U.S. patent application number 16/082004 was filed with the patent office on 2020-10-29 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, Kazuyuki TAKAISHI, Ryo-ma YAMAGUMA.
Application Number | 20200338641 16/082004 |
Document ID | / |
Family ID | 1000004985848 |
Filed Date | 2020-10-29 |
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United States Patent
Application |
20200338641 |
Kind Code |
A1 |
OZAKI; Yoshitomo ; et
al. |
October 29, 2020 |
METHOD FOR PRODUCING NICKEL POWDER
Abstract
Provided is a production method for maintaining the quality
while keeping a high operating rate of the reaction by continuously
feeding a solution, seed crystals, and hydrogen gas into a reactor
to produce nickel powder, and continuously discharging the
resulting powder. The method for producing nickel powder comprises
feeding a nickel ammine sulfate complex solution and seed crystals
into a reactor, and feeding hydrogen gas into the reactor to
subject a nickel complex ion in the nickel ammine sulfate complex
solution to a reduction treatment and to thereby produce nickel
powder, wherein, in the reduction treatment, while the nickel
ammine sulfate complex solution is being continuously fed into the
reactor, a temperature inside the reactor is controlled within the
range of 150 to 185.degree. C. and the feed rate of hydrogen gas is
controlled to maintain an inner pressure of the reactor in the
range of 2.5 to 3.5 MPa.
Inventors: |
OZAKI; Yoshitomo;
(Niihama-shi, JP) ; HEGURI; Shin-ichi;
(Niihama-shi, JP) ; TAKAISHI; Kazuyuki;
(Niihama-shi, JP) ; YAMAGUMA; Ryo-ma;
(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: |
1000004985848 |
Appl. No.: |
16/082004 |
Filed: |
March 3, 2017 |
PCT Filed: |
March 3, 2017 |
PCT NO: |
PCT/JP2017/008562 |
371 Date: |
September 4, 2018 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
B22F 2203/11 20130101;
B22F 2301/15 20130101; B22F 2999/00 20130101; B22F 2998/10
20130101; B22F 2201/013 20130101; B22F 9/26 20130101; B22F 2304/10
20130101; B22F 2203/13 20130101 |
International
Class: |
B22F 9/26 20060101
B22F009/26 |
Foreign Application Data
Date |
Code |
Application Number |
Mar 4, 2016 |
JP |
2016-041665 |
Apr 5, 2016 |
JP |
2016-075529 |
Apr 5, 2016 |
JP |
2016-075530 |
Dec 26, 2016 |
JP |
2016-251266 |
Claims
1. A method of producing nickel powder, comprising feeding a nickel
ammine sulfate complex solution and seed crystals into a reactor,
and feeding hydrogen gas into the reactor to subject a nickel
complex ion in the nickel ammine sulfate complex solution to a
reduction treatment and to thereby produce nickel powder having a
sulfur grade of lower than 0.01% by weight, wherein in the
reduction treatment, while the nickel ammine sulfate complex
solution containing polyacrylic acid in a concentration of 0.5 to
1.0 g/liter is being continuously fed into the reactor, a
temperature inside the reactor is controlled within a range of 150
to 185.degree. C. and a feed rate of hydrogen gas is controlled to
maintain an inner pressure of the reactor in a range of 2.5 to 3.5
MPa to produce a nickel powder slurry containing the nickel powder,
and thereafter, when the nickel powder slurry is extracted from the
reactor, a feed amount of the nickel ammine sulfate complex
solution and the seed crystals and a discharge amount of the nickel
powder slurry are adjusted to keep a given amount of the solution
in the reactor.
