Note: Descriptions are shown in the official language in which they were submitted.
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DESCRIPTION
HYDROMETALLURGICAL PLANT FOR NICKEL OXIDE ORE AND
METHOD FOR OPERATING THE HYDROMETALLURGICAL PLANT
Field of the Invention
[0001]
The present invention relates to a hydrometallurgical plant for nickel oxide
ores to recover nickel and cobalt from nickel oxide ores, and a method for
operating
the hydrometallurgical plant. The present application claims priority based on
Japanese Patent Application No.2013-046986 filed in Japan on March 8, 2013.
The total contents of the Patent Application are to be incorporated by
reference into
the present application.
Background Art
[0002]
In recent years, as a hydrometallurgical process for nickel oxide ores, high
pressure acid leach using sulfuric acid has been attracting attention. Unlike
pyrometallurgy, which is a conventional common refining process for nickel
oxide
ores, the high pressure acid leach does not include pyrometallurgical steps,
such as
reduction and drying, but includes consistent hydrometallurgical steps, and
therefore, is advantageous in terms of energy and cost. Furthermore, the high
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pressure acid leach has an advantage that a sulfide which contains nickel and
cobalt
and whose nickel grade is improved up to approximately 50% by mass
(hereinafter,
referred to as a "nickel-cobalt mixed sulfide" or a "Ni-Co mixed sulfide") can
be
obtained.
[0003]
The hydrometallurgical process for nickel oxide ores which makes use of the
high pressure acid leach includes steps, for example, illustrated in a
schematic
flowchart in Fig. 7. That is, the hydrometallurgical process includes: an ore
processing step in which a nickel oxide ore is ground to a predetermined size
and
made into slurry; a (high pressure acid) leaching step in which sulfuric acid
is added
to ore slurry and made to undergo a leaching treatment under high temperature
and
high pressure; a preliminary neutralization step in which a neutralization
(hereinafter, referred to as "preliminary neutralization") treatment is
applied to
leach slurry before the slurry undergoes multistage washing; a solid-liquid
separation step (hereinafter, also referred to as a "CCD step") in which the
leach
slurry obtained by the application of the preliminary neutralization treatment
is
made to undergo multistage washing to be solid-liquid separated into a leach
residue and a leachate containing an impurity element together with nickel and
cobalt; a neutralization step in which the pH of the obtained leachate is
adjusted so
that a neutralization precipitate containing the impurity element is separated
from
the leachate, whereby a post-neutralization solution containing zinc together
with
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nickel and cobalt is obtained; a dezincification step in which a sulfurizing
agent is
added to the post-neutralization solution to form a zinc sulfide and the zinc
sulfide
is separated therefrom, whereby a mother liquor for nickel recovery is
obtained; a
nickel recovery step in which a sulfurizing agent is added to the mother
liquor for
nickel recovery, whereby a mixed sulfide containing nickel and cobalt is
formed;
and a final neutralization step in which waste liquids (barren liquor) in the
nickel
recovery step and the residue in the CCD step are mixed and made to undergo a
neutralization treatment (refer to Patent documents 1 and 2).
[0004]
In the foregoing preliminary neutralization step in the hydrometallurgy, the
pH of the leach slurry obtained in the leaching step is adjusted so as to make
it
possible to efficiently perform multistage washing in the next step, namely
the CCD
step. Specifically, the leach slurry is fed into a neutralization tank, and a
neutralizer such as calcium carbonate is added thereto to adjust the pH of the
leach
slurry.
[0005]
Next, in the CCD step, the leach slurry obtained after the preliminary
neutralization is made to undergo multistage washing, thereby being separated
into
a leach residue and a leachate containing an impurity element together with
nickel
and cobalt. The separated leachate is sent to the neutralization step to be
made
into a post-neutralization solution, on the other hand, the leach residue is
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transported to the final neutralization step to be treated.
[0006]
In the dezincification step, the post-neutralization solution is fed into a
sulfurization reaction tank, and a sulfurizing agent, such as hydrogen sulfide
gas or
sodium hydrosulfide, is added thereto to make zinc, copper, and the like
contained
in the post-neutralization solution into respective sulfides. After the
sulfurization
treatment, solid-liquid separation is performed using a filter press or the
like to
obtain a mother liquor for nickel recovery from which zinc sulfide has been
removed.
[0007]
In the designing of a hydrometallurgical plant for nickel oxide ores, in the
case where the ore throughput (or the planned production amount) of the plant
is
high, for example, it can be mentioned that the plant is designed based on the
following two schemes. The schemes each are that: [i] a large-scale line is
provided (for example, as illustrated in Fig. 8, a line with a production
amount of
30,000 tons/year is provided); and [ii] two small-scale lines are provided
(for
example, as illustrated in Fig. 9, two lines each having a production amount
of
15,000 tons/year are provided).
[0008]
However, in the case of [i], particularly, in the designing of a leaching
treatment facility to perform the leaching step, it is not enough to merely
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industrially make the size of the facility larger. That is, it is necessary to
sufficiently consider a reactivity viewpoint that, in the leaching treatment
facility, a
predetermined leaching reaction needs to be efficiently and effectively caused
to
leach a valuable metal at a high leaching rate. In addition, in the case of
making a
facility size larger as mentioned above, there is an economic problem of an
increase
in repair cost as needed. Therefore, the scheme of merely industrially making
a
facility size larger is practically very difficult, and hence, it is
preferable to employ
a conventional facility on a scale of 10,000 tons/year to 15,000 tons/year (of
leach
slurry production amount in terms of the amount of nickel).
[0009]
Also in the case of [ii], the arrangement of a plurality of lines naturally
causes an increase in the number of facilities, whereby the cost of capital
investment is greatly increased. In addition, to perform an efficient refining
operation, connecting piping to mutually transport a process liquid between
the
lines is also needed (for example, refer to Patent document 3), thereby
causing a
further increase in cost.
[0010]
Hence, as a compromise between the foregoing schemes [i] and [ii], for
example, to design a plant based on the following scheme is easily come up
with.
That is:
[iii] Upstream steps are made up of two lines (a plurality of lines), and
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subsequent downstream steps are made up of one line (for example, as
illustrated in
Fig. 10, upstream steps, namely the preliminary neutralization step and
upstream
steps therefrom, are made up of two lines (a plurality of lines), and
downstream
steps, namely the CCD step and downstream steps therefrom, are made up of one
line, and consequently, a production amount of 30,000 tons/year is achieved).
[0011]
However, it has not been known at which point in a hydrometallurgical
process for nickel oxide ores steps are operationally preferably separated
into the
upstream steps and the downstream steps, and furthermore, a problem which is
caused by merging of lines at a downstream step and affects an efficient
operation
has not been known.
[0012]
As mentioned above, in the case where a design is made so as to separate
steps into upstream steps made up of a plurality of lines and downstream steps
made up of a single line, there is a possibility that property variations
between
process liquids (for example, leach slunies) transported from the respective
lines of
the upstream steps might be caused, whereby the process liquids which are not
uniform are transported to the downstream steps made up of a single line. In
such
case, reaction conditions in treatment facilities in the downstream steps are
not
uniform, whereby, not only efficient operations cannot be performed, but also
there
is a possibility that a poor reaction and the like might be caused to have an
impact
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on product quality.
[0013]
Furthermore, there is a problem that, in one of a plurality of lines in the
upstream steps, for example, in the case of the occurrence of a trouble such
as poor
leaching in the leaching step, or in the case of a startup operation after
operational
shutdown, even if no failure occurs in other lines, the whole of a plant has
to be
shut down because the lines are merged in the downstream step, whereby
operation
efficiency is considerably decreased.
[0014]
For example, Patent document 3 discloses a technique being such that, in a
plant having a plurality of identical process lines, treatment facilities in a
predetermined step are connected to each other by piping, whereby, even in the
case
where a trouble or the like occurs in a facility in a predetermined step on a
series of
steps, a decrease in operation efficiency is kept to a minimum, and thus, this
technique is operationally very effective. However, for the foregoing reason,
in
the case of a plant in which upstream steps are operated with two lines and
the lines
are merged into one line in a downstream step, the technique disclosed in
Patent
document 3 cannot be applied as it is.
Prior-Art Documents
Patent Documents
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[0015]
Patent document 1: Japanese Patent Application Laid-Open No. H06-116660
Patent document 2: Japanese Patent Application Laid-Open No.
2005-350766
Patent document 3: Japanese Patent Application Laid-Open No.
2011-225908
Summary of the Invention
Problems to be Solved by the Invention
[0016]
The present invention is proposed in view of such actual circumstances, and
an object of the present invention is to provide a hydrometallurgical plant
for nickel
oxide ores which is capable of increasing ore throughput thereby to improve
productivity without causing a poor reaction and a decrease in operation
efficiency,
and to provide a method for operating the hydrometallurgical plant.
Means to Solve the Problems
[0017]
The present inventors earnestly studied in order to achieve the foregoing
object. As a result, the inventors found that the foregoing problems can be
solved
in such a manner that, in a preliminary neutralization facility to apply a
preliminary
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neutralization treatment to leach slurry obtained after a leaching treatment,
neutralization treatment tanks are provided in two stages, and, neutralization
treatment tanks of a first of the two stages are provided in a plurality of
lines, and a
neutralization treatment tank of a second of the two stages is provided in a
single
line.
[0018]
That is, a hydrometallurgical plant for nickel oxide ores according to the
present invention is characterized by including at least: a leaching facility
provided
with leaching treatment tanks in a plurality of lines to apply a leaching
treatment to
a nickel oxide ore; a preliminary neutralization facility provided with
neutralization
treatment tanks in two stages to perform preliminary neutralization by which
pH of
leach slurry discharged from the leaching treatment tanks is adjusted to a
predetermined range; and a solid-liquid separation facility made up of a
single line
to perform solid-liquid separation of leach slurry pH-adjusted and discharged
from
the preliminary neutralization facility into a leachate and a leach residue in
a
solid-liquid separation tank, in which the preliminary neutralization facility
is
configured such that neutralization treatment tanks of a first of the two
stages are
provided in a plurality of lines so as to correspond to the respective lines
of the
leaching treatment tanks provided in the leaching facility, and leach slurries
which
are pH-adjusted in the neutralization treatment tanks constituting the first
stage in
the respective lines are merged in a neutralization treatment tank of a second
stage
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made up of a single line, and leach slurry merged in the neutralization
treatment
tank of the second stage is transported to the solid-liquid separation
facility.
[0019]
A method for operating a hydrometallurgical plant for nickel oxide ores
according to the present invention is a method for operating a
hydrometallurgical
plant to recover nickel and cobalt from a nickel oxide ore, in which the
hydrometallurgical plant for nickel oxide ores includes at least: a leaching
facility
provided with leaching treatment tanks in a plurality of lines to apply a
leaching
treatment to a nickel oxide ore; a preliminary neutralization facility
provided with
neutralization treatment tanks in two stages to perform preliminary
neutralization
by which pH of leach slurry discharged from the leaching treatment tanks is
adjusted to a predetermined range; and a solid-liquid separation facility made
up of
a single line to perform solid-liquid separation of leach slurry into a
leachate and a
leach residue in a solid-liquid separation tank, the leach slurry being pH-
adjusted
and discharged from the preliminary neutralization facility, in which, in the
preliminary neutralization facility, neutralization treatment tanks of a first
of the
two stages are provided in a plurality of lines so as to correspond to the
respective
lines of the leaching treatment tanks provided in the leaching facility, and a
neutralization treatment tank of a second of the two stages is made up of a
single
line, and leach slurries discharged from the respective neutralization
treatment tanks
of the first stage are merged in the neutralization treatment tank of the
second stage
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made up of a single line, and merged leach slurry is transported to the solid-
liquid
separation facility.
