JP2013213652A - Waste incinerator and waste incineration method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a grate-type waste incinerator capable of reducing the amount of hazardous substance generation, and performing the incineration of waste with ease using a low air ratio, and to provide a waste incineration method.SOLUTION: A grate-type waste incinerator includes: a combustion chamber which has a height of ≤3 m, includes a grate and combusts waste on the grate: a primary air blowing means for blowing primary combustion air from below the grate into the combustion chamber; a hot gas blowing means for blowing hot gas downward from a ceiling of the combustion chamber to an area between a combustion starting area and a main combustion area in the combustion chamber; and a gas blowing means for secondary combustion which blows gas for secondary combustion into a secondary combustion area. The hot gas blowing means has a plurality of hot gas blowing ports. By blowing hot gas opposing the upward flow of combustible gas and combustion gas generated from the waste, a stagnation area or a circulation area is formed immediately above a waste layer to provide a stable planar combustion area. By setting the arrangement and the position or the like of the hot gas blowing ports, the state of the planar combustion area is set to be a desired one.

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 a combustion start region is formed in the downstream space. The waste that ignites in the combustion start area and starts combustion is sent to the combustion grate, and the waste is pyrolyzed to generate flammable gas. The primary air for combustion sent from the bottom of the combustion grate The combustible gas and the solid content burn, and a main combustion region is formed in the space immediately above the combustion grate. Further, unburned components such as fixed carbon are completely burned on the post-combustion grate, and a post-combustion region is formed in a space immediately above the post-combustion grate. Thereafter, the ash remaining after combustion is discharged to the outside from the ash drop opening.

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

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

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

  Thus, although the advantage of performing low air ratio combustion is great, on the other hand, the problem that combustion becomes unstable in low air ratio combustion with an air ratio of 1.5 or less remains. 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 or ash melts and adheres to the furnace wall due to local high temperatures, and clinker is generated due to local high temperatures. There is a problem that the life of the battery is shortened.

  Under such circumstances, a waste incinerator capable of stably burning at a low air ratio of 1.5 or less has been studied and disclosed in Patent Document 1 (paragraph 0063). ). In this patent document, high temperature exhaust gas is led out from the outlet side of the secondary combustion region of the waste incinerator, dust is removed, and then mixed with air to be blown into the combustion chamber as high temperature gas, thereby obtaining the following effects.

  That is, it promotes thermal decomposition of waste by sensible heat and radiation of high temperature gas, promotes combustion of combustible gas generated by thermal decomposition of waste by blowing high temperature gas containing oxygen, and high temperature gas Is blown into the combustion chamber from the nozzle provided on the side wall of the combustion chamber (paragraph 0040), and the flow of the high-temperature gas is opposed to the combustible gas generated from the waste and the upward flow of the combustion gas, and 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. By blowing into the combustion chamber, the waste can be stably burned under the low air ratio combustion operation.

JP 2004-84981 A

  In combustion of waste in a waste incinerator, stable combustion of combustible gas generated by thermal decomposition of waste suppresses the generation of harmful substances such as CO and NOx generated by combustion It greatly contributes to that. In the waste incinerator described in Patent Document 1, high-temperature gas is blown into the combustion chamber from a nozzle provided on the side wall of the combustion chamber. Depending on the state of the waste supplied to the waste incinerator, the high-temperature gas blown from the side wall exerts the above-mentioned effect evenly over the entire combustion chamber from the vicinity of the side wall to the central part, and has a low air ratio. It may not always be possible to stably burn the combustible gas generated from the waste layer under the combustion operation.

  In addition, in the case of an incinerator with a large amount of waste incineration and a wide combustion chamber width, the high temperature gas blown from the side wall does not reach the vicinity of the center of the combustion chamber, and the combustion chamber from the vicinity of the side wall to the center portion. The combustion promotion effect and combustion stabilization effect described above cannot be exerted without bias. Therefore, there is a problem that the low air ratio combustion operation cannot be performed sufficiently.

  In view of such circumstances, the present invention is not limited to the size of the combustion chamber of the waste incinerator, even when a low air ratio combustion operation with an air ratio of 1.5 or less is performed, from the vicinity of the combustion chamber side wall to the central portion. A fire that can stably burn waste throughout the entire combustion chamber, suppress the generation of harmful substances such as CO and NOx, and perform low-air ratio combustion operations without any problems. It is an object to provide a lattice-type waste incinerator and a waste incineration method.

In order to solve the above problems, the first aspect of the present invention is:
A grate-type waste incinerator,
A combustion chamber having a grate and burning waste on the grate, the height of which is 3 m or less;
Primary air blowing means for blowing primary air for combustion into the combustion chamber from under the grate,
Hot gas blowing means for blowing hot gas downward from the ceiling of the combustion chamber toward an arbitrary region between the combustion start region and the main combustion region in the combustion chamber;
A secondary combustion gas blowing means for blowing secondary combustion gas into the secondary combustion region;
The high-temperature gas blowing means includes a plurality of high-temperature gas blowing ports, and blows the high-temperature gas against the upward flow of the combustible gas and the combustion gas generated from the waste, and the stagnation region directly above the waste layer or Adjusting the blowing flow rate or flow rate of the hot gas according to the state in the combustion chamber so that the planar combustion region is formed by forming a circulation region and the state of the planar combustion region is set to a desired state. A grate-type waste incinerator is provided.

The second aspect of the present invention is:
A grate-type waste incinerator,
A combustion chamber comprising a grate and burning waste on the grate;
Primary air blowing means for blowing primary air for combustion into the combustion chamber from under the grate,
High-temperature gas blowing means for blowing the hot gas downward from a position 1 to 3 m above the grate in the combustion chamber toward an arbitrary region between the combustion start region and the main combustion region in the combustion chamber; ,
A secondary combustion gas blowing means for blowing secondary combustion gas into the secondary combustion region;
The high-temperature gas blowing means includes a plurality of high-temperature gas blowing ports, and blows the high-temperature gas against the upward flow of the combustible gas and the combustion gas generated from the waste, and the stagnation region directly above the waste layer or Adjusting the blowing flow rate or flow rate of the hot gas according to the state in the combustion chamber so that the planar combustion region is formed by forming a circulation region and the state of the planar combustion region is set to a desired state. A grate-type waste incinerator is provided.

  In the above-described grate-type waste incinerator according to the first and second aspects of the present invention, the high-temperature gas blowing means includes a plurality of high-temperature gas blowing ports in the furnace width direction, and waste on the grate Depending on the state, the blowing flow rate or blowing flow rate of each hot gas blowing port can be adjusted.

  Further, in the grate-type waste incinerator, means for measuring the grate temperature or the gas temperature in the combustion chamber to grasp the state of the combustion chamber or the state of the waste on the grate, and the grasped state of the combustion chamber Or the adjustment means which adjusts the blowing flow rate or blowing flow rate of a hot gas blowing port according to the state of the waste on a grate can be provided.

  Moreover, the said high temperature gas blowing means can inject the high temperature gas whose temperature is the range of 100-400 degreeC, and whose oxygen concentration is the range of 5-30 volume%.

