JP2004077087A - Waste incinerator - Google Patents

Abstract

An object of the present invention is to provide a grate-type waste incinerator that circulates and blows exhaust gas into a furnace to perform stable combustion and reduce the generation of NOx.
On the side of a main combustion chamber (7) before a combustion stoker (4), thermal decomposition of refuse (2) is actively performed on a grate, and combustion gas generated as a result of the thermal decomposition forms a flame (14). Burning. This region is called a main combustion region, and a point at which the combustion forming the flame 14 ends is a burn-out point. After the burn-off point, the residue from which the thermal decomposition is completed and the volatile components are released is solid-burned, that is, so-called char combustion is performed. A nozzle 15 for blowing the exhaust gas or a mixed gas of the exhaust gas and the air into the main combustion chamber is provided above the grate in the region where the char combustion is performed.
[Selection diagram] Fig. 1

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
TECHNICAL FIELD The present invention relates to a grate type waste incinerator for incinerating waste such as municipal waste.
[0002]
[Prior art]
A grate type or fluidized bed type waste incinerator is widely used as an incinerator for incinerating waste such as municipal solid waste. FIG. 6 shows a schematic diagram of a representative example. The refuse 2 put into the hopper 1 is sent to a drying stoker 3 through a chute, dried by air from below and radiant heat in the furnace, and heated to ignite. The refuse 2 ignited and starting combustion is sent to a combustion stoker 4, where it is gasified by combustion air sent from below, and partly burns. Then, the unburned components are completely burned by the post-combustion stoker 5. The ash remaining after the combustion is taken out from the main ash chute 6.
[0003]
The combustion is performed in the main combustion chamber 7, and the flue gas is separated and discharged into the main flue 9 and the sub-flue 10 due to the presence of the intermediate ceiling 8. The exhaust gas passing through the main flue 9 contains almost no unburned gas and contains about 10% or more of oxygen. The exhaust gas passing through the auxiliary flue 10 contains about 8% of unburned gas. These exhaust gases are mixed in the secondary combustion chamber 11 and secondary combustion is performed to completely burn unburned gas. Exhaust gas from the secondary combustion chamber 11 is sent to a waste heat boiler 13, where the heat is exchanged, and then discharged to the outside via a cooling tower, a bag filter, and the like.
[0004]
When incinerating waste in such a grate-type waste incinerator, it is difficult to maintain a constant combustion state in the furnace because the waste consists of many substances with different properties. It is inevitable that the distribution of the temperature and the concentration of the combustion gas in the combustion chamber 7 become non-uniform temporally and spatially.
[0005]
Further, when the state of the flame is unstable, there is a problem that the flame is easily blown off and it is difficult to perform high-load combustion.
[0006]
As a method of effectively solving such a problem, the present inventor has proposed that one or more pairs of nozzles for ejecting gas are provided at opposed positions in the furnace, and the ejection direction of gas from each nozzle. The invention of a method for operating a waste incinerator was conducted in which the direction of at least one of a stagnation region and a swirl region was formed by the gas to be ejected. This invention is disclosed in JP-A-2001-108220 (Patent Document 1).
[0007]
In the prior application, at least one of the stagnation region and the swirl region is formed in the furnace by the gas ejected from the opposed nozzle.
[0008]
The “stagnation region” is a portion where the movement of the mixed gas of the combustion gas and the air (furnace gas) is slow and stagnates, and the “swirl region” is the swirl flow of the furnace gas. Area.
[0009]
When the stagnation region is formed, the flame tends to be located in front of this region, and the residence time of the gas in the furnace becomes longer, so that the flame is stabilized. Therefore, the concentration of unburned gas such as CO and HC decreases, the generation of dioxins decreases, and the local high-temperature region near the inner wall of the furnace decreases, so that the life of the refractory can be extended.
