Methods and apparatus for separating particles composed of different plastics

Abstract

To separate particles (6) composed of different plastics, the particles (6) are suspended in a first liquid (10) having a first density and separated into first light particles (11) with a lower density and first heavy particles (12) with a density of at least the first density. The first heavy particles (12) are dried and then separated into at least a first fraction (21) and a second fraction (22) based on their dielectric properties by a first electrostatic separation (19). Here, the particles of the second fraction (22) are electrostatically chargeable, and the particles of the first fraction (21) are not electrostatically charged based on their dielectric properties or are electrostatically charged in a manner different from that of the electrostatically chargeable particles of the second fraction (22). Then, the particles of the second fraction (22) are suspended in a second liquid (25) having a higher second density and separated into second light particles (27) with a lower density and second heavy particles (28) with a density of at least the second density. The second light particles (27) are dried and then separated into at least two additional fractions (34, 35) based on their dielectric properties by a second electrostatic separation (32).

Description

Technical Field

[0001] This invention relates to a method and apparatus for separating particles composed of different plastics. In particular, this invention relates to a method having the features of the preamble of independent claim 1 and an apparatus having the features of the preamble of independent claim 14.

[0002] Recycling plastics in high-quality products requires separating them into fractions of pure plastic species. Even when composite materials composed of different plastics do not exist, or when such composite materials can be separated into particles composed of only one type of plastic through crushing, this separation has proven challenging. Background Technology

[0003] A method for separating particles composed of different plastics, having the features of the preamble of independent claim 1, and a corresponding apparatus having the features of the preamble of independent claim 14, are known from DE 20 2021 000 353 U1. To produce polyvinyl chloride (PVC) recyclables containing up to 1% by weight of polyolefin from cable recyclables, firstly, by means of a density of 1.00 to 1.23 g / cm³... 3 The sink fraction is separated by flotation-sinking. This sink fraction is mechanically dried using a centrifuge and additional geothermal drying. Then, PVC is separated from the sink fraction by electrostatic separation. Here, considerable effort is made to mechanically pre-dry the sink fraction to a high degree of dryness, with a maximum residual moisture content of 0.4% by weight. It is well known that electrostatic separation can only be performed at a maximum residual moisture content of 0.2% by weight, which must be achieved in the subsequent thermal drying. The flotation-sinking method should not only separate the light fraction itself from the cable recyclables but also remove those fractions that prevent PVC from acquiring a specific charge during electrostatic separation. After the separation of the light fraction and subsequent mechanical and thermal drying, the PVC should be able to be charged based on its position in the electrostatic sequence, allowing the rubber, fluoroelastomer, and silicone elastomer portions present as heterogeneous materials to be electrostatically separated, achieving the required PVC purity and desired material properties. Furthermore, in known methods, non-ferrous metals are separated between drying and electrostatic separation using an eddy current separator. The results show that the known methods are only suitable for separating PVC particles from particles of other plastics.

[0004] A method for recycling plastics is known from GB 2 465 839 A. Plastic waste is crushed to an average particle size of 100 to 500 mm. Impurities are removed using a rotary screen, a ferrous metal separator, and / or manually. The plastic waste is then crushed to an average particle size of 50 to 150 mm. A non-ferrous metal separator and / or a plastic film separator are used in a second impurity removal step. Subsequently, the plastic material is granulated to an average particle size of 10 to 50 mm. The granulated plastic material is separated into a settling stream and a floating stream in a flotation cell. The settling stream and / or the floating stream are dried. The first optical separation is preferably performed using near-infrared technology. After the first optical separation, the plastic material is granulated to an average particle size of 2 to 10 mm. The granulated plastic material is then guided through a second flotation cell. Subsequently, the plastic material is dried and a second optical separation is performed. Electrostatic separation may be performed downstream of each optical separation.

[0005] A method for sorting and separating plastic waste is known from EP 2 484 506 A1. The plastic waste is crushed. The resulting fragments are cleaned with steam. The fragments are separated in two density separators using liquids of different densities. In an electrostatic separator, the density-separated fragments are further electrostatically separated. Summary of the Invention

[0006] The objective of this invention is to provide a method and apparatus for separating particles composed of different plastics, which can be used to obtain other high-quality pure particle fractions.

[0007] The objective of this invention is achieved by a method having the features of independent claim 1 and an apparatus having the features of independent claim 14. The dependent claims relate to preferred embodiments of the method and apparatus of this invention.

