Process for size reducton of ores using a water swellable polymer

Abstract

The invention concerns a process for the size reduction of ores from a mine in which at least one water-swellable polymer is added upstream of a crusher.

Description

[0001]PROCESS FOR SIZE REDUCTON OF ORES USING A WATER SWELLABLE POLYMER FIELD OF THE INVENTION The present invention concerns a process for the size reduction of ores from a mine. More precisely, in this process a water-swellable polymer is added upstream of a crusher. BACKGROUND OF THE INVENTION Once the ores that contain a valuable metal or industrial minerals are removed from the mine, a size reduction is generally performed to liberate the valuable minerals partly or totally and sometimes only to liberate specific rocks that are richer compared to the so-called gangue rock, followed by size classification stages (screening) and one or multiple separation stages (sorting, magnetic separation, gravity separation, flotation) on certain or all granular size fractions. Intermediate concentrates and tailings can be produced and are further crushed / grinded and processed to increase the liberation and enhance the recovery and the purity of concentrates. If these mineral processing stages are performed using wet processes, the produced fine concentrates and tailings are generally separated from the liquid media using thickeners and filters. If these mineral processing stages are performed using dry process, the produced coarse concentrates and tailings are generally separated from the liquid media using screens. While tailings are generally discarded as a pulp, a coarse rock material to be stacked, or as cake, the concentrates are used as such as finished products or undergo a pyrometallurgical or hydrometallurgical process to produce final or intermediate products. Natural water content of mined ores (between 5 and 40 % by weight) associated with specific mineralogy and ore particle size distribution induces a muddy or sticky behavior that may clog the crusher itself and the optional associated screening equipment, that we will name post-crushing control screen(s), used to send back to the crusher the oversized materials. During screening step of crushed ores passing the post crushing size control, screening efficiency of crushed ores can decrease if crushed ores are sticky and so are agglomerated. Water content of crushed ores induces agglomeration of crushed ores. DESCRIPTION OF THE INVENTION Surprisingly, The Applicant discovered that adding a water-swellable polymer to mined ores prior crushing step allows to decrease clogging in the crushing equipment (including optional fed hopper and control screen(s)) and to increase the throughput and the quality of crushed ores. Surprisingly, The Applicant also discovered that adding a water-swellable polymer to mined ores prior crushing step of crushed ores increase the throughput and the quality of the optional following dry screening step through one or several sieves required to produce different granular size fractions that are considered as final concentrates or tailings or products to further processed to recover the contained desired metal or industrial minerals. More precisely, the invention deals with a process for size reduction of ores from a mine which comprises the following successive steps: - mixing a water-swellable polymer P1 in powder form with mined ores before their introduction in a crusher, - introducing ores mixed with the polymer P1 into a crusher to produce crushed ores, said crusher being optionally equipped with a fed hopper and a post- crushing control screen, - optionally mixing a water-swellable polymer P2 in powder form to said crushed ores, after the exit from the crusher, or after the post-crushing control screen, - transferring the resulting crushed ores to a dry screening station, and / or a dry magnetic separation plant, and / or a train wagon, and / or a bulk carrier for sea shipping, and / or a downstream process. The process for size reduction of ores from the mines can be applied for all types of mined ores. A non-restrictive list of mined ores is base metal ores (copper, zinc, lead), iron ores, bauxite ores, nickel ores, cobalt ores, manganese ores, phosphate ores, coal ores, barite ores, fluorite ores, silver ores, gold ores, platinoids ores, rare-earth elements ores, industrial minerals ores. Water-swellable polymers P (P1 and P2) used in the process of the invention are cross-linked polymers and thus form three-dimensional networks. These water- swellable polymers are also known as super-absorbent polymers. Generally, they have a water absorption capacity of more than 10 times their volume. Water-swellable polymers P can be natural polymers, likes for instance cellulose or polysaccharides derivatives or they can be synthetic polymers or semi-synthetic (or semi-natural) polymers. Preferably water-swellable polymers P are synthetic polymers. According to the present