Process for the preparation of potassium bitartrate by treatment of brine

Abstract

The present invention relates to a process for preparing potassium bitartrate by treating a brine typically containing NaCl, KCl, CaSO4 and / or MgSO4 salts.

Description

Title of the invention: Process for the preparation of potassium bitartrate by treatment of a brine TECHNICAL FIELD OF THE INVENTION

[0001] The present invention relates to the preparation of potassium bitartrate by treatment of brine from the desalination of seawater. The process can furthermore make it possible to selectively recover NaCl. STATE OF THE ART

[0002] Potassium bitartrate is an organic compound with the chemical formula C4 O6H5K and the structural formula COOH-CHOH-CHOH-COOK. It is also known by the names monopotassium tartrate, potassium acid tartrate, potassium hydrogen tartrate, "cream of tartar", "white tartar" or "crystal (or crystals) of tartar".

[0003] Potassium bitartrate is used in the manufacture of food products, particularly baking powders, biscuits, pastries and confectionery, as a food stabilizer and to increase their heat tolerance. It is also used in metal processing, wire drawing, pyrotechnics, glassworks and watchmaking.

[0004] Potassium bitartrate is a by-product of winemaking. It is generally obtained from the sediment left on the barrels after the winemaking process. Once the vat is emptied of its wine, the walls are scraped. The crystals thus collected are cleaned, crushed and refined to form cream of tartar. The production of potassium bitartrate is limited or even insufficient because it is subject to hazards such as poor harvests.

[0005] At the same time, the production of drinking water by desalination of seawater leads to the discharge of a large quantity of brine. Brine is an aqueous solution loaded with ionic species capable of forming salts such as NaCl, MgCl2, KC1. Brine cannot be discharged as is into the environment and needs to be reprocessed, for example by being diluted with non-drinking water before being returned to the sea.

[0006] There is therefore a strong interest in recovering the salts contained in the brine resulting from the desalination of sea water.

[0007] Thus, there is, on the one hand, a need to have new methods for preparing potassium bitartrate and, on the other hand, a need to have new methods for recovering the brine from the desalination of sea water. Advantageously, the proposed process will make it possible to recover the potassium in the brine. by meeting the need for potassium bitartrate. Summary of the invention

[0008] The subject of the present invention is a process for preparing potassium bitartrate from brine obtained from the desalination of seawater, the process comprising the following steps:

[0009] a) elimination of at least 90% of the volume of water initially contained in the brine (1) leading to the formation of a suspension followed by the separation of the suspension into a filtrate (2) and a solid residue (3) comprising NaCl crystals;

[0010] b) bringing tartaric acid into contact with the filtrate (2) leading to the formation of a mixture (4) containing potassium bitartrate;

[0011] c) separation of the mixture (4) into a solid comprising the potassium bitartrate (5) formed in step b) and a filtrate (6) containing magnesium ions.

[0012] Other aspects of the invention are as described below. FIGURES

[0013] [Fig. 1] is an overall diagram illustrating the process for preparing potassium bitartrate according to the invention. DETAILED DESCRIPTION OF THE INVENTION

[0014] The various embodiments presented throughout the description can be used alone or in combination with each other, without limitation of combination.

[0015] The inventors have developed a process for preparing potassium bitartrate by treating brine from the desalination of seawater.

[0016] Advantageously, the method according to the present invention can be implemented to recover the potassium contained in the brine resulting from the desalination of seawater. The brine:

[0017] The brine useful in the process according to the invention comes from the desalination of sea water. The terms "sea water" designate water from an ocean or water from an inland sea or similar.

[0018] The brine mainly contains ionic species such as chloride ions, sodium ions, sulfate ions, magnesium ions, calcium ions, potassium ions and / or carbonate ions.

[0019] The brine useful in the process of the invention is conventionally a brine resulting from the desalination of seawater by distillation or reverse osmosis.

[0020] The water of the Atlantic Ocean has an average salinity of 35 g / L, or 3.5% by weight. Ocean water generally has a salinity ranging from 30 to 40 g / L, or 3 to 4% by weight. Inland seas or similar have a higher salinity, because evaporation concentrates the salt there.

[0021] A brine resulting from the desalination of seawater generally has a salinity ranging from 1.1 to 2 times, typically from 1.2 to 2 times or from 1.3 to 1.7 times the salinity of the seawater from which it originates.

