Sulfolane and di-iso-propanol lean amine blend operating temperature and pressure effect to natural gas sweetening using process simulation

Abstract

Blending physical and chemical solvents has shown to be promising for removing hydrogen sulfide, carbon dioxide and mercaptan from natural gas effectively. Studies show that using sulfolane and methyl di-ethylene amine blend yields better performance than traditional methods. However, the Shell process depicts that blending sulfolane with di-iso-propanol amine significantly minimizes the problem associated with amine re-circulation efficiency observed with the application of sulfolane and methyl di-ethylene amine. This study aimed at investigating the effect of temperature and pressure to the acid gas removal performance of sulfolane and di-iso-propanol lean solvent using Aspen HYSYS software. In addition, the determination of optimum blend ratio was considered. The acid gas composition of the natural gas stream was 16.9%. This is a hypothetical data used to mimic a relatively high acid gas content in a typical raw natural gas feed. During the process simulation, the lean solvent temperature and pressure were varied between 5 and 210 °C, and 20 and 250 bar, respectively, while maintaining the reactant flow rate at 819.5 kg/h. Findings informs that the optimum blend formulation obtained was 15% water, 15% sulfolane and 70% di-iso-propanol amine at operating temperature and pressure of 50 °C and 45.5 bar, respectively. At the end of the process, the acid gas composition reduced from 16.9 to 0.26%, with an increase in the methane composition by 16.12%. This was as a result of the reduction in the vapor point of the lean solvent, which significantly contributed to enhancing the contact time and efficiency between the gas feed and lean solvent. Hence, the sales gas specification for natural gas was met at lower operating temperature and pressure below 10 °C and 25 bar, respectively.