KR100306291B1 - Control method of flue gas mixture discharged from garbage incinerator - Google Patents

Abstract

The flue gas temperature at the outlet of the waste incinerator is measured by a thermometer 12 located at the outlet of the incinerator, and the NOx concentrations, CO concentrations and O2 concentrations in the flue gas are measured by the flue gas analyzers 14, 15 and 16 located in the flue gas pipe. Is measured. The observed values of the flue gas temperature and the NOx concentration, respectively, are compared with the corresponding reference values. Based on the results of the comparison, the water spray rate injected into the waste burning in the fire tray is adjusted. In addition, the flue gas temperature, the NOx concentration, the CO concentration, and the O ₂ concentration are compared with corresponding reference values, respectively. Based on this comparison result, the secondary combustion air feed rate injected into the combustion chamber 1a is adjusted.

Description

Control method of flue gas mixture discharged from waste incinerator

The present invention is directed to a method for controlling flue gas mixture discharged from a stoker type waste incinerator, in particular to stabilizing the internal temperature of the incinerator, and to control the combustion of non-combustible components such as CO and dioxin in flue gas and NOx (nitrogen oxide). A method for controlling the water spray rate and the secondary combustion air feed rate directed towards the reduction.

Municipal waste incinerators play an important role in the disposal of various wastes from social activities. Regarding waste incineration, the problem of the reduction of the NOx concentration and the CO concentration in the flue gas generated in incineration of waste has been recently emphasized, and the CO concentration is known to have a close correlation with the generation of dioxin. In order to cope with this phenomenon, the reduction of NOx concentration was attempted by nitrate removal of non-catalyst using ammonia, nitrate removal by catalyst or water spraying method inside incinerator. On the other hand, the reduction of the CO concentration becomes efficient under the control of the following measurement methods.

(1) maintaining the flue gas temperature at a temperature of 800 ° C. or higher;

(2) to ensure a long holding time of the flue gas at a high temperature level;

(3) Mix flue gas completely in flue gas pipe.

Secondary combustion air feed rate control is one of the practical operating methods for reducing CO concentration. For example, Japanese Patent Publication No. 7-332642 reduces CO concentration in flue gas by measuring the flue gas temperature at the outlet of the incinerator and oxygen concentration in the flue gas, and controlling the secondary combustion air feed rate to maintain each measured value at each target level. It shows how to boost waste incineration.

The characteristics and mixtures of the waste put into the hopper of the incinerator are not stable. Therefore, when the waste is introduced from the hopper to the incinerator, the heat generation value of the supplied waste is not stable, and flue gas temperature generated from the waste combustion fluctuates. This causes the generation of incombustible gases such as CO and the generation of NOx.

There is a tradeoff between a method for reducing non-combustible components such as CO in flue gas and a method for reducing NOx. As a result, simultaneously reducing the CO concentration and the NOx concentration only by combustion control remains an unsolved problem.

2 shows the relationship between flue gas temperature and CO concentration and NOx concentration at the incinerator outlet. As shown, if the flue gas temperature at the incinerator exit is maintained at a high temperature level, the CO concentration decreases but the NOx concentration increases. 3 shows the relationship between the secondary combustion air feed rate, the CO and NOx concentrations, and the flue gas temperature at the incinerator exit. 3 suggests that increasing the secondary combustion air feed rate increases the NOx concentration. However, this causes a problem that the NOx concentration increases when the excessive amount of the secondary combustion air is supplied to achieve complete combustion according to the combustion state. On the other hand, as shown in FIG. 4, the combustion temperature is reduced by the water spray rate, and the flue gas temperature at the incinerator outlet is reduced in order to reduce the concentration of NOx and incombustible components such as CO present in the flue gas.

Therefore, the conventional control technology provides a control method that aims to reduce only non-combustible components such as CO in flue gas through control of the secondary combustion air feed rate. However, the related art has a limitation in the combustion control method for reducing CO concentration in view of simultaneous reduction of NOx concentration. In addition, the measurement of dioxin in the flue gas is made by analyzing the flue gas sample collected by sucking the flue gas for 4 hours in a row. This type of analysis is not convinced that the point of combustion change during such a long sampling period contributes to the generation of dioxin.

The present invention has been completed to solve the above problems. It is an object of the present invention to provide a method of controlling a mixture of flue gases emitted from a waste incinerator in order to simultaneously reduce NOx and CO in the flue gases and incombustible components such as dioxins.

