Process integration analysis and some economic-environmental implications for an innovative environmentally friendly recovery and pre-treatment of steel scrap

The use of Zinc-coated steel (e.g. galvanized steel) in melting cycles based on Electric Arc Furnaces can increase the production of harmful dust and hazardous air emissions. This article describes a novel process to simultaneously preheat and remove the coating from the scrap surface before the melting phase. The zinc in coating is removed in the gas phase by chloride containing syngas combustion and collected in a dedicated recovery system. Two possible innovative process routes are described, which involve plastic waste pre-treatment, shredded plastic gasification/pyrolysis, steel scrap preheating and zinc recovery processes. The routes have been modeled in an integrated flowsheet, in order to allow a comprehensive simulation and optimization of the pretreatment processes. The process optimization results in possible energy savings of over 300 MJ/t of preheated scrap charged in the Electric Arc Furnace for steel production. Moreover, a comparison among different scenarios according to economic and environmental criteria has been carried out.