Pyrolysis and Detoxification of Waste Electrical and Electronic Equipment (WEEE) for Feedstock Recycling

Open Access

Abstract

The trends in waste electrical and electronic equipment (WEEE) generation shows that their volume constantly increases, while the current waste management technologies have proven to be insufficient in order to meet the strict criteria and the new legislations of the European Union. Pyrolysis and thermal treatment in general could be a valuable solution for closing the loop of materials and could contribute to the energy demands of modern society. Pyrolysis as a process and combination of other pre-treatment techniques was investigated with a focus on energy production, metal separation and feedstock recycling. In this work, several fractions of real WEEE have been tested based on the process requirements and the focus of each individual study. Firstly, the investigation was focused on the primary products of the process, revealing most of the environmental pollutants as well as the valuable monomers that can enhance feedstock recycling. A correlation of the process' final temperature with the evolution of the major products was performed. Moreover, a conceptual reaction mechanism of Bisphenol A decomposition was suggested based on the process products. Then, a reduction of the bromine content of the initial WEEE fraction was achieved by solvent extraction pre-treatment. Isopropanol and toluene were tested as solvents capable of removing one of the main flame retardants at WEEE fractions, Tetrabromobisphenol A. The results indicate that the reduction of bromine was successfully performed even at ~37%. This result was further confirmed by the reduction or total removal of brominated species in the pyrolysis products. The toluene seems to be a valuable option for the pre-treatment, since it can be provided by the pyrolysis process itself, making the entire treatment more sustainable and in accordance with the concept of circular economy. Density separators used in the sorting of WEEE materials usually produced high moisture content fractions. As soon as those fractions follow thermal treatment, the moisture will ...