U.S. patent application number 17/683422 was filed with the patent office on 2022-06-16 for apparatus for recovering lithium hydroxide.
The applicant listed for this patent is METSO OUTOTEC FINLAND OY. Invention is credited to Liisa HAAVANLAMMI, Sami KINNUNEN, Eero KOLEHMAINEN, Juho SAVIKANGAS, Marika TIIHONEN.
Application Number | 20220185686 17/683422 |
Document ID | / |
Family ID | 1000006167973 |
Filed Date | 2022-06-16 |
United States Patent
Application |
20220185686 |
Kind Code |
A1 |
TIIHONEN; Marika ; et
al. |
June 16, 2022 |
APPARATUS FOR RECOVERING LITHIUM HYDROXIDE
Abstract
An arrangement for recovering lithium hydroxide from a mineral
containing lithium, by pulping the raw material containing lithium
in the presence of water and an alkali metal carbonate, leaching
the obtained slurry twice, first at an elevated temperature, and
secondly in an aqueous solution containing an alkali earth metal
hydroxide, separating the thus obtained slurry into solids and a
solution containing lithium hydroxide, the latter being purified,
whereby lithium hydroxide monohydrate can be recovered from the
purified solution by crystallising, and finally separating the
solution obtained during the crystallization from the process and
recycling it to one or more of the previous process steps.
Inventors: |
TIIHONEN; Marika; (Espoo,
FI) ; HAAVANLAMMI; Liisa; (Espoo, FI) ;
KOLEHMAINEN; Eero; (Pori, FI) ; KINNUNEN; Sami;
(Pori, FI) ; SAVIKANGAS; Juho; (Pori, FI) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
METSO OUTOTEC FINLAND OY |
Tampere |
|
FI |
|
|
Family ID: |
1000006167973 |
Appl. No.: |
17/683422 |
Filed: |
March 1, 2022 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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16951066 |
Nov 18, 2020 |
11292725 |
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17683422 |
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PCT/FI2019/050275 |
Apr 5, 2019 |
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16951066 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
B01J 39/16 20130101;
B01D 61/58 20130101; C01D 15/02 20130101 |
International
Class: |
C01D 15/02 20060101
C01D015/02; B01D 61/58 20060101 B01D061/58; B01J 39/16 20060101
B01J039/16 |
Foreign Application Data
Date |
Code |
Application Number |
May 18, 2018 |
FI |
PCT/FI2018/050377 |
Claims
1.-83. (canceled)
84. An arrangement for recovering lithium hydroxide from a raw
material containing lithium the arrangement comprising: a pulping
unit for pulping the raw material containing lithium in the
presence of water and an alkali metal carbonate, a first leaching
unit for leaching a first slurry containing lithium at an elevated
temperature, a second leaching unit for leaching a second slurry
containing lithium carbonate, or a fraction thereof, in the
presence of water and an alkali earth metal hydroxide, a
solid-liquid-separation unit for separating a third slurry
containing lithium hydroxide into solids and a solution containing
lithium hydroxide, a purification unit connected to the
solid-liquid-separation unit, for purifying the solution obtained
from said separation unit, and a crystallising unit for recovering
lithium hydroxide monohydrate from a solution containing lithium,
which further comprises a line for carrying a solution from the
crystallizing unit to a point further upstream of the
crystallization unit, or back to the crystallization unit,
comprising a recycle line arranged between the crystallizing unit,
and/or a liquid section of a solid-liquid separation unit connected
to the crystallization unit, and the second leaching unit.
85. The arrangement according to claim 84, which includes a recycle
line leading from the first leaching unit, or from the liquid
section of a solid-liquid separation unit placed in connection with
said first leaching unit, either as line to the pulping unit or as
line to the first leaching unit, or a separate line and to each,
optionally at least to the pulping unit.
86. The arrangement according to claim 84, wherein the second
leaching unit is connected to a slurrying unit for mixing an alkali
earth metal hydroxide into an aqueous slurry.
87. The arrangement according to claim 84, which purification unit
includes an ion exchange unit or a membrane separation unit,
optionally a cation exchange unit, particularly containing a
selective cation exchange resin, and wherein the purification unit
most suitably is a combination of a membrane separation unit and an
ion exchange unit, wherein the membrane separation unit has an
outlet that is connected to an inlet of the ion exchange unit.
88. The arrangement according to claim 84, wherein the
crystallization unit, or a downstream purification unit, or a
downstream regeneration unit is connected to the second leaching
unit, or the downstream solid-liquid separation unit via liquid
line.
89. The arrangement according to claim 84, which comprises a
recycle line arranged between the crystallizing unit, and/or the
liquid section of a solid-liquid separation unit connected to the
crystallization unit, and an upstream unit.
90. The arrangement according to claim 84, which comprises a
recycle further line arranged between the crystallization unit,
and/or the liquid section of a solid-liquid separation unit
connected to the crystallization unit, and the pulping unit.
91. The arrangement according to claim 84, which comprises a
lithium precipitation unit connected to the crystallization unit or
the solid-liquid separation unit through a line, which unit in turn
optionally includes a feed inlet for feeding carbon dioxide or an
alkali metal carbonate to the unit.
92. The arrangement according to claim 84, which includes a
purification unit connected to the crystallization unit, and/or to
a solid-liquid separation unit connected to the crystallization
unit, wherein the solids obtained in the crystallization step can
be purified.
93. The arrangement according to claim 84, which includes a recycle
line leading from the first leaching unit, or from the liquid
section of a solid-liquid separation unit placed in connection with
said first leaching unit, to the pulping unit.
Description
FIELD OF THE INVENTION
[0001] The present invention relates to a method and an arrangement
for recovering lithium hydroxide.
BACKGROUND OF THE INVENTION
[0002] CN102115101 discloses a method for producing lithium
carbonate from spodumene mineral by performing a sulfuric acid
treatment in order to obtain lithium sulfate, followed by a step of
preparing the lithium carbonate mother liquor, from which the
carbonate product can be separated, and finally the lithium
hydroxide is obtained from the mother liquor by adding lime to
causticize said mother liquor. Also barium hydroxide is said to be
useful as a causticizing hydroxide.
