JP3619069B2

JP3619069B2 - Fly ash recycling process

Info

Publication number: JP3619069B2
Application number: JP22530799A
Authority: JP
Inventors: 松太郎長澤; 卓井上; 猛山中
Original assignee: Unitika Ltd
Current assignee: Unitika Ltd
Priority date: 1999-08-09
Filing date: 1999-08-09
Publication date: 2005-02-09
Anticipated expiration: 2019-08-09
Also published as: JP2001047001A

Description

【０００１】
【発明の属する技術分野】
本発明は、都市ごみなどの廃棄物を焼却又は溶融することによって、排ガスとともに排出される飛灰の再資源化処理法に関するものである。
【０００２】
【従来の技術】
従来、飛灰の再資源化処理法として、例えば、特開平６−１７０３５４号公報には、飛灰に鉱酸を添加して鉛以外の重金属を溶出せしめ、固液分離して鉛残渣として鉛を回収し、濾液はアルカリ剤を添加して亜鉛を主とする水酸化物として亜鉛を回収する方法が示されている。
【０００３】
【発明が解決しようとする課題】
しかしながら、この方法では、排水、残渣が副生し、無害に処理してから廃棄する必要があり、また、回収物の純度および収率も低いといった問題があった。本発明は、飛灰に含まれる鉛および亜鉛を効率的に回収するとともに、鉛、亜鉛以外の有価物も高収率、高純度で回収し、廃棄物を排出しない飛灰の再資源化処理法を提供することを目的とするものである。
【０００４】
【課題を解決するための手段】
本発明は、このような課題を解決するものであって、本発明の主旨は、次の５つの工程からなることを特徴とする廃棄物の焼却施設または溶融施設から排出される飛灰の再資源化方法である。
（ａ）飛灰に硫酸を加えて亜鉛を抽出したのち固液分離し、得られた亜鉛抽出濾液にｐＨ調整剤および硫化薬剤を加えて亜鉛を不溶化したのち固液分離して亜鉛不溶化残渣として亜鉛を回収する工程。
（ｂ）上記（ａ）工程で得られる亜鉛不溶化濾液中の不純物を凝集沈殿、キレート樹脂および活性炭を用いて除去したのち、蒸発濃縮して固形塩として塩類を回収するとともに、蒸発水を濃縮して水を回収する工程。
（ｃ）上記（ａ）工程で得られる硫酸を含む亜鉛抽出残渣にチオ硫酸アルカリ塩を加えて鉛を抽出したのち固液分離し、得られた鉛抽出濾液に硫化薬剤を加えて鉛を不溶化したのち固液分離して鉛不溶化物として鉛を回収する工程。
（ｄ）上記（ｃ）工程で得られる鉛不溶化濾液中の不純物を除去してチオ硫酸アルカリ液を回収する工程。
（ｅ）上記（ｂ）工程で得られる亜鉛不溶化濾液不純物、上記（ｃ）工程で得られる鉛抽出残渣および上記（ｄ）工程で得られる鉛不溶化濾液不純物の汚泥を乾燥後、溶融スラグとして回収する工程。
【０００５】
【発明の実施の形態】
以下、本発明を詳細に説明する。
本発明においては、まず、飛灰に硫酸を加えて亜鉛を抽出したのち固液分離し、亜鉛抽出濾液にｐＨ調整剤および硫化薬剤を加えて亜鉛を不溶化したのち固液分離して亜鉛不溶化残渣として亜鉛を回収する（（ａ）工程）。一方、亜鉛不溶化濾液は、凝集沈殿、キレート樹脂および活性炭を用いて不純物を除去したのち蒸発濃縮することによって塩類および凝縮水を回収する（（ｂ）工程）。
次いで、硫酸を含む亜鉛抽出残渣にチオ硫酸アルカリ塩を加えて鉛を抽出したのち固液分離し、鉛抽出濾液に硫化薬剤を加えて鉛を不溶化したのち固液分離して鉛不溶化残渣として鉛を回収する（（ｃ）工程）。一方、鉛不溶化濾液は凝集沈殿等により、不純物を除去してチオ硫酸アルカリ液を回収する（（ｄ）工程）。
