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Title:
PLANT AND PROCESS FOR THE RECOVERY OF METALS FROM THE FINE FRACTION OF CAR FLUFF
Document Type and Number:
WIPO Patent Application WO/2017/203413
Kind Code:
A1
Abstract:
A plant for treating the fraction <20 mm of car fluff comprises a first treatment line consisting of one or more ferromagnetic separators (1), followed by one or more eddy current separators (2) and one or more inductive sensor-based separators (3), as well as a preliminary screen (4) that divides the material into a superfine fraction of up to 6 mm in size and a fine fraction sized 6÷20 mm that is fed to the first line of treatment, while the superfine fraction is fed to a separate second line of treatment consisting of a crushing mill (5) followed by a first screen (6) which discards the fraction of material sized up to 0,8 mm, followed by one or more ferromagnetic separators (7) and one or more eddy current separators (8), followed by a second screen (10) dividing the material into a plurality of different dimensional fractions fed to a corresponding plurality of separating tables (9).

Inventors:
MOLTENI, Danilo (Via Giovanni XXIII 49, Manerbio BS, 25025, IT)
Application Number:
IB2017/052997
Publication Date:
November 30, 2017
Filing Date:
May 22, 2017
Export Citation:
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Assignee:
SGM MAGNETICS S.P.A. (Via Leno 2/D, Manerbio BS, 25025, IT)
International Classes:
B07B15/00; B03B9/00; B03B9/06
Domestic Patent References:
WO2000053324A12000-09-14
Foreign References:
US6086000A2000-07-11
US20130092609A12013-04-18
Other References:
"AUTOMOTIVE SHREDDER RESIDUE", AUTOMOTIVE ENGINEERING INTERNATIONAL, SAE INTERNATIONAL, WARRENDALE, PA, US, vol. 106, no. 9, 1 September 1998 (1998-09-01), pages 78 - 81, XP000779652, ISSN: 1543-849X
Attorney, Agent or Firm:
CONCONE, Emanuele (Società Italiana Brevetti S.p.A, Via Carducci 8, Milano MI, 20123, IT)
Download PDF:
Claims:
CLAIMS

1. Scrap metal recovery plant for scrap sized up to 20±25% mm, comprising a first treatment line that consists of one or more ferromagnetic separators (1), followed by one or more eddy current separators (2) that receive the negative coming from said ferromagnetic separators (1), followed by one or more inductive sensor-based recovery separators (3) that receive the negative coming from said eddy current separators (2), characterized in that it further includes a preliminary screen (4) that divides the scrap into a superfine fraction sized up to 6±25% mm and a fine fraction sized 6±25%÷20±25% mm that is fed to said first treatment line, as well as a second separate treatment line that receives said superfine fraction from said preliminary screen (4) and consists of a crushing mill (5) followed by a first screen (6) that discharges the fraction of material sized up to 0,8±25% mm, followed by one or more ferromagnetic separators (7) that receive the material coming from said first screen (6), followed by one or more eddy current separators (8) that receive the negative coming from said ferromagnetic separators (7), followed by a second screen (10) that receives the negative coming from said eddy current separators (8) and divides it into a plurality of different size fractions fed to a corresponding plurality of separating tables (9) each of which is set to treat the size fraction that it receives.

2. Plant according to claim 1, characterized in that the second screen (10) is realized so as to divide the material into three fractions corresponding to the size ranges 0,8±25%÷1,5±25% mm, 1,5±25%÷3±25% mm and 3±25%÷6±25% mm.

3. Plant according to claim 1 or 2, characterized in that it further includes a pre-concentration station upstream from the preliminary screen (4), said pre- concentration station comprising at least a gravimetric air sifter (11) followed by a preliminary separating table (12) that are suitable to remove the lightest portion from the scrap.

4. Plant according to claim 3, characterized in that the pre-concentration station further includes a dryer (13).

5. Plant according to claim 4, characterized in that the dryer (13) receives the material coming from the preliminary separating table (12) and is preferably followed by a second separating table (14).

6. Plant according to claim 4, characterized in that the dryer (13) is located upstream from the gravimetric air sifter (11).