[0003] CN 100455512 C discloses a process for preparing lithium
hydroxide monohydrate by adding sodium hydroxide to a lithium
sulfate solution in order to obtain liquid lithium hydroxide,
followed by cooling, filtering and separating the lithium hydroxide
from the sodium sulfate, whereafter a series of recrystallization
steps are performed to provide the pure lithium hydroxide
monohydrate.
[0004] In CN 1214981 C a similar process is described, wherein the
step of adding sodium hydroxide into the lithium sulfate solution
is carried out, followed by cooling and separating to obtain the
liquid lithium hydroxide. The lithium hydroxide solution is then
concentrated and crystallized, whereby a coarse lithium hydroxide
monohydrate product can be separated. In this publication the pure
lithium hydroxide monohydrate is obtained by reacting the coarse
product with barium hydroxide, followed by concentrating and
crystallizing.
[0005] However, these processes all proceed via the lithium
sulfate.
BRIEF DESCRIPTION OF THE INVENTION
[0006] An object of the present invention is thus to provide a
method and an arrangement for recovering lithium hydroxide with
high yield and high purity, typically of battery grade, without the
need for multiple purification steps.
[0007] Particularly, it is an object of the invention to provide a
method and an arrangement for recovering lithium hydroxide with
high yield and high purity, typically of battery grade, using
simple purification steps and recirculations.
[0008] Battery grade lithium hydroxide herein means lithium
hydroxide monohydrate crystals having a purity of 56.5%, or higher
of lithium hydroxide.
[0009] In addition, the process concept is sulphate and acid free,
without the formation of undesired crystallized byproducts. The
objects of the invention are achieved by a method and an
arrangement which is characterized by what is stated in the
independent claims. The preferred embodiments of the invention are
disclosed in the dependent claims.
[0010] The present invention relates to a method for recovering
lithium hydroxide from a raw material containing lithium. The
method comprises the following steps of [0011] pulping the raw
material containing lithium in the presence of water and an alkali
metal carbonate for producing a first slurry containing lithium,
[0012] leaching the first slurry containing lithium in a first
leaching step at an elevated temperature for producing a second
slurry containing lithium carbonate, [0013] leaching the second
slurry or a fraction thereof in a second leaching step in an
aqueous solution containing an alkali earth metal hydroxide for
producing a third slurry containing lithium hydroxide, [0014]
separating the third slurry into solids and a solution containing
lithium hydroxide by solid-liquid separation and providing a
purified solution containing lithium hydroxide, and [0015]
recovering lithium hydroxide monohydrate by crystallising from the
purified solution containing lithium hydroxide.
[0016] Preferably, the method further comprises the steps of [0017]
purifying the solution separated from the solids of the third
slurry in a separate purification step, and [0018] separating the
solution obtained during the crystallization from the process, and
recycling it to one or more of the previous process steps, or back
to the crystallization
[0019] According to an embodiment of the present invention the raw
material containing lithium can be any raw material from which it
is desired to recover lithium. Typically the raw material
containing lithium is selected from a mineral containing lithium,
preferably from spodumene, petalite or lepidolite or mixtures
thereof, most suitably from spodumene.
[0020] According to an embodiment of the present invention the raw
material containing lithium is selected from a mineral containing
lithium which has undergone heat treatment, whereby a particularly
preferred material is beta-spodumene.
[0021] According to an embodiment of the present invention the
first leaching solution is separated from the solids after the
first leaching step, whereby only the solids are carried to the
second leaching step.
[0022] According to an embodiment of the present invention the
first leaching solution is separated from the solids after the
first leaching step and is recycled either to the pulping step or
to the first leaching step, or a fraction to each.
[0023] According to an embodiment of the present invention the
solids are separated from the solution in the separation step by
any suitable solid-liquid separation method, typically by
thickening and/or filtering.
[0024] According to an embodiment of the present invention the
purifying step carried out on the solution obtained from the second
solid/liquid separation step, is preferably performed by ion
exchange, typically by using cation exchange resin.
[0025] According to an embodiment of the present invention the
crystallising of the lithium hydroxide monohydrate is performed by
heating and cooling, or alternatively by merely concentrating the
solution by heating.
[0026] According to an embodiment of the present invention the
bleed solution obtained while crystallizing the lithium hydroxide
monohydrate is recovered and recycled to one or more of the
previous process steps, for example the pulping step, the second
leaching step, a separation step, and/or back to the
crystallization step.
[0027] Optionally, the bleed solution obtained from the
crystallization step is pretreated prior to recycling it to
previous process steps, e.g. by carbonation, using a carbonate or
CO.sub.2.
[0028] When performing a first, optional, solid-liquid separation
between the leaching steps, it is possible to recover the solution
used in the first leaching step, containing any excess of the
leaching chemical, i.e. the alkali metal carbonate, and recycle it.
This recycling, in turn, reduces the need for a separate pH
adjustment in the later stages of the process, and likewise reduces
the chemical consumption in the process.
[0029] According to a preferred embodiment of the present
invention, when a first solid-liquid separation is carried out
between the two leaching steps, the obtained solids are partly
recovered and carried to a separate process for recovering pure
lithium carbonate.
[0030] When applying this preferred embodiment, the method can also
include the steps of recycling the crystallized lithium carbonate
to the second hydroxide leaching step.
[0031] The present invention relates also to an arrangement for
recovering lithium hydroxide from a raw material containing lithium
according to the above method, which arrangement comprises [0032] a
pulping unit 1 for pulping the raw material containing lithium in
the presence of water and an alkali metal carbonate, [0033] a first
leaching unit 2 for leaching a first slurry containing lithium at
an elevated temperature, [0034] a second leaching unit 3 for
leaching a second slurry containing lithium carbonate, or a
fraction thereof, in the presence of water and an alkali earth
metal hydroxide, [0035] a solid-liquid-separation unit 31 for
separating a third slurry containing lithium hydroxide into solids
and a solution containing lithium, and [0036] a crystallising unit
4 for recovering lithium hydroxide monohydrate from a solution
containing lithium.
