JP3843551B2 - Determination method of required amount of liquid chelating agent for fly ash treatment - Google Patents
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Description
【0001】
【発明の属する技術分野】
本発明は飛灰に液体キレート剤を加えて処理することにより飛灰中の重金属、特にPb溶出を防止するために必要な液体キレート剤の添加量を簡便に決定する方法に関する。
【0002】
【従来の技術】
近年、廃水や固体廃棄物中の重金属を捕集、固定化する方法として、アミン誘導体を用いる方法が提案されている。殊に、アミン誘導体の内、ジチオカルバミン酸及びその塩を用いる処理方法については、数多くの提案がなされており、廃水処理分野においては、特公昭56−39358号公報、特公平4−32717号公報等が挙げられる。
【0003】
これらの廃水処理分野で培われたジチオカルバミン酸塩に関する技術は、重金属含有固体廃棄物の処理に応用されている。具体的な重金属含有固体廃棄物の例としては、都市ゴミや産業廃棄物などの焼却プラントから排出される焼却灰や飛灰が挙げられる。飛灰は電気集塵機やバグフィルターで捕集されたのち埋め立てや海洋投棄されているが、これらの飛灰は有害な重金属を多く含んでおり、埋め立て地からの雨水等による鉛、水銀等の溶出は環境汚染の可能性がある。このため飛灰は特別管理廃棄物に指定され、法律で定められた(総理府令第5号)埋め立て溶出基準値を守るべく、「セメント固化法」、「酸その他の溶剤による抽出法」、「溶融固定化法」あるいは「薬剤添加法」のいずれかの処理を施して無害化した後、廃棄することが義務づけられており、無害化処理の判定は環境庁告示第13号法による溶出試験値(溶出濃度)が法律で定める埋め立て溶出基準値未満であるか否かで判断する。
【0004】
さらに、排ガス中の酸性成分(HCl、SOx等)の排出規制の強化に伴い、中和処理に安価な中和剤である消石灰を過剰に添加する焼却設備が増加してきた。その結果消石灰が飛灰に混入し、pH10以上のアルカリ飛灰が大部分を占めるようになり、特に有害成分であるPbの溶出が特に問題となっている。
【0005】
このように、飛灰中の有害成分特にPbの固定化に必要な液体キレート剤量を決定するには液体キレート剤を加えて処理した飛灰を環境庁告示第13号法により効果を判定し、決定するのが一般的であるが、その溶出試験値により薬剤添加量を決める従来の方法では、評価に長時間を要するため、経時的に変動する飛灰の性状に合わせた対応は非常に困難であった。このため現場における飛灰の性状変動に合わせた適正な薬剤処理を行うことが望まれていた。
【0006】
【発明が解決しようとする課題】
本発明の目的は上述した課題を解決し、飛灰中の有害成分、特にPbの固定化に必要な液体キレート剤の添加量を迅速に、さらに簡便に決定できる方法を提供することにある。
【0007】
【課題を解決するための手段】
本発明者等は上記の課題を解決すべく鋭意検討を重ねた結果、ジチオカルバミン酸基を有する液体キレート剤を飛灰に加えて飛灰中の重金属を固定化する方法において、飛灰中のPb及びCuの含有濃度を測定し、これらの測定値と上記液体キレート剤中のジチオカルバミン酸基濃度とから飛灰に添加するに必要な液体キレート剤の添加量を決定でき、さらに飛灰としてpH10以上となるものに対して有効であることを見出し、本発明を完成させるに至った。
【0008】
すなわち本発明は、ジチオカルバミン酸基を有する液体キレート剤を飛灰に加えて処理する方法において、該飛灰中のPb及びCuの含有濃度を測定し、これらの測定値と上記液体キレート剤中のジチオカルバミン酸基濃度とから該飛灰に添加するに必要な液体キレート剤の添加量を決定する方法に関し、さらに、液体キレート剤の添加量を下記(2)式により決定することに関する。
【0009】
A=(28×WCu+27×WPb+3.3)/α (2)
(式中、Aは液体キレート剤添加量(単位は重量%)であり、αは液体キレート剤中のジチオカルバミン酸基濃度(単位はmol/Kg)であり、WCuは飛灰中のCuの含有濃度(単位は重量%)であり、WPbは飛灰中のPb含有濃度(単位は重量%)である。)
尚、本明細書においては、液体キレート剤添加量とは処理対象の飛灰の全重量に対する添加する液体キレート剤重量の重量百分率である。
