JP3968986B2

JP3968986B2 - Method for determining required amount of chelating heavy metal immobilizing agent and method and apparatus for determining effect of immobilizing heavy metal on treated ash

Info

Publication number: JP3968986B2
Application number: JP2000327313A
Authority: JP
Inventors: 恒行吉田; 克美松本
Original assignee: Kurita Water Industries Ltd
Current assignee: Kurita Water Industries Ltd
Priority date: 2000-10-26
Filing date: 2000-10-26
Publication date: 2007-08-29
Anticipated expiration: 2020-10-26
Also published as: JP2002126685A

Description

【０００１】
【発明の属する技術分野】
本発明は、重金属含有灰にキレート系重金属固定化剤を加えて該重金属含有灰からの重金属の溶出を防止するための、該キレート系重金属固定化剤の必要添加量を簡易にかつ的確に決定する方法及びそのための装置に関する。本発明はまた、重金属含有灰にキレート系重金属固定化剤を加えて該重金属含有灰からの重金属の溶出を防止するための処理を行った処理灰について、その重金属固定化効果を簡易かつ的確に判定する方法及びそのための装置に関する。
【０００２】
【従来の技術】
都市ゴミ焼却工場等から排出される灰には、煙道の集塵機で捕集される飛灰と焼却炉の焼却残渣である焼却灰がある。このうち重金属含有率が高い飛灰に関しては、厚生省の定める方法により、適切な処理を施すことが義務付けられている。
【０００３】
厚生省の定める処理方法の一つに薬剤処理法があり、処理薬剤としては一般にキレート系薬剤、無機系薬剤が用いられている。
【０００４】
このような薬剤処理においては、薬剤コストを抑えた上で、重金属の溶出を確実に防止するために、薬剤を過不足なく適正な添加量となるように添加することが重要である。
【０００５】
また、処理済みの灰の重金属溶出防止効果が十分でない場合には、直ちに再処理を行う必要があることから、処理灰について、その重金属固定化効果が十分であるか否かの判定を現場にて迅速に行うことが重要である。
【０００６】
しかし、焼却炉で燃やすゴミ質、原料により、焼却飛灰の性状は大きく変化することから、薬剤の適正添加率を決定することは非常に困難である。また、現状では、処理灰の重金属固定化効果を現場にて迅速かつ簡易に行う方法も提案されていない。
【０００７】
従来、無機系薬剤については一部、最適添加率の決定方法が設定されている薬剤もあるが、液体キレート系薬剤については最適添加率の決定方法が存在しない。このため、一般的には、飛灰の性状に対して、過剰気味に添加率を設定するか、薬剤を添加混練処理した後に環境庁の定める溶出試験法（環境庁告示１３号試験法）に従って、重金属類（特に鉛、カドミウム）の溶出濃度を測定して最適添加量を決定するという手法が採用されている。
【０００８】
また、飛灰にキレート系薬剤を添加混練して処理した後、環境庁告示１３号試験と同様の条件で、即ち、６時間という長時間をかけて水中に重金属を溶出させ、この溶出液の酸化還元電位（ＯＲＰ）を測定して、薬剤添加量を決定する手法（特開平８−３０９３１２号公報）も提案されているが、この方法では飛灰の性状変動に即時的に対応した処理仕様を決定することができないため、安定した処理が困難であった。
【０００９】
この問題を解決し、キレート系薬剤の必要添加量を簡易かつ的確に決定する方法として、本出願人は先に、重金属含有灰の水スラリーにキレート系薬剤を添加してゆき、その単位添加量当りの酸化還元電位の低下量が予め設定した値になるまでに添加したキレート系薬剤添加量をもとに、必要添加量を割り出す方法を提案した（特開２０００−７０９０２号公報）。
【００１０】
【発明が解決しようとする課題】
特開２０００−７０９０２号公報に記載される方法であれば、予め酸化還元電位の低下量を設定してキレート系薬剤で滴定を行うことにより、キレート系薬剤の必要添加量を簡易かつ的確に決定することができるが、この方法では、この酸化還元電位の低下量の値を予め設定することが煩雑であるという不具合があった。即ち、ストーカ炉飛灰、流動床炉飛灰、溶融飛灰、焼却灰等の灰の種類によってこの酸化還元電位の低下量の設定値が異なる場合があり、また、重金属含有量が高い灰では滴定曲線が複雑となり、この値を設定するのが困難になる場合があった。
【００１１】
本発明は上記従来の問題点を解決し、重金属含有灰にキレート系重金属固定化剤を加えて該重金属含有灰からの重金属の溶出を防止するに当り、該キレート系重金属固定化剤の必要添加量をより一層簡易にかつ的確に決定することができるキレート系重金属固定化剤の必要添加量の決定方法及びそのための装置を提供することを目的とする。
【００１２】
本発明はまた、重金属含有灰にキレート系重金属固定化剤を加えて該重金属含有灰からの重金属の溶出を防止するための処理を行った処理灰について、その重金属固定化効果をより一層簡易にかつ的確に判定することができる処理灰の重金属固定化効果の判定方法及びそのための装置を提供することを目的とする。
【００１３】
【課題を解決するための手段】
請求項１のキレート系重金属固定化剤の必要添加量の決定方法は、重金属含有灰にキレート系重金属固定化剤を加えて該重金属含有灰からの重金属の溶出を防止するための、該キレート系重金属固定化剤の必要添加量を決定する方法において、該重金属含有灰と水とのスラリーに、一定量の該キレート系重金属固定化剤を添加したときの該スラリーの酸化還元電位を経時的に測定し、該キレート系重金属固定化剤添加後の該酸化還元電位の正の変化量を求め、この正の変化量に基いて前記必要添加量を決定することを特徴とする。
【００１４】
請求項２のキレート系重金属固定化剤の必要添加量の決定方法は、請求項１の方法において、該重金属含有灰と水とのスラリーに、一定量の該キレート系重金属固定化剤を間欠的に添加すると共に、該スラリーの酸化還元電位を経時的に測定し、該キレート系重金属固定化剤添加後の該スラリーの酸化還元電位の正の変化量が予め設定した値になるまで該キレート系重金属固定化剤を添加し、各該キレート系重金属固定化剤添加後の該スラリーの正の変化量の合計量を求め、この合計量に基いて前記必要添加量を決定することを特徴とする。
【００１５】
請求項３の処理灰の重金属固定化効果の判定方法は、重金属含有灰にキレート系重金属固定化剤を加えて該重金属含有灰からの重金属の溶出を防止するための処理を行った処理灰について、その重金属固定化効果を判定する方法において、該処理灰と水のスラリーに、一定量の該キレート系重金属固定化剤を添加したときの該スラリーの酸化還元電位を経時的に測定し、該キレート系重金属固定化剤添加後の酸化還元電位の正の変化量を求め、この正の変化量を予め設定した値と比較してこの結果に基いて該処理灰の重金属固定化効果を判定する処理灰の重金属固定化効果の判定方法であって、該処理灰と水とのスラリーに、一定量の該キレート系重金属固定化剤を間欠的に添加すると共に、該スラリーの酸化還元電位を経時的に測定し、該キレート系重金属固定化剤添加後の該スラリーの酸化還元電位の正の変化量が予め設定した値になるまで該キレート系重金属固定化剤を添加し、各該キレート系重金属固定化剤添加後の該スラリーの正の変化量の合計量を求め、この合計量を予め設定した値と比較してこの結果に基いて該処理灰の重金属固定化効果を判定することを特徴とする。
