Continuous hydrogen production by sorption enhanced steam methane reforming (SE-SMR) in a circulating fluidized bed reactor: Sorbent to catalyst ratio dependencies

Continuous hydrogen production by sorption enhanced steam methane reforming (SE-SMR) has been studied using a circulating fluidized bed reactor with calcined natural dolomite as CO₂ sorbent and Ni/NiAl2O4 as catalyst. A steam to methane ratio of 4 was used at 575 °C and ambient pressure. Two experiments, each run for 8 h, were carried out using two different volumetric catalyst to sorbent ratios; 20/80 (experiment A) and 50/50 (experiment B) respectively. In experiment A, run at lower than equilibrium conversion, an initial high conversion that dropped significantly after a few hours was observed, while in experiment B, a stable performance throughout the 8 h time-on-stream close to equilibrium conversion of methane was observed. The experiments show that a circulating fluidized bed reactor configuration is suited for SE-SMR for extended time of operation. The sorbent and catalyst materials we have used appear to have quite good mechanical properties at the time scale used (8 h), but only a fraction of the sorbent's CO₂ capacity appears to be in use.