Combustion apparatus and control method

Abstract

This invention provides a control method for waste incineration equipment that reduces NOx emissions. [Solution] The combustion apparatus comprises a furnace into which the gas after combustion flows, a furnace body that includes a drying stage, a combustion stage, and a post-combustion stage and burns and transports the material to be incinerated, and, when the upstream side in the transport direction of the material to be incinerated is referred to as the front and the downstream side in the transport direction is referred to as the rear, a primary combustion chamber having 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 provided 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 in a specific wavelength band, and means for calculating the detection position of the target in the specific wavelength, and increasing the reaction rate of reduction in the downstream reduction region by increasing the NOx concentration early by activating the reaction of the unburned gas at the detection position and promoting the generation of NOx.

Description

Technical Field

[0001] The present disclosure relates to a combustion device and a control method.

Background Art

[0002] There is a demand to reduce the emission amount of harmful gases discharged from waste incineration facilities. For example, in Patent Document 1, the surface temperature of waste in an incinerator is measured using infrared rays, and the temperature inside the furnace is measured using a temperature sensor, and combustion control is performed based on the measured waste surface temperature and furnace temperature, thereby reducing the emission amount of dioxins. Patent Document 1 does not disclose a control method for NOx reduction.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] There is a demand for a technology to reduce the emission amount of NOx.

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

Means for Solving the Problems

[0006] The combustion apparatus of the present disclosure comprises a furnace into which post-combustion gas flows, a furnace body that includes a drying stage, a combustion stage, and a post-combustion stage and conveys the material to be incinerated while burning it, and a primary combustion chamber having 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, with the upstream side in the conveying direction of the material to be incinerated being referred to as the front and the downstream side in the conveying direction being referred to as the rear, a secondary combustion chamber provided 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 in a specific wavelength band, and means for calculating the detection position of the target in the specific wavelength and activating the reaction of unburned gas at the detection position to promote the generation of NOx.

[0007] The control method of the present disclosure relates to a combustion apparatus comprising a furnace into which post-combustion gas flows, a furnace body that transports materials to be incinerated while burning them, and a primary combustion chamber having 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, with the upstream side in the transport direction of the materials to be incinerated being referred to as the front and the downstream side in the transport direction being referred to as the rear, a secondary combustion chamber provided 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. [Effects of the Invention]

[0008] According to the combustion apparatus and control method of this disclosure, NOx emissions can be reduced. [Brief explanation of the drawing]

[0009] [Figure 1] This figure shows an example of the configuration of a combustion equipment according to the present invention. [Figure 2] This is a block diagram showing the functional configuration of the control device according to the embodiment. [Figure 3]This figure shows an example of the installation position of the infrared camera in the embodiment. [Figure 4] This figure shows an example of gas flow inside the furnace when the low-NOx control of the embodiment is implemented. [Figure 5] This figure shows an example of gas flow inside the furnace when the low-NOx control of the embodiment is not applied. [Figure 6] This figure shows another example of gas flow in the furnace when the low-NOx control of the embodiment is not applied. [Figure 7] This is a diagram illustrating the location identification according to the embodiment. [Figure 8A] This is the first diagram illustrating the flow rate distribution of primary air according to the embodiment. [Figure 8B] This is a second figure illustrating the flow rate distribution of the primary air according to the embodiment. [Figure 8C] This is a third figure illustrating the flow rate distribution of the primary air according to the embodiment. [Figure 9] This flowchart shows an example of NOx reduction control according to the embodiment. [Figure 10] This figure shows the position where the flow rate of the primary air is increased according to the embodiment. [Figure 11] This figure illustrates a method for determining flow rate distribution according to an embodiment. [Figure 12] This figure shows an example of the hardware configuration of the control device according to the embodiment. [Modes for carrying out the invention]

[0010] Embodiments of this disclosure will be described below with reference to the drawings. In the following description, components having the same or similar function will be denoted by the same reference numerals. Duplication of descriptions of these components may be omitted. The following embodiments are not intended to limit the invention as claimed. Furthermore, not all combinations of features described in the embodiments are necessarily essential to the solution of the invention.

[0011] In the present disclosure, "based on XX" means "based at least on XX", and may include cases based on other elements in addition to XX. Also, "based on XX" is not limited to directly using XX, and may include cases based on something obtained by performing operations or processing on XX. In the present disclosure, "XX or YY" is not limited to either one of XX and YY, and may include both cases of XX and YY. This is the same when there are three or more selectable elements. "XX" and "YY" are arbitrary elements (for example, arbitrary information).

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

[0013] In the embodiments described below, for the sake of convenience of explanation, the side where the furnace body 30 is located with respect to the hopper 21 to be described later is defined as "rear", and the opposite side is defined as "front". In the following, for the sake of convenience of explanation, the upstream side in the conveying direction of the waste to be incinerated may be referred to as "front", and the downstream side in the conveying direction may be referred to as "rear". Also, the "front side" may be referred to as the "front side of the furnace", and the "rear side" may be referred to as the "rear side of the furnace". Also, "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 the waste combustion equipment of the present disclosure will be described with reference to FIGS. 1 to 12. (Overall configuration of combustion equipment) FIG. 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 that uses municipal waste, industrial waste, or biomass as the incinerated material S. Note that the combustion facility 1 is not limited to a stoker furnace, and may be another type of combustion facility. Hereinafter, for convenience of explanation, the "incinerated material" may be referred to as "garbage" in some cases. For example, the combustion facility 1 includes a control device 2, an incinerator 3, a waste heat recovery boiler 4, a desuperheater 5, a dust collector 6, a flue passage 7, and a chimney 8.