  Further, the hot gas blowing means can blow the hot gas at a flow rate 5 to 20 times the superficial velocity obtained by dividing the flow rate of the combustion chamber gas by the combustion chamber cross-sectional area.

  Furthermore, the high-temperature gas blowing means includes at least one of a return exhaust gas that returns a part of the exhaust gas discharged from the incinerator, a mixed gas of the return exhaust gas and air, air, a gas containing oxygen, and oxygen-enriched air. A hot gas supply source that supplies one as the hot gas can be provided.

  Also, a boiler having a secondary combustion region in the vicinity of the inlet can be bent and connected to the upper side of the combustion chamber.

The third aspect of the present invention is:
A waste incineration method using a grate-type waste incinerator,
Using a grate-type waste incinerator where the height of the combustion chamber for burning waste is 3 m or less,
Blowing primary air for combustion into the combustion chamber from below the grate,
Hot gas is blown downward from the combustion chamber ceiling toward any region between the combustion start region and the main combustion region in the combustion chamber,
Blowing secondary combustion gas into the secondary combustion area,
High-temperature gas is injected from multiple high-temperature gas injection ports in opposition to the upward flow of combustible gas and combustion gas generated from waste, forming a stagnation region or circulation region directly above the waste layer, and planar combustion A waste incineration method characterized by adjusting a flow rate or flow rate of hot gas in accordance with a state in a combustion chamber so that a region is fixed and a planar combustion region is in a desired state provide.

The fourth aspect of the present invention is:
Using a grate-type waste incinerator with a combustion chamber for burning waste,
Blowing primary air for combustion into the combustion chamber from below the grate,
Hot gas is blown downward from a position 1 to 3 m above the grate in the combustion chamber upward to any region between the combustion start region and the main combustion region in the combustion chamber,
Blowing secondary combustion gas into the secondary combustion area,
High-temperature gas is injected from multiple high-temperature gas injection ports in opposition to the upward flow of combustible gas and combustion gas generated from waste, forming a stagnation region or circulation region directly above the waste layer, and planar combustion A waste incineration method characterized by adjusting a flow rate or flow rate of hot gas in accordance with a state in a combustion chamber so that a region is fixed and a planar combustion region is in a desired state provide.

  In the waste incineration method according to the third and fourth aspects of the present invention described above, depending on the state of the waste on the grate from a plurality of hot gas inlets provided with hot gas in the furnace width direction, It can blow in by adjusting the blowing flow rate or blowing flow rate of each hot gas blowing port.

  In the waste incineration method, the grate temperature or the gas temperature in the combustion chamber is measured to grasp the state in the combustion chamber or the state of the waste on the grate, and the grasped state in the combustion chamber or on the grate Depending on the state of the waste, the blowing flow rate or blowing flow rate of the hot gas blowing port can be adjusted and blown.

  In this case, the high-temperature gas can have a temperature in the range of 100 to 400 ° C. and an oxygen concentration in the range of 5 to 30% by volume.

  Further, the high-temperature gas can be injected at a flow rate 5 to 20 times the superficial velocity obtained by dividing the flow rate of the combustion chamber gas by the cross-sectional area of the combustion chamber.

  Furthermore, the high-temperature gas may be at least one of a return exhaust gas that returns a part of the exhaust gas discharged from the incinerator, a mixed gas of the return exhaust gas and air, air, a gas containing oxygen, and oxygen-enriched air. it can.

  Note that the ratio Q1 of the oxygen amount per unit time supplied by the primary air for combustion to the theoretical oxygen amount per unit time required for burning the waste and the ratio of the oxygen amount per unit time supplied by the high-temperature gas Q2 and the ratio Q3 of the amount of oxygen per unit time supplied by the secondary combustion gas can satisfy the following expressions (1) and (2).

Formula (1)
Q1: Q2: Q3 = 0.75-1.10: 0.05-0.40: 0.10-0.40
Formula (2)
1.0 ≦ Q1 + Q2 + Q3 ≦ 1.5
Further, the ratio Q1 of the oxygen amount per unit time supplied by the primary air for combustion to the theoretical oxygen amount per unit time necessary for burning the waste, and the ratio of the oxygen amount per unit time supplied by the high temperature gas. Q2 and the ratio Q3 of the amount of oxygen per unit time supplied by the secondary combustion gas can satisfy the following expressions (3) and (4).

Formula (3)
Q1: Q2: Q3 = 0.80-1.00: 0.10-0.30: 0.10-0.30
Formula (4)
1.1 ≦ Q1 + Q2 + Q3 ≦ 1.3

  According to the present invention, the hot gas is blown downward from the blow port provided in the ceiling of the waste incinerator combustion chamber, and the hot gas blowing flow rate or flow rate is adjusted according to the state in the combustion chamber, A downward stagnation area or a circulation area where the gas flow circulates in the up and down direction directly above the waste layer by facing the downward flow of the hot gas and the upward flow of the combustible gas generated from the waste layer and the combustion gas. Since it can be formed over a wide range in the width direction and length direction of the combustion chamber, a planar combustion region can be fixed, and the air ratio is 1.5 or less regardless of the size of the incinerator. Even in the low air ratio combustion, waste and generated combustible gas can be stably burned. And since combustion is stabilized, the generation amount of harmful substances such as CO and NOx in the exhaust gas discharged from the waste incinerator can be suppressed.

  Furthermore, the thermal decomposition of waste can be promoted by radiation of a standing flat flame, etc., so the amount of waste supplied to the grate (grate load) and the amount of waste 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.

It is a lineblock diagram showing an outline of a waste incinerator concerning one embodiment of the present invention. It is a figure which shows arrangement | positioning of the hot gas blowing inlet in the waste incinerator shown in FIG. 1, and the air blowing inlet for secondary combustion. It is sectional drawing of the combustion chamber width direction explaining the combustion state in an incinerator. It is sectional drawing of the combustion chamber width direction explaining the combustion state in an incinerator.

  Hereinafter, the present invention will be described in detail according to various embodiments of the present invention. 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.

  First, a combustion state in an incinerator will be described with reference to FIG. 3 by comparing a conventional incinerator and an incinerator according to one embodiment of the present invention. 3A shows a combustion state in a conventional incinerator (a waste incinerator described in Patent Document 1), and FIG. 3B shows an incinerator according to one embodiment of the present invention. It is sectional drawing of the combustion chamber width direction which shows a combustion state.

  As shown in FIG. 3 (a), the conventional combustion furnace 20 is provided with a blowing port 23 in a side wall 21, and burns waste W on the grate 5 with combustion air A from below. . During the combustion of the waste W, the hot gas B is blown obliquely downward from the blow-in port 23 provided in the side wall 21 of the combustion chamber, and rises from the hot gas B and the waste layer W on the grate 5. A combustible gas generated by thermal decomposition and an upward flow of the combustion gas collide with each other to form a stagnation region where the flow is slow immediately above the waste layer W. Therefore, a combustible gas is burned to form a planar combustion region (planar flame) D. In such a conventional incinerator, stable combustion can be obtained even in a low air ratio combustion operation. However, in a combustion furnace having a large combustion chamber width, as shown in FIG. Since the high temperature gas B does not reach the vicinity of the center of the combustion chamber and a stagnation region cannot be formed, a planar combustion region cannot be formed in the center, and the combustible gas is not sufficiently burned, and the furnace width There is a problem of non-uniform combustion in the direction.

