A method and apparatus for stepwise recovery of aluminum and silver from crystalline silicon solar cells

Abstract

The application discloses a method for step-by-step recovery of aluminum and silver from crystalline silicon solar cells, comprising the following steps: pretreatment: the waste crystalline silicon photovoltaic module is physically disassembled to obtain solar cell fragments; alkaline leaching of aluminum: the solar cell fragments obtained in the pretreatment step are placed in a potassium hydroxide solution for leaching reaction, and after filtration, an aluminum-containing filtrate and a cell fragment with removed aluminum back field are obtained; aluminum recovery: carbon dioxide is introduced or acid is added into the aluminum-containing filtrate obtained in the alkaline leaching of aluminum step, high-purity aluminum hydroxide is precipitated, and after calcination, an aluminum oxide product is obtained; acid leaching of silver: the cell fragment with removed aluminum back field is placed in a nitric acid solution for leaching reaction, a silver electrode is dissolved in nitric acid to generate a silver nitrate solution, and after filtration, a silver-containing filtrate and a solid silicon fragment with silicon as a main component are obtained; and silver recovery: the silver-containing filtrate obtained in the acid leaching of silver step is recovered into elemental silver through electrolytic deposition.

Description

Technical Field

[0001] This invention relates to the field of methods and apparatus for the stepwise recovery of aluminum and silver from crystalline silicon solar cells, specifically to a method and apparatus for the stepwise recovery of aluminum and silver from crystalline silicon solar cells. Background Technology

[0002] With the rapid development of the photovoltaic industry, early-deployed crystalline silicon solar cells are gradually entering their end-of-life stage, making their green recycling and resource reuse an urgent issue to be addressed. Crystalline silicon cells contain approximately 1-2% aluminum and 0.1-0.2% silver, giving them significant recycling value.

[0003] Currently, wet chemical recovery is one of the mainstream technologies. Existing technologies, such as CN201510921908.0, employ hydrochloric acid leaching of aluminum and nitric acid leaching of silver. However, this process has the following inherent drawbacks: 1. Low value of aluminum products: The aluminum chloride solution obtained by leaching with hydrochloric acid has relatively low economic value and the subsequent processing is complicated.

[0004] 2. Silicon wafer damage: Strong acid environment severely corrodes the silicon substrate, resulting in reduced silicon resource recovery rate and impaired purity.

[0005] 3. Poor process compatibility: The hydrochloric acid system has poor compatibility with subsequent silicon resource recycling processes.

[0006] Therefore, there is an urgent need in this field for a recycling method that can recover aluminum at a high value. Summary of the Invention

[0007] The purpose of this invention is to provide a method and apparatus for stepwise recovery of aluminum and silver from crystalline silicon solar cells, in order to solve the problems mentioned in the background art.

[0008] To achieve the above objectives, the present invention provides the following technical solution: a method for stepwise recovery of aluminum and silver from crystalline silicon solar cells, comprising the following steps: Pre-processing: The waste crystalline silicon photovoltaic modules are physically disassembled to remove the junction box and aluminum frame. Then, the components of the laminate are separated by high-temperature pyrolysis. After pyrolysis, they are sorted to obtain photovoltaic glass, photovoltaic backsheet, photovoltaic ribbon and solar cell respectively. Alkaline leaching of aluminum: The solar cell fragments obtained in the pretreatment step are placed in a potassium hydroxide solution for leaching reaction. The aluminum back field reacts with potassium hydroxide to generate a soluble potassium aluminate solution, thereby removing the aluminum back field of the solar cell. After filtration, aluminum-containing filtrate and battery fragments with the aluminum back field removed are obtained. Using potassium hydroxide solution as a selective leaching agent for aluminum replaces the traditional hydrochloric acid. This not only avoids the introduction of chloride ions and corrosion of equipment, but more importantly, it generates a high-value aluminate solution that can be directly used to prepare high-purity aluminum hydroxide or alumina products, realizing the high-value recovery of aluminum. Aluminum recovery: Carbon dioxide or acid is introduced into the aluminum-containing filtrate obtained in the alkaline leaching process to precipitate high-purity aluminum hydroxide, which can be calcined to obtain alumina product. Acidic silver leaching: The battery fragments obtained from the alkaline aluminum leaching step with the aluminum back field removed are placed in a nitric acid solution for leaching reaction. The silver electrode is dissolved by nitric acid to generate silver nitrate solution. After filtration, a silver-containing filtrate and solid silicon fragments with silicon as the main component are obtained. Silver recovery: The silver-containing filtrate obtained in the acid leaching of silver is used to recover elemental silver through electrolytic deposition or chemical reduction. Alkaline leaching of aluminum first creates favorable conditions for subsequent acid leaching of silver. Because after alkaline leaching, the silver electrode is more fully exposed to the silicon wafer surface, allowing nitric acid to react more quickly and completely, thus significantly improving the silver leaching rate and recovery rate.