Effects of the Invention
[0020]
In the hydrometallurgical plant for nickel oxide ores according to the present
invention, a preliminary neutralization facility to apply a preliminary
neutralization
treatment to leach slurry is made up of neutralization treatment tanks in two
stages,
and neutralization treatment tanks of a first of the two stages are provided
in a
plurality of lines so as to correspond to respective leaching treatment tanks
provided
in a plurality of lines, and a neutralization treatment tank of a second of
the two
stages is provided in a single line. This enables ore throughput to be
increased
while facility costs are held down, and also enables variations in leach
slurry,
serving as a process liquid, to be eliminated, and a poor reaction and a
decrease in
operation efficiency to be effectively prevented.
[0021]
Furthermore, in the hydrometallurgical plant according to the present
invention, neutralization treatment tanks are provided in two stages as
mentioned
above, and therefore, the appropriate provision of piping to connect the
neutralization treatment tanks of the first stage to reaction tanks of
treatment
facilities in other steps enables, for example, an efficient startup operation
to be
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performed even at the lime of unusual operation such as plant startup, without
adversely affecting other lines in which a normal operation can be performed
and
furthermore with preventing a decrease in operation efficiency.
Brief Description of the Drawings
[0022]
Fig. 1 illustrates a configuration of a hydrometallurgical plant for nickel
oxide ores.
Fig. 2 is a flowchart of a hydrometallurgical process for nickel oxide ores by
high pressure acid leach.
Fig. 3 illustrates an operation flow of a normal operation.
Fig. 4 illustrates an operation flow of self-circulating transport from the
neutralization treatment tanks of the first stage to respective leaching
treatment
tanks.
Fig. 5 illustrates an operation flow to transport leach slurry from
neutralization treatment tanks of the first stage to the final neutralization
facility.
Fig. 6 illustrates an operation flow to transport leach slurry from
neutralization treatment tanks of the first stage to solid-liquid separation
tanks.
Fig. 7 is a schematic flowchart of a hydrometallurgical process by high
pressure acid leaching of nickel oxide ores.
Fig. 8 is a schematic flowchart of a hydrometallurgical process by high
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pressure acid-leaching of nickel oxide ores.
Fig. 9 is a schematic flowchart of a hydrometallurgical process by high
pressure acid leaching of nickel oxide ores.
Fig. 10 is a schematic flowchart of a hydrometallurgical process by high
pressure acid leaching of nickel oxide ores.
Detailed Description of the Invention
[0023]
Hereinafter, with reference to the drawings, a hydrometallurgical plant for
nickel oxide ores and a method for operating the hydrometallurgical plant
according
to the present invention will be described in detail in the following order.
It
should be noted that the present invention is not limited to the following
embodiment, and various changes can be made within the scope not deviating
from
the gist of the present invention.
1. Outline of hydrometallurgical plant for nickel oxide ores
2. Hydrometallurgy for nickel oxide ores
3. Configuration of hydrometallurgical plant and method for operating
hydrometallurgical plant
3-1. Basic configuration and operation flow of normal operation
3-2. Configuration for self-circulation and operation flow of
self-circulation
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3-3. Configuration for transport to final neutralization facility, and
operation flow of transport to final neutralization facility
3-4. Configuration for transport to solid-liquid separation tank, and
operation flow of transport to solid-liquid separation tank
3-5. Shift from unusual operation to normal operation
3-6. Conclusion
4. Examples
[0024]
<<1. Outline of hydrometallurgical plant for nickel oxide ores>>
The hydrometallurgical plant for nickel oxide ores according to the present
embodiment (hereinafter, also simply referred to as "hydrometallurgical
plant") is a
plant to perform a hydrometallurgical operation for nickel oxide ores, the
operation
including, for example, a leaching step by high pressure acid leach, a
preliminary
neutralization step, a solid-liquid separation step (CCD step), a
neutralization step, a
dezincification step, a sulfurization step, and a final neutralization step
(detoxification step).
[0025]
Specifically, as illustrated in the configuration of a hydrometallurgical
plant
in Fig. 1, a hydrometallurgical plant 10 according to the present invention
includes
at least: a leaching facility 11 provided with leaching treatment tanks to n)
in a
plurality (n) of lines to apply a leaching treatment to a nickel oxide ore; a
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preliminary neutralization facility 12 provided with neutralization treatment
tanks in
two stages to perform preliminary neutralization by which the pH of leach
slurries
discharged from the leaching treatment tanks 11(1to it) are adjusted to a
predetermined range; and a solid-liquid separation facility 13 made up of a
single
line to perform the solid-liquid separation of leach slurry which is pH-
adjusted and
discharged from the preliminary neutralization facility 12 in solid-liquid
separation
tanks.
[0026]
Furthermore, in the hydrometallurgical plant 10, the foregoing preliminary
neutralization facility 12 is configured such that neutralization treatment
tanks
12A(ito r) of a first of the two stages is provided in a plurality (n) of
lines so as to
correspond to the respective lines of the leaching treatment tanks 11(1 to n)
provided
in the leaching facility, and leach slurries which are pH-adjusted in the
neutralization treatment tanks 12A(i ton) of the first stage in the respective
lines are
merged in a neutralization treatment tank 12B of a second of the two stages
which
is made up of a single line. Then, leach slurry merged in the neutralization
treatment tank 12B of the second stage is transported to the solid-liquid
separation
facility 13.
[0027]
It should be noted that Fig. 1 illustrates a specific example of a plant
configuration in which the leaching treatment tanks 11(1 ton) and the
neutralization
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treatment tanks 12A(l
to o) of the first stage are provided in two lines (n = 2), but the
number of the lines are not limited to two.
[0028]
As mentioned above, the hydrometallurgical plant 10 is configured such that,
in the preliminary neutralization step and steps upstream therefrom
(hereinafter,
also referred to as "upstream steps"), a series of treatment facilities is
provided with
reaction tanks in two or more lines, and, in steps downstream from the
preliminary
neutralization step (hereinafter, also referred to as "downstream steps"), a
series of
treatment facilities is provided with reaction tanks in a single line (one
line). Such
configuration enables an increase in nickel oxide ore throughput, thereby
enabling
the production amount of a nickel-cobalt mixed sulfide (a product) to be
stably
increased, while reducing the number of parts and reducing facility costs, by
using a
leaching treatment facility of a size which has a track record of being
operated.
[0029]
Furthermore, according to the hydrometallurgical plant 10, leach slurries
obtained from the treatment facilities in a plurality of lines are merged in
the
neutralization treatment tank 12B of the second stage, and therefore, even if
variations in the pH and the like of the leach slurries arise, the variations
can be
eliminated, and thus a solid-liquid separation treatment can be applied to
uniform
leach slurry in the solid-liquid separation facility 13.
[0030]
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Furthermore, according to the hydrometallurgical plant 10, piping to connect
the neutralization treatment tanks 12A(i to to of the first stage to reaction
tanks of
treatment facilities in other steps is appropriately provided, whereby, for
example,
leach slurry in a state where a leaching treatment performed immediately after
a
plant operation startup or the like does not sufficiently proceed yet can be
prevented
from being transported to the solid-liquid separation step and steps
downstream
therefrom. This enables effective prevention of a poor reaction and a decrease
in
operation efficiency in the each step.
[0031]
Hereinafter, more specifically, the hydrometallurgical plant for nickel oxide
ores and the method for operating the hydrometallurgical plant according to
the
present embodiment will be described.
[0032]
<<2. Hydrometallurgy for nickel oxide ores>>
First, a hydrometallurgical process for nickel oxide ores which is performed
by the hydrometallurgical plant 10 according to the present embodiment will be
described. This hydrometallurgical process for nickel oxide ores is a
hydrometallurgical process by which nickel and cobalt are leached out and
recovered from a nickel oxide ore by using, for example, high pressure acid
leach
(HPAL).
[0033]
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Fig. 2 illustrates an example of a flowchart (a process chart) of a
hydrometallurgical process for nickel oxide ores by using high pressure acid
leach.
As illustrated in Fig. 2, the hydrometallurgical process for nickel oxide ores
includes: a leaching step Si in which sulfuric acid is added to slurry of
nickel oxide
ore and a leaching treatment is applied to the slurry under high temperature
and
high pressure; a preliminary neutralization step S2 in which preliminary
neutralization is performed to adjust the pH of obtained leach slurry to a
predetermined range; a solid-liquid separation step S3 in which multistage
washing
is applied to pH-adjusted leach slurry to separate a residue therefrom,
whereby a
leachate containing an impurity element together with nickel and cobalt is
obtained;
a neutralization step S4 in which the pH of the leachate is adjusted to
separate a
neutralization precipitate containing the impurity element therefrom, whereby
a
post-neutralization solution containing zinc together with nickel and cobalt
is
obtained; a dezincification step 5 in which a sulfurizing agent is added to
the
post-neutralization solution to form a zinc sulfide, and the zinc sulfide is
separated
and removed therefrom to obtain a mother liquor for nickel recovery which
contains
nickel and cobalt; and a nickel recovery step S6 in which a sulfurizing agent
is
added to the mother liquor for nickel recovery to form a mixed sulfide
containing
nickel and cobalt. This hydrometallurgical process further includes a final
neutralization step 7 in which a leach residue separated in the solid-liquid
separation step S3 and a barren liquor discharged in the nickel recovery step
S6 are
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recovered and rendered harmless.
[0034]
(1) Leaching step
(1-1) Leaching treatment
In the leaching step Si, a leaching treatment using, for example, high
pressure acid leach is applied to a nickel oxide ore. Specifically, sulfuric
acid is
added to ore slurry obtained by grinding a nickel oxide ore serving as a raw
material, and the ore slurry is pressurized under a high temperature of 220 C
to 280
C to be agitated, whereby leach slurry including a leachate and a leach
residue is
formed.
[0035]
As the nickel oxide ore used in the leaching step Si, what is called laterite
ore, such as limonite ore or saprolite ore, is mainly used. The nickel content
of a
laterite ore is usually 0.8% to 2.5% by weight, and the nickel is contained in
the
form of hydroxide or magnesium silicate mineral. Furthermore, the iron content
of the laterite ore is 10% to 50% by weight, and the iron is contained mainly
in the
form of trivalent hydroxide (goethite), but, a magnesium silicate mineral
contains
some divalent iron. Furthermore, in the leaching step Si, besides such
laterite ore,
an oxide ore containing valuable metals, such as nickel, cobalt, manganese,
and
copper, for example, a manganese lump present in a deep seabed is used.
[0036]
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In the leaching treatment in this leaching step Si, leaching reactions
expressed by the following formulas (1) to (3) and high temperature hydrolysis
reactions expressed by the following formulas (4) and (5) occur, whereby
nickel,
cobalt, and the like are leached out in the form of sulfate and a leached-out
iron
sulfate is fixed as hematite. It should be noted that, since the fixation of
iron ions
does not completely proceed, besides nickel, cobalt, and the like, divalent
and
trivalent iron ions are usually contained in a liquid portion of obtained
leach slurry.
[0037]
Leaching reaction
MO + H2SO4 ¨4 MS04 + H20 ... (1)
(where M in the formula represents Ni, Co, Fe, Zn, Cu, Mg, Cr, Mn, or the
like.)
