【０００１】
【発明の属する技術分野】
本発明は、有害重金属を含有する汚染土壌又は／及び燃焼灰、汚泥などの廃棄物を安定化する方法及び安定化装置に関するものである。安定化された処理物は、埋戻材、盛土材等の土木資材、汚泥等の水分調整材、家畜糞尿等の水分調整と脱臭を兼ねた処理材、土壌改良材等として利用することができる。
【０００２】
【従来の技術】
従来、汚染土壌又は廃棄物の処理方法として、次の方法が提案されている。
（１） 可溶性重金属を含有する土壌又は産業廃棄物に硫酸鉄と水を添加した後、カルシウム化合物を添加して適切な範囲のｐＨに調整することにより、土壌又は廃棄物を無害化処理する方法（例えば、特許文献１参照）。
（２） 重金属汚染土壌に硫酸鉄などの還元剤とセメント、石こうを添加し、５０〜１５０℃で熱処理を行うことにより、汚染土壌を安定化処理する方法（例えば、特許文献２参照）。
（３） 微粉状廃棄物をカルシウム成分の存在下で、必要に応じ固化促進剤及び／又は還元剤を添加混合して成型した後、大気圧下で、温度５０℃以上の水又は水蒸気中に３日間以上放置、養生することにより、廃棄物を固化処理する方法（例えば、特許文献３参照）。
【０００３】
【特許文献１】
特開２００１−１２１１３１号公報（第１頁）
【特許文献２】
特開２０００−１０２７７６号公報（第１頁、第２頁）
【特許文献３】
特開昭５６−１６１８８０号公報（第１頁）
【０００４】
【発明が解決しようとする課題】
これらの従来技術は、次のような問題点を有している。（１）の方法は、常温での処理のため、地域、季節等による雰囲気温度の違いにより、反応の進行程度のバラツキが大きい。また、ＣａＯ量、ＳｉＯ２ 量の調整を行っていないので、Ｃ−Ｓ−Ｈ等の水和物生成にバラツキがある。さらに、硫酸鉄と水の添加後、カルシウム化合物を添加するため、カルシウム化合物の分散が不十分となる。それらにより、多種の汚染土壌、産業廃棄物に対し、地域、季節にかかわらず、確実な安定化を図ることができない。
【０００５】
（２）の方法は、５０〜１５０℃の熱処理を行うため、地域、季節による処理効果の違いは少なくなるが、乾燥雰囲気での処理のため、水和反応進行が不十分である。また、ＣａＯ量、ＳｉＯ２ 量の調整を行っていないので、Ｃ−Ｓ−Ｈ等の水和物生成にバラツキがある。そのため、多種の汚染土壌に対し、確実な安定化を図ることができない。
【０００６】
（３）の方法は、混合、成型、３日以上の養生を行う方法であるので、処理コストが高い。また、ＣａＯ量、ＳｉＯ２ 量の調整を行っていないので、Ｃ−Ｓ−Ｈ等の水和物生成にバラツキがある。そのため、多種の微粉状廃棄物に対し、確実な安定化を図ることができない。
また、（１）、（２）、（３）とも、混合方法、混練方法、混練物状態についての具体的な記述はなく、本発明の方法における混練によるファニキュラー状態（粒子表面全体が液体でぬれ、数百μｍ 〜数十ｍｍの粒状体となっている状態）とすることは記載されていない。
【０００７】
本発明は上記の諸点に鑑みなされたもので、本発明の目的は、多種の汚染土壌又は／及び単独もしくは組み合わせた廃棄物を、季節、地域によらず、短時間で確実に安定化することができる方法及び装置を提供するものである。
【０００８】
【課題を解決するための手段】
上記の目的を達成するために、本発明の汚染土壌・廃棄物の安定化方法は、汚染土壌又は／並びに製紙スラッジ、木くず、有機系汚泥、ごみ、石炭などの燃焼灰及び汚泥の少なくともいずれかの廃棄物に石灰材及び／又はシリカ材を加え、ＣａＯ量を２．５〜３５重量％、ＳｉＯ２ 量を２５〜６５重量％に調整し、汚染土壌又は／及び廃棄物に対して０．２５〜１５重量％の還元材を溶解させた水による混練にてファニキュラー状態とした後、４０〜１００℃、０．５〜２４ｈ の蒸気処理にて安定な処理物とするように構成される（図１〜図３参照）。
【０００９】
この方法において、石灰材として、消石灰、生石灰、貝殻などのＣａＯを含む廃棄物焼成品、貝殻粉末、石灰石粉末及び主成分が炭酸カルシウムであるライムケーキの少なくともいずれかを用いることが好ましい。
また、シリカ材として、シリカヒューム、粘土及び白土の少なくともいずれかの非晶質ＳｉＯ２ の含有量が多い物質を用いることが好ましい。
また、還元材として、硫酸第一鉄・塩化第一鉄などの第一鉄塩、硫化ナトリウムなどの硫化物及びシュウ酸・ギ酸などの低級脂肪酸などの水に可溶性の物質の少なくともいずれかを用いることが好ましい。
【００１０】
本発明の汚染土壌・廃棄物の安定化装置は、汚染土壌又は／及び廃棄物と、石灰材及び／又はシリカ材に、還元材を溶解させた水を加えてファニキュラー状態に混練するための混練機と、この混練機からの混練物を投入し安定な処理物とするための、内部に水平軸の攪拌翼を有する略水平円筒容器型の水蒸気処理機とを備えたことを特徴としている（図１参照）。
【００１１】
また、本発明の安定化装置は、汚染土壌又は／及び廃棄物と、石灰材及び／又はシリカ材に、還元材を溶解させた水を加えてファニキュラー状態に混練するための混練機と、この混練機からの混練物を投入し安定な処理物とするための、容器が回転する略水平円筒容器型の水蒸気処理機とを備えたことを特徴としている（図２参照）。
【００１２】
