JP2017089928A - Stoker type incinerator and incinerator - Google Patents

Abstract

PROBLEM TO BE SOLVED: To promptly predict change of NOx concentration in exhaust gas.SOLUTION: An incinerator 1 includes: a primary combustion chamber 2 configured to supply primary air to wastes at each position of a conveyance route of the wastes conveyed by a plurality of fire grates to thereby combust the wastes; a secondary combustion chamber 3 configured to supply secondary air to unburned gas occurring in the primary combustion chamber 2 to thereby combust the unburned gas; and a discharge route 4 configured to guide exhaust gas discharged from the secondary combustion chamber 3 to atmosphere. A value of a target parameter group containing two or more of a flow rate of primary air, a temperature of primary air, a temperature in the primary combustion chamber 2, a flow rate of secondary air, a temperature in the secondary combustion chamber 3 and an oxygen concentration in the secondary combustion chamber 3 is acquired by a parameter value acquisition unit 5. At a NOx concentration predication unit 101, a predication value of a NOx concentration in exhaust gas is acquired based on the value of the target parameter group. Consequently, change of NOx concentration in exhaust gas can be predicted promptly.SELECTED DRAWING: Figure 1

Description

  The present invention relates to an incinerator.

  In order to reduce the NOx (nitrogen oxide) concentration of exhaust gas discharged from an incinerator, it has been conventionally performed to supply a reducing agent such as ammonia into the exhaust gas. As a measurement of the NOx concentration, a method of detecting the NOx concentration in a NOx concentration measuring unit at the rear stage of the bag filter and controlling the supply amount of the reducing agent based on the NOx concentration is employed. However, since the installation position of the NOx concentration measuring unit is away from the main body of the incinerator, it takes time until the NOx concentration measuring unit detects the increase in NOx concentration after the NOx concentration actually increases in the incinerator. Therefore, the change in the NOx concentration in the incinerator cannot be detected quickly.

  Therefore, for example, in the waste treatment facility of Patent Document 1, the oxygen concentration and temperature in a region where excess air is supplied to the exhaust gas are measured, and the concentration of thermal NOx generated in the exhaust gas based on these measured values. And the amount of reducing agent injected is feedforward controlled based on the predicted value.

Japanese Patent No. 4455349

  By the way, in the apparatus of Patent Document 1, assuming that the concentration of fuel NOx in the exhaust gas is stable at about 100 to 120 ppm, the concentration of only thermal NOx generated in the exhaust gas is predicted, and the amount of reducing agent injected By controlling the above, the NOx concentration at the smoke outlet is maintained below a certain level. In practice, however, the concentration of fuel NOx varies depending on the type of waste, combustion conditions, and the like. Therefore, a method capable of quickly predicting a change in NOx concentration of exhaust gas containing fuel NOx is required.

  The present invention has been made in view of the above problems, and has an object to quickly predict changes in the NOx concentration of exhaust gas.

  The invention according to claim 1 is a stoker-type incinerator, wherein primary waste is supplied to the waste at each position of a waste transport route transported by a plurality of grate to dispose the waste. A primary combustion chamber for burning, a secondary combustion chamber for supplying secondary air to unburned gas generated in the primary combustion chamber to burn the unburned gas, and exhaust gas discharged from the secondary combustion chamber to the atmosphere A discharge path that leads to the flow rate of the primary air, the temperature of the primary air, the temperature in the primary combustion chamber, the flow rate of the secondary air, the temperature in the secondary combustion chamber, and the oxygen concentration in the secondary combustion chamber A parameter value acquisition unit that acquires the value of the target parameter group including two or more of the above, and a NOx concentration prediction unit that acquires a predicted value of the NOx concentration of the exhaust gas based on the value of the target parameter group.

  The invention according to claim 2 is the stoker-type incinerator according to claim 1, wherein the target parameter group includes the temperature in the primary combustion chamber.

  The invention according to claim 3 is the stoker type incinerator according to claim 2, wherein the temperature in the primary combustion chamber includes temperatures at a plurality of positions in the primary combustion chamber.

  Invention of Claim 4 is the stoker type incinerator in any one of Claim 1 thru | or 3, Comprising: The said target parameter group is the flow volume of the said primary air, the temperature in the said primary combustion chamber, the said secondary combustion chamber It includes the temperature in the combustion chamber and the oxygen concentration in the secondary combustion chamber.

  The invention according to claim 5 is the stoker-type incinerator according to any one of claims 1 to 4, wherein EGR gas containing at least the exhaust gas is injected into the primary combustion chamber, and the target parameter group is: The flow rate, temperature or flow rate of the EGR gas is further included.

