JPS6112170B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides control of combustion improvers in the combustion management of various industrial furnaces, more specifically, based on the pressure oscillations in the furnace that occur during combustion or the minute pressure oscillation patterns superimposed on the pressure in the furnace, The present invention relates to an air ratio control method in a combustion furnace, which controls combustion improver such as air amount.

Generally, from the perspective of energy saving and pollution prevention,
Accurately determining the combustion state of a combustion furnace and maintaining combustion under appropriate conditions are very important issues.

The factors that affect the combustion state of the above combustion furnace are:
Details such as furnace characteristics, burner characteristics, operational factors, etc. are wide-ranging, but control of the air ratio, which is a combustion improver, plays a particularly important role in combustion management control.

By the way, conventional air ratio control involves predetermining a predetermined air ratio to the combustion amount by measuring the O ₂ concentration in the combustion exhaust gas and the amount of smoke, or visually observing the combustion state, and then setting it constant. The company operates under such conditions.

However, in an actual furnace, the amount of combustion constantly fluctuates, and the combustion state constantly changes due to factors that change over time, such as the furnace pressure, the state of burner dirt, and the leakage rate of combustion air. Furthermore, even when the combustion amount is the same, the combustion condition varies depending on factors such as the furnace temperature, the amount of atomization (the amount of atomized liquid fuel), and the position of the burner tip, so it is impossible to maintain the optimal combustion condition. .

Regarding these variable factors, unless the range is particularly abnormal, it is possible to maintain the optimum combustion state by controlling the air ratio. It is necessary to accurately control the combustion conditions according to the ever-changing combustion conditions.

Therefore, in the past, the first method was to find the optimal correlation between the fuel flow rate and the air ratio in advance and change the air ratio according to the fuel flow rate.
The second method is to control the air amount or air ratio setting device so that the O ₂ concentration is constant by continuous measurement of the O ₂ concentration.
A third method has been proposed in which the amount of combustion products such as CO, CO ₂ or smoke is measured and the air amount or air ratio setter is controlled based on the amount or ratio of each.

However, in the first method, if the burner conditions, combustion conditions, and operating conditions whose correlations have been determined in advance are even slightly disturbed, even if the air ratio is accurately controlled, there is no point at all.

In the second method, when the combustion amount decreases, the hearth load decreases, so the O ₂ concentration may be lower than during maximum combustion, and since the combustion state changes even when the furnace temperature changes, the O ₂ concentration remains constant. Related to the fact that it does not need to be the same, if there is a change in burner dirt, burner position, atomization amount, etc., even if the O ₂ concentration is constant, the combustion state will change significantly due to changes in other conditions, so smoke will not occur. or, conversely, a situation in which O ₂ is in excess relative to optimal combustion conditions. Furthermore, in this method, gas sampling is usually performed in the flue for analysis of combustion exhaust gas, and in this case, the combustion state may not be sufficiently reflected due to the influence of air entering from the outside.

In the third method, in addition to the same problems as the second method, it is possible to control at the lower limit of complete combustion by using things that occur during incomplete combustion, such as CO and smoke amount, as a control signal source. In the near future, sampling position determination and responsiveness will become particularly important factors, and if these are incorrect, smoke and other problems will occur frequently.

In short, each of the above methods does not directly measure the combustion state, and all of them have problems when there are wide varying factors such as in an actual furnace.

By the way, the applicant of this application filed the patent application No. 52-122229.
No. 2 (invention title: ``Method for determining combustion state''), using a combustion test furnace, detailed observations and studies were made on the combustion state under various combustion conditions, and it was found that approximately 20 mm ( water column)
After discovering the fact that the following minute pressure oscillations exhibit certain changes according to fluctuations in combustion conditions, and continuing research, we discovered the slowness and speed of combustion in the furnace, the length of the flame, and the flame properties (transparent flame, The combustion state, such as bright flame, smoke amount, etc., is clearly reflected in the minute pressure vibration pattern in the furnace, and the power spectrum density distribution obtained by converting the minute pressure vibration signal is used as an indicator for determining the combustion state. Based on this new knowledge, when performing combustion using various fuels such as gas and liquid in various industrial combustion furnaces, the furnace pressure can be overlapped with the furnace pressure using the furnace pressure extraction probe. detects minute pressure vibrations,
We have developed a ``combustion state judgment method'' that makes it possible to make an appropriate quantitative judgment of the combustion state by using the vibration pattern shown by the power spectrum density distribution etc. obtained by converting the minute pressure vibration signal as a judgment index. Proposed.

