Clean recycling of low-grade refractory limonitic waste using suspension magnetization roasting coupled with magnetic separation: A semi-industrial approach towards a waste utilization plan

Efficient utilization and clean recycling of low-grade refractory iron ore are essential to deal with the fast depletion of high-grade iron ore. A semi-industrial test of suspension magnetization roasting (SMR) for a low-grade refractory limonite waste with a grade of 32.46% by using reducing gases of CO and H-2 mixture was conducted. The optimal experiments conditions were determined at a temperature of 550 degrees C, a reducing gas flow of 3.3 m(3)/h, a reductant concentration of 30% and a total gas volume of 14.0 m(3)/h. The iron grade of 59.27% and a recovery of 96.30% were obtained in the semi-industrial continuous and stable operation experiment. The iron transformation was mainly in the order of mFe(2)O(3)center dot nH(2)O to Fe3O4, which was detected by X-ray diffraction and the relative resonance area of magnetite and gamma-Fe2O3 phase was 93.90% according to the result of Fe-57 Mossbauer spectral analysis. The peak of Fe3+ shifted to 710.11 eV and the area increased constantly, showing that the surface of Fe3O4 occurred in the X-ray photoelectron spectroscopy. The magnetic magnetization transformed from 0.1 to 27.71 A center dot m(2)center dot kg(-1) using the vibrating sample magnetometer (VSM). Cracks and a large number of holes in the roasted ores could be discovered by scanning electron microscopy (SEM) and the enrichment of iron elements could be reserved by mapping scan using energy dispersive spectrometry (EDS). The environmental protection methods of the SMR was investigated by discussing the carbon emissions challenges and exhaust pollution emission problems. This study demonstrates that the SMR is a green and effective tech-nology for low-grade limonite waste utilization.

Automated summary

Efficient utilization and clean recycling of low-grade refractory iron ore can be achieved through suspension magnetization roasting (SMR) using reducing gases of CO and H-2 mixture. In a semi-industrial test, the optimal conditions were determined, resulting in an iron grade of 59.27% and a recovery of 96.30%. The iron transformation was mainly from mFe(2)O(3)center dot nH(2)O to Fe3O4, and the magnetic magnetization increased from 0.1 to 27.71 A center dot m(2)center dot kg(-1). The SMR is a green and effective technology for low-grade limonite waste utilization.