EP0154207A1 - Method and device for separating electrically conducting non-ferrous metals - Google Patents

Abstract

In separating a mixture of solid material particles including non-magnetic electrically conductive metals into a light fraction and a heavy fraction, where the light fraction includes the non-magnetic particles, the mixture is directed into an upwardly extending airflow passageway from an inlet channel extending laterally from the passageway. The inlet channel is spaced between the inlet and outlet ends of the passageway. An alternating magnetic field is provided adjacent the entrance of the mixture into the airflow passageway for accelerating the particles in the desired direction. The mixture is fed through the inlet channel into the airflow passageway in layer form, preferably as a single layer. A main flow of air passes upwardly through the airflow passageway from the lower inlet end and develops a highly turbulent vortex-like airflow. The airflow, in combination with the magnetic field, effects separation of the light and heavy fractions of the material. A secondary flow of air is directed upwardly into the air flow passage in the region of the introduction of the mixture and accelerates the air flow and carries the light fraction upwardly to the outlet end of the passageway.

Description

The invention relates to a method for separating non-magnetic, electrically conductive metals from a mixture of solids from their feed direction in an air stream under the action of an alternating magnetic field and a device for carrying out this method with the help of an alternating magnetic field generator in an air duct with air supply at the lower end, with at least one Air discharge at the other end and with a feed opening for the solids mixture.

In the so-called eddy current separation, the feed material is passed between the poles of an alternating magnetic field generator, for example on a belt or in free fall. In this case, eddy currents are induced in the highly conductive components of the mixture to be separated, which build up their own magnetic fields which are opposed to the generating field and accordingly these components are accelerated by electromagnetic forces relative to the other components of the mixture. Eddy current separation can be used to separate non-ferromagnetic, highly electrically conductive materials, such as aluminum and copper, from scrap and waste, such as automobile shredder scrap, electronic scrap, glass waste and the like. If ferromagnetic parts are contained in this material, a magnetic separation must be provided before passing through the eddy current separating device, because ferromagnetic parts would clog the working gap of the eddy current separating device. Advantageously, the latter are preceded by other treatment stages, for example a wind sifting, because the If possible, forces to be used in eddy current separation should not be compensated for by collision with other parts, which in themselves can be eliminated with less effort.

Wind sifting is particularly suitable for separating lighter parts from heavier parts. The separation takes place according to the sinking speed in vertical or horizontal air flows. To separate them into specifically light and heavy products, the feed material has to be pre-classified very narrowly, if the grain shape is neglected, if the effort involved is to achieve appropriate separation results.

In an air classifier, the air flow directed against the particle flow to be separated can be adjusted so that small (and of course large), specifically heavy particles, which often differ greatly in shape from the spherical shape, sink downwards, while small, specifically light particles decrease from the air flow be carried upwards. Problems may arise from a proportion of relatively large, specifically light parts, which, in terms of its material, belongs to the lightweight material, but which decreases in accordance with its absolute weight or its ball-like form factor together with the specifically heavy proportion. If the strength of the air flow were increased, the larger, specifically lighter parts could also be carried with the light goods, but at the same time a significant proportion of the specifically heavier material would also be carried away with the light goods with a corresponding grain size and grain shape.

While smaller piece sizes of different specific weights can be separated relatively well by wind sifting, the eddy current separation requires a minimum grain size when separating non-ferrous metals from a solid mixture in a variable magnetic field, because a continuous Petite sorting with justifiable expenditure of material and energy is only meaningful using this method for material mixtures whose lower grain size is approximately 15 to 20 mm in diameter.

DE-OS 25 09 638 proposes a device for eddy current separation in an air duct which only favors the loosening of the feed material. Here the individual pieces of the mixture to be separated reach the air flow in free fall through the gap of an alternating magnetic field generator, the field of which migrates transversely to the direction of fall. A disadvantage of the known device is, above all, that the mixture pieces to be influenced electromagnetically in the sense of eddy current separation have to be moved laterally to the side of the falling particles and therefore collide with other parts and can be influenced accordingly. As a result, the proportion of incorrect discharges, provided that the feed material flow is not largely isolated, is quite high in both products due to hindrance or procrastination. The air blown in should serve to loosen the sorted goods in the feed chute before reaching the viewing zone and not to separate substances of different densities. In addition, a joint discharge of fine-grained, specifically lighter constituents together with the coarser, specifically lighter substances which are deflected by the alternating magnetic field generator are not taken into account. Ultimately, the individual pieces have no defined position and can therefore be rotated by the alternating magnetic field in a direction in which the respective field can exert only a relatively small separating force (e.g. lateral acceleration) due to eddy current separation on the respective individual piece.

