Computational design of H 2 SO 4 decomposer combined with SOFC for thermochemical hydrogen production

Abstract

Thermochemical methods, such as the sulfur-iodine cycle and hybrid sulfur cycle, are more advantageous than conventional hydrogen production methods, such as fossil fuel reforming and water electrolysis, for large-scale hydrogen production. Sulfuric acid decomposition is a highly endothermic reaction of the sulfur-iodine cycle. To sustain this endothermic process using high-temperature waste heat from solid oxide fuel cells (SOFCs), we propose an integrated thermochemical reactor combined with SOFC by taking a computational approach. First, a thermodynamic analysis was performed to evaluate the heat production of SOFC to sustain the thermochemical reaction in the combined reactor, resulting in a required waste heat of 0.565 kW from the SOFC that was obtained by consuming 0.0241 kg‧h−1 of H2 to process 1.0 kg‧h−1 of the H2SO4 mixture for the H2SO4 decomposer. For the SOFC inlet temperatures 923, 1023, and 1173 K, the corresponding SO3 conversions of the combined reactor were 72.1%, 77.3%, and 85.1%, respectively. A further increase of over 1200 K in the operating temperature led to a minor improvement in the SO3 conversion efficiency. In the SOFC section, the H2 mass fraction decreased from 67.9% to 10.8% in the anode channel, and 0.169 kW of electrical power was generated when the operating cell voltage and energy efficiency were 0.7 V and 53.71%, respectively.