[0022] Commonly, brine from seawater desalination, typically by reverse osmosis, has an average salinity ranging from 4.6 to 9.0% by weight, or from 4.6 to 6.0% by weight and can even range from 1 to 4.5% by weight.

[0023] The brine useful in the process according to the invention can therefore have an average salinity ranging from 4.6 to 9.0% by weight, or from 4.6 to 6.0% by weight and can even range from 1 to 4.5% by weight.

[0024] Table 1 describes an example of the ion composition of a brine resulting from the desalination of seawater compared to a composition of the seawater from which it is derived.

[0025] [Tables 1] Seawater (g / L) Brine (g / L) Na+ 10.56 16.87 K+ 0.38 0.88 Mg2+ 1.30 1.93 Ca2+ 0.40 0.67 Cl 19.36 40.02 SO42 2.70 6.56

[0026] Table 1: Chemical composition of a brine compared to that of seawater

[0027] The crystallization of the species contained in a brine leads to the formation of salt. For example, chlorine can combine into several salts: NaCl, MgCl2, KC1. Table 2 shows the calculated weights of the salts that can be extracted from seawater by crystallization.

[0028] [Tables2] Salts g / L NaCl 30 MgCl2 3.80 CaSO4 1.3 Na2SO4 0.9 KC1 0.86

[0029] Table 2: Average composition of a liter of sea water

[0030] Seawater has a pH of 7.7, a brine from seawater desalination has gener- typically a pH of 8.2. This basicity is associated with the salts contained in seawater.

[0031] The brine useful in the process according to the invention can have a pH ranging from 7.5 to 8.5 and typically 8.2.

[0032] The brine useful in the process according to the invention may have a density greater than 1.05 kg / L.

[0033] The brine resulting from the desalination of seawater used in the process according to the invention may be filtered beforehand when solid impurities are present. Step a) crystallization of NaCl

[0034] The process according to the invention comprises a step a) of removing at least 90% of the volume of water initially contained in the brine leading to the formation of a suspension followed by the separation of the suspension into a filtrate (2) and a solid residue (3) comprising NaCl crystals.

[0035] Optionally, the method may further comprise, prior to step a), a step of removing from 80% to less than 90%, typically from 80% to 85%, for example 80% of the volume of water initially contained in the brine, leading to the formation of a suspension followed by the separation of the suspension into a solid comprising CaSO4 crystals and a filtrate sent to step a). Advantageously, this step makes it possible to crystallize and selectively separate CaSO4 salts.

[0036] Advantageously, at the end of step a) the filtrate (2) obtained has a salt concentration ranging from 300 to 380 g / L, i.e. a salinity ranging from 30 to 38% by weight, which makes it possible to selectively promote the crystallization of NaCl with respect to that of CaSO4 or the magnesium salts, MgSO4 and MgCl2. The salt concentration is commonly determined by the density of the filtrate (2).

[0037] Typically, during step a) at least 95% by volume of water is removed relative to the volume of water initially contained in the brine, or at least 98% by volume and up to 99% by volume of water initially contained in the brine. Commonly, an amount of water ranging from 90 to 99% by volume of water initially contained in the brine is removed during step a).

[0038] The removal of water can be carried out by evaporation. Typically, the removal of water contained in the brine is carried out gradually, for example by successive evaporations. Advantageously, the water is removed gradually to selectively promote the crystallization of NaCl.

[0039] Generally, the evaporation of water is carried out at a temperature ranging from 20°C to 250°C, or even from 60 to 120°C or even from 80 to 100°C. Typically, the elimination of water is carried out in the open air.

[0040] The removal of water by evaporation can be accelerated by heating by any methods known to those skilled in the art. Generally, step a) is carried out at atmospheric pressure.

[0041] Generally, after removal of water, the crystallization of NaCl can be promoted depending on the temperature, for example at a temperature ranging from 20°C to 100°C and typically from 25°C to 45°C.

[0042] The solid (3) containing NaCl can be separated from the suspension as the water is removed and the NaCl crystallizes. The filtrate (2) is therefore a suspension or a solution in which at least 90% by weight of NaCl, or even at least 93% by weight of NaCl or even at least 95% by weight of NaCl has been removed relative to the quantity of NaCl contained in the brine resulting from the desalination of seawater.

[0043] The separation of the filtrate (2) and the solid (3) can be carried out by any method allowing the separation of a solid and a liquid. Typically, the separation is carried out by filtration, decantation, centrifugation and / or scraping.

