阅读说明：本技术 磷酸的制备 (Preparation of phosphoric acid ) 是由 D·迪巴 B·麦格尼 H·马祖兹 C·梅蒂维尔 J·蒙金 于 2018-11-09 设计创作，主要内容包括：本发明涉及由水相悬浮液工业制备磷酸的方法,该水性悬浮液包含水和在至少一种阴离子聚合物类型的添加剂存在下分散的至少一种磷酸盐材料的颗粒。通过用至少一种强酸处理该悬浮液来获得磷酸。通过选自丙烯酸、甲基丙烯酸的至少一种酸或其盐的聚合反应获得该聚合物。本发明涉及该阴离子聚合物的用途以及用于改善悬浮液的流变学和反应介质的流体动力学的方法,其中发生了用于制备磷酸的反应。(The present invention relates to a process for the industrial preparation of phosphoric acid from an aqueous suspension comprising water and particles of at least one phosphate material dispersed in the presence of at least one additive of anionic polymer type. Phosphoric acid is obtained by treating the suspension with at least one strong acid. The polymer is obtained by polymerization of at least one acid selected from acrylic acid, methacrylic acid or a salt thereof. The invention relates to the use of the anionic polymer and to a method for improving the rheology of suspensions and the hydrodynamics of the reaction medium, in which the reaction for preparing phosphoric acid takes place.)

1. A process for the preparation of phosphoric acid, which comprises treating an aqueous suspension (A) comprising water and particles of at least one phosphate material, said particles having a size between 10 and 400 μ M and being dispersed in the presence of at least one anionic polymer having a weight-average molecular weight (M) by means of at least one strong acid at a temperature in the range of 40 to 100 ℃_W) Between 1,000 and 90,000g/mol and obtained by polymerization of at least one acid chosen from acrylic acid, methacrylic acid or a salt thereof.

2. The method of claim 1, wherein the brookfield viscosity of the aqueous suspension (a), measured at 25 ℃,100 rpm and a phosphate material concentration of greater than 45 wt%, preferably greater than 60 wt%, 90 seconds after the preparation of the suspension, is less than 1500 mPa-s or less than 1200 mPa-s, more preferably less than 1000 mPa-s, more preferably less than 500 mPa-s or even less than 350 mPa-s or less than 200 mPa-s.

3. The process according to any one of claims 1 or 2, wherein the strong acid used is selected from sulfuric acid, nitric acid, hydrochloric acid and mixtures of these acids.

4. The production method according to any one of claims 1 to 3, wherein the strong acid used is sulfuric acid.

5. The production method according to any one of claims 1 to 4, wherein P of the produced phosphoric acid₂O₅The titer is greater than 25%, more preferably greater than 28% or 30%.

6. The production method according to any one of claims 1 to 5, which comprises

(a) Preparing a mixture of water, particles of phosphate material and at least one anionic polymer obtained by polymerization of at least one acid selected from acrylic acid, methacrylic acid or a salt thereof, optionally with stirring, to form an aqueous suspension (a);

(b) the aqueous suspension (a) is treated with at least one strong acid, preferably sulfuric acid, to form an aqueous phosphoric acid solution.

7. A method of preparation according to claim 6, comprising (c) separating an aqueous solution of phosphoric acid from phosphogypsum particles formed during treatment (b).

8. A method of manufacture according to claim 7, wherein the separated crystals of phosphogypsum

-an ellipsoid (Q1) of size about 250 μm or 220 and 350 μm, a semi-ellipsoid (Q2) of size about 150 μm or 125 and 160 μm, more dense or star-shaped phosphogypsum crystals (Q3) of size about 50 μm or 40-85 μm, preferably mainly more dense or star-shaped phosphogypsum crystals (Q3) of size about 50 μm or 40-85 μm; or

Has a sphericity (ratio of the radius of the inscribed circle of the particle to the radius of the circumscribed circle of the particle) close to 1.

9. A production process according to any of claims 7 and 8, wherein phosphogypsum particles are separated by filtration.

10. The process according to any one of claims 1 to 9, wherein the concentration of the aqueous phosphoric acid solution prepared is between 20% and 45%, preferably between 25% and 40%, more preferably between 30% and 35%, by weight of the phosphoric acid prepared.

11. The production method according to any one of claims 1 to 10, wherein the particles of the phosphate material are used in a dry form.

