Method for recycling aluminum from waste photovoltaic cells

Abstract

The invention discloses a method for recovering aluminum from a waste photovoltaic cell, which comprises the following steps of: treating the photovoltaic cell by using aqueous alkali with the mass concentration of 10-60%, filtering and collecting filtrate; introducing carbon dioxide gas into the filtrate, and collecting precipitates; and drying the precipitate, and grinding to obtain aluminum hydroxide powder. The aluminum recovery method is easy and convenient to operate and efficient, and has the excellent aluminum recovery rate and recovery purity.

Description

Technical Field

[0001] The invention belongs to the technical field of recycling waste photovoltaic battery groups, and in particular relates to a method for recycling aluminum from waste photovoltaic battery sheets. Background Art

[0002] Waste crystalline silicon solar cells are an important resource, containing valuable metal and non-metal resources such as aluminum, silver, and silicon. The rational recovery and utilization of valuable substances in waste photovoltaic cells can effectively alleviate environmental pressure and realize the recycling of resources. Efficient recovery and utilization of aluminum in these cells can not only turn waste into treasure, but also effectively reduce the consumption of aluminum resources. At present, the recycling and utilization of waste photovoltaic cells mainly focuses on the removal of metals and film layers such as silver on the surface of silicon wafers to obtain silicon wafers, while ignoring the full recovery and utilization of aluminum, or the purity and recovery rate of aluminum recovery are poor, and the recovery process mostly requires pre-treatment steps such as grinding, which is time-consuming and complicated. Therefore, there is an urgent need for a method that is simple to operate and can efficiently recover aluminum to improve the recovery rate and purity of aluminum. Summary of the invention

[0003] The present invention aims to solve at least one of the technical problems existing in the prior art to a certain extent. To this end, the present invention provides a method for recovering aluminum from photovoltaic cells, which can improve the recovery rate and purity of aluminum.

[0004] Therefore, in a first aspect of the present invention, the present invention provides a method for recovering aluminum from photovoltaic cells, comprising the following steps:

[0005] Treat the photovoltaic cell with an alkaline solution having a mass concentration of 10 to 60%, filter, and collect the filtrate;

[0006] Pass carbon dioxide gas into the filtrate and collect the precipitate;

[0007] The precipitate is dried and then ground to obtain aluminum hydroxide powder.

[0008] The alkali solution with a mass concentration of 10-60% can fully react with aluminum. If the concentration of the alkali solution is too low, the aluminum in the photovoltaic cell will not fully react with the alkali, which will lead to a lower recovery rate. If the concentration of the alkali solution is too high, the alkali solution will corrode the silicon on the photovoltaic cell, which will lead to the introduction of other impurities and will also be detrimental to the recovery of silicon.

[0009] After aluminum or aluminum oxide is generated in an alkaline solution, the main component of the filtrate is sodium aluminate (NaAlO 2 ). The chemical reaction that occurs is:

[0010] 2Al+2NaOH+2H 2 O=2NaAlO 2+3H 2 ↑;

[0011] Al 2 O 3 + 2NaOH=2NaAlO 2 +H 2 O.

[0012] Then, carbon dioxide gas is introduced into the filtrate to produce aluminum hydroxide (Al(OH) 3 ) precipitate. The chemical reaction that occurs is:

[0013] 2CO 2 +2Na 2 AlO 2 +3H 2 O=2Al(OH) 3 ↓+2Na 2 CO 3 .

[0014] Collect aluminum hydroxide (Al(OH) 3 ) precipitate, dry and grind. Thus, the recovery purity and recovery rate of aluminum hydroxide can be improved.

[0015] In addition, the photovoltaic cell can be directly placed in an alkaline solution to dissolve and remove the aluminum element and aluminum compounds in the aluminum back surface field or aluminum grid line on the photovoltaic cell without grinding, without reacting with other metals to introduce impurities. In addition, removing the aluminum back surface field or aluminum grid line is also conducive to further recycling of silicon wafers.

[0016] In some embodiments, the alkaline solution includes at least one of a sodium hydroxide solution or a potassium hydroxide solution.

[0017] In some embodiments, when an alkali solution with a mass concentration of 10-60% is used to treat a photovoltaic cell, the mass concentration of the alkali solution is 15-45%.

[0018] In some embodiments, the photovoltaic cell is treated with an alkaline solution having a mass concentration of 10 to 60%, and the treatment time is 5 to 40 minutes, preferably 10 to 30 minutes.

