Hyun Jung Yu  Dong Kyoo Park  Soo Nam Park  Hye Sung Lee  Changsik Choi

Vol. 32,  No. 1, pp. 61-68, Mar.  2026
10.7464/ksct.2026.32.1.61

CO2 liquefaction Cryogenic distillation Process simulation ASPEN plus

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This study presents a pilot-scale demonstration of a cryogenic distillation process for producing high-purity liquid CO2 from flue gas. A process simulation model was developed to analyze the behavior of a pilot plant operating at 35 bar by using Aspen Plus® with the Peng-Robinson equation of state. However, conventional equilibrium-based models exhibit limitations in accurately describing the partial condensation behavior observed in the pilot system. To address this, a modified modeling approach was proposed by incorporating finite heat removal in the condenser, followed by a pressure-enthalpy flash calculation. This approach accounts for the non-equilibrium nature of condensation, where the effective condensation temperature is governed by heat transfer conditions rather than the bulk vapor equilibrium. The revised model showed good agreement with the pilot-scale data, accurately reproducing the off-gas composition and CO2 purity, and predicting an off-gas flow rate of approximately 174 kg/h. Furthermore, the experimental results showed that adopting a partial condensation strategy at a bulk vapor temperature of –21.4oC, instead of the theoretical vapor liquid equilibrium temperature of –56 oC, is a robust method for achieving liquid CO2 with a purity of 96% while mitigating the risk of dry ice formation. These findings provide practical operation guidelines for the design and scalability of commercial CO2 liquefaction processes.