JP6443758B2 - Grate-type 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. Normally, a waste heat boiler for recovering waste heat is connected to the secondary combustion chamber, and the vicinity of the inlet of the waste heat boiler may be a secondary combustion chamber. Further, a primary air blowing mechanism for blowing primary air for combustion (referred to as 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, the waste thrown into the combustion chamber from the waste inlet is deposited on the dry grate and is generated by the primary air from below the dry grate and the radiant heat in the furnace. It is dried and heated to ignite. Waste that ignites and starts burning is sent from the dry grate onto the combustion grate, where the waste is pyrolyzed to generate flammable gas, and is combustible by the primary air sent from under the combustion grate. Gas and solids burn. Further, unburned components such as fixed carbon are completely burned on the post-combustion grate, and then the ash remaining after the combustion is discharged to the outside from the ash drop opening.

  Thus, in the grate-type waste incinerator, the waste is combusted by primary air blown from below the three-stage grate in the combustion chamber. Further, unburned combustible gas (referred to as unburned gas) contained in the combustion gas discharged from the combustion chamber is discharged into the secondary combustion chamber (connected to the combustion chamber) (secondary combustion air ( Combustion (referred to as secondary air). After the secondary combustion, the combustion exhaust gas is recovered by a waste heat boiler.

  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 low air ratio combustion is great.

  On the other hand, in order to completely burn the unburned gas in the exhaust gas generated in the waste incinerator, a part of the exhaust gas generated from the incinerator is mixed with the secondary combustion air and blown into the incinerator. Patent Document 1 discloses a combustion control method for controlling the amount of exhaust gas mixed with the amount of secondary combustion air so that the oxygen concentration in the exhaust gas discharged to the outside of the incinerator is constant. According to the combustion control method described in Patent Document 1, it is said that exhaust gas is cooled due to an excessive amount of secondary combustion air and is not completely combusted, and generation of unburned material due to lack of oxygen can be prevented.

JP-A-11-294740

  As described above, the advantage of performing low air ratio combustion is great, but on the other hand, low air ratio combustion with an air ratio of 1.5 or less causes a problem that 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.

  In the grate-type incinerator, even if the amount of air supplied to the incinerator is reduced and the low air ratio combustion is aimed at, the primary air supplied from the grate for drying, combustion, and post-combustion is about 1.2 air ratio If it is not supplied, the state of combustion of the waste will deteriorate, burning out will worsen, and this will lead to an increase in the unburned content in ash (increase in heat loss). Therefore, in order to operate at low air ratio combustion, attempts have been made to reduce the amount of secondary air, but there are the following problems. That is, if the operation of low air ratio combustion is aimed at and the amount of secondary air is reduced, unburned gas may not be completely burned, and CO gas on the order of several hundred ppm may remain in the combustion exhaust gas. It also causes the occurrence of. When the CO spike is generated, exhaust gas containing harmful substances is discharged outside the furnace, which is not preferable for preventing pollution. Therefore, it is difficult to realize low air ratio combustion.

  Even if the combustion control method described in Patent Document 1 is applied to secondary combustion of unburned gas in such low air-ratio combustion, secondary combustion may not be possible if the amount of supplied waste or properties fluctuate. It becomes stable, the generation of CO increases, the temperature of the flame rises locally, the formation of a local high temperature region causes a rapid increase in thermal NOx, a large amount of soot is generated, and sufficient secondary combustion is performed There may be a problem that unburned gas remains.

  In view of such circumstances, the present invention can perform sufficient secondary combustion of unburned gas even when low air ratio combustion is performed, can suppress generation of harmful gases such as CO and NOx, and waste. It is an object of the present invention to provide a grate-type waste incinerator and a waste incineration method capable of stably burning the waste.

  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. In the present invention, “upstream side” and “downstream side” refer to an upstream side and a downstream side along the moving direction of unburned gas.

<Grate-type waste incinerator>
Regarding the grate-type waste incinerator, the above-mentioned problems are solved by both the following first and second inventions.

<First invention>
A waste incinerator according to a first aspect of the present invention is a grate-type waste incinerator, comprising a grate and a combustion chamber for burning waste on the grate, connected to the combustion chamber and connected to the combustion chamber. In a grate-type waste incinerator having a secondary combustion chamber for secondary combustion of unburned gas and primary air supply means for blowing primary air from under the grate into the combustion chamber, the upstream of the secondary combustion chamber Secondary air supply means having a secondary air supply port for supplying secondary air to the side, and part of the exhaust gas discharged from the waste incinerator downstream from the position of the secondary air supply port as recirculated exhaust gas And a recirculation exhaust gas supply means for supplying from the recirculation exhaust gas supply port.

  In the waste incinerator of the first invention configured as described above, the secondary air is supplied from the secondary air supply port on the upstream side in the secondary combustion chamber, and the downstream side from the position where the secondary air is supplied. The recirculated exhaust gas is supplied from the recirculated exhaust gas supply port. As a result, the unburned gas discharged from the combustion chamber first comes into contact with the secondary air and combustion starts with sufficient oxygen supply, and further, recirculated exhaust gas is supplied downstream from the position of the secondary air supply port. By supplying the recirculated exhaust gas from the mouth, the unburned gas and the secondary air are sufficiently agitated and mixed by the stirring action of the recirculated exhaust gas flow, so that both are uniformly dispersed in the secondary combustion chamber. The unburned gas is efficiently and stably subjected to secondary combustion without causing a local oxygen deficiency or oxygen excess region in the combustion of the unburned gas.

  In addition, since a part of the high-temperature exhaust gas discharged from the waste incinerator is supplied as recirculation exhaust gas, the secondary combustion chamber can be maintained at a high temperature, and the unburned gas can be efficiently and stably supplied to the secondary combustion chamber. Burned.

  In such a first invention, the secondary air supply port and the recirculated exhaust gas supply port can be alternately arranged in the circumferential direction of the inner wall of the secondary combustion chamber.

  In this way, the secondary air and the recirculated exhaust gas supply port are alternately arranged in the circumferential direction of the inner wall of the secondary combustion chamber, thereby mixing the secondary air and the recirculated exhaust gas, Oxygen in the secondary air is diluted and there is no variation in oxygen concentration, preventing the formation of a locally high oxygen concentration region in the secondary combustion chamber, generating a local high temperature region and generating thermal NOx And the unburned gas can be combusted uniformly and stably in the secondary combustion chamber.

  In the first invention, the grate-type waste incinerator has an exhaust gas property detector that detects the exhaust gas property discharged from the waste incinerator and the exhaust gas property detected by the exhaust gas property detector. It is preferable to further have a control device for controlling the secondary air supply amount by the secondary air supply means and the recirculation exhaust gas supply amount by the recirculation exhaust gas supply means so as to be within the range.

  By providing such a control device, the secondary air supply amount and the recirculated exhaust gas supply amount are adjusted according to the exhaust gas properties to control the exhaust gas properties to be within a predetermined range. As a result, the generation of harmful substances such as CO and NOx can be suppressed and the unburned gas can be burned completely in the secondary combustion chamber, and the waste and unburned gas can be burned stably even in low air ratio combustion. And low air ratio combustion can be achieved.

