JP2004163009A - Operating method of waste incineration system and waste incineration system - Google Patents

Abstract

[PROBLEMS] To stabilize combustion in an incinerator to reduce NOx and CO in exhaust gas discharged from the incinerator, and to effectively use sensible heat and kinetic energy of high-temperature exhaust gas in an ash treatment furnace. The present invention provides an operation method of a waste incineration system and a waste incinerator that can save energy by performing the operation.
A high-temperature exhaust gas extracted from an ash treatment furnace for treating incineration ash is blown into a combustion chamber of a waste incinerator.
Further, high-temperature exhaust gas extracted from the ash treatment furnace 8 for treating incineration ash may be blown into the secondary combustion region 17 of the waste incinerator 70.
[Selection diagram] Fig. 1

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a method for operating a waste incineration system that incinerates waste such as general waste, industrial waste, and sewage sludge, and a waste incineration system suitable for performing such an operation method.
[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. 5 shows a schematic diagram of a typical example. The waste 32 put into the hopper 31 is sent to the drying stoker 33 through the chute, dried by the air from below and the radiant heat in the furnace, and heated to ignite.
The waste 32 that has ignited and started burning is sent to a combustion stoker 34, where it is thermally decomposed and gasified by combustion air sent from below, and partly burns. Further, the unburned components in the waste are completely burned by the post-combustion stoker 35. The ash remaining after the combustion is taken out from the main ash chute 36.
[0003]
The combustion is performed in the combustion chamber 37, the secondary combustion is performed in the secondary combustion chamber 41, and the combustible gas is completely burned. The exhaust gas from the secondary combustion chamber 41 is sent to a waste heat boiler 43, and after being subjected to heat exchange, is discharged to the outside via a cooling tower, a bag filter and the like.
[0004]
In such a grate or fluidized bed waste incinerator, when incinerating waste, it is difficult to maintain a constant combustion state in the furnace because the waste consists of many substances with different properties. Therefore, it is inevitable that the distribution of the temperature and the concentration of the combustion gas in the combustion chamber 37 become non-uniform temporally and spatially.
[0005]
As a method for solving such a problem, Japanese Patent Application Laid-Open No. H11-211044 (Patent Document 1) discloses a method in which a high-temperature gas generated by a regenerative burner is blown into a main combustion chamber or a secondary combustion chamber of an incinerator. Is disclosed.
[0006]
This technique is intended to reduce unburned gas, harmful substances, and the like containing a large amount of CO and aromatic hydrocarbons in exhaust gas generated in an incinerator.
[0007]
[Patent Document 1]
JP-A-11-211044
[0008]
[Problems to be solved by the invention]
Conventionally, in a waste incinerator, the ratio (air ratio) obtained by dividing the amount of air actually supplied to the furnace by the theoretical amount of air necessary for combustion of waste is about 1.7 to 2.0. This is larger than the air ratio required for general fuel combustion, ie, 1.05 to 1.2. The reason for this is that waste has a large amount of non-combustible components and is inhomogeneous as compared with other liquid fuels and gaseous fuels, so that a large amount of air is required for combustion. However, as the air ratio increases, the amount of exhaust gas also increases, and a large exhaust gas treatment facility is required.
[0009]
If the air ratio is reduced, the amount of exhaust gas is reduced, and the exhaust gas treatment facility is made compact. As a result, the entire waste incineration facility can be reduced in size and the facility cost can be reduced. In addition to this, the amount of chemicals for exhaust gas treatment can be reduced, so that operating costs can be reduced. Further, since the amount of heat lost due to the inability to recover heat can be reduced, the heat recovery rate of the waste heat boiler is improved, and accordingly, the power generation efficiency of waste power generation can be increased.
[0010]
As described above, although the advantage for the low air ratio combustion is great, there is a problem that the combustion becomes unstable in the low air ratio combustion. That is, when the fuel is burned at a low air ratio, the combustion becomes unstable, and the generation of CO increases, the flame temperature increases locally, the NOx sharply increases, a large amount of soot is generated, and the clinker is generated. In addition, there is a problem that the life of the refractory of the furnace is shortened due to the high temperature and the local high temperature. The combustion technique described in Patent Document 1 described above was insufficient to solve such a problem.
[0011]
The present invention has been made in order to solve the above-mentioned problem, and aims to reduce exhaust gas discharged from an incinerator by reducing NOx and CO by stabilizing combustion in the incinerator. It is an object of the present invention to provide a method of operating a waste incineration system and a waste incinerator that can save energy by effectively utilizing the sensible heat and kinetic energy of high-temperature exhaust gas.
[0012]
[Means for Solving the Problems]
The features of the present invention for solving such a problem are as follows.
[0013]
The invention according to claim 1 is a method for operating a waste incineration system, characterized in that a high-temperature exhaust gas extracted from an ash treatment furnace for treating incineration ash is blown into a combustion chamber of the waste incinerator.
[0014]
The invention according to claim 2 is the method for operating a waste incineration system according to claim 1, wherein an area in the combustion chamber into which the high-temperature exhaust gas is blown is in a range from a combustion start area to a main combustion area.
