U.S. patent application number 12/811643 was filed with the patent office on 2010-11-11 for process for producing sodium carbonate and/or sodium bicarbonate from an ore mineral comprising sodium bicarbonate.
This patent application is currently assigned to SOLVAY SA. Invention is credited to Francis M. Coustry, Jean-Paul Detournay.
Application Number | 20100282614 12/811643 |
Document ID | / |
Family ID | 39650511 |
Filed Date | 2010-11-11 |
United States Patent
Application |
20100282614 |
Kind Code |
A1 |
Detournay; Jean-Paul ; et
al. |
November 11, 2010 |
Process for producing sodium carbonate and/or sodium bicarbonate
from an ore mineral comprising sodium bicarbonate
Abstract
In a process to produce sodium carbonate and/or sodium
bicarbonate from an ore mineral comprising sodium bicarbonate, a
production solution comprising sodium carbonate is introduced into
less basic compartments of an electrodialyser comprising
alternating less basic and more basic adjacent compartments
separated from each other by cationic membranes, the more basic
compartments being delimited by anionic faces of bipolar membranes
on one side and by the cationic membranes on the other side; a
solution comprising sodium hydroxide is produced into the more
basic compartments by combination of sodium ions flux crossing the
cationic membrane and hydroxyl ions flux crossing the anionic face
of the bipolar membranes, and is then extracted from the
electrodialyser to be used as a reaction solution; the reaction
solution is put into contact with the mineral ore to form a
solution comprising sodium carbonate; and the solution comprising
sodium carbonate is divided into a part used as the production
solution and a remaining part used as a produced solution.
Inventors: |
Detournay; Jean-Paul;
(Brussels, BE) ; Coustry; Francis M.; (Alsemberg,
BE) |
Correspondence
Address: |
Solvay;c/o B. Ortego - IAM-NAFTA
3333 Richmond Avenue
Houston
TX
77098-3099
US
|
Assignee: |
SOLVAY SA
Brussels
BE
|
Family ID: |
39650511 |
Appl. No.: |
12/811643 |
Filed: |
January 6, 2009 |
PCT Filed: |
January 6, 2009 |
PCT NO: |
PCT/EP09/50075 |
371 Date: |
July 2, 2010 |
Current U.S.
Class: |
205/439 |
Current CPC
Class: |
C01D 7/126 20130101;
C01D 7/10 20130101; C01D 7/32 20130101; B01D 61/422 20130101; C01D
1/38 20130101 |
Class at
Publication: |
205/439 |
International
Class: |
C25B 3/00 20060101
C25B003/00 |
Foreign Application Data
Date |
Code |
Application Number |
Jan 8, 2008 |
EP |
08150104.1 |
Claims
1. A process to produce sodium carbonate and/or sodium bicarbonate
from an ore mineral comprising sodium bicarbonate, comprising:
introducing a production solution comprising sodium carbonate into
less basic compartments of an electrodialyser comprising
alternating less basic and more basic adjacent compartments
separated from each other by cationic membranes, the more basic
compartments being delimited by anionic faces of bipolar membranes
on one side and by the cationic membranes on the other side;
optionally extracting a solution comprising sodium bicarbonate from
the less basic compartments; producing a solution comprising sodium
hydroxide into the more basic compartments, by combination of flux
of sodium ions crossing the cationic membrane and flux of hydroxyl
ions crossing the anionic face of the bipolar membranes; extracting
the solution comprising sodium hydroxide from the more basic
compartments of the electrodialyser and using such solution to
constitute a reaction solution; putting the reaction solution into
contact with the mineral ore comprising sodium bicarbonate in order
to form a solution comprising sodium carbonate; and dividing the
solution comprising sodium carbonate into a part which is used to
constitute said production solution and a remaining part which
constitutes a produced solution.
2. The process according to claim 1, wherein the produced solution
is evaporated in order to produce a suspension comprising sodium
carbonate crystals, which are separated and valorized.
