JP3796646B2

JP3796646B2 - Treatment method for petroleum combustion ash

Info

Publication number: JP3796646B2
Application number: JP37327499A
Authority: JP
Inventors: 賢二野崎; 弘隆磯村; 啓一三浦
Original assignee: Taiheiyo Cement Corp
Current assignee: Taiheiyo Cement Corp
Priority date: 1999-12-28
Filing date: 1999-12-28
Publication date: 2006-07-12
Anticipated expiration: 2019-12-28
Also published as: JP2001192747A

Description

【０００１】
【発明の属する技術分野】
本発明は、石油系燃焼灰からバナジウムやニッケルなどの有価金属を分離回収する方法において、燃焼灰のスラリー濾液からニッケルを効率良く抽出する処理方法に関し、共存するマグネシウム等を殆ど抽出せずにニッケルを選択的に抽出できる処理方法に関する。
【０００２】
【従来の技術】
火力発電所や各種工業プラントのボイラー等は重油や石油コークス等の重質油系燃料を用いるものが多く、現在、多量の燃焼灰が排出されている。これらの大部分は埋め立て処分されているが、この燃焼灰にはバナジウム等の有価金属が含有されており、環境汚染の防止および再資源化の観点から、その有効利用が求められている。
【０００３】
このような重油灰等の石油系燃焼灰から有価金属を回収する方法が従来知られており、石油系燃焼灰またはその処理物のスラリーを固液分離した後に、その固形分をアンモニア浸出し、その浸出濾液を溶媒抽出処理することによってニッケルやバナジムを回収する方法が本出願によって先に提案されている(特開平11-207293号)。この溶媒抽出方法によれば浸出濾液の液性を酸性とアルカリ性に転々と切り替える必要がなく、一貫してアルカリ性下で抽出処理できるので処理作業の負担が少なく、しかも効率よくニッケル等を回収できる利点を有している。
【０００４】
この溶媒抽出方法において、ニッケル抽出溶媒としてリン酸系溶媒(D2EHPA:2-ethylhexylphsphoric acid等)が従来から知られている。ところが、このリン酸系溶媒は、ニッケルとマグネシウムの共存系ではニッケル抽出の際にマグネシウムの大部分が随伴して抽出されると云う問題がある。すなわち、リン酸系抽出剤ではマグネシウムの抽出ｐＨ域は弱酸性から中性の範囲に及ぶ。一方、ニッケルの抽出ｐＨ域は約６以上であり、マグネシウムの抽出域の一部と重複しているため、ニッケル抽出の際にマグネシウムの大部分が随伴して抽出され、両者を分離できない。このため、リン酸系抽出剤を用い両者を分離して抽出するには、ニッケルが抽出しない低ｐＨ側で先ずマグネシウムを抽出して浸出濾液から除き、次に浸出濾液のｐＨを上げてニッケルを抽出する二段階の処理が必要になる。
【０００５】
【発明の解決課題】
本発明は、石油系燃焼灰の処理方法について、リン酸系抽出剤を用いた溶媒処理における上記問題を解決したものであり、ニッケルとマグネシウムの共存系に対してマグネシウムを殆ど随伴せずにニッケルを抽出することができる両者の分離効果に優れた抽出処理方法を提供するものである。
【０００６】
本発明は以下の構成からなる石油系燃焼灰の処理方法に関する。
（１）石油系燃焼灰またはその処理物の濾液から溶媒抽出によってニッケルを抽出する処理方法において、濾液をｐＨ７.５〜８.５に調整し、バーサチック酸を用いて該濾液を洗浄し、該濾液に含まれるニッケルをバーサチック酸に抽出した後に、このバーサチック酸を希硫酸で洗浄してニッケルに随伴して抽出されたマグネシウムを希硫酸中に洗い出し、次に、さらに該バーサチック酸を濃硫酸で洗浄して該濃硫酸中にニッケルを逆抽出することを特徴とする石油系燃焼灰の処理方法。
【０００７】
本発明の上記処理方法(１)は以下の態様を含む。
（２）上記(１)の処理方法において、ニッケルを抽出したバーサチック酸の洗浄を濃度０.０１〜５g/lの希硫酸を用いてｐＨ２〜４の酸性下で行い、逆抽出を濃度１００〜３００g/lの濃硫酸を用いてｐＨ１以下での強酸性下で行う石油系燃焼灰の処理方法。
【０００８】
また、本発明は以下の構成からなる石油系燃焼灰の処理方法に関する。
（３）(イ)石油系燃焼灰またはその処理物を水性スラリーにする水浸出工程、(ロ)水性スラリーの濾液を酸性下で加熱してバナジウム化合物を析出させ、これを濾別回収するバナジウム回収工程、(ハ)上記水性スラリーの固形分にアンモニア水を加えて中性ないしアルカリ性下で酸化処理して含有金属を液中に浸出させるアンモニア浸出工程、(ニ)アンモニア浸出濾液にニッケル抽出溶媒を加えてニッケルを抽出する工程を有する処理方法において、ニッケル抽出溶媒としてバーサチック酸を用い、アンモニア浸出濾液をｐＨ７.５〜８.５に調整し、濾液に含まれるニッケルをバーサチック酸に抽出することを特徴とする石油系燃焼灰の処理方法。
