Combustion control method and combustion control device for refuse incinerator

Abstract

To provide a combustion control method that enables stable combustion in a stoker type refuse incinerator.SOLUTION: A combustion control method includes processes of: determining whether or not a moisture concentration in exhaust gas discharged from a secondary combustion chamber 5 is higher than a first set value; and increasing a ratio of primary air to be fed to a drying stoker 2 out of primary air to be fed to the drying stoker 2, a combustion stoker 3 and a post-combustion stoker 6 when the moisture concentration in the exhaust gas discharged from the secondary combustion chamber 5 is higher than the first set value.SELECTED DRAWING: Figure 1

Description

Technical Field

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

Background Art

[0002] The following Patent Document 1 describes a stoker-type (grate-type) garbage incinerator. In this garbage incinerator, the amount of secondary combustion air is adjusted based on the gas temperature in the primary combustion chamber and the gas temperature in the secondary combustion chamber, etc., thereby achieving combustion stabilization.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] The properties of the garbage input into the garbage incinerator are not constant. Therefore, a further method for realizing stable combustion is required.

[0005] The present invention has been made in view of the above-described situation. The main object of the present invention is to provide a technique for realizing stable combustion in a stoker-type garbage incinerator.

Means for Solving the Problems

[0006] The present invention can be expressed as the invention described in the following items.

[0007] (Item 1) A combustion control method for a garbage incinerator having a forced draft fan, a dust feeder, a drying stoker, a combustion stoker, a post-combustion stoker, a primary combustion chamber, and a secondary combustion chamber, The combustion air sent from the forced blower is distributed into primary air and secondary air, and the primary air is further distributed and supplied to the drying stoker, the combustion stoker, and the afterburning stoker. The secondary air is supplied to the secondary combustion chamber. a step of determining whether a moisture concentration in exhaust gas discharged from the secondary combustion chamber is higher than a first set value; when the moisture concentration in the exhaust gas discharged from the secondary combustion chamber is higher than the first set value, increasing a ratio of the primary air sent to the drying stoker, the combustion stoker, and the afterburning stoker to the drying stoker; A combustion control method for a garbage incinerator, comprising:

[0008] (Item 2) a step of determining whether an oxygen concentration in the exhaust gas is lower than a second set value; when the oxygen concentration in the exhaust gas is lower than the second set value, increasing a ratio of the secondary air in the combustion air, reducing a ratio of the primary air sent to the combustion stoker among the primary air sent to the drying stoker, the combustion stoker, and the afterburning stoker, and increasing a ratio of the primary air sent to the afterburning stoker; The combustion control method for a garbage incinerator according to Item 1, further comprising:

[0009] (Item 3) a step of determining whether a temperature in the primary combustion chamber is higher than a third set value; when the temperature in the primary combustion chamber is higher than the third set value, reducing a ratio of the primary air sent to the combustion stoker among the primary air sent to the drying stoker, the combustion stoker, and the afterburning stoker, and increasing a ratio of the primary air sent to the afterburning stoker; The combustion control method for a garbage incinerator according to Item 1 or 2, further comprising:

[0010] (Item 4) A step of determining whether the oxygen concentration in the exhaust gas is higher than a fourth set value; When the oxygen concentration in the exhaust gas is higher than the fourth set value, among the combustion air, a process of reducing the ratio of the secondary air, and among the primary air sent to the drying stoker, the combustion stoker, and the afterburning stoker, a process of increasing the ratio to the combustion stoker and reducing the ratio to the afterburning stoker; The combustion control method of the garbage incinerator according to item 1 or 2, further comprising this.

[0011] (Item 5) A step of determining whether the temperature in the primary combustion chamber is lower than a fifth set value; When the temperature in the primary combustion chamber is lower than the fifth set value, among the primary air sent to the drying stoker, the combustion stoker, and the afterburning stoker, a step of increasing the ratio to the combustion stoker and reducing the ratio to the afterburning stoker; The combustion control method of the garbage incinerator according to item 1 or 2, further comprising this.

