Clean Technology 2008
I. Abu-Mahfouz, S. Elnashaie, R. Ciocci
Penn State University at Harrisburg, US
bifurcation, fluidized bed, hydrogen, hydrocarbons, stability
Static Bifurcation (SB), which mostly exhibits itself as multiple steady states, is characteristic of a novel auto-thermal Circulating Fluidized Bed Membrane Steam Reformer (CFB_MSR) for hydrocarbons. The present paper focuses on the practical implications of this phenomenon on the behavior of this novel reformer with special emphasis on hydrogen yield. It is shown that SB prevails over a relatively wide range of parameters and has significant impacts on stability, start-up policy and hydrogen yield. At certain critical bifurcation points the reformer can quench to an idle state, while at other bifurcation points it may tend to run away. The SB is a result of the auto-thermicity nature of the CFB_MSR and although it adds certain degree of complexity to the design and operation of the unit; it has a very positive effect on its thermal efficiency. A parametric study is carried out in order to define the domain of the most efficient and safe operating conditions. In addition, the study aims to investigate the stability at these optimal parameters and discusses the need for a feedback control system. It is shown that an optimized and well controlled reformer of this kind is capable of superior hydrogen yields from a wide range of higher hydrocarbons including a renewable feedstock such as bio-oil from biomass.