JP2016186116A - Method for separating and recovering yttrium and nickel from solid oxide type fuel cell scrap - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for efficiently separating and recovering yttrium and nickel from solid oxide type fuel cell (SOFC) scrap by a simple method.SOLUTION: There is provided a method for separating and recovering yttrium and nickel from solid oxide type fuel cell scrap in which a slurry containing a granular solid of solid oxide type fuel cell scrap containing at least nickel and yttrium is subjected to water leaching and yttrium is leached more preferentially than nickel by adding an acid solution for pH adjustment to adjust the pH while heating the resulting slurry at 50°C or more, followed by solid-liquid separation to separate into a leached liquid containing yttrium and a leach residue containing nickel.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a method for separating and recovering yttrium and nickel from solid oxide fuel cell (SOFC) scrap.

  Various recovery techniques have been proposed for recycling metal from solid oxide fuel cell (SOFC) scrap. For example, in JP 2009-144220 A, solid electrolyte tanks such as lanthanum (La), strontium (Sr), gallium (Ga), magnesium (Mg), and cobalt (Co) are used from a used solid oxide fuel cell. Is described.

  In JP 2011-162816 A, an organic solvent containing a metal extractant is brought into contact with an aqueous solution having a pH of 1.0 by adding hydrochloric acid and hydrogen peroxide to waste containing rare metals discharged from a factory. And extracting yttrium (Y) by solvent extraction.

JP 2009-144220 A JP 2011-162816 A

  As described in Patent Documents 1 and 2, in the conventional metal recovery method, almost all of the metal to be recovered is dissolved with a strong acid, and then pH adjustment or solvent extraction with alkali is performed to obtain the necessary metal. The method of separating and recovering was generally used.

  However, such a method requires a large amount of acid for dissolving the entire amount of metal. When performing pH adjustment with alkali as described in Patent Document 1, an alkali for pH adjustment is further required. In the case of the processing method using solvent extraction as described in Patent Document 2, a solvent is required in addition to the acid for dissolution. That is, both methods of Patent Documents 1 and 2 require extra steps and chemical costs, and are not efficient recovery methods.

  In addition, the valuable material recovery method described in Patent Document 1 is an invention that targets an extremely small amount of contained elements such as lanthanum, and no method for recovering nickel and yttrium is described or suggested. Patent Document 2 also describes a method for extracting yttrium from a phosphor containing palladium, zirconium, platinum, rhodium, aluminum, and the like by using a solvent extraction method. However, nickel and yttrium are separated and recovered simultaneously. There is no mention or suggestion.

  In view of the above problems, the present invention relates to yttrium from solid oxide fuel cell scrap capable of separating and recovering nickel and yttrium from solid oxide fuel cell (SOFC) scrap efficiently and in a simple manner. A method for separating and recovering nickel is provided.

  As a result of intensive studies, the present inventor selected only yttrium without dissolving nickel after leaching with water instead of once dissolving all the nickel and yttrium to be collected with strong acid as in the past. It has been found that nickel and yttrium can be efficiently separated and recovered from SOFC scrap while reducing the number of processes compared to the prior art by performing acid leaching so as to dissolve it.

  In one aspect, the present invention completed based on the above knowledge is a water leaching treatment of a slurry containing particulate solid of a solid oxide fuel cell scrap containing at least nickel and yttrium while heating at 50 ° C. or higher. By adjusting the pH by adding a pH adjusting acid solution, yttrium is leached preferentially over nickel, and then separated into a post-leaching solution containing yttrium and a leaching residue containing nickel by solid-liquid separation. Is a method for separating and recovering yttrium and nickel from solid oxide fuel cell scrap containing

  In one embodiment, the method for separating and recovering yttrium and nickel from solid oxide fuel cell scraps according to the present invention has an yttrium leaching rate of 90% by mass or more in the leached liquid containing yttrium, and yttrium in the liquid after leaching. This includes leaching a slurry containing particulate solid of solid oxide fuel cell scrap so that the nickel concentration ratio (Y / Ni concentration ratio) is 50 or more.

