JP2015187517A - Stoker-type waste incinerator and waste incineration method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a stoker-type waste incinerator and a waste incineration method capable of reducing the height of a waste incineration plant, reducing the height of a plant building, and realizing compactification by suppressing a generation quantity of harmful matters such as CO and NOx and dispensing with a secondary combustion chamber.SOLUTION: A stoker-type waste incinerator comprises: high-temperature-gas blow-in means that includes high-temperature-gas blow-in ports 13 provided in a ceiling of a combustion chamber at a plurality of positions, respectively in an incinerator length direction that is a moving direction of waste on stokers 5, and high-temperature-gas supply means 24 supplying a high-temperature gas to the high-temperature-gas blow-in ports 13; gas-component-concentration measuring means 21 measuring a gas component concentration of at least one of oxygen, NOx, and CO in exhaust gas discharged from the incinerator; and high-temperature-gas blow-in control means 22 controlling a flow volume of the blown-in high-temperature gas so that the gas component concentration falls within a predetermined range based on a measurement value measured by the gas-component-concentration measuring means 21, the high-temperature-gas blow-in control means 22 enabling the combustion of a combustible gas generated from the waste to be terminated in the combustion chamber.

Description

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

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

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

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

  Thus, in the grate-type waste incinerator, the waste is burned by the primary combustion air blown from below the three-stage grate in the combustion chamber. Furthermore, unburned combustible gas contained in the combustion gas from the combustion chamber (referred to as unburned gas) receives and burns secondary combustion air in the secondary combustion chamber that is part of the waste heat boiler. (Called secondary combustion). 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 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, the high-temperature gas blown from the ceiling of the incinerator is increased in pyrolysis gas (combustible gas) and combustion gas generated by pyrolysis or combustion of waste. The counter flow field is effectively formed by colliding with the flow, and the stagnation region or the vertical circulation region is generated over a wide area. As a result, the flow of the combustible gas becomes gentle in the stagnation region or the circulation region, and stable combustion is performed. The flame is fixed in a flat shape, and an extremely stable combustion state is maintained.

  The waste incinerator of Patent Document 1 includes secondary combustion air blowing means for blowing secondary combustion air into the secondary combustion chamber, and the combustible gas contained in the gas discharged from the combustion chamber. Secondary combustion of unburned gas (unburned gas). In this way, combustion is stabilized by blowing high-temperature gas into the combustion chamber, and further, unburned gas is secondary-combusted in the secondary combustion chamber, so that oxygen, NOx, CO in exhaust gas discharged from the incinerator The concentration of NO is controlled within an appropriate range so that emission of harmful substances such as CO and NOx is less than the regulation value.

  In the waste incinerator, in order to decompose dioxins generated by combustion of waste and contained in the exhaust gas, the exhaust gas is heated at a temperature of 850 ° C. or more downstream from the final position where the combustion oxidant is supplied. It is required to secure a high-temperature holding region that retains for 2 seconds or more. In order to satisfy this requirement, since the position where the secondary combustion air is supplied is the final position, the height of the secondary combustion chamber is set so that the exhaust gas has a height so as to ensure a high temperature holding region. It is necessary to be high enough to allow a residence time of 2 seconds or more at a temperature of 850 ° C. or higher, and is usually designed as such. Therefore, the waste heat boiler including the secondary combustion chamber is often the highest in the waste incineration facility.

  However, in a waste incinerator in which high temperature gas is blown from the furnace ceiling as described in Patent Document 1 and secondary combustion air is blown into the secondary combustion chamber, the above-described requirement for securing the high temperature holding region will be satisfied. Then, the height of the waste incineration equipment is lowered, the height of the facility building that accommodates the waste incineration equipment is lowered to make it compact, and it is not possible to meet the demand for realizing a reduction in construction costs.

  In view of such circumstances, the present invention can stably perform the combustion of waste in a waste incinerator that blows high-temperature gas from the furnace ceiling, and can suppress the generation amount of harmful substances such as CO and NOx. A grate-type waste incinerator that can perform air-ratio combustion operations without problems, and can reduce the cost of construction by reducing the height of the waste incineration facility and reducing the height of the facility building. And providing a waste incineration method.

