Thermal Decomposition and Kinetics of Pentlandite-Bearing Ore Oxidation in the Air Atmosphere

Kristina Božinović,Miroslav Sokić,Branislav Marković,Nada Štrbac,Jovica Stojanović,Aleksandra Mitovski,Duško Minić

doi:10.3390/met11091364

Abstract

The roasting of sulfide ores and concentrates is one of the most important steps in pyrometallurgical metal production from primary raw materials, due to the necessity of excess sulfur removal, present in the virgin material. Pentlandite is one of the main sources for nickel pyrometallurgical production. The knowledge of its reaction mechanism, products distribution during oxidation and reaction kinetics is important for optimizing the production process. Raw pentlandite-bearing ore from the Levack mine (Ontario, Canada) was subjected to oxidative roasting in the air atmosphere. A chemical analysis of the initial sample was conducted according to EDXRF (Energy-Dispersive X-ray Fluorescence) and AAS (Atomic Adsorption Spectrometry) results. The characterization of the initial sample and oxidation products was conducted by an XRD (X-ray Diffraction) and SEM/EDS (Scanning Electron Microscopy with Energy Dispersive Spectrometry) analysis. Thermodynamic calculations, a phase analysis and construction of Kellogg diagrams for Ni-S-O and Fe-S-O systems at 298 K, 773 K, 923 K and 1073 K were used for proposing the theoretical reaction mechanism. A thermal analysis (TG/DTA—Thermogravimetric and Differential Thermal Analyses) was conducted in temperature range 298–1273 K, under a heating rate of 15° min−1. A kinetic analysis was conducted according to the non-isothermal method of Daniels and Borchardt, under a heating rate of 15° min−1. Calculated activation energies of 113 kJ mol−1, 146 kJ mol−1 and 356 kJ mol−1 for three oxidation stages imply that in every examined stage of the oxidation process, temperature is a dominant factor determining the reaction rate.

Highlights

Nickel has a long history of being used for coin manufacturing
The characterization of the initial pentlandite sample at 298 K and oxidation products at 673 K, 773 K, 873 K, 973 K and 1073 K was conducted by an X-ray diffraction method on a polycrystalline powder sample
For the investigated ore sample, the thermogravimetric and differential thermal analyses Metals 2021, 11, x FOR PEER REVIEWwere conducted in air atmosphere, with a heating rate of 15◦ min−1

Summary

Introduction

Nickel has a long history of being used for coin manufacturing. Nickel resistance to high temperatures, heat and good corrosion stability, allows its application in durable materials without replacement for a long time. Nickel is used in materials and alloys which can resist aggressive environments such as jet engines, offshore installations and power generation plants. Nickel is applied as an alloying element in cast irons, austenitic stainless steels and non-ferrous alloys. Nickel steel is widely used for armor plating. Other nickel alloys are used in boat propeller shafts and turbine blades. Nickel is used in batteries, including rechargeable nickel–cadmium batteries and nickel–metal hydride batteries used in hybrid vehicles. It is expected to form an ever-larger proportion of future batteries [1,2,3,4,5,6,7]; namely, pentlandite, complex nickel sulfide, may be used as is, in the electrochemical reaction of hydrogen evolution [8,9,10]

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