【０００９】
上記処理方法(３)は以下の態様を含む。
（４）上記(３)の処理方法において、石油系燃焼灰またはその処理物に水または硫酸を加えて水性スラリーにする水浸出工程において、水性スラリーの濾液を水浸出工程に循環して濾液中のバナジウム濃度を高める一方、ニッケルを含む固形分をアンモニア浸出工程に導く石油系燃焼灰の処理方法。
【００１０】
上記処理方法(４)は以下の態様を含む。
（５）上記(３)または(４)の処理方法において、アンモニア浸出の際に、空気導入して固液分離した後に過酸化水素を添加する二段階の酸化処理を行い、過酸化水素添加後の濾液を空気酸化工程に循環して再使用し、その空気酸化後の濾液をニッケル抽出工程に導く石油系燃焼灰の処理方法。
【００１１】
【発明の実施の態様】
以下、本発明を実施態様に基づいて詳細に説明する。
本発明の処理方法の概略を図１に示す。図示するように、本発明は石油系燃焼灰からバナジウムやニッケルなどを回収し、さらにはその残渣をセメント原料として利用することができる処理方法に関する。本発明の処理対象である石油系燃焼灰とは、タール質燃料、アスファルト、およびこれらをエマルジョン化したもの、重油、石油コークス、石油ピッチ等の石油系燃料を燃焼した際に生じる塵灰である。具体的は、発電所や各種工業プラントのボイラー等から排出される集塵灰等である。なお、通常、燃焼灰には未燃カーボンが含まれているがこれは除去して処理するのが好ましい。未燃カーボンは燃焼灰のスラリーを攪拌して静置すると液面に浮遊し、これを掻き取りあるいは流し出すことにより容易に除去することができる。
【００１２】
図示する本発明の処理方法は、石油系燃焼灰またはその処理物を水浸出する工程(Ａ)、水浸出スラリーの濾液からバナジウムを回収する工程(Ｂ)、水浸出の固形分にアンモニア水を加えて中性ないしアルカリ性下で酸化処理しつつ含有金属を液中に浸出させるアンモニア浸出工程(Ｃ)、アンモニア浸出濾液にニッケル抽出溶媒を加えてニッケルを抽出する溶媒抽出工程(Ｄ)を有している。以下、各工程について説明する。
【００１３】
( Ａ ) 水浸出工程
石油系燃焼灰に水や硫酸を加えて水性スラリーにし、液中にバナジウム等を浸出させる。この水性スラリーを固液分離し、その濾液をバナジウム回収工程に送る。この水浸出工程において、水性スラリーを濾過して固形分をアンモニア浸出工程に送る一方、濾液を水浸出工程に循環して再使用することにより濾液中のバナジウム濃度を高めると良い。濾液中のバナジウム濃度を高めることによってその回収率が向上する。
【００１４】
濾液を水浸出工程に循環する基準は、水性スラリーから固液分離された濾液中のニッケル濃度が１００ppm以下およびマグネシウム濃度が３０００ppm以下となる範囲内である。マグネシウム濃度がこれより高くなると硫酸マグネシウムアンモニウム等の影響によりマグネシウムが析出するので好ましくない。また、この濾液はバナジウム回収工程に送られるので、ニッケル濃度が上記範囲を超えると溶媒抽出工程で回収されるニッケル量が減少する。
【００１５】
( Ｂ ) バナジウム回収工程
水浸出工程の上記濾液にアンモニアを加えてｐＨ２〜４に調整し、好ましくは８０〜９０℃に加熱することにより酸化バナジウムを析出させる。なお、この酸化バナジウムを回収して炭酸ナトリウムや塩素酸ナトリウムを加え、液性を弱酸性に調整して酸化バナジウムを溶解し、液中の未溶解物を濾別した後に、この濾液にアンモニアないしアンモニア塩を加え、この濾液を７５〜８５℃程度に加熱してバナジン酸アンモニウムを再び沈殿させることにより、不純物の少ないバナジウム化合物を回収することができる。
【００１６】
( Ｃ ) アンモニア浸出工程
上記水浸出工程で固液分離した固形分にアンモニアと水を加えて中性ないしアルカリ性下で酸化処理することにより固形分に残留する金属分を液中に浸出させる。この固形分にはニッケルが含まれ、また水浸出で分離できなかったバナジウムが含まれている。なお、石油系燃焼灰には多量の硫黄分が含まれているので、これを水性スラリーにすると硫黄分が溶出して酸性の溶液となるが、これにアンモニアを加えてスラリーをｐＨ７〜９の弱アルカリ性(中性〜アルカリ性)に調整する。アンモニアの添加は常温下で良く、加熱する必要はない。
【００１７】
なお、このアンモニア浸出において二段階の酸化処理を行うことによりニッケルおよびバナジウムの浸出率を高めることができる。この酸化処理は、アンモニアを添加して中性〜アルカリ性に調整したスラリーに、空気を導入して攪拌し、スラリーに含まれるニッケルやバナジウム等を酸化する。この一段目の空気酸化の後にスラリーを固液分離し、その固形分に必要に応じてアンモニアを再度添加して液性を中性〜アルカリ性に調整し、これに過酸化水素を添加して二段目の酸化処理を行う。過酸化水素を添加したときには必要に応じてスラリーを攪拌すると良い。
【００１８】
上記酸化処理において、好ましくは、アンモニア浸出スラリーの液性をｐＨ７〜９に調整して空気酸化と過酸化水素による酸化を行い、スラリーの酸化還元電位が１００〜１５０mVになる範囲で空気酸化で終了し、次いで過酸化水素を添加して酸化処理を行い、スラリーの酸化還元電位が１５０mV以上になるようにその添加量を調整する。空気酸化のみでは液の酸化還元電位が短時間で１５０mV以上になるのは難しいので、この範囲まで空気酸化を行い、その次に、スラリーの酸化還元電位が１５０mV以上になるまで過酸化水素を加えて酸化する。