[0015]
According to a third aspect of the present invention, in the first or second aspect, the area in the combustion chamber into which the high-temperature exhaust gas is blown is an area having an ambient temperature of 400 ° C. or more and a flammable gas. This is the operation method of the incineration system.
[0016]
According to a fourth aspect of the present invention, in any one of the first to third aspects, the temperature (° C.) T of the high-temperature exhaust gas blown into the combustion chamber is 200 or more, and the temperature (° C.) T of the high-temperature exhaust gas The disposal according to any one of claims 1 to 3, wherein the relationship with the concentration (vol.%) C of oxygen contained in the high-temperature exhaust gas is within a range represented by the following formula (1). This is the operation method of the incineration system.
exp (8.05-0.23C) ≦ T ≦ exp (7.40-0.09C) (1)
A fifth aspect of the present invention is the waste incineration system according to any one of the first to fourth aspects, wherein the high-temperature exhaust gas is blown into the combustion chamber from at least a pair of gas outlets provided to face each other. Operating method.
[0017]
According to a sixth aspect of the present invention, there is provided a method for operating a waste incineration system, comprising injecting high-temperature exhaust gas extracted from an ash treatment furnace for treating incineration ash into a secondary combustion area of the waste incinerator. It is.
[0018]
The invention according to claim 7 is a waste incineration system including a waste incinerator and an ash processing furnace for treating incineration ash, wherein high-temperature exhaust gas extracted from the ash processing furnace is supplied to the waste incinerator. A waste incineration system comprising a high-temperature gas blowing means for blowing into a combustion chamber.
[0019]
An eighth aspect of the present invention is the waste incineration system according to the seventh aspect, wherein the high-temperature exhaust gas is blown into the combustion chamber from at least one pair of gas outlets provided to face each other.
[0020]
According to a ninth aspect of the present invention, in the seventh or eighth aspect, the high-temperature gas blowing means includes a high-temperature gas adjusting means for adjusting the oxygen concentration and the high-temperature exhaust gas temperature in the high-temperature exhaust gas extracted from the ash processing furnace. It is a waste incineration system characterized by the following.
[0021]
The invention according to claim 10 is a waste incineration system including a waste incinerator and an ash treatment furnace for treating incineration ash, wherein the incineration ash is treated in a secondary combustion area of the waste incinerator. A waste incineration system characterized by having gas blowing means for blowing high-temperature exhaust gas extracted from the inside of an ash processing furnace.
[0022]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, an embodiment of the present invention will be described.
[0023]
FIG. 1 is a schematic side sectional view showing one embodiment of a waste incineration system to which the present invention is applied. The waste incineration system shown in FIG. 1 is provided to a waste incinerator 70 having a waste heat boiler 12 (a grate-type double-flow furnace) and incineration ash discharged from the combustion chamber 3 of the waste incinerator 70. Although the case where the ash processing furnace 8 for performing the above processing is connected to form an integrated structure is shown, the present invention can be similarly applied when the ash processing furnace 8 is installed as an independent furnace. . The type of the ash processing furnace 8 is not particularly limited. For example, a rotary kiln type, fixed bed type melting furnace or heating furnace can be used.
[0024]
In FIG. 1, a waste 2 put into a hopper 1 is ignited and burned by combustion air supplied from below a grate in a combustion chamber 3 and radiant heat in a furnace. The grate (stoker) is provided to be inclined so as to go down as it goes away from the hopper 1. This grate has two steps, which are divided into three parts.
These three grate are called a drying stoker 25, a burning stoker 26, and a post-burning stoker 27 from the side closer to the hopper 1. In the drying stoker 25, drying and ignition of the waste 2 are mainly performed. The waste 2 is mainly burned in the combustion stoker 26, and the waste 2 is burned and thermally decomposed to release combustible gas together with the combustion gas. The combustion of the waste 2 in the combustion stoker 26 is substantially completed. On the post-combustion stoker 27, the unburned portion of the slightly remaining waste 2 is completely burned.
[0025]
Below and above the combustion chamber 3 on the opposite side of the hopper 1, a main flue 20 and a sub-flue 21 are provided, to which a secondary combustion area 17 of the waste heat boiler 12 is connected and provided. I have. In the combustion chamber 3, a barrier (intermediate ceiling) 11 for dividing the combustion gas is provided near the outlet of the combustion chamber 3, and the flow of the combustion gas is divided into the main flue 20 and the auxiliary flue 21. I'm shedding. The combustible gas and the combustion gas which are divided into the main flue 20 and the sub-flue 21 and discharged from the combustion chamber 3 are guided to the waste heat boiler 12 where they are mixed and stirred. The mixed and agitated combustible gas is subjected to secondary combustion in a secondary combustion region 17 which is a part of the waste heat boiler 12, and then heat-exchanged in the waste heat boiler 12, and the exhaust gas is treated by an exhaust gas treatment facility (not shown). It is cleaned and released into the atmosphere from the chimney.
