JP6146673B2 - Waste incinerator and waste incineration method - Google Patents

Description

  The present invention relates to a grate-type waste incinerator and a waste incineration method for incinerating waste such as municipal waste.

  Grate-type waste incinerators are widely used as incinerators for incinerating waste such as municipal waste. The outline of the configuration of the representative one will be described below.

  The grate-type waste incinerator has a three-stage grate (dry grate, combustion grate, and post-combustion grate) that is arranged in the direction of waste movement at the bottom of the combustion chamber that burns the waste. The secondary combustion chamber is connected to the outlet of the combustion chamber located above the post-combustion grate. The combustion chamber is provided with a waste inlet located above the dry grate. An ash drop port is provided at the downstream side of the post-combustion grate waste in the moving direction. Usually, the secondary combustion chamber is also a part of a waste heat boiler for waste heat recovery, and is in the vicinity of the inlet. Further, a combustion primary air blowing mechanism for blowing combustion primary air from below the grate of each of the dry grate, the combustion grate, and the post-combustion grate is provided.

  In such a grate-type waste incinerator, waste thrown into the combustion chamber from the waste inlet is deposited on the dry grate and dried by air from the bottom of the dry grate and radiant heat in the furnace. At the same time, the temperature is raised and ignition occurs. That is, immediately above the dry grate, a dry region is formed in the upstream space in the waste movement direction, and combustion occurs from the downstream space directly above the dry grate to the upstream space directly above the combustion grate. A starting region is formed. The waste that ignites in the combustion start area and starts combustion is sent from the dry grate onto the combustion grate, and the waste is pyrolyzed to generate combustible gas, and the combustion sent from the bottom of the combustion grate The primary air for combustion burns combustible gas and solid content, and a main combustion region is formed in the space immediately above the combustion grate. Further, unburned components such as fixed carbon are completely burned on the post-combustion grate, and a post-combustion region is formed in a space immediately above the post-combustion grate. Thereafter, the ash remaining after combustion is discharged to the outside from the ash drop opening.

  Thus, in the grate-type waste incinerator, the waste is burned by the primary combustion air blown from below the three-stage grate in the combustion chamber. Further, the unburned portion of the combustible gas contained in the combustion gas from the combustion chamber receives and burns secondary combustion air in the secondary combustion chamber.

  In a conventional grate-type waste incinerator, the ratio (air ratio) obtained by dividing the amount of air actually supplied into the incinerator by the theoretical amount of air necessary for combustion of the waste is usually about 1.6. . This is larger than 1.05 to 1.2 which is an air ratio necessary for combustion of general fuel. The reason for this is that waste has a higher incombustibility than liquid fuel or gaseous fuel as a general fuel and is inhomogeneous, so the efficiency of air utilization is low, and a large amount of air is required for combustion. It is to become. However, if the supply air is simply increased, the amount of exhaust gas increases as the air ratio increases, and accordingly, a larger exhaust gas treatment facility is required.

  If waste can be burned without any problems in a waste incinerator with a reduced air ratio, the amount of exhaust gas will be reduced, and the exhaust gas treatment facility will become compact. As a result, the entire waste incineration facility will be downsized. Equipment costs can be reduced. In addition, since the amount of chemicals used for exhaust gas treatment is reduced, the operating cost can be reduced. Furthermore, since the heat recovery rate of the waste heat boiler can be improved by reducing the amount of exhaust gas, the amount of heat that can not be recovered and discarded to the atmosphere is reduced, and the efficiency of power generation using waste incineration waste heat is reduced accordingly. Can be raised.

  Thus, the advantage of performing the low air ratio combustion is great, but on the other hand, the low air ratio combustion with the air ratio of 1.5 or less causes a problem that the combustion becomes unstable. In other words, when waste is burned at a low air ratio, combustion becomes unstable, CO generation increases, flame temperature rises locally, NOx increases rapidly, and soot is generated in large quantities. As a result, there is a problem that harmful substances in the exhaust gas increase, and waste and ash melt and adhere to the furnace wall due to local high temperatures, and clinker is generated, and the refractory life of the furnace wall is shortened. There is a problem of becoming.

  Under such circumstances, a waste incinerator capable of stably combusting at a low air ratio of 1.5 or less has been studied and disclosed in Patent Document 1. In this patent document 1, it is said that the following effects can be obtained by blowing high temperature gas into the combustion chamber from the ceiling of the combustion chamber of the waste incinerator.

  That is, promoting the thermal decomposition of waste by sensible heat and radiation of high temperature gas, promoting the combustion of combustible gas generated by thermal decomposition of waste by blowing high temperature gas containing oxygen, Gas is blown into the combustion chamber from the nozzle provided on the ceiling of the combustion chamber, and the flow of this high-temperature gas collides with the upward flow of combustible gas and combustion gas generated from waste, and the flow of gas flows directly above the waste layer. By forming a slow stagnation region, the flow of combustible gas becomes gentle, and the combustible gas is sufficiently mixed with the oxidant component, so that stable combustion is performed, and a flat flame is formed and kept standing. It is said that by burning high temperature gas into the combustion chamber, waste can be stably burned under low air ratio combustion operation.

  In such a grate-type waste incinerator, a dry region, a combustion start region, a main combustion region, and a post-combustion region are sequentially formed in the furnace from the upstream side in the waste movement direction. In the main combustion zone, the waste on the combustion grate is pyrolyzed and partially oxidized to generate a combustible gas, and the combustible gas and the solid content of the waste are combusted. When combustible gas burns, it forms a flame and burns. Thereafter, in the post-combustion region, unburned solids such as fixed carbon in the remaining waste are completely burned on the post-combustion grate. When solids burn, no flame is generated and soot burns.

  The main combustion region is a combustion region in which waste is thermally decomposed and partially oxidized to generate a combustible gas, and the combustible gas is combusted with a flame and the solid content of the waste is combusted. . The point at which combustion with a flame is substantially completed is called a burnout point, and becomes a boundary between the main combustion region and the post-combustion region. In the area after the burn-off point, a soot combustion area (post-combustion area) in which the unburned solid content in the waste is combusted.

  By grasping the position of this burn-off point in the incinerator, the position of the boundary between the main combustion region and the post-combustion region can be grasped. The fact that the position of the fuel cut point is at a predetermined position indicates that the main combustion region and the post-combustion region are formed in a preferable range, and that the waste is burned without any trouble.

  Patent Document 2 discloses a method for detecting the position of a fuel cut point. In this patent document 2, the image of the in-furnace image obtained by photographing the inside of the incinerator with the ITV camera is image-processed, and the region of the flame part is extracted by using the tendency of the brightness distribution of the in-furnace image. Is going to be detected. The ITV camera is directed from the rear end position of the furnace to the upstream side in the direction of movement of the waste on the grate to photograph the flame part.

JP2013-213652A JP 2000-179820 A

  In the combustion of waste in a waste incinerator, stable combustion of combustible gas generated by thermal decomposition of the waste suppresses the generation of harmful substances such as CO and NOx generated by the combustion. To make a big contribution. Therefore, in the waste incinerator described in Patent Document 1, high temperature gas is blown into the combustion chamber from a nozzle provided on the ceiling of the combustion chamber to stabilize combustion.

  According to such a waste incinerator of Patent Document 1, the high-temperature gas blown from the ceiling of the incinerator is increased in pyrolysis gas (combustible gas) and combustion gas generated by pyrolysis or combustion of waste. The counter flow field is effectively formed by colliding with the flow, and the stagnation region or the vertical circulation region is generated over a wide area. As a result, the flow of the combustible gas becomes gentle in the stagnation region or the circulation region, and stable combustion is performed. The flame is fixed in a flat shape, and an extremely stable combustion state is maintained.

  In addition, the position of the fuel cut point in the incinerator is grasped, and that the position of the fuel cut point is a predetermined position, the main combustion region and the post-combustion region are formed in a preferable range, and the combustion of waste is obstructed. It is said that it is done without.

  However, in a waste incinerator where high temperature gas is blown from the furnace ceiling as described in Patent Document 1, the in-furnace photographed image as in Patent Document 2 is image-processed to extract the flame area and When trying to apply the method of detecting the position, the following problems occur. That is, the flow of high-temperature gas blown from the furnace ceiling collides with the upward flow of combustible gas and combustion gas generated from waste, and forms a stagnation region where the flow is slow immediately above the waste layer. It is possible to form a flame and establish stable combustion, but the flame in the incinerator forms a flat flame, so the ITV camera takes a picture from the rear end position of the furnace toward the upstream side. However, it is difficult to accurately detect the position of the burnout point from the photographed image because only the image in which the range from the upstream side to the downstream side overlaps can be obtained, and the image becomes a narrow range in the vertical direction. It becomes.

  In addition, in a waste incinerator that blows in high-temperature gas, if the detected fuel cut point is not within the specified position range, the operation of the waste incinerator is controlled so that the fuel cut point is within the specified position range. How to do is not considered.

