JPH0833196B2 - Burner combustion controller - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a burner combustion control device used in combustion equipment such as a boiler.

(Prior Art) In a burner that burns liquid or gaseous fuel, it is desirable to maintain its combustion state optimally during combustion. Therefore, for example, as disclosed in JP-A-63-306310, a light intensity signal generated by a burner flame is converted into an electric signal by using a semiconductor such as a phototransistor, a photodiode or a solar cell. , There is one that performs combustion control using the integrated value of the power spectrum obtained as a result of frequency analysis of the vibration waveform. In addition, JP-A-60
As disclosed in Japanese Patent Publication No. 213725, a photoelectric sensor, a high-pass filter connected via an amplifier with an optical signal of a flame converted into an electric signal by the photoelectric sensor, and a signal output from this high-pass filter A first power spectrum detecting means for rectifying and converting to direct current and a bandpass filter for fixed vibration are provided, and the signal output from the highpass filter is passed in accordance with the frequency region of natural vibration in which oscillating combustion occurs, and rectification There is also known an air-fuel ratio detecting device including a second power spectrum detecting means for converting to a direct current and a calculating means for calculating a ratio or a difference between respective outputs of the first and second power spectrum detecting means. This one is
The air-fuel ratio can be determined by using the frequency component of the self-excited vibration of the optical signal of the flame generated by the oscillating combustion that clearly occurs in the air-rich or fuel-rich state where the air-fuel ratio greatly deviates from the value of 1 which is the ideal combustion state. It is something to detect. The second power spectrum detecting means detects the power spectrum of a component having a frequency within the frequency band of the natural vibration of the combustion device in the frequency band width of the output signal of the photoelectric sensor. However, in such a method of utilizing the light generated from the flame, when using a plurality of burners, good flame detection cannot be performed depending on the arrangement, or the flame of the burner is directly applied to the object to be heated. In some cases, the light sensor may not be able to detect light. Furthermore, because it requires an element such as a photodiode to convert the light from the flame into an electrical signal,
Special consideration was also needed for these easily damaged elements.

Further, the air-fuel ratio detecting device disclosed in Japanese Patent Laid-Open No. 60-213725 only detects the occurrence of oscillatory combustion in the combustion device.

In view of this, the present inventors have proposed a device in which instead of using light, an ionic current in the flame is captured to control the burner fuel (Japanese Patent Application No. 63-334619 (Japanese Patent Application Laid-Open No. 2-178517). Gazette)). This is the prior art of the present invention. This will be described with reference to the drawings. Reference numeral 1 in FIG.
What is indicated by is a furnace for heat-treating metal products and the like. A burner 2 is attached to the furnace 1, and a flame 3
Is to occur. A fuel supply pipe 4 and a combustion air supply pipe 5 are connected to the burner 2. The fuel supply pipe 4 is provided with a flow rate adjusting valve 6 and a flow meter 7, and the combustion air supply pipe 5 is provided with a flow rate adjusting valve 8. The opening of the fuel flow rate control valve 6 is controlled by the temperature controller 9. That is, the thermometer 10 is installed in the furnace 1, and the temperature controller 9 obtains the signal from the thermometer 10 and the signal from the upstream flow meter 7 to determine the set temperature from the difference between the furnace temperature and the set temperature. Is calculated and output.

This output is given to the fuel flow rate control valve 6 and the combustion air flow rate control valve 8. Therefore, when the temperature in the furnace deviates from the set temperature, the fuel and the air for combustion air are adjusted so as to return to the set temperature. The flow rate of the combustion air with respect to the flow rate of the fuel is calculated by the temperature controller 8 based on the fuel flow rate, but it is not preferable that the value be directly applied to the flow rate control valve 8 of the combustion air. . For example, when the door (not shown) of the furnace 1 is opened and air enters the furnace 1, if the flow rate control valve 8 is directly controlled by the output calculated based on the fuel flow rate, exhaust gas loss increases. If the atomization state of the fuel deteriorates due to the abnormality of the burner 2, if left as it is, a large amount of soot will be generated due to poor combustion. In order to eliminate such inconvenience, the output from the temperature controller 9 is corrected by the combustion air flow rate corrector 11, and then the flow rate control valve 8
Output.