  A sixth aspect of the present invention is the stoker-type incinerator according to any one of the first to fifth aspects, further comprising a NOx concentration measuring unit that measures the NOx concentration of the exhaust gas in the exhaust path, and the parameter A value acquisition unit acquires values of a plurality of measurement parameters including the target parameter group, and a function used to acquire the predicted value of the NOx concentration in the NOx concentration prediction unit is the NOx concentration measurement unit at a plurality of times Is obtained by multiple regression analysis using the measured value of the NOx concentration as a target variable and the values of the plurality of measurement parameters corresponding to the measured values of the NOx concentration at the plurality of times as explanatory variables.

  The invention according to claim 7 is an incinerator, in which primary air is supplied to burn waste, and secondary air is supplied to the unburned gas generated in the primary combustion chamber. A parameter value acquisition unit for acquiring values of a target parameter group including a secondary combustion chamber for burning unburned gas, an exhaust path for guiding exhaust gas discharged from the secondary combustion chamber to the atmosphere, and a temperature in the primary combustion chamber And a NOx concentration prediction unit that acquires a predicted value of the NOx concentration of the exhaust gas based on the value of the target parameter group.

  According to the present invention, it is possible to quickly predict a change in the NOx concentration of exhaust gas.

It is a figure which shows the structure of an incinerator. It is a figure which shows the flow of supply control of a reducing agent. It is a figure which shows the flow of the process which acquires a prediction function. It is a figure which shows the structure of the incinerator used for experiment. It is a graph which shows the relationship between the predicted value of NOx concentration, and the measured value of NOx concentration.

  FIG. 1 is a diagram showing a configuration of an incinerator 1 according to an embodiment of the present invention. As will be described later, the incinerator 1 in FIG. 1 is a stoker-type incinerator that burns while conveying waste by a plurality of grate (stalkers).

  The incinerator 1 includes a primary combustion chamber 2, a secondary combustion chamber 3, a discharge path 4, and a control unit 10. In the primary combustion chamber 2, waste is burned. The secondary combustion chamber 3 continues upward from the primary combustion chamber 2, and unburned gas such as ammonia generated in the primary combustion chamber 2 is burned. The discharge path 4 is continuous from the secondary combustion chamber 3 and guides the exhaust gas discharged from the secondary combustion chamber 3 to the atmosphere. The control unit 10 includes a NOx concentration prediction unit 101. The control unit 10 is also responsible for overall control of the incinerator 1.

  The primary combustion chamber 2 includes a supply unit 21, a grate unit 22, and a discharge unit 23. The supply unit 21 supplies waste into the primary combustion chamber 2. The grate portion 22 includes a plurality of grate arranged in the horizontal direction of FIG. The waste on the grate part 22 moves from the supply part 21 side toward the discharge part 23 by the reciprocating motion of the movable grate arranged every other in the plurality of grate. As described above, the plurality of grate of the grate unit 22 conveys the waste along the conveyance path from the supply unit 21 toward the discharge unit 23. As will be described later, air is supplied to the waste at each position in the conveyance path, and the waste is burned. Waste after combustion (mainly ash) is discharged out of the primary combustion chamber 2 by the discharge section 23. In addition, various things can be employ | adopted about the shape of a plurality of grate in the grate part 22, arrangement, operation, etc.

  The conveyance path on the grate 22 is roughly divided into three parts in the waste movement direction (the horizontal direction in FIG. 1 and hereinafter referred to as “conveyance direction”). In the part 221 on the supply unit 21 side in the transport path, waste is mainly dried, and in the central part 222, waste is mainly burned. In the portion 223 on the discharge unit 23 side in the transport path, waste is post-combusted mainly. In the following description, the three portions 221, 222, and 223 in the conveyance path are referred to as a drying stage 221, a combustion stage 222, and a post-combustion stage 223, respectively.

  The primary combustion chamber 2 further includes a plurality of primary air supply units 24. In the incinerator 1 of FIG. 1, three primary air supply units 24 are provided. The three primary air supply units 24 supply (spout) air toward the waste on the drying stage 221, the combustion stage 222, and the post-combustion stage 223. In the following description, the air supplied toward the waste on the grate portion 22 is referred to as “primary air”. Each primary air supply unit 24 is connected to an air supply source having a pump via a primary air measurement unit 51. The primary air measurement unit 51 measures the flow rate and temperature of the primary air supplied from the corresponding primary air supply unit 24 into the primary combustion chamber 2.