The present invention utilizes the "combustion state determination method" to provide a combustion furnace that can accurately control the air ratio while measuring momentary changes in the combustion state to maintain an optimal combustion state. This provides a new air ratio control method.

For this reason, the first invention according to the present invention detects vibrations in the furnace and analyzes their waveforms when combustion is performed in various industrial furnaces. This is an air ratio control method in a combustion furnace, characterized in that the air ratio in each combustion state is changed based on the signal compared with the waveform.

A second invention according to the present invention, in relation to the first invention, detects at least a specific frequency band in which the energy density changes when the combustion state changes in the furnace pressure vibration, and detects the heat cycle. The maximum energy level in the frequency band of the furnace pressure oscillation in the desired combustion state is set as the set value, and the air ratio is set according to the deviation between the energy level in the frequency band in each combustion state and the set value. This is a method for controlling the air ratio in a combustion furnace, characterized in that the air ratio is changed.

A third invention according to the present invention, in relation to the first invention, detects at least a specific frequency band in which the vibration energy density changes in response to a change in the combustion state when the combustion state changes, and detects the total vibration. Using the ratio of energy and vibration energy in a specific frequency band as an index, the vibration energy ratio during optimal combustion is set as a set value, and the air ratio is changed according to the deviation between the vibration energy ratio and the set value in each combustion state. This is an air ratio control method in a combustion furnace, characterized by the following.

Embodiments of the present invention will be described in detail below with reference to the accompanying drawings.

FIG. 1 shows an air ratio control device in a combustion furnace 1. The combustion furnace 1 includes a combustion burner 2, an in-furnace temperature detector 3, and an in-furnace pressure sampling probe 4.
A flue 21 for combustion exhaust gas is provided.

The temperature setting regulator 5 has a desired furnace temperature set value set in advance, compares the measured value measured by the temperature detector 3 with the set value, and outputs an output signal according to the deviation. occurs.

The fuel flow regulator 7 receives the output signal from the temperature setting regulator 5 via the restrictor 6, sets a flow rate setting value corresponding to the signal, and controls the fuel flow rate detector 13 installed in the pipe 10. The measured signal and the flow rate set value are compared, and a control signal corresponding to the deviation is given to the flow rate regulating valve 12. The restrictor 6 is used to temporarily stop fuel control in the event of an abnormal rise, fall, or significant fluctuation in the furnace temperature.

The continuously automatic variable ratio setter 8 sets the ratio between the fuel flow rate and the air flow rate, and is determined based on the type of fuel, furnace type, burner conditions, and other operating conditions. That is, the air volume is set according to a preset ratio using a signal from the temperature setting controller 5, and a control signal is given to the air volume controller 9, which controls the air flow rate arranged in the pipe 11. While measuring the flow rate with the detector 15, a control signal is given to the air flow control valve 14 according to the deviation from the signal from the ratio setting device 8.

On the other hand, in the combustion micro-pressure vibration measurement system, the in-furnace pressure is guided to the micro-pressure vibration detector 16 by the in-furnace pressure sampling probe 4, and an amplifier 17 detects the absolute value of the in-furnace pressure and the combustion micro-pressure vibration superimposed thereon. Separated into components,
The signal is then amplified and sent to the frequency analyzer 18.

The frequency analyzer 18 determines the energy distribution of vibration frequencies and outputs the energy level of a preset representative frequency or frequency band (described later) as an output signal.