2. A method of producing nickel powder, comprising feeding hydrogen
gas into a reactor, and feeding a nickel ammine sulfate complex
solution and seed crystals into the reactor to subject a nickel
complex ion in the nickel ammine sulfate complex solution to a
reduction treatment and to thereby produce nickel powder having a
sulfur grade of lower than 0.01% by weight, wherein in the
reduction treatment, the nickel complex ion in the nickel ammine
sulfate complex solution is reduced in such a manner that a slurry
containing ammonium sulfate and nickel powder are stored in the
reactor to form a liquid phase portion and a gaseous phase portion
in the reactor and an inner pressure of the gaseous phase portion
is controlled through the feeding of the hydrogen gas into the
reactor, a slurry containing seed crystals and the nickel ammine
sulfate complex solution containing polyacrylic acid in a
concentration of 0.5 to 1.0 g/liter are continuously fed into the
liquid phase portion, a temperature inside the reactor is
controlled in a range of 150 to 185.degree. C., and a feed rate of
the hydrogen gas is controlled to maintain an inner pressure of the
reactor in a range of 2.5 to 3.5 MPa to produce a nickel powder
slurry containing the nickel powder, and thereafter, when the
nickel powder slurry is extracted from the reactor, a feed amount
of the nickel ammine sulfate complex solution and the seed crystals
and a discharge amount of the nickel powder slurry are adjusted to
keep a given amount of the solution in the reactor.
3. (canceled)
4. The method of producing nickel powder according to claim 2,
wherein nickel powder having an average particle size in a range of
0.1 to 100 .mu.m is used as the seed crystals.
5. The method of producing nickel powder according to claim 2,
wherein nickel powder having an average particle size in a range of
0.1 to 10 .mu.m is used as the seed crystals.
6. The method of producing nickel powder according to claim 5,
wherein an amount of the seed crystals to be added is in a range of
1 to 100% by weight based on a weight of nickel contained in the
nickel ammine sulfate complex solution.
7. The method of producing nickel powder according to claim 6,
wherein the nickel ammine sulfate complex solution subjected to the
reduction treatment contains polyacrylic acid in an amount in a
range of 0.5 to 5% by weight based on a weight of the seed crystals
in the nickel ammine sulfate complex solution.
8. The method of producing nickel powder according to claim 7,
wherein in the reduction treatment, the nickel ammine sulfate
complex solution containing the seed crystals is continuously fed
into the reactor such that a reaction time of the reduction
treatment in the reactor takes 5 to 120 minutes.
9. The method of producing nickel powder according to claim 1,
wherein nickel powder having an average particle size in a range of
0.1 to 100 .mu.m is used as the seed crystals.
10. The method of producing nickel powder according to claim 1,
wherein nickel powder having an average particle size in a range of
0.1 to 10 .mu.m is used as the seed crystals.
11. The method of producing nickel powder according to claim 1,
wherein an amount of the seed crystals to be added is in a range of
1 to 100% by weight based on a weight of nickel contained in the
nickel ammine sulfate complex solution.
12. The method of producing nickel powder according to claim 1,
wherein the nickel ammine sulfate complex solution subjected to the
reduction treatment contains polyacrylic acid in an amount in a
range of 0.5 to 5% by weight based on a weight of the seed crystals
in the nickel ammine sulfate complex solution.
13. The method of producing nickel powder according to claim 1,
wherein in the reduction treatment, the nickel ammine sulfate
complex solution containing the seed crystals is continuously fed
into the reactor such that a reaction time of the reduction
treatment in the reactor takes 5 to 120 minutes.
Description
BACKGROUND
Field of the Invention
[0001] The present invention relates to a method for obtaining
nickel powder from a nickel ammine sulfate complex solution, and
specifically relates to a method for continuously adding a solution
and hydrogen gas etc., to a high pressure container, and
continuously discharging and recovering nickel powder.
Related Art
[0002] As a method for industrially producing nickel powder using a
hydrometallurgical process, a method for producing nickel powder
disclosed in Japanese Patent Application Laid-Open No. 2015-140480
is known, in which a raw material containing nickel is dissolved in
a solution of sulfuric acid, followed by liquid-purification step
of removing impurities contained in the dissolution, and thereafter
ammonia is added to the resulting nickel sulfate solution to form a
nickel ammine complex; and the nickel ammine sulfate complex
solution is then placed into a container at high temperature and
high pressure, and hydrogen gas is fed to reduce nickel in the
nickel ammine sulfate complex solution.
