Combustion control method and combustion control device for waste incinerators

Abstract

A combustion control method for realizing stable combustion in a stoker-type waste incinerator is provided. This combustion control method includes a step of determining whether the temperature of the secondary combustion chamber 5 is higher or lower than a first set value, and a step of setting the recirculation gas rate to a first target value when the temperature of the secondary combustion chamber 5 is higher than the first set value, and setting the recirculation gas rate to a second target value when the temperature of the secondary combustion chamber 5 is lower than the first set value. Here, the first target value is set to a value larger than the second target value.

Description

[Technical field]

[0001] The present invention relates to a combustion control method and a combustion control device for a waste incinerator. [Background technology]

[0002] The following Patent Documents 1 and 2 describe stoker-type (grate-type) waste incinerators.

[0003] In the waste incinerator of Patent Document 1 below, the amount of air for secondary combustion is adjusted based on the gas temperature in the primary combustion chamber and the gas temperature in the secondary combustion chamber, thereby stabilizing combustion.

[0004] In the waste incinerator of Patent Document 2 listed below, the temperature in the secondary combustion chamber is stabilized by controlling the flow rate of exhaust gas (circulating exhaust gas) that is discharged from the secondary combustion zone and then returned to the secondary combustion zone. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] JP 2004-293840 A [Patent Document 2] International Publication No. WO2004 / 092648 Summary of the Invention [Problem to be solved by the invention]

[0006] In the technology of Patent Document 1, since the secondary combustion air is introduced from outside the incinerator, the amount of exhaust gas may vary significantly depending on the amount of secondary combustion air introduced. This may result in a shortage of equipment capacity to remove harmful substances in the exhaust gas, which may make plant operation difficult.

[0007] In the technology of Patent Document 2, since the flow rate of the circulating exhaust gas is controlled, the amount of exhaust gas may vary significantly depending on the flow rate. For this reason, as with the technology of Patent Document 1, there is a risk that plant operation may become difficult.

[0008] The present invention has been made in consideration of the above-mentioned circumstances. A main object of the present invention is to provide a technique for realizing stable combustion without causing large fluctuations in the amount of exhaust gas in a stoker-type waste incinerator. [Means for solving the problem]

[0009] The present invention can be expressed as the inventions described in the following items.

[0010] (Item 1) A combustion control method for a refuse incinerator having a forced draft blower, a dust feeder, a drying stoker, a combustion stoker, a post-combustion stoker, a primary combustion chamber, and a secondary combustion chamber, comprising: The combustion air sent from the forced draft fan is divided into primary air and secondary air, The primary air is further divided and supplied to the drying stoker, the combustion stoker, and the post-combustion stoker; The secondary air is supplied to the secondary combustion chamber, determining whether the temperature of the secondary combustion chamber is higher or lower than a first set value; and when the temperature of the secondary combustion chamber is higher than the first set value, setting the recirculation gas rate to a first target value, and when the temperature of the secondary combustion chamber is lower than the first set value, setting the recirculation gas rate to a second target value, Here, the recirculation gas ratio is a ratio of exhaust gas returned to the secondary combustion chamber to the exhaust gas discharged downstream from the secondary combustion chamber, The first target value is set to a value greater than the second target value. A method for controlling combustion in a waste incinerator.

[0011] (Item 2) Furthermore, the waste incinerator has a denitrification reaction tower for detoxifying nitrogen oxides in the exhaust gas discharged downstream from the secondary combustion chamber, determining whether the temperature of the denitration reaction tower is higher or lower than a second set value; setting the recirculation gas ratio to a third target value when the temperature of the denitration reaction tower is higher than the second set value, and setting the recirculation gas ratio to a fourth target value when the temperature of the denitration reaction tower is lower than the second set value; The method further includes a step of comparing the target values ​​set in each of the steps among the first to fourth target values, and adjusting the recirculation gas rate by using the larger target value as an actual target value, The fourth target value is set to a value greater than the third target value. Item 1. A method for controlling combustion in a waste incinerator.

[0012] (Item 3) The fourth target value is set to a value greater than the first target value. Item 2. A method for controlling combustion in a waste incinerator.