【0010】
以下、本発明を詳細に説明する。
【0011】
本発明の方法において、その対象となる飛灰とは、特に限定されるものではないが、例えば、通常都市ゴミや産業廃棄物等の焼却施設から排出される焼却灰 (炉底灰)や電気集塵機、バグフィルタ−、マルチサイクロン等で捕集された灰塵、いわゆる飛灰等に適用でき、さらにpH10以上のアルカリ飛灰は好適に用いられる。ここで、飛灰のpHとは環境庁告示第13号法により得られた溶出液のpHを意味する。
【0012】
本発明の方法において用いられる液体キレート剤としては、ジチオカルバミン酸基を有する化合物を含んでおれば特に制限なく用いることができる。例えば、脂肪族もしくは芳香族アミン化合物から誘導されるジチオカルバミン酸又はその塩が使用でき、その製造法としては、通常、二硫化炭素とアミン化合物をアルカリ存在下に反応させて得ることができる。さらに、ジチオカルバミン酸基を有する化合物の塩としては、そのアルカリ金属、アルカリ土類金属又はアンモニウムとの塩が使用でき、この内、リチウム、ナトリウム、カリウム、マグネシム、カルシウム、バリウム、アンモニウムとの塩が好ましく用いられる。
【0013】
また、飛灰に液体キレート剤を加える際に、pH調整剤として、NaOH、Mg(OH)2、Ca(OH)2、FeCl2、FeCl3、Al2(SO4)3等を併用することもでき、また、加湿水として水等の液体を用いることもできる。
【0014】
本発明の方法においては、上記記載の飛灰に液体キレート剤を加えて飛灰中の重金属を固定化するわけであるが、固定化の条件としては、−20℃〜350℃の温度範囲、より好ましくは25℃〜300℃の温度範囲で、本発明の目的を達成できる時間処理すれば良い。また、両者の混合方法については、混練による方法、噴霧による方法、本処理剤スラリーもしくは本処理剤溶液に浸す方法等あらゆる方法を採用することができる。
【0015】
さらに本発明の方法の具体的な態様である、飛灰中のPb及びCuの濃度と添加する液体キレート剤中のジチオカルバミン酸基の濃度とから添加するに必要な液体キレート剤量を求める方法であるが、pH10以上のアルカリ飛灰について以下の実施例で示される従来法で得られるPb等の重金属の固定化に必要な液体キレート剤添加量と飛灰中のPb及びCuの含有濃度の関係を詳細に検討することより、添加するに必要な液体キレート剤量を求めるための計算式を決定することが例示できる。ここで、飛灰のpHとは環境庁告示第13号法で得られた溶出液のpHを意味し、上記(2)式中の液体キレート剤中のジチオカルバミン酸基濃度αは公知の方法であるキレート滴定等であらかじめ求められる。また、飛灰中のPb及びCuの含有濃度は公知の方法により測定でき、例えば、試料である飛灰を溶解後、溶解液を分析する湿式分析法(原子吸光分析法、誘導結合プラズマ発光分析法以下ICP発光分析法と記す)もしくは固体試料を溶解することなく分析する乾式分析法(蛍光X線分析法)などにより容易に得られる。
【0016】
計算式の具体的な決定方法については、従来の方法により得られるPb等の重金属の固定化に必要な液体キレート剤添加量と、飛灰中のPb及びCuの含有濃度につき、重回帰分析等の統計的な手法により解析し、飛灰中のPb等の重金属の固定化に必要な液体キレート剤添加量の算出式を求めることができ、例えば、上記(2)式が得られる。尚、このような計算式で決定される液体キレート剤添加量とは、飛灰中のPb等の重金属を固定化するために必要な液体キレート剤の最低添加量を意味しており、例えば上記(2)式で得られる添加量以上の液体キレート剤を加えれば飛灰中のPb等の重金属は固定化される。
【0017】
さらに、この計算式の求め方については、飛灰の処理形態により、適宜修正することも可能である。すなわち、処理対象の飛灰に対して液体キレート剤を加える処理工程が、バッチ方式による場合、連続的に処理を行う方式などがある。ここで、処理工程がバッチ方式の場合、1又は複数の処理対象飛灰に対して液体キレート剤の必要添加量が上記の方法により求められ処理されるが、必要に応じて、従来の方法により求められた液体キレート剤の必要添加量とを比較し、計算式を修正して実施することもできる。また、処理工程が連続方式の場合、処理対象である飛灰を一定区分に分割し、区分毎の液体キレート剤の必要添加量を求めた後、混練処理等を行う処理工程へ飛灰が送られる途中あるいは混練工程処理槽中に必要量又はそれ以上の液体キレート剤を加えることでよい。この連続方式の場合にも、バッチ方式と同様に、必要に応じて、従来の方法により求められた液体キレート剤の必要添加量とを比較し、計算式を修正して実施することもできる。
