TECHNICAL FIELD

The invention relates to a plant and a process for the recovery of plastic mixtures, in particular light plastic mixtures from ASR (shredded scrap from the automotive sector), resulting from separations of ASR after the separation of ferrous and non-ferrous metals and heavier plastic mixtures.

BACKGROUND ART

As is known, shredding plants for medium and large scrap exist, for example scrap from cars or vehicles in general, which comprise shredding machines in which vehicles are introduced in order to be subjected to a shredding or crushing process. What is obtained from these treatments, in addition to the scrap that is fed to electric arc furnaces, is a cluster of residual material known as ASR (Automotive Shredder Residue) with a very heterogeneous composition consisting of metallic, non-metallic, inert, plastic parts. An exemplary average composition of ASR comprises 44% by weight of light plastics, 40% by weight of heavy plastics, 7% by weight of non-ferrous metals, 5% by weight of ferrous metals, and the remaining 4% by weight includes other materials. The heavy and light plastics differ in density: the light plastics essentially consist of very low-density pile foams.

Residues from the automotive sector can be separated and recovered to obtain three main product groups: ferrous and non-ferrous metals, a mixture of heavy plastics and a mixture of light plastics requiring briquetting (or agglomeration in general) to facilitate transport and eventual reuse.

The share of residual material in the plastic component has a high calorific value, exceeding 13,000 kJ/kg and generally consists of mixtures of: plastics, rubbers, fibres, and polymers in general (more than 80% of the total materials present).

Italian patent 102015000051336 on behalf of the applicant clearly describes a process of separation and progressive screening of the different materials which form the ASR, once the metallic and non-metallic parts are separated, to reach that residue of plastics which, purified from further residues, can be treated to become fuel and which is therefore a more specific by product of the ASR.

The term plastics or plastic materials means light plastics (low-density, consisting of polyurethanes, foams, but also containing paper, fabrics, etc., with a pile density of about 100- 200 kg/m ³ ), heavy plastics (high-density, about 800-1000kg/m ³ ), such as polypropylene, polyvinylchloride, polyethylene terephthalate, acrylonitrile-styrene-butadiene), etc.

The separated metals can be marketed or used as scrap in melting processes. However, even part of the heavy plastics with high density and high calorific value can feed electric arc furnaces (EAF) as described in patent IT 102015000051336, or also be marketed. With regard to the light fraction (foams, polyurethanes, etc.) with a calorific value usually lower than that of high-density plastics, only partial use in the melting field is possible in accordance with the provisions of IT 102015000051336, however, some or all of the material which must in any case be transferred to landfill or ceded to cement plants remains. The recycling of the individual fractions obtainable from ASR is therefore not yet currently complete.

M. Notarnicola et al. (. Pyrolysis of automotive shredder residue in a bench scale rotary kiln; Waste Management 65 (2017) 92-103), M. Day et al. (. Pyrolysis of automobile shredder residue: an analysis of the products of a commercial screw kiln process ; Journal of Analytical and Applied Pyrolysis 37 (1996) 49-67) and Seon Ah Roh et al. ( Pyrolysis and gasification melting of automobile shredder residues ; Journal of the Air & Waste Management Association 63(10): 1137-1147, 2013) propose pyrolysis for the recovery of mixtures of ASR agglomerates. In this case the recovery of metals is worse because it is incorporated in the liquid and solid fractions of the hydrocarbons and the metals are still partly transported by the pyrolysis gases.

DISCLOSURE OF THE INVENTION

The object of the invention is to overcome the aforementioned drawbacks and to propose a plant and a process for the more efficient and complete recovery of mixtures of plastics previously and suitably separated from ASR which allows to reduce/eliminate the fraction to be transferred to landfill.

A further object of the present invention is to create a plant for the recovery and treatment of shredding residues of automotive scrap which allows the use of residual mixed plastics, but especially light ones, deriving from the ASR material separation process, profitably in steel mills through a recycling path which may be different from that of high-density plastics. Further objects or advantages of the invention will be apparent from the following description. In a first aspect of the invention, the object is achieved by a plant for the recovery of mixtures of plastics, in particular mixtures of light plastics from ASR comprising:

- an ASR separation plant as a source of fractions of light plastics and optionally fractions of heavy plastics, and

- downstream of said ASR separation plant, a reactor for the generation of fuel by means of pyrolysis of said fractions of light plastics and optionally of said fractions of heavy plastics which is adapted to be fed through said connection with said fractions of light plastics and optionally of said fractions of heavy plastics, wherein the fuel comprises one or more fuels selected from liquid, gaseous, and solid fuels, and wherein said ASR separation plant comprises a first plant part, provided with shredding and separation means configured to extract ferrous materials, non-ferrous metals and plastics from said ASR residues and to separate the plastics into heavy and light plastics.

