Action Behavior Of Sodium Chloride Accelerator In Magnesium - Reduced Oxygen Oxide Ore Coal Reduction

In recent years, with the continuous exploitation of nickel resources, the development has transferred the focus from nickel sulfide ore to laterite ore, and the characteristics of resource mining tend to be low grade. The nickel oxide ore, which located in Yunnan province of China, has the characteristics of low grade nickel, high silicon and magnesium. It belongs to the typical saprolitic low grade nickel laterite ore. As a result of the unique mineral compositions and complex mineral phase structures, the ore is not suitable for the main treatment processes, such as RKEF, Caron. In this study, the process of coal based reduction followed by magnetic separation was investigated. The research result will lay the theoretical basis for the realization of low cost, short process and efficient utilization of high-magnesium low-nickel oxide ore.A series of analysis methods, such as chemical analysis, X-ray diffraction, BET and so on, were used for the investigation of raw ore compositions, mineral phases, pore structure and the changes during the process of heat treatment, the distribution characteristics and regularity of nickel in raw ore were determined. The results indicate that 81.49% of nickel was associated with silicates, and nickel was well distributed in mineral in the form of isomorphism. In addition, lizardite, which contained a large amount of crystal water, is the main mineral phase in raw laterite ore. Then, in order to obtain the optimal experimental conditions, a number of chloridization tests with different added proportions of sodium chloride and coal along with different roasting temperatures and times was conducted systematically. The results indicate that for a ferronickel contents of 7.09% Ni and 67.90% Fe, recoveries of 98.31% nickel and 72.08% iron could be obtained by chloridizing the laterite ore at 1200℃ for 20 minutes with the addition of 10 wt.% sodium chloride and 8 wt pet coal followed by the application of a 150 mT magnetic field. Based on the analysis result of SEM, the distribution of ferronickel particles has a significant change. Thus, the related experiments were carried out to investigate the mechanism of action of sodium chloride during the chloridization and reduction process. The results show that the sodium chloride could promote the ore reduction by three ways:(1) the metallic oxides could be chloridized by hydrogen chloride, which generated by the pyrohydrolysis of sodium chloride, and then the metallic chlorides were reduced to form metals; (2) the metallic oxides would be chloridized by the way of interaction at high temperature; (3) olivine structure would be destroyed gradually with the increase of roasting temperature in the action of sodium chloride, and the sodium chloride existed in high-magnesium, low-nickel oxide ore could make the NiO isolate from NiO-bearing minerals. The NiO reacts with Fe2O3 at high temperature to form NiFe2O4, which is conductive to the formation of Ni-Fe alloy during the reduction process.