Recovery process for silver component of retired solar cell

Abstract

The invention belongs to the technical field of waste recovery, and particularly discloses a retired solar cell silver component recovery process, which comprises the following steps of: mechanically disassembling a retired crystalline silicon photovoltaic module to remove a metal aluminum outer frame and a junction box; and carrying out thermal decomposition to remove the EVA packaging adhesive film so as to obtain the crystalline silicon battery piece. Leaching a valuable metal element Ag in the retired crystalline silicon solar cell by using an organic acid system; the high-purity silver powder is recycled through the three steps of chlorination precipitation, ammonia water dissolution and organic reducing agent reduction. The method has the advantages that organic acid leaching and organic reducing agent reduction are adopted in the silver recovery process, the process is simple, operation is easy, and the safety coefficient is high; compared with other recovery methods, leaching of various impurity ions such as Cu and Pb is reduced, the silver recovery rate is high, and the purity is high; organic acid leaching and organic reducing agent reduction are adopted, so that wastewater is reduced, and environmental pollution is avoided.

Description

Technical Field

[0001] The invention belongs to the technical field of waste recycling, and in particular relates to a method for recycling silver components of retired solar cells. Background Art

[0002] Crystalline silicon solar cells are the most widely used solar cells in the world. They have the advantages of high cost performance, good adaptability and mature technology. Crystalline silicon solar cells have been developed for a long time and have mature production processes. They have been used on a large scale in actual production. As photovoltaic modules reach the end of their service life, recycling the silicon, silver, aluminum, copper and other resources contained in the cells and photovoltaic ribbons in retired photovoltaic modules is of great significance and benefit.

[0003] At present, the main steps of the method for recovering silver components from retired crystalline silicon solar cells are silver leaching-chlorination precipitation-precipitation dissolution-reduction. The leaching agent for leaching silver from retired crystalline silicon solar cells is mainly inorganic acid or inorganic acid mixed solution, but inorganic strong acid is very corrosive and volatile. In actual production, the operation is complicated and the risk factor is extremely high, and the wastewater generated will also pollute the environment. Although some processes can obtain higher purity silver powder, the process is complicated and the cost is high. Summary of the invention

[0004] The purpose of the present invention is to provide a process for recovering the silver component of retired solar cells, aiming to solve the shortcomings of the existing silver component recovery technology. The process flow of recovering the silver component by the method of the present invention is short, the operation is simple, and the silver recovery rate is high.

[0005] To achieve the above object, the present invention provides a process for recovering silver components from retired solar cells, comprising the following steps:

[0006] (1) Mechanically dismantle the retired crystalline silicon photovoltaic modules and remove the metal aluminum frame and junction box;

[0007] (2) removing the EVA encapsulation film by thermal decomposition to obtain a crystalline silicon cell;

[0008] (3) leaching valuable metal Ag in the retired crystalline silicon cell with an organic acid system to obtain a filtrate, wherein the organic acid system comprises an organic acid and an oxidant;

[0009] (4) The filtrate in step (3) is recovered through three steps of chlorination precipitation, ammonia solution, and organic reducing agent reduction to obtain high-purity silver powder, wherein the organic reducing agent includes one or more of ascorbic acid, reducing glucose, or acetone.

[0010] Preferably, the temperature range applied when pyrolysis is used to remove the EVA packaging film is 480-800°C.

[0011] Preferably, the organic acid system leaching agent is citric acid monohydrate (C 6 H 8 O 7 ·H 2 O) or methanesulfonic acid (MSA) with hydrogen peroxide (H 2 O 2 ) mixed acid solution.

[0012] Preferably, the organic acid concentration in the organic acid system leaching agent is in the range of 0.5 to 5 mol / L, 30% H 2 O 2 The dosage is 150ml / L~600ml / L.

[0013] Preferably, the temperature range of the organic acid system during leaching is 20-100° C.; the leaching time range is 30-180 min.

[0014] Preferably, during the organic acid system leaching process, the liquid-to-solid ratio of the organic acid system leaching agent to the battery cell is in the range of 20:1 to 60:1.

[0015] Preferably, the chlorine source in the chlorination precipitation step comprises HCl, NaCl, NH 4 One or more of Cl.

[0016] Preferably, the molar ratio of the organic reducing agent to the silver ions is in the range of 0.25-2.

[0017] Compared with the prior art, the technical solution of the present invention has the following beneficial effects:

[0018] (1) The silver recovery process of the present invention uses organic acid leaching and organic reducing agent reduction, which is simple in process, simple in operation and high in safety factor;

[0019] (2) Compared with other recovery methods, it reduces the leaching of various impurity ions such as Cu and Pb, and has a high silver recovery rate and high purity;

[0020] (3) The present invention uses organic acid leaching and organic reducing agent reduction to reduce wastewater generation and avoid environmental pollution. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 This is a process flow chart of recycling silver components of retired solar cells according to the present invention;

[0022] Figure 2 This is a SEM image of the front side of the cell after leaching in Example 1 of the present invention;

[0023] Figure 3 The SEM detection spectrum of AgCl prepared in Example 2 of the present invention;

[0024] Figure 4 is different n in Example 3 of the present invention 抗坏血酸 / n Ag+ Ratio, Ag + Reduction rate change trend. DETAILED DESCRIPTION

[0025] The present invention will be further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention, rather than to limit the present invention.

