Recovery of Cr, Ni and Fe from dust generated in stainless steelmaking

Abstract

During stainless steel production in an electric arc furnace, the dust generated amounts to around 1% of the charge weight. This dust contains chromium, zinc and other heavy metal oxides; therefore, its final disposal in special landfill sites is expensive. On the other hand, the content of chromium oxide (~9 wt%), nickel oxide (~2•5 wt%) and iron oxides (~47 wt%) can be recovered by reduction with carbon or Fe-Si. In this paper, the dust was physically and chemically characterised, and used in the manufacture of composite pellets with carbon and Fe-Si. These pellets were added to iron-carbon melts at a temperature around 1600°C. After smelting-reduction, the recovery yields of Cr, Ni, and Fe were determined. These yields were: (i) with Fe-75%Si as reductant -Ni ~90%, Cr ~90%, Fe ~90%; and (ii) with coal as reductant -Ni ~12%, Cr ~35%, Fe ~90%). A preliminary economic evaluation for Brazilian conditions showed that the process is sustainable depending on the landfill cost for dusts and the availability of inexpensive Fe-Si. When coal is used as reductant, the electric energy becomes the main cost component and the above recycling process becomes economically feasible with landfill costs higher than US$ 150 t -1 .

Effects of Fe2O3 on Reduction Process of Cr-Containing Solid Waste Self-Reduction Briquette and Relevant Mechanism

“…In conclusion, due to the relatively low chromium-iron ratio (Cr/(Fe + Cr)) of the A-type Cr-RB, the metal products are more likely to rapidly aggregate and separate from the slag. The low Cr Figure 13 shows that the initial reaction temperature (Tinitial) of Reactions (7) to (14) in the standard state are 712 °C, 655 °C, 653 °C, 1053 °C, 1248 °C, 1141 °C, 1253 °C, 1710 °C, respectively. Obviously, the initial reduction temperatures of iron-containing oxides are below 712 °C.…”

“…1/3Cr2O3(s) + 9/7C(s) = 2/21Cr7C3(s) + CO(g) Figure 13 shows that the initial reaction temperature (T initial ) of Reactions (7) to (14) in the standard state are 712…”

“…Fully recycling chromium in these solid wastes will not only improve enterprises' economic efficiency, but also reduce the risk of heavy metal pollution caused by Cr in solid wastes after being leached in the natural acidic or alkaline environment [6]. In all of Cr-containing solid wastes treatment technologies, high-temperature reduction technology using carbonaceous reductants has been paid extensive attention due to its unique characteristics compatible with metallurgical enterprises [5,[7][8][9][10]. Due to its excellent reactivity, self-reduction briquette bearing C was mostly adopted [11][12][13][14].…”

Reciclagem da poeira de aciaria elétrica na sinterização de minério de ferro visando a eliminação de zinco.

“…Analisando dois tipos de PAE com diferentes teores de zinco, Takano et al (27) observaram que em poeiras com baixos teores do metal, a maior parte se encontra na forma de ferritas ou espinélios. Aumentos dos teores de zinco promovem o crescimento da parcela de zincita presente na PAE.…”

Fe-Ni-Cr Crude Alloy Production from Direct Smelting of Chromite and Laterite Ores

“…Several studies [1]- [4] have been conducted on the phase equilibria, thermodynamics, kinetics and slag-metal equilibrium distribution of chromium and nickel in the production of ferrochromium and ferronickel, respectively. It has been found [5] that the amount of Cr, Ni and Fe recovery in the metal phase is controlled by the slag composition, oxygen partial pressure and melting temperature.…”