[0037] Preferably, the arrangement further comprises: [0038] a
purification unit 32 connected to the solid-liquid-separation unit
31, for purifying the solution obtained from said separation unit
31, and a line 403, 414 for carrying a solution from the
crystallizing unit 4 to a point further upstream of the
crystallizing unit (4), or back to the crystallization unit 4.
[0039] According to an embodiment of the invention the arrangement
comprises also the necessary lines for carrying the solutions to be
recycled to their intended units.
BRIEF DESCRIPTION OF THE DRAWINGS
[0040] In the following the invention will be described in greater
detail by means of preferred embodiments with reference to FIGS. 1,
2, 3, 4 and 5, which all show general flow diagrams and
arrangements of units of certain embodiments of the invention.
DETAILED DESCRIPTION OF THE INVENTION
[0041] An embodiment of the method of the invention, as presented
schematically in FIG. 1, is a method for recovering lithium
hydroxide from a raw material containing lithium, the method of
this particular embodiment including pulping 1 the raw material in
the presence of sodium carbonate, leaching the obtained slurry in a
first leaching step 2, followed by leaching in a second leaching
step 3, in the presence of calcium hydroxide, whereafter the
obtained slurry is separated 31 into solids and a liquid, whereby
the liquid can be carried to a crystallization step 4, for
producing high purity lithium hydroxide.
[0042] Another embodiment of the invention, as presented
schematically in FIG. 2, is a method for recovering lithium
hydroxide from a raw material containing lithium, this embodiment
further specifying that a first solid-liquid separation 21 can be
carried out already after the first leaching step 2, whereby at
least a fraction of the liquid fraction can be recycled to either
the pulping step 1, via line 211, or to the first leaching step 2,
via line 212.
[0043] Further embodiments of the invention are illustrated in
FIGS. 3 to 5, whereby FIG. 3 shows a number of optional details of
the method and arrangement of the invention, based on a specific
embodiment, and FIGS. 4 and 5 show a couple of specific options
relating to the purification step 32. All these options are
described in more detail below.
[0044] The dotted lines in the drawings indicate that the units
within these dotted lines can be combined in certain embodiments of
the invention.
[0045] In the present invention, the raw material containing
lithium is typically selected from spodumene, petalite, lepidolite
or mixtures thereof. The raw material is a preferably a
lithium-containing mineral in calcined form, more preferably
obtained by heat treating the raw material, most suitably by using
a temperature of approximately 1050.degree. C.
[0046] A particularly preferred mineral is spodumene, providing
beta-spodumene in a calcination step.
[0047] The method of the invention comprises pulping 1 the raw
material containing lithium in the presence of water and an alkali
metal carbonate for extracting the lithium from the raw material
and producing a first slurry containing lithium. The pulping 1 can
be performed in any suitable vessel or reactor by contacting a feed
containing lithium mineral with an alkali metal carbonate and water
for producing a first slurry containing lithium.
[0048] The alkali metal carbonate is preferably selected from
sodium and potassium carbonate, most suitably being at least partly
composed of sodium carbonate. Typically, the alkali metal carbonate
is present in excess. After pulping, the first lithium-containing
slurry is leached 2 for a first time for producing a second slurry
containing lithium carbonate.
[0049] The presence of alkali metal carbonate and process
conditions result in the formation of lithium carbonate and
analcime solids, which can be presented in the case of spodumene
and sodium carbonate with the following formula (1).
2LiAl(SiO.sub.3).sub.2+Na.sub.2CO.sub.3=2NaAl(SiO.sub.3).sub.2+Li.sub.2C-
O.sub.3 (1)
[0050] The first leaching 2 of the first slurry containing lithium
is typically performed in a suitable autoclave or series of
autoclaves at an elevated temperature.
[0051] In an embodiment of the invention, the first leaching step
is carried out at a temperature of 160 to 250.degree. C.,
preferably at a temperature of 200 to 220.degree. C. Likewise, the
first leaching step is preferably carried out at a pressure of 10
to 30 bar, preferably 15 to 25 bar. Suitable conditions for the
first leaching step are typically achieved using high-pressure
steam.
[0052] In another embodiment, at least a fraction of the water and
alkali metal carbonate carried to the pulping step is a recycled
aqueous solution containing said alkali metal carbonate.
[0053] An optional solid-liquid separation step 21 can be carried
out, wherein the solution can be separated from the solids after
the first leaching step 2, and the solids carried to the second
leaching step 3.
[0054] In an embodiment, the solution separated from the solids in
the optional separation step 21 is recycled to one or more of the
preceding steps.
[0055] Preferably, the solution is recycled either to the pulping
step or to the first leaching step, or a fraction to each. More
preferably, the solution is recycled to the pulping step.
[0056] In the second leaching step 3, the lithium-containing phase
(here typically the solids, or the entire second slurry) is leached
3 for a second time using a hydroxide reagent, i.e. an alkaline
earth metal hydroxide, followed by a separation of solids from the
solution by solid-liquid separation 31 and by the preparation of
lithium hydroxide-containing solution of relatively high
purity.
[0057] The alkali earth metal hydroxide used in the second leaching
step 3 is preferably selected from calcium and barium hydroxide,
more preferably being calcium hydroxide, optionally prepared by
reaction of calcium oxide (CaO) in the aqueous solution.
[0058] In an embodiment of the invention, the alkali earth metal
hydroxide used in the second leaching step 3 is mixed with water or
an aqueous solution prior to addition to the second leaching step
3.
[0059] Preferably, at least a fraction of the solution separated
from the solids in separation step 31, containing among others
lithium and sodium, is added to said second leaching step in the
form of a recycled solution, preferably mixed with fresh alkali
earth metal hydroxide prior to addition to the second leaching
step, more preferably mixed with fresh alkali earth metal hydroxide
in a separate slurrying step 30.
[0060] The second leaching step 3 is typically carried out at a
temperature of 10-100.degree. C., preferably 20-60.degree. C., and
most suitably 20-40.degree. C. Typically, the second leaching step
3 is carried out at atmospheric pressure.