The fuels produced may be gaseous, liquid or solid in nature, but are preferably liquid fuels, in particular oils, and/or gaseous, in particular gaseous fuels. Any liquid fuels produced can have different viscosities. The liquid fuels produced can comprise paraffins, Ao-paraffms, olefins, naphthenes, aromatics, etc. In other words, the fuel advantageously comprises one or more fuels selected from liquid, gaseous, and solid fuels.

Pyrolysis is a thermochemical decomposition process of organic materials, obtained by the application of heat and in the complete absence of an oxidizing agent (normally oxygen). In practice, if the material is heated in the presence of oxygen, a combustion occurs which generates heat and produces oxidized gaseous compounds; instead, by performing the same heating under anoxic conditions, the material undergoes the cleavage of the original chemical bonds with the formation of simpler molecules, such as the conversion of aromatics to cycloparaffms, isomerization reactions, ring-opening reaction, the cracking of long chain molecules into short chain molecules, etc. The heat provided to the pyrolysis process (which is endothermic) is then used to cleave the chemical bonds, implementing what is defined as thermally-induced homolysis. Using temperatures between 400 and 1,000°C, pyrolysis converts the solid-state material into liquid (so-called tar or pyrolysis oil) and/or gaseous (hydrocarbons, of generic formula CnH _m ) products, usable as fuels or as raw materials for subsequent chemical processes. The solid carbonaceous residue obtained can be further refined supplying products such as activated carbon. Pyrolysis products are both gaseous, liquid, and solid in proportions which depend on the pyrolysis methods (fast, slow, or conventional pyrolysis) and reaction parameters. A pyrolyzer differs from a gasifier in that it works in the absence of oxygen. A hot flow of an inert gas such as nitrogen is often exploited. The light flow of N2 (such as not to affect the composition of the gas produced) is also intended to maintain a lower overpressure in the reactor to reduce the risk of air ingress. The heating preferably occurs indirectly by means of burners located outside the reactor. The gasifier, on the other hand, works in the presence of small amounts of oxygen and also produces a partial oxidation and as a technology represents a middle ground between incinerators, which include a complete combustion of the treated material, and pyrolyzers.

This ASR waste separation and recovery technology is expected to have wide industrial application in the coming years, also facilitated by the enactment of standard UNI 10667 17:2018 which allows the transport and reuse in the steel industry of secondary plastics, as reducing agents in place of carbon, as long as the composition and calorific value comply with the limits imposed by the standard itself. This implies that part of the plastics (preferably the heavy ones with high density and high calorific value) can be fed into the EAF and the remaining part can be marketed. However, ASR waste separation technology also provides plastic materials for which another application, such as that proposed by the invention, must be found.

Both heavy and light plastic fractions are however characterized by the presence of a very low fixed carbon concentration (< 5%) and virtually all the carbon is developed from heated material such as hydrocarbon CnHm.

In a variant of the invention, the fractions of plastics comprise fractions of light plastics and fractions of heavy plastics intended for said pyrolysis in said reactor. The addition of heavier fractions to the fractions of light plastics increases the calorific value and allows to influence the composition of the fuels obtainable in the pyrolysis and allows to reduce the amount of solid residue to be transferred to landfill. The composition of mixtures of plastics subjected to pyrolysis can be adjusted to reduce the fixed carbon value as much as possible so as to increase the yield in gaseous and/or liquid fuels.

In a preferred variant of the invention, the fractions of plastics have a high calorific value and when subjected to pyrolysis are low in ash, and the resulting fuel contains a solid fuel fraction which is rich in carbon. An example of this type of application is the pyrolysis of tyres, which have a calorific value of about 30MJ/kg and a very low residual ash concentration. The fraction of heavy plastics is characterized by a calorific value similar to that of anthracite (28-30MJ/kg), while the light fraction has an average calorific value of 18-20 MJ/kg.

Therefore, the separation between the two groups of materials due to density also allows a classification of the calorific value. To better explain this concept, consider mixtures of representative but not exhaustive components, for the two classes and the relative calorific values (known in the literature):

Table 1

Solid fuel can be applied as a reducing agent in steel furnaces.

