Method for enriching and improving the solubility of phosphate ore processing tailings

Abstract

The present invention relates to a method for enriching phosphate ore processing tailings, most particularly to a method comprising washing and flotation steps making it possible to have a rich concentrate and to increase the solubility in its different forms of the processing concentrate.

Description

METHOD FOR ENRICHED AND IMPROVED IN THE SOLUBILITY OF PHOSPHATE ORE PROCESSING WASTE - TECHNICAL FIELD OF THE INVENTION

[0001] The present invention relates to a process for enriching phosphate wet treatment tailings, particularly by a process comprising two-stage desliming, screening, attrition and flotation steps to increase the P2O5 content and the solubility in its various forms of the treatment concentrate. STATE OF THE ART

[0002] The direct use of phosphates as fertilizer has seen a significant increase, especially in tropical and subtropical regions of Asia, Africa, and Latin America, which are covered with heavily leached and naturally infertile soils.

[0003] The essential characteristics of the soils in these regions suitable for fertilization by natural rock are their very high acidity (with pH levels of around 3 to 5.5 at most) as well as their strong deficiency in phosphorus, which limits agricultural yields in these regions.

[0004] Mineral processing techniques for enrichment depend primarily on the type of gangue minerals present in the ore being mined. Flotation remains one of the most widely used processes for mineral enrichment. In such processes, the ore is first crushed and then suspended in water. A collector is then added, often in combination with other additives such as foaming agents, pH regulators, dispersants, depressants, and / or stimulants (activators), which help separate the valuable minerals from the gangue minerals. After a conditioning period, the flotation process begins. This involves injecting air into the suspension to break up the fine ore particles and produce foam on the surface.

[0005] One of the major problems with this process is the losses generated by the crushing process, resulting in a significant amount of material with a particle size of less than 40 µm that cannot be enriched by a conventional flotation process. This leads to a degradation of the weight and metal yield of the washing, crushing, and flotation enrichment process (the fine granular fraction or fine fraction resulting from the washing, crushing, and flotation process). Disposing of this fine granular fraction in landfills results in substantial losses in the treatment processes because these tailings contain valuable minerals.

[0006] From the 1970s onwards, numerous research projects were undertaken to valorize fine granular wafers, leading to the development of new, so-called intensive flotation techniques. These technologies have proven their effectiveness and are used industrially, particularly for the valorization of coal, base metals, and industrial minerals.

[0007] Thus, there remains a need for the provision of a process which allows us to benefit from the treatment discharges from a classic washing, grinding and flotation process characterized by a low GLP (30%) and thus reduce the amount of sludge to be stored in the spreading basins. SUMMARY OF THE INVENTION

[0008] The invention aims to increase the solubility in its various forms of the concentrate obtained compared to the starting product, thus meeting the specifications of the Brazilian market and also advantageously reducing the amount of washing and grinding sludge formed.

[0009] The invention relates to a process for enriching the processing tailings of a phosphate ore, making it possible to improve the solubility in its various forms of the processing concentrate, comprising the following steps: - pulping and settling of the ore; - a succession of particle size separations of the cleaned ore so as to separate at least one fraction having a particle size of less than about 40 pm and a fraction having a particle size ranging from about 40 to about 200 pm; - particle size separation of the fraction having a particle size less than about 40 pm so as to separate a fraction having a particle size less than about 20 pm or less than about 10 pm and a fraction having a particle size ranging from about 20 to about 40 pm or from about 10 to about 40 pm; - flotation of the fraction having a particle size ranging from about 20 to about 40 pm or from about 10 to about 40 pm and of the fraction having a particle size ranging from about 40 to about 200 pm, leading to the obtaining of an ore enriched in phosphates. BRIEF DESCRIPTION OF THE DRAWINGS

[0010] Exemplary embodiments of the present invention will be more fully understood and appreciated from the following detailed description, taken together with the drawings in which,

[0011] FIG. 1 presents an embodiment of the process of the invention for discharges from spreading basins.

