PT106208B - PROCESS FOR PRODUCING SODIUM BICARBONATE. - Google Patents

Abstract

(A) CONTAINING SODIUM CARBONATE, COVERING SODIUM CARBONATE AND, AT LEAST, A IMPURITY CONSISTING IN A HYDROSOLOUS SALT OF ALKALINE METAL TO A CONCENTRATION CI (A) WHICH UNDERSTANDS THE FOLLOWING STEPS: A) MIXING THE CURRENT (A) CONTAINING SODIUM CARBONATE WITH AT LEAST PART OF A CURRENT (B) TO PRODUCE A CURRENT (C), B) BICARBONATAR ACORRENT (C) WITH A GAS (D) COMPREHENDING CO2 IN A DEVICE ( 1) CARBONATING TO PRODUCE A SUSPENSION (AND) AQUOSA UNDERSTANDING CRYSTALS (F) UNDERSTANDING SODIUM BICARBONATE CRYSTALS, (C) SEPARATING AQUOSA SUSPENSION IN ORDER TO OBTAIN CRYSTALS (F) UNDERSTANDING SODIUM BICARBONATE CRYSTALS, D, and at least one part of the mother's water (G) and removes part of the water from at least one portion of the mother's water (G) PART OF THE MOTOR WATER (G) TO GET THE CURRENT (B) (B) and an optional gas (H) in a deflection device (3), and (E) at least part of the current (B) to be recycled STEP A) so that the ratio of the CF (B) / CI (A) CONCENTRATIONS OF AT LEAST A DEFORMATION OF ALKALINE METALLIC SOLUBLE SALT IS AT LEAST 1.4 ALMOST AT LEAST 2, MOST VANTAGELY, AT LEAST 4 AND EVEN MORE VELT 7, EF) REMOVE REMAINING (I) FROM CURRENT (B) OR REMAINING (J) FROM MOTOR WATER (G) TO BE ADDITIONALLY PROCESSED.

Description

additionally processed.

DESCRIPTION

PROCESS TO PRODUCE SODIUM BICARBONATE

FIELD OF INVENTION

The invention relates to a process for producing sodium bicarbonate from a sodium carbonate-containing stream comprising sodium carbonate and at least one impurity consisting of an alkaline metal soluble salt, while minimizing a final purge volume. necessary to produce sodium bicarbonate and the loss of alkaline sodium associated with purging is also minimized.

BACKGROUND OF THE INVENTION Sodium bicarbonate (NaHCO ₃ ) is a moderately alkaline compound with a wide range of applications including uses in human food, animal feed, flue gas treatment and the chemical industries. Worldwide production of sodium bicarbonate in 2008 was estimated at 2.8 million tonnes. Most of its production is derived from natural and synthetic sodium carbonate (Na ₂ CO ₃ ). The production of sodium bicarbonate is mainly by the carbonation of an aqueous sodium carbonate solution with gaseous CO ₂ . The aqueous sodium carbonate solution may be from purified sodium carbonate dissolved in water or a partially decarbonated sodium bicarbonate slurry from the Solvay process or from a sodium carbonate solution taken from a sodium carbonate crystallizer fed with sodium carbonate. solutions derived from throne or nacolite ores.

When sodium bicarbonate is produced from solid refined sodium carbonate, the sodium carbonate content of impurities such as water-soluble alkali metal salts is sufficiently low that these impurities can be efficiently extracted from the sodium bicarbonate process. sodium with the final produced sodium bicarbonate. Thus no specific purge of such impurities is required in the corresponding sodium bicarbonate process.

However, when sodium bicarbonate is produced from synthetic calcined soda sodium carbonate streams (Solvay processes or natural calcined derivatives (trone related processes or sodium carbonate streams) contain high levels of soluble impurities and is required). a purge to control the level of impurities in the sodium bicarbonate process.This purge is generally elevated and fed back into the corresponding sodium carbonate process or sent to high capacity deposition ponds, such as the processes described in US7507388 or or in

In addition to sodium bicarbonate, sodium carbonate, also called calcined soda, is a large volume alkaline product with a total world production of 48 million tonnes in 2008 which is widely used in the glass, chemical and detergent industries, and also in the baking soda production industry. The principal processes for the production of sodium carbonate are the synthetic ammonia Solvay process, the ammonium chloride process (Hou process) derived from the Solvay process and the trone based processes.

Trone ore is a mineral containing up to 99% sodium sesquicarbonate (Na2CO3.NaHCO3.2H2O). Trona-based calcined soda is obtained from throne mineral deposits in Green River (Wyoming), Turkey, China and Kenya by conventional underground mining techniques or through solution mining or pond water processing. Wyoming's trone-based sodium carbonate comprises about 90% of total US calcined soda production.

A typical analysis of green river trona ore is as follows:

TABLE 1

Constituent Weight percentage Na ₂ CO ₃ 43.6 NaHCO ₃ 34.5 H ₂ O (crystalline and free humidity) 15.4 NaCl 0.01 Na ₂ SO ₄ 0.01 F Θ2θ3 0.14 Insoluble 6.3 Organic 0.3

Throne deposits contain various highly soluble impurities such as alkali metal halides (sodium chloride, potassium chloride, sodium fluoride, etc.), alkali metal sulfates (sodium sulfate, potassium sulfate etc.), nitrates alkali metals (sodium nitrate, potassium nitrate, etc.), alkali metal borates, alkali metal phosphates, etc. These highly soluble impurities are in various proportions according to the geographical location of the deposits. In particular, sodium chloride and sodium sulfate may represent several percentage units or several dozen percentage units of trone ore according to geographical location.

Throne deposits also include slightly soluble mineral or organic impurities.

Examples of slightly soluble minerals are: silicates, aluminates, titanates, alkali and alkaline earth vanadates, metal compounds and salts. Organic impurities come from organic sediments that have been captured during the formation of deposits and which often form oil shales during geological aging. Organic mineral soluble impurities may also be partially formed during mine processing or surface operations.

In particular, heat treatments, such as calcination, generally amplify the amount of some soluble impurities, such as sodium silicates, and sodium salts of organic compounds by thermal saponification.

The other insoluble or very slightly water-soluble mineral impurities found in or near the throne deposits are generally mixtures of different minerals, the most common being calcite, dolomite, pyrssonite, zeolite, feldspar, clay minerals, aluminum / iron silicate and sulfate. of calcium.

Two important techniques well known in the art are used to recover trona ore from trona ore deposits. The first technique is mechanical mining, also called conventional mining, such as a chamber and pillar operation or a longwall operation. The second technique is a solution mining recovery wherein the throne is dissolved with water and recovered as a solution.