[0012] (Item 6) The combustion stoker is configured to operate periodically, During the operation of the combustion stoker, further comprising a step of increasing the ratio of the secondary air among the combustion air. The combustion control method of the garbage incinerator according to item 1 or 2.

[0013] (Item 7) A step of determining whether the concentration of harmful substances in the exhaust gas discharged from the secondary combustion chamber is higher than a sixth set value; When it is determined that the concentration of harmful substances in the exhaust gas discharged from the secondary combustion chamber is higher than the sixth set value, among the primary air sent to the drying stoker, the combustion stoker, and the afterburning stoker, a step of reducing the ratio to the combustion stoker; The combustion control method of the garbage incinerator according to item 1 or 2, further comprising this.

[0014] (Item 8) A step of determining whether the concentration of harmful substances in the exhaust gas discharged from the secondary combustion chamber is higher than a sixth set value; When it is determined that the concentration of harmful substances in the exhaust gas discharged from the secondary combustion chamber is higher than the sixth set value, a step of reducing the amount of combustion air sent from the forced blower; The combustion control method for a garbage incinerator according to item 1 or 2, further comprising the above.

[0015] (Item 9) A combustion control device for a garbage incinerator having a forced blower, a dust feeder, a drying stoker, a combustion stoker, a post-combustion stoker, a primary combustion chamber, and a secondary combustion chamber, The combustion air sent from the forced blower is distributed into primary air and secondary air, The primary air is further distributed and supplied to the drying stoker, the combustion stoker, and the post-combustion stoker, The secondary air is supplied to the secondary combustion chamber, It further has a processing unit, When the moisture concentration in the exhaust gas discharged from the secondary combustion chamber is higher than a first set value, the processing unit increases the ratio of the primary air sent to the drying stoker, the combustion stoker, and the post-combustion stoker to the drying stoker. It is configured to perform the process of increasing the ratio, A combustion control device for a garbage incinerator.

Advantages of the Invention

[0016] According to the technology of the present invention, stable combustion can be realized in a stoker-type garbage incinerator.

Brief Description of the Drawings

[0017]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

Mode for Carrying Out the Invention

[0018] Hereinafter, a stoker-type garbage incinerator (hereinafter sometimes referred to as "garbage incinerator" or "incinerator") according to an 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.

[0019] (Configuration of the garbage incinerator of this embodiment) The garbage incinerator of this embodiment has a feeding device 1, a drying stoker 2, a combustion stoker 3, a primary combustion chamber 4, and a secondary combustion chamber 5 (see Fig. 1). Further, this garbage incinerator has a post-combustion stoker 6, a garbage input hopper 7, a processing unit 8 (see Fig. 2), and a forced draft fan 9. The feeding device 1, the drying stoker 2, the combustion stoker 3, and the post-combustion stoker 6 are configured to operate periodically (i.e., at a predetermined cycle) according to commands from the processing unit 8. Here, the processing unit 8 acquires the actual garbage input amount to the feeding device 1 through input from the user or an appropriate detection device (not shown), and determines the operation cycles of the feeding device 1, the drying stoker 2, the combustion stoker 3, and the post-combustion stoker 6 based on this garbage input amount. Specifically, if the actual garbage input amount to the feeding device 1 is excessive compared to the target value, the operation cycle is lengthened, and if the actual garbage input amount is too small compared to the target value, the operation cycle is shortened.

[0020] Furthermore, the garbage incinerator of this embodiment has a primary combustion chamber thermometer 41 for measuring the temperature inside the primary combustion chamber 4, a secondary combustion chamber thermometer 51 for measuring the temperature inside the secondary combustion chamber 5, an oxygen concentration meter 52 for measuring the oxygen concentration of the exhaust gas inside the secondary combustion chamber 5, a carbon monoxide concentration meter 53 for measuring the carbon monoxide concentration of the exhaust gas inside the secondary combustion chamber 5, and a moisture concentration meter 186 (described later) for measuring the moisture concentration in the exhaust gas.