The signal resulting from this analysis enters the vibration energy adjuster 19 and is compared with the value of the energy level (described later) of a preset frequency or frequency band. A correction signal is provided via 20 to modify the ratio of air flow to fuel flow.

The limiter 20 is a device for minimizing disturbance to the control system even when an abnormal value is detected in the frequency energy or the detection system, and functions similarly to the limiter 6.

In the above system, combustion micro-pressure vibrations can be measured at any location within the combustion furnace, air throat, burner tile, flue 21, etc. as long as the vibration propagation range is within the vibration propagation range. is most preferably measured within the combustion furnace 1.

The above-mentioned micro-pressure vibration detector 16 has a water column of -50 to +50 mm.
It is fully sensitive to pressure, and the frequency is 0 to 500.
It is preferable to use a device that can detect up to about Hz or higher, and it is preferable to use a micro-pressure transducer using a strain gauge or a crystal transducer to convert pressure vibrations into analog electrical signals.

When using micro-pressure vibration as a control signal, it may be used in a state where the micro-pressure vibration is superimposed on the absolute value of the furnace pressure, but when considering the drift of the micro-pressure vibration detector 16 etc., the micro-pressure vibration is superimposed on the furnace pressure. Separating and extracting only the micro-pressure vibration component provides better stability as a control signal.

Further, the frequency band of the micro-pressure vibration used as the control signal may cover the entire range from 0 to 500 Hz or more, but a low-pass filter or a band-pass filter may be incorporated into the amplifier 17 or the frequency analyzer 18. It may be limited to a specific frequency or frequency band and controlled by its energy level.

As the frequency analyzer 18, a vibration analyzer may be used, but it is desirable to be able to perform analysis in real time.
FORM) type digital vibration analyzer or octave band type analyzer can be adopted. The vibration analyzer may perform analysis processing to determine the pattern of micro-pressure vibration and use it as a control signal source, and obtaining a power spectrum is one example of this.

How to use the signal of the frequency analysis result is to compare the maximum energy level G of a specific frequency band in the optimal combustion state with the maximum energy level F in each combustion state, and for the maximum energy level, GF = 0. In addition to the method of controlling the air ratio, as shown in Figure 2a, where the vertical axis is the energy density and the horizontal axis is the frequency f, the vibration energy ∫ ^f (b) of a specific frequency band S in the optimal combustion state is Comparing _f (a)G(f)df and vibration energy ∫ ^f (b) _f (a)F(f)df in the specific frequency band S in each combustion state, ∫ ^f (b) _f (a )G(f)df−∫ ^f (b) _f (a)F(f)df=0
Also, as shown in Figure 2b, the vibration energy in a specific frequency band S that reflects the combustion state ∫ _S F(f)df and the total vibration energy in the entire frequency range ∫ ^∞ ₀ F (f)df and this ratio is the ratio in the optimal combustion state, that is, ∫ _S G(f)df/∫ ^∞ ₀ G
(f) A method of controlling to be equal to df, or a ratio b of the maximum energy level b of a specific frequency band S reflecting the combustion state to the maximum energy level a of frequencies in other regions, as shown in Fig. 2 c. /a and control the ratio so that it is equal to the ratio in the optimum combustion state can be adopted as appropriate.

In the configuration example shown in FIG. 1, the amount of air is controlled using the micro-pressure vibration signal through the ratio setting device 8, but it is also possible to directly control the amount of air using the micro-pressure vibration signal. . At the time of ignition in this case, it is desirable to manually set the amount of air to the required amount, and then shift to control using a micro-pressure vibration signal after the combustion state has stabilized.

As a combustion aid, in general combustion equipment,
Air is used, but in addition to this, oxygen is added to air to make it have a high O ₂ concentration, or in the case of pure oxygen, it is also possible to add O ₂ to the combustion gas, which has the same effect as combustion air. It is also applicable when adding .

Next, we will discuss the test results of the vibration characteristics investigation in the test furnace.

