Role of Exergy-Based Process Evolution for Sustainable Steel Making: Rotary Hearth Furnace with Electric Arc Furnace Smelting

In conjunction with an electric arc furnace (EAF) process, a rotary hearth furnace (RHF) has emerged as a supplementary ironmaking unit to produce extra iron from iron-bearing solid wastes from an integrated steel plant. Additionally, such units offer fuel-switching options to low-carbon input fuels. Exergy analysis is carried out for two variants of RHF, producing iron nuggets (ironmaking technology mark 3 process) or direct reduced iron (DRI; FASTMET process), involving cold/hot charging of DRI and scrap use in EAF. Process sustainability as characterized by higher exergy efficiency and lower CO2 emission has been analyzed for two variants of RHF-EAF steelmaking systems, blast furnace-basic oxygen furnace (BOF), scrap-EAF, and COREX-BOF process. Model-based information for these parameters for RHF-EAF process has been compared with other major steelmaking routes based on literature information. The RHF-EAF process variants with some modification in process flow display better sustainability with relatively higher exergy efficiencies and low CO2 emissions as compared to other steelmaking processes and reasonably meet sustainable steelmaking process evolution criterion.