Producing magnetite concentrate via self-magnetization roasting in N2 atmosphere: Phase and structure transformation, and extraction kinetics

In this work, a green self-magnetization roasting technology for producing magnetite was proposed without adding additional. The regulatory mechanisms of the main factors (siderite dosage, roasting temperature, and roasting time) on the self-magnetization roasting process were investigated. In-situ kinetic of the self-magnetization roasting process was analyzed by the infrared gas analyzer, and the phase transformation was investigated by in-situ X-ray diffraction and Mossbauer. Under the optimal roasting conditions of 30% siderite dosage, 730 degrees C, and 7.5 min, the iron concentrate with Fe grade 68.82% and Fe recovery 99.48% was obtained. The kinetic and phase transformation results indicated that the self-magnetization roasting process was divided into two stages: siderite pyrolysis in the prophase stage, and hematite reduced to magnetite by reductant (FeO and CO) from siderite pyrolysis in the anaphase stage. The SEM analyses showed that the newborn magnetite crystals were mainly coarse-grained and needles, which fitted the kinetics characteristics for the Nucleation model. Using self-magnetization roasting technology, siderite and hematite would promote mutual reduction to improve product magnetism and roasting efficiency without adding reductant. Also, self-magnetization roasting will enhance the utilization rate of siderite, and it contributes to energy conservation and CO2 emission reduction. (C) 2021 The Korean Society of Industrial and Engineering Chemistry. Published by Elsevier B.V. All rights reserved.

Automated summary

A green self-magnetization roasting technology for producing magnetite without additional additives was proposed and investigated in this study. The study revealed the regulatory mechanisms of main factors on the roasting process and showed that the process can be divided into two stages based on kinetic and phase transformation results. High-quality iron concentrate was obtained under optimal roasting conditions.