Modeling of sorption-enhanced steam reforming in a dual fluidized bubbling bed reactor

This paper highlights the use of a dual fluidized bed reactor system for producing hydrogen by sorption-enhanced steam methane reforming. Hydrogen concentrations of > 98% are predicted for temperatures of similar to 600 degrees C and a superficial gas velocity of 0.1 m/s, using a simple two-phase bubbling bed model for the reformer. The kinetics of the steam methane reforming and water-gas shift reactions are based on literature values, whereas experimentally derived carbonation kinetics are used for the carbonation of a dolomite. It is shown that the reformer temperature should not be < 540 degrees C or > 630 degrees C for carbon capture efficiencies to exceed 90%. Operating at relatively high solids circulation rates to reduce the need for fresh sorbent is predicted to give higher system efficiencies than for the case where fresh solid is added. This finding is attributed to the additional energy required to decompose both CaCO3 and MgCO3 in fresh dolomite.