The invention has for its object to improve a method of the type mentioned in such a way that the electrically conductive particles influenced by the alternating magnetic field can be additionally accelerated in the desired manner essentially without interference from neighboring particles. Based on the idea of subjecting the feed material to both air separation and eddy current separation in order to separate both the smaller parts (by wind separation) and the larger parts (by eddy current separation) into specifically heavier and specifically lighter or conductive and non-conductive pieces, This object is achieved in that the mixture of solids is fed to a wind-sifting main air stream in a single-layer layer as possible at an angle to the air flow direction, that under the action of the alternating magnetic field in the area of the feed both the large-grained light components, each consisting of non-magnetic, conductive material, and those due to of the form factor in the case of pure air separation into the heavy fraction of such material are transferred to the light material discharge, and that, preferably by adding additional air, the flow in the discharge area for the light is in the discharge zone is accelerated well.

As already mentioned in the introduction, due to their shape factor, particles that actually belong to the light goods also get into the heavy fraction in normal wind sifting; these are mostly spherically shaped particles. If, within the framework of the teaching according to the invention, one speaks of the "area of the material supply", then this point of the additional air supply in the flow direction can be located shortly after the material supply as well as - in the case of a corresponding arrangement of the alternating field generators - in the area of the alternating field generators in the flow direction even before the material supply .

With a device for performing the method, the above-mentioned object is achieved by an air classifier as an air duct whose material supply lies outside the air flow, the feed opening opening laterally into the air duct and in the mouth region a device for air acceleration in the flow direction and the alternating magnetic field generator with both in the direction of the air flow and also arranged transversely to a bottom edge of the material feed in the direction of force of the alternating magnetic field in the area of the feed opening.

The effect of the air acceleration is that the air flow velocity in the flow direction behind the feed opening is greater than before the feed opening; Due to the alternating magnetic field provided in this area of the speed jump of the air flow in the air classifier duct, with the polarity and direction of change appropriate according to the invention, it is achieved that electrically conductive particles can be raised from the area of lower air speed to the area of higher air speed up to a minimum grain size still to be detected by the eddy current separation . If the air classifier air flow is set to separate smaller (not covered by the eddy current separation), specifically lighter and specifically heavier particles, the eddy current separation combined with the additional or secondary air flow is an ideal means, even the relatively large, specifically light pieces of the mixture, e.g. Aluminum pieces with a spherical shape factor, to be sorted out by lifting these parts from the low air speed level to the higher air speed level and transporting them to the light goods with the stronger air flow. In the method according to the invention, there is also no risk that relatively small, specifically heavy parts get into the light goods. By means of the bottom edge according to the invention, which is preferably formed by an angular opening of the material feed into the air duct, the material is brought into the area of the air classifier and of the alternating magnetic field generator in a layer which is as single-layered as possible in contrast to the prior art.

• Fig. 1 den prinzipiellen Aufbau eines Luftkanals mit Windsichtung und Wirbelstromscheidung;
• Fig. 2 den prinzipiellen Strömungsverlauf im Luftkanal angrenzend an die Aufgabeöffnung;
• Fig. 3 das Fließschema der Luftströmung im gesamten System;
• Fig. 4 eine Alternativ-Ausführung des Luftkanals mit kombinierter Windsichtung und Wirbelstromscheidung; und
• Fig. 5 einen Schnitt längs der Linie V-V von Fig. 4.

