JPH1088250A - Method for recovering valuable metal from used nickel-hydrogen secondary battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To simply and efficiently recover the valuable metal by roasting, crushing and screening a used nickel-hydrogen secondary battery, melting a magnetic attractive material in minus sieve in an oxygen-containing atmosphere and removing slag. SOLUTION: The used nickel-hydrogen secondary battery is roasted at 350-1000 deg.C in oxidizing atmosphere or non-oxidizing atmosphere at atmospheric pressure or lower and crushed. This crushed material is screened with JIS-Z880 standard screen having <=4000μm normal size and the material in the minus sieve is magnetic-separated into the magnetic attractive material and the non- magnetic material. The obtd. magnetic attractive material is melted under the atmosphere containing oxygen at 1500-2000 deg.C and the slag containing rare- earth metals is removed to recover the valuable metal concns. By this method, the valuable metals of nickel, etc., can efficiently be recovered.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for recovering valuable metals such as nickel and cobalt from a used nickel-metal hydride secondary battery.

[0002]

2. Description of the Related Art Nickel-metal hydride rechargeable batteries include 1) nickel hydroxide as an active material, a hydrogen storage alloy, 2) porous nickel as a support for the active material, 3) an organic material such as a separator, and 4) an aqueous KOH solution. 5) It is composed of an iron battery container and has excellent characteristics. Therefore, the usage of nickel-metal hydride secondary batteries has increased as a secondary battery that replaces nickel-cadmium secondary batteries, and it is highly likely that the amount of used nickel-metal hydride secondary batteries will increase in the future.

In a nickel cadmium secondary battery, a cadmium compound is used as a negative electrode active material. Therefore,
Conventionally, in order to recover valuable metals from used nickel cadmium secondary batteries, used nickel cadmium secondary batteries are heated above the boiling point of cadmium to volatilize cadmium, and then recovered as metal cadmium or cadmium oxide. A so-called distillation recovery method has been performed in which a residue obtained by volatilizing cadmium is melted and recovered as a nickel-iron mixed scrap.

By the way, since a hydrogen storage alloy is used as a negative electrode active material of a nickel-metal hydride secondary battery and cadmium is not used, the above-mentioned step of volatilizing cadmium is unnecessary.

However, there have been few concrete proposals on the method of recovering valuable metals from used nickel-metal hydride secondary batteries, and the above-mentioned conventional methods for recovering valuable metals from used nickel-cadmium secondary batteries have been used. Applied to nickel-metal hydride secondary batteries. Therefore, there were the following problems. That is, (1) The rare earth element in the hydrogen storage alloy used as the negative electrode active material is mixed into the nickel-iron mixed scrap which is melted and recovered. When a nickel-iron mixed scrap mixed with a rare earth element is used, for example, as a raw material for stainless steel, the rare earth element is also mixed in the product stainless steel to reduce the oxidation resistance of the product stainless steel, and also remove the rare earth element in the stainless steel manufacturing process. Providing a step lowers the production efficiency of stainless steel.

(2) Since nickel is recovered as nickel-iron mixed scrap, there has been a problem that the recovered nickel-iron mixed scrap is mainly limited to raw materials for steel such as stainless steel.

[0007] In order to recover valuable metals such as cobalt and nickel from used nickel-metal hydride secondary batteries,
Techniques for roasting, crushing, and sieving are disclosed in JP-A-6-346160 and JP-A-7-207349, and techniques for magnetically selecting a pulverized product are described in JP-A-6-322452 and JP-A-7-245126. No. 6,086,045.

[0008]

SUMMARY OF THE INVENTION In view of the above circumstances, the present invention provides a method of recovering a valuable metal such as nickel or cobalt from a used nickel-metal hydride secondary battery as a high-grade alloy containing no iron or rare earth elements. The purpose is to provide.

[0009]

The method of the present invention for solving the above-mentioned problems comprises the following steps: (1) to remove organic substances contained therein and to reduce nickel or cobalt contained as oxides or hydroxides to metallic nickel or metallic cobalt; To do
A step of roasting the used nickel-metal hydride secondary battery to obtain a roasted product; (2) crushing the roasted product to obtain a crushed product in order to easily remove iron from valuable metals in the next sieving step Process,
(3) a step of sieving the crushed material to obtain an upper sieve and a lower sieve;
(4) a step of magnetically separating the undersize of the sieve to temporarily remove the rare earth element to obtain a magnetically adhered substance and a non-magnetically adhered substance; and (5) a step of secondary removing the rare earth element. Melting the kimono in an atmosphere containing oxygen, removing rare earth elements as oxides in the slag, and then recovering valuable metals from used nickel-metal hydride rechargeable batteries comprising recovering metals as valuable metal concentrates Is the way.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION The used nickel hydrogen 2 of the present invention
The method of recovering valuable metals from the secondary battery includes (1) a roasting step,
It comprises (2) crushing step, (3) sieving step, (4) magnetic separation step, and (5) melting step.

