Efficient design, operation, handling, and transportation of natural gas as liquefied natural gas (LNG) are controlled by its phase behavior. A phase, in a non-reacting system, is known to be stable when it is at its lowest Gibbs energy; an alternative criterion to the minimization of the Gibbs energy is presented for phase stability status determination of pure systems and mixtures. On this premise, the stability limit determination method by the Helmholtz stability criterion was employed for the determination of stability limits which were used to successfully generate stability limit profiles for LNG and its constituents. To further investigate the metastable region, a new and robust model was developed and successfully used to produce vapor and liquid spinodals as well as binodal curves for the LNG constituents. The model accurately predicted the critical points and was shown to be in very close agreement with the available predicted and experimental results.

中文翻译：

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确定液化天然气稳定性曲线的极限：一种热力学方法

液化天然气（LNG）的高效设计，操作，处理和运输受其相态控制。在非反应系统中，当相位处于最低吉布斯能量时，它是稳定的。为确定纯系统和混合物的相稳定性状态，提出了使吉布斯能量最小化的替代标准。在此前提下，采用了基于亥姆霍兹（Helmholtz）稳定性准则的稳定性极限确定方法来确定稳定性极限，以成功生成LNG及其成分的稳定性极限曲线。为了进一步研究亚稳态区域，开发了一个新的健壮模型并将其成功用于生产LNG成分的气液旋节线以及双节线曲线。