JP4277108B2 - Heavy metal recovery from fly ash - Google Patents
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- JP4277108B2 JP4277108B2 JP27279499A JP27279499A JP4277108B2 JP 4277108 B2 JP4277108 B2 JP 4277108B2 JP 27279499 A JP27279499 A JP 27279499A JP 27279499 A JP27279499 A JP 27279499A JP 4277108 B2 JP4277108 B2 JP 4277108B2
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
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Description
【０００１】
【発明の属する技術分野】
本発明は、重金属成分と塩素とを含むすべての飛灰に適用できる重金属回収方法に関し、特に、都市ゴミ焼却施設や産業廃棄物焼却場等における焼却炉や溶融炉あるいは汚泥を処理するセメントキルン等から発生する重金属含有飛灰の処理に好適な重金属の回収方法に関する。
【０００２】
【従来の技術】
一般事業所や一般家庭から排出されるゴミ（「都市ゴミ」または「一般廃棄物」と称されている）は都市ゴミ焼却施設や産業廃棄物焼却工場等に集められて焼却処分されており、その際に焼却炉から焼却灰や飛灰が発生するが、焼却灰は最終処分場に堆積され、飛灰については薬剤処理、または溶融炉、セメントキルン処理等の中間処理が施されている。
【０００３】
しかし、前記溶融炉やセメントキルン等での飛灰の中間処理においては、蒸気圧の高い鉛、亜鉛およびカドミウム等の重金属は炉内で揮発して排ガスに入り、この排ガスに入った重金属は排ガス処理設備のなかで凝縮して再び飛灰となっていた。すなわち、この再度の飛灰中には、前記のように鉛、銅、亜鉛およびカドミウム等の有用な重金属が含まれており、これらの飛灰から有用な重金属を回収する方法が求められていた。
【０００４】
このような飛灰について、特開平７−１０９５３３号公報には、飛灰を槽内の水に懸濁し、この懸濁液を酸またはアルカリの添加によりアルカリ域の適当値にｐＨ調整することによって飛灰中の重金属を水酸化物として沈殿させ、その殿物を回収する方法について開示している。また、本出願人も、先に、湿式処理方式によって対処する方法を出願しており（特開平８−１１７７２４号公報および特開平８−１４１５３９号公報）、このような湿式処理方法により、飛灰に含まれている銅等有用重金属を安定な形で分離し、重金属資源として有効に回収できるようになった。
【０００５】
すなわち、特開平８−１１７７２４号公報には、飛灰を水でスラリー化し、ｐＨ調整して浸出し、固液分離する第１工程と、該第１工程からの殿物をリパルプし、鉱酸により浸出溶解した後、固液分離して鉛産物を得る第２工程と、前記第１工程と前記第２工程からの酸性濾液に中和剤またさらに水流化ソーダを加えて亜鉛、銅を含む産物を濾別し、濾過水を排水液とする第３工程からなる方法が開示されており、また、特開平８−１４１５３９号公報には、飛灰を水と中和剤で中和して固液分離する第１工程と、該第１工程からの殿物をリパルプし、硫酸により浸出溶解して後、固液分離して鉛産物を得る第２工程と、該第２工程からの濾液に中和剤を加えて亜鉛、銅を含む産物を濾別する第３工程と、該第３工程の濾過水を該第１工程の中和液として繰返し、該第１工程からの濾液について硫化剤を添加して排液処理する方法が開示されている。
【０００６】
【発明が解決しようとする課題】
しかしながら、飛灰には重金属のほかにＳｉＯ2 、ＣａＯ、Ａｌ、Ｆｅ等のフラックス成分がかなりの量で含まれる場合が多く、前記の湿式処理方法ではこれらのすべてを回収工程に投入することから、回収コスト面に大きな負担がかかっていた。すなわち、初期設備コストが大きくなり、薬剤、動力等のランニングコストも大きいという問題が残されていた。また、回収した重金属含有殿物中に前記フラックス成分が一部入り込むため、製錬工程等に投入するための原料としては重金属品位が低く、さらに重金属品位を高める方法が望まれている状況にあった。
【０００７】