[0021] (Feeding device) The feeding device 1 pushes the garbage input from the garbage input hopper 7 toward the drying stoker 2 at a predetermined cycle, so that the garbage can be supplied to the upper part 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 to be collected from homes and incinerated. The collection routes and properties (e.g., moisture content) of waste are diverse and also vary depending on the region and time. In this embodiment, the so-called "household garbage" is used as a premise for explanation, but it is not restricted to this.

[0022] (Forced draft fan) The forced draft fan 9 is for sending combustion air into the garbage 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 can be adjusted by the processing unit 8.

[0023] (Dry stoker, combustion stoker, afterburning stoker) For the dry stoker 2, combustion stoker 3, and afterburning stoker 6, primary air preheated by the air preheater 19 is supplied through the corresponding forced draft air dampers 21, 31, and 61 respectively. The dry stoker 2 dries the supplied garbage with the primary air. The combustion stoker 3 burns the garbage by supplying primary air to the garbage supplied from the dry stoker 2. The afterburning stoker 6 cools the ash generated by the combustion in the combustion stoker 3 and further burns the unburned components that were not completely burned in the combustion stoker 3. The opening degrees of the forced draft air dampers 21, 31, and 61 are controlled by the processing unit 8.

[0024] Also, garbage layer level sensors 22, 32, and 62 are installed on the dry stoker 2, combustion stoker 3, and afterburning stoker 6 respectively, so that the height (level) of the garbage on each stoker can be detected. The outputs of the garbage layer level sensors 22, 32, and 62 are sent to the processing unit 8. Thereby, when the garbage height on any of the stokers is too high (for example, exceeding a certain set value), the operating cycle of the corresponding stoker is changed in the processing unit 8 so that the operating cycle becomes shorter, and the combustion of the garbage can be promoted.

[0025] (Primary combustion chamber and secondary combustion chamber) The exhaust gas from the primary combustion chamber 4 is sent to the secondary combustion chamber 5, where the unburned components in the exhaust gas are burned. Secondary air branched from the primary air is supplied to the secondary combustion chamber 5 through the secondary air damper 10. The downstream side of the secondary combustion chamber 5 is a boiler 11 having a superheater or the like for recovering the heat of the exhaust gas.

[0026] (Exhaust gas discharge path) The exhaust gas from the boiler 11 in the secondary combustion chamber 5 is discharged from the chimney 17 in a detoxified state through the bag filter 12, the denitration reaction tower 13, the induced draft fan 14, the chimney damper 16, etc. An instrument 18 for measuring the concentration of substances in various exhaust gases is attached to the chimney 17. Specifically, as the instrument 18 of the present embodiment, 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 are used. Among these, the hydrogen chloride concentration meter 181, the nitrogen oxide concentration meter 183, and the sulfur oxide concentration meter 182 measure the concentration of harmful substances (hydrogen chloride, nitrogen oxides, sulfur oxides) in the exhaust gas and function as harmful substance concentration sensors.

[0027] A part of the exhaust gas on the downstream side of the induced draft fan 14 is returned to the secondary combustion chamber 5 through the exhaust gas recirculation damper 15.

[0028] (Treatment unit) The treatment unit 8 (see FIG. 2) is configured to receive measurement values from various instruments (such as a thermometer and a concentration meter) in the incinerator of the present embodiment. Further, the treatment unit 8 determines whether the moisture concentration in the exhaust gas discharged from the secondary combustion chamber 5 is higher than a first set value, and when this moisture concentration is higher than the first set value, it performs a process of increasing the ratio of the primary air to the dry stoker 2. As the treatment unit 8 of the present embodiment, computer hardware, computer software, or a combination thereof can be used. The treatment unit 8 may be a combination of a plurality of functional elements, or may be implemented by a plurality of functional elements distributed at remote locations. The detailed operation of the treatment unit 8 will be described later as the operation of the garbage incinerator according to the present embodiment.

[0029] In addition, since the overall configuration of the garbage incinerator excluding the treatment unit 8 can be the same as that of the conventional one, a more detailed description of the entire garbage incinerator is omitted.