  On the other hand, as shown in FIG. 3 (b), the incinerator 1 according to one aspect of the present invention has a plurality of inlets 13 provided in the ceiling 22 in the furnace width direction, and waste W on the grate 5 is disposed. Combustion is performed by combustion air A from below. When the waste W is burned, the hot gas B is blown downward from the blowing port 13 provided in the ceiling 22, and the upward flow of the hot gas B and the combustible gas and the combustion gas rising from the waste W As a counter flow field, a slow stagnation region or a circulation region that circulates in the vertical direction is formed immediately above the waste layer W, and the planar combustion region (planar flame) E is set in the furnace width direction and the furnace length direction. To form uniformly. Thereby, even in a combustion furnace having a large furnace width, uniform and stable combustion is possible.

<Effect of blowing hot gas downward from the ceiling of the combustion chamber>
The effect of blowing hot gas downward from the ceiling of the combustion chamber will be described in detail.

  (1) The thermal decomposition of the waste W is promoted by the sensible heat and radiation of the high temperature gas.

  (2) The combustion of the combustible gas generated by the thermal decomposition of the waste W is promoted by blowing in the high-temperature gas containing oxygen.

  (3) The hot gas is blown downward into the combustion chamber from the inlet 13 provided in the ceiling 22 of the combustion chamber, the downward flow of the high temperature gas, and the upward flow of the combustible gas and the combustion gas generated from the waste W By forming a slow stagnation region or a circulation region where the flow circulates in the vertical direction directly above the waste layer, the flow of combustible gas becomes gentle and is sufficiently mixed with the oxidant component. Stable combustion is performed.

  In the stagnation region or circulation region immediately above the waste layer, the combustible gas is stably burned to form a flat combustion region (planar flame), which is present.

  (4) The thermal decomposition of the waste W is promoted by radiation of the standing flat flame.

By such actions, the waste W can be stably burned even under a low air ratio combustion operation. And since combustion is stabilized, combustible gas is fully burned and generation | occurrence | production of harmful substances, such as CO and NOx in the waste gas discharged | emitted from an incinerator, can be suppressed.

  Further, since the thermal decomposition of the waste W can be promoted by radiation of the standing flat flame E or the like, the amount of waste W supplied to the grate 5 (grate load) and the waste supplied to the combustion chamber The amount of heat of W (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.

Hereinafter, an embodiment of the present invention will be described.
FIG. 1 is a schematic sectional side view showing 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.

<Basic configuration of grate-type incinerator>
In the waste incinerator 1 shown in FIG. 1, the height of the combustion chamber 2 for burning the waste is 1 to 3 m, and the combustion chamber height of a conventional incinerator having a scale of about 100 tons / day of waste incineration is as high as that of the combustion chamber 2. Compared to being about 5 to 6 m, the height is ½ or less. Further, an example of a volume of the incinerator 1 is 90m ^3, equal to or less than about 1/2 of 190 m ³ of conventional incinerators.

  The grate-type waste incinerator facility is made compact by stably performing low air ratio combustion by blowing the high-temperature gas described later downward from the ceiling or the like, with the height of the combustion chamber 2 being 3 m or less. Thus, the equipment cost and operation cost can be greatly reduced.

  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 flow direction of the waste in the combustion chamber 2 so as to put the waste into the combustion chamber. This is a grate-type incinerator that includes a waste inlet 3 and a boiler 4 that is provided above the downstream side (the 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 a dry grate 5a, a combustion grate 5b, and a post-combustion grate 5c from the side closer to the waste inlet 3.

  In the dry grate 5a, waste is mainly dried and ignited. In the combustion grate 5b, waste is thermally decomposed and partially oxidized, and combustible gas and solid content generated by the thermal decomposition are combusted. On the post-combustion grate 5c, the remaining unburned matter in the waste is completely burned. The combustion ash after complete combustion is discharged from the ash drop opening 6.

  Wind boxes 7a, 7b, 7c, and 7d are provided below the dry grate 5a, the combustion grate 5b, and the post-combustion grate 5c, respectively. The combustion primary air A supplied by the blower 8 is supplied to the wind boxes 7a, 7b, 7c, 7d through the combustion primary air supply pipe 9, and combusts through the grate 5a, 5b, 5c. It is supplied into the chamber 2. The primary air A for combustion supplied from below the grate is used for drying and burning 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 the outlet of the combustion chamber 2, and the vicinity of the inlet of the waste heat boiler 4 is a secondary combustion region 10 in which unburned gas in the gas discharged from the combustion chamber 2 is burned. The unburned gas is subjected to secondary combustion in the secondary combustion region 10 which is a part of the waste heat boiler, and the combustion exhaust gas is recovered by the waste heat boiler 4 after the secondary combustion. After the heat is recovered, the combustion exhaust gas discharged from the waste heat boiler is neutralized with acidic gas by slaked lime and adsorbed dioxins by activated carbon, and further sent to a dust removal device (not shown) to produce a neutralization reaction product. , Activated carbon, dust, etc. are recovered. 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.

<Waste incinerator according to this embodiment>
In the grate-type incinerator in which the above apparatus is a basic configuration, the waste incinerator 1 according to the present embodiment is
The height of the combustion chamber 2 for burning waste is 1 to 3 m,
Primary air blowing means for blowing primary air for combustion into the combustion chamber 2 from below the grate 5;
Hot gas blowing means for blowing hot gas downward from the ceiling of the combustion chamber 2 toward an arbitrary region between the combustion start region in the combustion chamber 2 and the main combustion region;
A secondary combustion gas blowing means for blowing secondary combustion gas into the secondary combustion region;
The hot gas blowing means has a plurality of hot gas blowing ports, and blows hot gas in opposition to the upward flow of the combustible gas and combustion gas generated from the waste, and the stagnation region or circulation directly above the waste layer. Forming a region to establish a planar combustion region, and adjusting the flow rate or flow rate of the hot gas in accordance with the state in the combustion chamber so that the state of the planar combustion region becomes a desired state. It is a feature.

  In the present embodiment, the incinerator 1 includes a primary air supply system of primary air that serves as combustion air. In the primary air supply system, the primary air A from the air supply source is branched to the wind boxes 7a, 7b, 7c, and 7d of the dry grate 5a, the combustion grate 5b, and the post-combustion grate 5c through the pipe line 9, respectively. The pipe 9 is provided with a blower 8 and a damper 11 as a flow rate adjusting mechanism.

  The hot gas blowing means includes a hot gas supply source 12 provided outside the combustion chamber 2, a hot gas blowing port 13 for blowing the hot gas B into the combustion chamber 2, and the hot gas B from the hot gas supply source. It has a conduit 14 leading to the high temperature gas inlet and a damper 25 as a flow rate adjusting mechanism.