As mentioned above, accurately controlling the amount of air in a combustion furnace to maintain optimal combustion conditions is effective in reducing energy consumption and preventing pollution.
This is an important issue in terms of NOx suppression.

In other words, an excessive amount of air lowers the flame temperature and increases exhaust gas loss, causing _great damage to thermal efficiency.
The direction is that the generation will increase. On the other hand, if the amount of air is too small, CO and smoke will be generated, causing afterburning and the like, resulting in safety and pollution problems.

With the above problems as a background, we conducted an investigation of the air ratio and combustion state in a test furnace.

Figure 3 shows a 1 m × 4 m ^L test furnace with heavy oil combustion amount of 40 × 10 ⁴ Kcal/H, air ratio of 1.05,
Micropressure vibration waveform and frequency analysis results (power spectrum) when changed in 4 steps of 1.20, 1.40, and 1.90
In one example, the micro-pressure vibration waveform has vibration pressure (mm
H ₂ O), time (seconds) is plotted on the horizontal axis, energy density E, D (V ² ) is plotted on the vertical axis, and frequency f (Hz) is plotted on the horizontal axis for the frequency analysis results. The attached reference photos show the combustion conditions in each case.

When the air ratio is low, the main component of micropressure vibration is on the low frequency side, and as the air ratio increases, the main component tends to shift to the high frequency side. Note that the frequency analysis results are shown representatively in the range of 0 to 45 Hz. That is, as combustion progresses rapidly and becomes a sharp and short flame, the frequency components become higher.

The NOx concentration relative to the air ratio is shown on the vertical axis.
As shown in FIG. 4, which shows the (PPM) O ₂ 11% equivalent value and the air ratio (-) on the horizontal axis, NOx tends to increase as the air ratio increases in the normal range. In other words, as the frequency component increases
Since NOx concentration increases, it serves as an indicator for NOx countermeasures.

On the other hand, under other conditions, the air ratio and the heat flux from the flame (the amount of heat released from the flame per unit area/unit time,
The results of the investigation are shown in Figure 5, where the vertical axis is the heat flux from the flame (Kcal/ ^{m 2 ・}H) × 10 ⁴ and the horizontal axis is the furnace length (mm). .

According to this, the heat flux from the flame tends to increase as the air ratio decreases.

However, if the heat flux decreases below a certain value, the heat flux in the second half of the flame increases slightly, but the decrease in the first half of the flame is large, and the overall tendency is to worsen.

This is a case where the generation of smoke becomes significant, and it has become clear that lowering the air ratio to the limit where smoke is emitted is better in terms of fuel consumption and NOx. However, it goes without saying that the limit for smoke generation varies depending on the burner structure.

Thinking of this in terms of micro-pressure vibration, it means suppressing high frequency components and achieving a so-called slow combustion state, which is a combustion state in which low frequency components are the main component.

The characteristics of the micro-pressure vibration when transitioning from a rapid combustion state to a slow combustion state are that the pattern changes from a vibration component mainly consisting of high frequencies to a pattern mainly consisting of low vibration components, as well as a pattern that changes from a relatively high frequency level to a pattern mainly consisting of low vibration components.
In the band above 100Hz, there is a vibrational component that appears during rapid combustion and disappears during slow combustion. When determining the combustion state using micro-pressure vibrations, two methods are possible: one that looks at the frequency transition state, and the other that uses the energy level of a specific frequency band.

Next, examples will be specifically described.

FIG. 6 shows a schematic structure of a soaking furnace in which the present method and apparatus were implemented.

The furnace capacity is 6,600 ^L x 2,650 ^W x 3,875 ^H , the charging amount per charge is approximately 84 tons, and the combustion amount is heavy oil with a maximum water content of 400/kg.
H, one heat cycle is an average soaking oven of about 5 hours.