[0008] In the method for separating particles composed of different plastics according to the invention, the particles are suspended in a first liquid having a first density and separated into first light particles with a density lower than the first density and first heavy particles with a density at least the first density. At least the first light particles or the first heavy particles are dried into first dry particles. By a first electrostatic separation, based on their dielectric properties, the first dry particles are separated into at least a first fraction and a second fraction, wherein the particles of the second fraction are electrostatically chargeable. In the first electrostatic separation, the particles of the first fraction are not electrostatically charged based on their dielectric properties or are electrostatically charged in a manner different from that of the electrostatically chargeable particles of the second fraction, so that the particles of the first fraction and the second fraction can be separated in the first electrostatic separation. The particles of the electrostatically chargeable second fraction are suspended in a second liquid having a second density and separated into second light particles with a density lower than the second density and second heavy particles with a density at least the second density. At least the second light particles or the second heavy particles are dried into second dry particles. By a second electrostatic separation, based on their dielectric properties, the second dry particles are separated into at least two additional fractions. By means of repeated density separation using a second liquid, the second density typically differs from the first density of the first liquid by at least 0.10 g / cm³. 3 The electrostatically charged particles of the second fraction are further divided, from which other pure types of fractions can be obtained, to the point that it is actually worth the extra expense, especially for re-drying the particles after their second density separation by means of the second liquid.

[0009] The method according to the invention does not obtain additional pure-species particulate fractions by directly and sequentially separating the particles using liquids of different densities, as might seem obvious. Instead, a first drying and a first electrostatic separation are performed after the first density separation, and only one of the resulting fractions (whose particles are capable of electrostatic charging) is subjected to a second density separation, followed by re-drying and another electrostatic separation. This unexpectedly yields the advantage of additional pure-species particulate fractions; and this additional pure-species particulate fraction is only obtained when considering the associated high additional drying costs already mentioned.

[0010] Particularly advantageous is that at least the liquid with a higher density used in one of the density separation methods of the present invention is based on a solution of sodium hypophosphite in water, i.e., the density is adjusted by adding sodium hypophosphite to the water, wherein the liquid may contain, within a limited range, no more than 20% by weight, and typically no more than 10 or 5% by weight, other additives. These additives may be, for example, surfactants, which help the particles to be fully wetted by the corresponding liquid and prevent bubble entrainment. Both of these measures improve the quality of density separation. Sodium hypophosphite is readily soluble in water to achieve the desired higher density liquid. But most importantly, sodium hypophosphite can be readily and mechanically removed from the particles along with the liquid, and the sodium hypophosphite residue left after drying does not impede the electrostatic separation of the particles within the scope of the method of the present invention.

[0011] When adding surfactants to the first and / or second liquids in the method of this invention, care must be taken that these surfactants do not impair at least one subsequent electrostatic separation. Such impairment may be related to the use of antistatic agents, which, while helpful for density separation, can be very detrimental to subsequent electrostatic separation because they may also prevent the electrostatic charging of theoretically chargeable particles. Ethanol has proven to be a very suitable surfactant, which can be added to the first and / or second liquids without jeopardizing at least one subsequent electrostatic separation. Specifically, the first and / or second liquids may contain 5 to 10% by weight of ethanol. The resulting reduction in liquid density can be compensated for by the addition of sodium hypophosphite. The addition of ethanol to water does not limit the solubility of sodium hypophosphite in water within any scope relevant to this invention.

[0012] The first density of the first liquid can be 1.00 g / cm³. 3 + / - 0.03 g / cm 3 Preferably 1.00 g / cm 3 + / -0.01 g / cm 3 Specifically, the first liquid may consist at least predominantly of water. At this first density, it is preferable to dry the first heavy particles having at least the first density into first dry particles. In other words, by using the first density separation of the first liquid, particles with a density less than 1.00 g / cm³ are separated. 3 The light fraction may consist at least substantially of polyethylene (PE) and low-density ethylene propylene diene monomer (EPDM). In this specification and the appended claims, the term "substantially" shall be understood literally, meaning that the substance comprising the majority of each particle constitutes more than 50% by weight of the particle.

