Process for treating a used or defective photovoltaic panel

Abstract

The invention relates to a method for treating a used or defective photovoltaic panel (1) comprising: a) supplying a panel (1) comprising: a protective glass layer (2), a first cohesive layer (5) of a first polymer material, a layer (3) having a plurality of photovoltaic cells, a second cohesive layer (6) of a second thermoplastic polymer material having a glass transition temperature Tg, and a support plate (4) comprising at least a third polymer material; b) separating the support plate from a first assembly (7) by cryogenics, consisting of the stack of the remaining layers; c) separating the protective glass layer (2) from the first assembly (7) of step b), forming a second assembly (8); d) heat-treating the second assembly (8), forming a residue comprising components from the photovoltaic cells. Figure to be published with the abstract: Fig. 1

Description

Title of the invention: Method for treating a used or defective photovoltaic panel

[0001] The present invention relates to the photovoltaic panel sector. It relates in particular to a process for treating a used or defective photovoltaic panel in order to recycle the various materials composing the panel. State of the art

[0002] A photovoltaic panel converts sunlight captured by photovoltaic cells into electrical energy. Generally, an installation comprises several photovoltaic panels electrically connected to each other to deliver sufficient voltage for its intended use.

[0003] Typically, a photovoltaic panel comprises a stack of layers in the following order: - a protective layer of glass; - a first cohesive layer in a first polymer material (generally the first polymer material is an ethylene-vinyl acetate copolymer also known as EVA); - a layer containing a plurality of photovoltaic cells electrically connected to each other. Photovoltaic cells are mainly composed of silicon, but also include metals such as copper or silver; - a second cohesive layer made of a second polymer material (generally the second polymer material is also EVA); and, - a backsheet made of at least one third polymer material which forms the base of the photovoltaic panel. The backsheet may include, for example, a fluoropolymer, such as polyvinylidene fluoride also known as PVDF, and / or polyvinyl fluoride also known as PVF, and / or polyethylene terephthalate also known as PET, and / or polyethylene, also known as PE.

[0004] In the operating position, the photovoltaic panels are installed so that the protective layer of glass either located on top, facing upwards.

[0005] Photovoltaic panels have a lifespan of between 30 and 40 years. Furthermore, being installed outdoors, the panels can suffer damage due to weathering and other external events.

[0006] In the event that a photovoltaic panel ceases to be efficient, in particular because of its too low efficiency or degradation of the panel, it is removed from the installation.

[0007] In order to limit the environmental impact of photovoltaic panels, processes for treating discarded panels have been developed to allow the recovery of their components.

[0008] Processes for treating an existing photovoltaic panel typically include a step of separating the protective glass layer, a step of extracting the photovoltaic cells, and a step of treating these cells to recover the metals. The first and second steps can be combined.

[0009] The separation of the protective glass layer can be achieved by implementing a delamination step in which the glass layer is separated from the other layers by cutting into the first adjacent cohesive layer using a hot blade or a wire coated with diamond particles. This delamination step can also be used to separate the backing plate. There is also a subcritical humid atmosphere hydrothermal treatment (200°C, 20 bar) that allows the protective glass layer, and optionally the backing plate, to be separated.

[0010] What remains is the layer of photovoltaic cells sandwiched between the two adjacent cohesive layers, and possibly the support plate. The photovoltaic cells can then be extracted using thermal and / or chemical methods. Chemical methods are based on the oxidation and dissolution of the polymer material of the adjacent cohesive layers and have the disadvantage of requiring the use of harmful solvents that must then be treated. Thermal methods are based on the thermal decomposition of the polymer material of the adjacent cohesive layers, and possibly of the support plate. However, the decomposition of the support plate requires high temperatures, exceeding 500 °C, and releases harmful gaseous products such as hydrofluoric acid or other fluorinated compounds, which necessitates treatment of the outgoing gases.

[0011] After separation, the photovoltaic cells are subjected to chemical processing steps for the extraction and purification of the metals they contain. However, depending on the nature of the preceding steps, obtaining products with high purity is difficult.

[0012] Another existing process relies on the mechanical grinding of the panel coupled with various separation stages of the ground material, allowing the different components to be isolated. The separations may include air separation, density separation, sieving, or eddy current separation.

[0013] Document WO2015 / 092734 describes, in particular, a method of this type. This document describes a system for processing a photovoltaic panel comprising a cutting machine and a crusher for cutting and crushing the panel in a plurality of pieces. These are then sieved in a first sieve with mesh sizes designed to allow the pieces containing the glass from the protective glass layer to pass through. The remaining pieces are then broken into fragments of polymer material and a powder containing silica, copper, silver, and plastics. Passing through a sieve with appropriately sized mesh separates the powder from the plastic fragments. The remaining powder, containing silica, copper, silver, and plastics, is then sieved to separate its constituent materials.

[0014] This process is relatively complex to implement and it does not allow the recovery of different materials such as metals with high purity for reuse, therefore the yield of this process is low.

