| Coal fly ash (CFA), as the major solid waste of coal-fired power plants in China, its production is increasing year by year and brought tremendous pressure on the environment. It has become a worldwide problem to how efficient and high value-added and rational to use it. The main components of CFA are Al2O3, SiO2 and with high iron content usually when use it to produce primary Al-Si alloys. It is necessary to remove partial iron from CFA rare material to produce qualified primary Al-Si alloys and also reduce energy consumption in the carbothermic reduction process.At the beginning of this thesis, the theoretical analysis of the critical value of iron in the pretreated CFA has been study. The results showed that the critical value of iron has a certain correlation with the SiO2. On this basic, the magnetic separation and hydrometallurgy thermodynamic analysis of iron removal had been study, and illustrated it is feasible to remove iron with the above-mentioned method. And some conclusions recommended as follow after lots of deironing experiments as grinding, magnetic separation, magnetic roasting-magnetic separation, atmospheric pressure leaching, ultra-fine grinding and pressure leaching.First, the iron content in Yunnan region’s CFA is usually high, and it mainly in the form of hematite and magnetite. The total iron and alumina content in magnetic tailing is 7.08% and 27.34% respectively after magnetic separation with XCGS-Φ50 magnetic tube in the magnetizing current of 3A. The remove rate of iron is 58.41% and alumina loss rate is 7.0%, the tailing with the yield 77.01%. Whether add the magnetic roasting process has little effect. The large scale experiment with SLon-100 cycle type pulsating high gradient magnetic separator shows that, the remove rate of iron is 66.37% and alumina loss rate is 17.99% in the magnetizing current of 100A (B=0.192T). And the content of total iron, alumna and silica is 5.83%,24.54% and 50.06% respectively, which is regard as the best condition.Second, the atmospheric leaching for deironing shows that HCl and OA is better than H2SO4, HNO3 is the worst. While the mixed acid of HCl and OA performed worse than either acid signally. There are lots of cellular structures in the HCl and HF leaching residue, and the alumina content in it is 12.92%, i.e. the loss rate of alumina is 64.83%. The result of leaching after roasting with additive is unsatisfactory.Third, The leaching experiments of CFA after separated shows that the optimal conditions for deironing process are OA concentrate of 120 g/L, temperature of 85 ℃, liquid-solid ratio of 6:1 and reaction time of 120 min. Under the condition, the content of total iron, alumna and silica is 3.35%,23.03% and 56.27% respectively, the corresponding iron remove rate and alumina loss rate is 46.06% and 11.91%. The content of total iron, alumna and silica is 2.74%, 22.68% and 58.41% respectively, the corresponding iron remove rate and alumina loss rate is 21.97% and 6.04% after the 2nd leaching process as the same condition with the 1st stop.Fourth, the average grain size is 2.18μm after high energy ball milling for 8h. The pressure leaching results shows that HCl is better than OA. The content of total iron and alumina in the leaching residues decreases with the increasing of temperature, they are 18.82% and 3.16% respectively at180 ℃, while the trend may not be quite as obvious.Fifth, the optimum process flow is magnetic separation combine one step atmospheric leaching process. The content of total iron, alumna and silica is 3.35%,23.03% and 56.27% respectively, the corresponding iron remove rate and alumina loss rate is 81.64% and 26.90% after the whole flow.Last, the carbothermic reduction experiments show that Al-Si alloys appeared just when the temperature above of 2273K, and the residual iron mainly in the form of Al-Si-Fe alloys in the reduzate.
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