超临界CO_(2)萃取含油污泥中原油的多相平衡模型

A Multiphase Equilibrium Model of Supercritical CO_(2) Extraction of Crude Oil in Oily Sludge

超临界CO_(2)萃取含油污泥中原油的热力学本质是各组分在多相体系中相互传递并达到多相平衡的过程。准确预测萃取体系相态、相边界是萃取工艺条件优化的基础。原油中沥青质、H 2O等极性分子间的氢键缔合是影响多相平衡过程的关键因素,但传统基于立方型状态方程的相平衡方法忽略了上述缔合作用,导致多相平衡预测偏差大。针对这一问题,基于考虑缔合项的立方型状态方程,提出了含极性组分原油的特征化方法及多相平衡算法,分析了CO_(2)-油、CO_(2)-油-溶剂、CO_(2)-油-溶剂-H 2O的相平衡特征。结果表明:研究模型的计算结果与实验结果的平均相对偏差为3.58%~11.81%,相比于SRK-HV状态方程的平均相对偏差最大可降低10.20%。实例分析表明:当萃取体系中CO_(2)、油、H 2O的摩尔分数分别为70%、28%、2%时,最佳萃取条件为压力22000 kPa、温度323.15 K;不含H 2O萃取体系(CO_(2)、油的摩尔分数分别为70%、30%),最佳萃取条件为压力21000 kPa、温度323.15 K。

The thermodynamic nature of supercritical CO_(2) extraction of crude oil in oily sludge is a process where each component transfers to each other and reach multiphase equilibrium in the multiphase system.Accurate prediction of the phase state and boundary of the extraction system is the basis for optimizing extraction conditions.The hydrogen bond associations between various polar molecules such as asphaltene and H 2O in crude oil is the key factor of affecting the multiphase equilibrium.However,the traditional phase equilibrium method based on the cubic equation of state ignores the associations aforesaid,leading to a significant deviation in multiphase equilibrium.In reaction to the above problem,considering the cubic equations of state of associations,the paper proposes the characterization method and multiphase equilibrium algorithm of crude oil containing polar components,and analyzes the phase equilibrium characteristics of CO_(2)-oil,CO_(2)-oil-solvent,and CO_(2)-oil-solvent-H 2O.The results show that the absolute average relative deviation(AARD)between the calculation results and experimental results of the model is between 3.58%and 11.81%,which can be reduced by 10.20%at most as compared with AARD of the SRK-HV EoS.Case studies also indicate that when the mole fraction in CO_(2),oil and H 2O in the extraction system is 70%,28%and 2%respectively,the best extraction condition is under the the pressure of 22000 kPa and the temperature of 323.15 K;for the extracting system without H 2O,in which the mole fraction of CO_(2) and oil is 70%and 30%,respectively,the best extraction condition is under the pressure of 21000 kPa and the temperature of 323.15 K.