Recovery of high-grade copper from waste polyester imide enameled wires by pyrolysis and ultrasonic treatment

Recovery of high-grade copper from waste enameled wires can effectively alleviate the shortage of copper resources. In this paper, the evolution of pyrolytic products during pyrolysis of waste polyester imide enameled wires was analyzed and the thermal decomposition mechanism was presented. A technology consisting pyrolysis and ultrasonic was proposed to achieve deep decarbonization. The results showed that the pyrolysis process was mainly divided into two stages. Below 500 °C, polyester imide was first depolymerized into large monomer, and then pyrolytic oil containing ketones, imides, amines and aromatic compounds was generated by random fracture (three main ways) and free radical reactions. With increase of temperature, the free radical reactions of small molecules to produce carbon and pyrolytic gas were dominant. The decarbonization efficiency reached 99.99% and the high-grade copper was obtained under the optimal conditions. This study provided the theoretical basis for recycling high-grade copper from waste enameled wires.