Process for treating photovoltaic EVA (Ethylene Vinyl Acetate) by using supercritical carbon dioxide

Abstract

The invention discloses a process for treating photovoltaic EVA (Ethylene Vinyl Acetate) by using supercritical carbon dioxide, which comprises the following steps: placing a waste photovoltaic module in a reaction kettle, introducing carbon dioxide, adding a cosolvent, regulating to a supercritical state, and treating for 3-6 hours, so that an EVA adhesive film layer is expanded, and the interface bonding strength between the EVA adhesive film layer and glass, a battery and a back plate is obviously reduced; therefore, the glass layer and the EVA adhesive film layer can be easily peeled off. Therefore, according to the photovoltaic module treated by the process, the peeling force of the glass layer and the EVA adhesive film layer is reduced to 17.8 N from 36.9 N, and the peeling force can be further reduced to 13.2 N and 15.0 N by adding the cosolvent. The process has the advantages of low energy consumption, environment friendliness, high material recovery rate and the like, and can provide key technical support for green recovery of photovoltaic modules.

Description

Technical Field

[0001] This invention relates to the field of solar photovoltaic panel recycling technology, specifically to a process for treating photovoltaic EVA using supercritical carbon dioxide. Background Technology

[0002] As the core equipment for solar power generation, crystalline silicon photovoltaic modules contain not only high-value resources such as high-purity silicon, copper, and silver, but also pollutants such as lead, tin, and harmful polymers. Improper handling can lead to serious waste of resources and environmental pollution risks. Therefore, the green and efficient recycling of waste photovoltaic modules has become a key technological bottleneck for the sustainable development of the photovoltaic industry.

[0003] The core of photovoltaic (PV) module recycling lies in achieving efficient separation of each functional layer. While the disassembly technology for aluminum frames and junction boxes is relatively mature, the crystalline silicon solar cells, which account for 65% of the total cost of PV modules, are tightly encapsulated between the cover glass and the backsheet by an ethylene-vinyl acetate copolymer (EVA) film. Efficient removal of this EVA film is the key factor limiting recycling efficiency. As the core encapsulation material of PV modules (approximately 5.1% by mass), the EVA film is solid at room temperature. Its peel strength from the cover glass is greater than 30 N / cm, and its peel strength from the backsheet is greater than 20 N / cm, making complete removal difficult through simple methods. Currently, the separation technologies for EVA films in this field mainly fall into three categories:

[0004] One method is mechanical processing. The core principle of this method is to physically crush photovoltaic modules into mixed particles, and then use the differences in density and hardness of each component for separation operations such as sieving and magnetic separation. The specific process is to first disassemble the frame and junction box of the retired photovoltaic modules, then crush them into millimeter-sized particles using a crusher, and then pass them through equipment such as vibrating screens and air classifiers to achieve the initial separation of glass particles, metal particles and polymer particles.

[0005] The second method is pyrolysis. This method is based on the thermal degradation characteristics of EVA film. By heating at high temperatures, the EVA film is decomposed into small molecule gases or liquids, thereby releasing its adhesive properties. A typical process involves placing the pretreated photovoltaic module in a pyrolysis furnace and holding it at a high temperature above 400°C for a certain period of time to allow the EVA film to thermally decompose. Afterward, the module is cooled and the solid components such as glass and solar cells are separated, while the generated waste gas is collected and treated.

[0006] The third method is the chemical solvent method. This method utilizes the dissolving or swelling effect of organic solvents on the EVA film to weaken its bonding strength. Specifically, the photovoltaic module is disassembled and immersed in organic solvents such as trichloroethylene, toluene, and tetrahydrofuran. The EVA film is dissolved or swollen through the penetration of the solvent. After the film's bonding strength has significantly decreased, the components are manually or mechanically peeled off. Finally, the waste liquid is distilled for recovery or treated to render it harmless.

[0007] Based on the separation technologies described above, it is clear that none of them can efficiently reduce the interfacial adhesion strength between the EVA film and components such as glass and backsheet under mild and environmentally friendly conditions, thus making it difficult to achieve non-destructive and efficient separation of the various functional layers. Therefore, developing an efficient EVA film separation technology that meets the core requirements of photovoltaic module recycling is of significant practical importance. Summary of the Invention

[0008] The present invention aims to at least partially solve the technical problems in the above-mentioned technologies.

