JP4398021B2 - Method for recovering useful metals from alkaline secondary batteries - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method for recovering a useful metal from an alkaline secondary battery that recovers a useful metal that can be used as a raw material for the hydrogen storage alloy from an alkaline secondary battery using a hydrogen storage alloy as a negative electrode active material.
[0002]
[Prior art]
In recent years, metal hydride secondary batteries (hereinafter sometimes referred to as MH batteries) using a hydrogen storage alloy such as a rare earth metal-nickel alloy as a negative electrode active material have been used as high-capacity batteries to replace nickel-cadmium secondary batteries. Attention has been paid. Since the MH battery uses a hydrogen storage alloy as the negative electrode active material, it does not contain cadmium, which is a pollutant, unlike the nickel-cadmium battery, and is an environmentally friendly battery.
Hydrogen storage alloys as negative electrode active materials used in MH batteries contain a lot of expensive metals such as rare earth metal elements, nickel, cobalt, titanium, zirconium, vanadium, etc., so those useful metals from MH batteries after use etc. Various methods have been proposed in the past for recovering.
[0003]
For example, methods have been proposed in which a positive electrode active material and a negative electrode active material are separately recovered from a MH battery by specific gravity difference separation (Japanese Patent No. 2866005, Japanese Patent Laid-Open Nos. 10-189063, and 10-21969). . This method can separate and recover the active material of each electrode, but for that purpose, it is necessary to first separate only the active material, after the crushed battery is washed and sieved dry, Many steps are required, such as sieving again with a wet method, separating the active material and the others, and then separating the active material of the positive electrode and the negative electrode by separation of specific gravity. In addition, in the case of a used battery, the collected negative electrode active material is often difficult to use as a negative electrode active material as it is because the hydrogen storage alloy is often deteriorated due to oxidation or the like. Since the conductive auxiliary agent, the binder, and the like that are present cannot be separated, more steps are required for use as a raw material alloy, which is complicated and expensive.
Further, as a method of recovering the active material component as a salt, a method of recovering the rare earth metal component selectively in the form of fluoride or sulfuric acid double salt by dissolving the mixed active material of the positive electrode and the negative electrode with an acid (Japanese Patent Laid-Open No. 6-1994) No. 340930, JP-A-9-82371) and a method of selectively eluting rare earth metal components from a mixed active material of a positive electrode and a negative electrode and recovering them (JP-A-9-217133) have been proposed. In these methods, the battery is disassembled and separated into the active material and the rest, and then the active material is dissolved once to form a solution, which is separated and recovered for each element using a fractional precipitation method or a selective dissolution method. There is an advantage that it can be recovered with high purity. However, many processes and auxiliary materials are required, and in order to use as a raw material for the hydrogen storage alloy, it is necessary to start from reducing each compound, which requires many processes, and is complicated and costly. Take it.
Furthermore, as a method of recovering the active material component as an alloy, the negative electrode active material is separated from the battery and then dissolved, oxygen is introduced into the molten metal, and the rare earth metal component is recovered as an oxide, and the other components are recovered as metal. (Japanese Patent Laid-Open No. Hei 8-143984, Japanese Patent Laid-Open No. 9-71825) or a method in which a negative electrode active material is dissolved in a vacuum and then deoxygenated by adding a rare earth metal to improve the quality (Japanese Patent Laid-Open No. 10-30132) Etc. have been proposed. These methods require a step of separating the negative electrode active material from the battery and are not applicable to the positive electrode active material.
[0004]
[Problems to be solved by the invention]
Therefore, an object of the present invention is to provide a useful metal recovery method capable of recovering useful metals that can be used as raw materials for hydrogen storage alloys from an alkaline secondary battery using a hydrogen storage alloy as a negative electrode active material by a simple method. There is to do.
[0005]
[Means for Solving the Problems]
As a result of diligent investigations to solve the above problems, the present inventors firstly used a useful metal with few impurities that can be used as a raw material for a hydrogen storage alloy without separating the positive electrode and negative electrode active materials from the battery. The recovery method was focused on the reduction firing method. Then, by maintaining the atmosphere and temperature in the system in a specific range step by step, it is found that moisture removal, metal reduction, and removal of highly volatile metals can be performed in the same system to complete the present invention. It came.
