Operating method of sludge incineration equipment and sludge incineration equipment
The sludge incineration facility optimizes the supply of dried and dewatered sludge using a moving grate system to reduce drying equipment scale and N2O generation, addressing adhesiveness and combustion efficiency issues.
Patent Information
- Authority / Receiving Office
- JP · JP
- Patent Type
- Applications
- Current Assignee / Owner
- CANADEVIA CO LTD
- Filing Date
- 2024-12-23
- Publication Date
- 2026-07-03
Smart Images
Figure 2026111160000001_ABST
Abstract
Description
Technical Field
[0001] The present invention relates to an operation method of sludge incineration equipment and sludge incineration equipment to which this operation method is applied.
Background Art
[0002] Sewage sludge generated from sewage introduced into a sewage treatment plant has a high water content of 98 to 99% and is not suitable for incineration treatment. Therefore, when incinerating sewage sludge, it is dehydrated with a dehydrator such as a centrifugal dehydrator or a filter press type dehydrator to obtain dehydrated sludge, and the dehydrated sludge is dried with a dryer to a dry cake with a water content of 35 to 40%, and then carried into an incineration facility. As such an incineration facility, a stoker type incinerator described in Patent Document 1 is known. In the stoker type incinerator as described in Patent Document 1, a reciprocating grate completely burns the sludge with air supplied from below the grate while feeding out the sludge.
[0003] However, since the water content of dehydrated sludge is usually 76 to 80%, in order to dry the dehydrated sludge to a water content of 35 to 40% as described in Patent Document 1, a large-scale drying device is required, and there is a problem that the construction cost of the drying device is high. Moreover, since dehydrated sludge has high adhesiveness, if it is supplied to the incinerator in an insufficiently dried state, it may adhere to the grate and cannot be sent out, or it may become a large lump due to consolidation by the grate and it may be difficult to completely burn it in the incinerator.
[0004] In addition, depending on the combustion conditions in the incinerator, nitrous oxide (N2O) [also referred to as "nitrous oxide"], which is a greenhouse gas, is generated.
[0005] As a countermeasure, in Patent Document 2, hydrogen gas (H2) is blown into the combustion chamber of a waste incinerator, and the combustion gas containing hydrogen gas (H2) is secondarily combusted to raise the temperature of the combustion exhaust gas to about 1000°C or higher, and nitrous oxide (N2O) and nitrogen oxides (NOx) are thermally decomposed at high temperature to suppress the emission of nitrous oxide (N2O).
[0006] Patent Document 3 describes a method for reducing nitrous oxide generation by drawing out steam and ammonia gas generated from sludge from above the drying stoker, thereby raising the combustion gas temperature to over 850°C. [Prior art documents] [Patent Documents]
[0007] [Patent Document 1] Japanese Patent Publication No. 2005-257131 [Patent Document 2] Japanese Patent Publication No. 2005-291554 [Patent Document 3] Patent No. 5931593 [Overview of the Initiative] [Problems that the invention aims to solve]
[0008] The present invention aims to reduce the scale of the drying equipment in a stoker-type incinerator (specifically, the processing volume by the drying equipment or the number of drying equipment units) and, in addition, to suppress the generation of nitrous oxide. [Means for solving the problem]
[0009] The operating method of the sludge incineration facility of the present invention is: When operating a sludge incineration facility that sends sludge from upstream to downstream using a grate that moves back and forth between the upstream and downstream areas, The dried material is supplied to the grate, Dewatered sludge with a higher water content than the dried material is supplied onto the grate. The dry body containing the dewatered sludge is sent by a grate to a primary combustion chamber where the dry body and the dewatered sludge are burned. Combustion gases from the primary combustion chamber are sent to the secondary combustion chamber for re-combustion. The system is characterized by controlling the supply amount of dried material and the supply amount of dewatered sludge so that the concentration of nitrous oxide in the combustion gas discharged from the secondary combustion chamber is below a set value.
[0010] The sludge incineration equipment of the present invention is A sludge incineration facility that uses a grate that moves back and forth between the upstream and downstream sides to send sludge from upstream to downstream and incinerate the sludge, A drying supply device that supplies a drying material to the grate, A dewatered sludge supply device that supplies dewatered sludge with a higher water content than the dried body onto the grate, A primary combustion chamber that receives the dried body containing the dewatered sludge, which has been fed out by the grate, and burns the dried body and the dewatered sludge, A secondary combustion chamber that re-combusts the combustion gases sent out from the primary combustion chamber, The system is characterized by comprising a control device that controls the supply amount of dried material and the supply amount of dewatered sludge so that the concentration of nitrous oxide in the combustion gas discharged from the secondary combustion chamber is below a set value. [Effects of the Invention]
[0011] According to the operating method and sludge incineration equipment of the present invention, the amount of sludge processed by the drying equipment or the number of drying equipment required for drying the sludge supplied to the stoker-type incinerator can be reduced. Moreover, the amount of nitrous oxide generated can be reduced simply by controlling the amount of dewatered sludge and dried material supplied to the stoker-type incinerator. [Brief explanation of the drawing]
[0012] [Figure 1] This diagram shows a sludge incineration facility according to Embodiment 1. [Figure 2] This figure shows a modified example of the sludge incineration facility according to Embodiment 1. [Figure 3] This flowchart shows the first part of the flow chart for the operation method of the sludge incineration facility according to Embodiment 1. [Figure 4] This is a flowchart showing the later stages of the same flow. [Figure 5] This is a diagram showing that the grate in the drying section sends the dried sludge downstream. [Figure 6] This is a diagram showing that the grate sends the dried sludge on which the dewatered sludge is piled. [Figure 7] This is a detailed diagram of the main part in the flowchart of FIG. 4. [Figure 8] This is a detailed diagram of another main part in the flowchart of FIG. 4. [Figure 9] This is a schematic diagram of the sludge incineration facility according to Embodiment 2.
Mode for Carrying Out the Invention
[0013] [Embodiment 1] The sludge incineration facility 100 shown in FIG. 1 includes a stoker-type incinerator 1 and incinerates the incineration target. The incineration target is sent from the upstream of the incinerator 1 to the downstream combustion region 90 by the grate 12M. The combustion region 90 is a region where the incineration target is burned. The incineration target that reaches the combustion region 90 is burned and becomes incineration ash BA.
[0014] In the sludge incineration facility 100, the grate 12M sends out the dried body DB on which the dewatered sludge DS is piled as the incineration target. The dried body DB is a substance having a moisture content equal to or lower than that of the sludge supplied to a known incinerator. The dewatered sludge DS is sludge that has been dewatered, but has a higher moisture content than the dried body DB. The dewatered sludge DS is sludge that has not been dried.
