JP4013376B2 - Dioxin treatment method in ash - Google Patents

Description

【００２４】
表１から明らかなように、かさ密度が大きくなるにつれて、ダイオキシン類の分解率が高まっている。そしてＣにおけるダイオキシン類の分解率は９９％以上となり、この物理的性質を持つ粒状体に含まれるダイオキシン類が、分解炉２によって確実に熱分解され得ることを示している。なお、Ｃのかさ密度と同じかさ密度を持った粒状体は、３０μｍ以上あるいは数ｍｍといったものであっても、灰Ｃと同程度の分解率を示すことが確かめられている。
【００２５】
【発明の効果】
以上説明したように、第１の発明は、ごみ焼却処理施設などから捕集された灰が所定の粒径の粒状体に造粒されることにより、分解炉内での粒状体の流動性が変動の少ない安定した状態に保たれるので、施設の連続運転を停止するようなトラブルといったものが低減され、生産性が向上する。また、粒状体はある程度の重さと大きさを有しているので炉内で固着するといったことが起こりにくく、分解炉は長期に渡り安定してダイオキシン類を熱分解することができる。
【００２６】
第２の発明は、かさ密度が大きくなるように、灰を圧密して造粒するので、炉内に粒状体が固着するといったことが起こりにくく、灰の成分や性質によらず安定して粒状体が炉内で流動する。またこの粒状体は、輸送によって過度に大きな塊状となるといったことが生じにくく、冷却工程でも速やかに冷却され、冷却過程においてダイオキシン類が再合成することが少ない。さらに、灰は圧密されることによって体積が減少するので、分解炉の輸送効率を高めることが可能となり生産性を高めることができる。また、これに伴い排出される処理灰の体積量が圧密していない灰に比べて減少するので、排出される処理灰の後工程での処理コストを低減することが可能である。さらに、灰のかさ密度が大きくなるとダイオキシン類の分解率が向上するので、本発明の処理方法で示したように、灰をあらかじめ圧密した粒状体に造粒した後に分 解炉で熱分解処理をすることによって、安定して確実に灰に含まれるダイオキシン類を熱分解することが可能となり、ごみ焼却処理施設などでのダイオキシン類の処理対策に効果的に対応することが可能である。
【図面の簡単な説明】
【図１】 本発明方法の実施に使用する処理設備の一実施形態を示す構成図である。
【符号の説明】
１ 造粒手段
２ 分解炉[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a technique for processing dioxins contained in ash by putting ash collected from a waste incineration facility into a decomposition furnace and heating the ash.
[0002]
[Prior art]
In recent years, social interest in dioxins has increased. Commonly referred to as dioxins are PCDD (polychlorinated dibenzo-para-dioxin) and PCDF (polychlorinated dibenzofuran), and these organochlorine compounds are considered to be harmful to the human body. Dioxins are contained in incineration ash and fly ash (flying ash), which is the residue when incineration treatment is performed in waste incineration facilities such as municipal waste and industrial waste. Currently, in various directions, Dioxin disposal measures are taken at the waste incineration facility.
[0003]
Among these measures, a treatment method using a cracking furnace is known as one of the techniques for treating dioxins contained in ash collected from a waste incineration treatment facility. This treatment method is intended to dechlorinate and thermally decompose dioxins contained in the ash by heating the ash produced in a garbage incinerator or the like to a temperature of 300 to 500 ° C. or higher in an inert atmosphere. is there. Further, in this treatment, the ash dechlorinated and pyrolyzed in the cracking furnace is rapidly cooled in the cooling device, thereby preventing resynthesis of dioxins after the pyrolysis treatment.
[0004]
[Problems to be solved by the invention]
However, the ash generated from the waste incineration facility varies greatly in composition and physical properties depending on the climate and timing at the time of processing and the type of incinerator. Moreover, this ash is generally a fine powder of about 10 μm and tends to be hardened when moisture is accompanied. For this reason, if the ash contains a lot of moisture, the generated water vapor will condense at a low temperature in the furnace, and the ash will adhere to the furnace due to this condensation, or the ash has a low melting point metal. When a large amount of the compound is contained, the metal compound is likely to be melted by the heat in the furnace to fix the ash in the furnace. In addition, due to the sticking of ash in the furnace, the fluidity of the ash is deteriorated, and the continuous operation of the cracking furnace may be hindered. In addition, the ash adhered to the inner wall or the like in the furnace may decrease the heating efficiency of the furnace, and the dioxins contained in the ash may not be sufficiently thermally decomposed. Furthermore, the ash transported in the cracking furnace adheres and grows into a lump, and the large lump of ash is not cooled quickly in the cooling process, and dioxins are re-synthesized. It was.