[0026] Example 1

[0027] The photovoltaic module was mechanically disassembled by a frame dismantling machine to remove the metal aluminum frame and junction box, and then the encapsulation film was removed by pyrolysis at 500°C to obtain the crystalline silicon cell. 6 H 8 O 7 ·H 2 O concentration is 1 mol / L, 30% H 2 O 2 The dosage is 375ml / L, the leaching time is 2.5h, the leaching temperature is 60℃, and the liquid-to-solid ratio is 20:1. At this time, the Ag leaching rate is as high as 97.38%. SEM detection of the silver grid line on the front of the cell after leaching, such as Figure 2 As shown, the silver grid line on the front of the cell after leaching was tested by EDS, and the component analysis is shown in Table 1. After leaching, NaCl was used as a chlorine source for precipitation, n Cl - / n Ag + is 10, then Ag + The precipitation rate reached 99.95%. The precipitated AgCl was dissolved with ammonia water and the dispersant polyvinyl pyrrolidone (PVP) was added, and then the reducing agent ascorbic acid was added. 抗坏血酸 / n Ag + 0.75, Ag + The reduction rate is 99.96%. The silver powder reduced from silver chloride prepared by treating the leaching solution of retired crystalline silicon solar cells under this method system was subjected to EDS testing, and the component analysis is shown in Table 2.

[0028] Table 1 Composition analysis of silver grid lines on the front of the cell after leaching

[0029] element Mass fraction / % Atomic percentage / % C 2.66 5.80 O 1.95 3.21 N 2.03 3.80 Si 93.31 87.17 Ag 0.05 0.01

[0030] Table 2 Composition analysis of reduced silver powder

[0031] element Mass fraction / % Atomic percentage / % Ag 98.41 90.15 O 1.59 9.85

[0032] Example 2

[0033] The photovoltaic modules were mechanically disassembled by a frame dismantling machine to remove the metal aluminum frame and junction box, and then the encapsulation film was removed by pyrolysis at 500°C to obtain crystalline silicon cells. The crystalline silicon cells were leached with methanesulfonic acid concentrations of 2 mol / L and 30% H 2 O 2 The dosage is 375ml / L, the leaching time is 2h, the leaching temperature is 50℃, and the liquid-solid ratio is 20:1. At this time, the leaching rate of Ag is as high as 97.13%. After the leaching is completed, HCl is used as the chlorine source for precipitation. Cl - / n Ag + is 10, then Ag + The precipitation rate reached 99.91%. The prepared AgCl was tested by SEM. Figure 3 As shown. The precipitated AgCl was dissolved with ammonia water and the dispersant PVP was added, and then the reducing agent ascorbic acid was added. 抗坏血酸 / n Ag + is 0.5, Ag + The reduction rate is 99.93%.

[0034] Example 3

[0035] The photovoltaic module was mechanically disassembled by a frame dismantling machine to remove the metal aluminum frame and junction box, and then the encapsulation film was removed by pyrolysis at 500°C to obtain the crystalline silicon cell. 6 H 8 O 7 ·H 2 O concentration is 1 mol / L, 30% H 2 O 2 The dosage is 437.5 ml / L, the leaching time is 2 h, the leaching temperature is 50 ° C, and the liquid-to-solid ratio is 25:1. At this time, the leaching rate of Ag is as high as 97.52%. After the leaching is completed, HCl is used as the chlorine source for precipitation. Cl - / n Ag + is 10, then Ag + The precipitation rate reached 99.86%. The precipitated AgCl was dissolved with ammonia water and the dispersant PVP was added. Then, the reducing agent ascorbic acid was added to explore the different n 抗坏血酸 / n Ag + Ratio, Ag + The trend of reduction rate, such as Figure 4 As shown. 抗坏血酸 / n Ag+ The ratio increases, Ag + The reduction rate showed an overall upward trend, and the reduction rate was above 99.5%. 抗坏血酸 / n Ag + When the Ag + The reduction rate reached the highest value, which was 99.7%. Based on the principle of saving, n 抗坏血酸 / n Ag + is 1.25.

Claims

1. A process for recovering silver components from retired solar cells, characterized in that: The following steps are involved: (1) Mechanically dismantle the retired crystalline silicon photovoltaic modules and remove the metal aluminum frame and junction box; (2) removing the EVA encapsulation film by thermal decomposition to obtain a crystalline silicon cell; (3) leaching valuable metal Ag in the retired crystalline silicon cell with an organic acid system to obtain a filtrate, wherein the organic acid system comprises an organic acid and an oxidant; (4) The filtrate in step (3) is recovered through three steps of chlorination precipitation, ammonia solution, and organic reducing agent reduction to obtain high-purity silver powder, wherein the organic reducing agent includes one or more of ascorbic acid, reducing glucose, or acetone.

2. The process according to claim 1, characterized in that The temperature range applied when pyrolysis is used to remove the EVA encapsulation film is 480 to 800°C.

3. The process according to claim 1, characterized in that The organic acid system leaching agent is a mixed acid solution of one or both of citric acid monohydrate or methanesulfonic acid and hydrogen peroxide.

4. The process according to claim 3, characterized in that The organic acid concentration range of the organic acid system leaching agent is 0.5-5 mol / L, and the dosage of 30% H2O2 is 150ml / L-600ml / L.

5. The process according to claim 1, characterized in that The temperature range of the organic acid system leaching is 20-100°C; the leaching time range is 30-180 minutes.

6. The process according to claim 1, characterized in that During the leaching process of the organic acid system, the liquid-to-solid ratio of the organic acid system leaching agent to the battery cell is in the range of 20:1 to 60:

1.

7. The process according to claim 1, characterized in that The chlorine source in the chlorination precipitation step includes one or more of HCl, NaCl, and NH4Cl.

8. The process according to claim 1, characterized in that The molar ratio of the organic reducing agent to the silver ions is in the range of 0.25 to 2.

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