Evaluating the reduction-softening behaviour of blast furnace burden with an advanced test

Abstract

<div lang="en" class="abs"><p class="abs_header">Abstract</p><p>A ferrous burden loses its permeability in the cohesive zone of a Blast Furnace (BF), where the iron burden materials soften and melt. A tailor-made, high-temperature furnace named ARUL (Advanced Reduction under Load) was used here to study the reduction-softening behaviour of acid and olivine pellets and basic sinter under simulated BF gas, temperature and pressure conditions.The ARUL test showed the best reduction-softening properties for the basic sinter. The sinter sample resisted up to 1329°C and achieved a reduction degree of 90.2% until a gas-impermeable structure was formed in a packed bed, whereas the acid pellet lost its permeability at 1160°C and only reduced to a reduction degree of 48.7%. The olivine pellet had intermediate reduction-softening properties with a final temperature of 1252°C and a final reduction degree of 68.7%. The differences between the test materials were assessed as being caused mainly by different chemistry, but it was also revealed that the sinter sample remained its macro-porosity markedly better in relation to the pellets, providing routes for reducing gases.</p><p>The experimental results were compared to the phase diagrams calculated with the computational thermodynamic software FactSage. Phase diagrams for the 5-component FeO–SiO₂–CaO–MgO–Al2O₃ systems with constant CaO, MgO and Al₂O₃ contents were used to estimate the formation of liquid phases in the test materials. The computed phase diagrams gave an estimate of the liquid formation; however, some limitations were also found in the utilization of the computations because of the need to define the system in certain simplicity.</p></div>