Hydrogen Production in a Sorption-Enhanced Fluidized-Bed Membrane Reactor: Operating Parameter Investigation

Abstract

Sorption-enhanced steam reforming, assisted by membrane separation of H2 in a fluidized bed reactor, is simulated numerically based on a kinetic two-phase model. A residence time distribution function method is implemented to account for CO2 capture in continuous operation. The effects of operating pressure, total gas feed rate, solid recycle rate, fresh sorbent feed rate, effective membrane area, and permeate pressure on the performance of a continuous fluidized bed reactor are investigated. A CH4 conversion of >91% for operation at 0.6 MPa and 550 °C is predicted to be possible with the assistance of the sorbent and membranes. The reforming performance is very sensitive to the effective surface area of membranes. A sorbent fraction of >0.7 (by mass) is necessary to achieve a product with H2 selectivity of >98%, free of CO and CO2, for realistic membrane effectiveness factors. Adding fresh sorbent or increasing the sorbent mass fraction improves the H2 productivity for a moderate solids recycling rate. Effective CO2 capture rate depends greatly on the sorbent feed rate.