JP2004261773A - Heavy metal fixing agent for heavy metal-containing ash and method for treating the ash using the agent - Google Patents
Heavy metal fixing agent for heavy metal-containing ash and method for treating the ash using the agent Download PDFInfo
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【０００１】
【発明の属する技術分野】
本発明は、都市ゴミや産業廃棄物等の焼却プラントからの飛灰のような重金属含有灰を処理する際の重金属固定化剤、及びそれを用いる重金属含有灰の処理方法に関する。
更に、本発明は、重金属含有物、特に都市ゴミや産業廃棄物等の焼却プラントからの飛灰を処理するに際し、重金属固定化剤、及びそれを用いる処理物から重金属等の有害物質が溶出するのを防止する技術に関するものである。
【０００２】
【従来の技術】
都市ゴミや産業廃棄物等の焼却プラントから排出される飛灰は、電気集塵機（以下「ＥＰ」という）やバグフィルター（以下「ＢＦ」という）で捕集されたのち埋め立てされている。しかし、これら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、「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」又は「薬剤添加法」のいずれかの処理を施した後、廃棄することが義務づけられている。これらのうち薬剤添加法は、他の方法に比べ一般に装置及び取り扱いが簡便なため種々検討されている。
【０００３】
薬剤添加法とは、所定量の水と薬剤と焼却灰とを混練して反応させ、有害な重金属類を固定化する方法である。この目的で用いられる薬剤としては、重金属類とキレート化合物を形成して水に不溶性の安定な固定化物を形成する有機液体キレート系重金属固定化剤、リン酸（塩）、珪酸（塩）、炭酸（塩）、重炭酸（塩）などの無機系重金属固定化剤などが挙げられる。有機液体キレート系重金属固定化剤としては、ジアルキルジチオカルバミン酸のアルカリ金属塩及び／又はジアルキルジチオカルバミン酸基を分子内に２個以上有する化合物のアルカリ金属塩、具体的には、ジエチルジチオカルバミン酸のカリウム塩及び／又はＮ１，Ｎ２，Ｎ３，Ｎ５−テトラ（ジチオカルボキシ）テトラエチレンペンタミンのナトリウム塩及び／又はピペラジンビスジチオカルバミン酸のカリウム塩などがある。これらの有機液体キレート系重金属固定化剤を用いた場合、混練や成形工程でジチオカルバミン酸基が分解して二硫化炭素やアミン類の臭気が発生し、環境、労働安全衛生の観点から問題であった。さらに、このジチオカルバミン酸系の化合物にアミノカルボン酸系キレート剤を合わせた液体キレート剤がある（特許文献１、非特許文献１）。
【０００４】
【特許文献１】
特開２００２−１６６２４７
【非特許文献１】
「飛灰対策−有害物質除去・無害化・再資源化技術」第３７〜４１頁
【０００５】
【発明が解決しようとする課題】
また、上記の有機液体キレート系重金属固定化剤を用いた場合、混練や成形工程でジチオカルバミン酸基が分解し二硫化炭素やアミン類の臭気が発生し、環境・労働安全衛生の観点から問題であった。無機系重金属固定化剤は、有機液体キレート系重金属固定化剤に比べ十分な重金属固定効果が得られなかった。また、排ガス処理（窒素酸化物の低減）として尿素水やアンモニア水を焼却炉に吹き込む場合、排ガス中の成分との反応生成物（例えば塩化アンモニウム）が粉体状で飛灰中に移行し、飛灰中に塩化水素の処理に用いられる消石灰が含まれる場合、重金属処理のため薬剤と水を添加して混練すると、ｐＨがアルカリ側に傾くためアンモニアが追出されて発生するが、上記薬剤では、アンモニア臭気を抑制することができず環境・労働安全衛生の観点から問題であった。
