Title: METHOD FOR THE AUTOTHERMAL TREATMENT OF MATERIALS CONTAINING A MIXTURE OF PLASTIC AND

METAL MATERIALS

[1 ] CROSS-REFERENCE TO RELATED APPLICATIONS

[2] The present application claims priority to French Application No. 2201546 filed with the Intellectual Property Office of France on February 22, 2022 and entitled “METHOD FOR THE AUTOTHERMAL TREATMENT OF MATERIALS CONTAINING A MIXTURE OF PLASTIC AND METAL MATERIALS,” which is incorporated herein by reference in their entirety for all purposes.

[3] FIELD OF THE INVENTION

[4] The present invention belongs to the field of destruction and recycling of electronic waste.

[5] The present invention relates to a method for recovering metals contained in electronic waste, in particular used electronic boards, as well as to a plant suitable to the implementation of this method while limiting energy consumption.

[6] TECHNICAL BACKGROUND

[7] The increase in the use of electronic devices and other high-tech devices with a short lifespan such as smartphones, computers, video game consoles, servers for online data storage, on-board electronics in cars and other means of transportation, and more generally all electronics integrated into household appliances, generates an exponential amount of waste generally containing ferrous metals, copper, aluminum, zinc, rare and precious metals. This situation poses the problem of the recovery and treatment of the metals contained in these wastes. Thus, such wastes constitute a real metal deposit and a significant source of pollution.

[8] Metal recovery techniques are known and described in the literature, in particular in patent application W02007/099204 or in patent application EP 1 712 301 .

[9] However, not only are some of the above techniques expensive (especially due to the fine shredding required in some of them), but most of them provide imperfect sorting and often result in poor precious metal recovery performance.

[10] These techniques also have the disadvantage of being very energy consuming. These techniques are no longer in line with the evolution of standards that seek to limit the impact on the environment and reduce the use of fossil fuels. [11] Other metal recovery techniques, such as the one described in WO2010/055489, are also known. This technique, although it solves some of the problems mentioned above, comprising obtaining better yields, is still very energy consuming.

[12] Therefore, there is a real need to develop a method for the recovery of metals from electronic waste that overcomes the above-mentioned disadvantages. In particular, it is desirable to develop a simple method, consuming a minimum of energy, and not requiring a heavy treatment of the emitted gases, while allowing to obtain a good yield of recycled metals.

[13] DESCRIPTION OF THE INVENTION

[14] The invention relates firstly to a method for treating materials containing a mixture of plastic and metal materials, said method comprising the steps: a) shredding the materials to be processed, preferably to a shredded material with a diameter less than or equal to 30 mm; b) introducing the shredded materials obtained in step a) into a pyrolysis furnace , said pyrolysis furnace comprising 6 to 15 hearths, preferably 6 to 11 hearths; c) pyrolysis of the shredded materials in the furnace; d) injection of outside air into the pyrolysis furnace and partial combustion of the pyrolysis gases within said pyrolysis furnace, preferably the partial combustion is an amount of less than or equal to 5 % vol. of the gases resulting from the pyrolysis; characterized in that:

- the pressure in the pyrolysis furnace is lower than the external pressure, preferably 4 to 5 mmWg lower than the external pressure,

- the pyrolysis reaction is carried out at a temperature ranging from 350 to 650°C, preferably 500 to 550°C,

- the pyrolysis in step c) and the partial combustion in step d) are carried out under a reducing atmosphere.

[15] Advantageously, in step a) of the method according to the invention, the materials to be processed may be shredded by means of an industrial shredder comprising at least one rotor, preferably from one to four rotors, and preferably single rotor, with a calibration grid for elements with a diameter of less than 30 mm.

[16] Advantageously, the materials to be processed may be electronic waste, preferably used electronic boards. The shredding may be carried out up to a sieve pass having a maximum diameter (Dmax) of less than or equal to 30 mm. Step a) of the method according to the invention may be optional, in particularwhen the materials to be processed have undergone an upstream shredding or when they already have a maximum diameter less than or equal to 30 mm.

[17] Advantageously, the material to be processed has a content of volatile compounds (or volatile rate), in percentage by weight, in the range of 30 to 50%, preferably 35 to 45%.

[18] Advantageously, the method according to the invention may further comprise a step of determining the volatile rate of the material to be processed. This step is carried out upstream or in parallel with step a). It may also be carried out from a sample of shredded material obtained in step a).

