Method and apparatus for recovering materials from discarded solar panels

Abstract

A method for processing waste photovoltaic modules to separate constituent materials thereof, the method comprising the steps of subjecting the modules to a shredding process to produce a shredded material mix, classifying the shredded material mix in an eddy current separator to create at least two distinct, sorted output streams comprising a first output stream rich in non-conductive materials and a second output stream rich in mixed metallic materials, subjecting the first output stream to a first processing path comprising primarily sizing apparatus optimized for recovering brittle, non-conductive materials and subjecting the second output stream to a second, parallel processing path comprising milling and magnetic separation apparatus optimized for liberating and recovering metallic materials.

Description

METHOD AND APPARATUS FOR RECOVERING MATERIALS FROM DISCARDED SOLAR PANELSField

[0001] The present invention generally relates to methods and apparatus for recovering materials from discarded solar panels.Background

[0002] Silicon-based photovoltaic solar panels, or photovoltaic modules, are a fast-growing source of renewable energy. The effective disposal of discarded solar panels is a key challenge in view of the future glut of expired solar panels that is expected to arise in coming years. Currently, most solar panels that have lost their efficiency due to age, or that are defective, end up in landfills because that option costs a fraction of recycling them.

[0003] The disposal of discarded solar panels in landfills results in environmental pollution and means that useful materials contained in the discarded solar panels, such as copper, aluminium, ferrous metals, plastic, glass, and crystalline silicon, cannot be recovered, reused, and recycled in the circular economy.

[0004] In view of this background, there is an unmet need for improved methods for recovering constituent materials from discarded solar panels to help boost the circular economy in which waste and pollution are reduced by constantly reusing materials.Summary

[0005] According to the present invention, there is provided a method for processing waste photovoltaic modules to separate constituent materials thereof, the method comprising the steps of: subjecting the modules to a shredding process to produce a shredded material mix; classifying the shredded material mix in an eddy current separator to create at least two distinct, sorted output streams comprising a first output stream rich in non-conductive materials and a second output stream rich in mixed metallic materials; subjecting the first output stream to a first processing path comprising primarily sizing apparatus optimized for recovering brittle, non-conductive materials; andsubjecting the second output stream to a second, parallel processing path comprising milling and magnetic separation apparatus optimized for liberating and recovering metallic materials.

[0006] The shredding process may comprise a multi-stage process comprising a coarse shredding step followed by a fine shredding step.

[0007] The milling apparatus in the second processing path may comprise a hammer mill or a ring shredder.

[0008] The magnetic separation apparatus may be positioned downstream of the milling apparatus to remove ferrous metals from a pulverized material stream.

[0009] The second processing path may further comprise a final separation circuit downstream of the magnetic separation apparatus that is configured to recover a mixed non-ferrous metal concentrate.

[0010] The final separation circuit may comprise at least one cyclone separator.

[0011] The final separation circuit may further comprise a vibration table.

[0012] The sizing apparatus in the first processing path may comprise a trommel.

[0013] A dosing tank may be used to provide a controlled feed of the second output stream to the milling apparatus.

[0014] The present invention also provides apparatus for processing waste photovoltaic modules, comprising: at least one shredder for producing a shredded material mix from the modules; an eddy current separator configured as a multi-stream classifier to sort the shredded material mix and produce at least a first output stream rich in non-conductive materials and a second output stream rich in mixed metallic materials; a first processing path configured to receive only the first output stream, said path comprising primarily sizing apparatus; anda second processing path, arranged in parallel to the first path, configured to receive only the second output stream, said second path comprising milling and magnetic separation apparatus.

[0015] The at least one shredder may comprise a coarse shredder and a fine shredder arranged in sequence.

[0016] The milling apparatus may comprise a hammer mill or a ring shredder.

[0017] The magnetic separation apparatus may be located downstream of the milling apparatus.

[0018] The sizing apparatus may comprise a trommel.