【０００６】
本発明は、上記の課題に鑑みてなされたものであり、目的は、重金属含有物が含水した際に未固定の重金属類が溶出するのを抑制し、臭気の発生を抑制することのできる、新規な重金属固定化剤、並びに及びそれを用いた焼却灰の処理方法を提供するである。
【０００７】
【課題を解決するための手段】
本発明者らは、リン酸マグネシウムアンモニウム（以下「ＭＡＰ」ともいう）を加熱しアンモニアを放出させて得られるリン酸一水素マグネシウム（以下「ＭＨＰ」ともいう）を焼却灰の処理剤として応用することができないかどうかについて鋭意研究した結果、焼却灰処理物からの重金属類、臭気の漏洩を抑制できることを見出し、本発明を完成するに至った。
【０００８】
すなわち、本発明は、下記の手段により前記の課題を解決した。
（１）リン酸マグネシウムアンモニウムの加熱によりアンモニアを放出させて得る多孔質リン酸一水素マグネシウムを必須成分として含むことを特徴とする重金属固定化剤。
（２）前記リン酸一水素マグネシウムを、廃水のリンの回収プロセスにおいて生成されるリン酸マグネシウムアンモニウムから得ることを特徴とする前記（１）に記載の重金属固定化剤。
（３）前記多孔質リン酸一水素マグネシウムを粉砕して粒径を５００μｍ以下とすることを特徴とする前記（１）又は（２）に記載の重金属固定化剤。
（４）リン酸マグネシウムアンモニウム又はリン酸マグネシウムアンモニウムを含む化合物を粉砕、粉末化して得られる重金属固定化剤。
（５）前記（１）〜（４）のいずれか１項記載の重金属固定化剤を重金属含有灰に添加して混練することを特徴とする重金属含有灰の処理方法。
【０００９】
なお、本発明の実施態様としては、以下のものがある。
（ａ）廃水を脱リン処理してリン酸マグネシウムアンモニウムが主体の中間物を得る工程、該脱リン工程に次いで該中間物を物理的に脱水する工程、該脱水工程に次いで該物理的に脱水された中間物を約１００℃以上で約６０分以上加熱する工程、とからなるリン酸一水素マグネシウムを少なくとも含む生成物を製造する方法。
（ｂ）前記（ａ）記載の生成物を粉砕して粒径を約５００μｍ以下とする工程を更に含むことを特徴とする多孔質の生成物を製造する方法。
（ｃ）重金属含有灰に上記（ａ）又は（ｂ）記載の生成物及び水を添加して、混練し、灰に含まれる有害物質を固定化することを特徴とする重金属含有灰の処理方法。
【００１０】
すなわち本発明の骨子は、具体的に言うと、リン酸マグネシウムアンモニウム（ＭＡＰ）を加熱しアンモニアを放出させて得られるリン酸一水素マグネシウム（ＭＨＰ）を必須成分として含むことを特徴とする重金属固定化剤及びそれを用いて焼却灰からの重金属の溶出を防止する方法である。
【００１１】
【発明の実施の形態】
以下に本発明を詳細に説明する。
本発明の方法において対象となる重金属含有灰は、特に限定されるものではないが、通常都市ゴミや産業廃棄物の焼却施設から排出され、ＥＰ、ＢＦ、マルチサイクロン等で捕集された煤塵のような飛灰を指す。また、焼却灰、焼却残渣、更に汚染土壌、浚渫土壌なども対象に含まれる。
【００１２】
