Sustainability in Upstream Magnesia Refractories Manufacturing - Resources, Processing, and Reprocessing

This doctoral thesis investigates important aspects of upstream magnesia refractories manufacturing, focusing on resource management, magnesia production routes, and the reprocessing of spent magnesia–carbon refractories. Refractory magnesia is essential for high-temperature industries, especially steelmaking, but its production is associated with significant environmental burdens due to energy-intensive sintering and the geogenic CO₂ released during magnesite calcination. At the same time, the refractory industry is under increasing pressure to reduce emissions, develop circularity and secure long-term access to mineral resources. This thesis addresses these challenges through three interconnected perspectives: Resource, Process, and Reprocess.
The first part examines the limitations of conventional mineral resource depletion assessments, particularly within Life Cycle Assessment (LCA). This thesis argues that resources should not be understood merely as geological stocks, but as materials whose value depends on accessibility and functionality. A resource-accessibility framework is proposed based on three dimensions: intelligibility, ESG permissibility, and technical recoverability. From this perspective, depletion is not primarily caused by extraction, but by dissipation and poor management of materials in the anthroposphere.
The second part evaluates the environmental performance of three dead-burned magnesia (DBM) production routes: natural magnesia from magnesite (1) and synthetic magnesia from seawater (2) and from serpentine (3). A cradle-to-gate Conceptual Life Cycle Assessment was performed using inventories developed from process simulation, literature data, and industrial expertise. The results show that the Magnesite route presents the lowest overall environmental burden under the assessed conditions, despite unavoidable geogenic CO₂ emissions. The synthetic routes showed higher impacts, mainly due to reagent consumption and process complexity. The study contributes to the development of LCA in the refractory industry, showing how simulation-based inventories serve as enablers but still with some limitations.
The third part investigates recycling pathways for spent magnesia–carbon refractories. Primary and secondary recycling are confronted, shedding light on the downcycling effect. In the face of the challenges posed by the concentration routes, the Controlled Carbon Burnout (CCB) process is evaluated in industrial scale. CCB sinter presented high MgO content, suitable grain bulk density, and a substantially lower CO₂ footprint than virgin DBM.
Overall, this thesis shows that sustainable magnesia refractories depend on preserving resource accessibility and value across the whole chain, from source to processing, use, and reprocessing. The findings provide methodological advances and practical insights for enhanced sustainability across the refractory magnesia supply chain.