[0009] Therefore, this invention discloses a process for treating photovoltaic EVA using supercritical carbon dioxide, comprising the following steps:

[0010] S1: Remove the frame and junction box wires of the photovoltaic module and cut and break the photovoltaic module;

[0011] S2: Place the pretreated photovoltaic module in the reactor, add a co-solvent and introduce carbon dioxide;

[0012] S3: Adjust the temperature and pressure inside the reactor to a preset level, so that the carbon dioxide inside reaches a supercritical state and is maintained for a preset duration;

[0013] S4: After the preset time is reached, the reactor is rapidly cooled and depressurized;

[0014] S5: Remove the photovoltaic module from the reactor and peel off the glass layer and EVA film layer from the photovoltaic module.

[0015] The supercritical carbon dioxide treatment process for photovoltaic EVA disclosed in this invention has at least the following beneficial effects:

[0016] (1) High expansion efficiency: By utilizing the synergistic effect of supercritical carbon dioxide and co-solvent, the EVA film can be fully expanded in a short time;

[0017] (2) Low peel strength: The adhesion between EVA and glass interface is significantly reduced after treatment. The peel strength is about 36.9 N when untreated, and it drops to 17.8 N after supercritical carbon dioxide treatment, which can be easily peeled off.

[0018] (3) Mild conditions and low energy consumption and cost: The reaction temperature is generally controlled at 60-100℃, the energy consumption is much lower than that of heat treatment, and the processing cost is also lower than that of chemical method;

[0019] (4) Environmental protection and safety: Carbon dioxide is non-toxic, low-cost and recyclable, and does not produce harmful residues;

[0020] (5) High quality of material recycling: EVA film can be selectively separated, and silicon wafers and silver paste are almost undamaged; glass and backplane can be directly separated without residual pollution.

[0021] In addition, the supercritical carbon dioxide treatment process for photovoltaic EVA disclosed in this invention may also have the following additional technical features:

[0022] In one embodiment of the present invention, in step S1, the photovoltaic module is pre-treated, specifically as follows:

[0023] Remove the frame and junction box leads of the photovoltaic module, and cut and break the photovoltaic module.

[0024] In one embodiment of the present invention, in step S2, the co-solvent added to the reaction vessel is ethanol or water, and the solid-liquid ratio of the co-solvent to the photovoltaic module is 1:10.

[0025] In one embodiment of the present invention, in step S2, the co-solvent is determined according to the following steps:

[0026] S2.1: Select the photovoltaic modules from the same batch and divide them into 3 groups of photovoltaic modules with the same size and dimensions;

[0027] S2.2: Perform steps 1 to 4 for each group of photovoltaic modules, wherein,

[0028] In step S2, the reactants for each group of photovoltaic modules are: only carbon dioxide is introduced, ethanol is added and carbon dioxide is introduced, and water is added and carbon dioxide is introduced.

[0029] In step S3, the preset temperature, preset pressure, and preset duration of the reactor corresponding to each group of photovoltaic modules are the same;

[0030] S2.3: Measure the average stripping force and average thickness change of each group of photovoltaic modules;

[0031] S2.4: Establish the relationship between the reactants of each group of photovoltaic modules and the changes in the average stripping force and the average thickness;

[0032] S2.5: Based on the relationship between the reactants and the average peeling force and the average thickness change, select the material corresponding to the minimum value of the average peeling force or the maximum value of the average thickness change as the co-solvent.

[0033] In one embodiment of the present invention, in step S3, the preset temperature of the reactor is determined according to the following steps:

[0034] S3.1.1: Select the photovoltaic modules from the same batch and divide the photovoltaic modules into 6 groups, with each group having 3 photovoltaic modules of the same size and dimensions;

[0035] S3.1.2: Perform steps 1 to 4 for each group of photovoltaic modules, wherein,

[0036] In step S2, the reactants for each group of photovoltaic modules are water and carbon dioxide.

[0037] In step S3, the preset pressure and preset duration of the reactor corresponding to each group of photovoltaic modules are the same, and the test temperature of the reactor corresponding to each group of photovoltaic modules is different from 60 degrees Celsius to 120 degrees Celsius.