排ガス処理（窒素酸化物の低減）を目的として、排ガスに尿素水やアンモニア水を焼却炉に吹込む場合、排ガス中の成分との反応生成物（例えば塩化アンモニウム）が粉体状で飛灰中に移行し、飛灰中に消石灰（塩化水素の処理）が含まれる場合、乾燥状態では問題ないが、重金属処理のため薬剤と水を添加して加湿混練すると、ｐＨがアルカリ性側に傾くためアンモニアが追出されて発生する。このアンモニアは、上記排ガス処理に由来すると考えられているが、窒素を多く含むゴミの燃焼によっても生じるものと考えられる。また、重金属処理剤がキレート系の場合、これも高アルカリ性のためアンモニアの発生を助長する。
【００１３】
本発明における、上記の骨子を形成する態様での効果発現のメカニズムについては以下のように考えられる。ＭＡＰを加熱処理するとアンモニア（ＮＨ３）を放出しＭＨＰが得られる（反応式（１））。
（加熱） ＭｇＮＨ４ＰＯ４・６Ｈ２Ｏ（ＭＡＰ）→ＭｇＨＰＯ４（ＭＨＰ）＋６Ｈ２Ｏ↑＋ＮＨ３↑ …反応式（１）
このＭＡＰを加熱することで生成するＭＨＰは、結晶の表面や内部に多孔質を形成し、重金属類やアンモニウムイオン等のカチオン性物質を吸着する機能を有すると考えられる。
【００１４】
本発明に係る重金属固定化剤の焼却灰に対する好ましい添加割合は、焼却灰の重金属含有量、臭気原因物質含有量によって変動するが、焼却灰処理剤の必須成分であるＭＨＰとして０．１重量％以上が好ましく、１〜３０重量％がより好ましい。０．１重量％未満では十分な重金属固定化効果が得られない。更に、本発明においては、上記に説明したＭＨＰを、従来の有機液体キレート系重金属固定化剤、リン酸（塩）、珪酸（塩）、炭酸（塩）、重炭酸（塩）などの無機系重金属固定化剤、硫酸バンド、ポリ塩化アルミニウム（ＰＡＣ）、ポリ硫酸アルミニウム（ＰＡＳ）などのアルミニウム系凝集剤、硫酸第一鉄、硫酸第二鉄、塩化第二鉄、ポリ硫酸鉄などの鉄系凝集剤、セメント、樹脂酸などと組み合わせて用いることも可能である。
【００１５】
本剤（ＭＨＰ）は、市販品以外に排水処理の脱リン工程で排出されるリン酸マグネシウムアンモニウム（ＭＡＰ）、又はリン酸マグネシウムアンモニウム（ＭＡＰ）を含む化合物から製造できる。製造法の一例としてＭＡＰを含む化合物、混合物（純分９０％、粒径０．３〜２ｍｍ）を水切り後１００〜２００℃で６０分以上加熱し、内部の結晶水や揮発分を除去させ、ボールミルで粉砕し分取製造することもできる。本剤（ＭＨＰ）の粒径は１０〜５００μｍが好適である。本発明で用いるＭＨＰの原料となるＭＡＰは、汚泥の嫌気性消化脱離液などの廃水から、リンやアンモニア性窒素をイオン反応による晶析反応を利用して除去する、いわゆるＭＡＰ造粒法、又はリン酸、マグネシウム塩、アンモニウム塩を水中で同モル混合し脱水することで含水率４０〜５０％のものを得ることができる。
【００１６】
リン酸マグネシウムアンモニウム（ＭＡＰ）又はリン酸マグネシウムアンモニウム（ＭＡＰ）を含む化合物を加熱して製造する方法以外に、ミルなどの粉砕機による粉砕、粉末化の過程で摩擦熱により上記化合物からアンモニアや結晶水、その他揮発分をガスとして分離し、上記化合物の表面や内部に多孔質を形成させることができる。上記化合物は、通常、粒状又は破砕状、鱗状であるため重金属固定化剤として使用するには粉末状にすることにより、粉末化と加熱が同じ工程で実施できる。粉砕機には、市販の粉砕機が使用でき、ボールミル、ロールミルなどがある。粉砕機の運転条件は、重金属固定化剤の粒径を０．３ｍｍ以下にする条件で運転すれば、粉末状の重金属固定化剤の温度は数百度になり、本発明の加熱に相当する効果が得られる。
【００１７】
本発明の方法において、前記飛灰混練時の添加水は、あくまで飛灰と重金属固定化剤の他、その他の重金属処理剤（これらを総称して「重金属固定化剤」ということがある）を混練する添加水であり、重金属処理剤との混練状態が充分でない、あるいは処理して得られる飛灰が液状となる等、重金属処理に影響を与えないよう、混練の具合によっては抑制剤の濃度の調整が必要である。特に限定するものではないが、重金属の処理において使用する水の量は、処理した飛灰の廃棄を容易にするため、通常処理する飛灰に対して５〜５０重量％の範囲で使用される。