このような状況に鑑み、本発明の目的とするところは、有用重金属が多量のＳｉＯ2 、ＣａＯ、Ａｌ、Ｆｅ等のフラックス成分と共に含有されている飛灰の処理において、前記フラックス成分による処理負担を軽減し、有用重金属の回収コストの低減を図ることにあり、より具体的には、飛灰処理の早期の段階において、直接的に前記有用重金属とフラックス成分とを分別し、さらには、前記有用重金属を濃縮し、回収工程における必要処理量の低減を図ると共に、得られた重金属回収殿物中の重金属品位を高め、またさらには、フラックス成分の焼却炉、溶融炉またはセメントキルン等における再利用を図るにある。
【０００８】
【課題を解決するための手段】
上記の目的を達成するために鋭意研究した結果、飛灰中の有用重金属は微粒子中に多く存在し、逆にＳｉＯ2 、ＣａＯ、Ａｌ、Ｆｅ等のフラックス成分は粗い粒子中に含有されることを見出し、本発明を提供するに至ったものである。
すなわち、本発明は、第１に、亜鉛、銅、鉛のうちの少なくとも一種の重金属成分を含む飛灰から前記重金属成分を回収する方法において、前記飛灰を分級して得られる細粒部をｐＨ７以上のスラリーとし、固液分離することにより重金属含有殿物を回収することを特徴とする飛灰からの重金属の回収方法を、第２に、亜鉛、銅、鉛のうちの少なくとも一種の重金属成分と塩素とを含む飛灰から前記重金属成分を回収する方法において、前記飛灰を分級して得られる細粒部に鉱酸を加えてスラリー化し、ｐＨを５以下に調整して塩素を溶解させる塩素溶解工程と、該塩素溶解工程のスラリーにアルカリ剤を添加してｐＨを８〜１２に調整した後、固液分離することにより重金属含有殿物を塩素含有濾液から分離して回収する重金属含有殿物回収工程とからなることを特徴とする飛灰からの重金属の回収方法を、第３に、前記重金属含有殿物に鉱酸を加えてｐＨ５以下のスラリーとし、鉛を濃縮した鉛産物と濾液とに固液分離する鉛産物回収工程と、該鉛産物回収工程で得られた濾液をｐＨ８以上とし、銅と亜鉛を濃縮した銅・亜鉛産物と濾液に固液分離する銅・亜鉛産物回収工程とを有することを特徴とする第１または第２に記載の飛灰からの重金属の回収方法を、第４に、亜鉛、銅、鉛のうちの少なくとも一種の重金属成分を含む飛灰から前記重金属成分を回収する方法において、前記飛灰を分級して得られる細粒部をｐＨ７以上のスラリーとした後、硫化剤を添加し、固液分離することにより重金属含有殿物を回収することを特徴とする飛灰からの重金属の回収方法を、第５に、前記飛灰を分級する手段が、乾式サイクロンと湿式サイクロンのいずれかであることを特徴とする第１〜第４のいずれかに記載の飛灰からの重金属の回収方法を、第６に、前記分級操作における分級点が 5〜20μｍであることを特徴とする第１〜第５のいずれかに記載の飛灰からの重金属の回収方法を、第７に、分級した粗粒部を焼却炉と溶融炉とセメントキルンのいずれかに投入することを特徴とする第１〜第６のいずれかに記載の飛灰からの重金属の回収方法を提供する。
【０００９】
【発明の実施の形態】
焼却炉、溶融炉またはセメントキルン等の加熱炉から発生する飛灰には、前記のように、多量のＳｉＯ2 、ＣａＯ、Ａｌ、Ｆｅ等のフラックス含有成分が含有されている。これらのフラックス成分は炉内で加熱時、メカニカルダストとして捕集され、該して粗粒である。一方、飛灰中に含有されている重金属類はもともと加熱炉において金属単体あるいは塩化物等の化合物の形でヒュームやガスとして揮発して冷却されたものであって細粒をなしているものが多い。
【００１０】
以下、本発明の飛灰からの重金属の回収方法を、図面に従って説明する。
図１の工程図に示すように、先ず、飛灰を分級することによって篩上の粗粒部と篩下の細粒部に分別する。
粗粒部にはフラックス成分が主体のメカニカルダストが集まると共に、細粒部には重金属類が集まって重金属が濃縮される結果となり、重金属品位の高いものが得られる。従って、この篩下の細粒部のみをさらに重金属回収工程へ投入することにより、低コストで効率的な重金属回収が実現できることになる。一方、篩上の粗粒部はフラックスとして元の加熱炉に戻すことができる。
【００１１】
分級にあたっては、分級点の範囲を 5〜20μｍとし、好ましくは 5〜10μｍとする。基準となる分級点は、飛灰の種類によって多少異なるが、ほとんどの飛灰について、篩下の細粒部が 5μｍ未満では重金属の回収歩留りが下がり、逆に10μｍを超えると、メカニカルダストの混入が増し、フラックス成分との分離が不十分となり、特に、20μｍを超えると、分級の意味が薄れる。
【００１２】
分級手段は、乾式方式と湿式方式とのどちらも利用できるが、粗粒部のフラックス成分を元の加熱炉に戻すことを考慮すると乾式方式が望ましい。また、分級装置としても特に限定されるものではないが飛灰の粒度が全体的に細かく、 5〜20μｍの分級点を考慮すると、サイクロンが好ましい。
【００１３】