さらに、本発明の安定化装置は、汚染土壌又は／及び廃棄物と、石灰材及び／又はシリカ材に、還元材を溶解させた水を加えてファニキュラー状態に混練するための混練機と、この混練機からの混練物を投入するための、上部が開放された複数の小容器と、これらの小容器を順次導入し混練物を安定な処理物とするトンネル式水蒸気養生機と、水蒸気養生された処理物の入った小容器を持ち上げ、略水平方向に回転し、反転を行い、処理物を排出する構造の反転機とを備えたことを特徴としている（図３参照）。
【００１３】
本発明の方法及び装置において、多種の汚染土壌、廃棄物への適用のために、次の２つの組み合わせにて対応する。
（１） 石灰材及び／又はシリカ材の添加により、廃棄物等のＣａＯ量を２．５〜３５重量％、望ましくは３．５〜３５重量％、ＳｉＯ２ 量を２５〜６５重量％、望ましくは３０〜６０重量％に調整する。ＣａＯ量が下限未満ではＣ−Ｓ−Ｈなどの反応が進まず、一方、上限を超えると、フリーのＣａＯが多く残存し、安定化効果が不十分である。また、ＳｉＯ２ 量が下限未満、上限を超える場合には、Ｃ−Ｓ−Ｈ反応が十分進まず、安定化効果が不十分である。なお、ＣａＯ量を３．５〜３５重量％、ＳｉＯ２ 量を３０〜６０重量％とすることにより、より十分な固化が期待できる。
石灰材は、消石灰、生石灰、貝殻などの廃棄物焼成品などが適しているが、貝殻粉末、石灰石粉末、主成分が炭酸カルシウムであるライムケーキなどの廃棄物も適用できる。シリカ材はシリカヒューム、粘土、白土などの非晶質ＳｉＯ２ が多いものが適している。
【００１４】
（２） 廃棄物等のＣａＯ量に応じて、硫酸鉄などの還元材の添加量を調整する。すなわち、ＣａＯ量が多くなるに伴い、Ｃｒ６＋、Ｓｅなどの溶出が増加する傾向にあるので還元材量を増加させる。具体的には廃棄物等のＣａＯ量１重量％の増加に対し還元材量を０．２〜２重量％増加させ、廃棄物量に対して０．２５〜１５重量％の範囲で調整するのが適している。０．２５重量％未満ではＣｒ６＋、Ｓｅ、Ａｓ等を十分に還元・固定できず、１５重量％を超えると溶出液ｐＨが低くなり、安定化効果が不十分である。
還元材は第一鉄塩（硫酸鉄、塩化鉄など）、硫化物（硫化ナトリウムなど）、低級脂肪酸（シュウ酸、ギ酸など）などの水に可溶性物質が適している。特に、鉄塩はフェライト化物で有害重金属を固定する機能を有するので、この鉄塩を用いることがより好適である。また、硫酸塩はエトリンガイトを生成するので、安定化効果の促進に有効である。
【００１５】
また、短時間に確実に安定化させるために、次の２つの組み合わせにて対応する。
（１） 廃棄物等に石灰材及び／又はシリカ材を添加した後、還元材が溶解した溶液を加え、フルード数が０．５以上の高速で混練を行って、粒子全体が水でぬれるファニキュラー状態の混練物とする。ファニキュラー状態の混練物とすることにより、還元反応及び水和反応が十分に進行し、確実な安定化が図れる。フルード数が０．５未満では粒子表面全体が水でぬれたファニキュラー状態の混練物を製造できない。なお、フルード数は、Ｎ２ Ｒ／ｇ（Ｎ：回転数、Ｒ：攪拌翼径、ｇ：重力加速度）で表される無次元数であり、本発明では混練速度に対応している。
【００１６】
（２） ファニキュラー状態の混練物を４０〜１００℃、望ましくは６０〜９８℃、０．５〜２４ｈ 、望ましくは１〜１０ｈ 、湿度９０％以上で水蒸気処理を行う。その結果、粒子周辺の水分が保持され、温度が高くなるので、水和反応速度が速くなって、短時間の処理にて、確実に安定化が図れる。温度が下限未満では水和反応速度が遅くなり、上限を超える場合は処理装置が高価になる。時間が下限未満では水和反応進行が不十分であり、上限を超える場合は処理装置が高価になる。湿度が９０％未満であると、粒子周辺の水分が揮発するので、水和反応進行が不十分となる。
本発明においては、上記のＣａＯ量、ＳｉＯ２ 量、蒸気処理温度、蒸気処理時間は、本発明における数値範囲又は望ましい数値範囲を適宜組み合わせて用いることができる。
【００１７】
【発明の実施の形態】
以下、本発明の実施の形態について説明する。本発明は下記の実施の形態に何ら限定されるものではなく、適宜変更して実施することができるものである。
図１は本発明の実施の第１形態による汚染土壌・廃棄物の安定化装置を示している。
【００１８】
本実施形態の安定化装置は、汚染土壌又は／及び製紙スラッジ、木くず、有機系汚泥、ごみ、石炭などの燃焼灰、汚泥などの廃棄物単独、もしくは組み合わせた廃棄物と、石灰材及び／又はシリカ材に、還元材（例えば、硫酸第一鉄）を溶解させた水を加えてファニキュラー状態に混練するための混練機１０と、この混練機１０からの混練物を安定な処理物とするための、内部に水平軸１４の攪拌翼１６を有する略水平円筒容器型の水蒸気処理機１２とを主要構成機器として備えている。
【００１９】
混練機１０は、回転軸垂直のアイリッヒミキサ、ヘンシェルミキサなど、回転軸水平のタービュライザ、パドルミキサなどの高速回転で混練する機種が適している。攪拌翼１６を有する蒸気処理機１２は、水平軸が１本又は２本でもよく、加熱は外部加熱と内部加熱を併用するのが望ましい。内部加熱は空洞部１８の攪拌翼１６に水蒸気などを供給する方法、水蒸気を直接供給する方法のいずれでもよいが、内部湿度９０％以上を確実に確保できる水蒸気を直接供給することが望ましい。２０はジャケットである。
【００２０】
