JP3587241B2 - Method of treating incinerated ash and industrial waste disposal site using it - Google Patents

Description

【００３７】
同表でわかるように、山砂のｐＨがほぼ中性、粘性土のｐＨが弱酸性であるのに対し、泥岩のｐＨは強酸性を示した。また、酸化に伴う潜在的なｐＨを調べるｐＨ（Ｈ_２Ｏ_２）試験では、山砂と粘性土ではわずかなｐＨ低下しか観察されないのに対し、泥岩では１．８まで低下し非常に強い酸性を呈することがわかった。これは、パイライトの酸化による硫酸生成によるものと考えられる。
【００３８】
次に、試験材料が有する定量的なｐＨ緩衝能力を調べるため、石炭灰２００ｇ、湿潤状態の試験材料０〜２００ｇ及び蒸留水２００ｇを密閉容器に入れ、２００回／分の往復振とうを６時間行い、これをｐＨの変化が認められなくなるまで繰り返した。
【００３９】
その結果を図２に示す。同図は、上述の振とうを１０回繰り返したものであるが、同図でわかるように、石炭灰のみでは１３．８と非常に高いｐＨであるのに対し、石炭灰に対する試験材料の割合が大きくなるにつれてｐＨが低下すること、特に泥岩の場合にｐＨが大きく低下することがわかった。
【００４０】
次に、石炭灰と試験材料を層状に配置して連続通水した場合の試験材料のｐＨ緩衝能力を調べるため、カラム試験を行った。カラム試験は、直径１０ｃｍ、高さ１８０ｃｍのアクリル製円筒に試験材料と石炭灰を下から順に２４ｃｍ、９６ｃｍの厚みでそれぞれ積層し（石炭灰と試験材料の高さ比は４：１）、かかる状態でカラム上部から注水を行った。
【００４１】
図３に浸透水量とｐＨの関係を示す。同図でわかるように、山砂の場合にはｐＨ緩衝能力が持続せず、透水量が１０リットルを超えると、ｐＨが急激に上昇するのに対し、泥岩の場合には、実験終了（透水量３４リットル）までｐＨが基準上限値である８．６を上回ることはなかった。
【００４２】
図４に、カラム解体後のｐＨ分析結果を示す。同図でわかるように、石炭灰層のｐＨは、山砂を用いた場合と泥岩を用いた場合とでほとんど差がなく、どちらも透水によるアルカリイオンの溶脱が原因と思われる若干のｐＨ上昇が深さ方向に見られた。
【００４３】
一方、石炭灰層の下においては、山砂の場合には、石炭灰層のｐＨとほとんど変わりがない、すなわち石炭灰間隙水が山砂層からｐＨ緩衝を受けることなくそのまま通過したのに対し、泥岩の場合には、下方にいくにつれてｐＨが低下し、石炭灰間隙水が泥岩層からｐＨ緩衝を受けていることがわかった。
【００４４】
本実施形態では、焼却灰を石炭灰としたが、石炭灰以外に廃棄物等を焼却した後の灰についても本発明の焼却灰として取り扱うことができることは言うまでもない。
【００４５】
また、本実施形態では、泥岩４からなるｐＨ緩衝層５を石炭灰層３の上に配置するようにしたが、ｐＨ緩衝層５で生成される硫酸イオンが相対的に少ないのであれば、図５のように配置順序を入れ替え、ｐＨ緩衝層５を石炭灰層３の下に配置するようにしてもよい。
【００４６】
同図に示す変形例においては、石炭灰層３中のアルカリ分が土中を降下してｐＨ緩衝層５で生成された硫酸イオンと反応し、該ｐＨ緩衝層内にて中和反応が行われるとともに、降下したアルカリ分がｐＨ緩衝層５を構成する泥岩４内の粘土コロイド粒子に吸着してイオン交換作用が行われることとなるため、石炭灰２の中和は、上述の実施形態によりもさらに効率的に行われる。なお、ｐＨ緩衝層５の厚みを適宜調整することによって該ｐＨ緩衝層での硫酸イオンの生成量を比較的少なくすれば、石炭灰層３中のアルカリ分と反応せずに残存する硫酸イオンの量も少なくなり、地下水系に流入して該地下水を酸性化させるリスクを減少させることができる。
【００４９】
（第２実施形態）
【００５０】