【００１９】
二段階の酸化処理を行うことにより、スラリーに含まれる酸化し易い状態の金属分が最初の空気酸化によって液中に浸出する。この空気酸化では浸出せずに固形分に残留している金属分を次の過酸化水素の酸化処理によって液中に浸出させる。なお、最初に空気酸化を行うので過酸化水素による酸化処理の負担が軽減される。二段目の過酸化水素による酸化処理の後に固液分離を行い、その濾液の全量を一段目の空気酸化に循環する。この濾液の全量を空気酸化に返送することにより、アンモニア浸出工程全体の液量を増加せずに浸出効果を高めることができる。一方、過酸化水素による酸化処理後の固形分にはシリカ、アルミナや事前に除去されなかった未燃カーボンなどが含まれており、これをセメント原料として利用することができる。
【００２０】
酸化処理を伴うアンモニア浸出によって、水浸出では溶出しなかった焼却灰中のニッケルおよびバナジウムが溶出し、その浸出効果が格段に向上する。具体的には、酸化処理を行わないアンモニア浸出の場合にはバナジウムの浸出率は３０〜４０％であるが、酸化処理を併用したアンモニア浸出ではバナジウムの浸出率は９０％以上に大幅に向上する。これはバナジウムの価数が多くなり中性からアルカリ性下でイオン化し易い形態に転換するためと思われる。またニッケルの浸出率は、スラリーが酸性(ｐＨ３〜５程度)のときには２０〜３０％台であるが、中性〜アルカリ性(ｐＨ７〜９)では約７０〜１００％に達し、格段に浸出率が向上する。なお、以上の酸化処理を併用したアンモニア浸出は加熱下で行う必要はなく、常温下で良い。
【００２１】
(Ｄ)溶媒抽出工程
(D-1) ニッケル抽出
ニッケル抽出剤としてバーサチック酸を用い、アンモニア浸出濾液に含まれるニッケルをこの浸出濾液から抽出分離する。すなわち、上記アンモニア浸出濾液にバーサチック酸を混合して濾液中のニッケルイオンをバーサチック酸に抽出する。このニッケル抽出は、アンモニア浸出濾液のｐＨを弱アルカリ性、好ましくはｐＨ７.５〜８.５に調整して行うのが好ましい。バーサチック酸に抽出されたニッケルおよびマグネシウム等の濃度を浸出濾液ｐＨに対応して図２に示す。このグラフに示すように、ｐＨ７.５以上の範囲でニッケルの濃度は高くなる。一方、マグネシウムの濃度はｐＨ８.５付近では未だ低い。従ってｐＨ７.５〜８.５の範囲において、マグネシウムを殆ど抽出せずにニッケルを選択的に抽出することができる。
【００２２】
バーサチック酸の濃度は５％以上が適当であり、１０％以上が好ましい。バーサチック酸の濃度に対するニッケル抽出率の一例を図３のグラフに示す。図示するように、濾液のｐＨ９、混合時間３分のとき、バーサチック酸の濃度１０％、１５％、２０％におけるニッケルの抽出率は約８０％、約９０％、約９７％であり、高い抽出率が得られる。なお、従来のリン酸系抽出剤は濃度１０％のとき、ニッケルの抽出率は４０〜５０％程度であり、本発明のバーサチック酸に比べて大幅に低い。
【００２３】
(D-2) 抽出剤の洗浄
バーサチック酸をアンモニア浸出濾液から分離した後に、このバーサチック酸に希硫酸を混合して洗浄する。ニッケルに随伴して抽出されたマグネシウム(イオン)はこの洗浄によって希硫酸中に洗い出され、バーサチック酸から除去される。この洗浄はｐＨ２〜４の酸性下で行い、濃度０.０１〜５g/lの希硫酸を用いるのが良い。希硫酸の濃度に対するニッケルおよびマグネシウムの濃度(希硫酸に逆抽出される濃度)を図４に示す。このグラフに示すように、希硫酸の濃度が１g/l以下ではニッケルは殆ど洗浄されず、２g/l以上になるとニッケルの濃度が次第に高くなる。一方、マグネシウムの濃度は希硫酸の濃度が０.１g/lでも比較的高く、３g/l以上ではほぼ飽和する。従って、濃度０.０１〜５g/l、好ましくは０.１〜２g/lの希硫酸を用いることにより、ニッケルをバーサチック酸に残してマグネシウムを選択的に希硫酸中に洗い出すことができる。このマグネシウムは石膏の回収工程に導き、水酸化物として回収することができる。
【００２４】
(D-3) 逆抽出
希硫酸で洗浄したバーサチック酸に濃硫酸を混合し、この濃硫酸にバーサチック酸中のニッケル(イオン)を逆抽出する。この逆抽出はｐＨ１以下の酸性下で行い、濃度１００〜３００g/lの濃硫酸を用いるのが良い。混合後、濃硫酸とバーサチック酸を分離する。このバーサチック酸はニッケル抽出工程に循環して再度使用することができる。一方、分離した濃硫酸には逆抽出したニッケルが硫酸ニッケルの状態で含まれている。この濃硫酸液を４０〜８０℃程度に加熱して水分を蒸発させ、濃縮して硫酸ニッケルを回収することができる。または、この濃硫酸液を硫酸ニッケルの溶解度以下に冷却して析出させても良い。この硫酸ニッケルを濾過して回収し、乾燥すれば硫酸ニッケルの粉末を得ることができる。この濾液(濃硫酸)は逆抽出工程に循環して再利用することができる。
【００２５】
【実施例】
以下、本発明を実施例によって具体的に示す。
