Combined hydrogen sulfide removal and hydrate control for subsea application: Simulation study

The feasibility of the combination of hydrogen sulfide removal and dehydration is investigated in this work using Aspen Plus simulation software. First, the simulation model is validated against experimental data from the literature. Secondly, two process configurations are examined for the simultaneous removal of hydrogen sulfide and water vapor, and Aspen Plus limitations are discussed. Pressure of 100 bar was used in the absorption simulation, in order to simulate subsea high pressure while three different natural gas compositions, with increasing hydrogen sulfide content, were studied. The absorption performance using a mixed methyldiethanolamine (MDEA)-monoethylene glycol (MEG) solvent in one contactor was not possible due to convergence problems. Absorption of H
₂
S and CO
₂
in aqueous MDEA, and H
₂
O in aqueous MEG, including regeneration of the solvents, was therefore simulated separately and further analysis was performed. The specific reboiler duties required to meet the H
₂
S content specification for trouble-free gas transportation in the sweet gas, using an aqueous MDEA solution for optimum Liquid-to-Gas ratio in the absorber, are in agreement with values reported in the literature. Gas dehydration in order to meet the water dew point specifications was also investigated.