[0013] (Item 4) A combustion control device for a refuse incinerator having a forced draft blower, a dust feeder, a drying stoker, a combustion stoker, a post-combustion stoker, a primary combustion chamber, a secondary combustion chamber, and a treatment section, Further, a secondary combustion chamber thermometer for measuring a temperature of the secondary combustion chamber is provided, The combustion air sent from the forced draft fan is divided into primary air and secondary air, The primary air is further divided and supplied to the drying stoker, the combustion stoker, and the post-combustion stoker; The secondary air is supplied to the secondary combustion chamber, The processing unit is configured to determine whether the temperature of the secondary combustion chamber measured by the secondary combustion chamber thermometer is higher or lower than a first set value, and when the temperature of the secondary combustion chamber is higher than the first set value, to set a recirculation gas rate to a first target value, and when the temperature of the secondary combustion chamber is lower than the first set value, to set the recirculation gas rate to a second target value; Here, the recirculation gas ratio is a ratio of exhaust gas returned to the secondary combustion chamber to the exhaust gas discharged downstream from the secondary combustion chamber, The first target value is set to a value greater than the second target value. Combustion control device for waste incinerators. Effect of the Invention

[0014] According to the technology of the present invention, it is possible to achieve stable combustion in a stoker-type waste incinerator without causing large fluctuations in the amount of exhaust gas. [Brief description of the drawings]

[0015] [Figure 1] 1 is an explanatory diagram showing a schematic configuration of a waste incinerator according to one embodiment of the present invention; [Diagram 2] 1 is a schematic block diagram for showing the configuration of a main part of a waste incinerator according to one embodiment of the present invention. [Diagram 3] 2 is a flow chart for explaining the operation of a waste incinerator according to one embodiment of the present invention. [Figure 4] 2 is a flow chart for explaining the operation of a waste incinerator according to one embodiment of the present invention. [Diagram 5] 2 is a flow chart for explaining the operation of a waste incinerator according to one embodiment of the present invention. [Figure 6] 4 is a flow chart for explaining the transition of the target value of the recirculation gas rate by a waste incinerator according to one embodiment of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0016] Hereinafter, a stoker-type waste incinerator (hereinafter, sometimes referred to as a "waste incinerator" or "incinerator") according to one embodiment of the present invention will be described with reference to the accompanying drawings. Note that Fig. 1 is a schematic explanatory diagram, and the dimensional ratio and scale are not accurate.

[0017] (Configuration of the waste incinerator of this embodiment) The waste incinerator of this embodiment has a dust feeder 1, a drying stoker 2, a combustion stoker 3, a primary combustion chamber 4, and a secondary combustion chamber 5 (see FIG. 1). The waste incinerator also has a post-combustion stoker 6, a waste input hopper 7, a processing unit 8 (see FIG. 2), and a forced draft blower 9. The dust feeder 1, the drying stoker 2, the combustion stoker 3, and the post-combustion stoker 6 are configured to operate periodically (i.e., at a preset cycle) in response to a command from the processing unit 8. Here, the processing unit 8 acquires the actual amount of waste input to the dust feeder 1 by input from a user or by an appropriate detection device (not shown), and determines the operation cycle of the dust feeder 1, the drying stoker 2, the combustion stoker 3, and the post-combustion stoker 6 based on this amount of waste input. Specifically, if the actual amount of waste input to the dust feeder 1 is excessively large compared to a target value, the operation cycle is lengthened, and if the actual amount of waste input is too small compared to a target value, the operation cycle is shortened.

[0018] Furthermore, the waste incinerator of this embodiment has a primary combustion chamber thermometer 41 that measures the temperature in the primary combustion chamber 4, a secondary combustion chamber thermometer 51 that measures the temperature in the secondary combustion chamber 5, an oxygen concentration meter 52 that measures the oxygen concentration of the exhaust gas in the secondary combustion chamber 5, a carbon monoxide concentration meter 53 that measures the carbon monoxide concentration of the exhaust gas in the secondary combustion chamber 5, and a denitrification reaction tower thermometer 131 (described later) that measures the temperature of the denitrification reaction tower 13.

[0019] (Dust Feeding Device) The dust feeder 1 pushes the garbage input from the garbage input hopper 7 towards the drying stoker 2 at a preset cycle, thereby supplying garbage to the top of the drying stoker 2. Garbage is input into the garbage input hopper 7 by, for example, a crane (not shown). Here, "garbage" refers to waste that is collected from homes and the like and is to be incinerated. The collection routes and properties of waste (for example, moisture content) vary, and also differ depending on the region and time of year. This embodiment will be described assuming so-called "household garbage", but is not limited to this.

[0020] (forced draft blower) The forced draft fan 9 is for sending the combustion air into the inside of the incinerator. The combustion air from the forced draft fan 9 is divided into primary air and secondary air. The ratio of this division can be adjusted by the opening degree of the secondary air damper 10. The opening degree of the secondary air damper 10 is controlled by the processing unit 8.

