Recycling Plastics as a Resource for Electric Arc Furnace (EAF) Steelmaking: Combustion and Structural Transformations of Metallurgical Coke and Plastic Blends

Abstract

Recycling end of life products, such as waste tires and waste plastics in iron- and steelmaking permits their use as energy and material resources. The current paper discusses the combustion efficiencies of blends of metallurgical coke (MC) with plastics for electric arc furnace (EAF) steelmaking. Laboratory tests involved the combustion in a drop tube furnace (DTF) at 1473 K of MC premixed with different proportions of plastics, polypropylene (PP), and high-density polyethylene (HDPE) (10−30%) under a 20% O2 and 80% N2 gas mixture. In the tested conditions, coke−plastic blends indicated higher combustion efficiencies compared to coke. The gas-phase reactions appear to be influenced by the amount of volatile matter present in the carbonaceous matrix and its subsequent effect on the structural transformation of the particles because of the release of volatiles. The surface area of the coke−polymeric mixtures before and after combustion was found to be higher than the surface area of coke alone. The residual chars collected after the reaction in the DTF were characterized as a function of pore volumes and surface area of the particles. A previous study has demonstrated the possibility of partially replacing conventional coke in EAF steelmaking with end of life rubber tires. The present paper studies the potential replacement of MC with waste materials, such as PP and HDPE, as auxiliary fuels in EAF steelmaking. A comparison to previously reported combustion efficiencies for rubber blends is also provided.