[0038] S3.1.3: Measure the average thickness change of the three photovoltaic modules in each group;

[0039] S3.1.4: Establish the relationship between the test temperature and the average thickness variation for each group of photovoltaic modules;

[0040] S3.1.5: Based on the relationship between the test temperature and the average thickness change, select the test temperature corresponding to the maximum value of the average thickness change as the preset temperature.

[0041] In one embodiment of the present invention, in step S3, the preset duration of the reaction vessel is determined according to the following steps:

[0042] S3.2.1: Select the photovoltaic modules from the same batch and divide the photovoltaic modules into 3 groups, with each group having 3 photovoltaic modules of the same size and dimensions;

[0043] S3.2.2: Perform steps 1 to 4 for each group of photovoltaic modules, wherein,

[0044] In step S2, the reactants for each group of photovoltaic modules are water and carbon dioxide.

[0045] In step S3, the preset temperature and preset pressure of the reactor corresponding to each group of photovoltaic modules are the same, and the test duration of the reactor corresponding to each group of photovoltaic modules is different from 1 hour to 6 hours.

[0046] S3.2.3: Measure the average thickness change of the three photovoltaic modules in each group;

[0047] S3.2.4: Establish the relationship between the test duration and the average thickness change for each group of photovoltaic modules;

[0048] S3.2.5: Based on the relationship between the test duration and the average thickness change, select the test duration that satisfies the preset thickness change in step 5 as the preset duration.

[0049] In one embodiment of the present invention, in step S3, the preset pressure of the reactor is determined according to the following steps:

[0050] S3.3.1: Select the photovoltaic modules from the same batch and divide the photovoltaic modules into 3 groups, with each group having 3 photovoltaic modules of the same size and dimensions;

[0051] S3.3.2: Perform steps 1 to 4 for each group of photovoltaic modules, wherein,

[0052] In step S2, the reactants for each group of photovoltaic modules are water and carbon dioxide.

[0053] In step S3, the preset temperature and preset pressure of the reactor corresponding to each group of photovoltaic modules are the same, and the test pressure of the reactor corresponding to each group of photovoltaic modules is a different pressure between 8 MPa and 10.1 MPa.

[0054] S3.3.3: Measure the average thickness change of the three photovoltaic modules in each group;

[0055] S3.3.4: Establish the relationship between the test pressure and the average thickness change for each group of photovoltaic modules;

[0056] S3.3.5: Based on the relationship between the test pressure and the average thickness change, select the test pressure corresponding to the maximum value of the average thickness change as the preset pressure.

[0057] In one embodiment of the present invention, the co-solvent is water, the preset temperature is 60 degrees Celsius to 70 degrees Celsius, the preset pressure is 10 MPa, and the preset duration is 3 hours.

[0058] Additional features and advantages of this invention will be set forth in the description which follows, or may be learned by practicing the invention. Attached Figure Description

[0059] The technical solution and beneficial effects of the present invention will become apparent and readily understood from the following description in conjunction with the accompanying drawings, wherein: Figure 1 This is a process flow diagram of the supercritical carbon dioxide treatment process for photovoltaic EVA of the present invention. Figure 2 The curves showing the variation of the exfoliation force under different co-solvent conditions in the supercritical carbon dioxide treatment process of photovoltaic EVA according to the present invention are shown. Figure 3 The curve showing the change in EVA film thickness with the type of cosolvent in the supercritical carbon dioxide treatment process of photovoltaic EVA of the present invention; Figure 4 The curve of EVA film layer expansion thickness versus temperature is shown in the supercritical carbon dioxide treatment process of photovoltaic EVA of the present invention. Figure 5 The curve showing the change in EVA film thickness over time in the supercritical carbon dioxide treatment process of photovoltaic EVA according to the present invention. Figure 6 The curve shows the change in EVA film thickness with pressure in the supercritical carbon dioxide treatment process of photovoltaic EVA according to the present invention. Detailed Implementation

[0060] The technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments.

[0061] The process for treating photovoltaic EVA with supercritical carbon dioxide disclosed in this invention will now be described with reference to the accompanying drawings.

[0062] like Figure 1 As shown, a process for treating photovoltaic EVA using supercritical carbon dioxide includes the following steps:

[0063] S1: Remove the frame and junction box wires of the photovoltaic module and cut and break the photovoltaic module;

[0064] It should be noted that photovoltaic modules refer to complete photovoltaic modules that include a glass layer, an EVA encapsulant layer, a cell layer, and a backsheet layer.