[0005]
This invention is made | formed in view of such a problem, and it aims at preventing the sticking of the ash in a furnace and processing the dioxins contained in ash stably.
[0006]
[Means for Solving the Problems]
In order to solve the above-mentioned problem, the first invention is a method for charging ash collected from a waste incineration facility or the like into a cracking furnace and heating the ash, and collecting dioxins contained in the ash. A technique is adopted in which the ash is granulated in advance into granules having a predetermined particle diameter by a granulating means and then charged into a cracking furnace. In this treatment method, the ash is granulated in advance by a granulating means before being put into the cracking furnace, so that the formed granule is adjusted to a predetermined particle size, and the granular material in the cracking furnace is formed. Fluidity is kept stable with little fluctuation. In addition, since the granular material has a certain weight and size, it is unlikely to be fixed in the furnace, and the decomposition furnace can thermally decompose dioxins stably without lowering the heating efficiency. It becomes possible.
[0007]
A second invention employs a technique in which the granulation means granulates by compacting the ash in the first invention . Since this treatment method granulates by compacting the ash, the granulated granule is adjusted to a predetermined particle size having an appropriate hardness and weight by increasing the bulk density. In addition, since the granular material is in a state of solidified to some extent, it is difficult for the granular material to be fixed in the furnace due to the influence of moisture and a low melting point metal compound, and the granular material is stable in the furnace. While flowing, the thermal decomposition of dioxins is also performed stably. In addition, the granular material has a smaller contact area between the granular materials than the powder, and it is difficult for the granular materials to adhere to each other during transportation or the like to form a large lump. It is cooled and dioxins are less likely to be re-synthesized. The bulk density represents the weight per unit volume in a powder or granular solid.
[0008]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, an embodiment of the present invention will be described with reference to FIG. FIG. 1 shows an example of a basic configuration for treating dioxins contained in ash by granulating the collected ash and then putting it in a cracking furnace and heating it. In FIG. 1, reference numeral 1 denotes a granulating means for granulating ash, reference numeral 2 denotes a cracking furnace, and reference numeral 3 denotes a cooling device, which are sequentially arranged.
[0009]
The granulating means 1 is composed of a rolling device 4 and a granulating device 5. The rolling device 4 is intended to increase the bulk density of the granular material formed by the granulating means 1 by applying a predetermined pressure to the raw material. As the rolling device 4 of the present embodiment, a device including a rotatable twin roll 6 having a hydraulic cylinder is disposed. The rolling device 4 continuously passes the ash between the twin rolls 6 pushed at a predetermined pressure to form a rolled ash sheet. In addition to this, various devices such as a device for producing a sheet by pressing ash with a flat plate die can be applied to the rolling device 4.
[0010]
The granulator 5 aims to make the ash into a granular material having a predetermined particle size. Various granulators 5 are applicable, and the raw material is passed through a breaker that forms a granular material by crushing the raw material between twin rolls with a rotatable groove, or a screen in which a large number of holes are formed. There are a screen granulator for forming a granular material, a compression granulator for forming a granular material by press-molding a raw material with a roll or the like whose surface is processed to be uneven. Moreover, it becomes possible to granulate a stable granular material stably by using these apparatuses in combination.
[0011]
In the granulating apparatus 5 of the present embodiment, a breaker 7 and a screen granulator 8 are arranged downstream thereof. The breaker 7 includes a roll 9 having a blade for crushing the sheet, and twin rolls 10 and 11 which are arranged in two stages downstream of the roll 9 and have grooves formed on the circumferential surface. The screen granulator 8 includes a U-shaped screen 12 in which a number of holes corresponding to a target particle size are formed, and a rotor 13 that supplies raw material to the screen 12.