【0018】
本発明の方法によれば、飛灰中のPb及びCuの濃度と添加する液体キレート剤中のジチオカルバミン酸基の濃度とから添加するに必要な液体キレート剤量を求めることができる。これは、液体キレート剤中のジチオカルバミン酸基は多くの金属イオンと定量的に反応し、キレート錯体を形成して沈澱するが、飛灰中には様々な重金属を含有しており、経時的な濃度変化を伴うものの、ジチオカルバミン酸基のPb及びCuに対する選択性は他の重金属より高く、特にPbやCuイオンとは安定なキレート錯体を形成して沈澱する。従って、飛灰中のCuやPbともある一定の割合で反応するためであるものと考えられる。
【0019】
しかしながら、このような推定は本発明をなんら限定するものではない。
【0020】
【実施例】
以下、本発明を実施例を用いて更に詳細に説明するが、本発明はこれらに限定されるものではない。尚、以下の実施例ではジチオカルバミン酸基濃度が3.3mol/Kgの液体キレート剤(東ソー(株)製、商品名:TS−500)を使用し、供試試料としてはゴミ焼却場から発生する流動床飛灰73種を使用した。これらの内、50種は実施例1及び比較例1で、残りの23種は実施例2で使用した。また、これら73種の飛灰は環境庁告示第13号法により作製した溶出液pHが10以上のアルカリ飛灰である。
【0021】
実施例1
1)飛灰試料中のPb及びCu含有濃度分析
供試飛灰0.2gを硝酸と過塩素酸で加熱処理した後、不溶分をろ別し、ろ液を100mlへ定容した後、ICP発光分析法でPb及びCuの濃度を分析し、飛灰中のPb及びCuの含有濃度を求めた。
【0022】
2)環境庁告示第13号法による飛灰溶出液中のPb濃度測定
供試飛灰50gへ純水15gと液体キレート剤液の一定重量を加え混練した。混練した飛灰試料50gを1000ml三角フラスコへとり、純水500mlを加えた。これを6時間連続で振とうした後、孔径1ミクロンのグラスファイバーフィルターペーパーでろ過した後の溶液(溶出液)中のPb濃度をICP発光分析法で分析した。
【0023】
3)従来法によるPb固定化に必要な液体キレート剤添加量
液体キレート剤の添加重量を変え、2)の操作を繰り返す。ICP発光分析法でPbが検出されなくなった時(Pb<0.05mg/l)の液体キレート剤添加量の飛灰重量に対する重量百分率を液体キレート剤添加量とする。
【0024】
4)液体キレート剤添加量と飛灰中のPb及びCuの含有濃度の関係
50の供試飛灰について3)で得られたPb固定化に必要な液体キレート剤添加量と1)で得られた飛灰中のPb及びCuの含有濃度の関係を図1に示す。得られたデータよりその相関性を計算すると、Pb固定化に必要な液体キレート剤添加量と飛灰中のPbの含有濃度との相関係数は0.76、Pb固定化に必要な液体キレート剤添加量と飛灰中のCuの含有濃度との相関係数は0.77、Pb固定化に必要な液体キレート剤添加量と飛灰中のPb及びCuの含有濃度との重相関係数は0.92となり、液体キレート剤添加量と飛灰中のPb及びCuの含有濃度の間には正の相関関係が見られた。さらに、図1におけるPb固定化に必要な液体キレート剤添加量と1)で得られた飛灰中のPb及びCuの含有濃度の関係につき、重回帰分析により飛灰中のPb固定化に必要な液体キレート剤添加量算出式を求めると、前記した(2)式が得られた。
【0025】
5)従来法との比較
3)の従来法で得られた液体キレート剤添加量と前記(2)式に、1)で得られたPb及びCuの濃度を代入して得られた液体キレート剤添加量の計算値の関係を図2に示す。図2における実線は計算値と実測値が一致する点を結んだ線であり、この線より上側は計算式による液体キレート剤添加量が実測値より高く、Pb溶出が起こらない領域である。逆にこの線より下の領域は計算値が実測値より低くPb溶出が起こる領域である。図2から明らかなように供試した50の飛灰試料のうち実線より下側にはわずか3点、割合にすると6%にすぎず、上記 (2)式はPb固定化に必要な液体キレート剤添加量を適正に与えている。
【0026】
実施例2
新たな23の飛灰に対して実施例1の1)と同様にして飛灰中のPb及びCuの含有濃度を分析し、前記(2)式からPb固定化に必要な液体キレート剤添加量を算出した。次に実施例1の3)と同様に従来法でPb固定化に必要な液体キレート剤添加量を求め、両者の関係を図3に示す。図3から明らかなようにほとんどすべての飛灰試料に対して計算値は実測値を上回っており、Pb固定化に必要な液体キレート剤添加量を適正に与えており、(2)式の有効性が確認できた。
