JP5660931B2 - Method for recovering metal from spent solid oxide fuel cells - Google Patents

Method for recovering metal from spent solid oxide fuel cells Download PDF

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JP5660931B2
JP5660931B2 JP2011041338A JP2011041338A JP5660931B2 JP 5660931 B2 JP5660931 B2 JP 5660931B2 JP 2011041338 A JP2011041338 A JP 2011041338A JP 2011041338 A JP2011041338 A JP 2011041338A JP 5660931 B2 JP5660931 B2 JP 5660931B2
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JP2012178304A (en
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千歳　範壽
範壽 千歳
光明 松田
光明 松田
桂英 松島
桂英 松島
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Akita Prefecture
Mitsubishi Materials Corp
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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
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
    • Y02E60/30—Hydrogen technology
    • Y02E60/50—Fuel cells
    • 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
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
    • Y02P10/00—Technologies related to metal processing
    • Y02P10/20—Recycling

Description

本発明は、燃料電池の廃棄材料に含まれる金属を回収する方法に関する。更に詳しくは、使用済み固体酸化物形燃料電池の発電セルから金属を効率よく回収する方法に関するものである。   The present invention relates to a method for recovering a metal contained in a waste material of a fuel cell. More specifically, the present invention relates to a method for efficiently recovering metal from a power generation cell of a used solid oxide fuel cell.

従来、使用済みの発電セルを微粉末に粉砕し（第１工程）、この微粉末と水とを混合してパルプ濃度１０〜２０質量％のスラリーを作製し（第２工程）、このスラリーに酸を加えてｐＨ２〜４に調整し（第３工程）、このｐＨを調整したスラリーに濃度１〜２．２×１０-4ｍｏｌ／リットルの捕収剤を添加し（第４工程）、このスラリーを起泡させて第１金属微粒子を泡に付着させるとともに残りの第２金属微粒子を沈殿させ（第５工程）、この沈殿させた第２金属微粒子をろ過して沈殿物を得た後に（第６工程）、この沈殿物を洗浄し乾燥してＬａ，Ｓｒ，Ｇａ，Ｍｇ，Ｃｏを主成分とする固形物を作製し（第７工程）、更にこの固形物を微粉末に粉砕する（第８工程）、固体酸化物燃料電池の発電セルから金属を回収する方法が開示されている（例えば、特許文献１参照。）。この金属の回収方法では、第６工程と第７工程の間に、第６工程で得られた沈殿物を硝酸で処理してＳｍ，Ｓｒ，Ｃｏ及びＮｉを含む金属を浸出させる第１６工程と、この処理液を固液分離することによりＬａ，Ｓｒ，Ｇａ，Ｍｇ及びＣｏを含む浸出残渣を得る第１７工程とを更に含む。 Conventionally, a used power generation cell is pulverized into a fine powder (first step), and the fine powder and water are mixed to produce a slurry having a pulp concentration of 10 to 20% by mass (second step). An acid is added to adjust the pH to 2 to 4 (third step), and a collector having a concentration of 1 to 2.2 × 10 −4 mol / liter is added to the pH adjusted slurry (fourth step). After the slurry is bubbled to attach the first metal fine particles to the foam and the remaining second metal fine particles are precipitated (fifth step), the precipitated second metal fine particles are filtered to obtain a precipitate ( (Sixth step) The precipitate is washed and dried to produce a solid containing La, Sr, Ga, Mg, Co as the main component (seventh step), and this solid is further pulverized into a fine powder ( Eighth step), a method for recovering metal from a power generation cell of a solid oxide fuel cell is disclosed. Are (e.g., see Patent Document 1.). In this metal recovery method, between the sixth step and the seventh step, a sixteenth step of treating the precipitate obtained in the sixth step with nitric acid and leaching a metal containing Sm, Sr, Co and Ni; And a seventeenth step of obtaining a leaching residue containing La, Sr, Ga, Mg and Co by solid-liquid separation of the treatment liquid.

第６工程の次に第１６工程を経ることにより、第６工程でろ過して得られた第２金属微粒子の沈殿物から、第５工程の浮遊選鉱で分別しきれなかったＳｍ，Ｓｒ，Ｃｏ及びＮｉを除去できる。また第１６工程の次に第１７工程を経ることにより、第１６工程の処理液からＬａ，Ｓｒ，Ｇａ，Ｍｇ及びＣｏを含む浸出残渣を得ることができる。この結果、第６工程と第７工程の間に、第１６工程及び第１７工程を経ることにより、固体電解質層の原料となる金属を、第１６工程及び第１７工程を経ない場合より高い電解質品位で回収できるようになっている。   Sm, Sr, Co that could not be separated by the flotation in the fifth step from the precipitate of the second metal fine particles obtained by filtering in the sixth step by passing through the sixteenth step after the sixth step And Ni can be removed. Further, by passing through the seventeenth step after the sixteenth step, a leaching residue containing La, Sr, Ga, Mg and Co can be obtained from the treatment liquid in the sixteenth step. As a result, by passing through the sixteenth step and the seventeenth step between the sixth step and the seventh step, the metal that is the raw material of the solid electrolyte layer is higher than in the case of not passing through the sixteenth step and the seventeenth step. It can be collected with quality.

特開２００９−１４４２１９号公報（請求項１及び５、段落［００３９］〜段落［００４１］、図１）JP 2009-144219 A (Claims 1 and 5, paragraphs [0039] to [0041], FIG. 1)

しかし、上記従来の特許文献１に示された金属の回収方法では、固体電解質層の原料として用いられる回収金属の電解質品位が未だ低い、即ち固体電解質層を構成する回収金属の純度が未だ低いという問題点があった。   However, in the conventional metal recovery method disclosed in Patent Document 1, the quality of the recovered metal used as the raw material of the solid electrolyte layer is still low, that is, the purity of the recovered metal constituting the solid electrolyte layer is still low. There was a problem.

本発明の目的は、使用済みの固体酸化物形燃料電池の発電セルから固体電解質層を構成する金属を高い純度で回収することができる、使用済み固体酸化物形燃料電池セルから金属を回収する方法を提供することにある。   An object of the present invention is to recover metal from a used solid oxide fuel cell, which can recover the metal constituting the solid electrolyte layer with high purity from the power generation cell of the used solid oxide fuel cell. It is to provide a method.