The recovery of plastic materials from ASR and the transformation thereof into fuels represents an economic and ecological solution for the recovery of scraps which are otherwise not marketable or usable. The reactor preferably has heating devices, such as burners or resistors. The heating can occur indirectly (external heating devices) or directly (circulation of a gas, preferably hot, (inert) inside). Indirect reactor heating is preferred so as to avoid affecting the composition of the pyrolysis products.

The fuels produced can be used in various utilities of a steel plant, as they can be used, at least partially, to power the reactor itself. To this end, the fuel generation reactor is advantageously heated by burners fed at least partially by the fuels produced during the pyrolysis.

Various types of furnaces are suitable as reactors, for example elongated furnaces such as rotary kilns. Advantageously, they are provided with an inlet for feeding the material to be subjected to the thermochemical treatment, and at least one discharge for extracting the fuels produced. Then the reactor is ideally provided with a control unit which manages the components thereof and the composition of the fed products.

The reactor can have various sections, such as preheating zones, pyrolytic treatment zones, cooling zones, etc. Preferably, a material crushing device (cutting, grinding, shredding systems, etc.) is located upstream of the reactor chosen according to the needs of the particle size to be introduced. The furnace can be tilted. Mixing means and/or conveying elements can be included for conveying the material inside the furnace, for moving it from one zone to another, for discharging the pyrolysis products.

In an advantageous variant of the invention, the reactor is a rotary kiln. Rotary kilns are rotating furnaces of cylindrical shape, generally resting on rolling rollers which can be in different numbers depending on the static sizing performed. The rotation can be ensured by a gearmotor and the relative mechanical transmission which can be chain, sprockets or other gears. Generally, the load-bearing structure of the kiln consists of a thick steel tube. Depending on the material treated inside the kiln (corrosive, non-corrosive, melting, etc.) the drum material can be of a different type, or an internal refractory coating can be included.

Other suitable reactors are heated reservoir-type reactors, fixed bed reactors, screw reactors or other suitable devices with a heated surface for assistance in the thermochemical treatment.

In the reactors described, there is the possibility that the body rotates to move the material, but alternatively or additionally it is possible that they are provided with an internal screw or auger adapted to move the material. This movement can therefore be carried out separately or in combination with that of the kiln structure.

Advantageously, the ASR separation plant comprises a second plant part provided with means for treating and sizing plastics configured to transform said plastics into forms usable in said reactor, such as devices for briquetting light plastics. In a preferred embodiment, the second part of the invention comprises in this regard a thermo-mechanical transformation system of plastics and optionally fibre materials so as to produce dense briquettes without externally heating the material. Another embodiment of the system involves directly feeding the fraction of plastics already grinded into the ASR treatment plant before the metal separation. Preferably, the second plant part comprises a system for cutting and/or grinding plastics, in particular heavy plastics, and optionally briquettes wherein the cutting and/or grinding system is advantageously located downstream of said thermo-mechanical transformation system. This allows to obtain a material having a controlled and adequate granulometry with respect to the subsequent application thereof.

In exemplary form, the first plant part comprises one or more induced-current separator systems configured to separate the non-ferrous metals.

In an embodiment of the invention, the ASR separation plant further comprises one or more systems, preferably all, selected from the group consisting of a granulator and/or disintegrator system configured to reduce, preferably without pre-screening steps, shredding residues in a granular material stream; at least one magnetic separation system configured to separate ferrous materials from said granular material stream; at least one density separation and/or screening system configured to remove light plastics from said granular material stream, such as textiles, polyurethane foams, and possibly also paper, cardboard, and to classify the plastics into light and heavy fractions; at least one induced-current separator system configured to separate non- ferrous metals from the granular material stream.

According to a possible embodiment, the plastic classification system can include one or more size/density separation systems configured to separate heavy plastics, comprising for example mainly rubbers, polypropylene, polyethylene, resins, acrylonitrile butadiene styrene, polycarbonate, polystyrene, polyethylene terephthalate, etc., and one or more screening systems and/or gravimetric, and/or colorimetric separation systems or with spectroscopic sensors configured to separate the different plastics by dimensions, weight and composition (with and without chlorine).

The proposed plant allows the use of the fraction of light plastics for fuel generation via a pyrolysis process, advantageously at temperatures of about 800 - 1,000°C, wherein the different fuel fractions can be applied as a fuel or reducing agent in melting furnaces or as a fuel for burners in other applications.