図２は本発明の実施の第２形態による汚染土壌・廃棄物の安定化装置を示している。本実施形態の安定化装置は、汚染土壌又は／及び製紙スラッジ、木くず、有機系汚泥、ごみ、石炭などの燃焼灰、汚泥などの廃棄物単独、もしくは組み合わせた廃棄物と、石灰材及び／又はシリカ材に、還元材（例えば、硫酸第一鉄）を溶解させた水を加えてファニキュラー状態に混練するための混練機１０と、この混練機１０からの混練物を安定な処理物とするための、円筒容器２２が回転する略水平円筒容器型の水蒸気処理機１２ａとを主要構成機器として備えている。なお、本実施形態における水蒸気処理機１２ａは攪拌翼を有していない。
【００２１】
混練機１０は、回転軸垂直のアイリッヒミキサ、ヘンシェルミキサなど、回転軸水平のタービュライザ、パドルミキサなどが適している。円筒容器２２が回転する水蒸気処理機１２ａは、セメント焼成炉などに用いられているロータリ型円筒容器が適している。加熱は外部加熱と内部加熱を併用するのが望ましい。内部加熱は水蒸気を直接円筒内部（空洞部１８）に供給する方法が適している。２０はジャケットである。
【００２２】
図３は本発明の実施の第３形態による汚染土壌・廃棄物の安定化装置を示している。本実施形態の安定化装置は、汚染土壌又は／及び製紙スラッジ、木くず、有機系汚泥、ごみ、石炭などの燃焼灰、汚泥などの廃棄物単独、もしくは組み合わせた廃棄物と、石灰材及び／又はシリカ材に、還元材（例えば、硫酸第一鉄）を溶解させた水を加えてファニキュラー状態に混練するための混練機１０と、この混練機１０からの混練物を投入するための、上部が開放され、かつ反転用の治具又は係合用突起（図示略）を有する複数の小容器２４と、これらの小容器２４を順次導入し混練物を安定な処理物とするトンネル式水蒸気養生機（水蒸気処理機）２６と、水蒸気養生された処理物の入った小容器２４を持ち上げ、略水平方向に回転し、反転を行い、処理物を排出する構造の反転機２８とを主要構成機器として備えている。
【００２３】
混練機１０は、回転軸垂直のアイリッヒミキサ、ヘンシェルミキサなど、回転軸水平のタービュライザ、パドルミキサなどが適している。反転用の治具付きの上部が開放された小容器２４は、トンネル式水蒸気養生機２６内に設けたレール３０上を移動できるように、キャスター３２付きのものが適している。トンネル式水蒸気養生機２６は、一例として、壁が断熱材で構成され、内部に容器移動用のレール３０と、温度と湿度を維持するための水蒸気吹き出し管３４を有する構造である。反転機２８は小容器２４の持ち上げ、回転・反転を行い、処理物を排出する構造である。
【００２４】
混練物が投入された小容器２４は、例えば、プッシャー等により押されて移動させられる。また、反転機２８としては、例えば、小容器２４の両側に設けられた治具又は係合用突起を挟持部材で係合挟持して、上昇させた後、略水平方向に回転させ、ついで、反転させるようにした構造のもの等を挙げることができる。
【００２５】
【実施例】
以下に実施例及び比較例を示し、本発明の特徴とするところをより一層明確にする。
実施例１
有害重金属等（Ｃｄ、Ｐｂ、Ｃｒ６＋、Ａｓ、Ｔ−Ｈｇ、Ｓｅ、Ｆ、Ｂ）の溶出量が土壌環境基準を超える石炭灰（ＣａＯ：１．５重量％、ＳｉＯ２ ：６０重量％）１００重量部、消石灰３重量部を回転軸垂直の混練機に投入し、フルード数１．５（回転数５１０ｒｐｍ ）で２分間混合して混合粉体（ＣａＯ：３．７重量％、ＳｉＯ２ ：５８．３重量％）を製造した後、硫酸第一鉄２重量部を溶解させた水溶液３０重量部を加え、さらに３分間混練を行い、ファニキュラー状態の混練物を製造した。該混練物を反転用の治具付きの上部が開放された容器に投入し、容器を９５℃に保持したトンネル式水蒸気処理機に送り出して３時間処理を行った。処理後、反転機で処理物を取り出した。処理物の有害重金属等の溶出量は、土壌環境基準を満足した。また、該処理物を家畜糞尿に対して３０重量％混合した結果、ハンドリング性が良好となり、悪臭の発生も抑制された。
【００２６】
実施例２
有害重金属等の溶出量が土壌環境基準を超える製紙スラッジ灰（ＣａＯ：１８重量％、ＳｉＯ２ ：３３重量％）１００重量部、消石灰３重量部を回転軸垂直の混練機に投入し、フルード数１．５（回転数５１０ｒｐｍ ）で２分間混合して混合粉体（ＣａＯ：１９．６重量％、ＳｉＯ２ ：３２．０重量％）を製造した後、硫酸第一鉄６重量部を溶解させた水溶液５５重量部を加え、さらに３分間混練を行い、ファニキュラー状態の混練物を製造した。該混練物を９５℃に保持した容器が回転する水蒸気処理機に投入し、１時間処理を行った。処理物の有害重金属等の溶出量は、土壌環境基準を満足した。
【００２７】
実施例３
有害重金属等の溶出量が土壌環境基準を超える汚染土壌（水分：４５重量％、ＣａＯ：２．０重量％、ＳｉＯ２ ：３５重量％）１００重量部、製紙スラッジ灰（ＣａＯ：１８重量％、ＳｉＯ２ ：３３重量％）３０重量部、生石灰２重量部を回転軸水平の混練機に投入し（混合物成分：ＣａＯ：５．６重量％、ＳｉＯ２ ：３４．０重量％）、ただちに、硫酸第一鉄１．５重量部を溶解させた水溶液５重量部を加え、フルード数２．０（回転数６５０ｒｐｍ ）で３分間混練を行い、ファニキュラー状態の混練物を製造した。該混練物を９５℃に保持した二軸の攪拌翼を有する水蒸気処理機に投入し、２時間処理を行った。処理物の有害重金属等の溶出量は、土壌環境基準を満足した。
【００２８】
実施例４