Among the various ways in which sodium carbonate can be recovered from trona ore containing other salts and impurities, the most widely practiced is the so-called monohydrate process. In this process, a mined trona ore is ground, then calcined with crude sodium carbonate, then leached with water, the resulting aqueous solution is purified and fed to a crystallizer where pure crystals of sodium carbonate monohydrate are crystallized. The monohydrate crystals are separated from mother liquor and then dried over anhydrous sodium carbonate. Most of the mother liquor is recycled to the crystallizer. However, soluble impurities contained in trona ore tend to accumulate in the crystallizer. To prevent the accumulation of impurities, the mother liquor must be purged. Purge water representing significant quantities for industrial monohydrate plants is usually sent to an evaporation pond, also called a tailings pond. The significant amount of alkali that is lost. In addition, purge waters in environmental because of for storage.

Variants for producing throne ore, in particular, for solution, are:

contained in water from the storage ponds of scarce purging is consequently large amounts of evaporation raises problems availability of new areas sodium carbonate from when mining crystallization of refined sodium sesquicarbonate (sesqui) after water evaporation after calcination of sodium sesqui in calcined soda;

or alternatively, thermal decomposition (with steam) or chemical calcination (with caustic soda) of the dissolved sodium bicarbonate to make it dissolved sodium carbonate, then evaporation of water to crystallize pure sodium carbonate monohydrate.

In these embodiments, soluble impurities contained in the trone ore also tend to accumulate in sesqui or monohydrate crystallizers. To prevent the accumulation of impurities, the mother liquor must also be purged, raising the same environmental problems in evaporation ponds as the monohydrate process.

Several technical alternatives have been proposed to reduce the purge volume of calcined soda mills.

US2003 / 0143149 discloses a process for recovering sodium-based chemicals from sodium carbonate streams, such as purges and effluent streams, using a sodium carbonate decahydrate crystallizer from which Purified decahydrate is recovered and recycled to the monohydrate crystallizer and an impurity concentrated purge such as sodium sulfate is discarded. However, the purge reducing factor of this process is limited because, when a high concentration of impurities is reached, sodium carbonate and sodium sulfate form mixed hydrochloride salts. And if high amounts of sodium sulfate are recycled back to the carbonate monohydrate crystallizer, they produce burkeite crystals (Na.2CO3.2Na.2SO4) that are detrimental to the quality of sodium carbonate monohydrate.

US2004 / 0057892 discloses a process for the production of sodium carbonate and bicarbonate, according to which a purge water of a sodium carbonate monohydrate crystallizer is introduced into a sodium carbonate decahydrate crystallizer and Purified decahydrate crystals are converted to sodium bicarbonate. It has been observed that this process is not efficient when the purge liquid, depending on the source of the throne, contains high levels of impurities. High levels of sodium chloride in the purge liquid prevent gentle crystallization of sodium carbonate decahydrate.

US2926995 discloses a process for producing sodium bicarbonate crystals from sodium carbonate solutions containing sodium chloride from caustic soda-chloride electrolyte cells.

US7507388 discloses a process for producing sodium carbonate and bicarbonate from a pre-purified solution comprising bicarbonate which is first partially decarbonised and then used in a sodium bicarbonate line and a sodium carbonate monohydrate line. The sodium carbonate monohydrate crystallizer purge stream is sent to a mixed sodium carbonate decahydrate and sodium sesquicarbonate line where the resulting filtrate is discarded as the final process purge, or sent after dilution. For a light calcined soda line comprising a sodium bicarbonate intermediate carbonation step, the bicarbonate is separated from the filtrate and this filtrate is also discarded as a final purge. The total reported quantities of purges generated are very high (1.28 t purges per tonne of dense calcined soda) and correspond to 6 to 15 weight percentages of purged sodium carbonate per tonne of dense calcined soda produced.

US2009 / 0291038 (Solvay) discloses a process for the joint production of sodium bicarbonate and sodium carbonate crystals, according to which a solid powder derived from sodium sesquicarbonate, such as calcined trone, is dissolved in water, The resulting aqueous solution is introduced into a crystallizer, in which sodium carbonate crystals and a mother liquor are produced, and part of the mother liquor is removed from the crystallizer (carbonated (carbonated) crystallizer purge to produce valuable sodium bicarbonate crystals). and a second mother water, the second mother water optionally then sent to a storage pond.

It is taught herein that the mother liquor used for the crystallization of sodium bicarbonate should preferably contain at least 175 g / kg sodium carbonate and not more than g / kg sodium chloride no more. 20 g / kg sodium sulfate.

Consequently, the alkali purge level (carbonate or sent to a pond reduced compared to a purge decahydrate treatment, but it is still important and represents significant volumes sent to ponds. In addition, the final bicarbonate rich purge Sodium forms in the evaporation ponds a solid which is harder and less easy to collect and recycle by the calcined soda mill, as it comprises less easy to melt sodium carbonate decahydrate crystals and more sesquicarbonate and hard crystals. Unfused sodium bicarbonate.

US2011 / 112298 discloses a method for extending the life of tailings ponds produced from sodium carbonate containing purge streams, wherein the purge stream is treated with gaseous carbon dioxide, similar to the process of US2009 / 0291038, to produce sodium sesquicarbonate or baking soda before it is introduced into the pond. The sodium bicarbonate produced can be recovered prior to introduction of the treated purge stream into tailings ponds or recovered after deposition in the pond. The document does not refer to the further appreciation of the aqueous purge obtained when sodium bicarbonate is recovered. In addition, as in the process described in US2009 / 0291038, the final bicarbonate-rich purge forms in the evaporation ponds a solid which is harder and less easy to collect and recycle by the calcined soda plant as it comprises less easy-to-melt sodium carbonate decahydrate crystals and more non-melting hard sesquicarbonate and sodium bicarbonate crystals.

Thus, there is still a need in the bicarbonate and sodium carbonate industry, in view of the sustained development, to be able to further reduce the purge volume and reduce alkali loss simply without harming the operating conditions of the powders. associated processes.

SUMMARY OF THE INVENTION

Accordingly, the invention relates to a process for producing sodium bicarbonate from a sodium carbonate-containing stream (A) comprising sodium carbonate and at least one impurity consisting of a water-soluble alkali metal salt at a concentration Ci (A) comprising the following steps:

(a) mixing stream (A) containing sodium carbonate with at least part of stream (B) to produce stream (C);

b) bicarbonating stream (C) with a gas (D) comprising CO2 to produce an aqueous suspension (E) comprising crystals (F) comprising sodium bicarbonate crystals, separating the aqueous suspension (E) to obtain comprising crystals sodium bicarbonate on the one hand and an aqueous mother liquor (G) on the other

(d) partially decarbonate at least part of the aqueous mother liquor (G) and remove part of the water from at least part of the mother liquor (G) at least one alkali metal water-soluble salt impurity at a concentration Cf ( B) optional, recycle at least a part of at least alkaline

2, more so for the reason of the least, an impurity of at least: 1.4, advantageously, by the water-soluble salt of advantageously, at least 4 and still less advantageously metal 7, and mother liquor (G) to be still processed.

