Solar Thermochemical Decomposition of Hydrogen Sulfide to Hydrogen

Abstract

Hydrogen is considered the simplest element in existence and one of the most abundant in the earth found as part of another substance, such as water and hydrocarbon. Though of its simple structure, it has the highest energy content of any common fuel by weight. In the near future, due to its excessive energy content, it may become one of the most environmentally friendly automobile fuels. Most oil and gas reservoirs in the United Arab Emirates (UAE) are sour, enriched with a high amount of hydrogen sulfide (H2S) and sulfur species. It is desirable in many oil and gas industries to utilize H2S in hydrogen production, instead of operating the Sulfur Recovery Unit (SRU), which is not an economically viable process. The conversion of H2S into H2 and Sulfur is beneficial from both environmental and energy perspectives. The two-step thermochemical decomposition of H2S is considered as one of the most promising technologies for Hydrogen production. Despite the benefits of H2S splitting to H2 and S, no one up to now has come up with a technology for the production of hydrogen and sulfur that can be commercialized, replacing the existing SRU. But, the feasibility of various strategies for hydrogen production through splitting H2S into H2 and S has been reported in the literature. Among the various hydrogen production methods, the two-step thermochemical cycle of H2S using Nickel Sulfide renders the potential of obtaining high conversions of hydrogen and sulfur under less extreme operating conditions. Therefore, this research thesis focused on modeling a two-step solar thermochemical cycle using Nickel Sulfide as a catalyst. A multistep chemical kinetics model of the two-step thermochemical decomposition of H2S using Nickel Sulfide was developed using CHEMKIN® software to examine the key parameters that affect the overall cycling process and H2S conversion efficiency, including temperature and the behavior of adsorbed species on active catalyst sites during sulfurization & regeneration transient steps. A techno-economic evaluation of a scaled-up proposed two-step thermochemical decomposition process was also performed using Aspen Plus® process simulator to test the long-term competitiveness. Moreover, a sensitivity analysis was performed to investigate the market price of the products on the production capacity. It was evident from the obtained results, that the proposed process would have a bright future due to its economic value and the benefits it serves to the region.

Date of Award	Nov 2021
Original language	American English