  In view of such circumstances, the present invention accurately detects the position of a fuel cut point in a waste incinerator that blows high-temperature gas from the furnace ceiling, and incinerates the waste so that the position of the fuel cut point is within a predetermined position range. A grate that can control the operation of the furnace, stably burn waste, can suppress the generation of harmful substances such as CO and NOx, and can perform low air ratio combustion operation without problems An object of the present invention is to provide an incinerator and a waste incineration method.

  According to the present invention, the above-described problems are solved by the following configuration regarding the grate-type waste combustion furnace and the waste incineration method.

<Grate-type waste incinerator>
A grate-type waste incinerator comprising a grate and a combustion chamber for burning waste on the grate, and primary air blowing means for blowing primary air for combustion into the combustion chamber from under the grate And a high temperature gas blowing means for blowing high temperature gas downward from the ceiling of the combustion chamber, the furnace temperature in the furnace length direction, which is the direction of movement of waste on the grate, A fuel cut point position detecting means for detecting the highest position as the fuel cut point position, and a fuel cut point control means for controlling the fuel cut point position to be a predetermined position based on the output of the fuel cut point position detecting means; The high-temperature gas blowing means includes a first-stage and second-stage high-temperature gas injection port in the furnace length direction, a first-stage high-temperature gas supply means for supplying the first-stage high-temperature gas to the first-stage high-temperature gas injection port, Post-stage height for supplying post-stage hot gas to the hot gas inlet A high-temperature gas inlet at the front stage is provided on the ceiling from the rear part of the drying grate to the rear part of the combustion grate, and the high-temperature gas inlet at the rear stage is provided on the combustion grate. Provided on the ceiling from the rear to the front of the rear combustion grate, the burnout point position detection means is a hot gas inlet adjacent in the furnace length direction within the range from the dry grate to the rear combustion grate A plurality of temperature detecting means arranged at positions between each other, a front position of the frontmost hot gas inlet, and a rear position of the last hot gas inlet, and the position of the temperature detecting means showing the highest temperature are burned. A fuel cut point position determining means for determining a cut point, and the fuel cut point control means has a combustion operation amount adjusting means for operating a combustion state of waste, and outputs to the output from the fuel cut point position determining means. Based on the amount of combustion operation so that the fuel cut point is at the specified position Grate type waste incinerator, characterized in that has a controllable by the operation from the integer unit.

  In the present invention, the combustion operation amount adjusting means of the fuel cut point control means can be means for adjusting at least one of the feed rate of the grate and the primary air blowing amount.

  In the present invention, the fuel cut point control means can set the predetermined position of the fuel cut point position to the rearmost position of the combustion grate or the boundary position between the combustion grate and the rear combustion grate.

  Further, in the present invention, the first-stage high-temperature gas supply means supplies, as a first-stage high-temperature gas, a mixed gas or high-temperature air of return exhaust gas and high-temperature air to which a part of the exhaust gas discharged from the incinerator is returned, and the second-stage high-temperature gas The supply means can supply the return exhaust gas or the mixed gas of the return exhaust gas and the high-temperature air as the post-stage high-temperature gas.

  Further, in the present invention, the upstream high temperature gas supply means controls the oxygen concentration of the upstream high temperature gas to 12 to 21 dry volume%, and the downstream high temperature gas supply means controls the oxygen concentration of the downstream high temperature gas to 1 to 12 dry volume%. To be able to.

<Waste incineration method>
A waste incineration method using a grate-type waste incinerator having a combustion chamber, in which primary air for combustion is blown into the combustion chamber from below the grate, and the movement direction of the waste on the grate on the ceiling of the combustion chamber Among the hot gas inlets provided in the first and second stages in the furnace length direction, the downward direction from the former hot gas inlet arranged on the ceiling from the rear part of the drying grate to the rear part of the combustion grate In the waste incineration method in which the upstream hot gas is blown and the downstream hot gas is blown downward from the downstream hot gas inlet arranged on the ceiling from the rear of the combustion grate to the front of the rear combustion grate, in the furnace length direction In the range from the dry grate to the post-combustion grate, they are arranged at positions between adjacent hot gas inlets, at the front position of the foremost hot gas inlet, and at the rear position of the last hot gas inlet. Multiple temperature sensing hands Based on the output from the temperature detection step for detecting the temperature at each position, the fuel cut point position determination step for determining the position of the temperature detecting means showing the highest temperature as the fuel cut point, and the fuel cut point position determination step. A waste incineration method, comprising: a fuel cut point control step of operating and controlling a combustion operation amount adjusting means for operating a combustion state of waste so that the fuel cut point is at a predetermined position.

  In the present invention, the fuel cut point control step can adjust at least one of the feed rate of the grate and the primary air blowing amount by the combustion operation amount adjusting means.

  In the present invention, the fuel cut point control step can set the predetermined position of the fuel cut point position to the rearmost position of the combustion grate or the boundary position between the combustion grate and the post combustion grate.

  Further, in the present invention, a mixed gas or high-temperature air of return exhaust gas and high-temperature air to which a part of the exhaust gas discharged from the incinerator is returned is blown as a pre-stage high-temperature gas, and a mixed gas or return of return exhaust gas and high-temperature air is returned. The exhaust gas can be blown in as a post-stage hot gas.

  Furthermore, in the present invention, the oxygen concentration of the upstream high-temperature gas can be controlled to 12 to 21 dry volume%, and the oxygen concentration of the downstream high-temperature gas can be controlled to 1 to 12 dry volume%.

  As described above, in the present invention, in the grate waste incinerator and the waste incineration method in which high temperature gas is blown from the furnace ceiling, in the furnace length direction, adjacent in the range from the dry grate to the post-combustion grate. The temperature is detected at each position by a plurality of temperature detection means arranged at the position between the hot gas inlets, the front position of the frontmost hot gas inlet, and the rear position of the last hot gas inlet. The position of the temperature detection means that indicates the temperature of the fuel is determined as the fuel cutoff point, and based on the information on the determined fuel cutoff point, the combustion operation amount adjustment that manipulates the combustion status of the waste so that the fuel cutoff point is at the predetermined position Because the fuel cut point control is controlled by operating the means, the position of the fuel cut point is accurately detected and the operation of the waste incinerator is controlled so that the fuel cut point position is a predetermined position. The waste can be burned stably, and CO Can suppress the generation of harmful substances such as NOx, it is possible to carry out without any problems the low air ratio combustion operation.

  In the present invention, the high temperature gas is further blown from the ceiling of the combustion chamber, and the blow is blown into two stages, a front stage and a rear stage, and the front stage high temperature gas supply means and the rear stage high temperature gas supply means are connected to the front stage high temperature gas. Since the oxygen concentration of each of the latter-stage hot gases is controlled, the following effects are obtained.

(1) Combustion stabilization effect by injecting high-temperature gas High-temperature gas is injected downward from the injection port provided in the ceiling of the waste incinerator combustion chamber, and the thermal decomposition of waste is promoted by sensible heat and radiation of the high-temperature gas. Can promote combustion of combustible gas generated by pyrolysis of waste, and further, downward flow of hot gas and upward flow of combustible gas and combustion gas generated from waste layer And a stagnation region where the gas flow circulates just above the waste layer or a circulation region in which the gas circulates in the vertical direction can be formed over a wide range in the width direction and the length direction of the combustion chamber. Combustion is performed, and a planar combustion region (flame) can be established. Further, the thermal decomposition of the waste can be further promoted by radiation of a standing flat flame or the like. Thus, by blowing high-temperature gas, waste and generated combustible gas can be stably burned even in low air ratio combustion where the air ratio is 1.5 or less, regardless of the size of the incinerator. And since combustion is stabilized, the generation amount of harmful substances such as CO and NOx in the exhaust gas discharged from the waste incinerator can be suppressed.

(2) NOx generation suppression effect by two-stage injection of high-temperature gas The high-temperature gas blown from the ceiling of the combustion chamber is controlled separately and blown into two stages, the first and second stages. Since the oxygen concentration of each of the latter-stage hot gases is controlled, the combustion space is combined with the primary combustion air, and the atmosphere from the combustion start area to the main combustion area (front area) has a relatively low oxygen atmosphere. And a relatively oxygen-excess atmosphere in the post-combustion zone (the post-stage zone). As a result, the waste is thermally decomposed and partially oxidized in the front zone of the low-oxygen atmosphere, and is combustible as a gas component. The amount of NOx can be suppressed by obtaining the gas and the reducing gas and decomposing the generated NOx with the reducing gas obtained in the preceding region in the subsequent region of the oxygen-excess atmosphere.