invention, the term “synthetic polymers”, used in the plural, means a homopolymer or a copolymer or a homopolymer and / or copolymer mixture, a copolymer meaning a polymer prepared from at least two different monomers. This is therefore a copolymer (i) of at least one anionic monomer and / or (ii) of at least one other cationic monomer and / or (iii) of at least one non-ionic monomer and / or (iv) of at least one zwitterionic monomer. For synthetic water-swellable polymers P, preferred non-ionic monomer is acrylamide. The preferred anionic monomer is acrylic acid or acrylamido-tertiary butyl sulphonic (ATBS) acid and their salts. The preferred cationic monomer is quaternized or salified dimethylaminoethyl acrylate (ADAME). The salified form advantageously corresponds to the salts of alkali metals (Li, Na, K…), of alkaline earth metals (Ca, Mg…) or of ammonium (for example, the ammonium ion or a tertiary ammonium). The preferred salts are the sodium salts. Quaternized monomers, are prepared for example by means of a quaternizing agent of the R-X type, R being an alkyl group and X being a halogen or a sulfate. The quaternizing agent can be chosen from dialkyl sulfates containing 1 to 6 carbon atoms or alkyl halides containing 1 to 6 carbon atoms. Preferably, the quaternizing agent is chosen from methyl chloride, benzyl chloride, dimethyl sulfate, or diethyl sulfate. Synthetic water-swellable polymer P are crosslinked with crosslinking agent which can be selected from polyethylenically unsaturated monomers (having at least two unsaturated functions) such as, for example, vinylic functions, notably allylic, acrylic functions, or from the monomers having at least two epoxy functions. One can mention, for example, methylenebisacrylamide (MBA), triallylamine, tetraallylammonium chloride, 1,2-dihydroxyethylenebis-(N- acrylamide) and the mixtures thereof. Preferably crosslinking agent is methylenebisacrylamide (MBA). The quantity of crosslinking agent in synthetic water-swellable polymer P is advantageously between 5 and 5000 ppm with respect to the total weight of the monomers, more preferably between 100 and 1000 ppm. Preferably, synthetic water-swellable polymer P1 is a crosslinked copolymer of acrylamide and acrylic acid and / or its salts. More preferably, water-swellable polymer P1 is a copolymer of sodium acrylate and acrylamide crosslinked with methylenebisacrylamide. According to the invention, water-swellable polymers P are polymers in powder with an average particle size of between 10 μm and 1500 μm. Preferably, the average particle size of polymer P is around 800 μm. The average particle size refers to the average diameter measured with a laser diffraction particle analyzer according to the conventional techniques of the person skilled in the art. An example of the device to measure the average diameter is the Mastersizer by Malvern Instruments. Water-swellable polymers P are prepared advantageously by gel polymerization method. The hopper of the invention can be selected in the list: jaw crushers, giratory crushers, cone crushers, roll crushers. Mixing between the water-swellable polymer P1 in powder form and mined ores is performed before their introduction in a crusher. Mixing can be performed by all available means known by the skilled man of the art starting from the step of removing ores from the mine and introduction of mined ores in a crusher. Preferably, mixing of mined ores with water-swellable polymer P1 is performed by addition of water-swellable polymer P1 by means of a hopper located on the first part of a conveyor belt conveying mined ores to the crusher. According to another embodiment, mixing of mined ores with water-swellable polymer P1 is performed by simultaneous addition of water-swellable polymer P1 and mined ores in a hopper alimenting the crusher. Between 0,001 and 0,2 % by weight of water-swellable polymer P1 of total mined ore weight is mixed with mined ores before their introduction in a crusher, preferably between 0,01 and 0,10 % by weight and more preferably between 0,02 and 0,08 % by weight. Optionally, and preferably, an addition of water-swellable polymer P2 in powder form is performed after the exit from the crusher, and / or after the exit of its optional post-crushing control screen(s), on crushed ores previously mixed with the water-swellable polymer P1. Advantageously, the water-swellable polymer P2 is added in the middle of the crushed ores fall to improve its incorporation. Mixing between the water-swellable polymer P2 and crushed ores can be performed by all available means known by the skilled man of the art. Addition of the water-swellable polymer P2 can be performed before treatment of crushed ores in a dry screening station, and / or before a dry magnetic separation plant, and / or before their transport in bulk carrier or in train wagons, and / or before a bulk carrier for sea shipping, and / or before downstream processes likes pyrometallurgical