In order to achieve the above object, the present invention provides a method for controlling a mixture of flue gas discharged from a waste incinerator. That way:

(a) measuring the flue gas temperature at the incinerator outlet using a thermometer located at the outlet of the incinerator;

(b) measuring the NOx concentration, the CO concentration, and the O ₂ concentration of the flue gas using respective flue gas analyzers located in the flue gas pipe;

(c) comparing the observed flue gas temperature and the observed NOx concentration with respective reference values;

(d) adjusting the water spray rate sprayed on the waste combusted on the basis of the comparison result of step (c);

(e) comparing the observed flue gas temperature, NOx concentration, CO concentration, and O ₂ concentration with respective reference values;

(f) adjusting the secondary combustion air supply rate injected into the combustion chamber based on the comparison result of step (e).

The method for controlling the flue gas mixture further includes measuring an observed CO concentration percentage above the target CO concentration value per unit time and maintaining this percentage below the CO generation target percentage.

The method for controlling the flue gas mixture further comprises maintaining the observed flue gas temperature above the target lower limit temperature.

The method for controlling the flue gas mixture further includes measuring an average of the observed values of the flue gas temperature and maintaining the average between the target lower limit mean and the target upper limit mean.

The method for controlling the flue gas mixture comprises maintaining a percentage of the observed CO concentration above the target CO concentration value per unit time below the CO generation target percentage, and maintaining the observed flue gas temperature at the target lower limit temperature. Include.

The method for controlling the flue gas mixture includes maintaining an observed CO concentration percentage above the target CO concentration value per unit time below the target percentage of CO generation, and maintaining an average of the observed flue gas temperature above the target lower limit temperature. And maintaining an average value of the observed flue gas temperature between a target lower limit mean value and a target upper limit mean value.

In the method for controlling the flue gas mixture, the target CO concentration is 30 ppm and the CO generation target percentage is 2%.

In the method for controlling the flue gas mixture, the target lower temperature is about 850 ° C.

In the method for controlling the flue gas mixture, the lower limit average temperature is about 900 ° C and the upper limit average temperature is about 950 ° C.

In the method for controlling the flue gas mixture, the fuzzy reasoning method is applied to adjust the water spray rate and the secondary combustion air feed rate. In this fuzzy reasoning method, the parameters for setting the preceding conditions for inferring the water spray rate and the form of the preceding membership function, the parameters for setting the conditions for the preceding for inferring the secondary combustion air supply rate, and the membership of the preceding. Function types are assumed to be different from each other.

1 is a schematic diagram of a method for controlling a mixture of flue gas discharged from a waste incinerator according to the present invention and a waste incinerator to which the method is applied.

2 shows the relationship between flue gas temperature, NOx concentration and CO concentration at the incinerator outlet.

3 shows the relationship between combustion air supply rate, CO concentration, NOx concentration and flue gas temperature at the incinerator outlet.

4 shows the relationship between the water spray rate and the flue gas temperature at the incinerator exit.

5 (a) and 5 (b) show the flue gas temperature and CO and NOx concentrations at the incinerator outlet over time, and the response change at the water spray rate and secondary combustion air supply rate adjusted over time. Indicates.

Figures 6 (a) and 6 (b) show flue gas temperature and CO concentration and NOx concentration change at the incinerator outlet over time under the application of the control method according to the present invention, the water spray rate adjusted over time and 2 Reaction change in the secondary combustion air supply rate is shown.

Figure 7 shows the relationship between the percentage of CO generated above 30 ppm during the dioxin measurement period and the dioxin concentration at the bag filter inlet.

8 shows the relationship between the minimum value of the flue gas temperature at the incinerator exit and the dioxin concentration at the bag filter inlet during the dioxin measurement period.

9 (a) and 9 (b) show a prior membership function of the water spray rate for the control method using the fuzzy inference method according to the present invention.

10 (a) to 10 (e) show a prior membership function of the secondary combustion air feed rate for the control method using the fuzzy inference method according to the present invention.

11 (a) and 11 (b) show the results of prior art control of CO concentration and NOx concentration by the control method according to the present invention.

12 shows the relationship between the average value of the flue gas temperature at the outlet of the incinerator, the dioxin concentration and the NOx concentration.

13 shows the relationship between the standard deviation of the water spray rate and the dioxin concentration at the bag filter inlet.

