Process simulation investigation of decomposition of hydrogen sulfide into hydrogen and sulfur

  • Rasheed A. Adewale

Student thesis: Master's Thesis

Abstract

Presently, most of the acid gas (H2S) streams generated from amine gas sweetening and refinery upgrading operations are treated using the modified Claus process. In this process, sulfur and low-quality steam are produced by partial oxidation of H2S. Despite the modified Claus process's success in accomplishing the above tasks, it still has some disadvantages. Firstly, the relatively low conversion (93 to 97%) of the Claus process means that additional tail gas treatment unit is required to improve H2S clean-up efficiency. Secondly, a valuable commodity, which is hydrogen, is not recovered. This thesis presents a process simulation study on two process schemes for the decomposition of hydrogen sulfide into hydrogen and sulfur, namely—the thermal decomposition process and the Idemitsu-Kosan-Co Fe-Cl hybrid process. The thermal decomposition of H2S into Hydrogen and Sulfur was studied using a process simulator: ProMax®. A commercial Sulfur Recovery Unit (SRU), located in the region of Abu Dhabi, together with the H2S decomposition scheme of the Alberta Sulfur Research Limited was modeled and validated using plant data and field test results respectively. With the net percentage of the acid gas feed to cracking coils (split 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 fraction of 0.245. However, an optimization of the integrated model proved that the sulfur recovery could be restored to its initial value of 98.67 %. Cost estimation of the retrofit indicates that the capital cost which was evaluated to be US$ 3.6 M could be recovered in less than 4 years. The Idemitsu-Kosan-Co (IKC) Fe-Cl hybrid was modeled and validated with pilot-scale data using Aspen Plus®. The model was then scaled up based on the typical acid gas composition profile of one of Habshan plant's Sulfur Recovery Unit. With the solution flow rate and the components' concentration as the controlling parameters, the process was studied based on operability, reliability and economics. Operation at high ferric ions concentration was found to be more beneficial compared to high solution flow rate operations. The ferrous ion constituent of the solution proves to be instrumental in the downstream electrolysis operation for hydrogen recovery. High absorption temperature was found to be unfavorable for the absorption-oxidation of hydrogen sulfide while high pressure operations are advantageous. Cost estimates of the process indicate that the capital cost linked to IKC process can be recovered in less than 5 years.
Date of Award2014
Original languageAmerican English
SupervisorSofiane Abdallah Berrouk (Supervisor)

Keywords

  • Applied sciences
  • Decomposition chemistry
  • Hydrogen sulfides
  • Industrial processes
  • Chemical engineering
  • 0542:Chemical engineering

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