JP4850297B2 - Method for producing hydrogen storage alloy composition - Google Patents

Description

  The present invention relates to a method for newly producing a hydrogen storage alloy composition from a used waste nickel metal hydride secondary battery.

  As a method of recovering valuable metals such as nickel, cobalt, and rare earth metals from waste nickel metal hydride secondary batteries, for example, after crushing, crushing, and sieving the battery, coarse particles (plastic, iron, nickel substrate, etc.) And fine-grained parts (nickel hydroxide, hydrogen storage alloy), the fine-grained parts are dissolved in sulfuric acid containing alkali metal, impurities are removed from the cobalt-containing nickel solution, and then electrolytically treated to obtain nickel metal And a method for recovering the nickel-cobalt alloy has been proposed (Patent Document 1).

  When recovering valuable metals from waste nickel metal hydride secondary batteries in this way, the use of recovered valuable metals is broadened by reducing the carbon content in the recovered valuable metals. It has been reported that it is preferable to reduce the carbon content in valuable metals to be recovered when recovering elements. For example, in Patent Document 2, a rare-earth element (such as La, Ce, Pr, Nd, and Sm) that is easily oxidized when a valuable material recovered in an inert gas atmosphere or a hydrogen gas atmosphere is decarbonized is relatively oxidized. The knowledge that carbon contained in the valuables can be removed without the need to do so is disclosed.

However, when recovering the constituent elements of the hydrogen storage alloy from the waste nickel metal hydride battery, if the negative electrode mainly recovered material containing a large amount of the negative electrode active material is heat-treated in a hydrogen gas atmosphere, the positive electrode active material, particularly water, contained in the negative electrode active material is slightly contained therein. Since hydroxides such as nickel oxide oxidize rare earths (La, Ce, Pr, Nd, Sm, etc.), it has been gradually found that the recovery rate of rare earths is lower than other hydrogen storage alloy constituent elements.
In view of this, the invention according to Patent Document 3 is a method for recovering a constituent element of a hydrogen storage alloy capable of maintaining a high recovery rate of rare earths, and heat-treats a negative electrode-mainly recovered material containing the constituent element of a hydrogen storage alloy in a reducing atmosphere. Proposed a method for recovering the constituent elements of the hydrogen storage alloy, including the step of reducing the hydroxide in the anode-mainly recovered material and then heating the anode-mainly recovered material in a non-oxidizing atmosphere to remove carbon. is doing.

  Patent Document 4 discloses a method for recovering a useful metal from an alkaline secondary battery using a hydrogen storage alloy as a negative electrode active material, pulverizing and / or disassembling an alkaline secondary battery using a hydrogen storage alloy as a negative electrode active material, The obtained pulverized product and / or dismantled product is thermally decomposed and reduced in the presence of a reducing agent under the condition of 200 ° C. or higher while controlling the dew point to 0 ° C. or lower. From the obtained material, zinc, lithium, potassium A useful metal recovery method that volatilizes and removes highly volatile metals such as the above and their compounds is proposed.

JP-A-9-82371 JP 2002-327215 A JP 2005-113226 A JP 2001-131647 A

  By the way, when a new hydrogen storage alloy composition is manufactured (recycled) from a waste nickel metal hydride secondary battery, a negative electrode mainly recovered material containing a large amount of a negative electrode is recovered from the waste nickel metal hydride secondary battery, and the recovered material is recovered as described above. After the reduction treatment and decarbonization treatment as described above, this is put into a molten metal of the negative electrode active material constituent element (also referred to as “alloy molten metal”), heated and melted, and the obtained molten metal is cast to obtain a new hydrogen storage alloy composition. It is conceivable to produce a product. However, when the negative electrode main body recovered material is actually put into the molten alloy and melted by heating, the problem that the dissolution of the negative electrode main body recovered does not proceed and it is difficult to increase the yield.

  Therefore, the present invention provides a new method capable of increasing the melting efficiency when the negative electrode main body recovered from the waste nickel metal hydride battery is charged into the molten alloy of the negative electrode active material constituent element and heated and melted. To do.

