超临界CO2长输管道区别于输油输气管道,与部分液化烃类管道类似,需考虑临界温度和压力变化造成的相变甚至气化,同时需考虑干线阀门关闭造成的水击影响。以某CO2长输管道为例进行模拟计算,对超临界CO2管道输送进行水击和停输气化研究,结果表明:管道阀室阀门关闭会产生压力波,关阀位置影响水击压力变化,关阀时间对压力影响较小。关阀位置和地温条件均影响停输气化时间。考虑工程实践中管输介质通常为含杂质CO2,通过模拟分析其物性特点,发现杂质会改变CO2相特性,体现在改变其临界温度和临界压力,并产生一个气液两相包络线或区域,从而影响超临界区域。研究结果对超临界CO2长输管道输送工艺具有指导意义,可为CO2长输管道设计及运营提供科学依据和决策参考。

Supercritical CO2 long-distance transportation pipelines are different from oil and gas pipelines but are similar to some liquefied hydrocarbon pipelines. Operation of these pipelines need to consider the phase change or even gasification caused by variations in critical temperature and pressure. It is also necessary to consider the impact of water hammer caused by the closure of the trunkline valve. A particular CO2 long-distance pipeline is taken as an example for simulation calculation, and a study was conducted on the water hammer and gasification after shutdown of supercritical CO2 pipeline. The study results indicate that the valve closure in the pipeline valve chamber will generate pressure waves, and the location of the closed valve will affect the water hammer pressure change, while the valve closure speed has a minor impact on the pressure. Both the location of the closed valve and ground temperature conditions will affect the gasification time after shutdown. Considering that in engineering practice, the medium for pipeline transportation is usually CO2 with some impurities, and simulation analysis of its physical characteristics reveals that impurities can alter the CO2 phase behaviour. This is reflected in changes to its critical temperature and pressure, and the generation of a two-phase gas-liquid envelope or region, thus affecting the supercritical region. The research results provide guidance for the long-distance pipeline transmission of supercritical CO2 and offer scientific basis and decision-making references for the engineering design and operation of long-distance CO2 pipelines.