さらに、鉛不溶化残渣、塩類およびチオ硫酸アルカリ液を回収する際に排出する汚泥は、乾燥した後溶融固化して溶融スラグを回収する（（ｅ）工程）。
【０００６】
本発明に用いる硫酸注入量は、飛灰と硫酸の混合液ｐＨが２以下にするのが好ましく、該混合液ｐＨが３を超えると亜鉛の抽出性能が低下して好ましくない。
【０００７】
本発明の（ｂ）工程および（ｄ）工程で濾液中の不純物を除去する際に用いるアルカリ性薬剤としては、カセイソーダ、カセイカリ、消石灰などのアルカリ金属水酸化物、アルカリ土類水酸化物が挙げられる。注入量は、亜鉛不溶化濾液および鉛不溶化濾液のｐＨが５〜１２にするのが好ましい。ｐＨが５未満および１２以上の場合は、重金属類などの不純物除去率が低下して好ましくない。
【０００８】
本発明に用いるｐＨ調整剤としては、カセイソーダ、カセイカリ、消石灰などのアルカリ金属水酸化物、アルカリ土類水酸化物が挙げられる。注入量は、亜鉛抽出後の固液分離した水のｐＨが２〜８にするのが好ましい。ｐＨが２未満の場合は亜鉛の不溶化性能が低下し、ｐＨが８を越える場合はランニングコストが高くなり、いずれも好ましくない。
【０００９】
本発明の（ｂ）工程に用いる酸性薬剤としては、硫酸、塩酸などの鉱酸が挙げられる。注入量は亜鉛不溶化濾液の凝集沈殿上澄水のｐＨが４〜７にするのが好ましい。ｐＨが４未満および７以上の場合は、後工程のキレート樹脂吸着性能が低下して好ましくない。
【００１０】
本発明に用いる硫化薬剤としては、硫化ソーダ、水硫化ソーダ、硫化カリ、水硫化カリ、硫化カルシウムなどのアルカリ金属硫化物、アルカリ土類硫化物などが挙げられる。注入量は、飛灰中に含む亜鉛または鉛１当量に対して、硫化薬剤中の硫黄（Ｓ）１〜１０当量、特に１〜３当量が好ましい。１当量未満である場合は亜鉛または鉛の不溶化性能が低下し、１０当量を超える場合はランニングコストが高くなり、いずれも好ましくない。
【００１１】
本発明に用いるチオ硫酸アルカリ塩としては、チオ硫酸ナトリウム、チオ硫酸カリウム、チオ硫酸リチウム、チオ硫酸アンモニウム、チオ硫酸マグネシウム、チオ硫酸カルシウムなどが挙げられる。注入量は水溶液として用い、飛灰中に含む鉛１当量に対して、チオ硫酸アルカリ塩中のチオ硫酸基（Ｓ_２Ｏ_３ ^２−）として１〜１０００当量、特に５〜２００当量が好ましい。チオ硫酸アルカリ塩の添加量が１当量未満の場合は、鉛の抽出性能が低下し、１０００当量を超える場合はランニングコストが高くなり、いずれも好ましくない。
本発明に用いる凝集剤としては、従来から知られている通常のもの、例えばノニオン系高分子凝集剤やアニオン系高分子凝集剤が好ましく用いられる。
【００１２】
本発明における固液分離の方法としては、通常、脱水、沈殿、濾過などを行う。
【００１３】
以下、図面を参考にしつつ、本発明をさらに詳細に説明する。図１は、本発明の飛灰の再資源化処理法の一例を示す概略フロー図である。
図１において、飛灰１は、亜鉛回収処理設備２で処理され［第１抽出槽３（硫酸４注入）、第１脱水機５（高分子凝集剤６注入）、第１不溶化槽７（ｐＨ調整剤８および硫化薬剤９注入）、第２脱水機１０（高分子凝集剤１１注入）］、亜鉛抽出残渣３０と回収亜鉛１２が得られる。
【００１４】
亜鉛不溶化濾液１３は、第１不純物除去設備１４［第１凝集沈殿槽１５（アルカリ性薬剤１６および高分子凝集剤１７注入）、第１ｐＨ調整槽１８（酸性薬剤１９注入）、第１濾過塔２０、キレート樹脂塔２１、活性炭塔２２］で不純物が除去される。
【００１５】
亜鉛不溶化濾液１３の不純物が除去された処理水２３は、塩回収処理設備２４［晶析缶２５、第３脱水機２６］で回収塩２７が得られ、脱水濾液２８は晶析缶２５へ返送される。また、蒸発水を冷却して得た回収凝縮水２９は、冷却用水として再利用される。
【００１６】
