[h]). Moreover, in the work of Farhat , it is found that the total pressure at the top of the rectifier was decreased by 5% from its standard atmospheric pressure value (ie. 722 mm Hg), from that reason here the influence of this parameter will be examined too. presents the optimal control pattern for the column functioning with 5% decreased total pressure at the top of the rectifier. Alike in the previous case, the optimal control pattern start with the bang arc, on which is concatenated the longer singular arc, switching to the second bang arc, whereas both bang arcs are of extremely short duration. The previously described structure takes around 0.025 [h], after which the optimal control trajectory follows a similar pattern as in the previous cases: six zero and six bang arcs exist, whereas they again tend to be longer with time. In terms of recovery rate, this policy gives almost 20% less over the same time frame compared to the very first case presented in this paper. This means that it would take over 4.0 [h] to reach the acceptable yield. For this case, the influence of tray hold up can also be embedded. Fig 2b . depicts the optimal control pattern where both the parameters are varied: total pressure and tray hold up. The optimal control trajectory likely follows the same trace as explained before, but, the first part seems to be from a shorter duration as it takes only around 0.020 [h]. Afterwards, the structure is composed of: nine bang, nine zero, and two singular arcs, the latter is concatenated to the sixth bang arc on a time interval less than 0.025 [h]. Same as for the previous case, the decrease in tray hold-up outcomes in failure in recovery rate, as it gives almost 30% less compared to the very first examined above.