High-productivity, energy-efficient CO2 capture via a cascaded VTSA system integrated with methanation

In this study, we propose a cascaded vacuum-temperature swing adsorption process integrated with methanation (C-VTSA-Met), in which adsorbers are connected in series during both adsorption and desorption; desorption employs a staged H2 sweep. We evaluate C-VTSA-Met using numerical simulations and bench-scale experiments to quantify CO2 recovery and evaluate electrical separation energy at a space velocity (SV) of 1600 h–1. Simulations predict that the cascaded design achieves ≥95% recovery and ≥95% purity (95/95) at SV = 1600 h–1—four times the reference SV of single-stage VTSA-Met (SVref = 400 h–1)—while maintaining a separation energy of 0.702 GJ tCO2–1 assuming a vacuum-pump efficiency (ηvac = 0.72). Here, purity is defined on an inert basis as CO2/(CO2+inerts), and regeneration heat is supplied solely by recovered methanation waste heat, requiring no external heating. Under an energy-prioritized operating mode at SV = 400 h–1, the cascaded configuration yielded a separation energy of 0.147 GJ tCO2–1, one-fifth of the reference VTSA-Met. Bench-scale experiments using N2 as a surrogate sweep gas in a four-adsorber unit (zeolite 13X) achieved 98.9% CO2 recovery at a productivity of 1.59 tCO2 m–3 day–1; the separation energy inferred from the measured pressure-time profile (0.693 GJ tCO2–1, ηvac = 0.72) lies within the simulation range. Together, these results demonstrate that, at the simulation level, C-VTSA-Met can relax the conventional trade-off between throughput and energy efficiency in VTSA-Met systems. Full experimental verification of 95/95 performance under a real H2 sweep remains future work.