12. The preparation process according to any one of claims 1 to 10, wherein the phosphate material particles are used in the form of an aqueous suspension (B), preferably an aqueous suspension (B) having a phosphate material concentration of more than 45 wt.%.

13. The process according to claim 12, wherein the aqueous suspension (B) further comprises at least one anionic polymer according to claim 1.

14. The process according to claim 13, wherein the aqueous suspension (B) has a phosphate material concentration greater than 50%, preferably greater than 55%, more preferably greater than 60% or 65% or even greater than 70% or 75%.

15. The preparation process according to any one of claims 13 and 14, wherein the brookfield viscosity of the aqueous suspension (B), measured at 25 ℃,100 rpm and a phosphate material concentration of more than 45% by weight, preferably more than 60% by weight, at 90 seconds after the preparation of the suspension, is less than 1500 mPa-s or less than 1200 mPa-s, preferably less than 1000 mPa-s, more preferably less than 500 mPa-s or even less than 350 mPa-s or less than 200 mPa-s.

16. The method of any one of claims 1 to 15, wherein the polymer is partially or fully neutralized, preferably by a derivative comprising at least one element selected from lithium, sodium, calcium, magnesium and mixtures thereof, more preferably selected from sodium, calcium and mixtures thereof.

17. The production method according to any one of claims 1 to 16, wherein the anionic polymer is further obtained by polymerization using at least one ester of an acid selected from acrylic acid and methacrylic acid.

18. The production method according to any one of claims 1 to 17, wherein the weight average molecular weight (M) of the anionic polymer_W) Is 2,000 to 90,000g/mol, preferably 2,000 to 50,000g/mol, more preferably 2,000 to 10,000g/mol, more preferably 2,000 to 8,000 g/mol.

19. The preparation process according to any one of claims 1 to 18, wherein the amount of anionic polymer used (dry/dry) is between 0.1 and 5 wt. -%, preferably between 0.15 and 2 wt. -%, based on the amount of phosphate material.

20. The method of any one of claims 1 to 19, wherein the particles of phosphate material are less than 400 μ ι η in size, preferably less than 200 μ ι η, or less than 150 μ ι η, or greater than 10 μ ι η in size, preferably greater than 30 μ ι η in size.

21. The method of any one of claims 1 to 20, wherein the strong acid has a pKa of less than 4 or less than 3 or 2.5, or wherein the strong acid is selected from the group consisting of sulfuric acid, phosphoric acid, nitric acid, hydrochloric acid, and mixtures thereof.

22. Preparation process according to any one of claims 1 to 21, in which the aqueous suspension comprises a foam phase whose volume is reduced to 40% or even to 20% of the total volume of the suspension, or in which the aqueous suspension has an apparent density, measured by pycnometer at a solids content greater than 60% by weight, of between 1.5 and 2, preferably between 1.7 and 2.

23. A method for improving the hydrodynamics of a reaction for the production of phosphoric acid by treating an aqueous suspension (A) comprising particles of at least one phosphate material having a size between 10 and 400 μ M with at least one strong acid at a temperature in the range of 40 to 100 ℃, said method comprising the use of at least one anionic polymer having a weight average molecular weight (M) of said anionic polymer_W) Between 1,000 and 90,000g/mol and obtained by polymerization of at least one acid chosen from acrylic acid, methacrylic acid or a salt thereof.

24. Method of improving fluid dynamics according to claim 23, wherein the P present in the phosphate rock that has not been eroded during the acid treatment is preferably reduced by₂O₅By loss of P associated with phosphorus present in the crystal of phosphogypsum in the form of cocrystals₂O₅Loss, thereby reducing the loss of P₂O₅Equivalent weight represents phosphoric acid loss.

25. A method of improving fluid dynamics according to any one of claims 23 and 24, wherein the reaction to produce phosphoric acid, the polymer and the phosphate material are as defined in any one of claims 1 to 22.

Technical Field

The present invention relates to a process for the industrial preparation of phosphoric acid from an aqueous suspension comprising particles of water and at least one phosphate material, said particles being dispersed in the presence of at least one additive of anionic polymer type. Phosphoric acid is obtained by treating the suspension with at least one strong acid. The polymer is obtained by polymerization of at least one acid selected from acrylic acid, methacrylic acid or a salt thereof.

