Sulfuric acid decomposition in the iodine-Sulfur cycle using heat from a very high temperature gas-cooled reactor

Using the heat of high-temperature gas-cooled reactor to drive the thermochemical iodine sulfur cycle is an important way to produce hydrogen on a large scale. The sulfuric acid decomposition is the key reaction affecting the hydrogen production efficiency in this method, so efficient sulfuric acid decomposition is needed. The present study focuses on the temperature rise, phase change and chemical reactions of sulfuric acid in a bayonet heat exchanger. The evaporation-condensation model in a steady temperature field was used to simulate the different stages of the phase change process with the species transport model used to calculate the product proportions. Finally, the effects of two catalyst arrangements on the decomposition fraction were analyzed. The results show that the temperature in the catalytic core area reaches 1100 K which provides the heat required for the decomposition reaction. When the sulfuric acid flow rate is 0.36 kg/h, the two-phase flow section is about 0.22 m long to promote better heat transfer. The simulations show that square and circular catalysts give sulfuric acid decomposition fractions of 65% and 57%. The pressure drop of the two catalyst arrangements is almost the same, while the square catalyst has a higher decomposition fraction, which can improve the economics. This study provides a reference for optimizing catalyst selection based on the flow and heat transfer rates. (c) 2020 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.