WO2009103341A1

WO2009103341A1 - Density separation device and method for the selective separation of absorbent and non-absorbent material particles

Info

Publication number: WO2009103341A1
Application number: PCT/EP2008/052154
Authority: WO
Inventors: Kris Debaets; Hervé PACQUET; Rik Hoorelbeke
Original assignee: Solid Engineering Bvba
Priority date: 2008-02-21
Filing date: 2008-02-21
Publication date: 2009-08-27

Abstract

The invention relates to a density separation device (1) for separating solid material particles in a float and a sink fraction by means of a liquid medium, the specific gravity of said liquid medium being between the specific gravity of the particles of the float fraction and the specific gravity of the particles of the sink fraction, wherein the device is provided with a first discharge zone (3) for evacuating the float fraction as well as the medium by means of rotation, a second discharge zone (4) for evacuating the sink fraction by means of rotation and using first discharging elements (7a), and a separation zone (2) comprising a first slanting part (5) and a second slanting part (6) adjacent to the first slanting part (5), wherein the second slanting (6) part is provided with one or more second discharging elements (7a,7b), and wherein this first and second slanting part (5, 6) are sloping towards each other, such that, by means of rotation, the sink fraction that sank on the first slanting part (5) moves towards the second slanting part (6), whereupon the sink fraction is taken along with the discharging elements (7a, 7b) of the second slanting part (6) and a second discharge zone (2) for discharging towards the second discharge opening (40). The invention relates furthermore to a method for the selective separation of absorbent and/or non - ab sorbent material particles by means of a magnetic or magnetizable suspension, wherein the method comprises the subsequent steps of treating the material particles with water until the absorbent material particles are saturated with water; bringing the mate rial particles in the magnetic or magnetizable suspension, and separating the material particles by means of magnets.

Description

DENSITY SEPARATION DEVICE AND METHOD FOR THE SELECTIVE SEPARATION OF ABSORBENT AND NON-ABSORBENT MATERIAL

PARTICLES

The invention relates to a density separation device for separating solid material particles in a float and a sink fraction by means of a liquid medium, the specific gravity of said liquid medium being between the specific gravity of the particles of the float fraction and the specific gravity of the particles of the sink fraction, the device comprising - a separation zone that is provided for separating the solid material particles that are introduced in this separation zone in a float fraction and a sink fraction by means of rotation and using the said medium; a first discharge zone adjacent the separation zone at one side thereof for evacuating the float fraction as well as the medium through a first discharge opening by means of rotation; a second discharge zone adjacent the separation zone at the opposite side thereof for evacuating the sink fraction through a second discharge opening by means of rotation and using first discharging elements.

The separation in the device happens with the elementary principle of sinking and floating of solid material parts in a liquid medium with a known specific gravity.

Such a device is amongst others described in US 5,373,946, wherein solid particles in two fractions are separated by means of a medium, the specific gravity of said medium being between the specific gravity of the particles of the first fraction and the specific gravity of the particles of the second fraction. The preferred device having: a scrolled barrel made of a central mid-section in which the separation takes place; a device associated with the barrel for driving it rotatively along its longitudinal center line; mechanisms for feeding or injecting into the barrel both the solid particles to be separated and also the medium effecting this separation; a mechanism for removing the sink fraction from the central mid-section, this mechanism made of a scrolled cone, the lower end of the scrolled cone being attached to the central mid-section and having a diameter somewhat larger than the diameter of the central mid-section (also called "expanded cone"), while the higher end has a relatively smaller diameter through which the sinks are discharged; a mechanism for removing the float fraction from the central mid-section, and made of a cone whose lower end is attached to the central mid-section, while the higher discharge end serves as the point of overflow for the medium and float particles; and a mechanism to prevent the float particles from crossing over into the sink's cone and thus reporting with the sink particles. The central axis of the scrolled separation barrel, the scrolled cone for discharging the sinks and the cone for removing the float fraction forms an angle with the horizontal such that the level of the axis at the end of the cone for removing the float fraction adjacent to the scrolled separation barrel is lower than the level of the axis at the end of the scrolled cone for discharging the sinks.

