U.S. patent application number 15/559845 was filed with the patent office on 2018-03-01 for cobalt powder production method.
The applicant listed for this patent is SUMITOMO METAL MINING CO., LTD.. Invention is credited to Yasuo Doi, Shin-ichi Heguri, Osamu Ikeda, Yohei Kudo, Yoshitomo Ozaki, Kazuyuki Takaishi, Ryoma Yamaguma.
Application Number | 20180056399 15/559845 |
Document ID | / |
Family ID | 56977361 |
Filed Date | 2018-03-01 |
United States Patent
Application |
20180056399 |
Kind Code |
A1 |
Heguri; Shin-ichi ; et
al. |
March 1, 2018 |
COBALT POWDER PRODUCTION METHOD
Abstract
Provided is a production method for producing coarse particles
of high purity Co powder from a cobalt ammine sulfate complex
solution using fine Co powder and using industrially inexpensive
H.sub.2 gas.
Inventors: |
Heguri; Shin-ichi;
(Niihama-shi, Ehime, JP) ; Ozaki; Yoshitomo;
(Niihama-shi, Ehime, JP) ; Takaishi; Kazuyuki;
(Niihama-shi, Ehime, JP) ; Doi; Yasuo;
(Niihama-shi, Ehime, JP) ; Ikeda; Osamu;
(Niihama-shi, Ehime, JP) ; Yamaguma; Ryoma;
(Niihama-shi, Ehime, JP) ; Kudo; Yohei;
(Niihama-shi, Ehime, JP) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
SUMITOMO METAL MINING CO., LTD. |
Tokyo |
|
JP |
|
|
Family ID: |
56977361 |
Appl. No.: |
15/559845 |
Filed: |
March 16, 2016 |
PCT Filed: |
March 16, 2016 |
PCT NO: |
PCT/JP2016/058384 |
371 Date: |
September 20, 2017 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
C22B 3/08 20130101; C22B
23/0476 20130101; C22B 23/0484 20130101; B22F 9/26 20130101; B22F
2201/013 20130101; C22B 23/0461 20130101; B22F 2301/15 20130101;
B22F 3/16 20130101; C22B 23/043 20130101 |
International
Class: |
B22F 9/26 20060101
B22F009/26; C22B 3/08 20060101 C22B003/08; C22B 3/00 20060101
C22B003/00; B22F 3/16 20060101 B22F003/16 |
Foreign Application Data
Date |
Code |
Application Number |
Mar 23, 2015 |
JP |
2015-059760 |
Claims
1. A method of producing cobalt powder from a cobalt ammine sulfate
complex solution derived from a cobalt-containing material,
comprising: (1) a seed crystal addition step of adding cobalt
powder as seed crystals to the cobalt ammine sulfate complex
solution to form a mixed slurry; (2) a reduction step of blowing
hydrogen gas into the mixed slurry obtained in the seed crystal
addition step to precipitate a cobalt component in the mixed slurry
onto the seed crystals by hydrogen reduction reaction to form
cobalt powder, and thereby to form a reduced slurry containing the
cobalt powder; (3) a growth step of adding the cobalt ammine
sulfate complex solution to the cobalt powder obtained by
solid-liquid separation of the reduced slurry formed in the
reduction step (2) to form a slurry, blowing hydrogen gas into the
resulting slurry, and reducing, precipitating, and growing a cobalt
component in the slurry on a surface of the cobalt powder by
hydrogen reduction reaction to form a grown cobalt powder, and
thereby to form a slurry containing the grown cobalt powder; and
(4) a recovery step after the reduction step of subjecting the
reduced slurry containing the cobalt powder obtained in the
reduction step (2) to solid-liquid separation to separate and
recover the cobalt powder as a solid phase component, and another
recovery step after the growth step of subjecting the slurry
containing the cobalt powder obtained in the growth step (3) to
solid-liquid separation to separate and recover the cobalt powder
as a solid phase component.
2. The method of producing cobalt powder according to claim 1,
wherein, in the seed crystal addition step (1), a dispersant is
further added to the mixed slurry when the seed crystals are added
to the cobalt ammine sulfate complex solution to form the mixed
slurry.
3. The method of producing cobalt powder according to claim 1,
wherein, in the seed crystal addition step (1), an amount of the
seed crystals added is 1 to 200% by weight with respect to the
weight of cobalt in the cobalt ammine sulfate complex solution.