[0021] (Drying stoker, Combustion stoker, Post-combustion stoker) Primary air preheated by an air preheater 19 is supplied to the drying stoker 2, the combustion stoker 3, and the post-combustion stoker 6 via the corresponding forced air dampers 21, 31, and 61. The drying stoker 2 dries the supplied waste with the primary air. The combustion stoker 3 combusts the waste supplied from the drying stoker 2 by supplying primary air to the waste. The post-combustion stoker 6 cools the ash generated by combustion in the combustion stoker 3, and further combusts the unburned matter that was not completely burned in the combustion stoker 3. The opening degree of the forced air dampers 21, 31, and 61 is controlled by the processing unit 8.

[0022] Furthermore, the drying stoker 2, the combustion stoker 3, and the post-combustion stoker 6 are each provided with a garbage layer level sensor 22, 32, 62, which is capable of detecting the garbage height (level) on each stoker. The outputs of the garbage layer level sensors 22, 32, 62 are sent to the processing unit 8. As a result, when the garbage height on any of the stokers is too high (for example, exceeds a certain set value), the operating cycle of that stoker is changed in the processing unit 8 so as to shorten the operating cycle, thereby promoting the combustion of the garbage.

[0023] (Primary and secondary combustion chambers) Exhaust gas from the primary combustion chamber 4 is sent to the secondary combustion chamber 5, where unburned fuel in the exhaust gas is combusted. Secondary air branched off from the primary air is supplied to the secondary combustion chamber 5 via a secondary air damper 10. Downstream of the secondary combustion chamber 5 is a boiler 11 having a superheater and the like for recovering heat from the exhaust gas.

[0024] Exhaust gas from the boiler 11 in the secondary combustion chamber 5 passes through a bag filter 12, a denitrification reaction tower 13, an induced draft fan 14, a chimney damper 16, etc., and is discharged in a harmless state from a chimney 17.

[0025] (Denitrification tower) The denitration reaction tower 13 is for promoting the reaction between nitrogen oxides (NOx) in the exhaust gas and ammonia with a catalyst to render the exhaust gas harmless. A denitration reaction tower thermometer 131 is attached near the denitration reaction tower 13 to measure the temperature of the denitration reaction tower 13 (more specifically, the temperature of the exhaust gas immediately after it is discharged from the denitration reaction tower 13).

[0026] (concentration measurement) The chimney 17 is fitted with instruments 18 for measuring the concentrations of various substances in the exhaust gas. Specifically, the instruments 18 used in this embodiment include a hydrogen chloride concentration meter 181, a sulfur oxide concentration meter 182, a nitrogen oxide concentration meter 183, a carbon monoxide concentration meter 184, an oxygen concentration meter 185, and a moisture concentration (water vapor concentration) meter 186. Of these, the hydrogen chloride concentration meter 181, the nitrogen oxide concentration meter 183, and the sulfur oxide concentration meter 182 measure the concentrations of harmful substances (hydrogen chloride, nitrogen oxides, and sulfur oxides) in the exhaust gas, and function as harmful substance concentration sensors.

[0027] (Exhaust gas recirculation damper) A part of the exhaust gas downstream of the induced draft fan 14 is returned to the secondary combustion chamber 5 via an exhaust gas recirculation damper 15. The opening degree of the exhaust gas recirculation damper 15 is controlled by the processing unit 8, so that the processing unit 8 of this embodiment can control the recirculation gas rate. Here, the recirculation gas rate is the proportion of exhaust gas returned to the secondary combustion chamber 5 out of the exhaust gas discharged downstream from the secondary combustion chamber 5. Note that an exhaust gas circulation blower (not shown) can be used instead of the exhaust gas recirculation damper 15.

[0028] (Processing section) The processing unit 8 (see FIG. 2) receives measurement values ​​from various meters (such as a thermometer and a concentration meter) in the incinerator of this embodiment.

[0029] The processing unit 8 of this embodiment is adapted to determine whether the temperature of the secondary combustion chamber 5 is higher or lower than a first set value, and when the temperature of the secondary combustion chamber 5 is higher than the first set value, to set the recirculation gas ratio to a first target value, and when the temperature of the secondary combustion chamber 5 is lower than the first set value, to set the recirculation gas ratio to a second target value. Here, the first target value is set to a value larger than the second target value.

