Influence of MgO and Al2O3 Contents on Viscosity of Blast Furnace Type Slags Containing FeO

Abstract

The viscosities of CaO-SiO 2 -Al 2 O 3 -MgO-FeO slag were measured under conditions of C/Sϭ1.35-1.45, 10-18 mass% Al 2 O 3 , 3.5-10 mass% MgO and 5 mass% FeO. The bosh slag with 10 mass% Al 2 O 3 content had the lowest melting temperature and the widest solid-liquid coexisting region at about 5 mass% MgO, while in case of 14 mass% Al 2 O 3 , an increase in a MgO content from about 3.5 to 10 mass% raised the melting point of bosh slag. The viscosity of bosh slag also exhibited a minimum value at about 7 mass% MgO at temperatures above 1 723 K. However, it was not significantly changed with varying MgO content. On the hand, with increasing Al 2 O 3 content, the viscosity of bosh slag increased at a fixed C/S and MgO content. Based on the melting temperature and the behavior of viscosity at a fixed temperature, it could be proposed that the MgO and Al 2 O 3 contents in bosh slag should be maintained around 5 and 10 mass%, respectively, for high pulverized-coal ratio (PCR) and low slag volume operations in blast furnace.KEY WORDS: viscosity; bosh slag; blast furnace; slag volume reduction; slag structure; FT-IR. 100 rpm) were employed in 1 773 K to ensure that viscosity values were independent of rotation speed. All measurements were performed with cooling and holding temperature. The holding time for reaching equilibrium state was more than 30 min at each experimental temperature. A metal flange was utilized to fill the gap between the viscometer and the mullite reaction tube, and an Ar gas (0.4 L/min) was flown into the reaction chamber. After viscosity measurements were completed, the slag samples were reheated up to 1 773 K, and held for more than 3 h. Then, the slag sample was quenched to analyze slag composition and to measure the infrared spectra of the slag. According to the composition analysis of post-measurement slag using X-ray Fluorescence (Bruker-SRS3400), there was no significant change in any component of slags (less than 1 %).In order to confirm the reproducibility of viscosity values, some experiments for the same composition were carried out three times. The results show that differences between measurements were lower than 0.2 dPa · s (less than 0.5 %). Infrared Spectra MeasurementThe structure of the investigated slags was analyzed by FT-IR spectroscopy (JASCO, FT/IR-300 E). FT-IR trans- ISIJ International, Vol. 44 (2004) mitting spectra were recorded in the 4 000 -400 cm Ϫ1 range using a spectrometer equipped with a KBr (deuterated triglycine sulfate with potassium bromide windows) detector. A spectral resolution of 4 cm Ϫ1 was chosen. Each 2.0 mg sample was mixed with 200 mg of KBr in an agate mortar, and then pressed into 13 mm diameter pellets. The spectrum for each sample represents an average of 20 scans, which were each normalized to the spectrum of the blank KBr pellets. The FT-IR spectra were analyzed by computer software. Results and DiscussionIn the present study, the effects of MgO and Al 2 O 3 contents on the viscosities of the CaO-SiO 2 -Al 2 O 3 -MgO-FeO slags were investigate...

Influence of Al₂O₃ and MgO on the Viscosity and Stability of CaO–MgO–SiO₂–Al₂O₃ Slags with CaO/SiO₂=1.0

“…6,7) It is well known that Al 2 O 3 is an amphoteric oxide. 8,9) Al 2 O 3 behave as either a basic oxide or an acidic oxide depending on the slag composition. [10][11][12][13][14][15] In order to improve the properties of slag containing high Al 2 O 3 content, some researchers have investigated the effect of MgO addition on the viscosity.…”

Reduction Behavior of Carbon Composite Pellets Including Alumina and Silica at 1273 K and 1373 K

“…Especially, high alumina content in raw material is an inevitable situation for blast furnace operation as well as for direct reduction coupled with electric arc furnace production. There have been numbers of studies on high alumina blast furnace process in terms of slag volume, 4) slag viscosity [5][6][7] and sulfide capacities. 8) Characteristics of conventional blast furnace type slag i.e.…”

Effect of Al₂O₃/SiO₂ Ratio on the Viscosity and Structure of Slags

“…[1][2][3][4] The effect of alumina on the structure and physical properties of this slag system has attracted attention during the past decades due the amphoteric behavior of alumina. [5][6][7][8] Generally, the researchers studied how varying alumina content influences the structure or physicochemical properties of slag melts through either measurements of viscosity, 5,6) or measurements of structure directly using Fourier transformation infrared spectra (FT-IR), [7][8][9][10] Raman spectra 11,12) and Neutron diffraction.…”