Sulfur removal and recovery is essential for oil and gas industry, especially for upgrading of oil sands bitumen. Claus process can only recover elemental sulfur from H2S. However, hydrogen is needing commodity in the same industry section. A chemical route of converting H2S into H2 via the following chemical reactions has been developed. H2S + H2SO4 → SO2 + S + 2H2O (1) 2H2O + I2 + SO2 → H2SO4 + 2HI (2) 2HI → H2 + I2 (3) Including further oxidation of S from reaction (1) into SO2, the route can produce two moles of H2 from one mole of H2S. To engineer such a new chemistry into an industrial process, studies have been conducted for all the three reactions but focuses are given to reaction (2), the Bunsen reaction. This reaction has faced more challenges in engineering development including side reactions, product separation, corrosion hazard, and iodine vapor deposition which results in blockage of the facility. Dissolving iodine in toluene allows the Bunsen reaction to be run below the melting point of iodine, giving flexibility of operating the reaction at lower temperatures, which, in turn, leads to benefits such as mitigating the side reactions, reducing the corrosion potentials, and lowering the severity of iodine vapor deposition. The application of Corning Advanced-Flow Reactors (AFR), which are made of ceramic or glass material, further eases the corrosion concerns. The modulus design of the AFR allows for easy scaling up. And the heart shape design in the micro-flow channels provides excellent mass transfer capabilities. Direct electrolysis of HI in the HI-H2SO4 aqueous solution after Bunsen reaction shows that controlling the decomposition voltage can render HI to be split successively and H2SO4 to remain. After electrolysis, the hydrogen is sent to conditioning unit and then used for hydrotrating, the I2-toluene is circulated to the Bunsen reaction unit and the H2SO4 aqueous solution is sent for upgrading to higher concentrations. The upper boundary thermal efficiency of hydrogen production via the H2S splitting cycle has been determined. The plan design based on the research results has been performed. Further improvement of the process economics will make it possible to recover H2 from H2S. Hopefully in the near future both Claus process for sulfur removal and natural gas steam reforming for hydrogen production can be eliminated in heavy oil upgrading. After hydrotreating, the H2S can be sent to this H2S splitting processes for hydrogen recovery.

Engineering the H2S splitting cycle for oil sands bitumen upgrading: Can we recover hydrogen from H2S too?

252nd National Meeting (2016)

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