[0044] The solid (3) can be used in washing and / or centrifugation steps in order to recover purified NaCl salts which can then be used, for example, for human or animal food, the manufacture of soda (NaOH), chlorine (Cl2) or even bleach (NaCIO).

[0045] The filtrate (2) contains a quantity less than or equal to 5% by weight of NaCl salts and optionally of CaSO4, typically a quantity less than or equal to 4% by weight or even a quantity less than or equal to 3% by weight relative to the weight of the filtrate (2).

[0046] The filtrate (2) is then used in a step b) leading to the formation of potassium bitartrate. Step b) formation of potassium bitartrate

[0047] The process according to the invention comprises a step b) of bringing tartaric acid into contact with the filtrate (2) from step a) leading to the formation of a mixture (4) containing potassium bitartrate.

[0048] The contacting is generally carried out with stirring, for example mechanically. Step b) is commonly carried out at a temperature ranging from 10 to 40°C, or even at a temperature ranging from 15 to 35°C or even from 20 to 25°C, typically without external heating. Generally, step b) is carried out at atmospheric pressure.

[0049] The contacting of the tartaric acid can be carried out by one or more additions of tartaric acid. Typically, after the contacting of the tartaric acid, stirring is maintained for a period ranging from 3 to 24 hours (hours), commonly ranging from 4 to 23 hours or even from 15 to 23 hours.

[0050] Tartaric acid may be added in step b) in solid form or in liquid form. Generally, tartaric acid is added in liquid form, typically in aqueous solution. The aqueous solution of tartaric acid brought into contact with the filtrate (2) may have a concentration ranging from 0.1 to 2 mol / L, or from 0.1 to 1.5 mol / L, or even from 0.2 to 0.7 mol / L.

[0051] Tartaric acid can be added in step b) in a tartaric acid / KCl molar ratio of the filtrate (2) ranging from 1 to 12, typically from 2 to 10, or from 3 to 8, or even from 4 to 7.

[0052] The amount of KC1 salt in the filtrate (2) can be determined, for example, by elemental analysis and XRD.

[0053] Without being bound by any theory, the filtrate (2) has a high concentration of K+ ions which will be able to react with tartaric acid in its TH form and in its T2 form to form potassium tartrate (KHT).

[0054] The mixture (4) obtained at the end of step b) typically has a pH ranging from 1 to 3, typically from 1.2 to 1.5.

[0055] Step cl separation of potassium bitartrate by crystallization

[0056] The method according to the invention comprises a step c) of separating the mixture (4) into a solid comprising potassium bitartrate (5) and a filtrate (6) containing magnesium ions.

[0057] Typically, step c) of separation of the mixture (4) is carried out by crystallization.

[0058] Potassium bitartrate salt (also abbreviated KHT) has a low solubility in water, at most 5.7 g / L at 20°C, 45 g / L at 80°C and 61 g / L at 100°C. Typically, the solubility of the KHT salt decreases at low temperatures.

[0059] Depending on the quantity of KHT in the mixture (4), the crystallization separation step may be spontaneous or be promoted by lowering the temperature, for example to a temperature ranging from 10°C to 20°C. Crystallization may also be promoted by evaporation of a portion of the water from the mixture (4), for example at least 95% by volume or even 90 to 95% by volume of water relative to the volume of the mixture (4).

[0060] After crystallization of the KHT, a suspension is obtained. The suspension is generally filtered, resulting in the production of a solid (5) comprising the KHT and a filtrate (6) containing magnesium. The solid (5) thus obtained can be washed and then dried.

[0061] Typically, the KHT obtained is a white solid, with a slightly sandy, homogeneous texture. Possible traces of NaCl salts may be present in the solid.

[0062] The KHT obtained typically contains less than 1% by weight of impurities, or even less than 0.5% by weight relative to the weight of KHT. Commonly, the amount of impurities is in a range from 0.1 to 1% by weight relative to the weight of KHT.

[0063] The impurities can be NaCl, NaF and / or Na2SO4, commonly the impurities are NaCl.

[0064] The amount of impurities can be determined by DRX and / or chemical analysis methods as described below.

