Avaliação de Diferentes Abordagens na Solução do Problema de Equilíbrio Sólido-Líquido em Óleos Parafínicos

ABSTRACT In this paper, the computational efficiency in the solid-liquid equilibrium (SLE) problem for paraffinic oils was examined. Several different thermodynamic models were evaluated for liquid phase: the Peng-Robinson equation of state (PR-EOS), and the activity coefficient models for ideal solution, the predictive Wilson model, the predictive Universal Quasi-chemical (UNIQUAC) model, and UNIQUAC Functional-group Activity Coefficient (UNIFAC) model. The solid phase is characterized by the multisolid model and the prediction of solid phase formation is initially estimated by a thermodynamic stability test. Afterwards, the systems of non-linear equations (SNLE) formed by the thermodynamic equilibrium and the material balance equations was solved using Newton-Raphson method (multivariate). As far as we can see, there are no systematic studies addressing the effect of the model (and its complexity) on the computational effort of the algorithm. On the other hand, considering the high number of different components in the oil fractions studied, the robustness (due to different initial estimates), and the computational time are important aspects and were analyzed in this work.

摘要 本文针对石蜡基油料的固液平衡（Solid-Liquid Equilibrium, SLE）问题的计算效率展开研究。针对液相体系，本文评估了多款不同的热力学模型：彭-罗宾逊状态方程（Peng-Robinson Equation of State, PR-EOS）、理想溶液活度系数模型、预测型威尔逊模型、预测型通用准化学（Universal Quasi-chemical, UNIQUAC）模型，以及基团活度系数（UNIQUAC Functional-group Activity Coefficient, UNIFAC）模型。固相部分采用多固相模型进行表征，固相生成的预测首先通过热力学稳定性测试完成初步估算。随后，借助多元牛顿-拉夫逊法（Newton-Raphson Method）求解由热力学平衡方程与物料衡算方程构成的非线性方程组（System of Non-Linear Equations, SNLE）。据现有调研，目前尚无系统性研究探讨模型及其复杂度对算法计算量的影响。另一方面，鉴于所研究的油馏分中包含大量不同组分，算法的鲁棒性（针对不同初始估算值）与计算时长均为关键考量因素，本文亦对此展开了分析。