実施例１
重油質燃料の燃焼灰(V₂O₅:4.0wt％、Ni:0.4wt％、MgO:4.2wt％、NH₃:21.3wt％、SO₃:53.9wt％)を固体濃度２０％の水性スラリーとし、固液分離した固形分８kgにアンモニア水を加えてｐＨ８にし、これに空気(２０リットル/min)を導入して２時間攪拌した後に固液分離し、この固形分にアンモニア水を加え、さらに過酸化水素水(濃度31vol％)を３０ml加えて攪拌混合した後に濾過し、濾液の全量(14.6リットル)を空気酸化工程に循環して再度利用した。一方、上記空気酸化後の濾液２４００mlを抜き出し、このアンモニア浸出濾液のｐＨを８に調整した後に、８０mlずつにバーサチック酸(濃度30vol％)８０mlを加える。３分間混合後、バーサチック酸を浸出濾液から分離して希硫酸(濃度2g/l)８０mlを加えて３分間混合した後に希硫酸を分離した。次に、このバーサチック酸に濃硫酸(濃度200g/l)８０mlを加えて３分間混合した後に、濃硫酸を分離した。この濃硫酸をさらに新しい抽出液(上記成分)を用いて３０回抽出を繰り返して濃縮した。この硫酸液を蒸発して硫酸ニッケル２５.３４gを回収した。この硫酸ニッケル中のマグネシウム量は検出限界量以下であった。
【００２６】
実施例２
バーサチック酸濃度を３０vol％、希硫酸の濃度を５g/l、濃硫酸の濃度を２００g/lとした以外は実施例１と同様にして硫酸ニッケル２５.１２ｇを回収した。この硫酸ニッケル中のマグネシウム量は検出限界量以下であった。
【００２７】
実施例３
燃焼灰として、Ｎｉ量０.７７％、Ｍｇ量０.０８％および未燃カーボン６３％を含有する灰を用い、バーサチック酸濃度を３０vo/％、希硫酸の濃度を０.５g/l、濃硫酸の濃度を２００g/lとした以外は実施例１と同様にして硫酸ニッケル１０１.９ｇを回収した。なお、浸出条件は、灰１kgに対してアンモニア水１０リットルを加え、これを濾過した後に新しい灰を再度加えて浸出し、これを３回繰り返した。この硫酸ニッケル中のマグネシウム量は検出限界量以下であった。
【００２８】
比較例１
バーサチック酸に代えてリン酸系ニッケル抽出剤(濃度３０vol％)８０mlを用いた以外は実施例１と同様にしてニッケルを回収し、２５.８ｇの硫酸ニッケルを得た。この硫酸ニッケル中のマグネシウム含有量は０３８％であった。
【００２９】
【発明の効果】
本発明の処理方法によれば、石油系燃焼灰からバナジウムやニッケルを回収する際に、ニッケルとマグネシウムが共存する溶液から、ニッケルを容易にかつ効率よくマグネシウムから分離して抽出することができる。
従来のリン酸系抽出剤はマグネシウムの抽出ｐＨ域がニッケルよりも低ｐＨ域であるためニッケルを抽出するとマグネシウムも抽出されるが、本発明で用いるバーサチック酸の抽出ｐＨ域はリン酸系抽出液とは逆であり、そのニッケル抽出ｐＨ域はマグネシウムよりも低ｐＨ域であるので、ニッケル抽出の際にマグネシウムは殆ど抽出されず、従って、一段階の抽出処理でニッケルをマグネシウムから分離して抽出することができる。
【図面の簡単な説明】
【図１】本発明の処理方法の概略を示す工程図
【図２】浸出濾液のｐＨに対する抽出液中のニッケル濃度等のグラフ
【図３】抽出液の濃度に対するニッケル抽出率のグラフ
【図４】洗浄用の希硫酸濃度に対する希硫酸中のニッケルとマグネシウムの濃度を示すグラフ[0001]
BACKGROUND OF THE INVENTION
TECHNICAL FIELD The present invention relates to a method for efficiently extracting nickel from a slurry filtrate of combustion ash in a method for separating and recovering valuable metals such as vanadium and nickel from petroleum-based combustion ash. It is related with the processing method which can extract selectively.
[0002]
[Prior art]
Many boilers of thermal power plants and various industrial plants use heavy oil-based fuels such as heavy oil and petroleum coke, and a large amount of combustion ash is currently discharged. Most of these are disposed of in landfills, but this combustion ash contains valuable metals such as vanadium, and their effective use is required from the viewpoint of prevention of environmental pollution and recycling.