[0061] The presence of alkaline earth metal hydroxide and process
conditions result in the formation of lithium hydroxide, which can
be presented in the case of analcime, lithium carbonate and calcium
hydroxide with the following formula (2).
2NaAl(SiO.sub.3).sub.2+Li.sub.2CO.sub.3+Ca(OH).sub.2=2NaAl(SiO.sub.3).su-
b.2+CaCO.sub.3+2LiOH (2)
[0062] After the two leaching steps 2, 3 have been performed, the
obtained third lithium hydroxide-containing slurry is separated 31
into a solid phase and a solution. The separation 31 can be done
with any suitable solid-liquid separation method. For example, the
third slurry can be routed to a thickener, from where the overflow
can be routed directly to purification and the underflow can be
filtered further in order to recover all lithium hydroxide present
in the solution and separate it from solid impurities, or a simple
filtering technique can be used. Typically, all solid-liquid
separations described herein require a supply of washing water for
washing of the solids, although no such supply is separately
mentioned. The obtained solids from this separation of the third
slurry into solids and a solution are typically composed of
unwanted residues, which can be discarded, e.g. as tailings.
[0063] As stated above, the third slurry separated from the second
leaching step 3 is purified 32 before carrying it to the
crystallization step. This purification step is preferably based on
purification of dissolved ions and components, and more preferably
includes an ion exchange or a membrane separation, or both, most
suitably by using a cation exchange resin, particularly a selective
cation exchange resin.
[0064] The ion exchange can be performed for example by using a
method disclosed in Finnish patent 121 785.
[0065] Typically the purifying by ion exchange is performed by
using cation exchange resin, wherein the cation exchange group is
for example iminodiacetic acid (IDA) or aminophosphonic acid
(APA).
[0066] Selective cation exchange resins typically have a chelating
functional group attached to the resin matrix. These chelating
functional groups usually have a much higher selectivity towards
multi-valent metal cations, such as heavy and alkaline earth metal
cations, compared to the monovalent alkali metal cations (Li, Na,
K). Suitable resin functionalities are, for example the above
mentioned iminodiacetate and the aminophosphonate. These chelating
resins can be used to purify the typical cationic impurities, such
as calcium ions (Ca.sup.2+) from lithium hydroxide solutions.
[0067] In an embodiment, the step of purifying the solution
obtained from the third slurry is carried out at least partly using
a resin that has been regenerated in a separate regeneration
step.
[0068] Preferably, the regeneration step is carried out using a
recycled solution from a subsequent process step, more preferably
being the separated solution obtained during the crystallization,
optionally in purified form.
[0069] In a preferred embodiment, this regeneration is carried out
using at least acidic solution for metal elution, preferably being
hydrochloric acid (HCl), and an alkaline solution for
neutralization, preferably being sodium hydroxide (NaOH) or an
alkaline lithium hydroxide solution, more preferably a recycled
solution containing lithium hydroxide. Further, water can be fed to
the regeneration step. The regenerated resin can be fed back to the
ion exchange.
[0070] These purification and regeneration steps can, however, also
be combined, and carried out in the same purification unit.
[0071] The membrane separation can be carried out using a
semi-permeable membrane, which separates ionic or other dissolved
compounds from aqueous solutions. More precisely, the membrane
separation can be used to fractionate the dissolved ions and
compounds by their size (depending on the pore size of the membrane
material), and/or their charge (depending on the surface charge of
the membrane material). A positive surface charge repels cations
(with a stronger repelling action for multi-valent cations) and
attracts anions, and vice versa. These phenomena will enable the
purification of, for example, multi-valent metal cations, complexed
species (such as aluminium hydroxide complexes), polymeric species
(such as dissolved silica) and larger anions (e.g. sulfate and
carbonate ions) from lithium hydroxide solutions. With the membrane
separation, no regeneration is required.
[0072] Since lithium hydroxide is a strong alkali having a high
concentration of hydroxide ions, metals that are strongly complexed
by hydroxide ions (such as aluminium ions, Al.sup.3+) cannot be
purified by the above mentioned selective cation exchange resins.
Therefore, these ions are purified using the herein described
recirculations.
[0073] The selective cation exchange is preferably used in the
polishing removal of multivalent metal cations that form sparingly
soluble hydroxide compounds (typically calcium hydroxide). These
metals (or metal cations) should be removed, or at least their
concentrations should be reduced to very low levels in the solution
to be carried to the crystallization, in order to prevent them from
contaminating the crystallized lithium hydroxide monohydrate
product. The removal of these metals is not as efficient with
membranes, and is thus preferably done by ion exchange,
particularly with a selective cation exchange resin.
[0074] In case a membrane separation is carried out, either alone
or combined with an ion exchange, a recycle stream is provided from
the membrane separation, which is suitable for carrying to the
second leaching step 3.
[0075] In membrane separation, the retained ions and compounds will
end up in a concentrated fraction, typically called the
"retentate", which can be recycled to the second leaching step as
described above. The other obtained fraction is the permeated
liquid fraction, i.e. the "permeate", which is fed to the
crystallization, optionally via the ion exchange purification, if
these purifications are combined.
[0076] The fraction to which each ion and compound ends up in the
membrane separation depends on their characteristics: for example
their charge and size. This targeting of the retention can be done
based on selection of the desired membrane type, based on surface
charge and/or pore size.
[0077] For the charge, the targeted retained species would
typically be multivalent metal cations, for example: calcium ions
(Ca.sup.2+), magnesium ions (Mg.sup.2+) vs. permeated (or zero to
negatively retained) monovalent alkali metal cations, such as
lithium ions (Li.sup.+) or sodium ions (Na.sup.+).
[0078] For the size, the retained species would typically be larger
compounds, for example: polymeric species (such as dissolved
silica), complexed ions (such as aluminium hydroxide complexes),
and the largest types of anions (such as carbonate,
CO.sub.3.sup.2-, and sulfate, SO.sub.4.sup.2-), whereas the
smallest types of anions (such as hydroxide, OH.sup.-), are
permeated (or: has zero or negative retention).