That is, according to the present invention, a useful metal recovery method from an alkaline secondary battery using a hydrogen storage alloy as a negative electrode active material, the alkaline secondary battery using a rare earth-based hydrogen storage alloy as a negative electrode active material, And / or heating step (a) and the pulverized product and / or disassembled product obtained in step (a) in the presence of a reducing agent while controlling the dew point to 0 ° C. or lower under the condition of 200 ° C. or higher. A step (b) of decomposing and reducing, and a step (c) of volatilizing and removing a highly volatile metal such as zinc, lithium and potassium and a compound thereof from the material obtained in the step (b) at a temperature of 800 ° C. or higher. A useful metal recovery method from an alkaline secondary battery for recovering a useful metal that can be used as a raw material for a rare earth-based hydrogen storage alloy is provided.
[0006]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, the present invention will be described in more detail.
In the recovery method of the present invention, first, the step (a) of pulverizing and / or disassembling an alkaline secondary battery using a rare earth-based hydrogen storage alloy as a negative electrode active material is performed.
In the step (a), the alkaline secondary battery is not particularly limited as long as it uses a rare earth-based hydrogen storage alloy as a negative electrode active material, and normally used batteries can be used. The hydrogen storage alloy is usually composed of an alloy containing a rare earth metal and a transition metal.
[0007]
The battery can be crushed and / or disassembled (hereinafter sometimes simply referred to as crushing) using a known crushing and disassembling method. In batteries using rare earth hydrogen storage alloys, the hydrogen storage alloys are easily oxidized, and charged hydrogen storage alloys may ignite, so they should be crushed and disassembled in an inert gas atmosphere or wet. It is particularly preferable to carry out at around room temperature.
The size to be crushed is not particularly limited. Considering the efficiency of the next step (b), it is better to finely pulverize the surface area, but it is better to make it easier to separate the battery can body and the like. Therefore, in consideration of the balance of both, it is usually preferable to crush in a range of about 3 to 10 mm.
[0008]
In the recovery method of the present invention, next, the pulverized product and / or the disassembled product obtained in step (a) are heated in the presence of a reducing agent while controlling the dew point to 0 ° C. or lower under the condition of 200 ° C. or higher. Step (b) of decomposing and reducing is performed.
In step (b), moisture contained in the crushed material and dismantled material is removed while suppressing oxidation of the metal such as hydrogen storage alloy, and at the same time, transition metal compounds such as nickel, cobalt, and zinc are reduced to metal. To do.
[0009]
The reducing agent used in the step (b) is not particularly limited as long as it can reduce the above-mentioned transition metal compound. Preferred examples thereof include carbon for solids, and hydrogen gas and carbon monoxide gas for gases. These reducing agents may be used alone or in combination.
In the step (b), in the presence of the reducing agent, the pulverized product and / or the disassembled product obtained in the step (a) is thermally decomposed under the condition of 200 ° C. or higher and controlling the dew point to 0 ° C. or lower. And need to be reduced.
When the dew point is higher than 0 ° C., a metal such as a hydrogen storage alloy is violently oxidized. The dew point is preferably −5 ° C. or lower, more preferably −10 ° C. or lower. The dew point can be controlled by dilution with gas or reduced pressure.
The dew point must be controlled at 200 ° C. or higher, preferably 300 ° C. or higher, more preferably 400 ° C. or higher in order to advance the reduction reaction. When the temperature is lower than 200 ° C., it may take time for water removal or reduction reaction, or the reaction may not proceed. On the other hand, when the temperature is too high, it becomes difficult to control the dew point, so 800 ° C. or lower is preferable, preferably 700 ° C. or lower, more preferably 600 ° C. or lower.
[0010]
In step (b), the dew point in the atmosphere can be controlled by temperature and pressure control as described above, and can be controlled while measuring with a normal dew point meter. At this time, the reduction reaction is almost completed at the time when a sudden pressure drop or dew point decrease is observed after the dew point becomes substantially constant without control, so the next step is performed. Can move.
[0011]
When the water content of the crushed material and the dismantled material used in step (b) is large, it may be difficult to control the dew point even under the above temperature conditions. For example, moisture is removed at a temperature lower than 200 ° C. After that, the dew point may be controlled by setting the temperature to 200 ° C. or higher, or after the dehydration treatment after the completion of the step (a), the dew point may be used.
[0012]
In the recovery method of the present invention, next, a step (c) of volatilizing and removing a highly volatile metal such as zinc, lithium and potassium and its compound from the material obtained in the step (b) is performed.