[0026]
Then, the incineration ash 4 remaining after the combustion passes through the communication passage 5 and enters the unsuitable heat treatment detection / removal unit 6. The unsuitable heat treatment detection / removal unit 6 is provided with a detector for unsuitable heat treatment and a device for discharging the detected unsuitable heat treatment to the outside of the furnace. Inappropriate heat treatment may be selected and removed by a mechanical selection means such as a grid or a sieve instead of the heat treatment inappropriate object detection / removal unit. The incinerated ash 4 from which unsuitable materials for heat treatment have been removed is supplied to an ash processing furnace 8 through a lattice 7, and in the ash processing furnace 8, combustion heat of a heating burner or plasma heating and combustion of unburned substances in the ash The incineration ash is heated by the heat and the radiant heat in the furnace to be detoxified. The heavy metals in the incineration ash are heated and volatilized or enclosed in the molten slag, and the dioxins are volatilized and decomposed, and the heavy metals do not elute and become harmless treated ash containing almost no dioxins. Then, the treated ash is discharged from the chute 15 to the outside of the furnace.
[0027]
Here, the temperature in the ash treatment furnace 8 is set to at least 1300 ° C. or more, preferably 1400 ° C. or more so that the incinerated ash is melted in the case of the melting treatment, and the heavy metals in the incinerated ash are volatilized in the case of the heat treatment. At least 1000 ° C., preferably 1100 ° C. or more. The temperature of the high-temperature exhaust gas extracted from the ash processing furnace 8 is about 900 to 1450 ° C. at the outlet of the ash processing furnace 8.
[0028]
Further, since the combustion chamber 3 of the incinerator and the ash processing furnace 8 are connected to each other, the high-temperature incinerated ash discharged from the combustion chamber 3 is guided into the ash processing furnace 8 without being cooled. Therefore, the thermal efficiency is increased.
[0029]
Note that an extruder or a screw feeder for supplying the incineration ash 4 into the ash processing furnace 8 may be provided in the portion of the lattice 7.
[0030]
An adjustment damper 9 is provided between the heat treatment unsuitable object detection / removal unit 6 and the ash treatment furnace 8 in order to prevent combustion exhaust gas from flowing from the combustion chamber 3 side of the waste incinerator to the ash treatment furnace 8 side. It is preferable to provide them. Instead of providing the adjustment damper 9, the operation is performed so that the incineration ash 4 is always filled in the communication path 5 on the upstream side of the ash processing furnace 8, and the combustion exhaust gas is supplied from the combustion chamber 3 side to the ash processing furnace 8 side as a material seal. May be prevented.
[0031]
A gas blowing port 14 is provided in the ash processing furnace 8, and a mixed gas of fuel and air is blown into the ash processing furnace 8 at a high speed from the gas blowing port 14. The fuel may be a combustible gas generated in a waste incinerator (a combustible gas in the incinerator). Further, the blowing direction of the mixed gas is preferably a tangential direction of the inner wall of the ash processing furnace 8. By setting the blowing direction to be tangential to the inner wall of the ash processing furnace 8, a swirling flame or a tubular flame is generated in the ash processing furnace 8 by the blown gas mixture.
[0032]
Therefore, incineration ash is heated by radiation from these flames or direct heat transfer, and the inner wall of the furnace is heated substantially uniformly. Therefore, burning due to partial solidification of dust or slag or overheating of the inner wall is suppressed. Furthermore, the incineration ash and dust in the air current are collected at the surface layer of the inner wall due to the centrifugal effect of the swirling flow in the ash processing furnace, so that scattering of dust downstream from the ash processing furnace is suppressed.
[0033]
Further, the incineration ash in the ash processing furnace 8 may be heated by the plasma.
[0034]
The high-temperature exhaust gas generated in the ash processing furnace 8 is extracted from the ash processing furnace 8 by the high-temperature gas blowing means 10 and is blown into the combustion chamber 3 of the waste incinerator. The high-temperature exhaust gas is extracted from a position close to the incinerator of the ash processing furnace 8 in consideration of the fact that the piping for guiding the high-temperature exhaust gas to the combustion chamber 3 can reduce heat loss and equipment costs as much as possible. Is preferable.
[0035]
Here, the high-temperature gas blowing means can be constituted by a pipe 10a connecting the ash processing furnace 8 and the combustion chamber 3, and an exhaust gas circulation blower 10b.
[0036]
The high-temperature exhaust gas extracted from the ash processing furnace 8 may be mixed with another gas such as air or a part of the combustion exhaust gas discharged from the waste heat boiler 12. That is, a mixed gas obtained by mixing a high temperature exhaust gas extracted from the ash processing furnace 8 with a gas for adjusting the temperature and / or oxygen concentration may be used. As a means for mixing the high-temperature exhaust gas with another gas, a high-temperature gas adjusting means 10c described later can be used.
[0037]
A gas outlet 16 is provided on the side wall of the combustion chamber 3, and high-temperature exhaust gas extracted from the ash processing furnace 8 by the high-temperature gas blowing means 10 is blown into the combustion chamber 3 from the gas outlet 16. ing.