2Fe(OH)3 + 3H2SO4 Fe2(SO4)3 + 61120 ... (2)
FeO +112504 --+ FeSO4 + H20 (3)
= High temperature hydrolysis reaction
2FeSO4 + H2SO4 + 1/202 ¨4 Fe2(SO4)3 + 1120 ... (4)
Fe2(SO4)3 + 3H20 Fe203 + 3H2SO4 (5)
[0038]
The amount of sulfuric acid added in the leaching step Si is not particularly
limited, but sulfuric acid is added in an excessive amount so as to leach out
iron
contained in the ore. For example, 300 to 400 kg of sulfuric acid is added per
ton
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of ore. When the amount of sulfuric acid added per ton of ore is more than 400
kg,
sulfuric acid cost becomes higher, which is not preferable. It should be noted
that,
from a viewpoint of filterability of a hematite-containing leach residue to be
formed
in a subsequent step, namely the solid-liquid separation step S3, an
adjustment is
preferably performed in the leaching step S1 so that an obtained leachate has
a pH
of 0.1 to 1Ø
[0039]
(1-2) Leaching facility
In the hydrometallurgical plant 10 according to the present embodiment, the
leaching treatment in the foregoing leaching step S1 is performed in the
leaching
facility (high pressure acid leaching facility) 11.
[0040]
Specifically, as illustrated in Fig. 1, the leaching facility 11 in this
hydrometallurgical plant 10 is provided with the leaching treatment tanks 11(1
ton) in
a plurality (n) of lines (for example, n = 2 lines as illustrated in Fig. 1)
to apply the
leaching treatment to a nickel oxide ore. It should be noted that,
hereinafter, the
leaching treatment tank will be expressed as the "leaching treatment tank
11(0",
unless the number of lines is not specified. Furthermore, likewise, the
later-mentioned neutralization treatment tanks 12A(i ton) of the first stage
will be
expressed as the "neutralization treatment tanks 12A(n)".
[0041]
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As the leaching treatment tanks 11(n) in the lines constituting the leaching
facility 11, for example, a high temperature pressurizing vessel (autoclave)
is
employed. Into the leaching treatment tanks 11(n), for example, ore slurry
transported from an ore processing step, that is, a predetermined amount of
ore
slurry obtained by grinding an ore to a predetermined particle diameter is fed
from
inlet portions of the leaching treatment tanks 11(n).
[0042]
The size of the leaching treatment tanks 11(n) each made up of an autoclave
and the like is not particularly limited, but there may be employed a leaching
treatment tank having a size equivalent to that of a leaching treatment tank
which
has been conventionally employed for operations. For example, there may be
employed a leaching treatment tank on a scale of 10,000 tons/year to 20,000
tons/year of leach slurry production amount in terms of the amount of nickel.
As
mentioned above, the use of a leaching facility provided with conventional
leaching
treatment tanks in a plurality of lines enables an increase in nickel oxide
ore
throughput, thereby enabling the production amount of a nickel-cobalt mixed
sulfide obtained through downstream steps to be increased.
[0043]
Here, although details will be mentioned later, piping 21(n) to connect the
leaching treatment tank 11(n) to the neutralization treatment tank 12A(n) of
the first
stage, the tank 12A(n) being a constituent of the preliminary neutralization
facility
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12, may be connected to an inlet portion of the leaching treatment tank 11(0.
This
piping 21(n) is piping to connect the leaching treatment tank 11(n) and the
neutralization treatment tank 12A.(0 of the first stage which are in the same
line.
This piping 21(0 is what is called piping for self-circulation which makes it
possible
that circulating (self-circulating) transport of leach slurry discharged from
the
neutralization treatment tank 12A(n) of the first stage to the leaching
treatment tank
11(n) in the same line is performed by a transport pump 31. It should be noted
that
an operation for the self-circulation will be described later in detail.
[0044]
(2) Preliminary neutralization step
(2-1) Preliminary neutralization treatment
In the preliminary neutralization step S2, the pH of leach slurry obtained in
the leaching step Si is adjusted to a predetermined range. In the leaching
step Si
of performing the foregoing leaching treatment by high pressure acid leach, an
excessive amount of sulfuric acid is added from a viewpoint of improving a
leaching rate. Therefore, obtained leach slurry contains free sulfuric acid
(surplus
sulfuric acid not having involved in a leaching reaction), and has a very low
pH.
Hence, in the preliminary neutralization step S2, the pH of leach slurry is
adjusted
to a predetermined range so that, at the time of multistage washing in the
subsequent step, namely the solid-liquid separation step S3, washing is
efficiently
performed.
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[0045]
Specifically, leach slurry to be subjected to washing treatment preferably has
an adjusted pH of 2 to 6. When the leach slurry has a pH lower than 2, the
cost of
making facilities in downstream steps acid-resistant is needed. On the other
hand,
when the leach slurry has a pH higher than 6, there is a possibility that
nickel which
is leached out into a leachate (slurry) remains as a residue (precipitated) in
the
process of washing, whereby washing efficiency is reduced. It should be noted
that, in practical operations, an appropriate pH value may be selected within
the
foregoing pH range, based on the operational status of the leaching treatment
in the
leaching step S1 and the conditions of the pH of washing water to be used in
the
solid-liquid separation step S3 (in the case of acid rain, the pH is
approximately 5)
and the like.
[0046]
A method for adjusting pH is not particularly limited, but, for example, the
addition of a neutralizer such as calcium carbonate slurry enables pH to be
adjusted
to a predetermine range.
[0047]
(2-2) Preliminary neutralization facility
In the hydrometallurgical plant 10 according to the present embodiment, the
foregoing preliminary neutralization treatment in the preliminary
neutralization step
S2 is performed in the preliminary neutralization facility 12.
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[0048]
Specifically, as illustrated in Fig. 1, the preliminary neutralization
facility 12
in this hydrometallurgical plant 10 is provided with neutralization treatment
tanks
12A and 12B in two stages. Furthermore, of the neutralization treatment tanks
12A and 12B in two stages, the neutralization treatment tanks 12A(n) of a
first of the
two stages are provided in a plurality (n) of lines so as to correspond to the
respective lines of the leaching treatment tanks 11(n) provided in the
foregoing
leaching facility 11. On the other hand, the neutralization treatment tank 12B
of a
second of the two stages is provided in a single line, and it is configured
such that
leach slurries discharged from the neutralization treatment tanks 12A(n) of
the first
stage are merged in the neutralization treatment tank 12B of the second stage.
[0049]
For example, in the case where the leaching facility 11 is provided with
leaching treatment tanks (a leaching treatment tank 11(1), a leaching
treatment tank
11(2)) in two lines, a neutralization treatment tank 12A(1) and a
neutralization
treatment tank 12A(2) are provided as the neutralization treatment tanks 12A
of the
first stage so as to correspond to leaching treatment tanks 11(1) and 11(2),
respectively. Furthermore, the neutralization treatment tank 12B of the second
stage is made up of a treatment tank in a single line, and leach slurries
discharged
from the neutralization treatment tank 12A(j) and the neutralization treatment
tank
12A(2) of the first stage are merged in the neutralization treatment tank 12B
of the
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second stage.
[0050]
Here, in a normal operation, there easily arise variations in, for example,
the
pH of post-preliminary-neutralization slurries obtained by the preliminary
neutralization of leach slurries by using neutralization treatment tanks in a
plurality
of lines, and thus, the leach slurries obtained from the neutralization
treatment tanks
in the respective lines are not uniform. In the case where treatments in steps
downstream from the preliminary neutralization step are performed using such
leach slurries whose properties are not uniform between the lines, variations
in
reaction and the like arise, whereby an efficient operation cannot be
performed.
[0051]
Therefore, as mentioned above, in the present embodiment, the preliminary
neutralization facility 12 is provided with the neutralization treatment tanks
12A
and 12B in two stages, and steps are divided into upstream step and downstream
steps at a boundary between a first and a second of the two stages, and a
plurality of
lines are provided up to the neutralization treatment tanks 12A(,) of the
first stage,
and the lines are merged in the neutralization treatment tank 12B of the
second
stage. In such configuration, leach slurries are merged in the neutralization
treatment tank 12B of the second stage, and thus variations between slurries
can be
eliminated, whereby uniform leach slurry can be transported to the subsequent
step,
namely the solid-liquid separation step S3. Furthermore, this neutralization
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treatment tank 12B of the second stage can be made to work as a residence tank
(buffer), and therefore, the flow rate of leach slurry can be appropriately
adjusted
and stably transported to the solid-liquid separation step S3.
[0052]
Furthermore, the provision of the leaching treatment tanks 1100 in a plurality
of lines in the leaching step S1 leads to an increase in nickel oxide ore
throughput,
and the integration (merging) of the plurality of lines in the subsequent
step, namely
the preliminary neutralization step S2 achieves the merging of the lines at an
earlier
stage after the leaching treatment, whereby the number of parts of facilities
constituting the plant can be reduced. As mentioned above, in the
hydrometallurgical plant 10 according to the present embodiment, while the
number
of the parts is reduced to reduce facility costs effectively, nickel oxide ore
throughput can be effectively increased.
[0053]
A specific neutralization method in this preliminary neutralization facility
12
is such that low-pH leach slurries obtained from the leaching treatment tanks
11(n)
in the lines are fed into the neutralization treatment tanks 12A(n) of the
first stage
which correspond to the respective lines, and for example, a neutralizer such
as
calcium carbonate slurry is added thereto to neutralize the leach slurries.
After
that, the leach slurries neutralized in the neutralization treatment tanks
12A(n) of the
first stage in the respective lines are merged in the neutralization treatment
tank
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12B of the second stage, whereby a post-preliminary-neutralization leach
slurry is
obtained. It should be noted that, also in the neutralization treatment tank
12B of
the second stage, a neutralizer may be added to make fine adjustments of pH of
the
leach slurry. This addition enables pH-adjusted leach slurry to be more stably
subjected to a solid-liquid separation treatment.
[0054]
Here, to the neutralization treatment tank 12A(n) of the first stage in the
preliminary neutralization facility 12, the piping 21(n) to connect the
neutralization
treatment tank 12A(n) to the leaching treatment tank 11(n) in the leaching
facility 11
may be connected. This piping 21(n) is piping to connect the neutralization
treatment tank 12A(n) of the first stage and an inlet portion of the leaching
treatment
tank 11(n) which are in the same line. This piping 21(n) is what is called
piping for
self-circulation which makes it possible to perform circulating (self-
circulating)
transport of leach slurry from the neutralization treatment tank 12A(n) of the
first
stage to the leaching treatment tank 11(n) in the same line by using a
transport pump
31. It should be noted that the arrangement configuration of the piping
21(n) and
an operation for the self-circulation will be described later in detail.
[0055]
Furthermore, to the neutralization treatment tanks 12A(n) of the first stage
in
the preliminary neutralization facility 12, piping 22 to connect the
neutralization
treatment tanks 12A(n) and a final neutralization facility 14 in the final
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neutralization step (detoxification step) S7 can be connected. This piping 22
is led
individually from the neutralization treatment tanks 12A(n) of the first stage
in the
respective lines and connected to an inlet portion of the final neutralization
facility
14, or the piping 22 led from the respective lines is united at a
predetermined point
and connected to an inlet portion of the final neutralization facility 14, and
the
transport pump 31 provided in the piping 22 makes it possible that leach
slurry
discharged from the neutralization treatment tanks 12A(n) of the first stage
is
transported to the final neutralization facility 14. It should be noted that
an
arrangement configuration of the piping 22 and an operation for transporting
leach
slurry from the neutralization treatment tanks 12A(n) of the first stage to
the final
neutralization facility 14 will be described later in detail.
[0056]
Furthermore, to the neutralization treatment tanks 12A(n) of the first stage
in
the preliminary neutralization facility 12, piping 23 to connect the
neutralization
treatment tanks 12A(n) to solid-liquid separation tanks provided in multiple
stages in
the solid-liquid separation facility 13 for the solid-liquid separation step
S3 can be
connected. This piping 23 is led individually from the neutralization
treatment
tanks 12A(n) of the first stage in the respective lines and connected to inlet
portions
of the solid-liquid separation tanks provided in multiple stages, or the
piping 23 led
from the respective lines is united at a predetermined point and connected to
inlet
portions of the solid-liquid separation tanks provided in multiple stages, and
the
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transport pump 31 provided in the piping 23 makes it possible that leach
slurry
discharged from the neutralization treatment tanks 12A(0 of the first stage is
transported to a predetermined solid-liquid separation tank. It should be
noted that
an arrangement configuration of the piping 23 and an operation for
transporting the
leach slurry from the neutralization treatment tanks 12A(n) of the first stage
to a
predetermined solid-liquid separation tank will be described later in detail.