  A plurality of thermometers 52 (for example, thermocouple thermometers) are provided in the primary combustion chamber 2. The plurality of thermometers 52 are located above the grate portion 22. For example, the plurality of thermometers 52 are arranged at a height near the center between the grate portion 22 and the inlet of the secondary combustion chamber 3. The plurality of thermometers 52 preferably include a thermometer 52 located in the vicinity of the boundary between the drying stage 221 and the combustion stage 222 with respect to the transport direction. In the example of FIG. 1, several thermometers 52 are arranged above the portion on the combustion stage 222 side in the drying stage 221 and above the portion on the drying stage 221 side in the combustion stage 222. Also, several thermometers 52 are arranged above the portion of the combustion stage 222 on the side of the post-combustion stage 223. The number and arrangement of the thermometers 52 arranged in the primary combustion chamber 2 may be arbitrarily determined (the same applies to a thermometer 54 described later).

  The secondary combustion chamber 3 includes a first flue 31, a second flue 32, and a third flue 33. The first flue 31 extends upward continuously from the upper part of the primary combustion chamber 2. The second flue 32 is continuous from the upper part of the first flue 31 and extends downward along the first flue 31. The third flue 33 is continuous from the lower part of the second flue 32 and extends upward along the second flue 32. In the secondary combustion chamber 3, a relatively long gas flow path is formed by the first to third flues 31 to 33. Thereby, the state which exhaust gas becomes more than fixed temperature for a certain period of time is ensured.

  The secondary combustion chamber 3 further includes a plurality of secondary air supply units 34 that are ejection nozzles. The plurality of secondary air supply units 34 are provided in the first flue 31 in the vicinity of the primary combustion chamber 2, that is, in the vicinity of the inlet of the secondary combustion chamber 3. The plurality of secondary air supply units 34 supply (spout) air toward the gas flowing into the secondary combustion chamber 3 from the primary combustion chamber 2. Thereby, the high-temperature unburned gas generated in the primary combustion chamber 2 burns in the secondary combustion chamber 3. In the following description, the air supplied toward the gas flowing into the secondary combustion chamber 3 is referred to as “secondary air”. The above-described exhaust gas includes a gas after combustion with secondary air. The plurality of secondary air supply units 34 are connected to an air supply source having a pump via one secondary air measurement unit 53. The secondary air measurement unit 53 measures the flow rate of the secondary air supplied from the plurality of secondary air supply units 34 into the secondary combustion chamber 3.

  A plurality of thermometers 54 and one oxygen concentration meter 55 are provided in the secondary combustion chamber 3. The several thermometer 54 is each arrange | positioned in the 1st thru | or 3rd flue 31-33. The thermometer 54 in the 1st flue 31 is arrange | positioned above the some secondary air supply part 34 (position distant from the primary combustion chamber 2), for example. In the example of FIG. 1, the thermometer 54 in the first flue 31 is disposed near the center of the path of the gas flowing through the first flue 31. The same applies to the thermometer 54 in the second and third flues 32 and 33. The oxygen concentration meter 55 measures the oxygen concentration using laser light, and has an emitting portion and a light receiving portion that are arranged to face each other in the second flue 32. The oxygen concentration meter 55 may be disposed in the first flue 31 or the third flue 33.

  In the secondary combustion chamber 3, a plurality of reducing agent supply units 61 that are nozzles are provided. Among the plurality of reducing agent supply units 61, one reducing agent supply unit 61 is disposed in the first flue 31, and the remaining reducing agent supply unit 61 includes the first flue 31 and the second flue 32. It is arranged near the boundary. Each reducing agent supply unit 61 is connected to a reducing agent supply source via a flow rate adjusting unit 62. The reducing agent ejected from the reducing agent supply unit 61 denitrates the exhaust gas, that is, reduces the concentration of NOx in the exhaust gas. The reducing agent is, for example, ammonia. The reducing agent may be ammonia diluted water or urea diluted water. The number and arrangement of the reducing agent supply unit 61 may be arbitrarily determined.

The discharge path 4 is connected to the upper part of the third flue 33, that is, the outlet of the secondary combustion chamber 3. The discharge path 4 includes a temperature reducing tower 41 (or an economizer), a bag filter 42, and a chimney 43. The temperature reducing tower 41 supplies water to the exhaust gas discharged from the secondary combustion chamber 3 to reduce the temperature of the exhaust gas. The bag filter 42 removes the dust contained in the exhaust gas. The chimney 43 emits exhaust gas to the atmosphere. In the discharge path 4, a NOx concentration measuring unit 71 is provided between the bag filter 42 and the chimney 43. The NOx concentration measuring unit 71 measures the NOx concentration of the exhaust gas in the discharge path 4. The NOx concentration in the following explanation is an equivalent value of oxygen (O ₂ ) concentration of 12 percent.