[0019] The apparatus may further comprise a final separation circuit located downstream of the magnetic separation apparatus.

[0020] The final separation circuit may comprise at least one cyclone separator and a vibration table.

[0021] The apparatus may further comprise a dosing tank configured to provide a controlled feed to the milling apparatus.Brief Description of Drawings

[0022] Embodiments of the invention will now be described by way of example only with reference to the accompanying drawings, in which:Figure 1 is a flow chart of a method of recovering materials from photovoltaic modules according to a first example of the present invention;Figure 2 is a schematic floorplan view of apparatus for carrying out the first example method;Figure 3 is a flow chart of a method of recovering materials from photovoltaic modules according to a second example of the present invention; andFigure 4 is a schematic perspective view of apparatus for carrying out the second example method.Detailed DescriptionConstruction of Photovoltaic Modules

[0023] For convenience, the term "photovoltaic module" is used herein to comprehend the waste material to be processed. Such modules typically comprise a layered structure including glass, an aluminium frame, silicon solar cells, an EVA encapsulant, a polymeric backsheet, and metallic conductors such as copper, silver, tin, and steel. The present invention provides an effective method for separating and recovering these various constituent materials.First Example Method

[0024] Referring to Figure 1 , a method 300 for processing waste photovoltaic modules to separate their constituent materials according to a first example of the present invention may start at step 310 by subjecting the modules to a shredding process to produce a shredded material mix. In one implementation, the shredding process may comprise a multi-stage process comprising a coarse shredding step followed by a fine shredding step.

[0025] At step 320, the shredded material mix may be classified in an eddy current separator to create at least two distinct, sorted output streams comprising a first output stream rich in non-conductive materials and a second output stream rich in mixed metallic materials.

[0026] At step 330, the first output stream may be subjected to a first processing path comprising primarily sizing apparatus optimized for recovering brittle, non-conductive materials. In some implementations, the sizing apparatus in the first processing path may comprise a trommel.

[0027] At step 340, the second output stream may be subjected to a second, parallel processing path comprising milling and magnetic separation apparatus optimized for liberating and recovering metallic materials. In some implementations, the milling apparatus in the second processing path may comprise a hammer mill or a ring shredder. In some implementations, a dosing tank may be used to provide a controlled feed of the second output stream to the milling apparatus. In some implementations, the magnetic separation apparatus may be positioned downstream of the milling apparatus to remove ferrous metals from a pulverized material stream.

[0028] In some implementations, the second processing path may further comprise a final separation circuit downstream of the magnetic separation apparatus that is configured to recover a mixed non-ferrous metal concentrate. For example, the final separation circuit may comprise at least one cyclone separator. In some implementations, the final separation circuit may further comprise a vibration table.First Example Apparatus

[0029] One implementation of apparatus 200 for carrying out the first example method 300 will now be described by reference to Figure 2.Initial Size Reduction

[0030] Waste photovoltaic modules may be fed by a robotic arm 202 to a first shredding station 204. The use of a multi-stage shredding process may provide a robust and efficient practice for the size reduction of complex products. The coarse material from the first shredder 204 is then transferred to a twin shaft shredder 206 for a secondary, finer size reduction. An incline conveyor 208 may be employed to remove a specific waste stream between the shredding stages.Primary Separation and Classification

[0031] The finely shredded material mix may be transported via a lift / Z conveyor 210 to a buffer silo 212. From the silo 212, a lift / Z conveyor 214 may provide a controlled feed to an eddy current separator 216. The eddy current separator 216 may be configured to function as a multi-stream classifier. It may eject the bulk non-ferrous metals (primarily aluminium) while simultaneously sorting the remaining material into two distinct streams tailored for subsequent, optimized processing.Divergent, Parallel Processing

[0032] In a departure from conventional linear processing, the apparatus 200 may employ a divergent, parallel processing architecture, comprising a first processing path (Path A) and a second processing path (Path B).

