U.S. patent application number 16/081980 was filed with the patent office on 2019-01-10 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, Ryo-ma Yamaguma.
Application Number | 20190009343 16/081980 |
Document ID | / |
Family ID | 59743856 |
Filed Date | 2019-01-10 |
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United States Patent
Application |
20190009343 |
Kind Code |
A1 |
Heguri; Shin-ichi ; et
al. |
January 10, 2019 |
METHOD FOR PRODUCING NICKEL POWDER
Abstract
Provided is a method for producing nickel powder, wherein fine
nickel powder serving as seed crystals needed for production of
nickel powder is produced from a solution containing a nickel
ammine sulfate complex according to the amount needed for the
production of the nickel powder. The method for producing nickel
powder is characterized in that: the solution containing the nickel
ammine sulfate complex, an insoluble solid, and a dispersant are
continuously fed into a reaction vessel, followed by stirring to
prepare a solution containing a nickel complex ion; hydrogen gas is
blown into the prepared solution to reduce the nickel complex ion
in the solution containing the nickel complex ion, thereby forming
a precipitate of nickel particles on the surface of the insoluble
solid; and thereafter the post-reduction solution is extracted from
the reaction vessel.
Inventors: |
Heguri; Shin-ichi;
(Niihama-shi, JP) ; Ozaki; Yoshitomo;
(Niihama-shi, JP) ; Yamaguma; Ryo-ma;
(Niihama-shi, JP) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
SUMITOMO METAL MINING CO., LTD. |
Tokyo |
|
JP |
|
|
Family ID: |
59743856 |
Appl. No.: |
16/081980 |
Filed: |
February 22, 2017 |
PCT Filed: |
February 22, 2017 |
PCT NO: |
PCT/JP2017/006623 |
371 Date: |
September 4, 2018 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
B22F 1/0011 20130101;
B22F 9/26 20130101; B22F 2304/10 20130101; B22F 2999/00 20130101;
B22F 2301/15 20130101; B22F 2999/00 20130101; B22F 9/26 20130101;
B22F 2201/013 20130101 |
International
Class: |
B22F 9/26 20060101
B22F009/26; B22F 1/00 20060101 B22F001/00 |
Foreign Application Data
Date |
Code |
Application Number |
Mar 4, 2016 |
JP |
2016-042668 |
Claims
1. A method of producing nickel powder, wherein: a solution
containing a nickel ammine sulfate complex, an insoluble solid, and
a dispersant are continuously fed into a reaction vessel, followed
by stirring to prepare a solution containing a nickel complex ion;
hydrogen gas is blown into the solution containing the nickel
complex ion to reduce the nickel complex ion in the solution
containing the nickel complex ion, thereby forming a composite
including a precipitate of nickel particles on a surface of the
insoluble solid, to thereby prepare a reduced slurry containing the
composite; and thereafter, when the reduced slurry is extracted
from the reaction vessel, a feed amount of the solution containing
the nickel ammine sulfate complex, the insoluble solid, and the
dispersant and a discharge amount of the reduced slurry are
adjusted to keep a constant amount of the solution in the reaction
vessel.
2-7. (canceled)
8. The method of producing nickel powder according to claim 1,
wherein an amount of the dispersant to be added is controlled to
control the number of nickel powder obtained through the formation
of the precipitate of nickel in the reduction.
9. The method of producing nickel powder according to claim 8,
wherein the dispersant is a polyacrylate and the amount of the
dispersant to be added is in an amount of more than 1.0% by weight
and 10.0% by weight or less based on a weight of the insoluble
solid in the reaction vessel.
10. The method of producing nickel powder according to claim 8,
wherein the dispersant is a lignosulfonic acid and the amount of
the dispersant to be added is in an amount of more than 2.0% by
weight and 20.0% by weight or less based on a weight of the
insoluble solid in the reaction vessel.
11. The method of producing nickel powder according to claim 1,
wherein the dispersant is a polyacrylate and the amount of the
dispersant to be added is in an amount of more than 1.0% by weight
and 10.0% by weight or less based on a weight of the insoluble
solid in the reaction vessel.
12. The method of producing nickel powder according to claim 1,
wherein the dispersant is a lignosulfonic acid and the amount of
the dispersant to be added is in an amount of more than 2.0% by
weight and 20.0% by weight or less based on a weight of the
insoluble solid in the reaction vessel.