[0012] FIG. 2 presents an embodiment of the process of the invention for the discharges from a washing, grinding and flotation unit. DETAILED DESCRIPTION OF THE INVENTION

[0013] The following detailed description includes references to the accompanying drawings, which form part of the detailed description. The drawings show illustrations conforming to exemplary embodiments. The figures represent similar elements across different views; exemplary embodiments of this disclosure are described. For convenience, only certain elements within a single group may be labeled with numbers. The purpose of the drawings is to describe exemplary embodiments and not to produce. Therefore, the features shown in the drawings are chosen solely for convenience and clarity of presentation.Furthermore, the language used in this description has been chosen primarily for readability and instruction and may not have been chosen to delimit or circumscribe the inventive subject matter, as recourse to the claims is necessary to determine this inventive subject matter. These examples of embodiments are described in sufficient detail to enable a person skilled in the art to carry out the present subject matter. However, it will be obvious to a person with average skill in the art that the present invention can be implemented without these specific details. The embodiments can be combined, other embodiments can be used, or structural and logical modifications can be made without departing from the scope of the invention. The detailed description that follows should therefore not be taken in a restrictive sense.

[0065] Advantageously, the invention describes a process for enriching the tailings from the processing of a phosphate ore, thereby improving the solubility of the processed concentrate in its various forms. The process according to the invention increases the BPL (P2O5) (Bone Phosphorus of Lime; tricalcium phosphate) content and improves the solubility of the resulting concentrate in its various forms.

[0066] The present invention therefore relates to a process for enriching the processing tailings of a phosphate ore, making it possible to improve the solubility in its various forms of the processing concentrate comprising the following steps: - pulping and settling of the ore; - a succession of particle size separations of the cleaned ore so as to separate at least one fraction having a particle size of less than about 40 pm and a fraction having a particle size ranging from about 40 to about 400 pm; - particle size separation of the fraction having a particle size of less than about 40 pm so as to separate a fraction having a particle size of less than about 20 pm or less than about 10 pm and a fraction having a particle size ranging from about 20 to about 40 pm or from about 10 to about 40 pm; - flotation of the fraction having a particle size ranging from about 20 to about 40 pm or from about 10 to about 40 pm and of the fraction having a particle size ranging from about 40 to about 400 pm leading to the obtaining of an ore enriched in phosphates (flotation concentrate of the first stage of flotation of calcite and dolomite); - flotation of the fraction from the first stage of flotation having a particle size ranging from about 20 to about 40 pm or from about 10 to about 40 pm and of the fraction having a particle size ranging from about 40 to about 400 pm leading to the obtaining of an ore enriched in phosphates (flotation concentrate from the second stage of silicate flotation).

[0067] The process according to the invention allows for the efficient enrichment of phosphate ore processing tailings by flotation while improving the P₂O₅ content and the solubility of the resulting concentrate. In this description, the processing tailings consist of washing and grinding sludge as well as flotation tailings from conventional processes. The process according to the invention reduces the quantities of washing, grinding, and flotation tailings by approximately 32.35%.

[0068] Advantageously, the process of the present invention can be implemented on existing phosphate ore beneficiation plants using washing, crushing, and flotation, as well as on tailings already stored in settling ponds. Financial investments are therefore minimized.

[0069] Advantageously, the enrichment process according to the invention also makes it possible to remove heavy metals such as cadmium, nickel, chromium and / or zinc from phosphate ore.

[0070] The enrichment process according to the invention makes it possible to improve production capacities (by about 32%) and to increase the metal yield (by about 30%).

[0071] In particular, when the process is implemented using an ore such as that used in the examples, the process according to the invention makes it possible to remove at least 77.9% by weight of the cadmium in mg / k P2O5 present in the phosphate ore, advantageously at least 77.9% by weight of the cadmium in mg / k P2O5 is removed.

[0072] In particular, when the process is implemented using an ore such as that used in the examples, the process according to the invention makes it possible to remove at least 84.9% by weight of the chromium in mg / k P2O5 present in the phosphate ore, advantageously at least 84.9% by weight of the chromium in mg / k P2O5 is removed.

[0073] In particular, when the process is implemented using an ore such as that used in the examples, the process according to the invention makes it possible to remove at least 72% by weight of the zinc in mg / k P2O5 present in the phosphate ore, advantageously at least 72% by weight of the zinc in mg / k P2O5 is removed.

[0074] It is understood that the reductions indicated above will vary depending on the percentage of BPL in the ore entering the process. However, the process according to the invention remains optimal for any concentration of BPL in the incoming ore.

[0075] Advantageously, the process according to the invention makes it possible to extract clay (silica) from the fine waste (particle size less than approximately 10 or approximately 20 µm). The silica obtained is much more concentrated (approximately 54% vs. approximately 25%) in the raw feed waste.