3. The process according to claim 1, wherein a solution comprising
sodium bicarbonate is extracted from the less basic compartments of
the electrodialyser, this sodium bicarbonate-comprising solution
being afterwards cooled in order to produce a suspension comprising
sodium bicarbonate crystals, and the suspension being separated
into valorized sodium bicarbonate crystals and a sodium bicarbonate
mother liquor.
4. The process according to claim 3, wherein the sodium bicarbonate
mother liquor is debicarbonated and introduced into the less basic
compartments of the electrodialyser
5. The process according to claim 3, wherein the sodium bicarbonate
mother liquor is debicarbonated and introduced into the more basic
compartments of the electrodialyser.
6. The process according to claim 3, wherein the sodium bicarbonate
mother liquor is introduced into the less basic compartments of
another electrodialyser.
7. The process according to claim 6, wherein the concentration in
sodium carbonate of the sodium bicarbonate mother liquor is
sufficiently low so as to generate CO.sub.2 gas into the less basic
compartments of the other electrodialyser.
8. The process according to claim 7, wherein the generated CO.sub.2
is put into contact with at least part of the produced solution
comprising sodium carbonate, in order to produce sodium bicarbonate
crystals.
9. The process according to claim 1, wherein part of the reaction
solution comprising sodium hydroxide is mixed with a solution
comprising sodium bicarbonate, in order to convert at least part of
the sodium bicarbonate into sodium carbonate.
10. The process according to claim 1, wherein the mineral ore
comprising sodium bicarbonate is an underground trona or nahcolite
ore mineral.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] The present application is a U.S. national stage application
under 35 U.S.C. .sctn.371 of International Application No.
PCT/EP2009/050075 filed Jan. 6, 2009, which claims the priority
benefit of European Application No. 08150104.1 filed Jan. 8, 2008,
the whole content of such application being incorporated herein by
reference for all purposes.
TECHNICAL FIELD OF THE INVENTION
[0002] This invention relates to a process for producing sodium
carbonate and/or sodium bicarbonate from an ore mineral comprising
sodium bicarbonate, in particular from trona, nahcolite or from
other mineral underground ores, rich in sodium bicarbonate values,
such as Wegscheiderite or Decemite.
BACKGROUND OF THE INVENTION
[0003] Nahcolite is an ore consisting primarily of sodium
bicarbonate. There are for instance vast quantities of nahcolite in
the Piceance Creek Basin in Northwestern Colorado, which deposits
are in the form of beds and disseminated crystals in the Saline
Zone of the Green River formation.
[0004] Trona ore is a mineral that contains about 90-95% sodium
sesquicarbonate (Na.sub.2CO.sub.3.NaHCO.sub.3.2H.sub.2O). A vast
deposit of mineral trona is found in southwestern Wyoming near
Green River. This deposit includes beds of trona and mixed trona
and halite (rock salt or NaCl). By conservative estimates, the
major trona beds contain about 75 billion metric tons of ore. The
different beds overlap each other and are separated by layers of
shale. The quality of the trona varies depending on its particular
location in the stratum.
[0005] A typical analysis of the trona ore mined in Green River is
as follows:
TABLE-US-00001 TABLE 1 Constituent Weight Percent Na.sub.2CO.sub.3
43.6 NaHCO.sub.3 34.5 H.sub.2O (crystalline and free moisture) 15.4
NaCl 0.01 Na.sub.2SO.sub.4 0.01 Fe.sub.2O.sub.3 0.14 Insolubles
6.3
[0006] The sodium sesquicarbonate found in trona ore is a complex
salt that is soluble in water and dissolves to yield approximately
5 parts by weight sodium carbonate (Na.sub.2CO.sub.3) and 4 parts
sodium bicarbonate (NaHCO.sub.3), as shown in the above analysis.
The trona ore is processed to remove the insoluble material, the
organic matter and other impurities to recover the valuable alkali
contained in the trona.
