JP3650973B2 - Treatment method of acidic molten fly ash - Google Patents
Treatment method of acidic molten fly ash Download PDFInfo
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- JP3650973B2 JP3650973B2 JP02587195A JP2587195A JP3650973B2 JP 3650973 B2 JP3650973 B2 JP 3650973B2 JP 02587195 A JP02587195 A JP 02587195A JP 2587195 A JP2587195 A JP 2587195A JP 3650973 B2 JP3650973 B2 JP 3650973B2
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- 239000010881 fly ash Substances 0.000 title claims description 61
- 230000002378 acidificating effect Effects 0.000 title claims description 47
- 238000000034 method Methods 0.000 title claims description 16
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims description 28
- OYPRJOBELJOOCE-UHFFFAOYSA-N Calcium Chemical compound [Ca] OYPRJOBELJOOCE-UHFFFAOYSA-N 0.000 claims description 21
- 239000011575 calcium Substances 0.000 claims description 21
- 229910052791 calcium Inorganic materials 0.000 claims description 21
- 239000005077 polysulfide Substances 0.000 claims description 21
- 229920001021 polysulfide Polymers 0.000 claims description 21
- 150000008117 polysulfides Polymers 0.000 claims description 21
- 239000002699 waste material Substances 0.000 claims description 15
- 238000002844 melting Methods 0.000 claims description 13
- 230000008018 melting Effects 0.000 claims description 13
- 239000002253 acid Substances 0.000 claims description 9
- AXCZMVOFGPJBDE-UHFFFAOYSA-L calcium dihydroxide Chemical compound [OH-].[OH-].[Ca+2] AXCZMVOFGPJBDE-UHFFFAOYSA-L 0.000 claims description 9
- 239000000920 calcium hydroxide Substances 0.000 claims description 9
- 235000011116 calcium hydroxide Nutrition 0.000 claims description 9
- 229910001861 calcium hydroxide Inorganic materials 0.000 claims description 9
- 239000002893 slag Substances 0.000 claims description 9
- 239000002351 wastewater Substances 0.000 claims description 9
- 239000000203 mixture Substances 0.000 claims description 8
- 229960002089 ferrous chloride Drugs 0.000 claims description 7
- NMCUIPGRVMDVDB-UHFFFAOYSA-L iron dichloride Chemical compound Cl[Fe]Cl NMCUIPGRVMDVDB-UHFFFAOYSA-L 0.000 claims description 7
- 229910052500 inorganic mineral Inorganic materials 0.000 claims description 6
- 235000010755 mineral Nutrition 0.000 claims description 6
