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

• Cascaded VTSA architecture with bypass streams enhances CO 2 capture performance • Bench-scale tests show >95% CO 2 recovery at SV=1600 h –1 , validating simulations • Energy-prioritized mode achieves 0.147 GJ tCO 2 –1 separation energy at SV=400 h –1 • Cascaded architecture cuts surge-tank volume to one-third for methanation In this study, we propose a cascaded vacuum-temperature swing adsorption process integrated with methanation (cascaded VTSA-Met), in which adsorbers are connected in series during both adsorption and desorption. In the integrated concept and numerical simulations, desorption employs a staged H 2 sweep and regeneration heat is assumed to be supplied by recovered methanation waste heat. Bench-scale experiments were conducted using N 2 as a surrogate sweep gas and electric heating to emulate methanation waste heat, thereby validating the cascaded adsorption-desorption architecture under controlled dry-gas conditions with zeolite 13X. Simulations predict that the cascaded design achieves ≥95% recovery and ≥95% purity (95/95) at space velocity (SV) = 1600 h –1 —four times the reference SV of single-stage VTSA-Met (SV ref = 400 h –1 )—while maintaining a separation energy of 0.702 GJ tCO 2 –1 assuming a vacuum-pump efficiency ( η vac = 0.72). Here, purity is defined on an H 2 -free basis as CO 2 /(CO 2 +inerts). Under an energy-prioritized operating mode at SV = 400 h –1 , the cascaded configuration yielded a separation energy of 0.147 GJ tCO 2 –1 , one-fifth of the reference VTSA-Met. Bench-scale experiments achieved 98.9% CO 2 recovery at a productivity of 1.59 tCO 2 m –3 day –1 ; the separation energy inferred from the measured pressure-time profile (0.693 GJ tCO 2 –1 , η vac = 0.72) lies within the simulation range. These results demonstrate that, at the simulation level, the cascaded system can relax the conventional trade-off between throughput and energy efficiency in VTSA-Met systems. The 95/95 performance reported here remains simulation-based; full experimental verification under a real H 2 sweep is future work.