All-component recycling method for retired cadmium telluride thin-film solar cell

Abstract

The invention provides a method for recycling all components of a retired cadmium telluride thin-film solar cell, which comprises the following steps of: (1) mechanically dissociating a main body part of the solar cell to obtain front glass, back glass and wires enriched with Cd, Te and Sn, and directly recycling the back glass and the wires; (2) vulcanizing the front glass, and washing with water to obtain clean glass and tellurium-cadmium-tin mixed powder; (3) performing vacuum distillation on the tellurium-cadmium-tin-rich powder to obtain high-purity tellurium and cadmium-rich tin slag; and (4) the cadmium-rich tin slag is leached through a Na2S or NaHS solution, and CdS sediment and a Na2SnS3 solution are obtained. According to the method, the retired cadmium telluride thin-film solar cell is treated through a dry-wet combined method, and a multi-layer coating material is recycled in an echelon manner. Wherein the recovery rates of tellurium, cadmium and tin are all more than 98%, the glass substrate can be recovered by 100%, the purity of the obtained tellurium product reaches more than 99.9%, and the purity of the cadmium and tin products exceeds 98%. The method has the advantages of thorough component recovery, simple process flow, high added value of products and the like, and has a relatively good application prospect.

Description

Technical Field

[0001] The present invention belongs to the technical fields of metallurgical engineering, chemical engineering, and resource utilization of industrial solid waste, and particularly relates to a method for recovering tellurium, cadmium, and tin elements in waste cadmium telluride thin-film solar cells. Background Art

[0002] In today's world, the contradiction between resource and energy shortages and ecological environmental pollution has become increasingly prominent. As a pollution-free, renewable, and sustainable clean energy, solar energy has attracted more and more attention. Thin-film solar cells represented by cadmium telluride have advantages such as high conversion efficiency, low temperature coefficient, and good weak light effect, and their application scale is growing rapidly. However, after being decommissioned, a large number of waste cadmium telluride thin-film solar cells will be generated, and the heavy metal pollution elements in them will pose a serious threat to the ecological environment. In addition, valuable metal mineral resources such as tellurium and cadmium are facing exhaustion. Recycling the above-mentioned decommissioned cadmium telluride thin-film solar cells can effectively expand the types of tellurium and cadmium resources and relieve the pressure of resource shortage. Therefore, the harmless and resource-based treatment of decommissioned cadmium telluride thin-film solar cells is of great significance.

[0003] Currently, there are mainly two types of methods for recycling decommissioned cadmium telluride thin-film solar cells: pyrometallurgy and hydrometallurgy. The pyrometallurgical recycling method is based on the volatility of tellurium compounds or cadmium compounds to obtain metal compounds from the gas phase. For example, in Chinese Patent Document CN102180447A (System and method for recycling cadmium telluride CdTe), the cadmium telluride thin-film solar cell is calcined in a vacuum environment at 650 - 850 °C, and cadmium telluride sublimes and is enriched. This method does not treat cadmium sulfide and tin oxide films, resulting in resource waste and the glass substrate cannot be recycled. Chinese Patent Document CN109502559A (Method for recycling tellurium from cadmium telluride waste) mixes cadmium telluride waste with sulfur, performs sulfurization roasting in a protective gas, and then sublimes tellurium in a vacuum environment at 700 - 780 °C to be enriched. This method has high raw material requirements and a single recovery target, and is not suitable for the full-component recovery of cadmium telluride thin-film solar cells with delicate structures and rich in various valuable metals. Chinese Patent Document CN113564361A (Pyrometallurgical treatment and recycling process for cadmium telluride thin-film solar cells) crushes the cadmium telluride thin-film solar cell and heats it to 700 - 800 °C in an oxidizing atmosphere. The metal thin film is oxidized to tellurium oxide and cadmium oxide and enters the flue gas for recovery. The product of this method is a mixture of two metal oxides and needs further treatment, and the glass substrate is severely melted, affecting recycling and reuse.

