Thermochemical two-step water-splitting reactor with internally circulating fluidized bed for thermal reduction of ferrite particles

A thermochemical two-step water-splitting cycle using a redox system of iron-based oxides or ferrites was examined on hydrogen productivity and reactivity of ferrite in order to convert solar energy into hydrogen in sunbelt regions. In the present paper, a new concept is proposed for a windowed thermochemical water-splitting reactor, using an internally circulating fluidized bed of NiFe2O4/m-ZrO2NiFe2O4/m-ZrO2 particles, and thermal reduction of the bed is demonstrated on a laboratory scale by using a solar-simulating Xe-beam irradiation. The concept is that concentrated solar radiation passes through the transparent window and directly heats the internally circulating fluidized bed. The fluidized bed reactor enabled the NiFe2O4/m-ZrO2NiFe2O4/m-ZrO2 sample to remain in powder form without sintering and agglomerating during direct Xe-beam irradiation over 30 min. Approximately 45% of the NiFe2O4NiFe2O4 was converted to the reduced phase by the solar-simulated high-flux beam, and was then completely reoxidized with steam at 1000 °C to generate hydrogen.