| Nickel slag produced largely in the pyrometallurgical nickel production process contains about 40%total Fe,and fayalite(Fe2SiO4)is the main iron-rich phase.In this work,we investigated the transformation of the fayalite phase to the magnetite phase by a molten oxidation method,and the morphology and kinetic crystallization of magnetite crystals in molten slag.The results were given as follows:(1)The influences of temperature,holding time,airflow rate and stirring speed on the iron recovery were studied by orthogonal experiment.The optimal parameters of iron recovery from slag by molten oxidation were the oxidation temperature of 1500?,the airflow rate of 170 mL/min,the holding time of 40 min and the stirring rate of 60 r/min.In these conditions,the iron recovery is up to 78.2%.(2)The morphology of magnetite crystals under 1350?,1375?,1400?,1425? and 1450? were studied,respectively.In the initial crystallization stage,magnetite crystals precipitated as small particles.As the holding time increased,the particles gradually grew up and exhibited granular or skeletal shape.The magnetite crystals transformed granular shape at 1350-1400? for 60min,and skeletal shape at 1400-1450? for 60min,respectively.(3)According to the JMAK and Arrhenius equations,the kinetic model of magnetite crystal growth was established.The calculated values of n were 1.00,1.04,1.08,1.12 and 1.18 for 1350?,1375?,1400?,1425? and 1450?,respectively.The calculated activation energy Q was 70.62 kJ·mol-1.Therefore,the kinetic model of magnetite crystal growth could be written as:D1/n=347.23t·exp(-70.62×103/RT)... |
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