[19] Advantageously, the lower calorific value of the material to be processed is preferably greater than or equal to 7000 kcal/kg, preferably within a range of 7000 kcal/kg and 9000 kcal/kg.

[20] Advantageously, the method according to the invention may further comprise a step of determining the lower calorific value of the material to be processed. This step is carried out upstream or in parallel with step a). It may also be carried out from a sample of shredded material obtained in step a).

[21] Advantageously, in step b) of the method according to the invention, the materials may be fed into the pyrolysis furnace continuously or sequentially, and/or in an automated or manual manner. In step b), the furnace may be fed continuously with an hourly tonnage generally ranging from 2 tons to 12 tons per hour.

[22] Advantageously, the pyrolysis step c) may be conducted at a temperature ranging from 350 to 650°C, preferably 500 to 550°C. The pressure in the pyrolysis furnace is lower than the external pressure, preferably 4 to 5 mmWg lower than the external pressure. The pyrolysis in step c) is carried out in a reducing atmosphere.

[23] Advantageously, the air factor in the pyrolysis furnace may range from 0.7 to 0.98.

[24] Advantageously, the method according to the invention may further comprise a step c') of measuring the temperature in the furnace in step c). The temperature measurement may be carried out by means of a temperature probe, directly integrated in the pyrolysis furnace.

[25] Advantageously, in step d) of the method according to the invention, external air is injected into the pyrolysis furnace. By means of this air injection, it is possible to achieve partial combustion of the pyrolysis gases within the pyrolysis furnace. Preferably, the partial combustion of the pyrolysis gases in the pyrolysis furnace is less than or equal to 5% of the total pyrolysis gases. The partial combustion in step d) is carried out in a reducing atmosphere.

[26] Advantageously, the method according to the invention may further comprise a step d') of regulating the air injection of step d) as a function of the result of the temperature measurement of step c'). Preferably, the regulation of step d') is carried out so that the difference (in absolute value) between the setpoint temperature (temperature target for pyrolysis) and the actual temperature (measured within the furnace) is less than or equal to 20%, preferably less than or equal to 10% (|T°s _e tpoint - T°Actual| / 100).

[27] Advantageously, the air flow rate of the regulation of step d') may be carried out according to the following formula:

((T Setpoint " T Actual) / 1 00) * k*D max ^— Dcontrol, where, the setpoint temperature (T°setpoint) is the desired temperature for the pyrolysis reaction, the actual temperature (T°Actuai) is the temperature measured in a hearth, Dmax is the maximum air injection rate into the pyrolysis furnace, Dcontroi is the control rate of the air injection of step d).

[28] Advantageously, the coefficient k (unit T ^0-1 ) may be determined according to the intrinsic technical properties of the pyrolysis furnace, it may be qualified as a reactivity or sensitivity factor, a high k value will increase the air supply in the hearth and thus the energy related to the combustion process. The coefficient k may be determined according to the internal volume of a pyrolysis furnace hearth according to the formula k = V _he arth /20. For example, if a pyrolysis furnace hearth is 40 m ³ , then the coefficient k is equal to 2.

[29] When the actual temperature is lower than the setpoint temperature, the system regulates itself (e.g. opening of the regulation valves), allowing air to enter the reactor for the partial combustion of the gases resulting from the pyrolysis in the said pyrolysis furnace, until the actual temperature is equal to the setpoint temperature. The regulation of the system is proportional to the temperature difference between T° _se tpoint and T°actuai. When the actual temperature is higher than the setpoint temperature, the external air supply is reduced until the air supply is interrupted (e.g.: the control valves are closed).

[30] The regulation of the air injection, allows a direct control, in real time of the temperature, by the control of the quantity of gases resulting from the pyrolysis burned to generate calories in the furnace. The temperature regulation step d'), allows when the pyrolysis temperature becomes too high or too low, to regulate the volume of air injected in the pyrolysis furnace in step d), and thus the partial combustion of the pyrolysis gases. During the implementation of the method, a setpoint temperature is determined. According to the above algorithm, the difference between the setpoint temperature and the actual temperature determines the amount of air injected into the pyrolysis furnace in step d), and thus the amount of pyrolysis gases that will undergo combustion.