[0003] Because the reaction is performed at high temperature and
high pressure in such a production method as described above, batch
methods for production are often used from the viewpoint of ease of
handling and cost of the apparatus. However, in such batch methods
for production, a series of operation to open the reactor, place
the solution, tightly seal the reactor, heat the reactor, control
the temperature and the pressure, blow hydrogen gas into the
reactor to perform reduction, cool the reactor, and extract the
reaction product should be performed at each stage. For this
reason, the batch methods are not efficient because the methods
require large amounts of labor and time, reducing the operating
rate. Furthermore, influences of heating and/or cooling before and
after the reaction cannot be neglected, causing uneven precipitates
called scaling or a variation in particle size during the reaction
in some cases. In particular, uneven nickel powder produced due to
mixing of coarse nickel powder is more likely to cause wear or clog
of the facility during handling, reducing the operating rate. The
influences of uneven nickel powder as well as the labor to remove
it result in difficulties in maintaining the operating rate of the
reaction and the quality of products at constant levels.
[0004] Nickel powder obtained by the batch method has a problem
about the quality of impurities compared to the electrolytic nickel
in the form of a plate (sheet) obtained by standard
electrometallurgy. Specifically, the sulfur grade should be 0.01%
by weight or less to obtain the certification of high purity grade
in an international nickel market London Metal Exchange (LME). The
nickel powder obtained by the batch method may have higher sulfur
grade than that in the high purity nickel of the LME grade
specified in the LME, and are difficult to use in applications
where the electrolytic nickel is completely replaced.
[0005] An object of the present invention provides a method for
continuously feeding a solution, seed crystals, and hydrogen gas
into a reactor kept at high temperature and high pressure to
produce nickel powder, and continuously discharging and recovering
the produced powder, whereby a fine nickel powder with high purity
can be sufficiently grown, a variation in particle size can be
reduced to maintain the quality of the nickel powder, and a high
operating rate of the reaction can be maintained.
SUMMARY
[0006] A first aspect of the invention relates to a method of
producing nickel powder, where the method includes the steps of
feeding a nickel ammine sulfate complex solution and seed crystals
into a reactor, and feeding hydrogen gas into the reactor to
subject a nickel complex ion in the nickel ammine sulfate complex
solution to a reduction treatment and to thereby produce nickel
powder having a sulfur grade of lower than 0.01% by weight,
wherein, in the reduction treatment, while the nickel ammine
sulfate complex solution containing polyacrylic acid in a
concentration of 0.5 to 1.0 g/liter is being continuously fed into
the reactor, a temperature inside the reactor is controlled within
the range of 150.degree. C. or more and 185.degree. C. or less and
the feed rate of hydrogen gas is controlled to maintain an inner
pressure of the reactor in the range of 2.5 to 3.5 MPa to produce a
nickel powder slurry containing the nickel powder, and thereafter,
when the nickel powder slurry is extracted from the reactor, a feed
amount of the nickel ammine sulfate complex solution and the seed
crystals and a discharge amount of the nickel powder slurry are
adjusted to keep a given amount of the solution in the reactor.
[0007] A second aspect of the present invention relates to a method
of producing nickel powder, where the method includes the steps of
feeding hydrogen gas into a reactor, and feeding a nickel ammine
sulfate complex solution and seed crystals into the reactor to
subject a nickel complex ion in the nickel ammine sulfate complex
solution to a reduction treatment and to thereby produce nickel
powder having a sulfur grade of lower than 0.01% by weight,
wherein, in the reduction treatment, the nickel complex ion in the
nickel ammine sulfate complex solution is reduced in such a manner
that a slurry containing ammonium sulfate and nickel powder are
stored in the reactor to form a liquid phase portion and a gaseous
phase portion in the reactor and an inner pressure of the gaseous
phase portion is controlled through the feeding of the hydrogen gas
into the reactor, a slurry containing seed crystals and the nickel
ammine sulfate complex solution containing polyacrylic acid in a
concentration of 0.5 to 1.0 g/liter are continuously fed into the
liquid phase portion, a temperature inside the reactor is
controlled in the range of 150.degree. C. or more and 185.degree.
C. or less, and the feed rate of the hydrogen gas is controlled to
maintain an inner pressure of the reactor in the range of 2.5 to
3.5 MPa, to produce a nickel powder slurry containing the nickel
powder, and thereafter, when the nickel powder slurry is extracted
from the reactor, a feed amount of the nickel ammine sulfate
complex solution and the seed crystals and a discharge amount of
the nickel powder slurry are adjusted to keep a given amount of the
solution in the reactor.
[0008] Nickel powder having an average particle size in the range
of 0.1 to 100 .mu.m may be used as the seed crystals according to
the first aspect of the invention or the second aspect of the
invention.