  In the present invention, the exhaust gas property detector is at least one of an oxygen concentration meter, a CO concentration meter, and a NOx concentration meter, and the control device detects the oxygen concentration, CO concentration, and NOx concentration of the exhaust gas detected by the exhaust gas property detector. The secondary air supply amount by the secondary air supply means and the recirculation exhaust gas supply amount by the recirculation exhaust gas supply means are controlled based on at least one of the properties, so that the property falls within a predetermined range. Can do.

<Second invention>
A grate-type waste incinerator according to a second invention is a grate-type waste incinerator, comprising a grate and a combustion chamber for burning waste on the grate, connected to the combustion chamber and combusted. A secondary combustion chamber for secondary combustion of unburned gas from the chamber; primary air supply means for blowing primary air into the combustion chamber from below the grate; and hot gas from the ceiling or side wall of the combustion chamber to the combustion chamber. In a grate-type waste incinerator having high temperature gas supply means for blowing into a combustion chamber and combustion chamber recirculation exhaust gas supply means for blowing a part of exhaust gas discharged from a waste incinerator into the combustion chamber as combustion chamber recirculation exhaust gas Secondary air supply means having a secondary air supply port for supplying secondary air to the upstream side of the secondary combustion chamber, and exhaust gas discharged from the waste incinerator downstream from the position of the secondary air supply port Secondary combustion as part of secondary combustion chamber recirculation exhaust gas It is characterized by comprising a secondary combustion chamber recirculating exhaust gas supply means for supplying the chamber recirculating exhaust gas supply port.

  In the waste incinerator of the second invention configured as described above, the secondary air is supplied from the secondary air supply port on the upstream side in the secondary combustion chamber, and the downstream side from the position where the secondary air is supplied. Then, the secondary combustion chamber recirculation exhaust gas is supplied from the secondary combustion chamber recirculation exhaust gas supply port. As a result, the unburned gas discharged from the combustion chamber first comes into contact with the secondary air and combustion starts with sufficient oxygen supply, and further, the secondary combustion chamber is located downstream from the position of the secondary air supply port. The secondary combustion chamber recirculation exhaust gas is supplied from the recirculation exhaust gas supply port, and the unburned gas and the secondary air are sufficiently stirred and mixed by the stirring action of the secondary combustion chamber recirculation exhaust gas flow. Both are uniformly dispersed in the next combustion chamber, and the unburned gas is efficiently and stably subjected to secondary combustion without causing a local oxygen deficiency or oxygen excess region in the combustion of the unburned gas.

  In addition, since a part of the high-temperature exhaust gas discharged from the waste incinerator is supplied as recirculation exhaust gas, the secondary combustion chamber can be maintained at a high temperature, and the unburned gas can be efficiently and stably supplied to the secondary combustion chamber. Burned.

  In such a second invention, the secondary air supply ports and the secondary combustion chamber recirculation exhaust gas supply ports can be arranged alternately in the circumferential direction of the inner wall of the secondary combustion chamber.

  In this way, by arranging the secondary air supply port and the secondary combustion chamber recirculation exhaust gas supply port alternately in the circumferential direction of the inner wall of the secondary combustion chamber, the secondary air and the secondary combustion chamber Recirculation exhaust gas is mixed, secondary air oxygen is diluted and the variation in oxygen concentration is eliminated, preventing the formation of a locally high oxygen concentration region in the secondary combustion chamber, generating a local high temperature region Thus, generation of thermal NOx can be suppressed, and unburned gas can be combusted uniformly and stably in the secondary combustion chamber.

  In the second invention, the grate-type waste incinerator has an exhaust gas property detector that detects the exhaust gas property discharged from the waste incinerator and the exhaust gas property detected by the exhaust gas property detector. A control device for controlling the secondary air supply amount by the secondary air supply means and the secondary combustion chamber recirculation exhaust gas supply amount by the secondary combustion chamber recirculation exhaust gas supply means so as to be within the range; Preferably it is.

  By providing such a control device, the secondary air supply amount and the secondary combustion chamber recirculation exhaust gas supply amount are adjusted according to the exhaust gas properties to control the exhaust gas properties within a predetermined range. As a result, the generation of harmful substances such as CO and NOx can be suppressed and the unburned gas can be burned completely in the secondary combustion chamber, and the waste and unburned gas can be burned stably even in low air ratio combustion. And low air ratio combustion can be achieved.

  In the present invention, the exhaust gas property detector is at least one of an oxygen concentration meter, a CO concentration meter, and a NOx concentration meter, and the control device detects the oxygen concentration, CO concentration, and NOx concentration of the exhaust gas detected by the exhaust gas property detector. Based on at least one of the properties, a secondary air supply amount by the secondary air supply means and a secondary combustion chamber recirculation exhaust gas supply amount by the secondary combustion chamber recirculation exhaust gas supply means so that the properties are within a predetermined range And can be controlled.

<Waste incineration method>
Regarding the waste incineration method, the above-mentioned problems are solved by both the following third and fourth inventions.

<Third invention>
The waste incineration method of the third invention is a waste incineration method using a grate-type waste incinerator, comprising a grate and a combustion chamber for burning the waste on the grate, connected to the combustion chamber. Waste by a grate-type waste incinerator having a secondary combustion chamber for secondary combustion of unburned gas from the combustion chamber and primary air supply means for blowing primary air into the combustion chamber from below the grate In the incineration method, supply secondary air to the upstream side of the secondary combustion chamber, and supply a part of the exhaust gas discharged from the waste incinerator to the downstream side from the position where the secondary air is supplied as recirculated exhaust gas. It is characterized by.

  In such a third invention, the secondary air supply and the recirculated exhaust gas supply can be performed from supply ports arranged alternately in the circumferential direction of the inner wall of the secondary combustion chamber.

  According to this third invention, the same effect as the first invention is obtained.

  In the third invention, the exhaust gas properties discharged from the waste incinerator are detected, and based on the detected exhaust gas properties, the secondary air supply amount and the recirculated exhaust gas supply amount are set so that the exhaust gas properties are within a predetermined range. Can be controlled.

<Fourth Invention>
The waste incineration method of the fourth invention is a waste incineration method using a grate-type waste incinerator, and is connected to the combustion chamber to secondary combustion of unburned gas from the combustion chamber; The primary air supply means for blowing primary air into the combustion chamber from below the grate, the high temperature gas supply means for blowing high temperature gas into the combustion chamber from the ceiling or side wall of the combustion chamber, and the waste incinerator In a waste incineration method using a grate-type waste incinerator having a combustion chamber recirculation exhaust gas supply means for blowing a part of exhaust gas into the combustion chamber as a combustion chamber recirculation exhaust gas, a secondary is disposed upstream of the secondary combustion chamber. A feature is that a part of the exhaust gas discharged from the waste incinerator is supplied as a secondary combustion chamber recirculation exhaust gas to the downstream side from the position where the secondary air is supplied.

  In such a 4th invention, secondary air supply and secondary combustion chamber recirculation exhaust gas supply can be performed from the supply port arrange | positioned alternately by the circumferential direction of the inner wall of a secondary combustion chamber.

  According to this fourth invention, the same effect as the second invention is obtained.

  In the fourth invention, the exhaust gas property discharged from the waste incinerator is detected, and the secondary air supply amount and the secondary combustion chamber recirculation exhaust gas are set based on the detected exhaust gas property so that the exhaust gas property is within a predetermined range. The supply amount can be controlled.