A first advantage of the present invention is that it considerably reduces the amount of alkali loss in the purge of a sodium bicarbonate process or a sodium carbonate process in a smooth and inexpensive manner.

A second advantage of the present invention is that it is efficient over a wide spectrum of soluble impurities and a wide range of impurity concentrations.

A third advantage of the process of the present invention coupled with the second advantage is that it allows the use of sodium carbonate streams from synthetic sodium carbonate processes or natural sodium carbonate processes.

A fourth advantage of the present invention is that the obtained technical sodium bicarbonate contains less water soluble impurities than sodium carbonate that would be produced under equivalent water soluble impurity concentration conditions.

A fifth advantage of the present invention also associated with the second advantage is that it allows to exploit one or more trona deposits with different levels of soluble impurities, while being able to treat the various levels of purging a soda ash or sodium bicarbonate factory with the same process as described in the present invention.

A sixth advantage of the present invention is that it allows to send a tailings purging final (I) which has a low sodium bicarbonate content and is easier to recover and melt as it forms softer crystals of decahydrate and Less hard crystals of sodium sesquicarbonate and easier to recycle in a calcined soda plant if necessary.

A seventh advantage of the present invention is that it allows the purging flow to be minimized by preparing the process for dry purging or very small evaporation ponds or for re-introduction of purging into mined cavities.

An eighth advantage of the present invention is that it allows a final purge to be removed from a calcined soda or sodium bicarbonate process, reduced in alkaline sodium content and rich in natural salts such as sodium chloride or sulfate. which may originally come from the sea and which can be recycled back into the sea after dilution.

A ninth advantage of the present invention is that it decreases the size of the equipment and the corresponding investment, and the processing cost of an additional process of the concentrated (I) or (J) chain intended to remove and to valorize or reject part of the concentrated impurities.

A tenth advantage of the present invention is that it reduces the consumption of water for the production of calcined soda and / or the production of sodium bicarbonate by recovering it as condensate from evaporators to recycle it for leaching. calcined throne or for a throne solution mining.

An eleventh advantage of the present invention is that it allows to increase the production of valuable technical sodium bicarbonate from sodium alkaline streams comprising impurities.

A twelfth advantage of the present invention is that the obtained technical sodium bicarbonate is well suited for specific uses, such as flue gas mitigation, despite the high concentration of impurities.

BRIEF DESCRIPTION OF DRAWINGS

Figure 1 is a flow chart illustrating schematically the process of the present invention.

Figure 2 is a flow chart of a process according to an embodiment of the present invention.

The letters and reference numbers cited below refer to the accompanying drawings.

DEFINITIONS

For purposes of this disclosure, certain terms are intended to have the following meanings.

The term 'purge' refers to a stream collected from a part of a process for limiting the concentration of impurities in this process.

The term impurity refers to a compound other than sodium carbonate and / or sodium bicarbonate to be produced.

The term solubility refers to the water solubility of a compound in an aqueous solution.

The term carbonate refers to the action of increasing the total amount of carbonate (carbonate and bicarbonate) in a stream.

The term decarbonate refers to the action of decreasing the total amount of carbonate (carbonate and bicarbonate) in a stream.

The term bicarbonate refers to the action of increasing the amount of bicarbonate in a stream.

The term debicarbonate refers to the action of decreasing the amount of bicarbonate in a stream.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The present invention relates to a process for producing sodium bicarbonate from a sodium carbonate-containing stream (A) comprising sodium carbonate and at least one impurity consisting of a water-soluble alkali metal salt at a concentration C ₄ ( A) comprising the following steps:

(a) mixing stream (A) containing sodium carbonate with at least part of stream (B) to produce stream (C);

b) bicarbonating stream (C) with a gas (D) comprising CO2 to produce an aqueous suspension (E) comprising crystals (F) comprising sodium bicarbonate crystals, separating the aqueous suspension (E) to obtain comprising crystals sodium bicarbonate on the one hand and an aqueous mother liquor (G) on the other

d) partially decarbonating at least part of the aqueous mother liquor (G) and removing part of the water from at least part of the mother liquor (G) to obtain stream (B) with at least an impurity of water-soluble alkali metal salt at an optional Cf (B) concentration, recycle at least a portion such that the ratio of at least one water-soluble alkali metal salt impurity is at least: 1.4, advantageously, at least

2, more advantageously, at least 4 and even more advantageously 7, and remaining mother liquor (G) to be further processed.

In the present invention, the at least one impurity consisting of a soluble alkali metal salt is generally an inorganic water soluble salt selected from the group consisting of: sodium fluoride, sodium chloride, sodium bromide, sodium iodide, potassium chloride, sodium sulfite, sodium sulfate, potassium sulfate, sodium selenate, sodium nitrite, sodium nitrate, sodium hypochlorite, sodium chlorite, sodium phosphate, sodium aluminate, sodium borate, sodium silicate, sodium titanate sodium, sodium vanadate and combinations thereof. Advantageously, the water-soluble alkali metal salt is a water-soluble sodium or potassium salt, more advantageously a water-soluble sodium salt.

In one embodiment of the present invention, the at least one impurity consisting of a water-soluble alkali metal salt is sodium chloride (NaCl). In particular, the process has proven to be efficient even with high concentrations of sodium chloride at several dozen grams of NaCl per kilogram of current (B).

Advantageously, the concentration C _f (B) of sodium chloride is advantageously at least

130 g / kg, more advantageously at least 150 g / kg, even more advantageously at least 170 g / kg. The concentration Cf (B) of sodium chloride (NaCl) is generally a maximum of 300 g / kg, preferably a maximum of 260 g / kg, more preferably a maximum of 220 g / kg. Even more preferred is a maximum of 180 g / kg.

In another embodiment of the present invention, the at least one impurity consisting of a water-soluble alkali metal salt is sodium sulfate (Na ₂ SO ₄ ). In that case the sodium sulfate concentration Cf (B) is generally at least 20 g / kg, advantageously at least 40 g / kg, more advantageously at least 80 g / kg, preferably at least 120 g / kg. g / kg. The concentration C _f (B) of sodium sulfate is generally a maximum of 200 g / kg, preferably a maximum of 180 g / kg, more preferably a maximum of 160 g / kg.

Stream (A) may also comprise at least one other impurity selected from the group of partially water-soluble salts of: aluminum (Al), silver (Ag), arsenic (As), bismuth (Bi), cadmium (Cd), cobalt (Co), copper (Cu), iron (Fe), mercury (Mn), nickel (Ni), lead (Pb), titanium (Ti), thallium (Tl), zinc combinations. The concentration in corresponding elements cited chromium (Cr),

(Hg) molybdenum (Mo), manganese antimony (Sb), tin (Sn), (Zn), vanadium (V) and at your weight on chain (THE) of above are usually at gamma

between 1 ppb (part per billion) to 1000 ppm (part per million) of the element described for stream weight (A). And the concentrations are most often between 0.1 to 100 ppm. Such partially water-soluble salt impurities of the elements listed above are generally: carbonate, or bicarbonate, or hydroxide, or chloride, or sulfate, or nitrate, phosphate, or aluminate, or silicate salts of the corresponding elements.