[0065] S2: Place the pretreated photovoltaic modules in the reactor, add a co-solvent and introduce carbon dioxide;

[0066] It should be noted that in step S2, the pretreated photovoltaic module is placed in a container containing a co-solvent and placed at the bottom of the reactor. After the reactor lid is closed, the reactor is connected to a gas cylinder containing carbon dioxide gas. Then, the gas cylinder is opened to introduce carbon dioxide. When the pressure inside the reactor reaches 2 to 3 MPa, the introduction of carbon dioxide is stopped, the gas cylinder is closed, and the pipe connecting the reactor and the gas cylinder is disconnected.

[0067] It should also be noted that the co-solvent added to the reactor is ethanol or water, and the solid-liquid ratio of the co-solvent to the photovoltaic module is 1:10.

[0068] S3: Adjust the temperature and pressure inside the reactor to the preset level, so that the carbon dioxide inside reaches the supercritical state and is maintained for the preset time;

[0069] It should be noted that the heating and pressurizing device of the reactor is used first to raise the temperature and pressure inside the reactor to reach the set temperature and pressure conditions. Then, vibration, stirring and other methods can be used to promote the reaction and maintain this state until the set reaction time.

[0070] S4: After the preset time is reached, the reactor is rapidly cooled and depressurized;

[0071] It should be noted that after the reaction is complete, the carbon dioxide gas in the reactor should be quickly discharged and the temperature lowered. When the pressure inside the reactor is close to atmospheric pressure, the reactor lid should be opened.

[0072] S5: Remove the photovoltaic module from the reactor and peel off the glass layer and EVA film layer from the photovoltaic module.

[0073] The processing technology provided by this invention uses supercritical carbon dioxide to foam and expand the EVA film layer, which greatly reduces its stickiness and peeling force, improves the peeling efficiency of the EVA film layer, and does not produce harmful gases or harmful liquids, making it environmentally friendly and pollution-free.

[0074] In one embodiment of the present invention, in step S2, the co-solvent is determined according to the following steps:

[0075] S2.1: Select photovoltaic modules from the same batch and divide them into 3 groups of photovoltaic modules with the same size and dimensions;

[0076] S2.2: Perform steps 1 to 4 for each group of photovoltaic modules, wherein,

[0077] In step S2, the reactants for each group of photovoltaic modules are: only carbon dioxide is introduced, ethanol is added and carbon dioxide is introduced, and water is added and carbon dioxide is introduced.

[0078] Specifically, for each group of photovoltaic modules, three different reactants were set up: the first type was carbon dioxide only, the second type was carbon dioxide while adding ethanol, and the third type was carbon dioxide while adding water.

[0079] It should be noted that the pure carbon dioxide group only used supercritical carbon dioxide to treat the EVA film layer, the water and carbon dioxide group used water and supercritical carbon dioxide as co-solvents to treat the EVA film layer, the ethanol and carbon dioxide group used ethanol and supercritical carbon dioxide as co-solvents to treat the EVA film layer, and the untreated photovoltaic modules served as the control group for direct stripping force measurement.

[0080] In step S3, the preset temperature, preset pressure, and preset time of the reactor corresponding to each group of photovoltaic modules are the same;

[0081] It should be noted that the preset pressure in the above technical content is 9 MPa, the preset temperature is 100 degrees Celsius, and the reaction time is 3 hours;

[0082] S2.3: Measure the average stripping force and average thickness change of each group of photovoltaic modules;

[0083] It should be noted that for the measurement of peeling force, a force gauge was used after the experiment to measure the force required to peel the glass from the EVA encapsulant layer on the photovoltaic module. Three photovoltaic modules were used in each experiment, and for each module, the peeling force was measured four times, with the average value taken as the peeling force for that photovoltaic module. Finally, the average of the three measured peeling forces was taken as the final result for this set of data.

[0084] It should also be noted that, for the measurement of thickness change, the experiment used vernier calipers to measure the thickness before and after the reaction, calculated the increase in thickness as the thickness change value, and further calculated the ratio of the thickness change value to the thickness before the reaction.

