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- Density separation (2) (entfernen)
Organisationseinheit der BAM
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.
Small grain sizes of municipal solid waste incineration (MSWI) bottom ash (BA) contain elemental and chemically bonded metals in appreciable amounts, especially copper. As different copper species have in general a higher density compared to the prevalent minerals, processes for density separation seemed to be favorable for the recovery of copper. Investigations with a centrifugal classifier were therefore carried out with BA from MWSI which have been used for a few years as the covering material for a landfill. The results show an appreciable enrichment of the precious copper. The concentrates contained up to 60 mg/kg copper in the dry weight (DW) (in general about 30 – 40 mg/kg DW) with enrichment factors of around 20 and a copper recovery of up to 50 % (in general around 20 %). A test series in order to evaluate the potential benefit for sequential processing illustrate the low efficiency for a further processing of the tailings.