Combustion device and control method

Abstract

Provided is a control method of a refuse incineration facility capable of reducing a discharge amount of NOx. This combustion device comprises: a furnace into which a gas after combustion flows; a primary combustion chamber that is a furnace body including a drying stage, a combustion stage, and a post-combustion stage, and conveying the material to be incinerated while burning it, and that, when the upstream side in the conveying direction of the material to be incinerated is referred to as the front and the downstream side in the conveying direction is referred to as the rear, has a front ceiling portion extending forward from the furnace, a rear ceiling portion extending backward from the furnace, and a rear wall extending downward from the rear end of the rear ceiling portion; a secondary combustion chamber connected to the outlet side of the primary combustion chamber and having a secondary combustion gas supply nozzle; an optical measurement device for detecting an object of a specific wavelength band provided in the primary combustion chamber; and a means for calculating the detection position of the object of the specific wavelength and activating the reaction of unburned gas at the detection position to promote the generation of NOx, thereby increasing the NOx concentration at an early stage to increase the reaction speed of reduction in a downstream reduction region.

Description

Combustion device and control method

[0001] This disclosure claims priority to Japanese Patent Application No. 2024-154224, filed on September 6, 2024, the contents of which are incorporated herein by reference.

[0002] There is a demand for reducing the amount of harmful gases emitted from waste incineration facilities. For example, Patent Document 1 discloses a technology for reducing dioxin emissions by measuring the surface temperature of waste in an incinerator using infrared rays and measuring the temperature inside the furnace using a temperature sensor, and controlling combustion based on the measured waste surface temperature and furnace temperature. Patent Document 1 does not disclose a control method for reducing NOx.

[0003] Japanese Patent Application Laid-Open No. 2003-106509

[0004] There is a need for technology to reduce NOx emissions.

[0005] The present disclosure provides a combustion device and a control method that can solve the above-mentioned problems.

[0006] According to one aspect of the present disclosure, the combustion device comprises a furnace into which burned gas flows, a furnace body including a drying stage, a combustion stage, and a post-combustion stage, which transports the incineration material while burning it, and wherein the upstream side of the transport direction of the incineration material is referred to as the front and the downstream side of the transport direction as the rear, the combustion device comprises a primary combustion chamber having a front ceiling portion extending forward from the furnace, a rear ceiling portion extending rearward from the furnace, and a rear wall extending downward from the rear end of the rear ceiling portion, a secondary combustion chamber connected to the outlet side of the primary combustion chamber and having a secondary combustion gas supply nozzle, an optical measuring device provided in the primary combustion chamber for detecting targets of a specific wavelength band, and means for calculating the detection position of the target of the specific wavelength and activating the reaction of unburned gas at the detection position to promote the generation of NOx.

[0007] According to one aspect of the present disclosure, the control method is for a combustion apparatus including a furnace into which combustion gas flows, a furnace body including a drying stage, a combustion stage, and a post-combustion stage that transports the incineration material while burning it, where the upstream side in the transport direction of the incineration material is referred to as the front and the downstream side in the transport direction as the rear, a primary combustion chamber having a front ceiling portion extending forward from the furnace, a rear ceiling portion extending rearward from the furnace, and a rear wall extending downward from the rear end of the rear ceiling portion, a secondary combustion chamber connected to the outlet side of the primary combustion chamber and having a secondary combustion gas supply nozzle, and an optical measuring device provided in the primary combustion chamber that detects targets in a specific wavelength band, in which a computer calculates the detection position of the target of the specific wavelength and activates the reaction of unburned gas at the detection position to promote the generation of NOx.

[0008] According to the combustion device and control method described above, it is possible to reduce the amount of NOx emissions.

[0009] 1 is a diagram illustrating an example of the configuration of combustion equipment according to an embodiment. FIG. 2 is a block diagram illustrating the functional configuration of a control device according to an embodiment. FIG. 3 is a diagram illustrating an example of the installation position of an infrared camera according to an embodiment. FIG. 4 is a diagram illustrating an example of the flow of gas in a furnace when the NOx reduction control of an embodiment is performed. FIG. 5 is a diagram illustrating an example of the flow of gas in a furnace when the NOx reduction control of an embodiment is not applied. FIG. 6 is a diagram illustrating another example of the flow of gas in a furnace when the NOx reduction control of an embodiment is not applied. FIG. 7 is a first diagram illustrating position identification according to an embodiment. FIG. 8 is a second diagram illustrating position identification according to an embodiment. FIG. 9 is a first diagram illustrating the flow rate distribution of primary air according to an embodiment. FIG. 10 is a second diagram illustrating the flow rate distribution of primary air according to an embodiment. FIG. 11 is a flowchart illustrating an example of NOx reduction control according to an embodiment. FIG. 12 is a first diagram illustrating a position at which the flow rate of primary air is increased according to an embodiment. FIG. 13 is a second diagram illustrating a position at which the flow rate of primary air is increased according to an embodiment. FIG. 14 is a diagram illustrating a method for determining flow rate distribution according to an embodiment.

[0010] Hereinafter, embodiments of the present disclosure will be described with reference to the drawings. In the following description, components having the same or similar functions will be assigned the same reference numerals. Duplicate descriptions of those components may be omitted. The following embodiments do not limit the scope of the invention according to the claims. Not all combinations of features described in the embodiments are necessarily essential to the solution of the invention.

[0011] In this disclosure, "based on XX" means "based on at least XX" and may include cases where it is based on another element in addition to XX. "Based on XX" is not limited to cases where XX is used directly, but may also include cases where it is based on XX after calculation or processing. In this disclosure, "XX or YY" is not limited to cases where either XX or YY is used, but may include cases where both XX and YY are used. This also applies when there are three or more optional elements. "XX" and "YY" are arbitrary elements (for example, arbitrary information).

[0012] In this application, "acquire" is not limited to actively acquiring by sending a transmission request, but may also include passively receiving information transmitted from another device. "Acquire" is not limited to directly acquiring target information (information to be acquired) from the outside, but may also include generating and acquiring target information by performing calculations or processing on information acquired from the outside.