次に第２実施形態に係る焼却灰の処理方法及びそれを用いた産業廃棄物処分場について説明する。なお、上述の実施形態と実質的に同一の部品等については同一の符号を付してその説明を省略する。
【００５１】
本実施形態に係る焼却灰の処理方法にしたがって焼却灰としての石炭灰を埋設し、産業廃棄物処分場を構築するには、まず、図１（ａ）に示すように、ショベル等を用いて地盤を掘削し、埋設空間１を確保する。
【００５２】
次に、同図（ｂ）に示すように埋設空間１の底部に砂質土１１を埋設し、５０ｃｍ程度の厚みに敷き均した後、必要に応じて転圧し、防護層１２を形成する。
【００５３】
次に、同図（ｃ）に示すように、防護層１２の上に石炭灰２を埋設し、ブルドーザ等を用いて例えば３ｍ程度の厚みに敷き均した後、必要に応じて転圧し、焼却灰層としての石炭灰層３を形成するとともに、その上に例えば５０ｃｍ程度の厚みの硫化物含有物質としての泥岩４からなるｐＨ緩衝層５を同様に形成する。そして、かかる手順を繰り返すことで、石炭灰層３を最下層とし、石炭灰層３とｐＨ緩衝層５が下から順に交互に積層配置された廃棄物処分場を構築する。なお、必要であれば、最上層となる石炭灰層３若しくはｐＨ緩衝層５の上を覆土しておく。
【００５４】
本実施形態に係る焼却灰の処理方法及びそれを用いた産業廃棄物処分場においては、泥岩４からなるｐＨ緩衝層５が石炭灰２から溶出したアルカリ分に対して優れたｐＨ緩衝作用を発揮する。すなわち、泥岩４には粘土分が含まれており、該粘土分のコロイド粒子がアルカリ金属やアルカリ土類金属を吸着していわゆるイオン交換作用を果たすが、泥岩４にはパイライト（ＦｅＳ_２）及び酸性であるその酸化物も含まれており、それらが石炭灰２から溶出したアルカリ分を中和するとともに、パイライトが酸化されることによって多量の硫酸イオンが生成され、かかる硫酸イオンが石炭灰２から溶出したアルカリ分を効率的に中和する。
【００５５】
具体的に説明すると、ｐＨ緩衝層５で生成された硫酸イオンは、その下にある石炭灰層３中のアルカリ分と反応し、該石炭灰層内にて中和反応が行われる。また、石炭灰層３中のアルカリ分は、その下にあるｐＨ緩衝層５で生成された硫酸イオンと反応し、該ｐＨ緩衝層内にて中和反応が行われるとともに、ｐＨ緩衝層を構成する泥岩４内の粘土コロイド粒子に吸着してイオン交換作用が行われる。
【００５６】
ここで、最下層である石炭灰層３においては、上層のｐＨ緩衝層５による作用によって中和されないアルカリ分が残存することが考えられるが、かかる残存アルカリ分については、その下に配置された防護層１２によって環境への拡散が防止される。すなわち、残存アルカリ分は、防護層１２を構成する砂質土に含まれている粘土分のコロイド粒子に吸着されるため、地下水系に滲出する懸念はない。
【００５７】
なお、ｐＨ緩衝層５は最下層である石炭灰層３の上に配置してあるため、ｐＨ緩衝層５で生じた硫酸イオンは、石炭灰層３で中和されるとともにさらにその下にある防護層１２で阻止されるため、環境への拡散は未然に防止される。
【００５８】
以上説明したように、本実施形態に係る焼却灰の処理方法及びそれを用いた産業廃棄物処分場によれば、泥岩４からなるｐＨ緩衝層５が石炭灰２から溶出したアルカリ分に対して優れたｐＨ緩衝作用を発揮し、石炭灰２の中性化を大幅に促進させることが可能となる。
【００５９】
そのため、石炭灰を自然に中性化させる場合においてきわめて長期間を要するという弊害や、薬剤で中和させる場合において多額の費用を要するという弊害を生じることなく、比較的短期間にかつ低コストで貴重な土地資源である埋立地の跡地利用を早期に開始することができる。
【００６０】
また、薬剤による中和ではないため、化学的問題を発生させることなく長期間にわたって穏やかな持続性が期待できる、ｐＨ緩衝層５が泥岩４という土材料であるため、施工管理が容易であるとともに施工後の地盤力学特性が把握しやすいといった作用効果を奏するほか、急激なｐＨ低下による石炭灰からの重金属溶出、降雨による作用低下といったことを懸念する必要がない。
