Retrofitting amine absorption process for natural gas sweetening via hybridization with membrane separation

In chemical process industries, new external and internal conditions squeeze profit margin of conventional processes. In this challenging scenario, process retrofit is becoming a key issue for existing industrial chemical processes. Among various retrofitting designs, hybridization, which involves more than one technique by using their synergy, has good potential to overcome the limitations of the technologies involved, thus achieving cost-effective retrofit solutions. In this study, an amine absorption process, which removes acid components from natural gas, is retrofitted by adding a membrane unit(s) to sweeten a new feedstock with increased CO2 mole fraction from 0.082 to 0.20. As the existing plant is unsuitable for this new feedstock, two retrofit options: one-stage and two-stage membrane-absorption hybrid retrofit designs are analyzed. Results suggest 27% saving for the former and 11% for the latter, in separation cost per unit feed ($/kmol) compared to building a new amine absorption plant, highlighting the attractiveness of retrofitting the existing process through hybridization. The two retrofit designs are also analyzed for processing feed with different CO2 concentrations.