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

<Grate-type waste incinerator>
A grate-type waste incinerator comprising a grate and a combustion chamber for burning waste on the grate, a waste heat boiler connected to the combustion chamber and recovering heat from the combustion exhaust gas, and primary combustion air In a grate-type waste incinerator having primary air blowing means for blowing a gas from below the grate into the combustion chamber and high-temperature gas blowing means for blowing high-temperature gas downward from the ceiling of the combustion chamber. The blowing means includes a hot gas inlet provided on the ceiling of the combustion chamber at a plurality of positions in the furnace length direction, which is a moving direction of waste on the grate, and a hot gas supply for supplying hot gas to the hot gas inlet Gas component concentration measuring means for measuring at least one gas component concentration of oxygen, NOx, and CO of exhaust gas discharged from the incinerator, and the gas component concentration based on the measurement value measured by the gas component concentration measuring means But High temperature gas injection control means for controlling the flow rate of hot gas injection so as to be in a constant value range, and the high temperature gas injection control means enables combustion of combustible gas generated from waste to be terminated in the combustion chamber. A grate-type waste incinerator characterized by having

  In the present invention, the waste heat boiler preferably has a height that allows the exhaust gas to stay at a temperature of 850 ° C. or more for 2 seconds or more.

<Waste incineration method>
A grate-type waste incinerator comprising a grate and a combustion chamber for burning waste on the grate, a waste heat boiler connected to the combustion chamber and recovering heat from the combustion exhaust gas, and primary combustion air Waste incineration by a grate-type waste incinerator having primary air blowing means for blowing a gas from below the grate into the combustion chamber and high-temperature gas blowing means for blowing high-temperature gas downward from the ceiling of the combustion chamber In the method, high-temperature gas is blown from a high-temperature gas blow-in port provided on the ceiling of the combustion chamber at a plurality of positions in the furnace length direction, which is the moving direction of waste on the grate, and oxygen and NOx of exhaust gas discharged from the incinerator Combustion of combustible gas generated from waste by measuring the concentration of at least one gas component of CO and controlling the flow rate of high-temperature gas so that the gas component concentration falls within a predetermined range based on the measured value The combustion chamber Waste incineration process according to the grate type waste incinerator, characterized in that to end.

  In the present invention, the waste heat boiler preferably has a height that allows the exhaust gas to stay at a temperature of 850 ° C. or more for 2 seconds or more.

<High-temperature gas injection control>
In Patent Document 1 as a prior art, by supplying secondary combustion air to a secondary combustion chamber, secondary combustion of unburned combustible gas (unburned gas) flowing in from the combustion chamber is performed, and an incinerator is produced. The concentration of at least one gas (hereinafter referred to as “gas component concentration”) out of the oxygen, NOx, and CO of the exhaust gas discharged from the exhaust gas falls within an appropriate range as a regulation value. If the unburned gas is not burned sufficiently, in other words, if the unburned gas remains, the exhaust gas whose gas component concentration exceeds the regulation value is discharged and becomes a problem.

  According to the present invention, if the combustible gas generated in the combustion chamber is almost completely burned in the combustion chamber so that the unburned gas does not remain, the concentration of the gas component falls within the regulation value range, and the secondary combustion This is based on the idea that a secondary combustion chamber for supplying air and performing secondary combustion of unburned gas can be made unnecessary. In the present invention, the concentration of at least one gas (gas component concentration) of oxygen, NOx, and CO in the exhaust gas discharged from the incinerator is measured, and the combustion chamber is set so that the measured gas component concentration falls within the range of the regulation value. By controlling the flow rate of the high-temperature gas blown into the combustion chamber, the combustible gas is almost completely burned in the combustion chamber, and the outflow of unburned gas from the combustion chamber to the downstream side is eliminated.

  In the present invention, the amount of hot gas blown in is controlled so that the gas component concentration of the exhaust gas falls within the regulation value range, so that the generation of harmful substances such as NOx and CO is suppressed. Therefore, it is not necessary to provide a secondary combustion chamber in the waste heat boiler connected to the outlet side of the combustion chamber to burn the unburned gas and keep the gas component concentration of the exhaust gas within the regulation value range. Is a height that secures a sufficient area for heat recovery and a high temperature holding area where exhaust gas stays at a predetermined temperature (850 ° C.) or higher for a predetermined time (2 seconds) or longer to decompose harmful substances such as dioxins. As long as there is no need for a secondary combustion chamber as compared with conventional incineration facilities, the furnace can be made compact in the height direction.