In the fourth invention, the ratio Q1A of the amount of oxygen per unit time supplied by primary air to the theoretical amount of oxygen per unit time required for combustion of waste, and the amount of oxygen per unit time supplied by high-temperature gas Ratio Q1B, ratio Q1C of oxygen amount per unit time supplied by combustion chamber recirculation exhaust gas, ratio Q2 of oxygen amount per unit time supplied by secondary air, and secondary combustion chamber recirculation exhaust gas Can be set so as to satisfy the following expressions (1) and (2).
Q1A: Q1B: Q1C: Q2: Q3
= 0.93 to 1.10: 0.14 to 0.16: 0.09 to 0.11: 0.01 to 0.05: 0.01 to 0.05 (1)
1.2 ≦ Q1A + Q1B + Q1C + Q2 + Q3 ≦ 1.4 (2)

  In the first and third inventions configured as described above, the secondary air is supplied to the upstream side in the secondary combustion chamber, and the recirculated exhaust gas is supplied to the downstream side from the position where the secondary air is supplied. As a result, the unburned gas discharged from the combustion chamber first comes into contact with the secondary air to start combustion under sufficient oxygen supply, and further downstream from the position where the secondary air is supplied. By supplying the recirculated exhaust gas, the unburned gas and the secondary air are sufficiently stirred and mixed by the stirring action of the recirculated exhaust gas flow, so that both are uniformly dispersed in the secondary combustion chamber. The unburned gas is efficiently and stably subjected to secondary combustion without causing a local oxygen shortage or oxygen excess region in the combustion of the fuel gas. In addition, since a part of the high-temperature exhaust gas discharged from the waste incinerator is supplied as recirculated exhaust gas, the secondary combustion chamber can be maintained at a high temperature, and the unburned gas can be efficiently and stably supplied to the secondary combustion chamber. Burned.

  Furthermore, in the first and third inventions, the secondary air supply port and the recirculated exhaust gas supply port are arranged alternately in the circumferential direction of the inner wall of the secondary combustion chamber. Secondary air and recirculated exhaust gas are mixed, oxygen in the secondary air is diluted to eliminate variations in oxygen concentration, and a local region with high oxygen concentration is prevented from being formed in the secondary combustion chamber. Generation of a high temperature region and generation of thermal NOx can be suppressed, and unburned gas can be combusted uniformly and stably in the secondary combustion chamber.

  In the second and fourth inventions, the secondary air is supplied to the upstream side in the secondary combustion chamber, and the secondary combustion chamber recirculation exhaust gas is supplied to the downstream side from the position where the secondary air is supplied. As a result, the unburned gas discharged from the combustion chamber first comes into contact with the secondary air to start combustion under a sufficient oxygen supply, and further to the secondary side downstream from the position where the secondary air is supplied. By supplying the combustion chamber recirculation exhaust gas, the unburned gas and the secondary air are sufficiently stirred and mixed by the stirring action of the secondary combustion chamber recirculation exhaust gas flow. The unburned gas is efficiently and stably subjected to secondary combustion without causing a region where oxygen is uniformly dispersed and local oxygen deficiency or oxygen excess occurs in the combustion of the unburned gas. In addition, since a part of the high-temperature exhaust gas discharged from the waste incinerator is supplied as recirculated exhaust gas, the secondary combustion chamber can be maintained at a high temperature, and the unburned gas can be efficiently and stably supplied to the secondary combustion chamber. Burned.

  Furthermore, in the second and fourth inventions, the secondary air supply ports and the secondary combustion chamber recirculation exhaust gas supply ports are arranged alternately in the circumferential direction of the inner wall of the secondary combustion chamber. As a result, the secondary air and the secondary combustion chamber recirculation exhaust gas are mixed, the oxygen in the secondary air is diluted, and there is no variation in the oxygen concentration, and a locally high oxygen concentration region is formed in the secondary combustion chamber. It is possible to prevent the occurrence of thermal NOx due to the occurrence of a local high temperature region, and the unburned gas can be combusted uniformly and stably in the secondary combustion chamber.

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. (A) is a fracture | rupture perspective view about a secondary combustion chamber which shows an example of the position which blows in secondary air and recirculation waste gas into the secondary combustion chamber in FIG. 1, (B) is a figure which shows the modification. . It is a schematic block diagram of the waste incinerator which concerns on other embodiment of this invention.

  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.

  The waste incinerator according to the present embodiment is disposed above the combustion chamber 1 and on the upstream side (left side in FIG. 1) in the flow direction of the waste W in the combustion chamber, and the waste W is thrown into the combustion chamber 1. A fire that includes a secondary combustion chamber 3 and a waste heat boiler 4 that are connected to the waste inlet 2 to be disposed on the downstream side in the flow direction of the waste W in the combustion chamber 1 (the right side in FIG. 1). It is a grid type incinerator.

  At the bottom of the combustion chamber 1, there is provided a grate (stoker) 5 for burning the waste W while moving it. The grate 5 is provided in the order of a dry grate 5a, a combustion grate 5b, and a post-combustion grate 5c from the side closer to the waste inlet 2, and a waste layer is formed on the grate 5. ing.

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

  When the waste W is incinerated, moisture is first evaporated, then thermal decomposition and partial oxidation reaction occur, and combustible gas begins to be generated. A region where combustion of the waste W starts and combustible gas begins to be generated by thermal decomposition and partial oxidation of the waste W is referred to as a combustion start region. Next, the waste W 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 W is combusted. The region up to the point where the combustion accompanied by (combustion point) is completed is called the main combustion region. A region where the solid unburned matter in the waste W burns in a region after the burnout point is referred to as a soot combustion region (post-combustion region).

  Wind boxes 7a, 7b, and 7c are provided below the dry grate 5a, the combustion grate 5b, and the post-combustion grate 5c in the combustion chamber 1, respectively. The primary air supplied by the blower 8a is supplied to the wind boxes 7a, 7b, 7c through the primary air supply pipe 9, and is supplied into the combustion chamber 1 through the grate 5a, 5b, 5c. . The primary air supplied from below the grate 5 is used for drying and burning the waste W on the grate 5 and has a cooling action for the grate 5 and a stirring action for the waste W.

  A secondary combustion chamber 3 and a waste heat boiler 4 are connected to the gas outlet of the combustion chamber 1, and unburned gas contained in the combustion gas after combustion in the combustion chamber 1 is secondary in the secondary combustion chamber 3. Burned with air. The exhaust gas after combustion in the secondary combustion chamber 3 is recovered by the waste heat boiler 4. After the heat is recovered, the exhaust gas discharged from the waste heat boiler 4 is neutralized with acid gas by slaked lime and the like and adsorbed with dioxins by activated carbon in an exhaust gas treatment device system (not shown), and further to a dust removal device (not shown). The neutralized reaction product, activated carbon, dust and the like are collected. The 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.

  A part of the exhaust gas discharged from the waste heat boiler 4 is extracted and used as recirculated exhaust gas as described later.

  In the grate-type incinerator having such a basic configuration, the waste incinerator according to the present embodiment includes primary air supply means 10 that blows primary air into the combustion chamber 1 from below the grate 5, and two Secondary air supply means 20 for supplying secondary air to the upstream side in the secondary combustion chamber 3, and a part of the exhaust gas discharged from the waste incinerator downstream from the position where the secondary air is supplied is recirculated exhaust gas As well as a control device 40 for controlling the secondary air supply means 20 and the recirculation exhaust gas supply means 30.