  The present invention relates to a negative electrode-mainly recovered material in a method for producing a hydrogen storage alloy composition by heating and dissolving a negative electrode-mainly recovered material obtained from a waste nickel metal hydride secondary battery to a molten metal composed of a hydrogen storage alloy constituent element. A method for producing a hydrogen storage alloy composition is proposed in which aluminum is added to the molten metal simultaneously or sequentially.

  When the negative electrode main body recovered from the waste nickel metal hydride secondary battery is added to the molten metal comprising the hydrogen storage alloy constituent elements, aluminum is added to the molten metal simultaneously or sequentially with the negative electrode main body recovered, so that the negative electrode main body recovered It was found that the dissolution efficiency can be dramatically increased.

  Next, as an example of a preferred embodiment of the present invention, a method for producing a new hydrogen storage alloy composition by collecting a hydrogen storage alloy constituent element from a waste nickel metal hydride battery will be described. However, the scope of the present invention is not limited to the embodiment described below.

  A method for producing a hydrogen storage alloy composition as an example of a preferred embodiment of the present invention (hereinafter referred to as “the present embodiment”) is a method of deactivating a waste nickel metal hydride battery, if necessary, A composition containing an element, that is, a negative electrode main recovery material containing a large amount of the negative electrode active material (referred to as “this negative electrode main recovery material”) is selected (negative electrode recovery step), and then a polar solution such as water if necessary. The negative electrode mainly recovered material is washed to reduce the alkali metal salt concentration (cleaning step), and further dried as necessary (drying step), and then the positive electrode active material contained in the negative electrode mainly recovered material (Reduction process), and then carbon is removed from the main negative electrode recovery (decarbonization process), and the resulting negative electrode main recovery is combined with aluminum and a molten metal composed of hydrogen storage alloy constituent elements (“alloy melt”). In addition to dissolution by heating (Dissolution step), and, (casting process) by casting the negative electrode mainly recovery, etc. dissolved as needed, a method of producing a new hydrogen absorbing alloy composition.

  Here, in the present invention, the “negative electrode mainly recovered material” means a recovered material containing a large amount of the negative electrode active material. Specifically, the negative electrode constituent material is 50% by mass or more, preferably 50% by mass of the negative electrode active material. As described above, particularly preferably, the recovered material contains 80% by mass or more of the negative electrode active material, and also includes a recovered material made of a negative electrode constituent material.

(Negative electrode recovery process)
In order to selectively collect and recover the main negative electrode recovered material from the waste nickel metal hydride battery, for example, the waste nickel metal hydride battery is deactivated and then disassembled, and the main negative electrode recovered material containing a larger amount of the constituent elements of the hydrogen storage alloy. Can be sorted and recovered.

  The method for recovering the main negative electrode collection from the nickel metal hydride battery may be performed in the same manner as in the conventional method. For example, after the battery is deactivated, it is crushed using a shear crusher, pulverized by a wet method using a pulverizer, and then classified by a predetermined sieve (for example, 24 mesh). As such, the negative electrode mainly recovered material can be selected. In general, after classification, the finer ones contain more negative electrode active material and the coarser ones contain more positive electrode active material. However, the method for recovering the main negative electrode collection material is not limited to this method.

It is important that the negative electrode active material is a hydrogen storage alloy containing misch metal (also referred to as “Mm”), and is preferably a hydrogen storage alloy containing misch metal and nickel. More specifically, AB ₅ type hydrogen storage alloy containing Mm, AB ₂ type hydrogen storage alloy containing Mm, among them, for example, containing Ni and Al as B site metals, in addition to Mn, Co, Examples of the alloy include any one of Fe, Ti, Mg, V, Zn, and Zr, or a combination of two or more of these.
Misch metal (Mm) is an alloy containing a rare earth element (rare earth). In the AB ₅ type hydrogen storage alloy, it is a metal constituting the A site. In the present invention, La, Ce, Nd And an alloy containing one or more of the group consisting of Pr.

  To deactivate a battery means not to function as a battery. As a method of deactivation, there are arbitrary methods such as a method of freezing the electrolyte solution with liquid nitrogen or a refrigerator to make it non-functional, or a method of intentionally short-circuiting in an acidic solution.