This device however has some major disadvantages.

First of all, because of the fact that the separation barrel is provided with inner scrolls almost over its entire inner surface, it very frequently occurs that float particles that are introduced in the scrolled separation barrel by means of the feeding or injecting mechanisms, and that after their introduction are situated against the wall of the separation barrel, are systematically drawn to the scrolls that are present in the separation barrel, or in other words are "caught" in the inner scrolls, until the float particles arrive in the abovementioned expanded cone serving for discharging the sink particles, through which in the expanded cone a mixing occurs between the float and the sink fraction, seriously reducing the output of the device. Because this frequently occurs, it is necessary to apply pipes in order to force the float particles back in the direction of the discharge opening of the float fraction, increasing the turbulence in the liquid medium.

Furthermore, in order to reduce the risk that float particles are caught in the inner scrolls of the separation barrel, finally undesirably arriving in the expanded cone, the height between the scrolls and the level of the medium has to be enlarged, through which the device has to be disposed in a sloping way, or in other words the central axis of the scrolled separation barrel, the scrolled cone for discharging the sink fraction and the cone for removing the float fraction has to form an angle with the horizontal.

Furthermore, because of the fact that the medium may not flow out of the discharge side of the sink fraction, and there always has to be a forward flow toward the discharge side of the float fraction, the wall of the expanded cone has a steep slope along which the sink fraction has to climb up in order to be discharged. This firstly also reduces the output of the device, and has as a further consequence that this kind of separation barrel is very highly subjected to wear.

The purpose of the invention is therefore to provide a simpler density separation device for separating solid particles in a float and a sink fraction by means of a liquid medium, the specific gravity of said medium being between the specific gravity of the particles of the float fraction and the specific gravity of the particles of the sink fraction, having a higher output, and not showing the abovementioned disadvantages.

This purpose of the invention is attained by providing a density separation device for separating solid material particles in a float and a sink fraction by means of a liquid medium, the specific gravity of said liquid medium being between the specific gravity of the particles of the float fraction and the specific gravity of the particles of the sink fraction, the device comprising a separation zone that is provided for separating the solid material particles that are introduced in this separation zone in a float fraction and a sink fraction by means of rotation and using the said medium; a first discharge zone adjacent the separation zone at one side thereof for evacuating the float fraction as well as the medium through a first discharge opening by means of rotation; a second discharge zone adjacent the separation zone at the opposite side thereof for evacuating the sink fraction through a second discharge opening by means of rotation and using first discharging elements; wherein the separation zone comprises a first slanting part and a second slanting part adjacent to the first slanting part, wherein the second slanting part is provided with one or more second discharging elements, and wherein this first and second slanting part are sloping towards each other, such that, by means of rotation, the sink fraction of the first slanting part moves towards the second slanting part, whereupon the sink fraction is taken along with the first and second discharging elements of the second slanting part and the second discharge zone towards the second discharge opening.

In this way, a density separation device is obtained having a simple construction (for instance not needing an expanded cone) having a high output, that furthermore can be disposed horizontally, and that is less subjected to wear because there is no need to have a separation barrel with a steep slope, and that furthermore can work in a static or dynamic way.

In a preferred embodiment of a device according to the invention, the device comprises a first and a second rotatable barrel in the form of a truncated cone both having an equal largest diameter, wherein these barrels are connected to each other at the height of these largest equal diameters, and wherein the first discharge zone is situated in the first barrel, the second discharge zone is situated in the second barrel, and the separation zone is situated in the first as well as in the second barrel. Providing the barrels in the form of a truncated cone gives the additional advantage that solid barrels are obtained.

In a more preferred embodiment of a device according to the invention, the smallest diameter of the said barrels is different and forms the said first, respectively second discharge opening.

In a still more preferred embodiment of a device according to the invention, at both ends of the said barrels having the smallest diameter, a cylindrical part is provided

These cylindrical parts both have a bipartite purpose, i.e. on the one hand for forming treads to take care of the said rotation, and on the other hand, in case of a dynamic device, for forming parts for the recuperation of the medium.