上記分級点における分級後の篩上の粗粒部（サイクロンではアンダーフロー部）は飛灰全体重量の６０％以上を占め、このまま元の加熱炉に戻すことが可能であり、重金属を系内にとどめロスを防ぐことが可能である。一方、篩下の細粒部（サイクロンではオーバーフロー部）は飛灰全体重量の１０〜４０％で銅、亜鉛等有用重金属が濃縮されている。
【００１４】
先ず、分級した細粒部は水と混合してスラリー化させる。次いで、このスラリーを攪拌しながら、水酸化ナトリウム等のアルカリ剤を添加してｐＨを７以上、好ましくは９〜１２に調整することにより溶存金属を水酸化物態として析出させ、引き続き、固液分離して重金属殿物を回収する。この時、後の工程、例えば、排水処理で硫化物が問題とならない場合は、図１の工程図で括弧内に示しているとおり、アルカリ剤添加後に硫化剤を添加し、水酸化物態とならなかった重金属をさらに硫化物態として回収する方法を取り入れることにより、重金属含有殿物の回収を効率的に行える。
【００１５】
また、重金属含有殿物中の含有塩素を嫌う場合は、図２の飛灰処理工程図に示すとおり、分級した細粒部を水と混合してスラリー化させる。次いで、このスラリーを攪拌しながら硫酸等鉱酸を添加し、ｐＨを５以下、好ましくは３付近に調整して塩類態で含まれる塩素をできるだけ溶液に溶解させる。引き続き、水酸化ナトリウム等のアルカリ剤を添加して急速にｐＨを８〜１２まで上げる中和操作を行って固液分離することにより重金属含有殿物を塩類を含有する濾液から分離回収する。以上のように、飛灰スラリーを酸性域において十分に溶出させた後、中和操作を行うことにより、重金属含有殿物の塩素含有率を著しく減少させることができる。この塩素含有率の低い重金属含有殿物は、そのまま、製錬工程の原料とすることが可能である。
【００１６】
得られた重金属含有殿物は、鉛産物、銅・亜鉛産物に分別することにより、製錬工程における処理負担をさらに軽減することができる。この場合、図３に示すとおり、回収重金属含有殿物に水を加えてリパルプし、硫酸等の鉱酸を添加してｐＨを５以下、好ましくは３以下として固液分離し、鉛リッチな鉛産物と銅、亜鉛等が溶解した濾液を得る。この濾液に水酸化ナトリウム等のアルカリ剤を添加してｐＨを８以上として固液分離することによって銅または亜鉛を主体とする銅・亜鉛産物を得る。また、この分別処理によって得られる重金属産物はさらに塩素が低減されたものになる。濾液は篩下の細粒部をスラリー化する水として用いることができる。
【００１７】
【実施例】
［実施例１］
図１の工程図に従って飛灰処理を行った。すなわち、表１に示す成分の焼却炉から発生した飛灰200gを、2000mlの水で湿式サイクロンにかけ、10μｍを分級点として分級した。
アンダーフロー（ +10μm）部の粗粒部は濾過、脱水した後、重量を測定したところ、重量分布が 75%の150gであった。また、分析サンプルを採取して成分分析に供した。
一方、オーバーフロー（ -10μm）部の細粒部についても濾過、脱水操作を行い、重量測定を行ったところ、重量分布が 15%の30g であった。また、分析サンプルを採取して成分分析に供した。この細粒部は分析サンプル採取後、もとの濾液に戻してリパルプし、水酸化ナトリウム溶液でｐＨを１０．５に調整した後、濾過した。得られた重金属含有殿物を乾燥し、重量を測定したところ25g であった。また分析サンプルを採取して成分分析に供した。
得られた結果を表１に示した。
銅、亜鉛、鉛からなる有用重金属は、重量分布が12.5％の重金属含有殿物に濃縮されて回収された。また、粗粒部の成分を分級前の飛灰の成分と比較すると重金属類の品位は低く、ＣａＯ等フラックス成分が主体であり、フラックスとして焼却炉に利用できるものであった。
【００１８】
【表１】
［実施例２］
図２の工程図に従って飛灰処理を行った。すなわち、表２に示す溶融炉から発生した飛灰600gを、乾式サイクロンにより 5μｍを分級点として分級した。
濾過、乾燥後における篩上分に相当する +5μmの粗粒部は重量分布が70%の420gで、篩下分に相当する -5μm の細粒部は30% の180gであった。
篩下の細粒部 100gを水 1000mlでスラリー化し、硫酸を加えてｐＨを３とした（塩素溶解工程）。次いで、水酸化ナトリウム溶液でｐＨを１０．５に調整した後、濾過した（重金属含有殿物回収工程）得られた重金属含有殿物の一部を乾燥し、成分分析に供した。
得られた結果を表２に示した。
得られた重金属含有殿物には、銅、鉛、亜鉛が濃縮的に含有され、塩素分も低く、製錬原料として利用でき、また、粗粒部は重金属類の品位も低く、ＣａＯ等フラックス分が多く、再度焼却炉に利用できるものであった。
【００２０】
【表２】
［実施例３］
