Technical-economic assessment of advanced sorting of nonferrous metal scraps from waste incineration

NF metal scraps are an important resource to the metal recycling industry and bear considerable energy and cost savings potential in comparison with primary raw materials. Post-consumer NF metal items often end up in mixed municipal solid waste, for which an important treatment pathway is waste incineration. NF metals scraps produced during the treatment of the bottom ash are a mixture of metals and alloys, most importantly aluminium, copper, brass and zinc. In order to be useful to metal recycling processes, a density separation where mainly aluminium is transferred into a light fraction suitable for aluminium refining is a standard measure. The resulting heavy fraction is qualified for copper recycling. However, due to the presence of other metals a relatively high refining effort is needed. Further separation into a copper, brass and zinc fraction enables by-passing refining steps in copper recycling and enhanced recovery of zinc in dedicated recycling processes, thus increasing the market value. Here, classic mechanical sorting technologies reach their limits. This work evaluates the objective target and a technical solution to this sorting task and presents a methodology to answer its feasibility in the light of the economic situation. A case study showcases a technical-economic assessment of the current situation in Germany.