有害重金属等の溶出量が土壌環境基準を超える石炭灰（ＣａＯ：１．０重量％、ＳｉＯ２ ：５４重量％）１００重量部、ライムケーキ（水分：２５重量％、ＣａＣＯ３ ：７０重量％）１０重量部を回転軸垂直の混練機に投入し、フルード数１．５（回転数５１０ｒｐｍ ）で２分間混合して混合粉体（ＣａＯ：４．５重量％、ＳｉＯ２ ：４９．１重量％）を製造した後、硫酸第一鉄０．５重量部を溶解させた水溶液３１重量部を加え、さらに３分間混練を行い、ファニキュラー状態の混練物を製造した。該混練物を９５℃に保持した二軸の攪拌翼を有する水蒸気処理機に投入し、１時間処理を行った。処理物の有害重金属等の溶出量は、土壌環境基準を満足した。
【００２９】
比較例１
有害重金属等の溶出量が土壌環境基準を超える石炭灰（ＣａＯ：１．５重量％、ＳｉＯ２ ：６０重量％）１００重量部、消石灰３重量部を回転軸垂直の混練機に投入し、フルード数１．５（回転数５１０ｒｐｍ ）で２分間混合して混合粉体（ＣａＯ：３．７重量％、ＳｉＯ２ ：５８．２重量％）を製造した後、水３０重量部を加え、さらに３分間混練を行い、ファニキュラー状態の混練物を製造した。該混練物を９５℃に保持した二軸の攪拌翼を有する水蒸気処理機に投入し、２時間処理を行った。処理物の有害重金属等の溶出量において、Ｃｒ６＋（０．１５ｍｇ／Ｌ ）、Ｓｅ（０．０３ｍｇ／Ｌ ）が土壌環境基準を満足しなかった。
【００３０】
比較例２
有害重金属等の溶出量が土壌環境基準を超える石炭灰（ＣａＯ：１．５重量％、ＳｉＯ２ ：６０重量％）１００重量部を回転軸垂直の混練機に投入後、硫酸第一鉄２重量部を溶解させた水溶液３０重量部を加え、フルード数１．５（回転数５１０ｒｐｍ ）３分間混練を行い、ファニキュラー状態の混練物を製造した。該混練物を反転用の治具付きの上部が開放された容器に投入し、容器を９５℃に保持したトンネル式水蒸気処理機に送り出して５時間処理を行った。処理後、反転機で処理物を取り出した。処理物の有害重金属等の溶出量において、Ｂ（１．５ｍｇ／Ｌ ）、Ａｓ（０．０５ｍｇ／Ｌ ）が土壌環境基準を満足しなかった。
【００３１】
比較例３
有害重金属等の溶出量が土壌環境基準を超える石炭灰（ＣａＯ：１．５重量％、ＳｉＯ２ ：６０重量％）１００重量部、消石灰３重量部を回転軸垂直の混練機に投入し、フルード数０．２５（回転数８５ｒｐｍ ）で２分間混合して混合粉体（ＣａＯ：３．７重量％、ＳｉＯ２ ：５８．２重量％）を製造した後、硫酸第一鉄１重量部を溶解させた水溶液３３重量部を加え、さらに４分間混練を行い、ペンデュラー状態（粒子表面が均一に水でぬれていない状態）の混練物を製造した。該混練物を９５℃に保持した二軸の攪拌翼を有する水蒸気処理機に投入し、２時間処理を行った。処理物の有害重金属等の溶出量において、Ｃｒ６＋（０．１１ｍｇ／Ｌ ）、Ｓｅ（０．０２ｍｇ／Ｌ ）が土壌環境基準を満足しなかった。
【００３２】
【発明の効果】
本発明は上記のように構成されているので、つぎのような効果を奏する。
（１） 汚染土壌又は／及び廃棄物を安価な添加材と簡単な処理にて低コストで安定化を図ることができる。
（２） 還元材の還元作用と、還元材、石灰、シリカとの反応生成物であるフェライト、Ｃ−Ｓ−Ｈ、エトリンガイトにて有害重金属等の安定化が確実に図ることができる。
（３） 水蒸気処理を行うことにより、季節、地域にて異なる雰囲気温度の違いによる安定化効果の差異をなくし、短時間に安定化を図ることができる。
（４） 安定化物は、埋戻材、盛土材などの土木資材、汚泥等の水分調整材、家畜糞尿などの水分調整と脱臭を兼ねた処理材、土壌改良材などの多くの用途への展開を図ることができる。
【図面の簡単な説明】
【図１】本発明の実施の第１形態による汚染土壌・廃棄物の安定化装置の概略構成図である。
【図２】本発明の実施の第２形態による汚染土壌・廃棄物の安定化装置の概略構成図である。
【図３】本発明の実施の第３形態による汚染土壌・廃棄物の安定化装置の概略構成図である。
【符号の説明】
１０ 混練機
１２、１２ａ 水蒸気処理機
１４ 水平軸
１６ 攪拌翼
１８ 空洞部
２０ ジャケット
２２ 円筒容器
２４ 小容器
２６ トンネル式水蒸気養生機
２８ 反転機
３０ レール
３２ キャスター
３４ 水蒸気吹き出し管[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a method and a stabilizing device for stabilizing contaminated soil containing harmful heavy metals and / or waste such as combustion ash and sludge. The stabilized treated material can be used as a backfill material, a civil engineering material such as an embankment material, a moisture adjusting material such as sludge, a treating material having both moisture adjustment and deodorization such as livestock manure, a soil improving material, and the like. .