The invention relates to the use of the anionic polymer and to a method for improving the rheology of suspensions and the hydrodynamics of the reaction medium, in which the reaction for preparing phosphoric acid takes place.

In this way, a process for preparing an aqueous suspension comprising particles of water and at least one phosphate material, said particles being dispersed in the presence of at least one additive of anionic polymer type, is also particularly effective.

The phosphoric acid thus prepared is an indispensable product for the manufacture of fertilizers, in particular ternary fertilizers NPK, or binary fertilizers NP. Phosphoric acid is also used in food production, in particular for the acidification of beverages or for the treatment of metal surfaces or in the microelectronics field.

Background

Phosphate rock is an important source of raw materials for the production of phosphoric acid. Phosphoric acid (H)₃PO₄) It can be produced mainly by two methods: wet and thermal methods. The wet process is the most widely used process and phosphoric acid from this route can be used to produce phosphate fertilizers (diammonium phosphate or DAP, monoammonium phosphate or MAP or, triple superphosphate or TSP). The acid obtained by the thermal method has better performance than that of the acid obtained by the thermal methodHigh purity, and is generally used for pharmaceuticals or foods.

In wet production units, phosphoric acid is produced, in particular, by the action of strong acids on natural phosphate ores. Sulfuric acid is the most commonly used strong acid, in which case insoluble calcium sulfate is formed, which is separated by filtration to recover gypsum. The operating conditions are chosen so that the calcium sulphate precipitates in its dihydrate form, producing P, usually at a concentration of 26-32%, at 70-80 ℃₂O₅Or precipitated as hemihydrate, usually at a concentration of 40-52% at 90-110 deg.C to form P₂O₅. Evaporation can then be used to further concentrate the phosphoric acid, thereby optimizing the quality of the acid.

Typically, after extraction, the phosphate rock is processed into a dry form or a wet form mixed with water, for example to form a phosphate slurry.

In the latter case, the high concentration of phosphate rock enables a reduction in the amount of water used when treating a certain amount of phosphate rock. In addition to better resource management, reducing the amount of water in various stages of phosphoric acid production is of particular interest.

It is also important to be able to impart improved properties to the phosphate rock particles, in particular properties that increase the efficiency of the phosphoric acid production reaction, for example by improving the hydrodynamics of the phosphoric acid production reaction. It is therefore important to provide an improved process for the manufacture of phosphoric acid, in particular to increase the overall efficiency of the reaction for the production of phosphoric acid from phosphate rock.

Disclosure of Invention

The process for the preparation of phosphoric acid according to the present invention provides a solution to all or part of these problems, in particular by significantly improving the conditions for the preparation of phosphoric acid.

Accordingly, the present invention provides a process for the preparation of phosphoric acid, which comprises treating an aqueous suspension (a) comprising water and particles of at least one phosphate material, said particles having a size of from 10 to 400 μ M and being dispersed in the presence of at least one anionic polymer having a weight-average molecular weight (M) by means of at least one strong acid at a temperature in the range of from 40 to 100 ℃_W) Between 1,000 and 90,000g/mol and obtained by polymerization of at least one acid chosen from acrylic acid, methacrylic acid or a salt thereof.

The use of this anionic polymer in the process for the preparation of phosphoric acid according to the invention makes it possible to obtain a good compromise of the various properties of the preparation process (in particular the chemical yield of the reaction, the filterability and the phosphoric acid titer).

In a particularly advantageous manner, the preparation process according to the invention makes it possible to control the viscosity of the aqueous suspension (a).

Preferably, the brookfield viscosity of the aqueous suspension (a) measured at 25 ℃,100 rpm and a phosphate material concentration of more than 45 wt% at 90 seconds after preparation of the suspension is less than 1500 mPa-s or less than 1200 mPa-s, more preferably less than 1000 mPa-s, more preferably less than 500 mPa-s or even less than 350 mPa-s or less than 200 mPa-s for the preparation method according to the invention.

More preferably, the brookfield viscosity of the aqueous suspension (a) is less than 1500mPa · s or less than 1200mPa · s, more preferably less than 1000mPa · s, more preferably less than 500mPa · s or even less than 350mPa · s or less than 200mPa · s, measured at 25 ℃,100 rpm and a concentration of the phosphate material of more than 60% by weight, 90 seconds after the preparation of the suspension.