In the step (c), volatile removal of highly volatile metals such as lithium, potassium and zinc and their compounds contained in the reduced product obtained in the step (b) is mainly performed. By the step (c) , the highly volatile metal that is unnecessary to be usable as a raw material for the hydrogen storage alloy can be removed to a level that can be a raw material for the hydrogen storage alloy by a simple method. Further, the step (c), for example, in the case of performing step (b) is firing furnace or the like, it is possible to line Ukoto in the same system.
[0013]
In the step (c), the conditions for volatilizing and removing the highly volatile metal and its compound are usually 800 ° C. or higher, preferably 900 ° C. or higher, particularly preferably 1000 ° C. or higher. If the temperature is low, it takes time to remove the volatilization, and further, there is a possibility that sufficient removal cannot be performed.
[0014]
Step (c) is preferably performed under reduced pressure in a non-oxidizing atmosphere in order to efficiently remove highly volatile metals and the like. The atmosphere gas may be an inert gas, and when the reduction product in the step (b) is not sufficiently reduced, a reducing gas such as hydrogen gas can be used. In addition, when the pressure is high, it may take time for volatilization removal or may not be sufficiently removed. Therefore, the condition is usually 10 kPa or less, preferably 1 kPa or less, more preferably 600 Pa or less, and still more preferably 200 Pa or less is desirable.
[0015]
The treated product obtained in the step (c) is included in the positive electrode as a useful metal that can be used as a raw material for the hydrogen storage alloy, for example, transition metals such as Co, Ni, and Mn contained in the oxidized hydrogen storage alloy. Or a metal obtained by reducing Ni or the like, an unoxidized hydrogen storage alloy, or a mixture thereof.
In the recovery method of the present invention, when the recovered material is actually used as a raw material for the hydrogen storage alloy, various known purification methods can be combined as required.
[0016]
【The invention's effect】
In the method for recovering useful metals from the alkaline secondary battery according to the present invention, in particular, since step (b) is performed, no special sorting is required in step (a), and as a raw material for the hydrogen storage alloy in step (c). Unnecessary highly volatile metals and their compounds can be efficiently removed by a simple method, and can be used as a raw material for hydrogen storage alloys from alkaline secondary batteries using hydrogen storage alloys as negative electrode active materials by a simple method. Useful metals can be recovered.
[0017]
【Example】
EXAMPLES Hereinafter, although an Example and a comparative example demonstrate this invention further in detail, this invention is not limited to these.
Example 1
A used alkaline secondary battery using a rare earth-based hydrogen storage alloy as a negative electrode active material was crushed so as to pass through a 10 mm mesh using a uniaxial crusher while spraying water in the atmosphere.
500 g of the obtained hydrated crushed material was placed in a stainless steel vat, and a dew point meter was installed in a firing furnace provided in the exhaust gas path. Subsequently, after the pressure in the furnace was reduced to 10 Pa, the amount and temperature of hydrogen gas introduced were controlled so that the dew point was −5 ° C. while continuing the pressure reduction, and the temperature was increased to 400 ° C. After reaching 400 ° C., the hydrogen gas flow rate was fixed at 2 liters / minute when the dew point was stabilized, and maintained at 400 ° C. until the pressure in the furnace reached 100 Pa.
When the pressure in the furnace reached 100 Pa, the temperature was raised to 900 ° C. while flowing hydrogen gas, and maintained at 900 ° C. until a pressure decrease of 5 Pa was observed. After completion of the holding at 900 ° C., argon gas was introduced into the furnace to atmospheric pressure, cooled to room temperature, the treated product was taken out from the furnace, and the powder and the others were separated with a sieve having an opening of 500 μm. The obtained powder was measured with an ICP emission spectroscopic analyzer (trade name SPS-1700HVR, manufactured by Seiko Instruments Inc.) and an oxygen nitrogen analyzer (trade name EMGA-550FA, manufactured by Horiba, Ltd.). The results are shown in Table 1.
[0018]
Example 2
After carrying out to the hold | maintenance at 400 degreeC similarly to Example 1, argon gas was introduce | transduced instead of hydrogen gas, and when the pressure in a furnace became 100 Pa, it heated up at 1300 degreeC with flowing argon gas. The temperature was maintained at 1300 ° C. until a pressure decrease of 5 Pa was observed. After completion of the holding at 1300 ° C., the inside of the furnace was brought to atmospheric pressure with argon gas, cooled to room temperature, the treated product was taken out from the inside of the furnace, and separated with a sieve having an opening of 500 μm to obtain a recovered powder. Each measurement was performed on the obtained recovered powder in the same manner as in Example 1. The results are shown in Table 1.