[0030] (Operation of the garbage incinerator of this embodiment) Next, the operation of the above-described garbage incinerator will be further described with reference to FIGS. 3 to 8.

[0031] (During steady operation) In the garbage incinerator of this embodiment, the dust feeder 1, the drying stoker 2, the combustion stoker 3, and the afterburning stoker 6 operate at a predetermined cycle (for example, at 5-minute intervals), and the garbage is periodically charged into the primary combustion chamber 4 and can be stirred and burned. This is the same as a conventional garbage incinerator. Note that this predetermined cycle is determined by the processing unit 8 in this embodiment.

[0032] Here, in the garbage incinerator of this embodiment, the processing unit 8 determines whether the moisture concentration in the exhaust gas discharged from the secondary combustion chamber 5 (specifically, the moisture concentration measured by the moisture concentration meter 186) is higher than a first set value.

[0033] Also, in the garbage incinerator of this embodiment, the following determinations by the processing unit 8 are performed in parallel. · Whether the oxygen concentration in the exhaust gas is lower than a second set value; · Whether the temperature in the primary combustion chamber 4 is higher than a third set value; · Whether the oxygen concentration in the exhaust gas is higher than a fourth set value; · Whether the temperature in the primary combustion chamber 4 is lower than a fifth set value; · Whether the concentration of harmful substances in the exhaust gas discharged from the secondary combustion chamber 5 is higher than a sixth set value.

[0034] These determinations are performed at a cycle shorter than the operation cycle of the dust feeder 1 or the like. For example, it is preferably performed at a cycle within 1 / 10 of the operation cycle of the dust feeder 1 or the like, more preferably within 1 / 100. It is not necessary for the cycles of each determination to be the same, and they may be different.

[0035] (During combustion abnormality 1) When the processing unit 8 determines that the moisture concentration in the exhaust gas discharged from the secondary combustion chamber 5 is higher than the first set value (step SA-1 in FIG. 3), the processing unit 8 increases the ratio of the primary air sent to the drying stoker 2, the combustion stoker 3, and the afterburning stoker 6 to the drying stoker 2 (step SA-2 in FIG. 3). Specifically, the processing unit 8 · increases the opening degree of the drying stoker pushing air damper 21, and / or · reduces the opening degrees of the combustion stoker pushing air damper 31 and the afterburning stoker pushing air damper 61 By performing such processing, the ratio of the primary air to the drying stoker 2 is increased.

[0036] As a specific example of the first set value for the moisture concentration, it is any value between 20% and 25%, but it is not limited to this. In the present embodiment, the moisture concentration of the exhaust gas discharged from the chimney 17 measured by the moisture concentration meter 186 is used, but it is not limited to this. For example, the moisture concentration of the exhaust gas at the outlet of the secondary combustion chamber 5 or in the exhaust gas path from the secondary combustion chamber 5 to the chimney 17 may be used. The first set value can be set according to the measurement location of the moisture concentration.

[0037] The fact that the moisture concentration in the exhaust gas is higher than the first set value means that the moisture content of the garbage input from the garbage supply device 1 is excessive. In the present embodiment, by increasing the ratio of the primary air to the drying stoker 2, the drying of the garbage can be promoted. Then, good combustion of the garbage by the combustion stoker 3 can be promoted.

[0038] Here, in the present embodiment, the combustion air from the forced blower 9 is distributed into primary air and secondary air, and the distributed primary air is further distributed to the drying stoker 2, the combustion stoker 3, and the afterburning stoker 6. Therefore, even if the proportion of the primary air to the drying stoker 2 increases, the total amount of the combustion air is maintained almost constant. For example, in the case of a configuration in which the secondary air is introduced separately from the primary air by another blower, the total amount of the combustion air can greatly vary. On the other hand, it is difficult to greatly change the dosage of the harmful gas removal agent for the exhaust gas. For this reason, there is a risk that the harmful gas concentration will greatly vary due to the variation in the combustion air volume. In contrast, according to the present embodiment, since the total amount of the combustion air can be maintained almost constant, there is an advantage that the variation in the harmful gas concentration can be suppressed while promoting good combustion.

