U.S. patent application number 15/755147 was filed with the patent office on 2018-09-06 for method for producing nickel powder.
This patent application is currently assigned to SUMITOMO METAL MINING CO., LTD.. The applicant listed for this patent is SUMITOMO METAL MINING CO., LTD.. Invention is credited to Shin-ichi Heguri, Yoshitomo Ozaki.
Application Number | 20180250752 15/755147 |
Document ID | / |
Family ID | 59738789 |
Filed Date | 2018-09-06 |
United States Patent
Application |
20180250752 |
Kind Code |
A1 |
Ozaki; Yoshitomo ; et
al. |
September 6, 2018 |
METHOD FOR PRODUCING NICKEL POWDER
Abstract
Provided is a method for producing coarse particles of so-called
high purity nickel powder containing a small amount of impurities
and particularly having a low sulfur content from a nickel ammine
sulfate complex solution using fine nickel powder. The method for
producing nickel powder from a nickel sulfate solution includes the
treatment steps of: (1) a hydroxylation step of producing a
precipitate of nickel hydroxide; (2) a complexing step of forming a
mixture slurry containing a nickel ammine sulfate complex solution,
seed crystals, and the nickel hydroxide; (3) a reduction step of
forming a reduced slurry containing the nickel powder formed by
precipitation of a nickel component on the seed crystals: and (4) a
solid-liquid separation step of subjecting the reduced slurry
formed in the reduction step (3) to solid-liquid separation to
separately recover the nickel powder and a post-reduction
solution.
Inventors: |
Ozaki; Yoshitomo;
(Niihama-shi, JP) ; Heguri; Shin-ichi;
(Niihama-shi, JP) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
SUMITOMO METAL MINING CO., LTD. |
Tokyo |
|
JP |
|
|
Assignee: |
SUMITOMO METAL MINING CO.,
LTD.
Tokyo
JP
|
Family ID: |
59738789 |
Appl. No.: |
15/755147 |
Filed: |
August 24, 2016 |
PCT Filed: |
August 24, 2016 |
PCT NO: |
PCT/JP2016/074694 |
371 Date: |
February 26, 2018 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
B22F 2301/15 20130101;
B22F 2998/10 20130101; B22F 9/26 20130101; B22F 2999/00 20130101;
B22F 2999/00 20130101; B22F 9/26 20130101; B22F 2201/013 20130101;
B22F 2998/10 20130101; B22F 9/26 20130101; B22F 3/02 20130101; B22F
3/1007 20130101; B22F 2999/00 20130101; B22F 3/1007 20130101; B22F
2201/013 20130101 |
International
Class: |
B22F 9/26 20060101
B22F009/26 |
Foreign Application Data
Date |
Code |
Application Number |
Aug 31, 2015 |
JP |
2015-170115 |
Feb 23, 2016 |
JP |
2016-032519 |
May 19, 2016 |
JP |
2016-100070 |
Claims
1. A method of producing nickel powder containing a small amount of
impurities from a nickel sulfate solution containing the
impurities, comprising the process steps of: (1) a hydroxylation
step of adding an alkali to the nickel sulfate solution containing
the impurities to produce a precipitate of nickel hydroxide having
a decreased concentration of the impurities contained therein; (2)
a complexing step of adding a post-reduction solution obtained in a
solid-liquid separation step (4) and nickel powder as seed crystals
to the precipitate of nickel hydroxide having the decreased
concentration of the impurities contained therein and produced in
the hydroxylation step (1), and dissolving the precipitate of
nickel hydroxide, to form a mixture slurry containing a nickel
ammine sulfate complex solution, seed crystals, nickel hydroxide
and the impurities contained in the precipitate of nickel
hydroxide; (3) a reduction step of blowing hydrogen gas into the
mixture slurry formed in the complexing step (2) to form a reduced
slurry containing nickel powder formed by precipitation of a nickel
component in the mixture slurry on the seed crystals; and (4) a
solid-liquid separation step of subjecting the reduced slurry
formed in the reduction step (3) to solid-liquid separation to
separately recover the nickel powder and a post-reduction solution,
repeatedly sieving the recovered nickel powder by particle size and
subjecting a nickel powder having particles smaller than a
predetermined size as seed crystals to either or both of the
complexing step (2) and the reduction step (3), and, repeatedly
subjecting the recovered post-reduction solution to the complexing
step (2).
