JPS63105320A - Method and apparatus for combustion control - Google Patents

Abstract

PURPOSE:To permit quick and proper control, by a method wherein a difference between the amplitude signal of an optical power, obtained from flame, and the amplitude signal of the optical power corresponding to the proper percentage of O2 obtained previously from the flow rate of fuel is obtained and an output for eliminating the deviation is outputted to the control unit of the flow rate of combustion air. CONSTITUTION:A control unit 16 reads an optical power signal X0 from a converter 17 and obtains the average X of the movement of a total signal during DELTAt sec to obtain the absolute value Y0 of the difference, Then, the total sum of (n) pieces of data or the integral value Y of the difference during DELTAt sec is obtained and a curve (a), for example, corresponding to the flow rate Q of fuel is selected to obtain the integral value A corresponding to a proper O2 %. A difference B between a present value Y and the optimum value A is obtained and the amount of control C, in which the amount of control proportional to the difference B is added to the amount of control proportional to the integral value of the difference B, is operated so that the difference B becomes zero. The opening degree of a valve 9 in that case is compared with the same at present and a deviation is obtained by a temperature regulator 13 as an airflow rate regulating signal D to output it to a combustion air flow rate regulator 19. The regulator 19 receives the signals C, D and obtains an airflow rate regulating signal E from a compensating formula to output it to the valve 9 and regulate the opening degree of the same.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention is characterized in that the amplitude of the optical power of the 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 and device for controlling the flow rate of air for use.

2. Prior Art Conventionally, methods and devices for controlling combustion have been disclosed in Japanese Patent Application Laid-open No. 5
There are those disclosed in 9-138811 and 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 the shape of the flame is controlled to a constant level by the output of the .

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.

As a combustion control method and apparatus that do not have such drawbacks, there is one disclosed in the Netsu Sangyo Keizai Shimbun dated January 25, 1985.

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.

Note that a light power detector that can be used as a combustion state detection section of a combustion control device is described in Japanese Patent Application Laid-Open No. 59-13771.
No. 9, No. 59-109715, No. 59-12227, and No. 58-143274.

Problems to be Solved by the Invention Although the combustion control method and apparatus using the zirconia O2 sensor described above can easily control the combustion state in the furnace, it has the following drawbacks.

■Senna must be installed in the flue. If outside air enters through the inspection hole or structural gap between the combustion chamber outlet and the measurement part, the 02 concentration in the combustion chamber will be high. I mistakenly assumed that it had happened.

■A time lag occurs due to the flow of gas from the combustion chamber outlet to the measurement section.

■The zirconia 02 sensor has a 7F delay of 30 to 40 seconds. This becomes a bottleneck in performing faster control.

In place of the zirconia 02 sensor mentioned above,
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 is generally referred to as the air ratio (or 02 concentration in exhaust gas) and 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 and black smoke will be generated, which may also lead to misfires, 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, the light intensity generated by the flame of a burner that burns fuel such as heavy oil or gas is as follows, assuming that the amount of combustion is constant:
The second difference is due to the difference in air ratio (or 02 concentration in exhaust gas).
The light changes as shown in the figure, and the optical power signal exhibits a constantly oscillating sawtooth waveform. The optical power signal level shows a mountain-shaped change as shown in Fig. 2, and in the region (a) where the 02 concentration is higher than the peak value, the optical power signal level decreases as the 02 concentration increases, and the peak value In the region (b) where the 02 concentration is lower than the value, the optical power signal level also decreases as the 02 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.

The characteristics shown in FIGS. 2 and 3 are for a burner with a mechanism that holds the flame by swirling force, but a burner with a cone-shaped flame holder has completely opposite characteristics to the above.

The above characteristics are specific to each type of burner.

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 a value related to the fluctuation of optical power, and for example, the integrated value within a unit time of the sawtooth vibration portion, ie, the deviation integrated value, is scaled with respect to the average value of optical power shown in FIG.

