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Impurities in the CO2 stream should be removed to prevent eventual phase changes in CO2 transportation because a two-phase flow caused by the phase change in the pipeline necessitates additional overpressure and can induce equipment damage. In this study, CO2 compression and liquefaction (CCL) processes with a distillation column were used to remove non-condensable impurities and were compared with those with a flash. Three different feeds with a flow rate of 50.1 t/h (400,500 t/y) were supplied to the CCL processes and compressed to 65 bar to gauge pressure (barg) and 20 °C. Although the CO2 mixtures obtained through dehydration and flashing met the purity requirements for transportation and storage recommended in literature, the flash-separated CO2 product at 65 barg demonstrated the coexistence of gas and liquid phases, which restricted the temperature window for liquid CO2 transportation. When the distillation column was used instead of the flash, the operating temperature window at 65 barg widened by 3–6 °C owing to the high purity of CO2. However, the levelized cost of CO2 liquefaction (LCCL) increased by 2–4 $/t-CO2 varying with the feed purity because the distillation column consumed more cooling and heating duties than the flash. This study highlighted that a two-phase flow existed under certain operating conditions despite a high purity of CO2 (over 97 mol%), and the distillation column enhanced the operability of liquid CO2 transportation. [ABSTRACT FROM AUTHOR]

• A distillation column was used for CO 2 liquefaction with high purity and recovery. • Placing the distillation column after the last compressor (60 bar) was cost effective. • An optimal CO 2 recovery of 93 % was achieved under purity constraints, minimizing costs. • The CO 2 liquefaction cost at 80 bar was $22/t-CO 2 with 99.9 % purity and 93 % recovery. • A carbon tax of $100/t-CO 2 shifted the optimum recovery in distillation column to 96 %. CO 2 compression and liquefaction (CCL) requires recovery to be optimized under purity constraints for transportation and storage to minimize costs. CCL processes that operate at 1 million t/y were techno-economically analyzed to evaluate the levelized cost of CO 2 liquefaction (LCCL) and to examine the effect of carbon taxes on the LCCL. The processes included multistage compressors, temperature swing adsorption (TSA) for dehydration, and distillation columns for impurity removal. The same purity constraints were applied to four CCL processes that produce liquid CO 2 at 80 bar and 40 °C: (i) a CCL process without a distillation column (Reference case), and CCL processes with distillation columns placed after (ii) the seventh compressor (Case 1), (iii) the sixth compressor (Case 2), and (iv) the TSA unit (Case 3). The reference case failed to meet purity requirements, delivering an LCCL of $16/t-CO 2. On the other hand, Case 1 was the most cost-efficient among the three cases, delivering a minimum LCCL of $22/t-CO 2 at a recovery of 93 %, which is consistent with usual costs ($13–25/t-CO 2). Charging a carbon tax of $100/t-CO 2 on CO 2 emissions during the CCL process increased the minimum LCCL to $25/t-CO 2 for Case 1 and shifted the optimum recovery to 96 %. [Display omitted] [ABSTRACT FROM AUTHOR]