To design and operate safe and efficient CO₂-transportation systems for CO₂ capture and storage (CCS), engineers need simulation tools properly accounting for the fluid and thermodynamics of CO₂. As the transportation systems evolve into networks, it becomes important that these tools also account for impurities in the CO₂, which may significantly affect the thermophysical properties, directly impacting system design and safety. Tube-depressurization experiments provide crucial data to develop and validate models describing transient multiphase multicomponent flow in pipes. In this work, we perform experiments in a new facility with dense and fast instrumentation for both pressure and temperature. One experiment is for CO₂ with 1.8 mol % N₂, and one has 1.92 mol % He, both starting from 12 MPa and 25 ${}^{\circ }$C. In order to quantify the effect of impurities, the experiments are compared to results for pure CO₂ and analysed on the background of simulations. We employ a homogeneous equilibrium model (HEM) augmented in this work to account for the appearance of solid CO₂ in CO₂ mixtures. We observe that the moderate amounts of impurities significantly influence both pressure and temperature dynamics. In particular, the ‘pressure plateau’, a key quantity for the assessment of running-ductile fracture, increases as much as 4 MPa for CO₂-He compared to pure CO₂. A further insight is that models must account for solid CO₂ in order to capture the correct temperature development as the pressure decreases towards atmospheric conditions.

为了设计和运行用于 CO ₂捕获和封存 (CCS) 的安全高效的 CO ₂运输系统，工程师需要正确考虑 CO ₂流体和热力学的模拟工具。随着运输系统演变成网络，这些工具还必须考虑 CO _{2 中的}杂质，这可能会显着影响热物理特性，直接影响系统设计和安全性，这一点变得很重要。管道减压实验为开发和验证描述管道中瞬态多相多组分流的模型提供了关键数据。在这项工作中，我们在一个新设施中进行实验，该设施具有密集且快速的压力和温度仪器。一项实验是针对 CO₂具有 1.8 mol % N ₂，一个具有 1.92 mol % He，均从 12 MPa 和 25 ${}^{\circ }$C. 为了量化杂质的影响，将实验与纯 CO _{2 的}结果进行比较，并在模拟背景下进行分析。我们采用在这项工作中增强的均质平衡模型 (HEM) 来解释CO ₂混合物中固体 CO ₂的出现。我们观察到适量的杂质显着影响压力和温度动态。特别是，与纯 CO ₂相比，CO ₂ -He的“压力平台”（用于评估运行韧性断裂的关键量）增加了 4 MPa 。进一步的见解是模型必须考虑固体 CO ₂ 以便在压力向大气条件下降时捕捉正确的温度变化。