[0015] Only a part of the dewatered sludge DS to be incinerated is dried to a moisture content of 20 to 40% to form a dried body DB with low adhesiveness, and this is supplied onto the grate 12M. Then, the remaining dewatered sludge DS is supplied onto the dried body DB. This prevents the dewatered sludge DS from adhering to the grate 12M. By doing so, only a part of the dewatered sludge DS to be incinerated that should be dried is the dried body DB. As a result, the processing amount by the drying device or the number of drying devices can be reduced.
[0016] Dewatered sludge DS is clayey and highly adhesive to the grate 12M, so when it is sent to the grate 12M, it tends to form clumps. On the other hand, dried sludge DB has almost no adhesion to the grate 12M, so it does not form clumps even when sent to the grate 12M. When the grate 12M sends the dried sludge DB loaded with dewatered sludge DS, the dewatered sludge DS piled on the dried sludge DB moves toward and within the combustion area 90 together with the dried sludge DB without coming into contact with the grate 12M. Therefore, the incinerator 1 can incinerate the dewatered sludge DS and dried sludge DB together. Thus, while preventing the dewatered sludge DS from adhering to the grate 12M, it is possible to increase the amount of dewatered sludge DS that can be incinerated without drying treatment compared to known sludge incineration equipment, and the scale of the drying equipment required to dry the dewatered sludge DS can be reduced.
[0017] The dried sludge DB includes at least one of dried sludge DBS, which is obtained by drying sludge, and dried material other than dried sludge DBS. Dried sludge DBS generally refers to sludge with a moisture content of 40% or less. Dried material other than dried sludge DBS is a material that is readily available to sludge incinerators, such as silica sand, or a material that can be obtained from the sludge incineration facility 100, such as incineration ash BA. The dried material can also be other materials that are readily available as products, such as gravel, crushed stone, river sand, or mountain sand. Alternatively, the dried material may be a material recycled from waste, such as crushed slag. The sludge incineration facility 100 shown in Figure 1 uses only dried sludge DBS as the dried sludge DB.
[0018] The detailed configuration of the sludge incineration facility 100 according to Embodiment 1 will be described.
[0019] As shown in Figure 1, the sludge incineration facility 100 comprises an incinerator 1 for incinerating materials, a drying device 20 for drying sludge such as dewatered sludge DS into dried sludge DBS, a dried sludge supply device 2 for supplying dried sludge DBS to the incinerator 1, a dewatered sludge supply device 3 for supplying dewatered sludge DS to the incinerator 1, various sensors described later, and a control device 9. The various sensors are provided in the incinerator 1, the dried sludge supply device 2, and the dewatered sludge supply device 3. The dried sludge supply device 2 includes a screw feeder 81 equipped with a drive device 80 such as a motor. The dewatered sludge supply device 3 includes a screw feeder 83 equipped with a drive device 82 such as a motor. The control device 9 controls the drive device 80 of the dried sludge supply device 2 and the drive device 82 of the dewatered sludge supply device 3.
[0020] The incinerator 1 comprises a primary combustion chamber 11 which is a room for burning the material to be incinerated, a conveying device 12 provided in the primary combustion chamber 11, and a secondary combustion chamber 13 provided above the primary combustion chamber 11 for re-combusting the combustion gas G sent out from the primary combustion chamber 11.
[0021] The primary combustion chamber 11 has an inlet 111 for bringing in the dry material DB to be incinerated into the primary combustion chamber 11, and an outlet 112 for removing the incinerated ash BA generated after the material to be incinerated has been burned from the primary combustion chamber 11.
[0022] The conveying device 12 transports the materials to be incinerated from the upstream inlet 111 to the downstream outlet 112. The conveying device 12 has, in order from upstream, a drying stage 121, a combustion stage 122, and a post-combustion stage 123. The drying stage 121 sends the materials to be incinerated brought in from the inlet 111 to the downstream combustion stage 122 while drying them with air supplied from below the grates 12M, 12F. There are combustion areas 90 above the combustion stage 122 and above the post-combustion stage 123. The combustion stage 122 sends the dried materials to the downstream post-combustion stage 123 while burning them in the combustion area 90 with air supplied from below the grates 12M, 12F. The post-combustion stage 123 burns the unburned components contained in the incineration ash BA generated after the materials to be incinerated in the combustion area 90. The incinerated ash BA, from which the unburned components have been burned, is moved towards the discharge outlet 112.
[0023] The drying stage 121, combustion stage 122, and post-combustion stage 123 each have a plurality of grates 12M that reciprocate between the upstream and downstream, and a plurality of grates 12F whose positions are fixed. Each grate 12M, 12F has a grid-like passage through which high-temperature air for burning sludge passes. The sludge piled on each grate 12M, 12F is dried or burned by the air supplied from the passage.
[0024] The reciprocating grate 12M and the fixed grate 12F are arranged in an alternating, stepped pattern along the direction of transport of the material to be incinerated. In the sludge incineration facility 100 shown in Figure 1, the reciprocating grate 12M is located closest to the entrance 111.
[0025] The materials to be incinerated, brought into the incinerator 1 through the entrance 111, are sent downstream by a reciprocating grate 12M. The reciprocating grate 12M pushes the materials to be incinerated, which are piled on the fixed grate 12F, downstream. In addition, the materials to be incinerated piled on each grate 12M and 12F are supplied with drying or combustion air from below each grate 12M and 12F. Therefore, the materials to be incinerated are sent downstream by the reciprocating grate 12M while being dried or burned.
[0026] The secondary combustion chamber 13 is located above the drying stage 121. As a result, the high-temperature combustion gas G generated by combustion in the combustion stage 122 and the post-combustion stage 123 passes over the drying stage 121 and flows into the secondary combustion chamber 13. In the material to be incinerated, the parts exposed to the gas G become dry and therefore easier to burn.
[0027] The drying device 20 dries the dewatered sludge DS using thermal energy such as high-temperature steam or hot air. Therefore, the smaller the amount of dewatered sludge DS that needs to be dried, the smaller the size of the drying device 20 can be. The drying device 20 supplies the dried sludge DBS obtained by drying the dewatered sludge DS to the dried sludge supply device 2.
[0028] The dried sludge supply device 2 supplies dried sludge DBS onto the grates 12M and 12F of the drying stage 121. More specifically, the dried sludge supply device 2 includes a dried sludge storage tank 22 for temporarily storing the dried sludge DBS supplied from the drying device 20, and a dust supply device 23 for supplying the dried sludge DBS from the dried sludge storage tank 22 to the grates 12M and 12F of the drying stage 121.
[0029] The dust supply device 23 is a device that supplies dried sludge DBS from the inlet 111 onto the grates 12M and 12F of the drying stage 121. The dust supply device 23 is, for example, a pusher-type device that pushes the dried sludge DBS toward the grates 12M and 12F of the drying stage 121.
