Study of the influence of hydrogen and associated water vapor on the refractory materials

Sammanfattning

The increasing environmental concerns associated with traditional steelmaking processes necessitate a transition to more sustainable methods, particularly the utilization of hydrogen as a reductant or a fuel in metallurgical applications. This thesis investigates the influence of hydrogen (H₂), associated water vapor (H₂O) and carbon dioxide (CO2) on the performance of refractory materials, which are critical for high-temperature processes in the iron and steel industry. The study aims to comprehend the mechanisms of failure that these materials experience under hydrogen - rich atmospheres. However, not abundant literature about the current understanding of hydrogen-based metallurgical processes and the challenges they pose for refractory materials employed in furnace linings. To begin with, a database computing system in chemical thermodynamics software is employed to simulate those reactions and evaluated its reactivity and resulting products. Following this, selected refractory specimens were subjected to controlled high-temperature testing in a tube furnace, simulating atmospheres enriched with Ar, H₂ and CO₂. Those samples were analysed using microscopy characterization techniques, including light optical (LOM), and scanning electron (SEM) with energy-dispersive X-ray spectroscopy (EDS). The findings reveal significant alterations in the microstructural integrity of refractory materials when exposed to hydrogen and water vapor, including increased porosity, mass variation and diminished mechanical properties. Magnesia carbon suffered from embrittlement at 1000 and 1600 °C with H₂ and CO₂. Moreover, H₂ purified high alumina refractory and CO₂ increased Cr2O3 ratio. These changes attributed to chemical interactions between hydrogen and the refractory's constituents lead to phase transformations. The results provide critical insights into the performance limitations of traditional refractories in hydrogen-based metallurgical processes and emphasize the need for the development of advanced materials with enhanced resistance to such harsh conditions.