2. The method of producing nickel powder according to claim 1,
wherein repeated operation of sieving the nickel powder recovered
in the solid-liquid separation step (4) by particle size, and
adding a nickel powder having particles smaller than a
predetermined size as seed crystals to either or both of the
complexing step (2) and the reduction step (3) provides a nickel
powder coarser than the nickel powder of seed crystals.
3. The method of producing nickel powder according to claim 2,
wherein seed crystals to be added to either or both of the
complexing step (2) and the reduction step (3) have an average
particle size of 0.1 to 100 .mu.m.
4. The method of producing nickel powder according to claim 1,
wherein, in the complexing step (2), when the mixture slurry
containing the nickel ammine sulfate complex solution, the seed
crystals, and nickel hydroxide is formed, a dispersant is further
added to the mixture slurry.
5. The method of producing nickel powder according to claim 1,
wherein, in the complexing step (2), an amount of the seed crystals
added is 1 to 100% based on the weight of nickel in the nickel
ammine sulfate complex solution.
6. The method of producing nickel powder according to claim 1,
wherein the reduced slurry is sieved, and undersize nickel powder
and undersize reduced slurry of the resulting post-reduction
solution are repeatedly used as parts of the nickel powder as seed
crystals and the post-reduction solution in the complexing step
(2).
7. The method of producing nickel powder according to claim 6,
wherein the complexing step (2) is composed of two steps: a
dissolution step of adding the post-reduction solution to obtain
the nickel ammine sulfate complex solution; and a seed crystal
addition step of adding the mixture slurry containing either nickel
powder or nickel powder and the post-reduction solution.
8. The method of producing nickel powder according to claim 1,
wherein the nickel sulfate solution is obtained by dissolving, in a
sulfuric acid solution, at least one of nickel and cobalt mixed
sulfide, nickel sulfide, crude nickel sulfate, nickel oxide, nickel
hydroxide, nickel carbonate, and metallic nickel powder which is
recovered by leaching a nickel oxide ore.
9. The method of producing nickel powder according to claim 1,
wherein the nickel sulfate solution is obtained by: a leaching step
of dissolving a nickel-containing material having cobalt as an
impurity; and a solvent extraction step of adjusting pH of the
leachate containing nickel and cobalt obtained in the leaching step
and then separating the leachate into a nickel sulfate solution and
a cobalt-recovering solution by solvent extraction.
10. The method of producing nickel powder according to claim 1,
wherein a concentration of ammonium sulfate in the nickel ammine
sulfate complex solution is 100 to 500 g/L, and an ammonium
concentration is 1.9 or more in a molar ratio based on a nickel
concentration in the nickel ammine sulfate complex solution.
11. The method of producing nickel powder according to claim 1,
wherein, in the reduction step (3), hydrogen gas is blown while
maintaining the temperature in the range of 100 to 200.degree. C.
and the pressure in the range of 0.8 to 4.0 MPa.
12. The method of producing nickel powder according to claim 4,
wherein the dispersant contains a polyacrylate salt.
13. The method of producing nickel powder according to claim 1,
comprising: a nickel powder briquetting step of processing the
nickel powder obtained in the reduction step (3) into nickel
briquettes in a block form using a briquetting machine; and a
briquette sintering step of subjecting the resulting nickel
briquettes in the block form to sintering treatment under holding
conditions at a temperature of 500 to 1200.degree. C. in a hydrogen
atmosphere to form nickel briquettes as a sintered compact.
14. The method of producing nickel powder according to claim 1,
comprising an ammonium sulfate recovery step of concentrating the
post-reduction solution from the solid-liquid separation step (4)
to crystallize ammonium sulfate and recovering ammonium sulfate
crystals.
15. The method of producing nickel powder according to claim 1,
comprising an ammonia recovery step of adding an alkali to the
post-reduction solution from the solid-liquid separation step (4),
heating the resulting mixture to volatilize ammonia gas and
recovering the ammonia gas.
Description
BACKGROUND
Field of the Invention
[0001] The present invention relates to a method for obtaining high
purity nickel powder having a low sulfur content from a nickel
ammine sulfate complex solution and briquettes prepared by pressing
the powder.
[0002] Particularly, the present invention can be applied to the
treatment of an in-process intermediate solution generated from a
nickel hydrometallurgical process.
Description of the Related Art
[0003] A method for industrially producing nickel powder using a
hydrometallurgical process includes a method for producing nickel
powder by dissolving a raw material in a sulfuric acid solution
followed by removing impurities to obtain a nickel sulfate
solution, adding ammonia to the resulting nickel sulfate solution
to form an ammine complex of nickel, and feeding hydrogen gas into
the produced nickel ammine sulfate complex solution to reduce
nickel.
