Study on the Throttling Characteristics and Parameter Sensitivity Analysis of High-Pressure CO₂ Pipeline

The venting operation, which constitutes a critical preventive measure within pipeline integrity management, is essential for mitigating potential hazards arising from overpressure in CO₂ transmission system. During manual venting, the prevention of safe CO₂ pipeline venting primarily hinges on addressing two predominant issues: the risks associated with low temperature and the subsequent phenomenon of dry ice blockage. Equipment vibration caused by rapid venting and the impact force of CO₂ on vent pipes are also significant issues that cannot be overlooked. To illustrate the influence of key operational variables, this study conducted a comprehensive analysis, constructing a detailed throttling model to quantify how valve opening, inlet pressure, and inlet temperature collectively govern downstream conditions. Sensitivity analysis of these parameters was performed using multiple linear regression (MLR) and normalized sensitivity coefficients. Results indicate that valve opening is the most significant factor influencing throttling characteristics, accounting for over 60% of sensitivity in outlet temperature, outlet pressure, mass flow rate, and impact force, significantly impacting the safety and stability of the venting process. This study recommends a safe opening range of 60%~80% for DN50 ball valves to ensure adequate pressure relief capacity during venting while avoiding vibration impacts and low-temperature risks. The findings provide crucial reference for throttling structure design and field venting scheme formulation, demonstrating strong engineering applicability.