JP2015161444A - waste incinerator - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a waste incinerator capable of stably performing low air ratio combustion.SOLUTION: A stoker-type waste incinerator 1 comprises: a combustion chamber 2 including a stoker 5 and firing waste on the stoker 5; primary-air blowing means 9 blowing combustion primary air into the combustion chamber 2 from a ceiling 2A of the combustion chamber 2; and high-temperature-gas blowing means blowing high-temperature gas from the ceiling 2A of the combustion chamber 2 downward, the ceiling 2A of the combustion chamber 2 being provided inclined to be lower toward a rear portion in an incinerator length direction that is a moving direction of the waste on the stoker 5, the high-temperature-gas blowing means including high-temperature-gas blow ports 13 (13a, 13b, 13c) provided at a plurality of positions, respectively in the incinerator length direction; and high-temperature-gas supply means 24 supplying the high-temperature gas to the high-temperature-gas blow ports 13.

Description

  The present invention relates to a grate-type waste incinerator 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. Because it becomes. 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.

JP2013-213652A

  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, high-temperature gas blown from the ceiling of the incinerator is combusted with pyrolysis gas (including flammable gas) generated by pyrolysis or combustion of waste. The counter flow field is effectively formed by colliding with the upward flow with the gas, 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.

  Further, the unburned portion (unburned gas) of the combustible gas in the gas discharged from the combustion chamber is subjected to secondary combustion by the secondary combustion gas supplied to the lower part of the boiler provided downstream of the combustion chamber. A secondary combustion region is provided. By burning the unburned gas secondarily, the combustible gas generated from the waste is sufficiently burned, and the concentration of harmful substances such as CO and NOx contained in the exhaust gas is suppressed.

  However, if the amount of unburned gas discharged from the combustion chamber and flowing into the secondary combustion region becomes excessively large, the unburned gas burns violently in the secondary combustion region, generating a local high temperature field and increasing the amount of NOx generated. There may be a problem that the amount of combustible gas generated in the combustion chamber fluctuates and the combustion becomes unstable when the type or amount of waste varies.

  In view of such circumstances, the present invention has a problem that unburned gas burns violently in the secondary combustion region, a local high temperature field is generated, and the amount of NOx generated increases. In addition, the problem of unstable combustion of combustible gas in the combustion chamber can be prevented, and the combustion of waste can be performed stably, and the generation of harmful substances such as CO and NOx is suppressed. An object of the present invention is to provide a grate-type waste incinerator capable of performing a low air ratio combustion operation without problems.

  According to the present invention, the above-mentioned problems are solved by a grate-type waste combustion furnace having the following configuration of the first invention or the second invention.

<First invention>
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 grate-type waste incinerator having a high-temperature gas blowing means for blowing a high-temperature gas downward from the ceiling of the combustion chamber, the ceiling of the combustion chamber is a furnace length that is the moving direction of the waste on the grate The hot gas blowing means is provided so as to be lowered toward the rear in the direction, and the hot gas blowing means is provided at a plurality of positions in the furnace length direction to a hot gas blowing port provided on the ceiling of the combustion chamber, and to the hot gas blowing port. A grate-type waste incinerator comprising high-temperature gas supply means for supplying high-temperature gas.

<Second invention>
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 combustion chamber has a height from the grate to the ceiling of the waste on the grate. The hot gas blowing means is formed so as to be lowered toward the rear in the furnace length direction, which is the moving direction, and the hot gas blowing means includes a hot gas blowing port provided on the ceiling of the combustion chamber at a plurality of positions in the furnace length direction, and a hot gas. A grate-type waste incinerator comprising a high-temperature gas supply means for supplying a high-temperature gas to the inlet.