[0009] Nickel powder having an average particle size in the range
of 0.1 to 10 .mu.m may be used as the seed crystals according to
the first aspect of the invention or the second aspect of the
invention.
[0010] The amount of the seed crystals to be added according to the
above-described aspects may be in the range of 1 to 100% by weight
based on the weight of nickel contained in the nickel ammine
sulfate complex solution.
[0011] The nickel ammine sulfate complex solution that is subjected
to the reduction treatment may contain polyacrylic acid in an
amount in the range of 0.5 to 5% by weight based on the weight of
the seed crystals in the nickel ammine sulfate complex
solution.
[0012] The reduction treatment according to the invention may
include continuously feeding into the reactor the nickel ammine
sulfate complex solution containing the seed crystals such that the
reaction time of the reduction treatment in the reactor takes 5
minutes or more and 120 minutes or less.
[0013] According to the present invention, a nickel precipitate can
be formed on seed crystals and a grown nickel powder can be formed
thereon through the repeated reduction treatment with the
precipitation of nickel. In addition, nickel powder having a little
variation in size can be continuously obtained.
[0014] Also, because of the effect of the dispersant, the nickel
powder having lower sulfur grade can be extracted and recovered
from the solution in the form of fine powdery precipitate.
Furthermore, a coarse nickel powder having a spherical shape and a
smooth surface can also be obtained depending on the combination of
the particle size of the nickel powder and the concentration of the
dispersant.
[0015] The nickel powder produced in the present invention can be
used in applications of nickel pastes as an inner constitutional
substance of stacked ceramic capacitors. This production method can
grow particles through repetition of the reduction treatment with
hydrogen to obtain a high purity nickel metal of high quality while
maintaining a high operating rate of the reaction. This method
attains an industrially remarkable effect.
BRIEF DESCRIPTION OF DRAWINGS
[0016] FIG. 1 This illustrates an optical microscope photograph
(.times.50) of the nickel powder according to Example 1 of the
present invention.
[0017] FIG. 2 This illustrates an optical microscope photograph
(.times.100) of the nickel powder according to Example 2 of the
present invention.
[0018] FIG. 3 This illustrates an SEM photograph (.times.1000) of
the nickel powder according to Example 3 of the present
invention.
[0019] FIG. 4 This illustrates an SEM photograph (.times.500) of
the nickel powder according to Example 4 of the present
invention.
[0020] FIG. 5 This illustrates an optical microscope photograph 5A
(.times.50) and 5B its enlarged photograph (.times.100) of the
nickel powder according to Example 4 of the present invention.
DETAILED DESCRIPTION
[0021] The present invention is a method for producing nickel
powder including: producing nickel powder through a reduction
treatment with hydrogen gas blown into a reactor as a pressurized
container while adding seed crystals to a nickel ammine sulfate
complex solution and continuously feeding the seed crystals; and
continuously discharging the nickel powder from the pressurized
container. Moreover, a high purity, uniform fine nickel powder
having lower sulfur grade can be obtained by using a
dispersant.
[0022] Hereinafter, the method for producing nickel powder
according to the present invention will be described.
[0023] A nickel ammine sulfate complex solution that can be used in
the present invention is not particularly limited, but it is
suitable to use a nickel ammine sulfate complex solution obtained
by dissolving a nickel-containing 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, and nickel powder, with
sulfuric acid or ammonia to prepare a nickel-containing leachate
(solution containing nickel), subjecting the nickel-containing
leachate to a liquid-purification step such as solvent extraction,
ion exchange, or neutralization to remove impurity elements in the
solution, and adding ammonia to the resulting solution.
[0024] In the present invention, seed crystals are added to the
nickel ammine sulfate complex solution to form a slurry, which is
subjected to the reduction treatment.
[0025] The seed crystals added here are powder having an average
particle size of preferably 0.1 .mu.m or more and 100 .mu.m or
less, more preferably 0.1 .mu.m or more and 10 .mu.m or less.
[0026] Nickel powder is suitably used as a substance which does not
become impurities in the final nickel precipitate to contaminate
the precipitate. The nickel powder used as the seed crystals can be
prepared through addition of a reducing agent such as hydrazine to
the nickel ammine sulfate complex solution, for example.