or hydrometallurgical process. Preferably, addition of the water-swellable polymer P2 on crushed ores is performed by means of a hopper located on the first part of a conveyor belt conveying crushed ores for a next step of the process. Advantageously water swellable polymers in powder form P1 and P2 are the same. They may be different, but they are preferably the same. When water- swellable polymers P1 and P2 are the same, their characteristics in terms of monomer composition, of crosslinker nature, of particle size are the same. Between 0,001 and 0,2 % by weight of water-swellable polymer P2 of total crushed ores weight is added after the exit from the crusher, and / or after the exit of its optional post-crushing control screen(s), on crushed ores previously mixed with polymer P1, preferably between 0,01 and 0.10 % by weight, and more preferably between 0,02 and 0,08 % by weight. The invention and the advantages thereof will become more apparent from the following examples. Examples Water-swellable polymers The cross-linked polymer P1 used in the examples is a polymer obtained by gel polymerization of acrylamide, sodium acrylate and N,N’-methylenebisacrylamide (cross linking agent). The polymer P1 is in powder form and its monomeric composition is 30 mol % of sodium acrylate, 70 mol % of acrylamide and 600 ppm (by weight based on total monomers) of N,N’-methylenebisacrylamide. The cross-linked polymer P1 have a dry particle size distribution of 50-1200 microns and a gel capacity of 600 g of deionized water per gramme of polymer. In the examples, polymer P2 is the same as polymer P1. Iron ore In the following examples, a sticky raw iron ore was processed in a mineral processing pilot plant to study the influence of water-swellable polymer on crushing and optional post-crushing control screening and optional downstream operations. The mineralogical composition of the ore has not been analysed, but it was suspected to contain a significant proportion of clays, which would explain its particularly sticky and liquefying behaviour. At rest, particles of various sizes were agglomerated by the fine and probably clayey fraction. The moisture content of the ore was measured at around 24,5 % after oven-drying at 105°C for 24 hours. The particle size distribution (PSD) of the ore was measured by wet sieving to deagglomerate the particles. In detail, wet sieving operations for feed were carried out on a large rotary vibrating sieve sifter machine equipped with 63 mm, 45 mm, and 28 mm aperture sieves. The passing materials were then sieved with the same machine but equipped with 22,4 mm, 18 mm, and 13,2 mm aperture sieves. The passing materials was then further sieved on a laboratory vibrating sieve machine equipped with 9,5 mm and 6,3 mm aperture sieves. The obtained PSD of the original feed sample is shown in Figure 1. Test methods Crushing tests were carried out on identical one-ton batches. The iron ore was mixed with water-swellable polymer P1 by conveying the ore on an inclined “sauterelle” belt conveyor and adding on top of the conveyed ore the water- swellable polymer P1 using an electromagnetic vibrating feeder. A proper mixing was ensured by the resulting 4 meters high ore fall and a proper polymer swelling was ensured by respecting a three-hours latency period before the start of crushing tests. This is not the shortest swelling time observed industrially, but it was not possible to continuously feed the crusher and maintain a constant swelling time over the entire test period. This is why it was preferable to leave the polymer swollen properly for a few hours, to simulate the case where water-swellable polymer P1 is added upstream of an ore buffer stockpile, as it is often the case, notably for pre-homogenization reasons. Crushing was performed using a pilot plant scale cone crusher. Each batch of iron ore was placed at once in a large hopper which feeds the cone crusher by gravity. The time required to crush the entire content of the hopper was timed to calculate an average throughput. In the event of hopper clogging, identifiable by the fact that the crushing noise stopped before the hopper was completely emptied, the hopper was intensively unclogged by hammering on the hopper structure. During crushing, incremental sampling was performed on the output flow to form four batches: ^ A first batch to be wet sieved as a final step to determine the reference particle size distribution of the crushed materials and to simulate the influence of water-swellable polymer P1 on the crushing (example 1) ^ A second batch to be dry sieved using a 22,4 mm sieve, immediately after crushing to simulate the influence of water-swellable polymer P1 on the optional post-crushing control screening (example 2) ^ A third batch to be dry sieved using a 13,2 mm sieve, immediately after crushing to simulate the influence of addition of water-swellable polymer P1 as crushing aid on the performance of the optional