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Kinetic Simulations of H2 Production from H2S Pyrolysis in Sulfur Recovery Units Using a Detailed Reaction Mechanism

Ravikumar, Arjun, Raj, Abhijeet, Ibrahim, Salisu, Rahman, Ramees K., Al Shoaibi, Ahmed
Energy & Fuels 2016 v.30 no.12 pp. 10823-10834
capital, carbon dioxide, combustion, desulfurization, energy, feedstocks, fuels, furnaces, heat, hydrogen, hydrogen production, hydrogen sulfide, pyrolysis, steam, sulfur, wastes
Acid gas (H₂S and CO₂) is produced in large volumes worldwide from the desulfurization of hydrocarbon fuels and is utilized in sulfur recovery units (SRUs) to produce sulfur. However, the hydrogen content of acid gas is wasted as low-grade steam, which highlights the need for the efficient utilization of this resource. The production of H₂ from acid gas is desired, as it is an inexpensive feedstock. In this work, a kinetic study is conducted on H₂ production from acid gas in an industrial SRU to utilize its built-in inertia, while saving on the capital cost and enhancing the processing capacity of the SRU. The thermal energy generated during the combustion of acid gas in the reaction furnace (RF) is used for acid gas pyrolysis in the waste heat boiler (WHB) of the SRU. While this technique has been investigated previously, its realization at the industrial scale is hindered by low H₂ yield. This paper presents suitable means of enhancing H₂ production via operational modifications in RF and WHB. A detailed reaction mechanism, developed for acid gas combustion and pyrolysis and validated using experimental data from industrial furnaces and reactors, is used for the kinetic simulations of the SRU thermal unit. The results show that RF operational changes such as the extent of H₂S oxidation and feed preheating can increase H₂ yield from 3% to 38% in the WHB without changing the composition of the acid gas stream. This significant improvement in H₂ yield can help in realizing its production from acid gas in SRUs.