[0057]
It should be noted that Fig. 1 illustrates an aspect in which the foregoing
pipings 21, 22, and 23 are partly shared as common piping, and furthermore, a
transport pump to transport leach slurry is shared, but the present invention
is not
limited to this aspect. The pipings 21, 22, and 23 may be individually
provided,
and each of the pipings 21, 22, and 23 may be provided with a transport pump.
[0058]
(3) Solid-liquid separation step
(3-1) Solid-liquid separation treatment
In the solid-liquid separation step S3, multistage washing is applied to
pH-adjusted leach slurry obtained in the preliminary neutralization step S2,
whereby a leach residue and a leachate containing zinc as an impurity element
besides nickel and cobalt (a crude nickel sulfate solution) are separated.
[0059]
In the solid-liquid separation step S3, for example, leach slurry is mixed
with
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a washing liquid, and then, a solid-liquid separation treatment is applied
thereto
using a solid-liquid separation apparatus such as a thickener and using a
flocculant
supplied from a flocculant supply apparatus or the like. Specifically, first,
leach
slurry is diluted by a washing liquid, and then, a leach residue in the slurry
is
condensed as a precipitate by a thickener. This allows the amount of nickel
adhering to the leach residue to be reduced depending on the degree of the
dilution.
[0060]
In this solid-liquid separation step S3, it is preferable that, using solid-
liquid
separation tanks, such as thickeners, which are connected in multiple stages,
multistage washing is applied to leach slurry to perform solid-liquid
separation.
Specifically, as a multistage washing method, there may be employed a counter
current decantation (CCD) to bring leach slurry into contact with a
countercurrent
of a washing liquid. Thus, a washing liquid to be newly introduced in the line
can
be cut down, while the recovery rate of nickel and cobalt can be improved to
not
less than 95%.
[0061]
The washing liquid (washing water) is not particularly limited, but a washing
liquid which contains no nickel and does not affect the step is preferably
used.
Among such washing liquids, a washing liquid having a pH of Ito 3 is
preferably
used. This is because, in the case where aluminum is contained in a leachate,
a
washing liquid having a high pH causes the formation of a bulky aluminum
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hydroxide, thereby leading to poor sedimentation of a leach residue. Hence, it
is
beneficial that, as the washing liquid, a barren liquor having a low pH (a pH
of
approximately 1 to 3) which is obtained by the nickel recovery step S6 as a
downstream step is repeatedly used.
[0062]
The flocculant to be used is not particularly limited, and, for example, an
anionic flocculant may be used.
[0063]
(3-2) Solid-liquid separation facility
In the hydrometallurgical plant 10 according to the present embodiment, the
foregoing solid-liquid separation treatment in the solid-liquid separation
step S3 is
performed in the solid-liquid separation facility 13.
[0064]
Specifically, as illustrated in Fig. 1, thickeners (solid-liquid separation
tanks)
(CCD1 to CCD6) are connected in six stages to constitute the solid-liquid
separation facility 13 in the hydrometallurgical plant 10. To this solid-
liquid
separation facility 13, (pH-adjusted) leach slurry obtained after preliminary
neutralization in the preliminary neutralization step S2 is transported by a
transport
pump, and fed into a thickener (CCD1) of a first of the six stages. On the
other
hand, washing liquid (washing water) is fed into a thickener of a last stage,
namely
a thickener (CCD6) of a sixth of the six stages via not-illustrated piping.
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[0065]
In this solid-liquid separation facility 13, in the process of transport of
the
leach slurry fed into CCD1 from CCD1 to CCD2, CCD3, ... and CCD6 in this
order,
contact of the leach slurry with a countercurrent of a washing liquid fed into
CCD6
and the aggregation of a residue in the leach slurry are repeated, whereby a
leachate
adhering to the residue is washed. By this operation, a residue containing
valuable
metals such as nickel and having little leachate is discharged from the
thickener
CCD6 of the last stage. Specifically, the concentration of nickel in moisture
adhering to the residue is almost 0 g/L, and thus, a residue washed to have
the
nickel concentration of approximately 0.5 g/L at the maximum is discharged.
The
discharged residue is transported to the final neutralization step S7 to be
rendered
harmless.
[0066]
On the other hand, in the process of transport of the washing liquid fed into
CCD6 of the last stage from CCD6 to CCD5, CCD4, ... and CCD1 in this order,
the
washing liquid takes in moisture adhering to a residue in leach slurry.
Accordingly, the concentration of valuable metals such as nickel in the
washing
liquid increases, and, finally, the washing liquid is discharged as a leachate
from
CCD1, and transported to the subsequent step, namely the neutralization step
S4.
Specifically, as for the concentration of valuable metals in the washing
liquid fed
into CCD6, for example, the concentration of nickel is approximately 0 g/L at
the
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time of the feeding, and gradually increases to approximately 0.5 g/L in the
process
of the transport from CCD6 to CCD5, and increases to approximately 1 g/L in
the
process of the transport from CCD5 to CCD4, and finally a leachate discharged
from CCD1 has a nickel concentration of approximately 3 g/L.
[0067]
It should be noted that, in the foregoing example, solid-liquid separation
tanks such as thickeners are connected in six stages to be provided, but the
number
of connected stages is not limited to this, and may be suitably determined in
consideration of an installation space in the hydrometallurgical plant,
product
specifications, throughput capacity in a subsequent step and downstream steps
therefrom, and the like. Furthermore, a desired concentration of valuable
metals in
a leachate to be recovered is preferably suitably determined likewise.
Furthermore,
also the concentration of nickel in a liquid phase of each of the thickeners
(CCD)
constituting the solid-liquid separation facility 13 is not limited to the
foregoing
concentration.
[0068]
Here, as mentioned above, to inlet portions of solid-liquid separation tanks
such as thickeners provided in multiple stages, piping 23 to connect the solid-
liquid
separation tanks to the neutralization treatment tanks 12Aw of the first stage
which
constitute the preliminary neutralization facility 12 can be connected. This
piping
23 is led individually from the neutralization treatment tanks 12A(,) of the
first
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stage in the respective lines and connected to inlet portions of the solid-
liquid
separation tanks provided in multiple stages, or the piping 23 led from the
respective lines is united at a predetermined point and connected to inlet
portions of
the solid-liquid separation tanks provided in multiple stages, and a transport
pump
31 provided in the piping 23 makes it possible that leach slurry discharged
from the
neutralization treatment tanks 12A(n) of the first stage is transported to a
predetermined solid-liquid separation tank. It should be noted that an
arrangement
configuration of the piping 23 and an operation for transporting leach slurry
from
the neutralization treatment tanks 12A(fl) of the first stage to a
predetermined
solid-liquid separation tank will be described later in detail.
[0069]
(4) Neutralization step
In the neutralization step S4, the pH of a leachate (a crude nickel sulfate
solution) separated in the solid-liquid separation step S3 is adjusted,
whereby a
neutralization precipitate containing an impurity element is separated
therefrom to
obtain a post-neutralization solution containing zinc together with nickel and
cobalt.
[0070]
Specifically, in the neutralization step S4, while oxidation of the separated
leachate is prevented, a neutralizer such as calcium carbonate is added to the
leachate so as to adjust the pH of an obtained post-neutralization solution to
not
more than 4, preferably to from 3.0 to 3.5, more preferably to from 3.1 to
3.2,
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whereby the post-neutralization solution and neutralization precipitate slurry
which
contains trivalent iron as an impurity element are formed. Thus, in the
neutralization step S4, impurities, such as trivalent iron ions and aluminum
ions,
which remain in the solution are removed as a neutralization precipitate,
whereby
the post-neutralization solution to serve as a source of a mother liquor for
nickel
recovery is formed.
[0071]
The neutralization treatment in the neutralization step S4 is performed by a
neutralization facility. The neutralization facility is provided with, for
example, a
neutralization reaction tank to perform a neutralization reaction and a
separation
treatment tank such as a thickener to separate a neutralization precipitate
and a
post-neutralization solution which are obtained by a neutralization reaction.
This
neutralization facility is made up of a single line. In the neutralization
reaction
tank of the neutralization facility, a leachate (a crude nickel sulfate
solution)
discharged from CCD1 of the foregoing solid-liquid separation facility 13 is
fed,
and a neutralizer such as calcium carbonate is charged, whereby a
neutralization
reaction is caused. Furthermore, in the separation treatment tank, slurry
after a
neutralization reaction is fed, and the slurry is separated into a post-
neutralization
solution to serve as a mother liquor for nickel recovery and neutralization
precipitate slurry which contains trivalent iron as an impurity element. In
this
separation treatment tank, the neutralization precipitate slurry is extracted
from the
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bottom of the separation treatment tank. On the other hand, the post-
neutralization
solution from which the neutralization precipitate is separated overflows into
a
storage tank or the like to be stored, and then is transported to the
subsequent step,
namely the dezincification step S5.
[0072]
(5) Dezincification step
In the dezincification step S5, a sulfurizing agent such as hydrogen sulfide
gas is added to the post-neutralization solution obtained by the
neutralization step
S4 to perform a sulfurization treatment, whereby a zinc sulfide is formed, and
the
zinc sulfide is separated and removed to obtain a mother liquor for nickel
recovery
which contains nickel and cobalt (a post-dezincification solution).
[0073]
Specifically, for example, the post-neutralization solution containing zinc
together with nickel and cobalt is introduced into a pressurized vessel, and
hydrogen sulfide gas or the like is blown into a gas phase thereof, whereby
zinc is
selectively sulfurized in contrast to nickel and cobalt, and thus, a zinc
sulfide and a
mother liquor for nickel recovery are formed.
[0074]
The dezincification treatment in the dezincification step S5 is performed in a
dezincification facility. The dezincification facility includes, for example:
a
sulfurization reaction tank to perform a sulfurization reaction by blowing
hydrogen
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sulfide gas or the like into the post-neutralization solution; and a filter
device to
separate and remove zinc sulfide from a post-sulfurization-reaction solution.
This
dezincification facility is made up of a single line. Into the sulfurization
reaction
tank of the dezincification facility, the post-neutralization solution
transported
through the foregoing neutralization step S4 is fed, and a sulfurizing agent
such as
hydrogen sulfide gas is blown, whereby a sulfurization reaction is caused.
Furthermore, the filter device is made up of a filter cloth and the like, and
separates
zinc sulfide from a post-sulfurization-reaction solution containing zinc
sulfide to
form a mother liquor for nickel recovery. The obtained mother liquor for
nickel
recovery is transported to the subsequent nickel recovery step S6.
[0075]
(6) Nickel recovery step
In the nickel recovery step S6, a sulfitrizing agent such as hydrogen sulfide
gas is blown into the mother liquor for nickel recovery which is obtained by
separating and removing zinc as an impurity element in the form of zinc
sulfide in
the dezincification step S5, whereby a sulfurization reaction is caused to
form a
sulfide containing nickel and cobalt (a nickel-cobalt mixed sulfide) and a
barren
liquor.
[0076]
The mother liquor for nickel recovery is a sulfuric acid solution obtained by
reducing an impurity component in a leachate of nickel oxide ore through the
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neutralization step S4 and the dezincification step S5. It should be noted
that there
is a possibility for approximately a few g/L of iron, magnesium, manganese,
and the
like to be contained as impurity components in this mother liquor for nickel
recovery, but, these impurity components have lower stability as a sulfide,
compared to nickel and cobalt which are to be recovered, and hence, the
impurity
components are not contained in a formed sulfide.