[0033] Path A may comprise a low-energy path optimised for sizing non-conductive materials. It may receive a first stream from the separator 216 via a lift / Z conveyor 218, which feeds a glass silo 220. From the glass silo 220, another lift / Z conveyor 222 may move the material to a sizing circuit 224 comprising sieves 226, 228 and a trommel 230. This path may yield a sized glass cullet (containing crushed silicon) and a low-value mixed polymer stream.

[0034] Path B may comprise a higher-intensity path optimised for liberating and separating intermingled metals. It may receive a second, more complex stream from the separator 216 via a lift / Z conveyor 232, which feeds a dosing tank 234. An incline conveyor 236 may then provides a controlled feed to a milling apparatus 238, preferably a hammer mill or ring shredder. The pulverized material from the mill 238 may pass to a magnetic separation station 240 comprising underbelt and overbelt magnets. This post-milling placement may allow for a cleaner and more efficient magnetic extraction as the pulverization liberates the ferrous particles. The remaining non-magnetic material may proceed to a final separation circuit 242. This circuit 242 may comprise a first cyclone with a zigzag separator 244, second cyclone with a sieve 246, a vibration table 248, and a final sieve 250, may provide an effective sequence for sorting complex granulated materials based on density and size to recover a mixed nonferrous metal concentrate.Final Product Collection

[0035] All separated product streams may be transported to a bagging area 252 for collection. A plant-wide dust box 254 may provide ancillary dust collection.Second Example Method

[0036] Referring to Figure 3, a method 100 of recovering constituent materials from solar panels according to a second example of the present invention may start at step 110 by shredding or cutting the solar panels to produce shredded material. Prior to step 110, electrical cables and junction boxes may be removed from the solar panels. The constituent materials of the electrical cables and junction boxes may be recovered separately or in conjunction with the solar panels in the following steps of the method 100. The solar panels may, for example, comprise silicon-based photovoltaic solar panels. The constituent materials of the shredded material may therefore generally comprise fragments of copper, aluminium, ferrous metals, plastic, glass, and silicon.

[0037] Next, the method 100 may move to step 120 where the shredded material is magnetised to separate and recover the ferrous metals and produce remaining shredded material. The remaining shredded material may then be milled at step 130 to produce milled material. For example, the milling step 130 may comprise hammer milling to apply mechanical force to break the shredded material into particles or fragments of a desired size that is relatively smaller than that of the shredded material.

[0038] At step 140, the milled material may be cycloned to produce cycloned material. Next, the method 100 may move to step 150 by zigzag separating the cycloned material to recover the aluminium and produce zigzag separated material. The zigzag separated material may be cycloned at step 160 to produce remaining material.

[0039] The method 100 may end at step 170 by sieving and agitating the remaining material to recover the balance of materials, such as glass, plastic and silicon. The glass and silicon may be initially recovered together as a mixture of glass and silicon. The mixture of glass and silicon may be subsequently further processed, for example by one or more thermal, mechanical and chemical processes, to recover separate individual streams of glass and silicon for reuse or recycling.Second Example Apparatus

[0040] Referring to Figure 4, apparatus 10 for performing the second example method 100 may generally comprise a solar panel loading point 12, a first inclined conveyor 14, a shredder 16, a second inclined conveyor 18, a magnet 20 at the top of the second inclined conveyor 18, a mill 22, a first cyclone 24, a second cyclone 26, an agitator 28, and a pneumatic air system 30.

[0041] The first inclined conveyor 14 may be configured to continuously convey the solar panels (not shown) spaced apart from one another from the loading point 12 to the shredder 16 at a desired constant throughput. For example, the inclined conveyor 14 may comprise a chevron cleated rubber conveyor belt wherein the chevron cleats are sized and arranged to space the solar panels apart from one another during continuous feeding into the shredder 16. The chevron cleats may also be adjustable to suit different sized solar panels.