[0030] The processing unit 8 of this embodiment may be computer hardware, computer software, or a combination of these. The processing unit 8 may be a combination of multiple functional elements, or may be implemented by multiple functional elements distributed in remote locations. The detailed operation of the processing unit 8 will be described later as the operation of the waste incinerator according to this embodiment.

[0031] Moreover, the overall configuration of the waste incinerator, excluding the treatment section 8, can be the same as that of a conventional waste incinerator, and therefore a more detailed explanation of the waste incinerator as a whole will be omitted.

[0032] (Operation of the waste incinerator of this embodiment) Next, the operation of the above-mentioned waste incinerator will be further explained with reference to FIGS.

[0033] (During normal operation) In the waste incinerator of this embodiment, the dust feeder 1, drying stoker 2, combustion stoker 3, and post-combustion stoker 6 operate at a preset cycle (for example, every 5 minutes) to periodically feed waste into the primary combustion chamber 4 and agitate and burn the waste. This is similar to conventional waste incinerators. In this embodiment, this preset cycle is determined by the processing unit 8.

[0034] Here, in the waste incinerator of this embodiment, the processing unit 8 judges whether the temperature of the secondary combustion chamber 5 is higher or lower than a first set value (described later). Also, in the waste incinerator of this embodiment, the processing unit 8 judges whether the temperature of the denitrification reaction tower 13 is higher or lower than a second set value (described later).

[0035] (Operation based on secondary combustion chamber temperature) The processing unit 8 receives the temperature of the secondary combustion chamber 5 from the secondary combustion chamber thermometer 51, and determines whether the temperature of the secondary combustion chamber 5 is higher or lower than the first set value as described above (step SA-1 in FIG. 3).

[0036] When the temperature of the secondary combustion chamber 5 is higher than the first set value, the processor 8 sets the recirculated gas rate to a first target value (step SA-2 in FIG. 3). When the temperature of the secondary combustion chamber is lower than the first set value, the processor 8 sets the recirculated gas rate to a second target value (step SA-3 in FIG. 3). Here, as described above, the first target value is set to a value larger than the second target value. However, as described later, in this embodiment, the actual target value for the recirculated gas rate is determined by comparing it with a target value (described later) based on the temperature of the denitration reaction tower.

[0037] The first set value is, for example, any value between 900 and 950° C., but is not limited to this.

[0038] The first target value is, for example, a recirculation gas ratio of 25%, and the second target value is, for example, a recirculation gas ratio of 20%, but is not limited thereto. Different values ​​can be used depending on the plant conditions and operation policies.

[0039] (Operation based on denitration tower temperature) The processing unit 8 receives the temperature of the denitration reaction tower 13 from the denitration reaction tower thermometer 131, and determines whether the temperature of the denitration reaction tower 13 is higher or lower than the second set value as described above (step SB-1 in FIG. 4).

[0040] When the temperature of the denitration reaction tower 13 is higher than the second set value, the recirculation gas ratio is set to a third target value (step SB-2 in FIG. 4). When the temperature of the denitration reaction tower 13 is lower than the second set value, the recirculation gas ratio is set to a fourth target value (step SB-3 in FIG. 4). Here, the fourth target value is set to a value larger than the third target value.

[0041] The second set value is, for example, any value between 185 and 190° C., but is not limited to this.

[0042] The third target value is, for example, a recirculation gas rate of 20%, and the fourth target value is, for example, a recirculation gas rate of 30%, but is not limited to these values. Different values ​​can be used depending on the plant conditions and operation policies. In this embodiment, the second target value and the third target value are the same, but they may be different values.

[0043] (Determining the actual target value) At least two target values ​​can be provisionally obtained by the above-mentioned steps SA-1 to SA-3 and SB-1 to SB-3. In this case, the processing unit 8 of this embodiment compares the two target values ​​(corresponding to the "target values ​​set in each step" in the present invention) with each other, and sets the larger target value as the actual target value. Furthermore, the processing unit 8 uses this actual target value to adjust the opening of the exhaust gas recirculation damper 15 and adjust the recirculation gas rate. Here, if the recirculation gas rate does not increase even if the opening of the exhaust gas circulation damper 15 is increased to an opening exceeding 70%, for example, the recirculation gas rate can be increased by reducing the opening of the chimney damper 16 (i.e., closing the chimney damper 16).