In a most preferred embodiment of a device according to the invention, in the said cylindrical parts, a sieving part is integrated for recuperating the liquid medium. In order to obtain cylindrical parts having preferably (but not necessarily) the same diameter (because this is advantageous for the driving system of the rotation of the barrels, for instance by means of drive wheels), a third barrel in the form of a truncated cone is provided that is connected to the first barrel and that is situated at the opposite side of the second barrel, having the same smallest diameter as the smallest diameter of the first barrel, and having the same largest diameter as the diameter of the adjacent cylindrical part.

When such a third barrel is present, and in the case of a static device, preferably one or more lifters are provided for lifting the particles of the float fraction that are present in the first discharge zone over the connection edge of the first barrel with the third barrel.

In a favourable embodiment of a device according to the invention, the said discharging elements consist of inner scrolls that are provided on the inner surface of the said second rotatable barrel.

In an advantageous device according to the invention, the device comprises one or more primary stoppers for guiding the float particles towards the second discharge zone.

In a more advantageous device according to the invention, the device comprises one or more secondary stoppers for avoiding that float particles that are misplaced behind the primary stoppers would be taken along towards the second discharge opening with the first discharge elements of the second discharge zone.

The said stoppers preferably consist of curtains.

These curtains therewith are preferably carried out and arranged in the same way as the curtains as described in US 5,373,946.

In a favourable device according to the invention, the device is provided with introduction means for introducing the solid particles that have to be separated and the liquid medium in the separation zone. In a more favourable device according to the invention, the said introduction means consist of a shaking conveyor.

By using such a shaking conveyor, the solid material particles are introduced in a more uniform and single way into the separation zone.

In an advantageous embodiment of a device according to the invention, the device is a static device, wherein in the separation zone, one or more paddlers are provided that are placed in line with the said introduction means.

In a favourable device according to the invention, the device is disposed horizontally.

In this way, the longitudinal axis of the device is lying in a horizontal plane, through which the slope of the wall of the second barrel corresponding the discharge zone of the sink fraction can also be seriously reduced.

The invention furthermore relates to a method for the selective separation of absorbent and/or non-absorbent material particles by means of a magnetic or magnetizable suspension.

In WO 2006/106234, a method is described for separating mixed, especially used, synthesis organic materials which have been previously fragmented, comprising solid fragments, open cell foam fragments, fibrous composites and textiles, optionally fragments of wood and other contaminant materials, wherein the separation is carried out by a magnetic effect on the absorbent fragments that can be impregnated by a magnetic aqueous suspension.

The disadvantage of this method is that it is very difficult to recuperate the magnetic aqueous suspension since the magnetic aqueous suspension is completely absorbed by the absorbent materials. Furthermore, it is a very expensive solution because of the high use of magnetic suspension.

A further purpose of this invention therefore is to provide a more cost effective method for the selective separation of absorbent and non-absorbent material particles by means of a magnetic or magnetizable suspension, wherein the magnetic or magnetizable suspension can easily be removed from the absorbent materials.

This purpose of the invention is attained by providing a method for the selective separation of absorbent and non-absorbent material particles by means of a magnetic or magnetizable suspension, wherein the method comprises the subsequent steps of: treating the material particles with a liquid until the absorbent material particles are saturated with this liquid; bringing the material particles in the magnetic or magnetizable suspension; separating the material particles by means of a magnet system.

By treating absorbent material particles with a liquid, and then treating them with a magnetic or magnetizable suspension, a film layer of magnetic or magnetizable suspension is laid around the absorbent material particles, because diffusion or exchange of the magnetic or magnetizable parts in the suspension occurs between the surface of the absorbing materials and the magnetic or magnetizable parts, this contrary to the method according to the state of the art, in which the magnetic or magnetizable suspension can penetrate to the core of the absorbent material. Because of the presence of this film layer, first of all there is substantially no loss of magnetic or magnetizable suspension, and second of all, the film of magnetic or magnetizable suspension can be simply removed from the surface of the absorbent material particles, for instance by rinsing these material particles with water. Furthermore, the non-absorbent material particles will not have a film layer of magnetic or magnetizable suspension. Because of the fact that the absorbent material particles will have such a film layer, and the non-absorbent material particles will not, the separation of the material particles can be done on the basis of the possible presence of a film layer of magnetic or magnetizable suspension, wherein the material particles having a film layer of magnetic or magnetizable suspension will be attracted to the magnet(s) of the magnet system, while the material particles not having such a film layer will not be attracted to this magnet system. In an advantageous method according to the invention, the liquid with which the material particles are treated to be saturated is water.