硫酸を含む亜鉛抽出残渣３０は鉛回収処理設備３１［第２抽出槽３２（チオ硫酸アルカリ塩３３注入）、第４脱水機３４（高分子凝集剤３５注入）、第２不溶化槽３６（硫化薬剤３７注入）、第５脱水機３８（高分子凝集剤３９注入）］で処理され、その残渣は回収鉛４０となる。
【００１７】
鉛不溶化濾液４１は、第２不純物除去設備４２［第２凝集沈殿槽４３（アルカリ性薬剤４４および高分子凝集剤４５注入）、第２濾過塔４６］で不純物が除去され、回収チオ硫酸アルカリ液４７となる。
【００１８】
鉛抽出残渣４８、第１凝集沈殿槽の汚泥４９および第２凝集沈殿槽の汚泥５０は、溶融固化処理設備５１［乾燥機５２、溶融炉５３、冷却水槽５４］で溶融固化され回収溶融スラグ５５となる。
【００１９】
【実施例】
以下、実施例により本発明を具体的に説明するが、本発明はこれらの実施例に限定されるものではない。
【００２０】
実施例１
廃棄物焼却施設より排出されたＰｂ１．２６％、Ｚｎ４．５５％、Ｃｕ０．２６％、およびＫＣｌ、ＮａＣｌ、ＣａＣｌ_２などの可溶性塩類２３．７％を含む飛灰１を１０ｋｇ、亜鉛回収処理設備２の第１抽出槽３でｐＨが０．５になるまで５％硫酸１００Ｌを注入して亜鉛を抽出したのち、そのスラリーに０．１％ノニオン系高分子凝集剤６を１Ｌ注入して懸濁粒子を凝集させ、第１脱水機５で固液分離して、その脱水濾液は第１不溶化槽７でｐＨが２．０になるまでｐＨ調整剤８として２２％カセイソーダを注入してｐＨ調整し、硫化薬剤９として２０％水硫化ソーダ５．１Ｌ（３当量）を注入して亜鉛を不溶化したのち、そのスラリーに０．１％ノニオン系高分子凝集剤１１を０．１５Ｌ注入して亜鉛不溶化粒子を凝集させ、第２脱水機１０で水洗浄しながら固液分離して、その残渣は回収亜鉛１２となる。
【００２１】
一方、亜鉛不溶化濾液１３は、第１不純物除去処理設備１４の第１凝集沈殿槽１５でｐＨが１０になるまでアルカリ性薬剤１６として２２％カセイソーダを注入してｐＨ調整し、そのスラリーに０．１％アニオン系高分子凝集剤１７を０．６５Ｌ注入して懸濁粒子を凝集沈殿させる。その上澄水はｐＨ調整槽１８でｐＨが６になるまで酸性薬剤１９として１０％塩酸を注入してｐＨ調整し、砂を充填した第１濾過塔２０に線速度ＬＶ＝５ｍ／ｈで通液して懸濁物を完全に除去したのち、アミノカルボン酸型キレート樹脂を充填したキレート樹脂塔２１に空間速度ＳＶ＝５ｈ^−１で通液して残存した重金属を完全に除去し、さらにヤシガラ系活性炭を充填した活性炭塔２２に線速度ＬＶ＝５ｍ／ｈで通液して脱色する。
【００２２】
活性炭処理水２３は、塩回収処理設備２４の晶析缶２５で蒸発濃縮し、第３脱水機２６で固液分離して、その残渣は回収塩２７となり、脱水濾液２８は晶析缶へ返送する。また蒸発水を冷却して得た回収凝縮水２９は、冷却用水として再利用する。
【００２３】
硫酸を含む亜鉛抽出残渣３０は、鉛回収処理設備３１の第２抽出槽３２でチオ硫酸アルカリ塩３３として７％チオ硫酸ナトリウム５０Ｌ（３６．５当量）を注入して鉛を抽出したのち、そのスラリーに０．１％アニオン系高分子凝集剤３５を０．８Ｌ注入して懸濁粒子を凝集させて第４脱水機３４で固液分離して、その脱水濾液は第２不溶化槽３６で硫化薬剤３７として２０％水硫化ソーダ４５０ｍＬ（３当量）を注入して鉛を不溶化したのち、そのスラリーに０．１％アニオン系高分子凝集剤３９を０．１Ｌ注入して鉛不溶化粒子を凝集させて第５脱水機３８で水洗浄しながら固液分離して、その残渣は回収鉛４０となる。
【００２４】
鉛不溶化濾液４１は、第２不純物除去処理設備４２の第２凝集沈殿槽４３でｐＨが７になるまでアルカリ性薬剤４４として２２％カセイソーダを注入してｐＨ調整し、そのスラリーに０．１％アニオン系高分子凝集剤４５を０．５Ｌ注入して懸濁粒子を凝集沈殿させる。その上澄水は砂を充填した第２濾過塔４６に線速度ＬＶ＝５ｍ／ｈで通液して懸濁物を完全に除去し、回収チオ硫酸ナトリウム液４７として再利用する。
【００２５】