Likewise, the claimed process of the present invention has also been shown to be efficient with alkaline metal soluble salt of organic compounds, in particular with alkaline metal soluble salt of cerogen (the organic in shales are termed cerogen). When cerogenic organics comprise mono or di or multicarboxylic acids, the solubility of such organics increases and may be from a few dozen ppm by weight to several thousand ppm. Thus, in one embodiment of the present process, the at least one impurity consisting of an alkali metal soluble salt is an organic alkali metal soluble salt. Alcohol, ketone and aldehyde groups are also favorable for greater solubility of the organic counterparts in an aqueous sodium carbonate stream.

Sodium carbonate-containing stream (A) may be any stream made of a solid, a suspension of a solid in an aqueous solution or an aqueous solution, comprising sodium carbonate and suitable for feeding a sodium bicarbonate crystallizer.

In a first embodiment of the present process, the sodium carbonate-containing stream (A) is derived partly or wholly from crude sodium bicarbonate from a synthetic calcined soda process such as the synthetic ammonia Solvay process or the ammonium chloride Hou process . Advantageously, sodium carbonate-containing stream (A) is an aqueous solution which is derived partially or wholly from a partially decarbonated crude sodium bicarbonate paste from the synthetic Solvay ammonia process or from the ammonium chloride Hou process.

In a second variant of the present process, the sodium carbonate-containing stream (A) is derived partly or wholly from throne or nacolite. Preferably, the sodium carbonate-containing stream (A) is derived partially or wholly from throne. In the present invention the throne is generally processed by conventional mining. Advantageously, the throne may also be processed by solution mining. In fact, when the throne is processed by solution mining, the water-soluble alkali metal salts may be increased because of infiltration waters to adjacent ore layers that may contain water-soluble minerals. Generally such water soluble minerals comprise in particular alkali metal halides (fluorides, chlorides, bromides, iodides), water soluble salts of sulfates, borates, phosphates, aluminates, silicates, titanates, vanadates. This makes the present invention particularly suited for the production of technical sodium bicarbonate from solution mining processed throne.

Sodium carbonate-containing stream (A) may also be partially or wholly derived from tailings basin solids comprising sodium carbonate. This can be particularly advantageous if the solids in the tailings ponds considered are silicate and organic rich, as the sodium bicarbonate crystals formed in step b) will pick up most of the silica and part of the stream organic (C ), and this improves the flowability of the crystals (F).

In an advantageous embodiment of the first or second variant of the present process, sodium carbonate-containing stream (A) is an aqueous solution (A ') comprising sodium carbonate.

In a particular embodiment of the first or second variant of the present process, stream (A) is removed from a sodium carbonate crystallizer. In the present invention, sodium carbonate crystallizer means a crystallizer in which crystals comprising sodium carbonate are produced. The sodium carbonate crystallizer is selected from the group consisting of: anhydrous sodium carbonate crystallizer, sodium carbonate monohydrate crystallizer, sodium carbonate heptahydrate crystallizer, sodium carbonate decahydrate crystallizer sodium carbonate, a sesquicarbonate crystallizer, a wegscheiderite crystallizer (Na ₂ CO3.3NaHCC> 3 also called decemite) and combinations thereof. Advantageously, stream (A) is an aqueous solution (A ') removed from a sodium carbonate crystallizer.

Most advantageously, the aqueous solution (A ') is a purge of a sodium carbonate monohydrate crystallizer.

Accordingly, the present invention also relates to a process for the joint production of carbonate and sodium bicarbonate crystals comprising a first step of introducing a sodium carbonate solution comprising sodium carbonate and at least one impurity consisting of a water-soluble alkali metal salt, in a sodium carbonate crystallizer, produce a first aqueous suspension comprising sodium carbonate crystals, subject the first aqueous suspension to separation to obtain crystals comprising sodium carbonate on the one hand, which are recovered, and a mother liquor on the other, part of the sodium carbonate crystallizer mother liquor being removed to constitute the sodium carbonate-containing stream (A) for further processing according to the process for producing sodium bicarbonate of the present process.

In the embodiment particularly above the present invention, sodium carbonate crystallizer is advantageously fed with a sodium carbonate solution containing sodium carbonate and at least one impurity consisting of a water soluble alkali metal salt at a concentration C _o, and the ratio of the Cf (B) / Co concentrations of the at least one impurity is at least 14, advantageously at least 30, more advantageously at least 60 and even more advantageously at least 120.

In the present invention, the sodium carbonate crystallizer may also be an evaporation vessel or pond in which crystals comprising sodium carbonate compounds are formed.

In a special embodiment of the second variant of the present process, the aqueous solution (A ') is a purge of a sodium carbonate monohydrate crystallizer in combination with tailings basin solids derived from carbonate crystallizer purges. sodium.

In another special embodiment of the second embodiment of the present process, the process of the present invention is coupled with the process described in WO2011 / 138005A1 (Solvay) which is incorporated herein by reference. In this case, the process of the present invention further comprises:

(k) deposit the remainder (I) of stream (B) into a tailings pond and where part of the remaining sodium carbonate in the tailings pond crystallizes into a solid mass comprising sodium carbonate decahydrate and in which a solution is formed ( Q) concentrated comprising impurities selected from the group consisting of silicates, sodium chloride, sodium sulfate, organic matter and combinations of two or more thereof,

l) optionally contacting said solid mass with a leach solution to selectively dissolve at least a portion of a first impurity of the mass contacted with the leach solution to form a leach and a leach residue, collecting the residue leached, dissolve at least a portion of the leached residue in an aqueous medium to form a liquid; optionally performing a second impurity removal step comprising performing a magnesium treatment to form a treated liquid, said treatment comprising adding a magnesium compound to said liquid during dissolution of the leached residue or adding a magnesium compound to said liquid or a portion thereof upon dissolving the leached residue to form a water-insoluble material with at least a portion of a second impurity, and passing said treated liquid through at least one separation unit to remove the water-insoluble material and to obtain a purified solution;

m) providing said solid mass or said liquid or said purified solution as a feedstock to a process which produces a crystalline product comprising sodium carbonate, sodium bicarbonate, sodium sulfite or other derivatives.