[0077]
The nickel recovery treatment in the nickel recovery step S6 is performed in
a nickel recovery facility. The nickel recovery facility includes, for
example: a
sulfurization reaction tank to perform a sulfurization reaction by blowing
hydrogen
sulfide gas or the like into the mother liquor for nickel recovery; and a
solid-liquid
separation tank to separate and recover a nickel-cobalt mixed sulfide from a
post-sulfurization-reaction solution. This nickel recovery facility is made up
of a
single line. Into the sulfurization reaction tank of the nickel recovery
facility, the
mother liquor for nickel recovery transported through the foregoing
dezincification
step S5 is fed and a sulfiirizing agent such as hydrogen sulfide gas is blown,
whereby a sulfurization reaction is caused to form a nickel-cobalt mixed
sulfide.
Furthermore, the solid-liquid separation tank is made up of, for example, a
thickener and the like, and is configured to apply a sedimentation and
separation
treatment to post-sulfurization-reaction slurry containing the nickel-cobalt
mixed
sulfide, thereby separating and recovering the nickel-cobalt mixed sulfide as
a
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sediment from a bottom portion of the thickener. On the other hand, an aqueous
solution component is made to overflow, thereby being recovered as a barren
liquor.
It should be noted that the recovered barren liquor is a solution having a
very low
concentration of valuable metals such as nickel, and contains impurity
elements,
such as iron, magnesium, and manganese, which remain without being sulfurized.
This barren liquor is transported to the final neutralization step S7 to be
rendered
harmless.
[0078]
(7) Final neutralization step
(7-1) Final neutralization treatment
In the final neutralization step S7, the leach residue discharged from a
solid-liquid separation tank of the last stage (for example, CCD6) out of the
tanks
provided in multiple stages in the foregoing solid-liquid separation treatment
in the
solid-liquid separation step S3; a barren liquor containing impurity elements,
such
as iron, magnesium, and manganese, and recovered in the nickel recovery step
S6;
and the like are made to undergo a neutralization treatment (detoxication
treatment),
thereby being adjusted to have a pH in a predetermined range which meets an
effluent standard.
[0079]
A method for the pH adjustment is not particularly limited, but, for example,
pH can be adjusted to the predetermined range by the addition of a neutralizer
such
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as calcium carbonate slurry.
[0080]
(7-2) Final neutralization facility
In the hydrometallurgical plant 10 according to the present embodiment, the
foregoing neutralization treatment in the final neutralization step S7 is
performed in
the final neutralization facility 14.
[0081]
Specifically, as the final neutralization facility 14 in this
hydrometallurgical
plant 10, for example, a final neutralization treatment tank is provided in a
single
line. Specifically, into the final neutralization facility 14, the leach
residues
transported through the foregoing solid-liquid separation step S3 and the
barren
liquor transported through the nickel recovery step S6 are fed. Then, in the
reaction tank, while the leach residues and the barren liquor are mixed, the
pH of a
mixture thereof is adjusted to a predetermined range by a neutralizer, whereby
waste slurry (tailings) is formed. The tailings formed in this reaction tank
are
transported to a tailings dam (waste storage).
[0082]
Here, as mentioned above, to an inlet portion of the final neutralization
facility 14, piping 22 to connect the final neutralization facility 14 to the
neutralization treatment tanks 12A(n) of the first stage which are
constituents of the
preliminary neutralization facility 12 can be connected. This piping 22 is led
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individually from the neutralization treatment tanks 12A00 of the first stage
in the
respective lines and connected to the inlet portion of the final
neutralization facility
14, or the piping 22 led from the respective lines is united at a
predetermined point
and connected to the inlet portion of the final neutralization facility 14,
and a
transport pump 31 provided in the piping 22 makes it possible that leach
slurry
discharged from the neutralization treatment tanks 12A(n) of the first stage
is
transported to the final neutralization facility 14. It should be noted that
an
arrangement configuration of the piping 22 and an operation for transporting
the
leach slurry from the neutralization treatment tanks 12A(n) of the first stage
to the
final neutralization facility 14 will be described later in detail.
[0083]
<<3. Configuration of hydrometallurgical plant and method for operating
hydrometallurgical plant>>
<3-1. Basic configuration and operation flow of normal operation>
<3-1-1. Basic configuration>
As mentioned above, the hydrometallurgical plant 10 according to the
present embodiment includes at least: the leaching facility 11 provided with
the
leaching treatment tanks 11(n) in a plurality (n) of lines to apply a leaching
treatment
to a nickel oxide ore; the preliminary neutralization facility 12 provided
with the
neutralization treatment tanks 12A and 12B in two stages to perform
preliminary
neutralization by which the pH of leach slurries discharged from the leaching
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treatment tanks 11(n) is adjusted to a predetermined range; and the solid-
liquid
separation facility 13 made up of a single line to perform solid-liquid
separation of
leach slurry pH-adjusted and discharged from the preliminary neutralization
facility
12 in a solid-liquid separation tank (Fig. 1).
[0084]
Furthermore, as illustrated in Fig. 1, in the hydrometallurgical plant 10, the
preliminary neutralization facility 12 is configured such that the
neutralization
treatment tanks 12A(n) of the first stage are provided in a plurality (n) of
lines so as
to correspond to the respective lines of the leaching treatment tanks 11(n)
provided
in the leaching facility 11, and the leach slurries pH-adjusted in the
neutralization
treatment tanks 12A(n) of the first-stage in the respective lines are merged
in the
neutralization treatment tank 12B of the second stage made up of a single
line, and
furthermore, leachate merged in the neutralization treatment tank of the
second
stage is transported to the solid-liquid separation facility.
[0085]
According to the thus-configured hydrometallurgical plant 10, when leaching
treatment facilities each of which has a size having an operational track
record (for
example, 10,000 tons/year to 20,000 tons/year of leachate production amount in
terms of the amount of nickel) are used in a plurality lines, nickel oxide ore
throughput can be increased. Furthermore, in the subsequent downstream steps,
that is, in the steps downstream from the preliminary neutralization step, the
lines
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are united into one line, and therefore, the number of parts in the whole of
the plant
can be reduced, whereby facility costs are reduced.
[0086]
Furthermore, according to this hydrometallurgical plant 10, even in the case
where variations in pH and the like of leach slurries obtained from the
treatment
facilities (the leaching treatment tanks 11(n), the neutralization treatment
tanks
12,640 of the first stage) in the plurality of lines arise, the variations can
be
eliminated because the leached slurries discharged from the respective lines
are
merged in the neutralization treatment tank 12B of the second stage, and
consequently, a solid-liquid separation treatment can be applied to uniform
leach
slurry.
[0087]
Furthermore, although details will be described, according to this
hydrometallurgical plant 10, the pipings 21, 22, and 23 to connect the
neutralization
treatment tanks 12A(n) of the first stage to reaction tanks of the treatment
facilities
in other steps are appropriately provided. Thus, for example, leach slurry in
a
state where, immediately after plant operation startup or the like, a leaching
treatment does not sufficiently proceed yet can be prevented from being
transported
to the solid-liquid separation step S3 and steps downstream therefrom, and
accordingly, the occurrence of a poor reaction and a decrease in operation
efficiency in the each step can be effectively prevented.
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[0088]
<3-1-2. Operation flow of normal operation>
Here, an operation method for a normal operation of the foregoing
hydrometallurgical plant 10 will be described. Fig. 3 illustrates an operation
flow
of a normal operation. It should be noted that, here, description will be made
by
giving an example in which, as illustrated in Fig. 1 and Fig. 3, here,
treatment
facilities made up of a plurality of lines are made up of two lines (n = 2),
that is, "a
first line (1)" and "a second line (2)".
[0089]
As shown by solid-black arrows in Fig. 3, in this hydrometallurgical plant 10,
for example, slurry of nickel oxide ore (ore slurry) which are ground to a
predetermined size in an ore processing step or the like is fed into a
leaching
treatment tank 11(1) in the first line and a leaching treatment tank 11(2) in
the second
line which are provided in a leaching treatment facility 11, whereby a
leaching
treatment is applied to ore slurry in the leaching treatment tanks 11(1) and
11(2) in
the respective lines.
[0090]
Next, leach slurries obtained by the leach treatment in the leaching treatment
tanks 11(1) and 11(2) are transported to the preliminary neutralization
facility 12.
Specifically, leached slurries discharged from the leaching treatment tanks
11(1) and
11(2) are fed into neutralization treatment tanks 12A(1) and 12A(2) of the
first stage
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which correspond to the respective lines of the leaching treatment tanks 11(1)
and
11(2). Then, in the neutralization treatment tanks 12A(1) and 12A(2) in the
respective lines, a neutralizer is added to the fed leach slurries to adjust
the pH of
the slurries to a predetermined pH range.
[0091]
Next, leach slurries pH-adjusted in the neutralization treatment tanks 12A(1)
and 12A(2) of the first stage are transported to and fed into the
neutralization
treatment tank 12B of the second stage. That is, leach slurries which are
pH-adjusted in the neutralization treatment tank 12A(i) in the first line and
neutralization treatment tank 12A(2) in the second line, respectively, are
merged in
the neutralization treatment tank 12B of the second stage made up of a single
line.
Thus, the merging of leach slurries transported from the lines in the
neutralization
treatment tank 12B of the second stage enables variations in properties such
as pH
to be eliminated, whereby uniform leach slurry can be transported to
downstream
steps. It should be noted that, also in the neutralization treatment tank 12B
of the
second stage, a neutralizer may be added to the merged leach slurry to make
fine
adjustments of the pH of the leach slurry.
[0092]
In the transport of leach slurry to the neutralization treatment tank 12B of
the
second stage, the leach slurry is made to overflow and transported via pipings
24(1)
and 24(2) configured to connect the respective neutralization treatment tanks
12A(1)
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and 12A(2) of the first step to the neutralization treatment tank 12B of the
second
stage.
[0093]
Subsequently, leach slurry is discharged from the neutralization treatment
tank 12B of the second stage, and the leach slurry is transported to the solid-
liquid
separation facility 13. For example, as illustrated in Fig. 3, the solid-
liquid
separation facility 13 is a facility in which thickeners in six stages (CCD1
to CCD6)
are connected and which is configured to feed transported leach slurry into a
thickener of a first of the six stages. The transport of leach slurry to the
solid-liquid separation facility 13 is performed via piping 25 configured to
connect
an outlet portion of the neutralization treatment tank 12B of the second stage
to an
inlet portion of the thickener (CCD1) of the first stage, by using a transport
pump
32 provided in the piping 25.
[0094]
After that, in the solid-liquid separation facility 13, in the process of the
transport of fed leach slurry from CCD1 to CCD6 in this order, the slurry
comes
into contact with a countercurrent of a washing liquid fed into CCD6 of the
last
stage and residues in the slurry aggregate. Then, finally, a leachate having a
high
concentration of valuable metals such as nickel (a crude nickel sulfate
solution) is
discharged from CCD1. On the other hand, a leach residue having a low
concentration of valuable metals such as nickel is discharged from CCD6 of the
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final stage, and transported to the final neutralization facility 14 to be
rendered
harmless.
[0095]
<3-2. Configuration for self-circulation and operation flow of
self-circulation>
<3-2-1. Configuration for self-circulation>
At the time of startup (operation start, startup) of the hydrometallurgical
plant 10 after an periodic inspection and after a shutdown of one or both of
the two
lines, a predetermined time is needed until a leaching treatment in the
leaching
facility 11 reaches a level of normal (regular) operation. Specifically, in
the
leaching facility 11, a leaching treatment is performed under high temperature
and
high pressure, and therefore, an increase in temperature to a predetermined
temperature is needed. Therefore, in an early stage immediately after
operation
startup and the like, a treatment to leach out a valuable metal from ore
slurry is
scarcely started, and accordingly, from the leaching treatment tanks 11(1) and
11(2)
which constitute the leaching facility 11, leach slurry in a state in which
the
leaching treatment has not been sufficiently completed yet is discharged.