The combustion air flow rate compensator 11 constitutes a flow rate controller 12 for combustion air together with the temperature controller 9. The correction output for the combustion air flow rate corrector 11 is created in the following combustion control device. This will be explained. The electrode rod 13 is attached to a position facing the flame 3 generated by the burner 2 of the furnace 1, and the flame emitting portion 14 of the burner 2 is provided with a terminal 15. The electrode rod 13 is connected to the input side of the ion current interruption device 16, and the output side of the ion current interruption device 16 is connected to the input side of the detector 17. A terminal 15 is also connected to the detector 17, so that the detector 17 detects the ion current in the flame 3. The above-mentioned ionic current interruption device 16 acts to periodically interrupt the ionic current signal.

The output side of the detector 17 is connected to a frequency analyzer 19 such as an FFT analyzer via an amplifier 18 that amplifies the detected ion current signal, and frequency analysis of the ion current signal is performed. . An ion current oscillation controller 20 is connected to the output side of the frequency analyzer 19. This ion current oscillation controller 20 detects the combustion state from the power spectrum signal output by the frequency analyzer 19 and the output signal of the ion current interrupting device 16, and compares this with the optimal combustion state stored in advance. The air flow rate correction coefficient is obtained from the deviation, and the flow rate controller 12 outputs an output for obtaining the flow rate of the combustion air required to eliminate the deviation by the signal to the flow rate adjusting valve 8.

Here, a signal from the ion current interrupting device 16 input to the ion current vibration controller 20 will be described. As described above, the ion current interruption device 16 periodically interrupts the signal from the electrode 15, and by performing this interruption,
Used to know the effect of noise on the system. That is, when the power is cut off, the ion current oscillation controller 20 is informed that the power is being cut off, the power spectrum signal obtained at that time is judged to be noise, and the power spectrum signal when it is not cut off By removing it, the effect of noise is removed. Therefore, the ionic current interrupting device 16 informs the ionic current oscillation controller 20 whether or not the current is currently interrupted.

Next, the operation will be described. As described above, this device utilizes the characteristic that the oscillation frequency of the ion current in the combustion flame changes depending on the combustion state when the liquid and gas fuels are burned in the combustion device. As a method for detecting the change in the ion current in the combustion flame, there is a method for detecting the current level. In this device, the following is performed. That is, the flame 3 generated by combustion
In order to detect the ion current inside, as shown in FIG. 4, two electrode rods 13a and 13b are provided in parallel at the tip of the flame 3,
Measure the ionic current flowing between them, or
As shown in the figure, one electrode rod 3 is provided in the flame 3, and the ion current generated between this electrode rod 3 and the terminal 15 provided in the flame emission part 14 of the burner 2 is detected (the latter). See Fig. 3).

The ion current signal obtained by any one of these methods oscillates as shown in FIG. This signal is input to the frequency analyzer 19, and the power spectrum as shown in FIG. 7 is obtained. The power spectrum thus obtained is changed by changing the air-fuel ratio, which is one of the indicators of the combustion state, as shown in FIG.
The level of the high frequency component changes. As a method of converting this change into a control signal, there is a method shown in FIG. This is a method of using the ratio B / A of the integral value B of the specific frequency band and the integral value A of the entire frequency band in which the power spectrum largely changes due to the change of the combustion state.

FIG. 9 shows the change in the value obtained by the above method. As is clear from this figure, the value obtained by this method is the exhaust gas O ₂ emission rate (%), which is one indicator of the combustion state.
Will follow the changes in. Therefore, it is possible to control the combustion state by using this value. In addition, since the measurement is based on the vibration frequency of the ion current caused by combustion, the output becomes zero if there is no flame. This phenomenon can be used as a means for detecting the presence or absence of flame.

Next, the processing contents in the ion current vibration controller 20 will be described with reference to FIG. First, in step 4-1, a power spectrum signal is input, and in the next step 4-2, it is judged from the signal from the ion current interrupting device 16 whether or not the ion current signal line is currently interrupted, and it is interrupted. In some cases, the process proceeds to step 4-3, and the signal obtained by the noise coming from the outside of the device as shown in FIG. 14 and the noise generated inside the device is stored in the memory. If it is determined in step 4-2 that the power is not cut off, the process proceeds to step 4-4, where the power spectrum signal obtained from the signal obtained from the current flame is used to calculate the power spectrum stored in the memory in step 4-3. Remove the components and get the power spectrum signal from the true flame.