The remainder (I) of stream (B) or part (L) (as defined in the embodiment of Fig. 2) or part (J) of the mother liquor (G) are concentrated in soluble salts and other impurities present. in stream (A) containing sodium carbonate. Thus, in another embodiment of the present invention, the process further comprises the following steps:

n) discarding the remainder (I) of stream (B) or part (J) of mother liquor (G) or part (L) of liquid (K) in a solution mining cavity or mined cavity or injection deep well or

(o) recycle the remainder (I) of stream (B) or part (J) of mother liquor (G) or part (L) of liquid (K) into a solution mining cavity or mined cavity, and recover an aqueous solution of sodium carbonate from the solution mining cavity or mined cavity, wherein the recovered aqueous sodium carbonate solution comprises sodium chloride and / or sodium sulfate at a concentration of sodium chloride and / or sodium sulfate. sodium lower than the sodium chloride concentration and / or the sodium sulfate concentration in the remainder (I) or part (J) or part (L) ·

Steps n) or o) are particularly advantageous when sodium carbonate-containing stream (A) is derived partly or wholly from trone or nacolite as it allows the soluble salts originally present in the ore to be recycled within the mining cavity of the mine. or deep well. In addition, the pH of the final purges can be controlled according to the sodium bicarbonate content, since sodium bicarbonate is a natural pH buffer. Thus, the volume that is recycled in this cavity or mine or deep well is greatly reduced compared to the volume of the original ore extracted from the cavity or mine or deep well.

Generally sodium carbonate-containing stream (A) comprises at least 15 weight percent sodium carbonate, expressed as dry soluble salts.

Advantageously, stream (A) comprises at least: 20, more advantageously 24 weight percent sodium carbonate, expressed as dry soluble salts.

Stream (A) is advantageously selected from the group of purge and recycle streams of sodium carbonate or sesquicarbonate crystals, mine water streams, evaporative pond salt water streams, sodium carbonate decahydrate deposits. and water, other effluent streams and combinations thereof.

Stream (A) generally comprises at most: 98, advantageously 95, more advantageously 85 weight percent sodium carbonate, expressed as dry soluble salts. Where sodium carbonate-containing stream (A) is a suspension of a solid in an aqueous solution, or an aqueous solution, it generally comprises at most: 99, advantageously 90, more advantageously 80 weight percent. This allows to limit the number of recycles in the sodium bicarbonate cycle of the present invention.

If the sodium carbonate stream is derived from a solid stream or is an aqueous suspension or aqueous solution concentrated in sodium carbonate, water (N) may be added to the sodium carbonate containing stream (A), so that the combination of the with stream (A) forms a feedstock suitable for forming crystals (F) comprising sodium bicarbonate crystals when bicarbonated.

In particular, the amount of water (N) controlled to limit the density of the aqueous suspension to generally be at most 60 wt.%, Advantageously at most.

50% by weight, preferably at most 40% by weight, more preferably at most 35% by weight. Being the density of the solids suspension in an aqueous suspension, the weight ratio of the described solid to the aqueous suspension.

In the present invention, stream (A) generally comprises at least 2%, advantageously at least 3%, more advantageously at least 4% by weight of sodium chloride and / or sodium sulfate.

Stream (A) may contain a high level of sodium chloride and / or sodium sulfate. Advantageously, however, the concentration of stream (A) in sodium chloride and / or sodium sulfate should be limited to a maximum such that stream (G), corresponding to the mother liquor of the bicarbonate crystallizer separated in step c). , have a maximum concentration of 26% (260 g / kg) in sodium chloride or 20% (200 g / kg) by weight of sodium sulphate to avoid the limit of solubility of sodium chloride and / or sodium sulfate in the stream (G).

4

In the case of stream (A) comprising sodium chloride and sodium sulphate, the concentrations of these two impurities in stream (G), respectively marked [NaCl] (G) and [Na2SO ₄ ] (G), expressed in g / kg, must be advantageously limited according to the following equation;

[NaCl] (G) / 1.3 + [Na ₂ SO ₄ ] (G) <200 g / kg

Also when a significant concentration of other very soluble common ion salts with sodium ions, or chloride, or sulfate, in an accumulated proportion of at least 5% by weight of the accumulated amount of sodium chloride and sodium sulfate in the stream ( (A), these salt concentrations of impurities shall be added to the sum of the sodium chloride and sodium sulphate concentrations, and the latter sum shall be kept to a maximum of 20% by weight in the stream (G).

In the present invention, or used to control the concentration of the water-soluble alkali metal salt, such as sodium chloride, or sodium sulfate concentrations, in aqueous mother liquor (G) during bicarbonation step b). When the flow of currents (I) or (L)) increases, the concentration (s) Ci (G) of the alkali metal salt / water soluble salts (s) in the process cycle decreases / decreases, and vice versa. These flows may be adjusted so that at the target defined concentration of the water-soluble alkali metal salt in the aqueous mother liquor (G), or in or (or (L)), the flow of the water-soluble alkaline metal salt purged or (J) equalize the inlet flow of the water-soluble alkali metal salt entering the process (i.

e., through streams (A), (A '), (A' ') and (A' '')) minus the flow of the water-soluble alkali metal salt leaving the process with the

Generally when stream (A) is the aqueous purge of a monohydrate crystallizer, the purge NaCl concentration is at most 5% and the purge Na ₂ SO ₄ concentration is at most 7% by weight in the aqueous solution. In fact, a classic MVR (Mechanical Vapor Recompression) crystallizer cannot function at significantly higher NaCl levels than 2-3% without crystallizing anhydrous sodium carbonate, which causes operational difficulties. The triple effects monohydrate evaporator crystallizer operates at low temperatures and can accept high concentrations of NaCl, up to 4-5% depending on a variety of factors. A concentration of Na ₂ SO ₄ above 3 to 7% induces the formation of burkeite crystals (Na ₂ CO _{3 2} Na ₂ SO ₄ ) according to the crystallizer temperature (between 40 ° to 100 ° C).

A factory typical soda calcined Natural in highchair have an concentration Na2CC power supply> 3 at liquid in 28 to 30%, an concentration feed of about NaCl in 0.2% and / or an concentration feed from Na2SO ₄ about of 0, 05 a

0.2%, which means that a traditional prior art plant comprising a sodium carbonate crystallizer can operate between 10 and 20 concentration cycles. This number of concentration cycles is generally close to the ratio of: the final concentration to the soluble impurity feed concentration. This ultimately imposes product loss, purge volumes and the size of ponds and disposal in a natural calcined soda mill without recovery of valuable alkali.

The present invention makes it possible to substantially increase the concentration cycle from 10 to 75 cycles and even more simply. In addition, the present process allows to limit energy consumption and related costs described for total sodium carbonate production, when sodium carbonate stream (A) is a purge of a sodium carbonate crystallizer, since the purge generally represents 2 to 15% of the sodium carbonate stream entering the sodium carbonate crystallizer.