7. Scrap metal recovery process performed with a plant according to any of the preceding claims, characterized in that it includes the steps of:

a) screening, by means of a preliminary screen (4), with division of the material into a superfine fraction sized up to 6±25% mm and a fine fraction sized 6±25%÷20±25% mm, and subsequent feeding of said fractions respectively to the second and first treatment lines of the plant;

b) iron removal from said fine fraction, by means of one or more ferromagnetic separators (1);

c) main recovery of non-ferrous metals from the fine fraction, by means of one or more eddy current separators (2) that treat the negative resulting from step b);

d) recovery separation of residual non-ferrous metals from the fine fraction, by means of one or more inductive sensor-based separators (3) that treat the negative resulting from step c);

e) crushing of the friable material present in said superfine fraction, by means of a crushing mill (5);

f) screening, by means of a first screen (6), of the material resulting from step e) with discharge of the fraction sized up to 0,8±25% mm;

g) iron removal, by means of one or more ferromagnetic separators (7), from the material resulting from step f);

h) recovery of non-ferrous metals, by means of one or more eddy current separators (8) that treat the negative resulting from step g);

i) screening, by means of a second screen (10), of the negative resulting from step h) with division of the material into a plurality of different size fractions;

j) polishing separation of the size fractions resulting from step i), each of said fractions being separated by means of a corresponding separating table (9);

wherein the two groups of steps b)-d) and e)-j) can be carried out separately and independently.

8. Process according to claim 7, characterized in that it further includes a material pre-concentration step, prior to step a), by means of at least a gravimetric air sifter (11) and a subsequent preliminary separating table (12) that are suitable to remove the lightest portion from the scrap.

9. Process according to claim 8, characterized in that the pre-concentration step further includes a passage of the material through a dryer (13).

10. Process according to claim 9, characterized in that the passage of the material through the dryer (13) takes place after the passage through the gravimetric air sifter (11) and the preliminary separating table (12), and is preferably followed by a passage on a second separating table (14).

11. Process according to claim 9, characterized in that the passage of the material through the dryer (13) takes place prior to the passage through the gravimetric air sifter (11) and the preliminary separating table (12).

12. Process according to any of claims 7 to 11, characterized in that in step i) the screening is carried out so as to divide the material into three fractions corresponding to the size ranges 0,8±25%÷1,5±25% mm, 1,5±25%÷3±25% mm and

3±25%÷6±25% mm.

Description:
21.06.2017

PLANT AND PROCESS FOR THE RECOVERY OF METALS FROM THE FINE FRACTION OF CAR FLUFF

The present invention relates to the recovery of metals from scrap, and in particular to a plant and process for improving the rate of recovery and the rate of concentration of the metals recovered from the fine fraction of the material defined car fluff.

It is known that at the end of their life cars, and also other industrial and domestic products of large size and essentially ferrous composition, are ground with large hammer mills (so-called car shredders) which reduce them to pieces sized less than 150 mm so as to obtain ferrous scrap.

At the exit of these mills, the mixed ground material undergoes an action of iron removal by means of strong electromagnetic drums in order to recover and clean up the ferromagnetic steel (so-called proler), which represents about 70% of the total and is sold to steel works to be melted and reused. The remaining approximately 30% that is discarded from said electromagnetic drums, called car fluff is essentially composed of plastics, rubbers, polyurethane foams, glass, aluminum, copper, zinc, zinc alloy, lead, stainless steel, electrical wires, stone residues, iron oxides and some parts of ferromagnetic steel lost during the recovery of the proler.

The car fluff is then treated with appropriate rotating and/or vibrating screens to subdivide it into sizes suitable for the treatments that you want to use for the separation and recovery of metals. These sizes are typically defined as follows:

- Fine: indicatively under 20 mm and typically represents approximately 35% by weight of the total car fluff

- Median: approximately 20 to 40 mm and typically represents approximately 35% by weight of the total car fluff

- Large: indicatively between 40 and 120 mm and typically represents approximately 28%) by weight of the total car fluff

- Oversize: indicatively between 120 and 150 mm and typically represents about 2% by weight of the total car fluff.

Each fraction of the car fluff thus divided according to its size is treated in appropriate plants for the recovery of metals, except for the Oversize fraction which is treated manually, or sent back to the car shredder or even discarded without any metal recovery treatment.

