Method and equipment for conditioning low-metal plastic scrap

The present invention relates to a method and equipment for conditioning a light fraction that has been produced during the conditioning of low-metal scrap high in plastics.

Such a light fraction is obtained, for example, from the shredding of scrap vehicles. The shredding of scrap vehicles and similar material flows for material breakdown with the aim of improved material usage has been known for a long time. Scrap bodyshells, that are first stripped by local scrap vehicle reuse organizations of economically usable parts (substantially replacement parts) and unloaded of harmful substances (e.g. by removing operating fluids) are fed to shredder equipment without major pretreatment by shredder operations. In the established method management in carrying out the shredding process, process controls have been established in which the material mixture obtained is divided up into different fractions.

In the shredder equipment working on the principle of a hammer mill, the scrap bodyshell is broken into pieces the size of one's fist. Subsequently to the size reduction process, components capable of flying are suctioned off using a suitable suction machine and are segregated via a cyclone separator (the so-called light shredder fraction (SLF). The remaining air flow is fed to a dust removal. The remaining fraction that is not suctioned off is subsequently separated into a ferromagnetic fraction (so-called shredder scrap (SS)) and a non-ferromagnetic fraction (so-called heavy shredder fraction (SSF)), using a suitable magnetic separator.

The shredder scrap (SS) is used directly as secondary raw material in steel works, the heavy shredder fraction (SSF) is conditioned separately, and separated into metallurgically usable metal fractions and a metal-depleted residual fraction. Beside these residues from the heavy shredder fraction (SSF), the light shredder fraction (SLF) remains as an extremely heterogeneous mixtures of plastics, foamed plastics, rubber, textiles, glass, ceramics, wood, ferrous and nonferrous metals. According to present systems, the so-called shredder residues, thus formed by the light shredder fraction (SLF) and/or the residual fraction from the conditioning of the heavy shredder fraction (SSF) that is not metallurgically usable, are disposed of as waste, as a rule, or burnt in waste incineration plants. In the light of rising legal requirements (such as the EU scrap auto guide lines), rising landfill costs and rising requirements on landfill material, as high a rate of use of all the fractions created in the shredder process would be desirable. Thus, the Scrapped Car Regulation of Apr. 1, 1998 even provides for over 95 wt. % of a scrapped car having to be utilized as of the year 2015. In addition, increased requirements from the EU Scrapped Car Guideline passed in September, 2000 specify that, in scrap car utilization, the proportion of material streams utilizable again as materials and raw materials should be increased to at least 85 wt. %.

Utilization of light shredder fraction (SLF) of a safe quality (materially, for instance, in blast or cupola furnaces or even energetically, for instance, for use as fuel in cement works or power plants) is, according to current knowledge, only possible under ecologically or economically defensible conditions if the shredder residues or the light shredder fraction (SLF) are split up with the aid of suitable conditioning steps into as high-valued, homogeneous subfractions as possible.

European Published Patent Application No. 1 333 931 describes a method for the conditioning in common of shredder fractions in which, among other things, a qualitatively high value or materially or energetically usable lint fraction is able to be produced. In this context, in preprocesses, the light shredder fraction (SLF), the heavy shredder fraction (SSF) and the material flows created in the preprocesses are conditioned and, at least in parts, in a common main process, a raw lint fraction is produced by the segregation of at least one ferromagnetic fraction, an NE metal-containing fraction, a granulate fraction and a sand fraction. The raw-lint fraction thus produced, which is already very homogeneous, is split up in a further refining process by the successive process steps of treating with metal balls, dedusting and density separation into a metal-containing dust fraction, a lint fraction low in dust and metals, and a metallic fraction. The high-value lint fraction produced thereby may be used without a problem for material or energy purposes.

German Published Patent Application No. 102 24 133 describes a method for treating mud, which is supposed to be used for efficient mechanical dehydration in the preliminary stages of a later thermal treatment of the mud. It is proposed, among other things, that one feed in additives to the mud, in the form of a refined lint fraction, according to the method described in European Published Patent Application No. 1 333 931. Furthermore, reference is also made to the possibilities of an additional conditioning of the lint fraction thus refined, which includes the method steps of impact treatment, straining, density separation. The light fraction (lint) obtained from the density separation is combined with the overflow of the straining (also lint) and is submitted to the downstream alternative method steps of size reduction, agglomeration, pelletizing or briquetting. In addition, in the case of agglomeration, it is proposed that the material discharge of the agglomerate be submitted to the additional conditioning stages of sieving out non-agglomerated, lumpy parts, additional FE metal segregation, and material cooling during pneumatic conveying.