In a preferred method according to the invention, the magnetic suspension is a magnetite or a ferrosilicium suspension.

This magnetite or ferrosilicium suspension preferably consists out of a magnetic or magnetizable fine-grained dust.

In a more preferred method according to the invention, the material particles are brought in a magnetic or magnetizable suspension being the liquid medium in a density separation device.

In a favourable method according to the invention, the method is used for the selective separation of a light shredder fraction, wherein the method comprises the steps of removing the material particles having a size of more than 90 mm by means of a sieving system, and transporting these to a shredder; wet washing the material particles having a size of smaller than 90 mm on a first and second sieve having a different mesh opening, wherein the material particles are passed over a first sieve having a mesh opening of 12 mm, whereupon the material particles having a size of smaller than 12 mm are passed over a sieve having a mesh opening of 3 mm, and wherein this first and second sieve are sprayed with water until the absorbent material parts are saturated with water; - separating the material particles having a size of between 3 and 12 mm and of between 12 to 90 mm separately or together in a density separation device into a float and a sink fraction, wherein the medium of the density separation device is a magnetic or magnetizable suspension; separating the material particles of the float fraction by means of a magnetising system; washing the material particles of the sink fraction as well as the magnetic / magnetizable float fraction with water. By wet washing the material particles that have to be separated (i.e. those having a size of smaller than 90 mm), through which the absorbent materials become saturated with water, and by then separating these material particles in a density separation device using a magnetic or magnetizable suspension as the liquid medium, the absorbent material particles (of the sink fraction as well as of the float fraction) become slightly magnetic or magnetizable, or in other words will be provided with a magnetic or magnetizable film layer, through which a separation of these material particles can be done using a magnetising system.

Furthermore, using a density separation device has the advantage that the light shredder fraction can be separated in an efficient way, this in comparison with the use of for instance a shaker for separating the light shredder fraction.

In an advantageous method according to the invention, the material particles having a size smaller than 3 mm are dewatered in a dewatering screw.

In a preferred method according to the invention, the material particles are separated in a density separation device according to the invention as described above.

In the following detailed description, the characteristics and advantages of a device for separating solid material particles having uneven density according to the invention and a method for the selective separation of absorbent and/or non-absorbent material particles by means of a magnetic or magnetizable suspension according to the invention, which has been mentioned before, will be further clarified. The intention of this description is only to further explain the general principles of the present invention, therefore nothing in this description may be interpreted as being a restriction of the field of application of the present invention or of the patent rights demanded for in the claims.

In this description, by means of reference numbers, reference will be made to the attached figures, wherein in figure 1 a perspective view from above of a device for separating solid material parts of uneven density according to the invention is shown; figure 2 a view from above of the device as presented in figure 1 is shown; figure 3 a cross section in front view of a dynamic device for separating solid material parts of uneven density according to the invention is shown; figure 4 a cross section in view from above of the dynamic device as presented in figure 3 is shown figure 5 a cross section in front view of a static device for separating solid material parts of uneven density according to the invention is shown; figure 6 a cross section in view from above of the static device as presented in figure 5 is shown; - figure 7 is a schematic representation of a method for the selective separation of absorbent and non-absorbent material particles by means of a magnetic or magnetizable suspension.