[0038]
The region in the combustion chamber into which the high-temperature exhaust gas is blown is preferably in a range from a combustion start region to a main combustion region. This is because high-temperature exhaust gas is preferably blown into a region where a large amount of combustible gas is present in order to stabilize combustion. In the grate type or fluidized bed type waste incinerator, the area where a large amount of combustible gas exists is from the combustion start area to the main combustion area.
[0039]
When the waste is incinerated, first, moisture evaporates, then pyrolysis and partial oxidation reactions occur, and flammable gas starts to be generated. Here, the combustion start region is a region in which combustion of the waste starts and a combustible gas starts to be generated by thermal decomposition and partial oxidation of the waste. The main combustion region is a region in which waste is thermally decomposed and burned to generate flammable gas and burn with a flame, at which point the combustion with the flame is completed (burn-off point). The area up to. The area after the burn-off point is a char combustion area (hard combustion area) where solid unburned matter (char) in the waste is burned. In a grate incinerator, the combustion start area is the rear of the drying stoker, and the main combustion area corresponds to the combustion stoker.
[0040]
The high temperature exhaust gas is blown from the combustion start area in the combustion chamber 3 into the main combustion area to form a stagnation area or a swirl area immediately above the waste layer, thereby facilitating the mixing and stirring of the combustible gas generated from the waste. Therefore, as a result of stable combustion, generation of harmful substances such as CO, NOx, and dioxins can be suppressed. Further, the thermal decomposition of the waste is promoted by the radiant heat of the high-temperature exhaust gas, and the generation of combustible gas is performed smoothly.
[0041]
In FIG. 1, the gas outlet 16 is provided above the drying stoker 25 and the upper left side of the combustion stoker 26 corresponding to the main combustion region from the combustion start region in the combustion chamber 3. Here, the thermal decomposition reaction of the waste occurs at a temperature of about 200 ° C., and is almost completed when the temperature reaches about 400 ° C. By injecting the high-temperature exhaust gas into the region where the combustible gas is generated, the mixing and stirring of the combustible gas is promoted, and stable combustion is performed. In the example shown in FIG. 1, the gas outlet 16 is provided at the rear of the drying stoker 25 and the front of the combustion stoker 26 to blow hot exhaust gas at these positions. Depending on the composition and properties of the waste 2, the pyrolysis reaction may be completed at a higher temperature. In this case, the gas outlet 16 is also provided on the rear side (right side in the figure) from the position shown in FIG. Is preferred.
[0042]
Also, as shown in FIG. 1, the gas outlet 16 is located at a position not exceeding 1/2 of the height of the combustion chamber in each region of the main combustion region from the combustion start region, and more preferably, the height of the combustion chamber is It is preferable to provide at a height position not exceeding 1/3. Accordingly, the high temperature exhaust gas blown from the gas outlet 16 exhibits a flame holding effect immediately above the waste layer in the combustion chamber, so that a high temperature region (flame) can be localized just above the waste layer in the furnace. . Therefore, the thermal decomposition of the waste is efficiently performed, and the high-temperature region is further away from the ceiling, so that the extinction near the inner wall is reduced and the degree of burning of the ceiling can be reduced. The “combustion chamber height” refers to the height from the grate or fluidized bed to the ceiling of the combustion chamber in each part of the grate or fluidized bed.
[0043]
Further, it is preferable that the region in the combustion chamber into which the high-temperature exhaust gas is blown is a region where the ambient temperature is 400 ° C. or higher and a combustible gas exists. Thereby, the combustion of the combustible gas can be promoted.
[0044]
In the combustion chamber, a region where the ambient temperature is 400 ° C. or higher and a flammable gas is present is a region in which thermal decomposition of waste is promoted or a region in which thermal decomposition of waste is completed. Is a region where flammable gas is generated and a flame exists. For example, thermal decomposition of paper waste starts at about 250 ° C. and is completed at about 400 ° C. In the case of plastic waste, thermal decomposition starts at about 400 ° C., and completes at about 500 ° C.
[0045]
The high-temperature exhaust gas does not contribute to the combustion of the combustible gas even if it is blown into a region in which only the drying is performed without the thermal decomposition of the waste being started. Therefore, the effect of promoting the reduction of the NOx and the CO in the exhaust gas is small. That is, it is preferable to blow into a region where a large amount of combustible gas exists. By injecting the high-temperature exhaust gas into this region, the combustion of the combustible gas is performed stably.
[0046]
Therefore, for example, a high-temperature exhaust gas is blown into a region where the auxiliary flue gas containing a large amount of combustible gas and the main flue gas are mixed, that is, above the intermediate ceiling 11 and at the entrance of the secondary combustion region 17. The gas outlet may be provided at the side wall, the ceiling, the intermediate ceiling 11, and the entrance of the secondary combustion area 17.