【0027】
比較例1
実施例1の50種の未処理飛灰(液体キレート剤を添加する前の飛灰)試料に対して、以下の方法で溶出液を作製した。すなわち、飛灰試料50gを1000ml三角フラスコへとり、純水500ml加え、6時間連続で振とうした後、孔径1ミクロンのグラスファイバ−フィルタ−ペ−パ−でろ過した後の溶液を未処理飛灰の溶出液とする溶出液のpHをガラスイオン電極水素イオン濃度測定計で測定した。また、溶出液中のPb及びCuの濃度をICP発光分析法で分析した。Pb及びCuの溶出濃度と実施例1の3)で得られたPb固定化に必要なキレート剤添加量との関係を図4に示す。
【0028】
得られたデータよりその相関性を計算すると、Pb固定化に必要な液体キレート剤添加量と未処理飛灰からのPbの溶出濃度との相関係数は0.34、Pb固定化に必要な液体キレート剤添加量と未処理飛灰からのCuの溶出濃度との相関係数は0.50、Pb固定化に必要な液体キレート剤添加量と未処理飛灰からのPb及びCuの溶出濃度との重相関係数は0.52となり、液体キレート剤添加量と未処理飛灰からのPb及びCuの溶出濃度との間には何ら因果関係は見られなかった。また、溶出液のpHとPb及びCuの溶出率(未処理飛灰中に含有されるPb、Cuの量に対して、溶出されたもののそれぞれの比率)との関係を図5に示す。図5より飛灰からのPb及びCuの溶出率は溶出液のpHに無関係で飛灰によって異なることがわかる。このように、飛灰からのPbやCuの溶出濃度からその固定化に必要な液体キレート剤添加量を簡便な計算式により決定することはできなかった。
【図面の簡単な説明】
【図1】実施例1の結果を示すグラフである。図中、白丸は飛灰中のPb含有濃度を、黒丸は飛灰中のCu含有濃度を表す。図において、横軸(X軸)は液体キレート剤添加量(重量%)を、縦軸(Y軸)は飛灰中のPb及びCu含有濃度(対数表示)を表す。
【図2】実施例1の結果を示すグラフである。図において、横軸(X軸)は従来法により得られた液体キレート剤添加量(重量%、実測値)を、縦軸(Y軸)は本発明の方法により求められた液体キレート剤添加量(重量%、予測値)を表す。
【図3】実施例2の結果を示すグラフである。図において、横軸(X軸)は従来法により得られた液体キレート剤添加量(重量%、実測値)を、縦軸(Y軸)は本発明の方法により求められた液体キレート剤添加量(重量%、予測値)を表す。
【図4】比較例1の結果を示すグラフである。図中、白丸は未処理飛灰からのPb溶出濃度を、黒丸は未処理飛灰からのCu溶出濃度を表す。図において、横軸(X軸)は液体キレート剤添加量(重量%)を、縦軸(Y軸)は溶出された溶出液中のPb及びCu濃度(対数表示)を表す。
【図5】比較例1の結果を示すグラフである。図中、白丸は未処理飛灰からのPb溶出率を、黒丸は未処理飛灰からのCu溶出率を表す。図において、横軸 (X軸)は溶出液のpHを、縦軸(Y軸)は未処理飛灰より溶出された溶出液中のPb及びCuの溶出率を表す。
【符号の説明】
1:図2において、従来法で得られた液体キレート剤添加量(実測値)と前記(2)式に実施例1の1)で得られたPb及びCuの濃度を代入して得られた計算値が一致する点を結んだ線。
2:図3において、従来法で得られた液体キレート剤添加量(実測値)と前記(2)式に実施例1の1)で得られたPb及びCuの濃度を代入して得られた計算値が一致する点を結んだ線。
【発明の効果】
以上詳しく説明したように本発明によれば処理対象の飛灰中のPb及びCu含有濃度を分析することでPb等の固定化に必要な液体キレート剤の添加量を簡単な計算式により迅速かつ適正に決定することができ、飛灰の性状に対応した適正な薬剤処理を迅速に行うことができる。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method for easily determining the amount of liquid chelating agent added to prevent elution of heavy metals in fly ash, particularly Pb, by adding a liquid chelating agent to fly ash.
