|
General comment Mechanical upcycling that aims to fully recover components. Additional chemical processes are involved, referred as “mechanical recycling” . Several studies have investigated mechanical operations to recover glass and separate it from other parts. We sort these methods as M1, M2, M3, and M4. Inmethod M1, Granata et al. proposed a method to shred the module in atwo-rotor motor followed by hammer milling. Larger fractions (diameter > 0.08 mm) were identified as recoverable glass and smallfractions (diameter < 0.08 mm) were identified to contain Si andmetals that need further pyro/hydrometallurgical treatments. Afterthermal removal of the polymer residue from the glass, this methodproduces recyclable glass at a quantity 80–85%w of the PV module. A follow-up study further improved this process by replacing thecrushing and milling with triple shredding, achieving a glass recoveryrate of 91%w. In method M2, instead of thermal removal of theEVA residue, Yingli Solar developed a cryogenic process to delaminateSi modules. After cooling at sufficiently low temperatures (−196 °C),the interfacial bonding of the sandwich structures are weakened.Then, an abrasive grinding machine can easily peel Si powders fromplastic powders. In method M3, which targets at the unbroken glass pieces, Trina Solar investigated a glass detachment processunder oxidant hydrothermal subcritical conditions to detach the wholeglass sheet from the module. Note that, for M2 and M3 the recycling yield was unclear. Therefore, the viability should be furtherinvestigated and validated. In method M4, another reliable approachwas used: hot knife cutting. The Full Recovery End of Life Photovoltaic(FRELP) project demonstrated a pilot recycling approach that cuts apartthe entire module glass sheet by a high-frequency knife at slightlyelevated temperatures. 98%w of the glass was recovered, and the rest ofthe EVA/solar cell/backsheet sandwiches were sent to an incinerationplant for further treatment. Cutting has a clear advantage to detach glass in a single step to avoid multiple crushing and thermal processes. The hot-cutting concept has been implemented using differentdesigns, such as a heated cutting blade, a fast spinning steel brush, andchisel sheets. |
