Abstract A formulation for parameter estimation in cubic equations of state (CEOS) models for phase equilibrium thermodynamics is proposed. This formulation guarantees for the regressed parameters that the predicted mole fractions correspond to stable equilibria, when standard methods fail and demonstrably entail erroneous process simulation results. The present formulation overcomes these deficiencies, which is predicated on a bilevel structure extending Mitsos et al. (2009a). That is, an upper-level (parameter fitting) problem is minimized, subject to multiple lower-level problems, which encode thermodynamic stability. The CEOS constitutes an equality constraint on the lower level, which adds to the difficulty of the bilevel program. For the VLE of C5H12/H2S, it is demonstrated that the method permits an acceptable fit with physically sensible CEOS root values. Thus, the regressed parameter values may be applied to, e.g., process simulation.

中文翻译：

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受足够热力学稳定性准则约束的状态模型三次方程的参数估计

摘要 提出了相平衡热力学三次方程（CEOS）模型中参数估计的公式。当标准方法失败并且明显导致错误的过程模拟结果时，该公式为回归参数保证预测的摩尔分数对应于稳定的平衡。本公式克服了这些缺陷，这是基于扩展 Mitsos 等人的双层结构。(2009a)。也就是说，上层（参数拟合）问题被最小化，受到多个下层问题的影响，这些问题编码了热力学稳定性。CEOS 构成了对较低级别的平等约束，这增加了双层计划的难度。对于 C5H12/H2S 的 VLE，结果表明，该方法允许与物理上合理的 CEOS 根值进行可接受的拟合。因此，回归参数值可以应用于例如过程模拟。