[0042] The shredder 16 may be configured to shred the solar panels to produce shredded material. The shredder 16 may have hammers that are sized and arranged to cut the solarpanels into pieces or fragments of the desired size. A canopy may be provided above the shredder 16 that is connected to the pneumatic air system 30. The second inclined conveyor 18 may be configured to continuously convey the shredded material from the shredder 16 to the mill 22.

[0043] The magnet 20 may be configured to magnetise the shredded material to separate and recover the ferrous metals to produced remaining shredded material. The magnet 20 may, for example, be configured as an underbelt magnet 20 arranged under the end of the second inclined conveyor 18 before the mill 22. The recovery of the ferrous metals by the magnet 20 may prevent or minimise contamination of the aluminium and glass that are recovered downstream of the mill 22.

[0044] The mill 22 may be configured to mill the remaining shredded material to produce milled material. For example, the mill 22 may comprise a hammer mill 22 that is used to apply mechanical force to break the shredded material into fragments of a desired size. Depending on the desired particle or fragment size of the milled material, other milling apparatus 22 such as rollers, grinding mills and granulation mills may be effective. The wear plates and grates of the hammer mill 22 may be selectively varied in size and material to optimise particle sizes and yields of the milled material.

[0045] The first cyclone 24 may be configured to cyclone the milled material to produce cycloned material. The apparatus 10 may further comprise a zigzag separator 32 configured to zigzag separate the cycloned material to recover the aluminium and produce zigzag separated material. The first and second cyclones 24, 26 may, for example, each comprise oval cyclone separators. The first cyclone 24 may be connected to the second cyclone 26 using pneumatic air transfer. The second cyclone 26 may be configured to configured to cyclone the zigzag separated material to produce remaining material. A sieve 34 may be provided at the output of the second cyclone 26. The sieve 34 may be sized and dimensioned to allow remaining material of a desired size to be fed to the agitator 28.

[0046] The agitator 28 may be configured to agitate the remaining material to recover the glass and silicon. For example, the agitator 28 may comprise a conveyor that is agitated or vibrated to recover the glass and silicon as a mixture of these constituent materials. The glass and silicon mixture may be collected at a collection point 34, such as a bulka bag. The collected mixture of glass and silicon may be subsequently further processed, for example by one ormore supplementary thermal, mechanical and chemical processes, to recover separate individual streams of glass and silicon for reuse or recycling.

[0047] The pneumatic air system 30 may be interconnected by piping 36 to the shredder 16, mill 22, and first and second cyclones 24, 26. The pneumatic air system 30 may be configured to collect dust from, and pneumatically transfer materials between, the shredder 16, mill 22, and first and second cyclones 24, 26.

[0048] The components of the apparatus 200, 10, and their operations may be individually or sequentially controlled by predetermined user input via a control panel (not shown), or they may be individually or sequentially controlled by a programmed controller coupled to sensors (not shown), to optimise the throughput of the solar panels and the recovery yield of their constituent materials.

[0049] Embodiments of the present invention provide a method and related apparatus that are both generally and specifically useful for recovering materials from waste photovoltaic modules or discarded solar panels.

[0050] Conventional recycling methods often employ a linear processing design, where the entire heterogeneous mass of material is subjected to each processing step in sequence. A significant drawback of such linear processing is that all material, regardless of its nature, is subjected to the same energy-intensive steps. For instance, brittle, non-metallic fractions are unnecessarily subjected to milling and magnetic separation, leading to process inefficiency, higher energy consumption, and potential cross-contamination that downgrades the value of the final products. Embodiments of the present invention may provide a more intelligent process architecture that avoids these limitations.