【００１８】
【実施例】
次に、実施例により本発明をさらに詳細に説明する。但し、本発明は下記の実施例のみに限定されるものではない。
【００１９】
実施例１〜３及び比較例１〜２
（試験方法）
各実施例及び比較例で用いた試験法は以下の通りである。
（１）溶出試験
ＢＦ灰（鉛＝９６０ｐｐｍを含む）１００重量部に対して、水３０重量部を加え、更に所定量の重金属固定化剤を添加して、十分混練して一日間養生した。その後、サンプルを５ｍｍ以下に粉砕し、環境庁告示第１３号試験法に基づいて重金属の溶出試験を行った。
（２）臭気試験
ＢＦ灰（鉛＝９６０ｐｐｍを含む）２０ｇを１リットルのテドラーバックに入れ、水６ｇ（３０ｗ／ｗ％相当）と所定量の重金属固定化剤を添加して十分混練した。さらに空気５００ｍｌを注入して密閉し、５０℃で３０分間加温した後、アンモニア及び二硫化炭素の濃度の測定を行った。
【００２０】
（試験内容）
実施例１〜３及び比較例１〜２の試験内容を以下に示す。なお、ここで使用したＭＨＰは、純水に正りん酸、塩化マグネシウム及びアンモニア水を各々０．００３ｍｏｌ／リットルになるように添加し、水酸化ナトリウムでｐＨ８〜９に調製し、１時間攪拌後、２４時間静置し析出物を沈殿させ、５Ａろ紙で分離し調製したＭＡＰを１０５℃で加熱することにより得たものである。
実施例１
重金属固定化剤としてＭＨＰを３重量部添加し、重金属溶出試験、臭気試験を行った。
実施例２
重金属固定化剤としてＭＨＰを５重量部添加し、重金属溶出試験、臭気試験を行った。
実施例３
重金属固定化剤としてＭＨＰを１０重量部添加し、重金属溶出試験、臭気試験を行った。
【００２１】
比較例１
重金属固定化剤として、ジエチルジチオカルバミン酸カリウム塩を主成分とする有機液体キレート系薬剤（成分濃度５７重量％）を３重量部添加し、重金属溶出試験、臭気試験を行った。
比較例２
硫酸第二鉄を１０重量部添加し、重金属溶出試験、臭気試験を行った。
【００２２】
（試験結果）
実施例１〜３及び比較例１〜２の試験結果を第１表に示す。
【００２３】
【表１】
重金属固定化剤として、本発明に係るＭＨＰを用いて焼却灰を処理した場合（実施例１〜３）、鉛の溶出濃度は埋立基準値（総理府令５号）である０．３ｍｇ／リットル未満を満足し、アンモニア濃度は、有機液体キレートを用いて焼却灰を処理した場合（比較例１）、硫酸第二鉄を用いて焼却灰を処理した場合（比較例２）と比較し大幅に低減した。また、二硫化炭素は、ＭＨＰを用いて焼却灰を処理した場合（実施例１〜３）検出され無かったのに対し、有機液体キレートを用いて焼却灰を処理した場合（比較例１）では検出された。
【００２５】
【発明の効果】
本発明によれば、ＭＨＰを必須成分として含む本発明の重金属固定化剤、及びそれを用いた焼却灰の処理方法によれば、臭気化合物の発生を抑制し、処理焼却灰が含水した際に未固定の重金属類が溶出するのを極めて効率的に抑制することができる。[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a heavy metal-fixing agent for treating heavy metal-containing ash such as fly ash from an incineration plant for municipal waste or industrial waste, and a method for treating heavy metal-containing ash using the same.
