CN85101184B - Combustion system - Google Patents

Abstract

The present invention relates to a combustion system with a burner comprising a furnace for burning fuel and air injected into the furnace from the burner and generating a flame. It also includes a combustion condition measuring device for measuring fuel combustion conditions. The device uses the method of collecting flame light at a certain point in the flame and moving the point to measure the combustion conditions in areas spanning different flame layers. According to the combustion situation, the signal sent back by the measuring device is used to monitor or control the flame, and is used to control the waste discharge control device of the furnace to control the waste discharge generated by burning the fuel. Flame burning conditions can be quickly and highly accurately controlled by monitoring the flame.

Description

Combustion System

The invention relates to a combustion system suitable for a pulverized coal boiler, which is used to monitor and control the flame generated by the pulverized coal combustion, or to control a waste gas treatment device on the boiler.

Generally speaking, in terms of controlling the flame formed by fuel combustion in the boiler, the usual practice so far is this: first analyze the various components in the exhaust gas, and then send a control signal to the boiler control device according to the analysis results.

For example, assuming that it is necessary to measure the concentration of various nitrogen oxide gases (hereinafter referred to as NO _x ) in the exhaust gas, for this purpose, the usual practice so far is to guide the exhaust gas generated by combustion from the flue to various NO _x Analytical instrumentation to determine the concentration of _NOx . When it is not possible to directly lead the exhaust gas to the measuring instrument, a sampling extractor like a hypodermic needle is used to extract a sample of the exhaust gas from the flue, and then send the collected sample into the sample inlet of the NO _X measuring instrument to determine The concentration of _NOx .

No matter which method is used, it is necessary to collect exhaust gas samples and analyze samples, and generate control signals based on the analysis results to control the waste components discharged from the boiler. In addition to NO _X , carbon monoxide gas, oxygen and sulfurous acid gas are also They are all harmful components in the exhaust gas, which also need to be monitored. These gases have also been controlled by analyzing the exhaust gas from the flue, and according to the analysis results, each control signal is generated, but this method has its disadvantages, that is, because the exhaust gas is automatically The flue leads to various measuring instruments. If the combustion situation changes suddenly, how to deal with this change is difficult. When the flame becomes unstable and suspends above the burner, this sudden change may occur.

Another problem that should be solved for pulverized coal boilers is how to reduce the amount of unburned residual coal in the ash. This problem is very important, because it is very important to protect the environment from pollution and save energy. necessary. If the flame is formed by burning coal powder, it is necessary to control it by monitoring the flame to keep the combustion at a high efficiency, and it is required to minimize the residual amount of unburned coal in the ash. To determine the residual amount of unburned coal in the ash, it has hitherto been customary to collect fly ash directly from the flue, weigh a predetermined amount of ash, and then allow this ash sample to burn completely in oxygen by heating the ash Sampling, increase the temperature by 10-20 degrees Celsius every minute until it is raised to 850 degrees Celsius to fully burn, then weigh the ash sample again, so that the amount of unburned coal in the ash is equal to the first weighing , the weight of the ash sample before complete combustion minus the weight of the second weighed ash sample after complete combustion. This process is cumbersome and time-consuming, because of the many steps involved, and the use of balances and other instruments to indicate differential heat, which makes it impossible to implement rapid on-line control of the flame in real time; that is, without It is possible to feed back information on the measured amount of coal in the ash for timely control operations, thus making it impossible for this method to cope with sudden changes in combustion.

The methods of the prior art as mentioned above are methods aimed at effectively controlling the flame generated by the combustion of pulverized coal, relying on collecting the exhaust gas or fly ash at the outlet of the furnace and analyzing it. This approach therefore makes it impossible to have the necessary measures to cope with sudden changes in combustion conditions. In view of this situation, it has been thought of to observe the flame itself, in order to control it as accurately as possible. More specifically, it is possible to employ a method in which the combustion is controlled based on the gas concentration distribution and temperature distribution near the burner burner so as to keep the flame always in an optimum combustion state. Usually, the gas concentration distribution in the vicinity of the burner vent can be taken with a sampling probe inserted in the flame for testing; the temperature distribution can also be measured with a thermocouple inserted in the flame. But these methods are difficult to get precise measurements because the probe disturbs the flame. When samples are taken to determine the distribution of various gas concentrations, the various gas components in each sampling probe chemically react with each other, (for example, 2CO+O ₂ → 2CO ₂ ), resulting in accurate determination of the distribution of various gases The situation becomes impossible. Difficulties are also encountered when measuring the temperature distribution, since the temperature can change due to heat radiation from the furnace walls and temperature changes in the flame itself. In general, it is considered to be very difficult to accurately measure combustion by the prior art method, which relies on information on the concentration distribution of various gases in the vicinity of the burner port and on the temperature distribution in the furnace.

The present invention has been developed to avoid the disadvantages of the above-mentioned prior art methods, and it is therefore an object of the present invention to provide a combustion system which is capable of implementing a combustion control accurate enough to expediently cope with sudden changes in combustion conditions. Variety. The control of combustion is based on the accurate results obtained by observing the flame.