[0013] In the first electrostatic separation, in addition to the first and second fractions, the first dried particles can also be separated into a third fraction. Here, the first fraction may include particles without a significant electrostatic charge, the second fraction may include particles with a positive electrostatic charge, and the third fraction may include particles with a negative electrostatic charge. Electrostatic charging occurring within the scope of the first and second electrostatic separations can be—independently of each other—particularly induced by friction and / or discharge. The charge of each particle after electrostatic charging depends on its relative specific capacitance per unit area. Particles with moderate capacitance are neutral and form the first fraction. Particles with larger capacitance are positively charged and form the second fraction; particles with smaller capacitance are negatively charged and form the third fraction of the three fractions.

[0014] Specifically, the particles in the first fraction may consist mostly of plasticized PVC (PVC-w), while the particles in the third fraction are at least mostly composed of filler-containing EPDM and other high-density ethylene propylene diene monomer (EPDM) rubber (i.e., with a density greater than 1.00 g / cm³). 3 It consists of EPDM.

[0015] The second density of the second liquid (used for second density separation) can be 1.23 g / cm³. 3 + / - 0.03g / cm 3 And preferably 1.23 g / cm³ 3 + / - 0.01 g / cm 3 If the second light particles are dried into second dry particles, wherein the drying (as with the drying into the first dry particles) is preferably carried out mechanically first and then thermally, the second light particles may consist at least substantially of polyamide (PA) and polyurethane (PU). The second light particles can then be separated into another fraction consisting at least substantially of PA and another fraction consisting at least substantially of PU by a second electrostatic separation. The second heavy particles here consist at least substantially of fluoroelastomers, silicone elastomers, polyethylene terephthalate (PET), and / or cellulose acetate (CA).

[0016] In the method of this invention, conductive particles can be separated, for example, by eddy current separation. Here, eddy current separation can be performed upstream of the first electrostatic separation to allow for prior separation of conductive particles. Otherwise, the conductive particles would enter the first fraction, which is free of electrostatic charge. However, eddy current separation is not suitable for separating all conductive particles. For example, ferromagnetic particles cannot be separated by eddy current separation. In addition to particles of non-ferromagnetic metals, particles made of conductive plastics can also be separated.

[0017] Furthermore, ferromagnetic particles can be separated in the method of this invention. This is achieved, in particular, by means of an electromagnet through magnetic separation. Magnetic separation is also preferably carried out upstream of the first electrostatic separation. It can also separate ferromagnetic conductive particles that cannot be separated by eddy current separation. Particles made of plastics, which acquire ferromagnetic properties through appropriate metal additives, can also be removed by magnetic separation.

[0018] Furthermore, in the method of the present invention, electrically scalable particles can be separated. This can be achieved, for example, by means of a strong electric field gradient, which results in different magnitudes of forces in the direction of the electric field gradient depending on the polarizability of the particles.

[0019] In the method of the present invention, it is advantageous that the particle size at the start of separation is set to 1 mm to 6 mm, preferably 2 mm to 6 mm, for example by grinding and sieving, particularly preferably with an accuracy of at least + / - 1.5 mm, more preferably with an accuracy of at least + / - 1.0 mm. The fact that all particles are as identical in size as possible eliminates the influence of particle size, which in principle can occur in density separation, electrostatic separation, eddy current separation, magnetic separation, and electric field gradient separation using liquids. Particularly for density separation and electrostatic separation, it has proven advantageous that the particle size is not only set as precisely as possible, but also precisely within the range of 1 mm to 6 mm, with all particles falling within this range as much as possible, such that the average particle size is between 2.5 and 4.5 mm or between 2 and 5 mm, depending on the accuracy.

[0020] The apparatus according to the invention for separating particles composed of different plastics includes a first density separator designed to separate particles suspended in a first liquid having a first density into first light particles with a density lower than the first density and first heavy particles with a density at least the first density. The apparatus also includes a first dryer designed and arranged to dry the first light particles, or preferably the first heavy particles, into first dry particles; and a first electrostatic separator designed and arranged to separate the first dry particles into at least a first fraction and a second fraction based on their dielectric properties by first electrostatic separation, wherein the particles of the second fraction are electrostatically chargeable. The apparatus further includes a second density separator designed to separate electrostatically chargeable second fraction particles suspended in a second liquid having a second density into second light particles with a density lower than the second density and second heavy particles with a density at least the second density. The second dryer of the apparatus is designed and arranged to dry the second heavy particles, or preferably the second light particles, into second dry particles. The device then has a second electrostatic separator, which is designed and arranged to separate the second dry particles into at least two additional fractions based on their dielectric properties via a second electrostatic separation.

