超临界CO_(2)管道输送流动保障分析要点探讨

Discussion on flow assurance issues in supercritical CO_(2) pipeline transmission

近年来,随着碳捕集与封存的需求不断提高,CO_(2)管道成为关键支撑,大规模发展趋势明显。CO_(2)管道可采用气相、超临界相或密相输送的方式。相比气相输送,长距离CO_(2)管道采用超临界输送模式具有更好的经济性。与常规油品输送相比,超临界CO_(2)在输送过程中存在水击超压、热膨胀超压、降压相变、相变低温等问题,受超临界CO_(2)物性特点、输送工艺等影响,超临界CO_(2)流动保障值得系统性探讨。基于超临界CO_(2)输送工艺与运行特点,识别了超临界CO_(2)管道输送流动保障分析要点,探讨了超临界CO_(2)与常规油品的水击超压、热膨胀超压问题,具体开展了超临界CO_(2)计划性放空管体相态与温度分布研究。研究表明:超临界CO_(2)管道水击超压影响相对较小,但存在水击点下游降压相变风险;超临界CO_(2)管道停输后存在热膨胀超压风险;受地形影响,超临界CO_(2)管道计划性放空时存在不均匀相变与不均匀温度分布等问题;超临界CO_(2)管道计划性放空宜同步开展数值模拟分析,泄放过程温度监测方案还需进一步研究。研究成果可为超临界CO_(2)管道设计与运行提供相关借鉴。

In recent years,with the growing demand for carbon capture and storage,CO_(2) transmission pipelines have emerged as a key infrastructure,with a clear trend towards large-scale development.CO_(2) can be transported in pipelines through gaseous state,supercritical state or dense phase state.For long-distance CO_(2) transmission pipelines,the supercritical transportation mode is more economical compared with gaseous transmission.Compared with conventional oil transmission pipelines,supercritical CO_(2) transmission faces issues such as phase change,water hammer effect,and overpressure during the transmission process.Affected by its physical properties and transmission technology,its flow assurance deserves systematic discussion.Based on the supercritical CO_(2) transmission process and its operating characteristics,this study identifies key aspects of flow assurance analysis for supercritical CO_(2) pipelines.It explores the overpressure issues due to water hammer and thermal expansion between supercritical CO_(2) and conventional oil products.Additionally,it specifically conducts a study on the phase change and temperature distribution in the planned blowdown of supercritical CO_(2) in the pipelines.Research shows that the impact of water hammer overpressure on supercritical CO_(2) pipelines is relatively minor,but risk of decompression phase change downstream of the water hammer point do exist;moreover,stopping the flow in the supercritical CO_(2) pipeline can lead to thermal expansion and overpressure issues;and terrain influence can cause uneven phase change and temperature distribution during blowdown.Therefore,the planning for the blowdown of supercritical CO_(2) pipelines should incorporate numerical simulation analysis,and the temperature monitoring procedure during this process requires additional research.The research results can provide relevant reference for the design and operation of supercritical CO_(2) pipelines.