Circulating Fluid Bed for sorption enhanced steam methane reforming
H2 production with simultaneous capture of CO2 to reduce greenhouse gas emissions may be obtained by Sorption Enhanced Steam Methane Reforming (SE-SMR). The resulting product is a clean source of H2 that may be used in power generation without greenhouse gas emissions or in fuel cells after an additional purification step.
inGAP collaborators have developed a new reactor system for this process, currently demonstrated on lab-scale. The Circulating Fluidized Bed Reactor enables continuous SE-SMR operation, which is highly advantageous to industry because it removes the otherwise necessary step of plant shut-down to regenerate the catalyst.
There are three fundamental reactions in the SE-SMR unit.
1) CH4 (g) + H2O (g) ⇔ CO (g) + 3 H2 (g) [Reforming]
2) CO (g) + H2O (g) ⇔ CO2 (g) + H2 (g) [Water-gas shift]
3) MO (s) + CO2 (g) ⇔ MCO3 (s) [Sorption]
where MO is a metal oxide that captures CO2.
The overall reaction is CH4 (g) + 2 H2O (g) + MO (s) ⇔ MCO3 (s) + 4 H2 (g), and this shows that by applying a suitable sorbent (MO) the hydrogen yield will be very high. By using CaO as sorbent the yield will be around 98%. A schematic drawing of the process is given below together with an experiment's hydrogen yield and CO2 capture efficiency. In this particular work the maximum thermodynamic CO2 separation efficiency was 84% and that was almost reached in this experiment.