  The hot gas inlet 13 is provided at an arbitrary position on the ceiling of the combustion chamber 2 directly above the grate within the range from the downstream side of the dry grate 5a in the waste movement direction to the combustion grate 5b. In the example of FIG. 1, in the moving direction of the waste, that is, in the length direction of the combustion chamber 2, it is provided in three rows immediately above the grate downstream of the dry grate 5a and directly above the grate of the combustion grate 5b. It has been.

  The hot gas inlets 13 are provided at a plurality of locations in the width direction of the combustion chamber 2 (the direction perpendicular to the paper surface in FIG. 1). Accordingly, the hot gas inlets 13 are arranged at a plurality of positions in the length direction and the width direction of the combustion chamber 2. FIG. 2 is a perspective view in which the furnace wall of the main part of the waste incinerator shown in FIG. 1 is omitted, but shows an arrangement example of the hot gas inlet 13. That is, the hot gas inlet 13 extends from the combustion start region (immediately above the grate at the downstream side of the dry grate 5a) to the main combustion region (immediately above the grate of the combustion grate 5b) and in the width direction of the combustion chamber. It is provided over the entire area.

  Further, the direction of the high temperature gas inlet 13 is determined so that the high temperature gas B is blown downward. Thus, the hot gas is blown from the combustion start region toward the main combustion region, which is formed immediately downstream of the dry grate 5a and directly above the combustion grate 5b.

  The boiler 4 which has the secondary combustion area | region 10 in the vicinity of the inlet_port | entrance is good also as the arrangement | positioning bent and connected above the combustion chamber 2, as shown in FIG. By adopting such a shape and arrangement of the boiler 4, the height of the incinerator 1 composed of the combustion chamber 2 and the boiler 4 can be made lower than that of the conventional incinerator, and the cost of the incinerator is reduced. can do.

  Further, the incinerator 1 includes a secondary combustion gas (secondary air) supply system that blows the secondary combustion gas into the secondary combustion region 10 corresponding to the vicinity of the inlet of the boiler 4. The secondary combustion gas supply system feeds the secondary combustion gas C from the secondary combustion gas supply source into the secondary combustion gas inlet 15 provided in the secondary combustion region 10 via the pipe 18. The pipe 18 is provided with a blower 16 and a damper 17 as a flow rate adjusting mechanism. The secondary combustion gas inlet 15 is provided on the peripheral wall of the boiler 4 so as to blow the secondary combustion gas C into the secondary combustion region 10 in the vicinity of the inlet of the boiler 4.

  Note that the configuration of the pipes and the like for supplying the primary combustion air and the secondary combustion gas is not limited to those shown in the drawings, and can be appropriately selected depending on the scale, shape, application, etc. of the incinerator.

  In such an incinerator of this embodiment, a waste layer is formed on the dry grate 5a and the combustion grate 5b, and due to the combustion, the space in the combustion chamber 2 is directly above the waste layer. The following areas are formed.

  A dry region is formed in the upstream range of the dry grate 5a, which is positioned directly above the dry grate 5a and below the waste inlet 3, and combustion starts in the downstream range of the dry grate 5a. A region is formed. That is, the waste on the dry grate 5a is dried in the upstream range, ignited in the downstream range, and combustion starts.

  The waste on the combustion grate 5b carried from the dry grate 5a is thermally decomposed and partially oxidized here, and the combustible gas generated from the waste and the solid content in the waste are combusted. The waste is substantially burned on the combustion grate 5b. Thus, a main combustion region is formed immediately 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. Thereafter, a post-combustion region is formed on the post-combustion grate 5c.

  Most of the combustible gas generated in the combustion chamber 2 is combusted in the combustion chamber 2, and the remaining unburned gas is secondary corresponding to the vicinity of the inlet of the boiler 4 connected above the post-combustion grate 5c. The gas flows into the combustion region 10 where secondary combustion gas is supplied and secondary combustion occurs.

<Outline of incineration method>
The incinerator according to the present embodiment as described above is operated in the following manner to incinerate waste.

  First, when the waste is introduced into the waste inlet 3, the falling waste is deposited on the dry grate 5a and is moved onto the combustion grate 5b and onto the post-combustion grate 5c by the operation of each grate. And a waste layer is formed 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, drying is performed in the upstream region of the drying grate 5a and ignition (combustion start) is performed in the downstream region. On the combustion grate 5b, pyrolysis and partial oxidation of waste are mainly performed, and combustible gas and solid content are combusted. 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. The combustion ash after complete combustion is discharged from the ash drop opening 6. In a state where the waste is burning in this way, a dry region, a combustion start region, a main combustion region, and a post-combustion region are formed in the space immediately above each grate 5a, 5b, 5c.

  As described above, the waste heat boiler 4 is connected to the outlet of the combustion chamber 2, and the vicinity of the inlet of the waste heat boiler 4 is the secondary combustion region 10. Therefore, the unburned gas which is the unburned portion of the combustible gas generated in the combustion chamber 2 is guided to the secondary combustion region 10, where it is mixed and stirred with the secondary combustion gas C, and is subjected to secondary combustion. After the secondary combustion, the combustion exhaust gas is recovered by the waste heat boiler 4. After the heat is recovered, the combustion exhaust gas discharged from the waste heat boiler 4 is neutralized with acidic gas by slaked lime and adsorbed dioxins by activated carbon, and further sent to a dust removal device (not shown). The reaction product, activated carbon, dust, etc. are recovered. The combustion exhaust gas that has been dedusted and detoxified by the dust removing device 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.

  Next, the blowing of the primary combustion air, the high temperature gas, and the secondary combustion gas will be described in detail.

<Blowing primary air for combustion>
The primary combustion air A passes through the primary combustion air supply pipe 9 from the blower 8 and wind boxes 7 a, 7 b, provided at the lower portions of the dry grate 5 a, the combustion grate 5 b, and the post-combustion grate 5 c, respectively. After being supplied to 7c and 7d, it is supplied into the combustion chamber 2 through the grate 5a, 5b and 5c. The flow rate of the primary combustion air A supplied into the combustion chamber 2 is adjusted by a flow rate adjusting damper 11 provided in the primary combustion air supply pipe 9, and further supplied to the wind boxes 7a, 7b, 7c, 7d. The flow rate to be adjusted is adjusted by a flow rate adjustment damper (not shown) provided in each supply pipe provided to be branched to each wind box. Further, the configuration of the primary combustion air supply pipe 9 and the like for supplying the air boxes 7a, 7b, 7c, and 7d and the primary combustion air A is not limited to the illustrated one, and the scale, shape, application, etc. of the incinerator Can be appropriately selected.

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

<Blowing high temperature gas>
<Effect of hot gas blowing>
The hot gas B is blown downward toward the waste layer in an arbitrary region between the combustion start region and the main combustion region in the combustion chamber 2. This is because in order to stabilize combustion, it is preferable to blow a high-temperature gas into a region where a flame exists and a large amount of combustible gas exists. In the grate-type waste incinerator, the region where a large amount of combustible gas exists is from the combustion start region to the main combustion region.

  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 region is a region 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 is a region where waste is thermally decomposed, partially oxidized and burned, combustible gas is generated and burned with a flame, and combustion with a flame is completed ( This is the area up to the burnout point. In a region after the burn-out point, a char combustion region (post-combustion region) in which solid unburnt (char) in the waste is combusted is obtained. In the grate-type waste incinerator, the combustion start area corresponds to the space above the dry grate 5a, and the main combustion area corresponds to the space above the combustion grate 5b.