[0085] S2.4: Establish the relationship between the reactive materials of each group of photovoltaic modules and the changes in average stripping force and average thickness;

[0086] like Figure 2 As shown, the relationship between peeling force, thickness variation and different reactants is established, thereby determining the optimal treatment conditions for the peeling and removal of EVA film layer;

[0087] In this embodiment, the measured data is organized as shown in Table 1:

[0088] Table 1. Changes in thickness and peeling force with reactants

[0089] reactants Thickness variation (mm) Proportion Exploitative power (cattle) carbon dioxide 0.81 20.75% 17.8 carbon dioxide and water 0.93 23.48% 13.2 carbon dioxide and ethanol 0.85 21.71% 15.0 Unprocessed 36.9

[0090] S2.5: Based on the relationship between the reactants and the changes in average peeling force and average thickness, select the material corresponding to the minimum value of average peeling force or the maximum value of average thickness change as the co-solvent.

[0091] Depend on Figure 2 As shown in Table 1, under carbon dioxide conditions, the peeling force required to peel the glass from the EVA film layer after the reaction was 17.8 N; under carbon dioxide and ethanol conditions, the peeling force required to peel the glass from the EVA film layer after the reaction was 15.0 N; under carbon dioxide and water conditions, the peeling force required to peel the glass from the EVA film layer after the reaction was 13.2 N; at the same time, the peeling force required to peel the glass from the EVA film layer in the untreated photovoltaic module was also measured as a control group, and the measurement was performed in the same way as above, and the final peeling force was 36.9 N.

[0092] like Figure 3 The figure shows the variation curves of EVA thickness with different co-solvents as determined in the embodiments of this application. According to Table 1 and... Figure 3 The results show that the supercritical carbon dioxide and water conditions used in this invention cause significant expansion of the EVA film (thickness expansion of 23.48%) and a significant reduction in the peel strength of the glass layer (peeling force decreased from 36.9 N to 13.2 N), thereby achieving efficient separation of photovoltaic EVA and demonstrating significant advantages. Therefore, water is the optimal co-solvent.

[0093] It should be noted that, as can be seen from the above technical content, the greater the expansion of the EVA film layer, the smaller the required peeling force.

[0094] For the remaining technical details of this embodiment, please refer to the above technical details, which will not be repeated here.

[0095] In one embodiment of the present invention, in step S3, the preset temperature of the reactor is determined according to the following steps:

[0096] S3.1.1: Select the same batch of photovoltaic modules and divide them into 6 groups, with each group having 3 photovoltaic modules of the same size and dimensions;

[0097] S3.1.2: Perform steps 1 to 4 for each group of photovoltaic modules, wherein,

[0098] In step S2, the reactants for each group of photovoltaic modules are water and carbon dioxide.

[0099] In step S3, the preset pressure and preset time of the reactor corresponding to each group of photovoltaic modules are the same, and the test temperature of the reactor corresponding to each group of photovoltaic modules is different from 60 degrees Celsius to 120 degrees Celsius.

[0100] S3.1.3: Measure the average thickness change of the three photovoltaic modules in each group;

[0101] S3.1.4: Establish the relationship between the test temperature and the average thickness variation for each group of photovoltaic modules;

[0102] S3.1.5: Based on the relationship between test temperature and average thickness change, select the test temperature corresponding to the maximum value of average thickness change as the preset temperature.

[0103] It should be noted that, based on the technical content of the above embodiments, the co-solvent in this embodiment is water, the preset pressure is 8 MPa, and the preset duration is 3 hours;

[0104] The test temperatures for the six groups of photovoltaic modules were 65.6 degrees Celsius, 77.6 degrees Celsius, 88.4 degrees Celsius, 98.3 degrees Celsius, 105.2 degrees Celsius, and 112.2 degrees Celsius, respectively. After the reaction was completed, the thickness change of each group was measured.

[0105] For the measurement of thickness change, the experiment used vernier calipers to measure the thickness before and after the reaction, calculated the increase in thickness as the thickness change value, and further calculated the ratio of the thickness change value to the thickness before the reaction.

[0106] The measured data were compiled and are shown in Table 2. The relationship between thickness change and temperature was established to determine the optimal processing conditions for the peeling and removal of the EVA film layer.