Description
BACKGROUND
Field of the Invention
[0001] The present invention relates to a method for producing fine
nickel powder available as seed crystals from a solution containing
a nickel ammine sulfate complex, and the invention can be applied,
in particular, in a treatment for controlling the number of nickel
powder generated to requirement.
Related Art
[0002] Methods for producing fine nickel powder have been known
including atomization methods of dispersing molten nickel in gas or
water to obtain fine powder, and dry processes, such as CVD
processes, of volatilizing nickel, and reducing the nickel in a
gaseous phase to obtain nickel powder as described in Japanese
Patent Application Laid-Open No. 2005-505695.
[0003] Methods for producing nickel powder by a wet process have
been known including a method of producing nickel powder using a
reducing agent as described in Japanese Patent Application
Laid-Open No. 2010-242143, and an atomization thermal decomposition
method of atomizing a nickel solution in a reduction atmosphere at
a high temperature to obtain nickel powder through a thermal
decomposition reaction as described in Japanese Patent No. 4286220.
However, these methods are not economical because these methods
require expensive reagents and a large amount of energy.
[0004] In contrast, a method as described in "The Manufacture and
properties of metal powder produced by the gaseous reduction of
aqueous solutions", Powder metallurgy, No. 1/2 (1958), 40-52 is
industrially inexpensive and useful, in which hydrogen gas is fed
to a nickel ammine sulfate complex solution to reduce nickel ions
in the complex solution, obtaining nickel powder. However, this
method tends to produce coarse particles of the nickel powder, and
has difficulties in producing a fine powder which can be used as
seed crystals.
[0005] When particles are produced from an aqueous solution and are
grown, a small amount of fine crystals called seed crystals is
added, and a reducing agent is fed thereto to grow the seed
crystals into a powder having a predetermined particle size.
[0006] The seed crystals used in this method are often obtained
through pulverization of a product, which requires labor, reduces
the yield, and thus increases cost. In addition, the pulverization
does not necessarily produce seed crystals having an optimal
particle size or optimal properties.
[0007] Furthermore, an appropriate amount of seed crystals is
always required to stably advance the operation to produce nickel
powder. On the other hand, preparation of excess seed crystals
increases stock in progress and the labor for management thereof,
thus reducing the production efficiency.
[0008] As described above, a method for stably obtaining an amount
of seed crystals needed for the actual operation has been
demanded.
[0009] Accordingly, an object of the present invention is to
provide a method for producing nickel powder, wherein fine nickel
powder serving as seed crystals required for production of nickel
powder is produced from a solution containing a nickel ammine
sulfate complex according to the amount needed for the production
of the nickel powder.
SUMMARY
[0010] A first aspect of the present invention relates to a method
for producing nickel powder, wherein: a solution containing a
nickel ammine sulfate complex, an insoluble solid, and a dispersant
are continuously fed into a reaction vessel, followed by stirring
to prepare a solution containing a nickel complex ion; hydrogen gas
is blown into the prepared solution to reduce the nickel complex
ion in the solution containing the nickel complex ion, thereby
forming a composite including a precipitate of nickel particles on
a surface of the insoluble solid, to thereby prepare a reduced
slurry containing the composite; and thereafter, when the reduced
slurry is extracted from the reaction vessel, a feed amount of the
solution containing the nickel ammine sulfate complex, the
insoluble solid, and the dispersant and a discharge amount of the
reduced slurry are adjusted to keep a constant amount of the
solution in the reaction vessel.
[0011] The present invention also relates to a method for producing
nickel powder, wherein the amount of the dispersant to be added in
the first aspect is controlled to control the number of nickel
powder obtained through the formation of the precipitate of nickel
in the reduction.
[0012] The present invention further relates to a method for
producing nickel powder, wherein the dispersant in the first and
eighth aspects is a polyacrylate and the amount of the dispersant
to be added is in an amount of more than 1.0% by weight and 10.0%
by weight or less based on a weight of the insoluble solid in the
reaction vessel.
[0013] The present invention additionally relates to a method for
producing nickel powder, wherein the dispersant in the first and
eighth aspects is a lignosulfonic acid and the amount of the
dispersant to be added is in an amount of more than 2.0% by weight
and 20.0% by weight or less based on a weight of the insoluble
solid in the reaction vessel.