A method is described in German Published Patent Application No. 197 55 629 for conditioning the light shredder fraction from shredder systems, in which the complex light shredder fraction is subdivided by size reduction and separation into the four subtractions: shredder sand (substantially removed inert materials such as glass, sand, dirt), shredder granulate (substantially plastics granulate), metal granulate (substantially of isolated iron, copper and aluminum) and shredder lint (light substances capable of flying), the subtractions being supposed to be so homogeneous that they are able to be fed to a material and/or an energetic utilization.

Finally, in European Published Patent Application No. 1 337 341 a method is described for the joint conditioning of shredder fractions, in which the primary material flows created during the conditioning of the light shredder fraction and the heavy shredder fraction in preprocesses are fed, at least in part, to a common main process for the final conditioning. At least a ferromagnetic fraction, a fraction containing nonferrous metals, a granulate fraction, a sand fraction and a lint fraction are produced as end products. Let it be pointed out that the end products are able to be fed either directly to a material or energetic utilization, or that they may, if necessary, be processed further in additional refinement steps to form usable products of high quality.

Example embodiments of the present invention provide a method and equipment, using which a light fraction, produced during the conditioning of low-metal scrap high in plastics, is able to be refined further such that a highly pure end product is obtained for highly efficient material utilization, but also for better energetic utilization.

According to the method of example embodiments of the present invention for conditioning a light fraction (lint), produced during the conditioning of low-metal, scrap high in plastics, at least the following method steps are carried out, one after the other:

applying stresses to the light fraction using impact and/or shock; classifying the light fraction into at least two light fraction classes; separation of at least one light fraction class into at least one light material fraction and one heavy material fraction; and cleaning at least the light material fraction.

By cleaning the light material fraction (lint) obtained by the separation, one obtains a very pure output substance, whereby a clearly improved raw material use but also an energetic use is made possible.

The cleaning may take place in a dry state, namely by deducting. In this context, the light material fraction is freed in a centrifuge of heavy metal-encumbered dust (the latter substantially including lead and zinc), and the remaining material depleted in heavy metal thus becomes responsive to higher requirements on environmental compatibility.

It may be provided that the classification of the light fraction takes place by sieving, preferably at a diameter of hole of about 5-8 mm. In the selection of the hole diameter, by the sieving, at least a first light fraction class having an average part size range of <5-8 mm and a second light fraction class having an average part size range of >5-8 mm may be produced, which are easily processed further or are able to be split up.

The light material fraction (lint) obtained by separating the light fraction (raw lint) on average preferably has a bulk material weight of <250 kg/m3 and the heavy material fraction (granulate) obtained on average has a bulk material weight of >250 kg/m 3 , especially >400 kg/m 3 .

The light fraction (raw lint) that is to be further refined, may be a light fraction high in fiber, particularly having an average bulk material weight of <0.2 t/m 3 , which is produced in a preprocess in the conditioning of low-metal scrap high in plastics (the latter being preferably at least partly shredder residues of scrap containing metal).

It may be provided that, for producing the light fraction (raw lint) during the conditioning of low-metal scrap high in plastics, at least the following method steps be carried out one after the other:

isolation of ferromagnetic components; isolation of a first raw sand fraction; isolation of metallic, non-ferromagnetic components; isolation of coarse components; reduction in size; isolation of a first raw sand fraction; and sorting into at least one light fraction and one heavy fraction.

The light fraction (raw lint) produced in this manner represents an ideal output material for the method hereof, that may easily be further refined.

Before the impact treatment, the light fraction may be submitted to an Fe segregation.

The light material fraction, after cleaning, may be submitted to an agglomeration, particularly a discontinuous one, in order to transform the light material fraction (cleaned lint) into a state of being able to trickle. Before the agglomeration, however, the light material fraction should then be fed to a buffer, in order to ensure a decoupling of the agglomeration stage from the preprocess, and with that, an interference-free process operation. The agglomeration temperature selected should be approximately 100° C.-180° C., preferably approximately 140° C. The agglomeration being created should be cooled, in order, on the one hand, to prevent being able to handle it and, on the other hand, to prevent the self-ignition of the material in a storage bin or a prepackaging device. A first cooling using water already takes place in the agglomerator itself, cooling to about 45° C.-65° C., preferably to about 50° C.-60° C. taking place. After that, a further cooling/drying of the agglomerate may follow, in which a cooling, preferably using air (e.g. an air-conveying fan) takes place to environmental temperature. In this instance, a residual humidity content of <1.5% is aimed for, the latter being able to be achieved by an appropriate setting of the retention time in a suitable pneumatic conveying system.