Details of the invention are explained on the basis of the schematic representation of exemplary embodiments. Show it:

• Figure 1 shows the basic structure of an air duct with wind separation and eddy current separation.
• 2 shows the basic flow pattern in the air duct adjacent to the feed opening;
• 3 shows the flow diagram of the air flow in the entire system;
• 4 shows an alternative embodiment of the air duct with combined wind sifting and eddy current separation; and
• 5 shows a section along the line VV of FIG. 4th

In the exemplary embodiment according to FIG. 1, the substances to be separated are sorted in the upward air flow 1 in a vertically arranged, zigzag-shaped air duct 2 designed as an air classifier. Alternatively, differently shaped, vertical or horizontal air ducts can also be used. The material to be separated is fed into the air duct 2, preferably via a cellular wheel sluice 3 as material feed, in the upper third of the air duct 2. The associated feed opening 4 of the air duct 2 is optionally connected to the cellular wheel sluice 3 via a trough 5 or another conveying means. The feed opening 4 is preferably provided in the upper third or, viewed in the direction of the air flow 1, in the last third of the air duct 2. At the transition from the channel 5 into the air duct 2, ie in the area of the feed opening 4 a bottom edge A is provided, which in its simplest embodiment is formed by the opening of the channel 5 into the air channel 2 at the feed opening 4, which opening is provided in this area at an angle to the longitudinal axis of the air channel 2. The material to be separated via the feed opening 4 into the air duct 2, which can consist of specifically heavier particles 6 and specifically lighter particles 7 according to FIG. 2, falls in the air duct 2 and is sucked in via a main air supply 8 at the lower end of the duct 2 Air flow 1 sucked off via an air discharge 9 at the upper end of the duct. In a zigzag design of the air duct according to the detailed drawing according to FIG. 2, there is a highly turbulent air flow within the duct 2, which favors the desired separation, with so-called vortex rollers 10 and 11. The upward main flow forms approximately accordingly in duct 2 arrows 12 and 13.

The air duct 2 according to FIGS. 1 and 2 has a secondary air supply 14 in the transition region B to the discharge zone 16, which is approximately at the level of the confluence (feed opening 4) of the material supply into the air duct 2, through which an additional air flow 15 is introduced into the duct 2 . The additional air flow 15 is added to the air flow 1 sucked in via the main air supply 8, so that in the upper or second area, the discharge zone 16, of the air channel 2 adjoining the feed opening 4, a stronger air flow 13 is established than in the previous area 33 of the channel. The secondary air supply 14 can - as shown - consist of a line; but it can also open into the discharge zone of channel 2 with several lines, even in a ring at several points.

The light material discharged upward in the air duct 2 is transported by the air flow 13 via a pipeline 17 into a cyclone 18 in which the solid parts are separated from the carrier air flow. The solid particles separated in the cyclone 18 are expediently discharged via a rotary valve 19, while the cleaned air according to FIG. 3 is conducted to the suction side of a blower 21 via a pipeline 20 (see FIG. 3). In the further course, the air flow in the circuit can be directed back to air duct 2. In addition, fresh air can be introduced into the circulating air circuit via a valve 22. The pressure side of the blower 21 can be connected to the main air supply 8 of the air duct 2 via a pipe 23. Partial air flows can be directed via a valve 24 for dust separation into a filter 25 and via a line 26 to the secondary air supply 14 of the air duct 2. Valves 27 and 28, for example, are used to control the air quantities in the secondary air supply 14 and in the main air supply 8. While the light goods according to FIGS. 1 and 2 are transported with the air flow 13 to the cyclone 18, the heavier goods come against the air flow 12 to the channel floor 29 and is discharged there, for example, via a cellular wheel sluice 30 (FIG. 1).

In contrast to a conventional air classifier, the present device has, in addition to the secondary air supply 14, an alternating magnetic field generator 31 which, according to FIGS. 1 and 2, is arranged directly adjacent to the bottom edge A below the feed opening 4. In the exemplary embodiment according to FIGS. 1 and 2, the variable magnetic field of the alternating magnetic field generator 31 is preferably oriented at right angles to the feed material flow 32, that is to say transversely to the bottom edge A. Alternatively, alternating magnetic field generators can also be used, which are installed on the two side surfaces of the channel 2 in the area of the feed opening 4, the field of which migrates in the direction of the air flow 13 (see, for example, the exemplary embodiment according to FIGS. 4 and 5). As field generator 31, single or multi-phase controlled coil systems with mains frequency as well as those coils that are operated with voltages of higher frequency. Air coils or iron core coils can be used.