* Explanation of symbols for main parts of the drawings

1: furnace 1a: combustion chamber

2: Hopper 3a: Drying tray

3b: combustion burner 3c: afterburner

4: drop port 5: primary combustion air fan

6: incinerator exit 7: chimney

8a: heat exchanger 8b: boiler

9: secondary combustion air intake 10: secondary combustion air fan

11: bag filter 12: thermometer

13: water spray rate regulator 13a: water spray nozzle

14: NOx concentration meter 15: CO concentration meter

16: O ₂ concentration meter 17: secondary combustion air control means

18: water spray control means

(1) A method of controlling a flue gas mixture discharged from a waste incinerator according to one aspect of the present invention includes the steps of: measuring flue gas temperature at the incinerator outlet using a thermometer installed at the outlet of the incinerator; Measuring the NOx concentration, the CO concentration, and the O ₂ concentration of the flue gas by using corresponding flue gas analyzers respectively located in the flue gas pipe; Comparing the observed flue gas temperature and the observed NOx concentration with respective reference values; Adjusting the water spray rate sprayed on the waste combusted on the grate based on the comparison result; Comparing the observed flue gas temperature, the NOx concentration, the CO concentration and the O ₂ concentration with respective reference values; And adjusting the secondary combustion air supply rate injected into the combustion chamber based on the comparison result.

As can be seen from FIG. 4 showing the relationship between the water spray rate and the flue gas temperature at the incinerator exit and FIG. 2 showing the relationship between the flue gas temperature at the incinerator exit and the NOx concentration, the amount of NOx generated is not lit. In order to lower the burning temperature of the waste in the bed, it is reduced by increasing the water spray rate from the grate to the burning combustor and thus the flue gas temperature at the incinerator outlet. However, if the water spray rate is excessively increased to suppress the generation of NOx, as shown in FIG. 2, the flue gas temperature at the outlet of the incinerator is reduced, thereby increasing the CO concentration. To avoid this drawback, each regularly observed value of this flue gas at the incinerator outlet is compared with its respective reference value, and the water spray rate is adjusted to maintain the flue gas temperature at the outlet of the incinerator at the reference value to suppress NOx and CO generation. do.

As shown in FIG. 3 showing the relationship between the flue gas temperature at the outlet of the incinerator and the NOx concentration and the CO concentration with respect to the secondary combustion air supply rate (Nm ³ / h: Nm ³ is the amount of air at 0 ° C and 1 atmosphere (m 3) )). The flue gas temperature at the incinerator exit is highest in the dark. Active secondary combustion in dark areas results in lower CO concentrations. In the left region of the dark region, the secondary combustion air supply rate is low and the oxygen necessary for secondary combustion is insufficient so that secondary combustion is poor. This results in higher CO concentrations and lower flue gas temperatures at the incinerator exit. In the right area of the dark area, the secondary combustion air feed rate is high and the temperature inside the incinerator is reduced so that the flue gas temperature at the incinerator exit is reduced. And this causes the combustion to be incomplete despite the sufficient amount of oxygen for secondary combustion, leading to an increase in the CO concentration. In addition, since the amount of secondary combustion air increases and the NOx concentration increases, the NOx degree and CO concentration can be reduced at once if the operating state of the secondary combustion air is maintained in a dark region.

Second combustion with respect to the air supply rate flue gas temperatures and on the basis of the above findings on the relationship between NOx concentration and CO concentration of the flue gas temperature and NOx concentration and CO concentration and the O ₂ concentration at the furnace exit in the furnace exit is Regularly measured and measured values are compared with each reference value. The secondary combustion air feed rate is then adjusted based on the above comparison results to operate the incinerator in the dark region shown in FIG. Regular measurements of flue gas temperatures at the incinerator outlets and NOx concentration measures to maintain and monitor combustion conditions allow for rapid response to changes in combustion conditions. Short measurement intervals often increase control and provide fine control of incinerator operation.

(2) According to another embodiment of the invention, the method for controlling the mixture of flue gas according to (1) maintains the observed CO concentration percentage above the CO concentration value per unit time below the target percentage of CO generation. It is.