The light fraction may be submitted to a metal segregation after the agglomeration. The lint material, slightly magnetized and treated with balls during the agglomeration, may be submitted, in this instance, to a metal segregation using a highly effective neodymium magnet. Nonmagnetic material carried along up to this point (e.g. copper particles or plastic granulate) is isolated and fed to an additional, separate process. What is left behind is a highly refined shredder lint agglomerate.

However, pelletting or briquetting of the light material fraction (cleaned lint) is also possible as an alternative to the agglomeration shown. In this case too, buffering of the light material fraction (cleaned lint) makes great sense, and is expedient especially with respect to making certain of great material availability.

It should be mentioned that the light material fraction (lint) obtained by the separation is merged with at least one light fraction class obtained by the classification. This will be the second light fraction class, having an average part size range of >5-8 mm, which is also present in the form of lint, and is thus available for a process-optimized joining together of these material flows.

The equipment according to example embodiments of the present invention for conditioning a light fraction, produced during the conditioning of low-metal scrap high in plastics, has devices by which consecutive method steps are able to be carried out:

applying stresses to the light fraction using impact and/or shock; classifying the light fraction into at least two light fraction classes; separation of at least one light fraction class into at least one light material fraction and one heavy material fraction; and cleaning at least the light material fraction.

By cleaning the light material fraction (lint) obtained by the separation, one obtains a very clean output substance, whereby a clearly improved material use but also an energetic use is made possible.

A device provided for applying stress to the light fraction (raw lint) using impact and/or shock may be in the form of at least one rotor impact mill or at least one hammer mill. When a rotor impact mill is used, the distance between stator and rotor may be to be set between 3 mm and 5 mm. In that manner, a very good application of stress of the light fraction may be ensured using the desired ball treatment of copper strands or metal wires and other interfering substances that are still included in the light fraction.

If a hammer mill is selected for the mechanical application of stress to the light fraction, then it may be ensured by the selection of a suitable screen hole size and suitable striking tools that the retention time in the hammer mill is sufficient to lead to a satisfactory ball treatment of the copper strands and the metal wires.

A device for isolating ferromagnetic components, preferably at least one magnetic separator, particularly a magnetic drum or an overband magnetic device may be connected upstream of the device for applying stress to the light fraction using impact and/or shock.

Furthermore, the device for applying stress to the light fraction using impact and/or shock may have connected downstream from them a classification device, particularly a screening device having a hole size of about 5-8 mm.

The classification device may have a density separation device connected downstream from it, preferably a separating table in combination with an air sifting device, for the separation of at least one light fraction class into a light material fraction and a heavy material fraction. The density separation device, especially the air sizing device, may include a device for a regulatable dust removal by suction. The air sizing device may be situated over the separating table, for instance, and may have a suction device that is able to be regulated such that the speed of the suctioning air may be set as a function of the size or the weight of the particles to be suctioned.

The density separation device may have connected downstream from it a device for surface cleaning of at least the light material fraction, preferably in the form of a centrifuge having its axis of rotation aligned vertically. An effective depletion in the light fraction of heavy metal-containing dust is achieved thereby.

The device for surface cleaning may have connected downstream from it an agglomeration device, especially one that works discontinuously. In this context, a buffer may be connected upstream of the agglomeration device.

A cooling and drying device, preferably in the form of an air-conveying fan and/or in the form of a cooling water supply device may be connected downstream of the agglomeration device.

It may be provided for the ferromagnetic metal segregation to connect at least one neodymium magnet downstream from the agglomeration device.

Example embodiments of the present invention are described in more detail below with reference to the appended Figures.

FIG. 1 is a schematic flow chart of the successive process steps for obtaining a light fraction LF (raw lint) high in plastics and a heavy fraction SF (raw granulate) high in plastics.

FIG. 2 is a schematic flow chart of a first part of the successive process steps for conditioning the light fraction LF (raw lint).

FIG. 3 is a schematic flow chart of a second part of the successive process steps for conditioning the light fraction LF (raw lint).

The schematic flow chart shown in FIG. 1 shows the process sequence in the conditioning of low-metal scrap high in plastics KA so as to obtain a heavy fraction SF high in plastics, and a light fraction LF high in plastics, which may be connected, for example, downstream from a shredder process of scrap vehicles.