downstream dry screening station (example 3) ^ An optional fourth batch to be dry sieved in the same way but after a mixing stage of the crushed materials with a water-swellable polymer P2 to simulate the influence of a second water-swellable polymer addition on the optional downstream dry screening station (example 4) The wet sieving operations to determine the PSD of the dry sieving feed were carried out on a large rotary vibrating sieve sifter machine equipped with 63 mm, 45 mm and 28 mm aperture sieves using the first sample of crushed materials. The passing materials were then sieved with the same machine but equipped with 22,4 mm, 18 mm, and 13,2 mm aperture sieves. The passing materials was then further sieved on a laboratory vibrating sieve machine equipped with 9,5 mm, 6,3 mm, 4 mm, and 2,5 mm aperture sieves. Wet sieving was continued until complete sieving is achieved. The dry sieving operations were carried out on a large rotary vibrating sieve sifter machine equipped with 22,4 mm or 13,2 mm aperture sieves. The operation time for dry sieving was set at 3 minutes. The sieving efficiency was calculated using the formulas: Example 1 With this example, the applicant aims to highlight the influence of the addition of water-swellable polymer P1 on crusher throughput and size reduction. The polymer P1 dosage was 0.1 weight % (wet basis), which is relatively a high dosage considering that the swelling time was significant enough to get a proper water absorption and allows to transform the sticky / muddy iron ore into a crusty / fragile agglomerate. The first comparison criterion is the crusher throughput calculated from the time required to crush one tonne of iron ore with the pilot plant scale cone crusher. Test results are indicated in Table 1. Table 1 : Effect of water-swellable polymer P1 addition on crusher throughput Test P1 dosage Crushing time Crusher throughput E1-1 0 21,3 min 2,8 t / h E1-2 0,1 % 4,8 min 12,5 t / h This example shows an improvement of 344 % of the crusher throughput when water-swellable polymer P1 was used. The applicant would like to mention that beyond these values, they observed: ^ A relatively free flowing of materials from the hopper to the cone crusher when water-swellable polymer P1 was used. ^ A difficult transfer from the hopper to the cone crusher in absence of water-swellable polymer which required numerous hammer blows to unblock the base of the hopper. At industrial level, with larger equipment, transfer should be less problematic, but remain present to a lesser extent. ^ A jerky discharge of crushed material, probably due to accumulation in the crusher in the absence of water-swellable polymer suggested by the presence of residual ore stuck in the crusher at the end of the test. The second comparison criterion is the particle size distribution of the crushed materials determined by wet sieving. The results are indicated in Erreur ! Source du renvoi introuvable.. These data indicate an increase in the size reduction factor in the absence of water-swellable polymer, which can probably be explained by an accumulation of sticky material in the crusher leading to material over-crushing. Example 2 With this example, the applicant aims to highlight the influence of the addition of water-swellable polymer P1 on the efficiency if the optional post-crushing control screening. To simulate the optional post-crushing control screening, the crushed materials were dry sieved using a 22,4 mm sieve. As for example 1, the water-swellable polymer P1 was added before crushing and the dosage was 0,1 weight % (wet basis). To carry out comparative trials, the materials were divided up so that exactly 20 kg of material was used for each trial. The coning and quartering sampling method was used. Considering the significant reaction time between the ore moisture and the water- swellable polymer P1 before crushing and the additional mixing offered by the crushing stage, the applicant considered that this sampling operation and the associated manual operations did not give a gain in water absorption compared to an industrial case where the post-crushing control screening is performed immediately after the crushing stage. The applicant therefore considered this example to be relevant to the desired demonstration. Test results are indicated in Table 2. Table 2 : Effect of water-swellable polymer P1 addition on sieving at 22,4 mm Sieving P1 Passing Passing Undersize Undersize Test method dosage (kg) (%) recovery ratio :1 E2-1 Wet 0 19,6 98,0 % / / E2-2 Dry 0 18,5 92,5 % 94,4 % 2,75 E2-3 Wet 0.1 % 18,4 92,0 % / / E2-4 Dry 0.1 % 17,8 8,0 % 96,7 % 0,37 In this example, the absence of water-swellable polymer led to an over-crushing of this sticky ore meaning more particles with size lower than the 22,4 mm sieve opening (98,0 % compared to 92,0 %). However, despite a more favourable particle size distribution, it was observed that the undersize recovery was lower in absence