[0039] Furthermore, in the present embodiment, since the primary air is distributed to the drying stoker 2, the combustion stoker 3, and the afterburning stoker 6, the proportion of the primary air sent to the combustion stoker 3 and the afterburning stoker 6 will decrease by the amount by which the proportion of the primary air sent to the drying stoker 2 increases. Thereby, in the present embodiment, there is also an advantage that the variation in the exhaust gas volume can be suppressed and the management of the plant becomes easy.

[0040] Thereafter, when the moisture concentration in the exhaust gas becomes lower than the first set value (that is, when it returns to the normal value), the processing unit 8 returns the proportion of the primary air sent to the drying stoker 2, the combustion stoker 3, and the afterburning stoker 6 (that is, the distribution ratio of the primary air).

[0041] In addition, in this specification, "increasing the ratio" or "decreasing the ratio" may not only mean simply changing the target value stepwise, but also controlling proportionally. For example, when the moisture concentration in the exhaust gas is 20%, the opening degree of the drying stoker forced air damper 31 is set to 2%, and when the moisture concentration is 25%, the opening degree of the drying stoker forced air damper 31 is set to 10%, and the damper opening degree in between may be determined proportionally according to the moisture concentration.

[0042] (During abnormal combustion 2) When the processing unit 8 determines that the oxygen concentration in the exhaust gas is lower than the second set value (step SB-1 in FIG. 4), the processing unit 8 performs processing to increase the ratio of secondary air in the combustion air, and among the primary air, reduces the ratio to the combustion stoker 3 and increases the ratio to the afterburning stoker 6 (steps SB-2 to SB-4 in FIG. 4). These operations can also be performed by operating the combustion stoker forced air damper 31 and the afterburning stoker forced air damper 61 by the processing unit 8.

[0043] Specifically, the processing unit 8 increases the ratio of secondary air by operating the opening degree of the secondary air damper 10. Further, the processing unit 8 can reduce the ratio to the combustion stoker 3 and increase the ratio to the afterburning stoker 6 among the primary air by operating the opening degrees of the combustion stoker forced air damper 31 and the afterburning stoker forced air damper 61. Here, in the present embodiment, the oxygen concentration in the exhaust gas is obtained by the exhaust gas oxygen concentration meter 52.

[0044] As a specific example of the second set value for the oxygen concentration, it is any value within 4.5 to 5.5%, but it is not limited to this.

[0045] The fact that the oxygen concentration in the exhaust gas is lower than the second set value means that the garbage is overburning. If overburning continues for a long time, the durability of the primary combustion chamber 4 etc. may deteriorate and the operation cost of the incinerator may increase. According to the present embodiment, by the above-described operation, overburning of the garbage can be suppressed, and while protecting the primary combustion chamber 4 etc., normal combustion can be performed. After that, when the oxygen concentration in the exhaust gas becomes higher than the second set value (that is, when it returns to the normal value), the processing unit 8 returns the distribution ratio of the primary air to the original state.

[0046] Here, in the present embodiment, it is also possible to proportionally control the distribution ratio of the primary air according to the oxygen concentration in the exhaust gas before and after the second set value of the oxygen concentration. For example, when it is 0.5% lower than the second set value, the combustion stoker forced air damper 31 is closed by 2% from the initial opening degree, and the afterburning stoker forced air damper 61 is opened by 5%. However, when it is 1.0% lower than the second set value of the oxygen concentration, the combustion stoker forced air damper 31 may be closed by 10% from the initial opening degree, and the afterburning stoker forced air damper 61 may be opened by 20%.