Besides the low-metal plastics scrap from a shredder process, other plastic scrap may also be conditioned with the aid of the method and system described herein. When scrap vehicles are used, first of all, in a conventional shredder process, metal-containing scrap is first broken down by a size reduction process in a shredder. There follows an isolation of a light shredder fraction SLF, that is capable of flying, by a suction device. The heavy material flow that is not capable of flying, that remains after the suction, is separated on a magnetic separator into a ferromagnetic fraction and a non-ferromagnetic fraction. The ferromagnetic fraction is designated as shredder scrap, and it represents the primary product of the shredder that is able to be utilized directly in metallurgy. The remaining, heavy non-ferromagnetic fraction is designated as heavy shredder fraction SSF.

The light shredder fraction SLF is further conditioned, by itself or together with the heavy shredder fraction SSF and perhaps with additional low-metal scraps, and when they are submitted to the process described herein, they are designated as low-metal scrap high in plastics KA. This plastic scrap has a metal proportion of <20%, preferably a metal proportion in the range of magnitude of 5%.

One or more feed containers B 1 and/or B 2 are provided for feeding the low-metal plastics scrap, so as to decouple the conditioning process from upstream processes, such as the shredder process.

In a first method step V 1 , ferromagnetic components FE are isolated as a ferromagnetic fraction, using a magnetic separator MA 1 , and this fraction is able to be fed to a metallurgical conditioning process for recycled material utilization. This is followed by an isolation V 2 of a first raw sand fraction RS 1 using a screening device SE 1 , which in the exemplary embodiment has a size of hole in the range of 10-12 mm. Because of the isolation of this raw sand fraction, the subsequent process steps are relieved with respect to the isolated raw sand fraction. Next after method step V 2 , there is a process step V 3 , “segregation of non-ferromagnetic metal components” (non-ferromagnetic metal fraction), such as copper, brass and aluminum. A device NE 1 may be used in this instance, for eddy current segregation or for sensitive metal isolation using color detection or off color detection. The use of the equipment VARISORT of the firm of S & S GmbH may be provided for this purpose. The subsequent process step V 4 of the isolation of coarse components substantially reduces wear in next process step V 5 of the main size reduction. A device ST, so-called air knife systems, may be used in process step V 4 for the isolation of the coarse components SG for air current separation. After the isolation of the heavy material, in process step V 5 a size reduction takes place of the remaining fractions, using a hammer mill HM. The size reduction takes place in this instance such that the volume of the light fraction LF (raw lint) contained in the remaining fractions is increased, whereby in a later process step V 7 an improved and cleaner fraction splitting up of the remaining fractions into a light fraction LF (raw lint) and a heavy fraction SF (raw granulate) is possible. A device (WS) for air sizing is provided for splitting up the remaining fraction, according to the exemplary embodiment. The heavy fraction SF (raw granulate) has an average bulk material weight of 0.3 t/m 3 . Between process step V 5 of size reduction, preferably at 20 mm, and process step V 7 of splitting up the remaining fractions, a process step V 6 is provided, in which a second raw sand fraction RS 2 is isolated using a screening device SE 2 . The size of hole of screening device SE 2 is preferably in the range of 4-6 mm.

Light fraction LF (raw lint) thus produced is refined by the method shown in FIGS. 2 and 3 , FIG. 2 showing the first part of the method (method steps VF 1 to VF 5 or optional method steps VF 6 , VF 6 ″) and FIG. 3 showing the second part of the method (method steps VF 6 to VF 9 ). During the refinement, light fraction LF is submitted in a first process step VF 1 to the segregation of the ferromagnetic components FE, which are broken down during the reduction in size in process step V 5 . A magnetic separator MA 2 is preferably used for this, for instance, a magnetic drum or an overband magnetic device.

In a next method step VF 2 , the material is submitted to a mechanical application of stress, particularly an impact treatment, preferably in a rotor impact mill or a hammer mill HM, whereby metal wires or copper wires and metal strands and copper strands present in the material are treated with metal balls.

Subsequently, in a downstream method step VF 3 , the material is fed to a classification device, preferably a screening device SE having a hole diameter of 5-8 mm. From this are created two light fraction classes LF 1 and LF 2 , first light fraction class LF 1 having the screen undersize material (smaller components of the screening material) having an average part size range of <5-8 mm, and second light fraction class LF 2 having the screen oversize having an average part size range of >5-8 mm. The second light fraction class LF 2 has a predominantly lint-type consistency.