[0002]
[Prior art]
Conventionally, the following method has been proposed as a method for treating contaminated soil or waste.
(1) A method for detoxifying soil or waste by adding iron sulfate and water to a soil or industrial waste containing a soluble heavy metal and then adding a calcium compound to adjust the pH to an appropriate range. (For example, see Patent Document 1).
(2) A method of stabilizing contaminated soil by adding a reducing agent such as iron sulfate, cement, and gypsum to the heavy metal contaminated soil and performing a heat treatment at 50 to 150 ° C (for example, see Patent Document 2).
(3) After finely pulverized waste is molded by adding and mixing a solidification accelerator and / or a reducing agent, if necessary, in the presence of a calcium component, the mixture is placed in water or steam at a temperature of 50 ° C. or higher under atmospheric pressure. A method of solidifying waste by leaving and curing for at least three days (for example, see Patent Document 3).
[0003]
[Patent Document 1]
JP 2001-121131 A (page 1)
[Patent Document 2]
JP-A-2000-102776 (pages 1 and 2)
[Patent Document 3]
JP-A-56-161880 (page 1)
[0004]
[Problems to be solved by the invention]
These conventional techniques have the following problems. In the method (1), since the treatment is performed at room temperature, the degree of progress of the reaction varies greatly depending on the ambient temperature depending on the region, season, and the like. In addition, since the amounts of CaO and SiO 2 are not adjusted, there is variation in the formation of hydrates such as CSH. Furthermore, since the calcium compound is added after the addition of iron sulfate and water, the dispersion of the calcium compound becomes insufficient. As a result, reliable stabilization of various types of contaminated soil and industrial waste cannot be achieved regardless of the region and season.
[0005]
In the method (2), since the heat treatment is performed at 50 to 150 ° C., the difference in the treatment effect depending on the region and season is reduced, but the treatment in a dry atmosphere causes insufficient progress of the hydration reaction. In addition, since the amounts of CaO and SiO 2 are not adjusted, there is variation in the formation of hydrates such as CSH. Therefore, reliable stabilization of various types of contaminated soil cannot be achieved.
[0006]
The method (3) is a method in which mixing, molding, and curing are performed for three days or more, so that the processing cost is high. In addition, since the amounts of CaO and SiO 2 are not adjusted, there is variation in the formation of hydrates such as CSH. Therefore, it is not possible to stably stabilize various kinds of fine powdery waste.
Further, in (1), (2) and (3), there is no specific description about the mixing method, the kneading method, and the kneaded material state, but the funicular state by kneading in the method of the present invention (the whole particle surface is liquid). (Wet, granular state of several hundred μm to several tens of mm) is not described.
[0007]
The present invention has been made in view of the above points, and an object of the present invention is to stably stabilize various kinds of contaminated soil or / and wastes singly or in combination in a short time regardless of the season or region. The present invention provides a method and apparatus capable of performing the following.
[0008]
[Means for Solving the Problems]
In order to achieve the above object, the method for stabilizing contaminated soil / waste of the present invention comprises contaminated soil or / and / or at least one of burning ash and sludge such as paper sludge, wood chips, organic sludge, garbage, and coal. A lime material and / or a silica material are added to the waste, and the amount of CaO is adjusted to 2.5 to 35% by weight and the amount of SiO 2 is adjusted to 25 to 65% by weight. After being kneaded with water in which 25 to 15% by weight of a reducing agent is dissolved, a kneaded state is formed in a funicular state, and then a stable processed material is formed by steaming at 40 to 100 ° C. for 0.5 to 24 hours. (See FIGS. 1-3).
[0009]
In this method, it is preferable to use, as the lime material, at least one of calcined waste products containing CaO, such as slaked lime, quicklime, shells, shell powder, limestone powder, and lime cake whose main component is calcium carbonate.
As the silica material, it is preferable to use a substance having a high amorphous SiO 2 content of at least one of silica fume, clay and clay.
In addition, as the reducing agent, at least one of a water-soluble substance such as a ferrous salt such as ferrous sulfate and ferrous chloride, a sulfide such as sodium sulfide, and a lower fatty acid such as oxalic acid and formic acid is used. Is preferred.
[0010]
The stabilizing device for contaminated soil and waste of the present invention is a device for adding water in which a reducing agent is dissolved to contaminated soil or / and waste, lime and / or silica, and kneading the mixture into a funicular state. A kneader and a substantially horizontal cylindrical vessel-type steam processor having a stirring blade with a horizontal axis therein for charging the kneaded material from the kneader to obtain a stable processed product. (See FIG. 1).
[0011]
Further, the stabilizing apparatus of the present invention is a kneader for adding water in which a reducing agent is dissolved to contaminated soil or / and waste, lime and / or silica, and kneading the mixture into a funicular state. It is characterized by having a substantially horizontal cylindrical container-type steam processor in which the container rotates, for putting the kneaded material from the kneader into a stable processed product (see FIG. 2).