The horizontal axis shows 02% in the exhaust gas. , curves a, b,
Curve c shows the relationship between the exhaust gas 0□ ratio and the deviation integral value for various combustion amounts of fuel, and the curve d shows the relationship between the exhaust gas 02% and the integral value at the optimal air ratio where incomplete combustion does not occur as described above. It shows.

Therefore, for example, if the combustion amount is set to 6043/h and the integral value detected from the burner flame is Y, then the corresponding 02% (c) is a reasonable 0□) and the deviation ( This deviation (E) is the deviation B of the integral value.
It can be read from the above figure that it corresponds to .

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

The combustion control method and device according to the present invention stores the data shown in FIG. 4 or FIG. The aim is to output a control signal to eliminate the problem.

That is, in order to solve the above-mentioned problems, the present invention provides a flow rate signal of fuel in a combustor that receives supply of liquid or gaseous fuel and combustion air to form a flame, and a flow rate signal of 0.2% in the exhaust gas of the combustor. When the signal is obtained and the O2% deviates from the appropriate 02 ratio for the fuel flow rate, the deviation is calculated and an output to eliminate the deviation is sent to the combustion air flow rate adjustment section. In the combustion control method, an optical power signal is detected from the flame to obtain a signal regarding the optical power amplitude therefrom, and this is then converted into a signal regarding the optical power amplitude corresponding to a reasonable 0.2% of the fuel flow rate obtained in advance. A method is adopted in which the deviation is determined by comparing the deviation, and then an output to eliminate the vaginal deviation is applied to the combustion air flow rate adjustment section.

In addition, a flow rate signal of the fuel in a combustor that receives liquid or gaseous fuel and combustion air to form a flame and a 02% signal in the exhaust gas of the combustor are obtained, and the 02% is the flow rate of the fuel. In a combustion control device that calculates the deviation when it deviates from a reasonable 02% and outputs an output to the combustion air flow rate adjustment section to eliminate the deviation, the 02% signal in the exhaust gas is used. An optical sensor is provided at the rear of the combustor to obtain a signal regarding the amplitude of the optical power, and the relationship data between the signal regarding the polarization of the optical power for various fuel flow rates and the 02% signal in the exhaust gas and the various fuel flow rates are provided. storing reference data regarding the amplitude of optical power corresponding to a reasonable 0□% for the fuel flow rate; A configuration is adopted that includes a control unit that compares the data with the data and outputs an output to the combustion air flow rate adjustment unit to eliminate the deviation.

Working liquid or gaseous fuel and combustion air are supplied to the combustor and a flame is formed to begin operation of the furnace, turbine, etc.

According to the combustion control method of the present invention, an optical power signal is detected from a flame, a signal relating to amplitude is obtained therefrom, and this is compared with a desired 0□ corresponding signal to obtain an output that eliminates the deviation.

Therefore, it is possible to control 00□ in the exhaust gas without directly detecting 02%.

Further, according to the combustion control device of the present invention, the optical sensor detects the optical power from the flame of the combustor and sends it to the control section.

The control section generates a signal regarding amplitude from the optical power.

The control unit also receives a fuel flow rate signal.

As a result, the control unit compares the signal regarding the amplitude with the reference data of FIG. 4 stored in advance, and
The deviation between this value and a reasonable 0% is calculated as the deviation of the value related to the amplitude, and an output for eliminating this deviation is provided to the combustion air flow rate adjustment section.

Therefore, the air ratio is always maintained at an appropriate value, and stable combustion is maintained. Further, since the optical power is detected in the furnace when the combustor is a burner, prompt and appropriate control can be performed without causing a time lag or the like.

Example The present invention will be specifically explained below with reference to various examples.

(Embodiment 1) FIG. 1, FIG. 4, and FIG. 6 show a first embodiment of the present invention.

In FIG. 1, reference numeral 1 denotes a furnace for heat-treating metal products and the like. A wall of the furnace 1 is provided with a flue s2 for charging metal products and the like and a flue 3 for discharging exhaust gas.

The furnace 1 is provided with a burner 4 which is a combustor, and in this case is a type of burner 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 temperature control device.