[0015] A problem which then arises and which the present invention aims to solve is to provide an economical and efficient process for separating and recovering the valuable materials from the different layers of a photovoltaic panel. Summary of the invention

[0016] In order to solve this problem, a process for treating a used or defective photovoltaic panel is proposed. This process comprises the following steps: a) a step of supplying a used or defective photovoltaic panel comprising a stack of layers assembled in the following order: a protective glass layer, a first cohesive layer of a first polymer material, a layer having a plurality of photovoltaic cells, a second cohesive layer of a second thermoplastic polymer material having a glass transition temperature Tg and a support plate comprising at least a third polymer material; b) a first cryogenic separation step in which the temperature of at least part of the used or defective photovoltaic panel is lowered to a temperature Tinf below the glass transition temperature Tg of the second polymer material and the support plate is separated from a first assembly consisting of the stack of remaining layers; c) a second step of separating the protective glass layer during which at least part of the protective glass layer is removed from the first set of step b), and a second set is obtained; d) a heat treatment step of the second set from step c) in which the second set is heat-treated, in particular under nitrogen, at a temperature Ts sufficient to decompose the first and second materials polymers of the first and second cohesive layers and a residue is obtained comprising components from photovoltaic cells.

[0017] The sequence of steps presented makes it possible to process a used or defective photovoltaic panel by first separating the support plate, then the protective glass layer, before recovering the photovoltaic cells.

[0018] The present invention proposes, in particular, to separate the support plate in a first separation step by cryogenics. Cryogenics makes it possible to recover the support plate without damaging it, thus enabling its recycling. Indeed, during step b) by cryogenics, the temperature of the photovoltaic panel, specifically of the support plate and the cohesive material, is lowered so that it is below the glass transition temperature of the second thermoplastic polymer material, allowing it to reach a hardening state. The hardening of the second cohesive layer then makes it easier to separate the support plate from the adjacent cohesive layer without damaging it. Furthermore, the cryogenic separation is carried out at a low temperature, which avoids the production of polluting and hazardous gases, as is the case with heat treatment processes.

[0019] Removing the support plate prior to the heat treatment step also allows the temperature of the treatment process and the amount of heat to be supplied during this step to be reduced, since the temperature required to decompose the first and second polymer materials of the first and second cohesive layers is generally lower than the temperature required to decompose the polymer material(s) constituting the support plate.

[0020] Preferably, the second separation step c) is a physical separation step, not involving any chemical compound. This avoids the need to handle solvents or other chemical compounds.

[0021] Advantageously, the process may further include a step e) of extraction and purification of silicon contained in said residue and initially present in the photovoltaic cells.

[0022] In addition to its use in photovoltaic cells, silicon is a widely used element in industry for its semiconductor properties or for the synthesis of silicone. It is notably used in electronic circuits. This step thus allows the extraction and purification of silicon for reuse.

[0023] Step e) may include at least one of the following substeps: - a sub-step el) of extracting silver and copper contained in said residue and initially present in the photovoltaic cells, - a sub-step e2) of extraction of aluminium contained in said residue and initially present in the photovoltaic cells.

[0024] Photovoltaic cells generally contain metals that can be rare, such as silver, or high-value, such as copper. It is therefore advantageous and preferable to recover and purify them for reuse.

[0025] Advantageously, step a) may include at least one of the following features: - the supplied photovoltaic panel has an intact or degraded protective glass layer; - at least one third polymer material of the support plate is chosen from polyvinylidene fluoride, polyvinyl fluoride, polyethylene and polyethylene terephthalate; - the first polymer material of the first cohesive layer is ethylene-vinyl acetate; - the second polymer material of the second cohesive layer is ethylene-vinyl acetate.

[0026] Advantageously, step b) may include at least one of the following features: - cold air at temperature Tinf is projected at a junction between the support plate and the second cohesive layer; - when the second polymer material reaches the temperature Tinf, it is mechanically treated and the support plate is separated from the second cohesive layer; - the temperature Tinf is less than 230 K; - cold air is projected at the junction between the support plate and the second cohesive layer at a speed greater than 1 ms'.

[0027] In step b), cold air can advantageously be projected at the junction between the support plate and the second cohesive layer to locally cool the cohesive layer and the support plate, allowing them to be separated, for example by means of a separation system comprising a movable blade or other means. Localized cooling also reduces the energy required to cool the support plate and the cohesive material, as it is more efficient.

[0028] Advantageously, in step b), cold air can be generated by means of at least one cold air production system chosen from a vortex tube, a Peltier device and a heat pump.

[0029] The cold air production systems presented make it possible to generate cold air at low cost. Preferably, the cold air production system is a vortex tube.

[0030] Advantageously, in step b), the generated cold air can be projected onto the photovoltaic panel by at least one flat blowing nozzle coupled to a cold air outlet of at least one cold air production system.

[0031] The use of at least one flat blow nozzle makes it possible to cool a precise and localized area and thus to efficiently cool the photovoltaic panel, and in particular the junction between the support plate and the second cohesive layer.

