Fig. 5-7 Composition of the laboratory-scale apparatus of continuous hydrogen production To verify the continuous hydrogen production by the I-S process, experiments have been conducted with a laboratory-scale test apparatus. The apparatus is made with quartz, and operates at a pressure of one atmosphere. Electric heaters are used to maintain the temperature of the chemical reactors, concentrator, decomposer and distillation column. In the future, the energy needed for water decomposition will be supplied by high-temperature helium from the HTGR.

Fig. 5-8 The production rate of hydrogen and oxygen in a continuous experiment with the laboratory-scale apparatus The result of the continuous hydrogen production experiment was shown. The production rate of hydrogen is about 1.2 liters/hour and oxygen is 0.6 liters/hour, clearly in agreement with the theoretical volume ratio. Consequently, stable hydrogen production is demonstrated by this experiment using the I-S process.

Hydrogen is a promising candidate for a clean energy system in the future, but only if it can be produced on a large scale and at low price. The most reasonable method of hydrogen production is via electrolysis in using existing technologies. However, the electrolysis method is unsuitable from the standpoints of the efficiency of electricity generation and the necessity conversion from convenient electricity to hydrogen gas. JAERI is engaged in development of a process for hydrogen production from water using heat generated by the High-Temperature Gas-cooled Reactor (HTGR). This thermochemical hydrogen production method uses a chemical process which can decomposes water into hydrogen and oxygen using a combination of several chemical reactions, and chemical components are recycled. An Iodine-Sulfur (I-S) process consisting of decompose sulfuric acid, decomposed iodic acid and Bunsen reactions has been studied at JAERI. A 24-hour continuous experiment using the laboratory-scale apparatus has been conducted to verify that the process can produce hydrogen in a closed-cycle operation.

Reference H. Nakajima et al., Hydrogen Production by Iodine-Sulfur Process for Thermochemical Decomposition of Water, Proc. Int. Hydrogen and Clean Energy Symp., IHCH '95, 251 (1995).

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