JPS63105322A - Combustion control - Google Patents

Abstract

PURPOSE:To permit combustion control, prominent in response, by a method wherein the average value of movements during a predetermined time is obtained from the light power of flame and the integral value of a difference between an upper value and a lower value than the average value is compared with the integral value of deviation with respect to a proper O2 %, previously obtained. CONSTITUTION:An A/D converter 17 converts a light signal from a light sensor 15, converting a light power emitted from combustion flame 14 into an electric signal, into a digital signal. A combustion airflow corrector 19 integrates the electric signal from the converter 17 during a unit time to operate an average value, integrates a deviation with respect to the average value during a unit time to obtain the integral value of the deviation, receives the flow rate signal of fuel form a fuel flow meter 8 to obtain the integral value of a deviation corresponding to the optimum O2 % and compares these values to output an output for eliminating these deviations to the flow rate regulating valve 9 of combustion air.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention is characterized in that the amplitude of the optical power of a combustion flame is
Using the fact that there is a proportional relationship with %, the signal regarding the amplitude of optical power obtained during operation of the combustor is compared with the signal regarding the amplitude of optical power corresponding to the appropriate 02%, and the combustion is performed to eliminate the deviation. The present invention relates to a combustion control method for controlling the flow rate of air for use.

Conventional technology Conventionally, a method for controlling combustion has been disclosed in Japanese Patent Application Laid-open No. 59-13.
Some of these are disclosed in Japanese Patent No. 8811 and Japanese Patent No. 58-146124.

The former, JP-A No. 59-138811, places a combustion sensor made of a semiconductor in the flame, monitors the combustion state based on changes in its electrical resistance, and stops combustion when oxygen deficiency or misfire is detected. This is what we are trying to do.

The latter, published in JP-A No. 58-146124, uses an optical measuring device to spectrally analyze the emission spectrum of the flame, determine the temperature distribution of the flame from this, and compare this with the temperature distribution of the flame under optimal combustion conditions. It outputs a control signal, and uses this output to control the shape of the flame.

However, the former only turns combustion ON and OFF, but does not control the combustion flame itself in the furnace. Furthermore, since the latter spectroscopically analyzes the emission spectrum, it has the disadvantage that the detection section and control section become complicated.

January 2, 1985 as a combustion control that does not have such drawbacks.
There is something disclosed in the Netsu Sangyo Keizai Shimbun on the 5th.

This is done by installing a zirconia 02 sensor in the flue to measure 02% of the exhaust gas passing through the flue, and using this 02% as an indicator, the blower is set to the optimum amount of forced air for combustion according to the load conditions. The rotation speed of the motor is controlled by an inverter. 7 Regarding the use of optical power to detect the combustion state, see JP-A-59-137719 and JP-A-59-109715.
No. 59-12227 and No. 58-143274.

Problems to be Solved by the Invention Although combustion control using the zirconia 02 sensor described above can easily control the combustion state in the furnace, it has the following drawbacks.

■ Since the sensor must be installed in the flue, if outside air enters through the inspection hole or the gap created between the combustion chamber outlet and the measurement part, the 02 concentration in the combustion chamber will increase. I mistakenly judge it as something.

■ Due to the flow of gas from the combustion chamber outlet to the measuring section,
A time lag occurs.

■ Zirconia 02 sensor has a response delay of 30 to 40 seconds. This becomes a bottleneck in performing faster control.

In place of the above zirconia 02 sensor, the above JP-A-59-
Although it is conceivable to use the optical sensors described in No. 137719, etc., these optical sensors simply detect optical power and cannot be immediately applied.

Means to solve the problem Combustion conditions vary greatly depending on the mixture ratio of fuel and air, and that ratio, generally referred to as the air ratio (or 0° concentration in exhaust gas), is an important point in combustion management. . For example, if the air ratio is increased too much, exhaust gas loss increases, thermal efficiency decreases and NOx increases, resulting in poor combustion conditions. On the other hand, if the air ratio is made too small, incomplete combustion will occur, producing black smoke, and may also lead to misfire, which is also not a good combustion condition.