[0015] The incinerator 3 is a furnace that burns the incinerated material S while conveying the incinerated material S input from a storage section (not shown) that temporarily stores the collected incinerated material S. Exhaust gas is generated in the incinerator 3 due to the combustion of the incinerated material S in the incinerator 3. The generated exhaust gas is sent to a waste heat recovery boiler 4 provided above the incinerator 3. The waste heat recovery boiler 4 heats water by performing heat exchange between the exhaust gas generated in the incinerator 3 and water to generate steam. The exhaust gas that has passed through the waste heat recovery boiler 4 is cooled in the desuperheater 5 and then sent to the dust collector 6. After the dust and soot are removed from the exhaust gas in the dust collector 6, the exhaust gas is discharged into the atmosphere through the flue passage 7 and the 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 firebox 60, a blower mechanism 70, a first EGR nozzle 91, and a second EGR nozzle 93.

[0017] The supply mechanism 20 is a mechanism that temporarily stores the incinerated material S input from a storage section (not shown) and sequentially supplies it toward the processing space V of the furnace body 30 described later. The supply mechanism 20 has, for example, a hopper 21, a feeder 22, a moisture meter 23, and a watering device 24.

[0018] The hopper 21 is a storage section provided to supply the incinerated material S into the furnace body 30. The hopper 21 has an inlet section into which the incinerated material S is input and an outlet section that communicates with the processing space V of the furnace body 30 described later. The incinerated material S carried by a crane is input into the hopper 21.

[0019] The feeder 22 is located at the bottom of the hopper 21. The feeder 22 is formed, for example, in the shape of a plate along the bottom of the hopper 21. The feeder 22 is driven by the control device 2 and is capable of reciprocating along the direction from the hopper 21 toward the processing space V of the furnace body 30. The feeder 22 pushes the material to be incinerated S accumulated inside the hopper 21 toward the processing space V of the furnace body 30. The moisture meter 23 is a measuring instrument that detects information regarding the moisture content (e.g., moisture ratio or amount of moisture) of the material to be incinerated S that is fed into the hopper 21. The water spraying device 24 is a device that adjusts the moisture content of the material to be incinerated S by spraying water on it.

[0020] The furnace body 30 is installed adjacent to the hopper 21 and is a device that burns the material to be incinerated S while transporting it. Hereinafter, the direction in which the material to be incinerated S is transported in the combustion device 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 a drying stage 30a, a combustion stage 30b, and a post-combustion stage 30c in that order, from upstream to downstream in the transport direction D. The furnace body 30 transports the material to be incinerated S from upstream to downstream while burning it. The drying stage 30a is located upstream of the combustion stage 30b and the post-combustion stage 30c, and is a region that dries the material to be incinerated S supplied from the hopper 21 prior to combustion on the stoker 40. The combustion stage 30b and the post-combustion stage 30c are regions in which the material to be incinerated S, which has passed through the drying stage 30a and is in a dried state, is burned on the stoker 40. In the combustion stage 30b, diffusion combustion occurs due to pyrolysis gas generated from the material to be incinerated S, and a flame F is produced. In the post-combustion stage 30c, fixed carbon combustion occurs after the diffusion combustion of the material to be incinerated S, so no flame F is produced.

[0022] The furnace body 30 includes, for example, a furnace temperature sensor 31 and a furnace pressure sensor 35. The furnace temperature sensor 31 is, for example, a thermocouple and detects the temperature inside the furnace body 30 (sometimes referred to as "the furnace"). The furnace pressure sensor 35 detects the pressure inside the furnace body 30. Multiple furnace temperature sensors 31 may be provided.

[0023] The furnace body 30 includes, for example, a visible light camera 32 and an infrared camera 33. The visible light camera 32 and the infrared camera 33 photograph the inside of the furnace body 30. For example, the visible light camera 32 and the infrared camera 33 are installed at the downstream end of the furnace body 30 in the transport direction D (hereinafter referred to as the "furnace tail") and photograph the upstream side in the transport direction D from the furnace tail.

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

[0025] The infrared camera 33 may be composed of multiple infrared cameras arranged in a stereo configuration, for example. The visible light camera 32 and infrared camera 33 may also be installed at a different location (such as the left and / or right wall of the furnace body 30) instead of at the furnace tail. Furthermore, either or both of the visible light camera 32 and infrared camera 33 may be omitted. In addition, a depth camera, stereo camera, multispectral camera, laser, etc., may be provided instead of / in addition to the infrared camera 33.

[0026] The stoker 40 includes a plurality of grates 41. The plurality of 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, the combustion stage 30b, and the post-combustion stage 30c described above. The plurality of grates 41 include fixed grates and movable grates. The fixed grates are fixed to the upper surfaces of the wind boxes 50a to 50e, which will be described later. The movable grates reciprocate along the transport direction D at a constant speed, thereby transporting the material to be incinerated S on the movable grates and fixed grates (on the stoker surface 40a) downstream while stirring and mixing them.