[0047]
The high-temperature exhaust gas has a temperature (° C.) at the time of injection of 200 ° C. or higher, and the temperature (° C.) T of the high-temperature exhaust gas and the concentration (vol.%) C of oxygen contained in the high-temperature exhaust gas. Is preferably adjusted so as to satisfy the following equation (1).
exp (8.05-0.23C) ≦ T ≦ exp (7.40-0.09C) (1)
FIG. 2 shows the relationship between the temperature and the oxygen concentration represented by the above equation (1). Here, line A
T = exp (8.05-0.23C)
Line B is
T ≦ exp (7.40-0.09C)
C line
T = 200
Is equivalent to
[0048]
By blowing high-temperature exhaust gas having the oxygen concentration and temperature in the area surrounded by the A-line, B-line, and C-line into the combustion chamber, the thermal decomposition of waste is promoted and a stagnation area is formed in the space above the waste. As a result, a stable flame can be stabilized. Furthermore, as a result of promoting the mixing of the pyrolysis gas, uniform and stable combustion is promoted, so that the generation of NOx and CO can be significantly reduced.
[0049]
In the region below the line A, the amount of oxygen is insufficient, and the temperature of the gas to be blown is low, so that the combustion of the combustible gas becomes unstable, and as a result, the generation of CO increases. Further, in a region above the B line, high-temperature combustion occurs, and as a result, thermal decomposition and gasification of waste are excessively promoted, and flammable gas is locally burned, so that NOx increases. Further, in a region below the line C, the degree of heating of the waste by radiant heat and sensible heat from the gas to be blown is small, so that thermal decomposition of the waste is not promoted. For example, when the oxygen concentration in the high-temperature exhaust gas is 12%, the temperature of the high-temperature exhaust gas that achieves both low NOx and low CO is in the range of 200 to 550 ° C. When the oxygen concentration in the high-temperature exhaust gas is 15%, the temperature of the high-temperature exhaust gas that achieves both low NOx and low CO is in the range of 200 to 400 ° C.
[0050]
In FIG. 1, at least a pair of gas outlets 16 are provided opposite to both side surfaces of the furnace, and high-temperature exhaust gas is blown from the gas outlets 16. Here, the gas outlet 16 is preferably provided so that the gas blowing direction is horizontal or downward.
[0051]
The combustible gas generated from waste usually flows upward. Therefore, when the blowing direction of the high-temperature exhaust gas is upward, the flow of the combustible gas and the flow of the high-temperature exhaust gas have the same velocity component, and the effect of stirring is reduced, and the effect of blowing the high-temperature exhaust gas is reduced. On the other hand, when the blowing direction of the high temperature exhaust gas is horizontal or downward, the rising combustible gas and the high temperature exhaust gas are well stirred, and the combustion of the combustible gas can be promoted. In order to promote such a stirring action, it is preferable that the gas outlet is provided downward, but if the gas outlet is formed too much, the high-temperature exhaust gas will not reach the entire furnace width direction. Therefore, it is particularly preferable that the angle is in the range of 10 to 20 degrees downward. In general, a factor that is effective in blowing high-temperature exhaust gas is 3T. These are temperature (Temperature), stirring (Turbulence), and residence time (Time). In particular, by blowing high-temperature exhaust gas downward, the stirring (Turbulence) and residence time (Time) can be improved.
[0052]
Further, in order to exert a stirring action of the high-temperature exhaust gas on the entire furnace width direction, it is preferable that the blowing speed of the high-temperature exhaust gas is set to 10 m / sec or more. By providing gas outlets at opposing positions on both sides of the furnace and performing such high-speed blowing, a flammable gas stagnation region is formed in the incinerator. As a result, the residence time of the combustible gas in the furnace increases, and the reaction time with the high-temperature exhaust gas increases, so that the reaction is sufficiently performed. In order to form the stagnation region, it is particularly effective to set the gas outlet downward.
[0053]
FIG. 3 shows an AA ′ sectional view and a BB ′ sectional view in order to show the arrangement of the gas outlets in FIG. However, in FIG. 3, structures not related to the present invention are not shown. In FIG. 3, reference numeral 60 denotes a stagnation region, 61 denotes a furnace wall, 62 denotes a furnace ceiling, 63 denotes a high-temperature exhaust gas, 64 denotes a swirling flow portion, and 65 denotes a combustible gas.
[0054]
High-temperature exhaust gas 63 is ejected from a pair of gas outlets 16 provided on the left and right sides of the furnace wall 61, and when viewed in a sectional view taken along the line AA '(a) of FIG. Collision. Therefore, the stagnation region (combustion stable region) 60 in which the movement of the gas in the furnace is slow and stagnates is formed in the central portion of the furnace.
[0055]
FIG. 3B shows another embodiment, and is a plan sectional view. The directions of the gas outlets 16 are such that their central axes are parallel to each other and are separated by a predetermined distance, so that the high-temperature exhaust gas 63 passes by a predetermined distance at the center of the furnace. Therefore, a swirling flow portion (swirl region) 64 is formed at the center of the furnace.
[0056]
That is, in this embodiment, the stagnation region 60 or the swirling flow portion 64 is formed at the center of the furnace when viewed in plan. Therefore, as described above, the flame is stabilized and the mixing of the gases is promoted.