[0030] The dewatered sludge supply device 3 is a device that supplies dewatered sludge DS onto the dried sludge DBS supplied to the grates 12M and 12F. The dewatered sludge supply device 3 has a dewatered sludge storage tank 31 for temporarily storing the dewatered sludge DS, and a distributed supply device 32 that supplies the dewatered sludge DS from the dewatered sludge storage tank 31 from above onto the dried sludge DBS piled on the grates 12M and 12F.
[0031] The distributed supply device 32 distributes and supplies the dewatered sludge DS on top of the dried sludge DBS. Distributing and supplying the dewatered sludge DS means piling the dewatered sludge DS at multiple locations on top of the dried sludge DBS that are far apart from each other. By distributing and supplying the dewatered sludge DS on top of the dried sludge DBS, it is possible to prevent a large amount of dewatered sludge DS from being supplied to a specific location. This prevents the layer thickness of the dewatered sludge DS from becoming excessively thick in certain areas, thereby allowing the dewatered sludge DS to be burned uniformly in the incinerator 1. As a result, the dewatered sludge DS can be burned stably and completely.
[0032] The distributed supply device 32 supplies dewatered sludge DS onto the dried sludge DBS piled on the grates 12M and 12F. By piling the dewatered sludge DS on top of the dry sludge DBS, which is sandy and has almost no adhesive properties, it is possible to prevent the dewatered sludge DS from adhering to the grates 12M and 12F, or from being pressed against the grates 12M and 12F and forming large clumps.
[0033] The distributed supply device 32 preferably supplies dewatered sludge DS onto the dried sludge DBS piled on the grates 12M and 12F in the drying stage 121. The dewatered sludge DS supplied in the drying stage 121 is exposed to gas G generated in the combustion area 90. The dewatered sludge DS exposed to gas G dries out and becomes more combustible.
[0034] The distributed supply device 32 more preferably supplies dewatered sludge DS on top of the dried sludge DBS piled up at the position closest to the inlet 111, as shown in Figure 1. The position closest to the inlet 111 means the upstream position among the positions where the layer of dried sludge DBS is formed on the grates 12M and 12F. This maximizes the time that the dewatered sludge DS supplied to the incinerator 1 is exposed to the gas G. Therefore, the dewatered sludge DS becomes easier to burn.
[0035] The configuration of the distributed supply device 32 is arbitrary, as long as it is a device that distributes and supplies dewatered sludge DS onto dried sludge DBS. For example, it may be composed of multiple screw feeders that can shape the sludge according to the shape of the screw grooves, or it may be composed of a molding machine that generates multiple molded sludges with a uniform shape for the dewatered sludge DS.
[0036] The cross-sectional area of the molded sludge should preferably be as small as possible, because molded sludge with a small cross-sectional area dries more easily. However, molding sludge with a small cross-sectional area requires a large amount of power from the molding machine. Therefore, the cross-sectional area of the molded sludge is determined by considering the balance between the amount of dewatered sludge DS and the power required to mold the dewatered sludge DS.
[0037] The various sensors described above include a determination sensor for determining whether or not a layer of dried sludge DBS and a layer of dewatered sludge DS have been formed, and a control sensor for adjusting the supply amount of dried sludge DBS and the supply amount of dewatered sludge DS.
[0038] The determination sensor includes a dry sludge sensor 4 for measuring the amount of dried sludge DBS supplied to the grates 12M and 12F, and a dewatered sludge sensor 5 for measuring the amount of dewatered sludge DS supplied on top of the dried sludge DBS.
[0039] Specifically, the dry sludge sensor 4, as shown in Figure 1, consists of a first level gauge for measuring the amount of dried sludge DBS supplied to the grates 12M and 12F by measuring the height of the dried sludge DBS piled on the grates 12M and 12F.
[0040] As shown in Figure 1, the dry body sensor 4, configured as a first level gauge, measures the height of the dry sludge DBS layer piled on grates 12M and 12F upstream of the point where the dewatered sludge supply device 3 supplies dewatered sludge DS. More specifically, the dry body sensor 4, configured as a first level gauge, measures the height from a reference position to the surface of the dry sludge DBS layer. The reference position is determined as appropriate. For example, the position of grates 12M and 12F located below the dry body sensor 4 can serve as the reference position.
[0041] The dry body sensor 4, illustrated in Figure 1, is used to measure the height of the dry sludge DBS layer piled on the reciprocating grate 12M located at the upstreammost position. As a first-level gauge, the dry body sensor 4 can directly measure whether a layer of dry sludge DBS of sufficient height to carry the dewatered sludge DS has formed on the reciprocating grate 12M.
[0042] The dry body sensor 4, configured in the first level gauge, is a non-contact type sensor. Non-contact dry body sensors 4 include ultrasonic, electromagnetic wave, and laser type level gauges. The dry body sensor 4, configured in the first level gauge, may also be a video camera that captures images of the dried sludge DBS.
[0043] The dewatered sludge sensor 5 is a second-level meter that measures the amount of dewatered sludge DS supplied onto the dry sludge DBS by measuring the height of the dewatered sludge DS piled on the dry sludge DBS.
[0044] The dewatered sludge sensor 5, configured as a second level meter, is used to measure the height of the layer of dewatered sludge DS piled on the dried sludge DBS downstream of the point where the dewatered sludge supply device 3 supplies the dewatered sludge DS.
[0045] The dewatered sludge sensor 5, configured in the second level gauge, is used to measure the height from a reference position to the surface of the dewatered sludge layer DS. The reference position can be determined as appropriate. For example, the reference position may be the surface of the dried sludge DBS located below the second level gauge 51. The dewatered sludge sensor 5 configured in the second level gauge can directly measure the amount of dewatered sludge DS piled on top of the dried sludge DBS. The dewatered sludge sensor 5 configured in the second level gauge is preferably a non-contact sensor or a video camera, similar to the dried body sensor 4 configured in the first level gauge.
[0046] The adjustment sensor includes a first moisture content meter 6 for measuring the moisture content of the dried sludge DBS supplied to the grates 12F and 12M, a second moisture content meter 7 for measuring the moisture content of the dewatered sludge DS supplied on top of the dried sludge DBS, a thermometer 8 for measuring the temperature of the combustion gas G generated by incinerating the materials to be incinerated, and an N2O concentration meter 28 for detecting the concentration of nitrous oxide in the combustion gas G discharged from the secondary combustion chamber 13.
[0047] The first moisture content meter 6 is installed in the dried sludge supply device 2. This allows the first moisture content meter 6 to measure the moisture content of the dried sludge DBS that the dried sludge supply device 2 supplies to the grates 12M and 12F.