[0009] Preferably, in the alkaline aluminum leaching step, the mass fraction of potassium hydroxide solution is 20-30%, the molar ratio of aluminum to potassium hydroxide is 1:20, the reaction temperature is 30-50℃, and the reaction time is 0.5-0.6h.

[0010] Preferably, a silicon dissolution inhibitor is added to the potassium hydroxide solution in the alkaline aluminum leaching step, which effectively slows down the corrosion of the silicon substrate by KOH and controls the silicon loss rate at a low level. The inhibitor is one or two of nitrite and stannate, and the amount added is 0.5% to 3% of the mass of the battery fragments.

[0011] Preferably, in the acidic silver leaching step, the concentration of the nitric acid solution is 30-40 mol / mL, the reaction temperature is 40-80℃, the molar ratio of silver to nitric acid is 1:150, and the reaction time is 0.5-0.7h.

[0012] Preferably, before the acid leaching silver step, the battery fragments are rinsed with water, and during the acid leaching silver step, the filtered solid silicon fragments are rinsed with water.

[0013] An apparatus for the above method includes rollers mounted on a support frame and arranged front and rear. A feed inlet is located at the center of the front end of each roller. A nozzle with a spray port at its lower end is located at the center of the roller, extending rearward from the roller and connected to a liquid feed pipe capable of adding different liquids. The roller contains five compartments: an alkaline chamber, an alkaline rinsing chamber, an acidic chamber, an acidic rinsing chamber, and a discharge chamber. The alkaline chamber can be lined with stainless steel and a micro-arc oxidation ceramic layer. The acidic chamber can be lined with Hastelloy and PTFE. The rinsing chamber can have a PTFE sheet surface. The liquid feed pipes include an alkaline liquid pipe, an acidic liquid pipe, a water pipe, and a silica dissolution inhibitor pipe. Each compartment includes two partitions, left and right, with their inner ends inclined away from each other. Adjacent partitions of adjacent compartments are sealed together. A drain pipe is connected to the rear bottom of each compartment. The discharge chamber has a discharge port at its bottom. The apparatus also includes a rotating mechanism to drive the rollers to rotate.

[0014] Preferably, the rotating mechanism includes two front and rear gear rings arranged around the circumference of the drum and a gear connected to the gear rings. The gear is rotatably mounted on a support frame. The gear is connected to a motor, which drives the gear rings to rotate, thereby driving the drum to rotate.

[0015] Preferably, the adjacent partitions of two adjacent dividing cavities are sealed together in a triangular shape, and the partitions are sealed and fixed on the inner wall, front wall and rear wall of the roller. Here, the inner wall refers to the circumference of the roller away from the axis.

[0016] Preferably, the partition is connected to the inner wall of the roller by an elastic rubber strip to achieve pressure-induced flipping, and the front and rear ends of the partition and the end pointing towards the center of the roller are open. A matching telescopic plate is inserted into the partition, and the adjacent telescopic plates of two adjacent partitions are connected by a soft triangular rubber plate. The front and rear ends of the rubber plate abut against the front and rear walls of the roller to achieve sealing, and the front and rear ends of the telescopic plate are provided with a first sealing strip for sealing. The first sealing strip is integrally formed with the rubber plate. The front and rear ends of the partition are also provided with a second sealing strip for sealing. The second sealing strip is integrally formed with the bottom rubber strip. A pressure vent is provided between the adjacent partitions of two adjacent partitions on the roller to ensure pressure balance, and a vent hole is provided on the side of the bottom of the partition cavity near the vent.