鉛抽出残渣４８、第１凝集沈殿槽の汚泥４９、第２凝集沈殿槽の汚泥５０は、溶融固化処理設備５１の乾燥機５２で水分率２０％まで乾燥したのち、溶融炉５３で温度１４００℃にて溶融し、冷却水槽５４で水砕して回収スラグ５５となる。
【００２６】
このようにして得られた回収亜鉛、回収塩、回収凝縮水、回収鉛、回収チオ硫酸ナトリウム液、回収スラグの組成分析結果および回収率を表１に示す。
【００２７】
【表１】

【００２８】
この結果より、回収亜鉛は乾量として０．７１ｋｇを得てその純度は５７．８８％および収率は９０．７％、回収塩は乾量として２．４６ｋｇを得てその純度は９８．４％および収率は１０２％、回収凝縮水は４２．７ｋｇを得、回収鉛は乾量として０．１９ｋｇを得てその純度は６２．７５％および収率は９４．４％、チオ硫酸ナトリウム液は１０．２ｋｇを得、回収スラグは６．１６ｋｇを得て環境庁告示第４６号法による溶出試験値がＰｂ０．０１ｍｇ／Ｌ以下、Ｃｄ０．００５ｍｇ／Ｌ以下であった。
【００２９】
このように、焼却飛灰中に含有していた亜鉛および鉛は高純度、高収率で回収でき、さらに塩類、チオ硫酸ナトリウム液、溶融スラグも高純度、高収率で回収でき、環境汚染もない。
【００３０】
【発明の効果】
以上のように、本発明によれば、飛灰に硫酸を加えて亜鉛を抽出したのち固液分離し、亜鉛抽出濾液にｐＨ調整剤と硫化薬剤を加えて亜鉛を不溶化したのち固液分離して、亜鉛不溶化残渣から亜鉛が回収でき、亜鉛不溶化濾液は、凝集沈殿、キレート樹脂および活性炭を用いて不純物除去したのち塩類と凝縮水が回収できる。
【００３１】
また、硫酸を含む亜鉛抽出残渣は、チオ硫酸アルカリ塩を加えて鉛を抽出した後固液分離し、鉛抽出濾液に硫化薬剤を加えて鉛を不溶化したのち固液分離して鉛不溶化残渣から鉛が回収でき、鉛不溶化濾液は、不純物除去したのちチオ硫酸アルカリ液が回収できる。
【００３２】
さらに、鉛抽出残渣および各不純物除去時の汚泥は、乾燥したのち溶融固化して溶融スラグが回収できる。
これら回収された亜鉛と鉛は製錬原料に、塩類は化学工業原料に、凝縮水は工程内の冷却用水に、チオ硫酸アルカリ液はチオ硫酸アルカリ塩の希釈液に、溶融スラグは路盤材等に、それぞれ再利用できる。なお、溶融スラグは重金属類が溶出しないなど環境汚染の心配がない。すなわち、廃棄物ゼロの資源循環型飛灰再資源化処理を可能とする方法である。
【図面の簡単な説明】
【図１】本発明の飛灰の再資源化処理方法の一例を示す概略フロー図である。
【符号の説明】
１飛灰
２亜鉛回収処理設備
３第１抽出槽
４硫酸
５第１脱水機
６高分子凝集剤
７第１不溶化槽
８ｐＨ調整剤
９硫化薬剤
１０第２脱水機
１１高分子凝集剤
１２回収亜鉛
１３亜鉛不溶化濾液
１４第１不純物除去処理設備
１５第１凝集沈殿槽
１６アルカリ性薬剤
１７高分子凝集剤
１８第１ｐＨ調整槽
１９酸性薬剤
２０第１濾過塔
２１キレート樹脂塔
２２活性炭塔
２３処理水
２４塩回収処理設備
２５晶析缶
２６第３脱水機
２７回収塩
２８脱水濾液
２９回収凝縮水
３０亜鉛抽出残渣
３１鉛回収処理設備
３２第２抽出槽
３３チオ硫酸アルカリ塩
３４第４脱水機
３５高分子凝集剤
３６第２不溶化槽
３７硫化薬剤
３８第５脱水機
３９高分子凝集剤
４０回収鉛
４１鉛不溶化濾液
４２第２不純物除去処理設備
４３第２凝集沈殿槽
４４アルカリ性薬剤
４５高分子凝集剤
４６第２濾過塔
４７回収チオ硫酸アルカリ液
４８鉛抽出残渣
４９第１凝集沈殿槽の汚泥
５０第２凝集沈殿槽の汚泥
５１溶融固化処理設備
５２乾燥機
５３溶融炉
５４冷却水槽
５５回収溶融スラグ[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method for recycling fly ash discharged together with exhaust gas by incinerating or melting waste such as municipal waste.