(Washing process)
In most nickel metal hydride batteries, an alkaline aqueous solution containing potassium hydroxide is used as the electrolytic solution, and therefore there is a possibility that the alkaline aqueous solution is adhered to the negative electrode main recovery material. When heat treatment is performed on the negative electrode main body recovered with the alkaline aqueous solution, the misch metal (Mm) is oxidized to reduce the recovery rate of the misch metal (Mm), and the solubility is lowered in the subsequent dissolution step. Since dross may occur, it is preferable to remove the alkali metal salt from the negative electrode main body recovered in advance before the reduction step.

As a method for removing the alkali metal salt, an alkaline substance such as potassium hydroxide (KOH) is obtained by washing the negative electrode mainly recovered with a polar solution such as water at 0 ° C. to 100 ° C. or a weakly acidic aqueous solution. It is preferred to remove the metal salt. At this time, it is preferable to repeat the washing treatment as necessary.
However, other methods may be adopted as long as an alkali metal salt such as potassium hydroxide (KOH) can be removed.

  After this step, the K content is preferably less than 0.02%, particularly preferably less than 0.015%, and particularly preferably less than 0.01%. If the amount of K is less than 0.02%, the yield can be further improved, and the surface of the alloy is hardly oxidized due to deliquescence. Therefore, it is necessary to control the dew point of the atmosphere to 0 ° C. or lower in the subsequent hydroxyl group removal step. There is no.

(Drying process)
In the case where the negative electrode main product is washed with water or other polar solution as described above, it is preferable to perform drying thereafter.
The water or other polar solution adhering in the above step can be removed in the next reduction step, so that this drying step can be omitted, but the target substance to be reduced in the next step is Because of the difference, it is preferable to interpose this drying step in view of efficiency.

  The drying method is arbitrary and may be naturally dried or may be stored or passed through a drying apparatus and dried.

(Reduction process)
Next, the negative electrode-mainly recovered material is heat-treated in a reducing atmosphere to reduce the positive electrode active material, particularly hydroxides, particularly nickel hydroxide (eg, NiOOH), cobalt hydroxide, etc. contained in the recovered material. It is preferable to do this.

As a reduction method, heat treatment may be performed in a reducing atmosphere. Preferably, heating is performed in a hydrogen atmosphere at 100 ° C. to 350 ° C., preferably 160 ° C. to 240 ° C., and more preferably 200 ° C. ± 20 ° C. At this time, if the heating temperature is 100 ° C. or higher, the reaction rate is not significantly reduced. Further, if the heating temperature is 220 ° C. or less, the oxidation of rare earth can be prevented by about 100%. However, if estimated from the peak intensity of CeO ₂ by X-ray diffraction, about 10% of the rare earth at 250 ° C. Since about 20% may be oxidized at 400 ° C., it is preferable to promote the reaction by heating at a temperature up to 350 ° C. when at least about 20% rare earth oxidation loss is allowed.
The hydrogen atmosphere is preferably an atmosphere made of high-purity hydrogen gas with little oxidizing impurities such as moisture and oxygen, but is not particularly limited.

As the reaction apparatus, either a closed type that seals gas or a fluid type that flows gas can be used, but in the case of a closed type, the partial pressure of the reducing gas gradually decreases due to water vapor or the like. Industrially, the fluid type is preferable.
The heating means may be any of electric heating, gas combustion heating, and other heating means.
In addition to hydrogen gas, ammonia decomposition gas and other gases can be used as the reducing gas. However, carbon monoxide cannot reduce Ni and Co at 450 ° C. or lower. Hydrogen gas is particularly preferable because it can be used in a decarbonization step of the next step and can be processed in a common reactor (one furnace).

(Decarbonization process)
Next, the negative electrode main recovered material reduced as described above is heat-treated in a non-oxidizing atmosphere to remove at least part of the carbon contained in the negative electrode main recovered material by converting it into a hydrocarbon gas. It is preferable to do this.

  The non-oxidizing atmosphere means an atmosphere in which carbon can be removed by reduction or the like without substantially oxidizing metal or alloy by heating, and an inert gas atmosphere, a hydrogen gas atmosphere, a water vapor atmosphere, or an inert gas-water vapor. It can be appropriately selected from an atmosphere and an inert gas-water vapor-hydrogen gas atmosphere. The inert gas includes argon, nitrogen, helium and the like, and the non-oxidizing atmosphere is particularly preferably a hydrogen gas atmosphere which is a reducing atmosphere.