  In the present invention, the control of the high temperature gas blown into the combustion chamber by the measured values of the gas component concentrations of oxygen, NOx, CO, etc. in the exhaust gas is performed when the measured gas component concentrations are increased or decreased from a predetermined value range. The high-temperature gas blowing amount (flow rate) is adjusted as follows.

Exhaust gas component concentration state Blowing hot gas flow rate adjustment・ Oxygen concentration Increase from the specified range → Decrease the hot gas flow rate slightly Decrease from the specified range → Increase the hot gas flow rate (shortage of combustion oxygen)
・ CO concentration Increase from the specified range → Increase the hot gas flow rate (combustion is inactive due to lack of oxygen)
Decrease from the specified range → Maintain current status ・ NOx concentration Increase from the specified range → Decrease the hot gas flow rate (Excessive combustion due to excessive oxygen)
Decrease from specified range → Maintain current status

  As described above, in the present invention, high-temperature gas is blown into the combustion chamber, and the oxygen, NOx, and CO gas component concentrations in the exhaust gas discharged from the incinerator are measured and controlled to an appropriate range for disposal. Since the high-temperature gas injection flow rate is adjusted so that combustible gas generated from the object can be completely burned in the combustion chamber, the unburned portion of the combustible gas (unburned gas) is discharged from the combustion chamber. No longer flows into the waste heat boiler. Thus, in the present invention, the combustible gas can be completely burned in the combustion chamber by the high-temperature gas injection control means, and the oxygen, NOx, and CO gas component concentrations in the exhaust gas can be controlled within an appropriate range. As a result, it is not necessary to provide a secondary combustion chamber in the waste heat boiler. The waste heat boiler secures a sufficient area for heat recovery, and the exhaust gas is heated at a predetermined temperature (850 ° C.) in order to decompose harmful substances such as dioxins. As long as the high-temperature holding region for retaining the liquid for a predetermined time (2 seconds) or more is sufficient as described above, the furnace can be made compact in the height direction as the secondary combustion chamber becomes unnecessary as compared with the conventional incineration equipment. .

  As a result, the height of the waste incineration equipment is lowered and the height of the facility building is lowered to make the equipment compact, and devices such as a secondary combustion air supply pipe and a blower are not required, and construction costs can be reduced.

  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. The amount of harmful substances such as CO and NOx in the exhaust gas generated can be suppressed. In addition, because thermal decomposition and combustion of waste can be promoted, the volume of the combustion chamber can be reduced relative to the amount of waste incineration, the furnace height of the incinerator can be reduced, and waste incineration can be achieved. Equipment and operating costs can be reduced by making the furnace 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.

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

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

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

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

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

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

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

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

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

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

  In the grate-type incinerator having such a basic configuration, the waste incinerator 1 according to the present embodiment includes a primary air blowing means for blowing the primary air for combustion into the combustion chamber from below the grate, and a combustion The ceiling of the chamber is provided with hot gas blowing ports at a plurality of positions in the furnace length direction, and hot gas blowing means for blowing the hot gas downward from the hot gas blowing port.

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

<High-temperature gas blowing means>
In the present embodiment, the waste incinerator 1 includes high temperature gas blowing means for blowing high temperature gas downward from the ceiling 2 </ b> A of the combustion chamber 2. The hot gas blowing means is provided with hot gas blowing ports 13 (13a, 13b, 13c, 13d, 13e) on the ceiling 2A 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. Moreover, the hot gas inlet 13 is provided in the ceiling 2A from the dry grate 5a to the front part of the rear combustion grate 5c in the furnace length direction. The high-temperature gas blowing means further includes a high-temperature gas supply device 24 that supplies a high-temperature gas to the high-temperature gas blow-in port 13, a pipe that guides the high-temperature gas to the high-temperature gas blow-in port 13, and a regulating valve 14 as a flow rate adjusting mechanism. have.