[0027] The weight of the seed crystals to be added is preferably 1%
by weight or more and 100% by weight or less based on the weight of
the nickel in the nickel ammine sulfate complex solution. A content
of less than 1% by weight cannot sufficiently achieve the effect of
reducing uneven precipitation. A content of more than 100% by
weight has no influences over the effect; rather, it results in
excess addition of the seed crystals.
[0028] A dispersant may also be then added to disperse the seed
crystals in the slurry.
[0029] Any polyacrylate dispersant can be used without particular
limitation. Suitable is sodium polyacrylate because it is
industrially available at low cost.
[0030] If the dispersant is added, the amount thereof to be added
is suitably in the range of 0.5 to 5% by weight based on the weight
of the seed crystals. A content of less than 0.5% does not achieve
any dispersing effect. A content of more than 5% has no influences
over the dispersing effect; rather, such an addition is excess
addition of the dispersant.
[0031] Alternatively, the polyacrylic acid may be added such that
the concentration thereof is 0.5 to 1.0 g/liter based on the amount
of the nickel ammine sulfate complex solution. The seed crystals
added at this time are preferably seed crystals having an average
particle size of 0.1 .mu.m or more and 10 .mu.m or less.
[0032] In the present invention, for example, "to" in the
description of 0.5 to 5% by weight indicates 0.5% by weight or more
and 5% by weight or less.
[0033] In the next step, the slurry prepared by adding the seed
crystals or the seed crystals and the dispersant in the nickel
ammine sulfate complex solution is continuously placed into a
reaction vessel of a container resistant to high pressure and high
temperature where a slurry containing ammonium sulfate and nickel
powder is stored and the inner pressure is controlled with hydrogen
gas. Thereby, a liquid phase portion occupied by the slurry and a
gaseous phase portion are formed within the reaction vessel.
Alternatively, the slurry containing the seed crystals or the
slurry containing the seed crystals and the dispersant, and the
nickel ammine sulfate complex solution are continuously charged
into a reaction vessel of a container resistant to high pressure
and high temperature where a slurry containing ammonium sulfate and
nickel powder is stored and the inner pressure is controlled with
hydrogen gas. Thereby, a slurry is formed, and a liquid phase
portion occupied by the slurry and a gaseous phase portion having
an inner pressure controlled with hydrogen gas is formed within the
reaction vessel.
[0034] Subsequently, in the slurry continuously charged into the
reaction vessel, the nickel complex ion contained in the nickel
ammine sulfate complex solution is reduced with hydrogen gas to
precipitate nickel on the seed crystals added and grow the nickel
precipitate into nickel powder. The nickel powder slurry, i.e., the
slurry containing the grown nickel powder is simultaneously formed,
ant is continuously discharged.
[0035] The reaction temperature at this time is preferably in the
range of 150.degree. C. or more and 185.degree. C. or less. A
reaction temperature of less than 150.degree. C. reduces the
reduction efficiency. A reaction temperature of more than
185.degree. C. has no influences over the reaction; rather, it is
not suitable because it increases loss of thermal energy.
[0036] Furthermore, the gaseous phase portion of the reaction
vessel preferably is under a pressure maintained in the range of
2.5 to 3.5 MPa during the reaction. A pressure of less than 2.5 MPa
reduces the reaction efficiency. A pressure of more than 3.5 MPa
has no influences over the reaction; rather, it increases loss of
hydrogen gas.
[0037] A reduction treatment accompanied by the precipitation of
nickel under such conditions can form a nickel precipitate on seed
crystals and thus a grown nickel powder, continuously yielding
nickel powder having a little variation in size.
[0038] Moreover, because of the effect of the dispersant, nickel
having lower sulfur grade can be extracted and recovered from the
solution in the form of a fine powdery precipitate. In addition, a
coarse nickel powder having a spherical shape and a smooth surface
can also be yielded depending on the combination of the particle
size of the nickel powder and the concentration of the
dispersant.
[0039] The nickel powder produced as described above can be used in
applications of nickel pastes as an inner constitutional substance
of stacked ceramic capacitors. Besides, particles can be grown
through repetition of the reduction with hydrogen to produce fine
nickel metal with high purity and uniformity which has a particle
size of 20 .mu.m or less and is suitable for handling.
EXAMPLES
[0040] Hereinafter, the present invention will be described by way
of Examples.