[0014] The present invention can provide a method for economically
and efficiently producing fine nickel powder, which is optimal as
the seed crystals used in production of nickel powder, from a
nickel ammine sulfate complex solution through reduction and
precipitation using hydrogen gas according to the amount needed,
and which exhibits a remarkable industrial effect.
BRIEF DESCRIPTION OF DRAWINGS
[0015] FIG. 1 This is a production flowchart in a method for
producing nickel powder according to the present invention, in
which a dispersant and an insoluble solid are added.
[0016] FIG. 2 This is a graph illustrating a change in the
concentration of nickel in the solution after the reaction in
Reference Examples 1 to 4 where sodium polyacrylate is used.
[0017] FIG. 3 This is a graph illustrating a change in the
concentration of nickel in the slurry of Reference Comparative
Example 2 (dispersant is not added) plotted against the reaction
time, where the change is caused by the concentration of the
dispersant during the reduction with hydrogen.
[0018] FIG. 4 This is a graph illustrating the relation between the
number of nickel powder and the amount of sodium polyacrylate added
according to Reference Example 5.
[0019] FIG. 5 This is a graph illustrating the relation between the
number of nickel powder and the amount of sodium lignosulfonate
added according to Reference Example 6.
[0020] FIG. 6 This is a graph illustrating the comparison in
particle size distribution between the insoluble solid (nickel
powder) as seed crystals and the produced nickel powder according
to Example 7.
DETAILED DESCRIPTION
[0021] The present invention is a method for producing nickel
powder by adding a dispersant and an insoluble solid as seed
crystals to a nickel ammine sulfate complex solution, and blowing
hydrogen gas thereinto, wherein a target amount of fine nickel
powder is produced through control of the amount of dispersant to
be added.
[0022] Hereinafter, the method for producing nickel powder
according to the present invention will be described with reference
to the production flowchart in FIG. 1.
[Nickel Ammine Sulfate Complex Solution]
[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 depending on the components 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.
[Mixing Step]
[0024] In this step, first, a dispersant is added to the nickel
ammine sulfate complex solution.
[0025] Any polyacrylate or lignosulfonate dispersant can be used in
this step without particular limitation. Among those industrially
available at low cost, suitable polyacrylates are calcium
polyacrylate, sodium polyacrylate and potassium polyacrylate, and
suitable lignosulfonates are calcium lignosulfonate, sodium
lignosulfonate, and potassium lignosulfonate.
[0026] The concentration of ammonium sulfate in the solution is
preferably in the range of 10 to 500 g/L in conjunction with the
production method illustrated in FIG. 1. A concentration of more
than 500 g/L is beyond the solubility, precipitating crystals. A
concentration of less than 10 g/L is difficult to achieve because
ammonium sulfate is newly generated by the reaction.
<Addition of Insoluble Solid>
[0027] In the production method according to the present invention
illustrated in FIG. 1, in the next step, an insoluble solid, which
is at least insoluble in the nickel ammine sulfate complex solution
having an adjusted concentration of the dispersant and serves as a
matrix for a precipitate, is added to the complex solution.
[0028] Any insoluble solid having low solubility to the nickel
ammine sulfate complex solution, an ammonium sulfate aqueous
solution, or an alkali solution can be added here without
particular limitation. For example, nickel powder, iron powder,
alumina powder, zirconia powder, or silica powder can be used.
[0029] Unlike the conventional methods generally used in which
powder is precipitated using seed crystals to make it into a
product containing the seed crystals, in the present invention,
after the necessary precipitation of particles onto the surface of
the insoluble solid is completed, the insoluble solid is separated
from the yielded and grown precipitate, and only the powder of the
separated precipitate is extracted as a product. Such a method in
the present invention is intended to avoid the influences of
impurities in the seed crystals itself over the product.
[0030] Any amount of insoluble solid can be added without
particular limitation. The amount thereof is selected according to
the type of the solid such that the insoluble solid can be mixed
with the nickel ammine sulfate complex solution through stirring.
As one example, an amount of about 50 to 100 g/L may be added.
[0031] The insoluble solid can also have any shape and size without
particular limitation. Suitable are those having strength to stand
impact or friction and having a smooth surface so as to effectively
separate the nickel precipitate, because the nickel precipitates on
the surface of the insoluble solids may be separated through
application of collision or vibration as described later.
