杂质对管道输送CO_2相特性的影响规律

Impact of impurities on the phase behavior of CO_2 in pipeline transportation

碳捕集利用封存(CCUS)技术作为改善气候的重要选择,安全输送是其关键性纽带环节。管道输送被认为是陆上输送CO2的最优形式,管输CO2中所含杂质将影响CO2相平衡及物性参数变化规律,进而影响管道运行。采用与已知实验值对比的方法优选状态方程,计算含杂质气体及水蒸气的多组分CO2相平衡线及物性参数,与纯组分CO2对比分析可知:PR方程在CO2等极性体系的气液相平衡及物性方面优于其他状态方程。非极性及弱极性杂质通过影响泡点线使两相区扩大,强极性杂质通过影响露点线使两相区扩大。CO2管输过程中,在一定温度、压力下,其密度和黏度会发生突变,比热容会出现极值,而杂质会改变突变和极值的对应温度和压力,采用高温、高压下的超临界态输送可以使其管内流动更稳定。

Carbon capture, utilization and storage （CCUS） is an important option to improve the climate, for which safe transport is a prerequisite. Pipeline transportation is considered as the optimal form to transport carbon dioxide （CO2） on land. However, impurities contained in CO2 pipeline have impact on phase equilibrium and variation of physical parameters of CO2, thereby the operation of the pipeline. Compared with the known experimental methods, state equations are selected to calculate the phase equilibrium line and physical parameters of multicomponent CO2 containing impurities and water vapor. A comparative analysis of pure component and multicomponent CO2 reveals that PR equation is better than other state equations in the aspects of the vapor-liquid phase equilibrium and physical properties of CO2 and other polar systems. Nonpolar and weakly polar impurities that affect the bubble-point line expand the two-phase region while strongly polar impurities that affect the dew-point line expand the two-phase region. During pipeline transportation, density and viscosity of CO2 have mutations at a certain temperature and pressure and heat capacity takes on extreme point, while the impurities will change the mutations and the corresponding extreme temperature and pressure. Supercritical state transportation under high-temperature and high-pressure can make it more stable of pipe flow.