Therefore, a good combustion condition is combustion at the lowest air ratio that does not cause incomplete combustion.

Note that the air ratio and the 02 concentration in the exhaust gas have the following relationship.

By the way, in a type of burner whose flame is held by swirling force, the light intensity generated from the flame of the burner is determined by the combustion amount (
When the fuel flow rate (fuel flow rate) is constant, the difference in air ratio (or 0° concentration in exhaust gas) causes changes as shown in the curve ■ in Figure 2, and the optical power signal always changes as shown in Figure 3. Shows a vibrating sawtooth waveform. The optical power signal level shows a mountain-shaped change as shown in Figure 2, and in the region (A) where the O2 concentration is higher than the peak value, the optical power signal level decreases as the O2 concentration increases, and The region (b) where the O2 concentration is lower than the peak value has a characteristic that the optical power signal level also decreases as the O2 concentration decreases.

However, as shown in FIG. 3, the oscillation of the optical power signal exhibits a characteristic in which the width of the oscillation increases as the 02 concentration decreases.

Further, the characteristics described above do not change even when the combustion amount is changed, but when the combustion amount is increased, the oscillation width of the optical power signal becomes larger, and conversely, when the combustion amount is decreased, the oscillation width of the optical power signal becomes smaller.

Furthermore, when a burner with a cone-shaped flame holder is used, the light intensity changes as shown by curve H in FIG. 2. However, regarding the vibration of the optical power signal, contrary to FIG. 3, the vibration width becomes smaller as the 02 concentration decreases.

Based on the above findings, the present inventors obtained data as shown in FIG. 4 regarding a type of burner that holds flame by swirling force.

In this figure, the vertical axis indicates the value related to the amplitude of the optical power. For example, the unit time Δ of the sawtooth vibration part with respect to the average value M of the optical power as shown in FIG. The value is scaled. The horizontal axis shows 02% in the exhaust gas.

Curves a, b, and c are exhaust gas 0 for various combustion amounts of fuel.
The curve d shows the relationship between 2% and the deviation integral value, and the curve d is the exhaust gas 0□% at the optimal air ratio where incomplete combustion does not occur as described above.
It shows the relationship between and the integral value.

Therefore, for example, if the combustion rate is set to 706/h and the integral value detected from the burner flame is Y, the corresponding o2% (c) will deviate from the appropriate 02% (d) ( E), and this deviation (E) is the deviation B of the integral value.
It can be read from the above figure that it corresponds to .

Further, the present inventors obtained data shown in FIG. 5 regarding a type of burner having a cone-shaped flame holder.

The combustion control method according to the present invention utilizes data as shown in FIG. 4 or 5 above, and performs control to eliminate the deviation B based on the deviation B obtained from comparing this data with the detection signal It is intended to output a signal.

That is, in order to solve the above problems, the present invention obtains a flow rate signal of fuel supplied to a combustor and a 02% signal in the exhaust gas of the combustor, and determines that the 02% is appropriate for the flow rate of the fuel. In a combustion control method in which the deviation is calculated when it deviates from 0.02%, and an output to eliminate the deviation is provided to the combustion air flow rate adjustment section, 0.2% of the exhaust gas is converted into optical power. Detected from the flame of the above combustor,
From the optical power, find the moving average value within a predetermined time, and also find the deviation integral value of the value above and below it, and then correspond to the appropriate 0.2% of the current fuel flow rate found in advance. A method is adopted in which the deviation is calculated by comparing it with the deviation integral value obtained, and an output to eliminate the deviation is provided to the combustion air flow rate adjusting section.

Optical power is detected from the flame formed in the working combustor and this optical bar is processed to obtain a control output.

Therefore, it is possible to control O2% in the exhaust gas without directly detecting the O2%. As a result, it is possible to use a relatively inexpensive optical sensor instead of an expensive zirconia 0° sensor.Also, when the combustor is a burner, it is nothing but detecting the combustion state in the furnace. Compared to the conventional method of detecting in the flue, combustion 1a can be detected without any time lag.
J control can be performed.