本発明の第１の観点は、Ｓｍ，Ｓｒ及びＣｏの元素を含む空気極層と、Ｎｉ，Ｃｅ及びＳｍの元素を含む燃料極層の間に、Ｌａ，Ｓｒ，Ｇａ，Ｍｇ及びＣｏの元素を含む固体電解質層が配された積層構造を有する使用済み固体酸化物形燃料電池セルから金属を回収する方法において、上記使用済みの発電セルを粉砕して粒径７０〜１５０μｍで最大ピークとなる粒度分布を有する微粉末を作製する第１工程と、この第１工程の微粉末と水とを混合してパルプ濃度が１０〜２０質量％となるようにスラリーを作製する第２工程と、この第２工程で作製したスラリーに酸を添加して上記スラリーをｐＨ２〜４の範囲に調整する第３工程と、この第３工程でｐＨ調整したスラリーに濃度１．０〜２．２×１０-4ｍｏｌ／リットルの捕収剤を添加する第４工程と、この第４工程の捕収剤を添加したスラリーを起泡させて金属微粒子を泡に付着させるとともに残りの金属微粒子を沈殿させる第５工程と、この第５工程で沈殿させた金属微粒子をろ過して沈殿物を得る第６工程と、この第６工程で得られた沈殿物を硝酸で処理してＳｍ，Ｓｒ，Ｃｏ及びＮｉを含む金属を浸出させる第７工程と、この第７工程の処理液から浮遊固形分を除去する第８工程と、この第８工程で浮遊固形分が除去された処理液を固液分離することによりＬａ，Ｓｒ，Ｇａ，Ｍｇ及びＣｏを含む浸出残渣を得る第９工程と、この第９工程で得られた浸出残渣を洗浄し乾燥してＬａ，Ｓｒ，Ｇａ，Ｍｇ及びＣｏを主成分とする固形物を得る第１０工程と、この第１０工程で得られた固形物を微粉末に粉砕する第１１工程とを含むことを特徴とする。 According to a first aspect of the present invention, an element of La, Sr, Ga, Mg and Co is provided between an air electrode layer containing elements of Sm, Sr and Co and a fuel electrode layer containing elements of Ni, Ce and Sm. In the method of recovering a metal from a used solid oxide fuel cell having a laminated structure in which a solid electrolyte layer containing is disposed, the used power generation cell is pulverized and has a maximum peak at a particle size of 70 to 150 μm A first step for producing a fine powder having a particle size distribution, a second step for producing a slurry so that the pulp concentration is 10 to 20% by mass by mixing the fine powder of the first step and water, and this A third step in which acid is added to the slurry prepared in the second step to adjust the slurry to a pH in the range of 2 to 4, and a concentration of 1.0 to 2.2 × 10 − in the slurry adjusted in pH in the third step. the addition of ToOsamuzai of 4 mol / liter 4 steps, a fifth step in which the slurry added with the collecting agent in the fourth step is foamed to attach the metal fine particles to the foam and the remaining metal fine particles are precipitated, and the metal precipitated in the fifth step A sixth step of obtaining a precipitate by filtering the fine particles, a seventh step of treating the precipitate obtained in the sixth step with nitric acid and leaching a metal containing Sm, Sr, Co and Ni; Eighth step of removing suspended solids from the treatment liquid of the seven steps, and leaching containing La, Sr, Ga, Mg and Co by solid-liquid separation of the treatment liquid from which the suspended solids were removed in the eighth step A ninth step for obtaining a residue; a tenth step for obtaining a solid material mainly composed of La, Sr, Ga, Mg and Co by washing and drying the leaching residue obtained in the ninth step; An eleventh step of pulverizing the solid material obtained in the step into a fine powder; It is characterized by including.

本発明の第１の観点の方法では、使用済みの固体酸化物形燃料電池の発電セルを、粒径７０〜１５０μｍで最大ピークとなる粒度分布を有する微粉末に粉砕し、この微粉末と水とを混合して作製されたスラリーに酸を加えた後に捕収剤を添加し、このスラリーを起泡させて金属微粒子を泡に付着させるとともに残りの金属微粒子を沈殿させ、この沈殿させた金属微粒子をろ過して得られた沈殿物を硝酸で処理して所定の金属を浸出させ、この処理液から固体酸化物層にとって不純物となる浮遊固形分を除去し更に固液分離して所定の金属を含む浸出残渣を得た後に、この浸出残渣を洗浄し乾燥して得られた所定の金属を主成分とする固形物を微粉末に粉砕したので、使用済みの固体酸化物形燃料電池の発電セルから固体電解質層を構成する金属を高い純度で回収することができる。   In the method according to the first aspect of the present invention, a power generation cell of a used solid oxide fuel cell is pulverized into a fine powder having a particle size distribution having a maximum particle size of 70 to 150 μm, and the fine powder and water After adding an acid to the slurry prepared by mixing and collecting a collector, the slurry is foamed to attach the metal fine particles to the foam, and the remaining metal fine particles are precipitated, and the precipitated metal Precipitates obtained by filtering the fine particles are treated with nitric acid to leach predetermined metals, and floating solids that become impurities for the solid oxide layer are removed from the treatment liquid, and solid-liquid separation is performed to separate the predetermined metals. After the leaching residue containing slag was obtained, the leaching residue was washed and dried, and the solid material containing a predetermined metal as a main component was pulverized into fine powder. Gold constituting the solid electrolyte layer from the cell It can be recovered in a high purity.

本発明実施形態の使用済み固体酸化物形燃料電池の発電セルから金属を回収する方法を示す工程図である。It is process drawing which shows the method of collect | recovering metals from the electric power generation cell of the used solid oxide fuel cell of embodiment of this invention. 実施例１と比較例１及び２の微粉末の粒度分布をそれぞれ示す図である。It is a figure which shows the particle size distribution of the fine powder of Example 1 and Comparative Examples 1 and 2, respectively.

次に本発明を実施するための形態を図面に基づいて説明する。固体酸化物形燃料電池は、一般に、空気極層と燃料極層の間に固体電解質層が配された積層構造を有する発電セルと、この発電セルの空気極層の外側に積層させた空気極集電体と、発電セルの燃料極の外側に積層させた燃料極集電体と、空気極集電体の外側に積層された空気極集電体側セパレータと、燃料極集電体の外側に積層された燃料極側セパレータとを備える。   Next, an embodiment for carrying out the present invention will be described with reference to the drawings. A solid oxide fuel cell generally includes a power generation cell having a laminated structure in which a solid electrolyte layer is disposed between an air electrode layer and a fuel electrode layer, and an air electrode laminated outside the air electrode layer of the power generation cell. A current collector, a fuel electrode current collector laminated outside the fuel electrode of the power generation cell, an air electrode current collector side separator laminated outside the air electrode current collector, and an outside of the fuel electrode current collector And a stacked fuel electrode side separator.