- 239000011707 mineral Substances 0.000 claims description 6
- DPLVEEXVKBWGHE-UHFFFAOYSA-N potassium sulfide Chemical compound [S-2].[K+].[K+] DPLVEEXVKBWGHE-UHFFFAOYSA-N 0.000 claims description 6
- 229910052979 sodium sulfide Inorganic materials 0.000 claims description 6
- GRVFOGOEDUUMBP-UHFFFAOYSA-N sodium sulfide (anhydrous) Chemical compound [Na+].[Na+].[S-2] GRVFOGOEDUUMBP-UHFFFAOYSA-N 0.000 claims description 6
- 238000004898 kneading Methods 0.000 claims description 5
- 239000002912 waste gas Substances 0.000 claims 1
- 229910001385 heavy metal Inorganic materials 0.000 description 16
- 239000007789 gas Substances 0.000 description 13
- VEXZGXHMUGYJMC-UHFFFAOYSA-N Hydrochloric acid Chemical compound Cl VEXZGXHMUGYJMC-UHFFFAOYSA-N 0.000 description 11
- 238000010828 elution Methods 0.000 description 7
- HEMHJVSKTPXQMS-UHFFFAOYSA-M Sodium hydroxide Chemical compound [OH-].[Na+] HEMHJVSKTPXQMS-UHFFFAOYSA-M 0.000 description 6
- 238000007922 dissolution test Methods 0.000 description 5
- VTYYLEPIZMXCLO-UHFFFAOYSA-L Calcium carbonate Chemical compound [Ca+2].[O-]C([O-])=O VTYYLEPIZMXCLO-UHFFFAOYSA-L 0.000 description 4
- XEEYBQQBJWHFJM-UHFFFAOYSA-N Iron Chemical compound [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 description 4
- UCKMPCXJQFINFW-UHFFFAOYSA-N Sulphide Chemical compound [S-2] UCKMPCXJQFINFW-UHFFFAOYSA-N 0.000 description 4
- 239000002956 ash Substances 0.000 description 4
- ODINCKMPIJJUCX-UHFFFAOYSA-N Calcium oxide Chemical compound [Ca]=O ODINCKMPIJJUCX-UHFFFAOYSA-N 0.000 description 3
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- 229910000019 calcium carbonate Inorganic materials 0.000 description 2
- 239000000292 calcium oxide Substances 0.000 description 2
- 235000012255 calcium oxide Nutrition 0.000 description 2
- 239000002738 chelating agent Substances 0.000 description 2
- 239000003795 chemical substances by application Substances 0.000 description 2
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- 239000003381 stabilizer Substances 0.000 description 2
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- VYZAMTAEIAYCRO-UHFFFAOYSA-N Chromium Chemical compound [Cr] VYZAMTAEIAYCRO-UHFFFAOYSA-N 0.000 description 1
- RWSOTUBLDIXVET-UHFFFAOYSA-N Dihydrogen sulfide Chemical compound S RWSOTUBLDIXVET-UHFFFAOYSA-N 0.000 description 1