In the present invention, partial debicarbonation of the aqueous mother liquor (G) and removal of part of the water in step d) may be accomplished by any means known in the art. Partial debicarbonation and removal of part of the water may be carried out in one step or in several steps. Generally, decarbonation is caustic soda to be performed by chemical calcination using transforming part of the liquid sodium bicarbonate (G) into sodium carbonate, or carried out by thermal decarbonation using steam or using a boiler to thermally decompose part of sodium bicarbonate into carbonate. sodium, water and CO2 ·

Thermal debicarbonation is preferred using steam or a boiler.

Removal of part of the water from the liquid (G) may be carried out in a descending film evaporator, or in a boiler, or in a forced circulation evaporator, or in a forced circulation evaporator crystallizer known in the art.

The process of the invention is illustrated in Figure 1 (Fig. 1). Stream (A) containing sodium carbonate is mixed with part of stream (B) to produce stream (C). Stream (C) is bicarbonated with a gas (D) comprising CO2 in a carbonation device 1 to produce an aqueous suspension (E) comprising crystals (F), said crystals (F) comprising sodium bicarbonate crystals. Suspension (E) is separated into crystals (F) comprising sodium bicarbonate crystals on the one hand and an aqueous mother liquor (G) on the other with a separation device 2. The aqueous mother liquor (G) is partially decarbonated and part of the water is removed to obtain stream (B) and an optional gas (H) comprising CO2 in a debarking device 3. Thus, stream (B) is more concentrated. in water-soluble salt content than stream (G). At least part of the stream (B) is recycled to form stream (C) in combination with stream (A). The remainder (I) of stream (B) is removed from the cycle or a portion (J) of aqueous mother liquor (G) is removed for further processing.

Figure 2 is a flow chart of a process according to an embodiment of the present invention. In this embodiment, the debarking and removal of part of the water from the stream (G) is carried out in two steps and the optional recycling of water and gas (H) of CO2 is described in the dotted lines. In this embodiment, the sodium carbonate containing stream (A) is mixed with optional water (N) to form an aqueous solution (A ') comprising sodium carbonate, and with a stream (B) to produce a stream (C). . Stream (C) is bicarbonated with a gas (D) comprising CO2 in a carbonation device 1 to produce an aqueous suspension (E) comprising crystals (F), said crystals (F) comprising sodium bicarbonate crystals. Suspension (E) is separated into crystals (F) comprising sodium bicarbonate crystals on the one hand and an aqueous mother liquor (G) on the other with a separating device 2. The aqueous mother liquor (G) is debicarbonated in a debarbonation device 3 to produce a depleted or depleted sodium bicarbonate mother liquor (K) and a vapor (H) comprising carbon dioxide, and the mother liquor (K) It is partially evaporated to remove at least part of the water in an evaporator 4 to obtain stream (B) and water vapor (P). Stream (B) may be a clear liquid or a paste. Optionally, part or all of the water vapor (P) may be recycled to the debarking device and injected directly, or after steam recompression, or may be recycled to the debarking device as indirect heating by a boiler.

At least part of the concentrated stream (B) is recycled to form stream (C) in combination with stream (A).

The remainder (B) is removed, and / or a portion (J) of the aqueous mother liquor (G) is removed from the cycle, and / or part of the mother liquor of the cycle to be additionally in fact useful for controlling at least one impurity consisting of water-soluble alkali metal salt in the aqueous mother liquor during bicarbonation step b) in the bicarbonation device 1.

In a variant of this embodiment, a stream (A '') containing sodium carbonate, such as mine waters, tailings pond waters, or dilute waters, may be added to depleted or depleted mother liquor (K). baking soda before partially evaporating to remove part of the water to give the concentrated stream (B). This may be advantageous to avoid the solubility limit of the sodium carbonate and / or water soluble alkali metal salt in the evaporator.

In another variant of this embodiment, if a stream (Ά '' ') containing sodium carbonate, such as mine waters, tailings pond waters, or dilute waters, has a sodium bicarbonate content, or a water and a sodium bicarbonate content, to be first decreased before being recycled into the bicarbonation device, a suitable point for introducing this stream into the process is in the debarking device 3 with the aqueous mother liquor (G).

Optionally, in the case of the embodiment illustrated in Fig. 2, gas (H) is partially used to bicarbonate stream (C) with gas (D).

In fact, gas (H) comprises a high CO2 content and the remainder is mainly steam (water vapor) which can be reused in step b) without water condensation or with water condensation and removal of water before introducing it. stream (D) to control the water balance of the present process together with the water withdrawals from stream (F), (I), (L), (J), (P), and total water inlets from currents (A), (Α ^Λ ), (A ''), (A ^{,, f} ).

In the present process, in step b), gas (D) is a gas comprising at least:

20, advantageously 30, more advantageously 40%, even more advantageously 80% by volume of

CO2 expressed as dry gas.

Bicarbonation step b) is performed at any temperature compatible with the known domain of sodium bicarbonate. Preferably, it is carried out at a temperature of

at least: 20 ° C, advantageously 38 ° C, more advantageously

Even more advantageously 70 ° C.

Too high a temperature may be detrimental to CO2 absorption when the pressure above atmospheric pressure is not achieved. Thus, bicarbonation step b) is generally carried out at a temperature of up to: 100 ° C, advantageously 90 ° C, more advantageously 80 ° C and even more advantageously 75 ° C.

In the present invention, the crystals (F) obtained in step b) comprise sodium bicarbonate crystals. Advantageously, the operating point (concentrations of sodium bicarbonate, sodium carbonate and water-soluble alkali metal salt (s) such as NaCl and Na ₂ SO ₄ ) in the carbonation step must be controlled so that it remains in the sodium bicarbonate domain of the solubility diagram. This is achieved by supplying C0 ₂ sufficient in the bicarbonation device so that the sodium carbonate concentration in the mother liquor (G) bicarbonation device is less than the limit of sodium carbonate concentration to the solubility of the indicated sodium sesquicarbonate [ Na ₂ CO ₃ ] (sesqui) at operating temperature.

If [X] (G) represents soluble salt concentrations expressed in g / kg NaCl, or Na ₂ SO ₄ , or the sum of NaCl and Na ₂ SO ₄ concentrations if both salts are present, this is generally achieved. between 20 ° to 80 ° C when the sodium carbonate concentration of the mother liquor (G), marked [Na ₂ CO ₂ ] (G), is lower than the following value (expressed in g / kg):

170 - 0.66 [X] (G) (g / kg)

A safety margin should be considered so that the sodium carbonate concentration is preferably at most this value minus 5 g / kg, more preferably at most this value minus 10 g / kg and, Most preferred is this maximum minus 20 g / kg.