  The direction of the hot gas blowing port 13 is determined so that the hot gas is blown downward. Thus, the high temperature gas is provided from the high temperature gas inlet 13 so as to blow from the dry region A1 toward the front region of the post combustion region A4. Moreover, the hot gas from the hot gas blowing port 13e located on the most downstream side may be blown toward the region immediately after the fuel cut point.

  The hot gas inlet 13 is provided at a plurality of locations in the furnace width direction (a direction perpendicular to the paper surface in FIG. 1 and a left-right direction in FIG. 2).

  The high-temperature gas inlet 13 is a collective adjustment valve 14 provided in one pipe, and individual pipes branched for the individual high-temperature gas inlets 13a, 13b, 13c, 13d, and 13e. High temperature gas is blown into the combustion chamber 2 through the regulating valves 14a, 14b, 14c, 14d, and 14e. Therefore, the amount of the hot gas to be blown can be controlled collectively by adjusting the collective adjustment valve 14 with respect to the five hot gas blowing ports 13a, 13b, 13c, 13d, and 13e. The adjusting valves 14a, 14b, 14c, 14d, and 14e can be separately controlled by adjusting them independently, and can be adjusted by both.

  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 12 to 21 dry volume%.

<High-temperature gas injection control means>
In the present embodiment, a gas component concentration meter 21 as a gas component concentration measuring means for measuring the gas component concentration of the exhaust gas and a signal from the gas component concentration meter 21 are received at the outlet of the waste heat boiler 4 of the incinerator 1. And the high-temperature gas blowing control device 22 for controlling the adjusting valve 14 or 14a, 14b, 14c, 14d, 14e of the hot gas blowing means described above.

  In this embodiment, the gas component concentration meter 21 has an oxygen concentration meter 21a, a NOx concentration meter 21b, and a CO concentration meter 21c. Upon receiving a signal from the gas component concentration meter (21a, 21b, 21c), the high-temperature gas injection control device 22 receives the collective adjustment valve 14, the individual adjustment valves 14a, 14b, 14c, 14d, 14e, and the collective adjustment valve 14; Control which adjusts the opening degree of at least one of the individual regulating valves 14a, 14b, 14c, 14d and 14e is performed.

  In the present invention having such a high-temperature gas injection control device 22, the gas component concentration meter 21 (21a, 21b, 21c) measures the oxygen concentration in the exhaust gas, the CO and NOx gas component concentrations, and these gas component concentrations. When one or more of them are not within the predetermined value range, the hot gas blowing control device 22 adjusts the hot gas blowing amount so that the gas component concentration falls within the predetermined value range. At least one opening degree of the regulating valve 14 and the individual regulating valves 14a to 14e is controlled.

  In the present invention, the configuration of the above-described primary air for combustion, pipes for supplying high-temperature gas and the like is not limited to the illustrated one, and can be appropriately selected depending on the scale, shape, application, etc. of the incinerator. In the present invention, the combustible gas in the combustion chamber is burned by controlling the blowing of the high-temperature gas without supplying the secondary combustion gas, so the pipe for supplying the secondary air No road is necessary.

  Next, an outline of the incineration situation in the apparatus of the present embodiment configured as described above, and an operation by high-temperature gas blowing control 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 for combustion via the wind boxes 7a, 7b, 7c, 7d, whereby the waste in 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 exhaust gas is heat 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.

<High-temperature gas injection control>
The gas component concentration meter 21 (21a, 21b, 21c) provided at the outlet of the waste heat boiler 4 of the incinerator 1 measures the oxygen concentration in the exhaust gas, the gas component concentration of CO, and NOx. When one or more of them are not within the predetermined value range, the batch adjustment valve 14 is used to adjust the hot gas blowing amount by the hot gas blowing control device 22 so that the concentration falls within the predetermined value range. The at least one opening degree of the individual regulating valves 14a to 14e is controlled. When the state of each gas component concentration measured by the gas component concentration meters 21a, 21b, and 21c has a tendency to increase or decrease from a predetermined value range, how is the high-temperature gas flow to be blown in response to the tendency? Whether the adjustment is adjusted or not is as follows.