[0076] Advantageously, the process according to the invention allows for the extraction of 92% silica.

[0077] Advantageously, the process according to the invention allows the extraction of 84% CaCO3.

[0078] The phosphate ore useful in the context of the invention is typically a phosphate ore having a BPL content less than or equal to 45% by weight relative to the total weight of the ore. The ores commonly have a particle size less than or equal to approximately 500 µm.

[0079] Generally, phosphate ore has an DI 00 less than or equal to about 500 pm, typically less than or equal to about 500 pm.

[0080] “DI 00” means that 100% by mass of the ore considered has a size less than or equal to DI 00.

[0081] Phosphate ore may also exhibit one or more of the following characteristics: - a quantity of cadmium less than or equal to 27 ppm, typically ranging from 5 to 27 ppm or from 7 to 30 ppm; - a quantity of chromium less than or equal to 305 ppm, typically ranging from 119 to 305 ppm; a quantity of nickel less than or equal to 81 ppm, typically ranging from 19 to 81 ppm; - an amount of MgO less than or equal to 5.3% by weight relative to the total weight of the raw charge, typically ranging from 0.6 to 5.3% by weight.

[0082] Phosphate ore may also contain silicates and carbonates from dolomite.

[0083] Table 1 describes an example of the composition of a phosphate ore from a deposit in the Gantour basin in Morocco. Table 1: Chemical analyses of the composition of a phosphate ore (% expressed by weight)

[0084] Table 1 shows primarily that the raw phosphate ore has a very low BPL content, corresponding to a low-phosphate cut. It also appears that it is desirable to reduce the magnesium (MgO), silica, CO2, and cadmium content of the ore.

[0085] Pulping involves suspending the ore in water. Pulping breaks down the ore and typically allows for subsequent wet separation to obtain different fractions of specific particle sizes.

[0086] The pulp typically comprises 28 to 35% by weight of solids, preferably 40 to 60% by weight of solids.

[0087] Pulping is typically carried out at room temperature (20-30°C).

[0088] The settling process breaks down agglomerates attached to the ore and cleans it, making it suitable for subsequent operations such as cutting and flotation. Settling is ideally carried out at a solids content between 28 and 35%.

[0089] The desliming process is typically carried out for 10 to 15 minutes.

[0090] A series of particle size separations of the cleaned ore is then carried out. This allows for the separation of at least one fraction with a particle size of less than approximately 40 µm and a fraction with a particle size ranging from approximately 40 to approximately 400 µm.

[0091] Typically, the series of particle size separations is carried out in such a way as to lead to the following particle size fractions:

[0092] A coarse fraction with a particle size greater than 1000 pm corresponding to the vegetation removed in the case where discharges from spreading basins are treated, which can be evacuated for example by a belt conveyor for disposal on a spoil heap;

[0093] A fraction with a particle size ranging from approximately 40 pm to approximately 400 pm, corresponding to a fraction intended to be enriched by flotation;

[0094] A fraction with a particle size ranging from approximately 10 pm to approximately 40 pm or from approximately 20 pm to approximately 40 pm intended to be enriched by flotation;

[0095] A fraction with a particle size of less than about 20 pm or less than about 10 pm corresponding to washing and grinding sludge, which can be treated with the discharges from the first flotation stage for example in settling tanks to recover as much water as possible.

[0096] Particle size separation steps are carried out using all methods known to those skilled in the art that allow for the separation of grains according to their particle size distribution. Typically, particle size separation steps are carried out by screening, centrifugation (centrifugal decanter), hydrocycloning (hydrocyclone, microhydrocyclone), or using a hydrosizer.

[0097] Typically, the particle size separation of coarse fractions (> 1000 pm) is carried out by screening, the particle size separation of intermediate fractions (between about 400 and about 200 pm) is carried out by means of a hydrosizer, the particle size separation of fine fractions (between 40 and 160 pm) is carried out by a hydrocyclone and the particle size separation of ultrafine fractions (< 20 pm) by a micro-hydrocyclone or a centrifugal decanter (typically without flocculants).