  The heating conditions in the decarbonizing step are preferably 350 to 1050 ° C. and 5 minutes to 10 hours. At this time, the reaction rate can be increased by heating at 750 ° C. or higher.

  By heat treatment under an inert gas atmosphere, oxygen, hydrogen, and water vapor contained in the negative electrode main recovery material act reductively or oxidatively, and at least a part of carbon is used as a gas such as hydrocarbon or carbon dioxide. Can be removed. In the hydrogen gas atmosphere, at least a part of the carbon in the negative electrode mainly recovered product is reduced by hydrogen, converted into lower hydrocarbons, etc., and removed from the recovered product.

  By performing the decarbonization process in this way, the carbon concentration can be reduced to 1000 ppm (0.1 mass%) or less, and depending on conditions, to 100 ppm (0.01 mass%) or less.

(Dissolution process)
Next, it is important to add and heat-melt aluminum together with the negative electrode main body recovery material, that is, simultaneously or sequentially with the negative electrode main body recovery material, to the molten alloy composed of the hydrogen storage alloy constituent elements. It is preferable to prepare (referred to as “composition preparation”) so as to obtain a desired composition in the process.

  At this time, as means for adding aluminum to the molten alloy simultaneously or sequentially with the negative electrode main recovery material, for example, aluminum (Al) may be mixed with the negative electrode main recovery material and added to the molten alloy in a mixed state. Alternatively, aluminum may be added to the molten alloy first, and immediately after that, the negative electrode main recovered material may be sequentially added to the molten alloy, or the negative electrode main recovered material may be added to the molten alloy first and immediately thereafter. Aluminum may be sequentially added to the molten metal. In any case, in the molten alloy, it is important that the negative electrode mainly recovered material is present in the vicinity of the aluminum melted in the molten metal.

  In addition, aluminum is added to the molten metal first, and the negative electrode main body recovered material is sequentially added to the molten metal “immediately after that”, or the negative electrode main body recovered material is first added to the molten metal, and “immediately thereafter” the molten aluminum material is molten. “Immediately” in the case of sequentially adding to each other means that any of them added first will float on the molten metal for a certain period of time, so that they are preferably added within the floating range while they are floating It is.

An apparatus (including a furnace) for performing heating and melting is arbitrary. For example, heat melting can be performed using a high frequency melting furnace or a low frequency melting furnace.
Moreover, the molten alloy to which the present negative electrode mainly recovered material is added may be a molten metal composed of a hydrogen storage alloy constituent element, and the composition thereof can be adjusted as appropriate. Even a molten metal obtained by melting the negative electrode active material may be a molten metal made of a mother alloy for producing the negative electrode active material.

  In this way, by adding aluminum to the molten alloy at the same time or sequentially with the main negative electrode recovered material and dissolving it by heating, the dissolution efficiency of the main negative electrode recovered material, in particular, the dissolution rate can be significantly increased. Although the reason why the dissolution efficiency is increased has not been investigated, it can be inferred as follows. That is, it is considered that the negative electrode mainly recovered material is added to the molten alloy and melted, not simply being melted by heat, but the oxides on the surface are reduced and dissolved in the molten metal. Aluminum has a relatively low melting point among the constituent elements of hydrogen storage alloys. In addition, when dissolved, it has the property of reducing the metal oxide with high reaction heat. Therefore, the viscosity of the molten metal is reduced by the aluminum melted in the high-temperature molten metal, and the main negatively recovered material in the mixed state is reduced by the heat of reaction at the time of melting, and the dissolution efficiency of the negatively recovered material is dramatically increased. Can be inferred.

The aluminum added to the molten alloy together with the negative electrode main body recovered may be metal aluminum or an aluminum alloy. From the viewpoint of the effect, metal aluminum is more preferable.
The aluminum added to the molten alloy together with the negative electrode main body recovered is preferably granular or powdery, among which aluminum particles are classified using a sieve having a particle size of 2 mm to 10 mm, that is, a mesh size of 2 mm to 10 mm. Preferably there is.
At this time, the amount of aluminum to be added is preferably 10% by mass or more, particularly 20% by mass or more, particularly 30% by mass or more of the negative negative electrode main body recovery material from the viewpoint of increasing the dissolution rate of the main negative electrode main body recovery material. .

