energies Article CO 2 Recycling in the Iron and Steel Industry via Power-to-Gas and Oxy-Fuel Combustion Jorge Perpiñán 1 , Manuel Bailera 1,2 , Luis M. Romeo 1, * , Begoña Peña 1 and Valerie Eveloy 3   Citation: Perpiñán, J.; Bailera, M.; Romeo, L.M.; Peña, B.; Eveloy, V. CO 2 Recycling in the Iron and Steel Industry via Power-to-Gas and Oxy-Fuel Combustion. Energies 2021, 14, 7090. https://doi.org/10.3390/ en14217090 Academic Editor: Attilio Converti Received: 27 September 2021 Accepted: 22 October 2021 Published: 29 October 2021 Publisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affil- iations. Copyright: © 2021 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (https:// creativecommons.org/licenses/by/ 4.0/). 1 Escuela de Ingeniería y Arquitectura, Universidad de Zaragoza, María de Luna 3, 50018 Zaragoza, Spain; jorge.perpinan@unizar.es (J.P.); mbailera@unizar.es (M.B.); bpp@unizar.es (B.P.) 2 Graduate School of Creative Science and Engineering, Waseda University, Tokyo 169-8555, Japan 3 Department of Mechanical Engineering, Khalifa University, Abu Dhabi P.O. Box 127788, United Arab Emirates; valerie.eveloy@ku.ac.ae * Correspondence: luismi@unizar.es Abstract: The iron and steel industry is the largest energy-consuming sector in the world. It is responsible for emitting 4–5% of the total anthropogenic CO 2 . As an energy-intensive industry, it is essential that the iron and steel sector accomplishes important carbon emission reduction. Carbon capture is one of the most promising alternatives to achieve this aim. Moreover, if carbon utilization via power-to-gas is integrated with carbon capture, there could be a significant increase in the interest of this alternative in the iron and steel sector. This paper presents several simulations to integrate oxy-fuel processes and power-to-gas in a steel plant, and compares gas productions (coke oven gas, blast furnace gas, and blast oxygen furnace gas), energy requirements, and carbon reduction with a base case in order to obtain the technical feasibility of the proposals. Two different power-to-gas technology implementations were selected, together with the oxy blast furnace and the top gas recycling technologies. These integrations are based on three strategies: (i) converting the blast furnace (BF) process into an oxy-fuel process, (ii) recirculating blast furnace gas (BFG) back to the BF itself, and (iii) using a methanation process to generate CH 4 and also introduce it to the BF. Applying these improvements to the steel industry, we achieved reductions in CO 2 emissions of up to 8%, and reductions in coal fuel consumption of 12.8%. On the basis of the results, we are able to conclude that the energy required to achieve the above emission savings could be as low as 4.9 MJ/kg CO 2 for the second implementation. These values highlight the importance of carrying out future research in the implementation of carbon capture and power-to-gas in the industrial sector. Keywords: ironmaking; power-to-gas; iron and steel industry; methanation; oxy-fuel combustion; top gas recycling 1. Introduction The iron and steel sector is one of the most energy- and carbon-intensive in the world. Iron and steel making processes are still mostly coal-based and thus highly dependent on fossil fuels, releasing a substantial amount of CO 2 [1]. According to the Intergovernmental Panel on Climate Change (IPCC), the steel industry accounts for 4–5% of the total world CO 2 emission. It is the second largest consumer of industrial energy, consuming around 616 Mtoe (25.8 EJ) [2]. The iron and steel industry has a complex structure. However, only a limited number of processes are used worldwide that use similar energy resources and raw materials. Globally, steel is produced using two main routes, the blast furnace–basic oxygen furnace route (BF-BOF) and the direct scrap smelting route (electric arc furnace (EAF)). The BF-BOF route uses mainly iron ore, and depending on the facility, up to 30% scrap. The EAF route mainly uses scrap, and depending on the facility, up to 30% iron and iron ore [2–4]. Another fundamental difference between the two routes is the nature of the energy input. In the case of the BF-BOF, mainly coke is used as fuel, while the EAF route produces Energies 2021, 14, 7090. https://doi.org/10.3390/en14217090 https://www.mdpi.com/journal/energies