[0007] The most valuable alkali produced from trona is sodium
carbonate. Sodium carbonate is one of the largest volume alkali
commodities made in the United States. In 1992, trona-based sodium
carbonate from Wyoming comprised about 90% of the total U.S. soda
ash production. Sodium carbonate finds major use in the
glass-making industry and for the production of baking soda,
detergents and paper products.
[0008] A common method to produce sodium carbonate from trona ore
is known as the "monohydrate process". In that process, crushed
trona ore is calcined (i.e., heated) into crude sodium carbonate
which is then dissolved in water. The resulting water solution is
purified and fed to a crystallizer where pure sodium carbonate
monohydrate crystals are crystallized. The monohydrate crystals are
separated from the mother liquor and then dried into anhydrous
sodium carbonate. This process is however very energy intensive,
mainly due to the calcination step, which requires the use of large
quantities of coal, fuel, gas or mixtures thereof.
[0009] On the other side, sodium bicarbonate is a product with a
wide range of interesting properties and a very wide range of
applications from high tech ingredients for the pharma industry to
the human food and animal feed, and to the use in flue gas
treatment. In flue gas treatment sodium bicarbonate is most likely
among the most efficient chemicals for the removal of a wide range
of pollutants (most notably the acidic one), and its use is limited
only by the competition of less efficient but much cheaper
chemicals such as lime or even limestone.
[0010] The production of sodium bicarbonate is currently almost
entirely made by the carbonation of sodium carbonate. In Europe,
the carbonation is usually made in situ in the soda ash plants from
CO.sub.2 coproduced during the production of soda ash (mainly the
CO.sub.2 generation in the lime kilns). In USA, the carbonation is
usually made in separate plants which purchase independently the
soda ash and the CO.sub.2 and combine them. Because of the nature
of this most important process, the production cost of the sodium
bicarbonate is even above the cost of the sodium carbonate.
[0011] Attempts to reduce the energy consumption for the production
of sodium carbonate and bicarbonate have been made, by the use of
electrodialytic methods. U.S. Pat. No. 4,636,289 discloses a method
for recovering sodium carbonate from trona and other mixtures of
sodium carbonate and sodium bicarbonate. In U.S. Pat. No.
4,636,289, sodium hydroxide is produced in electrodialytic cells
and used to solution mine the mineral ore. However, this process
requires the introduction of sodium sulfates into the acid
compartments of the electrodialysers, which appears to be difficult
to put into practice in a cost effective and efficient way.
SUMMARY OF THE INVENTION
[0012] The invention aims at producing sodium carbonate and/or
sodium bicarbonate from ore minerals, in a simple, economical way,
avoiding the large energy consumption of the known processes.
[0013] In consequence, the invention concerns a process to produce
sodium carbonate and/or sodium bicarbonate from an ore mineral
comprising sodium bicarbonate according to which: [0014] a
production solution comprising sodium carbonate is introduced into
the less basic compartments of an electrodialyser comprising
alternating less basic and more basic adjacent compartments
separated from each other by cationic membranes, the more basic
compartments being delimited by the anionic faces of bipolar
membranes on one side and by the cationic membranes on the other
side; [0015] a solution comprising sodium hydroxide is produced
into the more basic compartments, by combination of the flux of
sodium ions crossing the cationic membrane and the flux of hydroxyl
ions crossing the anionic face of the bipolar membranes; [0016] the
solution comprising sodium hydroxide is extracted from the more
basic compartments of the electrodialyser and used to constitute a
reaction solution; [0017] the reaction solution is put into contact
with the mineral ore comprising sodium bicarbonate in order to form
a solution comprising sodium carbonate; [0018] the solution
comprising sodium carbonate is divided into a part which is used to
constitute the production solution and a remaining part which
constitutes a produced solution.
[0019] In the process according to the invention, a solution
comprising sodium bicarbonate is optionally extracted from the less
basic compartments.
BRIEF DESCRIPTION OF THE DRAWINGS
[0020] FIG. 1 illustrates one particular embodiment of a process
according to the invention.