<Primary air supply means>
In the present embodiment, the waste incinerator includes primary air supply means 10 for primary air that serves as combustion air in the combustion chamber 1. The primary air supply means 10 passes from the air supply source (not shown) through the primary air supply pipe 9 to the wind boxes 7a, 7b, 7c of the dry grate 5a, the combustion grate 5b, and the post-combustion grate 5c. It has branch supply pipes 9a, 9b, 9c for sending primary air, a blower 8a provided in the primary air supply pipe 9, and a damper 8b as a flow rate adjusting mechanism.

<Secondary air supply means>
The waste incinerator includes secondary air supply means 20 that supplies secondary air that becomes air for secondary combustion in the secondary combustion chamber 3. The secondary air supply means 20 passes air from an air supply source provided outside from the secondary air supply port 22 provided at the upstream position in the secondary combustion chamber 3 via the pipe line 21. A blower 23 and a damper 24 as a supply amount adjusting mechanism are provided in the pipeline 21. The damper 24 is adjusted in opening degree by a control device 40 described later to adjust the secondary air supply amount.

  The secondary air supply ports 22 are provided at a plurality of locations distributed on the peripheral surface of the inner wall of the secondary combustion chamber 3 in the upstream position in the secondary combustion chamber 3, that is, in the lower region. The secondary air supply port 22 preferably has a secondary air blowing angle into the secondary combustion chamber 3 in a range downward from the horizontal direction and a downward angle greater than 0 degrees and 45 degrees or less. As a result, the secondary air collides against the flow of the unburned gas rising in the secondary combustion chamber 3, and the stirring and mixing of the unburned gas and the secondary air are promoted.

<Recirculation exhaust gas supply means>
The waste incinerator further includes a recirculated exhaust gas supply means 30 that feeds back a part of the exhaust gas discharged from the incinerator as a recirculated exhaust gas into the secondary combustion chamber 3. The recirculation exhaust gas supply means 30 passes through a recirculation exhaust gas pipe 31 provided by branching to a duct 4a for exhausting exhaust gas from the waste heat boiler 4, and the position of the secondary air supply port 22 in the secondary combustion chamber 3 A recirculated exhaust gas is blown into the secondary combustion chamber 3 from a recirculated exhaust gas supply port 32 provided at a more downstream position (that is, an upper position). A blower 33 and a supply amount are supplied to the pipe 31. A damper 34 as an adjustment mechanism is provided. The opening of the damper 34 is adjusted by a control device 40 to be described later to adjust the recirculated exhaust gas supply amount. In the embodiment shown in FIG. 1, a part of the exhaust gas discharged from the waste heat boiler 4 is extracted and used as recirculated exhaust gas. An exhaust gas extracted from another position of the exhaust gas flow path may be used.

  Similar to the secondary air supply port 22, the recirculated exhaust gas supply ports 32 are distributed in the lower region of the secondary combustion chamber 3 on the peripheral surface of the inner wall of the secondary combustion chamber 3 and are provided at a plurality of locations. In this embodiment, it is located close to the secondary air supply port 22 and downstream (ie, upward). As in the case of the secondary air supply port 22, the recirculation exhaust gas supply port 32 preferably has a blowing angle that is downward from the horizontal direction and a downward angle that is greater than 0 degree and not more than 45 degrees. By doing so, the recirculated exhaust gas collides with the flow of the unburned gas rising in the secondary combustion chamber 3, and the stirring and mixing of the unburned gas, the secondary air, and the recirculated exhaust gas are promoted.

  The positional relationship between the secondary air supply port 22 and the recirculated exhaust gas supply port 32 in the present embodiment shown in FIG. 1 is as shown in FIG. As another form of the positional relationship, as shown in FIG. 2B, the recirculation exhaust gas supply port 32 is arranged at a downstream position (that is, the upper side) near the secondary air supply port 22, and the circumferential direction Then, you may make it position both alternately. By doing so, the recirculated exhaust gas is satisfactorily stirred with respect to the secondary air, and the secondary air and the recirculated exhaust gas are sufficiently mixed.

  When the horizontal cross section of the secondary combustion chamber 3 is rectangular, the recirculated exhaust gas supply port 32 is arranged on the back wall of the secondary combustion chamber 3 connected to the downstream back wall of the combustion chamber 1. Preferably, the secondary air supply port 22 is provided on both side walls orthogonal to the back wall, and the height of the secondary air supply port 22 is arranged upstream of the height of the recirculated exhaust gas supply port 32. With such a positional relationship, the secondary air and the recirculated exhaust gas are sufficiently mixed with the unburned gas flowing into the secondary combustion chamber 3, and the amount of CO generated can be efficiently suppressed.

<Control device>
In the present embodiment, an exhaust gas property detector 41 as a gas property measuring means for measuring exhaust gas properties such as exhaust gas component concentration, and a signal from the exhaust gas property detector 41 are provided in a duct 4a serving as an outlet of the waste heat boiler 4. And a control device 40 for controlling the supply amount adjustment mechanism of the secondary air supply means 20 described above and for controlling the supply amount adjustment mechanism of the recirculated exhaust gas supply means 30.

  In this embodiment, the exhaust gas property detector 41 includes an oxygen concentration meter 41a, a NOx concentration meter 41b, and a CO concentration meter 41c. When the control device 40 receives a signal from the exhaust gas property detector 41, the opening degree of the damper 24 of the supply amount adjustment mechanism of the secondary air supply means 20 and the damper 34 of the supply amount adjustment mechanism of the recirculation exhaust gas supply means 30 are detected. Control to adjust the opening.

  In the present invention having such a control device 40, the exhaust gas property detector 41 measures the oxygen concentration in the exhaust gas and the gas component concentrations of CO and NOx, and one or more of these gas component concentration measurement values are measured. When not within the predetermined range, the control device 40 causes the secondary air supply amount of the secondary air supply means 20 and the recirculated exhaust gas supply of the recirculated exhaust gas supply means 30 so that the gas component concentration falls within the predetermined range. At least one of the opening degree of the damper 24 of the supply amount adjustment mechanism of the secondary air supply means 20 and the opening degree of the damper 34 of the supply amount adjustment mechanism of the recirculated exhaust gas supply means 30 is controlled so as to adjust the amount.

  Next, an overview of the incineration situation in the apparatus of the present embodiment configured as described above, the atmosphere in the secondary combustion chamber, the control of blowing in secondary air and recirculated exhaust gas, and actions related thereto will be sequentially described. .

<Overview of incineration>
First, when the waste W is introduced into the waste inlet 2, the dropped waste W is supplied into the combustion chamber 1 by a waste supply device (not shown), and is deposited on the dry grate 5a. By movement of 5b and 5c, it moves on the combustion grate 5b and on the post-combustion grate 5c, and forms a layer of waste W on each grate 5a, 5b and 5c. Each grate 5a, 5b, 5c receives primary air for combustion via wind boxes 7a, 7b, 7c, whereby the waste W in each grate 5a, 5b, 5c is dried and burned. .

  The waste W is mainly dried and ignited on the dry grate 5a. The waste W starts to burn in the combustion grate 5b, and further, the waste W is thermally decomposed and partially oxidized to generate a combustible gas. The combustible gas burns with a flame, and the waste The solid content in W is combusted. The combustion of the waste W is substantially completed on the combustion grate 5b. On the post-combustion grate 5c, unburned components such as fixed carbon in the waste W that remains slightly are completely burned. The combustion ash after complete combustion is discharged from the ash drop opening 6.