4. The method of producing cobalt powder according to claim 1,
wherein the cobalt ammine sulfate complex solution is obtained by:
a leaching step of dissolving the cobalt-containing material
containing nickel and impurities; a nickel separation step of
adjusting a pH of the leachate containing cobalt, nickel, and
impurities and obtained in the leaching step and then separating
the leachate into a crude cobalt sulfate solution and a nickel
recovery solution by solvent extraction; a solution purification
step of removing the impurities from the crude cobalt sulfate
solution obtained in the nickel separation step by any one or a
combination of solvent extraction, a sulfurization method, and a
neutralization method to obtain a cobalt sulfate solution; and a
complexing step of subjecting the cobalt sulfate solution to
complexing treatment with ammonia.
5. The method of producing cobalt powder according to claim 4,
wherein the cobalt-containing material is at least one of cobalt
and nickel mixed sulfide, crude cobalt sulfate, cobalt oxide,
cobalt hydroxide, cobalt carbonate, and metallic cobalt powder.
6. The method of producing cobalt powder according to claim 4,
wherein 2-ethylhexylphosphonic acid mono-2-ethylhexyl ester or
di-(2,4,4-trimethylpentyl)phosphinic acid is used as a solvent in
the solvent extraction of the solution purification step and the
nickel separation step.
7. The method of producing cobalt powder according to claim 1,
wherein, in the seed crystal addition step (1), the cobalt ammine
sulfate complex solution has an ammonium sulfate concentration of
100 to 500 g/l, and an ammonium concentration of 1.9 or more by
mole with respect to a cobalt concentration in the cobalt ammine
sulfate complex solution.
8. The method of producing cobalt powder according to claim 1,
wherein, regarding the hydrogen reduction reaction in the reduction
step (2) and the growth step (3), hydrogen reduction is performed
by maintaining a temperature of 120 to 250.degree. C. and a
pressure of 1.0 to 4.0 MPa.
9. The method of producing cobalt powder according to claim 2,
wherein the dispersant comprises one or more of an acrylate and a
sulfonate.
10. The method of producing cobalt powder according to claim 1,
further comprising: a cobalt powder briquetting step of processing
the cobalt powder having high purity and obtained in the growth
step (3) into cobalt briquettes in a block form using a briquetting
machine; and a briquette sintering step of sintering the resulting
cobalt briquettes in the block form under a condition of
maintaining a temperature of 500 to 1200.degree. C. in a hydrogen
atmosphere to form cobalt briquettes as a sintered compact.
11. The method of producing cobalt powder according to claim 1,
further comprising an ammonium sulfate recovery step of
concentrating a solution after reaction obtained by separating the
cobalt powder as the solid phase component by the solid-liquid
separation in the recovery steps (4) after the reduction step (2)
and the growth step (3), to precipitate ammonium sulfate to recover
ammonium sulfate crystals.
12. The method of producing cobalt powder according to claim 1,
further comprising an ammonia recovery step of adding an alkali to
a solution after reaction obtained by separating cobalt powder as
the solid phase component by the solid-liquid separation in the
recovery steps (4) after the reduction step (2) and the growth step
(3), and heating the resulting mixture to volatilize and recover
ammonia gas.
13. The method of producing cobalt powder according to claim 4,
wherein the ammonia recovered in the ammonia recovery step is
recycled in production processes in the method of producing the
cobalt powder, and used as an alkali for pH adjustment in the
nickel separation step, as an alkali for neutralization when the
neutralization method is used in the solution purification step,
and as an alkali used in the complexing step 4.
14. The method of producing cobalt powder according to claim 4,
wherein the seed crystals of the cobalt powder in the seed crystal
addition step (1) is cobalt powder formed by adding a reducing
agent to the cobalt sulfate solution obtained in the solution
purification step 4.
15. The method of producing cobalt powder according to claim 4,
wherein the seed crystals of the cobalt powder in the seed crystal
addition step (1) is cobalt powder formed by hydrogen reduction
reaction in which an insoluble solid is added to the cobalt ammine
sulfate complex solution obtained in the complexing step 4 and
hydrogen gas is blown into the resulting mixture at high
temperature and high pressure.
16. Cobalt briquettes obtained using the methods of claim 1.
Description
BACKGROUND
Field of the Invention
[0001] The present invention relates to a method for obtaining high
purity cobalt powder from a cobalt ammine sulfate complex solution
and briquettes prepared by shaping the powder.
Description of the Related Art
[0002] A method for industrially producing cobalt powder using a
hydrometallurgical process includes a method for producing cobalt
powder by dissolving a raw material in a sulfuric acid solution
followed by removing impurities to obtain a cobalt sulfate
solution, adding ammonia to the resulting cobalt sulfate solution
to form an ammine complex of cobalt, and feeding hydrogen gas into
the produced cobalt ammine sulfate complex solution to reduce
cobalt.