DETAILED DESCRIPTION
[0021] A bipolar membrane is an ion exchange membrane comprising
one cationic face--permeable for the cations and impermeable for
the anions and an other anionic face--permeable for the anions and
impermeable for the cations. Such membrane can be produced by the
juxtaposition of two monopolar membranes. Under a sufficient
electric field, and in aqueous solution, the only possible reaction
is the splitting of water at the interface between the two
monopolar membranes into H.sup.+ and OH.sup.- which then cross
respectively the cationic and anionic monopolar membrane and exit
the membrane into the adjacent compartments. It is recommended that
the bipolar membranes are produced by the process as described in
the patent application WO 01/79335 in the name of SOLVAY, in
particular as described in its claims.
[0022] In the process according to the invention, the
electrodialyser contains at least two types of compartments and two
types of membranes, cationic and bipolar. In some embodiments it
can contain additional types of compartments and anionic
membranes.
[0023] In a preferred embodiment of the process, the electodialyser
comprises only two types of compartments and only cationic and
bipolar membranes. In this embodiment, wherein the less basic and
more basic compartments of the electrodialyser are separated by an
alternation of cationic and bipolar membranes, each compartment is
thus delimited on one side by a cationic membrane, and on the other
side by a bipolar membrane.
[0024] In the process according to the invention, the sodium
hydroxide reacts with the sodium bicarbonate contained in the
mineral ore. The resulting sodium carbonate, thanks to its high
solubility is easily solubilized from the ore, which allows to
extract efficiently the sodium values of the mineral ore. The
reaction solution comprises advantageously at most 120 g/kg,
preferably at most 100 g/kg sodium hydroxide and at most 40 g/kg
preferably 30 g/kg sodium carbonate. It is nevertheless preferable
that the reaction solution comprises at least 40 g/kg, more
preferably 50 g/kg sodium hydroxide.
[0025] Usually, the reaction solution will be made by mixing the
solution comprising sodium hydroxide which is extracted from the
more basic compartments with fresh water or recycle waters, in
order to dilute it.
[0026] However, the solution comprising sodium hydroxide can be
advantageously used as such to form the reaction solution and put
directly into contact with the mineral ore. Depending on the
particular circumstances, the output from the more basic
compartments will have to be reintroduced in their input, in order
to get the best sodium hydroxide concentration.
[0027] The control of the composition of the reaction solution
allows to regulate the composition of the produced solution. It is
advantageous that the produced solution comprises advantageously at
least 200 g/kg, preferably 250 g/kg sodium carbonate.
[0028] In a recommended embodiment of the process according to the
invention, at least part of the produced solution is evaporated in
order to produce a suspension comprising sodium carbonate crystals,
which are separated and valorized. The evaporation can be made as
in the monohydrate process, preferably by using mechanical vapor
recompression. The sodium carbonate monohydrate crystals are then
preferably processed into dense soda ash.
[0029] In the process according to the invention, a production
solution comprising sodium carbonate is introduced into the less
basic compartments of the electrodialyser. Due to the flux of
Na.sup.+ ions through the cationic membrane and an incoming flux of
H.sup.+ ions, at least part of the entering sodium carbonate is
transformed into sodium bicarbonate, forming an output solution
comprising sodium bicarbonate.
[0030] Depending on the concentrations in sodium carbonate and
sodium bicarbonate of the first production solution, it can also
happen in advantageous embodiments, that sodium bicarbonate is
converted into carbon dioxide at the output of the less basic
compartments of the cell. The carbon dioxide can then be reacted
with sodium carbonate solutions at other stages of the process, in
order to produce sodium bicarbonate crystals.
[0031] In a recommended embodiment of the process, a solution
comprising sodium bicarbonate is extracted from the less basic
compartments of the electrodialyser, this solution being afterwards
cooled in order to produce a suspension comprising sodium
bicarbonate crystals. The suspension is separated into sodium
bicarbonate crystals to be valorized and a sodium bicarbonate
mother liquor. The mother liquor is then preferably debicarbonated,
in order to produce on one side a gas comprising CO.sub.2 and on
the other side a debicarbonated solution depleted in sodium
bicarbonate and enriched in sodium carbonate. The debicarbonated
solution contains preferably not more than 60 g/kg, more preferably
50 g/kg, most preferably 40 g/kg sodium bicarbonate. The
debicarbonated solution can be mixed with the production solution
and introduced into the electrodialyser. It can also be mixed with
the produced solution in order to form the reaction solution. The
debicarbonation can be performed by vapor or preferably by air
stripping.
