Abstract
AbstractCarbonyl sulfide (COS), carbon disulfide (CS2), and mercaptans (e.g., CH3SH) are unwanted sulfurous species that are produced in sulfur recovery units (SRUs). They can cause equipment corrosion, reduce catalyst activity, and are pollutants for the environment. This necessitates process optimization to minimize their formation in the SRUs using an accurate kinetic model. In this paper, new reactions of COS and mercaptans are studied using the CBS‐QB3 level of theory, and their kinetics are evaluated using transition state theory. Such reactions are added to a detailed SRU reaction mechanism, and the updated mechanism is validated using the data on COS and mercaptans from lab‐scale experimental setups and an industrial plant. Compared to the previous models, significant improvements in the predicted concentrations of the important species such as COS, carbon monoxide (CO), and sulfur oxides (SO and SO2) are observed due to the inclusion of the new reactions in the mechanism. The simulation studies in a homogeneous reactor within the temperature range of 800–2000 K revealed that furnace temperatures near 1300 K are required to minimize CO and COS formation, while ensuring the oxidation of methane (CH4), mercaptans, and aromatics. Mercaptan formation mainly took place at low temperatures near 900 K. Claus furnace simulations are conducted using industrial feed and operating conditions to show that the optimized inlet air temperature and fuel gas flow rate can assist in simultaneously reducing the emissions of CO and harmful sulfurous species such as COS, CH3SH, and CS2 from the furnace.
Published Version
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