[0051] Embodiments of the first example of the invention may advantageously depart from conventional linear or sequential recycling methods by providing a divergent, parallel processing architecture, which is a hallmark of sophisticated process engineering. In these embodiments, an eddy current separator may be used not merely for its conventional purpose of extracting a single product, but is advantageously employed as a multi-stream classifier or sorting gate. This initial classification step may divide a complex, shredded feedstock into multiple, specifically tailored streams, enabling each stream to be processed subsequently in a dedicated, optimized manner.

[0052] Embodiments of the invention in this configuration may provide the technical advantage of allowing each downstream processing path to be specifically optimised for the material stream it receives. A first stream, rich in simple, non-conductive materials, may be sent to a low-energy sizing path. A second, more complex stream containing intermingled metals may be sent to a separate, more intensive path involving milling and multi-stage metal separation. This may avoid the inefficiencies of conventional linear processes by not subjecting the entire material volume to the most aggressive processing steps, thereby increasing overall process efficiency, reducing energy consumption, and enhancing the purity of the recovered endproducts.

[0053] Unless the context requires otherwise, the word "comprising" means "including but not limited to," and the word "comprises" has a corresponding meaning.

[0054] Any reference to prior art is not an admission that the prior art is common general knowledge.

[0055] The scope of the invention supported by the above examples is defined by the claims that follow.

Claims

Claims1. A method for processing waste photovoltaic modules to separate constituent materials thereof, the method comprising the steps of: subjecting the modules to a shredding process to produce a shredded material mix; classifying the shredded material mix in an eddy current separator to create at least two distinct, sorted output streams comprising a first output stream rich in non-conductive materials and a second output stream rich in mixed metallic materials; subjecting the first output stream to a first processing path comprising primarily sizing apparatus optimized for recovering brittle, non-conductive materials; and subjecting the second output stream to a second, parallel processing path comprising milling and magnetic separation apparatus optimized for liberating and recovering metallic materials.

2. The method of claim 1 , wherein the shredding process comprise a multi-stage process comprising a coarse shredding step followed by a fine shredding step.

3. The method of claim 1 , wherein the milling apparatus in the second processing path comprises a hammer mill or a ring shredder.

4. The method of claim 1, wherein the magnetic separation apparatus is positioned downstream of the milling apparatus to remove ferrous metals from a pulverized material stream.

5. The method of claim 1, wherein the second processing path further comprises a final separation circuit downstream of the magnetic separation apparatus that is configured to recover a mixed non-ferrous metal concentrate.

6. The method of claim 5, wherein the final separation circuit comprises at least one cyclone separator.

7. The method of claim 6, wherein the final separation circuit further comprises a vibration table.

8. The method of claim 1, wherein the sizing apparatus in the first processing path comprises a trommel.

9. The method of claim 1, wherein a dosing tank is used to provide a controlled feed of the second output stream to the milling apparatus.

10. Apparatus for processing waste photovoltaic modules, comprising: at least one shredder for producing a shredded material mix from the modules; an eddy current separator configured as a multi-stream classifier to sort the shredded material mix and produce at least a first output stream rich in non-conductive materials and a second output stream rich in mixed metallic materials; a first processing path configured to receive only the first output stream, said path comprising primarily sizing apparatus; and a second processing path, arranged in parallel to the first path, configured to receive only the second output stream, said second path comprising milling and magnetic separation apparatus.

11. The apparatus of claim 10, wherein the at least one shredder comprises a coarse shredder and a fine shredder arranged in sequence.

12. The apparatus of claim 10, wherein the milling apparatus comprises a hammer mill or a ring shredder.

13. The apparatus of claim 10, wherein the magnetic separation apparatus is located downstream of the milling apparatus.

14. The apparatus of claim 10, wherein the sizing apparatus comprises a trommel.

15. The apparatus of claim 10, further comprising a final separation circuit located downstream of the magnetic separation apparatus.

16. The apparatus of claim 15, wherein the final separation circuit comprises at least one cyclone separator and a vibration table.

17. The apparatus of claim 10, further comprising a dosing tank configured to provide a controlled feed to the milling apparatus.

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