In order to obtain the above control output, the moving average value within a predetermined time is determined from the optical power, and the deviation integral value of the value above and below the moving average value is determined. Perform comparison calculation with the deviation integral value related to %.

Since the calculation is performed using the deviation integral value in this way, an appropriate control output can be obtained, and therefore combustion control with excellent responsiveness can be performed.

Embodiment An embodiment of the present invention will be explained based on FIGS. 1 to 4 and FIG. 6.

FIG. 6 shows a heat treatment furnace using the combustion control method according to the present invention.

In FIG. 6, reference numeral 1 indicates a furnace body, and a door 2 for charging metal products and the like and a flue 3 for discharging exhaust gas are provided on the wall of the furnace body 1, respectively.

In this case, the burner 4, which is a combustor provided in the furnace body 1, is of a type that maintains flame by swirling airflow.

A pipe 5 for supplying fuel and a pipe 6 for supplying combustion air are connected to the burner 4, the pipe 5 is provided with a flow rate control valve 7 and a flow meter 8, and the pipe 6 is provided with a flow rate control valve 9. ing.

The fuel flow control valve 7 is controlled by a fuel control device.

The device includes a temperature sensor 10 consisting of a thermocouple that detects the temperature inside the furnace 1 and a fuel control section 11.

The fuel control unit 11 includes a temperature converter 12 and a combustion amount regulator 13.
The signal from the temperature sensor 10 is converted into a predetermined output signal by the temperature converter 12, and this is sent to the combustion amount regulator 1.
3, the temperature is compared with a predetermined set temperature, and a control signal is output for adjusting the opening degree of the control valve 7 so that the fuel that can maintain the set temperature reaches the burner 4.

The combustion air flow control valve 9 is controlled by a combustion air control device.

The device includes an optical sensor 15 that converts the optical power emitted from the combustion flame 14 of the burner 4 into an electrical signal, and a combustion air control device that receives the signal, generates a control signal, and outputs it to the combustion air flow control valve 9. 16.

The optical sensor 15 is composed of a Ge photodiode, an S1 photodiode, a phototransistor, a solar cell, etc., and is fixed at a location facing the flame 14.

The combustion air control unit 16 includes an A/D converter 17 that converts the optical signal from the optical sensor 15 into a digital signal, and the converter 1
The electric signal from 7 is integrated over a unit time to calculate the average value, and the deviation from this average value is integrated over a unit time to obtain the integrated deviation value.Then, the optimum 02% is determined by receiving the fuel flow signal from the fuel flow meter 8. The combustion air flow rate corrector 19 calculates and compares the integral deviation value corresponding to the deviation, and outputs an output to the combustion air flow rate control valve 9 to eliminate the deviation.

The operation of this combustion air control section 16 will be explained based on the flowchart of FIG.

The optical power signal Xo from the A/D converter 17 is read into the combustion air flow rate corrector 19 (step 1), and then Δ is calculated as the moving average X of all the signals per second (step 2.3).
.

That is, in step 2, the oldest data Xn of the n pieces of data whose past Δ was measured per second is deleted, and the current signal Xo is input in its place. Then, in step 3, the moving average X is calculated by dividing by n, which is the sum of n data of X1NXn.

Next, the absolute value Yo of the difference between the current optical power signal Xo and the moving average is determined (step 4).

Yo is read, past Δ is used to erase the most past Yn of data for seconds (step 5), and deviation integral value Y, which is the sum of n pieces of data for Δ seconds, is determined (step 6).

Once Y is determined, the fuel flow ■Q, for example, 701/h is read (step 7), and the curve example corresponding to Q, tba (Fig. 4) is selected, and it corresponds to a reasonable 02% (d) for Q. The deviation integral value A is determined (step 8). Then, the deviation and B, which are the deviations between the current value Y and the optimum value A, are determined (step 9).

After that, the control amount proportional to B and B so that B becomes O
A control amount C is calculated by adding a control amount proportional to the integral value of (step 10).