  As described above, by blowing high temperature gas, for example, even in low air ratio combustion where the air ratio is 1.5 or less, waste and generated combustible gas can be stably burned and discharged from the waste incinerator. The amount of CO generated in the exhaust gas emitted can be suppressed. Further, the NOx is decomposed by the generated reducing gas by the two-stage blowing of the high temperature gas at the front stage and the rear stage, and the amount of NOx in the exhaust gas discharged from the waste incinerator can be suppressed. In addition, because thermal decomposition and combustion of waste can be promoted, the volume of the combustion chamber can be reduced relative to the amount of waste incineration, the furnace height of the incinerator can be reduced, and waste incineration can be achieved. Equipment costs and operating costs can be reduced by making the equipment compact.

BRIEF DESCRIPTION OF THE DRAWINGS The outline structure of the waste incinerator which concerns on one Embodiment of this invention is shown, (A) is a longitudinal cross-sectional view in a furnace length direction, (B) is a BB arrow line view in (A). It is sectional drawing of the furnace width direction explaining the combustion state in the waste incinerator shown in FIG. It is sectional drawing of the furnace length direction explaining the combustion state in the waste incinerator shown in FIG.

  Embodiments of the present invention will be described below with reference to the accompanying drawings. The technical scope of the present invention is not limited by these embodiments, and can be implemented in various forms without changing the gist of the invention. Further, the technical scope of the present invention extends to an equivalent range.

  Hereinafter, the basic configuration, each component device, and operation of the grate-type incinerator of one embodiment of the present invention will be described.

<Basic configuration of grate-type incinerator>
1A and 1B show a schematic configuration of a waste incinerator according to an embodiment of the present invention. First, a basic configuration of a waste incinerator and an overview of an incineration method according to an embodiment of the present invention will be described, and then details of each component device will be described. In this embodiment, the upstream side of the combustion chamber in the movement direction (furnace length direction) of the waste in the combustion chamber is referred to as a front portion, and the downstream side is referred to as a rear portion.

  The waste incinerator 1 according to the present embodiment is disposed above the combustion chamber 2 and the upstream side of the combustion chamber 2 in the flow direction of waste (left side in FIG. 1A), and the waste is disposed in the combustion chamber 2. A grate provided with a waste inlet 3 for charging into the inside, and a waste heat boiler 4 provided continuously above the downstream side of the combustion chamber 2 in the waste flow direction (the right side of FIG. 1A) It is a type incinerator.

  At the bottom of the combustion chamber 2, there is provided a grate (stoker) 5 that burns while moving the waste. The grate 5 is provided in the order of the dry grate 5a, the combustion grate 5b, and the post-combustion grate 5c from the side closer to the waste inlet 3, that is, from the upstream side. A waste layer W is formed on the lattice 5b.

  In the dry grate 5a, waste is mainly dried and ignited. In the combustion grate 5b, waste is thermally decomposed and partially oxidized, and the combustible gas and solid matter generated by the thermal decomposition are combusted. When the combustible gas burns, a flame is formed. On the post-combustion grate 5c, the unburned solids in the remaining waste are completely burned. When the solids in the waste burn, no flame is generated and the soot burns. The combustion ash after complete combustion is discharged from the ash drop opening 6.

  In the incinerator of this embodiment, the following regions are formed in the space in the combustion chamber 2 and in the space immediately above the waste layer.

  A dry region A1 is formed above the upstream range (front part) of the dry grate 5a in the waste flow direction, which is positioned directly above the dry grate 5a and below the waste input port 3. Is done.

  A combustion start region A2 is formed above the upstream range (front part) of the combustion grate 5b from the downstream range (rear part) of the dry grate 5a. That is, the waste in the dry grate 5a is dried in the upstream range, ignited in the downstream range, and combustion starts in the range up to the upstream range (front) of the combustion grate 5b.

  The waste on the combustion grate 5b is thermally decomposed and partially oxidized here to generate a combustible gas, and the combustible gas and the solid content of the waste are combusted. The waste is substantially burned on the combustion grate 5b. Thus, the main combustion region A3 is formed above the combustion grate 5b.

  Thereafter, the unburned matter such as fixed carbon in the remaining waste is completely burned on the post-burning grate 5c. A post-combustion region A4 is formed above the post-combustion grate 5c.

  When the waste is incinerated, water evaporation occurs first, followed by thermal decomposition and partial oxidation reaction, and combustible gas begins to be generated. Here, the combustion start area A2 is an area where combustion of waste starts and combustible gas begins to be generated by thermal decomposition and partial oxidation of the waste. The main combustion region A3 is a combustion in which waste is thermally decomposed and partially oxidized to generate a combustible gas, and the combustible gas is combusted with a flame and the solid content of the waste is combusted. This is an area up to the point where the combustion with the flame is completed (burn-off point). In the area after the burnout point, the soot combustion area (post-combustion area A4) in which the solid unburned matter in the waste is combusted.

  The dry region A1, the combustion start region A2, the main combustion region A3, and the post-combustion region A4 will be described later again.

  Wind boxes 7a, 7b, 7c, and 7d are provided below the dry grate 5a, the combustion grate 5b, and the post-combustion grate 5c in the combustion chamber 2, respectively. The combustion primary air P supplied by the blower 8 is supplied to the wind boxes 7a, 7b, 7c and 7d through the combustion primary air supply pipe 9, and combusts through the fire grates 5a, 5b and 5c. It is supplied into the chamber 2. The primary combustion air P supplied from below the grate is used for drying and burning the waste on the grate 5a, 5b, 5c, cooling action of the grate 5a, 5b, 5c, Has a stirring action.

  A waste heat boiler 4 is connected to an outlet on the downstream side of the combustion chamber 2, and an unburned portion (unburned gas) of the combustible gas in the gas discharged from the combustion chamber 2 near the inlet of the waste heat boiler 4. It becomes the secondary combustion area | region 10 which burns. The secondary combustion gas is blown into the secondary combustion region 10 which is a part of the waste heat boiler, and the unburned gas is subjected to secondary combustion. After this secondary combustion, the combustion exhaust gas is recovered by the waste heat boiler 4 as heat. . After heat recovery, the combustion exhaust gas discharged from the waste heat boiler is neutralized with acid gas by slaked lime, etc. and dioxins are adsorbed by activated carbon in an exhaust gas treatment system (not shown), and further to a dust removal equipment (not shown). The neutralized reaction product, activated carbon, dust and the like are collected. The combustion exhaust gas that has been dedusted and detoxified by the dust removing device is attracted by an attraction fan (not shown) and released from the chimney into the atmosphere. Further, a part of the combustion exhaust gas after being dust-removed by the dust removing device is used as a return exhaust gas to be described later.

  In the grate-type incinerator having such a basic configuration, the waste incinerator 1 according to the present embodiment includes a primary air blowing unit that blows primary combustion air into the combustion chamber from below the grate, and a furnace High temperature gas blowing means for blowing high temperature gas downward from the ceiling of the combustion chamber is provided.

<Primary air blowing means>
In the present embodiment, the waste incinerator 1 includes a primary air supply system of primary air that serves as combustion air. The primary air supply system passes the primary air P from the air supply source through the primary air supply pipe 9 for combustion, and the wind boxes 7a, 7b, 7c of the dry grate 5a, the combustion grate 5b, and the post-combustion grate 5c, respectively. , 7d from the branch supply pipe, and the combustion primary air supply pipe 9 is provided with a blower 8 and a damper 11 as a flow rate adjusting mechanism.

<High-temperature gas blowing means>
In the present embodiment, the waste incinerator 1 includes a high temperature gas blowing means for blowing a high temperature gas downward from the ceiling of the combustion chamber. The high-temperature gas blowing means includes two stages of a high-temperature gas inlet at the front and rear stages in the furnace length direction, which is the direction of movement of waste on the grate, and a high-temperature at the front stage for supplying the front-stage high-temperature gas to the high-temperature gas inlet at the front stage Gas supply means and latter-stage hot gas supply means for supplying the latter-stage hot gas to the latter-stage hot gas inlet, and the former-stage hot-gas inlet is provided on the ceiling from the rear of the drying grate to the rear of the combustion grate The rear hot gas inlet is provided in the ceiling from the rear part of the combustion grate to the front part of the rear combustion grate.

  The hot gas blowing means blows hot gas from the upstream hot gas blowing port toward the region from the combustion start region to the main combustion region, and hot gas is blown from the hot gas blowing port of the rear stage to the front of the rear combustion region or the combustion. Blow toward the area immediately after the cut point.

  In the present embodiment, the high temperature gas blowing means includes a front-stage high-temperature gas supply device 24 and a rear-stage high-temperature gas supply device 25 provided outside the combustion chamber 2, and a front-stage high-temperature gas injection port for blowing high-temperature gas into the combustion chamber 2. 13. A damper 14 as a flow rate adjusting mechanism, a high-temperature gas blow-in port 15 at the rear stage, a damper 16 as a flow rate adjusting mechanism, and a conduit for guiding the high-temperature gas to the high-temperature gas blow-in ports 13 and 15.