[0027] The discharge chute 43 is a device that drops the incinerated material S, which has turned into ash after combustion, into an ash extrusion device located below the furnace body 30. The discharge chute 43 is installed at the rear of the furnace body 30.

[0028] Multiple wind boxes 50a to 50e are provided below the stoker 40 and supply primary air for combustion to the inside of the furnace body 30 through the stoker 40. In this embodiment, the multiple wind boxes 50a to 50e are arranged in a line in the transport direction D, for example, corresponding to multiple grates 41. Wind box 50a is provided with a wind box pressure sensor 51a for detecting the pressure inside wind box 50a. The pressure inside wind box 50a corresponds to the pressure of the primary air supplied from wind box 50a to the inside of the furnace body 30. Similarly, wind boxes 50b, 50c, 50d, and 50e are provided with wind box pressure sensors 51b, 51c, 51d, and 51e, respectively. Wind boxes 50a to 50e may be collectively referred to as wind box 50, and 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 the combustion gases flow into it. That is, the exhaust gas generated by the combustion of the material to be incinerated S in the furnace body 30 flows through the furnace 60 to the waste heat recovery boiler 4. The furnace 60 includes a front wall 60a located on the front side of the space through which the exhaust gas flows, and a rear wall 60b located on the rear side of the space through which the exhaust gas flows. The front wall 60a and the rear wall 60b each extend, for example, in the vertical direction. If the upstream side in the direction of transport of the material to be incinerated S is referred to as the front, and the downstream side in that direction is referred to as the rear, the furnace 60 has a front ceiling section 55 extending forward from the furnace 60, a rear ceiling section 57 extending backward from the furnace 60, and a rear wall 59 extending downward from the rear end of the rear ceiling section 57. This space is called the primary combustion chamber. Furthermore, the space connected to the outlet side of the primary combustion chamber and forming the lower part of the furnace 60 is called the secondary combustion chamber.

[0030] The blowing mechanism 70 supplies combustion air to the furnace body 30 and the furnace 60. The blowing 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 blower 71 is a forced-air blower that pressurizes combustion air into the furnace body 30 and the furnace 60. The blower 71 includes, for example, a first blower 71A and a second blower 71B. The first blower 71A pressurizes primary combustion air into the furnace body 30 (e.g., processing space V, primary combustion chamber) through a primary air line 72 and a plurality of air boxes 50a to 50e. The second blower 71B pressurizes secondary combustion air into the furnace 60 (e.g., processing space V', secondary combustion chamber) through a secondary air line 74.

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

[0033] The air preheater 73 is a heat exchanger that preheats the primary air supplied under pressure from the first blower 71A. For example, the air preheater 73 is installed in the middle of the primary air line 72. The air preheater 73 has a preheating 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 into the front wall 60a of the furnace 60 and supplies secondary air from the front wall 60a of the furnace 60 to the space inside the furnace 60 (exhaust gas flow path). On the other hand, the second supply port 74b opens into the rear wall 60b of the furnace 60 and supplies secondary air from the rear wall 60b of the furnace 60 to the space inside the furnace 60 (exhaust gas flow path). One or more (for example, 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 installed in the middle of 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 installed in the middle of 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 the combustion air supplied to the furnace body 30. The first air pressure sensor 77 is installed in the middle of 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 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 portion), carbon dioxide concentration (hereinafter referred to as "CO2 concentration"), NOx concentration, and the air ratio in the primary combustion zone of the exhaust gas. The gas sensor 81 is installed, for example, in the flue 7, but may also be installed inside the chimney 8, or in another location (for example, a place where post-combustion gas can be detected).

[0037] The first EGR nozzle 91 is located in the rear ceiling section 57 in a region behind the center of the rear ceiling section 57 in the direction of transport of the material to be incinerated S, or on the rear wall 59 extending downward from the rear end of the rear ceiling section 57. The first EGR nozzle 91 discharges EGR, air, or EGR mixed with air forward.

[0038] The second EGR nozzle 93 is located in the rear ceiling section 57, in a position forward of the first EGR nozzle 91. The second EGR nozzle 93 discharges EGR, air, or EGR mixed with air (an example of a second combustion gas) from the rear ceiling section 57 toward the drying stage 30a or the combustion stage 30b. The second EGR nozzle 93 is equipped with 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. Figure 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 comprises an acquisition unit 2a, a location identification unit 2b, a distribution 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 low NOx control of this embodiment, the visible light camera 32 and the infrared camera 33 are used to measure the release locations of various gases inside the furnace. Multiple infrared cameras 33 may be provided, as illustrated in Figure 3. Figure 3 is a top view of the furnace body 30. Multiple infrared cameras, such as infrared cameras 33-1 to 33-14, may be provided on the side of the furnace body 30 to capture the diagonal front side over the drying stage 30a, the combustion stage 30b, and the post-combustion stage 30c, or multiple infrared cameras, such as infrared cameras 33-15 to 33-16, may be provided on the ceiling side near the post-combustion stage 30c. By providing multiple infrared cameras 33-1 to 33-16, etc., and analyzing the images captured by each camera, the release locations of various gases can be detected with high accuracy.