図３の工程図に従って重金属含有殿物を処理した。すなわち、実施例２で得られた湿状態の重金属含有殿物に水1000mlを加えてリパルプした後、硫酸を加えてｐＨを２に調整して濾過し、鉛産物を得た（鉛産物回収工程）。得られた鉛産物は乾燥した後、成分分析に供した。さらに、濾別された溶液に水酸化ナトリウム溶液を加えてｐＨ９．５に調整した後、濾過した（銅・亜鉛産物回収工程）。得られた銅・亜鉛産物は乾燥した後、成分分析に供した。
得られた成分分析結果を原料の重金属含有殿物の成分と共に表３に示した。
分級処理とｐＨ調整処理を経由して有用重金属が濃縮された重金属含有殿物から、塩素も低く、さらに有利に製錬工程に使用できる鉛分が濃縮された鉛産物と銅・亜鉛分が濃縮された銅・亜鉛産物を分別回収することができた。
【００２２】
【表３】
［比較例１］
実施例１で用いた飛灰と同一ロットの焼却飛灰を、分級操作を行うことなく、その 200gに水 2000mlを加えてリパルプし、水酸化ナトリウム溶液でｐＨを１０．５に調整した後、濾過し、得られた重金属含有殿物を乾燥し、成分分析に供した。
得られた結果を原料飛灰の成分と共に表４に示した。
この結果から、重金属含有殿物は、塩素を除いては重量が低減した分だけ濃縮された形で、有用重金属やフラックス成分については、実質的に殆ど変化がない状態であった。
【００２４】
【表４】
［比較例２］
実施例２で用いた飛灰と同一ロットの溶融飛灰600gについて、分級操作を行わなかったほかは、実施例２と同様の処理操作でスラリー化を行い、ｐＨ調整し、濾過して重金属含有殿物を得た。さらに、この重金属含有殿物について、実施例３と同様の処理操作を行って鉛産物と銅・亜鉛産物を分別回収した。
得られた産物等の重量と成分分析結果を原料溶融飛灰の成分と共に表５に示した。
重金属含有殿物からの鉛産物と銅・亜鉛産物との分別回収は行われるものの、飛灰からのフラックス成分は殆ど除去できなかった。
【００２６】
【表５】
【発明の効果】
亜鉛等重金属を含む飛灰の処理において、先ず、飛灰を分級することにより、重金属を濃縮した状態の細粒部を得て、重金属回収対象物としたから、飛灰中のフラックス成分による過剰な処理が不要となり、回収コストの低減が図れるという効果を奏する。
また、重金属が濃縮された細粒部について、ｐＨ調整操作により塩素を分離した後、重金属分の析出を図るようにすることにより、重金属の製錬工程における処理負担が軽減されるという効果が得られる。
得られた重金属含有殿物について、ｐＨ調整操作によって鉛産物と銅・亜鉛産物とに分別処理することにより、重金属の製錬工程における処理負担がさらに軽減されるという効果が得られる。
重金属含有殿物の回収に際し、水酸化物態重金属の析出後、さらに硫化剤を添加することにより残留溶存重金属を硫化金属態として効率的に回収できるという効果が得られる。
飛灰の分級手段としてサイクロンを用いることにより、粒度の細かい飛灰の分級処理が効率的に行えるという効果が得られる。
細粒部の分級点範囲を 5〜20μｍとすることにより重金属の回収が良好に行われるという効果が得られる。
さらに、分級による粗粒部を焼却炉等加熱炉に返戻することにより、フラックス分の再利用が図れ、総合的な重金属回収コストが低減されるという効果を奏する。
【図面の簡単な説明】
【図１】本発明の飛灰からの重金属含有殿物回収方法の工程図である。
【図２】塩素溶解工程を含む本発明の飛灰からの重金属含有殿物回収方法の工程図である。
【図３】図１または図２の回収方法によって得られた重金属含有殿物からの重金属の分別回収方法の工程図である。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a heavy metal recovery method applicable to all fly ash containing heavy metal components and chlorine, and in particular, an incinerator, a melting furnace, a cement kiln for treating sludge, etc. in a municipal waste incineration facility, an industrial waste incinerator, etc. It is related with the collection | recovery method of the heavy metal suitable for the process of the heavy metal containing fly ash which generate | occur | produces from.