[0013] In the embodiment described below, for convenience of explanation, the side where the furnace body 30 is located relative to the hopper 21 described below is defined as the "rear" and the opposite side as the "front". For convenience of explanation, the upstream side in the transport direction of the incineration material may be referred to as the "front" and the downstream side in the transport direction as the "rear". The "front side" may be referred to as the "front furnace side" and the "rear side" may be referred to as the "end of furnace side". "Left" and "right" are defined based on the direction from the hopper 21 toward the furnace body 30.

[0014] <Embodiment> Hereinafter, the low-NOx control of a waste incineration facility according to the present disclosure will be described with reference to Figures 1 to 12. (Overall Configuration of the Combustion Facility) Figure 1 is a diagram showing an example of the configuration of a combustion facility according to an embodiment. For example, the combustion facility 1 is a stoker furnace for incinerating materials S such as municipal waste, industrial waste, or biomass. The combustion facility 1 is not limited to a stoker furnace and may be another type of combustion facility. For ease of explanation, the "materials to be incinerated" may be referred to as "waste" below. For example, the combustion facility 1 includes a control device 2, an incinerator 3, a heat recovery boiler 4, a cooling tower 5, a dust collector 6, a flue 7, and a chimney 8.

[0015] The incinerator 3 is a furnace that combusts collected incineration materials S that are fed from a storage section (not shown) that temporarily stores the collected incineration materials S while transporting them. Exhaust gas is generated in the incinerator 3 as the incineration materials S are burned inside the incinerator 3. The generated exhaust gas is sent to a heat recovery boiler 4 located at the top of the incinerator 3. The heat recovery boiler 4 heats water and generates steam by exchanging heat between the exhaust gas generated in the incinerator 3 and water. The exhaust gas that passes through the heat recovery boiler 4 is cooled in a cooling tower 5 and then sent to a dust collector 6. After soot and dust are removed from the exhaust gas in the dust collector 6, it is discharged into the atmosphere through a flue 7 and a chimney 8.

[0016] The incinerator 3 has, for example, a supply mechanism 20, a furnace body 30, a stoker 40, a discharge chute 43, a plurality of wind boxes 50a to 50e, a furnace 60, a blower mechanism 70, a first EGR nozzle 91, and a second EGR nozzle 93.

[0017] The supply mechanism 20 temporarily stores the materials S to be incinerated that are fed from a storage section (not shown) and sequentially supplies the materials S to the treatment space V of the furnace body 30 (described later). The supply mechanism 20 includes, for example, a hopper 21, a feeder 22, a moisture meter 23, and a sprinkler device 24.

[0018] The hopper 21 is a storage section provided to supply the materials to be incinerated S into the furnace body 30. The hopper 21 has an inlet section for introducing the materials to be incinerated S and an outlet section that leads to a processing space V of the furnace body 30, which will be described later. The materials to be incinerated S are introduced into the hopper 21 after being transported by a crane.

[0019] The feeder 22 is provided at the bottom of the hopper 21. The feeder 22 is formed, for example, in the shape of a plate that fits along the bottom of the hopper 21. The feeder 22 is driven by the control device 2 and is capable of reciprocating movement in a direction from the hopper 21 toward the treatment space V of the furnace body 30. The feeder 22 pushes the materials S to be incinerated that have accumulated inside the hopper 21 toward the treatment space V of the furnace body 30. The moisture meter 23 is a measuring device that detects information regarding the moisture content (e.g., moisture percentage or moisture amount) of the materials S to be incinerated that are fed into the hopper 21. The sprinkler device 24 is a device that adjusts the moisture content of the materials S to be incinerated by sprinkling water on the materials S.

[0020] The furnace body 30 is provided adjacent to the hopper 21 and is a facility for combusting the materials to be incinerated S while transporting them. Hereinafter, the transport direction of the materials to be incinerated S in the combustion facility 1 will be referred to as the "transport direction D." The transport direction D may also be referred to as the "depth direction."

[0021] The furnace body 30 has, from upstream to downstream in the conveying direction D, a drying stage 30a, a combustion stage 30b, and a post-combustion stage 30c, in this order. The furnace body 30 conveys the incineration material S from upstream to downstream while combusting it. The drying stage 30a is located upstream of the combustion stage 30b and the post-combustion stage 30c, and is a region where the incineration material S supplied from the hopper 21 is dried prior to combustion on the stoker 40. The combustion stage 30b and the post-combustion stage 30c are regions where the incineration material S, dried after passing through the drying stage 30a, is combusted on the stoker 40. In the combustion stage 30b, diffusion combustion occurs due to pyrolysis gases generated from the incineration material S, generating a flame F. In the post-combustion stage 30c, fixed carbon combustion occurs after diffusion combustion of the incineration material S, so no flame F is generated.

[0022] The furnace body 30 has, for example, an in-furnace temperature sensor 31 and an in-furnace pressure sensor 35. The in-furnace temperature sensor 31 is, for example, a thermocouple, and detects the temperature inside the furnace body 30 (sometimes referred to as "inside the furnace"). The in-furnace pressure sensor 35 detects the pressure inside the furnace body 30. A plurality of in-furnace temperature sensors 31 may be provided.

[0023] The furnace body 30 has, for example, a visible light camera 32 and an infrared camera 33. The visible light camera 32 and the infrared camera 33 photograph the interior of the furnace body 30. For example, the visible light camera 32 and the infrared camera 33 are provided at the downstream end (hereinafter referred to as the "furnace foot") of the furnace body 30 in the conveying direction D, and photograph the area from the furnace foot to the upstream side in the conveying direction D.

[0024] The visible light camera 32 photographs, for example, the flame F. The infrared camera 33 photographs the gas inside the furnace. The interior of the furnace is photographed by the infrared camera 33, which is equipped with a filter that transmits specific wavelengths tailored to the gas species present in the furnace (CO: 2125-2245 nm, CO2: 4160-4360 nm, H2O: 1375-1425 nm, NH3: 1500-1600 nm, background (flame transmission): 3800-4000 nm). The results of imaging by the visible light camera 32 and the infrared camera 33 are sent to the control device 2.

[0025] The infrared camera 33 may be composed of a plurality of infrared cameras arranged in a stereo system, for example. The visible light camera 32 and the infrared camera 33 may be provided at other positions (such as the left and / or right side walls of the furnace body 30) instead of at the furnace bottom of the furnace body 30. One or both of the visible light camera 32 and the infrared camera 33 may be omitted. Furthermore, instead of / in addition to the infrared camera 33, a depth camera, a stereo camera, a multispectral camera, a laser, etc. may be provided.

