U.S. patent application number 09/816654 was filed with the patent office on 2001-12-27 for process of recovering valuable metal.
Invention is credited to Sakai, Minoru, Yasuda, Kiyotaka.
Application Number | 20010054331 09/816654 |
Document ID | / |
Family ID | 27342773 |
Filed Date | 2001-12-27 |
United States Patent
Application |
20010054331 |
Kind Code |
A1 |
Yasuda, Kiyotaka ; et
al. |
December 27, 2001 |
Process of recovering valuable metal
Abstract
A method for recovering a valuable metal including the steps of:
recovering valuables from scraps containing the valuable metal; and
removing at least part of carbon contained in the recovered
valuables by heating the valuables in a non-oxidizable atmosphere,
and a method for recovering a valuable metal including the steps
of: thermally treating a melted mixture including the valuable
metal and slag with a flux component to separate the valuable metal
in a liquid phase from the slag in another liquid phase. In
accordance with the present invention, the valuable metal in the
scrap can be easily recovered.
Inventors: |
Yasuda, Kiyotaka;
(Hiroshima, JP) ; Sakai, Minoru; (Hiroshima,
JP) |
Correspondence
Address: |
SUGHRUE, MION, ZINN, MACPEAK & SEAS, PLLC
2100 PENNSYLVANIA AVENUE, N. W.
WASHINGTON
DC
20037-3213
US
|
Family ID: |
27342773 |
Appl. No.: |
09/816654 |
Filed: |
March 26, 2001 |
Current U.S.
Class: |
75/628 ;
75/406 |
Current CPC
Class: |
C22B 7/003 20130101;
Y02P 10/20 20151101; C22B 23/026 20130101 |
Class at
Publication: |
75/628 ;
75/406 |
International
Class: |
C22B 007/00 |
Foreign Application Data
Date |
Code |
Application Number |
Mar 24, 2000 |
JP |
2000-83159 |
Mar 2, 2001 |
JP |
2001-57669 |
Mar 13, 2001 |
JP |
2001-69681 |
Claims
What is claimed is:
1. A method for recovering a valuable metal comprising the steps
of: recovering valuables from scraps containing the valuable metal;
and removing at least part of carbon contained in the recovered
valuables by heating the valuables in a non-oxidizable
atmosphere.
2. The method as defined in claim 1, wherein the scraps containing
the valuable metal are a scrapped nickel-hydrogen secondary
cell.
3. The method as defined in claim 1, wherein the valuables are
selected from the group consisting of materials recovered from a
positive electrode, materials recovered from a negative electrode
and a mixture thereof.
4. The method as defined in claim 1, wherein the non-oxidizable
atmosphere is selected from the group consisting of an inert gas
atmosphere, a hydrogen gas atmosphere, a vapor atmosphere, an inert
gas-vapor atmosphere and an inert gas-vapor-hydrogen gas
atmosphere.
5. The method as defined in claim 1, wherein the heating in the
carbon-removing step is conducted at a temperature between 350 and
1050.degree. C. for 5 minutes to 10 hours
6. The method as defined in claim 1, wherein the heating in the
carbon-removing step is conducted while the valuables are
stirred.
7. The method for recovering the valuable metal as defined in claim
1 further comprising the step of heating the recovered valuable
metal for melting.
8. A method for recovering a valuable metal comprising the steps
of: thermally treating a melted mixture including the valuable
metal and slag with a flux component to separate the valuable metal
in a liquid phase from the slag in another liquid phase.
9. The method for recovering the valuable metal as defined in claim
8, wherein the flux component is boron oxide.
10. The method for recovering the valuable metal as defined in
claim 8, wherein the flux component is a mixture containing boron
oxide and calcium oxide.
11. A method for recovering a valuable metal comprising the steps
of: recovering valuables from scraps containing the valuable metal
and slag; removing at least part of carbon contained in the
recovered valuables by heating the valuables in a non-oxidizable
atmosphere to provide a melted mixture including the valuable metal
and the slag; and thermally treating the melted mixture with a flux
component to separate the valuable metal in a liquid phase from the
slag in another liquid phase.
Description
BACKGROUND OF THE INVENTION
[0001] (a) Field of the Invention
[0002] The present invention relates to a method for conveniently
and less expensively recovering a valuable metal, and more in
detail to the method for recovering the valuable metal from a scrap
material including the valuable metal such as nickel, cobalt and
rare earth metals in a scrapped nickel-hydrogen secondary cell.
[0003] (b) Description of the Related Art
[0004] As a means for recovering the valuable metal from a scrap
material including the valuable metal such as nickel, cobalt and
rare earth metals in a scrapped nickel-hydrogen secondary cell, a
method is disclosed in JP-A-9(1997)-82371 which includes steps of
separating coarse particles (plastics iron and foamed nickel) from
fine particles (nickel hydroxide and hydrogen- storing alloy) by
crushing the scrapped nickel-hydrogen secondary cell followed by
filtration, dissolving the fine particles with sulfuric acid
containing an alkali metal to form a cobalt-containing nickel
solution, removing impurities therefrom, and recovering the nickel
metal and a nickel-cobalt alloy. However, the step of the
recovering the valuable metal such as the nickel is quite
complicated.
[0005] In the valuable metal recovery from the scrap including the
valuable metal, the reduction of the carbon content in the
recovered metal must be performed thereby broadening the usage
thereof, in addition to the increase of the recovery yield and the
simplification of the recovery process. The reduction of the carbon
after the recovery requires an undesirable additional step
requesting further time and cost.