[0002]
[Prior art]
Conventionally, as a method for recycling fly ash, for example, in JP-A-6-170354, a mineral acid is added to fly ash to elute heavy metals other than lead, followed by solid-liquid separation and lead as a lead residue. A method is shown in which zinc is recovered as a hydroxide mainly composed of zinc by adding an alkali agent to the filtrate.
[0003]
[Problems to be solved by the invention]
However, this method has a problem in that wastewater and residue are by-produced and need to be disposed of after being treated harmlessly, and the purity and yield of the recovered product are low. The present invention efficiently recovers lead and zinc contained in fly ash, recovers valuable materials other than lead and zinc in high yield and high purity, and recycles fly ash without discharging waste It is intended to provide a law.
[0004]
[Means for Solving the Problems]
The present invention solves such problems, and the gist of the present invention is to recycle fly ash discharged from a waste incineration facility or melting facility characterized by the following five steps. This is a resource recycling method.
(A) Add sulfuric acid to fly ash to extract zinc and then separate into solid and liquid, add pH adjuster and sulfurizing agent to the obtained zinc extract filtrate to insolubilize zinc, then separate into solid and liquid to obtain zinc insolubilized residue The process of recovering zinc.
(B) After removing impurities in the zinc insolubilized filtrate obtained in the step (a) using coagulation precipitation, chelating resin and activated carbon , the solution is evaporated and concentrated to recover the salt as a solid salt, and the evaporated water is concentrated. Recovering water.
(C) Extracting lead by adding alkali thiosulfate to the zinc extraction residue containing sulfuric acid obtained in step (a) above, followed by solid-liquid separation, and adding lead sulfide filtrate to insolubilize lead Then, the process of solid-liquid separation and recovery of lead as lead insolubilized material.
(D) A step of removing the impurities in the lead-insolubilized filtrate obtained in the step (c) to recover an alkali thiosulfate solution.
(E) The zinc insolubilized filtrate impurities obtained in the step (b), the lead extraction residue obtained in the step (c) and the sludge of the lead insolubilized filtrate impurities obtained in the step (d) are recovered as molten slag after drying. Process.
[0005]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, the present invention will be described in detail.
In the present invention, first, sulfuric acid is added to fly ash to extract zinc, followed by solid-liquid separation, a pH adjuster and a sulfurizing agent are added to the zinc extraction filtrate to insolubilize zinc, and then solid-liquid separation is performed to obtain a zinc insolubilized residue. To recover zinc (step (a)). On the other hand, the zinc insolubilized filtrate recovers salts and condensed water by evaporating and concentrating after removing impurities using coagulation precipitation, chelating resin and activated carbon (step (b)).
Then, lead thiosulfate is added to the zinc extraction residue containing sulfuric acid, lead is extracted and then separated into solid and liquid, and then the lead extraction filtrate is added with a sulfurizing agent to insolubilize lead and then separated into solid and liquid to lead as a lead insolubilized residue. Is recovered (step (c)). On the other hand, the lead-insolubilized filtrate removes impurities by agglomeration precipitation or the like and collects the alkali thiosulfate solution (step (d)).
Furthermore, the sludge discharged when collecting the lead-insolubilized residue, salts, and alkali thiosulfate solution is dried and then melted and solidified to recover molten slag (step (e)).
[0006]
The sulfuric acid injection amount used in the present invention is preferably such that the mixed solution pH of fly ash and sulfuric acid is 2 or less, and if the mixed solution pH exceeds 3, the extraction performance of zinc is lowered, which is not preferable.
[0007]
Examples of the alkaline agent used when removing impurities in the filtrate in the steps (b) and (d) of the present invention include alkali metal hydroxides such as caustic soda, caustic potash, slaked lime, and alkaline earth hydroxides. . The amount of injection is preferably such that the pH of the zinc insolubilized filtrate and lead insolubilized filtrate is 5-12. When the pH is less than 5 or 12 or more, the removal rate of impurities such as heavy metals decreases, which is not preferable.
[0008]
Examples of the pH adjusting agent used in the present invention include alkali metal hydroxides such as caustic soda, caustic potash and slaked lime, and alkaline earth hydroxides. The injection amount is preferably set to a pH of 2 to 8 for the solid-liquid separated water after zinc extraction. When the pH is less than 2, the insolubilization performance of zinc is lowered, and when the pH exceeds 8, the running cost is increased, which is not preferable.
[0009]
Examples of the acidic agent used in the step (b) of the present invention include mineral acids such as sulfuric acid and hydrochloric acid. The injection amount is preferably 4 to 7 so that the pH of the coagulated sediment supernatant of the zinc insolubilized filtrate is 4-7. When the pH is less than 4 or 7 or more, the chelate resin adsorption performance in the subsequent step is lowered, which is not preferable.
