Hydrogen Production by Thermochemical Water Splitting; Membrane IS Process

Abstract

The concept of the membrane iodine–sulfur (IS) process to produce H₂ by the thermochemical decomposition of water with solar heat of approximately 650 °C was proposed. In the conventional IS process, the decomposition of SO₃ in the H₂SO₄ decomposition process requires a high temperature heat of approximately 900 °C. As SO₃ will be decomposed at 650 °C when using solar heat, a technology to improve the conversion rate in the SO₃ decomposition reaction is required. In addition, the conventional IS process has technical problems such as excessive amount of I₂ required in the Bunsen reaction (approx. nine times the amount required for the reaction) and a low conversion rate in the HI decomposition reaction. To solve these problems, research was conducted to apply membrane technology to the three main reactions of the IS process, namely the Bunsen reaction, SO₃ decomposition, and HI decomposition. The thermal mass balance calculation of the membrane IS process showed that the H₂ production efficiency of 40% or more can be obtained at 650 °C.