- 229910021578 Iron(III) chloride Inorganic materials 0.000 description 1
- HCHKCACWOHOZIP-UHFFFAOYSA-N Zinc Chemical compound [Zn] HCHKCACWOHOZIP-UHFFFAOYSA-N 0.000 description 1
- JNVCSEDACVAATK-UHFFFAOYSA-L [Ca+2].[S-]SSS[S-] Chemical compound [Ca+2].[S-]SSS[S-] JNVCSEDACVAATK-UHFFFAOYSA-L 0.000 description 1
- 229910052785 arsenic Inorganic materials 0.000 description 1
- RQNWIZPPADIBDY-UHFFFAOYSA-N arsenic atom Chemical compound [As] RQNWIZPPADIBDY-UHFFFAOYSA-N 0.000 description 1
- 229910052793 cadmium Inorganic materials 0.000 description 1
- BDOSMKKIYDKNTQ-UHFFFAOYSA-N cadmium atom Chemical compound [Cd] BDOSMKKIYDKNTQ-UHFFFAOYSA-N 0.000 description 1
- 150000004649 carbonic acid derivatives Chemical class 0.000 description 1
- 229910052804 chromium Inorganic materials 0.000 description 1
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- 238000004140 cleaning Methods 0.000 description 1
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- FANSKVBLGRZAQA-UHFFFAOYSA-M dipotassium;sulfanide Chemical compound [SH-].[K+].[K+] FANSKVBLGRZAQA-UHFFFAOYSA-M 0.000 description 1
- VDQVEACBQKUUSU-UHFFFAOYSA-M disodium;sulfanide Chemical compound [Na+].[Na+].[SH-] VDQVEACBQKUUSU-UHFFFAOYSA-M 0.000 description 1
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Landscapes
- Processing Of Solid Wastes (AREA)
- Gasification And Melting Of Waste (AREA)
Description
【０００１】
【産業上の利用分野】
本発明は廃棄物やその焼却残渣を溶融処理する際に発生する溶融飛灰の処理方法に関する。都市ごみ、産業廃棄物、汚泥等の焼却残渣を、減容化及び無害化するために、溶融処理することが行なわれる。これらを溶融処理すると、溶融スラグの他に溶融飛灰が発生するが、一般に溶融スラグは水砕固化され、また溶融飛灰はこれに含まれる重金属類が溶出しないように薬剤で安定化処理される。本発明は上記のような溶融飛灰のうちで特に酸性溶融飛灰の処理方法に関するものである。
【０００２】
【従来の技術】
従来、溶融飛灰の処理方法として、溶融飛灰に水及びキレート剤をそれぞれ所定割合で加えて混練する方法が提案されている（特開平５−８７３２４）。ところが、この従来法は、用いるキレート剤が高価であるため、非経済的である。
【０００３】
一方、焼却残渣の処理方法としては、焼却残渣に２価鉄を加え、撹拌及び加熱する方法が提案されている（特開平６−１３４４３６）。そこで、溶融飛灰についても、これに２価鉄、例えば塩化第１鉄を加えて混練することが考えられる。実際、塩化第１鉄を加えて混練する方法は、例えば都市ごみの焼却残渣のうちで焼却炉に残る焼却灰を溶融処理する場合、発生する溶融飛灰はｐＨ１１〜１２程度のアルカリ性を示し、かかるアルカリ性溶融飛灰に対しては相応に効果を奏する。しかし、単に塩化第１鉄を加えて混練する方法は、都市ごみ等を焼却処理する際に排ガスと共に飛散して通常は下流側の集塵機で捕集される焼却飛灰を溶融処理する場合、プラスチックやゴム類の廃棄物を溶融処理する場合、更にはこれらを焼却灰と共に溶融処理する場合、発生する溶融飛灰はｐＨ３〜６程度の酸性を示し、かかる酸性溶融飛灰に対しては効果を奏せず、これに含まれる重金属類の溶出を充分に防止できない。
【０００４】
【発明が解決しようとする課題】
本発明が解決しようとする課題は、従来法では、非経済的であるか、或は酸性溶融飛灰に含まれる重金属類の溶出を充分に防止できない点である。