  Next, supply control of the reducing agent during normal operation of the incinerator 1 will be described with reference to FIG. In the control unit 10, the flow rate and temperature of the primary air acquired by the plurality of primary air measuring units 51, the temperature acquired by the plurality of thermometers 52 in the primary combustion chamber 2, and the secondary air measuring unit 53 A plurality of measurement parameters including the flow rate of the secondary air, the temperatures acquired by the plurality of thermometers 54 in the secondary combustion chamber 3, and the oxygen concentration acquired by the oxygen concentration meter 55 in the secondary combustion chamber 3 Is input every predetermined time (almost always). In the following description, a plurality of configurations for acquiring values of a plurality of measurement parameters (a plurality of primary air measurement units 51, a plurality of thermometers 52, a secondary air measurement unit 53, a plurality of thermometers 54, and an oxygen concentration meter 55). Is collectively referred to as parameter value acquisition unit 5. The parameter value acquisition unit 5 may include a configuration for acquiring values of other measurement parameters. Further, the sum of the flow rates of primary air in the plurality of primary air measurement units 51, the difference between the temperature in the thermometer 54 of the first flue 31 and the temperature in the thermometer 54 of the second flue 32, and the like are measurement parameters. It may be included in a plurality of measurement parameters.

  In the incinerator 1, a function for obtaining a predicted value of the NOx concentration of exhaust gas (hereinafter referred to as “prediction function”) is obtained in advance by processing described later, and is stored in the NOx concentration prediction unit 101. Of the plurality of measurement parameters, two or more measurement parameters (hereinafter referred to as “target parameter group”) used in the prediction function are determined. In the present embodiment, the target parameter group includes the flow rate of primary air, the temperature in the primary combustion chamber 2, the temperature in the secondary combustion chamber 3, and the oxygen concentration in the secondary combustion chamber 3. Specifically, the target parameter group includes the flow rate of the primary air in the combustion stage 222, the temperature in the primary combustion chamber 2 above the part on the combustion stage 222 side in the drying stage 221, and the part on the drying stage 221 side in the combustion stage 222. It includes the temperature in the primary combustion chamber 2 above, the temperature in the secondary combustion chamber 3 in the first flue 31, and the oxygen concentration in the secondary combustion chamber 3.

  The NOx concentration prediction unit 101 acquires the predicted value of the NOx concentration by substituting the values of the target parameter group included in the plurality of measurement parameters into the prediction function (step S1). In this processing example, the value of the target parameter group and the predicted value of the NOx concentration are normalized values in the same way as the prediction function acquisition process described later. Actually, since the exhaust gas flows from the primary combustion chamber 2 to the exhaust path 4 via the secondary combustion chamber 3, the values of the target parameter group used for calculating the predicted value of the NOx concentration at a certain time are different from each other. May contain the value obtained. For example, the value of the target parameter group may include the value of the parameter related to the primary combustion chamber 2 and the value of the parameter related to the secondary combustion chamber 3 acquired after a predetermined time elapses after the value is acquired. Good.

  In the control unit 10, the flow rate of the reducing agent to be supplied into the secondary combustion chamber 3 by the reducing agent supply unit 61 is calculated based on the predicted value of the NOx concentration by the NOx concentration prediction unit 101 (step S <b> 2). In the calculation of the flow rate of the reducing agent, the minimum flow rate of the reducing agent that obtains a high denitration rate in the exhaust gas is calculated according to the predicted value of the NOx concentration of the exhaust gas. And according to the said flow volume, the flow volume adjustment part 62 is controlled, and a reducing agent is supplied in the secondary combustion chamber 3 (step S3). The reducing agent supply unit 61 that actually ejects the reducing agent may be arbitrarily determined, and reducing agents may be ejected from all the reducing agent supply units 61. Acquisition of the predicted value of the NOx concentration, calculation of the flow rate of the reducing agent, and supply of the reducing agent into the secondary combustion chamber 3 (steps S1 to S3) are always repeated while the incinerator 1 is operating. It is. Thereby, the high denitration rate in exhaust gas is implement | achieved, suppressing that a reducing agent is discharged | emitted to air | atmosphere (leakage of a reducing agent).

