Nonmonotonic Behavior in Hydrogen Production from the Steam Reforming of Higher Hydrocarbons in a Circulating Fluidized Bed Membrane Reformer

Abstract

The nonmonotonic behavior observed in hydrogen production from the steam reforming of higher hydrocarbons over nickel catalyst in an earlier-suggested novel circulating fast fluidized bed membrane reformer (CFFBMR) (Chen et al. AIChE J. 2003, 49 (5), 1250−1265) is extensively investigated. The investigation is carried out using kinetic model simulation at 623−823 K and 1013 kPa. Hydrogen-permselective membranes are used under cocurrent and countercurrent operations. The results show that the yield of hydrogen decreases at 623−723 K and then increases at 723−823 K. At 623 K, heptane is not fully converted, and thermodynamic equilibrium is not established. In contrast at 723−823 K, heptane is fully converted, and thermodynamic equilibrium is established. The strong methanation reaction at 723 K makes the hydrogen yield much lower, whereas at 823 K, the steam reforming of methane becomes increasingly important, enhancing the production of hydrogen. Using hydrogen-permselective membranes, the thermodynamic eq...