  In FIG. 1, the hot gas inlet 13 is installed on the ceiling of the combustion chamber 2 above the dry grate 5 a and the combustion grate 5 b corresponding to the main combustion region from the combustion start region in the combustion chamber 2. Yes. Here, the thermal decomposition reaction of waste occurs at a temperature of about 200 ° C., and is almost completed when the temperature reaches about 400 ° C.

  In the example shown in FIG. 1, since the downstream part of the dry grate 5a and the upper part of the combustion grate 5b correspond to the main combustion area from the combustion start area, a high temperature gas inlet 13 is provided above these positions to provide a high temperature gas. B is blowing. Depending on the composition and properties of the waste, the thermal decomposition reaction may be completed at a higher temperature. In this case, a high-temperature gas inlet should also be provided downstream of the position shown in FIG. Is preferred.

  By blowing the hot gas B downward into an arbitrary region between the combustion start region and the main combustion region in the combustion chamber 2 and directly above the waste layer, the hot gas B blown downward is a waste Facing the upward flow of combustible gas and combustion gas generated by thermal decomposition and partial oxidation of the gas, both gas flows collide to form a counterflow field, and a flat stagnation region with a flat flow just above the waste layer or above and below A circulation region that circulates in the direction is generated.

  This stagnation or circulation region has a slow flow rate, so there is a fixed flame in which combustible gas burns, that is, there is a flat combustion region (planar flame) directly above the waste layer, which is combustible. Gas is burned stably. As a result, stable combustion is performed even in low air ratio combustion, and generation of soot can be suppressed while suppressing generation of harmful substances such as CO, NOx, and dioxins. For this reason, low air ratio combustion can be performed without hindrance.

  In addition, since a planar combustion region is present immediately above the waste layer, the waste is heated by thermal radiation and sensible heat from the combustion region, and thermal decomposition and partial oxidation are promoted.

<High temperature gas inlet>
The hot gas inlet 13 is provided at an arbitrary position on the ceiling of the combustion chamber 2 immediately above the grate within the range of the combustion grate 5b from the downstream side in the moving direction of the waste of the dry grate 5a. The combustion chambers 2 are arranged along a plurality of rows in the width direction and the length direction. The hot gas inlet 13 may be a nozzle type or a slit type.

  High temperature such as arrangement position, arrangement number, arrangement interval, blowing direction, blowing port shape (related to spreading shape of blowing hot gas), hot gas blowing flow velocity, blowing flow rate, etc. The setting and operating conditions of the gas inlet 13 are set in accordance with the processing amount, volume, shape, waste property, etc. of the waste incinerator, so that the state of the planar combustion region is set to a desired state, that is, planar The combustion region is set or adjusted so that the combustion region is uniformly and stably formed and stays within the combustion chamber.

  A favorable state of the flow of hot gas facing the upward flow from the waste so that a planar combustion region is formed over a wide range in the width direction and the length direction immediately 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, the blowing direction, the blowing gas flow velocity, and the blowing flow rate of the hot gas so that the hot gas flow is in a preferable state. Set or adjust one.

  In addition to providing the hot gas inlet 13 on the ceiling of the combustion chamber 2, the hot gas inlet 13 may be provided within a range of 1 to 3 m from the grate.

  By setting the height position of the hot gas inlet 13 to be in a range of 1 to 3 m from the grate in each region from the combustion start region to the main combustion region, immediately above the waste layer in the combustion chamber 2, A counter flow field is generated by the hot gas B blown from the hot gas blowing port 13 and the upward flow of the combustible gas and the combustion gas generated from the waste layer, and a planar combustion region is made to stand just above the waste layer. And combustion of waste can be performed stably.

  In order to provide the hot gas blowing port 13 in a range of 1 to 3 m from the grate, a hot gas blowing member including a plurality of hot gas blowing ports 13 and a pipe for supplying the hot gas to the blowing port 13 in the combustion chamber 2 is provided. Try to arrange.

  In FIG. 1, a hot gas blowing port 13 is provided on the ceiling of the combustion chamber 2, and the hot gas B is blown downward from here toward the waste layer. Here, as a blowing direction of the high temperature gas B, 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 when the blown hot gas B collides with the combustible gas generated by thermal decomposition and partial oxidation of the waste and the upward flow of the combustion gas is used as the counter flow field. This is because a suitable counter flow field is not formed when the blowing direction of is in a range larger than 20 ° from the perpendicular to the waste layer.

<Preparation of hot gas>
The temperature of the hot gas B blown from the hot gas blowing port 13 is preferably in the range of 100 to 400 ° C, more preferably about 200 ° C. When a gas having a temperature lower than 100 ° C. is blown, the temperature in the furnace decreases, combustion becomes unstable, and CO increases. When gas exceeding 400 ° C. is blown in, the flame temperature in the combustion chamber becomes extremely high, and problems such as the generation of clinker are promoted.

  The oxygen concentration contained in the high temperature gas B is preferably about 5 to 30% by volume, and preferably 5 to 15% by 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 high-temperature gas B having the gas temperature and oxygen concentration includes a return exhaust gas that is a part of the exhaust gas downstream from the secondary combustion region 10, a mixed gas of the return exhaust gas and air, air, and oxygen. It is preferable to use at least one of the gas to be used and oxygen-enriched air. The return exhaust gas is used by returning a part of exhaust gas discharged from the waste filter, that is, exhaust gas obtained by removing and neutralizing the exhaust gas discharged from the waste incinerator. At least one of the return exhaust gas, the return exhaust gas and air mixed gas, air, oxygen-containing gas and oxygen-enriched air is heated by steam generated in the waste heat boiler as necessary, and the temperature and oxygen concentration Is blown into the main combustion chamber as a high-temperature gas that satisfies the above predetermined conditions.

  Thus, by adjusting the mixing ratio of the return exhaust gas and air when preparing the high temperature gas, the heating conditions such as the return exhaust gas, the return exhaust gas and air mixed gas, etc., the temperature and oxygen concentration of the high temperature gas can be set as desired. Range.

<High-temperature gas blowing flow rate, blowing flow rate>
The hot gas B blown from the hot gas blow-in port 13 is preferably blown into an arbitrary region between the combustion start region and the main combustion region in the combustion chamber 2 at a blowing speed of about 5 to 20 m / s. The injection speed of 5 to 20 m / s is a relative speed of 5 to 20 times the superficial velocity in the combustion chamber 2 (flow rate obtained by dividing the gas flow rate in the combustion chamber by the cross-sectional area of the combustion chamber, about 1 m / s at the maximum). This is because the counter flow field can be formed without being affected by the gas flow in the combustion chamber, and the stagnation region or the circulation region can be stably formed.

  The blowing flow rate of the high temperature gas B is adjusted by adjusting the blowing flow rate of the high temperature gas B, for example, by adjusting the blowing amount of the blower that sends the high temperature gas B or the opening degree of the flow rate adjustment damper.