[0047] (During abnormal combustion 3) When the processing unit 8 determines that the temperature in the primary combustion chamber 4 is higher than the third set value (step SC-1 in FIG. 5), the processing unit 8 reduces the ratio of the primary air to the combustion stoker 3 and increases the ratio to the afterburning stoker 6 (steps SC-2 to SC-3 in FIG. 5). These operations can also be performed by operating the combustion stoker forced air damper 31 and the afterburning stoker forced air damper 61 by the processing unit 8. Here, in the present embodiment, the temperature in the primary combustion chamber 4 is obtained by the primary combustion chamber thermometer 41.

[0048] As a specific example of the third set value, it is any value between 950 and 1000 °C, but it is not limited to this.

[0049] The fact that the temperature in the primary combustion chamber 4 is higher than the third set value means that the waste is overburning. If the overburning continues for a long time, the durability of the primary combustion chamber 4 and the like may deteriorate, and the operation cost of the incinerator may increase. According to the present embodiment, by the above-described operation, it is possible to suppress the overburning of the waste, protect the primary combustion chamber 4 and the like, and perform normal combustion.

[0050] After that, when the temperature in the primary combustion chamber 4 becomes lower than the third set value (that is, when it returns to the normal value), the processing unit 8 returns the distribution ratio of the primary air to the original state.

[0051] (During abnormal combustion 4) When the processing unit 8 determines that the oxygen concentration in the exhaust gas is higher than the fourth set value (step SD-1 in FIG. 6), the processing unit 8 reduces the ratio of secondary air among the combustion air, increases the ratio of the primary air to the combustion stoker 3, and reduces the ratio to the afterburning stoker 6 (steps SD-2 to SD-4 in FIG. 6). These operations can be performed by the processing unit 8 operating the combustion stoker pushing air damper 31 and the afterburning stoker pushing air damper 61. The adjustment of the ratio of the secondary air can be performed by the processing unit 8 operating the secondary air damper 10.

[0052] As a specific example of the fourth set value for the oxygen concentration, it is any value between 6.0% and 6.5%, but it is not limited to this.

[0053] The fact that the oxygen concentration in the exhaust gas is higher than the fourth set value means that the combustion of the garbage is insufficient. According to the present embodiment, by the above-described operation, the combustion of the garbage can be promoted and normal combustion can be performed. Also, as described above, in the present embodiment, when it is determined that the oxygen concentration in the exhaust gas is higher than the fourth set value, the ratio of the secondary air is reduced. When the oxygen concentration in the exhaust gas is high, the unburned components in the exhaust gas are also small, and the secondary air acts to cool the exhaust gas, leading to a decrease in the temperature of the secondary combustion chamber. Therefore, in the present embodiment, by reducing the ratio of the secondary air, a decrease in the temperature of the secondary combustion chamber can be suppressed. Also, in the present embodiment, when it is determined that the oxygen concentration in the exhaust gas is higher than the fourth set value, the ratio of the primary air to the afterburning stoker 6 is reduced, so that similarly, the exhaust gas cooling effect by the primary air can be suppressed, and as a result, a decrease in the temperature of the secondary combustion chamber can be suppressed.

[0054] After that, when the oxygen concentration in the exhaust gas becomes lower than the fourth set value (that is, when it returns to the normal value), the processing unit 8 returns the distribution ratio of the primary air to the original state.

[0055] (During abnormal combustion 5) When the processing unit 8 determines that the temperature in the primary combustion chamber 4 is lower than the fifth set value (step SE-1 in FIG. 7), the processing unit 8 increases the ratio of the primary air to the combustion stoker 3 and decreases the ratio to the afterburning stoker 6 (steps SE-2 to 3 in FIG. 7). These operations can also be performed by the processing unit 8 operating the combustion stoker forced-air damper 31 and the afterburning stoker forced-air damper 61.

[0056] Specific examples of the fifth set value are any values within the range of 800 to 850 °C, but are not limited thereto.

[0057] The fact that the temperature in the primary combustion chamber 4 is lower than the fifth set value means that the combustion of the waste is insufficient. According to the present embodiment, by the above-described operation, the combustion of the waste can be promoted and normal combustion can be performed.

[0058] After that, when the temperature in the primary combustion chamber 4 becomes higher than the fifth set value (that is, when it returns to the normal value), the processing unit 8 returns the distribution ratio of the primary air to the original state.