[0032] Considering the effective separation of the insoluble solid
from the nickel precipitate on the surface thereof, the insoluble
solid suitably used in the actual operation has a rounded shape
such as a spherical or elliptical shape and has a diameter of about
0.05 to 3 mm. Preferably, the insoluble solid according to the
present invention is used after adhering substances to the surface
of the insoluble solid are removed through the application of
collision or impact to the insoluble solid prior to the
precipitation of nickel.
[0033] Furthermore, the insoluble solid after the separation of the
nickel precipitate can be subjected to a pre-treatment such as
washing, when necessary, and can be repeatedly used.
<Addition of Dispersant>
[0034] The present invention is characterized in that the insoluble
solid is used as seed crystals, and the dispersant is added. The
dispersant can sufficiently disperse the added insoluble solid in a
complex solution to generate a fine nickel precipitate on the
surface of the insoluble solid. The dispersant is added desirably
in an appropriate amount in the range of 1.0 to 20.0% by weight of
the weight of the insoluble solid added to the complex solution. In
particular, a polyacrylate and a lignosulfonate are preferred.
[0035] 1. Case where a Polyacrylate is Used as Dispersant
[0036] In the case where the insoluble solid is used as seed
crystals and a polyacrylate is used as a dispersant (production
method illustrated in the production flowchart in FIG. 1), the
amount of the dispersant to be added is more than 1.0% by weight
and 10.0% by weight or less based on the weight of the insoluble
solid added to the slurry, and desirably 2.0% by weight or more and
6.0% by weight or less.
[0037] At an addition amount of 1.0% by weight or less, the nickel
powder does not precipitate. An amount of 2.0% by weight or more is
preferred because the insoluble solid can be sufficiently dispersed
to control the number of generated nickel powder proportionately
with the amount of the dispersant added.
[0038] In contrast, the seed crystals tend to be increased even if
the upper limit of the amount of the dispersant is beyond 6.0% by
weight. An excess large number of seed crystals generated causes
handling difficulties and aggregation between the dispersants.
Considering the effect commensurate with the amount of the
dispersant added, such an upper limit is not preferred.
Accordingly, the upper limit is 10.0% by weight or less, more
preferably 6.0% by weight or less.
[0039] 2. Case where a Lignosulfonate is Used as Dispersant
[0040] In the case where a lignosulfonate is used as a dispersant
(production method illustrated in the production flowchart in FIG.
1), the amount of the dispersant to be added is 2.0% by weight or
more and 20.0% by weight or less based on the weight of the
insoluble solid added to the slurry. An amount of 2.0% by weight or
less cannot yield nickel powder, so that the amount of the
dispersant is required to be more than 2.0% by weight. In
particular, an amount of more than 5.0% by weight is preferred
because the number of nickel powder generated can be controlled
proportionately with the amount of the dispersant added.
[Reduction and Precipitation Step]
[0041] Next, the nickel complex ion in the slurry is reduced with
hydrogen to form a composite including the insoluble solid and a
nickel precipitate on the surface thereof. This "reduction and
precipitation step" can be performed in a batch manner and a
continuous manner.
[0042] First, in the "reduction and precipitation step" where the
reduction and the precipitation are performed in batch, a slurry
formed of a dispersant and an insoluble solid added is charged into
a reaction vessel in a container resistant to high pressure and
high temperature. Hydrogen gas is blown into the slurry contained
in the reaction vessel of the container resistant to high pressure
and high temperature to reduce the nickel complex ion in the
slurry, thereby forming a reduced slurry containing a composite
including the insoluble solid contained in the slurry and nickel
generated as a precipitate on the surface thereof.
[0043] At this time, the reaction temperature is preferably in the
range of 150 to 200.degree. C. A reaction temperature of less than
150.degree. C. reduces the reduction efficiency. A reaction
temperature of higher than 200.degree. C. has no influences over
the reaction; rather, such a temperature is not suitable because it
increases loss of thermal energy.
[0044] Furthermore, the pressure during the reaction is preferably
1.0 to 4.0 MPa. A pressure of less than 1.0 MPa reduces the
reaction efficiency. A pressure of more than 4.0 MPa has no
influences over the reaction; rather, it increases loss of hydrogen
gas.
