Thermochemical two-step water splitting by internally circulating fluidized bed of NiFe2O4 particles: Successive reaction of thermal-reduction and water-decomposition steps

Thermochemical two-step water splitting using a redox system of iron-based oxides or ferrites is a promising process for producing hydrogen without CO2 emission by the use of high-temperature solar heat as an energy source and water as a chemical source. In this study, thermochemical hydrogen production by two-step water splitting was demonstrated on a laboratory scale by using a single reactor of an internally circulating fluidized bed. This involved the successive reactions of thermal-reduction (T-R) and water-decomposition (W-D). The internally circulating fluidized bed was exposed to simulated solar light from Xe lamps with an input power of 2.4-2.6 kW(th) for the T-R step and 1.6-1.7 kW(th) for the subsequent W-D step. The feed gas was switched from an inert gas (N-2) in the T-R step to a gas mixture of N-2 and steam in the W-D step. NiFe2O4/m-ZrO2 and unsupported NiFe2O4 particles were tested as a fluidized bed of reacting particles, and the production rate and productivity of hydrogen and the reactivity of reacting particles were examined. Copyright (C) 2011, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.