According to the present invention, a kind of combustion system is provided, and this system comprises a furnace that incinerates the fuel injected from the burner; It also includes a combustion condition measurement device, when a flame is generated in the combustion device, it is used to measure the degree of combustion of the fuel in each layer of the flame. In addition, it also includes the device for monitoring or controlling the flame and the waste emission control device connected to the rear of the furnace; in the monitoring process, the signal sent by the above-mentioned combustion situation measuring device is used.

Select a special waveband, collect the light emitted by the flame in the flame zone across different layers, and perform spectral analysis on the collected light, and use this method to obtain information about the combustion of the fuel, and determine the combustion of the fuel based on this information . The information obtained is about the temperature, the air ratio of the flame, the concentration of nitrogen oxides and hydrogen in the combustion exhaust gases, and the amount of unburned fuel in the fly ash determined from the intensity and luminescence pattern of the emitted light in this particular wavelength range. This information can then be used to determine the combustion of the fuel that produced the flame. According to the previously determined combustion conditions, the amount of air and fuel sprayed into the furnace by the burner and the spraying angle of air and fuel can be adjusted, so that the flame can reach the best state, or the denitrification device or dust collection device can be controlled to achieve Satisfactory effective control of waste emissions.

Fig. 1 is a front view of the combustion system of the present invention, providing an example of collecting light in the region of the flame formed by combustion;

Figure 2 is a sectional view of the section taken along line II-II in Figure 1;

Figure 3 and Figure 4 are for explaining the optical system and schematic diagram of collecting light;

Figure 5 is a vertical sectional view of a burner showing another example of light collection in the flame zone, different from the example in Figure 1;

Fig. 6 is a view explaining the experimental apparatus for burning gaseous fuel by using the method of collecting light;

Figure 7 is a sectional view taken along line VII-VII in Figure 6;

Fig. 8 is a view for explaining the apparatus for incinerating pulverized coal experiment using the method of collecting light;

Fig. 9 represents the result obtained by spectroscopic observation of the light emitted by the flame;

Figure 10 represents the relationship between the luminous light intensity and the flame-air ratio of the flame generated by combustion;

Fig. 11 shows the relationship between the luminous light intensity of the _C2 group and the concentration of various gas components in the exhaust gas and the residual amount of unburned fuel in the ash;

Fig. 12 shows the relationship between NO luminous intensity and NO _X concentration in exhaust gas;

Figure 13 shows the spectral bands of different wavelengths obtained by OH group luminescence;

Fig. 14 is a graph showing an example of flame temperature distribution.

Fig. 15 is an illustration for explaining an example of a filter box used for measuring the intensity of light emitted by a flame.

Figures 16-a, 16-b and 16-c are three diagrams explaining normal and abnormal flames;

Fig. 17 is a diagram of a combustion system, which includes an embodiment of the present invention, which shows the manner in which the present invention controls the combustion of fuel;

Figure 18 is a vertical sectional view of the burner used to effectively control the flame shown in Figure 17;

Fig. 19 is a sectional view taken along line XIX-XXIX in Fig. 18.

What Fig. 1 and Fig. 2 represent is that according to the combustion system that the present invention proposes, the situation near the flame area that collects light, stove 10 is equipped with a burner 20, ejects general flame 30 therefrom, and this flame extends to the inside of stove 10 all the time, The light that flame 30 sends is collected through observation hole 40 and 41, and the light beam collected like this is converted into electric signal by mirror box 50 and 51 and sends to a signal processor 60, when receiving the electric signal that mirror box 50 and 51 send signal, the signal processor 60 sends a control signal.

Referring to Figures 3 and 4, there is shown a light collecting optical system which will be described more later to explain the light collecting principle used in the combustion system of the present invention. Generally speaking, the function of a convex lens is to gather the rays incident in parallel to make them converge on the focal point. More specifically, when the parallel rays are incident on the convex lenses 52 and 53, a high-intensity beam is formed at the focal point. Therefore, placing photodetectors 54 and 55 at the focal point where parallel rays converge can obtain the information contained in the parallel rays incident on convex lenses 52 and 53, and combining convex lens 52 and photodetector 54 into a signal device can All the information contained in the parallel light passing through the furnace 10 is injected into the photodetector 54. If the convex lens 53 and the photodetector 55 are combined into another device, as shown in Figure 3, these two devices are combined into an optical system , so that the two groups of parallel rays incident on the convex lenses 52 and 53 intersect each other inside the furnace 10, the output information of the photodetectors 54 and 55 can be simultaneously transmitted to an information processor, and the two groups of parallel rays can be processed simultaneously. the information contained. In this way, the information contained in the hatched area of the furnace 10 in FIG. 3 can be processed and the results of the information processing by this single processor can be sent out. Then, when it is necessary to obtain information in an area facing different flame layer bands with a symmetrical shape of the garden, it can be moved from the right end of the stove 10 to the left end of the stove by moving a parallel light beam as shown in dotted line in Fig. 3 . This will serve this purpose.

The principle of collecting parallel ray information can be understood by referring to the description made in relation to FIG. 3 . But in actual practice, it is necessary to improve the spatial resolution. To achieve this goal, an optical system as shown in Figure 4 can be used. In this optical system, the characteristics of the convex lens are used twice, and only one point of flame is used. The emitted light is converged by the convex lens and collected by the photodetector 58 . Rays in front of and behind the focus can also be converged. For example, combining the optical system in Figure 3 with the optical system in Figure 4, and making the optical path of the former perpendicular to the optical path of the latter can greatly improve the spatial resolution in information processing, because light The output of the detector 58 and the output of the photodetector 59 can be output to an information processor at the same time. In the optical system shown in Fig. Move left and right.

