THERMALANALYSIS AND KINETICS OF NATURAL MILLERITE OXIDATION PROCESS

Abstract

As an important source for nickel extraction, millerite (NiS) has been investigated in the past, however there is still a notable deficiency in literature data regarding its behaviour and phase transformations at elevated temperatures. In order to better understand millerite oxidation process, the characterization of the initial sample and its oxidation products was investigated. Thermal and kinetic analysis were performed in order to identify phase transformations, propose a possible reaction mechanism and to determine the kinetic parameters of the process when heating the sample in the temperature range from 25 ^oC to 1000 ^oC. Experimental results showed that thermal decomposition end-products consist of nickel oxide and spinel phase trevorite as well as hematite and maghemite at elevated temperatures. Kinetic analysis results indicate that oxidative roasting occurs in kinetic field, with temperature-dependant reactions.