For the first step, ie. low-pressurized column (N 1 =23), as expected the initial and final arc match with maximum distillate rate (infinite reflux condition, rectifier). It is to note that, the instantaneous pique that appeared after 0.47 [h], will be disregarded. The optimal control trajectory is composed of 3 bang arcs of maximal distillate rate, but, even three consecutive singular arcs with the tendency to reach approximately 27.30%/3.64%22.73%% from the maximal distillate rate. It is to note that, the latter mentioned, are taking over (more than any particular bang arc), approximately 23% of the total time In summary, the optimal control has the equal number of arcs of each type: 4 bang arcs, 3 arcs of zero control, and, 3 singular arcs. Finally, there are 8 switchings between different types of optimal control.