Study On The Thermal Decomposition Behavior Of Magnesia-based Nickel-poor Laterite Ore

The nickel is widely applied in various industries for its special physicochemical properties.At present,the over exploitation of high-grade nickel sulphide causes the focus of nickel mining gradually shift to low-grade but resource-rich nickel oxide ore.In Yunnan,China,the latereitic nickel ore is characterized by high silicon,low-grade nickel as well as complex ore phase,which is suitable for production and utilization by pyrometallurgy technology.The paper mainly concentrates on the related problems of the thermal decomposition of ores during the pysometallurgical process and the laws and mechanism of thermal decomposition of ores-phase transformation during the coal-based reduction process.The results of study have certain instructive meanings in the actual reproduction of such ores.In this paper,the study is based on high-magenesium low-nickel oxide ore from Yunnan areas.Analysis methods,such as Chemical analysis,X-ray diffraction,scanning electron microscopy,had been utilized for the further study of composition and mineral phase.The roasting dissociation experiment was conducted to investigate the mineral phase transformation during thermal decomposition of laterite ore.And t he thermal decomposition process of the ore was described by theoretical calculations.Its result showed that the main component of the laterite ore is serpentine[Mg₃Si₂O₅?OH?₄].When heating up to 612?,the serpentine reduction occurs and an amorphous silicate is formed,which benefits for the subsequent reduction process.When reheating up to 817?,the recrystallization reduction takes place,resulting in a dense olivine,enstatite and a small amount of Si O₂,which is not conductive to the subsequent reduction.The calculated results are in line with the experimental outcomes.Through the theoretical calculation,the sequence of oxygen ion detachment was investigated during the reduction of nickel serpentine and the time period of reduction was predicted.The change of ore phase structure and its effect on the reduction process were discussed in the paper.Lastly,the nickel-iron alloy was produced by coal-based direct reduction and smelting of high-magenesium low-nickel oxide ore.The theoretical analysis and tests showed that the melting temperature of ore is higher than 1500?.Based on the L9?33?orthogonal test,it shows that a nickel-iron alloy with a nickel grade of 7.91%,recovery rate of 82%and a nickel-iron content of 84.23%can be produced in condition of melting temperature reaching1600?,carbon ratio 2.0 and 45-minitue calcinations time.