  The upstream high temperature gas supply device 24 mixes the return exhaust gas and the high temperature air to prepare a high temperature gas, and supplies the high temperature gas to the upstream high temperature gas inlet 13. Here, the “returned exhaust gas” is a part of the exhaust gas after the exhaust gas discharged from the incinerator is neutralized by the exhaust gas treatment system and removed by the dust removing device. The high-temperature air is generated by heating air with a heater. The pre-stage high temperature gas supply device 24 adjusts the mixing ratio by adjusting the flow rates of the return exhaust gas and the high temperature air to adjust the temperature and oxygen concentration of the high temperature gas. Moreover, the front | former stage high temperature gas supply apparatus 24 may supply only high temperature air as high temperature gas. On the other hand, the rear-stage hot gas supply device 25 supplies the returned exhaust gas as a high-temperature gas to the rear-stage hot gas inlet 15. Further, the rear-stage hot gas supply device 25 may supply a mixed gas of the return exhaust gas and the high-temperature air as the rear-stage hot gas.

  The upstream high temperature gas supplied from the upstream high temperature gas supply means has an oxygen concentration of 12 to 21% by volume, and the downstream high temperature gas supplied from the downstream high temperature gas supply means has an oxygen concentration of 1 to 12dry volume%. Is preferred.

  The upstream high-temperature gas inlet 13 is a range from the downstream side (rear part) of the moving direction (furnace length direction) of the waste of the dry grate 5a to the downstream side (rear part) of the combustion grate 5b on the ceiling of the combustion chamber 2 It is provided at a position directly above the grate. Moreover, the high temperature gas inlet 13 (13a, 13b, 13c) of the front | former stage is arrange | positioned in the multiple positions (three places) of the furnace length direction within said range.

  The rear stage high temperature gas inlet 15 is provided at a position directly above the grate from the downstream side (rear part) of the combustion grate 5b to the upstream side (front part) of the rear combustion grate 5c on the ceiling of the combustion chamber 2. Yes.

  In the hot gas blowing means, the directions of the hot gas blowing ports 13 and 15 are determined so that the hot gas is blown downward. Thus, the upstream hot gas is blown from the upstream hot gas inlet 13 toward the region from the combustion start region A2 to the rear of the main combustion region A3, and the downstream hot gas is injected from the downstream hot gas inlet 15 into the main combustion region. It is provided so as to blow from the rear part of A3 toward the front part of the rear combustion area A4. Moreover, the hot gas from the hot gas blowing port 15 in the subsequent stage may be blown toward the region immediately after the fuel cut point.

  As shown in FIG. 2, the hot gas inlets 13 and 15 are provided at a plurality of locations in the furnace width direction (a direction perpendicular to the paper surface in FIG. 1A and a vertical direction in FIG. 1B). Is provided. Moreover, the high temperature gas inlets 13 and 15 may be arrange | positioned in the several position of a furnace length direction, respectively within said range (refer FIG. 1 (B)).

<Flame cut point detection means>
In the main combustion region A3, the waste is thermally decomposed and partially oxidized to generate a combustible gas. The combustible gas is combusted with a flame and the solid content of the waste is combusted. The detection of the position of the burnout point, which is the point at which combustion with a flame is substantially completed, will be described. The burnout point is the boundary between the main combustion region and the post-combustion region. In the area after the burn-off point, a soot combustion area (post-combustion area) in which the unburned solid content in the waste is combusted. In the furnace length direction, the furnace temperature changes in the range from the drying area A1 to the post-combustion area A4 in the furnace, and combustion with a flame is substantially completed at the fuel cut point, and the furnace temperature becomes the highest. In this embodiment, it has the fuel cut point position detection means which detects the position of the fuel cut point in the furnace length direction, and the fuel cut point position control means which controls the position.

  The fuel cut point position detection means includes a plurality of temperature detection means and a fuel cut point position determination means.

  The temperature detecting means includes a position between adjacent hot gas inlets in the range from the dry grate to the post-combustion grate in the furnace length direction, a front position of the frontmost hot gas inlet, and the last hot gas. A plurality of them are arranged in each of the rear positions of the air inlets. The fuel cut point position determining means determines the position of the temperature detecting means showing the highest temperature among the plurality of temperature detecting means as the fuel cut point.

  In FIG. 1B, the plurality of temperature detecting means 16a to 16e, for example, thermocouples, are provided on both side walls facing each other in the furnace width direction.

  As seen in FIG. 1 (B), the hot gas inlets 13a to 13c and 15 provided at intervals in the furnace length direction are provided in two rows at intervals in the furnace width direction. The temperature detecting means 16a to 16e provided on the side walls are provided between the high temperature gas injection ports 13a and 13b adjacent in the furnace length direction, between 13b and 13c, between 13c and 15, and the foremost high temperature gas injection. It is arrange | positioned in each position of the front of the opening | mouth 13a, and the back of the last hot gas blowing inlet 15. FIG. Thus, the in-furnace temperature at each position is detected by each temperature detecting means 16a to 16e.

  The temperature detecting means 16a to 16e are preferably provided on both side walls as illustrated in the case of a large furnace having a large furnace width, but provided on one side wall in the case of a small furnace having a small furnace width. It is also good.

  Although not shown, the fuel cut point position determination means has a determination means for determining the position in the furnace length direction of the temperature detection means that has detected the maximum temperature as the fuel cut point from the detected temperatures received from the temperature detection means 16a to 16e. doing.

  In the present embodiment, as described above, the temperature detection means 16a to 16e are used for relative comparison determination by comparing the temperatures of the temperature detection means in order to find the position of the highest furnace temperature in the furnace length direction. Yes, not to know the absolute value of the temperature itself. Therefore, it is sufficient for all the temperature detection means to be disposed at the same furnace height direction position and furnace width direction position. Moreover, it is preferable that the furnace height direction position of the temperature detection means is an upper position within 1 m from the upper surface of the waste layer so that the temperature detection means does not contact the waste layer deposited on the grate.

<Flame cut point position control means>
The fuel cut point position control means (not shown) has a combustion operation amount adjusting means for operating the state of combustion of waste, and is based on the fuel cut point position information output from the fuel cut point position determination means. It can be controlled by an operation by the combustion operation amount adjusting means so that the cut point is a predetermined position. When the fuel cut point determined by the fuel cut point position determining unit is different from the predetermined position, the combustion operation amount adjusting unit adjusts the combustion operation amount as described below, thereby setting the fuel cut point to the predetermined position. Control to do.

  The combustion operation amount adjusting means of the fuel cut point control means is means for adjusting at least one of the feed rate of the grate 5 (5a to 5c) and the amount of primary air P blown. Adjustment of the amount of blowing in primary air P is performed, for example, by adjusting the opening degree of dampers 7a-1 to 7d-1 provided in wind boxes 7a to 7d, respectively.

  When it detects that waste with high calorific value (calorie), that is, low moisture content, has been supplied to the combustion chamber by changing the amount of evaporation of the boiler, the fuel cut point position is moved to the predetermined position In order to perform the control, the waste on the grate is agitated by increasing the feed rate of the grate 5 to promote the drying / combustion of the waste, or the drying grate and the combustion grate of the primary air P Control to move the fuel cut point position to the upstream side by increasing the amount blown into the rear and reducing the amount blown into the post-combustion grate to promote waste drying and combustion . Further, in order to move the fuel cut point position to the downstream side and control it to a predetermined position, the stirring speed of the waste on the grate is suppressed by slowing the feed rate of the grate 5, and the drying / To mitigate combustion, or to reduce the amount of primary air P blown into the dry grate and increase the amount blown into the combustion grate and post-combustion grate to mitigate waste drying and combustion Control which moves a fuel cut point position to the downstream is performed by at least one of these.

  When detecting that the waste with a low calorific value (calorie), that is, with a large amount of moisture, has been supplied to the combustion chamber by fluctuations in the amount of evaporation of the boiler, etc., the fuel cut point position is moved upstream to a predetermined position. In order to perform the control, the residence time of the waste on the grate is increased by slowing the feed rate of the grate 5 to reliably dry and burn the waste, or the dry grate of the primary air P Increase the amount of fuel injected into the combustion grate and decrease the amount of injection into the post-combustion grate to promote the drying and combustion of waste and move the fuel cut point position upstream. To control. In addition, in order to control the fuel cut point position to the downstream side to make it a predetermined position, the residence time of the waste on the grate is shortened by increasing the feed rate of the grate 5 and the waste is dried.・ Mitigate combustion, or reduce the amount of primary air P blown into the dry grate and increase the amount blown into the combustion grate and post-combustion grate to mitigate waste drying and combustion Control which moves a fuel cut point position to the downstream is performed by at least one of these.

  In the present embodiment, the fuel cut point position control means sets the predetermined position of the fuel cut point position to the rearmost position of the combustion grate 5b or the boundary position between the combustion grate 5b and the rear combustion grate 5c.