<Adjustment of hot gas blowing flow rate and blowing flow rate-Adjustment for each blowing port>
When there are a plurality of high-temperature gas injection ports 13, the high-temperature gas B does not necessarily have to be injected from each of the high-temperature gas injection ports 13 at an equal flow rate. For example, the flow velocity of each high-temperature gas blow-in port 13 can be appropriately changed so as to be different.

  FIG. 4 is a cross-sectional view in the combustion chamber width direction showing a combustion state in the incinerator 1 according to one aspect of the present invention. When the waste W is not uniformly deposited on the grate 5 in the width direction (for example, when the layer thickness of the waste W on the left grate 5 is thick as shown in FIG. 4) or The amount and composition of the combustible gas generated by the thermal decomposition of the waste W when the type and the moisture content of the waste W are different and the heat generation amount of the waste W is uneven and uneven in the width direction. Becomes non-uniform depending on the location in the combustion chamber, and when the high temperature gas B is blown from the plurality of high temperature gas injection ports 13 at the same flow velocity or flow rate, the counter flow field between the high temperature gas and the upward flow of the flammable gas becomes the combustion chamber. There is a possibility that stable combustion may not be performed because the stagnation region or the circulation region is not formed stably in the width direction.

  Therefore, in the present embodiment, each of the hot gas supply pipes 14 respectively connected to the hot gas inlets 13a and 13b at different positions along the combustion chamber width direction, two positions in FIG. Dampers 26a and 26b that can individually adjust the flow rate are provided. Further, the grate temperature or the gas temperature in the combustion chamber at a plurality of positions along the combustion chamber width direction is measured, the state of the waste W on the grate 5 is grasped, and the state of the waste W on the grate 5 ascertained Accordingly, by adjusting the opening degree of the dampers 26a, 26b connected to the hot gas blowing ports 13a, 13b at the corresponding positions, the hot gas blowing flow rate or the blowing flow rate from the hot gas blowing ports 13a, 13b, respectively. Adjust individually. Thereby, according to the state of the waste W on the grate 5 along the combustion chamber width direction, the hot gas blowing flow rate or the blowing flow rate from the hot gas blowing ports 13a and 13b at two positions are individually adjusted. Thus, stable combustion is performed.

  For example, when the amount of accumulated waste W is large or when the heat generation amount of the waste W is high, the amount of generated combustible gas is increased, and the calorie generated by the combustion of the combustible gas is increased. The temperature and the gas temperature in the combustion chamber rise. And as shown in FIG. 4, the layer thickness of the waste W on the left grate is thick, the amount of combustible gas is large, and the gas temperature in the combustion chamber is 800 to 900 ° C. and other regions (in FIG. 4). If the temperature is higher than 700 to 800 ° C. of the waste W on the right grate), the hot gas blowing flow rate from the hot gas blowing port 13a at the corresponding position is changed to the other hot gas blowing port 13b. The opening degree of the damper 26a is adjusted so that the flow rate increases to 1.2 to 1.5 times the flow rate of high-temperature gas blown from the exhaust gas, so that a sufficient balance can be achieved with respect to the upward flow of the increased combustible gas or the like. A high-temperature gas at a flow rate is blown, a stagnation region or a circulation region is uniformly and stably formed in the combustion chamber, and a planar combustion region (planar flame) E is made to stand and perform stable combustion.

  In this way, stable combustion can be maintained in the combustion chamber even if the state of the waste W varies.

<Adjustment of high-temperature gas injection flow rate and flow rate according to combustion chamber conditions>
It is preferable to adjust the hot gas blowing flow rate or the blowing flow rate in accordance with the fluctuation of the state in the combustion chamber. The amount and composition of the combustible gas and combustion gas generated from the waste vary as the amount and type of waste supplied to the combustion chamber 2 vary. It is preferable to adjust the blowing flow rate or the blowing flow rate of the hot gas B so that the planar combustion region is fixed immediately above without fluctuation.

  In order to grasp the condition in the combustion chamber, the fluctuation is detected by measuring the grate temperature and the gas temperature in the combustion chamber. Also, if the combustion state of the combustible gas changes, the CO concentration, oxygen concentration, etc. in the combustion exhaust gas will fluctuate, so by measuring the CO concentration, oxygen concentration of the exhaust gas discharged from the boiler, and detecting the change The state in the combustion chamber may be grasped, and the blowing flow rate or blowing flow rate of the hot gas B may be adjusted in accordance with the state.

  By blowing high-temperature gas as described above, a stable stagnation region or circulation region can be formed in the vicinity of the waste layer in the furnace, and a flat combustion region can be established, so that stable combustion can be achieved even with low air ratio combustion. It is possible to suppress generation of harmful substances such as CO, NOx, dioxins and the like, and to suppress generation of soot. For this reason, the amount of air blown into the entire incinerator can be reduced, and low air ratio combustion can be performed without problems.

<Blowing in secondary combustion gas>
The secondary combustion gas is blown into the secondary combustion region 10 and the unburned gas is subjected to secondary combustion. As the secondary combustion gas, it is preferable to use a gas having a temperature in the range of room temperature to 200 ° C. and an oxygen concentration in the range of 15 to 21% by volume.

  As the secondary combustion gas C, only the secondary air for combustion supplied by the blower, the gas in which the diluent is mixed with the secondary air for combustion after supply of the blower and the oxygen concentration is adjusted, after passing through the dust removing device Only the return exhaust gas (circulation exhaust gas) from which a part of the exhaust gas is extracted, or a gas in which the secondary air for combustion and the circulation exhaust gas are mixed can be used. Diluents such as nitrogen and carbon dioxide are conceivable.

  It is preferable that one or a plurality of the secondary combustion gas inlets 15 be installed so that gas can be blown in a direction in which a swirling flow is generated in the secondary combustion region. By blowing the secondary combustion gas C in the direction in which the swirl flow is generated in the secondary combustion region, the gas temperature and oxygen concentration distribution in the secondary combustion region can be made uniform and averaged. Combustion is stably performed, generation of a local high temperature region is suppressed, and exhaust gas can be further reduced in NOx. Furthermore, since the mixing of the unburned gas and the oxidant is promoted, the combustion stability is improved and complete combustion can be achieved, so that the exhaust gas can be reduced in CO.

  It is preferable to adjust the flow rate of the secondary combustion gas so that the gas temperature in the secondary combustion region is in the range of 800 to 1050 ° C. When the gas temperature in the secondary combustion region is less than 800 ° C., combustion becomes insufficient and CO increases. Further, when the gas temperature in the secondary combustion region exceeds 1050 ° C., the generation of clinker in the secondary combustion region is promoted, and further NOx increases.

<Distribution of oxygen amount ratio to achieve low air ratio combustion>
In the waste incinerator of the present embodiment, the air oxygen amount ratio distribution of the gas to be injected for realizing the low air ratio combustion will be described.