In a subsequent method step VF 4 , first light fraction class LF 1 is submitted to a density separation. As density separation device DT, a separating table is preferably used in combination with an air sizing device. It should be emphasized that density separation device DT (preferably the air sizing device) is equipped with a regulatable dust removal by suction, whereby light fraction class LF 1 is split up into a very light dust fraction STF 1 (which preferably is suctioned off already upon entry into density separation device DT), a light material fraction LF 1 -LG as well as a heavy material fraction LF 1 -SG.

Heavy material fraction LF 1 -SG has a granulate-shaped consistency having an average bulk material weight of about 400-500 kg/m 3 , and includes copper in the form of strands or wires. Heavy material fraction LF 1 -SG is fed to an additional processing module VM.

Light material fraction LF 1 -LG is submitted, in a subsequent method step VF 5 , to cleaning by a special cleaning device RE.

In this context, cleaning device RE includes at least one centrifuge, in which a dry surface cleaning of light material fraction LF 1 -LG takes place. Specifically, light material fraction LF 1 -LG is dedusted using the centrifuge, that is, it is freed of heavy metal-encumbered dust STF 2 (substantially including lead and zinc).

Light material fraction LF 1 -LG thus cleaned may subsequently be fed to pelletizing VF 6 ′ in a pelletting device PE or briquetting VF 6 ″ in a briquetting device BE, but it (LF 1 -LG) is preferably fed to agglomeration VF 6 . Agglomeration VF 6 of light material fraction LF 1 -LG takes place in a suitable agglomeration device AGE at approximately 100° C. to 180° C., preferably at approximately 140° C. to 170° C., according to a discontinuous method, until a consistency is reached of the material (LF 1 -LG) where it is able to trickle. Based on the discontinuous agglomeration, a device of a material buffer P is required before agglomeration VF 6 . This, however, offers the advantage of the decoupling of method step VF 6 from the upstream method steps, and offers the possibility of undertaking an additional charging B of material buffer P with other materials, even impact-treated materials.

The agglomerate created by agglomeration VF 6 is cooled already while in the agglomerator using cooling water at about 50-60° C. The agglomerate may subsequently be cooled using a cooling device KE, but may be cooled further (VF 7 ) to the environmental temperature. Cooling device KE may work with water, in this instance. However, cooling with air is also conceivable, for instance, the air of an air-conveying fan. In particular when cooling by water has taken place, drying VF 8 is recommended using a suitable drying device TE. Drying VF 8 may take place, for example, by air, even heated air. Method steps VF 7 and VF 8 may also be performed in parallel.

Finally, the agglomerate is fed to a metal segregation VF 9 , a neodymium magnet being preferably used as metal segregation device MA 3 , which achieves very high separating efficiency while having small dimensions. Using of metal segregation device MA 3 , the magnetic materials (during the agglomeration process, lint-type material (LF!-LG) became slightly magnetic) is isolated from the non-magnetic, predominantly copper-containing materials. Consequently, as the end products there are created a highly refined shredder lint agglomerate (SFA) and a copper/plastics granulate G. Copper/plastics granulate G (just as heavy material LF 1 -SG) is also fed to further processing module VM.

AGE agglomeration device

B charging of material buffer P

B 1 , B 2 feed container

BE briquetting device

DT density separation

FE ferromagnetic components

G copper/plastics granulate

HM hammer mill

KA low-metal plastics scrap high in plastics

KE cooling device

KU plastic material

LF light fraction, produced during the conditioning of plastics scrap low in metal

LF 1 1 st light fraction class having an average part size <5-8 mm

LF 1 -LG light material produced by density separation of 1 st light fraction class LF 1

LF 1 -SG heavy material produced by density separation of 1 st light fraction class LF 1

LF 2 2 nd light fraction class having an average part size >5-8 mm

MA 1 metal segregation device

MA 2 metal segregation device

MA 3 metal segregation device

NE non-ferromagnetic metal parts

NE 1 device for segregating non-ferromagnetic metal parts

P material buffer

PE pelletting device

RE cleaning device (centrifuge)

RS 1 first raw sand fraction

RS 2 second raw sand fraction

SE sifting device

SE 1 first sifting device

SE 2 second sifting device

SF heavy fraction, produced during the conditioning of plastics scrap low in metal

SFA shredder lint agglomerate

SG heavy material

ST device for isolating heavy material

STF 1 dust fraction, freed by method step VF 4

STF 2 dust fraction, freed by method step VF 5

TE drying device

VM processing module, which includes further processing steps

V 1 -V 7 process steps for conditioning low-metal plastic scrap

VF 1 -VF 9 process steps for conditioning light fraction LF (raw lint), produced during the conditioning of low metal scrap KA high in plastics

WS device for splitting up into a light fraction and a heavy fraction