U.S. patent application number 16/078071 was filed with the patent office on 2019-02-14 for method for producing nickel powder.
The applicant listed for this patent is SUMITOMO METAL MINING CO., LTD.. Invention is credited to Shin-ichi HEGURI, Yoshitomo OZAKI.
Application Number | 20190047052 16/078071 |
Document ID | / |
Family ID | 59685078 |
Filed Date | 2019-02-14 |
![](/patent/app/20190047052/US20190047052A1-20190214-D00001.png)
United States Patent
Application |
20190047052 |
Kind Code |
A1 |
HEGURI; Shin-ichi ; et
al. |
February 14, 2019 |
METHOD FOR PRODUCING NICKEL POWDER
Abstract
Provided is a method for producing coarse particles of high
purity nickel powder from a nickel ammine sulfate complex solution
using industrially-inexpensive hydrogen gas and fine nickel powder.
The method for producing nickel powder, including performing the
following processes (1) to (5), wherein a sulfuric acid solution
containing nickel and cobalt is subjected to (1) a pH adjusting
step, (2) a solvent extraction step, (3) a complexing step for
obtaining a nickel ammine sulfate complex solution, (4) a reduction
step for obtaining a reduced slurry containing nickel powder, and
(5) a solid-liquid separation step of performing solid-liquid
separation to obtain nickel powder and a solution after reduction,
and solution after reduction repeatedly using the solution after
reduction in either or both of (2) the solvent extraction step and
(3) the complexing step.
Inventors: |
HEGURI; Shin-ichi;
(Niihama-shi, JP) ; OZAKI; Yoshitomo;
(Niihama-shi, JP) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
SUMITOMO METAL MINING CO., LTD. |
Tokyo |
|
JP |
|
|
Family ID: |
59685078 |
Appl. No.: |
16/078071 |
Filed: |
February 15, 2017 |
PCT Filed: |
February 15, 2017 |
PCT NO: |
PCT/JP2017/005528 |
371 Date: |
August 21, 2018 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
B22F 2304/10 20130101;
C22B 5/12 20130101; C22B 23/04 20130101; B22F 3/1007 20130101; B22F
9/26 20130101; C22B 3/0005 20130101; C22B 1/16 20130101; B22F
1/0011 20130101; B22F 2301/15 20130101; C22B 23/0453 20130101; Y02P
10/234 20151101; B22F 2201/013 20130101; Y02P 10/20 20151101 |
International
Class: |
B22F 9/26 20060101
B22F009/26; B22F 1/00 20060101 B22F001/00; B22F 3/10 20060101
B22F003/10; C22B 5/12 20060101 C22B005/12; C22B 3/00 20060101
C22B003/00; C22B 1/16 20060101 C22B001/16 |
Foreign Application Data
Date |
Code |
Application Number |
Feb 22, 2016 |
JP |
2016-030801 |
Claims
1. A method of producing nickel powder, comprising performing
processes (1) to (5) on a sulfuric acid solution containing nickel
and cobalt: (1) a pH adjusting step of adding an alkali hydroxide
to the sulfuric acid solution containing nickel and cobalt to
obtain a pH-adjusted solution; (2) a solvent extraction step of
bringing the pH-adjusted solution obtained in the pH adjusting step
into contact with an extractant to separate into a raffinate and an
organic phase after extraction, and then bringing the organic phase
after extraction into contact with a solution after reduction which
mainly contains sodium ions, magnesium ions, sulfate ions, and
ammonium ions as impurities and is obtained in a subsequent
solid-liquid separation step to separate into an aqueous phase
after exchange containing nickel and an organic phase after
exchange containing cobalt and the impurities; (3) a complexing
step of adding ammonium sulfate or a solution after reduction
obtained in a solid-liquid separation step described below and
ammonium sulfate to the aqueous phase after exchange obtained in
the solvent extraction step to obtain a nickel ammine sulfate
complex solution; (4) a reduction step of blowing hydrogen gas into
a mixture slurry prepared by adding seed crystals to the nickel
ammine sulfate complex solution obtained in the complexing step, to
form a nickel powder by precipitation of nickel on a surface of the
seed crystals to obtain a reduced slurry containing the nickel
powder; and (5) the solid-liquid separation step of subjecting the
reduced slurry obtained in the reduction step to solid-liquid
separation to obtain a nickel powder and the solution after
reduction which mainly contains sodium ions, magnesium ions,
sulfate ions, and ammonium ions as impurities, and then recycling
the resulting solution after reduction in either or both of the
solvent extraction step and the complexing step, and repeatedly
operating sieve of the resulting nickel powder by particle size and
addition of a nickel powder having a particle size smaller than a
predetermined particle size to either or both of the complexing
step and the reduction step as seed crystals to obtain a coarse
nickel powder.