[0019] In some embodiments, when carbon dioxide gas is introduced into the filtrate, the control parameters satisfy at least one of the following:

[0020] (1) The time for introducing carbon dioxide gas is 5 to 15 minutes;

[0021] (2) The rate of introducing carbon dioxide gas is 2 to 15 L / min.

[0022] In some embodiments, when carbon dioxide gas is introduced into the filtrate, the control parameters satisfy at least one of the following:

[0023] (I) The time for passing carbon dioxide gas is 10 to 15 minutes;

[0024] (II) The rate of introducing carbon dioxide gas is 5 to 10 L / min.

[0025] In some embodiments, after the carbon dioxide gas is introduced into the filtrate, a static treatment is further performed, and the static treatment time is 5 to 60 minutes.

[0026] In some embodiments, the carbon dioxide gas is introduced into the filtrate, comprising the steps of:

[0027] Pass carbon dioxide gas into the filtrate, let it stand for treatment, and collect the precipitate;

[0028] Carbon dioxide gas was introduced into the remaining filtrate until no precipitate was produced.

[0029] In some embodiments, before using the 10-60% mass concentration alkaline solution to treat the photovoltaic cell, pretreatment is also included; the pretreatment includes removing dirt from the surface of the photovoltaic cell.

[0030] Compared with the prior art, the present invention has the following beneficial technical effects:

[0031] The method for recovering aluminum from photovoltaic cells of the present invention comprises removing dirt from the surface of the discarded photovoltaic cells, removing the aluminum back surface field or the aluminum grid line with an alkaline solution, filtering the aluminum-containing alkaline solution, and introducing carbon dioxide gas to generate precipitated aluminum hydroxide. The precipitate is collected, dried, and ground to prepare aluminum hydroxide powder. The operation is simple, and no complicated pre-treatment process such as grinding is required, and the method has a high aluminum recovery rate and recovery purity.

[0032] Additional aspects and advantages of the present invention will be given in part in the following description and in part will be obvious from the following description, or will be learned through practice of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] The above and / or additional aspects and advantages of the present invention will become apparent and easily understood from the description of the embodiments in conjunction with the following drawings, in which:

[0034] Figure 1 The present invention is a flow chart of recovering aluminum from photovoltaic cells. DETAILED DESCRIPTION

[0035] The embodiments of the present invention are described in detail below. The embodiments described below are exemplary and are only used to explain the present invention, and should not be understood as limiting the present invention.

[0036] It should be noted that the terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first" and "second" may explicitly or implicitly include one or more of the features. Further, in the description of the present invention, unless otherwise specified, the meaning of "plurality" is two or more.

[0037] The endpoints and any values ​​of the ranges disclosed in this article are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of each range, the endpoint values ​​of each range and the individual point values, and the individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed in this article.

[0038] In this document, the terms “include” or “comprising” are open expressions, that is, including the contents specified in the present invention but not excluding other contents.

[0039] In the prior art, the recycling process generally requires grinding the silicon wafer into powder and then adding an acid solution to form a mixed solution of metal ions. After the mixed solution is formed, the separation and extraction of the metals is complicated and time-consuming.

[0040] Therefore, in a first aspect of an embodiment of the present invention, the present invention provides a method for recovering aluminum from a photovoltaic cell, comprising the following steps:

[0041] Treat the photovoltaic cell with an alkaline solution having a mass concentration of 10 to 60%, filter, and collect the filtrate;

[0042] Pass carbon dioxide gas into the filtrate and collect the precipitate;

[0043] The precipitate is dried and then ground to obtain aluminum hydroxide powder.

[0044] The alkali solution with a mass concentration of 10-60% can fully react with aluminum. If the concentration of the alkali solution is too low, the aluminum in the photovoltaic cell will not fully react with the alkali, which will lead to a lower recovery rate. If the concentration of the alkali solution is too high, the alkali solution will corrode the silicon on the photovoltaic cell, which will lead to the introduction of other impurities and will also be detrimental to the recovery of silicon.

[0045] After aluminum or aluminum oxide is generated in an alkaline solution, the main component of the filtrate is NaAlO 2 The chemical reaction that occurs is:

[0046] 2Al+2NaOH+2H 2 O=2NaAlO 2 +3H 2 ↑;

[0047] Al 2 O 3 + 2NaOH=2NaAlO 2 +H 2 O.

[0048] Then, carbon dioxide gas is introduced into the filtrate to produce Al(OH) 3 The chemical reaction that occurs is:

[0049] 2CO 2 +2Na 2 AlO 2 +3H 2 O=2Al(OH) 3 ↓+2Na 2 CO 3 .

[0050] Collect Al(OH) 3 The precipitate is dried and ground. Thus, the recovery purity and recovery rate of aluminum hydroxide can be improved.