【０００５】
【課題を解決するための手段】
しかして本発明は、廃棄物やその焼却残渣を溶融処理する際に発生する酸性溶融飛灰の処理方法であって、酸性溶融飛灰に消石灰を加えてｐＨを８．５以上にし、次に多硫化カルシウムを酸性溶融飛灰１００重量部当たり０．１〜１０重量部加え、更に鉱酸を加えてｐＨを８．５〜１０．０に調整した後、水として廃棄物やその焼却残渣を溶融処理する際に発生する溶融スラグを水砕固化するのに用いた循環水又は廃棄物やその焼却残渣を溶融処理する際に発生する排ガスを水洗浄するのに用いた排水を酸性溶融飛灰１００重量部当たり１０〜３５重量部加えて混練することを特徴とする酸性溶融飛灰の処理方法に係る。
【０００６】
本発明において処理対象となる酸性溶融飛灰は、廃棄物やその焼却残渣を溶融処理する際に排ガスと共に飛散して通常は下流側の集塵機で捕集される溶融飛灰のうち、酸性を示す溶融飛灰である。かかる酸性溶融飛灰は、焼却飛灰を溶融処理する場合、プラスチックやゴム類を溶融処理する場合、更にはこれらを焼却灰と共に溶融処理する場合に発生し、ｐＨが３〜６程度を示す。
【０００７】
本発明では先ず、酸性溶融飛灰に消石灰（水酸化カルシウム）を加えて混合し、そのｐＨを８．５以上にする。消石灰は、粉状であり、また安価で入手し易く、しかも過剰に加えてもｐＨが極度に上がらず、ガスの発生もないので、使用に有利である。これに対して水酸化ナトリウムはアルカリ性が強過ぎ、粉状のものを工業的に入手し難い。また炭酸カルシウムは酸性域でガスを発生する。更に生石灰（酸化カルシウム）は安定性が悪く、炭酸カルシウムや消石灰に変化し易い。
【０００８】
本発明では次に、多硫化カルシウム（ＣａＳ4）を酸性溶融飛灰１００重量部当たり０．１〜１０重量部加える。通常、市販されている貝殻虫駆除用の石灰硫黄含剤（２８重量％程度の多硫化カルシウム含有品）を元の酸性溶融飛灰１００重量部当たり多硫化カルシウム換算で０．１〜１０重量部加えて混合するのが入手の容易性から見て有利である。多硫化カルシウムは硫化物作製作用を有し、酸性溶融飛灰に含まれる重金属類を硫化物の形にする。硫化物の形になった重金属類は炭酸塩や水酸化物の形の重金属類よりも水に対する溶解度が小さく、より安定である。多硫化カルシウムの加える量を酸性溶融飛灰１００重量部当たり０．１重量部未満にすると、酸性溶融飛灰に通常含まれる重金属類の濃度等との関係で、その溶出を充分に防止することができず、逆に１０重量部超にすると、後のｐＨ調整との関係で重金属類によってはその溶出が増え、いずれにしても不都合である。
【０００９】
多硫化カルシウムに代えて、多硫化カルシウムと硫化ナトリウム（Ｎａ2Ｓ）及び／又は硫化カリウム（Ｋ2Ｓ）との混合物を加えるのが好ましい。多硫化カルシウムは安価であるが、硫化物作製作用がやや弱く、酸性溶融飛灰に含まれる重金属類を充分に硫化物の形にすることができない場合がある。これに対して硫化ナトリウムや硫化カリウムは硫化物作製作用が強く、硫化反応が短時間で進行する。しかし、硫化ナトリウムや硫化カリウムは高価である。したがって、経済性及び硫化物作製作用の双方から見て、多硫化カルシウムと硫化ナトリウム及び／又は硫化カリウムとの混合物を加えるのが好ましいのである。
【００１０】
多硫化カルシウムを加える場合でも、或は多硫化カルシウムと硫化ナトリウム及び／又は硫化カリウムとの混合物を加える場合でも、前述したように酸性溶融飛灰のｐＨを８．５以上にしておく。これらを酸性溶融飛灰にそのまま加えると、有毒な硫化水素ガスが発生するので、安全を見込むのである。
【００１１】
本発明では更に、鉱酸を加えてｐＨを８．５〜１０．０の範囲に調製する。多硫化カルシウム、或は多硫化カルシウムと硫化ナトリウム及び／又は硫化カリウムとの混合物を加えると、ｐＨがよりアルカリ性に傾くので、更に鉱酸、例えば塩酸を加えて、そのｐＨを８．５〜１０．０の範囲に調製するのである。ｐＨが８．５〜１０．０の範囲を外れると、酸性溶融飛灰に含まれる鉛や亜鉛等の両性金属は酸性域でもアルカリ性域でもその溶出が増え、またカドミウムは酸性域で、ヒ素はアルカリ性域でそれぞれその溶出が増える。
【００１２】
鉱酸に代えて、塩化第１鉄を加えるのが好ましい。通常、塩化第１鉄の高濃度水溶液、例えば３０重量％前後の水溶液を加えて混合し、ｐＨを８．５〜１０．０の範囲に調整する。塩化第１鉄は還元作用を有し、酸性溶融飛灰に含まれる有害な６価クロムを３価クロムに還元する。これに対して塩化第２鉄は還元作用がない。
【００１３】
本発明では最後に、上記のようにｐＨを８．５〜１０．０の範囲に調整した後、水として用いる循環水又は排水を元の酸性溶融飛灰１００重量部当たり１０〜３５重量部加えて混練する。循環水又は排水の加える量を酸性溶融飛灰１００重量部当たり１０重量部未満にすると、酸性溶融飛灰を充分に泥状化することができず、逆に３５重量部超にすると、酸性溶融飛灰がスラリー状になってしまい、いずれにしてもハンドリング性が悪く、不都合である。
【００１４】