[0045] Next, the slurry formed of the dispersant and the insoluble
solid added is continuously fed into a reaction vessel of a
container resistant to high pressure and high temperature, and
hydrogen gas is continuously blown into the slurry flowing in the
reaction vessel to reduce nickel complex ion in the slurry.
Thereby, a reduced slurry containing a composite including the
insoluble solid and a nickel precipitate formed on the surface
thereof is obtained. After the reduction reaction to generate the
nickel precipitate, the resulting reduced slurry is continuously
extracted and recovered from the reaction vessel, and is fed to the
subsequent step.
[0046] In other words, by performing the reduction reaction by such
a continuous step, the time required to replace the slurry or set
the conditions for the reduction treatment can be reduced, and an
improvement in production efficiency can be expected. Control of
the flow rate of the slurry enables the adjustment of the amount of
production, resulting in a reduction in size of the reaction vessel
and economical advantages such as a reduction in capital investment
and repairs of facilities.
[0047] In such a reduction and precipitation step, the reaction
temperature is preferably in the range of 150 to 200.degree. C. A
reaction temperature of less than 150.degree. C. reduces the
reduction efficiency. A reaction temperature of higher than
200.degree. C. has no influences over the reaction; rather, it is
not suitable because it increases loss of the thermal energy.
[0048] Furthermore, a pressure of 1.0 to 4.0 MPa is preferably
applied to a gaseous phase portion in the reaction vessel during
the reaction. A pressure of less than 1.0 MPa reduces the reaction
efficiency. A pressure of more than 4.0 MPa has no influences over
the reaction; rather, it increases loss of hydrogen gas.
[0049] Because of the effect of the dispersant in the reduction and
precipitation treatment according to the present invention, the
insoluble solid can be sufficiently dispersed in the slurry. In
such a state, a nickel precipitate in the form of a finely powdery
precipitate can be formed on the surface of the insoluble solid.
Nickel can be extracted and recovered from the nickel ammine
sulfate complex solution. Furthermore, the amount of nickel powder
generated through precipitation can also be adjusted through the
adjustment of the amount of the dispersant to be added.
[Separation Step]
[0050] This step is performed when the insoluble solid is used. In
this case, the nickel precipitate generated in the reduction and
precipitation step adheres to the surface of the insoluble solid,
and cannot be used in such a state. For this reason, the nickel
precipitate formed on the surface of the insoluble solid is
separated from the insoluble solid, and is recovered.
[0051] Examples of specific separation methods include a method of
placing an insoluble solid and a nickel precipitate into water to
avoid oxidation due to heat generated, colliding the insoluble
solids each other under rotating to separate the nickel precipitate
from the surface of the insoluble solid, and sieving the nickel
precipitate to obtain nickel powder; a method of rotating a nickel
precipitate on a wet sieve, and simultaneously sieving the
separated nickel precipitate to obtain nickel powder; or a method
of separating a solution through ultrasonic vibration, and sieving
the resulting nickel precipitate to obtain nickel powder. Any sieve
having an opening smaller than the insoluble solid can be used in
the sieving step.
[0052] The nickel powder thus produced can be used in application
to nickel pastes as an inner constitutional substance of stacked
ceramic capacitors, for example. Besides, high purity nickel metal
can be produced through repetition of the reduction with hydrogen
using the recovered nickel powder as seed crystals to grow
particles.
EXAMPLES
[0053] Hereinafter, the present invention will be described by way
of Examples and Reference Examples.
Reference Example 1
[Mixing Step]
[0054] 336 g of nickel sulfate hexahydrate, which amount is
equivalent to 75 g of nickel content, 330 g of ammonium sulfate,
and 191 ml of 25% aqueous ammonia were added to prepare a nickel
ammine sulfate complex solution. According to the production flow
in FIG. 1, first, 75 g of nickel powder having an average particle
size (D50) of 85 .mu.m as an insoluble solid serving as a
precipitation matrix for seed crystals, and sodium polyacrylate
having a molecular weight of 4000 as a dispersant in an amount of
1.5 g was added, which was equivalent to 2% by weight of the weight
of the insoluble solid serving as seed crystals. Pure water was
added so that the volume of the solution was adjusted to 1000 ml.
Thereby, a slurry was formed.
[Reduction and Precipitation Step]
[0055] The resulting slurry was then placed into an internal
cylindrical can of an autoclave. The slurry was heated to
185.degree. C. with stirring. While the temperature was maintained,
hydrogen gas was blown and fed into the slurry from a hydrogen tank
so that the pressure in the autoclave became 3.5 MPa.