[0051] As an example, the mass concentration of the alkaline solution is 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, 50%, 55%, 60%, etc.

[0052] In addition, the photovoltaic cell can be directly placed in an alkaline solution to dissolve and remove the aluminum element and aluminum compounds in the aluminum back surface field or aluminum grid line on the photovoltaic cell without grinding, without reacting with other metals to introduce impurities. In addition, removing the aluminum back surface field or aluminum grid line is also conducive to further recycling of silicon wafers.

[0053] As an example, the photovoltaic cell includes but is not limited to at least one of a BSF cell, a PERC cell, a Topcon cell, an IBC cell, and a HJT cell.

[0054] In some embodiments, the alkaline solution includes at least one of a sodium hydroxide solution or a potassium hydroxide solution.

[0055] Based on the properties of the aluminum film layer, it is easy to react with sodium hydroxide solution or potassium hydroxide solution, thereby improving the recovery purity and recovery rate of aluminum hydroxide.

[0056] In some embodiments, when the photovoltaic cell is treated with an alkali solution having a mass concentration of 10-60%, the mass concentration of the alkali solution is 15-45%, thereby further improving the recovery purity and recovery rate of aluminum hydroxide.

[0057] As an example, the mass concentration of the alkaline solution is 15%, 20%, 25%, 30%, 35%, 40%, 45%, etc.

[0058] In some embodiments, the photovoltaic cell is treated with an alkaline solution having a mass concentration of 10 to 60%, and the treatment time is 5 to 40 minutes, preferably 10 to 30 minutes.

[0059] When the alkaline solution treatment time is 5 to 40 minutes, preferably 10 to 30 minutes, it is ensured that the aluminum can fully react with the alkali, and the alkaline solution will not corrode the silicon in the photovoltaic cell, and the introduction of impurities is avoided. Thus, the recovery purity and recovery rate of aluminum hydroxide can be further improved.

[0060] As an example, the alkali treatment time is 5 min, 10 min, 15 min, 20 min, 25 min, 30 min, 35 min, 40 min, etc.

[0061] In some embodiments, when carbon dioxide gas is introduced into the filtrate, the control parameters satisfy at least one of the following:

[0062] (1) The time for introducing carbon dioxide gas is 5 to 15 minutes;

[0063] (2) The rate of introducing carbon dioxide gas is 2 to 15 L / min.

[0064] The parameters of the carbon dioxide gas introduction are controlled to ensure that a sufficient amount of carbon dioxide gas is introduced into the filtrate to completely precipitate the aluminum for recovery, thereby increasing the recovery rate of aluminum hydroxide.

[0065] As an example, the time for introducing carbon dioxide gas is 5 min, 7 min, 9 min, 11 min, 13 min, 15 min, etc.

[0066] As an example, the rate of introducing carbon dioxide gas is 2 L / min, 4 L / min, 6 L / min, 8 L / min, 10 L / min, 12 L / min, 14 L / min, 15 L / min, etc.

[0067] In some embodiments, when carbon dioxide gas is introduced into the filtrate, the control parameters satisfy at least one of the following:

[0068] (I) The time for passing carbon dioxide gas is 10 to 15 minutes;

[0069] (II) The rate of introducing carbon dioxide gas is 5 to 10 L / min.

[0070] Thereby, the recovery rate of aluminum hydroxide can be further improved.

[0071] As an example, the time for introducing carbon dioxide gas is 10 min, 11 min, 12 min, 13 min, 14 min, 15 min, etc.

[0072] As an example, the rate of introducing carbon dioxide gas is 5 L / min, 6 L / min, 7 L / min, 8 L / min, 9 L / min, 10 L / min, etc.

[0073] In some embodiments, after the carbon dioxide gas is introduced into the filtrate, a static treatment is further performed, and the static treatment time is 5 to 60 minutes.

[0074] The main component of the filtrate is sodium aluminate. After the carbon dioxide gas is introduced into the filtrate, a certain reaction time is required to make the reaction more complete. When the static treatment time is 5 to 60 minutes, it will be able to fully react and form a sufficient amount of aluminum hydroxide precipitation. In this way, the recovery rate of aluminum hydroxide can be further improved.

[0075] As an example, the static treatment time is 5 min, 15 min, 20 min, 25 min, 30 min, 35 min, 40 min, 45 min, 50 min, 55 min, 60 min, etc.

[0076] In some embodiments, the carbon dioxide gas is introduced into the filtrate, comprising the steps of:

[0077] Pass carbon dioxide gas into the filtrate, let it stand for treatment, and collect the precipitate;

[0078] Carbon dioxide gas was introduced into the remaining filtrate until no precipitate was produced.