According to the principle of the light collection method described in Fig. 3 and Fig. 4, the information of the fuel burning situation at any selected position in the flame can be obtained.

In the method shown in Fig. 3 and Fig. 4, the above-mentioned viewpoint is used to collect light. Figure 5 shows an example where an optical fiber connected to a burner is used to collect light. More specifically, the burner 20 has an optical fiber 130 connected to its body, and the optical fiber is inserted in a cooling tube 120 for collecting light emitted by a flame 30 near the burner 20 of the burner 20 . In this construction the light collecting means are mounted on the burner 30, so that no difficulties arise even if the furnace is large in size, since no openings are required in the furnace.

The light is collected by a large depth-of-field condenser lens 140 mounted at the inlet end of the optical fiber 130 . The light is guided through the optical fiber 130 to the mirror box 150 where an image is reproduced.

To convert optical signals into electrical signals, photoelectric converters such as photomultipliers or photodiode arrays can be used.

Figures 6-8 show several experimental setups for obtaining information on fuel combustion, which were developed based on the analysis of the light collected by the light collection method described above. The arrangement shown in Figures 6 and 7 is suitable for use in a burner 20 for burning gaseous fuels. In such a burner, air and fuel gas are pre-mixed and introduced to a burner 160 where they are combusted to form a flame 170 . The light emitted by the flame 170 enters and collects through several light collecting holes 190 on the furnace 180 . The collected light passes through a highly sensitive optical device, ie, the light chopper 200, and then goes to the spectrum analyzer 210. In this way, a spectrum of radiated light having a desired wavelength is obtained, and the intensity of the radiated light is converted into an electrical signal by a photomultiplier 220 and sent to a signal processor 230 . Use a pump to extract some of the exhaust gas generated by combustion, and then test it with a gas chromatograph 250 to determine the concentration of oxygen, hydrogen and carbon monoxide, while the _NOx (nitrogen oxide) in the exhaust gas is determined with a _NOx meter 260, This _NOx meter is a meter that measures luminescence from a chemical source.

Fig. 8 is the case of using pulverized coal as fuel, the pulverized coal is pneumatically conveyed to the burner 300 by the air 290 carrying the pulverized coal from the coal delivery hopper 270, and is mixed with the combustion air 290 near a burner port of the burner 300 and burn to form a flame. The light emitted by the flame enters the spectrum analyzer 210 through an observation hole 310 , so as to obtain the luminescence spectrum of the required wavelength.

Exhaust gas is led to and passes through a flue 320, and enters an exhaust gas analyzer 330. This analyzer includes a NO _x meter, an oxygen concentration meter and a carbon monoxide concentration meter to analyze the exhaust gas. As for the formation of pulverized coal combustion A dust sampler 340 is used to extract a dust sample from the dust filtered by the flue 320, and then a thermal differential indicating balance is used to determine the residual amount of unburned coal in the dust sample.

Fig. 9 shows the results obtained by spectral analysis of the light emitted by the flame formed by burning gaseous fuel and pulverized coal using the apparatus shown in Fig. 6 and Fig. 8 . The abscissa in FIG. 9 represents the wavelength of the emitted light, and the ordinate represents the light intensity of the light emitted by the flame. The results in the figure show that the luminescence of chemical substances can be observed in the flame, these are the light emitted by OH group, NH group, CH group, _C2 group, _NH2 group and NO. Since various chemical substances emit light at their special wavelengths, the relationship between the emitted light wavelength and light intensity is used to measure the emitted light from chemical substances and with special wavelengths to study the combustion of fuel.

Figure 10 shows the relationship between the luminous intensity of the above-mentioned chemical substances and the air ratio of the flame generated by burning the fuel. The air ratio is calculated from the concentrations of oxygen, carbon monoxide and hydrogen as determined by exhaust gas analysis. In experiments, this air ratio has been varied by varying the amount of air and fuel delivered to the burner.

As can be seen from Figure 10, OH group 350, CH group 360, CN group 370, NO ^* group 380 and NH group 390, when the air ratio is close to 1, all have the maximum luminous intensity, although the curves are different, But the luminous intensity curve of C ₂ base 400 increases with the decrease of air ratio.

Judging from the results obtained by measuring the luminous intensity curves of the above chemical substances, people can understand that, in a cross-reference manner, the luminous intensity of at least one chemical substance is studied, or the differential coefficient at a point on the luminous intensity curve ( dr/dI) value, you can get a more accurate air ratio. Therefore, if as shown in Figure 10, the relationship between the air ratio and the luminous intensity of each chemical substance is determined, the air ratio can be known immediately by observing the flame situation, without the need to calculate the oxygen in a certain time difference. , the concentration of carbon monoxide and hydrogen, in exhaust gas analysis, gas sampling is a time-consuming process.

Therefore, knowing the relationship between the air ratio and the luminous intensity of each chemical substance as shown in Figure 10, the air ratio can be known immediately by observing the flame to cope with the sudden change that may occur in the combustion of the fuel that generates the flame. The combustion thus achieves high fuel efficiency and minimizes environmental pollution, both of which are desirable.

