摘要
Vacuum pressure swing adsorption (VPSA) has been proposed for CO2 capture from blast furnace top gas owing to its high CO2 partial pressure, but prior studies have rarely achieved the pipeline-specification purity. This work develops and systematically evaluates a hybrid VPSA-cryogenic distillation process to overcome this limitation and benchmarks it against amine scrubbing using validated process models. Multistage pressure equalization increases CO2 purity from 69% in a 2-bed to 87% in an 8-bed/4-stage VPSA while sustaining 90% recovery with zeolite 13X. Subsequent cryogenic distillation further raises purity to 99.9% with electricity use of 265-333 kWh/tonne CO2, more than a 50% reduction compared to reflux-intensive VPSA reported in the literature. Cost analysis identifies an optimal VPSA outlet purity of 78% as the most economical threshold; additional stages increase capital without proportional benefits, whereas fewer beds raise energy penalties from added CO compression and cooling. Amine scrubbing with monoethanolamine is 34-58% more cost-effective than the VPSA-cryogenic process across regional energy prices, enabled by fast absorption kinetics and lower capital requirements. It is particularly economical in the U.S., where the steam-to-electricity cost ratio is lowest. The VPSA-cryogenic process becomes competitive only when electricity falls below $0.06/kWh and steam exceeds $19.9/MMBTU. These results establish design thresholds and cost-energy trade-offs that guide CO2 capture strategies for steelmaking decarbonization.