[0032] Preferably, step c) can be chosen from (i) a delamination separation step and (ii) a grinding separation step followed by mechanical separation.

[0033] Separation by delamination, particularly using a hot blade or a wire coated with diamond particles, allows the protective glass layer to be recovered intact and free of impurities. The protective glass layer can then be easily reused, for example, to manufacture windows. Separation by delamination is particularly well-suited to processing panels with an intact protective glass layer.

[0034] Separation by grinding is preferably used when the protective glass layer is very damaged and worn, i.e. degraded, for example broken, which does not allow it to be recovered intact.

[0035] Advantageously, in step d), the second assembly from step c) can be heated to a temperature of 300°C to 400°C.

[0036] The second assembly is subjected to a high temperature sufficient to decompose the first and second polymer materials of the first and second cohesive layers.

[0037] In a preferred embodiment, the process according to the invention consists solely of steps a) to d), and optionally of step e).

[0038] Another object of the invention relates to an installation for processing a used or defective photovoltaic panel implementing the process according to any one of the preceding claims, comprising: - a section A of supply of a used or defective photovoltaic panel comprising a stack of layers in the following order: a protective layer of glass, a first cohesive layer of a first polymer material, a layer having a plurality of photovoltaic cells, a second cohesive layer of a second thermoplastic polymer material having a glass transition temperature Tg and a support plate comprising at least a third polymer material; - a first separation section B comprising a cryogenic unit in which the temperature of at least part of the used or defective photovoltaic panel is lowered to a temperature Tinf below the glass transition temperature Tg of the second polymer material, and the support plate is separated from a first assembly consisting of the stack of the remaining layers; - a second separation section C of the protective glass layer in which at least part of the protective glass layer is removed from the first set, and a second set is obtained; - a heat treatment section D of the second assembly in which the second assembly is heat-treated, in particular under nitrogen, at a sufficient temperature Ts to decompose the first and second polymer materials of the first and second cohesive layers and obtain a residue comprising components from the photovoltaic cells; and, - means of transporting the photovoltaic panel, the first assembly and the second assembly from one section to the other to implement the process described above.

[0039] The components from photovoltaic cells may include silicon and metals, including copper, silver and aluminum. The installation may then include a silicon extraction and purification section (E).

[0040] Advantageously, the cryogenic unit may include at least one cold air outlet positioned opposite a junction between the support plate and the second cohesion layer.

[0041] Advantageously, the cryogenic unit may include at least one cold air production system selected from a vortex tube, a Peltier device and a heat pump.

[0042] Preferably, the cryogenic unit may include at least one flat blow nozzle coupled to a cold air outlet from at least one cold air production system. Detailed description of the figures

[0043] Other features and advantages of the invention will become apparent from the following description of particular embodiments of the invention, given by way of example but not limitation, with reference to the accompanying drawings in which:

[0044] [Fig.1] is a schematic view of a photovoltaic panel;

[0045] [Fig.2] is a flowchart illustrating the steps for implementing the process according to the invention according to an embodiment. Detailed description of the invention

[0046] Process

[0047] The process according to the invention is a process for treating a used or defective photovoltaic panel in order to recover the materials composing it.

[0048] The process includes a step a) of supplying a used or defective photovoltaic panel comprising a stack of layers, a first step b) of separation by cryogenics producing a first assembly consisting of a first stack of the remaining layers, a second step c) of separating the protective glass layer from the first assembly producing a second assembly and a step d) of heat treatment of the second assembly during which the second assembly is heat treated, in particular under nitrogen, to obtain a residue comprising components from the photovoltaic cells.

[0049] The process may also include an optional step e) of extraction and purification of silicon typically present in components from photovoltaic cells.

[0050] The alternative configurations of the different stages of the process presented below can be combined according to the treatment objective decided.

[0051] Step a) of supplying a used or defective photovoltaic panel

[0052] Step a) is a step of supplying a used photovoltaic panel or defective. Such a panel comprises a stack of layers in the following order: a protective glass layer, a first cohesive layer of a first polymer material, a layer presenting a plurality of photovoltaic cells, a second cohesive layer of a second polymer material and a support plate comprising at least a third polymer material.

[0053] Step a) is for example carried out in a section supplying panel A.

[0054] The photovoltaic panel supplied for processing is a used or defective panel, namely one that has been used and / or is being discarded, for example because its performance has degraded or because it is damaged or defective. The used or defective photovoltaic panels that can be used in the present invention may have an intact protective glass layer or a protective glass layer that has been degraded, in particular by weathering or mechanical damage, for example, showing impacts and / or cracks, or even broken.

[0055] Fig. 1 illustrates a photovoltaic panel 1 supplied and treated according to the invention in the position of use, i.e. when the protective glass layer is located upwards, in the direction of the sun.

[0056] The panel 1 comprises, firstly, a protective layer of glass 2.

