Numerical study of hydrogen production via sorption-enhanced steam methane reforming in a fluidized bed reactor at relatively low temperature

Production of hydrogen by sorption enhanced methane steam reforming (SE-SMR) process at a relatively low temperature in a two-dimensional cylindrical bubbling fluidized bed reactor was studied using an Eulerian–Eulerian approach. The study aims to investigate the influence of operating pressure, superficial velocity, catalyst-to-adsorbent ratio (C/A, weight) and sorption kinetics on the SE-SMR process. A H2 concentration of >87% on a dry basis can be obtained at 500 °C and 0.1 MPa using hydrotalcite-like compounds (HTC) as CO2-acceptor. A relatively low catalyst-to-adsorbent ratio (∼0.5) is preferable for reducing operating cost and enhancing hydrogen production. Higher operating pressure is favorable for the utilization of sorbent, but unfavorable for the conversion of methane. Simulations prove that sorbents with slow kinetics can only serve as CO2 acceptor, but cannot enhance the methane steam reforming (SMR) process effectively. Another interesting observation is that the way the superficial velocity affects the CO2 capture efficiency is determined by the sorption kinetics. For HTC, it is the bigger bubble size rather than the reduction of gas residence time that mainly accounts for the decrease of the CO2 capture efficiency under higher velocities investigated.

► A H2 concentration of >87% can be obtained at 500 °C in a fluidized bed reactor.
► We provide a new explanation for the influence of velocity on the enhancement of different sorbents.
► Sorption kinetics determines the roles that sorbent play in a fluidized bed reactor.