発電セルの固体電解質層に使用される材料は、酸化物イオン伝導体であり、例えば、一般式：Ｌａ1-XＳｒXＧａ1-Y-ZＭｇYＡZＯ3（式中、ＡはＣｏ，Ｆｅ，Ｎｉ及びＣｕからなる群より選ばれた１種又は２種以上の元素、Ｘ＝０．０５〜０．３、Ｙ＝０〜０．２９、Ｚ＝０．０１〜０．３、Ｙ＋Ｚ＝０．０２５〜０．３）で表されるランタンガレート系酸化物イオン伝導体などが使用される。また発電セルの燃料極層は、例えば、一般式：Ｃｅ1-mＢmＯ2（式中、ＢはＳｍ，Ｌａ，Ｇｄ，Ｙ及びＣａからなる群より選ばれた１種又は２種以上の元素、ｍは０＜ｍ≦０．４）で表されるＢ（但し、ＢはＳｍ，Ｌａ，Ｇｄ，Ｙ及びＣａからなる群より選ばれた１種又は２種以上の元素を示す。以下、同じ）ドープされたセリア粒とニッケル粒とで構成された多孔質焼結体からなることが知られている。更に空気極は、（Ｓｍ，Ｓｒ）ＣｏＯ3や、（Ｌａ，Ｓｒ）ＭｎＯ3などのセラミックスで構成されている。 The material used for the solid electrolyte layer of the power generation cell is an oxide ion conductor, for example, a general formula: La 1-X Sr X Ga 1-YZ Mg Y AZ 3 (where A is Co, One or more elements selected from the group consisting of Fe, Ni and Cu, X = 0.05 to 0.3, Y = 0 to 0.29, Z = 0.01 to 0.3, Y + Z = 0.025 to 0.3) is used. The fuel electrode layer of the power generation cell is, for example, a general formula: Ce 1-m B m O 2 (wherein B is one or more selected from the group consisting of Sm, La, Gd, Y and Ca) Wherein m is 0 <m ≦ 0.4) B (where B represents one or more elements selected from the group consisting of Sm, La, Gd, Y and Ca). The same applies hereinafter). It is known that the porous sintered body is composed of doped ceria grains and nickel grains. Furthermore, the air electrode is made of ceramics such as (Sm, Sr) CoO 3 and (La, Sr) MnO 3 .

本発明は、Ｓｍ，Ｓｒ及びＣｏの元素を含む空気極層と、Ｎｉ，Ｃｅ及びＳｍの元素を含む燃料極層との間に、Ｌａ，Ｓｒ，Ｇａ，Ｍｇ及びＣｏの元素を含む固体電解質層が配された積層構造を有する使用済み固体酸化物形燃料電池の発電セルから金属を回収する方法である。具体的には、例えば、空気極層が（Ｓｍ0.5Ｓｒ0.5）ＣｏＯ3のセラミックスにより構成され、燃料極層がＣｅ0.8Ｓｍ0.2Ｏ2とニッケル粒とで構成された多孔質焼結体により構成され、固体電解質層がＬａ0.8Ｓｒ0.2Ｇａ0.8Ｍｇ0.15Ｃｏ0.05Ｏ3のランタンガレート系酸化物イオン伝導体により構成された発電セルなどから金属を回収する方法である。 The present invention relates to a solid electrolyte containing La, Sr, Ga, Mg and Co elements between an air electrode layer containing Sm, Sr and Co elements and a fuel electrode layer containing Ni, Ce and Sm elements. This is a method for recovering a metal from a power generation cell of a used solid oxide fuel cell having a laminated structure in which layers are arranged. Specifically, for example, the air electrode layer is composed of (Sm 0.5 Sr 0.5 ) CoO 3 ceramics, and the fuel electrode layer is composed of a porous sintered body composed of Ce 0.8 Sm 0.2 O 2 and nickel particles. In this method, the solid electrolyte layer recovers metal from a power generation cell or the like in which the lanthanum gallate oxide ion conductor of La 0.8 Sr 0.2 Ga 0.8 Mg 0.15 Co 0.05 O 3 is used.

本発明の実施の形態では、図１に示すように、次の第１工程１〜第１１工程１１を経ることにより、上記使用済みの発電セルのうち固体電解質層を構成する金属（固体電解質層の原料となる金属）を高い純度で回収することができる。第１工程１では、使用済み固体酸化物形燃料電池の発電セルを粉砕し、粒径が１０〜２００μｍ、好ましくは４０〜７０μｍの範囲内であって、しかも粒径７０〜１５０μｍ、好ましくは１００〜１３０μｍで最大ピークとなる粒度分布を有する微粉末を作製する。粉砕には衝撃作用による粉砕能力に優れ、摩砕作用により単体分離性が向上し、細かく粉砕し過ぎない等の理由から、複数の金属球を用いた振動ボールミルではなく、タングステンカーバイドセルなどを用いた振動型ディスクミルにて粉砕することが好適である。また粉砕後の微粉末の平均粒径を１０〜２００μｍの範囲内に限定したのは、下限値未満では後述の第５工程５における浮遊選鉱の速度が遅くなり効率が低下してしまい、上限値を越えると粒子が重くなり過ぎ、第５工程５で浮遊すべき金属微粒子の浮揚が困難になるからである。更に粉砕後の微粉末の粒度分布において最大ピークとなる粒径を７０〜１５０μｍの範囲内に限定したのは、下限値未満では浮遊選鉱の速度が遅くなり、捕収剤の消費量が増加したり、ろ過性が悪化するなどの不具合があり、上限値を越えると粒子が重くなり過ぎ、第５工程５で浮遊すべき金属微粒子の浮揚が困難になるからである。なお、微粉末の平均粒径及び粒度分布は、マイクロトラック粒度分析計（日機装株式会社製のＦＲＡ９２２０）を用いて測定した。また、微粉末の平均粒径としては、上記分析計で測定されたメディアン径を用いた。更に、微粉末の最大ピークとなる粒度分布の粒径としては、上記分析計で測定されたモード径（最頻粒子径）を用いた。   In the embodiment of the present invention, as shown in FIG. 1, the metal (solid electrolyte layer) constituting the solid electrolyte layer in the used power generation cells through the following first step 11 to eleventh step 11. Metal) can be recovered with high purity. In the first step 1, the power generation cell of the used solid oxide fuel cell is pulverized to have a particle size of 10 to 200 μm, preferably 40 to 70 μm, and a particle size of 70 to 150 μm, preferably 100. A fine powder having a particle size distribution with a maximum peak at ˜130 μm is prepared. For pulverization, use of tungsten carbide cells, etc., instead of a vibrating ball mill using multiple metal balls, because of excellent grinding ability by impact action, improved single unit separation by grinding action, and fine grinding. It is preferable to pulverize with a vibration type disk mill. In addition, the average particle size of the fine powder after pulverization is limited to the range of 10 to 200 μm. If the average particle size is less than the lower limit, the flotation rate in the fifth step 5 described later is slowed and the efficiency is lowered. This is because the particles become too heavy and the metal fine particles to be floated in the fifth step 5 are difficult to float. Furthermore, the maximum peak particle size distribution in the particle size distribution of the fine powder after pulverization is limited to the range of 70 to 150 μm. If the particle size is less than the lower limit, the flotation rate becomes slow and the consumption of the collection agent increases. If the upper limit is exceeded, the particles become too heavy, and it becomes difficult to float the metal fine particles that should be suspended in the fifth step 5. The average particle size and particle size distribution of the fine powder were measured using a Microtrac particle size analyzer (FRA 9220 manufactured by Nikkiso Co., Ltd.). The median diameter measured with the analyzer was used as the average particle diameter of the fine powder. Furthermore, the mode diameter (mode particle diameter) measured with the above-mentioned analyzer was used as the particle diameter of the particle size distribution that gives the maximum peak of the fine powder.