[0017] Preferably, the vent is sealed with an elastic membrane. The membrane serves to seal the vent and, in turn, provides elastic pressure after liquid is poured out, causing the partition to return to its original position. It should be noted that the rubber strip, rubber sheet, first sealing strip, and second sealing strip mentioned here can be made of acid and alkali resistant rubber, such as fluorine-containing rubber, or other tough materials, with acid and alkali resistance and toughness as the main characteristics.

[0018] Compared with the prior art, the beneficial effects of the present invention are: Maximizing the value of aluminum products: Compared with aluminum chloride obtained by the hydrochloric acid method, the potassium aluminate solution obtained by this invention is an ideal raw material for preparing high-purity aluminum hydroxide / alumina, significantly improving the product value.

[0019] Effective protection of silicon resources: By using alkaline inhibitors and mild process conditions, the loss of silicon during recycling is greatly reduced, thus protecting silicon substrates with recycling value.

[0020] High silver recovery rate: Alkali immersion in aluminum first fully exposes the silver grid lines, and subsequent nitric acid immersion in silver is more thorough, with the silver recovery rate remaining stable at over 98%.

[0021] Environmentally friendly: It avoids pollution from chloride ions and hydrochloric acid mist, making the process cleaner. The alkaline leaching solution can be recycled or used to prepare products, reducing the emission of waste gas, wastewater, and solid waste.

[0022] The flip-over partition and the telescopic plate, when flipped, are squeezed by battery fragments and can shrink, reducing their height and facilitating flow into the next compartment. Attached Figure Description

[0023] Figure 1 The flowchart of the method of the present invention; Figure 2 This is a schematic diagram of the structure of the first embodiment of the device of the present invention; Figure 3 This is a first axonometric view of a first embodiment of the device of the present invention; Figure 4 This is a second axonometric view of the first embodiment of the device of the present invention; Figure 5 This is a schematic diagram of the structure of the second embodiment of the device of the present invention; Figure 6 This is an axonometric view of a second embodiment of the device of the present invention; Figure 7 This is a schematic diagram of the telescopic plate of the second embodiment of the device of the present invention; Figure 8 This is an exploded view of the connection between the telescopic plate and the partition plate in the first embodiment of the device of the present invention; In the diagram: 1. Roller; 2. Feed inlet; 3. Spray nozzle; 4. Liquid feed pipe; 5. Baffle plate; 6. Drain pipe; 7. Discharge outlet; 8. Gear ring; 9. Gear; 10. Rubber strip; 11. Telescopic plate; 12. Rubber sheet; 13. First sealing strip; 14. Second sealing strip; 15. Vent; 16. Membrane. Detailed Implementation

[0024] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0025] Please see Figure 1 This invention provides a method for the stepwise recovery of aluminum and silver from crystalline silicon solar cells: Example

[0026] A method for stepwise recovery of aluminum and silver from crystalline silicon solar cells includes the following steps: Pre-processing: The waste crystalline silicon photovoltaic modules are physically disassembled to remove the junction box and aluminum frame. Then, the components of the laminate are separated by high-temperature pyrolysis. After pyrolysis, they are sorted to obtain photovoltaic glass, photovoltaic backsheet, photovoltaic ribbon and solar cell respectively. Alkaline leaching of aluminum: The solar cell fragments obtained in the pretreatment step are placed in a potassium hydroxide solution for leaching. The aluminum back field reacts with potassium hydroxide to generate a soluble potassium aluminate solution, thus removing the aluminum back field of the solar cell. After filtration, an aluminum-containing filtrate and the battery fragments with the aluminum back field removed are obtained. Using potassium hydroxide solution as a selective leaching agent for aluminum replaces traditional hydrochloric acid. This not only avoids the introduction of chloride ions and corrosion of equipment, but more importantly, it generates a high-value-added aluminate solution that can be directly used to prepare high-purity aluminum hydroxide or alumina products, achieving high-value recovery of aluminum. The mass fraction of the potassium hydroxide solution is 20%, the molar ratio of aluminum to potassium hydroxide is 1:20, the reaction temperature is 30℃, and the reaction time is 0.5h. Adding a silicon dissolution inhibitor to the potassium hydroxide solution effectively slows down the corrosion of the silicon substrate by KOH, keeping the silicon loss rate at a low level. The inhibitor is one or both of nitrite and stannate, and the amount added is 0.5% to 3% of the mass of the battery fragments.