Next, in step 4-5, the integrated value A of the entire frequency band of the power spectrum signal is calculated as shown in FIG. 12, and in step 4-6 the integrated value B of the specific frequency band is calculated. Here, the specific frequency band is a frequency band in which the power spectrum changes most significantly due to changes in the combustion state. Next, in step 4-7, the integrated value ratio J ← B / (AB) is obtained.
On the other hand, the integral value ratio (power spectrum ratio) K of the optimum combustion state for various fuel flow rates has been obtained in advance, and the data is set in the ion current vibration controller 20, and the current state in step 4-8. Then, the difference L ← J−K from the integral value ratio J of is calculated, and in step 4-9, the combustion air flow rate correction coefficient M is calculated from the deviation L.

Combustion air flow rate correction coefficient M thus obtained
From the ion current oscillation controller 20 to the combustion air flow compensator
It is output to 11. The combustion air flow rate corrector 11 receives the reference air flow rate signal N from the temperature controller 9 in addition to the combustion air flow rate correction coefficient M. The reference air flow rate signal N is calculated by the temperature controller 9 based on the fuel flow rate signal. Then, the combustion air flow rate compensator 11 obtains the signals M and N, performs a correction calculation by this, outputs the result to the flow rate control valve 8, and adjusts its opening.

(Problems to be Solved by the Invention) In the above-described prior art of the present invention, although there is a great effect that the drawbacks of the conventional method of utilizing the light generated from the flame can be eliminated, the configuration is various. The circuit is complicated because it has various control tables for adapting it to an industrial furnace and also has a frequency analyzer. Therefore, for example, when this combustion control device is installed in a small-scale industrial furnace that performs simple combustion control only on and off, there is a problem that the equipment cost is increased with respect to the effect obtained by that. The present invention, like the prior art, utilizes ionic current as the detection state of the flame combustion state.

Here, a method of detecting the flame combustion state by the ion current will be described. The change of the ion current with respect to the time axis in a certain combustion state has an oscillating waveform as shown in FIG. In the above-mentioned prior art, this vibration waveform is obtained by a frequency analyzer as a power spectrum as shown in FIG. Since this power spectrum changes with the change of the air-fuel ratio as shown in FIG. 7, by obtaining the integral ratio of the entire frequency band A and the specific frequency band B as shown in FIG. By obtaining the proportional relationship between the exhaust gas O ₂ and the integral ratio (power spectrum ratio) as shown in (3), the combustion control was performed by the power spectrum ratio which is an index instead of O ₂ %.

The feature of the present invention is that the same control as in the prior art is performed by using circuits such as a filter and an integrator without using the frequency analyzer used in the prior art.

(Means for Solving the Problems) As means for solving the above problems, the present invention provides an electrode rod 13 provided so as to enter the tip of the flame 3 emitted by the burner 2 and the flame radiating portion 14 of the burner 2. A burner combustion control device having an ionic current detection sensor for detecting an ionic current generated between the ionic current detection sensor and the terminal 15 provided in the, and an amplifier 18 for amplifying a signal from the ionic current detection sensor is provided. A low-pass filter 21 for removing high-frequency components in the ionic current is connected to the output side, and the low-pass filter 21
In addition, a circuit that rectifies and integrates the signal current that has passed through the low-pass filter 21 (rectifier 22 and integration circuit 23), and a signal that has passed through the high-pass filter 24 that removes low-frequency components in the signal current that has passed through the low-pass filter 21. A circuit that rectifies and integrates the current (rectifier 25 and integration circuit 26) is connected in parallel, and the integrated value output from both circuits is used to calculate and output the correction value of the supply air amount relative to the fuel amount (calculator 2
7), a supply air amount control means (air flow rate correction controller 28) for controlling the supply air amount according to the correction value output is provided.

(Operation) With the above configuration, when the burner 2 of the furnace 1 radiates the flame 3, the electrode rod 13 provided so as to enter the tip of the flame 3 and the terminal provided on the flame radiating portion 14 of the burner 2 Ion current generated between 15 and 15 is found, the integrated value of the entire frequency band is obtained from the bottom high frequency component that changes in relation to the difference in the air-fuel ratio of the signal of the ion current, and the higher side that greatly changes depending on the air-fuel ratio Since the integral value of the frequency component band of is calculated, the rate of change of the power spectrum integral ratio with respect to the air ratio becomes large, and a reliable correction value of the supply air amount with respect to the fuel supply amount can be calculated and output. The flame 3 can be adjusted. Further, since it is not necessary to use the frequency analyzer, the fuel control similar to that of the prior art can be performed by the circuit which is simpler and cheaper than that of the above-mentioned prior art.