第２工程２では、第１工程１で粉砕した微粉末と水とを混合し、パルプ濃度が１０〜２０質量％の範囲内、好ましくは１２．５質量％となるようにスラリーを作製する。パルプ濃度を１０〜２０質量％の範囲内に限定したのは、下限値未満では回収率が低下し、上限値を越えると電解質品位が低下するからである。   In the second step 2, the fine powder pulverized in the first step 1 and water are mixed, and a slurry is prepared so that the pulp concentration is in the range of 10 to 20% by mass, preferably 12.5% by mass. The reason why the pulp concentration is limited to the range of 10 to 20% by mass is that the recovery rate decreases when the pulp concentration is less than the lower limit value, and the electrolyte quality decreases when the upper limit value is exceeded.

第３工程３では、第２工程２で作製したスラリーに酸を添加して、スラリーをｐＨ２〜４の範囲内、好ましくはｐＨ３に調整する。スラリーのｐＨを２〜４の範囲内に限定したのは、スラリーのｐＨが上記範囲から外れると、電解質品位が低下するからである。またｐＨ調整に使用する酸は、緩衝作用によりｐＨ調整が容易であるという理由から、酒石酸、クエン酸などのカルボン酸を使用することが好ましく、また粒子表面を清浄に保つという理由から、硝酸や硫酸などを使用することが好ましい。   In the third step 3, an acid is added to the slurry prepared in the second step 2, and the slurry is adjusted to a pH in the range of 2 to 4, preferably pH 3. The reason why the pH of the slurry is limited to the range of 2 to 4 is that the electrolyte quality is lowered when the pH of the slurry is out of the above range. The acid used for pH adjustment is preferably a carboxylic acid such as tartaric acid or citric acid because it is easy to adjust the pH by buffering action, and nitric acid or citric acid is used because the particle surface is kept clean. It is preferable to use sulfuric acid or the like.

第４工程４では、第３工程３でｐＨ調整したスラリーに濃度１．０〜２．２×１０-4ｍｏｌ／リットル、好ましくは１．２〜２．０ｍｏｌ／リットルの捕収剤を添加する。捕収剤の濃度を１．０〜２．２×１０-4ｍｏｌ／リットルの範囲内に限定したのは、下限値未満では電解質品位が低下し、上限値を越えると回収率が低下するからである。捕収剤には、空気極層と燃料極層に対する捕収効果が認められるという理由により、ドデシルベンゼンスルホン酸ナトリウム、ドデシルスルホン酸ナトリウム又はオレイン酸ナトリウムなどが好ましい。 In the fourth step 4, a collector having a concentration of 1.0 to 2.2 × 10 −4 mol / liter, preferably 1.2 to 2.0 mol / liter, is added to the slurry whose pH has been adjusted in the third step 3. . The reason why the concentration of the collecting agent is limited to the range of 1.0 to 2.2 × 10 −4 mol / liter is that the electrolyte quality decreases when the concentration is less than the lower limit, and the recovery rate decreases when the upper limit is exceeded. It is. As the collection agent, sodium dodecylbenzenesulfonate, sodium dodecylsulfonate, sodium oleate, or the like is preferable because the collection effect on the air electrode layer and the fuel electrode layer is recognized.

第５工程５では、第４工程４で捕収剤を添加したスラリーに、必要に応じ起泡剤として少量のメチルイソブチルカービノールやパイン油を添加し、浮遊選鉱法により、浮遊する金属微粒子と、沈殿する金属微粒子とに分離する。浮遊選鉱は、その選別原理により多油浮選法、水面浮選法、及び泡沫浮選法の３者に分類されるが、本発明では、これらのうちの泡沫浮遊選鉱法により選鉱を行う。泡沫浮遊選鉱法とは、微粉末原鉱と水の混合物に、少量の起泡剤、捕収剤などを加えて、機械的に気泡を導入し、その気泡に特定の鉱物微粒子を付着させ、空気の浮力で表面に鉱物微粒子を浮揚させて選鉱する方法である。本発明の第５工程５では、この泡沫浮遊選鉱法により、気泡に付着して浮揚し浮遊する金属微粒子と、気泡に付着せずに沈降して沈殿する金属微粒子とに分離する。気泡に付着して浮揚し浮遊する金属微粒子は、主に空気極層に含まれるＳｍ、Ｓｒ及びＣｏを含む金属微粒子と、燃料極層に含まれるＮｉ、Ｃｅ及びＣｏを含む金属微粒子である。一方、気泡に付着せずに沈降して沈殿する金属微粒子は、主に固体電解質層に含まれるＬａ、Ｓｒ、Ｇａ、Ｍｇ及びＣｏを含む金属微粒子である。このように、主に固体電解質層の金属微粒子が沈殿する技術的理由は、空気極層、燃料極層に比べて捕収剤による疎水性被膜形成の作用が小さいためであると推察される。   In the fifth step 5, a small amount of methyl isobutyl carbinol or pine oil is added as a foaming agent as necessary to the slurry to which the collection agent has been added in the fourth step 4, and the floating fine metal particles and , Separated into fine metal particles that precipitate. The flotation is classified into three types, that is, a multi-oil flotation method, a water surface flotation method, and a foam flotation method according to the selection principle. In the present invention, the flotation is performed by the foam flotation method. The foam flotation method adds a small amount of foaming agent, collection agent, etc. to a mixture of fine powder ore and water, mechanically introduces bubbles, and attaches specific mineral fine particles to the bubbles, This is a method in which mineral fine particles are levitated on the surface by the buoyancy of air and are selected. In the fifth step 5 of the present invention, the foam flotation method separates the fine metal particles that float and float on the bubbles and the fine metal particles that settle and settle without adhering to the bubbles. The metal fine particles that float and float by adhering to the bubbles are mainly metal fine particles containing Sm, Sr and Co contained in the air electrode layer and metal fine particles containing Ni, Ce and Co contained in the fuel electrode layer. On the other hand, the metal fine particles that settle and settle without adhering to the bubbles are metal fine particles mainly containing La, Sr, Ga, Mg, and Co contained in the solid electrolyte layer. Thus, it is speculated that the technical reason for the precipitation of the metal fine particles mainly in the solid electrolyte layer is that the action of forming the hydrophobic film by the collecting agent is smaller than that of the air electrode layer and the fuel electrode layer.