Further, the present invention, when treating fly ash from incineration plants such as heavy metal-containing materials, especially municipal garbage and industrial waste, heavy metal fixing agent, and harmful substances such as heavy metals are eluted from the treated material using the same. This is related to the technology for preventing the occurrence of an accident.
[0002]
[Prior art]
Fly ash discharged from incineration plants, such as municipal garbage and industrial waste, is collected by an electric dust collector (hereinafter, referred to as "EP") or a bag filter (hereinafter, referred to as "BF"), and then landfilled. However, these fly ash contains a lot of harmful heavy metals, and the elution of lead, mercury, etc. by rainwater from the landfill may cause environmental pollution. For this reason, fly ash is designated as a specially controlled waste, and is subjected to any of the following methods: "solidification method for cement", "extraction method with acid or other solvent", "melt fixation method" or "chemical addition method". , Are obliged to be disposed of. Among them, the drug addition method is generally studied in various ways because the device and handling are generally simpler than other methods.
[0003]
The chemical addition method is a method in which a predetermined amount of water, a chemical and incinerated ash are kneaded and reacted to fix harmful heavy metals. Chemicals used for this purpose include organic liquid chelating heavy metal fixing agents that form chelate compounds with heavy metals to form stable immobilized products insoluble in water, phosphoric acid (salt), silicic acid (salt), carbonate (Salts) and inorganic heavy metal fixing agents such as bicarbonate (salts). Examples of the organic liquid chelating heavy metal fixing agent include alkali metal salts of dialkyldithiocarbamic acids and / or alkali metal salts of compounds having two or more dialkyldithiocarbamic acid groups in the molecule, specifically, potassium salts of diethyldithiocarbamic acid. and / or N 1, N 2, N 3 , N 5 - tetra (dithiocarboxy) potassium salt of sodium salt of tetraethylene pentamine and / or piperazine bis dithiocarbamate and the like. When these organic liquid chelate-based heavy metal fixing agents are used, the dithiocarbamic acid group is decomposed in the kneading and molding steps to generate odors of carbon disulfide and amines, which is a problem from the viewpoint of the environment and occupational health and safety. Was. Further, there is a liquid chelating agent obtained by combining an aminocarboxylic acid-based chelating agent with this dithiocarbamic acid-based compound (Patent Document 1, Non-Patent Document 1).
[0004]
[Patent Document 1]
JP-A-2002-166247
[Non-patent document 1]
"Fly ash countermeasures-Hazardous substance removal / harmlessness / recycling technology", pp. 37-41
[Problems to be solved by the invention]
In addition, when the above organic liquid chelate-based heavy metal fixing agent is used, the dithiocarbamic acid group is decomposed in the kneading and molding steps, and odors of carbon disulfide and amines are generated. there were. The inorganic heavy metal fixing agent could not obtain a sufficient heavy metal fixing effect as compared with the organic liquid chelating heavy metal fixing agent. Also, when urea water or ammonia water is blown into an incinerator as an exhaust gas treatment (reduction of nitrogen oxides), a reaction product (for example, ammonium chloride) with a component in the exhaust gas moves into fly ash in a powder form, When slaked lime used for the treatment of hydrogen chloride is contained in fly ash, if a chemical and water are added and kneaded for heavy metal treatment, the ammonia is expelled because the pH is inclined to the alkali side, but the above chemical is generated. Therefore, ammonia odor could not be suppressed, which was a problem from the viewpoint of environment and occupational health and safety.
[0006]
The present invention has been made in view of the above problems, the object is to suppress the elution of unfixed heavy metals when the heavy metal-containing material is hydrated, it is possible to suppress the generation of odor, A novel heavy metal fixing agent and a method for treating incineration ash using the same.