酸性溶融飛灰と混練する水としては、廃棄物やその焼却残渣を溶融処理する際に発生する溶融スラグを水砕固化するのに用いた循環水を用いる。廃棄物やその焼却残渣を溶融処理すると、溶融スラグが発生する。一般に溶融スラグは水砕固化される。水砕固化では通常、新たに冷却水を補充しつつ、一度使用した冷却水を循環水として再使用するが、その一方で繰り返しの再使用により汚染された循環水の一部を抜き出している。抜き出した循環水には重金属類が濃縮されており、これをそのままでは放水できない。そこで、かかる循環水を上記のような酸性溶融飛灰と混練する水として用いると、結果的に循環水に含まれる重金属類をも安定化できる。
【００１５】
また酸性溶融飛灰と混練する水としては、廃棄物やその焼却残渣を溶融処理する際に発生する排ガスを水洗浄するのに用いた排水を用いる。廃棄物やその焼却残渣を溶融処理する際に発生する排ガスには各種の酸性ガス（ＨＣｌやＳＯＸ等）が含まれているので、これを除去するため、通常排ガスを水酸化ナトリウム水溶液で洗浄する。洗浄に用いた排水には排ガス中の重金属類、特に水銀が捕集されており、これをそのままでは放水できない。そこで、かかる排水を上記のような酸性溶融飛灰と混練する水として用いると、結果的に排水に含まれる重金属類をも安定化できる。
【００１６】
【実施例】
実施例１
都市ごみの焼却灰と焼却飛灰との混合物を溶融処理したときの排ガスからバグフィルタで捕集した酸性溶融飛灰（ｐＨ５．０）を処理した。消石灰（市販の消石灰特号、ＪＩＳ−Ｒ９００１）を酸性溶融飛灰１００重量部当たり５重量部加えて混合し、そのｐＨを８．５以上にした。次に多硫化カルシウム（２．７５重量％の多硫化カルシウム水希釈液）を元の酸性溶融飛灰１００重量部当たり０．２５重量部（多硫化カルシウム換算量）加えて混練した。更に塩酸（３７．２重量％の濃塩酸）を１．２重量部加えて混練し、ｐＨを９．０に調整した。最後にこの混練物に水として前記の混合物を溶融処理したときの溶融スラグを水砕固化するのに用いた循環水を元の酸性溶融飛灰１００重量部当たり２０重量部加えて混練した。得られた混練物について溶出試験（昭和４８年環境庁告示１３号）を行なった。処理条件を表１に、また溶出試験結果を表３に示した。
【００１７】
実施例２
実施例１と同様に、消石灰を酸性溶融飛灰に加えて混合し、次に多硫化カルシウムを加えて混練した。更に塩酸（３７．２重量％の濃塩酸）を１．１重量部加えて混練し、ｐＨを９．４に調整した。最後にこの混練物に水として前記の混合物を溶融処理したときの排ガスを洗浄するのに用いた排水を元の酸性溶融飛灰１００重量部当たり２０重量部加えて混練した。得られた混練物について実施例１と同様に溶出試験を行なった。処理条件を表１に、また溶出試験結果を表３に示した。
【００１８】
参考例１〜２０及び比較例１〜１０
加えた薬剤等の種類及び／又はその添加量を変え、また水として工業用水を用いて、実施例１や２と同様に行なった。処理条件を表１及び表２に、また溶出試験結果を表３及び表４に示した。
【００１９】
【表１】
【表２】
表１及び表２において、
添加量：元の酸性溶融飛灰１００重量部当たりの添加量（水の添加量は各例いずれも２０重量部）
＊１：ＧＥＯＳＴＡ−Ｆ１３（鐘淵化学工業社製の無機系安定化剤）
＊２：ＮＥＷ−エポルバ５００（ミヨシ油化社製の高分子系安定化剤）
ｐＨ：最終的に得られた混練物のｐＨ
【００２２】
【表３】
【表４】
表３及び表４において、
判定：○は産業廃棄物埋立基準（平成６年１１月７日付の総理府令第６１号）を達成しており、重金属類が充分に不溶出化（安定化）されていることを、×は上記産業廃棄物埋立基準を達成していないことを意味する
【００２５】
【発明の効果】
既に明らかなように、以上説明した本発明には、酸性溶融飛灰に含まれる重金属類の溶出を経済的且つ充分に防止でき、また結果的に溶融スラグを水砕固化するのに用いた循環水や排ガスを水洗浄するのに用いた排水に含まれる重金属類をも安定化できるという効果がある。[0001]
[Industrial application fields]
The present invention relates to a method for treating molten fly ash generated when melting waste and its incineration residue. Incineration residues such as municipal waste, industrial waste, and sludge are melted to reduce the volume and make them harmless. When these are melted, molten fly ash is generated in addition to molten slag. Generally, molten slag is granulated and solidified, and the molten fly ash is stabilized with chemicals so that the heavy metals contained in it are not eluted. The The present invention relates to a method for treating acidic molten fly ash among the above molten fly ash.