【００６１】
また、本実施形態に係る焼却灰の処理方法及びそれを用いた産業廃棄物処分場によれば、石炭灰層３を最下層とするとともに該最下層の下に防護層１２を配置したので、最下層の石炭灰層３内にアルカリ分が残存したとしても、その下に配置された防護層１２によって環境への拡散が防止されるとともに、ｐＨ緩衝層５で生じた硫酸イオンは、石炭灰層３で中和されるとともにさらにその下にある防護層１２で阻止されることとなり、残存アルカリ分や硫酸イオンが地下水系に滲出するのを確実に防止することが可能となる。
【００６２】
本実施形態では、焼却灰を石炭灰としたが、石炭灰以外に廃棄物等を焼却した後の灰についても本発明の焼却灰として取り扱うことができることは言うまでもない。
【００６５】
【発明の効果】
以上述べたように、本発明に係る焼却灰の処理方法及びそれを用いた産業廃棄物処分場によれば、硫化物含有物質からなるｐＨ緩衝層が焼却灰から溶出したアルカリ分に対して優れたｐＨ緩衝作用を発揮し、焼却灰の中性化を大幅に促進させることが可能となる。
【００６６】
そのため、焼却灰を自然に中性化させる場合においてきわめて長期間を要するという弊害や、薬剤で中和させる場合において多額の費用を要するという弊害を生じることなく、比較的短期間にかつ低コストで貴重な土地資源である埋立地の跡地利用を早期に開始することができる。
【００６７】
【図面の簡単な説明】
【図１】第１実施形態に係る焼却灰の処理方法の施工手順を示した断面図。
【図２】第１実施形態に係る焼却灰の処理方法の作用を確認するための実験結果を示したグラフ。
【図３】同じく第１実施形態に係る焼却灰の処理方法の作用を確認するための実験結果を示したグラフ。
【図４】同じく第１実施形態に係る焼却灰の処理方法の作用を確認するための実験結果を示したグラフ。
【図５】変形例に係る焼却灰の処理方法を示した断面図。
【図６】第２実施形態に係る焼却灰の処理方法及びそれを用いた産業廃棄物処分場を示した断面図。
【符号の説明】
２ 石炭灰（焼却灰）
３ 石炭灰層（焼却灰層）
４ 泥岩（硫化物含有物質）
５ ｐＨ緩衝層
１１ 砂質土
１２ 防護層[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a method for treating incinerated ash such as coal ash generated in large quantities from a thermal power plant and an industrial waste disposal site using the same.
[0002]
[Prior art]
Most of the incinerated ash, such as coal ash generated from thermal power plants and ash generated after incineration of waste, is almost landfilled unless it can be recycled, but such incinerated ash, especially coal ash, is discarded. In the case of landfill treatment at a landfill, high-alkaline leaching water is generated with permeation of rainwater, and if left as it is, alkali components may flow into the groundwater system together with rainwater.