[31] The steps d) of injecting outside air and d') of regulating the air injection allow the following parameters to be maintained:

- the pyrolysis reaction is conducted at a temperature ranging from 350 to 650°C, preferably 500 to 550°C, and

- the air factor in the furnace is maintained in a range from 0.7 to 0.98.

[32] Advantageously, the method according to the invention may further comprise a step e) of total combustion, under oxidizing atmosphere, of the remaining gases resulting from the pyrolysis of step c) in an post-combustion chamber. By "remaining gases" is meant the gases from step c) which are not burned in step d) to maintain the temperature in the furnace.

[33] Advantageously, step e) may be followed by a step f) of gas neutralization with sodium bicarbonate.

[34] Advantageously, the method according to the invention may further comprise a preliminary step a') of preheating the furnace, by means of burners integrated into the pyrolysis furnace and maintaining the temperature within a range of 350 to 650°C, preferably 500 to 550°C, said step a') being carried out until the amount of energy generated in step d) is sufficient for the method to operate in autothermal mode. Step a') is carried out before step c). Step a') constitutes the start-up of the method according to the invention. At this stage, there is no autothermal mode of the method yet. It is the initiation of the method. Step a ¹ ) is stopped as soon as the conditions for maintaining the temperature by autothermal mode are met in the device in which the method is carried out. The method according to the invention is the stationary regime following step a'). The duration of step a') may be in the range of 24 to 72 hours, depending on the size of the furnace and the number of hearths.

[35] The result of the pyrolysis of the materials to be processed is the obtaining of pyrolysis gases and pyrolyzed (solid) materials. The (majority) fraction of the pyrolysis gases (which is not burnt in step d)) is burnt in the post-combustion chamber in step e). The pyrolyzed materials are extracted from the pyrolysis furnace and may undergo subsequent processing. They may be extracted continuously or sequentially, and/or automatically or manually, in quantities ranging from 1 to 6 tons per hour.

[36] Advantageously, the method according to the invention may further comprise:

- a step g) of first magnetic separation carried out on the pyrolyzed materials, providing on the one hand a ferrous metal fraction and on the other hand non-ferrous residues, followed by

- a step h) of second magnetic separation carried out on the non-ferrous residues, providing on the one hand a non-ferrous metal fraction and on the other hand nonmagnetic residues comprising precious metals, the first magnetic separation being carried out by means of a magnet or electromagnet. Step h) may be carried out by means of an eddy current separator.

[37] Advantageously, the first magnetic separation g) may be carried out by means of a magnet or electromagnet.

[38] Advantageously, the second magnetic separation h) may be carried out by means of an eddy current separator.

[39] Advantageously, the ferrous metal fraction may comprise iron and/or iron derivatives, and eventually gold.

[40] Advantageously, the non-ferrous metal fraction may comprise aluminum and/or zinc.

[41] Advantageously, the non-magnetic residues may comprise copper, lead, tin, glass fibers, carbon and/or precious metals, comprising gold, silver, platinum, palladium, rhodium, ruthenium, iridium and/or osmium.

[42] Advantageously, the ferrous metal fraction may be combined with the nonmagnetic residues after the second magnetic separation.

[43] Advantageously, the method may further comprise a subsequent step i) of treatment of the non-magnetic residues allowing to recover the copper contained in the non-magnetic residues and/or to recover precious metals contained in the nonmagnetic residues, in particular selected from gold, silver, lead, tin, platinum, palladium, rhodium, ruthenium, iridium and/or osmium.

[44] DEFINITIONS

[45] Electronic waste: electronic waste is defined as used materials comprising electronic components. Electronic waste may comprise individual electronic components, smartphones, computers, video game consoles, servers for online data storage, on-board electronics in cars and other means of transportation, and more generally all electronics integrated into household products, and any other appliances containing electronic boards. Preferably, the electronic waste comprises or consists of electronic boards, i.e., boards consisting of printed circuits on which electronic components are soldered. The remainder of the method is therefore described in relation to the recycling of electronic boards. However, the method may also be applied to other types of starting materials, i.e. generally materials (preferably used or waste materials) comprising a metal fraction (in particular a metal fraction containing precious metals) and a plasticfraction. The plastic fraction may comprise epoxy resins, polyethylene or polyvinyl chloride. And the metal fraction may comprise ferrous metals, copper, lead, aluminum, zinc, precious metals (gold, silver, platinum, palladium, rhodium, ruthenium, iridium, osmium). For example, the method may be applied to automotive shredder residues. Preferably, the used materials comprising electronic components have a volatile rate ranging from 30 to 50%, preferably 35 to 45%. Preferably, the used materials comprising electronic components have a lower calorific value of at least 7642 kcal/kg.