In the exemplary embodiment, the separation process can be seen more precisely from the detailed drawing of the zigzag-shaped air duct 2 according to FIG. 2. As already explained, the strength of the air flow 13 after the secondary air supply 14 in the second channel area 16 is substantially higher than that of the air flow 12 in the channel area 33 in front of the feed opening 4. The separation proceeds in such a way that the feed material via the rotary valve 3 and the Inlet nozzle 5 is passed into the zigzag-shaped air duct 2.

In contrast to the prior art, the bottom edge A in the invention ensures that the feed material is or can be brought into the area of the air classifier and of the alternating magnetic field generator in a layer which is as single-layered as possible. In contrast, in the prior art, the material to be sorted falls over the entire cross section of a vertical shaft into the separation zone.

In the invention, a vertical feed is deliberately dispensed with and the material to be sorted is introduced laterally into the separation zone of the air duct, so that in the case of the embodiment according to FIGS. 1 and 2 it is constantly on a floor, namely the trough 5 up to the actual one Separation zone is brought up. In this version lie the material particles usually always have their largest area on the floor; this surface is then also exposed to the alternating magnetic field generated adjacent to the bottom edge A, which is known to achieve a maximum repelling effect in the direction transverse to the bottom edge A.

The alternative possibility mentioned above, in which the field moves in the direction of the air flow in the case of alternating magnetic field generators installed on the two side surfaces of the channel, will be discussed in more detail in connection with the explanation of the exemplary embodiment according to FIGS. 4 and 5.

The air velocity in the first or lower channel region 33 of the air channel 2 lying in the flow direction in front of the feed opening 4 is set in such a way that small, specifically heavy particles sink downward and small, specifically light particles are carried upwards by the air flow and discharged to the light material. For the discharge of large, specifically light parts, e.g. made of aluminum, the alternating magnetic field generator 31 is inserted into the light material. In the variable magnetic field 34 of this component, eddy currents are induced in the larger, specifically lighter, electrically highly conductive pieces to be deflected. The eddy currents, in turn, are surrounded by a magnetic field which is directed towards the excitation field 34, as a result of which the (electrically conductive) larger, specifically lighter constituents 7 are discharged into the discharge or discharge zone 16 in the second or upper channel region which is subjected to higher air speeds. With a corresponding specification of the air speed, in particular by the appropriately metered supply of air to the secondary air supply 14, the portions of the feed material deflected by means of the alternating magnetic field can be safely transported into the cyclone 18 connected downstream.

A second exemplary embodiment of the device for separating electrically highly conductive non-ferrous metals with a combined wind sifting and eddy current separation is explained with reference to FIGS. 4 and 5. The separation takes place here in an air duct 35 which is vertical or inclined by up to 45 ° to the vertical with an air flow 36 flowing from bottom to top. This passes through a main air supply 108 at the lower end of the air duct, which also has a cellular wheel sluice 130 for removing the heavy goods 3 through a pipe 117 to a cyclone, etc. The air duct 35, like the air duct 2 according to FIGS. 1 and 2, has a lateral feed opening 104 with a feed conveyor 105 and a rotary valve 103 and a secondary air supply 114, which is arranged so that there is a higher air speed above the feed opening 104 than in the lower part of the air duct 35. Additional secondary air supply lines can be arranged above the supply line 114 in order to ensure that heavy parts are discharged more reliably.

4, in the area of the feed opening 104, similar to the exemplary embodiment described above, merges into the air duct 35 via a bottom edge A ₁ , and in the simplest embodiment again by merely angular relative position of the longitudinal axes of the feed 105 and duct 35.

The air duct 35 should preferably have a rectangular cross section. A linear motor is preferably an alternating magnetic field generator 37. For example, a double stator design with opposite side faces of the air duct 35 arranged poles 38 and 39 is suitable (cf. the sectional view according to FIG. 5). The direction 40 of the two linear motors of the Doppelsta The traveling fields generated in the embodiment shown are in the same direction as the air flow 36 in the channel 35. The field change of the alternating magnetic field generator 37 thus runs with the excitation frequency always from bottom to top in the direction of arrow 40. In the present case, the linear motors are preferably subjected to electrical multiphase, with voltages at the mains frequency or higher frequency up to approx. 1000 Hz.