<Secondary combustion gas supply means>
Further, the waste incinerator 1 of the present embodiment includes a secondary combustion gas supply system that blows the secondary combustion gas into the secondary combustion region 10 corresponding to the vicinity of the inlet of the waste heat boiler 4. The secondary combustion gas supply system feeds the secondary combustion gas Q from the secondary combustion gas supply source to the secondary combustion gas inlet 17 provided in the secondary combustion region 10 via the pipe 12. The pipe 12 is provided with a blower 18 and a damper 19 as a flow rate adjusting mechanism. The secondary combustion gas inlet 17 is provided on the peripheral wall of the waste heat boiler 4 so as to blow the secondary combustion gas Q into the secondary combustion region 10 in the vicinity of the inlet of the waste heat boiler 4. Most of the combustible gas generated in the combustion chamber 2 is combusted in the combustion chamber 2, and the remaining unburned gas corresponds to the vicinity of the inlet of the waste heat boiler 4 connected above the post-combustion grate 5c. The gas flows into the secondary combustion region 10 where secondary combustion gas is supplied and secondary combustion is performed.

  In the present invention, the configuration of the pipeline for supplying the primary air for combustion, the high-temperature gas, and the secondary combustion gas is not limited to those shown in the drawings, and may be appropriately selected depending on the scale, shape, application, etc. Can be selected.

  Next, an overview of the incineration situation in the apparatus of the present embodiment configured in this way, fuel cut point position detection, fuel cut point position control, combustion primary air, hot gas, combustion secondary air blowing The operation will be described sequentially.

<Overview of incineration>
First, when waste is input into the waste input port 3, the dropped waste is supplied into the combustion chamber 2 by a waste supply device (not shown) and deposited on the dry grate 5a. The operation moves on the combustion grate 5b and onto the post-combustion grate 5c, and forms a layer of waste W on each grate. Each grate receives the primary air P for combustion via the wind boxes 7a, 7b, 7c, 7d, whereby the waste of each grate is dried and burned.

  Wastes are mainly dried and ignited on the dry grate 5a. That is, the waste of the dry grate 5a is dried in the upstream range of the dry grate 5a, ignited in the downstream range of the dry grate 5a, and up to the upstream range (front part) of the combustion grate 5b. Combustion starts in the range. A dry region A1 is formed above the upstream range (front part) of the dry grate 5a in the waste flow direction. A combustion start region A2 is formed above the upstream range (front part) of the combustion grate 5b from the downstream range (rear part) of the dry grate 5a. On the combustion grate 5b, pyrolysis and partial oxidation of waste are mainly performed to generate a combustible gas. The combustible gas burns with a flame, and solids in the waste are combusted. A main combustion region A3 is formed above the combustion grate 5b. This combustion region is a region up to a point (combustion point) where combustion with a flame is completed. The combustion of the waste is substantially completed on the combustion grate 5b. On the post-combustion grate 5c, unburned components such as fixed carbon in the remaining waste are completely burned. In the region after the burn-off point, the solid unburned portion (char) in the waste is burned, and a post-combustion region A4 is formed above the post-combustion grate 5c. The combustion ash after complete combustion is discharged from the ash drop opening 6. With the waste burning in this manner, as seen in FIG. 1, the space immediately above each grate 5a, 5b, 5c has a dry region A1, a combustion start region A2, a main combustion region A3, and a rear region. A combustion region A4 is formed.

  As described above, the waste heat boiler 4 is connected to the outlet of the combustion chamber 2, and the vicinity of the inlet of the waste heat boiler 4 is the secondary combustion region 10. Therefore, the unburned portion (unburned gas) of the combustible gas generated in the combustion chamber 2 is guided to the secondary combustion region 10 where it is mixed and stirred with the secondary combustion gas Q, and is subjected to secondary combustion. After the secondary combustion, the exhaust gas is recovered by the waste heat boiler 4. After heat recovery, the exhaust gas discharged from the waste heat boiler 4 is neutralized with acid gas by slaked lime, adsorbed dioxins with activated carbon, and sent to a dust removal device (not shown). The reaction product, activated carbon, dust, etc. are recovered. The exhaust gas that has been dedusted and detoxified by the dust remover is attracted by an attracting fan (not shown) and released from the chimney into the atmosphere. In addition, as said dust removal apparatus, dust removal apparatuses, such as a bag filter system and an electrostatic dust collection system, can be used, for example. Further, a part of the exhaust gas after being removed by the dust removing device is used as the return exhaust gas.

<Fuel cut point position detection>
As described above, when the waste burns on the grate 5 (5a to 5c), a plurality of temperature detecting means 16a to 16e provided on the side wall of the furnace at the upper position of the grate by the burnout point position detecting means. In each case, the temperature at each position in the furnace length direction is detected. As described above, the fuel cut point position detection means also has a fuel cut point position determination means, and in the furnace length direction of the temperature detection means that detects the highest temperature among the temperature detection means 16a to 16e. Is determined to be the burnout point position.

<Fire cut point position control>
When the fuel cutoff point position is obtained by the fuel cutoff point position determination means, the fuel cutoff point position control means is controlled so that the position becomes a predetermined position. The control is performed by the combustion operation amount adjusting means of the fuel cut point position control means.

  In the present embodiment, the predetermined position is set at the rearmost position of the combustion grate 5b or the boundary position between the combustion grate 5b and the post-combustion grate 5c. The combustion state is manipulated by performing at least one of the adjustment of the feed speed 5c and the opening adjustment of the dampers 7a-1 to 7d-1 for adjusting the flow rate.

  When detecting that the waste with high calorific value (calorie), that is, low moisture content is supplied to the combustion chamber by fluctuation of boiler evaporation, etc., the determined fuel cut point is downstream from the predetermined position. In order to control the fuel cut point position to the upstream position, the waste on the grate is stirred by increasing the feed rate of the grate 5 to promote the drying and combustion of the waste. Or increasing the amount of primary air P blown into the dry grate and combustion grate and reducing the amount blown into the post-combustion grate to promote the drying and combustion of waste Thus, the fuel cut point position is moved to the upstream side and controlled to a predetermined position.

  Further, in order to control the determined fuel cut point upstream from the predetermined position and move the fuel cut point position to the downstream side to make the predetermined position, the grate can be controlled by slowing the feed rate of the grate 5 Suppressing the agitation of the above waste and mitigating the drying and combustion of the waste, or reducing the amount of primary air P blown into the dry grate and the amount blown into the combustion grate and post-combustion grate In order to reduce the drying / combustion of the waste and control the fuel cut point position to the downstream side to achieve a predetermined position.

  When the amount of calorific value (calorie) is low, that is, when waste with a large amount of water is supplied to the combustion chamber is detected by fluctuations in the amount of boiler evaporation, the determined fuel cut-off point is downstream of the predetermined position. In order to control the fuel cut point position to the upstream side to make it a predetermined position, the residence time of the waste on the grate is increased by slowing the feed rate of the grate 5, and the waste drying / Increase the amount of primary air P blown into the dry grate and combustion grate and reduce the amount blown into the post-combustion grate to promote the drying and combustion of waste. By at least one of the above, control is performed to move the fuel cut point position to the upstream side so as to be a predetermined position.

  Further, in order to control the determined fuel cut point upstream from the predetermined position and move the fuel cut point position downstream to the predetermined position, the waste is increased by increasing the feed rate of the grate 5 The residence time on the grate is shortened to reduce the drying / combustion of the waste, or the amount of primary air P blown into the dry grate is reduced and blown into the combustion grate and the post-combustion grate By increasing the amount and at least one of reducing the drying / combustion of the waste, the fuel cut-off point position is moved to the downstream side and controlled to a predetermined position.

  Thus, the fuel cut point determined by the fuel cut point position determination means is controlled to be a predetermined position. By setting the fuel cut point to a predetermined position, the main combustion region and the post-combustion region are formed in a preferable range, and the combustion of waste is stably performed.

<Blowing primary air for combustion>
The primary air P for combustion passes from the blower 8 through the primary air supply pipe 9 for combustion, and wind boxes 7a, 7b, 7c provided at the lower portions of the dry grate 5a, the combustion grate 5b, and the post-combustion grate 5c, respectively. , 7d and then supplied into the combustion chamber 2 through the grate 5a, 5b, 5c. The flow rate of the combustion primary air P supplied into the combustion chamber 2 is adjusted by a flow rate adjusting damper 11 provided in the combustion primary air supply pipe 9, and further a command from the fuel cut point position control means. Based on the above, the flow rate supplied to each wind box 7a, 7b, 7c, 7d is adjusted by the dampers 7a-1 to 7d-1 provided in the respective supply pipes that are branched from each wind box. Further, the configurations of the air boxes 7a, 7b, 7c, 7d and the combustion primary air supply pipe 9 for supplying the combustion primary air P are not limited to those shown in the figure, but the incinerator scale, shape, application, etc. Can be appropriately selected.

  As the primary air P for combustion, it is preferable to use a gas having a temperature in the range of room temperature to 200 ° C. and an oxygen concentration in the range of 15 to 21 dry volume%. As the primary air P for combustion, any one of air, oxygen-containing gas and return exhaust gas may be used, or a mixed gas thereof may be used.

