Assessment of a multistep revamping methodology for cleaner steel production

Abstract

A novel revamping methodology is proposed to achieve the decarbonization of currently operating integrated steel mills (step 0) without reducing steel production levels. Such a method encompasses four successive steps involving cleaner and more energy efficient technological pathways for steel production.The decarbonization strategy is reported: step 1, partial replacement of coke with recycled plastic in a conventional Blast Furnace – Basic Oxygen Furnace (BF-BOF) plant; step 2, implementation of a Direct Reduction-Electric Arc Furnace (DR-EAF) line combined with the BF-BOF plant; step 3, complete shut-down of the BF-BOF line and full operation of two DR-EAF lines fed by CH4; step 4, installation of an alkaline electrolyzer and use of 100% green H2 as a reducing agent in the DR plants.The gradual replacement of the integrated steel mill with DR-EAF lines causes a progressive drop in CO2 emissions, ranging from 8.5 Mt/y at step 0 to a minimum of 0.68 Mt/y at step 4 (92% decrease).Coke replacement with recycled plastic in the blast furnace in step 1 leads to a slight decrease in CO2 emissions without altering the structural layout of the plant. In step 2, the combined operation of BF-BOF and DR-EAF lines determines a 39% decrease in CO2 emission compared to the initial configuration, while keeping total steel production constant. Step 3 involves two DR-EAF lines fed by CH4 and reduces the CO2 emissions by 75% compared to the initial configuration. The operation of two DR-EAF lines increases the electricity consumption, especially when 100% green H2 is involved as a reducing agent in step 4. By increasing the scrap mass fraction in the EAFs of step 4, both electricity and H2 demands of the DR plant are expected to decrease, while the CO2 emission levels remain almost unchanged, leading to about 92% total CO2 emissions reduction compared to the initial configuration (provided that green electricity is used). By assuming an initial 10% scrap mass fraction at the EAFs inlet of step 4, the demand of green hydrogen is significant, thus requiring the installation of a 1.42 GW electrolyzer. The capital expenditure (CAPEX) estimated upon completion of the revamping methodology amounts to approximately 2.97 B€. The transition towards a full decarbonization of steel production technologies is demonstrated to be technically feasible, though strictly dependent upon the large availability of low emissions electric power and scrap material.