[0006] In JP-A-2000-67935, a method for recovering valuables from a
scrapped nickel-hydrogen secondary cell is disclosed which includes
the steps of crushing the scrapped nickel-hydrogen secondary cell,
filtrating the valuables in the crushed cell, thermally treating
the valuables in an oxidizable atmosphere, and thermally melting
the valuables in a reducing atmosphere to provide a melted metal.
Carbon in the valuables is removed by the oxidation in the thermal
oxidation step.
[0007] However, in the method, although the carbon content in the
valuables is reduced in the thermal oxidation step conducted in a
higher temperature, the valuable metals such as nickel, cobalt and
rare earth metals are simultaneously oxidized. Accordingly, the
method is not an effective process for recovering the valuable
metals.
[0008] In the conventional method for recovering the valuable
metal, the carbon contained in the scrapped nickel-hydrogen
secondary cell remains in the valuable metals after the recovery.
When the content of the carbon in the valuable metals is reduced,
the valuable metals are oxidized. Therefore, the desired valuable
metals cannot be obtained.
[0009] Even when the carbon is effectively removed from the
valuable metals recovered in this manner, the recovered valuable
metals frequently contain slag initially contained in the scraped
cell. The slag irremovable by a simple separation procedure is a
bar to the recycle of the recovered valuable metals.
SUMMARY OF THE INVENTION
[0010] In view of the foregoing, an object of the present invention
is to provide a method for recovering a valuable metal with reduced
carbon content without substantial oxidation of the valuable metal,
and another method for separating the valuable metal from slag.
[0011] The present invention provides, in a first aspect thereof, a
method for recovering a valuable metal including the steps of:
recovering valuables from scraps containing the valuable metal; and
removing at least part of carbon contained in the recovered
valuables by heating the valuables in a non-oxidizable atmosphere
(hereinafter referred to as "first invention").
[0012] In accordance with the first invention, the valuable metals
with higher quality and the lower carbon content can be recovered
without oxidizing the valuable metals by a thermal treatment of the
recovered valuables containing the carbon and oxygen in the
non-oxidizable atmosphere.
[0013] The present invention provides, in a second aspect thereof,
a method for recovering a valuable metal including the steps of
thermally treating a melted mixture including the valuable metal
and slag with a flux component to separate the valuable metal in a
liquid phase from the slag in another liquid phase (hereinafter
referred to as "second invention").
[0014] In accordance with the second invention, though the melted
mixture of the valuable metals and the slag is hardly separated
from each other by the conventional separation method, the melted
mixture is separated into the heavier melted metal and the lighter
melted slag by addition of, with heating, the flux component such
as boron oxide and boron oxide+calcium oxide, thereby recovering
the valuable metal having the higher purity in a liquid-liquid
separating manner.
[0015] The present invention provides, in a third aspect thereof, a
method for recovering a valuable metal including the steps of;
recovering valuables from scraps containing the valuable metal and
slag; removing at least part of carbon contained in the recovered
valuables by heating the valuables in a non-oxidizable atmosphere
to provide a melted mixture including the valuable metal and the
slag; and thermally treating the melted mixture with a flux
component to separate the valuable metal in a liquid phase from the
slag in another liquid phase (hereinafter referred to as "third
invention").
[0016] In accordance with the third invention, the valuable metal
in the scraps can be recovered by utilizing the combined procedures
of the first and second inventions.
[0017] The above and other objects, features and advantages of the
present invention will be more apparent from the following
description.
BRIEF DESCRIPTION OF DRAWINGS
[0018] FIG. 1 is a flowchart showing a method of the present
invention which is applied to recovery of valuable metals in a
scrapped nickel-hydrogen secondary cell.
PREFERRED EMBODIMENTS OF THE INVENTION
[0019] Now, the present invention is more specifically
described.
[0020] The method of the first invention is characterized by the
removal of the carbon in the recovered valuable metals without
substantially oxidizing the valuable metals by thermally treating
the valuables recovered from the scrap containing the valuable
metals in the non-oxidizable atmosphere. After the carbon-removing
step, the melting step may be added in which the de-carbonized
valuable metal is heated for melting.
[0021] The scrap containing the valuable metals includes a scrapped
nickel-cadmium cell and a scrapped lithium ion cell in addition to
the scrapped nickel-hydrogen secondary cell.
[0022] The valuable metals recovered in this manner usually contain
slag originating from the starting cell. The second invention
implements the separation of the valuable cells from the slag. The
object for the separation in the second invention is not restricted
to that from the scrapped material but includes metals containing
slag in an ordinary refining process.
[0023] The "valuables" in the present invention refers to
composition containing the valuable metal to be recovered and
occasionally refers to the recovered valuable metals.
[0024] Then, an example of the present invention for recovering
valuable metals in a scrapped material will be described referring
to FIG. 1 showing the recovery of valuable metals in a scrapped
nickel-hydrogen secondary cell.
[0025] A valuables recovering step may be performed similarly to
the conventional valuables recovering method When the scraps
containing the valuable metals are the scrapped nickel-hydrogen
secondary cell, the cell is crushed by using a shearing machine, is
broken into pieces in a wet condition and is classified by using a
sieve. After the non-classified substances remaining on the sieve
are subjected to the magnetic screening for removing non-magnetized
substances such as plastics and paper, small amounts of the
plastics and paper are removed by burning.
[0026] Further, when the cell includes foamed nickel as an
electrode plate, the electrode plate may be reduced in hydrogen or
thermally treated in an inert gas atmosphere for recovering the
valuables.
[0027] The valuables obtained in this manner include materials
recovered from a negative electrode mainly containing nickel and
materials recovered from a positive electrode mainly containing a
hydrogen-storaging alloy, and further include an organic binder and
a specified amount of carbon.