[46] LCV: "Lower Calorific Value" is defined as the amount of heat released by the complete combustion of a unit of combustible, the water vapor being assumed to be non-condensed and the heat not recovered.

[47] HCV: "Higher calorific value" is defined as the amount of energy released by the complete combustion of a unit of combustible, the steam being assumed to be condensed and the heat recovered.

[48] Volatile rate: Volatile rate is defined as the result of a fire loss test expressed as a percentage by weight of dry matter. Change in mass resulting from heating a solid sample under specified conditions. The test method may be carried out according to the following standards EN 15402 or EN 12879.

[49] Pyrolysis: pyrolysis is defined as the chemical decomposition of a substance obtained by intense heating in the absence of oxygen (i.e. in a reducing atmosphere).

[50] Autothermal mode: "Autothermal mode" is defined as the maintenance of the temperature necessary for the pyrolysis reaction is ensured entirely by the energy generated within the reactor by the partial combustion of the pyrolysis gases, when the method operates in stationary regime (i.e. when its start-up is completed). Autothermal mode is maintained by the combination of temperature and reducing atmosphere. Autothermal mode is the result of fine-tuning the air injection in step d) to the temperature of the furnace. See step o') temperature measurement and step d') and the algorithm for controlling the air injection according to the temperature measurement.

[51] Air factor: "Air factor" is defined as defined as the ratio between the measured air volume and the volume of the air/gas mixture of a stoichiometric combustion (Vmeasured air I Vmixture).

[52] Reducing atmosphere: in general, "reducing atmosphere" is defined as a gas essentially free of oxygen, i.e. whose O2 volume % does not exceed 6% of the total quantity of gas. The term "reducing atmosphere" is thus used in the pyrolysis furnace chamber when the % by volume of O2 does not exceed 6% of the total quantity of gas in the furnace chamber. In the specific context of the invention, the reducing atmosphere for the implementation of the method according to the invention is a gas whose O2 volume % does not exceed 1 % of the total amount of gas. Thus, in the context of the invention, when one speaks of a reducing atmosphere in the pyrolysis furnace chamber, it is referring to the embodiment in which the % by volume of O2 does not exceed 1 % of the total quantity of gas in the furnace chamber.

[53] Oxidizing atmosphere: "oxidizing atmosphere" is defined as a gas comprising oxygen, that is to say whose % of O2 is higher than 6%.

[54] Shredding means: the shredder may be an industrial type shredder and must be equipped with a sieve having a Dmax less than or equal to 30 mm. The shredder may be an industrial type shredder comprising at least one rotor, preferably one to four rotors, and preferably a single rotor, with a calibration sieve for elements with a diameter of less than 30 mm.

[55] The method according to the invention may be carried out in a Multiple Hearth Furnace (MHF). Multiple hearth furnaces are incineration or pyrolysis devices generally used for paste-like waste, sludge and shredded solids which are introduced into a deck cylinder and swept from upper deck to lower deck by horizontal arms. Incineration or pyrolysis is done progressively. In the context of the invention, the pyrolysis furnace may comprise multiple hearths. The furnace may comprise from 6 to 15 hearths, preferably from 6 to 11 hearths. The furnace may comprise a central shaft, with the hearths arranged along the central shaft. A furnace is generally composed of a hearth, an air injection point vault or burners and four arms comprising rabbles, said arms forming helical paths. "Central shaft" is defined as the axis of rotation on which the arms are fixed. The speed of rotation of the shaft is generally between 1 and 3 rpm, preferably between 2 and 3 rpm for the purposes of the invention.

[56] Advantageously, in the method according to the invention, steps a, a', b, c, c', d, d', e, f, g and h may be carried out simultaneously when carrying out the method according to the invention.