  In such first and second inventions, the waste layer and ceiling on the grate in the rear region in the furnace length direction where the amount of combustible gas generated by the thermal decomposition of waste increases. As the distance from the hot gas inlet becomes closer, the momentum of the hot gas becomes stronger, and the effect of stabilizing the combustion by forming the counter flow field by blowing the hot gas from the ceiling is further increased. Since the combustion chamber height is reduced and the space is narrowed in the region, mixing of the combustible gas with the high-temperature gas and primary air is promoted, so that the combustible gas is sufficiently burned and the combustible gas is not burned. The amount of minute (unburned gas) flowing to the secondary combustion region is reduced. Therefore, it is possible to prevent the unburned gas from burning vigorously in the secondary combustion region, generating a local high temperature field, and increasing the NOx generation amount.

  In addition, since the distance from the hot gas inlet to the waste layer is reduced in the post-combustion region, the flow speed of the hot gas that is blown downward from the ceiling and reaches the waste layer becomes sufficiently high and flows out of the combustion chamber. Since it acts to suppress the flow of gas, the unburned gas is prevented from flowing into the secondary combustion region, the time for the combustible gas to stay in the combustion chamber is lengthened, and the combustible gas is sufficient in the combustion chamber. Is burned.

  In the first invention or the second invention, the high temperature gas supply means is configured to heat one of the mixed gas of the return exhaust gas and the high temperature air, a part of the exhaust gas discharged from the incinerator, the high temperature air, and the return exhaust gas. It is preferable to supply as gas.

  As described above, in the present invention, in the grate-type waste incinerator that blows high-temperature gas from the furnace ceiling, the ceiling is formed low toward the rear in the furnace length direction, or the height from the grate to the ceiling is reduced. As a result, the distance between the waste layer and the hot gas inlet becomes closer in the rear region where the amount of combustible gas generated by thermal decomposition of the waste increases, and the momentum of the hot gas is strong. By blowing high temperature gas from the ceiling, the effect of forming a counter flow field and stabilizing combustion is further increased, and furthermore, the height of the combustion chamber is reduced and the space is narrowed in the rear region. Since the mixing with the high temperature gas and the primary air is promoted, the combustible gas is sufficiently burned, and the amount of unburned combustible gas (unburned gas) flowing into the secondary combustion region is reduced. Therefore, it is possible to prevent the unburned gas from burning vigorously in the secondary combustion region, generating a local high temperature field, and increasing the NOx generation amount.

  In addition, since the distance from the hot gas inlet to the waste layer is reduced in the post-combustion region, the flow rate of the hot gas that is blown downward from the ceiling and reaches the waste layer can be sufficiently increased. Since it acts to suppress the flow of gas flowing out of the chamber, it is possible to prevent unburned gas from flowing into the secondary combustion region, to increase the time that the combustible gas stays in the combustion chamber, and to burn in the combustion chamber The sex gas can be burned sufficiently and stably.

  In this way, even when the type and amount of waste change, the combustion of the waste can be performed stably, the generation amount of harmful substances such as CO and NOx can be suppressed, and the low air ratio combustion operation can be performed. It can be done without any problems.

  In the present invention, since the high temperature gas is blown from the ceiling of the combustion chamber, the following effects are also obtained.

[Combustion stabilization effect by high-temperature gas injection]
Combustion generated by thermal decomposition of waste can be promoted by injecting hot gas downward from the blow-off port provided on the ceiling of the waste incinerator combustion chamber, and sensible heat and radiation of the high-temperature gas can accelerate the thermal decomposition of the waste. In addition, the downward flow of the hot gas and the upward flow of the combustible gas generated from the waste layer collide with the upward flow of the combustion gas, and the gas flow directly above the waste layer. Can be formed over a wide range in the width direction and the length direction of the combustion chamber, so that stable 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.

  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. It is possible to suppress the amount of harmful substances such as CO and NOx in the exhaust gas. 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.