[0041] The position identification unit 2b identifies the position where the amount of primary air supplied to the reactor is increased in order to achieve low NOx emissions. The distribution determination unit 2c determines the distribution ratio of primary air supplied into the furnace from each of the wind chambers 50a to 50e. The control unit 2d controls the primary air flow rate by controlling the primary air dampers 75a to 75e so that the flow rate of primary air supplied from the wind boxes 50a to 50e into the furnace matches the distribution ratio determined by the distribution determination unit 2c.

[0042] (NOx reduction control) Next, the NOx reduction control of this embodiment will be described with reference to Figure 4. In this embodiment, the location (depth direction) of unburned gases (CO, NH3) and burned gases (CO2, H2O) is estimated from the image captured by the infrared camera 33, and primary air is preferentially supplied to the combustion location in order to actively generate NOx upstream of the stoker 40 (for example, upstream of the primary combustion chamber, which is the reduction region, for example, the first half of the drying stage 30a to the combustion stage 30b). This generates NOx (partial oxidation) directly above the layer where the waste is burned, which is then reduced in the furnace tail space and completely burned in the furnace 60. In the furnace tail space, the unburned material generated by char combustion acts as a reducing agent.

[0043] Arrows 1-4 in Figure 4 show the gas flow inside the furnace when the low-NOx control of this embodiment is implemented. The volatile gases burned by the primary air introduced from below the stoker 40 are drawn into the furnace tail space as shown in the figure, and flow along the space inside the furnace body 30 toward the furnace 60. In the example in Figure 4, a relatively large amount of primary air is supplied into the furnace from the wind box 50b where the flame F is located. By increasing the amount of primary air at the position of the flame F, the N contained in the fuel is oxidized, and the generation of NOx is promoted. At arrow 1, volatile gas release and gas transport are occurring. To reduce NOx, it is important to promote combustion at the position where the volatile gas is released. At arrows 2 and 3, reductive combustion is occurring. Next, compared to the conventional control shown in Figures 5 and 6, the region in which reductive combustion occurs can be made wider. By widening the region of reductive combustion, time required for NOx reduction can be secured. At arrow 4, complete combustion is occurring. By widening the reductive combustion region, N decreases at the position indicated by arrow 4 compared to conventional control, suppressing NOx generation at the position indicated by arrow 4 (secondary combustion chamber), and as a result, the amount of NOx emitted from the combustion equipment 1 can be reduced.

[0044] For comparison, Figure 5 shows an example of gas flow in the furnace when the low-NOx control of this embodiment is not applied. The gas flow path and direction are the same as in Figure 4. In Figure 5, a relatively large amount of primary air is supplied into the furnace from the wind box 50c downstream of the flame F. At the position of arrow 1, due to a lack of oxygen, the fuel N cannot be released from the aromatic ring. At the furnace tail position indicated by arrow 2, a region with a high O2 concentration is locally formed, and an oxidative combustion region is generated. 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 low-NOx control of this embodiment is not applied. The gas flow path and direction are the same as in Figure 4. In Figure 6, primary air is supplied to the furnace from each wind box 50a to 50e in roughly equal proportions. At the position of arrow 1, volatile gas is released; at the position of arrow 2, gas transport takes place; at the position of arrow 3, reductive combustion occurs; and at the position of arrow 4, complete combustion occurs. If the mixing of air and volatile components is insufficient by the combustion stage 30b, N is not sufficiently released from the aromatic ring in the reduction region at arrow 3. As a result, the residence time of NOx in the reduction region is insufficient, and it flows out to the outlet without being fully reduced. Also, N remains in the complete combustion region at arrow 4, increasing NOx generation. Therefore, NOx is not reduced in this example.

[0046] The nitrogen (N) in the incinerated material S exists bound to hydrocarbons, and this is oxidized to form NOx. When suppressing NOx using a two-stage combustion method of reduction and oxidation, it is necessary to complete the chemical reaction between NOx and the reducing substance in the first stage reduction zone to form N2, and to ensure that as little NOx as possible remains in the second stage oxidation zone. The problem here is that when the nitrogen is bound to hydrocarbons, it does not become N2 through the reduction reaction, and if the nitrogen in the hydrocarbons remains until the oxidation zone, oxidation occurs there, resulting in NOx formation. Therefore, in the reduction zone, it is necessary to convert the nitrogen in the hydrocarbons into NOx as early as possible. In this embodiment, as shown in Figure 4, the location where volatile gases are released is identified, and the amount of primary air supplied to the identified location is increased to oxidize the nitrogen in the volatiles early and convert it into NOx. By doing so, the reduction zone is widened, allowing sufficient residence time for NOx in the reduction zone to convert NOx into N2, and suppressing NOx generation in the oxidation zone. Furthermore, by promoting NOx generation and increasing the NOx concentration early, the reaction rate of reduction in the subsequent reduction region can be increased. This enables low NOx emissions. Generally, primary air is controlled to adjust the flame position, but in this embodiment, the distribution of primary air is controlled with the aim of promoting NOx generation in the reduction region.