The material to be subjected to pyrolysis from ASR can, for example, in order to increase the calorific value or influence the type of fuel mixture produced, be integrated with other materials, such as heavy plastics, biochar, plastics comprising carbon fibres etc. Staged thermochemical treatments, for example initially pyrolysis at lower temperatures and subsequently heating at higher temperatures, are also conceivable. Separation devices, as widely known to those skilled in the art, can be provided to classify and separate the different types of fuels produced. In an advantageous variant of the invention, the plant for the recovery of mixtures of plastics further comprises a feeding device of solid slag at T > 800 °C, in particular from a melting and/or refining plant for metallurgical products, arranged near said reactor in order to feed it with slag. This embodiment is particularly advantageous if a steel mill is provided near the reactor site. Slag, i.e., the foamy set of oxides and residues from melting in a melting furnace, currently finds few uses and is simply cooled in air with water outside and then disposed of/buried. With the introduction into the reactor, together with the plastics, the thermal potential thereof can be used to support the pyrolysis of the plastics in the reactor so as to obtain the fuel. Slag is an inert or poorly reactive material, thus its task is to provide energy (by conduction) for endothermic reactions and sequester the ashes (generally CaO + S1O2 + AI2O3) present in the mixtures of plastics.

Preferably the slag is supplied at a high temperature, above 1,000 °C, to lead to the formation of fuel in gaseous form, which is purer and easier to then store for later use. Alternatively, a liquid fuel can be obtained, however in this case it will be necessary to carry out cleaning/separation steps from slag residues. In general, the solid slag feed temperature range for the pyrolysis of the polymer mixture is within the range 800°C - 1,400°C.

The presence of slag in the reactor can contribute to the pyrolysis by assisting burners or other heating elements of the reactor to even avoid the use thereof altogether.

It is obviously possible to add catalysts to the materials to be subjected to the thermochemical treatment to accelerate the process and/or have an influence on the composition of the mixture produced. A catalyst determines the degree of transformation of the reagents not only by means of the type thereof, but also by the reagent/catalyst ratio. The slag itself can contain catalytically active species such as iron residues, present as such or by reduction of Fe _x O _y with the reducing agents present in the decomposition products of the polymer mixtures.

For example, the plant can include a hydroprocessing unit for removing oxygen, nitrogen and sulphur compounds and/or a scrubber for removing chlorides from the products.

The pyrolytic treatment can be aided by steam cracking plants, in which water vapour reacts with carbon to produce CO and Fb, as reducing agents.

The pyrolysis can be controlled inter alia by intervening on the composition of the reagents, temperature and/or pressure, thereby influencing the composition of the fuels produced, which advantageously comply with the respective national requirements and regulations. As already indicated above with regard to the ASR separation plant and the function of the various components thereof, it is possible to efficiently separate the main components of ASR scrap shredding residues, in particular ferrous materials, non-ferrous metals and plastics. Advantageously, the shredding/disintegration and separation means immediately produce a fraction which is small and homogeneous, the composite material is divided and disintegrated in the structure thereof and the metals are deformed and granulated. This step allows to separate all the different components from each other in a simple and clean manner in the subsequent part: ferrous materials from non-ferrous materials, plastic mixtures from fibre mixtures. Fractions of fibre and plastic mixtures can be transferred to a subsequent operational step with means which can select the recyclable plastic fraction from the mixture or treat and size the mixed plastics so as to transform them into material adapted to be used in the pyrolysis reactor (mainly light plastics) mentioned above or directly in steel plants such as blast furnaces, arc furnaces or the like to partially replace carbon (mainly heavy plastics).

The plant and the process described below according to the invention include treating fractions of plastics obtained from the separation of ASR by means of pyrolysis, then pyrolyzing plastic subsets of the ASR obtained after the separation of metal, ferrous and non-ferrous fractions.

A second aspect of the invention relates to a process for the recovery of mixtures of plastics, particularly mixtures of light plastics from ASR comprising the following steps:

(I) providing light plastics and optionally heavy plastics, through an ASR separation which includes one or more first sequential steps of shredding and separating ASR residues adapted to extract ferrous materials, non-ferrous metals and light and heavy plastics,

(II) pyrolysis of said light plastics and optionally of said heavy plastics, preferably in a rotary kiln, producing fuels in gaseous and/or liquid and/or solid form, wherein preferably a part of the fuels produced is used to heat the reactor.

Preferably, the provision of light plastics is accompanied by obtaining further fractions from ASR which can be marketed and/or used inside a steel mill.

