Revisiting the softening and melting behavior of sinter under simulated blast furnace conditions: Part I – Thermodynamic and experimental insights on working line

Background: Due to the complex reaction conditions within the blast furnace (BF), often termed a “black box”, previous research has largely relied on oversimplified experimental setups. This limitation has significantly impeded the accurate investigation of the detailed mechanisms governing the softening and melting (S&M) behaviors of sinter ore. To address these challenges, this study establishes experimental conditions designed to more closely replicate the internal BF environment, guided by the concept of the BF working line. Methods: A novel Blast Furnace Simulator, equipped with an in-line mass spectrometry (MS) gas analyzer, was employed to replicate the BF conditions with high fidelity. The exhaust gas compositions were continuously monitored and quantified, enabling precise calculations of the indirect, direct, and overall reduction degrees during the experiment. Significant Findings: A mechanistic understanding of key S&M behaviors, including mechanical softening at 1000 °C, physico-chemical softening at 1150 °C, and the sharp pressure drop accompanied by the collapse of the core-shell structure at 1330 °C, is characterized. The findings underscore the critical role of the core-shell structure in maintaining gas diffusion pathways, which are closely tied to the permeability performance of BF operations. These insights into S&M mechanisms under simulated BF conditions provide a strong foundation for advancing research on hydrogen-enriched BF operations.