Fundamentals of Silico-Ferrite of Calcium and Aluminium (SFCA) Iron Ore Sinter Bonding Phase Formation: Effects of Basicity and Magnesium on Crystallisation during Cooling

Abstract

The effects of basicity and Mg addition on the crystallisation during cooling of complex Ca-rich ferrite iron ore sinter bonding phases SFCA and Fe-rich SFCA was investigated using in situ synchrotron X-ray diffraction. In synthetic iron ore sinter mixtures, cooling of a high temperature (T = 1 623 K) assemblage comprising magnetite and melt showed that decreasing basicity from B = 4.0 to 3.0 and 2.5 resulted in the formation of a Fe-rich SFCA phase being suppressed, with SFCA being the only Ca-rich ferrite phase to form initially from the melt at B = 2.5. Increasing the Mg concentration in the sinter mixtures to 1 and 3 wt% MgO resulted in an overall suppression of the amount of Ca-rich ferrite phase formation. However, Mg addition caused the formation of Fe-rich SFCA to be favoured over SFCA, with SFCA not observed to form at all during cooling in the 3 wt% MgO mixture. The absence of SFCA in the high-Mg experiment was rationalised on the basis that the Fe-rich SFCA structure accommodates more Fe 2 + than the SFCA structure, thereby stabilising Fe-rich SFCA relative to SFCA through replacement substitution of Fe 2 + by Mg 2 + . Observation of Fe-rich SFCA in sinter may be an indicator of localised high basicity, and/or, high Mg concentration, within a sinter blend.KEY WORDS: iron ore sinter; in situ synchrotron X-ray diffraction; complex Ca-rich ferrite iron ore sinter bonding phases; SFCA; crystallisation during cooling; CaO:SiO 2 ratio; Mg addition.

Low Carbon Sinter Making: Use of Inert Gas to Improve Sinter RDI

“…SFCA phase due to its acicular structure also helps in arresting crack propagation and improve both RDI and RI. 3,30,31) Few selected samples of varying RDI were analysed for phase quantification, and in line with the above findings, it can be observed that an increase in SFCA and Magnetite phase Fig. 9, RDI is also improved.…”

[Retracted] Effect of Basicity on the Microstructure of Sinter and Its Application Based on Deep Learning

“…Secondly, the proper addition of Al 2 O 3 in the liquid phase of the sintering aids in the formation of acerous calcium ferrite. Webster et al [ 9 ] used in situ S-XRD (synchrotron X-ray diffraction) to study the effect of basicity on the crystallization of the effective bonding phase of SFCA (silico-ferrite of calcium and aluminum) and Fe-rich SFCA in the sinter during cooling. The formation of Fe-rich SFCA is inhibited when the basicity is decreased from 4.0 to 2.5, but SFCA crystallizes from the melt during the cooling of material with basicity of 2.5.…”

Comprehensive Technologies for Iron Ore Sintering with a Bed Height of 1000 mm to Improve Sinter Quality, Enhance Productivity and Reduce Fuel Consumption

“…Quicklime has a finer particle size and better dispersion compared with other fluxes, thus it can be uniformly distributed in the material layer during the granulation process, which is beneficial for the formation of liquid phase SFCA during the sintering process, as a result, the sinter consolidation strength and yield is improved. 18,19) Secondly, the high material-temperature of the mixture play significant role in eliminating the over-wetting zone in sintering layer and improving the sintering indices. Active quicklime has a absolutely high content of CaO with released large amount of heat during digestion, which can effectively increase the temperature of the material mixture.…”