[0002]
[Prior art]
Conventionally, as a method for treating molten fly ash, a method has been proposed in which water and a chelating agent are respectively added to molten fly ash at a predetermined ratio and kneaded (Japanese Patent Laid-Open No. 5-87324). However, this conventional method is uneconomical because the chelating agent used is expensive.
[0003]
On the other hand, as a method for treating the incineration residue, a method of adding divalent iron to the incineration residue, stirring and heating has been proposed (JP-A-6-134436). Therefore, it is conceivable to melt kneaded fly ash by adding divalent iron such as ferrous chloride thereto. Actually, the method of kneading by adding ferrous chloride is, for example, when melting incineration ash remaining in the incinerator among incineration residues of municipal waste, the generated molten fly ash exhibits alkalinity of about pH 11-12, The alkaline molten fly ash has a corresponding effect. However, the method of simply adding ferrous chloride and kneading is a method of plasticizing when incineration fly ash that is scattered with exhaust gas and normally collected by a dust collector on the downstream side is incinerated when municipal waste is incinerated. When the wastes of rubber and rubber are melt-treated, and further when these are melt-treated with incinerated ash, the generated molten fly ash exhibits an acidity of about pH 3 to 6, and is effective against such an acid molten fly ash. It does not play, and the elution of heavy metals contained therein cannot be sufficiently prevented.
[0004]
[Problems to be solved by the invention]
The problem to be solved by the present invention is that the conventional method is uneconomical or cannot sufficiently prevent elution of heavy metals contained in the acidic molten fly ash.
[0005]
[Means for Solving the Problems]
Thus, the present invention is a method for treating acidic molten fly ash generated when melting waste and its incineration residue, and adding slaked lime to the acidic molten fly ash to a pH of 8.5 or higher, After adding 0.1 to 10 parts by weight of calcium polysulfide per 100 parts by weight of acidic molten fly ash and further adding mineral acid to adjust the pH to 8.5 to 10.0, the waste and its incineration residue are added as water. Acid melt fly ash used for water washing of exhaust water generated when melt processing the circulating water or waste and its incineration residue used to granulate and solidify molten slag generated during melting The present invention relates to a method for treating acidic molten fly ash characterized by adding 10 to 35 parts by weight per 100 parts by weight and kneading.
[0006]
The acidic molten fly ash to be treated in the present invention is acidic among the molten fly ash that is scattered with the exhaust gas and normally collected by the downstream dust collector when the waste and its incineration residue are melted. Molten fly ash. Such acidic molten fly ash is generated when melting incinerated fly ash, melting plastics and rubbers, and further melting them with incinerated ash, and has a pH of about 3-6.
[0007]
In the present invention, first, slaked lime (calcium hydroxide) is added to and mixed with acidic molten fly ash, and the pH is adjusted to 8.5 or higher. Slaked lime is advantageous in use because it is in powder form, is inexpensive and easily available, and even when added in excess, the pH does not increase extremely and gas is not generated. On the other hand, sodium hydroxide is too alkaline and it is difficult to obtain a powdery product industrially. Calcium carbonate generates gas in the acidic region. Furthermore, quick lime (calcium oxide) is not stable and easily changes to calcium carbonate or slaked lime.
[0008]
Next, in the present invention, calcium polysulfide (CaS 4 ) is added in an amount of 0.1 to 10 parts by weight per 100 parts by weight of the acidic molten fly ash. Usually, 0.1 to 10 parts by weight in terms of calcium polysulfide per 100 parts by weight of the original acidic molten fly ash containing commercially available lime sulfur-containing agent for combating shellworms (containing about 28% by weight of calcium polysulfide) In addition, mixing is advantageous in view of availability. Calcium polysulfide has a sulfide producing action, and turns heavy metals contained in acidic molten fly ash into a sulfide form. Heavy metals in the form of sulfides are less stable and more stable in water than heavy metals in the form of carbonates and hydroxides. When the amount of calcium polysulfide added is less than 0.1 parts by weight per 100 parts by weight of acidic molten fly ash, its elution is sufficiently prevented in relation to the concentration of heavy metals normally contained in acidic molten fly ash On the other hand, if it exceeds 10 parts by weight, the elution of some heavy metals increases due to the subsequent pH adjustment, which is inconvenient.