[0027] Aluminum recovery: Carbon dioxide or acid is introduced into the aluminum-containing filtrate obtained in the alkaline leaching process to precipitate high-purity aluminum hydroxide, which can be calcined to obtain alumina product. Acidic silver leaching: The battery fragments obtained from the alkaline aluminum leaching step, after removing the aluminum back field, are rinsed with water and then placed in a nitric acid solution for leaching reaction. The silver electrode is dissolved by the nitric acid to generate silver nitrate solution. After filtration, a silver-containing filtrate and solid silicon fragments with silicon as the main component are obtained. The concentration of the nitric acid solution is 30 mol / mL, the reaction temperature is 40℃, the molar ratio of silver to nitric acid is 1:150, and the reaction time is 0.5h.

[0028] Silver recovery: The silver-containing filtrate obtained in the acid leaching of silver is used to recover elemental silver through electrolytic deposition or chemical reduction. Alkaline leaching of aluminum first creates favorable conditions for subsequent acid leaching of silver. Because after alkaline leaching, the silver electrode is more fully exposed to the silicon wafer surface, allowing nitric acid to react more quickly and completely, thus significantly improving the silver leaching rate and recovery rate.

[0029] like Figures 2-4 An apparatus for the above method includes a roller 1 mounted on a support frame and arranged front and rear. A feed inlet 2 is located at the center of the front end of the roller 1. A nozzle 3 with a spray nozzle at its lower end is located at the center of the roller 1. The nozzle 3 extends rearward from the roller 1 and is connected to a liquid feed pipe 4 capable of adding different liquids. The nozzle 3 is rotatably connected to the roller 1 and is mounted on the support frame. The roller 1 contains five compartments: an alkaline chamber, an alkaline rinsing chamber, an acidic chamber, an acidic rinsing chamber, and a discharge chamber. The alkaline chamber can be lined with 316L stainless steel and a micro-arc anodized ceramic layer. The acidic chamber can be lined with Hastelloy and PTFE. The rinsing chamber can be lined with PTFE sheets. The liquid feed pipe 4 includes an alkali pipe, an acid pipe, a water pipe, and a silicon dissolution inhibitor pipe. Each dividing chamber includes two partitions 5, one on the left and one on the right, with their inner ends inclined in opposite directions. This allows battery fragments to be poured into the next dividing chamber without rotating 90°. There are five dividing zones. Therefore, when the required dividing chamber is at the bottom, the left one is not at the leftmost point, but rather slightly lower. Thus, the inclined part of the partition 5 makes it easier to pour. The adjacent partitions 5 of two adjacent dividing chambers are sealed together. A drain pipe 6 is connected to the rear bottom of each dividing chamber. A discharge port 7 is provided at the bottom of the discharge chamber. The system also includes a rotating mechanism that drives the roller 1 to rotate. The rotating mechanism includes two front and rear gear rings 8 arranged around the circumference of the roller 1 and a gear 9 connected to the gear rings 8. The gear 9 is rotatably mounted on a support frame and is connected to a motor. The gear 9 drives the gear rings 8 to rotate, thereby driving the roller 1 to rotate.