When this negative electrode mainly recovered material and aluminum are mixed and added to the molten alloy in a mixed state, it may be poured directly into the molten alloy in the mixed state. However, when it is poured into the molten metal as it is, the mixture floats on the molten metal. It is even more preferable to bundle the mixture into a molten metal with a member composed of one or more of hydrogen-absorbing alloy constituent elements such as aluminum, nickel, and magnesium. .
At this time, the shape of the member for bundling the negative electrode mainly collected material is not particularly limited, and may be, for example, a bag shape, a cylindrical shape, a string shape, a band shape, a ribbon shape, or other shapes, such as a net or a foil. You may make it wrap. Specifically, the mixture may be wrapped in aluminum foil and poured into the molten metal.

The temperature at which the negative electrode main product is melted, in other words, the melt temperature of the molten alloy is preferably 1200 to 1600 ° C, particularly 1300 to 1550 ° C, and particularly preferably 1400 to 1500 ° C.
Moreover, it is preferable to perform a melt | dissolution process in inert gas atmosphere, such as in argon, in order to suppress the oxidation of a valuable metal, ie, a hydrogen storage alloy constituent element.

In addition, when the composition is prepared in this melting step, the element amount of the negative electrode main recovery material is analyzed in advance, the element amount of the negative electrode main recovery material, the amount of Al added together with the negative electrode main recovery material, The composition and amount of the molten alloy, the amount of Al added together with the main negative electrode recovery, and the input amount of the main negative electrode recovery so that the total value of the element amount of the molten alloy is the target product composition Is preferably adjusted.
In addition, when bundled with a member consisting of one or more hydrogen storage alloy elements and put into the molten metal, it is preferable to analyze the element amount of the member to be bundled and adjust the total element amount added thereto. .
At this time, after adding Al together with the negative electrode main body recovered and heating and dissolving in a short time, a hydrogen storage alloy constituent element such as Ni or Co is further added to adjust the target composition. Good.

(Casting process)
In the melting step, the molten metal obtained by heating and melting the main negative electrode recovered material can be poured into a mold as necessary and cast into a desired shape.
However, the casting process can be omitted.
Further, for example, the production purpose of this embodiment is not to produce a mother alloy, that is, a hydrogen storage alloy that can be used as a negative electrode active material as it is, but a hydrogen storage alloy is manufactured by adjusting the composition by appropriately adding components later. In the case of manufacturing an alloy as an intermediate material (referred to as “mother alloy”), it can be cast as described above, or once the molten alloy of the mother alloy is manufactured, The composition can be appropriately casted to prepare a hydrogen storage alloy composition, and then cast as described above.

  Also in the casting process, it is preferable to perform in an inert gas atmosphere such as in argon in order to suppress oxidation of valuable metals, that is, hydrogen storage alloy constituent elements.

(Hydrogen storage alloy composition as a product)
The hydrogen storage alloy composition produced in the present embodiment can be made into a hydrogen storage alloy composition that can be used as a negative electrode active material of a nickel-metal hydride battery by the above-described composition preparation. It can also be set as the hydrogen storage alloy composition which can be utilized as a mother alloy for negative electrode active materials.
When producing a hydrogen storage alloy composition that can be used as a negative electrode active material of a nickel metal hydride battery, appropriate components such as La, Ce, Nd, Pr, Ni, Al, Mn, Co, Fe, Ti, V, Zn, Mg, Cu, Y, Rb, Gd, Tm, Lu, Zr, etc., or a combination of two or more of these is added and melted to produce an alloy. What is necessary is just to manufacture the hydrogen storage alloy composition which can be utilized as.

(Other)
In this embodiment, the raw material recovered from the waste nickel metal hydride battery is used as a starting material. However, a member composed of one or more hydrogen storage alloy elements and a hydrogen storage alloy layer is selectively extracted. If possible, it is not limited to the raw material taken out from the waste nickel metal hydride battery. For example, in heat pumps, storage devices for natural energy such as solar and wind power, hydrogen storage devices, actuators, fuel cells, etc., a member consisting of one or more hydrogen storage alloy elements and a hydrogen storage alloy layer is selected. It can be used as a starting material if it can be taken out.