As can be seen in Figure 5 (a), which shows the change over time in flue gas temperature at the incinerator exit, the general pattern of CO concentration under inadequate combustion conditions in the incinerator has a high concentration profile with spikes for several minutes to several ten minutes. Gives. When the spike-shaped portion of the CO concentration profile is calculated as the incidence per unit of time during the measurement period of the dioxin concentration, the result corresponds to a plot using the mark ① in Figure 7 of the dioxin TEQ concentration at the bag filter inlet (nano-g / Nm ³ TEQ concentration is the concentration expressed as toxic equivalence; addictive equivalent amount is expressed by a changed value as a sum of the 2.3.7.8.-TCDD toxicity of dioxin-isomer). The combustion state shown in FIG. 6 (a) corresponds to a plot using the mark ② in FIG. Higher incidences of CO concentration spikes result in higher dioxin concentrations. When CO is generated in the spike pattern, incomplete combustion occurs and dioxin is discharged from the incinerator without decomposition. Therefore, the operation of not causing the spike CO pattern is performed by adjusting the water spray rate and the secondary combustion air supply rate using the above-described control method that does not exceed the target CO concentration.

(3) According to another embodiment of the present invention, a method for controlling the mixture of flue gas according to (1) is to maintain the observed flue gas temperature at the incinerator outlet above the target lower limit temperature.

Regarding the relationship between the flue gas temperature at the incinerator outlet and the dioxin concentration at the bag filter inlet in response to changes in combustion conditions in the incinerator, the higher minimum value of the flue gas temperature at the incinerator outlet during the dioxin concentration measurement Dioxin concentration at the inlet is kept at a low level. The TEQ concentration at the bag filter inlet is shown in FIG. When the flue gas temperature at the outlet of the incinerator is not reduced during the dioxin concentration measurement, a complete combustion state is maintained and the dioxin in the flue gas is decomposed. Therefore, the operation of maintaining the flue gas temperature at the outlet of the incinerator at the target lower limit level is carried out using the method (1) described above so that the water spray rate and the second combustion air supply rate are maintained so that the observed value of the flue gas temperature at the outlet of the incinerator is kept above the lower limit temperature. By controlling it.

(4) According to another embodiment of the present invention, the method for controlling the mixture of flue gas according to (1) ranges the average value of the flue gas temperature observed at the incinerator outlet between the target lower limit mean value and the target upper limit mean value. To stay within. Regarding the relationship between the flue gas temperature average value at the incinerator outlet caused by the change of combustion state inside the incinerator and the change of the dioxin concentration and the NOx concentration at the bag filter inlet, the higher average flue gas temperature at the incinerator outlet is the TEQ concentration and the NOx concentration. As shown in FIG. 12 expressing the relationship between the concentrations, the decomposition of the incombustible components results in a low dioxin concentration. However, flue gas at the incinerator outlet has a higher average flue gas temperature which increases the combustion temperature of the gas in the incinerator, thus increasing the NOx concentration. On the one hand, the lower average flue gas temperature at the incinerator exit leads to higher dioxin concentrations and lower NOx concentrations. Therefore, the operation of the incinerator is above the target lower limit value and by adjusting the water injection rate and the second combustion air supply rate to maintain the average flue gas temperature at the outlet of the incinerator using the method (1) above and between the target lower limit value and the upper limit value. The average flue gas temperature at the incinerator outlet is kept above the target lower limit average value and below the target upper limit average value.

(5) According to another aspect of the present invention, the method for controlling the mixture of flue gas according to (1) maintains the observed CO concentration percentage above the target CO concentration value per unit time below the target percentage of CO generation. Keep the flue gas temperature observed at the exit of the incinerator above the target lower limit.

Dioxin decomposition in flue gas reduces the water spray rate and secondary combustion air feed rate using the method (1) described above to prevent the generation of spike-shaped CO concentration contours and to maintain the flue gas temperature at the incinerator exit at the target lower limit level. It is confirmed by adjusting.

(6) According to another embodiment of the invention, the method for adjusting the mixture of flue gas according to (1) is characterized in that the percentage of the observed CO concentration exceeding the target CO concentration per unit time is less than or equal to the target percentage of CO generation. And maintain the observed flue gas temperature at the outlet of the incinerator above the target lower limit temperature, and maintain the average value of the flue gas temperature observed at the outlet of the incinerator between the target lower limit mean value and the target upper limit mean value. The suppression of dioxin and NOx generation in flue gas prevents the generation of spike-shaped CO concentration profile, keeps flue gas temperature at the incinerator outlet above the target lower limit, and sets the average value of the flue gas temperature at the outlet of the incinerator. It is confirmed by adjusting the water spray rate and the secondary combustion air feed rate using the above-mentioned adjustment method (1) to maintain between the upper limit average values.

