JP2004216289A - Method for heat dechlorination and decomposition of dioxin contained in incinerator fly ash and apparatus therefor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a heat dechlorination and decomposition technique for dioxins-containing incinerator fly ash for carrying out stable dechlorination and decomposition of dioxins by preventing adhesion of fly ash in the inner face of a rotary kiln and thereby suppressing decrease of heat transfer efficiency. <P>SOLUTION: The technique for dechlorination and decomposition of dioxins contained in fly ash comprises the steps of introducing the fly ash separated from a flue gas of a refuse incinerator 9 into an external heating type rotary kiln 3 and heating it at 300-500°C. Fly ash is heated while being mixed with a coarse material having a particle size larger than that of the fly ash and a higher specific gravity than that of the fly ash in the inside of the external heating type rotary kiln 3. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
TECHNICAL FIELD The present invention relates to a method and an apparatus for dechlorinating and decomposing dioxins contained in fly ash by subjecting fly ash separated from exhaust gas from a refuse incinerator (mainly a gasification and melting furnace) to heat treatment.
[0002]
[Prior art]
2. Description of the Related Art Conventionally, as a technique for dechlorinating and decomposing dioxins in fly ash generated in a garbage incinerator, a heat dechlorination and decomposition technique for heating fly ash to 300 to 500 ° C. is known (for example, see Patent Document 1). ).
An example of a conventional thermal dechlorination decomposition technique will be described with reference to FIG.
This heat dechlorination decomposition technology uses an externally heated rotary kiln 3 and is provided with a fly ash hopper 2 for temporarily storing fly ash of a refuse incinerator containing dioxins, and a rotary rotary The main components are an externally heated rotary kiln 3 that heats fly ash at a high temperature by a cylinder 30 to dechlorinate and decompose dioxins, and a cooler 4 that prevents recombination of decomposed dioxins.
[0003]
[Patent Document 1]
Japanese Patent Application Laid-Open No. 2000-205544
Fly ash separated from the exhaust gas from the refuse incinerator is introduced into the inside of the externally heated rotary kiln 3 from the fly ash hopper 2 and heat-treated at 300 ° C. to 500 ° C. to be contained in the fly ash. The dioxins are dechlorinated and decomposed, and fly ash after the heat treatment is introduced into the cooler 4 to prevent resynthesis of dioxins.
[0005]
[Problems to be solved by the invention]
However, in such a conventional thermal dechlorination / decomposition technique, fly ash often adheres to the inner surface of the rotary rotary cylinder 30 serving as a heat transfer surface due to chlorine contained.
Due to the adhered fly ash, the heat transfer efficiency is reduced, and as a result, there is a problem that a temperature rise failure is caused, and not only the dioxin decomposition efficiency is reduced but also the equipment is stopped due to a blockage failure.
[0006]
The present invention has been made in order to solve the above-described problems, and prevents fly ash from sticking to the inner surface of a rotary rotary cylinder, thereby suppressing a decrease in heat transfer efficiency and achieving stable operation. It is an object of the present invention to provide a method and an apparatus for thermally dechlorinating and decomposing incinerator fly ash containing dioxins, which are capable of dechlorinating and decomposing dioxins.
[0007]
[Means for Solving the Problems]
In order to solve the above-mentioned problems, a method for thermally dechlorinating and decomposing incinerator fly ash containing dioxins according to the present invention (claim 1) comprises:
By introducing fly ash separated from the exhaust gas from the garbage incinerator into an externally heated rotary kiln and heat-treating it to 300 ° C to 500 ° C, the dioxins contained in the fly ash are dechlorinated and decomposed. So,
The fly ash was heat-treated in the externally heated rotary kiln while being mixed with coarse particles having a particle size larger than the fly ash and a specific gravity larger than the fly ash.
