Process analyses on sorption-enhanced electrified steam methane reforming for near-zero emission hydrogen production with CO2 capture by calcium looping thermochemical reaction

Abstract

The predominant hydrogen production method is steam methane reforming, which generates substantial CO₂ emissions from both the reforming reaction and the combustion required to drive the process. Sorption-enhanced steam methane reforming (SESMR) enables the in-situ CO₂ removal during the reforming reaction, enhancing hydrogen yield. Replacing combustion with renewable electricity for reforming reaction can eliminate combustion-related emissions and flue gas heat loss. However, the intrinsic randomness, intermittency, and instability of renewable electricity present significant challenges to maintaining continuous and stable operation. This study introduces a process that innovatively leverages the mass and energy flow matching characteristics of the calcium looping with renewable electricity driving calcination, thermochemical energy storage, and sorption-enhanced steam methane reforming, thereby establishing the sorption-enhanced electrified steam methane reforming (SEESMR) process. The SEESMR exploits the dual functions of sorbent as both an energy carrier and a CO₂ carrier. Renewable electricity facilitates calcination in the regenerator, storing energy in the form of chemical energy and sensible heat. This stored energy is subsequently utilized in the reformer during CO₂ adsorption, providing the requisite energy to drive methane reforming and produce hydrogen. First and second law analyses indicate that SEESMR demonstrates a 7.90 percentage point improvement in thermal efficiency compared to SESMR through the substitution of combustion heating with electric heating and a high-efficiency heat recovery. Additionally, this modification reduces exergy losses by up to 53.2 % through elimination of combustion in SESMR. Furthermore, SEESMR enables continuous hydrogen production from renewable electricity, achieves a 35 % cost reduction within the current fuel pricing framework in China compared to direct electric heating methane reforming. This study may provide a stable, efficient and economical approach to zero carbon hydrogen production and large-scale renewable energy accommodation.