[0003] For example, Japanese Translation of PCT International
Application Publication No. JP-T-08-503999 describes a process for
producing cobalt powder by adding silver as seed crystals during
the reduction reaction to precipitate cobalt on the seed
crystals.
[0004] Specifically, the process is a method of producing cobalt
powder from an ammoniacal cobalt sulfate solution, including:
adding silver sulfate or silver nitrate to the solution in an
amount such that the proportion of soluble silver to cobalt is
about 0.3 g to 10 g of silver per kg of cobalt to be reduced,
adding an organic dispersant in an amount effective for preventing
the aggregation of cobalt metal powder to be produced, and heating
the resulting solution at a temperature in a range of 150 to
250.degree. C. with stirring at a hydrogen pressure of 2500 to 5000
KPa for a time sufficient to reduce cobalt sulfate to cobalt metal
powder.
[0005] However, the method has had a problem that affects product
quality because the incorporation of silver derived from seed
crystals into the product cannot be avoided.
[0006] There is also a method of obtaining cobalt powder using a
reducing agent other than hydrogen gas.
[0007] For example, Japanese Patent Laid-Open No. 2010-242143
discloses cobalt powder suitable as conductive particles for
conductive paste and multilayer capacitors, and a method for
producing the same. The method provides a method for producing
metal powder by a liquid phase reduction method that is improved so
that a particle aggregate may be hardly produced. Specifically, the
method for producing metal powder includes a first step of
dissolving a metal compound, a reducing agent, a complexing agent,
and a dispersant to prepare an aqueous solution containing metal
ions derived from the metal compound and a second step of adjusting
the pH of the aqueous solution to reduce the metal ions with the
reducing agent to precipitate the metal powder.
[0008] However, this production method requires high cost since a
large amount of expensive chemicals is used, and has had
economically disadvantageous problem for applying the method to the
industrial cobalt smelting process as described above.
[0009] Further, Translation of PCT International Application
Publication No. JP-T-2006-516679 discloses a method for recovering
nickel and cobalt using ammonia.
[0010] This method is a method for the recovery of nickel and
cobalt from nickel and cobalt-containing laterite ores, including:
a) roasting feed ore in a reducing atmosphere in a rotary kiln to
selectively reduce the nickel and cobalt, wherein either no, or
less than 2.5% by weight of reducing agent is added to the feed ore
prior to roasting; b) leaching the reduced ore with an aerated
solution of ammoniacal ammonium carbonate to extract the nickel and
cobalt into a leach solution; and c) separating the ore tailings
from the leach solution and recovering the nickel and cobalt by a
process selected from ammoniacal solvent extraction, precipitation
techniques or ion exchange.
[0011] Further, Japanese Patent Laid-Open No. 06-116662 discloses a
method for recovering copper, nickel, and cobalt from an ammonia
solution using hydrogen.
[0012] This method provides a method of efficiently leaching
copper, nickel, and cobalt from a deep-sea oxide mineral using
hydrogen. Specifically, activated hydrogen is provided to deep-sea
oxide mineral particles dispersed in an ammonia-ammonium salt
solution in the presence of a hydrogen-reducible reaction medium;
the reaction medium is reduced by the activated hydrogen; and the
above deep-sea oxide mineral is reduced by the reaction medium to
thereby leach copper, nickel, and cobalt in the mineral as ammine
complex ions.
[0013] However, this method requires a catalyst in which noble
metal such as platinum is carried on the surface of an inert solid
in order to accelerate the reduction reaction, and the method
cannot be said to be advantageous considering the cost required for
the amount of the catalyst and the replenishment for the natural
decrease of the catalyst required when performed on an industrial
scale.
[0014] Although various processes for producing cobalt powder have
been proposed as described above, there has been no method for
producing high purity cobalt powder using industrially inexpensive
hydrogen gas.
[0015] In such a situation, the present invention intends to
provide a production method for producing coarse particles of high
purity cobalt powder from a cobalt ammine sulfate complex solution
using fine cobalt powder and using industrially inexpensive
hydrogen gas.