[0019]
Example 3
A used alkaline secondary battery using a rare earth-based hydrogen storage alloy as a negative electrode active material was crushed so as to pass through a 10 mm mesh using a uniaxial crusher while spraying water in the atmosphere.
500 g of this hydrated crushed material was put into a stainless steel vat, 20 g of carbon powder was added and mixed as a reducing agent, and then placed in a firing furnace. Subsequently, the pressure in the furnace was reduced to 10 Pa, and while continuing the pressure reduction, the amount and temperature of argon gas introduced were controlled so that the dew point was 0 ° C., and the temperature was increased to 600 ° C. After reaching 600 ° C., the flow rate of argon gas was fixed at 2 liters / minute when the dew point was stabilized, and the temperature was maintained at 600 ° C. until the pressure in the furnace reached 100 Pa. When the pressure in the furnace reached 100 Pa, the temperature was raised to 1000 ° C. and kept at 1000 ° C. until a pressure decrease of 5 Pa was observed. After completion of the holding at 1000 ° C., the pressure was changed to atmospheric pressure with argon gas, cooled to room temperature, the treated product was taken out from the furnace, and separated with a sieve having an opening of 500 μm to obtain a recovered powder. Each measurement was performed on the obtained recovered powder in the same manner as in Example 1. The results are shown in Table 1.
[0020]
Example 4
The recovered powder was obtained in the same manner as in Example 1 except that carbon monoxide gas was used instead of hydrogen gas as the reducing agent. Each measurement was performed on the obtained recovered powder in the same manner as in Example 1. The results are shown in Table 1.
[0021]
Comparative Example 1
A recovered powder was obtained in the same manner as in Example 1 except that argon gas was used instead of hydrogen gas. Each measurement was performed on the obtained recovered powder in the same manner as in Example 1. The results are shown in Table 1. Comparative Example 1 is an example in which no reducing agent is used in step (b).
[0022]
Comparative Example 2
A used alkaline secondary battery using a rare earth-based hydrogen storage alloy as a negative electrode active material was crushed so as to pass through a 10 mm mesh using a uniaxial crusher while spraying water in the atmosphere.
500 g of this hydrated crushed material was placed in a stainless steel vat and placed in a firing furnace. Subsequently, after reducing the pressure in the furnace to 10 Pa, the amount and temperature of hydrogen gas introduced were controlled so that the dew point was −5 ° C. while continuing the pressure reduction, and the temperature was increased to 400 ° C. After reaching 400 ° C., the hydrogen gas flow rate was fixed at 2 liters / minute when the dew point was stabilized, and maintained at 400 ° C. until the pressure in the furnace reached 100 Pa.
After completion of the holding at 400 ° C., argon gas was introduced into the furnace to atmospheric pressure and cooled to room temperature. Next, the processed product was taken out from the furnace and separated with a sieve having an opening of 500 μm to obtain a recovered powder. Each measurement was performed on the obtained recovered powder in the same manner as in Example 1. The results are shown in Table 1. In addition, this comparative example 2 is an example which does not perform a process (c).
[0023]
Comparative Example 3
A recovered powder was obtained in the same manner as in Example 1 except that the dew point was 5 ° C. Each measurement was performed on the obtained recovered powder in the same manner as in Example 1. The results are shown in Table 1. Comparative Example 3 is an example in which the dew point is set to a condition exceeding 0 ° C.
[Table 1]

Claims (2)

A useful metal recovery method from an alkaline secondary battery using a hydrogen storage alloy as a negative electrode active material,
A step (a) of crushing and / or disassembling an alkaline secondary battery using a rare earth-based hydrogen storage alloy as a negative electrode active material;
A step (b) of thermally decomposing and reducing the pulverized product and / or the disassembled product obtained in the step (a) in the presence of a reducing agent while controlling the dew point to 0 ° C. or lower under the condition of 200 ° C. or higher;
A rare earth system comprising a step (c) of volatilizing and removing a highly volatile metal such as zinc, lithium and potassium and a compound thereof from the material obtained in step (b) at a temperature of 800 ° C. or higher. A method for recovering useful metals from alkaline secondary batteries, which recovers useful metals that can be used as raw materials for hydrogen storage alloys. The recovery method according to claim 1 , wherein the volatilization removal in the step (c) is performed under a condition of 10 kPa or less in a non-oxidizing atmosphere .