Optimization of a thermochemical process to increase metal recycling from WEEE

In order to enable a sustainable supply, the recovery of raw materials from secondary resources offers promising potential. Waste Electrical and Electronic Equipment (WEEE) is a source of various metals and polymers, but also includes hazardous substances. Therefore, a process for a thermo-chemical treatment of different fractions from WEEE were developed and optimized. With the aim to dehalogenate pyrolysis products and recover base and precious metals from shredder residues as well as gallium, indium and tantalum from Liquid Crystal Displays (LCD) and tantalum capacitors, three thermochemical technology approaches were developed. From shredder residues, not only a concentrate of char and metals was produced, but also liquid and gaseous fuels. The char-metal mixture can be utilized directly in integrated copper smelters in order to recycle contained metals. Special attention was given on how formations of dioxins and furans (PXDD/F) can be suppressed and on how already formed PXDD/F can be decomposed continuously. Regarding LCD, the developed technology is able to extract >99 wt.-% of indium selectively from LCD by using waste polyvinylchloride (PVC). For the last mentioned feedstock, a combination of pyrolytic and mechanical treatment was developed and optimized, which is able to form a concentrate of nearly 80 wt.-% tantalum.