1 is a longitudinal sectional view in a furnace length direction showing a schematic configuration of a waste incinerator according to an embodiment of the present invention. It is sectional drawing of the furnace width 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>
FIG. 1 shows 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 on the combustion chamber 2 and on the upstream side (left side in FIG. 1) in the waste flow direction of the combustion chamber 2, and throws the waste into the combustion chamber 2. It is a grate-type incinerator provided with a waste charging port 3 and a waste heat boiler 4 provided continuously above the downstream side (right side in FIG. 1) in the waste flow direction of the combustion chamber 2. .

  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.

  The ceiling 2A in the combustion chamber 2 extends from the dry grate 5a to the vicinity of the rear part of the combustion grate 5b in the furnace length direction, and is inclined so as to become lower toward the rear (downstream side). That is, the height from the grate 5 to the ceiling 2A is lowered toward the rear.

  In the combustion chamber 2, waste is dried and ignited mainly in the dry grate 5 a. 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 secondarily burned. . 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 this embodiment includes a primary air blowing means for blowing the primary air for combustion into the combustion chamber from below the grate, and a furnace A plurality of hot gas blowing ports are provided in the longitudinal direction, and hot gas blowing means for blowing the hot gas downward from the ceiling of the combustion chamber.

<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 this embodiment, the waste incinerator 1 is provided with a high temperature gas blowing means for blowing a high temperature gas downward from the ceiling 2A of the combustion chamber 2 inclined downward toward the rear. The hot gas blowing means includes a plurality of hot gas blowing ports 13 in the furnace length direction, which is the moving direction of waste on the grate 5, and a hot gas supply means for supplying hot gas to the hot gas blowing ports, A hot gas inlet is provided in the ceiling 2A in a range from the rear part of the dry grate 5a to the rear part of the combustion grate 5b.

  In the present embodiment, the high temperature gas blowing means includes a high temperature gas supply device 24 provided outside the combustion chamber 2, a high temperature gas blowing port 13 for blowing high temperature gas into the combustion chamber 2, and a damper 14 as a flow rate adjusting mechanism. And a conduit for guiding the high temperature gas to the high temperature gas inlet 13.

  The hot gas supply device 24 mixes return exhaust gas and hot air to prepare a hot gas, and supplies the hot gas to the hot 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 hot gas supply device 24 adjusts the mixing ratio by adjusting the flow rates of the return exhaust gas and the hot air to adjust the temperature and oxygen concentration of the hot gas. Moreover, the high temperature gas supply device 24 may supply only high temperature air or only return exhaust gas as a high temperature gas.

  The high temperature gas supplied from the high temperature gas supply means preferably has an oxygen concentration of 5 to 21 dry volume%, more preferably 5 to 15 dry volume%.

  The hot gas inlet 13 is located in the ceiling 2A of the combustion chamber 2 from the downstream side (rear part) of the waste grate 5a in the waste movement direction (furnace length direction) to the downstream side (rear part) of the combustion grate 5b. It is provided at a position directly above the grate. Moreover, the high temperature gas injection port 13 is arrange | positioned in several positions (three places of 13a, 13b, 13c in the example of FIG. 1) in the furnace length direction within said range. Accordingly, as described above, since the ceiling 2A of the combustion chamber 2 is inclined downward toward the rear part in the furnace length direction, the high-temperature gas inlets 13a, 13b, and 13c located at three locations in the furnace length direction are sequentially provided. It is provided at a low position. That is, the height from the grate 5 to the hot gas inlets 13a, 13b, and 13c is sequentially reduced, and the hot gas inlets 13a, 13b, and 13c are rearward in the furnace length direction with respect to the upper surface of the waste layer. As it goes, the arrival speed of the hot gas to the waste layer increases.

  In the hot gas blowing means, the direction of the hot gas blowing port 13 is determined so that the hot gas is blown downward. Thus, the hot gas is provided from the hot gas inlet 13 so as to blow from the combustion start region A2 toward the rear region of the combustion region A3. Therefore, as already described, since the hot gas inlets 13a, 13b, 13c are positioned lower toward the rear in the furnace length direction, the speed of the hot gas reaching the upper surface of the waste on the grate is It is faster in the rear region of the combustion region A3 than in the combustion start region A2. Moreover, the hot gas from the hot gas blowing port 13c located on the most downstream side may be blown toward the region immediately after the fuel cut point.