[0003]
A method for recovering valuable metals from petroleum-based combustion ash such as heavy oil ash has been conventionally known, and after solid-liquid separation of the slurry of petroleum-based combustion ash or its treated product, the solid content is leached with ammonia, A method for recovering nickel or vanadium by subjecting the leached filtrate to solvent extraction has been proposed previously (Japanese Patent Laid-Open No. 11-207293). According to this solvent extraction method, there is no need to switch the liquidity of the leaching filtrate between acidic and alkaline, and the extraction process can be consistently performed under alkaline conditions, so the burden of processing work is small and nickel can be recovered efficiently. have.
[0004]
In this solvent extraction method, a phosphoric acid solvent (D2EHPA: 2-ethylhexylphsphoric acid, etc.) is conventionally known as a nickel extraction solvent. However, the phosphoric acid solvent has a problem that in the coexistence system of nickel and magnesium, most of the magnesium is extracted along with nickel extraction. That is, in the case of a phosphoric acid-based extractant, the extraction pH range of magnesium ranges from weakly acidic to neutral. On the other hand, the extraction pH range of nickel is about 6 or more and overlaps with a part of the extraction range of magnesium. Therefore, most of the magnesium is extracted along with nickel extraction, and the two cannot be separated. For this reason, in order to separate and extract both using a phosphoric acid-based extractant, magnesium is first extracted and removed from the leaching filtrate on the low pH side where nickel is not extracted, and then the pH of the leaching filtrate is increased to remove nickel. Two steps of extraction are required.
[0005]
[Problem to be Solved by the Invention]
The present invention solves the above-mentioned problems in the solvent treatment using a phosphoric acid-based extractant for a method for treating petroleum-based combustion ash. Nickel is hardly associated with the coexistence system of nickel and magnesium. It is an object of the present invention to provide an extraction processing method that is capable of extracting odor and is excellent in the separation effect between the two.
[0006]
The present invention relates to a method for treating petroleum combustion ash having the following configuration.
(1) In a processing method for extracting nickel from a filtrate of petroleum-based combustion ash or its treated product by solvent extraction, the filtrate is adjusted to pH 7.5 to 8.5, the filtrate is washed with versatic acid, After extracting nickel contained in the filtrate to versatic acid, this versatic acid is washed with dilute sulfuric acid, and magnesium extracted accompanying nickel is washed into dilute sulfuric acid. Then, the versatic acid is further washed with concentrated sulfuric acid. A method for treating petroleum combustion ash, comprising washing and back-extracting nickel into the concentrated sulfuric acid.
[0007]
The processing method (1) of the present invention includes the following aspects.
(2) In the treatment method of (1) above, washing of versatic acid from which nickel has been extracted is carried out under acidic conditions of pH 2 to 4 using dilute sulfuric acid having a concentration of 0.01 to 5 g / l, and back extraction is performed at a concentration of 100 to A method for treating petroleum combustion ash, which is performed under strong acidity at a pH of 1 or less using 300 g / l of concentrated sulfuric acid.
[0008]
Moreover, this invention relates to the processing method of the petroleum-type combustion ash which consists of the following structures.
(3) (b) Water leaching step for converting petroleum combustion ash or its treated product into aqueous slurry, (b) Vanadium compound is precipitated by heating the filtrate of aqueous slurry under acidic condition, and collecting this by filtration A recovery step, (c) an ammonia leaching step in which ammonia water is added to the solid content of the aqueous slurry and oxidized in a neutral or alkaline condition to leach the contained metal into the liquid, and (d) a nickel extraction solvent in the ammonia leaching filtrate. In the treatment method having the step of extracting nickel by adding Versatic acid as the nickel extraction solvent, adjusting the ammonia leaching filtrate to pH 7.5-8.5, and extracting the nickel contained in the filtrate to Versatic acid A method for treating petroleum combustion ash characterized by the following.
[0009]
The processing method (3) includes the following aspects.
(4) In the treatment method of (3) above, in the water leaching step to add water or sulfuric acid to petroleum combustion ash or its treated product to form an aqueous slurry, the filtrate of the aqueous slurry is circulated in the water leaching step. A method for treating petroleum-based combustion ash that increases the vanadium concentration of the steel and leads the solid content containing nickel to the ammonia leaching process.
[0010]
The processing method (4) includes the following aspects.
(5) In the treatment method of (3) or (4) above, when ammonia is leached, a two-stage oxidation treatment is performed in which hydrogen peroxide is added after air introduction and solid-liquid separation. A method for treating petroleum combustion ash that circulates and reuses the filtrate in the air oxidation step and leads the filtrate after the air oxidation to the nickel extraction step.
[0011]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, the present invention will be described in detail based on embodiments.
An outline of the treatment method of the present invention is shown in FIG. As shown in the figure, the present invention relates to a treatment method capable of recovering vanadium, nickel and the like from petroleum combustion ash and further utilizing the residue as a cement raw material. The petroleum-based combustion ash to be treated in the present invention is dust ash generated when burning petroleum-based fuels such as tar fuel, asphalt, and emulsions thereof, heavy oil, petroleum coke, and petroleum pitch. . Specifically, it is dust collection ash discharged from boilers of power plants and various industrial plants. Normally, unburnt carbon is contained in the combustion ash, but it is preferable to remove it and treat it. Unburned carbon floats on the liquid level when the slurry of combustion ash is stirred and left to stand, and can be easily removed by scraping or flowing it out.