[0098] The process of the present invention is characterized by a screening step of the fraction passing through a cut-off of approximately 40 µm. In known enrichment processes, this fraction is typically discarded (washing and grinding sludge). The particle size separation performed on this fraction makes it possible to separate an ultrafine fraction with a particle size of less than approximately 20 µm from a fraction with a particle size ranging from approximately 20 to approximately 40 µm, or, depending on the chosen cut-off threshold, to separate an ultrafine fraction with a particle size of less than approximately 10 µm from a fraction with a particle size ranging from approximately 10 to approximately 40 µm.

[0099] The particle size separation of the fraction with a particle size less than approximately 40 µm is typically carried out using centrifugal clarifiers (typically without flocculants) or micro-hydrocyclones. Cutting the fraction at approximately 40 µm and then at approximately 10 or 20 µm (i.e., in two stages) prevents clogging of the micro-hydrocyclones. Indeed, a direct cut at approximately 10 or 20 µm without first cutting at 40 µm leads to systematic clogging of the micro-hydrocyclones. [000100] The fraction having a particle size ranging from approximately 20 to approximately 40 µm or from approximately 10 to approximately 40 µm is then subjected to the flotation step. It is mixed with the fraction having a particle size ranging from approximately 40 to approximately 400 µm. The mixture is then subjected to the calcite and dolomite flotation step in the first flotation stage after attrition and desliming. It should be noted that the process of the invention does not require the use of intensive flotation. [000101] The fraction with a particle size less than about 20 pm or less than about 10 pm corresponding to the washing and grinding sludge produced by the conventional process can be sent and mixed with the discharges from the first flotation stage in settling tanks to be subjected to a thickening step allowing the water to be recovered from the washing and grinding sludge.The fraction with a particle size of less than about 20 pm or less than about 10 pm may prove useful for chemical industries producing sulfuric acid because it is rich in reactive silicas. [000102] Before flotation, attrition and desliming are typically carried out. The attrition step is generally performed in an attritioner and allows the phosphate grains to be released from the silicate and carbonate gangue. Desliming removes the finest suspended particles. Following attrition and desliming, the fraction with a particle size ranging from approximately 40 to approximately 400 µm is subjected to the first flotation step of the calcite and dolomite, while the fraction not retained at the cut of approximately 40 µm can undergo a further narrowing with a cut at approximately 10 or approximately 20 µm.The fraction with a particle size of less than about 20 pm or less than about 10 pm is discarded and typically sent mixed with the first stage flotation rejects to settling tanks while the fraction with a particle size of about 20 to about 40 pm or about 10 to about 40 pm is directed to flotation (it will be pre-mixed with the fraction of about 40 to about 400 pm). [000103] Generally, in the process of the present invention, the fractions not retained at the cut of about 20 µm or about 10 µm are eliminated (constitute waste). [000104] Flotation of the fraction or fractions having a particle size ranging from about 40 to about 400 pm and of the fraction or fractions having a particle size ranging from about 20 to about 40 pm or from about 10 to about 40 pm leads to an ore enriched in phosphates. [000105] First stage flotation allows the removal by flotation of carbonates, dolomite present in the washing, grinding and flotation waste, the non-floating part corresponds to the concentrate of the first flotation stage constituting the feed of the second stage dedicated to the removal of silicates in this feed, the non-floating part of the second stage corresponds to the flotation concentrate. [000106] The flotation tailings, consisting mainly of carbonates and dolomite, must be mixed with the washing tailings of less than about 10 µm or about 20 µm before being sent to settling tanks to undergo a thickening step allowing the water to be recovered. This water can only be recycled at the stage preceding the thickening of the concentrate from the first flotation stage. [000107] The flotation tailings of silicates can be sent to other settling tanks to undergo a thickening step allowing the water to be recovered without this water being mixed with the recycled water from the first stage or the water from the stages preceding it. [000108] The fraction or fractions having a particle size ranging from about 40 to about 400 pm and the fraction or fractions having a particle size ranging from about 20 to about 40 pm or from about 10 to about 40 pm are, in the first instance, conditioned with the flotation reagents and then flotation is carried out. [000109] The fraction or fractions having a particle size ranging from about 40 to about 400 pm and the fraction or fractions having a particle size ranging from about 20 to about 40 pm or from about 10 to about 40 pm are obtained from the non-flotation of the first stage of flotation are conditioned with the flotation reagents and then a second flotation is carried out. [000110] Flotation enrichment can be achieved by reverse flotation in two stages. [000111] First-stage flotation is generally carried out in the presence of an acid, for example sulfuric acid, which acts as a pH regulator "4.5 to 5". [000112] Flotation is also carried out in the presence of phosphoric acid which acts as a depressant for apatite. [000113] The carbonate collector may be selected from the following list of fatty acids or a mixture of the constituents of this list: Oleic Acid and Sodium Dodecyl Sulfate (SDS), Tall Oil and Anionic Phospholane, Linoleic Acid (LA), Linolenic Acid (LNA), Monocarboxylic Fatty Acid, Tall Oil, Dodecanedioic Acid, Sebacic and Adipic Acid, Sodium Oleate, Carboxymethylcellulose, Ethylene Glycol, Sodium Palmitate, Pataua Oil, Andiroba Oil, Sodium Potassium Double Tartrate, Non-ionic Polymers Containing Polyethylene Oxide (PEO), Cetyl Potassium Phosphate. This list does not in any way limit the choice of fatty acid. [000114] Flotation reagents can be used in combination with foaming and antifoaming agents to adjust the foaming effect. [000115] The flotation reagents at the second stage are: [000116] phosphoric esters corresponding to the following formula: RI - O - P(=O) - (OH)2 (I) in which RI is an alkyl group, linear or branched, saturated or unsaturated, comprising 