[0065] The filtrate (6) contains magnesium ions, typically at least 1% by weight of magnesium, generally at least 1.3% by weight of magnesium or even 1 to 1.5% by weight of magnesium relative to the weight of the filtrate (6). Advantageously, the filtrate (6) can be recovered, for example by being sent to fertilizer factories. The filtrate (6) rich in magnesium ions can be used as a trace element for the preparation of fertilizers. Installation

[0066] The method described above can be implemented in a potassium bitartrate preparation plant which can comprise

[0067] - a container capable of containing brine (1) resulting from the desalination of water from sea ​​;

[0068] - a crystallizer connected to the container capable of containing the brine (1), typically to carry out the elimination of water by evaporation which can lead to the production of a filtrate (2) and a solid residue (3);

[0069] - a washing and separation unit such as a washing column and / or a cen trifugeuse, capable of washing and separating the solid residue (3);

[0070] - one or more pipes connected to the crystallizer which can allow withdraw and send the filtrate (2) to a contacting unit;

[0071] - one or more pipes connected to the contacting unit which can allow the introduction of tartaric acid;

[0072] - the contacting unit which can contain the filtrate (2) and tartaric acid and which can lead to the formation of a mixture (4) containing potassium bitartrate;

[0073] - one or more pipes connected to the contacting unit which can allow the mixture (4) to be withdrawn to a separation unit;

[0074] - the mixture separation unit (4) comprising for example a crystallizer and a filtration means for recovering on the one hand solid potassium bitartrate (5) and on the other hand a filtrate (6);

[0075] - a washing and separation unit such as a washing column and / or a cen trifugeuse, capable of washing and separating solid potassium bitartrate (5);

[0076] - one or more pipes to allow the filtrate (6) separated into the mixture separation unit (4).

[0077] An example of implementation of the method according to the invention is illustrated in [Fig. 1].

[0078] The implementation of a typical installation for preparing KHT according to the invention is described below. The brine to be treated from the desalination of seawater (1) contained in a tank is sent to a crystallizer-type separation unit so as to carry out step a) of removing the water and separating the NaCl salts (3). The NaCl salt crystals (3) formed in the crystallizer can be transferred to a washing column and then to a centrifuge. The filtrate (2) from step a) is sent to a container so as to carry out step b) of KHT formation by adding tartaric acid. The mixture containing the KHT (4) is sent to a separation unit so as to carry out step c) of separation of the KHT which can be washed in a washing column, possibly followed by centrifugation to recover the solid KHT (5). The filtrate (6) containing magnesium can also be recovered. Methods

[0079] A DRX (X-ray Diffractometric) analysis method used can for example be carried out using a Burker D8 diffractometer with Cu Ka radiation in the range of 15 to 55 20, with a step size of 0.02 and a collection time of 2.5 s / step. The processing can be carried out using the Highscore Plus software based on the COD19 data.

[0080] The methods for carrying out chemical analyses can, for example, be carried out for:

[0081] - Sodium, potassium and calcium, flame spectrophotometry.

[0082] - Magnesium, complexometric titration.

[0083] - Sulfate SO42 by gravimetric method.

[0084] - Chlorine Cl by the potentiometric method. EXAMPLES

[0085] The following non-restrictive examples illustrate examples of embodiments of the invention. Example 1

[0086] In this example, the treated brine is a brine from desalination of Jorf Lasfar seawater with a density of 1.045 g / L, with a concentration of 1.38 g / L of potassium chloride (KC1), 6.08 g / L of magnesium chloride (MgCl2) and 48 g / L of sodium chloride (NaCl).

[0087] This brine is subjected to evaporation in order to obtain the elimination of 90% of the volume of water from the brine is eliminated by evaporation. The evaporation is facilitated by an external heating of the Bunsen burner type.

[0088] The sodium chloride (3) is separated by filtration. A filtrate (2) is recovered.

[0089] Then IL of filtrate (2) having a KC1 concentration of 13 g / L, is brought into contact with racemic tartaric acid (167.12g, 1.11 mol) with stirring for 4h at 25°C. The mixture (4) obtained is a suspension having a pH of 1.28. The suspension is filtered. The solid (5) recovered is washed with distilled water and then dried.

[0090] After drying, a white solid (KHT) with a homogeneous, slightly sandy texture was obtained. Its quality was identified by chemical analysis and DRX by com parison with high purity commercial KHT containing approximately 21% by weight of K2O.

[0091] Chemical analyses have shown that the product obtained by our process is composed of 21% by weight of K2O (18% by weight of K), which confirms the high purity of the KHT produced. Example 2

[0092] In this example, the same brine as in Example 1 is treated.