[0079] Based on the above, it is particularly preferred to combine
a membrane separation with an ion exchange, most suitably by first
carrying out a membrane separation, and then an ion exchange for
polishing removal of multivalent metal cations.
[0080] Finally, crystals of lithium hydroxide monohydrate are
recovered by crystallising 4 from the purified lithium-containing
solution. The crystallizing is typically performed by heating the
purified solution containing lithium to a temperature of
approximately the boiling point of the solution, to evaporate the
liquid, or by recrystallizing the monohydrate from a suitable
solvent.
[0081] In an embodiment of the invention, two or more
crystallization units are used, preferably being sequentially
arranged.
[0082] The method of the invention enables production of pure
lithium hydroxide monohydrate with excellent yield and purity in a
continuous and simple process, typically providing battery grade
lithium hydroxide monohydrate crystals, having a purity of 56.5% or
higher of lithium hydroxide.
[0083] In another embodiment, the purified solution containing
lithium hydroxide is mixed with one or more solutions recycled from
subsequent steps of the method before being carried to the
crystallization step 4, or these solutions can be fed separately to
the crystallization 4.
[0084] Preferably, the crystallization step 4 is followed by a
solid-liquid separation step 41.
[0085] The bleed solution obtained while crystallizing 4 the
lithium hydroxide monohydrate can be recovered and recycled to one
or more of the previous process steps, for example the pulping step
1, second leaching step 3, a separation step 31, and/or back to the
crystallization step 4.
[0086] Thus, it is preferred to recycle at least a fraction of the
solution separated from the crystallization step to a preceding
step with lower alkalinity, or back to the crystallization step
4.
[0087] The advantage achieved by recycling said fraction to a
preceding step with lower alkalinity is that some impurities in the
crystallization liquids (e.g. aluminium and silicon) have a
solubility that increases with increasing alkalinity (e.g. caused
by increasing lithium hydroxide concentration), whereby these
alkali-soluble impurities can be removed by recycling them in
solution to a step of lower alkalinity. One preferred alternative
is to recycle at least a fraction of said crystallization liquid,
or bleed solution, to the second leaching step 3, or to a preceding
step (typically the pulping or first leaching), from which they can
be carried to the second leaching step 3. In said lower alkalinity
environment, these impurities form sparingly soluble compounds
(e.g. aluminium hydroxide), and can be discarded with the solids in
separation step 31. Also soluble carbonate ions are carried to the
second leaching step 3, or to a preceding step (typically the
pulping 1 or first leaching 2, from which they can be carried to
the second leaching step) using this recycle option. Carbonate ions
form sparingly soluble compounds in the second leaching step 3 and
can be discarded with the solids in the separation step 31.
[0088] In an embodiment of the invention, at least a fraction of
the solution separated from the crystallization step is recycled to
the second leaching step, and optionally a further fraction to the
pulping step. The advantage of these recycling options is that the
soluble impurities remaining in the liquids after crystallization
(main impurities being sodium, potassium, aluminium and carbonate
ions, as well as soluble silicon and silicates) can be circulated
upstream, where they can be removed. Particularly in the leaching
steps, these impurities form sparingly soluble compounds, which can
be discarded as solids after the second leaching step. Without this
recycling option, these impurities are typically concentrated in
the crystallization step, and contaminated in the product.
[0089] In another embodiment, at least a fraction of the solution
separated from the crystallization step is recycled back to the
crystallization step. In a typical crystallization process, the
crystallization slurry is maintained in a continuous circulation,
from which product crystals are continuously separated, and the
advantage of recycling at least a fraction of the remaining mother
liquid is that it increases the yield of the process.
[0090] As mentioned above, it is preferred to recycle at least a
fraction of the solution separated from the crystallization step to
the second leaching step or back to the crystallization. It is,
however, particularly preferred to recycle the solution at least to
the second leaching, or advantageously to both the second leaching
and the crystallization.
[0091] In a further embodiment, at least a fraction of the solution
separated from the crystallization step is carried to a lithium
precipitation step, which preferably is carried out as a
carbonation, wherein the solution is reacted with either carbon
dioxide or an alkali metal carbonate in order to form a lithium
carbonate slurry.
[0092] This optional lithium precipitation step has the advantage
of reacting lithium hydroxide contained in the crystallization
bleed solution into the corresponding carbonate. This lithium
hydroxide should preferably not be returned to the pulping or first
leaching steps of the process.
[0093] After the optional lithium precipitation step, the lithium
carbonate slurry is preferably subjected to a solid-liquid
separation step, from which at least a fraction of the solids is
carried to a conversion step. In this preferred conversion step,
the solids are mixed with an alkali earth metal slurry, the
conversion step preferably performed at a temperature close to the
boiling point of water, more preferably at a temperature of 90 to
100.degree. C., whereby the lithium carbonate of the solids is
solubilized as lithium hydroxide, also forming calcium
carbonate.
[0094] After the optional lithium precipitation step, the lithium
carbonate slurry is preferably subjected to a solid-liquid
separation step, from which at least a fraction of the solids is
carried to a conversion step, and then recycled to the solid-liquid
separation step following the second leaching step.
[0095] Preferably, at least a fraction of the solution separated
from the solids after the optional lithium precipitation step is
recycled to the pulping step, or to the first leaching step, or a
fraction to each, more preferably at least a fraction to the
pulping step.
[0096] The advantage achieved by recycling said fraction to pulping
or first leaching is that some impurities (e.g. sodium and
potassium) have a high solubility in the crystallization liquids,
but these impurities form sparingly soluble compounds (e.g.
analcime) in the pulping and/or first leaching step and they can be
discarded in the separation step 31.
[0097] In an embodiment of the invention, the solids obtained in
the crystallization step, containing crystals of lithium hydroxide
monohydrate, are purified using a washing solution before recovery
as the product.
[0098] The purified crystals of lithium hydroxide monohydrate are
preferably separated from the washing solution, are dried, and
thereafter recovered.