Gas component concentration status Blowing / adjustment adjustment of hot gas flow rate・ Oxygen concentration Increase from the specified range → Decrease the hot gas flow rate slightly Decrease from the specified range → Increase the hot gas flow rate (shortage of combustion oxygen)
・ CO concentration Increase from the specified range → Increase the hot gas flow rate (combustion is inactive due to lack of oxygen)
Decrease from the specified range → Maintain current status ・ NOx concentration Increase from the specified range → Decrease the hot gas flow rate (Excessive combustion due to excessive oxygen)
Decrease from specified range → Maintain current status

  In this way, by controlling the amount of hot gas injected into the combustion chamber with the hot gas injection control device, combustion of combustible gas generated from waste can be terminated in the combustion chamber, and unburned gas flows out of the combustion chamber. As a result, the oxygen, NOx, and CO gas component concentrations in the exhaust gas can be controlled within an appropriate range, so that it is not necessary to provide a secondary combustion chamber in the waste heat boiler. In order to secure a sufficient area for heat recovery of the gas and to secure a high temperature holding area in which the exhaust gas stays at a predetermined temperature (850 ° C.) or more for a predetermined time (2 seconds) or more in order to decompose the harmful substances of dioxins Compared to conventional incineration equipment, the need for a secondary combustion chamber is eliminated, so the furnace can be made compact in the height direction, the facility building height is reduced, and the construction cost is reduced. Kill.

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

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

<Combustion stabilization by hot gas injection>
As seen in FIG. 1, hot gas is blown from the hot gas inlet 13 (13a, 13b, 13c, 13d, 13e) from the dry region A1 toward the front region of the post-combustion region A4 and discarded. It is blown downward toward the material layer W.

  The hot gas is blown downward by blowing the hot gas downward into the region from the drying region A1 in the combustion chamber 2 to the front portion of the post-combustion region A4 and directly above the waste layer W from the hot gas blowing port 13. The high-temperature gas opposes 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. A region or a circulation region that circulates in the vertical direction is generated. Since the gas flow speed is slow in these regions, a flame in which the combustible gas burns is fixed, that is, a planar combustion region (planar flame) E is immediately above the waste layer W (FIG. 2). See), combustible gas is burned stably.

  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.

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

  Next, the preparation of the high-temperature gas and the inlet 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 12 to 21 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 drying region A1 to the main combustion region A3 becomes excessively low-oxygen atmosphere due to the blowing of the high-temperature gas, and the amount of combustible gas generated by the thermal decomposition of the waste is Excessive amount of unburned gas (unburned gas) in the combustible gas that flows into the secondary combustion area without being burned in the combustion chamber is unsuitable, and is unsuitable. If the oxygen concentration is higher than the upper limit, flammable This is unsuitable because high temperature field is generated due to excessive combustion of the gas 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 above problem occurs when the oxygen concentration is 12 to 21 dry volume%. Is more preferable because it can be surely 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 provided at a position directly above the grate in the range from the dry grate 5a to the upstream side (front part) in the moving direction of the rear combustion grate 5c on the ceiling of the combustion chamber 2.

  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 To control, at least one of the arrangement position, the number of arrangements, the arrangement interval, the blowing direction, and the shape of the blowing port of the hot gas blowing port 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.

  By blowing the hot gas downward from the blow-off port provided on the ceiling of the waste incinerator combustion chamber, the downward flow of the hot gas and the upward flow of combustible gas and combustion gas generated from the waste layer It is possible to form a stagnation region where the gas flow stagnates just above the waste layer or circulates in the vertical direction over the waste layer over a wide range in the combustion chamber width direction and furnace length direction. Regardless of the size of the incinerator, that is, the width and height of the combustion chamber, waste and combustible gas generated even in low air ratio combustion with an air ratio of 1.5 or less Can be burned stably. 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.