(Explanation of terms)
In the present invention, the “hydrogen storage alloy” means an AB ₅ type alloy represented by LaNi ₅ , an AB ₂ type alloy represented by ZrV _0.4 Ni _1.5 , an AB type alloy or an A ₂ B type ( A variety of alloys such as alloys including A ₂ B _{7 are} included.
The “hydrogen storage alloy constituent element” means an element composed of one or a combination of two or more of the elements constituting the hydrogen storage alloy. Among them, an AB ₅ type hydrogen storage alloy having a CaCu ₅ type crystal structure, specifically, Mm (Misch metal), which is a rare earth-based mixture, is used at the A site, and metal elements such as Ni, Al, Mn, and Co are used at the B site. A hydrogen storage alloy using bismuth and its constituent elements are preferred as the object of the present invention.
The “hydrogen storage alloy composition” is a composition composed of a hydrogen storage alloy constituent element, and the shape thereof may be any of a block shape, a molded body shape, and a powder shape.

In addition, in the present invention, when “X to Y” (X and Y are arbitrary numbers) is described, it means “X or more and Y or less” unless otherwise specified. It includes the meaning of “small”.
Furthermore, when “X or more” (X is an arbitrary number) or “Y or less” (Y is an arbitrary number) is described, it is “preferably greater than X” or “preferably less than Y”. The intention of

  EXAMPLES Hereinafter, although this invention is demonstrated based on an Example, this invention is not limited to an Example.

<Quantitative elemental analysis>
Put 0.2 g of a measurement sample (hydrogen storage alloy composition) in a 250 ml beaker, add 10 ml of nitric acid to dissolve it with heating, add 10 ml of hydrochloric acid to completely dissolve it, and then transfer it to a 100 ml volumetric flask. Water was added to obtain 100 ml of an aqueous solution. The aqueous solution was diluted 50 times, and each element was quantified using an ICP emission spectrometer (model SPS-3100 manufactured by SII Nanotech).

<Measurement of carbon concentration>
The carbon concentration of the measurement sample (hydrogen storage alloy composition) was measured on a sample weighed to 0.5 g. However, the measurement of the negative electrode mainly collected material was performed on a sample weighed to 0.2 g because the sample board was damaged due to a rapid exothermic reaction during sample combustion. The analyzer and measurement conditions are as follows.

・ Analyzer: Carbon analyzer in solids (Horiba, EMIA-110)
・ Carrier gas: Oxygen (purity 99.95% or more), gas pressure 0.75 ± 0.05kgf / cm ²
・ Measurement conditions: Standard setting conditions described in the EMIA-110 instruction manual (combustion setting time is changed to 60 seconds)

<Oxygen concentration measurement>
The oxygen concentration of the measurement sample was measured under the following conditions using the following analyzer for the sample weighed to 0.02 g.

・ Analyzer: Solid oxygen oxygen analyzer (Horiba, EMGA-620W)
・ Carrier gas: He (purity 99.995% or more), gas pressure 0.35 ± 0.02Mpa
・ Crucible: Graphite crucible ・ Measurement conditions: Standard setting conditions described in the EMGA-620W instruction manual (1 mode analysis conditions (1) 5.00, 500 kW; changed to 75 sec)
・ Measurement mode: STANDARD BLOCK operation mode in BLOCK mode

Example 1
A used waste nickel metal hydride battery is frozen and deactivated with liquid nitrogen, dry crushed using a biaxial shear crusher, then crushed by a wet method using a crusher, and then washed with water. Plastic, paper, and the like were removed, and then classified with a sieve (28 mesh). The unclassified material on the sieve was magnetically sorted with 2000 to 3000 gauss to remove the negative electrode Fe substrate. The classified product under the sieve was a negative electrode active material-based recovered material (negative electrode-based recovered material) in which the negative electrode hydrogen storage alloy was concentrated.

