Sensitivity analyses and optimization of a gas sweetening plant for hydrogen sulfide and carbon dioxide capture using methyldiethanolamine solutions

The selective removal of hydrogen sulfide (H2S) in the presence of carbon dioxide using Methyldiethanolamine (MDEA) solutions is a significant process in the petroleum and natural gas industries. An industrial plant with an energy consumption of 3.36 GJ/mol CO2 was simulated and validated using rigorous kinetic and equilibrium models for H2S-CO2-MDEA-H2O system that are incorporated into the Amine Package in Aspen HYSYS®. A modified Murphee-type vapor tray efficiency of 15% for CO2 and 100% for H2S was utilized to account for the non-ideal behavior of the stages. Sensitivity analyses were performed on circulation rate (L/G = 0.6-2 kg/kg), stripper pressure (50-220 kPa), lean amine temperature (45-65 °C), number of absorber stages (8-14), and concentration of MDEA (15-50 wt%). These process variables were evaluated with respect to percentage recovery of sour gaseous components and normalized reboiler duty. The sensitivity analyses results showed that the circulation rate and the MDEA concentration are the two main factors improving process performance. The optimized scenarios exhibited better selective H2S absorption and higher energy savings.