Next, a process for obtaining a prediction function for obtaining a predicted value of the NOx concentration will be described with reference to FIG. In the prediction function acquisition process, first, while the waste is burned in the incinerator 1, the parameter value acquisition unit 5 acquires the values of a plurality of measurement parameters every predetermined time (step S11). Further, the measured value of the NOx concentration of the exhaust gas in the discharge path 4 is acquired every predetermined time by the NOx concentration measuring unit 71 (step S12). Then, multiple regression analysis is performed using the measured values of NOx concentration at a plurality of times as objective variables and the values of a plurality of measurement parameters corresponding to the measured values of NOx concentrations at the plurality of times as explanatory variables (step S13). . For example, when there are N measurement parameters (N is an integer of 2 or more), the i-th measurement parameter (i is an integer of 1 to N) is set to X _i , and the coefficient for the measurement parameter is set to a _i. Assuming that the NOx concentration is α, Equation 1 is used in the multiple regression analysis. Β in Equation 1 indicates an intercept.

(Equation 1)
α = (a ₁ X ₁ + a ₂ X ₂ +... + a _N X _N ) + β

  In the multiple regression analysis, in each of the plurality of measurement parameters and the NOx concentration, the values at a plurality of times are normalized so that the average value becomes 0 and the variance becomes 1. Further, if necessary, the time change of the measured value of the NOx concentration is compared with the time change of the value of each measurement parameter. For example, the value of the measurement parameter is changed to the time so that the peak positions of each other approximately match. Shifted in the direction of the axis. That is, the value of the measurement parameter at a time before the time is associated with the measured value of the NOx concentration at each time. Depending on the time required for the exhaust gas discharged from the secondary combustion chamber 3 to reach the NOx concentration measuring section 71, the outlet of the secondary combustion chamber 3 or the like as in the incinerator 1a of FIG. A measured value of the NOx concentration of the exhaust gas sampled at the inlet of the discharge path 4 or the like may be acquired.

Subsequently, the measurement parameter whose absolute value is a coefficient a _i larger than a predetermined value (for example, 0.01 in Table 1) among a plurality of coefficients a _i obtained by multiple regression analysis is the target. It is determined as a parameter group (step S14). In the present embodiment, the flow rate of primary air in the combustion stage 222, the temperature in the primary combustion chamber 2 above the part on the combustion stage 222 side in the drying stage 221 and the primary above the part on the drying stage 221 side in the combustion stage 222. The temperature in the combustion chamber 2, the temperature in the secondary combustion chamber 3 in the first flue 31, and the oxygen concentration in the secondary combustion chamber 3 are determined as target parameter groups. The target parameter group may be a predetermined number of measurement parameters having the largest coefficient a _i or the like. The target parameter group is only an example, and the target parameter group is a combination of various measurement parameters according to the result of the multiple regression analysis.

When the target parameter group is determined, the multiple regression analysis using the measured value of the NOx concentration by the NOx concentration measuring unit 71 as an objective variable and the value of the target parameter group as an explanatory variable is performed again using Equation 1, and Equation 1 The function for which the coefficient a _i has been determined at step S15 is acquired as a prediction function (step S15). The prediction function is stored in the NOx concentration prediction unit 101 and used to obtain the predicted value of the NOx concentration as described above. Note that the coefficient a _i determined in step S13 may be used as it is in the prediction function. Further, in step S1 of FIG. 2, the prediction function may be modified so that a predicted value of the NOx concentration that is not normalized can be acquired using the value of the target parameter group that is not normalized.

  Next, an experiment relating to prediction of NOx concentration will be described. FIG. 4 is a diagram showing the configuration of the incinerator 1a used in this experiment. The incinerator 1a includes a primary combustion chamber 2, a secondary combustion chamber 3, and a parameter value acquisition unit 5. The primary combustion chamber 2 includes a supply unit 21, a grate unit 22, and a discharge unit 23. The grate unit 22 includes ten grate 224 (movable grate and fixed grate) arranged in the horizontal direction of FIG. In the incinerator 1a, each slit grate 224 is provided with one slit-shaped primary air supply unit 24. The secondary combustion chamber 3 includes a first flue 31, a second flue 32, and a plurality of secondary air supply units 34. The first flue 31 extends upward continuously from the upper part of the primary combustion chamber 2. The second flue 32 extends laterally continuously from the top of the first flue 31. The plurality of secondary air supply units 34 are provided in the first flue 31 in the vicinity of the primary combustion chamber 2, that is, in the vicinity of the inlet of the secondary combustion chamber 3.

