FIELD OF INVENTION
The invention relates to a method and plant for the recovery of lithium
carbonate from contaminated lithium bromide. The lithium bromide, being contaminated
with metals and/or organic compounds and the carbonate preferably being sodium carbonate.
Preferably, the lithium carbonate is recovered using sodium carbonate
BACKGROUND OF INVENTION
Lithium bromide (LiBr) is used in large quantities in several applications
such as heating pumps and cooling systems including refrigerators. One example is
absorption heating pumps used to provide energy to households. In Sweden there a
total waste of approximately 73 million tons of LiBr and 62 million tons are waste
from the industry. The reasons why lithium bromide solutions are discarded depends
on several factors such as the concentration of antifoam agents and/or anticorrosive
agents are to high or to low in the lithium bromide solution when the solution is
delivered from the manufacture. Furthermore, often contaminants arise during the
use of the lithium bromide solution in a plant, a plant in which the lithium bromide,
circulate in a closed systems. The total result is that the lithium bromide solution
contain large amounts of contaminants, such as metals, organic compounds such as
toxic compounds, or other organic or unorganic substances, such as chlorine, iron,
chromium, sulphur, copper, antifoam, tensides, anticorrosive agents etc.
Today, it is not possible to deposit discarded lithium bromide solutions
in Sweden due to the presence of environmental hazardous substances in the discarded
lithium bromide such as the environmental hazard bromide. The large amounts of discarded
lithium carbonate are therefor deposited in large containers within the industry.
During the storage of the discarded lithium bromides, in solution or in a dried
form, leach water may arise. Leach water containing the above mentioned environmental
hazardous substances. The leach water may find the way out into the ground water
and the ground resulting in that the environmental hazardous substances end up in
the ground water and in the ground and is exposed to microorganisms and fishes.
These environmental hazardous substances are often toxic for both microorganisms
and fishes, which are one of the reasons why they are not allowed to be deposited
directly in our environment. One example of a toxic substance is bromide, which
is present in large quantities in lithium bromide solutions.
Sometimes the storage of discarded lithium bromide solutions result
in that the container used for the storage break and the discarded lithium bromide
solution leach out and reach the ground water and the ground as above. The storage
of these large quantities of discarded lithium bromide also occupies large areas
within the industry, areas, which could be used for other more economic purposes.
There is an increased demand from both nature and different groups
of people that we should try to reuse as much as possible to reduce the still increasing
mountain of different kinds of waste and also try to minimise the reduction of our
limiting nature resources. Today there is no method available for the recovery of
discarded contaminated lithium bromide solutions.
A method for the recovery of contaminated discarded lithium bromide
would reduce the amount of discarded contaminated lithium bromide and furthermore
reduce the pressure of toxic bromides on the environment.
BRIEF DISCLOSURE OF THE INVENTION
The object of the present invention is to provide an economic method
and a plant for the recovery of lithium carbonate from contaminated lithium bromide,
such as discarded lithium bromide. By the availability of such a method the recovered
lithium carbonate may economically be reused in several industries, such as the
lithium battery industry, the concrete industry, by ceramics and in the production
of clinkers and tiles.
Preferably, the recovery of lithium carbonate utilises sodium carbonate
for the recovery of lithium carbonate from lithium bromide. Hereby both lithium
carbonate and sodium bromide are recovered as final products. The recovered sodium
bromide may be reused in the pulp industry or other industries where there is a
need of an antibacterial- and/or antimould-agent.
In a first embodiment, the invention relates to a method for recovery
of lithium carbonate recovery from a metal contaminated lithium bromide comprising
the steps of; providing a solution of the metal contaminated lithium bromide; heating
the metal contaminated lithium bromide to a temperature of from about 25 to about
45° C; maintaining the temperature throughout the method, adding sodium carbonate
in solid form to the heated metal contaminated lithium bromide solution and precipitating
solid lithium carbonate.
In a second aspect, the invention relates to a method of lithium carbonate
recovery from an organic compound contaminated lithium bromide comprising the steps
of; creating a solution of the organic compound contaminated lithium bromide; adding
saturated sodium carbonate preheated to a temperature of 25 -45° C to the organic
compound contaminated lithium bromide solution and precipitation of solid lithium
carbonate.
Accordingly, the invention relates to a plant in which the methods
are used and the use of the recovered lithium carbonate.
The invention provides completely new economic method for the recovery
of lithium carbonate from discarded contaminated lithium bromide, which reduces
the problems of poisoning the ground water and the ground with bromides which are
toxic for microorganisms and fishes, reduced the waste with our nature resources
and furthermore provide the market with economically interesting lithium carbonate.