[0048] The second moisture content measuring instrument 7 is provided in the dewatered sludge supply device 3. This allows the second moisture content measuring instrument 7 to measure the moisture content of the dewatered sludge DS that the dewatered sludge supply device 3 supplies onto the dried sludge DBS.
[0049] The first moisture content measuring instrument 6 and the second moisture content measuring instrument 7 can be composed of, for example, infrared, electrical resistance, capacitance, or microwave type moisture meters.
[0050] The thermometer 8 is positioned in the secondary combustion chamber 13 near the primary combustion chamber 11. This allows the thermometer 8 to measure the temperature of the gas G that flows from the primary combustion chamber 11 into the secondary combustion chamber 13.
[0051] The N2O concentration meter 28 is installed between the outlet of the secondary combustion chamber 13 and the downstream chimney (not shown) (but including the chimney). In the example shown in the figure, the N2O concentration meter 28 is installed inside the flue 29 between the secondary combustion chamber 13 and the chimney (not shown).
[0052] The control device 9 controls the drive unit 80 for the screw feeder 81 of the dry material supply device 2 and the drive unit 82 for the screw feeder 83 of the dewatered sludge supply device 3. The control device 9 also controls the dust supply device 23 of the dry material supply device 2 based on detection signals from various sensors to control the amount of dried sludge DBS supplied to the grates 12M and 12F. The control device 9 also controls the dispersion supply device 32 of the dewatered sludge supply device 3 based on detection signals from various sensors to control the amount of dewatered sludge DS supplied onto the dried sludge DBS.
[0053] Specifically, if the dust supply device 23 is of the pusher type, the control device 9 controls the reciprocating speed of the pusher, the stroke of the pusher, and the time interval between the pusher's forward and reverse movements.
[0054] Preferably, the control device 9 controls the dust supply device 23 and the dispersion supply device 32 based on the measurement results of the first moisture content meter 6, the second moisture content meter 7, the thermometer 8, and the N2O concentration meter 28. Here, the approximate calorific value of the dried sludge DBS can be estimated from the moisture content of the dried sludge DBS. Also, the approximate calorific value of the dewatered sludge DS can be estimated from the moisture content of the dewatered sludge DS.
[0055] In addition, the temperature of the gas G flowing from the primary combustion chamber 11 to the secondary combustion chamber 13 is a quantity that represents the combustion state of the material to be incinerated in the primary combustion chamber 11. Therefore, the control device 9 can adjust the supply amount of dried sludge DBS and dewatered sludge DS so that the material to be incinerated in the primary combustion chamber 11 maintains an appropriate combustion state.
[0056] For example, if the temperature of gas G detected by the thermometer 8 is likely to fall below a predetermined temperature, the control device 9 can raise the temperature of gas G by controlling the dust supply device 23 to increase the supply amount of dried sludge DBS, which has a high calorific value. Conversely, if the temperature of gas G is likely to rise above a predetermined temperature, the control device 9 can lower the temperature of gas G by controlling the distribution supply device 32 to increase the supply amount of dewatered sludge DS, which has a low calorific value.
[0057] In this way, by adjusting the supply amount of dried sludge DBS and dewatered sludge DS using the control device 9, the temperature of the gas G flowing from the primary combustion chamber 11 to the secondary combustion chamber 13 can be controlled to a range of 900 to 1100°C, thereby reducing the amount of nitrous oxide generated. In other words, simply by adjusting the supply amount of dried sludge DBS and dewatered sludge DS using the control device 9, the amount of nitrous oxide generated can be reduced without applying any other methods. The details will be described later.
[0058] [Modified form of Embodiment 1] To adjust the supply amount of dried sludge DBS and dewatered sludge DS by the control device 9, a dried sludge sensor 4 and a dewatered sludge sensor 5 are provided to detect the amount of dried sludge DB and dewatered sludge DS supplied to the primary combustion chamber 11. In the sludge incineration facility 100 shown in Figure 1, both the dried sludge sensor 4 and the dewatered sludge sensor 5 are composed of level gauges. However, other configurations can be used for the dried sludge sensor 4 and the dewatered sludge sensor 5.
[0059] Figure 2 shows an example in which a supply amount recorder is used for both the dry body sensor 4 and the dewatered sludge sensor 5. In detail, the dry body sensor 4 can be in the form of a first supply amount recorder for directly measuring the amount of dry sludge DBS supplied to the grates 12M and 12F. Similarly, the dewatered sludge sensor 5 can be in the form of a second supply amount recorder for directly measuring the amount of dewatered sludge DS supplied by the dewatered sludge supply device 3 onto the dry sludge DBS.
[0060] The dry body sensor 4, configured in the first supply amount recorder, can be installed, for example, on the screw feeder 81 for the dry body DB, as shown in the figure. With this configuration, the dry body sensor 4 does not need to be installed inside the incinerator 1, as in the form of the level meter shown in Figure 1, making installation easier compared to the level meter form. Similarly, the dewatered sludge sensor 5, configured in the second supply amount recorder, can be installed on the screw feeder 83 for the dewatered sludge DS, so it does not need to be installed inside the incinerator 1, making installation easier compared to the level meter form.
[0061] [Operation method of the sludge incineration facility 100 using the control device 9 of Embodiment 1] The following describes the processing performed by the control device 9, that is, the operation method of the sludge incineration facility 100.
[0062] As shown in Figure 3, once processing begins, the control device 9 controls the dry material supply device 2 in step S1 to supply the dried sludge DBS shown in Figure 1 to the grates 12M and 12F. More specifically, the control device 9 controls the operation of the dust supply device 23. If the dust supply device 23 is a pusher type, the control device 9 starts the reciprocating motion of the pusher. Once the operation of the dust supply device 23 begins, the dried sludge DBS is supplied onto the reciprocating grates 12M in the drying stage 121. The dried sludge DBS is obtained by drying the dewatered sludge DS with the drying device 20.
[0063] A portion of the dried sludge DBS supplied onto the reciprocating grate 12M falls into the space SP1 created by the reciprocating motion of the grate 12M, as shown in Figure 5. The dried sludge DBS that falls from the reciprocating grate 12M is piled up on the fixed grate 12F. The dried sludge DBS piled up on the fixed grate 12F is pushed downstream by the reciprocating grate 12M.
[0064] In this way, the dried sludge DBS is gradually sent downstream. In the following explanation, the reciprocating grate 12M is assumed to be moving back and forth, except in emergencies and other exceptions. Therefore, the dried sludge DBS supplied to grates 12M and 12F is always moving downstream, except in exceptional circumstances.
[0065] In step S2, the control device 9 determines whether or not dried sludge DBS has been loaded onto the grates 12M and 12F based on the measurement results from the dry body sensor 4.