[0032] In order to produce a solution comprising sodium hydroxide
into the more basic compartments of the electrodialyser, it is
necessary to limit the flux of sodium bicarbonate which could be
introduced into those compartments. In fact, the maximum flux of
HCO.sup.3- ions entering into the more basic compartments is
limited by the flux of OH.sup.- ions and Na.sup.+ ions introduced
into them through the bipolar and cationic membranes. The more
basic compartments can be advantageously fed by introducing into
them the debicarbonated solution produced in the recommended
embodiment described just above. Alternatively, it can be fed by a
diluted sodium carbonate solution, containing advantageously at
least 20 g/kg sodium carbonate, but at most 70 g/kg, preferably at
most 50 g/kg sodium carbonate.
[0033] In a preferred embodiment, the more basic compartments are
not fed by any solution coming from the outside. In this
embodiment, the more basic compartments contain only NaOH produced
in situ into those compartments by combination of Na.sup.+ and
OH.sup.- ions (crossing the cationic membranes and the anionic
faces of the bipolar membranes), the input flow to the compartments
being taken from their output (recirculation), with only supply of
water, if necessary. In a variant of this embodiment, even the
supply of external water is avoided, the less basic compartments
being only fed by water passing through the ion exchange membranes
into them.
[0034] The process according to the invention can be run with only
one electrodialyser. It is however possible to use several
electrodialysers, the output from some of them being used as input
for others.
[0035] For instance, in a recommended embodiment of the process
according to the invention, the solution comprising sodium
bicarbonate which is extracted from the less basic compartments of
the electrodialyser is introduced into the less basic compartments
of another electrodialyser. In this embodiment, it is preferable
first to cool the solution comprising sodium bicarbonate extracted
from the less basic compartments of the first electrodialyser and
separate the sodium bicarbonate crystal which appears due to the
cooling. The mother liquor is then introduced into the other
electrodialyser. Additionally, in this embodiment, it is
recommended that the concentration in sodium carbonate of the
solution comprising sodium bicarbonate which is introduced into the
other electrodialyser is sufficiently low so as to generate
CO.sub.2 gas into the less basic compartments of this other
electrodialyser. Indeed, when all the sodium carbonate entering the
less basic compartments has been transformed into sodium
bicarbonate as a consequence of Na.sup.+ ions passing the cationic
membranes, any additional flux of Na.sup.+ ions passing through
those membranes has the consequence of destroying sodium
bicarbonate into CO.sub.2 and water. The generated CO.sub.2 gas is
then advantageously used to react with part of the sodium carbonate
solution produced through the contact with the mineral ores, in
order to produce sodium bicarbonate crystals. This reaction can be
performed in gas-liquid contactors suitable for the carbonation of
sodium carbonate solutions. Depending on the circumstances, the
sodium carbonate solution can be first concentrated by any suitable
means, before its carbonation.
[0036] According to the invention, the sodium hydroxide is produced
in the electrodialyser out of a sodium carbonate solution and the
sodium carbonate solution is in turn very simply obtained by using
part of the solution produced by the reaction of the sodium
hydroxide with the sodium bicarbonate part of the mineral ore.
Different mineral ores can be utilized and the mineral ores can be
put into contact with the reaction solution in very different ways,
for instance in surface equipments using excavated mineral ores.
The simplicity of this process allows to use it at large industrial
scale. It is particularly interesting to introduce the reaction
solution underground and put it into contact with subterranean
mineral ore deposits. The solution comprising sodium carbonate is
then formed underground and extracted by conventional solution
mining techniques. This embodiment is suited to Trona, Nahcolite,
Wegscheiderite or Decemite mineral underground ores. In a
particularly preferred embodiment, the mineral ore comprising
sodium bicarbonate is an underground trona or nahcolite ore
mineral.