[0010]
In addition, the average value of the exhaust gas temperature can be increased accordingly, and the power generation efficiency can be improved by the high efficiency operation of the waste heat boiler. In addition, since the controllable range of the air ratio is expanded, the two-stage combustion can be strengthened, and the NOx can be reduced.
[0011]
When the swirling region is formed, mixing between the gases is promoted, and the local high-temperature region and the local low-temperature region are reduced. Therefore, the service life of the refractory can be prolonged, and the average value of the exhaust gas temperature can be increased, so that the power generation efficiency can be increased by the highly efficient operation of the waste heat boiler.
[0012]
Japanese Patent Application Laid-Open No. 2001-108220 proposes to use exhaust gas from a waste incinerator as a gas blown into the furnace for such a purpose. This is to effectively utilize sensible heat contained in exhaust gas. As described above, in order to increase the thermal efficiency by utilizing the sensible heat contained in the exhaust gas, circulating a part of the exhaust gas and blowing it into the furnace is described in JP-A-2001-108220. The method is not limited to the case where the stagnation area and the turning area are formed, but is a well-known general energy saving method.
[0013]
[Patent Document 1]
JP 2001-108220 A
[Problems to be solved by the invention]
However, in the case of a waste incinerator, unlike a general combustion furnace, there are the following problems when exhaust gas circulation is performed. That is, unlike a general combustion furnace, in a waste incinerator, the combustion state in the main combustion chamber is not stable. Therefore, the flame temperature rises locally and the nitrogen in the air is oxidized, and the generation of NOx increases rapidly, and the nitrogen content remaining in the char, which is the residue after the waste is pyrolyzed and burned as a gas, In addition, there is a problem that NOx is generated at a high temperature.
[0015]
The present invention has been made in view of such circumstances, and in a grate type waste incinerator in which exhaust gas is circulated and blown into the furnace, waste combustion that can perform stable combustion and suppress generation of NOx It is an object to provide a waste incinerator.
[0016]
[Means for Solving the Problems]
A first means for solving the above problem is a grate-type waste incinerator, which has gas blowing means for blowing exhaust gas or a mixed gas of exhaust gas and air into a main combustion chamber, wherein the gas blowing means is provided. Is a waste incinerator (claim 1), which is provided above each stoker in a region where char combustion is performed.
[0017]
Char combustion refers to a state in which the residue (char) from which the waste is thermally decomposed and volatile components are released is burning (solid combustion). In this case, if the area where char combustion is performed is in a high-temperature and oxidizing atmosphere, nitrogen in the char reacts to generate NOx. In order to suppress the reaction between nitrogen and oxygen in the char, it is effective to lower the temperature of the char combustion region and to bring the atmosphere of the char combustion region closer to a reducing atmosphere to lower the conversion rate to NOx. .
[0018]
In this means, exhaust gas from a waste incinerator or a mixed gas of exhaust gas and air is blown from gas blowing means (nozzles, etc.) provided above each stoker in a region where char combustion is performed. Accordingly, the temperature of the char combustion region can be lowered, and the atmosphere of the char combustion region can be close to the reducing atmosphere, so that the generation of NOx can be reduced. In particular, by setting the oxygen concentration in the exhaust gas or the mixed gas of the exhaust gas and the air to 15% or less, the temperature of the char combustion region is reduced, and the conversion ratio of N in the char to NOx is suppressed. As a result, generation of NOx is suppressed.
[0019]
It is preferable that the oxygen concentration of the exhaust gas discharged from the waste incinerator or the mixed gas of the exhaust gas and the air be 10% or less, because the atmosphere in the char combustion region can be reliably reduced. In addition, it is preferable to blow in the exhaust gas from the waste incinerator as exhaust gas from which dust in the exhaust gas has been removed by a dust collector, since dust trouble such as dust adhering to a pipe and clogging can be prevented.
