Treatment method for waste solar cells

Abstract

The method for treating waste solar cells according to the present invention is characterized in that it is a method for continuously treating waste solar cells, and the method includes a heating step: by heating a solar cell module having a resin backsheet, etc. in a thermal decomposition furnace, the resin component contained in the solar cell module is melted and oxidized and decomposed; the heating step is carried out in the following manner: in a state where the solar cell module is placed on a porous ceramic support (A) and the ceramic support (A) is placed on a porous material (B) loaded with a transition metal oxide, it is moved in the furnace from the inlet to the outlet of the thermal decomposition furnace; and, the thermal decomposition furnace includes a temperature rising part in the stage where the temperature of the solar cell module rises and a combustion part in the stage where the resin component undergoes oxidative decomposition, and the oxygen concentration in the combustion part is controlled in the range of 6 vol% or more and less than 15 vol%.

Description

Technical Field

[0001] The present invention relates to a method for treating waste solar cells. More specifically, it relates to a method for recovering valuable substances by removing resin components such as a backsheet and a sealing resin layer from a solar cell module and separating them into glass, cell units, silver, an aluminum frame, etc. Background Art

[0002] In order to achieve a low-carbon society, efforts are being made to accelerate the reduction of CO by utilizing renewable energy represented by solar power generation. 2 Although the introduction of solar power generation has made remarkable progress, on the other hand, technical problems in the recycling of solar cell modules at the time of disposal have been pointed out.

[0003] A conventional solar cell module has a three-layer structure with tempered glass on the surface, a sealing resin layer on the inside, and a backsheet on the back. In the sealing resin layer, wires (interconnectors) that connect the cell units of the solar cells are wired. The sealing resin is required to have transparency, flexibility, adhesiveness, tensile strength, weather resistance, etc., and ethylene-vinyl acetate copolymer (hereinafter simply referred to as "EVA") is usually used, and it is heated and pressed to play a role in bonding the tempered glass, cell units, and backsheet. If this solar cell module is heated using an electric furnace or the like in an oxidizing atmosphere, EVA melts at 80 to 120°C, a deacetylation reaction of EVA occurs around 350°C, and a thermal decomposition reaction of the polyethylene part as the main chain proceeds violently around 450°C. Techniques for recovering and recycling solar cell modules by performing such thermal decomposition have been disclosed (see Patent Documents 1 and 2).

[0004] However, since the thermal decomposition reaction around 450°C proceeds explosively, thermal decomposition of a solar cell module of about 1 m × 2 m size can cause a fire and is not suitable for large-scale operation. To solve this technical problem, a method for recycling a constituent material of a solar cell element has been disclosed, which includes the following steps: feeding it into a continuous heat treatment furnace in which the oxygen concentration is maintained at 1.0 vol% or more and 3.0 vol% or less, releasing and removing acetic acid gas, which is one of the EVA decomposition gases, in a preheating and decomposing section set at 300 to 400°C, and then desorbing EVA decomposition gases other than acetic acid in a heat treatment section set at 400 to 550°C, and removing the EVA sealing material from the solar cell element to separate the cell unit section and the glass substrate (see Patent Document 3).

[0005] Furthermore, the present applicant has proposed a method for recovering valuable substances from a solar cell module having a resin backsheet and a sealing resin layer, the method comprising: a stacking step of stacking the solar cell module on a heat-resistant porous molding with the backsheet surface facing downward; and a heating step of heating a stack comprising the solar cell module and the porous molding in a heating furnace in an oxidizing atmosphere with an oxygen concentration of 15% or more to melt and then burn the resin component (see Patent Document 4).

[0006] Prior Art Documents

[0007] Patent Documents

[0008] Patent Document 1: Japanese Patent Laid-Open No. 11-165150

[0009] Patent Document 2: Japanese Patent Laid-Open No. 2007-59793

[0010] Patent Document 3: Japanese Patent Laid-Open No. 2014-108375

[0011] Patent Document 4: International Publication No. 2020 / 031661

[0012] Non-Patent Documents

[0013] Non-Patent Document 1: Polymer Journal, Vol. 64, No. 9 (2007) Summary of the Invention

[0014] Problems to be Solved by the Invention

[0015] In the method provided in Patent Document 3, the oxygen concentration is controlled very low so as not to cause a rapid combustion reaction, and resin components such as EVA are thermally decomposed under heating conditions in two stages. However, controlling the oxygen concentration and temperature in the furnace under the conditions of Patent Document 3 is complex and very technical in operation, so it cannot be said to be a simple method.

