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Research Papers

# New Solar Water-Splitting Reactor With Ferrite Particles in an Internally Circulating Fluidized Bed

[+] Author and Article Information

Graduate School of Science and Technology, Niigata University, 8050 Ikarashi 2-nocho, Nishi-ku, Niigata 950-2181, Japan

Shingo Takahashi, Hiroki Yamamoto

Graduate School of Science and Technology, Niigata University, 8050 Ikarashi 2-nocho, Nishi-ku, Niigata 950-2181, Japan

Tatsuya Kodama2

Graduate School of Science and Technology, Niigata University, 8050 Ikarashi 2-nocho, Nishi-ku, Niigata 950-2181, Japan

1

Corresponding author.

2

Also at Department of Chemistry and Chemical Engineering, Faculty of Engineering, Niigata University, 8050 Ikarashi 2-nocho, Nishi-ku, Niigata 950-2181, Japan.

J. Sol. Energy Eng 131(1), 011007 (Jan 07, 2009) (9 pages) doi:10.1115/1.3027511 History: Received July 29, 2007; Revised March 11, 2008; Published January 07, 2009

## Abstract

The thermal reduction of metal oxides as part of a thermochemical two-step water-splitting cycle requires the development of a high-temperature solar reactor operating at $1000–1500°C$. Direct solar energy absorption by metal-oxide particles provides direct efficient heat transfer to the reaction site. This paper describes the experimental results of a windowed small reactor using an internally circulating fluidized bed of reacting metal-oxide particles under direct solar-simulated Xe-beam irradiation. Concentrated Xe-beam irradiation directly heats the internally circulating fluidized bed of metal-oxide particles. $NiFe2O4∕m‐ZrO2$ (Ni-ferrite on zirconia support) particles are loaded as the working redox material and are thermally reduced by concentrated Xe-beam irradiation. In a separate step, the thermally reduced sample is oxidized back to Ni-ferrite with steam at $1000°C$. The conversion efficiency of ferrite reached 44% $(±1.0%)$, which was achieved using the reactor at $1kW$ of incident Xe lamp power. The effects of preheating temperature and $NiFe2O4∕m‐ZrO2$ particle size on the performance of the reactor for thermal reduction using an internally circulating fluidized bed were evaluated.

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## Figures

Figure 1

Schematic of solar reactor concept using an internally circulating fluidized bed of reacting particles

Figure 2

Water-splitting reactor with an internally circulating fluidized bed

Figure 3

Photographs of water-splitting reactor with quartz cap: (a) inside; (b) overall reactor

Figure 4

Water-splitting reactor inside the sun simulator

Figure 5

Fixed-bed reactor of quartz tube for the WD step

Figure 6

Time variations in hydrogen production and ferrite conversion using a normal fluidized bed reactor composed of a quartz tube. The reactor body was preheated to 900°C during irradiation in the TR step. N2 gas flow rate was 4Ndm3min−1. Error bars showed uncertainty values at a 95% confidence interval.

Figure 7

XRD patterns of the NiFe2O4∕m‐ZrO2 sample; (a) original, (b) after the TR step using the internally circulating fluidized bed reactor, and (c) after the subsequent WD step

Figure 8

Time variations in hydrogen production rate per gram of material (including NiFe2O4 and m‐ZrO2) during the WD step

Figure 9

Variation in the bed temperature of the annulus region during the TR step at a preheating temperature of 900°C. h1–h7 are located in the annulus region of the fluidized bed at different heights in 5mm increments (h1 is the top temperature and h7 is the bottom temperature)

Figure 10

Comparison of hydrogen production for NiFe2O4∕m‐ZrO2 powder with different particle sizes between 106–212μm and 212–1000μm. The reactor was preheated at 700°C. N2 gas flow rates were 4Ndm3min−1 for the draft tube and 2Ndm3min−1 for the annulus region.

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