  In another embodiment, the method for separating and recovering yttrium and nickel from solid oxide fuel cell scrap according to the present invention includes adding a pH adjusting acid solution to adjust the pH to 2-6.

  In yet another embodiment of the method for separating and recovering yttrium and nickel from solid oxide fuel cell scraps according to the present invention, the acid solution for adjusting pH includes hydrochloric acid, nitric acid or organic acid.

  In another embodiment of the method for separating and recovering yttrium and nickel from solid oxide fuel cell scrap according to the present invention, the cumulative distribution diameter (d90) of the particulate solid of the solid oxide fuel cell scrap is 1 mm or less. Including.

  In another embodiment, the method for separating and recovering yttrium and nickel from solid oxide fuel cell scrap according to the present invention is a method of preparing a solid oxide slurry of solid oxide fuel cell scrap before producing a solid solid slurry. The method further includes oxidizing and roasting the granular solid of the fuel cell scrap.

  In another embodiment, the method for separating and recovering yttrium and nickel from solid oxide fuel cell scraps according to the present invention is a method of solid-liquid separation after dissolving nickel by acid leaching the leaching residue containing nickel. To obtain a nickel solution.

  According to the present invention, it is possible to separate and recover Y and Ni from solid oxide fuel cell (SOFC) scrap in an efficient and simple manner. A method can be provided.

It is a flowchart which shows the separation / recovery method of yttrium and nickel from the solid oxide fuel cell scrap which concerns on embodiment of this invention. It is a graph showing the relation between the leaching rate of yttrium in the leached solution containing yttrium and the Y / Ni concentration ratio when hydrochloric acid is used as the pH adjusting acid solution. It is a graph showing the relationship between the leaching rate of yttrium in the leached solution containing yttrium and the Y / Ni concentration ratio when sulfuric acid is used as the pH adjusting acid solution.

Embodiments of the present invention will be described below with reference to the drawings.
As shown in FIG. 1, a method for separating and recovering yttrium and nickel from solid oxide fuel cell (SOFC) scrap according to an embodiment of the present invention includes a step of pulverizing SOFC scrap and a solid obtained by pulverization. A solid oxide fuel cell scrap granular solid slurry obtained by mixing granular fuel cell scrap solids with water is obtained, and a step of water leaching the slurry, and the slurry after the water leaching treatment are acidified. A step of leaching, a step of separating the leachate obtained by acid leaching into solid-liquid separation into a post-leaching solution containing yttrium and a leaching residue containing nickel, a step of further leaching the leaching residue containing nickel, and Separating the leachate obtained by acid leaching into a solid-liquid separation and separating it into a post-leaching solution containing nickel and a leach residue containing a metal such as zinc (Zn) other than nickel. No.

  As the solid oxide fuel cell (SOFC) scrap, a solid oxide fuel cell scrap containing at least nickel and yttrium can be used. More specifically, samarium (Sm), strontium (Sr), cobalt ( Between an air electrode layer containing an element such as Co) and a fuel electrode layer containing an element such as nickel (Ni), cerium (Ce), and samarium (Sm), yttrium (Y), zirconium (Zr), iron ( A unit cell in which a solid electrolyte layer containing Fe), chromium (Cr), cobalt (Co), zinc (Zn), manganese (Mn), or the like is sandwiched, or a cell stack in which unit cells are stacked is used.

  Although not limited to the following, the main metal contained in the solid oxide fuel cell (SOFC) scrap according to the present embodiment includes 10 to 70% by mass of nickel and 5 to 40% by mass of yttrium. In addition, a material containing 0.1 to several% by mass of Zr, Fe, Cr, Co, and Ce as other metals and 0.1% by mass or less of Zn, Mn, Sm, Sr, and the like is preferably used. In particular, a material containing 30 to 60% by mass of nickel and 10 to 30% by mass of yttrium can be more suitably used.

  In the pulverization step, the solid oxide fuel cell (SOFC) scrap is roughly pulverized into a granular solid. The pulverization is performed so that the cumulative distribution diameter (d90) of the particulate solid of the solid oxide fuel cell (SOFC) scrap is 1 mm or less. This makes it possible to more efficiently separate and recover yttrium and nickel from solid oxide fuel cell (SOFC) scrap. The lower limit value of the cumulative distribution diameter (d90) of the granular solid of SOFC scrap is not limited to the following, but it is set to 0.1 μm, for example, in view of bulky increase in volume, handling property after pulverization, and the like. be able to.