  The parameter value acquisition unit 5 includes 13 thermometers 52 (including thermometers denoted by reference numerals 52 </ b> A to 52 </ b> C) arranged in the primary combustion chamber 2 and two thermometers arranged in the secondary combustion chamber 3. And a thermometer 54 (including a thermometer labeled 54A). The thirteen thermometers 52 are dispersed in a wide range in the primary combustion chamber 2 as shown in FIG. Two thermometers 54 are disposed in the first and second flues 31, 32, respectively. The parameter value acquisition unit 5 further includes ten primary air measurement units 51 (including a primary air measurement unit denoted by reference numeral 51A) and one secondary air measurement unit 53. The ten primary air measurement units 51 are connected to the ten primary air supply units 24, respectively. The secondary air measurement unit 53 is connected to a plurality of secondary air supply units 34. In FIG. 4, two measurement seats 59 are provided in the second flue 32, and gas sampling is performed in one measurement seat 59. The oxygen concentration, carbon monoxide concentration, carbon dioxide concentration and NOx concentration of the sampled gas are measured externally.

  When the prediction function is acquired in the incinerator 1a of FIG. 4, while the waste is burned, the values of a plurality of measurement parameters in the parameter value acquisition unit 5 (sampled gas oxygen concentration, carbon monoxide concentration, carbon dioxide concentration) And the measured value of the NOx concentration of the sampled gas is repeatedly obtained (FIG. 3: steps S11 and S12). The value of each measurement parameter and the measured value of the NOx concentration are normalized. The multiple regression analysis using the measured values of the NOx concentrations at a plurality of times as objective variables and the values of a plurality of measurement parameters corresponding to the measured values of the NOx concentrations at the plurality of times as explanatory variables uses the above equation (1). (Step S13).

  In this experiment, the flow rate of primary air acquired by each of the ten primary air measurement units 51, the total flow rate of primary air in the ten primary air measurement units 51, and the secondary air acquired by the secondary air measurement unit 53. , The total flow of primary air and secondary air, the temperatures acquired by the 13 thermometers 52 in the primary combustion chamber 2, and the two thermometers 54 in the secondary combustion chamber 3, respectively. The temperature, the temperature difference between the two thermometers 54, and the oxygen concentration, carbon monoxide concentration, and carbon dioxide concentration of the sampled gas are measurement parameters.

The results of the multiple regression analysis are shown in Table 1. Table 1 shows the measurement parameters with the coefficient a _i in Equation 1 being the first to sixth largest. “Primary air flow rate A” in Table 1 indicates the primary air flow rate by the primary air measurement unit denoted by reference numeral 51A in FIG. 4, and is expressed as “primary combustion chamber temperature A”, “primary combustion chamber temperature B”, “ “Primary combustion chamber temperature C” indicates a temperature measured by a thermometer denoted by reference numerals 52A, 52B, and 52C in FIG. “Secondary combustion chamber temperature A” indicates a temperature measured by a thermometer denoted by reference numeral 54A in FIG. “Oxygen concentration” indicates the oxygen concentration of the sampled gas.

  Here, in the primary combustion chamber 2, the thermometers 52A and 52C are located above the drying stage in the waste transport path, and the thermometer 52B is located above the combustion stage. The primary air measurement unit 51A measures the flow rate of primary air supplied toward the waste on the combustion stage. The reason why the coefficient with respect to the temperature by the thermometers 52A and 52C above the drying stage is large is considered that the thermal decomposition of waste in the drying stage affects the amount of NOx generated. The reason why the primary air flow rate by the primary air measurement unit 51A in the combustion stage and the coefficient for the temperature by the thermometer 52B are large is that the combustion state of waste in the combustion stage affects the amount of NOx generated. It is possible that The reason why the coefficient with respect to the temperature by the thermometer 54A arranged in the first flue 31 is large is that the nitrogen component in the first flue 31 (mainly nitrogen component contained in unburned gas such as ammonia derived from waste). It is conceivable that the reaction may affect the amount of NOx generated. The higher the oxygen concentration, the more likely the nitrogen in the waste becomes NOx, and the larger the coefficient for the oxygen concentration.

In this experiment, six measurement parameters shown in Table 1 are determined as a target parameter group (step S14). Then, the multiple regression analysis using the measured value of the NOx concentration of the sampled gas as the objective variable and the value of the target parameter group as the explanatory variable was performed again using Equation 1, and the coefficient a _i was determined in Equation 1. A function is acquired as a prediction function (step S15).

  FIG. 5 is a graph showing the relationship between the predicted value of NOx concentration indicated by the prediction function and the measured value of NOx concentration. In FIG. 5, three types of points are plotted, and waste is burned under different conditions. In FIG. 5, since the linearity is seen in the relationship between the predicted value of NOx concentration and the measured value of NOx indicated by the prediction function, it can be said that the NOx concentration can be accurately predicted by the prediction function.