(Embodiment) Next, one embodiment of the present invention will be described with reference to FIG. 1 by focusing on the same members as those in FIG. At the tip of the flame 3 emitted by the burner 2 of the furnace 1, an electrode rod 13 is attached so as to enter the tip of the flame 3, and the flame radiating part 14 of the burner 2 is attached.
Is provided with a terminal 15. The electrode rod 13 is connected to the input side of an amplifier 18 which amplifies the ion current generated between the electrode rod 13 and a terminal 15 provided on the flame emitting portion 14 of the burner 2. The output side of the amplifier 18 is connected to a low-pass filter 21 that removes high-frequency components in the ionic current, and the latter stage, which is the output side, is divided into two system paths.

A rectifier 22 that rectifies the signal current that has passed through the low-pass filter 21 and an integrating circuit 23 that smoothes the rectified pulsating current and converts it into a direct current are connected to one of the two paths. In the other of the two paths, a high-pass filter 24 that removes low-frequency components in the signal current that has passed through the low-pass filter 21, and a rectifier 25 and rectifier that rectifies the signal current that has passed through the high-pass filter 24. An integrating circuit 26 for smoothing the subsequent pulsating flow and converting it into a direct current is connected.

These two paths merge at the output sides of the integrating circuits 23 and 26, and are connected to the input side of a computing unit 27 that computes the relationship between the entire frequency band and the specific frequency band. An air flow rate correction controller 28 that functions as a combustion control meter that receives the output signal and controls combustion is connected to the output side of the calculator 27. The output side of the air flow rate correction controller 28 is connected to the modtrol motor 29. A combustion air supply pipe 31 for supplying air by a combustion air supply fan 30 is connected to the burner 2. Inside the combustion air supply pipe 31, a semi-fixed damper valve 32 and the aforementioned Compensation damper valve 33 that is opened and closed by the modtrol motor 29
Are provided.

A fuel injection pump 34 is connected to the upstream side of the flow meter 7 in the middle of the fuel supply pipe 4, and a fuel cutoff valve 35 is connected to the downstream side of the flow meter 7. The fuel injection pump 34, the fuel cutoff valve 35, and the combustion air supply fan 30 are
It is connected to the output side of a master controller 36 which receives the output signal of the thermometer 10 and processes it.

The burner combustion control device thus configured operates as follows. When the burner 2 in the furnace 1 is burning, the thermometer 10 detects the temperature in the furnace 1 and sends it to the master controller 36, and the electrode rod 13 causes the flame emitting part 14 of the burner 2 to move.
The ionic current is detected between the terminal 15 and the terminal 15. The signal from the thermometer 13 is the master controller 36.
When the input reaches the upper limit of the preset temperature, the master controller 36 compares the value with the preset temperature set therein beforehand, and the combustion air feeding fan 30 and the fuel supply A stop signal is transmitted to the fuel injection pump 34 and the fuel cutoff valve 35 which are connected in the middle of the pipe 4, and these operations are stopped. Then, when the temperature detected by the thermometer 13 reaches the lower limit of the set temperature, a start signal is transmitted to each of the devices 30, 34, 35 that have stopped operating. This restarts the operation.

The fuel control during operation in a fixed state with a fuel amount of 100% is adjusted by the semi-fixed damper valve 32 provided in the combustion air supply pipe 31 so as to be slightly air-rich on the safety side. The adjusted semi-fixed damper valve 32 is fixed. On the other hand, the flame ion current flowing between the terminal 15 provided on the flame radiating portion 14 of the burner 2 and the electrode rod 13 is amplified by the amplifier 18, the high frequency component in the signal is removed by the low pass filter 21, and then the signal is removed. Is branched into two paths. The signal current flowing through one of the two paths is rectified by the rectifier 22 by the output signal from the low-pass filter 21, and smoothed by the integration circuit 23 after rectification (integrated value A ). The signal of the integrated value A is input to the calculator 27.

