Improving recyclability of organic-coated metallic-coated steels : Primary steelmaking: final report

A system for the preparation and decoating of organic coated/galvanised scrap has been developed. Scrap preparation via a shrear shedder was found to yield an open-faced feedstock which was suitable for the subsequent wet chemical decoating stage (acidic and caustic media). A number of environmentally friendly treatment processes were examined for applicability to waste streams from the wet chemical treatment process; super criticalwater oxidation (SCWO), wet air oxidation (WAO) and microwave pyrolysis methods were found to be effective for treating polymeric waste streams (paint residues). Electrolysiscould be an option for zinc and heavy metal recovery/removal.At the time of writing, the environmental impact of direct charging of coated steels during steelmaking appears to be acceptable as current technologies adequately control organic emission levels. However, significant changes in environmental legislation could make prior decoating an effective option for steelmakers. Niche markets may also be able to exploit this technology where clean scrap and/or large volumes of coated scrap have to be used (e.g. EAF steelmaking)