Softening-melting mechanism of basic pellets under hydrogen-enriched reduction

Abstract

Hydrogen-rich blast furnace ironmaking is an important low-carbon technology to reduce CO₂ emissions of steel industry, and its effect on softening-melting performance has a great influence on blast furnace ironmaking. In this paper, the softening-melting properties of basic pellets with hydrogen-rich based on high pellets ratio ironmaking were studied. The microstructure evolution and softening-melting mechanism of pellets during the process were investigated. The results show that when the hydrogen concentration increases from 0% to 12%, the initial softening temperature (T₁₀) decreases from 1209°C to 1197°C, the melting starting temperature (T_s) and dripping temperature (T_d) increase respectively, which means bottom the cohesive zone descends. S-value decreases from 458.55kPa·°C to 293.33kPa·°C. In hydrogen-rich condition, hydrogen will not gather on the surface of pellets like CO to form a dense iron shell. More FeO is produced on the surface and inside of pellets, which forms the low-melting-point slag phase with gangue and reduces the initial softening temperature. And after entering the melting stage, the FeO produced inside decreases, resulting a high melting point of slag, So, the dripping temperature increases from 1412°C to 1458°C.