[0030] The pre-treated battery fragments are added to the alkaline chamber of drum 1 through inlet 2. Then, the switch of the alkaline solution pipe is opened, potassium hydroxide is added, and then closed. The silicon dissolution inhibitor pipe is opened, silicon dissolution inhibitor is added, and then closed. The motor drives drum 1 to rotate slightly forward and backward to promote the full reaction of the battery fragments in the alkaline chamber. Then, the drain pipe 6 in the chamber is opened to remove the reacted liquid. Then, the motor drives drum 1 to rotate clockwise, and the battery fragments inside enter the alkaline rinsing chamber. The water pipe is opened for rinsing, and then the liquid is drained through the corresponding drain pipe 6. Alternatively, drum 1 can be mixed by rotating forward and backward. Then, it continues to rotate and enters the acidic chamber. The acid pipe is opened to introduce acid. Then, drum 1 mixes slightly by rotating forward and backward. Then, the corresponding drain pipe 6 is opened to drain the liquid. Then, the fragments continue to rotate and slide down to the lowest acidic rinsing chamber. The water pipe in the liquid material pipe 4 is opened for rinsing, and then the liquid is drained through the corresponding drain pipe. Then, it continues to rotate to the discharge chamber to pour out the remaining liquid. Then, it rotates in the opposite direction to the alkaline chamber and battery fragments are added again.

[0031] The adjacent partitions 5 of two adjacent dividing chambers are sealed together in a triangular shape, and the partitions 5 are sealed and fixed on the inner wall, front wall and rear wall of the roller 1. Here, the inner wall refers to the circle of the roller 1 away from the axis. Example

[0032] A method for stepwise recovery of aluminum and silver from crystalline silicon solar cells includes the following steps: Pre-processing: The waste crystalline silicon photovoltaic modules are physically disassembled to remove the junction box and aluminum frame. Then, the components of the laminate are separated by high-temperature pyrolysis. After pyrolysis, they are sorted to obtain photovoltaic glass, photovoltaic backsheet, photovoltaic ribbon and solar cell respectively. Alkaline leaching of aluminum: The solar cell fragments obtained in the pretreatment step are placed in a potassium hydroxide solution for leaching. The aluminum back field reacts with potassium hydroxide to generate a soluble potassium aluminate solution, thus removing the aluminum back field of the solar cell. After filtration, an aluminum-containing filtrate and the battery fragments with the aluminum back field removed are obtained. Using potassium hydroxide solution as a selective leaching agent for aluminum replaces traditional hydrochloric acid. This not only avoids the introduction of chloride ions and corrosion of equipment, but more importantly, it generates a high-value-added aluminate solution that can be directly used to prepare high-purity aluminum hydroxide or alumina products, achieving high-value recovery of aluminum. The mass fraction of the potassium hydroxide solution is 30%, the molar ratio of aluminum to potassium hydroxide is 1:20, the reaction temperature is 50℃, and the reaction time is 0.6h. Adding a silicon dissolution inhibitor to the potassium hydroxide solution effectively slows down the corrosion of the silicon substrate by KOH, keeping the silicon loss rate at a low level. The inhibitor is one or both of nitrite and stannate, and the amount added is 3% of the mass of the battery fragments.

[0033] Aluminum recovery: Carbon dioxide or acid is introduced into the aluminum-containing filtrate obtained in the alkaline leaching process to precipitate high-purity aluminum hydroxide, which can be calcined to obtain alumina product. Acidic silver leaching: The battery fragments obtained from the alkaline aluminum leaching step, after removing the aluminum back field, are rinsed with water and then placed in a nitric acid solution for leaching reaction. The silver electrode is dissolved by the nitric acid to generate silver nitrate solution. After filtration, a silver-containing filtrate and solid silicon fragments with silicon as the main component are obtained. The concentration of the nitric acid solution is 40 mol / mL, the reaction temperature is 80℃, the molar ratio of silver to nitric acid is 1:150, and the reaction time is 0.7h.

[0034] Silver recovery: The silver-containing filtrate obtained in the acid leaching of silver is used to recover elemental silver through electrolytic deposition or chemical reduction. Alkaline leaching of aluminum first creates favorable conditions for subsequent acid leaching of silver. Because after alkaline leaching, the silver electrode is more fully exposed to the silicon wafer surface, allowing nitric acid to react more quickly and completely, thus significantly improving the silver leaching rate and recovery rate.