  Here, a comparative example is assumed in which the flow rate of the reducing agent to be supplied into the secondary combustion chamber 3 is determined using the measured value of the NOx concentration measuring unit 71 provided in the discharge path 4 of FIG. In the NOx concentration measuring unit 71, it is difficult to measure the NOx concentration in the exhaust gas containing high-temperature exhaust gas or dust, so in the exhaust path 4, the downstream side (chimney 43 side) of the temperature reducing tower 41 and the bag filter 42. The NOx concentration measuring unit 71 is disposed at the center. Therefore, in the comparative example using the measurement value of the NOx concentration measuring unit 71, the flow rate of the reducing agent cannot be determined so as to follow the fluctuation of the NOx concentration in the secondary combustion chamber 3 in which the reducing agent supply unit 61 is provided. .

  In contrast, in the incinerator 1, the flow rate of primary air, the temperature of primary air, the temperature in the primary combustion chamber 2, the flow rate of secondary air, the temperature in the secondary combustion chamber 3, and the oxygen in the secondary combustion chamber 3. The parameter value acquisition unit 5 acquires the value of the measurement parameter using the concentration as the measurement parameter. The NOx concentration prediction unit 101 acquires the predicted value of the NOx concentration of the exhaust gas based on the prediction function prepared in advance and the value of the target parameter group that is the measurement parameter used in the prediction function. . Thereby, the NOx concentration change of the exhaust gas in the secondary combustion chamber 3 can be quickly predicted (detected) (that is, the current NOx concentration of the exhaust gas can be predicted quickly), and roughly follows the fluctuation of the NOx concentration. As described above, the flow rate of the reducing agent ejected from the reducing agent supply unit 61 can be determined. As a result, a high denitration rate in the exhaust gas is realized while suppressing an excessive increase in the concentration of the reducing agent in the exhaust gas discharged to the atmosphere.

  By the way, since the temperature in the primary combustion chamber 2 and the secondary combustion chamber 3 is lower in the stoker-type incinerator 1 than in the gasification melting furnace or the like, the amount of thermal NOx generated by the reaction of nitrogen in the air Is limited to some extent. On the other hand, fuel NOx generated by combustion of nitrogen in waste (including combustion of nitrogen components contained in unburned gas such as ammonia derived from waste) is almost always generated. The amount of fuel NOx generated is considered to be greatly influenced by the temperature in the primary combustion chamber 2. Therefore, from the viewpoint of accurately predicting the concentration of NOx including fuel NOx, it is preferable that the target parameter group includes the temperature in the primary combustion chamber 2. Further, it can be said that the temperature in the primary combustion chamber 2 includes the temperatures at a plurality of positions in the primary combustion chamber 2 so that the concentration of NOx including fuel NOx can be predicted more accurately. Of course, the NOx concentration predicted by the NOx concentration prediction unit 101 may include the concentration of thermal NOx.

  In the incinerator 1, a gas containing exhaust gas (hereinafter referred to as “EGR gas”) may be ejected in the primary combustion chamber 2. The EGR gas is, for example, a mixture of exhaust gas that has passed through the bag filter 42 and air. The EGR gas may be a gas containing only the exhaust gas. That is, EGR gas contains at least exhaust gas. In FIG. 1 and FIG. 4, the EGR gas supply part 25 which ejects EGR gas is shown with the broken line. The number and arrangement of the EGR gas supply units 25 may be changed as appropriate. When the EGR gas is ejected in the primary combustion chamber 2, the target parameter group used for obtaining the predicted value of the NOx concentration preferably includes the flow rate, temperature, or flow rate of the EGR gas. As a result, the NOx concentration can be predicted with higher accuracy in consideration of the EGR gas.

  Various modifications are possible in the incinerator 1.

In the above embodiment, the NOx concentration measurement value by the NOx concentration measurement unit 71 is an objective variable, and a multiple regression analysis using multiple measurement parameter values corresponding to the NOx concentration measurement value as explanatory variables facilitates a prediction function. However, the prediction function may be obtained by another analysis method or the like. In addition, as a model of the prediction function, an expression other than Equation 1 (for example, an expression including X _i ² ) may be used. Furthermore, a table that can specify the predicted value of the NOx concentration by referring to the value of the target parameter group may be used.

