Nuclear Production of Hydrogen, Fourth Information Exchange ...

EXECUTIVE SUMMARY
iodine concentration. The experimental data suggest that existing models overestimate iodine vapour
concentration at low pressures, but underestimate it at higher pressures. HI and H 2 O concentrations
match current models fairly well at low iodine pressures. Hydrogen formation at higher pressures
must be accounted for while using these techniques. CEA will use the new data to construct a new
thermodynamic model for the S-I cycle.
Dr. Max Gorensek of SRNL presented on the efficiency of a recuperative bayonet decomposition
reactor for the thermochemical sulphur cycle. SRNL conducted a study to analyse heat transfer
characteristics of a bayonet-style decomposer for the sulphuric acid decomposition section. A pinch
analysis of the reactor was completed, and a statistical design of experiments was presented.
A temperature-enthalpy curve for the reactor was generated for the pinch analysis. Statistical methods
were then used to determine operating windows and conditions for minimum heat requirements.
A heuristic approach was adopted after surface response and neural network modelling techniques
failed. High temperatures, low pressures and high sulphuric acid feed concentrations led to the best
results. Reactor operating temperature may be lowered to 825°C to alleviate materials concerns, but
the potential efficiency advantage of sulphur cycle over direct electrolysis is impacted. Dropping the
reactor outlet temperature below 825°C does not lead to an efficient process.
Dr. Kikwang Bae of KIER presented on the development status of the HIx decomposition process
in Korea. The paper examined the advantages and disadvantages of the S-I cycle, and described the
programme at KIER for development of the process. KIER is implementing electro-electro dialysis (EED)
for production of super-azeotropic HI in water. Initial experimental results showed stable hydrogen
production for a period of five hours. An earlier version of an experimental device to demonstrate the
process in glass is being upgraded to increase safety and durability. Current membrane technology
does not allow for efficient use of EED alone, but KIER is studying the concept of combining EED with
reactive distillation. Cycle efficiency as a function of EED cell potential was presented, along with
results of experiments designed to optimise conditions in the Bunsen reaction section. KIER intends to
build a device similar to the SNL-CEA-GA demonstration apparatus and operate it starting in 2011.
It will be designed for a 200 litre per hour output of hydrogen.
Dr. Frikkie van Niekerk of North-West University, South Africa, presented on the situation of
South Africa. Global and South African energy concerns were outlined, followed by PBMR and SASOL
strategies to address these concerns. South Africa ranks 12 th in the world for CO 2 emissions per capita.
From 2006, demand for power was greater than the domestic supply. Nuclear power is expected to
supply 30% of energy needs by 2030 (currently 6%). A business plan for hydrogen production was
reviewed, as was a down-select process for determining a thermochemical cycle for implementation.
The S-I cycle, hybrid sulphur and high-temperature electrolysis were considered, with hybrid sulphur
being selected. Current efforts are under way to resolve the remaining technical challenges with
electrolysers. Preliminary work on a plasma-arc process for conversion of CH 4 to syngas was
presented, with comparisons to standard SMR. Finally, steps to finalise and implement the hydrogen
business plan were discussed.
Dr. Anne Saturnin of CEA presented on behalf of Dr. Jean Leybros of CEA about the ILS experiment
for the hybrid sulphur cycle at CEA Marcoule. The paper described the CEA programme to develop the
hybrid sulphur process. CEA has operated a pilot device since April 2008. To reduce sulphur build-up
on the cathode, CEA is developing new membranes with reduced SO 2 transport characteristics and
good ionic conductivity. To reduce cell voltages, CEA is testing higher activity anodic catalysts and
also porous anodes. A flow sheet has been developed with 42% thermodynamic efficiency. Capital
costs for a 1 000 mole H 2 /sec plant are estimated at just over EUR 1 billion. Sensitivity studies were
conducted to determine major cost drivers for the process. Future efforts will include continued
experimental work, in addition to improved simulations of the electrochemical portions of the flow
sheet. This integrated approach will assist in analysing the potential of the hybrid sulphur process in
comparison with other thermochemical cycles.
Dr. William Summers of SRNL presented on the development status of the hybrid sulphur cycle.
SRNL is studying the hybrid sulphur process. They are developing a PEM-based electrolyser design.
This leverages fuel cell technology. Stated advantages are smaller footprint, decreased cell potential,
simpler hydrogen recovery and lower capital cost. Experimentally, progress has been made in
identifying key membrane and catalyst characteristics for the electrolyser. Pt and Pt alloy catalysts
exhibit excellent performance for the oxidation of SO 2 oxidation. Oxidation kinetics is the largest
contributor to overpotential losses. Single and multi-cell stacks have been operated, and reduction of
12 NUCLEAR PRODUCTION OF HYDROGEN – © OECD/NEA 2010