[0047] (Identifying the release location of volatile gases) Next, we will explain how to identify the release location of volatile gases. The positioning unit 2b acquires images of the inside of the furnace from an infrared camera 33 equipped with filters that transmit specific wavelengths (CO: 2125-2245nm, CO2: 4160-4360nm, H2O: 1375-1425nm, NH3: 1500-1600nm, background imaging (flame transmission): 3800-4000nm) corresponding to the gas type, and identifies the volatile component release location and the main combustion location. The flame transmission filter used for background imaging is used to more accurately identify the release locations of CO, NH3, H2O, and CO2 by taking the difference between the image taken with this filter and the image taken with filters of other wavelengths. The flame transmission filter is not essential. Positioning can be achieved in the simplest form by combining a single camera (infrared camera 33) with monocular depth estimation technology. For example, the positioning unit 2b identifies the maximum emission position in images captured by an infrared camera 33 equipped with a filter that transmits wavelengths of unburned components (CO, NH3), and calculates the distance from the infrared camera 33 to the identified emission position by monocular depth estimation. Also, for example, the positioning unit 2b identifies the position of the maximum change in brightness in images captured by an infrared camera 33 equipped with a filter that transmits wavelengths of burned components (H2O, CO2), and calculates the distance from the infrared camera 33 to the identified emission position by monocular depth estimation. An example of an image captured by the infrared camera 33 is shown in Figure 7(a), and a schematic of monocular depth estimation is shown in Figure 7(b). Figure 7(a) is an image captured with a CO filter attached. 71 and 72 are emission positions (positions with high CO concentration).

[0048] Furthermore, for example, the location identification unit 2b may estimate the concentrations of CO, CO2, H2O, and NH3, and identify the location of active combustion as the release location of volatile gases from the differential values ​​of the concentrations. For example, the location identification unit 2b acquires images of the gas information in a steady state and the incinerated material S in an instant by changing the filters for CO, CO2, H2O, and NH3 and taking pictures for several seconds each. The location identification unit 2b then generates an average image or a standard deviation image of the images taken in each wavelength band by image processing, and uses a function that defines the relationship between temperature, density, and brightness ratio, which has been constructed on a theoretical basis, to calculate the density of each gas from the temperature (or the measured value from the furnace temperature sensor 31) and brightness obtained from the image and the said function, and converts the density to concentration. For example, the progress of the reaction can be calculated from the CO concentration and the CO2 concentration ratio. Furthermore, for H2O, assuming a maximum H2O concentration of 20%, and taking the measured concentration as 10%, the reaction progress can be calculated as 10% / 20% = 0.5. The gas concentration and reaction progress are used to determine how much flow rate to supply to the specified location (described later). In addition, the location identification unit 2b may calculate the location of active combustion from the differential value of the calculated concentration and identify the calculated location as the release location of volatile gas. The closer the location of active combustion is to the upstream side of the temporary combustion chamber, the more it can be considered that NOx generation is promoted. The order in which the concentrations of each gas type are measured is as follows: first, already burned components (CO2, H2O), then unburned components (NH3, CO), and finally, the reaction progress is calculated. If there are discrepancies in the evaluation results of volatile matter release based on estimated CO and NH3 concentrations, reaction progress evaluation based on H2O concentration, and CO / CO2 ratio (for example, the evaluation based on CO concentration shows a high amount of volatile matter, while the evaluation based on the CO / CO2 ratio shows a low amount), the values ​​should be trusted in the following order of priority: estimated CO concentration > estimated NH3 concentration > reaction progress evaluation based on H2O concentration > CO / CO2 ratio (with estimated CO concentration having the highest priority).

[0049] Note that the location determination using camera 33 described above is just one example. Other embodiments may be as follows. (a) Instead of installing filters for various gases, images of the inside of the furnace may be captured using a multispectral camera, and images of the wavelength band corresponding to each gas type may be obtained by digital filtering. (b) Multiple infrared cameras equipped with the above-mentioned filters may be prepared, and the emission locations of volatile gases may be estimated from the images captured by each of the multiple cameras, and the three-dimensional location of the emission locations of the volatile gases may be determined by combining these estimation results. Alternatively, two infrared cameras equipped with monocular depth estimation may be placed in positions that can compensate for each other's blind spots, and the emission locations of volatile gases may be estimated from the images captured by each of the two cameras, and the emission locations of the volatile gases may be determined by combining these estimation results. (c) The flame position (volatile matter release position) is estimated using a machine learning system that has learned the relationship between various plant data (e.g., furnace temperature, pressure, flow rate in wind chambers 50a-50e, etc.) and flame position. (d) The distance from the visible light camera 32 installed at the rear of the furnace to the visible light camera 32 is calculated from the position of the luminescence of the flame (the position behind the flame) included in the image captured by the visible light camera 32. In this case, since the exact location of the front of the flame is unknown, the flame position (the position of release of volatile gases) is estimated to be a predetermined length in front 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-CO regions are identified by laser CT measurement. (f) A temperature sensor is installed along the longitudinal direction of the stoker 40, and the position where the measured temperature is highest, or the position where the measured temperature is above a predetermined threshold, is estimated as the flame position (the release position of volatile gas).