  As described above, the secondary combustion chamber 3 and the waste heat boiler 4 are connected to the outlet of the combustion chamber 1, and unburned gas contained in the combustion gas after combustion in the combustion chamber 1 is converted into the secondary combustion chamber 3. Burned in. The combustion exhaust gas after combustion in the secondary combustion chamber 3 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 discharged from the waste heat boiler 4 is extracted and used as recirculated exhaust gas described later.

<Atmosphere of secondary combustion chamber>
It is preferable to adjust the flow rates of the secondary air and the recirculated exhaust gas so that the gas temperature in the secondary combustion chamber 3 is in the range of 800 to 1050 ° C. The reason is that if the gas temperature in the secondary combustion chamber 3 is less than 800 ° C., the combustion becomes insufficient and CO increases, and the gas temperature in the secondary combustion chamber 3 exceeds 1050 ° C. This is because exceeding this promotes the generation of clinker in the secondary combustion chamber 3 and further increases NOx.

  Next, in this embodiment, the control of the secondary air supply amount and the recirculated exhaust gas supply amount based on the exhaust gas properties (gas component concentration) will be described in detail.

  The control based on the exhaust gas oxygen concentration will be described as an example of the exhaust gas property (gas component concentration).

<Control of secondary air supply based on exhaust gas oxygen concentration>
In the present embodiment, the oxygen concentration of the exhaust gas at the outlet of the waste heat boiler 4 is measured by the oxygen concentration meter 41a, and the secondary air supply amount and the recirculated exhaust gas supply amount are controlled based on the change tendency of the oxygen concentration. However, Table 1 shows the relationship between the oxygen concentration change tendency, the CO concentration in the exhaust gas, the NOx concentration change tendency in the exhaust gas, the adjustment of the secondary air supply amount, and the adjustment of the recirculation exhaust gas supply amount.

<Adjustment of secondary air supply>
Generation of harmful substances such as CO, NOx, and DXN (dioxins) when combustible gas generated by waste and thermal decomposition in the combustion chamber 1 is combusted within the range of appropriate oxygen concentration and temperature. Most suppressed. In Table 1, when the oxygen concentration in the exhaust gas in the vicinity of the boiler outlet is higher than the predetermined range, the CO concentration discharged from the combustion chamber 1 is in a state of decreasing or no change, but the NOx concentration is increasing. Become. Therefore, the secondary air supply amount is decreased, the oxygen supply amount to the secondary combustion chamber 3 is decreased, and combustion in the secondary combustion chamber 3 is appropriately performed. On the other hand, when the oxygen concentration in the exhaust gas near the outlet of the waste heat boiler 4 is lower than the predetermined range, the exhausted NOx concentration decreases or remains unchanged, but the CO concentration increases. . Therefore, the secondary air supply amount is increased, the oxygen supply amount to the secondary combustion chamber 3 is increased, and combustion in the secondary combustion chamber 3 is appropriately performed.

<Adjustment of recirculated exhaust gas supply>
Generation of harmful substances such as CO, NOx, and DXN (dioxins) when combustible gas generated by waste and thermal decomposition in the combustion chamber 1 is combusted within the range of appropriate oxygen concentration and temperature. Most suppressed. In Table 1, when the oxygen concentration in the exhaust gas in the vicinity of the boiler outlet is higher than the predetermined range, the CO concentration discharged from the combustion chamber 1 is in a state of decreasing or no change, but the NOx concentration is increasing. Become. Regarding the suppression of the generation of NOx, since the improvement effect by stirring in the secondary combustion chamber is low, it is desirable not to change the supply amount of the recirculated exhaust gas. However, when the NOx concentration is extremely high and the NOx generation reaction has continued in the secondary combustion chamber, the supply amount of the recirculated exhaust gas is increased by a small amount, and the stirring of the secondary air is promoted. Reduce NOx concentration. Further, when the oxygen concentration in the exhaust gas near the outlet of the waste heat boiler 4 is lower than the predetermined range, the exhausted NOx concentration decreases or remains unchanged, but the CO concentration increases. Therefore, the secondary air supply amount is increased to increase the oxygen concentration in the secondary combustion chamber, and the recirculated exhaust gas supply amount is increased to promote the stirring of the secondary air. As a result, the CO concentration is reduced so that the combustion in the secondary combustion chamber 3 is properly performed.

  In the above-described embodiment, the oxygen concentration meter 41a is used as the exhaust gas property detector 41. However, as the exhaust gas property detector 41, the oxygen concentration meter 41a and the NOx concentration meter 41b are used instead of the oxygen concentration meter 41a. Alternatively, at least one of the CO concentration meters 41c may be used. Based on at least one of the oxygen concentration, CO concentration, and NOx concentration of the exhaust gas detected by the exhaust gas property detector 41, the control device 40 controls each supply amount so that the property falls within a predetermined range. Can be.

  FIG. 3 shows a schematic configuration of a waste incinerator according to another embodiment of the present invention.

  In this embodiment, in addition to the configuration of the previous embodiment shown in FIG. 1, high temperature gas supply means for supplying high temperature gas to the combustion chamber of the waste incinerator, a part of the exhaust gas discharged from the waste incinerator Is also provided with a combustion chamber recirculation exhaust gas supply means for blowing into the combustion chamber as a combustion chamber recirculation exhaust gas. Hereinafter, the high temperature gas supply means and the combustion chamber recirculation exhaust gas supply means will be described.

<High temperature gas supply means>
In this embodiment, the waste incinerator includes a high-temperature gas supply unit that blows high-temperature gas downward from the ceiling of the combustion chamber or blows it from the side wall. The high temperature gas supply means has a high temperature gas supply device (not shown) and a high temperature gas supply port 11 on the ceiling or side wall of the combustion chamber at a plurality of positions in the furnace length direction, which is the moving direction of waste on the grate 5. doing. In this embodiment, the hot gas supply port 11 is provided as two hot gas supply ports 11a and 11b.

  The hot gas supply ports 11a and 11b are provided above the combustion grate 5b.

  The high-temperature gas supply device receives high-temperature air and recirculated exhaust gas, mixes them, and blows them into the furnace as the high-temperature gas from the high-temperature gas supply ports 11a and 11b.

  The “recirculated exhaust gas” used here as a part of the high-temperature 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 “hot air” is generated by heating air with a heater. The hot gas supply device adjusts the mixing ratio by adjusting the flow rates of the recirculated exhaust gas and hot air to adjust the temperature and oxygen concentration of the hot gas. Further, the high temperature gas supply device may supply only high temperature air or only recirculated exhaust gas as the high temperature gas.

  In this embodiment, when the high temperature air and the recirculated exhaust gas are mixed with the high temperature gas supply device to prepare the high temperature gas, the mixing ratio is adjusted by adjusting the respective flow rates of the high temperature air and the recirculated exhaust gas. By adjusting at least one of adjusting the oxygen concentration in the high temperature gas and adjusting the flow rate of the high temperature gas by a damper or the like, the amount of oxygen supplied by the high temperature gas into the combustion chamber can be adjusted.

<Combustion chamber recirculation exhaust gas supply means>
The combustion chamber recirculation exhaust gas supply means has a recirculation exhaust gas supply device (not shown) for supplying a part of the exhaust gas discharged from the incinerator and a recirculation exhaust gas supply port 12. The recirculated exhaust gas supply port 12 is provided above the combustion grate 5b. The recirculated exhaust gas supply device receives a part of the exhaust gas discharged from the incinerator and dedusted by a dust collector (not shown). It blows into the furnace through the mouth 12.