The combustion micro-pressure oscillation measurement and control device in this example is the same as that described in FIG.
In particular, the configuration of the combustion micro-pressure vibration measurement system is shown in Figure 7. The individual explanations will be omitted as they overlap with those in FIG. 1, but in order to examine the waveform analysis results, a pen-written oscillograph 22 is installed in the amplifier 17 so that the waveform can be recorded, and a frequency analyzer 18 is installed. The difference is that a recording device 23 is incorporated into the second embodiment.

Prior to this implementation, we first investigated the occurrence of vibrations, including the furnace characteristics. Conventionally, the air ratio of this furnace was set at a constant value, and was set at 1.45.

First, the optimal air ratio was determined by measuring the O ₂ concentration in the exhaust gas and the amount of smoke during maximum combustion, or by visually observing the combustion state.

When the combustion amount is maximum, the load on the furnace is the highest, the flame is large and long, the combustion state is slow, and smoke is likely to occur, so the air ratio is usually set under the conditions of maximum combustion.

When setting the air ratio in the past, there was a tendency to set the safety factor relatively high in anticipation of fluctuations in the combustion state, but in the case of this example, the air ratio was adjusted to match the combustion state. can be controlled,
The air ratio was set to 1.4 by reducing the safety factor. The actual air ratio is determined from the exhaust gas composition.
It is about 1.2.

Figure 8, which is similar to Figure 2, investigates the occurrence of micro-pressure oscillations over one heat cycle under this constant air ratio setting condition, and for seven levels of combustion amount. The micro-pressure vibration waveform and frequency analysis results (power spectrum) are shown in comparison. Note that this measurement example is a result at a position within the air throat 400 mm from the burner tip position due to constraints on actual furnace equipment.

According to this, extremely strong vibrations have been detected in the most intense part of combustion immediately after fuel injection, or in vibration components that originally exist on the air. According to the frequency analysis results, it contains frequency components of 100 Hz or more, which cannot be determined from the micro-pressure vibration waveform (the frequency that can be tracked by the pen-written oscillograph 22 is 60 to 80 Hz).

According to the frequency analysis results, a characteristic feature is that vibration components of 100Hz or higher gradually increase as the combustion amount decreases.

Estimating from this vibration pattern, it is considered that the combustion state is transitioning from a slow state to a rapid state as the combustion amount decreases. Visual observation of the flame showed that it was burning slowly at maximum combustion, but as the amount of combustion decreased, it became more rapid and a sharp, short flame was formed. The reasons for this are an increase in the amount of intruding air due to a decrease in combustion rate, an increase in the amount of combustion air due to errors in the control system, and an increase in the relative proportion when the rate of combustion decreases because the amount of heavy oil atomization medium is constant. It is possible that this is the case. Note that the amount of the atomizing medium is usually determined based on the conditions where smoke is most likely to occur, that is, the maximum combustion amount.

As described above, at a constant air ratio that is optimally set at maximum combustion, the combustibility itself changes as the combustion amount changes, and this is also reflected in the vibration pattern (especially in the 100Hz to 200Hz range). ).

Therefore, the range of the bandpass filter built into the frequency analyzer 18 is set to 100Hz as a lower limit and 100Hz as an upper limit.
I set it to 200Hz and extracted frequency components only in this range.

Maximum combustion in this range (optimally adjusted conditions)
Since the maximum energy of is 0.2×10 ⁻³ (V ² ), this value was set in the vibration energy regulator 19. Note that smoke occurs below this value.

If the energy level of the set frequency band becomes higher than the set value, a signal is issued to lower the air ratio according to the deviation, and if it becomes lower, the air ratio is increased.

In this way, if the energy level of the representative frequency band is given to the vibration energy regulator 19,
Thereafter, automatic control is performed to constantly ensure the optimum air ratio in accordance with the combustion state, even if not only the combustion amount but other factors change.

As mentioned above, FIG. 9 shows the measurement and analysis results of vibration when air ratio control is performed using the maximum energy level of a specific frequency band as an index.

As is clear from the figure, the maximum energy level within a specific frequency band is 0.2×
It becomes a constant value of 10 ^-3 (V ² ), and it can be seen that the optimal combustion state set at the beginning is maintained.