[0004] The general feature of the hydrometallurgical method is that after the cadmium telluride thin-film solar cell is crushed, a leaching agent with strong acidity and oxidizing properties is used to make the film components enter the solution, and then the elements in the solution are separated and purified by different methods. For example, Chinese patent document CN102953081A (a method and system for recovering tellurium and cadmium from a module containing cadmium telluride) uses nitric acid or sulfuric acid plus hydrogen peroxide to leach cadmium telluride and cadmium sulfide films, and then obtains tellurium and cadmium elements by electrochemical methods. Chinese patent document CN102953080A (a method for recovering tellurium from a cadmium telluride-containing component) uses a nitric acid solution containing additives such as sulfates, hydroxides and organic matter to leach cadmium telluride and cadmium sulfide films, and then obtains tellurium and cadmium elements by electrochemical methods. Chinese patent document CN103199147A (a recycling method for cadmium telluride thin film solar cells) uses a mixed solution of sulfuric acid and hydrogen peroxide to leach cadmium telluride and cadmium sulfide films, and then adds polyaluminium chloride solution and activated carbon powder to obtain a mixture of tellurium compounds and cadmium compounds. Chinese patent document CN109082527A (a mechanical abrasion recycling method for cadmium sulfide thin film solar cells) uses a method of mechanical corrosion plus high-pressure water flow to obtain each metal film from a glass substrate, uses a mixed solution of sulfuric acid and hydrogen peroxide to leach, and obtains tellurium dioxide by extraction and addition of alkali solution. Chinese patent document CN108866340A (a microwave irradiation recycling method for cadmium telluride thin film solar cells) uses a method of microwave irradiation plus high-pressure water flow to separate each metal film from a glass substrate, uses a mixed solution of sulfuric acid and hydrogen peroxide to leach, and obtains tellurium dioxide by extraction and addition of alkali solution. Chinese patent document CN114132902A (Method for recovering cadmium telluride waste) uses a mixed solution of sulfuric acid and hydrogen peroxide to leach cadmium telluride waste, adds sulfurous acid solution to obtain tellurium element, and further purifies tellurium by vacuum distillation. H2O2 is introduced into the filtrate. 2 S gas, to obtain cadmium sulfide precipitation. Chinese patent document CN110980658A (recovery method of cadmium telluride waste), uses a mixed solution of hydrochloric acid and sodium chlorate to leach cadmium telluride and cadmium sulfide film, adds hydrochloric acid and sodium sulfite to the leachate to obtain tellurium dioxide precipitation, and then adds sodium hydroxide to the filtrate to obtain cadmium hydroxide precipitation. The common point of the above recovery methods is that after the cadmium telluride thin-film solar cell is crushed, the metal elements are introduced into the solution by leaching, and then each metal is separated and purified from the solution. The general disadvantages of this type of method are poor working environment, easy to produce a large amount of cadmium-containing wastewater, the product purity obtained by chemical precipitation method is low, and the raw material is glass fragments with a film thickness of only one thousandth, the leaching process is inefficient, and the economic benefit is not high.

[0005] None of the above existing recycling methods have dealt with the transparent TCO layer (tin oxide film) of cadmium telluride thin-film solar cells, resulting in waste of resources and the inability to directly recycle the glass. Therefore, developing a cadmium telluride thin-film solar cell recycling technology with reasonable design, low equipment investment and operating costs, full-element recycling of glass and metal, and high comprehensive recovery rate has great scientific significance and application prospects. Summary of the Invention

[0006] The technical problem to be solved by the present invention is to overcome the deficiencies of the prior art and provide a method for the full-component recycling and utilization of retired cadmium telluride thin-film solar cells with low cost, simple process, high metal recovery rate, and environmental friendliness.

[0007] To solve the above technical problems, the present invention adopts the following technical solutions.

[0008] A method for the full-component recycling and utilization of retired cadmium telluride thin-film solar cells includes the following steps:

[0009] (1) The retired cadmium telluride thin-film battery is processed by methods such as thermal dissociation, pressure water cutting, and mechanical cutting to obtain the front glass, back glass, and wires coated with CdTe / CdS / SnO 2 thin films, among which the back glass and wires can be directly recycled;

[0010] (2) During the low-temperature sulfidation process, valuable metals and the front glass matrix are efficiently separated. The sulfidation treatment induces the phase transformation and dissociation of the valuable metal coating, and then after washing and filtering, a tellurium-rich cadmium-tin powder and recyclable front glass are obtained;

[0011] (3) The tellurium-rich cadmium-tin powder is prepared into high-purity tellurium products and cadmium-rich tin powder by vacuum distillation;

[0012] (4) The cadmium-rich tin mixed powder is leached with sodium sulfide or sodium hydrosulfide solution and filtered to successfully separate cadmium and tin, obtaining relatively high-purity Na 2 SnS 3 and CdS.

[0013] For the above method for the full-component recycling and utilization of retired cadmium telluride thin-film solar cells, preferably, in step (1), the separation method of the front glass and the back glass includes one or more of thermal dissociation, pressure water cutting, and mechanical cutting.