[0026] The stoker 40 includes multiple grates 41. The multiple grates 41 form a stoker surface 40a, which is the bottom surface of the furnace body 30. The material to be incinerated S is supplied in layers to the stoker surface 40a by the supply mechanism 20. The stoker surface 40a is provided across the drying stage 30a, combustion stage 30b, and post-combustion stage 30c described above. The multiple grates 41 include a fixed grate and a movable grate. The fixed grate is fixed to the upper surface of the wind boxes 50a to 50e, which will be described later. The movable grate moves back and forth at a constant speed along the transport direction D, stirring and mixing the material to be incinerated S on the movable grate and the fixed grate (on the stoker surface 40a) while transporting it downstream.

[0027] The discharge chute 43 is a device that drops the incineration material S that has been burned and turned into ash into an ash extrusion device located below the furnace body 30. The discharge chute 43 is provided at the end of the furnace body 30.

[0028] The multiple wind boxes 50a to 50e are provided below the stoker 40 and supply primary air for combustion into the furnace body 30 through the stoker 40. In this embodiment, the multiple wind boxes 50a to 50e are arranged side by side in the conveying direction D, corresponding to the multiple fire grates 41, for example. The wind box 50a is provided with a wind box pressure sensor 51a that detects the pressure inside the wind box 50a. The pressure inside the wind box 50a corresponds to the pressure of the primary air supplied from the wind box 50a to the furnace body 30. Similarly, the wind boxes 50b, 50c, 50d, and 50e are provided with wind box pressure sensors 51b, 51c, 51d, and 51e, respectively. The wind boxes 50a to 50e may be collectively referred to as wind boxes 50, and the wind box pressure sensors 51a to 51e may be collectively referred to as wind box pressure sensor 51.

[0029] The furnace 60 extends upward from the top of the furnace body 30. The furnace 60 is positioned above the grate 41, and post-combustion gas flows into it. Specifically, exhaust gas generated by the combustion of the incineration material S in the furnace body 30 flows through the furnace 60 to the heat recovery steam generator 4. The furnace 60 includes a front wall 60a located at the front of the space through which the exhaust gas flows and a rear wall 60b located at the rear of the space through which the exhaust gas flows. The front wall 60a and the rear wall 60b each extend vertically, for example. If the upstream side in the transport direction of the incineration material S is referred to as the front and the downstream side in that transport direction as the rear, the furnace 60 has a front ceiling portion 55 extending forward from the furnace 60, a rear ceiling portion 57 extending rearward from the furnace 60, and a rear wall 59 extending downward from the rear end of the rear ceiling portion 57. This space is referred to as the primary combustion chamber. The space connected to the outlet side of the primary combustion chamber and constituting the lower part of the furnace 60 is called the secondary combustion chamber.

[0030] The blower mechanism 70 supplies combustion air to the inside of the furnace body 30 and the furnace 60. The blower mechanism 70 includes, for example, a blower 71, a primary air line 72, an air preheater 73, a secondary air line 74, a damper 75, and an air flow sensor 76.

[0031] The blowers 71 are forced draft blowers that pressurize and send combustion air into the furnace body 30 and the furnace 60. The blowers 71 include, for example, a first blower 71A and a second blower 71B. The first blower 71A pressurizes and sends primary air for combustion into the furnace body 30 (e.g., the treatment space V and the primary combustion chamber) through a primary air line 72 and the multiple air boxes 50a to 50e. The second blower 71B pressurizes and sends secondary air for combustion into the furnace 60 (e.g., the treatment space V' and the secondary combustion chamber) through a secondary air line 74.

[0032] The primary air line 72 connects the first blower 71A to the multiple wind boxes 50a-50e. One or more (e.g., multiple) primary air dampers 75A are provided along the primary air line 72. In this embodiment, the multiple primary air dampers 75a-75e are provided in one-to-one correspondence with the multiple wind boxes 50a-50e. The primary air damper 75a changes the flow rate of primary air flowing from the primary air line 72 into the corresponding wind box 50a depending on the opening degree of the primary air damper 75a. The same applies to the primary air dampers 75b-75e. In other words, the distribution ratio of primary air among the multiple wind boxes 50a-50e (i.e., which wind box 50a, etc., is prioritized for supplying primary air into the furnace body 30) is changed depending on the opening degree of the multiple primary air dampers 75a-75e.

[0033] The air preheater 73 is a heat exchanger that preheats the primary air that is pressure-fed from the first blower 71A. For example, the air preheater 73 is provided midway along the primary air line 72. The air preheater 73 has a preheat temperature sensor 73a that detects the temperature of the preheated primary air.

[0034] The secondary air line 74 connects the second blower 71B and the furnace 60. In this embodiment, the secondary air line 74 has a first supply port 74a and a second supply port 74b. The first supply port 74a opens to the front wall 60a of the furnace 60 and supplies secondary air from the front wall 60a to the space within the furnace 60 (exhaust gas flow path). On the other hand, the second supply port 74b opens to the rear wall 60b of the furnace 60 and supplies secondary air from the rear wall 60b to the space within the furnace 60 (exhaust gas flow path). One or more (e.g., multiple) secondary air dampers 75B are provided along the secondary air line 74.

[0035] The air flow sensor 76 detects the flow rate of combustion air supplied to the furnace body 30 and the furnace 60. The air flow sensor 76 includes, for example, a first air flow sensor 76A and a second air flow sensor 76B. The first air flow sensor 76A is provided in the primary air line 72 and detects the flow rate of primary air supplied through the primary air line 72. The second air flow sensor 76B is provided in the secondary air line 74 and detects the flow rate of secondary air supplied through the secondary air line 74. The first air pressure sensor 77 detects the pressure of combustion air supplied to the furnace body 30. The first air pressure sensor 77 is provided in the primary air line 72 and detects the pressure of primary air supplied through the primary air line 72.

[0036] The gas sensor 81 is a sensor that detects components in the exhaust gas. The gas sensor 81 can detect, for example, the oxygen concentration (hereinafter referred to as "O2 concentration"), carbon monoxide concentration (hereinafter referred to as "CO concentration") (unburned carbon), carbon dioxide concentration (hereinafter referred to as "CO2 concentration"), or NOx concentration contained in the exhaust gas, the air ratio in the primary combustion zone, etc. The gas sensor 81 is provided, for example, in the flue 7, but may also be provided inside the chimney 8 or in another location (for example, a location where post-combustion gas can be detected).