[0002]
[Prior art]
Garbage discharged from general offices and households (referred to as “urban waste” or “general waste”) is collected and incinerated at municipal waste incineration facilities and industrial waste incineration plants. At that time, incineration ash and fly ash are generated from the incinerator, but the incineration ash is deposited at the final disposal site, and the fly ash is subjected to chemical treatment or intermediate treatment such as melting furnace and cement kiln treatment.
[0003]
However, in the intermediate treatment of fly ash in the melting furnace, cement kiln, etc., heavy metals such as lead, zinc and cadmium with high vapor pressure volatilize in the furnace and enter the exhaust gas. It condensed in the processing equipment and became fly ash again. That is, in this second fly ash, useful heavy metals such as lead, copper, zinc and cadmium are contained as described above, and a method for recovering useful heavy metals from these fly ash has been demanded. .
[0004]
JP-A-7-109533 discloses such fly ash by suspending fly ash in water in a tank and adjusting the pH of the suspension to an appropriate value in the alkali range by adding acid or alkali. It discloses a method for precipitating heavy metal in fly ash as a hydroxide and collecting the residue. Further, the present applicant has also filed a method for coping with the wet processing method (JP-A-8-117724 and JP-A-8-141539). Useful heavy metals such as copper contained in can be separated in a stable form and can be effectively recovered as heavy metal resources.
[0005]
That is, JP-A-8-117724 discloses a first step in which fly ash is slurried with water, pH adjusted and leached, and solid-liquid separation, and the residue from the first step is repulped, and mineral acid The second step of leaching and dissolving after solid-liquid separation to obtain a lead product, and adding the neutralizing agent or further hydrous soda to the acidic filtrate from the first step and the second step to contain zinc and copper A method comprising a third step of separating a product and using filtered water as a drainage liquid is disclosed, and JP-A-8-141539 discloses neutralizing fly ash with water and a neutralizing agent. A first step of solid-liquid separation, a second step of repulping the residue from the first step, leaching and dissolving with sulfuric acid, and then solid-liquid separation to obtain a lead product, and a filtrate from the second step A third step of adding a neutralizer to the product to filter out the product containing zinc and copper, and the filtered water of the third step of the first step Repeat as the sum solution, a method of draining process by adding a sulfurizing agent are disclosed for filtrate from the first step.
[0006]
[Problems to be solved by the invention]
However, fly ash often contains a considerable amount of flux components such as SiO 2 , CaO, Al, and Fe in addition to heavy metals, and all of these are put into the recovery process in the wet processing method. The recovery cost was a heavy burden. That is, the initial equipment cost has been increased, and the running costs for chemicals, power, etc. have been increased. In addition, since the flux component partially enters the recovered heavy metal-containing porcelain, the raw material used for the smelting process has a low heavy metal quality, and there is a demand for a method for further improving the heavy metal quality. It was.
[0007]
In view of such a situation, the object of the present invention is to treat the heavy ash containing a large amount of flux components such as SiO 2 , CaO, Al, Fe, etc. More specifically, the useful heavy metals are separated from the flux components directly in the early stage of the fly ash treatment, and more specifically, Concentrate useful heavy metals to reduce the amount of processing required in the recovery process, improve the quality of heavy metals in the resulting heavy metal recovery deposits, and further recycle flux components in incinerators, melting furnaces, cement kilns, etc. There is to use.
[0008]
[Means for Solving the Problems]
As a result of earnest research to achieve the above-mentioned purpose, a lot of useful heavy metals in fly ash are present in fine particles, and conversely, flux components such as SiO 2 , CaO, Al, and Fe are contained in coarse particles. Has been found to provide the present invention.