Example 1
[0041] A pressurized container (autoclave) having an inner volume
of 190 liter was used as a reaction vessel. A solution slurry (90
liter) containing ammonium sulfate (269 g/L) and nickel powder (100
g/L) was placed into the reaction vessel. The reaction vessel was
covered with a lid to maintain the temperature at 185.degree. C.
Hydrogen gas was then blown into the reaction vessel to control the
pressure to 3.5 MPa.
[0042] In the next step, the starting solution containing 150
g/liter of ammonium sulfate and a nickel ammine sulfate complex
solution (concentration of nickel: 110 g/L) was added to the
pressurized container at a flow rate of 1 liter per minute, and
further a nickel seed crystal slurry (concentration of slurry: 300
g/L) was added at a flow rate of 0.25 liter per minute to advance a
reduction treatment.
[0043] The nickel powder used here as the seed crystals forming the
nickel seed crystal slurry had an average particle size of 1 .mu.m.
Hydrogen gas was blown into the reaction vessel such that the inner
pressure of the pressurized container was maintained at 3.5
MPa.
[0044] The following operation was continued for four hours: while
the amount of the solution stored in the pressurized container was
being controlled in the range of 90 liter.+-.5 liter, the nickel
powder slurry containing the nickel powder produced in the
reduction treatment was continuously extracted from the pressurized
container. The reaction time in the reduction treatment in the
reactor was 75 minutes from the charge of the starting solution and
the seed crystal slurry to the extraction of the nickel powder
slurry.
[0045] As shown in Table 1-1, the extracted nickel powder slurry
contained 0.28 g/L of nickel, and the reduction rate (reaction
rate), namely, the proportion of hydrogen gas used in the
precipitation reaction of the nickel powder was 99.6%.
[0046] As shown in Table 1-2, particles having a particle size of
100 .mu.m to 300 .mu.m were 99% or more of the particle diameter
distribution, indicating that a sufficiently grown nickel powder
was obtained.
[0047] In the entire particle diameter distribution, the proportion
of particles having a particle size of more than 300 .mu.m was less
than 0.1%, the proportion of particles having a particle size of
more than 150 .mu.m and 300 .mu.m or less was 91%, the proportion
of particles having a particle diameter of more than 100 .mu.m and
150 .mu.m or less was 8.3%, the proportion of particles having a
particle diameter of more than 75 .mu.m and 100 .mu.m or less and
the proportion of particles having a particle diameter of more than
45 .mu.m and 75 .mu.m or less both were less than 0.1%, and the
proportion of particles having a particle diameter of 45 .mu.m or
less was 0.7%.
[0048] As shown in FIG. 1, although the particles having uneven
shapes and aggregation are observed, it was confirmed that nickel
powder having a little variation in particle size distribution can
be continuously produced. The sulfur grade was 0.062%.
TABLE-US-00001 TABLE 1-1 Reaction time 4 [Hours] Concentration of
Ni in Ni powder slurry 0.28 [g/L] Reduction rate 99.6 [%] S grade
0.062 [%]
TABLE-US-00002 TABLE 1-2 Reaction time 4 [Hours] Particle size
[.mu.m] Particle size distribution [%] 300 <0.1 300~+150 91
150~+100 8.3 100~+75 <0.1 75~+45 <0.1 ~45 0.7
Example 2
[0049] The same reactor as in Example 1 was used. A solution slurry
(90 liter) containing ammonium sulfate (205 g/L), polyacrylic acid
(concentration: 1 g/L), and nickel powder (concentration: 105 g/L)
was placed into the reactor. The reaction vessel was covered with a
lid to maintain the inner temperature at 185.degree. C.
[0050] Hydrogen gas was then blown into the gaseous phase portion
in the reactor to control the inner pressure of the container to
3.5 MPa.
[0051] In the next step, a starting solution containing a nickel
ammine sulfate complex solution (concentration of nickel: 83 g/L)
and ammonium sulfate at a concentration of 120 g/L was fed into the
reactor at a flow rate of 1 liter per minute, and simultaneously
the nickel seed crystal slurry (concentration of slurry: 150 g/L)
was continuously fed into the reactor at a flow rate of 0.5 liter
per minute to advance the reduction treatment.