[0021] Preferably, the electrostatic separator is designed to separate the first dried particles into a first fraction, a second fraction, and a third fraction, wherein the first fraction comprises particles without a significant electrostatic charge, the second fraction comprises particles with a positive electrostatic charge, and the third fraction comprises particles with a negative electrostatic charge.

[0022] As previously mentioned, the dryer may have mechanical and thermal components, such as a centrifuge and an infrared furnace. Furthermore, the device may additionally, particularly upstream of the first electrostatic separator, have an eddy current separator and / or a magnetic separator and / or an electric field gradient separator.

[0023] As an electrostatic separator, commercially available industrial electrostatic separators can be used to perform electrostatic charging through friction and / or discharge.

[0024] Advantageous improvements of the present invention are derived from the claims, description and drawings.

[0025] The advantages of the features and combinations of features mentioned in the specification are merely exemplary and may take effect alternatively or cumulatively, without necessarily being enforced by embodiments of the invention.

[0026] Regarding the disclosure of the original application and patent—but not the scope of protection—the following applies: Other features can be derived from the drawings, particularly the geometry shown and the relative dimensions of the various components and their relative arrangement and functional connections. Combinations of features from different embodiments or different claims, also deviating from the chosen referential relationships in the claims, are possible and encouraged herein. This also applies to features shown in separate drawings or mentioned in their descriptions. These features may also be combined with features from different claims. Similarly, features listed in the claims may be omitted for use in other embodiments of the invention, but this does not apply to the independent claims of the granted patent.

[0027] The number of features mentioned in the claims and description should be understood to mean exactly that number or more, without the need for the adverb "at least". Therefore, for example, when referring to a first dryer, it should be understood that there is exactly one first dryer, two first dryers, or more first dryers. A feature mentioned in a claim may be supplemented by other features or may be a unique feature possessed by the subject matter of the corresponding claim.

[0028] The reference numerals included in the claims do not constitute a limitation on the scope of protection of the claims. They are only used to make the claims easier to understand. Attached Figure Description

[0029] The present invention will now be further explained and described based on the preferred embodiments shown in the accompanying drawings.

[0030] Figure 1 This is a flowchart of the method according to the present invention, and also a block diagram of the apparatus according to the present invention for separating particles made of different plastics. Detailed Implementation

[0031] Figure 1 The process flow of the method according to the invention and the structure of the device 1 according to the invention are explained. Raw material 2 can be so-called cable recycling 3, the main components of which can be plasticized polyvinyl chloride (PVC-W), polyethylene (PE), polyamide (PA), polyurethane (PU), fluoroelastomer, silicone elastomer, ethylene-propylene-diene rubber (EPDM), polyethylene terephthalate (PET), cellulose acetate (CA), copper (Cu), and / or aluminum (Al). Particles 6 with an average particle size in the range of 1 to 6 mm are obtained by grinding and sieving 4 in the particle size setting device 5. Here, fine fractions 7, the so-called "Fines," are separated from the particles 6.

[0032] In the subsequent first density separation 8 in density separator 9, the particles 6 are suspended at a first density of 1.00 g / cm³. 3 In the first liquid 10, it was then separated into floating particles with a density of less than 1.00 g / cm³. 3 The density of the first light particle 11 and the density of the sinking particles are at least 1.00 g / cm³. 3 The first heavy particles 12. The first light particles 11 are at least mostly low-density PE and EPDM particles.

[0033] The first heavy particles 12 undergo a first drying 13 in the first dryer 14. The first drying 13 yields first dried particles 15. In the eddy current separation 16 within the eddy current separator 17, non-ferromagnetic conductive particles 18 are separated. The conductive particles 18 are composed at least largely of aluminum, copper, and conductive EPDM.

[0034] The remaining first dried particles 15 undergo a first electrostatic separation 19 in the first electrostatic separator 20. Here, the first dried particles 15 are separated into a first fraction 21, a second fraction 22, and a third fraction 23. The third fraction 23 comprises negatively charged particles and consists at least largely of higher-density EPDM that has not yet been separated. The first fraction 21 comprises neutral particles, i.e., particles that are at most weakly electrostatically charged and consists at least largely of PVC-w. The second fraction 22 comprises the first dried particles 15 that are positively charged.