[0057]
In FIG. 3A, the size of the stagnation region 60 can be controlled by changing the flow rates of the high-temperature exhaust gas ejected from the two gas outlets 16 in the same manner. Further, by providing a difference between the flow rates of the high-temperature exhaust gas ejected from the two gas outlets 16, the position of the stagnation region 60 in the left-right direction of the furnace can be changed. Further, by changing the direction of the gas outlet 16 to the same direction in the front-rear direction of the furnace, the position of the stagnation region 60 in the front-rear direction of the furnace can be changed.
[0058]
In FIG. 3B, the size of the swirling flow portion 64 can be changed by changing the interval between the two high-temperature exhaust gases 63. Further, by providing a speed difference between the two high-temperature exhaust gases 63, it is possible to change the position in the left-right direction of the furnace where the swirling flow portion 64 is formed. Further, by changing the speeds of the two high-temperature exhaust gases 63 in the same manner, the speed of the swirling flow can be changed.
[0059]
FIG. 3C is a cross-sectional view taken along the line BB ′ of FIG. 1, in which the high-temperature exhaust gas 63 blown out from the gas blowout ports 16 provided downward on the furnace walls 61 on both sides is turned into a flammable gas. 5 shows a state in which a stagnation region 60 is formed by colliding with the stagnation region 65. In the stagnation region 60, stable combustion flame is formed as a result of stable combustion. As a result, unlike the prior art, even under low air ratio combustion conditions, the combustion instability in the combustion start region is not amplified, soot and the like are suppressed, and uniform and stable combustion can be expected.
[0060]
In order to exert a stirring action, it is also effective to blow high-temperature exhaust gas into the furnace from the gas outlet 16 as a swirling flow.
[0061]
Further, since blowing the high-temperature exhaust gas to sufficiently stir the gas near the furnace side wall also has an effect of stabilizing the combustion, it is preferable that the blowing speed be at least 10 [m / sec] or more.
[0062]
Further, the blowing amount of the high-temperature exhaust gas is 10 vol. % To 70 vol. %, More preferably 20 vol. % To 30 vol. % Is preferable. The amount of high-temperature exhaust gas to be blown is preferably as small as possible in consideration of exhaust gas treatment and the like. However, when the blowing amount is small, CO and the like are likely to be generated, and the waste cannot be completely burned. Therefore, while monitoring the amount of CO and NOx discharged, the amount of high-temperature exhaust gas to be blown is set to 10 vol. % To 70 vol. %, More preferably 20 vol. % To 30 vol. % Is preferable.
[0063]
Here, the primary air is air that is blown for the purpose of burning waste, and is air that is blown in a conventional waste incinerator that does not blow high-temperature exhaust gas. In general, in the case of a grate type furnace, it is blown from a wind box below a grate, and in the case of a fluidized bed type furnace, it is blown from below a fluidized bed.
[0064]
The blowing amount of the high-temperature exhaust gas is 10 vol. %, The momentum required for stirring the gas in the furnace is not provided, and the effect of blowing the high-temperature gas may not be sufficiently exhibited. The amount of high-temperature gas blown was 70 vol. %, The effect of reducing NOx and CO in exhaust gas is saturated, and it is not only meaningless to increase the amount of high-temperature gas blown, but also the amount of exhaust gas is increased unnecessarily, leading to an increase in exhaust gas treatment equipment. Not preferred.
[0065]
Further, the blowing amount of the high-temperature exhaust gas was set to 20 vol. % To 30 vol. % Is more preferable because the total amount of air blown into the incinerator can be reduced, so that combustion at a lower air ratio becomes possible.
[0066]
In particular, if there is a change in the composition and properties of the waste, the amount of primary air injected may be smaller than the theoretical air amount required to burn the waste, in which case a large amount of high-temperature exhaust gas Is preferably blown to promote complete combustion of waste and to prevent generation of CO.
[0067]
Further, the blowing amount of the high temperature exhaust gas is 10 vol. Of the theoretical air amount necessary for burning the waste. % To 70 vol. %, More preferably 20 vol. % To 30 vol. % May be used.
[0068]
In the above-described embodiment, the primary air amount is used as the reference value of the blowing amount of the high-temperature exhaust gas.However, in some cases, the primary air amount may be equal to or less than the theoretical air amount necessary for completely burning the waste. is there. In such a case, the blowing amount of the high-temperature exhaust gas is set to 10 vol. Of the theoretical air amount necessary for burning the waste. % To 70 vol. %, More preferably 20 vol. % To 30 vol. % May be used. The theoretical amount of air is determined from the composition and properties of the waste.
[0069]
Although FIG. 1 shows a furnace having the intermediate ceiling 11, it is needless to say that the present invention can be applied to a furnace having no such intermediate ceiling.
The high-temperature exhaust gas may be blown from one side surface of the furnace. Furthermore, you may make it blow in from an intermediate ceiling or a ceiling, not from the side of a furnace.