【００１７】
請求項４のキレート系重金属固定化剤の必要添加量の決定装置は、重金属含有灰にキレート系重金属固定化剤を加えて該重金属含有灰からの重金属の溶出を防止するための、該キレート系重金属固定化剤の必要添加量を決定する装置において、該重金属含有灰と水とのスラリーを調製する手段と、該スラリーに該キレート系重金属固定化剤を間欠的に添加する手段と、該キレート系重金属固定化剤を添加したときの該スラリーの酸化還元電位を経時的に測定する手段と、該酸化還元電位の正の変化量を算出する手段と、算出された酸化還元電位の正の変化量が予め設定した値になるまでキレート系重金属固定化剤を添加し続け、そのときまでの酸化還元電位の正の変化量を合計する手段と、この正の変化量の合計値を重金属の固定化に必要な該キレート系重金属固定化剤量に換算する手段とを備えてなることを特徴とする。
【００１８】
請求項５の処理灰の重金属固定化効果の判定装置は、重金属含有灰にキレート系重金属固定化剤を加えて該重金属含有灰からの重金属の溶出を防止するための処理を行った処理灰について、その重金属固定化効果を判定する装置において、該処理灰と水とのスラリーを調製する手段と、該スラリーに該キレート系重金属固定化剤を間欠的に添加する手段と、該キレート系重金属固定化剤を添加したときの該スラリーの酸化還元電位を経時的に測定する手段と、該酸化還元電位の正の変化量を算出する手段と、算出された酸化還元電位の正の変化量が予め設定した値になるまでキレート系重金属固定化剤を添加し続け、そのときまでの酸化還元電位の正の変化量を合計する手段と、この正の変化量の合計値を該処理灰の重金属固定化効果の判定値に換算する手段とを備えてなることを特徴とする。
【００１９】
即ち、本発明者らは、重金属含有灰にキレート系重金属固定化剤（以下単に「キレート剤」と称す。）を加えて重金属の溶出を防止するに当って、重金属の溶出を確実に防止することができる必要最低限のキレート剤の添加量を決定する方法について種々検討した結果、重金属含有灰の水スラリーにキレート剤を添加すると酸化還元電位（ＯＲＰ）が一旦低下した後再び上昇すること、そして、このＯＲＰの上昇量（正の変化量）がキレート剤の必要添加量と相関することを見出した。
【００２０】
これは、次のような理由によるものと考えられる。
【００２１】
即ち、キレート剤は還元性物質であるため、その溶液中の濃度はＯＲＰを測定することで予測できる。重金属含有灰の水スラリー中にはＰｂ等の重金属等が溶解しているが、これにキレート剤を添加した場合、添加直後はキレート剤と重金属等の反応が十分でなく、スラリー中にはキレート剤が溶解して残留している（従って、ＯＲＰが低い）が、時間の経過と共にこれが重金属等と徐々に反応して沈殿することにより、スラリー中のキレート剤濃度は減少していく（従って、ＯＲＰが上昇していく）。
【００２２】
従って、このＯＲＰの上昇量（正の変化量）を測定することにより、重金属等に消費されたキレート量を求めることができる。
【００２３】
このＯＲＰの正の変化量と、環境庁告示１３号試験で求めた灰の重金属の固定に必要なキレート剤添加量とは相関するので、この正の変化量と環境庁告示１３号試験によるキレート剤の必要添加量との検量線を作成しておき、被処理灰のＯＲＰの正の変化量を測定し、この測定値から検量線でその灰に対してのキレート剤の必要添加量を予測することができる。
【００２４】
また、この重金属含有灰の水スラリーに一定量のキレート剤を間欠的に添加すると、キレート剤の添加毎に一旦ＯＲＰが低下した後上昇するが、この上昇量は、キレート剤の間欠添加を繰り返すと次第に小さくなり、最終的にはキレート剤を添加してもＯＲＰが殆ど変化しなくなる。このときまでのキレート剤の添加毎のＯＲＰの正の変化量を合計して得られる合計値であれば、より一層正確に環境庁告示１３号試験で求めた灰の重金属の固定に必要なキレート剤添加量と相関する。
【００２５】
従って、予めこのＯＲＰの正の変化量の合計値とキレート剤の必要添加量との検量線を作成しておき、被処理灰のＯＲＰの正の変化量を測定し、この測定値から検量線でその灰に対してのキレート剤の必要添加量を予測することができる。
【００２６】
同様に、重金属含有灰にキレート剤を加えて重金属の溶出防止処理を施した処理灰の水スラリーにキレート剤を添加したときのＯＲＰの正の変化量は、当該処理灰の重金属固定化効果と相関し、この正の変化量が所定値以下であれば、重金属固定化効果は十分であり、これを超える場合は、重金属固定化効果が不十分であるから、この正の変化量の合計値を予め設定した値と比較してこの結果に基いて該処理灰の重金属固定化効果を判定することができる。
【００２７】
この重金属固定化効果の判定に当って、この正の変化量の合計値の算出結果と上述の検量線とから、当該処理灰の再処理に際しての必要追加添加量を求めることもできる。
【００２８】
なお、この必要添加量を求めるための検量線は、現場毎、例えば、焼却炉１基毎に作成しておくことが好ましい。
【００２９】
【発明の実施の形態】
以下に本発明の実施の形態を詳細に説明する。
【００３０】
まず、本発明のキレート剤の必要添加量の決定方法及び装置について説明する。
【００３１】
キレート剤の必要添加量の決定に当っては、まず、重金属含有灰について、前述のＯＲＰの正の変化量或いはその合計値を測定する。
【００３２】
本発明において、ＯＲＰの正の変化量を測定するには、まず、重金属含有灰又はその処理灰を水に添加して１〜１０分程度攪拌混合してスラリー（以下、このスラリーを「灰スラリー」と称す場合がある。）を調製する。この灰スラリーの調製に当って、重金属含有灰又はその処理灰と水との混合割合は、液固比（Ｌ（ｍＬ）／ｓ（ｇ））で１０〜１０００、特に８００〜１０００程度とするのが好ましい。
【００３３】
次に、この灰スラリーに一定量のキレート剤を添加して更に撹拌し、このときのスラリーのＯＲＰを継続的に測定する。前述の如く、キレート剤は、灰スラリーに添加された直後においては、灰スラリー中の重金属と反応せずに残留しているため、図１に示す如く、灰スラリーのＯＲＰはキレート剤の添加により一旦低下して最低値Ｅ_ｍｉｎをとるが、その後、灰スラリー中の重金属と反応してキレート剤が消費され、灰スラリー中のキレート剤濃度が低下するに伴って、灰スラリーのＯＲＰは徐々に上昇し、ある値Ｅ_ｍａｘで上げ止まり、その値で一定となる。このＯＲＰの最低値Ｅ_ｍｉｎとＯＲＰが上げ止った点Ｅ_ｍａｘとの差ΔＥを正の変化量とする。
【００３４】
なお、このＯＲＰの正の変化量の測定に当たり、灰スラリーに添加するキレート剤の添加量が少な過ぎると、キレート剤添加後のＯＲＰの低下幅が小さく、Ｅ_ｍｉｎとＥ_ｍａｘとの差ΔＥが明確に現れないために、測定誤差を引き起こし易い。逆に、このキレート剤の添加量が過度に多くても、不経済であるため、このＯＲＰの正の変化量を測定する際のキレート剤の添加量は、灰スラリー中の灰に対してキレート剤の有効純分として０．１〜５．０好ましくは０．５〜１．０重量％で、好ましくは、予想されるキレート剤の必要添加量の１／１０〜１／５程度の量とするのが好ましい。
【００３５】