The plant and the process according to the invention are specifically intended for the treatment of the Fine fraction, that in traditional plants undergoes the following treatment steps:

I. Deferrization: by means of one or more ferromagnetic separators for the recovery of the residual ferromagnetic steel still present in the car fluff.

II. Main recovery of non-ferrous metals: by means of one or more eddy current separators for the recovery of a mixture of non-ferrous metals with a prevailing presence of aluminum, such mixed material being defined Zorba in the field on the basis of the definition specified by the American association ISRI (Institute of Scrap Recycling Industries, www.isri.org).

III. Recovery separation of non-ferrous metals: by means of one or more inductive sensor-based separators equipped with pneumatic or, rarely, mechanic ejection devices for the recovery of non-ferrous metals which for their characteristics are hardly recovered by the eddy current separators, namely stainless steel and copper electric wires (naked or still covered by their insulating sheaths).

IV. Polishing separation: in the negative of the second and third steps there are residual metals that have not been recovered due to their small size or poor reactivity to the previous separators, these metals being typically in the order of 2÷3% for non-ferrous metals and 5÷8% for ferrous ones, and separating tables are used for the recovery of these residual metals of small or very small size.

A drawback of conventional plants resides in the fact that these separating tables are not able to properly separate the metals from the other materials since in this phase the car fluff is often too moist and the shape factor and apparent density of its various components, such as glass and stone materials, are extremely similar to those of the metals to be recovered, in particular of aluminum alloys and copper electric wires still covered by their insulating sheaths. Therefore the various components of the car fluff though having different absolute density, at the outlet of the separating tables end up mixed with lighter metals, such as aluminum alloys and copper electric wires still covered by their insulating sheaths, which in part are conveyed to the light fraction outlet of the separating table together with plastic and most of glass and stone materials, whereas a still significant portion of glass and stone materials is conveyed to the heavy fraction outlet of the separating table thus polluting the recovered heavier metals.

The object of the present invention is to provide a plant and a process that overcome the above-mentioned drawbacks. This object is achieved by means of a plant and a process in which the material is divided into a superfine fraction (indicatively <6 mm) and a fine fraction proper that are treated on two distinct recovery lines, the line for the treatment of the superfine fraction comprising a crushing mill, prior to the ferromagnetic separator, with the purpose not of completely grinding the material but just that of reducing to powder the friable material, followed by a screen for the separation of the powdered material, whereas the line for the treatment of the fine fraction proper does not include separating tables. Other advantageous features are listed in the dependent claims.

The fundamental advantage of the present plant and process is therefore to be able to better separate in the polishing step the inert materials from the heavy metals in order to arrive at a concentration of the metals> 95% significantly higher than the concentration that can be achieved in the prior art.

A second significant advantage of this plant and process stems from the fact that light metals such as aluminum alloys and copper electric wires with plastic sheath are not lost into the light fraction of the separating tables.

Another important advantage of the above plant and process is given by its simplicity and low cost, which make it reliable and also suitable for the upgrading of existing plants.

Further advantages and characteristics of the plant and process according to the present invention will become apparent to those skilled in the art from the following detailed description of three embodiments thereof with reference to the accompanying drawings in which:

- Fig. l is a flow diagram schematically showing a first embodiment of the invention;

- Fig.2 is a flow diagram schematically showing a second embodiment of the invention; and

- Fig.3 is a flow diagram schematically showing a third embodiment of the invention

Referring to Fig.1 and to what was mentioned above about the stations/treatment steps, there is seen that a plant/process according to a first embodiment of the present invention conventionally includes in a first treatment line a ferromagnetic separator 1 and an eddy current separator 2 for the removal from car fluff of ferrous metals and Zorba, followed by a recovery separator 3 whose operating principle is based on the recognition of metal objects by means of an inductive sensors system and on the separation (ejection) of said metal objects by means of air jets, synchronized by an electronic system, which divert their trajectory and allow their physical separation from the treated material flow.

Note that an inductive sensor-based separator can be calibrated to separate only the copper wires or only the pieces of stainless steel or both simultaneously, in which case the work mode is defined all metals recovery. In the case where the separator is calibrated only for the separation of the copper wires the work mode is defined wire recovery, while in the case where it is calibrated only for the separation of pieces of stainless steel the work mode is defined Zurik recovery, with the term Zurik which corresponds to a concentrate of mixed metals with a prevailing presence of stainless steel according to the definition specified by the American association ISRI (Institute of Scrap Recycling Industries, www.isri.org).