[0012]
The cracking furnace 2 is a device that heats the granular material to 300 to 500 ° C. or higher while transporting the granular material, and various rotary kilns, screw-type furnaces, and the like are applied. The cooling device 3 has a water-cooled jacket or an air-cooled jacket structure, and includes a coolant supply means for supplying a coolant, and quickly cools the granular material heated in the decomposition furnace 2. The cracking furnace 2 and the cooling device 3 are provided with gas supply means 14 for supplying an inert gas. The inert gas supplied is a gas that promotes the dechlorination and thermal decomposition of dioxins in the cracking furnace 2, and a nitrogen gas or an argon gas is used. Further, in order to remove harmful substances contained in the gas discharged from the cracking furnace 2 and the cooling device 3, the adsorption unit 15 is connected to the discharging unit of the cracking furnace 2 and the cooling device 3.
[0013]
Then, an example of the processing method of the dioxins in the ash which concerns on this invention using the above structural examples is demonstrated with reference to FIG. In this treatment method, ash is granulated into granules having a predetermined particle diameter, and the granules are put into a decomposition furnace 2 and heated to thermally decompose dioxins contained in the ash. Hereinafter, it will be described in detail along the flow of ash.
[0014]
First, ash is put into the rolling device 4. The ash input here is ash collected from a waste incineration facility or the like, and the rolling device 4 rolls the input ash between the twin rolls 6 so that the ash has a thickness of about several mm to 1 cm. The sheet is formed. The pressure at this time is, for example, a value of 10 to 20 MPa, and this pressure is set in advance to a predetermined value so that a sheet having an appropriate thickness and hardness can be formed. Moreover, you may add the binder for promoting granulation to the ash before rolling according to the property etc. of ash. Water can also be used for this binder.
[0015]
The sheet formed by the rolling device 4 is granulated into a granular body having a predetermined particle size by the granulating device 5. First, the breaker 7 crushes the sheet to granulate a granular material having a certain particle size. In this breaker 7, the roll 9 crushes the sheet to form a granular material having a particle size of, for example, several centimeters, and then the twin rolls 10 and 11 crush the granular material stepwise to form a fine granular material. To do. Next, the screen granulator 8 passes the granules formed by the breaker 7 through the screen 12 in which a large number of holes are formed, and adjusts the granules having a particle size of 30 μm to several mm.
[0016]
In other words, the ash collected from the waste incineration facility is mainly a powder having a particle size of around 10 μm. The ash is formed into a sheet by the granulating means 1 and then finely crushed in stages. Granules having a particle size of 30 μm to several mm are granulated. The particle size of the formed granular material is a particle size that does not hinder each function such as transportation in the processing apparatus, and is determined to be an appropriate particle size corresponding to the processing apparatus. For example, the particle size of the granular material is set to 80 so that the cracking furnace 2 and the cooling device 3 used for flowing the collected ash as it is can be used as it is for flowing the granular material. Doing things such as adjusting to ~ 100 μm.
[0017]
Moreover, the rolling apparatus 4 with which the granulation means 1 is equipped aims at granulating a granule with a large bulk density by positively compacting ash. Since the granular material having a large bulk density has an appropriate hardness and weight, it is unlikely to be fixed in the cracking furnace 2. In addition, the contact area between the granular materials is smaller than that of the powder, and the granular materials are less likely to adhere to each other during transportation to form an excessively large lump. For this reason, the granular material has a stable fluidity, and it is difficult to cause trouble in transportation of the granular material. Further, since the volume of the ash is reduced by being compacted, it is possible to increase the transport efficiency in the cracking furnace 2, and the volume of the treated ash to be discharged is smaller than that of the unconsolidated ash.
[0018]
The granulated granule is put into the cracking furnace 2. The granular material in the cracking furnace 2 is heated to a temperature of 300 to 500 ° C. or higher in an inert atmosphere. As a result, the dioxins contained in the granular material are thermally decomposed by dechlorination or the like, and change into a harmless substance for the human body. As described above, since the granular material is compacted and granulated, there is almost no trouble such as sticking of the granular material in the furnace or transportation of the granular material. Therefore, the cracking furnace 2 stably performs the thermal decomposition treatment. It can be carried out.