[0037] The first EGR nozzle 91 is provided in an area of ​​the rear ceiling portion 57 rearward of the center of the rear ceiling portion 57 in the transport direction of the incineration material S, or on the rear wall 59 extending downward from the rear end of the rear ceiling portion 57. The first EGR nozzle 91 discharges EGR, air, or EGR mixed with air forward.

[0038] The second EGR nozzle 93 is provided in a position in front of the first EGR nozzle 91 in the rear ceiling portion 57. The second EGR nozzle 93 discharges EGR, air, or EGR mixed with air (an example of a second combustion gas) from the rear ceiling portion 57 toward the drying stage 30a or the combustion stage 30b. The second EGR nozzle 93 includes an angle adjustment mechanism 97 that can change the direction in which the EGR is discharged.

[0039] (Control device) Next, the control device 2 will be described. Fig. 2 is a block diagram showing the functional configuration of the control device 2. The control device 2 controls the combustion equipment 1. For example, the control device 2 controls the combustion of the material to be incinerated S in the furnace body 30. The control device 2 has various functions, but only the functions related to the low NOx control according to this embodiment will be described.

[0040] The control device 2 includes an acquisition unit 2a, a position identification unit 2b, an allocation determination unit 2c, and a control unit 2d. The acquisition unit 2a acquires images captured by the visible light camera 32 and the infrared camera 33. In the NOx reduction control of this embodiment, the visible light camera 32 and the infrared camera 33 are used to measure the release positions of various gases within the furnace. Multiple infrared cameras 33 may be provided, as illustrated in FIG. 3. FIG. 3 is a top view of the furnace body 30. As with the infrared cameras 33-1 to 33-14, multiple infrared cameras may be provided on the side of the furnace body 30 across the drying stage 30a, the combustion stage 30b, and the post-combustion stage 30c to capture images of the obliquely forward side. Alternatively, as with the infrared cameras 33-15 to 33-16, multiple infrared cameras may be provided on the ceiling near the post-combustion stage 30c. By providing a plurality of infrared cameras 33-1 to 33-16 and analyzing the images taken by each camera, the release positions of various gases can be detected with high accuracy.

[0041] The position specifying unit 2b specifies a position where the amount of primary air supplied into the furnace should be increased to achieve low NOx emissions. The allocation determining unit 2c determines the allocation ratio of the primary air supplied into the furnace from each of the air boxes 50a to 50e. The control unit 2d controls the primary air dampers 75a to 75e to control the flow rate of primary air supplied into the furnace from the air boxes 50a to 50e so that the flow rate of primary air supplied into the furnace from each of the air boxes 50a to 50e is the allocation ratio determined by the allocation determining unit 2c.

[0042] (NOx Reduction Control) Next, the NOx reduction control of this embodiment will be described with reference to FIG. 4. In this embodiment, the positions (depth direction positions) of unburned gases (CO, NH) and burned gases (CO, HO) are estimated from images captured by the infrared camera 33, and primary air is preferentially sent to the combustion position to actively generate NOx upstream of the stoker 40 (e.g., upstream of the primary combustion chamber, which is the reduction zone, e.g., the first half of the drying stage 30a to the combustion stage 30b). As a result, NOx is generated (partially oxidized) directly above the layer where the waste is burning, and then reduced in the furnace end space and completely combusted in the furnace 60. In the furnace end space, unburned gas generated by char combustion serves as a reducing agent.

[0043] Arrows 1 to 4 in Figure 4 indicate the flow of gas within the furnace when the NOx reduction control of this embodiment is implemented. Volatile gases combusted by primary air introduced from below the stoker 40 are drawn into the furnace tail space as shown and flow along the space within the furnace body 30 toward the furnace 60. In the example of Figure 4, a relatively large amount of primary air is supplied to the furnace from the wind box 50b where the flame F is present. Increasing the amount of primary air at the position of the flame F oxidizes the N contained in the fuel, promoting the generation of NOx. Arrow 1 indicates the release and transport of volatile gases. To achieve low NOx, it is important to promote combustion at the location where the volatile gas is released. Arrows 2 and 3 indicate reductive combustion. Next, the area where reductive combustion occurs can be made wider compared to the conventional control shown in Figures 5 and 6. By widening the reductive combustion area, the time required for NOx reduction can be secured. Arrow 4 indicates complete combustion. By widening the reductive combustion region, N is reduced at the position of arrow 4 compared to conventional control, and NOx generation at the position of arrow 4 (secondary combustion chamber) is suppressed, resulting in a reduction in NOx emitted from the combustion equipment 1.

[0044] For comparison, Figure 5 shows an example of gas flow in a furnace when the NOx reduction control of this embodiment is not applied. The gas flow path and flow direction are the same as those in Figure 4. In Figure 5, a relatively large amount of primary air is supplied to the furnace from the wind box 50c downstream of the flame F. At the position of arrow 1, there is a lack of O, so the N in the fuel cannot be released from the aromatic ring. At the end of the furnace position of arrow 2, a region with a high O2 concentration is locally formed, creating an oxidative combustion region. As a result, NOx is generated at the positions of arrows 3 and 4. In this example, NOx is not reduced.

[0045] Figure 6 shows another example of gas flow in the furnace when the NOx reduction control of this embodiment is not applied. The gas flow path and flow direction are the same as in Figure 4. In Figure 6, primary air is supplied to the furnace from each of the air boxes 50a to 50e at approximately the same ratio. At the position of arrow 1, volatile gas is released, at the position of arrow 2, gas transport occurs, at the position of arrow 3, reductive combustion occurs, and at the position of arrow 4, complete combustion occurs. If the air and volatile matter are not sufficiently mixed by the time of the combustion stage 30b, nitrogen is not sufficiently released from the aromatic ring in the reduction region indicated by arrow 3. As a result, the residence time of NOx in the reduction region is insufficient, and the NOx flows out to the outlet without being fully reduced. N remains in the complete combustion region indicated by arrow 4, increasing the generation of NOx. Therefore, NOx is not reduced in this example.

