Performance analysis of natural gas sweetening unit with amine solution and blends

Abstract

In this study, raw natural gas data from Uch gas field located in Dera-Bugti of Balochistan, Pakistan is simulated for performance analysis over amine absorber unit in Aspen HYSYS V9.0. The primary amine, MDEA was selected to remove bulk CO2 and reduce H2S to ppm level, where secondary amines, MEA, DEA and Sulfolane were selected to observe CO2 levels in sweet gas. The primary amine in isolation and blend with secondary amine was simulated and analysed over absorber performance. The absorber performance is reported as CO2, H2S and water content in sweet gas, hydrocarbons in rich amine and its temperature. MDEA in isolation resulted in minimum 14.13 and 12.78 mol% CO2 in sweet gas and rich amine temperature of 81.11oC and 82.13oC with 24 and 30-Trays, respectively at 2500 m3 /h of lean amine recirculation rate. Among the tested blends, MDEA/MEA, MDEA/Sulfolane showed no significant improvement on absorber performance compared to isolated MDEA. However, MDEA/DEA blends indicated that CO2 in sweet gas can be reduced to 12.07, 3.41, 1.85 mol% with rich amine temperature of 89.05, 111.72 and 124.80oC, respectively. The lowest CO2 detected of 1.85 mol% was achieved with 40 mol% MDEA and 15 mol% DEA blend at 2500 m3 /h recirculation rate and rich amine temperature of 124.80oC. The results indicated that MDEA/DEA blend has the potential to attain CO2 of less than 2 mol%. The higher rich amine temperature raise concern that can be resolved by using heat stabilized salt.