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Hydrogen sulfide exists mostly as a detrimental byproduct in the gas processing units as well as refineries, and it must be eliminated from natural gas streams. In a Sulfur Recovery Unit (SRU), hydrogen sulfide is converted into the elemental sulfur during the modified Claus process. Efficiency of sulfur recovery units significantly depends on the reaction furnace temperature. In this work, the effect of oxygen and acid gas enrichment on the reaction furnace temperature and accordingly on sulfur recovery is studied, using both numerical modeling and process simulation. Then, simulation and numerical model are benchmarked against the experimental data of an SRU unit. The validated model provides spotlight on optimizing the upstream sulfur removal unit as well as the oxygen purification process. Two cases of acid gas streams with low and high H2S content, 30% and 50%, are studied to investigate the effect of operating parameters on the overall recovery. Finally, average errors of the models are presented. According to the absolute difference with experimental values, the developed numerical model shows great potential for accurately estimating overall efficiency of the recovery unit.

Abstract: In this experimental study, a kinetic model has been developed for Fischer–Tropsch synthesis reactions by using sol–gel technique and Fe/Ni/Al2O3 as the catalyst (40% Fe/60% Ni/40wt.%Al2O3) in a differential fixed-bed micro reactor assuming no internal or external diffusion. Operating conditions of the reactor were as follows: total pressure 1–12atm ; Temperature 220–260°C; H2/CO feed ratio 1.5–2; gas hourly space velocity 2100–7000cm3(STP)/h/gcat and conversions of 6–37% of hydrogen and 7–21% of carbon monoxide. Mass transfer limitations were investigated by changing synthesis gas velocity in reactors which differ in size. Based on the hypothesis that water inhibits the intrinsic Fischer–Tropsch (FT) reaction rate in the iron-FT synthesis, all rate expressions in this study were in inverse ratio to number of vacant sites and CO and water content. The obtained data in this study were checked using “complete form of Langmuir–Hinshelwood–Hougan–Watson (LHHW)” which has been proposed by Van der Laan and Botes. The kinetic parameters were determined using Levenberg–Marquardt (LM) method. The activation energy and heat of adsorption of CO and water were 103.81, −56.82 and −25.62kJ/mol, respectively. [Copyright &y& Elsevier]