(7) According to another embodiment of the present invention, the method for controlling the mixture of flue gas according to (2) or (5) selects a target CO concentration of 30 ppm and a target percentage of CO generation of 2%. . As can be seen in FIG. 7, the dioxin concentration is effectively reduced when the target CO concentration and the target percentage of CO generation are set to 30 ppm and 2%, respectively.

(8) According to another embodiment of the present invention, the method for controlling the mixture of flue gas according to (3) or (5) selects a target lower limit temperature of about 850 占 폚. As can be seen in FIG. 8, the dioxin concentration is effectively reduced when the target lower limit temperature is set to about 850 ° C.

(9) According to another embodiment of the present invention, the method for controlling the mixture of flue gas according to (4) or (6) selects a lower limit average temperature of about 900 ° C and an upper limit average temperature of about 950 ° C. do. As can be seen in FIG. 12, when the target lower limit average value is set to about 900 DEG C and the target upper limit average value is set to about 950 DEG C, the dioxin concentration and the NOx concentration in the flue gas are effectively reduced.

(10) According to another embodiment of the present invention, the method for controlling the flue gas mixture according to (1) controls the water spray rate and the secondary combustion air feed rate using the fuzzy inference method. This fuzzy reasoning method is a form of membership function of parameters and premises for setting up preconditions for inferring water spray rates, and a form of membership function of parameters and premises for setting up preconditions for inferring secondary combustion air supply rates. Shall be different from each other. For example, NOx concentration and non-combustion component concentration are normally suppressed by adjusting the secondary combustion air supply rate. When the flue gas temperature at the incinerator outlet exceeds the pre-determined high reference value, the water spray rate as well as the secondary combustion air feed rate are adjusted to suppress the increase in NOx concentration and the flue gas temperature at the incinerator outlet. Limiting the water spray rate adjustment (increase) minimizes the disadvantages of water spray. The relationship between the standard deviation in the water spray rate and the TEQ concentration at the bag filter inlet suggests that greater variation in the water spray rate leads to higher dioxin concentrations as shown in FIG. Thus, when a lot of water is sprayed and the water spray cools the contents of the incinerator, all the sprayed amount is not necessarily evaporated to vapor to cool the contents of the incinerator, but the portion of the water to be sprayed is attached to the waste. When wastes containing water are burned, the combustion condition deteriorates, leading to the generation of incombustible components such as dioxins and CO. However, this disadvantage can be avoided by limiting the water spray rate adjustments described above.

1 shows a method of controlling the flue gas mixture discharged from a waste incinerator according to the invention and shows a schematic diagram of the waste incinerator used in the method according to the invention. The hopper 2 is located above the furnace 1. The waste introduced into the furnace 1 from the hopper 2 is transported in the order of the drying tray 3a, the combustion tray 3b, and the post combustion tray 3c in the combustion chamber 1a. Under each flame grate 3a, 3b, 3c, primary combustion air for drying or burning enters the primary combustion air fan 5. The waste is mainly dried in the drying glove 3a, burned in the combustion glove 3b and then completely burned to ash in the afterburn gasket 3c. Ash falls out of the furnace at the drop port 4. On the other hand, from the secondary combustion air secondary combustion air intake 9 sent from the secondary combustion air fan 10, it is introduced into the upper portion of the combustion zone above the grate 3b and 3c. The water supplied from the water spray rate regulator 13 is sprayed from the water spray nozzle 13a at the upper portion of the combustion zone on the grate 3b and 3c. The burned flue gas discharged from the incinerator outlet 6 is led to the chimney 7 through the bag filter 11 and discharged to the atmosphere. During the passage, the hot flue gas heats the heat exchanger 8a to boil the water in the boiler 8b. This generates steam used for power generation, heat source supply, and the like.

