A heavy non-ferrous metal fraction (< 50 mm) of municipal solid waste incineration bottom ashes from wet-mechanical treatment was separated by screening, magnetic separation and eddy-current separation into ferrous metals, non-ferrous metals and residual sub-fractions. The non-ferrous metal fractions were divided and subjected to (i) a washing process, (ii) dry abrasion and (iii) no mechanical pre-treatment to study the effect of resulting different surface properties on a subsequent X-ray fluorescence sorting into precious metals, zinc, copper, brass, stainless steel and a residual fraction. The qualities of the X-ray fluorescence output fractions were investigated by chemical analyses (precious metal fraction and the residual fraction), pyrometallurgical tests and subsequent chemical analyses of the metals and slags produced by the melting processes (zinc, copper, brass and stainless steel fraction). Screening directs brass and stainless steel primarily into the coarser fractions, while copper and residual elements were rather transferred into the finer fractions. X-ray fluorescence sorting yielded zinc, copper, brass, stainless steel and precious metals fractions in marketable qualities. Neither a negative nor a positive impact of mechanical pre-treatment on the composition of these fractions was identified. Solely the yield of the brass fraction in the grain size 16–20 mm decreased with increasing mechanical pre-treatment. The pre-treatment also had no impact on yield and quality of the products of pyrometallurgical tests.
Raw material potential of municipal solid waste incineration ashes for metal recovery and mineral carbonationAbstract Mineral processing of municipal solid waste incineration bottom ash yields high-value mineral and metallic intermediate products.Montanuniversität Leoben has been investigating recycling methods for these waste flows together with Brantner Group, a company running a slag treatment plant (Brantner Wet Slag Process) in Hohenruppersdorf, for several years.Whereas the focus of the AKRosA II project was on enrichment of critical and potentially critical metals, the aim of the Research Studio Austria CarboResources was mineral carbonation. The processing method developed for recovery of nonferrous metals is based on conventional mechanical processing (screening, magnetic separation, eddy current separation) and sensorbased sorting technologies (XRF sorting). The innovative methodology for carbon capture and utilisation is the production of chemically precipitated calcium carbonate by decoupled dissolution, precipitation and carbonation processes. The grain-size specific sinks for critical and potentially critical raw materials in the heavy fraction of MSWI bottom ash 0-16 mm could be specified and high-value nonferrous metal concentrates (zinc, brass, stainless steel . . . ) could be produced. Additionally, contaminants from intermediate mineral products could largely be removed and calcium carbonate could be synthesised for industrial applications.
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