[0107] Table 2. Thickness variation with temperature

[0108] Temperature (degrees Celsius) Thickness variation (mm) Proportion 65.6 0.95 25.22% 77.6 0.83 22.52% 88.4 0.47 12.07% 98.3 0.83 21.37% 105.2 0.83 21.55% 112.2 0.81 20.75%

[0109] like Figure 4 As shown, it is a curve of EVA film thickness change with experimental temperature, from Figure 4 As shown in Table 2, except for the data at 88.4 degrees Celsius, the thickness expansion ratio is above 20% at other temperatures, and the thickness expansion ratio is the largest at 65.6 degrees Celsius. Therefore, the optimal temperature parameter for this process can be determined to be 60 to 70 degrees Celsius.

[0110] For the remaining technical details of this embodiment, please refer to the above technical details, which will not be repeated here.

[0111] In one embodiment of the present invention, in step S3, the preset duration of the reaction vessel is determined according to the following steps:

[0112] S3.2.1: Select the same batch of photovoltaic modules and divide them into 3 groups, with each group having 3 photovoltaic modules of the same size and dimensions;

[0113] S3.2.2: Perform steps 1 to 4 for each group of photovoltaic modules, wherein,

[0114] In step S2, the reactants for each group of photovoltaic modules are water and carbon dioxide.

[0115] In step S3, the preset temperature and preset pressure of the reactor corresponding to each group of photovoltaic modules are the same, and the test duration of the reactor corresponding to each group of photovoltaic modules is different from 1 hour to 6 hours.

[0116] S3.2.3: Measure the average thickness change of the three photovoltaic modules in each group;

[0117] S3.2.4: Establish the relationship between the test duration and the average thickness variation for each group of photovoltaic modules;

[0118] S3.2.5: Based on the relationship between test duration and average thickness change, select the test duration that satisfies the preset thickness change in step 5 as the preset duration.

[0119] It should be noted that, based on the technical content of the above embodiments, the co-solvent in this embodiment is water, the preset pressure is 8 MPa, and the preset temperature is 100 degrees Celsius.

[0120] The test durations for the three groups of photovoltaic modules were 1 hour, 3 hours, and 6 hours, respectively. After the reaction was completed, the thickness changes of each group were measured.

[0121] For the measurement of thickness change, the experiment used vernier calipers to measure the thickness before and after the reaction, calculated the increase in thickness as the thickness change value, and further calculated the ratio of the thickness change value to the thickness before the reaction.

[0122] The measured data were compiled and are shown in Table 3. The relationship between thickness change and time was established to determine the optimal processing conditions for EVA peeling and removal.

[0123] Table 3. Thickness variation over time

[0124] Time (hours) Thickness variation (mm) Proportion 1 0.56 14.69% 3 0.83 21.37% 6 1.09 28.30%

[0125] like Figure 5 The figure shown is a curve illustrating the change in EVA thickness over time, as determined in an embodiment of this application. Figure 5 As shown in Table 3, the expansion of the EVA film thickness gradually increases with time. However, with increasing time, the burden on the equipment and the energy consumption of the system also increase accordingly. The optimal time of 6 hours, where the thickness change is greatest, was not selected here. A reaction time of 3 hours is sufficient to meet the process requirements, and energy consumption and cost will be lower. Therefore, the optimal reaction time for the process is 3 hours.

[0126] For the remaining technical details of this embodiment, please refer to the above technical details, which will not be repeated here.

[0127] In one embodiment of the present invention, in step S3, the preset pressure of the reactor is determined according to the following steps:

[0128] S3.3.1: Select the same batch of photovoltaic modules and divide them into 3 groups, with each group having 3 photovoltaic modules of the same size and dimensions;

[0129] S3.3.2: Perform steps 1 to 4 for each group of photovoltaic modules, wherein,

[0130] In step S2, the reactants for each group of photovoltaic modules are water and carbon dioxide.

[0131] In step S3, the preset temperature and preset pressure of the reactor corresponding to each group of photovoltaic modules are the same, and the test pressure of the reactor corresponding to each group of photovoltaic modules is different from 8 MPa to 10.1 MPa.

[0132] S3.3.3: Measure the average thickness change of the three photovoltaic modules in each group;

[0133] S3.3.4: Establish the relationship between the test pressure and the average thickness variation for each group of photovoltaic modules;

[0134] S3.3.5: Based on the relationship between test pressure and average thickness change, select the test pressure corresponding to the maximum value of average thickness change as the preset pressure.

[0135] It should be noted that, based on the technical content of the above embodiments, the co-solvent in this embodiment is water, the preset duration is 3 hours, and the preset temperature is 100 degrees Celsius;

[0136] The test pressures for the three groups of photovoltaic modules were 8 MPa, 8.81 MPa and 10.1 MPa, respectively. After the reaction was completed, the thickness change of each group was measured.