[0009]
Instead of calcium polysulfide, it is preferable to add a mixture of calcium polysulfide and sodium sulfide (Na 2 S) and / or potassium sulfide (K 2 S). Calcium polysulfide is inexpensive, but its sulfide preparation action is somewhat weak, and heavy metals contained in acidic molten fly ash may not be able to be made into a sufficient sulfide form. On the other hand, sodium sulfide and potassium sulfide have a strong sulfide preparation action, and the sulfurization reaction proceeds in a short time. However, sodium sulfide and potassium sulfide are expensive. Therefore, it is preferable to add a mixture of calcium polysulfide and sodium sulfide and / or potassium sulfide in view of both economy and sulfide preparation action.
[0010]
Whether calcium polysulfide is added or a mixture of calcium polysulfide and sodium sulfide and / or potassium sulfide is added, the pH of the acidic molten fly ash is set to 8.5 or more as described above. If these are added as they are to the acidic molten fly ash, toxic hydrogen sulfide gas is generated, so safety is expected.
[0011]
In the present invention, a mineral acid is further added to adjust the pH to a range of 8.5 to 10.0. When calcium polysulfide or a mixture of calcium polysulfide and sodium sulfide and / or potassium sulfide is added, the pH tends to become more alkaline, so a mineral acid such as hydrochloric acid is added to adjust the pH to 8.5-10. In the range of 0.0. When the pH is out of the range of 8.5 to 10.0, the elution of amphoteric metals such as lead and zinc contained in the acidic molten fly ash increases in both acidic and alkaline regions, cadmium is in the acidic region, and arsenic is Each elution increases in the alkaline region.
[0012]
Instead of mineral acid, it is preferable to add ferrous chloride. Usually, a high concentration aqueous solution of ferrous chloride, for example, an aqueous solution of around 30% by weight is added and mixed to adjust the pH to a range of 8.5 to 10.0. Ferrous chloride has a reducing action and reduces harmful hexavalent chromium contained in acidic molten fly ash to trivalent chromium. In contrast, ferric chloride has no reducing action.
[0013]
In the present invention, finally, after adjusting the pH to the range of 8.5 to 10.0 as described above, 10 to 35 parts by weight of circulating water or waste water used as water is added per 100 parts by weight of the original acidic molten fly ash. Knead. If the amount of circulating water or wastewater added is less than 10 parts by weight per 100 parts by weight of acidic molten fly ash, the acidic molten fly ash cannot be sufficiently mudified. Fly ash becomes a slurry, which is inconvenient and poor in handling.
[0014]
As the water to be kneaded with the acidic molten fly ash, the circulating water used to granulate and solidify the molten slag generated when melting the waste and its incineration residue is used. When waste or its incineration residue is melted, molten slag is generated. Generally, molten slag is granulated and solidified. In granulation and solidification, cooling water that has been used once is usually reused as circulating water while being replenished with cooling water. On the other hand, a part of circulating water contaminated by repeated reuse is extracted. The extracted circulating water is concentrated with heavy metals and cannot be discharged as it is. Therefore, when such circulating water is used as water to be kneaded with the acidic molten fly ash as described above, heavy metals contained in the circulating water can be stabilized as a result.
[0015]
Further, as the water to be kneaded with the acidic molten fly ash, the waste water used for washing the exhaust gas generated when the waste and its incineration residue are melted is used. The exhaust gas generated when melting waste and its incineration residue contains various acid gases (HCl, SO X, etc.). In order to remove this, the exhaust gas is usually washed with an aqueous sodium hydroxide solution. To do. The wastewater used for cleaning collects heavy metals in exhaust gas, especially mercury, and cannot be discharged as it is. Therefore, when such waste water is used as water for kneading with the above-described acidic molten fly ash, heavy metals contained in the waste water can be stabilized as a result.