[0020]
Further, since the exhaust gas contains acidic gases such as HCl and SOx, it is preferable to set the temperature of the exhaust gas to be equal to or higher than the acid dew point temperature so as to avoid acid dew point corrosion resulting from these gases. It is needless to say that the temperature need not be controlled in the case of using the exhaust gas after treating the acidic gas.
[0021]
From the standpoint of reducing atmosphere only, it is preferable to blow the exhaust gas as it is, but the unburned portion of the gas generated by pyrolysis of the waste by the combustion stoker may remain in the furnace. Therefore, when it is necessary to replenish oxygen in order to burn this unburned portion, it is possible to improve the combustion state by blowing a mixture of air and exhaust gas.
[0022]
A second means for solving the above-mentioned problem is a grate-type waste incinerator, which has gas blowing means for blowing exhaust gas or a mixed gas of exhaust gas and air into a main combustion chamber. A waste incinerator (claim 2) is provided above each stoker in a range from the center of the combustion stoker to the end point of the post-burning stoker.
[0023]
On the combustion stoker, waste gasification and combustion are performed, and char combustion may start from the rear side of the center. On the post-burning stoker, char combustion is mainly performed. Therefore, by providing the gas blowing means in this region, the effect of the first means can be obtained.
[0024]
A third means for solving the above-mentioned problem is a grate-type waste incinerator, which has gas blowing means for blowing exhaust gas or a mixed gas of exhaust gas and air into a main combustion chamber. Is provided above each stoker in a range from the burn-out point of the waste to the end point of the post-burning stoker (claim 3).
[0025]
The burn-out point is a point at which combustion with a flame is completed, and a region after the burn-out point is a char combustion region. Therefore, by providing the gas blowing means in this region, the effect of the first means can be obtained.
[0026]
A fourth means for solving the above problem is a grate type waste incinerator, which has gas blowing means for blowing exhaust gas or a mixed gas of exhaust gas and air into a main combustion chamber, wherein the gas blowing means is provided. Is characterized by being provided above each stoker in an area where intense combustion of waste is performed (claim 4).
[0027]
Fierce combustion means that unburned components and chars in the waste burn without forming a flame (solid combustion). Therefore, by providing the gas blowing means above the respective stokers in the region where the waste is intensely burned, the operation and effect of the first means can be achieved.
[0028]
A fifth means for solving the problem is a grate-type waste incinerator, which has gas blowing means for blowing exhaust gas or a mixed gas of exhaust gas and air into the furnace, wherein the gas blowing means is The ash discharge chute is provided in a space above the ash discharge chute (claim 5).
[0029]
The ash discharge chute is provided at the furnace bottom as described above. Char combustion is performed by a post-burning stoker at the bottom of the furnace. However, N content in the char may be converted to NOx due to an oxidizing atmosphere caused by air blown from below the grate. Therefore, by blowing the exhaust gas or the mixed gas of the exhaust gas and the air into this portion, the temperature and the oxygen concentration of the atmosphere can be reduced, and the conversion of N in the char to NOx can be suppressed.
[0030]
A sixth means for solving the above problem is a grate-type waste incinerator having a secondary combustion chamber for secondary-combustion of a gas discharged from a main combustion chamber, wherein exhaust gas or exhaust gas is used. Gas blowing means for blowing a mixed gas of air and air into the furnace, wherein the gas blowing means is provided at the entrance of the secondary combustion chamber or at the exit of the main combustion chamber (Claim 6). It is.
[0031]
Dust is present in the gas from the main combustion chamber near the entrance of the secondary combustion chamber or near the exit of the main combustion chamber. Since this region is in an oxidizing atmosphere under the influence of at least one of the blowing air from below the grate and the secondary combustion air, N in the dust is converted to NOx to generate NOx. Therefore, by blowing the exhaust gas or the mixed gas of the exhaust gas and the air into this portion, the temperature and the oxygen concentration of the atmosphere can be reduced, and the conversion of N in the dust to NOx can be suppressed.