A preferred density separation device (1 ) for separating solid material particles in a float and a sink fraction by means of a liquid (separation) medium (not shown in the figures) according to the invention, as shown in the figures 1 to 6, wherein the specific gravity of said liquid medium is between the specific gravity of the particles of the float fraction and the specific gravity of the particles of the sink fraction, comprises three zones, i.e. - a separation zone (2) that is provided for separating the solid material particles that are introduced in this separation zone (2) in a float fraction and a sink fraction by means of rotation and using the said medium; a first discharge zone (3) adjacent the separation zone (2) at one side thereof (in the figures on the right side) for evacuating the float fraction as well as the medium through a first discharge opening (30) by means of rotation; a second discharge zone (4) adjacent the separation zone (2) at the opposite side thereof (in the figures on the left side) for evacuating the sink fraction through a second discharge opening (40) by means of rotation and using first discharging elements (7a).

The distribution of the liquid medium over the different zones is part of the adjustment of the device (1 ) dependent on the applicable separation of solid material particles. As can be seen in figures 3 to 6, the separation zone (2) comprises a first slanting part (5) and a second slanting part (6) adjacent to the first slanting part (5), wherein the second slanting part (6) is provided with one or more discharging elements (7a). This first and second slanting part (5, 6) are sloping towards each other, such that, by means of rotation, the sink fraction that sinks on the first slanting part (5) moves towards the second slanting part (6), whereupon the sink fraction is taken along with the discharging elements (7a, 7b) of the second slanting part (6) and the second discharge zone (2) towards the second discharge opening (40). As can be seen on figures 3 to 6, the discharging elements (7a) of the second discharge zone (4) are following the inner scrolls (7b) of the second slanting part (6).

As furthermore can be seen in figures 3 to 6, the density separation device (1 ) comprises a first rotatable barrel (13) and a second rotatable barrel (14) in the form of a truncated cone, both having an equal largest diameter (15), wherein these barrels (13, 14) are connected to each other at the height of these largest equal diameters (15).

The first discharge zone (3) is situated in the first barrel (13), while the second discharge zone (4) is situated in the second barrel (14). The separation zone (2) is situated in the first as well as in the second barrel (13, 14).

The smallest diameter (23) of the first barrel (13) is different than the smallest diameter (24) of the second barrel (14). These smallest diameters (23, 24) form the first and second discharge opening (30, 40).

The said first and second discharging elements preferably consist of inner scrolls (7a, 7b) that are provided on the inner surface of the second rotatable barrel (14).

At both ends of the said barrels (13, 14) having the smallest diameter (23, 24), a cylindrical part (8, 9) is provided. In each of these cylindrical parts (8, 9), a sieving part is integrated for recuperating the liquid medium. There, the liquid medium is collected and flows to a pump tank. The dewatered solid material particles then leave the density separation device (1 ) for further working. The pump tank is provided with a circulation pump, preferably having a controllable flow. Furthermore, in order to avoid stoppage of the opening of the sieving parts, optionally a high pressure cleaning system can be provided at the height of the sieving parts.

These cylindrical parts (8, 9) preferably, but not necessarily, have the same diameter (31 ). In order to obtain cylindrical parts (8, 9) having the same diameter

(31 ), a third barrel (18) in the form of a truncated cone is preferably provided that is connected to the first barrel (13) and that is situated at the opposite side of the second barrel (14). This third barrel (18) has the same smallest diameter (28) as the smallest diameter (23) of the first barrel (13), and having the same largest diameter (29) as the diameter (31 ) of the cylindrical parts (8, 9). This third barrel (18) is also provided for taking the float fraction away from the first discharge zone (3) out of the device (1 ).

All rotatable barrels (13, 14, 18) preferably are made out of sheet metal work. In this way, the complete device (1 ) can turn around its longitudinal axis on independent drive wheels (not shown in the figures) that are controlled together, and that run along the outer surface of these barrels (13, 14, 18).

The solid material particles that have to be separated by means of the density separation device (1 ) as shown in figures 1 to 6, are introduced in the device (1 ) by means of introduction means (16). It is important that these solid material particles are introduced in the separation zone (2). The introduction means preferably consist of a shaking conveyor (16).