[0066] For example, as shown in Figure 1, if the dry body sensor 4 is in the form of a level gauge, the control device 9 determines that dry sludge DBS has been loaded onto the grates 12M and 12F if the measurement result of the dry body sensor 4, which is configured as the first level gauge, indicates that the thickness, i.e., height, of the dry sludge DBS layer is above a predetermined level. The "above a predetermined level" height of the dry sludge DBS layer used by the control device 9 for determination is set as a guideline for the amount that the dry sludge DBS being sent downstream can move while loaded with dewatered sludge DS.
[0067] The height of the dried sludge DBS layer is preferably greater than or equal to the height of the reciprocating grate 12M. In this way, as shown in Figure 6, only the dried sludge DBS flows into the space SP1 created by the reciprocating grate 12M pushing out the dried sludge DBS. Therefore, it is possible to prevent the dewatered sludge DS from being directly pushed out toward the reciprocating grate 12M.
[0068] Furthermore, if the dry sludge sensor 4 is in the form of a first supply amount recorder, as shown in Figure 2, the control device 9 determines that dry sludge DBS has been loaded onto the grates 12M and 12F when the amount of dry sludge DBS recorded by the dry sludge sensor 4 exceeds a predetermined amount. The amount of dry sludge DBS is set based on the amount that dry sludge DBS can move downstream while loaded with dewatered sludge DS.
[0069] If, in step S2, the control device 9 determines that no dried sludge DBS has been loaded onto the grates 12M and 12F, the control device 9 returns to step S1. On the other hand, if, in step S2, the control device 9 determines that dried sludge DBS has been loaded onto the grates 12M and 12F, the process proceeds to step S3.
[0070] In step S3, the control device 9 controls the dewatered sludge supply device 3 to supply dewatered sludge DS onto the dried sludge DBS. Specifically, the control device 9 operates the distribution supply device 32. At this time, the control device 9 performs control corresponding to the specific configuration of the distribution supply device 32.
[0071] In step S4, the grate 12M sends the dry sludge DBS, on which the dewatered sludge DS is piled, to the combustion area 90 at the top of the combustion stage 122. As a result, the dewatered sludge DS piled on the dry sludge DBS moves along with the dry sludge DBS. The dry sludge DBS and dewatered sludge DS sent to the combustion area 90 at the top of the combustion stage 122 are burned in the combustion area 90. Therefore, the sludge incineration plant 100 can burn the materials to be burned without drying all of the dewatered sludge DS, by drying only a portion of the dewatered sludge DS in the drying device 20 in order to obtain the dry sludge DBS. Thus, the sludge incineration plant 100 can reduce the size of the drying device 20 required.
[0072] The dried sludge DBS and dewatered sludge DS are completely combusted to produce incinerated ash BA. After the dried sludge DBS and dewatered sludge DS have been completely combusted through the combustion stage 122 and the post-combustion stage 123, the resulting incinerated ash BA is discharged from the outlet 112 to the outside of the primary combustion chamber 11.
[0073] In step S5, the dewatered sludge sensor 5 measures the amount of dewatered sludge DS. As shown in Figure 1, if the dewatered sludge sensor 5 is in the form of a second level gauge, the height of the dewatered sludge DS is measured. Also, as shown in Figure 2, if the dewatered sludge sensor 5 is in the form of a second supply amount recorder, the amount of dewatered sludge DS supplied by the dewatered sludge supply device 3 to the primary combustion chamber 11 is measured.
[0074] In step S6 shown in Figure 4, the control device 9 determines whether each measured value is within the reference range based on the measurement results of the dry body sensor 4 and / or the measurement results of the dewatered sludge sensor 5. The reference range is the allowable range of the amount of dry sludge DBS and the allowable range of the amount of dewatered sludge DS, which allows the dry sludge DBS on which the dewatered sludge DS is loaded to maintain mobility.
[0075] In step S6, if the control device 9 determines that the measured values of the amount of dried sludge DBS and the amount of dewatered sludge DS are within the standard range, the control device 9 proceeds to step S8. On the other hand, in step S6, if the control device 9 determines that the measured values of the amount of dried sludge DBS and the amount of dewatered sludge DS are not within the standard range, the control device 9 proceeds to step S7.
[0076] In step S7, the control device 9 controls the amount of dried sludge DBS supplied by the dry sludge supply device 2 and the amount of dewatered sludge DS supplied by the dewatered sludge supply device 3. As a result, the amount of dried sludge DBS supplied to the grates 12M and 12F and the amount of dewatered sludge DS piled on the dried sludge DBS are adjusted so that each amount, i.e., each measured value, falls within the reference range.
[0077] If the dust supply device 23 is of the pusher type, the control device 9 controls the reciprocating speed of the pusher, etc. Similarly, the control device 9 controls the distributed supply device 32 to adjust it appropriately according to its configuration.
[0078] In step S8, the first moisture content meter 6 measures the moisture content of the dried sludge DBS supplied to the incinerator 1. The measurement result of the moisture content of the dried sludge DBS is output from the first moisture content meter 6 to the control device 9. In step S9, the second moisture content meter 7 measures the moisture content of the dewatered sludge DS supplied to the incinerator 1. The measurement result of the moisture content of the dewatered sludge DS is output from the second meter 7 to the control device 9.
[0079] In step S10, the thermometer 8 measures the temperature of the gas G flowing from the primary combustion chamber 11 into the secondary combustion chamber 13. The measurement result of the gas G temperature is output from the thermometer 8 to the control device 9.
[0080] In step S11, the control device 9 controls the dust supply device 23 and the distributed supply device 32 based on the measurement results of the moisture content of the dried sludge DBS, the moisture content of the dewatered sludge DS, and the temperature of the gas G. In this way, the combustion area 90 is maintained in an appropriate combustion state. Specifically, if the temperature of the thermometer 8 is lower than the standard value, the control device 9 controls the supply of dried sludge DBS, which has a higher calorific value than dewatered sludge DS, to increase. If the temperature of the thermometer 8 is higher than the standard value, the control device 9 controls the supply of dewatered sludge DS, which has a lower calorific value than dried sludge DBS, to increase.
[0081] Therefore, the control device 9 can supply dried sludge DBS and dewatered sludge DS to the primary combustion chamber 11 in order to maintain an appropriate combustion state.
[0082] According to the sludge incineration method described above, the combined moisture content of the incinerated material, consisting of dried sludge DBS and dewatered sludge DS, can be made higher than the moisture content of the incinerated material previously supplied to known incinerators. As a result, the amount of incinerated material that needs to be dried can be reduced. Therefore, the processing volume by the drying equipment 20 or the number of drying equipment 20 units, i.e., the scale of the drying equipment 20, can be reduced.