Furthermore, it is obvious that the case of using multiple inductive sensor-based separators in a same station/step is understood to refer to separators positioned one after the other where each separator receives and works the negative of the previous separator, i.e. the fraction of material not ejected by the previous separator, to achieve the further recovery of metals either missed by previous separators or intentionally left by the preceding separator in the case of multiple sensor-based separators calibrated in Zurik recovery or wire recovery mode that work in cascade.

A first novel aspect of the present invention lies in the fact that the incoming material is previously screened on a preliminary screen 4 dividing it into a superfine fraction (approximately <6 mm) and a fine fraction proper, so that only the fine fraction sized 6÷20 mm is fed to the ferromagnetic separator 1 while the superfine fraction <6 mm is treated in a second distinct recovery line.

Consequently, when the fine fraction sized 6÷20 mm is treated according to the traditional process, the non-ferrous electro-conductive metals, thanks to their size greater than 6 mm, can be recovered by the eddy current separator 2 with a level of concentration above 95%, i.e. with a level of pollution from glass, stone materials and plastics lower than 5%. In addition, the inductive sensor-based separator 3 easily separates copper electric wires still provided with their plastic insulating sheaths, such wires being typically sized >6 mm, and it is not necessary to provide separating tables for treating the negative of the inductive sensor-based separator 3 since the material size >6 mm renders useless a polishing separation due to the negligible amount of metals in said negative.

A second novel aspect of the present invention lies in the second recovery line intended to treat the superfine fraction <6 mm, said second line providing in particular the addition of a crushing mill 5 and a screen 6 arranged before the separators, so that the latter operate on a material free of glass, stone materials and other friable materials. To this purpose, at the outlet of the crushing mill 5 the material passes on a screen 6 set indicatively at 0,8 mm which separates the powdered and crumbled material (glass + stone materials) from all the metals ending up in the fraction greater than 0,8 mm along with other non-metallic materials that are not friable, such as plastics.

Crushing mills for pulverizing/crumbling the friable material can be of different types, indicatively they may be impact mills (e.g. Mag'Impact from Magotteaux of Vaux-sous-Chevremont, Belgium) or ball mills (e.g. the Ball Mill model from Shanghai Joyal Machinery Co. of Shanghai, China). Irrespective of the exact type of mill, the friable material being treated therein is pulverized and crumbled while the non-friable material such as metals and plastics that are softer and more ductile are deformed at most but not pulverized.

After sieve 6, the fraction greater than 0,8 mm is passed on a ferromagnetic separator 7 to recover the ferrous particles and then, for the non-ferromagnetic part, on an eddy current separator 8 which recovers with a concentration level higher than 95% the vast majority of the non-ferrous electro-conductive metals and especially all the aluminum pieces which are the ones that react more to the eddy current separators and do not allow a precise separation on the separating tables.

In this second line it is not necessary to provide an inductive sensor-based separator to treat the negative of the eddy current separator 8, because the material size <6 mm makes useless a recovery separation due to the negligible amount of stainless steel and copper electrical wires in said negative.

In the second part, the polishing separation is carried out through separating tables

9 (e.g. the TTS model from Trennso Technik of WeiBenhorn, Germany) which treat the portion of material not separated in the preceding separators, as mentioned above. The negative from the eddy current separator 8 consists of a mixture of heavy metals having a density greater than 6, since there is no more aluminum, and inert material such as plastics with actual and apparent density lower than 2.

The material is first passed on a multiple screen 10 dividing the material into three dimensional fractions corresponding indicatively to 0,8÷1,5 mm, 1,5÷3 mm and 3÷6 mm, and each dimensional fraction is fed to a corresponding separating table 9 suitably calibrated and dimensioned, so that by working with more homogenous material it works more accurately. Given the large difference in both actual and apparent density between metallic and non-metallic parts, it is possible to achieve a very precise separation between them where all the residual heavy metals, namely zinc, lead and the so-called red metals such as brass, copper, bronze and their alloys, etc. end up in the heavy fraction with a concentration above 95%.

