Kinetics of Oxidation of Divalent Iron to Trivalent State in Liquid FeO-CaO-SiO2 Slags

Abstract

This work was devoted to the kinetics studies of the oxidation of divalent iron in liquid FeOCaO-SiO 2 slags to the trivalent state. The experiments were carried out using a thermogravimetric technique (TGA) in the temperature range of 1623 K to 1773 K (1350°C to 1500°C) in an oxidizing atmosphere. The reaction products after oxidation were analyzed by X-ray diffraction and optical and scanning electron microscopy. The results obtained show that during the first 10 to 15 minutes of oxidation, 70 to 90 pct of the Fe 2+ in the slag was oxidized. Kinetic analysis of the TGA results indicates that the oxidation process may consist of three distinct steps, viz an initial incubation period, followed by a chemical-reaction-controlled stage, and later, a diffusion-control stage. Appropriate mathematical relationships were set up for the first two consecutive steps. After combining these equations suitably as the mechanism of oxidation shifts from one form to another, the experimental results for the first two parts could be reproduced. A linear correlation was found between the thermodynamic activity of FeO in the slag and the degree of oxidation.

Crystallization and Beneficiation of Magnetite for Iron Recycling from Nickel Slags by Oxidation-Magnetic Separation

“…4FeO + O2 = 2Fe2O3 (4) 3Fe2SiO4 + O2= 2Fe3O4+3SiO2 (5) 3Fe2SiO4 + 3CaO + O2 = 2Fe3O4 +3CaSiO3 (6) 4Fe3O4 + O2 = 6Fe2O3 (7) Figure 2. The flowsheet of the oxidation and separation process.…”

“…Numerous scholars have studied the oxidation of the iron-bearing phase in slag systems. Semykina [5] presented the kinetics of the oxidation of divalent Calcium oxide (CaO) powder with a purity of 99.9%, supplied by Damao chemical reagents Co., Ltd. (Tianjin, China), was employed as the modifier. Alumina crucibles for holding the slags were of 99.99% purity, and were 50 mm in diameter, 80 mm in height, and 1 mm in thickness.…”

“…Semykina [5] presented the kinetics of the oxidation of divalent iron to a trivalent state in liquid FeO-CaO-SiO2 slags. Zhang [6] studied the oxidation mechanism of CaO-FeOx-SiO2 slag with high iron content in a pure oxygen atmosphere.…”

“…Although the oxidation of iron-bearing phases in metallurgical slags have been studied [5][6][7][8]13], few reports about the influence of factors on the crystallization of magnetite phases in nickel slag were available. In this work, holding time, temperature, air flow rate, basicity, particle size and magnetic flux were adjusted to study their influence on the crystallization behavior of magnetite phases, attempting to provide a scientific basis for the recovery of iron sources from nickel slags.…”

Chemical Thermodynamic Processes at Metal-Mold Interface

“…2) The composition of gas-phase in contact with solidified metal, depending on the mold mixture composition, can vary in a wide range in terms of CO, CO 2 Carbon (IV)oxide can be produced and consumed according to reactions (7,8,9).…”