  The ratio Q1 of the amount of oxygen per unit time supplied by the primary combustion air A blown into the combustion chamber from below the grate with respect to the theoretical amount of oxygen per unit time necessary for the combustion of waste, and the combustion in the combustion chamber The ratio Q2 of the amount of oxygen per unit time supplied by the high-temperature gas B injected into an arbitrary region between the start region and the main combustion region, and the secondary combustion gas C injected into the secondary combustion region The ratio Q3 of the amount of oxygen supplied per unit time is to blow each gas so as to satisfy the following formulas (1) and (2), more preferably the following formulas (3) and (4). Is preferred. By controlling the ratio of blowing each gas so as to satisfy the following formulas (3) and (4), the amount of air supplied to the entire incinerator can be reduced at a lower low air ratio of 1.3 or less. Combustion can be realized.

Formula (1)
Q1: Q2: Q3 = 0.75-1.10: 0.05-0.40: 0.10-0.40
Formula (2)
1.0 ≦ Q1 + Q2 + Q3 ≦ 1.5
Formula (3)
Q1: Q2: Q3 = 0.80-1.00: 0.10-0.30: 0.10-0.30
Formula (4)
1.1 ≦ Q1 + Q2 + Q3 ≦ 1.3
Here, the theoretical oxygen amount per unit time required for the combustion of the waste is the amount of oxygen required for the combustion per unit mass of the waste determined from the properties and components of the waste put 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.

  Q1 is the ratio of the amount of oxygen per unit time supplied by the primary combustion air A supplied from below the grate 5 into the combustion chamber 2, and the flow rate of the primary combustion air A is increased or decreased. To make adjustments. Q2 is adjusted by increasing or decreasing the flow rate of the hot gas B that is blown into an arbitrary region between the combustion start region and the main combustion region in the combustion chamber 2. Further, Q3 is adjusted by increasing or decreasing the flow rate of the secondary combustion gas C injected into the secondary combustion region.

  In the following, Q1 + Q2 + Q3 is described as λ.

  By setting Q1, Q2 and Q3 in the above range, low oxygen ratio combustion (1.0 ≦ λ ≦ 1.5) (ie, corresponding to low air ratio combustion) was performed in a waste incinerator. Even in this case, 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.

<Distribution of oxygen amount ratio to achieve combustion at lower air ratio (less than 1.3 air ratio)>
As a more preferable distribution ratio capable of achieving stable lower combustion with a low air ratio by suppressing generation of unburned waste and harmful substances, Q1: Q2: Q3 = 0.90: 0.15: Based on 015, λ = 1.20, λ is in the range of 1.1 to 1.3 and Q1, Q2, Q3 is in the above range based on the composition and properties of the waste put into the incinerator adjust.

  Specific examples of Q1, Q2, Q3, and λ will be described below.

Q1: Q2: Q3 = 0.90: 0.05: 0.25, λ = 1.20
Q1: Q2: Q3 = 0.90: 0.10: 0.20, λ = 1.20
Q1: Q2: Q3 = 0.90: 0.20: 0.10, λ = 1.20
Q1: Q2: Q3 = 0.90: 0.25: 0.05, λ = 1.20
Q1: Q2: Q3 = 1.00: 0.05: 0.15, λ = 1.20
Q1: Q2: Q3 = 1.00: 0.10: 0.10, λ = 1.20
Q1: Q2: Q3 = 1.00: 0.15: 0.05, λ = 1.20
Q1: Q2: Q3 = 0.85: 0.10: 0.25, λ = 1.20
Q1: Q2: Q3 = 0.85: 0.20: 0.15, λ = 1.20
Q1: Q2: Q3 = 0.80: 0.15: 0.25, λ = 1.20
Q1: Q2: Q3 = 0.80: 0.20: 0.20, λ = 1.20
Q1: Q2: Q3 = 0.75: 0.20: 0.20, λ = 1.15
Q1: Q2: Q3 = 0.80: 0.15: 0.20, λ = 1.15
Q1: Q2: Q3 = 0.80: 0.10: 0.20, λ = 1.10.
Q1: Q2: Q3 = 0.80: 0.15: 0.15, λ = 1.10
Q1: Q2: Q3 = 0.85: 0.20: 0.25, λ = 1.30
Q1: Q2: Q3 = 0.90: 0.15: 0.25, λ = 1.30
Q1: Q2: Q3 = 1.00: 0.10: 0.20, λ = 1.30
Hereinafter, adjustment criteria for Q1, Q2, and Q3 will be described.

[Adjustment Criteria for Combustion Primary Air Ratio Q1]
Q1 is 0.90 for drying and burning normal municipal waste, etc., and Q1 is set when burning waste with low ash content or low moisture, such as plastic. The ratio is reduced to about 0.75 to 0.85, and the ratio Q2 of the hot gas is increased instead.

[Adjustment criteria for high-temperature gas ratio Q2]
To burn waste such as ordinary municipal waste, Q2 is based on 0.15, waste with little ash and moisture, and most combustible, such as plastic, or waste with a large volatile content Q2 is increased to about 0.20 to 0.25. If Q2 is small, the above-described effect of high-temperature gas blowing cannot be obtained sufficiently, and CO increases. If Q2 is increased beyond the above range, low air ratio combustion cannot be achieved, fuel costs for preparing high temperature gas, etc. increase, the temperature in the combustion chamber becomes excessive, and clinker is generated on the inner wall. Or NOx increases, which is not preferable.

[Adjustment standard of secondary combustion gas ratio Q3]
First, as a standard operation standard of a waste incinerator, Q1 and Q2 are determined in consideration of the composition and properties of waste based on the above standard, and then a standard value of Q3 is set. Q3 is adjusted within a range of 0.10 to 0.40 with 0.15 as a reference.

  The combustion state in the secondary combustion region is adjusted by adjusting the value of Q3.

  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 Q1 and Q2, adjustment is made to increase or decrease 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 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.

Measuring means are as follows.
Gas temperature: Temperature sensor (thermocouple, radiation thermometer)
O ₂ concentration in gas: Oxygen concentration meter
CO concentration in gas: CO concentration meter
NOx concentration in gas: NOx concentration meter
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 a local high temperature region is suppressed, and CO, NOx, etc. A waste incinerator and a waste incineration method capable of reducing the amount of harmful gas generated are provided. Furthermore, since it can be burned at a lower air ratio than before, the total amount of exhaust gas discharged from the incinerator can be greatly reduced, and the waste incinerator and waste that can improve the recovery efficiency of waste heat An incineration method is provided.

  Using the conventional high-temperature gas blow-in incinerator shown in Patent Document 1 (comparative example) and the incinerator of this embodiment (example), combustion simulation of a process of incinerating waste at an incineration amount of 120 t / day is performed. The NOx concentration and CO concentration in the exhaust gas were compared.

The results are shown in Table 1 below.

  From Table 1 above, in the embodiment, the furnace volume can be reduced to about 1/2 of the comparative example, the air ratio can be lowered and the combustion operation can be performed, and the generation amount of harmful gases such as CO and NOx is reduced. I confirmed that I can do it.