The optimum air flow rate for the current fuel flow rate Q is determined, the opening degree of the valve 9 in that case is compared with the current opening degree, and whether the valve 9 is opened or closed more than the current degree and the degree thereof are determined as an air flow rate adjustment signal. D is determined by the combustion amount regulator 13 and output to the combustion air flow rate corrector 19 (step 11).

The corrector 19 obtains C and D, calculates the air flow rate adjustment signal E from the following correction equation (step 12), outputs this to the valve 9, and adjusts its opening degree (step 13).

In this formula, C is % data and is a value within the range of 0 to 100%. When c = o ~ 56%, the valve opening degree is decreased, and when C = 50 ~ 100%, the valve opening degree is increased. For example, when C = 40%, E = 0.8D, and C = 60%. Then, E = 1.2D.

As a result, D obtained by calculation 1 is corrected by C to increase or decrease, and is output as E to the valve 9.

In this way, the furnace 1 is constantly operated in the optimum combustion state, and 02% of the exhaust gas (d) is discharged from the furnace through the flue 3.

Note that 02% may temporarily increase due to new material being taken in and taken out from door 2, but that 02% may increase temporarily.
Since a 2% change is immediately detected by the optical sensor 15, the control valve 9 is immediately adjusted to quickly return to the appropriate 0%.

Although the above embodiment is intended for a heat treatment furnace, if the target is a boiler or the like, a pressure sensor may be provided in place of the temperature sensor 10 of the fuel control unit 11, and the combustion amount regulator 13 may be replaced with a steam pressure setting method. It's good.

Effects of the Invention As described above, the present invention detects optical power from the flame formed in the combustor and processes this optical power to obtain a control output. control becomes possible. Therefore, 0 is expensive as a sensor.
It is possible to use a relatively inexpensive optical sensor instead of a ° sensor, which is useful for combustion control of furnaces, gas turbines, etc.

In addition, since the combustion state can be detected in the furnace, compared to the conventional method of detecting exhaust gas while passing it through the flue, it is possible to quickly respond to sudden changes of 0.2% due to opening and closing of the furnace. Even if air leaks from gaps in the road, the detection results will not be affected.

Furthermore, since the output is calculated by calculating the deviation integral value from the optical power, an appropriate control output can be obtained.

[Brief explanation of the drawing]

Fig. 1 is a flowchart showing the procedure for obtaining the control output of the combustion control method according to the present invention, Fig. 2 is a graph showing the relationship between optical power and exhaust gas O2% under a constant combustion amount, and Fig. 3 is a graph showing the relationship between the combustion amount and the exhaust gas O2%. Figure 4 is a graph showing the relationship between optical power and time when 02% is kept constant and 02% is varied. The figure is a graph similar to FIG. 4 for different types of burners, and FIG. 6 is a diagram of a control system for a heat treatment furnace using the present invention. 1: Furnace, 4: Burner, 8: Fuel flow meter, 9: Combustion air flow control valve, 13: Combustion amount regulator, 15: Optical sensor, 1
6: Combustion air control unit, 17: A/D converter, 19: Combustion air flow rate corrector. Applicant: Toyota Motor Corporation Representative Ichikawa Seki (1 other person) Fig. 1 Fig. 2 P-shape Power/S 02 (%) Fig. 3 Fig. 4 Fig. 2 Medium furnace gas 02% [% 1 Fig. 5 Feather and Puzu 02[%]

Claims (1)

[Claims] When a flow rate signal of fuel supplied to a combustor and a signal of O_2% in the exhaust gas of the combustor are obtained, and the O_2% deviates from an appropriate O_2% for the flow rate of the fuel, In a combustion control method in which the deviation is calculated and an output for eliminating the deviation is sent to the combustion air flow rate adjusting section, O_2% in the exhaust gas is detected from the flame of the combustor as optical power. , find the moving average value within a predetermined time from the optical power, find the deviation integral value of the value above and below it, and then calculate this to a reasonable O_2% for the current fuel flow rate found in advance. The combustion control method described above is characterized in that the deviation is calculated by comparing it with a corresponding integrated deviation value, and an output for eliminating the deviation is provided to the combustion air flow rate adjusting section.