[0050] (Estimation of pressure loss, etc.) As described above, in this embodiment, NOx is actively generated in the drying stage 30a to the combustion stage 30b, and the NOx is reduced in the furnace tail space. To promote NOx generation, the supply amount of primary air is increased at or slightly upstream of the volatile gas release point. In order to control the flow rate of primary air supplied to the furnace to a desired value, it is necessary to consider the pressure loss of the primary air dampers 75a to 75e, the leak between the wind boxes 50a to 50e (wind boxes 50a to 50e have holes, and if there is a pressure difference between adjacent wind boxes 50, primary air flows to the adjacent wind box 50), and the pressure loss of the grate 41. Therefore, ventilation tests are conducted before waste is loaded and during furnace shutdown, and the relationship between the opening degree of the primary air dampers 75a to 75e, the pressure loss, and the leak is calculated.

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

[0052] In the ventilation test, the pressure loss coefficient and leak rate of each windbox damper are determined individually. For example, as shown in Figure 8B, with no debris layer present, only one damper, such as primary air damper 75a, is operated, while the other primary air dampers 75b to 75e are closed. The opening degree of primary air damper 75a is varied, and the relationship between the opening degree of primary air damper 75a and the pressure loss is determined from the difference between the measured value of windbox pressure sensor 51a and the measured value of first air pressure sensor 77. In addition, the flow rate of leak 50ab is calculated from the difference between the measured value of windbox pressure sensor 51a and the measured value of windbox pressure sensor 51b. For example, the average value of the leak flow rate when the opening degree of primary air damper 75a is varied may be calculated. Similarly, for primary air dampers 75b to 75e, the relationship between the damper opening degree and damper pressure loss, and the leak flow rate between adjacent windboxes 50 are calculated.

[0053] Next, as shown in Figure 8C, the pressures measured by the wind box pressure sensors 51a to 51e are made equal to eliminate leakage between wind boxes, the grates 41a to 41e are opened and closed, and the pressure loss of the grates 41a to 41e is calculated from the pressures measured by the furnace pressure sensor 35, the first air pressure sensor 77, and the wind box pressure sensors 51a to 51e (it is assumed that the pressure loss of the grates 41a to 41e is the same value). Then, during the operation of the combustion equipment 1, the pressure loss of the waste layers Sa to Se is estimated from the pressure measured by the first air pressure sensor 77, the pressure measured by the wind box pressure sensors 51a to 51e, the pressure measured by the furnace pressure sensor 35, the pressure loss of the primary air dampers 75a to 75e calculated in the prior ventilation test, and the pressure loss of the grates 41a to 41e (it is assumed that the pressure loss of the waste layers Sa to Se is the same value).

[0054] The distribution determination unit 2c calculates the distribution of primary air to be supplied to the primary combustion chamber through wind boxes 50a to 50e, taking into account the pressure loss of primary air dampers 75a to 75e, the pressure loss of the grate 41, the pressure loss of the waste layer, and the leak between wind boxes. For example, suppose the total flow rate loss resulting from the pressure loss of primary air dampers 75a to 75e, the pressure loss of the grate 41, and the pressure loss of the waste layer is "5", and the leak between wind boxes is "1" for all of them, and we want to supply 60% of the total primary air to the furnace from wind box 50a and 10% each from wind boxes 50b to 50e. Let Xa be the flow rate of primary air supplied to the furnace from wind box 50a, and Xb... be the flow rate of primary air supplied to the furnace from wind box 50b. Considering pressure loss and leakage between windboxes, the flow rate of primary air supplied from windbox 50a to the furnace is Xa - 5 (pressure loss) - 1 (leak to windbox 50b), and the flow rate of primary air supplied from windbox 50b to the furnace is Xb - 5 (pressure loss) - 1 (leak to windbox 50c) + 1 (leak from windbox 50a), ... The distribution determination unit 2c calculates Xa to Xe such that the result is 6:1:1:1:1. At this time, the distribution determination unit 2c sets the distribution ratios of windboxes 50a to 50e, for example, so that the sum of the distribution ratios of primary air supplied to the primary combustion chamber falls within the range of 0.9 to 1.05. Furthermore, in this embodiment, NOx generation is promoted by supplying a large amount of primary air to the volatile gas release location, but it has been confirmed that the final NOx emission can be reduced by supplying 50-80% of the total primary air to the wind box 50 corresponding to the volatile gas release location (see below).

[0055] (operation) Figure 9 is a flowchart showing an example of low-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 H2O, respectively. Next, the positioning unit 2b estimates the distance in the depth direction of the emission position using monocular depth estimation technology (step S2). The positioning unit 2b identifies the emission position based on the brightness of the image acquired in step S1. If there are multiple emission positions, all emission positions are identified. Next, the positioning unit 2b estimates the distance from the infrared camera 33 for all identified emission positions using monocular depth estimation technology. After estimating the emission positions, the positioning unit 2b then estimates the unburned gas position (the volatile gas emission position mentioned above) (step S3). For unburned gases such as CO2 and NH3, the positioning unit 2b estimates the position with the maximum emission intensity as the unburned gas position (the volatile gas emission position mentioned above). Furthermore, for already burned gases such as H2O and CO2, the location identification unit 2b estimates the location of unburned gases (the volatile matter release location mentioned above) based on the location where the change in brightness is large. The location identification unit 2b also calculates the CO and NH3 concentrations, the reaction progress of H2O, the CO / CO2 ratio, etc.