  From the viewpoint of obtaining the predicted value of the NOx concentration quickly and accurately, the target parameter group includes the flow rate of primary air, the temperature of the primary air, the temperature in the primary combustion chamber 2, and the secondary air, which are measurement parameters. Preferably, two or more explanatory variables are used, including two or more of the flow rate, the temperature in the secondary combustion chamber 3 and the oxygen concentration in the secondary combustion chamber 3. In this case, in order to obtain the NOx concentration including the NOx concentration generated in the primary combustion chamber 2 and the NOx concentration generated in the secondary combustion chamber 3 with higher accuracy, the target parameter group is: Including at least one of a flow rate of primary air, a temperature of primary air, and a temperature in primary combustion chamber 2, and a flow rate of secondary air, a temperature in secondary combustion chamber 3, and an oxygen concentration in secondary combustion chamber 3 It is preferable that at least one of these is included.

  The above-described method for obtaining the predicted value of the NOx concentration of exhaust gas based on the value of the target parameter group can be employed in an incinerator other than a stoker type incinerator (for example, a gasification melting furnace). In this case, from the viewpoint of predicting the concentration change of NOx including fuel NOx quickly and with a certain degree of accuracy, the target parameter group including the temperature in the primary combustion chamber 2 (only the temperature in the primary combustion chamber 2 is used). It is preferable that the predicted value of the NOx concentration of the exhaust gas is acquired based on the above.

  In the incinerator 1, the predicted value of the NOx concentration may be used for purposes other than determination of the flow rate of the reducing agent. For example, the flow rate of the primary air may be adjusted based on the predicted value of the NOx concentration, and the NOx concentration in the exhaust gas may be reduced.

  The configurations in the above-described embodiments and modifications may be combined as appropriate as long as they do not contradict each other.

DESCRIPTION OF SYMBOLS 1,1a Incinerator 2 Primary combustion chamber 3 Secondary combustion chamber 4 Exhaust path 5 Parameter value acquisition unit 71 NOx concentration measurement unit 101 NOx concentration prediction unit 224 Grate

Claims (7)

A stoker-type incinerator,
A primary combustion chamber in which primary air is supplied to the waste at each position of a waste transport path transported by a plurality of grate to burn the waste;
A secondary combustion chamber for supplying secondary air to unburned gas generated in the primary combustion chamber and burning the unburned gas;
An exhaust path for guiding exhaust gas discharged from the secondary combustion chamber to the atmosphere;
2 or more of the flow rate of the primary air, the temperature of the primary air, the temperature in the primary combustion chamber, the flow rate of the secondary air, the temperature in the secondary combustion chamber, and the oxygen concentration in the secondary combustion chamber. A parameter value acquisition unit for acquiring values of target parameter groups;
A NOx concentration prediction unit for obtaining a predicted value of the NOx concentration of the exhaust gas based on the value of the target parameter group;
A stoker-type incinerator characterized by comprising: A stoker-type incinerator according to claim 1,
The stoker type incinerator, wherein the target parameter group includes a temperature in the primary combustion chamber. A stoker-type incinerator according to claim 2,
The stoker-type incinerator, wherein the temperature in the primary combustion chamber includes temperatures at a plurality of positions in the primary combustion chamber. A stoker-type incinerator according to any one of claims 1 to 3,
The stoker-type incinerator, wherein the target parameter group includes a flow rate of the primary air, a temperature in the primary combustion chamber, a temperature in the secondary combustion chamber, and an oxygen concentration in the secondary combustion chamber. A stoker-type incinerator according to any one of claims 1 to 4,
EGR gas containing at least the exhaust gas is ejected in the primary combustion chamber,
The stoker type incinerator, wherein the target parameter group further includes a flow rate, a temperature, or a flow rate of the EGR gas. A stoker-type incinerator according to any one of claims 1 to 5,
A NOx concentration measuring unit that measures the NOx concentration of the exhaust gas in the exhaust path;
The parameter value acquisition unit acquires values of a plurality of measurement parameters including the target parameter group,
The function used for obtaining the predicted value of the NOx concentration in the NOx concentration prediction unit uses the measured value of the NOx concentration by the NOx concentration measurement unit at a plurality of times as an objective variable, and the function of the NOx concentration at the plurality of times. A stoker-type incinerator characterized by being obtained by multiple regression analysis using the values of the plurality of measurement parameters corresponding to measurement values as explanatory variables. An incinerator,
A primary combustion chamber for supplying primary air to burn waste,
A secondary combustion chamber for supplying secondary air to unburned gas generated in the primary combustion chamber and burning the unburned gas;
An exhaust path for guiding exhaust gas discharged from the secondary combustion chamber to the atmosphere;
A parameter value acquisition unit for acquiring a value of a target parameter group including the temperature in the primary combustion chamber;
A NOx concentration prediction unit for obtaining a predicted value of the NOx concentration of the exhaust gas based on the value of the target parameter group;
An incinerator characterized by comprising.

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