[0099] The spent washing solution is, in turn, preferably separated
from the purified crystals of lithium hydroxide monohydrate, and is
recycled to the crystal washing step or to a step of regenerating a
resin intended for being carried to the purification step, or to
the crystallization step, or a fraction of the spent washing
solution is recycled to two or all three of these steps.
[0100] It is particularly preferred to recycle at least a fraction
of this spent washing solution (or crystallization mother liquid)
to the regeneration step, since the solution is relatively pure and
contains uncrystallized lithium hydroxide, which should be reused,
particularly in a step upstream from the crystallization, or in the
crystallization. Thus, the regeneration 33 is an option for the
recycling.
[0101] The present invention relates also to an arrangement for
recovering lithium hydroxide from a raw material containing lithium
according to the method of the present invention. The referral
numbers referring to FIG. 1 in connection with the description of
the method correspond to the referral numbers used in connection
with the description of the arrangement, thus the method steps of
the method correspond to the units of the arrangement. The
arrangement comprises [0102] a pulping unit 1 for pulping the raw
material containing lithium in the presence of water and an alkali
metal carbonate, [0103] a first leaching unit 2 for leaching a
first slurry containing lithium at an elevated temperature, [0104]
a second leaching unit 3 for leaching a second slurry containing
lithium carbonate, or a fraction thereof, in the presence of water
and an alkali earth metal hydroxide, [0105] a
solid-liquid-separation unit 31 for separating a third slurry
containing lithium hydroxide into solids and a solution containing
lithium hydroxide, [0106] a purification unit 32 connected to the
solid-liquid-separation unit 31, for purifying the solution
obtained from said separation unit 31, and [0107] a crystallising
unit 4 for recovering lithium hydroxide monohydrate from a solution
containing lithium, [0108] which further comprises a line 403, 414
for carrying a solution from the crystallizing unit 4 to a point
further upstream of the crystallizing unit 4, or back to the
crystallization unit 4.
[0109] In an embodiment of the invention, the arrangement further
comprises a calcination unit 10 for heat treating the raw material
intended to be carried to the pulping unit 1.
[0110] The pulping unit 1 preferably contains also a feed inlet 101
for supplying the raw material containing lithium to the unit
1.
[0111] Further, an inlet 111 can be added, in connection with the
pulping unit 1, for carrying a recycled aqueous solution containing
alkali metal carbonate to the pulping unit 1.
[0112] The first leaching unit 2 is preferably an autoclave.
[0113] In an embodiment, the first leaching unit 2 is connected to
the pulping unit 1 via a slurry line 102.
[0114] In an embodiment, a solid-liquid separation unit 21 is
arranged between the first leaching unit 2 and the second leaching
unit 3.
[0115] Preferably, a recycle line 211, 212 leads from the first
leaching unit 2, or from the liquid section of a solid-liquid
separation unit 21 connected to said first leaching unit 2, to a
unit upstream from said first leaching unit 2.
[0116] More preferably, a recycle line 211, 212 leads from the
first leaching unit 2, or from the liquid section of a solid-liquid
separation unit 21 placed in connection with said first leaching
unit 2, either as line 211 to the pulping unit 1 or as line 212 to
the first leaching unit 2, or a separate line 211 and 212 to
each.
[0117] Even more preferably, a recycle line 211 leading from the
first leaching unit 2, or from the liquid section of a solid-liquid
separation unit 21 connected to said first leaching unit 2, to the
pulping unit 1.
[0118] In an embodiment of the invention, the second leaching unit
3 is a tank reactor, preferably a stirred tank reactor.
[0119] Preferably, the second leaching unit 3 includes an inlet 303
for alkali earth metal hydroxide or an aqueous slurry thereof.
[0120] In another embodiment, the second leaching unit 3 is
connected to a slurrying unit 30 for mixing an alkali earth metal
hydroxide into an aqueous slurry.
[0121] In a further embodiment, the second leaching unit 3 is
connected to the first leaching unit 2, or to a downstream
solid-liquid separation unit 21, via a slurry line 203.
[0122] The purification unit 32 used in the purification of the
solution separated from the third slurry preferably includes a
membrane separation unit or an ion exchange unit, or both,
preferably an ion exchange unit, and more preferably a cation
exchange unit, particularly being a selective cation exchange
unit.
[0123] In a preferred embodiment (see FIG. 3), where the
purification unit 32 is an ion exchange unit, it is connected to a
regeneration unit 33 for regenerating a purification resin. This
regenerated resin can then be fed via a recycle line 332 back to
the ion exchange unit 32. However, these purification and
regeneration steps can also be carried out in a single unit 32 (see
dotted line around units 32 and 33 of FIG. 3).
[0124] No such regeneration is required when the purification unit
32 is a membrane separation unit (see FIG. 4). However, in the case
a membrane separation unit is used, the unit provides two streams,
one being a purified solution, which can be carried directly to the
crystallization unit 4, while the other is a recycle stream, which
is suitable for carrying to the second leaching unit 3, for example
via a recycle line 323.
[0125] In a further embodiment of the invention (see FIG. 5), the
arrangement of the invention can include both an ion exchange unit
32a and a membrane separation unit 32b, and thus also a
regeneration unit 33. Due to the presence of the membrane
separation unit 32b, a recycle stream can be provided, carrying a
recycle stream via line 323 to the second leaching unit 3.
[0126] In said embodiment it is particularly preferred to position
the ion exchange unit 32a downstream from the membrane separation
unit 32b.
[0127] In an embodiment of the invention, the arrangement includes
two or more crystallization units 4, preferably being sequentially
arranged.
[0128] Preferably, the crystallization unit 4, or a downstream
purification unit 32, or an optional regeneration unit 33, is
connected to the second leaching unit 3, or the downstream
solid-liquid separation unit 31 via liquid line 304.
[0129] In an embodiment, the arrangement comprises a solid-liquid
separation unit 41 connected to the crystallization unit 4 for
separating the crystals obtained in the crystallization unit 4 from
the spent solution.
[0130] Preferably, a recycle line 403, 414 is arranged between the
crystallizing unit 4, and/or the liquid section of the solid-liquid
separation unit 41 connected to the crystallization unit 4, and an
upstream unit.
