Thorsteinn I Sigfusson
The Taming of the Proton
Appendix III
Advanced
Thermochemical Cycles
Iodine-sulphur process
The iodine-sulphur process is based on the
decomposition of two acids at high temperature; sulphuric acid which yields
oxygen and SO2 and hydrogen iodide (HI) which yields hydrogen and
iodine. Iodine and SO2 react at low temperature in the presence of
water to reconstitute these two acids (Bunsen reaction):
(1)
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H2SO4 ® H2O + SO3 + ½ O2
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400-600°C
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(2)
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SO3 ® SO2 + ½ O2
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800-900°C
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(3)
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2HI ® H2 + I2
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(4)
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SO2 + 2H2O + I2 ® H2SO4 (aq) + 2HI(aq)
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20-120°C
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Westinghouse hybrid cycle
The Westinghouse hybrid cycle has the
advantage of requiring only sulphur.
(1)
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SO2 + 2H2O ® H2SO4 + H2
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20-110°C
|
UT-3 cycle
(1)
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CaO + Br2 ® CaBr2 + ½ O2
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550°C
|
(2)
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CaBr2 + H2O ® CaO + 2HBr
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725°C
|
(3)
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FeO4 + 8HBr ® 3FeBr2 + 4H2O + Br2
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250°C
|
(4)
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3FeBr2 + 4H2O ® Fe3O4 + 6HBr + H2
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575°C
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