In the exemplary embodiment according to FIGS. 4 and 5, the coarser, specifically lighter portions of the feed material are raised with the help of an alternating magnetic field generator 37 into the area of higher air speed above the secondary air supply 14 and discharged to the light material with the stronger air flow. The entire separation process proceeds similarly to that already described for the exemplary embodiment according to FIGS. 1 and 2.

The slightly different arrangement of the alternating magnetic field generator 37 compared to the exemplary embodiment according to FIGS. 1 and 2, however, initially leads to a somewhat different behavior of the feed material in the area of the feed opening 104. Here, the material or the individual particles tipping over the bottom edge A ₁ initially only turns the surfaces of the alternating magnetic field generators to the unfavorable narrow side. However, as soon as the individual particles are exposed to the air flow 36 in the air classifier 35, they turn, with certainty going through a position in which the larger area of each particle will face one of the surfaces of the alternating magnetic field generator 37, at which moment it will be full Eddy current magnetic pulse in the direction transverse to the bottom edge A _{1 of} the feed is obtained. Within the scope of the invention there is also the possibility for this embodiment of the bottom of the feed 105 to be approximately V-shaped, in order thereby to predefine the supplied particles a position which is more favorable in relation to the alignment with the alternating magnetic field generator, before reaching the channel 35. Of course, the feed 105 does not necessarily have to run horizontally, as shown in FIG. 4, as long as a bottom edge is formed only in the region of its confluence with the channel 35. In addition, the magnetic field generators (38, 39) do not necessarily have to be arranged in exactly opposite positions, as shown in FIG. 5, but could also be attached at the same height but offset from the plane of the drawing.

Claims (8)

1. A method for separating non-magnetic, electrically conductive metals from a solid mixture from their feed direction in an air stream under the action of an alternating magnetic field, characterized in that the solid mixture is fed to a wind-sifting main air stream in a single-layer layer as possible at an angle to the air flow direction that under the action of the alternating magnetic field in the area of the feeder, both the large-grained light components, each consisting of non-magnetic conductive material, and the parts of such material that reach the heavy fraction due to the form factor in pure wind separation are transferred to the light material discharge, and preferably by adding additional air in the area the flow of goods in the discharge zone for the light goods is accelerated. 2. Device for performing the method according to claim 1, with the help of an alternating magnetic field generator (31, 37) in an air duct (2, 35) with air supply at the lower end, with at least one air discharge on at the other end and with a feed opening for the solid mixture (6, 7) characterized by an air classifier as an air duct (2, 35) whose material feed (3, 4, 5) lies outside the air flow (1, 36), the feed opening (4, 104) opens laterally into the air duct (2, 35) and in the mouth region (B, B ₁ ) a device for air acceleration in the direction of flow and the alternating magnetic field generator (31, 37) with both in the direction of the air flow and transversely to a bottom edge (A, A ₁ ) of the material feed (3, 4, 5) in the area of the feed opening (4, 104) aligned with the direction of force of the alternating magnetic field. 3. Apparatus according to claim 2, characterized in that the device for accelerating air consists of a secondary air supply (14) opening into the transition region to the discharge zone of the light material fraction. 4. The device according to claim 3, characterized in that the device for accelerating air consists of a cross-sectional constriction of the discharge zone (16) relative to the clear cross section of the lower air duct (33). 5. The device according to one or more of claims 2 to 4, characterized in that the alternating magnetic field generator (31, 37) is arranged at the transition of the feed opening (4, 104) to the air duct (2, 35). 6. The device according to one or more of claims 1 to 4, characterized by a zigzag design of the air duct (2). 7. The device according to one or more of claims 2 to 6, characterized by the use of a single or multi-phase controlled coil system as an alternating magnetic field generator (31). 8. The device according to one or more of claims 2 to 4, characterized by the arrangement of the area of the air duct (35) adjoining the feed opening (104) and the secondary air supply (114) between the poles (38, 39) of an alternating magnetic field generator (37) with moving in the direction of the air flow (36) magnetic field (40) (Fig. 4 and 5).

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