[0083] In detail, in known stoker-type sewage sludge incinerators, when dewatered sludge with a moisture content of 76-80% is introduced, the dewatered sludge has high adhesive properties, causing it to adhere to the grate or form large clumps, making complete combustion of the dewatered sludge difficult. To solve this problem, in known stoker-type sewage sludge incinerators, all of the dewatered sludge is dried in a drying device to a moisture content of, for example, 20-40%, and then introduced into the incinerator 11 as dried sludge with almost no adhesive properties. However, drying all of the dewatered sludge to a moisture content of 20-40% in a drying device requires a large-scale drying device, which presents a problem.
[0084] In contrast, with the incinerator 1 described above, even dewatered sludge DS with a moisture content of 40-80% can be completely burned without adhering to the grates 12M and 12F or forming large clumps, because it sits on top of the dried sludge DBS. Specifically, only a portion of the dewatered sludge DS to be incinerated is dried to a moisture content of 20-40% to create a less adhesive dried body DB, which is then supplied onto the grates 12M and 12F. The remaining dewatered sludge DS is then supplied on top of the dried body DB, preventing the dewatered sludge DS from adhering to the grates 12M and 12F. Therefore, only a portion of the dewatered sludge DS to be incinerated needs to be dried, which reduces the size of the drying equipment 20.
[0085] The moisture content of the sludge to be incinerated, or the mass ratio of dried sludge (DBS) to dewatered sludge (DS), varies depending on the sludge incineration method and / or the moisture content of the dewatered sludge (DS). Here, the moisture content of the sludge to be incinerated includes the total moisture content of the incinerated material, which includes both dried sludge (DBS) and dewatered sludge (DS).
[0086] Regarding the moisture content of the sludge to be incinerated, for example, if the goal is to recover the thermal energy of the incineration exhaust gas and use it for heating equipment within the facility, a lower moisture content in the sludge allows for the recovery of more thermal energy. In this case, a moisture content of 40-65% is desirable. On the other hand, if the goal is not to recover energy from the incineration exhaust gas, a higher moisture content in the sludge allows for a smaller drying unit 20. In this case, a moisture content of 60-80% is desirable.
[0087] Regarding the mass ratio of dried sludge DBS and dewatered sludge DS, for example, if the moisture content of the dewatered sludge DS is 78% and the moisture content of the sludge to be incinerated is set to 60%, then 62% by mass of the dewatered sludge DS to be processed is dried to a moisture content of 20% in the drying device 20 before being transported to the incinerator 1. The remaining 38% by mass of the dewatered sludge DS is then transported directly to the incinerator 1. As a result, the moisture content of the sludge to be incinerated becomes 60%. This allows for a reduction of approximately 40% in the size of the drying device 20.
[0088] Regarding the mass ratio of dried sludge DBS and dewatered sludge DS, for example, if the moisture content of the dewatered sludge DS is 78% and the moisture content of the sludge to be incinerated is set to 70%, then 37% by mass of the dewatered sludge DS to be processed is dried to a moisture content of 20% in the drying device 20 before being transported to the incinerator 1. The remaining 63% by mass of the dewatered sludge DS is then transported directly to the incinerator 1, resulting in a moisture content of 70% for the sludge to be incinerated. This allows for a reduction in the size of the drying device 20 by approximately 60%.
[0089] Returning to Figure 4, in step S12, the control device 9 controls the amount of dried sludge DBS and dewatered sludge DS supplied to the primary combustion chamber 11 so that the temperature of the combustion gas G detected by the thermometer 8, i.e., the temperature of the combustion gas G flowing from the primary combustion chamber 11 to the secondary combustion chamber 13, is between 900 and 1100°C.
[0090] As is generally known, burning sludge at 900-1100°C reduces the concentration of nitrous oxide (N2O) in the combustion gas G compared to burning it at temperatures outside this range. In this case, the present invention has the advantage that it is only necessary to control the supply amount of dried sludge DBS and dewatered sludge DS to the primary combustion chamber 11, without adding any special chemicals or performing any special treatments to the combustion chamber 11 in order to achieve a combustion temperature of 900-1100°C.
[0091] Therefore, according to the present invention, since the incineration treatment in the incinerator 11 is performed with the dewatered sludge DS stacked on top of the dried sludge DBS as described above, the incineration treatment can be performed without drying the entire amount of dewatered sludge. Furthermore, by stacking the highly adhesive dewatered sludge DS on top of the dried sludge DBS, it is possible to prevent the dewatered sludge DS from coming into contact with the grate 12 of the stoker structure of the incinerator 11 and causing problems. Moreover, by simply controlling the supply amounts of dried sludge DBS and dewatered sludge DS to the incinerator 11, the concentration of nitrous oxide (N2O) in the combustion gas G can be reduced.
[0092] In step S13, the concentration of nitrous oxide (N2O) in the combustion gas G is reduced by a method different from that used in step S12. Specifically, an N2O concentration meter 28, or N2O concentration sensor, installed in the flue 29 measures the N2O concentration in the gas G after combustion in the secondary combustion chamber 13 has finished. When the measured N2O concentration exceeds a set value, or is predicted to exceed a set value, the supply amount of dried sludge DBS is increased and the supply amount of dewatered sludge DS is decreased. In this way, the concentration of nitrous oxide (N2O) in the combustion gas G can be reduced simply by controlling the supply amounts of dried sludge DBS and dewatered sludge DS to the incinerator 11.
[0093] In the following step S14, the control device 9 determines whether or not it is permissible to terminate the combustion of the material to be burned. Whether or not it is permissible to terminate the combustion of the material to be burned is determined by whether or not the operator has instructed the sludge incineration equipment 100 to terminate its operation. If the control device 9 determines that the combustion of the material to be burned should not be terminated, the control device 9 returns to step S6. On the other hand, if the control device 9 determines that it is permissible to terminate the combustion of the material to be burned, the control device 9 terminates the combustion of the material to be burned and the process ends.
[0094] The details of the process in step S12 will be explained with reference to Figure 7. Once the process in step S11 is completed, in step S121, a substep of step S12, it is determined whether the temperature of the combustion gas G detected by the thermometer 8 is less than 900°C. If the temperature of the combustion gas G is less than 900°C, in order to raise this temperature to 900°C or higher, in step S123, control is performed to increase the amount of dried sludge supplied from the dry sludge supply device 2 to the primary combustion chamber 11 and to decrease the amount of dewatered sludge supplied from the dewatered sludge supply device 3 to the primary combustion chamber 11. This control is a feedforward control that increases or decreases the amount by a predetermined amount based on the gas temperature detection result. The amount of increase or decrease in supply, i.e., the control amount, can be set by experimental values or empirical values.