In carrying out the process according to the invention, the phosphate material particles are treated in an aqueous suspension (a) comprising water and phosphate material particles dispersed in the presence of an anionic polymer.

According to the invention, the phosphate material is processed to a particle form with a size of less than 400 μm. More preferably, the particles are less than 200 μm or less than 150 μm in size. Furthermore, the size of these particles is greater than 10 μm, preferably greater than 30 μm.

Thus, for the preparation method according to the invention, the particle size of the phosphate material may be in the range of 10 to 400 μm or 10 to 200 μm or 10 to 150 μm. Preferably, the size may also be in the range of 30 to 400 μm or 30 to 200 μm or 30 to 150 μm.

For the preparation method according to the invention, the granules of phosphate material can be processed in dry form. For the preparation process according to the invention, the phosphate material particles can also be processed in the form of an aqueous suspension (B).

Preferably, the aqueous suspension (B) has a phosphate material concentration of more than 45 wt.%. More preferably, the aqueous suspension (B) has a phosphate material concentration of more than 50%, more preferably more than 55%, more preferably more than 60% or 65% or even more than 70% or 75%. Most preferably, the aqueous suspension (B) also comprises at least one anionic polymer according to the invention.

Still more preferably, the brookfield viscosity of the aqueous suspension (B), measured at 25 ℃,100 rpm and a phosphate material concentration of more than 45 wt%, preferably more than 60 wt%, at 90 seconds after preparation of the suspension, is less than 1500mPa · s or less than 1200mPa · s, preferably less than 1000mPa · s, more preferably less than 500mPa · s or even less than 350mPa · s or less than 200mPa · s.

Particularly preferably, the brookfield viscosity of the aqueous suspension (B) is less than 1500mPa · s or less than 1200mPa · s, preferably less than 1000mPa · s, more preferably less than 500mPa · s or even less than 350mPa · s or less than 200mPa · s, measured at 25 ℃,100 rpm and a phosphate material concentration of more than 60% by weight, 90 seconds after the preparation of the suspension.

Preferably, for the preparation process according to the invention, the dispersion of the particles of phosphate material in water is carried out by means of a suitable device with stirring. More preferably with mechanical agitation. The preparation of the aqueous suspension (a) or the aqueous suspension (B) according to the invention can be carried out at different temperatures. Preferably, it is carried out at a temperature between 10 and 60 ℃, more preferably between 20 and 50 ℃ or between 25 and 50 ℃.

The use of the polymer according to the invention in the course of the reaction for preparing phosphoric acid thus makes it possible to control the nature of the reaction medium and, in particular, the viscosity of the reaction medium. The polymer used according to the invention is not a flocculant.

For a constant concentration of particles of phosphate material and constant stirring conditions, the reaction medium has a particularly reduced viscosity in the presence of the polymer according to the invention compared to a reaction medium not comprising a polymer. This allows a better control of the fluid dynamics of the reaction medium; so that it is improved.

In a particularly advantageous manner, the preparation process according to the invention thus makes it possible to control the fluid dynamics of the reaction medium used for preparing phosphoric acid. Thus, and for the preparation process of the present invention, it is preferred that the hydrodynamics of the reaction medium for the preparation of phosphoric acid is improved by the anionic polymer used. The use of anionic polymers reduces the viscosity of the suspension produced by the preparation reaction, increasing the reynolds number, and thus improving the hydrodynamics of the phosphoric acid preparation reaction according to the following formula:

wherein

-R_eWhich is a representation of the reynolds number,

- ρ represents the density of the fluid [ kg/m ]³]，

Vmoy represents the characteristic velocity m/s of the fluid,

d represents a characteristic dimension [ m ],

- η represents the dynamic viscosity [ Pa · s ] of the fluid.

Preferably, the process according to the invention is carried out under turbulent or very turbulent conditions. Preferably, the reynolds number is greater than or equal to 2,100, preferably greater than 2,500 or 3,000, or even greater than these values, when carrying out the process according to the invention. Preferably, the process according to the invention makes it possible to increase the reynolds number compared with a medium which does not comprise a polymer according to the invention. Preferably, the increase in reynolds number is greater than 10% or greater than 20%.