2. The method of producing nickel powder according to claim 1,
wherein in the solvent extraction step, the resulting organic phase
after exchange is brought into contact with water to separate into
a cobalt-recovering solution and an organic phase after stripping,
and then the organic phase after stripping is recycled as the
extractant.
3. (canceled)
4. The method of producing nickel powder according to claim 1,
wherein the nickel powder being sieved to have the particle size
smaller than the predetermined particle size has an average
particle size of 0.1 to 100 .mu.m.
5. The method of producing nickel powder according to claim 1,
wherein, in the reduction step, a dispersant containing one or more
selected from polyacrylic acid, acrylate salts, and sulfonate salts
is further added during the preparation of the mixture slurry.
6. The method of producing nickel powder according to claim 1,
wherein, in the reduction step, an amount of the seed crystals
added is 1 to 100% based on the weight of nickel in the nickel
ammine sulfate complex solution.
7. The method of producing nickel powder according to claim 1,
wherein the sulfuric acid solution containing nickel and cobalt
includes at least one of nickel and cobalt mixed sulfide, crude
nickel sulfate, nickel oxide, nickel hydroxide, nickel carbonate,
and metal nickel powder.
8. The method of producing nickel powder according to claim 1,
wherein the extractant is 2-ethylhexylphosphonic acid
mono-2-ethylhexyl ester or di-(2,4,4-trimethylpentyl)phosphinic
acid.
9. The method of producing nickel powder according to claim 1,
wherein a concentration of the ammonium sulfate in the nickel
ammine sulfate complex solution is in a range of 100 to 500 g/L,
and a molar ratio of the ammonium concentration to the
concentration of nickel in the complex solution is 2.0 or
higher.
10. The method of producing nickel powder according to claim 1,
wherein the reduction step is performed while maintaining a
temperature in a range of 150 to 200.degree. C. and a pressure in a
range of 1.0 to 4.0 MPa.
11. The method of producing nickel powder according to claim 1,
comprising: a nickel powder briquetting step of processing the
nickel powder obtained through the reduction step and the
solid-liquid separation step 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.
12. The method of producing nickel powder according to claim 1,
comprising an ammonium sulfate recovery step of concentrating the
solution after reduction obtained in the solid-liquid separation
step to crystallize ammonium sulfate and recovering ammonium
sulfate crystals.
13. The method of producing nickel powder according to claim 1,
comprising an ammonia recovery step of adding an alkali to the
solution after reduction obtained in the solid-liquid separation
step, 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 from a nickel ammine sulfate complex solution
and briquettes prepared by pressing the nickel powder.
[0002] Particularly, the present invention can be applied to the
treatment of an in-process intermediate solution generated from a
nickel hydrometallurgical process.
Related Art
[0003] Methods for industrially producing nickel powder using a
hydrometallurgical process are known including 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, P. 40-52
describes a process for producing nickel powder by adding an iron
compound as seed crystals during a reduction reaction to
precipitate nickel onto the iron compound, but the problem is that
iron derived from the seed crystals is mixed in the final product
in this process.
[0005] Furthermore, methods for obtaining nickel powder using a
reducing agent other than hydrogen gas also have been proposed.
[0006] For example, Japanese Patent Application Laid-Open No.
2005-240164 discloses nickel powder which is inexpensive, is
excellent weatherability, has low electric resistance in the state
where the nickel powder is mixed with a resin, reduces the initial
electric resistance and the electric resistance during use, can be
stably used for a long time, and is suitable for conductive
particles for a conductive paste and a conductive resin, and a
method for producing the nickel powder.
[0007] The nickel powder disclosed in Japanese Patent Application
Laid-Open No. 2005-240164 contains 1 to 20% by mass of cobalt and
the balance consisting of nickel and inevitable impurities,
includes secondary particles in which primary particles aggregate,
and contains 0.8% by mass or less of oxygen. According to the
description, preferably, cobalt is contained only in the surface
layer portions of the secondary particles and the cobalt content in
the surface layer portion is 1 to 40% by mass.