6 to 18 carbon atoms. [000117] Amines and their salts typically corresponding to the following formulas: R — O — (CFLjs — NEE , where R is an alkyl group with 10-14 carbon atoms, R — O — (CFLjs — NH — (CFLjs — NEE , where R is an alkyl group with 10 or more carbon atoms. For example, dodecylamine (C 12), tetradecylamine (C 14), and hexadecylamine (C 16). [000118] Flotation reagents can be used in combination with foaming and antifoaming agents to adjust the foaming effect. [000119] The process according to the invention allows the obtaining of an ore enriched in phosphates. Typically, the ore has a quantity of BPL greater than at least 54% compared to the quantity of BPL of the ore subjected to the process, or even greater than 63 to 65% or even 66 to 67%. [000120] Generally, the ore obtained by the process according to the invention also has improved solubility compared to the feed product of the process. [000121] Generally, the ore obtained by the process according to the invention also has a reduced quantity of heavy metals. [000122] The enriched ore may exhibit one or more of the following characteristics: - an NZ solubility greater than or equal to 9%, typically ranging from 9% to 9.3% or from 9.3% to 9.76%; - a quantity of cadmium less than or equal to 14 ppm, typically ranging from 14 to 13 ppm or even from 13 to 12 ppm; - a quantity of nickel less than or equal to 31 ppm, typically ranging from 20 to 31 ppm or even from 16 to 20 ppm; - a quantity of chromium less than or equal to 120 ppm, typically ranging from 100 to 120 ppm or even from 92 to 120 ppm; - a zinc content of 217 ppm or less, typically ranging from 190 to 217 ppm or from 191 to 217 ppm; and - an amount of MgO less than or equal to 0.88% by weight relative to the total weight of the raw charge, typically ranging from 0.55 to 0.88% by weight or from 0.55 to 0.88% by weight. [000123] FIG. 1 describes a first preferred embodiment of the process of the invention for discharges stored at the level of spreading dikes comprising the following steps: i. particle size separation with a cut at 1000 pm of the degreased fraction leading to the formation of a fraction having a particle size less than or equal to 1000 pm; ii. particle size separation with a cut at 400 pm of the fraction having a particle size less than or equal to 1000 pm leading to the formation of a fraction having a particle size greater than 400 pm and less than or equal to 1000 pm and a fraction having a particle size less than or equal to 400 pm; iii. particle size separation with a cut at 40 pm of the fraction having a particle size less than or equal to 400 pm leading to the formation of a fraction having a particle size ranging from 40 pm to 400 pm (intended for flotation) and a fraction having a particle size less than 40 pm; iv. particle size separation with a cut at 20 pm of the fraction having a particle size less than 40 pm leading to the formation of a fraction having a particle size ranging from 20 pm to 40 pm (intended for flotation after attrition and desliming) and a fraction having a particle size less than 20 pm (rejects); v. attrition of the fractions having a particle size ranging from 40 pm to 400 pm, and of the fraction having a particle size ranging from 20 pm to 40 pm, leading to the formation of an attrited fraction; vi. particle size separation with a cut at 40 pm of the attrited fraction leading to the formation of an attrited fraction having a particle size ranging from 40 pm to 400 pm (intended for flotation) and an attrited fraction having a particle size less than 40 pm; vii. particle size separation with a cut at 20 pm of the attrited fraction having a particle size less than 40 pm leading to the formation of an attrited fraction having a particle size ranging from 20 pm to 40 pm (intended for flotation) and a fraction having a particle size less than 20 pm (rejects); viii. flotation of fractions having a particle size ranging from 40 pm to 400 pm and of fractions having a particle size ranging from 20 pm to 40 pm leading to the obtaining of a phosphate-enriched ore concentrate free of calcite and dolomite; ix. flotation at the second stage of the enriched ore leading to the obtaining of a phosphate-enriched ore concentrate free of calcite, dolomite and silicates. [000124] In some embodiments, steps iv. and vii. are carried out with a break at 10 pm. [000125] FIG. 2 describes another preferred embodiment of the process of the invention for waste products directly from a washing, grinding and flotation unit comprising the following steps: i. particle size separation with a cut-off at 400 pm leading to the formation of a fraction with a particle size greater than 400 pm and a fraction with a particle size less than or equal to 400 pm; ii. particle size separation with a cut at 40 pm of the fraction having a particle size less than or equal to 400 pm leading to the formation of a fraction having a particle size ranging from 40 pm to 400 pm (intended for flotation) and a fraction having a particle size less than 40 pm; iii. particle size separation with a cut at 20 pm of the fraction having a particle size less than 40 pm leading to the formation of a fraction having a particle size ranging from 20 pm to 40 pm (intended for flotation after attrition and desliming) and a fraction having a particle size less than 20 pm (rejects); iv. attrition of the fractions having a particle size ranging from 40 pm to 400 pm, and of the fraction having a particle size ranging from 20 pm to 40 pm, leading to the formation of an attrited fraction; v. particle size separation with a cut at 40 pm of the attrited fraction leading to the formation of an attrited fraction having a particle size ranging from 40 pm to 400 pm (intended for flotation) and an attrited fraction having a particle size less than 40 pm; vi. particle size separation with a cut at 20 pm of the attrited fraction having a particle size less than 40 pm leading to the formation of an attrited fraction having a particle size ranging from 20 pm to 40 pm (intended for flotation) and a fraction having a particle size less than 20 pm (rejects); vii. flotation of fractions with a particle size ranging from 40 pm to 400 pm and of fractions with a particle size ranging from 20 pm to 40 pm leading to the obtaining of a phosphate-enriched ore concentrate free of calcite and dolomite; viii. Second-stage flotation of the enriched ore leading to the production of a phosphate-enriched ore concentrate free of calcite, dolomite and silicates. [000126] In some embodiments, steps iv. and vii. are carried out with a break at 10 pm. [000127] The process according to the invention is particularly intended for the treatment of sludge from the washing, crushing and flotation of phosphates and other ores