[0093] The brine is subjected to a step of eliminating 80% of the volume of water initially contained in the brine is eliminated by evaporation. Evaporation is facilitated by an external heater of the Bunsen burner type.

[0094] Only CaSO4 crystallizes and is then separated by filtration. A filtrate depleted in CaSO4 is obtained. Tartaric acid is added to the filtrate.

[0095] This addition does not allow the formation of potassium bitartrate. DRX analyses did not detect the presence of KHT.

[0096] Without being bound by any theory, it is possible that the presence of excess sodium in the brine does not allow the formation of potassium bitartrate. Example 3

[0097] In this example, the same brine as in Example 1 is treated.

[0098] In this example, a process for manufacturing bitartrate is implemented. potassium similar to that of Example 1, but with 70% removal by evaporation by volume of water. The brine contains calcium sulfate salts.

[0099] Thus, the brine is subjected to a step of eliminating 70% of the initial water volume initially contained in the brine is eliminated by evaporation. Evaporation is facilitated by an external heater such as a Bunsen burner.

[0100] Tartaric acid in its ionic form TH reacts with potassium to give potassium tartrate (KHT), and in its T2 form with calcium to give neutral calcium tartrate (CaT). XRD analyses showed the formation of two major phases of KHT and CaT. The removal of only 70% by volume of water from the brine therefore does not allow the selective formation of KHT with high purity.

Claims

Claims

1. A process for preparing potassium bitartrate from a brine obtained from the desalination of seawater, the process comprising the following steps: a) removing at least 90% of the volume of water initially contained in the brine (1) leading to the formation of a suspension followed by the separation of the suspension into a filtrate (2) and a solid residue (3) comprising NaCl crystals; b) bringing tartaric acid into contact with the filtrate (2) leading to the formation of a mixture (4) containing potassium bitartrate; c) separating the mixture (4) into a solid comprising the potassium bitartrate (5) formed in step b) and a filtrate (6) containing magnesium ions.

2. The method of claim 1, wherein the brine has a pH ranging from 7.5 to 8.5 and / or a salinity ranging from 4.6 to 9.0% by weight.

3. A method according to either of claims 1 or 2, wherein the brine is obtained from the desalination of seawater by distillation or reverse osmosis.

4. Method according to any one of claims 1 to 3, in which the elimination of the water contained in step a) is carried out progressively, typically by successive evaporations.

5. A method according to any one of claims 1 to 4, wherein the filtrate (2) from step a) has a salinity ranging from 30 to 38% by weight.

6. A method according to any one of claims 1 to 5, comprising, prior to step a), a step of removing 80% of the volume of water initially contained in the brine leading to the formation of a suspension followed by the separation of the suspension into a solid comprising CaSO4 crystals and a filtrate sent to step a).

7. A method according to any one of claims 1 to 6, wherein at least 95% by volume or at least 98% by volume and up to 99% by volume of the water initially contained in the brine is removed in step a).

8. Method according to any one of claims 1 to 7, in which the filtrate (2) contains a quantity of NaCl salts and optionally CaSO4 less than or equal to 5% by weight relative to the weight of the filtrate (2).

9. A method according to any one of claims 1 to 8, wherein step b) is carried out at a temperature ranging from 10 to 40°C, or even at a temperature ranging from 15 to 35°C or even from 20 to 25°C.

10. Process according to any one of claims 1 to 9, in which the tartaric acid is brought into contact with the filtrate (2) in a tartaric acid / KCl molar ratio ranging from 1 to 12, typically from 2 to 10, or from 3 to 8, or even from 4 to 7.

11. Method according to any one of claims 1 to 10, in which after step b), stirring is maintained for a period ranging from 3 hours to 24 hours.

12. Method according to any one of claims 1 to 11, in which the mixture (4) obtained at the end of step b) has a pH ranging from 1 to 3, typically from 1.2 to 1.

5.

13. A method according to any one of claims 1 to 12, wherein step c) of separating the potassium bitartrate (5) is carried out by crystallization.

14. Process according to any one of claims 1 to 13, in which the potassium bitartrate (5) obtained at the end of step c) contains less than 1% by weight of impurities, or even less than 0.5% by weight relative to the weight of potassium bitartrate (5).

15. A method according to any one of claims 1 to 14, wherein the filtrate (6) contains at least 1% by weight of magnesium, generally at least 1.3% by weight of magnesium relative to the weight of the filtrate (6).