This allows crystallization mainly of sodium bicarbonate. Then, if the corresponding crystals are separated from their mother liquor (G) which is concentrated to NaCl and / or Na ₂ SO ₄ , and optionally the obtained crystals are washed when necessary to remove high levels of impregnated mother liquor. and soluble salts, such as NaCl or Na ₂ SO ₄ , the content of crystals (F) comprising sodium bicarbonate crystals is generally at least 40 wt% or at least 50 wt%, preferably at least 60 wt%, more preferably at least 80 wt% and most preferably at least 90 wt% sodium bicarbonate. Crystals (F) generally comprise at most 50 wt%, at most 30 wt%, or at most 20 wt%, preferably at most 10 wt%, more preferably at most 5 wt% and most preferably at most 3 wt% sodium carbonate.

The content of crystals (F) in soluble salts, such as sodium chloride and / or sodium sulfate, is generally at most 10 wt.%, Preferably at most 4 wt.%, More preferably. at most 1% by weight.

According to the end use of crystals (F) obtained comprising sodium bicarbonate crystals, the process of the present invention may further comprise:

g) optionally washing crystals comprising sodium bicarbonate to produce optionally washed crystals comprising sodium bicarbonate, drying optionally washed crystals comprising sodium bicarbonate.

As an alternative, there is the possibility of partially or totally calcining the sodium bicarbonate instead of just drying the crystals.

In that case, the process according to the present invention further comprises the steps of:

g) optionally washing the sodium bicarbonate crystals to produce optionally washed crystals comprising sodium bicarbonate,

i) calcining crystals (F) comprising sodium bicarbonate crystals or optionally washed crystals comprising sodium bicarbonate into calcined crystals comprising sodium carbonate.

By partially or totally calcining the sodium bicarbonate of the crystals in step i), a gas (0) comprising carbon dioxide is produced. Carbon dioxide and water may be wholly or partially recovered and recycled to the bicarbonation step.

Thus, the process of the present invention may further comprise the step:

j) recovering at least part of the gas (0) comprising carbon dioxide and recycling it to step b).

EXAMPLES

The following examples are intended to exemplify the invention only and are not intended to limit the scope of the claimed invention.

Example 1

Table 1 exemplifies a mass flow diagram of an embodiment of the process of the present invention as described in Figure 2, wherein the main soluble salt impurity of sodium carbonate stream (A) is sodium chloride.

This example shows the strong interest in the case where the sodium carbonate stream (A) is a purge of a sodium carbonate crystallizer: the final purge (I) mass flow is 226 kg / h, which represents less than two quarter of the original purge (A) value at 1000 kg / h, and the sodium carbonate perimeter of the final purge (I) is 27 kg / h, thus reducing the initial value factor from initial 242, thanks to almost 9 mass kg / h of recycle cycle carbonate compared to purge sodium (A) associated with a debicarbonation device and an evaporator of the present process.

By comparison, prior art US2009 / 0291038 (Solvay) shows in Example 1 of the corresponding document a reduction in the loss of alkali sodium in the final purge by 60%, compared to about 90% in the present example, and a reduction 10% of the initial purge mass flow compared to about 77% in the present example.

Example 2

In this example, the same data from Table 1 can illustrate a mass flow sheet of an embodiment of the process of the present invention as described in Figure 2, wherein the main soluble salt impurity of sodium carbonate stream (A) is sodium sulfate (Na ₂ SO ₄ ). In this case, sodium chloride (NaCl) mass flows and sodium chloride (NaCl) concentrations should be interpreted respectively as Na2SC> 4 mass flows and Na2SC> 4 concentrations instead of those of NaCl.

Example 3 to 7 (EQ to E6)

In this example, equipment and operating conditions similar to Example 1 of US2009 / 0291038 (Solvay) were used, but the bicarbonation was carried out in batch in a 3 liter stirred reactor at 70 ° C with CO2 gas at a concentration of 100% by vol. dry and saturated with water, with one hour of residence time.

The obtained crystals were filtered, washed with water and ethanol, dried for 24 hours at room temperature.

Table 2 presents the results of the analysis of the initial and final mother liquor, the obtained crystals, the suspension density (solid weight reported by the weight of the suspension) and also the particle size distribution of the obtained crystals.

If the disclosure of any patent, patent applications, and publications which are incorporated herein by reference conflict with the present disclosure to the extent that they may make a term confusing, this disclosure should take precedence.

Table 1: Example 1 - Mass Balance Flowchart

Chain (THE) (THE) (B) (W) (D) (AND) (F) (G) (H) (I) (K) (0) If calcined Phase net net net net gas folder Sun. net gas net net gas Flow (kg / h) 1000 500 1477 1751 94 1845 345 1500 28 226 1472 127 Liquid NaHCO ₃ 13 7th 56 54 68 68 9th 50 Na ₂ CO ₃ 242 121 176 270 44 44 27 55 NaCl 39 20 255 236 236 236 39 236 h ₂ o 706 353 990 1192 1154 1154 151 1132 Liquid Total 1000 500 1477 1751 1500 1500 226 1472 Mass fraction (g / kg) NaHCO ₃ 13 13 38 31 45 45 38 Na ₂ CO ₃ 242 242 119 154 29 29 119 NaCl 39 39 173 134 157 157 173 h ₂ o 706 706 670 681 769 769 670 Solid Flow (kg / h) NaHCO ₃ 345 345 Na ₂ CO ₃ 0 0 Total solid 345 345 Gas Flow (kg / h) h ₂ o 0 23 37 C0 ₂ 94 5th 90 Total Gas 94 28 127

Table 2 - Operating conditions, and chemical and physical analysis of crystals obtained from examples 3 to 7 (referenced respectively EO, E2, E3, E6).

Test Ref. No. E0 E2 E3 E6 Temperature ° C 70 70 70 70 Residence time H 1 1 1 1 Initial mother water NaHCO ₃ g / kg 79 54 44 45 Na ₂ CO ₃ g / kg 49 52 52 50 NaCl g / kg 136 144 153 75 N3.2SO4 g / kg - - - 75 h ₂ o g / kg 736 750 751 755 Total g / kg 1000 1000 1000 1000 Ultimate Bittern NaHCO ₃ g / kg 50 48 45 62 Na ₂ CO ₃ g / kg 11 20 10 17 NaCl g / kg 146 153 165 78 N3.2SO4 g / kg - - - 77 h ₂ o g / kg 793 779 780 766 Total g / kg 1000 1000 1000 1000 Final dry solid NaHCO ₃ g / kg 942 915 908 906 Na ₂ CO ₃ g / kg 29 38 41 38 NaCl g / kg 9th 30 42 8th N3.2SO4 g / kg - - - 8th h ₂ o g / kg 20 17 9th 40 Suspension Density wt% 6.9 6.3 6.5 4.7 Dist. the size of particle dlO pm 121 41 39 50 d50 pm 376 129 125 126 d90 μπι 678 280 415 566

Lisbon, March 14, 2012

Claims (19)