[0002]
[Prior art]
In recent years, a method using an amine derivative has been proposed as a method for collecting and immobilizing heavy metals in waste water or solid waste. In particular, many treatment methods using dithiocarbamic acid and its salts among amine derivatives have been proposed. In the wastewater treatment field, Japanese Patent Publication No. 56-39358, Japanese Patent Publication No. 4-32717, etc. Is mentioned.
[0003]
The technology related to dithiocarbamate cultivated in the wastewater treatment field has been applied to the treatment of heavy metal-containing solid waste. Specific examples of heavy metal-containing solid waste include incineration ash and fly ash discharged from incineration plants such as municipal waste and industrial waste. Fly ash is collected by an electrostatic precipitator or bag filter, and then landfilled or dumped into the ocean. These fly ash contains a lot of harmful heavy metals, and elution of lead, mercury, etc. by rainwater from the landfill site. There is a possibility of environmental pollution. For this reason, fly ash is designated as specially managed waste, and the “cement solidification method”, “extraction method with acids and other solvents”, “ It is obliged to dispose of the product after detoxifying it by applying either the melt-fixing method or the chemical addition method. Judgment is made based on whether or not (elution concentration) is less than the landfill elution reference value stipulated by law.
[0004]
Furthermore, with the tightening of emission regulations for acidic components (HCl, SOx, etc.) in exhaust gas, incineration facilities that excessively add slaked lime, which is an inexpensive neutralizing agent, to neutralization have increased. As a result, slaked lime is mixed in the fly ash, and alkaline fly ash having a pH of 10 or more occupies most of the ash, and in particular, elution of Pb, which is a harmful component, is particularly problematic.
[0005]
Thus, in order to determine the amount of liquid chelating agent necessary for immobilization of harmful components in fly ash, especially Pb, the effect of fly ash treated by adding liquid chelating agent is determined by the Environmental Agency Notification No. 13 However, since it takes a long time to evaluate the conventional method of determining the amount of drug added based on the dissolution test value, the response to the characteristics of fly ash that varies over time is extremely high. It was difficult. For this reason, it has been desired to perform an appropriate chemical treatment in accordance with fluctuations in the properties of fly ash on site.
[0006]
[Problems to be solved by the invention]
An object of the present invention is to solve the above-described problems and to provide a method capable of quickly and more easily determining the amount of a liquid chelating agent necessary for immobilizing harmful components in fly ash, particularly Pb.
[0007]
[Means for Solving the Problems]
As a result of intensive studies to solve the above problems, the present inventors have added a liquid chelating agent having a dithiocarbamic acid group to fly ash to immobilize heavy metals in fly ash. In addition, the content of Cu and Cu can be measured, and the amount of liquid chelating agent required to be added to the fly ash can be determined from these measured values and the dithiocarbamate group concentration in the liquid chelating agent. As a result, the present invention was completed.
[0008]
That is, the present invention is a method in which a liquid chelating agent having a dithiocarbamic acid group is added to fly ash to measure the concentration of Pb and Cu in the fly ash, and these measured values and the liquid chelating agent in the liquid chelating agent are measured. The present invention relates to a method for determining the addition amount of a liquid chelating agent necessary for adding to the fly ash from the dithiocarbamic acid group concentration, and further relates to determining the addition amount of the liquid chelating agent by the following equation (2).
[0009]
A = (28 × W Cu + 27 × W Pb +3.3) / α (2)
(In the formula, A is the amount of liquid chelating agent added (unit: wt%), α is the concentration of dithiocarbamate group in the liquid chelating agent (unit: mol / Kg), and W Cu is the amount of Cu in fly ash. content level (in wt%) is, W Pb is (the unit% by weight) Pb concentration of the fly ash is.)
In the present specification, the liquid chelating agent addition amount is a weight percentage of the weight of the liquid chelating agent added to the total weight of the fly ash to be treated.
[0010]
Hereinafter, the present invention will be described in detail.
[0011]
In the method of the present invention, the target fly ash is not particularly limited, but, for example, incineration ash (furnace bottom ash) or electricity discharged from incineration facilities such as municipal waste and industrial waste. It can be applied to ash dust collected by a dust collector, bag filter, multi-cyclone, etc., so-called fly ash, and alkaline fly ash having a pH of 10 or more is preferably used. Here, the pH of fly ash means the pH of the eluate obtained by the Environmental Agency Notification No. 13 method.
[0012]
The liquid chelating agent used in the method of the present invention can be used without particular limitation as long as it contains a compound having a dithiocarbamic acid group. For example, dithiocarbamic acid derived from an aliphatic or aromatic amine compound or a salt thereof can be used, and as a production method thereof, carbon disulfide and an amine compound are usually reacted in the presence of an alkali. Furthermore, as a salt of a compound having a dithiocarbamic acid group, a salt with an alkali metal, an alkaline earth metal or ammonium can be used, and among these, a salt with lithium, sodium, potassium, magnesium, calcium, barium, ammonium is used. Preferably used.
