CO2 compression is considered as one of the challenges in CO2 capture and sequestration (CCS). In enhanced oil recovery (EOR) applications where CO2 is pressurized to supercritical pressure (e.g. 150 bar) before injection into a well, CO2 compression could reduce natural gas combined cycle power plants net power by about 4%. In this paper, several CO2 pressurization strategies, such as compression or liquefaction and pumping using an open cycle or closed cycles, were explored and evaluated. New CO2 liquefaction cycles based on single refrigerant and cascade refrigerants were developed and modeled using HYSYS software. The developed models were validated against experimental data. The considered refrigerants for CO2 liquefaction are NH3, CO2, C3H8 and R134a. One of the developed vapor compression CO2 liquefaction cycles that use NH3 as a refrigerant at an optimized liquefaction pressure resulted in 5.1% less power consumption than the conventional multi-stage compression cycle as well as 27.7% less power consumption than the open CO2 liquefaction cycle. Sensitivity analysis was carried out to explore the effect of heat exchangers pressure drop, compressors isentropic efficiency and seawater temperature on the power savings. The results show that the developed liquefaction cycle outperforms the conventional multi-stage compression cycle in almost all cases explored.

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