SUMMARY
[0016] A first aspect of the present invention to solve such a
problem is a method for producing cobalt powder, including the
following steps (1) to (4) of: (1) a seed crystal addition step of
adding cobalt powder as seed crystals to a cobalt ammine sulfate
complex solution to form a mixed slurry; (2) a reduction step of
blowing hydrogen gas into the mixed slurry obtained in the seed
crystal addition step to precipitate a cobalt component in the
mixed slurry onto the seed crystals by hydrogen reduction reaction
to form cobalt powder, and thereby to form a reduced slurry
containing the cobalt powder; (3) a growth step of adding the
cobalt ammine sulfate complex solution to the cobalt powder
obtained by solid-liquid separation of the reduced slurry formed in
the reduction step to form a slurry, blowing hydrogen gas into the
resulting slurry, and reducing, precipitating, and growing a cobalt
component in the slurry on the surface of the cobalt powder by
hydrogen reduction reaction to form a grown cobalt powder, and
thereby to form a slurry containing the grown cobalt powder; and
(4) a recovery step after the reduction step of subjecting the
reduced slurry containing the cobalt powder obtained in the
reduction step (2) to solid-liquid separation to separate and
recover the cobalt powder as a solid phase component, and another
recovery step after the growth step of subjecting the slurry
containing the cobalt powder obtained in the growth step (3) to
solid-liquid separation to separate and recover the cobalt powder
as a solid phase component.
[0017] A second aspect of the present invention is a method for
producing cobalt powder according to the first aspect, wherein, in
the seed crystal addition step (1), a dispersant is further added
to the mixed slurry when the seed crystals are added to the cobalt
ammine sulfate complex solution to form a mixed slurry.
[0018] A third aspect of the present invention is a method for
producing cobalt powder according to the first and second aspects,
wherein, in the seed crystal addition step (1), the amount of the
seed crystals added is 1 to 200% by weight with respect to the
weight of cobalt in the cobalt ammine sulfate complex solution.
[0019] A fourth aspect of the present invention is a method for
producing cobalt powder according to the first to third aspects,
wherein the cobalt ammine sulfate complex solution is obtained by:
a leaching step of dissolving the cobalt-containing material
containing nickel and impurities; a nickel separation step of
adjusting a pH of the leachate containing cobalt, nickel, and
impurities and obtained in the leaching step and then separating
the leachate into a crude cobalt sulfate solution and a nickel
recovery solution by solvent extraction; a solution purification
step of removing the impurities from the crude cobalt sulfate
solution obtained in the nickel separation step by any or a
combination of solvent extraction, a sulfurization method, and a
neutralization method to obtain a cobalt sulfate solution; and a
complexing step of subjecting the cobalt sulfate solution to
complexing treatment with ammonia.
[0020] A fifth aspect of the present invention is a method for
producing cobalt powder according to the fourth aspect, wherein the
cobalt-containing material is at least one of cobalt and nickel
mixed sulfide, crude cobalt sulfate, cobalt oxide, cobalt
hydroxide, cobalt carbonate, and metallic cobalt powder.
[0021] A sixth aspect of the present invention is a method for
producing cobalt powder according to the fourth and fifth aspects,
wherein a solvent used in the solvent extraction of the nickel
separation step and the solution purification step is
2-ethylhexylphosphonic acid mono-2-ethylhexyl ester or
di-(2,4,4-trimethylpentyl)phosphinic acid.
[0022] A seventh aspect of the present invention is a method for
producing cobalt powder according to the first to third aspects,
wherein, in the seed crystal addition step (1), the concentration
of ammonium sulfate in the cobalt ammine sulfate complex solution
is 100 to 500 g/l, and the ammonium concentration is 1.9 or more by
mole with respect to the concentration of cobalt in the complex
solution.
[0023] An eighth aspect of the present invention is a method for
producing cobalt powder according to the first aspect, wherein,
regarding the hydrogen reduction in the hydrogen reduction
reactions in the reduction step (2) and the growth step (3),
hydrogen reduction is performed by maintaining the temperature of
120 to 250.degree. C. and the pressure of 1.0 to 4.0 MPa.
[0024] A ninth aspect of the present invention is a method for
producing cobalt powder according to the second aspect, wherein the
dispersant includes one or more of an acrylate and a sulfonate.
[0025] A tenth aspect of the present invention is a method for
producing cobalt powder according to the first aspect, including: a
cobalt powder briquetting step of processing the high purity cobalt
powder obtained in the growth step (3) into cobalt briquettes in a
block form using a briquetting machine; and a briquette sintering
step of sintering the resulting cobalt briquettes in the block form
under the condition of maintaining the temperature of 500 to
1200.degree. C. in a hydrogen atmosphere to form cobalt briquettes
as a sintered compact.
[0026] An eleventh aspect of the present invention is a method for
producing cobalt powder according to the first aspect, including an
ammonium sulfate recovery step of concentrating a solution after
reaction obtained by separating cobalt powder as a solid phase
component by the solid-liquid separation in the recovery steps (4)
after the reduction step (2) and the growth step (3), to
precipitate ammonium sulfate to recover ammonium sulfate
crystals.