In this negative electrode mainly recovered material (also referred to as “recycled raw material”), the ratio of the negative electrode active material was 88 mass%, the remainder was mixed with the positive electrode active material, and the Co concentration was 9.6 mass%.
In addition, as a result of chemical analysis (ICP method and carbon analyzer) of the concentration of each element in the negative electrode main collection (recycled raw material), the mass% of each element amount is: Mm: 30.6%, Ni: 52.7% , Mn: 4.4%, Al: 1.5%, Co: 9.6%, C: 1.2%. The oxygen concentration was 5.0%. Mm is a misch metal that is a rare earth mixture of La, Ce, Nd, and Pr, and the amount of each component in Mm (mass% in the recovered material) is La: 10.3%, Ce: 14. The results were 3%, Nd: 4.5%, and Pr: 1.5%.

The negative electrode mainly recovered material (recycle raw material) obtained in this way was used in a high-purity hydrogen atmosphere (H ₂ 99.9999999%, O ₂ <0.02 ppm, H ₂ O (dew point)) using a fluid rotary furnace (1 rpm). Heat treatment at −80 ° C., CO ₂ <0.01 ppm) at 200 ° C. for 3 hours to reduce the positive electrode active material mixed in the negative electrode main body recovered, followed by 900 ° C. in the hydrogen atmosphere, The carbon was removed by heat treatment for 1 hour to obtain a treated negative electrode main body recovered material.
The obtained treated negative electrode main product had a carbon concentration of 0.03% and an oxygen concentration of 4.0%.

  200 g of the above treated negative electrode main body recovered material and 162.8 g of granular aluminum having a particle size of 2 mm to 10 mm classified by a 2 mm mesh sieve and a 10 mm mesh sieve are mixed, and 362.8 g of the mixture in a mixed state is 2 etc. Each was wrapped in aluminum foil (3.7 g). Two packages wrapped with aluminum foil in this way were set in a raw material charging container in a high frequency induction furnace chamber.

On the other hand, molten alloy was prepared as follows using a high-frequency induction furnace chamber.
That is, the mass ratio of each element is Mm (Mm is a misch metal that is a rare earth mixture of La, Ce, Nd, and Pr, etc.), and the amount of each component in Mm (in the recovered material) %), La: 11.0%, Ce: 15.4%, Nd: 5.0%, Pr: 1.6%): 33.12%, Ni: 59.7%, Mn : Each elemental metal was weighed and mixed so as to be 5.2% (the balance was Al added). The obtained mixture is put in a crucible and fixed to a high-frequency induction furnace, and after that, the pressure is reduced to 10 ⁻⁴ to 10 ⁻⁵ Torr, argon gas is introduced, and the alloy is heated and melted at 1400 ° C. in an argon gas atmosphere. A molten metal was prepared.

  The mixture wrapped in aluminum foil from the above-described raw material charging vessel was charged into the molten alloy surface thus prepared, and was heated and dissolved in an argon gas atmosphere. About 9 kg of the obtained molten metal was poured at a rate of 4 kg / second into a water-cooled copper mold having a total mass of 200 kg and cooled to room temperature (casting). The obtained alloy lump was roughly crushed with a jaw crusher and then pulverized and classified with a disk mill to produce a product (hydrogen storage alloy composition).

  When the obtained product (hydrogen storage alloy composition) was quantitatively analyzed, Co: 0.15 mass%, La: 10.49 mass%, Ce: 15.47 mass%, Nd: 4.95 mass%, They were Pr: 1.61 mass%, Ni: 60.2 mass%, Al: 1.87 mass%, Mn: 5.26 mass%.

(Comparative Example 1)
In Example 1, a product (hydrogen storage alloy composition) was obtained in the same manner as in Example 1 except that granular aluminum was not mixed in the treated negative electrode main body recovered material (aluminum foil was naturally used).

  When the obtained product (hydrogen storage alloy composition) was analyzed by ICP, Co: 0.05% by mass, La: 10.93% by mass, Ce: 15.46% by mass, Nd: 4.80% by mass, Pr : 1.54% by mass, Ni: 60.1% by mass, Al: 1.85% by mass, and Mn: 5.27% by mass.

(Example 2-6 / Comparative Example 2)
The product (hydrogen storage alloy composition) in the same manner as in Example 1 except that the amount of granular aluminum added, the mass of the aluminum foil enclosing it, and the composition of the molten alloy to which these were added were changed as shown in Table 2. Got.
When the obtained product (hydrogen storage alloy composition) was analyzed by ICP, the results were as shown in Table 1 below. Each numerical value of Table 1 is mass%.