[0007]
[Means for Solving the Problems]
The present inventors apply magnesium monohydrogen phosphate (hereinafter, also referred to as “MHP”) obtained by heating magnesium ammonium phosphate (hereinafter, also referred to as “MAP”) to release ammonia as a treating agent for incinerated ash. As a result of intensive studies on whether or not it is possible, the present inventors have found that the leakage of heavy metals and odors from the incinerated ash treated product can be suppressed, and have completed the present invention.
[0008]
That is, the present invention has solved the above-mentioned problems by the following means.
(1) A heavy metal fixing agent comprising, as an essential component, porous magnesium monohydrogen phosphate obtained by releasing ammonia by heating magnesium ammonium phosphate.
(2) The heavy metal immobilizing agent according to (1), wherein the magnesium monohydrogen phosphate is obtained from magnesium ammonium phosphate produced in a process of recovering phosphorus from wastewater.
(3) The heavy metal immobilizing agent according to the above (1) or (2), wherein the porous magnesium monohydrogen phosphate is pulverized to have a particle size of 500 μm or less.
(4) A heavy metal fixing agent obtained by pulverizing and pulverizing magnesium ammonium phosphate or a compound containing magnesium ammonium phosphate.
(5) A method for treating heavy metal-containing ash, comprising adding the heavy metal-fixing agent according to any one of (1) to (4) to the heavy metal-containing ash and kneading the mixture.
[0009]
The embodiments of the present invention include the following.
(A) a step of dephosphorizing wastewater to obtain an intermediate mainly composed of magnesium ammonium phosphate, a step of physically dehydrating the intermediate after the dephosphorization step, and a step of physically dehydrating the intermediate after the dehydration step Heating the obtained intermediate at about 100 ° C. or more for about 60 minutes or more.
(B) A method for producing a porous product, further comprising a step of pulverizing the product according to (a) to a particle size of about 500 μm or less.
(C) A method for treating heavy metal-containing ash, comprising adding the product described in (a) or (b) and water to the heavy metal-containing ash, kneading the mixture, and fixing harmful substances contained in the ash. .
[0010]
That is, the gist of the present invention, specifically, contains magnesium monohydrogen phosphate (MHP) obtained by heating magnesium ammonium phosphate (MAP) to release ammonia as an essential component, and is characterized in that it is fixed to a heavy metal. It is a method for preventing heavy metals from being eluted from incineration ash using the same.
[0011]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, the present invention will be described in detail.
The heavy metal-containing ash which is the subject of the method of the present invention is not particularly limited, but is usually discharged from an incineration facility for municipal garbage or industrial waste and collected from EP, BF, multi-cyclones and the like. Refers to such fly ash. Also, incineration ash, incineration residue, contaminated soil, dredged soil, etc. are included in the target.
[0012]
When urea water or ammonia water is blown into an incinerator for the purpose of exhaust gas treatment (reduction of nitrogen oxides), reaction products (for example, ammonium chloride) with components in the exhaust gas are in powder form and fly ash. When slaked lime (hydrogen chloride treatment) is contained in fly ash, there is no problem in the dry state. However, when a chemical and water are added for heavy metal treatment and humidified and kneaded, the pH tends to the alkaline side and ammonia Is expelled. This ammonia is considered to be derived from the above-described exhaust gas treatment, but is also considered to be generated by combustion of dust containing much nitrogen. When the heavy metal treating agent is a chelate-based agent, it also promotes the generation of ammonia due to its high alkalinity.
[0013]
In the present invention, the mechanism of the effect manifestation in the above-described embodiment for forming the skeleton is considered as follows. When the MAP is heated, ammonia (NH 3 ) is released to obtain MHP (reaction formula (1)).
(Heating) MgNH 4 PO 4 .6H 2 O (MAP) → MgHPO 4 (MHP) + 6H 2 OＮＨ + NH 3 ↑ ... Reaction formula (1)
MHP generated by heating the MAP is considered to have a function of forming a porous material on the surface or inside of the crystal and adsorbing a cationic substance such as heavy metals or ammonium ions.
