Abstract
This study examines the hydrogen reduction behavior of saprolitic nickel ore using a gas-permeating fixed-bed reactor operated under a 75% H₂–25% Ar atmosphere at temperatures ranging from 500 to 900 °C for a duration of 2 hours. The reduction progress was evaluated by monitoring mass loss before and after hydrogen reduction process. Comprehensive characterization was conducted on the initial and final samples using X-ray fluorescence (XRF) analysis, Fe²⁺/Fe_total measurements, X-ray diffraction (XRD), and scanning electron microscopy (SEM) to elucidate chemical, microstructural, and phase evolution throughout the reduction process. The results show that mass loss increases systematically with increasing temperature, indicating enhanced reduction reactions at elevated temperatures. Phase analysis reveals a clear transformation sequence, with the original ore—initially dominated by goethite and hydrous magnesium silicate phases—progressively decomposing and recrystallizing into higher-temperature phases such as forsterite, enstatite, fayalite, and discrete metallic phases. These findings improve understanding of temperature-dependent reduction mechanisms in saprolitic ores and provide useful insights for the development of cleaner, hydrogen-based nickel processing routes aimed at reducing carbon emissions in nickel production.