<Distribution of oxygen amount ratio to achieve low air ratio combustion>
Next, in order to realize low air ratio combustion in the waste incinerator of the present embodiment, a preferable range of the oxygen amount ratio distribution of each gas to be supplied will be described.

The ratio Q1A of the amount of oxygen per unit time supplied by the primary air blown into the combustion chamber from below the grate to the theoretical amount of oxygen per unit time required for combustion of waste, and the high-temperature gas blown into the combustion chamber The ratio Q1B of the oxygen amount per unit time supplied, the ratio Q1C of the oxygen amount per unit time supplied by the combustion chamber recirculation exhaust gas blown into the combustion chamber, and the secondary air blown into the secondary combustion chamber The ratio Q2 of the oxygen amount per unit time supplied and the ratio Q3 of the oxygen amount per unit time supplied by the secondary combustion chamber recirculated exhaust gas blown into the secondary combustion chamber are expressed by the following equation (1) and It is preferable to adjust the supply amount of each gas so as to satisfy (2). Combustion at a low air ratio with an air ratio of 1.4 or less by controlling the ratio of supplying each gas so that the following equations (1) and (2) are satisfied. Can be realized.
Q1A: Q1B: Q1C: Q2: Q3
= 0.93 to 1.10: 0.14 to 0.16: 0.09 to 0.11: 0.01 to 0.05: 0.01 to 0.05 (1)
1.2 ≦ Q1A + Q1B + Q1C + Q2 + Q3 ≦ 1.4 (2)

Here, the theoretical oxygen amount per unit time required for the combustion of the waste is the amount of oxygen necessary for the combustion per unit mass of the waste determined from the properties and components of the waste introduced into the combustion chamber. It is determined by the product (Nm ³ / hr) of (Nm ³ / kg) and the incineration rate (kg / hr) of waste in the incinerator.

  The value of Q1A is a ratio of the oxygen amount per unit time supplied by the primary air supplied from below the grate into the combustion chamber to the theoretical oxygen amount, and increases or decreases the supply amount of the primary air. Adjust by. Further, the value of Q1B is adjusted by increasing or decreasing the supply amount of the high temperature gas supplied into the combustion chamber. Further, the value of Q1C is adjusted by increasing or decreasing the supply amount of the combustion chamber recirculation exhaust gas supplied into the combustion chamber. The value of Q2 is adjusted by increasing or decreasing the supply amount of secondary air supplied to the secondary combustion chamber. The value of Q3 is adjusted by increasing or decreasing the supply amount of the secondary combustion chamber recirculated exhaust gas supplied to the secondary combustion chamber.

  In the following, Q1A + Q1B + Q1C + Q2 + Q3 is described as λ.

  By setting the ratio Q1A: Q1B: Q1C: Q2: Q3 within the range of the above formulas (1) and (2), low oxygen ratio combustion (1.2 ≦ λ ≦ 1.4) (that is, in a waste incinerator) , Which corresponds to low air ratio combustion), the generation amount of harmful gases such as CO and NOx can be reduced, and the total amount of exhaust gas discharged from the incinerator can be greatly reduced.

<Evidence of oxygen amount ratio distribution range>
The grounds for defining Q1A: Q1B: Q1C: Q2: Q3 within a range that satisfies the above expressions (1) and (2) will be described.

≪Primary air oxygen amount Q1A≫
If the ratio Q1A of the amount of oxygen supplied by the primary air to the theoretical amount of oxygen necessary for waste combustion is less than the lower limit, the oxygen concentration in the combustion chamber decreases, the CO concentration in the exhaust gas increases, The incomplete combustion of the product is not preferable because the amount of heat loss increases and the amount of ash discharged increases. Also, if it exceeds the upper limit value, it means that the amount of primary air supply is large, the amount of exhaust gas generated increases, an excessive load is applied to the exhaust gas treatment facility, and the amount of heat taken out of the boiler by the exhaust gas increases. Since the heat recovery rate in a boiler will fall, it is not preferable.

≪High-temperature gas oxygen amount Q1B≫
If the ratio Q1B of the amount of oxygen supplied by the high-temperature gas to the theoretical amount of oxygen necessary for waste combustion is less than the lower limit value, a stable combustion field is not formed above the waste layer, and waste from the combustion flame The radiant heat given to the furnace is reduced, which makes it impossible to efficiently burn waste. Also, if it exceeds the upper limit value, it means that the amount of high-temperature gas supplied is large, the amount of exhaust gas generated increases, an excessive load is applied to the exhaust gas treatment facility, and the amount of heat taken out of the boiler by the exhaust gas increases. Not only is the heat recovery rate in the boiler lowered, but a large amount of energy is required for heating the air to adjust the high temperature gas, which increases the operating cost.

≪Combustion chamber recirculation exhaust gas oxygen amount Q1C≫
When the ratio Q1C of the oxygen amount supplied by the combustion chamber recirculation exhaust gas to the theoretical oxygen amount necessary for waste combustion is less than the lower limit value, the action of stirring the combustion chamber becomes low, and the combustible generated by thermal decomposition of the waste Since mixing of gas and oxygen becomes insufficient and combustion becomes insufficient, the CO concentration and NOx concentration in the exhaust gas increase, which is not preferable. On the other hand, if the amount exceeds the upper limit value, the recirculated exhaust gas having a relatively low temperature is excessively injected into the furnace, so that a region having a low temperature is locally formed, resulting in insufficient combustion and CO in the exhaust gas. This is not preferable because the concentration increases.

≪Secondary air oxygen amount Q2≫
If the ratio Q2 of the oxygen amount supplied by the secondary air to the theoretical oxygen amount necessary for waste combustion is less than the lower limit value, the combustion reaction of the unburned gas in the secondary combustion chamber is not sufficiently performed, and the secondary combustion This is not preferable because the CO concentration in the exhaust gas at the chamber outlet increases. On the other hand, if it exceeds the upper limit, a region where the oxygen concentration is locally high and the oxygen partial pressure rises in the secondary combustion chamber and NOx is easily generated, which is not preferable.

≪Secondary combustion chamber recirculation exhaust gas oxygen amount Q3≫
If the ratio Q3 of the oxygen amount supplied by the secondary combustion chamber recirculation exhaust gas to the theoretical oxygen amount necessary for waste combustion is less than the lower limit value, the action of stirring the secondary combustion chamber becomes low, and the unburned gas and Since the mixing with the secondary air is insufficient and the combustion becomes insufficient, the CO concentration in the exhaust gas increases, or the region where the oxygen concentration is locally high in the secondary combustion chamber due to insufficient stirring, This is not preferable because a low region is formed and the NOx concentration and CO concentration in the exhaust gas increase. On the other hand, if the value is larger than the upper limit value, the secondary air is diluted with the recirculated exhaust gas, the oxygen concentration is lowered, and the combustion becomes insufficient, which is not preferable because the CO concentration in the exhaust gas increases.

<Preferable range of oxygen amount ratio distribution>
As a preferable oxygen amount ratio distribution that can achieve stable low air ratio combustion by suppressing generation of unburned waste and harmful substances, Q1A: Q1B: Q1C: Q2: Q3 = 1.00: 0 .15: 0.10: 0.02: 0.03, with λ = 1.30 as a reference, λ is 1.2 to 1.4 based on the composition and properties of the waste thrown into the incinerator Adjust Q1A, Q1B, Q1C, Q2, and Q3 within the above range. Below, the adjustment reference | standard of Q1A, Q1B, Q1C, Q2, Q3 is demonstrated.