<Combustion stabilization by hot gas injection>
As seen in FIG. 1A, the upstream hot gas is blown from the upstream hot gas inlet 13 (13a, 13b, 13c) toward the region from the combustion start region A2 to the rear portion of the main combustion region A3. Then, the rear-stage hot gas is blown from the rear-stage hot gas injection port 15 toward the front region of the rear combustion region A4 from the rear portion of the main combustion region A3. In the region from the combustion start region A2 to the front portion of the post-combustion region A4, it is blown downward toward the waste layer W. In order to stabilize the combustion, it is preferable to blow the pre-stage high-temperature gas into a region where there is a flame and a large amount of combustible gas. Therefore, from the combustion start region A2 where the combustible gas is present to the main combustion region A3. Blow high temperature gas into the area up to the rear.

  From the front stage high temperature gas inlet 13 and the rear stage hot gas inlet 15, the high temperature gas is directed from the combustion start area A2 in the combustion chamber 2 to the front part of the rear combustion area A4 and directly above the waste layer W. The high-temperature gas blown downward is opposed to the upward flow of combustible gas and combustion gas generated by thermal decomposition and partial oxidation of the waste, and both gas flows collide with each other. A flat stagnation region with a slow flow or a circulation region that circulates in the vertical direction is formed immediately above the layer W. Since the gas flow speed is slow in these regions, a flame in which the combustible gas burns is fixed, that is, a planar combustion region (planar flame) E (see FIG. 2) is defined immediately above the waste layer W. Present, and combustible gas is stably burned.

  In addition to the fact that the waste is heated by thermal radiation and sensible heat of the high-temperature gas, thermal decomposition and partial oxidation are promoted, a planar combustion region (planar flame) E (see FIG. 2) immediately above the waste layer. ), The waste is heated by the thermal radiation and sensible heat from the flat flame E, and the thermal decomposition and partial oxidation are further promoted. In addition, the combustion of the combustible gas generated by the thermal decomposition of the waste is promoted by blowing in the high-temperature gas containing oxygen.

  Thus, the waste W can be stably burned even under the low air ratio combustion operation. As a result, it is possible to suppress the generation of harmful substances such as CO, NOx, and dioxins even in low air ratio combustion. For this reason, low air ratio combustion can be performed without hindrance.

<NOx reduction by high-temperature gas two-stage injection>
In a waste incinerator, nitrogen contained in waste and nitrogen in the air react at high temperatures to generate NOx. When exhaust gas discharged from the incinerator is discharged from the chimney into the atmosphere, the NOx concentration must be below the regulation value, so NOx is removed in the exhaust gas treatment system, but the amount of NOx generated in the incinerator Suppressing this is a fundamental measure, and this is desired. In the present embodiment, high temperature gas is blown from two stages of high temperature gas inlets of the front and rear stages, the oxygen concentration of the front stage high temperature gas is controlled to 12 to 21 dry volume%, and the oxygen concentration of the rear stage high temperature gas is 1 to 12 dry volume%. When the high temperature gas is blown from the high temperature gas inlet 13 in the previous stage, a low oxygen atmosphere is formed to generate a reducing gas, and NOx is decomposed by this reducing gas. The amount can be suppressed.

  FIG. 3 is a cross-sectional view in the furnace length direction for explaining the combustion state in the waste incinerator. As shown in FIG. 3, first, when blowing the upstream hot gas from the upstream hot gas inlet 13, at least one of the oxygen concentration and the supply amount of the upstream hot gas was adjusted and combined with the primary air for combustion. By adjusting the oxidant supply amount, the region from the combustion start region A2 to the main combustion region A3 is, for example, a low oxygen concentration of 0 to 2 dry volume% (local air ratio is 0.6 to 0.8). Use an oxygen atmosphere. By pyrolysis and partial oxidation of waste in a low oxygen atmosphere, combustible gas and reducing gas (CO, HCN, NHn, CmHn) are generated as gas components (CO and CmHn are combustible). The generated combustible gas is burned uniformly and stably in the planar combustion region formed as described above. The reducing gas is used so as to be led downstream in the combustion chamber and decompose NOx. When a low oxygen atmosphere is formed in the region from the combustion start region A2 to the main combustion region A3, if the local air ratio is smaller than 0.6, the generation of reducing gas becomes excessive, and excess NHn causes NOx on the downstream side. Is generated, or the generation of flammable gas is excessive and the generation of unburned gas is excessive, which is not suitable. If the oxygen concentration is higher than 2 dry volume% (air ratio is 0.8), a low oxygen atmosphere is generated. In other words, the amount of reducing gas generated is small and unsuitable. Therefore, the oxygen concentration in the region from the combustion start region A2 to the main combustion region A3 is preferably 0 to 2 dry volume% (air ratio is 0.6 to 0.8). .

  Next, when the rear-stage hot gas is blown from the rear-stage hot gas inlet 15, at least one of the oxygen concentration and the supply amount of the rear-stage hot gas is adjusted, and the oxidant supply amount combined with the combustion primary air is adjusted. Then, the region of the post-combustion region A4 is, for example, an oxygen-excess atmosphere in which the region has an oxygen concentration of 5 to 8 dry volume% (local air ratio is 1.3 to 1.6). If the oxygen concentration in the oxygen-excess atmosphere is less than 5 dry volume% (air ratio is 1.3), the solid combustion of the waste is not performed sufficiently and becomes unburned and unsuitable, and the oxygen concentration becomes 8 dry volume% (local air ratio). Is larger than 1.6), the amount of NOx generated increases and becomes unsuitable. Therefore, the oxygen concentration in the post-combustion region A4 is preferably 5 to 8 dry volume% (air ratio is 1.3 to 1.6).

  The supply amount of the high-temperature gas is adjusted, for example, by the front-stage high-temperature gas supply device 24 and the rear-stage high-temperature gas supply device 25 adjusting the blower flow rate of the blower that sends the high-temperature gas and the opening degree of the dampers 14 and 16. The The adjustment of the oxygen concentration of the high temperature gas will be described later.

  In the waste incinerator of the embodiment of FIG. 1 (A), the high temperature gas blowing means adjusts the oxygen concentration of the high temperature gas by the contents described later in the front stage high temperature gas supply device 24 and the rear stage high temperature gas supply device 25. By adjusting the supply amount of the high temperature gas supplied to the high temperature gas inlets 13 and 15 by adjusting the blower air flow rate and adjusting the opening degree of the dampers 14 and 16, respectively, the combustion start region A2 to the main combustion region A3 are adjusted. The oxygen concentration (local air ratio) in the region and the region in front of the rear combustion region A4 is controlled to a predetermined range.

  In the present embodiment, as shown in FIG. 3, an oxygen concentration meter 31 provided on the side wall of the combustion chamber and measuring the oxygen concentration in the region from the combustion start region A2 to the main combustion region A3 in the combustion chamber 2, and the rear The oxygen concentration is measured by another oxygen concentration meter 32 that measures the oxygen concentration in the front region of the combustion region A4. Based on the measured oxygen concentration, the oxygen concentration (air ratio) in each region is within a predetermined range. Thus, the supply amount of hot gas or the oxygen concentration is controlled.

NOx generated from the combustion start region A2 to the post-combustion region A4 reacts with the above-described reducing gas in an oxygen-excess atmosphere and is decomposed, and the NOx content in the exhaust gas is reduced and discharged. In addition, of the reducing gas that contributes to the reaction with NOx, the excess of HCN and NHn reacts with oxygen in an oxygen-excess atmosphere and is decomposed or N ₂ is not emitted as it is. Does not occur.

  In order to extract the exhaust gas from the incinerator and discharge it from the chimney, the in-furnace gas is attracted by a fan, and the in-furnace gas is guided toward the exhaust gas outlet. In the present embodiment, the distance in the furnace length direction between the upstream hot gas inlet 13 and the upstream hot gas inlet 15 is set so that the in-furnace gas passes in a time of 0.5 to 1.5 seconds. It is preferable to do. It is preferable to react the generated reducing gas with NOx within the above time because the reaction efficiency becomes high. If this time is slower than 1.5 seconds, the amount of radicals in the reducing gas reacting with NOx is increased, and the reaction with NOx is greatly reduced. If it is earlier than 0.5 seconds, the reducing gas and NOx are reduced. This reaction is not suitable because NOx remains and NOx is generated from excess NHn, and thus the above time is preferably 0.5 to 1.5 seconds.

  Next, the preparation of the high-temperature gas, the blowing port, the blowing flow velocity / blowing amount, and the blowing of the secondary combustion gas will be sequentially described.

