Title: Thermal decomposition of SO₃

Authors: Hidetoshi Karasawa, Akira Sasahira, Kuniyoshi Hoshino

Addresses: Power & Industrial Systems R&D Laboratory, Hitachi Ltd., 7-2-1 Omika, Hitachi, Ibaraki, 319-1221, Japan. ' Power & Industrial Systems R&D Laboratory, Hitachi Ltd., 7-2-1 Omika, Hitachi, Ibaraki, 319-1221, Japan. ' Power Systems, Hitachi Works, Hitachi Ltd., 3-1-1 Saiwai, Hitachi, Ibaraki, 317-8511, Japan

Abstract: The iodine–sulphur and the Westinghouse methods are recognised as thermochemical methods for producing hydrogen from water. Thermal decomposition of SO₃ is an important process in both methods. This study used a flow-type apparatus to evaluate the decomposition of SO₃ to SO₂ and O₂. The SO₃ decomposition rate was measured by the temperature dependence of oxygen concentration using a chemical kinetic model and the reaction was assumed to be a homogeneous reaction of first order. The decomposition rate constant without catalyst was estimated to be 2.23 × 10¹² exp(–39,295/T) s^-1. When hematite was used as the catalyst, the decomposition rate constant increased to 6.79 × 10⁵ exp(–20,021/T) s^-1. A chemical dynamics calculation showed the decomposition ratio of SO₃ for cases with the catalyst reached 0.9 within about 20 sec at 1173 K. Catalyst use would be effective for decreasing the size of a SO₃ decomposer at temperatures lower than 1273 K.

Keywords: catalyst; oxygen; rate constant; sulphur trioxide; sulphuric acid; thermal decomposition; hydrogen production; chemical kinetics; nuclear energy; nuclear power; hydrogen energy.

DOI: 10.1504/IJNHPA.2006.011247

International Journal of Nuclear Hydrogen Production and Applications, 2006 Vol.1 No.2, pp.134 - 143

Published online: 07 Nov 2006 *

Full-text access for editors Full-text access for subscribers Purchase this article Comment on this article