Measurement of high pressure phase équilibria. Closed circuti methods

Observation and the acquisition of information enable us to get to know our real world, to quantify the phenomena that surround us and to explain them. It's also an opportunity to open the door to discovery and innovation. So a good "designer-experimenter" has a role of prime importance of which he or she should be proud, because it is necessary and indispensable if we are to progress.

Using the results obtained through experimentation, it's natural and useful to try and develop a theory, the so-called "fundamental" approach. However, in the first instance, the difficulty of satisfying human needs may be such that we have to make do with more or less empirical approaches, known as "applied" approaches, with the adjustment of parameters for particular systems with a view to a short-term industrial purpose. Secondly, good experimental data is always there for theorists to improve existing models or obtain new ones. Numerous citations in favor of experimental work can be found at: http://www.drichon.wix.com/thermoadvices .

These remarks apply to all fields. In process engineering, we are generally concerned with more or less complex mixtures of chemicals. In such mixtures, deviations from ideality are often far from negligible, and become increasingly important as compounds become more disparate and pressure and temperature conditions more extreme. Phase equilibrium data form the basis for the design and optimization of separation processes, such as distillation, which relies on the distribution of compounds between phases.

Since experimental data, particularly phase equilibrium data, are the fundamental cradle for the development of thermodynamic models and industrial processes, we will focus here on obtaining them. A critical review of the various methods is offered, following a few preliminary remarks.

In this dossier [J 1 030] we deal with closed-circuit methods, where the mixture remains in the equilibration section consisting of the equilibration cell and the circulation tubing (recirculation), all at equilibration temperature. In the following [J 1 031] file, we deal with open-circuit methods in which the mixture or one of the compounds is continuously introduced into the equilibration section, where it remains for a variable length of time (at equilibrium temperature) before exiting. In the latter case,...