[0012]
The treatment method of the present invention shown in the figure includes a step (A) of leaching petroleum combustion ash or its treated product, a step (B) of recovering vanadium from the filtrate of the water leaching slurry, and adding ammonia water to the solid content of the water leaching. In addition, it has an ammonia leaching step (C) for leaching the contained metal into the liquid while oxidizing it under neutral or alkaline conditions, and a solvent extraction step (D) for extracting nickel by adding a nickel extraction solvent to the ammonia leaching filtrate. ing. Hereinafter, each step will be described.
[0013]
( A ) Water leaching step Water or sulfuric acid is added to petroleum-based combustion ash to form an aqueous slurry, and vanadium or the like is leached into the liquid. This aqueous slurry is subjected to solid-liquid separation, and the filtrate is sent to a vanadium recovery step. In this water leaching step, the aqueous slurry is filtered and the solid content is sent to the ammonia leaching step, while the filtrate is recycled to the water leaching step and reused to increase the vanadium concentration in the filtrate. Increasing the vanadium concentration in the filtrate improves its recovery.
[0014]
The standard for circulating the filtrate to the water leaching step is within a range in which the nickel concentration in the filtrate separated from the aqueous slurry is 100 ppm or less and the magnesium concentration is 3000 ppm or less. A magnesium concentration higher than this is not preferable because magnesium precipitates due to the influence of magnesium ammonium sulfate and the like. Moreover, since this filtrate is sent to a vanadium collection | recovery process, if nickel concentration exceeds the said range, the amount of nickel collect | recovered by a solvent extraction process will reduce.
[0015]
( B ) Vanadium recovery step Ammonia is added to the filtrate in the water leaching step to adjust the pH to 2 to 4, and preferably heated to 80 to 90C to precipitate vanadium oxide. The vanadium oxide is recovered, sodium carbonate or sodium chlorate is added, the liquidity is adjusted to weak acidity to dissolve the vanadium oxide, and undissolved substances in the liquid are filtered off. By adding an ammonia salt and heating the filtrate to about 75 to 85 ° C. to precipitate ammonium vanadate again, a vanadium compound with less impurities can be recovered.
[0016]
( C ) Ammonia leaching step Ammonia and water are added to the solid content separated by solid-liquid separation in the water leaching step, and the metal content remaining in the solid content is converted into the liquid by oxidizing under neutral or alkaline conditions. Let leaching. This solid content contains nickel and vanadium that could not be separated by water leaching. Since petroleum-based combustion ash contains a large amount of sulfur, when it is made into an aqueous slurry, the sulfur is eluted and an acidic solution is added. To this, ammonia is added to make the slurry pH 7-9. Adjust to weak alkalinity (neutral to alkaline). Ammonia may be added at room temperature and does not need to be heated.
[0017]
In addition, the leaching rate of nickel and vanadium can be increased by performing a two-step oxidation process in this ammonia leaching. In this oxidation treatment, air is introduced into a slurry adjusted to be neutral to alkaline by adding ammonia and stirred to oxidize nickel, vanadium, and the like contained in the slurry. After the first stage of air oxidation, the slurry is separated into solid and liquid, and ammonia is added again to the solid content as necessary to adjust the liquidity to neutral to alkaline. Stage oxidation is performed. When hydrogen peroxide is added, the slurry may be stirred as necessary.
[0018]
In the above oxidation treatment, preferably, the ammonia leaching slurry is adjusted to pH 7-9 to perform oxidation with air and hydrogen peroxide, and the oxidation is completed within a range where the oxidation-reduction potential of the slurry becomes 100 to 150 mV. Then, hydrogen peroxide is added to perform oxidation treatment, and the amount of addition is adjusted so that the oxidation-reduction potential of the slurry is 150 mV or more. Since it is difficult for the oxidation-reduction potential of the liquid to reach 150 mV or more in a short time with only air oxidation, perform air oxidation to this range, and then add hydrogen peroxide until the oxidation-reduction potential of the slurry becomes 150 mV or more. Oxidize.
[0019]
By performing the two-stage oxidation treatment, the metal component in the slurry which is easily oxidized is leached into the liquid by the first air oxidation. In this air oxidation, the metal remaining in the solid content without leaching is leached into the liquid by the subsequent oxidation treatment of hydrogen peroxide. Since air oxidation is performed first, the burden of oxidation treatment with hydrogen peroxide is reduced. Solid-liquid separation is performed after the oxidation treatment with the second stage hydrogen peroxide, and the entire amount of the filtrate is circulated to the first stage air oxidation. By returning the entire amount of the filtrate to air oxidation, the leaching effect can be enhanced without increasing the amount of liquid in the entire ammonia leaching process. On the other hand, the solid content after the oxidation treatment with hydrogen peroxide contains silica, alumina, unburned carbon that has not been removed in advance, and can be used as a cement raw material.
