The effect of pre-roasting on chloridizing volatilization of nickel laterite ore

• Pre-roasting promotes nickel laterite chloridizing roasting effectively. • Pore size and mineral structure change are decisive for roasting effect. • The pre-roasting process can be devided to three stages of phase transformation. • High temperature and long time may lead to a decrease in roasting efficiency. Existing studies on nickel laterite ores are constrained by two critical gaps: the integration of pretreatment and roasting processes is scarcely employed, and the regulatory mechanism of pre-roasting on chlorination volatilization remains unelucidated. To address these issues, this study investigated the impact of pre-roasting on the chlorination volatilization effect of hematite-type nickel red mud ore. Combining the results of TG-DSC and XRD analysis, the pre-roasting process can be divided into three stages: the dehydroxylation of goethite and chromium oxyhydroxide at 275°C, followed by the phase transformation of hematite and chromium(III) oxide at 380°C and 805°C, respectively. These mineralogical changes, coupled with modified pore structure, synergistically enhance the reactivity of the ore toward chlorination by improving mass transfer efficiency. The optimal chlorination performance occurs with a roasting temperature of 900°C and a duration of 2 h. Further increasing temperature or time proves detrimental to the roasting process due to sintering and pore closure. This work advances the understanding of pre-roasting regulation in chlorination systems and provides a technically feasible process route for the industrial extraction of nickel and cobalt from low-grade nickel laterite ore, contributing to sustainable utilization of nickel resources and meeting the growing clean energy demand.