[0004] For example, POWDER METALLURGY, 1958, No. 1/2, pp. 40-52
describes a process for producing nickel powder by adding an iron
compound as seed crystals during the reduction reaction to
precipitate nickel on the iron compound, but the process is
problematic in that iron derived from the seed crystals is mixed
into the product.
[0005] Further, a method for obtaining nickel powder using a
reducing agent other than hydrogen gas has also been proposed.
[0006] For example, Japanese Patent Laid-Open No. 2005-240164
discloses nickel powder which is inexpensive, is excellent in
weatherability, has low electric resistance in a state where it is
kneaded with a resin, reduces initial electric resistance and
electric resistance in use, can be stably used over a long period
of time, and is suitable as conductive particles for a conductive
paste and a conductive resin, and a method for producing the
same.
[0007] The nickel powder disclosed in Japanese Patent Laid-Open No.
2005-240164 contains 1 to 20% by mass of cobalt with the balance
consisting of nickel and unavoidable impurities, includes secondary
particles in which primary particles are aggregated, and has an
oxygen content of 0.8% by mass or less. Cobalt is contained only in
the surface layer part of the secondary particles, and it is said
that the cobalt content in the surface layer part is preferably 1
to 40% by mass. When the nickel powder is intended to be obtained
by the disclosed production method, cobalt will coexist. Therefore,
the method is not suitable for an application in which nickel and
cobalt are present in combination, for example, in a nickel oxide
ore; these metals are separated; and each metal is intended to be
economically recovered as high purity metal.
[0008] Further, Japanese Patent Laid-Open No. 2010-242143 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.
[0009] 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.
[0010] However, this production method requires high cost since an
expensive chemical is used, and is not economically advantageous
for applying the method to a process operated on a large scale as
the above nickel smelting.
[0011] Although various processes for producing nickel powder have
been proposed as described above, a method for producing high
purity nickel powder using industrially inexpensive hydrogen gas
has not been proposed.
[0012] In these circumstances, the present invention intends to
provide a method for producing coarse particles of so-called high
purity nickel powder containing a smaller amount of impurities and
particularly having a low sulfur content from a nickel ammine
sulfate complex solution using industrially inexpensive hydrogen
gas and using fine nickel powder.
SUMMARY
[0013] The first aspect of the present invention to solve the above
problem is a method for producing nickel powder containing a small
amount of impurities from a nickel sulfate solution containing the
impurities, including the following process steps (1) to (4):
[0014] (1) a hydroxylation step of adding an alkali to the nickel
sulfate solution containing the impurities to produce a precipitate
of nickel hydroxide having a decreased concentration of the
impurities contained therein; [0015] (2) a complexing step of
adding a post-reduction solution obtained in a solid-liquid
separation step (4) and nickel powder as seed crystals to the
precipitate of nickel hydroxide having the decreased concentration
of the impurities contained therein and produced in the
hydroxylation step (1), and dissolving the precipitate of nickel
hydroxide, to form a mixture slurry containing a nickel ammine
sulfate complex solution, seed crystals, nickel hydroxide and the
impurities contained in the precipitate of nickel hydroxide; [0016]
(3) a reduction step of blowing hydrogen gas into the mixture
slurry formed in the complexing step (2) to form a reduced slurry
containing nickel powder formed by precipitation of a nickel
component in the mixture slurry on the seed crystals; and [0017]
(4) the solid-liquid separation step of subjecting the reduced
slurry formed in the reduction step (3) to solid-liquid separation
to separately recover the nickel powder and a post-reduction
solution, repeatedly sieving the recovered nickel powder by
particle size and subjecting a nickel powder having particles
smaller than a predetermined size as seed crystals to either or
both of the complexing step (2) and the reduction step (3), and
repeatedly subjecting the recovered post-reduction solution to the
complexing step (2).
[0018] The second aspect of the present invention is a method for
producing nickel powder according to the first aspect, wherein
repeated operation of sieving the nickel powder recovered in the
solid-liquid separation step (4) by particle size, and adding a
nickel powder having particles smaller than a predetermined size as
seed crystals to either or both of the complexing step (2) and the
reduction step (3) provides a nickel powder coarser than the nickel
powder of seed crystals.
[0019] The third aspect of the present invention is a method for
producing nickel powder according to the second aspect, wherein
seed crystals to be added to either or both of the complexing step
(2) and the reduction step (3) have an average particle size of 0.1
to 100 .mu.m.
