An integrated system analysis model is developed for processes involving two interacting countercurrent separation cascades coupled through a single-solvent circulation loop. The overall process model reveals interesting trends characterizing the dependence of the strippant (energy) required for achieving a given solute fractional recovery on the system design and operating variables. There is a minimum solvent circulation rate corresponding to infinite stripping agent requirements. The stripping agent requirements are minimized at an optimum solvent circulation rate and an optimum partition of the total system separation capacity between the two cascades. The developed rational design optimization method is compared with existing rule of thumb approach to the process design of coupled separation operations.