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Alternate thermochemical cycles for advanced hydrogen production

Description: Experimental studies have validated three classes of thermochemical cycles (Bismuth sulfate-sulfuric acid, magnesium sulfate-magnesium iodide, and oxide-based) based on high temperature solids decomposition as an endothermic step. Such cycles offer the possibility of high efficiency when coupled with high temperature isothermal heat sources. Methods for handling solids in high temperature decomposition reactions have been tested. The results suggest that efficient and practical cycles can be based on such reactions.
Date: January 1, 1982
Creator: Bowman, M.G.; Hollabaugh, C.M.; Jones, W.M. & Mason, C.F.V.
Partner: UNT Libraries Government Documents Department

Reactions for improving efficiencies in thermochemical cycles related to the sulfur dioxide-iodine process

Description: A modification of the sulfur dioxide-iodine cycle which uses magnesium oxide, magnesium sulfite and magnesium iodide is examined with particular emphasis on decreasing the amount of water employed and thereby increasing the efficiency. The key reaction is that of iodine with magnesium oxide and magnesium sulfite hexahydrate with no additional water. This produces 77% of the total possible sulfate as well as magnesium iodide, hydrogen iodide and hydrogen at 523/sup 0/K. The efficiency of this cycle varies between 58% and 39% depending on the amount of heat that can be recovered. This is the first example of a cycle where there is no large energy burden due to evaporation.
Date: January 1, 1982
Creator: Mason, C.F.V. & Bowman, M.G.
Partner: UNT Libraries Government Documents Department

Thermochemical processes for solar hydrogen production

Description: The use of solar energy to produce hydrogen from water is an attractive concept that merits a continuing research and development effort. The base technology being developed for solar thermal power can be applied effectively in the production of hydrogen from water. Hydrogen production could be based on advanced water electrolysis and economic solar hydrogen become an eventual reality even if advanced processes do not prove to be feasible. Thermochemical cycles for decomposing water promise higher efficiencies if cycles can be developed that match the characteristics of solar heat sources. At present, cycles based on sulfuric acid are the most fully developed processes and they can be adapted to solar thermal systems and serve as standards of comparison for new cycles as they are discovered and developed. Advanced cycles based on solids decomposition reactions should interface advantageously with solar thermal systems and several cycles based on such reactions are under experimental evaluation.
Date: January 1, 1982
Creator: Bowman, M.G.
Partner: UNT Libraries Government Documents Department

Alternate sulfate thermochemical hydrogen cycles for use with nuclear process heat

Description: The chemical reactions in the bismuth sulfate-sulfuric acid and magnesium sulfate-magnesium iodide cycles are discussed. Cycles based on solid decomposition reactions are better suited for high temperature isothermal heat sources than for gas cooled reactors. The bismuth cycle might possibly be adapted to a high temperature gas cooled system since the equilibrium dessociation pressure reaches one atmosphere at approximately 1035K and additional heat is required at lower temperatures to dry the solid and effect the low temperature reactions required to close the cycle. Two methods for conducting high temperature solid decomposition operations were tested. The first system involved a rotary kiln, which was used to study the decomposition of ZnSO/sub 4/ (to ZnO), La/sub 2/(SO/sub 4/)/sub 3/ (to La/sub 2/O/sub 2/SO/sub 4/) and Co/sub 3/O/sub 4/ (to CoO). The results of these studies, and some runs with Bi/sub 2/O(SO/sub 4/)/sub 2/ (to form Bi/sub 2/O/sub 2/ /sub 3/(SO/sub 4/)/sub 0/ /sub 7/) are tabulated. Early attempts to study Bi/sub 2/O(SO/sub 4/)/sub 2/ decomposition in a fluidized bed system were unsuccessful since these sulfate particles would not fluidize satisfactorily. Therefore, a dual-particle fluidized bed system was constructed for use with rapid, high temperature decomposition reactions. The dual-particle fluidized bed concept was tested by studies of ZnSO/sub 4/ decomposition. In these experiments, a constant flow of argon carrier gas was passed through the fluidized bed and the quantity of ZnSO/sub 4/ varied to obtain different mol ratios of carrier gas to sulfate feed. Temperatures were measured by means of a thermocouple on the exterior of the quartz tube containing the fluidized bed. The results from two series of experiments are tabulated.
Date: January 1, 1981
Creator: Bowman, M.G.
Partner: UNT Libraries Government Documents Department