[0057] The protective layer 2 can be a resistant transparent glass plate. It helps to protect the other layers of panel 1, and in particular the photovoltaic cells, against weathering, mechanical damage and corrosion. The transparency of the glass allows sunlight to pass through the protective layer 2.

[0058] To improve its strength, the glass used may be tempered glass. Tempered glass is glass treated to improve its mechanical properties, particularly in terms of impact resistance. The treatment may be thermal tempering or chemical tempering.

[0059] The protective glass layer 2 can have a thickness that can vary from 2 mm to 3.5 mm.

[0060] Under the protective glass layer 2, the photovoltaic panel 1 comprises a layer 3 having a plurality of photovoltaic cells sandwiched between two cohesive layers 5 and 6.

[0061] The cells allow sunlight to be captured and converted into direct current. The cells can be electrically connected to each other in series, in parallel, or a combination of these two connections.

[0062] The plurality of photovoltaic cells of layer 3 are typically installed in the same plane, and are not generally stacked on top of each other, but arranged side by side.

[0063] The number of cells in layer 3 can vary depending on the use and / or dimensions of the photovoltaic panel. For example, layer 3 can comprise from 10 to 200 cells, each typically capable of delivering a voltage of 0.2V to 2V.

[0064] Photovoltaic cells may consist mainly (more than 50% by mass) of silicon, which allows the flow of electrons. The silicon may be in monocrystalline or polycrystalline form.

[0065] The cells may also include metals such as silver in the form of metallic contacts deposited on the silicon, and aluminum as a thin protective layer of the silicon.

[0066] The cells may, in addition, include copper used to form wires and make electrical contacts.

[0067] For example, photovoltaic cells may comprise, by mass, a percentage of silicon of 85% to 95%, a percentage of aluminium of 5% to 15% and a percentage of copper of 1% to 2%, a percentage of silver of 0.5% to 2%.

[0068] Under layer 3 of the plurality of photovoltaic cells, the panel 1 includes a support plate 4 comprising at least a third polymer material.

[0069] The support plate 4, or backsheet, provides structural support to the photovoltaic cells and helps to dissipate the heat produced by them.

[0070] The third polymer material can be chosen from polyvinylidene fluoride (PVDF), polyvinyl fluoride (PVF), polyethylene (PE) and polyethylene terephthalate (PET).

[0071] The support plate 4 may comprise, or be made of, a single polymer material, or it may comprise, or be made of, several layers of polymer material, for example, two layers of PVDF with a layer of PET in the center, or two superimposed layers of PET and a third layer of PE, or two layers of PET.

[0072] The support plate 4 can have a thickness that can vary from 70 pm to 400 pm.

[0073] The photovoltaic panel 1 further comprises: - a first cohesive layer 5 in a first polymer material located between the protective glass layer 2 and the layer 3 of the plurality of photovoltaic cells, - a second cohesive layer 6 in a second polymer material located between the layer 3 of the plurality of photovoltaic cells and the support plate 4.

[0074] The first 5 and second 6 cohesive layers thus encapsulate the photovoltaic cell layer 3, and ensure cohesion with the other layers of panel 1. They also provide electrical insulation while preventing air and moisture from reaching the photovoltaic cells.

[0075] The first cohesive layer 5 also ensures good transmission of sunlight and resistance to UV waves.

[0076] The second polymer material is a thermoplastic polymer material having a glass transition temperature Tg

[0077] A thermoplastic polymer is a polymer that has the ability to transition from a hardened state to a softened state when heated. The thermoplastic polymer thus exhibits a glass transition temperature that characterizes this change of state. Indeed, when the polymer's temperature is below its glass transition temperature, it is in a hardened state, while when its temperature is above its glass transition temperature, it is in a softened state.

[0078] The first and second polymer materials, once heated, form a hermetic rubber layer around the cells and between the other layers of panel 1.

[0079] The first and second polymer materials may be the same polymer materials or different polymer materials. The first polymer material may, in particular, also be a thermoplastic polymer.

[0080] The most frequently used polymer material for the first and / or second polymer material is EVA, in particular cross-linked EVA, suitable for forming an adhesive layer. EVA is a copolymer of ethylene and vinyl acetate.

[0081] Such EVA-based polymers, particularly those based on cross-linked EVA, are commonly used in the manufacture of photovoltaic panels and are well known to those skilled in the art. Usable EVA-based polymer materials may have a melting point of 130 to 150 °C. Usable cross-linked EVA-based polymers include, for example, 25 to 35% vinyl acetate. They typically contain peroxides, and possibly adhesion-promoting silanes, UV absorbers, antioxidants, and / or light stabilizers, including hindered amine light stabilizers (HALS). Formulations of usable EVA-based polymers as adhesive films in photovoltaic panels are described, for example, in document WO 99 / 27588.

[0082] EVA has a glass transition temperature between -10°C and -50°C (inclusive). This glass transition temperature depends in particular on the copolymer content (vinyl acetate content).

[0083] The first and second cohesion layers can each have a thickness that can vary from 300 to 800 pm.