[0046] The nitrogen in the incineration material S exists in a state bound to hydrocarbons, which is oxidized to become NOx. To suppress NOx using a two-stage combustion method involving reduction and oxidation, NOx must be converted to N2 by completing a chemical reaction with reducing substances in the first-stage reduction zone, and as little NOx as possible must remain in the second-stage oxidation zone. The problem here is that when the nitrogen is bound to hydrocarbons, it does not undergo a reduction reaction to become N2. If the nitrogen in the hydrocarbons remains in the oxidation zone, oxidation occurs in the oxidation zone and the hydrocarbons are converted to NOx. Therefore, in the reduction zone, it is necessary to convert the nitrogen in the hydrocarbons to NOx as quickly as possible. Therefore, in this embodiment, as shown in Figure 4, the location where volatile gas is being released is identified, and the amount of primary air supplied to the identified location is increased to quickly oxidize the nitrogen in the volatiles to NOx. This widens the reduction zone, allowing sufficient residence time for NOx in the reduction zone to convert NOx to N2 and suppress the generation of NOx in the oxidation zone. By promoting the generation of NOx and increasing the NOx concentration early, the reduction reaction rate in the subsequent reduction zone can be increased, thereby achieving low NOx. Generally, primary air control is often performed to adjust the flame position, but in this embodiment, the distribution of primary air is controlled to promote the generation of NOx in the reduction zone.

[0047] (Identifying the Location of Volatile Gas Release) Next, a method for identifying the location of volatile gas release will be described. The location identification unit 2b acquires images of the furnace interior taken by an infrared camera 33 equipped with a filter that transmits specific wavelengths tailored to the gas species (CO: 2125-2245 nm, CO2: 4160-4360 nm, H2O: 1375-1425 nm, NH3: 1500-1600 nm, background photography (flame transmission): 3800-4000 nm), and identifies the location of volatile gas release and the main combustion location. The flame-transmitting filter for capturing background images is used to more accurately identify the locations of CO, NH3, H2O, and CO2 release by subtracting the image captured with this filter from images captured with filters of other wavelengths. The flame-transmitting filter is not essential. The simplest form of position identification is achieved by combining a single camera (infrared camera 33) with monocular depth estimation technology. For example, for an image captured by an infrared camera 33 equipped with a filter that transmits wavelengths of unburned fuel (CO, NH), the position identification unit 2b identifies the maximum light emission position and calculates the distance from the infrared camera 33 to the identified light emission position using monocular depth estimation. For example, for an image captured by an infrared camera 33 equipped with a filter that transmits wavelengths of burned fuel (H2O, CO2), the position identification unit 2b identifies the maximum position of brightness change and calculates the distance from the infrared camera 33 to the identified light emission position using monocular depth estimation. An example of an image captured by the infrared camera 33 is shown in FIG. 7A, and an overview of monocular depth estimation is shown in FIG. 7B. FIG. 7A shows an image captured with a CO filter attached. Reference numerals 71 and 72 indicate light emission positions (positions with high CO concentrations).

[0048] For example, the position identification unit 2b may estimate the concentrations of CO, CO2, H2O, and NH3, and then identify the location of active combustion as the release location of volatile gases from the differential values ​​of the concentrations. For example, the position identification unit 2b may capture images of steady-state gas information and instantaneous states of the incineration material S by changing filters for CO, CO2, H2O, and NH3 for each band for several seconds. The position identification unit 2b then generates an average image or standard deviation image of the images captured in each wavelength band through image processing, and calculates the density of each gas from the temperature (or the measured value of the furnace temperature sensor 31) and brightness obtained from the image using a theoretically constructed function that defines the relationship between temperature, density, and brightness ratio, and converts the density to concentration. For example, the reaction progress can be calculated from the concentration ratio of CO concentration to CO2 concentration. For H2O, the maximum H2O concentration may be assumed to be 20%, the measured concentration may be 10%, and the reaction progress may be calculated as 10% / 20% = 0.5. The gas concentration and reaction progress are used to determine the flow rate to be supplied to the identified position (described below). Furthermore, the position identification unit 2b may calculate the position of active combustion from the differential value of the calculated concentration and identify the calculated position as the release position of the volatile gas. The closer the position of active combustion is to the upstream side of the primary combustion chamber, the more NOx generation can be considered to be promoted. The concentration of each gas species is measured in the following order: first, burned components (CO2, H2O), then unburned components (NH3, CO), and then the reaction progress is calculated. If there are differences in the evaluation results of the amount of volatile matter released between the estimated values ​​of CO and NH3 concentrations, the reaction progress evaluation value based on the H2O concentration, and the CO / CO2 ratio (for example, the evaluation based on the CO concentration indicates a high amount of volatile matter, while the evaluation based on the CO / CO2 ratio indicates a low amount), the values ​​are trusted in the following order of priority: estimated CO concentration value > estimated NH3 concentration value > reaction progress evaluation value based on the H2O concentration > CO / CO2 ratio (the CO concentration estimate has the highest priority).

[0049] The above-described method of identifying the position using the camera 33 is one example. Other examples include the following: (a) Instead of attaching filters for various gases, images of the inside of the furnace may be captured using a multispectral camera, and images in wavelength bands corresponding to each gas type may be obtained using digital filtering. (b) Multiple infrared cameras equipped with the above filters may be prepared, and the volatile gas release position may be estimated from the images captured by the multiple cameras. These estimation results may then be combined to identify the three-dimensional location of the volatile gas release position. Two infrared cameras equipped with monocular depth estimation may be positioned so as to compensate for each other's blind spots. The volatile gas release position may be estimated from the images captured by the two cameras. These estimation results may then be combined to identify the volatile gas release position. (c) The flame position (volatile gas release position) may be estimated using a machine learning device that has learned the relationship between various plant data (e.g., furnace temperature, pressure, flow rate of the wind boxes 50a to 50e, etc.) and the flame position. (d) The distance from the light emission position of the luminous flame (the position behind the flame) included in the image captured by the visible light camera 32 installed at the end of the furnace to the visible light camera 32 is calculated. In this case, since it is not possible to accurately determine the location of the front of the flame, the flame position (the position where volatile gas is released) is estimated to be a predetermined length forward of the position indicated by the calculated distance from the visible light camera 32. (e) One or more laser beams are emitted into the furnace, and high CO2 areas are identified by laser CT measurement. (f) Temperature sensors are installed in the longitudinal direction of the stoker 40, and the position where the measured temperature is highest or where the measured temperature is above a predetermined threshold is estimated to be the flame position (the position where volatile gas is released).