[0003]
Therefore, even after the landfill disposal is completed, the leachate from the coal ash is collected in the collection and drainage structure laid on the bottom of the disposal site, and the pH of the leachate is set to a predetermined drainage standard, for example, 5.8 to 8.6. The water is pumped up until neutralization is cleared, neutralized, and then discharged to prevent the exuded components from the landfill material from diffusing into the environment.
[0004]
[Problems to be solved by the invention]
However, the elution of alkali content from incinerated ash such as coal ash is prolonged, and the above-mentioned work is also performed over a long period of time, thus requiring only a large processing cost for elution of alkali content. However, the use of the landfill, which is a valuable land resource, has been delayed, or the use of the landfill has become substantially difficult.
[0005]
The present invention has been made in view of the above-described circumstances, and a method for treating incinerated ash that can promptly start using the site of the incinerated ash when landfilling the incinerated ash, and industrial waste disposal using the same. The purpose is to provide a place.
[0006]
[Means for Solving the Problems]
In order to achieve the above object, the method for treating incinerated ash according to the present invention, when burying incinerated ash, disposes the incinerated ash as an incinerated ash layer and forms the incinerated ash layer. A pH buffer layer made of a sulfide-containing substance is disposed in an upper layer or a lower layer, and the sulfide-containing substance is mudstone.
[0007]
In addition, the method for treating incineration ash according to the present invention includes, as described in claim 2, an incineration ash layer made of incineration ash and a pH buffer layer made of a sulfide-containing substance so that the incineration ash layer becomes the lowermost layer. The sulfide-containing substance is made of mudstone by alternately stacking and arranging a protective layer made of sandy soil under the lowermost layer.
[0008]
In addition, the industrial waste disposal site according to the present invention includes an incineration ash layer made of incineration ash and a pH buffer layer made of a sulfide-containing substance such that the incineration ash layer becomes the lowermost layer. The sulfide-containing substance is made of mudstone by alternately stacking and arranging a protective layer made of sandy soil under the lowermost layer.
[0012]
In the method for treating incineration ash according to the first aspect of the present invention, the pH buffer layer made of a sulfide-containing substance exerts an excellent pH buffering action on alkalis eluted from the incineration ash. In other words, sulfide-containing substances also include pyrite and its oxides, which neutralize alkalis eluted from incineration ash and generate a large amount of sulfate ions by oxidizing pyrite. The sulfate ions efficiently neutralize the alkali eluted from the incineration ash.
[0013]
It is optional to place the pH buffer layer above or below the incineration ash layer, but if the pH buffer layer is placed above the incineration ash layer, the sulfate ions generated in the pH buffer layer will It descends and reacts with the alkali in the incineration ash layer, and a neutralization reaction is performed in the incineration ash layer. When the pH buffer layer is arranged below the incineration ash layer, the incineration ash The alkali content in the layer drops and reacts with sulfate ions generated in the pH buffer layer, and a neutralization reaction is performed in the pH buffer layer.
[0014]
The sulfide-containing substance means a substance containing sulfide or sulfate ions generated by oxidizing the sulfide.
[0015]
Here, in the present invention, since mudstone is used in particular as the sulfide-containing substance, in addition to the above-mentioned effects, the colloid particles of the contained clay adsorb alkali metals and alkaline earth metals and perform a so-called ion exchange action. Also, the function and effect described above can be achieved.
[0016]
Even when such a clay particle-containing substance is used, it is optional to arrange the pH buffer layer above or below the incineration ash layer, but when the pH buffer layer is arranged below the incineration ash layer, As a result, the dropped alkali is adsorbed on the clay colloid particles constituting the pH buffer layer, and an ion exchange action is performed.
[0017]
In the method for treating incinerated ash according to the second aspect of the present invention and the industrial waste disposal site according to the third aspect, as in the first aspect of the present invention, the pH buffer layer made of a sulfide-containing substance has an alkali eluted from the incinerated ash. It exerts an excellent pH buffering action on the minute. In other words, sulfide-containing substances also include pyrite and its oxides, which neutralize alkalis eluted from incineration ash and generate a large amount of sulfate ions by oxidizing pyrite. The sulfate ions efficiently neutralize the alkali eluted from the incineration ash.
