Effect of basicity on wuestite sinter reducibility under simulated blast furnace conditions

In this study, synthetic sinters with different basicity (CaO/SiO2=0, 0.5 and 2.0) were prepared at 1300 degree C and prereduced at 900 degree C using low potential reducing gas (LPRG; 20%CO, 20%CO2, 5%H2 and 55%N2). The prereduced sinters were subsequently reduced to metallic iron at 950-1100 degre...

Full description

Saved in:
Bibliographic Details
Published in:Ironmaking & steelmaking 2014-07, Vol.41 (6), p.418-429
Main Author: Mousa, E A
Format: Article
Language:English
Subjects:
Basicity
Calcium ferrites
Formations
Reduction
Scanning electron microscopy
Silicon dioxide
Sinter
Online Access:Get full text
Tags: Add Tag
No Tags, Be the first to tag this record!
Description
Summary:In this study, synthetic sinters with different basicity (CaO/SiO2=0, 0.5 and 2.0) were prepared at 1300 degree C and prereduced at 900 degree C using low potential reducing gas (LPRG; 20%CO, 20%CO2, 5%H2 and 55%N2). The prereduced sinters were subsequently reduced to metallic iron at 950-1100 degree C using relatively high potential reducing gas (HPRG; 30%CO, 5%CO2, 10%H2 and 55%N2). Both LPRG and HPRG were selected to simulate the gas composition in the blast furnace upper and lower shaft respectively. High pressure mercury porosimeter, X-ray phase analysis, optical and scanning electron microscope were used for the analysis of the prepared and reduced sinters. In the original basic sinter, calcium ferrite (CaFe2O4) and dicalcium silicate (Ca2SiO4) phases were identified as well as the main Fe2O3 phase, whereas wollastonite [Ca2.87Fe0.13(SiO3)3] and silica (SiO2) were formed in the acidic sinter. The prereduction in sinters with LPRG at 900 degree C resulted in the formation of wuestite (Fe0.902O) phase. The subsequent reduction in wuestite sinters to metallic iron using HPRG at 950-1100 degree C was found to be the highest for basic sinter and the least for acidic sinter. The higher reduction rate of basic sinter was attributed to the enhancement of wuestite reducibility through the formation of calcium ferrites. The lower reduction rate of wuestite in acidic sinter was attributed to the formation of hard reducible fayalite (Fe2SiO4) and ferrobustamite [(Ca0.5Fe0.5)SiO3] phases. The rate controlling mechanism during the reduction process was estimated by the correlation between apparent activation energy calculation and microstructure investigations.
ISSN:0301-9233
1743-2812
DOI:10.1179/1743281213Y.0000000136