Alternate sulfate thermochemical hydrogen cycles for use with nuclear process heat

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.