• Energy Research

Abstract Recycling of polycrystalline silicon, amorphous silicon and CdTe photovoltaic panels was investigated by studying two alternative routes made up of physical operations: two blade rotors crushing followed by thermal treatment and two blade rotors crushing followed by hammer crushing. Size distribution, X-ray diffraction and X-ray fluorescence analysis of obtained products were carried out in order to evaluate their properties as valuable products. Results showed that for all kinds of investigated photovoltaic modules the two blade rotors crushing followed by hammer crushing and eventually by a thermal treatment of d >1 mm fractions, was the best option aiming to a direct recovery of glass.

Different kinds of panels (Si-based panels and CdTe panels) were treated according to a common process route made up of two main steps: a physical treatment (triple crushing and thermal treatment) and a chemical treatment. After triple crushing three fractions were obtained: an intermediate fraction (0.4-1mm) of directly recoverable glass (17%w/w); a coarse fraction (>1mm) requiring further thermal treatment in order to separate EVA-glued layers in glass fragments; a fine fraction (<0.4mm) requiring chemical treatment to dissolve metals and obtain another recoverable glass fraction. Coarse fractions (62%w/w) were treated thermally giving another recoverable glass fraction (52%w/w). Fine fractions can be further sieved into two sub-fractions: <0.08mm (3%w/w) and 0.08-0.4mm (22%w/w). Chemical characterization showed that 0.08-0.4mm fractions mainly contained Fe, Al and Zn, while precious and dangerous metals (Ag, Ti, Te, Cu and Cd) are mainly present in fractions <0.08mm. Acid leaching of 0.08-0.4mm fractions allowed to obtain a third recoverable glass fraction (22%w/w). The process route allowed to treat by the same scheme of operation both Si based panels and Cd-Te panels with an overall recycling rate of 91%.