[0013]
In addition, when adding a liquid chelating agent to fly ash, NaOH, Mg (OH) 2 , Ca (OH) 2 , FeCl 2 , FeCl 3 , Al 2 (SO 4 ) 3, etc. should be used in combination. Moreover, liquids, such as water, can also be used as humidification water.
[0014]
In the method of the present invention, a liquid chelating agent is added to the fly ash described above to immobilize heavy metals in the fly ash, but as the immobilization conditions, a temperature range of −20 ° C. to 350 ° C., More preferably, the treatment may be performed in a temperature range of 25 ° C. to 300 ° C. for a time that can achieve the object of the present invention. Moreover, about the mixing method of both, all methods, such as the method by kneading | mixing, the method by spraying, the method immersed in this processing agent slurry or this processing agent solution, are employable.
[0015]
Furthermore, in a specific embodiment of the method of the present invention, a method for determining the amount of liquid chelating agent necessary for addition from the concentration of Pb and Cu in fly ash and the concentration of dithiocarbamic acid group in the liquid chelating agent to be added. There is a relationship between the concentration of Pb and Cu contained in the fly ash and the amount of liquid chelating agent added necessary for immobilizing heavy metals such as Pb obtained by the conventional method shown in the following examples for alkaline fly ash of
[0016]
About the specific determination method of the calculation formula, multiple regression analysis, etc., for the amount of liquid chelating agent necessary for immobilization of heavy metals such as Pb obtained by conventional methods, and the concentration of Pb and Cu in fly ash, etc. The calculation formula of the amount of liquid chelating agent added necessary for immobilizing heavy metals such as Pb in fly ash can be obtained, for example, the above formula (2) is obtained. In addition, the liquid chelating agent addition amount determined by such a calculation formula means the minimum addition amount of the liquid chelating agent necessary for immobilizing heavy metals such as Pb in fly ash. If a liquid chelating agent of an addition amount or more obtained by the formula (2) is added, heavy metals such as Pb in fly ash are immobilized.
[0017]
Further, the calculation formula can be appropriately corrected depending on the fly ash processing mode. That is, when the treatment process for adding the liquid chelating agent to the fly ash to be treated is based on a batch method, there is a method of performing the treatment continuously. Here, when the processing step is a batch system, the required addition amount of the liquid chelating agent is obtained and processed by the above method for one or a plurality of processing target fly ash, but if necessary, by a conventional method It can also be carried out by comparing the calculated amount of liquid chelating agent required and correcting the calculation formula. In addition, when the treatment process is a continuous process, the fly ash to be treated is divided into certain categories, the required amount of liquid chelating agent added for each category is determined, and then the fly ash is sent to the treatment step where the kneading process is performed. A necessary amount or more of a liquid chelating agent may be added in the middle of the process or in the kneading process treatment tank. Also in the case of this continuous method, as in the case of the batch method, if necessary, the required amount of liquid chelating agent obtained by a conventional method can be compared, and the calculation formula can be corrected.
[0018]
According to the method of the present invention, the amount of liquid chelating agent required for addition can be determined from the concentration of Pb and Cu in fly ash and the concentration of dithiocarbamic acid groups in the liquid chelating agent to be added. This is because the dithiocarbamic acid group in the liquid chelating agent reacts quantitatively with many metal ions to form a chelate complex and precipitates, but the fly ash contains various heavy metals, Although accompanied by a change in concentration, the selectivity of the dithiocarbamic acid group to Pb and Cu is higher than that of other heavy metals, and in particular, it forms a stable chelate complex with Pb and Cu ions to precipitate. Therefore, it is considered that this is because Cu and Pb in the fly ash react at a certain ratio.
[0019]
However, such estimation does not limit the present invention.
[0020]
【Example】
EXAMPLES Hereinafter, although this invention is demonstrated further in detail using an Example, this invention is not limited to these. In the following examples, a liquid chelating agent having a dithiocarbamic acid group concentration of 3.3 mol / Kg (trade name: TS-500, manufactured by Tosoh Corporation) is used, and the test sample is generated from a garbage incinerator. 73 fluidized bed fly ash was used. Of these, 50 were used in Example 1 and Comparative Example 1, and the remaining 23 were used in Example 2. These 73 types of fly ash are alkaline fly ash having an eluate pH of 10 or more prepared by the Environmental Agency Notification No. 13 method.