[0012]
Further, the stabilizing device of the present invention is a kneader for contaminating soil or / and waste, lime and / or silica, and adding water in which a reducing agent is dissolved to knead the mixture into a funicular state. A plurality of small containers having an open top for charging the kneaded material from the kneading machine, a tunnel-type steam curing machine for sequentially introducing these small containers to stably process the kneaded material, and a steam curing device. It is characterized in that it is provided with a reversing machine configured to lift the small container containing the processed material, rotate the container in a substantially horizontal direction, perform inversion, and discharge the processed material (see FIG. 3).
[0013]
In the method and apparatus of the present invention, the following two combinations are used for application to various types of contaminated soil and waste.
(1) by the addition of lime material and / or silica material, CaO amount from 2.5 to 35 wt%, such as a waste, preferably 3.5 to 35 wt%, the amount of SiO 2 25 to 65 wt%, preferably Is adjusted to 30 to 60% by weight. When the amount of CaO is less than the lower limit, the reaction of C—S—H or the like does not proceed. On the other hand, when the amount exceeds the upper limit, a large amount of free CaO remains and the stabilizing effect is insufficient. When the amount of SiO 2 is less than the lower limit or exceeds the upper limit, the CSH reaction does not proceed sufficiently, and the stabilizing effect is insufficient. Incidentally, the amount of CaO from 3.5 to 35 wt%, by the amount of SiO 2 and 30 to 60 wt% can be expected more sufficient solidification.
As the lime material, fired waste products such as slaked lime, quick lime, and shells are suitable, but waste such as shell powder, limestone powder, and lime cake whose main component is calcium carbonate can also be used. As the silica material, a material containing a large amount of amorphous SiO 2 such as silica fume, clay, and clay is suitable.
[0014]
(2) The amount of the reducing agent such as iron sulfate is adjusted in accordance with the amount of CaO in the waste. That is, as the amount of CaO increases, the elution of Cr 6+ , Se and the like tends to increase, so the amount of the reducing agent is increased. Specifically, the amount of the reducing agent is increased by 0.2 to 2% by weight with respect to the increase of 1% by weight of CaO such as waste, and is adjusted in the range of 0.25 to 15% by weight with respect to the amount of waste. Are suitable. If it is less than 0.25% by weight, Cr 6+ , Se, As, etc. cannot be sufficiently reduced and fixed, and if it exceeds 15% by weight, the pH of the eluate becomes low and the stabilizing effect is insufficient.
As the reducing agent, a water-soluble substance such as ferrous salt (iron sulfate, iron chloride, etc.), sulfide (sodium sulfide, etc.), lower fatty acid (oxalic acid, formic acid, etc.) is suitable. In particular, since an iron salt has a function of fixing a harmful heavy metal with a ferrite compound, it is more preferable to use the iron salt. In addition, since sulfate produces ettringite, it is effective in promoting a stabilizing effect.
[0015]
In addition, in order to stabilize in a short time, the following two combinations are used.
(1) After adding lime and / or silica to waste, etc., add a solution in which a reducing agent is dissolved, knead at a high speed with a Froude number of 0.5 or more, and wet the whole particles with water. It is a kneaded material in a curable state. By forming the kneaded material in a funicular state, the reduction reaction and the hydration reaction sufficiently proceed, and reliable stabilization can be achieved. If the Froude number is less than 0.5, a kneaded material in a funicular state in which the entire particle surface is wet with water cannot be produced. The Froude number is a dimensionless number represented by N 2 R / g (N: rotation speed, R: stirring blade diameter, g: gravitational acceleration), and corresponds to the kneading speed in the present invention.
[0016]
(2) The kneaded material in a funicular state is subjected to steam treatment at 40 to 100 ° C, desirably 60 to 98 ° C, 0.5 to 24 hours, desirably 1 to 10 hours, and a humidity of 90% or more. As a result, the moisture around the particles is retained and the temperature is increased, so that the hydration reaction speed is increased, and the stabilization can be surely achieved in a short time. When the temperature is lower than the lower limit, the hydration reaction rate is slow, and when the temperature is higher than the upper limit, the processing apparatus becomes expensive. If the time is less than the lower limit, the progress of the hydration reaction is insufficient, and if the time exceeds the upper limit, the processing apparatus becomes expensive. If the humidity is less than 90%, the water around the particles volatilizes, so that the progress of the hydration reaction becomes insufficient.
In the present invention, CaO amount of the, SiO 2 amount, steaming temperature, the steaming time may be used in combination of numerical ranges or desired numerical ranges of the present invention as appropriate.
[0017]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described. The present invention is not limited to the following embodiments at all, and can be implemented with appropriate modifications.
FIG. 1 shows an apparatus for stabilizing contaminated soil and waste according to a first embodiment of the present invention.
[0018]
The stabilizing device of the present embodiment includes waste singly or combined waste such as contaminated soil or / and paper ash sludge, wood waste, organic sludge, refuse, combustion ash such as coal, sludge, and lime and / or A kneader 10 for adding water in which a reducing agent (for example, ferrous sulfate) is dissolved to a silica material and kneading the mixture in a funicular state, and a kneaded product from the kneader 10 is a stable processed product. For this purpose, a substantially horizontal cylindrical vessel type steam processor 12 having a stirring blade 16 of a horizontal shaft 14 therein is provided as a main component.
[0019]
As the kneading machine 10, a model that performs high-speed kneading such as a turbulizer or a paddle mixer with a horizontal rotation axis such as an Erich mixer or a Henschel mixer with a vertical rotation axis is suitable. The steam processor 12 having the stirring blade 16 may have one or two horizontal axes, and it is desirable to use both external heating and internal heating for heating. The internal heating may be performed by a method of supplying steam or the like to the stirring blades 16 of the hollow portion 18 or a method of directly supplying steam. However, it is desirable to directly supply steam that can reliably secure an internal humidity of 90% or more. 20 is a jacket.