The dissolution rate (mass%) of the treated negative electrode main body recovered in Table 2 below is a value calculated by the following formula.
Co dissolution rate (%) = (Co content in the hydrogen storage alloy composition after casting / Co content in the recycled material) × 100

(Discussion)
As a result, when the negative electrode mainly recovered material is introduced into the molten alloy composed of the hydrogen storage alloy constituent elements, the melting efficiency of the negative electrode mainly recovered material is dramatically increased by introducing aluminum into the alloy molten metal together with the negative electrode mainly recovered material. I found out that I could do it.
As a result of observing the state that the negative electrode main body recovered melts, the input aluminum melts and floats on the molten metal to form an aluminum film, and the aluminum film reacts with the negative electrode main body recovery to recover the negative electrode main body. It was found that dissolution of the product was promoted.
Further, it was found that the amount of aluminum to be added is preferably 10% by mass or more, particularly 20% by mass or more, and particularly preferably 30% by mass or more with respect to the recovered material mainly composed of the negative electrode active material.
In addition, in the said Example, although it deactivated with liquid nitrogen, it has confirmed that the same effect is acquired also when it freezes with -150 degreeC refrigerator and deactivated.

Furthermore, about Example 2-6 and Comparative Example 2, the result of having examined the dissolution rate of Mm is shown in Table 3.
In Table 3, the dissolution rate (%) of Ce and La was calculated as follows.
Ce dissolution rate (%) = (Ce content in the hydrogen storage alloy composition after casting / Ce content in the recycled material) × 100
La dissolution rate (%) = (La content in hydrogen storage alloy composition after casting / La content in recycled material) × 100

(Discussion)
From this, when the negative electrode main body recovery material is thrown into the molten alloy composed of the hydrogen storage alloy constituent elements, the misch metal (Mm) is dissolved in the negative electrode main body recovery material by introducing aluminum into the molten alloy together with the negative electrode main body recovery material. It was found that the recovery rate of misch metal (Mm) can be dramatically increased.
In the above examples, La and Ce were tested, but almost the same effect could be confirmed for Nd and Pr.

Claims (4)

  In the method of producing a hydrogen storage alloy composition by adding a negatively recovered material obtained from a waste nickel metal hydride secondary battery to a molten metal composed of a hydrogen storage alloy constituent element and heating and dissolving the same, sequentially or sequentially with the negative electrode recovered material A method for producing a hydrogen storage alloy composition, comprising adding aluminum to the molten metal.   The discarded nickel metal hydride battery is disassembled, and the negative electrode-mainly collected material selected and recovered from the battery is heat treated in a reducing atmosphere to reduce the hydroxide in the recovered material, and then the recovered material is removed. The method for producing a hydrogen-absorbing alloy composition according to claim 1, wherein aluminum is added to the molten metal simultaneously or sequentially with a negative electrode main body recovered after heating in an oxidizing atmosphere to remove carbon. A negative electrode recovery step of selecting the negative electrode main recovery from the waste nickel metal hydride battery, a reduction step of reducing the positive electrode active material contained in the negative electrode main recovery, and a decarbonization step of removing carbon from the negative electrode main recovery; Simultaneously or sequentially with the negative electrode main recovery material, aluminum is added to the molten metal composed of the hydrogen storage alloy constituent element and heated and dissolved, and the hydrogen storage unit includes a casting process for casting the main negative electrode main recovery material and the like. A method for producing an alloy composition. After deactivating the waste nickel metal hydride battery, a negative electrode recovery step of selecting the negative electrode main recovery material, a cleaning step of reducing the alkali salt of the negative electrode main recovery material with a polar solution, and a drying step of drying next, A reduction step of reducing the positive electrode active material contained in the negative electrode main recovery material, a decarbonization step of removing carbon from the negative electrode main recovery material, and aluminum in the hydrogen storage alloy constituent element simultaneously or sequentially with the negative electrode main recovery material A method for producing a hydrogen-absorbing alloy composition, comprising: a melting step of heating and melting in addition to a molten metal comprising: a casting step of casting the melted main negative electrode recovered material and the like.