また、ＯＲＰが上げ止まるまでの測定時間（図１中のＴ）は、撹拌条件等によっても異なるが、一般的には、５００〜２０００秒、好ましくは１０００〜１５００秒程度である。
【００３６】
このＯＲＰの正の変化量から、重金属含有灰のキレート剤の必要添加量を求めるには、数種類の重金属含有灰について上記と同様にしてＯＲＰの正の変化量を測定すると共に、環境庁告示１３号試験によりキレート剤の添加量を変えたときの当該重金属含有灰からの重金属の溶出量を測定し、溶出量を一定以下とするために必要とされるキレート剤の添加量を測定し、この結果から、検量線を作成しておく。そして、キレート剤の必要添加量を求めたい重金属含有灰について上記と同様にしてＯＲＰの正の変化量を測定し、予め作成した検量線から、このＯＲＰの正の変化量に対応するキレート剤の必要添加量を求め、添加量を決定する。
【００３７】
なお、検量線の作成に当っても、キレート剤の必要添加量の決定に当っても、ＯＲＰの正の変化量の測定を複数回行い、その平均値を算出して用いても良い。
【００３８】
また、ＯＲＰの正の変化量の合計値を求めるには、上記と同様にして灰スラリーを調製し、この灰スラリーを撹拌しながら、一定量のキレート剤を間欠的に添加すると共に、ＯＲＰを継続的に測定する。前述の如く、灰スラリーに一定量のキレート剤を間欠的に添加すると、キレート剤の添加毎に灰スラリー中のキレート剤濃度が高くなって、一旦ＯＲＰが低下した後、キレート剤と灰スラリー中の重金属との反応でキレート剤が消費されることでＯＲＰが上昇する。図２に示す如く、この上昇量ΔＥ_１〜ΔＥ_ｎは、キレート剤の間欠添加（図２において、Ｃはキレート剤の添加時を示す。）を繰り返すと次第に小さくなり（即ち、ΔＥ_１＞ΔＥ_２＞ΔＥ_３＞ΔＥ_４＞ΔＥ_５…＞ΔＥ_ｎ）、最終的にはキレート剤を添加してもＯＲＰが殆ど変化しなくなる、このときまでのキレート剤の添加毎のＯＲＰの正の変化量を合計する（ΔＥ_１＋ΔＥ_２＋ΔＥ_３＋ΔＥ_４＋ΔＥ_５…＋ΔＥ_ｎ）。
【００３９】
このＯＲＰの正の変化量の合計値の測定において、キレート剤を間欠添加する際の時間間隔は、添加されたキレート剤が灰スラリー中の重金属と完全に反応するまでの時間である必要はなく、キレート剤の大部分が反応する程度の時間で良い。一般的には、その作業効率の面から６０〜６００秒、特に１２０〜３００秒に１回の間隔でキレート剤を添加し、次のキレート剤の添加の直前でＯＲＰを測定して正の変化量を求めるのが好ましい。
【００４０】
そして、このＯＲＰの正の変化量が３〜４ｍＶ程度となったときを、ＯＲＰが殆ど変化しなくなったときと判断してよい。
【００４１】
このようにしてＯＲＰの正の変化量の合計値を求める場合、１回に添加するキレート剤の添加量が過度に少ないと、キレート剤の間欠添加を何回も繰り返す必要があり、効率が悪くなる。キレート剤の添加量が多過ぎてもキレート剤の必要添加量と相関する適正なＯＲＰの正の変化量の合計値を求めることができないことから、１回に添加するキレート剤の添加量は、灰スラリー中の灰に対して、キレート剤の有効純分として０．１〜０．２重量％で、好ましくは予想されるキレート剤の必要添加量の１／５０〜１／２５程度の量とし、キレート剤の間欠添加を３〜１０回繰り返すことにより、ＯＲＰの正の変化量の合計値が算出することができるようにするのが好ましい。
【００４２】
このＯＲＰの正の変化量の合計値から、重金属含有灰のキレート剤の必要添加量を求めるには、数種類の重金属含有灰について上記と同様にしてＯＲＰの正の変化量の合計値を測定すると共に、環境庁告示１３号試験により当該重金属含有灰からの重金属の溶出を確実に防止するために必要とされるキレート剤の添加量を測定し、この結果から、検量線を作成しておく。そして、キレート剤の必要添加量を求めたい重金属含有灰について上記と同様にしてＯＲＰの正の変化量の合計値を求め、予め作成した検量線から、このＯＲＰの正の変化量の合計値に対応するキレート剤の必要添加量を求め、添加量を決定する。
【００４３】
なお、検量線の作成に当っても、キレート剤の必要添加量の決定に当っても、ＯＲＰの正の変化量の合計値の測定を複数回行い、その平均値を算出して用いても良い。
【００４４】
このような本発明のキレート剤の必要添加量の決定方法は、該重金属含有灰と水とのスラリーを調製する手段と、該スラリーに該キレート系重金属固定化剤を間欠的に添加する手段と、該キレート系重金属固定化剤を添加したときの該スラリーの酸化還元電位を経時的に測定する手段と、該酸化還元電位の正の変化量を算出する手段と、算出された酸化還元電位の正の変化量が予め設定した値になるまでキレート系重金属固定化剤を添加し続け、そのときまでの酸化還元電位の正の変化量を合計する手段と、この正の変化量の合計値を重金属の固定化に必要な該キレート系重金属固定化剤量、例えば、環境庁告示１３号試験量に換算する手段とを備えてなる本発明の装置を用いて、容易に実施することができる。この装置は、さらに前記スラリー調製手段のスラリー容器及び配管系を洗浄する手段を備えるのが好適である。
【００４５】
次に、本発明の処理灰の重金属固定化効果の判定方法及び装置について説明する。この装置は、さらに前記スラリー調製手段のスラリー容器及び配管系を洗浄する手段を備えるのが好適である。
【００４６】
本発明の処理灰の重金属固定化効果の判定方法に従って、処理灰の重金属固定化効果を判定するには、前述と同様にして、この処理灰のＯＲＰの正の変化量の合計値を求め、この正の変化量の合計値を予め設定した値と比較して、この設定値よりも大きければ重金属固定化効果が不十分であり、この設定値以下であれば重金属固定化効果が十分であると判定する。
【００４７】
即ち、前述の方法に従って、処理灰のＯＲＰの正の変化量の合計値を測定した場合、重金属固定化効果が十分なものは、キレート剤の消費が殆どないことから、ＯＲＰの正の変化量の合計値は理論的にはゼロとなる。従って、例えば、このＯＲＰの正の変化量の合計値が３〜４ｍＶ以下であるような処理灰は重金属固定化効果が十分であると判定することができる。
【００４８】
本発明の処理灰の重金属固定化効果の判定方法の実施に当っては、このようにして重金属固定化効果を判定すると共に、前述の本発明のキレート剤の必要添加量の決定方法の説明にある検量線を用いて、処理不良と判定された処理灰を再処理する際のキレート剤の必要追加添加量を求めるのが好ましい。
【００４９】
このような本発明の処理灰の重金属固定化効果の判定方法は、該処理灰と水とのスラリーを調製する手段と、該スラリーに該キレート系重金属固定化剤を間欠的に添加する手段と、該キレート系重金属固定化剤を添加したときの該スラリーの酸化還元電位を経時的に測定する手段と、該酸化還元電位の正の変化量を算出する手段と、算出された酸化還元電位の正の変化量が予め設定した値になるまでキレート系重金属固定化剤を添加し続け、そのときまでの酸化還元電位の正の変化量を合計する手段と、この正の変化量の合計値を該処理灰の重金属固定化効果の判定値に換算する手段とを備えてなる本発明の装置を用いて、容易に実施することができる。この装置は、さらに前記スラリー調製手段のスラリー容器及び配管系を洗浄する手段を備えるのが好適である。
【００５０】
【実施例】
以下に実験例及び実施例を挙げて本発明をより具体的に説明する。
【００５１】
なお、以下において、用いた供試灰の成分分析結果は表１に示す通りであり、また、これらの供試灰にキレート剤（栗田工業（株）製「アッシュナイトＳ−８０１」）を各種の添加量で添加混練した処理灰の環境庁告示１３号試験結果は表２に示す通りである。
【００５２】
【表１】