[0032]
A seventh means for solving the above-mentioned problem is a grate-type waste incinerator, which has an intermediate ceiling, and a flue through which exhaust gas flows through the intermediate ceiling is connected to a main flue at a lower part of the furnace exit side. A gas flue means for blowing exhaust gas or a mixed gas of flue gas and air into the furnace, wherein the gas blow means is provided in the main flue portion. (Claim 7).
[0033]
The main flue is also provided at the bottom of the furnace as described above. Dust also exists in this main flue region, and if this region has an oxidizing atmosphere, N in the dust is converted to NOx. Therefore, by blowing the exhaust gas or the mixed gas of the exhaust gas and the air into this portion, the temperature and the oxygen concentration of the atmosphere can be reduced, and the conversion of N in the dust to NOx can be suppressed.
[0034]
An eighth means for solving the above-mentioned problem is a grate-type waste incinerator, which has first and second gas blowing means for blowing exhaust gas or a mixed gas of exhaust gas and air into a main combustion chamber. The first gas injecting means includes an area where char combustion is performed, an area between the center of the combustion stoker and an end point of the post-combustion stoker, and an area from the burning start point of waste to the end point of the post-combustion stoker. The second gas blowing means is provided above each of the stokers in at least one of a region between the ash discharge chute and a region between the ash discharge chute and at least one of the regions where the intense combustion of waste is performed. It is provided at at least one of the entrance of the next combustion chamber and the exit of the main combustion chamber (claim 8).
[0035]
This means is a combination of at least one of the first to fourth means and at least one of the fifth and sixth means. Therefore, it is possible to achieve an operational effect obtained by combining the operational effects of the combined means.
[0036]
A ninth means for solving the above problem is a grate-type waste incinerator, which has an intermediate ceiling, and a flue through which exhaust gas flows by the intermediate ceiling is connected to a main flue at a lower part of a furnace exit side. A first flue gas blowing means for blowing flue gas or a mixed gas of flue gas and air into a main combustion chamber, wherein the first flue gas is blown into the main combustion chamber. Means include the area where char combustion is taking place, the area between the center of the combustion stoker and the end of the post-burning stoker, the area between the burn-off point of the waste and the end of the post-burning stoker, and At least one of the regions where the intense combustion is performed is provided above each stoker, and the second gas blowing means is provided in the main flue portion. (Claim 9).
[0037]
This means is a grate-type waste incinerator, which has an intermediate ceiling, and a flue through which exhaust gas flows through the intermediate ceiling is a main flue at the lower part of the furnace exit side and a sub-flue at the upper central part of the furnace. And a combination of at least one of the first to fourth means and the seventh means. Therefore, it is possible to achieve an operational effect obtained by combining the operational effects of the combined means.
[0038]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a diagram showing a first embodiment of the present invention. The refuse 2 put into the hopper 1 is sent to a drying stoker 3 through a chute, dried by air from below and radiant heat in the furnace, and heated to ignite. The refuse 2 ignited and starting combustion is sent to a combustion stoker 4, where it is gasified by combustion air sent from below, and partly burns. Then, the unburned components are completely burned by the post-combustion stoker 5. The ash remaining after the combustion is taken out from the main ash chute 6.
[0039]
The combustion is performed in the main combustion chamber 7, and the combustion exhaust gas is subjected to secondary combustion in the secondary combustion chamber 11 to completely burn unburned components. Exhaust gas from the secondary combustion chamber 11 is sent to a waste heat boiler 13, where the heat is exchanged, and then discharged to the outside via a cooling tower, a bag filter, and the like.
[0040]
On the pre-combustion stoker 4 side of the main combustion chamber 7, the drying and thermal decomposition of the refuse 2 are actively performed on the grate, and the gas generated by the thermal decomposition forms a flame 14 and burns. I have. This region is called a main combustion region, and a point at which the combustion forming the flame 14 ends is a burn-out point. After the burn-off point, the release of volatile components and the thermal decomposition are completed, the residue is solid-burned, and so-called char combustion is performed.