[0037] Depending on the circumstances, it can also be advantageous
to mix part of the reaction solution with a solution comprising
sodium bicarbonate already at hand, in order to convert at least
part of the sodium bicarbonate into sodium carbonate.
[0038] The annexed FIG. 1 illustrates a particular embodiment of
the invention. A production solution 1 comprising sodium carbonate
is introduced into the less basic compartments of an
electrodialyser 2 comprising alternating less basic and more basic
compartments. A solution 3 comprising sodium bicarbonate is
extracted from the less basic compartments and a solution 4
comprising sodium hydroxide is extracted from the more basic
compartments of the electrodialyser. The solution 3 is cooled in
the crystallizer 5, resulting in sodium bicarbonate crystals 6 and
a mother liquor 7. The mother liquor 7 is debicarbonated by air
stripping in the contactor 8, resulting in CO.sub.2 gas 9 and
debicarbonated mother liquor 10, part of which (10') is sent back
to the electrodialyser and part of which is mixed with the solution
4 comprising sodium hydroxide together with fresh water 11, to form
the reaction solution 12. The reaction solution 12 is injected into
a subterranean trona mine 13. A solution comprising sodium
carbonate 14 is extracted from the trona mine. A produced solution
14' is taken out of this solution 14 and sent to an evaporator (not
represented), wherein sodium carbonate monohydrate crystals are
formed. Those crystals are thereafter valorized, for instance by
transformation into dense soda ash. The remaining part of the
solution 14 is sent to the electrodialyser, constituting after
mixing with debicarbonated mother liquor 10' the production
solution 1.
[0039] Details and particularities of the invention will appear
from the description of the following example.
Example
[0040] The process illustrated by the FIG. 1 is operated in the
following way. A quantity of 0.024 m.sup.3/h of a production
solution comprising 110 g/kg sodium carbonate and 32 g/kg sodium
bicarbonate is introduced at a temperature of 29.degree. C. into
the less basic compartments of an electrodialyser. The
electrodialyser comprise bipolar membranes produced by ASTOM, model
NEOSEPTA BP-1E and cationic membranes NAFION.RTM. 324, produced by
DuPont. A current density of 1 kA/m.sup.2 is applied to the
elementary cell. A solution 3 comprising 117 g/kg sodium
bicarbonate and 20 g/kg sodium carbonate at a temperature of
65.degree. C. is extracted from the less basic compartments of the
electrodialyser at a flow rate of 0.023 m.sup.3/h. This solution is
cooled to 30.degree. C. in a crystallizer, resulting in a
production of 0.78 kg/h of sodium bicarbonate crystals. A solution
4 comprising 357 g/kg of sodium hydroxide is extracted from the
more basic compartments of the electrodialyser at a flow rate of
0.002 m.sup.3/h and a temperature of 65.degree. C. After mixing
with 0.007 m.sup.3/h water and 0.003 m.sup.3/h debicarbonated
mother liquor 10'', a reaction solution comprising 68 g/kg NaOH and
27 g/kg Na.sub.2CO.sub.3 is introduced at a flow rate of 0.012
m.sup.3/h and at a temperature of 50.degree. C. into a trona mine
comprising trona ore having the composition described in the
introductory part of this specification, the temperature of the ore
being approximately 25.degree. C. A solution 14 comprising 280 g/kg
Na.sub.2CO.sub.3 is extracted from the mine at a flow rate of 0.014
m.sup.3/h and a temperature of approximately 30.degree. C. A part
of 0.008 m.sup.3/h is subtracted from this solution 14 for
evaporation and sodium carbonate crystallization.
[0041] The remaining flow rate is mixed with 0.02 m.sup.3/h of
debicarbonated mother liquor 10' containing 50 g/kg sodium
carbonate and 43 g/kg sodium bicarbonate.
* * * * *