Comparison between Reducibilities of Columnar Silico-ferrite of Calcium and Aluminum (SFCA) Covered with Slag and Acicular SFCA with Fine Pores

Abstract

Reducibilities of silico-ferrite of calcium and aluminum (SFCA) have been examined using high temperature X-ray diffraction (XRD) analysis including the effect of hydrogen. Two types of sample were prepared: columnar SFCA covered with slag and acicular SFCA with fine pores, denoted by 'Columnar SFCA' and 'Acicular SFCA', respectively. These samples were synthesized using chemical reagents and iron ore powders. XRD analysis was applied to the samples heated in a condition simulating a blast furnace. Oxygen partial pressure was controlled by gas mixtures of CO-CO 2 -He, and there were some cases where 3.9 vol% of hydrogen gas was added to the mixture. The microstructures of the samples before and after heating were observed by electron probe microanalysis (EPMA). XRD profiles indicated: (i) both SFCA samples were reduced to Fe via calcio-wüstite (CW), (ii) the reduction from 'Acicular SFCA' to CW took place at lower temperatures than that of 'Columnar SFCA' during the heating cycle up to 1 000°C, and (iii) CW produced from 'Acicular SFCA' was reduced to Fe earlier than CW from 'Columnar SFCA' at 1 000°C. These results suggest that SFCA and CW phases in 'Acicular SFCA' have higher reducibility than those in 'Columnar SFCA'. This would be because 'Acicular SFCA' consists of smaller SFCA particles with fine pores. BSE images have revealed that such microstructures still remained even after the reduction to CW. Additions of hydrogen promoted reduction of 'Columnar SFCA' more effectively, and this effect was observed more remarkably in the reduction from CW to Fe than from SFCA to CW.

Comparison of the Mineralogy of Iron Ore Sinters Using a Range of Techniques

“…Iron ore sinter remains an important feed for the production of iron and steel, and research continues into the improvement of sinter quality for economic and environmental reasons [1,2].…”

Effect of Temperature, Time, and Cooling Rate on the Mineralogy, Morphology, and Reducibility of Iron Ore Sinter Analogues

“…16 Other work by Mezibricky and Frolichova 7 and Takayama et al 8 has demonstrated that using a morphological approach to distinguishing between SFCA and SFCA-I types is problematic, since both phases can exhibit similar textures. Similarly, Cai et al 9 produced both columnar and acicular (i.e., platy) textures of SFCA in their work, identifying both as SFCA using XRD.…”

“…Ó 2020 The Author(s) 1250°C, while SFCA is formed at higher temperatures > 1250-1300°C and may also crystallize from a melt upon cooling. 5,6 SFCA-I is high in iron and low in silica, with approximate composition of 84 wt% Fe 2 O 3,7 wt% CaO, 1 wt% SiO 2 , and 2 wt% Al 2 O 3 11 ; SCFA is low in iron and high in silica, with approximate composition of 60-76 wt% Fe 2 O 3, [7][8][9][10] wt% CaO, 3-10 wt% SiO 2,[4][5][6][11][12][13][14] wt% Al 2 O 3 , and 0.7-1.5 wt% MgO. 1,2,12 Recently Mumme (2003) 13 and Webster et al (2012) 5 have identified additional forms of SFCA, denoted as SFCA-II and Fe-rich SFCA, respectively.…”

Ore Assimilation and Secondary Phases by Sintering of Rich and High-Gangue Iron Ores

“…As typical secondary compounds in lime-fluxed iron ore sinters, calcium ferrites and calcium silicates form the sinter matrix. Recent works dealing with the mineralogy of iron ore sinters mostly focus on the complex calcium ferrite phase [10][11][12]. During the ferrite formation process, silica and alumina enter the structure, which results in crystallization of aluminosilicoferrites of calcium (often referred to as SFCA, short for silico-ferrite of calcium and aluminum).…”