Figure 11 shows the relationship between the intensity of C2 _- based emitted light and the concentration of various gas components in the exhaust gas and the amount of unburned fuel in the fly ash. The relationship between the intensity of C2 _- based emitted light and the concentration of various gas components in the exhaust gas was obtained by experimenting with the device shown in Figure 6. The corresponding relationship obtained using the apparatus shown in Fig. 8 shows the same tendency. The relationship between the intensity of C2 _- based emitted light and the amount of unburned fuel in the fly ash was obtained using the setup shown in Figure 8.

It is known from experience that there is a proportional relationship between the intensity of emitted light of _C2 base and the hydrogen concentration 430 and the _{concentration} of carbon monoxide gas 410 in the waste gas. have a negative correlation. Thus, the emission intensity of the _C2 -based chemical shows how efficiently the combustion proceeds. That is to say, when the combustion condition deteriorates and the fuel burns incompletely, the concentration of carbon monoxide will increase, and hydrogen gas will also be found present. These gases are flammable. When oxygen is present, these gases burn off. Therefore, if these gases are released into the atmosphere, they will pollute the environment and waste energy. Therefore, it is important to control fuel combustion to minimize the concentration of these gases in the exhaust gas based on the observation of C2 _- based emission intensity.

In terms of oxygen concentration 420, if the amount of oxygen delivered to the burner is greater than that required to achieve complete combustion, it will not only overburden the blower, but also lower the combustion temperature because a large amount of air is supplied to achieve Combustion with excess oxygen must simultaneously feed a large amount of nitrogen, and nitrogen does not directly participate in combustion. Therefore, it is also necessary to monitor the concentration of oxygen to make combustion proceed with high efficiency.

Hitherto, it has been customary to lead the exhaust gas from the flue to a measuring instrument to take a sample of the exhaust gas, and then analyze the sampled sample to determine the concentration of these gases, as described above. This method has its disadvantages. Since the combustion conditions may change, the concentrations of various gases will also change. However, until all the gases in the furnace have such concentration changes and are detected by analytical instruments, the combustion conditions will not change. to be discovered. In other words, the method cannot quickly cope with sudden changes in conditions that may occur in the combustion, making the method ineffective in controlling the combustion as a result.

With regard to the amount of unburned fuel residue 440 in the fly ash, it was found that there is a positive correlation between the amount of fuel residue and the intensity of the _C2- based emitted light, which was mentioned earlier, and in this regard, It is important to monitor the amount of unburned fuel remaining in the fly ash for efficient combustion. But so far it has not been possible to use the online fast operation method to realize the feedback control of the combustion situation.

Since it is now clear that there is a positive correlation of the kind shown in Figure 11 between the intensity of the C2 _- based emitted light and the amount of unburned fuel residue 440 in the fly ash, it is possible to use the on-line rapid operation method Feedback control of fuel combustion is implemented.

According to the above, it is known that there are two relationships, one is the emitted light intensity of the _C2 group, the other is the concentration of oxygen, hydrogen and carbon monoxide in the exhaust gas and the residual amount of unburned fuel in the ash , once the correlation of these two aspects as shown in Figure 11 is established, the exhaust gas can be determined immediately only by collecting the flame light through the light collection hole and analyzing the intensity of the emitted light with a special wavelength emitted by the _C2 group. Concentrations of oxygen, hydrogen and carbon monoxide in the gas and unburned fuel residues in the ash without collecting flue gas and fly ash samples, so that the on-line rapid operation method can be used to implement combustion feedback Control is possible.

When implementing the above control method, it is not enough to use only one piece of information to achieve highly accurate control of the combustion situation. It is also necessary to collect and analyze at least two pieces of information at the same time in cooperation with each other before drawing a conclusion. The invention can obtain more than two pieces of information at the same time from the luminescence analysis of the chemical substance of the flame, which makes the control of the combustion situation more accurate and reliable.

Figure 12 shows the relationship between the intensity of NO ^* emitted light and the concentration of _NOx in exhaust gas. Curves 450 and 460 in the figure represent two situations in which the ratio of air in the combustion is different from each other. Now it is clear that there is a positive correlation between the intensity of emitted light of NO ^* and the concentration of NO _x in the exhaust gas. Curves 450 and 460 are in This aspect is the same.

Therefore, once the correlation relationship between the intensity of NO ^* emitted light and the concentration _{of NOx} in the exhaust gas is established as shown in Figure 12, it can be determined immediately only by collecting the flame light and analyzing the light intensity of the characteristic wavelength of NO ^* _NOx concentration in exhaust gas. This makes it possible to implement the feedback control of the combustion situation by using the online rapid operation method.

