Simulation of hydrogen production from thermal decomposition of hydrogen sulfide in sulfur recovery units

Large amounts of H₂S are produced globally, mostly from the gas sweetening process of sour natural gas. H₂S is usually considered to be an industrial waste product but has been identified as a resource for hydrogen and sulfur in recent years to render sweet gas production a cleaner process. In this study, thermal decomposition of H₂S into hydrogen and sulfur was studied using a process simulator: ProMax^®. A commercial SRU (sulfur recovery unit), located in the region of Abu Dhabi, together with the H₂S splitting scheme of the Alberta Sulfur Research Limited were modeled and validated using plant data and field test results, respectively. With the net amount fraction of the acid gas feed to cracking coils (split amount fraction) considered as the controlling parameter, its effect on hydrogen production, thermal reactor energy requirement, burner flame stability, steam production, Claus reactors' temperature and sulfur recovery of the primary SRU were investigated using the integrated model and plant data. Reduction in sulfur recovery of about 0.31% of the primary SRU was recorded as a result of the retrofit for a split amount fraction of 0.245. However, optimization of the integrated model proved that the sulfur recovery could be restored to its initial value of 98.67%. Cost estimation analysis of the retrofit indicates that the capital investment could be recovered in less than four years.