of water-swellable polymer. In detail, despite a more favourable particle size distribution in the absence of water-swellable polymer, the mass of particles smaller than 22,4 mm in the non- passing was 1,1 kg in the absence of water-swellable polymer and 0,6 kg in the presence of water-swellable polymer P1. This difference due to the sticky nature of the ore in the absence of water-swellable polymer is further illustrated by the undersize ratio in the non-passing which was significantly lower than 1 (0,37:1) in the presence of water-swellable polymer P1 and significantly higher than 1 (2,75:1) in the absence of water-swellable polymer confirming that the addition of water-swellable polymer P1 and the observed transition from a sticky ore to a crusty / fragile agglomerate before the crushing stage improves the efficiency of the optional post-crushing control screening. More generally, in the industrial case of continuous screening, the passage of sticky material through the screen generates several problems 1) a progressive narrowing of screen openings which progressively reduces screening efficiency and ultimately leads to complete clogging and 2) closed circuit of sticky materials which are rejected by the screens and returned to the crusher, resulting in an accumulation in the system, progressively reducing crushing and screening performance. In both cases, operations must be stopped to wash the equipment slowing down the production. As a preventive measure, the crusher feed rate can be voluntarily slowed down to improve fines passage through the control screen, or the control screen can be bypassed but it reduces the calibration of the crushed product, thus affecting downstream operations. Example 3 With this example, the applicant aims to highlight the influence of the addition of water-swellable polymer P1 on optional downstream operations positively sensitive to the use of water-swellable polymers such as dry screening station. To simulate the optional downstream dry screening station, the crushed materials were dry sieved using a 13,2 mm sieve. As for previous examples, the water- swellable polymer P1 was added before crushing and the dosage was 0,1 weight % (wet basis). The applicant considered an industrial situation of absence of optional post- crushing control screening to have a more reliable comparison. Indeed, in absence of water-swellable polymer, a significant retention of sticky fines was observed on the 22,4 mm opening sieve. Removing about 1 kg of the stickiest fines would have distorted the comparison of the sieving efficiency using a 13,2 mm sieve. To carry out comparative trials, the materials were also divided up so that exactly 20 kg of material was used for each trial. The coning and quartering sampling method was used. Considering the significant reaction time between the ore moisture and the water- swellable polymer P1 before crushing and the additional mixing offered by the crushing stage, the applicant considered that this sampling operation and the associated manual operations did not give a gain in water absorption compared to an industrial case where the post-crushing control screening is performed immediately after the crushing stage. The applicant therefore considered this example to be relevant to the desired demonstration. Test results are indicated in Table 3. Table 3 : Effect of water-swellable polymer P1 addition on sieving at 13,2 mm P1 Passing Passing Undersize Undersize Test Sieving dosage (kg) (%) recovery ratio :1 E3-1 Wet 0 15,2 76,0 % / / E3-2 Dry 0 10,1 50,5 % 66,4 % 1,06 E3-3 Wet 0,1 % 11,2 56,0 % / / E3-4 Dry 0,1 % 10,1 50,5 % 90,2 % 0,13 In this example, the absence of water-swellable polymer led to an over-crushing of this sticky ore meaning more particles with size lower than the 13,2 mm sieve opening (76,0% compared to 56,0%). However, despite a more favourable particle size distribution, it was observed that the undersize recovery was significantly lower in absence of water-swellable polymer due to an observed clogging of the sieve. In detail, despite a more favourable particle size distribution in the absence of water-swellable polymer, the mass of particles smaller than 13,2 mm in the non- passing was 4,1 kg in the absence of water-swellable polymer and 1,1 kg in the presence of water-swellable polymer P1. This difference due to the sticky nature of the iron ore in the absence of water-swellable polymer is further illustrated by the undersize ratio in the non-passing which was significantly lower than 1 (0,13:1) in the presence of water-swellable polymer P1 and close to 1 in the absence of water-swellable polymer confirming that the addition of water- swellable polymer P1 and the observed transition from a sticky ore to a crusty / fragile agglomerate before the crushing stage improve the efficiency of the optional post-crushing control screening. More generally, in the industrial case of continuous screening, since the screen(s) openings