Abstract
Carbon capture, utilization, and storage (CCUS) technologies are rapidly evolving as governments place an emphasis on lowering carbon emissions. Ultramafic ores containing high magnesium with low-grade nickel and cobalt are common in Canada. CanmetMINING is developing a flowsheet that combines carbon sequestration and concomitant EV battery grade Ni and Co production for a variety of mining-impacted ultramafic rocks, including low-grade, tailings, and waste rock. The process initiates with an acidic (bio)leach to dissolve Ni, Co, and Mg. Potential methods to separate Ni and Co are ion exchange, solvent extraction, and hydrogen sulfide precipitation. To ensure efficiency and a lower capex, an ambient-conditioned carbon capture phase was studied where dissolved Mg mineralizes carbon (as stable magnesium carbonates). Leaching, Ni and Co separation, and batch carbon mineralization experiments have been conducted on four different samples with varying mineralogy. For carbon capture, the variables examined are retention time, pH, concentrations, agitation, mixing speeds, Mg-C molar ratio, and feeding pathways (how the contents are fed and contacted). Experiments showed that 85-95% of the magnesium available for carbon capture gets converted to magnesium carbonate. The reaction conditions influence the mineralogy of the final product. Therefore, studying the properties of different forms of magnesium carbonates are vital for the process design. Development of the carbon capture phase is the primary objective for CanmetMINING. This includes experimenting with continuous flow. Product aging and resting tests are being designed to evaluate long-term storage and stability. A pilot plant operation is the long-term goal of the project.