[0020] The fourth aspect of the present invention is a method for
producing nickel powder according to the first to the third
aspects, wherein, in the complexing step (2), when the mixture
slurry containing the nickel ammine sulfate complex solution, the
seed crystals, and nickel hydroxide is formed, a dispersant is
further added to the mixture slurry.
[0021] The fifth aspect of the present invention is a method for
producing nickel powder according to the first to the fourth
aspects, wherein, in the complexing step (2), the amount of the
seed crystals added is 1 to 100% based on the weight of nickel in
the nickel ammine sulfate complex solution.
[0022] The sixth aspect of the present invention is a method for
producing nickel powder according to the first to the fifth
aspects, wherein the reduced slurry is sieved, and the undersize
nickel powder and the undersize reduced slurry of the resulting
post-reduction solution are repeatedly used as parts of the nickel
powder as seed crystals and the post-reduction solution in the
complexing step (2).
[0023] The seventh aspect of the present invention is a method for
producing nickel powder according to the sixth aspect, wherein the
complexing step (2) is composed of two steps: a dissolution step of
adding the post-reduction solution to obtain the nickel ammine
sulfate complex solution: and a seed crystal addition step of
adding the mixture slurry containing either nickel powder or nickel
powder and the post-reduction solution.
[0024] The eighth aspect of the present invention is a method for
producing nickel powder according to the first aspect, wherein the
nickel sulfate solution is obtained by dissolving, in a sulfuric
acid solution, at least one of nickel and cobalt mixed sulfide,
nickel sulfide, coarse nickel sulfate, nickel oxide, nickel
hydroxide, nickel carbonate, and metallic nickel powder which is
recovered by leaching a nickel oxide ore.
[0025] The ninth aspect of the present invention is a method for
producing nickel powder according to the first aspect, wherein the
nickel sulfate solution is obtained by: a leaching step of
dissolving a nickel-containing material having cobalt as an
impurity; and a solvent extraction step of adjusting pH of the
leachate containing nickel and cobalt obtained in the leaching step
and then separating the leachate into a nickel sulfate solution and
a cobalt-recovering solution by solvent extraction.
[0026] A tenth aspect of the present invention is a method for
producing nickel powder according to the first aspect, wherein the
concentration of ammonium sulfate in the nickel ammine sulfate
complex solution is 100 to 500 g/L, and the ammonium concentration
is 1.9 or more in a molar ratio based on the nickel concentration
in the nickel ammine sulfate complex solution.
[0027] The eleventh aspect of the present invention is a method for
producing nickel powder according to the first aspect, wherein in
the reduction step (3) hydrogen gas is blown while maintaining the
temperature in the range of 100 to 200.degree. C. and the pressure
in the range of 0.8 to 4.0 MPa.
[0028] The twelfth aspect of the present invention is a method for
producing nickel powder according to the fourth aspect, wherein the
dispersant contains a polyacrylate salt.
[0029] A thirteenth aspect of the present invention is a method for
producing nickel powder according to the first aspect, including: a
nickel powder briquetting step of processing the nickel powder
obtained in the reduction step (3) into nickel briquettes in a
block form using a briquetting machine; and a briquette sintering
step of subjecting the resulting nickel briquettes in the block
form to sintering treatment under holding conditions at a
temperature of 500 to 1200.degree. C. in a hydrogen atmosphere to
form nickel briquettes as a sintered compact.
[0030] The fourteenth aspect of the present invention is a method
for producing nickel powder according to the first aspect,
including an ammonium sulfate recovery step of concentrating the
post-reduction solution from the solid-liquid separation step (4)
to crystallize ammonium sulfate and recovering ammonium sulfate
crystals.
[0031] The fifteenth aspect of the present invention is a method
for producing nickel powder according to the first aspect,
including an ammonia recovery step of adding an alkali to the
post-reduction solution from the solid-liquid separation step (4),
heating the resulting mixture to volatilize ammonia gas and
recovering the ammonia gas.
Advantageous Effect of Invention
[0032] According to the present invention, in a method for
producing nickel powder using hydrogen gas from a nickel ammine
sulfate complex solution, high purity nickel powder containing a
smaller amount of impurities can be easily obtained and an
industrially remarkable effect can be thus achieved.
BRIEF DESCRIPTION OF DRAWING
[0033] FIG. 1 is a production flow chart of nickel powder according
to the present invention.
DETAILED DESCRIPTION
[0034] The present invention is characterized in that high purity
nickel powder containing a smaller amount of impurities is produced
from a nickel ammine sulfate complex solution by subjecting a
process solution of the hydrometallurgical process to steps (1) to
(4) as shown below, in the method for obtaining nickel powder from
a nickel ammine sulfate complex solution.