[0018]
Specifically, the sulfate ions generated in the pH buffer layer react with the alkali component in the incineration ash layer thereunder, and a neutralization reaction is performed in the incineration ash layer. Further, the alkali component in the incineration ash layer reacts with sulfate ions generated in the pH buffer layer thereunder, and a neutralization reaction is performed in the pH buffer layer.
[0019]
Here, among the alkali components contained in the bottom incineration ash layer, it is conceivable that they remain without being neutralized by the action of the upper pH buffer layer. The protective layer prevents diffusion to the environment. That is, since the remaining alkali is adsorbed by the colloid particles of the clay contained in the sandy soil constituting the protective layer, there is no fear of seepage into the groundwater system.
[0020]
Since the pH buffer layer is disposed on the bottom incineration ash layer, sulfate ions generated in the pH buffer layer are neutralized by the incineration ash layer and further blocked by a protective layer thereunder. Therefore, diffusion to the environment is prevented beforehand.
[0021]
The sulfide-containing substance means a substance containing sulfide or sulfate ions generated by oxidizing the sulfide.
[0022]
Here, also in claim 2 and claim 3, since mudstone is particularly used as the sulfide-containing substance, in addition to the above-described action, the colloid particles of the contained clay adsorb alkali metals and alkaline earth metals. It also has the effect of performing a so-called ion exchange action.
[0023]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of a method for treating incinerated ash according to the present invention and an industrial waste disposal site using the same will be described with reference to the accompanying drawings. In addition, the same reference numerals are given to components and the like that are substantially the same as those in the related art, and description thereof is omitted.
[0024]
(1st Embodiment)
[0025]
In order to bury coal ash as incineration ash according to the method for treating incineration ash according to the present embodiment, first, as shown in FIG. To secure.
[0026]
Next, as shown in FIG. 2B, coal ash 2 is buried in the burying space 1 and spread to a thickness of, for example, about 3 m using a bulldozer or the like. The coal ash layer 3 is formed.
[0027]
Next, mudstone 4 as a sulfide-containing substance is buried on the coal ash layer 3 ((c) in the same figure) and spread to a thickness of, for example, about 50 cm using a bulldozer or the like. Pressure is applied to form a pH buffer layer 5. If necessary, cover the pH buffer layer with soil.
[0028]
In the method for treating incineration ash according to the present embodiment, the pH buffer layer 5 made of the mudstone 4 exhibits an excellent pH buffering action against alkali eluted from the coal ash 2. That is, the mudstone 4 contains pyrite (FeS ₂ ) and its acidic oxide, which neutralizes the alkali eluted from the coal ash 2 and oxidizes the pyrite to produce a large amount of sulfuric acid. Ions are generated, and the sulfate ions fall down in the soil and react with the alkali in the coal ash layer 3, so that a neutralization reaction is performed in the coal ash layer.
[0029]
Since the pH buffer layer 5 is disposed on the coal ash layer 3, by appropriately adjusting the thickness of the pH buffer layer 5, the sulfate ions generated in the pH buffer layer can be removed from the coal ash layer 3. Almost consumed for neutralization, there is little concern that it will diffuse around and acidify groundwater.
[0030]
As described above, according to the method for treating incineration ash according to the present embodiment, the pH buffer layer 5 made of the mudstone 4 exhibits an excellent pH buffering action against alkali eluted from the coal ash 2, Neutralization of the ash 2 can be greatly promoted.
[0031]
Therefore, there is no disadvantage that it takes a very long time to neutralize coal ash naturally, and there is no disadvantage that a large amount of cost is required to neutralize it with chemicals. The use of the landfill site, a valuable land resource, can be started early.
