Hydrogen from an Internally Circulating Fluidized Bed Membrane Reactor

Abstract

A novel fluidized bed membrane reactor has been developed for the production of high-purity hydrogen based on steam methane reforming (SMR). The reactor incorporates perm-selective membranes for in-situ removal of hydrogen from the reactor, thus shifting the thermodynamic equilibrium of the SMR reaction. The membranes also eliminate the need for downstream hydrogen purification.The endothermic reaction duty is provided either by external heating of the vessel wall or through direct air injection into the fluidized catalyst bed (autothermal reforming). The gas flow pattern within the fluidized bed induces internal circulation of catalyst particles between the central reaction (permeation) zone and outer heating zones. The circulating hot catalyst particles from the oxidation zone carry the required endothermic heat of reaction for the reforming while ensuring that the palladium membranes are not exposed to high temperatures or to oxygen. Another characteristic of the reactor configuration is that very little of the nitrogen present in the oxidation air reaches the reaction zone, thus maintaining the hydrogen driving force for the perm-selective membranes.The reactor concept was proven in a pilot reactor (0.13 m diameter, 2.3 m tall). A number of variables were studied, including steam-to-carbon ratio, temperature and pressure. The pilot reactor was operated with both external heating and direct air addition. Pure hydrogen (99.999+%) was obtained from the reactor and an equilibrium shift was demonstrated. The maximum pure hydrogen recovery obtained from the pilot reactor was 0.96 mol H2/mol CH4, limited by the installed membrane surface area for these tests.

Steam reforming of heptane in a fluidized bed membrane reactor

“…In that case, operation at 550 • C is sufficient to achieve high conversion, equivalent to that at temperatures above 800 • C without membranes [41]. Temperatures >550 • C, although not essential, could improve the hydrogen yield further by enhancing the equilibrium conversion, as well as the hydrogen permeation.…”

“…Selective removal of hydrogen from the reaction environment via permselective Pd alloy membranes drives the equilibrium methane steam reforming and water gas shift conversions forward, thereby significantly enhancing the hydrogen yield [36][37][38][39]. The fluidized bed and membrane reactor concepts developed at the University of British Columbia [40,41], has been commercialized by Membrane Reactor Technologies [42]. Rakib et al [43] provided a FBMR model for steam reforming of heptane, and predicted that an FBMR for higher hydrocarbons can result in a compact reformer system, combining pre-reforming, reforming and hydrogen purification in a single unit.…”

Gas and particle circulation in an internally circulating fluidized bed membrane reactor cold model

“…This concept has been patented and tested at high temperatures and pressures Boyd et al, 2005;Xie et al, 2006). …”

Autothermal Reforming of Methane with Integrated CO2 Capture in a Novel Fluidized Bed Membrane Reactor. Part 1: Experimental Demonstration

“…Recently, Patil et al [15] indeed demonstrated the absence of temperature gradients and mass transfer limitations to the membrane surface in a Fluidized Bed Membrane Reactor (FBMR) for methane steam reforming. Also Boyd et al [20], Abashar and Elnashaie [21] and Chen et al [22] showed the good performance of FBMRs for autothermal reforming of methane without problems associated with mass transfer limitations or temperature profiles.…”