[0016] In addition, the materials of the backsheets of early solar cells applied in Patent Documents 1 to 3 were almost all weather-resistant polyvinyl fluoride (hereinafter simply referred to as "PVF"). Now, the cheaper polyethylene terephthalate (hereinafter simply referred to as "PET") has become mainstream, and two-layer or three-layer backsheets such as PVF / PET, PVDF / PET, PVF / PET / PVF, and PVDF / PET / PVDF laminated with PET single layer, PVF, or fluorine-based resin such as polyvinylidene fluoride (hereinafter simply referred to as "PVDF") are also widely used, and backsheets using PET account for the majority.

[0017] Fluorine-based resins such as PVF and PVDF thermally decompose at the same temperature as EVA, so there is no problem with existing thermal decomposition methods. However, PET melts at 250°C and starts to thermally decompose near 400°C. Due to the presence of benzene rings and ester groups, it involves multiple thermal decomposition reactions. Sometimes, carbides with complex bonding between benzene rings are by-produced, forming black "soot", and the glass with "soot" attached is difficult to reuse. In addition, it has been reported that even when burned at 850°C, the residue amount of this "soot" remains 9% (see Non-Patent Document 1).

[0018] Therefore, in the technology of Patent Document 3 that reduces the oxygen concentration, even if EVA can be thermally decomposed, PET will not be completely thermally decomposed. Therefore, if a solar cell module using a backsheet containing PET is heat-treated, it will be full of "soot", and inorganic powders such as titanium oxide and calcium carbonate contained in the backsheet will also remain. Therefore, more advanced separation technologies are needed to recover valuable substances.

[0019] On the other hand, in the method of Patent Document 4, by arranging a heat-resistant material loaded with a transition metal oxide in the furnace, the "soot" generated when aromatic resins such as PET burn can be suppressed, and the valuable substances that can be reused in the solar cell module can be easily recovered and processed. However, if the solar cell module is continuously heat-treated in an oxidizing atmosphere with an oxygen concentration of 15% or more, due to the sharp rise in temperature caused by the explosive combustion accompanied by flames, the temperature control will deviate significantly to the upper limit, making it difficult to perform stable processing. As a result, new technical problems that were not exposed in these batch processes, such as an increase in processing cost or incomplete processing, were found.

[0020] In summary, the problem of the present invention is to provide a method for continuously treating waste solar cells with stable temperature control in order to recover valuable substances contained in solar cell modules having a resin-made backsheet, etc.

[0021] Means for Solving the Problems

[0022] The inventors of the present invention conducted in-depth research to solve the above technical problems. As a result, it was found that by moving the solar cell module in the furnace from the inlet to the outlet of the thermal decomposition furnace in a state where the solar cell module is placed on a porous ceramic support and the ceramic support is placed on a porous material loaded with a transition metal oxide, and performing heat treatment continuously, and controlling the oxygen concentration in the combustion part in the stage where the resin component undergoes oxidative decomposition within a specific range, the resin component can be burned gently and stably and removed. As a result, processing can be performed with stable temperature control, and thus the present invention was completed.

[0023] That is, the present invention relates to a method for treating waste solar cells, which is characterized in that it is a method for continuously treating waste solar cells, and includes a heating step: by heating a solar cell module having a resin backsheet and a sealing resin layer in a thermal decomposition furnace, the resin components contained in the solar cell module are melted and oxidized and decomposed. The heating step is carried out in the following manner: with the solar cell module placed on a porous ceramic support (A) and the ceramic support (A) placed on a porous material (B) loaded with a transition metal oxide, the solar cell module is moved in the furnace from the inlet of the thermal decomposition furnace to the outlet. Moreover, the thermal decomposition furnace includes a heating section in the stage of temperature rise of the solar cell module and a combustion section in the stage of oxidative decomposition of the resin components, and the oxygen concentration in the combustion section is controlled in the range of 6 vol% or more and less than 15 vol%.