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

The control unit 11 includes a temperature converter 12 and a temperature regulator 13, and the temperature converter 12 converts the signal from the temperature sensor 10 into a predetermined output signal, which is received by the temperature regulator 13 and adjusted to a predetermined setting. A comparison calculation is made with the temperature, and a control signal is output for adjusting the opening degree of the control valve 7 so that fuel that can maintain the set temperature reaches the burner 4.

The combustion air flow control valve 9 is controlled by a combustion 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 control section 16 that receives the signal, generates a control signal, and outputs it to the combustion air flow control valve 9. We are prepared.

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

The control unit 16 includes a converter 17 that receives an optical signal from the optical sensor 15 and converts it into an electrical signal, and integrates the electrical signal from the converter 17 over a unit time to calculate an average value, and calculates the deviation from this average value over a unit time. an integrator 18 that integrates and outputs a deviation integral value; and an integrator 18 that receives the output from the integrator 18 and receives a fuel flow rate signal from the fuel flow meter 8, and
The current integrated deviation value is compared with the pre-stored reference data shown in FIG. It consists of a regulator 19 for controlling the

The operation of this control section 16 will be explained based on chart 70 in FIG.

Optical power signal X from converter 17. is read (step 1), and then the moving average X of all the signals for Δ seconds is determined (fans 7'-2, 3).

That is, in step 2, the most past data Xn of the n pieces of data measured in past Δ seconds is erased, and the current signal XO is input in its place. Then, in step 3, the moving average X is calculated by dividing the sum of n pieces of data X1 to Xn by n.

Next, the current optical power signal X. The absolute value Y of the difference between and the moving average X. (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, read the fuel flow rate Q, for example 6 oA/h (step 7), select the curve corresponding to Q, for example a (Fig. 4), and calculate the deviation integral value corresponding to a reasonable value of 02% for Q. Find A (Stella 7'8). Then, the deviation Be, which is the difference between the current value Y and the optimum value A, is determined (step 9).

After that, the control amount B is proportional to B so that B becomes 0.
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 temperature regulator 13 and output to the combustion air flow rate regulator 19 (step 11).

The regulator 19 obtains C and D, calculates an 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, Cf'i% data is 0 to 100
The value is within the range of %. 020-50% is a decrease in the valve opening, and when C=50-100% is an increase in the valve opening. For example, when C=40%, E=0.8D and C=60%.
In this case, E=1.2D.

As a result, it is outputted to the valve 9 as E after being corrected to increase or decrease by the calculated DI-1:C.

In this way, furnace 1 always operates in the optimum combustion state, and the
The exhaust gas will be discharged from the flue 3 to the outside of the furnace.

It should be noted that it is said that 02% will temporarily increase due to the new loading and unloading of materials from door 2, but that 02% will 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%.

(Example 2) FIG. 7 shows a state in which the combustion control method and device according to the present invention are used in a heating device.

The furnace 20 is surrounded by an outer shell 21, a burner 22 serving as a combustor is installed at a predetermined location, and a large number of heat exchange tubes 23 are installed at a location facing the burner 22.

In addition, a heating air supply duct 25 equipped with a fan 24 is connected to the outer shell 21 at a location close to the heat exchange tube 23 , and a duct 27 for supplying heating air to the living area 26 is connected to the duct 25 away from the duct 25 . connected to the point.

For this purpose, the heating air enters the outer shell 21 from the duct 25 by the fan 24, is heated at the heat exchanger tube 23, and is sent as hot air through the duct 27 to the living area 26.

Heat exchanger tube 23 receives combustion flame 28 from burner 22
The heated exhaust gas is guided to the chimney 30 by the smoke exhaust fan 29 and discharged outside the system.

A mixing box 31 and a mixing box 32 for mixing the warm air from the duct 27 and the living area return air are installed in the living area 26. A distribution duct 33 extends from the mixing fan 32 toward each living room.

Therefore, the warm air from the duct 27 is mixed with return air in the mixing box 31, adjusted to an appropriate temperature, and then sent from the mixing box 32 to each living room.