  Next, the solid solid of the solid oxide fuel cell scrap obtained in the pulverization step is mixed with water to produce a slurry containing the solid solid of the solid oxide fuel cell scrap. Considering the improvement of the leaching rate of Y and the separation efficiency from Ni, the concentration of the slurry (solid content) is preferably adjusted to 2 to 50% by mass, and more preferably 5 to 30% by mass.

  Next, the slurry containing the particulate solid of the solid oxide fuel cell scrap is leached with water (water leaching treatment). The water leaching treatment can be performed while heating at room temperature, preferably 60 ° C. or higher, more preferably 80 ° C. or higher. Although not limited to the following, the water leaching treatment is preferably performed at, for example, 100 ° C. or less.

  The treatment time for the water leaching treatment is 5 hours or longer, more preferably 18 hours or longer. Even if the treatment time of the water leaching treatment is too long, the leaching rate of nickel and yttrium may not be significantly improved. Therefore, the treatment time is not limited to the following, but can be, for example, 100 hours or less. By performing the water leaching process, it is possible to advance the yttrium and nickel leaching process, which will be described later, faster than in the case where the water leaching process is not performed, thereby improving the efficiency of the process.

  Next, an acid solution for pH adjustment is added to the slurry containing the solid solid of the solid oxide fuel cell scrap after the water leaching treatment to adjust the pH to 2 to 6, and the solid oxide fuel cell scrap granular Yttrium contained in the solid is leached preferentially over nickel. If the pH is less than 2, the amount of the acid solution for pH adjustment increases, so that the cost is increased and the processing efficiency as a whole may decrease. If the pH is higher than 6, yttrium may not sufficiently leach out. The pH of the solution during pH adjustment varies depending on the acid species, but is preferably 3 to 5, for example, and more preferably 3.5 to 4.5.

  In the yttrium leaching treatment, the slurry containing the solid solid of the solid oxide fuel cell scrap is heated at 50 ° C. or higher. By heating at 50 ° C. or higher, only yttrium can be preferentially leached from the slurry containing yttrium and nickel. When leaching is performed at a temperature lower than 50 ° C., only yttrium may not be sufficiently leached from a slurry containing yttrium and nickel. Although there is no restriction | limiting in particular in the upper limit of temperature, Considering efficiency aspects, such as power consumption by heating, can be set to about 90 degreeC, for example.

  It is preferable to use a strongly acidic solution, more specifically an organic acid such as hydrochloric acid, nitric acid, or methanesulfonic acid, as the pH adjusting acid solution used for the yttrium leaching treatment. FIG. 2 is a graph showing the relationship between the leaching rate of yttrium in the leached solution containing yttrium and the Y / Ni concentration ratio when hydrochloric acid is used as the pH adjusting acid solution. The acid concentration used in the acid solution for pH adjustment is not particularly limited. However, if the concentration is too high, the pH is too low and nickel is liable to be leached, and if it is too thin, it takes time to decrease to the set pH or the pH does not decrease. There is a case. On the other hand, as shown in FIG. 3, when sulfuric acid is used, nickel is also leached in addition to yttrium, and preferential leaching treatment of yttrium may not be performed.

  The leaching treatment time is defined as the end time when the change in pH of the solution is almost eliminated. The leaching treatment time is not limited to the following, but is, for example, 1 to 30 hours, more typically 3 to 20 hours. If the leaching process is performed for a long time, dissolution of nickel starts in addition to yttrium, so that only yttrium may not be selectively leached from the SOFC scrap containing yttrium and nickel. If the leaching treatment is too short, the yttrium leaching rate in the leached liquid containing yttrium obtained by solid-liquid separation described later may not be improved.

