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WP4: Project 6
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Design implications of hydrogen production
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Investigators: Professor R. Allen
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A Generation IV reactor, such as the VHTR, is considered an essential element of the international drive to harness nuclear heat for the zero emission production of hydrogen. Working within KNOO, as well as with nuclear industry representatives from Europe and the US, the Sheffield team will consider in detail the thermodynamic limitations of the available cycles and the extent to which these impact on the reactor design, particularly in so far as it places limits on the upper temperature for process use. Since Gen IV reactors are expected to provide process temperatures up to 1000oC, they open up the possibility of coupling to possible production routes which take advantage of the higher Carnot efficiencies the high temperatures provide. Examples include steam methane reforming and thermochemical cycles (TCs). TCs are zero- emission chemical routes that serve to split water into hydrogen and oxygen. High temperature electrolysis is also being considered.
Out of over 100 TCs identified so far, the one normally regarded internationally as having the greatest potential for success is the Sulphur Iodine Process. It involves only fluids, which provides for more certain design. Despite the worldwide interest in the process and because of its complexity, there is no modern flowsheet generally available. The initial part of this phase of the programme will concentrate on developing such a flowsheet and benchmarking it against the best of the data likely to emerge from Japan, France and the US in the next few years. The resulting flowsheet, mounted on a commercial package such as Chemcad, will be made available to stakeholders as a deliverable from the project. This work will be subsequently extended, at an appropriate level of detail, to processes involving electrolysis and chemical conversion as well as to improved versions of the SI process. The efficiency with which the SI process can generate hydrogen is limited by conventional Carnot Cycle considerations. Other cycles, for example radical extensions of the Westinghouse Cycle, involving new electrochemical steps, will be considered for their ability to release the Carnot constraints and potentially allow hydrogen production from a wider range of reactor types. The potential for overall process improvement will be investigated.
Nuclear training is a key element of KNOO and the research will interact as necessary with WP2 in terms of materials performance as it may influence system design. At the end of the first year of the project, a report will be produced examining in detail the technical issues surrounding coupling hydrogen production with VHTR plant as well as providing a review of the state of international research programmes in the field and a forward strategy for a UK contribution in the area.
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