[0020]
FIG. 2 shows an apparatus for stabilizing contaminated soil and waste according to a second embodiment of the present invention. The stabilizing device of the present embodiment includes waste singly or combined waste such as contaminated soil or / and paper ash sludge, wood waste, organic sludge, refuse, combustion ash such as coal, sludge, and lime and / or A kneader 10 for adding water in which a reducing agent (for example, ferrous sulfate) is dissolved to a silica material and kneading the mixture in a funicular state, and a kneaded product from the kneader 10 is a stable processed product. And a substantially horizontal cylindrical container type steam processor 12a in which the cylindrical container 22 rotates. In addition, the steam processor 12a in this embodiment does not have a stirring blade.
[0021]
As the kneader 10, a turbulizer with horizontal rotation axis, a paddle mixer, or the like, such as an Erich mixer or a Henschel mixer with a vertical rotation axis, is suitable. As the steam processor 12a in which the cylindrical container 22 rotates, a rotary type cylindrical container used in a cement firing furnace or the like is suitable. It is desirable to use external heating and internal heating in combination. For the internal heating, a method of supplying steam directly to the inside of the cylinder (hollow portion 18) is suitable. 20 is a jacket.
[0022]
FIG. 3 shows an apparatus for stabilizing contaminated soil and waste according to a third embodiment of the present invention. The stabilizing device of the present embodiment includes waste singly or combined waste such as contaminated soil or / and paper ash sludge, wood waste, organic sludge, refuse, combustion ash such as coal, sludge, and lime and / or A kneader 10 for adding water in which a reducing agent (for example, ferrous sulfate) is dissolved to a silica material and kneading the mixture in a funicular state, and an upper part for charging the kneaded material from the kneader 10. Are open and have a plurality of small containers 24 having a reversing jig or an engaging projection (not shown), and a tunnel type steam curing machine for sequentially introducing these small containers 24 to stably process the kneaded material. (Steam processing machine) 26 and a reversing machine 28 configured to lift the small container 24 containing the steam-cured treated material, rotate it in a substantially horizontal direction, perform inversion, and discharge the treated material, as main components. Have.
[0023]
As the kneader 10, a turbulizer with horizontal rotation axis, a paddle mixer, or the like, such as an Erich mixer or a Henschel mixer with a vertical rotation axis, is suitable. The small container 24 having an open jig for turning over and having a caster 32 is suitable so as to be able to move on a rail 30 provided in a tunnel-type steam curing machine 26. As an example, the tunnel-type steam curing machine 26 has a structure in which a wall is formed of a heat insulating material, and has a rail 30 for moving the container and a steam blowing pipe 34 for maintaining the temperature and the humidity inside. The reversing machine 28 has a structure in which the small container 24 is lifted, rotated and inverted, and the processed material is discharged.
[0024]
The small container 24 into which the kneaded material has been put is moved by being pushed by, for example, a pusher or the like. Further, as the reversing device 28, for example, a jig or an engaging protrusion provided on both sides of the small container 24 is engaged and clamped by a clamping member, raised, and then rotated in a substantially horizontal direction. And the like.
[0025]
【Example】
Hereinafter, examples and comparative examples are shown to further clarify features of the present invention.
Example 1
Harmful heavy metals (Cd, Pb, Cr 6+, As, T-Hg, Se, F, B) coal ash elution amount of exceeding soil environment standard (CaO: 1.5 wt%, SiO 2: 60 wt%) 100 parts by weight and 3 parts by weight of slaked lime are put into a kneader having a rotating shaft perpendicular thereto, and mixed at a Froude number of 1.5 (rotational number of 510 rpm) for 2 minutes to obtain a mixed powder (CaO: 3.7% by weight, SiO 2 : 58.3% by weight), 30 parts by weight of an aqueous solution in which 2 parts by weight of ferrous sulfate was dissolved was added, and the mixture was further kneaded for 3 minutes to produce a kneaded product in a funicular state. The kneaded material was put into a container having an opening at the top and provided with a jig for inversion, and was sent out to a tunnel-type steam treatment machine maintained at 95 ° C. for 3 hours of treatment. After the processing, the processed material was taken out by a reversing machine. The amount of harmful heavy metals and the like eluted from the treated product satisfied the soil environmental standards. In addition, as a result of mixing the treated product with livestock manure at 30% by weight, the handleability was improved and the generation of offensive odor was suppressed.
[0026]
Example 2
Paper sludge ash elution of harmful heavy metals exceeds the environmental quality standards for soil (CaO: 18 wt%, SiO 2: 33 wt%) 100 parts by weight was charged with lime and 3 parts by weight to the rotation shaft vertical kneader, the Froude number 1.5 (rotational speed 510 rpm) for 2 min mixing a mixed powder (CaO: 19.6 wt%, SiO 2: 32.0 wt%) was prepared and dissolved ferrous 6 parts by weight of sulfuric acid 55 parts by weight of the aqueous solution was added, and the mixture was further kneaded for 3 minutes to produce a kneaded material in a funicular state. The kneaded material was put into a steam processor in which a container maintained at 95 ° C. was rotated, and was treated for 1 hour. The amount of harmful heavy metals and the like eluted from the treated product satisfied the soil environmental standards.
