Phase composition and thermal properties of the Sakharinskoe deposit oxidized nickel ore

Abstract

X-ray diffraction, optical microscopy and X-ray microanalysis were used to determine the composition and distribution of elements in the main mineral constituents of oxidized nickel ore at the Sakhalin deposit (goethite, hematite, serpentine, talc and chlorite). The main fraction of nickel is concentrated in iron oxides, where its content reaches 2,4 %, while in magnesium silicates it does not exceed 0,4 %. The sequence and temperature intervals of transformations were established when heating ore in inert and reducing media by means of thermal analysis methods combined with mass-spectrometric analysis of gases and subsequent X-ray phase analysis of products. The temperature regimes of ore roasting for the reduction of nickel and iron from their minerals were justified. The temperature regimes of sample heating are assumed to be close to the conditions implemented in industrial units (electric furnaces) where the rate of charge heating varies within 5—15 degrees/min, up to the melting point (1450 °С) of ferronickel and slag. It is proposed to use information on material composition, thermal properties and metal forms in ore to select regimes and technologies for their pyro-or hydrometallurgical processing. Nickel and iron recovery from oxides in CO environment occurs above 800 °С, while serpentines remain stable up to 1200 °С. The use of coke as a reducing agent allows reducing iron and nickel from serpentines at temperatures above 1250 °С. The obtained data were used to substantiate the operating conditions of roaster and electric furnaces during ferronickel smelting from oxidized ores. When roasting, resulting ferronickel particles will contain 2—4 % Ni. Completing recovery processes in the electric furnace will ensure metal recovery from magnesium silicates, which will slightly increase the nickel content in ferro-nickel.