[57] The invention also relates to a pyrolysis furnace 1 comprising:

- a first inlet 11 of materials containing a mixture of plastic and metal materials;

- a set of double flap valves 12, preferably a set of two double flap valves 12, connected to the inlet 1 1 ;

- a pyrolysis reactor 13 comprising from 6 to 15 hearths 14, preferably from 6 to 11 hearths 14, and a central shaft 15, connected to the set of valves 12 ;

- a set of modulation valves 16, connected to the pyrolysis reactor 13;

- a second air inlet 17 connected to the set of modulation valves 16;

- a first outlet 18 of pyrolyzed materials connected to the pyrolysis reactor 13; and

- a second outlet 19 connectable to an post-combustion chamber 2 independent of the pyrolysis furnace 1 .

[58] “Connected" is defined as a direct or indirect connection between two elements.

[59] Advantageously, the first inlet 11 may be connected to at least one shredding means 3. The first inlet 11 may be connected to a set of valves 12. The valves 12 may be double flap valves (e.g., pendulum valve). The use of double flap valves ensures that the furnace is sealed when the shredded materials are introduced in step b) of the method according to the invention. The first inlet 11 may comprise at least two double flap valves, and preferably two valves. Preferably, the first inlet 11 divides into at least two inlets, via a distribution system, each controlled by a double flap valve 12. The distribution system may be a fixed 50/50 (mass ratio) distribution system.

[60] Advantageously, the pyrolysis reactor 13 may comprise from 6 to 15 hearths 14. Preferably, the pyrolysis reactor 13 comprises from 6 to 1 1 hearths 14. The reactor may have a volume/dimensions ranging from 200 to 380 m ³ . Each hearth, whether identical or different, may have a volume ranging from 30 to 40 m ³ . The hearths 14 may further comprise at least one burner. Each hearth may have up to two burners. These burners allow the implementation of step d) of the method according to the invention. The burners may be gas burners, for example of the EMB3 type, and may be supplied with natural gas. The central shaft may comprise 4 arms per hearth. The central shaft is hollow and is configured to allow the circulation of air in the shaft and to avoid deformations or alterations related to the increase of its temperature, without this air coming into contact with the inner part of the pyrolysis reactor 13. The shaft may comprise a water seal 20 at its ends. Water seal means a water guard preventing the air circulating in the shaft from entering the furnace. The reactor 13 may further be provided with temperature sensors (preferably two temperature sensors). The temperature sensors may be generally positioned on the inner wall of the reactor. The temperature sensors may be thermocouples.

[61] Advantageously, a set of modulation valves 16 is connected to the pyrolysis reactor 13. The modulation valves 16 are arranged halfway up each furnace hearth. The furnace 1 may comprise at least one modulation valve 16 per hearth 14. The modulation valves 16 may be of any type. The modulation valves (also known as automatic valves) may be equipped with positioning sensors that indicate a percentage of opening and closing of the valve. Each valve may be controlled by an actuator whose continuous variations in position change the size of the orifice through which the fluid (in this case air) passes. In this way, the pressure drop across the valve is modulated when a fluid passes through, with the result that the flow rate through the valve is controlled. This makes it possible to open or close the valve in an extremely precise way according to the regulation required by the step d’). The modulation valves 16 allow the regulation of the step d').

[62] Advantageously, the second air inlet 17 may be connected to the modulating valve assembly 16. The second air inlet 17 may comprise a fan, a control valve and one or more temperature sensors. The second air inlet 17 may comprise one or more distribution systems for distributing air to the various modulation valves 16.

[63] Advantageously, the first outlet 18 is used to discharge the pyrolyzed materials (solids) from the pyrolysis reactor 13. The first outlet 18 is connected to the pyrolysis reactor 13.

[64] Advantageously, the second outlet 19 is used to discharge the gases resulting from the pyrolysis of the materials to be processed, from the pyrolysis reactor 13 (the fraction that was not burned in step d)). The second outlet is connected to an afterburning chamber 2 independent of the pyrolysis furnace 1 .

[65] Advantageously, each double flap valve 12 may be equipped with measurement points to monitor the flow rates. The control valves 16 are configured to adapt the air injection in order to homogenize the combustion according to the temperature and the control algorithm of step d’). [66] The combustion thus made, is carried out according to the addition of air thus limiting the use of the burners. The method according to the invention, in stationary regime, is self-supplied with energy by the partial combustion of the pyrolysis gases and operates in autothermal mode.

[67] The invention also relates to a plant for processing materials containing a mixture of plastic and metal materials comprising:

- at least one shredding means 3;

- a pyrolysis furnace 1 according to the preceding claim; and

- an post-combustion chamber 2.