≪Q1A, Q1B, Q1C adjustment standards≫
When normal waste such as municipal waste is dried and burned, the total of Q1A, Q1B, and Q1C supplied to the combustion chamber is based on 1.25, and waste with low ash and low moisture, such as When burning plastic or the like, the total of Q1A, Q1B, and Q1C is reduced to about 1.15 to 1.20, and instead, Q2 for secondary air is increased.

≪Q2 adjustment standard for secondary air≫
When combusting waste such as ordinary municipal waste, Q2 by secondary air is 0.02 as a standard, and waste with little ash, moisture, and most combustibles, such as plastic, or volatilization When burning a large waste, the amount of combustible gas generated in the combustion chamber increases and the amount of unburned gas increases and the combustion in the secondary combustion chamber increases. Therefore, Q2 is set to about 0.04 to 0.05. Increase the amount so that unburned gas is burned sufficiently in the secondary combustion chamber. While operating the waste incinerator constantly, when the Q2 for the secondary air is set constant, the combustion status in the incinerator changes, and the exhaust gas properties such as the component concentration in the exhaust gas change Adjusts the combustion state in the secondary combustion chamber by adjusting at least one of Q2 for the secondary air and Q3 for the secondary combustion chamber recirculation exhaust gas based on the measured value of the exhaust gas property It is preferable to make it.

≪Q3 adjustment standard for secondary combustion chamber recirculation exhaust gas≫
While operating the waste incinerator constantly, Q3 for the secondary combustion chamber recirculation exhaust gas is set to be constant within a range of 0.01 to 0.05 with 0.03 as a reference, When the combustion status in the incinerator changes and the exhaust gas properties such as the component concentration in the exhaust gas change, based on the measured values of the exhaust gas properties, Q2 for the secondary air and Q3 for the secondary combustion chamber recirculated exhaust gas It is preferable to adjust the combustion state in the secondary combustion chamber by adjusting at least one of the above.

  In actual operation of a waste incinerator, even if it operates with standard operating standards, the combustion status in the incinerator may change, and the amount of harmful substances in the exhaust gas emitted may vary. Therefore, while maintaining the determined values of Q1A, Q1B, and Q1C, adjustments are made to increase / decrease Q2 and Q3 based on a factor for monitoring the situation in the waste incinerator.

  By adopting such a combustion control method, even if the combustion situation in the incinerator changes, it can be adjusted so that the combustion is performed stably, and finally harmful substances in the exhaust gas discharged from the waste incinerator The amount can be easily controlled, and the combustion control system of the incinerator can be simplified.

  Here, as the factors for monitoring the situation in the waste incinerator, for example, the exhaust gas temperature near the outlet of the secondary combustion region where the secondary combustion of the unburned gas discharged from the combustion chamber or the boiler outlet is performed, the exhaust gas It is preferable to set any one or more of oxygen concentration, CO concentration, and NOx concentration.

≪Preferred example of oxygen amount ratio distribution≫
Preferred examples of Q1A: Q1B: Q1C: Q2: Q3, λ will be described below.
Q1A: Q1B: Q1C: Q2: Q3
= 1.00: 0.15: 0.10: 0.02: 0.03, λ = 1.30
Q1A: Q1B: Q1C: Q2: Q3
= 1.00: 0.15: 0.10: 0.01: 0.04, λ = 1.30
Q1A: Q1B: Q1C: Q2: Q3
= 1.00: 0.15: 0.10: 0.04: 0.01, λ = 1.30
Q1A: Q1B: Q1C: Q2: Q3
= 1.05: 0.15: 0.10: 0.02: 0.03, λ = 1.35
Q1A: Q1B: Q1C: Q2: Q3
= 1.05: 0.15: 0.10: 0.01: 0.04, λ = 1.35
Q1A: Q1B: Q1C: Q2: Q3
= 1.05: 0.15: 0.10: 0.04: 0.01, λ = 1.35
Q1A: Q1B: Q1C: Q2: Q3
= 0.95: 0.15: 0.10: 0.02: 0.03, λ = 1.25
Q1A: Q1B: Q1C: Q2: Q3
= 0.95: 0.15: 0.10: 0.01: 0.04, λ = 1.25
Q1A: Q1B: Q1C: Q2: Q3
= 0.95: 0.15: 0.10: 0.04: 0.01, λ = 1.25
Q1A: Q1B: Q1C: Q2: Q3
= 1.10: 0.15: 0.10: 0.02: 0.03, λ = 1.40
Q1A: Q1B: Q1C: Q2: Q3
= 1.10: 0.15: 0.10: 0.01: 0.04, λ = 1.40
Q1A: Q1B: Q1C: Q2: Q3
= 1.10: 0.15: 0.10: 0.04: 0.01, λ = 1.40

  As described above, according to the present invention, even when low air ratio combustion is performed in a waste incinerator, the stability of combustion is maintained, the occurrence of local high temperature regions is suppressed, and CO, NOx, etc. A waste incinerator capable of reducing the amount of harmful gas generated is provided. Furthermore, since a low air ratio combustion can be performed, a waste incinerator and a waste incineration method that can significantly reduce the amount of exhaust gas discharged from the incinerator and improve the recovery efficiency of waste heat are provided.

DESCRIPTION OF SYMBOLS 1 Combustion chamber 3 Secondary combustion chamber 5 Grate 10 Primary air supply means 11 High temperature gas supply port 12 Combustion chamber recirculation exhaust gas supply port 20 Secondary air supply means 22 Secondary air supply port 30 Recirculation exhaust gas supply means 32 Recirculation Exhaust gas supply port, secondary combustion chamber recirculation exhaust gas supply port 40 Control device 41 Exhaust gas property detector

Claims (9)