Figure 13 shows the luminescence spectrum of the OH group, which has been confirmed to exist widely in flames. This spectrum is the result of the analysis of what is usually called the vibrational rotation spectrum of the OH group. Fig. 13 is a graph, the ordinate represents the light intensity of emitted light, and the abscissa represents the wavelength of light. The temperature can be determined by calculating the value of the position of the peak line on the abscissa axis (wavelength) and the position on the ordinate axis (radiated light intensity) in the graph. The calculation uses the following equation:

ln(I _ω /ω ⁴ p g)＝-E/KT+constant term

Among them: I _ω : the emitted light intensity of a certain wavelength,

ω: the reciprocal of the wavelength of a certain spectral line,

p: the probability of jumping to the energy level E of the wavelength corresponding to ω,

g: multiplication factor,

K: Boltzmann constant,

T: absolute temperature

The value of g is the value inherent in the substance or OH group, and the values of P and E are related to ω. These values can be obtained by calculation methods.

The calculation process is as follows: first determine the intensity of the spectral line obtained from the spectral analysis, then calculate the value on the left side of the equation, and then draw the relationship between this amount and E, so that the value of T can be calculated, because the straight line The slope is equal to 1/KT because K is a constant.

Figure 13 shows the results of spectral analysis of the OH radical emission light at an arbitrary point in a certain flame.

The situation mentioned above can be summarized as follows: if the light is collected at a point in the flame formed by burning fuel and spectroscopically analyzed to obtain the vibration-rotation spectrum of the OH group, then the vibration-rotation spectrum of the OH group given by the spectral analysis is By calculation, the temperature at the light collection point can be known. Therefore, the temperature at many points in the flame can be calculated by the above method to obtain the temperature distribution in the flame.

Figure 14 shows a flame temperature distribution diagram. The flame was generated by burning fuel with a burner in the test apparatus shown in FIG. 6 .

In the prior art, it has hitherto been customary to insert several thermocouples into the flame in order to know the temperature distribution in the vicinity of the burner nozzle. This prior art method has the great disadvantage that when the thermocouples are inserted into the flame, the flame is disturbed, making it difficult to obtain an accurate temperature distribution. The present invention completely avoids this disadvantage of the prior art, making it possible to obtain a far more accurate temperature distribution, since the present invention detects the temperature of the flame optically without touching the flame.

Thus, according to the method of the present invention, one can definitely obtain the flame temperature distribution near the burner nozzle by optical means without contacting the flame. In this method, the spectral analysis is performed on the spectrum emitted by the OH radicals in the flame, and the results of the spectral analysis are input into a signal processor, which includes a computing device for calculating the temperature distribution, a storage fuel incineration A storage circuit for the flame temperature distribution information in the best case, a comparison circuit for comparing the calculated temperature distribution with the optimal temperature distribution stored in the storage circuit and outputting a signal, and a signal output from the comparison circuit and input to the control circuit circuit. Then output a control signal, this method utilizes the control signal to control the burning of fuel with high precision and efficiency. The control is based on the flame temperature distribution obtained by spectral analysis of the light emitted by the flame.

As mentioned above, the method by which people can collect the luminescence of chemical sources from the flame and perform spectral analysis to determine the combustion of the fuel is based on the luminescence pattern in a specific wave obtained by the flame emission light intensity or spectral analysis. . This enables people to implement the control of fuel combustion conditions with high efficiency and precision, so as to quickly cope with any possible changes in combustion conditions. In addition, the above-mentioned method enables people to obtain a lot of information about the combustion situation, based on the spectral analysis of the flame light, without directly contacting the flame; the control of the combustion situation can be carried out based on the spectral analysis results of a lot of information.

The intensity of the emitted light and the luminescence pattern of the flame in a certain wavelength band are obtained by means of a spectral analysis device, which may be a spectrometer equipped with a photodetector, a filter or any other known instrument capable of performing a similar function.

Figure 15 shows a filter box 470 for measuring light intensity, and the light beam 480 collected from the flame enters the filter box 470 through the light collection hole 481 on the filter box. Light beam 480 passes sequentially through dichroic filters 490, 491 and 492 to pass some wavelengths of light while not passing other wavelengths of light. Dichroic filters 490, 491 and 492 can be arbitrarily selected to reflect any desired wavelength of light. Light of any wavelength is reflected by each dichroic filter 490, 491 and 492 and focused by a convex lens 500, and the light is collected on one of the photodetectors 510, 511 and 512 to become light with high intensity. Thus, the intensity of light at the wavelength of interest can be measured at each of the photodetectors 510, 511 and 512. The filter box 470 has been shown and described above. It can reflect light of three different wavelengths, but the present invention is not limited to this specified number of wavelengths of light, because the collected flame light can be reflected by the filter box 470 with as many wavelengths as possible. Then, utilize the filter box 470 of the type shown in Figure 15 to be able to collect the required number of flame lights of different wavelengths from the flame at the same time, and then perform spectral analysis on it, so that information in many different wave bands can be obtained simultaneously, which This makes the filter box a very useful tool in collecting a range of flame light information and considering this many information in a cross-referenced manner to make a judgment.

It has been pointed out and described above how the light collected from the flame is spectroscopically analyzed to obtain information in specific wavelength bands, and how to obtain various other information from it, including the air ratio and temperature of the flame. Oxygen, hydrogen, Concentrations of carbon monoxide and nitrogen oxides (NO _x ), and the amount of unburned fuel residue in the ash. This method is based on the intensity of light emitted by the flame and the emission pattern in specific wavelength bands, using optical methods and does not require direct contact with the flame. As shown in Figure 15, the use of a filter box allows us to simultaneously decompose the collected flame light into the desired number of light of many different wavelengths. In the light collecting optical system shown in Fig. 4, the light collecting lens can be moved forward and backward, thereby changing the position of the focal point. Like this, utilize filter box 470 shown in Fig. 15 to replace photodetector 58 shown in Fig. 4, just can obtain a lot of information in the flame region at the same time as mentioned above, and this flame region spans several different flame layer zones .

