乙烯淤浆聚合物体系的相平衡计算

乙烯淤浆聚合反应体系的流程模拟与优化过程中气液相平衡的准确计算影响到聚乙烯生成量和聚乙烯分子量的模拟. 通过再参数化含链扰动统计缔合流体理论(Perturbed-Chain Statistical Associating Fluid Theory, PC-SAFT)状态方程，建立了乙烯淤浆聚合体系物性的计算方法. 以文献数据为基准，利用Polymers Plus软件平台，分别得到了乙烯、氢气、己烷、聚乙烯、氮气纯组分的PC-SAFT方程的模型参数，并在准确确定纯组分模型参数的基础上，得到了乙烯-己烷、氢气-己烷、氮气-己烷、以及聚乙烯-乙烯、聚乙烯-己烷组分二元交互系数. 计算结果表明，采用再参数化PC-SAFT状态方程可以准确计算乙烯淤浆聚合反应体系的纯组分物质性质和两组分之间的相平衡. 同时对工业过程中5个不同牌号聚乙烯的反应器内气液平衡状态进行了模拟计算，氢气与乙烯在气相的摩尔比与工业分析值能很好地吻合，最大误差为7.5%.

Modeling of Phase Equilibrium in Ethylene Slurry Polymerization System

In modeling and optimization of ethylene slurry polymerization process, the phase equilibrium computation accuracy has decided the polyethylene production quantity and the molecular weight simulation accuracy. The equation of state of perturbed-chain statistical associating fluid theory (PC-SAFT) was applied to predict thermodynamic properties and phase equilibrium data in ethylene slurry polymerization system through Polymers Plus software. The related parameters of pure components of ethylene, hydrogen, hexane, polyethylene and nitrogen were obtained based on literature data. The interaction parameters of binary systems between ethylene and hexane, hydrogen and hexane, ethylene and hydrogen, ethylene and polyethylene, hexane and polyethylene were regressed. Comparing the results from modeling and literatures, the reparameterized equation of state of PC-SAFT can exactly predict component thermodynamic properties and phase equilibrium of binary system. The predictions of the ratio between hydrogen and ethylene in molar fraction are in agreement with those from plant.