Claims

DEMANDS 1. Process for enriching the processing tailings of a phosphate ore, making it possible to improve the solubility of the concentrate in its various forms, comprising the following steps: - pulping and settling of the ore for the waste from the spreading ponds; - a series of particle size separations of the cleaned ore so as to separate at least one fraction with a particle size less than approximately 40 µm and a fraction with a particle size ranging from approximately 40 to approximately 400 µm; - particle size separation of the fraction with a particle size less than approximately 40 µm so as to separate a fraction with a particle size less than approximately 20 µm or less than approximately 10 µm and a fraction with a particle size ranging from approximately 20 to approximately 40 µm or from approximately 10 to approximately 40 µm - two-stage flotation of the fraction having a particle size of about 20 to about 40 pm or about 10 to 40 pm and of the fraction having a particle size of about 40 to about 400 pm, or about 40 to about 160 pm, or about 40 to about 200 pm, or about 40 to about 400 pm, leading to the obtaining of an ore enriched in phosphates.

2. The process according to claim 1, wherein the particle size separation steps are carried out by screening, centrifugation, hydrocycloning or by means of a hydrosizer.

3. The process according to claim 1, wherein the succession of particle size separations includes a particle size separation with a cut-off at 1000 pm leading to a fraction having a particle size less than or equal to 1000 pm and to a fraction having a particle size greater than 1000 pm.

