Abstract:

Battery-grade lithium carbonate (Li₂CO₃ ≥ 99.5 wt%) is recovered from spodumene-rich pegmatite ore by energy-intensive processes having considerable environmental impacts. Spodumene concentrate generated upstream undergoes a thermal activation step that contributes greatly to lifecycle greenhouse gas emissions associated with Li₂CO₃ production. Further downstream, crude Li₂CO₃ is conventionally recovered by alkaline precipitation from an acidic leachate, then purified via carbonation, which consumes pressurized CO₂ to generate water-soluble lithium bicarbonate. The aqueous bicarbonate is separated from insoluble impurities before depressurizing to recrystallize battery-grade Li₂CO₃. A novel carbonation process variant was recently reported, whereby combustion exhaust gas, such as that generated during thermal activation of spodumene concentrate, was compressed and utilized to purify crude Li₂CO₃ while about one-third of utilized CO₂ was captured from the exhaust in high purity. Thus, the Li₂CO₃-purification process was adapted to co-generate―rather than depend upon―a source of pure CO₂. This work’s purpose is to explore how process operating conditions impact recoveries and purities of battery-grade Li₂CO₃ and captured CO₂ to inform upscaled process models that enable predictive comparisons of techno-economic performance for conventional versus novel Li₂CO₃-production pathways. Techno-economic analysis predicts that co-generation of pure CO₂ and avoided consumption thereof under current market conditions substantially improves the novel scenario’s net profit annually and accumulated over an operating plant lifetime. This work demonstrates long-term economic incentive for chemically integrating post-combustion capture of CO₂ from exhaust otherwise unutilized during production of a critical mineral commodity under anticipated ranges of operating and market conditions.

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Dr. Lindsay Hounjet

Biography