[0010]
Examples of the sulfurizing agent used in the present invention include sodium sulfide, sodium hydrosulfide, potassium sulfide, potassium hydrosulfide, calcium sulfide, and other alkali metal sulfides, alkaline earth sulfides, and the like. The amount of injection is preferably 1 to 10 equivalents, particularly 1 to 3 equivalents of sulfur (S) in the sulfurized chemical with respect to 1 equivalent of zinc or lead contained in the fly ash. When the amount is less than 1 equivalent, the insolubilization performance of zinc or lead is lowered, and when it exceeds 10 equivalents, the running cost is increased.
[0011]
Examples of the alkali thiosulfate used in the present invention include sodium thiosulfate, potassium thiosulfate, lithium thiosulfate, ammonium thiosulfate, magnesium thiosulfate, and calcium thiosulfate. The injection amount is used as an aqueous solution, and preferably 1 to 1000 equivalents, particularly 5 to 200 equivalents, as the thiosulfate group (S ₂ O ₃ ²⁻ ) in the alkali thiosulfate salt with respect to 1 equivalent of lead contained in the fly ash. When the amount of alkali thiosulfate added is less than 1 equivalent, the lead extraction performance is reduced, and when it exceeds 1000 equivalents, the running cost increases, which is not preferable.
As the flocculant used in the present invention, a conventionally known ordinary one, for example, a nonionic polymer flocculant or an anionic polymer flocculant is preferably used.
[0012]
As the solid-liquid separation method in the present invention, dehydration, precipitation, filtration and the like are usually performed.
[0013]
Hereinafter, the present invention will be described in more detail with reference to the drawings. FIG. 1 is a schematic flow diagram showing an example of the fly ash recycling method of the present invention.
In FIG. 1, fly ash 1 is processed by a zinc recovery treatment facility 2 [first extraction tank 3 (sulfuric acid 4 injection), first dehydrator 5 (polymer flocculant 6 injection), and first insolubilization tank 7 (pH Conditioner 8 and sulfurizing agent 9 injection), second dehydrator 10 (polymer flocculant 11 injection)], zinc extraction residue 30 and recovered zinc 12 are obtained.
[0014]
The zinc insolubilized filtrate 13 includes a first impurity removal facility 14 [first coagulation sedimentation tank 15 (injection of alkaline agent 16 and polymer coagulant 17), first pH adjustment tank 18 (injection of acidic agent 19), first filtration tower 20, Impurities are removed by the chelate resin tower 21 and the activated carbon tower 22].
[0015]
The treated water 23 from which the impurities of the zinc insolubilized filtrate 13 have been removed has recovered salt 27 obtained by the salt recovery treatment facility 24 [crystallization can 25, third dehydrator 26], and the dehydrated filtrate 28 is returned to the crystallization can 25. Is done. The recovered condensed water 29 obtained by cooling the evaporated water is reused as cooling water.
[0016]
The zinc extraction residue 30 containing sulfuric acid is separated into lead recovery treatment equipment 31 [second extraction tank 32 (injected alkali thiosulfate 33), fourth dehydrator 34 (injection of polymer flocculant 35), and second insolubilization tank 36 (sulfurizing agent). 37), a fifth dehydrator 38 (polymer flocculant 39 injection)], and the residue becomes recovered lead 40.
[0017]
In the lead insolubilized filtrate 41, impurities are removed by the second impurity removal equipment 42 [second coagulation sedimentation tank 43 (injection of alkaline agent 44 and polymer coagulant 45), second filtration tower 46], and recovered alkali thiosulfate 47 It becomes.
[0018]
The lead extraction residue 48, the sludge 49 of the first coagulation sedimentation tank, and the sludge 50 of the second coagulation sedimentation tank are melted and solidified by the melt solidification processing equipment 51 [dryer 52, melting furnace 53, cooling water tank 54] and recovered molten slag 55. It becomes.
[0019]
【Example】
EXAMPLES Hereinafter, although an Example demonstrates this invention concretely, this invention is not limited to these Examples.
[0020]
Example 1
10 kg of fly ash 1 containing 1.26% Pb, 4.55% Zn, 0.26% Cu, and 23.7% soluble salts such as KCl, NaCl, CaCl ₂ discharged from the waste incineration facility, zinc recovery treatment facility In the first extraction tank 2, 100 L of 5% sulfuric acid was injected until the pH reached 0.5 to extract zinc, and then 1 L of 0.1% nonionic polymer flocculant 6 was injected into the slurry. The turbid particles are agglomerated and separated into solid and liquid by the first dehydrator 5, and the dehydrated filtrate is adjusted to pH by injecting 22% caustic soda as a pH adjuster 8 until the pH becomes 2.0 in the first insolubilization tank 7. Then, 5.1 L (3 equivalents) of 20% sodium hydrosulfide was injected as the sulfide chemical 9 to insolubilize zinc, and then 0.15 L of 0.1% nonionic polymer flocculant 11 was injected into the slurry. Agglomerate insolubilized particles and second dehydration Solid-liquid separation is performed while washing with water in the machine 10, and the residue becomes recovered zinc 12.