The furnace 20 is equipped with an optical sensor 34 and a control section 35 as in the first embodiment.

The control unit 35 includes a converter 36, an integrator 37, and a regulator 38, and performs calculations similar to those shown in FIG. It is meant to be done.

The damper 39 is provided with a link mechanism 40 for rotating the damper 39 and an actuator 41 for driving the link mechanism 40, and the above output is made to the actuator 41.

As a result, the furnace 20 is maintained in the optimum combustion state as in the first embodiment, and therefore efficient heating is achieved.

(Third Embodiment) This embodiment differs from the second embodiment in that the combustion air supply duct 42 in the second embodiment is connected to the hot air supply duct 27, as shown in FIG.

Therefore, the combustion air is preheated to the burner 22 which is the combustor.
will be supplied to Therefore, the temperature of the combustion flame 28 becomes higher, the combustibility improves, and less combustible fuel such as heavy oil can be used.

Furthermore, since the space required for combustion can be reduced, the heating furnace can be made smaller.

(Example 4) FIG. 9 shows a hot water boiler using the present invention.

The furnace 43 is surrounded by a sealed tank 44 made of heat insulating material.
A water supply pipe 45 and a hot water outlet pipe 46 are connected to the sealed tank 44 .

A burner 47 serving as a combustor is installed in the furnace 43, and a monitoring window 49 is installed at a location facing the combustion flame 48.

An opening/closing lid 50 is connected to the monitoring window 49 via a hinge 51, and a glass 52 is fitted into the opening/closing lid 50.
An optical sensor 53 is fixed to the glass 52.

For this reason, dirt such as soot can be easily removed from the front surface of the optical sensor 53 by wiping the lath 52, and therefore accurate signals can be detected.

In addition, a control section 56 is provided which controls the damper 55 in the combustion air supply duct 54 in response to a signal from the optical sensor 53, as in the above embodiment 2.3.

Also, a temperature sensor 57 for detecting water temperature. The temperature sensor 5
Turns on the fuel supplied to the burner 47 in response to the signal from 7.
-) A temperature control device including a control section 58 that sends an FF signal to the fuel supply valve is also provided.

(Embodiment 5) FIG. 11 shows a case where the present invention is applied to an oil-fired smoke tube boiler.

In this figure, reference numeral 59 is a cylindrical furnace that is laid down on its side, with a burner 60 installed at one end and an optical sensor 6 at the other end.
1 is installed.

The optical power signal of the combustion flame detected from the optical sensor 61 is processed in the same manner as in the previous embodiment to generate a combustion control signal.

(Embodiment 6) FIG. 12 shows a case where the present invention is applied to a water tube boiler.

In this case, the optical sensor 62 is installed near the burner 63, and the combustion state is controlled by the optical power signal from there as in the previous embodiment.

(Embodiment 7) FIG. 13 shows a vertical water tube boiler to which the present invention is applied.

In this case, the burner 64 is located at the top, and the optical sensor 65 is located at the bottom, facing the burner 64.

Effects of the Invention Since the combustion control method according to the present invention has the above configuration, 02% control in exhaust gas can be performed by detecting a signal related to the amplitude of optical power. Therefore, the control output can be easily obtained regardless of the position of the exhaust gas passage. Therefore, it is useful for combustion control in furnaces, gas turbines, etc.

Further, it is possible to perform quick and appropriate combustion control without causing the time lag caused by the conventional zirconia 02 sensor system. For example, when charging material into a furnace, the value of 0.2% changes suddenly, but it is necessary to be able to respond immediately even in such a case.

Furthermore, according to the present invention, the following effects can also be achieved. In other words, heat treatment furnaces, melting furnaces, etc. have two combustion chambers for one combustion chamber.
In many cases, more than one burner is installed for combustion heating. In the case of a single furnace like this, in the conventional combustion control method, which uses 02% of the exhaust gas as the indicator, 02% of the flue gas
Because each burner is controlled uniformly based on the final value, it is impossible to adjust the air ratio of each burner. In contrast, in this method, by using optical sensors that correspond to the flames on each side of the burner flame, it is possible to maintain each combustion state optimally.For example, in the case of a tunnel-shaped continuous heating furnace, 02% due to leakage of outside air in the center of the body
This makes it possible to more appropriately adjust the air ratio of each burner in cases where a difference occurs.