As can be seen in the figures 3 to 6, the device (1 ) is provided with one or more primary stoppers (10) for guiding the float particles towards the first discharge zone (30). The device (1 ) furthermore comprises secondary stoppers (1 1 ) for avoiding that float particles that are misplaced behind the primary stoppers (10) would be taken along towards the second discharge opening (40) with the first discharge elements (7a) of the second discharge zone (4). The said stoppers (10, 11 ) preferably consist of curtains. As can be seen in figure 6, these curtains (10, 11 ) are suspended onto a suspension construction (20) that straight across the assembly of rotatable parts of the density separation device (1 ), i.e. the first, second and third barrel (13, 14, 18) and the cylindrical parts (8, 9). They end below the level of the liquid medium and abut against the wall of the respective barrels (13, 14). In figure 4, this suspension construction (20) is not shown, but is also present.

Furthermore, one or more paddlers (17) can be provided that are placed in line with the said introduction means (16) for completely plunging the floating particles in the liquid medium, having as a purpose to evacuate the air out of the cavities of solid material particles having an open cell structure as much as possible.

Also the paddlers (17) and the shaking conveyor (16) are preferably suspended to the suspension construction (20).

The density separation device (1 ) according to the invention can be a dynamic device, as well as a static device.

When the density separation device (1 ) is a dynamic device, as can be seen in figures 3 and 4, the liquid medium having a known density is continuously filled such that a drive volume is created and a separation bath comes into being. In this way, a constant overflow is created at the height of the first discharge opening (30). In this way, solid material particles that are lighter then the liquid separation medium float, and are transported towards the first discharging opening (30) by means of the introduction of the drive volume. Material parts that are heavier then the liquid separation medium will sink under gravity towards the deepest part of the device (1 ), at which point it is transported towards the second discharge opening (40) below the first and second stoppers and below the introduction means (16).

When the density separation device (1 ) is a static device, as can be seen in figures 5 and 6, no drive volume is created. In this way, one or more of the above described paddles (17) are provided in the separation zone (2) for moving the float particles towards the first discharge opening (30). Furthermore, as can be seen in figures 5 and 6, preferably one or more lifters (19) are provided for lifting the particles of the float fraction that are present in the first discharge zone (3) over the connection edge (32) of the first barrel (13) with the third barrel (18). The density separation device (1 ) preferably has a controllable rate per minute through which the discharge volume of the float and sink fraction and the capacity of the device (1 ) can be controlled stepless.

The method according to the invention for the selective separation of absorbent and/or non-absorbent material particles by means of a magnetic or magnetizable suspension (see figure 7), comprises the subsequent steps of treating the material particles with a liquid, preferably water, until the absorbent material particles are saturated with water, in this way filling the holes that are present in the open cell structure of the absorbent materials particles with liquid (step B); bringing the material particles in the magnetic or magnetizable suspension, in this way laying a film layer of magnetic or magnetizable suspension around the said already with liquid treated absorbent material particles (step C).; - separating the material particles by means of magnets using the possible presence of a film layer of magnetic or magnetizable suspension (step D).

This method is amongst others used in the working principle for the separation of a light shredder fraction. This working principle preferably comprises the following:steps:

Step A Feeding the light shredder fraction in a dosing device (50) wherein the material can be dosed. By means of a conveyer belt, the fraction goes to one or more sieves removing the material particles having a size of more than 90 mm by means of a sieving system. The particles having a size of more than 90 mm are transported to a shredder.

Step B: Wet washing the material particles having a size of smaller than

90 mm by means of a spraying installation (51 ) on a first and second sieve having a different mesh opening, wherein the material particles are passed over a first sieve having a mesh opening of 12 mm, whereupon the material particles having a size of smaller than 12 mm are passed over a sieve having a mesh opening of 3 mm, and wherein this first and second sieve are sprayed with water until the absorbent material parts are saturated with water. After use, this water is passed over a rotatable sieve, f.i. a Rotasieve®, in order to remove hair and fibres (not shown in figure 7).