(1) Roasting Step First, a used nickel metal hydride secondary battery is roasted to obtain a roasted product. This roasting is performed in order to decompose, burn or volatilize and remove the organic substances used for the separator and the like.

When the roasting atmosphere is an oxidizing atmosphere or a non-oxidizing atmosphere equal to or lower than the atmospheric atmosphere, nickel present as an oxide or hydroxide as an active material is reduced by the above-mentioned reduction action of organic substances which decompose, burn or volatilize. And cobalt are reduced to produce ferromagnetic metallic nickel and metallic cobalt.

If the roasting temperature is too low, the above-mentioned reduction does not proceed, and the recovery rate of nickel and cobalt decreases. On the other hand, if the roasting temperature is too high, the hydrogen-absorbing alloy existing as an active material and the metallic nickel dissolve, and in the subsequent step, The burden on removing rare earth elements increases. Therefore, the roasting temperature is 350-100.
The temperature is preferably set to 0 ° C.

(2) Crushing Step Next, the roasted product is crushed to obtain a crushed product. In this crushing, most of the metals constituting the nickel-metal hydride secondary battery have iron as a battery container, and the iron battery container is less susceptible to crushing than other components, and is relatively large even after crushing. Utilizing what remains as particles, it is carried out to make it easier to remove iron from nickel and cobalt in the next sieving step.

By the way, the iron battery container which is hard to be crushed is hardly crushed by ordinary crushing until it is mixed under a JIS-Z8801 standard sieve having a nominal size of 4000 μm or less (“the nominal size is 4000 μm”). The following JIS-Z8801 standard sieve is hereinafter simply referred to as "4000 μ
m or less "). Therefore, in the next sieving step, 40
Valuable metals are contained under the sieve with a sieve of 00 μm or less with good sieving properties (that is, almost no contamination of valuable metals on the sieve)
It is preferred to perform crushing to a degree. By this crushing, iron can be contained on the sieve with good sieving properties in the next sieving step (that is, almost no mixing of iron under the sieve).
If the crushing is not performed to the above degree, the valuable metal grade under the sieve obtained in the next sieving step is reduced, or the distribution ratio of the valuable metal to the sieve is reduced. This crushing method is not particularly limited as long as the battery container and other components can be separated, and there is no need to finely crush.

(3) Sieving Step Further, the crushed material is sieved to obtain an upper sieve and a lower sieve. It is preferable to use a sieve having a size of 4000 μm or less so that valuable metals in the crushed material are contained below the sieve, and iron in the crushed material is contained on the sieve with good sieving property. The sieve having a size of 4000 μm or less can be appropriately selected according to the crushing state of the crushed material. Excessively fine sieves reduce the yield of valuable metals.

The above sieve can be supplied to the nickel-iron mixed scrap processing step in the above-mentioned conventional technique.

(4) Magnetic Separation Step Since the obtained sieve is a mixture of a hydrogen storage alloy containing metallic nickel, metallic cobalt and a rare earth element, it is a ferromagnetic substance by magnetic separation in order to remove the rare earth element temporarily. Metallic nickel and metallic cobalt are separated from a non-magnetic material, a hydrogen storage alloy, as a magnetically adhered material and a non-magnetically adhered material, respectively.

Since a part of the hydrogen storage alloy is present in the electrode made of metallic nickel, it is inevitable that the hydrogen storage alloy is mixed into the magnetic material.

Since most of the non-magnetically adhered material is a hydrogen storage alloy, it can be reused as a base material of the hydrogen storage alloy. In addition, the magnetic separation step separates non-magnetically adhered substances which are mostly hydrogen storage alloys, so that the burden of secondary removal of rare earth elements from the magnetically adhered substances in the next melting step can be greatly reduced.

(5) Melting Step As described above, the magnetic substance is made of metallic nickel, metallic cobalt,
And a hydrogen storage alloy containing a rare earth element and nickel as main components, so that the magnetized material is melted in an oxygen-containing atmosphere such as an electric furnace, and the rare earth element is removed as an oxide in the slag to remove the rare earth element. Is secondarily removed.