The waste incinerator includes secondary combustion air control means 17 and water spray control means 18. The secondary combustion air control means 17 receives signals generated from the thermometer 12, the NOx concentration meter 14, the CO concentration meter 15, and the O ₂ concentration meter 16 at the outlet of the incinerator, and performs a designated calculation. The control signal is prepared and the control signal is generated in the secondary combustion air supply fan 10. The water spray control means 18 receives the signals generated by the thermometer 12 and the NOx densitometer 14, performs the specified calculations, prepares the control signals and generates these signals to the water spray regulator 13. A computer is used for this control means 17 and 18, for example. In the control means 17 and 18, control value calculation based on the input signal is performed at regular intervals. Since fluctuations in flue gas temperature and flue gas mixture at the incinerator outlet occur within tens of seconds to minutes, it is appropriate to perform calculations at intervals between tens of seconds and minutes.

Description of the water spray control means 18 shown in FIG. 1 is given in Table 1 and Table 2 when the water spray rate adjustment is performed by fuzzy evaluation method based on the observed value of the flue gas temperature and the observed value of NOx concentration at the incinerator exit. On the basis of Table 1 lists fuzzy rules for the case of fuzzy control. Table 2 rearranges (1) to (5) in Table 1.

TABLE 1

TABLE 2

In Table 2, the preceding (input) consists of the temperature and NOx concentration at the incinerator outlet, and the following (output) is the increase / decrease in the water spray rate. The calculation of each rule is made based on the respective membership functions shown in FIG. Flue gas thermometer calculation and NOx concentration calculation at the incinerator exit are performed based on the functions shown in Figs. 9 (a) and 9 (b), respectively. Then, the increase / decrease amount of the water spray rate is calculated by adding up the respective calculation results of the rules (1) to (5). However, if no calculation satisfies a given condition, the associated output is assumed to be zero for the calculation.

The water spray rate control means 18 shown in FIG. 1 performs the above-mentioned calculation and integrates the calculation result of each trailing rule and outputs the result of the entire rule. The integration of the results of each subsequent rule inference is done using a general method of fuzzy operations such as min-max or product-sum. The reasoning result obtained by the water spray rate control means 18 is output to the water spray rate regulator 13, and the water spray rate is adjusted.

The following describes the singleton method, which is a fuzzy control application mode suitable for control with a small amount of calculation, with reference to FIG.

First, the preceding membership function is used to calculate the goodness of fit. Figure 9 (a) shows the preceding membership function for the flue gas at the incinerator exit. Under the "low temperature at the furnace exit" that condition incinerator outlet when the observed flue gas temperature Te of the goodness of fit is a _1, the under morning edition of "suitable temperature in the furnace exit" with a _2, "high at the furnace outlet temperature "are each represented by a ₃ under the conditions of.

Figure 9 (b) shows the preceding membership function for NOx concentration. When the observed NOx concentration is NOx, the goodness of fit is b ₁ under the conditions of "suitable NOx concentration" and the goodness of fit is b ₂ under the conditions of "high NOx concentration", respectively.

From these membership functions, the goodness of fit X ₁ corresponding to the rule (1) of Table 2 is calculated by equation (1). The goodness of fit is X ₁ (= a ₁ ) because rule (1) corresponds to “low temperature at incinerator exit”. Similarly, the goodness of fit of rule (2) X ₂ (= a ₂ ) is equation (2), the goodness of fit of rule (3) X ₃ (= b ₁ ) is equation (3), and the goodness of fit of rule (4) X ₄ (= a ₃ ) is each represented by formula (4). The goodness-of-fit X ₅ of rule (5) corresponds to "high temperature and high NOx concentration at the incinerator exit" and thus becomes (a ₃ xb ₂ ) as represented by equation (5).

[Equation 1]

[Equation 2]

[Equation 3]

[Equation 4]

[Equation 5]

The amount of change y ₁ to y ₅ of each water spraying rate is then measured inferred from the following. And in order to derive the inference result (Z), it is given in (6).

[Equation 6]

The current value Vk of the water spray rate is obtained from the inference result Z obtained in equation (6) and the preceding value V _K-1 of the water spray rate output.

[Equation 7]

Next, the purge control method is used in the secondary combustion air control means 17 shown in FIG. 1 based on the observed values of the flue gas temperature, the secondary combustion air supply rate, the CO concentration, the NOx concentration, and the O2 concentration at the incinerator outlet. The following describes the execution of the secondary combustion air supply rate control. Table 3 shows the fuzzy rules under fuzzy control application. Table 4 summarizes the rules (1) to (12) in Table 3.