[0008] However, in the case of attempts to obtain nickel powder
according to the disclosed production method, cobalt coexists and
therefore, this method is not suitable for an application: in which
nickel and cobalt coexist, for example, in a nickel oxide ore;
these metals are separated; and each metal is intended to be
economically recovered as high purity metal.
[0009] Furthermore, Japanese Patent Application 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.
[0010] 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.
[0011] 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.
[0012] Although such a variety of processes for producing nickel
powder have been proposed as described above, any method for
producing high purity nickel powder using an industrially
inexpensive hydrogen gas has not been proposed.
[0013] In such circumstances, an object of the present invention is
to provide a method for producing coarse particles of high purity
nickel powder from a nickel ammine sulfate complex solution using
industrially inexpensive hydrogen gas and fine nickel powder.
SUMMARY
[0014] A first aspect of the present invention to solve the
problems is a method for producing nickel powder, including
performing the following processes (1) to (5) on a sulfuric acid
solution containing nickel and cobalt:
[0015] (1) a pH adjusting step of adding an alkali hydroxide to the
sulfuric acid solution containing nickel and cobalt to obtain a
pH-adjusted solution;
[0016] (2) a solvent extraction step of bringing the pH-adjusted
solution obtained in the pH adjusting step into contact with an
extractant to separate into a raffinate and an organic phase after
extraction, and then bringing the organic phase after extraction
into contact with a solution after reduction to separate into an
aqueous phase after exchange containing nickel and an organic phase
after exchange;
[0017] (3) a complexing step of adding ammonium sulfate or a
solution after reduction obtained in a subsequent solid-liquid
separation step and ammonium sulfate to the aqueous phase after
exchange obtained in the solvent extraction step to obtain a nickel
ammine sulfate complex solution;
[0018] (4) a reduction step of blowing hydrogen gas into a mixture
slurry prepared by adding seed crystals to the nickel ammine
sulfate complex solution obtained in the complexing step, to form a
nickel powder by precipitation of nickel on the surface of the seed
crystals to obtain a reduced slurry containing the nickel powder;
and
[0019] (5) the solid-liquid separation step of subjecting the
reduced slurry obtained in the reduction step to solid-liquid
separation to obtain a nickel powder and a solution after
reduction, and recycling the resulting solution after reduction in
either or both of the solvent extraction step and the complexing
step.
[0020] A second aspect of the present invention is a method for
producing nickel powder, wherein in the solvent extraction step
according to the first aspect, the resulting organic phase after
exchange is brought into contact with water to separate into a
cobalt-recovering solution and an organic phase after stripping,
and then the organic phase after stripping is recycled as the
extractant.
[0021] A third aspect of the present invention is a method for
producing nickel powder, wherein in the solid-liquid separation
step according to the first aspect, repeated operation of sieving
the resulting nickel powder by particle size, and adding a nickel
powder having a particle size smaller than a predetermined particle
size as seed crystals to either or both of the complexing step and
the reduction step provides a coarse nickel powder.
[0022] A fourth aspect of the present invention is a method for
producing nickel powder, wherein the nickel powder being sieved to
have the particle size smaller than the predetermined particle size
according to the third aspect has an average particle size of 0.1
to 100 .mu.m.
[0023] A fifth aspect of the present invention is a method for
producing nickel powder, wherein, in the reduction step according
to the first aspect, a dispersant containing one or more selected
from polyacrylic acid, acrylate salts, and sulfonate salts is
further added during the preparation of the mixture slurry.
[0024] A sixth aspect of the present invention is a method for
producing nickel powder, wherein, in the reduction step according
to the first aspect, the amount of the seed crystals added is 1 to
100% based on the weight of nickel in the nickel ammine sulfate
complex solution.
[0025] A seventh aspect of the present invention is a method for
producing nickel powder, wherein the sulfuric acid solution
containing nickel and cobalt according to the first aspect includes
at least one of nickel and cobalt mixed sulfide, crude nickel
sulfate, nickel oxide, nickel hydroxide, nickel carbonate, and
metal nickel powder.
[0026] An eighth aspect of the present invention is a method for
producing nickel powder, wherein the extractant according to the
first aspect is 2-ethylhexylphosphonic acid mono-2-ethylhexyl ester
or di-(2,4,4-trimethylpentyl)phosphinic acid.
[0027] A ninth aspect of the present invention is a method for
producing nickel powder, wherein the concentration of the ammonium
sulfate in the nickel ammine sulfate complex solution according to
the first aspect is in the range of 100 to 500 g/L, and a molar
ratio of the ammonium concentration to the concentration of nickel
in the complex solution is 2.0 or higher.