Preferably, the process according to the invention comprises one or more further steps of treating and sizing plastics adapted to transform said plastics into additive material for use in steel plants such as blast furnaces, electric arc furnaces or the like and/or inside the reactor according to the invention. Advantageously, the process comprises one or more or all of the following sequential steps: shredding ASR so as to obtain a stream of granular material; extraction of ferrous materials from the granular material stream by magnetic separation; extraction from the granular material stream of plastics and the classification thereof into light plastics and heavy plastics by density separation and/or screening; extraction of non-ferrous metals from the granular material stream by means of induced currents; wherein the step of extracting light plastics by density separation from the granular material stream is of particular importance.

Advantageously, the process can comprise at least one thermo-mechanical treatment step of the plastics so as to obtain bricks or cylinders.

Preferably, the plastics can be subjected to a cutting and/or grinding step.

In exemplary form, during the process according to the invention, the non-ferrous metals are treated by a further induced-current separation step, so as to separate the main constituent components thereof.

A preferred variant of the method according to the invention includes that the fuel obtained is fed to melting furnaces or other steelworks energy consuming processes.

In an advantageous variant of the invention, the plastics provided in step (I) and subject to pyrolysis in step (II) comprise low-density plastics having dimensions < 30 mm and/or granular plastics with a preferential size < 10 mm obtained by briquetting and subsequent granulation of said low-density plastics having dimensions < 30 mm. Advantageously, these fractions have a higher calorific value in the case of the non-granulated material between 16,000 and 20,000 kJ/kg, preferably between 17,000 and 18,500 kJ/kg, and in the case of the granulated material between 21,000 and 25,000 kJ/kg, preferably between 22,500 and 23,500 kJ/kg.

Preferably, the carbon content by weight of these fractions is greater than 45%, more preferably greater than 50%. The ash content in an elemental dry analysis of the material is preferably less than 40%.

Exemplary fractions for such fractions of plastics are illustrated below with reference to figures 3 and 4.

In an advantageous variant of the invention, the plastics provided in step (I) and subject to pyrolysis in step (II) comprise high density plastics, preferably in granular form with size < 10 mm. Advantageously, these fractions have a higher calorific value between 31,000 and 32,500 kJ/kg, while the lower calorific value is preferably between 29,000 and 31,000 kJ/kg. Preferably, the carbon content by weight of these fractions is greater than 60%. The ash content in an elemental dry analysis of the material is preferably less than 25%.

Exemplary fractions for such fractions of plastics are illustrated below with reference to figures 3 and 4.

Such a composition of the material which feeds the reactor or which is subjected to pyrolysis allows to obtain fuels in different forms. In advantageous forms of the invention, for temperatures in the reactor between 650 and 700 °C, the gaseous fraction is present in an amount < 50% (m/m), the liquid fraction in an amount < 20% (m/m) and the solid fraction in an amount < 40% (m/m), while for temperatures in the reactor within the range 700 °C < T < 1,200 °C, the gaseous fraction is present in an amount of 60 - 80% (m/m), the liquid fraction in an amount < 10% (m/m) and the solid fraction in an amount < 30% (m/m).

As already illustrated above with reference to the plant according to the invention, the pyrolysis in step II occurs in an embodiment of the invention in the presence of slag from a melting process, in particular at temperatures above 1,000 °C to obtain the fuels mostly in gaseous form. The term 'mostly' indicates an amount of at least 50% (m/m).

The features described for one aspect of the invention can be transferred mutatis mutandis to the other aspects of the invention, as noted by the interweaving of the descriptions of the plant and process according to the invention.

There are mainly two advantages in using light plastic fractions to produce fuel:

The costs of placing the non-marketable plastic fraction in landfill/cement plants are eliminated.

A fuel, in particular gas and/or oil, is produced with a commercial value of about 500 €/1000 litres of oil or 30 €/MWh for the gas.

Industrial applicability is obvious considering the waste is recovered from the automotive sector (ASR) to produce a valuable product (fuel and reducing agent) which can be used in other plants, such as steel mills.

Said objects and advantages will be further highlighted during the description of preferred embodiment examples of the invention provided by way of example, without limitation. Embodimentst and further features of the invention are the object of the dependent claims. The description of the preferred examples of execution of the plant and the process for the recovery of mixtures of plastics is provided by way of non-limiting example in the drawings appended hereto. In particular, unless specified otherwise, the number, shape, dimensions and materials of the plant and of the individual components may vary, and equivalent elements may be applied without deviating from the inventive concept.