[0035] The second fraction, 22, has a density of 1.22 g / cm³. 3The second liquid 25 undergoes a second density separation 24 in the second density separator 26, thereby separating it into liquids with densities lower than 1.22 g / cm³. 3 The second light particle 27 has a density of at least 1.22 g / cm³. 3 The second heavy particles 28. The second light particles 27 are dried into second dried particles 31 in the second drying 29 in the second dryer 30. The second dried particles 31 undergo a second electrostatic separation 32 in the second electrostatic separator 33.

[0036] The second dry particles 31 are separated into two additional fractions 34 and 35 by a second electrostatic separation 32, the particles having different electrostatic charges. Here, one fraction 34 includes negatively charged or weakly positively charged particles, which are at least predominantly composed of PA, while the other fraction 35 includes strongly positively charged particles, which are at least predominantly composed of PU.

[0037] The heavy second particulate 28 includes particles composed of fluoroelastomers, silicone elastomers, PET and CA, and can also be dried and subjected to further electrostatic separation, but this is not shown here.

[0038] The method of the present invention utilizes not only the density differences of the plastics contained in raw material 2 (i.e., cable recycling 3), but also the different electrostatic rechargeability, as listed in the table below. Here, capacitance in microcoulombs per square meter represents the electrostatic charge per unit area that can be electrostatically charged by the particles (not made to be conductive) made of their respective plastics under the same conditions.

[0039] Electrostatic separation does not occur directly in terms of capacitance (i.e., the strength of chargeability). For electrostatic separation to occur, a difference in capacitance must exist. In a mixture of three plastics, the plastic with medium capacitance behaves neutrally during electrostatic charging (e.g., by friction), meaning the corresponding particles are not significantly electrostatically charged. The particles of the high-capacitance plastic are positively charged; the particles of the low-capacitance plastic are negatively charged. Although the capacitance of all listed plastics is positive, this is indeed the case. For example, PVC-w behaves neutrally, while PA, PU, ​​PET, CA, silicone, and fluoroelastomers are positively charged, and PE and EPDM rubber are negatively charged.

[0040] List of reference numerals in the attached diagram: 1 Equipment 2 Raw materials 3. Cable Recycling 4. Grinding and sieving 5. Particle size setting device 6 particles 7 Fine fractions 8 First density separation 9 First density separator 10 First Liquid 11 First Lightweight Particles 12 First Heavy Particle 13 First Drying 14 First Dryer 15 First Dry Particles 16. Eddy Separation 17. Eddy Separator 18 Non-ferromagnetic conductive particles 19 First Electrostatic Separation 20 First electrostatic separator 21 First fraction 22 Second fraction 23 Third fraction 24 Second density separation 25 Second Liquid 26 Second density separator 27 Second Light Particles 28 Second Heavy Particles 29 Second drying 30. Other fractions (second dryer) 31 Second Dry Particles 32 Second electrostatic separation 33 Second electrostatic separator 34 Other fractions 35. Other fractions.

Claims

1. A method for separating microparticles (6) composed of different plastics, - wherein, The particles (6) are suspended in a first liquid (10) having a first density and separated into first light particles (11) with a density lower than the first density and first heavy particles (12) with a density at least the first density. - Wherein, at least the first light particle (11) or the first heavy particle (12) is dried into the first dry particle (15), and - Wherein, the first dry particles (15) are separated into at least a first fraction (21) and a second fraction (22) based on their dielectric properties by a first electrostatic separation (19), wherein the particles of the second fraction (22) are electrostatically chargeable, and wherein the particles of the first fraction (21) are not electrostatically charged based on their dielectric properties or are electrostatically charged in a manner different from that of the electrostatically chargeable particles of the second fraction (22). Its features are, - The electrostatically chargeable particles of the second fraction (22) are suspended in a second liquid (25) having a second density different from the first density and separated into second light particles (27) with a density lower than the second density and second heavy particles (28) with a density at least the second density. - Wherein, at least the second light particle (27) or the second heavy particle (28) is dried into a second dry particle (31), and - Wherein, the second dry particles (31) are separated into at least two additional fractions (34, 35) based on their dielectric properties by a second electrostatic separation (32).

2. The method of claim 1, wherein, The first liquid (10) or the second liquid (25), having at least the larger of the first density and the second density, is based on a sodium hypophosphite solution in water.

3. The method of claim 1 or 2, wherein, At least the first liquid (10) or the second liquid (25) has 5 to 10 percent ethanol by weight.