TABLE 3

TABLE 4

An example of the calculation method in the control unit for the secondary combustion air under the control of the fuzzy control method will be described below with reference to FIG. First, the operation is performed for the preceding goodness of fit. In FIG. 10 (a), the corresponding goodness of fit when the observed flue gas temperature at the incinerator outlet is Te and under the condition that the temperature of the incinerator outlet is low is a1. In a similar manner, the goodness-of-fit for the condition “temperature is suitable” is a ₂ and for “high temperature” is a ₃ . In addition, the O ₂ concentration observed with respect to O ₂ concentration at the furnace exit of the second 10 (b) "is high O ₂ concentration" a O when ₂ days as shown in Figure is fit for the condition is b _1, and "suitable B ₂ under the condition "and b ₃ for" low. " Regarding the present value of the secondary combustion air supply rate, the goodness of fit under the condition of "low" is c ₁ and c ₂ for "suitable" when the observed value is F2 _now , as shown in FIG. 10 (c). high "for about a ₃ c. Regarding the NOx concentration at the incinerator exit, the goodness of fit under the condition of "high" is d ₁ and d ₂ for "suitable" when the observed NOx concentration is NOx. With respect to the CO concentration at the incinerator exit, the goodness of fit under the condition "high" is e ₁ and e ₂ for "suitable" when the observed CO concentration is CO, as can be seen in Figure 10 (e).

Using these results, the goodness of fit X ₁ for Rule (1) in Table 4 is calculated by Equation (8). The goodness-of-fit for X ₁ is "a ₁ and c ₃ " because rule (1) corresponds to the condition of "low temperature at the incinerator exit and high current secondary combustion air supply rate". In the same manner, equations (9) to (19) are applied by calculating the corresponding goodness of fit (X ₂ to X ₁₂ ) for rules 2 to 12.

[Equation 8]

[Equation 9]

[Equation 10]

[Equation 11]

[Equation 12]

[Equation 13]

[Equation 14]

[Equation 15]

[Equation 16]

[Equation 17]

Equation 18

[Equation 19]

The amount of change Y ₁ to Y ₁₂ in the secondary combustion air feed rate is then measured to make inferences later. Inference is calculated by equation (20) which derives the inference result (Z).

[Equation 20]

As a result, the present value U _k of the secondary combustion air feed rate output is obtained from the inference result Z and the preceding value U _k-1 of the secondary combustion air feed rate output.

[Equation 21]

Regarding the relationship between the average flue gas temperature at the incinerator outlet and the TEQ concentration and the NOx concentration at the bag filter inlet, as shown in FIG. This results in lower dioxin concentrations and higher NOx concentrations due to the increased combustion temperatures of the flue gases. Conversely, lower average flue gas temperatures at the incinerator outlet result in higher dioxins and lower NOx concentrations. Therefore, in the embodiment of the present invention, the target lower limit average flue gas temperature at the incinerator outlet is set to about 900 ° C, and the target upper limit average flue gas temperature is set to about 950 ° C. With this setting, the dioxin concentration and the NOx concentration in the flue gas can be effectively suppressed at the same time.

With respect to the secondary combustion air supply rate controlled by the secondary combustion air feed rate control means 17 and the water spray rate controlled by the water spray rate control means 17, the observed input and the water spray rate of the secondary combustion air supply rate control means 17 The observed inputs of the control means 18 are different. In other words, the parameters for setting the preceding conditions for performing fuzzy inference are different (see Table 4 and Table 2). In addition, the forms of the preceding membership functions are also different (see FIGS. 10 and 9). Therefore, these controls do not affect each other. According to an embodiment of the present invention, normally the amounts of NOx and non-combustible components are suppressed by adjusting the secondary combustion air feed rate. If the flue gas temperature at the outlet of the incinerator exceeds the specified high threshold, the rate of supply of secondary combustion air as well as the water spray rate is adjusted to reduce the amount of NOx and incombustible components. By limiting (increasing) the water spray rate, the shortcomings of water spray can be avoided as far as possible. That is, when the contents of the furnace are cooled by injecting a large amount of water, all of the sprayed water does not necessarily become steam to generate steam to cool the contents of the incinerator, but some of the sprayed water clings to the waste. When the waste containing water is burned, the combustion is worsened and CO is generated. This phenomenon can be seen in FIG. When the water spray rate is maintained at a rate of 2.5K1 / h for about 30 minutes at a high flue gas temperature at the incinerator exit, a high CO concentration of more than 100 ppm is then shown. However, in FIG. 6 (an embodiment of the present invention), the flue gas temperature at the outlet of the incinerator fluctuates in the temperature range of 870 to 960 ° C and the water spray rate maintains the current level (Fig. 9 (a) and the table 2) It does not bring about these changes.