To supplement the above matter, in order to use the micro-pressure vibration pattern as an index of the combustion state, it is necessary to express it uniquely, and the above-mentioned energy level is just one example.

In actual furnaces, the total energy of micro-pressure vibrations may be attenuated with turndown depending on the measurement conditions.

In such a case, it would naturally be problematic to simply use an increase or decrease in the energy level of a specific frequency as an indicator of the combustion state.

Even under these conditions, when the combustibility changes sharply during turndown, even though the total vibration energy level decreases, the micro-pressure vibration energy above 100Hz tends to increase relatively. If the micro-pressure vibration energy ratio is used, the micro-pressure vibration pattern and the combustion state can be uniquely expressed.

Let E _T be the total energy of micro-pressure vibrations, E _H be the energy of micro-pressure vibrations above 100Hz (a region where there is a difference in micro-pressure vibrations when combustibility changes), and R _E be the energy ratio, R _E = Defined as E _H / _ET . (R _E = 0 to 1.0) R
An increase in the value of _E indicates that the combustibility is rapidly increasing, and a decrease in R _E indicates that the combustion is toward the slow combustion side.

Including the results in Figure 8, the measurement results of micro-pressure vibrations over several heat cycles before air ratio control by vibration are organized by R _E , and the vertical axis is the energy ratio R E =E H /E T , and the horizontal axis is the energy ratio R _E =E _H /E _T . Figure 10 shows the heavy oil flow rate (/H) on the axis.

As is clear from the figure, before the control using micro-pressure vibration, the value of R _E increases with turndown, indicating that the combustibility improves rapidly.

Since the energy ratio level at maximum combustion is approximately 0.3 (adjusted to optimal combustion at maximum combustion),
The vibration energy regulator 19 is set to 0.3 (electrically equivalent to the energy level 0.2×10 ^-3 (V ² ) mentioned above), and the air ratio is controlled using this setting. The results are summarized in R _E. It is shown in FIG. 11 which is similar to FIG.

The energy ratio is approximately at a level of 0.3, indicating that the combustion state at maximum combustion is maintained throughout the entire combustion range.

The vibration measurement results in this case are shown in Figure 1 as shown in Figure 8.
Shown in Figure 2. The figure shows that over the entire combustion range, especially
It can be seen that the micro-pressure vibrations above 100Hz are becoming smaller.

As described above, if the energy ratio of a specific frequency band to the total energy of micro-pressure vibration is used as a parameter, the combustion state can be determined even if the absolute level of vibration changes due to turndown or the like.

Figure 13 shows the changes over time in the results of an operation in which the air ratio was automatically controlled by micro-pressure vibrations, in comparison with data from conventional operations. The vertical axis shows furnace temperature (°C), heavy oil flow rate (/H), exhaust gas O ₂ (%) and air ratio setting, and the horizontal axis shows time (H).

The results show that the air ratio changes with fluctuations in combustion amount and furnace temperature, and the O ₂ concentration in the exhaust gas decreases accordingly.

That is, even during maximum combustion, the air ratio gradually decreases because the combustibility improves as the furnace temperature rises, and the amount of combustion decreases.As the combustibility improves, the ratio tends to decrease.

In this case, the load factor on the furnace was reduced, and no smoke was observed even though the air ratio was significantly reduced. Note that almost the same results were obtained whether the maximum energy level or the vibration energy ratio was used as an index of the micropressure vibration pattern.

By adopting the above method and equipment, we were able to save an additional 10% on fuel, which was previously a soaking furnace with heat management and relatively low fuel consumption.

As is clear from the above explanation, the present invention
Basically, we perform waveform analysis of pressure vibration inside the furnace.
The system compares the vibration waveform in the optimum combustion state with the vibration waveform in each combustion state, which changes from moment to moment, and changes the air ratio in each combustion state based on the measured signal, making it possible to automatically adjust the air ratio. As long as the combustion state can be corrected through control, an optimal combustion state can be maintained no matter what factors change.