[0070]
In these embodiments, the high-temperature gas blowing means 10 for blowing the high-temperature exhaust gas extracted from the ash processing furnace 8 into the combustion chamber 3 of the waste incinerator has a high-temperature exhaust gas extracted from the ash processing furnace 8. It is preferable to include a high-temperature gas adjusting means 10c for adjusting the oxygen concentration in the medium and the high-temperature exhaust gas temperature. When the temperature and the oxygen concentration of the high-temperature exhaust gas extracted from the ash processing furnace 8 are 200 ° C. or more and satisfy the range of the above-mentioned formula (1), the temperature and the oxygen concentration are directly used in the combustion chamber 3. This is because the temperature and oxygen concentration of the high-temperature exhaust gas extracted from the ash processing furnace 8 may not be included in the predetermined range.
[0071]
FIG. 4 shows an example of the embodiment of the high-temperature gas blowing means 10 according to the present invention. In FIG. 4, the combustion gas from the combustion chamber 3 is guided to a waste heat boiler 12, where it is subjected to secondary combustion in a secondary combustion region 17, which is a part of the combustion gas. The cleaning treatment is performed in the facility 36, and the air is discharged to the atmosphere from the chimney 38 via the blower 37.
[0072]
The exhaust gas blowing means 10 shown in FIG. 4 includes a pipe 10a for connecting a gas outlet provided in the ash processing furnace 8 and a gas outlet 16 provided in the combustion chamber 3, an exhaust gas circulating blower 10b, It has a high-temperature gas adjusting means 10c for adjusting the oxygen concentration and the exhaust gas temperature in the high-temperature exhaust gas extracted from the inside. If the high-temperature exhaust gas contains dust, a dust removing device is provided before the exhaust gas circulation blower 10b.
[0073]
Here, the high-temperature gas adjusting means 10c includes a gas mixing device 50 provided in the middle of the pipe 10a, an air supply pipe 51 connected to the gas mixing device 50, and a gas mixing device 50. And a connected flue gas supply pipe 52.
[0074]
The air supply pipe 51 supplies outside air to the gas mixing device 50 by a blower 56, and the combustion exhaust gas supply pipe 52 supplies a part of the combustion exhaust gas discharged from the waste heat boiler 12 to the gas mixing device 50 by the blower 57. Each gas is mixed in the gas mixing device 50. Further, before the gas mixing device 50 of the pipes 10a, 51, 52 connected to the gas mixing device 50, flow control valves 53, 54, 55 for adjusting the flow rates of the respective gases are provided. The respective flow rates are controlled by signals from the flow rate control device 58. The flow control device 58 controls the opening of the flow control valves 53, 54, 55 so that the temperature and the oxygen concentration of the high-temperature exhaust gas blown into the combustion chamber 3 fall within a predetermined range.
[0075]
When the temperature and oxygen concentration of the high-temperature exhaust gas can be adjusted by the amount of air supplied from the air supply pipe 51 to the gas mixing device 50, the combustion exhaust gas supply pipe 52 does not need to be provided.
[0076]
As described above, this embodiment has a function of adjusting the oxygen concentration and the temperature of the high-temperature exhaust gas blown into the combustion chamber 3. Concentration and temperature can be kept in appropriate ranges. When it is desired to adjust the flow rate and the flow velocity of the high-temperature exhaust gas to be blown, the adjustment may be performed by means such as adjusting the rotation speed of each of the blowers 10b, 56, and 57.
[0077]
Here, the gas mixing device 50 may be an ejector device. In this case, the air supplied from the air supply pipe 51 is guided to an ejector device, which is used as a driving flow to mix and suck high-temperature exhaust gas from the ash processing furnace 8 and blow it into the combustion chamber 3. I do. This eliminates the need for the blower 10b for extracting the high-temperature exhaust gas from the ash processing furnace 8, thereby simplifying the apparatus configuration and reducing troubles due to dust and the like contained in the high-temperature exhaust gas. Become.
[0078]
Further, in the present invention, the high temperature exhaust gas extracted from the ash processing furnace 8 for processing incineration ash is used as a secondary combustion area for performing secondary combustion of combustible gas generated in the combustion chamber 3 of the waste incinerator. It is preferable to have a gas blowing means 68 for blowing into 17.
[0079]
Here, the gas blowing means 68 is composed of a pipe 68a connecting a gas outlet provided in the ash processing furnace 8 and a gas outlet 13 provided on the upstream side in the secondary combustion area 17, and a blower 68b. You. It is preferable that one or a plurality of the gas outlets 13 are arranged so that high-temperature exhaust gas extracted from the ash processing furnace 8 can be blown in a direction in which a swirling flow is generated in the secondary combustion region 17. The high-temperature exhaust gas extracted from the ash processing furnace 8 is swirled and blown into the secondary combustion region, thereby introducing new air and increasing the excess air ratio as in the conventional blowing of secondary combustion air. Without stirring, the inside of the secondary combustion region can be agitated. In addition, in the conventional blowing of the secondary combustion air, the temperature of the secondary combustion region is not sufficiently increased, and the secondary combustion may not be completely performed. By blowing into the next combustion zone, the temperature can be raised and improved. As described above, since the flammable gas is stirred and mixed in the secondary combustion region to increase the ambient temperature, complete combustion of the flammable gas in the secondary combustion region can be performed, and emission of dioxins can be achieved. Can be maintained at the temperature condition of the secondary combustion region. Thereby, emission of harmful substances such as CO, NOx, and dioxins in the exhaust gas can be suppressed. Further, the sensible heat of the high-temperature exhaust gas extracted from the ash processing furnace 8 can be recovered by the exhaust heat boiler 12.
