Fig. 3 shows results obtained operating the column at 10.1 MPa,
its isothermal section at 42 ◦C, with S/F 60, 100, and 140. Each
point on the curves correspond to a different top stage temperature
T1, with the condition T1 > T. Both for Fig. 3 and throughout
this work, the optimal feed location was chosen defining it as the
one giving the best results on raffinate mass fraction and recovery,
being constant all the operating variables. Throughout this work,
the observation was made that the optimal feed stage NF is the
one minimizing the function
XF − Xj
, where XF and Xj are the
5-component vectors ofthe mass fractions ofthe feed and ofthe liquid
in equilibrium at the generic stage j (on solvent-free basis). This
condition also corresponds to liquid composition profiles, in terms
of heavy and light components on solvent-free basis, such that the
feed composition is intermediate between the liquid compositions
of the two adjacent stages, or it is very close to this condition.
As