[0056] Next, the position identification unit 2b determines whether the estimated unburned portion location is more than a predetermined length away from the tip of the wind box directly below it (step S4). Refer to Figure 10 here. Figure 10(a) is an example where the unburned portion location is more than a predetermined length away from the tip (upstream end) of the wind box directly below it. Figure 10(b) is an example where the unburned portion location is close to the tip of the wind box directly below it and is not more than a predetermined length away. If the unburned portion location is more than a predetermined length away from the tip of the wind box directly below it (step S4; Yes, as in Figure 10(a)), the position identification unit 2b controls the wind box 50b directly below it (step S5). If the unburned portion location is not more than a predetermined length away from the tip of the wind box directly below it (step S4; No, as in Figure 10(b)), the position identification unit 2b controls the wind box 50a immediately preceding (upstream of) the wind box 50b directly below the unburned portion location (step S6). The position identification unit 2b notifies the distribution determination unit 2c of the airbox identified as the control target. Steps S4 to S6 enable the primary air to be appropriately supplied to the unburned portion location.

[0057] Next, the distribution determination unit 2c determines the distribution of primary air to be supplied to the wind boxes 50a to 50e (step S7). The distribution determination unit 2c has a map or function with the CO concentration estimate, NH3 concentration estimate, H2O reaction progress, CO / CO2 ratio, etc. on the horizontal axis and the target primary air ratio for the controlled wind box (target value for the distribution of primary air supplied to the controlled wind box 50) on the vertical axis (for example, Figure 11). The distribution determination unit 2c refers to this map based on the CO concentration estimate, etc., and determines the target primary air ratio corresponding to the CO concentration estimate, etc. This map is created so that the target primary air ratio is set in the range of 50 to 80%. The distribution determination unit 2c determines the distribution for the controlled wind box 50 in this way, and for the remaining wind boxes 50, for example, distributes the primary air so that the supply amount is equal. The distribution determination unit 2c takes into account the pressure loss of dampers and other components calculated in the prior ventilation test, the leakage between the wind boxes 50, etc., and calculates the distribution ratio of primary air supplied from each wind box 50a to 50e to the furnace so that the actual amount of primary air supplied from each wind box 50a to 50e matches the determined primary air distribution ratio. The calculated distribution ratio is then output to the control unit 2d. The control unit 2d controls the primary air dampers 75a to 75e according to the distribution ratio. As a result, the amount of primary air supplied from wind boxes 50a to 50e to the furnace is controlled to match the primary air distribution ratio determined by the distribution determination unit 2c.

[0058] (effect) As described above, according to this embodiment, the location where volatile gases are generated by the combustion of waste is estimated based on images captured by the infrared camera 33, etc. Then, by supplying a large amount of primary air (50-80% of the total) to that estimated location, the reaction of unburned gases is activated and NOx generation is promoted. By promoting NOx generation early in the stage when waste is combusted in the primary combustion chamber, which is the reduction zone, the remaining time spent in the primary combustion chamber can be allocated to reduction, for example, the space at the end of the furnace can be used as a reduction zone. Furthermore, by promoting NOx generation early, the NOx concentration is increased early, and the reaction rate of reduction in the downstream reduction zone is increased. This suppresses the generation of NOx in the subsequent complete combustion and reduces the amount of NOx emitted from the incineration equipment 1.

[0059] Figure 12 shows an example of the hardware configuration of the control device. Computer 900 includes a CPU 901, main memory 902, auxiliary memory 903, input / output interface 904, and communication interface 905. The control device 2 described above is implemented in computer 900. The functions described above are stored in the auxiliary memory 903 in the form of programs. The CPU 901 reads the program from the auxiliary memory 903, expands it in the main memory 902, and executes the above processing according to the program. The CPU 901 also allocates a memory area in the main memory 902 according to the program. The CPU 901 also allocates a memory area in the auxiliary memory 903 to store the data being processed according to the program.

[0060] Furthermore, a program to implement all or part of the functions of the control device 2 may be recorded on a computer-readable recording medium, and the program recorded on this recording medium may be loaded into a computer system and executed to perform processing by each functional unit. Here, "computer system" includes hardware such as the OS and peripheral devices. Also, if a WWW system is used, "computer system" also includes the homepage provisioning environment (or display environment). Furthermore, "computer-readable recording medium" refers to portable media such as CDs, DVDs, USBs, and storage devices such as hard disks built into the computer system. In addition, if this program is distributed to computer 900 via a communication line, computer 900 that receives the distribution may load the program into main memory 902 and execute the above processing. Furthermore, the above program may be for implementing only a part of the functions described above, and may also be able to implement the above functions in combination with programs already recorded in the computer system.

[0061] As described above, several embodiments relating to this disclosure have been explained, but all of these embodiments are presented as examples and are not intended to limit the scope of the invention. These embodiments can be carried out 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 variations are included in the scope and spirit of the invention, as well as in the claims and their equivalents.

