Modelling and Simulation of Acid Gas Absorption from Natural Gas by Amine Solution Using Aspen HYSYS

This work has been carried out to model and simulate a typical acid gas absorption process using Aspen HYSYS process simulator. The chemical components involved in the process development were water, methane, ethane, propane, higher alkanes, carbon dioxide, hydrogen sulphide, nitrogen and amines: monoethanolamine (MEA), diethanolamine (DEA), triethanolamine (TEA) and methyldiethanolamine (MDEA). The fluid package selected for the simulation before entering the simulation environment was Acid Gas – Chemical Solvents. In the simulation environment, the model was developed by picking an absorber from the Model Palette, placing it and assigning the input and the output streams involved before inputting the parameters required for model convergence. The carbon dioxide-rich feed gas was made to enter the absorber at the bottom inlet stream while the lean amine stream entered at the top inlet and showered down on the uprising gas thereby trapping the carbon dioxide molecules within the gas. The top product from the absorber was the treated gas while the amine solution and the trapped carbon dioxide left the absorber as the bottom product. Different simulations were run to investigate the performance of the amines under the same operating conditions. It was discovered that, of all the four amine solvents considered in this work for the removal of carbon dioxide by chemical absorption, MEA had the highest efficiency but would require more dehydration because it had the highest water content. DEA was also found to scrub the carbon dioxide down to acceptable levels. However, TEA and MDEA barely scrubbed any carbon dioxide under these conditions, as their carbon dioxide compositions were found to be unacceptable. The analyses of the results obtained from the simulations indicated that Aspen HYSYS can be used to study the process of acid gas absorption successfully.