The Effects of Al2O3 and SiO2 on the Formation Process of Silico-Ferrite of Calcium and Aluminum (SFCA) by Solid-State Reactions

Fei Liao,Xing-Min Guo

doi:10.3390/min9020101

Abstract

The silico-ferrite of calcium and aluminum (SFCA) is a significant crystalline phase that bonds in high basicity sinter. Al2O3 and SiO2 play an important role in the formation of SFCA in the Fe2O3–CaO–SiO2–Al2O3 system, but the effect mechanism of Al2O3 and SiO2 on the formation of SFCA is unclear. To investigate this effect, sintering experiments were carried out with different temperatures and different times. It was found that the reaction of Al2O3 with CaFe2O4 (CF) as an initial product was easier to form during the calcium iron aluminum oxide (CFA) than that of SiO2 with CF to form SFC. This was due to the former directly forming to CFA while the latter initially formed Ca2SiO4 (C2S) and Ca2.5Fe15.5O25, and then SFC. It was also observed that when Al2O3 and SiO2 existed simultaneously, the Al2O3 initially reacted with CF to form CFA at 1100 °C, while the SiO2 participated in the formation of SFCA at 1150 °C without the formation of SFC. Moreover, it was understood that these were different effects in that the Al2O3 promoted the transformation from the orthorhombic crystal system to the triclinic crystal system, while the SiO2 dissolved into CFA to form the SFCA phase when Al2O3 existed.

Highlights

Silico-ferrites of calcium and alumina (SFCA) is a vital bonding phase in the high basicity sinter as a main material in blast furnace for iron-making, the formation process of SFCA has been studied by many researchers [1,2,3,4,5]
Inoue and Ikeda [6] first reported that the SFCA was a solid solution of calcium ferrite with CaSiO3 –Ca(Fe, Al)6 O10 which existed in the CaO–Fe2 O3 –Al2 O3 –SiO2 system
Scarlett et al [16,17] reported that CaFe2 O4 (CF) appeared as an original in the calcium ferrite phase before the Al2 O3 and SiO2 participated in the formation of SFCA

Summary

Introduction

Silico-ferrites of calcium and alumina (SFCA) is a vital bonding phase in the high basicity sinter as a main material in blast furnace for iron-making, the formation process of SFCA has been studied by many researchers [1,2,3,4,5]. Ding et al [10,11] studied the formation mechanism and the crystal structure of SFC in which Fe2 O3 , CaFe2 O4 (CF) and Ca2 SiO4 reacted to form the SFC that belongs to a triclinic crystal structure. The SFC phase, CFA phase, and SFCA phase had the same crystal structure and similar XRD patterns. Scarlett et al [16,17] reported that CF appeared as an original in the calcium ferrite phase before the Al2 O3 and SiO2 participated in the formation of SFCA. Rietveld quantitative methods were used to study the reaction rate of SiO2 and Al2 O3 with CF These results are helpful in understanding the important role of Al2 O3 and SiO2 in the SFCA formation process

Sample Preparation

Results and Discussion

The4 SiO

Phase Composition of Calcium Ferrites Formation with Temperature

Conclusions