气体杂质对管道输送CO_2相态的影响

Impact of gas impurities on CO_2 phase state in pipeline transportation

CO_2的捕集、利用和封存(CCUS)是当前环保的热点话题,而管道输送是CCUS技术的关键环节。CO_2气源含有各种杂质,杂质对CO_2的相态有着很大影响,因此了解含杂质的CO_2的相态特征并了解其与纯CO_2性质的不同是开展CCUS技术研究的基础。通过对状态方程的对比研究,确定PR方程作为计算含杂质的CO_2相态的状态方程,并用HYSYS软件对含杂质的CO_2的基本相态特征及物化性质进行了研究。得到了延长油田含杂质的CO_2的临界温度Tc=30.36℃,临界压力Pc=7.55MPa,相比纯CO_2,含杂质的CO_2的临界温度降低,临界压力升高,且相态图中出现了两相区域,表明了杂质的存在增加了CO_2管道输送的难度;在临界点附近,压力和温度的微小变化将引起CO_2流体密度、粘度、导热系数和压缩系数较大幅度的改变。

CO2 capture, utilization and storage （CCUS） is the hot topic of current environmental protection, and pipeline transportation is a key part of CCUS technology. The CO2 gas sources contain a variety of impurities, which have a great influence on the phase state of CO2. Therefore, knowing the phase characteristics of impurities-containing CO2 and understanding its difference from the pure CO2 is the basis of CCUS technology research. By comparing the equations of state, the PR equation was determined as the equation of state for calculating the phase states of impurities-containing CO2, and the HYSYS software was used to study the basic phase behavior and physicochemical properties of the impurities-containing CO2. The critical temperature and pressure of the impurities-containing CO2 in Yanchang Pretroleum were calculated to be 30.36℃ and 7.55MPa, respectively. Compared with pure CO2, the critical temperature of impurities-containing CO2 decreases and the critical pressure increases, and the phase diagram shows two phase region, indicating that the presence of impurities increases the difficulty of transporting CO2 by pipelines. Near the critical point, a small change in pressure and temperature will cause a significant change in the density, viscosity, thermal conductivity and compressibility of the CO2 fluid.