[0027] A twelfth aspect of the present invention is a method for
producing cobalt powder according to the first aspect, including an
ammonia recovery step of adding an alkali to a solution after
reaction obtained by separating cobalt powder as the solid phase
component by the solid-liquid separation in the recovery steps (4)
after the reduction step (2) and the growth step (3), and heating
the resulting mixture to volatilize and recover ammonia gas.
[0028] A thirteenth aspect of the present invention is a method for
producing cobalt powder according to the first aspect, wherein the
ammonia recovered in the ammonia recovery step is recycled in the
production processes in the method for producing the cobalt powder
according to the first aspect, and used as an alkali for pH
adjustment in the nickel separation step according to the fourth
aspect, as an alkali for neutralization when the neutralization
method is used in the solution purification step according to the
fourth aspect, and as an alkali used in the complexing step
according to the fourth aspect.
[0029] A fourteenth aspect of the present invention is a method for
producing cobalt powder according to the first aspect, wherein the
seed crystals of the cobalt powder in the seed crystal addition
step (1) is cobalt powder formed by adding a reducing agent to the
cobalt sulfate solution obtained in the solution purification step
according to the fourth aspect.
[0030] A fifteenth aspect of the present invention is a method for
producing cobalt powder according to the first aspect, wherein the
seed crystals of the cobalt powder in the seed crystal addition
step (1) is cobalt powder formed by hydrogen reduction reaction in
which an insoluble solid is added to the cobalt ammine sulfate
complex solution obtained in the complexing step according to the
fourth aspect and hydrogen gas is blown into the resulting mixture
at high temperature and high pressure.
[0031] A sixteenth aspect of the present invention is cobalt
briquettes obtained using the methods of the first to fifteenth
aspects.
[0032] In a method for producing cobalt powder using hydrogen gas
from a cobalt ammine sulfate complex solution, high purity cobalt
powder and cobalt briquettes can be efficiently obtained by
employing the present invention, and an industrially remarkable
effect can be thus achieved.
BRIEF DESCRIPTION OF DRAWINGS
[0033] FIG. 1 is a production flow chart of cobalt powder according
to the present invention.
[0034] FIG. 2 is a view showing the change in the average particle
size by the number of times of the growth step in Example 1.
DETAILED DESCRIPTION
[0035] According to the present invention, in the production method
for obtaining cobalt powder from a cobalt ammine sulfate complex
solution, it is characterized in that high purity cobalt powder
containing a smaller amount of impurities is produced from the
cobalt ammine sulfate complex solution by subjecting a process
solution of the hydrometallurgical process to the steps (1) to (4)
in sequence discussed below.
[0036] Hereinafter, the method for producing high purity cobalt
powder according to the present invention will be described with
reference to the production flow chart of high purity cobalt powder
according to the present invention shown in FIG. 1.
[Leaching Step]
[0037] First, the leaching step is a step of dissolving a
cobalt-containing material, serving as a starting material, such as
an industrial intermediate including one or a mixture selected from
cobalt and nickel mixed sulfide, crude cobalt sulfate, cobalt
oxide, cobalt hydroxide, cobalt carbonate, and cobalt powder, with
sulfuric acid to leach cobalt to produce a leachate, and can be
performed by a known method disclosed in Japanese Patent Laid-Open
No. 2005-350766 and the like.
[Nickel Separation Step]
[0038] Next, the pH of the leachate is adjusted, and the resulting
leachate is subjected to the nickel separation step.
[0039] This nickel separation step is a step of bringing an organic
phase into contact with a pH-adjusted leachate (aqueous phase),
which is obtained in the leaching step and then subjected to pH
adjustment, to exchange the components in each phase, thereby
increasing the concentration of some components in the aqueous
phase and reducing the concentration of other different
components.
[0040] In the present invention, "2-ethylhexylphosphonic acid
mono-2-ethylhexyl ester" or "di-(2,4,4-trimethylpentyl)phosphinic
acid" is used as the organic phase to selectively extract cobalt in
the leachate of the aqueous phase, and a crude cobalt sulfate
solution is obtained by stripping using sulfuric acid.
[0041] Further, ammonia produced in an ammonia recovery step as
described below may be used as the aqueous ammonia used for pH
adjustment during this step.