[0027]
Example 3
The amount of elution of deleterious heavy metals and the like exceeds the environmental quality standards for soil contaminated soil (water content: 45 wt%, CaO: 2.0 wt%, SiO 2: 35 wt%) 100 parts by weight, paper sludge ash (CaO: 18 wt%, 30 parts by weight of SiO 2 : 33% by weight) and 2 parts by weight of quicklime were put into a kneader having a horizontal rotating shaft (mixture component: CaO: 5.6% by weight, SiO 2 : 34.0% by weight), and immediately 5 parts by weight of an aqueous solution in which 1.5 parts by weight of ferrous iron were dissolved was added, and the mixture was kneaded at a Froude number of 2.0 (at a rotation speed of 650 rpm) for 3 minutes to produce a kneaded material in a funicular state. The kneaded material was charged into a steam processor having a biaxial stirring blade maintained at 95 ° C., and treated for 2 hours. The amount of harmful heavy metals and the like eluted from the treated product satisfied the soil environmental standards.
[0028]
Example 4
Coal ash amount eluted exceeds environmental quality standards for soil toxic heavy metals (CaO: 1.0 wt%, SiO 2: 54 wt%) 100 parts by weight, lime cake (water content: 25 wt%, CaCO 3: 70 wt%) 10 parts by weight were put into a kneader having a rotating shaft perpendicular thereto, and mixed at a Froude number of 1.5 (rotational number of 510 rpm) for 2 minutes to obtain a mixed powder (CaO: 4.5% by weight, SiO 2 : 49.1% by weight). ) Was added, 31 parts by weight of an aqueous solution in which 0.5 part by weight of ferrous sulfate was dissolved, and kneading was further performed for 3 minutes to produce a kneaded material in a funicular state. The kneaded material was charged into a steam processor having a biaxial stirring blade maintained at 95 ° C., and treated for 1 hour. The amount of harmful heavy metals and the like eluted from the treated product satisfied the soil environmental standards.
[0029]
Comparative Example 1
Coal ash elution of harmful heavy metals exceeds the environmental quality standards for soil (CaO: 1.5 wt%, SiO 2: 60 wt%) 100 parts by weight was charged with lime and 3 parts by weight to the rotation shaft vertical kneader, fluid After mixing at a number of 1.5 (at 510 rpm) for 2 minutes to produce a mixed powder (CaO: 3.7% by weight, SiO 2 : 58.2% by weight), 30 parts by weight of water was added, and 3 parts by weight were added. The mixture was kneaded for a minute to produce a kneaded material in a funicular state. The kneaded material was charged into a steam processor having a biaxial stirring blade maintained at 95 ° C., and treated for 2 hours. Regarding the elution amount of harmful heavy metals and the like in the treated product, Cr 6+ (0.15 mg / L) and Se (0.03 mg / L) did not satisfy the soil environmental standards.
[0030]
Comparative Example 2
100 parts by weight of coal ash (CaO: 1.5% by weight, SiO 2 : 60% by weight) in which the amount of harmful heavy metals and the like exceed the soil environmental standard is put into a kneader having a vertical rotating shaft, and then ferrous sulfate 2% 30 parts by weight of an aqueous solution in which the above-mentioned parts were dissolved were added and kneaded for 3 minutes at a Froude number of 1.5 (at a rotation speed of 510 rpm) to produce a kneaded material in a funicular state. The kneaded material was put into a container having an opening at the top with a jig for inversion, and sent out to a tunnel-type steam treatment machine maintained at 95 ° C. for 5 hours of treatment. After the processing, the processed material was taken out by a reversing machine. B (1.5 mg / L) and As (0.05 mg / L) did not satisfy the soil environmental standards in the amount of harmful heavy metals and the like eluted from the treated product.
[0031]
Comparative Example 3
Coal ash elution of harmful heavy metals exceeds the environmental quality standards for soil (CaO: 1.5 wt%, SiO 2: 60 wt%) 100 parts by weight was charged with lime and 3 parts by weight to the rotation shaft vertical kneader, fluid After mixing at a number of 0.25 (rotation speed: 85 rpm) for 2 minutes to produce a mixed powder (CaO: 3.7% by weight, SiO 2 : 58.2% by weight), 1 part by weight of ferrous sulfate is dissolved. 33 parts by weight of the aqueous solution was added, and the mixture was further kneaded for 4 minutes to produce a kneaded product in a pendulum state (a state in which the particle surface was not uniformly wet with water). The kneaded product was charged into a steam processor having a biaxial stirring blade maintained at 95 ° C., and treated for 2 hours. Regarding the elution amount of harmful heavy metals and the like in the treated product, Cr 6+ (0.11 mg / L) and Se (0.02 mg / L) did not satisfy the soil environmental standards.
[0032]
【The invention's effect】
The present invention is configured as described above, and has the following effects.
(1) Contaminated soil or / and waste can be stabilized at low cost with inexpensive additives and simple treatment.
(2) The reducing action of the reducing agent and stabilization of harmful heavy metals and the like can be reliably achieved by ferrite, CSH, and ettringite, which are reaction products of the reducing agent, lime, and silica.
(3) By performing the steam treatment, it is possible to eliminate the difference in the stabilizing effect due to the difference in the ambient temperature between the seasons and the regions, and to stabilize in a short time.
(4) Stabilized materials are used in many applications such as backfill materials, civil engineering materials such as embankment materials, moisture control materials such as sludge, treatment materials that combine moisture control and deodorization such as livestock manure, and soil improvement materials. Can be achieved.
[Brief description of the drawings]
FIG. 1 is a schematic configuration diagram of an apparatus for stabilizing contaminated soil and waste according to a first embodiment of the present invention.
FIG. 2 is a schematic configuration diagram of an apparatus for stabilizing contaminated soil and waste according to a second embodiment of the present invention.
FIG. 3 is a schematic configuration diagram of an apparatus for stabilizing contaminated soil and waste according to a third embodiment of the present invention.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 10 Kneader 12, 12a Steam processing machine 14 Horizontal shaft 16 Stirrer blade 18 Cavity part 20 Jacket 22 Cylindrical container 24 Small container 26 Tunnel type steam curing machine 28 Reversing machine 30 Rail 32 Caster 34 Steam blowing pipe