DESCRIPTION OF PREFERRED EMBODIMENT EXAMPLES

Fig. 1 illustrates a schematic image of an embodiment of the plant for the pyrolysis of mixtures of plastics from ASR according to the invention with a reactor in the form of a rotary kiln.

Fig. 2 illustrates a block diagram of a plant and process for the treatment and recovery of ASR waste which includes the recovery of almost all the individual fractions obtainable from the separation of the ASR.

Fig. 3 shows an image of a fraction of low-density plastics suitable for feeding the pyrolysis plant according to the invention.

Fig. 4 shows an image of briquettes and granulated material produced by the fraction of low-density plastics of figure 3.

Fig. 5 shows an image of high-density plastic fractions after granulation.

Fig. 1 illustrates a schematic image of an embodiment of the thermochemical treatment plant of mixtures of plastics from ASR according to the invention with a reactor in the form of a rotary kiln. The thermochemical treatment plant is referred to overall with reference numeral 100 and includes a tank 102 which contains light plastics (a possible source for these materials is illustrated in figure 2) and optionally heavy plastics. From this tank 102 it is possible to add the aforementioned reagents by means of an automatic weight dispenser 104 and a feeder, for example of the screw or conveyor belt type 106, ensuring downstream, by means of an air exclusion system 108, the absence of oxygen, towards a rotary kiln or furnace with auger 111. The pyrolysis of the plastics occurs inside the rotary kiln 111, forming fuel in solid, liquid (oils) and gaseous form. The product containing these three fractions is conveyed into a separator 112, for example an oil scrubber, to separate the solids and oils 114, while the gases and vapours reach a washing unit 116 to remove any traces of HC1, nitrogen oxides or sulphur. An induced draft fan 118 sucks the purified gas which can be used as fuel 120 in any plant or be recycled to heat the rotary kiln 111 with relative burners 122, which can however also be fed by external gases 124 or resistors. The solid product 128 can be separated from the liquid fuel (oils) 130 for example by centrifugation in a centrifuge separator 126.

Fig. 2 illustrates a block diagram of a plant and a process for the treatment and recovery of ASR material 12 which includes the reuse of practically all the individual fractions obtainable from the separation of the ASR in an ASR treatment and separation plant 10 implemented by a thermochemical treatment plant 310 of the type illustrated in figure 1. The plant 10 essentially comprises a first part 110 for separating residues from the shredding of ELV (end of life vehicles) with shredders, for example ASR material 12, in the main components thereof and a second part 210 related to the preparation and sizing of plastics to be sent to a steel plant 40 such as a blast furnace, an electric arc furnace or the like or to the pyrolysis plant 310. Although in the description below reference will be made to the specific application of an electric arc furnace 40, the same considerations can also be referred in general to other steel plants.

The first part 110 related to the separation of materials and the sorting thereof basically comprises a single treatment line with a stream of material F. A granulator system 11 is included as a first element of this treatment line, which can be for example a mill with vertical rotor and rotating star cams, by means of which all the ASR material 12 is shredded, without prior screening, up to a size such as to optimize the recovery of the different fractions. The size of the granulated material can range from 0 to 30 mm, preferably from 0 to 20 mm. The function of the granulator system 11 is therefore to reduce the material in size, both through a material disintegration mechanism, which involves the separation of the different constituents of a composite material, such as metal cables, and by granulating the metal and plastic fraction. During this first dimension reduction step, as a consequence of the mechanisms of reciprocal friction between the materials, the latter are heated, favouring the reduction of residual humidity. A stream of mixed granular material of suitable size and density for subsequent treatments and a first fraction of light plastics 16 exits from such a granulator system 11.

A magnetic separation system 13 is provided downstream of the granulator system 11, for example a magnetic tape or drum system or any other system known per se, capable of separating the ferrous material fraction 14 from the rest of the granular material stream.

A density separation system 15 is included downstream of the magnetic separation system 13, which is used to remove light plastics 16, possibly also in the form of fibres, from the stream F of granular material.

The remaining granular material stream is sent to an induced-current separator system 19 which is intended to separate non-ferrous metal components or fractions 20 from the main ASR material stream. The induced-current separator system 19 is capable of producing a clean ejected fraction, for example aluminium, based on machine settings, and a remaining mixed fraction, which includes mixed plastic material and copper.

Following the induced-current separator system 19, a further screening separation system 21 can be provided, to separate a further fraction of light plastics 16, line 22, and the fraction of heavy plastics 24, line 23, from the main material stream.

