Effect of H₂ addition on process of primary slag formation in cohesive zone

Based on the technology of gas-injection blast furnace (BF), the characteristics of primary slag formation with H₂ addition were researched. The results indicate that, compared with traditional BF, the primary melt is formed at a lower temperature, which promotes the deformation of the solid burden particles. With the increase in temperature and H₂ content, the quantity of formed melt containing FeO decreases sharply, corresponding to the crystallization of solid 2CaO·SiO₂ during reduction. A wider softening range and narrower melting zone could be found in the gas-injection BF with a higher reduction potential. The permeability of burden layer is ameliorated as a result of decreased melt quantity. The influence of H₂ on the high-temperature properties of burden is not so conspicuous when the H₂ addition is from 10 to 15 vol.% against 5 to 10 vol.%. What is more, the slag shows a better liquidity with the decrease in basicity, owing to the transformation of melt composition from a primary phase field with high melting point to that with low melting point. The process of slag forming in gas-injection BF is characterized by earlier melt formation, less primary slag, higher melting temperature, better permeability and better liquidity, and the phase compositions of primary slag are close to those of final slag.