13 shows the relationship between the standard deviation of the water spray rate and the dioxin concentration at the bag filter inlet. As can be seen in the figure, the variation in water spray rate decreases, thus increasing the dioxin concentration. Therefore, it is possible to limit the water spray rate adjustment (increase) as described above to avoid an increase in the dioxin concentration in the bag filter.

The CO concentration and the NOx concentration are measured under the control of the secondary combustion air feed rate 롸 water spray rate using the control means 17 and 18 shown in FIG. FIG. 11 shows the result of the embodiment of the present invention and an example where only the secondary combustion air supply rate is controlled. FIG. 11 (a) shows the observation result of the Example of this invention, and the observation data of CO concentration and NOx concentration are plotted for 6 hours. Spike-shaped high CO concentrations are not shown in both the eleventh (a) and the eleventh (b). However, with regard to the NOx concentration, the eleventh (a) of the embodiment also suppresses the average value to 50 ppm even if the eleventh (b) is given an average value of 70 ppm.

As described above, according to the present invention, each observed value of flue gas temperature and NOx concentration at the incinerator outlet is compared with a corresponding reference value and the water spray rate is adjusted based on the comparison result. As a result, the flue gas temperature at the outlet of the incinerator is stabilized and the NOx concentration is controlled to a specified level. In addition, at the incinerator outlet, the flue gas temperature at the incinerator outlet, because each observed value of flue gas temperature, NOx concentration, CO concentration, O2 concentration is compared with the corresponding reference value and the secondary combustion air supply rate is adjusted based on the comparison result. And the O2 concentration is stabilized and the CO concentration and the NOx concentration are controlled at respective designated levels. Therefore, the generation of NOx and non-combustible components is suppressed, and the generation of addictive components such as dioxins is suppressed.

Claims (9)

(a) measuring the flue gas temperature at the incinerator outlet using a thermometer located at the outlet of the incinerator; (b) measuring the NOx concentration, the CO concentration, and the O ₂ concentration of the flue gas using respective flue gas analyzers located in the flue gas pipe; (c) comparing the observed flue gas temperature and the observed NOx concentration with respective reference values; (d) adjusting the water spray rate sprayed on the waste combusted on the basis of the comparison result of step (c); (e) comparing the observed flue gas temperature, NOx concentration, CO concentration, and O ₂ concentration with respective reference values; and (f) adjusting a secondary combustion air supply rate injected into the combustion chamber based on the comparison result of step (e). 2. The method of claim 1, wherein adjusting the secondary combustion air feed rate comprises: measuring a percentage of the observed CO concentration above a target CO concentration per unit time; The control method of the flue gas mixture discharged from the waste incinerator further comprises the step of maintaining the percentage below the target percentage of CO generation. The method of claim 1, wherein adjusting the water spray rate (d) and adjusting the secondary combustion air feed rate (f) further comprise maintaining the observed flue gas temperature above a target lower limit temperature. Control method of the flue gas mixture discharged from the waste incinerator. 2. The method of claim 1, wherein adjusting the water spray rate (d) and adjusting the secondary combustion air feed rate (f) comprise: measuring an average of observed values of flue gas temperature; And maintaining said average value between a target lower limit mean value and a target upper limit mean value. 3. The method of claim 2, wherein adjusting the water spray rate (d) and adjusting the secondary combustion air feed rate (f) further comprise maintaining the observed flue gas temperature above a target lower limit temperature. Control method of the flue gas mixture discharged from the waste incinerator. 6. The method of claim 5, wherein adjusting the water spray rate (d) and adjusting the secondary combustion air feed rate (f) comprise: measuring an average of observed values of flue gas temperature; And maintaining the average value of the flue gas temperature between a target lower limit mean value and a target upper limit mean value; and controlling the flue gas mixture discharged from the waste incinerator. The method according to claim 2 or 5, wherein the target CO concentration is 30 ppm and the target percentage of CO generation is 2%. 6. The method according to claim 3 or 5, wherein the target lower limit temperature is about 850 ° C. The control method according to claim 4 or 6, wherein the lower limit average temperature is about 900 ° C and the upper limit average temperature is about 950 ° C.

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