[0050] (Estimation of Pressure Loss, etc.) As described above, in this embodiment, NOx is actively generated in the drying stage 30a through the combustion stage 30b and reduced in the furnace end space. To promote NOx generation, the amount of primary air supplied is increased at or slightly upstream of the volatile gas release position. To control the flow rate of primary air supplied to the furnace to a desired value, factors such as pressure loss in the primary air dampers 75a-75e, leakage between the air boxes 50a-50e (the air boxes 50a-50e have holes, so that primary air flows into the adjacent air box 50 if there is a pressure difference between them), and pressure loss in the grate 41 must be taken into consideration. Therefore, a ventilation test is conducted before waste is added or during furnace shutdown, and the relationship between the opening degree of the primary air dampers 75a-75e, pressure loss, and leakage is calculated.

[0051] 8A to 8C show schematic diagrams of the primary air supply system. Grates 41a to 41b represent the grates corresponding to wind boxes 50a to 50e, respectively, and materials to be incinerated Sa to Se represent materials to be incinerated S transported onto grates 41a to 41b, respectively. Leak 52ab represents a leak between wind boxes 50a and 50b, 52bc represents a leak between wind boxes 50b and 50c, 52cd represents a leak between wind boxes 50c and 50d, and 52de represents a leak between wind boxes 50d and 50e.

[0052] In the ventilation test, the pressure loss coefficient and leakage for each wind box damper are calculated. For example, as shown in FIG. 8B , with no dust layer present, only one damper, e.g., primary air damper 75a, is operated, while the other primary air dampers 75b to 75e are closed. The opening of primary air damper 75a is varied, and the relationship between the opening of primary air damper 75a and pressure loss is calculated from the difference between the measurement values ​​of wind box pressure sensor 51a and first air pressure sensor 77. The flow rate of leakage 52ab is calculated from the difference between the measurement values ​​of wind box pressure sensor 51a and wind box pressure sensor 51b. For example, the average leakage flow rate when the opening of primary air damper 75a is varied may be calculated. Similarly, the relationship between damper opening and damper pressure loss and the leakage flow rate between adjacent wind boxes 50 are calculated for primary air dampers 75b to 75e.

[0053] Next, as shown in FIG. 8C , the pressures measured by the wind box pressure sensors 51a-51e are equalized to eliminate leaks between the wind boxes, and the grates 41a-41e are opened and closed. The pressure losses of the grates 41a-41e are calculated from the pressures measured by the furnace pressure sensor 35, the first air pressure sensor 77, and the wind box pressure sensors 51a-51e (assuming the pressure losses of the grates 41a-41e are the same). Then, during operation of the combustion equipment 1, the pressure losses of the waste layers Sa-Se are estimated from the pressure measured by the first air pressure sensor 77, the pressure measured by the wind box pressure sensors 51a-51e, the pressure measured by the furnace pressure sensor 35, the pressure losses of the primary air dampers 75a-75e calculated in a prior ventilation test, and the pressure losses of the grates 41a-41e (assuming the pressure losses of the waste layers Sa-Se are the same).

[0054] The distribution determination unit 2c calculates the distribution of primary air to be supplied to the primary combustion chamber through the wind boxes 50a-50e, taking into account the pressure loss of the primary air dampers 75a-75e, the pressure loss of the grate 41, the pressure loss of the waste layer, and leakage between the wind boxes. For example, suppose the total flow loss resulting from the pressure loss of the primary air dampers 75a-75e, the pressure loss of the grate 41, and the pressure loss of the waste layer is "5," the leakage between the wind boxes is all "1," and it is desired that 60% of the total primary air be sent into the furnace from the wind box 50a and 10% of the total primary air be sent from the wind boxes 50b-50e. The flow rate of primary air supplied into the furnace from the wind box 50a is set to Xa, the flow rate of primary air supplied into the furnace from the wind box 50b to Xb, etc. Considering pressure loss and leakage between the wind boxes, the flow rate of primary air supplied from wind box 50a to the furnace is Xa - 5 (pressure loss) - 1 (leakage to wind box 50b), the flow rate of primary air supplied from wind box 50b to the furnace is Xb - 5 (pressure loss) - 1 (leakage to wind box 50c) + 1 (leakage from wind box 50a), and so on. The allocation determination unit 2c calculates Xa to Xe so that this result is 6:1:1:1:1. At this time, the allocation determination unit 2c sets the allocation ratio for each of wind boxes 50a to 50e so that the total allocation ratio of primary air supplied to the primary combustion chamber falls within the range of 0.9 to 1.05, for example. In this embodiment, the generation of NOx is promoted by sending a large amount of primary air to the position where the volatile gas is released, but it has been confirmed that the final amount of NOx emissions can be reduced by sending 50 to 80% of the total primary air to the air box 50 corresponding to the position where the volatile gas is released (described later).

[0055] (Operation) FIG. 9 is a flowchart showing an example of NOx reduction control according to the embodiment. The acquisition unit 2a acquires an image of a specific wavelength (Step S1). For example, the acquisition unit 2a acquires images of wavelengths corresponding to CO, CO2, NH3, and H20, respectively. Next, the position identification unit 2b estimates the depth of the light-emitting position using monocular depth estimation technology (Step S2). The position identification unit 2b identifies the light-emitting position based on the brightness of the image acquired in Step S1. If there are multiple light-emitting positions, all of the light-emitting positions are identified. Next, the position identification unit 2b estimates the distance from the infrared camera 33 for all of the identified light-emitting positions using monocular depth estimation technology. After estimating the light-emitting positions, the position identification unit 2b then estimates the unburned component position (the volatile component release position) (Step S3). For unburned gases such as CO2 and NH3, the position identification unit 2b estimates the maximum light-emitting intensity position as the unburned component position (the volatile component release position). For burned gases such as H2O and CO2, the position identification unit 2b estimates the position where the brightness change is large as the unburned gas position (the volatile matter release position described above). The position identification unit 2b calculates CO and NH3 concentration estimates, the reaction progress of H2O, the CO / CO2 ratio, etc.