  Next, the leachate obtained by the leaching treatment is separated into a post-leaching solution containing yttrium and a leaching residue containing nickel by solid-liquid separation. According to the process which concerns on this embodiment, it processes so that the yttrium leaching rate of the liquid after leaching containing yttrium may be 90 mass% or more. Here, “the yttrium leaching rate of the liquid after leaching containing yttrium” indicates the ratio of the Y concentration in the liquid after leaching to the Y concentration contained in the granular solid of SOFC scrap.

  By this leaching treatment, the concentration ratio of yttrium and nickel (Y / Ni concentration ratio) in the leached solution containing yttrium is 50 or more (for example, the nickel concentration is 1 g / L or less with respect to the yttrium concentration of 50 g / L). Yes, more preferably 70 or more, and still more preferably 100 or more. That is, according to the treatment method according to this embodiment, yttrium can be leached with high efficiency, and yttrium can be leached at a concentration 50 times higher than nickel. The upper limit of the Y / Ni concentration ratio in the liquid after leaching depends on the yttrium concentration contained in the SOFC scrap, but is about 10,000, for example.

  The leaching residue containing nickel further dissolves nickel by acid leaching using a mineral acid or the like. Thereafter, the obtained leachate is subjected to solid-liquid separation to obtain a post-leaching solution containing nickel (nickel solution) and a residue containing other metal components such as zinc.

  In the conventional method in which solid oxide fuel cell scrap is acid leached and yttrium and nickel are completely leached while adding a base as a pH adjuster, the behavior of yttrium and nickel is similar. Only one of them could not be leached selectively. According to the method for separating and recovering yttrium and nickel from solid oxide fuel cell scrap according to the present embodiment, acid leaching is performed by adjusting pH so that yttrium is leached selectively (preferentially) compared to nickel. Thus, only yttrium can be selectively and efficiently leached with a necessary minimum amount of chemical solution in a simpler method than conventional methods, and yttrium and nickel can be separated efficiently.

  In addition, before producing the solid solid slurry of the solid oxide fuel cell scrap, the solid solid of the solid oxide fuel cell scrap may be oxidized and roasted. Oxidation roasting further improves the separation efficiency between yttrium and nickel.

  Examples of the present invention will be described below together with comparative examples, but these examples are provided for better understanding of the present invention and its advantages, and are not intended to limit the invention.

Example 1
As the SOFC scrap, an SOFC scrap containing 50% by mass of nickel and 20% by mass of yttrium was roughly pulverized into a granular solid having a cumulative distribution diameter (d90) of 1 mm or less. 10 kg of slurry having a slurry (solid content) concentration of 200 g / L was prepared by adding water to the coarsely pulverized SOFC scrap granular solid. The slurry was subjected to a water leaching treatment for 18 hours while being heated to 60 ° C. After the water leaching treatment, 100 g / L dilute nitric acid was added as a pH adjusting acid solution to adjust the pH to 4.5, and the yttrium was leached by treatment for 10 hours, followed by solid-liquid separation and leaching containing yttrium. It separated into a post-solution and a leaching residue containing nickel. As a result of measuring the liquid after leaching with an ICP mass spectrometer, the leaching rate of yttrium was 100% and nickel was 0.3%. The Y / Ni concentration ratio of the liquid after leaching was 160.

(Example 2)
It implemented like Example 1 except the temperature of water leaching having been 80 degreeC. As a result of measuring the liquid after leaching with an ICP mass spectrometer, the leaching rate of yttrium was 100% and nickel was 0.33%. The Y / Ni concentration ratio of the liquid after leaching was 156.

Example 3
The same procedure as in Example 2 was performed except that the time of water leaching was changed to 5 hours. As a result of measuring the leached solution with an ICP mass spectrometer, the leaching rate of yttrium was 100% and nickel was 0.4%. The Y / Ni concentration ratio of the liquid after leaching was 123.

Example 4
The same procedure as in Example 1 was performed except that the temperature of water leaching was room temperature and the time was 60 hours. As a result of measuring the liquid after leaching with an ICP mass spectrometer, the leaching rate of yttrium was 100% and nickel was 0.54%. The Y / Ni concentration ratio of the liquid after leaching was 111.