[0095] In step S121, if the temperature of the combustion gas G detected by the thermometer 8 is 900°C or higher, the decision in step S122 is made. Specifically, in step S122, if the temperature of the combustion gas G is below the first set temperature, and the temperature drop gradient of the combustion gas G detected by the thermometer 8 at the time of detection is greater than or equal to the set value, that is, if the temperature of the combustion gas G is rapidly decreasing, it is predicted that there is a high probability that the temperature of the combustion gas G will fall below 900°C, and the process in step S123 is performed in the same manner. Then the process proceeds to the next step S124. The first set temperature can be set appropriately in the range of 900°C to 1000°C, for example. Specifically, it can be set to 920°C, for example.
[0096] Conversely, in step S122, (i) The temperature of the combustion gas G detected by the thermometer 8 exceeds the first set temperature, or (b) When the temperature of the combustion gas G is below the first set temperature, but the temperature drop gradient of the combustion gas G is less than the set value, that is, when the temperature of the combustion gas G is below the first set temperature, but it is determined that the temperature of the combustion gas G is not dropping rapidly, Since it is determined that the temperature of the combustion gas G is unlikely to fall below 900°C, the process in step S123 is skipped, and the process proceeds to step S124.
[0097] In step S124, it is determined whether the temperature of the combustion gas G detected by the thermometer 8 exceeds 1100°C. If the temperature of the combustion gas G exceeds 1100°C, in step S126, control is performed to reduce the amount of dried sludge supplied from the dry sludge supply device 2 to the primary combustion chamber 11 and to increase the amount of dewatered sludge supplied from the dewatered sludge supply device 3 to the primary combustion chamber 11. This control is also a feedforward control, which increases or decreases the amount by a predetermined amount based on the gas temperature detection result. After that, the process proceeds to step S13.
[0098] In step S124, if the temperature of the combustion gas G detected by the thermometer 8 is 1100°C or lower, in step S125, if the temperature of the combustion gas G is above the second set temperature and the temperature rise gradient of the combustion gas G detected by the thermometer 8 at the time of detection is above the set value, that is, if the temperature of the combustion gas G is rising rapidly, it is predicted that there is a high possibility that the temperature of the combustion gas G will exceed 1100°C, and the process in step S126 is performed in the same manner. Then the process proceeds to the next step S13. The second set temperature can be set appropriately in the range of, for example, 1000°C to 1100°C. Specifically, it can be set to 1080°C, etc.
[0099] Conversely, in step S125, (i) The temperature of the combustion gas G detected by the thermometer 8 is below the second set temperature, or (b) When the temperature of combustion gas G is above the second set temperature, but the temperature rise gradient of combustion gas G is less than the set value, that is, when the temperature of combustion gas G is below the second set temperature, but it is determined that the temperature of combustion gas G is not rising rapidly, Since it is determined that the temperature of the combustion gas G is unlikely to exceed 1100°C, the process in step S126 is skipped, and the process proceeds to step S13.
[0100] Note that the order of steps S121 to S123 and steps S124 to S126 can be reversed; steps S124 to S126 can be performed first, followed by steps S121 to S123.
[0101] The processes in steps S121 to S123 can also be made into a loop that repeats these processes multiple times. Similarly, the processes in steps S124 to S126 can also be made into a loop that repeats these processes multiple times.
[0102] Alternatively, the processes in steps S121 to S123 and steps S124 to S126 can be combined into a single process, creating a loop that repeats these processes S121 to S126 multiple times.
[0103] In steps S123 and S126, both the process of increasing or decreasing the amount of dried sludge supplied and the process of increasing or decreasing the amount of dewatered sludge supplied are performed. However, if the temperature of the combustion gas G can be kept within the range of 900 to 1100°C by increasing or decreasing only one of these processes, then it is acceptable to control it in that manner.
[0104] The details of the process in step S13 will be explained with reference to Figure 8. Once the process in step S12 is completed, in step S131, a substep of step S13, it is determined whether the N2O concentration in the combustion gas G, measured by the N2O concentration meter 28, exceeds the first set concentration. The first set concentration can be set appropriately based on, for example, social regulatory values. Specifically, it can be set to a value such as 10 ppm.
[0105] In step S131, if the N2O concentration in the combustion gas G exceeds the first set concentration, in step S133, control is performed to increase the amount of dried sludge supplied from the dry sludge supply device 2 to the primary combustion chamber 11, and to decrease the amount of dewatered sludge supplied from the dewatered sludge supply device 3 to the primary combustion chamber 11. Then, the process proceeds to the next step S134.
[0106] In step S131, if the N2O concentration measured by the N2O concentration meter 28 is less than or equal to the first set concentration, the decision in step S132 is made. Specifically, in step S132, if the N2O concentration measured by the N2O concentration meter 28 is greater than or equal to the second set concentration, and the N2O concentration increase gradient measured by the N2O concentration meter 28 at the time of detection is greater than or equal to the set value, that is, if the N2O concentration is rising rapidly, it is predicted that there is a high possibility that the N2O concentration of the combustion gas G will exceed the first set concentration, and the process in step S133 is carried out in the same manner. Then the process proceeds to the next step S134. The second set concentration can be set to an appropriate value less than the first set concentration, for example. Specifically, it can be set to a value such as 1 ppm.
[0107] Conversely, in step S132, (i) The N2O concentration measured by the N2O concentration measuring instrument 28 is less than the second set concentration, or (b) If the N2O concentration measured by the N2O concentration measuring instrument 28 is equal to or greater than the second set concentration, but the N2O concentration increase gradient is less than the set value, that is, if the N2O concentration of combustion gas G is equal to or greater than the second set concentration, but it is determined that the N2O concentration of combustion gas G will not increase rapidly, Since it is determined that the N2O concentration of the combustion gas G is unlikely to exceed the first set concentration, the process in step S133 is skipped, and the process proceeds to step S134.
[0108] In step S134, it is determined whether the N2O concentration measured by the N2O concentration meter 28 after processing in steps S131 to S133 is below the first set concentration. If it is determined that the N2O concentration is below the first set concentration, the process proceeds to step S14. If it is determined that the N2O concentration exceeds the first set concentration, the process returns to step S131. This process of returning from step S134 to step S131 forms a feedback loop. That is, the process performed by the control device 9 in step S13 is feedback control, which increases or decreases the supply amount while measuring the N2O concentration in the combustion gas G with the N2O concentration meter 28.
[0109] The processes in step S12 and step S13 can also be performed in reverse order, such as performing step S13 first and then step S12. Furthermore, if performing either step S12 or step S13 alone is sufficient to reduce the N2O concentration in the combustion gas G to a predetermined level or lower, then performing only one of these processes is also acceptable.
[0110] [Embodiment 2] The configuration of the sludge incineration facility 200 according to Embodiment 2 will be described with reference to Figure 9.