[0032]
In addition, since it is not neutralization by chemicals, gentle sustainability can be expected for a long period without causing a chemical problem. Since the pH buffer layer 5 is a soil material called mudstone 4, construction management is easy. In addition to the effect of easily understanding the ground mechanical characteristics after construction, there is no need to worry about the elution of heavy metals from coal ash due to a sudden drop in pH or the decrease in effect due to rainfall.
[0033]
Further, by appropriately adjusting the thickness of the pH buffer layer 5, it becomes possible to substantially consume the sulfate ions generated in the pH buffer layer for neutralization in the coal ash layer 3, and excess sulfate ions diffuse to the surroundings. It is possible to prevent the groundwater from being acidified.
[0034]
Next, the effects of the method for treating incineration ash according to the present embodiment have been confirmed by experiments, and the outline thereof will be described below.
[0035]
First, two types of coal ash were used as incineration ash, and mountain sand and clayey soil as sandy soil were used as test materials in addition to mudstone as a material constituting the pH buffer layer. The properties were examined. Table 1 shows the results.
[0036]
[Table 1]

[0037]
As can be seen from the table, the pH of mountain sand was almost neutral and the pH of clayey soil was slightly acidic, while the pH of mudstone was strongly acidic. In addition, in a pH (H ₂ O ₂ ) test for examining the potential pH associated with oxidation, only a slight decrease in pH was observed in mountain sand and clayey soil, whereas in mudstone, the pH decreased to 1.8, indicating a very strong acidity. Was found to be present. This is considered to be due to sulfuric acid generation due to pyrite oxidation.
[0038]
Next, in order to examine the quantitative pH buffering ability of the test material, 200 g of coal ash, 0 to 200 g of a wet test material and 200 g of distilled water were placed in a closed container, and reciprocated shaking at 200 times / min was performed for 6 hours. This was repeated until no change in pH was observed.
[0039]
The result is shown in FIG. In the figure, the above-described shaking was repeated 10 times. As can be seen from the figure, the ratio of the test material to the coal ash was very high, whereas the coal ash alone had a very high pH of 13.8. It has been found that the pH decreases as the pH increases, especially in the case of mudstone.
[0040]
Next, a column test was carried out to examine the pH buffering capacity of the test material when the coal ash and the test material were arranged in layers and passed continuously through water. In the column test, the test material and coal ash were laminated on the acrylic cylinder having a diameter of 10 cm and a height of 180 cm with a thickness of 24 cm and 96 cm, respectively, from the bottom (the height ratio between the coal ash and the test material was 4: 1). Water was injected from the top of the column in this state.
[0041]
FIG. 3 shows the relationship between the amount of permeated water and pH. As can be seen from the figure, in the case of mountain sand, the pH buffer capacity is not maintained, and when the water permeability exceeds 10 liters, the pH rises sharply. The pH did not exceed the reference upper limit of 8.6 up to a volume of 34 liters).
[0042]
FIG. 4 shows the results of pH analysis after disassembly of the column. As can be seen from the figure, the pH of the coal ash layer shows little difference between the case of using mountain sand and the case of using mudstone. Was seen in the depth direction.
[0043]
On the other hand, under the coal ash layer, in the case of mountain sand, there is almost no difference from the pH of the coal ash layer, i.e., while the coal ash pore water passed through the mountain sand layer without receiving a pH buffer, In the case of mudstone, the pH decreased as going down, and it was found that the coal ash pore water was pH buffered from the mudstone layer.
[0044]
In the present embodiment, the incinerated ash is coal ash, but it goes without saying that ash after incineration of waste and the like other than coal ash can also be handled as the incinerated ash of the present invention.
[0045]
In the present embodiment, the pH buffer layer 5 made of the mudstone 4 is arranged on the coal ash layer 3. 5, the pH buffer layer 5 may be arranged below the coal ash layer 3.