Step C: Separating the material particles having a size of between 3 and 12 mm and of between 12 to 90 mm separately or together in a density separation device (1 ) into a float and a sink fraction, wherein the medium of the density separation device (1 ) is a magnetic or magnetizable suspension. When bringing the material particles in contact with the magnetic or magnetizable suspension, only the material particles with absorption characteristics will be provided with a film layer of magnetic or magnetizable suspension. This can be particles of the float fraction as well as the sink fraction, thus resulting in material particles of the float fraction and/or sink fraction being provided with a film, and material particles of the float fraction and/or the sink fraction not having a film. Preferably, the density separation device that is used is a device (1 ) as described above. Step D: Separating the float fraction by means of magnetising system (52). This magnetising system (52) comprises at least one strong magnet, preferably more than one such magnet, that each are provided in a conveyor (also called "somersault magnets") (53) (on figure 7, one such magnet is shown). When more than one such magnet is provided, they are placed serially. The speed of each conveyor can be controlled independently. The magnets must be made out of a magnetic material having a magnetic force as strong as possible, such as a neodymium magnet. The magnetic / magnetizable material particles are then transported to a third transporting conveyor (not shown in figure 7) towards one common point, while the non-magnetic material / magnetizable material particles are led over a shaking conveyor at which point this material is washed before it is processed further. Step E: The magnetic / magnetizable material particles of the float fraction as well as the sink fraction are washed with water by means of a spraying system (54), this in order to remove the film layer that was laid around the absorbent materials of these fractions. The washing water of both is subsequently led over cyclones (not shown in figure 7) or magnets [for instance a wet drum (55)] in order to recuperate the liquid separation medium maximally, this being a well known technique in the separation on the basis of density.

The material particles having a size smaller than 3 mm are preferably dewatered in a dewatering screw.

Using such a method for for instance separating a ASR (auto shredder residue) - fraction, normally leads to 3 output materials:

1. material having a density higher than the density of the applied liquid separation medium, and that consequently sink, being particularly metals, cables, heavy rubbers and heavy plastics (especially chlorated and bromated plastics); 2. materials consisting of polyurethane foams, carpets, textile-like materials and some kinds of wood material; 3. materials consisting of all kinds of plastics, wood and lighter rubbers, having a density lower than the density of the applied liquid separation medium, and that consequently float.

Claims

C L A I M S

1. Density separation device (1 ) for separating solid material particles in a float and a sink fraction by means of a liquid medium, the specific gravity of said liquid medium being between the specific gravity of the particles of the float fraction and the specific gravity of the particles of the sink fraction, the device comprising a separation zone (2) that is provided for separating the solid material particles that are introduced in this separation zone (2) in a float fraction and a sink fraction by means of rotation and using the said medium; a first discharge zone (3) adjacent the separation zone (2) at one side thereof for evacuating the float fraction as well as the medium through a first discharge opening (30) by means of rotation; - a second discharge zone (4) adjacent the separation zone (2) at the opposite side thereof for evacuating the sink fraction through a second discharge opening (40) by means of rotation and using first discharging elements (7a); characterised in that the separation zone (2) comprises a first slanting part (5) and a second slanting part (6) adjacent to the first slanting part (5), wherein the second slanting part (6) is provided with one or more second discharging elements (7b), and wherein this first and second slanting part (5, 6) are sloping towards each other, such that, by means of rotation, the sink fraction that sank on the first slanting part (5) moves towards the second slanting part (6), whereupon the sink fraction is taken along with the first and second discharging elements (7a, 7b) of the second slanting part (6) and the second discharge zone (2) towards the second discharge opening (40).

2. Device according to claim 1 , characterised in that the device (1 ) comprises a first and a second rotatable barrel (13, 14) in the form of a truncated cone both having an equal largest diameter (15), wherein these barrels (13, 14) are connected to each other at the height of these largest equal diameters (15), and wherein the first discharge zone (3) is situated in the first barrel (13), the second discharge zone (4) is situated in the second barrel (14), and the separation zone (2) is situated in the first as well as in the second barrel (13,

14).

3. Device according to claim 2, characterised in that the smallest diameter (23, 24) of the said barrels (13, 14) is different and form the said first, respectively second discharge opening (30, 40).

4. Device according to claim 3, characterised in that at both ends of the said barrels (13, 14) having the smallest diameter (23, 24), a cylindrical part (8, 9) is provided.