That is, the first aspect of the present invention is a method for recovering the heavy metal component from fly ash containing at least one heavy metal component of zinc, copper, and lead. Secondly, a method for recovering heavy metal from fly ash, which is characterized by recovering heavy metal-containing residue by solid-liquid separation with slurry having a pH of 7 or higher. Second, at least one heavy metal of zinc, copper, and lead In the method of recovering the heavy metal component from the fly ash containing the component and chlorine, mineral acid is added to the fine particle part obtained by classifying the fly ash to make a slurry, and the pH is adjusted to 5 or less to dissolve the chlorine. A chlorine dissolving step to be performed, and an alkali agent is added to the slurry of the chlorine dissolving step to adjust the pH to 8 to 12, and then the heavy metal containing residue is separated and recovered from the chlorine containing filtrate by solid-liquid separation. Containment times Thirdly, the method for recovering heavy metals from fly ash characterized by comprising the steps of: adding a mineral acid to the heavy metal-containing porcelain to form a slurry having a pH of 5 or less; A lead product recovery step for solid-liquid separation, and a copper / zinc product recovery step for solid-liquid separation of the filtrate obtained in the lead product recovery step to a pH of 8 or higher and a copper / zinc concentrate and filtrate. The method for recovering heavy metal from fly ash according to 1 or 2 above, characterized in that it has fourth, and said heavy metal component from fly ash containing at least one kind of heavy metal component of zinc, copper and lead. In the recovery method, the fine-grained portion obtained by classifying the fly ash is made into a slurry having a pH of 7 or more, and then a sulfide is added and the heavy metal-containing residue is recovered by solid-liquid separation. The fifth method for recovering heavy metals from fly ash The method for recovering heavy metals from fly ash according to any one of claims 1 to 4, wherein the means for classifying fly ash is either a dry cyclone or a wet cyclone, The method for recovering heavy metals from fly ash according to any one of claims 1 to 5, characterized in that the classification point in the classification operation is 5 to 20 μm. Seventh, the classified coarse particles are made into an incinerator. A method for recovering heavy metal from fly ash according to any one of the first to sixth aspects, wherein the method is charged into either a melting furnace or a cement kiln.
[0009]
DETAILED DESCRIPTION OF THE INVENTION
As described above, fly ash generated from a heating furnace such as an incinerator, melting furnace, or cement kiln contains a large amount of flux-containing components such as SiO 2 , CaO, Al, and Fe. These flux components are collected as mechanical dust when heated in the furnace and are coarse. On the other hand, heavy metals contained in fly ash are those that have been vaporized and cooled as fume or gas in the form of simple metals or compounds such as chlorides in a heating furnace, and have fine particles. Many.
[0010]
Hereinafter, a method for recovering heavy metals from fly ash according to the present invention will be described with reference to the drawings.
As shown in the process diagram of FIG. 1, first, fly ash is classified to be classified into a coarse part on the sieve and a fine part on the sieve.
As a result, mechanical dust mainly composed of a flux component gathers in the coarse grain part, and heavy metals gather in the fine grain part to concentrate heavy metal, thereby obtaining a heavy metal of high quality. Therefore, by introducing only the fine particles under the sieve into the heavy metal recovery step, it is possible to realize efficient heavy metal recovery at low cost. On the other hand, the coarse particle part on a sieve can be returned to the original heating furnace as a flux.
[0011]
In classification, the range of classification points is 5 to 20 μm, preferably 5 to 10 μm. The standard classification point varies slightly depending on the type of fly ash, but for most fly ash, the recovery yield of heavy metals decreases if the fine grain part under the sieve is less than 5 μm, and conversely, if it exceeds 10 μm, mechanical dust is mixed. And the separation from the flux component becomes insufficient. In particular, when it exceeds 20 μm, the meaning of classification is reduced.
[0012]
As the classification means, either a dry method or a wet method can be used, but the dry method is desirable in consideration of returning the flux component of the coarse grain portion to the original heating furnace. Further, the classifier is not particularly limited, but the fly ash has a fine particle size as a whole, and a cyclone is preferable in consideration of a classification point of 5 to 20 μm.
[0013]
The coarse part on the sieve after classification at the classification point (underflow part in the cyclone) occupies 60% or more of the total weight of the fly ash, and can be returned to the original heating furnace as it is. It is possible to prevent loss. On the other hand, the fine-grained part under the sieve (the overflow part in the cyclone) is 10 to 40% of the total weight of the fly ash and is enriched with useful heavy metals such as copper and zinc.
[0014]
First, the classified fine granule is mixed with water to form a slurry. Next, while stirring this slurry, an alkaline agent such as sodium hydroxide is added to adjust the pH to 7 or more, preferably 9 to 12, thereby precipitating the dissolved metal as a hydroxide state, Separate and collect heavy metal objects. At this time, if sulfide is not a problem in the subsequent process, for example, wastewater treatment, as shown in parentheses in the process diagram of FIG. Incorporation of a method for recovering heavy metals that have not yet been produced as sulfides enables efficient recovery of heavy metal-containing materials.