[0014]
The preferable addition ratio of the heavy metal fixing agent according to the present invention to the incineration ash varies depending on the heavy metal content and the odor-causing substance content of the incineration ash, but is 0.1% by weight as MHP which is an essential component of the incineration ash treatment agent. The above is preferable, and 1 to 30% by weight is more preferable. If it is less than 0.1% by weight, a sufficient heavy metal fixing effect cannot be obtained. Furthermore, in the present invention, the above-described MHP is converted to a conventional organic liquid chelate-based heavy metal fixing agent, an inorganic compound such as phosphoric acid (salt), silicic acid (salt), carbonic acid (salt), bicarbonate (salt) and the like. Heavy metal fixing agent, sulfate band, aluminum-based flocculant such as polyaluminum chloride (PAC), polyaluminum sulfate (PAS), iron-based such as ferrous sulfate, ferric sulfate, ferric chloride, and polyiron sulfate It is also possible to use in combination with a coagulant, cement, resin acid and the like.
[0015]
The present agent (MHP) can be produced from magnesium ammonium phosphate (MAP) discharged in the dephosphorization step of wastewater treatment or a compound containing magnesium ammonium phosphate (MAP) in addition to commercially available products. As an example of the production method, a compound containing MAP, a mixture (pure content: 90%, particle size: 0.3 to 2 mm) is drained and heated at 100 to 200 ° C. for 60 minutes or more to remove internal crystallization water and volatile components, It can also be prepared by pulverizing with a ball mill. The particle size of this agent (MHP) is preferably from 10 to 500 μm. MAP, which is a raw material of MHP used in the present invention, is a so-called MAP granulation method for removing phosphorus and ammonia nitrogen from wastewater such as anaerobic digestion and desorption liquid of sludge by utilizing crystallization reaction by ion reaction. Alternatively, phosphoric acid, magnesium salt, and ammonium salt are mixed in water in the same molar amount and dehydrated to obtain a water content of 40 to 50%.
[0016]
In addition to the method of manufacturing by heating magnesium ammonium phosphate (MAP) or a compound containing magnesium ammonium phosphate (MAP), ammonia and crystals are formed from the above compound by frictional heat in the process of pulverization and pulverization by a pulverizer such as a mill. Water and other volatile components can be separated as a gas to form a porous material on the surface or inside of the compound. Since the above compound is usually in the form of granules, crushed, or scale, it is powdered for use as a heavy metal fixing agent, so that powdering and heating can be performed in the same step. As the pulverizer, a commercially available pulverizer can be used, and examples thereof include a ball mill and a roll mill. If the operating conditions of the pulverizer are operated under the condition that the particle diameter of the heavy metal fixing agent is 0.3 mm or less, the temperature of the powdery heavy metal fixing agent becomes several hundred degrees, and the effect corresponding to the heating of the present invention is obtained. Is obtained.
[0017]
In the method of the present invention, the added water at the time of the fly ash kneading includes, in addition to the fly ash and the heavy metal fixing agent, other heavy metal treating agents (these may be collectively referred to as “heavy metal fixing agent”). The added water to be kneaded, the kneading state with the heavy metal treating agent is not sufficient, or the fly ash obtained by the treatment becomes liquid, so as not to affect the heavy metal treatment, depending on the degree of kneading, the concentration of the inhibitor. Needs to be adjusted. Although not particularly limited, the amount of water used in the treatment of heavy metals is usually in the range of 5 to 50% by weight based on the fly ash to be treated, in order to facilitate disposal of the treated fly ash. .
[0018]
【Example】
Next, the present invention will be described in more detail with reference to examples. However, the present invention is not limited to only the following examples.
[0019]
Examples 1-3 and Comparative Examples 1-2
(Test method)
The test methods used in each example and comparative example are as follows.
(1) Dissolution test To 100 parts by weight of BF ash (containing 960 ppm of lead), 30 parts by weight of water was added, a predetermined amount of a heavy metal fixing agent was further added, and the mixture was sufficiently kneaded and cured for one day. Thereafter, the sample was pulverized to a size of 5 mm or less, and a dissolution test of heavy metals was conducted based on the 13th test method notified by the Environment Agency.