[0021]
Example 1
1) Concentration analysis of Pb and Cu in fly ash sample 0.2g of test fly ash was heat-treated with nitric acid and perchloric acid, then the insoluble matter was filtered off, the filtrate was made up to 100 ml, and then ICP emission was performed. The concentration of Pb and Cu was analyzed by an analysis method to determine the concentration of Pb and Cu in the fly ash.
[0022]
2) Measurement of Pb concentration in fly ash eluate according to Notification No. 13 of the Environment Agency To 50 g of test fly ash, 15 g of pure water and a constant weight of a liquid chelating agent solution were added and kneaded. 50 g of the kneaded fly ash sample was taken into a 1000 ml Erlenmeyer flask and 500 ml of pure water was added. This was shaken continuously for 6 hours, and then the Pb concentration in the solution (eluate) after being filtered through glass fiber filter paper having a pore size of 1 micron was analyzed by ICP emission spectrometry.
[0023]
3) Addition amount of liquid chelating agent necessary for Pb immobilization by the conventional method Change the addition weight of the liquid chelating agent and repeat the operation of 2). When Pb is no longer detected by ICP emission analysis (Pb <0.05 mg / l), the weight percentage of the amount of liquid chelating agent added to the fly ash weight is defined as the amount of liquid chelating agent added.
[0024]
4) Relationship between addition amount of liquid chelating agent and Pb and Cu content concentration in fly ash For test fly ash of 50, obtained in 1) with addition amount of liquid chelating agent necessary for Pb immobilization obtained in 3) The relationship between the Pb and Cu content concentrations in the fly ash is shown in FIG. When the correlation is calculated from the obtained data, the correlation coefficient between the addition amount of the liquid chelating agent necessary for Pb immobilization and the Pb content concentration in the fly ash is 0.76, and the liquid chelate necessary for Pb immobilization. Correlation coefficient between the additive addition amount and the Cu concentration in the fly ash is 0.77, and the multiple correlation coefficient between the addition amount of the liquid chelating agent necessary for Pb immobilization and the Pb and Cu concentration in the fly ash Was 0.92, and a positive correlation was found between the amount of liquid chelating agent added and the concentration of Pb and Cu contained in the fly ash. Furthermore, regarding the relationship between the amount of liquid chelating agent addition necessary for Pb fixation in FIG. 1 and the Pb and Cu concentration in fly ash obtained in 1), it is necessary for Pb fixation in fly ash by multiple regression analysis. When a formula for calculating the amount of liquid chelating agent added was obtained, the above-described formula (2) was obtained.
[0025]
5) Comparison with the conventional method Liquid chelating agent obtained by substituting the added amount of the liquid chelating agent obtained by the conventional method of 3) and the concentration of Pb and Cu obtained by 1) into the formula (2). The relationship of the calculated amount of addition is shown in FIG. The solid line in FIG. 2 is a line connecting points where the calculated value and the measured value coincide with each other, and the area above this line is a region where the liquid chelating agent addition amount by the calculation formula is higher than the actually measured value and Pb elution does not occur. Conversely, the area below this line is the area where the calculated value is lower than the actually measured value and Pb elution occurs. As is clear from FIG. 2, of the 50 fly ash samples tested, only 3 points below the solid line and only 6% in proportion, the above equation (2) is a liquid chelate necessary for Pb immobilization. The additive amount is given appropriately.
[0026]
Example 2
The contents of Pb and Cu in the fly ash were analyzed for 23 new fly ash in the same manner as in 1) of Example 1, and the amount of liquid chelating agent added for Pb immobilization required from the formula (2) Was calculated. Next, as in 3) of Example 1, the amount of liquid chelating agent added necessary for Pb immobilization was determined by the conventional method, and the relationship between the two is shown in FIG. As is clear from FIG. 3, the calculated values for almost all fly ash samples exceed the actual measured values, giving the appropriate amount of liquid chelating agent necessary for Pb immobilization. The sex was confirmed.
[0027]
Comparative Example 1
For the 50 untreated fly ash samples of Example 1 (fly ash before the addition of the liquid chelating agent), an eluate was prepared by the following method. That is, 50 g of a fly ash sample is put into a 1000 ml Erlenmeyer flask, 500 ml of pure water is added, shaken continuously for 6 hours, and then filtered with a glass fiber filter paper having a pore size of 1 micron, the solution after treatment is untreated. The pH of the eluate used as the ash eluate was measured with a glass ion electrode hydrogen ion concentration meter. The concentration of Pb and Cu in the eluate was analyzed by ICP emission analysis. FIG. 4 shows the relationship between the elution concentrations of Pb and Cu and the amount of chelating agent added necessary for Pb immobilization obtained in 3) of Example 1.