[0035] Hereinafter, the method for producing high purity nickel
powder according to the present invention will be described with
reference to the production flow chart of high purity nickel powder
according to the present invention shown in FIG. 1.
[Leaching Step]
[0036] First, the leaching step is a step of dissolving a
nickel-containing material, serving as a starting material, such as
an industrial intermediate including one or a mixture of two or
more selected from nickel and cobalt mixed sulfide, crude nickel
sulfate, nickel oxide, nickel hydroxide, nickel carbonate, nickel
powder, and the like with sulfuric acid to leach nickel to produce
a leachate (sulfuric acid solution containing nickel), and is
performed by a known method, for example, disclosed in Japanese
Patent Laid-Open No. 2005-350766.
[Solvent Extraction Step]
[0037] Next, the pH of the leachate is adjusted, and the resulting
leachate is subjected to the solvent extraction step.
[0038] This step is a step of bringing an organic phase into
contact with the leachate, 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
and reducing the concentration of other different components in an
aqueous phase.
[0039] 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 impurity
elements, particularly cobalt, in the leachate as a cobalt
recovering solution to obtain a nickel sulfate solution having a
low cobalt concentration.
[0040] In addition, aqueous ammonia produced in the ammonia
recovery step to be described below can be also used as the aqueous
ammonia used for pH adjustment during this step.
(1) Hydroxylation Step
[0041] In the present invention, an alkali is added to a nickel
sulfate solution obtained through the above steps to produce a
precipitate of nickel hydroxide, thereby separating a precipitate
of the solid component from the liquid component.
[0042] As a result of this treatment, most impurities contained in
nickel sulfate are separated into the liquid component, so that the
concentration of impurities contained in the precipitate of nickel
hydroxide as the solid component can be decreased.
[0043] As an alkali to be added here, sodium hydroxide, calcium
hydroxide, or the like that can be industrially inexpensively
obtained in large amounts is preferably used.
(2) Complexing Step
[0044] The complexing step is composed of two steps, specifically a
dissolution step and a seed crystal addition step, wherein first,
in the dissolution step, ammonia in the form of a post-reduction
solution obtained by subjecting the reduced slurry obtained in the
reduction step (3) to solid-liquid separation is added to the
precipitate of nickel hydroxide obtained in the hydroxylation step
(1), so as to form a mixed solution of nickel hydroxide and the
post-reduction solution, thereby complexing treatment is performed
to produce a nickel ammine sulfate complex which is an ammine
complex of nickel, and thus a nickel ammine sulfate complex
solution thereof is formed.
[0045] At this time, the ammonium concentration can be adjusted by
adding ammonia gas or aqueous ammonia. The ammonia is added so that
the ammonium concentration at that time may be 1.9 or more in a
molar ratio based on the concentration of nickel in the solution.
If the ammonium concentration of the ammonia to be added is less
than 1.9, nickel will not form an ammine complex, but a precipitate
of nickel hydroxide will be produced.
[0046] Further, in order to adjust the concentration of ammonium
sulfate, ammonium sulfate can be added in this step.
[0047] 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, and it is
difficult to achieve a concentration of less than 100 g/L in terms
of the metal balance in the process.
[0048] Further, the ammonia gas or aqueous ammonia produced in the
ammonia recovery step to be described below can be also used as the
ammonia gas or aqueous ammonia used in this step.
[0049] Subsequent to the dissolution step, a seed crystal addition
step is performed by adding the nickel powder having an average
particle size of 0.1 to 5 .mu.m as seed crystals in the form of a
nickel powder slurry to the produced nickel ammine sulfate complex
solution, so as to form a mixture slurry containing the seed
crystals, the nickel ammine sulfate complex solution, and nickel
hydroxide.
[0050] The weight of the seed crystals added at this time is
preferably 1 to 100% based on the weight of nickel in the nickel
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. Further, if the weight
of the seed crystals is more than 100%, the amount of the seed
crystals used will be a large amount, which requires much cost for
producing seed crystals and is not economical.
[0051] Further, a dispersant may be added at the same time. Since
the seed crystals are dispersed by adding the dispersant, the
efficiency of the subsequent reduction step can be increased.
[0052] The dispersant used here is not particularly limited as long
as it has a sulfonate, but a lignosulfonate is preferred as a
dispersant that can be industrially inexpensively obtained.