(2) Odor test 20 g of BF ash (containing 960 ppm of lead) was placed in a 1-liter Tedlar bag, and 6 g of water (corresponding to 30 w / w%) and a predetermined amount of a heavy metal fixing agent were added and kneaded sufficiently. Further, 500 ml of air was injected and sealed, and the mixture was heated at 50 ° C. for 30 minutes, and then the concentrations of ammonia and carbon disulfide were measured.
[0020]
(contents of the test)
The test contents of Examples 1 to 3 and Comparative Examples 1 and 2 are shown below. The MHP used here was prepared by adding orthophosphoric acid, magnesium chloride, and aqueous ammonia to pure water at a concentration of 0.003 mol / liter, adjusting the pH to 8 to 9 with sodium hydroxide, and stirring for 1 hour. The MAP was left standing for 24 hours to precipitate a precipitate, which was obtained by heating MAP prepared by separating with a 5A filter paper at 105 ° C.
Example 1
3 parts by weight of MHP was added as a heavy metal fixing agent, and a heavy metal elution test and an odor test were performed.
Example 2
5 parts by weight of MHP was added as a heavy metal fixing agent, and a heavy metal elution test and an odor test were performed.
Example 3
10 parts by weight of MHP was added as a heavy metal fixing agent, and a heavy metal elution test and an odor test were performed.
[0021]
Comparative Example 1
As a heavy metal fixing agent, 3 parts by weight of an organic liquid chelating agent (component concentration 57% by weight) containing potassium diethyldithiocarbamate as a main component was added, and a heavy metal elution test and an odor test were performed.
Comparative Example 2
10 parts by weight of ferric sulfate was added, and a heavy metal elution test and an odor test were performed.
[0022]
(Test results)
Table 1 shows the test results of Examples 1 to 3 and Comparative Examples 1 and 2.
[0023]
[Table 1]
When the incinerated ash was treated with the MHP according to the present invention as a heavy metal fixing agent (Examples 1 to 3), the lead elution concentration was less than the landfill standard value (Prime Minister Ordinance No. 5) of 0.3 mg / liter. And the ammonia concentration is significantly reduced when the incinerated ash is treated with the organic liquid chelate (Comparative Example 1), as compared with the case where the incinerated ash is treated with ferric sulfate (Comparative Example 2). did. In addition, carbon disulfide was not detected when incinerated ash was treated using MHP (Examples 1 to 3), whereas in the case where incinerated ash was treated using an organic liquid chelate (Comparative Example 1). was detected.
[0025]
【The invention's effect】
According to the present invention, according to the heavy metal fixing agent of the present invention containing MHP as an essential component, and the method for treating incinerated ash using the same, the generation of odorous compounds is suppressed, and when the treated incinerated ash contains water, Elution of unfixed heavy metals can be suppressed very efficiently.
Claims (5)
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Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP2005230657A (en) * | 2004-02-18 | 2005-09-02 | Ebara Engineering Service Co Ltd | Treatment method for incineration fly ash and treatment agent |
| CN107150060A (en) * | 2017-05-08 | 2017-09-12 | 天津壹鸣环境科技股份有限公司 | A kind of domestic garbage incineration flyash high concentration wet method perfusion mould bag processing method and system |
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Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP2005230657A (en) * | 2004-02-18 | 2005-09-02 | Ebara Engineering Service Co Ltd | Treatment method for incineration fly ash and treatment agent |
| CN107150060A (en) * | 2017-05-08 | 2017-09-12 | 天津壹鸣环境科技股份有限公司 | A kind of domestic garbage incineration flyash high concentration wet method perfusion mould bag processing method and system |
| CN107150060B (en) * | 2017-05-08 | 2022-06-24 | 天津壹鸣环境科技股份有限公司 | Method and system for treating high-concentration fly ash generated by burning household garbage by filling mold bags through wet method |
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