Valorization of Waste Printed Circuit Board Using Pyrolysis and Metal Extraction

Abstract

Waste printed circuit boards (WPCBs) are one of the most vital components of any waste electrical and electronic equipment (WEEE) and contribute about 4–7% of the total E-waste. WPCBs consist of a heterogeneous mixture of approximately 30% polymers, 30% metals and 40% ceramic materials. This thesis work explores viable routes to recover these materials from WPCB using a combination of pyrolysis and metal extraction via hydrometallurgical processing, and performs a techno-economic assessment of the proposed plant. Pyrolysis is a thermochemical technology that converts organic materials to valuable oil and gas fractions. However, the brominated flame retardants (BFRs) present in WPCB are transferred into the product fractions, making these products unsuitable for use due to environmental concerns. The bromine content in the gas can be controlled by scrubbing; however, removing it from the oil fraction is difficult. The performance of the embedded metals in WPCB was evaluated to reduce bromine transfer in oil. The metal extraction was performed using acid leaching and cementation. Finally, a plant containing comminution, pyrolysis and metal extraction sections was simulated using Aspen Plus® software, and its techno-economic assessment was performed.