[0008]
In addition, the method for thermally dechlorinating and decomposing incinerator fly ash containing dioxins according to the present invention (claim 2) comprises:
In the thermal dechlorination decomposition method according to claim 1,
The specific gravity of the coarse particles was 1 or more, and the particle size was 0.1 mm to 10 mm.
[0009]
In addition, the method for thermally dechlorinating and decomposing incinerator fly ash containing dioxins according to the present invention (claim 3) comprises:
In the thermal dechlorination decomposition method according to claim 1 or 2,
The mixing ratio of the coarse particles to the fly ash was 1% to 50% by weight.
[0010]
In addition, the method for thermally dechlorinating and decomposing incinerator fly ash containing dioxins according to the present invention (claim 4) comprises:
In the thermal dechlorination decomposition method according to claim 1 or 2 or 3,
After discharging the fly ash and coarse particles heat-treated in the mixed state from the externally heated rotary kiln, the fly ash and the coarse particles are separated, and the separated coarse particles are returned to the externally heated rotary kiln and circulated. The embodiment was made to reuse.
[0011]
In addition, the method for thermally dechlorinating and decomposing incinerator fly ash containing dioxins according to the present invention (claim 5) comprises:
In the thermal dechlorination decomposition method according to claim 4,
In this embodiment, the coarse particles separated from the fly ash are returned to the externally heated rotary kiln while being heated.
[0012]
In addition, the apparatus for heating and dechlorinating incinerator fly ash containing dioxins of the present invention (claim 6) comprises:
A fly ash hopper for temporarily storing fly ash from a refuse incinerator containing dioxins and a fly ash discharged from the fly ash hopper are introduced, and the fly ash is heated at 300 ° C to 500 ° C to obtain dioxin. An externally heated rotary kiln that dechlorinates and degrades
A fly ash discharged from the externally heated rotary kiln is provided, and a cooler for preventing re-synthesis of dioxin decomposed by cooling the fly ash is provided. Is larger than the particle size of fly ash and has a configuration in which coarse particles having a specific gravity larger than the specific gravity of fly ash are accommodated.
[0013]
Further, the apparatus for heating and dechlorinating incinerator fly ash containing dioxins of the present invention (claim 7) comprises:
In the thermal dechlorination apparatus according to claim 6,
A coarse separator for separating mixed fly ash and coarse particles discharged from an externally heated rotary kiln;
A mode is provided in which a coarse particle return conveyor for returning the coarse particles separated by the coarse particle separator to the externally heated rotary kiln is provided.
[0014]
Further, the apparatus for heating and dechlorinating incinerator fly ash containing dioxins according to the present invention (claim 8) comprises:
The thermal dechlorination decomposition method according to claim 7,
In the embodiment, the coarse particle separator is a gravity separator using a specific gravity difference between fly ash and coarse particles or a screen separator using a particle diameter difference between fly ash and coarse particles.
[0015]
In addition, the apparatus for heating and dechlorinating incinerator fly ash containing dioxins of the present invention (claim 9) comprises:
The thermal dechlorination apparatus according to claim 7 or 8,
In the embodiment, a heater for heating the coarse particles is provided in the middle of the coarse particle transfer conveyor.
[0016]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to examples shown in the drawings. The specific configuration of the present invention is not limited to this embodiment.
FIG. 1 is a system flow diagram of an apparatus for thermally dechlorinating and decomposing incinerator fly ash containing dioxins according to one embodiment of the present invention.
[0017]
The thermal dechlorination apparatus 1 of this embodiment is incorporated in an exhaust gas treatment system 99 provided in a gas melting furnace 9 as a refuse incinerator.
In the gas melting furnace 9, dust is fed from a dust supply device 91 provided at the furnace upper portion, and a supporting gas (oxygen) is supplied from a gas supply nozzle 92 provided at the furnace bottom portion, and the fed dust is dried to form an upper layer. Through the zone, it is pyrolyzed and carbonized in the middle layer pyrolysis zone, and the carbonized ash (char) is melted and discharged in the lower melting zone.