  As described above, a plurality of the high-temperature gas inlets 13 are provided in the furnace length direction, and together with this, as shown in FIG. 2, the furnace width direction (the direction perpendicular to the paper surface in FIG. 1). Are also provided at multiple locations.

<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. of the incinerator. Can be selected.

  Next, an outline of the incineration situation in the apparatus of the present embodiment configured as described above, and actions by blowing in primary combustion air, high temperature gas, and secondary combustion air will be sequentially described.

<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.

<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. 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% by 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. 1, the hot gas flows from the combustion start area A2 to the rear part of the combustion area A3 from the hot gas inlet 13 (13a, 13b, 13c) located in the ceiling 2A inclined downward in the furnace length direction. And blown downward toward the waste layer W. That is, in order to stabilize the combustion, it is preferable to blow 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 to the combustion region A3, which is a region where a large amount of combustible gas exists. Hot gas is blown into the area up to the rear.

  High temperature blown downward by blowing hot gas downward from the hot gas blowing port 13 into the region from the combustion start region A2 in the combustion chamber 2 to the rear part of the combustion region A3 and directly above the waste layer W. The gas is opposed to the upward flow of combustible gas and combustion gas generated by thermal decomposition and partial oxidation of waste, and both gas flows collide with each other. Or the circulation area | region which circulates in an up-down direction arises. Since these regions have a slow gas flow rate, a flame in which the combustible gas burns is fixed, that is, a planar combustion region (planar flame) is present immediately above the waste layer W, and the combustible gas is present. Is stably burned.

  In addition to the fact that wastes are heated by thermal radiation and sensible heat of high-temperature gas, and thermal decomposition and partial oxidation are promoted, a planar combustion region (planar flame) is present directly above the waste layer. The waste is heated by thermal radiation and sensible heat from the flat flame, and 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.

  In such a combustion situation, the combustion chamber ceiling is formed low toward the rear in the furnace length direction, or the height from the grate to the ceiling is reduced, so that flammability generated by thermal decomposition of waste In the rear region where the amount of gas is increased, the distance between the waste layer and the hot gas inlet becomes closer, the momentum of the hot gas becomes stronger, and the hot gas is blown from the ceiling to form a counter flow field and burn. The effect of stabilizing becomes larger. Furthermore, since the combustion chamber height is lowered and the space is narrowed in the rear region, mixing of the combustible gas with the high temperature gas and the primary air is promoted, so that the combustible gas is sufficiently burned and the combustible gas is combusted. The amount of unburned part (unburned gas) flowing into the secondary combustion region is reduced. Therefore, it is possible to prevent the unburned gas from burning vigorously in the secondary combustion region, generating a local high temperature field, and increasing the NOx generation amount.

  Furthermore, the distance between the ceiling 2A of the combustion chamber 2 and the waste is narrower immediately below the high temperature gas inlet 13c located rearward (downstream) in the furnace length direction, compared to the front (upstream side). In other words, in addition to the small cross-sectional area of the flow path through which the combustion gas flows toward the outlet of the combustion chamber, the speed of the hot gas blown out from the ceiling 2A and reaching the upper surface of the waste is high, in other words Since the momentum is strong, the flow of combustion gas to the secondary combustion region 10 is suppressed. Therefore, it is possible to prevent the combustible gas from flowing into the secondary combustion region 10 without being burned, and to increase the time during which the combustible gas stays in the combustion chamber 2, and most of the combustible gas is in the combustion chamber 2. Burned in. The unburned portion of the combustible gas that could not be burned in the combustion chamber 2 flows into the secondary combustion region. Accordingly, it is possible to prevent the combustible gas from excessively flowing into the secondary combustion region, and to prevent the unburned gas from burning vigorously in the secondary combustion region to generate a local high-temperature field and increase the amount of NOx generated. .