When the flame formed by fuel combustion is abnormal, the following method can be used to quickly detect this abnormal combustion with high accuracy.

See Figure 16-a, Figure 16-b and Figure 16-c. There is a burner 540 for burning pulverized coal in the central part of the figure, and this burner has a pulverized coal injection port 520 and a combustion-supporting air supply port 530 that forms a concentric garden on the outer circle, and the burner that is usually used is exactly this structure.

Figure 16-a shows a flame 550, which is generated by burning coal powder. But here too much pulverized coal is supplied and too little air is supplied, so we will see that when the combustion is as before, the resulting flame 550 lacks a central part because the air supply is insufficient and the fuel in the central part is not for being burned.

Fig. 16-b shows the flame 550 lacking its outer peripheral portion because the flame in the outer peripheral portion is extinguished due to excessive air supply.

The flame 550 shown in Figure 16-c has a normal shape where the supply of pulverized coal and the supply of combustion air are just balanced so that the combustion proceeds satisfactorily.

The flame shapes 550 shown in Figures 16-a and 16-c are unsatisfactory because their shapes indicate that the fuel is not being burned with high efficiency.

The conventional various flame control methods so far all have their shortcoming, and this is exactly if the combustion situation changes, and flame 550 becomes the shape shown in Figure 16-a or Figure 16-b, all this will pass through for a long time just can from It is found in the change of flue gas, and the change of flue gas is so weak that it is not easy to find this change.

When using the method of the present invention, it is possible to quickly and reliably determine whether the flame 550 has a normal shape as shown in Figure 16-c, or an abnormal shape as shown in Figure 16-a or 16-b. Normal shape, the steps that need to be taken for doing this point only need to check the method of luminescence facing the different layers of the flame along the direction shown by the dotted line in the figure.

More specifically, according to the method of the present invention, the data of the normal shape flame 550 shown in Figure 16-c is stored in the memory of a computer in advance, these data include the distribution of the air ratio in the flame and the temperature distribution in the flame , while the temperature distribution is determined according to the light intensity emitted by the flame and the luminous mode in a specific wavelength band. When the burner is running, this method must be used to continuously observe the light emitted by the flame area along the dotted line shown in Figure 16-a to Figure 16-c, when it is found that the flame 550 appears as shown in Figure 16-a or Figure 16- When the combustion situation shown in b, just take necessary steps immediately to improve the combustion situation, that is to say when the shape shown in Figure 16-a appears in flame 550, people only need to reduce the supply of pulverized coal, and when flame 550 With the shape shown in Figure 16-b, one only needs to reduce the combustion air supply.

The flame 550 has a tendency that once it becomes out of shape, it is often difficult to return it to its normal shape. Therefore, the recommended method is to explore the transition process of the flame from normal to abnormal, that is, the flame changes from the normal shape shown in Figure 16-c to the abnormal shape shown in Figure 16-a or Figure 16-b In the process of change, after the flame has become the shape shown in Figure 16-a or Figure 16-b, the abnormal shape of the flame 550 can naturally be detected by a television camera. But when the abnormality of the shape of the flame 550 is not obvious or the shape of the flame 550 is transitioning from normal to abnormal, it is often very difficult to find the change of the flame shape.

This shortcoming of prior art does not exist in the present invention, because the method used in the present invention is to carry out spectral analysis to flame light to determine the emission pattern of emission light intensity and light, thereby know the distribution of each relevant parameter in the flame, This enables one to detect small changes in the glow of the flame. This makes it known that the flame is transitioning from the normal shape shown in Figure 16-c to the abnormal shape shown in Figure 16-a or Figure 16-b. This method also enables people to detect whether the flame is transitioning to the shape of Figure 16-a or to the shape of Figure 16-b, so that the control of the flame has a high degree of accuracy.

This view was obtained because the light emitted by the flame was spectroscopically analyzed to select a specific wavelength band, and the intensity of the emitted light and the emission pattern at each wavelength were studied in a cross-referenced manner. When the flame is in the stage of transition from normal shape to abnormal shape, it is possible that the distribution of emitted light intensity of a certain wavelength does not change, but the distribution of emitted light intensity of other wavelengths may change.

For example, when the flame changes from the normal shape shown in Figure 16-c to the abnormal shape shown in Figure 16-a, the amount of fuel supplied to the pulverized coal injection port 520 located in the center of the burner gradually increases. At this time, the intensity of the emitted light of the OH group or the emission pattern of the OH group, which can display temperature information, hardly changes much.

At this point, the temperature of the flame should drop somewhat, since combustion near the center of the burner tends to be incomplete. But because the outer layer of the flame that the environment burner center line forms the multilayer concentric garden has very strong heat radiation, makes flame temperature not change much. As a result, the intensity of emitted light of the OH group and the emission pattern of the OH group hardly changed.