[0084] Optionally, the used or defective photovoltaic panel may include a metal frame, for example made of aluminum (not shown in the figures), surrounding an outer edge of the stack of layers of the panel as well as a rubber sealing gasket.

[0085] The aluminum frame ensures the stability of the structure and prevents torsional forces that could break the panel. It does not cover the protective glass layer 2 so as not to block sunlight. The sealing gasket further ensures the installation is watertight.

[0086] The photovoltaic panel may also include a junction box protecting the panel against overcurrent and copper connection cables allowing the panel to be connected to an electrical circuit.

[0087] The treatment process may thus include, upstream of step a), a pre-dismantling step of the photovoltaic panel during which the cables, the junction box as well as the aluminium frame and the sealing gasket when present will be removed.

[0088] This step can be performed manually or automatically.

[0089] First step b) of separation

[0090] The first step b) of separation is a cryogenic separation step of the support plate 4 from the other layers and in particular from the second cohesion layer 6.

[0091] During the first step b) of separation, the temperature of at least a part of the photovoltaic panel is lowered to a temperature Tinf lower than the temperature of glass transition Tg of the thermoplastic polymer material of the second cohesive layer, then the support plate 4 is separated from a first set 7 consisting of the stack of the remaining layers.

[0092] The first assembly 7 is thus made up of the protective glass layer 2, the first cohesive layer 5, the layer 3 comprising the plurality of photovoltaic cells and the second cohesive layer 6.

[0093] The first separation step b) can be implemented in a first separation section B comprising a cryogenic unit. The cryogenic unit may include at least one cold air production system, preferably equipped with at least one flat blower nozzle, and optionally at least one separation system.

[0094] During step b), cold air can advantageously be projected at a junction between the support plate 4 and the second cohesion layer 6, for example parallel to the plane of each layer.

[0095] The cold air is at a temperature Tinf chosen according to the glass transition temperature of the second polymer material of the second cohesive layer. It is typically strictly lower than the glass transition temperature of the second polymer material, preferably by at least -10 °C.

[0096] An example of usable temperatures is for EVA, a Tinf temperature preferably below -50°C, for example from -60°C to -50°C.

[0097] Cold air can be projected onto the photovoltaic panel, particularly at the junction of the layers, at a projection speed of at least 1 m / sec, for example from 2 to 35 m / s.

[0098] Cold air can be generated by at least one cold air production system forming part of the cryogenic unit. The cold air production system may include a vortex tube, a Peltier device and / or a heat pump.

[0099] A vortex tube, also called a Ranque-Hilsch tube, is a thermodynamic device for producing cold air. Compressed air is injected tangentially into the tube, creating a vortex effect that results in a rapid, swirling flow of air, which is then slowed by a conical valve at the tube's outlet. Thus, some of the air exits through the conical valve while some flows back in the opposite direction through the tube. The heat exchange between the incoming and outgoing compressed air cools the compressed air.

[0100] Compressed air can have a pressure of 5 to 10 bars.

[0101] An example of a vortex tube usable in the present invention is described in document EP2713118B1.

[0102] A Peltier device, also called a "Peltier effect thermoelectric device", is based on the Peltier effect, which is a thermoelectric phenomenon in which a Heat transfer is caused by an electric current produced when conductive materials are connected at points of contact. Thus, when two connected metal plates are subjected to a direct current voltage, the plate charged with positive electrons heats up, while the one charged with negative electrons cools down.

[0103] Thus, the Peltier device comprises a series of pairs of conductors with different electrical conductivities through which an electric current flows to create a temperature gradient between two, generally opposite, faces of the module. Consequently, a Peltier device has a cold face and a hot face, which can be reversed by reversing the direction of current flow in the Peltier device. A Peltier device is generally characterized by the temperature difference it can maintain between its cold and hot faces, the cold face having a lower temperature than the hot face. Preferably, the Peltier device is designed to have a sufficient temperature difference to reach the temperatures required for a particular application. The temperature gradient between the faces of the Peltier module can be modulated by controlling the voltage applied to the Peltier device by the power source.

[0104] A heat pump, on the other hand, transfers thermal energy from a low-temperature environment to a high-temperature environment. A heat pump typically comprises a compressor to compress air, a condenser, an expansion valve, and an evaporator. Its operating principle will not be detailed here, as it is well known to those skilled in the art.

[0105] Once generated, the cold air can be projected by one or more flat blowing nozzles coupled to a cold air outlet of the cold air production system.

[0106] The flat blowing nozzle may have a single outlet through a flat orifice, or several outlets through several flat orifices. This type of nozzle facilitates the projection of cold air into a localized area of ​​the panel, particularly at the junction of the support plate 4 and the second cohesive layer 6.

[0107] The cryogenic unit includes at least one cold air outlet, for example at least one flat blow nozzle, which can be positioned opposite the junction between the support plate 4 and the second cohesion layer 6 to separate them.