It should be noted that the three streams of the material screened with the multiple screen 10 are actually conveyed to three corresponding hoppers (not shown) to feed at programmed times, i.e. in batches and not in line, the respective separating tables 9 which, as is well known, perform a good separation if they work with a constant average flow rate equivalent to the calibration flow rate of the table itself.

The second embodiment illustrated in Fig.2 differs from the first embodiment in that it provides a station/step of pre-concentration of the material so as to further reduce the amount of material treated in the above described plant part. To this purpose, the material is first passed through a gravimetric air separator 11 (e.g. the Wind Sifter model from Trennso Technik of WeiBenhorn, Germany) and on a preliminary separating table 12 which remove the lighter parts such as sponges, textile fibers, wood fibers and most of the light plastics, thus reducing the mass of the material by about 40%.

As an additional option, the material from the preliminary separating table 12 can be treated in a dryer 13 to better detect the density difference between the metals and the non-metallic material which for the most part can absorb moisture and see its density increase considerably until it reduces the difference with the density of metals. Typically, the dryer is of the tunnel type with forced passage of a gas-, diesel fuel- or electricity-heated hot air (e.g. the Electric Rotary Dryer model from Ferrex Engineering of Ajax, Ontario, Canada). The dried material can be worked better also by a possible second separating table 14 which eliminates another about 10% of the light part.

Finally, Fig.3 shows a third embodiment similar to the second one in that it provides for a material pre-concentration station/step, but in this case the possible dryer 13 is placed upstream from the gravimetric air separator 11 and the preliminary separating table 12 and no second separating table 14 is possibly envisaged.

It should be noted that in the configuration of Fig.2 the dryer 13 operates on the material which has already lost about 40% of the mass, and thus it is evident that the energy cost of drying is reduced. The configuration of Fig.3 is preferable, on the other hand, if the moisture of the lighter parts, such as sponges, textile fibers, etc. were so high that it would not allow the gravimetric air separator 11 and the preliminary separating table 12 to work properly.

It should also be noted that the presence of the optional dryer 13 is also useful to make more friable the light material that could reach anyway the crushing mill 5, so that this light material can be better crumbled and pulverized in mill 5 and subsequently eliminated in screen 6.

By way of example, there is considered the operation of a plant according to Fig.2 capable of treating 18 ton/h of fine fraction of car fluff av ' g a moisture content of 20 to 35%.

As explained above, in the pre-concentration step the lighter part of the material consisting essentially of sponges, textile fibers, wood fibers and light plastics, which are about 40% in mass, is discarded by means of components 11, 12. The remaining 60%, equal to about 10,8 tons, passes into dryer 13 which eliminates about 10% of moisture so that the material is best processed by the subsequent separating table 14 which eliminates another about 10% of the lighter part.

The positive (heavy) fraction which goes forward, equal to about 8,5 tons, is suitable for being screened by the preliminary screen 4 dividing it into a superfine fraction <6 mm, equal to approximately 40% of the screened mass (3,4 t), and a fine fraction proper sized 6÷20 mm equal to about 60% of the screened mass (5,1 t) which is directly sent to the ferromagnetic separator 1 (for example, of the type described in EP 1755786). Here, there is carried out the recovery of the ferromagnetic steel present, representing about 9,8% of the treated mass (0,5 t), and the removal of ferromagnetic powder, mostly iron oxide and inert material mixed with iron oxide, representing about 29,4% of the treated mass (1,5 t).

The remaining material is processed by the eddy current separator 2 which recovers the electro-conductive metals (Zorba) representing about 9% of the mass of the fraction sized 6÷20 mm (0,46 t). The residue is finally treated by the inductive sensor- based separator 3 which recovers approximately 7% of the mass essentially composed of Zurick mixed with copper wires (0,36 t). The waste of the fraction sized 6÷20 mm also includes 0,6 t of glass and stone materials representing about 11,8% of the mass and 1,68 t of plastic, rubber and various inerts representing the remaining about 33% of the mass.

The superfine fraction <6 mm is passed into the crushing mill 5 which has the function of crumbling and pulverizing the glass and the stone materials present while the metals, plastics and rubbers undergo only pressing and substantially do not crush and do not change size. Then the material is screened at 0,8 mm on screen 6 by discarding about 1,36 t of glass and crumbled stone materials, representing 40% of the superfine fraction <6 mm, while the rest is deferrizated by the ferromagnetic separator 7 (e.g. of the type described in EP 1755786) which recovers ferromagnetic steel and removes ferromagnetic dust, which altogether correspond to approximately 25% of the mass (0,85 t).