Also advantageously, the preparation process according to the invention makes it possible to maintain or increase the chemical yield of the reaction compared with the processes for preparing phosphoric acid of the prior art. Thus, in a preferred manner, the process for producing phosphoric acid according to the present invention achieves a chemical yield of the reaction for producing phosphoric acid of greater than 90% (based on the phosphorus equivalent weight in the initial phosphate material). More preferably, according to the present invention, the chemical yield of the reaction for the preparation of phosphoric acid is greater than 92%, more preferably greater than 94% or even 95% or even greater than 96% or 98% (by weight of phosphorus equivalents in the starting phosphate material).

In a particularly advantageous manner, the preparation process according to the invention makes it possible to reduce the amount of residual sulfate ions in the aqueous solution of phosphoric acid prepared, compared with the processes for preparing phosphoric acid of the prior art. Preferably, the aqueous phosphoric acid solution contains residual sulfate ions at a concentration of 20 to 35g/L by weight. More preferably, the aqueous phosphoric acid solution contains residual sulfate ions at a weight concentration of 22 to 26 g/L.

Also advantageously, the preparation method according to the invention makes it possible to obtain an aqueous solution of phosphoric acid with particularly advantageous titers of phosphoric acid compared to the methods of the prior art for preparing phosphoric acid. Preferably, P of the phosphoric acid prepared₂O₅The titer is greater than 25%, more preferably greater than 28% or 30%.

Also advantageously, the preparation method according to the invention makes it possible to obtain an aqueous phosphoric acid solution having a particularly advantageous concentration (by weight of phosphoric acid) compared with the processes for preparing phosphoric acid of the prior art. Preferably, the concentration of the aqueous phosphoric acid solution prepared is between 20% and 45%, more preferably between 25% and 40%, even more preferably between 30% and 35% by weight of the phosphoric acid prepared.

The process for the preparation of phosphoric acid according to the invention comprises treating an aqueous suspension (a) comprising water and particles of at least one phosphate material with at least one strong acid.

Preferably, according to the present invention, the aqueous suspension (a) may be prepared in advance. Thus, the method for preparing phosphoric acid according to the present invention may comprise:

(a) preparing a mixture of water, particles of phosphate material and at least one anionic polymer obtained by polymerization of at least one acid selected from acrylic acid, methacrylic acid or a salt thereof, optionally with stirring, to form an aqueous suspension (a);

(b) treating the aqueous suspension (a) with at least one strong acid to form an aqueous phosphoric acid solution.

In carrying out the process for preparing phosphoric acid according to the invention, the particles of the phosphate material are attacked by the acid during the treatment of the aqueous suspension (a) with the strong acid. During this acid attack, phosphogypsum particles are formed.

Phosphogypsum is gypsum derived from phosphorus. It is calcium sulfate. Different forms of calcium sulfate may exist, including calcium sulfate hydrate, calcium sulfate dihydrate, or calcium sulfate anhydrite.

Preferably, according to the invention, the strong acid used for the treatment of the aqueous suspension (a) is a mineral strong acid. More preferably, according to the invention, the strong acid has a pKa of less than 4 or less than 3, or even less than 2.5. Even more preferably, the strong acid is selected from the group consisting of sulfuric acid, phosphoric acid, nitric acid, hydrochloric acid, and mixtures thereof. Even more preferably, the strong acid is sulfuric acid, phosphoric acid, or a mixture thereof.

The crystals of phosphogypsum formed during the preparation process according to the invention may have different shapes or sizes.

Advantageously, the preparation method according to the invention makes it possible to obtain specific phosphogypsum granules during the treatment with sulphuric acid. In a particularly advantageous manner, the preparation process according to the invention makes it possible to obtain specific crystalline forms of phosphogypsum granules which can be isolated very efficiently, in particular by filtration. And very advantageously, these phosphogypsum granules have the form of needles (a), platelets (B) and dense crystals or polycrystalline aggregates (C). In addition to their particular morphology, these different crystalline forms may be characterized by size, typically according to the sizes shown in table 1.

TABLE 1

Preferably, the preparation process according to the invention makes it possible to obtain gypsum crystals with improved filterability. Advantageously, these gypsum crystals have a dense morphology. In particular, the three dimensions (length, width and thickness) of these crystals are relatively similar. Preferably, the gypsum crystals obtained by carrying out the preparation process according to the invention have a general morphology close to spherical or conforming to the shape of a spherical or quasi-spherical volume, owing to these relatively close dimensions. Therefore, preferably, the production method according to the present invention makes it possible to obtain gypsum crystals having a sphericity (ratio between the radius of the inscribed circle of the particles and the radius of the circumscribed circle of the particles) of approximately 1, which is the deviation of the particle shape from the spherical particles.

