CONTINUOUS-FLOW SYSTEM DEMONSTRATION AND EVALUATION OF THERMAL EFFICIENCY FOR THE MAGNESIUM SULFUR IODINE THERMOCHEMICAL WATER-SPLITTING CYCLE

The Mg-S-I thermochemical water-splitting cycle, consisting of (1) redox reaction of sulfur dioxide and iodine with magnesium oxide in aqueous phase, (2) hydrolysis of magnesium iodide, (3) thermal decomposition of magnesium sulfate, and (4) thermal dissociation of hydrogen iodide, was studied. In reaction 1, magnesium sulfate is precipitated and separated from magnesium iodide solution by the common ion effect of magnesium ion under highly concentrated conditions. On the basis of the experimental results of the reaction conditions, yields of the constituent reactions, and the amount of water used in the cycle, thermal efficiency of the whole Mg-S-I cycle was evaluated to be 17-39% as a function of the overall heat recovery (65-85%). A continuous flow system for the whole cycle including solid reactant transportation was developed and successfully demonstrated for 33 h with roughly constant production of 0.5 dm3of hydrogen and 0.25 dm3of oxygen per hour. © 1990, American Chemical Society. All rights reserved.