5. Device according to claim 4, characterised in that in the said cylindrical parts (8, 9), a sieving part is integrated for recuperating the liquid medium.

6. Device according to any one of claims 2 to 5, characterised in that a third barrel (18) in the form of a truncated cone is provided that is connected to the first barrel (13) and that is situated at the opposite side of the second barrel (14), having the same smallest diameter (28) as the smallest diameter (23) of the first barrel (13), and having the same largest diameter (29) as the diameter (31 ) of the adjacent cylindrical part (9).

7. Device according to claim 6, characterised in that in the case of a static device, one or more lifters (19) are provided for lifting the particles of the float fraction that are present in the first discharge zone (3) over the connection edge of the first barrel (13) with the third barrel (18).

8. Device according to any one of claims 2 to 7, characterised in that the said discharging elements consist of inner scrolls (7a, 7b) that are provided on the inner surface of the said second rotatable barrel (14).

9. Device according to any one of claims 1 to 8, characterised in that the device (1 ) comprises one or more primary stoppers (10) for guiding the float particles towards the second discharge zone (4).

10. Device according to claim 9, characterised in that the device (1 ) comprises one or more secondary stoppers (1 1 ) for avoiding that float particles that are misplaced behind the primary stoppers (10) would be taken along towards the second discharge opening (40) with the first discharge elements (7a) of the second discharge zone (4).

1 1. Device according to claim 9 or 10, characterised in that the said stoppers (10, 1 1 ) consist of curtains.

12. Device according to any one of claims 1 to 11 , characterised in that the device (1 ) is provided with introduction means (16) for introducing the solid particles that have to be separated and the liquid medium in the separation zone (2).

13. Device according to claim 12, characterised in that the said introduction means (16) consist of a shaking conveyor.

14. Device according to any one of claims 1 to 13, characterised in that the device is a static device, wherein in the separation zone, one or more paddlers (17) are provided that are placed in line with the said introduction means (16).

15. Device according to any one of claims 1 to 14, characterised in that the device (1 ) is disposed horizontally.

16. Method for the selective separation of absorbent and/or non-absorbent material particles by means of a magnetic or magnetizable suspension, characterised in that the method comprises the subsequent steps of treating the material particles with liquid until the absorbent material particles are saturated with this liquid (step B); - bringing the material particles in the magnetic or magnetizable suspension (step C); separating the material particles by means of magnets (step E).

17. Method according to claim 16, characterised in that the liquid with which the material particles are treated to be saturated is water.

18. Method according to claim 16 or 17, characterised in that the magnetic suspension is a magnetite or a ferrosilicium suspension.

19. Method according to any one of claims 16 to 18, characterised in that the material particles are brought in a magnetic or magnetizable suspension being the liquid medium in a density separation device (1 ).

20. Method according to any one of claims 16 to 19, characterised in that the method is used for the selective separation of a light shredder fraction, wherein the method comprises the steps of removing the material particles having a size of more than 90 mm by means of a sieving system, and transporting these to a shredder (step

A); wet washing the material particles having a size of smaller than 90 mm on a first and second sieve having a different mesh opening, wherein the material particles are passed over a first sieve having a mesh opening of 12 mm, whereupon the material particles having a size of smaller than

12 mm are passed over a sieve having a mesh opening of 3 mm, and wherein this first and second sieve are sprayed with water until the absorbent material parts are saturated with water (step B); separating the material particles having a size of between 3 and 12 mm and of between 12 to 90 mm separately or together in a density separation device (1 ) into a float and a sink fraction, wherein the medium of the density separation device is a magnetic or magnetizable suspension (step C); separating the material particles float fraction by means of magnetising system (52) (step D); washing the material particles of the sink fraction as well as the magnetical / magnetized float fraction with water (step E);

21. Method according to claim 20, characterised in that the material particles having a size smaller than 3 mm are dewatered in a dewatering screw.

22. Method according to any one of claims 16 to 21 , characterised in that the material particles are separated in a density separation device according to any one of claims 1 to 15.