[Solution Purification Step]
[0042] The solution purification step is a step of reducing
impurities contained in the crude cobalt sulfate solution obtained
in the nickel separation step, and the step is performed by any one
or a combination of solvent extraction of selectively extracting
impurity elements in the crude cobalt sulfate solution using
"2-ethylhexylphosphonic acid mono-2-ethylhexyl ester" or
"di-(2,4,4-trimethylpentyl)phosphinic acid" as the organic phase to
obtain a high purity cobalt sulfate solution, a sulfurization
method of adding a sulfurizing agent such as hydrogen sulfide gas,
sodium sulfide, potassium sulfide, and sodium hydrogen sulfide to
selectively precipitate and remove impurities, and a neutralization
method of adding an alkali such as sodium hydroxide, calcium
hydroxide, sodium carbonate, calcium carbonate, and magnesium
hydroxide to selectively precipitate and remove impurities.
[Complexing Step]
[0043] The complexing step is a step of adding ammonia in the form
of ammonia gas or aqueous ammonia to the high purity cobalt sulfate
solution obtained in the solution purification step to subject the
solution to complexing treatment to produce a cobalt ammine sulfate
complex which is an ammine complex of cobalt, thus forming a cobalt
ammine sulfate complex solution thereof.
[0044] The ammonia is added so that the ammonium concentration at
this time may be 1.9 or more by mole based on the concentration of
cobalt in the solution. If the concentration of the ammonia to be
added is less than 1.9, cobalt will not form an ammine complex, but
a precipitate of cobalt hydroxide will be produced.
[0045] Further, in order to adjust the concentration of ammonium
sulfate, ammonium sulfate may be added in this step.
[0046] The concentration of ammonium sulfate at this time is
preferably 100 to 500 g/L. If the concentration is more than 500
g/L, solubility will be exceeded to precipitate crystals to prevent
operation. Further, it is difficult to achieve a concentration of
less than 100 g/L in terms of the metal balance in the process.
[0047] Also, ammonia produced in the ammonia recovery step as
described below may be used as the ammonia gas or aqueous ammonia
used in this step.
[Steps of Producing Cobalt Powder from Cobalt Ammine Sulfate
Complex Solution]
[0048] The steps of producing cobalt powder from the high purity
cobalt ammine sulfate complex solution shown by the treatment steps
in FIG. 1 will be described below.
(1) Seed Crystal Addition Step
[0049] This is the step of adding cobalt powder as seed crystals in
the form of a cobalt powder slurry to the cobalt ammine sulfate
complex solution to form a mixed slurry containing the seed
crystals.
[0050] The weight of the seed crystals added at this time is
preferably 1 to 200% by weight based on the weight of cobalt in the
cobalt ammine sulfate complex solution. If the weight of the seed
crystals is less than 1%, the reaction efficiency during the
reduction in the next step will be significantly reduced, which is
not preferred. Further, if the weight of the seed crystals exceeds
200%, the amount of the seed crystals used will be excessively
large, which generates a problem in the handling of the seed
crystals and is not economical because the production of the seed
crystals requires much cost. Thus, such an amount of seed crystals
used is not preferred.
[0051] The cobalt powder can be produced by mixing a reducing agent
with the high purity cobalt sulfate solution obtained in the
solvent extraction step.
[0052] The reducing agents which can be used here include, but are
not limited to, hydrazine and sodium sulfite which are widely used
industrially.
[0053] At this time, an alkali may also be mixed, and pH is
preferably adjusted to 7 to 12 using sodium hydroxide.
[0054] Further, a reaction temperature is preferably 25 to
80.degree. C. If the temperature is less than 25.degree. C.,
reaction time will increase, and the industrial application of the
long reaction time will not be realistic. On the other hand, if the
temperature is higher than 80.degree. C., the material of a
reaction vessel will be limited to increase the cost of equipment.
Further, the particle size of the cobalt powder produced can be
reduced by adding a small amount of surfactant at this time.
[0055] As an another method of producing seed crystals, the seed
crystals can be produced by blowing hydrogen gas into a cobalt
ammine sulfate complex solution under the conditions of the
reduction step to be described below. At this time, recovery
efficiency can be improved by adding an insoluble solid, such as
iron powder, alumina balls, and zirconia balls, and a dispersant to
the cobalt ammine sulfate complex solution.
[0056] The dispersant may be added to the mixed slurry containing
seed crystals at the same time. Since the seed crystals are
dispersed by adding the dispersant, the reaction efficiency in the
reduction step as the next step can be effectively improved.
[0057] The dispersants used here include, but are not limited to,
those having one or more of an acrylate and a sulfonate, and
polyacrylates and lignin sulfonates are preferred as those which
can be industrially inexpensively obtained.