The preparation method according to the invention thus allows an efficient filtration of the phosphogypsum particles. Thus, the overall chemical yield of phosphoric acid production is particularly advantageous. According to the invention, P in phosphogypsum generated in the process of preparing strong acid solution is treated₂O₅Loss of titer versus P of phosphate rock feedstock₂O₅Comparison of titers to evaluate as P₂O₅Equivalent weight represents the total chemical yield of phosphoric acid production. For recovery of impregnation P₂O₅And for P₂O₅Loss titration is performed on gypsum crystals present in unreacted or cocrystallized form. The overall yield was then estimated according to the equation

Wherein

YLd represents the chemical yield (%),

-Pt represents P in gypsum₂O₅The total loss of (a) is,

CaOpp represents the CaO titre in phosphate,

CaOgy represents the CaO titer in gypsum,

-P₂O₅pp represents P in phosphate₂O₅The titer.

Advantageously, the implementation of the preparation process according to the invention increases the chemical yield of the phosphoric acid preparation. The improvement results in particular from unreacted P during the preparation of phosphoric acid₂O₅Loss limitation of (D), cocrystallization of P in gypsum₂O₅Reduced loss of, or better separation of, gypsum, thus making it possible to reduce the P still impregnated in the solid residue of filtration₂O₅Is lost.

Preferably, according to the invention, the isolated phosphogypsum crystals are oval and have a size of about 250 μm or of 220-350 μm (Q1). Also preferably, according to the invention, the isolated phosphogypsum crystals are semi-elliptical and have a size of about 150 μm or a size of 125-160 μm (Q2). Also preferably, according to the invention, the isolated phosphogypsum crystals are more dense or star-shaped and have a size of about 50 μm or a size of about 40-85 μm (Q3).

Preferably, the preparation process according to the invention comprises (c) separating the aqueous solution of phosphoric acid from the phosphogypsum crystals formed during the treatment (b). More preferably, these phosphogypsum crystals are isolated by filtration.

Preferably, the preparation process of the present invention improves the separation of gypsum crystals from phosphoric acid by filtration. More preferably, the filtration coefficient or filterability is improved by more than 0.5tP compared to a separation process without the use of a polymer₂O₅/m²D or 1tP₂O₅/m²D or even 2tP₂O₅/m²/d。

The essential feature of the aqueous suspension (a) implemented according to the invention is that it comprises particles of at least one anionic polymeric binding water and at least one phosphate material. The anionic polymer according to the invention is obtained by polymerization of at least one acid selected from acrylic acid, methacrylic acid or a salt thereof.

In the preparation of the anionic polymers used according to the invention, the polymerization reaction uses at least one anionic monomer comprising at least one polymerizable ethylenically unsaturated group and at least one carboxylic acid functional group, in particular an anionic monomer comprising at least one polymerizable ethylenically unsaturated group and at least one carboxylic acid functional group. Preferably, the anionic monomer is selected from acrylic acid, methacrylic acid, salts of acrylic acid, salts of methacrylic acid. The polymerization reaction may also use both acrylic acid and methacrylic acid and salts thereof.

The polymer used according to the invention may also be a copolymer obtained by polymerization using at least one other acid chosen from acrylic acid, methacrylic acid, maleic acid, itaconic acid and salts thereof, and at least one other comonomer, which may be an ester of an acid chosen from acrylic acid and methacrylic acid.