[0131] More preferably, a recycle line 403 is arranged between the
crystallizing unit 4, and/or the liquid section of the solid-liquid
separation unit 41 connected to the crystallization unit 4, and the
second leaching unit 3, and optionally a further line arranged
between the crystallization unit 4, and/or the liquid section of
the solid-liquid separation unit 41 connected to the
crystallization unit 4, and the pulping unit 1.
[0132] In an embodiment of the invention, the arrangement comprises
a lithium precipitation unit 42 connected to the crystallization
unit 4 or the solid-liquid separation unit 41 through a line
421.
[0133] Preferably, the lithium precipitation unit 42 includes a
feed inlet 422 for feeding carbon dioxide or an alkali metal
carbonate to the unit 42.
[0134] More preferably, the arrangement includes a solid-liquid
separation unit 43 connected to and downstream from the lithium
precipitation unit 42.
[0135] Even more preferably, the lithium precipitation unit 42,
and/or a solids section of a solid-liquid separation unit 43
connected to said lithium precipitation unit 42, is connected via a
recycle line 434 to a conversion unit 44.
[0136] In an embodiment of the invention, the conversion unit 44
contains an inlet 344 for alkali earth metal hydroxide or an
aqueous slurry thereof.
[0137] Preferably, the conversion unit 44 is connected to a
slurrying unit 30 for mixing an alkali earth metal hydroxide into
an aqueous slurry, and from which slurry can be fed to the
conversion unit 44.
[0138] More preferably, the conversion unit 44 is connected via
line 443 to the second leaching unit 3, and/or to the solid-liquid
separation unit 31 connected to the second leaching unit 3.
[0139] In an embodiment, the liquid section of a solid-liquid
separation unit 41, 43, preferably a unit 43 following the optional
precipitation unit 42, is connected via line 431 to the pulping
unit 1, whereby at least a fraction of the solution obtained in the
separation unit 41, 43 can be recycled to said pulping unit 1.
[0140] Alternatively, the liquid section of said solid-liquid
separation unit 41, 43, preferably a unit 43 following the optional
precipitation unit 42, is connected via a further recycle line 432
to the first leaching unit 2, whereby at least a fraction of the
solution obtained in the separation unit 41, 43 can be recycled to
said first leaching unit 2.
[0141] The solids obtained in separation unit 41, 43, preferably a
unit 43 following the optional precipitation unit 42, can
optionally be recycled to a conversion unit 44 for solubilization,
particularly via a recycle line 434.
[0142] In an embodiment, the liquid section of the solid-liquid
separation unit 41 is connected to the crystallization unit 4 via
recycle line 414, for recycling the spent solution separated from
the crystallization step back to the crystallization unit 4.
[0143] In another embodiment of the invention, the arrangement
includes a purification unit 45 connected to the crystallization
unit 4, and/or to a solid-liquid separation unit 41 connected to
the crystallization unit 4, wherein the solids obtained in the
crystallization step can be purified.
[0144] Preferably, the purification unit 45 includes a feed inlet
451 for feeding a washing solution into the purification unit
45.
[0145] In an embodiment, the arrangement includes a solid-liquid
separation unit 46 connected to and downstream from the
purification unit 45, for separating the purified crystals of
lithium hydroxide monohydrate from the spent washing solution.
[0146] Preferably, the purification unit 45, or a solid-liquid
separation unit 46, connected to and downstream from the
purification unit 45 is connected via a recycle line 452 to the
upstream purification unit 32, or to an optional regeneration unit
33.
[0147] More preferably, a solid-liquid separation unit 46 connected
to and downstream from the purification unit 45 is connected via a
recycle line 464 to the crystallization unit 4.
[0148] Even more preferably, a solid-liquid separation unit 46
connected to and downstream from the purification unit 45 is
connected via a recycle line 465 to the purification unit 45.
[0149] In another option, the arrangement of the invention
comprises a combined purification unit 41, 45, 46 for purifying the
crystals obtained in the crystallization unit 4 from the spent
solution, and separating the purified crystals from the spent
washing solution.
[0150] In this alternative option, the recycle line 414 connects
the combined unit 41, 45, 46 to the crystallization unit. Likewise,
the feed inlet 451 is connected to the combined purification unit
41, 45, 46. Further, the recycle line 452 connects the combined
purification unit 41, 45, 46 is connected to the upstream
purification unit 32, or to a separate regeneration unit 33, and
the recycle 464 line connects the combined purification unit 41,
45, 46 to the crystallization unit (4). Finally, the recycle line
465 connects a solids section of the combined purification unit 41,
45, 46 to the liquid section of the same combined unit 41, 45,
46.
[0151] In an embodiment of the invention, the arrangement includes
a drying unit 47, connected to the crystallization unit 4, or
connected to a solids section of a solid-liquid separation unit 41,
46 downstream from the crystallization unit 4, wherein the obtained
crystals of lithium hydroxide monohydrate can be dried.
[0152] Preferably, the drying unit 47 includes a product outlet 471
through which the final, battery grade, product can be
recovered.