[0079] Carbon dioxide gas is introduced into the filtrate for multiple times so that the sodium aluminate dissolved in the filtrate can react as completely as possible to generate aluminum hydroxide for recovery, thereby further improving the recovery rate of aluminum hydroxide.

[0080] In some embodiments, before the photovoltaic cell is treated with an alkaline solution having a mass concentration of 10-60%, a pretreatment is also included; the pretreatment includes removing dirt from the surface of the photovoltaic cell, thereby further improving the recovery purity and recovery rate of aluminum hydroxide.

[0081] The aluminum recovery process of the present invention is shown in Figure 1 .

[0082] The scheme of the present invention will be explained below in conjunction with the embodiments. It will be appreciated by those skilled in the art that the following embodiments are only used to illustrate the present invention and should not be considered as limiting the scope of the present invention. Where specific techniques or conditions are not indicated in the embodiments, the techniques or conditions described in the literature in this area or the product specifications are used. The reagents or instruments used are not indicated by the manufacturer and are all conventional products that can be obtained commercially.

[0083] Embodiment 1:

[0084] Using alkaline solution to recover aluminum from waste photovoltaic cells, the steps are as follows:

[0085] Step 1: Place the discarded photovoltaic cells in an ultrasonic cleaning tank to clean and remove surface dirt;

[0086] Step 2: Immerse the photovoltaic cell in a potassium hydroxide solution with a mass concentration of 35% for 30 minutes at room temperature to dissolve and remove the aluminum back field or aluminum grid line;

[0087] Step 3: Filter the solution and collect the filtrate;

[0088] Step 4: introduce carbon dioxide gas into the filtrate at a rate of 10 L / min for 10 min and allow to stand for 15 min to form a white precipitate;

[0089] Step 5: Filter the filtrate after standing in step 4 to collect the precipitated material;

[0090] Step 6: Repeat steps 4 to 5 for the remaining liquid. No white precipitate is produced after three cycles.

[0091] Step 7: The obtained white precipitate is dried and ground to prepare powdered aluminum hydroxide.

[0092] Embodiment 2:

[0093] The difference between Example 2 and Example 1 is that in step 2 of Example 2, the mass concentration of the potassium hydroxide solution is 10%, and the reaction time is 40 min.

[0094] Embodiment 3:

[0095] The difference between Example 3 and Example 1 is that in step 2 of Example 3, the alkaline solution is a sodium hydroxide solution with a mass concentration of 60%, and the reaction time is 5 min.

[0096] Embodiment 4:

[0097] The difference between Example 4 and Example 1 is that the ventilation time of carbon dioxide in step 4 of Example 4 is 5 minutes, and the filtrate is left to stand for 5 minutes. No white precipitate is produced after six cycles of step 6.

[0098] Embodiment 5:

[0099] The difference between Example 5 and Example 1 is that the ventilation time of carbon dioxide in step 4 of Example 5 is 15 minutes, and the filtrate is left to stand for 60 minutes. No white precipitate is produced after two cycles of step 6.

[0100] Comparative Example 1:

[0101] The difference between Comparative Example 1 and Example 1 is that in step 2 of Comparative Example 1, the mass concentration of the potassium hydroxide solution is 5%, and the reaction time is 60 minutes. The aluminum back surface field and the aluminum grid line still remain, and the aluminum is not completely removed.

[0102] Comparative Example 2:

[0103] The difference between Comparative Example 1 and Example 1 is that in step 2 of Comparative Example 2, the mass concentration of the potassium hydroxide solution is 65%, and the reaction time is 5 minutes. The aluminum back surface field and the gate line are completely removed, and there are traces of silicon corrosion on the surface of the silicon wafer.

[0104] Comparative Example 3:

[0105] The difference between Comparative Example 3 and Example 1 is that in step 4 of Comparative Example 3, the ventilation time of carbon dioxide is 15 minutes, and the filtrate is left to stand for 3 minutes. The precipitation is not complete, which affects the judgment of whether new precipitation is formed when carbon dioxide is introduced next time.

[0106] The aluminum recovery rate, aluminum hydroxide purity and recovery rate of all the above embodiments and comparative examples were tested, and the results are shown in Table 1.