[0056] Next, the position identification unit 2b determines whether the estimated unburned fuel position is more than a predetermined distance from the tip of the wind box directly below (step S4). Reference is now made to FIGS. 10A and 10B. FIG. 10A shows an example in which the unburned fuel position is more than a predetermined distance from the tip (upstream end) of the wind box directly below. FIG. 10B shows an example in which the unburned fuel position is close to the tip of the wind box directly below, but is not more than a predetermined distance away. If the unburned fuel position is more than a predetermined distance from the tip of the wind box directly below (step S4; Yes, in the case of FIG. 10A), the position identification unit 2b selects the wind box 50b directly below as the control target (step S5). If the unburned fuel position is not more than a predetermined distance from the tip of the wind box directly below (step S4; No, in the case of FIG. 10B), the position identification unit 2b selects the wind box 50a immediately before (upstream of) the wind box 50b directly below the unburned fuel position as the control target (step S6). The position specifying unit 2b notifies the allocation determining unit 2c of the wind box specified as the control target. By steps S4 to S6, primary air can be appropriately sent to the unburned fuel position.

[0057] Next, the allocation determination unit 2c determines the allocation of primary air to be supplied to the wind boxes 50a-50e (step S7). The allocation determination unit 2c has a map or function with the estimated CO concentration, estimated NH3 concentration, H2O reaction progress, CO / CO2 ratio, etc. on the horizontal axis and the target primary air ratio for the wind box to be controlled (the target value for the allocation of primary air to be supplied to the wind box 50 to be controlled) on the vertical axis (see, for example, FIG. 11). The allocation determination unit 2c references this map based on the estimated CO concentration, etc., and determines the target primary air ratio corresponding to the estimated CO concentration, etc. This map is created so that the target primary air ratio is set in the range of 50 to 80%. The allocation determination unit 2c determines the allocation for the wind box 50 to be controlled in this way, and for the remaining wind boxes 50, allocates primary air so that the supply amount is equal, for example. The allocation determination unit 2c calculates the allocation ratio of primary air to be supplied from each of the air boxes 50a to 50e to the furnace, taking into account pressure losses of dampers and other factors calculated in a prior ventilation test, leakage between the air boxes 50, and the like, so that the amount of primary air actually supplied from the air boxes 50a to 50e matches the determined allocation ratio of primary air, and outputs the calculated allocation ratio to the control unit 2d. The control unit 2d controls the primary air dampers 75a to 75e in accordance with the allocation ratio. As a result, the amount of primary air supplied from the air boxes 50a to 50e to the furnace is controlled to match the allocation ratio of primary air determined by the allocation determination unit 2c.

[0058] (Effects) As described above, according to this embodiment, the location where volatile gases are being generated by waste combustion is estimated based on images captured by the infrared camera 33 or the like. Then, by supplying a large amount of primary air (50% to 80% of the total) to that estimated location, the reaction of unburned gas is activated and NOx generation is promoted. By promoting NOx generation early during the waste combustion process in the primary combustion chamber, which serves as the reduction zone, the remaining time spent in the primary combustion chamber can be allocated to reduction; for example, the hearth space can be used as the reduction zone. By promoting NOx generation early, the NOx concentration increases early, increasing the reduction reaction rate in the downstream reduction zone. This suppresses the generation of NOx during subsequent complete combustion and reduces NOx emissions from the incineration system 1.

[0059] 12 is a diagram showing an example of the hardware configuration of a control device. A computer 900 includes a CPU 901, a main storage device 902, an auxiliary storage device 903, an input / output interface 904, and a communication interface 905. The above-described control device 2 is implemented in the computer 900. The above-described functions are stored in the auxiliary storage device 903 in the form of a program. The CPU 901 reads the program from the auxiliary storage device 903, loads it into the main storage device 902, and executes the above-described processing in accordance with the program. The CPU 901 allocates a storage area in the main storage device 902 in accordance with the program. The CPU 901 allocates a storage area in the auxiliary storage device 903 for storing data being processed in accordance with the program.

[0060] A program for implementing all or part of the functions of the control device 2 may be recorded on a computer-readable recording medium, and the program may be loaded into a computer system and executed to perform processing by each functional unit. The term "computer system" as used herein includes hardware such as an OS and peripheral devices. If a WWW system is used, the term "computer system" also includes the homepage provision environment (or display environment). The term "computer-readable recording medium" refers to portable media such as CDs, DVDs, and USBs, as well as storage devices such as hard disks built into the computer system. If the program is distributed to the computer 900 via a communication line, the computer 900 may load the program into the main storage device 902 and execute the processing described above. The program may be for implementing part of the functions described above, or may be capable of implementing the functions described above in combination with a program already stored in the computer system.

[0061] As described above, several embodiments according to the present disclosure have been described, but all of these embodiments are presented as examples and are not intended to limit the scope of the invention. These embodiments can be implemented in various other forms, and various omissions, substitutions, and modifications can be made without departing from the spirit of the invention. These embodiments and their modifications are included in the scope of the invention and its equivalents as defined in the claims, as well as in the scope and spirit of the invention.

[0062] <Additional Notes> The combustion device and the control method described in the embodiment can be understood, for example, as follows.

[0063] (1) A combustion apparatus according to a first aspect includes a furnace into which combustion gas flows, a furnace body including a drying stage, a combustion stage, and a post-combustion stage for transporting incinerated materials while combusting them, where the upstream side in the transport direction of the incinerated materials is referred to as the front and the downstream side in the transport direction as the rear, a primary combustion chamber having a front ceiling extending forward from the furnace, a rear ceiling extending rearward from the furnace, and a rear wall extending downward from the rear end of the rear ceiling, a secondary combustion chamber connected to the outlet side of the primary combustion chamber and having a secondary combustion gas supply nozzle, an optical measuring device installed in the primary combustion chamber for detecting targets of a specific wavelength band, and means for calculating the detection position of the target of the specific wavelength and activating the reaction of unburned gas at the detection position to promote the generation of NOx. This allows NOx to be generated early in the first half of the primary combustion chamber, which is the reduction zone, thereby lengthening the residence time of NOx in the reduction zone and ensuring time to complete the reduction. By promoting the generation of NOx early, the NOx concentration can be increased early and the reduction reaction rate in the downstream reduction zone can be increased, thereby reducing the amount of NOx emissions.

