Iron Removal from a High-lithium Coal Fly Ash by Magnetic Separation

This is an essay in the field of mineral processing engineering. In this study, coal fly ash from a power plant in Guizhou was used as the research object. A series of test methods were comprehensively applied to the determination of the mineral composition and element content of coal fly ash. The results show that the main minerals in coal fly ash are mullite, quartz and iron minerals (5.46% magnetite and 4.77% hematite) , and the main chemical components are SiO₂, Al₂O₃ and Fe₂O₃, with the contents of 36.88%, 20.89% and 14.58%, respectively. In addition, the content of lithium is as high as 307 g/t, which shows a certain comprehensive utilization value. Particle size analysis shows that the cumulative yield of coal fly ash below 75 μm is as high as 83.4%, which indicates that the overall particles are finer. Lithium and iron are mainly concentrated in the -75 μm fraction. Reduction roasting was used to convert the weakly magnetic hematite in coal fly ash into strong magnetic magnetite, and then the wet magnetic separation method was used to remove iron from the fly ash. The results show that with the residual carbon in coal fly ash as the reducing agent, the roasting temperature 700 ℃, the roasting time 45 min, and the magnetic field strength 240 mT, and followed by a magnetic separation process of "one roughing-two sweeping", the iron removal rate reaches 63.27%, and the lithium recovery is 80.31%.