[0108] To carry out this step, the panel 1 can be installed horizontally so that the support plate 4 is facing upwards, with the protective glass layer of the panel resting, for example, on a workbench or other support. Alternatively, the panel 1 can be installed horizontally so that the support plate 4 is facing downwards, with the panel then suspended by cables or a suction / aeration system. The upper layer can then be held in place. A vertical positioning of the panel 1 is also possible.

[0109] Next, to separate the support plate 4 and the second cohesion layer 6 from the first assembly 7, a separation system can be used.

[0110] The separation system may include one or more blades or wires coated with diamond particles, and / or an operator. In the case of a blade, it may be manipulated manually or automatically. The blade(s) or wire(s) may advantageously be applied to the surface of the support plate 4 so that the second cohesive layer 6 is separated from the support plate 4.

[0111] In one embodiment, the blade or wire and the flat blowing nozzle can be moved progressively, for example around the periphery of the panel and / or towards the inside of the panel, so as to perform the separation as it is carried out. However, they can also be fixed, in which case the panel is moved.

[0112] Second step c) of separation

[0113] The second separation step c) allows the protective glass layer of the first set 7 of step b) to be removed to obtain a second set 8.

[0114] The second assembly 8 is thus made up of the first cohesion layer 5, the layer 3 of the plurality of photovoltaic cells and the second cohesion layer 6.

[0115] The second step c) is for example implemented in a second separation section (C).

[0116] In a first embodiment, step c) can be a separation step by delamination.

[0117] Step c) can then be applied to intact or slightly degraded protective glass coatings. However, if the protective glass coating is severely degraded, it may be more difficult to remove it using this method.

[0118] Delamination separation consists of peeling the protective glass plate lengthwise from the first cohesive layer 6, generally using a hot blade. The heated blade is applied to the junction between the protective glass plate 2 and the first cohesive layer 6 so as to soften the second cohesive layer at the point of application and peel off the protective glass layer 2.

[0119] The hot blade can be heated to a temperature of 200°C to 500°C, preferably from 250°C to 350°C, for example to 300°C.

[0120] At the end of this step, the second assembly thus takes the form of a set of remaining assembled layers, namely the first cohesion layer 5, the layer 3 of the plurality of photovoltaic cells and the second cohesion layer 6.

[0121] Alternatively, delamination could be carried out using a diamond-coated wire positioned at the junction between the protective glass plate 2 and the first cohesive layer 6. Heating is then unnecessary. However, the yarn is displaced during delamination. An oscillatory or circular motion can then be applied to the yarn.

[0122] During this step, the first assembly 7 can be installed on a means of transport, such as a conveyor, as if it were in the position of use, namely horizontally with the protective glass layer 2 facing upwards. It can then be moved to the blade or wire that will peel off the protective glass layer 2. A separation system such as the one described above can be used.

[0123] The delamination step can in particular be carried out at the same time as the cryogenic step.

[0124] In another embodiment, step c) can be a separation step by grinding followed by mechanical separation.

[0125] Grinding can be carried out in a crusher and allows the first assembly 7 to be fragmented. During the grinding of the first assembly 7, the different fragments will not have the same size depending on their composition. In particular, the fragments including the protective glass layer 2 may have a smaller particle size and mass than the other fragments.

[0126] To separate the fragments from the protective glass layer 2, a sieve or an air separator can be used. In the case of the sieve, the mesh size can be chosen to allow the fragments containing the protective glass layer 2 to pass through while retaining the fragments containing the remaining layers. The air separator sorts the fragments according to their mass. An air jet is directed at the fragments, and depending on their velocity (proportional to their mass), the fragments are directed into different collection bins. This separates the glass fragments from the other fragments.

[0127] At the end of this step, the second assembly is thus presented in the form of a grind of the set of remaining assembled layers, namely a grind of the first cohesion layer 5, of the layer 3 of the plurality of photovoltaic cells and of the second cohesion layer 6.

[0128] Heat treatment step d)

[0129] The heat treatment step d) consists of heating the second assembly 8, preferably under a nitrogen flow, to a temperature Ts sufficient to decompose the first and second polymer materials of the first 5 and second 6 cohesive layers and thus obtain a residue comprising components from the photovoltaic cells. This residue may typically comprise, or be composed of, fragments of photovoltaic cells resulting from the handling of the cells or from their prior grinding.

[0130] The heat treatment step d) can be implemented in a heat treatment section D, which may in particular include a pyrolysis furnace.

[0131] During this step, the second assembly 8 can be heated to a temperature of 300°C to 400°C, preferably under a nitrogen flow, preferably with a purity level of 98 to 100%. If the nitrogen flow is not pure, it may also contain oxygen. The use of nitrogen is preferable to another gas, such as CO2, in order to avoid the formation of metal carbides, which would then be difficult to process for the recovery of metals, particularly silver and copper.

[0132] Heating the first and second layers allows the first and second polymers composing them to decompose, in particular by deacetylation and chain cleavage.

