Optimising H 2 production from model biogas via combined steam reforming and CO shift reactions

Abstract

H 2 production was studied through steam reforming of a clean model biogas in a fluidized-bed reactor followed by two stages of CO shift reactions (fixed-bed reactors). The steam reforming of biogas was performed over 11.5 wt.% Ni/Al 2O 3 and a molar CH 4/CO 2 ratio of 1.5 was employed as clean model biogas. Excess steam resulted in strong inhibition of carbon formation and an almost complete CH 4 (>98%) conversion was achieved. To optimise H 2 production, CO shift reactions were carried out at high (523–723 K) and low temperatures (423–523 K) using commercial catalysts, based on Cu/Fe/Cr and Cu/Zn, respectively. Increasing steam concentrations led to a lean CO, high H 2 product. The final product compositions following low temperature CO shift reaction (steam to dry gas ratio of 1.5 at 483 K) yielded H 2 at 68% and a CO concentration of 0.2% (equivalent to CO conversion of >99%).