Recovery of copper from small grain size fractions of municipal solid waste incineration bottom ash by means of density separation

ABSTRACT

Small grain size fractions of municipal solid waste incineration (MSWI) bottom ash (BA) contain elemental and chemically bonded metals in appreciable amounts, especially copper. Investigations with a centrifugal concentrator were carried out using samples, which had been treated with different impact devices. Partly the impacts of single devices were visible in outlines, but mostly the surfaces of the metals were still covered with mineral residues. To generate copper rich fractions, parameters of the separation process should ensure mass yields <2%, best between 0.5 and 1%. The density of the concentrates is then generally >3.2 g/cm³. Best results were achieved with material from a special treatment train which is adapted to grain sizes <2 mm. Reliable copper contents between 20 and 40% (single runs >50%) could be realised. However, considering the required mass yields, referred to this subset only 150–170 g copper would be recovered from 1 Mg MSWI BA. Furthermore, this copper is only in parts present in elemental form. A dependable added value of such treatment step seems to be given only, if that enables a recycling of the mineral aggregates (tailings) in parallel to avoid landfill costs.

KEYWORDS:

• Municipal solid waste incineration (MSWI)
• bottom ash (BA)
• density separation
• copper
• mineral aggregates
• design of experiments (DOE)

Acknowledgements

This paper is originated in the framework of following federal funded project: Support Code 033R086A – German Federal Ministry of Education and Research (BMBF). Special thanks to Marie Hoffmann, Ute Kalbe, Franz-Georg Simon and all partners of the funded project as well as the all staff of BAM 4.3.