New Approach: The thermodynamic models, the stage-to-stage calculations and the optimization have been implemented using MATLAB R , version 9.3 2017. More information about the used models and the parameters for the examples can be found in the A. For the models (enthalpy, vapor pressure, activity coefficients) implemented in MATLAB R the parameters are taken from the commercial flowsheet simulater Aspen Plus R , version 11 2019. The models have been validated using example data obtained with Aspen Plus R . The calculations with the new method. have been performed on a 64-Bit Windows computer with 16 GB of RAM and an Intel R Core TM i7-8665U processor. The time was measured using the MATLAB R -function timeit.