(2) Reduction Step
[0058] Hydrogen gas is blown into the mixed slurry obtained in the
seed crystal addition step (1) and cobalt is precipitated from the
solution onto the seed crystals by the hydrogen reduction reaction
at high pressure.
[0059] At this time, reaction temperature is preferably 120 to
250.degree. C. If the temperature is less than 120.degree. C.,
reduction efficiency will be reduced, and even if the temperature
exceeds 250.degree. C., the reaction will not be accelerated, and
the loss of thermal energy and the like will increase, which is not
preferred.
[0060] Further, the pressure during the reaction is preferably 1.0
to 4.0 MPa. If the pressure is less than 1.0 MPa, reaction
efficiency will be reduced, and even if the pressure exceeds 4.0
MPa, there will be no influence on the reaction, and the loss of
hydrogen gas will increase.
[0061] In the liquid of the mixed slurry, magnesium ions, sodium
ions, sulfate ions, and ammonium ions are mainly present as
impurities, but since these impurities all remain in the solution,
high purity cobalt powder can be produced.
(3) Growth Step
[0062] To the slurry obtained by adding the cobalt ammine sulfate
complex solution obtained in the complexing step described above to
the high purity cobalt powder, is fed hydrogen gas at high pressure
according to the same method as the reduction step (2), to reduce
and precipitate the cobalt component in the slurry onto the high
purity cobalt powder by the hydrogen reduction reaction, thereby to
form a slurry containing grown cobalt particles.
[0063] Further, high purity cobalt powder having a larger particle
size can be produced by repeating this growth step a plurality of
times. Further, the high purity cobalt powder having a larger
particle size is separated into high purity cobalt powder and a
solution after reaction by a recovery step. The resulting high
purity cobalt powder may be finished into the shape of briquettes,
which are coarser, more difficult to oxidize, and more easily
handled, through the briquetting and briquette firing steps
described below.
[0064] Furthermore, the ammonium sulfate contained in the solution
after reaction obtained in the recovery step can be recovered in an
ammonium sulfate recovery step, or ammonia can also be recovered in
an ammonia recovery step.
(4) Recovery Steps after Reduction Step and Growth Step
[0065] The reduced slurry formed in the reduction step (2) or the
slurry containing the grown cobalt particles formed in the growing
step (3) is subjected to solid-liquid separation to recover high
purity cobalt powder and a solution after reaction.
[Cobalt Powder Briquetting Step]
[0066] The high purity cobalt powder produced by the present
invention is dried and then processed for shaping with a
briquetting machine or the like to obtain cobalt briquettes in a
block form as a product form.
[0067] Further, in order to improve the processability to form the
briquettes, a material that does not impair the product quality
such as water may be added as a binder to the cobalt powder
depending on conditions.
[Briquette Sintering Step]
[0068] The cobalt briquettes prepared in the briquetting step is
subjected to roasting and sintering in a hydrogen atmosphere to
make a briquette sintered compact. This treatment is performed for
increasing the strength and removing ammonia, sulfur, and carbon
components remaining in a very small amount, and the roasting and a
sintering temperature of the treatment is preferably 500 to
1200.degree. C. If the temperature is less than 500.degree. C., the
sintering will be insufficient, and even if the temperature exceeds
1200.degree. C., the efficiency will hardly change but the loss of
energy will increase.
[Ammonium Sulfate Recovery Step]
[0069] Ammonium sulfate and ammonia are contained in the solution
after reaction produced in the recovery step (4).
[0070] Thus, ammonium sulfate can be recovered as ammonium sulfate
crystals by heating and concentrating the solution after reaction
to crystallize ammonium sulfate.
[Ammonia Recovery Step]
[0071] On the other hand, an alkali is added to the solution after
reaction to adjust the pH to a range of 10 to 13, and then the
resulting solution can be heated to volatilize ammonia as a gas to
recover the ammonia.
[0072] The alkali used here preferably includes, but is not limited
to, sodium hydroxide and slaked lime, because they are industrially
inexpensive.
[0073] Further, the recovered ammonia gas is brought into contact
with water to produce aqueous ammonia, and the resulting aqueous
ammonia may also be repeatedly used for the pH adjustment before
the nickel separation step to which ammonia is added, in the
solution purification step in the case of using the solvent
extraction, and in the complexing step.
EXAMPLES
[0074] The present invention will be described below in more detail
using Examples.