[0041]
In the embodiment shown in FIG. 1, a nozzle 15 for blowing exhaust gas or a mixed gas of exhaust gas and air into the main combustion chamber is provided above a grate in a region where the char combustion is performed. In the case of FIG. 1, the installation position is in the range from the center of the combustion stoker 4 to the end point of the post-burning stoker, and is also the range from the burn-out point of the waste to the end point of the post-burning stoker. In addition, it is an area where intense combustion of waste is performed. By blowing the exhaust gas or the mixed gas of the exhaust gas and the air into such a position, as described above, the conversion of N in the char to NOx is suppressed, and the generation of NOx is suppressed.
[0042]
FIG. 2 is a view showing a second embodiment of the present invention, and the configuration of the waste incinerator is the same as that shown in FIG. In the present embodiment, a nozzle 15 for blowing exhaust gas or a mixed gas of exhaust gas and air into the main combustion chamber is provided in a space above the main ash chute 6, which is an ash discharge chute. By doing so, as described above, the temperature and oxygen concentration of the atmosphere of the post-combustion stoker of the furnace bottom can be reduced, and the conversion of N in the char to NOx can be suppressed.
[0043]
FIG. 3 is a view showing a third embodiment of the present invention, and the configuration of the waste incinerator is the same as that shown in FIG. In the present embodiment, a nozzle 15 for blowing exhaust gas or a mixed gas of exhaust gas and air into the main combustion chamber is provided at the entrance of the secondary combustion chamber 11. By doing so, as described above, the temperature and oxygen concentration can be reduced at this portion, and the conversion of N in the dust to NOx can be suppressed.
[0044]
FIG. 4 is a diagram showing a fourth embodiment of the present invention. In this embodiment, an intermediate ceiling 8 is provided in the main combustion chamber 7, and combustion is performed in the main combustion chamber 7. The flue gas is separated into the main flue 9 and the sub-flue 10 due to the presence of the intermediate ceiling 8 and mixed in the secondary combustion chamber 11, where secondary combustion is performed and the unburned portion is completely removed. To burn. In the present embodiment, a nozzle 15 for blowing exhaust gas or a mixed gas of exhaust gas and air into the main combustion chamber is provided in the main flue portion.
[0045]
By doing so, the temperature and oxygen concentration at this portion can be reduced, and the conversion of N in the dust to NOx can be suppressed.
[0046]
FIG. 5 is a schematic diagram showing a configuration of an apparatus that generates a mixed gas of air and exhaust gas and blows the mixed gas into the furnace in each of the above embodiments.
[0047]
Exhaust gas discharged from the waste heat boiler 13 of the waste incinerator 21 passes through the dust collector 22, is then drawn by the draw fan 23, and is discharged from the chimney 24. The exhaust gas on the outlet side of the induction fan 23 is taken out, and the mixing device 25 mixes the air and the exhaust gas. Then, this mixed gas is blown into the furnace from the nozzle 15 by the air supply fan 26 as described above. When the concentration of oxygen in the exhaust gas is sufficiently high, only the exhaust gas may be blown without being mixed with air.
[0048]
【The invention's effect】
INDUSTRIAL APPLICABILITY As described above, according to the present invention, in a grate-type waste incinerator that circulates and exhausts exhaust gas into a furnace, a waste incinerator that can perform stable combustion and suppress generation of NOx Can be provided.
[Brief description of the drawings]
FIG. 1 is a schematic diagram showing a first embodiment of the present invention.
FIG. 2 is a schematic diagram showing a second embodiment of the present invention.
FIG. 3 is a schematic diagram showing a third embodiment of the present invention.
FIG. 4 is a schematic diagram showing a fourth embodiment of the present invention.
FIG. 5 is a schematic diagram showing a configuration of an apparatus for producing a mixed gas of exhaust gas and air.