Furthermore, the measurement method does not require a constant amount of gas, and a simple pressure conduit is sufficient, which is different from the gas analysis method, and maintenance is extremely simple and practical.

Furthermore, since the signal source is pressure vibration, the response to the detector is much faster than that of the gas analysis method, and waveform analysis can be performed simultaneously in real time, so the overall response is much faster than that of the gas analysis method. It is possible to quickly correct the combustion condition to the optimum state.

[Brief explanation of the drawing]

Figure 1 is a configuration diagram of the air ratio control device, Figures 2a, 2b, and 2c are graphs showing examples of frequency analysis methods, and Figure 3 is the air ratio, micropressure vibration, and power spectrum. Figure 4 is a chart showing the relationship between air ratio and NOx. Figure 5 is a graph showing the relationship between air ratio and NOx.
The figure is a graph showing the relationship between the air ratio and the heat flux from the flame, Figure 6 is a schematic diagram of a soaking furnace, Figure 7 is a partial configuration diagram of the air ratio control device, and Figure 8 is a diagram showing the details of one heat cycle. Chart showing pressure vibration and power spectrum, Figure 9 is a chart showing power spectrum during micro-pressure vibration control, Figure 10 is a graph showing vibration energy ratio before vibration control, Figure 11 is after vibration control. Graph showing energy ratio,
FIG. 12 is a chart showing vibration waveforms and power spectra during vibration control, and FIG. 13 is a graph showing changes over time in operating factors. DESCRIPTION OF SYMBOLS 1... Combustion furnace, 2... Combustion burner, 3... Furnace temperature detector, 4... Furnace pressure sampling probe, 5... Temperature setting regulator, 6... Limiter, 7
...Fuel flow rate regulator, 8...Continuously automatic variable ratio setter, 9...Air amount regulator, 10...Fuel piping line, 11...Combustion air piping line, 12...
...Fuel flow rate control valve, 13...Fuel flow rate detector, 1
4...Air flow rate control valve, 15...Air flow rate detector, 16...Detector, 17...Amplifier, 18...
Frequency analyzer, 19... Vibration energy regulator,
20... Restrictor, 21... Flue, 22... Pen writing oscillograph, 23... Recording device, 24... Soaking furnace, 25... Furnace pig, 26... Burner tile.

Claims (1)

[Scope of Claims] 1. When combustion is performed in various industrial furnaces, pressure vibrations in the furnace are detected and their waveforms are analyzed, and a predetermined frequency distribution or frequency corresponding to the vibration waveform of the desired combustion state is determined. The energy distribution (strength distribution) or the vibration energy of a specific frequency band is set as a set value, and those values corresponding to the vibration waveform of each combustion state are compared, and based on that signal, the An air ratio control method in a combustion furnace, characterized by changing the air ratio. 2. A method of detecting pressure fluctuations in the furnace and controlling the air ratio based on the signals when combustion is carried out in various industrial furnaces, which detects at least one of the pressure fluctuations in the furnace when the combustion state changes. A specific frequency band in which the vibration energy density changes correspondingly is detected, and using the maximum energy level within that frequency band as an index, the maximum value of the vibration energy level in the frequency band of the furnace pressure vibration in the desired combustion state is set. value,
An air ratio control method in a combustion furnace, characterized in that the air ratio is changed according to the deviation between the maximum energy level of the frequency band and the set value in each combustion state. 3. A method of detecting pressure fluctuations in the furnace and controlling the air ratio based on the signals when combustion is carried out in various industrial furnaces, which detects at least one of the pressure fluctuations in the furnace when the combustion state changes. A specific frequency band in which the vibration energy density changes correspondingly is detected, and using the ratio of the total vibration energy to the vibration energy of the specific frequency band as an index, the vibration energy ratio during optimal combustion is set as a set value, and the vibration in each combustion state is A method for controlling an air ratio in a combustion furnace, characterized in that the air ratio is changed according to a deviation between an energy ratio and the set value.