[0018]
Exhaust gas (product gas) generated by thermal decomposition in the gas melting furnace 9 rises in the furnace and is introduced into the exhaust gas processing system 99.
The exhaust gas processing system 99 is provided with a gas combustion chamber 93, a combustion gas cooling chamber 94, and a dust collector 95 (a bag filter, an electric dust collector, and the like) in this order from the upstream side. After passing through the induction blower 96, the air is finally discharged from the chimney 97 to the outside air.
[0019]
The thermal dechlorination apparatus 1 according to the present embodiment mainly includes a fly ash hopper 2, an externally heated rotary kiln 3, and a cooler 4, and further includes a coarse particle separator 5, a fly ash transfer line 6, , A coarse particle return conveyor 7 and a heater 8 are added.
[0020]
The externally heated rotary kiln 3 includes a rotary rotary cylinder 30, an external heating case 31 for externally heating the rotary rotary cylinder 30, and a feeder 32 for supplying fly ash from the inlet of the rotary rotary cylinder 30 to the inside. Outlet champ 33 for discharging the heated fly ash from the outlet of the rotary rotary cylinder 30.
[0021]
The rotary rotary cylinder 30 is inclined slightly downward in the direction of the outlet, so that fly ash is continuously discharged while moving the fly ash in the direction of the outlet along with the rotational movement.
Further, the rotary rotary cylinder 30 is heated by an external heating case 31 equipped with a heating means such as a heat transfer heater, and the inner surface is heated to a set temperature (for example, 550 ° C.) equal to or higher than the dioxin decomposition temperature. Thereby, the accommodated fly ash receives heat from the inner surface of the rotary rotary cylinder 30 and is heated at the dioxin decomposition temperature.
The rotary rotary cylinder 30 may be a single cylinder type or a multi-tube filling type.
[0022]
The rotary rotary cylinder 30 contains coarse particles.
As the coarse particles, small metal particles such as silica stone and iron are used, and those having a particle size of about 0.1 mm to 10 mm can be used, but 0.5 mm, 1 mm, 2 mm, 3 mm, 4 mm, It is preferable to use one of about 5 mm.
The specific gravity of the coarse particles is preferably at least one in view of the specific gravity of fly ash being 0.3 to 0.4.
The mixing ratio of the coarse particles to the fly ash is 1% to 50% by weight. When the mixing ratio exceeds 50%, the amount of the coarse particles is too large, and the fly ash receives heat from the inner surface of the rotary rotary cylinder 30. And the efficiency of dechlorination and decomposition of dioxin decreases.
[0023]
Next, a heat dechlorination decomposition method using the heat dechlorination decomposition apparatus 1 of the present embodiment will be described.
First, a preheating operation is performed before the fly ash to be treated is supplied to the externally heated rotary kiln 3.
By this preheating operation, the inner surface of the rotary rotary cylinder 30 is heated to a set temperature equal to or higher than the dioxin decomposition temperature, and the simultaneously contained coarse particles are continuously discharged from the rotary rotary cylinder 30 in a preheated state. Is done.
[0024]
The coarse particles preheated in the rotary rotary cylinder 30 move inside the rotary rotary cylinder 30, are continuously discharged, are introduced into the coarse particle separator 5 from the outlet champ 33, and pass therethrough. After that, it is continuously returned to the entrance of the rotary rotary cylinder 30 by the coarse particle return conveyor 7.
[0025]
A heater 8 is attached to the coarse-grained material return conveyor 7, and the coarse-grained material being returned is heated by the heater 8 (for example, 550 ° C.). As the coarse particle return conveyor 7, a conveyor capable of external heating, such as a screw conveyor or a drag chain conveyor, is used.
[0026]
After performing the preheating operation as described above, fly ash is supplied to the externally heated rotary kiln 3 and the main operation is performed by the thermal dechlorination apparatus 1.