[0046]
In the modification shown in the figure, the alkali content in the coal ash layer 3 descends in the soil and reacts with the sulfate ions generated in the pH buffer layer 5, and a neutralization reaction takes place in the pH buffer layer. At the same time, since the dropped alkali is adsorbed on the clay colloid particles in the mudstone 4 constituting the pH buffer layer 5 and ion exchange is performed, the neutralization of the coal ash 2 is performed by the above-described embodiment. Is also performed more efficiently. If the amount of sulfate ions generated in the pH buffer layer 5 is relatively reduced by appropriately adjusting the thickness of the pH buffer layer 5, the sulfate ions remaining without reacting with the alkali component in the coal ash layer 3 can be removed. The volume is also reduced and the risk of entering the groundwater system and acidifying the groundwater can be reduced.
[0049]
(2nd Embodiment)
[0050]
Next, a method for treating incinerated ash according to the second embodiment and an industrial waste disposal site using the same will be described. It is to be noted that the same reference numerals are given to components and the like that are substantially the same as those in the above-described embodiment, and description thereof will be omitted.
[0051]
In order to bury coal ash as incineration ash according to the incineration ash treatment method according to the present embodiment and construct an industrial waste disposal site, first, as shown in FIG. Excavate the ground to secure the buried space 1.
[0052]
Next, as shown in FIG. 1B, a sandy soil 11 is buried in the bottom of the burying space 1 and spread to a thickness of about 50 cm, and then pressed as necessary to form a protective layer 12.
[0053]
Next, as shown in FIG. 3C, the coal ash 2 is buried on the protective layer 12 and spread to a thickness of, for example, about 3 m using a bulldozer or the like. A coal ash layer 3 as an ash layer is formed, and a pH buffer layer 5 made of mudstone 4 as a sulfide-containing substance having a thickness of, for example, about 50 cm is similarly formed thereon. By repeating such a procedure, a waste disposal site in which the coal ash layer 3 and the pH buffer layer 5 are alternately stacked from the bottom, with the coal ash layer 3 being the lowermost layer, is constructed. If necessary, the soil is covered on the coal ash layer 3 or the pH buffer layer 5 which is the uppermost layer.
[0054]
In the method for treating incinerated ash according to the present embodiment and the industrial waste disposal site using the same, the pH buffer layer 5 composed of the mudstone 4 exhibits an excellent pH buffering action on the alkali eluted from the coal ash 2. I do. That is, the mudstone 4 contains a clay component, and the colloid particles of the clay component adsorb an alkali metal or an alkaline earth metal to perform a so-called ion exchange action. However, the mudstone 4 contains pyrite (FeS ₂ ) and Acid oxides are also included, which neutralize the alkalis eluted from the coal ash 2 and oxidize pyrite to generate a large amount of sulfate ions. To efficiently neutralize the alkali eluted from
[0055]
More specifically, the sulfate ion generated in the pH buffer layer 5 reacts with an alkali component in the coal ash layer 3 thereunder, and a neutralization reaction is performed in the coal ash layer. Further, the alkali component in the coal ash layer 3 reacts with the sulfate ions generated in the pH buffer layer 5 thereunder, thereby performing a neutralization reaction in the pH buffer layer and constituting the pH buffer layer. Adsorbed on the clay colloid particles in the mudstone 4 to perform the ion exchange action.
[0056]
Here, in the coal ash layer 3, which is the lowermost layer, it is conceivable that an alkali component that is not neutralized by the action of the upper pH buffer layer 5 remains, but such a remaining alkali component is disposed thereunder. The protective layer 12 prevents diffusion into the environment. That is, the remaining alkali is adsorbed by the colloidal particles of the clay contained in the sandy soil constituting the protective layer 12, so that there is no fear of seepage into the groundwater system.
[0057]
Since the pH buffer layer 5 is disposed on the coal ash layer 3 which is the lowermost layer, the sulfate ions generated in the pH buffer layer 5 are neutralized by the coal ash layer 3 and further below. Since it is blocked by the protective layer 12, its diffusion into the environment is prevented.