[0028] Then, the valuables physically classified in this manner are
thermally treated in the non-oxidizable atmosphere to oxide at
least part of only the carbon, thereby removing the oxidized carbon
or carbon monoxide and carbon dioxide (carbon-removing step).
[0029] The non-oxidizable atmosphere refers to an atmosphere in
which carbon can be removed by oxidation without substantially
oxidizing a metal and an alloy by means of heating and is selected
from the group consisting of an inert gas atmosphere, a hydrogen
gas atmosphere, a vapor atmosphere, an inert gas-vapor atmosphere
and an inert gas-vapor-hydrogen gas atmosphere. The inert gas
includes argon, nitrogen and helium, and the preferable
non-oxidizable atmosphere is the hydrogen gas atmosphere.
[0030] The heating in the carbon-removing step may be conducted
preferably at 350 to 1050.degree. C. for 5 minutes to 10 hours and
more preferably at 400 to 750.degree. C. for 30 minutes to 5 hours.
The heating below 350.degree. C. cannot take place the condensation
dehydration reaction of a metal compound such as nickel hydroxide
contained in the valuables and lowers the recovery yield due to the
slow reaction rate. The heating above 1050.degree. C. cannot
significantly increase the treating efficiency and lowers the
energy efficiency of the metal recovery.
[0031] The thermal treatment in the inert gas atmosphere attributes
to the reductive or the oxidative removal of the at least part of
the carbon by means of oxygen, hydrogen and vapor contained in the
recovered valuables, and simultaneously reduces part of a
deteriorated metal oxide to the corresponding metal.
[0032] At least part of the carbon in the valuables is reduced in
the hydrogen atmosphere to lower hydrocarbons to be removed from
the valuables.
[0033] In the vapor atmosphere, at least part of the carbon in the
valuables is denaturated or oxodized with the vapor to be removed
from the valuables.
[0034] After at least part of the carbon in the valuables is
removed in the carbon-removing step, the valuables are converted
into the valuable metal which is then recovered as the cool solid
metal upon the stopping of the heating in the carbon-removing
step.
[0035] Some of the metals are preferably recovered as the melted
metal depending on the usage. In such a case, the metals after the
carbon-removing step are heated continuously with the heating of
the carbon-removing step or are re-heated after the stop of the
heating of the carbon-removing step, thereby recovering the
valuable metals as the melted metals (melting step). The melting
step is not indispensable.
[0036] The atmosphere for the heating in the melting step is
preferably an inert gas atmosphere such as argon for suppressing
the oxidation of the valuable metals.
[0037] In the method of the present invention including the above
requirements, the carbon-removing step in the inert gas atmosphere
effectively utilizes the hydrogen and the oxygen contained in the
scrap containing the valuable metals can remove at least part of
the carbon contained in the scrap without substantially oxidizing
the metals easily oxidized such as Misch metal.
[0038] The carbon-removing step in the hydrogen gas atmosphere
reductively removes at least part of the carbon contained in the
scrap by means of the hydrogen contained in the atmosphere without
substantially oxidizing the metals easily oxidized such as Misch
metal.
[0039] The carbon-removing step in the vapor atmosphere removes at
least part of the carbon contained in the scrap by means of the
oxidation or denaturation without substantially oxidizing the
metals easily oxidized such as Misch metal.
[0040] The carbon-removing step conducted in this manner does not
substantially accompany the oxidation and reduces the carbon
content in the valuables to 1000 ppm (0.1% in weight) or less or to
100 ppm (0.01% in weight) or less depending on conditions.
[0041] Although the carbon in the recovered valuables can be easily
removed by the conventional oxidation treatment, the treatment
further oxidizes the other metal components such as nickel, cobalt
and the Misch metal, thereby requiring additional vast energy for
reducing the oxidized metals to lower the efficiency.
[0042] On the other hand, the carbon-removing step in the present
invention enables the carbon removal in the valuables without
accompanying the oxidation of the metal components to require no
additional step for reducing the scrap and enables the simple
recovery of the valuable metals from the scrap.
[0043] In the ordinary operation, slag originating from the scrap
is contained in the recovered valuable metal. Accordingly, the
valuable metal after the carbon-removing step is a mixture between
the metal and the slag.
[0044] Then, a flux component is added to the thus obtained mixture
in the third invention, and to the thus obtained mixture or a
separately obtained mixture of this kind in the second invention.
In the second invention, the flux component may be added to the
solid mixture followed by the melting or to the melted mixture.
[0045] The flux component has a function of separating the melted
valuable metals from the melted slag, and is preferably selected
from metal compounds usually metal oxides which have melting points
around that of the valuable metals. Preferable flux component
includes born oxide (B.sub.2O.sub.3), the boron oxide+calcium oxide
(CaO), the boron oxide+magnesium oxide (MgO) and the boron
oxide+lithium oxide (LiO). An amount of the flux component is
preferably 5 to 100% in weight with respect to the total amount of
the valuables and the slag, and more preferably 10 to 50% in
weight.
[0046] When the mixture containing the flux component is maintained
in the melted state, the mixture are subjected to liquid-liquid
separation or divided into the melted metal having a larger
specific gravity and the melted slag having a smaller specific
gravity. Accordingly, the valuable metal having the higher purity
can be recovered rather simply.
[0047] When the valuable metal is recovered from the valuables
containing the Misch metal oxide (MmOx), for example, the valuable
metal cannot ordinarily be separated unless the valuables are
heated to the melting point of the Misch metal, for example, to the
melting point of lanthanum oxide, that is, to 2310.degree. C.
