Carbon capture and utilisation in the steel industry : A study exploring the integration of carboncapture technology and high-temperature coelectrolysisof CO2 and H2O to produce synthetic gas

University essay from KTH/Energiteknik; KTH/Energiteknik

Author: Julia Sjoberg Elf; Kristoffer Wannheden Espinosa; [2017]

Keywords: ;

Abstract: The present thesis studies the potential for introducing the technology of co-electrolysis of carbondioxide (CO2) and water (H2O) through a Solid Oxide Electrolyser Cell (SOEC) in a top gas recyclingblast furnace (TGR-BF) in a steel plant. TGR-BF, commonly presented in literature as a promisingcarbon capture and storage (CCS) pathway for the steel industry, can drastically decrease theseemissions by successively recycling up to 90 % of the top gas from a blast furnace (EU, 2014) andsequestering the CO2 from the highly carbon concentrated remaining top gas. Blast furnaces (BF)represent about 20 % of the total carbon dioxide emissions of a steel plant (Carpenter, 2012). Based onthe current research status of SOEC, this report aims at exploring the utilisation of carbon dioxidecaptured from TGR-BF through a simultaneous electrolysis of CO2 and H2O, a novel and highly efficientpathway of producing valuable synthetic gas (syngas), used in chemical and industrial applications.It is important to note that neither of the technologies is yet in commercialisation phase, and that thesuggested installation would presently not be possible, but nevertheless provides an interesting pathwaytowards closing the carbon cycle of steelmaking. To give an idea of the magnitude of the SOECinstallation and its syngas production if combined with TGR-BF, an analysis of existing case studies ofeach technology was made. The SOEC system modelled by Fu et al. (2010) was scaled to fit the CO2emissions of Ruukki Metals steel plant in Raahe, Finland, for which data is abundant and reliable. Tohighlight the integration potential of the two separate technologies, a conceptual process flow chart wasdesigned and a literature review of the respective technologies performed, allowing the identification ofintegration challenges, presented in the analysis. The literature study reveals that challenges for thesystem include: gas purity requirements, gas composition requirements, scalability, life-timecompatibility, plant complexity and high variation of plant infrastructure. In the discussion, difficultiesrelated to a technology shift in a traditional industry are considered. For further research, mathematicalmodelling of thermodynamics of the system as well as an economic assessment are recommended.

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