[0021]
On the other hand, the zinc insolubilized filtrate 13 is adjusted to pH by injecting 22% caustic soda as an alkaline agent 16 in the first coagulation sedimentation tank 15 of the first impurity removal treatment equipment 14 until the pH becomes 10, and 0.1% is added to the slurry. 0.65 L of% anionic polymer flocculant 17 is injected to agglomerate and precipitate suspended particles. The supernatant water is pH adjusted by injecting 10% hydrochloric acid as an acidic agent 19 in the pH adjusting tank 18 until the pH reaches 6, and is passed through the first filtration tower 20 filled with sand at a linear velocity LV = 5 m / h. After the suspension is completely removed, the remaining heavy metal is completely removed by passing the solution through the chelate resin tower 21 filled with the aminocarboxylic acid type chelate resin at a space velocity SV = 5 h ^−1. The activated carbon tower 22 filled with activated carbon is passed through the activated carbon tower 22 at a linear velocity LV = 5 m / h for decolorization.
[0022]
The activated carbon-treated water 23 is evaporated and concentrated in a crystallization can 25 of a salt recovery treatment facility 24, and is solid-liquid separated by a third dehydrator 26. The residue becomes recovered salt 27, and the dehydrated filtrate 28 is returned to the crystallization can. To do. The recovered condensed water 29 obtained by cooling the evaporated water is reused as cooling water.
[0023]
The zinc extraction residue 30 containing sulfuric acid was extracted by injecting 50 L (36.5 equivalents) of 7% sodium thiosulfate as the alkali thiosulfate salt 33 in the second extraction tank 32 of the lead recovery treatment facility 31 and then extracting the lead. 0.8 L of 0.1% anionic polymer flocculant 35 is injected into the slurry to agglomerate the suspended particles, and solid-liquid separation is performed by the fourth dehydrator 34. The dehydrated filtrate is sulfided by the second insolubilization tank 36. After injecting 450 mL (3 equivalents) of 20% sodium hydrosulfide as the drug 37 to insolubilize lead, 0.1 L of 0.1% anionic polymer flocculant 39 is injected into the slurry to agglomerate lead insolubilized particles. The fifth dehydrator 38 performs solid-liquid separation while washing with water, and the residue becomes recovered lead 40.
[0024]
The lead insolubilized filtrate 41 was adjusted to pH by injecting 22% caustic soda as an alkaline agent 44 in the second coagulation sedimentation tank 43 of the second impurity removal treatment equipment 42 until the pH reached 7, and 0.1% anion was added to the slurry. 0.5 L of the polymer flocculant 45 is injected to agglomerate and precipitate the suspended particles. The supernatant water is passed through a second filtration tower 46 filled with sand at a linear velocity LV = 5 m / h to completely remove the suspension, and is reused as a recovered sodium thiosulfate solution 47.
[0025]
The lead extraction residue 48, the sludge 49 in the first coagulation sedimentation tank, and the sludge 50 in the second coagulation sedimentation tank are dried to a moisture content of 20% by the dryer 52 of the melt solidification processing equipment 51, and then the temperature is 1400 ° C. in the melting furnace 53. And is crushed in a cooling water tank 54 to form a recovered slag 55.
[0026]
Table 1 shows the composition analysis results and the recovery rates of the recovered zinc, recovered salt, recovered condensed water, recovered lead, recovered sodium thiosulfate solution, and recovered slag thus obtained.
[0027]
[Table 1]

[0028]
As a result, the recovered zinc obtained 0.71 kg as a dry amount with a purity of 57.88% and a yield of 90.7%, and the recovered salt obtained a dry amount of 2.46 kg with a purity of 98.4. % And yield is 102%, recovered condensed water is 42.7 kg, recovered lead is 0.19 kg as dry weight, its purity is 62.75%, yield is 94.4%, sodium thiosulfate solution Was 10.2 kg, the recovered slag was 6.16 kg, and the dissolution test values by the Environmental Agency Notification No. 46 method were Pb 0.01 mg / L or less and Cd 0.005 mg / L or less.
