Modeling of a Bayonet Reactor for Sulfuric Acid Decomposition in Thermo-Electrochemical Sulfur Based Hydrogen Production Processes

The Hybrid Sulfur process is one of the most advanced thermo-electrochemical cycles to produce hydrogen by water splitting. It is comprised of only two global reaction steps: a low temperature electrochemical exothermic section and a high temperature endothermic thermal section operating at temperatures on the order of 800 °C. The latter section realizes the decomposition of sulfuric acid into sulfur dioxide. The paper shows and discusses the simulation results obtained for a bayonet based high temperature reactor that decomposes the sulfur trioxide into sulfur dioxide. A detailed transport phenomena model has been set up using a finite volume discretization approach. It includes mass, energy and momentum balance equations, with suitable kinetics expressions that simulate the catalyst performance. A preliminary configuration of the reactor has been examined and simulated, with results demonstrating the effective performance of the component. A sulfur dioxide production yield of about 28 wt% (with corresponding sulfur trioxide reduction from 69 wt% down to about 33 wt%) has been achieved at temperatures on the order of 790 °C and operating pressures of 14 bar.