Hybrid solvent loop CO2 capture process for zero-emission hydrogen production

Abstract

Natural gas reforming with CO2 capture is expected to play a crucial role in producing low-carbon hydrogen under the net-zero emission scenario. This work focuses on optimizing the CO2 capture processes for zero-emission hydrogen production, targeting an ultra-high CO2 capture ratio of 99.9 % from the shifted syngas. We present a novel hybrid solvent loop CO2 capture process that enhances capture efficiency by overcoming the inherent trade-off between CO2 absorption kinetics and capacity in conventional processes. This is achieved by utilizing two independent solvent loops, each operating within its optimal performance range. In the lower section of the absorber, a high-capacity solvent, aqueous potassium carbonate, is used to leverage the high CO2 partial pressure. In the upper section, a fast-kinetic solvent, aqueous monoethanolamine, is employed to reduce CO2 concentration to 100 ppm. The conventional process, split-flow process with a multi-pressure stripper, and the hybrid solvent loop process are modeled in Aspen Plus® and compared. Our results demonstrate that the proposed hybrid solvent loop configuration outperforms conventional methods, significantly reducing the CO2 regeneration duty by 25 % and total equivalent work by 16 %. This process enhances the feasibility of low-carbon hydrogen production and supports the goal of achieving net-zero emissions.