[0096]
In the case where such leach slurry is transported as it is to treatment
facilities in which the preliminary neutralization step S2 and the solid-
liquid
separation step S3 are performed, an obtained leachate has a greatly low
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concentration of valuable metals, and a poor sulfurization reaction and a
decrease in
operation efficiency in the nickel recovery step S6 and the like are caused.
Such
low concent-ration of valuable metals is caused particularly by leach slurry
discharged at an early stage immediately after start of the leaching treatment
in the
leaching treatment tanks 11(1) and 11(2) and waste water for temperature
increase
and the like, discharged from the leaching facility 11 when, under a status
where
one line is normally operated, other lines are started up.
[0097]
Therefore, as illustrated in Fig. 4, in the hydrometallurgical plant 10
according to the present embodiment, installed are pipings 21(1) and 21(2) to
connect
neutralization treatment tanks 12A(i) and 12A(2) of the first stage in the
preliminary
neutralization facility 12 to the leaching treatment tanks 11(1) and 11(2) in
the
leaching facility 11, respectively. The pipings 21(1) and 21(2) are to connect
the
neutralization treatment tanks 12A(1) and 12A(2) of the first stage and inlet
portions
of the leaching treatment tanks 11(1) and 11(2), respectively, in which the
neutralization treatment tank 12A(1) and the leaching treatment tank 11(1),
and the
neutralization treatment tank 12A(2) and the leaching treatment tank 11(2) are
in the
same line, respectively. That is, for example, the piping 21(2) connects the
leaching treatment tank 1 1 (2) in the second line to the neutralization
treatment tank
12A(2) in the second line.
[0098]
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The pipings 21(1) and 21(2) enable a process liquid for increasing a
temperature of the leaching treatment tanks 11(1) and 11(2) (a liquid for
temperature
increase) and low-nickel-concentration leach slurries discharged from the
leaching
treatment tanks 11(1) and 11(2) to be circulated between the leaching
treatment tanks
11(1) and 11(2) and the neutralization treatment tanks 12A(1) and 12A(2),
respectively,
at the time of the foregoing startup after start of operation. Thus, the
pipings 21(1)
and 21(2) are piping for self-circulation which is capable of self-circulation
of leach
slurries discharged from the neutralization treatment tanks 12A(i) and 12A(2)
of the
first stage and process liquids to the leaching treatment tanks 11(1) and
11(2),
respectively, in which the neutralization treatment tank 12A(1) and the
leaching
treatment tank 11(1) , and the neutralization treatment tank 12A(2) and the
leaching
treatment tank 11(2) are in the same line, respectively.
[0099]
As illustrated in Fig. 4, the pipings 21(1) and 21(2) may extend from the
neutralization treatment tanks 12A(i) and 12A(2) of the first stage,
respectively, and
then, be merged at a predetermined point (in Fig. 1 and Fig. 4, an
installation point
of the transport pump 31), branch out again, and be connected to the leaching
treatment tanks 11(1) and 11(2), respectively, or completely independent
piping may
be installed in every line. Furthermore, the pipings 21(1) and 21(2) are
provided
with a transport pump 31, and leach slurries discharged from the
neutralization
treatment tanks 12A(1) and 12A(2) are transported to the leaching treatment
tanks
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11(1) and 11(2), respectively, by the transport pump 31.
[0100]
Furthermore, for example, between the neutralization treatment tanks 12A(1)
and 12A(2) and the foregoing transport pump 31, ON/OFF valves 42(1) and 42(2)
to
control the transport of leach slurry are provided inside the pipings 21(1)
and 21(2),
respectively. Then, although details will be described later, when leach
slurry is
made to self-circulate between the neutralization treatment tanks 12A(1) and
12A(2)
of the first stage and the leaching treatment tanks 11(1) and 11(2), the
ON/OFF
valves 42(1) and 42(2) are brought into an ON state ("open" state) to make
possible
the transport of discharged leach slurry. It should be noted that, at the time
of the
foregoing normal operation, the ON/OFF valves 42(1) and 42(2) provided in the
respective pipings for self-circulation 21(1) and 21(2) are in an OFF state
("closed"
state).
[0101]
<3-2-2. Operation flow of self-circulation>
Next, an operation method in the self-circulation using the foregoing pipings
for self-circulation 21(1) and 21(2) in the hydrometallurgical plant 10 will
be
described using an operation flow of the self-circulation illustrated in Fig.
4. It
should be noted that, as illustrated in Fig. 4, description will be made by
taking, as
an example, a case where self-circulation operation is performed in treatment
facilities in the second line out of a plurality of lines, that is, the first
line and the
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second line. Hereinafter, likewise, an operation performed after startup of
treatment facilities on the second line will be taken as an example and
described.
[0102]
For example, at a stage where treatment facilities only in the second line are
started up, that is, at an early stage immediately after operation startup or
the like,
even if a leaching treatment is applied to ore slurry in the leaching
treatment tank
11(2) of the leaching facility 11, for example, temperature increase in the
leaching
treatment tank 11(2) is insufficient, whereby obtained leach slurry is in an
insufficient leached state. Furthermore, immediately after the operation
startup, a
process liquid (a liquid for temperature increase) such as warm water is fed
to
perform a temperature increase treatment in order to increase the temperature
of the
leaching treatment facility 11(2).
[0103]
Then, at such stage, as shown by flows indicated by hollow arrows in Fig. 4,
leach slurry or a process liquid is discharged from the leaching treatment
tank 11(2)
and transported to the neutralization treatment tank 12A(2) of the first stage
in the
same line. After that, the leach slurry or the process liquid is self-
circulated
between the neutralization treatment tank 12A(2) of the first stage and the
leaching
treatment tank 11(2) via the piping 21(2) to connect the neutralization
treatment tank
12A(2) and the leaching treatment tank 11(2).
[0104]
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Specifically, in the self-circulation of leach slurry or a process liquid, the
ON/OFF valve 42(2) provided in the piping for self-circulation 21(2) to
connect the
neutralization treatment tank 12A(2) of the first stage to the leaching
treatment tank
11(2) is brought into an ON state ("open" state). Then, the leach slurry or
the
process liquid is circulated from the neutralization treatment tank 12A(2) to
the
leaching treatment tank 11(2) by the transport pump 31 provided in the piping
for
self-circulation 21(2).
[0105]
This self-circulation operation is performed until, for example, the
temperature of the leaching treatment tank 11(2) is sufficiently increased. It
should
be noted that, at the time of this self-circulation, the supply of ore slurry
and the
supply of sulfuric acid to the leaching treatment tank 11(2) are suspended.
Therefore, when leach slurry is circulated, the leach slurry has a valuable
metal
concentration of substantially approximately 0 g/L in terms of the amount of
nickel.
[0106]
As mentioned above, in the hydrometallurgical plant 10 according to the
present embodiment, the provision of the pipings 21(1) and 21(2) to connect
the
neutralization treatment tanks 12A(1) and 12A(2) of the first stage to the
leaching
treatment tanks 11(1) and 11(2), respectively, makes possible the self-
circulation of
leach slurry or a process liquid for temperature increase at an early stage
immediately after operation startup or the like. This can prevent leach slurry
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containing little nickel and a process liquid from being transported to
downstream
steps such as the solid-liquid separation step S3.
[0107]
<3-3. Configuration for transport to final neutralization facility, and
operation flow of transport to final neutralization facility>
<3-3-1. Configuration for transport to final neutralization facility>
Furthermore, even in a state where, in a startup operation after operation
start,
for example, temperature increase in the leaching treatment tank 11(2) is
completed
and the supply of ore slurry and sulfuric acid is started, leaching treatment
is not
sufficiently carried out yet in the leaching treatment tank 11(2), and
accordingly,
leach slurry having a desired nickel concentration is not discharged. Such
leach
slurry immediately after start of leaching in which little nickel and the like
are
leached out cannot still be transported to the subsequent step.
[0108]
Therefore, as illustrated in Fig. 5, in the hydrometallurgical plant 10
according to the present embodiment, installed is the piping 22 to connect the
neutralization treatment tanks 12(1) and 12A(2) of the first stage in the
preliminary
neutralization facility 12A to the leaching treatment tanks 11(1) and 11(2) in
the
leaching facility 11 and the final neutralization facility 14. This piping 22
is led
individually from the neutralization treatment tanks 12A(1) and 12A(2) of the
first
stage in the respective lines and connected to an inlet portion of the final
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neutralization facility 14, or the piping 22 led from the respective lines is
united at a
predetermined point and connected to the inlet portion of the final
neutralization
facility 14.
[0109]
The piping 22 is provided with a transport pump 31, and configured to
transport leach slurries discharged from the neutralization treatment tanks
12A(1)
and 12A(2) of the first stage to the final neutralization facility 14 by the
transport
pump 31.
[0110]
Furthermore, for example, between the neutralization treatment tanks 12A(1)
and 12A(2) and the foregoing transport pump, the ON/OFF valves 42(1) and 42(2)
to
control transport of leach slurry are provided inside the piping 22. Then,
although
details will be described later, when leach slurry is transported from the
neutralization treatment tanks 12A(1) and 12A(2) of the first stage to the
final
neutralization facility 14, the ON/OFF valves 42(1) and 42(2) are brought into
an ON
state ("open" state) to make possible the transport of the discharged leach
slurry.
It should be noted that, at the time of the foregoing normal operation, the
ON/OFF
valves 42(1) and 42(2) provided in the piping for transport to the final
neutralization
facility 14 is in an OFF state ("closed" state).
[0111]
<3-3-2. Operation flow of transport to final neutralization facility>
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Next, an operation method in the transport to the final neutralization
facility
14 by using the foregoing piping 22 in the hydrometallurgical plant 10 will be
described using an operation flow of Fig. 5. It should be noted that, as
illustrated
in Fig. 5, description will be given by taking, as an example, a case where an
operation to transport leach slurry to the final neutralization facility 14 in
treatment
facilities in the second line out of a plurality of lines, that is, the first
line and the
second line.
[0112]
For example, at a stage where a startup operation is performed for the
treatment facilities only in the second line and then temperature increase in
the
leaching treatment tank 11(2) is completed, a leaching treatment has proceeded
in
the leaching treatment tank 11(2) little by little, but not been sufficiently
completed
yet, and therefore, discharged leach slurry has a low nickel concentration.
[0113]
Then, at such stage, as shown by flows indicated by hollow arrows in Fig. 5,
first, leach slurry is discharged from the leaching treatment tank 11(2) and
transported to the neutralization treatment tank 12A(2) of the first stage in
the same
line. After that, leach slurry is transported from the neutralization
treatment tank
12A(2) to the final neutralization facility 14 via the piping 22 to connect
the
neutralization treatment tank 12A(2) to the final neutralization facility 14.
[0114]
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Specifically, in the transport of leach slurry to the final neutralization
facility
14, an ON/OFF valve 43 provided in the foregoing piping for self-circulation
21(2)
(piping to connect the neutralization treatment tank 12A(2) of the first stage
and the
leaching treatment tank 11(2)) is brought into an OFF state ("closed" state).
Next,
the ON/OFF valve 42(2) provided in the piping 22 to connect the neutralization
treatment tank 12A(2) of the first stage and the final neutralization facility
14 is
brought into an ON state ("open" state). Then, leach slurry is transported
from the
neutralization treatment tank 12A(2) to the final neutralization facility 14
by the
transport pump 31 provided in the piping 22.
