Toward energy-efficient sour gas treatment: exergy-based modeling and response surface methodology optimization of a diethanolamine absorption process

Gas sweetening is the removal of acid gases, such as CO 2 and H 2 S, from natural gas using amine solvents. This process is widely used in the petroleum industry but is often energy-intensive. Thus, it is important to evaluate and improve process efficiency. In the present study, an exergy analysis is conducted on a diethanolamine-based gas sweetening unit. The goal is to identify inefficiencies and guide optimization. The process is modeled in Aspen HYSYS and validated against design data. The analysis shows that the absorber column causes the most exergy destruction, about 77.4 MW. To improve performance, key operating variables, such as solvent circulation rate, diethanolamine concentration, and solvent inlet temperature to the absorber, are first evaluated individually by sensitivity analysis. These variables are then optimized together using Response Surface Methodology. Under optimized conditions, total exergy destruction drops to about 73.8 MW. This is about a 5% improvement in exergy efficiency while meeting all process requirements. These results illustrate that multivariable optimization can improve the thermodynamic performance of the gas sweetening process.