[0133] During this step, the first and second layers can be heated for a chosen time so as to limit the diffusion of metals present in the photovoltaic cells, and in particular the diffusion of copper into the silicon. For example, the heating time can be from 5 to 20 minutes, most often from 10 to 20 minutes.

[0134] Due to the prior removal of the support plate, which is generally made of polymer materials that degrade at higher temperatures than those constituting the cohesive layers, it is not necessary to heat the second assembly as much to decompose the polymers of the remaining layers, which makes it possible on the one hand to reduce the energy consumed to carry out this decomposition, and on the other hand to reduce the heating time and thus the diffusion of metals within the silicon.

[0135] Optional step e) of silicon extraction and purification

[0136] The treatment process may also include an optional step e) of extracting and purifying the silicon present in the residue exiting step d) in order to recover and reuse it. Optional step E may, in particular, be implemented in an extraction and purification section E, comprising, for example, one or more tanks, reactors, or columns.

[0137] Step e) of extraction and purification may include a substep e) of silver and copper extraction. During this substep, the residue from step d) is typically contacted with a first acidic medium to dissolve the silver. The first acidic medium may include at least one acid, for example, an organic acid selected from citric acid or an inorganic acid selected from persulfuric acid, chromic acid, and nitric acid. The first acidic medium used may have an acid concentration of between 2 mol.L⁻¹ and 16 mol.L⁻¹ (inclusive). The residue may then be rinsed with wash water to remove the acidic medium from the residue. This implementation is particularly suitable when c) is a separation step by grinding. Alternatively, particularly when step c) is a separation step by delamination, the extraction substep el) can be a separation by sieving of the copper wires present in the residue.

[0138] Step e) of extraction and purification may also include a substep e2) of aluminum extraction. In this substep, the residue, in particular the residue from step d) or the residue from substep e1), is contacted with a second acidic medium to dissolve the aluminum. The second acidic medium comprises at least one acid selected from nitric acid, hydrochloric acid, and tetrafluoric acid. The second acidic medium used may have an acid concentration of between 1 mol.L⁻¹ and 20 mol.L⁻¹ (inclusive). The residue may then be rinsed with wash water to remove the acidic medium from the residue.

[0139] Substep e1) (when it is a chemical extraction) and substep e2) can each be carried out independently for a time ranging from 1 to 20 minutes, generally at room temperature.

[0140] In a preferred embodiment, step e) includes at least one step e1) and at least one step e2), which makes it possible to recover a residue containing essentially silicon, in particular containing 99% to 99.99% by mass of silicon.

[0141] Installation description

[0142] On [Fig.2] described below, the solid lines with arrows correspond to means of transporting the photovoltaic panel from one section to another, for example by conveyors, pallets or trolleys.

[0143] With reference to [Fig.2], the installation 100 for processing used or defective photovoltaic panels includes a section A for supplying a used or defective photovoltaic panel suitable for carrying out step (a), a first separation section B suitable for carrying out step b) of the process, a second separation section C suitable for carrying out step c) and a heat treatment section D suitable for carrying out step d) of the process.

[0144] Section A of the supply may provide the used or defective photovoltaic panel to be processed. It includes, for example, means for receiving and transporting the photovoltaic panels to be processed. This step may be automated using conveyor(s) and robot(s), but it may also be partially automated using only conveyor(s) and operators.

[0145] Optionally, this section may include a pre-dismantling part of the panel during which an operator removes the cables, the junction box as well as the aluminum frame of the panel, and a possible sealing gasket.

[0146] The first separation section B comprises a cryogenic unit. The cryogenic unit may include at least one cold air production system, and preferably at least one flat blower nozzle. This section may optionally include at least one separation system. The cold air production system may be selected from a vortex tube, a Peltier device, and a heat pump. The separation system may be an automated moving blade or a moving blade manipulated by an operator.

[0147] The first set 7 exiting the first separation section B is then transported to the second separation section C in which the protective glass layer is removed.

[0148] The second separation section C may include a hot blade or wire delamination device, or a crusher and a separation system (air separator or sieve).

[0149] The second set 8 exiting the second separation section C, in the form of assembled layers or a pulverized material, is then transported to the heat treatment section D.

[0150] The heat treatment section D may include a pyrolysis furnace to implement step d) of the process.

[0151] Optionally, the installation 100 may include a silicon extraction and purification section E. This section E may, for example, include one or more tanks, reactors or columns, or sieves, in particular to carry out substeps e1) and e2).