[0014] For the above method for the full-component recycling and utilization of retired cadmium telluride thin-film solar cells, preferably, in step (1), the separation method of the EVA film includes one or more of mechanical / artificial peeling and oxidative roasting.

[0015] For the above method for the full-component recycling and utilization of retired cadmium telluride thin-film solar cells, preferably, in step (2), the sulfidation roasting temperature is 400 - 500 °C, and the time is 0.5 - 2 h.

[0016] In the above-mentioned method for recycling all components of retired cadmium telluride thin-film solar cells, preferably, in step (2), the sulfurizing agent includes one or more of sulfur, sulfide, thiosulfate, etc.

[0017] In the above-mentioned method for recycling all components of retired cadmium telluride thin-film solar cells, preferably, in step (2), the sulfurization roasting atmosphere includes one or more of air, argon, and the like.

[0018] In the above-mentioned method for recycling all components of retired cadmium telluride thin-film solar cells, preferably, in step (3), the vacuum distillation conditions are vacuum degree ≤10 Pa, temperature 300-800° C., and time 0.5-4 h.

[0019] In the above-mentioned method for recycling all components of retired cadmium telluride thin-film solar cells, preferably, in step (4), the leaching temperature is 20-80°C, the leaching time is 0.5-2h, and the volume mass ratio of powder to leaching solution is 1g:3-30mL.

[0020] In the above-mentioned method for recycling all components of retired cadmium telluride thin-film solar cells, preferably, in step (4), the type of leaching solution includes one or more of sodium sulfide solution, sodium hydrosulfide, and sodium thiosulfate solution.

[0021] In the above-mentioned method for recycling all components of retired cadmium telluride thin-film solar cells, preferably, in step (4), the leaching is carried out under mechanical stirring, ultrasound or microwave conditions.

[0022] Compared with the prior art, the advantages of the present invention are:

[0023] (1) The present invention provides a method for recycling all components of retired cadmium telluride thin-film solar cells. First, the retired cadmium telluride thin-film solar cell panels are dissociated as a whole after pyrolysis-mechanical stripping to obtain the front glass, wires and back glass with valuable metal coating, wherein the wires and back glass can be directly recycled; the front glass plate with valuable metal coating is subjected to low-temperature sulfurization treatment to make the valuable metal film undergo phase transformation and dissociate from the front glass substrate, thereby obtaining a clean glass plate and cadmium telluride-rich tin powder that can be directly recycled; based on the volatility of tellurium, the cadmium telluride-rich tin powder is vacuum distilled to obtain high-purity tellurium element and cadmium-rich tin powder; finally, cadmium and tin are separated by selective leaching to obtain sodium thiostannate and cadmium sulfide, which can be sold as intermediate chemical products. The method for recycling all components of retired cadmium telluride thin-film solar cells of the present invention can achieve a recovery rate of more than 98% for the three valuable metals of tellurium, cadmium and tin, 100% recovery of the glass substrate, and a purity of more than 99.9% for the obtained tellurium product, and a purity of more than 98% for the cadmium and tin products.

[0024] (2) The present invention uses the method of overall dissociation to separate the front and rear glasses of retired cadmium telluride solar cells, and a complete glass substrate can be obtained, achieving efficient and non-destructive recycling of the glass; low-temperature sulfurization roasting causes the valuable metal coating to undergo phase transformation and dissociate from the front glass. Low-temperature sulfurization has the advantages of simple operation, low energy consumption, low raw material cost, high dissociation efficiency and degree, etc., which is conducive to industrial application; high-purity tellurium, cadmium, and tin products are gradually separated through vacuum distillation-leaching, realizing the efficient recycling of all components of retired cadmium telluride thin-film materials. The present invention has good economic efficiency and environmental friendliness, and conforms to the concept of green and sustainable development. Brief Description of the Drawings

[0025] Figure 1 It is a schematic process flow diagram for the short-process full-component recycling and utilization of retired cadmium telluride thin-film solar cells of the present invention.

[0026] Figure 2 It is a physical diagram (a) and a structural composition diagram (b) of a retired cadmium telluride thin-film solar cell of the present invention.

[0027] Figure 3 It is a SEM surface scan diagram of the front glass with a metal coating of the present invention.

[0028] Figure 4 It is an XRD pattern of the tellurium-rich cadmium-tin powder prepared by the present invention.

[0029] Figure 5 It is a physical picture and SEM surface scan result of the tellurium-rich cadmium-tin powder prepared by the present invention.

[0030] Figure 6 It is an optical photograph of the clean front glass after removing the metal coating prepared by the present invention.