[0056] A sample of reduced slurry was extracted from the sample
outlet of the autoclave every two minutes after the start of feed
of hydrogen gas, and was subjected to solid liquid separation. The
concentration of nickel in the filtrate was analyzed.
[0057] As the reaction progresses, nickel is precipitated as
powder, and in turn, the concentration of nickel in the filtrate is
reduced by the amount of the nickel precipitate. As shown in FIG.
2, from the calculation of a change in the concentration of nickel,
80% or more of nickel could be reduced and recovered in 30
minutes.
[0058] After the lapse of 30 minutes from the start of feeding
hydrogen gas, the feed of hydrogen gas was stopped, and the
internal cylindrical can was cooled. After the cooling, the slurry
in the internal cylindrical can was filtered to recover 42.7 g of
precipitated nickel powder.
[0059] The recovered nickel powder was observed. It was confirmed
that fine nickel powder usable as seed crystals was generated.
Reference Example 2
[0060] Nickel powder was produced, and was recovered by the same
method and conditions as in Reference Example 1 except that 4.5 g
of sodium polyacrylate, which amount is equivalent to 6% by weight
of the weight of the seed crystals, was added.
[0061] The results are shown in FIG. 2. As shown in FIG. 2, 80% or
more of nickel could be reduced and recovered in 30 minutes as in
Reference Example 1.
Reference Example 3
[0062] Nickel powder was produced, and was recovered by the same
method and conditions as those in Reference Example 1 except that
7.5 g of sodium polyacrylate, which amount is equivalent to 10% by
weight of the weight of the seed crystals, was added.
[0063] The results are shown in FIG. 2. As shown in FIG. 2, 80% or
more of nickel could be reduced and recovered in 30 minutes as in
Reference Example 1.
Reference Example 4
[0064] Nickel powder was produced, and was recovered by the same
method and conditions as in Reference Example 1 except that 0.75 g
of sodium polyacrylate, which amount is equivalent to 1% by weight
of the weight of the seed crystals, was added.
[0065] The results are shown in FIG. 2. As shown in FIG. 2, from
the calculation of a change in the concentration of nickel, about
50% of nickel could be reduced and recovered in 30 minutes.
Reference Comparative Example 1
[0066] Nickel powder was prepared with the same solution
composition and reduction conditions as in Reference Example 1
except that the dispersant and the insoluble solid were not
added.
[0067] The concentration of nickel in the sampled solution was
reduced from 75 g/L to about 45 g/L. Any nickel powder could not be
recovered from the solution after the blowing of hydrogen gas was
completed. It was confirmed that scaling of plate-like nickel was
generated at the side walls inside the internal cylindrical can and
the stirrer.
Reference Comparative Example 2
[0068] Nickel powder was produced by the same method as in
Reference Example 1 except that the dispersant was not added and 75
g of nickel powder as an insoluble solid was added.
[0069] The results are shown in FIG. 3. As shown in FIG. 3, from
the calculation of a change in the concentration of nickel, only
about 20% of nickel could be recovered in 30 minutes.
Reference Example 5
[0070] 191 ml of 25% aqueous ammonia was added to a solution
containing 336 g of nickel sulfate hexahydrate, which amount is
equivalent to 75 g of nickel, and 330 g of ammonium sulfate to
prepare a nickel ammine sulfate complex solution. Furthermore,
according to the production flow illustrated in FIG. 1, a solution
of sodium polyacrylate having a molecular weight of 4000 and a
concentration of 40% was added in an amount of 0.38 g, 1.88 g, 3.75
g, 7.5 g, and 11.3 g to the resulting nickel ammine sulfate complex
solution, respectively, and the total volume of the solutions was
adjusted to 1000 ml. Thereby, five solutions were prepared.
[0071] 75 g of nickel powder having an average particle size (D50)
of 85 .mu.m as an insoluble solid serving as the precipitation
matrix was added to each of the resulting solutions to prepare a
desired slurry. The net amounts of the sodium polyacrylate added
here were equivalent to 0.2% by weight, 1.0% by weight, 2.0% by
weight, 4.0% by weight, and 6.0% by weight, respectively, based on
the amount of the insoluble solid.