[0028] A tenth aspect of the present invention is a method for
producing nickel powder, wherein the reduction step according to
the first aspect is performed while maintaining a temperature in
the range of 150 to 200.degree. C. and a pressure in the range of
1.0 to 4.0 MPa.
[0029] A eleventh aspect of the present invention is a method for
producing nickel powder, including a nickel powder briquetting step
of processing the nickel powder obtained through the reduction step
and the solid-liquid separation step according to the first aspect
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] A twelfth aspect of the present invention is to provide a
method for producing nickel powder, including an ammonium sulfate
recovery step of concentrating the solution after reduction
obtained in the solid-liquid separation step according to the first
aspect to crystallize ammonium sulfate into ammonium sulfate
crystals and recovering the ammonium sulfate crystals.
[0031] A thirteenth aspect of the present invention is to provide a
method for producing nickel powder, including an ammonia recovery
step of adding an alkali to the solution after reduction obtained
in the solid-liquid separation step according to the first aspect,
heating the resulting mixture to volatilize ammonia gas and
recovering the ammonia gas.
[0032] According to the present invention, in the method for
producing nickel powder using hydrogen gas from a nickel ammine
sulfate complex solution, high purity nickel powder can be easily
obtained by using seed crystals which do not contaminate the
products.
BRIEF DESCRIPTION OF DRAWING
[0033] FIG. 1 is a production flow chart for nickel powder
according to the present invention.
DETAILED DESCRIPTION
[0034] The present invention is a method for producing a nickel
powder from a nickel ammine sulfate complex solution and is
characterized in that high purity nickel powder containing a
smaller amount of impurities is produced from the nickel ammine
sulfate complex solution by subjecting a process solution, which is
an intermediate product of a hydrometallurgical process, to the
steps (1) to (5) as shown below.
[0035] Hereinafter, the method for producing a high purity nickel
powder according to the present invention will be described with
reference to the production flow chart for the high purity nickel
powder according to the present invention illustrated in FIG.
1.
[Leaching Step] and "(1) pH Adjusting 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 (solution containing nickel), and is performed by a
known method, for example, disclosed in Japanese Patent Application
Laid-Open No. 2005-350766.
[0037] Next, the pH of the leachate is adjusted using alkali
hydroxide in "(1) pH adjusting step", and the leachate is fed to
"(2) solvent extraction step".
[(2) Solvent Extraction Step]
[0038] In this "(2) solvent extraction step", the leachate, which
is obtained in the leaching step and then subjected to pH
adjustment, is brought into contact with an organic phase. Thereby,
components such as nickel and cobalt are distributed in the organic
phase to extract nickel and cobalt. This organic phase is then
brought into contact with an aqueous phase as which sulfuric acid
or ammonium sulfate is used in the initial stage of production and
the solution after reduction repeatedly fed back from "(4)
reduction step" is used during the production. Thereby, nickel is
distributed in the aqueous phase to increase the nickel
concentration in the aqueous phase and thus reduce the
concentrations of other different components.
[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 to achieve a high
effect of forming a nickel ammine sulfate complex solution with
high purity.
[(3) Complexing Step]
[0040] In this step, ammonium sulfate is added to the high-purity
nickel ammine sulfate complex solution obtained in the "(2) solvent
extraction step" to completely convert the nickel in the complex
solution into the form of an ammine complex.
[0041] At this time, ammonia is adjusted such that the molar ratio
of the concentration of ammonium sulfate to the concentration of
nickel in the solution becomes 2.0 or higher. If the concentration
of ammonium in ammonium sulfate to be added is less than 2.0,
nickel does not form an ammine complex, undesirably causing the
precipitation of nickel hydroxide.
[0042] In addition, ammonium sulfate is already contained in the
solution after reduction repeatedly fed back in the "(2) solvent
extraction step". In this "(3) complexing step", ammonium sulfate
is added only by an amount to make up for a shortage such that the
molar ratio of the concentration of ammonium sulfate to the
concentration of nickel in the solution is maintained 2.0 or
higher.
[0043] Furthermore, in this step, the concentration of ammonium
sulfate is preferably 100 to 500 g/L. A concentration of more than
500 g/L is beyond the solubility in the solution, causing
precipitation of crystals. A concentration of less than 100 g/L is
difficult to achieve in consideration of the balance of metals in
the process.
