Carbon Footprint and Energy Transformation Analysis of Steel Produced via a Direct Reduction Plant with an Integrated Electric Melting Unit

Abstract

AbstractThe production of flat steel products is commonly linked to highly integrated sites, which include hot metal generation via the blast furnace, basic oxygen furnace (BOF), continuous casting, and subsequent hot-rolling. In order to reach carbon neutrality a shift away from traditional carbon-based metallurgy is required within the next decades. Direct reduction (DR) plants are capable to support this transition and allow even a stepwise reduction in CO2 emissions. Nevertheless, the implementation of these DR plants into integrated metallurgical plants includes various challenges. Besides metallurgy, product quality, and logistics, special attention is given on future energy demand. On the basis of carbon footprint methodology (ISO 14067:2019) different scenarios of a stepwise transition are evaluated and values of possible CO2equivalent (CO2eq) reduction are coupled with the demand of hydrogen, electricity, natural gas, and coal. While the traditional blast furnace—BOF route delivers a surplus of electricity in the range of 0.7 MJ/kg hot-rolled coil; this surplus turns into a deficit of about 17 MJ/kg hot-rolled coil for a hydrogen-based direct reduction with an integrated electric melting unit. On the other hand, while the product carbon footprint of the blast furnace-related production route is 2.1 kg CO2eq/kg hot-rolled coil; this footprint can be reduced to 0.76 kg CO2eq/kg hot-rolled coil for the hydrogen-related route, provided that the electricity input is from renewable energies. Thereby the direct impact of the processes of the integrated site can even be reduced to 0.15 kg CO2eq/kg hot-rolled coil. Yet, if the electricity input has a carbon footprint of the current German or European electricity grid mix, the respective carbon footprint of hot-rolled coil even increases up to 3.0 kg CO2eq/kg hot-rolled coil. This underlines the importance of the availability of renewable energies. Graphical Abstract