【００５３】
【表２】

【００５４】
実験例１
５０００ｍＬのタンクに脱イオン水３０００ｍＬと各供試灰及びＡ−１灰のＮｏ．３の処理灰（キレート剤添加率１０重量％対灰）５ｇをそれぞれ入れ、撹拌機を用いて１０分間十分に撹拌してスラリーを作成した。これに１００倍に希釈したキレート剤（アッシュナイトＳ８０１）を３０ｍＬ添加して、緩やかに撹拌しながら、ＯＲＰ計（東亜電波社製、電極：白金、Ａｇ−ＡｇＣｌ、３．３ＭＫＣｌ）を用いてそのスラリーのＯＲＰを１８００秒（３０分）間にわたって測定した。この結果を、横軸に経過時間、縦軸にＯＲＰとして図３に示す。
【００５５】
図３より、環境庁告示１３号試験でのキレート剤の必要添加量が多い供試灰（Ａ−３灰）ほどＯＲＰの正の変化量（上昇量）が多いことがわかる。
【００５６】
この正の変化量と環境庁告示１３号試験でのキレート剤の必要添加量との関係を図４に示す。図４より、このＯＲＰの正の変化量とキレート剤の必要添加量とには相関があることがわかる。
【００５７】
実験例２
５０００ｍＬのタンクに脱イオン水３０００ｍＬと供試灰Ａ−１又はＡ−２の５ｇをそれぞれ入れ、撹拌機を用いて１０分間十分に撹拌してスラリーを作成した。このスラリーを緩やかに撹拌しながら、これに１００倍に希釈したキレート剤（アッシュナイトＳ８０１）を５ｍＬずつ１８０秒毎に滴定して、ＯＲＰ計でそのスラリーのＯＲＰの正の変化が殆どなくなるまで測定した。この結果を、横軸に経過時間、縦軸にＯＲＰとして図５に示す。また、このときのＯＲＰの正の変化量の合計値を横軸に、環境庁告示１３号試験でのキレート剤の必要添加量を横軸にとったグラフを図６に示す。
【００５８】
図５，６より、滴定時間内でのＯＲＰの変化が殆ど無くなるまでの正の変化量の合計値は環境庁告示１３号試験でのキレート剤の必要添加量が多い供試灰（Ａ−２灰）ほど多いことがわかる。
【００５９】
実施例１
都市ゴミ焼却炉から排出された飛灰について、実験例２と同様にして滴定を行い、ＯＲＰの正の変化量の合計値を求め、この値から、実験例２の図６の検量線に基いて、キレート剤の必要添加量を決定して処理を行ったところ、３ヶ月間にわたって十分な重金属固定化効果を継続して得ることができた。
【００６０】
【発明の効果】
以上詳述した通り、本発明のキレート系重金属固定化剤の必要添加量の決定方法及び装置によれば、重金属含有灰の処理に先立ち、キレート剤の適正添加量を容易かつ的確に求めることができ、
▲１▼ 現場における測定も容易であることから、処理する重金属含有灰の性状変動に対応して即時的にかつきめ細かい薬注制御を行うことができ、これにより、安定かつ確実な処理を行える。
▲２▼ キレート剤の過剰添加が不要となり、薬剤コストの低減を図ることができる。
といった効果が奏される。
【００６１】
また、本発明の処理灰の重金属固定化効果の判定方法及び装置によれば、重金属含有灰にキレート剤を添加して処理した後の処理灰について、その重金属固定化効果を容易かつ的確に求めることができ、現場における判定も容易である上に、必要追加添加量も容易に求めることができることから、処理不良の処理灰を確認して直ちに再処理を行うことができ、これによりより一層確実な処理を行える。
【図面の簡単な説明】
【図１】灰にキレート剤を添加したときのＯＲＰの経時変化を示すグラフである。
【図２】灰にキレート剤を間欠的に添加したときのＯＲＰの経時変化を示すグラフである。
【図３】実験例１において求めたＯＲＰの経時変化を示すグラフである。
【図４】実験例１において求めたＯＲＰの正の変化量とキレート剤の必要添加量との関係を示すグラフである。
【図５】実験例２において求めたＯＲＰの経時変化を示すグラフである。
【図６】実験例２において求めたＯＲＰの正の変化量の合計値とキレート剤の必要添加量との関係を示すグラフである。[0001]
BACKGROUND OF THE INVENTION
The present invention simply and accurately determines the required amount of the chelating heavy metal immobilizing agent to prevent elution of heavy metal from the heavy metal containing ash by adding the chelating heavy metal immobilizing agent to the heavy metal containing ash. And a device therefor. The present invention also provides a simple and accurate effect of immobilizing heavy metals on treated ash that has been treated to prevent elution of heavy metals from the heavy metal-containing ash by adding a chelate heavy metal fixing agent to the heavy metal-containing ash. The present invention relates to a determination method and an apparatus therefor.
[0002]
[Prior art]
Ashes discharged from municipal waste incineration plants and the like include fly ash collected by a dust collector in a flue and incineration ash that is an incineration residue of an incinerator. Of these, fly ash with a high content of heavy metals is obliged to be treated appropriately by the method stipulated by the Ministry of Health and Welfare.
[0003]
One of the treatment methods defined by the Ministry of Health and Welfare is a chemical treatment method, and chelate chemicals and inorganic chemicals are generally used as treatment chemicals.
[0004]
In such drug treatment, it is important to add a drug in an appropriate amount without excess or deficiency in order to reliably prevent elution of heavy metals while suppressing drug cost.
[0005]
In addition, if the effect of preventing the heavy metal elution from the treated ash is not sufficient, it is necessary to immediately reprocess the treated ash. It is important to do it quickly.
[0006]
However, since the properties of incineration fly ash vary greatly depending on the quality of the garbage burned in the incinerator and the raw materials, it is very difficult to determine the appropriate rate of chemical addition. At present, no method has been proposed for quickly and simply performing the effect of fixing heavy metals on treated ash on site.
[0007]
Conventionally, some inorganic chemicals have a method for determining an optimum addition rate, but there is no method for determining an optimum addition rate for a liquid chelate type drug. For this reason, generally, according to the dissolution test method (Environment Agency Notification No. 13 test method) established by the Environment Agency after setting the addition rate in an excess manner to the properties of fly ash or adding and kneading the chemicals The method of measuring the elution concentration of heavy metals (especially lead and cadmium) and determining the optimum addition amount is adopted.
[0008]
Further, after adding and kneading the chelating agent to fly ash, the heavy metal was eluted in water under the same conditions as in the Environmental Agency Notification No. 13 test, that is, over a long period of 6 hours. A method for measuring the oxidation-reduction potential (ORP) and determining the amount of drug added (JP-A-8-309912) has also been proposed. In this method, however, processing specifications that immediately respond to fluctuations in fly ash properties. Therefore, stable processing is difficult.
[0009]
As a method for solving this problem and determining the necessary addition amount of the chelating agent simply and accurately, the applicant first added the chelating agent to the water slurry of heavy metal-containing ash and added the unit addition amount. A method has been proposed in which the required amount of addition is calculated based on the amount of chelate-based drug added until the amount of reduction in peroxidation reduction potential reaches a preset value (Japanese Patent Laid-Open No. 2000-70902).
[0010]
[Problems to be solved by the invention]
According to the method described in Japanese Patent Application Laid-Open No. 2000-70902, the required amount of chelating agent is simply and accurately determined by setting a reduction amount of the oxidation-reduction potential in advance and titrating with the chelating agent. However, in this method, there is a problem that it is complicated to set the value of the reduction amount of the oxidation-reduction potential in advance. That is, the set value of the reduction amount of this redox potential may differ depending on the type of ash such as stoker furnace fly ash, fluidized bed furnace fly ash, molten fly ash, incineration ash, etc. In some cases, the titration curve becomes complicated and it is difficult to set this value.
[0011]
The present invention solves the above-mentioned conventional problems and adds a chelate heavy metal immobilizing agent to heavy metal-containing ash to prevent elution of heavy metal from the heavy metal-containing ash. It is an object of the present invention to provide a method for determining the required addition amount of a chelating heavy metal immobilizing agent and an apparatus therefor, which can determine the amount more simply and accurately.
[0012]
The present invention also further simplifies the effect of immobilizing heavy metals on treated ash that has been treated to prevent elution of heavy metals from the heavy metal-containing ash by adding a chelating heavy metal fixing agent to the heavy metal-containing ash. It is an object of the present invention to provide a method for determining the effect of immobilizing heavy metal on treated ash and an apparatus therefor that can be accurately determined.
[0013]
[Means for Solving the Problems]