[Step for Producing Nickel Powder from Nickel Ammine Sulfate
Complex Solution]
[0044] A step for producing a nickel powder from a nickel ammine
sulfate complex solution will be described below.
<(a) Seed Crystal Addition Step>
[0045] To the nickel ammine sulfate complex solution obtained in
the complexing step, a nickel powder having an average particle
size of 1 to 20 .mu.m is added as seed crystals in the form of a
slurry of nickel powder to prepare a mixture slurry containing the
seed crystals.
[0046] 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.
[0047] 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.
[0048] The dispersant used here is not particularly limited as long
as it has an acrylate or a sulfonate, but a lignosulfonate is
preferred as a dispersant that can be industrially inexpensively
obtained.
[(4) Reduction Step]
[0049] Hydrogen gas is blown into the mixture slurry obtained in
"(a) seed crystal addition step" to generate a reduced slurry in
which nickel in the solution is precipitated on the seed crystals.
At this time, the reaction temperature is preferably 100 to
200.degree. C. A reaction temperature of less than 100.degree. C.
reduces the efficiency of the reduction. A reaction temperature of
higher than 200.degree. C. has no influences over the reaction but
increases loss of thermal energy or the like.
[0050] 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.
[0051] In the liquid of the mixture slurry obtained in "(a) seed
crystal addition step", magnesium ions, sodium 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.
[(5) Solid-Liquid Separation Step]
[0052] Next, the reduced slurry obtained in "(4) reduction step" is
subjected to solid-liquid separation to recover a high purity
nickel powder as a solid phase component and a solution after
reduction as a liquid phase component.
[(b) Nickel Exchange Step]
[0053] The solution after reduction obtained in "(5) solid-liquid
separation step" is repeatedly fed back to "(2) solvent extraction
step", obtaining a nickel ammine sulfate complex solution having an
increased concentration of nickel.
<(c) Growth Step>
[0054] The nickel ammine sulfate complex solution having the
increased concentration of nickel obtained in "(b) nickel exchange
step" is added to the high purity nickel powder recovered in "(5)
solid-liquid separation step", and hydrogen gas is fed by the same
method as in "(4) reduction step". Thereby, nickel is reduced and
precipitated on the high purity nickel powder so as to be able to
grow particles.
[0055] In addition, the repetition of the growth step, that is, use
of the resulting high purity nickel powder instead of the high
purity nickel powder from "(5) solid-liquid separation step" can
produce high purity nickel powder having higher bulk density and a
larger particle size.
[0056] Further, the resulting nickel powder may be finished into
the shape of briquettes that are coarser, not easily oxidized, and
easily handled through a nickel powder briquetting step and a
briquette firing step as described below.
[Nickel Powder Briquetting Step]
[0057] 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.
[0058] Further, in order to improve the processability to form the
briquettes, a material that does not impair the product quality
such as water is added as a binder to the nickel powder depending
on the case.
[Briquette Sintering Step]
[0059] 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 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.
EXAMPLES
[0060] Hereinafter, the present invention will be described in more
details with reference to Examples.
Example 1
[(a) Seed Crystal Addition Step]
[0061] 191 ml of 25% aqueous ammonia was added to a solution
containing 330 g of ammonium sulfate and a nickel sulfate solution
with 75 g of nickel, and the total amount of the solution was
adjusted to 1000 ml to prepare a nickel ammine sulfate complex
solution. 7.5 g of nickel powder having an average particle size of
2 .mu.m was added to the resulting solution as seed crystals to
prepare a mixture slurry.
[(4) Reduction Step]
[0062] The mixture slurry prepared in "(a) seed crystal addition
step" was heated to 185.degree. C. with stirring in an autoclave,
and hydrogen gas was blown and fed into the mixture slurry so that
the inner pressure of the autoclave became 3.5 MPa, to perform a
nickel powder generating treatment as a reduction treatment.
[0063] After one hour had passed from the feed of hydrogen gas, the
feed of hydrogen gas was stopped, and the autoclave was cooled.
[(5) Solid-Liquid Separation Step]
[0064] The reduced slurry obtained after the cooling was subjected
to a solid-liquid separation by filtration to recover a high purity
nickel powder having a small size and a solution after reduction.
At this time, 70 g of nickel powder was recovered. The
concentration of nickel in the solution after reduction was 5
g/L.