Further, since the combustion control device according to the present invention detects optical power using an optical sensor, the sensor can be installed at any location facing the flame. Therefore, it is not limited to the flue like the conventional zirconia O2 sensor. Therefore, it can be easily assembled.

[Brief explanation of the drawing]

Fig. 1 is a schematic vertical sectional view showing an example of applying the present invention to a furnace, Fig. 2 is a graph showing an example of the relationship between optical power and 02%, and Fig. 3 is a graph showing an example of the relationship between optical power and 02%. A graph showing the relationship between optical power and time when changing 0.02%,
Figure 4 is a graph showing the relationship between optical power deviation integral value and 02% using combustion amount as a parameter, Figure 5 is a graph similar to Figure 4 regarding different types of burners, and Figure 6 is combustion control. A flowchart of the arithmetic processing performed by the control unit of the device, FIG. 7 is a schematic vertical sectional view when the present invention is applied to a heating device, and FIG. 8 is a schematic vertical cross-sectional view of the combustion air supply path of FIG. 9 is a schematic vertical sectional view when the present invention is applied to a hot water boiler, FIG. 10 is an enlarged view of the X section in FIG. 9, and FIGS. 11, 12, and 13 are views showing the present invention. FIG. 3 is a schematic vertical cross-sectional view when used in an oil-fired furnace tube boiler, a water tube boiler, and a vertical water tube boiler, respectively. 1: Furnace, 4: Burner, 8: Fuel flow meter, 9: Combustion air flow control valve, 14: Combustion flame, 15: Optical sensor, 16:
Control part% 20: Furnace, 22: Burner, 28: Combustion flame, 3
4: Optical sensor, 35: Control unit, 39: Damper, 43: Furnace, 48: Combustion flame, 49: Monitoring window, 52 Nigarasu, 53
: Optical sensor, 55: Damper, 56; Control unit, 59: Furnace,
60: burner, 61, 62: optical sensor. 63.64: Burner, 65: Optical sensor.

Claims (2)

[Claims] (1) Obtain a flow rate signal of the fuel in a combustor that receives liquid or gaseous fuel and combustion air to form a flame, and a signal of O_2% in the exhaust gas of the combustor, and determine whether the O_2% of the fuel is In a combustion control method in which when the flow rate deviates from a reasonable O_2%, the deviation is calculated and an output for eliminating the deviation is sent to the combustion air flow rate adjustment section. is detected and a signal regarding the optical power amplitude is obtained therefrom, and then this is compared with a signal regarding the optical power amplitude corresponding to a reasonable O_2% for the fuel flow rate obtained in advance to determine the deviation thereof, and then the deviation thereof is determined. The above-mentioned combustion control method is characterized in that an output for eliminating the deviation is applied to the above-mentioned combustion air flow rate adjusting section. (2) Obtain the flow rate signal of the fuel in the combustor that receives liquid or gaseous fuel and combustion air to form a flame, and the O_2% signal in the exhaust gas of the combustor, and determine whether the O_2% of the fuel is In a combustion control device that calculates the deviation when the flow rate deviates from a reasonable O_2% and outputs an output to the combustion air flow rate adjustment section to eliminate the deviation, the O_2% in the exhaust gas is calculated. An optical sensor is provided at the rear of the combustor to obtain a signal relating to the amplitude of the optical power, and relationship data between the signal relating to the amplitude of the optical power and the O_2% signal in the exhaust gas for various fuel flow rates and the various fuel flow rates are provided. storing reference data regarding the amplitude of optical power corresponding to a reasonable O_2% for the fuel flow rate; The above-mentioned combustion control device is characterized in that the above-mentioned combustion control device is provided with a control unit that performs an output to the above-mentioned combustion air flow rate adjustment unit to compare and eliminate the deviation.