Iron Recovery By Red Mud Reduction Roasting-magnetic Separation Study On The Mechanism Of

Although red mud is the tailing of aluminum oxide in the industrial production,it is an important secondary resource.In recent years,there are many studies on the recycling of iron from red mud,among which the most common methods are acid leaching method and roast reduction process.However,the quality of concentrate separated by the former method is usually not high,while the latter method will consume much energy.Therefore,this paper studies the magnetized roasting of red mud for the recycling of iron and the action mechanism of additives in the roasting process,which has important significance for the comprehensive recycling of red mud and the cyclic utilization of secondary resources.Taking Bayer red mud of Shandong as research object,the paper conducts the process test of magnetized roasting of red mud for the separation and recycling of iron,and mainly studies the influences of reducing agents and additives on the effect of recycling for iron,and deeply analyzes the mechanism of roast reduction process for red mud.Finally,the study draws the following crucial conclusions:1.Without additives,iron concentrates with grades of 56.08%and 57.19%and recovery rates of 87.89%and 91.25%can be obtained in coal-based and gas-based conditions respectively.The additives of dolomite and phosphogypsum have no obvious influence or exist an inhibiting effect on the process of magnetized roasting of red mud for the separation of iron.With sodium sulfate as the additive,the grade and recovery rate of iron concentrate can reach 60.65%and 94.01%respectively,increased by 3.46%and 2.76%respectively compared with those without additives.2.The results of thermodynamic calculation show that at lower temperatures,carbon monoxide（CO）as the reducing agent is more beneficial to the reduction of iron in red mud.There are fayalite and hercynite in the reaction system of red mud,which cannot be decomposed by pulverized coal or CO in the range of test temperatures.Dolomite,phosphogypsum and sulfate sodium are successively added and decomposed as Mg O,Ca O,Ca S,Na₂O,and Na₂S,which can promote the decomposition of fayalite.However,only Na₂O and Na₂S can promote the decomposition of hercynite.3.According to phase analysis,after the magnetized roasting,hematite and goethite in red mud can be converted to magnetite,and few aluminous spinels are produced.Compared with pulverized coal,CO as the reducing agent is more conducive to the generation of magnetite.With dolomite and phosphogypsum as additives,the strength of diffraction peak of magnetite has no obvious change.When sodium sulfate is added,sodium aluminate occurs in the roasted ore of red mud and the strength of diffraction peak of magnetite increases significantly.The results of SEM show that in the roasted ore with sodium sulfate,elements of aluminum,silicon and sodium concentrate together and it is judged that sodium aluminosilicate is produced combined with XRD.Compared with the situation without additives,grains of ferroferric oxides are more concentrated and grow better,which is more conducive to the separation of iron concentrate.