[0024] Effects of the Invention

[0025] In the present invention, resin components such as EVA and PET melted before ignition penetrate into the heat-resistant porous molded body, so that the surface area is enlarged and combustion proceeds gently. Therefore, a sharp combustion reaction does not occur and stable combustion can be achieved. In addition, "soot" generated when aromatic resins such as PET are burned can be suppressed, and valuable substances that can be reused in the solar cell module can be easily recovered. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 A schematic diagram (with an aluminum frame) showing an embodiment of the present invention.

[0027] Figure 2 A schematic diagram (without an aluminum frame) showing an embodiment of the present invention.

[0028] Figure 3 A schematic diagram showing an overview of the thermal decomposition furnace used in the examples and comparative examples.

[0029] Figure 4 A graph showing changes in the furnace temperature and oxygen concentration in the examples and comparative examples. DETAILED DESCRIPTION OF THE INVENTION

[0030] Hereinafter, the present invention will be described in detail.

[0031] The method for treating waste solar cells of the present invention is characterized in that it is a method for continuously treating waste solar cells, and includes a heating step: by heating a solar cell module having a resin backsheet and a sealing resin layer in a thermal decomposition furnace, the resin components contained in the foregoing solar cell module are melted and oxidized and decomposed,

[0032] The above-mentioned heating process is carried out as follows: in a state where the above-mentioned solar cell module is placed on a porous ceramic support (A) and the above-mentioned ceramic support (A) is placed on a porous material (B) loaded with a transition metal oxide, the above-mentioned solar cell module is moved in the furnace from the inlet to the outlet of the above-mentioned thermal decomposition furnace, and,

[0033] The inside of the above-mentioned thermal decomposition furnace includes a heating section in the stage of temperature rise of the above-mentioned solar cell module and a combustion section in the stage of oxidative decomposition of the above-mentioned resin component, and the oxygen concentration in the above-mentioned combustion section is controlled in the range of 6 vol% or more and less than 15 vol%.

[0034] <Heating process>

[0035] The heating process in the treatment method of the present invention is the following process: by heating a solar cell module having a resin backsheet and a sealing resin layer in a thermal decomposition furnace, the resin component contained in the solar cell module is melted and oxidatively decomposed.

[0036] In the above-mentioned heating process, in a state where the solar cell module is placed on a porous ceramic support (A) and the above-mentioned ceramic support (A) is placed on a porous material (B) loaded with a transition metal oxide (see Figure 1 ), the above-mentioned solar cell module is moved in the furnace from the inlet to the outlet of the thermal decomposition furnace. At this time, it is preferable to place the solar cell module on the ceramic support (A) with the back plate surface facing downward. In addition, in order to improve the treatment efficiency of waste solar cells, it is preferable to move a plurality of solar cell modules continuously in such a manner that there are a plurality of heated solar cell modules in the thermal decomposition furnace. It should be noted that when heating a workpiece including a solar cell module, a ceramic support (A), and a porous material (B), in order to prevent their placement from collapsing or toppling during movement in the furnace, it may be placed in an iron tray with a grid or the like.

[0037] In the above-mentioned heating process, the inside of the thermal decomposition furnace includes a heating section in the stage of temperature rise of the solar cell module and a combustion section in the stage of oxidative decomposition (combustion) of the above-mentioned resin component. Generally, the inlet side of the thermal decomposition furnace is the heating section and the outlet side is the combustion section, but as long as the temperature rises as the solar cell module moves from the inlet side to the outlet side in the furnace and the above-mentioned resin component melts and undergoes oxidative decomposition, there is no need to clearly define the boundary between the heating section and the combustion section in the thermal decomposition furnace.

[0038] Combustion in the present invention refers to an oxidation reaction in which organic substances such as EVA and PET contained in the backsheet and sealing resin layer of the solar cell module react with oxygen in the atmosphere.

[0039] Therefore, the combustion temperature can be appropriately determined according to the resin constituting the backsheet, but is preferably 425 to 575 °C. If it is 425 °C or higher, it is higher than the thermal decomposition temperatures of EVA and PET, and combustion will occur. In addition, if it is 575 °C or lower, rapid combustion can be suppressed, and breakage of the glass of the solar cell module can be prevented.

[0040] It should be noted that the aforementioned melting starts at a temperature lower than the aforementioned combustion temperature. In order to obtain the aforementioned combustion temperature, generally, the temperature of the solar cell module is gradually increased from room temperature before entering the thermal decomposition furnace, and the melting temperature can be obtained during this heating process.

