New EAF Dust Treatment Process with the Aid of Strong Magnetic Field

Abstract

A new EAF dust treatment process named as "Lime Addition and Magnetic Separation Process (LAMS Process)" has been proposed to recover zinc oxide from the dust and to use solid residue as a flux for steel refining. The LAMS Process consists of the reaction of EAF dust with CaO followed by the adequate crushing and high gradient magnetic separation. The basic principle of this process has been established by revealing the phase equilibria in the CaO-Fe 2 O 3 -ZnO system where Ca 2 Fe 2 O 5 can be in equilibrium with pure ZnO rather than ZnFe 2 O 4 , which is the major component of EAF dust, at higher CaO region. The conversion of zinc ferrite in EAF dust to ZnO and Ca 2 Fe 2 O 5 has been experimentally demonstrated by heating the dust with double molar amount of CaO at 1 173 and 1 373 K. It has also been demonstrated that the formed ZnO and Ca 2 Fe 2 O 5 can be separated by the strong magnetic field. Therefore, it may be possible to recover ZnO from EAF dust without the carbothermic reduction like Waelz process.

Substance Flow Analysis of Zinc Associated with Iron and Steel Cycle in Japan, and Environmental Assessment of EAF Dust Recycling Process

“…Based on the heat balance, the input energies required for the LAMS process are essentially simple heating energy up to around 1 000°C and for the rotation of the kiln type reactor. It has also demonstrated that approximately 77 % of ZnFe 2 O 4 in the dust was able to be converted to ZnO and Ca 2 Fe 2 O 5 at 1 100°C at 3 h, 19) which was almost equivalent reaction efficiency for ZnO formation with the Waelz process because the general operating condition of the Waelz process is 6 to 8 h treatment at around 1 200°C. 26) Thus, the input energies of the LAMS process are assumed to be the same as those required in the Waelz process (heavy oil and electric power input).…”

“…The authors 19) have shown that the enthalpy change of Eq. (4) at the boiling point of zinc is approximately Ϫ34.9 kJ/mol (exothermic) while that of Eq.…”

“…Based on this background, the authors 18,19) have proposed a new process for dust treatment by reacting CaO with ZnFe 2 O 4 in the dust to form free ZnO and Ca 2 Fe 2 O 5 , according to the following basic reaction. The basic principle and the results of the feasibility study on this new process have been described in our another publication.…”

“…The basic principle and the results of the feasibility study on this new process have been described in our another publication. 19) Exothermic nature of Eq. (4) is a benefit of the new process.…”

“…[13][14][15][16][17][18][19] The purposes of this study are as follows: (1) to identify the material flow of zinc associated with steel production, and (2) to estimate the environmental effects (energy consumption and CO 2 emission reduction) of some intermediate dust treatment processes.…”