[0115]
This transport operation of leach slurry to the final neutralization facility
14
is performed, for example, when the nickel concentration of leach slurry
discharged
from the leaching treatment tank 11(2) is lower than the nickel concentration
of a
liquid phase in a thickener of the last stage (CCD6) out of thickeners
provided in
multiple stages in the solid-liquid separation facility 13. It should be noted
that, at
this stage, that is, at a stage of the transport operation to the final
neutralization
facility 14, leach slurry has a valuable metal concentration of, for example,
approximately 0 to 5 g/L in terms of the amount of nickel.
[0116]
As mentioned above, in the hydrometallurgical plant 10 according to the
present embodiment, the provision of the piping 22 to connect the
neutralization
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treatment tanks 12A(I) and 12A(2) of the first stage to the final
neutralization facility
14 makes it possible that leach slurry discharged at a stage where a leaching
treatment has not sufficiently proceed yet after operation start is
transported to the
final neutralization facility 14. This can prevent leach slurry having a low
nickel
concentration from being transported to downstream steps such as the solid-
liquid
separation step S3.
[0117]
<3-4. Configuration for transport to solid-liquid separation tank, and
operation flow of transport to solid-liquid separation tank>
<3-4-1. Configuration for transport to solid-liquid separation tank>
Furthermore, even in the case where a leaching treatment gradually proceeds
after operation startup and the nickel concentration of leach slurry
discharged from
the leaching treatment tank 11(2) becomes higher than the nickel concentration
of a
leachate in the thickener of the last stage (CCD6) in the solid-liquid
separation
facility, unless the nickel concentration of the leach slurry is sufficiently
high, the
leach slurry cannot be transported to a subsequent step. That is, in the case
where
the nickel concentration of the leach slurry is lower than a desired nickel
concentration of leach slurry to be transported to the neutralization
treatment tank
12B of the second stage, the leach slurry cannot be transported to a
subsequent step.
[0118]
Therefore, as illustrated in Fig. 6, in the hydrometallurgical plant 10
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according to the present embodiment, installed is the piping 23 to connect the
neutralization treatment tanks 12(1) and 12A(2) of the first stage in the
preliminary
neutralization facility 12 to the solid-liquid separation tanks (thickeners)
provided
in multiple stages in the solid-liquid separation facility 13. This piping 23
is led
individually from the neutralization treatment tanks 12A(1) and 12A(2) of the
first
stage in the respective lines and connected to inlet portions of the solid-
liquid
separation tanks, or the piping 23 led from the respective lines is united at
a
predetermined point and connected to the inlet portions of the solid-liquid
separation tanks. More specifically, this piping 23 extends from the
neutralization
treatment tanks 12A(i) and 12A(2) of the first stage in the direction of the
solid-liquid separation facility 13, and branches out so as to be coupled to
each of
the solid-liquid separation tanks (CCD1, CCD2, ... and CCD6) which are
connected
in multiple stages and constitute the solid-liquid separation facility 13.
[0119]
This piping 23 is provided with a transport pump 31 and is configured to
transport leach slurry discharged from the neutralization treatment tanks
12A(i) and
12A(2) of the first stage to a predetermined solid-liquid separation tank in
the
solid-liquid separation facility 13 by the transport pump 31.
[0120]
Furthermore, for example, between the neutralization treatment tanks 12A(1)
and 12A(2) and the foregoing transport pump 31, the ON/OFF valves 42(1) and
42(2)
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to control the transport of leach slurry are provided inside the piping 23.
Then,
although details will be described later, when leach slurry is transported
from the
neutralization treatment tanks 12A(1) and 12A(2) to a predetermined solid-
liquid
separation tank in the solid-liquid separation facility 13, the ON/OFF valves
42(1)
and 42(2) are brought into an ON state ("open" state) to make possible the
transport
of discharged leach slurry. It should be noted that, at the time of the
foregoing
normal operation, the ON/OFF valves 42(1) and 42(2) provided in the piping 23
for
the transport to a predetermined solid-liquid separation tank is in an OFF
state
("closed" state).
[0121]
Furthermore, this piping 23 is provided with an ON/OFF valve 44 to control
the transport of leach slurry at each of junctions toward the respective
multistage-connected solid-liquid separation tanks. This provision makes it
possible to control the transport of leach slurry to a solid-liquid separation
tank
which is an appropriate transport destination in accordance with the nickel
concentration of the leach slurry to be transported. A method for the control
of a
transport destination may be such that a switchover valve to perform
switchover
among transfer destinations is provided at a predetermined junction, whereby
switchover control is carried out by the switchover valve.
[0122]
<3-4-2. Operation flow of transport to solid-liquid separation tank>
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Next, an operation method in the transport to solid-liquid separation tanks
constituting the solid-liquid separation facility 13 by using the foregoing
piping 23
in the hydrometallurgical plant 10 will be described using an operation flow
of Fig.
6. It should
be noted that, as illustrated in Fig. 6, description will be given by
taking, as an example, a case where an operation to transport leach slurry to
a
solid-liquid separation tank of a second stage (CCD2) in the solid-liquid
separation
facility 13 in treatment facilities in the second line out of a plurality of
lines, that is,
the first line and the second line.
[0123]
For example, even if there is a state where a startup operation of treatment
facilities in the second line is performed and then a leaching treatment
gradually
proceeds, unless the leaching treatment sufficiently proceeds to a normal
operation
level, the nickel concentration of leach slurry discharged from the leaching
treatment tank 11(2) is low, and therefore, the leach slurry is not allowed to
be
transported to a subsequent step. Specifically, for example, even in the case
where
a leaching treatment proceeds and the valuable metal concentration of leach
slurry
is more than 5 g/L in terms of the amount of nickel, when the nickel
concentration
of the leach slurry is lower than a desired nickel concentration of leach
slurry to be
transported to the neutralization treatment tank 12B of the second stage, the
leach
slurry is not allowed to be transported to a subsequent step.
[0124]
= CA 02904569 2015-09-08
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Then, in such case, as shown by flows indicated by hollow arrows in Fig. 6,
first, leach slurry is discharged from the leaching treatment tank 11(2) and
transported to the neutralization treatment tank 12A(2) of the first stage in
the same
line. After that, leach slurry is transported from the neutralization
treatment tank
12A(2) to the solid-liquid separation facility 13 via the piping 23 to connect
the
neutralization treatment tank 12A(2) to the solid-liquid separation facility
13.
[0125]
At this time, in accordance with the valuable metal concentration of leach
slurry, the leach slurry is transported to a solid-liquid separation tank
corresponding
to the valuable metal concentration. For example, in the case where the
valuable
metal concentration of leach slurry is 2.5 g/L in terms of the amount of
nickel, the
leach slurry is transported to the solid-liquid separation tank of the second
stage
(CCD2) in which a liquid phase has a concentration of approximately 2.5 g/L in
terms of the amount of nickel at the time of normal (regular) operation. A
transport destination is thus appropriately controlled in accordance with the
valuable metal concentration of leach slurry, whereby the first line under the
normal
operation can be prevented from being affected, and an efficient operation
becomes
feasible.
[0126]
Specifically, in the transport of leach slurry to CCD2 in the solid-liquid
separation facility 13, the ON/OFF valve 43 provided in the foregoing piping
for
= CA 02904569 2015-09-08
, c
63 (12-403; ST14PCT1)
self-circulation 21(2) (piping to connect the neutralization treatment tank
12A(2) of
the first stage to the leaching treatment tank 11(2)) is brought into an OFF
state
("closed" state). Furthermore, an ON/OFF valve 45 provided in the foregoing
piping 22 to transport leach slurry to the final neutralization facility 14
(piping to
connect the neutralization treatment tank 12A(2) of the first stage to the
final
neutralization facility 14) is brought into an OFF state ("closed" state).
[0127]
Next, the ON/OFF valve 42(2) provided in the piping 23 to connect the
neutralization treatment tank 12A(2) of the first stage to the solid-liquid
separation
facility 13 is brought into an ON state ("open" state). Then, leach slurry is
transported from the neutralization treatment tank 12A(2) of the first stage
to the
solid-liquid separation facility 13 by a transport pump 31 provided in the
piping 23.
At this time, ON/OFF valves 44 provided at junctions for branching toward
respective solid-liquid separation tanks in the solid-liquid separation
facility 13 are
controlled to transport the leach slurry to CCD2. Specifically, an ON/OFF
valve
44 at a junction toward CCD2 is brought into an ON state ("open" state), on
the
other hand, other ON/OFF valves 44 at respective junctions toward from CCD1,
CCD3 to CCD6 are brought into an OFF state ("closed" state).
[0128]
As mentioned above, in the hydrometallurgical plant 10 according to the
present embodiment, the provision of the piping 23 to connect the
neutralization
CA 02904569 2015-09-08
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=
64 (12-403; ST14PCT1)
treatment tanks 12A(1) and 12A(2) of the first stage to the solid-liquid
separation
facility 13 makes it possible that leach slurry having not sufficiently
undergone a
leach treatment yet after start of operation and having a low nickel
concentration is
transported to a predetermined solid-liquid separation tank. This can prevent
low-nickel-concentration leach slurry from being transported with being mixed
with
leach slurry discharged from a line in which the normal operation continues,
and
prevent poor reactions and a decrease in operation efficiency in downstream
steps.
[0129]
<3-5. Shift from unusual operation to normal operation>
Then, when a predetermined amount of time has elapsed since start of
operation and the valuable metal concentration of leach slurry discharged from
the
leaching treatment tank 11(2) and operation conditions such as a flow rate for
liquid
transport return to the levels of the normal operation, the foregoing routes
for an
unusual operation are closed, and the normal operation is performed using a
route
for the normal operation.
[0130]
That is, leach slurry discharged from the leaching treatment tank 11(2) is
transported to the neutralization treatment tank 12A(2) of the first stage,
and then,
leach slurry is made to overflow into the neutralization treatment tank 12B of
the
second stage via the piping 24(2) to connect the neutralization treatment tank
12A(2)
of the first stage to the neutralization treatment tank 12B of the second
stage.
= CA 02904569 2015-09-08
= .
= , =
. ,
65 (12-403;
ST14PCT1)
Then, leach slurry is transported from the neutralization treatment tank 12B
of the
second stage to CCD1 in the solid-liquid separation facility 13 to undergo a
solid-liquid separation treatment.
[0131]
<3-6. Conclusion>
As mentioned above, the hydrometallurgical plant 10 according to the
present embodiment makes it possible that, while facility costs are reduced,
nickel
oxide ore throughput is increased, whereby the production amount of a
nickel-cobalt mixed sulfide is improved. Furthermore, even in the case where
variations in the properties, such as pH, of leach slurries obtained from
treatment
facilities in a plurality of lines arise, the leach slurries discharged from
the
respective lines are merged in the neutralization treatment tank 12B of the
second
stage, and therefore, the variations can be eliminated, whereby a solid-liquid
separation treatment can be applied to uniform leach slurry.
[0132]
Furthermore, since this hydrometallurgical plant 10 is provided with the
foregoing pipings 21, 22, and 23, leach slurry having a low nickel
concentration can
be prevented from being transported to downstream steps at an unusual time
such as
startup of treatment facilities. This can prevent a poor reaction and a
decrease in
operation efficiency in downstream steps.
[0133]
= CA 02904569 2015-09-08
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Furthermore, in the hydrometallurgical plant 10, the foregoing pipings 21, 22,
and 23 are connected from the neutralization treatment tanks 12A(1) and 12A(2)
of
the first stage in the preliminary neutralization facility 12 made up of
neutralization
treatment tanks in two stages. Thus, an operation in one line where the normal
operation continues to be performed is not affected. That is, as illustrated
in the
examples of Figs. 4 to 6, it is made possible that, in the second line under a
startup
operation, leach slurry is self-circulated, or transported to the final
neutralization
facility 14 and the solid-liquid separation facility 13, while, in the first
line, the
normal operation is performed as shown by flows indicated by a solid-black
arrows.