Claims

Demands

1. A method for treating a used or defective photovoltaic panel (1) characterized in that it comprises the following steps: - a) a step of supplying a used or defective photovoltaic panel (1) comprising a stack of layers assembled in the following order: a protective glass layer (2), a first cohesion layer (5) in a first polymer material, a layer (3) having a plurality of photovoltaic cells, a second cohesion layer (6) in a second thermoplastic polymer material having a glass transition temperature Tg and a support plate (4) comprising at least a third polymer material; - b) a first cryogenic separation step in which the temperature of at least part of the used or defective photovoltaic panel (1) is lowered to a temperature Tinf lower than the glass transition temperature Tg of the second polymer material and the support plate is separated from a first assembly (7) consisting of the stack of the remaining layers; - c) a second step of separating the protective glass layer (2) during which at least part of the protective glass layer (2) is removed from the first assembly (7) of step b), and a second assembly (8) is obtained; - d) a heat treatment step of the second assembly (8) of step c) during which the second assembly (8) is heat treated, in particular under nitrogen, at a temperature Ts sufficient to decompose the first and second polymer materials of the first and second cohesion layers (5, 6) and a residue is obtained comprising components from the photovoltaic cells.

2. Processing method according to claim 1, characterized in that the process further comprises a step e) of extraction and purification of silicon contained in said residue and initially present in the photovoltaic cells.

3. Processing method according to claim 2, characterized in that step e) comprises at least one of the following substeps: - a substep e1) of extraction of silver and copper contained in said residue and initially present in the photovoltaic cells, - a substep e2) of extraction of aluminium contained in said residue and initially present in the photovoltaic cells.

4. A treatment method according to any one of claims 1 to 3, characterized in that step a) comprises at least one of the following features: - the supplied photovoltaic panel (1) has an intact or degraded protective glass layer (2); - at least one third polymer material of the support plate (4) is selected from polyvinylidene fluoride, polyvinyl fluoride, polyethylene and polyethylene terephthalate; - the first polymer material of the first cohesive layer (5) is ethylene-vinyl acetate; - the second polymer material of the second cohesive layer (6) is ethylene-vinyl acetate.

5. A treatment method according to any one of claims 1 to 4, characterized in that step b) comprises at least one of the following features: - cold air at temperature Tinf is projected at a junction between the support plate (4) and the second cohesive layer (6); - when the second polymer material reaches temperature Tinf, it is mechanically treated and the support plate (4) is separated from the second cohesive layer (6); - the temperature Tinf is less than 230 K; - the cold air is projected at the junction between the support plate (4) and the second cohesive layer (6) at a speed greater than 1 ms.

6. A treatment method according to any one of claims 1 to 5, characterized in that in step b), cold air is generated by means of at least one cold air production system selected from a vortex tube, a Peltier device and a heat pump.

7. Processing method according to claim 6, characterized in that in step b), the generated cold air is projected onto the photovoltaic panel by at least one flat blow nozzle coupled to a cold air outlet of at least one cold air production system.

8. Processing method according to any one of claims 1 to 7, characterized in that step c) is selected from (i) a separation step by delamination and (ii) a separation step by grinding followed by mechanical separation.

9. Processing method according to any one of claims 1 to 8, characterized in that in step d), the second set (8) from step c) is heated to a temperature of 300°C to 400°C.

10. Installation (100) for processing a used or defective photovoltaic panel (1) implementing the process according to any one of the preceding claims, comprising: - a section (A) for supplying a used or defective photovoltaic panel (1) comprising a stack of layers in the following order: a protective layer of glass (2), a first cohesive layer (5) of a first polymer material, a layer (3) having a plurality of photovoltaic cells, a second cohesive layer (6) of a second thermoplastic polymer material having a glass transition temperature Tg and a support plate (4) comprising at least a third polymer material;- a first separation section (B) comprising a cryogenic unit in which the temperature of at least part of the used or defective photovoltaic panel (1) is lowered to a temperature Tinf below the glass transition temperature Tg of the second polymer material, and the support plate (4) is separated from a first assembly (7) consisting of the stack of the remaining layers; - a second separation section (C) of the protective glass layer (2) in which at least part of the protective glass layer (2) is removed from the first assembly (7), and a second assembly (8) is obtained; - a heat treatment section (D) of the second assembly (8) in which the second assembly (8) is treated; hermically, in particular under nitrogen, at a sufficient temperature Ts to decompose the first and second materials into the polymer of the first and second cohesive layers (5, 6) and obtain a residue comprising components from the photovoltaic cells; and, - means of transporting the photovoltaic panel (1), the first assembly and the second assembly from one section to the other to implement the process according to any one of the preceding claims.

11. Installation for processing a used or defective photovoltaic panel according to claim 10, characterized in that the components from the photovoltaic cells include silicon and metals, and in that the installation further includes a silicon extraction and purification section (E).

12. Installation for processing a used or defective photovoltaic panel according to claim 10 or 11, characterized in that the cryogenic unit includes at least one cold air outlet positioned opposite a junction between the support plate and the second cohesion layer.

13. Installation for processing a used or defective photovoltaic panel according to any one of claims 10 to 12, characterized in that the cryogenic unit comprises at least one cold air production system selected from a vortex tube, a Peltier device and a heat pump.

14. Installation for the treatment of a used or defective photovoltaic panel according to claim 13, characterized in that the cryogenic unit comprises at least one flat blow nozzle coupled to a cold air outlet from at least one cold air production system.

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