Nuclear Production of Hydrogen, Fourth Information Exchange ...

SOUTH AFRICA’S NUCLEAR HYDROGEN PRODUCTION DEVELOPMENT PROGRAMME
The basic reactions for the HyS process are:
H 2SO 4 → SO 2 + ½O 2 + H 2O
SO 2 + 2H 2O → H 2SO 4 + 2H + + 2e –
2H + + 2e – → H2
H 2O → H 2 + ½O 2
(decomposition reaction)
(oxidation at anode)
(reduction at cathode)
(net reaction)
The Pebble Bed Modular Reactor (PBMR) Process Heat Plant (PHP) team consisting of PBMR,
Westinghouse, Shaw Stone and Webster, Technology Insights and M-Tech Industrial has performed
extensive work over the past few years to identify the most promising thermochemical water-spitting
hydrogen production processes (Greyvenstein, 2006; Kuhr, 2006; Van Ravenswaay, 2007).
These studies identified the hybrid sulphur process (HyS), the sulphur-iodine (S-I) process and
the high temperature steam electrolysis (HTSE) process as the main contenders for medium-term
commercial water-splitting hydrogen production.
In order to further distinguish between these three processes, further in-depth evaluations were
made in the following categories: i) readiness (vendor/supplier development, regulatory infrastructure
development); ii) process design (process complexity, availability of processing consumables,
feedstock processing requirements, product/waste stream processing requirements, safety, health
and environmental risk); iii) enhancement potential (cost enhancement potential, hydrogen production
efficiency); iv) performance (operability, availability); iv) cost (plant capital cost, hydrogen product cost).
From these evaluations, the HyS process was identified as the most promising large scale
water-splitting processes using nuclear heat due to the following reasons: i) It is the technology
closest to commercialisation. ii) It is a significant user of high-temperature process heat. iii) It is the
best fit for near-term implementation. iv) It has increased international interest. v) This process has
the potential to produce hydrogen at competitive costs. vi) The research and innovation requirement
for the HyS appear to be achievable within a reasonable time frame of approximately 10 years.
Figure 4 shows a diagram of a typical PBMR process heat plant coupled to a HyS plant.
Figure 4: Typical PBMR process heat plant coupled
to a hybrid sulphur hydrogen production process
208 NUCLEAR PRODUCTION OF HYDROGEN – © OECD/NEA 2010