[0020]
By ammonia leaching accompanied by oxidation treatment, nickel and vanadium in the incinerated ash that was not eluted by water leaching are eluted, and the leaching effect is remarkably improved. Specifically, in the case of ammonia leaching without oxidation treatment, the leaching rate of vanadium is 30 to 40%, but in the ammonia leaching combined with oxidation treatment, the leaching rate of vanadium is greatly improved to 90% or more. . This seems to be because the vanadium has a higher valence and is converted from a neutral to an alkaline form that is easily ionized. Further, the leaching rate of nickel is about 20-30% when the slurry is acidic (pH 3-5), but reaches about 70-100% when the slurry is neutral to alkaline (pH 7-9). improves. Note that ammonia leaching using the above oxidation treatment in combination does not need to be performed under heating, and may be performed at room temperature.
[0021]
(D) Solvent extraction step
(D-1) Nickel extraction Versatic acid is used as a nickel extractant, and nickel contained in the ammonia leaching filtrate is extracted and separated from the leaching filtrate. That is, versatic acid is mixed with the ammonia leached filtrate to extract nickel ions in the filtrate into versatic acid. This nickel extraction is preferably carried out by adjusting the pH of the ammonia leaching filtrate to weakly alkaline, preferably pH 7.5 to 8.5. FIG. 2 shows the concentration of nickel, magnesium, and the like extracted into versatic acid corresponding to the leaching filtrate pH. As shown in this graph, the nickel concentration increases in the range of pH 7.5 or higher. On the other hand, the concentration of magnesium is still low around pH 8.5. Therefore, in the range of pH 7.5 to 8.5, nickel can be selectively extracted without substantially extracting magnesium.
[0022]
The concentration of versatic acid is suitably 5% or more, preferably 10% or more. An example of the nickel extraction rate with respect to the concentration of versatic acid is shown in the graph of FIG. As shown in the figure, when the pH of the filtrate is 9 and the mixing time is 3 minutes, the extraction rate of nickel is about 80%, about 90%, about 97% at a concentration of 10%, 15% and 20% of versatic acid. Rate is obtained. In addition, when the concentration of the conventional phosphoric acid-based extractant is 10%, the nickel extraction rate is about 40 to 50%, which is significantly lower than the versatic acid of the present invention.
[0023]
(D-2) Washing of extractant After the versatic acid is separated from the ammonia leaching filtrate, the versatic acid is mixed with dilute sulfuric acid and washed. Magnesium (ion) extracted along with nickel is washed out in dilute sulfuric acid by this washing and removed from the versatic acid. This washing is preferably performed under acidic conditions of pH 2 to 4, and dilute sulfuric acid having a concentration of 0.01 to 5 g / l is preferably used. FIG. 4 shows the concentration of nickel and magnesium with respect to the concentration of dilute sulfuric acid (concentration back-extracted with dilute sulfuric acid). As shown in this graph, nickel is hardly washed when the concentration of dilute sulfuric acid is 1 g / l or less, and the concentration of nickel gradually increases when the concentration is 2 g / l or more. On the other hand, the concentration of magnesium is relatively high even when the concentration of dilute sulfuric acid is 0.1 g / l, and is almost saturated at 3 g / l or more. Therefore, by using dilute sulfuric acid having a concentration of 0.01 to 5 g / l, preferably 0.1 to 2 g / l, magnesium can be selectively washed out in dilute sulfuric acid while leaving nickel in versatic acid. This magnesium can be recovered in the gypsum recovery process as a hydroxide.
[0024]
(D-3) Back extraction Concentrated sulfuric acid is mixed with versatic acid washed with dilute sulfuric acid, and nickel (ion) in versatic acid is back extracted with this concentrated sulfuric acid. This back-extraction is performed under acidic conditions of pH 1 or lower, and concentrated sulfuric acid having a concentration of 100 to 300 g / l is preferably used. After mixing, concentrated sulfuric acid and versatic acid are separated. This versatic acid can be recycled and reused in the nickel extraction process. On the other hand, the separated concentrated sulfuric acid contains back-extracted nickel in the form of nickel sulfate. This concentrated sulfuric acid solution can be heated to about 40 to 80 ° C. to evaporate water, and concentrated to recover nickel sulfate. Alternatively, this concentrated sulfuric acid solution may be cooled to below the solubility of nickel sulfate and precipitated. The nickel sulfate can be collected by filtration and dried to obtain nickel sulfate powder. This filtrate (concentrated sulfuric acid) can be circulated and reused in the back extraction step.
[0025]
【Example】
Hereinafter, the present invention will be specifically described by way of examples.
Example 1
Heavy oil fuel combustion ash (V ₂ O ₅ : 4.0 wt%, Ni: 0.4 wt%, MgO: 4.2 wt%, NH ₃ : 21.3 wt%, SO ₃ : 53.9 wt%) aqueous slurry with a solid concentration of 20% Ammonia water was added to 8 kg of solid content separated into solid and liquid to adjust to pH 8, air (20 liters / min) was introduced into this and stirred for 2 hours, followed by solid-liquid separation. Ammonia water was added to this solid content, Further, 30 ml of hydrogen peroxide solution (concentration 31 vol%) was added and stirred and mixed, followed by filtration. The entire amount of the filtrate (14.6 liters) was circulated in the air oxidation step and reused. On the other hand, 2400 ml of the filtrate after air oxidation is extracted, and after adjusting the pH of the ammonia leaching filtrate to 8, 80 ml of versatic acid (concentration 30 vol%) is added to each 80 ml. After mixing for 3 minutes, versatic acid was separated from the leaching filtrate, 80 ml of dilute sulfuric acid (concentration 2 g / l) was added and mixed for 3 minutes, and then dilute sulfuric acid was separated. Next, 80 ml of concentrated sulfuric acid (concentration 200 g / l) was added to this versatic acid and mixed for 3 minutes, and then concentrated sulfuric acid was separated. The concentrated sulfuric acid was further extracted 30 times with a new extract (the above components) and concentrated. The sulfuric acid solution was evaporated to recover 25.34 g of nickel sulfate. The amount of magnesium in this nickel sulfate was below the detection limit.
