Abstract:
Pyrolysis disposal is an effective way to realize efficient treatment and recycling of waste PV modules. The pyrolyzable part of waste PV modules mainly includes organic films and fluorinated backsheets. Given that it is impossible to completely separate the organic film and fluorine-containing backsheet. the study of the co-pyrolysis of organic film and fluorine-containing backsheet as well as the migration and transformation of fluorine-containing substances is the key to realize the efficient and environmentally friendly treatment of waste PV modules. In this paper, the reaction molecular dynamics (ReaxFF MD) method was used to study the individual pyrolysis behaviors of ethylene vinyl acetate copolymer (EVA) and polyvinylidene fluoride (PVDF) polymers, and the generation and transformation of oxygen/fluorine-containing substances in the process of co-pyrolysis of these two polymers were further investigated, which reveals the influence of different reaction temperatures on the interactions between the two polymers. The results show that ReaxFF MD can better fit the pyrolysis behaviors and product distributions of EVA and PVDF; during the co-pyrolysis process, PVDF promotes the decomposition of EVA to generate CO
2, and CO
2 will further react with the residual carbon from the pyrolysis of PVDF in carbon gasification reaction; EVA not only inhibits the secondary condensation reaction of the pyrolysis products derived from PVDF, but also promotes the generation of small molecule fluorine-containing organic compounds; In addition, EVA can enhance the generation and release of HF from PVDF, and the enhancement is more significant under high temperature conditions. This study not only comprehensively reveals the interaction between EVA and PVDF during the co-pyrolysis process, but also clarifies the key role of reaction temperature in optimizing the synergistic effect of the two and the directional migration and transformation of F elements.