<Preparation of hot gas>
The temperature of the hot gas blown from the hot gas blowing ports 13 and 15 is preferably in the range of 100 to 400 ° C, more preferably about 150 to 200 ° C. When a gas having a temperature of less than 100 ° C. is blown, the temperature in the furnace decreases, combustion becomes unstable, and the amount of CO generated increases. When a gas exceeding 400 ° C. is blown, the flame temperature in the combustion chamber becomes extremely high, which causes problems such as promotion of clinker generation. By setting the temperature of the high-temperature gas to about 150 to 200 ° C., the occurrence of the above-described problem can be suppressed and the energy for heating the air can be set to an appropriate range, which is more preferable.

  The oxygen concentration of the high-temperature gas (also referred to as “pre-stage high-temperature gas”) blown from the front-stage high-temperature gas blow-in port 13 is 12 to 21 dry volume%, and the high-temperature gas blown from the rear-stage high-temperature gas blow-in port 15 The oxygen concentration of the “hot gas” is preferably adjusted to 1 to 12 dry volume%. Thereby, the above-mentioned effect is exhibited more effectively, and the reduction of NOx and the reduction of CO of exhaust gas is further promoted.

  The grounds for setting the oxygen concentration of the pre-stage hot gas in the above range are as follows. When the region from the combustion start region A2 to the main combustion region A3 is in a low oxygen atmosphere, if the oxygen concentration of the pre-stage high temperature gas is lower than the lower limit, the generation of reducing gas becomes excessive, and excess NHn leads to the downstream side. NOx is generated or flammable gas is excessively generated, and the amount of unburned gas (unburned gas) flowing into the secondary combustion area without being burned in the combustion chamber becomes excessive. If the oxygen concentration is higher than the upper limit, a low oxygen atmosphere is not obtained, and the amount of reducing gas generated is small and unsuitable. Therefore, the oxygen concentration of the upstream high-temperature gas is preferably 12 to 21 dry volume%.

  The grounds for setting the oxygen concentration of the latter-stage hot gas in the above range are as follows. When the front region of the post-combustion region A4 is in an oxygen-excess atmosphere, if the oxygen concentration of the post-stage hot gas is lower than the lower limit, the solid combustion of the waste is not performed sufficiently and becomes unburned and unsuitable, If it is higher than the upper limit, a high-temperature field is generated and the amount of NOx generated increases, which is inappropriate. Therefore, the oxygen concentration of the latter-stage hot gas is preferably 1 to 12 dry volume%.

  In this embodiment, a mixed gas or high-temperature air of return exhaust gas and high-temperature air that returns a part of the exhaust gas discharged from the incinerator is used as the pre-stage high-temperature gas so that the high-temperature gas has the gas temperature and oxygen concentration described above. Used as the rear stage high-temperature gas is a return exhaust gas or a mixed gas of the return exhaust gas and high-temperature air. As the return exhaust gas, a part of the exhaust gas that has been subjected to neutralization treatment of acid gas, dioxins treatment, and dust removal treatment by the above-described exhaust gas treatment system and dust removal device is used for the exhaust gas discharged from the incinerator. . The high-temperature air is generated by heating air by heat exchange with steam generated by a waste heat boiler. In this embodiment, the return exhaust gas, the return exhaust gas and high-temperature air mixed gas, and the high-temperature air are heated by heat exchange with the steam generated in the waste heat boiler as necessary, and the temperature and oxygen concentration are set to the predetermined values. It is blown into the combustion chamber as a high-temperature gas that satisfies the following conditions.

  In this way, adjusting the mixing ratio of the return exhaust gas and hot air when preparing the high temperature gas, the return exhaust gas, the return exhaust gas and high temperature air mixed gas, the heating conditions of the high temperature air, etc., the temperature of the high temperature gas, oxygen Bring the concentration to the desired range.

<High temperature gas inlet>
The upstream high-temperature gas inlet 13 is within the range from the downstream side (rear part) of the waste grate 5a in the movement direction to the downstream side (rear part) of the combustion grate 5b in the movement direction of the waste grate 5a. It is provided at a position directly above the grate.

  The rear-stage high-temperature gas inlet 15 is located on the ceiling of the combustion chamber 2 immediately above the grate from the downstream side (rear part) in the moving direction of the combustion grate 5b to the upstream side (front part) in the moving direction of the rear combustion grate 5c. Is provided.

  A plurality of front-stage high-temperature gas injection ports 13 and rear-stage high-temperature gas injection ports 15 are arranged in the width direction of the combustion chamber 2. In the embodiment shown in FIG. 1, the hot gas inlets 13 are arranged at three locations in the furnace length direction within the above range, but the hot gas inlets 13 and 15 are not limited to the above range. Each of them may be arranged at a plurality of positions in the furnace length direction. The hot gas blowing ports 13 and 15 may be nozzle type or slit type.

  The state of the flow of high-temperature gas facing the upward flow from the waste is made favorable so that a planar combustion region is formed over a wide range in the width direction and the furnace length direction directly above the waste layer in the combustion chamber In order to control, at least one of the arrangement position, the number of arrangements, the arrangement interval, the blowing direction, the shape of the blowing port, the blowing flow rate and the blowing flow rate of the hot gas is set or adjusted.

  In FIG. 1, the hot gas is blown downward from the hot gas blowing ports 13 and 15 toward the waste layer. Here, as a blowing direction of the high temperature gas, it is desirable to blow in a blowing direction in an angle range from a perpendicular to the waste layer to 20 °. This is because the flow field generated by the collision of the blown hot gas with the combustible gas generated by thermal decomposition and partial oxidation of waste and the upward flow of the combustion gas is used as the counter flow field. This is because an appropriate counter flow field is not formed when the entraining direction is in a range larger than 20 ° from the perpendicular to the waste layer.

  For example, the high-temperature gas blowing speed is controlled by, for example, dampers 14 and 16 serving as a flow rate adjusting mechanism provided in a blower for adjusting a blower amount of a blower that the high-temperature gas supply device 24 and a high-temperature gas supply device 25 respectively supply high-temperature gas, respectively. It is adjusted by adjusting the opening degree of the gas and adjusting the flow rate of hot gas.

  When there are a plurality of hot gas injection ports 13 and 15 in the furnace width direction or the furnace length direction of the combustion chamber, the high temperature gas does not necessarily have to be injected from each of the high temperature gas injection ports 13 and 15 at an equal flow rate, and the scale of the incinerator Depending on the shape, application or waste properties, amount, waste layer thickness, etc., the blowing flow rate from the hot gas blowing ports 13 and 15 can be appropriately changed so as to be different.

  When there are a plurality of high-temperature gas injection ports 13 and 15 in the furnace width direction or the furnace length direction of the combustion chamber, the high-temperature gas does not necessarily have to be injected from each of the high-temperature gas injection ports 13 and 15 at an equal flow rate. Depending on the scale, shape, application or waste property, amount, waste layer thickness, etc., the blow flow rate from each of the high temperature gas blow ports 13, 15 can be appropriately changed.

  In response to fluctuations in the amount of combustible gas and combustion gas generated from the waste in the combustion chamber 2, high-temperature gas injection is performed so that the planar combustion region is fixed immediately above the waste layer W without fluctuation. It is preferable to adjust the flow rate. When the state of the planar combustion region changes, the combustion state of the combustible gas changes and the CO concentration, oxygen concentration, etc. in the combustion exhaust gas change, so the CO concentration and oxygen concentration of the exhaust gas discharged from the boiler are monitored as monitoring factors. You may make it adjust the blowing flow rate of hot gas according to the measurement and the change.

  The high-temperature gas blow-in flow rate is adjusted, for example, by the front-stage high-temperature gas supply device 24 and the rear-stage high-temperature gas supply device 25 adjusting the flow rate of the blower sending the high-temperature gas and the openings of the dampers 14 and 16, respectively. It is adjusted by etc.

<Injection of secondary combustion gas>
The secondary combustion gas Q is blown into the secondary combustion region 10, and the unburned gas from the combustion chamber 2 is subjected to secondary combustion. As the secondary combustion gas, it is preferable to use a gas having a temperature in the range of room temperature to 200 ° C. and an oxygen concentration in the range of 15 to 21 dry volume%. As the secondary combustion gas, air, a gas containing oxygen, a return exhaust gas, or a mixed gas thereof may be used.

  It is preferable to install one or more secondary combustion gas inlets 17 so that gas can be blown in the direction in which the swirling flow is generated in the secondary combustion region. By blowing the secondary combustion gas Q in the direction in which the swirling flow is generated in the secondary combustion region 10, the gas temperature and oxygen concentration distribution in the secondary combustion region 10 can be made uniform and averaged. Subsequent combustion is performed stably, generation of a local high temperature region is suppressed, and exhaust gas can be further reduced in NOx. Furthermore, since the mixing of the unburned gas and the oxidant is promoted, the combustion stability is improved and complete combustion can be achieved, so that the exhaust gas can be reduced in CO.

  As the secondary combustion gas Q, only the secondary air for combustion supplied by the blower, the gas adjusted by adjusting the oxygen concentration by mixing the diluent with the secondary air for combustion after the blower is supplied, and after passing through the dust removing device Only the return exhaust gas from which a part of the exhaust gas is extracted, or a gas in which the secondary air for combustion and the return exhaust gas are mixed can be used.