(Example 5)
The same procedure as in Example 1 was performed, except that the SOFC scrap granular solid was oxidized and roasted at 800 ° C. for 4 hours before the slurry of the SOFC scrap granular solid was produced. The leaching rate of yttrium was 100% and nickel was 0.2%. The Y / Ni concentration ratio of the liquid after leaching was 280.

(Example 6)
The leaching residue containing nickel obtained in Example 1 was dissolved in 18% dilute hydrochloric acid and then solid-liquid separated to obtain a nickel solution. The nickel leaching rate was 98%.

(Example 7)
The same procedure as in Example 1 was performed except that the pH adjusting acid solution for adjusting the pH was 100 g / L methanesulfonic acid. As a result of measuring the leached solution with an ICP mass spectrometer, the leaching rate of yttrium was 100% and nickel was 0.5%. The Y / Ni concentration ratio of the liquid after leaching was 80.

(Example 8)
The same operation as in Example 1 was carried out except that the pH was adjusted to 4.0. As a result of measuring the liquid after leaching with an ICP mass spectrometer, the leaching rate of yttrium was 100% and nickel was 0.7%. The Y / Ni concentration ratio of the liquid after leaching was 60.

(Comparative Example 1)
Except that the acid solution for pH adjustment was used in dilute sulfuric acid, the same procedure as in Example 1 was carried out. However, leaching did not proceed, and the leached solution was measured with an ICP mass spectrometer. As a result, yttrium could not be separated with high efficiency.

(Comparative Example 2)
The same procedure as in Example 4 was performed except that the time of water leaching was 2 hours. As a result of measuring the liquid after leaching with an ICP mass spectrometer, the leaching rate of yttrium was 98% and nickel was 0.61%. The Y / Ni concentration ratio of the liquid after leaching was 31.

(Comparative Example 3)
Except that the pH adjustment was carried out at room temperature, it was carried out in the same manner as in Example 1. However, leaching did not proceed and the leaching solution was measured with an ICP mass spectrometer. As a result, the yttrium leaching rate was only about 50%. Could not be separated with high efficiency.

(Comparative Example 4)
The same operation as in Example 1 was carried out except that the pH was adjusted to 1. As a result of measuring the liquid after leaching with an ICP mass spectrometer, the leaching rate of yttrium was 100%, but nickel was 20% and the Y / Ni concentration ratio was 2, and the separation between yttrium and nickel could not be improved. .

Claims (7)

  A slurry containing particulate solid of solid oxide fuel cell scrap containing at least nickel and yttrium is subjected to water leaching treatment, and pH is adjusted by adding a pH adjusting acid solution while heating the slurry at 50 ° C. or higher. Yttrium is preferentially leached and then separated into a post-leaching solution containing yttrium and a leaching residue containing nickel. Separation and recovery method.   The solid oxide form so that the yttrium leaching rate of the leached liquid containing yttrium is 90% by mass or more and the yttrium and nickel concentration ratio (Y / Ni concentration ratio) in the leached liquid is 50 or more. The method for separating and recovering yttrium and nickel from solid oxide fuel cell scraps according to claim 1, comprising leaching a slurry containing particulate solids of fuel cell scraps.   The method for separating and recovering yttrium and nickel from solid oxide fuel cell scraps according to claim 1 or 2, comprising adjusting the pH to 2 to 6 by adding the acid solution for pH adjustment.   The method for separating and recovering yttrium and nickel from solid oxide fuel cell scrap according to any one of claims 1 to 3, wherein the pH adjusting acid solution is hydrochloric acid, nitric acid or an organic acid.   The yttrium from the solid oxide fuel cell scrap according to any one of claims 1 to 4, wherein the cumulative distribution diameter (d90) of the particulate solid of the solid oxide fuel cell scrap is 1 mm or less. And nickel separation and recovery method.   6. The method according to claim 1, further comprising oxidizing and roasting the granular solid of the solid oxide fuel cell scrap before producing the solid solid slurry of the solid oxide fuel cell scrap. A method for separating and recovering yttrium and nickel from solid oxide fuel cell scraps as described.   The solid oxide according to any one of claims 1 to 6, comprising obtaining a nickel solution by solid-liquid separation after dissolving nickel by acid leaching the leaching residue containing nickel. Of yttrium and nickel from fuel cell scrap