The system can be integrated with various density separation or screening devices to obtain a more differentiated classification of the fractions of plastics by dimension and weight.

At least four fractions of materials are obtained from the process or method performed by the first part of the plant 110: a fraction of light plastics 16, mainly comprising fibres and polyurethanes; a fraction of heavy or hard plastics 24; a fraction of ferrous materials 14; and one or more fractions of non-ferrous metals 20, for example aluminium and copper.

To increase the purity of the one or more non-ferrous metal fractions 20, for example to divide the copper from the aluminium, a further induced-current separator system 28 can be included, whereby a separation of the main constituent components is obtained, for example an aluminium fraction 29 and a copper fraction 30.

As symbolized by the illustrated arrows, the aluminium fraction 29, the copper fraction 30, the ferrous material fraction 14 and the non-ferrous metal fraction 20 which have not been subjected to further treatment by the induced-current separator system 28, can be placed directly on the market, block 31. The light plastics 16 and heavy or hard plastics 24 can undergo further treatment steps in order to improve the dimensional and transportability characteristics thereof, see the second part of the plant 210 and especially for the purpose of making them suitable for use as additive material, which can be used for example as a reducing agent in steel plants such as electric arc furnaces 40, blast furnaces or the like or in reactors 111 for thermochemical treatment which will be illustrated below.

The present description of the specific ASR separation plant is merely one example. Other configurations of separator elements of individual ASR fractions, in particular of light and heavy plastic fractions, in other ASR separation systems can also be useful for the purposes of the invention to provide the plastic fractions intended for pyrolysis and do not depart from the scope of protection as defined in the claims.

The fraction of light plastics 16 can be bulky and thus difficult to transport and manage but still adapted to feed the pyrolysis reactor. If the material must be transported, thickening by means of a thermo-mechanical transformation system 32 is appropriate. The fraction of light plastics 16 and fibres is transformed into a series of briquettes or compact cylinders, which have a high density and high mechanical features.

The thermo-mechanical transformation system 32 can comprise, by way of example only, an extruder, known per se, provided for example with two augers capable of compressing the plastic material. The compression of the plastic material causes an increase in the temperature, solely by pressure and friction, until the portion of thermoplastic materials present in the fraction of light plastics 16 softens. Through such a system it is therefore not necessary to provide heat, as it is the pressure and friction between the plastics which generate an increase in temperature, which can be varied by modifying the stream of material, so as to adjust it according to needs and the material.

Optionally, binding additives such as thermoplastic materials, coal, sawdust and other biomass can be added during the extrusion step.

As a function of the use of the briquettes or plastic cylinders obtained by the previous steps, it is possible to include a cutting and/or grinding system 33, located downstream of the thermo mechanical transformation system 32 and adapted to obtain material in granular form, line 38, which is used as an additive material, having for example the function of reducing agent 34, to be fed to the furnace 40 or to be fed to a pyrolysis reactor 111. Such a cutting and/or grinding system 33 can include, for example, a cutting mill, known per se and whose operation is based on a rotating cylinder provided with knives and a grille which allows the exit of the material having a certain size or cut.

Merely by way of example, it can be included that the material exiting the cutting and/or grinding system 33 has a size or cut ranging from 2 to 6 mm or any other cut appropriate for subsequent introduction into the furnace 40. Alternatively, the cylinders or briquettes, obtained by the thermo-mechanical transformation system 32, can be used directly as additive material, having for example the function of fuel (line 41) or reducing agent 34, line 39.

The fraction of heavy plastics 24 can also be sent to the grinding process, for example in the same cutting and/or grinding system 33 described above, so as to obtain a more homogeneously sized fraction.

In any case, it can be expected that the fraction of heavy plastics 24 will be used as is, without further treatment, as reducing agent. As can be seen, the heavy plastics 24 in granular form can be placed directly on the market of reducing agents, block 37.

As mentioned at the beginning of the description, the additive material, having for example the function of reducing agent 34 obtained from light plastics and heavy plastics can advantageously be used at least partially to replace carbon in a furnace 40, for example an electric arc furnace 40. In the case of use of granulated plastic material, line 38, as additive material 34, such granulated material can be pneumatically injected under the slag through the use of a pneumatic lance. Alternatively, as mentioned, the briquettes or cylinders produced, line 39, can be fed directly to the furnace 40. In this case the briquettes will be loaded inside the feeding basket of the furnace. Table 2 below compares the chemical composition of carbon typically used in an electric arc furnace (EAF), i.e., metallurgical coke, and the ashes thereof, with a composition example of additive material 34 (called SynCa, synthetic carbon), consisting of the mixture of recycled plastics (consisting of a mixture of light and heavy fraction) and the ashes thereof. Table 2

* averaged data obtained from experimentation. They are intended as a reference and not as a precise value.