[0028]
When the correlation is calculated from the obtained data, the correlation coefficient between the added amount of the liquid chelating agent necessary for Pb immobilization and the elution concentration of Pb from untreated fly ash is 0.34, which is necessary for Pb immobilization. The correlation coefficient between the added amount of liquid chelating agent and the elution concentration of Cu from untreated fly ash is 0.50, and the added amount of liquid chelating agent necessary for Pb immobilization and the elution concentration of Pb and Cu from untreated fly ash The correlation coefficient was 0.52, and no causal relationship was found between the amount of liquid chelating agent added and the elution concentrations of Pb and Cu from untreated fly ash. In addition, FIG. 5 shows the relationship between the pH of the eluate and the elution rate of Pb and Cu (the ratios of elution with respect to the amounts of Pb and Cu contained in the untreated fly ash). FIG. 5 shows that the elution rate of Pb and Cu from the fly ash is different depending on the fly ash regardless of the pH of the eluate. Thus, the amount of liquid chelating agent required for immobilization from the elution concentration of Pb and Cu from fly ash could not be determined by a simple calculation formula.
[Brief description of the drawings]
1 is a graph showing the results of Example 1. FIG. In the figure, white circles represent the Pb-containing concentration in the fly ash, and black circles represent the Cu-containing concentration in the fly ash. In the figure, the horizontal axis (X axis) represents the amount of liquid chelating agent added (% by weight), and the vertical axis (Y axis) represents the Pb and Cu content concentration (logarithmic display) in the fly ash.
2 is a graph showing the results of Example 1. FIG. In the figure, the horizontal axis (X-axis) represents the amount of liquid chelating agent added (weight%, measured value) obtained by the conventional method, and the vertical axis (Y-axis) represents the amount of liquid chelating agent added obtained by the method of the present invention. (% By weight, predicted value).
3 is a graph showing the results of Example 2. FIG. In the figure, the horizontal axis (X-axis) represents the amount of liquid chelating agent added (weight%, measured value) obtained by the conventional method, and the vertical axis (Y-axis) represents the amount of liquid chelating agent added obtained by the method of the present invention. (% By weight, predicted value).
4 is a graph showing the results of Comparative Example 1. FIG. In the figure, white circles represent Pb elution concentrations from untreated fly ash, and black circles represent Cu elution concentrations from untreated fly ash. In the figure, the horizontal axis (X axis) represents the amount of liquid chelating agent added (% by weight), and the vertical axis (Y axis) represents the Pb and Cu concentrations (logarithm display) in the eluted eluate.
5 is a graph showing the results of Comparative Example 1. FIG. In the figure, white circles represent Pb elution rates from untreated fly ash, and black circles represent Cu elution rates from untreated fly ash. In the figure, the horizontal axis (X axis) represents the pH of the eluate, and the vertical axis (Y axis) represents the elution rate of Pb and Cu in the eluate eluted from untreated fly ash.
[Explanation of symbols]
1: Obtained by substituting the liquid chelating agent addition amount (actually measured value) obtained by the conventional method and the Pb and Cu concentrations obtained in 1) of Example 1 into the formula (2) in FIG. A line connecting points where calculated values match.
2: In FIG. 3, obtained by substituting the liquid chelating agent addition amount (actual value) obtained by the conventional method and the Pb and Cu concentrations obtained in 1) of Example 1 into the formula (2). A line connecting points where calculated values match.
【The invention's effect】
As described above in detail, according to the present invention, the amount of liquid chelating agent necessary for immobilization of Pb and the like can be quickly determined by a simple calculation formula by analyzing the Pb and Cu concentration in the fly ash to be treated. It can be determined appropriately, and appropriate chemical treatment corresponding to the properties of fly ash can be performed quickly.
Claims (3)
A=(28×W A = (28 × W CuCu +27×W+27 x W PbPb +3.3)/α (1)+3.3) / α (1)
(式中、Aは液体キレート剤最低添加量(単位は重量%)であり、αは液体キレート剤中のジチオカルバミン酸基濃度(単位はmol/Kg)であり、W(In the formula, A is the minimum amount of liquid chelating agent added (unit:% by weight), α is the concentration of dithiocarbamic acid group in the liquid chelating agent (unit: mol / Kg), W CuCu は飛灰中のCuの含有濃度(単位は重量%)であり、WIs the Cu concentration in fly ash (unit: wt%), W PbPb は飛灰中のPb含有濃度Is the concentration of Pb in fly ash (単位は重量%)である。)(Unit is% by weight). )
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