廢棄矽晶太陽能板矽資源化

Abstract

隨著低碳排的目標，光伏技術正在迅速發展，全球的太陽能板安裝量呈指數增長，與此同時，世界正在應對廢棄太陽能板數量激增的問題。最早發展的技術為矽晶太陽能板，也是當前佔據市場的主要類型。矽晶太陽能板顧名思義光吸收層是由矽晶所構成，雖然矽是地球上數一數二豐富的資源，但隨著高科技發展，矽廣泛應用於半導體業，為促進生活便利不可或缺的材料，然而製造高純度的矽會導致環境污染。如果能有效回收矽，不僅可以節約自然資源也可以降低環境污染。 本研究使用微波裂解前處理方式，去除廢棄矽晶太陽能板中的黏著劑乙烯醋酸乙烯酯（ethylene vinyl acetate, EVA）；接著使用兩階段濕式冶金法來依序回收鋁元素及銀元素；最後使用兩步驟化學蝕刻法，將矽晶上的反抗射塗層（anti-reflection coating, ARC）及發射極層（emitter）去除，回收高純度矽晶。 在微波裂解前處理程序中，以 150 W 功率下反應 40 分鐘，將廢棄矽晶太陽能板層與層間的 EVA 完全去除。於第一階段濕式冶金，利用 9 M 硫酸於反應溫度 70℃ 下將 92.33% 金屬鋁從矽晶上回收；而第二階段濕式冶金，使用 5 M 硝酸於常溫下將金屬銀完全從矽晶上回收，並進一步以鹽酸純化出氯化銀固體。最後化學蝕刻依序使用磷酸及氫氧化鉀，分別將 ARC 層及 emitter 層去除。 本研究成果顯示，使用微波裂解進行前處理能於更短時間內去除黏著劑，降低反應程序的能源消耗。兩步驟的濕式冶金，減低金屬回收間相互干擾，良好的分離鋁及銀。兩步驟的化學蝕刻，避免使用到氫氟酸，降低程序中的危險性。

With the benefits of greenhouse gas emission reduction global installation of solar panels using photovoltaic (PV) technology is growing exponentially. At the same time, the world needs to cope with a surge in the number of waste solar panels. The crystalline silicon solar panels are currently the dominant ones in the solar panel market. The absorbing layer of a crystalline silicon solar panel is composed of crystalline silicon. Silicon is one of the most abundant minerals on Earth and it is widely used in the semiconductor industry and is also an indispensable material in our daily lives. However, manufacturing high-purity silicon may cause environmental pollution. If we can recycle silicon, it not only conserves natural resources, but also reduces environmental pollution. In this study, microwave pyrolysis (MP) pre-treatment was used to remove the adhesive ethylene vinyl acetate (EVA) from waste crystalline silicon solar panels. A two-stage hydrometallurgical process was sequentially used to recover aluminum and silver elements. Finally, a two-step chemical etching was used to remove the anti-reflection coating (ARC) and emitter layer on the crystal silicon. Consequently, high-purity silicon could be recovered. Removal of the EVA between the layers of a waste crystalline silicon solar panel was successfully achieved by MP at 150 W treat in 40 minutes. Sulfuric acid and nitric acid were used to hydrometallurgical by the waste crystalline silicon solar cell for aluminum and silver recovery. Using 9 M sulfuric acid at 70 ℃, 92.33 % of aluminum was recovered. Silver was completely recovered with 5 M nitric acid under room temperatures, and the solid silver chloride was purified using hydrochloric acid. Finally, chemical etching was conducted, using phosphoric acid and potassium hydroxide, to remove the ARC layer and the emitter layer. Results of this study show that using MP pre-treatment could remove EVA in a short period of time with less energy consumption. The two-step hydrometallurgical process avoided interferences between the aluminum and silver recovery and achieved a good separation of aluminum and silver. The two-step chemical etching avoided the use of hydrofluoric acid and minimize the health risk during the treatment process.