FIG. 6 is a schematic diagram of a conventional waste incinerator.
[Explanation of symbols]
1: hopper 2: refuse 3: dry stoker 4: combustion stoker 5: post-burning stoker 6: main ash chute 7: main combustion chamber 8: intermediate ceiling 9: main flue 10: auxiliary flue 11: secondary combustion chamber 13 : Waste heat boiler 14: Flame 15: Nozzle 21: Waste incinerator 22: Dust collector 23: Induction fan 24: Chimney 25: Mixing device

Claims (9)

A grate-type waste incinerator, which has gas blowing means for blowing exhaust gas or a mixed gas of exhaust gas and air into a main combustion chamber, wherein the gas blowing means is provided in a region where char combustion is performed. A waste incinerator, which is provided above a stalker. A grate-type waste incinerator having gas blowing means for blowing exhaust gas or a mixed gas of exhaust gas and air into a main combustion chamber, wherein the gas blowing means extends from the center of the combustion stoker to the end point of the post-combustion stoker. A waste incinerator characterized by being provided above each stoker in the range up to. A grate-type waste incinerator having gas blowing means for blowing exhaust gas or a mixed gas of exhaust gas and air into a main combustion chamber, wherein the gas blowing means is provided with a post-combustion stoker from a burn-off point of the waste. A waste incinerator provided above each stoker in a range up to an end point of the waste incinerator. A grate-type waste incinerator, which has gas blowing means for blowing exhaust gas or a mixed gas of exhaust gas and air into a main combustion chamber, wherein the gas blowing means is an area where intense waste combustion is performed. 2. The waste incinerator according to claim 1, wherein the waste incinerator is provided above each stoker. A grate-type waste incinerator having gas blowing means for blowing exhaust gas or a mixed gas of exhaust gas and air into the furnace, wherein the gas blowing means is provided in a space above the ash discharge chute. A waste incinerator characterized by the following. A grate-type waste incinerator having a secondary combustion chamber for secondary combustion of gas discharged from a main combustion chamber, wherein gas blowing means for blowing exhaust gas or a mixed gas of exhaust gas and air into the furnace. Wherein the gas blowing means is provided at the entrance of the secondary combustion chamber or at the exit of the main combustion chamber. A grate-type waste incinerator, which has an intermediate ceiling, and the flue through which exhaust gas flows is divided into a main flue at the lower part of the furnace exit side and a sub-flue at the upper center of the furnace. A waste incinerator, comprising: gas blowing means for blowing exhaust gas or a mixed gas of exhaust gas and air into the furnace, wherein the gas blowing means is provided in the main flue portion. A grate-type waste incinerator, comprising first and second gas blowing means for blowing exhaust gas or a mixed gas of exhaust gas and air into a main combustion chamber, wherein the first gas blowing means comprises char combustion. Area, the area from the center of the combustion stoker to the end of the post-combustion stoker, the area from the burnout point of the waste to the end of the post-combustion stoker, and the intense combustion of the waste. The second gas blowing means is provided at an upper portion of each stoker in at least one region of the ash discharge chute, and at least one of the space above the ash discharge chute, the entrance of the secondary combustion chamber, and the exit of the main combustion chamber. A waste incinerator characterized by being provided at a location. A grate-type waste incinerator, which has an intermediate ceiling, and the flue through which exhaust gas flows is divided into a main flue at the lower part of the furnace exit side and a sub-flue at the upper center of the furnace. The apparatus has first and second gas blowing means for blowing exhaust gas or a mixed gas of exhaust gas and air into a main combustion chamber, wherein the first gas blowing means has an area where char combustion is performed, combustion At least one of a region from the center of the stalker to the end of the post-burning stoker, a region from the burn-out point of the waste to the end of the post-burning stoker, and a region where the waste is intensely burned; Wherein the second gas blowing means is provided in the main flue section, wherein the second gas blowing means is provided in each of the stokers.

Images