But often lightweight plastics have too low a calorific or reducing value to be used as additives in furnaces. In order to avoid the transfer thereof to landfills or cement plants, the depicted plant has been integrated with a plant for the thermochemical treatment 310 thereof.

The light plastics 16, despite their processing in the device 32, being non-optimal- due to the low calorific value and/or reducing power - for use in the furnace 40 it is sent to a rotary kiln 111 in which it is heated, optionally together with heavy plastics. The plastics are transformed into fuel 120, 130 which can partly feed (arrow 121) the rotary kiln 111 and partly be used in other parts of the plant (block 123) or in melting furnaces 40 of steelworks (arrow 131). The solid products 128 of the reactions occurring in the rotary kiln 111 can feed the electric furnace 40 (arrow 129).

In the furnace 40, for example electric arc furnace, the advantages of adding polymers are not only linked to economic savings in replacing at least part of the carbon with a recovery material, which is cheaper than carbon. If managed correctly, the injection of the polymer fraction allows to obtain a slag with high foaming properties, capable of shielding the arc and therefore reducing energy consumption and noise problems in the plant.

In the application in furnaces 40, for example electric arc furnaces, some potentially negative features of the plastic fractions are easily managed. The presence of ferrous metal residues is positive, the presence of metal residues such as copper and aluminium (already separated for the most part by parasitic currents) can be easily managed through the percentage of carbon substitution, thus through dilution.

Another advantageous possibility is to continuously monitor the quality parameters of the steel and slag so as to manage the flow of fuel (for example fuel 131 from the pyrolysis plant 310) or reducing agent, such as SynCa (synthetic carbon), indicated in block 34, or solid fuel 128 which can be fed so as not to affect the quality of the steel. Therefore, compared to other technologies for using ASR material, the present method and the present plant advantageously produce a waste fraction to be landfilled below 5% by weight of the total: all the fractions find a use thereof in the market or become a substitute for carbon or are treated in a pyrolytic reactor to produce fuels.

Compared to other technologies for the partial replacement of coal in the electric arc furnace EAF, the present method and the present plant produce a fraction of plastics cleaned of metals, mainly by virtue of the steps carried out in the first part of the plant 110

Compared to other technologies for the partial replacement of carbon in EAF furnaces, the present method and the present plant produce a fraction which can be pneumatically injected under the slag, allowing a better control of the amount added, a better use of the material with respect to basket loading, and avoids the possibility of being sucked into the flue gas system before performing the function thereof.

Furthermore, the light or heavy plastics, treated as described above, as such, in granular or briquetted form, can be used to produce fuels or reducing agents for use in furnaces in a plant for the pyrolysis 310 thereof.

Fig. 3 shows an image of a fraction of low-density plastics suitable for feeding the pyrolysis plant according to the invention.

Fig. 4 shows an image of briquettes (above) and granulate material (below) produced by the fraction of low-density plastics of figure 3, in this regard the material visible in figure 3 has been previously reduced in size < 30 mm, for example with a grinder described in the aforementioned Italian patent, and as such could be fed to the pyrolysis reactor. Light plastics can also be fed in granular form with a preferential size < 10 mm obtained by briquette production and subsequent granulation.

An example of the composition and calorific value of the material shown in figures 3 and 4, i.e., the light, non-granulated or granulated fraction of the mixture of plastics separated from ASR, is given in table 3 below: Table 3

Fig. 5 shows an image of high-density plastic fractions after granulation (size < 10 mm), i.e., of a fraction of heavy plastics. The following table 4 shows an example composition and calorific value of the high-density polymer fraction shown in figure 5.

Table 4

During implementation, further embodiment modifications or variants not described herein can be added to the plant and the process for the recovery of plastic mixtures from ASR, object of the invention, without thereby departing from the scope of the invention. If such modifications or such variants should fall within the scope of the following claims, they should all be considered protected by the present patent. In practice, the materials used, as well as dimensions, numbers and shapes, as long as they are compatible with the specific and not otherwise specified use, may be different, according to requirements. Although the present invention has been described with reference to specific examples, those skilled in the art will certainly be able to produce many other equivalent forms of plants, having the features expressed in the claims and therefore all of which falling within the scope of protection defined by them.