[0137] For the measurement of thickness change, the experiment used vernier calipers to measure the thickness before and after the reaction, calculated the increase in thickness as the thickness change value, and further calculated the ratio of the thickness change value to the thickness before the reaction.

[0138] The measured data were compiled and are shown in Table 4. The relationship between thickness change and pressure was established to determine the optimal processing conditions for EVA film layer peeling and removal.

[0139] Table 4. Thickness variation with pressure

[0140] Pressure (megapascals) Thickness variation (mm) Proportion 8.00 0.83 21.37% 8.81 1.03 25.75% 10.10 1.09 28.13%

[0141] like Figure 6 The figure shown is a curve illustrating the change in EVA film thickness as a function of pressure, as determined in an embodiment of this application. Figure 6 As shown in Table 4, the expansion of the EVA film layer gradually increases with increasing pressure. At around 10 MPa, the expansion of the EVA film layer already shows a very significant increase. With further increases in pressure, the expansion and separation effect of the EVA film layer may further improve. Currently, within the experimental range, the optimal pressure condition for the process is 10 MPa.

[0142] For the remaining technical details of this embodiment, please refer to the above technical details, which will not be repeated here.

[0143] In one embodiment of the present invention, the co-solvent is water, the preset temperature is 60 to 70 degrees Celsius, the preset pressure is 10 MPa, and the preset duration is 3 hours.

[0144] In summary, the supercritical carbon dioxide treatment process for photovoltaic EVA disclosed in this invention has at least the following beneficial effects:

[0145] (1) High expansion efficiency: By utilizing the synergistic effect of supercritical carbon dioxide and co-solvent, the EVA film can be fully expanded in a short time;

[0146] (2) Low peel strength: The adhesion between EVA and glass interface is significantly reduced after treatment. The peel strength is about 36.9 N when untreated, which is reduced to 17.8 N after supercritical carbon dioxide treatment, 15.0 N after adding ethanol, and 13.2 N after adding water, which can be easily peeled off.

[0147] (3) Mild conditions and low energy consumption and cost: The reaction temperature is generally controlled between 60 degrees Celsius and 100 degrees Celsius, and the energy consumption is much lower than that of the heat treatment method and the processing cost is also lower than that of the chemical method;

[0148] (4) Environmental protection and safety: Carbon dioxide is non-toxic, low in cost and recyclable, and does not produce harmful residues; the co-solvents used, such as water and ethanol, are green and environmentally friendly solvents.

[0149] (5) High quality of material recycling: EVA film can be selectively separated, and silicon wafers and silver paste are almost undamaged; glass and backplane can be directly separated without residual pollution.

[0150] Although embodiments of the present invention have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Those skilled in the art can make changes, modifications, substitutions and variations to the above embodiments within the scope of the present invention.

Claims

1. A process for treating photovoltaic EVA using supercritical carbon dioxide, characterized in that, Includes the following steps: S1: Remove the frame and junction box wires of the photovoltaic module and cut and break the photovoltaic module; S2: Place the pretreated photovoltaic module in the reactor, add a co-solvent and introduce carbon dioxide; S3: Adjust the temperature and pressure inside the reactor to a preset level, so that the carbon dioxide inside reaches a supercritical state and is maintained for a preset duration; S4: After the preset time is reached, the reactor is rapidly cooled and depressurized; S5: Remove the photovoltaic module from the reactor and peel off the glass layer and EVA film layer from the photovoltaic module.

2. The process for treating photovoltaic EVA with supercritical carbon dioxide as described in claim 1, characterized in that, In step S1, the photovoltaic module undergoes pretreatment, specifically as follows: Remove the frame and junction box leads of the photovoltaic module, and cut and break the photovoltaic module.

3. The process for treating photovoltaic EVA with supercritical carbon dioxide as described in claim 1, characterized in that, In step S2, the co-solvent added to the reaction vessel is ethanol or water, and the solid-liquid ratio of the co-solvent to the photovoltaic module is 1:

10.