The method for determining the required addition amount of the chelate heavy metal immobilizing agent according to claim 1 comprises adding the chelate heavy metal immobilizing agent to the heavy metal containing ash to prevent elution of heavy metal from the heavy metal containing ash. In the method of determining the required addition amount of the heavy metal fixing agent, the oxidation-reduction potential of the slurry when a certain amount of the chelate heavy metal fixing agent is added to the slurry of the heavy metal-containing ash and water is changed over time. Measured, a positive change amount of the oxidation-reduction potential after addition of the chelate heavy metal immobilizing agent is obtained, and the necessary addition amount is determined based on the positive change amount.
[0014]
The method for determining the required addition amount of the chelate heavy metal immobilizing agent according to claim 2 is the method according to claim 1, wherein a certain amount of the chelate heavy metal immobilizing agent is intermittently added to the slurry of the heavy metal-containing ash and water. And measuring the oxidation-reduction potential of the slurry over time until the positive change amount of the oxidation-reduction potential of the slurry after the addition of the chelate heavy metal fixing agent becomes a preset value. A heavy metal fixing agent is added, a total amount of positive change amount of the slurry after each chelate heavy metal fixing agent is added, and the necessary addition amount is determined based on the total amount. .
[0015]
The method for determining the effect of immobilizing heavy metal on treated ash according to claim 3 is about treated ash that has been treated to prevent elution of heavy metal from the heavy metal-containing ash by adding a chelating heavy metal fixing agent to the heavy metal-containing ash. In the method for determining the effect of immobilizing heavy metal, the oxidation-reduction potential of the slurry when a certain amount of the chelating heavy metal immobilizing agent is added to the slurry of the treated ash and water is measured over time, The positive change amount of the oxidation-reduction potential after addition of the chelate heavy metal fixing agent is obtained, and the positive change amount is compared with a preset value, and the heavy metal fixing effect of the treated ash is determined based on the result. A method for determining the effect of immobilizing a heavy metal on a treated ash, wherein a certain amount of the chelating heavy metal immobilizing agent is intermittently added to a slurry of the treated ash and water, and the oxidation-reduction potential of the slurry is changed over time. The chelate heavy metal immobilizing agent was added until the positive change amount of the oxidation-reduction potential of the slurry after addition of the chelate heavy metal immobilizing agent reached a preset value. The total amount of positive change amount of the slurry after the addition of the fixing agent is obtained, and the total amount is compared with a preset value, and the effect of fixing the heavy metal of the treated ash is determined based on the result. It is characterized by that.
[0017]
Claim 4 The apparatus for determining the required amount of chelating heavy metal immobilizing agent is to add the chelating heavy metal immobilizing agent to heavy metal-containing ash to prevent elution of heavy metal from the heavy metal-containing ash. In the apparatus for determining the required addition amount of the agent, means for preparing a slurry of the heavy metal-containing ash and water, means for intermittently adding the chelating heavy metal fixing agent to the slurry, and chelating heavy metal fixation Means for measuring the oxidation-reduction potential of the slurry over time when the agent is added, means for calculating a positive change amount of the oxidation-reduction potential, and a positive change amount of the calculated oxidation-reduction potential in advance. Continue adding the chelating heavy metal immobilizing agent until the set value is reached, then add a positive amount of redox potential up to that point, and the total value of this positive amount of change is necessary for immobilizing heavy metals. Na Characterized by comprising a means for converting the system heavy metal immobilizing agent amount.
[0018]
Claim 5 The apparatus for determining the effect of immobilizing heavy metal on treated ash is a method for adding a chelate heavy metal immobilizing agent to heavy metal-containing ash and treating the treated ash to prevent elution of heavy metal from the heavy metal-containing ash. In the apparatus for determining the immobilization effect, means for preparing a slurry of the treated ash and water, and the chelate heavy metal immobilizing agent to the slurry Intermittently Means for adding, means for measuring the redox potential of the slurry over time when the chelating heavy metal immobilizing agent is added, means for calculating a positive change amount of the redox potential, The chelating heavy metal immobilizing agent is continuously added until the calculated positive change amount of the oxidation-reduction potential reaches a preset value, and the means for summing the positive change amount of the oxidation-reduction potential up to that time, Means for converting the total positive change amount into a judgment value of the heavy metal immobilization effect of the treated ash; It is characterized by comprising.
[0019]
That is, the present inventors reliably prevent elution of heavy metals by adding a chelate heavy metal fixing agent (hereinafter simply referred to as “chelating agent”) to heavy metal-containing ash to prevent elution of heavy metals. As a result of various investigations on how to determine the minimum amount of chelating agent that can be added, the addition of a chelating agent to an aqueous slurry of heavy metal-containing ash causes the oxidation-reduction potential (ORP) to decrease and then increase again. And it discovered that the increase amount (positive change amount) of this ORP correlated with the required addition amount of a chelating agent.
[0020]
This is considered due to the following reasons.
[0021]
That is, since the chelating agent is a reducing substance, the concentration in the solution can be predicted by measuring ORP. Although heavy metals such as Pb are dissolved in the heavy metal-containing ash water slurry, when a chelating agent is added to this, the reaction between the chelating agent and heavy metal is not sufficient immediately after the addition, and the slurry does not contain a chelating agent. Although the agent is dissolved and remains (thus, the ORP is low), the chelant concentration in the slurry decreases as it gradually reacts and precipitates with heavy metals and the like over time (therefore, the concentration of the agent decreases accordingly). ORP will rise).
[0022]
Therefore, the amount of chelate consumed by heavy metals or the like can be determined by measuring the increase amount (positive change amount) of the ORP.
[0023]
Since this positive change in ORP correlates with the amount of chelant added necessary for fixing heavy metals in ash determined in the Environmental Agency Notification No.13 test, this positive change amount and the chelate in the Environmental Agency Notification No.13 test Prepare a calibration curve with the required addition amount of the agent, measure the positive change in ORP of the treated ash, and predict the required addition amount of the chelating agent for the ash from the measured value using the calibration curve can do.
[0024]