[(b) Nickel Exchange Step]
[0065] An organic solvent containing 10 g/L nickel was mixed with
the solution after reduction recovered in "(5) solid-liquid
separation step" so that a ratio of an organic phase to an aqueous
phase became 10/L. Subsequently, the mixed solution was settled,
and the concentration of nickel in the aqueous phase in the mixed
solution settled was 100 g/L.
[(c) Growth Step]
[0066] Then, the total amount of the high purity nickel powder
having the small size obtained in "(5) solid-liquid separation
step" was added to the nickel ammine sulfate complex solution
having the increased concentration of nickel obtained in "(b)
nickel exchange step" to prepare a slurry.
[0067] The slurry was heated to 185.degree. C. with stirring in an
autoclave. Hydrogen gas was blown and fed into the mixture slurry
so that the inner pressure of the autoclave became 3.5 MPa.
[0068] 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 2
[0069] 75 g of nickel powder having an average particle size of 1
.mu.m as seed crystals was added to 1000 ml of the same nickel
ammine sulfate complex solution as in Example 1. The slurry was
heated to 185.degree. C. with stirring in an autoclave, and
hydrogen gas was blown and fed into the mixture slurry so that the
inner pressure of the autoclave became 3.5 MPa.
[0070] 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. The recovered nickel
powder was washed with pure water, and the grade of impurities in
the nickel powder was analyzed. The mixing of Mg and Na into the
nickel powder was not observed, and high purity Ni powder was able
to be produced.
Example 3
[0071] 191 ml of 25% aqueous ammonia was added to a solution
containing 22.5 g of the seed crystals used in Example 1, 1.5 g of
lignin sodium sulfonate, 336 g of nickel sulfate, and 330 g of
ammonium sulfate, and the total amount of the solution was adjusted
to 1000 ml to prepare a mixture slurry.
[0072] Then, the mixture slurry was heated to 185.degree. C. with
stirring in an autoclave, and hydrogen gas was blown and fed into
the mixture slurry so that the inner pressure of the autoclave
became 3.5 MPa. After one hour had passed from the feed of hydrogen
gas, the feed of hydrogen gas was stopped, and the autoclave was
cooled. 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 treatment by filtration to recover
nickel powder.
[0073] At this time, the concentration of nickel in the solution
after reaction was 0.4 g/L, and the rate of reduction of 99% or
higher could be obtained.
Example 4
[0074] 191 ml of 25% aqueous ammonia was added to a solution
containing 336 g of nickel sulfate and 330 g of ammonium sulfate
concentration, and the total amount of the solution was adjusted to
1000 ml. 75 g of nickel powder having an adjusted particle size of
1 .mu.m was added to the solution to prepare a mixture slurry.
[0075] The mixture slurry was heated to 185.degree. C. with
stirring in an autoclave, and hydrogen gas was blown and fed into
the mixture slurry so that the inner pressure of the autoclave
became 3.5 MPa to subject the slurry to nickel powder growing
treatment which is reduction treatment.
[0076] 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
nickel powder having a small size.
[0077] 191 ml of 25% aqueous ammonia was added to a solution
containing the recovered nickel powder having the small size, 336 g
of nickel sulfate, and 330 g of ammonium sulfate, and the total
amount of the solution was adjusted to 1000 ml. Again, the slurry
was heated to 185.degree. C. with stirring in the autoclave.
Hydrogen gas was blown and fed into the mixture slurry so that the
inner pressure of the autoclave became 3.5 MPa, to perform a
particle growing treatment, followed by a solid-liquid separation
by filtration. Thereby, a nickel powder having grown particles was
recovered.
[0078] This operation was repeated 10 times to further grow the
nickel powder.
[0079] The nickel powder obtained by this operation had a sulfur
content of 0.04%.
[0080] 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.
Comparative Example 1
[0081] A mixed solution of 45 ml of pure water, 20 g of nickel
sulfate hexahydrate, 15 g of ammonium sulfate, and 10 ml of 28%
aqueous ammonia without seed crystals was placed into an autoclave.
While stirring the solution, hydrogen gas was fed to 3.5 MPa. The
temperature was heated to 185.degree. C., and was maintained for 6
hours. After the cooling, the inside of the autoclave was examined.
A precipitate as a scale adhered to the container and the stirring
blade, and no powdery nickel was produced.
Comparative Example 2
[0082] The reduction step was performed under the same conditions
as in Example 3 except that that lignin sodium sulfonate was not
added. As a result, 33 g of nickel powder could be recovered, and
the recovery rate was only 14%.
* * * * *