(3) Reduction Step
[0053] The reduction step is a step of forming a reduced slurry
containing nickel powder that is formed by blowing hydrogen gas
into the obtained mixture slurry to reduce and precipitate a nickel
component in the solution on the seed crystals.
[0054] At this time, reaction temperature is preferably 100 to
200.degree. C. If the temperature is lower than 100.degree. C., and
more preferably lower than 150.degree. C., reduction efficiency
will be reduced, and even if the temperature is higher than
200.degree. C., there will be no influence on the reaction, and the
loss of thermal energy and the like will increase.
[0055] Further, the pressure during the reaction is preferably 0.8
to 4.0 MPa. If the pressure is less than 0.8 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.
[0056] In the liquid of the resulting mixture slurry, magnesium
ions, sodium ions, calcium ions, sulfate ions, and ammonium ions
are mainly present as impurities, but since all the ions remain in
the solution, high purity nickel powder can be produced.
[0057] Further, nickel hydroxide in the liquid of the mixture
slurry reacts with ammonium ions produced by reduction reaction, is
dissolved as a nickel ammine complex in the solution, reacts with
hydrogen gas, and is thus reduced, so that nickel is precipitated
on the seed crystals.
(4) Solid-Liquid Separation Step
[0058] The reduced slurry produced in the previous reduction step
(3) is subjected to solid-liquid separation, thereby separately
recovering high purity nickel powder containing a small amount of
impurities and a post-reduction solution. The high purity nickel
powder is repeatedly fed to either or both of the complexing step
(2) as seed crystals and the reduction step (3) as nickel powder to
be subjected to particle growth.
[0059] Meanwhile, in this step, the recovered post-reduction
solution is repeatedly used as a substitute for aqueous ammonia in
the complexing step (2).
[0060] Specifically, the recovered high purity nickel powder
containing a small amount of impurities and having a small size or
the same pulverized to have a smaller size is repeatedly fed as
seed crystals to the complexing step (2). The nickel powder is
further added to a nickel ammine sulfate complex solution obtained
in the complexing step (2). Hydrogen gas is then fed in the
reduction step (3) to reduce and precipitate nickel on the high
purity nickel powder, so as to be able to grow particles.
[0061] Further, by repeating the feeding to the reduction step for
a plurality of times, high purity nickel powder having higher bulk
density and a larger particle size can be produced.
[0062] Further, the resulting high purity nickel powder may be
finished into the shape of briquettes that are coarser, not easily
oxidized, and easily handled through the nickel powder briquetting
step and briquette firing step as described below.
[0063] Furthermore, an ammonia recovery step may be provided.
[Nickel Powder Briquetting Step]
[0064] The high purity nickel powder produced by the present
invention is dried and then processed for shaping with a
briquetting machine or the like to obtain nickel briquettes in a
block form as a product form.
[0065] 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 nickel powder
depending on the case.
[Briquette Sintering Step]
[0066] The nickel briquettes prepared in the briquetting step is
subjected to roasting and sintering in a hydrogen atmosphere to
prepare a briquette sintered compact. This treatment is performed
for increasing the strength and removing ammonia and a sulfur
component remaining in a very small amount, and the roasting and
sintering temperature of the treatment is preferably 500 to
1200.degree. C. If the temperature is lower 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]
[0067] The post-reduction solution produced by the solid-liquid
separation step (4), in which the nickel powder is separated as a
solid phase, after the reduction step (3) contains ammonium sulfate
and ammonia.
[0068] Thus, the ammonium sulfate can be recovered as ammonium
sulfate crystals by subjecting the post-reduction solution to the
ammonium sulfate recovery step, in which the post-reaction solution
is heated and concentrated to precipitate ammonium sulfate.
[Ammonia Recovery Step]
[0069] Further, ammonia can be recovered by adding an alkali to the
post-reduction solution to adjust the pH to 10 to 13 and then
heating the resulting solution to volatilize ammonia gas.
[0070] The alkali used here suitably includes, but is not limited
to, caustic soda and slaked lime, because they are industrially
inexpensive.
[0071] Further, the recovered ammonia gas can produce aqueous
ammonia by bringing it into contact with water, and the resulting
aqueous ammonia can be repeatedly used in the process.
EXAMPLES
[0072] The present invention will be described below in more detail
using Examples.
Example 1
[0073] To 1000 ml of a nickel sulfate solution with a nickel
concentration of 120 g/L, was added 800 ml of slaked lime adjusted
to have a slurry concentration of 200 g/L, so as to obtain 116 g of
nickel hydroxide.