[0015]
Moreover, when disposing of the chlorine contained in the heavy metal-containing residue, as shown in the fly ash treatment process diagram of FIG. 2, the classified fine-grained portion is mixed with water to be slurried. Next, a mineral acid such as sulfuric acid is added while stirring the slurry, the pH is adjusted to 5 or less, preferably around 3, and chlorine contained in the salt state is dissolved in the solution as much as possible. Subsequently, an alkali agent such as sodium hydroxide is added and a neutralization operation for rapidly increasing the pH to 8 to 12 is performed to separate and recover the heavy metal-containing residue from the salt-containing filtrate. As described above, after the fly ash slurry is sufficiently eluted in the acidic region, the chlorine content of the heavy metal-containing residue can be significantly reduced by performing the neutralization operation. This heavy metal-containing residue having a low chlorine content can be used as a raw material for the smelting process as it is.
[0016]
By separating the obtained heavy metal-containing porcelain into lead products and copper / zinc products, the processing burden in the smelting process can be further reduced. In this case, as shown in FIG. 3, water is added to the recovered heavy metal-containing porcelain and repulped, and a mineral acid such as sulfuric acid is added to separate the solid and liquid to a pH of 5 or less, preferably 3 or less. A filtrate in which the product and copper, zinc, etc. are dissolved is obtained. A copper / zinc product mainly composed of copper or zinc is obtained by adding an alkaline agent such as sodium hydroxide to the filtrate and solid-liquid separation with a pH of 8 or higher. Further, the heavy metal product obtained by this fractionation treatment is further reduced in chlorine. The filtrate can be used as water for slurrying the fine-grained portion under the sieve.
[0017]
【Example】
[Example 1]
The fly ash treatment was performed according to the process diagram of FIG. That is, 200 g of fly ash generated from an incinerator having the components shown in Table 1 was subjected to a wet cyclone with 2000 ml of water and classified using 10 μm as a classification point.
The coarse part of the underflow (+10 μm) part was filtered and dehydrated, and the weight was measured. As a result, the weight distribution was 150 g of 75%. An analysis sample was collected and used for component analysis.
On the other hand, the fine particle part of the overflow (−10 μm) part was filtered and dehydrated and weighed. As a result, the weight distribution was 15%, 30 g. An analysis sample was collected and used for component analysis. After collecting the analysis sample, this fine-grained portion was returned to the original filtrate and repulped, and the pH was adjusted to 10.5 with a sodium hydroxide solution, followed by filtration. The obtained heavy metal-containing article was dried and weighed 25 g. An analytical sample was collected and subjected to component analysis.
The obtained results are shown in Table 1.
Useful heavy metals consisting of copper, zinc, and lead were recovered after being concentrated to a heavy metal-containing porcelain with a weight distribution of 12.5%. In addition, when the coarse-grained components were compared with the components of fly ash before classification, the quality of heavy metals was low, and flux components such as CaO were mainly used and could be used as flux in the incinerator.
[0018]
[Table 1]
[Example 2]
The fly ash treatment was performed according to the process diagram of FIG. That is, 600 g of fly ash generated from the melting furnace shown in Table 2 was classified using a dry cyclone with a classification point of 5 μm.
The +5 μm coarse part corresponding to the sieve top after filtration and drying was 420 g with a weight distribution of 70%, and the fine grain part of −5 μm corresponding to the bottom part was 30% 180 g.
Slurry 100g of the fine-grained portion under the sieve with 1000ml of water and add sulfuric acid to adjust the pH to 3 (chlorine dissolving step). Next, the pH was adjusted to 10.5 with a sodium hydroxide solution, followed by filtration (heavy metal-containing residue collecting step). A part of the obtained heavy metal-containing residue was dried and subjected to component analysis.
The obtained results are shown in Table 2.
The resulting heavy metal-containing porcelain contains copper, lead, and zinc in a concentrated manner, has a low chlorine content, can be used as a raw material for smelting, and the coarse particles have low quality of heavy metals, such as CaO flux. It was a lot and could be used again for the incinerator.
[0020]
[Table 2]
[Example 3]
The heavy metal containing residue was processed according to the process diagram of FIG. That is, 1000 ml of water was added to the wet heavy metal-containing porridge obtained in Example 2 and repulped, and then the sulfuric acid was added to adjust the pH to 2, followed by filtration to obtain a lead product (lead product recovery step) ). The obtained lead product was dried and subjected to component analysis. Further, a sodium hydroxide solution was added to the filtered solution to adjust the pH to 9.5, followed by filtration (copper / zinc product recovery step). The obtained copper / zinc product was dried and subjected to component analysis.