[0041] Considering the treatment of exhaust gas, etc., the heating in the aforementioned heating step should be carried out in a thermal decomposition furnace. As the aforementioned thermal decomposition furnace, there is no particular limitation as long as it is a gas furnace or an electric furnace, etc. that can obtain the aforementioned combustion temperature and can introduce the object to be treated including the porous material (B), the ceramic support (A), and the solar cell module, and a known thermal decomposition furnace can be used.

[0042] As a method for heating the inside of the thermal decomposition furnace, there is no particular limitation as long as the aforementioned combustion temperature can be obtained. For example, in the case of a gas furnace, a method of heating an oxygen-containing gas with a gas nozzle, etc. and circulating it inside the thermal decomposition furnace can be cited. As the oxygen-containing gas, for example, a mixed gas of a combustible gas such as liquefied petroleum gas and city gas and air, etc. can be cited.

[0043] In the aforementioned heating step, by controlling the oxygen concentration in the aforementioned combustion part within the range of 6 vol% or more and less than 15 vol%, the resin component can be burned gently and stably and removed. The lower limit value of the aforementioned oxygen concentration is preferably 7 vol%, more preferably 8 vol%, the upper limit value is preferably 14.8 vol%, and more preferably 14.5 vol%. It should be noted that even if the oxygen concentration instantaneously deviates from the aforementioned range, as long as it can be immediately controlled within the aforementioned range, there are no particular problems in operation.

[0044] As a method for controlling the oxygen concentration in the aforementioned combustion part, there is no particular limitation. For example, in the case of a gas furnace using a mixed gas of liquefied petroleum gas and air as the oxygen-containing gas, the mixing ratio of air can be adjusted according to the oxygen concentration in the combustion part.

[0045] In the method of the present invention, it is preferable to recover the valuable substances remaining on the aforementioned ceramic support (A) after the aforementioned heating step. The aforementioned valuable substances are preferably at least one selected from the group consisting of glass, cell units, silver, and aluminum frames, etc. It should be noted that the aforementioned silver, for example, originates from electrodes, etc.

[0046] In the method of the present invention, in order to efficiently recover the aforementioned valuable substances, before heat treatment, a metal mesh or the like that does not prevent the resin that melts during combustion from moving to the ceramic support (A) is provided between the solar cell module and the aforementioned ceramic support (A). It is also effective to recover the processed valuable substances together with the metal mesh. This is because the processed product after the resin as the sealing tape melts and burns will become a state in which glass, battery cells, etc. are dispersed on the ceramic support, making it difficult to recover.

[0047] <Solar cell module>

[0048] Any non-double-sided glass type solar cell module with a resin backsheet can be used in the present invention. Specifically, single-crystalline silicon solar cells, polycrystalline silicon solar cells, amorphous silicon solar cells, heterojunction solar cells, CIS solar cells, CIGS solar cells, CdTe solar cells, etc. can be cited. For the aluminum frame of the solar cell module, the aluminum frame can be removed before thermal decomposition from the advantage of not needing to cut the ceramic support (A) according to the size of the aluminum frame, thus making the operation simple. Or it can be removed after thermal decomposition in order to reduce the possibility of glass breakage during removal.

[0049] <Ceramic support (A)>

[0050] The porous ceramic support (A) that can be used in the present invention can be used without any limitation as long as it is stable at the subsequent combustion temperature (specifically, around 425°C to 575°C) and has a porous structure. As specific materials, stable and conventional ceramic materials such as alumina, zirconia, silicon nitride, silicon carbide, cordierite, ferrite, barium titanate, lead zirconate titanate, forsterite, zircon, mullite, steatite, aluminum nitride, etc. can be cited.

[0051] The pore diameter of the porous material is not particularly limited, but it is preferably in the range of 0.1 to 5 mm that is easy to penetrate when EVA, PET, etc. melt near 450°C. The number of pores on the surface is not particularly limited, and it is expected to be 5 to 50 pixels per inch (hereinafter simply referred to as "ppi"). The porosity is not limited either, and it is expected to be around 50 to 95%. It is particularly preferred to use a material with a three-dimensional skeleton structure of continuous pores.