[0059] (During abnormal combustion 6) When the processing unit 8 determines that the concentration of harmful substances in the exhaust gas discharged from the secondary combustion chamber 5 is higher than the sixth set value (step SF-1 in FIG. 8), the processing unit 8 reduces the ratio of the primary air sent to the drying stoker 2, the combustion stoker 3, and the afterburning stoker 6 to the combustion stoker 3 (step SF-2 in FIG. 8). Here, the concentration of harmful substances in the present embodiment is the concentration of harmful substances in the exhaust gas after the addition of a chemical for removing harmful substances in the denitration reaction tower 13 or the like (that is, after exhaust gas treatment). The fact that any of the concentrations of harmful substances in the exhaust gas discharged from the secondary combustion chamber 5 is higher than the corresponding sixth set value means that the amount of additive (chemical for removing harmful substances) added to the exhaust gas is insufficient for some reason. According to the present embodiment, by the above-described operation, the combustion of the waste can be suppressed and the amount of harmful substances in the exhaust gas can be reduced. As a result, the concentration of harmful substances in the exhaust gas can be kept low.

[0060] Thereafter, when the concentration of harmful substances in the exhaust gas becomes lower than the corresponding sixth set value (that is, when it returns to the normal value), the processing unit 8 returns the distribution ratio of the primary air to its original state.

[0061] As a specific example of the sixth set value, the hydrogen chloride concentration in the exhaust gas is any value from -10 to -20 ppm from the reference value, the sulfur oxide concentration is any value from -10 to -20 ppm from the reference value, and the sulfur oxide concentration is any value from -10 to -20 ppm from the reference value, but it is not limited to these. Here, the reference value means the emission standard concentration (ppm) determined for each facility.

[0062] Further, in the present embodiment, when the processing unit 8 determines that the concentration of harmful substances is higher than the sixth set value, the processing unit 8 operates the forced draft fan 9 and also performs an operation of reducing the amount of combustion air sent from the forced draft fan 9 (combustion air amount reduction operation) (step SF-3 in FIG. 8). Thereby, since the amount of exhaust gas can be reduced, the shortage of the additive concentration can be eliminated, and the concentration of harmful substances in the exhaust gas can be more effectively suppressed. Here, in the present embodiment, the combustion air amount reduction operation may be omitted, or a configuration in which only this combustion air amount reduction operation is performed may be adopted.

[0063] (Operation of the combustion stoker) During the operation of the combustion stoker 3, the processing unit 8 of the present embodiment operates so as to increase the ratio of the secondary air in the combustion air. Further, after the operation of the combustion stoker 3 ends, the processing unit 8 returns the ratio of the secondary air to its original state (that is, the state before the operation of the combustion stoker 3).

[0064] During the operation of the combustion stoker 3, the amount of unburned gas accompanying combustion increases. Therefore, by increasing the ratio of the secondary air, the combustion of the unburned gas can be promoted.

[0065] Note that the description of the above embodiment is merely an example and does not show the essential configuration of the present invention. The configuration of each part is not limited to the above as long as the gist of the present invention can be achieved.

[0066] Here, in this specification, "higher than or lower than the set value" shall include the case where it is the same value as the set value.

Explanation of Signs

[0067] 1 Feeding device 2 Dry stoker 21 Dry stoker pushing air damper 22 Dry stoker refuse layer level sensor 3 Combustion stoker 31 Combustion stoker pushing air damper 32 Combustion stoker refuse 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 Afterburning stoker 61 Afterburning stoker pushing air damper 62 Afterburning stoker refuse layer level sensor 7 Refuse input hopper 8 Processing unit 9 Pushing blower 10 Secondary air damper 11 Boiler 12 Bag filter 13 Denitration reaction tower 14 Induced draft blower 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 garbage incinerator having a forced draft fan, a dust feeder, a drying stoker, a combustion stoker, a post-combustion stoker, a primary combustion chamber, and a secondary combustion chamber, wherein 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, a step of determining whether the moisture concentration in the exhaust gas discharged from the secondary combustion chamber is higher than a first set value, when the moisture concentration in the exhaust gas discharged from the secondary combustion chamber is higher than the first set value, increasing the ratio of the primary air sent to the drying stoker among the primary air sent to the drying stoker, the combustion stoker, and the post-combustion stoker A combustion control method for a garbage incinerator having the above steps.

