric signals processed in the sensor amplifier in the first embodiment.

FIG. 6 is a waveform diagram showing a comparison between two types of electric signals obtained by the processing in the sensor amplifier in the first embodiment.

FIG. 7 is a graph showing the relationship between power spectrum intensity and frequency for three types of exhaust gas recirculation rates.

FIG. 8 is a graph showing a general relationship between a power change rate and an exhaust gas recirculation rate.

FIG. 9 is a graph for explaining the correlation between the second vibration power and the exhaust gas recirculation rate.

FIG. 10 is a graph showing the relationship between the second vibration power stored in the polygonal line table and the fuel flow rate.

[11] The combustion control method for combustion device obtained as a result of the implementation of the first embodiment, is a graph showing the relationship between the O ₂ 4% in terms of NO _X concentration and the fuel flow rate.

FIG. 12 is a graph showing the relationship between CO concentration and fuel flow rate, which is obtained as a result of implementing the combustion control method for the combustion apparatus according to the first embodiment.

FIG. 13 is a schematic configuration diagram of a combustion device to which the combustion control method for the combustion device according to the first embodiment is applied.

FIG. 14 is a functional block diagram illustrating signal processing in a sensor amplifier and a combustion control device in a combustion control method for a combustion device according to a third embodiment.

FIG. 15 is a graph showing the relationship between the O ₂ 4 conversion NO _X concentration and the exhaust gas recirculation rate.

FIG. 16 is a schematic configuration diagram of a combustion device to which a combustion control method for a combustion device according to a conventional example is applied.

[Explanation of symbols]

10 ... Main body, 11 ... Combustion chamber, 12 ... Exhaust gas duct, 13
... Combustion air supply duct, 14 ... Exhaust gas recirculation duct,
15 ... Liquid chamber, 16 ... Furnace wall, 17 ... Burner, 20 ... Fuel supply section, 30 ... Sensor amplifier, 31 ... Photosensor, 32 ... Current / voltage converter, 33 ... DC / AC converter, 34 ... Integrator , 35 ... Analog divider, 36 ... Amplifier, 37 ... Ion current probe, 50 ... Combustion control device, 51 ... A / D converter, 52 ... DSP, 53 ... FFT processing section, 54 ... First
Moving average processing unit, 55 ... First moving average number table, 5
6 ... 2nd moving average processing part, 57 ... 2nd moving average frequency table, 58 ... Broken line table, F ... Combustion flame, RD ... Exhaust gas recirculation amount adjustment damper, WF ... Blower fan, OL ...

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Toshiharu Tachibana 1 Toyota Town, Toyota City, Aichi Prefecture, Toyota Motor Corporation (72) Inventor Toshiyuki Otsubo 1 Toyota Town, Toyota City, Aichi Prefecture Toyota Motor Corporation

Claims (6)

[Claims] 1. A combustion control method for a combustion apparatus, which supplies an inert gas together with combustion air to a combustion chamber, comprising: a first step of detecting a turbulent flow state of combustion flame in the combustion chamber by a turbulent flow state detecting means; And a second step of adjusting the supply amount of the inert gas so as to realize a predetermined turbulent flow state in which the turbulent flow state of the flame does not reach incomplete combustion. . 2. A combustion control method for a combustion apparatus having an exhaust gas recirculation system for supplying a part of the exhaust gas discharged from the combustion chamber to the combustion chamber again together with the combustion air, wherein the turbulent flow state detecting means is provided in the combustion chamber. A third step and a third step of detecting the turbulent flow state of the combustion flame and extracting the vibration component of the flame light and the representative component of the emission intensity of the flame from the turbulent flow state data detected by the turbulent flow state detection means. With respect to the vibration component extracted in, by combining a frequency analysis process of calculating the intensity integral value in the entire frequency region, and an effect removal process for removing the effect of the emission intensity representative component on the vibration component A fourth step of obtaining the first vibration power by applying the first vibration power, the first vibration power obtained in the fourth step, and a predetermined turbulent flow state in advance A fifth step of comparing the calculated second vibration power and determining an exhaust gas recirculation amount for matching the first vibration power with the second vibration power, and an exhaust gas recirculation determined in the fifth step. And a sixth step of adjusting the exhaust gas recirculation amount adjusting valve based on the amount, and adjusting the amount of exhaust gas mixed into the combustion air. 3. The combustion control method for a combustion device according to claim 2, wherein in the fourth step, the influence removing process of dividing the vibration component by the emission intensity representative component is performed, and the influence removing process is performed. A combustion control method for a combustion device, wherein the first vibration power is obtained by performing the frequency analysis processing on the applied vibration component. 4. The combustion control method for a combustion device according to claim 2, wherein in the fourth step, the frequency analysis process is performed on the vibration component, and the vibration component subjected to the frequency analysis process is emitted by the light emission. A combustion control method for a combustion apparatus, wherein the first vibration power is obtained by performing the influence removal process of dividing by a strength representative component. 5. The combustion control method for a combustion device according to any one of claims 1 to 4, wherein the turbulent flow state detecting means converts a turbulent flow state of flame light into an electric signal. A combustion control method for a combustion apparatus, which is an optical sensor that outputs a turbulent flow state data. 6. The combustion control method for a combustion device according to claim 1, wherein the turbulent flow state detecting means converts a turbulent flow state of flame light into an electric signal. A combustion control method for a combustion apparatus, which is an ion current sensor that outputs a turbulent flow state data.