Local thermodynamic models for high pressure process calculations

This paper discusses the local thermodynamic model concept in the context of high pressure chemical processes where equations of state are usually required for performing thermodynamic property evaluations. Functional forms for local K-value models are developed by simplifying the rigorous equations governing fluid phase equilibria. The local models have imbedded adjustable parameters that are evaluated by regression against either experimental data or thermodynamic properties calculated with more rigorous theoretically based models. During the course of the calculations the parameters in the local models are updated periodically, thereby ensuring that the local models continually provide accurate values for thermodynamic properties. Use of the concepts for process calculations is demonstrated in an example problem.