Thermodynamic modeling of sulfuric acid decomposer integrated with 1 MW tubular SOFC stack for sulfur-based thermochemical hydrogen production

Highlights: • Integration of sulfuric acid decomposer with tubular SOFC stack is thermodynamically studied. • Equilibrium conversion, energy assessment, and influence of operating conditions is investigated. • SO₃ decomposition performance is assessed with different catalysts. • Energy requirement for H₂SO₄ decomposition, SO₂ production capacity, and thermal efficiency of integrated system are analyzed using pinch analysis. This study developed a thermodynamic model of a set of sulfuric acid decomposers for thermochemical hydrogen production. It was integrated with a 1 MW tubular-type solid oxide fuel cell (SOFC) stack. With the model, we evaluated the feasibility of the combined production of electric power, heat, and sulfur dioxide for thermochemical H₂ production. The integrated reactor model consists of three parts: i) SOFC submodel, ii) sulfuric acid decomposition (SAD) submodel, and iii) sulfur trioxide decomposition (STD) submodel with the catalysts Pt/γAl₂O₃ and WX-1. The efficiency of the integrated system was evaluated at a low-pressure range by polarization and efficiency curves for the SOFC, as well as pinch analysis for the SAD. The highest SOFC efficiency and SO₂ production were achieved at 1.25 bar, whereas the lowest fuel consumption and heat demand for SO₂ production were achieved at 3.0 bar. Furthermore, WX-1 performed better in the high-temperature range, whereas Pt/γAl₂O₃ performed better than WX-1 under low-temperature conditions. The Pt-supported catalyst could achieve SO₃ conversion of 66% and SO₂ yield of 57% at a gas temperature of 1025 K using the proposed integrated reactor design.