The remaining 35% of the mass (1,19 t) passes on the eddy current separator 8 for the recovery of the light electro-conductive metal (aluminum or aluminum alloys and magnesium) which is about 8% of the mass (0,27 t). The negative is passed to the multiple screen 10 dividing it into the three fractions of 0,8÷1,5 mm, 1,5÷3 mm and 3÷6 mm which are sent to the corresponding separating tables 9. At this point the dried material screened into homogeneous fractions is essentially made up of plastics for about 18% (0,61 t) with density 1÷1,8 and heavy metals for about 9% (0,31 t) with density 5÷8,9 and is therefore easily worked with separating tables 9.

The object of the present invention is therefore to optimize the recovery and concentration of metals present in the Fine fraction <20 mm of the car fluff while minimizing the costs, and in particular to make actually possible to recover the heavy metals in the superfine fraction <6 mm through the correct use of the separating tables. This is particularly beneficial since in recent years the industry has increasingly focused on the recovery of the small size metals present in all sectors of recycling (including waste from electrical/electronic equipment and incinerator ash), trying to divide light metals, mostly aluminum and aluminum-magnesium alloys, from heavy metals mostly containing the so-called red metals often containing precious metals such as silver, gold, platinum, palladium, etc. which greatly increase their value.

Since these metals are largely present in electronic components and since the use of electronics also greatly increased in automobiles, it is of particular interest to those in the industry to have a plant/process suitable for the purpose according to the teachings of the present invention, which however is not to be understood as limited specifically to the treatment of car fluff.

The steps of the process for the treatment of car fluff carried out in the plant described above can therefore be summarized as follows:

a) screening, by means of a preliminary screen, with division of the material into a superfine fraction <6 mm and a fine fraction sized 6÷20 mm;

b) iron removal from the fine fraction sized 6÷20 mm, by means of one or more ferromagnetic separators;

c) main recovery of non-ferrous metals, by means of one or more eddy current separators that treat the negative resulting from step b);

d) recovery separation of residual non-ferrous metals, typically stainless steel and copper wires, by means of one or more inductive sensor-based separators that treat the negative resulting from step c);

e) crushing of the friable material present in the superfine fraction <6 mm separated in step a), by means of a crushing mill;

f) screening, by means of a powder screen, of the material resulting from step e) with discharge of the fraction <0,8 mm;

g) iron removal, by means of one or more ferromagnetic separators, from the material resulting from step f);

h) recovery of non-ferrous metals, by means of one or more eddy current separators that treat the negative resulting from step g);

i) screening, by means of a multiple screen, of the negative resulting from step h) with division of the material into a plurality of different size fractions;

j) polishing separation of each of the size fractions resulting from step i), by means of a corresponding separating table.

It should be noted that the process steps have been listed as above for the sake of an easy disclosure, however since the plant carrying out the process includes two recovery lines that operate in a distinct and parallel manner it is clear that the two groups of steps b)-d) and e)-j) can be carried out separately and independently. The sequence of the steps is therefore referred only to each of the two groups of steps relating to the respective recovery line, step a) being the only common step preliminary to both groups of steps.

The method may further comprise a step of material pre-concentration step, prior to step a), by means of at least a gravimetric air sifter and a subsequent separating table as well as preferably also a dryer that can be arranged upstream from said air sifter or downstream from said separating table, in this latter case a further separating table being possibly provided after the dryer.

It is obvious that the embodiments of the plant/process according to the invention described and illustrated above are just examples susceptible of various modifications. In particular, the exact number, type and arrangement of the inductive sensor-based separators can vary depending on the specific application, same as the number of separating tables 9 that treat the different size fractions in the polishing step.

It is also clear that the values of the dimensional intervals of the different fractions may vary according to specific operational requirements, therefore the above-described sieving values for the Fine fraction and for screens 4, 6 and 10 are intended as indicative and not strictly limitative since deviations from these values in the order of ± 25% are predictable, i.e. the preliminary screening 4, for example, could be set to have a screening threshold of the superfine fraction ranging from 4,5 mm to 7,5 mm.