Process for producing sodium bicarbonate from a sodium carbonate-containing stream (A) comprising sodium carbonate and at least one impurity consisting of a water-soluble alkali metal salt at a concentration C1 (A), characterized in that said process comprises the following steps: The) mix the current (A) containing carbonate in sodium with at least part of a chain (B) for produce a current (C), B) bicarbonate the current (C) with a gas (D) understanding C0 ₂ to produce an suspension (AND) aqueous comprising crystals (F), understanding sodium bicarbonate crystals, c) separating the aqueous suspension (E) to obtain crystals (F) comprising sodium bicarbonate crystals on the one hand and an aqueous mother liquor (G) on the other; (d) partially decarbonate at least part of the aqueous mother liquor (G) and remove part of the water from at least part of the mother liquor (G) to obtain stream (B) with at least an impurity of water-soluble alkali metal salt at a concentration C _f (B) and an optional gas (H), e) recycling at least part of the stream (B) to step a) so that the concentration ratio C _f (B) / Ci (A) of at least one alkali metal water-soluble salt impurity is at least 1.4, advantageously at least 2, more advantageously at least 4, and even more advantageously 7, and f) remove the remaining (I) from the stream (B) or the remaining (J) from the mother liquor (G) to be further processed. Process according to Claim 1, characterized in that the at least one impurity consisting of a water-soluble alkali metal salt is an inorganic water-soluble salt selected from: sodium fluoride, sodium chloride, sodium bromide, sodium iodide, chloride of potassium, sulfite in sodium, sulfate in sodium, sulfate in potassium, selenate in sodium, nitrite in sodium, nitrate in sodium hypochlorite in sodium, chlorite in sodium, phosphate in sodium, sodium aluminate, sodium borate, sodium silicate, sodium titanate, sodium vanadate and combinations thereof. Process according to Claim 2, characterized in that the water-soluble alkali metal salt is a water-soluble sodium or potassium salt, advantageously a water-soluble sodium salt. Process according to any one of the preceding claims, characterized in that the stream (A) also comprises at least one other impurity selected from partially water-soluble salts of aluminum (Al), silver (Ag), arsenic (As), bismuth (Bi), Cadmium (Cd), Cobalt (Co), Chromium (Cr), Copper (Cu), Iron (Fe), Mercury (Hg), Molybdenum (Mo), Manganese (Mn), Nickel (Ni), Lead (Pb), antimony (Sb), tin (Sn), titanium (Ti), tellurium (T1), zinc (Zn), vanadium (V) and combinations thereof. Process according to Claim 1, characterized in that one of the at least one impurity consisting of a water-soluble alkali metal salt is a water-soluble organic alkali metal salt. Process according to Claim 1, characterized in that one of the at least one impurity consisting of a water-soluble alkali metal salt is sodium chloride (NaCl). Process according to Claim 6, characterized in that the sodium chloride (NaCl) concentration C _f (B) is at least 130 g / kg. Process according to Claim 1, characterized in that one of the at least one impurity consisting of a water-soluble alkali metal salt is sodium sulfate (Na ₂ SO ₄ ). Process according to Claim 8, characterized in that the concentration C _f (B) of sodium sulphate (Na ₂ SO ₄ ) is at least 20 g / kg, advantageously at least 40 g / kg, more advantageously. at least 80 g / kg, preferably at least 120 g / kg. Process according to Claim 1, characterized in that the stream (A) is removed from a sodium carbonate crystallizer selected from the group consisting of: anhydrous sodium carbonate crystallizer, a sodium carbonate monohydrate crystallizer a sodium carbonate heptahydrate crystallizer, a sodium carbonate decahydrate crystallizer, a sodium sesquicarbonate crystallizer, a wegscheiderite crystallizer and combinations thereof; Advantageously, the sodium carbonate crystallizer is a sodium carbonate monohydrate crystallizer. 11. Process according to claim 10, characterized in that the sodium carbonate crystallizer is fed with a sodium carbonate solution containing sodium carbonate and at least one impurity consisting of a water soluble alkali metal salt at a concentration C _a and wherein the ratio of C _f (B) / C ₀ concentrations of at least one impurity is at least 14, advantageously at least 30, more advantageously at least 60, and even more advantageously at least 120. . Process according to Claim 1, characterized in that the sodium carbonate from stream (A) is derived partly or wholly from trona recovered by mechanical mining or solution mining. Process according to Claim 1, characterized in that the stream (A) is partially or wholly derived from tailings basin solids comprising sodium carbonate. Process according to claim 1, characterized in that stream (A) is an aqueous solution comprising sodium carbonate, advantageously stream (A) is a purge of: a crystallizer of sodium carbonate monohydrate. A process according to claim 1, characterized in that in step d) the optional gas (H) is a gas comprising at least 20, advantageously at least 30, more advantageously at least 40, even more advantageously at least 80% by volume of CO ₂ expressed as dry gas. Process according to Claim 1, characterized in that step b) is carried out at a temperature of at least 20 ° C, advantageously at least 38 ° C, more advantageously at least 55 ° C and even more advantageously. at least 70 ° C. A process according to claim 1, further comprising: g) optionally washing crystals (F) comprising sodium bicarbonate to produce optionally washed crystals comprising sodium bicarbonate, h) drying the crystals (F) comprising sodium bicarbonate crystals or optionally washed crystals. A process according to claim 1, further comprising: g) optionally washing crystals optionally washed bicarbonate crystals (F) comprising producing crystals comprising sodium to sodium bicarbonate, (F) comprising sodium bicarbonate crystals or optionally washed crystals comprising sodium bicarbonate to calcined crystals comprising sodium. A process according to claim 1, further comprising: n) discarding the remainder (I) of stream (B) or part (J) of mother liquor (G) or part (L) of liquid (K) in a solution mining cavity or mined cavity or injection deep well or (o) recycle the remainder (I) of stream (B) or part (J) of mother liquor (G) or part (L) of liquid (K) into a solution mining cavity or mined cavity, and recover an aqueous solution of sodium carbonate from the solution mining cavity or mined cavity, wherein the recovered aqueous sodium carbonate solution comprises sodium chloride and / or sodium sulfate at a concentration of sodium chloride and / or sodium sulfate. sodium lower than the sodium chloride concentration and / or the sodium sulfate concentration in the remainder (I) or part (J) or part (L). Process for the joint production of sodium carbonate and bicarbonate crystals, characterized in that it comprises in a first step introducing a sodium carbonate solution comprising sodium carbonate and at least one impurity consisting of a water-soluble alkali metal salt in a crystallizer. sodium carbonate, producing a first aqueous suspension comprising sodium carbonate crystals, subjecting the first aqueous suspension to separation, to obtain crystals comprising sodium carbonate on the one hand, and a mother liquor on the other. another, part of the mother liquor being removed from the sodium carbonate crystallizer to form the sodium carbonate-containing stream (A) for further processing according to the process for producing sodium bicarbonate of any preceding claim.