[0052] Nickel powder having an average particle size of 1 .mu.m was
used as the nickel powder forming the nickel seed crystal slurry.
Hydrogen gas was blown such that the inner pressure of the reactor
was maintained at 3.5 MPa.
[0053] While controlling the amount of solution stored in the
reactor to be in the range of 90 liter.+-.5 liter, the slurry
subjected to the reduction treatment was continuously extracted.
This operation was continued for hours. The extracted slurry
subjected to the reduction treatment was subjected to solid liquid
separation using a Nutsche funnel into nickel powder and filtrate.
The resulting nickel powder was washed, and was vacuum dried. The
reaction time in the reduction treatment in the reactor was 60
minutes from the charge of the starting solution and the seed
crystal slurry to the extraction of the nickel powder slurry.
[0054] The reduction rate (reaction rate), namely, the proportion
of hydrogen gas used in the precipitation reaction of the nickel
powder was 98.9%.
[0055] The resulting nickel powder had a finer average particle
size D50 of 5.2 .mu.m but had a less variation in size than those
of Example 1 (see FIG. 2). Furthermore, the sulfur grade was
0.003%, which indicates that a high purity nickel powder having a
low sulfur grade lower than the sulfur quality (0.01%) specified as
the LME grade was obtained.
TABLE-US-00003 TABLE 2 Reaction time 16 [Hours] Reduction rate 98.9
[%] Particle size (D50) 5.2 [.mu.m] S grade 0.003 [%]
Example 3
[0056] A solution (90 liter) containing ammonium sulfate (205 g/L),
nickel powder (105 g/L), and polyacrylic acid (1 g/L) was placed
into a reactor having the same structure as in Example 1 and having
a volume of 90 liter to maintain the temperature at 185.degree. C.
Hydrogen gas was blown into the reaction vessel to control the
pressure at 3.5 MPa.
[0057] In the next step, a starting solution containing a nickel
ammine sulfate complex solution (concentration of nickel: 83 g/L)
and ammonium sulfate at a concentration of 120 g/L was added to
this pressurized container at a rate of 1 liter/min, and
simultaneously a nickel seed crystal slurry (slurry content: 150
g/L) was added at a rate of 0.5 liter/min. Moreover, polyacrylic
acid at a concentration of 1 g/L was added to the nickel ammine
sulfate complex solution in the starting solution, which was fed to
the reactor. Hydrogen gas was blown into the pressurized container
such that its pressure became 3.5 MPa. The extracted nickel powder
forming the nickel powder slurry had an average particle size of
5.9 .mu.m.
[0058] While the amount of the solution in the pressurized
container was being managed in the range of liter.+-.5 liter, the
nickel powder slurry was continuously extracted. This operation was
continued for 12 hours. The reaction time in the reduction
treatment in the reactor was 60 minutes from the charge of the
starting solution and the seed crystal slurry to the extraction of
the nickel powder slurry.
[0059] At this time, the reduction rate or the reaction rate was
96.8%.
[0060] The sulfur grade was 0.003%, which was lower than the sulfur
grade (0.01%) specified as the LME grade.
[0061] The nickel powder had a particle size D50 of 6.4 .mu.m,
which indicates that a very fine powder could be stably obtained as
shown in FIG. 3.
TABLE-US-00004 TABLE 3 Reaction time 12 [Hours] Reduction rate 96.8
[%] Particle size (D50) 6.4 [.mu.m] S grade 0.003 [%]
Example 4
[0062] A starting solution (90 liter) containing ammonium sulfate
(200 g/L), nickel powder (11 g/L), and polyacrylic acid (0.1 g/L)
was placed into the 90 liter reactor the same as that in Example 1
to maintain the temperature at 185.degree. C. Hydrogen gas was
blown thereinto to control the pressure at 3.5 MPa.
[0063] A starting solution having a composition containing a nickel
ammine sulfate complex solution (concentration of nickel: 83 g/L)
and 360 g/L of ammonium sulfate was added to the reactor at a flow
rate of 1 liter/min, and a nickel seed crystal slurry
(concentration: 33 g/L) was added at a rate of 0.5 liter/min.
Hydrogen gas was blown into the pressurized container such that its
pressure was maintained at 3.5 MPa, to advance the reduction
treatment.