That is, fly ash contained in the exhaust gas from the gas melting furnace 9 is separated and collected by the dust collector 95, and the separated and collected fly ash is collected in the fly ash hopper 2.
This fly ash is fine particles having a particle size of 1 μm to 20 μm, and contains harmful dioxins in addition to metal oxides and salts.
As one method of detoxifying dioxin, a method of decomposing by heating to a temperature in the range of about 300 ° C. to 500 ° C. has been put to practical use. However, since fly ash contains salts and the like, heat transfer It often adheres to the inner surface of the rotary rotary cylinder 30 serving as a surface to hinder heat transfer.
For the purpose of preventing fly ash from adhering to such a heat transfer surface, coarse particles (silica sand or small metal particles) are accommodated in the rotary rotary cylinder 30, and the coarse particles allow the heat transfer surface to be heated. By polishing the inner surface of the rotary rotary cylinder 30 to prevent fly ash from adhering to the heat transfer surface.
[0027]
In the thermal dechlorination decomposition method of the present embodiment, fly ash is supplied from the fly ash hopper 2 into the rotary rotary cylinder 30 via the rotary valve 21 and the feeder 32, following the preheating operation.
Fly ash flows into the rotary rotary cylinder 30 rotating from the inlet of the rotary rotary cylinder 30 and is mixed with the heated coarse particles.
Inside the rotary rotary cylinder 30, the fly ash is heated by receiving heat from the inner surface of the rotary rotary cylinder 30 serving as a heat transfer surface, and when it reaches a dioxin decomposition temperature, dioxin is decomposed.
At this time, since the inner surface of the rotary rotary cylinder 30 serving as a heat transfer surface is polished with coarse particles, it is possible to prevent fly ash from adhering, and at the same time, it has a function of stirring fly ash. The effect of heat transfer to fly ash can also be improved.
[0028]
The mixture of the fly ash and the coarse particles heated inside the rotary rotary cylinder 30 is transferred with the rotation of the rotary rotary cylinder 30 and discharged to the outlet champ 33, and then is discharged to the coarse separator 5. It is introduced continuously, where fly ash and grit are separated.
The coarse particle separator 5 may be of a screen type or a gravity type utilizing a specific gravity difference between fly ash and coarse particles.
[0029]
The fly ash separated by the coarse particle separator 5 is immediately sent to the cooler 4 through the fly ash transfer line 6, thereby preventing re-synthesis of dioxin.
On the other hand, the separated coarse particles are returned to the inlet of the rotary rotary cylinder 30 by the coarse particle return conveyor 7, and are heated by the heater 8 on the way.
As a result, the coarse particles can be returned to the rotary rotary cylinder 30 in a heated state, thereby preventing the rotary rotary cylinder 30 from cooling and stabilizing the dioxin treatment temperature at an appropriate temperature.
[0030]
【The invention's effect】
As described above, in the present invention, the coarse ash is accommodated in the externally heated rotary kiln, and the coarse ash is mixed with fly ash for heat treatment. Can be prevented from sticking to the inner surface of the member. Thus, a decrease in heat transfer efficiency is suppressed, and stable dechlorination of dioxins can be performed. At the same time, the effect of stirring fly ash is also provided, so that the heat transfer effect to fly ash can be improved.
[0031]
Further, if fly ash discharged from the externally heated rotary kiln and coarse particles are separated by a coarse particle separator, and the separated coarse particles are returned to the externally heated rotary kiln to be circulated and reused. Items 4 and 7), the coarse particles can be continuously supplied to and stored in the externally heated rotary kiln, and the work efficiency can be improved.
[0032]
Further, when the coarse particles are heated and returned to the externally heated rotary kiln (claims 5 and 8), the rotary rotary cylinder is prevented from cooling and the dioxin treatment temperature is stabilized at an appropriate temperature. In addition, since the heating efficiency can be improved, the equipment of the externally heated rotary kiln can be reduced in size.