[0019]
Then, the pyrolyzed granular material is sent to the cooling device 3 and rapidly cooled in an inert atmosphere. The cooling device 3 is intended to prevent dioxins thermally decomposed in the cracking furnace 2 from being re-synthesized during the cooling process. When the particle size of the ash formed in a lump shape during transportation is as large as several centimeters, the ash may not be quickly cooled during the cooling process, but the granulated granule as described above is 30 μm to several When the particle size is mm, the cooling device 3 can quickly cool the granular material.
[0020]
Further, in the cracking furnace 2 and the cooling device 3, even when a harmful substance such as dioxins is included in the gas, the gas is adsorbed by the adsorbing unit 15 together with the inert gas sent from the gas supply means 14. To remove harmful substances such as dioxins in the gas.
[0021]
By the treatment method as described above, it is possible to realize a process for stably treating dioxins contained in ash. Note that the configurations and processing methods shown in the above-described embodiments are merely examples, and various modifications can be made without departing from the spirit of the present invention.
[0022]
Next, Table 1 shows the decomposition rate of dioxins in ash and granules in three different granulated states. In the table, A is an ungranulated ash in a collected state, and B and C are granules obtained by compacting and granulating the ash by the granulating means 1. Compared to B, C is in a more compact state and has a higher bulk density.
[0023]
[Table 1]

[0024]
As is clear from Table 1, the decomposition rate of dioxins increases as the bulk density increases. The decomposition rate of dioxins in C is 99% or more, which indicates that the dioxins contained in the granular material having this physical property can be reliably thermally decomposed by the decomposition furnace 2. In addition, it has been confirmed that a granular material having the same bulk density as C has a decomposition rate comparable to that of ash C even if it is 30 μm or more or several mm.
[0025]
【The invention's effect】
As described above, according to the first invention , the ash collected from the waste incineration facility or the like is granulated into granules having a predetermined particle size, whereby the fluidity of the granules in the cracking furnace is increased. Since a stable state with little fluctuation is maintained, troubles such as stopping the continuous operation of the facility are reduced, and productivity is improved. Further, since the granular material has a certain weight and size, it is unlikely to be fixed in the furnace, and the decomposition furnace can thermally decompose dioxins stably over a long period of time.
[0026]
In the second invention , since the ash is compacted and granulated so as to increase the bulk density, it is difficult for the granular material to stick in the furnace, and the ash is stably granulated regardless of the components and properties of the ash. The body flows in the furnace. In addition, the granular material is unlikely to become an excessively large lump by transportation, and is quickly cooled even in the cooling process, and dioxins are hardly re-synthesized in the cooling process. Furthermore, since the volume of ash is reduced by being consolidated, it is possible to increase the transport efficiency of the cracking furnace and increase the productivity. Moreover, since the volume amount of the processed ash discharged | emitted with this reduces compared with the ash which is not compacted, it is possible to reduce the processing cost in the post process of the discharged processed ash. Furthermore, as the bulk density of ash increases, the decomposition rate of dioxins increases. Therefore, as shown in the treatment method of the present invention, the ash is granulated into pre-consolidated granules and then pyrolyzed in a cracking furnace. By doing so, it becomes possible to thermally decompose the dioxins contained in the ash stably and reliably, and it is possible to effectively cope with measures for treating dioxins in a waste incineration facility.
[Brief description of the drawings]
FIG. 1 is a configuration diagram showing an embodiment of a processing facility used for carrying out the method of the present invention.
[Explanation of symbols]
1 Granulation means 2 Cracking furnace

Claims (1)

In a method of treating dioxins contained in the ash by heating the ash collected from a waste incineration facility into a cracking furnace (2) and heating it,
After the ash is granulated by granulating means (1) to form a sheet of ash by rolling the ash between twin rolls (6), the sheet is crushed by a breaker (7) and granulated. After crushing to form fine granules, the fine granules are passed through a screen (12) in which a large number of holes are formed to prepare granules with a predetermined particle size, and then charged into the cracking furnace (2). And
The granule heated in the cracking furnace (2) is quickly cooled by a cooling device (3),
Furthermore, the dioxins contained in the exhaust gas from the furnace and the cooling device are removed by the adsorption section (15).

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