Thermodynamic Modeling and Analysis of Boil-off Gas Generation and Self-Pressurization in Liquefied Carbon Dioxide Tanks

Abstract

The importance of the safe transport of liquefied carbon dioxide (LCO2) is increasing owing to environmental issues. When transporting a low-temperature liquid, boil-off gas generation and self-pressurization occur due to heat ingress, affecting the holding time of a low-temperature liquid tank. This study developed and compared three thermodynamic self-pressurization models to estimate the holding time of LCO2: Thermal homogeneous model (THM), Thermal two-zone model (TTZM), and Thermal multi-zone model (TMZM). Thermodynamic differential equations were solved for THM, and software was used for TTZM. For TMZM, the parameters were optimized using experimental data to determine the heat ratio parameter f and heat transfer parameters K1 and K2. THM and TTZM estimated an unreasonably long holding time, approximately 42 days. The TMZM, however, showed a satisfactory holding time of 12–13 days. These results can help predict the self-pressurization in the storage tanks of LCO2 and be applied to actual LCO2 carrier cargo handling systems, with the modeling results indicating that the 12–13 days of LCO2 self-pressurization based on the TMZM appears to be the most suitable.

Keywords

• boil-off gas
• lco2
• self-pressurization
• thermodynamic model