[0058]
As described above, according to the method for treating incinerated ash according to the present embodiment and the industrial waste disposal site using the same, the pH buffer layer 5 made of the mudstone 4 is used for the alkali content eluted from the coal ash 2. It exhibits an excellent pH buffering action and can greatly promote the neutralization of coal ash 2.
[0059]
Therefore, there is no disadvantage that it takes a very long time to neutralize coal ash naturally, and there is no disadvantage that a large amount of cost is required to neutralize it with chemicals. The use of the landfill site, a valuable land resource, can be started early.
[0060]
In addition, since it is not neutralization by chemicals, gentle sustainability can be expected for a long period without causing a chemical problem. Since the pH buffer layer 5 is a soil material called mudstone 4, construction management is easy. In addition to the effect of easily understanding the ground mechanical characteristics after construction, there is no need to worry about the elution of heavy metals from coal ash due to a sudden drop in pH or the decrease in effect due to rainfall.
[0061]
In addition, according to the incineration ash treatment method according to the present embodiment and the industrial waste disposal site using the same, the coal ash layer 3 is used as the lowermost layer and the protective layer 12 is disposed below the lowermost layer. Even if alkali remains in the lowermost coal ash layer 3, it is prevented from diffusing into the environment by the protective layer 12 disposed thereunder, and the sulfate ions generated in the pH buffer layer 5 are removed by the coal ash. While being neutralized by the layer 3 and further blocked by the protective layer 12 therebelow, it is possible to reliably prevent the residual alkali component and sulfate ions from seeping into the groundwater system.
[0062]
In the present embodiment, the incinerated ash is coal ash, but it goes without saying that ash after incineration of waste and the like other than coal ash can also be handled as the incinerated ash of the present invention.
[0065]
【The invention's effect】
As described above, according to the method for treating incinerated ash according to the present invention and the industrial waste disposal site using the same, the pH buffer layer made of a sulfide-containing substance is excellent in alkali content eluted from incinerated ash. It exerts a pH buffering effect and greatly promotes the neutralization of incineration ash.
[0066]
Therefore, it does not take a long time to neutralize incinerated ash naturally, and a large amount of cost is required to neutralize it with chemicals. The use of the landfill site, a valuable land resource, can be started early.
[0067]
[Brief description of the drawings]
FIG. 1 is a sectional view showing a construction procedure of a method for treating incineration ash according to a first embodiment.
FIG. 2 is a graph showing experimental results for confirming the operation of the incineration ash treatment method according to the first embodiment.
FIG. 3 is a graph showing experimental results for confirming the operation of the incineration ash treatment method according to the first embodiment.
FIG. 4 is a graph showing experimental results for confirming the operation of the incineration ash treatment method according to the first embodiment.
FIG. 5 is a sectional view showing a method of treating incineration ash according to a modification.
FIG. 6 is a sectional view showing a method of treating incineration ash according to a second embodiment and an industrial waste disposal site using the method.
[Explanation of symbols]
2 Coal ash (incineration ash)
3 Coal ash layer (incineration ash layer)
4 Mudstone (sulfide-containing substances)
5 pH buffer layer 11 Sandy soil 12 Protective layer

Claims (3)

When burying incineration ash, the incineration ash is arranged as an incineration ash layer and a pH buffer layer made of a sulfide-containing substance is arranged on the upper or lower layer of the incineration ash layer, and the sulfide-containing substance is mudstone A method for treating incinerated ash, characterized in that: An incineration ash layer made of incineration ash and a pH buffer layer made of a sulfide-containing substance are alternately stacked so that the incineration ash layer becomes the lowermost layer, and a protective layer made of sandy soil is provided below the lowermost layer. A method for treating incinerated ash, wherein the sulfide-containing substance is mudstone. An incineration ash layer made of incineration ash and a pH buffer layer made of a sulfide-containing substance are alternately stacked so that the incineration ash layer becomes the lowermost layer, and a protective layer made of sandy soil is provided below the lowermost layer. An industrial waste disposal site, which is disposed, wherein the sulfide-containing substance is mudstone.

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