[68] Advantageously, the shredding means are adapted to perform a shredding down to a sieve pass Dmax less than or equal to 30 mm. The shredding means 3 may be an industrial shredder. It may comprise at least one rotor, preferably from one to four rotors, and preferably single-rotor, with a calibration grid for elements with a diameter of less than 30 mm.

[69] Advantageously, the plant according to the invention may further comprise a primary magnetic separator. The primary magnetic separator may comprise a magnet or electromagnet arranged above a conveyor belt.

[70] Advantageously, the plant according to the invention may further comprise a secondary magnetic separator. The secondary magnetic separator may comprise an eddy current separator.

[71] Advantageously, the plant according to the invention may further comprise a pyrolysis gas collection line 21 feeding the combustion chamber 2, and possibly, at the outlet of the combustion chamber, a contact chamber 4 fed by an input of activated carbon and an input of sodium bicarbonate. The pyrolysis gas collection line 21 feeds a combustion chamber 2, which is also fed by an air supply line (not shown). The combustion chamber 2 may be of the cylindrical metal chamber type protected by one or more layers of bricks.

[72] Advantageously, at the outlet of the combustion chamber 2, a collection pipe for the combustion products feeds the cooling means. The cooling means may for example consist of a cooling tower, fed by a water spray injection, or a flue gas cooling exchanger (air-flue gas or water-flue gas). A collection pipe for the cooled combustion products is connected to the outlet of the cooling means and feeds a contact chamber. A supply of activated carbon and a supply of sodium bicarbonate are also provided at the inlet of the contact chamber. The contact chamber may be of the cylindrical type with a sufficient volume to have a residence time of the combustion products of about two seconds. At the outlet of the contact chamber, a collection pipe for the treated products feeds a filter at the outlet of which a line for the recovery of purified gases and a line for the recovery of halogens are provided. The filter may be of the bag filter or electro-filter type. A preliminary cooling system may be provided upstream of the cooling means. This preliminary cooling system comprises a sampling line at the outlet of the combustion chamber, which feeds an exchanger, then joins the collection line of the combustion products. The exchanger is also fed by a heat transfer fluid supply. The heat transfer fluid outlet ensures energy recovery.

[73] Advantageously, the plant according to the invention may comprise a storage means positioned between the shredding means 3 and the furnace 1. This may be a silo.

[74] The present invention overcomes the drawbacks of the prior art. In particular, it provides a simple and particularly energy-efficient method for obtaining a good yield of recycled metals.

[75] The direct pyrolysis of materials previously only coarsely shredded (fine shredding is not necessary) allows to obtain a direct mixture of the different constituents in individualized form: in particular the carbonaceous residues on the one hand and the different metals on the other hand.

[76] The method according to the invention also makes it possible, thanks to the autothermal phase (steps c, c', d and d'), to considerably limit the energy consumption in the treating of materials containing a mixture of plastics and metals.

[77] Advantageously, the invention also has one or more of the advantageous features listed below.

[78] The method according to the invention makes it possible to eliminate the epoxy resins and the plastics constituting the electronic boards as well as the chlorine and a great part of the bromine while avoiding a loss of metals by oxidation or distillation taking into account the low temperature and the non-oxidizing conditions of the operation. The material is thus concentrated in metals. The method according to the invention allows during the cooling of the combustion gases produced during the pyrolysis to recover under good conditions the energy contained in these gases. The material thus pyrolyzed may be treated advantageously in the traditional tools of copper metallurgy by freeing itself from certain technological limits of these tools and more precisely from the content of volatile materials (carbon chains) and halogens. In the case of the treatment of electronic boards, the decomposition of epoxy resins during pyrolysis has the effect of releasing all the components attached to the support: copper, electronic components, metallic components. The method according to the invention maximizes the metal recovery yield, i.e. minimizes the metal losses during the method. And above all, the autothermal operation of the method, thanks to the partial combustion of the gases resulting from pyrolysis in the pyrolysis furnace in order to regulate the temperature, makes the method according to the invention almost independent of fossil energy during the implementation of the method.

[79] The method according to the invention also makes it possible to separate the aluminum from the other metals during the method, so as to facilitate the downstream treatment of the recovered metals. In the case of pyro-metallurgical methods, the aluminum presents a behavior which is detrimental to the fluidity of the slag. In the case of hydro-metallurgical methods, aluminum, because of its chemical reactivity, leads to an overconsumption of chemical reagents. The treatment of the gases resulting from pyrolysis (comprising post-combustion) makes it possible to make the method clean without requiring heavy handling of halogens, sulfur compounds or heavy metal emissions.