[0029]
In this way, zinc and lead contained in incineration fly ash can be recovered with high purity and high yield, and salts, sodium thiosulfate solution and molten slag can also be recovered with high purity and high yield, and environmental pollution Nor.
[0030]
【The invention's effect】
As described above, according to the present invention, sulfuric acid is added to fly ash to extract zinc, followed by solid-liquid separation, and then a pH adjusting agent and a sulfurizing agent are added to the zinc extraction filtrate to insolubilize zinc , followed by solid-liquid separation. Thus, zinc can be recovered from the zinc insolubilized residue, and the zinc insolubilized filtrate can recover salts and condensed water after removing impurities using coagulation precipitation, chelating resin and activated carbon .
[0031]
In addition, zinc extraction residue containing sulfuric acid is extracted from lead by adding alkali thiosulfate and then separated into solid and liquid, then sulfurized chemicals are added to the lead extraction filtrate to insolubilize lead, and then solid and liquid are separated from the lead insolubilized residue. Lead can be recovered, and the lead insolubilized filtrate can recover the alkali thiosulfate solution after removing impurities.
[0032]
Furthermore, the lead extraction residue and sludge at the time of removal of each impurity can be dried and then melted and solidified to recover molten slag.
These recovered zinc and lead are used as smelting raw materials, salts are used as chemical industrial raw materials, condensed water is used as cooling water in the process, alkali thiosulfate is used as a diluted solution of alkali thiosulfate, molten slag is used as roadbed materials, etc. Each can be reused. Note that the molten slag does not cause environmental pollution such as heavy metals do not elute. In other words, this is a method that enables resource-recycling fly ash recycling with zero waste.
[Brief description of the drawings]
FIG. 1 is a schematic flowchart showing an example of a method for recycling fly ash according to the present invention.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Fly ash 2 Zinc recovery processing equipment 3 1st extraction tank 4 Sulfuric acid 5 1st dehydrator 6 Polymer flocculant 7 1st insolubilizer 8 pH adjuster 9 Sulfide chemical | medical agent 10 2nd dehydrator 11 Polymer flocculant 12 Collected zinc 13 Zinc insolubilized filtrate 14 First impurity removal treatment facility 15 First coagulation sedimentation tank 16 Alkaline chemical 17 Polymer coagulant 18 First pH adjustment tank 19 Acidic chemical 20 First filtration tower 21 Chelate resin tower 22 Activated carbon tower 23 Treated water 24 Salt Recovery treatment facility 25 Crystallization can 26 Third dehydrator 27 Recovered salt 28 Dehydrated filtrate 29 Recovered condensed water 30 Zinc extraction residue 31 Lead recovery treatment facility 32 Second extraction tank 33 Alkali thiosulfate 34 Fourth dehydrator 35 Polymer aggregation Agent 36 Second Insolubilization Tank 37 Sulfide Agent 38 Fifth Dehydrator 39 Polymer Coagulant 40 Recovered Lead 41 Lead Insolubilized Filtrate 42 Second Impurity Removal Treatment Equipment 43 Second Coagulation Precipitation Tank 44 Lucariic agent 45 Polymer flocculant 46 Second filtration tower 47 Recovery alkali thiosulfate 48 Lead extraction residue 49 Sludge in first coagulation sedimentation tank 50 Sludge in second coagulation sedimentation tank 51 Melting and solidification treatment equipment 52 Dryer 53 Melting furnace 54 Cooling water tank 55 Recovery molten slag

Claims

A recycling method for fly ash discharged from a waste incineration facility or melting facility characterized by the following five steps.
(A) Add sulfuric acid to fly ash to extract zinc and then separate into solid and liquid, add pH adjuster and sulfurizing agent to the obtained zinc extract filtrate to insolubilize zinc, then separate into solid and liquid to obtain zinc insolubilized residue The process of recovering zinc.
(B) After removing impurities in the zinc insolubilized filtrate obtained in the step (a) using coagulation precipitation, chelating resin and activated carbon , the solution is evaporated and concentrated to recover the salt as a solid salt, and the evaporated water is concentrated. Recovering water.
(C) Extracting lead by adding alkali thiosulfate to the zinc extraction residue containing sulfuric acid obtained in step (a) above, followed by solid-liquid separation, and adding lead sulfide filtrate to insolubilize lead Then, the process of solid-liquid separation and recovery of lead as lead insolubilized material.
(D) A step of removing the impurities in the lead-insolubilized filtrate obtained in the step (c) to recover an alkali thiosulfate solution.
(E) The zinc insolubilized filtrate impurities obtained in the step (b), the lead extraction residue obtained in the step (c) and the sludge of the lead insolubilized filtrate impurities obtained in the step (d) are recovered as molten slag after drying. Process.