However, the addition of the flux component such as B.sub.2O.sub.3
to converts the Misch metal into MmOx--B.sub.2O.sub.3, having the
melting point of about 1300.degree. C. The liquid-liquid separation
of the valuable metal can be achieved by heating the mixture to
this melting point. When the boron oxide is used as the flux
component for the valuable metal recovery, only the valuable metals
other than the Misch metal are recovered because the Misch metal is
converted into the MmOx--B.sub.2O.sub.3 which is then included in
the slag as mentioned before.
[0048] Although the boron oxide itself is preferably used with
respect to the valuable metal recovery, the higher activity of the
boron oxide make take place the following reaction depending on the
conditions.
Mm+B.sub.2O.sub.3.fwdarw.MmOx+B
[0049] The liberated boron may be mixed into the recovered valuable
metals as an impurity. The combination of the boron oxide and the
calcium oxide suppresses the activity of the boron and prevents the
mixing of the boron into the valuable metal.
[0050] As mention before, the valuable metal with the slag having
the reduced amount of the carbon can be recovered from the scrap in
accordance with the first invention by using the carbon-removing
step.
[0051] The mixture containing the metal and the slag can be
separated by using the flux component in accordance with the second
invention.
[0052] The valuable metal in the scrap can be recovered by using
the valuables-recovering step, the carbon-removing step and the
valuable metal-recovering step in accordance with the third
invention.
EXAMPLES
[0053] Although Examples of the method for recovering the valuable
metals of the present invention will be described, the present
invention shall not be deemed to be restricted thereto.
Valuables Recovering Step
[0054] A scrapped nickel-hydrogen secondary cell was dry-crushed by
using a shearing machine (Rotoplex Cutting Mill made by Alpine A.G.
of Germany). The crushed cell was wet-broken into pieces by using
an attriction machine, the broken pieces were then classified by
using a sieve (28 mesh). After the non-classified substances
remaining on the sieve are subjected to the magnetic screening at
2000 to 3000 Gauss for removing non-magnetized substances such as
plastics and paper, small amounts of the plastics and paper are
removed by burning. The residue after the burning was crushed by
using a vibration mill ("T-100 Type" available from Kawasaki Heavy
Industries Kabusuki Kaisha), and classified by using a sieve (24
mesh), thereby separating the metal iron from the foamed nickel.
The foamed nickel was concentrated to fine particles having 24 mesh
or less and recovered.
[0055] On the other hand, the valuables such as nickel hydride and
nickel hydroxide acting as active components of the cell were
concentrated into the classified material having passed through the
sieve of 28 mesh obtained by the wet-crushing and the following
classification. The valuables thus obtained were roughly divided
into two, such materials mainly composed of the positive electrode
and the negative electrode, and the mixture thereof was also
prepared.
[0056] Next, the materials recovered from the positive electrode
(Examples 1 to 13), from the negative electrode (Examples 14 to 26)
and the mixtures thereof (Examples 27 to 32) were subjected to the
carbon removing step and the melting step, and amounts of carbon
and oxygen in the valuable metals obtained were chemically
analyzed.
Example b 1
[0057] After 3 g of the materials recovered from the positive
electrode (carbon content and oxygen content were 1.27% in weight
and 6.5% in weight, respectively) obtained in the carbon-removing
step was subjected to the carbon-removing treatment
(carbon-removing step) at 400.degree. C. for one hour while an
argon gas was flown at a rate of 200 cc/minutes, the material was
further heated at 1400.degree. C. for one hour in the argon
atmosphere to be recovered as a melted metal. The carbon content
and the oxygen content of the melted metal thus obtained were
reduced to 0.93% in weight and 6.5% in weight, respectively. The
results are summarized in Table 1.
Examples 2 to 7
[0058] The materials recovered from the positive electrode having
substantially same composition as that of Example 1 were subjected
to the carbon-removing step at a temperature and a period of time
specified in Table 1 while an atmosphere gas was flown, and then
was melted with heat under the same condition as those of Example 1
The carbon contents and the oxygen contents in the melted metals
obtained by the treatments were shown in Table 1. When the
experiment was conducted in the hydrogen atmosphere, the flow gas
was replaced with an argon gas after a specified period of time for
the reaction of the carbon-removing step and the metal was cooled.
"Ar(H.sub.2O)" in Table 1 refers to an argon gas saturated with
vapor.
Examples 8 to 13
[0059] materials recovered from the positive electrode having
substantially same composition as that of Example 1 were subjected
to the carbon-removing step at a temperature and a period of time
specified in Table 1 in an atmosphere gas flow and the materials
recovered from the positive electrode were rotated (agitated), and
then were melted with heat under the same condition as those of
Example 1. The carbon contents and the oxygen contents in the
materials obtained by the treatments were shown in Table 1.