[0026]
Example 2
25.12 g of nickel sulfate was recovered in the same manner as in Example 1 except that the concentration of versatic acid was 30 vol%, the concentration of dilute sulfuric acid was 5 g / l, and the concentration of concentrated sulfuric acid was 200 g / l. The amount of magnesium in this nickel sulfate was below the detection limit.
[0027]
Example 3
As combustion ash, ash containing Ni content 0.77%, Mg content 0.08% and unburned carbon 63%, Versatic acid concentration 30 vo /%, dilute sulfuric acid concentration 0.5 g / l, concentrated 101.9 g of nickel sulfate was recovered in the same manner as in Example 1 except that the concentration of sulfuric acid was changed to 200 g / l. As leaching conditions, 10 liters of aqueous ammonia was added to 1 kg of ash, and after filtering this, new ash was added again and leached, and this was repeated three times. The amount of magnesium in this nickel sulfate was below the detection limit.
[0028]
Comparative Example 1
Nickel was recovered in the same manner as in Example 1 except that 80 ml of a phosphoric acid-based nickel extractant (concentration: 30 vol%) was used instead of versatic acid to obtain 25.8 g of nickel sulfate. The magnesium content in this nickel sulfate was 038%.
[0029]
【The invention's effect】
According to the treatment method of the present invention, when vanadium or nickel is recovered from petroleum combustion ash, nickel can be easily and efficiently separated and extracted from a solution in which nickel and magnesium coexist.
The conventional phosphoric acid-based extractant has a magnesium extraction pH range lower than that of nickel. Therefore, when nickel is extracted, magnesium is also extracted. However, the extraction pH range of versatic acid used in the present invention is a phosphate-based extract. In contrast, the nickel extraction pH range is lower than that of magnesium, so magnesium is hardly extracted during nickel extraction. Therefore, nickel is extracted by separating it from magnesium in a one-step extraction process. can do.
[Brief description of the drawings]
FIG. 1 is a process diagram showing an outline of the treatment method of the present invention. FIG. 2 is a graph of nickel concentration in the extract with respect to pH of the leached filtrate. FIG. 3 is a graph of nickel extraction rate with respect to the concentration of the extract. ] Graph showing the concentration of nickel and magnesium in dilute sulfuric acid versus the concentration of dilute sulfuric acid for cleaning

Claims

In the processing method of extracting nickel by solvent extraction from the filtrate petroleum combustion ash or its processed product, the filtrate pH 7. 5 to 8. Adjusted to 5, and wash the filtrate with versatic acid, contained in the filtrate After extracting nickel into versatic acid, the versatic acid is washed with dilute sulfuric acid, magnesium extracted with nickel is washed into dilute sulfuric acid, and then the versatic acid is further washed with concentrated sulfuric acid. A method for treating petroleum combustion ash, wherein nickel is back-extracted into the concentrated sulfuric acid .

2. The treatment method according to claim 1, wherein the washing of the versatic acid from which nickel has been extracted is carried out using dilute sulfuric acid having a concentration of 0.01 to 5 g / l under acidic conditions of pH 2 to 4, and back extraction is carried out at a concentration of 100 to 300 g / l. A method for treating petroleum-based combustion ash, which is performed under strong acidity using concentrated sulfuric acid at a pH of 1 or less.

(A) A water leaching step for converting petroleum-based combustion ash or its treated product into an aqueous slurry, (b) a vanadium recovery step for heating the filtrate of the aqueous slurry under acidic conditions to precipitate a vanadium compound, and collecting this by filtration; (C) Ammonia leaching step in which ammonia water is added to the solid content of the aqueous slurry and oxidized under neutral or alkaline conditions to leach the contained metal into the liquid. (D) A nickel extraction solvent is added to the ammonia leached filtrate. in the processing method having a step of extracting nickel, and characterized by using a versatic acid as nickel extraction solvent, adjusting the ammonia leach filtrate pH 7. 5 to 8. 5, extracts the nickel contained in the filtrate versatic acid A method for treating petroleum combustion ash.

4. The treatment method according to claim 3, wherein in the water leaching step of adding petroleum or sulfuric acid to petroleum-based combustion ash or its treated product to form an aqueous slurry, the aqueous slurry filtrate is circulated to the water leaching step to reduce the vanadium concentration in the filtrate. A method for treating petroleum-based combustion ash that leads to an ammonia leaching process while increasing the solid content including nickel.

5. The treatment method according to claim 3, wherein, during ammonia leaching, two-stage oxidation treatment is performed in which hydrogen peroxide is added after air introduction and solid-liquid separation, and the filtrate after addition of hydrogen peroxide is subjected to an air oxidation step. A method of treating petroleum-based combustion ash that is circulated and reused for recycling the air-oxidized filtrate to the nickel extraction process .