Other comonomers that can be used for preparing the copolymers according to the invention include nonionic monomers chosen from esters of acids comprising at least one monocarboxylic acid function, in particular from acrylic acid, methacrylic acid, salts of acrylic acid, salts of methacrylic acid and mixtures thereof. Examples of such comonomers include compounds selected from: styrene; vinyl caprolactam; alkyl acrylates, especially acrylic acid C₁-C₁₀Alkyl esters, preferably acrylic acid C₁-C₄Alkyl esters, more preferably methyl acrylate, ethyl acrylate, propyl acrylate, isobutyl acrylate, n-butyl acrylate; alkyl methacrylates, especially methacrylic acid C₁-C₁₀Alkyl esters, preferably methacrylic acid C₁-C₄Alkyl esters, more preferably methyl methacrylate, ethyl methacrylate, propyl methacrylate, isobutyl methacrylate, n-butyl methacrylate; aryl acrylates, preferably phenoxyethyl acrylate; aryl methacrylates, preferably phenoxyethyl methacrylate. Particular preference is given to methyl acrylate, ethyl acrylate, propyl acrylate, isobutyl acrylate, n-butyl acrylate, methyl methacrylate, ethyl methacrylate, propyl methacrylate, isobutyl methacrylate and n-butyl methacrylate.

Other comonomers that can be used for the preparation of the copolymers according to the invention include compounds selected from: 2-acrylamido-2-methylpropanesulfonic acid, 2-acrylamido-2-methylpropanesulfonic acid salt, ethoxymethacrylic acid sulfonic acid salt, sodium methallylsulfonate, styrenesulfonic acid and salts thereof.

Preferably, the anionic polymer according to the invention is prepared in the absence of acrylamide or in the absence of N, N' -methylenebisacrylamide; the polymers according to the invention are not crosslinked.

Preferably, the polymers used according to the invention are partially or fully neutralized. More preferably, from at least one derivative selected from the group consisting of alkali metals, alkaline earth metals and mixtures thereof, in particular from derivatives comprising at least one element selected from the group consisting of lithium, sodium, calcium, magnesium and mixtures thereof (e.g. NaOH, KOH, Ca (OH)₂) To partially or fully neutralize the polymer. Sodium, calcium and mixtures thereof are particularly preferred. As the neutralization of sodium and calcium, NaOH, Ca (OH) can be used₂And mixtures thereof. The respective proportions of sodium and calcium may vary widely. For example, the Na/Ca molar ratio may range from 98/2 to 30/70, preferably from 95/5 to 40/60, more preferably from 90/10 to 30/70 or from 90/10 to 40/60, even more preferably from 70/30 to 40/60, especially 50/50.

Preferably, the weight average molecular weight (M) of the anionic polymers used according to the invention_W) Between 2,000 and 90,000g/mol, preferably between 1,000 or 2,000 and 50,000g/mol, even more preferably between 1,000 or 2,000 and 10,000g/mol, more preferably between 1,500 or 2,000 and 8,000 g/mol. According to the invention, the weight-average molecular weight (M) is measured by Size Exclusion Chromatography (SEC)_W)。

Preferred polymers for use according to the invention are homopolymers of acrylic acid or copolymers of acrylic acid and 2-acrylamido-2-methylpropanesulfonic acid, in particular neutralized homopolymers of acrylic acid or neutralized copolymers of acrylic acid and 2-acrylamido-2-methylpropanesulfonic acid. More particularly preferred polymers for use according to the invention are neutralized homopolymers of acrylic acid or neutralized copolymers of acrylic acid and 2-acrylamido-2-methylpropanesulfonic acid, the weight average molecular weight (M) of which_W) Between 1,000 and 10,000g/mol, preferably betweenBetween 1,500 and 8,000 g/mol. Examples of particularly preferred copolymers to be used according to the invention are selected from

Polymer (P1): it is a homopolymer having a molecular weight of 5,000g/mol, which is obtained by polymerizing acrylic acid in the presence of copper sulfate, iron sulfate, hydrogen peroxide and 2- (1-carboxyethylmercaptothiocarbonylthio) propionic acid (DPTTC-CAS No.6332-91-8), and neutralizing with sodium and calcium (70/30 moles based on the amount of acrylic acid);

polymer (P2): it is a homopolymer having a molecular weight of 4,200g/mol, which is obtained by polymerizing acrylic acid in the presence of copper sulfate, iron sulfate, hydrogen peroxide and sodium hypophosphite, and neutralizing with sodium and calcium (90/10 moles based on the amount of acrylic acid);

polymer (P3): which is a polymer having a molecular weight of 4,800g/mol, obtained by polymerizing acrylic acid in the presence of sodium persulfate and sodium hypophosphite, and neutralizing with sodium and calcium (50/50 moles based on the amount of acrylic acid);

polymer (P4): it is a copolymer having a molecular weight of 3,800g/mol obtained by polymerizing acrylic acid and 2-acrylamido-2-methylpropanesulfonic acid (mass 77.5/12.5) in the presence of sodium persulfate and sodium hypophosphite and neutralizing with sodium and calcium (50/50 moles based on the amount of acrylic acid);

polymer (P5): it is a homopolymer having a molecular weight of 4,200g/mol, which is obtained by polymerizing acrylic acid in the presence of copper sulfate, iron sulfate, hydrogen peroxide and sodium hypophosphite, and neutralizing with sodium and calcium (30/70 moles based on the amount of acrylic acid).