1 TABLE 1 Temp. Hour Gas and Gas Flow Rotation C Content O Content
(.degree. C.) (h) (cc/min.) (rpm) (weight %) (weight %) Positive --
-- -- -- 1.27 6.5 Electrode Ex. 1 400 1 Ar-200 -- 0.93 4.3 2 400 1
H.sub.2-200 -- 0.35 4.1 3 800 1 H.sub.2-200 -- 0.21 4.7 4 800 1
Ar(H.sub.2O)-200 -- 0.04 6.2 5 1000 1 Ar(H.sub.2O)-200 -- 0.05 6.4
6 800 1 Ar(H.sub.2O),H.sub.2-200 -- 0.13 6.0 7 1000 1
Ar(H.sub.2O),H.sub.2-200 -- 0.04 6.0 8 600 1 H.sub.2-200 10 0.07
2.9 9 800 1 H.sub.2-200 10 0.08 3.2 10 1000 1 H.sub.2-200 10 0.01
2.8 11 600 1 H.sub.2-1000 10 0.11 2.5 12 800 1 H.sub.2-1000 10 0.06
1.9 13 1000 1 H.sub.2-1000 10 0.01 1.9
Observations in Examples 1 to 13
[0060] Judging from the experimental results of Examples 1 to 13,
the reduction of the carbon contents and the oxygen contents were
confirmed in all the Examples by conducting the carbon-removing
step. This shows that part of the carbon in the valuable metal was
removed and that the oxygen in the oxidized nickel, cobalt and
manganese in the scrapped nickel-hydrogen secondary cell was
reduced, and the nickel hydroxide in the negative electrode was
hydrolyzed to be converted into nickel oxide which was further
reduced to the metal. The amount of the decrease of the carbon
increased with the elevation of the temperature so long as the
other conditions were the same (excluding Examples 4 and 5). The
change of the inert gas atmosphere to the hydrogen gas atmosphere
increased the amount of the decrease of the carbon.
[0061] When the carbon-removing step was conducted is without
rotation, the carbon content was decreased as low as to 0.04% in
weight. The carbon content was further decreased to 0.01% in weight
while the valuables were rotated at a temperature of 1000.degree.
C. in the hydrogen atmosphere.
[0062] The rate-determining step of the carbon-removing step was
the collision between the molecules, and the reduction of the
carbon was accelerated by the rotation or the agitation of the
materials recovered from the positive electrode to be treated.
[0063] The carbon content of Examples 4 and 5 in the
carbon-removing step conducted in the vapor atmosphere decreased to
0.04 to 0.05% in weight. The result shows the vapor will be enough
for carbon removal if the purpose is only to remove the carbon from
the materials.
[0064] In Examples 1 to 7 in which no rotations were conducted
including Examples 4 and 5, the oxygen contents decreased to only
about 4% in weight, and those of Examples 4 and 5 were 6% in weight
which was a similar level to that of the raw material, and the
oxygen decrease was insufficient.
Example 14
[0065] After 3 g of the materials recovered from the negative
(carbon content and oxygen content were 0.54% in weight and 22.5%
in weight, respectively) obtained in the carbon-removing step were
subjected to the carbon-removing treatment (carbon-removing step)
at 400.degree. C. for one hour while an argon gas was flown at a
rate of 200 cc/minutes, the material was further heated at
1400.degree. C. for one hour in the argon atmosphere to be
recovered as a melted metal. The carbon content and the oxygen
content of the melted metal thus obtained were reduced to 0.22% in
weight and 18.0% in weight, respectively. The results are
summarized in Table 2.
Examples 15 to 20
[0066] The materials recovered from the negative electrode having
substantially same composition as that of Example 14 were subjected
to the carbon-removing step at a temperature and a period of time
specified in Table 2 while an atmosphere gas was flown, and then
were melted with heat under the same condition as those of Example
14. The carbon contents and the oxygen contents in the melted
metals obtained by the treatments were shown in Table 2. When the
experiment was conducted in the hydrogen atmosphere, the flow gas
was replaced with an argon gas after a specified period of time for
the reaction of the carbon-removing step and the metal was
cooled.
Examples 21 to 26
[0067] The materials recovered from the negative electrode having
substantially same composition as that of Example 14 were subjected
to the carbon-removing step at a temperature and a period of time
specified in Table 2 while an atmosphere gas was flown and the
materials recovered from the negative electrode were rotated
(agitated), and then were melted with heat under the same condition
as those of Example 14. The carbon contents and the oxygen contents
in the melted metals obtained by the treatments were shown in Table
2.
Observations in Examples 14 to 26
[0068] Judging from the experimental results of Examples 14 to 26,
similarly to those of Examples 1 to 13, the reduction of the carbon
contents and the oxygen contents were confirmed in all the Examples
by conducting the carbon-removing step. This shows that part of the
carbon in the valuable metal was removed and that the oxygen in the
oxidized nickel, cobalt and manganese in the scrapped
nickel-hydrogen secondary cell was reduced, and the nickel
hydroxide in the negative electrode was hydrolyzed to be converted
into nickel oxide which was further reduced to the metal. The
amount of the decrease of the carbon increased with the elevation
of the temperature so long as the other conditions were the same
(excluding Examples 25 and 26). The change of the inert gas
atmosphere to the hydrogen gas atmosphere increased the amount of
the decrease of the carbon.
[0069] Different from the materials recovered from the positive
electrode, the carbon content was decreased to 0.01% in weight in
the carbon-removing step even without the rotation. This is because
the initial carbon content was small.
[0070] The carbon-removing effect affected by the rotation was not
constant, and the remarkable effect did not appear.
[0071] The carbon content was deceased to the order of 0.0-0.02% in
weight in the carbon-removing step in the hydrogen gas atmosphere.
The oxygen content increased with the temperature rise under the
same conditions (excluding Examples 17 and 18), and increased to
0.63% in weight in Example 26.
