Thermodynamic study of evolution of sinter phases at different alumina level

Abstract

Though sintering is controlled by kinetics of various reactions and is far from equilibrium, a thermodynamic analysis can provide useful inputs on melt formation and helps understand deviation from actual process conditions. The thermodynamic software 'FACTSAGE™' was used for this study. The general sequence of reactions during the heating cycle is as follows: decomposition of calcium carbonate to calcined lime; formation of calcium ferrites/silicates; decomposition of calcium ferrites, reduction of haematite to magnetite and formation of spinel and silicates; assimilation of ferrites, silicates, spinel and magnetite into the melt. During the cooling stage, the amount of melt decreased with subsequent precipitation of phases such as magnetite, ferrites, silicates, spinel and formation of haematite. It is very much clear that the sinter made by using higher alumina levels generate fewer amounts of oxides and more slag phase compared to its low alumina counterpart.

Improving High-Alumina Iron Ores Processing via the Investigation of the Influence of Alumina Concentration and Type on High-Temperature Characteristics

“…Increased alumina concentration increases the viscosity and decreases the fluidity of liquid phase [20,21,27,28]. According to the previous studies [22][23][24]29], the increasing Al 2 O 3 content contributes to the formation of SFCA, leading to a higher proportion of SFCA in sinter. However, the excessive increase of Al 2 O 3 content (>1.0%) is expected to result in a drastic deterioration in the properties of SFCA.…”

“…At a relatively lower Al 2 O 3 content (<2.0%), increasing the Al 2 O 3 content is favorable to liquid phase fluidity as to diaspore, kaolinite, and free state alumina. This is probably owing to that the proper addition of alumina contributes to the formation of SFCA and then weakening the adverse effect of alumina on liquid phase fluidity to some extent [22][23][24]29]. As the Al 2 O 3 content is above 2.0%, its increase is detrimental to liquid phase fluidity for all alumina types, but the influence degrees are different.…”

“…Liquid phase fluidity represents the effective bonding behavior of liquid phase [20,21]. Characteristics of the bonding matrix act as the generative properties of the bonding matrix mainly including its morphology, component, and formation amount [22][23][24]. The product sinter with high strength and good reducibility is desired for blast furnace production.…”

“…Many researches on high-temperature characteristics of iron ores with various alumina concentration have been carried out [18][19][20][21][22][23][24][25][26][27][28][29]. It is found that high Al 2 O 3 content tends to promote the lowest assimilation temperature and namely weakens the assimilability [18,19].…”

Effect of Thermodynamic Melt Formation Characteristics on Liquid Phase Fluidity of Iron Ore in the Sintering Process

“…This suggests that OD has a higher Al 2 O 3 content to promote the formation of high melting point minerals. With the increase in sintering temperature, melilite minerals gradually react to decompose and form liquid phase; thus, the formation rate of the liquid phase slows down in the high temperature stage (1250~1300 • C) [16,17].…”