Non-isothermal kinetics study on carbothermic reduction of nickel laterite ore

Abstract

In this paper, the non-isothermal reduction kinetics of nickel laterite with graphite was investigated under argon atmosphere. The reduction of nickel laterite was carried out at different heating rates (10, 15 and 20 K/min) and the evolved gas was detected by mass spectrometer in real time. The activation energies were determined by Kissinger-Akahira-Sunose (KAS) method and the reaction kinetics were determined by model-fitting (Coats-Redfern) method. The results showed that the reduction process can be divided into three stages according to the conversion degree (α): α = 0–0.45, α = 0.45–0.75, and α = 0.75–1.0, respectively. In the first stage, the average activation energy was 351.03 kJ/mol and the kinetic model fitted the two-dimensional diffusion function. In the second stage, the model of three-dimensional diffusion function was determined as the kinetic function and the average activation energy was 322.89 kJ/mol. In the third stage, the average activation energy was 341.45 kJ/mol and the kinetic model was in accordance with the chemical reaction function. The phase transformation as well as reaction mechanism during reduction were also analyzed which explained the reduction kinetics of nickel laterite.