[0052] As the shape of the ceramic support (A), there is no particular limitation, but in order to be configured in such a way that the resin used in the solar cell does not fall, it is preferable to use a plate-shaped ceramic support. In addition, from the viewpoint of being able to suppress the generation of "soot" due to the leakage of the molten resin component to the outside of the aforementioned ceramic support (A), the size (area) of the surface of the stacked backsheet of the aforementioned ceramic support (A) is preferably as large as possible within the range that can fit into the aluminum frame without removing the aluminum frame (seeFigure 1 ), when removing the aluminum frame from the solar cell module, it is preferably larger than the bottom area of the backsheet (see Figure 2 ).

[0053] The thickness of the ceramic support (A) is not limited in any way, but is preferably about 10 to 60 mm.

[0054] As the aforementioned ceramic support (A), products such as alumina, silicon carbide, and cordierite, which are called ceramic foams, ceramic filters, or ceramic foam filters, are preferred.

[0055] When treating waste solar cells by the method of the present invention, the aforementioned solar cell modules are stacked on the aforementioned ceramic support (A) with their back surfaces facing downwards. By positioning the back surface downwards, the resin components constituting the backsheet and the sealing resin layer are melted by heating, and then flow out towards the ceramic support (A) due to the action of gravity.

[0056] The ceramic support (A) is porous, so the contact area between the flowing resin and the atmosphere in the thermal decomposition furnace becomes larger. Therefore, the combustion efficiency is improved by further heating, thereby suppressing the generation of "soot".

[0057] <Porous material (B)>

[0058] In the porous material (B) loaded with transition metal oxide used in the present invention, the transition metal oxide has the ability to adsorb oxygen in the oxidized state and decompose the organic compounds having an aromatic ring generated by oxidative decomposition during the combustion of the aromatic resin. For example, chromium(III) oxide is in a reduced state at room temperature and is emerald green, but if heated to 400 °C or higher in the presence of oxygen, it will adsorb oxygen and change color to dark green in the oxidized state.

[0059] When the present inventors coated chromium(III) oxide on a ceramic support similar to the aforementioned ceramic support (A) (for example, a ceramic filter) and placed it in the furnace, it was found that almost no "soot" adhered to the ceramic filter. It is considered that the organic compounds having an aromatic ring are decomposed by the transition metal oxide, thereby suppressing the generation of "soot". The same phenomenon is known to occur in iron(III) oxide, copper(II) oxide, titanium(IV) oxide, etc.

[0060] In summary, when at least a part of the resin constituting the backsheet is an aromatic resin such as PET (a resin having an aromatic group as part of the repeating unit), from the viewpoint of being able to suppress the generation of "soot", it is preferable to previously have the aforementioned transition metal oxide present in the furnace.

[0061] As the aforementioned transition metal oxides, for example, oxides of scandium, titanium, vanadium, chromium, manganese, iron, cobalt, nickel, copper, zinc, yttrium, zirconium, niobium, molybdenum, technetium, ruthenium, rhodium, palladium, silver, cadmium, lanthanum, cerium, praseodymium, neodymium, promethium, samarium, europium, gadolinium, terbium, dysprosium, holmium, erbium, thulium, ytterbium, lutetium, hafnium, tantalum, tungsten, rhenium, osmium, iridium, platinum, gold, and mercury can be used without any limitation.

[0062] Among them, preferably selected are: oxides of the first transition elements of scandium, titanium, vanadium, chromium, manganese, iron, cobalt, nickel, and copper; oxides of the second transition elements of yttrium, zirconium, niobium, molybdenum, technetium, ruthenium, rhodium, and palladium; oxides of the third transition elements of lanthanum, cerium, praseodymium, neodymium, promethium, samarium, europium, gadolinium, terbium, dysprosium, holmium, erbium, thulium, ytterbium, lutetium, hafnium, tantalum, tungsten, rhenium, osmium, iridium, platinum, and gold. More preferably, transition metal oxides such as rutile-type or anatase-type titanium(IV) oxide, chromium(III) oxide, iron(III) oxide, and copper(II) oxide can be appropriately utilized. They can be in the state of composite oxides.

[0063] In order to increase the contact area, the aforementioned transition metal oxides are preferably supported on the porous material (B) and pre-exist in the furnace. As the porous material (B), similar to the aforementioned ceramic support (A), as long as it is stable at the combustion temperature of the resin component, materials of the same material can be listed. The shape of the porous material (B) is not particularly limited as long as it can be made into a so-called catalyst carrier, but it is more preferably a plate-shaped porous molded body similar to the ceramic support (A) on which the aforementioned solar cell module is placed.