[Brief description of the drawings]
FIG. 1 is a system flow diagram of an apparatus for thermally dechlorinating and decomposing incinerator fly ash containing dioxins according to one embodiment of the present invention.
FIG. 2 is a system flow diagram showing one example of a conventional apparatus for thermally dechlorinating and decomposing incinerator fly ash containing dioxins.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Heat dechlorination decomposition apparatus 2 Fly ash hopper 21 Rotary valve 3 External heating rotary kiln 30 Rotary rotary cylinder 31 External heating case 32 Feeder 33 Outlet champer 4 Cooler 5 Coarse particle separator 6 Fly ash transfer line 7 Coarse particle Return conveyor 8 Heater 9 Gas melting furnace 91 Dust supply device 92 Gas supply nozzle 93 Gas combustion chamber 94 Combustion gas cooling room 95 Dust collector 96 Induction blower 97 Chimney 99 Exhaust gas treatment system

Claims (9)

By introducing fly ash separated from the exhaust gas from the garbage incinerator into an externally heated rotary kiln and heat-treating it to 300 ° C to 500 ° C, the dioxins contained in the fly ash are dechlorinated and decomposed. So,
The fly ash, inside the external heating rotary kiln, the particle diameter is larger than the particle diameter of the fly ash, and the specific gravity is subjected to heat treatment in a state of being mixed with coarse particles larger than the specific gravity of the fly ash Dechlorination decomposition method of incinerator fly ash containing dioxins. In the thermal dechlorination decomposition method according to claim 1,
A method for heating and dechlorinating incinerator fly ash containing dioxins in which the specific gravity of the coarse particles is 1 or more and the particle size is 0.1 mm to 10 mm. The thermal dechlorination decomposition method according to claim 1 or 2,
A method for heating and dechlorinating incinerator fly ash containing dioxins in which the mixing ratio of coarse particles to fly ash is 1% to 50% by weight. The method according to claim 1, 2 or 3, wherein the fly ash and the coarse particles heat-treated in a mixed state are discharged from the externally heated rotary kiln, and then the fly ash and the coarse particles are separated. A method for thermally dechlorinating and decomposing incinerator fly ash containing dioxins, in which the separated coarse particles are returned to an externally heated rotary kiln and recycled for reuse. In the thermal dechlorination decomposition method according to claim 4,
A method for thermally dechlorinating and decomposing incinerator fly ash containing dioxins, wherein the coarse particles separated from the fly ash are returned to an externally heated rotary kiln while being heated. A fly ash hopper for temporarily storing fly ash from a refuse incinerator containing dioxins,
An externally heated rotary kiln that introduces fly ash discharged from the fly ash hopper and heat-treats the fly ash to 300 ° C. to 500 ° C. to dechlorinate and decompose dioxins;
A fly ash discharged from the externally heated rotary kiln is provided, and a cooler for preventing re-synthesis of dioxin decomposed by cooling the fly ash is provided. A heat dechlorination / decomposition apparatus for incinerator fly ash containing dioxins, characterized by containing coarse particles having a particle size larger than the fly ash particle size and a specific gravity larger than the fly ash specific gravity. The thermal dechlorination apparatus according to claim 6,
A coarse separator for separating mixed fly ash and coarse particles discharged from an externally heated rotary kiln;
An apparatus for heating and dechlorinating incinerator fly ash containing dioxins, comprising: a coarse particle return conveyor for returning coarse particles separated by the coarse particle separator to the externally heated rotary kiln. In the thermal dechlorination decomposition method according to claim 7,
The incinerator fly ash containing dioxins, wherein the coarse particle separator is a gravity separator using a specific gravity difference between fly ash and coarse particles or a screen separator using a particle size difference between fly ash and coarse particles. Heat dechlorination equipment. The thermal dechlorination apparatus according to claim 7 or 8,
A device for heating and dechlorinating incinerator fly ash containing dioxins, wherein a heater for heating the coarse particles is provided in the middle of the coarse particle transfer conveyor.

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