Reduction Behavior of EAF Slags Containing Cr2O3 Using Aluminum at 1793 K

Abstract

The simultaneous reduction kinetics of Cr 2 O 3 , MnO, FeO, and SiO 2 in the EAF slag by aluminum has been investigated at 1 793 K to understand the reduction mechanism of each oxide in the stainless steelmaking conditions. The reduction degree of MnO reached about 90 % and that of FeO and Cr 2 O 3 reached about 80 % for 5 min. The reduction degree of SiO 2 continuously increased up to about 55 % for 20 min, followed by a constant value. The reduction of each oxide by aluminum was found to be controlled by the diffusional mass transfer process in slag phase from the simple kinetic analysis. The mass transfer coefficient of each oxide was in order of 'MnOϾCr 2 O 3 ХFeOϾ ϾSiO 2 ' in the present system. The reduction rate constant (log K°M O , where MO represents Cr 2 O 3 , FeO, MnO, and SiO 2 ) linearly increases by increasing the product of diffusion coefficient and the activity of each oxide (log[D M · a MO ]) in the slag.

Selective elemental concentration during the solidification of stainless steel slags for increased Cr recovery with MnO addition

“…One approach is the reduction of CrO x with reducing agents such as C, Al, and Si to lower the overall CrO x content in the slag before tapping. This approach is complicated under industrial operating conditions, and the economic value of treating waste residues with low Cr content is not high 8‐10 . Another approach is the selective precipitation of Cr hydroxides (Cr(OH) 3 ) by leaching Cr ions from the slag, which are subsequently calcined to obtain a Cr product (CrO x ).…”

“…This approach is complicated under industrial operating conditions, and the economic value of treating waste residues | 6013 WANG ANd SOHN with low Cr content is not high. [8][9][10] Another approach is the selective precipitation of Cr hydroxides (Cr(OH) 3 ) by leaching Cr ions from the slag, which are subsequently calcined to obtain a Cr product (CrO x ). However, this approach produces large amounts of acid-based waste liquor, and the escaped Cr may be released into the waste liquor, followed by transfer into either carbonate particles or byproducts that cause serious secondary pollution.…”

Determination of CaO–SiO2–MgO–Al2O3–CrOx Liquidus

“…P roducing high‐quality stainless or specialty steel with a high material and energy efficiency requires a good slag practice. Important issues include refractory degradation, 1 chromium reduction, 2,3 and slag foaming, 4,5 which are all greatly influenced by the presence of MgO·Cr 2 O 3 spinel‐based solid precipitates in the slag. Further, recycling of the slag requires mechanical and chemical stability, which also depend on the microstructure formed during cooling.…”

Modelling of the Refining Processes in the Production of Ferrochrome and Stainless Steel

“…On the other hand, the oxidized chromium may be reduced from the slag back to metal by using ferrosilicon, carbon, calcium carbide or aluminium. (Arh & Tehovnik, 2007;Park et al, 2004) When modelling the oxidation reactions, one always has to consider the competing oxidation reactions of carbon, chromium and silicon as well as in some cases aluminium and titanium.…”

“…However, the overall reduction degrees of these oxides decresed in the order of MnO (90 %), Cr 2 O 3 (70 %), SiO 2 (59 %) and FeO (40 %). (Park et al, 2004) EAF slag's ability to generate foam from injected or generated gas can be quantified with the foam index, , for which the mathematical definition as well as the correlation with the slag properties is given in equation (5) (Ito & Fruehan, 1989;Kerr & Fruehan, 2000, 2004Zhang & Fruehan, 1995 (Ito & Fruehan, 1989;Kerr & Fruehan, 2000, 2004Zhang & Fruehan. 1995).…”