In addition, when a certain amount of chelating agent is intermittently added to the heavy metal-containing ash water slurry, the ORP once decreases after every addition of the chelating agent, but this rising amount repeats intermittent addition of the chelating agent. When the chelating agent is added, the ORP hardly changes. If it is the total value obtained by adding up the positive change amount of ORP for every addition of chelating agent up to this time, the chelate necessary for fixing heavy metals in ash determined more accurately in the Environmental Agency Notification No. 13 test It correlates with the additive amount.
[0025]
Therefore, a calibration curve between the total value of the positive change amount of the ORP and the required addition amount of the chelating agent is prepared in advance, the positive change amount of the ORP of the ash to be treated is measured, and the calibration curve is obtained from the measured value. The required amount of chelating agent added to the ash can be predicted.
[0026]
Similarly, the amount of positive change in ORP when adding a chelating agent to an aqueous slurry of treated ash obtained by adding a chelating agent to heavy metal-containing ash and carrying out elution prevention treatment of heavy metal is the effect of immobilizing heavy metal on the treated ash. If the positive change amount is less than or equal to the predetermined value, the heavy metal fixing effect is sufficient, and if it exceeds this value, the heavy metal fixing effect is insufficient. Strange By comparing the total value of the amount of formation with a preset value, the heavy metal immobilization effect of the treated ash can be determined based on this result.
[0027]
In determining this heavy metal immobilization effect, this positive Strange From the calculation result of the total value of the amount of conversion and the above-mentioned calibration curve, it is also possible to determine the necessary additional addition amount for reprocessing the treated ash.
[0028]
In addition, it is preferable to prepare a calibration curve for obtaining the necessary addition amount for each site, for example, for each incinerator.
[0029]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described in detail.
[0030]
First, the determination method and apparatus of the required addition amount of the chelating agent of this invention are demonstrated.
[0031]
In determining the required addition amount of the chelating agent, first, the above-mentioned positive change amount of ORP or the total value thereof is measured for heavy metal-containing ash.
[0032]
In the present invention, in order to measure the positive change amount of ORP, first, heavy metal-containing ash or its treated ash is added to water and stirred and mixed for about 1 to 10 minutes. Is prepared.) Is prepared. In preparing this ash slurry, the mixing ratio of heavy metal-containing ash or its treated ash and water is about 10 to 1000, particularly about 800 to 1000 in terms of liquid-solid ratio (L (mL) / s (g)). Is preferred.
[0033]
Next, a certain amount of chelating agent is added to the ash slurry and further stirred, and the ORP of the slurry at this time is continuously measured. As described above, immediately after the chelating agent is added to the ash slurry, it remains without reacting with the heavy metal in the ash slurry. Therefore, as shown in FIG. Once lowered, the minimum value E _min After that, the chelating agent is consumed by reacting with the heavy metal in the ash slurry, and as the chelating agent concentration in the ash slurry decreases, the ORP of the ash slurry gradually increases to a certain value E _max At this point, it stops rising and becomes constant at that value. Minimum value E of this ORP _min And point where ORP stopped raising _max The difference ΔE with respect to is a positive change amount.
[0034]
In addition, in the measurement of the positive change amount of the ORP, if the amount of the chelating agent added to the ash slurry is too small, the decrease width of the ORP after adding the chelating agent is small, and E _min And E _max Difference ΔE does not appear clearly, so that measurement errors are likely to occur. On the other hand, since it is uneconomical if the amount of this chelating agent added is excessively large, the amount of chelating agent added when measuring the positive change amount of this ORP is the same as the amount of chelate in the ash slurry. 0.1 to 5.0, preferably 0.5 to 1.0% by weight as an effective pure content of the agent, and preferably about 1/10 to 1/5 of the expected required addition amount of the chelating agent It is preferable to do this.
[0035]
In addition, the measurement time (T in FIG. 1) until the ORP stops increasing is generally 500 to 2000 seconds, preferably about 1000 to 1500 seconds, although it varies depending on the stirring conditions and the like.
[0036]
In order to obtain the required addition amount of the chelating agent for heavy metal-containing ash from the positive change amount of ORP, the positive change amount of ORP was measured in the same manner as described above for several types of heavy metal-containing ash, and the Environment Agency Notification 13 Measure the amount of heavy metal elution from the heavy metal-containing ash when the amount of chelating agent added is changed by the No. test, and measure the amount of chelating agent added to keep the elution amount below a certain level. Create a calibration curve from the results. Then, for the heavy metal-containing ash for which the required addition amount of the chelating agent is to be obtained, the positive change amount of the ORP is measured in the same manner as described above, and from the calibration curve prepared in advance, the chelating agent corresponding to the positive change amount of the ORP is measured. Obtain the required addition amount and determine the addition amount.
[0037]
In addition, even when preparing a calibration curve, determining the required addition amount of a chelating agent, the positive change amount of ORP may be measured a plurality of times, and the average value may be calculated and used.
[0038]
In addition, in order to obtain the total value of the positive change amount of ORP, an ash slurry is prepared in the same manner as described above, and while stirring this ash slurry, a certain amount of chelating agent is intermittently added, and ORP is added. Measure continuously. As described above, when a certain amount of chelating agent is intermittently added to the ash slurry, the chelating agent concentration in the ash slurry increases each time the chelating agent is added, and once the ORP decreases, the chelating agent and the ash slurry The ORP is increased by the consumption of the chelating agent in the reaction with the heavy metal. As shown in FIG. 2, the amount of increase ΔE ₁ ~ ΔE _n Is gradually reduced (ie, ΔE) when intermittent addition of the chelating agent (in FIG. 2, C indicates the time of addition of the chelating agent) is repeated. ₁ > ΔE ₂ > ΔE ₃ > ΔE ₄ > ΔE ₅ …> ΔE _n Finally, even if the chelating agent is added, the ORP hardly changes, and the positive change amount of the ORP for each addition of the chelating agent up to this time is summed (ΔE ₁ + ΔE ₂ + ΔE ₃ + ΔE ₄ + ΔE ₅ ... + ΔE _n ).
[0039]