A grate-type waste incinerator,
A combustion chamber comprising a grate and burning waste on the grate;
A secondary combustion chamber connected to the combustion chamber for secondary combustion of unburned gas from the combustion chamber;
A boiler connected to the secondary combustion chamber;
In a grate-type waste incinerator having primary air supply means for blowing primary air from under the grate into the combustion chamber,
Secondary air supply means having a secondary air supply port for supplying secondary air to the upstream side of the secondary combustion chamber, and waste on the upstream side of the secondary combustion chamber and downstream of the position of the secondary air supply port Recycled exhaust gas supply means that supplies a part of the exhaust gas discharged from the incinerator as a recirculated exhaust gas from the recirculated exhaust gas supply port, an oxygen concentration meter that measures the oxygen concentration of the exhaust gas at the boiler outlet, and an oxygen concentration meter A control device for controlling the secondary air supply amount and the circulating exhaust gas supply amount based on the measured oxygen concentration in the exhaust gas ,
When the oxygen concentration in the exhaust gas in the vicinity of the boiler outlet is higher than the predetermined range, the control device reduces the secondary air supply amount and does not change the recirculated exhaust gas supply amount or increases the secondary air supply amount. When the combustion in the secondary combustion chamber is controlled so as to promote stirring and reduce the NOx concentration from the state where the exhausted NOx concentration increases, and when the oxygen concentration in the exhaust gas near the boiler outlet is lower than the predetermined range, The secondary air supply amount is increased, the recirculated exhaust gas supply amount is increased to promote the stirring of the secondary air, and the CO concentration is reduced in the secondary combustion chamber so as to reduce the CO concentration from the state where the discharged CO concentration increases. A grate-type waste incinerator characterized by controlling combustion .   The grate-type waste incinerator according to claim 1, wherein the secondary air supply port and the recirculated exhaust gas supply port are alternately arranged in the circumferential direction of the inner wall of the secondary combustion chamber. A grate-type waste incinerator,
A combustion chamber comprising a grate and burning waste on the grate;
A secondary combustion chamber connected to the combustion chamber for secondary combustion of unburned gas from the combustion chamber;
A boiler connected to the secondary combustion chamber;
Primary air supply means for blowing primary air from under the grate into the combustion chamber;
Hot gas supply means for blowing hot gas into the combustion chamber from the ceiling or side wall of the combustion chamber;
In a grate-type waste incinerator having combustion chamber recirculation exhaust gas supply means for blowing a part of exhaust gas discharged from a waste incinerator into the combustion chamber as combustion chamber recirculation exhaust gas,
Secondary air supply means having a secondary air supply port for supplying secondary air to the upstream side of the secondary combustion chamber, and waste on the upstream side of the secondary combustion chamber and downstream of the position of the secondary air supply port Recycled exhaust gas supply means that supplies a part of the exhaust gas discharged from the incinerator as a recirculated exhaust gas from the recirculated exhaust gas supply port, an oxygen concentration meter that measures the oxygen concentration of the exhaust gas at the boiler outlet, and an oxygen concentration meter A control device for controlling the secondary air supply amount and the circulating exhaust gas supply amount based on the measured oxygen concentration in the exhaust gas ,
When the oxygen concentration in the exhaust gas in the vicinity of the boiler outlet is higher than the predetermined range, the control device reduces the secondary air supply amount and does not change the recirculated exhaust gas supply amount or increases the secondary air supply amount. When the combustion in the secondary combustion chamber is controlled so as to promote stirring and reduce the NOx concentration from the state where the exhausted NOx concentration increases, and when the oxygen concentration in the exhaust gas near the boiler outlet is lower than the predetermined range, The secondary air supply amount is increased, the recirculated exhaust gas supply amount is increased to promote the stirring of the secondary air, and the CO concentration is reduced in the secondary combustion chamber so as to reduce the CO concentration from the state where the discharged CO concentration increases. A grate-type waste incinerator characterized by controlling combustion .   The grate-type waste incinerator according to claim 3, wherein the secondary air supply port and the secondary combustion chamber recirculation exhaust gas supply port are alternately arranged in the circumferential direction of the inner wall of the secondary combustion chamber. A waste incineration method using a grate-type waste incinerator,
Combustion chamber having a grate and burning waste on the grate, a secondary combustion chamber connected to the combustion chamber for secondary combustion of unburned gas from the combustion chamber, and connected to the secondary combustion chamber In a waste incineration method by a grate-type waste incinerator having a boiler and primary air supply means for blowing primary air from under the grate into the combustion chamber,
Secondary air is supplied to the upstream side of the secondary combustion chamber, and a part of the exhaust gas discharged from the waste incinerator is supplied downstream from the position where the secondary air is supplied as recirculated exhaust gas. If the oxygen concentration in the exhaust gas near the boiler outlet is higher than the predetermined range, the secondary air supply amount and the circulating exhaust gas supply amount are controlled based on the measured oxygen concentration measurement value in the exhaust gas. A state in which the secondary air supply amount is decreased on the upstream side of the secondary combustion chamber and the recirculated exhaust gas supply amount is not changed or increased by a small amount to promote the agitation of the secondary air and increase the exhausted NOx concentration If the oxygen concentration in the exhaust gas near the boiler outlet is lower than the specified range, the secondary air supply amount is increased and the recirculated exhaust gas supply is controlled. Grate-type waste incineration characterized by controlling the combustion in the secondary combustion chamber so as to reduce the CO concentration from the state in which the CO concentration to be discharged is increased by increasing the stirring of the secondary air Waste incineration method in the furnace.   The waste incineration method in a grate-type waste incinerator according to claim 5, wherein the secondary air supply and the recirculated exhaust gas supply are performed from supply ports arranged alternately in the circumferential direction of the inner wall of the secondary combustion chamber. . A waste incineration method using a grate-type waste incinerator,
Combustion chamber having a grate and burning waste on the grate, a secondary combustion chamber connected to the combustion chamber for secondary combustion of unburned gas from the combustion chamber, and connected to the secondary combustion chamber Boiler, primary air supply means for blowing primary air from below the grate into the combustion chamber, high temperature gas supply means for blowing high temperature gas from the ceiling or side wall of the combustion chamber, and a waste incinerator In a waste incineration method using a grate-type waste incinerator having combustion chamber recirculation exhaust gas supply means for blowing a part of exhaust gas discharged from the combustion chamber recirculation exhaust gas into the combustion chamber,
Secondary air is supplied to the upstream side of the secondary combustion chamber, and a part of the exhaust gas discharged from the waste incinerator is supplied downstream from the position where the secondary air is supplied as secondary combustion chamber recirculation exhaust gas . Measure the oxygen concentration of the exhaust gas at the boiler outlet, control the secondary air supply amount and the circulating exhaust gas supply amount based on the measured oxygen concentration measurement value in the exhaust gas, and the oxygen concentration in the exhaust gas near the boiler outlet is higher than the predetermined range In this case, the secondary air supply amount is decreased on the upstream side of the secondary combustion chamber and the recirculated exhaust gas supply amount is not changed or increased by a small amount to promote the stirring of the secondary air, and the NOx concentration discharged. When the combustion in the secondary combustion chamber is controlled so as to reduce the NOx concentration from the state where the NO increases, and the oxygen concentration in the exhaust gas near the boiler outlet is lower than the predetermined range, the secondary air supply amount is increased, Recirculation A grate system characterized by controlling the combustion in the secondary combustion chamber so as to reduce the CO concentration from the state in which the CO concentration to be discharged is increased by increasing the gas supply amount to promote the stirring of the secondary air and increasing the discharged CO concentration Waste incineration method in a waste incinerator.   The grate-type waste incinerator according to claim 7, wherein the secondary air supply and the secondary combustion chamber recirculation exhaust gas supply are performed from supply ports arranged alternately in the circumferential direction of the inner wall of the secondary combustion chamber. Waste incineration method. A ratio Q1A of the amount of oxygen per unit time supplied by primary air to a theoretical amount of oxygen per unit time required for combustion of waste, and a ratio Q1B of the amount of oxygen per unit time supplied by high-temperature gas; Ratio Q1C of oxygen amount per unit time supplied by combustion chamber recirculation exhaust gas, Ratio Q2 of oxygen amount per unit time supplied by secondary air, and unit supplied by secondary combustion chamber recirculation exhaust gas The waste in the grate-type waste incinerator according to claim 7 or 8, wherein the ratio Q3 of the amount of oxygen per hour is set so as to satisfy the following expressions (1) and (2): Incineration method.
Q1A: Q1B: Q1C: Q2: Q3
= 0.93 to 1.10: 0.14 to 0.16: 0.09 to 0.11: 0.01 to 0.05: 0.01 to 0.05 (1)
1.2 ≦ Q1A + Q1B + Q1C + Q2 + Q3 ≦ 1.4 (2)

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