[0064] While the amount of the solution stored in the reactor was
being managed in the range of 90 liter.+-.5 liter, the nickel
powder slurry subjected to the reduction treatment was continuously
extracted from the reactor. This operation was continued for 6
hours. The nickel powder forming the 33 g/L nickel seed crystal
slurry had an average particle size of 53 .mu.m. The reaction time
in the reduction treatment in the reactor was 60 minutes from the
charge of the starting solution and the seed crystal slurry to the
extraction of the nickel powder slurry.
[0065] The reduction rate or the reaction rate was 89.0%.
[0066] The recovered nickel powder has a sulfur grade of 0.01%,
which satisfied the sulfur grade (0.01%) specified as the LME
grade.
[0067] The nickel powder had a particle size D50 of 78.0 .mu.m,
which indicates that a sufficiently grown nickel powder was
obtained. As shown in FIGS. 4 and 5, the nickel powder was obtained
in the form of particles having very smooth surfaces and having a
true spherical shape.
TABLE-US-00005 TABLE 4 Reaction time 6 [Hours] Reduction rate 89.0
[%] Particle size (D50) 78.0 [.mu.m] S grade 0.01 [%]
Example 5
[0068] A pressurized container (autoclave) having an inner volume
of 190 liter and having inner walls lined with titanium was used as
a reactor (reaction vessel). A solution slurry (90 liter)
containing 205 g/liter of ammonium sulfate, 1 g/liter of
polyacrylic acid, and 105 g/liter of nickel powder was placed into
this reactor. The reactor was covered with a lid to maintain the
temperature at 185.degree. C.
[0069] Hydrogen gas was then blown into the gaseous phase portion
of the reactor to control the inner pressure of the container to
3.5 MPa. In the next step, a nickel ammine sulfate complex solution
(concentration of nickel: g/liter) and a solution containing 120
g/liter of ammonium sulfate were fed into this reactor at a flow
rate of 1 liter per minute, and simultaneously 150 g/liter of
nickel powder slurry was continuously fed into the reactor at a
flow rate of 0.5 liter per minute.
[0070] Nickel powder having an average particle size of 1 .mu.m was
used for forming the nickel powder slurry. Hydrogen gas was blown
into the reactor such that the inner pressure was maintained at 3.5
MPa.
[0071] In the next step, while the amount of the solution in the
reactor was being controlled in the range of 90 liter.+-.5 liter,
the nickel powder slurry was continuously extracted. This operation
was continued for hours. The extracted nickel powder slurry was
subjected to solid liquid separation using a Nutsche funnel into
nickel powder and a filtrate. The resulting nickel powder was
washed, and was vacuum dried.
[0072] The reduction rate (reaction rate), namely, the proportion
of hydrogen gas used in the precipitation reaction of the nickel
powder was 98.9%.
[0073] The resulting nickel powder had an average particle size D50
of 5.2 .mu.m. A fine nickel powder could be stably obtained.
Comparative Example 1
[0074] A solution having the same composition as in Example 1 was
continuously fed, at the same flow rate, into the same reactor as
in Example 1 without containing polyacrylic acid, and was reduced
with hydrogen gas under the same condition as that in Example 1 to
obtain a nickel powder slurry. The nickel powder slurry was
subjected to solid liquid separation to obtain nickel powder. The
reduction rate or the reaction rate was 99.6%.
[0075] In the particle size distribution of the resulting nickel
powder, the proportion of particles having a particle size of 100
.mu.m to 300 .mu.m was 99% or more. In the entire particle size
distribution, the proportion of particles having a particle size of
more than 300 .mu.m was less than 0.1%, the proportion of particles
having a particle size of more than 150 .mu.m and 300 .mu.m or less
was 91%, the proportion of particles having a particle size of more
than 100 .mu.m and 150 .mu.m or less was 8.3%, the proportion of
particles having a particle size of more than 75 .mu.m and 100
.mu.m or less and the proportion of particles having a particle
size of more than 45 .mu.m and .mu.m or less both were less than
0.1%, and the proportion of particles having a particle size of 45
.mu.m or less was 0.7%. The resulting nickel powder was not fine as
the nickel powder according to the present invention.
[0076] As described above, it was confirmed that a fine nickel
powder can be continuously and efficiently obtained by use of the
method according to the present invention.
* * * * *