第６工程６では、第５工程５で沈殿させた金属微粒子をろ過し、この金属微粒子の沈殿物を得る。   In the sixth step 6, the metal fine particles precipitated in the fifth step 5 are filtered to obtain a precipitate of the metal fine particles.

第７工程７では、第６工程６で得られた金属微粒子の沈殿物を、濃度０．８〜４ｍｏｌ／リットル、好ましくは１．５〜２ｍｏｌ／リットルの硝酸で処理して、Ｓｍ，Ｓｒ，Ｃｏ及びＮｉを含む金属を浸出させる。第６工程６でろ過して得られた金属微粒子の沈殿物は、この第７工程７を経ることにより、第５工程５の浮遊選鉱で分別しきれなかったＳｍ，Ｓｒ，Ｃｏ及びＮｉを除去できるため、高い電解質品位で固体電解質層の金属を回収できる。硝酸の濃度を０．８〜４ｍｏｌ／リットルの範囲内に限定したのは、下限値未満では空気極層や燃料極層の一部が浸出し難く、上限値を越えると燃料極層に含まれるＮｉが酸化被膜を形成して浸出し難くなるからである。また、硝酸で処理する際の温度は、１０〜４０℃、好ましくは１５〜３０℃に設定される。硝酸で処理する際の温度が１０〜４０℃の範囲内であれば、空気極層、燃料極層を選択的に浸出させる点において好適であり、下限値未満では浸出速度が低下し、上限値を越えると固体電解質層が浸出してしまい、好ましくない。更に、第６工程で得られた金属微粒子の沈殿物を硝酸で処理すると、浮揚して浮遊する僅かな固形分が発生する。この浮遊固形分が発生するのは次の理由によるものと考えられる。第６工程で得られた金属微粒子の沈殿物を硝酸で処理すると、多孔質の燃料極層を構成する成分のうちニッケル粒は溶けるけれども、Ｃｅ0.8Ｓｍ0.2Ｏ2はあまり溶けない。また燃料極層中のニッケル粒は固体電解質とＣｅ0.8Ｓｍ0.2Ｏ2との接着剤の役割を果たしている。このニッケル粒が溶け出すと、Ｃｅ0.8Ｓｍ0.2Ｏ2を多く含む固形分が気泡を取込んだ状態で浮揚し、浮遊固形分となる。このＣｅ0.8Ｓｍ0.2Ｏ2を多く含む固形分は固体電解質層にとって不純物であるため、Ｃｅ0.8Ｓｍ0.2Ｏ2を多く含む固形分を除去することは、固体電解質層を構成する金属を高い純度で回収するためには好ましい。 In the seventh step 7, the metal fine particle precipitate obtained in the sixth step 6 is treated with nitric acid having a concentration of 0.8 to 4 mol / liter, preferably 1.5 to 2 mol / liter, and Sm, Sr, A metal containing Co and Ni is leached. Through the seventh step 7, the precipitate of fine metal particles obtained by filtration in the sixth step 6 removes Sm, Sr, Co and Ni that could not be separated by the flotation in the fifth step 5. Therefore, the metal of the solid electrolyte layer can be recovered with high electrolyte quality. The concentration of nitric acid was limited to the range of 0.8 to 4 mol / liter because the air electrode layer and a part of the fuel electrode layer were not easily leached below the lower limit value, and included in the fuel electrode layer when the upper limit value was exceeded. This is because Ni forms an oxide film and is difficult to leach out. Moreover, the temperature at the time of processing with nitric acid is set to 10-40 degreeC, Preferably it is 15-30 degreeC. If the temperature at the time of processing with nitric acid is within the range of 10 to 40 ° C., it is suitable in that the air electrode layer and the fuel electrode layer are selectively leached. A solid electrolyte layer leaching out is not preferable. Furthermore, when the metal fine particle precipitate obtained in the sixth step is treated with nitric acid, a slight solid content that floats and floats is generated. It is thought that this floating solid is generated for the following reason. When the precipitate of metal fine particles obtained in the sixth step is treated with nitric acid, nickel particles dissolve among components constituting the porous fuel electrode layer, but Ce 0.8 Sm 0.2 O 2 does not dissolve much. The nickel particles in the fuel electrode layer serve as an adhesive between the solid electrolyte and Ce 0.8 Sm 0.2 O 2 . When the nickel particles are melted, the solid content containing a large amount of Ce 0.8 Sm 0.2 O 2 floats in a state where air bubbles are taken in, and becomes a floating solid content. Since the solid content containing a large amount of Ce 0.8 Sm 0.2 O 2 is an impurity in the solid electrolyte layer, the removal of the solid content containing a large amount of Ce 0.8 Sm 0.2 O 2 allows the metal constituting the solid electrolyte layer to have a high purity. Preferred for recovery.

第８工程８では、第７工程７の処理液から固体電解質層にとって不純物となる浮遊固形分を除去する。この浮遊固形分を除去する方法としては、網やヘラを用いて浮遊固形分をすくい取る方法や、処理液を浮遊固形分とともにオーバーフローさせる方法などが挙げられる。この浮遊固形分は、固体電解質層にとっては不純物であるけれども、空気極層や燃料極層等の他の部材の原料として活用できる。   In the eighth step 8, floating solids that are impurities for the solid electrolyte layer are removed from the treatment liquid in the seventh step 7. Examples of the method for removing the floating solids include a method of scooping up the floating solids using a net or a spatula, and a method of overflowing the treatment liquid together with the floating solids. Although this floating solid is an impurity for the solid electrolyte layer, it can be used as a raw material for other members such as an air electrode layer and a fuel electrode layer.