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

[0063] (1) A combustion apparatus according to the first embodiment comprises a furnace into which post-combustion gas flows, a furnace body that includes a drying stage, a combustion stage, and a post-combustion stage and burns and transports the material to be incinerated, and, when the upstream side in the transport direction of the material to be incinerated is referred to as the front and the downstream side in the transport direction is referred to as the rear, a primary combustion chamber having 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 provided 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 in a specific wavelength band, and means for calculating the detection position of the target in the specific wavelength and activating the reaction of unburned gas at the detection position to promote the generation of NOx. This allows for the early generation of NOx in the first half of the primary combustion chamber, which is the reduction region, thereby extending the residence time of NOx in the reduction region and ensuring sufficient time for reduction to be completed. Furthermore, by promoting early NOx generation, the NOx concentration can be increased earlier, increasing the reaction rate of reduction in the downstream reduction region. As a result, NOx emissions can be reduced.

[0064] (2) The combustion apparatus according to the second embodiment is the combustion apparatus according to (1) to (2), wherein the opening of a damper provided in the flow path that supplies primary air to the primary combustion chamber is controlled to increase the flow rate of primary air sent to the detection position to 50-80% of the total primary air supplied to the primary combustion chamber, thereby activating the reaction of the unburned gas. This allows for the early generation of NOx and a longer residence time in the NOx reduction region.

[0065] (3) The combustion apparatus according to the third embodiment is the combustion apparatus of (1) to (2), wherein the distribution of primary air to be supplied to each of the plurality of wind boxes is calculated by considering the pressure loss of the dampers provided for each of the plurality of wind boxes arranged along the transport path below the transport path for transporting the material to be incinerated, and the amount of primary air leakage between adjacent wind boxes. By taking into account pressure loss and leakage between windboxes, the distribution ratio of primary air supplied to the primary combustion chamber through each windbox can be accurately determined.

[0066] (4) The combustion apparatus according to the fourth embodiment is the combustion apparatus of (1) to (3), wherein, with respect to a plurality of wind boxes which are primary air supply ports arranged along the transport path below the transport path for transporting the material to be incinerated, if the distance from the upstream end in the transport direction of the wind box located directly below the detection position to the detection position is greater than or equal to a predetermined value, the amount of primary air supplied from the wind box directly below is increased, and if the distance is less than the predetermined value, the amount of primary air supplied from the wind box located one step upstream from the wind box directly below is increased. This ensures that primary air is reliably supplied to the location where unburned gases are present, thereby activating NOx generation.

[0067] (5) A control method relating to a fifth aspect of a combustion apparatus comprising a furnace into which post-combustion gas flows, a furnace body that transports materials to be incinerated while burning them, including a drying stage, a combustion stage, and a post-combustion stage, wherein, when 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 is referred to as the rear, the combustion apparatus comprises a primary combustion chamber having 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 provided 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 the unburned gas at the detection position to promote the generation of NOx. [Explanation of Symbols]

[0068] 1... Combustion equipment, 2... Control device, 2a... Acquisition unit, 2b... Position identification unit, 2c... Distribution determination unit, 2d... Control unit, 3... Incinerator, 21... Hopper, 22... Feeder, 23... Moisture measuring instrument, 24... Sprinkler system, 30... Furnace body, 31... 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 section, 57...Rear ceiling section, 59...Rear wall, 60...Furnace, 60a...Front wall, 60b...Rear wall, 70...Ventilation 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, 903...Auxiliary memory, 904...Input / output interface, 905...Communication interface

Claims

1. The furnace into which the combustion gases flow, A furnace body that includes a drying stage, a combustion stage, and a post-combustion stage, and which transports 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 is referred to as the rear, the primary combustion chamber 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 is provided connected to the outlet side of the primary combustion chamber and has a secondary combustion gas supply nozzle, An optical measuring device provided in the primary combustion chamber for detecting targets in a specific wavelength band, A means for calculating the detection position of the target at the aforementioned specific wavelength, and for activating the reaction of unburned gas at the detection position to promote the generation of NOx, A combustion device equipped with the following features.

2. By controlling the opening of a damper provided in the flow path that supplies primary air to the primary combustion chamber, the flow rate of primary air sent to the detection position is increased to 50-80% of the total primary air supplied to the primary combustion chamber, thereby activating the reaction of the unburned gas. The combustion apparatus according to claim 1, comprising:

3. The distribution of primary air to be supplied to each of the multiple wind boxes is calculated by considering the pressure loss of the dampers provided at each of the multiple wind boxes arranged along the transport path below the transport path for transporting the material to be incinerated, and the amount of primary air leakage between adjacent wind boxes. The combustion apparatus according to claim 2.

4. Regarding a plurality of wind boxes, which are primary air supply ports, arranged along the transport path below the transport path for transporting the material to be incinerated, if the distance from the upstream end in the transport direction of the wind box located directly below the detection position to the detection position is greater than or equal to a predetermined value, the amount of primary air supplied from the wind box directly below is increased; if the distance is less than the predetermined value, the amount of primary air supplied from the wind box located one step upstream from the wind box directly below is increased. The combustion apparatus according to claim 1 or claim 2.

5. A combustion apparatus comprising a furnace into which post-combustion gas flows, a furnace body that transports materials to be incinerated while burning them, and a primary combustion chamber having 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, with the upstream side in the transport direction of the materials to be incinerated being referred to as the front and the downstream side in the transport direction being referred to as the rear; a secondary combustion chamber provided 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 in a specific wavelength band, Computers The detection position of the target at the aforementioned specific wavelength is calculated, and the reaction of the unburned gas at the detection position is activated to promote the generation of NOx. Control method.

Images