Mixed burden softening-melting property optimization based on high-silica fluxed pellets

Abstract

The development of a high proportion of pellets smelting process suitable for China's resource structure can promote low carbon and green development of blast furnace ironmaking. The differences in metallurgical properties, phase evolution, microstructure, and softening-melting characteristics between high-silica acid pellets and high-silica fluxed pellets were compared and analyzed. The high content of low-melting-point liquid phases such as Fe 2 SiO 4 within the high-silica acid pellets, leads to a low initial softening temperature, and a higher amount of quartz in the form of solid phase mass points will reduce the fluidity of the slag and makes the permeability index deteriorate. The high-silica fluxed pellets slag is mostly in the form of Ca 2 SiO 4 , softening-melting behavior, and the permeability of the material layer improving significantly. Using high basicity sinters with a high proportion of fluxed pellets, although not effective in reducing slag amount, was observed to have a synergistic optimizing effect on the softening-melting behavior of the mixed burden. As the proportion of fluxed pellets increases from 35% to 45%, T d decreases from 1455 °C to 1427 °C, and the melting zone narrows from 139 °C to 109 °C, S-value reduced from 1147.98 kPa·°C to 440.36 kPa·°C. With the increase in the proportion of high-silica fluxed pellets, the position of the cohesive zone moves up, the viscosity of the slag decreases, fluidity increases and the permeability of the material layer gradually increases. • Dendritic quartz increases acid pellets' slag phase viscosity and reduces fluidity. • The flux containing calcium optimizes the slag phase composition of the pellets. • The cohesive zone of the high-silica fluxed pellets becomes narrower and the permeability is significantly improved. • As the proportion of high-silica fluxed pellets increases, the permeability of mixed burden gradually improves.