[0111] The sludge incineration plant 200 according to Embodiment 2 differs from the sludge incineration plant 100 according to Embodiment 1 in that it uses a sandy dry material DBM that does not adhere to the grates 12M and 12F as the dry material DB. With this configuration, the sludge incineration plant 200 does not need to dry the dewatered sludge DS to produce dried sludge DBS because the dry material DBM plays the same role as dried sludge DBS. Therefore, there is no need to provide the drying device 20 shown in Figure 1. The differences between Embodiment 2 and Embodiment 1 will be mainly described below.
[0112] As shown in Figure 9, the dried material supply device 21 of the sludge incineration plant 200 according to Embodiment 2 differs from the dried material supply device 2 shown in Figure 1. In addition, the various sensors measure the dried material DBM instead of the dried sludge DBS. Specifically, the dried material sensor 4 shown in Figure 9 measures the amount of dried material DBM.
[0113] The dried material supply device 21 shown in Figure 9 includes a dried material storage tank 25 for temporarily storing dried material DBM, instead of the dried sludge storage tank 22 shown in Figure 1. The dust supply device 23 supplies dried material DBM to the grates 12M and 12F of the drying stage 121, instead of the dried sludge DBS shown in Figure 1. Since there is no need to dry the dewatered sludge DS if the dried material DB is dried material DBM, the dried material supply device 21 shown in Figure 9 does not require a drying device 20 like the dried material supply device 2 shown in Figure 1. Therefore, the dried material supply device 21 shown in Figure 9 can reduce the space required for installation and thus reduce the cost required for installation.
[0114] The operating method of the sludge incineration equipment 200 according to Embodiment 2 is the same as the operating method of the sludge incineration equipment 100 according to Embodiment 1.
[0115] In some cases, the dried sludge DBS shown in Figure 1 and the dried material DBM shown in Figure 9 can be used in combination. [Explanation of Symbols]
[0116] 1 Incinerator 2, 21 Dry material supply device 3. Dewatered sludge supply device 8 Thermometer 9 Control device 11 Primary combustion chamber 12M, 12F grate 13. Secondary combustion chamber 28 N2O concentration meter 90 Combustion Range 100, 200 sludge combustion facilities DS dewatered sludge DB dried form DBS dried sludge DBM (Dry, Sandy Material) G Combustion gas
Claims
1. When operating a sludge incineration facility that sends sludge from upstream to downstream using a grate that moves back and forth between the upstream and downstream areas, The dried material is supplied to the grate. Dewatered sludge with a higher water content than the dried material is supplied onto the grate. The dry body containing the dewatered sludge is sent by a grate to a primary combustion chamber where the dry body and the dewatered sludge are burned. Combustion gases from the primary combustion chamber are sent to the secondary combustion chamber for re-combustion. A method for operating a sludge incineration plant, characterized by controlling the supply amount of dried material and the supply amount of dewatered sludge so that the concentration of nitrous oxide in the combustion gas discharged from the secondary combustion chamber is below a set value.
2. The method for operating a sludge incineration facility according to claim 1, characterized in that the supply amount of dried material and the supply amount of dewatered sludge are controlled so that the temperature of the combustion gas flowing from the primary combustion chamber to the secondary combustion chamber is 900 to 1100°C.
3. The method for operating a sludge incineration facility according to claim 2, characterized in that when the temperature of the combustion gas flowing from the primary combustion chamber into the secondary combustion chamber falls below 900°C or is predicted to fall below 900°C, the supply amount of dry material is increased and the supply amount of dewatered sludge is decreased, and when the temperature of the combustion gas flowing from the primary combustion chamber into the secondary combustion chamber falls above 1100°C or is predicted to fall above 1100°C, the supply amount of dry material is decreased and the supply amount of dewatered sludge is increased.
4. A method for operating a sludge incineration facility according to claim 1 or 2, characterized by measuring the concentration of nitrous oxide in the combustion gas discharged from the secondary combustion chamber and controlling the supply amount of dried material and the supply amount of dewatered sludge so that the measured concentration of nitrous oxide is below a set value.
5. The method for operating a sludge incineration facility according to claim 4, characterized in that when the measured value of the concentration of nitrous oxide in the combustion gas discharged from the secondary combustion chamber exceeds a set value or is predicted to exceed a set value, the amount of dried material supplied and the amount of dewatered sludge supplied is increased.
6. The method for operating a sludge incineration plant according to claim 1, characterized in that at least one of dried sludge obtained by drying dewatered sludge and a dried material that does not adhere to the grate is used as the dried material.
7. A sludge incineration facility that uses a grate that moves back and forth between the upstream and downstream sides to send sludge from upstream to downstream and incinerate the sludge, A drying supply device that supplies a drying material to the grate, A dewatered sludge supply device that supplies dewatered sludge with a higher water content than the dried body onto the grate, A primary combustion chamber that receives the dried body containing the dewatered sludge, which has been fed out by the grate, and burns the dried body and the dewatered sludge, A secondary combustion chamber that re-combusts the combustion gases sent out from the primary combustion chamber, A sludge incineration facility characterized by comprising a control device that controls the supply amount of dried material and the supply amount of dewatered sludge so that the concentration of nitrous oxide in the combustion gas discharged from the secondary combustion chamber is below a set value.
8. It is further equipped with a thermometer to measure the temperature of the combustion gas flowing from the primary combustion chamber into the secondary combustion chamber. The sludge incineration facility according to claim 7, characterized in that the control device controls the supply amount of dried material and the supply amount of dewatered sludge so that the temperature of the combustion gas measured by a thermometer is 900 to 1100°C.
9. The sludge incineration equipment according to claim 8, characterized in that the control device increases the supply amount of dried material and decreases the supply amount of dewatered sludge when the temperature of the combustion gas flowing from the primary combustion chamber into the secondary combustion chamber falls below 900°C or is predicted to fall below 900°C, and decreases the supply amount of dried material and increases the supply amount of dewatered sludge when the temperature of the combustion gas flowing from the primary combustion chamber into the secondary combustion chamber falls above 1100°C or is predicted to fall above 1100°C.
10. The device further includes a concentration measuring device for measuring the concentration of nitrous oxide in the combustion gas emitted from the secondary combustion chamber. The sludge incineration facility according to claim 7 or 8, characterized in that the control device controls the supply amount of dried material and the supply amount of dewatered sludge so that the concentration of nitrous oxide measured by the concentration measuring device is below a set value.
11. The sludge incineration facility according to claim 10, characterized in that the control device controls the amount of dried material supplied and the amount of dewatered sludge supplied when the measured value of the concentration of nitrous oxide in the combustion gas discharged from the secondary combustion chamber exceeds a set value or is predicted to exceed a set value.
12. The sludge incineration equipment according to claim 7, characterized in that the dried material is at least one of dried sludge obtained by drying dewatered sludge and a dried material that does not adhere to the grate.