DETAILED DESCRIPTION OF THE INVENTION
The invention relates to a method and plant for the recovery of lithium
carbonate from contaminated lithium bromide. The lithium bromide may be discarded
lithium bromide which may be discarded from heating pumps, ventilation systems,
absorption heating pumps, refrigerators or any other sources from which the lithium
bromide is supposed to be discarded.
The lithium bromide may be contaminated by metals and/or organic compounds.
Metals such as Cu2+, Cr3+, Cr6+, Fe2+
and/or organic compounds such as tensides, anticorrosive agents and antifoaming
agents. Tensides, anticorrosive agents and antifoaming agents well-known to a person
skilled in the art.
Depending on if lithium bromide is contaminated with metals or organic
substances, slightly different methods are necessary to use to enable a successful
recovery of lithium carbonate.
Recovery of lithium carbonate from lithium bromide contaminated with
metals.
We have surprisingly found that by the use of a preheated lithium
bromide solution during our recovery method it is possible to obtain a lithium carbonate
being substantially free from the contaminating metals.
The metal contaminated lithium bromides are discarded lithium bromides
such as lithium bromides that have been used in heating pumps and cooling plants
including refrigerators. These metal contaminated lithium bromides may be contaminated
with one or more metals such as Cu2+, Cr3+, Cr6+,
Fe2+, preferably Cr3+ and Cr6+. The metals may
bind more or less strongly to lithium and thereby render it more difficult to recover
lithium in the form of lithium carbonate.
The method according to the present invention makes use of several
steps through out the method, which makes the recovery of lithium in the form of
lithium carbonate possible. Firstly the metal contaminated lithium bromides are
provided in the form of a solution. The metal contaminated lithium bromide solution
is heated to a temperature of from about 25 to about 45° C, such as from about 30°
C to about 45° C or from about 35° C to about 40° C to enable a successful separation
of the contaminating metals from lithium.
The temperature to be chosen depends among others, the concentration
on the metal contaminated lithium bromide solution and/or the concentration of the
contaminating metals.
For example a metal contaminated lithium bromide solution having a
concentration of ≤ 10 % may preferably be heated to a temperature above 35° C
and a metal contaminated lithium bromide solution having a concentration of ≥
25% may preferably be heated to a temperature above 25° C. A metal contaminated
lithium bromide solution having a concentration of from about 10% to about 25% may
be heated to a temperature of at least 25° C.
However, the temperature is also dependent on the concentration of
the contaminating metals such as a contamination of about 49 µg/l of one or more
metals, the metal contaminated lithium bromide solution may be heated to a temperature
from about 30 °C to about 35° C and a contamination of 50 µg/l of one or more metals,
the metal contaminated lithium bromide solution may be heated to a temperature from
about 35 ° C to about 45° C.
After the metal contaminated lithium bromide solution has been heated,
the solution is maintained at that temperature throughout the method to secure the
contaminating metals remains in solution.
Carbonate is the added in a solid form to the heated metal contaminated
lithium bromide solution, preferably the carbonate is sodium carbonate. The carbonate
may be added in an amount of from about 0.1 to about 31 g/l of metal contaminated
lithiumbromide solution. Preferably the added carbonate is a carbonate solution
such as sodium carbonate and added in a concentration of 50 % (weight/volume). The
carbonate is preferably added under stirring of the lithium bromide solution. Carbonate
is added continuously and lithium carbonate start to precipitate in the form of
solid lithium carbonate. However, the metals remain in the solution due to the increased
temperature of the metal contaminated lithium bromide solution and thereby the metals
are separated from lithium and enables the possibility to obtain lithium carbonate
which is substantially free from metals.
When sodium carbonate is used as carbonate source, a metal containing
sodium bromide solution is obtained together with the solid lithium carbonate. The
metal containing sodium bromide solution may be further purified using methods well-known
for a person skilled in the art, such as ion exchangers selective for certain metal
ions to obtain purer forms of sodium bromide.
The precipitated lithium carbonate is at least 90 % pure lithium carbonate,
such as from about 90 % to 100 % pure lithium carbonate, or from about 95 % to 100
% pure lithium carbonate or from about 98 % to 100 % pure lithium carbonate or 99.1
%, 99.2 %, 99.3 %, 99.4 %, 99.5 %, 99.6 %, 99.7 %, 99. 8 % or 99.9 % pure lithium
carbonate.
The precipitated lithium carbonate may further be dried at a temperature
of < 600 °C, such as from about 100 °C to about 600 °C, preferably > 100 °C.