[80] BRIEF DESCRIPTION OF THE FIGURES

[81] [Fig. 1] Figure 1 shows schematically an example of a pyrolysis furnace according to the invention, the reference signs corresponding to those given above.

[82] [Fig. 2] Figure 2 shows a schematic representation of a material processing plant for materials containing a mixture of plastic and metal materials according to the invention, the reference signs corresponding to those given above.

[83] [ Fig. 3] Figure 3 shows the gas consumption of the plant in the example below, over a period from January 2021 to December 2021 (kWh).

[84] EXAMPLE

[85] The invention is now described in more detail and in a non-limiting manner in the following example application.

[86] Treatment of electronic waste in autothermal mode.

[87] With reference to Figures 1 and 2, a treatment plant for electronic waste according to the invention schematically comprises the following. The example corresponds to the use of the treatment plant described in Figure 2, in connection with the furnace in Figure 1. [88] At the entrance of the treatment plant there is a supply line for bulk electronic waste. This electronic waste supply line feeds shredding means 3. The shredding means comprise a shredder of the knife type allowing the size of the waste to be reduced to a Dmax of less than 30 mm.

[89] The raw material to be processed comes from a precious metal concentration facility for electronic waste. It is mainly electronic boards. The following calculations and assumptions are based on samples taken during the month of November 2020.

[90] Determination of the lower calorific value of the sample

[91] The materials to be processed are electronic cards from waste electrical and electronic equipment. Laboratory measurements were carried out in order to measure the lower calorific value of the material to be processed.

[92] For the measurement of the lower calorific value of the material sample to be processed, the received materials were shredded to a size smaller than 30 mm in order to achieve optimal sample analysis. Some materials that were too hard to be shred were extracted and counted as inert in the analysis and calculation.

[93] The following tests have been carried out according to the indicated standards in order to evaluate the different characteristics of the material mixture to be processed:

- Humidity according to EN 15414-3 ;

- Volatile according to EN 15402 ;

- Ash according to EN 15403;

- Carbon, hydrogen, nitrogen analysis according to EN 15407;

- Higher Calorific Value (HCV).

[94] Since it is not the product itself that burns but rather the gases resulting from pyrolysis. We need to evaluate the LCV of the gases themselves. To do this, we have made the following assumption:

- No oxygen is released from pyrolysis,

- 100% of the volatile matter is released,

- 100% of the ashes remains solid,

- Part of the carbon is gasified,

- Part of the carbon remains solid (char).

[95] Under these assumptions and considering the different energy levels required to form CO2, H2 O and NO2, and respecting the measured proportions, a Carbon base molecule was considered with an LCV of 9915.975 kcal/kg (41160 kJ/kg or 26203 kJ/Nm3).

[96] The "No Oxygen" assumption being quite strong, a more realistic gas was considered with 20% oxygen released by the pyrolytic method. This gives a recalculated LCV of 7642 kcal/kg (31945 kJ/kg or 25586 kJ/Nm3).

[97] The result of this measurement of the lower calorific value of the material to be processed is 7642 kcal/kg.

[98] The material to be processed has a volatile rate of about 30-50%.

[99] Implementation of the method according to the invention.

[100] As the calorific value of the material to be processed is satisfactory, the method is carried out in the reactor and the plant according to figures 1 and 2.

[101] In step a), the electronic boards are shredded at the shredding means 3. The shredding is preferably carried out to a size Dmax of 30 mm (Dmax being defined as the sieve pass). The shredded cards are then stored in a silo (not shown) arranged between the shredding means 3 and the pyrolysis furnace 1 .

[102] In step b), the materials shredded in step a) are then introduced into the reactor 13 of a pyrolysis furnace 1 of the method according to the invention. The silo feeds the pyrolysis furnace 1 at about 3 tons per hour, via the first inlet 1 1 .

[103] The first inlet 1 1 comprises a distribution system and two double flap valves 12. The double flap pendulum valves 12 ensure the tightness of the pyrolysis furnace inlet 1 : they act as an airlock and thus prevent any uncontrolled air supply. This system further allows the quantity of raw material injected into the furnace to be divided into two separate points.