第９工程９では、第８工程８の浮遊固形分が除去された処理液を、例えば、ろ過のような方法で固液分離することにより、Ｌａ，Ｓｒ，Ｇａ，Ｍｇ及びＣｏを含む浸出残渣を得る。   In the ninth step 9, the leaching residue containing La, Sr, Ga, Mg and Co is obtained by solid-liquid separation of the treatment liquid from which the suspended solids in the eighth step 8 are removed, for example, by a method such as filtration. Get.

第１０工程１０では、第９工程９で得られた浸出残渣を洗浄した後、乾燥させて、Ｌａ，Ｓｒ，Ｇａ，Ｍｇ及びＣｏを主成分とする固形物を得る。洗浄及び乾燥は、特に限定されるものではないが、水、エタノール又はイソプロパノールで洗浄することが好ましく、乾燥は熱風乾燥にて、１２０〜１５０℃の温度で乾燥することが好ましい。   In the tenth step 10, the leaching residue obtained in the ninth step 9 is washed and then dried to obtain a solid containing La, Sr, Ga, Mg and Co as main components. Although washing | cleaning and drying are not specifically limited, It is preferable to wash | clean with water, ethanol, or isopropanol, and drying is preferable to dry at the temperature of 120-150 degreeC by hot air drying.

第１１工程１１では、第１０工程１０で得られた固形物を、平均粒径が０．５〜１０μｍの範囲内、好ましくは１．３μｍである微粉末に粉砕する。平均粒径が０．５〜１０μｍの範囲内にある微粉末は、固体電解質の緻密体を作製する点において好適だからである。また粉砕には、粒径分布の狭い粒子が安定して得られ、過度の粉砕を防いで粒度調整が容易である等の理由から、複数のセラミック球を用いた回転ボールミルにて粉砕することが好適である。   In the eleventh step 11, the solid matter obtained in the tenth step 10 is pulverized into a fine powder having an average particle diameter in the range of 0.5 to 10 μm, preferably 1.3 μm. This is because fine powder having an average particle size in the range of 0.5 to 10 μm is preferable in terms of producing a solid electrolyte dense body. For pulverization, particles with a narrow particle size distribution can be stably obtained, and it is possible to pulverize with a rotating ball mill using a plurality of ceramic spheres for the purpose of preventing excessive pulverization and adjusting the particle size. Is preferred.

以上、本発明の実施の形態における第１工程１〜第１１工程１１を経ることにより、特に第１工程１において粒径７０〜１５０μｍ、好ましくは１００〜１３０μｍで最大ピークとなる粒度分布を有する微粉末に粉砕し、第８工程８において処理液から固体電解質層にとって不純物となる浮遊固形分を除去することにより、使用済みの固体酸化物形燃料電池の発電セルから、固体電解質層を構成する金属、即ち固体電解質層の原料となる金属を高い純度で回収することができる。   As described above, through the first step 11 to the eleventh step 11 in the embodiment of the present invention, in particular, the first step 1 has a particle size distribution that has a maximum particle size of 70 to 150 μm, preferably 100 to 130 μm. The metal constituting the solid electrolyte layer from the power generation cell of the used solid oxide fuel cell by pulverizing into powder and removing floating solids that become impurities for the solid electrolyte layer from the treatment liquid in the eighth step 8 That is, the metal used as the raw material of the solid electrolyte layer can be recovered with high purity.

なお、以下の第１２工程１２〜第２８工程２８を経ることにより、第５工程５で浮遊した金属微粒子から、使用済みの発電セルの電解質層に含まれる金属を回収できる。第１２工程１２では、上記第５工程１５で浮遊選鉱法により泡に付着して浮揚し浮遊する金属微粒子を、濃度０．８〜４ｍｏｌ／リットルの硝酸で処理して、Ｓｍ，Ｓｒ，Ｃｏ及びＮｉを含む金属を浸出させる。この泡に付着して浮揚し浮遊する金属微粒子は、主に燃料極層及び空気極層の原料である金属が含まれるけれども、第５工程５で沈殿しきれなかった固体電解質層の原料である金属も多く含まれるため、固体電解質層の原料である金属も回収できる。また硝酸で処理する際の温度は１０〜４０℃、好ましくは１５〜２５℃である。   In addition, by passing through the following 12th process 12-28th process 28, the metal contained in the electrolyte layer of a used power generation cell can be collect | recovered from the metal microparticles | floating suspended in the 5th process 5. In the twelfth step 12, the fine metal particles that float and float on the bubbles by the flotation method in the fifth step 15 are treated with nitric acid having a concentration of 0.8 to 4 mol / liter, and Sm, Sr, Co, and A metal containing Ni is leached. The fine metal particles that float and float by adhering to the bubbles are the raw materials of the solid electrolyte layer that could not be fully precipitated in the fifth step 5 although the metal that is the raw material of the fuel electrode layer and the air electrode layer is mainly included. Since a large amount of metal is contained, the metal that is the raw material of the solid electrolyte layer can also be recovered. Moreover, the temperature at the time of processing with nitric acid is 10-40 degreeC, Preferably it is 15-25 degreeC.

第１３工程１３では、第１２工程１２の処理液を、例えば、ろ過のような方法で固液分離することによりＬａ，Ｓｒ，Ｇａ，Ｍｇ，Ｃｏ及びＣｅを含む浸出残渣を得る。第１４工程１４では、第１３工程１３で得られた浸出残渣を濃度５〜１２ｍｏｌ／リットルの塩酸で浸出処理してＬａ，Ｓｒ，Ｇａ，Ｍｇ及びＣｏを含む金属を浸出させる。また塩酸で処理する際の温度は６０〜８０℃に設定される。第１５工程１５では、第１４工程１４の処理液をろ過することによりＬａ，Ｓｒ，Ｇａ，Ｍｇ及びＣｏを主として含有するろ液を得る。   In the thirteenth step 13, the leaching residue containing La, Sr, Ga, Mg, Co and Ce is obtained by solid-liquid separation of the treatment liquid in the twelfth step 12 by a method such as filtration. In the fourteenth step 14, the leaching residue obtained in the thirteenth step 13 is leached with hydrochloric acid having a concentration of 5 to 12 mol / liter to leach metals containing La, Sr, Ga, Mg and Co. Moreover, the temperature at the time of processing with hydrochloric acid is set to 60-80 degreeC. In the fifteenth step 15, a filtrate mainly containing La, Sr, Ga, Mg and Co is obtained by filtering the treatment liquid in the fourteenth step.