[0044] In this embodiment, the combustion air from the forced draft blower 9 is divided into primary air and secondary air, so the overall amount of combustion air is maintained almost constant. Furthermore, in this embodiment, the recirculation gas rate is adjusted, so the fluctuation in the amount of exhaust gas that is the target of harmful substance removal can be suppressed to a low level. This has the advantage that the operation of the denitrification reaction tower 13 and chemical injection in the harmful substance removal becomes easier to manage, and the plant becomes easier to operate. On the other hand, if secondary air is introduced from the outside, the amount of combustion air itself fluctuates greatly. In addition, if the recirculation gas amount is adjusted instead of the recirculation gas rate, the amount of exhaust gas that is the target of harmful substance removal may fluctuate greatly, making it difficult to manage the operation of the denitrification reaction tower 13 and chemical injection in the harmful substance removal, and the plant operation may become complicated.

[0045] In addition, in this embodiment, the target value can be changed depending on the temperature of the denitration reaction tower 13, so that the function of the denitration reaction tower 13 can be easily maintained. Here, in this embodiment, as described above, the fourth target value (specifically, 30%) is set to a value greater than the third target value (specifically, 20%). As a premise, when the temperature of the denitration reaction tower 13 drops, the activity of the denitration catalyst drops, and the efficiency of the denitration reaction deteriorates. When the recirculation gas rate increases, the amount of exhaust gas sent to the denitration reaction tower 13 increases slightly, so that it becomes easier to maintain the temperature of the exhaust gas from the secondary combustion chamber 5 to the denitration reaction tower 13, and it becomes easier to maintain the temperature of the denitration reaction tower 13 at a high temperature. This makes it possible to maintain the function of the denitration reaction tower 13. On the other hand, in this embodiment, since the recirculation gas rate is adjusted instead of the amount of recirculation gas, there is an advantage that the fluctuation in the amount of exhaust gas can be suppressed low as described above, and the complexity of plant operation can be avoided.

[0046] Furthermore, in this embodiment, when the temperature of the secondary combustion chamber 5 is higher than the first set value, the recirculation gas rate can be increased (see step SA-2 in FIG. 3). Since the temperature of the recirculation gas is generally lower than the temperature of the secondary combustion chamber 5, this embodiment can prevent overheating of the secondary combustion chamber 5. Also, in this embodiment, when the temperature of the secondary combustion chamber 5 is lower than the first set value, the recirculation gas rate can be decreased (see step SA-3 in FIG. 3). As a result, this embodiment can prevent a decrease in the temperature of the secondary combustion chamber 5.

[0047] On the other hand, in this embodiment, of the provisionally set target values, a higher target value is adopted as the actual target value (see step SC-2 in FIG. 5). Adopting a higher target value ultimately means that maintaining the temperature of the denitration reaction tower 13 takes priority over adjusting the temperature of the secondary combustion chamber 5. For example, even if the second target value (specifically, a recirculation gas rate of 20%) is obtained in step SA-3, if the state is as in step SB-3, the fourth target value (specifically, a recirculation gas rate of 30%) will be adopted. As a result, in this embodiment, the temperature of the denitration reaction tower 13 can be made high, and as a result, plant operation that prioritizes suppression of the concentration of harmful substances becomes possible.

[0048] In this embodiment, the fourth target value is set to a value larger than the first target value. That is, even if the first target value is obtained as the recirculation gas rate required for suppressing the temperature of the secondary combustion chamber 5 (step SA-2 in FIG. 3), if the temperature of the denitration reaction tower 13 is too low (step SB-3 in FIG. 4), the fourth target value is used (step SC-2 in FIG. 5). As a result, the operation of the denitration reaction tower 13 is prioritized, and the recirculation gas rate can be further increased. In this respect, too, it is possible to operate the plant with priority given to suppression of the concentration of harmful substances.

[0049] The transition state of the recirculation gas rate finally adopted by the above-mentioned operation is shown in FIG.

[0050] The above embodiment is merely an example, and does not represent essential configurations of the present invention. The configurations of the various components are not limited to those described above, as long as they can achieve the gist of the present invention.

[0051] In the above embodiment, the first or second target value is compared with the third or fourth target value to determine the actual target value, but it is possible to set the first or second target value as the actual target value without performing this comparison. In this case, the temperature of the denitration reaction tower 13 is not taken into consideration.

[0052] Also, for example, it is possible to operate the system based on the first or second target value during normal operation (see FIG. 3), and when the third or fourth target value is set (see FIG. 4), compare the obtained target value (see FIG. 5) to adjust the recirculation gas rate. Conversely, it is also possible to operate the system based on the third or fourth target value during normal operation, and when the first or second target value is set, compare the obtained target value to adjust the recirculation gas rate.

