Figs. 12 and 13 illustrate the selection of operating conditions
that optimize the number of stages and the amount of
solvent in countercurrent columns operating at high pressures for
points A and B, based on the minimum volume criteria for the
separation task defined in Table 2. Optimization studies to minimize
the amount of solvent in liquid–liquid extraction have been
reported in the literature [56]. Minimizing the amount of solvent
in liquid–liquid extraction is equivalent to optimizing the column
volume in multistage gas extraction.