2. A step of determining whether the oxygen concentration in the exhaust gas is lower than a second set value, when the oxygen concentration in the exhaust gas is lower than the second set value, increasing the ratio of the secondary air among the combustion air, and reducing the ratio of the primary air sent to the combustion stoker and increasing the ratio of the primary air sent to the post-combustion stoker among the primary air sent to the drying stoker, the combustion stoker, and the post-combustion stoker The combustion control method for a garbage incinerator according to claim 1, further having the above steps.

3. A step of determining whether the temperature in the primary combustion chamber is higher than a third set value, when the temperature in the primary combustion chamber is higher than the third set value, reducing the ratio of the primary air sent to the combustion stoker and increasing the ratio of the primary air sent to the post-combustion stoker among the primary air sent to the drying stoker, the combustion stoker, and the post-combustion stoker The combustion control method for a garbage incinerator according to claim 1 or 2, further having the above steps.

4. A step of determining whether the oxygen concentration in the exhaust gas is higher than a fourth set value, when the oxygen concentration in the exhaust gas is higher than the fourth set value, reducing the ratio of the secondary air among the combustion air, and increasing the ratio of the primary air sent to the combustion stoker and reducing the ratio of the primary air sent to the post-combustion stoker among the primary air sent to the drying stoker, the combustion stoker, and the post-combustion stoker The combustion control method of the garbage incinerator according to claim 1 or 2, further comprising

5. a step of determining whether the temperature in the primary combustion chamber is lower than a fifth set value; when the temperature in the primary combustion chamber is lower than the fifth set value, among the primary air sent to the drying stoker, the combustion stoker, and the afterburning stoker, increasing the ratio to the combustion stoker and decreasing the ratio to the afterburning stoker The combustion control method of the garbage incinerator according to claim 1 or 2, further comprising

6. the combustion stoker is configured to operate periodically, and further comprising a step of increasing the ratio of the secondary air among the combustion air during the operation of the combustion stoker The combustion control method of the garbage incinerator according to claim 1 or 2.

7. a step of determining whether the concentration of harmful substances in the exhaust gas discharged from the secondary combustion chamber is higher than a sixth set value; when it is determined that the concentration of harmful substances in the exhaust gas discharged from the secondary combustion chamber is higher than the sixth set value, reducing the ratio to the combustion stoker among the primary air sent to the drying stoker, the combustion stoker, and the afterburning stoker The combustion control method of the garbage incinerator according to claim 1 or 2, further comprising

8. a step of determining whether the concentration of harmful substances in the exhaust gas discharged from the secondary combustion chamber is higher than a sixth set value; when it is determined that the concentration of harmful substances in the exhaust gas discharged from the secondary combustion chamber is higher than the sixth set value, reducing the amount of combustion air sent from the forced blower The combustion control method of the garbage incinerator according to claim 1 or 2, further comprising

9. A combustion control device for a garbage incinerator having a forced blower, a dust feeder, a drying stoker, a combustion stoker, an afterburning stoker, a primary combustion chamber, and a secondary combustion chamber, the combustion air sent from the forced blower is distributed into primary air and secondary air, the primary air is further distributed and supplied to the drying stoker, the combustion stoker, and the afterburning stoker, the secondary air is supplied to the secondary combustion chamber, and further having a processing unit When the moisture concentration in the exhaust gas discharged from the secondary combustion chamber is higher than a first set value, the processing unit is configured to perform a process of increasing the ratio of the primary air sent to the drying stoker, the combustion stoker, and the afterburning stoker to the drying stoker. A combustion control device for a garbage incinerator.

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