4. The method of any of the preceding claims, wherein, said first density is 1.00 g / cm 3 + / - 0.03 g / cm 3 and preferably 1.00 g / cm 3 + / - 0.01 g / cm 3 and wherein said first heavy fine particles (12) are preferably mechanically and thermally dried to first dry fine particles (15).

5. The method of claim 4, wherein, The first lightweight particle (11) is composed at least mostly of low-density polyethylene (PE) and / or ethylene propylene diene monomer (EPDM).

6. The method according to any one of the preceding claims, wherein, The first dry particles (15) are separated into a first fraction (21), a second fraction (22) and a third fraction (23), wherein selectively, the first fraction (21) includes particles without electrostatic charge, the second fraction (22) includes particles with positive electrostatic charge, and the third fraction (23) includes particles with negative electrostatic charge.

7. The method according to claim 6 when dependent on claim 4 or 5, wherein, The first fraction (21) is composed at least largely of plasticized polyvinyl chloride (PVC-w), and the third fraction (23) is composed at least largely of high-density ethylene propylene diene monomer (EPDM).

8. The method according to any one of the preceding claims, wherein, said second density is 1.23 g / cm 3 + / - 0.03 g / cm 3 and preferably 1.23 g / cm 3 + / - 0.01 g / cm 3 and wherein said second light fine particles (27) are preferably mechanically and thermally dried to second dry fine particles (31).

9. The method according to claim 8, wherein, The second dry microparticle (31) is composed at least substantially of polyamide (PA) and polyurethane (PU) and is separated by a second electrostatic separation (32) into another fraction (34) composed at least substantially of PA and another additional fraction (35) composed at least substantially of PU, and wherein the second heavy microparticle (28) is composed at least substantially of fluoroelastomer, silicone elastomer, polyethylene terephthalate (PET) and / or cellulose acetate (CA).

10. The method according to any one of the preceding claims, wherein, Conductive particles are selectively separated by eddy current separation (18).

11. The method according to any one of the preceding claims, wherein, Ferromagnetic particles can be selectively separated by magnetic separation.

12. The method according to any one of the preceding claims, wherein, Electro-polarizable particles can be selectively separated by electric field gradient separation.

13. The method according to any one of the preceding claims, wherein, The particle size of the microparticles (6) is selectively set to fall within the range of 1 mm to 6 mm by grinding and sieving (4).

14. The method of claim 13, wherein, The particle size of the microparticles (6) is set to a value with an accuracy of + / - 1.5 mm and preferably + / - 1.0 mm.

15. An apparatus (1) for separating microparticles (6) composed of different plastics, having - A first density separator (9) is configured to separate particles (6) suspended in a first liquid (10) having a first density into first light particles (11) with a density lower than the first density and first heavy particles (12) with a density at least equal to the first density. - A first dryer (14), configured and arranged to dry the first light particles (11) or the first heavy particles (12) into first dry particles (15), and - A first electrostatic separator (20) is configured and arranged to separate first dry particles (15) into at least a first fraction (21) and a second fraction (22) based on their dielectric properties by a first electrostatic separator (19), wherein the particles of the second fraction (22) are electrostatically chargeable, and wherein the particles of the first fraction (21) are not electrostatically charged based on their dielectric properties or are electrostatically charged in a manner different from that of the electrostatically chargeable particles of the second fraction (22). Its features are, - A second density separator (26) is configured to separate electrostatically chargeable particles of the second fraction (22) suspended in a second liquid (25) having a second density into second light particles (27) with a density lower than the second density and second heavy particles (28) with a density at least equal to the second density. - A second dryer (30), configured and arranged to dry the second light particles (27) or the heavy particles (28) into second dry particles (31), and - A second electrostatic separator (33) is constructed and arranged to separate the second dry particles (31) into at least two additional fractions (34, 35) based on their dielectric properties by a second electrostatic separator (32).

16. The device according to claim 15, wherein, The first dryer (14) is arranged to dry the first heavy particles (12) into first dry particles (15).

17. The device according to claim 15 or 16, wherein, The first electrostatic separator (20) is configured to separate the first dry particles (15) into a first fraction (21), a second fraction (22) and a third fraction (23), wherein selectively, the first fraction (21) comprises particles without electrostatic charge, the second fraction (22) comprises particles with positive electrostatic charge, and the third fraction (23) comprises particles with negative electrostatic charge.

18. The device according to claim 15, 16 or 17, wherein, The second dryer (30) is arranged to dry the second light particles (27) into second dry particles (31).

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