are smaller than those of the optional post-crushing control screen, there is proportionally more fine particles to treat which means that the sticky behaviour of ores is amplified. Without the addition of water-swellable polymer, the ore adheres to the screen narrowing the openings which progressively reduces screening efficiency, decreases the fines recovery, decreases the quality of the produced coarse materials, and ultimately results in a clogging and complete liquefaction of sticky ores onto the screen. In such situation, the operators regularly need to stop the dry screening station to wash the equipment slowing down the production. As a preventive measure, the feed rate can be slowed down to improve passage of fines through the screen(s). The applicant observed industrially that the addition of water-swellable polymer P1 limit the occurrence of these maintenance shutdowns, increases the maximum possible throughput without occurrence of screen clogging events but also improves the fines recovery and the quality of the produced coarse materials. Example 4 With this example, the applicant aims to highlight the influence on optional downstream operations positively sensitive to the use of water-swellable polymers such as dry screening station of the addition of water-swellable polymer P2 after the crushing or after the optional post-crushing control screening. To simulate the optional downstream dry screening station, the crushed materials were dry sieved using a 13,2 mm sieve. As for previous examples, the water- swellable polymer P1 was added before crushing and the dosage was 0,1 weight % (wet basis). However, unlike the previous examples, an addition of 0,05 % (wet basis) of water-swellable polymer P2 is performed with one of the four samples taken during the crushing stage. In detail, a 20 kg sample, obtained by the coning and quartering sampling method, of ore crushed with water-swellable polymer P1, which has therefore already largely lost its sticky appearance, was spread out on a tray and the water-swellable polymer P2 was placed on the sample. This sample was passed three times through a riffle splitter to ensure proper mixing between the ore and the water-swellable polymer P2. A short latency period of 5 minutes was respected to better compare results with the test where the sieving takes place immediately after crushing. The applicant still considered an industrial situation of absence of optional post- crushing control screening for this example. Test results are indicated in Table 4. Table 4 : Effect of dual addition of water-swellable polymers P1 and P2 addition on sieving at 13,2 mm P1 P2 Passing Passing Undersize Undersize Test Sieving dosage dosage (kg) (%) recovery ratio :1 E4-1 = Wet 0,1 % 0 11,2 56,0 % / / E3-3 E4-2 = Dry 0,1 % 0 10,1 50,5 % 90,2 % 0,13 E3-4 E4-3 Dry 0,1 % 0,05 % 10,8 54,0 % 96,4 % 0,05 In this example, the addition of water-swellable polymer P2 slightly improved the passage of fines through the sieve, showing that a further transition to a brittle crusty agglomerate material was possible by increasing the dosage of superabsorbent. This example is not the most suitable for this demonstration, as the water- swellable polymer P1 dosage was high and the swelling period before crushing was significant, meaning that water absorption by water-swellable polymer P1 was almost optimal. The gain from a water-swellable polymer P2 addition is therefore limited, although visible. The risk of clogging is greater on dry screening stations than on crushers and associated optional control screen, as the openings of the screen(s) are reduced in dry screening stations, making this equipment less resilient to the sticky nature of the ores. In certain situations, for example when entire crusher throughput does not pass through the dry screening station, it is advisable to limit the water- swellable polymer P1 dosage and increase the water-swellable polymer P2 dosage. To demonstrate that the water-swellable polymer P2 addition is useful in a case where the water-swellable polymer P1 dosage is lower and / or the reaction period between the ore and the water-swellable polymer is shorter, the applicant repeated the previous series of tests with a water-swellable polymer P1 dosage of 0,05 %. Test results are indicated in Table 5. Table 5 : Effect of dual addition of water-swellable polymers P1 and P2 addition on sieving at 13,2 mm P1 P2 Passing Passing Undersize Undersize Test Sieving dosage dosage (kg) (%) recovery ratio :1 E4-4 Wet 0,05% 0 12,3 61,5% / / E4-5 Dry 0,05% 0 9,9 49,5% 80,5% 0,31 E4-6 Dry 0,05% 0,05% 11,8 59,0% 95,9% 0,06 This second series of tests shows more clearly the advantages of adding water- swellable polymer P2 on the dry screening operations in certain cases where it was not necessary to push the dosage of water-swellable polymer P1 beyond what was required to ensure good performance of the crusher and the optional post- crushing control screen.