But at the same time, the intensity distribution of the emitted light of the _C2 group and the CH group changes. That is, the emitted light intensity of _C2 groups and CH groups near the front face of the pulverized coal injection port 520 tends to increase. C ₂ and CH groups are said to be the precursors of soot because soot condenses from their vapor state. The reason for the increase in the emitted light intensity of the _C2 group and the CH group is due to the fact that near the pulverized coal injection port, an incomplete combustion zone is locally formed due to the gradual increase of the fuel supply.

Thus, in view of the above, one can clearly understand that, according to the method of the present invention, observing the light emitted by the flame and analyzing the observation results in a cross-referenced manner can enable one to detect the transition of the flame from a normal shape to an abnormal shape, So that people have a high degree of accuracy in the control of the combustion situation.

Fig. 17 is an embodiment according to the combustion system of the present invention, and the light that flame 650 sends is collected by light collecting device 660 and leads to spectral analyzer 680 through optical fiber 670, and spectral analyzer 680 is equipped with a converter, is used for Convert various optical signals representing the light intensity of the emitted light in the flame and the luminous mode in a specific wavelength band into electrical signals. After these electrical signals are amplified by the amplifier 690, they are sent to a control component 700. The amplifier 690 converts the electrical signals generated by the converter. amplified, and the input of the converter is an optical signal representing the intensity of the emitted light and the light-emitting mode in an optional waveband, the control unit 700 includes a memory 720 for storing the observed intensity of the emitted light under optimal combustion conditions A comparator 710 is used to compare the output signal of the amplifier 690 with the output signal of the memory 720, and a controller 730 is used to output the signal to control the fuel combustion situation. The control unit 700 also includes an air spread regulator 740, a pulverized coal spread regulator 750, a pulverized coal supply regulator 760 and an air supply regulator 770, and the signal output by the controller 730 is sent to these air supply regulators .

The output signal of the control unit 700 is used to adjust the air and fuel quantities supplied to the burner 640 and to adjust the dispersion of air and fuel at the outlet of the burner burner. More specifically, the output signal of the air supply regulator 770 is sent to an automatic control valve installed between the blower 630 and the burner 640, so as to control the amount of air supplied by the blower to the burner so that it is always an optimum amount, The output signal of the pulverized coal supply regulator 760 is transmitted to an automatic control valve installed between the pulverized coal supply injection hopper 620 and the burner 640, so as to regulate the pulverized coal quantity supplied to the burner, so that it is always an optimal quantity. The output signals of the air dispersal regulator 740 and the pulverized coal dispersal regulator 750 are sent to the driving device of the air dispersing regulator and the driving device of the pulverized coal dispersing regulator installed on the burner respectively (see Figure 18) to control the air flow respectively. And the spreading of pulverized coal keeps it in the best condition.

Please refer to FIGS. 18 and 19 for understanding about the dispersion of coal powder and air. The signal output by the air dispersion regulator 740 in FIG. 17 is sent to the driving device 890 of the air dispersion regulator. The spreading of the air is controlled by appropriately changing the direction in which the three-dimensional air nozzle 840 ejects the air. The signal output by the pulverized coal spreading regulator 750 shown in Figure 17 is sent to the driving device 850 of the pulverized coal spreading regulator, and the pulverized coal that is pneumatically transported to the burner is sent to the place via the line 860, and then passes through a nozzle Opening 870 just ejects, and the spreading of pulverized coal is to regulate with the size of opening degree of nozzle opening 870, and the size of opening is that the cone 880 that is contained in pulverized coal nozzle opening place moves inwardly or outwards and controls.

But there is a limit to simply adjusting the burner to exercise control over air and coal dust dispersion.

When the situation beyond the above-mentioned control ability occurs, the combustion system of the present invention will be used to implement the control of the combustion situation.

A coal-fired power plant generally includes a boiler 800, a denitrification device 810, a dust collector 820 and a flue 830, as shown in Figure 17. The denitrification device generally increases or decreases with the load of the power plant to remove _NOx amount of reducing agent. The operation of dust collector 820 is steady state because it has no ability to cope with load fluctuations.

As a whole, the combustion system is intended to have the effect of reducing unburned fuel residue and NO _X concentration at the same time. When the fuel is pulverized coal, if it is burned under the condition of complete combustion, the residual amount of unburned fuel can be reduced, but the concentration of NO _X in the exhaust gas will increase. When the situation is opposite, that is, if the Combustion of fuel under the condition of incomplete combustion can reduce the _NOx concentration in the exhaust gas, but the residual amount of unburned fuel will increase. In other words, only controlling the combustion of fuel cannot reduce the residual amount of unburned fuel and the concentration of NO _x at the same time. When the combustion conditions are conducive to reducing the amount of unburned fuel residue, the concentration of _NOx will increase; when the combustion conditions are conducive to reducing the concentration of _NOx , the amount of unburned fuel residue will increase. As mentioned above, the dust collector 820 is not well able to cope with load fluctuations, which makes the residual amount of unburned fuel in the exhaust gas remain substantially constant.

For the burner, it is convenient to reduce the residual amount of unburned fuel by making the combustion proceed under the condition of complete combustion. But this makes the _NOx concentration in the exhaust gas very high.

