Impurity-driven variations in CO2 critical flow dynamics: Modeling approaches for enhanced CCS safety

Haifan Liao, Xinying Wang, Kuang Yang, Zhenghui Hou and Haijun Wang

Energy, 2025, vol. 323, issue C

Abstract: Carbon Capture and Storage (CCS) is a vital technology for reducing emissions, yet ensuring safe transport of CO2 and preparedness for potential leak incidents remains critical for public acceptance. Given that captured CO2 inevitably contains various impurities, it is essential to evaluate their influence on decompression behavior and critical mass flux predictions during pipeline ruptures. In this study, we investigate how different impurity compositions affect decompression dynamics and critical mass flux through classical critical flow models, in conjunction with impurity levels specified by current CCS standards. Initially, several models were evaluated for predicting the critical mass flux of pure CO2, with results indicating that the Delayed Equilibrium Model (DEM) generally outperforms others in terms of predictive accuracy. Notably, the presence of impurities elevates the pressure plateau during phase transitions, which can lead to an underestimation of critical mass flux when using standard models. Furthermore, the GERG-2008 equation of state (EOS) yields a higher pressure plateau compared to the Peng-Robinson (PR) EOS, consequently predicting a lower critical mass flux. The study also highlights differences in acoustic properties between DEM and the Homogeneous Equilibrium Model (HEM). Specifically, DEM exhibits a higher speed of sound at low void fractions, resulting in higher critical mass flux predictions under impurity-rich conditions. Recognizing the potential safety risks and economic implications of these discrepancies, we propose a new correlation that adjusts the critical mass flux of pure CO2 by incorporating thermodynamic parameters to account for impurity effects. This approach provides a practical and efficient method for improving engineering calculations and ensuring more reliable leakage response designs. Overall, our findings offer critical insights for enhancing safety management in CCS operations and support the broader integration of CCS technologies in real-world applications.

Keywords: Critical flow; CCS; Decompression; Critical mass flux prediction; Impurity impact (search for similar items in EconPapers)
Date: 2025
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Persistent link: https://EconPapers.repec.org/RePEc:eee:energy:v:323:y:2025:i:c:s0360544225014926

DOI: 10.1016/j.energy.2025.135850

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