Claims

CLAIMS 1. A process for size reduction of ores from a mine which comprises the following successive steps: - mixing a water-swellable polymer P1 in powder form with mined ores before their introduction in a crusher, - introducing ores mixed with the polymer P1 into a crusher to produce crushed ores, said crusher being optionally equipped with a fed hopper and a post-crushing control screen, - optionally mixing a water-swellable polymer P2 in powder form to said crushed ores, after the exit from the crusher, or after the post- crushing control screen, - transferring the resulting crushed ores to a dry screening station, and / or a dry magnetic separation plant, and / or a train wagon, and / or a bulk carrier for sea shipping, and / or a downstream process.

2. A process according to claim 1 wherein, water-swellable polymer P1 is a synthetic polymer.

3. A process according to claim 2 wherein, the synthetic water-swellable polymer P1 is a crosslinked copolymer of acrylamide and acrylic acid and / or its salts.

4. A process according to any of the previous claims wherein, mixing of mined ores with water-swellable polymer P1 is performed by addition of water- swellable polymer P1 by means of a hopper located on the first part of a conveyor belt conveying mined ores to the crusher.

5. A process according to claims 1 to 3 wherein, mixing of mined ores with water-swellable polymer P1 is performed by simultaneous addition of water-swellable polymer P1 and mined ores in a hopper alimenting thecrusher.

6. A process according to any of the previous claims wherein, an addition of water-swellable polymer P2 in powder form is performed after exit from the crusher and / or after the exit of its optional post-crushing control screen(s), on crushed ores previously mixed with the water-swellable polymer P1.

7. A process according to claim 6 wherein, addition of water-swellable polymer P2 on crushed ores is performed by means of a hopper located on the first part of a conveyor belt conveying crushed ores for a next step of the process.

8. A process according to any of the previous claims wherein, water-swellable polymers in powder form P1 and P2 are the same.

9. A process according to any of the previous claims wherein, between 0,001 and 0,2 % by weight of water-swellable polymer P1 of total mined ore weight is mixed with mined ores before their introduction in a crusher.

10. A process according to claims 6 and 7, wherein, between 0,001 and 0,2 % by weight of water-swellable polymer P2 of total wet crushed ores weight is added after exit from the crusher and / or after the exit of its optional post- crushing control screen(s), of crushed ores previously mixed with water- swellable polymer P1.

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