The combustion system of the present invention is primarily intended to control the combustion of fuel in the burner. But the combustion system can be made in such a way that it can output a signal to the waste discharge control system installed in the rear of the furnace 800, that is, connected to the flue of the furnace. When it is found that the flame in the furnace belongs to the type that can increase the _NOx concentration in the exhaust gas, the reducing agent amount control signal generator 790 of the control unit 700 sends a signal to the denitrification device 810 to increase the amount of reducing agent to reduce the exhaust gas The concentration of NO _X in the When it is found that the flame belongs to the type that will increase the residual amount of unburned fuel in the exhaust gas, the control mode of the fuel combustion situation should be to make the fuel burn under the complete combustion situation, because the distance between the electrodes of the dust collector 820 can be improved. Voltage to cope with changes in power plant load, which was mentioned earlier. In other words, control of the combustion conditions is achieved by increasing the air supply to the burner. But if this step is taken, the flame will change in the direction that will increase the _NOx concentration, so a signal must be sent to the denitrification device 810 at the same time to increase the amount of reducing agent.

If the dust collector 810 is improved in the future so that the inter-electrode voltage can change with the change of the load, the inter-electrode voltage control signal generator 780 in the control unit 700 can generate a signal to directly control the dust collector 810 .

In other words, when the flame in the furnace 800 tends to increase the amount of unburned fuel remaining in the fly ash, all that is required is to signal the dust collector 820 to increase the voltage across its electrodes. .

It is clear from an understanding of the foregoing that the combustion system of the present invention can take measures to reduce the amount of unburned fuel residue in the fly ash and the _NOx concentration in the exhaust gas. These measures are to control the fuel combustion of the burners and to control the waste discharge control devices located at the rear of the furnace 800 , including the denitrification device 810 and the dust collector 820 .

According to the present invention, the light emitted by the flame in the burner is spectroscopically analyzed to select a specific wavelength band and to determine the intensity and pattern of emitted light. According to the obtained results, it is possible to judge the fuel combustion without contacting the flame, so as to control the combustion of the burner to reduce the residual amount of unburned fuel in the fly ash and the concentration of _NOx in the exhaust gas. In this way, a lot of information on various chemical substances with different luminescent wavelengths can be obtained, and then, under cross-reference, observation conclusions on fuel combustion can be made. Since the observation of the flame itself forms the basis of the control, the control of the combustion of the fuel can be carried out rapidly and with a high degree of accuracy.

Claims (13)

1. A combustion system, comprising: a furnace for burning the fuel ejected from the burner; a monitoring device for regulating the quantity of at least one of the fuels and the quantity of air entering the furnace on the basis of signals from the combustion condition measuring device; Combustion measurement device, including a light-collecting optical device, used to collect light emitted from the inside of the flame from at least two directions, so as to obtain information for controlling the combustion of the flame, and a spectrum analysis device, used to collect light from the light-collecting optical device Spectral analysis of the light to select a specific wave band, characterized in that: the light collection optical device collects the light emitted by flames at different places, and obtains information on the combustion of fuel in flame areas across different layers. 2. A combustion system as claimed in claim 1, wherein the above-mentioned combustion condition measuring device further includes a spectral analysis device for performing spectral analysis on the light collected by the light-collecting optical device, and it is characterized in that: the above-mentioned spectral analysis selects a special The combustion condition measurement device utilizes the emission mode or emission intensity information of the light of the specific wave band emitted by the OH group, NH group, CN group, CH group, _C2 group and NO group emitted from the flame, as well as information about the flame temperature and Air ratio, fuel residual amount of unburned oil in combustion exhaust gas, nitrogen oxides, carbon monoxide, hydrogen and oxygen concentration information, comparison of predetermined luminescence pattern or intensity corresponding to normal flame obtained according to the following relationship Combustion conditions and luminous patterns or luminous intensities in a plurality of specific frequency bands of selected wavelengths of the flame in the furnace to determine whether the flame in the furnace is burning normally, and through the level of the predetermined position in the flame of the furnace The combustion condition of the furnace can be determined by obtaining the emission pattern or emission intensity of the same specific wavelength band in each light wavelength of the flame from at least two directions. 3. A combustion system as claimed in claim 2, characterized in that the above-mentioned light-collecting optical device includes a lens, which is used to collect the fuel combustion emitted from the inside of the flame from two directions and obtained at the intersection point of the optical axes of the lens. information of the condition; and movement means for moving the optical axis of at least one lens. 4. A combustion system comprising: a stove for burning fuel ejected from the burner; monitoring means for regulating the amount of at least one of the fuels and the amount of air entering the furnace, based on signals from the combustion measuring means; and Combustion measuring device includes an optical device for collecting light, which is used to collect the light emitted by the flame, and the feature is that the optical device for collecting light can move point by point in the flame area spanning several different layers to collect the light emitted by the flame at various points Information; The waste discharge device is connected to a flue of the furnace, and is used to control the waste discharge device according to the signal sent by the combustion measurement device. 5. A combustion system as claimed in claim 4, characterized in that at least said means for monitoring or controlling the flame and said means for controlling the exhaust gas discharge means comprise a control unit means for controlling the air ejected from the burner The amount of fuel injected from the burner, and the control of the spread angle of the air and fuel injected from the burner into the furnace. 6. A combustion system as claimed in claim 4, wherein said waste discharge control means is controlled by said monitoring or control means.

Images