Claims (17)

A grate-type waste incinerator,
A combustion chamber having a grate and burning waste on the grate, the height of which is 3 m or less;
Primary air blowing means for blowing primary air for combustion into the combustion chamber from under the grate,
Hot gas blowing means for blowing hot gas downward from the ceiling of the combustion chamber toward an arbitrary region between the combustion start region and the main combustion region in the combustion chamber;
A secondary combustion gas blowing means for blowing secondary combustion gas into the secondary combustion region;
The high-temperature gas blowing means includes a plurality of high-temperature gas blowing ports, and blows the high-temperature gas against the upward flow of the combustible gas and the combustion gas generated from the waste, and the stagnation region directly above the waste layer or Adjusting the blowing flow rate or flow rate of the hot gas according to the state in the combustion chamber so that the planar combustion region is formed by forming a circulation region and the state of the planar combustion region is set to a desired state. A grate-type waste incinerator characterized by A grate-type waste incinerator,
A combustion chamber comprising a grate and burning waste on the grate;
Primary air blowing means for blowing primary air for combustion into the combustion chamber from under the grate,
High-temperature gas blowing means for blowing the hot gas downward from a position 1 to 3 m above the grate in the combustion chamber toward an arbitrary region between the combustion start region and the main combustion region in the combustion chamber; ,
A secondary combustion gas blowing means for blowing secondary combustion gas into the secondary combustion region;
The high-temperature gas blowing means includes a plurality of high-temperature gas blowing ports, and blows the high-temperature gas against the upward flow of the combustible gas and the combustion gas generated from the waste, and the stagnation region directly above the waste layer or Adjusting the blowing flow rate or flow rate of the hot gas according to the state in the combustion chamber so that the planar combustion region is formed by forming a circulation region and the state of the planar combustion region is set to a desired state. A grate-type waste incinerator characterized by   The hot gas blowing means includes a plurality of hot gas blowing ports in the furnace width direction, and adjusts the blowing flow rate or flow rate of each hot gas blowing port according to the state of waste on the grate. The grate-type waste incinerator according to claim 1 or 2.   Measure the grate temperature or gas temperature in the combustion chamber to understand the condition in the combustion chamber or the state of waste on the grate, and depending on the grasped state in the combustion chamber or the state of waste on the grate The grate-type waste incinerator according to any one of claims 1 to 3, further comprising adjusting means for adjusting a blowing flow rate or a blowing flow rate of the hot gas blowing port.   5. The hot gas blowing means blows hot gas having a temperature in the range of 100 to 400 ° C. and an oxygen concentration in the range of 5 to 30% by volume. The described grate-type waste incinerator.   6. The hot gas blowing means blows hot gas at a flow rate of 5 to 20 times the superficial velocity obtained by dividing the flow rate of the combustion chamber gas by the cross-sectional area of the combustion chamber. The grate-type waste incinerator described in 1.   The high-temperature gas blowing means includes at least one of a return exhaust gas that returns a part of the exhaust gas discharged from the incinerator, a mixed gas of the return exhaust gas and air, air, a gas containing oxygen, and oxygen-enriched air. The grate-type waste incinerator according to any one of claims 1 to 6, further comprising a high-temperature gas supply source that supplies high-temperature gas.   The grate-type waste incinerator according to any one of claims 1 to 7, wherein a boiler having a secondary combustion region in the vicinity of the inlet is bent and connected to the upper side of the combustion chamber. A waste incineration method using a grate-type waste incinerator,
Using a grate-type waste incinerator where the height of the combustion chamber for burning waste is 3 m or less,
Blowing primary air for combustion into the combustion chamber from below the grate,
Hot gas is blown downward from the combustion chamber ceiling toward any region between the combustion start region and the main combustion region in the combustion chamber,
Blowing secondary combustion gas into the secondary combustion area,
High-temperature gas is injected from multiple high-temperature gas injection ports in opposition to the upward flow of combustible gas and combustion gas generated from waste, forming a stagnation region or circulation region directly above the waste layer, and planar combustion A waste incineration method characterized by adjusting a flow rate or flow rate of hot gas in accordance with the state in the combustion chamber so that the region is fixed and the state of the planar combustion region is set to a desired state. A waste incineration method using a grate-type waste incinerator,
Using a grate-type waste incinerator with a combustion chamber for burning waste,
Blowing primary air for combustion into the combustion chamber from below the grate,
Hot gas is blown downward from a position 1 to 3 m above the grate in the combustion chamber upward to any region between the combustion start region and the main combustion region in the combustion chamber,
Blowing secondary combustion gas into the secondary combustion area,
High-temperature gas is injected from multiple high-temperature gas injection ports in opposition to the upward flow of combustible gas and combustion gas generated from waste, forming a stagnation region or circulation region directly above the waste layer, and planar combustion A waste incineration method characterized by adjusting a flow rate or flow rate of hot gas in accordance with the state in the combustion chamber so that the region is fixed and the state of the planar combustion region is set to a desired state.   Depending on the state of the waste on the grate, the hot gas is blown in by adjusting the flow velocity or flow rate of each hot gas from multiple hot gas blowers provided in the furnace width direction. The waste incineration method according to claim 9 or 10.   Measure the grate temperature or combustion chamber gas temperature to determine the condition in the combustion chamber or the waste on the grate, and the hot gas according to the grasped combustion chamber condition or the waste on the grate The waste incineration method according to any one of claims 9 to 11, wherein the blowing is performed by adjusting a blowing flow rate or a blowing flow rate of the blowing port.   The waste incineration method according to any one of claims 9 to 12, wherein the high-temperature gas has a temperature in a range of 100 to 400 ° C and an oxygen concentration in a range of 5 to 30% by volume.   The waste incineration method according to any one of claims 9 to 13, wherein the high-temperature gas is injected at a flow rate of 5 to 20 times the superficial velocity obtained by dividing the gas flow rate in the combustion chamber by the cross-sectional area in the combustion chamber.   The high-temperature gas is at least one of a return exhaust gas that returns a part of the exhaust gas discharged from the incinerator, a mixed gas of the return exhaust gas and air, air, a gas containing oxygen, and oxygen-enriched air. The waste incineration method according to any one of claims 9 to 14. The ratio Q1 of the amount of oxygen per unit time supplied by the primary air for combustion to the theoretical amount of oxygen per unit time required for combustion of waste;
A ratio Q2 of oxygen amount per unit time supplied by the high-temperature gas;
The ratio Q3 of the amount of oxygen per unit time supplied by the secondary combustion gas is
The waste incineration method according to any one of claims 9 to 15, wherein the following formulas (1) and (2) are satisfied.
Formula (1)
Q1: Q2: Q3 = 0.75-1.10: 0.05-0.40: 0.10-0.40
Formula (2)
1.0 ≦ Q1 + Q2 + Q3 ≦ 1.5 The ratio Q1 of the amount of oxygen per unit time supplied by the primary air for combustion to the theoretical amount of oxygen per unit time required for combustion of waste;
A ratio Q2 of oxygen amount per unit time supplied by the high-temperature gas;
The ratio Q3 of the amount of oxygen per unit time supplied by the secondary combustion gas is
The waste incineration method according to any one of claims 9 to 15, wherein the following expressions (3) and (4) are satisfied.
Formula (3)
Q1: Q2: Q3 = 0.80-1.00: 0.10-0.30: 0.10-0.30
Formula (4)
1.1 ≦ Q1 + Q2 + Q3 ≦ 1.3

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