  Thus, if the amount of unburned gas discharged from the combustion chamber and flowing into the secondary combustion region becomes excessive, the unburned gas burns violently in the secondary combustion region, generating a local high-temperature field and increasing the amount of NOx generated. It is possible to suppress the occurrence of the problem that the combustion of the combustible gas in the combustion chamber becomes unstable when the kind of the waste or the supply amount varies. In addition, the waste W can be stably burned even under a 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.

  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 port 13 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.

  Moreover, it is preferable that the oxygen concentration of the high temperature gas blown from the high temperature gas blowing port 13 is adjusted to 5 to 21 dry volume%, more preferably 5 to 15 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 high-temperature gas in the above range are as follows. If the oxygen concentration of the high-temperature gas is lower than the lower limit, the region from the combustion start region A2 to the main combustion region A3 becomes excessively low-oxygen atmosphere due to the high-temperature gas blowing, and the amount of combustible gas generated by the thermal decomposition of the waste Is unsuitable because the amount of unburned combustible gas (unburned gas) that flows into the secondary combustion region without being burned in the combustion chamber becomes excessive, and is unsuitable. If the oxygen concentration is higher than the upper limit, Combustion of the combustible gas is excessive and a high temperature field is generated and the amount of NOx generated is unsuitable. Therefore, the oxygen concentration of the high temperature gas is preferably 5 to 21 dry volume%, and the oxygen concentration is 5 to 15 dry volume%. This is more preferable because the problem can be reliably avoided.

  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 high-temperature gas so that the high-temperature gas has the gas temperature and oxygen concentration described above. It is done. 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 hot gas inlet 13 is a fire within the range from the downstream side (rear part) of the waste grate 5a in the moving direction to the downstream side (rear part) of the combustion grate 5b in the ceiling 2A of the combustion chamber 2. It is provided at a position directly above the grid.

  A plurality of hot gas inlets 13 are arranged in the width direction of the combustion chamber 2. The hot gas inlet 13 may be a nozzle type or a 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 port 13 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.

  The high-temperature gas blowing speed is adjusted, for example, by adjusting the opening of the damper 14 as the flow rate adjusting mechanism provided in the pipe line or the flow rate adjustment mechanism of the blower that sends the high-temperature gas to the high-temperature gas supply device 24. It is adjusted by adjusting the flow rate.

  When there are a plurality of high-temperature gas injection ports 13 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 at an equal flow rate. Depending on the use or waste properties, amount, waste layer thickness, etc., the blowing flow rate from each hot gas blowing port 13 can be appropriately changed so as to be different.

  When there are a plurality of high-temperature gas injection ports 13 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 high-temperature gas injection port 13 at an equal flow rate. Depending on the use or waste properties, amount, waste layer thickness, and the like, the flow rate of blow from each hot gas blow-in port 13 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 hot gas blowing flow rate is adjusted, for example, by the high temperature gas supply device 24 adjusting the flow rate by adjusting the air flow rate of the blower that sends the high temperature gas and the opening degree of the damper 14.

<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% by 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 a grate-type waste incinerator that blows high-temperature gas from the combustion chamber ceiling, the ceiling is formed low toward the rear in the furnace length direction or the height from the grate to the ceiling. In the rear region where the amount of combustible gas generated by thermal decomposition of waste increases, the distance between the waste layer and the hot gas inlet becomes closer, and the The momentum becomes stronger, and the effect of stabilizing the combustion by forming the counter flow field by blowing high temperature gas from the ceiling becomes greater. Furthermore, since the combustion chamber height is lowered and the space is narrowed in the rear region, mixing of the combustible gas with the high temperature gas and the primary air is promoted, so that the combustible gas is sufficiently burned and the combustible gas is combusted. The amount of unburned fuel flowing into the secondary combustion region can be reduced. Therefore, it is possible to prevent the unburned gas from burning vigorously in the secondary combustion region, generating a local high temperature field, and increasing the NOx generation amount.