The amount of anionic polymer used may vary widely for the process according to the invention. Preferably, the amount of anionic polymer used (dry/dry) is between 0.05 and 5 wt%, more preferably between 0.1 and 2 wt%, based on the amount of phosphate material. Also preferably, for the preparation process according to the invention, the amount of anionic polymer used (dry/dry) is between 0.1 and 5% by weight, based on the amount of phosphate material. For the preparation process according to the invention, more preferably, the amount of anionic polymer used (dry/dry) is between 0.15 and 2% by weight, based on the amount of phosphate material.

The acid treatment of the aqueous suspension (a) is improved due to the specific properties imparted to the particles of the phosphate material in combination with the anionic polymer used according to the invention. Thus, the aqueous suspension (a) comprises a foam phase, the volume of which is limited or even zero during the acid treatment. Preferably, during the treatment of the aqueous suspension (a) by a strong acid according to the invention, the suspension comprises a foam phase, the volume of which is reduced to 40% or even to 20% of the total volume of the suspension.

Advantageously, the aqueous suspension (a) according to the invention has an apparent density, measured by pycnometer at a solids content greater than 60% by weight, of between 1.5 and 2, preferably between 1.7 and 2.

During the acid treatment of the aqueous suspension (a) according to the invention, the reaction conditions for the preparation of phosphoric acid are changed. Thus, the use of anionic polymers according to the invention makes it possible to vary the reaction parameters for the preparation of phosphoric acid.

Thus, in addition to the process for preparing phosphoric acid from the aqueous suspension (a), the present invention also relates to a process for improving the hydrodynamics of the phosphoric acid preparation reaction.

The present invention therefore provides a method for improving the hydrodynamics of a reaction for the production of phosphoric acid by treating an aqueous suspension (a) comprising particles of at least one phosphate material having a size of 10 to 400 μ M with at least one strong acid at a temperature in the range of 40 to 100 ℃, said method comprising the use of at least one anionic polymer having a weight average molecular weight (M) of_W) Between 1,000 and 90,000g/mol and obtained by polymerization of at least one acid chosen from acrylic acid, methacrylic acid or a salt thereof.

Preferably, the method of improving fluid dynamics according to the invention makes it possible to reduce the sum P₂O₅Equivalent weight represents phosphoric acid loss. In a particularly preferred manner, the method for improving the fluid dynamics according to the invention makes it possible to reduce the acid treatment processP present in uneroded phosphate rock₂O₅By loss of P associated with phosphorus present in the crystal of phosphogypsum in the form of cocrystals₂O₅Equivalent loss, thereby reducing the amount of P₂O₅Equivalent weight represents phosphoric acid loss.

Also preferably, the method of improving fluid dynamics according to the present invention increases the overall efficiency of the phosphoric acid production reaction.

For the method for improving fluid dynamics according to the present invention, the characteristics of the reaction for producing phosphoric acid are the characteristics of the reaction for producing phosphoric acid defined according to the present invention.

For the method of improving the fluid dynamics according to the present invention, the polymer is an anionic polymer used in the reaction for preparing phosphoric acid defined according to the present invention.

For the method of improving fluid dynamics according to the present invention, the phosphate material is a phosphate material used in the reaction for preparing phosphoric acid defined according to the present invention.

The particular, advantageous or preferred features of the production process according to the invention make it possible to define in an analogous manner the particular, advantageous or preferred method of improving the flow dynamics according to the invention.

In a particularly efficient manner, the different aspects of the invention make it possible to increase the efficiency of the different stages of using the phosphate material. In particular, the present invention can significantly improve the overall chemical yield of the treatment of phosphate rock for the production of phosphoric acid.

Detailed Description

The following examples illustrate various aspects of the present invention.