[0074] The nickel hydroxide was added together with 12.8 g of
nickel powder having an average particle size of 2 .mu.m as seed
crystals to 1700 ml of a mixture of a nickel sulfate solution
having a nickel concentration of 30 g/L and an ammonium sulfate
solution having an ammonia concentration of 40 g/L, and then the
mixture was stirred to prepare a mixture slurry.
[0075] The mixture slurry was heated to 185.degree. C. in an
autoclave with stirring, and hydrogen gas was blown and fed into
the slurry so that the pressure in the autoclave became 3.5 MPa to
subject the mixture slurry to the reduction step. The reduced
slurry was subjected to the solid-liquid separation step by
filtration to recover nickel powder having grown particles.
[0076] At this time, the recovered nickel powder had an average
particle size of 65 .mu.m and the amount of the nickel powder
recovered was 119 g.
[0077] Further, the recovered nickel powder was washed with pure
water and then analyzed for the impurity content in the nickel
powder.
[0078] The results are shown in Table 1. The mixing of Mg and Na
into the nickel powder was not observed, and high purity Ni powder
was able to be produced.
TABLE-US-00001 TABLE 1 Ni Mg Na Example 1 -- <0.005%
<0.005%
Example 2
[0079] To 1000 ml of a nickel sulfate solution having a nickel
concentration of 120 g/L, was added 800 ml of slaked lime adjusted
to have a slurry concentration of 200 g/L, to obtain 116 g of
nickel hydroxide.
[0080] The 116 g of nickel hydroxide was mixed with a nickel ammine
sulfate solution having a nickel concentration of 30 g/L, 232 ml of
25% aqueous ammonia and 225 g of ammonium sulfate, and then pure
water was added to the mixture to prepare 1000 ml of a solution. 20
g of nickel powder having an average particle size of 1 .mu.m was
added as seed crystals to the solution, to prepare a mixture
slurry.
[0081] Next, the prepared mixture slurry was heated to 120.degree.
C. with stirring in an autoclave, and hydrogen gas was blown and
fed into the slurry so that the pressure in the autoclave became
3.5 MPa to subject the slurry to nickel powder production treatment
which is reduction treatment.
[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 reduced slurry obtained after cooling was
subjected to solid-liquid separation by filtration to recover high
purity nickel powder having a small size. The nickel powder
recovered at this time was 70 g.
[0083] Next, 116 g of nickel hydroxide was added to the
post-reduction solution after the above solid-liquid separation, so
as to prepare a slurry. To the slurry, was added the entire amount
of the recovered high purity nickel powder having a small size to
prepare a mixture slurry.
[0084] The mixture slurry was heated to 120.degree. C. with
stirring in an autoclave, and hydrogen gas was blown and fed into
the slurry so that the pressure in the autoclave became 3.5
MPa.
[0085] 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
nickel powder having grown particles.
Example 3
[0086] The post-reduction solution obtained in the solid-liquid
separation step of Example 1 was used for a part of an ammonia
source to prepare a mixture slurry. The slurry was subjected to the
reduction step under the same conditions as those in Example 1, and
then subjected to the solid-liquid separation step, so as to
recover nickel powder having grown particles. Nickel powder similar
to that in Example 1 was recovered.
Example 4
[0087] To a solution containing the nickel powder prepared under
the same conditions as in Example 1, 336 g of nickel sulfate and
330 g of ammonium sulfate, was added 191 ml of 25% aqueous ammonia,
and the total volume of the mixture was adjusted to 1000 ml. The
resultant was subjected again to the reduction step and the
solid-liquid separation step under the same conditions as in
Example 1 to prepare nickel powder having grown particles. This
operation was repeated 10 times using the prepared nickel powder to
further grow particles of the nickel powder.
[0088] The recovered nickel powder had an average particle size of
111 .mu.m, such that the particle size grew to a size 1.7 times the
size of the nickel powder of Example 1.
[0089] The nickel powder obtained by the repeated operation had a
sulfur content of 0.04%. Sodium and magnesium were at a minimum
limit of determination or lower levels similar to Table 1
above.
[0090] Then, the obtained nickel powder was heated to 1000.degree.
C. in a 2% hydrogen atmosphere and held for 60 minutes. Nickel
powder obtained after the holding had a sulfur content of 0.008%,
and the sulfur content could be further reduced by roasting.
Example 5
[0091] To 1000 ml of a nickel ammine sulfate complex solution shown
in Table 2, was added 75 g of nickel powder having an average
particle size of 1 .mu.m as seed crystals. Then, the resulting
mixture was heated to 185.degree. C. with stirring in an autoclave,
and hydrogen gas was blown and fed into the mixture so that the
pressure in the autoclave became 3.5 MPa.