[104] The pyrolysis furnace 1 is an MHF type furnace (Multiple Hearth Furnace), whose reactor 13 has a volume equal to 100 m ³ .

[105] In parallel to step a), step a') of preheating the furnace is carried out. The burners of the different hearths are activated until the internal temperature reaches the setpoint value of 500°C.

[106] The power of the plant is about 1000 kW. Reactor 13 has 6 hearths 14.

[107] The duration of step a ¹ ) is 60 hours: the furnace is heated to a temperature of about 500°C in the reactor 13, essentially in the absence of oxygen (in a reducing or neutral medium % 02 = 0). More precisely, the burners of the hearths 14 are regulated with an air defect and the air factor (ratio between the combustion air and the theoretical neutral combustion air) is between 0.7 and 0.9. At the end of step a'), the pyrolysis temperature of step c) is 500°C.

[108] When the temperature in reactor 13 reaches 500 degrees, step a') is completed (burners are turned off) and steps c) and d) are carried out and the shredded materials may then be fed into the furnace.

[109] The duration of the pyrolysis is adjusted in order to obtain a complete decomposition of the carbon chains composing the plastic fraction (in particular the chains of epoxy resins). For example, the duration is about 30 minutes. The furnace shaft is rotating constantly (approx. 2 rpm), the shredded material spends approximately 7 minutes in each hearth before going down to the lower hearth or the outlet.

[110] In practice, only one pilot burner is kept in operation per hearth in order to comply with the EN 746-2 standard. This burner does not participate in maintaining the temperature of furnace 1. It is independent of steps c) and d). This burner is a safety measure to avoid any potential explosion, it only provides a flame and its calorific contribution is negligible.

[111] The pyrolysis furnace comprises the elements described in figure 1 .

[112] The pyrolysis gases generated in the pyrolysis furnace 1 do not escape through the first inlet 11 because the furnace operates with a slight depression - 5 mmWg. This depression allows to limit the entry of air inside the furnace, which could lead to the passage of reducing atmosphere into oxidizing atmosphere, followed by a strong rise in temperature of the furnace which could lead to accidents (explosion).

[113] The temperature and the flow of injected air are controlled according to the algorithm indicated in the following formula ((T° _se tpoint - Tactual) I 100) * k*D _m ax = □regulation. In the example, the coefficient k is equal to 2.

[114] In this example, the total air flow rate injected into a hearth of the pyrolysis furnace (Dtotai), this flow rate being the sum of the initial air flow rate (at the start of the pyrolysis) and the regulation air flow rate of the regulation stage.

[115] Table 1 summarizes the measurements made according to the volatile rate present in the materials to be processed:

[table 1]

[116] Table 1 : Dtotai = (57.2*VR%-1708.7)+((T° setpoint " T actua ) / 100) k*Dmax ) (linear regression). The coefficient k = 2 (unit T°-1 ). If the setpoint temperature is exceeded, the control valves are closed. In the example, the setpoint temperature is 500°C.

[117] The pyrolysis gases, which are not burnt in step d), are discharged via the second outlet 19 and conveyed to the post-combustion chamber 2.

[118] The pyrolyzed materials are discharged via the first outlet 18, possibly cooled and then led for subsequent processing (cooling, magnetic separation, etc.).

[119] The processing capacity of the plant tested in this example is in the order of 2 to 3 tons per hour.

[120] In this example, the burners were only used for start-up and uniform heating of the MHF furnace and, the autothermal mode was started when the furnace was uniformly fed, i.e., about 20 min after the start of step b) with material to be processed.

[121] The burners provide the necessary support in case of loss of the desired temperature profile on one or more hearths. The temperature is stabilized at 500°C thanks to a set of modulating valves which will open by an automatic regulation in a progressive way. This regulation is done via the above algorithm.

[122] Then, the pyrolyzed materials were recovered and treated as described in WO20 10/055489, concerning the metal separation and treatment of pyrolysis gases in the post-combustion chamber.

[123] The gas consumption of the plant, before the commissioning of the method according to the invention was 940,292 kWH in May 2021 , for a pyrolysis plant with an equivalent process volume. [124] After two months of operation, a considerable decrease in gas consumption of about 44% (530,000 kWh in July 2021) has been observed (see figure 3) and attests to the efficiency of the method, of the pyrolysis furnace 1 and more generally of the plant according to the invention.