.FreeFluids.Columns.MulticomponentDistillationFUG

It is a non standard implementation of the Fenske-Underwood-Gilliland shortcut method for multicomponent distillation.

The following simplifications are made:

- The distribution of components between the distillate and bottom, obtained by the Fenske equation for total reflux, is considered valid for the actual and minimum reflux.

- It is considered just one pinch point, close to the feed composition. As the distillate composition is taken from the Fenske's equation, only one Underwood set of equations is needed in order to calculate the minimum reflux. This may give poor calculation if there is an important distribution of any component between distillate and bottom.

The feed must be specified as flow, in kmol/h or kg/h. The top light, and the bottom heavy, can be specified as flow or concentration. Flow is recommended for best convergence.

The model is lacking one equation. You can configure the needed equation by selecting the required parameter. It is done at the graphical menu under the "Operating conditions" tab. You can select one of the options as true: fix the reflux to a constant value, or as a multiplier of the minimum reflux. Or fix the heat exchange at the condenser or the reboiler. Or you can add the extra equation (for example the value of the vpor flow at the stripping section) by hand.