  Diluents such as nitrogen and carbon dioxide are conceivable.

  It is preferable to adjust the flow rate of the secondary combustion gas so that the gas temperature in the secondary combustion region 10 is in the range of 800 to 1050 ° C. When the gas temperature in the secondary combustion region 10 is less than 800 ° C., the combustion of the unburned gas becomes insufficient and the CO in the exhaust gas increases. Moreover, when the gas temperature in the secondary combustion area | region 10 exceeds 1050 degreeC, the production | generation of clinker in the secondary combustion area | region 10 will be encouraged, and NOx will increase further.

  As described above, according to the present invention, in the grate waste incinerator and the waste incineration method for blowing high temperature gas from the furnace ceiling, in the furnace length direction, within the range from the dry grate to the post-combustion grate. The temperature is detected at each position by a plurality of temperature detection means arranged at positions between adjacent high temperature gas injection ports, a front position of the frontmost high temperature gas injection port, and a rear position of the last high temperature gas injection port. The position of the temperature detecting means showing the highest temperature is determined as the fuel cut point, and the combustion operation amount adjusting means for operating the combustion state of the waste is operated based on the determination result so that the fuel cut point is set to the predetermined position. Therefore, the position of the fuel cut point is accurately detected, and the operation of the waste incinerator is controlled so that the position of the fuel cut point is a predetermined position, thereby stabilizing the combustion of the waste. Of harmful substances such as CO and NOx The amount can be suppressed, it is possible to carry out without any problems the low air ratio combustion operation.

  According to the present invention, the hot gas is further blown downward from the blow-in opening provided in the ceiling of the waste incinerator combustion chamber, so that the downward flow of the hot gas, the combustible gas generated from the waste layer, and combustion Forming a stagnation area where the gas flow circulates just above the waste layer or a circulation area where it circulates in the vertical direction over a wide range in the width direction of the combustion chamber and the furnace length direction by colliding with the upward flow of gas. Therefore, it is possible to establish a planar combustion zone, and even in the low air ratio combustion where the air ratio is 1.5 or less, regardless of the size of the incinerator, that is, the width and height of the combustion chamber. And the combustible gas generated can be stably burned. And since combustion is stabilized, the generation amount of harmful substances such as CO and NOx in the exhaust gas discharged from the waste incinerator can be suppressed. Furthermore, the thermal decomposition of waste can be promoted by radiation of a standing flat flame, etc., so the amount of waste supplied to the grate (grate load) and the amount of waste heat supplied to the combustion chamber (furnace) Load) can be increased. For this reason, the volume of the combustion chamber can be reduced relative to the amount of waste incineration, the furnace height of the incinerator can be reduced, and the waste incineration equipment can be made compact to reduce equipment costs and operating costs. Can do.

  Further, according to the present invention, the waste incinerator and the waste that can suppress the generation of NOx and reduce the generation amount of harmful gases such as CO and NOx by blowing high-temperature gas from the two-stage high-temperature gas blowing ports. An incineration method is provided. Furthermore, since the combustion can be performed at a lower air ratio than before, the total amount of exhaust gas discharged from the incinerator can be further greatly reduced, and a waste incinerator and a waste incineration method that can improve the recovery efficiency of waste heat are provided. The

DESCRIPTION OF SYMBOLS 1 Waste incinerator 2 Combustion chamber 5 Grate 5a Dry grate 5b Combustion grate 5c Post combustion grate 7a-1-7d-1 Combustion operation amount adjustment means (damper)
13, 15 Hot gas injection ports 16a to 16e Temperature detection means 24 Pre-stage high-temperature gas supply device 25 Post-stage high-temperature gas supply device

Claims (10)

A grate-type waste incinerator,
A combustion chamber comprising a grate and burning waste on the grate;
Primary air blowing means for blowing primary air for combustion into the combustion chamber from under the grate,
In a grate-type waste incinerator having hot gas blowing means for blowing hot gas downward from the ceiling of the combustion chamber,
A fuel cut point position detecting means for detecting a position where the furnace temperature is highest in the furnace length direction as a fuel cut point position;
A fuel cut point control means for controlling the fuel cut point position in the furnace length direction to be a predetermined position based on the output of the fuel cut point position detection means;
The high-temperature gas blowing means includes a first-stage and second-stage high-temperature gas injection port in the furnace length direction, which is the moving direction of waste on the grate, and a first-stage high-temperature gas injection port that supplies the first-stage high-temperature gas to the first-stage high-temperature gas injection port A high-temperature gas supply means and a post-stage high-temperature gas supply means for supplying a post-stage high-temperature gas to a post-stage high-temperature gas injection port, and the front-stage high-temperature gas injection port extends from the rear part of the drying grate to the rear part of the combustion grate And a high-temperature gas inlet in the rear stage is provided in the ceiling from the rear part of the combustion grate to the front part of the rear combustion grate,
The burn-off point position detection means includes, in the furnace length direction, positions between adjacent hot gas inlets in the range from the dry grate to the post-combustion grate, the front position of the frontmost hot gas inlet, and the last A plurality of temperature detection means respectively disposed at the rear position of the high temperature gas inlet, and a fuel cut point position determination means for determining the position of the temperature detection means showing the highest temperature as the fuel cut point,
The fuel cut point control means has a combustion operation amount adjusting means for manipulating the combustion state of the waste, and based on the output from the fuel cut point position determining means, the combustion operation amount is set so that the fuel cut point is set to a predetermined position. A grate-type waste incinerator characterized in that it can be controlled by an operation with an adjusting means.   2. The grate-type waste incinerator according to claim 1, wherein the combustion operation amount adjusting means of the fuel cut point control means is means for adjusting at least one of a feed rate of the grate and a primary air blowing amount.   The fuel cut point control means sets the predetermined position of the fuel cut point position to the rearmost position of the combustion grate or the boundary position between the combustion grate and the rear combustion grate. Grate-type waste incinerator. The pre-stage high-temperature gas supply means supplies, as the pre-stage high-temperature gas, a mixed gas or high-temperature air of return exhaust gas and high-temperature air in which a part of the exhaust gas discharged from the incinerator is returned,
4. The grate-type waste according to claim 1, wherein the post-stage hot gas supply means supplies the return exhaust gas or the mixed gas of the return exhaust gas and the hot air as the post-stage hot gas. Incinerator. The pre-stage high temperature gas supply means controls the oxygen concentration of the pre-stage high temperature gas to 12 to 21 dry volume%,
The grate-type waste incinerator according to any one of claims 1 to 4, wherein the latter-stage hot gas supply means controls the oxygen concentration of the latter-stage hot gas to 1 to 12 dry volume%. A waste incineration method using a grate-type waste incinerator with a combustion chamber,
Blow primary air for combustion into the combustion chamber from below the grate,
Of the high-temperature gas inlets provided in the front and rear stages in the furnace length direction, which is the moving direction of waste on the grate, on the ceiling of the combustion chamber, from the rear part of the dry grate to the rear part of the combustion grate Blow the front high-temperature gas from the front high-temperature gas injection port arranged on the ceiling, and downward from the rear high-temperature gas injection port arranged on the ceiling from the rear of the combustion grate to the front of the rear combustion grate In the waste incineration method in which high temperature gas is blown into the latter stage,
In the furnace length direction, the position between adjacent hot gas inlets in the range from the dry grate to the post-combustion grate, the front position of the foremost hot gas inlet, and the rear position of the last hot gas inlet A temperature detection step of detecting the temperature at each position by a plurality of temperature detection means respectively disposed in
A fuel cut point position determining step for determining the position of the temperature detecting means showing the highest temperature as the fuel cut point;
A fuel cut point control step of operating and controlling the combustion operation amount adjusting means for operating the combustion state of the waste so as to set the fuel cut point to a predetermined position based on the output in the fuel cut point position determination step. Waste incineration method characterized by that.   The waste incineration method according to claim 6, wherein the burn-off point control step adjusts at least one of a grate feed rate and a primary air blowing amount by a combustion operation amount adjusting means.   The fuel cut point control step sets the predetermined position of the fuel cut point position at the rearmost position of the combustion grate or the boundary position between the combustion grate and the rear combustion grate. Waste incineration method.   A mixed gas or high-temperature air of return exhaust gas and high-temperature air in which a part of the exhaust gas discharged from the incinerator is returned is blown as a pre-stage high-temperature gas, and a mixed gas or return exhaust gas of the return exhaust gas and high-temperature air is used as a post-stage high-temperature gas. The waste incineration method according to any one of claims 6 to 8, wherein blowing is performed.   10. The oxygen concentration of the upstream hot gas is controlled to 12 to 21 dry volume%, and the oxygen concentration of the downstream hot gas is controlled to 1 to 12 dry volume%, according to claim 6. Waste incineration method.

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