Utilization of ZnSO sub 4 Decomposition in Thermochemical Hydrogen Cycles

摘要

It was found that the ZnSO sub 4 decomposition reaction can be used as the high temperature step in a number of thermochemical cycles. It is especially applicable as a substitute for the H sub 2 SO sub 4 decomposition step in H sub 2 SO sub 4 -based cycles, and significantly improves the efficiency of such cycles. In this study, the effects of heatup rate on the decomposition of ZnSO sub 4 as it is heated through an alpha - beta transition at 1015 K were looked at. It was found that a rapid heatup of fine ZnSO sub 4 particulates through this transition leads to fracturing of the ZnSO sub 4 crystallites and significantly enhances its subsequent decomposition rate at approx. 1043 K. Evidence was found for an autocatalytic decomposition process in fine ZnSO sub 4 particulates with either rapid or slow heatup rates. We believe that a combination of (1) fracturing of the crystallites, and (2) surface catalysis by ZnO to equilibrate the SO sub 3 /SO sub 2 /O sub 2 gaseous products, contributes to the observed autocatalytic behavior. (ERA citation 05:020234)