[0064] (2) A combustion device according to a second aspect is the combustion device of (1) to (2), in which the opening of a damper provided in a flow path that supplies primary air to the primary combustion chamber is controlled to increase the flow rate of the primary air sent to the detection position to 50 to 80% of the total amount of the primary air supplied to the primary combustion chamber, thereby activating the reaction of the unburned gas. This allows NOx to be generated early and the residence time of the NOx in the reduction zone to be extended.

[0065] (3) A combustion apparatus according to a third aspect is the combustion apparatus of (1) to (2), in which the allocation of the primary air to be supplied to each of the plurality of wind boxes is calculated taking into account the pressure loss of the dampers provided for each of the plurality of wind boxes arranged along the conveying path below the conveying path for conveying the materials to be incinerated, and the amount of primary air leaking between adjacent wind boxes. By taking into account the pressure loss and the leak between the wind boxes, the allocation ratio of the primary air to be supplied to the primary combustion chamber through each wind box can be accurately realized.

[0066] (4) A fourth aspect of the combustion device is the combustion device of any one of (1) to (3), in which, for a plurality of wind boxes that are the supply ports of the primary air and are arranged along the conveying path below the conveying path for conveying the incineration material, if the distance from the upstream end in the conveying direction of the wind box arranged directly below the detection position to the detection position is equal to or greater than a predetermined value, the amount of primary air supplied from the wind box directly below the detection position is increased, and if the distance is less than the predetermined value, the amount of primary air supplied from the wind box one wind box upstream of the wind box directly below the detection position is increased. This allows primary air to be reliably sent to a position where unburned gas exists, thereby activating the generation of NOx.

[0067] (5) A control method according to a fifth aspect is a combustion apparatus comprising: a furnace into which combustion gas flows; a furnace body including a drying stage, a combustion stage, and a post-combustion stage, which transports the incinerated material while burning it; a primary combustion chamber having a front ceiling portion extending forward from the furnace, a rear ceiling portion extending rearward from the furnace, and a rear wall extending downward from the rear end of the rear ceiling portion, where the upstream side of the transport direction of the incinerated material is referred to as the front and the downstream side of the transport direction as the rear; a secondary combustion chamber connected to the outlet side of the primary combustion chamber and having a secondary combustion gas supply nozzle; and an optical measuring device provided in the primary combustion chamber for detecting targets of a specific wavelength band; wherein a computer calculates the detection position of the target of the specific wavelength and activates the reaction of unburned gas at the detection position to promote the generation of NOx.

[0068] According to the combustion device and control method described above, it is possible to reduce the amount of NOx emissions.

[0069] 1...Combustion equipment, 2...Control device, 2a...Acquisition unit, 2b...Location identification unit, 2c...Allocation determination unit, 2d...Control unit, 3...Incinerator, 21...Hopper, 22...Feeder, 23...Moisture meter, 24...Sprinkler device, 30...Furnace body, 31...Inner furnace temperature sensor, 32...Visible light camera, 33...Infrared camera, 40...Stoker, 41...Grate, 50...Wind box, 51...Wind box pressure sensor, 55...Front ceiling unit Reference Signs List 57: rear ceiling portion, 59: rear wall, 60: furnace, 60a: front wall, 60b: rear wall, 70: blower mechanism, 71: blower, 73: air preheater, 75: damper, 81: gas sensor, 91: first EGR nozzle, 93: second EGR nozzle, 900: computer, 901: CPU, 902: main memory device, 903: auxiliary memory device, 904: input / output interface, 905: communication interface

Claims

1. A combustion device comprising: a furnace into which post-combustion gas flows; a furnace body including a drying stage, a combustion stage, and a post-combustion stage that transports the materials to be incinerated while burning them, wherein the upstream side in the transport direction of the materials to be incinerated is referred to as the front and the downstream side in the transport direction as the rear, and wherein a primary combustion chamber has a front ceiling section extending forward from the furnace, a rear ceiling section extending rearward from the furnace, and a rear wall extending downward from the rear end of the rear ceiling section; a secondary combustion chamber connected to the outlet side of the primary combustion chamber and having a secondary combustion gas supply nozzle; an optical measuring device that detects objects of a specific wavelength band that is provided in the primary combustion chamber; and means that calculates the detection position of the object of the specific wavelength and activates the reaction of unburned gas at the detection position to promote the generation of NOx.

2. The combustion device according to claim 1, further comprising: controlling the opening of a damper provided in a flow path that supplies primary air to the primary combustion chamber, thereby increasing the flow rate of primary air sent to the detection position to 50 to 80 percent of the total amount of primary air supplied to the primary combustion chamber, thereby activating the reaction of the unburned gas.

3. A combustion device as described in claim 2, wherein the allocation of the primary air to be supplied to each of a plurality of wind boxes is calculated taking into consideration the pressure loss of the dampers provided for each of a plurality of wind boxes arranged along the conveying path below the conveying path that conveys the materials to be incinerated, and the amount of primary air leaking between adjacent wind boxes.

4. A combustion device as described in claim 1 or claim 2, wherein, for a plurality of wind boxes that are primary air supply ports arranged along a conveying path below the conveying path that conveys the material to be incinerated, if the distance from the upstream end in the conveying direction of the wind box arranged directly below the detection position to the detection position is equal to or greater than a predetermined value, the primary air supplied from the wind box directly below the detection position is increased, and if the distance is less than the predetermined value, the primary air supplied from the wind box one position upstream of the wind box directly below the detection position is increased.

5. A control method for a combustion device comprising a furnace into which post-combustion gas flows, a furnace body including a drying stage, a combustion stage, and a post-combustion stage that transports materials to be incinerated while burning them, where the upstream side in the transport direction of the materials to be incinerated is referred to as the front and the downstream side in the transport direction as the rear, a primary combustion chamber having a front ceiling portion extending forward from the furnace, a rear ceiling portion extending rearward from the furnace, and a rear wall extending downward from the rear end of the rear ceiling portion, a secondary combustion chamber connected to the outlet side of the primary combustion chamber and having a secondary combustion gas supply nozzle, and an optical measuring device provided in the primary combustion chamber that detects objects of a specific wavelength band, wherein a computer calculates the detection position of the object of the specific wavelength and activates the reaction of unburned gas at the detection position to promote the generation of NOx.

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