2 TABLE 2 Temp. Time Gas and Gas Flow Rotation C Content O Content
(.degree. C.) (h) Rate (cc/min.) (rpm) (weight %) (weight %)
Negative -- -- -- -- 0.54 22.5 Electrode Ex. 14 400 1 Ar-200 --
0.22 18.0 15 500 1 H.sub.2-200 -- 0.05 2.6 16 800 1 H.sub.2-200 --
0.01 1.1 17 800 1 Ar(H.sub.2O)-200 -- 0.16 15.3 18 1000 1
Ar(H.sub.2O)-200 -- 0.04 15.8 19 800 1 Ar(H.sub.2O),H.sub.2-200 --
0.18 0.95 20 1000 1 Ar(H.sub.2O),H.sub.2-200 -- 0.02 0.66 21 600 1
H.sub.2-200 10 0.14 1.35 22 800 1 H.sub.2-200 10 0.12 1.05 23 1000
1 H.sub.2-200 10 0.03 0.89 24 600 1 H.sub.2-1000 10 0.03 1.25 25
800 1 H.sub.2-1000 10 0.01 0.86 26 1000 1 H.sub.2-1000 10 0.02
0.63
Example 27
[0072] After 3 g of the mixture including the materials recovered
from the negative electrode and the positive electrode (carbon
content and oxygen content were 0.91% in weight and 16.2% in
weight, respectively) obtained in the valuables recovering step was
subjected to the carbon-removing treatment (carbon-removing step)
at 300.degree. C. for one hour while an argon gas was flown at a
rate of 200 cc/minutes, the material was further heated at
1400.degree. C. for one hour in the argon atmosphere to be
recovered as a melted metal. The carbon content and the oxygen
content of the melted metal thus obtained were reduced to 0.88% in
weight and 11.2% in weight, respectively. The results are
summarized in Table 3 wherein "+:-" refers to the mixing ratio
between the materials recovered from the positive and negative
electrodes.
Examples 28 to 32
[0073] The mixture having substantially same composition as that of
Example 27 was subjected to the carbon-removing step at a
temperature and a period of time specified in Table 3 while an
atmosphere gas was flown, and then was melted with heat under the
same condition as those of Example 27. The carbon contents and the
oxygen contents in the melted metals obtained by the treatments
were shown in Table 3.
Observations in Examples 27 to 32
[0074] Judging from the experimental results of Examples 27 to 32,
the reduction of the carbon contents and the oxygen contents were
confirmed in all the Examples by conducting the carbon-removing
step. Especially under the hydrogen gas atmosphere (Example 32),
the carbon content and the oxygen content were reduced to 0.01% in
weight and 1.1% in weight, respectively. This shows that part of
the carbon in the valuable metal was removed and that the oxygen in
the oxidized nickel, cobalt and manganese in the scrapped
nickel-hydrogen secondary cell was reduced, and the nickel
hydroxide in the negative electrode was hydrolyzed to be converted
into nickel oxide which was further reduced to the metal It was
conjectured that the carbon removal was efficiently carried out by
the vapor produced by the hydrolysis.
[0075] Judging from these results, it was elucidated that the
carbon content in the valuables could be largely decreased when the
mixture including the materials recovered from the positive and
negative electrodes was treated in the carbon-removing step during
the recovery of the valuable metal from the scrapped cell without
separating the mixture.
3 TABLE 3 Temp. Time Gas and Gas Flow C Content O Content (.degree.
C.) (h) (cc/min.) +:- (weight %) (weight %) Mixture -- -- -- 1:1
0.91 16.2 Exam- 27 300 1 Ar-200 1:1 0.88 11.2 ple 28 400 1
H.sub.2-200 1:1 0.16 7.4 29 500 1 H.sub.2-200 1:1 0.18 4.2 30 800 1
H.sub.2-200 1:1 0.01 3.7 31 800 1 H.sub.2-200 1:0 0.21 4.7 32 800 1
H.sub.2-200 0:1 0.01 1.1
Valuable Metal Recovering Step
[0076] The valuables thus obtained had the composition of about 60%
in weight of cobalt and nickel, about 33% in weight of the Misch
metal and about 7% in weight of manganese and aluminum.
[0077] Then, the nickel and the cobalt were recovered from the
mixture including the valuables and slag or the mixture including
the same composition of the valuables prepared from commercially
available metals and slag.
Example 33
[0078] After 5 g of boron oxide acting as a flux component was
added to 10 g of a mixture including the valuables obtained in
Example 1 and slag, it was heated to 1300.degree. C. in a reaction
vessel having an argon atmosphere therein for 30 minutes for
proceeding the reaction. Thereby, an upper layer of the melted slag
and a lower melted metal appeared in the reaction vessel, and the
two layers were separated from each other by decantation.
[0079] After the decantation, 6.1 g of the valuable metal was
obtained, and 1.0 g of transparent slag and 0.3 g of other slag
were also obtained. The valuable metal was collected as much as
possible, but the slag which was basically useless was recovered
for analysis and a considerable amount of the slag was not
collected. The experimental conditions, and the amounts of the
recovered valuable metal and slag were summarized in Table 4.
[0080] The analysis of the recovered valuable metal revealed that
the recovered metal included 97% in weight of
nickel+cobalt+manganese (the individual composition included 86% in
weight of the nickel, 8.4% in weight of the cobalt and 5.4% in
weight of the manganese), 3% in weight of the boron, 0.57% in
weight of unidentified carbon compounds and 0.02% in weight of
unidentified oxygen compounds. The results of the analysis were
summarized in Table 5. The recovery and the analysis of most of the
slag were not practiced. Such slag is indicated by "-" in Tables 4
and 5.