4. The process according to claim 3, wherein the succession of particle size separations comprises a particle size separation with a cut at 400 pm of the fraction having a particle size less than or equal to 1000 pm leading to the formation of a fraction having a particle size greater than 400 pm and less than or equal to 1000 pm and a fraction having a particle size less than or equal to 400 pm.

5. The process according to claim 4 in which the succession of particle size separations comprises a particle size separation with a cut at about 40gm of the fraction having a particle size less than or equal to about 400 gm leading to the formation of a fraction having a particle size ranging from about 40 gm to about 400 gm and a fraction having a particle size less than about 40 gm.

6. The process according to claim 1 wherein prior to the flotation step, an attrition of the fraction having a particle size ranging from about 40 gm to about 400 gm followed by desliming at about 40 gm leading to the formation of a fraction having a particle size ranging from about 40 gm to about 160 gm and a fraction having a particle size less than about 40 gm, the fraction having a particle size ranging from about 40 gm to about 400 gm obtained being subjected to the flotation step.

7. The process according to claim 4, wherein the fraction having a particle size ranging from approximately 400 gm to approximately 1000 gm is rejected at the first rejection basin.

8. The process according to claim 6, wherein the fraction having a particle size of less than approximately 40 gm obtained after crushing and screening is subjected to particle size separation with a cut-off at approximately 20 gm or approximately 10 gm, resulting in a fraction having a particle size ranging from approximately 20 gm to approximately 40 gm or from approximately 10 gm to approximately 40 gm, and a fraction having a particle size of less than approximately 20 gm or less than 10 gm, the resulting fraction having a particle size ranging from approximately 20 gm to approximately 40 gm or from approximately 10 gm to approximately 40 gm being subjected to the flotation step after attrition and desliming.

9. The process according to claim 8, wherein the conditioning for flotation is carried out as follows: - flotation in the first stage is carried out in the presence of an acid, preferably sulfuric acid and / or phosphoric acid, which acts as a regulator of pH 4.5 to 5; - flotation is also carried out in the presence of phosphoric acid which acts as a depressant of apatite; - the carbonate collector may be chosen from the following list of fatty acids or a mixture of the constituents of this list: oleic acid and sodium dodecyl sulfate (SDS), tall oil fatty acids and anionic phospholane, linoleic acid (LA), linolenic acid (LNA), monocarboxylic fatty acid, tall oil, dodecanedioic acid, sebacic and adipic acid, sodium oleate, carboxymethylcellulose, ethylene glycol, sodium palmitate, pataua oil, andiroba oil, sodium potassium double tartrate, non-ionic polymers containing polyethylene oxide (PEO), cetyl potassium phosphate; and in which flotation reagents may be used in combination with foaming and antifoaming agents to adjust the foaming effect.

10. The process according to claim 9 wherein the flotation concentrate "non-floated product" undergoes thickening, giving rise to an Overflow and an Underflow.

11. The process according to any one of claims 1 to 10 wherein the fractions having a particle size less than about 20 pm and the flotation rejects (greater than 20 pm) and the Overflow are rejected at the level of a first settling tank and spreading basin.

12. The process according to claim 11, wherein the return of water from the first settling tank, the first spreading basin and any addition of fresh water at this stage can only be used upstream of the first flotation stage.

13. The process according to claim 1, wherein the conditioning of the Underflow for the second flotation is carried out as follows: - the flotation reagents at the second stage are: phosphoric esters corresponding to the following formula: Ri - O - P(=O) - (OH)2 (I), in which RI is an alkyl group, linear or branched, saturated or unsaturated, comprising 6 to 18 carbon atoms; Amines and their salts typically correspond to the following formulas: R — O — (CFLjs — NH3 , where R is an alkyl group with 10-14 carbon atoms, R — O — (CH)? — NH — (CFLjs — NLh , where R is an alkyl group with 10 or more carbon atoms, optionally dodecylamine (C12), tetradecylamine (C14), and hexadecylamine (C16); and where Flotation reagents can be used in combination with foaming and antifoaming agents to adjust the foaming effect.

14. The process according to claim 13, wherein the floated product "reject from the second flotation" is sent to the level of the second settling tank and spreading basin.

15. The process according to claims 10 and 14, wherein recycled water or any fresh water supplement can only be used downstream of the thickening step.

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