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HYTHEC – Solar
Production of Hydrogen by the Sulfur-Iodine and Westinghouse Thermochemical
Cycles |
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Participants:
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CEA (F)
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DLR (D)
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University of Sheffield (UK)
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Università degli Studi – Roma
tre (I)
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Empresarios Agrupados (E)
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ProSim SA (F)
Contact:
Funding:
Duration:
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Front view of porous absorber reactor after mounting |
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Background
Among the
most promising processes for massive hydrogen production are
thermochemical cycles (besides electrolysis) using water as the raw
material and process heat from either concentrated solar energy or
nuclear power plants. This project focuses on two sulfur family
processes: Westinghouse (WH) and Sulfur-Iodine (S_I) process. The WH
process is a hybrid electrochemical/thermochemical cycle for decomposing
H2O into H2 and O2 with the use of SO2 which is then converted into
H2SO4 and SO3 as intermediate stage. The S_I process makes use of SO2
and I2 which are converted to H2SO4 and HI.
Objectives
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Develop
solar heated sulfur-based thermochemical processes for the production of
hydrogen
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perform a
comparative as-sessment of solar, nuclear, and hybrid heated S_I and WH
thermochemical cycles
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improve
chemical processing and efficiency of both processes.
Achievements
in 2006
A first
evaluation of both S_I and WH cycles has been completed. The analysis
included flow-sheeting, sizing of solar components, conceptual
industrial process scale-up, and preliminary economic evaluation.
Experimental results were obtained for the H2SO4 solar decomposition and
the H2 production step. Major achievements:
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Well
established chemical engineering methods were applied and specific
materials and devices were chosen in order to deal with the
chemically aggressive high tem-perature environment containing
sulfuric acid. In particu-lar, the interaction of a nuclear power
plant with a chem-ical plant will require special safety
considerations.
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The
design of a solar receiver-reactor for the H2SO4 de-composition
process was iteratively improved by a series of experimental
campaigns at DLR’s Solar Furnace, and the
appropriateness of the reactor concept was demonstrated.
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The
H2SO4 decomposition proceeded at conversion rates up to 30% when
only homogeneous splitting occurred at the porous absorber made of
SiSiC. Conversion rates up to about 90% were achieved when using
absorbers coated with catalysts.
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Steady
state analysis of the chemical process chain in-cluded mass and
energy balances. At the design point, a thermal efficiency of 38% (HHV)
is predicted. Layout and optimization is completed for 50 MWth and
300 MWth solar plants, respectively.
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Preliminary process flow sheets have been elaborated for hybrid
operation, i.e. feeding solar and nuclear high temperature heat
simultaneously to the process.
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Publication:
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Roeb M.,
Noglik A., Monnerie N., Schmitz M., Sattler C., Cerri G., de Maria G.,
Giovannelli A., Orden A., de Lo-renzo D., Cedilo J., LeDuigou A.,
Brogard J.-M. (2006) Development and verification of process concepts
for the splitting of sulfuric acid by concentrated solar radiation, Proc.
13th SolarPACES International Symposium, June 20-23, Seville, Spain.
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