[0064] Regarding the method of supporting the aforementioned transition metal oxides on the porous material, known techniques can be used without any limitation. Specifically, it is usually a method of impregnating and supporting a solution containing the transition metal oxides on the porous material by dip coating, wash coating, spraying, or spin coating. Subsequently, the simplest method is to remove the solution by heating above the boiling point of the solution. In addition, thermal spraying technology that sprays a substance obtained by melting the transition metal oxides onto the porous material can be utilized.

[0065] In the present invention, the ceramic support (A) on which the solar cell module is placed is placed on the porous material (B) loaded with the aforementioned transition metal oxides.

[0066] It should be noted that it is preferably a method in which the porous material (B) loaded with the transition metal oxides does not directly contact the solar cell module, and more preferably a method in which it is arranged below the solar cell module and does not directly contact it. This is because it is not easy to cause contamination of the porous material (B) by non-combustible components such as fillers contained in the backsheet of the solar cell module, etc. When the porous material (B) loaded with the transition metal oxides is repeatedly used, no regeneration treatment, etc. is required.

[0067] Regarding the size of the aforementioned porous material (B), from the viewpoint of the stability of the object to be processed including the solar cell module, it is preferable that the stacking surface of the porous material (B) is equal to or larger than the bottom area of the aforementioned ceramic support (A). As the thickness of the aforementioned porous material (B), about 10 to 60 mm is preferable.

[0068] Examples

[0069] Hereinafter, the present invention will be described in more detail based on examples, but the present invention is not limited by any of these examples.

[0070] [Example 1]

[0071] Using Figure 3 The thermal decomposition furnace 20 shown in the figure is used, and the object to be processed 23 including the solar cell module 7 is moved in the furnace from the left side (entrance side) to the right side (exit side) of the thermal decomposition furnace section 22 by the chain conveyor 24, thereby performing heat treatment.

[0072] As the solar cell module 7, an experiment was conducted using the "REC solar panel" manufactured by REC (cell unit type: REC PE polycrystalline solar cell unit, size: 1665 mm × 991 mm × 38 mm). The aluminum frame 10, junction box, and connector were removed using a scraper and a hammer before the heat treatment without damaging the glass.

[0073] As the ceramic filter of the ceramic support (A) 2, a FCF-2 (made of silicon carbide) 10 ppi 400 mm × 300 mm × 30 mm t (porosity 87.8%) manufactured by Seisen Filter was used.

[0074] While suspending Wako Grade 1 chromium(III) oxide (manufactured by Fujifilm Wako Pure Chemical Corporation) in water and stirring, the above-mentioned ceramic filter was impregnated and dip-coated, and dried at 450 °C to obtain the porous material (B) 1. The mass before coating was 1480 g, and the mass after coating and drying was 1790 g.

[0075] An iron tray with a grid of 2100 mm × 1210 mm × 50 mm was fabricated, and 21 ceramic filters coated with chromium oxide were used. The porous material (B) 1 of 2100 mm × 1200 mm × 30 mm t was provided at the lowermost stage. The ceramic support (A) 2 of 2100 mm × 1200 mm × 30 mm t was provided in the middle section above it using 21 ceramic filters of 400 mm × 300 mm × 30 mm t. Further, the aforementioned solar cell module 7 was provided thereon with the backsheet 3 on the lower side.

[0076] The thermal decomposition furnace 20 is used as a gas furnace. As this gas furnace, a step-feed chain blow-type hot air circulation heat treatment apparatus with a furnace length of 5400 mm, an inner furnace width of 2300 mm, and an inner furnace height of 280 mm is used. As the gas nozzle section 21, a metal burner MJPE-200K is used, and a mixed gas of liquefied petroleum gas and air is burned for heating. The heated mixed gas is supplied by squeezing through a slit from the lower side of the thermal decomposition furnace section 22 with an Adachi Kiko "6.0-LF ultimate load fan" (450 m 3 / min, 2.0 kPa, 30 kW), and is blown violently onto the porous material (B) 1 to enable heat exchange, and a part of the circulated heated gas is discharged.