[0072] The resulting mixture slurries were placed into an internal
cylindrical can of an autoclave. Each slurry was heated to and held
at 185.degree. C. with stirring. In this state, hydrogen gas was
blown and fed into the slurry so that the pressure in the autoclave
became 3.5 MPa. After the lapse of 60 minutes from the start of
feeding hydrogen gas, the feed of hydrogen gas was stopped, and the
internal cylindrical can was cooled.
[Separation Step]
[0073] After the cooling, the slurry in the internal cylindrical
can was filtered to recover a composite of the insoluble solid and
a nickel precipitate. The insoluble solid as the matrix and the
nickel precipitate on the surface of the insoluble solid were
separated under vibration using a wet sieve having an opening of 75
.mu.m to recover nickel powder.
[0074] The particle size of the recovered nickel powder under the
sieve was measured with a particle size distribution analyzer (made
by Microtrac, Inc., trade name 9320-X100 type) to determine the
particle size distribution.
[0075] Assuming that the recovered nickel powder was a true sphere,
using the determined average particle size: D and the nickel
density: p=8.9 g/cm.sup.3, the number of recovered nickel powder
was calculated from Expression (1):
[Expression 1]
The Number of nickel powder=(Mass of recovered nickel
powder)/[8.9.times.4.pi..times.(D/2).sup.3/3] (1)
[0076] The relation between the number of nickel powder calculated
from Expression (1) and the amount of sodium polyacrylate added is
shown in FIG. 4.
[0077] From FIG. 4, it is found that there is a correlation between
the amount of sodium polyacrylate added and the number of nickel
powder, and that the amount of nickel powder generated can be
adjusted by the amount of sodium polyacrylate added. In particular,
it is found that an amount of added sodium polyacrylate of 1.0% by
weight or less cannot yield nickel powder, and an amount of more
than 1.0% by weight can control the number of generated nickel
powder proportionately with the amount of sodium polyacrylate
added.
Reference Example 6
[0078] Nickel powder was produced by the same method as in
Reference Example 1 except that sodium lignosulfonate was used as a
dispersant in amounts of 1.5 g, 3.0 g, 4.5 g, 7.5 g, 11.3 g, and
15.0 g, respectively. The amounts of insoluble solid of sodium
lignosulfonate added are equivalent to 2.0% by weight, 4.0% by
weight, 6.0% by weight, 10.0% by weight, 15.0% by weight, and 20.0%
by weight, respectively.
[0079] For the resulting nickel powder, the number of nickel powder
was calculated as in Reference Example 5 through calculation using
Expression (1).
[0080] The relation between the number of nickel powder calculated
from Expression (1) and the amount of sodium lignosulfonate added
is shown in FIG. 5.
Example 7
[0081] Water and 3 g/l of sodium polyacrylate as a dispersant,
which amount is equivalent to 2% by weight of the weight of an
insoluble solid, were added to a nickel ammine sulfate complex
solution containing 83 g/L of nickel ions, 120 g/L of ammonium
sulfate, and 182 g/L of 25% aqueous ammonia and nickel powder
having an average particle size (D50) of 90 .mu.m as the insoluble
solid to prepare a seed crystal slurry containing nickel powder
having a concentration of 165 g/L.
[0082] The nickel ammine sulfate complex solution and the seed
crystal slurry prepared above were then continuously fed to an
autoclave using a pump. While the autoclave was held at 185.degree.
C. with stirring, hydrogen gas was blown and fed into the slurry
from a hydrogen tank so that the pressure in the cylindrical can of
the autoclave became 3.5 MPa. At this time, after hydrogen gas was
blown into the slurry, the slurry in the autoclave was stagnated
for one hour. To keep a constant amount of the solution in the
autoclave, the feed and discharge amounts of the nickel ammine
sulfate complex solution and the seed crystal slurry were adjusted,
and the slurry after the reaction was continuously extracted and
recovered from the autoclave.
[0083] The number of nickel powder was calculated through the
calculation using Expression (1) from the weight of the obtained
nickel powder.
[0084] As a result, Table 1 shows that the number of particles
increased, and the particle size distribution in FIG. 6 shows that
fine nickel powder was produced.
TABLE-US-00001 TABLE 1 Seed Produced nickel crystals*.sup.1 powder
The number of nickel powder 410 18000 [.times.10.sup.6 particles/L]
*.sup.190 .mu.m nickel powder
* * * * *