As mentioned above, in the hydrometallurgical plant 10, neutralization
treatment
tanks are provided in two stages and only neutralization treatment tanks of a
first of
the two stages are provided in a plurality of lines, whereby a startup
operation at the
time of start of operation (unusual operation) can be performed without
affecting
the one of the two lines.
[0134]
It should be noted that, in the case where the unusual operation is performed
in one of the lines (for example, the second line), compared with a case where
the
normal operation is performed in both of the lines, the liquid amount of leach
slurry
transported to the neutralization treatment tank 12B of the second stage is
smaller.
Therefore, the performance of a pump for the normal operation and throughput
in
downstream steps are reduced to a level corresponding to the foregoing liquid
CA 02904569 2015-09-08
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67 (12-403; ST14PCT1)
amount, and the operation continues to be performed. However, as mentioned
above, in another of the lines (for example, the first line), the normal
operation can
be performed without stopping the operation, and therefore, the quality and
the like
of a product is not affected at all.
[0135]
Fig. 1 and Figs. 3 to 6 illustrate a configuration in which pipings 21, 22,
and
23 used for the unusual operation are partly shared. Furthermore, the
transport
pump 31 to transport leach slurry through those pipings 21, 22, and 23 is also
shared. However, the present invention is not limited to this, and, as a
matter of
course, the pipings 21, 22, and 23 may be completely individually provided,
and
each of the pipings 21, 22, and 23 may be provided with a transport pump. In
this
hydrometallurgical plant 10, it is beneficial that, in consideration of a
transport
route and the like, the arrangement of the piping is suitably determined. It
should
be noted that piping is preferably shared in a sharable portion of the piping
to make
possible a reduction in the number of facilities and costs.
[0136]
Furthermore, Fig. 1 and Figs. 3 to 6 illustrate an aspect in which all of the
pipings 21, 22, and 23 used for the unusual operation are provided, but, an
aspect in
which any one or two of the pipings are provided may be adopted.
[0137]
<<4. Examples >>
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Next, Examples adopting the present invention will be described, but the
present invention is not limited to the following Examples.
<Examples>
[0138]
<Operation of hydrometallurgical plant>
<Operation Example 1>
In a hydrometallurgical plant for nickel oxide ores, treatment facilities were
configured as illustrated in Fig. 1, and a 30-day hydrometallurgical operation
was
carried out.
[0139]
That is, an operation was performed by the hydrometallurgical plant 10
including: the leaching treatment facility 11 having the leaching treatment
tanks
11(1) and 11(2) in two lines; and the preliminary neutralization facility 12
provided
with neutralization treatment tanks in two stages, in which the neutralization
treatment tanks 12A(i) and 12A(2) of a first of the two stages were provided
in the
two lines so as to correspond to the respective leaching treatment tanks, and
the
neutralization treatment tank 12B of a second of the two stages was provided
in a
single line. It should be noted that, in the solid-liquid separation facility
13, as
illustrated in Fig. 1, thickeners (CCD1 to CCD6) were connected in six stages
to
perform multistage washing.
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[0140]
As a result, during the period of 30 days, poor leaching and the like in the
leaching facility in which high pressure acid leach was performed were not
caused,
and the operation did not stop in both of the two lines. Furthermore, the
production amount of a nickel-cobalt mixed sulfide obtained by this operation
was
2500 tons in terms of the amount of nickel, and there was no problem with the
quality of the product.
[0141]
It should be noted that set values of the valuable metal concentrations in
liquid phases of CCDs of the stages in the solid-liquid separation facility 13
were
not more than 3 g/L for CCD1, not more than 2.5 g/L for CCD2, not more than 2
g/L for CCD3, not more than 1.5 g/L for CCD4, not more than 1 g/L for CCD5,
and
not more than 0.5 g/L for CCD6, in terms of the amount of nickel.
[0142]
<Operation Example 2>
Using the same plant as the hydrometallurgical plant 10 used in Operation
Example 1, a 30-day hydrometallurgical operation was carried out. It should be
noted that set values of the valuable metal concentrations in liquid phases of
CCDs
of the stages in the solid-liquid separation facility 13 were the same as
those in
Operation Example 1.
[0143]
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In the operation of Operation Example 2, during the period of the operation,
shutdowns occurred five times due to facility troubles in the leaching
treatment tank
11(1) in the first line or the leaching treatment tank 11(2) in the second
line.
Accordingly, the shutdown and startup operations of a line in which the
facility
troubles arose were performed five times. At this time, in the startup
operation, as
illustrated in Fig. 4 to Fig. 6, the unusual operation was performed in
accordance
with the nickel concentration of leach slurry discharged from the leaching
treatment
tank 11(1) or 11(2). It should be noted that, in such startup operation, an
average
time required from a shutdown to a return to normal was one day.
[0144]
As a result of the 30-day operation, the production amount of a nickel-cobalt
mixed sulfide obtained by this operation was 2075 tons (approximately 83% of
that
in Operation Example 1), and there was no problem with the quality of the
product.
[0145]
<Operation Example 3>
Using the same plant as the hydrometallurgical plant 10 used in Operation
Example 1, a 30-day hydrometallurgical operation was carried out. It should be
noted that set values of the valuable metal concentrations in liquid phases of
CCDs
of the stages in the solid-liquid separation facility 13 were the same as
those in
Operation Example 1.
[0146]
= CA 02904569 2015-09-08
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ST14PCT1)
Also in Operation Example 3, as is the case with Operation Example 2,
during the period of the operation, poor leaching occurred five times in the
leaching
treatment tank 11(1) in the first line or the leaching treatment tank 11(2) in
the second
line. Accordingly, the shutdown and startup operations of a line in which the
poor
leaching occurred were performed five times. At this time, in Operation
Example
3, the whole of the hydrometallurgical plant 10 was shut down. It should be
noted
that, in such startup operation, an average time required from a shutdown to a
return
to normal was two days.
[0147]
As a result of the 30-day operation, an obtained nickel-cobalt mixed sulfide
had no problem in product quality, but the production amount thereof was very
small, namely 1300 tons (approximately 52% of that in Operation Example 1),
and
thus a sufficient amount of a nickel-cobalt mixed sulfide cannot be produced.
[0148]
The reason why, although a production amount equal to approximately 67%
of that in Operation Example 1 was expected with theoretical simple
calculation, an
actual production amount was 1300 tons was considered that the whole of the
hydrometallurgical plant 10 was shut down when poor leaching occurred. That
is,
it is considered that, since the whole of the plant was shut down, the need to
perform the shutdown and re-startup of operation in the dezincification step
S5, the
nickel recovery step S6, or the like arose, and furthermore, operation
startups of the
= CA 02904569 2015-09-08
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ST14PCT1)
treatment facilities in the plant were timed to each other, and therefore,
excessive
shutdown time was needed.
[0149]
<Operation Example 4>
Using the same plant as the hydrometallurgical plant 10 used in Operation
Example 1, a 30-day hydrometallurgical operation was carried out.
[0150]
Also in Operation Example 4, as is the case with Operation Example 2,
during the period of the operation, poor leaching occurred five times in the
leaching
treatment tank 11(11) in the first line or the leaching treatment tank 1 1 (2)
in the
second line. Accordingly, the shutdown and startup operations of a line in
which
the poor leaching occurred were performed five times. At this time, in
Operation
Example 4, leach slurry discharged from the leaching treatment tank 11(1) or
11(2)
under the startup operation, that is, leach slurry having not sufficiently
undergone a
leach treatment yet and accordingly having a low nickel concentration was
transported as it was to the neutralization treatment tank 12B of the second
stage via
the neutralization treatment tank 12A(1) or 12A(2) of the first stage. It
should be
noted that, in such startup operation, an average time required from a
shutdown to a
return to normal was two days.
[0151]
As a result of the 30-day operation, the production amount of an obtained
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ST14PCT1)
nickel-cobalt mixed sulfide was 2250 tons (approximately 90% of that in
Operation
Example 1), but, the quality of the product was worse. Specifically, the
percentage of valuable metals in the nickel-cobalt mixed sulfide decreased and
varied, and thus, the nickel-cobalt mixed sulfide was a defective item which
is not
allowed to be delivered as a product, and accordingly had to be disposed of.
[0152]
The reason for this is considered that, also in the startup operation (unusual
operation), leach slurry obtained in a stage where leach treatment was not
sufficiently completed yet was transported to downstream steps as it was. That
is,
it is considered that leach slurry having a low nickel concentration was
transported
to downstream steps, and solid-liquid separated, and sulfurization treatment
was
applied to an obtained leachate having a low nickel concentration in the
nickel
recovery step S6, and therefore, a poor sulfurization reaction was caused, and
as a
result, the quality of the product was worse.
[0153]
It should be noted that, although set values of the valuable metal
concentrations in liquid phases of CCDs of the stages in the solid-liquid
separation
facility 13 were the same as those in Operation Example 1, leach slurry having
a
low concentration was frequently accepted, and therefore, concentrations in
the
solid-liquid separation tanks (CCD) varied more widely, thereby preventing
stable
operations from being performed.
= CA 02904569 2015-09-08
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[0154]
<Variations in nickel concentration of overflow liquid>
Next, in a case where the leaching treatment tank 11(1) or 11(2) in one line
(the first line or the second line) in the leaching step S1 stopped due to a
facility
trouble, and then a startup operation was performed, variations in the nickel
concentration of an overflow liquid in a solid-liquid separation tank (CCD1)
of the
first stage in each of the following Operation Example 5 and Operation Example
6
were examined.
[0155]
<Operation Example 5>
In Operation Example 5, as is the case with the foregoing Operation Example
2, only in a shutdown line, circulation to a leaching treatment tank was
performed at
the time of temperature increase, and then, acid leaching was started, an
operation
for liquid transport to the final neutralization facility 14 (in the final
neutralization
step S7) or a solid-liquid separation tank having a suitable nickel
concentration was
performed in accordance with the nickel concentration until the nickel
concentration reached a predetermined concentration (refer to Fig. 4 to Fig.
6).
[0156]
The following table 1 shows variations in the nickel concentration (g/L) of an
overflow liquid from the solid-liquid separation tank (CCD1) of the first
stage in the
case of performing the foregoing operation. As shown in Table 1, it is found
that,
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in this Operation Example 5, the nickel concentration was maintained very
stably at
the same level since operation startup. Furthermore, in a sulfurization
reaction in
the sulfurization step as a downstream step of treating this overflow liquid,
the
reaction stably proceeded without causing a poor reaction and the like.
[0157]
<Operation Example 6>
In Operation Example 6, as is the case with the foregoing Operation Example
4, all of a liquid at the time of temperature increase in a shutdown line and
a
leachate having a nickel concentration not reaching a predetermined
concentration
yet immediately after start of acid leaching were transported to the
preliminary
neutralization tank 12B of the second stage in the same manner as in a line in
which
the normal operation continued.
[0158]
The following table 1 shows variations in the nickel concentration (g/L) of an
overflow liquid from the solid-liquid separation tank (CCD1) of the first
stage in the
case of performing the foregoing operation. As shown in Table 1, it is
understood
that the nickel concentration sharply decreased from operation startup for
half a day.
Thus, such sharp decrease in the nickel concentration made it very difficult
to
control the sulfurization reaction in a sulfurization step as a downstream
step,
whereby a poor sulfurization reaction and an excessive sulfurization reaction
were
caused.
= CA 02904569 2015-09-08
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403; ST14PCT1)
[0159]
[Table 1]
Nickel concentration of overflow liquid (g/L)
Operation Example 5 Operation Example 6
Start 3.2 3.0
2 hours later 3.1 3.3
4 hours later 3.3 2.8
6 hours later 3.3 2.4
8 hours later 3.2 2.1
hours later 3.0 2.5
12 hours later 3.2 2.8
14 hours later 3.1 2.9
16 hours later 3.3 3.1
18 hours later 3.2 3.2