[0092] 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 nickel powder,
which was washed with pure water and then analyzed for the impurity
content in the nickel powder.
[0093] The results are shown in Table 2.
[0094] The mixing of Mg and Na into the nickel powder was not
observed, and high purity Ni powder was able to be produced.
TABLE-US-00002 TABLE 2 Ni Mg Na Nickel ammine sulfate 75 0.1 7.0
complex solution [g/L] [g/L] [g/L] High purity nickel -- <0.005%
<0.005% powder
Example 6
[0095] To a nickel ammine sulfate solution prepared by mixing 135 g
of nickel sulfate hexahydrate, 191 ml of 25% aqueous ammonia, 169 g
of ammonium sulfate and pure water, was added 75 g of nickel
hydroxide. Pure water was added thereto so that the total volume of
the solution was adjusted to 1000 ml. 15 g of nickel powder having
an average particle size of 1 .mu.m was added as seed crystals, to
prepare a mixture slurry.
[0096] The mixture slurry was heated to 100.degree. C. with
stirring in an autoclave, and hydrogen gas was fed into the mixture
slurry so that the pressure in the autoclave became 3.5 MPa to
subject the slurry to nickel powder production treatment.
[0097] 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 reduced slurry obtained after cooling was
subjected to solid-liquid separation by filtration to recover high
purity nickel powder having a small size. The rate of nickel
reduction was 58%.
Example 7
[0098] With the use of the same mixture slurry as in Example 6, the
same operation as in Example 6 was performed under conditions of
the temperature of 100.degree. C., and the pressure within an
autoclave of 0.8 MPa. The resulting rate of nickel reduction was
56%.
Example 8
[0099] With the use of the same mixture slurry as in Example 6, the
same operation as in Example 6 was performed under conditions of
the temperature of 120.degree. C., and the pressure within an
autoclave of 3.5 MPa. The resulting rate of nickel reduction was
74%.
Example 9
[0100] With the use of the same mixture slurry as in Example 6, the
same operation as in Example 6 was performed under conditions of
the temperature of 120.degree. C., and the pressure within an
autoclave of 2.0 MPa. The resulting rate of nickel reduction was
74%.
Example 10
[0101] With the use of the same mixture slurry as in Example 6, the
same operation as in Example 6 was performed under conditions of
the temperature of 120.degree. C., and the pressure within an
autoclave of 1.5 MPa. The resulting rate of nickel reduction was
74%.
[0102] As understood from the results of Examples 6 to 10 shown in
Table 3, high purity nickel was produced in all examples, and the
rates of reduction were not significantly affected by pressure and
were significantly decreased due to decreases in temperature.
TABLE-US-00003 TABLE 3 Temperature Pressure Rate of Ni reduction
[.degree. C.] [MPa] [%] Example 6 100 3.5 58 Example 7 100 0.8 56
Example 8 120 3.5 74 Example 9 120 2.0 74 Example 10 120 1.5 74
Comparative Example 1
[0103] Nickel powder was prepared under the same conditions as in
Example 1 except that the hydroxylation step in Example 1 was not
performed, 191 ml of 25% aqueous ammonia was added to a nickel
sulfate solution containing 75 g of nickel and, a solution
containing 330 g of ammonium sulfate, the solution was adjusted to
have a total volume of 1000 ml, and then to the solution was added
7.5 g of nickel powder having an average particle size of 1 .mu.m
as seed crystals, so as to prepare a mixture slurry.
[0104] The recovered nickel powder was washed with pure water and
then analyzed for the impurity content in the nickel powder.
[0105] The results are shown in Table 4. The mixing of Mg and Na
into the nickel powder was at levels higher than those in Example
1. In addition, an average particle size and the amount of the
nickel powder recovered were almost equivalent to those in Example
1.
TABLE-US-00004 TABLE 4 Ni Mg Na Comparative -- 0.02% 0.02% example
1
Comparative Example 2
[0106] With the use of the same method as in the above Comparative
Example 1, nickel powder was prepared without performing the
hydroxylation step. The nickel powder was repeatedly subjected to
the same method as in the above Example 3 for 10 times, to grow
particles. The sulfur content in the nickel powder obtained by the
repeated operation was 0.1%. Hence, high purity nickel powder
equivalent to that having a sulfur content of 0.04% obtained in
Example 3 of the present invention could not be obtained.
* * * * *