Example 1
(1) Seed Crystal Addition Step
[0075] To a solution containing cobalt sulfate in which 75 g of
cobalt was contained and 330 g of ammonium sulfate, was added 191
ml of 25% aqueous ammonia to prepare a solution, which was adjusted
so that the total volume of the solution was 1000 ml. To the
resulting solution, were added 75 g (100% based on the weight of
cobalt) of cobalt powder having an average particle size of 10
.mu.m as seed crystals and 12.5 g of sodium polyacrylate (40%
solution) as a dispersant to prepare a mixed slurry.
(2) Reduction Step
[0076] The mixed slurry prepared in the seed crystal addition step
was charged to an autoclave and heated to 185.degree. C. with
stirring, and then hydrogen gas was blown and fed into the mixed
slurry so that the pressure in the autoclave became 3.5 MPa to
subject the mixed slurry to cobalt powder production treatment
which is reduction treatment.
[0077] After the lapse of one hour from the start of feeding
hydrogen gas, the feed of hydrogen gas was stopped, and the
autoclave was cooled.
(3) Recovery Step after Reduction Step
[0078] A reduced slurry obtained after cooling was subjected to
solid-liquid separation by filtration, and the slurry was separated
to recover high purity cobalt powder having a small size and a
solution after reaction. The cobalt powder recovered at this time
was 141 g.
(4) Growth Step
[0079] Next, to a solution containing cobalt sulfate in which 75 g
of cobalt is contained and 330 g of ammonium sulfate, was added 191
ml of 25% aqueous ammonia to prepare a solution, which was adjusted
so that the total volume of the solution was 1000 ml.
[0080] To the resulting solution, was added the entire amount of
the high purity cobalt powder having the small size obtained in the
above recovery step after the reduction step as seed crystals to
prepare a mixed slurry.
[0081] The mixed slurry was charged to an autoclave and heated to
185.degree. C. with stirring, and hydrogen gas was blown and fed
into the slurry so that the pressure in the autoclave became 3.5
MPa.
[0082] After the lapse of one hour from the start of feeding
hydrogen gas, the feed of hydrogen gas was stopped, and the
autoclave was cooled. A slurry obtained after cooling was subjected
to solid-liquid separation by filtration to recover high purity
cobalt powder having grown particles.
[0083] A portion of the cobalt powder was divided to measure the
particle size using a known method, and the remainder was added as
the cobalt powder having a small size described in the above growth
step to repeat the growth step in which the cobalt powder having a
small size is subjected to the reduction with hydrogen gas in the
autoclave.
[0084] FIG. 2 shows the average particle size (.mu.m) of cobalt
powder versus the number of times of the growth step (which is the
number of times of repetition) (times). It was verified that the
cobalt powder grew and coarsened for every repetition.
[0085] The number of times of repetition may be optionally
determined taking the productivity and the economical efficiency,
such as required size of powder and required facility size and
labor, into consideration.
Example 2
[0086] To 1000 ml of a cobalt ammine sulfate complex solution shown
in Table 1, was added 75 g of cobalt powder having an average
particle size of 10 .mu.m as seed crystals. Then, the resulting
mixture was charged to an autoclave and then heated to 185.degree.
C. with stirring, and hydrogen gas was blown and fed into the
mixture so that the pressure in the autoclave became 3.5 MPa.
[0087] After the lapse of one hour from the start of feeding
hydrogen gas, the feed of hydrogen gas was stopped, and the
autoclave was cooled. A slurry obtained after cooling was subjected
to solid-liquid separation by filtration to recover cobalt powder,
which was washed with pure water and then analyzed for the impurity
content in the cobalt powder.
[0088] The results are shown in Table 1.
[0089] The mixing of Mg, Na and Ca into the cobalt powder was not
observed, and high purity cobalt powder was able to be
produced.
TABLE-US-00001 TABLE 1 Co Mg Na Ca Cobalt ammine sulfate 31 0.9 31
0.2 complex solution [g/L] High purity cobalt powder -- <0.005
<0.005 <0.005 [wt %]
Comparative Example 1
[0090] To a solution containing cobalt sulfate in which 75 g of
cobalt is contained and 330 g of ammonium sulfate, was added 191 ml
of 25% aqueous ammonia to prepare a solution, which was adjusted so
that the total volume of the solution was 1000 ml.
[0091] The slurry was charged to an autoclave without adding seed
crystals, and then hydrogen gas was fed until the pressure in the
autoclave became 3.5 MPa, with stirring, followed by heating to
185.degree. C. followed by holding the temperature for one hour.
The amount of cobalt powder which was able to be recovered from the
inside of the autoclave after cooling was only 1 g.
[0092] As having been described above, the use of the present
invention allows us to efficiently obtain high purity cobalt powder
and cobalt briquettes.
* * * * *