Techno-economic analysis of combustion exhaust utilization during lithium carbonate production with integrated CO2 capture

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 improves the novel scenario’s annual net profit by 72 %. 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. Beyond its apparent economic benefit, this technology offers a predicted 2.3-fold average reduction in CO2 emissions relative to the traditional Li2CO3-production pathway.