[0080]
The high temperature exhaust gas blown into the secondary combustion region 17 may be mixed with air or combustion exhaust gas for adjusting the temperature and / or oxygen concentration of the high temperature exhaust gas. By adjusting the temperature and / or oxygen concentration of the high-temperature exhaust gas, it becomes possible to further reduce the concentration of CO, NOx, dioxins, and the like in the exhaust gas discharged from the waste heat boiler 12.
[0081]
【The invention's effect】
As described above, according to the present invention, stabilization of combustion in an incinerator reduces NOx and CO in exhaust gas discharged from the incinerator, and further reduces high-temperature exhaust gas in the ash treatment furnace. Provided are an operation method of a waste incineration system and a waste incineration system capable of saving energy by effectively utilizing sensible heat and kinetic energy.
[Brief description of the drawings]
FIG. 1 is a schematic side sectional view showing one embodiment of a waste incineration system to which the present invention is applied.
FIG. 2 is a diagram showing the relationship between the temperature of hot exhaust gas blown into a combustion chamber and the oxygen concentration according to the present invention.
FIG. 3 is a diagram showing an AA ′ section and a BB ′ section in FIG. 1;
FIG. 4 is a diagram showing an example of an embodiment of a high-temperature gas blowing means according to the present invention.
FIG. 5 is a schematic configuration diagram showing an example of a waste incinerator according to the related art.
[Explanation of symbols]
1 Hopper
2 waste
3 Combustion chamber
4 incineration ash
5 connecting passage
6 Unsuitable heat treatment detection / removal unit
7 Grid
8 Ash treatment furnace
9 Adjustment damper
10 Hot gas injection means
10a piping
10b Exhaust gas circulation blower
10c Hot gas adjusting means
11 Barrier (intermediate ceiling)
12 Waste heat boiler
13,16 Gas outlet
14 Gas inlet
15 Chute for processing ash discharge
17 Secondary combustion zone
20 Main flue
21 Secondary flue
22 Plastic injection means
25 dried stoker
26 Burning Stoker
27 Afterburning stoker
50 gas mixing device
51 Air supply piping
52 Flue gas supply piping
53, 54, 55 Flow control valve
56,57 blower
58 Flow control device
60 Stagnation area (combustion stable area)
61 Furnace wall
62 Furnace ceiling
63 High temperature exhaust gas
64 swirling flow section (swirl area)
65 flammable gas
68 Gas injection means
68a piping
68b blower
70 Waste incinerator

Claims (10)

A method for operating a waste incineration system, comprising blowing high-temperature exhaust gas extracted from an ash processing furnace for treating incineration ash into a combustion chamber of the waste incinerator. The method for operating a waste incineration system according to claim 1, wherein an area in the combustion chamber into which the high-temperature exhaust gas is blown is in a range from a combustion start area to a main combustion area. The method for operating a waste incineration system according to claim 1 or 2, wherein a region in the combustion chamber into which the high-temperature exhaust gas is blown is a region where the ambient temperature is 400 ° C or higher and a combustible gas is present. The temperature (° C.) T of the high-temperature exhaust gas blown into the combustion chamber is 200 or more, and the relationship between the temperature (° C.) T of the high-temperature exhaust gas and the concentration (vol.%) C of oxygen contained in the high-temperature exhaust gas is shown. The method for operating a waste incineration system according to any one of claims 1 to 3, wherein the range is represented by the following equation (1).
exp (8.05-0.23C) ≦ T ≦ exp (7.40-0.09C) (1) The method for operating a waste incineration system according to any one of claims 1 to 4, wherein the high-temperature exhaust gas is blown into the combustion chamber from at least a pair of gas outlets provided to face each other. A method for operating a waste incineration system, comprising blowing high-temperature exhaust gas extracted from an ash treatment furnace for treating incineration ash into a secondary combustion area of the waste incinerator. A waste incineration system comprising a waste incinerator and an ash processing furnace for treating incineration ash, wherein a high-temperature exhaust gas extracted from the ash processing furnace is blown into a combustion chamber of the waste incinerator. A waste incineration system comprising gas injection means. The waste incineration system according to claim 7, wherein the high-temperature exhaust gas is blown into the combustion chamber from at least a pair of gas outlets provided opposite to each other. The high-temperature gas injection means includes a high-temperature gas adjusting means for adjusting the oxygen concentration and the high-temperature exhaust gas temperature in the high-temperature exhaust gas extracted from the ash processing furnace. Waste incineration system. A waste incineration system including a waste incinerator and an ash processing furnace for processing incineration ash, wherein the secondary combustion area of the waste incinerator is extracted from an ash processing furnace for processing incineration ash. Waste incineration system characterized by having gas blowing means for blowing hot exhaust gas.

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