Since the rare earth element has a very strong affinity for oxygen, it is possible to sufficiently remove the rare earth element as slag even if the atmosphere containing oxygen is simply melted in the atmosphere. By adjusting the composition by blowing air, the rare earth element can be more quickly removed.

The melting point of nickel, the melting point of cobalt, and the melting point of nickel-rare earth element alloy are each 145.
Since it is 5 ° C., 1495 ° C., and 1300 ° C. to 1400 ° C., the melting temperature needs to be 1500 ° C. or higher,
2000 ° C. or less is desirable from the viewpoint of furnace maintenance.

The metal (nickel-cobalt alloy) recovered as a valuable metal concentrate has a low content of iron and rare earth elements, and can be effectively used as a raw material for producing purified nickel and purified cobalt in existing processes. It is. Further, the slag containing the removed rare earth element can be supplied to a step of recovering the rare earth element and treated.

[0025]

EXAMPLE Ten used cylindrical nickel-metal hydride secondary batteries having a diameter of 20 mm and a height of 50 mm were allowed to stand in a tubular furnace in a nitrogen atmosphere and calcined at 800 ° C. for 30 minutes. Next, the obtained roasted product was cut using a good cutter manufactured by Ujiie Seisakusho, a kind of shear crusher, with a blade width of 10 mm and a blade gap of 0 m.
m. The crushed material has a nominal size of 4000 μm J
It was sieved with an IS-Z8801 standard sieve.

The sieve was dissolved in aqua regia and analyzed by atomic absorption spectrometry for nickel, cobalt, iron and rare earth elements (subsequent component analysis was carried out in the same manner).

[0027] The sieve was screened using a solenoid type magnetic screener manufactured by Takaha Kagaku Kogyo Co., Ltd. The magnetic force was set at 920 Oersted. The non-magnetic material was subjected to component analysis, and the magnetic material was put in an alumina crucible, melted at 1500 ° C., and reacted for 1 hour while blowing 1 liter / min of oxygen. After the reaction was completed, the cooled melt was separated into a slag component and a metal component, and the components were analyzed. Table 1 shows the results of the component analysis.

[0028]

[Table 1]

The obtained metal component containing nickel and cobalt has a low content of iron and rare earth impurities such as La, Ce, and Pr, so that purified nickel and purified cobalt can be easily obtained by an existing process.

[0030]

According to the present invention, valuable metals such as nickel and cobalt can be easily and efficiently recovered from used nickel-metal hydride secondary batteries.

Claims (6)

[Claims] 1. A step of roasting a used nickel-metal hydride secondary battery to obtain a roasted product, a step of crushing the roasted product to obtain a crushed product, and a step of sieving the crushed product to obtain an upper sieve and a lower sieve. A step of magnetically filtering under the sieve to obtain a magnetically adhered material and a non-magnetically adhered material, and melting the magnetically adhered material in an atmosphere containing oxygen to remove slag generated thereby, and then converting the metal into a valuable metal concentrate A method for recovering valuable metals from a used nickel-metal hydride secondary battery, comprising the step of recovering. 2. The used nickel-hydrogen secondary battery according to claim 1, wherein the roasting is performed in an oxidizing atmosphere or a non-oxidizing atmosphere in which the roasting atmosphere is equal to or lower than the atmospheric atmosphere, and the roasting temperature is 350 to 1000 ° C. For recovering valuable metals from coal. 3. The crushing is performed in the next sieving step to a nominal size of 40.
The method according to claim 1 or 2, wherein the valuation is performed with a JIS-Z8801 standard sieve having a size of 00 µm or less so that valuable metals are contained under the sieve with good sieving properties.
3. The method for recovering valuable metals from a used nickel-metal hydride secondary battery according to the item 1. 4. The sieve has a nominal size of 40 so that valuable metals are contained below the sieve and iron is contained on the sieve with good sieving properties.
The method for recovering valuable metals from used nickel-metal hydride secondary batteries according to claim 1, 2 or 3, wherein the method is performed with a JIS-Z8801 standard sieve having a size of 00 µm or less. 5. The melting is performed at a melting temperature of 1500 to 2000.
The method for recovering valuable metals from a used nickel-metal hydride secondary battery according to any one of claims 1 to 4, which is performed at a temperature of 0 ° C. 6. The method for recovering valuable metals from used nickel-metal hydride secondary batteries according to claim 1, wherein the oxygen-containing melting atmosphere is prepared by blowing oxygen or air.