4. The process for treating photovoltaic EVA with supercritical carbon dioxide as described in claim 3, characterized in that, In step S2, the co-solvent is determined according to the following steps: S2.1: Select the photovoltaic modules from the same batch and divide the photovoltaic modules into 3 groups of photovoltaic modules with the same size and dimensions; S2.2: Perform steps 1 to 4 for each group of photovoltaic modules, wherein, In step S2, the reactants for each group of photovoltaic modules are: only carbon dioxide is introduced, ethanol is added and carbon dioxide is introduced, and water is added and carbon dioxide is introduced. In step S3, the preset temperature, preset pressure, and preset duration of the reactor corresponding to each group of photovoltaic modules are the same; S2.3: Measure the average stripping force and average thickness change of each group of photovoltaic modules; S2.4: Establish the relationship between the reactants of each group of photovoltaic modules and the changes in the average stripping force and the average thickness; S2.5: Based on the relationship between the reactants and the average peeling force and the average thickness change, select the material corresponding to the minimum value of the average peeling force or the maximum value of the average thickness change as the co-solvent.

5. The process for treating photovoltaic EVA with supercritical carbon dioxide as described in claim 3, characterized in that, In step S3, the preset temperature of the reactor is determined according to the following steps: S3.1.1: Select the photovoltaic modules from the same batch and divide the photovoltaic modules into 6 groups, with each group having 3 photovoltaic modules of the same size and dimensions; S3.1.2: Perform steps 1 to 4 for each group of photovoltaic modules, wherein, In step S2, the reactants for each group of photovoltaic modules are water and carbon dioxide. In step S3, the preset pressure and preset duration of the reactor corresponding to each group of photovoltaic modules are the same, and the test temperature of the reactor corresponding to each group of photovoltaic modules is different from 60 degrees Celsius to 120 degrees Celsius. S3.1.3: Measure the average thickness change of the three photovoltaic modules in each group; S3.1.4: Establish the relationship between the test temperature and the average thickness variation for each group of photovoltaic modules; S3.1.5: Based on the relationship between the test temperature and the average thickness change, select the test temperature corresponding to the maximum value of the average thickness change as the preset temperature.

6. The process for treating photovoltaic EVA with supercritical carbon dioxide as described in claim 3, characterized in that, In step S3, the preset duration of the reaction vessel is determined according to the following steps: S3.2.1: Select the photovoltaic modules from the same batch and divide the photovoltaic modules into 3 groups, with each group having 3 photovoltaic modules of the same size and dimensions; S3.2.2: Perform steps 1 to 4 for each group of photovoltaic modules, wherein, In step S2, the reactants for each group of photovoltaic modules are water and carbon dioxide. In step S3, the preset temperature and preset pressure of the reactor corresponding to each group of photovoltaic modules are the same, and the test duration of the reactor corresponding to each group of photovoltaic modules is different from 1 hour to 6 hours. S3.2.3: Measure the average thickness change of the three photovoltaic modules in each group; S3.2.4: Establish the relationship between the test duration and the average thickness change for each group of photovoltaic modules; S3.2.5: Based on the relationship between the test duration and the average thickness change, select the test duration that satisfies the preset thickness change in step 5 as the preset duration.

7. The process for treating photovoltaic EVA with supercritical carbon dioxide as described in claim 3, characterized in that, In step S3, the preset pressure of the reactor is determined according to the following steps: S3.3.1: Select the photovoltaic modules from the same batch and divide the photovoltaic modules into 3 groups, with each group having 3 photovoltaic modules of the same size and dimensions; S3.3.2: Perform steps 1 to 4 for each group of photovoltaic modules, wherein, In step S2, the reactants for each group of photovoltaic modules are water and carbon dioxide. In step S3, the preset temperature and preset pressure of the reactor corresponding to each group of photovoltaic modules are the same, and the test pressure of the reactor corresponding to each group of photovoltaic modules is a different pressure between 8 MPa and 10.1 MPa. S3.3.3: Measure the average thickness change of the three photovoltaic modules in each group; S3.3.4: Establish the relationship between the test pressure and the average thickness change for each group of photovoltaic modules; S3.3.5: Based on the relationship between the test pressure and the average thickness change, select the test pressure corresponding to the maximum value of the average thickness change as the preset pressure.

8. The process for treating photovoltaic EVA with supercritical carbon dioxide as described in claim 3, characterized in that, The co-solvent is water, the preset temperature is 60 to 70 degrees Celsius, the preset pressure is 10 MPa, and the preset duration is 3 hours.

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