[0016]
【Example】
Example 1
The acidic molten fly ash (pH 5.0) collected by the bag filter from the exhaust gas when the mixture of municipal waste incineration ash and incineration fly ash was melted was treated. Slaked lime (commercially available slaked lime, JIS-R9001) was mixed by adding 5 parts by weight per 100 parts by weight of acidic molten fly ash, and the pH was adjusted to 8.5 or higher. Next, calcium polysulfide (2.75 wt% calcium polysulfide water diluted solution) was added and kneaded by adding 0.25 parts by weight (calculated amount of calcium polysulfide) per 100 parts by weight of the original acidic molten fly ash. Further, 1.2 parts by weight of hydrochloric acid (37.2% by weight concentrated hydrochloric acid) was added and kneaded to adjust the pH to 9.0. Finally, 20 parts by weight of the circulating water used for pulverizing and solidifying the molten slag when the above mixture was melted as water was added to this kneaded product per 100 parts by weight of the original acidic molten fly ash and kneaded. The kneaded product thus obtained was subjected to a dissolution test (environmental agency notification No. 13 in 1973). The treatment conditions are shown in Table 1, and the dissolution test results are shown in Table 3.
[0017]
Example 2
As in Example 1, slaked lime was added to the acidic molten fly ash and mixed, and then calcium polysulfide was added and kneaded. Furthermore, 1.1 parts by weight of hydrochloric acid (37.2 wt% concentrated hydrochloric acid) was added and kneaded to adjust the pH to 9.4. Finally, 20 parts by weight of the waste water used to wash the exhaust gas when the mixture was melted as water was added to this kneaded product per 100 parts by weight of the original acidic molten fly ash and kneaded. The obtained kneaded product was subjected to a dissolution test in the same manner as in Example 1. The treatment conditions are shown in Table 1, and the dissolution test results are shown in Table 3.
[0018]
Reference Examples 1-20 and Comparative Examples 1-10
It carried out similarly to Example 1 and 2 using the industrial water as water, changing the kind and / or addition amount of the chemical | medical agent etc. which were added. The treatment conditions are shown in Tables 1 and 2, and the dissolution test results are shown in Tables 3 and 4.
[0019]
[Table 1]
[Table 2]
In Table 1 and Table 2,
Addition amount: Addition amount per 100 parts by weight of the original acidic molten fly ash (the addition amount of water is 20 parts by weight in each example)
* 1: GEOSTA-F13 (an inorganic stabilizer manufactured by Kaneka Corporation)
* 2: NEW-Epolva 500 (polymer stabilizer manufactured by Miyoshi Yuka)
pH: pH of the finally obtained kneaded material
[0022]
[Table 3]
[Table 4]
In Table 3 and Table 4,
Judgment: ○ indicates that industrial waste landfill standards (Prime Ministerial Ordinance No. 61 dated November 7, 1994) have been achieved, and heavy metals have been sufficiently undissolved (stabilized). Means that the above industrial waste landfill standards have not been achieved.
【The invention's effect】
As is apparent from the above, the present invention described above can economically and sufficiently prevent elution of heavy metals contained in the acidic molten fly ash and, as a result, the circulation used to granulate and solidify the molten slag. There is an effect that the heavy metals contained in the waste water used for washing water and exhaust gas can be stabilized.
Claims (3)
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP02587195A JP3650973B2 (en) | 1995-01-20 | 1995-01-20 | Treatment method of acidic molten fly ash |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP02587195A JP3650973B2 (en) | 1995-01-20 | 1995-01-20 | Treatment method of acidic molten fly ash |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| JPH08197034A JPH08197034A (en) | 1996-08-06 |
| JP3650973B2 true JP3650973B2 (en) | 2005-05-25 |
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| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP02587195A Expired - Fee Related JP3650973B2 (en) | 1995-01-20 | 1995-01-20 | Treatment method of acidic molten fly ash |
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| Country | Link |
|---|---|
| JP (1) | JP3650973B2 (en) |
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| Publication number | Publication date |
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| JPH08197034A (en) | 1996-08-06 |
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