4 TABLE 4 Yield After Experimental Conditions Reaction (g) Positive
Flux Trans- Temp. Time Atmos- Electrode Component parent Other
(.degree. C.) (m) phere (g) (g) Metal Slag Slag Exam- 33 1300 30 Ar
10 B.sub.2O.sub.3 (5) 6.1 1.0 0.3 ple 34 1300 30 Ar 10
B.sub.2O.sub.3 (5) 6.7 4.1 -- 35 1300 120 Ar 10 B.sub.2O.sub.3 (5)
6.7 3.4 -- 36 1300 5 Ar 5 B.sub.2O.sub.3 (1) 3.0 -- -- 37 1300 5 Ar
5 B.sub.2O.sub.3 (2) 3.0 -- -- 38 1300 5 Ar 5 B.sub.2O.sub.3 (1)
2.9 -- -- 39 1300 5 Ar 5 B.sub.2O.sub.3 (2) 2.9 -- -- 40 1300 5 Ar
5 B.sub.2O.sub.3 --CaO (2) 3.2 -- -- 41 1300 5 Ar 5 B.sub.2O.sub.3
--CaO (1) 3.0 -- -- 42 1300 5 Ar 5 B.sub.2O.sub.3 -- 2.8 -- -- CaO
(0.5) 43 1300 30 Ar 5 B.sub.2O.sub.3--CaO (3) 3.0 -- -- 44 1300 30
Ar 5 B.sub.2O.sub.3 (3) 3.2 -- -- Comp. 1 1300 30 Ar 5 None 0.9 --
-- Exam- 2 1400 30 Ar 5 None 1.4 -- -- ple Positive electrodes of
Examples 34, 35, 43 and 44 were a mixture of valuables prepared by
commercially available metals and slag. During the reaction, inside
of the vessel was agitated 100 times by using an alumina bar in
Examples 36 to 39 and Comparative Example 2. A molar mixture of 1:1
was used after the melting at 1200.degree. C. as
B.sub.2O.sub.3--CaO.
Examples 34 to 44
[0081] The valuable metals were recovered from the mixture
including the valuables and the slag similarly to Example 33 under
the conditions specified in Table 4. The results were shown in
Tables 4 and 5.
5 TABLE 5 Analytical Value of Recovered Material (weight %)
Transparent Metal Slag Other Slag Mm Ni, Co, Mn B C O Mm Ni, Co Mm
Ni, Co Exam- 33 0.1 97 3 0.57 0.02 24 0 43 16 ple 34 0 95 5 0.04
0.02 50 2.5 -- -- 35 0 95 5 0.01 0.02 48 0.5 -- -- 36 0 99 0.8 0.50
0.16 -- -- -- -- 37 0 99 1 0.62 0.03 -- -- -- -- 38 0 99 0.9 0.05
0.03 -- -- -- -- 39 0 99 0.9 40 0.1 99.4 0.5 0.79 0.03 -- -- -- --
41 0.23 99.4 0.2 0.76 0.04 -- -- -- -- 42 0 99.8 0.2 0.72 0.04 --
-- -- -- 43 1.2 92.5 4.6 0.03 0.17 -- -- -- -- 44 0 94 5.1 0.015
0.01 0.1 -- 16 67 Comp. 1 6 94 -- 0.51 0.51 0.1 -- -- -- Exam- 2 0
99.7 -- -- -- -- -- ple The metal composition of Example 34
included 82% in weight of Ni, 17% in weight of Co and 6.6% in
weight of Mn. The analysis of C and O could be conducted in Example
39 and Comparative 2 because the amounts of the samples were too
small. Only the composition of Example 41 included 0.04% in weight
of Ca.
Comparative Examples 1 and 2
[0082] The valuable metals were recovered from the mixture
including the valuables and the slag similarly to Example 33 by
using no flux component under the conditions specified in Table 4.
The results were shown in Tables 4 and 5.
Observations in Examples 34 to 44 and Comparative Examples 1 and
2
[0083] As mentioned before, the metal composition in the valuables
obtained from the scrap included about 60% in weight of Ni+Co,
about 33% in weight of the Misch metal and about 7% in weight of
Mn+Al. Considering that the Misch metal could not be recovered, the
theoretical recovery is about 60 to 65% in weight. As apparent from
Example 33, except that almost all the Misch metal was mixed into
the recovered slag, almost all the metal could be recovered as the
melted valuable metals because the other metals such as the nickel
was not mixed into the slag. The recovering amount per 10 g of the
positive electrode was 5.6 to 6.7 g which was nearly to the
theoretical value. Accordingly, the valuable metals could be
recovered almost quantitatively by means of the valuable metal
recovering step in which the flux component was added.
Examples 45 to 52 and Comparative Example 3
[0084] Similarly to Example 33, the mixture of the valuables and
the slag added with or without boron oxide was heated and reacted
in a reaction vessel having an argon atmosphere therein under the
experimental conditions specified in Table 6. The valuable metals,
transparent slag and other slag were obtained in yields shown in
Table 6, and subjected to the ICP analysis. The results of the
analysis were shown in Table 7.
6 TABLE 6 Yield After Experimental Conditions Reaction (g) Positive
Flux Trans- Temp. Time Atmos- Electrode Component parent Other
(.degree. C.) (m) phere (g) (g) Metal Slag Slag Exam- 45 1300 30 Ar
2.5 B.sub.2O.sub.3 (5) 1.34 1.53 1.37 ple 46 1300 30 Ar 5
B.sub.2O.sub.3 (5) 2.41 0.80 0.16 47 1300 30 Ar 7.5 B.sub.2O.sub.3
(5) 4.23 1.61 0.29 48 1300 30 Ar 10 B.sub.2O.sub.3 (5) 6.11 1.02
0.30 49 1300 30 Ar 15 B.sub.2O.sub.3 (5) 8.69 3.15 -- 50 1300 30 Ar
10 B.sub.2O.sub.3 (10) 3.71 3.21 -- 51 1300 30 Ar 10 B.sub.2O.sub.3
(5) 6.67 4.06 -- 52 1300 120 Ar 10 B.sub.2O.sub.3 (5) 6.66 3.43 --
* 3 1300 30 Ar 5 None 0.87 -- -- *Comparative Example
Examples 53 to 63 and Comparative Examples 4 and 5
[0085] Similarly to Example 33, the mixture of the valuables and
the slag added with or without boron oxide was heated and reacted
in a reaction vessel having an argon atmosphere therein under the
experimental conditions specified in Table 8. The valuable metals,
transparent slag and other slag were obtained in yields shown in
Table 8.