第１６工程１６では、第１５工程１５で得られたろ液にアルカリを加えた後、炭酸塩を加えて沈殿を析出させる。アルカリとしては、水酸化ナトリウムや水酸化カリウムが挙げられる。炭酸塩としては、炭酸ナトリウムや炭酸カリウムが挙げられる。アルカリを加えた後のｐＨとしては８〜１２が好ましい。第１７工程１７では、第１６工程１６で生成した沈殿を、例えば、ろ過のような固液分離を行った後、洗浄してＬａ，Ｓｒ，Ｇａ及びＭｇの酸化物と、Ｓｒの炭酸塩を得る。第１８工程１８では、第１７工程１７で得られた酸化物と炭酸塩を焼成し、ランタンガレート系酸化物とした後、平均粒径が０．５〜１０μｍの範囲内、好ましくは１．３μｍである微粉末に粉砕する。   In the sixteenth step 16, an alkali is added to the filtrate obtained in the fifteenth step 15, and then a carbonate is added to precipitate a precipitate. Examples of the alkali include sodium hydroxide and potassium hydroxide. Examples of the carbonate include sodium carbonate and potassium carbonate. As pH after adding an alkali, 8-12 are preferable. In the seventeenth step 17, the precipitate produced in the sixteenth step 16 is subjected to solid-liquid separation such as filtration, and then washed to obtain oxides of La, Sr, Ga and Mg, and a carbonate of Sr. obtain. In the 18th step 18, the oxide and carbonate obtained in the 17th step 17 are baked to obtain a lanthanum gallate oxide, and then the average particle size is in the range of 0.5 to 10 μm, preferably 1.3 μm. Grind to a fine powder.

次に本発明の実施例を比較例とともに詳しく説明する。   Next, examples of the present invention will be described in detail together with comparative examples.

＜実施例１＞
図１に示すように、先ず使用済みの発電セルを、タングステンカーバイドセルなどを用いた振動型ディスクミルで、平均粒径が４７μｍである微粉末であって、しかも粒径１０５μｍで最大ピークとなる粒度分布を有する微粉末に粉砕した後（第１工程１）、蒸留水７００ミリリットルに、この微粉末１００ｇを入れ、パルプ濃度が１２．５質量％になるようにスラリーを作製した（第２工程２）。このスラリーに酒石酸を添加してｐＨを３に調整し（第３工程３）、捕収剤の濃度が１．８５×１０-4ｍｏｌ／リットルとなるように、捕収剤としてドデシルベンゼンスルホン酸ナトリウムを所定量添加した（第４工程４）。次いでこのスラリーを浮選機（太田機械製作所製：ファーレンワルド浮選試験機）にて起泡させることにより、泡に付着させて浮揚し浮遊する金属微粒子と、沈降して沈殿する金属微粒子とに分離した（浮遊選鉱法：第５工程５）。このときの撹拌機の回転速度を１３００〜１４００ｒｐｍとし、エアの送量を４００〜６００ミリリットル／分とした。次に沈殿させた金属微粒子をろ過により回収した後（第６工程６）、この沈殿物を濃度２ｍｏｌ／リットルの硝酸６００ミリリットルに入れて、室温で２時間浸出処理を行った（第７工程７）。この浸出処理で処理液に発生した浮遊固形分をヘラで取り除いた後（第８工程８）、処理液を固液分離して浸出残渣を得た（第９工程９）。更にこの浸出残渣を水で洗浄し乾燥させた後に（第１０工程１０）、回転ボールミルで粉砕して平均粒径１．３μｍの固体電解質層を構成する金属となる微粉末を得た（第１１工程１１）。 <Example 1>
As shown in FIG. 1, first, a used power generation cell is a vibration type disk mill using a tungsten carbide cell or the like, and is a fine powder having an average particle size of 47 μm and has a maximum peak at a particle size of 105 μm. After being pulverized into fine powder having a particle size distribution (first step 1), 100 g of this fine powder was put into 700 ml of distilled water, and a slurry was prepared so that the pulp concentration would be 12.5% by mass (second step). 2). Tartaric acid is added to this slurry to adjust the pH to 3 (third step 3), and dodecylbenzenesulfonic acid as a collecting agent so that the concentration of the collecting agent is 1.85 × 10 −4 mol / liter. A predetermined amount of sodium was added (fourth step 4). Next, the slurry is foamed with a flotation machine (manufactured by Ota Machinery Co., Ltd .: Fahrenwald flotation tester), and thereby the fine metal particles that float and float on the foam and the fine metal particles that settle and settle. Separated (flotation method: fifth step 5). The rotational speed of the stirrer at this time was 1300 to 1400 rpm, and the air feed rate was 400 to 600 ml / min. Next, the precipitated fine metal particles were collected by filtration (sixth step 6), and the precipitate was put into 600 ml of nitric acid having a concentration of 2 mol / liter, and leaching treatment was performed for 2 hours at room temperature (seventh step 7). ). After removing the floating solids generated in the treatment liquid by this leaching treatment with a spatula (eighth step 8), the treatment liquid was subjected to solid-liquid separation to obtain a leaching residue (9th step 9). Further, this leaching residue was washed with water and dried (10th step 10), and then pulverized with a rotating ball mill to obtain a fine powder which becomes a metal constituting the solid electrolyte layer having an average particle size of 1.3 μm (11th step). Step 11).

＜比較例１＞
第１工程において、使用済みの発電セルを、タングステンカーバイドセルなどを用いた振動型ディスクミルで、平均粒径が３７μｍである微粉末であって、しかも粒径６０μｍで最大ピークとなる粒度分布を有する微粉末に粉砕したこと以外は、実施例１と同様の方法により固体電解質層を構成する金属となる微粉末を得た。 <Comparative Example 1>
In the first step, the used power generation cell is a vibration type disk mill using a tungsten carbide cell or the like, and is a fine powder having an average particle size of 37 μm, and further has a particle size distribution having a maximum peak at a particle size of 60 μm. The fine powder used as the metal which comprises a solid electrolyte layer was obtained by the method similar to Example 1 except having grind | pulverized to the fine powder which has.

＜比較例２＞
浸出処理で処理液に発生した浮遊固形分をヘラで取り除くという第８工程を行わなかったこと以外は、実施例１と同様の方法により固体電解質層を構成する金属となる微粉末を得た。 <Comparative example 2>
A fine powder serving as a metal constituting the solid electrolyte layer was obtained in the same manner as in Example 1 except that the eighth step of removing floating solids generated in the treatment liquid by the spatula with a spatula was not performed.

