Improving properties of fluxed iron ore pellets with high-silica by regulating liquid phase

With rapid development of the pellet production under the background of green development, high-quality iron concentrates were gradually exhausted; thus, using high-silica iron concentrates was expected to be a promising way to relieve resource pressure for pellet production. However, increasing the proportion of high-silica acid pellets into the furnace led to worse blast furnace slag, and the metallurgical properties of high-silica pellets were imperfect. To understand the reciprocal effects of basicity (CaO/SiO2) and MgO content on the properties of the high-silica pellets, the phase compositions and microstructure were investigated using X-ray diffraction and scanning electron microscope, equipped with energy dispersive X-ray spectrometry. The results indicated that simply increasing MgO content from 0 to 2.50 wt.% could decrease the reduction swelling index, but the compressive strength rapidly declined due to the formation of magnesioferrite. However, adding CaO to 2.50 wt.% MgO pellets greatly improved the pellet qualities, which could be attributed to a substantial increase in the amount of high-melting-point silicate liquid phase.