[0107] Table 1 Aluminum recovery rate, aluminum hydroxide purity and recovery rate results of the embodiments and comparative examples

[0108] serial number Aluminum recycling rate Aluminum hydroxide purity Aluminum hydroxide recovery rate Example 1 99.3％ 92.1％ 99.0％ Example 2 99.0％ 91.9％ 98.7％ Example 3 99.2％ 91.8％ 99.0％ Example 4 99.0％ 91.9％ 98.9％ Example 5 99.1％ 91.7％ 99.0％ Comparative Example 1 85.2％ 91.6％ 99.2％ Comparative Example 2 99.4％ 87.3％ 90.6％ Comparative Example 3 99.0％ 91.8％ 85.4％

[0109] As can be seen from Table 1, the aluminum recovery rate, aluminum hydroxide purity and recovery rate of Examples 1-5 are all excellent. In Comparative Example 1, because the concentration of the alkali-treated potassium hydroxide solution is too low, the reaction is insufficient, the aluminum back field and aluminum grid lines still remain, and the aluminum is not completely removed, resulting in a poor aluminum recovery rate. In Comparative Example 2, because the mass concentration of the alkali-treated potassium hydroxide solution is too high, the alkali solution corrodes the surface of the silicon wafer, and impurities are introduced into the solution, resulting in poor purity of aluminum hydroxide. In Comparative Example 3, because the filtrate is not allowed to stand for enough time and is not completely precipitated, the aluminum hydroxide recovery rate is poor.

[0110] Therefore, it is shown that the method of recovering aluminum from photovoltaic cells of the present invention has excellent aluminum recovery rate, excellent aluminum hydroxide purity and recovery rate.

[0111] In the description of this specification, the description with reference to the terms "one embodiment", "some embodiments", "example", "specific example", or "some examples" etc. means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described may be combined in any one or more embodiments or examples in a suitable manner. In addition, those skilled in the art may combine and combine the different embodiments or examples described in this specification and the features of the different embodiments or examples, without contradiction.

[0112] Although the embodiments of the present invention have been shown and described above, it is to be understood that the above embodiments are exemplary and are not to be construed as limitations of the present invention. A person skilled in the art may change, modify, replace and vary the above embodiments within the scope of the present invention.

Claims

1. A method for recovering aluminum from photovoltaic cells, characterized in that: The following steps are involved: Treat the photovoltaic cell with an alkaline solution having a mass concentration of 10 to 60%, filter, and collect the filtrate; Passing carbon dioxide gas into the filtrate and collecting the precipitate; The precipitate is dried and then ground to obtain aluminum hydroxide powder.

2. The method for recovering aluminum from photovoltaic cells according to claim 1, characterized in that: The alkaline solution includes at least one of a sodium hydroxide solution or a potassium hydroxide solution.

3. The method for recovering aluminum from photovoltaic cells according to claim 1 or 2, characterized in that: In the method of using an alkali solution with a mass concentration of 10 to 60% to treat the photovoltaic cell sheet, the mass concentration of the alkali solution is 15 to 45%.

4. The method for recovering aluminum from photovoltaic cells according to claim 1 or 2, characterized in that: In the treatment of the photovoltaic cell sheet with an alkali solution having a mass concentration of 10 to 60%, the treatment time is 5 to 40 minutes, preferably 10 to 30 minutes.

5. The method for recovering aluminum from photovoltaic cells according to claim 1, characterized in that: When the carbon dioxide gas is introduced into the filtrate, the control parameters satisfy at least one of the following: (1) The time for introducing carbon dioxide gas is 5 to 15 minutes; (2) The rate of introducing carbon dioxide gas is 2 to 15 L / min.

6. The method for recovering aluminum from photovoltaic cells according to claim 1 or 5, characterized in that: When the carbon dioxide gas is introduced into the filtrate, the control parameters satisfy at least one of the following: (I) The time for passing carbon dioxide gas is 10 to 15 minutes; (II) The rate of introducing carbon dioxide gas is 5 to 10 L / min.

7. The method for recovering aluminum from photovoltaic cells according to claim 1, characterized in that: After the carbon dioxide gas is introduced into the filtrate, the method further comprises a standing treatment, wherein the standing treatment time is 5 to 60 minutes.

8. The method for recovering aluminum from photovoltaic cells according to claim 1 or 5, characterized in that: The step of introducing carbon dioxide gas into the filtrate comprises the following steps: Pass carbon dioxide gas into the filtrate, let it stand for treatment, and collect the precipitate; Carbon dioxide gas was introduced into the remaining filtrate until no precipitate was produced.

9. The method for recovering aluminum from photovoltaic cells according to claim 1, characterized in that: Before the photovoltaic cell is treated with the alkaline solution having a mass concentration of 10 to 60%, a pretreatment is also included; the pretreatment includes removing dirt from the surface of the photovoltaic cell.

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