[0035] like Figures 5-8Compared to Embodiment 1, the difference lies in the connection between the partitions 5. Preferably, the partitions 5 and the inner wall of the roller 1 are connected by an elastic rubber strip 10 to achieve pressure-induced flipping. The front and rear ends of the partitions 5, as well as the end pointing towards the center of the roller 1, are open. A matching telescopic plate 11 is inserted into the partition 5, and adjacent telescopic plates 11 of two adjacent partition chambers are connected by a soft triangular rubber plate 12. The front and rear ends of the rubber plate 12 abut against the front and rear walls of the roller 1 to achieve a seal. A first sealing strip 13 is provided at the front and rear ends of the telescopic plate 11 for sealing. The first sealing strip 13 is integrally formed with the rubber plate 10. The front and rear ends of the partitions 5... The end is also provided with a second sealing strip 14 for sealing. The second sealing strip 13 is integrally formed with the bottom rubber strip 10. A pressure vent 15 is provided between the adjacent partitions 5 of the two adjacent partitions on the roller 1 to ensure pressure balance. A vent hole is provided on the side of the bottom of the inner cavity of the partition 5 near the vent 15. The vent hole is to ensure that the internal gas can be discharged when the telescopic plate 11 is extended and retracted. It should be noted that the rubber strip 10, rubber plate 12, first sealing strip 13 and second sealing strip 14 mentioned here can be made of acid and alkali resistant rubber, such as fluorine-containing rubber, or other tough materials, with acid and alkali resistant and tough as the main features. Compared to the fixed partition 5 in Embodiment 1, here the main difference is that during tilting, due to the pressure of the battery fragments themselves, the adjacent partitions 5 of adjacent dividing chambers move closer together, and the telescopic plates 11 inside them also squeeze each other and retract into the partition 5, reducing the height. This makes it easier to tilt the battery fragments. The more battery fragments there are, the greater the squeezing force and the greater the contraction, making it easier for the battery fragments to cross over and flow into the next dividing chamber, thereby improving the conversion efficiency of the dividing chamber. If the partition 5 is made shorter, although it is convenient to tilt, the storage capacity is small, and it is easy to spill into adjacent dividing chambers when mixing in both forward and reverse directions. Therefore, a mechanism is set here that uses the weight of the battery fragments themselves to squeeze and contract to reduce the crossing height during rotation, namely the telescopic plate 11 and the rubber plate 12.

[0036] As a preferred method, the vent 15 is sealed by an elastic membrane 16. The membrane 15 serves to seal and isolate the vent from the outside environment, making it safer. At the same time, it can expand to provide elastic recovery force after liquid is spilled, causing the partition 5 to return to its original position.

[0037] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A method for stepwise recovery of aluminum and silver from crystalline silicon solar cells, characterized in that, Includes the following steps: Pre-processing: The waste crystalline silicon photovoltaic modules are physically disassembled to remove the junction box and aluminum frame. Then, the components of the laminate are separated by high-temperature pyrolysis. After pyrolysis, they are sorted to obtain photovoltaic glass, photovoltaic backsheet, photovoltaic ribbon and solar cell respectively. Alkaline leaching of aluminum: The solar cell fragments obtained in the pretreatment step are placed in a potassium hydroxide solution for leaching reaction. The aluminum back field reacts with potassium hydroxide to generate a soluble potassium aluminate solution, thereby removing the aluminum back field of the solar cell. After filtration, aluminum-containing filtrate and battery fragments with aluminum back field removed are obtained. Aluminum recovery: Carbon dioxide or acid is introduced into the aluminum-containing filtrate obtained in the alkaline leaching process to precipitate high-purity aluminum hydroxide, which can be calcined to obtain alumina product. Acidic silver leaching: The battery fragments obtained from the alkaline aluminum leaching step with the aluminum back field removed are placed in a nitric acid solution for leaching reaction. The silver electrode is dissolved by nitric acid to generate silver nitrate solution. After filtration, a silver-containing filtrate and solid silicon fragments with silicon as the main component are obtained. Silver recovery: The silver-containing filtrate obtained in the acid leaching of silver is used to recover elemental silver by electrolytic deposition or chemical reduction.