  Further, the distance between the ceiling of the combustion chamber and the waste is narrower in the rear (downstream side) in the furnace length direction than in the front (upstream side), that is, the combustion gas is discharged from the combustion chamber. In addition to the small cross-sectional area of the flow path toward the top, the high-temperature gas that blows out from the ceiling and reaches the upper surface of the waste is fast and strong, so the combustion gas flows out to the secondary combustion region The flow is suppressed. For this reason, the inflow of the combustible gas to the secondary combustion region without being burned is suppressed, the time for which the combustible gas stays in the combustion chamber can be lengthened, and most of the combustible gas is combusted in the combustion chamber. The unburned portion of the combustible gas that could not be combusted in the combustion chamber flows into the secondary combustion region. Accordingly, it is possible to prevent the combustible gas from excessively flowing into the secondary combustion region, and to prevent the unburned gas from burning vigorously in the secondary combustion region to generate a local high-temperature field and increase the amount of NOx generated. .

  Thus, if the amount of unburned gas discharged from the combustion chamber and flowing into the secondary combustion region becomes excessively large, the unburned gas burns intensely in the secondary combustion region, generating a local high temperature field and increasing the amount of NOx generated. It is possible to suppress the occurrence of the problem that the combustion of the combustible gas in the combustion chamber becomes unstable when the kind of the waste or the supply amount varies. In addition, the waste W can be stably burned even under a 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.

  Further, according to the present invention, the downward flow of the high-temperature gas and the waste by blowing the high-temperature gas downward from the inlet provided in the ceiling of the combustion chamber of the waste incinerator inclined downward toward the downstream side, The gas flow is directly above the waste layer while colliding the upward flow of the combustible gas generated from the bed with the upward flow of the combustion gas and suppressing excessive inflow of the flammable gas from the combustion chamber to the secondary combustion zone. Since a gentle stagnation region or a circulation region that circulates in the vertical direction can be formed over a wide range in the width direction of the combustion chamber and the furnace length direction, a planar combustion region can be established, and the incinerator Regardless of the size, that is, the width and height of the combustion chamber, waste and combustible gas can be stably combusted even in low air ratio combustion where the air ratio is 1.5 or less. 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.

1 Waste Incinerator 2 Combustion Chamber 2A Ceiling 5 Grate 9 Primary Combustion Air Supply Pipe (Means)
13, 24 Hot gas blowing means 13 Hot gas blowing port 24 Hot gas supply device

Claims (3)

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,
The ceiling of the combustion chamber is provided so as to be lowered toward the rear in the furnace length direction, which is the direction of movement of waste on the grate,
The high-temperature gas blowing means includes a high-temperature gas blowing port provided in the ceiling of the combustion chamber at a plurality of positions in the furnace length direction, and a high-temperature gas supply unit that supplies the high-temperature gas to the high-temperature gas blowing port. Characteristic grate-type waste incinerator. 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,
The combustion chamber is formed so that the height from the grate to the ceiling becomes lower toward the rear in the furnace length direction, which is the direction of movement of waste on the grate,
The high-temperature gas blowing means includes a high-temperature gas blowing port provided in the ceiling of the combustion chamber at a plurality of positions in the furnace length direction, and a high-temperature gas supply unit that supplies the high-temperature gas to the high-temperature gas blowing port. Characteristic grate-type waste incinerator.   The high-temperature gas supply means supplies, as a high-temperature gas, any one of a mixed gas of high-temperature air, high-temperature air, and mixed gas of return exhaust gas and high-temperature air in which a part of the exhaust gas discharged from the incinerator is returned. A grate-type waste incinerator according to claim 1 or claim 2.

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