The metals including the toxic bromide remain in the solution and
may be recovered therefrom by other methods.
The recovered lithium carbonate may be used in several industries
such as the production of lithium batteries, the concrete industry, by ceramics
and in the production of clinkers and tiles.
When sodium carbonate is used for the recovery of lithium carbonate,
the sodium bromide solution may be reused in the pulp industry or other industries
where there is a need of an antibacterial- and/or antimould-agent.
The method for recovery of lithium carbonate from a metal contaminated
lithium bromide may be used alone or in combination with the method mentioned below
in the case a discarded lithium bromide being contaminated with both one or more
metals and one or more organic compounds. When both of the methods are needed, the
order in which the two methods are combined are of no importance and may vary.
Recovery of lithium carbonate from lithium bromide contaminated with
organic compounds.
We have surprisingly found that by the use of a preheated saturated
carbonate, such as sodium carbonate during recovery of lithium carbonate from an
organic compound contaminated lithium bromide solution it is possible to obtain
a lithium carbonate being substantially free from the contaminating organic compounds.
The organic compound contaminated lithium bromides may be discarded
lithium bromides such as lithium bromides that have been used in heating pumps and
cooling plants including refrigerators to replace freon. These organic contaminated
lithium bromides may be contaminated with one or more organic compounds such as
tensides, anticorrosive agents and antifoaming agents.
The method according to the present invention makes use of several
steps through out the method, which makes the recovery of lithium in the form of
lithium carbonate possible. Firstly the organic contaminated lithium bromides are
provided in the form of a solution obtained either directly from the contaminated
lithium bromide or after the contaminated lithium bromide has been separated from
contaminating metals using the method described above.
Then carbonate is added in a saturated preheated from, preheated to
a temperature of from about 25 -45° C, such as from about 35° C to about 45° C.
Preferably the carbonate is sodium carbonate such as in example 2. The carbonate
is added under stirring of the organic compound contaminated lithium bromide solution.
Carbonate is added continuously and lithium carbonate start to precipitate in the
form of solid lithium carbonate. However, the organic compounds remain in the solution
and thereby the organic compounds are separated from lithium.
The precipitated lithium carbonate is at least 90 % pure lithium carbonate,
such as from about 90 % to 100 % pure lithium carbonate, or from about 95 % to 100
% pure lithium carbonate or from about 98 % to 100 % pure lithium carbonate or 99.1
%, 99.2 %, 99.3 %, 99.4 %, 99.5 %, 99.6 %, 99.7 %, 99. 8 % or 99.9 % pure lithium
carbonate.
The precipitated lithium carbonate may further be dried at a temperature
of < 600 ° C, such as from about 100 ° C to about 600° C, preferably > 100
°C.
The recovered lithium carbonate may be used in several industries
such as the production of lithium batteries, the concrete industry, by ceramics
and in the production of clinkers and tiles.
Furthermore the invention relates to a plant using one or both of
the above mentioned methods. The plant may preferably be a closed system
Additionally the invention relates to use of lithium carbonate which
has been recovered, from discarded contaminated lithium bromide by the methods according
to the invention. The lithium bromide, being contaminated with one or more metals
and/or organic compounds. The invention also relates to use of sodium bromide when
sodium carbonate is used for the recovery of lithium carbonate.
EXAMPLES
EXAMPLE 1
100 litre 10 % (weight/volume) of LiBr-solution contaminated with
49 µg/l of Cr2+ was preheated to a temperature of 40 ° C. 6.1 kg of solid
sodium carbonate was added under stirring of the LiBr-solution. The temperature
was kept constant. 4.25 kg of lithium carbonate were precipitated in the form of
a lithium carbonate cake and 100 litre of sodium bromide in solution. The sodium
bromide solution also contained 49 µg/l of Cr2+ and was further treated
using a selective ion exchangers. The lithium carbonate cake was found to be 99.6
% pure lithium carbonate.
EXAMPLE 2
100 litre 50 % (weight/volume) of LiBr-solution contaminated with
50 µg/l of antifoam agent held at a temperature of 25° C. Saturated sodium carbonate
was added to the LiBr-solution under stirring of the LiBr-solution. The mixture
was heated to a temperature of 30° C and 421.25 kg of lithium carbonate were precipitated
in the form of a lithium carbonate cake and 100 litre of sodium bromide in solution
containing the antifoam agent. The lithium carbonate cake was found to be 99.6 %
pure lithium carbonate.
Preparation of saturated sodium carbonate:
- 30.5 kg of solid sodium carbonate was mixed with 60.4 litre of water prior addition
to the lithium bromide solution.
