Select thermodynamic models for process simulation
A Practical Guide to a Three Steps Methodology

Chapter 5 - Case Studies

The choice of a modelling approach is very often guided by the experience on other systems, or by the availability of parameter databases. This is acceptable in the sense that most industrial computations are based on previous cases that worked correctly. Yet, it may also be dangerous, and it is then recommended to submit the problem to a thermodynamic analysis.

Our purpose in this book is to help the engineer in selecting, fitting and validating the appropriate model for his or her particular application. In the following part of this work, a number of case studies will be presented with the intention of showing that, although the problem in each case is quite different, a common path can be identified for reaching the solution:

  1. Evaluate the most appropriate model:
    This will require going back to the three previous chapters, and answering the basic questions developed in table 1.1: what properties are required?; what is the fluid composition?; what phases can be present?
  2. Search for the most significant physical data:
    It has been stressed that validation and/or parameter fitting requires data. What data are available and how to use them will depend on the need of the engineer.
  3. Evaluate the results
    This step allows validating or invalidating the chosen model. If the quality is not acceptable, a new model should be chosen or the need for further data acquisition will be recognized.

In this chapter, which is an introduction to the case studies, a first section summarizes the proposed procedure for a thermodynamic analysis, and a second section lists some of the major processes found in the chemical and petroleum industry, along with some key questions that can help the process engineer in his analysis.