[0053] In this specification, "higher" or "lower" than the set value includes the case where the value is the same as the set value. Therefore, when the value is the same as the set value, whether to judge it to be on the high or low side can be appropriately determined according to the operation policy. [Explanation of symbols]

[0054] 1 Dust Feeding Device 2. Drying Stoker 21 Drying stoker forced air damper 22 Drying stoker garbage layer level sensor 3 Combustion Stoker 31 Combustion stoker forced air damper 32 Combustion stoker garbage layer level sensor 4 Primary Combustion Chamber 41 Primary combustion chamber thermometer 5 Secondary Combustion Chamber 51 Secondary combustion chamber thermometer 52 Exhaust gas oxygen concentration meter 53 Exhaust gas carbon monoxide concentration meter 6 Post-combustion stoker 61 Post-combustion stoker forced air damper 62 Post-combustion stoker garbage layer level sensor 7 Garbage hopper 8 Processing section 9. Forced draft blower 10 Secondary air damper 11 Boiler 12 Bag filter 13 Denitrification tower 131 Denitrification reaction tower thermometer 14 Induced draft fan 15 Exhaust gas recirculation damper 16 Chimney damper 17 Chimney 18 Instruments 181 Hydrogen chloride concentration meter 182 Sulfur oxide concentration meter 183 Nitrogen oxide concentration meter 184 Carbon monoxide concentration meter 185 Oxygen Concentration Meter 186 Moisture concentration (water vapor concentration) meter 19 Air preheater

Claims

1. A combustion control method for a refuse incinerator having a forced draft blower, a dust feeder, a drying stoker, a combustion stoker, a post-combustion stoker, a primary combustion chamber, and a secondary combustion chamber, comprising: The combustion air sent from the forced draft fan is divided into primary air and secondary air, The primary air is further divided and supplied to the drying stoker, the combustion stoker, and the post-combustion stoker; The secondary air is supplied to the secondary combustion chamber, determining whether the temperature of the secondary combustion chamber is higher or lower than a first set value; and setting a recirculation gas rate to a first target value when the temperature of the secondary combustion chamber is higher than the first set value, and setting the recirculation gas rate to a second target value when the temperature of the secondary combustion chamber is lower than the first set value, Here, the recirculation gas ratio is a ratio of exhaust gas returned to the secondary combustion chamber to the exhaust gas discharged downstream from the secondary combustion chamber, The first target value is set to a value greater than the second target value. A method for controlling combustion in a waste incinerator.

2. Furthermore, the waste incinerator has a denitrification reaction tower for detoxifying nitrogen oxides in the exhaust gas discharged downstream from the secondary combustion chamber, determining whether the temperature of the denitration reaction tower is higher or lower than a second set value; setting the recirculation gas ratio to a third target value when the temperature of the denitration reaction tower is higher than the second set value, and setting the recirculation gas ratio to a fourth target value when the temperature of the denitration reaction tower is lower than the second set value; and comparing the first to fourth target values ​​set in each of the steps with each other and adjusting the recirculation gas rate by using the larger target value as an actual target value, The fourth target value is set to a value greater than the third target value.

2. The method for controlling combustion in a waste incinerator according to claim 1.

3. The fourth target value is set to a value greater than the first target value.

3. The method for controlling combustion in a waste incinerator according to claim 2.

4. A combustion control device for a refuse incinerator having a forced draft blower, a dust feeder, a drying stoker, a combustion stoker, a post-combustion stoker, a primary combustion chamber, a secondary combustion chamber, and a treatment section, Further, a secondary combustion chamber thermometer for measuring the temperature of the secondary combustion chamber is provided, The combustion air sent from the forced draft fan is divided into primary air and secondary air, The primary air is further divided and supplied to the drying stoker, the combustion stoker, and the post-combustion stoker; The secondary air is supplied to the secondary combustion chamber, the processing unit is configured to determine whether the temperature of the secondary combustion chamber measured by the secondary combustion chamber thermometer is higher or lower than a first set value, and when the temperature of the secondary combustion chamber is higher than the first set value, to set a recirculation gas rate to a first target value, and when the temperature of the secondary combustion chamber is lower than the first set value, to set the recirculation gas rate to a second target value; Here, the recirculation gas ratio is a ratio of exhaust gas returned to the secondary combustion chamber to the exhaust gas discharged downstream from the secondary combustion chamber, The first target value is set to a value greater than the second target value. Combustion control device for waste incinerators.

Images