＜比較試験１及び評価＞
実施例１と比較例１及び２の第１工程で作製された微粉末の平均粒径及び粒度分布を、マイクロトラック粒度分析計（日機装株式会社製のＦＲＡ９２２０）を用いて測定した。その結果を表１及び図２に示す。 <Comparative test 1 and evaluation>
The average particle size and particle size distribution of the fine powders produced in the first step of Example 1 and Comparative Examples 1 and 2 were measured using a Microtrac particle size analyzer (FRA 9220 manufactured by Nikkiso Co., Ltd.). The results are shown in Table 1 and FIG.

また、実施例１と比較例１及び２で得られた微粉末０．２ｇを王水で溶解した後、蒸発・乾固し、希塩酸で再溶解して不溶分を除去し、更にＩＣＰ分析装置（ジャーレルアッシュ社製：ＩＣＡＰ−８８）で電解質品位を測定した。その結果を、第８工程（浮遊固形分の除去）の有無とともに、表１に示す。   In addition, 0.2 g of the fine powder obtained in Example 1 and Comparative Examples 1 and 2 was dissolved in aqua regia, evaporated and dried, then redissolved with dilute hydrochloric acid to remove insolubles, and further an ICP analyzer The electrolyte quality was measured by (Jarrel Ash Co., Ltd .: ICAP-88). The results are shown in Table 1 together with the presence or absence of the eighth step (removal of suspended solids).

Figure 0005660931
表１から明らかなように、第１工程で作製された微粉末の粒度分布における最大ピーク時の粒径が６０μｍと小さい比較例１では、電解質品位が９８．５％と低く、また第８工程で浮遊固形分を除去しなかった比較例２では、電解質品位が９８．０％と低かったのに対し、第１工程で作製された微粉末の粒度分布における最大ピーク時の粒径が１００μｍと比較的大きく、しかも第８工程で浮遊固形分を除去した実施例１では、電解質品位が９９．３％と高くなった。これらのことから、第１工程で作製された微粉末の粒度分布における最大ピーク時の粒径が７０〜１５０μｍの範囲内に入っており、また第８工程で固体電解質層にとって不純物となる浮遊固形分を除去することが、使用済みの発電セルから固体電解質層を構成する金属を高い純度で回収するために効果的であることが確認された。
Figure 0005660931
 As is clear from Table 1, in Comparative Example 1 in which the maximum peak particle size in the particle size distribution of the fine powder produced in the first step is as small as 60 μm, the electrolyte quality is as low as 98.5%, and the eighth step In Comparative Example 2 in which the suspended solids were not removed, the electrolyte quality was as low as 98.0%, whereas the particle size distribution of the fine powder produced in the first step had a maximum peak particle size of 100 μm. In Example 1, which was relatively large and the floating solid content was removed in the eighth step, the electrolyte quality was as high as 99.3%. From these facts, the particle size distribution at the maximum peak in the particle size distribution of the fine powder produced in the first step is within the range of 70 to 150 μm, and the floating solid that becomes an impurity for the solid electrolyte layer in the eighth step It was confirmed that removing the component was effective for recovering the metal constituting the solid electrolyte layer from the used power generation cell with high purity.

Claims (1)

Ｓｍ，Ｓｒ及びＣｏの元素を含む空気極層と、Ｎｉ，Ｃｅ及びＳｍの元素を含む燃料極層の間に、Ｌａ，Ｓｒ，Ｇａ，Ｍｇ及びＣｏの元素を含む固体電解質層が配された積層構造を有する使用済み固体酸化物形燃料電池セルから金属を回収する方法において、
前記発電セルを粉砕して粒径７０〜１５０μｍで最大ピークとなる粒度分布を有する微粉末を作製する第１工程と、
前記第１工程の微粉末と水とを混合してパルプ濃度が１０〜２０質量％となるようにスラリーを作製する第２工程と、
前記第２工程で作製したスラリーに酸を添加して前記スラリーをｐＨ２〜４の範囲に調整する第３工程と、
前記第３工程でｐＨ調整したスラリーに濃度１．０〜２．２×１０-4ｍｏｌ／リットルの捕収剤を添加する第４工程と、
前記第４工程の捕収剤を添加したスラリーを起泡させて金属微粒子を泡に付着させるとともに残りの金属微粒子を沈殿させる第５工程と、
前記第５工程で沈殿させた金属微粒子をろ過して沈殿物を得る第６工程と、
前記第６工程で得られた沈殿物を硝酸で処理してＳｍ，Ｓｒ，Ｃｏ及びＮｉを含む金属を浸出させる第７工程と、
前記第７工程の処理液から浮遊固形分を除去する第８工程と、
前記第８工程で浮遊固形分が除去された処理液を固液分離することによりＬａ，Ｓｒ，Ｇａ，Ｍｇ及びＣｏを含む浸出残渣を得る第９工程と、
前記第９工程で得られた浸出残渣を洗浄し乾燥してＬａ，Ｓｒ，Ｇａ，Ｍｇ及びＣｏを主成分とする固形物を得る第１０工程と、
前記第１０工程で得られた固形物を微粉末に粉砕する第１１工程と
を含むことを特徴とする金属の回収方法。 A solid electrolyte layer containing La, Sr, Ga, Mg, and Co elements was disposed between the air electrode layer containing Sm, Sr, and Co elements and the fuel electrode layer containing Ni, Ce, and Sm elements. In a method for recovering a metal from a spent solid oxide fuel cell having a laminated structure,
A first step of pulverizing the power generation cell to produce a fine powder having a particle size distribution with a maximum particle size of 70 to 150 μm;
A second step of mixing the fine powder of the first step and water to produce a slurry such that the pulp concentration is 10 to 20% by mass;
A third step of adding an acid to the slurry prepared in the second step to adjust the slurry to a pH in the range of 2-4;
A fourth step of adding a collection agent having a concentration of 1.0 to 2.2 × 10 −4 mol / liter to the slurry adjusted in pH in the third step;
A fifth step of causing the slurry to which the collection agent of the fourth step has been added to foam to attach the metal fine particles to the foam and to precipitate the remaining metal fine particles;
A sixth step of obtaining a precipitate by filtering the metal fine particles precipitated in the fifth step;
A seventh step of treating the precipitate obtained in the sixth step with nitric acid to leach out a metal containing Sm, Sr, Co and Ni;
An eighth step of removing suspended solids from the treatment liquid of the seventh step;
A ninth step of obtaining a leaching residue containing La, Sr, Ga, Mg and Co by solid-liquid separation of the treatment liquid from which the suspended solids have been removed in the eighth step;
A tenth step in which the leaching residue obtained in the ninth step is washed and dried to obtain a solid containing La, Sr, Ga, Mg and Co as main components;
An eleventh step of pulverizing the solid material obtained in the tenth step into a fine powder.
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