REFERENCE NUMBERS
[0153] The reference numbers according to an embodiment of the
present invention, as used in FIGS. 1 to 5, are shown below (some
of these units and lines being optional):
TABLE-US-00001 10 calcination unit 1 pulping unit 101 feed inlet
for supplying raw material to the pulping unit 1 102 slurry line
for carrying a first slurry from the pulping unit 1 to the first
leaching unit 2 111 feed inlet for supplying recycled solution to
the pulping unit 1 2 first leaching unit 203 slurry line for
carrying a second slurry from the first leaching unit 2 to the
second leaching unit 3 21 solid-liquid separation unit 211 recycle
line from separation unit 21 to pulping unit 1 212 recycle line
from separation unit 21 to first leaching unit 2 3 second leaching
unit 30 slurrying unit for mixing an alkali earth metal hydroxide
into an aqueous slurry 303 inlet for supplying alkali earth metal
hydroxide or an aqueous solution thereof to the second leaching
unit 3 304 liquid line for carrying a third slurry from the second
leaching unit 3, or from the separation unit 31, to the
purification unit 32 or to the optional regeneration unit 33 31
solid-liquid separation unit 313 recycle line for carrying a
solution obtained from the separation unit 31 to the second
leaching unit 3, or to the optional slurrying unit 30 32
purification unit downstream from the S/L separation unit 31, and
upstream from the crystallization unit 4 323 recycle line for
carrying a recycle stream from the purification unit 32 to the
second leaching unit 3 33 regeneration unit 332 recycle line for
carrying a regenerated stream from the regeneration unit 33 to the
purification unit 32 4 crystallizing unit 401 recycle line from
crystallizing unit 4 to pulping unit 1 (not shown in the drawings)
403 recycle line from crystallizing unit 4, or the separation unit
41, to the second leaching unit 3 41 solid-liquid separation unit
414 recycle line from a downstream point of the crystallization
unit 4, or from the separation unit 41, back to the crystallizing
unit 4 42 lithium precipitation unit 421 slurry line for carrying a
reacted slurry from the crystallization unit 4, or the separation
unit 41, to the lithium precipitation unit 42 422 feed inlet for
supplying carbon dioxide or an alkali metal carbonate to the
precipitation unit 42 43 solid-liquid separation unit 431 recycle
line for carrying a solution from the precipitation unit 42, or the
separation unit 43, to the pulping unit 1 432 recycle line for
carrying a solution from the precipitation unit 42, or the
separation unit 43, to the first leaching unit 2 434 recycle line
for carrying a solid fraction from the lithium precipitation unit
42, or the separation unit 43, to the conversion unit 44 44
conversion unit 344 inlet for supplying the conversion unit with
alkali earth metal hydroxide or an aqueous slurry thereof 443
recycle line for carrying slurry from the conversion unit 44 to the
second leaching unit 3 or the separation unit 31 45 purification or
washing unit 451 feed inlet for supplying washing solution to the
purification or washing unit 45 452 recycle line for carrying spent
washing solution to the upstream purification unit 32, or to an
optional regeneration unit 33 46 solid-liquid separation unit 464
recycle line for carrying spent solution from purification unit 45
or the separation unit 46 to the crystallization unit 4 465 recycle
line for carrying spent solution from purification unit 45 or the
separation unit 46 to the purification or washing unit 45 47 drying
unit 471 product outlet for crystallized and optionally purified
and dried lithium hydroxide monohydrate
[0154] It will be obvious to a person skilled in the art that, as
the technology advances, the inventive concept can be implemented
in various ways. The invention and its embodiments are not limited
to the examples described above but may vary within the scope of
the claims.
EXAMPLES
Example 1
[0155] The soda leaching was carried out on a slurry containing
lithium, and obtained by pulping a beta-spodumene mineral sample.
The leaching was performed in an autoclave with the presence of
high-pressure steam and at a temperature of 220.degree. C. with a
retention time of 1.5 h, with an initial solids content of 29.5
wt-%, a sodium to lithium excess in the feed of 10%, giving a pH of
about 11.5.
[0156] The solids were separated from the obtained leached solution
through filtration, and the obtained solid fraction was carried to
a second leaching vessel, where leaching tests were carried out as
shown in the following Table 1:
TABLE-US-00002 TABLE 1 Temper- Time ature Li Na Al Ca Mn Mg P K Fe
Si B Be S Ti Bi Test h .degree. C. pH mg/L mg/L mg/L mg/L mg/L mg/L
mg/L mg/L mg/L mg/L mg/L mg/L mg/L mg/L mg/L CL1 1 38 10.9 6610 630
51 11 <1 <1 <50 30 <2 161 <2 <1 <20 <1
<5 CL1 2 35 10.9 6820 687 77 11 <1 <1 <50 31 <2 169
<2 <1 <20 <1 <5 CL2 1 22 11.4 6840 528 <5 34
<1 <1 <50 22 <2 16 <2 <1 <20 <1 <5 CL2 2
22 11.4 6870 528 8 25 <1 <1 <50 23 <2 26 <2 <1
<20 <1 <5
[0157] These tests showed that the used .about.10% Ca(OH).sub.2
excess to lithium content was sufficient to provide the desired
end-result, i.e. a lithium hydroxide solution with a low content of
impurities. Also the temperature of 20-40.degree. C. was
sufficient. The lower temperature of 22.degree. C. produced a more
pure solution in general, particularly in relation to the content
of aluminium and silicon. Further, the aluminium and the silicon
are efficiently reduced with the help of the recycling steps of the
present invention.
[0158] The calcium concentration in the solution was higher at this
lower temperature compared to the concentration achieved at the
higher temperatures.
Example 2
[0159] The LiOH production process was carried out as a bench scale
pilot according to the flow sheet shown in FIG. 3 (without the
recycling line 432). The purification step 32 was performed with
selective cation exchange. The raw material was a calcined
beta-spodumene concentrate, with 6.5% Li.sub.2O concentration. In
the second leaching step 3, the solid residue obtained after S/L
separation 31 contained mainly analcime and calcium carbonate, and
had an average Li concentration of 0.2%, which corresponded to a Li
extraction of 91%. High purity LiOH.H.sub.2O crystals were produced
with a single crystallization stage. With the flow sheet shown in
FIG. 3 (without the recycling line 432), the average impurity
profile of the product crystals is shown in Table 2. From Table 2
it can be seen that low Al and Ca contents can be achieved due to
selective cation exchange purification and applied circulation of
solutions.
TABLE-US-00003 TABLE 2 Impurity analysis of product
LiHO.cndot.H.sub.2O crystals Al Cr Mn Ni Cu Cd Pb Be B Na Mg ppm
ppm ppm ppm ppm ppm ppm ppm ppm ppm ppm <20 <1 <1 <1
<1 <1 <1 <10 <5 <200 <1 P K Ca Ti Fe Zn Bi
SO.sub.4 C Cl.sup.- ppm ppm ppm ppm ppm ppm ppm ppm % % <10
<50 <5 <10 <1 <5 <20 <10 <0.2 <0.005
* * * * *