In the measurement of the total value of the positive change amount of the ORP, the time interval when the chelating agent is intermittently added does not have to be the time until the added chelating agent completely reacts with the heavy metal in the ash slurry. The time required for most of the chelating agent to react is sufficient. Generally, from the viewpoint of the working efficiency, a chelating agent is added at intervals of once every 60 to 600 seconds, particularly 120 to 300 seconds, and the ORP is measured immediately before the addition of the next chelating agent to positive change. It is preferred to determine the amount.
[0040]
Then, when the positive change amount of the ORP becomes about 3 to 4 mV, it may be determined that the ORP hardly changes.
[0041]
Thus, when calculating | requiring the total value of the positive variation | change_quantity of ORP, when the addition amount of the chelating agent added to 1 time is too small, it is necessary to repeat intermittent addition of a chelating agent many times, and efficiency is bad. Become. Even if the amount of the chelating agent added is too large, it is not possible to obtain the total value of the appropriate ORP positive change amount that correlates with the required amount of the chelating agent, so the amount of the chelating agent added at one time is: 0.1 to 0.2% by weight as the effective pure content of the chelating agent with respect to the ash in the ash slurry, preferably about 1/50 to 1/25 of the expected addition amount of the chelating agent It is preferable that the total value of the positive change amount of the ORP can be calculated by repeating the intermittent addition of the chelating agent 3 to 10 times.
[0042]
In order to obtain the required addition amount of the chelating agent for heavy metal-containing ash from the total value of the positive change amount of ORP, the total value of the positive change amount of ORP is measured in the same manner as described above for several types of heavy metal-containing ash. At the same time, the amount of addition of the chelating agent required to reliably prevent elution of heavy metals from the heavy metal-containing ash is measured by the Environmental Agency Notification No. 13 test, and a calibration curve is prepared from the results. Then, for the heavy metal-containing ash for which the required addition amount of the chelating agent is to be obtained, the total value of the positive change amount of the ORP is obtained in the same manner as described above, and the total value of the positive change amount of the ORP is obtained from the calibration curve prepared in advance. The required addition amount of the corresponding chelating agent is obtained and the addition amount is determined.
[0043]
In addition, even when preparing a calibration curve, when determining the required addition amount of a chelating agent, the total value of the ORP positive change amount is measured several times, and the average value may be calculated and used. good.
[0044]
Such a method for determining the required addition amount of the chelating agent of the present invention comprises means for preparing a slurry of the heavy metal-containing ash and water, and means for intermittently adding the chelating heavy metal fixing agent to the slurry. A means for measuring the oxidation-reduction potential of the slurry over time when the chelating heavy metal immobilizing agent is added, a means for calculating a positive change amount of the oxidation-reduction potential, and a calculated oxidation-reduction potential. The chelate heavy metal immobilizing agent is continuously added until the positive change amount reaches a preset value, and a means for summing the positive change amount of the oxidation-reduction potential up to that time, and the total value of the positive change amount, It can be easily carried out by using the apparatus of the present invention comprising the amount of the chelating heavy metal immobilizing agent necessary for immobilizing heavy metals, for example, means for converting to the amount tested for the Environmental Agency Notification No. 13 test amount. This apparatus preferably further comprises means for washing the slurry container and the piping system of the slurry preparation means.
[0045]
Next, a method and apparatus for determining the effect of immobilizing heavy metal on treated ash according to the present invention will be described. This apparatus preferably further comprises means for washing the slurry container and the piping system of the slurry preparation means.
[0046]
In order to determine the heavy metal immobilization effect of the treated ash according to the method for determining the heavy metal immobilization effect of the treated ash of the present invention, in the same manner as described above, the positive change in the ORP of the treated ash is determined. Quantity Find the total value and this positive change Quantity The total value is compared with a preset value, and if it is larger than this set value, the heavy metal fixing effect is insufficient, and if it is less than this set value, it is determined that the heavy metal fixing effect is sufficient.
[0047]
That is, according to the above-mentioned method, the positive change of the treated ash ORP Quantity When the total value is measured, the effect of immobilizing heavy metals is sufficient. Quantity The total value is theoretically zero. Thus, for example, this positive change in ORP Quantity It can be determined that the treated ash having a total value of 3 to 4 mV or less has a sufficient heavy metal immobilization effect.
[0048]
In carrying out the method for determining the effect of immobilizing heavy metal in the treated ash of the present invention, the effect of immobilizing heavy metal is determined in this way, and the method for determining the required addition amount of the chelating agent of the present invention is described. It is preferable to use a certain calibration curve to determine the necessary additional addition amount of the chelating agent when reprocessing the treated ash determined to be defective.
[0049]
Such a method for determining the effect of immobilizing heavy metal on treated ash according to the present invention comprises means for preparing a slurry of the treated ash and water, and adding the chelating heavy metal immobilizing agent to the slurry. Intermittently Means for adding, means for measuring the redox potential of the slurry over time when the chelating heavy metal immobilizing agent is added, means for calculating a positive change amount of the redox potential, The chelating heavy metal immobilizing agent is continuously added until the calculated positive change amount of the oxidation-reduction potential reaches a preset value, and the means for summing the positive change amount of the oxidation-reduction potential up to that time, Means for converting the total positive change amount into a judgment value of the heavy metal immobilization effect of the treated ash; It can implement easily using the apparatus of this invention provided with. This device is Before It is preferable to provide means for washing the slurry container and piping system of the slurry preparation means.
[0050]
【Example】
Hereinafter, the present invention will be described in more detail with reference to experimental examples and examples.
[0051]
In addition, in the following, the component analysis result of the used test ash is as shown in Table 1, and various chelating agents ("Ashnite S-801" manufactured by Kurita Kogyo Co., Ltd.) are used for these test ash. Table 2 shows the results of the Environmental Agency Notification No. 13 test of the treated ash that was added and kneaded in an amount of.
[0052]
[Table 1]