  As described above, according to the present invention, a stable stagnation region or a circulation region can be formed in the vicinity of the waste layer in the combustion chamber by blowing high-temperature gas. Regardless of the size of the incinerator, even when low air ratio combustion with an air ratio of 1.5 or less is performed, the stability of combustion is maintained over the entire width direction and length direction in the combustion chamber, Provided are a waste incinerator and a waste incineration method capable of reducing the generation amount of harmful gases such as CO and NOx. Furthermore, since the combustion can be performed at a lower air ratio than before, the total amount of exhaust gas discharged from the incinerator can be further greatly reduced, and a waste incinerator and a waste incineration method that can improve the recovery efficiency of waste heat are provided. The

  In addition, the thermal decomposition of waste can be promoted by radiation of standing flat flames, etc., so the amount of waste supplied to the grate (grate load) and the amount of waste supplied to the combustion chamber (furnace Load) can be increased. For this reason, the volume of the combustion chamber can be reduced with respect to the amount of waste incineration, the furnace height of the incinerator can be reduced, and the waste incineration equipment can be made compact, thereby reducing the equipment cost and operation cost. be able to.

  Further, in the present invention, the high temperature gas injection control means can combust the combustible gas completely in the combustion chamber, and the gas component concentrations of exhaust gas oxygen, NOx, and CO can be controlled within an appropriate range. It is not necessary to provide a secondary combustion chamber in the waste heat boiler. The waste heat boiler secures a sufficient area for heat recovery and exhaust gas at a predetermined temperature (850 ° C.) or higher in order to decompose harmful substances such as dioxins. The height of the high-temperature holding region for retaining for a predetermined time (2 seconds) or more is sufficient, and the furnace can be made more compact in the height direction because the secondary combustion chamber is not required as compared with conventional incineration equipment. For this reason, the waste incineration equipment is lowered in height and the facility building height is lowered to make it compact, and no equipment such as a secondary combustion air supply pipe or a blower is required, and construction costs can be reduced.

DESCRIPTION OF SYMBOLS 1 Waste incinerator 2 Combustion chamber 4 (Waste heat) Boiler 5 Grate 5a Dry grate 5b Combustion grate 5c Post combustion grate 13 (13a, 13b, 13c, 13d, 13e) Hot gas inlet 21 (21a, 21b, 21c) Gas component concentration measuring means (gas component concentration meter)
22 High-temperature gas injection control device 24 High-temperature gas supply device (means)

Claims (4)

A grate-type waste incinerator comprising a grate and a combustion chamber for burning waste on the grate, a waste heat boiler connected to the combustion chamber and recovering heat from the combustion exhaust gas, and primary combustion air In a grate-type waste incinerator having primary air blowing means for blowing a gas from below the grate into the combustion chamber, and hot gas blowing means for blowing a hot gas downward from the ceiling of the combustion chamber,
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, which is a moving direction of waste on the grate, and a high temperature gas for supplying the hot gas to the hot gas blowing port. Hot gas blowing means comprising gas supply means;
A gas component concentration measuring means for measuring at least one gas component concentration of oxygen, NOx, and CO of exhaust gas discharged from the incinerator;
High temperature gas blowing control means for controlling the flow rate of hot gas so that the gas component concentration falls within a predetermined value range based on the measurement value measured by the gas component concentration measuring means,
A grate-type waste incinerator characterized in that combustion of combustible gas generated from waste can be terminated in a combustion chamber by means of high-temperature gas blowing control means.   2. The grate-type waste incinerator according to claim 1, wherein the height of the waste heat boiler is such that the exhaust gas can stay at a temperature of 850 ° C. or more for 2 seconds or more. A grate-type waste incinerator comprising a grate and a combustion chamber for burning waste on the grate, a waste heat boiler connected to the combustion chamber and recovering heat from the combustion exhaust gas, and primary combustion air Waste incineration by a grate-type waste incinerator having primary air blowing means for blowing a gas from below the grate into the combustion chamber and high-temperature gas blowing means for blowing high-temperature gas downward from the ceiling of the combustion chamber In the method
High temperature gas is blown from a high temperature gas injection port provided on the ceiling of the combustion chamber at a plurality of positions in the furnace length direction, which is the moving direction of waste on the grate,
Measure the concentration of at least one of the oxygen, NOx, and CO in the exhaust gas discharged from the incinerator, and control the hot gas flow rate so that the gas component concentration falls within the specified value range based on the measured value. ,
A waste incineration method using a grate-type waste incinerator, wherein combustion of combustible gas generated from waste is terminated in a combustion chamber.   The waste heat boiler according to claim 3, wherein the height of the waste heat boiler is such that the exhaust gas can stay at a temperature of 850 ° C or higher for 2 seconds or longer.

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