[0031] Figure 7 It is a SEM surface scan result of the clean front glass prepared by the present invention.

[0032] Figure 8 It is an optical photograph of the high-purity tellurium product and cadmium-tin-rich powder prepared by the present invention. Detailed Embodiments

[0033] The present invention will be further described below in conjunction with the drawings in the specification and specific preferred embodiments, but the protection scope of the present invention is not limited thereby. The materials and instruments used in the following embodiments are all commercially available.

[0034] A method for recycling all components of a retired cadmium telluride thin-film solar cell of the present invention, the process flow is as Figure 1 shown, and it includes the following steps:

[0035] (1) Cadmium telluride thin-film solar cells produced by an international solar photovoltaic module manufacturer, with a single-piece size of 0.6m * 1.2m. The structure from top to bottom is front glass (3mm), SnO 2 film (0.6μm), CdS film (0.4μm), CdTe film (4μm), EVA film (0.5mm), back glass (3mm), and wires, etc. The front glass coated with three metal films and the back glass adhered with EVA film are integrally separated by thermal dissociation at 400°C in an air atmosphere to obtain clean glass.

[0036] (2) Sodium sulfide is added to the metal coating on the front glass. Multiple coated glasses are stacked and sent into the furnace for sulfidation roasting at 450°C for 2h. After roasting, the gray metal film on the glass surface turns into yellow / orange flakes. The clean glass can be obtained by washing with water, and the washing solution is filtered to obtain a filter residue rich in valuable metals. The chemical composition of the filter residue is Cd 36.09wt.%, Sn 7.54wt.%, Te 42.03wt.%, S 14.34wt.%.

[0037] (3) Take the above-mentioned tellurium-rich cadmium-tin powder for vacuum distillation at 500°C, maintain the vacuum degree at 10Pa, and keep the temperature for 2h. Silver-gray high-purity tellurium and yellow cadmium-rich tin filter residue can be obtained, and the recovery rate of tellurium reaches 98.31%. The purity of the tellurium product is analyzed by ICP to reach 99.9wt.%, in which the Cd content is ≤0.05ppm, the Sn content is ≤0.05ppm, and the composition of the cadmium-rich tin filter residue is Cd 61.68wt.%, Sn 12.40wt.%, Te 1.68wt.%, S 24.24wt.%.

[0038] (4) Take the above-mentioned yellow cadmium-rich tin filter residue and leach it in a sodium sulfide solution with a concentration of 140g / L. After reacting at 40°C for 2h, filter to obtain sodium thiosnate solution and cadmium-rich product. The tellurium-cadmium-tin content in the sodium thiosnate product is Cd 0.29wt.%, Sn 98.96wt.%, Te 0.75wt.%, and the cadmium content in the cadmium-rich residue is higher than 99wt.%, realizing the efficient separation of tin and cadmium.

[0039] Figure 2 This is the physical and structural diagram of the retired cadmium telluride thin-film solar cell module used in the present invention. The main components of the battery panel from top to bottom are front glass, metal coating, EVA organic binder, and back glass. The metal coating includes valuable metal compounds such as CdTe, CdS, and SnO 2 etc., which have high recycling value. Figure 3 This is the SEM surface scan of the front glass with metal coating in the retired cadmium telluride thin-film solar cell of the present invention. The metal coating and the front glass substrate are tightly combined and difficult to separate. The thickness of the CdTe layer is about 4um, the thickness of the CdS layer is about 200nm, SnO2 The thickness of the layer is about 5 mm. Figure 4 XRD pattern of the tellurium-rich cadmium tin powder prepared by the present invention, Te / CdS / SnS 2 The diffraction peak angles and intensities of the three compounds all conform to the standard diffraction peak PDF cards, and no obvious impurity peaks are found, indicating that after low-temperature sulfidation roasting, the metal coating layer is successfully completed the phase transformation and separated from the front glass substrate. Figure 5 Te / CdS / SnS prepared by the present invention 2 SEM-EDS results of the Te / CdS / SnS mixed powder prepared by the present invention. The particle size is 1-10 μm. The surface scan results show that the Te element exists in the elemental form, and the distribution regions of the Cd element and the S element overlap, and the distribution regions of the Sn element and the S element overlap. The above detection data analysis shows that after the sulfidation roasting of the cadmium telluride thin-film solar cell by this method, the product is Te / CdS / SnS 2 mixed powder, realizing the efficient enrichment of valuable metals. Figure 6 The clean front glass prepared by the present invention. The picture shows that the cleanliness and light transmittance of the glass are very high. Combining Figure 7 with the SEM surface scan results of the clean front glass in , after the separation by low-temperature sulfidation roasting, the metal coatings on the front glass are all removed, and the impurity content on the glass surface is extremely low. Figure 8 The physical pictures of the high-purity tellurium and cadmium-rich tin powder prepared by the present invention. The high-purity tellurium is uniformly silver-white, and the cadmium tin powder is bright yellow.