In the other one of the two systems, the low-frequency component in the signal is removed by the high-pass filter 24, then rectified by the rectifier 25, smoothed by the integrating circuit 26 and converted into direct current (integral value B), and then the operation is performed. Input to the container 27. B / (A-
The calculation of B) is performed, and the result is the air flow rate correction controller.
Entered in 28. From this signal, the air flow rate correction controller 28 outputs a signal corresponding to the air flow rate correction coefficient obtained by the processing of steps 4-8 and subsequent steps in the flowchart of FIG.
Will be sent to. With this, the modtrol motor 29 adjusts the correction damper valve 33 to perform optimum combustion control. In this embodiment, the correction damper valve
Although 33 is a separate body from the semi-fixed damper valve 32, they can also be combined.

In this combustion control device, since the ion current resulting from combustion is measured, the output becomes 0 without the flame 3. Therefore, the function as a means for detecting the presence or absence of flame can be used together with the combustion control.
Here, a general initial air-fuel ratio adjustment for an industrial furnace or the like for performing on / off combustion control will be described. In the on / off control, the fuel amount is naturally 0 or 100%,
Normally, the amount of fuel air is adjusted and fixed with a damper valve etc. according to the 100% fuel flow rate. In this case, it is general to set the air amount slightly higher than the optimum air amount so as to be on the safe side. When operating throughout the year, the air density changes due to the temperature difference between summer and winter,
Normally, the air volume is set according to the summer when the air density becomes low. Also in this case, make the air rich so that you can enter the safe side.

Assuming that the temperature difference between the air in summer and winter is 30 deg and the amount of O ₂ in the exhaust gas in summer is 5%, the air volume decreases to 0.9 in winter when summer is 1. Therefore, in the summer and winter, when the damper opening is the same, the air becomes more air-rich in winter than in summer, and the amount of O _{2 in} the exhaust gas is about
It becomes 6.6% and the exhaust gas loss becomes large. On the other hand, if the combustion control device of the present invention is used, this point will be greatly improved.

(Advantages of the Invention) Since the present invention is a burner combustion control device configured as described above, it is very simple compared to the above-mentioned prior art developed to achieve the same object. Despite the structure, the same function can be obtained. Therefore, the installation cost can be remarkably reduced by installing in a small-scale industrial furnace that performs simple combustion control only on and off.

[Brief description of drawings]

FIG. 1 is a circuit diagram of an embodiment of the present invention, FIG. 2 is a circuit diagram of a prior art to the present invention, and FIG. 3 is a process in the ion current vibration controller of FIG. Flowchart diagrams for explaining the contents, FIGS. 4 and 5 are side views showing the positional relationship between the burner and the electrode rod, FIG. 6 is a graph showing changes in ion current with the passage of time, and FIG. 7 is a power spectrum. 8 is a graph showing the relationship with the frequency, FIG. 8 is a graph for explaining a method of changing the change in the level of the changing high frequency component into a control signal by changing the air-fuel ratio, and FIG. 9 is an exhaust gas. 6 is a graph showing the relationship between O ₂ and the power spectrum ratio. 1 …… Furnace 2 …… Burner 3 …… Flame 13 …… Electrode rod 14 …… Radiating part 15 …… Terminal 18 …… Amplifier 21 …… Low pass filter 22,25 …… Rectifier 23,26 …… Integrator circuit 24… … High-pass filter 27 …… Calculator 28 …… Air flow compensation controller 29 …… Modtrol motor 31 …… Combustion air supply pipe 33 …… Compensation damper valve

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Kazuya Tomatsu 1 Toyota Town, Toyota City, Aichi Prefecture, Toyota Motor Corporation (72) Inventor Toshiharu Tachibana 1, Toyota Town, Aichi Prefecture, Toyota Motor Corporation (56) References JP-A-63-306310 (JP, A) JP-A-60-213725 (JP, A)

Claims (1)

[Claims] 1. Burning of a burner having an ionic current detection sensor for detecting an ionic current generated between an electrode rod provided so as to enter a tip portion of a flame emitted by the burner and a terminal provided in a flame radiating portion of the burner. A control device is provided with an amplifier for amplifying a signal from the ion current detection sensor, a low-pass filter for removing high-frequency components in the ion current is connected to the output side of the amplifier, and the low-pass filter is passed through the low-pass filter. A circuit that rectifies and integrates the signal current and a circuit that rectifies and integrates the signal current that has passed through the high-pass filter that removes low-frequency components in the signal current that has passed through the low-pass filter are connected in parallel,
A burner characterized in that it is provided with a supply air amount control means for calculating and outputting a correction value of the supply air amount with respect to the amount of fuel by the integrated value output from both circuits, and controlling the supply air amount according to the correction value output. Combustion control device.