Improving energy efficiency for a low-temperature CO₂ separation process in natural gas processing

Abstract

Conventional amine sweetening process is limited to treating gas with high content of CO2, due to significant energy demand for the regeneration of solvent and the compression of CO2 product for Enhanced Oil Recovery (EOR) or sequestration. Although distillation processes operating at sub-ambient conditions have been regarded as an economic and energy-efficient alternative to amine sweetening process, it is not straightforward to materialize the full benefits of the low temperature distillation process in practice because of complex design interactions existed. The distillation process for carbon dioxide separation operated at sub-ambient conditions are modeled with commercial simulator Aspen HYSYS (R). A range of thermodynamic packages are screened for the selection of the most appropriate one to be used, while the validation of the process modeling is made with reference data. Understanding on the dependence of energy cost on the key design and operating variables is obtained with sensitivity studies, with which energy-efficient selection of column configurations and operating conditions throughout the process is made. Suggestion is also made for improving energy efficiency for the process without compromising separation process, by setting different operating pressure and introducing new configuration involving stream splitting and merging.