[0077] The object to be treated 23 including the solar cell module 7, the ceramic support (A) 2, and the porous material (B) 1 prepared as described above is held for 6.5 minutes respectively in three regions in the furnace from the inlet side to the outlet side of the thermal decomposition furnace section 22 and is transported step by step, and a heat treatment for a total of 19.5 minutes is performed with the thermal decomposition furnace 20. The inlet side is the temperature-rising section 27, and the region where the resin component contained in the solar cell module 7 burns is the combustion section 28. It should be noted that a thermocouple thermometer is added to the upper center of the ceramic support (A) 2 in the middle section to measure the temperature of the object to be treated 23.

[0078] During the heat treatment, the proportion of air in the supplied mixed gas is adjusted by the oxygen concentration measurement section 26 so that the oxygen concentration in the combustion section 28 is in the range of 6 vol% or more and less than 15 vol%, and the heating temperature and supply amount of the supplied mixed gas are adjusted so that the temperature of the object to be treated 23 in the combustion section 28 is 470 °C or more.

[0079] When the heat treatment is performed as described above, as a result, as Figure 4 shown, by controlling the oxygen concentration in the combustion section 28 during the heat treatment in the range of 6 vol% or more and less than 15 vol%, the temperature in the furnace can be stably controlled in the range of 470 to 530 °C. That is, it was found that stable temperature control and treatment of the object to be treated 23 can be achieved by slow combustion without flames in a low-oxygen atmosphere. After the heat treatment, the tempered glass 6 was successfully recovered without being broken, and the battery cells 5 and the inorganic powder were also successfully recovered. Furthermore, no attachment of "soot" was observed on the ceramic filter at the lowermost stage used as the porous material (B) 1.

[0080] [Comparative Example 1]

[0081] Under the condition that the oxygen concentration in the combustion section 28 is made 15 vol% or more by using the oxygen concentration measurement section 26, the heat treatment of the object to be treated 23 including the solar cell module 7 is performed in the same manner as in Example 1 except for this. As a result, asFigure 4 As shown, due to the explosive combustion accompanied by flames, the temperature inside the furnace rises sharply, so countermeasures such as suppressing the supply amount of the supply gas need to be taken. That is, it has been found that it is difficult to stably control the temperature inside the furnace under normal oxygen atmosphere, and as a result, the processing cost increases.

[0082] Explanation of reference numerals

[0083] 1: Porous material (B) loaded with transition metal oxide

[0084] 2: Porous ceramic support (A)

[0085] 3: Back plate

[0086] 4: Sealing resin layer (EVA)

[0087] 5: Battery unit

[0088] 6: Tempered glass

[0089] 7: Solar cell module (X)

[0090] 8: Shed board or wire mesh

[0091] 9: Gas furnace or electric furnace

[0092] 10: Aluminum frame

[0093] 20: Pyrolysis furnace

[0094] 21: Gas nozzle part

[0095] 22: Pyrolysis furnace part

[0096] 23: Object to be processed

[0097] 24: Chain conveyor

[0098] 25: Temperature measurement part

[0099] 26: Oxygen concentration measurement part

[0100] 27: Heating part

[0101] 28: Combustion part

Claims

1. A method for treating waste solar cells, characterized in that, it is a method for continuously treating waste solar cells, and the method includes a heating step: by heating a solar cell module having a resin backsheet and a resin layer for sealing in a thermal decomposition furnace, the resin component contained in the solar cell module is melted and oxidized and decomposed, the heating step is carried out in the following manner: in a state where the solar cell module is placed on a porous ceramic support (A) and the ceramic support (A) is placed on a porous material (B) loaded with a transition metal oxide, the solar cell module is moved in the furnace from the inlet to the outlet of the thermal decomposition furnace, and, the thermal decomposition furnace contains a heating part in the stage where the temperature of the solar cell module rises and a combustion part in the stage where the resin component undergoes oxidative decomposition, and the oxygen concentration in the combustion part is controlled in the range of 6 vol% or more and less than 15 vol%.

2. The method for treating waste solar cells according to claim 1, wherein, there are a plurality of the solar cell modules in a heated state in the thermal decomposition furnace.

3. The method for treating waste solar cells according to claim 1 or 2, wherein, after the heating step, valuable substances remaining on the ceramic support (A) are recovered.

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