High-voltage pulse crushing and physical separation of polycrystalline silicon photovoltaic panels

High-voltage pulse crushing technology combined with sieving and dense medium separation was applied to a photovoltaic panel for selective separation and recovery of materials. The panel was first separated into glass and back sheet layers by high-voltage pulse crushing through microexplosions or shock waves transmitted in the Al electrode and Si substrate (primary crushing step). Then the glass and bus-bar electrode could be separated from the encapsulant by high-voltage pulse crushing of the glass layer. The bus-bar electrode of the back sheet layer could also be separated by further high-voltage pulse crushing. After sieving the products obtained from the secondary crushing step of the glass layer, glass was mainly distributed in the size fraction range of 45-850 μm with a small amount of Si powder. However, purification of the glass (removal of Si powder) could be achieved by dense medium separation at a specific gravity of 2.4. Base metals, such as Cu, Sn, and Pb could be recovered in the large size fraction (1.0-8.0 mm). Ag used in the finger and bus-bar electrodes was highly condensed in the sieved product fraction with sizes of less than 20 μm, 2.0-4.0, and 4.0-8.0 mm, and its content exceeded 3000 mg/kg. However, the amount of Ag in these fractions represented only 33.2% of the total amount of Ag in the panel. Thus, to increase the Ag recovery ratio, other separation methods will be needed. We confirmed that dense medium separation at a specific gravity of 3.0 could achieve Ag condensation from the Si and glass, and that this represents a promising option for enhanced Ag recovery from crushed products.