[0040] The above are only the preferred embodiments of the present invention, and do not impose any form of limitation on the present invention. Although the present invention has been disclosed as above with the preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art can make many possible changes and modifications to the technical solution of the present invention by using the above-disclosed methods and technical contents, or modify it into an equivalent embodiment with equivalent changes. Therefore, any simple modification, equivalent replacement, equivalent change and modification made to the above embodiments according to the technical essence of the present invention without departing from the technical solution of the present invention still fall within the scope of the protection of the technical solution of the present invention.

Claims

1. A method for recycling all components of retired cadmium telluride thin-film solar cells, characterized in that: The following steps are involved: (1) Retired cadmium telluride thin-film batteries are processed by thermal dissociation, pressure water cutting, mechanical cutting and other methods to obtain front glass, back glass and wires coated with CdTe / CdS / SnO2 thin films, of which the back glass and wires can be directly recycled; (2) The sulfurization process efficiently separates the valuable metals and the front glass substrate. The sulfurization treatment induces the valuable metal coating to undergo phase transformation and dissociation, and then the cadmium tin telluride-rich powder and recyclable front glass are obtained through washing and filtration; (3) preparing high-purity tellurium product and cadmium-rich tin powder by vacuum distillation of the tellurium-rich cadmium tin powder; (4) The cadmium-rich tin mixed powder was leached with sodium sulfide or sodium hydrosulfide solution and filtered to successfully separate cadmium and tin to obtain Na2SnS3 and CdS with higher purity.

2. The method for recycling all components of retired cadmium telluride thin-film solar cells according to claim 1, characterized in that: In step (1), the front glass and the back glass are tightly bonded by the EVA organic film, and are processed by thermal dissociation, pressure water cutting, mechanical cutting and other methods to separate the complete front glass, back glass and wires.

3. The method for recycling all components of retired cadmium telluride thin-film solar cells according to claim 1, characterized in that: In step (1), the EVA film on the back glass can be efficiently removed by mechanical stripping or low-temperature pyrolysis below 400° C. to obtain a high-purity glass plate.

4. The method for recycling all components of retired cadmium telluride thin-film solar cells according to claim 1, characterized in that: In step (1), the surface of the front glass is coated with a 3-5 μm CdTe film, a 0.1-0.5 μm CdS film, and a 0.3-0.8 μm SnO2 film, which has significant recycling value. After adding a sulfurizing agent to the coating on the front glass, low-temperature sulfurization and calcination are performed at 400-500°C to separate the valuable metal coating and the front glass plate.

5. The method for recycling all components of retired cadmium telluride thin-film solar cells according to claim 1, characterized in that: In step (2), when a vulcanizing agent is added to the valuable metal coating layer of the front glass for low-temperature vulcanization separation, the physical state of the vulcanizing agent includes solid and liquid, and the addition forms include spraying, immersion and coating.

6. The method for recycling all components of retired cadmium telluride thin-film solar cells according to claim 1, characterized in that: In step (2), the types of the vulcanizing agent used for low-temperature vulcanization roasting include sulfur, sulfide, thiosulfate and other reagents.

7. The method for recycling all components of retired cadmium telluride thin-film solar cells according to claim 1, characterized in that: In step (2), the cadmium telluride tin powder obtained by the sulfurization roasting enrichment contains 36.09wt.% Cd, 7.54wt.% Sn, 42.03wt.% Te, and 14.34wt.% S. The powder is gray-green in color and has a particle size of 1-10μm.

8. The method for recycling all components of retired cadmium telluride thin-film solar cells according to claim 1, characterized in that: In step (3), the vacuum distillation conditions are vacuum degree ≤ 10 Pa and temperature 400-600°C.

9. The method for recycling all components of retired cadmium telluride thin-film solar cells according to claim 1, characterized in that: In step (4), the leaching temperature is 20-80° C., the leaching time is 0.5-2 h, and the volume mass ratio of powder to leaching solution is 1 g: 3-30 mL.

10. The short-process full-component recycling method for retired cadmium telluride thin-film solar cells according to claim 1, characterized in that: In step (4), the types of leaching agents include sulfuric acid, hydrochloric acid, ammonia water, sodium sulfide solution, etc.

Images