7 TABLE 7 ICP Analysis Results (weight %) La Ce Nd Pr Ni Mn Al Co B
Ga ToThl C O Valuable Metal Example 45 0.0 0.0 0.0 0.0 89.0 0.9 0.0
0.0 98.7 0.81 0.02 46 0.0 0.0 0.0 0.0 89.0 2.4 0.0 0.0 100.1 0.51
0.02 47 0.0 0.0 0.0 0.0 86.0 4.1 0.0 0.0 3.3 98.6 0.51 0.05 48 0.1
0.0 0.0 0.1 88.0 5.4 0.0 0.1 103.2 0.57 0.02 49 0.0 0.0 0.0 0.0
84.0 3.5 0.0 0.0 100.1 0.36 0.04 50 0.0 0.0 0.0 0.0 89.0 4.3 0.0
0.0 0.0 96.0 0.11 0.03 51 0.0 0.0 0.0 0.0 82.0 6.6 0.0 0.0 5.3
110.9 0.04 0.02 52 0.0 0.0 0.0 0.0 85.0 6.2 0.0 0.0 5.3 114.5 0.01
0.02 * 3 1.4 4.0 1.1 0.3 84.0 8.7 4.0 8.7 0.1 112.4 0.51 0.02
Transparent Slag Example 45 14.0 7.0 2.2 0.7 0.0 3.4 11.0 0.0 15.0
53.3 0 22.3 46 20.0 9.4 2.9 1.0 0.2 4.1 11.0 0.0 12.0 60.6 0.02
22.3 47 24.0 12.0 3.5 1.1 0.0 3.4 9.8 0.0 10.0 63.8 0.03 22.3 48
26.0 13.0 3.9 1.2 0.1 2.7 9.2 0.0 9.3 65.4 0.07 22.3 49 24.0 12.0
3.6 1.1 0.1 3.9 10.0 0.0 9.7 64.4 0.06 *** 50 11.0 5.0 1.6 0.5 0.5
0.9 7.4 0.1 14.0 17.0 57.9 0.04 *** Other Slag Example 45 2.1 0.9
0.3 0.1 0.4 0.6 2.7 0.0 28.0 35.1 0.02 *** 46 12.0 5.5 1.7 5.8 29.0
3.1 6.2 3.0 10.0 76.4 ** *** 47 4.6 2.3 0.7 0.2 3.6 1.2 3.4 0.4
23.0 39.5 0.23 *** 48 26.0 12.0 3.7 1.4 7.4 3.2 8.0 0.8 8.6 71.1
1.21 *** 49 16 24 7.3 2.2 2.2 2.6 9.1 0.26 8.6 72.26 0.08 *** 50 16
23 7.2 2.2 0.41 2.4 9.8 0.07 8.8 69.88 0.05 *** * Comparative
Example ** Amount of sample was too small *** Higher oxygen
content
[0086] Since the above embodiments are described only for examples,
the present invention is not limited to the above embodiments and
various modifications or alternations can be easily made therefrom
by those skilled in the art without departing from the scope of the
present invention.
8 TABLE 8 Yield After Experimental Conditions Reaction (g) Positive
Flux Trans- Temp. Time Atmos- Electrode Component parent Other
(.degree. C.) (m) phere (g) (g) Metal Slag Slag Exam- 53 1300 5 Ar
5 B.sub.2O.sub.3 (1) 3.0 -- -- ple 54 1300 5 Ar 5 B.sub.2O.sub.3
(1.5) 2.9 -- -- 55 1300 5 Ar 5 B.sub.2O.sub.3 (2) 3.0 -- -- 56 1300
5 Ar 5 B.sub.2O.sub.3 (1) 2.9 -- -- 57 1300 5 Ar 5 B.sub.2O.sub.3
(1.5) 2.9 -- -- 58 1300 5 Ar 5 B.sub.2O.sub.3 (2) 1.6 -- -- 59 1300
5 Ar 5 B.sub.2O.sub.3--CaO (2) 3.2 -- -- 60 1300 5 Ar 3
B.sub.2O.sub.3--CaO (1) 3.0 -- -- 61 1300 5 Ar 5 B.sub.2O.sub.3--
2.8 -- -- CaO (0.5) 62 1300 30 Ar 5 B.sub.2O.sub.3--CaO (3) 3.0 --
-- 63 1300 30 Ar 5 B.sub.2O.sub.3--CaO (3) 3.2 -- -- * 4 1400 30 Ar
5 None 1.4 -- -- 5 1300 30 Ar 3 None 1.1 -- -- Positive electrodes
of Examples 62 and 63 were a mixture of valuables prepared by
commercially available metals and slag. During the reaction, inside
of the vessel was agitated 100 times by using an alumina bar in all
Examples. A molar mixture of 1:1 was used after the melting at
1200.degree. C. as B.sub.2O.sub.3--CaO. * Comparative Example
* * * * *