The obtained component analysis results are shown in Table 3 together with the components of the raw material containing heavy metal.
From heavy metal-containing condensate enriched with useful heavy metals via classification treatment and pH adjustment treatment, lead products enriched in lead and copper / zinc are enriched in lead that can be advantageously used in smelting processes. The collected copper and zinc products could be collected separately.
[0022]
[Table 3]
[Comparative Example 1]
The incinerated fly ash of the same lot as the fly ash used in Example 1 was repulped by adding 2000 ml of water to 200 g thereof without performing a classification operation, and the pH was adjusted to 10.5 with a sodium hydroxide solution. The resulting heavy metal-containing material was dried and subjected to component analysis.
The obtained results are shown in Table 4 together with the components of the raw material fly ash.
From these results, the heavy metal-containing residue was concentrated by the amount reduced in weight except for chlorine, and there was substantially no change in useful heavy metals and flux components.
[0024]
[Table 4]
[Comparative Example 2]
About 600g of molten fly ash of the same lot as the fly ash used in Example 2, except that the classification operation was not performed, slurrying was performed by the same processing operation as in Example 2, pH adjustment, filtration, and heavy metal content I got a temple. Furthermore, this heavy metal-containing residue was subjected to the same treatment operation as in Example 3 to separate and collect lead products and copper / zinc products.
Table 5 shows the weight of the obtained product and the results of component analysis together with the components of the raw material molten fly ash.
Although fractional recovery of lead products and copper / zinc products from heavy metal-containing porcelain was carried out, the flux components from fly ash could hardly be removed.
[0026]
[Table 5]
【The invention's effect】
In the treatment of fly ash containing heavy metals such as zinc, first, fly ash is classified to obtain a fine-grained portion in a state where heavy metals are concentrated, and the heavy metal is recovered. This eliminates the need for unnecessary processing and reduces the collection cost.
Moreover, the effect of reducing the processing burden in the heavy metal smelting process can be obtained by separating the chlorine by a pH adjustment operation and then precipitating the heavy metal content in the fine-grained portion where the heavy metal is concentrated. It is done.
About the obtained heavy metal containing porcelain, the effect that the processing burden in the refining process of heavy metal is further reduced is acquired by carrying out separation processing to a lead product and a copper and zinc product by pH adjustment operation.
In collecting the heavy metal-containing material, after the precipitation of the hydroxide heavy metal, an additional effect is obtained that the remaining dissolved heavy metal can be efficiently recovered as a sulfided metal state by adding a sulfurizing agent.
By using a cyclone as the fly ash classification means, it is possible to obtain an effect that the fly ash classification process with fine particle size can be performed efficiently.
By setting the classification point range of the fine-grained portion to 5 to 20 μm, the effect that the heavy metal can be recovered well can be obtained.
Furthermore, by returning the coarse-grained portion by classification to a heating furnace such as an incinerator, the flux can be reused, and the overall heavy metal recovery cost can be reduced.
[Brief description of the drawings]
FIG. 1 is a process diagram of a method for recovering a heavy metal-containing residue from fly ash according to the present invention.
FIG. 2 is a process diagram of a method for recovering heavy metal-containing residue from fly ash according to the present invention including a chlorine dissolution process.
FIG. 3 is a process diagram of a method for separating and recovering heavy metals from heavy metal-containing articles obtained by the recovery method of FIG. 1 or FIG.
Claims (5)
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| JP27279499A JP4277108B2 (en) | 1999-09-27 | 1999-09-27 | Heavy metal recovery from fly ash |
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| JP27279499A JP4277108B2 (en) | 1999-09-27 | 1999-09-27 | Heavy metal recovery from fly ash |
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| JP4431767B2 (en) * | 2003-10-27 | 2010-03-17 | Ｄｏｗａメタルマイン株式会社 | Wet ash processing method |
| JP4505840B2 (en) * | 2005-01-17 | 2010-07-21 | 日鉱金属株式会社 | Method for recovering valuable materials from molten fly ash |
| JP5251109B2 (en) * | 2007-12-18 | 2013-07-31 | 宇部興産株式会社 | Method and system for treating dust extracted from exhaust gas from cement kiln |
| JP5279311B2 (en) * | 2008-03-27 | 2013-09-04 | 太平洋セメント株式会社 | Method for treating fine powder containing calcium component and lead component |
| EP2455500A1 (en) * | 2010-11-22 | 2012-05-23 | Costech International S.p.A. | Process of treating end-of-life cathode ray tubes for lead and soluble silicates recovery |
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