2. The method for stepwise recovery of aluminum and silver from crystalline silicon solar cells according to claim 1, characterized in that: In the alkaline aluminum leaching step, the mass fraction of potassium hydroxide solution is 20-30%, the molar ratio of aluminum to potassium hydroxide is 1:20, the reaction temperature is 30-50℃, and the reaction time is 0.5-0.6h.

3. The method for stepwise recovery of aluminum and silver from crystalline silicon solar cells according to claim 1, characterized in that: A silicon dissolution inhibitor is added to the potassium hydroxide solution in the alkaline aluminum leaching step. The inhibitor is one or two of nitrite and stannate, and the amount added is 0.5% to 3% of the mass of the battery fragment.

4. The method for stepwise recovery of aluminum and silver from crystalline silicon solar cells according to claim 1, characterized in that: In the acidic silver leaching step, the concentration of the nitric acid solution is 30–40 mol / mL, the reaction temperature is 40–80℃, the molar ratio of silver to nitric acid is 1:150, and the reaction time is 0.5–0.7 h.

5. The method and apparatus for stepwise recovery of aluminum and silver from crystalline silicon solar cells according to claim 1, characterized in that: Before the acid leaching silver step, the battery fragments are rinsed with water, and during the acid leaching silver step, the filtered solid silicon fragments are rinsed with water.

6. An apparatus for the method of stepwise recovery of aluminum and silver from a crystalline silicon solar cell according to any one of claims 1 to 5, characterized in that, The device includes a roller (1) mounted on a support frame and positioned at the front and rear. The roller (1) has a feed inlet (2) at the center of its front end. The roller (1) has a spray pipe (3) with a nozzle at its lower end at the center. The spray pipe (3) extends backward out of the roller (1) and is connected to a liquid feed pipe (4) that can add different liquids. The roller (1) has five compartments: an alkaline compartment, an alkaline flushing compartment, an acidic compartment, an acidic flushing compartment, and a discharge compartment. Each compartment includes two partitions (5) on the left and right sides. The inner ends of the two partitions (5) are inclined in opposite directions. The adjacent partitions (5) of two adjacent compartments are sealed together. The bottom rear side of each compartment is connected to a drain pipe (6). The discharge compartment has a discharge port (7) at its bottom. The device also includes a rotating mechanism that drives the roller (1) to rotate.

7. The apparatus for stepwise recovery of aluminum and silver from crystalline silicon solar cells according to claim 6, characterized in that: The rotating mechanism includes two front and rear gear rings (8) arranged around the circumference of the roller (1) and a gear (9) connected to the gear rings (8). The gear (9) is rotatably mounted on the support frame and is connected to a motor.

8. The apparatus for stepwise recovery of aluminum and silver from crystalline silicon solar cells according to claim 6, characterized in that: The adjacent partitions (5) of two adjacent partition chambers are sealed together in a triangular shape, and the partitions (5) are sealed and fixed on the inner wall, front wall and rear wall of the roller (1).

9. The apparatus for stepwise recovery of aluminum and silver from crystalline silicon solar cells according to claim 6, characterized in that: The partition (5) is connected to the inner wall of the roller (1) by an elastic rubber strip (10) to achieve pressure flipping. The front and rear ends of the partition (5) and the end pointing to the center of the roller (1) are open. A matching telescopic plate (11) is inserted into the partition (5). The adjacent telescopic plates (11) of two adjacent partition chambers are connected by a soft triangular rubber plate (12). The front and rear ends of the rubber plate (12) abut against the front and rear walls of the roller (1) to achieve sealing. The front and rear ends of the telescopic plate (11) are provided with a first sealing strip (13) for sealing. The front and rear ends of the partition (5) are also provided with a second sealing strip (14) for sealing. A pressure vent (15) is provided between the adjacent partitions (5) of two adjacent partition chambers on the roller (1). A vent hole is provided on the side of the bottom of the inner cavity of the partition (5) near the vent (15).

10. The apparatus for stepwise recovery of aluminum and silver from crystalline silicon solar cells according to claim 9, characterized in that: The vent (15) is sealed by an elastic membrane (16).

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