[0053]
[Table 2]

[0054]
Experimental example 1
In a 5000 mL tank, 3000 mL of deionized water and each test ash and A-1 ash No. 3 g of treated ash 3 (chelating agent addition rate: 10% by weight with respect to ash) was added, and the mixture was sufficiently stirred for 10 minutes using a stirrer to prepare a slurry. 30 mL of a chelating agent (Ashnite S801) diluted 100 times was added thereto, and while gently stirring, an ORP meter (manufactured by Toa Denpa Inc., electrode: platinum, Ag-AgCl, 3.3M KCl) was used. The ORP of the slurry was measured over 1800 seconds (30 minutes). The results are shown in FIG. 3 with elapsed time on the horizontal axis and ORP on the vertical axis.
[0055]
From FIG. 3, it can be seen that the test ash (A-3 ash) in which the amount of the chelating agent added in the Environmental Agency Notification No. 13 test is larger, the greater the amount of positive change (increase) in the ORP.
[0056]
FIG. 4 shows the relationship between this positive change amount and the required addition amount of the chelating agent in the Environmental Agency Notification No. 13 test. FIG. 4 shows that there is a correlation between the positive change amount of the ORP and the necessary addition amount of the chelating agent.
[0057]
Experimental example 2
In a 5000 mL tank, 3000 mL of deionized water and 5 g of test ash A-1 or A-2 were respectively added, and sufficiently stirred for 10 minutes using a stirrer to prepare a slurry. While slowly stirring this slurry, titrate 5 mL of chelating agent (Ashnite S801) diluted 100 times every 180 seconds and measure until the ORP meter shows almost no positive change in ORP of the slurry. did. The results are shown in FIG. 5 with elapsed time on the horizontal axis and ORP on the vertical axis. Further, FIG. 6 is a graph in which the horizontal axis represents the total value of the positive changes in ORP at this time, and the horizontal axis represents the required addition amount of the chelating agent in the Environmental Agency Notification No. 13 test.
[0058]
5 and 6, the total value of the positive change amount until the change in ORP within the titration time almost disappeared is the test ash (A-2) in which the amount of chelating agent required in the Environmental Agency Notification No. 13 test is large. It can be seen that there are more ash).
[0059]
Example 1
For the fly ash discharged from the municipal waste incinerator, titration is performed in the same manner as in Experiment Example 2, and the total value of the positive change amount of ORP is obtained. From this value, the calibration curve in FIG. Then, when the necessary addition amount of the chelating agent was determined and the treatment was performed, a sufficient heavy metal immobilization effect could be continuously obtained for 3 months.
[0060]
【The invention's effect】
As described above in detail, according to the method and apparatus for determining the required addition amount of the chelate heavy metal immobilizing agent of the present invention, it is possible to easily and accurately determine the appropriate addition amount of the chelating agent prior to the treatment of the heavy metal-containing ash. Can
(1) Since on-site measurement is also easy, it is possible to immediately and finely control chemical injection in response to changes in the properties of the heavy metal-containing ash to be processed, thereby enabling stable and reliable processing.
(2) It is not necessary to add an excessive amount of chelating agent, and the cost of the drug can be reduced.
Such an effect is produced.
[0061]
Moreover, according to the determination method and apparatus for the heavy metal immobilization effect of the treated ash of the present invention, the heavy metal immobilization effect is easily and accurately obtained for the treated ash after adding the chelating agent to the heavy metal-containing ash and treating it. In addition, it is easy to determine at the site, and the required additional amount can be easily obtained, so it is possible to immediately check the processing ash that has failed to be reprocessed, which makes it even more reliable. Can be processed.
[Brief description of the drawings]
FIG. 1 is a graph showing changes in ORP over time when a chelating agent is added to ash.
FIG. 2 is a graph showing changes in ORP over time when a chelating agent is intermittently added to ash.
FIG. 3 is a graph showing a change with time of ORP obtained in Experimental Example 1;
4 is a graph showing a relationship between a positive change amount of ORP obtained in Experimental Example 1 and a necessary addition amount of a chelating agent. FIG.
5 is a graph showing the temporal change of ORP obtained in Experimental Example 2. FIG.
6 is a graph showing the relationship between the total value of the positive change amounts of ORP obtained in Experimental Example 2 and the necessary addition amount of a chelating agent. FIG.

Claims

In a method for determining a necessary addition amount of the chelate heavy metal fixing agent for adding a chelate heavy metal fixing agent to the heavy metal containing ash to prevent elution of heavy metal from the heavy metal containing ash,
Measure the oxidation-reduction potential of the slurry over time when a certain amount of the chelate heavy metal immobilizing agent is added to the slurry of heavy metal-containing ash and water,
Obtain the positive change amount of the redox potential after addition of the chelate heavy metal immobilizing agent,
A method for determining a required addition amount of a chelating heavy metal immobilizing agent, wherein the required addition amount is determined based on the positive change amount.

The method according to claim 1, wherein a certain amount of the chelate heavy metal fixing agent is intermittently added to the slurry of heavy metal-containing ash and water, and the oxidation-reduction potential of the slurry is measured over time. The chelate heavy metal fixing agent is added until the positive change amount of the oxidation-reduction potential of the slurry after the addition of the chelate heavy metal fixing agent becomes a preset value, A method for determining a required addition amount of a chelating heavy metal immobilizing agent, wherein a total amount of positive change amounts of the slurry is obtained and the required addition amount is determined based on the total amount.

In the method for judging the effect of immobilizing heavy metal, with respect to the treated ash that has been treated to prevent elution of heavy metal from the heavy metal-containing ash by adding a chelate heavy metal fixing agent to the heavy metal-containing ash,
Measure the oxidation-reduction potential of the slurry over time when a certain amount of the chelating heavy metal immobilizing agent is added to the slurry of the treated ash and water,
Obtain the positive change amount of the redox potential after adding the chelating heavy metal immobilizing agent,
A method for determining the heavy metal immobilization effect of the treated ash by comparing the positive change amount with a preset value and determining the heavy metal immobilization effect of the treated ash based on the result ,
A constant amount of the chelate heavy metal immobilizing agent is intermittently added to the slurry of the treated ash and water, and the oxidation-reduction potential of the slurry is measured over time. The chelate heavy metal immobilizing agent is added until the positive change amount of the oxidation-reduction potential of the slurry reaches a preset value, and the positive change amount of the slurry after the addition of each chelate heavy metal immobilizing agent is increased. A method for determining a heavy metal immobilization effect of treated ash, wherein a total amount is obtained, the total amount is compared with a preset value, and the heavy metal immobilization effect of the treated ash is determined based on the result .

In an apparatus for determining a necessary addition amount of the chelate heavy metal fixing agent to prevent elution of heavy metal from the heavy metal containing ash by adding a chelate heavy metal fixing agent to the heavy metal containing ash,
Means for preparing a slurry of the heavy metal-containing ash and water;
Means for intermittently adding the chelating heavy metal immobilizing agent to the slurry;
Means for measuring the redox potential of the slurry over time when the chelating heavy metal immobilizing agent is added;
Means for calculating a positive change amount of the redox potential;
Means for continuing to add the chelate heavy metal immobilizing agent until the calculated positive change amount of the redox potential reaches a preset value, and summing up the positive change amount of the redox potential until that time;
A means for converting the total value of the positive change amounts into the amount of the chelate heavy metal immobilizing agent necessary for immobilizing heavy metals, and determining the required addition amount of the chelate heavy metal immobilizing agent apparatus.

In the apparatus for judging the effect of immobilizing heavy metal, with respect to the treated ash that has been treated to prevent elution of heavy metal from the heavy metal-containing ash by adding a chelate heavy metal fixing agent to the heavy metal-containing ash,
Means for preparing a slurry of the treated ash and water;
Means for intermittently adding the chelating heavy metal immobilizing agent to the slurry;
Means for measuring the redox potential of the slurry over time when the chelating heavy metal immobilizing agent is added;
Means for calculating a positive change amount of the redox potential ;
Means for continuing to add the chelate heavy metal immobilizing agent until the calculated positive change amount of the redox potential reaches a preset value, and summing up the positive change amount of the redox potential until that time;
Means for converting the total value of the positive change amounts into a determination value for the heavy metal immobilization effect of the treated ash, and a determination device for the heavy metal immobilization effect of the treated ash.